Facile synthesis of microsphere copper cobalt carbonate hydroxides electrode for asymmetric supercapacitor

Porous microspheres copper cobalt carbonate hydroxides (Cu_xCo_2-xCH) pseudocapacitive electrode material comprised of nanoplates via a facile hydrothermal method were presented. Significantly, the crystalline structure, morphology and electrochemical performance of the Cu_xCo_2-xCH can be readily manipulated by varying the Cu/Co molar ratios. Among various stoichiometries of Cu_xCo_2-xCH porous microspheres studied, Cu_1.79Co_0.21CH consisted of nanoplates with a mean thickness of ∼35 nm showed a high specific capacitance of 789 F g^-1 at a current destiny of 1 A g^-1 and good rate ability. Furthermore, the optimized Cu_1.79Co_0.21CH electrode also exhibited remarkable high cycling stability, ca 77.5% after 3000 charge/discharge cycles at current density of 5 A g^-1. An asymmetric device was constructed from optimized Cu_1.79Co_0.21CH materials on nickel foam (NF) as cathode electrode and graphene on NF as anode electrode in a 6 M KOH electrolyte. The asymmetric Cu_1.79Co_0.21CH/NF//graphene/NF supercapacitor device delivered a specific capacitance of 60.5 F g^-1 in a potential range of 0-1.6 V. A high energy density of 21.5 W h kg^-1 was achieved at the power density of 200 W kg^-1. More significantly, the designed device exhibited excellent cycling stability with 73.3% capacity retention after 5000 cycles.