Characterization of Active Material Deposited at the Nickel Hydroxide Electrode by Electrochemical Impregnation

Abstract

The electrochemical impregnation of porous nickel sintered plates has been investigated to gain a better understanding of the structure, texture, and composition of the deposited active material. It was found that the nature of this material depends on the temperature of the impregnation bath. Below 60°C, an α‐type nickel hydroxide forms, while above 60°C this same α phase appears simultaneously with and a crystallized phase in major proportion exhibiting structural features similar to those of nickel hydroxy‐nitrate. This crystallized phase presents properties (ionic exchange, transformation into ), which are very similar to that of α‐type nickel hydroxides. Its formation is probably due to corrosion of the nickel sintered plate. Scanning‐electron‐microscopy examinations of the electrodes show that the growth of the active material is isotropic and starts at the metallic nickel particles, which act as nuclei. Whatever the impregnation temperature, the active material is not stable; the transformation of the active material into the more stable β nickel hydroxide takes place rapidly at the beginning of the cell life.