Enhancement of Energy Density in the BOPP-Based Sandwich-Structured Film by the Synergistic Effect of BaTiO3@Polyaniline Hybrid Dielectric Fillers

A series of polyaniline-coated BaTiO3 (BaTiO3@PANI) hybrid dielectric fillers were prepared through the in situ oxidative polymerization of aniline. The morphology of the hybrid fillers can be controlled by the ratio of aniline and BaTiO3 particles. Mulberry-like and core–shell BaTiO3@PANI composite particles are prepared successfully. The two kinds of dielectric fillers were introduced into the poly(vinylidene fluoride) (PVDF) matrix separately or simultaneously. The dielectric loss can be suppressed by the synergetic effect of these two hybrid fillers while enhancing the dielectric constant at the same time. The finite element simulation results showed that the surface morphology of adjacent hybrid fillers played an important role in the dielectric performance. The fillers were introduced in the biaxially oriented polypropylene (BOPP)-based sandwich-structured film; specifically, the outer layer was BOPP and the middle layer was the composites consisting of chlorinated polypropylene (CPP)/PVDF blends and the hybrid fillers. The energy storage density of the sandwich-structured film was improved significantly compared to that of the BOPP film. The highest discharge energy density was 7.31 J/cm3 at 450 MV/m, and the charge–discharge efficiency was 77.3% with 30 wt % hybrid fillers in the middle layer.