Thermal runaway behaviour of a cylindrical lithium-ion battery during charge and discharge processes: A comprehensive numerical study

Lithium-ion batteries (LIBs) may experience thermal runaway (TR) accidents during charge and discharge processes. To ensure the safe operation of batteries, it is very important to analyse the TR characteristics during charge and discharge processes. In this work, we have developed a coupled electrochemical thermal (ECT) – TR (ECT-TR) model for a commercial 18,650 type 2.6 Ah NCM523/graphite battery. This model allows for the examination of TR features under different ambient temperatures, effective heat transfer coefficients (h), and C-rates during both charge and discharge processes. We first analysed the temporal evolution of the battery's surface center temperature and the heat generated by chemical reactions under a spectrum of environmental variables. Subsequently, we introduce a battery risk map that delineates distinct zones, including the safe zone, battery chemical reaction zone, battery failure zone, and TR zone, across varying environmental conditions. The results suggest that the battery's TR risk during the charge process exceeds that during the discharge process, with both exhibiting reduced risk compared to that during the cycle process. However, it is noteworthy that the risk of accelerated battery aging due to chemical reactions is more pronounced in the discharge process compared to the charge process.