Template-Free Preparation of α-Ni(OH) Nanosphere as High-Performance Electrode Material for Advanced Supercapacitor.

Although it is one of the promising candidates for pseudocapacitance materials, Ni(OH) is confronted with poor specific capacitance and inferior cycling stability. The design and construction of three-dimensional (3D) nanosphere structures turns out to be a valid strategy to combat these disadvantages and has attracted tremendous attention. In this paper, a 3D α-Ni(OH) nanosphere is prepared via a facile and template-free dynamic refluxing approach. Significantly, the α-Ni(OH) nanosphere possesses a high specific surface area (119.4 m/g) and an abundant porous structure. In addition, the as-obtained α-Ni(OH) electrodes are investigated by electrochemical measurements, which exhibit a high specific capacitance of 1243 F/g at 1 A/g in 6 M KOH electrolyte and an acceptable capacitive retention of 40.0% after 1500 charge/discharge cycles at 10 A/g, which can be attributed to the sphere's unique nanostructure. Furthermore, the as-assembled Ni(OH)-36//AC asymmetric supercapacitor (ASC) yields a remarkable energy density of 26.50 Wh/kg, with a power density of 0.82 kW/kg. Notably, two ASCs in series can light a 2.5 V red lamp sustainably for more than 60 min, as well as power an LED band with a rated power of 25 W. Hence, this 3D α-Ni(OH) nanosphere may raise great potential applications for next-generation energy storage devices.