One-pot synthesis of nickel-cobalt hydroxyfluorides nanowires with ultrahigh energy density for an asymmetric supercapacitor.

A novel and unique nickel-cobalt hydroxyfluorides (NiCo-HF) nanowires material is fabricated by one-pot solvothermal synthesis method for asymmetric supercapacitor. The synthesis mechanism and factors that influence the formation of the NiCo-HF nanowires have been further discussed. The as-prepared NiCo-HF electrode exhibits a high specific capacitance of 3,372.6 F g-1, and the capacitance retention of 94.3% can be achieved at a high current density of 20 A g-1 after 10,000 cycles. The outstanding electrochemical performance of the electrode can be attributed to the synergistic effect of the nanowires morphology and complicated redox process of active material. Furthermore, an asymmetric supercapacitor assembled with NiCo-HF nanowires as positive electrode and activated carbon as the negative electrode shows an ultrahigh energy density of 83.6 Wh kg-1 at a power density of 379.4 W kg-1 and an excellent cycling stability with 86.3% capacitance retention after 10,000 cycles, indicating that this novel material has great promise for potential application in energy storage device.