Giant energy storage of flexible composites by embedding superparaelectric single-crystal membranes

Flexible organic-based composites embedding nanosheet-like inorganics with high energy storage density (U) are imperatively demanded for applications in portable electronics and sensors. However, the breakdown phases can easily bypass the discontinuous nanosheets, leading to the failure of conduction barriers. Here, continuous flexible Sm-doped BiFeO₃-BaTiO₃ (Sm-BFBT) membranes with superparaelectric characteristics were synthetized via etching a water-soluble Sr₃Al₂O₆ buffer layer. With the single-crystal Sm-BFBT membranes embedded into poly(vinylidene fluoride), a giant U of 46.4 J/cm³ at 770 MV/m is achieved in the sandwich-structured composites, attributed to a formation of depolarized field induced by interfacial ions. Meanwhile, the composites exhibit a stable U of ∼20 J/cm³ at 550 MV/m during bending process, owing to the excellent flexibility of Sm-BFBT membranes originating from nanodomain switching. The proposed composites containing flexible 2D inorganic membranes offer unprecedented structural insights into the integration of high energy storage and stability of bending, and suggest potential uses in flexible energy storage devices.