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 (C
m) 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%.