Battery Technologies, Inc.

Apollo Energy Systems, Incorporated

Varta Batterie Aktiengesellschaft

Karl Kordesch

Klaus Tomantschger

Josef Gsellmann

Martin Cifrain

Josef Daniel-Ivad

Viktor Hacker

Robert Flack

Robert D Findlay

Erkut Oran

Wilhelm Harer

Robert Fankhauser

Gottfried Faleschnin

Ronald Ujj

In a gas diffusion electrode the electrolyte must penetrate the pares of the electrode structure to a certain extent to establish the optimum interface between gas and liquid electrolyte, but it should not reach the gas-side of the electrodes. The best equilibrium of the so-called three phase zone (porous current collector-reaction gas-liquid electrolyte) is achieved by adequate wetproofing the porous structure with a polymeric substance as repellency agent. The polymeric substance serves also as a binder. During operation of the electrodes, the wetproofing material may lose its hydrophobicity for various reasons and the result is a penetration into the pores structures, reducing the interface between liquid and gas, notice by a loss of performance. By adding small amounts of wetproofing agents to the gases supplied to the electrodes, the original three-phase condition is maintained, or, if it is already partially degenerated, means and methods for its re-establishment are described. The invention claims substances and techniques for such maintenance and regeneration processes.

Additives to the gas supply of fuel cells with circulating electrolytes and means to regenerate used stacks

Fuel cell electrodes are described which comprise a non-woven network of conductive fibers, such as a carbon fleece, nickel foam sheet or stainless steel wool layer, plus additional activated carbon material, carrying one or more catalyst components and at least one polymeric substance as binder and/or repellancy agent to establish three zone interfaces (liquid-solid-liquid) or three phase interfaces (gas-liquid-solid). The electroactive catalyzed material is embedded into the conductive structure by specified deposition processes, such as coating, blading or spraying.

Electrodes for alkaline fuel cells with circulating electrolyte

This method for hydrogen production from ammonia is based on the catalytic dissociation of gaseous ammonia in a cracker. A catalytic fixed bed is used. The ammonia cracker supplies a fuel cell (for example, an alkaline fuel cell AFC) with a mixture of hydrogen and nitrogen. Most of the supplied hydrogen is burned in the ammonia cracker for the supply of the energy needed for the ammonia dissociation process.

Ammonia cracker for production of hydrogen

Low mercury or mercury free primary or secondary alkaline manganese dioxide-zinc cell that comprises a manganese dioxide cathode with a manganese dioxide active material and a conductive powder. The active material and powder are uniformly mixed and pressed to form a porous cathode body. The cell further comprises a gelled zinc anode, a separator between the cathode and the anode, and an alkaline electrolyte. The anode gel comprises a modified starch as a gelling agent capable of releasing hydrogen gases developed during slow corrosion of zinc in the anode. A hydrogen recombination system can be used in the cell to limit inside pressure within permitted limits by recombining the evolved hydrogen.

Low mercury or mercury free alkaline manganese dioxide-zinc cell

Porous electrodes for use in fuel cells and other electrochemical cells are disclosed. Principally, the electrodes a catalytically active layer on a porous conductive substrate, which catalytically active layer is derived from non-noble metals. The loading of the catalytically active layer is lower in terms of weight of catalyst per unit area of geometrical electrode surface than heretofore. Several alternative methods of forming the electrode are taught, including impregnating a porous conductive substrate with a metal salt solution, followed by chemical or thermal formation of the porous catalytically active layer; or mixing the catalytically active material with the material of the porous conductive substrate, followed by fabrication of the electrode; or depositing pyrolitic carbon from the gas phase onto a porous conductive substrate, at elevated temperatures in a gas atmosphere. The electrode may also have a porous metallic current collector, and also a further gas diffusion layer. If used as a fuel cell anode, a further small amount of noble metal is included in the porous catalytically active layer. Porous electrodes of this invention have particular utility in alkaline primary or secondary cells as auxiliary gas recombining electrodes, especially as oxygen consuming auxiliary transfer electrodes.

Metal and metal oxide catalyzed electrodes for electrochemical 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.

Recombination of evolved oxygen in galvanic cells using transfer anode

This invention relates to rechargeable alkaline electrochemical cells, having manganese dioxide cathodes. Generally, those cells have zinc anodes and an alkaline electrolyte, but several other options are considered. In any event, the present invention provides an improved cell by providing a pre-conditioned manganese dioxide cathode, where the net oxidation state of the cathode at the time that the cell is finally assembled and sealed is such that the manganese dioxide is, in fact, MnOx where x is between 1.70 and 1.90. The preconditioned cell may be preconditioned by cycling the cathode in a unsealed cell, then replacing the zinc anode and sealing the cell; or by adding a reduction agent to the manganese dioxide cathode prior to the time when the cell is finally assembled and sealed; or by adding an overcharge reserve material to the cathode. By pre-conditioning the active cathode material, essentially partially reducing the oxidation state, the cumulative capacity of the cell, and its cycle life, are improved. Since the first cycle of a sealed manganese dioxide-zinc cell is a discharge, followed by a re-charge, the present invention assures that the re-charge efficiency of the cell is improved. In that manner, essentially a complete re-charge of the cell can be effected, even following the first discharge cycle. The invention also contemplates that the preconditioned manganese dioxide cathode may also be utilized, with a suitable non-aqueous electrolyte, in a rechargeable manganese dioxide-lithium cell.

Rechargeable alkaline manganese dioxide-zinc cell having improved

A resistance free constant voltage taper charger for batteries in which a voltage regulator of a conventional type is combined with a conventional instrumentation amplifier in such a way that the output voltage increases by the same amount as a reference voltage coupled to the input of the amplifier is varied. The result will be that the voltage at the final output is constant. The same basic circuit can be complemented with two switches and with a sample and hold circuit controlled by a pulse generator so that in short pulse periods the voltage regulator is disabled and the resistance free electrochemical battery voltage is samples, and during the longer intervals between the periods the sampled and stored value is used to regulate the output voltage so that the electrochemical voltage remains unchanged.

Method and a taper charger for the resistance free charging of a

A rechargeable alkaline electrochemical cell has a manganese dioxide cathode and a zinc anode. The cathode is mixed with graphite or other conductive carbon and a binder, and is contained by a metallic screen which also serves as an oxygen evolution catalyst. The screen also serves to contain the cathode in place as it tends to expand under use. A diaphram is provided to separate the cathode and anode; an alkaline electrolyte contains the cathode and anode, and the other components of the cell.

Rechargeable alkaline manganese cells with zinc anodes

Rechargeable alkaline manganese dioxide - zinc cell of the type comprising a metal container including a porous cathode consisting of a plurality of adjoining blocks, a zinc anode and a separator separating the cathode and anode, and an electrolyte impregnating the cathode and contacting with said separator and anode, in which a cloth-like material like graphite cloth, nickel sinter or other fabric material (which wet the electrolyte) is inserted between otherwise contacting blocks of the cathode body and it substantially decreases internal resistance owing to the fact that the electrolyte impregnates the porous cloth material and will thus have a larger contacting area with the cathode body.

Rechargeable alkaline manganese dioxide-zinc cell with low internal

In rechargeable or primary, electrochemical cells, hydrogen may evolve. The invention concerns the use of an auxiliary electrode material to catalyse the recombination of pressurized hydrogen, for example, the hydrogen being at pressures ranging from 5 to 15 psig up to pressure relief of the cell. The cell is a sealed cell having a metal oxide cathode, a zinc anode and aqueous, alkaline electrolyte contacting both anode and cathode. The auxiliary electrode material, which may be mixed with the cathode material or be formed into a discrete auxiliary electrode, comprises a porous substrate and a catlyst for the absorbtion of pressurized hydrogen by the electrolyte. The substrate may be carbon, graphite or metal. The catalyst may be carbon, catalytically active noble metals, salts and oxides of lead, nickel, titanium, lanthanum, chromium, tantalum and alloys thereof, and the metals or mixtures of carbon with the salts or oxides.

Catalytic recombination of corrosion evolved 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 comprises porous carbon bonded with PTFE and is used in a cell having a zinc anode, a metal oxide cathode and an aqueous alkaline electrolyte contacting both anode and cathode.

Catalytic recombination of evolved oxygen in galvanic cells

A rechargeable galvanic element with constant-volume positive manganese dioxide electrode. In a rechargeable galvanic element having an alkaline electrolyte and a positive manganese dioxide electrode the volumetric change of the electrode body caused by phase transformation, which entails undesired contact losses, is largely prevented by exertion of a steady pressure upon the electrode surfaces. For a concentric electrode arrangement, this can be done with particular effectiveness. For example, the pre-pressed MnO.sub.2 electrode can be forced into a rigid cylindrical metal cage, while the annular slot enclosed by the housing cup, lid and bottom insulation is occupied by the zinc electrode. In other cases, continuous take-off contact is preferable, using pressure springs or tensioned metal mesh which extend over the flat electrodes.

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Graz, Austria

Karl Kordesch