Regulating SiO2 interlayer morphology towards synergistically reinforced dielectric properties and thermal conductivity in Si/PVDF composites

Abstract

Polymeric composites integrating large dielectric constant (ε), minimal loss with elevated breakdown strength (E_b) and thermal conductivity (TC), exhibit concern in electrical and power industry. To enhance the TC and E_b while suppressing loss in silicon (Si)/poly (vinylidene fluoride, PVDF), the Si@silica (SiO₂) was prepared by high-temperature oxidation, and subsequently doped into PVDF. The Si@SiO₂/PVDF displays lower loss since the SiO₂ layer prevents direct contact between Si particles， inhibiting long-distance electron migration. Moreover, the SiO₂ introduces traps to immobilize charge carriers, elevating the E_b. In particular, changing the amorphous SiO₂ shell to crystalline one accelerates phonon transport, leading to enhanced TC. The dielectric parameters and TC of the Si@SiO₂/PVDF can be synergistically tuned by adjusting the SiO₂′ morphology and thickness. The theoretical calculation uncovers the underlying mechanisms for both charge and phonon transport in the composites. This developed Si@SiO₂/PVDF composites with excellent dielectric performances and large TC showcase widespread applications.