Homogeneous core–shell NiCo2S4 nanostructures supported on nickel foam for supercapacitors

In this study, we report the fabrication of NiCo2S4 with a homogeneous core–shell nanostructure in which NiCo2S4 nanotubes are wrapped by NiCo2S4 nanosheets. The core–shell structured NiCo2S4 was in situ grown on nickel foam and can be directly applied as a supercapacitor electrode. Electrochemical tests demonstrate that the NiCo2S4 electrode achieved a high specific capacitance of 1948 mF cm−2 at a current density of 1 mA cm−2, a good rate capability, and an excellent cycling stability. The outstanding performance of the NiCo2S4 electrode can be attributed to its core–shell architecture with good mechanical and electrical contact and rich redox reactions, as well as high transport rate for both electrolyte ions and electrons. By applying NiCo2S4 as the positive electrode and porous carbon as the negative electrode, an asymmetric supercapacitor device was fabricated and it exhibited an excellent electrochemical performance. These results demonstrate that the homogeneous core–shell NiCo2S4 nanostructure is promising for supercapacitor applications.