A two-step hydrothermal synthesis approach to synthesize NiCo2S4/NiS hollow nanospheres for high-performance asymmetric supercapacitors

Abstract

In this work, a high-performance asymmetric supercapacitor device based on NiCo2S4/NiS hollow nanospheres as the positive electrode and the porous activated carbon as the negative electrode was successfully fabricated via a facile two-step hydrothermal synthesis approach. This NiCo2S4/NiS//activated carbon asymmetric supercapacitor achieved a high energy density of 43.7Whkg−1 at a power density of 160Wkg−1, an encouraging specific capacitance of 123Fg−1 at a current density of 1mAcm−2, as well as a long-term performance with capacitance degradation of 5.2% after 3000 consecutive cycles at 1mAcm−2. Moreover, the NiCo2S4/NiS electrode also demonstrated an excellent specific capacitance (1947.5Fg−1 at 3mAcm−2) and an outstanding cycling stability (retaining 90.3% after 1000 cycles). The remarkable electrochemical performances may be attributed to the effect of NiS doping on NiCo2S4 which could enlarge the surface area and increase the surface roughness.