Solvent Effect of Room Temperature Ionic Liquids on Electrochemical Reactions in Lithium鈥揝ulfur Batteries

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• 作者：Jun-Woo Park ; Kento Yamauchi ; Eriko Takashima ; Naoki Tachikawa ; Kazuhide Ueno ; Kaoru Dokko ; Masayoshi Watanabe
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 7, 2013
• 年：2013
• 卷：117
• 期：9
• 页码：4431-4440
• 全文大小：530K
• 年卷期：v.117,no.9(March 7, 2013)
• ISSN：1932-7455

文摘

A room temperature ionic liquid (RTIL), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)amide ([DEME][TFSA]), was used as an electrolyte solvent for lithium鈥搒ulfur (Li鈥揝) batteries. Li[TFSA] was dissolved into [DEME][TFSA] to prepare the electrolytes, and a molecular solvent鈥攖etraethylene glycol dimethyl ether (TEGDME)鈥攚as used for Li[TFSA] as a reference. Discharge鈥揷harge tests of Li鈥揝 cells using these electrolytes were carried out. The discharge鈥揷harge cycle stability and Coulombic efficiency of a cell with an RTIL electrolyte were found to be surprisingly superior to those of a cell with TEGDME electrolyte. The poor cycle stability of the cell with the TEGDME electrolyte was attributed to the dissolution of lithium polysulfides (Li₂S_m), which were generated as reaction intermediates through a redox process at the S cathode in the Li鈥揝 cell. RTIL has low donor ability owing to the weak Lewis basicity of [TFSA]^{鈭?/sup> anion, whereas conventional ether-based molecular solvents such as TEGDME have high donor ability. The dissolution of Li₂S_m was significantly suppressed owing to the weak donor ability of RTIL. In the RTIL electrolyte, Li₂S_m was immobilized on the electrode, and the electrochemical reaction of the S species occurred exclusively in the solid phase. These results clearly prove a novel solvent effect of RTILs on the electrochemical reactions of the S cathode in Li鈥揝 cells.}