Significant Enhancement of Energy Storage Performances by Regulating the Dielectric Contrast between Adjacent Layers in the Heterostructural Composites

Polymer-based composites with high discharged energy density and energy efficiency are tremendously desired for modern electronic systems. In this study, a bilayer heterostructural composite (named as THV/xBT) with excellent energy storage performances was constructed by one layer of a BaTiO3 nanoparticles (BT nps)-filled P(VDF-HFP) composite and another layer of a pure poly(tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene) (THV) polymer with a moderate dielectric constant and high breakdown strength. The experimental and finite element simulation results indicate that the space charges could accumulate at the interfaces between THV/P(VDF-HFP) and BT nps/P(VDF-HFP) by regulating the dielectric contrast between these two adjacent layers. It improves not only the interfacial polarization but also the breakdown strength and limits the leakage current density of THV/xBT composites. As a result, the THV/5BT composite delivers the best energy storage performance with the discharged energy density of 22.7 J/cm3, and an energy efficiency of 79.0% is achieved. This work might open up a way for structural design of polymer-based composites with remarkable energy storage performances.