▎ 摘　　要

A facile one step hydrothermal process is developed for the synthesis of NiCo2S4@reduced graphene oxide (NiCo2S4@RGO) composite as electrode for electrochemical supercapacitors. This NiCo2S4@RGO electrode exhibits an ultrahigh specific capacitance of 2003 F g(-1) at 1 A g(-1) and 1726 F g(-1) at 20 A g(-1) (86.0% capacitance retention from 1 A g(-1) to 20 A g(-1)), excellent cycling stabilities (86.0% retention after 3500 cycles). Moreover, an asymmetric supercapacitor is successfully assembled by using NiCo2S4@RGO nanoparticle as the positive electrode and active carbon(AC) as the negative electrode in 2 M KOH electrolyte. The fabricated NiCo2S4@RGO//AC asymmetric supercapacitor exhibits a high energy density of 21.9 Wh kg(-1) at a power density of 417.1 W kg(-1) and still remains an impressive energy density of 13.5 Wh kg(-1) at a large power density of 2700 W kg(-1). The results demonstrate that the NiCo2S4@RGO composite is a promising electrode material as supercapacitors in energy storage. (C) 2017 Published by Elsevier B.V.