A high-performance asymmetric supercapacitor based on Ni3S2-coated NiSe arrays as positive electrode

Abstract

NiSe rods coated with cotton-like Ni₃S₂ were directly grown on nickel foam through a two-step process, comprising selenization and electrodeposition. The as-obtained NiSe/Ni₃S₂ composite electrode exhibited excellent electrochemical properties, with a high specific capacitance of 8.81 F cm⁻² (1259.3 F g⁻¹) at a current density of 4 mA cm⁻², which was better than the value of pure NiSe electrode (5.17 F cm⁻²; 861.8 F g⁻¹) at the same current density. Moreover, an asymmetric supercapacitor (ASC) was fabricated using NiSe/Ni₃S₂ electrode and AC electrode as positive electrode and negative electrode, respectively. This ASC extended the potential window to 1.6 V and was possessed of a superior energy density of 38.7 W h kg⁻¹ at a power density of 192 W kg⁻¹, with outstanding cycling stability (85.9% retention after 10 000 cycles).