Symmetric transparent and flexible supercapacitor based on bio-inspired graphene-wrapped Fe₂O₃ nanowire networks

Transition metal oxides with high specific capacitance materials are ideal for a new generation of high-performance transparent supercapacitors but are rarely reported. Commonly, the synthesis of the required nanostructured materials is a crucial step required to achieve the transparency of the device. In this study, a Fe₂O₃ nanowire network transparent film is developed simply through air-solution interface reactions and wrapped in graphene shells for use as transparent electrodes. The Fe₂O₃ nanowire networks surrounded by the graphene layer exhibit an effective encapsulation structure, providing rapid three-dimensional electron and ion transport pathways. The specific areal capacitance (3.3 mF cm^-2 at a scan rate of 10 mV s^-1) was greatly improved, which is at least one hundred times higher than that for transparent devices based on planar chemical vapor deposition graphene. Furthermore, the films have a power density of 191.3 W cm^-3, which is higher than that of electrolytic capacitors, an energy density of 8 mWh cm^-3, which is comparable to that of lithium thin-film batteries, and superior cycling stability.