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.