Ultrafine core-shell BaTiO3@SiO2 structures for nanocomposite capacitors with high energy density

Dielectric capacitors are irreplaceable energy-storage components in pulsed power systems, but the low energy density (U_e) of existing material systems restricts their miniaturization and further application. In this work, a novel polymer/ceramic nanocomposite is fabricated using core-shell BaTiO₃@SiO₂ (BT@SO) structures with a diameter less than 10 nm. Such ultrafine nanostructure not only provides a high insulating SiO₂ layer to optimize the microstructure and dielectric response as normal core-shell structures, but also has almost tenfold larger interfaces than conventional 100 nm fillers to realize a high polarization, which can effectively improve the breakdown strength as well as the electrical displacement of the composite simultaneously. With a simple and universal 0–3 type structure, in which 0-dimentional nanoparticles are embedded in a 3-dimentional connected polymer matrix, the BT@SO/PVDF nanocomposite shows outstanding energy storage performance with U_max = 11.5 J/cm³ at 420 kV/mm. Experimental result and phase field simulation both confirm the superiority of the ultrafine nanostructures in enhancing the energy density of the dielectric nanocomposite, providing a new technological way for the design of high energy-density composites.