Tailoring the phase composition of carbon-coated nickel sulfides to achieve a high specific capacitance

As significant transition metal sulfides, nickel sulfides integrated with carbon were successfully synthesized in the presence of polyethylenimine and glutaraldehyde with a solvothermal route at 180 °C followed by carbonization. Glutaraldehyde prevented complete sulfur loss and allowed the formation of a mixed phase of nickel sulfide. The electrochemical performances of pure NiS₂, NiS@C0, NiS₂/NiS@C1, and NiS₂/NiS@C2 electrodes were tested by a series of measurements. The specific capacitances obtained from GCD analysis were 698, 1160, 1484, and 908 F g^-1 at 1 A g^-1 for NiS₂, NiS@C0, NiS₂/NiS@C1, and NiS₂/NiS@C2 electrodes, respectively. The results implied that the NiS₂/NiS@C1 electrode possessed the highest specific capacitances and this study can be a good reference for the preparation of other hybrid metal sulfides as pseudocapacitive electrode materials.