Battery Technologies, Inc.

Erkut Oran

Klaus Tomantschger

Karl Kordesch

Kordesch, Karl

Klaus Tomanstchger

In rechargeable or primary electrochemical cells, hydrogen may evolve. The invention concerns the use of an auxiliary electrode material comprising manganese dioxide and a catalyst as the oxidant providing for the recombination of pressurized hydrogen, for example, the hydrogen being at pressures ranging from from substantially zero gauge pressure up to the relief pressure of the cell. The cell is a sealed cell having a manganese dioxide cathode, a zinc anode and aqueous electrolyte contacting both anode and cathode. The aqueous electrolyte may be alkaline or it may be ammonium chloride or zinc chloride, or mixtures thereof. The auxiliary electrode material, which may be mixed with the cathode material or be formed into a discrete auxiliary electrode, may optionally comprise a porous substrate, and in any event comprises MnO.sub.2 and a catalyst for the recombination of pressurized hydrogen with the MnO.sub.2. The substrate may be carbon black or graphite; the catalyst may be a metal, metal salt or metal oxide of elements such as lead, nickel, titanium, lanthanum, chromium, vanadium, tantalum and catalytically active alloys thereof. Most particularly, the catalyst may be silver, platinum, silver oxide, or silver dioxide.

Catalytic recombination of hydrogen in alkaline cells

In rechargeable, electrochemical cells, oxygen may evolve on charge, overcharge or any reversal of polarity. The invention concerns an auxiliary, electrochemical, transfer electrode to catalyze the recombination of such oxygen with the anode mass. The auxiliary electrode may comprise a porous carbon bonded with PTFE, or it may comprise a zinc gel having graphite particles and/or metal-plated zinc particles--where the metal that plates the zinc particles may be copper, or may be any of cobalt, cadmium, nickel, or silver. The auxiliary electrode for rectangular electrodes as used in flat plate or jelly roll cells may have the catalytically active material PTFE bonded to the current collector. The cell is generally one having a zinc anode, a metal oxide cathode (usually manganese dioxide), and an aqueous alkaline electrolyte (usually potassium hydroxide) contacting both anode and cathode.

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Willowdale, Canada

Erkut Oran