Effect of synthesis conditions on characteristics of the precursor material used in NiO·OH/Ni(OH)2 electrodes of alkaline batteries

The synthesis of nickel hydroxide occurs by many stages. When the precipitating reagent is NH4OH solution, the precipitation of nickel hydroxide occurs between pH 8.0 and 8.6. For pH between 8.6 and 10.0, a soluble complex such as [Ni(NH3)6]2+ is formed. The precipitation of nickel hydroxide happens again after the pH equals 10.0. Finally, there occurs the ageing of α-Ni(OH)2. A mixture of α-Ni(OH)2 and β-Ni(OH)2 phases is formed when the solid state reaction is not totally completed. One adsorbed layer becomes very hard with the exit of the water intercalated in the α-Ni(OH)2. In presence of KOH solution occurs the formation and the ageing of α-Ni(OH)2. Synthesis was characterized by the following techniques: X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA) and gravimetric thermal analysis (GTA), and specific surface area and UV–vis spectroscopy.