Preparation And Phase Change Properties Of Graphite-based Phase Change Microcapsules

In this paper,modified graphene phase change microcapsules?E-rGO/Paraffin?were prepared by modified graphene which grafted by amidogen as wall material and paraffin wax as core material.?E-rGO-SiO₂/Paraffin?which enhance thermal cycle stability of microcapsules can obtained by introduce silica into modified graphene.The E-rGO-SiO₂/Paraffin was applied to the lithium-ion battery pack thermal management system,and the performance of the battery was studied as well.The structure,microstructure and energy storage properties of were investigated by XRD,SEM,FT-IR and DSC.The graphene that grafted amine group by ethylenediamine while reducing was used as wall material to prepare E-rGO/Paraffin.The thermal conductivity and other thermal performances of phase change microcapsules with 10%of modified graphene were characterized by SEM?DSC and other methods which indicated that the melting enthalpy of E-rGO/Paraffin is 100.3J/g,and the thermal conductivity increased to 0.757W/?m·K?which is 4.0 times higher than that of pure phase change material.The optimum reaction conditions that prepared modified grapheme microcapsules were as follows:the ultrasonic power was 105W before the GO was gravitated by ethylenediamine,8000rpm stirring,the content of graphene was 10%.Good morphology microcapsules can be obtained with 89.5%coating rate under reaction conditions above.Silica was introduced into E-rGO as composite wall material in order to improve the thermal cycling stability of phase change microcapsules and E-rGO-SiO₂/Paraffin was obtained.The cnditons when preparing the microcapsules were that pH=2.4?while preparing prepolymer?,1%of modified graphene,the ratio of water to silicon was 1:1,and 8000rpm stirring.With the conditions above good morphology,whose average particle size is about 20?m can be obtained.The enthalpy of melting was 78.54J/g,with 70.1%encapsulation,and the thermal conductivity increased to 0.693W/?m·K?which was 3.7 times higher than that of pure paraffin.The enthalpy of melting was only 5.6%lossed after100 cycles of hot and cold cycles,which indicated that the microcapsules had high cyclic stability.The surface temperature of battery was studied with different environmental temperature and different discharge magnification by adding E-rGO-SiO₂/Paraffin into Lithium-ion battery pack thermal management system.The surface temperature of batteries inside the battery pack decreased 6? when the condition is 25? and 1C discharge.When test condition changed to 40? and 0.7C discharge the surface temperature of battery was decreased by 4.7? and 8 ? was decreased by 1C discharge.The temperature of the battery can be reduced effectively with the addition of E-rGO-SiO₂/Paraffin and the safety performance of the battery pack was enhanced as well.