Novel core–shell-structured ironbark-like TiO 2 as fillers for excellent discharged energy density of nanocomposites

The perpendicular orientation of nanowires to electric fields would greatly improve the breakdown strengths ( E b ) of polymer-based nanocomposites; however, the relatively small polarization at small filler fraction, and thus the unsatisfactory discharged energy density ( U d ), greatly restrict their further application. In this study, x vol.% TO@TO/PVDF nanocomposites with superior energy storage performances have been fabricated, where the ironbark-like TiO 2 fillers (TO@TO) with core–shell structures lead to greatly enhanced polarization and E b simultaneously. The former is due to the coupling effects of the increased interfacial polarization, while the latter is due to the enhanced path tortuosity of electric tree growing at small TO@TO fraction. Strikingly, an excellent U d of 13.1 J/cm 3 was achieved in the 1.5 vol.% TO@TO/PVDF nanocomposite at 383 MV/m, which is greatly increased by 220% compared with that of pure PVDF (5.98 J/cm 3 ). The primary results might provide a strategy to design and fabricate nanocomposites with satisfactory energy storage performances as well as the flexible and easy processing ability at small filler fraction.