Self-supporting graphene aerogel electrode intensified by NiCo2S4 nanoparticles for asymmetric supercapacitor

Transition bimetallic nickel cobalt sulfide has attracted extensive attention as a novel electrode for supercapacitors. In this study, facial solvothermal method is applied to prepare NiCo(2)S(4 )nanoparticles and nanosheets immobilized on graphene aerogel (NiCo2S4/GA). The microstructure of NiCo2S4 is significantly affected by altering the pH of the solution. Typically, the uniformly dispersed NiCo2S4 nanoparticles with diameter 25.94 nm are successfully grown on GA when the solution pH is 8.2. The NiCo2S4/GA electrode delivers an improved specific capacitance of 704.34 Fg(-1) at 1 Ag-1, and maintains a favorable rate capability of 60.1% at 10 A g(-1). Moreover, 80.3% of the initial specific capacitance is maintained after 1500 cycles at 2 Ag-1. The impressive electrochemical performance results from the NiCo2S4 with high capacitance and GA with three-dimensional porous nanostructure, which can not only reduce the contact resistance but also efficiently shorten the electron and ion transport path. Furthermore, the solid-state asymmetric supercapacitor device based on NiCo2S4/GA electrode can present energy density of 20.9 Wh kg(-1) at a power density of 800.2 W kg(-1) and desirable cycling stability, showing the great application potential in the field of energy storage devices. (C) 2019 Published by Elsevier Ltd.