Energy Storage Capability of PVDF-Based Nanocomposites Significantly Enhanced by BaTiO3@BaxSr1–xTiO3 with Multi-Layer Gradient Core–Shell Structure Nanofillers

Electrostatic capacitors have high power density, but how to improve the energy storage density of electrostatic capacitors has always been the key to solving energy problems in the background of the energy crisis. Designing multi-layer core–shell inorganic nanofillers is an effective way to break the contradiction between high dielectric constant and high breakdown strength in nanocomposites to improve the energy storage performance. Herein, polyvinylidene fluoride (PVDF)-based nanocomposites are proposed, which are filled with multi-layer core–shell structured inorganic BaTiO3@BaxSr1–xTiO3@DA nanoparticles (BT@BST@DA NPs). In the optimized 2 wt % PVDF/BaTiO3@BaxSr1–xTiO3@DA nanoparticle (PVDF/BT@BST@DA NPs) nanocomposite material, a high discharge energy density of 13.75 J/cm3 (370 MV/m) can be obtained, as well as excellent discharge efficiency. The dielectric performance and energy storage density of 2 wt % PVDF/BT@BST@DA NPs are proven to be better than 2 wt % PVDF/BaTiO3@DA nanoparticles (PVDF/BT@DA NPs). This work provides a strategy for the development of dielectrics for electrostatic capacitors with high energy storage density.