Ni(OH)₂ Nanosheets Grown on Reduced Graphene Oxide for Supercapacitor Electrodes

Ni(OH)2 has low production cost and high theoretical specific capacity, while on account of the poor electronic conductivity, it shows inferior electrochemical performance including cycling stability and rate capability. This work focuses on a composite material that is in situ grown Ni(OH)2 nanosheets on reduced graphene oxide (rGO), and employing the fewer-defect rGO to build a three-dimensional conductive network provides outstanding conductivity. The specific capacitances (Cm) of the Ni(OH)2/rGO (NHG) electrode are 2776 F·g–1 at 2 A·g–1 and even 1570 F·g–1 at 50 A·g–1, demonstrating remarkable rate capability. It indicates that the combination of the nano grown Ni(OH)2 and rGO conductive substrate shortens the ion diffusion path and increases the electron transfer rate; hence, the composite rate capability has been significantly improved. The composite materials and active carbon were combined to be an asymmetric supercapacitor, which had a high energy density of 39.24 Wh·kg–1 at 1962 W·kg–1. After 10,000 cycles at 5 A·g–1, the capacity retains 91.4%.