Carbon-supported Co₉S₈ hollow spheres assembled from ultrathin nanosheets for high-performance supercapacitors

The hydrothermal approach was used to build ultrathin Co₉S₈ nanosheets into a core–shell hollow framework called Co₉S₈@RGO, which was aided by carbon. In addition, the porous RGO matrix efficiently enhances the movement of electrons and ions. The Co₉S₈ nanosheets inserted into the RGO architecture significantly minimize the clustering of RGO nanosheets while offering several locations for pseudocapacitance responses at the same time. The Co₉S₈@RGO nanocomposites exhibited an exceptionally high specific capacitance of 3255 Fg⁻¹ within a potential range of 0.5 V at a current density of 1 Ag⁻¹. In addition, a type of supercapacitor called an asymmetric supercapacitor (ASC) was created using Co₉S₈@RGO as the positive electrode and activated carbon (AC) as the negative electrode. This ASC demonstrated a density of 88.8 Whkg⁻¹ at a power density of 635 Wkg⁻¹. Furthermore, it maintained an energy density of 67.5 Whkg⁻¹ at a power density of 1565 Wkg⁻¹. Additionally, it exhibited excellent cycle stability, with 80.61% specific capacity preservation at a current density of 10 Ag⁻¹ after 10,000 periods. The Co₉S₈@RGO composite has a straightforward and inexpensive production process, as well as exceptional performance, which makes it an optimal electrode material for electrochemical devices that store energy.