Research on the impact of high-temperature aging on the thermal safety of lithium-ion batteries

Understanding the thermal safety evolution of lithium-ion batteries during high-temperature usage conditions bears significant implications for enhancing the safety management of aging batteries. This work investigates the thermal safety evolution mechanism of lithium-ion batteries during high-temperature aging. Similarities arise in the thermal safety evolution and degradation mechanisms for lithium-ion batteries undergoing cyclic aging and calendar aging. Employing multi-angle characterization analysis, the intricate mechanism governing the thermal safety evolution of lithium-ion batteries during high-temperature aging is clarified. Specifically, lithium plating serves as the pivotal factor contributing to the reduction in the self-heating initial temperature. Additionally, the crystal structure of the cathode induced by the dissolution of transition metals and the reductive gas generated during aging attacking the crystal structure of the cathode lead to a decrease in thermal runaway triggering temperature. Furthermore, the loss of active materials and active lithium during aging contributes to a decline in both the maximum temperature and the maximum temperature rise rate, ultimately indicating a decrease in the thermal hazards of aging batteries.