Design and preparation of ternary polymer nanocomposites for high energy density film capacitors

High discharge energy density (Ue) film capacitors are important for miniaturization and integration in power electronic applications. The Ue of a polymer film is mainly dependent on Weibull's breakdown strength (Eb) and dielectric constant (epsilon r). This work aims to develop ternary nanocomposites composed of polycarbonate (PC), Al2O3 nanoparticles (Al2O3 NPs) and BaTiO3 nanowires (BT NWs) for capacitive energy-storage. Al2O3 NPs have a wide bandgap and are expected to enhance Eb owing to their insulating nature, while BaTiO3 nanowires (BT NWs) are ferroelectric and are expected to provide a high epsilon r. To overcome local electric-field distortion at the interface due to the mismatch in epsilon r, core-shell structured BT@SiO2 NWs are prepared. The Eb of the composite containing 1.0 wt% Al2O3 NPs and 6.0 wt% BT@SiO2 NWs can reach 626 MV/m while that of the pure PC is 465 MV/m. As a result, its Ue reaches 12.12 J/cm3, which is improved by 211% that of the pure PC. Its discharge efficiency is 83.5%. A finite element analysis corroborates the superiority of the ternary polymer nanocomposites for dielectric energy-storage.