Dynamic Overcharge Performance and Mechanism of Lithium-Ion Batteries during High-Temperature Calendar Aging

Battery safety plays a critical role in ensuring the reliable operation of lithium-ion batteries during the service lifetime. Lithium-ion batteries often remain in a static state for extended periods during vehicle applications, particularly in high-temperature conditions, which poses significant challenges to their safety performance. In this content, this work investigates the evolution of overcharge performances and underlying mechanism during high-temperature calendar aging. The findings reveal that overcharge tolerance, represented by thermal runaway triggering temperature and duration time, decreases with aging. Simultaneously, thermal hazards, indicated by maximum temperature and maximum temperature rise rate, also diminish with aging. Multidimensional characterization demonstrates that lithium plating, gas generation, and transition metal dissolution are key failure mechanisms leading to performance degradation. Specifically, the reduced thermal stability of the anode and cathode is identified as the primary cause of the decline in overcharge tolerance. In contrast, the loss of active materials and active lithium emerges as the major factor contributing to the reduction in thermal hazard with aging.