Controlled synthesis of a hierarchical CuNi2O4@SnS nanocauliflower-like structure on rGO as a positive electrode material for an asymmetric supercapacitor

In this paper, a hierarchical CuNi2O4@SnS@rGO nanocauliflower-like structure was grown on Ni foam for the first time via a novel two-step synthesis. Through a hydrothermal method, SnS@rGO was prepared and after this a facile and commendable electrodeposition process was used for fabricating CuNi2O4 on it. The hierarchical CuNi2O4@SnS@rGO/NF is a promising electrode material for building up an impressive supercapacitor. The morphology and structure of the prepared samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, energy dispersive spectroscopy (EDS), elemental mapping analysis, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). N-2 adsorption tests showed that the specific surface area of CuNi2O4@SnS@rGO/NF (295.82 m(2) g(-1)) is much higher than that of SnS@rGO/NF (168.53 m(2) g(-1)). The electrochemical properties of the modified electrodes have been studied in detail at various scan rates using cyclic voltammetry, galvanostatic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (ESI). As a result, the nanocauliflower-like structure of CuNi2O4@SnS@rGO/NF exhibits a high specific capacitance of 1061 F g(-1) and the specific capacity of 177 A h g(-1) at a current density of 1 A g(-1). The specific capacitance of CuNi2O4@SnS@rGO/NF is more than the capacitance of the individual modified electrodes and shows good stability during long-term cycling with perfect cycling stability up to 3000 cycles and a high energy density of 688 W h kg(-1) at a power density of 3892 W kg(-1) in a KOH (3 mol L-1) electrolyte. Also, a CuNi2O4@SnS@rGO/NF//AC asymmetric supercapacitor was assembled, which displayed excellent electrocapacitive performance. The flexible asymmetric supercapacitor exhibits high energy density (589 W h kg(-1)), and long cycle life (86.7% of capacitance retention after 3000 cycles).

Automated summary

In this study, a hierarchical CuNi2O4@SnS@rGO nanocauliflower-like structure was successfully grown on Ni foam for the first time, showing impressive specific surface area and excellent electrochemical properties, indicating great potential for application in supercapacitors.