Fe O nanoparticle-decorated TiO2 nanofiber ... - Nano Research · nanofiber hierarchical heterostructures with improved lithium-ion battery performance over a wide temperature range

Nano Res

Fe3O4 nanoparticle-decorated TiO2 nanofiber

hierarchical heterostructures with improved lithium-ion

battery performance over a wide temperature range

Heng-guo Wang2 Guang-sheng Wang1 Shuang Yuan3 De-long Ma3 Yang Li1 and Yu

Zhang1()

Nano Res Just Accepted Manuscript bull DOI 101007s12274-014-0655-0

httpwwwthenanoresearchcom on November 28 2014

copy Tsinghua University Press 2014

Just Accepted

This is a ldquoJust Acceptedrdquo manuscript which has been examined by the peer-review process and has been

accepted for publication A ldquoJust Acceptedrdquo manuscript is published online shortly after its acceptance

which is prior to technical editing and formatting and author proofing Tsinghua University Press (TUP)

provides ldquoJust Acceptedrdquo as an optional and free service which allows authors to make their results available

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in these ldquoJust Acceptedrdquo manuscripts To cite this manuscript please use its Digital Object Identifier (DOIreg)

which is identical for all formats of publication

Nano Research

DOI 101007s12274-014-0655-0

TABLE OF CONTENTS (TOC)

Fe3O4 nanoparticle-decorated TiO2

nanofiber hierarchical heterostructures

with improved lithium-ion battery

performance over a wide temperature

Heng-guo Wang Guang-sheng Wang

Shuang Yuan De-long Ma Yang Li and

Yu Zhang

Beihang University China

Fe3O4 nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures are fabricated

by combining the electrospinning technique with the hydrothermal method and the

resulting materials show improved lithium-ion battery performance over a wide

temperature range due to the synergistic effect of binary composition as well as the

unique feature of the hierarchical nanofibers

Provide the authorsrsquo webside if possible

Author 1 webside 1

Author 2 webside 2

Heng-guo Wang2 Guang-sheng Wang1 Shuang Yuan3 De-long Ma3 Yang Li1 and Yu Zhang1()

Received day month year

Revised day month year

Accepted day month year

(automatically inserted by

the publisher)

copy Tsinghua University Press

and Springer-Verlag Berlin

Heidelberg 2014

KEYWORDS

hierarchical

heterostructures wide

temperature range

Improved performance

lithium-ion batteries

ABSTRACT

A facile strategy was designed for the fabrication of Fe3O4

nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures (FTHs)

through combining the versatility of the electrospinning technique and

hydrothermal growth method Hierarchical architecture of Fe3O4 nanoparticle

decorated on TiO2 nanofiber is designed for the successful integration of binary

components to address the structural stability and low capacity In the resulted

unique architecture of FTHs the 1D heterostructures relieve the strain caused

by severe volume change of Fe3O4 during the numerous charge-discharge

cycles and thus suppress the degradation of the electrode material As a result

FTHs show excellent performance including higher reversible capacity

excellent cycle life and good rate performance at wide temperature range due

to the synergistic effect of binary composition of TiO2 and Fe3O4 as well as the

1 Instruction

In recent years rechargeable lithium-ion batteries

(LIBs) successfully capture the portable electronic

market because they have been considered as an

effective and green electrochemical energy storage

device However graphite the most commonly used

anode material in commercial LIBs have limited

theoretical capacity (372 mAh g-1) due to their

intercalation mechanism which is far from adequate

to meet the upcoming markets of electric

transportation and renewable energies There is a

general consensus that the breakthrough of energy

density necessarily requires passage from classical

intercalation reactions to conversion reactions [1-2]

Nano Research

DOI (automatically inserted by the publisher)

Address correspondence to Yu Zhang email jadebuaaeducn

Review ArticleResearch Article Please choose one

| wwweditorialmanagercomnaredefaultasp

2 Nano Res

However even after decade of intensive efforts the

application of conversion-based materials is still

seriously hampered by the terrible capacity

degradation and poor rate performance Therefore

there is highly desirable to simultaneously improve

cyclic life energy- and power- density of LIBs

Transition metal oxides (TMOs) are very

promising conversion-based anode materials which

exhibit many attractive advantages of low cost

environmental friendliness natural abundance and

especially much higher theoretical capacity (500-1000

mAh g-1) greatly spurring the rapid development of

this field [3-13] However TMOs still suffer from

poor cyclability that is associated with the severe

agglomerations and large volume change during

charge-discharge Alternatively TiO2 has been

investigated intensively because of its robustness in

cycle retention and chemical stability [14-17] The

very low volume change of less than 4 during Li+

insertionextraction intrinsically endows TiO2 the

enhanced structural stability and prolonged cycle life

[18-21] However the low theoretical capacity (168

mAh g-1) and the poor rate capability of TiO2 still

seriously hinder its widespread use in LIBs

Recently various metal oxidesTiO2

nanocomposites especially with one-dimensional

(1D) nanostructures have been suggested to

overcome the demerits of both materials thus

improving the anode performance in LIBs such as

MoO2TiO2 [22] Fe2O3TiO2 [2324] CoOTiO2 [25]

SnO2TiO2 [26-28] Also we have demonstrated the

successful integration of individual components into

the unique nanostructures could endow the

composite electrode materials with the improved LIB

performance [25] On one hand the presence of TiO2

stem can effectively maintain the mechanical

integrity of electrode materials during Li+

insertionextraction ions On the other hand not only

coating with metal oxides overcomes the high cost of

coating with noble metals (Au Ag etc) [2930] but

also the low specific capacity of TiO2 can be

compensated by the electroactive metal oxides with

high capacity However some rare transition metal

oxides are not suitable to be used for electrode

materials in the case of large-scale energy storage

from a viewpoint of the sustainability Fe-based

oxides otherwise are more earth-abundant low cost

and environmental friendliness Among these

Fe-based oxides Fe3O4 features both high capacity

and high electronic conductivity [31-39] thus its

coating on TiO2 nanofibers could be killing three

birds with one stone - the rate performance and

specific capacity of TiO2 nanofibers and the cycle life

of Fe3O4 nanoparticles could be simultaneously

improved by the synergistic effect between Fe3O4 and

TiO2 This inspires us to design Fe3O4TiO2 composite

materials to investigate the synergistic effect of

binary composition and the unique nanostructures

thus preparing anode materials with improved LIB

performance

Herein Fe3O4 nanoparticle-decorated TiO2

nanofiber hierarchical heterostructures (FTHs) were

prepared by combining the electrospinning and the

hydrothermal method TiO2 nanofiber is chosen as

stems to induce the growth of heterostructured Fe3O4

nanoparticle Interestingly the TiO2 stem could

maintain the structural integrity and the sufficient

interspaces between Fe3O4 nanoparticles could

accommodate the volume expansion of Fe3O4 during

chargedischarge process So when FTHs are tested

as anode materials for LIBs it shows excellent

performance including higher reversible capacity

excellent cycle life and good rate performance at

wide temperature range due to the synergistic effect

of binary composition of TiO2 and Fe3O4 as well as

the unique feature of the hierarchical nanofibers

2 Experimental

21 Synthesis of FTHs

The hierarchical Fe3O4TiO2 nanofibers were

synthesized by the electrospinning technique and

hydrothermal method [25] In a typical process

electrospun TiO2 nanofibers (20 mg) were put into

Teflon-lined autoclave (50 mL) with a ethylene glycol

(EG 25 mL) solution consisting of FeCl3middot6H2O (025 g)

polyethylene glycol (PEG 025 g) and sodium

acetate (NaAc 09 g) After the autoclave was sealed

and heated at 200 for 16 h the as-obtained

composite was collected out washed with ethanol

and deionized water respectively and then dried

under vacuum at 50 for 12 h For comparison the

TiO2Fe3O4 nanofibers with few secondary Fe3O4

nanoparticles (FTHfs) were also prepared by adding

FeCl3middot6H2O (005 g) and the free Fe3O4 nanoparticles

were also prepared without the addition of TiO2

wwwtheNanoResearchcom∣wwwSpringercomjournal12274 | Nano Research

3 Nano Res

nanofibers

22 Characterization

Scanning electron microscopy (SEM) images were

collected with a Hitachi S-4800 instrument

Transmission electron microscope (TEM) images

were carried out with a Tecnai G2 using 200 kV X-ray

diffraction (XRD) patterns were carried out with a

Rigaku-Dmax 2500 diffractometer using Cu Kα

radiation X-ray photoelectron spectroscopy (XPS)

analysis was conducted with ESCALAB MK II X-ray

instrument

23 Electrochemical Evaluation

70 wt active materials (FTHs FTHfs TiO2

nanofibers Fe3O4 nanoparticles and TiO2-Fe3O4

mixture) 20 wt acetylene black and 10 wt

polyvinylidene fluoride (PVDF) were mixed in

N-methyl-2-pyrrolidone (NMP) and then uniformly

pasted on copper foil After finally dried in vacuum

at 80 for 12 h to remove the solvent the work

electrodes were pressed and cut into disks Thin

lithium foil was used as the counter electrode

Celgard 2400 membrane was used as separator and

lithium hexafluorophosphate LiPF6 (1 M) in ethylene

carbonatedimethyl carbonate (ECDMC 11 vol )

was employed as the electrolyte Galvanostatic

chargedischarge experiments were conducted in a

voltage range of 001-30 V with a Land Battery

Measurement System (Land China) The cyclic

voltammetry (CV 001-3 V 01 mV s-1) and

electrochemical impedance spectroscopy (EIS 01-700

kHz 5 mV) were conducted using a VMP3

Electrochemical Workstation (Bio-logic Inc)

3 Results and discussion

Scheme 1 illustrates the overall synthesis procedure

employed for the preparation of FTHs which is

briefly composed of the electrospinning and the

hydrothermal method Herein no surface

pretreatments are needed to introduce new surface

functional groups or additional covalent andor

noncovalent interconnectivity As a result perfectly

hierarchical heterostructures were obtained in high

yield The morphology of the prepared samples is

characterized by scanning electron microscopy (SEM)

and transmission electron microscopy (TEM) Fig 1(a)

and 1(b) show SEM images of bare TiO2 nanofibers

and FTHs The bare TiO2 non-woven nanofibers with

average diameter about 220 nm (Fig 1(a) inset) have

a relatively smooth surface The resulting materials

show hierarchical nanostructure and have diameters

of about 250 nm (Fig 1(b) inset) From TEM image in

Fig 1(c) it is obvious that the secondary Fe3O4

nanoparticles grow on the surface of TiO2 nanofibers

From the High-resolution transmission electron

microscopy (HRTEM) image of the heterojunction

region (Fig 1(d)) the observed two set of lattice

fringe spacings of 035 and 0254 nm are consistent

with the (101) plane of the anatase crystal structure of

TiO2 and the (311) plane of the cubic magnetite Fe3O4

respectively From the HRTEM image (Fig 1(e)) of

the nanoparticle it is also concluded that the

secondary Fe3O4 nanoparticles successfully grow on

the surface of the TiO2 nanofibers Furthermore

energy-dispersive X-ray spectroscopy (EDS)

characterization (Fig S1 in the Electronic

Supplementary Material (ESM)) also confirms that

FTHs include Fe Ti and O indicating the presence

of both Fe3O4 and TiO2 And EDS line scanning along

the cross section of FTHs (Fig 1(f)) further shows

that Fe is present only outside the TiO2 nanofibers

but not inside As a result Fe3O4

nanoparticle-decorated TiO2 nanofiber results in the

formation of the hierarchical Fe3O4TiO2 coreshell

nanofibers Moreover the thicknesses of the

secondary Fe3O4 nanoparticles are controllable by

simply changing the experimental parameters (Fig

S2 in the ESM)

The crystallographic structure of the prepared

samples is investigated by powder X-ray diffraction

(XRD) As shown in Fig 2(a) all the diffraction peaks

could be indexed to anatase TiO2 (JCPDS file No

21-1272) and cubic magnetite Fe3O4 (JCPDS file No

19-0629) X-ray photoelectron spectroscopy (XPS)

characterization is further carried out to analyze the

elemental composition As shown in Fig 2(b) the

XPS spectrum of FTHs shows the presence of the

Ti2p O1s and Fe2p peak For the high-resolution

Fe2p (Fig 2(b) inset) it is observed that two peaks of

Fe2p32 and Fe2p12 appear at 711 and 724 eV

respectively which demonstrates the secondary

nanostructures are Fe3O4 Then inductively coupled

plasma atomic emission spectrometry (ICP-AES) is

also carried out to test the actual iron contents in

4 Nano Res

each sample The results show that the iron contents

are 140 and 182 wt in FTHs with few secondary

Fe3O4 nanoparticles (FTHfs) and FTHs respectively

The electrochemical performance of FTHs is

investigated as anode materials for LIBs Fig 3(a)

shows its cyclic voltammetry (CV) curves Two pairs

of redox current peaks can be clearly identified

during the cathodic and anodic scans In the first

cycle two current peaks appear at ~175 and ~21 V

respectively which can be regarded as the signature

of the lithium insertionextraction processes in the

anatase framework In addition the sharp reduction

peak at ~07 V can be ascribed to the conversion of

Fe3O4 to Fe and the formation of amorphous Li2O as

well as their irreversible reaction with the electrolyte

which may lead to the irreversible capacity At the

same time the wide oxidation peak at ~17 V could

be assigned to the reversible oxidation of Fe0 to Fe3+

during the anodic process [3839] For comparison

bare TiO2 nanofibers and Fe3O4 nanoparticles are also

tested The two pairs of well-shaped redox peaks for

TiO2 nanofibers (Fig S3(a) in the ESM) and Fe3O4

nanoparticles (Fig S3(b) in the ESM) are in good

agreement with those for FTHs Note that as

expected there is only a slight decrease in the peak

current during the subsequent cycles for TiO2

nanofibers indicating the highly reversible redox

reactions of TiO2 nanofibers In contrast the peak

current of the redox peaks of Fe3O4 nanoparticles

drops dramatically during the subsequent scans

indicating seriously irreversible reactions have taken

place in the Fe3O4 electrode thus leading to a severe

capacity fading upon charge-discharge cycling

Therefore we anticipate the reinforcement of Fe3O4

nanoparticles by stable TiO2 nanofibers can

effectively alleviate the severe capacity fading

Fig 3(b) shows the discharge-charge curves of

FTHs at 100 mA g-1 Consistent with the above CV

analysis two discharge plateaus at ~175 and 07 V

and two charge plateaus at ~17 and 21 V can be

clearly observed These voltage profiles are

characteristic of both Fe3O4-based and TiO2-based

materials The initial discharge and charge capacities

are found to be 7836 and 4945 mAh g-1 respectively

corresponding to a Coulombic efficiency of 631

Furthermore in the successive cycles the capacity of

the electrode scarcely decays and it can still deliver a

reversible capacity of 4545 mAh g-1 even after 200

cycles (Fig 3(b) and 3(c)) On the contrary the bare

TiO2 nanofibers electrode only exhibits a lower

reversible capacity of 202 mAh g-1 (Fig S4(a) in the

ESM) Although the Fe3O4 nanoparticles exhibits

higher initial discharge capacity of 10634 mAh g-1

(Fig S4(b) in the ESM) it suffers severe capacity

fading (decrease to 1577 mAh g-1 only after 70 cycles)

(Fig S4(c) in the ESM) which is lower than that of

FTHs indicating that the successful integration of

binary TiO2-Fe3O4 components can favourably inherit

the respective advantages from both TiO2 and Fe3O4

individual components Most importantly even at

high current densities the FTHs still exhibits good

cyclic capacity retention and it is able to deliver a

reversible capacity as high as 1878 mAh g-1 even

after 400 cycles at a current density of 1 A g-1 The

reversible capacity is maintained at 1343 mAh g-1

when the current density is increased to 2 A g-1 Even

at the very high current density of 3 A g-1 the

reversible capacity still higher than 1122 mAh g-1

(Fig 3(d)) On the contrary such high current density

results in the very lower reversible capacity of 92

mAh g-1 for bare TiO2 nanofibers (Fig S5(a) in the

ESM) and severe capacity fading (decrease to 128

mAh g-1 only after 50 cycles) (Fig S5(b) in the ESM)

It is obvious that FTHs demonstrate superior cyclic

capacity retention over the bare TiO2 nanofibers and

Fe3O4 nanoparticles counterpart thanks to the

synergistic effect Fig 3(e) shows the rate

performance of FTHs in comparison with that of

bare TiO2 nanofibers and Fe3O4 nanoparticles (Fig S6

in the ESM) At current densities of 02 04 06 2 4

and 6 A g-1 the reversible capacities of FTHs are 4814

3354 2978 1991 995 and 65 mAh g-1 respectively

which are about two times larger than that of bare

TiO2 electrode Most importantly when the current

density is reduced after the back and forth high rate

and 120 cycles measurement a discharge capacity of

3702 mAh g-1 can be recovered On the contrary the

Fe3O4 nanoparticles show bad rate performance

especially at high current density it shows scarcely

no capacity due to the large volume expansion and

severe particle aggregation which results in the

electrode pulverization capacity loss and poor

cycling stability

As a battery delivers high power large heat (the

so-called Joule effect) can be generated during the

chargedischarge process which would heat up the

5 Nano Res

battery thus increasing the battery temperature

[40-42] Meanwhile in view of the changeability of

the ambient temperature it is thus of great

importance to investigate the temperature-dependent

performance of FTHs for practical applications

Measurements are carried out at 0 25 and 50

(Fig 3(e)) Interestingly at high temperature (50 )

FTHs can exhibit much enhanced rate performance

of 605 2691 and 70 mAh g-1 at the current densities

of 200 2000 and 6000 mA g-1 respectively Moreover

the voltage of the discharge plateaus and Coulombic

efficiency increase with the increase of temperature

(Fig S7 in the ESM) This might be attributed to

decrease of the battery resistance and increase of the

ion mobility of the electrolyte at elevated

temperature However at high temperature (50 )

the cycling stability decreases which could be

attributed to the degradation of the

electrodeelectrolyte interface and the decomposition

of the electrolyte promoted by high temperature

[40-42] On the contrary at low temperature (0 )

the cycling stability increases which could be

attributed to the formation of the stable solid

electrolyte interphase (SEI) film promoted by low

temperature In addition at low temperature (0 degC)

the battery can still deliver a high capacity of more

than 320 mAh g-1 at a current density of 200 mA g-1

Such promising results clearly demonstrate that

FTHs electrode is capable of working over a wide

temperature range

hierarchical heterostructures display good

electrochemical performance which could be

attributed to the successful integration of individual

components into the unique nanostructures The

controlled construction of 1D hierarchical structures

is convenient for keeping the effective contact areas

of active materials conductive additives and

electrolyte by preventing the self-aggregation of the

nanomaterials [7] providing more active sites for

lithium ion accesses to ensure a high utilization of

electrode materials and buffering drastic volume

change of the active materials occurring during

cycling Moreover the selection of proper metal

oxides including high capacity and high electronic

conductivity of Fe3O4 as hierarchical heterostructure

and durable electrochemically active TiO2 as stem

takes advantages of the merits of individual

components The enhancement more likely originates

from their synergistic effects instead of the simple

mix of two components which is elaborated as

follows On one hand the enhanced capacity of

hierarchical heterostructure compared with the bare

TiO2 nanofibers can be easily understood by the

addition of a higher capacity component Fe3O4

Additionally the Fe3O4 branches not only boost the

electronic conductivity of FTHs but also increase the

reversible electrochemical reaction of TiO2 with Li To

compare the conductivity of these samples the

electrochemical impedance spectroscopy (EIS)

measurements are carried out and the Nyquist plots

are depicted (Fig 4) All the Nyquist plots show a

semicircular loop at high-to-medium frequencies

and a sloping straight line is observed at low

frequencies The radius of the semicircular loop of

FTHs electrode is much smaller than that of the bare

TiO2 electrode indicating that the incorporation of

Fe3O4 could significantly enhance the conductivity of

FTHs which is vital for improving the

electrochemical performance In addition it is noted

that the electrochemical reaction mechanism of Fe3O4

with Li can be described by Fe3O4 + 8Li+ + 8e-

3Fe0 + 4Li2O As for TiO2 the electrochemical reaction

mechanism with Li can be written as TiO2 + xLi+ + xe-

4LixTiO2 Hence the presence of Fe nanoparticles

at the interface between Fe3O4 and TiO2 may improve

the reaction reversibility of TiO2 with Li and further

result in a higher reversible capacity [43] On the

other hand the synergistic effects endow the

as-prepared electrode material with structural

integrity In order to demonstrate the existence of

synergistic effects we compare the cycling

performance of TiO2Fe3O4 hierarchical

heterostructures with that of TiO2-Fe3O4 physical

mixture in the same proportion with FTHs (Fig 3(f))

Obviously the TiO2Fe3O4 nanofibers with few

secondary Fe3O4 nanoparticles (FTHfs) could inherit

the good cycling performance of TiO2 and also show

the increased capacity compared with bare TiO2

nanofibers With the increase of secondary Fe3O4

nanoparticles FTHs show the more increased

performance On the contrary although the

TiO2-Fe3O4 physical mixture electrode exhibits higher

initial discharge capacity it suffers severe capacity

fading These results clearly demonstrate Fe3O4

nanoparticle-decorated TiO2 nanofiber hierarchical

6 Nano Res

heterostructures could result in the synergistic effects

which play very important role in keeping the

structural integrity thus enhancing the cycling

performance To confirm the structural integrity of

FTHs electrode we observed the morphology of

FTHs after charge-discharge cycles using SEM and

TEM After cycling FTHs still maintained their

hierarchical heterostructures without any mechanical

degradation coinciding with the original

morphology (Fig S8(a) and inset in the ESM) Herein

the reason can be the following the 1D hierarchical

heterostructures may relieve the strain caused by

severe volume change of Fe3O4 during the numerous

charge-discharge cycles and thus suppress the

degradation of the electrode material as

schematically demonstrated in Fig 5(a) In contrast

TiO2-Fe3O4 physical mixture could not buffer the

large volume expansion (Fig S8(b) in the ESM) and

part of Fe3O4 nanoparticles were disintegrated into

nanoparticles (Fig S9 in the ESM) during Li+

insertionextraction resulted from the large volume

expansion of Fe3O4 as schematically demonstrated in

Fig 5(b) These observations corroborate that

hierarchical heterostructures are very effective for

accommodating the large volume expansion of Fe3O4

nanoparticles and improving cycle life

4 Conclusions

In summary we fabricated Fe3O4

heterostructures by a facile effective and scalable

method Interestingly the electrochemical results

clearly demonstrated that the advantageous

integration of TiO2 and Fe3O4 into 1D hierarchical

nanostructure can foster strengths and circumvent

weaknesses of individual components and thus

simultaneously exerts higher reversible capacity

excellent cyclability and good rate performance

which would open up new idea in the combination

of the merits of individual components to develop

high performance electrode materials for LIBs The

proposed synthesis strategy can be easily extended to

prepare other composite metal oxide materials

which can be used in broad fields including

electrochemical capacitors and sensors

Acknowledgements

This work is financially supported by the

fundamental research funds for the central

universities the National Natural Science

Foundation of China (Grant No 51372007 and

21301014)

Electronic Supplementary Material Supplementary

material (EDS spectrum of FTHs SEM images of

FTHfs CVs charge-discharge curves cycling

performance and rate performance of TiO2

nanofibers and Fe3O4 nanoparticles) is available in

the online version of this article at

httpdxdoiorg101007s12274---

(automatically inserted by the publisher) References

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C Paik U SnO2 encapsulated TiO2 hollow nanofibers as

anode material for lithium ion batteries Electrochem

Commun 2012 22 81-84

[28] Jeun J-H Park K-Y Kim D-H Kim W-S Kim

H-C Lee B-S Kim H Yu W-R Kang K Hong

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battery anode with excellent high rate cyclability

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[29] Nam S H Shim H S Kim Y S Dar M A Kim J G

Kim W B Ag or Au nanoparticle-embedded

one-dimensional composite TiO2 nanofibers prepared via

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[30] He B L Dong B Li H L Preparation and

electrochemical properties of Ag-modified TiO2 nanotube

anode material for lithium-ion battery Electrochem

Commun 2007 9 425-430

[31] Taberna P L Mitra S Poizot P Simon P Tarascon J

M High rate capabilities Fe3O4-based Cu

nano-architectured electrodes for lithium-ion battery

applications Nat Mater 2006 5 567-573

[32] Zhang W M Wu X L Hu J S Guo Y G Wan L J

Carbon coated Fe3O4 nanospindles as a superior anode

material for lithium-ion batteries Adv Funct Mater 2008

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[33] Zhu T Chen J S Lou X W Glucose-assisted one-pot

synthesis of FeOOH nanorods and their transformation to

Fe3O4carbon nanorods for application in lithium ion

batteries J Phys Chem C 2011 115 9814-9820

[34] Wu Y Wei Y Wang J P Jiang K L Fan S S

Conformal Fe3O4 sheath on aligned carbon nanotube

scaffolds as high-performance anodes for lithium ion

batteries Nano Lett 2013 13 818-823

[35] Lv P P Zhao H L Zeng Z P Wang J Zhang T H

Li X W Facile preparation and electrochemical properties

of carbon coated Fe3O4 as anode material for lithium-ion

batteries J Power Sources 2014 259 92-97

[36] Ito S Nakaoko K Kawamura M Ui K Fujimoto K

Koura N Lithium battery having a large capacity using

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electrochemical characterization versus lithium of Fe3O4

electrodes made by electrodeposition Adv Funct Mater

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core-shell nanorods as anode materials for lithium-ion

batteries Electrochem Commun 2008 10 1879-1882

[39] Zhou G Wang D W Li F Zhang L Li N Wu Z S

Wen L Lu G Q Cheng H M Graphene-wrapped Fe3O4

8 Nano Res

anode material with improved reversible capacity and

cyclic stability for lithium ion batteries Chem Mater 2010

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effects on temperature-dependent performance of LiCoO2

in lithium batteries J Power Sources 2006 158

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of temperature on the capacitance of carbon nanotube

supercapacitors ACS Nano 2009 3 2199-2206

[42] Yan J Sumboja A Khoo E Lee P S V2O5 loaded on

SnO2 nanowires for high-rate Li ion batteries Adv Mater

2011 23 746-750

[43] Zhou W W Cheng C W Liu J P Tay Y Y Jiang J

Jia X T Zhang J X Gong H Hng H H Yu T Fan

H J Epitaxial growth of branched α-Fe2O3SnO2

nano-heterostructures with improved lithium-ion battery

performance Adv Funct Mater 2011 21 2439-2445

9 Nano Res

Figure 1 Morphology characterization Low- and high-

resolution (inset) SEM images of (a) bare TiO2 nanofibers and (b)

FTHs (c) Typical TEM image of the single FTH (d) HRTEM

image of the heterojunction region (e) HRTEM image of the

surface nanoparticle (f) TEM image and line-scanning (indicated

by a line) elemental mapping along the cross section

Figure 2 Phase analysis (a) XRD patterns of bare TiO2

nanofibers and FTHs (b) Survey XPS spectrum and

high-resolution Fe2p spectra of FTHs (inset)

Figure 3 Electrochemical properties (a) CVs of FTHs at a scan

rate of 01 mV s-1 in the range of 3-001 V (b) Discharge and

charge curves of FTHs at 100 mA g-1 (c) Cycling performance of

bare TiO2 nanofibers and FTHs at 100 mA g-1 (d) Rate

performance of bare TiO2 nanofibers and FTHs obtained at 25

(e) Rate performance of FTHs obtained at 0 25 and 50 at

different current densities (f) Cycling performance of bare TiO2

nanofibers FTHfs FTHs and TiO2-Fe3O4 physical mixture at 100

mA g-1

Figure 4 Electrochemical impedance spectra Nyquist plots

before cycling for bare TiO2 nanofibers Fe3O4 nanoparticles and

FTHs by applying an AC voltage of 5 mV amplitude at 01 to 700

10 Nano Res

Figure 5 Scheme of the proposed mechanism Schematics of the

electrochemical process in various configuration electrodes (a)

FTHs and (b) TiO2-Fe3O4 physical mixture

Scheme 1 Schematic diagram showing the strategy for

preparation of the FTHs

Nano Res

Electronic Supplementary Material

Supporting information to DOI 101007s12274--- (automatically inserted by the publisher)

Experimental Section

Materials

Poly(vinyl pyrrolidone) (PVP Mw = 1 300 000 Aldrich) acetic acid (AR Aladdin Reagent) ethanol (AR

Aladdin Reagent) titanium butyloxide (CP Aladdin Reagent) FeCl3middot6H2O (AR Aladdin Reagent) polyethylene

glycol (PEG AR Aladdin Reagent) sodium acetate (NaAc AR Aladdin Reagent) ethylene glycol (EG AR

Aladdin Reagent) N-methylpyrrolidone (NMP Aladdin Reagent AR) acetone (AR Shanghai Chemicals

China) acetylene black (Hong-xin Chemical Works) polyvinylidenefluoride (PVDF DuPont Company 999)

Separator (polypropylene film Celgard 2400) Electrolyte for lithium ion batteries (1 M LiPF6 in ethylene

carbonate (EC)dimethyl carbonate (DMC) with the weight ratio of 11 Zhangjiagang Guotai-Huarong New

Chemical Materials Co Ltd All the reagents used in the experiment were of analytical grade purity and were

used as received De-ionized water with the specific resistance of 182 MΩcm was obtained by reversed

osmosis followed by ion-exchange and filtration

Nano Res

Figure S1 Energy-dispersive X-ray spectroscopy (EDS) spectrum of FTHs on TEM girds

Figure S2 (a) Low- and (b) high- resolution SEM images of the few secondary Fe3O4 nanoparticle-decorated TiO2 nanofiber

hierarchical heterostructures For comparison the TiO2Fe3O4 nanofibers with few secondary Fe3O4 nanoparticles (FTHfs) were also

prepared under the same condition instead of the addition of FeCl3middot6H2O (005 g)

Nano Res

Figure S3 CVs of bare TiO2 nanofibers (a) and Fe3O4 nanoparticles (b) at a scan rate of 01 mV s-1 in the range of 3-001 V

Figure S4 Discharge and charge curves of bare TiO2 nanofibers (a) and Fe3O4 nanoparticles (b) at 100 mA g-1 (c) Cycling performance

of Fe3O4 nanoparticles at 100 mA g-1

Nano Res

Figure S5 Cycling performance of FTHs (a) bare TiO2 nanofibers (b) and Fe3O4 nanoparticles (c) at various current densities of 1 2

and 3 A g-1

Figure S6 Rate performance of Fe3O4 nanoparticles at various current densities

Nano Res

Figure S7 Discharge and charge curves of FTHs at a current density of 200 mA g-1 obtained at 0 (a) 25 (b) and 50 (c) (d) The

discharge curves of FTHs electrode tested at a current density of 200 mA g-1 at different temperatures

Figure S8 (a) SEM and (inset) TEM images of FTHs electrode after 20 cycles at 100 mA g-1 (b) SEM images of TiO2-Fe3O4 physical

mixture electrode after 20 cycles at 100 mA g-1

Nano Res

Figure S9 (a) Low- and (b) high- resolution SEM images of Fe3O4 nanoparticles before cycling (c) Low- and (d) high- resolution SEM

images of Fe3O4 nanoparticles after 60 cycles at 100 mA g-1

Manuscript

TABLE OF CONTENTS (TOC)

Fe3O4 nanoparticle-decorated TiO2

nanofiber hierarchical heterostructures

with improved lithium-ion battery

performance over a wide temperature

Heng-guo Wang Guang-sheng Wang

Shuang Yuan De-long Ma Yang Li and

Yu Zhang

Beihang University China

Fe3O4 nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures are fabricated

by combining the electrospinning technique with the hydrothermal method and the

resulting materials show improved lithium-ion battery performance over a wide

temperature range due to the synergistic effect of binary composition as well as the

Provide the authorsrsquo webside if possible

Author 1 webside 1

Author 2 webside 2

the publisher)

Heidelberg 2014

KEYWORDS

hierarchical

temperature range

ABSTRACT

1 Instruction

Nano Research

2 Nano Res

performance

2 Experimental

3 Nano Res

nanofibers

22 Characterization

instrument

S2 in the ESM)

4 Nano Res

cycling stability

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

the publisher)

Heidelberg 2014

KEYWORDS

hierarchical

temperature range

ABSTRACT

1 Instruction

Nano Research

2 Nano Res

performance

2 Experimental

3 Nano Res

nanofibers

22 Characterization

instrument

S2 in the ESM)

4 Nano Res

cycling stability

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

2 Nano Res

performance

2 Experimental

3 Nano Res

nanofibers

22 Characterization

instrument

S2 in the ESM)

4 Nano Res

cycling stability

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

3 Nano Res

nanofibers

22 Characterization

instrument

S2 in the ESM)

4 Nano Res

cycling stability

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

4 Nano Res

cycling stability

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

5 Nano Res

temperature range

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

6 Nano Res

4 Conclusions

Acknowledgements

21301014)

Nature 2000 407 496-499

2005 17 582-586

2009 42713-723

Chem Soc 2011 133 17146-17148

Nano Lett 2010 10 4750-4755

Phys 2011 13 16735-16740

4215-4220

2013 23 4345-4353

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

7 Nano Res

Environ Sci 2012 5 5604-5618

6417-6420

2014 27 632-637

2006 18 1421-1426

101021nl503378a

Chem Rev 2007 107 2891-2959

212-220

2 3912-3918

5 6559-6566

1834-1840

Commun 2012 22 81-84

Nanoscale 2013 5 8480-8483

Commun 2007 9 425-430

18 3941-3946

319-322

2006 16 2281-2287

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

8 Nano Res

22 5306-5313

1419-1424

2011 23 746-750

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

9 Nano Res

mA g-1

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

10 Nano Res

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

Nano Res

Materials

Nano Res

and 3 A g-1

Nano Res

Manuscript

Nano Res

and 3 A g-1

Nano Res

Manuscript

Nano Res

and 3 A g-1

Nano Res

Manuscript

Nano Res

and 3 A g-1

Nano Res

Manuscript

Nano Res

Manuscript

Nano Res

Manuscript

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Fe O nanoparticle-decorated TiO2 nanofiber ... - Nano Research · nanofiber hierarchical heterostructures with improved lithium-ion battery performance over a wide temperature range