Improved polarization and energy density in boron nitride nanosheets/poly(vinylidene fluoride-chlorotrifluoroethylene) nanocomposite with trilayered architecture regulation.

A polymer film capacitor with high energy density has attracted great attention in recent decades to fulfil the requirements of miniaturization and light weight for electronics and energy storage systems. The multi-layered nanocomposite exhibits an effective route for developing polymer film with large energy capability due to the advantage of each layer. Here, two sandwich constructions of boron nitride nanosheets (BNNSs)/poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) nanocomposite film were designed to investigate the effects of architecture regulation on energy storage performance, i.e. the nanocomposite serving as an inner layer with pristine films as outer layers, in which the nanocomposite film delivers a strongly polarized behavior and the pristine polymer provides a high breakdown strength. The BNNSs were liquid exfoliated from boron nitride bulk assisted with fluoro hyperbranched copolymer that was adsorbed on the surface of nanosheets via CH-π non-covalent interactions. The presence of fluoro segments improves the compatibility between the nanosheets and the P(VDF-CTFE) matrix. The maximum polarization of 7.9 μC cm-2 at 300 MV m-1 is achieved in the tailored sandwich film, and the discharged energy density of 9.1 J cm-3 is obtained in the current nanocomposite, which benefits from the barrier effect between adjacent layers induced by the redistribution of electric field and emerging charge traps at the interfaces. This sandwich BNNSs/P(VDF-CTFE) nanocomposite provides an insightful prospect for structural design with respect to the advanced application of the polymer film capacitor.