DE2040346A1 - Metal / air cell - Google Patents

Description

PATENT ADVOCATE

MONKS 5

FEfCHENBACHSTR. SI

TEL «63251

693

R / P 6th

Lsesona Corporation, Warwick. Rhode Island, USA

Metal / air cell

In the patent application P 19 29 209.2 of the same applicant is a metal / air cell made of a cylindrical housing with ventilation holes «one concentric in this case arranged cathode made of a hydrophobic gas-permeable, liquid-impermeable polymer and an electrolyte facing electrocatalytic layer on the inner surface this foil «of an anode arranged axially in the cathode from a porous "consumable metal, for example Zinc, and a closure part for the housing that this is sealed liquid-tight and that also serves as a holder for the anode. On the catalytic layer of the cathode can still a hydrophilic separator are located, and the entire tree between cathode and anode is during operation of the Cell filled with electrolyte, the electrolyte being in a dry state before use and to the cell

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To make ready for use, can be activated by filling up with water or in liquid Zis tand, for example in the form of a thick paste or a QeIa, can be present.

When such a cell is operated, oxygen from the air is converted into hydroxyl ions at the cathode, which through the electrolytes migrate and oxidize zinc to zinc oxide at the anode. When the cathode and anode are outside the electrolyte are connected to each other, the electrons emitted at the anode migrate through this connection in the direction of Cathode. Oa in these reactions, however, the anode and the electrolyte are subject to physical and chemical changes » the internal pressure on the cathode increases gradually. For example, the volume of the electrochemical The conversion of the zinc oxide formed is one third greater than that of the converted zinc. By increasing the internal pressure on the cathode there is at a given time a separation of the catalytic layer of the cathode from the Foil made of the hydrophobic polymer and to interrupt the contact between the cathode and the cathode connection, which is generally formed by one end plate of the housing.

The object of the invention is to counteract this destructive influence of the increase in the internal pressure on the cathode.

The invention is based on a metal / air or metal / oxygen cell which has an anode made from a metal that is consumed, a cathode which is deformable by pressure and which surrounds the anode and is arranged at a distance from it , with a thin-walled, electrically conductive porous support and in intimate contact with these one layer on top of one

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Electro-catalytic material on its inner surface facing the anode, an electrolyte in the space between the anode and cathode _a means to seal off the anode, cathode and electrolyte from the environment and ventilation means surrounding the cathode, which allow air or oxygen to access the cathode )· having. The cell is characterized in that the valve means include a cathode which surrounds it, adjoins it and moves it outwards. Has an increase in the internal pressure of the cell preventing part made of an insulating material.

This part preferably consists of one when heated shrinking material that remains in the shrunk or contracted state after the end of the heat treatment, and is for example a pipe made of polyvinyl chloride, irradiated polyethylene,

modified nylon, polytrifluoroethylene, polydifluoroethylene, polyethylene terephthalate, etc. \ if the cell is heated before use * this material shrinks and thereby increases the inwardly directed forces on the cathode, so that inward and outward pressures on the cathode can equalize.

In the drawings is

Figure 1 is a perspective view of a preferred one Embodiment of a metal / air cell according to Invention,

Figure 2 shows a cross section through the cell of Figure 1 and

FIG. 3 shows an enlarged partial view of the cell of the figures 1 and 2.

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BATH ORIGINAL

The cell 10 has a cylindrical shape. It contains a tubular cathode or oxygen electrode 11 ″, which is preferably made of a gas-permeable, hydrophobic polyamide 12 made of, for example, polytetrafluoroethylene and one electrocatalytic layer 1? consists of, for example, silver particles in a binder of, for example, polytetrafluoroethylene particles. In the electrocatalytic Layer 13 can be a metal net 14, preferably made of nickel.

A hydrophilic separator 17 made, for example, of glassine in be arranged intimate contact with this catalytic layer, and the entire space 16 between cathode and anode with the exception of this separator and a current collector 15 is with anode material, which consists of amalgamated zinc powder, and an electrolyte, for example potassium hydroxide filled in the form of an oil or paste.

At each end of the cell there is an insulating plate 18 made of plastic, Oummi or the like. Through which the cell fluids is tightly sealed against the environment. At each end of the cell there is also a metallic connection plate 19 for the cathode and 20 for the anode as well Dlohtungeteile 21 and 22 to isolate the jacket 23 against the connecting plates 19 and 20. The jacket 23 consists of a rigid material, preferably a sheet metal or a hard plastic in the form of a cylinder tube. This jacket has a number of holes 24 through the air can reach the cathode from outside.

During operation of the cell, the anode and electrolyte are subject to chemical changes. For example, forms zinc oxide on the anode and potassium carbonate in the electrolyte. As mentioned, is the volume of what is formed

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BATH

Zinc oxide about a third larger than that of the converted Zinc. The chemical changes are therefore accompanied by a physical change in the cell, which aich in an expansion of the cell body predominantly radially from it Axis manifested outwards. As a result, the cathode is defeated a constantly increasing internal pressure, which leads to a deformation of the cathode *, especially in its middle section, leads and tension at the point of their contact with lon Sealing parts and the associated metallic connection plate evokes. This can considerably shorten the life of the ZeIXo, as it leads to separation of the cathode layers, 12, 13 and 14, as well as possibly also to a tearing of the electrolytic layer 1> and / or or the polymer membrane 12 and to a destruction of the electrical connection between the metal mesh 14 and the metallic connection plate 19 can come.

To this effect, which shortens the life of the cell To counteract the internal pressure on the cathode, a part 25 is provided according to the invention, which surrounds the Kathot'e and lies close to it. For a cell of cylindrical This part 25 is a thin-walled tube made of elmm electrically insulating material that absorbs the outward pressure caused by expansion of the cell body able to take up on the cathode 11. Suitable materials are for example vinyl polymers and rubber. Desired, if necessary the part 25 can surround the cathode so tightly that there is a inwardly directed pressure exerts on them and thus, when the cell expands, poems outward equalizes the pressure.

Like the cell jacket 23 , the part 25 also has a number of ventilation holes 26 through which air can reach the cathode .

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The anode material can be any of those used in the known metal / air or metal / oxygen cells Anode materials are »that react with the electrolytes capable and more electropositive than oxygen. Suitable materials are, for example, lead, zinc, «iron», cadmium, Aluminum and magnesium. The anode is preferably made of porous zinc. But it can also be made of a solid sheet or consist of a metal rod.

Suitable electrolytes are alkali hydroxides, mixtures of alkali hydroxides, acidic or basic anhydrides or hydrolyzable salts, for example alkali oxides and salts of weak acids, ammonium salts of strong acids, oxides of Non-metals such as phosphorus and the like. Preferably, the electrolyte is an alkali hydroxide such as potassium hydroxide, which in turn preferably, in the form of an aqueous gel or an aqueous one Fast is present.

The cathode has an electrically conductive, porous, pressure deformable support in contact with a catalytic metal or a mixture of a catalytic metal Metal with a hydrophobic polymer such as a polyhaloalkylene, a polyester, a polyalkylene or the like. The expression "deformable by pressure" includes materials that are very flexible and can be matured. As mentioned, the cathode also preferably has a gas-permeable one hydrophobic polymer membrane to which the electrolytic layer adheres as the inner surface facing the electrolyte. The catalytic material can be a metal, an oxide one Metal or an alloy of a metal of the group IB, IIB, IV, V, VI, VII or VIII of the periodic table, if necessary. mixed with a binder made from one of the above-mentioned hydrophobic polymers. The electrically conductive porous

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A network of any kind, the electrolyte, can be used as a carrier against corrosion-resistant metal, for example one Metal of the second or third triad of group VIII, nickel, cobalt, silver, gold, an iron alloy, titanium, Hafnium, zirconium, chromium, an alloy of these metals and the like. It is essential that the polymer membrane is in Is in contact with the electrocatalyst and the metal mesh. The cell is rendered inoperable by stripping. Such decoating is, as mentioned above, prevented by the invention.

The seals and sealing points of the cell are preferably made of non-conductive, low-density materials, such as plastics, for example a polyalkylene or the like.

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Claims (8)

Claims \ U) Metal / air or metal / oxygen cell, which has an anode made of a metal that is being consumed, a cathode deformable by pressure, surrounding the anode and at a distance from it, with a thin-walled, electrically conductive porous support and in intimate contact with this a layer of an electrocatalytic material on its inner surface facing the anode, an electrolyte in the space enclosed by the cathode, means to close the anode, cathode and electrolyte liquid-tight against the environment and ventilation means surrounding the cathode, which prevent the access of air or Allowing oxygen to the cathode, because the ventilating means has a part (25) surrounding the cathode, lying close to it and preventing its outward movement when the internal pressure of the cell rises. 2. Cell according to claim 1, characterized in that the part (25) consists of a material which shrinks when exposed to heat. j5. Cell according to claim 1, characterized in that the part (25) is a thin-walled part is made of an elastic material. 4. Cell according to claim 1, characterized in that it is cylindrical. 5. Cell according to claim 4, characterized in that the anode is an alkaline 209808/1009 Paste, the cathode surrounding the anode tubular 1st and that the ventilation means are tubular and 'the said part (25) surrounds comprise a perforated rigid shell. " 6. Cell naoh claim 5 * characterized ic h η et «that the hydrophobic membrane of the cathode consists of polytetrafluoroethylene» 7 · Cell according to one of the preceding claims «characterized in that the anode is made of zinc» the electrolyte consists of an alkali hydroxide and the electrocatalyst consists of silver. 8. Cell according to one of the preceding claims « characterized by “that between a hydrophilic separator is arranged on the cathode and the anode * 209808/1009 Blank page