Parameter Identification,Optimization And Thermal Simulation Application Of Electrochemical-thermal Coupling Model Of Lithium Battery

Lithium-ion batteries are widely used in new energy vehicles and energy storage systems due to their long life,high energy density and high specific energy.However,the state of large-capacity lithium-ion batteries is greatly affected by temperature.Too high temperature can easily lead to thermal runaway,and too low temperature can lead to a decrease in discharge capacity.In addition,the uneven temperature distribution of the battery will also affect the performance and safety of the battery.Therefore,thermal management of the battery is required.Identifying the parameters of the electrochemical-thermal coupling model of lithium batteries quickly and effectively is an important part of building the model,and it is also a hot spot of current academic research.Because the model requires many parameters,the measurement of some parameters requires expensive experimental equipment,and the experimental process is complicated and can not be completed under general conditions.The parameters of the reference and the parameters of the target battery may be very different due to different types and models,so this situation can lead to large errors.The simple and efficient transfer of battery heat is a major problem that needs to be solved in current thermal management technology: Air cooling technology has low heat dissipation efficiency;liquid cooling technology may cause safety accidents due to coolant leakage;phase change material cooling technology costs are high.Aiming at the parameter problem,this paper uses the algorithm to identify and optimize the difficult-to-measure parameters according to the model principle.The obtained simulation results are compared with the experimental results to verify the rationality of the parameter identification and optimization methods.Aiming at the technical problem of thermal management,a design of total immersion cooling based on silicone oil is proposed and verified by simulation and experiment.This article is organized as follows:Firstly,the solid-phase reaction,solid-liquid phase reaction and liquid-phase microscopic particle motion law in the pseudo-two-dimensional electrochemical model are analyzed in detail,and the heat generation mechanism and electrochemical-thermal coupling principle of the three-dimensional thermal model are further elaborated.These principle are the theoretical basis for the following research.Secondly,the experiments to obtain battery geometric parameters,specific heat capacity and positive and negative open circuit voltages are introduced.The genetic algorithm was further studied,and the genetic algorithm was used to identify the positive and negative lithium intercalation intervals and the heat generation influencing factors,and then the electrochemical model was obtained.The correlation between the voltage curve simulated by this model and the actual measurement results can reach up to 0.994,the correlation of the heat generation curve can reach up to 0.977.And studying the heat source of the battery under different circumstances.After that,the neural network algorithm was analyzed in detail,the algorithm model was built with MATLAB,and the thermal conductivity of the three-dimensional thermal model was optimized by using the model.Comparing the simulation results with the experimental results,the maximum error is 0.3 °C,which is much smaller than the results before optimization,which verifies the feasibility of the neural network algorithm to optimize the thermal model parameters.And studying the temperature distribution of the single cell under different current rates.Finally,12 strings of 50 Ah battery packs were simulated using the electrochemical-thermal coupling model built before,and the temperature distribution of the battery packs was studied.A silicone oil-based full immersion cooling structure was further designed,and it was found that the temperature of the structure at a rate of 1C was 0.5°C lower than that of the air-cooled structure,which was safer and simpler than the liquid-cooled structure.In this paper,it is also verified through experiments that silicone oil has no effect on the normal operation of lithium-ion batteries and can prevent thermal runaway to a certain extent,ensuring the safety of batteries.