Dual-Strategy to Construct Aqueous-Based Symmetric Supercapacitors with High Volumetric Energy Density

Carbon-based supercapacitors have been widely used in electric vehicles because of their high-power density, long cycle life and fast charge/discharge rates. However, low volumetric energy density severely limits their application for miniaturized electronic devices. Here, we have demonstrated a carbon-based symmetric supercapacitor by using a three-dimensional porous graphene with high density as the electrode material and a 17M NaClO4 water-in-salt electrolyte with a 2.1V electrochemical stability window. The device exhibited high specific capacitance (145.3Fcm(-3) at 0.5Ag(-1)), excellent rate performance (70.0% capacitance retention even at 50Ag(-1)), high volumetric energy density (22.3WhL(-1) at 333.4WL(-1) based on the total mass of active materials) and excellent cycle stability with 99.1% capacitance retention after 10,000 cycles at 5Ag(-1). The performance of this device was superior to the most current supercapacitors based on carbon materials. This effective dual-strategy of simultaneously regulating capacitance and potential window can greatly promote the further development of aqueous carbon-based supercapacitors.