Sandwich-Structured BNNS/rGO-g-POSS/PVDF Composites with Significantly Enhanced Dielectric and Energy Storage Performance

The improvement in energy storage performance of graphene/polymer composites has long been restricted by insufficient breakdown strength (Eb) and high dielectric loss, both of which result from conductive losses caused by the aggregation of graphene nanosheets. In this paper, aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS-NH2) encapsulated graphene oxide (GO) (GO-g-POSS) hybrids were prepared to inhibit the restacking of graphene and block the formation of conductive paths. Furthermore, the design of sandwich-structured films is also an efficient approach to improving the breakdown performance of composite materials. Novel sandwich-structured composite films containing outer layers of BNNS/PVDF films and a middle rGO-g-POSS/PVDF layer were successfully prepared by the layer-by-layer assembly process. The B-0.50-B sandwich-structured composites achieved an optimal discharge energy storage density (Ue) of 9.08 J cm−3 and Eb of 432 MV m−1.