Lithium Battery Mechanism Model Simulation And Its Application In Phase Change Heat Dissipation

In recent years,under the vigorous promotion of national policies,the new energy vehicle industry has developed rapidly.However,with the gradual increase in the application of electric vehicles,accidents of spontaneous combustion of electric vehicles have occurred frequently in the past two years.For the design of thermal management system,thermal simulation can be carried out by establishing a reliable battery model,and further optimized by optimizing the battery heat dissipation parameters to get the best battery heat dissipation method to maintain the battery temperature within a certain range.Compared with experimental methods,numerical simulation can save time cost and economic cost.Compared with the commonly used equivalent circuit model,the pseudo-two-dimensional model has higher theoretical accuracy,but the pseudo-two-dimensional model has a large number of mutually coupled partial differential equations and involves many parameters,of which the parameter measurements are often time-costly and economically expensive,so the study of simplification and parameter identification of the pseudo-two-dimensional model is especially critical.This paper focuses on the parameter identification of the electrochemical model of the battery and the application of electrochemical simulation in phase change heat dissipation.Taking 18650 cylindrical battery as the experimental object,a simplified model of the electrochemical model of the battery is established,and the parameters are identified by using genetic algorithm in combination with the measured voltage curve.Then,we use the identified parameters to simulate the battery heat dissipation and obtain the optimal ratio of composite phase change materials.Firstly,we investigate the current frequent safety accidents,which reflect the importance of battery heat dissipation,the difficulty of parameter identification in the simulation of lithium-ion electrochemical model,and introduce the background and significance of the study.In addition,the current research status of battery models,parameter identification,and battery cooling methods is investigated.Then,the basic principle of the P2D model and its simplified model based on it,namely the SP2D model,are introduced.The SP2D model in this paper simplifies the polynomial distribution of solid-phase lithium ion concentration and liquid-phase lithium ion concentration.The electrochemical-thermal model is also presented with the heat generation mechanism and the computational expressions of the relevant thermal physical parameters.Then,the SP2D model is built in MATLAB/simulink.The reliability of the SP2D model is verified using the parameters and results from the literature.The model is analyzed for the average sensitivity index at different discharge depths for two different multiplier constant current discharge conditions,0.05 C and 2C.Using the measured voltage curves under the two operating conditions,the parameters are identified for pairs cs,0,n,cs,0,p and Ds,n,Ds,p,ks,n,ks,p,RSEI,n,and RSEI,p,respectively,using a genetic algorithm.Finally,the parameters identified in Chapter 3 are used to simulate the paraffin-expanded graphite phase change heat dissipation in COMSOL to obtain the optimal ratio combination of heat dissipation,which minimizes the surface temperature rise of the battery,and is verified by experimental results.In addition,the optimization module of COMSOL is used to optimize the parameters of expanded graphite volume fraction,battery spacing and copper foam thickness in the heat dissipation system of paraffin/expanded graphite-copper foam,so as to ensure the maximum temperature and maximum temperature difference of the module within a certain range,and at the same time minimize the total mass of the battery heat dissipation system.