One-step solvothermal synthesis and electrochemical properties of graphene-supported dendritic CoNi2S4 nanostructures

One of the main challenges for the high-performance energy storage device is to develop advanced electrode materials with a high energy density at a high power. In this study, a facile one-step route was designed for the synthesis of graphene-supported dendritic CoNi2S4 nanostructures constructed by abundant nanorods. The investigation showed that the introduction of graphene oxide (GO) could efficiently restrain the production of the impurity, α-NiS, and could affect the shape of CoNi2S4 and improve the electrochemical properties of CoNi2S4. When the reaction was carried out in the system containing the Ni2+/Co2+/GO mass ratio of 133/67/60, the as-prepared sample (labeled as CoNi2S4/rGO-60) exhibited the best electrochemical properties. At a current density of 1 A g−1, the specific capacitance reached 1224 F g−1; and at a high current density of 20 A g−1, the specific capacitance still achieved 768 F g−1, indicating the excellent rate capability of the as-obtained electrode. After 3000 cycle at a current density of 4 A g−1 in a three-electrode system, the specific capacitance of 81% was still kept, implying the good cycle stability. The enhanced electrochemical performance could be attributed to the synergistic effect between CoNi2S4 and rGO. Furthermore, the electrochemical performances of the asymmetric device assembled by CoNi2S4/rGO and activated carbon (AC) were also investigated.