Ni(OH) Nanoflakes Supported on 3D Ni Se Nanowire Array as Highly Efficient Electrodes for Asymmetric Supercapacitor and Ni/MH Battery.

Porous Ni(OH) nanoflakes are directly grown on the surface of nickel foam supported Ni Se nanowire arrays using an in situ growth procedure to form 3D Ni Se @Ni(OH) hybrid material. Owing to good conductivity of Ni Se , high specific capacitance of Ni(OH) and its unique architecture, the obtained Ni Se @Ni(OH) exhibits a high specific capacitance of 1689 µAh cm (281.5 mAh g ) at a discharge current of 3 mA cm and a superior rate capability. Both the high energy density of 59.47 Wh kg at a power density of 100.54 W kg and remarkable cycling stability with only a 16.4% capacity loss after 10 000 cycles are demonstrated in an asymmetric supercapacitor cell comprising Ni Se @Ni(OH) as a positive electrode and activated carbon as a negative electrode. Furthermore, the cell achieved a high energy density of 50.9 Wh L at a power density of 83.62 W L in combination with an extraordinary coulombic efficiency of 97% and an energy efficiency of 88.36% at 5 mA cm when activated carbon is replaced by metal hydride from a commercial NiMH battery. Excellent electrochemical performance indicates that Ni Se @Ni(OH) composite can become a promising electrode material for energy storage applications.