Thermal Characteristics Of Lithium Ion Battery And Its Thermal Management Of Battery Module

Lithium-ion batteries have attracted much attention as the core of electric vehicles and other energy storage devices,and their changes have been greatly affected by temperature,the lithium ion battery obtains the best performance of charging and discharging and cycling life at the temperature of293.15K³23.15K,the thermal management system can solve the heat accumulation during the charging and discharging of battery modules,besides,it can also figure out the difference between battery modules.The LiNi_0.5Co_0.2Mn_0.3O₂（523）cylindrical lithium ion battery is chosen as the object of experimental research.Firstly,the discharging and heat generation characteristics of the battery are tested by the charging and discharging tests of single battery in several temperatures.Secondly,based on the theoretical basis of CFD,the model of heat generation is established according to the battery concentration model,and the static and dynamic conditions of the battery pack are studied.In the end,the thermal management design and experimental verification of the battery pack are carried out.The specific contents are as follows:（1）By building up the battery temperature test experimental platform,the battery performance of charging and discharging is tested in temperature from 253.15K to 313.15K,the results show that the discharging characteristics of the battery are poor at low temperature,the activity of the negative electrode material is reduced;the capacity and initial working voltage of battery at normal temperature 303.15k are reduced by 45%and 10%compared with the low temperature 253.15K,the ion diffusion rate in the electrolyte inside the battery is slow,resulting in an increase in internal resistance;by studying the reversible heat and irreversible heat of the ternary lithium battery,the heat generation rate of the battery is calculated,selecting the battery concentration model to simulate the temperature rise,The temperature rise and trend of the battery are predicted well by CFD.The results show that the maximum simulation error is less than 1.5K,which has better temperature predictability.（2）Dynamic condition simulation of electric vehicle battery packs is carried out,and several urban working conditions and climbing conditions are used for research.The simulation results show that the normal urban dynamic conditions are not strong,and are smaller than the power consumption of the 2C constant current discharge of the single cell.In addition,the analysis of different static conditions of different grid types,different rates and different structures for the battery pack has been carried out.The results show that the impact on the battery pack is not great when selecting the grid of the battery pack and structure of rectangle;the heat generation study under different rates shows that in the case of 2C and above rate discharge under natural convection without auxiliary heat dissipation,the internal temperature reaches 327K exceeding the suitable temperature of the lithium battery,and along with the phenomenon of heat accumulation,and difference between the internal batteries is large,and it is necessary to design a heat dissipation for the group heat generation characteristics.（3）A liquid-cooled battery model is established for solving the high temperature of the central area of the battery pack and the internal temperature difference,and a 4×4 battery module is selected as the research object.The parameters are optimized by CFD technology to gain the best inlet velocity,pipe diameter,coolant temperature,etc.,and simulated heat generation analysis under multiple static conditions.Finally,the feasibility of the heat dissipation scheme was verified by experiments.