Hierarchical mesoporous carbon sphere@nickel cobalt sulfide core–shell structures and their electrochemical performance

• The reaction involved green synthesis without further sulfurization or post-heat treatment.
• The CS@Ni–Co-S core–shell microstructures exhibited a high capacitance of 724.4 F g− 1 at 2 A g− 1 in a 6 M KOH electrolyte.
• High energy density (58.0 Wh kg− 1 at 1440 W kg− 1) and high power density (34.2 Wh kg− 1 at 7200 W kg− 1) were observed.

The pursuit for renewable sources of energy has increased rapidly due to the continuous depletion of non-renewable sources. Supercapacitors have attracted considerable attention because they can store electrical energy. In this study, a hierarchical mesoporous carbon sphere@nickel cobalt sulfide (CS@Ni–Co-S) core–shell was synthesized using a facile hydrothermal method. The reaction involved green synthesis without further sulfurization or post-heat treatment. The CS@Ni–Co-S core–shell microstructures exhibited a high capacitance of 724.4 F g− 1 at 2 A g− 1 in a 6 M KOH electrolyte. Good specific retention of 86.1% and high Coulombic efficiency of 97.9% were obtained after 2000 charge–discharge cycles. High energy density (58.0 Wh kg− 1 at 1440 W kg− 1) and high power density (34.2 Wh kg− 1 at 7200 W kg− 1) were observed. Through this study, a cost-effective and simple synthesis of CS@Ni–Co-S as an active electrode showed favorable electrochemical performance.