Simulation of lithium-ion battery thermal runaway considering active material volume fraction effect

The multi-physics solver BatteryFOAM couples with the side reaction model for thermal runaway (TR) simulations, including the electrolyte decomposition (E) and solid electrolyte interface layer decomposition (SEI), and the reaction of the electrolyte with graphite intercalated lithium (NE-E) and the reaction of positive electrode active material with the electrolyte (PE-E). This solver is used to study the lithium-ion battery (LIB) TR at different conditions. The published experimental results are used to validate the effectiveness and practicability of BatteryFOAM in predicting the temperature under constat high temperature. We also discuss the reactant concentration, reaction rate, and heat release rate during the LIB TR. The influences of the external factor of the equal equivalent heat transfer (h) on the battery TR is considered, and the sequence in which the battery reaches the critical temperature rising rate (RTR, 60 K/min) and the separator failure temperature (Tsep) is predicted. The results demonstrate that overall the exothermic reaction peaks arise sequentially from SEI decomposition, PE-E reaction, NE-E reaction, and electrolyte decomposition, and NE-E reaction has three exothermic peaks induced by other three side reactions. PE-E reaction contributes more heat for fuse energy to trigger TR, but the NE-E reaction and electrolyte decomposition mainly accounts for the runaway energy. In addition, increasing SEI and electrolyte decomposition intensity is found no effect on the TR temperature. Besides, the rapid reaching to RTRis caused by the high heat release rate of positive electrode active material with electrolyte. Results further show that reducing the fNE-E within 5.0 % will significantly reduce TR risk.