Defect-engineered rGO−CoNi2S4 with enhanced electrochemical performance for asymmetric supercapacitor

To explore the effect of sulfur vacancies in transition metal sulfide on the electrochemical properties of anode materials, the graphene oxide (GO) and CoNi₂S₄ were used as the raw materials to synthesize the rGO₁₀−CoNi₂S_4−x composite electrode materials by the solvothermal method. The obtained rGO₁₀−CoNi₂S_4−x electrode materials with sulfur vacancies consist of nanoflakes and nanorods. The galvanostatic charge−discharge test of the rGO₁₀−CoNi₂S_4−x electrode materials shows a great specific capacitance of 3050.1 F/g at a current density of 1 A/g. Moreover, the electrode materials still remain rate capability retention of 86.1% when the current density increases from 1 to at 10 A/g. The rGO₁₀−CoNi₂S_4−x composite containing sulfur vacancies has higher specific capacitance and better rate capability in comparison to the pristine rGO−CoNi₂S₄ without containing sulfur defects. The optimized rGO₁₀−CoNi₂S_4−x composite electrode materials with sulfur vacancies exhibit outstanding cycle stability and rate performance.