Revealing the impact of extreme temperatures and dynamic conditions on thermal safety of NCA/Si-graphite battery

The thermal safety of lithium-ion batteries continues to pose a significant challenge for electric vehicle (EV) applications. Given the complex aging processes of batteries under extreme temperatures and dynamic conditions, accurately predicting and preventing thermal runaway (TR) is of critical importance. In this study, a cyclic aging test simulating equivalent vehicle operating conditions was first conducted for NCA/Si-graphite battery, followed by an overheating-induced TR test. This research quantitatively analyzes the evolution of TR criticality with respect to heating power, state of charge (SOC), and temperature, both before and after battery aging. It was observed that separator melting does not coincide with the occurrence of an internal short circuit or TR. Furthermore, differential scanning calorimetry (DSC) tests were employed to evaluate the thermal stability of battery components and to elucidate the influence of aging mechanisms on TR behavior. The results indicate that the exothermic reactions between the anode-electrolyte and cathode-anode materials constitute the primary heat source during battery TR. Aging-induced side effects, such as solid electrolyte interphase growth and lithium deposition, were found to significantly impact the TR trigger time. A novel mechanism of TR, driven by the reaction between intercalated lithium and the electrolyte, is revealed. The findings of this study provide valuable insights for advancing research on battery design and development, TR prevention strategies, and battery management systems.