Evaluation of Heat Generation and Thermal Degradation of Lithium Ion Batteries by a Calorimetry Method

With the wide application of lithium-ion batteries (LIBs), it is important to understand the internal heating effects and thermal runaway behavior of such batteries to evaluate their thermal safety and improving thermal management systems. The heat generation of LiCoO2/graphite LIBs under various conditions was compared using calorimetry and electrochemical methods. The heat generation results of the two methods in the process of charging/discharging at different current rates were consistent, but the calorimetry method is simple, convenient, and more feasible. The greater the working current, the greater the irreversible heat generation. Through the identification of the thermal runaway behavior, it was found that the change of the onset temperature of self-heating reactions fluctuates in a narrow range. Thermal runaway after battery degradation is more likely to be triggered by the degradation of thermal stability.