EMITFSI - an ionic liquid electrolyte for lithium batteries
EMITFSI - an ionic liquid electrolyte for lithium batteries
The ionic liquid, 1-ethyl-3-methylimidazolium bis- (trifluoromethylsulfonyl)-imide (EMITFSI) was studied as an electrolyte for rechargeable lithium batteries. This work focused on two main topics: cathodic stability and lithium ion transport.
Addition of LiTFSI to EMITFSI resulted in a decrease in the conductivity (e.g. from 10.5 to 5.6 mS cm-1 for 0.47 mol dm-3) and the lithium ion diffusion coefficient was found to be 1.2 x 10-7 cm2 s-1 for 0.47 mol dm-3 added Li salt. The transference number for lithium ions in LiTFSI/EMITFSI was found to be proportional to the concentration of the lithium salt. The measured value of 0.04 for 0.47 mol dm-3 is significantly higher than that of LiBF4/EMIBF4 at the same concentration and temperature. This may be explained with two factors; the differences in size and dissociation level of the anions.
The charge/discharge rate performance of LiFePO4 carbon composite electrodes with various thicknesses in different concentrations of LiTFSI/EMITFSI electrolytes was studied using 3-electrode cells. At fast charge or discharge rates, discharge capacities were approximately inversely proportional to C-rate. Differences in rate performance were found between charge and discharge and for different concentration of lithium salt in the ionic liquid. Two models are proposed to explain above phenomena; a transmission circuit to represent electrolyte resistance, and a salt depletion model simplified by the assumption of a compact discharge front.
An optimised cell was designed and constructed according to the above findings, using a 14 μm LiFePO4 positive electrode, 0.47 mol dm-3 LiTFSI/EMITFSI and a lithium negative electrode. The cell gave a discharge capacity of more than 100 mAh g-1 over 850 cycles.
University of Southampton
Wakizaka, Yasuaki
a2fcf618-ec3b-4fdf-95ff-5fcefd8f3549
2007
Wakizaka, Yasuaki
a2fcf618-ec3b-4fdf-95ff-5fcefd8f3549
Wakizaka, Yasuaki
(2007)
EMITFSI - an ionic liquid electrolyte for lithium batteries.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The ionic liquid, 1-ethyl-3-methylimidazolium bis- (trifluoromethylsulfonyl)-imide (EMITFSI) was studied as an electrolyte for rechargeable lithium batteries. This work focused on two main topics: cathodic stability and lithium ion transport.
Addition of LiTFSI to EMITFSI resulted in a decrease in the conductivity (e.g. from 10.5 to 5.6 mS cm-1 for 0.47 mol dm-3) and the lithium ion diffusion coefficient was found to be 1.2 x 10-7 cm2 s-1 for 0.47 mol dm-3 added Li salt. The transference number for lithium ions in LiTFSI/EMITFSI was found to be proportional to the concentration of the lithium salt. The measured value of 0.04 for 0.47 mol dm-3 is significantly higher than that of LiBF4/EMIBF4 at the same concentration and temperature. This may be explained with two factors; the differences in size and dissociation level of the anions.
The charge/discharge rate performance of LiFePO4 carbon composite electrodes with various thicknesses in different concentrations of LiTFSI/EMITFSI electrolytes was studied using 3-electrode cells. At fast charge or discharge rates, discharge capacities were approximately inversely proportional to C-rate. Differences in rate performance were found between charge and discharge and for different concentration of lithium salt in the ionic liquid. Two models are proposed to explain above phenomena; a transmission circuit to represent electrolyte resistance, and a salt depletion model simplified by the assumption of a compact discharge front.
An optimised cell was designed and constructed according to the above findings, using a 14 μm LiFePO4 positive electrode, 0.47 mol dm-3 LiTFSI/EMITFSI and a lithium negative electrode. The cell gave a discharge capacity of more than 100 mAh g-1 over 850 cycles.
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Published date: 2007
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Local EPrints ID: 466452
URI: http://eprints.soton.ac.uk/id/eprint/466452
PURE UUID: 44c1ccbe-2c7e-4c81-95d3-5ef2aa09cbc0
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Date deposited: 05 Jul 2022 05:17
Last modified: 16 Mar 2024 20:42
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Author:
Yasuaki Wakizaka
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