Self-Assembled Nickel Hydroxide Three-Dimensional Nanostructures: A Nanomaterial for Alkaline Rechargeable Batteries

α- and β-Ni(OH) 2 with three-dimensional (3D) nanostructures were synthesized in a water-in-oil reverse micelle/microemulsion system. The form and shape of Ni(OH) 2 can be readily tuned by adjusting experimental parameters of the reverse micelle/microemulsion system. α-Ni(OH) 2 with dandelion-like nanostructures was obtained in the reverse microemulsion of cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/ n -pentanol with a molar ratio of H 2 O to surfactant of 40; β-Ni(OH) 2 phase with flower-like nanostructures was formed in the reverse micelles of the same composition with a molar ratio of H 2 O to surfactant of 10. Electrochemical measurements of the as-synthesized α-Ni(OH) 2 phase showed that the 3D α-Ni(OH) 2 nanostructures exhibited superior cycling reversibility and improved capacity compared with commercial Ni(OH) 2 .