Investigation On The Liquid Cooling Thermal Management System Of Lithium Ion Pouch Type Battery Module Based On Electrochemical-Thermal Coupling Model

Lithium ion pouch type batteries,with the structure of stacked electrode pairs,have been widely utilized with the advantages of 1)high capacity,2)reliable safety performance,3)light weight,etc.However,lithium ion pouch type batteries have the risk of the large maximum temperature rise,which may cause safety issues of large capacity reduction and thermal runaway,especially under the conditions of high discharge rate and high depth of discharge.The research results on the simulation model and thermal management system of the lithium ion pouch type batteries show that the multi-physics simulation method based on the electrochemical-thermal coupling model could improve the simulation accuracy and reliability of the transient temperature field of the soft battery,and thus improve the cooling efficiency of the thermal management system.However,how to establish an electrochemical-thermal coupling model for pouch type batteries and how to simulate the transient temperature fields of lithium ion pouch type single cells,battery modules,and liquid-cooled systems have been the prior issue to be solved urgently.Therefore,the multi-physics coupling model and the lumped parameter model have been established for 35 Ah single cells,140 Ah battery module and liquid cooling thermal management system,which could be utilized to study and analyze the related variables(electrochemical domain,temperature Field and flow field).The effect of depth of discharge and discharge rate on the three-dimensional temperature field of battery cells and battery modules have been discussed.The influence of direction of the inlet of the liquid cooling structure as well as the velocity of the inlet to the heat management system have also been discussed.Therefore,the main innovations and highlights of this research could be listed as follows:(1)The electrochemical model and thermal model the lithium ion batteries have been analyzed and established,which could be utilized to establish and verify the electrochemical-thermal coupling model with the method of multi-physics coupling method.The results show that the variables such as the depth of discharge and the discharge rate could firstly affect the electrochemical variables,such as the battery terminal voltage and battery polarization overpotential,which would affect the thermal performance of lithium ion batteries.(2)The heat generation rate as well as three-dimensional temperature distribution of battery single cell and battery module have been simulated transiently based on the verified electrochemical-thermal coupling model and the lumped parameter model.Based on the simulation results,the effect of depth of discharge and discharge rate has been investigated.The results show that there would be obvious thermal issues on the lithium ion pouch type cell module under the condition of high depth of discharge and high discharge rate,which may result in thermal runaway.Therefore,the heat management system of liquid cooling should be utilized.(3)The U-shaped flow channels of battery management system have been designed based on the transient distribution of hot spot location on the lithium ion battery module.Therefore,the three-dimensional temperature field has been simulated transiently on the battery module and cooling channel through the multi-physics coupling method.The study has investigated the influence of the cooling structure,inlet flow velocity and other parameters on the temperature distribution of the battery module,which could be utilized to improved the cooling performance and provide a theoretical basis for the improvement.