Ultrahigh Energy Storage Capacitors Based on Freestanding Single‐Crystalline Antiferroelectric Membrane/PVDF Composites

Abstract Inorganic/organic dielectric composites are very attractive for high energy density electrostatic capacitors. Usually, linear dielectric and ferroelectric materials are chosen as inorganic fillers to improve energy storage performance. Antiferroelectric (AFE) materials, especially single‐crystalline AFE oxides, have relatively high efficiency and higher density than linear dielectrics or ferroelectrics. However, adding single‐crystalline AFE oxides into polymers to construct composite with improved energy storage performance remains elusive. In this study, high‐quality freestanding single‐crystalline PbZrO₃ membranes are obtained by a water‐soluble sacrificial layer method. They exhibit classic AFE behavior and then 2D–2D type PbZrO₃/PVDF composites with the different film thicknesses of PbZrO₃ (0.1‐0.4 µm) is constructed. Their dielectric properties and polarization response improve significantly as compared to pure PVDF and are optimized in the PbZrO₃(0.3 µm)/PVDF composite. Consequently, a record‐high energy density of 43.3 J cm⁻³ is achieved at a large breakdown strength of 750 MV m⁻¹. Phase‐field simulation indicates that inserting PbZrO₃ membranes effectively reduces the breakdown path. Single‐crystalline AFE oxide membranes will be useful fillers for composite‐based high‐power capacitors.