Tunable BT@SiO2 core@shell filler reinforced polymer composite with high breakdown strength and release energy density

Barium titanate@silicon dioxide (BT@SiO2) core@shell fillers with an average diameter of 100 nm were prepared by a facile sol–gel synthesis. The thickness of SiO2 shell can be easily tuned by varying different mass ratio of BT to tetraethyl orthosilicate (TEOS). Polyvinylidene fluoride (PVDF) based composite films reinforced by BT and BT@SiO2 were fabricated via a solution casting method. The effects of SiO2 shell on morphology structure, wettability, interfacial adhesion, dielectric, electrical and energy performances of composites were investigated. Compared with BT/PVDF, BT@SiO2/PVDF composites show significantly increased breakdown strength due to enhanced interfacial adhesion and suppressed charge carrier conduction. Benefiting from enhanced breakdown strength and reduced remnant polarization induced by SiO2 shell, BT@SiO2/PVDF shows increased release energy density (energy density which can be fully discharged and applicable). Especially, BT@SiO2/PVDF with SiO2 thickness of 4 nm exhibits the highest release energy density of 1.08 J/cm3 under applied electric field of 145 kV/mm.