Spreading GO nanosheets-coated nickel foam decorated by NiCo2O4/NiCo2S4 nanoarrays for high-performance supercapacitor electrodes

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

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.

Micro-controlling of the grain boundaries in NiCo2O4/NiCo2S4 nanowires for enhanced charge storage

In this work, the micro-controlling of the grain boundaries in NiCo₂O₄/NiCo₂S₄ nanowire arrays was achieved by exposing them to a sulfur containing atmosphere at 300 °C with different exposure times. The results showed that the capacitance of the optimal NiCo₂S₄ sample reached 400 μA h cm^-2 at 30 mA cm^-2 with a current retention rate of 58.6%. The assembled NiCo₂O₄/NiCo₂S₄//activate carbon electrode delivered a capacitance of 299.2 μA h cm^-2 and 241.7 μA h cm^-2 at a current density of 3 mA cm^-2 and 30 mA cm^-2, respectively. The cycling tests showed a good current retention rate of 88.1% after 8000 cycles. Besides, the NiCo₂O₄/NiCo₂S₄ composite exhibited a power density of 480.1 W kg^-1 at an energy density of 47.87 W h kg^-1, and 4773.66 W kg^-1 at 38.67 W h kg^-1, which indicated its potential for practical applications.