Study On Electrochemical Model And Simplified Method Of Li-ion Battery For Vehicle

Lithium-ion power battery is the most widely used energy source in new energy vehicles.As one of the core components of new energy vehicles,the power battery replaces the fuel tank in traditional vehicles.The accurate power battery model and effective battery management system in new energy vehicles can improve the driving range and the battery life.However,the establishment of accurate power battery model is the difficulty of improving the battery management system.In this paper,18650 lithium-ion battery is taken as the research object.The electrochemical model and its simplified method of lithium-ion battery are studied.The main research contents include:(1)The quasi two dimensional electrochemical model was used to simulate the discharge process of 18650 Li-ion battery.Based on the quasi two-dimensional electrochemical model,the discharge mechanism of the battery is studied.By simulating the change of battery internal in the process of battery discharge,the changes of balance potential,polarization potential and liquid phase potential in battery internal are analyzed,and the reasons and influencing factors of the changes are described.(2)The simplification methods and principles of the three simplified electrochemical models of lithium-ion battery,which are single particle model,three parameter single particle model and extended single particle model,are studied.The sensitivity analysis of the key parameters in the battery model is carried out to determine the range of parameters in the parameter identification.Particle swarm optimization is used to identify the parameters in the three parameter single particle model and the extended single particle model.The estimation results of the three parameter single particle model and the extended single particle model are compared,and the advantages and disadvantages of the two models in the simulation process are studied.(3)COMSOL software was used to build a three-dimensional thermal model of lithium-ion battery.The change process of the thermal components in the discharge process of lithium-ion battery is simulated,and the change of the surface temperature of the battery is simulated.Combined with the three-dimensional heat generation model of the battery,a simplified method of the heat generation model of the battery is proposed.(4)The 18650 lithium-ion battery was designed for discharge experiment.The voltage and temperature changes of the battery were collected and the experimental data were processed by wavelet algorithm.Through three parameter single particle model and extended single particle model,the simulation model of lithium-ion battery based on experimental data is established to predict the change of battery voltage under different conditions in the experiment.The extended single particle model is used to build the heat generation model of the battery to estimate the change of the battery temperature during the discharge process.The reliability and accuracy of the battery model and heat generation model are verified by lithium-ion battery experiments.