Nanoflower Ni(OH)2 grown in situ on Ni foam for high-performance supercapacitor electrode materials

Abstract

Supercapacitors hold huge potential to bridge the gap between conventional capacitors and secondary batteries in terms of high-power density, long cycle lifetime and fast charge/discharge rate. Research in the area of transition metal compounds as supercapacitor electrode materials has attracted increasing attention due to the high energy density that can be achieved by these devices compared to electric double-layer capacitors and the long cycle stability when compared to batteries. In this work, we report the one-step synthesis of nickel hydroxide powder and nickel hydroxide directly grown on nickel foam under varying experimental conditions. The formation of flower-like nanostructured α- and β-Ni(OH)₂, assembled from nanosheets, was observed and a suggestion for the formation process is proposed. The α-Ni(OH)₂ electrode obtained has a high specific surface area of 164 m² g⁻¹ and a significantly enhanced specific capacitance (2814 F g⁻¹ at 3 A g⁻¹), both higher than previously reported α-Ni(OH)₂. Information obtained through characterisation of alpha and beta phases by PXRD, SEM, BET, FTIR and TGA were used in combination with electrochemical studies to rationalise the different electrochemical performance of these 2 phases in terms of their cycle stability and capacitance. This provides guidance for further development and future commercial applications of nickel hydroxide materials for energy storage systems.