Study On Thermal Runaway Characteristics Of Lithium-ion Battery Under Local High Temperature Surface Heat Source

In recent years,the electric vehicle industry has achieved rapid development when the problems of environmental pollution and energy shortage become serious increasingly,and the lithium-ion battery,as the core component,has attracted much attention.However,the further promotion and use of the electric vehicle are severely limited by the fire accidents caused by thermal runaway of the lithium-ion battery.Therefore,it is urgent to understand the thermal runaway characteristics of lithium-ion batteries.In this paper,from the perspective of the thermal runaway propagation characteristics in the battery module,the thermal runaway characteristics of lithium-ion batteries under the contact of local high temperature surface heat source are simulated.In this paper,the working principle,heat generation and heat transfer mechanism of lithium-ion batteries are studied,the triggering inducement,triggering mechanism and the type of gas produced by the reaction are analyzed,and it is pointed out that the thermal runaway of lithium-ion batteries triggered by local high temperature surface heat source is a kind of thermal abuse,which provides a theoretical basis for studying the thermal runaway characteristics of lithium-ion batteries under local high temperature surface heat source.According to the internal structure characteristics of lithium-ion battery,this paper established the thermal runaway model of lithium-ion battery under the contact of local high temperature surface heat source in COMSOL simulation software,and verified the rationality and accuracy of the simulation model through the comparison of simulation and test results.The thermal runaway characteristics of lithium-ion batteries under different local high temperature surface heat source triggering modes are simulated and analyzed.In addition,the internal and external factors that affect the thermal runaway of lithium-ion batteries are discussed,and the influence rule of heat dissipation conditions and the thermal stability of positive electrode materials on the thermal runaway of lithium-ion batteries is studied in detail.The research results show that surface heat source located in the upper one third of the battery surface,165 ? surface heat source temperature is the critical temperature of lithiumion battery thermal runaway,higher than 165 ? battery thermal runaway will happen;In the process of the thermal runaway of lithium-ion batteries triggered by local high temperature surface heat source,the SEI film(Solid Electrolyte Interface)decomposition and the reaction between negative electrode and electrolyte to generate heat are the main reasons for driving the battery temperature to rise so as to trigger the thermal runaway of the battery,while the reaction between positive electrode and electrolyte is the main reason for the sudden and sharp rise of the battery temperature.When the battery heat is on the thermal runaway,the heat generate rate of the positive electrode reacts with the electrolyte is the maximum.Improving the heat dissipation conditions can improve the heat dissipation coefficient of the battery surface,delay the occurrence of thermogenic side reactions,and reduce the reaction heat generation rate,so as to prevent or delay thermal runaway of the battery.In addition,the initial temperature of reaction between anode and electrolyte increases with increasing the thermal stability of positive electrode materials,when the initial temperature of the reaction is high enough,the reaction between the positive electrode and the electrolyte is not triggered at high temperature,and the battery will not occur thermal runaway.In this paper,the thermal runaway characteristics of lithium-ion batteries under the local high temperature surface heat source are studied,which provides engineering application guidance for preventing or delaying the thermal runaway of the battery.