Abstract: A thermal-chemical coupling model of lithium-ion batteries was established in a COMSOL software to investigate the thermal runaway characteristics of lithium-ion batteries at local high temperatures. The model contains five side reactions: the solid electrolyte interface membrane decomposition reaction, the reaction between negative electrode active material and electrolyte, the reaction between positive electrode active material and electrolyte, the electrolyte decomposition reaction, and the binder decomposition reaction. By using this model analyzed the influence of local high temperature on the heat generation of the side reactions of the lithium-ion battery and the temperature distribution of the diaphragm. The results show that heating only a single tab does not cause thermal runaway inside battery; All the five side-reactions generates heat when heating simultaneously both ends of lithium-ion battery tabs, this phenomenon will lead to trigger battery thermal runaway; Thermal-runaway inside lithium-ion battery propagates firstly in the horizontal direction and then in the vertical direction. 

Key words: power batteries, lithium-ion batteries, electrode tab, thermal runaway, local heating, side reactions; solid electrolyte interface (SEI) film