Anti-cognition in lithium-ion battery electrolytes: Comparable performance with degraded electrolyte

Abstract

The stability of electrolytes is extremely important for the lithium-ion battery industry. However, research on electrolyte stability is lacking. Many film-forming additives are investigated to improve the interface stability of the cathode and electrolyte. However, many additives are unstable even in ambient environments, which results in additional costs in electrolyte cryogenic transportation and storage. Herein, we conduct in-depth research on the performance of high-voltage batteries influenced by the stability additives containing electrolytes. The capacity retention is only 44% and 20% after 150 cycles using standard (STD) electrolyte in LiNi0.5Mn1.5O4/Li and xLi2MnO3·(1-x) LiMO2/Li batteries, respectively. Film-forming additives usually promote the cycling performance of batteries. Surprisingly, after storage for 30 days, the batteries with yellowing electrolyte show better cycling performances. The LiNi0.5Mn1.5O4/Li and xLi2MnO3·(1-x) LiMO2/Li batteries achieve 92% and 75% capacity retention with a coulombic efficiency of 99.2% and 99.1% after 150 cycles, respectively, which performs better than fresh electrolyte. Following measurements indicate that the additive decomposition product can contribute to the formation of surface films, which inhibits continuous decomposition of the electrolyte and impedes pulverization of the cathode electrode. This work counters current conceptions of degraded electrolyte and is informative for the industrial applications of unstable additive-containing electrolytes.