Esb Incorporated

El Sayed Megahed

Patrick J Spellman

Carol Ruth Buelow

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 high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide (AgO)/monovalent silver oxide (Ag.sub.2 O) depolarizer blend, a separator between said negative electrode and depolarizer blend, and an alkaline electrolyte consisting essentially of potassium hydroxide. The surface of the depolarizer blend adjacent to the separator is coated with a layer of silver. The reduced surface layer of the depolarizer provides improved stability of the depolarizer blend in the alkaline electrolyte, and it provides the cell with a single voltage plateau during discharge. The cell is characterized by a maximum open circuit voltage of about 1.75 volts. The surface of the depolarizer blend can be reduced to form the silver layer either prior to being placed in the cell container or after the blend is consolidated in the container. The amount of divalent silver oxide present in the depolarizer blend is critical, and the blend may contain up to about 70% by weight of divalent silver oxide and still achieve a single voltage plateau during discharge. The cell has a high drain rate capability whereby it can be pulsed, said cell being capable of providing a flash amperage greater than an average of 0.20 amperes per square centimeter of cell cross-sectional area.

High drain rate, primary alkaline cell having a divalent silver

A method for manufacturing a stable divalent silver oxide depolarizer mix wherein the mix is treated with a mild reducing solution of a reducing agent such as methanol followed by a treatment with a strong reducing solution of a reducing agent such as hydrazine to form a layer of silver on the surface of the depolarizer mix. The depolarizer mix is specially prepared for use in a primary alkaline cell which is discharged at a single voltage plateau, and the preliminary treatment of the mix with the mild reducing solution permits the incorporation of greater amounts of divalent silver oxide in the mix, thereby increasing the electrochemical capacity while still providing a single voltage plateau discharge. The treatment with the mild reducing solution generally requires soaking the mix in a solution containing a reducing agent for up to about 10 minutes and may be carried out at either room or elevated temperature. The subsequent treatment with a strong reducing solution may also require up to about 10 minutes at either room or elevated temperature, with the purpose to provide a substantially continuous and electrolyte permeable layer of silver on the surface of the depolarizer mix. The depolarizer mix is particularly adapted for use in a 'button' cell construction, and it may contain from about 50% by weight to about 100% by weight of divalent silver oxide and still provide a cell with a single voltage plateau discharge.

Method of manufacturing a stable divalent silver oxide depolarizer mix

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

El Sayed Megahed