One-step solvothermal synthesis of mixed nickel–cobalt sulfides as high-performance supercapacitor electrode materials

In this work, mixed nickel-cobalt sulfides (NCSs) were prepared by a facile solvothermal method. Structural and morphological characterization of synthesized materials were confirmed by X-ray diffractometry, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy. Electrochemical measurements revealed that mixed NCSs exhibit pseudocapacitor behaviour and their capacitance was strongly dependent on the composition. Interestingly, the electrochemical performance of the mixed NCSs has been significantly improved in comparison to the pristine nickel sulfide or cobalt sulfide. Particularly, the mixed NCS prepared at a nickel:cobalt molar ratio of 3:1 exhibited a specific capacitance of 2599.6 F g−1 at a scan rate of 10 mV s−1 (or 1345 F g−1 at a current density of 2 A g−1) and retained 95% of its initial capacitance after 3000 charge-discharge cycles. The excellent electrochemical performances of NCSs indicate they are promising candidate for supercapacitor electrode. •One-step solvothermal synthesis of mixed nickel-cobalt sulfides (NCSs).•The electrochemical performances of the mixed NCSs are significantly improved in comparison to NiS2 and CoS2.•The mixed NCS exhibited a maximal specific capacitance of 2599.6 F g−1 at 10 mV s−1 or 1345 F g−1 at 2 A g−1.