In-situ synthesis of NiCo2S4@graphene composite for high-performance supercapacitor

Binary transition metal sulfides have garnered widespread concentration result from their superior electrical conductivity and outstanding capacitance. However, their poor cycling stability hinders their applications in energy storage devices. The objective of this study is to devise and prepare graphene and NiCo2S4 composite (NiCo2S4@graphene) using a simple one-step hydrothermal modality. Graphene is used as a conductive substrate, and NiCo2S4 nanoparticles are formed in situ and homogeneously anchored on graphene nanosheets through C-S-C covalent bonds. For example, the NiCo2S4@graphene composite has a high specific capacitance of 918.0 C g−1 at a current density of 1 A g−1 and enhanced cycling stability (90.1% after 6000 cycles). In addition, the asymmetric supercapacitor was fabricated with NiCo2S4@graphene as the positive electrode and graphene (GR) as the negative electrode, and the device provided a maximum energy density of 49.8 Wh kg−1 at a power density of 845.3 Wh kg−1. Besides, the capacitance retention rate was as high as 92.0% after 1000 cycles. The superior electrochemical properties of the NiCo2S4@graphene material verified its huge potential for realistic applications.