Fabrication of a low defect density graphene-nickel hydroxide nanosheet hybrid with enhanced electrochemical performance

The development of efficient energy storage devices with high capacity and excellent stability is a demanding necessary to satisfy future societal and environmental needs. A hybrid material composed of low defect density graphene-supported Ni(OH)₂ sheets has been fabricated via a soft chemistry route and investigated as an advanced electrochemical pseudocapacitor material. The low defect density graphene effectively prevents the restacking of Ni(OH)₂ nanosheets as well as boosting the conductivity of the hybrid electrodes, giving a dramatic rise in capacity performance of the overall system. Moreover, graphene simultaneously acts as both nucleation center and template for the in situ growth of smooth and large scale Ni(OH)₂ nanosheets. By virtue of the unique two-dimensional nanostructure of graphene, the as-obtained Ni(OH)₂ sheets are closely protected by graphene, effectively suppressing their microstructural degradation during the charge and discharge processes, enabling an enhancement in cycling capability. Electrochemical measurements demonstrated that the specific capacitance of the as-obtained composite is high as 1162.7 F/g at a scan rate of 5 mV/s and 1087.9 F/g at a current density of 1.5 A/g. In addition, there was no marked decrease in capacitance at a current density of 10·A/g after 2000 cycles, suggesting excellent long-term cycling stability.