Electrochemical-thermal Modeling And Performance Analysis Of Ternary Lithium Battery For Ultra-Fast Charging Technology

With the increasing attention paid to new energy vehicles with low fuel consumption and low emission in all countries of the world,electric vehicles,mainly powered by electric energy,especially lithium ion batteries with high specific energy,are the best choice for the new generation of vehicles that can meet the requirements of energy and environment.However,mileage anxiety,charging anxiety and battery anxiety caused by factors such as endurance mileage and charging speed limit the promotion and popularization of electric vehicles.Ultra-fast charging technology can greatly shorten the charging time and help to solve the charging anxiety of electric vehicles,but the heat generation of batteries in the process of rapid charging needs to be solved first.Therefore,building a reasonable and accurate heat generation model of lithium-ion battery is not only important for studying the heat generation rate and temperature field information of the battery under ultra-fast charging conditions,but also of great significance for guiding the battery design,thermal management system design and charging method design under fast and ultra-fast charging conditions.The charging and discharging test bench of the power batteries is established and a prismatic ternary lithium ion battery with 14Ah capacity is as research objects.The charging experiments are carried out at different charging rates(0.5C,1C and 1.5C)and different ambient temperatures(15?,25?,35? and 45?).According to the experimental results,the basic performance of the ternary lithium ion battery and its electrochemical and temperature characteristics are obtained,which provide data basis for establishing and verifying the pseudo two dimensional(P2D)electrochemical-three dimensional(3D)thermal model of the ternary lithium ion battery.A P2D electrochemical-3D thermal finite element model of ternary lithium ion battery are established by using the interface of lithium ion battery in COMSOL Multiphysics software.The charging processes of lithium ion battery are simulated and calculated respectively at 0.5C,1C and 1.5C charging rates.The results of the charging curves and the temperature variation curves of relevant measuring points are compared with the experiments which verify the accuracy of the P2D electrochemical-3D thermal finite element model.The model is used to simulate the charging process of ternary lithium-ion batteries at four ultra-fast charging rates of 3C,4C,5C and 6C.The external characteristics,electrochemical characteristics and thermal characteristics of the batteries under ultra-fast charging conditions are analyzed according to the simulation results.The results show that with the increase of charging rate,the capacity achieved by the ternary lithium ion battery in the constant current phase is rapidly reduced,the polarization phenomenon of the battery is more serious,the heat generation rate is obviously improved,and the maximum temperature and the maximum temperature difference at the cutoff of constant current charging are gradually increased.In addition,the heat generated at the tabs also has a significant effect on the temperature distribution of the battery.The 3C and 6C are used as the typical conditions of fast and ultra-fast charging respectively.The P2D electrochemical-3D thermal finite element model is used to study the effects of structural design parameters and key material parameters on the electrochemical and thermal characteristics of ternary lithium ion battery.The thickness of the positive electrode and its particle size,the thickness of the negative electrode,the material and its particle size,the thickness of the separator,and the electrolyte material all affect the electrochemical reaction process inside the lithium ion battery,resulting in the differences of the heat generation rate and temperature field of the battery during charging.The three-dimensional size of the cell,the three-dimensional size of the tab and its arrangement affect the heat transfer and heat dissipation process of the battery,so that the battery has different temperature distributions at the time of charge cutoff.The maximum lithium intercalation concentration of the positive electrode has little effect on the charging process and temperature field of the battery.