Study On Thermal Behavior Of Lithium-ion Battery For Electric Vehicle

Energy crisis and environmental problems pops up as the auto industry rapidly develops, thus the electric vehicles on behalf of the new-energy autos overwhelm the future auto market. Among them the lithium-ion batteries become the mainstream power source by virtue of its excellent performance as well as comparative advantage. As the core component of new-energy autos, the charge and discharge properties, durability and reliability of the power battery can directly impact the overall performance. While proper thermal management on power battery system can effectively improve the performance and service life of battery pack, therefore its reliability and safety. Hence, it is of great practical significance and application value to proceed the study about core technology of lithium-ion power battery thermal management system.On the basis of comparison and summary on the research situation of battery heat generation rate and thermal model at home and abroad, this paper focuses on the three-dimensional electrochemical-thermal model of lithium-ion batteries to study on thermal behavior of power battery, thermal analysis on lithium-ion power battery is carried on to study the law of heat generation, heat transfer and heat dissipation via hydromechanics. The heat generation rate model and thermal behavior model of power battery are made to achieve simulation analysis and calculation on lithium-ion power battery cell and module thermal behavior. The temperature distribution of the power battery cell and module under different thermal conditions is obtained when charging and discharging in constant-rate. Finally, through battery cell and module charge and discharge temperature experiment, the correctness of the applied lithium-ion power battery thermal behavior is tested to provide theoretical ground and reference guide for the designing and developing lithium-ion power battery thermal management system. The paper mainly concerns the following:Firstly, study in terms of principles on lithium-ion power battery caloricity is conducted. Through analysis and summary of the current study concerning battery heat generation rate and its influencing factors, the heat generation rate model which coupled internal impedance Joule heat, polarization heat, side reaction heat and electrochemical reaction heat is employed. Meanwhile, the Digatron power testing system conducts analysis of internal impedance on lithium-ion power battery to accurately obtain variation attributes of the lithium-ion power battery Ohm resistance and polarization resistance. Afterwards, MATLAB and ADVISOR are applied to analyze and calculate lithium-ion power battery heat generation rate of constant-rate charging and discharging and in driving cycle. The lithium-ion power battery heat in driving cycle can be correctly predicted, which grounds the follow-up study for battery thermal behavior.Secondly, based on the accurate lithium-ion battery heat generation rate, according to the principle of lithium-ion power battery heat transfer and heat dissipation, a cylindrical thermal behavior model is create. FLUENT simulation analysis on it is proceeded via hydromechanics, temperature varies with the heat dissipation of lithium-ion power battery cell and module in constant-rate charging and discharging, to know the law of lithium-ion power battery heat generation, heat transfer and heat dissipation to ensure the demanding air speed of battery module in the proper range of temperature at the air entrance on conditions of diverse rate charges or discharges. The reference of the power of fan of battery pack is provided accordingly.At last, lithium-ion power battery pack test bench is set and the temperature test of power battery pack in certain constant-rate charge or discharge under different thermal conditions is conducted via Digatron battery test system. The change data on the battery module temperature field is collected, and compares with simulated temperature results. The comparison shows the change trend of the experimental temperatures is in concord with simulated temperatures, confirming the feasibility and correctness of lithium-ion power battery heat generation rate model and thermal behavior model applied.