DE8316979U1 - ELECTROCHEMICAL ELEMENT - Google Patents

Description

- ΙΟ

'Bürkle KG

7033 Herrenberg

Electrochemical element

The invention relates to an electrochemical 20

Element according to the preamble of the claim

A well-known electrochemical element of this type is the Daniell element ("Lexikon der Physik",

Franckh'sche Verlagshandlung Stuttgart, 2nd edition, 25

1959, page 199], which has the system Cu / CuSO ./ZnSO ₄ / Z3i * The acidic zinc and copper sulphate solutions that form the two electrolytes, which have both pH values below 7, are separated by a porous clay wall. When power is delivered, U

Zinc of the zinc electrode forming the negative anode in solution, with the positive zinc ions being the negative SO ions through the porous clay wall pull over to yourself, * The positive ones that are released

, _e copper inner migrations to the second electrode, which the cäo

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forms positive cathode and is a copper plate. The opposite reactions take place when charging. The Daniell element thus forms a secondary element. It has the disadvantage, among other things, that its energy density and thus its capacity is relatively small, because the copper sulfate solution serving as the second electrolyte is rapidly depleted, since the S0 ₄ ~ ions of the copper sulfate solution, which form the acid residue, migrate more rapidly into the zinc sulfate solution, which forms the first electrolyte Exhaustion of this secondary energy. Mixing of the two electrolytes also inevitably occurs through the porous clay wall, since it must have such permeability that the negative acid residues SO _{4 of} the second electrolyte can migrate into the first electrolyte as carriers of the negative charges. This necessary permeability for the acid residues "SO." makes the porous clay wall necessarily permeable for the metal ions Zn and Cu of the electrolytes, since these have a lower atomic weight than the molecular weight of the acid residue SO. is equivalent to. The Daniell element could therefore not be introduced into practice to any significant extent and essentially only played the role of a voltage standard in the early days of electrical engineering.

5537 - 12 -

To avoid the described depletion of the copper sulfate solution, a Meidinger element was used known in which by a storage vessel with copper sulfate crystals for maintaining the Concentration of the copper sulphate solution of the Daniell element tes was taken care of. This is - however structurally - complex " and yet avoids relatively rapid exhaustion of the element and its rapid self-discharge not. The energy density of both the Daniell and the Meidinger element is also relatively low,

d. H. With a given capacity (in WhI, it requires a relatively large volume.

It is therefore an object of the invention to provide an electrochemical element of the type mentioned at the beginning

Art to create, which have low self-discharge, long service life and high energy density can.

According to the invention, this object is achieved by a

electrochemical element according to claim 3 solved.

This electrochemical element according to the invention exhibits only very little self-discharge. Of the

second electrolyte is not used up, because at the 30th

Discharge OH-ions the charge carriers and, if so

it is a secondary element when charging H-ions the charge carriers form in the electrolyte and migrate through the partition. The molecular weight the OH ion is very low, namely 3 7 and 35

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the atomic weight of the Η-ions is only j.

In any case, this molecular weight or this atomic weight is smaller than the atomic weight of the metal ions in the second electrolyte if, as is preferred, the second electrolyte contains at least one metal compound in dissolved form. It is also possible to provide the second electrolyte in such a way that the chemical compound dissolved in it is not a metal compound but, for example, an aqueous ammonia solution. The ammonia NH ₄ Cl in the water forms NH ₄ OH molecules with elimination of the chlorine, the molecular weight of which is 35, i.e. more than twice as large as that of the OH ions. The partition separating the first from the second electrolyte - ²⁰ , -S-tets__sp. au ^ sg_eb.ildeJtL_ werden, __ that_you both the '.

in the first electrolyte containing, optionally hydrated metal ions, as well as those in the second Electrolytes containing, if appropriate, hyeratised metal ions or other molecules with larger Molecular weights other than that of OH molecules does not let through, but only the OH ions and of course also the Η ions, as these have an even lower atomic weight. Furthermore, the partition can be used should be chosen moderately so that they are also the solvent of the electrolytes, which are then identical chemical Have constitution, preferably water, lets through.

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The element according to the invention can also be used as a non-rechargeable Primary element are formed »Also, in this case the partition must not be permeable to the electrolyte contained in the first Acid residues.

Another advantage of elements according to the invention is that they can receive very high energy density, since they only need small amounts of electrolytes because they do not become depleted when discharging. The electrolytes can in general be expedient liquids, but optionally also pasty in character or at least one electrolyte can be absorbed in a porous carrier medium.

The volume of an element according to the invention can be very small due to the low electrolyte requirement being held. Elements according to the invention can also be produced and are relatively inexpensive In addition, it is environmentally friendly as it does not contain any toxic components, such as B. mercury and cadmium too need to contain.

The element according to the invention is distinguished in the case of its formation or its use as Secondary element is also characterized by the fact that it is subjected to very large numbers of charge and discharge cycles can be. In contrast to the known metal-oxygen secondary elements, which are mostly designed as metal-air secondary elements, no dendrites on the first when loading

5537 - - 15 -

Electrode. The invention thus eliminates all of the previously known metal » Oxygen elements through the dendrites that occur on the first electrode when charging Difficulties affecting the practical use of the known metal-oxygen elements many times over prevented and at least greatly reduced the number of achievable charging and discharging cycles, so that metal-oxygen secondary elements have so far not been compared to the essentially more expensive ones and less environmentally friendly elements of the lead = · and nickel / cadmium accumulators. The invention therefore also eliminates these previously present in metal-oxygen secondary elements basic difficulties in a simple way.

Those migrating from the second into the first electrolyte when the element according to the invention is discharged OH ions can with the metal of the first electrode or with in the first electrolyte contained metal ions enter into at least one compound, in particular metal hydroxide and / or Form metal oxide, which is optionally precipitated from the first electrolyte, but in the first electrolyte-containing area of the element remains. When training the invention As a secondary element, positive Η ions migrate through the charging from the second electrolyte Partition wall through into the first electrolyte

and reduce the 35 formed in it during unloading

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Metal compound or compounds to positively charged metal ions and water molecules. the Metal ions then migrate to the first electrode and combine with those already on it Metal atoms so strong that the first electrode is a solid electrode, its thickness when charging grows approximately evenly due to the metal ions continuously attaching to it. Inshe- ^ In particular, no dendrites are formed and no grainy, easily wipeable deposits on it arriving metal ions. This regression of the first electrode during charging to a turn massive, inherently solid electrode of approximately uniform thickness allows very high numbers of charges * * and discharge cycles. The invention thus in particular also creates the possibility of Metal-oxygen secondary elements with previously unattainable high numbers of charge and discharge cycles to accomplish. In the aforementioned dendrites, those in the known metal-oxygen secondary elements arise during charging and not in the case of metal-oxygen secondary elements according to the invention more arise, it is a needle-shaped structure that emerges from the first electrode during charging outgrowth and which can easily break off and which are also easy to short-circuit and generally right

quickly to the useless of the secondary element ~

to lead.

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Under a metal-oxygen Element'ist also '' of the · * ^Fa -ll i it understood that it is a so-called metal-air Elesaent is, therefore, the oxygen supplied by the ambient atmospheric air at the. If necessary, it is also possible to send the oxygen to other sources

take, for example pure - oxygen available- -. or watch it in a granary, e.g., brownstone, as is the case with the Leclanche element. The latter can then be considered in particular come when the element according to the invention is provided as a primary element, that is, not rechargeable is. Compared to the well-known Leclanche element, which has a single electrolyte, has a primary element formed according to such a development of the invention with manganese dioxide

as an oxygen carrier, inter alia, the advantage that, instead of zinc, metal generating higher voltages can be provided for the first electrode, preferably aluminum. The first electrolyte can then be a C 25 aluminum salt solution, for example an aqueous aluminum sulfate solution. An aluminum-oxygen element according to the invention (including aluminum-air element) theoretically enables electrical voltages of approx. 2.7 volts, which are therefore very high, regardless of whether it is used as a primary element or a secondary element. With such an aluminum-oxygen element, you can use batteries of a predetermined DC voltage with a smaller number of batteries connected in series one after the other.

switched elements than those most commonly used today

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Lead-. Accumulators or. Nickel / cadmium batteries achieve.

When the element according to the invention is designed as a metal-oxygen element, the oxygen cathode forms the second electrode, which forms the positive pole of the element when discharging. As mentioned, the oxygen can preferably pass through atmospheric air can be supplied. The oxygen cathode can preferably act as a catalyst Contains activated carbon powder. In the activated carbon powder or directly adjacent to it, a metallic Perforated plate or grid in contact with the activated carbon powder to which the positive pole of the element is galvanically connected. This positive pole can both the positive pole when discharging and the positive in the case of a secondary element Form a pole when charging. However, it is also possible and can preferably be provided that the element when designed as a metal-oxygen secondary element, a third electrode on v / eist, to which for charging the positive pole of the charging current source is connected, whereby the third electrode is outside the active However, carbon powder is still within the second electrolyte. This has the advantage that the atomic oxygen that forms on the third electrode when charging is removed from the activated carbon-n can be, so does not need to get to it, and atomic oxygen can d ^ 'e activated carbon oxidize and thus accelerate the aging of the element. Since the element according to the invention is very

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can withstand many charging and discharging cycles , it ages very slowly and it is therefore particularly useful to also switch off the oxidation of the activated charcoal, which is a source of aging, which can be done by the described measure of the third electrode, which is during charging is not changed. The partition separating the first and second electrolytes may be of any suitable configuration that gives the characteristics described in claim 1. In the simplest case it can

be a single molecular sieve whose separation limit __ is greater than 3 7 so that OK ions can pass through '

they can walk through. In the present invention, molecular sieves are diaphragms, membranes, for example membranes known per se for reverse osmosis, which are sufficiently stable with respect to the electrolyte with which they come into contact. The separation limit of a molecular sieve is understood to mean that it lets through molecules with a molecular weight less than the separation limit and does not let through molecules with a molecular weight greater than the separation limit. In the invention, the separation limit of the molecular sieve must therefore be greater than 17 . However, it must not be too large either, but must be made in such a way that it does not let through the metal ions of the first electrolyte and possibly also of the second electrolyte that take part in the electrochemical reactions that take place during discharging, and also of the second electrolyte in the second electrolyte

_5537 _t - 20 -

existing undissociated hydroxide compounds, such as potassium hydroxide if the second electrolyte Potash is »

Ö The first electrolyte can be an acidic electrolyte its pH value is then less than 7. It is, however, also conceivable that its pH in many cases it can also expediently be equal to 7 or slightly greater than 7. A pH of 7 or et— |

what is greater than 7 assumes that the first electrolyte does not only contain metal salt in solution, but at least one basic additive that brings its pH to 7 or a little above raises. This leads to the fact that metal oxide is formed to an increased extent when discharging and, if that The solvent of the first electrolyte is water, less water in the metal hydroxide when discharging is bound. The water consumption during unloading is therefore lower and the water supply in the element can be given a correspondingly smaller volume and thus the element can be given a slightly smaller volume.

The second electrolyte can expediently have a pH value greater than 7, since this makes it relatively high Discharge currents of the element can be achieved, however, it is also possible in special cases to adjust the pH value of the second electrolyte should be set to approximately 7 if relatively low discharge currents are sufficient. It it should also be mentioned here that the discharge currents

^ can also be enlarged by forming the second electrode from noble metal, but this is expensive. The
second electrode a cheap oxygen electrode

or, if it is made of metal, it can be 35

• 5537 - 21 -

suitably consist of a cheap metal, which is positive against the first electrode when discharging.

Let us give an example of the range in which the separation limit of a molecular sieve must be if it alone forms the dividing wall: It is assumed that the first electrode is made of zinc and the second electrode is an air electrode. The first electrolyte is an aqueous zinc sulfate solution and the second electrolyte is potassium hydroxide solution, i. h an aqueous KOH solution, the partition should then be permeable to water. Be H and OH ions. On the other hand, it should not be permeable to the metal ions, KOH and SO ₄ . The metal ions have atomic weights of 65.4 (zinc or!, 39.1 (potassium !. The acid radical SO ₄ has a molecular weight of 96, KOH 1. 56 _f § Demzuf_olqe_muß__dAe__Treiingr_enze of Molekulars iebes

larger than water, that is to say 1S, and - since the potassium ions hydrate, as usually all metal ions - be smaller than that of hydrated potassium ions. Hydrated potassium ions have a molecular weight of more than 50, so that the upper separation limit of the molecular sieve may actually be much greater than 39.1 (potassium), even more than 50. If the dividing wall is designed as a single molecular sieve, the potassium ions of the second electrolyte must not be able to pass through the molecular sieve, since they have a strong affinity for the acid residue SO _{4 of} the zinc sulfate and therefore

migrate into the first electrolyte and generate dendrites there when charging.

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Molecular sieves are more expensive, the smaller their separation limit and the greater their resistance _t they oppose to ion migration during discharging or charging. It is therefore on

it is desirable to be able to use molecular sieves with a relatively large separation limit. This succeeds according to a Further education -. in that the partition is not is formed from a single molecular sieve, but from two molecular sieves and one between there is a third electrolyte in them. It then succeeds with the use of a suitable one third electrolyte to achieve that the separation limit of the two molecular sieves is greater _as das_Atomgewich.t that in the second electrolyte may be hydrated metal ions, which are preferably alkali metal ions can, especially potassium, sodium or lithium ions. This is likely due to having alkali metal compounds Experiments carried out can be explained by the fact that in itself alkali metal ions have a strong affinity for the first Line of possible acid residues of most electrolytes have, for example, to S0, ions, but this affinity cannot sum outbreak come when the third electrolyte is chosen so that it contains the metals of the second Electrolytes lose their ability between the third and the first electrolyte Molecular sieve to pass. For this purpose, the third electrolyte can preferably be so selected be that it contains a metal salt dissolved in a solvent, the solvent being expedient may correspond to the solvent of the first and the second electrolyte. The metal of the third

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Electrolyte-dissolved metal salt may preferably be the metal of the second electrolyte and the acid residue the acid residue of the first electrolyte speak.

If, for example, the first electrolyte consists of an aqueous zinc sulfate solution and the second electrolyte consists of potassium hydroxide solution, the third electrolyte can expediently consist of an aqueous solution of potassium sulfate. In this example it is sufficient if the separation limit of the molecular sieves is smaller than the molecular weight of KOH (potassium hydroxide), although it may be larger than the atomic weight of potassium, i.e. greater than 39.1 and smaller may be all. 5'6,1, for example, the separation limit may be 50 * Each molecular sieve is then indeed for the potassium ion itself, permeable, not likewise self-evident for H, OH, and H ₃ O, but for KOH, Zn and SO ₄ . Although the potassium ions themselves could pass through the molecular sieves, they at least do not pass through the molecular sieve of a separation limit that separates the third electrolyte from the first electrolyte

39.1 and less than 56.1, because the potassium atoms in the third electrolyte at all ^ O do not have the tendency to separate the third electrolyte from the first electrolyte Molecular sieve migrate, suggesting their binding to those located in the third electrolyte

5537-24

S0 ₄ ions are likely to be due. In principle, the metal ions in the second electrolyte, e.g. B. potassium ions, normally high affinity for the acid residues in the first electrolyte, for example SO ^. Due to the described design of the dividing wall, according to which it consists of two molecular sieves and the third electrolyte, this affinity does not develop, since the same acid residues are already present in the third electrolyte and those bound to these acid residues

^ g metal ions then no longer have an affinity for the same acid residues in the first electrolyte. In this way, a partition designed in this way acts for metal ions of the second electrolyte, even if these two molecular

2Q sieve per se permeable for these metal ions are like a barrier that prevents their transition into the first electrolyte. It is also conceivable that the acid residues in the first and third electrolytes can be chemically different.

^It is important that the partition, if its molecular sieves are permeable to metal ions or the like of the second electrolyte, which should not get into the first electrolyte, the third electrolyte so lowers the affinity of these metal ions or the like to the acid residue in the first electrolyte or completely eliminates the fact that these metal ions or the like. From the third electrolyte do not migrate into the first electrolyte.

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Draw metal-oxygen elements formed according to the invention

due to very high energy densities, low ge:

weight and long service life and, in the case of training as a secondary element, also by large numbers achievable charge and discharge cycles.

Although it is preferred that the electrochemical element be a metal-oxygen element is, however, it is also possible to design it so that its second electrode is also a metal electrode. This second The metal electrode must be designed in such a way that it forms the positive xathode when discharging. For example this second electrode could consist of nickel and the first electrode of zinc or aluminum. Other metals are also coming for the two metal electrodes. It is important that even with such a two Element having metal electrodes in the second electrolyte during discharge OH ions continuously develop, which can migrate to the first electrode as charge transport carriers.

The first electrode of the element can in many cases with special The advantage of an aluminum electrode is that it has a particularly high electrical voltage of the new type Element allows. Aluminum is also inexpensive and lightweight, and is also trivalent. Aluminum therefore enables the creation of elements with a particularly high energy density,

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struggle with weight and volume. However, other metals can also be used for the first electrode are, preferably zinc or magnesium j or, for example, iron, lithium or the like.

According to a further development of the invention, provision can be made for small amounts of the first electrode Alkaline earth metal are added and / or in the first electrolyte before the first charging of the element still undissolved alkaline earth metal hydroxide, preferably calcium hydroxide, is contained in the first time Charging the element dissolves in the first electrolyte, so that the alkaline earth metal then dissolves first charge is deposited on the first electrode together with the main metal of the electrode. In fact in the latter case one can proceed so that

2Q the massive first electrode only through the first Charge is formed by placing a metallic support, e.g. B. a metal lid of the container of the element and in the chamber containing the first electrolyte metal hydroxide, for. B.

in pasty form, from which the main metal for the first electrode is then split off during charging, which metal then migrates to the metallic carrier mentioned and is deposited here in a massive layer, which becomes thicker with the charging, as the first electrode. By adding small amounts of alkaline earth metal to the main metal of the first electrode, the deposition of the metal ^Ί ions of the main metal on the first electrode can be further improved during charging

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even better uniformity of the addition of the metal tones of the dissociated in the first electrolyte Metalsaizes to the first electrode when charging. The addition of alkaline earth metal can be small, for example five percent by volume of the main metal of the first electrode »The

. _ First electrolyte can be used exclusively or in essentially only contain metal ions that correspond to the metal salt dissolved in it. If in it still contains at least one other metal in dissolved form / can do this in order to achieve special effects

2g may be provided, as preferably the one described above Addition of small amounts of alkaline earth metal. The first electrolyte can be used as a metal salt expediently metal sulfate, γ-Metallhyärogensulfat, Metallnitrat.-and / or Metal chloride contained in dissolved form.

As a metal salt, the first electrolyte can advantageously also be a metal salt of a water-soluble organic Acid, preferably a mono-, di- or tribasic carboxylic acid or hydroxycarboxylic acid in solution. Examples of such acids are acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, Lactic acid, malic acid, tartaric acid and citric acid, acetic acid, oxalic acid and citric acid are particularly preferred.

If several different metal salts are dissolved in the first electrolyte, their metal is expediently the same metal, for example

'Aluminum. Other metal salts may also be used, for example metal bromides, metal iodides or the like. Preferably, the first electrolyte may contain a single metal salt.

At least one electrolyte can be an aqueous solution

be, d. H. contain water as a solvent.

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However, in some cases, other solvents are also used conceivable, preferably alcohols and their derivatives.

The second electrolyte can preferably be an aqueous potassium hydroxide solution. For example, the second Electrolyte be a potassium hydroxide solution, which contains 20-45 percent by weight potassium hydroxide. According to the invention Electrochemical elements can be designed or used in a position-independent or position-dependent manner. If that Element is completely closed to the outside, it can easily be used as a position-independent element be designed, be it as a primary element or as a secondary element.

If elements according to the invention are rechargeable as secondary elements, a certain amount can in many cases Dependency of the position of the regression of its metal electrode or metal electrodes during recharging exist. This is explained using an example. ;

If the first electrolyte is so affected that metal hydroxide is precipitated in it during discharge is, then this is deposited when the element is at rest according to the force of gravity. Stands the element so that this metal hydroxide collects at a point from where the metal ions split off from it do not migrate evenly to the first electrode the first electrode can be thickened near the accumulated metal hydroxide come, which can become thick and thick in the course of several or many charging cycles. It However, this is not a matter of dendrites, so that such thickenings do not normally interfere and only after a large number of charging cycles

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can disturb. If there is a risk of such thickening disturbs, one can easily arrange the operating position of the element in such a way that Metal hydroxide is deposited evenly on the partition opposite the first electrode by the partition roughly flat "is uTTct / extends roughly horizontally and vertical entertainment! "that to her preferably about parallel first electrode is arranged. In the case of elements arranged in a stationary manner during operation, for example with elements that are used to store solar energy, you can easily. this, approximately horizontal extension of the Provide a partition. Conversely, when the element is in a vehicle that is subject to fluctuations while driving is arranged in the frame of a battery, then the powdered deposited metal hydroxide when the vehicle is in operation, due to the shaking and shaking in an essentially even distribution and during charging the first electrode is formed with an approximately evenly growing one Thick back. The element is then in this case despite the metal hydroxide's precipitation during of discharging practically irrespective of the position, provided that the metal hydroxide through the Shaking and shaking when the vehicle is moving is largely kept in suspension. If on the other hand, too When the vehicle is moving, the metal hydroxide largely or completely follows gravity accumulates at a certain point on the element,

then it is also useful to arrange it so that its partition is at rest of the vehicle roughly horizontally judicially. tet is ..

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5537 - 30 -

A particularly advantageous further development of the invention provides that in the first electrolyte an intermediate wall which is permeable to the first electrolyte and which is impermeable to the reaction products which arise during discharging and which are insoluble in the first electrolyte is movable in the direction of the anode up to and including the contact from the back facing away from the anode is supported on a rigid perforated grid. It can be provided that this vertical relative movement between partition and anode is limited by stops so that a predetermined minimum distance between them cannot be undershot, or that partition and anode can come into contact with one another with pressure. Such a possibility of relative movement between the anode and the partition wall τ, which can preferably be achieved by vertical mobility of the partition wall with a fixed arrangement of the anode - the solid reaction products deposited on the anode during discharge, such as metal oxide and the like, which for example can have a powdery consistency, pressed against the anode through the partition and can thus also be compressed, with electrolyte located between them during the compression, including from itself

when discharging forming water, is partially pushed out and flow through the partition wall can. The compacted reaction products can also slip on the anode through the partition wall be prevented. The density of the reaction products can be determined by the size of the load on the partition provide in the desired manner. The distance between the partition wall is created by these reaction products and the anode according to their increasing volume during discharging through the

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5537-31-

existing print enlarged. If "during charging, the reaction products are again formed in the electrolyte decompose of metal ions, the distance between the partition and the anode is then possibly reduced again until the partition is in contact with the anode. It is also advantageous that the movable partition Can press dendrites against the anode. The closer the partition is pressed to the anode, the lower the amount of electrolyte between the partition and the anode. This will increase the tendency of the Anode to form 'metal oxides and metal hydroxides, reinforced, that is, such reaction products do not go into solution, but fail faster. The reaction products are distributed more evenly over the entire surface of the partition and thus ensure a more uniform loading Coating on the anode. Another advantage is that smaller amounts of hydrogen are used when charging develop, the smaller the distance between the anode and the partition wall. This affects especially advantageous in the case in which the element is exposed to shaking movements or in an inclined position because then the reaction products cannot collect in one place and so a possibility of thickening avoiding the anode at one point during charging.

The partition is expediently designed so that although it is for the electrolyte and thus also for the water that forms is permeable, but for the solid reaction products that form at the anode during discharge, such as metal oxide and the like, as well as being impermeable to dendrites.

According to a preferred embodiment, the partition is flexible and preferably also compressible and is particularly preferably in shape

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of a cushion. In this case, for example with their edge firmly to the edge of the anode or to the container wall of the element or be connected to another part immovably arranged relative to the anode. Therefore one sees further preferred embodiment abutment on the Container wall of the element before, on which spring means are arranged, the other hand with the edge dev Communicating partition wall. Such pen means. can for example be made of fiberglass material or not from the electrolyte or the reaction products vulnerable materials exist. It has been found to be particularly useful when the partition wall has sufficient inherent rigidity having. This can be achieved in that the partition consists of a frame to which the Can attack spring means, and in which the material of the partition is clamped.

Foam plastics with sufficient elasticity are primarily used as the material for the partition wall and open pores are taken into account, the The diameter of the pores allows the electrolyte and water to pass through, solid reaction products but does not let through. The material for the partition wall can also be a fiber fleece from opposite the Reaction products and the electrolyte resistant materials, the crossing points of the fibers are preferably set. In particular, alkali-resistant nonwovens made of plastics are used for this purpose or cellulose in question. As a rule, fiber fleeces do not have sufficient inherent rigidity, see above that it is beneficial to place them on a grid, mesh

or screen, for example a SJochgitter aufzu-, _j install which is fixedly connected to a frame "

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If the partition consists of a foam plastic, it can be advantageous in many cases to use the the anode facing surface of the intermediate wall to arrange a diaphragm for the first electrolyte permeable, but for the unloading, reaction products insoluble in the first electrolyte are impermeable ..

It goes without saying that the invention is not limited to an approximately flat design of the first electrode and the partition ^/ [and, if applicable, the second and / or the third electrode \ . There are also other trainings

possible, e.g. concentric arrangement of electrodes • and the partition.

Elements according to the invention can preferably be assembled to form batteries or accumulators, who dare to try their high energy density, their small volume and their low weight, among other things. Also excellent as accumulators for storing solar energy and also for use in motor vehicles suitable.

As mentioned above, alkali lye is preferably suitable for the second electrolyte. In some cases, however \, other solutions for the second electrolyte

■ come into question, especially those with a basic reaction

■ Solutions, for example aqueous ammonia solution? -

In the drawing are exemplary embodiments of the inventor

shown.

The two Figures 1 and 2 aeigen in a schematic representation each a longitudinal section through an electrochemical metal ^ air secondary element 10. The in, Fig. 1 Element 10 shown has a stand on feet 18 'for the purpose of air access to its perforated bottom 18

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Existing, pot-shaped container 16 made of plastic, in the ceiling 44 of which has a ventilation hole 45 and on whose rigid, horizontally directed, flat perforated base 18, which forms a flat perforated plate, the air electrode 11 is arranged. This air electrode 11 has a horizontal, flat layer of activated carbon powder 12 as a catalyst, which, together with a second liquid electrolyte 25 and a flat, horizontally directed perforated metal plate, clears the space between a gas-permeable, but liquid-impermeable diaphragm 14 and a gas- and liquid-permeable flat filter 15, which can be, for example, an alkali-resistant fiber fleece made of plastic fibers and whose pore size is smaller than the grain size of the activated carbon powder 12, fills.

The perforated metal plate 13, the holes of which are filled with the activated carbon powder 12, lies on the Diaphragm 14 open. The activated carbon powder 12, however, extends beyond the perforated plate 13 up to the top to filter 15.

The perforated metal sheet 13 consists of a metal, neither when loading nor. Glue discharging the element 10 reacts, for example made of nickel. This perforated plate 13 is galvanically connected to the positive discharge terminal 19, which is home to discharging of the element 10 whose positive pole 19 forms. 35

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At a distance above the filter 15 extends a second, gas and liquid permeable, flat / metallic perforated plate 20 horizontally and parallel to him / the galvanically to the charging positive pole 21 of the element 10 is connected. A positive charging voltage is applied to this positive charging pole 21 during charging created. At a short distance above this perforated plate 20, which forms a third electrode / is a flat and also horizontally extending partition, designated as a whole by 22 arranged, consisting of two spaced-apart, planar, horizontally parallel to each other extending molecular sieves 23, 23 'and one filling the space between them third liquid electrolyte 24 consists.

The second electrolyte 25 fills the space between the diaphragm 14 and the molecular sieve 23 ^l and can also expediently be liquid.

At a distance above the partition 22 is a plate-shaped, flat, also horizontal extending, massive first electrode 27 made of metal, which is arranged on a plate-shaped, flat carrier 26 is. The carrier 26 consists of plastic, the underside with a vapor-deposited 'layer 2 * 6' a metal which does not participate in the electrochemical reactions and which makes contact with the electrode 27 is vaporized and is galvanically connected to the negative pole 30 of the element 10. The metal electrode 27 forms the negative one Anooard of this element 10. Through the carrier 26 and the first electrode 27 passes a plastic pipe 37 containing the first electrolyte two chambers 36 and 46, as shown, with one another

connects.

5537 -'36 -

The container 16 as well as the carrier 26 take to the electrochemical reactions

not part, so they are constantly inactive. The container and the plastic of the carrier 26 can for example Made of polyethylene, polypropylene, PVC or the like. Consist.

The space between the horizontal upper side formed by the molecular sieve 23 of the Partition 22 and the first electrode 27 is filled with a first liquid electrolyte 31, in which it is an aqueous metal salt solution, the metal of which corresponds to the metal or the main metal i

corresponds to the first electrode 27.

The one between the two molecular sieves 23, 23 ' third electrolyte 24 of partition 22

is also an aqueous metal salt solution, the ^

Acid residue the acid residue in the first electrolyte |

· Can correspond to 31 dissolved metal salt. The second Electrolyte 25 can be an alkali, the alkali metal of which is the same as the metal in the third electrolyte dissolved metal salt can correspond. The alkali is also an aqueous solution. The concentrations the metal compounds dissolved in the three electrolytes 24, 25 are not critical, should, however, be coordinated so that none of the electrolytes has the tendency to one To withdraw neighboring electrolytes / barrels to a disruptive extent, so that each electrolyte has the fills in the space assigned to it.

The volumes of the electrolytes 24, 25 and 31 remain essentially the same during charging and discharging. Under 35

ft "M" "If * · · ·

5537 - 37 -

Circumstances can arise when the element overloads lO will> electrolytically decompose solvent. However, this can be seen in the increase in charging

Detect voltage and, if necessary, ensure that charging is automatically terminated if the increase in charging voltage indicates the risk of overcharging. Other ways to J exist ₀ avoid overloaded.

^ ^{The top} and bottom sides of the ceiling 44 and the

Carrier 2 6 bounded uppermost chamber forms a compensation chamber 46, through which -problem-free "ensured is that all electrolytes always fill the interior of the element 10 to the required extent by

I _I the Ausglexchskammer 46 contains the first electrolyte

und.die molecular sieves 23, 23 'for those made from water

existing solvent are permeable.

20th

The two molecular sieves 23, 23 'of the partition 22

are sealed on the peripheral wall of the container 16 attached, for example, clamped in a manner not shown. The lower diaphragm 14 can

<- · 25 can be glued onto the perforated base 18, for example.

The filter 15 is also on the peripheral wall of the container 16 sealed attached.

There is also a vent line 33, which consists of the one containing the second electrolyte 25 Chamber 34 of element 10 through the container circumferential wall up to the ceiling 44 to the outside leads to the discharge of oxygen produced in the second electrolyte 25 during charging. 35

«38 -

The layer 26 'consists of a metal / that during charging and discharging the element 10 no galvanic voltage to the perforated plates 13,: 20 is developed and therefore remains inactive. For example, it can be made of nickel and the two metallic Perforated plates 13, 20 can then also expediently be made of this metal, for example nickel

exist.
Γ-

In contrast, the metal of the first electrode 27 dissolves during discharge until it is used up. ^The layer 26 'is unable to produce any current delivery, so that the element 10 is then completely discharged. When recharging, the first metal electrode 27 is formed again on the metal layer 26 'of the carrier 26 without dendrites being formed. The first metal electrode 27, which is forming again, is solid in itself and there is therefore no risk of metal breaking off from it.

r- ^25th

The line leading from the chamber 36 of the element containing the first electrolyte into the chamber 46 can also be the derivation of hydrogen, the reduction that takes place during charging in the first electrolyte remains unused, serve from the chamber 36.

It should be mentioned that the molecular sieves 23, 23 'have a -35

'j ί ί ί *

5537 - 39 -

It should also be mentioned here that for better discharge of the oxygen gas bubbles formed during charging in the second electrolyte and possibly the hydrogen gas bubbles formed in the first electrolyte to the lines 33, 37 it can be useful that the element 10 is slightly horizontal during operation is inclined, which can be achieved, for example, by slightly different heights of the feet 18 '. Or one can also provide that the molecular sieve 23 and also the first electrode 27 with support 26 are inclined slightly to the horizontal and the other parts in the electrolyte, such as the molecular sieve 23, the diaphragm 14, etc., are aligned horizontally. If necessary , a slight curvature of the molecular sieve 23 'designed as a diaphragm (the molecular sieve 23 can correspond to the molecular sieve 23' and also be a diaphragm) and the first electrode can be provided, the vent lines 33 then at the highest points of this curvature open into the relevant chambers 36, 34.

The mode of operation of this element is described using the following examined example:

Separation limit may have the oxygen molecule ^ |

(O ₂ ) lets through. Nevertheless, the %

Oxygen forming in the second electrolyte 25 does not pass through the molecular sieve 23, but collects on this to form gas bubbles, which then escape to the outside through the vent line 33 can.

5537. - 40 _

The first electrode 27 was made of zinc when examined. The first electrolyte 31 consisted of an aqueous zinc sulfate solution, pH approx. 4-6. The third electrolyte 24 consisted of aqueous potassium sulfate solution, pH value approx. 5-8. The second electrolyte 25 consisted of potassium hydroxide solution. The molecular sieves 23, 23 'each had a separation limit of 50, so that they were not _{permeable to zinc, nor to SO 4} and KOH. In contrast, these molecular sieves are permeable to H, OH and H ₂ O. The third electrode 20 | and the perforated plate 13 consisted of nickel. ^ ₅ During unloading, poles 19, 30 were connected to one another via line 40 and a load 41 and the following processes then took place during unloading:

At the air cathode 11 beginning at the diaphragm 14 the following reaction occurs as air penetrates through the diaphragm 14:

2 H ₂ O + O ₂ + 4e ~ —f> 4 0H ~ The oxygen comes from the ambient air.

The OH ions formed in this way migrate as charge carriers through the Partition 22 through into the first electrolyte 31 and in it then plays on the first electrode 27 the following reaction:

2 Zn + 4 OH "~» 2 Zn (OH) ₂ + 4e ~

The zinc hydroxide Zn (OH) _{2 which formed} was precipitated and sank onto the flat, horizontally directed molecular sieve 23 'and was deposited here in a uniform layer. Once all of the zinc

j "5537 - 41 -

of the first electrode 27 was consumed, this secondary element 10 was discharged.

After the discharge, the element 10 was charged again using the positive pole of the charging voltage source to the charging pole 21 and the negative pole of the charging voltage source to the pole 30 in not shown Way was connected. The charging voltage was about 1.8.V, whereby it should be mentioned that the When discharging, a voltage of approx. 1.2 to 1.3 V can easily be taken from the element.

When charging, the following reaction takes place in the second electrolyte:

1 H ₂ O- 4e ~ __ * 0 ^ + 4 H ⁺

The third electrode 20 does not change.

The sap substance O _{2 that forms} escapes through the vent line 33. The Η-ions that form in the second electrolyte 25 migrate as charge carriers through the third electrolyte 24 of the partition 22 and its molecular sieves 23, 23 'into the first electrolyte 31 and it plays out the following reaction occurs in it:

30th

Zn (OH) ₂ + 4 H ⁺ -ψ 2 Zn ⁺⁺ + 4

The here from the zinc hydroxide Zn (OH) - free resulting zinc ions were found to be uniform,

massive zinc layer 27 on the metal layer 26'35

* · «■ <# t» 4 | I 11 (1 It

# * * * 4 * ti I i I «· · *! * #! (IfI

* · · 44 · ΙΙ · | III

5537 _ 42_

of the carrier 26 down. The first electrode 27 thus emerged again as a massive, flat, zinc layer of approximately the same thickness. It adheres very firmly to the carrier metal, can

So don't peel off. When the electrode 27 was re-formed, no dendrites were formed, see above that a high number of charge and discharge cycles 2Q can be achieved with this element 10.

It was found that the potassium ions in the third electrolyte 2 did not pass through the molecular sieve 23 during charging or discharging, or during the rest of the time, although its separation limit was 50, i.e. this molecular sieve as well as the molecular sieve 23 per se Potassium ions permeable to / from. It can be assumed that this surprising effect is based on the fact that the potassium ions in the third electrolyte 24 have no affinity for the acids present in the first electrolyte 31. had more, because in the third electrolyte they were attached to the acid residues SO. were sufficiently firmly tied and this connection K “SO. has a molecular weight of approx. 174 above the separation limit of the molecular sieve 23. The second and third electrolytes 25 and 24 are therefore not irreversibly diluted. It was also found that the self-discharge of the secondary element 10 is extremely low, so that _f when no current is drawn, its charge over very long time reserves.

The mentioned separation limit of the molecular sieves 23, 23 'was smaller than the atomic weight of zinc and that

5537 - 43 -

Molecular weight of SO And from KO'H so that they, nor the Säürerest SO _4, more Kaliümhydroxid transmit _p neither zinc.

That in Pig. The element shown in FIG. 2 shows a further preferred embodiment of the invention, the same reference symbols in FIGS. 1 and 2 have the same meaning, so that on the relevant remarks regarding their Meaning and mode of action on Pig. 1 can be referenced.

The essential difference between the embodiments of FIGS. 1 and 2 is that in the embodiment according to FIG. 2, the second molecular sieve 23 'and thus also the third electrolyte 24 are omitted. Further is in the first. Electrolyte 31, an intermediate wall arranged 5G, the permeable to the first electrolyte 31, but for the resulting during discharge, in the first electric soldering that 31 u nlöslich en Rea tio n sprodukte 52 is impermeable. The partition 50 is elastic and can be moved in the direction of the anode 27 and is supported with the rear side facing away from the anode on a rigid perforated grid 54. On the other side of the intermediate wall 50 lies a diaphragm 51 which is permeable to the first electrolyte but impermeable to the reaction products 52, so that the reaction products cannot penetrate into the intermediate wall 50. This intermediate wall 50 is somewhat compressed and presses the diaphragm 51 against the reaction products 52 and thus against the anode 27 in a resilient manner. In the freshly charged state of the element 10, the elastic intermediate wall 50 - optionally with the diaphragm 51 arranged thereon - can practically completely lie against the anode 27.

_ 44 5537

The partition 50 preferably consists of an open-pored elastic foam plastic. Instead of such an elastic foam plastic, an elastic, compressible fiber fleece or the like can optionally be used. It is also possible to make the partition 50 rigid so that it has a certain inherent rigidity, and to load them by means of locally narrowly limited spring means in the direction of the anode 27. In this case, the perforated grid 54 can be omitted and replaced by abutments for the spring means.

In the embodiment according to FIG. 2, it has proven to be useful shown that the chamber 36 of the chamber 46 »which also contains the first electrolyte 31 and with the Chamber "56 is connected via a plastic line 37, through a membrane inserted into the plastic line 37 53 is separated, so that the first electrolyte 31 can flow unhindered from the chamber 36 into the chamber 46 can and vice versa, but no reaction products 52 can get from the chamber 36 into the chamber 46. Through this the unimpeded flow of the first electrolyte 31 is ensured, in particular in the case of an inclined or vertical position of element 10.

The operation of the element 10 according to the embodiment according to FIG. 2 is essentially the same as the operation shown in FIG. When the Element 10, the diaphragm 51 is pressed by means of the intermediate wall 50 practically until it rests against the anode 27. The further a discharge of the element 10 then proceeds, the more the anode 27 is eroded, but there are the reaction products 52 formed are more voluminous and thereby cause an ever-increasing distance between the Anode 27 and the surface of the diaphragm 51. By the constant pressure of the intermediate wall 50 over the diaphragm 51 on the reaction products 52, the latter are prevented from migrating. So you essentially stay on

5537 ^w 45 -

Location of their origin and can therefore be used in particular when the element 10 is in an inclined or vertical position no accumulations in the area of the plastic pipe 37 ■ educate.

After the element 10 has been completely or practically completely discharged, that is to say when practically all of it The anode metal is converted into metal ions Element 10 is reloaded in a conventional manner. Ever furthermore the metal ions are converted into the uncharged metallic state and are never on the anode 27 the more strongly the diaphragm E51 rests against the anode 27. During this process, the metal ions attach only a short way back, which largely suppresses the evolution of hydrogen.

Claims (1)

β I Ik * t - 1 - • ft * «· Ι ι ■ a ι« a n «ι ι in the tfc · * «··· β ι IkI · t sprue hey 1. Electrochemical element, which is a metallic first electrode, which forms its negative anode, and one that reacts chemically with it during discharge, first electro- has lytes and furthermore has a second electrode, which · forms the positive cathode to which a second electrolyte is assigned, that of the first electrolyte is separated by a porous partition, thereby characterized in that negative in the second electrolyte (25) when discharging the element (10) OH ions are formed as charge carriers for which the Partition wall (22) is permeable, and that the partition wall (22) as one of the passage of the metal and the acid residues the metal salt dissolved in the first electrolyte (31) from entering the second electrolyte (25) w irks. - 2 - 2. Element according to claim 1, characterized in that it is a rechargeable secondary element (10) and the partition wall (22) for positively charged electrolytes which form in the second electrolyte (25) during charging Hydrogen ions are permeable, so that they migrate into the first electrolyte (31) can. ./ "3. Element according to claim 1, characterized in that f it is a non-rechargeable primary element. 15th ■ 4. Element according to one of the preceding claims, characterized in that the dividing wall (22.) has a single molecular sieve (23), the separation limit of which is made so that it is for the OH and for Η ions and preferably also .for the solvent der.Elektrolyten, is permeable, but not for the other molecules contained in the second electrolyte (25)., and / c the ions. 25th 5i element according to one of claims 1 to 3, characterized in that the partition (22) has two molecular sieves (23, 23 '), between which there is a third electrolyte (24), such that the "transfer of cations from the second electric yten ¹ (25) into the first electrolyte (31) is prevented, with the exception of Wasserstoffkatxonen. 35 5537 6. Element according to claim 5, characterized in that the third electrolyte (24) dissolved metal salt contains, preferably alkali metal salt. 7. Element according to claim 6, characterized in that the acid residue in the third electrolyte (24) dissolved metal salt enfepricht the acid residue of the metal salt dissolved in the first electrolyte (31). 8. Element according to claim 6, characterized in that the acid residue in the third electrolyte (24) T5 dissolved metal salt is more acidic than the acid residue of the metal salt dissolved in the first electrolyte (31), 9. Element according to claim 6, 7 or 8, characterized in that the metal of the third electrolyte (24) dissolved metal salt is the metal of a metal compound dissolved in the second electrolyte (25) is equivalent to. 10. Element according to claim 6, 7j S or 9, characterized in that that the acid residue of the metal salt of the third electrolyte (24) is one atomic weight above that Separation limit of the molecular sieve separating the third electrolyte (24) from the third second electrolyte (25) (23). - 4 - 11 element according to one of the preceding claims, characterized in that the second electrode (11) is an oxygen cathode, preferably is an air cathode, which forms the positive PoI ^ (19) of the element (10) when discharging. 10 12. Element according to claim 1.1, characterized in that that the second electrode (11) has activated carbon powder (12) as a catalyst. 1i3. Element according to claim 12, characterized in that that the activated carbon (12) is contacted by a metal grid or the like (13) « .Ϊ4. Element according to claim 12 or 15, characterized in that that it has a third electrode (20) which are used to connect a positive pole of the element to be charged Charging current source is used and that the third electrode is outside of the activated carbon powder (12), however is still within the second electrolyte (25). T5 element according to claim 14 / characterized, that the activated carbon layer (12) by an impermeable to its activated carbon powder, however, for the second electrolyte (25) permeable filter (15) from the one above it Area of the second electrolyte in which the third electrode (20) is located, is separated. 35 -δ- 16. Element according to one of the preceding claims, characterized in that the second electrolyte (25) has a vent line (33) is assigned for oxygen formed during charging. 17. Element according to any one of claims 1 to 10, characterized in that the second electrode is also a metal electrode used in Discharge forms the positive pole. 1.8. Element according to one of the preceding claims, characterized in that the second Electrolyte has a pH greater than 7. 1! 9. Element according to one of the preceding claims, characterized in that the first electrolyte a vent line (45) is assigned for the hydrogen that is used in the Charging in the first electrolyte occurring chemical reduction remains unused. 20, element according to one of the preceding claims, characterized in that the first electrode (27) is an aluminum electrode. * «11-4 4 * & • · * · * 6« Λ * Il · λ m * · I «· ti ·» ti. «« · I I i ί i. . . , 4 III ·· ■■ · · a. «. 21, element according to one of claims 1 to 19, characterized in that the first electrode (27) is a zinc electrode. 22 «element according to one of claims 1 to 19, characterized in that the first electrode (27) is a magnesium electrode. 23. Element according to one of the preceding claims, characterized in that small amounts of alkaline earth metal are added to the first electrode (27) are and / or in the first electrolyte (31) before the first charging of the element a low Amount of alkaline earth metal hydroxide, preferably calcium hydroxide, is contained in the first time Charges dissolve in the first electrolyte and its alkaline earth metal then adheres to the first electrode (27) precipitates together with their main metal. 24 ·. Element according to one of the preceding claims, characterized in that the first electrolyte (31) Contains exclusively or essentially only metal ions which are the same as the metal in it dissolved metal salt correspond. 25. Element according to one of the preceding claims, characterized in that the first electrolyte (31) contains a metal sulfate in dissolved form as the metal salt. 26, element according to any one of claims 1 to 24, characterized. characterized in that the first electrolyte (31) contains a metal hydrogen sulfate in dissolved form as the metal salt. - 7 - 27. Element according to one of claims 1 "to 24, characterized in that that the first electrolyte (31) contains a metal nitrate dissolved as a metal salt. 28. Element according to one of claims 1 to 24, characterized in that that the first electrolyte (31) contains a metal chloride dissolved as a metal salt. 29. Element according to one of claims 1 to 24, characterized in that that the first electrolyte (31) as a metal salt is a metal salt of a water-soluble organic Contains dissolved acid. 30. Element according to claim 29, characterized in that the first electrolyte (31) is a metal salt as the metal salt a water-soluble mono-, di- or tribasic carboxylic acid or hydroxycarboxylic acid in dissolved form » 31. Element according to claim 30, characterized in that the first electrolyte (31) is a metal salt as the metal salt contains dissolved acetic acid. 32. Element according to claim 30, characterized in that the first electrolyte (31) is a metal salt as the metal salt which contains dissolved citric acid. 33. Element according to any one of the preceding claims, characterized in that at least one Electrolyte is an aqueous solution. 34. Element according to claim 33, characterized in that that the second electrolyte (25) is aqueous alkali lye / which is preferably 20 to 45 percent by weight Contains alkali hydroxide. 35. Element according to one of the preceding claims, characterized in that its electrodes (11, 27) and the partition wall (22) are approximately flat and spaced one above the other and their operating positions are preferably approximately horizontal. 36. Element according to claim 35, characterized in that that the partition (22) is located vertically below the first electrode (27). 37 · Element according to one of the preceding claims, characterized in that the solvents of the electrolytes (24; 25,31) are the same chemical compound and the partition (22) is permeable to this solvent. 38, element according to claim 34, characterized in that that the second electrolyte is potassium hydroxide and / or sodium hydroxide solution. 39, element according to one of the preceding claims, characterized in that the first electrolyte has a pH value of less than 7. '40. Element according to one of Claims 1 to 38, characterized in that the first electrolyte has a pH equal to 7 or et vas greater than 7. 41 · .Element according to at least one of claims 1 to 40, characterized characterized in that in the first electrolyte (31) one for the first electrolyte (31) permeable, but for the electrolyte created during discharge in the first (31) Insoluble reaction products (52) impermeable t 1 β I t »II Il L " ₉ " l "" 5537 Partition (50) in sight of the anode (27) up to is movable to rest against it and with the rear side facing away from the anode (27) it attaches to a rigid one I support grid (54). 42. Element according to claim 41, characterized in that the intermediate wall (50) is formed by an elastic, open-pore cushion made of foam plastic, fiber fleece or the like, which is attached to a rigid perforated grid or abutment (31) permeable for a.en harvesting electrolyte (31) 54) is supported. 43. Element according to claim 41 or 42, characterized in that the intermediate wall (50) has an inherent rigidity which is tearing out and by spring means or the like supporting at least one abutment (54) siGh is loaded on the anode (27). 44. Element according to at least one of claims 41 to 43> characterized in that on the anode (27) to- | ^: swept surface of the partition (50) a slide phragm (51) is arranged, which is permeable for the first electrolyte (31), but for the discharge resulting, in the first electrolyte (31) insoluble reaction products (52) is impermeable.