Study On Preparation And Performance Of Insulating And Thermal Conductive Silicone Rubber Composites Based On Battery Thermal Management

The thermal conductivity of silicone rubber（SR）is only 0.2 W/（m·k）,which cannot be directly used as the thermal conductivity material for the cooling of EVs battery packs in battery thermal management.Generally,thermal conductive fillers are added to the SR matrix to improve the thermal conductivity of SR composites.To prepare highly thermally insulating SR composites,hexagonal boron nitride（h-BN）was used as the main thermal filler in this paper,and Ag NPs-h-BN were prepared by modified silver nanoparticles（Ag NPs）with h-BN,and electrostatic self-assembly method was used to mix the modified h-BN（mh-BN）and carbon fiber（CF）to prepare the mh-BN@CF composite filler,then filled into the SR matrix to prepare Ag NPs-h-BN/SR and mh-BN@CF/SR composites.Fourier transform infrared spectroscopy（FTIR）,scanning electron microscopy（SEM）,and thermogravimetric analyzer（TGA）were used to characterize the chemical properties,surface morphology,and thermal stability of SR composites.The effects of filler mixing method,filler amount,and filler filling ratio on the thermal conductivity,mechanical properties,and electrical insulation properties of SR composites were studied.Finally,the SR composites were applied to the battery thermal management system（BTMS）,and the temperature and temperature difference of the battery pack were simulated and analyzed through computational fluid dynamics（CFD）.The study found that:（1）The Ag NPs-h-BN composite filler was prepared by modified the h-BN particles with Ag NPs,the optimal content of Ag NPs exists.That is,when the Ag NPs content is 2.2g and the filling amount is 90phr,the thermal conductivity of the Ag NPs-h-BN/SR composite is1.28W/（m·k）.In terms of mechanical properties and electrical insulation,the tensile strength of the Ag NPs-h-BN/SR composites are 4.93 MPa when the filling amount is 50 phr,compared with h-BN/SR composites,the tensile strength is increased by 18.8%,the elongation at break was slightly reduced to 212%,and the volume resistivity was maintained at 10¹⁵Ω·cm.（2）When the mass ratio of mh-BN:CF=7:3,mh-BN@CF/SR composites have the highest thermal conductivity.When the amount of mh-BN@CF fillers are 54phr,the thermal conductivity of mh-BN@CF/SR composites is 1.30W/（m·K）.Compared with h-BN/CF/SR and h-BN/SR composites,the thermal conductivity is increased by 23.7%and 57.4%,respectively,and the thermal conductivity is increased by 400.4%compared to the SR matrix.The tensile strength of mh-BN@CF/SR composite is 5.82Mpa,and the elongation at break is 305.1%.Compared with h-BN/CF/SR composites,the tensile strength and elongation at break of mh-BN@CF/SR composites increased by 12%and 26%,respectively,and compared with h-BN/CF/SR composites,the tensile strength and elongation at break of mh-BN@CF/SR composites increased by 13%and 145.3%,respectively.In addition,the volume resistivity of the mh-BN@CF/SR composite is about 1.5×10¹⁵Ω·cm.（3）Using CFD to simulate BTMS simulation,it was found that the maximum temperature of the battery pack using mh-BN@CF/SR composites were reduced by 9.1K compared to SR composites as the cooling channel material,which indicated that the ecvellent thermal conductivity of the mh-BN@CF/SR composites prepared by self-assembly of mh-BN@CF filled into the SR matrix is helpful for the heat dissipation of battery packs.