Urchin-like NiCo2S4 structures synthesized through a one-step solvothermal process for high-performance supercapacitors

Nickel cobalt sulfides (NiCo2S4) have attracted considerable attention as electrode materials for super capacitors. Herein, a sea-urchin-like NiCo2S4 material was synthesized through a one-step solvothermal process. Polyethylene glycol (PEG) 200 and thiourea were used as a shape-control agent and sulfur source for in-situ sulfuration, respectively. The urchin-like NiCo2S4 was characterized by X-ray powder diffraction, scanning electron microscopy, Brunauer-Emmett-Teller surface area, and electrochemical measurements. The resulting NiCo2S4 with ion diffusion-favored structure demonstrated remarkable electrochemical characteristics for supercapacitor with a high specific capacitance (1334 F/g at 0.5 A/g) and superior rate capability (78.1% of the original capacity from 0.5 to 20 A/g) in 6 M KOH aqueous solution. Furthermore, an asymmetric supercapacitor was assembled using NiCo2S4 as a positive electrode and activated carbon (AC) as a negative electrode. A NiCo2S4//AC device exhibited a high energy density of 37.32 Wh/kg at a power density of 317.8 W/kg with capacity retention of 91.9% and up to 2000 charge/discharge cycles at 3 A/g. The results demonstrate that the sea-urchin-like NiCo2S4 has potential applications in supercapacitors. (C) 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.