Tailoring morphology of pure terephthalic acid induced beta nickel hydroxide using ultrasonication and alkalization for efficient energy storage

Abstract

β-Ni(OH)2 is one of the effective battery-type active materials of battery supercapacitor hybrid (BSH). Two-dimensional structure can supply large surface area for conducting redox reactions and abundant open spaces for ion diffusion. It is promising to design favorable morphology of β-Ni(OH)2 as the active material of BSH. In this study, the novel β-Ni(OH)2 layered structure decorated with nanoparticles is synthesize on a nickel foam using the hydrothermal process and post treatments. Pure terephthalic acid is verified to be indispensable for synthesizing nickel metal organic framework (Ni-MOF) in the hydrothermal process. Ultrasonication is used to break the large accordion-like structure of Ni-MOF into small pieces. Alkalization is applied to fully convert Ni-MOF into β-Ni(OH)2. Better electrochemical performance is achieved for β-Ni(OH)2 synthesized from Ni-MOF, which presents the largest specific capacitance (CF) of 1171 F/g at 3 A/g. A BSH is assembled using the Ni-MOF derived β-Ni(OH)2 on a nickel foam as the positive electrode and the activated carbon on a nickel foam as the negative electrode. The maximum energy density of 6.50 Wh/kg at 0.14 kW/kg, and excellent cyclic stability with the CF retention of 82% and Coulombic efficiency higher than 96% after 8000 charge/discharge cycles are achieved for the BSH.