The insight of micro-short circuits caused by electrochemo-mechanical stress crosstalk in all-solid-state Li metal batteries

Abstract

Puzzling micro-short circuit behaviors have been widely observed when utilizing Li metal anodes (LMAs) in all-solid-state batteries (ASSBs). Previous studies on Li/Li symmetrical cells have revealed a failure mechanism involving mechanical damage of solid-state electrolytes (SSEs). However, a comprehensive investigation of stress crosstalk between electrodes and their effect on micro-short circuit behaviors in full cells is still lacking. This work investigates three cathode materials (sulfur, NCM811, and LiCoO2) with varying volume changes and compares the short-circuit behavior when paired with the LMAs under identical conditions. Our pressure measurements and cohesive zone model-based finite element analysis indicate that sulfur and NCM811 materials undergo opposite directions of volume changes compared to Li metal anodes during cycling. In this case, the resultant force caused by stress crosstalk between electrodes will lead to more severe damage to SSE grain boundaries. In contrast, LiCoO2 material exhibits consistent volume change direction with the Li metal anode during cycling, resulting in relatively weak mechanical damage to SSEs. Finally, we propose an active pressure control system that helps to alleviate stress crosstalk and enhance cycling life. This study offers new insights into the stress crosstalk between electrodes in full cells, which is essential for developing high-performance ASSLMBs.