Symmetric transparent and flexible supercapacitor based on bio-inspired graphene-wrapped FeO 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 FeO nanowire network transparent film is developed simply through air-solution interface reactions and wrapped in graphene shells for use as transparent electrodes. The FeO 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 at a scan rate of 10 mV s) 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, which is higher than that of electrolytic capacitors, an energy density of 8 mWh cm, which is comparable to that of lithium thin-film batteries, and superior cycling stability.