All-Graphene\nOxide Flexible Solid-State\nSupercapacitors with Enhanced Electrochemical Performance

Abstract

The\nrapid development of flexible and wearable electronics has led to\nan increase in the demand for flexible supercapacitors with enhanced\nelectrochemical performance. Graphene oxide (GO) and reduced GO (rGO)\nexhibit several key properties required for supercapacitor components.\nAlthough solid-state rGO/GO/rGO supercapacitors with unique structures\nare promising, their moderate capacitance is inadequate for practical\napplications. Herein, we report a flexible solid-state rGO/GO/rGO\nsupercapacitor comprising H₂SO₄-intercalated\nGO electrolyte/separator and pseudocapacitive rGO electrodes, which\ndemonstrate excellent electrochemical performance. The resulting supercapacitor\ndelivered an areal capacitance of 14.5 mF cm^–2,\nwhich is among the highest values achieved for any rGO/GO/rGO supercapacitor.\nHigh ionic concentration and fast ion conduction in the H₂SO₄-intercalated GO electrolyte/separator and abundant\nCH defects, which serve as pseudocapacitive sites on the rGO electrode,\nwere responsible for the high capacitance of this device. The rGO\nelectrode, well separated by the H₂SO₄ molecular\nspacer, supplied highly efficient ion transport channels, leading\nto excellent rate capability. The highly packed rGO electrode and\nhigh specific capacitance resulted in a high volumetric energy density\n(1.24 mWh cm^–3) observed in this supercapacitor.\nThe structure, without a clear interface between GO and rGO, provides\nextremely low resistance and flexibility for devices. Our device operated\nin air (25 °C 40%) without the use of external electrolytes,\nconductive additives, and binders. Furthermore, we demonstrate a simple\nand versatile technique for supercapacitor fabrication by combining\nphotoreduction and electrochemical treatment. These advantages are\nattractive for developing novel carbon-based energy devices with high\ndevice performance and low fabrication costs.