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The electrochemical behavior of ␣and ␤͑II͒-type zinc-substituted nickel hydroxides is studied during a galvanostatic cycling in a KOH electrolyte. It is shown that these materials exhibit very stable capacities during long-term cycling. When using an 8 M KOH electrolyte, the ␤͑III͒/␤͑II͒ system is stabilized, after the initial formation of ␥-type phases during the first charges. The higher the amount of zinc in the starting material, the faster this stabilization occurs. The substitution of zinc for nickel is also shown to delay the formation of the ␥-phase upon charge, when various KOH electrolytes, with increasing concentrations, are successively used. A model is proposed to explain these results; it is based on several processes, occurring simultaneously either via the solution or through solid-state reactions, with a partial loss of zinc.

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