Mechanical properties and thermal runaway study of automotive lithium-ion power batteries

As the most widely used power battery for pure electric vehicles, lithium-ion battery has been studied in detail, including electrochemical performance and mechanical safety. This paper focuses on the mechanical response and thermal runaway phenomena caused by external mechanical stress of lithium-ion batteries at different states of charge (SOC). The results show that the SOC affects the mechanical strength as well as the temperature of the battery under external stress. When stress is applied to the cell, the higher the SOC of the cell, the higher its stiffness and surface temperature. The force is determined to propagate layer by layer based on the dynamic analysis approach of stress propagation theory. The velocity is inversely proportional to the stress propagation distance. Excessive impact velocity will lead to concentration of stress in the battery, which will lead to short circuit and thermal runaway phenomenon of the battery. The findings of these phenomena are of guiding significance to the safety study of electric vehicle lithium-ion batteries.