Growth of cobalt-nickel layered double hydroxide on nitrogen-doped graphene by simple co-precipitation method for supercapacitor electrodes

Nitrogen-doped graphene/Co-Ni layered double hydroxide (RGN/Co-Ni LDH) is synthesized by a facile co-precipitation method. Transmission electron microscopy images indicated that the formation of Co-Ni(OH)(2) nanoflakes with the good dispersion anchored on the surfaces of the nitrogen-doped graphene sheets. The nitrogen-doped graphene composites delivered the enhanced electrochemical performances compared to the pure Co-Ni LDH due to the improved electronic conductivity and its hierarchical layer structures. The high specific capacitance of 2092 F g(-1) at current density of 5 mA cm(-2) and the rate retention of 86.5% at current density of 5-50 mA cm(-2) are achieved by RGN/Co-Ni LDH, higher than that of pure Co-Ni LDH (1479 F g(-1) and 76.5%). Moreover, the two-electrode asymmetric supercapacitor, with the RGN/Co-Ni LDH composites as the positive electrode and active carbon as the negative electrode material, exhibits energy density of 49.4 Wh kg(-1) and power density of 101.97 W kg(-1) at the current density of 5 mA cm(-2), indicating the composite has better capacitive behavior.