Research On Power Batteries Thermal Management Technology Based On PCM

Energy crisis and environmental pollution pop up as the auto industry rapidly develops. New-energy autos represented by electric vehicles will become the mainstream of the future development direction due to more unique advantages than traditional vehicles in energy utilization and emissions reduction. As the core component of new-energy autos, power batteries whose security will influence the overall performance of the vehicles. However the reasonable thermal management technology can effectively improve the performance and life,etc and ensure the highest temperature and the maximum temperature difference in the operating temperature range. Therefore in-depth study of power battery thermal management technology has very important significance.Based on the power battery thermogenesis mechanism and the research current situation of thermal management technology at home and abroad,this paper focuses on PCM thermal management technology. Copper foam(CF)/paraffin composite was prepared and its performance were characterized. Experiments about graphite/paraffin and copper foam/paraffin42110phase change modules were processed. Finally, by analyzing the heat dissipation effect about PCM and air cooling module during the EV actual operation process, the thermal management technology based on PCM cooling was studied and evaluated. It provides certain reference significance for the actual research of power battery thermal management system. The paper mainly concerns the following:First, the heat production principles of the LiFePO4batteries are researched and relative main factors during the, mainly including the solid electrolyte interface(SEI) film and anode decomposition, reaction of cathode and electrolyte and electrolyte decomposition etc. From the angle of heat transfer, we analyze the heat generated by the module and the phase change materials usage with phase change materials (PCM) cooling,also the theoretical formula is given. Battery heat generation mechanism analysis has important guiding significance for subsequent experimental study.Secondly, the copper foam/paraffin composites were prepared and its properties were characterized via coefficient of thermal conductivity test, scanning electron microscope (SEM) and X-Ray diffraction (XRD) test. Thermal conductivity coefficient test result shows that the conductivity coefficient of composite materials,compared with pure paraffin(0.21W·m-1·K-1), was increased15.93times and reaches4.3W·m-1·K-1owing to the copper foam addition. Copper foam as additives, makes up the defect of the paraffin wax with low thermal properties and contribute to the excellent performance of the composites. SEM figure shows the hole in pure copper foam were completely filled by liquid paraffin which guarantees enough filling volume for improving the thermal conductivity performance of composite materials. XRD test results indicate that the addition of copper foam does not affect the chemical stability of paraffin wax as matrix and no new phase is formed after the composite.Test results of copper foam/paraffin42110phase change module show the highest temperature and the maximum difference can be controlled respectively within55℃and5℃The experiment data of graphite/paraffin phase change module indicates the maximum temperature rises with the increase of discharge rate which comes to40.89℃at5.0C discharge rate and peak temperature difference is within5℃,and the performance can meet the heat dissipation demand. The maximum temperature reaches32.38℃at3.0C discharge rate under low-temperature condition Peak temperature at5.0C discharge rate under super high temperature situation comes to44.72℃.And the data of two modules show both have excellent controlling-temperature and evening-temperature performance.Finally, loading test data shows that peak temperature comes to36℃on the ground which is57.7%lower than that of air cooling module.The maximum temperature difference of air-cooled module reaches6.8℃and PCM cooling module is2℃on200slope. Both plain and different slope road conditions, heat dissipation performance of PCM cooling technology is superior to that of air cooled. Through the overall assessment about the current cooling technologies, PCM cooling technology is better than air cooling in the effect, system complexity, maintenance, etc.It will have a strong competitiveness and development potential in the future.