Ni(OH)2/rGO Nanocomposites for Asymmetric Supercapacitors

A Ni(OH)2/reduced graphene oxide (rGO) nanocomposite with a well-defined hexagonal nanosheet morphology was synthesized via a one-step hydrothermal approach using graphene oxide (GO) and nickel sulfate hexahydrate (NiSO4·6H2O) as precursors. Crucially, a commercial-level high mass loading of 8 mg·cm–2 was successfully achieved on the electrode. Structural analysis confirmed that the incorporation of rGO effectively prevents the agglomeration of Ni(OH)2 nanosheets, while forming an interconnected three-dimensional (3D) conductive network. This unique structure enhances the overall electrical conductivity and facilitates rapid ion diffusion even under heavy mass loading conditions. Electrochemical characterization in a three-electrode system revealed that the composite synthesized with a GO concentration of 1 mg·mL–1 (NG-1) exhibited remarkable rate capability across current density ranging from 0.5 to 5 A·g–1. At a current density of 0.5 A·g–1, it delivered a superior specific capacity of 369.5 C·g–1. When assembled into an asymmetric supercapacitor with activated carbon (AC), the hybrid device delivered a specific capacitance of 101.6 F·g–1 (174.4 C·g–1) at 0.5 A·g–1. More remarkably, it demonstrated exceptional cycling stability with 102.2% initial capacitance retention after 10,000 charge–discharge cycles at 2 A·g–1, confirming the excellent electrochemical stability of the NG-1 electrode. Notably, the assembled device attained an energy density of 36.12 Wh·kg–1 at a power density of 400 W·kg–1, significantly surpassing conventional electrochemical double-layer capacitors. The Ni(OH)2/rGO nanocomposites developed in this work combine facile synthesis with outstanding electrochemical properties, providing a promising material solution for high-power energy storage applications.