Journal
ELECTROCHIMICA ACTA
Volume 353, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2020.136559
Keywords
Solvate ionic liquid; Si electrode; Fluoroethylene carbonate; Solid electrolyte interphase
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Funding
- JSPS KAKENHI [15H05758, 16H06053]
- JST ALCA-SPRING, Japan [JPMJAL1301]
- Grants-in-Aid for Scientific Research [16H06053] Funding Source: KAKEN
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The design of battery electrolytes with superior transport, thermal, and electrochemical properties is a key consideration in the development of high-energy-density batteries. To this end, an equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4) is of interest because it forms a thermally and electrochemically stable solvate ionic liquid (SIL), [Li(G4)][TFSA]. In this study, fluoroethylene carbonate (FEC) was added to [Li(G4)][TFSA] in an attempt to improve transport properties of the SIL and to modify the chemical composition of the solid electrolyte interphase (SEI) formed on Si electrodes. The addition of FEC had a negligible impact on the Li ion coordination structure in [Li(G4)][TFSA] while enhancing its ionic conductivity nearly twofold. The Si electrode in [Li(G4)][TFSA] with the FEC additive showed a stable and reversible capacity in long-term cycling with high Coulombic efficiency. X-ray photoelectron spectroscopy revealed that the chemical composition of the SEI formed in [Li(G4)][TFSA] with the FEC additive was significantly different from that in the electrolyte without FEC. The FEC-addition-derived SEI most likely consists of carbonates and LiF, retarding electrolyte decomposition and, thus, improving the electrochemical performance of the Si electrode therein. (c) 2020 Elsevier Ltd. All rights reserved.
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