Significantly improved energy density of BaTiO₃ nanocomposites by accurate interfacial tailoring using a novel rigid-fluoro-polymer

Dielectric nanocomposites incorporating core–shell structured nanoparticles have drawn increasing attention in recent years for energy storage applications. Among the many key factors, the thickness and the chemical structure of the interfacial layer are rarely investigated. This work presents a novel approach to precisely tailor the interfacial layer thicknesses by modulating the polymerization degree of a rigid liquid-crystalline fluoro-polymer. BaTiO3@rigid-fluoro-polymer nanoparticles with a range of interfacial thicknesses were prepared by a surface-initiated reversible-addition–fragmentation chain transfer polymerization method. The frequency dependent dielectric properties and energy storage capability of dielectric nanocomposites based on a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) P(VDF-TrFE-CTFE) matrix and the modified BaTiO3 nanofiller were investigated. The results demonstrated that the permittivity, breakdown strength and energy density of the polymer nanocomposites were significantly affected by the thickness of the rigid-fluoro-polymer shell around BaTiO3. Moreover, a high discharged energy density of 16.18 J cm−3 was achieved in nanocomposites containing 5 vol% BaTiO3, when the shell thickness was approximately 11 nm. The findings provide a new and innovative approach to prepare dielectric composites with high energy density, and enable a deeper understanding of the influence of the interfacial layer thickness on the dielectric performance.