Simulation Of Heat And Mass Transfer In Vacuum Drying Process Of LiFePO₄power Battery

With the rapid popularization of new energy vehicles,power battery as the core component of new energy vehicles has a direct impact on the performance and safety of new energy vehicles.In recent years,the research of the power battery is focused on the improvement of the battery positive electrode material,the reaction mechanism of the material inside the battery charging and discharging state,but the battery manufacturing process,especially the more important drying process,is less mentioned.In this paper,the LiFeP04 power battery is the research object.Based on the basic principle of vacuum drying of the heat and mass transfer and combined with the electrode material drying technology of power battery,the first two times of the drying processes in preparation processes were simulated by the way of simulation.By the above research,get the heat and mass transferring of the LiFePO4 battery mathematical physics which is based on the simplified model,provide the theoretical basis for the optimization of the enterprise actual production process.In this paper,the physical parameters of the power battery were analyzed,and the internal structure of the battery was observed by the method of physical disassembly and electron microscope scanning(SEM).The energy spectrum of the cathode coating material was analyzed.Its elements were obtained and the synthesis method was deduced.The data obtained and the manufacturers mentioned parameters are compared to verify the accuracy of the parameters,which provides data support for the following work.Then,in this paper,based on drying process of LiFePO4 power battery,two basic mathematical physics models of the heat and mass transfer were established.And meanwhile,the two models are deduced by the complicated calculation using the related methods of higher mathematics,and finally analytical solution of the model is got.Then,in this paper,use the MATLAB software,combined with the drying process of electrode materials to simulate two electrode material drying process relatively,and get the variation law of parameters of electrode materials in vacuum drying process with time and location.The results were also analyzed and discussed.The research shows that the variation law of the drying processes of the powder and the pole piece are very close in mass transferring.Overall,with the development of time,water of LiFePO4 powder and pole piece of in the drying process decrease gradually,but in different time,different locations,the rates of water reduction are different.In addition,the water near the vacuum side begins to decrease at first,and the water near the heat source side begins to decrease after a period of time.In heat transfer,compared with the powder material,the heat transfer process of the piece is faster.It can complete the process in less than half an hour.This is for that the thickness of the pole piece is relatively thin,although its thermal diffusivity is smaller than the thermal diffusivity of the powder material,but the thickness of the pole piece is two orders of magnitude smaller than the thickness of the powder.The heat conduction rate of the pole piece is faster on the whole.Finally,this paper uses COMSOL to respectively simulate the two drying process of LiFePO4 material.Go on geometry modeling and calculation focused on the one dimensional model and three-dimensional model,the variation of physical properties of electrode material with time and position during vacuum drying was obtained,and the corresponding cloud pictures and graphs are given.It shows that the COMSOL simulation results are consistent with the MATLAB calculation results,and verifies the mathematic model to solve the correctness of the results.In this paper,the mathematical modeling and analysis of the drying process of the electrode material in the process of preparation are conducted.And use COMSOL to conduct physical simulation which is closer to real condition.the physical simulation of COMSOL is closer to real condition and The heat and mass transfer mechanism in the vacuum drying process of LiFePO4 power battery was studied,which provides a theoretical support for the optimization of the drying process of LiFePO4 power battery.