LOW-ZINC-SOLUBILITY ELECTROLYTES FOR USE IN ZINC NICKEL-OXIDE CELLS

Novel electrolytes, prepared by substituting KF and K2CO3 for a portion of the KOH traditionally used in Zn/KOH/NiOOH cells, were investigated in order to determine their effect on the rate of Zn active material redistribution (shape change) and Zn/NiOOH cell cycle-life performance. The solubilities of Zn species in these electrolytes are 20-25% of the Zn solubility in strongly alkaline [approximately 30 weight percent (w/o)] electrolytes. The rate of Zn electrode shape change was significantly less than that in cells with KOH, KOH-KF, or KOH-K2CO3 electrolytes. Vented cells constructed with KOH-KF electrolytes showed capacity-loss rates as low as 0.07%/cycle, which may be compared to values of 0.4-0.5%/cycle in cells with approximately 30 w/o KOH electrolyte. A sealed cell constructed with the novel KOH-KF-K2CO3 electrolyte showed a capacity-loss rate of 0.09%/cycle, and exhibited no dendritic shorts after 575 cycles at 100% depth of discharge.