Gradient design of ultrasmall dielectric nanofillers for PVDF-based high energy-density composite capacitors

Dielectric capacitors are key devices in pulsed power systems for their high power density. To improve the energy density, compact nanocomposite films comprising PVDF polymer and core-shell BaTiO3@TiO2 nanoparticles are prepared, in which the BaTiO3 (d ~ 8 nm) nanoparticles are encapsulated by the amorphous TiO2 shell layer. Compared to the conventional BaTiO3/PVDF nanocomposite, the BaTiO3@TiO2/PVDF nanocomposite in this report takes advantage of the small particle size and the gradient dielectric design of the interface, which enhances the electric displacement as high as 65% and the breakdown strength of 20% simultaneously. A maximal discharged energy density of 11.34 J·cm−3 is achieved under an electric field of 420 kV·mm−1 in the nanocomposite film containing 5 vol% BaTiO3@10 wt%TiO2. Therefore, the gradient design of ultrasmall dielectric nanofillers shows high potential in fabrication of high energy-density nanocomposite. [Display omitted] •Utilizing large specific surface area and gradient structure of ultrasmall fillers, high εr and Eb are both obtained.•The dielectric constant and breakdown strength can be enhanced 20% and 65% respectively.•A maximal energy density of 11.34 J/cm3 at 420 kV/mm is obtained.