Universal Construction of Electrical Insulation and High-Thermal-Conductivity Composites Based on the In Situ Exfoliation of Boron Nitride-Graphene Hybrid Filler

Hexagonal boron nitride (h-BN), with excellent thermal conductivity and insulation capability, has garnered significant attention in the field of electronic thermal management. However, the thermal conductivity of the h-BN-enhanced polymer composite material is far from that expected because of the insurmountable interfacial thermal resistance. In order to realize the high thermal conductivity of polymer composite thermal interface materials, herein, an in situ exfoliation method has been employed to prepare a boron nitride nanosheet-graphene (BNNS-Gr) hybrid filler. After being incorporated into a poly(ethylene glycol) (PEG) matrix, the thermal conductivity of composites is significantly improved on the premise of electrical insulation. Furthermore, a three-dimensional (3D) thermally conductive framework using this hybrid filler as the raw material has also been constructed. After incorporating poly(ethylene glycol) (PEG) through a vacuum impregnation method, this ordered structure effectively resolves the leakage issue in phase-change composites during actual working conditions and showcases enhanced thermal conductivity of 2.45 W m^–1 K^–1 at 10 vol %, along with excellent electrical insulation, shape stability, and cyclic stability. The modified Hashin–Shtrikman model and the Foygel nonlinear model prove that compounding graphene with BN reduces the interfacial thermal resistance of polymer composites for both disordered and ordered systems. This indicates that the in situ exfoliation strategy is an effective method to fabricate the nanofiller for reducing the interfacial thermal resistance of composites.