Template-Free Preparation of α-Ni(OH) 2 Nanosphere as High-Performance Electrode Material for Advanced Supercapacitor.

Although it is one of the promising candidates for pseudocapacitance materials, Ni(OH) 2 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) 2 nanosphere is prepared via a facile and template-free dynamic refluxing approach. Significantly, the α-Ni(OH) 2 nanosphere possesses a high specific surface area (119.4 m 2 /g) and an abundant porous structure. In addition, the as-obtained α-Ni(OH) 2 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) 2 -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) 2 nanosphere may raise great potential applications for next-generation energy storage devices.