Asymmetric All-Metal-Oxide Supercapacitor with Superb Cycle Performance.

Metal oxides have great potential for developing high-performance supercapacitors due to their high specific capacitances. However, achieving high energy densities while maintaining good rate capability and long cycle life has proved to be challenging. We propose herein a strategy for constructing all-metal-oxide asymmetric supercapacitors (ASCs), in which both the cathode and anode are based on metal oxides, and demonstrate their outstanding electrochemical performance. We anchored SnO2 nanoparticles on the surface of reduced graphene oxide (RGO) through Sn-O-C bonds (as the cathode of ACSs), and employed low-crystalline RGO/MoO3 nanosheets as the anode, based on the large work function difference between SnO2 and MoO3 . The resulting ASC can operate stably at 1.8 V in neutral aqueous electrolyte and deliver an energy density of up to 33 W h kg-1 , which remains at 13.8 W h kg-1 even at 37.5 kW kg-1 . Moreover, the ASC exhibits a good cycling stability of 92.5 % capacitance retention after 20 000 cycles.