Novel fabrication of hollow and spinous NiCo2S4 nanotubes templated by natural silk for all-solid-state asymmetric supercapacitors.

Recently, ternary cobalt nickel sulfide, performing as the promising electrode material for supercapacitors has obtained great interests. Herein, the hollow and spinous NiCo2S4 nanotubes are designed and prepared through a simple hydrothermal reaction using the natural silk as the template. The spinous Ni-Co precursors are grown on the natural silk through a facile hydrothermal strategy and the hollow structure is obtained by decomposing the silk via hydrothermal sulfurization. After the calcination treatment, the hollow and spinous NiCo2S4 nanotubes are applied as the electrode material and exhibit better electrochemical performance than the solely vulcanized samples. In addition, owing to the unique hollow and spinous structure of NiCo2S4 nanotubes, the supercapacitor electrode material shows good specific capacitance (630 F g-1 at 1 A g-1), low internal resistance Rs (0.68 Ω) and high capacitance retention (91% after 3000 cycles) at 10 A g-1. Furthermore, an all-solid-state asymmetric supercapacitor is self-assembled with the SC400 composite and exhibits an energy density of 52.34 Wh kg-1 at the power density of 2206.37 W kg-1. Additionally, a blue LED indicator can be powered by connecting two ASCs in series. The prepared hollow and spinous NiCo2S4 nanotubes with excellent electrochemical properties can envision promising applications in energy storage devices and nanotechnology.