Core-shell structured BaTiO3@SiO2@PDA for high dielectric property nanocomposites with ultrahigh energy density

Flexible nanocomposite dielectrics with high dielectric constant and discharge energy density have broad application prospects in the field of energy storage. However, dielectrics with high dielectric constant tend to have a high dielectric loss. Herein, we prepared a dielectric composite material with ultra-high discharge energy density by modifying the interface between nanoparticles and poly(vinylidene fluoride-co-hexafluoropropylene) (P[VDF-HFP]). After coating a shell of insulating amorphous SiO₂ (~7 nm) outside the barium titanate (BT), the electric field concentration and current density inside BT particles can be significantly reduced. In addition, coating the SiO₂ shell with a polydopamine (PDA) shell (~7 nm) not only enhances the interface interaction between the nanoparticles and the polymer matrix, but also can form lots of microcapacitors in the composite. As a result, an ultra-high discharge energy density of 13.78 J/cm³ at the expense of relatively inconspicuous efficiency (~59.8%) in the BT@SiO₂@PDA/P (VDF-HFP) with 2.5 wt% loading has been achieved under 460 kV/mm. This is mainly attributed to the increases of dielectric constant from 12.1 to 14.2 and the relatively low dielectric loss (0.086) at 100 Hz. Moreover, compared with the pure P (VDF-HFP) (400 kV/mm), the breakdown voltage of the composite with 2.5 wt% loading is surged to 460 kV/mm, which benefited from the hindrance of nanoparticles on carrier migration at low content. This work has realized a thin-film dielectric with ultra-high discharge energy density through a novel design of the nanoparticle structure, providing a theoretical direction for the development of polymer dielectric capacitors.