Hierarchical NiCoO@CuS composite electrode with enhanced surface area for high-performance hybrid supercapacitors.

Hierarchical binder-free NiCoO@CuS composite electrodes have been successfully fabricated on a nickel foam surface using a facile hydrothermal method and directly used as a battery-type electrode material for supercapacitor applications. The surface morphological studies reveal that the composite electrode exhibited porous NiCoO nanograss-like structures with CuS nanostructures. The surface area of the composite is significantly enhanced (91.38 m g) compared to NiCoO (52.16 m g), with a predominant pore size of 3-6 nm. This synergistic combination enhanced the electrode's electrochemical properties. The NiCoO@CuS electrode delivered an impressive specific capacitance of 141.13 mA h g at 1 A g, surpassing the performance of the bare NiCoO electrode. The composite electrode also exhibited excellent rate capability and cycling stability, retaining 87.49% of its initial capacity at high current densities and 88.62% after 3000 cycles. A hybrid supercapacitor (HSC) device assembled using NiCoO@CuS and G-ink electrodes attained a peak energy density of 28.85 W h kg at a power density of 238.2 W kg, outperforming many reported HSCs. Additionally, the HSC device demonstrated exceptional cycling stability, retaining 87.59% of its initial capacitance after 4000 cycles. The superior performance of the NiCoO@CuS composite electrode is attributed to the synergistic combination of NiCoO and CuS, which promotes interfacial electron separation and facilitates rapid electron transfer.