While at low (4°C) temperatures, addition of ammonia to aqueous metal nitrate solutions induces the precipitation of 𝛼-nickel hydroxide and at high (25–65°C) temperatures, 𝛽-Ni(OH)2 is formed. The crystallinity of the product improves at higher temperatures of precipitation and the product obtained at 65°C is devoid of various disorders such as stacking faults, turbostraticity and interstratification. This provides a simple and efficient alternative to the hydrothermal synthesis of crystalline 𝛽-Ni(OH)2. The temperature induced control over phase selection provides direct experimental evidence for the metastability of 𝛼-nickel hydroxide. Crystalline 𝛽-Ni(OH)2 is, however, a poor electrode material for alkaline secondary cells and exhibits a capacity of only 75 ± 10 mAh/g, against the theoretically expected 289 mAh/g.
Volume 42 | Issue 6
Click here for Editorial Note on CAP Mode