Suppressing charge injection and preventing the extension of electrical trees of polymer-based composites through two-dimensional metal–organic frameworks nanosheets

Electrostatic capacitors have become an essential enabling technology in electronics and electrical power systems. The utilization of composite dielectric has significantly improved the discharged energy density (Ud). Nevertheless, optimizing the compatibility between fillers and polymers to further achieve miniaturization, lightweight, and integration remains a significant challenge. In this work, a novel composite film composed of two-dimensional (2D) metal–organic framework [Ni3(OH)2(1,4-benzenedicarboxylate)2-(H2O)4]⋅2H2O (2D Ni-MOF) nanosheets and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) have been prepared. 2D Ni-MOF nanosheets possess superior interface area and dispersibility, which could interact well with the polymer matrix to form high-quality composite films. Meanwhile, Ni-MOF nanosheets act as ordered scattering centers to prevent the extension of electrical trees and introduce deep trap energy levels to trap the generated carriers. Remarkably, the ultralow content of 2D Ni-MOF nanosheets (∼0.25 wt%) synergistically improves dielectric constant and breakdown strength, thus achieving highly Ud of 21.16 J/cm3 at 600 MV/m. Such a simple, environmentally friendly, and mass-producible preparation process explores a promising new paradigm for high-performance electrostatic capacitors.