Studies of pasted nickel electrodes to improve cylindrical nickel–zinc cells

The aim of the present paper was to study the influence of foam type as well as nickel and cobalt additives on cell performance and cycle life of cylindrical nickel–zinc cells. Experiments have shown that discharge capacity depends on the foam type of nickel electrodes and is significantly improved by using thicker foam substrates (2.2 mm). AA-size nickel–zinc cells constructed of two thinner nickel electrode layers (1.6 mm) displayed stronger decline in capacity during cycle life due to a very low zinc/nickel hydroxide ratio (1.1–1.2). The addition of nickel and cobalt powder was investigated by means of resistivity measurements of PVA-bonded nickel hydroxide films. This study elucidated that small amounts of cobalt (2–8 wt.%) caused an extreme decline in resistivity. Admixture of nickel also lowered resistivity but not as great as cobalt. The cell performance turned out to be contrary to resistivity measurements; nickel–zinc cells prepared with a less conductive slurry delivered higher capacities. However, discharge capacity decreased rapidly after prolonged cell cycling, as the zinc/nickel hydroxide ratio of these cells was also considerably reduced.