High capacitance and rate capability of a Ni3S2@CdS core–shell nanostructure supercapacitor

Abstract

Hierarchical Ni₃S₂@CdS core–shell nanostructures on nickel foam were synthesized by a one-step hydrothermal method for the first time. As supercapacitor materials, the Ni₃S₂@CdS core–shell nanostructures exhibited a high capacitance of 3.15 F cm⁻² (2100 F g⁻¹) at a current density of 2 mA cm⁻², and 86.7% of the original capacitance was retained even at a high current density of 15 mA cm⁻², suggesting excellent rate capability. An asymmetric supercapacitor based on Ni₃S₂@CdS as the positive electrode, porous carbon as the negative electrode and KOH as the electrolyte can work steadily at a voltage of 1.5 V, and presented excellent electrochemical performance. After 4000 charge–discharge cycles at a current density as large as 6 mA cm⁻², 130% of the initial capacitance was maintained. The asymmetric supercapacitor exhibited a high energy density of 127.5 W h kg⁻¹ at a current density of 2 mA cm⁻² and with a corresponding power density of 0.995 kW kg⁻¹. The above-mentioned results indicate that Ni₃S₂@CdS could be a potential candidate for supercapacitors.