Dehydration of Chemically and Electrochemically Impregnated (CI and EI) Nickel Hydroxide Electrodes

Nickel hydroxide electrodes prepared by chemical and electrochemical impregnation (CI and EI) have different crystal structures due in part to the amount of water in the active materials [ β ‐ or α ‐ Ni ( OH ) 2 ] . In order to understand the relationship between the structure and the water content, for the EI electrode, x‐ray diffraction (XRD) and thermogravimetric analysis (TGA) were used. TGA of CI and EI electrodes in air, nitrogen, and vacuum revealed that there are two types of chemical reactions which take place in the electrode material, one due to dehydration and the other due to decomposition of hydroxide to oxide. The dehydration of EI electrode active material also resulted in a decrease of the “ c ” spacing of the unit cell due to water removal from planes perpendicular to the “ c ” axis of nickel hydroxide crystals.