Phase-controlled growth of nickel hydroxide nanostructures on nickel foam for enhanced supercapacitor performance

The development of nickel-based electrode materials has always been a hot spot in the field of electrochemical energy. It is well known that nickel hydroxide nanostructures in situ grown on nickel foam has been well applied in supercapacitors, which can further be employed as a precursor to fabricate other nickel-based compounds and their composites as electrode materials. In this work, the controllable growth and phase transformation from initial β-Ni(OH)2 to nitrated α-Ni(OH)2 [i.e. Ni3(NO3)2(OH)4] in situ on nickel foam have been successfully achieved through a traditional mild hydrothermal route by tuning the concentration of reactants. The electrochemical studies show that the specific capacitance of α-type nickel hydroxide electrode is much higher than that of β-type. The former exhibits a large gravimetric capacitance of 2075 F g−1 at a current density of 0.5 A g−1. The asymmetric supercapacitor can provide a high specific energy of 31.5 Wh kg−1 at a specific power of 388 W kg−1 within a voltage window of 1.55 V. Therefore, this research develops a controllable preparation methodology for electrode materials of high-performance supercapacitors, which are also of great significance for the design of more new nickel-based electrode materials.