Thermal Analysis And Heat Dissipation Optimization Design Of Lithium-ion Batteries

Under the tremendous pressure of the energy shortage and environmental degradation,the development of new energy vehicles that use electric energy instead of fossil fuels such as oil is booming and has received strong support from the state.However,while its explosive development,its security issues have become increasingly prominent.As one of the core components of electric vehicles,power batteries are directly related to the endurance mileage and life of electric vehicles.Lithium-ion batteries have become the mainstream choice for power batteries due to their high energy density,long cycle life,low self-discharge rate,no memory effect and environmental friendliness.However,as people's pursuit of electric vehicles is getting higher and higher,the energy density of lithium-ion batteries is getting higher and higher,and their thermal safety issues are becoming more and more important.This paper focuses on the thermal effects of lithium-ion batteries and the heat dissipation design of battery modules mainly carry out the following research:(1)A series of performance test experiments were carried out for the lithium ion battery selected in this paper.It includes charging and discharging voltage curve test with different charge and discharge rates at different temperatures;battery discharge capacity test at different temperatures;battery charge and discharge resistance test at different temperatures;and temperature rise test at different ambient temperatures.Through the above tests,the characteristics of the lithium-ion battery are directly related to the temperature,and the obtained data results are used as the basis and verification basis for the subsequent simulation.(2)The geometry,working principle and heat generation,heat dissipation mechanism of lithium ion battery were analyzed.According to the theory of heat transfer,the heat transfer model of lithium ion battery was established,and the methods for solving the parameters such as heat capacity,density,thermal conductivity and heat generation rate of the battery required in the model were introduced.Using the advisor software to simulate the output current and heat generation rate of the battery pack under typical conditions of electric vehicles,including NEDC,UDDS,HWFET,constant speed 100km/h,constant speed 40km/h,slope 10%,etc..(3)The computational fluid dynamics theory and simulation software were briefly introduced.The polynomial fitting was used to solve the heat generation rate of the battery,and the calculation model of the single lithium ion was established by using ICEM.The user-defined function(UDF)compiling function in FLUENT was used to simulate the temperature rise of lithium-ion batteries under different discharge rates.The results were compared with the temperature rise data measured above,and the feasibility of the simulation method is verified.(4)The temperature distribution of the battery module without heat dissipation was simulated and analyzed.A micro-channel liquid-cooled pipeline with a semi-enclosed form of the battery was designed and simulated under different liquid flow rates and temperatures.According to the simulation results,the heat dissipation structure was optimized twice.After comparative analysis,the heat dissipation effect of the battery temperature control and the uniform temperature was finally achieved.In summary,this paper used theoretical analysis,simulation research,experimental verification and other means to study the thermal effect of lithium-ion battery and heat dissipation structure design,which can provide certain reference value for the thermal management design of lithium-ion battery.