METAL/OXYGEN BATTERY OR FUEL CELL WITH OXYGEN CATHODE CONTAINING OXYGEN CONCENTRATOR AND REGULATING MEANS OF CONTROLLING ITS SUPPLY

Abstract: The present invention relates generally to the use of an oxygen concentrator to supply fairly high purity oxygen under pressure to a zinc/oxygen battery. The oxygen is supplied in a controlled manner.

Description: METAL/OXYGEN BATTERY OR FUEL CELL WITH OXYGEN CATHODE CONTAINING OXYGEN CONCENTRATOR AND REGULATING MEANS OF CONTROLLING ITS SUPPLY Technical Field The present invention relates generally to the use of an oxygen concentrator to supply fairly high purity oxygen under pressure to a zinc/oxygen battery. The oxygen is supplied in a controlled manner. Background Of The Invention Metal-air batteries utilize multiple electrochemical cells. Each cell is comprised of an air permeable cathode, a metallic anode, and an aqueous electrolyte. Because they use oxygen from air as a reactant in the electrochemical reaction rather than a heavier material, metal-air batteries have a relatively high-energy density. During discharge of the zinc-air cell, oxygen from ambient air is converted at the cathode to hydroxide ions, zinc is oxidized at the anode through a reaction with the hydroxide ions, and electrons are released to provide energy. One of the problems with the zinc-air battery is gating or valving the oxygen into the battery. You need to shut off the oxygen when the battery is not under load and then match the oxygen flow rate to the load during use. The second problem is controlling the water inside the battery. And the third is dispersing the oxygen over the cathode area inside the battery for the efficient oxidation of all of the zinc. One solution to these problems is supplying the battery with pressurized air. The difficulty of this system resides in the management of the humidity and temperature within the battery given the large volumes of air flowing through the battery to supply the oxygen. It is an object of this invention to solve the air flow problem by using an oxygen concentrator to supply fairly high purity oxygen under pressure to the zinc oxygen battery in a controlled manner. This and other objects of the invention will become obvious as described herein. Summary Of The Invention The present invention provides a better solution to solving the problem of providing oxygen in a metal-air battery. The combination of the oxygen concentrator in a zinc/oxygen battery wherein the oxygen is supplied in a controllable and controlled manner is disclosed. Description Of The Figure Figure 1 is a diagram of the oxygen concentrator in a battery. Detailed Description Of The Invention Metal-air batteries contain an anode which is made from metals that can be oxidized during discharge in a metal-oxygen cell to produce electrical energy. Such metals include lead, zinc, lithium, iron, cadmium, aluminum, and magnesium. Zinc is normally preferred because of its availability, energy density, safety, and relatively low cost. An electrolyte is also provided. Generally, an aqueous electrolyte solution of the Group I metal hydroxides is used. For example, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, or the like. Metal-air batteries have an air permeable cathode. This invention utilizes an oxygen concentrator instead of air as the reactant. Since air only contains about 20% oxygen, a greater flow of air is required to provide the required oxygen for the cathode. Concentrating the oxygen to the air permeable cathode simplifies the battery design. A rotary compressor (1 ), driven by a battery or air flow past a moving vehicle is used to create pressurized air. A variable compressor controlled by a feedback loop can also be used. Optionally, the air can be passed over water to humidify it. This humidifier (3) can be placed before or after the oxygen concentrator (5), but preferably after the oxygen concentrator. The compressed air passed through an oxygen concentrator which contains molecular sieves or membranes which allow >95% of the oxygen to pass through and the nitrogen is vented. The oxygen that is concentrated contains a small amount of carbon dioxide, nitrogen, and water and is referred to as "high purity oxygen." Preferred oxygen concentrators use zeolite molecular sieve or absorbent material. Activated carbon molecular sieve to absorb the argon can also be used in combination with the zeolite. The carbon dioxide in the oxygen stream exiting the oxygen concentrator can be absorbed by a small cartridge (7) of absorbent material such as calcium oxide or lithium hydroxide. The oxygen can be humidified (9) either as it exits the cartridge or prior to the concentration apparatus. In very arid climates, a water reservoir is used (11 ). Humidifier valves (13) which are controlled by a water sensor (19) in the battery can be used to control the amount of water entering the battery (15). An oxygen flow rate valve (17) is used to control the amount of oxygen entering the battery. The control of the flow rate of the oxygen to the battery matches the load of the battery (23). The pressurized oxygen flow also insures complete mixing or dispersion of oxygen throughout oxygen electrode. A pressure relief value is used to vent the remaining gas and water to the atmosphere (25). This battery contains a pressure release valve to release the nitrogen and water to the air. The nitrogen is desorbed form the zeolite by a regenerative purge flow or through the use of two zeolite beds. In a two step cycle, one bed or pair of beds (one zeolite and one carbon) receives a high pressure air as feed gas which pressurizes the beds and establishes oxygen flow. Simultaneously the high pressure gas in the other beds is vented to a lower pressure and this depressurization serves to desorb the nitrogen and argon previously adsorbed during the high pressure phase of the cycle (see, US 4,880,443 issued in 1989). While the use of the oxygen concentrator in large batteries for electrical vehicles is preferred, there are smaller oxygen concentrators which could be used to make smaller batteries. The oxygen inlet of the air manager system is set initially to a predetermined position based upon the status of the load to control the amount of oxygen supplied to the cell. In order to ensure that the oxygen flow reacts with the entire surface of the cathode, the direction of the oxygen flow may be changed by a plurality of baffles (21) incorporated into the pathway of the oxygen. The baffles used for changing the direction of the flow of the oxygen define a serpentine path across the surface of the cathode covering essentially all points of the surface. Preferably, the cathode has an inlet and outlet and a plurality of baffles to define a torturous path for the oxygen to flow from inlet to outlet. A catalytic element can be placed in the path of the oxygen flow for catalyzing the recombination of the hydrogen and oxygen gas generated by a rechargeable metal oxygen battery. This same oxygen concentrator technology can be applied to a fuel cell which uses hydrogen as the anode. The oxygen concentrator provides a more efficient source of oxygen for these cells. Carbon monoxide in the air can poison the fuel cell. Using the oxygen concentrator to purify the source of oxygen can prevent or limit this interference by carbon monoxide and other impurities in the air.

Claims: What is claimed is: 1. A metal-oxygen cell having an oxygen cathode, a metal anode and an electrolyte, said cell characterized in that it comprises a means for concentrating oxygen to supply high-purity oxygen to the cathode and a means for controlling oxygen entering the cathode comprising a current monitoring circuit connected to measure an output current drawn from the metal/oxygen cell by a load during operation, and an oxygen control circuit responsive to said current drawn to open said means for admitting oxygen from the concentrator for a predetermined time. 2. A cell according to Claim 1 , wherein said oxygen concentrator contains zeolite molecular seives. 3. A cell according to Claim 1 or 2, wherein said oxygen concentrator comprises two zeolite beds, one of which is regenerated by lowering the pressure in it. 4. A cell according to any of Claims 1- 3, wherein said oxygen concentrator contains an absorbent carbon bed. 5. A cell according to any of Claims 1- 4, wherein said metal anode is zinc. 6. A cell according to any of Claims 1- 5, wherein said electrolyte is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide. 7. A fuel cell having an oxygen cathode, a hydrogen anode, and an electrolyte, said cell characterized in that it comprises a means for oxygen entering the cathode comprising a current monitoring circuit connected to measure an output current drawn from the metal/oxygen cell by a load during operation, and an oxygen control circuit responsive to said current drawn to open said means for admitting oxygen from the concentrator for a predetermined time. 8. A fuel cell according to Claim 7, wherein said oxygen concentrator contains zeolite molecular seives. 9. A fuel cell according to Claim 7 or 8, wherein said oxygen concentrator comprises two zeolite beds, one of which is regenerated by lowering the pressure in it. 10. A fuel cell according to any of Claims 7-9, wherein said oxygen concentrator contains an absorbent carbon bed.

Inventors: CAMDEN JAMES BERGER, GARTSTEIN VLADIMIR, CAMDEN, JAMES, BERGER, GARTSTEIN, VLADIMIR
Applicants: CAMDEN JAMES BERGER, GARTSTEIN VLADIMIR, PROCTER & GAMBLE, CAMDEN, JAMES, BERGER, GARTSTEIN, VLADIMIR, THE PROCTER & GAMBLE COMPANY
Application year: 1999
Main classification: H01M12
IPC codes: H01M8, H01M12