Research On Thermal Runaway Characteristics Of Vehicle Lithium-ion Power Battery Under Thermal-electrical Abuse

The fire problem of new energy vehicles caused by the thermal runaway of lithium-ion batteries has been the pain point of the development of the industry,which seriously threatens the lives and property safety of the people.Thermal runaway has become a bottleneck problem restricting the development of new energy vehicles,and hindered the large-scale application and promotion of new energy vehicles.This paper takes the ternary lithium-ion power battery as the research object,considers the internal reaction mechanism and heat generation of the lithium-ion battery during thermal runaway,and establishes a lithium-ion battery thermal runaway model under external thermal abuse and a lithium-ion battery thermal runaway model under electrical abuse.Using temperature as a coupling factor,a thermal runaway model of thermal abuse of lithium-ion batteries is established.The effects of different parameters on the thermal characteristics and electrochemical parameters of lithium-ion batteries are analyzed,and the thermal runaway characteristics and development rules of lithium-ion batteries under different abuse conditions are revealed.(1)Introduce the working principle of lithium-ion battery,and explain the mechanism of heat generation and heat transfer of lithium-ion battery from the perspective of heat transfer.The triggering factors of thermal runaway of lithium-ion batteries are analyzed,and the causes of thermal runaway of lithium-ion batteries are innovatively divided into transient mutation and quantitative and qualitative accumulation.The products of lithium-ion battery side reactions are illustrated,the characteristics of lithium-ion battery thermal runaway triggered by the abuse of external heat sources are highlighted,and the chemical kinetic models of different side reactions are described.(2)The three-dimensional layered physical model of the lithium-ion battery is established,and then thermal runaway is triggered by thermal abuse and electrical abuse respectively,and its thermal runaway characteristics and development process are analyzed.In the analysis of thermal abuse,the boundary conditions of lithium-ion batteries under thermal abuse are simplified,the influence of heat source temperature,heat source position and heat dissipation coefficient on the thermal runaway characteristics of lithium-ion batteries are analyzed,and the overall battery and separator temperatures are also analyzed.In the analysis of electrical abuse,the boundary conditions of lithium-ion batteries under electrical abuse are simplified,the charging rate and the effect of overcharging are analyzed,and the changes in the overall temperature,internal resistance and total heat of the battery are also analyzed.(3)The thermal runaway characteristics of lithium-ion batteries under thermal-electric coupling abuse have been studied.By studying the mechanism of thermal runaway thermalelectric coupling abuse and using temperature as an element of the coupling of thermal and electrochemical fields,a thermal-electric coupling abuse model for lithium-ion batteries was established.By comparing the position of the lithium-ion battery heat source and the rate of charge and discharge,the effects of different charge rates,different heat source positions and whether overcharge on the internal parameter changes and thermal runaway of the lithiumion battery were analyzed.(4)Carry out experiments to verify the established thermal-electric coupling abuse model.The temperature comparison of lithium-ion batteries under thermal-electric coupling abuse proves that the accuracy of the established model meets the requirements;at the same time,a monitoring scheme for thermal runaway characteristic parameters is developed.Realize the real-time monitoring of the thermal safety status of lithium-ion batteries through the fusion of smoke-gas-temperature multi-parameters;formulate an early warning and fire extinguishing strategy,and develop a prototype of an automatic fire extinguishing device for a power battery system,and carry out fire extinguishing experiments to verify the early warning and extinguishing strategy.