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

Barium titanate@silicon dioxide (BT@SiO 2 ) core@shell fillers with an average diameter of 100   nm were prepared by a facile sol–gel synthesis. The thickness of SiO 2 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@SiO 2 were fabricated via a solution casting method. The effects of SiO 2 shell on morphology structure, wettability , interfacial adhesion, dielectric , electrical and energy performances of composites were investigated. Compared with BT/PVDF, BT@SiO 2 /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 SiO 2 shell, BT@SiO 2 /PVDF shows increased release energy density (energy density which can be fully discharged and applicable). Especially, BT@SiO 2 /PVDF with SiO 2 thickness of 4   nm exhibits the highest release energy density of 1.08   J/cm 3 under applied electric field of 145   kV/mm.