US Patent RE40727 Alkaline cells having low toxicity rechargeable zinc electrodes

A nickel zinc alkaline cell has a zinc oxide negative electrode supported on a conductive substrate, an alkaline electrolyte, and a positive electrode having nickel hydroxide paste supported on a conductive substrate. The negative zinc oxide electrode comprises 85% to 95% zinc oxide powder, 1% to 10% bismuth oxide, 1% to 2% of a binder, and 0.05% to 5% by weight of a fluoride salt chosen from the group consisting of: sodium, potassium, rubidium, caesium, lithium, and mixtures thereof. Typically, the fluoride salt is potassium fluoride, in the amount of 0.5% by weight of the zinc oxide.