One-Step Solvothermal Synthesis of 3D Hierarchical NixCo9-xS8 Structures for High-Performance Supercapacitors

Three-dimensional flowerlike NixCo9-xS8 nanosheets with polyvinyl pyrrolidone as the agent dictating the material morphology have been synthesized by means of a one-step solvothermal synthesis procedure. The synthetically facile 3D NixCo9-xS8 nanosheets (P-NixCo9-xS8) achieve high specific surface area and outstanding electrochemical performance. When applied as an electrode material, it demonstrates excellent specific capacitance of 1319.76 Fg(-1) at 1 Ag-1, and good rate performance of 1040.4 Fg (-1) 1 at 20 Ag (-1). Also, the material achieves remarkable cycling stability that still retains 93.7% of max capacity after 1500 cycles at the high current density of 10 Ag-1. Even after 4000 cycles, a maximum capacity of 71.2% is retained. Additionally, the P-NixCo9-xS8//AC asymmetric supercapacitor (ASC) prepared exhibits excellent capacitive performance with a high specific capacitance (119.9 Fg(-1)), high energy density (43.80 Wh kg(-1) at 821.25 Wkg(-1)) and high power density (30.30 Wh kg(-1) at 15.58 kWkg(-1)).