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 degrees C with different exposure times. The results showed that the capacitance of the optimal NiCo2S4 sample reached 400 mu A 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 mu A h cm(-2) and 241.7 mu A 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.