Significantly enhanced energy storage performance promoted by ultimate sized ferroelectric BaTiO3 fillers in nanocomposite films

Polymer nanocomposite that consists of dispersed particle fillers and a flexible polymer matrix shows comprehensive excellent dielectric properties and thus is considered as promising dielectric layers in high-performance energy-storage capacitors. However, the commonly employed high permittivity particle fillers cause inevitable dielectric strength deterioration and seriously impede the energy density and reliability of the nanocomposite. To solve this problem, ultimate sized ferroelectric nanofillers, 6.9 nm BaTiO3 nanocrystals, are introduced into a poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) polymer matrix to realize both the high dielectric constant and enhanced breakdown strength. The influence of nanoparticle fraction on the microstructure and dielectric properties of the composite films is investigated. Compared to the polymer-ceramic composites with coarse particle fillers, significantly enhanced breakdown strengths (≥330 kV/mm) are observed in the nanocomposite films containing 10–40 vol.% BaTiO3 nanofillers. In consequence, a maximal discharged energy density of 9.7 J/cm3 is obtained, which confirms that these ultimate sized nanocrystals can perform as superior high permittivity fillers in the nanocomposites for energy storage applications.