Oxidation mechanism of cobalt hydroxide to cobalt oxyhydroxide

Although cobalt hydroxide is currently added to Ni(OH), paste to prepare nickel composite electrodes used in Ni-based rechargeable alkaline batteries, its redox chemistry in alkaline media is still poorly documented. The Co(OH)(2)-->CoOOH oxidation reaction in KOH media was investigated, and found to be dependent upon the experimental conditions, namely, temperature, oxidizing agent and reaction time. In addition, this reaction was shown, as determined by means of X-ray diffraction, electronic microscopy and atomic absorption measurements, to occur through a two step mechanism process involving first a dissolution process followed by a solid state reaction. This dissolution step enables preparation, by adjusting the cycling conditions, of cobalt oxyhydroxide with well defined morphology and texture, thereby providing an opportunity to optimize its efficiency as an additive in nickel electrodes.