Slight overdischarge cycling-induced severe degradation of electrochemical and mechanical properties of lithium-ion batteries

Abstract

Overdischarge as a typical electrical abuse condition is most likely to be encountered in the practical use of electric vehicles (EVs) and grid storage, which has a great impact on the safety of lithium-ion batteries (LIBs). In this study, the short-term slight overdischarge cycles are focused on, and the impact of overdischarge on battery performance degradation is analyzed by multiple methods including electrochemical analysis and structural characterization. Mechanical tests of the disassembled battery components are carried out. The results indicate that overdischarge causes more significant damage to the cathode. With the progression of the overdischarge cycle, the cathode active particles undergo damage and detachment. The dramatic changes in morphology and structure directly lead to increased impedance, a substantial decrease in reversible capacity, and a significant decline in mechanical properties. Additionally, the loss of lithium inventory and the degradation of the separator's performance cannot be overlooked. The changes not only greatly shorten battery service life but also increase the hidden danger of battery safety.