Enhancing energy density of poly(vinylidene fluoride) composite film via addition of N-doped carbon modified boron nitride and sandwich-structural engineering

•Boron nitride nanosheet with N-doped carbon modification as novel dielectric filler.•Enhanced compatibility and interfacial polarization between filler and PVDF matrix.•Simultaneously increased dielectric constant and breakdown strength.•Outstanding energy density and efficiency achieved in sandwich-structured film.