Tuning the MOF-derived Fe fillers and crystal structure of PVDF composites for enhancement of their energy storage density.

[Display omitted] • The MOF-derived Fe significantly improve the polarization of PVDF-based composites. • A high breakdown strength is obtained by adjusting crystalline structure of PVDF. • The enhanced energy density of 28.9 J/cm3 is achieved at ultralow filler fractions. Polymer-based capacitors are essential energy storage components in the electronic and electrical industries, which is benefit for their high power density and fast charge–discharge capabilities. However, the low energy density of polymer-based capacitors limits their miniaturization and intelligent applications. In this study, we present the novel poly(vinylidene fluoride) (PVDF)-based composites with exceptional energy storage performance at the submicron metal filler loadings. Guided by synergistically improving the dielectric constant and breakdown strength of polymer-based composites, metal–organic framework (MOF)-derived Fe fillers and Press & Heat (P&H) cycles are mainly implemented. The polymer-based composites exhibit a superior dielectric constant of 15.3, while simultaneously maintain a high breakdown strength of 617.1 MV/m. The excellent energy density of 28.9 J/cm3 is obtained at the ultralow filler loading of 0.2 wt%. Synergistic tuning the loading content of MOF-derived Fe and optimizing the P&H cycles not only leads to a novel composite dielectrics with outstanding energy storage properties, but also presents a new strategy for exploring high-performance capacitive polymer composites. [ABSTRACT FROM AUTHOR]