Ni III, IV hydroxides

Nickel hydroxides of oxidation state two and higher have been used as the active material in the positive electrodes of several alkaline batteries for more than a hundred years [99MCB]. Bode et al. [66BOD/DEH] established the scheme depicted below. 

The charge and discharge cycles of nickel batteries involve two different pairs of solid phases. Oxidation of p-Ni(OH)2 produces p-NiOOH, oxidation of a-Ni(OH)2 produces y-NiOOH. The end-products of these cycles are interconnected by dehydration and overcharge. For the crystallographic properties of Ni(II) hydroxides and Ni(Ill, IV) hydroxides see Section V.3.2.2.1 and Sections V.3.2.3.1, V.3.2.3.2, respectively. 

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