Research On Thermal Simulation Strategy For Lithium-ion Batteries Based On Multi-physics Fields Theory

Lithium ion battery has many advantages such as large energy density,high voltage and good cycle performance.Lithium-ion batteries are used in transportation,electronic communications,aerospace and other fields,so it is important to improve the security and reliability of the lithium ion battery.Thermal safety is an important part of lithium ion battery safety performance.A poor thermal management results in a short life and even an explosion of lithium-ion batteries.Thermal simulation is an important means to guide the design and use of lithium-ion batteries.Therefore,it is very important to study the thermal simulation method of li-ion batteries.Based on the multi-physics field analysis,this project focuses on the core of the thermal simulation method of lithium-ion battery pack,and mainly carries out the following work:Firstly,this paper analyzes the working process of lithium ion batteries,summarizes the key roles that affect battery work and describes them by the mathematical methods.In order to simplify the partial differential equations,this paper uses the approximate analytic solutions instead of numerical solutions.The parameters with physical significance are obtained by reduction of the relevant equations and an incentive response method is used to identify the operating conditions.This paper analyzes the thermal behavior of lithium ion battery,decouples the related thermal parameter identification process,designs the related identification experiment and carry out the experiment.Secondly,this paper conducts parameter identification for commercial lithium ion battery.In this paper,the thermal simulation of lithium ion battery is carried out by means of finite element analysis and multi-physical field simulation software.Compared with the actual experimental results,this paper verifies the accuracy of the multi-physical field simulation analysis method and the reliability of the parameter identification method.On this basis,this paper simulates the thermal behavior of lithium ion battery,analyzes the distribution of the batteries' temperature,and compares it with the temperature of the sample point in the actual experiments,in order to verify the reliability of the simulation method.Finally,a fast temperature estimation method for lithium ion battery is proposed by analyzing the partial differential equation of thermal behavior correlation of lithium ion battery,and using approximate function instead of analytical solution method.On the premise of ensuring accuracy,the requirement of battery thermal simulation on simulation environment and simulation time is reduced,which lays a foundation for the online application of thermal simulation in battery management system.