High capacitance and rate capability of Ni3S2@CdS core–shell nanostructures supercapacitor
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 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 current densities as large as 6 mA cm–2, 130% of initial capacitance was maintained. Asymmetric supercapacitor exhibited a high energy density of 127.5 Wh kg−1 at a current density of 2 mA cm–2 and with the corresponding power density of 0.995 kW kg−1. The above results indicate that Ni3S2@CdS could be a potential candidate of supercapacitors.