Electrochemical Modeling And Simulation Of Lithium-ion Power Batteries

The power batteries of electric vehicle have a significant impact on mileage of car,safety of car and vehicle performance. And how to accurately estimate the battery’s state ofcharge and state of health, predict the lifetime of the battery, ensure the safe and stableoperation of the battery are the key technologies of battery development. Therefore, it isessential to establish a precise model for the characteristic analysis and performanceoptimization of the battery. This paper around the lithium-ion power battery electrochemicalmodeling mainly has done the following areas:First of all, this paper clarifies the background and significance of the study oflithium-ion power battery electrochemical modeling, then lithium-ion power batterycompared with several kinds of common power battery, explaining the reason whylithium-ion power battery as the research object, and then introduces two kinds of commonlyused battery models, focuses on the domestic and foreign research status of electrochemicalmodels and numerical simulation methods.Next, introducing the classification of lithium-ion battery, the internal structure andworking principle of lithium-ion battery, and introducing the mathematical formulas andtheir boundary conditions of the universal quasi two-dimensional electrochemical model indetail, describing the meaning of each variable in the quasi two-dimensional model in detail,analyzing the complexity of the quasi two-dimensional model and identifying the use ofquasi two-dimensional model in this paper.Based on the nonlinear and strong coupled quasi two-dimensional model, making twoimportant assumptions, then solving the charge conservation equation, the liquid phaseOhm’s law and the Butler-Volmer kinetic equation, and processing the solid phase diffusionequation by finite difference method, the partial differential equatio（nPDE）are converted toa set of ordinary differential equations（ODEs）, deriving the electrochemical average valuemodel. Finally obtaining state equation model which current as the input, the voltage and thestate of charge（SOC） as the outputs. Then, using the FORTRAN simulation program basedon the quasi two-dimensional model written by J. Newman to verify the rationality and validity of two assumptions of the average value model, comparing the voltage of quasitwo-dimensional with the voltage of the average value model under same battery parameters,Preliminarily verifying the accuracy of the average value model.Last, analyzing internal parameters of the lithium-ion battery, identifying six mainparameters to be identified, further analyzing the sensitivity of the six parameters on thevoltage, and using genetic algorithm to complete the identification of the six parameters,verifying the validity of identification method and the accuracy of identification results byimporting identification results into the average value model. Finally, doing offlinesimulation of lithium-ion battery under variable working condition based on electrochemicalaverage value model, comparing each variable curve of electrochemical average value modelwith each variable curve of quasi two-dimensional model. Analyzing the voltage error curveand SOC error curve of electrochemical average value model, verifying simulation result ofelectrochemical average value model under variable working condition. Eventually,completing electrochemical modeling and simulation of lithium-ion power battery.