| With the increasing depletion of globalized fossil energy and serious pollution of the ecological environment,there is an urgent need to find a clean energy that can replace fossil fuels.Lithium ion batteries have become the primary alternative to fossil fuels due to their high specific energy,high specific power and high voltage platform.However,due to the frequent thermal safety problems during the use of lithium-ion batteries,the development and popularization of electric vehicles have been limited.Therefore,in order to avoid the problem of heat generation affecting the normal use of the battery,it is necessary to accurately analyze the heat generation and heat dissipation characteristics of the lithium ion battery.The main research contents of this article are as follows:A lithium ion power battery charging and discharging test platform was built,and a 10 Ah lithium iron phosphate lithium ion battery was tested at different rates(1C,2C,3C)and different ambient temperatures(-10?,5?,20?,35?,50?)discharge test,analyzed the temperature and discharge rate on the battery temperature rise and capacity.For the lithium iron phosphate lithium ion battery used in the experiment,a full threedimensional electrochemical-thermal coupling model was built in the multiphysics simulation software of COMSOL Multiphysics.Distribution characteristics.The results show that the established full three-dimensional electrochemical thermal coupling model can obtain results that are difficult to obtain by traditional experimental methods such as local potential distribution and current density distribution of the battery;during the constant current discharge of the lithium ion battery,there is a significant temperature gradient inside the single cell,Especially in the transition area between the tab and the plate,the battery temperature gradient changes the most;the temperature rise rate of the battery at different locations during the discharge process is not the same,in the early discharge,the temperature rise rate of the pole area is the largest,away from the bottom of the battery The rate of regional temperature rise is relatively small,but there is a tendency to increase in the later stage of discharge.Through the three-dimensional electrochemical-thermal coupling model,the average heat generation rate of the single lithium ion battery was obtained,and the obtained single heat generation rate was substituted into the battery module to study the temperature field change of the battery module during the discharge process.The results show that with the increase of the charge and discharge rate,the maximum temperature rise and temperature difference of the battery pack continue to rise.At the end of the 2C discharge,the maximum temperature of the lithium ion battery pack is 324 K,an increase of 26 K,and the internal temperature difference of the battery pack reaches 5K.According to the heat conduction characteristics of the lithium ion battery,the lateral cooling method of the lithium ion battery pack is designed,and the temperature field of the lithium ion battery pack is analyzed by factors such as different charge and discharge rates,different cooling pipe shapes,different cooling liquid flow rates and positions Impact.The results show that the maximum temperature of the lithium ion battery module decreases significantly with the increase of the cooling flow rate,but when the cooling flow rate is greater than 0.1m / s,continuing to increase the cooling liquid inlet speed has little effect on the temperature rise of the battery pack;The temperature change of the 2C battery pack shows that the cooling method of the square flow channel is better than the cooling method of the circular flow channel of equal cross-sectional area,and the cooling effect of the square flow channel is more obvious at a large magnification. |
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