Esb Incorporated

Carol Ruth Buelow

El Sayed Megahed

Patrick J Spellman

An alkaline battery having a divalent silver oxide (AgO) positive active material (cathode) in which a sulfide additive is incorporated into the alkaline electrolyte on the positive side of the battery separator or barrier or is added to the positive active material is provided. The sulfide additive improves the stability of the divalent silver oxide (AgO) active material in the aqueous alkaline electrolyte without adversely affecting the electrochemical reaction during the discharge of the battery. The additive consists of a sulfide of cadmium, calcium, mercury, tin, tungsten, or mixtures thereof.

Additive for an alkaline battery employing divalent silver oxide

A primary alkaline cell having a stable divalent silver oxide depolarizer mix comprising a negative electrode (anode), a divalent silver oxide (AgO) depolarizer mix, a separator between said negative electrode and depolarizer mix, and an alkaline electrolyte. The surface of the depolarizer mix is treated with a mild reducing solution to form a reduced layer surrounding the mix, and the surface of the reduced layer adjacent to the separator is coated with a layer of silver. The reduced layer surrounding the depolarizer mix in combination with the layer of silver provides improved stability of the depolarizer mix in the alkaline electrolyte and a single voltage plateau during discharge of the cell. The primary alkaline cell is characterized by a maximum open circuit voltage of about 1.75 volts. The silver layer on the surface of the reduced layer surrounding the depolarizer mix can be formed by treating the reduced layer with a strong reducing solution to form a substantially continuous and electrolyte permeable silver layer, or alternatively, the silver layer may be formed by placing a silver screen, expanded silver metal, perforated silver foil or porous silver powder layer on top of the reduced layer surrounding the depolarizer mix and adjacent to the separator. It is preferred that the layer of silver be substantially continuous and electrolyte permeable which may be accomplished by treating the reduced layer surrounding the mix with a strong reducing solution. When forming the layer of silver by treating the reduced layer with a strong reducing solution, it is preferred that the depolarizer mix surrounded by the reduced layer be consolidated in a cathode container prior to treating it with the strong reducing solution. The depolarizer mix may contain from about 50% by weight to about 100% by weight of divalent silver oxide based on the total silver oxide content and still provide a cell with a single voltage plateau discharge.

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Madison, WI, United States of America

Carol Ruth Buelow