Significantly improved breakdown strength and energy density of tri-layered polymer nanocomposites with optimized graphene oxide

Abstract Advanced electrostatic capacitors with great energy densities are urgently needed for practical applications in high-performance energy storage devices. Herein, poly (methyl methacrylate) (PMMA) is employed as two outer layers to provide excellent insulation characteristic, while ferroelectric copolymer poly (vinylidene fluoride-co-hexafluoropropene) P(VDF-HFP) with dispersed graphene oxide (GO) as the inter layer to enhance dielectric constant (K) and electrical displacement (D). The resulting trilayered nanocomposites exhibit highest electrical displacement difference (Dmax-Drem) value of 7.17 μC cm−2 at a low filler loading of 2 wt% GO under an electrical field of 300 MV m−1. The breakdown strength (Eb) of the designed trilayered nanocomposites are prominently improved at least one order of magnitude in comparison to other configuration films such as single-layered and reversed trilayer structures, as verified by the leakage current measurements and the finite element simulations with 3D models. The trilayered nanocomposites deliver an ultrahigh energy density of 10 J cm−3 and a discharged efficiency of 77% at an applied electrical field of 300 MV m−1, which is among the best energy storage performance under the identical electric field reported so far. The potential applications of the trilayered nanocomposites for energy storage have been further demonstrated by stable performance over a 40,000 charge-discharge cycling.