Effect of cobalt addition to nickel hydroxide as a positive material for rechargeable alkaline batteries

Nickel hydroxide powder is used widely as an active material in pasted-type nickel electrodes. The effect on the electrochemical behaviour of cobalt addition (0.19–9.9 wt.%) to the nickel hydroxide powder is investigated. The physical properties of several nickel hydroxide powders containing different amounts of cobalt compound are examined by inductively coupled spectroscopy, laser diffraction, BET, X-ray diffraction and scanning electron microscopy measurements. The interlayer distance of the layered nickel hydroxide diminishes to a small value with increase in cobalt content. Moreover, the charge and discharge potentials of nickel hydroxide samples decrease with an increase in cobalt content. The chemical diffusion coefficients of the proton (D) in the nickel hydroxide samples with different amounts of cobalt are measured by a current-pulse relaxation technique. The D and D0 values increase with an increase in cobalt content, and the activation energy for proton diffusion is in the 0.20–0.33 eV range.