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Development of blended PMMA+PVDF based nano-
Composite solid polymer electrolytes with Magnesium
Triflate , MgCF3SO3 as host salt, Ethylene Carbonate (EC)
as plasticizer and Al2O3, SiO2, MgO as nano fillers”
UGC MINOR RESEARCH PROJECT REPORT
SUBMITTED TO
UGC-SERO-HYDERABAD
BY
Dr.S.SAROJINI MSc., MPhil, Ph.d
PRINCIPAL INVESTIGATOR,UGC-MRP (No.F. MRP-5226/14 (SERO/UGC), dated March 2014)
PG AND RESEARCH DEPARTMENT OF PHYSICS
QUEEN MARY’S COLLEGE (AUTONOMOUS)
(Affiliated to the University of Madras)
CHENNAI-600 004
June- 2016
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ACKNOWLEDGEMENT
I wish to record my sincere thanks to Dr. Bagerathi Ph.D, Principal (i/c), Queen Mary’s
College (A), Chennai- 4, for having provided all facilities to do UGC-MINOR research project.
I am grateful to Dr. Hemamalini Rajagopal M. Sc., M. Phil., Ph.D. Assistant Professor
& Head, PG and Research Department of Physics, Queen Mary’s College (A), Chennai – 4, for
her moral and constant encouragement. My sincere thanks are due to Dr. Mrs. G.Usha, MSc.
MPhil, Ph.D, Associate Professor, PG and Research Department of Physics and Dr. Mrs. R.
Sarumathy MSc. MPhil, Ph.D, Associate Professor & Head, Department of Chemistry for
assessing my project proposal and their encouragement,
I express my sincere thanks to Prof. Dr. S. Austin Suthanthiraraj, Professor and Head,
Department of Energy, University of Madras, Guindy Campus for permitting me to do my
project work in the department of Energy and utilize all facilities. I also express my gratitude
Dr .B. Muthuraman, Assistant Professor, Department of Energy for his invaluable guidance. I
wish to thank Ms. K. Sowthari (MSc.,Ph.D), research scholar, Department of energy University
of madras, Guindy Campus, for her help in completing this work successfully.
I express my sincere thanks to Dr. Dillip K Satpathy, Department of physics, IIT
Madras for allowing us to carry out AC impedance analysis and also wish to register my thanks
to Ms. Karthika C of research scholar in Low Temperature Physics Lab, IIT Madras, for help in
completing my analysis.
I would like to thank Dr. Jayavel, Director, Department of Nano Science and
Technology, Anna university, Chennai-600025 for allowing us to utilize the facilities available
in the department of nanoscience and nanotechnology for DSC, XRD and SEM studies. I also
thank Dr. Murthy Babu, Director, Department of Nano Science and Technology, Anna
University, Chennai-600025 for his help during characterization studies. I also wish to express
my thanks to research scholars in Department of Nano science and technology, Anna University ,
Guindy Campus, for their invaluable help in completing this work successfully. My personal
thanks to Mr. Selva Raj of Nano Science department, Anna University, Chennai-600025 in
completing all characterization studies.
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I wish to thank Mr .Nagaraj, of Nuclear physics department, University of Madras,
Gundy campus, Chennai-25 to carryout XRD analysis and Instrumentation department, Ethiraj
college, Chennai for FTIR studies.
It is my great privilege to record my sincere thanks to various Instrumentation
Laboratories such as Low temperature physics Lab, IIT Madras, Department of Nano science
and Technology (SEM, DSC), Anna University, Department of Nuclear physics (XRD) at
university of Madras, Guindy Campus, and Ethiraj College for women, Chennai (FTIR) for their
Help in undergoing characterization studies. Also, I acknowledge FIST-CENTRAL
INSTRUMENTATION FACILITY, QMC, for cyclic voltametry analysis and FTIR analysis.
I sincerely thank all faculty members, Department of Physics, Queen Mary’s College, for
their constant encouragement and support. I express my thanks to my students Ms.Prathiba,
Ms.Suvetha, Ms.C.Sugana, Ms.Anjali.C, Ms.N. A. Jothi and Ms. C. Sakuntala for their
sincere efforts and cooperation in completing this project work. I am very much thankful to
office assistants of UGC-QMC, Ms. Pankajam (Retd.) and Ms.Vandana for their help in
carrying out this research project.
I would like to thank UGC for providing necessary grant as UGC minor Research
Project and Joint secretary, UGC-SERO.HYDERABAD, for their timely help in releasing grants
for finishing the project successfully within the stipulated time period.
(Dr.S.SAROJINI MSC., MPhil. Ph.D)
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I. Introduction
1.1 POLYMER
Polymers form a very important class of materials without which the life seems very difficult.
They are all around us in everyday use; in rubber, in plastic, in resins, and in adhesives and
adhesives tapes. The word polymer is derived from greek words, poly = many and mers = parts
or units of high molecular mass each molecule of which consist of a very large number of single
structural units joined together in a regular manner. In other words polymers are giant molecules
of high molecular weight, called macromolecules, which are build up by linking together of a
large number of small molecules, called monomers. The reaction by which the monomers
combine to form polymer is known as polymerization. The polymerization is a chemical reaction
in which two or more substances combine together with or without evolution of anything like
water, heat or any other solvents to form a molecule of high molecular weight. Many polymers
that were developed in past which had their unique properties and applications. During the
period of 1940-1960s, the polymer industry and academia have realized the requirement of new
polymers. But the cost of bringing a new polymer to market and its commercial production
seemed unviable. The polymer industry and academia both focused on developing a polymer
material of novel and valuable properties. In this way, polymer blends became key components
of current polymer research and technology. Mixing of two or more polymers at their matrix
level is termed as polymer blends. It is a physical mixture of two or more polymers which are not
linked by covalent bond. When two or more polymers are completely miscible down to the
segmental level, they form a single homogeneous phase. Their properties are generally
proportional to the ratio of the polymers in the blend, and the polymer blend is called
homogeneous blends. Polymer blend provides a new desirable polymeric material for a variety of
applications. It has many advantages such as simple to prepare, easier to control of physical
properties by compositional changes and possession of better properties compared to individual
polymer component.
Though extensive research has been carried out, very few polymer blend electrolytes
have been found to show significant comprehensive properties which can fulfill the practical
requirements. The opportunity to develop or improve on properties to meet specific customer
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needs includes
The capability toreduce material cost with or without little sacrifice in properties.
Permit the much more rapid development of modified polymeric materials to meet
emerging needs by by-passing the polymerization step.
Extended service temperature range.
Light weight
The ability to improve the process and ability of materials which are otherwise limited
in their ability to be transformed into finished products.
Increased toughening.
Improved modulus and hardness.
Improved barrier property and flame retardant property.
Improved impact and environmental stress cracking resistance, etc.
Traditionally, polymers have been used as an insulators, sheathing, capacitor films in electric
devices, and die pads in integrated circuits. A special form of polymer, the plastics, has been
widely used for machine and device components. Following is a summary of the many
advantages of polymers as industrial materials:
Light weight
Ease in processing
Low cost of raw materials and processes for producing polymers
High corrosion resistance
High electrical resistance
High flexibility in structures
High dimensional stability
1.2 SOLID POLYMER ELECTROLYTES
In consistence with the rapid progress being witnessed in terms of size and thickness
reduction of electronic devices and development of multimedia industries in recent years, the
technological demand has been increasing to fabricate miniaturized portable devices. It is almost
universally accepted that such combination of size and thickness can only be obtained by using
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non-conventional electrodes and electrolyte materials. Polymers have been customized as
electron or ion conductors when combined with appropriate salts, their ionic conductivity can be
put to use as a polymer electrolyte. The promising rechargeable battery technology is using a
polymer electrolyte in a solid state cell is sandwiched between two electrodes. The laminate
construction of such cells offers flexibility of shape size, light weight and durable, which is
advantageous for portable power source applications. However at the present time, the
conductivity of these batteries is very low at room temperature, compared with those of liquid
electrolytes.
Therefore, research is being aimed at increasing conductivity through the use of new
polymers in conjunction with various salts, fillers and plasticizers and new polymers. Solid
polymer electrolytes have received considerable attention because of their potential applications
in various electrochemical devices. Several studies have been performed to get a better
understanding of this new class of solid polymer electrolytes. In their optimal form, they consist
of rubbery materials of low glass transition temperature Tg, in which free volume is large enough
to allow ion migration through local jumps associated with the polymer segmental motion. In
such materials, Tg is strongly affected by salt concentration. Furthermore, ion mobility decreases
markedly with decreasing temperature toward Tg.
These two features make it difficult to understand the effects of cation-polymer and ion-
ion, short-range interactions on conduction of these materials. Still this problem can be
circumvented by using linear, branched or cross-linked copolymers. Ion conducting solids are the
materials which exhibit high ionic conductivity, typically in the range of ~ 10-5 - 10-1 Scm-1, and
negligible electronic conductivity. These solids are also known as solid electrolytes, or fast ion
conductors.
The development of solid electrolytes has been driven by their tremendous technological
applications in the areas of energy storage, energy conversion and in the field of environment
monitoring. These materials are used as electrolytes and electrode separators in various
electrochemical devices like, fuel cells, batteries, super capacitors, sensors, etc. By virtue of
being a solid, solid electrolytes possess numerous advantages over liquid electrolytes like,
absence of liquid containment and leakage problem, ability to operate with highly reactive
electrodes over a wide range of temperature, and the possibility of miniaturization.
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The ion transport in solid electrolytes is governed by some structural and nonstructural
properties like, crystal structure, lattice arrangement, mobile ion concentration, size of the mobile
ions, ionic polarizability, ion-ion interaction, ion interaction with the supporting matrix, number
and the accessibility of occupancy sites, ion conduction pathway etc. On the basis of their
microstructure and the physical properties, the solid electrolytes are classified into four major
categories:
Framework crystalline solid electrolytes
Amorphous-glassy solid electrolytes
Composite solid electrolytes
Polymer electrolytes
Out of the above four categories, polymer electrolytes are one of the most widely studied
solid electrolytes.
The film formability with desirable mechanical, thermal and electrochemical stability
makes polymer electrolytes more attractive than the conventional liquid electrolytes and the
brittle crystalline/polycrystalline, composite, and glassy solid electrolytes. Innumerable amount
of work has been done on polymer electrolytes in the last few years which are excellently
covered in several reviews. The polymer electrolytes are further classified as
Conventional dry solid polymer electrolytes,
Plasticized solid polymer electrolytes,
Rubbery electrolytes,
Polyelectrolytes,
Gel polymer electrolytes,
Composite polymer electrolytes.
The conventional dry solid polymer electrolytes (SPE) are basically the polymer-salt
complexes prepared by dissolving suitable ion donating salts/acids into high molecular weight
polymers which act as a host. Examples of such host polymers are polyethylene oxide (PEO),
polypropylene oxide (PPO), polyvinyl pyrrolidone (PVP) etc. The ion transport in these polymer
electrolytes is governed by local relaxation as well as segmental motion of the polymer chains
which are more favored by high degree of amorphicity of the host polymers. But, many host
polymers are partially crystalline in nature which is an unfavorable property for achieving high
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ionic conductivity. Plasticization is one of the most adopted approaches used to suppress the
crystallinity of polymer electrolytes. In the plasticization, a substantial amount of a liquid
plasticizer, namely, low molecular weight poly(ethylene glycol) (PEG) and/or aprotic organic
solvents, such as ethylene carbonate (EC), propylene carbonate (PC), diethylene carbonate
(DEC), dimethylsulfoxide (DMSO), etc is added to the dry SPE matrix.
PLASTICIZED SOLID POLYMER ELECTROLYTES
The addition of the liquid phases in the SPEs leads to the decrease in the crystallinity and
the glass transition temperature of the host polymer and promote the segmental motion of the
polymer chains, which, in turn, results into the higher ionic conductivity of the plasticized
polymer electrolytes at ambient conditions.
The high dielectric constants of the organic plasticizers like EC and PC also help in
dissociation of ion aggregates, i.e. create more free ions, which further results into the higher
electrical conductivity of the plasticized polymer electrolytes.
FORMATION OF POLYMER-SALT COMPLEXES
A polymer such as PEO and a metal salt such as alkali metal salt are dissolved in suitable
solvents. The solvent may be one component or it may be a two-component mixture;
alternatively the polymer may be dissolved in one solvent and the salt in another, the two
solutions being subsequently mixed, after a substantial stirring period to ensure adequate mixing,
the solvent is allowed to evaporate and a thin cast film is formed. The nature of the films formed
from given reactants are quite different depending on whether moisture is present or excluded,
and on whether the system has been heated or not.
There are two energetically significant stages for the electrolyte formation. Initially the
lattice energy of the salt is overcome by the process of dissolution in the casting solvent then the
salt is transferred from the casting solvent to the polymer, it is helpful to regard the latter as an
“immobile solvent”. In the case of PEO-MX (alkali salt) complexes, cation M+ coordinates with
lone pairs of electrons on the heteroatom (oxygen) in the polymer chain. The anion remains in
close proximity to preserve local charge neutrality.
The most common examples concern complexes between PEO and alkali metal salts, MX
as the solvating hetero atom, here oxygen, acts as a donor for the cation M+ and the anion X–,
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generally of large dimension stabilizes the PEO-MX complex. PEO has the same repeat unit as
simple crown ether, Ex:- CH2-CH2-O; typically about 105 repeat units are joined, to give a
polymer or relative molar mass ~ 6x105 so that the end groups on the polymer chain have a
virtually insignificant effect on the chemistry of the system. With some alternative comb and
network polymers that are coming into use, the PEO side chains are only two or three repeat
units in length and end group effect can be important.
(– CH2 – CH2 CH2 – CH2 -)n
O
M+-------X–
If the interaction between the cation and the polymer chain is strong, then a type of
localized “chemical cross–linking” occurs and the material may become highly structurally
organized, leading to the formation of a high melting crystalline phase.
Weak interactions, especially in dilute systems can lead to the formation of crystalline
PEO regions. In some systems, both crystalline complex and crystalline PEO may be present.
Polymer complexes generally have a multiphase nature consisting of salt-rich crystalline phase,
pure polymer crystalline phase and amorphous phase with dissolved salt. If the cation-polymer
interaction is too strong, then clearly the cations will have a very low mobility. This is not the
only problem that results from over – strong cation – polymer interactions. Typically, a given
cation is linked at any one instant of time, to four or more oxygen’s, which often are located on
more than one polymer chain; thus, transient ionic cross-links are formed which greatly restrict
the local freedom of motion which depends on the length of the polymer chain. Kakihana et al
have shown that ionic motion depends on the ability of the polymer chains to flex, and so the
rigidity imposed by the transient cross links (induced by the cations) also impedes the mobility
of this anions. In addition, many cations interact with PEO in such a way that crystalline high
melting salt-polymer complexes are formed. For effective complexation/salvation of salts in
polymers, the following criterion can be taken as “thumb rules”.
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The polymers should be of low glass transition temperatures (Tg) for their flexible
backbone, which will ensure the complexation. The low Tg can be attained either by
choosing the polymers of low cohesive energy (such as PEO, PPO, PEI etc.) or by
plasticizing the polymers of high Tg.
The lattice energy of the salts should be lower for which, salts of larger anions such as I,
CIO4–, CIO3
–, CF3SO3, SCN– etc., are most suitable.
The concentration of polar groups (or solvating heteroatom) responsible for complexation
of cations, should be as large as possible.
POLYELECTROLYTE
Polyelectrolyte is another category of polymer electrolytes in which polymers possess ion
generating groups attached to their main chain. The most important and well known product of
this class is Nafion. The Nafion membranes produced by DuPont are currently in use in portable
fuel cell application. These membranes exhibit high proton conductivity, good chemical stability
and mechanical integrity.
GEL POLYMER ELECTROLYTES (GPES)
Gels, in general, are defined as the solids with continuous liquid phase enclosed into a
continuous solid skeleton. In GPEs, liquid phases are normally the organic liquid electrolytes,
which are obtained by dissolving ion donating salts into the organic solvents
plasticizers, entrapped into the solid polymer network which provides dimensional stability
to gel electrolytes. It is observed that the larger amount of liquid electrolyte present in the
polymer matrix gives rise to better ionic conductivity but diminishes the mechanical integrity of
GPEs.
COMPOSITE POLYMER ELECTROLYTES
Therefore, in order to improve the mechanical integrity, GPEs are dispersed with micro-
and nano-sized ceramic fillers like SiO2, Al2O3, TiO2, BaTiO3 etc. It is found that the dispersion
of ceramic fillers not only improves mechanical strength but also improves the electrical
conductivity of the GPE systems.The dispersion of ceramic fillers has proved its worth in almost
all the classes of polymer electrolytes as, composite dry SPEs, composite plasticized SPEs,
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composite polyelectrolyte, and composite GPEs. Polymer electrolytes support variety of ions,
like Li+, H+, Na+, K+, Mg++, Cu++ etc, for transport. A large number of such polymer electrolytes
have been developed in view of their various applications.
MAGNESIUM ION CONDUCTORS
Since last decade magnesium ion conducting material and specifically gel polymer
electrolytes are reported fairly in literature. These polymer electrolytes have found their practical
application in Mg-batteries and other electrochemical devices. The significant attention towards
rechargeable magnesium battery system is due to important characteristics of the magnesium
metal which are its high charge density, considerably negative electrode potential, high melting
point (922 K), low cost, ease of handling, disposal and low toxicity.
Nevertheless, lithium-ion batteries are relatively expensive and suffer from some safety
limitations. Magnesium-based rechargeable battery system has attracted attention due to its
performance capabilities that are close to those of lithium-based alternatives.
Magnesium is an attractive anode material for batteries of high specific energy because it
has a low electrochemical equivalence (12.15 g) and a considerably negative electrode potential
2.3 V). In addition, it is cost effective due to natural abundance and safer than lithium.
The search for Mg2+ ion containing polymer electrolytes can be interesting not only for
understanding the multivalent cationic conductivity mechanism in the polymer, but also due to
their lower cost, and ease of handling and fabrication as thin film membranes. Several methods,
such as co-polymerization, plasticization, blending and addition of ceramic fillers have been used
to modulate conductivity of the polymer electrolytes.
Materials showing Mg2+ conductivity are advantages due to the following reasons.
Magnesium metal is more stable than Lithium. It can be handled safely in oxygen and
atmosphere unlike lithium which requires high purity are on or lithium atmosphere.
Therefore, safety problems associated with magnesium metal are minimal.
Global raw materials resources of magnesium are plentiful and thus, it is much cheaper
than the lithium.
PLASTICIZERS
Polymers used for coating often result in brittle films, which may lead to crack
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formation, being responsible for the failure of the functionality of the coating. Plasticizers are
added to avoid the internal strain leading to these defects and to ensure appropriate film
properties. In general plasticizers are low molecular weight non-volatile liquids at room
temperature with a high boiling point and mostly insoluble in water The right choice of
plasticizer and the adequate concentration are very important for the resulting film properties of
the coating The amount added should be sufficient to reduce the brittle character of the polymer,
but not to be as much to cause sticking of the coated product while processing or storage
Plasticizers are mostly used in concentrations between 5-30% wt based on the dry polymer
weight, depending on the type of plasticizer, the polymer to be plasticized, as well as on the
system applied e.g. organic solution or aqueous dispersion. Solubility of the polymer in the
plasticizer is a pre-requirement, to assure the necessary compatibility of the two components.
The plasticizer increases the molecular mobility of the polymer by interpenetrating with the
polymer chain segments.
This decreases the cumulative intermolecular forces along the polymer chains, leading to
a reduction in cohesion and a more open structure of the polymer. Superior mechanical
properties of the film are the result of the reduced brittleness and improved flexibility. The
effectiveness of the plasticizer can be quantified by the decrease of the tensile strength and
modulus as well as the reduction of the glass transition temperature (Tg).
Plasticizers for plastics are additives, most commonly phthalate esters applications. The
majority is used in films and cables. It was commonly thought that plasticizers work by
embedding themselves between the chains of polymers, spacing them apart, and thus
significantly lowering the glass transition temperature for the plastic and making it softer;
however it was later shown that the free volume expansion could not account for all of the
effects of plasticization. For plasticizer added, the lower their cold flex temperature will be. This
means that the plastic will be more flexible and its durability will increase as a result of it.
Plasticizers make it possible to achieve improved compound processing characteristics, while
also providing flexibility in the end-use product. Ester plasticizers are selected based upon cost-
performance evaluation. The rubber compounder must evaluate ester plasticizers for
compatibility, processibility, permanence and other performance properties.
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This line provides an array of performance benefits required for the many elastomer
applications such as tubing and hose products, flooring, wall-coverings, seals and gaskets, belts,
wire and cable, and print rolls. Low to high polarity esters provide utility in a wide range of
elastomers including nitrile, polychloroprene, and chlorinated polyethylene. Plasticizer-elastomer
interaction is governed by many factors such as solubility parameter, molecular weight, and
chemical structure. Compatibility and performance attributes are key factors in developing a
rubber formulation for a particular application.
EFFECTS OF FILLERS
Traditionally, most filler were considered as additives, which, because of their
unfavorable geometrical features, surface area, or surface chemical composition, could only
moderately increase the modulus of the polymer, whereas strength (tensile, flexural) remained
unchanged or even decreased.
Their major contribution was in lowering the cost of materials by replacing the most
expensive polymer; other possible economic advantages were faster molding cycles as a result of
increased thermal conductivity and fewer rejected parts due to war page. Depending on the type
of filler, other polymer properties could be affected; for example, melt viscosity could be
significantly increased through the incorporation of fibrous materials. On the other hand, mold
shrinkage and thermal expansion would be reduced, a common effect of most inorganic fillers.
An additional example of families of fillers imparting distinct new properties is given by
the pearlescent pigments produced by platelet core–shell technologies. These comprise platelets
of mica, silica, alumina, or glass substrates coated with films of oxide nanoparticles, for
example, TiO2, Fe2O3, Fe3O4, and Cr2O3. The addition of nano-filler retards the re crystallization
of polymer chain since the size of filler is very small compared to the polymer host, the filler is
able to penetrate into the polymer matrix and prenotes an interaction between filler, plasticizer
and polymer chain molecular consequently, the cohesive force between the polymer chain is
reduced and provides a more flexible chain sequential motion Tg can be lowered with the
addition of filler.
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1.3 APPLICATIONS OF POLYMER ELECTROLYTES
Polymers with dissolved ionic salts have a relatively high ionic conductivity and therefore
have a potential application as solid electrolytes. The solid state ion conducting polymers are
used as electrolytes in different electrochemical devices such as
Electrochemical Batteries
Electrochemical sensors
Fuel cells
Super capacitors
Memory devices
High-vacuum electrochemistry
Electro chromic display devices
Thermoelectric generators and Electrochemical switching .
In the present research work, it is planned to carry out an extensive experimental
investigation based on blended PMMA and PVDF /Magnesium triflate systems by
incorporating Ethylene Carbonate (EC) as plasticizers and Al2O3 , SiO2 and MgO as
nanofiller to study their physical properties with an ultimate aim of understanding the
structural aspects responsible for the phenomenon of fast ionic conduction in such systems
using a wide range of analytical methods including structural studies, morphological studies,
complex ac impedance analysis, thermal analysis, and electrical conductivity studies. The
proposed system could be represented as
System I: {(PMMA/PVDF: MgCF3SO3: EC} + a wt% MgO
(where a = 5, 10, 15 and 20 mol %)
System II: {(PMMA/PVDF: MgCF3SO3: EC} + b wt% Al2O3
(where b = 5, 10, 15 and 20 mol %)
System III: {(PMMA/PVDF: MgCF3SO3: EC} + c wt% SiO2
(where c = 5, 10, 15 and 20 mol %)
2. Objectives
The main objectives of the present research work are as follows,
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i). Preparation of a new series of solid polymer electrolytes of
System I: {(PMMA/PVDF: MgCF3SO3: EC} + a wt% MgO
(where a = 5, 10, 15 and 20 mol %)
System II: {(PMMA/PVDF: MgCF3SO3: EC} + b wt% Al2O3
(where b = 5, 10, 15 and 20 mol %)
System III: {(PMMA/PVDF: MgCF3SO3: EC} + c wt% SiO2
(where c = 5, 10, 15 and 20 mol %)
by solution casting method .
ii). Analysis of the above solid polymer electrolytes using Differential Scanning Calorimetry
(DSC), X-Ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) Spectroscopy
techniques in order to find out the constituent phases present in these solid polymer
electrolyte materials,
iii) Surface morphological analysis using Scanning electron microscopy (SEM), Field
emission Scanning electron microscopy (FESEM) analytical technique to investigate
molecular surface structures and their electronic properties coupled with EDAX analysis.
iv). Measurement of electrical conductivity, at different temperatures and evaluation of ionic
transport number (tion ) by AC/DC method.
v). Fabrication of solid state batteries using the above best conducting solid polymer
electrolytes and MnO2+C cathode materials and study of various battery discharge
characteristics.
2. SCOPE OF THE PRESENT INVESTICATION
The science of solid polymer electrolytes is a highly specialized interdisciplinary field,
which encompasses the disciplines of electrochemistry, polymer science, organic chemistry and
inorganic chemistry. A solid and/or gel polymer electrolyte consists of host salt dissolved in a
polymer matrix in which ionic conductivity occurs. The host salt dissociates into ions, which
contribute to the conductivity.
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Polymer electrolytes have potential applications in electrochemical devices such as
polymer batteries, super capacitors, sensors and electro chromic devices. Solid polymer
electrolytes exhibit a number of advantages, which include providing ionic transport in
comparison with liquid electrolytes, chemically compatible with electrode materials, possessing
good mechanical strength and flexibility as well as leak free.
For application in lithium polymer batteries, such electrolytes should have high ionic
conductivity at ambient, sub-ambient and elevated temperatures; appreciable transference
number, good window stabilities and compatibility with the electrodes and ion conducting
electrolyte materials have motivated substantial interest in the field of Solid State Ionics owing to
their potential applications in many electrical and electronic devices. The major advantages of
using solid polymer-based electrolytes are their good mechanical stability and flexibility, ease of
fabrication of thin films of desirable sizes, improved electrode electrolyte contacts and hence
enhanced electrical conductivity at ambient temperature.
Poly (methyl methacrylate) (PMMA), has been chosen as a host polymer for the present
study, due to its outstanding chemico-physical properties which represent a particularly suitable
polymer component for the embodiment of both microscopic and nanoscopic functional
inorganic fillers. The wide use of such a matrix has to be traced back to the favorable
combination of chemical and physical properties and easy processing. It has been well
established that PMMA acts as a good host material for dielectric materials. PMMA-Ceramic
composites exhibit remarkably low dielectric loss at high frequency, which makes them potential
material for the capacitors in high frequency application.
It is an amorphous polymer and it is a colorless, transparent, plastic with an excellent life
period and good mechanical properties systems were determined. It has a dielectric constant of
2.8 - 4 particularly in the low frequency region, it is 3-4. Poly (methyl methacrylate) (PMMA)x is
a successful host polymer.
However, PMMA based solid polymer electrolytes are known to exhibit very low ionic
conductivity of the order of 10-10 to 10-11 Scm-1at ambient temperature which is inadequate for
any device application.
Here our present effort has been focused mainly towards improving the ionic
conductivity with appreciable mechanical stability in the case of a PMMA based solid polymer
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electrolyte at room temperature. Today, solid polymer blending is a versatile and widely used
method for optimizing the cost-performance balance and increasing the range of potential
applications, especially for fluoropolymers such as PVDF which is often blended with
amorphous polymers, among which poly (methyl methacrylate) (PMMA) has been the most
studied compatible polymer owing to its low cost, optical properties, performance advantages
and its nature of miscibility with other polymers in the melting state. In this endeavor,
PMMA/PVDF based blended solid polymer electrolyte has been prepared using solution casting
technique.
An attempt has been made to a (PVDF)x - (PMMA)1-x solid polymer electrolyte system
with appropriate stoichiometric compositions. The inherent merits of using blend based solid
polymer electrolytes are exemplified by several research groups .In general ,a negative change in
free energy is essential for miscibility of solid polymer blends. This requirement is met by blends
of (PMMA)x and (PVDF)1-x. The PMMA is the host polymer and the PVDF is the co-polymer.
The studies of ionic conductivity in terms of AC impudence analysis were intended to the
blended matrix of (PMMA)x - (PVDF)1-x by our research group. The ac impedance study of the
synthesized blended solid polymer electrolytes under four different compositions (PMMA)x -
(PVDF)1-x,where 1-x = 95, 90, 85 and 80 mol % respectively revealed the best conduction
composition as (PMMA)50 - (PVDF)50 with the electrical conductivity value of 4.4496 × 10-10
Scm-1 at room temperature (303 K). Polymer electrolytes with sufficiently high room
temperature ionic conductivity have good mechanical properties and can be prepared as thin
films. Polymer metal salt complexes have gained technological importance as electrolyte
materials for the solid state electrochemical devices such as batteries, fuel cells, electro chromic
windows and super capacitors.
The electrical conductivity of these polymer–salt electrolytes can be controlled by
varying the salt content and by adding suitable plasticizers and inert fillers. Many types of
polymers have been studied in the pursuit to develop solid electrolyte systems with high room
temperature conductivity. Investigations on ionically (Li+, Na+, Ag+, Mg2+, etc) conducting
polymer-solution complexes are focused primarily due to their significant potential for a wide
range of electrochemical applications including solid state thin film batteries, portable devices,
sensors etc. Practical, primary aqueous magnesium batteries were developed and there have
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already been several studies on nonaqueous magnesium electrochemistry in connection with
R&D of rechargeable Mg batteries.
But in view of the natural abundance of magnesium, its rather low equivalent weight (12
g per Faraday (F), as compared to 7 g/F for Li or 23 g/F for Na), its low price of 2700/ton
(metallic Li is currently about 24 times more expensive than metallic Mg and its safety
characteristics. Metallic magnesium should be examined as a potential alternative negative
electrode for applications in which cost control is critical. Its electrode potential is less negative
than that of lithium. More serious is the fact that magnesium electrochemistry at or near ambient
temperature is rather poorly understood, and a substantial research effort will be required in
order to develop competitive secondary magnesium electrodes.
The trifluoromethanesulfonate (triflate) ion, CF3SO3- , has proved to be an extremely
important probe of ionic association in polymer salt complexes. In the triflate ion, the symmetric
SO3 stretching is non degenerate, hence multiple bands in this spectral region must necessarily
result from anions in different potential energy environments. In turn, these different
environments are interpreted as due to different ionic species, e.g., “free” ions, ion pairs, and
ionic aggregates. The anti symmetric SOS stretching mode of the isolated triflate ion is doubly
degenerate.
In the presence of a sufficiently large cation-anion interaction which does not preserve
the axial symmetry of the anion, this mode will split into two components as the degeneracy is
lifted. Hence in our present investigation, in order to achieve high ionic conductivity at ambient
temperature, we planned to introduce Magnesium triflate as salt complex in the blended polymer
matrix of (PMMA)50 - (PVDF)50. To improve the ionic conductivity at ambient temperature, a
plasticizer may be added to the system. Among the plasticizers, in order to ensure strong
dissociation, solvents having relatively high dielectric constants have been preferred, i.e.,
ethylene carbonate EC.
Nano-size particles are known to provide an order of magnitude increase in ionic
conductivity higher than micro-size particles and hence nano-size fillers are very interesting ones
and are prove to improve ionic conductivity of polymer complex substantially. In this study, we
intend to use MgO, Al2O3and SiO2 as nano filler. The advantages of incorporating the fillers are
19
twofold. One is the enhancement in ionic conductivity at low temperatures and the other one is to
improve the stability at the interface with electrodes.
The synthesis and characterization studies in terms of structural and electrical analysis were
intended to the blended matrix of
System I (((PMMA + PVDF)y - (Mg2CFSO3)1-y)z- (EC)1-z )a - (MgO)1-a
where 1-a = 20,15,10 and 5 mol % respectively
System II (((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))b- (Al2O3)1-b
where 1-b = 20,15,10 and 5 mol % respectively.
System III (((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))a- (SiO2)1-c
where 1-c = 20,15,10 and 5 mol % respectively.
The aim of the present study also includes testing the ionic nature of the best conducting
polymer electrolyte systems I, II and III by undergoing transference number measurement by
ac/dc polarization method, electrochemical stability by cyclic voltametry analysis and
fabrication of solid-state battery with the best conducting polymer system as electrolyte along
with Magnesium anode and MnO2+C as cathode.
3. Materials and methods used in present investigation
3.1 POLY (METHYL METHACRYLATE) (PMMA)
Poly (methyl methacrylate) (PMMA) x is a transparent thermoplastic often used as a
lightweight or shatter-resistant alternative to glass. Although it is not technically a type of glass,
the substance has sometimes historically been called acrylic glass. Chemically, it is the synthetic
polymer of methyl methacrylate.
Fig 3.1 Structure of PMMA Fig 3.2 PMMA Molecular formula
PMMA is a strong and lightweight material. It has a density of 1.17–1.20 g/cm3, which is
less than half that of glass. It also has good strength, higher than both glass and polystyrene.
However PMMA’s impact strength is still significantly lower than polycarbonate and some
20
engineered polymers. PMMA ignites at 733 K and burns, forming carbon dioxide, water, carbon
monoxide and low-molecular-weight compounds, including formaldehyde. PMMA swells and
dissolves in many organic solvents.
It also has poor resistance to many other chemicals on account of its easily hydrolyzed
ester groups. Nevertheless, its environmental stability is superior to most other plastics such as
polystyrene and polyethylene, and PMMA is therefore often the material of choice for outdoor
applications. PMMA has a maximum water absorption ratio of 0.3–0.4% by weight. Tensile
strength decreases with increased water absorption. Its coefficient of thermal expansion is
relatively high at (5–10) × 10 5 K 1.
Table 3.1 Physical and Electrical Properties of PMMA
Other uses:
PMMA, in a purified form, is used as the matrix in laser dye-doped solid-state gain media
for solid state dye lasers.
PMMA is used as a shield to stop beta radiation emitted from radioisotopes.
Small strips of PMMA are used as dosimeter devices during the Gamma Irradiation
process. The optical properties of PMMA change as the gamma dose increases, and can
be measured with a spectrophotometer.
Physical and Electrical Properties
Chemical formula - (C5O2H3)n
Density - 1.18 g/cm3
Melting point - 160ºC ((320 °F; 433 K)
Refractive index - 1.4905 at 589.3 nm
Tensile strength - 55 - 80MN/m2
Electrical resistivity - 1014 - 1015 cm
Dielectric constant - 2.8 - 4
Ionic conductivity - 3.19 × 10-11 S cm-1
Dielectric strength - 17.7 – 60 KV/mm
21
PMMA can be used as a dispersant for ceramic powders to stabilize colloidal suspensions
in non-aqueous media. Due to its high viscosity upon dissolution, it can also be used as
binder material for solution deposition processes, e.g. printing of solar cells.
A backlight-reactive tattoo ink using PMMA microcapsules has been developed.
PMMA has also been used extensively as a hybrid rocket fuel.
Artificial fingernails are sometimes made of acrylic.
3.2 POLY VINYLIDENE FLUORIDE (PVDF)
Poly vinylidene fluoride or poly vinylidene difluoride (PVDF) is a highly non-reactive
and pure thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.
PVDF is a special plastic material in the fluoropolymer family. It is used generally in
applications requiring the highest purity, strength, and resistance to solvents, acids, bases and
heat and low smoke generation during a fire event. Compared to other fluoropolymers, it has an
easier melt process because of its relatively low melting point of around (450 K).
It has a low density (1.78 g/cm3) compared to the other fluoropolymers. It is available as
piping products, sheet, tubing, films, plate and an insulator for premium wire. It can be injected,
molded or welded and is commonly used in the chemical, semiconductor, medical and defense
industries, as well as in lithium ion batteries. It is also available as a crosslinked closed cell foam,
used increasingly in aviation and aerospace applications.
Properties
PVDF namely Polyvinylidene fluoride is a kind of crystal polymer with low melting
point (433 K - 443 K), high mechanical properties, good resistance to wear, to corrosion, to
weather and as well with good electric insulation, high dielectric constant. Also it is anti-
ultraviolet ray, anti-radiation and easily machined. With low processing temperature and good
melting flow, it could be processed easily to make pipe, plate, rod, film and fiber. Its heat
conductivity is poor. PVDF has a glass transition temperature (Tg) of about 308 K and is
typically 50–60% crystalline.
22
Fig 3.3 Molecular formula of PVDF
Applications
PVDF is commonly used as insulation on electrical wires, because of its combination of
flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat
resistance.
The piezoelectric properties of PVDF are used in advantage with manufacture tactile
sensor arrays, inexpensive strain gauges and lightweight audio transducers. Piezoelectric panels
made of PVDF are used on the Venetia Burney Student Dust Counter, a scientific instrument of
the New Horizons space probe that measures dust density in the outer solar system. In the
biomedical sciences PVDF is used in immunoblotting as an artificial membrane, usually with
0.22 or 0.45 micrometers pore sizes, on which proteins are transferred using electricity. PVDF is
resistant to solvents and, therefore, these membranes can be easily stripped and reused to look at
other making it very convenient. PVDF membranes may be used in other biomedical
applications as part of a membrane filtration device, often in the form of a syringe filter, or wheel
filter. The various properties of this material such as heat resistance, resistance to chemicals,
corrosion and low protein binding properties make this material valuable in the biomedical
sciences for preparation of medications as a sterilizing filter, and as a filter to prepare samples
for High Performance Liquid Chromatography and other advanced analytical techniques in
which small amounts of particulate can damage sensitive and expensive equipment.
PVDF transducers have the advantage of being dynamically more suitable for modal
testing applications than semi-conductor piezo resistive transducers, and more compliant for
structural integration than piezo ceramic transducers.
23
3.3 MAGNESIUM TRIFLATE (Mg2CFSO3)
Magnesium Trifluoromethanesulfonate is one of numerous organo-metallic compounds sold
by American Elements under the trade name AE Organo-Metallics for uses requiring non-
aqueous solubility such as recent solar energy and water treatment applications.
Fig 3.4 Molecular formula of Mg2CFSO3
Similar results can sometimes also be achieved with nanoparticles and by thin
film deposition. Dysprosium Trifluoromethanesulfonate is generally immediately available in
most volumes. High purity, submicron and nanopowder forms may be considered.
Additional technical, research and safety information is available. Magnesium (atomic
symbol: Mg, atomic number: 12) is a Block S, Group 2, Period 3 element with an atomic mass of
24.3050. The number of electrons in each of Magnesium's shells is [2, 8, 2] and its electron
configuration is [Ne] 3s2. The magnesium atom has a radius of 160 pm and a Van der Waals
radius of 173 pm. Magnesium was discovered by Joseph Black in 1775 and first isolated by Sir
Humphrey Davy in 1808. Magnesium is the eighth most abundant element in the earth's crust
and the fourth most common element in the earth as a whole.
In its elemental form, magnesium has a shiny grey metallic appearance and is an extremely
reactive material and also found in minerals such as brucite, carnallite, dolomite, magnesite,
olivine and talc. Commercially, magnesium is primarily used in the creation of strong and light
weight aluminum-magnesium alloys, which have numerous advantages in industrial applications.
The name "Magnesium" originates from a Greek district in Thessaly called Magnesia.
3.4 ETHYLENE CARBONATE
Ethylene carbonate is the organic compound with the formula (CH2O)2CO. It is classified
as the carbonate ester of ethylene glycol and carbonic acid. At room temperature (298 K)
ethylene carbonate is a transparent crystalline solid, practically odorless and colorless, and
somewhat soluble in water. In the liquid state (M.P 307 K - 310 K) it is a colorless odorless
liquid. Dielectric constant, 89.6 at 313 K. Ethylene carbonate is used as a solvent for lubricants,
24
as a crosslinking agent in the super absorber polymer production, in separation of gas washing
process and oil filled, as an intermediate in the synthesis of polycarbonate diol as well as for
lithium ion batteries and photochromic applications.
Fig.3.5 Structure of Ethylene carbonate ((CH2O)2 CO)
It is further used as a component in coatings and paints (e.g. waterborne latex wall paint),
thinners, paint removers, cleaning agents as well as in agrochemicals. Ethylene carbonate is a
colorless to yellowish solid of fruity odor.
It is non-flammable and non- explosive. Its physical state is solid, with melting point
309 K, Boiling point 520 K, Non-flammable, and Non-explosive. Among plasticizer used such as
Propylene Carbonate (PC), Ethylene Carbonate (EC), Poly ethylene glycols (PEG) etc, EC is
more favorable possess comparable in cost and
slightly higher dielectric constants which favors dissociation of ion pairs into free cations
and anions and this increase ionic conductivity. However, introduction of plasticizer leads to
derivative in mechanical properties of polymer electrolytes. However, addition of micro sized
and nano-sized fillers were shown to improve the ionic conductivity of polymer electrolytes by
recent researchers.
3.5 DIMETHYLFORMAMIDE AS SOLVENT
Dimethylformamide is an organic compound with the formula (CH3)2NC(O)H.
Commonly abbreviated as DMF, this odorless liquid is miscible with water and the majority of
organic liquids. Dimethylformamide is odorless whereas technical grade or degraded samples
often have a fishy smell due to impurity of dimethylamine. As its name indicates, it is a
derivative of formamide, the amide of formic acid. DMF is a polar (hydrophilic) aprotic
solvent with a high boiling point.
25
PROPERTIES
As for most amides, the spectroscopic evidence indicates partial double bond character
for the C-N and C-O bonds. Thus, the infrared spectrum shows a C=O stretching frequency at
only 1675 cm 1, whereas a ketone would absorb near 1700 cm-1. The methyl groups in
equivalent on the NMR time scale, giving rise to two singlet’s of 3 protons each at 2.97 and 2.88
in heproton NMR spectrum.
DIMETHYLFORMAMIDE STRUCTURE
Fig. 3.6 Dimethylformamide Structure
DMF is hydrolyzed by strong acids and bases, especially at elevated temperatures. With sodium
hydroxide, DMF converts to format and dimethylamine.
APPLICATIONS
The primary use of DMF is as a solvent with low evaporation rate. DMF is used in the
production of acrylic fibers and plastics. It is also used as a solvent in peptide coupling for
pharmaceuticals, in the development and production of pesticides, and in the manufacture
of adhesives, synthetic leathers, fibers, films, and surface coatings.
It is used as a reagent in the Bouveault aldehyde synthesis and in the Vilsmeier-Haack
reaction, another useful method of forming aldehydes.
It is a common solvent in the Heck reaction.
It is also a common catalyst used in the synthesis of acyl halides, in particular the
synthesis of acyl chlorides from carboxylic acids using oxalyl or thionyl chloride.
DMF penetrates most plastics and makes them swell. Because of this property DMF is
suitable for solid phase peptide synthesis and as a component of paint strippers.
26
DMF is used as a solvent to recover olefins such as 1, 3-butadiene via extractive
distillation.
It is also used in the manufacturing of solvent dyes as an important raw material. It is
consumed during reaction.
Pure acetylene gas cannot be compressed and stored without the danger of explosion.
Industrial acetylene gas is, therefore, dissolved in dimethylformamide and stored in metal
cylinders or bottles.
USES
As a common and cheap reagent, DMF has many uses in the research laboratory.
DMF is effective at separating and suspending carbon nano tubes, and is recommended
by the NIST for use in near infrared spectroscopy of such
DMF can be utilized as a standard in proton NMR allowing for a quantitative
determination of an unknown compound.
In the synthesis of organ metallic compounds, it is used as a source of carbon
monoxide ligands.
DMF is a common solvent used in electro spinning.
DMF is a solvent commonly used in the solvothermal synthesis of Metal Organic
Frameworks.
3.6 MAGNESIUM OXIDE (MgO)
Metal oxides play a very important role in many areas of chemistry, physics and material
science. The metal elements are able to form a large diversity of oxide compounds. These can
adopt a vast number of structural geometries with and electronic structure that can exhibit
metallic, semiconductor or insulator character. In technological applications oxides are used in
the fabrication of microelectronic circuits, sensors, piezoelectric devices, fuel cells, coatings for
the passivation of surfaces against corrosion, and as catalysts. In the emerging field of
nanotechnology, a goal is to make nanostructures or nano arrays with special properties with
respect to those of bulk or single particle species. Oxides nanoparticles can exhibit unique
physical and chemical properties due to their limited size and a high density of corner or edge
surface sites.
27
Among the metal oxides, magnesium oxide (MgO) is widely used in chemical industry as
a scrubber for a pollutant gases (CO2, NOX, SOX) and as catalyst support. It exhibits a rock salt
structure like oxides of other alkaline earth metals. The non –polar [100] face is by far the most
stable surface, and properties of MgO usually display a cubic shape. For example, when Mg
metal is burnt in air, the MgO smoke particles that are formed are almost perfect cubes having
[100] faces. Magnesium is a block 3 element, while oxygen is a block p, period 2 elements.
Magnesium oxide refers to the compound MgO. MgO is also an oxide of magnesium that which
is a Meta stable compound. Magnesium oxide nano particles are odorless and non-toxic. They
possess high hardness, high purity and high melting point. Magnesium oxide nano particles
appear as white powder form.
CRYSTAL STRUCTURE
Fig 3.6 MgO has a cubic structure as shown in figure.
Some of the essential physical properties of MgO are listed in table with reference to the
CRC handbook of Physics and Chemistry. Density of the magnesium oxide 3.58 g/cm3, molar
mass 40.3 g/mol, conductivity value of 10-7 - 10 -8 Scm-1 and dielectric constant is 9.5(373 K),
soluble in water and insoluble in ethanol.
THERMAL PROPERTIES
Some of the essential thermal properties of MgO as listed in Table 2.2, with reference
to the CRC handbook of physics chemistry, dielectric strength of magnesium oxide insulation
decrease with temperature. Dielectric Constant approximately in a frequency range 60 Hz to 400
Hz.
28
Table 3.3 Physical Properties of Magnesium Oxide
Properties Metric
Melting point 3098 K
Boiling point 3873 K
Thermal conductivity 53(2) W/M/K
Specific heat capacity 0.209 CAL/g. K(273 K)
APPLICATION
Magnesium oxide nanoparticles can be applied in electronics, catalysis, ceramics,
petrochemical products, coatings and many other fields.
Magnesium oxide nanoparticles can be used along with wood chips and shavings to make
materials such as sound-proof, light-weight, heat-insulating refractory fiber board and metallic
ceramics. The microstructure of the powder is of prime importance in both technical
applications.
As a fire retardant used for chemical fiber and plastics trades.
In refractory fiber and refractory material, magnetite-chrome brick, filler for refractory
coating.
Refractory and insulating instrument, electricity, cable, optical material, material for
steel-smelting furnace and other high-temperature furnaces heating material and ceramic
base plate.
Fuel additive, cleaner, antistatic agent and corrosion inhibitor.
The important physical and chemical properties of EDTA are melting point is 523 K,
density 0.86 g/cm3. EDTA molecular weight is 292.25 g/mol-1. It is soluble in water for 0.5
g/L, molecular formula is C10H16N2O.
3.7 ALUMINIUM OXIDE (Al2O3)
The introduction of nano-sized ceramicfillers into polymer electrolytes has become an
attractive approach since it can improve both mechanical stability and ionic conductivity of the
electrolytes system. Al2O3 is significant in its use to produce aluminium metal, as
29
an abrasive owing to its hardness, and as a refractory material owing to its high melting point.
Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical
formula Al2O3. It is one of the most commonly occurring of several aluminium oxides, and
specifically identified as aluminum (III) oxide. It is commonly called alumina. It commonly
occurs in its crystalline polymorphic phase Al2O3, in which it composes the mineral corundum,
varieties of which form the precious gemstones ruby and sapphire.
Fig. 3.7 Al2O3 Structure
Table 3.4 Physical Properties of Aluminium Oxide (Al2O3) Molecular formula Al2O3 Molar mass 101.96 g mol 1
Density 3.95-4.1 g/cm3
Appearance white solid crystal Melting point 2345 K
Boiling point 3250 K
Odour Odorless
Solubility in water Insoluble
Table 3.5 Electrical properties of Aluminium Oxide (Al2O3)
99.5% Aluminum Oxide Mechanical
Units of Measure SI/Metric
Density gm/cc 3.89
Thermal Conductivity W/m°K 35
Dielectric Strength ac-kv/mm 16.9
30
Dielectric Constant @ 1 MHz 9.8
Volume Resistivity Ohm cm >1014
The dispersing of Al2O3 tends to increase the ionic conductivity of solid polymer
electrolyte. On decreasing the size of the Al2O3 from micrometer to nanometer, the ionic
conductivity is enhanced significantly. Dispersion of this filler to the solid polymer electrolyte
cell or battery performance of the system is maintained at 95% of the initial capacity after 100
cycles.
3.8 Silicon dioxide (SiO2)
Silicon dioxide (SiO2 ) nanoparticles, also known as silica nanoparticles or nanosilica,
are the basis for a great deal of bio medical research due to their stability, low toxicity and
ability to be functionalized with a range of modules and polymers. Nano-silica particles are
divided into P-type and S-type according to their structure. The P-type particles are
characterized by numerous pores having a pore rate of 0.61ml/g. The S-type particles have as
comparatively smaller surface area. The P-type nano-silica particles exhibit a higher ultraviolet
reflectivity when compared to the S-type. Silicon belongs to Block P, period 3 while Oxygen
belongs to Block P, Period2 of the periodic table.
Chemical Properties
The following tables list the chemical properties of silicon oxide
Chemical Data
Chemical Symbol SiO2
CAS No 7631-86-9
Group Silicon 14, Oxygen 16
Electronic Configuration Silicon [Ne] 3s2 3p2
Oxygen [He] 2s2 2p4
31
Chemical Composition
Element Content %
Silicon 46.83
Oxygen 53.33
Physical Properties
Silicon dioxide nano particles appear in the form of a white powder. The table below
provides the physical properties of these nano particles.
Properties Metric
Density 2.4g/cm3
BP 2230 °C(lit.)
MP >1600 °C(lit.)
Thermal conductivity 1.1W/m-K - 1.4W/m-K
Relative dielectric constant 3.7 - 3.9
Dielectric strength 10 V/cm
density 2.2-2.6 g/mL at 25 °C
DC resistivity 10 cm
Molar Mass 59.96g/mol
Application
The following are the applications of silica nanoparticles:
32
As an additive in rubber and Plastics
As an strengthening filler for concrete and other construction composites
As a stable, non-toxic platform for biomedical applications such as drug delivery
and therapeutics
3.9 SYNTHESIS OF MAGNESIUM OXIDE (MgO) BY WETCHEMICAL REACTION
METHOD (SOL-GEL METHOD)
The method adopted for the synthesis of (MgO) magnesium oxide for use as nanofiller in
polymer electrolyte system is wet chemical reaction method or sol gel method. Chemicals used
in this reaction method were of analytical purity and were used without further purification. The
single phase MgO nano particles were synthesized by wet chemical technique, in which
magnesium chloride (MgCL2.2H2O - 203.31 g/mol) was used as main precursor material.
The doping percentage adopted was very low as EDTA was sparingly soluble in the mixture.
The yield was good enough to carry on measurements and characterization. For the synthesis of
0.1% of ethylene dintrilo tetra acetic acid doped magnesium oxide, 1M solution of NaOH was
prepared by dissolving 4g of NaOH in 100 ml of double distilled water in a beaker. To that was
added, 0.1 g solution of EDTA (0.29 g) and the mixture was constantly stirred until a
homogeneous solution of EDTA with NaOH was obtained.
Then 1g solution of MgCl2 (2.0331 g) was added to this mixture and allowed to stir for
4hrs and then the resultant mixture was centrifuged for about 60 min and washed with water
several times to neutralize the pH of the solution.
The resultant product was filtered with a fine filter paper and the product thus obtained
was kept in hot air oven at 333 K for 2 hrs and then heated in a muffle furnace at 583 K for 3 hrs.
The resultant product was ground in a mortor with a pestle into a grayish white powder and used
for further characterization and analysis.
TRANSMISSION ELECTRON SPECTROSCOPIC ANALYSIS (TEM)
Fig. 3.9 shows TEM micrograph of synthesized MgO nanoparticle. The micrograph
reveal the cubic structure of MgO nanoparticles though they seem to be agglomerated indicating
that the capping concentration can further be increased to enhance better capping, keeping in
33
mind, the choice of solvent for better solubility. The dominantly cubic structures are roughly 32
nm in size.
Fig.3.9 TEM Image of the MgO doped EDTA nanoparticles - 200 nm scale
3.10 SYNTHESIS OF Al2O3 NANO PARTICLE BY SOL- GEL METHOD
We intended to synthesis Aluminum Oxide nano particle by sol-gel method for use us
nano filler in the polymer electrolyte system. To Synthesis Al2O3 nano particle, 2.66 g of
AlCl3 was dissolved in 20 ml of distilled water in 100 m beaker and placed in
magnetic stirrer. 0.8 g of sodium hydroxide was dissolved in 20 ml of distilled water and
placed in magnetic stirrer. Two solutions were prepared separately. NaOH solution was
added drop by drop to AlCl3 solution under constant stirring to get a homogeneous
solution. Then the solution is left for 1 hr, with a molar ratio 1 : 1 Which results in the
formation of white bulky solution.
The residue obtained is dried in hot air oven at a temperature of about 373 K for
1 hour and 30 min. The dried precursor was crushed into fine powder form by mortar and pestle.
The dried Al2O3 powder was used for synthesis of polymer complex and different
characterization studies. SCANNING ELECTRON MICROSCOPY (SEM) RESULTS OF SYNTHESIZED PURE
Al2O3
Scanning electron microscopy is extremely versatile for providing surface morphology of
synthesised material over a wide range of magnification. At one extreme, Scanning electron
microscopy complements the optical microscopy for studying the texture, topography and
34
surface features of solid pieces. Because of the depth focus of SEM instruments, the resulting
pictures have a spread like petals. In the most common or standard detection mode, the
secondary electron imaging in SEM can produce very high-resolution images of a sample
surface, revealing details about less than 1 to 5 nm in size.
The SEM micrograph of pure Al2O3 synthesized by sol-gel method is shown in Fig.2.7.
SEM micrograph depicts tiny white dots along with small darker regions. The pure Al2O3 grains
are getting spreaded. The formations of petals are spread around like a flower. They also look
like a flower like clusters. Mostly particles are clustered. A tiny cluster under observation was
taken inorder to arrive at the particle size of the synthesized Al2O3.
Calculation of particle size
The scale observed in the SEM micrograph was 10 µm for 3 cm scale. A tiny cluster chosen for
calculation was having 0.5 cm length under 3 cm scale.
10 µm = 3 cm
Particle size x = 0.5 cm
x = 0.5 cm x 10 µm / 3 cm = 1.66 µm = 166 nm.
Hence the particle size for the synthesized Al2O3 powder by sol-gel method from SEM analysis
was found to be 166 nm.
35
Fig. 3.10 Scanning Electron Microscopy (SEM) Graph of pure Al2O3
PARTICLE SIZE MEASUREMENT USING PSA
Fig.2.8 shows PSA analysis is undertaken for the synthesized Al2O3 by sol-gel method a
most prominent peak with 45% intensity was observed at the diameter of 250 nm along with less
intensity peaks at 64.7 nm and 2241 nm respectively. From the particle size analyser we could
recognize the size of the particle as 250 nm. SEM micrograph under 2 µm scale i.e, 200 nm
scales attribute the particle size as 166 nm whereas PSA reveals 250 nm. Hence we could
approximate the average size of the particle as 208 nm.
36
Fig. 3.11 Particle Size Analysis (PSA) Graph of pure Al2O3
3.11 SYNTHESIS OF POLYMER ELECTROLYTE SYSTEM BY SOLUTION CASTING
TECHNIQUE
Blended polymer solid electrolytes have attracted much attention since, they exhibit low
ionic conductivity. Recently, Further enhancement of ionic conductivity as well as mechanical
properties have been achieved by dispersing the crystalline metal oxides, as fillers in the
magnesium oxide conducting polymer solid electrolytes to improve their electrochemical
properties.
Thin film solid polymer electrolyte system may be prepared easily by chemical and
physical methods. Several methods are already available for the preparation of good quality solid
polymer electrolyte films which include solution casting, hot pressing, film blowing, thermal
evaporation, laser evaporation, gaseous discharge, sputtering and so on.
37
Of all the above mentioned techniques, the present investigation deals with the most
commonly employed method namely solution casting technique, by which thin solid polymer
electrolytes may be produced with appreciably high efficiency and stability. Following system
was intended to prepare by solution casting technique by substituting the respective raw
materials according to the system chosen
Polymethyl metha acrylate (PMMA), Polyvinylidene fluoride (PVDF), magnesium
triflate (Mg2CFSO3) as host salt are the promising host polymer matrices, ethylene carbonate
(EC) as a plasticizer, which are most suitable for the development of polymer solid electrolytes.
The crystalline magnesium oxide (MgO) have been synthesized as fillers for the development of
composite polymer solid electrolytes for magnesium battery applications. Solution casting is the
easiest method for the preparation of the polymer solid electrolyte films.
PREPARATION OF SOLID POLYMER ELECTROLYTE
The pure and blended polymer electrolytes were prepared by solution casting technique.
Appropriate quantities of starting materials were taken in the weight ratio according to the
stoichiometric compositions to arrive at the following systems
Preparation of Solid Polymer Electrolyte System
((PMMA + PVDF)y - (Mg2CFSO3)1-y, where 1-y = 60, 50, 40, 30 and 20 mol %
respectively.
Preparation of Solid Polymer Electrolyte System
((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z, where 1-z = 25, 20, 15, 10 and
5 mol % respectively.
Preparation of Solid Polymer Electrolyte System-I
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a,
where 1-a = 25, 15, 10 and 5 mol % respectively .
Preparation of Solid Polymer Electrolyte System ((PMMA + PVDF)y - (Mg2CFSO3)1-y, where
1-y = 60, 50, 40, 30 and 20 mol % respectively.
The pure and blended polymer electrolytes were prepared by solution casting technique.
Appropriate quantities of starting materials were taken in the weight ratio according to the
stoichiometric compositions to arrive at the following systems. The raw materials poly (methyl
38
methacrylate) (PMMA) with high molecular weight (99600 g/mol) and poly (vinylidene
fluoride) (PVDF) with high molecular weight(275000 g/mol). Magnesium triflate (Mg2CFSO3)
with molecular weight (32244 g/mol) respectively were taken according to the stoichiometric
compositions for preparation by solution casting technique in which they were dissolved in
dimethyl formamide (DMF) solvent and the solution was subjected to magnetic stirring for
approximately 6 h at room temperature till it becomes homogeneous.
The homogeneous solution was poured into different flat petridishes and dried in vaccum
oven at 333 K at a pressure of 25 Torr for 24h to evaporate the residual solvents. The films were
transparent and light white colour dry and free-standing in nature. The complete procedure of the
solution casting method of SPE is shown as
Fig.3.12 Flow chart representation for the preparation of
((PMMA + PVDF)y - (Mg2CFSO3)1-y blended polymer solid electrolyte films.
Thus film samples of varying compositions of ((PMMA + PVDF)50 - (Mg2CFSO3)50, of
blended polymer along with magnesium triflate as host salt were obtained.
Preparation of Solid Polymer Electrolyte System-
((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z, where 1-z = 25, 20, 15, 10
39
and 15 mol % respectively.
The raw materials poly (methyl methacrylate) (PMMA) with high molecular weight (99600
g/mol) and poly (vinylidene fluoride), (PVDF) with high molecular weight
(275000 g/mol). Magnesium triflate (Mg2CFSO3) with molecular weight (32244 g/mol) Ethylene
carbonate(EC) (molecular weight - 8806 g/mol), respectively were taken according to the
stoichiometric compositions where 1-z = 25, 20, 15, 10 and 5 mol % respectively.
In a mixing of polymer electrolyte system with plastizer in order to improve the
flexibility for preparation by solution casting technique in which they were dissolved in dimethyl
formamide (DMF) solvent and the solution was subjected to magnetic stirring for approximately
6 h at room temperature till it becomes homogeneous. The homogeneous solution was poured
into different flat petridishes and dried in vacuum oven at 333K at a pressure of 25 Torr for 24h
to evaporate the residual solvents.
The films are transparent and light white colour, dry and free-standing in nature. Thus
film samples of varying compositions of ((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z, where
1-z = 25, 20, 15, 10 and 5 mol % respectively and, solid polymer electrolyte system with EC as
plasticizer were obtained and stored in darkened desiccators.
Preparation of Solid Polymer Electrolyte System- I
(((PMMA+ PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a, where 1-a = 20, 15, 10
and 5 mol % respectively. System I represents the polymer electrolyte system with EC as plasticizer and MgO as
nanofillers in order to improve the ionic conductivity of the synthesized system II were added
MgO with particle size 32 nm prepared by wet chemical method with EDTA as a catalyst is used
as nanofiller. The raw materials includes poly (methyl methacrylate) (PMMA) with high
molecular weight (99600 g/mol) and poly (vinylidene fluoride) (PVDF) with high molecular
weight (275000 g/mol).
Magnesium triflate (Mg2CFSO3) with molecular weight (32244 g/mol) Ethylene
carbonate (EC) (molecular weight - 8806 g/mol) and Magnesium oxide (MgO) prepared by wet
chemical method respectively were taken according to the stoichiometric compositions for
preparation by solution casting method with dimethyl formamide (DMF) as solvent and the
40
solution was subjected to magnetic stirring for approximately 6hrs at room temperature till it
becomes homogeneous. The homogeneous solution was poured into different flat petri dishes
and dried in vacuum oven at 333 K at a pressure of 25 Torr for 24hrs to evaporate the residual
solvents. The films were transparent and light white colour dry and free-standing in nature.
Preparation of solid Polymer Electrolyte System II
(((PMMA+ PVDF)y- (Mg2CFSO3)1-y)z -(EC)1-z)a -(Al2O3)1-b ,where 1-b = 20,15,10 and 5 mol
% respectively.
Composite solid polymer electrolytes (CSPEs)
are formed with the dispersion of nano-sized Al2O3
(250 µm) into Solid polymer electrolyte system
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)b -
(Al2O3)1-b. The appearance of these alumina composite
solid polymer electrolytes is less transparent and is
whitish in colour due to the nature of Al2O3. It is
revealed that this type of ceramic filler is insoluble but
is dispersible into the polymeric matrices. The raw
materials poly (methyl methane cry late) (PMMA) with high molecular weight (Mw=99600
g/mol) , poly (vinylidene fluoride), (PVDF) with high molecular weight (Mw=275000 g/mol) ,
Magnesium trifluoromethanesulfonate (Mg2CFSO3 ) with molecular weight (Mw = 32244
g/mol) , Ethylene Carbonate (EC) with molecular weight (Mw = 8806 g/mol) and Aluminum
oxide (Al2O3) with molecular weight (Mw = 133.34 g/mol) prepared by sol-gel method. The
solid polymer electrolyte system represents with EC as plasticizer and Al2O3 as nano filler in
order to improve the ionic conductivity of the synthesized system.
The raw materials poly(methyl methane cry late) (PMMA) with high molecular weight
(Mw=99600) and poly(vinylidene fluoride), (PVDF) with high molecular weight (Mw=275000)
purchased from Sigma Aldrich (US) with purity 97% and 97% respectively were taken
according to the stoichiometric compositions for preparation by solution casting technique in
which they were dissolved in dimethly formamide (DMF) solvent and the solution was subjected
to magnetic stirring for approximately 6hrs at room temperature till it becomes homogeneous.
41
The homogeneous solution was poured into cleaned petri dishes and evaporated slowly at room
temperature under vacuum to ensure removal of the solvent traces. After drying, the films were
pealed from petri dishes and kept in vacuum dessicators for further use. Thus film samples of
varying compositions of different intended systems were stored in darkened dessicators for
further investigations.
Preparation of solid Polymer Electrolyte System III
(((PMMA+ PVDF)y- (Mg2CFSO3)1-y)z -(EC)1-z)a -(SiO2)1-c ,where 1-c = 20,15,10 and 5 mol %
respectively.
The raw materials poly (methyl methane cry late) (PMMA) with high molecular weight
(Mw=99600 g/mol) , poly (vinylidene fluoride), (PVDF) with high molecular weight
(Mw=275000 g/mol) , Magnesium trifluoromethanesulfonate (Mg2CFSO3 ) with molecular
weight (Mw = 32244 g/mol) , Ethylene Carbonate (EC) with molecular weight (Mw = 8806
g/mol) and silicon dioxide (Sio2) of 10-20 nm particles with molecular weight Mw = 60.08
g/mol. The solid polymer electrolyte system represents with EC as plasticizer and Sio2 as nano
filler in order to improve the ionic conductivity of the synthesized system.
The raw materials were taken according to the stoichiometric compositions for
preparation by solution casting technique in which they were dissolved in dimethly formamide
(DMF) solvent and the solution was subjected to magnetic stirring for approximately 6 hrs at
room temperature till it becomes homogeneous. The homogeneous solution was poured into
cleaned petri dishes and evaporated slowly at room temperature under vacuum to ensure removal
of the solvent traces. After drying, the films were pealed from petri dishes and kept in vacuum
dessicators for further use. Thus film samples of varying compositions of different intended
systems were stored in darkened dessicators for further investigations.
4. Experimental techniques
Experimental techniques employed for characterization of different material properties
have been discussed in terms Powder X-Ray Diffraction (XRD), Scanning Electron Microscopy
(SEM), Transmission Electron Microscope (TEM), Fourier Transform Infra-Red (FTIR) were
42
used to study structural / morphological / spectroscopic responses while Differential Scanning
Calorimetry (DSC) were carried out in order to evaluate their structural characteristics, AC
impedance analysis were carried out on all synthesized polymer electrolyte system I, II and III
to explore their ionic conduction.
Characterization studies X-ray diffraction analysis
The purity, structural property and constituent phases of the freshly prepared samples
were subjected to powder X-ray diffraction analysis by JEOL (JDX - 8030) X-ray
diffractrometer using Cu-K radiation( = 1.5406 A°) in the 2 range from 10° to 80°.
Fourier Transform infrared spectroscopy (FTIR)
The FTIR spectrum indicates the details of functional groups present in the synthesized
sample and the spectra were recorded over the wave number range 4000-650 cm-1 using Agilent
CARY 630 IR Spectrometer.
Differential scanning calorimetry (DSC)
Differential scanning calorimetry (DSC) analysis of the present system was performed by
using DSC Instrument MALVERN Metteler Toledo. The measurements were carried out in
nitrogen atmosphere at a heating rate of 20º C/min in the temperature range of room temperature
to 700 K.
Scanning electron microscopy (SEM)
The synthesized polymer electrolyte systems were scanned with scanning electron microscope
namely SEM HV VEGA 3 TESCAN with an accelerating voltage of 5-15 kV for surface
morphological analysis.
AC impedance analysis
The complex impedance measurements were carried out using a computer - controlled Germany
NOVA control technology NOVA control Alpha-n analyser in the frequency range
20 Hz – 10 MHz over the temperature range 303 – 393 K. All the observed impedance plots
were best fitted internally by means of the Boukamp equivalent circuit software package
incorporated within the computer controlled system. During the present investigation, the
frequency response of a variety of compositions of the chosen system was measured in terms of
43
the real (Z') and imaginary (Z'') parts of the complex impedance (Z*) at different temperatures.
The point of intersection of the impedance plots on the real axis in the high-frequency region was
taken as the bulk resistance (Rb) of the sample [8]. The electrical conductivity ( ) of the sample
was estimated using the relationship
AR
t
b
(1)
Where ‘t’ is the thickness of the specimen and A is the area of cross-section. Transference number data evaluated using ac impedance / dc polarization technique:
Ionic conductivity remains the primary concern in the evaluation of a polymer
electrolyte. However, conductivity measurements only provide information on the total transport
of charges and do not differentiate between the current carried by cations and anions respectively
even in fully dissociated systems. Transport or transference number measurements, on the other
hand, are expected to provide information on the mobility of different species within a polymer
electrolyte. The mobility of magnesium cations in a polymer electrolyte is important when they
are used in magnesium ion – based devices.
Most often, it has been assumed that the only mobile species are cations and anions, M+
and X-, and experimental data have been interpreted in such a way as to give transport numbers
(t). It should be noted that transport number and transference number, both of which are used in
polymer electrolyte studies, are different terms. The transference number (ti) is defined as the net
number of Faradays of charge carried across the reference plane by the cation constituent in the
direction of the cathode during the passage of one Faraday of charge across the plane. For an
associated system, containing only M+, X-, MX, M2X+ and MX2-, the transference number of the
X constituent, tx, may be related to the individual transport numbers by
A similar equation for the cation transference number, tM, may be given and tM + tx = 1. The sum
of the transport numbers for all charged species is unity, and it is the same in the case of the
transference numbers for all salt constituents too. When a salt is dissociated fully into two simple
species, the transport numbers are equal to the transference numbers. Since ion association is a
tX = (tX-+2tMX2
- - tM2X
+)
44
common phenomenon in polymer electrolytes, the transference number is predominantly used to
study the mobility of different species.
During the present investigation, cationic transference numbers were obtained using the
combination of dc polarization and ac impedance technique, which was originally developed by
Bruce and Vincent for ideal solid electrolytes. A standard symmetric electrochemical cell of the
type Mg/single ion conductor/Mg was polarized by application of a small dc potential ( V = 20
mV), and the resulting transient current was measured. The transference number was calculated
using the following equation
Where Io denotes the initial current, Is, steady state current, Ro, initial interfacial
resistance, Rs the steady–state interfacial resistance and tMg+ is the transference number of silver
ions at room temperature. The initial current, Io, is considered to be due to migration of both
cations and anions. Because of the cell polarization, the current decreases over time to a steady-
state value, Is, which is considered to be due to the migration of the cations only. Also, the
interfacial resistances of the passivating layers (solid electrochemical interface between
electrodes and solid polymer electrolyte or SEI) before and after dc polarization were
determined by electrochemical impedance spectroscopy (EIS) as the initial (Ro) and steady-state
(Rf) resistances
Magnesium transference number (tMg2+) is one of the most important parameter in the
case of magnesium ion conducting polymer electrolytes. The transference number (tMg2+) is
defined as the net number of Faradays of charge carried across the reference plane by cation
constituent in the direction of the cathode during the passage of 1 Faraday of charge across the
plane. The polarization due to concentration gradient in the cell is minimized while the fraction
of current polymer complex was measured by the steady – state technique which involved a
combination of ac and dc measurements with the aid of a pair of symmetrical and reversible
magnesium electrodes by mounting the specimens between the pair of electrodes at room
temperature employing an applied dc voltage of 20 mV. The potential (20 mV) was applied to a
symmetric cell Mg / polymer electrolyte / Mg in order to carry out transport number
measurement where in magnesium ion approaches unity. Hence, a relatively high cation
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
45
transference number may effectively eliminate the concentration gradients within the
electrochemical power devices and ensure the working power density. In general, the transport of
ions in polymer electrolytes acquires a better understanding of the nature of the conducting
species.
Magnesium transference number (tMg2+) was measured by the steady-state t(h)20echnique
which involved a combination of ac and dc measurement(h)20s. The complex impedance response of
the Mg / polymer electrolyte / Mg cell was first measured to determine the cell resistances. It was
followed by the dc polarization run, in which a small voltage pulse ( V=0.2V) was applied to
the cell until the polarization current reached the steady-state. Finally, the complex impedance
response of the cell was measured again to determine the cell resistance after dc polarization.
Cyclic Voltammetry (CV):
46
The system starts off with an initial potential at which no redox can take place.
At a critical potential during the forward scan, the electroactive species will begin to be reduced.
After reversal of potential; scan direction and depletion of the oxidized species the reverse
reaction, oxidation, takes place.
Working Of Voltmmetry
Three electrode cell:
It requires a precise control of the potential at the electrode. It has been three electrode
cell setup. Such as
Working Electrode (WE)
Counter Electrode(CE)
Reference Electrode(RE)
No current through Reference Electrode (RE) ideally. So we use reference electrode to
provide precise control of potential at the Working Electrode (WE) and the forcing
current from Working Electrode (WE) to Reference Electrode (RE) is measured.
47
The Working Electrode:
The most important electrode in CV is the working electrode. It can be made from a variety of
materials including, such as Platinum, Gold, Silver, Glassy carbon, Nickel and Palladium.
The reference electrode:
The reference electrode is usually made from silver/ silver chloride (Ag/AgCl) or
saturated calomel (SCE). This electrode’s potential is known and constant as the potential
difference between the working electrode and the reference electrode.
The counter electrode (CE): The counter electrode is known as the auxiliary electrode. Its purpose is to conduct
electricity from the signal source into the solution, maintaining the correct current. Experimental Setup:
Electrolyte is usually added to the test solution to ensure sufficient conductivity. The
combination of the solvent, electrolyte, working electrode material determines the range of the
potential. Electrodes are static and sit in unstirred solutions during CV run. Since cyclic
voltammetry usually alters the charge of the analyte, it is common for reduced or oxidized
analyte to precipitate out onto the electrode. This layering of analyte can insulate the electrode
surface, display its own redox activity in subsequent scans, or at the very least alter the electrode
surface. For this and other reasons it is often necessary to clean electrodes between scans. To run
cyclic voltammetry experiments at high scan rates a regular working electrode is insufficient.
High scan rates create peaks with large currents and increased resistances which result in
distortions. Ultra microelectrodes can be used to minimize the current, resistance.
Applications:
Analytical:
• Quantitative determination of organic and inorganic compounds in solutions
• Quantitative determination of pharmaceutical compounds
• Determination of metal ion concentrations in water to sub–ppb levels
• Detection of eluted analytes in HPLC and flow injection analysis
Reaction mechanism:
• Fundamental studies of oxidation and reduction processes in various media
• Determination of redox potentials
48
Electrolyte
CATHODE (+ve) ANODE (-ve) Mg2+
(((PMMA+ PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)5 - (Al2O3)5,
• Determination of number of electrons in redox reactions
• Measurement of kinetic rates and constants
• Determination adsorption processes on surfaces
• Determination electron transfer and reaction mechanisms
• Determination of thermodynamic properties of solvated species …..etc 2.12. Fabrication and Characterization of Solid State Battery:
Fabrication of solid state battery Preparation of Mg2+|polymer electrolyte|MnO2+Graphite cell All-Solid-State Batteries have been fabricated by sandwiching the newly synthesized polymer
electrolyte between appropriate electrode materials in the cell
Fabrication Of Solid State Battery- Mg2+|polymer electrolyte|MnO2+Graphite cell
Configuration: Mg (anode) /SEP/MnO2 + Graphite (cathode). The cell performance testing has
been done by discharging the batteries under load conditions and recording the cell-potential
discharge profiles as a function of time.The Polymer electrolyte film was sandwiched between
this MnO2 + graphite (cathode) and Mg (anode). The solid state battery was fabricated by
sandwiching nanocomposite polymer electrolyte film between anode and cathode pellets.
Preparation of Electrode Materials:
Negative electrode (anode) preparation:
Magnesium anode in the form of circular discs (area = 1.3 cm2) were obtained by
pelletizing the magnesium powder. These discs were polished with successive grades of emery
papers to a smooth finish and dried.
Positive electrode (cathode) preparation:
49
Positive electrode (cathode) materials were prepared in order to fabricate solid state magnesium
battery. Commercially available MnO2 and graphite were used as raw materials for cathode. The
Mg cells have been characterized by charge-discharge studies at room temperature (25 °C) under
different constant current conditions. In addition to charge discharge method, the electrochemical
impedance of the Mg-cells has also been measured by a.c. impedance spectroscopic technique.
50
4. Results and Discussion-System I
The present chapter briefly discusses the preparation and characterization techniques of
the synthesized solid polymer electrolyte System –I, (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -
(EC)20)a - (MgO)1-a where 1-a = 20, 15, 10 and 5 mol % respectively. Different compositions of
the synthesized systems by solution casting method were subjected to various characterization
techniques like XRD, SEM, DSC, FTIR and AC impedance analysis associated with transport
number measurement and fabrication of solid state battery and their experimental results are
presented and discussed here from the research point of view.
4.1.1 X-ray diffraction analysis
Fig.4.1.1 includes XRD patterns obtained for the present system (((PMMA + PVDF)50 -
(Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a, where 1-a = 20,15,10 and 5 mol% respectively under
investigation along with the best conducting compositions of blended polymer system, polymer
electrolyte system with magnesium triflate salt and plasticized polymer electrolyte system with
Ethylene carbonate as plasticizer namely (PMMA + PVDF)50 , ((PMMA + PVDF)50 -
(Mg2CFSO3)50 and ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80- (EC)20 respectively.
Fig. 4.1.1 Powder XRD patterns of solid polymer electrolyte system
A- (PMMA)50 + (PVDF)50, B- ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50
51
C- ((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20 D- (((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20)80 - (MgO)20 E- (((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20)85 - (MgO)15 F- (((PMMA + PVDF)50- (Mg(CF3SO3)2)50)80 - (EC)20)90 - MgO)10, G- (((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20)95 - (MgO )5.
The observed room temperature X-ray diffraction patterns has been characterized by very less
intense peaks which tends to suggest the formation of a relatively disordered type of material
within these specimens. It is clear from the XRD pattern of (PMMA)50 + (PVDF)50, (Fig. 4.1.1A)
that blended sample exhibited the characteristics peaks at 2 = 20.84, 26.8 and 32.1 with less
intensity which corresponds to [1 1 0] and [0 2 1] reflection planes of PVDF .
The diffraction pattern as shown in Fig.4.1.1B clearly indicates that the crystallinity in
PMMA+PVDF system is further disturbed by the addition of Mg2CFSO3. It is revealed that the
blended polymer has undergone significant structural reorganisation while adding the plasticizer
and Mg (CF3SO3)2 salt. The plasticized effect may induce significant interaction with Ethylene
carbonate within the polymer matrix. The interaction between the PMMA, plasticizer and Mg
(CF3SO3)2salt contributes a much lower crystallinity and enhances the structural disorderliness.
The best conducting composition in (PMMA + PVDF)50 shows less intense peaks at 2 = 20.56º
whereas the best conducting composition of ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50 records
very less intense peak at 2 = 30.68º with complete amorphous background. The broader peaks
and occurrence of new shoulder peak reveal that the amorphous nature of the film increases as a
function of plasticizers concentration. The changes of the intensities of the broad characteristic
peak, shoulder peak and intense peaks give strong evidence that EC mixture added into polymer
matrices interact with the (PMMA+PVDF) blended polymer in the backbone and enhanced the
amorphous nature of the plasticized polymer. The increase in the amorphous nature of plasticized
polymer causes a reduction in the energy barrier for the segmental motion in polymer electrolyte.
Therefore, higher ionic conductivity could be obtained at higher amorphous nature of polymer.
The best conducting composition in ((PMMA + PVDF) 50 - (Mg (CF3SO3)2)50)80 - (EC)20
shows a feeble intense peak at 2 = 30.24º with disordered background. However, with a further
addition of nanoparticle MgO, peaks corresponding to 2 = 32.16, 37.14 and 44.16º occurs with
less intensity for the MgO concentration of 20 mol% . The intensities of these peaks decrease
when the content of MgO decreases suggesting the formation of disorderd nature. The XRD
52
pattern denoted as (F) and (G) appears almost peak free and hence confirms the formation of
amorphous nature because of the introduction of MgO nanofiller which may account for high
ionic conduction. From literature study, it was shown that pure MgO nanoparticle shows peaks at
= 18.6, 37.9, 42.7 and 66.7º respectively. In the present XRD patterns, those peaks were not
present indicating the complete interaction of MgO filler with the polymer matrix.
4.1.2 FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
Fig. 4.1.2 shows the spectra recorded for the best conducting compositions of blended
polymer system, polymer electrolyte system with magnesium triflate salt and plasticized polymer
electrolyte system with Ethylene carbonate as plasticizer namely (PMMA + PVDF)50 , ((PMMA
+ PVDF)50 - (Mg (CF3SO3)2)50 and ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50) 80- (EC)20
respectively along with the four different compositions of system III (((PMMA + PVDF)50 -
(Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a, where 1-a = 20, 15, 10 and 5 mol% respectively.
The characteristic peak at 3449 cm-1 indicates OH stretching, 2984 cm-1 indicates the
presence of C-H aliphatic stretching. For pure PMMA the frequency at 842 cm-1 is assigned to
C-H rocking vibrations. The frequencies at 2950 cm-1 and 1242 cm-1 are assigned to CH2
stretching and O-CH2 deformation vibrations of pure PMMA. An absorption peak at 1718cm-1
could be considered as C=O stretching vibration due to PMMA . Absorption at 1485cm-1
indicates the presences of CH2 symmetric stretching vibration due to PVDF. The peak at
1144 cm-1 was believed to be affected by the symmetric stretching vibration of the S=O bond
affiliated with the SO3- group .
The absorption band at 900 cm-1 is assigned to be totally symmetric vibrations of
per chlorate ions. C-F stretching vibrations were found to occur at 1200 cm-1 and CF2 stretching
vibrations at 1050 cm-1 respectively. The absorption band at 881 cm-1 is the characteristic
frequency of vinylidine compound . An additional spectral feature observed at 984 cm-1 on
addition of magnesium triflate into the polymer may be assigned to symmetric SO3 stretching of
free triflate ion which emerges to be sensitive for the dissociation of the magnesium salt due to
the feeble ion pairing between the cation (Mg2+) and anion (CF3SO3-) within the metal salt
. The peak present at 1141 cm-1 is found to show variation with the increase in nano filler MgO
content. The broadened peak becomes a sharp absorption peak with the value shifted slightly
53
with the decreasing content of MgO. The same behavior is resulted for the peak at
1725 cm-1. For different composition of filler content, 1-b = 20, 15, 10 and 5 mol% respectively,
variation in the case of an absorption peak occurs near about 1407 cm-1. For the composition,
5 mol % of MgO, there appears an absorption peak at 1407 cm-1. The characteristic peaks present
due to different functional groups of the polymer system were found to be shifted towards the
decreasing values on decreasing the content of nanofiller added. Thus, the above spectral
features appear to confirm the appreciably good complexation within the present nanocompostie
polymer electrolyte system which confirms a substantial changes in the network and likely to
have an influence on the ionic conduction of the solid electrolyte system.
Fig.4.1.2. FTIR spectra observed in solid polymer electrolyte system A- (PMMA + PVDF)50, B- ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 ,
C - ((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20 , D - (((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20)80 - (MgO)20 , E - (((PMMA + PVDF)50 - (Mg(CF3SO3)2)50)80 - (EC)20)85 - (MgO)15 , F- (((PMMA + PVDF)50- (Mg (CF3SO3)2)50)80 - (EC)20)90 - (MgO)10, G - (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)95 - (MgO )5.
54
4.1.3 DIFFERENCIAL SCANNING CALORIMETRY (DSC)
DSC curves obtained for three different systems namely (PMMA+PVDF)50 - (Mg (CF3SO3)2)50, ((PMMA+PVDF)50 - (Mg (CF3SO3)2)50)80-(EC)20 and (((PMMA+PVDF)50 - (Mg (CF3SO3)2)50)80-(EC)50)20)90 - (MgO)10 respectively were shown in Fig 4.1.3 as A, B, and C
Fig.4.1.3. The DSC curves obtained
for the best composition of the
synthesized systems namely
A. (PMMA+PVDF)50- (Mg (CF3SO3)2)50, B. ((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20 C. (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)90 - (MgO)10
respectively. For pure PVDF, the glass transition temperature would be observed at 239 K
whereas for pure PMMA, the same could be around 372 K. In the case of the system with the
addition of Mg2CFSO3 as host salt to the blended matrix namely (PMMA+PVDF)50-
( Mg (CF3SO3)2)50, the peak at 649 K represents the melting temperature of the synthesized
sample with sharp exothermic peak along with the shoulder at 567 K, which may be attributed as
due to melting point of intermediate phase formed. The peak at 381 K could be regarded as the
glass transition temperature of the synthesized blended sample. It was inferred from the DSC
curves that the above mentioned peaks were getting shifted towards lesser values as indicated in
the figure as A, B and C. For the curve denoted as ‘C’ which represents the best conducting
composition of the system with the addition of nanofiller, MgO, variations in the values of the
peaks were noted. Also, one new exothermic peak is observed at 361 K which may be attributed
due to the probable interaction between the filler particles and polymer host indicating the
reorganization of the polymer.
55
4.1.4 Scanning electron microscopy (SEM) SEM micrograph obtained for the synthesized solid polymer electrolyte systems namely
(PMMA+PVDF)50-( Mg (CF3SO3)2)50,((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20 and
(((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)90-(MgO)10 respectively were shown in Fig
4.1.4 with as a, b, and c respectively. Fig 4.1.4 (a) shows a non-uniform nature of grains with rod
like structure in the background. The calculated average grain size could be taken as 120 nm.
a) (b) (c) Fig.4.1.4 SEM images of (a) (PMMA+PVDF)50-( Mg (CF3SO3)2)50 ,(b)((PMMA+PVDF)50- (Mg (CF3SO3)2)50)80-(EC)20, (c) (((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)90-(MgO)10 Fig 4.1.4 (b) which accounts for the polymer system with Mg (CF3SO3)2 host salt with added
plasticizer shows clear disordered background with more space for movement. Here, a grain
appears more legibly as cluster with diameter of 350 nm. Fig 4.1.4 (c) shows unevenly
distributed grains in the form of clusters with voids facilitating movement of ions which in turn
provides high conducting pathways of this best conducting composition with 10 mol%
nanofiller, MgO. The clusters look like a flower like arrangement in many places representing
the agglomeration of particles due to the interaction of polymer matrix with the filler. Mostly all
the grains were fairly regular with most of the grains looks like a petal. A tiny grain is taken for
the calculation of grain size under 1 m scale and the average size calculated was 100 nm
diameters.
56
4.1.5 AC Impedance analysis
The complex impedance measurements were carried out on film specimens of all the
blended polymer system with magnesium triflate salt and plasticized polymer electrolyte system
with Ethylene carbonate as plasticizer and MgO as nanofiller namely ((PMMA + PVDF)y -
(Mg (CF3SO3)2)1-y,where 1-y = 60, 50, 40, 30 and 20 mol % respectively, and (((PMMA +
PVDF)50 - (Mg (CF3SO3)2)50)z - (EC)1-z, where 1-z = 25, 20, 15, 10 and 5 mol % respectively,
and (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a where 1-a = 20, 15, 10 and
5 mol % respectively, in the frequency range 20 Hz to 10 MHz Accordingly, all the synthesized
solid films were loaded with blocking electrode on either side under a stainless steel top
electrode with diameter 20mm and bottom electrode (diameter 40mm). All the complex
impedance measurements were carried out by keeping these solid polymer electrolyte films in
between two steel electrodes.
It was established by our research group that pure PMMA specimen exhibits conducting
value of 2.4262×10-11 Scm-1 where as pure PVDF specimen have 2.9625×10-11 Scm-1 as
conducting value at room temperature . The AC impedance study of the synthesized blended
solid polymer electrolytes under four different compositions (PMMA)x - (PVDF)1-x,where 1-x =
95, 90, 85 and 80 mol % respectively by our research group revealed that the various
compositions of this system exhibits electrical conductivity values of the order 10-10 Scm-1 at
room temperature 303 K, particularly composition corresponding to (PMMA)50 - (PVDF)50
exhibits an electrical conductivity value of 4.4496×10-10 Scm-1 which could be considered as best
conducting composition as ((PMMA)50 – (PVDF)50).
4.1.5.1 SYSTEM – I: (PMMA + PVDF)y - (Mg (CF3SO3)2)1-y In order to evaluate the electrical ionic conductivity values, the complex impedance
measurements were carried out on film specimens of all the stoichiometric compositions of the
system I (PMMA + PVDF)y - (Mg (CF3SO3)2)1-y where 1-y = 60, 50, 40, 30 and 20 mol %
respectively and their values are shown in Table.4.1.1. It is seen that the various compositions of
this system which includes Magnesium triflate as host salt exhibits electrical conductivity values
of the order of 10-9 Scm-1 at room temperature 303 K.
It is noted that, the particular composition (PMMA + PVDF)50 - (Mg (CF3SO3)2)50,
exhibits an electrical conductivity value of 1.559 × 10-8 Scm-1 at room temperature (303 K)
57
which could be considered as best conducting compositions of all the five synthesized samples of
the present mixed system. The evaluated electrical conductivity value of this present system
establishes the
fact that the ionic values are increased by two orders of magnitude which may be the result of the
addition of host salt.
Table-4.1.1: Room temperature electrical conductivity of obtained for system
((PMMA)50 + (PVDF)50)y - (Mg (CF3SO3)2)1-y
COMPOSITION (1-y) ROOM TEMPERATURE ELECTICAL ONDUCTIVITY
(Scm-1)
((PMMA)50+(PVDF)50)80-(Mg (CF3SO3)2)20 ((PMMA)50+(PVDF)50)70-( Mg (CF3SO3)2)30 ((PMMA)50+PVDF)50)60-( Mg (CF3SO3)2)40 ((PMMA)50+(PVDF)50)50-( Mg (CF3SO3)2)50 ((PMMA)50+(PVDF)50)40-( Mg (CF3SO3)2)60
7.689×10-9
3.220×10-9
5.590×10-9
1.559×10-8
1.098×10-8
4.1.5.2 SYSTEM II: ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)z - (EC)1-z The electrical conductivity values obtained at room temperature for five different
compositions of the system with the addition of Ethylene carbonate as plasticizer of the present
system II viz, ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)z - (EC)1-z where 1-z = 25, 20, 15, 10 and
5 mol % respectively are shown in the Table 4.1.2. It was inferred from the table that different
compositions of this present system II with the addition of EC as plasticizer exhibits electrical
conductivity of the order of 10-8 Scm-1 at room temperature 303 K. It is noted that for the
particular composition ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20 shows an electrical
conductivity value of 2.541×10-8 Scm-1 at room temperature (303 K) which could be considered
as best conducting compositions of all the four synthesized samples of the present mixed system.
4.1.5.3 SYSTEM – III: (((PMMA + PVDF) 50 - (Mg (CF3SO3)2)50)80 - (EC) 20) a - (MgO) 1-a Complex impedance measurements were carried out on all film specimens of four
different stoichiometric compositions of the polymer electrolyte system III
(((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a with the addition of MgO as
58
nanofiller, where 1-a= 20, 15, 10 and 5mol % respectively in order to evaluate the electrical ionic
conductivity values and tabulated in Table.4.1.3.The evaluated values of electrical ionic
conductivity values lies in the order of 10-6 S cm-1 at room temperature 303K.
Table- 4.1.2: Room temperature electrical conductivity of obtained for system ((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)z - (EC)1-z where 1-z = 25, 20, 15, 10 and 5 mol% respectively.
Fig.4.1.5 Room Temperature complex impedance plots for (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a , where 1-a = 20, 15, 10 and 5 mol % respectively.
Composition (1-z)
Room temperature Electrical conductivity (S cm-1)
((PMMA+PVDF)50-( Mg (CF3SO3)2)50)95-(EC)5 ((PMMA+PVDF)50-( Mg (CF3SO3)2)50)90-(EC)10 ((PMMA+PVDF)50-( Mg (CF3SO3)2)50)85-(EC)15 ((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-EC)20 ((PMMA+PVDF)50-( Mg (CF3SO3)2)50)75-(EC)25
1.350×10-8
1.158×10-8
5.490×10-9
2.541×10-8
2.096×10-8
0 .0 0 E + 0 0 0 2 .0 0 E + 0 0 7 4 .0 0 E + 0 0 7 6 .0 0 E + 0 0 7 8 .0 0 E + 0 0 70
1 0 0 0 0 0 0 0
2 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0
6 0 0 0 0 0 0 0
7 0 0 0 0 0 0 0
8 0 0 0 0 0 0 0
Z"(O
hm)
Z '(O h m )
A M g O 2 0 % B M g O 1 5 % C M g O 1 0 % D M g O 5 %
A
B
CD
59
It is noted that for the particular composition (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 -
(EC)20)90 - (MgO)10 which exhibits an electrical conductivity value of 1.26×10-6 Scm-1 at room
temperature (303K) could be considered as best conducting compositions of all the four
synthesized samples of the present mixed system.
Table- 4.1.3: Room temperature electrical conductivity values obtained for system III (((PMMA + PVDF)50 - (Mg (CF3SO3)2)50)80 - (EC)20)a - (MgO)1-a, where 1-a = 20, 25, 10 and 5mol% respectively.
The observed results in terms of electrical conductivity values of the present system
strongly attribute the fact that the increase in values of conductivity of the order of 5 magnitude
would be due to the addition of nanofiller MgO which resulted in high conduction pathways and
responsible for the increase of conductivity.
Hence the aim of our present investigation has been arrived at with in terms of high ionic
conductivity values. Fig.4.1.5 shows the room temperature complex impedance plots obtained
for the four different compositions of the mixed system (((PMMA + PVDF)50 - (Mg
(CF3SO3)2)50)80 -(EC)20)b - (MgO)1-b , where 1-a= 20, 15, 10 and 5 mol % respectively. The
observed impedance plots are depressed semicircles with the x-axis as generally observed for
polymer electrolyte systems.
Composition (1-a)
Room temperature Electrical conductivity
(Scm-1)
(((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)80-(MgO)20 (((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)85-(MgO)15 (((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)90-MgO)10 (((PMMA+PVDF)50-( Mg (CF3SO3)2)50)80-(EC)20)95-(MgO)5
1.43×10-7 6.5×10-7 1.29×10-6 4.58×10-7
60
Temperature dependence of complex impedance plots
Fig.4.1.6 depicts the complex impedance plots obtained at different temperatures
(303- 393 K) for a composition corresponding to 1-a = 10 mol % in the mixed system (((PMMA
+ PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))a - (MgO)1-a. Figure implies that the point of intersection
on the real axis is shifted towards origin and the diameter of the semicircular arc decreases with
increase in temperature and hence the value of bulk resistance (Rb) decreases at elevated
Fig 4.1.6 Complex impedance plots obtained for the system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)90 - (MgO)10 under different
temperature values.
Temperatures which in turn lead to an increase in the electrical conductivity value with increase
in temperature.
TEMPERATURE VARIATION OF ELECTRICAL CONDUCTIVITY IN THE SYSTEM OF
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)90 - (MgO)10
Generally, the temperature-dependence of electrical conductivity ( ) of an ideal super
ionic material or solid polymer electrolyte system may be expressed by the Arrhenius equation
where 0 is the pre-exponential factor, ‘Ea’ the activation energy for ionic migration within the
solid required for an ion to hop from one defect site to another, ‘k’ the Boltzmann constant and
(T) = ( 0/T) exp(-Ea/KT)
0 1 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 6 0 0 0 0 0 0 00
1 0 0 0 0 0 0 0
2 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0
6 0 0 0 0 0 0 0
z"(o
hm)
z ' ( o h m )
A M G O ( 3 0 3 K ) B M G O ( 3 2 3 K ) C M G O ( 3 4 3 K ) D M G O ( 3 6 3 K ) E M G O ( 3 8 3 K )
m g o 9 0 t e m p v a r i a t i o nA
B
C
D
E
61
‘T’ is the absolute temperature. For all the four different systems under study, Arrhenius plots of
log T versus 1/T were drawn in the temperature range 298-463 K. The increase in conductivity
is observed in all compositions in terms of a sharp increase in conductivity when temperature
increased. The Activation energy values were calculated from the best fits of Arrhenius plots in
the temperature range 303 - 350 K.
Fig.4.1.7 Plots of log T versus 1/T of the polymer electrolyte system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))a - (MgO)1-a,
where 1-a = 20, 15, 10 and 5 mol % respectively (303-393K).
Fig.4.1.7 represents the plots of log T versus 1/T obtained for four different
compositions of the mixed system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)a - (MgO)1-a,
where 1-a = 20, 15, 10 and 5 mol % respectively (303 – 393 K).
Best fit patterns of all the observed Arrhenius plots shown in Fig.4.1.7 were drawn with
accuracy for the evaluation of relevant activation energy (Ea) data corresponding to individual
compositions. As a consequence, the estimated values of activation energies for the set of four
different compositions in the temperature range 303 - 350 K were found to be 0.110, 0.128,
0.109, 0.268 eV respectively. From these results, it is clear that highly conducting specimen
namely those corresponding to 1-b = 10 mol % possesses very low activation energy of 0.109 eV
2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
log
sigm
a(S
cm
-1)
(1000/T )(K ) -1
A M gO 20% B M gO 15% C M gO 10 % D M gO 5%
A
B
C
D
Activa tion Energy
62
for conduction in good agreement with the observed trend of conductivity among the polymer
electrolytes
4.1.6 Transference number data evaluated using ac impedance / dc polarization technique:
Ionic conductivity remains the primary concern in the evaluation of a polymer
electrolyte. However, conductivity measurements only provide information on the total transport
of charges and do not differentiate between the current carried by cations and anions respectively
even in fully dissociated systems. Transport or transference measurements, on the other hand, are
expected to provide information on the mobility of different species within a polymer electrolyte.
The mobility of magnesium cations in a polymer electrolyte is important when they are used in
magnesium ion – based devices.
Most often, it has been assumed that the only mobile species are cations and anions, M+
and X-, and experimental data have been interpreted in such a way as to give transport numbers
(t). It should be noted that transport number and transference number, both of which are used in
polymer electrolyte studies, are different terms. The transference number (ti) is defined as the net
number of Faradays of charge carried across the reference plane by the cation constituent in the
direction of the cathode during the passage of one Faraday of charge across the plane. For an
associated system, containing only M+, X-, MX, M2X+ and MX2-, the transference number of the
X constituent, tx, may be related to the individual transport numbers by
A similar equation for the cation transference number, tM, may be given and tM + tx = 1.
The sum of the transport numbers for all charged species is unity, and it is same in the case of the
transference numbers for all salt constituents too. When a salt is dissociated fully into two simple
species, the transport numbers are equal to the transference numbers. Since ion association is a
common phenomenon in polymer electrolytes, the transference number is predominantly used to
study the mobility of different species.
During the present investigation, cationic transference numbers were obtained using the
combination of dc polarization and ac impedance technique, which was originally developed by
Bruce and Vincent for ideal solid electrolytes. A standard symmetric electrochemical cell of the
tX = (tX-+2tMX2
- - tM2X
+)
63
type Mg/single ion conductor/Mg was polarized by application of a small dc potential ( V = 20
mV), and the resulting transient current was measured. The transference number was calculated
using the following equation
Where Io denotes the initial current, Is, steady state current, Ro, initial interfacial
resistance, Rs the steady–state interfacial resistance and tMg+ is the transference number of silver
ions at room temperature. The initial current, Io, is considered to be due to migration of both
cations and anions. Because of the cell polarization, the current decreases over time to a steady-
state value, Is, which is considered to be due to the migration of the cations only. Also, the
interfacial resistances of the passivating layers (solid electrochemical interface between
electrodes and solid polymer electrolyte or SEI) before and after dc polarization were
determined by electrochemical impedance spectroscopy (EIS) as the initial (Ro) and steady-state
(Rf) resistances
Fig.4.1.8 AC impedance plots obtained before and after polarization for the best
conducting composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))90 - (MgO)10
Magnesium transference number (tMg2+) is one of the most important parameter in the
case of magnesium ion conducting polymer electrolytes. The transference number (tMg2+) is
defined as the net number of Faradays of charge carried across the reference plane by cation
constituent in the direction of the cathode during the passage of 1 Faraday of charge across the
plane.
The polarization due to concentration gradient in the cell is minimized while the fraction
of current polymer complex was measured by the steady – state technique which involved a
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
0 5 0 0 0 1 0 0 0 0 1 5 0 0 0 2 0 0 0 0 2 5 0 0 0 3 0 0 0 0 3 5 0 0 00
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
3 0 0 0 0
3 5 0 0 0
ZSin
, Z"
(Ohm
)
Z C o s , Z ' (O h m )
B e f o r e p o la r i z a t io n a f t e r p o la r iz a t io n
64
combination of ac and dc measurements with the aid of a pair of symmetrical and reversible
magnesium electrodes by mounting the specimens between the pair of electrodes at room
temperature employing an applied dc voltage of 20 mV. The potential (20 mV) was applied to a
symmetric cell Mg / polymer electrolyte / Mg in order to carry out transport number
measurement wherein magnesium ion approaches unity. Hence, a relatively high cation
transference number may effectively eliminate the concentration gradients within the
electrochemical power devices and ensure the working power density. In general, the transport of
ions in polymer electrolytes acquires a better understanding of the nature of the conducting
species.
Fig.4.1.9 Current versus Time plot for the best conducting composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))90 - (MgO)10 in ac/dc method
Magnesium transference number (tMg2+) was measured by the steady-state technique
which involved a combination of ac and dc measurements. The complex impedance response of
the Mg / polymer electrolyte / Mg cell was first measured to determine the cell resistances. It was
followed by the dc polarization run, in which a small voltage pulse ( V=0.2V) was applied to
the cell until the polarization current reached the steady-state. Finally, the complex impedance
response of the cell was measured again to determine the cell resistance after dc polarization.
The transference number was calculated using the following equation
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 00 .0 0 0
0 .0 0 2
0 .0 0 4
0 .0 0 6
0 .0 0 8
0 .0 1 0
0 .0 1 2
0 .0 1 4
Cur
rent
(A
)
T im e (S e c )
C u r re n t v s tim e
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
65
was found to be tMg+=0.6765 with the following data
If=0.00078 A, Io=0.013 A, V=20mV, Ro=1104 and Rf =1.2284e4 respectively. The high
value of tMg+ implies the fact that the major contribution to the electrical conductivity values of
the synthesized polymer electrolyte was due to the magnesium ions only. A large cationic
transference number would be a desired property of an electrolyte material so that they could
be very well used in fabrication of solid state batteries.
4.1.7 Cyclic Voltammetry measurement:
Cyclic voltammetric studies have been carried out on the symmetrical cell Mg/ best conducting
solid Polymer Electrolyte /MnO2 +C. In Cell, the film was in contact with the foil of Mg which
was used as reversible electrode and MnO2 +C as cathode, recorded at room temperature (28°C).
The magnesium foil served as the current collector in cell. Cyclic voltammetric study on the two
cells further confirms the Mg2+ ion conduction in the solid polymer electrolyte film. The cathode
and anodic current peaks are distinctly observed for cell. This suggests that the cathode
deposition and anodic oxidation of Mg are facile at Mg / polymer electrolyte /MnO2+C
electrolyte interface and hence it is the indicative of Mg2+ ion conduction in the solid polymer
electrolyte film. It may be noted that the cathodic/anodic peak potentials are separated by several
volts.
4.1.10 Cyclic voltametry graph of a Mg | polymer electrolyte |MnO2+C performed at a
scan rate of 0.1 Vs-1.
66
This system is performed at a scan rate of 0.1 Vs-1.This is possible because the
experiments were carried out with the symmetrical cell with two electrode geometry without
using reference electrode. Initial voltage applied was 1.2 V with the two segment and sample
interval of 0.001.The cyclic voltametry graph obtained was shown in fig.4.1.10.
4.1.8 Fabrication of solid state battery using best conducting composition as polymer
electrolyte:
These cells were put in glass housing unit for their characterization with the configuration
of Mg (anode) /Best conducting composition of polymer electrolyte /MnO2 + Graphite (cathode)
as
Mg (anode) / (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))90 - (MgO)10 / MnO2 +
Graphite (cathode). The open circuit voltage (OCV) and cell potential measurements were
carried out with the help of a high impedance digital Keithley 6568A model electrometer. The
batteries were discharged under load condition (lM ) and the cell potentials were monitored as a
function of time. To check the initial voltage obtainable from the fabricated cell and to ensure
proper electrode-electrolyte contacts, open circuit voltage has been measured over a period of-
24h, Open circuit voltage value 112 mV was obtained and short circuit current has been
measured as 13.2×10-9 A.
4.2 Results and discussion -System II
In the present investigation, considerable effort has been devoted towards understanding
the structural aspects of polymer electrolyte system. The crystalline structure of the sample was
obtained by powder X-Ray Diffraction analysis (XRD), spectral analysis by Fourier Transform
Infra-Red spectroscopy (FTIR), and phase analysis by Differential Scanning Calorimetric
analysis (DSC), and surface morphological studies by Scanning Electron Microscopy (SEM) and
AC impedance analysis to exhibit the ionic conductivity of the synthesized samples associated
with transport number measurement and fabrication of solid state battery.
4.2.1 POWDER X-RAY DIFFRACTION ANALYSIS
The powder XRD patterns obtained for the different compositions of the polymer
electrolyte system synthesized by solution casting technique with Magnesium triflate as host salt,
Ethylene carbonate as plasticizer and Alumina as nano filler are depicted in Fig. 4.2.1 under
67
stoichiometric composition of (((PMMA + PVDF) 50 - (Mg2CFSO3)50)80 - (EC)20)a - (Al2O3)1-b,
where 1-b = 20, 15, 10 and 5 mol % respectively .
Fig. 4.2. 1 Powder XRD patterns of solid polymer electrolyte system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)b- (Al2O3)1-b , where 1-b = 20, 15, 10 and 5 mol % respectively
XRD studies were carried out using JEOL (JDX-8030) X-ray diffractometer with Cu-K
as target material of wavelength 1.540598 ź in the 2 range from 200 to 800.
As shown in the Fig. 4.2.1, XRD patterns (A), (B), (C) and (D) corresponds to the content
of Al2O3 as 1-b=20, 15, 10 and 5 mol % respectively. From literature study, it was shown that
pure Al2O3 nanoparticle shows peaks at 2 = 45.5, 63.3 and 66.2º respectively. In our present
study wherein metal oxide Al2O3 is added to the already established disordered structure of
polymer complex with Magnesium triflate as host salt, Ethylene carbonate as plasticizer,
henceforth shows very less intense peaks except a sharp intense peak at
=31.6 º suggesting the formation of the new phase formed as intermediate product as a result
of interaction between the polymer system with the nano filler added. The intensity of the peak
increases up to the concentration of 10 mol % Al2O3 and broadening also reduced by this
addition.. For 5 mol % Al2O3 this crystalline peak disappears and complete halo results,
suggesting amorphous nature of the sample.
20 30 40 50 60 70 80
Inte
nsity
(a.u
)
2 ( deg)
(A) Al2O3 (20%) (B) Al
2O
3(15%)
(C) Al2O3(10%) (D) Al
2O
3(5%)
31.7662.64
31.56
28.8631.54
32.42
46.38
A
B
C
D
28.16
66.4
66.4
66.4
68
The XRD pattern also shows very less intense peaks at 2 = 66.2º which may be
accountable for the pure Al2O3 nanoparticle. This peak also disappears for 5 mol % Al2O3
corresponding to the highly disordered nature of the polymer complex system which indicates
the complete interaction of the polymer system with the nanoparticle added. This appearance of
amorphous nature of the sample may account for the high conducting pathways.
4.2.2 FOURIER TRANSFORM INFRA-RED SPECTROSCOPY (FTIR)
Fourier Transform Infra-Red (FTIR) spectroscopic technique has been used to
characterize the chain structure of the host polymer and to determine the probable reaction of
multifunctional monomers including rearrangements and isomerization. This technique was used
by many researchers to provide information on cation-oxygen interactions in a wide range of
polymer salt systems. FTIR spectroscopy has been carried out to probe ion-polymer and filler-
polymer interactions in the polymer electrolytes at the microscopic level. In this present work,
FTIR spectroscopy has been used to establish interactions between the polymer, salt and filler.
Such interactions may include changes in the vibrational modes of the atoms or molecules within
the material. The instrument used in the present study was Cary 630 FTIR spectrometer in the
wave number region of 4000-400 cm-1with the scan rate of 64 per sec.
Fig. 4.2.2 FTIR spectra observed in solid polymer electrolyte system (((PMMA + PVDF)50
- (Mg2CFSO3)50)80 - (EC)20)a - (Al2O3)1-b , where 1-b = 20, 15, 10 and 5 mol % respectively.
6 0 0 9 0 0 1 2 0 0 1 5 0 0 1 8 0 0 2 1 0 0 2 4 0 0 2 7 0 0 3 0 0 0
9 8 4
9 8 4
9 8 4
% T
rans
mitt
ance
(a.u
)
W a v e n u m b e r ( c m - 1 )
( A ) A l 2 O 3 ( 2 0 % )( B ) A l
2O
3 ( 1 5 % )
( C ) A l2O
3 ( 1 0 % )
( D ) A l2O
3 ( 5 % )
A
B
D
1 1 4 41 7 2 0
1 7 2 5
1 7 2 0
1 7 2 2
1 4 4 0
1 4 3 6
1 4 0 7
1 1 4 0
1 1 4 0
1 1 4 4
7 4 9
7 4 9
8 3 6
7 4 9
7 5 2
1 4 3 6
F T I R
1 5 7 6
1 5 7 8
1 5 5 9
1 5 7 6 c
9 8 4
69
Fig. 4.2.2 shows the FTIR spectrum which indicates the details of functional groups
present in the synthesized sample and the spectra were recorded over the range of
4000-400 cm-1. It was inferred that observed functional groups were present in the wave number
range of 3000-620 cm-1 region.
An absorption peak at 1720 cm-1 could be considered as the presence of carbonyl group
C=O due to PMMA. The band at 987 cm-1 is the characteristic absorption peak of PMMA,
together with the bands at 1062 cm-1 and 843 cm-1. The characteristic CH3 asymmetric stretching
at 2952 cm-1 , deformation at 1451 cm-1 , wagging at 988 cm-1 , rocking at 1733 cm-1 were
corresponds to PMMA. The characteristic peak at 1144 cm-1 indicates the presence of symmetric
stretching vibration of the S=O bond affiliated with the SO3- group. It can also be assumed that
the absorption peak at 749 cm-1 could be due to the metal oxide (Al2O3) added. C-F stretching
vibrations were found to occur at 1200 cm-1 and CF2 stretching vibrations at 1050 cm-1
respectively. The absorption band at 881 cm-1 is the characteristic frequency of vinylidine
compound. The absorption band at 900 cm-1 is assigned to be totally symmetric vibrations of per
chlorate ions. An additional spectral feature observed at 984 cm-1 on addition of magnesium
triflate into the polymer may be assigned to symmetric SO3 stretching of free triflate ion which
emerges to be sensitive for the dissociation of the magnesium salt due to the feeble ion pairing
between the cation (Mg2+) and anion (CF3SO3-) within the metal salt. The characteristic peaks
present due to different functional groups of the polymer system were found to be shifted
towards the decreasing values on decreasing the content of nanofiller added.
4.2.3 DIFFERENTIAL SCANNING CALORIMETRIC ANALYSIS
Fig. 4. 2.3. DSC curve
obtained for the best composition
of the mixed system (((PMMA +
PVDF)50 - (Mg2CFSO3)50)80 -
(EC)20)90 - (Al2O3)10
3 5 0 4 0 0 4 5 0 5 0 0 5 5 0 6 0 0 6 5 0 7 0 0
Hea
t flo
w (w
/mg)
exo
T e m p e r a tu re (K )
A l2 O 3 (9 0 % )
3 6 9 .7 7
4 5 5 .4 2 5 3 0 .3 2
5 8 8 .4 2
6 3 5 .6 0
6 5 4 .7 1
70
Differential scanning calorimetric studies were carried out using Mettler Toledo Instrument. The
DSC curves thus obtained for the best composition of the mixed system (((PMMA+PVDF)50 -
(Mg2CFSO3)50)80 - (EC)20)90-(Al2O3)10 is presented in the Fig. 4.2.3 in the temperature range 350
to 700 K.
For pure PVDF, the glass transition temperature would be observed at 331K whereas for
pure PMMA, the same could be around 544K. An endothermic peak is observed around 355 K in
this investigation may be attributed to the melting temperature of (PMMA)50 + (PVDF) 50
blended polymer film i.e a change in crystalline structure may result from polymer-copolymer
interactions in the amorphous phase resulting in changes of phase transitions.The shoulder at
455.4 K may correspond to the new phase formed due to the addition of Mg2CFSO3. The glass
transition temperature would be observed at 530.32 K. An Exothermic peak observed at 654.71
K in this investigation may be attributed to the melting temperature of (((PMMA+PVDF)50 -
(Mg2CFSO3)50)80 - (EC)20)90-(Al2O3)10 blended polymer film ie., a change in crystalline structure
may result from polymer-copolymer interaction in the amorphous phase resulting in change of
phase transitions.
4.2.4 SCANNING ELECTRON MICROSCOPY (SEM)
71
Fig. 4.2.4 Scanning Electron Microscopic (SEM) image for the solid polymer electrolyte system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)90 - (Al2O3)10
Fig. 4.2.4 shows the scanning electron microscopic (SEM) image obtained for blended
(((PMMA + PVDF)50 -(Mg2CFSO3)50)80 - (EC)20)90 - (Al2O3)10 polymer electrolyte system. It is
clear from figure that the micrographic image of (((PMMA + PVDF)50 -(Mg2CFSO3)50)80 -
(EC)20)90 -(Al2O3)10 that grains are irregularly arranged as clusters of flowers. They could be
considered as agglomerates of the constituent grains of the blended polymer system with the
addition of salt, plasticizer and the nano filler. It was established by our research group that
polymer system with the addition of Magnesium triflate as host salt, Ethylene carbonate as
plasticizer shows a disordered nature with the presence of voids. The presence of voids/defect
centers clearly paves way for the nanoparticle to move from one place to another and henceforth
contributing for the high conduction. The nanoparticle Al2O3 added with 166nm diameter could
easily move through the already formed clusters. They even cling on to the clusters easily
forming grains of various sizes. One such clearly visible seen grain has been selected for the
calculation of grain size and was found to be smaller than 0.5 µm (500 nm) in size and some of
the grains as small as 0.2 µm (200 nm)are also noted. Another remarkable observation was the
retention of ultra-fine grain size in this microstructure, as even most of the grains were less than
1µm in size, with a narrow size distribution. This improvement may be closely related to the
addition of nanofiller Al2O3 with 166nm size. This increase form of amorphous nature in terms
of formation of clusters of varying sizes and the presence of more and more voids, in the case of
the synthesized solid polymer electrolyte system are expected to lead to enhanced ionic
conductivity in accordance with the present XRD analysis.
4.2.5 AC IMPEDANCE ANALYSIS
In order to evaluate the electrical ionic conductivity values of the synthesized solid
polymer electrolytes , the complex impedance measurement were carried out on film specimens
of all the four compositions of the present mixed system (((PMMA + PVDF)50 -
(Mg2CFSO3)50)80 - (EC)20)b - (Al2O3)1-b , where 1-b=20, 15, 10 and 5% respectively using a
72
computer –controlled Germany NOVA control technology NOVA control Alpha-n analyser
(precision LCR meter) in the frequency range frequency range 20 Hz to 10 MHz and in the
temperature range 300-393 K. Accordingly, all the synthesized solid films were loaded with
blocking electrode on either side under a stainless steel top electrode with diameter 20mm and
bottom electrode (diameter 40 mm).All the complex impedance measurement were carried out
by keeping these solid polymer electrolyte film in between two steel electrode.
The plots of Z in terms of its real part (Z’) and imaginary part (Z”) could thus be
obtained. The point of intersection of the impedance plot on the real axis at the low frequency
region, within the frequency range under investigation predominantly gives the bulk resistance
(Rb) of the sample, thus eliminating other effects such as electrode polarization, grain
boundaries, etc. The bulk conductivity of a given sample may be expressed as
b
Where ‘t’ is the thickness of the film in cm, A the area covered by the steel electrode in contact
with the specimen in square cm and Rb is the bulk resistance of the material derived from the
intercept of the complex impedance plot i.e., Nyquist plot on the real axis in . The parallel
circuit software developed by Boukamp et. al. has been effectively used to extract the accurate
value of bulk resistance (Rb) from the intercept on the real axis at the low frequency end of the
relevant Nyquist plot. The electrical conductivity values obtained at room temperature for four
different compositions of the system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)b -
(Al2O3)1-b , where 1-b = 20,15,10 and 5 mol, % respectively by complex impedance analysis are
presented in Table. 4.2.1 From table, it is seen that the various compositions of this system
exhibits electrical conductivity values of the order 10-7 S cm-1 at room temperature 303 K.
The electrical conductivity values obtained for the four different compositions of the above
mentioned system were found to be 1.090×10-7, 2.266×10-7, 5.245×10-7 and
3.063×10-7 Scm-1 respectively. It was inferred from the Table. 4.2.1 that the solid polymer
electrolyte system with the Al2O3 content of 10% exhibits high ionic conductivity value of
5.245×10-7 Scm-1.
73
Table. 4.2.1 Room temperature electrical conductivity values obtained for the system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))b - (Al2O3)1-b, where 1-b = 20, 15, 10 and 5
mol % respectively
Composition(1-b) Electrical Conductivity (Scm-1)
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -(EC)20)80 - (Al2O3)20
1.090×10-7
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -(EC)20)85 - (Al2O3)15
2.266×10-7
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -(EC)20)90 - (Al2O3)10
5.245×10-7
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -(EC)20)95 - (Al2O3)5
3.063×10-7
Henceforth the system with the stoichiometric composition of (((PMMA + PVDF)50-
(Mg2CFSO3)50)80 –(EC)20)90-(Al2O3)10 could be regarded as the best conducting composition of
the present synthesized polymer electrolyte system and the same has been depicted in Fig. 4.5.
Fig. 4.2.5 Compositional variation of conductivity of the present solid polymer electrolyte system
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)))b-
(Al2O3)1-b, where 1-b= 20,15,10 and 5 mol % respectively
Fig. 4.2.6 shows the set of room temperature Impedance (Nyquist-plot) plots of the four
different compositions of the mixed system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -(EC)20)))b -
(Al2O3)1-b, where 1-b = 20,15,10 and 5 mol % respectively. The inset diagram shows the room
80:20 85:15 9 0:1 0 9 5:5
0 .00 0000 1
0 .00 0000 2
0 .00 0000 3
0 .00 0000 4
0 .00 0000 5
0 .00 0000 6
Con
duct
ivity
,
com posistion
74
temperature Impedance (Nyquist-plot) plots of the compositions
1-b = 20 and 15 mol % respectively for clarity.
Interestingly, each Nyquist plot consists of a depressed semicircular arc, thus revealing
the presence of a bulk resistance (Rb) in parallel connection with a geometric capacitance (Cg) as
reported earlier in the case of other solid electrolyte materials. Generally, fast ionic conductors
are polycrystalline in nature with inter granular grain boundary effects and could not be
represented as single parallel RC equivalent circuit which exhibits complete semicircular arc.
Instead, they are represented as series combination of number of parallel RC elements
representing distribution of conducting elements of various grains present in the system.
Fig. 4.2.6 Room temperature Impedance (Nyquist-plot) plots of the four different compositions of the mixed system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))b -(Al2O3)1-b, where 1-b = 20,15,10 and 5 mol % respectively.
Hence, the complex impedance plot of the present solid electrolyte system appears to
have two incomplete semicircular arcs including a high frequency one corresponding to bulk
resistance (Rb) of the sample in parallel with geometric capacitance Cg and a low frequency arc
representing double layer capacitance Cdl of the electrode-electrolyte interface. Extrapolation of
0.00E+000 2.00E+007 4.00E+007 6.00E+007 8.00E+007 1.00E+0080.00E+000
2.00E+007
4.00E+007
6.00E+007
8.00E+007
1.00E+008
0 50000001000000015000000200000002500000030000000350000004000000045000000500000000
5000000
10000000
15000000
20000000
25000000
30000000
35000000
40000000
45000000
50000000
-Z"O
hm)
Z' (Ohm)
A,AL2O3 (10) B,AL2O3 (5)
A
B
-Z"O
hm)
Z' (ohm)
(A) Al2O
3 (20%)
(B) Al2O
3 (15%)
(C) Al2O
3 (10%)
(D) Al2O3 (5%)
A
B
C
D
75
this plot produces a depressed semicircle. Hence, from the point of intersection of the
semicircular part on the Z'-axis, the corresponding value of Rb was determined by employing the
Boukamp equivalent circuit software with an excellent accuracy, for all the four different
specimens. The observed trend in bulk resistance and the respective impedance plots are found to
be similar to that of many superionic conductors.
TEMPERATURE DEPENDENCE OF COMPLEX IMPEDANCE PLOTS
Fig. 4.2.7 depicts the complex impedance plots obtained at different temperatures
(303- 393 K) for a composition corresponding to 1- b= 10 mol % in the mixed system
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)))b-(Al2O3)1-b. It is also obvious from Fig. 4.2.7
that the point of intersection on the real axis is shifted towards origin and the diameter of the
semicircular arc decreases with increase in temperature and hence the value of bulk resistance
(Rb) decreases at elevated temperatures which in turn leads to an increase in the electrical
conductivity value with increase in temperature .
Fig. 4.2.7 Complex impedance plots obtained at different temperatures (303- 393 K) for the best conducting composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))90 - (Al2O3)10
0.00E+000 2.00E+007 4.00E+007 6.00E+0070
10000000
20000000
30000000
40000000
50000000
60000000
70000000
(B)Al2O
3 (303 K)
(A)Al2O
3 (323 K)
(C)Al2O
3 (343 K)
(D)Al2O
3 (363 K)
(E)Al2O3 (383 K)
Z"(O
hm)
Z'(Ohm)
76
TEMPERATURE-DEPENDENT ELECTRICAL CONDUCTIVITY DATA
Normally any solid state device will be subjected to rigorous ambient condition
compatibility in order to know about their stability against temperature, pressure, environmental
changes etc. One of the main criteria considered in almost all fast ionic solids would be variation
of electrical conductivity with temperature. It was expected to be a linear variation in such a way
that conductivity values increases with respect to increase in temperature obeying Arrhenius
relation
(T) = ( 0 / T) exp (-Ea / kT2 )
where 0 is the pre-exponential factor, Ea, the activation energy for ionic migration within the
solid, k, the Boltzmann constant and T is the absolute temperature . For all the four different
systems under study, Arrhenius plots of log T versus 1/T were drawn in the temperature range
303-393 K. The increase in conductivity is observed in all compositions in terms of a sharp
increase in conductivity at this particular temperature range. The Activation energy values were
calculated from the best fits of Arrhenius plots in the temperature range 303 - 350 K.
Fig. 4.2.8 depicts the plots of log T versus 1/T obtained for four different
compositions of the mixed system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))b -
(Al2O3)1-b, where 1-b = 20,15,10 and 5 mol % respectively in the temperature (T) range
303-393 K.
2 .5 2 .6 2 .7 2 .8 2 .9 3 .0 3 .1 3 .2 3 .3 3 .4
0 .50 .60 .70 .80 .91 .01 .11 .21 .31 .41 .51 .61 .71 .81 .92 .02 .12 .22 .3
5+Lo
g(S
cm-1)
(1000/T )(K -1)
A ,A L 2O 3 (2 0 ) B ,A L 2O 3 (1 5 ) C , A L 2O 3 (1 0 ) D ,A L 2O 3 (5 )
A
B
C
D
77
Fig. 4.2.8 Arrhenius plots of log T versus 1/T four different compositions of the mixed
system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))b - (Al2O3)1-b, where 1-b = 20,
15,10 and 5 mol % respectively (303-393K).
Best fit patterns of all the observed Arrhenius plots shown in Fig. 4.2.8 were drawn with
accuracy for the evaluation of relevant activation energy (Ea) data corresponding to individual
compositions. As a consequence, the estimated values of activation energies for the set of four
different compositions containing 1-b=20,15,10 and 5 mol % respectively of Al2O3 in the
temperature range 303-350 K were found to be 0.178, 0.082, 0.024 and 0.105eV respectively as
given in Table. 4.2.2. From these results, it is clear that highly conducting specimen namely
those corresponding to 1-a = 10 mol % possesses very low activation energies for conduction in
good agreement with the observed trend of conductivity among the polymer electrolytes.
Table. 4.2.2 Temperature-dependent electrical conductivity data obtained for the mixed
system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))b - (Al2O3)1-b, where 1-b = 20, 15,
10 and 5 mol % respectively (303-393K).
Composition, 1-b
(mol %)
Conductivity Equation
Log10 T)=log10 0-Ea/2.303kT
Activation Energy
Ea(eV)
20
log10 T=1.55-0.305(103/T) 0.1783
15
log10 T=3.192-0.416 (103/T) 0.0826
10
log10 T=2.352-0.124 (103/T) 0.0246
5
log10 T=2.649-0.532(103/T) 0.1056
The ionic conductivity increases with increasing temperature. This can be explained from
the free volume model. As the temperature increases, the polymer electrolyte can expand easily
and produces free volume. Therefore, more ions, solvated molecules, or the polymer segments
78
can move into the free volume. This enhances the ion and polymer segmental mobility which, in
turn, enhances the ionic conductivity. The conductivity of the filler-added system is higher than
the plasticized system and always exhibits the highest conductivity from 298 to 373 K. The
conductivity enhancement possibly results from the Lewis acid–base-type oxygen and OH surface
groups on the alumina grains, which interact with the cations and anions. This provides additional
sites which creates favorable high conducting pathways within the vicinity of grains for the
migration of ions. This is reflected as an increased mobility for the migrating ions. 4.2.6 Transport number (tMg
2+) measurement: Mobile anions and cations other than Mg2+ may create a concentration gradient across the
synthesized electrolyte and accumulate at the electrode surface and be absorbed or decomposed
on the electrode thereby reducing the power density achievable from the battery system.
Therefore, a large value of Mg ionic transference number (tMg2+) is generally desired for the
practical application of the GPE. A typical DC polarization current vs time plot and AC
impedance plots obtained before and after polarization were shown in Fig 4.2.10 and 4.2.9
respectively. The transference number was calculated using the following equation
Where Io denotes the initial current, Is, steady state current, Ro, initial interfacial
resistance, Rs the steady–state interfacial resistance and tMg+ is the transference number of silver
ions at room temperature. The initial current, Io, is considered to be due to migration of both
cations and anions. Because of the cell polarization, the current decreases over time to a steady-
state value, Is, which is considered to be due to the migration of the cations only. The value of
tMg2+ at room temperature was found to be 0.2658.
The value of tMg2+ observed for the polymer electrolyte has been found to be 0.2658 at
room temperature (25°c). This value suggests the predominant contribution of Mg ion
conduction towards total ionic conductivity. As the Mg ionic transport number is large, reverse
polarization within the polymer electrolyte may be avoided and this polymer electrolyte could
therefore be effectively used to fabricate batteries for practical uses.
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
79
Fig.4.2.9 AC impedance plots obtained before and after polarization for the best
conducting composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))90 - (Al2O3)10
A large cationic transference number would be a desired property of an electrolyte
material so that the concentration gradient across electrolyte may be minimized in an
electrochemical cell [(((PMMA+ PVDF)50 - (Mg2CFSO3)50)80 (EC)20)90 - (Al2O3)10,] .
Accordingly, a constant polarization potential (DC) of 20 mV was applied across the cell
configuration Mg | Polymer Electrolyte | Mg. A typical plot of variation of current observed as a
function of time for Polymer Electrolyte with 5 wt% Al2O3, nanofiller was shown in Fig.4.2.9
which shows its AC impedance plots measured before and after polarization. The To calculated
cationic transference number (tMg2+) value for the synthesized polymer electrolyte at room
temperature was found to be 0.256.
-10000 0 10000 20000 30000 40000 50000 60000 70000 80000
0
10000
20000
30000
40000
50000
60000
B
A
R aR b
R a=36471.2628R b=31413.6096
80
Fig.4.2.10 DC polarization current vs time during polarization of the
cell Mg | Polymer Electrolyte | Mg with a potential of 0.020V at 25 °C with I =0.0223 A
and Is=0.00214 A.
4.2.6 Cyclic Voltammety measurement:
Cyclic voltammetric studies have been carried out on the symmetrical cell Mg/ solid
Polymer Electrolyte /MnO2 +C. In Cell, the film was in contact with the foil of Mg which was
used as reversible electrode and MnO2 +C as cathode , recorded at room temperature (28°C). The
magnesium foil served as the current collector in cell. Cyclic voltammetric study on the two cells
further confirms the Mg2+ ion conduction in the solid polymer electrolyte film. The cathode and
anodic current peaks are distinctly observed for cell. This suggests that the cathode deposition
and anodic oxidation of Mg are facile at Mg / polymer electrolyte /MnO2+C electrolyte interface
and hence it is the indicative of Mg2+ ion conduction in the solid polymer electrolyte film. It may
be noted that the cathodic/anodic peak potentials are separated by several volts.
81
This system is performed at a scan rate of 0.1 Vs-1.This is possible because the
experiments were carried out with the symmetrical cell with two electrode geometry without
using reference electrode.
Fig.4.2.11 Cyclic voltametry graph of a Mg | polymer electrolyte |MnO2+C performed at a
scan rate of 0.1 Vs-1.
4.2.7 Fabrication of solid state battery :
These cells were put in glass housing unit for their characterization. The open circuit
voltage (OCV) and cell potential measurements were carried out with the help of a high
impedance digital Keithley 6568A model electrometer. The batteries were discharged under load
condition (lM ) and the cell potentials were monitored as a function of time. To check the initial
voltage obtainable from the fabricated cell and to ensure proper electrode-electrolyte contacts,
open circuit voltage has been measured over a period of- 24h, Open circuit voltage value 90.8
mV was obtained and short circuit current has been measured as 33.3 nA..
Scan rate=0.1 Vs-1.
82
4.3 RESULTS AND DISCUSSION-SYSTEM-III
In the present investigation, the synthesized polymer electrolyte system with silicon
dioxide as nanofiller has been subjected to various characterization techniques in order to
explore the effect of addition of nanofiller. The crystalline structure of the sample was obtained
by powder X-Ray Diffraction analysis (XRD), spectral analysis by Fourier Transform Infra-Red
spectroscopy (FTIR), and phase analysis by Differential Scanning Calorimetric analysis (DSC),
and surface morphological studies by Field Emission Scanning Electron Microscopy (FESEM)
and AC impedance analysis to exhibit the ionic conductivity of the synthesized samples
associated with transport number measurement and fabrication of solid state battery.
4.3.1 POWDER X-RAY DIFFRACTION ANALYSIS
The powder XRD patterns obtained for the different compositions of the polymer
electrolyte system synthesized by solution casting technique with Magnesium triflate as host salt,
Ethylene carbonate as plasticizer and silicon dioxide as nano filler are depicted in Fig. 4.3.1
under stoichiometric composition of (((PMMA + PVDF) 50 - (Mg2CFSO3)50)80 - (EC)20)c- (SiO2)1-
c where 1-c = 20, 15, 10 and 5 mol % respectively.
Fig. 4.3. 1 Powder XRD patterns of solid polymer electrolyte system (((PMMA + PVDF)50 -
10 20 30 40 50 60 70
2 in deg
a=80% b=85% c=90%d=95%
a=80 %
b=85 %
c=90 %
d=95%
Inte
nsity
(arb
.uni
ts)
83
(Mg2CFSO3)50)80 - (EC)20)c- (SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol % respectively
XRD studies were carried out using JEOL (JDX-8030) X-ray diffractometer with Cu-K
as target material of wavelength 1.540598 ź in the 2 range from 20º to 80º. The broad peak
formed at 2 =14ºand less intense broad peak at 2 =27º may corresponds to the amorphous
polymer PMMA. The XRD pattern generally shows peak free pattern with halos structure
indicating amorphous nature of the synthesized polymer electrolytes. This feature tends to
indicate a relatively higher amorphous phase formation within the complexed polymer
electrolyte film. Also, it is observed that the amorphous phase increases while increasing the
concentration of SiO2 which indicate that the nanocrystalline SiO2 particles are well dispersed in
the polymer matrix. Upon addition of salt and nanofiller, absence of well defined crystalline
peaks occurs owing to the interaction between filler, salt and polymer complexes. The fact that
no peaks corresponding to the salt and nanofiller were present in the XRD pattern tends to
indicate the complete amalgamation of polymer, salt and nanofiller with no distinct phase
separation.
4.3.2 DIFFERENTIAL SCANNING CALORIMETRIC ANALYSIS
The DSC curves obtained for the different composition of the mixed system
(((PMMA+PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c-(SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol %
respectively is presented in the Fig. 4.3.2 in the temperature range 350 to 700 K. For pure PVDF,
the glass transition temperature would be observed at 331K whereas for pure PMMA, the same
could be around 544K. An endothermic peak is observed around 568 K in this investigation may
be attributed to the melting temperature of (PMMA)50 + (PVDF) 50 blended polymer film i.e a
change in crystalline structure may result from polymer-copolymer interactions in the amorphous
phase resulting in changes of phase transitions.
84
Fig. 4. 3.2. DSC curve obtained for the best composition of the mixed system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c- (SiO2)1-c , where 1-c = 20, 15,
10 and 5 mol % respectively.
The shoulder at around 370 K may correspond to the glass transition temperature of the
synthesized polymer systems. This value increases when the concentration of nanofiller decreses
from 1-c=20 % till 1-c=10% .For 1-c=5%, the glass transition temperature was found to be
decreased to 368.0 K which may be attributed to the best ionic nature which could be proved in
conductivity studies. An Exothermic peak observed at 644.4 K in this investigation may be
attributed to the melting temperature of (((PMMA+PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c-
( SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol % respectively. This exothermic peak is slightly
shifted to 653.0 K for the compostion with 1-c=5%. A change in crystalline structure may result
from polymer-copolymer interaction in the amorphous phase resulting in change of phase
transitions resulting in intermediate phase at around 568.4 K as shown in Fiq.4.3.2 . This peak
value also varies according to the nanofiller composition. For 1-c=5% composition, this peak
value appears at 566.7 K.
4 0 0 5 0 0 6 0 0 7 0 0 8 0 0
Hea
t flo
w (w
/mg)
Tem p eratu re (K )
a = 8 0 % b = 8 5 % c= 9 0 % d = 9 5 %
a = 8 0 %
b = 8 5 %
c = 9 0 %
d = 9 5 %
3 6 9 .8
5 6 8 .4
6 4 4 .4
3 7 1 .5
5 6 8 .4
6 4 4 .4
3 7 3 .3
5 7 1 .9
6 4 4 .4
3 6 8 .0
5 6 6 .7
6 5 3 .0
85
4.3.3 FOURIER TRANSFORM INFRA-RED SPECTROSCOPY
Fig. 4.3.3 FTIR spectra observed in solid polymer electrolyte system (((PMMA +
PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c- (SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol %
respectively.
The FTIR analysis helps in investigating different functional groups available in the
synthesized system confirming the presence of various groups. In this present investigation,
Fourier transform infrared spectroscopy analysis was undertaken with a view to ascertain the
various functional groups of the synthesized polymer electrolyte system (((PMMA+PVDF)50 -
(Mg2CFSO3)50)80 - (EC)20)c-( SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol % respectively using
Agilent CARY 630 IR Spectrometer and the spectra were recorded over the wave number range
of 4000-400 cm-1 but characteristic functional groups appears only in the range 4000-650 cm-1.
Fig. 4.3.3 shows the spectra recorded for the four different compositions of polymer electrolyte
system with magnesium triflate salt and plasticized polymer electrolyte system with Ethylene
carbonate as plasticizer and silicon dioxide as nanofiller namely (((PMMA+PVDF)50 -
(Mg2CFSO3)50)80 - (EC)20)c-( SiO2)1-c , where 1-c = 20, 15, 10 and 5 mol % respectively.
For composition with 1-c=20% mol fraction, the characteristic peak at 1050 cm-1
represents CF2 stretching vibrations. An absorption peak at 1729.48 cm-1 could be considered as
500 1000 1500 2000 2500 3000 3500 4000 4500
Wavenumber (cm-1)
a=80%b=85% c=90% d=95%
a=80%
b=85%
c=90%
d-95%
% o
f Tra
nsm
ittan
ce (a
rb.u
nits
)
1051.31729.481441.2
1127.21441.3 1725.3
2940.5
2940.6
2940.0
2940.0 3284.31725.31441.3
1127.2
1170.3
1441.3 1725.31051.3
86
C=O stretching vibration due to PMMA. The peak due to CH3 asymmetric deformation at 1456
cm-1 downshifts to 1440 cm-1 for the polymer electrolyte system. The characteristic peak at 2940
cm-1 is assigned to CH2 stretching vibrations of pure PMMA. FTIR spectrum of pure nanosized
SiO2 shows the peak at 1122 cm-1 assigned to Si-O-Si asymmetric stretching. In this present
polymeric system, the peak at 1122 cm-1 was believed to be affected by the presence of % of
composition of SiO2. For 1-c=20%,the peak downshifts to 1051.3 cm-1 whereas for 1-c=15%,it
occurs at 1127.2 cm-1.for the composition with 1-c=10% mol fraction, this Si-O-Si asymmetric
stretching splits into peaks at 1051.3 and 1170.3 cm-1 respectively. For the composition with 5%
SiO2 nanofiller, the broadened peak becomes a sharp absorption peak with the value shifted
slightly with the decreasing content of SiO2. Si-O-Si asymmetric stretching occurs at 1127.3
cm-1, In addition with that new peak was found to occur at 3284.3 cm-1 may correspond to
stretching vibration of Si-OH groups .Hence the changes in the FTIR result provides convincing
evidence for polymer-filler interaction. Thus, the above spectral features appear to confirm the
appreciably good complication within the present nano compostie polymer electrolyte system
which confirms a substantial changes in the network and likely to have an influence on the ionic
conduction of the solid electrolyte system.
4.3.4 FIELD EMISSION SPECTROSCOPY
Fig.4.3.4 shows the FESEM micrograph obtained for the best conducting
composition of the present system namely (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)95-
(SiO2)5.. The observed pattern in the micrograph shows flower like arrangement scattered non-
uniformly in the 5 micron range. This clearly suggests the point that synthesized polymer
electrolyte system does not possess crystalline nature with uniform nature ,instead the
micrograph confirms the irregular arrangement conforming the amorphous nature of the prepared
sample which is the pre-requiste for the polymer ion conducting samples. The micrograph
exhibits non-uniform distribution of particles size throughout the filler.
87
Fig. 4.3.4 FESEM micrograph obtained for the best conducting polymer electrolyte
system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)95- (SiO2)5.
4.3.5 AC IMPEDANCE ANALYSIS
During the present investigation, the frequency response of a variety of compositions of
the chosen system was measured in terms of the real (Z') and imaginary (Z'') parts of the complex
impedance (Z*) at different temperatures. The point of intersection of the impedance plots on the
real axis in the high-frequency region was taken as the bulk resistance (Rb) of the sample. The
electrical conductivity ( ) of the sample was estimated using the relationship
b (1)
Where ‘t’ is the thickness of the specimen and A is the area of cross-section.
The complex impedance measurements were carried out using a computer - controlled
Germany NOVA control technology NOVA control Alpha-n analyser in the frequency range 20
Hz – 10 MHz over the temperature range 303 – 393 K. All the observed impedance plots were
best fitted internally by means of the Boukamp equivalent circuit software package incorporated
within the computer.
88
Thus, the complex impedance measurements were carried out on film specimens of all
the blended polymer system with magnesium triflate salt and plasticized polymer electrolyte
system with Ethylene carbonate as plasticizer namely
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c - (SiO2)1-c where
1-c = 20, 15, 10 and 5 mol % respectively, with SiO2 as nanofiller in the frequency range 20 Hz
to 10 MHz.. Accordingly, all the synthesized solid films were loaded with blocking electrode
on either side under a stainless steel top electrode with diameter 20mm and bottom electrode
(diameter 40mm).All the complex impedance measurements were carried out by keeping these
solid polymer electrolyte films in between two steel electrodes.Complex impedance
measurements were carried out on all film specimens of four different stoichiometric
compositions of the polymer electrolyte system III (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 -
(EC)20)c - (SiO2)1-cwith the addition of SiO2 as nanofiller, where 1-c = 20, 15, 10 and 5 mol %
respectively in order to evaluate the electrical ionic conductivity values and tabulated in
Table.4.3.1.
The evaluated values of electrical ionic conductivity values lies in the order of10-5 S cm-1at
room temperature 303K. It is noted that for the particular composition
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)95 - (SiO2)5 which exhibits an electrical
conductivity value of 2.917×10-5 Scm-1 at room temperature (303K) could be considered as best
conducting compositions of all the four synthesized samples of the present mixed system.
The observed results in terms of electrical conductivity values of the present system
strongly attribute the fact that the increase in values of conductivity values of the order of 5
magnitude would be due to the addition of nanofiller SiO2 which resulted in high conduction
pathways and responsible for the increase of conductivity.Hence the aim of our present
investigation has been arrived at with in terms of high ionic conductivity values resulting in
increased conductivity values of order of 5 magnitude due to the addition of silicon dioxide as
nanofiller. Such higher values of conductivity are attributed to the higher amorphicity of the
materials and space charge defects generated around SiO2 nanoparticles in the polymer matrix.
89
Table- 4.3.1: Room temperature electrical conductivity values obtained for system III
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c - (SiO2)1-c, where 1-c = 20, 25, 10 and
5mol% respectively.
Fig.4.3.5 shows the room temperature complex impedance plots obtained for the four
different compositions of the mixed system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c - (SiO2)1-c , where
1-c = 20, 15, 10 and 5 mol % respectively. The observed impedance plots are depressed
semicircles with the x-axis as generally observed for polymer electrolyte systems.
Composition (1-c)
Room temperature Electrical conductivity
(Scm-1)
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)80-
( SiO2)20
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)85-
( SiO2)15
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)90-
(SiO2)10
(((PMMA+PVDF)50-(Mg2CFSO3)50)80-(EC)20)95-
( SiO2)5
2.186×10-5
2.249×10-5
2.668×10-6
2.917×10-5
90
Fig. 4.3.5 Room Temperature complex impedance plots for
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)c - (SiO2)1-c ,
where 1-c = 20, 15, 10 and 5 mol % respectively
Temperature dependence of complex impedance plots
Fig.4.3.6 depicts the complex impedance plots obtained at different temperatures
(303- 393 K) for a composition corresponding to 1-c = 5 mol % in the mixed system (((PMMA +
PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))c - (SiO2)1-c. Figure implies that the point of intersection
on the real axis is shifted towards origin and the diameter of the semicircular arc decreases with
increase in temperature and hence the value of bulk resistance (Rb) decreases at elevated
temperatures which in turn leads to an increase in the electrical conductivity value with increase
Fig 4.3.6 Complex
impedance plots
obtained for the system
(((PMMA + PVDF)50 -
(Mg2CFSO3)50)80 -
(EC)20)95- (SiO2)5 under
different temperature
values.
0 5 0 0 0 0 0 01 0 0 0 0 0 0 01 5 0 0 0 0 0 02 0 0 0 0 0 0 02 5 0 0 0 0 0 03 0 0 0 0 0 0 03 5 0 0 0 0 0 04 0 0 0 0 0 0 00 . 0 0 E + 0 0 02 . 0 0 E + 0 0 84 . 0 0 E + 0 0 86 . 0 0 E + 0 0 88 . 0 0 E + 0 0 81 . 0 0 E + 0 0 91 . 2 0 E + 0 0 91 . 4 0 E + 0 0 91 . 6 0 E + 0 0 91 . 8 0 E + 0 0 92 . 0 0 E + 0 0 92 . 2 0 E + 0 0 92 . 4 0 E + 0 0 92 . 6 0 E + 0 0 92 . 8 0 E + 0 0 93 . 0 0 E + 0 0 93 . 2 0 E + 0 0 9
-Z"
(Ohm
)
Z ' ( O h m )
a - 8 0 % b = 8 5 % c = 9 0 % d = 9 5 %
a
b
d
c
0 10000000 20000000 30000000 40000000 50000000 600000000.00E+000
2.00E+008
4.00E+008
6.00E+008
8.00E+008
1.00E+009
1.20E+009
1.40E+009
-Z"
(Ohm
)
Z ' (Ohm)
298 K 308 K 318 K 328 K 338 K 348 K 358 K 368 K
91
TEMPERATURE VARIATION OF ELECTRICAL CONDUCTIVITY IN THE SYSTEM OF
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)95- (SiO2)5
Generally, the temperature-dependence of electrical conductivity ( ) of an ideal super
ionic material or solid polymer electrolyte system may be expressed by the Arrhenius equation
where 0 is the pre-exponential factor, ‘Ea’ the activation energy for ionic migration within the
solid required for an ion to hop from one defect site to another, ‘k’ the Boltzmann constant and
‘T’ is the absolute temperature. For all the four different systems under study, Arrhenius plots of
log T versus 1/T were drawn in the temperature range 298-463 K. The increase in conductivity
is observed in all compositions in terms of a sharp increase in conductivity when temperature
increased. The Activation energy values were calculated from the best fits of Arrhenius plots in
the temperature range 303 - 425 K.
Fig.4.3.7 Plots of log T versus 1/T of the polymer elcectrolyte system
(((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))c- (SiO2)1-c, where
1-c = 20, 15, 10 and 5 mol % respectively (303-425K).
2 .3 2 .4 2 .5 2 .6 2 .7 2 .8 2 .9 3 .0 3 .1 3 .2 3 .3 3 .4
4 .8
4 .9
5 .0
5 .1
5 .2
9 5 % 9 0 % 8 5 % 8 0 %
7+ L
og(
T)
1 0 00 /T (K -1 )
(T) = ( 0/T) exp(-Ea/KT)
92
Fig.4.3.7 represents the plots of log T versus 1/T obtained for four different compositions of the
mixed system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))c- (SiO2)1-c, where
1-c = 20, 15, 10 and 5 mol % respectively (303-425K).
Best fit patterns of all the observed Arrhenius plots shown in Fig.4.3.7 were drawn with
accuracy for the evaluation of relevant activation energy (Ea) data corresponding to individual
compositions. As a consequence, the estimated values of activation energies for the set of four
different compositions in the temperature range 303 - 350 K were found to be 0.110, 0.128,
0.109, 0.268 eV respectively as given in Table 4.3.2. From these results, it is clear that highly
conducting specimen namely those corresponding to 1-c = 5 mol % possesses very low
activation energy of .0395 eV for conduction in good agreement with the observed trend of
conductivity among the polymer electrolytes
Table.4.3.2.Temperature-dependent electrical conductivity data obtained for the
Synthesized polymer system with SiO2 as nanofiller
The conductivity of the filler-added system is higher than the plasticized system and
always exhibits the highest conductivity from 298 to 425 K. The conductivity equation tabulated
above represents that the Arrhenius behavior is satisfied in the present system.
Composition,
(1-c)
(mol%)
Conductivity Equation
Log10 T) = log10 0 - Ea/2.303 kT
Activation Energy
Ea (eV)
20 log10 T = 5.473 - 0.202 (103/T) 0.040
15 log10 T = 5.591 - 0.231 (103/T) 0.046
10 log10 T = 6.011 - 0.346 (103/T) 0.069
5 log10 T = 5.604 – 0.199(103/T) 0.0395
93
4.3.6 Transport number (tMg2+) measurement by ac/dc method:
Mobile anions and cations other than Mg2+ may create a concentration gradient across the
synthesized electrolyte and accumulate at the electrode surface and be absorbed or decomposed
on the electrode thereby reducing the power density achievable from the battery system.
Therefore, a large value of Mg ionic transference number (tMg2+) is generally desired for the
practical application of the GPE. A typical DC polarization current vs time plot and AC
impedance plots obtained before and after polarization were shown in Fig 4.3.8 and 4.3.9
respectively. The transference number was calculated using the following equation
Where Io denotes the initial current, Is, steady state current, Ro, initial interfacial
resistance, Rs the steady–state interfacial resistance and tMg+ is the transference number of silver
ions at room temperature. The initial current, Io, is considered to be due to migration of both
cations and anions. Because of the cell polarization, the current decreases over time to a steady-
state value, Is, which is considered to be due to the migration of the cations only. The value of
tMg2+ at room temperature was found to be 0.7039.
Fig.4.3.8 Current vs Time plot of ac/dc polarization method for the best conducting composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))95- (SiO2)5,
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
0 50 1 00 150 2 00 250 30 00 .000 0
0 .000 1
0 .000 2
0 .000 3
0 .000 4
0 .000 5
Cur
rent
(A
)
T im e (Sec)
C u rre n t v s tim e
94
The value of tMg2+ observed for the polymer electrolyte has been found to be 0.7039 at
room temperature (25°c) with the following data as Io=0.00051 A, If=0.0001 A, V=20mV,
Ro=3568 and Rf=5213 respectively.This value suggests the predominant contribution of Mg
ion conduction towards total ionic conductivity. As the Mg ionic transport number is large,
reverse polarization within the polymer electrolyte may be avoided and this polymer electrolyte
could therefore be effectively used to fabricate batteries for practical uses.
Fig.4.3.9 Complex impedance plots obtained before and after polarization of polymer electrolyte system (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)))95- (SiO2)5,
4.3.7 Cyclic Voltammety measurement:
Cyclic voltammetric studies have been carried out on the symmetrical cell Mg/ solid
Polymer Electrolyte /MnO2 +C. In Cell, the film was in contact with the foil of Mg which was
used as reversible electrode and MnO2 +C as cathode, recorded at room temperature (28°C). The
magnesium foil served as the current collector in cell. Cyclic voltammetric study on the two cells
further confirms the Mg2+ ion conduction in the solid polymer electrolyte film. The cathode and
anodic current peaks are distinctly observed for cell. This suggests that the cathode deposition
0 2000004000006000008000001000000120000014000001600000180000020000002200000240000026000000
1000000
2000000
3000000
4000000
ZSin
, Z"
(Ohm
)
ZCos , Z' (Ohm)
before polarization After polarization
95
and anodic oxidation of Mg are facile at Mg / polymer electrolyte /MnO2+C electrolyte interface
and hence it is the indicative of Mg2+ ion conduction in the solid polymer electrolyte film. It may
be noted that the cathodic/anodic peak potentials are separated by several volts.
Fig.4.3.10 Cyclic voltametry graph of a Mg | polymer electrolyte |MnO2+C performed at a
scan rate of 0.1 Vs-1.
This system is performed at a scan rate of 0.1 Vs-1.This is possible because the
experiments were carried out with the symmetrical cell with two electrode geometry without
using reference electrode. The initial voltage was set at 1.2 V and the final voltage in the loop
was found to be -0.4 V .Figure clearly shows the hysteresis loop characterizing the electrolyte
property. The composite exhibits good cycling performance in the potential range -0.4 to 1.2V
which is the electrochemical stability of the synthesised polymer electrolyte.
4.3.8 Fabrication of solid state battery :
These cells were put in glass housing unit for their characterization. The open circuit
voltage (OCV) and cell potential measurements were carried out with the help of a high
impedance digital Keithley 6568A model electrometer. The batteries were discharged under load
condition (lM ) and the cell potentials were monitored as a function of time. To check the initial
voltage obtainable from the fabricated cell and to ensure proper electrode-electrolyte contacts,
96
open circuit voltage has been measured over a period of- 24h, Open circuit voltage value 82 mV
was obtained and short circuit current has been measured as 2.4×10-9 A..
5. CONCLUSION
System-I
The present investigation involves the preparation, structural and electrical characterization
studies on three different systems namely system A-((PMMA + PVDF)y - (Mg2CFSO3)1-y,
where 1-y = 60, 50, 40, 30 and 20 mol % respectively, System - B ((PMMA + PVDF)y -
(Mg2CFSO3)1-y)z - (EC)1-z, where 1-z = 25, 20, 15, 10 and 5 mol % respectively, System-I
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a ,where
1-a = 20, 15, 10 and 5 mol % respectively. The above mentioned systems were prepared by
solution-casting technique. The prepared thin films are flexible in nature without losing its
mechanical integrity.
In system I the MgO nanofiller of 32 nm size prepared by wet chemical method is added to
arrive at nanocomposite solid polymer electrolyte systems in four different compositions
namely 1-b = 20, 15, 10 and 5 mol % respectively. The synthesized MgO nanofillers size was
confirmed by TEM study.
Experimental techniques such as X-ray diffraction analysis, Fourier transform infrared
spectroscopy (FTIR), differential scanning calorimetry (DSC), complex impedance
analysis, and surface morphological studies involving optical microscopy have been
employed during the course of this present investigation
AC complex impedance analysis as a function of frequency at room temperature were
carried out on all the synthesized samples in the form of film, loaded with stainless steel
electrodes on both sides the frequency range of 20 Hz to 10 MHz and from room
temperature 303 K.
Pure PMMA and pure PVDF polymer samples exhibits conducting values of the order of
2.4262 × 10 -11 Scm-1 and 2.9625 × 10 -11 Scm-1 respectively. The best electrical
conductivity of blended polymer matrix (PMMA + PVDF)y shown by our research group
was 4.449 x 10-10 Scm-1 .
97
The electrical conductivity values measured by AC impedance analysis for the first
system ((PMMA + PVDF)y - (Mg2CFSO3)1-y, under study were tabulated and
(PMMA + PVDF)50 - (Mg2CFSO3)50 was regarded as best conducting composition with
the ionic conductivity value of 1.559 × 10-8 Scm-1. Similarly, the best conductivity
composition of system II was identified as
((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20 with the ionic conductivity value of
2.54 × 10-8 Scm-1.
The best electrical conductivity of the system
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a ,where
1-a = 20, 15, 10 and 5 mol % was found to be is 1.26×10-6 Scm-1 with 10 mol % MgO.
Hence we were able to achieve the increase in conductivity of the order of 5 magnitudes
which shows the ability of the synthesized system as ion conducting polymer electrolyte.
Hence an ultimate aim of arriving at a new family of highly performing electrolyte
materials for ambient conditions was highly satisfied with the obtained results.
FTIR results for three different systems I, II and III showed various functional groups
present in the system. The occurrence of complexation is determined based on the
changes in the shifting of the peak, peak intensity and formation of new peaks.
The XRD results for three systems I, II and III namely
((PMMA + PVDF)y - (Mg2CFSO3)1-y, where 1-y = 60, 50, 40, 30 and 20 mol %
respectively, ((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z, where
1-z = 25, 20, 15, 10 and 5 mol % respectively,
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a, where
1-a = 20, 15, 10 and 5 mol % respectively implied the amorphous nature of polymer
electrolyte system with less intense peaks observed.
The DSC analysis for three systems namely ((PMMA + PVDF)y - (Mg2CFSO3)1-y,
((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z, and
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a showed the phase changes
in terms of exothermic peak, and their respective shifting.
98
SEM micrographs obtained for three system I, II and III as morphological studies clearly
showed formation of clusters of varying sizes and the presence of more and more voids,
which are expected to lead to enhanced ionic conductivity in accordance with the present
XRD analysis.
The transference number was calculated using the following equation
was found to be tMg+=0.6765 with the following data If=0.00078 A, Io=0.013 A,
V=20mV,
Ro=1104 and Rf =1.2284e4 respectively. The high value of tMg+ implies the fact
that the major contribution to the electrical conductivity values of the synthesized polymer
electrolyte was due to the magnesium ions only and respective impedance plots along with
current Vs time plots were drawn. In present study, the electrochemical cell stability
window has been studied by cyclic voltametry analysis which showed reversibility in the
peaks confirming polymer electrolyte nature with Mg2+/ polymer electrolyte / MnO2+C
cell. The open circuit voltage and short circuit current were measured for fabricated solid
state battery of cell configuration Mg2+/ polymer electrolyte / MnO2+C as 112 mV and
13.2×10-9 Amp. respectively.The present study suggests ionic nature of the prepared
polymer electrolyte system which would be used effectively in micro-power devices.
In conclusion, the present study pertaining to synthesis and characterization of
nanocomposite solid polymer electrolyte material
(((PMMA + PVDF)y - (Mg2CFSO3)1-y)z - (EC)1-z)a - (MgO)1-a,
where 1-a = 20, 15, 10 and 5 mol % respectively has indicated the formation of fast ion
conducting materials in these systems and demonstrated their use as solid electrolytes for
ambient temperature solid state device applications.
System-II
The present work involves mainly an in-depth analysis of the phenomenon of
enhancement of ionic transport with improved physico - chemical properties in the case
of a series of new nanocomposite polymer electrolytes by initiating appropriate
tMg+ = Is/Io (( V- IoRo)/ ( V- IsRf))
99
complex formation in a favorable environment between Magnesium triflate
(Mg2CF3SO3) salt and a high molecular weight amorphous polymer viz., PMMA along
with co-polymer PVDF in conjunction with plasticizer in a four different compositions
of metal oxide nanofiller namely Al2O3.
Four groups of PMMA based solid polymer electrolyte system consisting of
(((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))b- (Al2O3)1-b ,where 1-b=20,15,10
and mol 5% respectively have been prepared using solution-casting technique. These
thin films are flexible in nature without losing its mechanical integrity. In this work, a
high molecular weight polymer PMMA of 996,000 is used as a host polymer and PVDF
with high molecular weight (Mw=275000) as co-polymer to form a polymer blend.
Magnesium trifluoromethanosulfonate (Mg2CFSO3) with molecular weight (Mw =
32244 g/mol) and Ethylene Carbonate (EC) with molecular weight (Mw = 8806 g/mol)
were used according to their stoichiometric compositions. Then, the Al2O3 nanofiller of
208nm size prepared by sol-gel wet chemical method is added to arrive at
nanocomposite solid polymer electrolyte systems in four different compositions namely
1-a=20, 15,10 and 5 mol % respectively. The synthesized Al2O3 nanofiller’s size was
confirmed by SEM morphological study and Particle size analysis technique.
Experimental techniques such as X-ray diffraction analysis, Fourier transform infrared
spectroscopy (FT-IR), differential scanning calorimetry (DSC), complex impedance
analysis, and surface morphological studies involving optical microscopy have been
employed during the course of the present investigation
AC complex impedance analysis as a function of frequency at room temperature were
carried out on all the synthesized samples in the form of film, loaded with stainless steel
electrodes on both sides in the frequency range of 20 Hz to 10 MHz and from room
temperature 303K to 393K. Pure PMMA and pure PVDF polymer samples exhibits
conducting value of 2.4262 × 10 -11 S cm-1 and 2.9625× 10 -11 S Cm-1 respectively. The best
electrical conductivity of blended polymer matrix (PMMA + PVDF)y shown by our
research group is 4.449 x 10-10 S cm-1 . The best electrical conductivity of the present
system (((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))b- (AL2O3)1-b under study was
found to be is 5.245 x 10-7 S cm-1 with 5 mol % AL2O3 . Hence we were able to achieve the
100
increase in conductivity of the order of 4 magnitudes which shows the potentiality of the
synthesized polymer system. Hence an ultimate aim of arriving at a new family of highly
performing electrolyte materials for ambient conditions was achieved with the obtained
results.
FTIR results indicated that the complexation has occurred between the host polymer,
plasticiser and nano fillers. The occurrence of complexation is determined based on the
changes in the shifting of the peak, peak intensity and formation of new peaks. The XRD
results also implied that the amorphous nature of polymer electrolyte is increased with the
best conducting composition as the intensity of the characteristic peaks is reduced and
amorphous nature is interpreted. The changes in the amorphous nature are determined
through the changes in the peak intensity and the diffraction peaks in the results obtained The
DSC analysis showed the phase changes in terms of exothermic peak. For the SEM
characterization, the morphological studies clearly showed formation of clusters of varying
sizes and the presence of more and more voids, which are expected to lead to enhanced ionic
conductivity in accordance with the present XRD analysis.
Magnesium ionic transport number (tMg2+ ) is found to be 0.2 658 at room temperature
by ac/dc polarization method and respective impedance plots along with current Vs time
plots were drawn. In present study, the electrochemical cell stability window has been
studied by cyclic voltametry analysis which showed reversibility in the peaks confirming
polymer electrolyte nature with Mg2+/ polymer electrolyte / MnO2+C cell. The open circuit
voltage and short circuit current were measured for fabricated solid state battery of cell
configuration Mg2+/ polymer electrolyte / MnO2+C as 90.8 mV and 33.3 nA respectively.
The present study suggests ionic nature of the prepared polymer electrolyte system which
would be used effectively in micro-power devices. .
In conclusion, the present study pertaining to synthesis and characterization of
nanocomposite solid polymer electrolyte material
(((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))b- (AL2O3)1-b ,where 1-b=20,15,10 and
mol 5% respectively has indicated the formation of fast ion conducting materials in these
101
systems and demonstrated their use as solid electrolytes for ambient temperature solid state
device applications.
System -III
Four groups of PMMA+PVDF based solid polymer electrolyte system consisting of
(((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))c- (SiO2)1-c ,where 1-c=20,15,10 and
5 mol % respectively with silicon dioxide nanofiller have been prepared using solution-
casting technique. These thin films are flexible in nature without losing its mechanical
integrity.
The XRD results also implied that the amorphous nature of polymer electrolyte is
increased with the best conducting composition as the intensity of the characteristic
peaks is reduced and amorphous nature is interpreted. FTIR results indicated that the
complexation has occurred between the host polymer, plasticizer and nano fillers. The
occurrence of complexation is determined based on the changes in the shifting of the
peak, peak intensity and formation of new peaks
The DSC analysis for (((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))c- (SiO2)1-c
,where 1-c=20,15,10 and mol 5% respectively showed the phase changes in terms of
exothermic peak, and their respective shifting. The FESEM micrograph showed non-
uniform distribution of particles suggesting amorphicity and complete miscibility of the
reactants.
The AC impedance analysis carried out four different samples of synthesize polymer
electrolyte system (((PMMA + PVDF)y-( Mg2CFSO3)1-y ))z- (EC)1-z ))c- (SiO2)1-c ,where
1-c=20,15,10 and mol 5% respectively. The evaluated values of electrical ionic
conductivity values lies in the order of10-5 S cm-1at room temperature 303K. It is noted
that for the particular composition (((PMMA + PVDF)50 - (Mg2CFSO3)50)80 - (EC)20)95 -
(SiO2)5 which exhibits an electrical conductivity value of 2.917×10-5 Scm-1 at room
temperature (303K) could be considered as best conducting compositions of all the four
synthesized samples of the present mixed system, with 6 orders of magnitude increase in
conductivity.
102
The value of tMg2+ observed for the polymer electrolyte has been found to be 0.7039 at
room temperature (25°c) with the following data as Io=0.00051 A, If=0.0001 A,
V=20mV,Ro=3568 and Rf=5213 respectively.This value suggests the predominant
contribution of Mg ion conduction towards total ionic conductivity. The composite
exhibits good cycling performance in the potential range -0.4 to 1.2V which is the
electrochemical stability of the synthesised polymer electrolyte.
The open circuit voltage (OCV) and cell potential measurements were carried out with
the help of a high impedance digital Keithley 6568A model electrometer. Open circuit
voltage value of 82 mV was obtained and short circuit current has been measured as
2.4×10-9 A.
In the present investigation, we established the fact that the synthesized sample possesses ionic
properties and high conductivity value for the best conducting composition, which would be used
as solid polymer electrolyte in the fabrication of all solid state batteries for micro-power device
applications. We are planning to undertake the detailed AC impedance analysis in terms of
normalized impedance spectra, modulus spectra, dielectric constant analysis, frequency
dependent conductivity analysis etc. which we hope will throw light on many ionic phenomenon
involved in the synthesized solid polymer electrolytes for further battery studies.
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