Study On Liquid Cooling Optimization Of Lithium-ion Battery Module For Electric Vehicle

Lithium-ion batteries,as the power source of pure electric vehicles,are of great significance for solving the current energy shortage and environmental pollution problems.In order to ensure the economical,efficient,and safe operation of pure electric vehicles,the research on thermal management technology for lithium-ion batteries is particularly important.This paper takes the soft-packed lithium-ion battery as the research object,and uses the method of theoretical analysis and calculation,numerical simulation,and experiments to study the liquid cooling optimization of lithium-ion battery module for Electric Vehicle.The main research contents and results of this article are as follows:(1)Based on the knowledge of thermodynamics and heat transfer,the expression of heat generation of lithium ion batteries is summarized and simplified,and the main heat transfer methods of lithium ion batteries and heat conduction and convection heat transfer formula formulas are determined.(2)The temperature rise tests of the single lithium-ion batterie at different discharge rates were carried out.The test results showed that: During the discharge process,the high temperature area of the unit battery is the middle of the battery body and the area near the positive electrode,and the temperature in the negative electrode area is the lowest;The temperature rise rate of the battery decreases first and then increases;the higher the discharge rate,the greater the maximum battery temperature and the maximum temperature difference.(3)Discharge internal resistance and entropy thermal coefficient of a single-cell lithium-ion battery obtained through experimental measurements.With reference to the battery heat generation model proposed by Bernadi,the heat generation rates of the battery at ambient temperatures of 0℃,25 ℃,and 40℃and discharge rates of 0.5C,1C,and 2C were obtained.The average specific heat capacity,density and heat conduction coefficient of the single-cell lithium-ion battery were calculated by the method of parameter lumped average.(4)Based on the theory of CFD,using HyperMesh and STAR-CCM +,a 3D simulation model of a single cell is established.The simulation model was used to study the temperature field of the single-cell lithium-ion battery,and the validity of the thermal simulation model of the single-cell battery established in this paper was verified.At the same time,the study of temperature field simulation of the single lithium-ion battery and module under different ambient temperatures was carried out.The results show that: The low temperature not only greatly increases the heat output of the battery,but also worsens the temperature uniformity of the battery;the battery heat production under the high temperature does not change much,and it will slightly improve the battery temperature uniformity;under natural convection heat transfer condition,the operating temperature and temperature difference of the lithium-ion battery module are relatively high,and a cooling device needs to be added to the battery module for proper cooling.(5)A 3D simulation model for liquid cooling of lithium-ion battery modules was established.The model was used to study the optimized design of the coolant parameters and the structure of the liquid-cooled plate.Finally,the optimized coolant inlet temperature,the flow of the coolant and the optimized structure of the liquid-cooled plate were determined.(6)Lithium-ion battery module liquid-cooled test bench was constructed,and the lithium-ion battery module temperature rise test was performed at an ambient temperature of 25℃,a coolant temperature of 25℃,and a coolant flow rate of 20g/s,and the discharge rate is 1C.Comparing the obtained temperature data with the simulation data under the same working conditions,the results show that the established liquid-cooling model of the lithium-ion battery module has higher accuracy and the liquid-cooling system is effective and the cooling effect is good.Finally,experimental research on the liquid cooling system of lithium-ion battery modules under different ambient temperatures and different discharge rates was carried out.The result shows that under different operating conditions,the liquid cooling system established and optimized in this paper can control the operating temperature of the lithium-ion battery module within a reasonable range.Excluding the low-temperature and large-rate discharge conditions,the maximum temperature difference of the battery modules is within 5℃,indicating that the temperature uniformity of the battery modules is better.The liquid-cooled plate structure and the entire liquid-cooled system designed in this paper have a very good effect on the cooling of battery modules.