In order to understand the textural and structural modifications involved in the electrochemical cycling of the nickel hydroxide/oxyhydroxide electrode (NOE), well defined divalent nickel hydroxides (alpha- and beta-types) have been prepared and characterized. The alpha-type phases present a pseudo-bidimensional structure and each nickel hydroxide layer can be considered as a surface layer with water molecules and hydroxyl vacancies compensated by adsorbed anionic species from the mother precipitation solution. Ageing of these phases in KOH electrolyte leads to the alpha-->beta transformation by a dissolution-recrystallization phenomenon via the electrolyte, and an Ostwald ripening in KOH is observed for these beta(ex alpha) phases. Textural and structural changes during the electrochemical cycling of NOE are studied : it is shown that the beta(II)-->gamma(III)-->beta(II) transformation occurs directly in the solid state.