Nickel Hydroxide as an Active Material for the Positive Electrode in Rechargeable Alkaline Batteries

Spherical nickel hydroxide powders coprecipitated with the additives Ca(OH)2, Co(OH)2, and Zn(OH)2 were prepared through a spraying technique. These powders, which have a higher tapping density and a much smaller pore volume and crystalline size than conventional powders, were used as the active materials of nickel hydroxide electrodes. The effects of the Ca(OH)2, Co(OH)2, and Zn(OH)2 additions on electrode properties such as charge-discharge, reversibility of the electrode reaction, and cycle life, were studied. The relationship between the electrode swelling and the formation of g-NiOOH was also investigated. The results show that nickel hydroxide powders having a smaller crystallite size show better electrode characteristics such as lower overpotential, higher plateau discharge potential, and higher capacity. The utilization of the active material in the electrodes illustrates that for general use it is better to add Co21, while for a wider temperature range, it would be better to consider the addition of Ca21. The cycle life of the electrode containing Zn21 was improved obviously because there was less electrode swelling due to much reduced formation of g-NiOOH.