PVDF-Based Dielectric Composite Films with Excellent Energy Storage Performances by Design of Nanofibers Composition Gradient Structure

The dielectric polymer-based films with excellent energy storage properties have been considered as potential candidates for flexible capacitors. In this study, the hierarchical gradient structures of the 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanofibers (BZCT NFs) are designed in the polyvinylidene fluoride (PVDF) composite films. The composite films with different compositions of BZCT NFs gradient structure were prepared by layer-by-layer electrospinning, hot-pressing, and quenching processes. The microstructures and electrical properties have been studied, and the results indicate that the BZCT NFs gradient structures can simultaneously improve the polarization and the breakdown strength of the PVDF-based composite films, leading to the enhancement of energy storage density (9.8 J/cm3) compared to that of pristine PVDF films (4.2 J/cm3). This work provides an efficient route to improve the energy storage properties of polymer-based composite films by structure modulation.