Li/LiCoO2 Cell Performance Using Ionic Liquids Composed of N,N-Diethyl-N-methyl-N-(2-methoxyethyl)ammonium - Effect of Anionic Structure

Abstract

TTo elucidate the reason why a rate performance of a Li/LiCoO2 cell with the use of FSA ([(FSO2)2N]−)-ILs gave best results compare with the other ILs, we investigated anionic structure dependence of thermal properties, viscosity, conductivity, electrochemical windows. Furthermore, an effect of Li salt addition on viscosity a Li+ and an apparent charge transfer resistance (RCT) of a Li anode and a LiCoO2 composite cathode in ILs were also investigated. For this purpose, we selected N122.1O2+ (N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium) as a counter cation since the cation forms ILs with various anions such as BF4−, CF3BF3−,C2F5BF3−, C0C0− (FSA−), C1C1− (TFSA−), TSAC−, C2C2− (BETA−), PF6−, and FAP−. As a results, the good performance observed in FSA-ILs was attributed to the no significant increase of the viscosity with the addition of a Li salt and the lowest RCT on the LiCoO2.