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Understanding ionic structure and dynamics in novel electrolytes ; Paving the way to improved energy storage.
Maria Forsyth
Typical electrolyte materials for electrochemical devices
• Batteries• Solar Cells• Fuel Cells• Actuators• Capacitors• Sensors
• Solvent based electrolytes.• Ionic Liquids• Gels and Polymer Electrolytes• Ceramic Conductors eg Li3N.• Plastic crystal fast-ion
conductors.
Electrolyte Families Devices
How to optimise electrolytes for target device?• Need to characterise ion transport and its relationship to structure / speciation – NMR perfect tool • Use Chemical shift, wide line, relaxation measurements, diffusion, imaging…multinuclear, variable temperature
Dr.Luke O’DellDeakin NMR Facility Co-director
NMR imaging of Zn/air battery
AnodeZn + 4OH- Zn(OH)4
-2 + 2e-
CathodeO2 + 2H2O + 4e- 4OH-
??
~1 M OH- conc.
~5 M OH- conc.
~10 M OH- conc.
+ =
Ti mesh Zn ribbon High pH KOH(aq)
Collaboration with Dr. Melanie Britton, Uni. Birmingham
- METAL/AIR BATTERIES- FLOW BATTERIES
ACES (I) PROJECTS• Zinc• Magnesium• Air electrodes for energy generation and storage
ACES (II) PROJECTS• Zinc Flow batteries• Reversible Metal Air batteries• Microfluidics and batteries for soft robotics
J. Sunarso, A. A. J. Torriero, W. Zhou, P. C. Howlett and M. Forsyth, Journal of Physical Chemistry C, 2012,
116, 5827-5834.
T. Khoo, P. C. Howlett, M. Tsagouria, D. R. MacFarlane and M. Forsyth, Electrochimica Acta, 2011, 58,
583-588.
T. J. Simons, A. A. J. Torriero, P. C. Howlett, D. R. MacFarlane and M. Forsyth, Electrochemistry
Communications, 2012, 18, 119-122.
Reversible Air cathode catalysisProton ConductorsElectrode 3D structuring
Approaches to Zn2+ IL based electrolytes
NTf2
Inclusion of Oxygen Decreases Viscosity
Decrease likelihood of Metal-AnionComplexation i.e. -
Zn2+ + 4[A-] [Zn(A)4]2-
Ether oxygen coordination Positively charged Zinc Complexes
Mega Kar, D.R. MacFarlane, B.J. Winther-Jensen and M. Forsyth PCCP 2013Mega Kar, etal PCCP (submitted)
Mega Kar
Metal deposition/cycling from ILsNovel ILs for Zn2+ Complexation – the affect of the cation
Mega Kar
4
• Novel ILs with ether containing cations, designed to chelate Zn2+.
• When paired with NTf2 anion, Zn2+ can be deposited and stripped.
• Increase in ether oxygen leads to more negative Zn2+ reduction current, suggesting stronger chelation.
M.Kar etal PCCP (2013)
8
Effect of Anions on Zn2+ Voltammetry
Zn(dca)2 displays:
• Lower OPD
• High Current Density
• High Solubility
Scan Rate – 100 mVs-1
WE – 1 mm GCCE – Pt wireRE – 100 mM AgOTf in [emim][dca]Contains 3 wt% H2O
T.J. Simons, A.A.J. Torriero, P.C. Howlett, D.R. MacFarlane, M. Forsyth, Electrochem. Commun., 18 (2012) 119-122.
Tristan Simons
Effect of Cation on Zn plating/stripping - pyrrolidinum vs immidazolium
T. J.Simons, D.R. MacFarlane, M. Forsyth & P.C.Howlett, ChemElectroChem, 2014.
Modelling the Electrode/Electrolyte interface to understand
electrochemical behaviour
Confidential 10Early results suggest layering is preferred for pyrrolidinum cation at
Carbon electrode corresponding to poorer echem for Zn2+ Zn
Erlendur Jonsson
O2 Redox chemistry - Phosphonium based IL/water
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
Cur
rent
den
sity
/ m
A c
m-2
1.5 % wt. water 4.5 % wt. water
Potential / V vs Ag/Ag+
-1.50 -1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
Cur
rent
den
sity
/ m
A cm
-2
Potential / V vs. Ag/Ag+
Reversible O2/ O2●- process in
the presence of high quantities of water due to ion paring interactions
Improved performance toward the ORR upon addition of water
Cristina Pozo-Gonzalo et al. The Journal of Physical Chemistry Letters, 2013, 1834-1837.
O2/ O2●-
1.5 wt% H2O
P
C6H13C6H13C6H13
C14H29
Cl+Dr. Cristina Pozo-
Gonzalo
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
-0.3
-0.2
-0.1
0.0
0.1
0.2
Curr
ent d
ensi
ty /
mA
cm
-2
Potential / V vs Ag/Ag+
c)
N2-saturated
O1
R1
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
Potential / V vs Ag/Ag+
Curr
ent d
ensi
ty /
mA
cm
-2
b)
N2-saturated
O1
R1
Role of anion on reversibility of the 1 e- process
P
C6H13C6H13C6H13
C14H29
anion+
Anion: Cl, TFSI, dca-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
-0.2
-0.1
0.0
0.1
Cur
rent
den
sity
/ m
A c
m-2
Potential / V vs Ag/Ag+
N2-saturated
a)
R1
O1
[P66614]Cl
[P66614][TFSI][P66614]dca
• Kinetics
• Current density
Cristina Pozo-Gonzalo et al. The Journal of Physical C, 2014
N
N N
N-SS
CF3F3C
OO O
O
Other energy storage technologies under investigation include – Lithium, Sodium, Magnesium and Supercaps.
Fast Charge/Discharge of Li Metal Batteries Using An Ionic Liquid Electrolyte
S S
N-propyl-N-methylpyrrolidinium (C3mpyr+) Bis(fluorosulfonyl)imide (FSI)
H Yoon, PC Howlett, AS Best, M Forsyth, DR MacFarlane, Journal of The Electrochemical Society 160 (10), A1629-A1637
Dr Hyun (Martin) Yoon
Typical IL electrolyte for a Li cell
Much higher Li content- Equimolar mixture of salts
0 20 40 60 80 100 120 140
3.95
4.00
4.05
4.10
4.15
4.204.2V constant current (CC) charging cut off
4C, 5C, FSI only
3C
2C
Vo
lta
ge
(V
)
Capacity (mAh.g-1)
1C
Phosphonium FSI ILs – Fluid and High Electrochemical Stability in ‘mixed salts’
Gaetan Girard
Trimethyl isobutyl phosphonium bis(fluorosulfonyl)imide
3.2 mol/kg LiFSI
High stability and cycling efficiency even at 4.3V
Li cycled at eq. 0.5C x 50 cycles (0.5 Ccm-2)
3.8 molkg-1 LiFSI
Deposition morphology improved at high LiFSI
Advanced Characterisation of the interface-In collaboration with Nante University - Director IMN, Prof. D. Guyomard
And Cambridge Uni ( NMR) - Dr. P. Bayley)
Sodium Batteries – cheaper alternatives to Li- Need low temperature electrolytese.g. IL electrolytes, Na Ionomers (polymers)
In collaboration with Prof. Michel Armand and Teofilo Rojo, CIC Energinieu, Spain
Na+
ARC DP grant
S S
N-propyl-N-methylpyrrolidinium (C3mpyr+) Bis(fluorosulfonyl)imide (FSI)
50 mol% or 3.24 mol.kg-1
W: Ni, C: Ag, R: 10 mmol.kg-1 AgNTf2 in C4mpyrNTf2, 20 mV.s-1
25 oC 50 oC
75 oC 100 oC-4 -3 -2 -1 0
-12
-6
0
I (m
A.c
m-2)
E (V vs. Ag | AgNTf2)
1st 2nd 3rd 4th 5th
-4 -3 -2 -1 0-40
-30
-20
-10
0
10
I (m
A.c
m-2)
E (V vs. Ag | AgNTf2)
1st 2nd 3rd 4th 5th
-4 -3 -2 -1 0-10
-5
0
5
I (m
A.c
m-2)
E (V vs. Ag | AgNTf2)
1st 2nd 3rd 4th 5th
-4 -3 -2 -1 0-40
-30
-20
-10
0
10
20
30
I (m
A.c
m-2)
E (V vs. Ag | AgNTf2)
1st 2nd 3rd 4th 5th
Eg. Mixed NaFSI/Ionic Liquid electrolytes
Na | Na symmetric cells show improved stability with highest NaFSI in C3mpyrFSI
Highest NaFSI concentration gives BEST cycling performance M.Forsyth , P. Howlett, M.Yoon, M.Hilder D.Macfarlane, M.Armand Prov. Patent submitted (2015)
0.57 mol/kg (15 mol%) NaFSI 2.16 mol/kg (40 mol%) NaFSI
3.24 mol/kg (50 mol%) NaFSI
Interfacial resistance significantly decreased with highest NaFSI
0 5000 10000 15000
0
5000
10000
15000 0.17 mol.kg-1
0.36 mol.kg-1
0.57 mol.kg-1
0.81 mol.kg-1
1.08 mol.kg-1
1.39 mol.kg-1
2.16 mol.kg-1
3.24 mol.kg-1
-Z'' (
)
Z' ()
0 1000 2000 3000
0
1000
2000
3000 0.17 mol.kg-1
0.36 mol.kg-1
0.57 mol.kg-1
0.81 mol.kg-1
1.08 mol.kg-1
1.39 mol.kg-1
2.16 mol.kg-1
3.24 mol.kg-1
-Z'' (
)
Z' ()
GEIS 10 uA, 100 KHz – 300mHz, R.T.
R1 R2
CPE1
R3
CPE2
Element Freedom Value Error Error %R1 Fixed(X) 0 N/A N/AR2 Fixed(X) 0 N/A N/ACPE1-T Fixed(X) 0 N/A N/ACPE1-P Fixed(X) 1 N/A N/AR3 Fixed(X) 0 N/A N/ACPE2-T Fixed(X) 0 N/A N/ACPE2-P Fixed(X) 1 N/A N/A
Data File:Circuit Model File:Mode: Run Simulation / Freq. Range (0.001 - 1000000)Maximum Iterations: 100Optimization Iterations: 0Type of Fitting: ComplexType of Weighting: Calc-Modulus
Dot points : real data, Line: fitting data with the model
Can we understand this concentration phenomenon?
What is the effect of ion speciation?
What is the effect on electrochemistry, SEI?
[Na][TFSI]3-2 , CN=5-6 [Na][FSI]4
-3 , CN=4 [Na][FSI]5-4 , CN=5
Summary• Electrolyte chemistry crucial for optimised
electrochemical performance (rate and stability) of energy storage devices
• Ionic liquids can be designed for different battery systems– Imidazolium Dicyanamide seems optimal for Zn cycling– FSI or TFSI preferred for Li and Na – Phosphonium gives enhanced echem stability– Mixed IL/inorganic salts have been discovered to give best
Na performance
• Using simulations and NMR to understand behaviors
Acknowledgements – ARC, ACES and DU for funding, Deakin and Monash research teams.
PLASTIC CRYSTALS
31P
19F
31P
1H
NMR perfect tool
NMR SPRITE Imaging of Plastic Crystal Electrolyte- Effect of cooling rate
Slow Cool leads to oriented domains and higher ionic diffusion higher conductivity
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