Techniques to improve the usability of nickel-hydrogen cells

The voltages at which the different charging and discharging peaks occur in a nickel electrode were investigated for a set of six representative electrodes. The impact of cycling temperature, electrolyte concentration, and cycling history on these different electrodes resulted in alterations in the usable capacities of the electrodes and/or the efficiency of the charging reaction. The cobalt level in the active material, the KOH concentration of the electrolyte, and the cycling temperature were all found to impact the position of the charging peaks of the beta and the gamma charging reactions. The position of the oxygen evolution characteristic was found to be mainly a function of the cycling temperature. The findings of these studies resulted in recommendations for selecting certain cell design factors and charging protocols that will lead to improved cycle lives and higher levels of usable cell capacities. (C) 2003 The Aerospace Corporation. Published by Elsevier Science B.V. All rights reserved.