Thermal runaway chain reaction determination and mechanism model establishment of NCA-graphite battery based on the internal temperature

The measurement of battery internal temperature directly affects the determination of the sequence of thermal runaway chain reaction and the choice of model heat sources, and the optimal combination identification of kinetic parameters corresponding to each heat source is the premise of establishing model. This paper focuses on the Lix(Ni0.8Co0.15Al0.05)O2-graphite pouch battery with built-in thermocouple. Based on the stage division of thermal runaway behavior and the decoupling of irreversible exothermic reaction between battery components, the thermal runaway mechanism is determined. Then, the optimal combination of kinetic parameters is determined by combining the DSC tests under variant heating rates, the Kissinger's method and the genetic algorithm. Furthermore, a thermal runaway model considering hierarchical properties is established, and the thermal contribution of six exothermic reactions at each stage of thermal runaway is quantified. Anode+electrolyte and cathode+anode contribute 53.8% and 18.7% respectively to the heat accumulation before thermal runaway. Internal short circuit accounts for 27.5%, and the heat is released instantaneously, directly triggering thermal runaway. This work has important reference significance for the design of battery safety warning system and the battery modification strategy.