Significantly enhanced energy storage properties in sandwich-structured polymer composites with self-assembled boron nitride layers

Electrostatic capacitors have attracted tremendous attention in modern electron systems. Herein, we report a new design of sandwich-structured composite boron nitride-poly(vinylidene fluoride-co-hexafluoropropylene)/barium titanate-boron nitride (BN-P(VDF-HFP)/BT-BN) via interfacial self-assembly combined with the solution casting method. In this composite, the outer layers are the self-assembled BN films with high insulation to provide high breakdown strength (Eb) and resist the charge injection, whereas the middle layer contains the high permittivity (εr) BaTiO3 nanoparticles to provide high electrical polarization. Experimental results show that the Eb and discharged energy density (Ue) of BN-P(VDF-HFP)/BT-BN composites can be significantly improved with BN layer. The sandwich-structured composites of BN-3-BN show a high Ue of 19.4 J/cm3 at 550 MV/m, which is much greater than the corresponding single-layer composite. Further, the finite element results indicate that the designed sandwich-structure was contributing to improved Eb and Ue. Therefore, this study provides a novel strategy to enhance energy density in dielectric materials, which has great potential in high-performance electrostatic capacitor.