Optimizing energy storage density of the multi–layer composite of poly(vinylidene fluoride) and nano–Ni plated CaCu3Ti4O12 with an ultralow filling content

Surface modification of nanoceramics with high dielectric constant can increase dielectric constant of polymer composites voiding excessive dielectric loss, however, low discharged energy density (Ud) of composites at a low loading limits potential applications in high–energy–storage devices under low electric field. Herein, Ni–plated CaCu3Ti4O12 nanoparticle (CCTO@Ni) is used to improve the electric properties of the poly(vinylidene fluoride) monolayer composites (C/PVDF), and an ultralow loading of 0.5 vol% promotes the largest Ud of 2.53 J/cm3 at 230 MV/m, resulting from MWS interface polarization and Coulomb barrier effect included by CCTO@Ni fillers, which is used to further prepare three kinds of multi–layer structured C/PVDF composites by solution casting layer by layer. Comprehensive testing shows that the PVDF–C/PVDF–PVDF–C/PVDF–PVDF five–layer film (P–C–P–C–P) enhances the dielectric constant and breakdown strength to contribute the maximal Ud of 6.65 J/cm3 at 297.8 MV/m, which is 118% larger than that of pure PVDF. Above excellent characteristics are attributed to the interface polarization of the middle C/PVDF layer and the alleviating and blocking effect of the middle and outer PVDF layers, which are clarified in depth by the finite element simulation and enhanced breakdown model.