Development of lightweight nickel electrodes for zinc/nickel oxide cells

A method for fabricating lightweight nickel electrodes has been developed by electrochemical impregnation of two different nickel fiber substrates. The electrochemical impregnation technique was applied galvanostatically at 35–50 mA/cm² in acidic solutions of nickel and cobalt nitrates (pH = 3). The nickel and cobalt contents of impregnated and formed electrodes was analyzed with atomic absorption spectrometry (AAS) and the amount of active nickel hydroxide was calculated. NiOOH electrode cycle-life performance testing was carried out in alkaline electrolyte (4.2–6.9 M KOH, 1 M LiOH) at a ∼C/5 rate during charge and discharge. Electrodes based on substrate materials of high porosity (90%, FN 090 Nickel Felt, Sorapec) deliver excellent specific capacities of 133–145 mAh/g in moderately alkaline electrolyte (4.2 M KOH) with an active material utilization of 67–95% depending on the quantity of co-precipitated cobalt (1.3–8.3%). NiOOH electrodes using substrates with lower porosity (81%, Fibrex 50/50 = fiber/Ni powder, National Standard) obtain very stable specific capacities (400 cycles) of 91–93 mAh/g with a utilization rate of 110% in highly alkaline electrolytes (6.9 M KOH).