Three-dimensional porous graphene/nickel cobalt mixed oxide composites for high-performance hybrid supercapacitor

Transition metallic mixed oxides have gained great interest for hybrid supercapacitor because of their extremely low cost and excellent electrochemical performance. Herein, we report a novel approach of overabundant metallic-ions- induced combination and space confined Ostwald ripening strategy to synthesize three-dimension graphene (3DG)/metal organic framework composite which could be transformed into 3DG/NixCo1-xO aerogel with NixCo1-xO nanoparticles well dispersed on graphene framework. The hierarchical structure provides highly interconnected porous conductive network and enhances contact between NixCo1-xO nanoparticle and graphene greatly. Electrochemical measurement indicates that the 3DG/NixCo1-xO electrode delivers a specific capacitance of 697.8 F g(-1), remarkable rate performance with 89% capacitance retention at current density of 20 A g(-1), and outstanding cycle stability with 81% specific capacitance retention after 10,000 cycles. An optimized hybrid supercapacitor adopting 3DG/NixCo1-xO composite as the cathode and 3DG as the anode is constructed, which shows a superior energy density of 27.2 W h kg(-1) at a power density of 725 W kg(-1) and satisfactory cycle stability of 86% capacitance retention after 10,000 cycles at a current density of 5 A g(-1).