Research And Simulation Of Thermal Characteristics Of Lithium Battery Based On Electric Thermal Coupling Model

Lithium batteries have many advantages such as good circulating performance,high safety and high energy density,and meet the needs of new energy vehicles.But lithium batteries also have a number of thermal safety problems,such as accumulating a lot of heat during rapid charging,causing temperatures to rise rapidly.Inadequate battery heat dissipation not only reduces the performance of the battery itself,but can even cause thermal safety problems such as fires and explosions.Only by understanding the thermal characteristics of batteries in abnormal working conditions can we make a breakthrough in thermal safety and optimize thermal management design,which is of great significance to the development of new energy vehicle industry.Aiming at the above problems,this paper analyzes the working mechanism,heat dissipation performance and abnormal working condition of ternary lithium-ion battery,and discusses its thermal runaway mechanism under thermal abuse,mechanical abuse and electrical abuse.Using COMSOL software,based on the simulation model,the basic control equation is written and the electric-thermal coupling model of lithium battery is established.Then the basic characteristics of the battery were experimented,the necessary basic test parameters were obtained,and the accuracy of the lithium battery electricthermal coupling model was verified with the relevant literature.By means of COMSOL software,the internal reaction mechanism of lithium batteries under different recharge and discharge multiplication,different air velocity,fin structure,thermal runaway condition is analyzed,and the activation process and temperature field change of lithium thermal battery are simulated.The results show that the temperature of the cell increases with the increase of discharge multiplication and decreases with the increase of external air rate.Increasing the fin structure can optimize the heat dissipation performance of the battery.Under the condition of heat runaway,heat accumulates gradually inside the cell,leading to chemical side reactions,and heat runaway with heat accumulation.In a needle-piercing model,a steel needle piercing causes a short circuit inside the battery,instantaneous piercing generates a lot of heat,triggers a side reaction,and finally causes the heat to get out of control.In high temperature heating models,the higher the ambient temperature,the more intense the side reaction of the battery and the higher the temperature.In overcharge models,the longer the overcharge time,the worse the stability of voltage and temperature;Simulate the activation process of lithium thermal battery,observe the distribution of heat source during activation of lithium thermal battery,and analyze the change of temperature field of lithium thermal battery.