Heat transfer enhanced phase change microcapsule with graphene for battery thermal management

A new type of thermal enhanced phase change microcapsules using graphene-silica dioxide composite as wall material and paraffin as core material was prepared by sol-gel method. Graphene acts as a wall material and thermal enhancement material. Silica is introduced into the wall material to further enhance the mechanical strength of the wall material. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to test the microcapsule morphology, chemical structure and thermal properties of phase change microcapsules. The results show that pH value and dropping rate of the prepolymer droplet influence on the morphology of microcapsules. The prepared graphene-silica dioxide composite based phase change microcapsules have smooth surfaces and a high degree of sphericity. The encapsulation rate is 70.1 % and the size is about 20 mu m. The melting enthalpy of it is 78.54J/g and the thermal conductivity of it increases by 3.67 times compared with pure paraffin. Modified graphene grafted with amino group was obtained by functional reduction of graphene oxide with ethylenediamine. In this paper, this modified graphene is called E-rGO. Traditional battery thermal management methods (natural cooling, air cooling and liquid cooling) have low heat dissipation efficiency and complex system. In this paper, E-rGO-SiO2/ paraffin was applied to the thermal management system of lithium-ion power battery. Under the working conditions of 40 degrees C and 1C, the surface temperature of the battery can be reduced by up to 8.7 degrees C.