The Influence of Nickel-Hydroxide Composition and Microstructure on the High-Temperature Performance of Nickel Metal Hydride Batteries

A special precipitation process developed at Ovonic Battery Company has been utilized to produce spherical, high-density nickel-hydroxide powders with different chemical compositions. These powders were tested in sealed, cylindrical C-cell size nickel metal hydride batteries to study the effect of chemical composition on high-temperature performance. Charging measurements were made at 25, 45, and . It was found that coprecipitated cobalt in the presence of magnesium, zinc, and calcium increases the voltage gap between the oxygen-evolution potential and the midpoint voltage of the battery. The larger voltage gap dramatically increases the charge acceptance of the battery, improving its charging efficiency (normalized to the room-temperature value) from around 50% for conventional nickel hydroxide to 85% for the improved materials when measured at .