Developing And Manufacturing The Phase Change Composite Materials For The Heat Management Of The Electric Vehicle Batteries

In recent years,significant achievements have been made in electric vehicles,which benefits from the vigorous development of the new energy vehicle industry in China.The power battery is the core part of the electric vehicle.The development of electric vehicle is inseparable from the development of battery technology.The technical problems of reliability and safety of power battery are the bottleneck of the development of the electric vehicle,especially the thermal management system of power battery.If there is no efficient thermal management system,the battery mileage and battery life will decline rapidly.It may lead to Thermal runaway and even lead to electric vehicle fire and explosion.The composite phase change material can effectively control the battery pack’s temperature through its phase change process,thus improving the temperature uniformity between the batteries.In this paper,the selective laser sintering 3D printing technology is used to manufacture composite phase change materials,which can effectively solve battery heat dissipation and improve the reliability and safety of the battery.The detailed content of this thesis is as follows:(1): In order to improve the fluidity of phase change material(PCM)powder for selective laser sintering(SLS)3D printing technology,a preparation method of PCM powder by liquid nitrogen cooling and grinding in liquid nitrogen was designed: the paraffin wax is ground after liquid nitrogen is cooled and hardened,and the micro-silica gel is added to the process of grinding so that the paraffin can keep the powder shape after it is restored to normal temperature.The powder obtained has good fluidity and can be used for selective laser sintering 3D printing.(2): In order to prepare paraffin / expanded graphite composite phase change material powder with good fluidity,two preparation methods of composite phase change material powder were designed: Grinding after melting in water bath method and Direct mechanical grinding mixing method.The differences in the powders’ properties prepared by the two methods were compared,and the micro morphology,particle size distribution,dynamic fluidity,and thermal properties of the powders prepared by the two methods were tested.Finally,the composite powder composed of 80% paraffin + 15% expanded graphite + 5% micro silica gel prepared by the direct mechanical grinding mixing method has the best comprehensive performance.This composite powder was successfully fabricated by selective laser sintering3 D printing technology.(3): Through the heat transfer simulation,the results show that the more the content of expanded graphite is,the higher the thermal conductivity of paraffin / expanded graphite composite phase change material is.The paraffin / expanded graphite composite phase change material with a thermal conductivity channel can significantly improve the heat transfer efficiency.The application of composite phase change materials in the battery thermal management system can effectively keep the battery operating temperature in a suitable range.Combined with the forced air-cooling system,the overall thermal runaway of the battery can be prevented.