Hierarchical NiCo2O4@CuS composite electrode with enhanced surface area for high-performance hybrid supercapacitors

Abstract

Hierarchical binder-free NiCo₂O₄@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 NiCo₂O₄ nanograss-like structures with CuS nanostructures. The surface area of the composite is significantly enhanced (91.38 m² g⁻¹) compared to NiCo₂O₄ (52.16 m² g⁻¹), with a predominant pore size of 3–6 nm. This synergistic combination enhanced the electrode's electrochemical properties. The NiCo₂O₄@CuS electrode delivered an impressive specific capacitance of 141.13 mA h g⁻¹ at 1 A g⁻¹, surpassing the performance of the bare NiCo₂O₄ 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 NiCo₂O₄@CuS and G-ink electrodes attained a peak energy density of 28.85 W h kg⁻¹ at a power density of 238.2 W kg⁻¹, 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 NiCo₂O₄@CuS composite electrode is attributed to the synergistic combination of NiCo₂O₄ and CuS, which promotes interfacial electron separation and facilitates rapid electron transfer.