Improved energy storage capability in sandwiched PEI/P(VDF-CTFE)/PEI dielectric composite film

Designing polymer dielectrics with high energy density and high charge-discharge efficiency remains a significant challenge due to the inherent trade-off between the enhancement of electrical displacement and dielectric reliability. In this work, a multiscale hierarchical design featuring a sandwich-structured film with pristine polyetherimide (PEI) as outer layers and a middle film of P(VDF-CTFE) composite embedded with hierarchical AgNbO₃and boron nitride nanosheets (AN@BN hybrid particles) has been developed to address this issue. The addition of AN@BN hybrid particles regulates the mobility of local carriers, resulting in the depression of conduction loss under an external applied field. The optimized sandwiched composite (S-AN5@BN-0.5) achieves a high discharged energy density of 11.6 J cm^-3with a charge-discharge efficiency of 82% at 450 MV m^-1. The enhanced dielectric reliability of the resultant sandwiched film is ascribed to the presence of an outer linear PEI layer, and the inhibitory effect of the intermediate layer BN on charge aggregation also contributes to the high charge-discharge efficiency. This work demonstrates a feasible pathway for designing advanced dielectric composites by rationally integrating complex hybrid fillers within sandwiched polymer films.