Constructing bidirectional-matched interface between polymer and 2D nanosheets for enhancing energy storage performance of the composites

Interfacial engineering, specifically core-shell architecture with highly insulating inorganic shell layer is generally adopted to improve the energy storage density (Ue) of polymer composites. However, the amorphous inorganic shell layer seems to be the only choice, as substantial interfacial tension arose from the core-shell lattice mismatch. Especially for the 2D nanosheets with high aspect ratio and highly crystallized surface, free volume between interfacial region is inevitably formed, restricting further Ue improvements of polymers. Here, bidirectional matched (bm) aluminum oxide interface transition regions are constructed between polyimide (PI) and Ca2Nb3O10 (CNO) nanosheets to prepare the composites (PI/CNO@AO). The bm-interface includes the inner core-shell lattice matched region and the outer shell-matrix structure matched region, and the gradual transition between them has been confirmed. Numerous experimental and characterization results manifested the successful construction of the bm-interface, and the interface could intrinsically depress the carrier transportation and electric conduction of the composites. Meanwhile, the simulated electric breakdown paths evolution in the PI/CNO@AO composites further confirms the results. Consequently, excellent energy storage performance of the composites is obtained at both conventional and high-temperature environments. The bm-interface design strategy holds great promises and may blaze new trails in preparing high energy density polymer dielectric capacitors.