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

Abstract

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. Keywords: Energy storage, Polymer nanocomposites, Interfaces, Dielectric, Core-shell