Thermal runaway modeling of large format high-nickel/silicon-graphite lithium-ion batteries based on reaction sequence and kinetics

Commercial large format high-nickel/silicon-graphite (NCM811/SiC) lithium-ion batteries have been applied in long range electric vehicles for their exceptional high energy density. However, fire and explosions caused by these high-energy batteries arouse safety concerns. Mathematical model is a powerful method to study and predict the hazardous thermal behaviors but have not been well established due to lack of the detailed side reaction sequence and kinetics of the NCM811/SiC chemistry. This paper reveals that the thermal interactions between the high energy materials dominate the heat generation process and determines the detailed side reaction sequence and thermal kinetics based on experiments. A cell thermal runaway model considering the reaction sequence is then established based on the kinetics and achieves accurate prediction of the cell thermal behaviors. The validated model is further employed to investigate the thermal deterioration originated from high-energy NCM811/SiC chemistry. According to the simulations, the thermal interactions between SiC-electrolyte, NCM811-electrolyte and NCM811-SiC can lead to maximum temperature increase by 318 °C, 222 °C and 174 °C, respectively, with total heat rising by 29%, 20% and 17%, when compared with the conventional Li[Ni1/3Co1/3Mn1/3]O2/graphite chemistry.