DE1796023A1 - Electrochemical gas diffusion electrode with an air oxygen electrode and a soluble metal electrode - Google Patents

Description

22.818 (32.6o4) August 15, 1968

Yardney International Corp., New York N.Y. Iool3, 4o-52 Leonard Street

Electrochemical gas diffusion electrode with an air oxygen electrode and a soluble metal electrode

The invention relates to an electrochemical gas diffusion cell with an atmospheric oxygen electrode from a a metallic electrode carrier, carbon or precious metal coated carbon and a hydrophobic plastic containing catalyst mixture, a soluble positive metal electrode made of zinc, magnesium or the like. and an alkaline electrolyte, and has a particularly expedient configuration for the subject, through which the Cell structure is significantly simplified and manufacturing costs are reduced.

Electrochemical gas diffusion cells with an atmospheric oxygen electrode and a soluble zinc electrode are known to have a high specific power, for example 155 to 335 Wh / kg with a 1/2 hour to 100 hour discharge current. In addition, the zinc anode sufficient and stable at temperatures between 4 and 75 G ^{0 0} C Lastly

ο such a gas diffusion cell also works for you

heavily depleted electrolyte, so that towards others

JJ diffusion systems, which are used to generate a maximum

Ot energy must work in a free electrolyte

ω weight saving is obtained. Gas diffusion electrodes of the aforementioned type have both mechanical and also from an electrochemical point of view for recharging

BATH ORIGINAL

systems shown as geei _T gnet. For a long service life, however, the air oxygen electrodes must contain a noble metal as a catalyst, e.g. platinum, rhodium, palladium, iridium or other metals of the platinum group, which means that their production costs are very high required conductors. Difficulties also arise from the fact that the hydrophobic property of the atmospheric oxygen electrode decreases with frequent use and the resulting passage of K electrolyte results in a loss of capacity.

In contrast, the invention is based on the object To design gas diffusion cells with atmospheric oxygen electrodes and soluble metal electrodes in such a way that one Much cheaper production is achieved without the mechanical and electrochemical properties are impaired as a result.

This object is achieved according to the invention in that the Atmospheric oxygen electrode for embedding a τοη one Separator coated soluble metal electrode or the inflow of air has a pocket or bag shape

Due to the hash or bag shape of the air-release electrode, it has great mechanical strength, see above that an additional support frame for the electrodes could advantageously be omitted. Especially 1st the production is particularly easy. So there is always one Possibility of two trough-shaped, curved atmospheric oxygen-209808/0653

Afc. '. ViN :,.: · ■ /.-,

8A0OFHG1NAL

to place electrode foils with their edges against each other and weld them together there, with one edge a! filling opening is left free. In this case, the hydrophobic plastic compound is advantageously used for welding of the electrode so that, after welding, a fluid-tight connection at the weld seams is present. The self-supporting, stable, pocket-shaped air oxygen electrode also has the advantage that the conductors can be easily attached without any special effort. For this purpose it is provided according to the invention that on a common longitudinal edge of the atmospheric oxygen electrode film the metallic electrode support protrudes freely and is bent into a tubular round stefc on the a conductor is connected.

But there is also the possibility of obtaining a bag-shaped air oxygen electrode by having a Electrode foil bent in a cylindrical shape and with its Longitudinal edges are welded, one of which has a protruding metallic electrode carrier bent into a dog web has, while a cap is welded to the bottom edge.

There is the possibility of adding a soluble, from one to one, air oxygen electrode designed according to the invention Separator sheathed metal electrode to be used, this with the associated separator with dry potassium hydroxide is impregnated, so that only water needs to be filled through a pocket opening for activation. It

209808/0653

8AP ORIGINAL

but there is also the other way around, in the pocket-shaped atmospheric oxygen electrode a to about Use floor-reaching air duct and provide an air outlet opening at the other end so that air flows through the inside of the pocket-shaped electrode. This run is on everyone On the side of the atmospheric oxygen electrode, a soluble metal electrode encased by a separator is attached. The cell set is located in a housing which is filled with an aqueous cooling solution.

The electrochemical gas diffusion cells designed according to the invention have a compact design and are particularly suitable for the delivery of larger amounts of electricity per Weight or volume unit. If it is a pocket design with an embedded soluble electrode it can be used as a primary element, i.e. exchanged for a new element after use will.

The object of the invention is shown in the drawing using several exemplary embodiments, namely show FIG. 1 shows a pocket-shaped atmospheric oxygen electrode in a side view,

Figure la the subject of Figure 1 in. A plan view, Figure Ib the subject of Figure 1 in a plan view,

but with slightly modified edge parts, Figure 2 shows a cylindrical air oxygen electrode in a side view,

20980 8/06 5 3

0AlDbRIQINAL

2a shows the object of FIG. 2 in a plan view, FIG. 3 shows a further exemplary embodiment of a pocket-shaped one Atmospheric oxygen electrode on the side

white electrolyte view with a special filling channel,

FIG. 3a shows the object of FIG. 3 in a top view, Figures 4 and 4a different embodiments for the connection of the edge parts of atmospheric oxygen electrode foils,

FIG. 5 shows a further exemplary embodiment with a special configuration of the positive current conductor on the cell head,
FIG. 5a shows the object of FIG. 5 in an enlarged side view,

Figure 6 shows a further embodiment of an atmospheric oxygen electrode into which air is filled, and

FIG. 6a shows the object of FIG. 6 in a section along line 6a-6a.

In a preferred embodiment, one has electrochemical gas diffusion cell has a bag-shaped air electrode in which an anode-separator package is arranged is. The air electrode is made up of two electrode foils, which are shaped like a trough by pressure, the edges of which lie against one another to form a pocket. The pocket is sized to allow expansion the negative electrode allowed during discharge. So there is one air electrode film on each each side of the separator-encased anode. After inserting the anode encased by the separator, the

209808/065 3

8AD ORIGINAL

Both air electrode foils are sealed on three edges and thus form a liquid-tight pocket. The fourth edge is also heat sealed, but with a liquid passage provided so that liquid can be introduced into the cell for activation if necessary.

The air electrode is so active that no additional ! Beams but only spacers between the cells for the air flow space are required. These spacers from about 2.5 to 7.5 mm between the cells are rib-like elements, for example waterproof cardboard strips, which are arranged to form chambers at a distance of about 6.4 to 12.7 mm, the area the strip is perpendicular to the cell surface. The rib-like strips also serve to form a suitable pressure for liquid contact between the air electrode and the separators, if greater Number of cells is merged.

The power connection between the cells is made by bending the negative connecting wire to an opposite one Collector element. Preferably, a portion of the support grid is left without a catalyst mass and becomes one tubular round bar bent over. The negative connection lead of the neighboring cell is inserted into this web and the latter pressed together so that a contact is made.

BATH ORIGINAL

The atmospheric oxygen electrode is a carbon electrode, outer the two foils forming the pocket by mixing pure carbon or metal-plated carbon and a hydrophobic plastic emulsion, for example a Teflon emulsion, by drying the mixture at a temperature of about 60 to 25o ⁰ C and by heating the dried mixture at 15o to 360 ⁰ C and a lack of oxygen. The sintered mixture is then mixed with a wetting agent or lubricant, for example glycol, the decomposition temperature of which is below that of the hydrophobic plastic and which does not leave undesired residues in the electrode die when decomposed. This mixture is then pressed together to form a foil, which is then applied to an electrode carrier, for example a nickel grid or a nickel-plated expanded metal. This electrode foil is finally heated to about 370 ° for the purpose of decomposing the wetting agent or lubricant. According to the invention, such electrode foils are pressed into a trough shape and two foils shaped in this way are processed into a pocket-shaped atmospheric oxygen electrode.

One preferably serves as the anode or negative electrode

'the end
Zinc electrode, or an a el ent "" magnesium or another

active metal.

They are produced in the usual way, for example by pressing or by applying zinc oxide in a paste and a binder on an ager and subsequent charging to metallic zinc, or by pressing (liner

209808/0653

BATH ORIGINAL

Mixture of metallic zinc powder and a suitable other on a cheap electrode carrier, for example an expanded metal foil made of zinc. Charging is not required when using spongy zinc powder. The powder can can also be processed into electrodes using special roller devices.

The use of active zinc powder requires special measures in powder production. Production from an alkaline solution saturated with ZnO appears to be most suitable. According to another process, zinc is _{precipitated from a ZnSO 4} solution by reduction

In the further production of the zinc electrode, dry KOH is incorporated according to the invention in the pores of the electrode and those of the separator. For this purpose, the zinc electrodes and the layers of the separator made of Pellon, for example, are soaked in a 31% KOH solution for 10 minutes. The electrodes are then heated to 60 ° C. in a vacuum oven and dried for a treatment time of approximately 4 hours. They are then placed in the pocket of the atmospheric oxygen electrode and the cell unit formed in this way is closed in such a way that only a part remains free for filling in water for the purpose of activation. The finished cell is then packed in a moisture-proof protective bag to protect it from air and moisture. If the whole cell unit is simply immersed in a water container, the absorption time is about 2 minutes. Electrical tests with anodes of this type showed that the same efficiency was achieved

■ * ,: BADOJIiGlNAL

as can be achieved with liquid KOH solution.

The following list contains the technical data a 30-ampere-hour cell. With multi-cell batteries several such cells are used, e.g. 21, 24 cells or the like.

Zinc electrode:

1 plate / cell

Height: 156.6 mm; Width: 76.2 mm I = o, ll

Active area: 119.1 cm ² χ 2 = 238.2 cm ²

Amount of Zn: 6og / cell; Zn density: 1.83 g / cm ^ Electrode carrier: copper

Conductor: copper wire 4 χ 0.4 mm dia.

Theoretically. Capacity: 60 g / cell _ 4.8 4 Ah

1.123 g / Ah ~

Nominal output: 60 g / cell _ ^ _{0 0}

2 g / Ah

Air oxygen electrode:

2 electrode foils / cell

Height 165.1 mm; Width: 88.9 mm I - o, o2

Active area: 147 cm ² χ 2 = 294 cm ² Catalyst: carbon

hydrophobic film: 0.2mm 6o ~ 65 porosity Electrode carrier: nickel-plated straight iron Current conductor: nickel-plated Cn 4 x 0.4 mm diameter,

209808/0653

'' ORIGINAL

Separator;

1 U-shell made of Pellon 25o5 K (o.13 mm) 1 sachet of Pellon 25o5 ML (0.25 - 0.36 ma)

Electrolyte;

Solid impregnation in the Zn and the separators: 14 g solid KOH

Spacers:

5.1 mm; 2.54 mm for the two end cells.

Figures 1, la and Ib show a rectangular cell with an air electrode 2, which has a pocket for receiving an electrode encased in an absorbent separator 3 1, e.g. a zinc or magnesium electrode. It consists of a rolled carbon Teflon electrode, those between Io and 90 $ Teflon as well as carbon or platinum-plated Contains coal in one or more layers, which are applied to an electrically conductive (knight carrier.

The air electrode is manufactured by applying the hydrophobic catalyst film to a straw-conducting grid-shaped electrode carrier, which protrudes freely from the catalyst mass on a band. The electrode foils are shaped into a trough 5 so that a more or less rectangular recess is created opposite the edges 6. The grid-shaped electrode carrier protrudes freely at at least one of the edges 6, with all edges optionally also being able to be designed in this way. The inner surface of 209808/0653 facing the electrolyte

Electrode foil is hydrophobic. Two such electrode foils are assembled so that their troughs 5 form a pocket or form a chamber, these being heat-sealed, i.e. welded, on at least three edges 6. To the freely protruding edge of the electrode carrier is a current conductor 7 by welding, soldering or bending into one tubular edge web 4 attached. The heat-sealed edge is approximately 1.6 to 6.4 mm wide. The heat seal or welding takes place at about 21o to 33o ° C for less than a minute using a Pressure that the catalyst film to about Io to 50 # of its Original thickness compresses. The protruding edge of the electrode holder on one or both sides of the air electrode is used to connect the positive current conductor 7. The connection is carried out in such a way that when the cell discharges only one «. A drop of 1 ohm occurs. The current conductor 7 can be at the head of the electrode or optionally also at one of them Sides be attached. Only a corresponding design of the protruding electrode carrier edge is essential.

The electrode edges can be directly heat-sealed with one another are as shown in Figures 1 and la i3t. over the edges can also be a plastic or metal rail ^ are clamped (see. Figure Ib), which increases the mechanical strength of the cell. Furthermore, the edges of the electrode foils can be crimped and then heat sealed (see FIGS. 4a and 5).

209808/0653

ORIGINAL

The atmospheric oxygen electrode can be rectangular or tubular or be cylindrical. The rectangular version is shown in Figure 1 and the tubular in Figure 2.

As FIG. 1 shows, the negative electrode 1 in an absorbent separator 3 is made of, for example, a nonwoven Wrapped in polyamide felt, cotton felt or cellulose paper and provided with a conductor 9. The ones in the separator encased negative electrode can be either permanently or detachably attached in the pocket in case the air φ Oxygen electrode is to be made available for further use.

Instead of heat sealing the cell head, it is also possible to use one not shown in the drawing Provide a filling hole having a lid that is welded or welded to the upper edge of the atmospheric oxygen electrode is attached to it by means of a rail or bar made of plastic or metal.

In the case of the cylindrical cell according to FIG. 2, only one edge Io is welded and a positive current conductor 11 is connected to the protruding electrode carrier, which can be applied to the outer electrode surface. The base 12 of the cell is sealed by means of a polyethylene bottom cap 13 which is heat-sealed on the lower edge, so that a liquid-tight seal is created. The Teflon film of the cathode melts in the heat seal with the base cap 13. The welding can also be performed by sonication. 209808/0653

,. _r 8ÄD ORIGINAL

Another version is shown in Figure 3. Since the Teflon film of the air electrode can be heat-sealed like polyethylene, C-II, nylon or the like. The edges can be turned into a plastic frame 14 process, which has an electrolyte filling channel for introducing the required amount of electrolyte (rapid activation) 15 may contain. For the power connection of the air electrode, the electrode carrier 16 can be connected to one or protrude several pages over the edge of the plastic frame, as Figure 3 shows. The positive conductors are bent or welded to this electrode carrier. The main advantage of the plastic frame is its mechanical support and carrier function.

The inventive design of the air acid material electrode, the best possible use is made possible because

1 «, the cell for its relatively short lifespan is not more needs to be particularly roughened,

2. The use of dry electrolyte eliminates the need to transport water and

3. Metal elements such as power lines, as well as elements for connecting power to multiple cells in consideration the short battery load can also be carried out in a weight-saving manner.

In the embodiment according to FIGS. 6 and 6a, two negative electrodes 21 or zinc plates are each an absorbent one Separators 23, for example, encased in Pellon, are arranged on both sides of the air electrode. The air electrode 22 is preferably made of rolled out carbon Teflon

209808/0653

BAO ORIGINAL

containing electrode foils between Io and 9o i "Teflon and carbon or platinum carbon in one or more layers coated on a current-conducting electrode carrier.

Two electrode foils 22 are attached to each cell unit three edges sealed gas-tight. Aa fourth edge is an opening for the introduction of air by means of the seal a metallic feed pipe 38 in the pocket 45 released. The air flows in the direction of the arrows into the pocket 45, the main pipeline at 42 and the Distribution pipes are denoted by 44. After the air has reached the bottom of the pocket 45 via the pipe end 44a, it flows between the outer surface of the relevant distributor pipe 44 and the inner wall of the pocket 45 above. Bas outflow of air from the pocket 45 can be about an opening 46 takes place, as indicated by the arrow 48.

To make the pocket 45 dimensionally stable, a carrier is in it 5 ο made of fiberglass, as Figure 6 shows. The electrolyte 22 essentially fills the remaining space in housing 54, which can be made of a plastic material such as polystyrene. A lid 56 made of a suitable plastic, e.g., epoxy resin, is sealed to the housing 54 by a sealant 58, e.g. an epoxy resin. The air electrodes 22 can be connected in a suitable manner to the metal tube 38 via a current conductor 6o, while dfe · current conductor 62 for

the zinc electrodes 21 are provided. 209808/0653

* 8ABOBiGiNAl

The embodiment according to FIGS. 6 and 6a essentially has the advantage that there is no frame for the electrodes
is required. In addition, manufacturing costs are saved due to the relatively simple and easy construction,

Due to the parallel position of the air and zinc electrodes continue to receive an increase in the ampere-hourly output.

2 09 808/0653

Claims (6)

Patent claims: Electrochemical gas diffusion cell with an air oxygen electrode made of a carbon or precious metal-coated one applied to a metallic electrode carrier Carbon and a hydrophobic plastic containing catalyst mixture, a soluble positive Metal electrode made of zinc, magnesium or the like. and an alkaline electrolyte, characterized in that the Atmospheric oxygen electrode for embedding a soluble metal electrode encased by a separator or for Inflow of air has a pocket or bag shape. 2. Electrochemical Gasdiffusioiaelle according to claim 1, characterized in that two trough-shaped air oxygen electrode foils (2) with their edges lie against one another and are welded to one another, with a filling opening being left free at one edge. 3. Electrochemical gas diffusion cell according to claims and 2, characterized in that on a common longitudinal edge of the atmospheric oxygen electrode foils (2) the metallic electrode carrier protrudes freely and is bent into a tubular round stefc (4) to which a Conductor (7) is connected. 4. Electrochemical gas diffusion cell according to claim 1, characterized in that an atmospheric oxygen electrode film (Io) bent in a cylindrical shape and with their longitudinal 2 0 9 8 0 8/0653 edges are welded to one another, one of which has a protruding metallic one bent over to form a round web (11) Has electrode carrier and a cap (13) is welded to the bottom edge. 5. Electrochemical gas diffusion cell according to claims 1 to 4, characterized in that the in the pocket-shaped Soluble metal electrode (1) inserted into the air oxygen electrode and the separator (3) impregnated with dry KOH and the activation takes place by adding water. 6. Electrochemical gas diffusion cell according to claims 1 and 2, characterized in that in the pocket-shaped Atmospheric oxygen electrode (22) extending to approximately the ground Air supply pipe (4o) inserted, an air outlet opening (46) provided on the upper hand and one each soluble metal electrode (21) enclosed by a separator (23) on each side of the atmospheric oxygen electrode in one common, filled with liquid electrolyte cell housing is arranged. 209808/0653 Blank page