Thermal Analysis Of Lithium Ion Battery For Vehicle

The development of electric vehicles has provided an effective way to solve the energy crisis and improve the living environment.Lithium ion battery is one of the main power sources of electric vehicles,due to its excellent electrochemical performance.The working process of lithium ion battery is greatly influenced by itself and the external environment temperature,thereby reducing the safety performance of the electric vehicle.So the analysis of thermal characteristics of lithium ion battery and providing proper methods for thermal management of lithium-ion batteries are of great importance to improving the safety of electric vehicles,reducing energy consumption and improve the quality of the environment.In this paper,18650 cylindrical lithium ion battery was used as the research object.Based on the electrochemical and thermal properties of the single cell,the charge-discharge characteristics of the battery and influencing factors of heat generation were explored.To control the battery temperature,a parallel ventilation system is designed.The effect of the cooling system and the traditional serial ventilation system were analyzed by means of simulation.The main work is as follows:First of all,based on the charge conservation equation,the mass conservation equation and the electrode dynamics theory,the electrochemical model of 18650 lithium manganese oxide battery was established.The electrochemical performance of the constant current charge and discharge process was analyzed by this model.In the charging process,with the increase of charging rate,battery charging process "Voltage platform" is higher and the platform duration is shorter and the charging capacity of the battery is smaller.In the discharging process,with the increase of discharging rate,battery discharging process "voltage platform" is lower and the platform duration is shorter and the discharging capacity of the battery is smaller.Secondly,combined with heat transfer theory,established a battery electrochemical thermal coupling model.The effects of external adiabatic conditions,natural convection conditions,low forced convection conditions and air-cooled conditions on the battery temperature were analyzed.According to the average temperature changes in heat generation process under the adiabatic condition,heat energy of the battery were calculated.The results show that the air cooling condition has a greater influence on the temperature of the lithium ion battery.Finally,compared and analyzed the heat dissipation of the traditional serial ventilation cooling system and the designed parallel ventilation cooling system.From different aspects,such as the internal temperature,single cell battery surface temperature,and different conditions of entrance,the designed parallel ventilation cooling system is superior to the traditional serial ventilation cooling system.