▎ 摘　　要

Nickel-cobalt binary oxide/reduced graphene oxide (G-NCO) composite with high capacitance is synthesized via a mild method for electrochemical capacitors. G-NCO takes advantages of reduced graphene oxide (RGO) and nickel-cobalt binary oxide. As an appropriate matrix, RGO is beneficial to form homogeneous structure and improve the electron transport ability. The binary oxide owns more active sites than those of nickel oxide and cobalt oxide to promote the redox reaction. Attributed to the well crystallinity, homogeneous structure, increased active sites, and improved charge transfer property, the G-NCO composite exhibits highly enhanced electrochemical performance compared with G-NiO and G-Co3O4 composites. The specific capacitance of the G-NCO composite is about 1750 F g(-1) at 1 A g(-1) together with capacitance retention of 79 % (900/1138 F g(-1)) over 10,000 cycles at 4 A g(-1). To research its practical application, an asymmetric supercapacitor with G-NCO as positive electrode and activated carbon as negative electrode was fabricated. The asymmetric device exhibits a prominent energy density of 37.7 Wh kg(-1) at a power density of 800 W kg(-1). The modified G-NCO composite shows great potential for high-capacity energy storage.