Construction of Cu₇KS₄@Ni_xCo_1–x(OH)₂ Nano-Core–Shell Structures with High Conductivity and Multi-Metal Synergistic Effect for Superior Hybrid Supercapacitors

Reasonable design of materials with complex nanostructures and diverse chemical compositions is of great significance in the field of energy storage. Cu7KS4 (CKS) is considered a potential electrode material for supercapacitors due to its superior electrical conductivity. Transition metal hydroxides are widely used as electrode materials for supercapacitors due to their high theoretical specific capacitance (Cs); however, single metal species with limited active sites restrict their further applications for energy storage. Herein, through a hydrothermal reaction, CKS nanorods were prepared, and then binary metal hydroxide NixCo1–x(OH)2 nanosheets were generated directly on CKS nanorods through a one-step hydrothermal reaction to form a nano-core–shell structure (NCSS). By regulating the mole ratio of nickel nitrate to cobalt nitrate, the resulting Ni0.75Co0.25(OH)2 nanosheets with the best electrochemical activity were prepared and supported on CKS nanorods to form a CKS@N0.75C0.25OH NCSS. The as-prepared CKS@N0.75C0.25OH NCSS has a larger specific surface area, which can provide more active sites, while the abundant metal species composition can generate abundant redox reactions to boost the pseudocapacitance. The prepared CKS@N0.75C0.25OH/NF electrode exhibits outstanding specific capacitance and cycle life. The assembled CKS@N0.75C0.25OH/NF//AC all-solid-state asymmetric supercapacitor achieves a high energy density of 88.7 Wh kg–1 at a power density of 849.9 W kg–1 with superior cycle life. Therefore, the use of polymetallic hydroxides to construct NCSS electrodes has great research significance and broad application prospects.