Heat Dissipation Structure Design Of LiFePO₄Power Battery For Electric Vehicle

The power lithium-ion battery has been widely used in electric vehicles for its high energy density, high work voltage and long cycle life. However, the battery will generate a lot of heat in the working process. Once the heat can’t dissipate immediately, it would lead to dramatically increasing of the battery temperature and then cause serious accident. Thus, during the battery’s working process, reducing the heat generation and enhancing the surface cooling are both necessary to ensure the security usage of power battery. The traditional means to design a small capacity battery is no longer use for large battery, so this paper will optimize the thermal structure in power battery design in other to realize that the battery will have the minimus heat production but the maximum heat dissipation at the surface after optimization.Firstly, this work used3.2V/50Ah LiFePO4power battery produced by Lithium Force Holdings Co. Ltd for experimental analysis and built up the laboratory platform to measure the power batteries’ thermal and electrical parameters. The experiment results showed that either higher or lower temperature will have negative effects on the battery’s discharge performance; besides, the battery had a lower output capacity when discharge at large rate, and it caused a temperature increased. When discharge at same rate, the battery temperature distribution at different position is different:the highest temperature is at positive pole, the second is at negative pole, the minimum is at the surface center.Secondly, this paper used the ANSYS software to simulate the optimizing of the battery thermal structure focus, mainly focus on the two sides:First, Optimizing the size structure of the battery by analysis four types battery’s thermal performances when discharged at the same rate, and then compare the thermal parameters of those different battery types. Second, after the first step, the battery then used for study the internal electrode performance with the coupled electric-thermal model, then discuss the influence of existing electrode on the heat generation and electric parameters of battery.For checking, the numerical dates of the battery surface temperature was compared to the experimental dates, the results give a good agreement between those dates. Moreover, the numerical results showed that when increasing the positive and negative pole opposition placement and width, the active material’s utilization rate on the electrode would improve accompany, and the electric field distribution would express more uniform and produce less heat.Finally, the simulation result optimalize structure show as the the positive and negative tab of electrode unit size is60mmx30mm and relatively placed on both sides of the electrode, the electrode unit’s heat generation is about one fifth of the electrode unit that the positive and negative tab are adjacent placement and the size are30mm×30mm and40mmx30mm electrode unit and its current density and voltage distribution is more uniform than the latter two electrode unit. So the methods of optimizing external battery size and internal structure of electrode can rearrange the battery with strengthen heat dissipation and produce low heat.