Facile preparation and high capacitance performance of copper sulfide microspheres as supercapacitor electrode material

Copper sulfide (Cu₂S) microspheres were easily prepared by reducing copper sulphate with ascorbic acid in sodium thiosulfate solution at room temperature and employed copper sulphate and sodium thiosulfate as Cu and S sources, respectively. The as-prepared Cu₂S microspheres were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties including cyclic voltammetry, galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy were also investigated. The experimental results showed that the as-prepared Cu₂S microspheres based on the three-electrode test system exhibited a maximum specific capacitance of 444.2 F g⁻¹, and the energy density was up to 25.4 Wh·kg⁻¹ with high power density of 4.1 kW kg⁻¹ at the current density of 1 A g⁻¹. Furthermore, Cu₂S microspheres also showed outstanding long-term cycling stability with more than 87% capacitance retention over 6000 cycles due to their microspheres structure, which facilitate efficient charge transport and promote electrolyte diffusion. The Cu₂S-1:1.5 was used as a positive electrode for the fabrication of asymmetric supercapacitor along with reduced GO as the negative electrode, which delivered the high energy density up to 18.6 Wh·kg⁻¹ along with long cycling life and retains up to 89% specific capacitance after 6000 cycles. The excellent results suggest that the Cu₂S microsphere is a promising candidate as electrode material for high performance supercapacitors.