Influence of substituted zinc on stacking faults in nickel hydroxide

Abstract

The evolution of the structure of zinc-substituted nickel hydroxides (α or β phases) during ageing in the KOH electrolytic medium was studied. The ageing leads to β-phases that contain zinc ions in tetrahedral sites of the interslab space, as shown by the EXAFS study. These interslab zinc ions entail in the aged materials a stabilization of the ideal ABAB oxygen packing, leading to a marked decrease of the number of stacking faults, and prevent especially deformation faults. As far as the electrochemical behaviour is concerned, the presence of zinc in tetrahedral sites of the interslab space links the successive slabs and prevents formation of the γ/α couple upon cycling. Moreover, it leads to an improvement of the electrochemical properties of the electrode (chargeability and conductivity of the material in the reduced state).