Study Of Characteristics And Structural Design Of Li-Ion Battery Based On An Electrochemical-thermal Coupled Model

With the increasingly and seriously environmental problems and the energy crisis continued to intensify,the development of electric vehicles is considered to be the key factor to improve the environment and relieve the energy crisis.The critical challenges to enlarge the market share of electric vehicles are how to cut the cost,and promote the performance,reliability and safety.When lithium ion batteries are employed for the electric vehicle energy storage system,its performance,energy density,thermal stability directly restricts the development of electric vehicles.In the premise of ensuring safety and thermal stability,the development of high power,high specific energy,high specific energy and how to design a thermal management system with simple structure,high efficiency have been focused by academic and industrial fields.In this work,the Li[Ni_1/3Co_1/3Mn_1/3]O₂?NCM?/graphite 18650-sized lithium ion battery with high specific energy is studied.An electrochemical-thermal coupled model is developed by using COMSOL software.The model was also validated by the experimental data in which the batteries were charged and discharged in different ambient temperatures and discharge rates.Based on the electrochemical-thermal coupled model,the NCM/graphite 18650-sized lithium ion battery are analyzed and investigated I terms of the behaviors of lithiation and delithiation of electrode,the electrochemical reaction,heat and mass transfer.By using the electrochemical-thermal coupled model,the influence of thickness on discharge performance,heat and mass transfer,temperature distribution of the NCM/graphite 18650-sized lithium ion battery is examined.The relationship between the maximum temperature rise,the energy efficiency,the thermal energy conversion efficiency and electrode thickness under different cooling conditions are investigated.Under the condition of controllable temperature,the thickness of the electrode can be improved and to increase the energy density.The numerical simulation by using COMSOL software as the simulation platform is conducted to comparative analysis type flat tube twining,wrap in ground battery liquid cooling structure,the heat conducting sheet wrapped around the battery and connected with the flat pipe for the 18650 type lithium ion battery.The evaluation method of thermal management system is established based on temperature,temperature difference,pressure loss and cooling energy consumption to compare and select cooling method.The research results can provide guidance for the design and optimization of the cooling structure of the cylindrical power battery module.