Research On Heat Generation Model And Thermal Management Of The High Rate Pouch Lithium-ion Battery

The lithium-ion battery have gradually become the main power source.At the same time,they are also widely used in electronic products and other fields.However,the lithium-ion battery need to be within a suitable temperature range to exert their high performance.However,the lithium-ion battery need to work in a suitable temperature range.When the lithium-ion battery discharge at a large rate,they will generate a lot of heat,which will causs the battery temperature to rise rapidly.At this time,the battery thermal management system（BTMS）is required to make the battery pack.cool down.Based on this,this paper established a lumped thermal model and an electrothermal coupling model of the pouch lithium-ion battery,which accurately simulated the temperature and voltage characteristics of the pouch lithium battery under high-rate discharge.Then,the cold plate cooling system of the pouch lithium-ion battery pack was designed and optimized based on the optimal thermal model.First,a series of parameter measurement experiments for the pouch lithium-ion battery were designed and carried out according to the heat transfer and heat generation characteristics of the lithium-ion battery,including temperature rise test,open circuit voltage test,terminal voltage test,internal resistance test and entropy coefficient test.The experimental datas are processed.Then the influence of temperature on different parameters of the lithium-ion battery were analyzed.And the experimental data of the internal resistance and entropy coefficient of the pouch lithium-ion battery under different ambient temperatures and different SOCs are obtained.Then this paper used silica gel/PI heating film to heat the pouch lithium-ion battery in an adiabatic environment.By using its temperature response during heating,the thermophysical parameters of the lithium-ion battery can be successfully identified.The volume heat production rate formulas of pouch lithium-ion battery under different discharge rates were established by polynomial fitting.The lumped heat model of the pouch lithium-ion battery were established by using STAR-CCM+software.Temperature simulation of high discharge rate were performed.The simulation data showed that the established lumped thermal model has high accuracy.The MAE between simulation and experiment data was less than 1℃,and the AMPE was less than2%.Then according to the basic principle of the electro-thermal coupling model,this paper conducted offline parameter identification on the resistance and capacitance data of the second-order equivalent circuit model.Then the resistance and capacitance data of different temperatures and SOCs were obtained.By using MATLAB/Simulink,an electro-thermal coupling model of the pouch lithium battery was built.The temperature simulation data of the two heat generation models were compared with the experimental data,and it was found that the temperature simulation accuracy of the lumped thermal model was higher,but the electro-thermal coupling model had its unique advantages in simulating the external voltage characteristics of the battery.Finally,the cold plate channel structure of the battery pack was designed and optimized based on the lumped heat generation model of the pouch lithium-ion battery.A lithium-ion battery pack composed of 12 pouch lithium-ion batteries in series was simulated for the temperature field.It was found that without a cooling system,the temperature of the inner central area of the lithium-ion battery pack reached 65.38℃ due to heat accumulation.Therefore,the lithium-ion battery thermal management system（BTMS）is indispensable.Then the heat dissipation performance of the parallel channel cold plate and the serpentine channel cold plate were simulated and compared.The results showed that the cooling performance of the serpentine channel cold plate was better than that the parallel channel cold plate,but the pressure drop of the serpentine channel cold plate was larger.Finally,the design of the serpentine channel was optimized by orthogonal experimental design to obtain the optimal combination of different structural parameters.A three-factor four-level test was carried out by using the L₁₆（4⁵）orthogonal table.Through the range analysis of the orthogonal test results,it was found that the channel thickness（h）and the channel number（n）had a greater impact on the performance and loss of the cold plate,and the channel width（l）has the least impact.By analyzing the influence of a single factor on the cooling performance of the battery pack,a relatively optimal model of the serpentine channel structure was obtained.The maximum temperature of the lithium-ion battery pack under the relatively optimal cooling scheme was 44.57℃,the maximum temperature difference was 4.93℃,and the cold plate power loss was also low.