Numerical simulation and analysis of the effect of charging and discharging on the thermal runaway of lithium-ion batteries under external heating conditions

As one of the most widely used energy storage devices, lithium-ion batteries often operate under complex conditions, making their safety performance a key issue. By coupling a coupled electrochemical-thermal model and a thermal runaway model, the dynamic impact of charging and discharging operations on lithium-ion battery thermal runaway behavior triggered by external heating is systematically revealed herein. The thermo-electrical behavior of the battery under different charge and discharge rates (1C, 3C, and 5C) is compared. The simulation results show that under the same external conditions, there is a significant linear relationship between the time of thermal runaway and the charge/discharge rate. The extra irreversible heat generated by charge and discharge operations accelerates the process of thermal runaway, with the thermal runaway time at 1C rate being 692 s, 33 s earlier than that at 0C rate. This also means that higher charge and discharge rates will linearly shorten the time to the start of thermal runaway. The decomposition reaction of the solid electrolyte interphase (SEI) layer causes a sudden increase in temperature, while the reaction between the positive electrode and the electrolyte dominates the critical heat release. The discharge process generates more electrochemical heat than the charge process, for example, 1528.89J at 3C discharge, is much higher than that at the same rate charge condition. The feedback mechanism of polarization heat-dominated irreversible heat generation accelerating the SEI layer decomposition during discharge is revealed. In addition, there are differences in voltage collapse characteristics under charge and discharge modes, reflecting the coupling of the dynamic state of charge and thermal runaway mechanisms.