Effect of Nucleophilic Lithium Trimethylsiloxide on Chemical and Electrochemical Aspects of Electrophilic Carbonate-based Solvents for Lithium-ion Batteries

摘要

Although inorganic functional additives have received much attention in lithium-ion batteries, the underlying chemical reactivity of inorganic additives is not well understood. In this study, we perform a systematical analysis to verify the chemical reactivity between carbonate-based solvents and a lithium trimethylsiloxide (LiOTMS) that has a high nucleophilic characteristic in molecular structures. The ex situNMR and GC-MS analyses for electrolyte mixtures indicate that the electrophilic carbonate-based solvents are easily decomposed by chemical reactions initiated by nucleophilic substitution or addition of LiOTMS and the estimated reaction pathway is clarified based on spectroscopic evidence. In addition, it is confirmed that chemically decomposed adducts are further decomposed on electrode surface by the electrochemical reaction in the charging process, leading to serious fading of the cell. These results indicate that the nucleophilicity of the inorganic additive is a significant criterion in determining its availability in the cell.