Thermal Behavior and Failure Mechanism of Large Format Lithium-Ion Battery

Thermal runaway (TR) behavior of 38 Ah lithium-ion batteries with various states of charge (SOC) is experimentally investigated in this work using extended volume plus accelerating rate calorimeter (EV+ ARC). Some of the critical kinetic parameters, such as onset exothermic temperature ( T onset ), temperature of TR ( T TR ), and maximum temperature ( T max ), can be obtained to characterize the risks of TR event. The impact of SOC on thermal stability of the battery is researched. It is found that the higher the SOC state, the lower the battery safety. Thermal features of both the cathode and anode, as well as the materials, are also investigated. The morphology and the structure change of the materials are characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). Finally, a general theory is proposed and detailed reactions are summarized in this work. The thermal runaway follows a mechanism of chain reactions, during which the decomposition reactions of the battery component materials occur one after another.