Component of an electrochemical cell, bipolar plate, electrochemical cell and electrochemical system with such a component

Abstract

The present invention relates to a component of an electrochemical cell, in particular a separator plate or a cell frame of an electrochemical cell. Furthermore, the present invention also relates to a bipolar plate, an electrochemical cell, and an electrochemical system such as a fuel cell, an electrolyzer, or a redox flow battery.

Description

[0001] The present invention relates to a component of an electrochemical cell, in particular a separator plate or a cell frame of an electrochemical cell. Furthermore, the present invention also relates to a bipolar plate, an electrochemical cell, and an electrochemical system such as a fuel cell, an electrolyzer, or a redox flow battery.

[0002] In electrochemical cells, particularly for separator plates or cell frames, sealing structures are used, for example, to delimit and seal through-openings through the respective separator plate or the cell frame to the outside or to delimit and seal flow areas of media from one another. Sealing structures are also used to seal the entire layer from the outside. In electrochemical cells, high pressures occur between adjacent layers when these are pressed together to form a cell stack. Since the pressing essentially involves static pressures and due to the high space requirements for the supply and discharge of reaction starting materials and end products as well as for areas with flow channels for media such as the electrochemical reaction, i.e. the so-called flow area or flow field, sealing structures are conventionally used in electrochemical cells such asFuel cells typically do not use compression limiters for their respective sealing structures. However, this has been accepted for various reasons until now. The disadvantage of this approach is that, for example, the channels embossed into the separator plate relax over time. The distance to the adjacent plate decreases in the area of ​​the channels, and the cross-section of the channel structures embossed into the respective layer is reduced. This also reduces the flow cross-sections of these channel structures, so that the same amount of media requires higher pressure or smaller amounts of media are passed through. Depending on the medium, this significantly impairs the performance of the respective electrochemical cell or its cooling.

[0003] This is also due to the fact that such metallic separator layers are usually manufactured from coil material, such as titanium, by forming them, in that they are punched out and then formed into the respective component in a further punching and / or embossing process.

[0004] The problem of relaxation of the formed layer material in the area of ​​embossed channels is particularly evident in components for electrolyzers, fuel cells, and the like, since the separator layers are usually made of relatively soft materials. Due to the high screw forces required to seal the high pressures, particularly in electrolyzers, and the use of relatively soft materials in the area of ​​electrochemical cells, the relaxation of the embossed sealing structures plays a greater role than in other areas with lower pressures. This relaxation is particularly important for exclusively embossed deformation limiters, so that they cannot guarantee effective limitation of the compression of adjacent sealing structures in the long term.

[0005] The present invention therefore has for its object to provide a component of an electrochemical cell, in particular separator plates or cell frames of electrochemical cells, in particular for fuel cells, electrolyzers or redox batteries and bipolar plates used therein, in which the long-term stability of the dimensioning of the embossed flow channels and the long-term stability of the sealing elements are improved.

[0006] This object is achieved by the component according to claim 1, the bipolar plate according to claim 13, the electrochemical cell according to claim 15, and the electrochemical system according to claim 16. Advantageous developments of the component, the bipolar plate, the electrochemical cell, and the electrochemical system are given in the respective dependent claims.

[0007] Such components, in particular separator plates or cell frames in electrochemical cells, have at least one metallic layer, in particular made of titanium.

[0008] According to the invention, at least one free edge of the metallic layer, for example a peripheral edge of a through-opening or an outer edge of the metallic layer, is folded over onto itself at least in sections, once or multiple times, forming one or more folded layers. This increases the thickness of the component by a multiple of the layer thickness of the metallic layer. Such folds can be used in particular as deformation limiters for adjacent channels, e.g. in flow areas or distribution areas of separator plates. They are also suitable as deformation limiters for adjacent sealing structures, for example embossed structures such as sealing beads or sealing beads in the form of elastomer injection moldings. These sealing structures can be arranged in the same layer that is folded over or on further metallic layers or non-metallic layers adjacent to the metallic layer.For the function as a deformation limiter, it is only essential that the folded layer is located adjacent to the channels or sealing structure to be protected when viewed from above on the respective first metallic layer.

[0009] The inventive design of the component of an electrochemical cell makes it possible to increase the thickness of the first metallic layer in certain regions to a multiple of the layer thickness, thus providing a deformation limiter at different locations, particularly in the area of ​​free edges of the first metallic layer. In fact, the essential structures to be protected, namely flow channels or sealing structures, are also typically located in this area, namely around port openings / through-holes and at the outer edge of the respective first metallic layer, so that their deformation can be limited.

[0010] The present invention takes advantage of the fact that components for electrochemical systems with a metallic layer are usually manufactured by a punching / embossing process. The resulting portion of material that is no longer required is not completely removed during the punching process, but is used according to the invention. For this purpose, for example, the material is not completely removed along the peripheral edge, for example a media passage opening, but rather portions of material are left standing during punching, which are then folded over onto the layer itself and thus increase the layer thickness by several times the individual layer thickness, forming a folded edge as part of the peripheral edge of the media passage opening. The folding can be carried out once or multiple times, so that the total layer thickness can be increased not only by one time the layer thickness, but also by several times.

[0011] It is also possible to achieve such a thickening by at least twice the layer thickness by folding two different areas of the same free edge or different free edges onto one another. The folds, which are arranged at least partially one above the other when viewed from the plane of the metallic layer, can be arranged on the same side of the metallic layer or on two different sides of the metallic layers.

[0012] An advantage of the inventive design of the metallic layer is that no additional material is required for the deformation limiter, and the non-compressible material stacking creates a very stable compression limit. In particular, the compression limiter is far more stable than when using a separate elastomer stopper or other embossed structures as compression limiters. Furthermore, a fold is easy to produce, as only standard tooling is required. Material usage is also more sustainable, as portions of material from the same metallic layer that would otherwise not be required are used to manufacture the deformation limiter.

[0013] Advantageously, multiple folds can also be produced stacked on top of each other. It is also possible to produce multiple folds adjacent to each other. The different folds can be on the same side of the metal layer or on different sides of the same metal layer.

[0014] Particularly in the case of multiple folds, it is possible for the fold edges for fold layers that are at least partially superimposed when viewed from the plane of the layer to run parallel to one another, and therefore the fold layers extend in opposite directions starting from the fold edge. It is also possible for the fold edges for the first fold layer and the second fold layer or further fold layers to run at an angle α with α ≠ 0°, in particular perpendicular to one another, and therefore the extension directions of the fold layers starting from the respective fold edge do not run parallel to one another, in particular at an angle, in particular perpendicular to one another.

[0015] According to the invention, the deformation limitation by the respective folded layer can be further improved by incorporating embossed structures into the folded layer, at least in some regions, and / or by coating the folded layer. As embossed structures, wave-shaped or trapezoidal cross-sections arranged in multiple successive rows have proven particularly advantageous for reinforcing the deformation limitation or for further modifying the folded layer, for example, its elasticity or thickness.

[0016] By processing the area that is intended to form or forms a fold layer, the fold layer can be reduced or thickened. For example, in an area where two fold layers lie directly on top of each other, one fold layer can have a thinned area so that the other fold layer lies on top of this thinned area.

[0017] A suitable free edge at which such a fold can be produced is, in particular, the peripheral edge of through-openings in the first metallic layer, in particular through-openings for the supply or discharge of media. The fold according to the invention can also be produced on the outer edge of the first metallic layer. The fold can advantageously be formed adjacent to the respective structure to be supported, e.g., a channel-containing flow area or a sealing structure.

[0018] The first metallic layer can also be coated, whereby the coating can be applied to one or both sides and / or to each of the coated sides in certain areas or even over the entire surface. Elastomers, metals, metal oxides, nitrides, carbides, and graphite are particularly suitable as coating materials, depending on the function of the respective coating on the metallic layer.

[0019] The present invention further relates to a bipolar plate for electrochemical cells, which has at least one separator plate (single-layer bipolar plate) or several separator plates (multi-layer, in particular two-layer separator plates), wherein one or more of the separator plates of the bipolar plate are configured as a component according to the invention. It is also possible to configure a cell frame for a stack of electrochemical cells as a component according to the invention.

[0020] In the case of two-layer separator plates, it is also possible within the scope of the present invention to fold both layers of the two-layer separator plate together or jointly, so that the folded layers of each of the two layers of the two-layer separator plate form a folded layer, wherein the two folded layers come to lie, in particular directly, on top of one another. In this case, the two-layer separator plate therefore forms a common, likewise two-layer folded layer. However, it is also possible to fold the two layers of a two-layer separator plate separately. The separate folding can take place one after the other or simultaneously in such a way that the two folded layers come to lie, in particular directly, on top of one another, or the two folded layers are separated from one another by an unfolded section of one of the two layers of the two-layer separator plates.

[0021] The invention further relates to an electrochemical cell having a component according to the invention, in particular an electrochemical cell with a bipolar plate according to the invention as described above or a cell frame according to the invention and a membrane electrode assembly.

[0022] According to the invention, stacks of such electrochemical cells and bipolar plates are also encompassed by the present invention, in particular also electrochemical systems such as fuel cells, electrolyzers, redox flow batteries and the like.

[0023] Some examples of components according to the invention are given below, wherein the same or similar reference numerals designate the same or similar elements, so that the description may not be repeated.

[0024] Furthermore, the following examples contain a plurality of advantageous features that further develop the invention and / or are optional, each of which can also individually further develop the present invention according to claim 1. In particular, such further developing and / or optional features can also be used together in any combination, both as combinations from the same example and as combinations of features from different examples, in order to further develop the present invention.

[0025] It shows Fig. 1 a separator plate of a bipolar plate in plan view; Fig. 2 a section along the line AA of the Fig. 1; Fig. 3 a plan view of a section of a variant in the area of ​​line AA; Fig. 4 shows another example of a deformation limiter according to the invention; Fig. 5 shows another example of a deformation limiter according to the invention; Fig. 6 another example of a deformation limiter according to the invention.

[0026] Fig. Figure 1 shows a bipolar plate 1, in particular a separator plate of the bipolar plate 1, formed as the first metallic layer 2, in a top view. Two adjacent bipolar plates of this type, together with a membrane electrode assembly (MEA) arranged between them, form an electrochemical cell. A fuel cell or an electrolyzer, for example, is formed from a plurality of such bipolar plates or electrochemical cells.

[0027] The separator plate 2 has 8 different regions within its outer edge, each providing different functions. First, an electrochemically active region, a so-called flow region 4, is located approximately centrally within the separator plate 2. Reactants are conducted in this region and the electrochemical reaction is carried out.

[0028] Adjacent to this flow area 4 are through-openings 3a, 3b, 3c, 3d, 3e and 3f. The through-openings 3a and 3b serve, in the case of use of the separator plate in an electrolyzer, to discharge hydrogen from the flow area 4. The corresponding distribution structure or collection structure with flow channels between these openings 3a and 3b and the flow area 4 are located on the back of the separator plate 2, which is not shown in the view, and are not shown.

[0029] The openings 3c and 3d serve, when the separator plate is used in an electrolyzer, to supply water to the flow region 4. For this purpose, distribution structures 5c and 5d are arranged between these openings 3c and 3d, respectively, and the flow region 4. These distribution structures contain flow channels that lead from the through-openings 3c and 3d, respectively, to the flow region 4. Furthermore, through-openings 3e and 3f are arranged, which, when the separator plate is used in an electrolyzer, serve to remove oxygen and water. These through-openings 3e and 3f are also connected to the flow region 4 via distribution structures 5e and 5f, but now on the side of the flow region 4 opposite the flow regions 5c and 5d. The distribution structures 5e and 5f also have channels that lead from the flow region to the through-openings 3e and 3f.

[0030] The flow area 4, distribution structures 5c, 5d, 5e, 5f, and through-holes 3c, 3d, 3e, and 3f are enclosed by a sealing structure 6c, which in this example is designed as an embossed sealing bead. However, it is also possible to use an elastomer sealing bead as the sealing structure 6c.

[0031] The through-openings 3a and 3b are also each surrounded by a sealing structure 6a (for the through-opening 3a) or 6b (for the through-opening 3b) which is closed in itself and runs all the way around the respective through-opening, which in the present example is designed as an embossed sealing bead.

[0032] When the bipolar plate 1 is pressed together in an electrolyzer comprising a plurality of bipolar plates, the three regions shown are each surrounded by a sealing bead 6a, 6b, and 6c and sealed off from the outside. The sealing structures 6a, 6b, and 6c are compressed. The channel structures of regions 5c, 5d, 5e, 5f, and 4 are also compressed to a certain extent. Over time, it is possible that the channel structures in regions 5 and 4 will be further compressed as the sealing structures relax. This reduces the cross-sections of the channels in regions 5c, 5d, 5e, 5f, and 4, thus increasing the resistance for the media flowing through them, reducing the media throughput, and / or increasing the energy required to flow media through the channels at a specific flow rate.

[0033] On the other hand, when a separator plate is densely packed with functional elements, as in Fig. 1, there is hardly any space for deformation limiters, which not only serve as deformation limiters for the sealing structures 6a, 6b and 6c, but also limit the deformation of the channels in the areas 4, 5c, 5d, 5e, 5f.

[0034] The present invention proposes folding a material region from the edges of the peripheral edges 7a to 7f of the through-openings 3a to 3f onto the first metallic layer of the separator plate, forming folded edges (outer edges of the respective fold at free-standing ends of the fold) 13a and 13b, 13d and 13e and folded edges (edges at which the layer material is deflected towards the fold) 14a to 14f. Here, two folded layers 10a.1 and 10a.2 are formed from the peripheral edge 7a, as shown by the example of the peripheral edge 7a of the through-opening 3a, which come to lie on the layer 2 itself and thus increase the thickness of the separator layer 2 in this area. As will be seen below from Fig. As can be seen from Figure 2, there is even a double fold in these fold areas, so that the thickness of the separator layer is actually tripled.

[0035] Similarly, two corresponding folds 10b.1 and 10b.2 are formed from the peripheral edge 7b of the through-opening 3b. A double fold is also formed between the through-opening areas 3c and 3d, in that a first fold 10c is formed from the peripheral edge 7c of the through-opening 3c and a second fold 10d is formed from the peripheral edge 7d of the through-opening 3d, wherein the fold 10d lies at least partially on the fold 10c.

[0036] Accordingly, between the through-openings 3e and 3f, two folds 10e and 10f are formed from the peripheral edges 7e and 7f of the through-openings 3e and 3f, which are arranged at least partially on top of one another.

[0037] Fig. 2 shows a cross section through the metallic layer 2 of the Fig. 1 along the line A - A. Adjacent to the through-opening 3a is the sealing bead 6a, which extends with its bead roof in Fig. 1 in the direction of the viewer. At the peripheral edge 7a of the through opening 3a, the metallic layer of the separator plate 2 is folded over twice onto itself to form two folded layers 11a.1 and 12a.1 with folded edges 14a.1 and 15a.1. The edge of the metallic layer 2 and the fold 12a.1 forms a folded edge 13a.1. The folded edge 14a.1 in the area of ​​the fold 11a.1 forms the peripheral edge 7a of the through opening 3a. Since the fold 11a.1 and the fold 12a.1 triple the thickness of the separator plate, these two folds form a very stable, non-compressible deformation limiter for the sealing bead 6a and adjacent flow channels.

[0038] The deformation limiters 10a.2, 10b.1 and 10b.2 in Fig. 1 are designed in the same way, so their description is not repeated here.

[0039] The deformation limiters between the through openings 3c and 3d, or 3e and 3f, are designed differently. These deformation limiters consist of two folds 10c and 10d, or 10e and 10f. Since the deformation limiter with folds 10c and 10d between the openings 3c and 3d is designed in the same way as the deformation limiter with folds 10e and 10f between the openings 3e and 3f, only the deformation limiter between the openings 3c and 3d will be described in more detail below.

[0040] This deformation limiter is formed by two folds 10c and 10d. Fold 10c is folded from the peripheral edge 7c of the opening 3c onto the metallic layer of the separator plate 2. Fold 10d is then folded from the peripheral edge 7d of the through-opening 3d onto fold 10c. Thus, the two folds 10c and 10d lie one above the other on the metallic layer 2, thereby tripling the thickness of the metallic layer 2 in this area. The two folds 10c and 10d are folded onto the same side of the metallic layer 2, but could also be folded onto different sides of the metallic layer 2.

[0041] Fig. 3 shows a simplified variant of the separator plate 2 in an oblique view in the cutout around a through opening 3. To form a deformation limiter for adjacent channels or sealing structures (in Fig. 3 not shown), the metallic layer 2 is folded over itself along the folded edge 14 to form a folded layer 11. This leads to a doubling of the thickness of the separator plate 2 in the area of ​​the fold 11 and thus to a deformation limitation for adjacent structures.

[0042] Fig. 4 shows a further variant of a deformation limiter according to the invention in a separator plate 2. As previously in Fig. 3 shows a first folded layer 11 made of the material cut out by the through-opening 3, folded along the peripheral edge 7 of the through-opening 3 and along a folded edge 14 onto the first metallic layer 2. The fold has an elongated shape that follows the elongated shape of the through-opening 3. In contrast to Fig. 3, the longitudinal ends of the folded layer 11 are now folded over along fold edges 15.1 and 15.2 onto the folded layer 11, forming further folds / folded layers 12.1 and 12.2. These further folds 12.1 and 12.2 have a folded edge 13.1 and 13.2, respectively, as the layer end, and folded edges 15.1 and 15.2, which run perpendicular to the folded edge 13 of the first folded layer 11. Thus, the direction of extension of the folds 12.1 and 12.2, from the folded edge 15.1 to the folded edge 13.1, or from the folded edge 15.2 to the folded edge 13.2, also runs perpendicular to the course of the folded layer 11 from the folded edge 14 to the folded edge 13.

[0043] Fig. Figure 5 shows another example of a metallic layer 2 of a separator plate in an oblique view in a cutout. A double fold with a first fold 11 and a second fold 12 is now formed from the material of the through-opening 3. The first fold 11 has a folded edge 14, which in its area forms a portion of the peripheral edge 7 of the through-opening 3. The second fold 12 has a folded edge 15 and is folded over onto the first fold 11. Thus, in this area of ​​the two folds 11 and 12, the layer thickness of the separator layer 2 is essentially tripled compared to the layer thickness of the first metallic layer. However, the second fold 12 further comprises an embossed wave structure 16 which comprises parallel beads extending parallel to the fold edge 15 and the fold edge 13 and from one side of the fold 12 to the opposite side of the fold 12.By means of this additional wave structure 16, the increase in thickness of the separator plate 2 caused by the folds 11 and 12 is further modified, so that increases in thickness of the separator plate 2 that deviate from the multiple of the layer thickness are also possible.

[0044] The wave structure 16 can also have trapezoidal cross sections as further embodiments of the wave structure 16.

[0045] Fig. 6 shows in oblique view a design of a deformation limiter as in Fig. 4, whereby the folded layer 11 is not yet completely folded over onto the metallic layer 2 for better illustration. In contrast to Fig.4, the second fold 12.2 projects beyond the first fold 12.1. In the area where the first fold 11, the second fold 12.1, and the third fold 12.2 overlap, the thickness of the second fold 12.2 is reduced. This is achieved by providing a step 17 on the side of the second fold 12.2 facing the fold 11, at which step the thickness of the folded layer 12.2 decreases, starting from the folded edge 15.2 to the folded edge 13.2 of the second fold 12.2. This also makes it possible to create non-integer multiples of the original layer thickness of the metallic layer of the separator plate 2 in the area of ​​the deformation limiter.

Claims

[1] Component of an electrochemical cell, in particular separator plate or cell frame of the electrochemical cell, with at least one first metallic layer characterized by that the metallic layer adjacent to at least one free edge of the metallic layer is folded over onto itself at least in sections once or several times to form one or more folded layers and thus increases the thickness of the component, advantageously by one or more than one layer thickness of the metallic layer. [2] Component of an electrochemical cell according to the preceding claim, characterized by that the metallic layer is folded over itself several times, in that the metallic layer is folded over itself a first time to form a first folded layer and the first folded layer is folded over itself to form a second folded layer. [3] Component of an electrochemical cell according to one of the preceding claims, characterized bythat the metallic layer is folded over on itself several times in that a first region of the metallic layer is folded over on itself to form a first folded layer on the first surface of the metallic layer and a second region of the metallic layer is folded over on itself to form a second folded layer on the first surface or the second surface of the metallic layer facing away from the first surface, wherein the first folded layer and the second folded layer are arranged one above the other at least in regions when viewed from above onto the first surface of the metallic layer. [4] Component according to one of the preceding claims, characterized by that the metallic layer is folded several times to form at least two folded layers, wherein the direction of extension of the folded edge of at least two folded layers runs parallel or not parallel to one another, in particular perpendicular to one another. [5] Component according to one of the preceding claims, characterized by that the metallic layer is folded several times to form at least two folded layers, wherein the two folded layers are arranged on the same surface of the metallic layer or on opposite surfaces of the metallic layer. [6] Component according to one of the preceding claims, characterized by that at least one of the folded layers has embossed structures at least in some areas. [7] Component according to the preceding claim, characterized by that at least one of the folded layers, which has embossed structures, has a wave-shaped or trapezoidal cross-section at least in sections in the area of ​​the embossed structures [8] Component according to one of the preceding claims, characterized bythat at least one of the folded layers has a smaller layer thickness, at least in the region in which it is immediately adjacent to another folded layer and arranged above or below another folded layer, than outside this region. [9] Component according to one of the preceding claims, characterized by that the first metallic layer or a further layer adjacent to the first metallic layer has an elastic element, in particular an elastomer or an embossed structure, in particular a sealing bead, which is arranged adjacent to the folded section in a plan view of the first metallic layer. [10] Component according to one of the preceding claims, characterized by that the free edge is a peripheral edge of a through-opening in the first metallic layer, in particular a through-opening for the supply or discharge of a medium or an outer edge of the first metallic layer. [11] Component according to one of the preceding claims, characterized by that the metallic layer is provided with a coating on one, several or all of the surfaces of the metallic layer in the region of the component thickened by folding over the first metallic layer. [12] Component according to the preceding claim, characterized by that the coating comprises or consists of one, several or all of the materials from a group containing an elastomer, metals, metal oxides, nitrides, carbides and graphite. [13] Bipolar plate for electrochemical cells with a component according to one of the preceding claims. [14] Bipolar plate according to the preceding claim, characterized byin that it has a second metallic layer which is adjacent to and in contact with the first metallic layer, wherein the second layer, when viewed from the plane of the first metallic layer, has an elastic element, in particular an elastomer or an embossed structure, in particular a sealing bead, adjacent to the folded section in the first metallic layer. [15] Electrochemical cell, characterized by that it comprises at least one bipolar plate according to one of the preceding claims and a flat membrane electrode assembly (MEA). [16] Electrochemical system, in particular fuel cell, electrolyzer or redox flow battery, characterized by a stack of electrochemical cells according to the preceding claim, arranged adjacent to one another and sealed to one another parallel to the layer plane of the first metallic layer.

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