In situ derived volcanic rock-like hydrates of nickel and cobalt sulfates on nickel-cobalt metal-organic framework for high-performance supercapacitors

The metal-organic framework-derived sulfate hydrates exhibit exceptional energy storage performance due to their remarkable synergistic effect. In this study, the volcanic rock-like structure of nickel and cobalt sulfates hydrates (VNCSH) was derived in situ using a nickel-cobalt metal-organic framework as a substrate by a solvothermal method. Through the characterization analysis, the structure continues the porous structural characteristics of MOF materials with abundant active sites and prominent crystal morphology, which is conducive to the full contact with the electrolyte, accelerates the ion transfer, and improves the stability of the material. The VNCSH as an electrode has a high specific capacity of 1418.2 F g⁻¹ at a current density of 2 A g⁻¹ and maintains a high capacity of 870.9 F g⁻¹ when the current density is increased to 10 A g⁻¹. Furthermore, the assembled VNCSH//AC asymmetric supercapacitor device demonstrated a remarkable energy density of 146.2 Wh kg⁻¹ at a power density of 725.8 W kg⁻¹, while maintaining a capacity retention of 66.2% after undergoing 6000 cycles at a current density of 10 A g⁻¹. These results indicate that VNCSH with volcanic rock-like morphology holds significant promise for advanced supercapacitor applications.