Sealing arrangement, bipolar plate and arrangement for an electrochemical system and electrochemical system

Abstract

The present invention relates to a sealing arrangement, a bipolar plate, and an arrangement for an electrochemical system, as well as to an electrochemical system. The electrochemical system can be, for example, a fuel cell stack, an electrolyzer, or a redox flow battery.

Description

[0001] The present invention relates to a sealing arrangement, a bipolar plate, and an arrangement for an electrochemical system, as well as to an electrochemical system. The electrochemical system can be, for example, a fuel cell stack, an electrolyzer, or a redox flow battery.

[0002] In general, electrochemical systems such as electrolyzers or fuel cell stacks typically comprise a stack of single electrochemical cells, each comprising a plurality of layers, including at least one separator plate and one membrane electrode assembly (MEA), with each single cell bounded by two adjacent separator plates. The stack of single electrochemical cells may comprise two end plates that compress the single electrochemical cells together and provide stability to the stack. Furthermore, the single electrochemical cells may comprise gas diffusion layers (GDL) or porous transport layers (PTL) disposed between the separator plate and the membrane electrode assembly.The separator plate can fulfill several functions: indirect electrical contact between electrodes of the membrane electrode assembly (MEA), separation of media such as water, oxygen, or hydrogen, and electrical connection between adjacent individual electrochemical cells. The separator plate is often also referred to as a bipolar plate.

[0003] The separator plate comprises at least one through-opening, sometimes also called a port, as an inlet or outlet for passing a fluid through the separator plate, a flow field with an electrochemically active region, and an intermediate fluid guide structure for guiding the fluid between the through-opening and the flow field.

[0004] The separator plate can, for example, be single- or multi-layered. While separator plates in fuel cells are often double-layered to allow cooling fluid to flow between the two individual layers, separator plates in electrolyzers are typically single-layered, as additional cooling is not necessary. Double-layer separator plates are also sometimes found in electrolyzer applications. In this case, for example, the flow field can be designed as an additional metallic layer mounted on a metallic base plate to form the bipolar plate.

[0005] In addition to the separator plates, MEA, GDL or PTL mentioned above, further layers can be provided. For example, cell frames and / or cell seals can be arranged between adjacent separator plates to seal the cells. The stack of individual electrochemical cells must be sealed from the outside, since a fluid or medium within the individual electrochemical cells is often under excess pressure compared to the external pressure. The fluid can, for example, comprise hydrogen, air or oxygen, water and / or mixtures thereof. In an electrolyzer, a pressure difference between the environment and the interior of an electrochemical cell can often be more than 20 bar. For example, on the product side, the H 2 -side, the pressure can be up to 40 bar, for example, while the pressure on the reactant side, for example the H 2O-side, is only up to 2 bar. It is therefore important to seal the fluid flow field from the environment and also within the electrochemical system. To this end, the electrochemical system can have at least one cell frame surrounding the outer edge of each of the individual electrochemical cells to achieve a sealing effect. Furthermore, the electrolyzer can include one or more sealing layers or cell seals for each of the individual electrochemical cells to enhance the sealing effect.

[0006] To seal the flow field and / or the through-holes, sealing beads molded into the separator plates, elastomer seals molded onto a metal layer of the separator plate, or combinations thereof are often used. To prevent leaks, it is important that the elastomer seal is bonded as tightly as possible to the metal layer. If the elastomer seal no longer seals well, the separator plate, including the elastomer seal and the metal layer, must be replaced during repair or maintenance. If the separator plate is to be reused, the elastomer seal must be removed, which is a very complex process, and a new elastomer seal must be applied.

[0007] The aforementioned elastomer seals or sealing beads are located in the main force connection, i.e., along the compression force used to press the stack of separator plates together. Reliable compression of the seals across the entire stack is therefore typically highly dependent on manufacturing tolerances and operating conditions. The operating pressures of modern electrolyzers, up to 40 bar or even more, can quickly become problematic with the seals currently used.

[0008] Conventional sealing concepts often feature a groove formed in the metal layer to accommodate an elastomer seal, with the elastomer seal typically being injection-molded into the groove. Due to the groove and the injection-molded elastomer seal, the space required in the compression direction is relatively large. Furthermore, in such sealing concepts, the metal layer is in contact with the fluid, which influences the material selection for the metal layer.

[0009] There is therefore a continuous need to further increase the tightness of the system, prevent or at least reduce pressure loss or fluid loss, and / or increase the safety of the system. The present invention was conceived to meet this need or to at least partially solve the aforementioned problems.

[0010] The present invention is defined by the subject matter according to the independent claims. Further developments are described in the dependent claims and the following description.

[0011] According to a first aspect, a sealing arrangement for an electrochemical system is proposed. The sealing arrangement comprises: - a frame-shaped layer with a recess, wherein the layer surrounds an electrochemically active region in a frame-shaped manner, wherein the recess extends over this region and has an inner edge, wherein the layer additionally has at least one through-opening with an inner edge for the passage of a fluid, and - a first elastomeric sealing element which rests against the inner edge of the through-opening and projects laterally into the through-opening in order to seal the through-opening and / or - a second elastomeric sealing element which rests against the inner edge of the recess and projects laterally into the recess in order to seal the recess.

[0012] Thus, only the first sealing element or only the second sealing element, or a combination of both sealing elements, can be provided. Such a sealing arrangement is sometimes also known as a cell frame, since the sealing arrangement extends in a frame-like manner and is suitable for use in an electrochemical cell, particularly for sealing the electrochemical cell. The sealing arrangement can, for example, be provided on the cathode side and / or the anode side of an electrochemical cell.

[0013] In its intended use, the sealing assembly is pressed together with other elements or layers. During the pressing process, the first sealing element and / or the second sealing element are typically in a force shunt and are pressed laterally or radially toward the areas to be sealed, i.e., the through-hole or recess. This has the advantage that manufacturing tolerances and operating parameters play a lesser role in the sealing potential.

[0014] It can be provided that the first sealing element rests all the way around the inner edge of the through-opening and / or that the second sealing element rests all the way around the inner edge of the recess. When the sealing arrangement is used as intended, the first sealing element and / or the second sealing element are usually in contact with the fluid. The sealing arrangement is usually designed so that the layer does not come into contact with the fluid, see description further below. This means that materials can be used for the layer that are normally unsuitable for use in the electrochemical system due to contact with the fluid. For example, plastics, metals or combinations thereof can be used for the layer, which are more cost-effective and / or easier to process than materials conventionally used for the cell frame, such as stainless steel or titanium.

[0015] The layer often has a first side (first flat side) and a second side (second flat side), which are arranged opposite one another and usually extend flatly. It can be provided that the first sealing element and / or the second sealing element protrude beyond the first side of the layer and / or the second side of the layer in an unpressed state of the sealing arrangement in the vertical direction - i.e. the pressing direction, which is aligned parallel to a surface normal of the layer, e.g. the z-direction. The horizontal direction is parallel to the layer or to the layer plane. When the sealing arrangement is pressed, the vertical projection is pressed laterally in the direction of the recess or the through-opening, so that the corresponding sealing element is essentially flush with the layer in the pressed state.

[0016] In many embodiments, the first sealing element is molded onto the inner edge of the through-opening and / or the second sealing element is molded onto the inner edge of the recess. In these embodiments, the first sealing element and / or the second sealing element can be configured, in particular, as edge-molded sealing profiles.

[0017] The sealing arrangement can optionally have an elastomeric fluid guide structure with a plurality of fluid passages for conducting a fluid from the through-opening to the recess or vice versa. Typically, the fluid guide structure is formed integrally with the first sealing element and / or the second sealing element. In some examples, the fluid guide structure connects the first sealing element to the second sealing element, in particular by a material fit. Thus, it can be provided that the first sealing element and the second sealing element are formed from a single elastomeric element. The fluid passages can be formed as depressions in the fluid guide structure, which extend between elevations of the fluid guide structure. Alternatively, the fluid passages can be completely surrounded by the elastomeric material of the fluid guide structure in a direction perpendicular to a flow direction of the fluid.

[0018] In some embodiments, the recess and the through-opening form a common opening in the frame-shaped layer. In this case, the recess and the through-opening can be spatially separated from one another by the elastomeric fluid-conducting structure, in particular, separated from one another only by the elastomeric fluid-conducting structure. Thus, only the material of the fluid-conducting structure can extend between the recess and the through-opening, without any material of the layer being present.

[0019] The sealing arrangement or the position of the sealing arrangement can have at least two through-openings. On the anode side, one of these through-openings can then be designed as a fluid inlet for the fluid, while the other of the through-openings can be designed as a fluid outlet for the same fluid and another fluid. On the cathode side, both through-openings can be designed as fluid outlets. The recess is then arranged between the two through-openings, in particular between the two through-openings in the direction of fluid flow.

[0020] The layer can be made of a metallic material such as aluminum, steel, titanium, stainless steel, plastic, and / or combinations thereof. Since the layer preferably does not come into contact with the fluid during the intended use of the sealing arrangement (see above), the layer can be made of a material that does not need to be corrosion-resistant, such as aluminum or (non-stainless) steel.

[0021] For example, the first sealing element and / or the second sealing element are made of fluororubber, FKM, and / or ethylene-propylene-diene rubber, EPDM, and / or a silicone. The first sealing element and the second sealing element can be made of the same material or different materials. The first sealing element and / or the second sealing element can each be formed in one piece. Optionally, both sealing elements can be configured as an integral part of a single sealing element.

[0022] According to an additional aspect of the present specification, a further sealing arrangement for an electrochemical system is provided. The sealing arrangement comprises a frame-shaped layer with a recess, wherein the layer surrounds an electrochemically active region in a frame-like manner. The recess extends over this region and has an inner edge. The layer additionally has at least one through-opening with an inner edge for conducting a fluid. The sealing arrangement further comprises an elastomeric fluid guide structure with a plurality of fluid passages for conducting a fluid from the through-opening to the recess or vice versa.

[0023] The additional sealing arrangement can be combined with the features of the sealing arrangement described above. Thus, the additional sealing arrangement can be combined with the first sealing element and / or the second sealing element of the type described above (see above). The additional sealing arrangement can also be used without the first sealing element and / or the second sealing element.

[0024] According to a further aspect of the present invention, a bipolar plate for an electrochemical system is provided. The bipolar plate comprises a flow field with an electrochemically active region and at least one through-opening for the passage of a fluid. The bipolar plate is substantially flat between the flow field and the through-opening. Furthermore, the bipolar plate is substantially flat in a first region adjacent to the through-opening and circumferentially around the through-opening and / or in a second region adjacent to the flow field and circumferentially around the flow field. In particular, the bipolar plate has no sealing elements such as sealing beads, elastomer seals, and / or recesses for receiving elastomer seals in the aforementioned regions.The sealing of the through-hole and / or the flow field, as well as the fluid flow between the through-hole and the flow field, are thus handled by the sealing arrangement described above, while the bipolar plate is designed for electrical contact and separation or distribution of the media. Because the bipolar plate itself does not have an elastomer seal around the through-holes and the flow field, the bipolar plate can be relatively easily removed, maintained, possibly cleaned, possibly recoated, and reused during servicing.

[0025] The bipolar plate mentioned can in particular be used with one or both of the sealing arrangements described above. The sealing arrangement assumes sealing functions, for example, and ensures that the through-openings of the bipolar plate are sealed by means of the first sealing element and the flow field of the bipolar plate is sealed by means of the second sealing element. In addition, the sealing arrangement assumes the fluid conduction function between the through-opening and the flow field via the elastomeric material of the fluid guide structure. Typically, the flow field has a plurality of channels formed into the bipolar plate, for example by means of embossing, hydroforming, and / or deep drawing. The bipolar plate can, for example, be single-layer or double-layered. The bipolar plate can, for example, be made of titanium or stainless steel.

[0026] According to a third aspect, an arrangement for an electrochemical system is provided. The arrangement comprises at least one sealing arrangement of the type described above and at least one bipolar plate of the type described above. The sealing arrangement and the bipolar plate are positioned relative to one another such that the through-openings of the bipolar plate and the sealing arrangement are arranged one above the other and the frame-shaped layer surrounds the flow field with the electrochemically active region of the bipolar plate. The first sealing element is designed to seal the through-opening of the bipolar plate. Alternatively or additionally, the second sealing element is designed to seal the electrochemically active region of the bipolar plate.

[0027] It can be provided that the through-opening formed in the bipolar plate is smaller than the through-opening formed in the layer. The first sealing element and / or the second sealing element of the layer contact the bipolar plate. A plate body of the layer and a plate body of the bipolar plate can be made of different or identical materials. Because preferably only the sealing elements of the layer are in contact with the fluid, the layer can be made of a different material than the bipolar plate, in particular from a material other than the relatively expensive titanium.

[0028] Two sealing arrangements of the type described above can be provided for each bipolar plate. The arrangement can have two sealing arrangements arranged on opposite sides of the bipolar plate, wherein the first sealing elements of the sealing arrangements seal the through-opening of the bipolar plate on both sides of the bipolar plate and / or the second sealing elements of the sealing arrangements seal the electrochemically active region of the bipolar plate on both sides of the bipolar plate. The first of the two sealing arrangements can be provided on a cathode side of the bipolar plate, while the second of the two sealing arrangements can be provided on an anode side of the bipolar plate. In this case, the respective sealing arrangements are preferably arranged with respect to the bipolar plate such that their fluid guidance structures face the bipolar plate and, in particular, rest on the bipolar plate.

[0029] In addition, the arrangement can also have at least one insulating layer and / or insulating coating for electrical insulation. The insulating layer and / or insulating coating can be arranged on one side or both sides of the sealing arrangement. The insulating layer and / or insulating coating can be arranged between the frame-shaped layer of the sealing arrangement and the bipolar plate. The insulating coating can consist of a plastic layer. The plastic layer can comprise a polyester, in particular polyethylene terephthalate (PET), or polyethylene naphthalate (PEN), a polyimide (PI), or a polyetheretherketone (PEEK). These materials enable reliable electrical insulation with a process-reliable layer-like application and a low layer thickness. According to one development, the plastic layer comprises a plastic film laminated to the structurally rigid layer.For example, the plastic film is bonded to the structurally rigid layer by means of an adhesive, in particular by means of an acrylic adhesive. Alternatively, the frame-shaped layer of the sealing arrangement can be arranged between the insulation layer and the bipolar plate. Preferably, there is no additional layer or coating between the first sealing element or the second sealing element and the bipolar plate, so that the respective sealing element rests directly on the bipolar plate. The respective sealing element is thus designed to seal the insulation layer from the at least one through-opening of the layer and / or the recess of the layer, so that the insulation layer does not come into contact with the fluid during normal use of the arrangement. The first sealing element and / or the second sealing element are often also designed to be electrically insulating.

[0030] The arrangement may further comprise a membrane electrode assembly (MEA) located between two sealing assemblies and / or a porous transport layer (PTL) or gas diffusion layer (GDL) arranged between the MEA and the flow field of the bipolar plate. The arrangement may also be suitable for anion exchange membrane electrolysis (AEM), e.g., for the conversion of CO 2 .

[0031] According to a further aspect, an electrochemical system is proposed, preferably an electrolyzer or fuel cell stack. The system comprises a plurality of sealing assemblies of the type described above, a plurality of bipolar plates of the type described above, and / or a plurality of stacked assemblies of the type described above.

[0032] The electrochemical system can, for example, be an electrolyzer. However, the present document is not limited to an electrolyzer. Alternatively, the electrochemical system can also be a fuel cell system or a redox flow battery. In an embodiment in which the electrochemical system is an electrolyzer, water is often the reaction medium, while hydrogen or oxygen can be the product medium(s). In a fuel cell system, hydrogen and oxygen are often the reaction media, while water is the product medium.

[0033] The system can also be suitable for anion exchange membrane electrolysis (AEM), e.g. for the conversion of CO 2 .

[0034] Exemplary embodiments of the sealing arrangement, the bipolar plate, the assembly, and the electrochemical system are illustrated in the attached figures and explained in more detail in the following description. They show: Fig. 1 an exploded view of a single cell of an electrolyzer according to the prior art; Fig. 2 a plan view of a bipolar plate according to the prior art; Fig. 3 schematically shows a perspective view of a bipolar plate according to an embodiment; Fig. 4 schematically shows a perspective view of a cathode-side sealing arrangement according to an embodiment; Fig. 5 schematically shows an enlarged view of a section of the Fig. 4; Fig. 6 schematically shows a perspective view of an anode-side sealing arrangement according to an embodiment; Fig. 7 schematically shows an enlarged view of a section of the Fig. 6; Fig. 8 schematically shows a perspective view of a composite of bipolar plate and anode-side and cathode-side sealing arrangement, with a view of the anode side; Fig. 9 schematically shows an enlarged view of a section of the Fig. 8; Fig. 10 schematically shows a perspective view of a composite of bipolar plate and cathode-side and anode-side sealing arrangement, with a view of the cathode side; Fig. 11 schematically shows an enlarged view of a section of the Fig. 10; Fig. 12 the association of Fig. 8 with section lines AA and BB drawn; Fig. 13 a sectional view along section AA of the Fig. 12; Fig. 14 a sectional view along section BB of the Fig. 12; Fig. 15 in two sub - figures, a sectional view of a composite of bipolar plate, cathode - side and anode - side sealing arrangements in the area of a through - opening in the uncompressed state and in the compressed state; and Fig. 16 a sectional view of an arrangement of bipolar plates, sealing arrangements and other components.

[0035] Here and hereinafter, recurring features in different figures are each denoted with the same or similar reference signs.

[0036] Fig. 1 shows an exploded view of an electrochemical single cell 9, wherein the single cell 9 is a component of an electrolyzer. Electrolyzers typically comprise a plurality of stacked single cells 9. The single cell 9 comprises two separator plates 1 and 2, two cell frames 42 and 44, a sealing layer 45 and a membrane electrode assembly 40 with media diffusion structures 41 and 43. The media diffusion structure 43 comprises, for example, layers of carbon fleece, while the media diffusion structure 41 comprises metal, e.g. titanium. The separator plate 1 is arranged here, for example, on the anode side of the single cell 9. The separator plate 2 is arranged on the cathode side of the single cell 9 in the exemplary embodiment shown. The individual layers are pressed together to form a single cell. The individual layers each have fluid feedthroughs 46, 47, 50 arranged in alignment one above the other for the inlet and outlet of the fluid.Leading out water, oxygen and hydrogen as well as positioning holes 48.

[0037] By projecting the cell frame 44 onto the separator plate 2, a flow field of the separator plate 2 is defined. By projecting the cell frame 42 onto the separator plate 1, a flow field 3 of the separator plate 1 is defined. The cell frame 42 has distribution channels (not shown) for distributing the introduced water. The through-openings 46, 47 are in fluid communication with the flow field 3 so that a medium can be conducted from the through-opening 46 to the flow field 3 or from the flow field 3 to the through-opening 47. When a potential is applied, hydrogen (or oxygen) can be generated in the electrolyzer from the supplied water. This can be discharged through the distribution channels 49 in the cell frame 44. It can then leave the cell through the through-openings 50. While the Fig. While the separator plates 1 shown in Figure 1 have a round outer contour, other shapes are also possible. For example, the separator plates 1, 2 can have a rectangular outer contour, see Figure 1. Fig. 2.

[0038] The separator plates 1, 2 from Fig. 1 and Fig. 2 are exemplary separator plates according to the state of the art.

[0039] As already indicated above, the pressure difference between the environment and the interior of the electrochemical cell 9 can exceed 20 bar. Often, the pressure on the product side, for example, the hydrogen side, is up to 40 bar, while the pressure on the reactant side, for example, the water side, is only up to 2 bar. Therefore, sealing structures are provided to separate the individual areas from each other.

[0040] For example, elastomer seals are used, which are arranged around the areas to be sealed, e.g., flow field 3 or through-holes 46, 47, 50. The elastomer seal is usually not provided over the entire surface, but only on the areas of the separator plate 1, 2 to be sealed and is firmly connected to the plate body of the respective separator plate 1, 2.

[0041] In the Fig. Figure 2 schematically shows a plan view of a separator plate 1 for an electrolyzer. The separator plate 1 comprises a metallic layer 10, which, for example, consists at least predominantly or entirely of titanium or stainless steel or alloys thereof. The metallic layer 10 can have a thickness of at least 0.1 mm and / or at most 0.8 mm. The separator plate 1 has a flow field 3, which is designed to distribute the water supplied from the through-openings 4 as evenly as possible. For this purpose, channel structures 6 are optionally provided in the flow field 3. The through-openings 5 ​​are designed to discharge hydrogen, wherein on the side of the separator plate shown, the fluid through-openings 5 ​​are surrounded by an elastomer seal 7. The elastomer seal 7 ensures, on the one hand, that the water cannot escape and, on the other hand, that hydrogen or ambient air cannot enter.

[0042] Separator plates of fuel cells are often designed in two layers, so that each layer can be processed individually, such as embossed, surface-treated, injection-molded, etc. Separator plates 1, 2 of electrolyzers, on the other hand, are often designed in a single layer. For this reason, sealing elements 7 of separator plates in electrolyzers must be provided on both sides of a single layer 10. Furthermore, the arrangement of sealing elements in a separator plate of an electrolyzer leads to an accumulation of different sealing elements in a small space. The sealing elements are also arranged alternately to seal both sides of the separator plate. The separator plate thus exhibits a high degree of complexity when sealing the through-openings 4, 5 or the flow field 3, both due to the close spacing of the sealing elements and the alternate arrangement.

[0043] As mentioned at the beginning, there is therefore a constant need to improve the tightness of electrolyzers and fuel cell stacks.

[0044] The Fig. 3-14 relate to various aspects and embodiments of the present invention.

[0045] The Fig. 3 shows a plan view of a bipolar plate 1 according to an embodiment of the invention. As the bipolar plate 1 of the Fig. 1 and Fig. 2 also has the bipolar plate of the Fig. 3 a flow field 3 with an electrochemically active region and a plurality of through-openings 4, 5 for conducting a fluid. The flow field 3 has a plurality of channels 6, which are formed into the bipolar plate 1, for example by hydroforming, embossing and / or deep drawing. The bipolar plate 1 is generally single-layered, but can also be double-layered, for example in an embodiment in which the flow field 3 is mounted as an additional layer on a base plate. Centering holes 8 are often provided for receiving centering pins so that the bipolar plate 1 can be aligned or centered.

[0046] In comparison and in contrast to the bipolar plate 1 of the Fig. 1 and Fig. 2 that the bipolar plate 1 is essentially flat between the flow field 3 and the through-opening 4, 5, i.e., it is designed as a flat surface there. Outside the flow field 3 and apart from any through-openings 4, 5, 8, in particular everywhere outside the aforementioned regions 3, 4, 5, 8, the bipolar plate is designed as a flat, flat plate. The flat region 11 of the bipolar plate comprises, for example, a first partial region 12 and a second partial region 13. The first flat region 12 borders the through-opening 4, 5 and completely surrounds the through-opening 4, 5. The second flat region 13 borders the flow field 3 and completely surrounds it. In the aforementioned regions 11, 12, 13, the bipolar plate has no sealing elements or other elevations or depressions.Thus, these areas 11, 12, 13 are free of sealing beads, elastomer seals, elastomer beads and / or recesses for receiving sealing elements.

[0047] The bipolar plate 1 has two opposite sides 17, 19, wherein in the Fig. 3 only the first side 17 (front side of the bipolar plate 1) is visible and the second side 19 (back side of the bipolar plate 1) is hidden from the viewer. Due to the absence of sealing elements in the bipolar plate 1, both sides 17, 19 of the bipolar plate 1 can be designed the same or identically, so that the bipolar plate 1 has an axis of rotational symmetry running through the plane of the bipolar plate 1 and parallel to the plane of the bipolar plate 1. A rotation of 180° about this axis of rotational symmetry results in the same arrangement of the bipolar plate 1, apart at most from the fact that the channels 6 in the flow field 3 are oriented the other way around. In the exemplary embodiment shown, the bipolar plate 1 is single-layer and made of titanium.

[0048] The sealing of the flow field 3 and the sealing of the fluid passages 4, 5 are realized by a sealing arrangement 15, 16 separate from the bipolar plate, which is described below.

[0049] The Fig. 4-7 show perspective views of a sealing arrangement 15, 16 for an electrochemical system, wherein the sealing arrangement 15, 16 is used in particular for sealing the areas 3, 4, 5 of the bipolar plate 1 of the Fig. 3 is designed.

[0050] The sealing arrangement 15, 16 comprises a frame-shaped layer 20, which can be made of metal and / or plastic. The frame-shaped layer 20 comprises a recess 23 with an inner edge 26. The layer 20 or the inner edge 26 of the recess 23 surrounds an electrochemically active region in a frame-like manner, with the recess 23 extending over this region. The recess 23 is preferably aligned with the electrochemically active region of the flow field 3 of the bipolar plate 1 of the Fig. 3 so that the recess 23 of layer 2 and the electrochemically active area of ​​the bipolar plate 1 overlap.

[0051] The layer 20 additionally has at least one through-opening 24, 25 with an inner edge 27, 28 for the passage of a fluid. The through-openings 24, 25 of the layer 20 are typically aligned with the through-openings 4, 5 of the bipolar plate 1 of the Fig. 3. The through-openings 4, 24 and through-openings 5, 25 stacked on top of one another in an electrochemical cell form fluid lines 29 through which reaction or product media can flow. The layer 20 of the sealing arrangement 15, 16 can, for example, have at least two through-openings 24, 25. In the figures, the through-openings 24, 25 of the sealing arrangement 15, 16 or the through-openings 4, 5 of the bipolar plate are provided with the same reference numerals if they transport fluid(s) flowing on the anode side or the cathode side of the bipolar plate 1. For example, in the case of an electrolyzer, the through-openings 5, 25 are designed to transport the hydrogen generated in the electrochemical cell. The through openings 4, 24 are designed for the inlet of water or the outlet of water and oxygen.The layer 20 of the sealing arrangement 15, 16 has a first side 21 (front side) and a second side 22 (rear side), which are arranged opposite one another.

[0052] The sealing arrangement 15, 16 also has a first elastomeric sealing element 31, 33, which rests against the inner edge 27, 28 of the through-opening 4, 5 and projects laterally into the through-opening 24, 25 to seal the through-opening 24, 25. The first sealing element 31, 33 rests, in particular, circumferentially against the inner edge 27, 28 of the through-opening 24, 25. The first sealing element 31, 33 is typically injection-molded onto the inner edge 27, 28 of the through-opening 24, 25 in an edge-molding process.

[0053] In addition, the sealing arrangement 15, 16 has a second elastomeric sealing element 32, which rests against the inner edge 26 of the recess 23 and projects laterally into the recess 23 to seal the recess 23. The second sealing element 32 rests, in particular, circumferentially against the inner edge 26 of the recess 23. The second sealing element 32 is typically molded onto the inner edge 26 of the recess 23 in an edge-molding process. The first sealing element 31, 33 and / or the second sealing element 32 are often also electrically insulating.

[0054] In the intended use of the sealing arrangements 15, 16, the first sealing element 31 and the second sealing element 32 are preferably in contact with the respective fluid that flows through the passage opening 24, 25 or through the recess 23. The position 20 or the material of the position 20 cannot be in contact with the fluid (or fluids) due to the sealing of the sealing elements 31, 32. As a result, materials for the position 20 can be used which may not be chemically resistant to the fluids used or may be incompatible with the fluids used under the operating conditions of the electrochemical cell, such as H 2 , O 2 and H 2 O are. As a result, more cost-effective and / or mechanically more advantageous materials can be used which cannot be used in conventional systems in which the material of the position 20 comes into contact with the fluids.

[0055] To allow the fluid to flow from the through-opening 24, 25 to the recess 23 and thus to the electrochemically active region, a fluid guide structure 34 with a plurality of fluid passages 35 can be provided. The fluid guide structure 34 is preferably also formed from an elastomer and is designed to guide the fluid from the through-opening 24, 25 to the recess 23 or vice versa. The fluid guide structure 34 is sometimes also called a distribution or collection region because fluid is distributed there from the through-opening to the electrochemically active region or is collected from the electrochemically active region and guided to the through-opening. It can be provided that the fluid guide structure 34 is formed integrally with the first sealing element 31, 33 and / or the second sealing element 32. Furthermore, the fluid guide structure 34 can connect the first sealing element 31, 33 to the second sealing element 32, in particular by means of a material bond.It can also be provided that the first sealing element 31, the second sealing element 32 and the fluid guide structure 34 are formed by the same element, cf. one-piece sealing element 30 in . Fig. 4-5. Similarly, the first sealing element 33, the second sealing element 32 and the fluid guiding structure 34 can be formed by the same element, cf. one-piece sealing element 30 in Fig. 6-7.

[0056] The recess 23 and the through-opening 24, 25 can form a common opening in the frame-shaped layer 20. In other words, the recess 23 and the through-opening 24, 25 of the layer 20 merge into one another before the sealing elements 31, 32, 33 are molded onto the layer 20 and / or before the sealing elements 31, 32, 33 are connected to the layer 20, or they are not separated from one another by metallic material of the layer 20. The spatial separation of the through-opening 24, 25 and the recess 23 is only achieved by the provision of the fluid-guiding structure 34, whereby the fluid-guiding structure 34, on the other hand, enables the fluidic connection of the through-opening 24, 25 and the recess. The recess 23 and the through-opening 24, 25 can therefore be spatially separated from each other only by the elastomeric fluid guide structure 34. In particular, in the Fig. 8-12 the second side 22 of the layer 20 and thus also the back of the fluid guide structure 34 is shown, while in the Fig. 4-7, the first side 21 of the layer 20 or the front side of the fluid guide structure 34 is shown. In the fluid flow direction between the through-openings 24 and the recess 23 of the anode-side sealing arrangement 16 ( Fig. 8, Fig. 9) or between the through-openings 25 and the recess 23 of the cathode-side sealing arrangement 15 ( Fig. 10, Fig. 11) no material of the metallic layer 20 runs.

[0057] Separating elements 39, such as finger-shaped webs, can be provided in layer 20 to fluidically separate adjacent through-openings 24, 25, which can conduct the same fluids. The fluid guide structure 34 is preferably connected to end sections of the finger-shaped separating elements 39 or rests on layer 20 in the region of the end sections of the separating elements 39. The optional separating elements 39 provide the sealing arrangement 15, 16 with additional mechanical stability by shortening the distance to be bridged by the fluid guide structure 34.

[0058] Exemplary materials for the first sealing element 31, 33, the second sealing element 32, the fluid guide structure 34 or the one-piece sealing element 30 are fluororubber, FKM and / or ethylene-propylene-diene rubbers, EPDM and / or silicone.

[0059] Embodiments with a first sealing element 31, 33, a second sealing element 32, and a fluid-guiding structure 34 are described above. It should be noted that embodiments are conceivable in which the sealing arrangement has only a first sealing element 31, 33 (i.e., no second sealing element 32), only a second sealing element 32 (i.e., no first sealing element 31, 33), or neither of the two sealing elements 31, 32, 33. In all of the cases mentioned here, the sealing arrangement 15, 16 can have the fluid-guiding structure 34.

[0060] The Fig. 8-12 each show an arrangement 100 for an electrochemical system. By stacking a plurality of arrangements 100, the electrochemical system can be realized. The arrangement 100 comprises the sealing arrangements 15, 16 of the Fig. 4-7 and the bipolar plate 1 of the Fig. 3. Here, the sealing arrangements 15, 16 are arranged on both sides of the bipolar plate 1, i.e. on opposite sides 17, 19 of the bipolar plate 1, so that a sandwich arrangement of the elements 15, 1, 16 is formed. In this case, the first side 21 of the respective sealing arrangement 15, 16 is usually facing the bipolar plate 1, so that in the Fig. 8-12, the second side 22 of the sealing arrangement 15, 16 becomes visible. Furthermore, each sealing arrangement 15, 16 and the bipolar plate 1 are positioned relative to one another such that the through-openings 4, 5 of the bipolar plate 1 and the through-openings 24, 25 of the respective sealing arrangement 15, 16 are arranged one above the other to form fluid lines 29. Furthermore, each sealing arrangement 15, 16 and the bipolar plate 1 are aligned relative to one another such that the frame-shaped layer 20 surrounds the flow field 3 with the electrochemically active region of the bipolar plate 1. The first sealing element 31, 33 is designed to seal the through-opening 4, 5 of the bipolar plate 1. Furthermore, the second sealing element 32 is designed to seal the electrochemically active region of the flow field 3 of the bipolar plate 1.The sealing arrangement 15 thus seals the areas 3, 4, 5 on the front side 17 of the bipolar plate 1, while the sealing arrangement 16 seals the areas 3, 4, 5 on the back side 19 of the bipolar plate.

[0061] The sealing arrangements 15, 16 are generally positioned such that their fluid guide structures 34 face the bipolar plate 1. The fluid passages 35, which are formed as channel-shaped recesses, are thus covered by the bipolar plate 1.

[0062] It is typically provided that the through-opening 4, 5 formed in the bipolar plate 1 is smaller than the corresponding through-opening 24, 25 formed in the layer 20. In other words, the bipolar plate 1 projects laterally further into the fluid line 29 formed by the through-opening 4, 5 and the corresponding through-opening 24, 25 than the sealing arrangement 15, 16 or the sealing elements 31, 32, 33 of the sealing arrangement 15, 16.

[0063] For the best possible sealing of areas 3, 4, 5 of the bipolar plate 1, it is advantageous if the first sealing element 31, 33 and / or the second sealing element 32 of layer 20 contact the bipolar plate 1. This can also ensure that the layer 20 does not come into contact with the fluid during operation of the electrochemical cell. This can provide for a plate body of layer 20 and a plate body of the bipolar plate 1 to be made of different materials. Furthermore, it can be provided for the plate body of layer 20 to be composed of several parts, i.e., segmented using methods from the prior art.

[0064] In an unpressed state of the sealing arrangement 15, 16, the first sealing element 31, 33 and the second sealing element 32 protrude in the vertical direction beyond the first side 21 of the layer 20 and / or the second side 22 of the layer 20, cf. Fig. 14A, Fig. 15A. The vertical direction is defined so that it is parallel to the compression force and perpendicular to the surface normal of the sealing arrangement 15, 16, cf. z-direction in the Fig. 13-15. The projection 51 of the respective sealing element 31, 32, 33, which in the unpressed state of the sealing arrangements 15, 16 projects beyond the flat sides 21, 22 of the layer 20, is in particular in the Fig. 13-15. When pressing the sealing arrangement 15, 16 together with the bipolar plate 1, the projection 51 is pressed laterally in the direction of the recess 23 or the through opening 24, 25, so that the corresponding sealing element 31, 32, 33, in the pressed state, is essentially flush with the layer 20, cf. Fig. 14B and Fig. 15B. The sealing elements 31, 32, 33 can be dimensioned or designed such that their lateral extension in the compressed state of the sealing arrangement 15, 16 does not protrude beyond the bipolar plate 1, more precisely: an edge of the bipolar plate 1 in the region of the through opening 4, 5, into the fluid line 29.

[0065] Optionally, a gap 36 can run on the surface between the fluid guide structure 34 and the nearest sealing element 31, 32 in order to provide space for the fluid guide structure 34 to deflect during compression, cf. Fig. 9 and Fig. 11.

[0066] According to the figures shown, the sealing arrangement 15 is designed to be arranged in a cathode compartment of the electrolyzer, while the sealing arrangement 16 is arranged in an anode compartment of the electrolyzer. However, the invention is not limited to this. The sealing arrangements 15, 16 can also be used in a fuel cell stack or in other electrochemical systems.

[0067] In the Fig. 4-14 it can further be seen that in the cathode-side sealing arrangement 15 the through-openings 4, 24 for the passage of water and / or oxygen are completely sealed all the way around by the first sealing element 31, while hydrogen generated in the electrochemically active region can pass through the fluid guide structure 34 to the through-openings 5, 25 and the fluid line 29.

[0068] Accordingly, in the anode-side sealing arrangement 16, the passage openings 5, 25 for the passage of hydrogen are completely sealed by the first sealing element 31, while water can pass from the passage openings 4, 24 through the fluid guide structure 34 to the electrochemically active region or the flow field 3. From the electrochemically active region, the generated oxygen can flow together with the unreacted water through the fluid guide structure 34 to the passage openings 4, 24.

[0069] In the sandwich arrangement 100 of the Fig. 14, Fig. 15, one sealing arrangement 15, 16 completely seals the through-openings all around, while the other sealing arrangement 16, 15 allows fluid flow from or to the electrochemically active area of ​​the bipolar plate. In the sectional drawing of the sandwich arrangement 100 of the Fig. 15 shows beveled or stamped edges 52 of the sealing arrangements 15, 16, to which the elastomeric sealing element 31 is molded. The advantage here is that the elastomeric sealing contour, which lies directly against the stamped edges 52, does not protrude significantly beyond the contours of the non-stamped parts of the sealing arrangements in the unpressed state. Thus, in the pressed state, the sealing effect can be achieved according to Fig. 15B.

[0070] The arrangement 100 may comprise further layers. For example, the arrangement 100 comprises at least one insulation layer, which is arranged between the frame-shaped layer 20 of the sealing arrangement 15, 16 and the bipolar plate 1. Alternatively, the frame-shaped layer 20 of the sealing arrangement 15, 16 may be arranged between the insulation layer and the bipolar plate 1. To ensure the sealing function, the insulation layer should not extend between the sealing element 31, 32, 33 and the bipolar plate 1. The respective sealing element 31, 32, 33 should therefore lie directly on the bipolar plate 1, even if further layers are present. Further additional elements are described in the Fig. 1, which is shown with the arrangement 100 of the Fig. 8-14 can be combined. Thus, the arrangement can further comprise a membrane electrode assembly (MEA) 40, which is arranged on the side of the flow field 3 of the bipolar plate 1 and / or a porous transport layer (PTL) 41 or gas diffusion layer (GDL) 43, which is arranged between the MEA and the flow field 3 of the bipolar plate 1. This can be seen in Fig. 16. Fig. 16 shows, from top to bottom, sections of a sealing arrangement 16, a bipolar plate 2, a sealing arrangement 15, a membrane electrode unit 40, another sealing arrangement 16 and a bipolar plate 1.

[0071] The resulting sealing lines of the sealing elements 33a and 32a are shown as dashed lines L1 to L4, projected onto the underlying MEA 40 and the fluid guide structure 34b of the subsequent sealing arrangement 16. The sealing lines L1 and L2 of the sealing element 33a seal the through-openings 24. The sealing line L3 seals the cathode chamber of the active region, whereas L4 seals the anode chamber. The fluid guide structure 34b transfers the pressure to the bipolar plate 1.

[0072] It will be apparent to the person skilled in the art that the features of the above-described Fig. 1-16 can be combined with each other, provided they do not contradict each other, and can be claimed individually. List of reference symbols 1 separator plate 2 separator plate 3 Flow field 4 Fluid passage opening 5 Fluid passage opening 6 channel structures 7 Elastomer seal 8 Centering opening 9 electrochemical cell 10 metallic layer of the bipolar plate 11 flat area 12 flat area 13 flat area 15 Sealing arrangement 16 Sealing arrangement 17 first page 18 Centering opening 19 second page 20 frame-shaped layers 21 first page 22 second page 23 Recess 24 passage opening 25 passage opening 26 Inner edge of the recess 27 Inner edge of the passage opening 28 Inner edge of the passage opening 29 Fluid line 30 one-piece sealing element 31 first elastomeric sealing element 32 second elastomeric sealing element 33 first elastomeric sealing element 34 Fluid guide structure 34a Fluid guide structure 34b Fluid guide structure 35 Fluid feedthrough 36 gap 37 Inner edge of the fluid passage opening 38 Inner edge of the fluid passage opening 39 Separator 40 membrane electrode assembly 41 Media diffusion structure 42 cell frames 43 Media diffusion structure 44 cell frames 45 Sealing layer 46 Fluid passage opening 47 Fluid passage opening 48 Positioning hole 49 hydrogen distribution channels 50 hydrogen through holes 51 overhang 52 bevelled / embossed edges of the sealing arrangements 15,16 100 arrangement L1 sealing line L2 sealing line L3 sealing line L4 sealing line

Claims

[1] Sealing arrangement (15, 16) for an electrochemical system, comprising - a frame-shaped layer (20) with a recess (23), wherein the layer (20) surrounds an electrochemically active region in a frame-shaped manner, wherein the recess (23) extends over this region and has an inner edge (26), wherein the layer (20) additionally has at least one through-opening (24, 25) with an inner edge (27, 28) for the passage of a fluid, and - a first elastomeric sealing element (31, 33) which rests against the inner edge (27, 28) of the through-opening (24, 25) and projects laterally into the through-opening (24, 25) in order to seal the through-opening (24, 25) and / or - a second elastomeric sealing element (32) which bears against the inner edge (26) of the recess (23) and projects laterally into the recess (23) in order to seal the recess (23), the sealing arrangement further comprising an elastomeric fluid guide structure (34) with a plurality of fluid passages (35) for passing a fluid from the through opening (24, 25) to the recess (23) or vice versa. [2] Sealing arrangement (15, 16) according to claim 1, wherein the first sealing element (31, 33) rests circumferentially on the inner edge (27, 28) of the through-opening (24, 25) and / or wherein the second sealing element (32) rests circumferentially on the inner edge (26) of the recess (23), wherein the first sealing element (31, 33) and / or the second sealing element (32) are in contact with the fluid during the intended use of the sealing arrangement (15, 16). [3] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the layer (20) has a first side (21) and a second side (22) which are arranged opposite one another, wherein the first sealing element (31, 33) and / or the second sealing element (32) project in a non-pressed state of the sealing arrangement (15, 16) in the vertical direction beyond the first side of the layer (20) and / or the second side of the layer (20). [4] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the first sealing element (31, 33) is injection-molded onto the inner edge (27, 28) of the through-opening and / or the second sealing element (32) is injection-molded onto the inner edge (26) of the recess (23). [5] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the fluid guide structure (34) is formed integrally with the first sealing element (31, 33) and / or the second sealing element (32). [6] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the fluid guide structure (34) connects the first sealing element (31, 33) to the second sealing element (32), in particular in a materially bonded manner. [7] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the recess (23) and the through-opening (24, 25) form a common opening in the frame-shaped layer (20), wherein the recess (23) and the through-opening (24, 25) are separated from one another by the elastomeric fluid guide structure (34). [8] Sealing arrangement (15, 16) according to one of the preceding claims, comprising at least two through-openings (24, 25) which are designed as a fluid inlet and a fluid outlet, respectively, wherein the recess (23) is arranged between the two through-openings (24, 25). [9] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the layer (20) is made of a metallic material such as aluminum, titanium or stainless steel, plastic and / or combinations thereof, wherein the first sealing element (31, 33) and the second sealing element (32) are made of the same material, in particular of fluororubber, FKM, and / or ethylene-propylene-diene rubbers, EPDM and / or a silicone. [10] Sealing arrangement (15, 16) according to one of the preceding claims, wherein the first sealing element (31, 33) and / or the second sealing element (32) are each formed in one piece and optionally both are designed as an integral part of a single sealing element (30). [11] Sealing arrangement (15, 16) for an electrochemical system, comprising a frame-shaped layer (20) with a recess (23), wherein the layer (20) surrounds an electrochemically active region in a frame-shaped manner, wherein the recess (23) extends over this region and has an inner edge (26), wherein the layer (20) additionally has at least one through-opening (24, 25) with an inner edge (27, 28) for the passage of a fluid, the sealing arrangement further comprising an elastomeric fluid guide structure (34) with a plurality of fluid passages (35) for the passage of a fluid from the through-opening (24, 25) to the recess (23) or vice versa. [12] Bipolar plate (1) for an electrochemical system, comprising: - a flow field (3) with an electrochemically active region and - at least one through-opening (4, 5) for passing a fluid, wherein the bipolar plate (1) between the flow field (3) and the through opening (4, 5) is substantially flat, wherein the bipolar plate (1) is substantially flat in a first region (12) adjacent to the through-opening (4, 5) and circumferentially around the through-opening (4, 5) and / or in a second region (13) adjacent to the flow field (3) and circumferentially around the flow field (3), and the bipolar plate (1) in said regions (12, 13) in particular has no sealing elements such as sealing beads, elastomer seals and / or recesses for receiving elastomer seals. [13] Bipolar plate (1) according to the preceding claim, wherein the flow field (3) comprises a plurality of channels (6) formed in the bipolar plate (1). [14] Arrangement (100) for an electrochemical system, comprising at least one sealing arrangement (15, 16) according to one of claims 1 to 11 and the bipolar plate according to one of claims 12 to 13, wherein the sealing arrangement (15, 16) and the bipolar plate (1) are positioned relative to one another such that the through-openings (4, 5) of the bipolar plate and the through-openings (24, 25) of the sealing arrangement (15, 16) are arranged one above the other and the frame-shaped layer (20) surrounds the flow field (3) with the electrochemically active region of the bipolar plate (1), wherein the first sealing element (31, 33) is designed to seal the through-opening (4, 5) of the bipolar plate (1) and / or wherein the second sealing element (32) is designed to seal the electrochemically active region of the bipolar plate (1). [15] Arrangement (100) according to the preceding claim, wherein the through-opening (4, 5) formed in the bipolar plate (1) is smaller than the through-opening (24, 25) formed in the layer (20). [16] Arrangement (100) according to one of the two preceding claims, wherein the first sealing element (31, 33) and / or the second sealing element (32) of the layer (20) contact the bipolar plate (1). [17] Arrangement (100) according to the preceding claim, wherein a plate body of the layer (20) and a plate body of the bipolar plate (1) consist of different materials. [18] Arrangement (100) according to one of claims 14-17, comprising two sealing arrangements (15, 16) which are arranged on opposite sides of the bipolar plate (1), wherein the first sealing elements (31, 33) of the sealing arrangements (15, 16) seal the through-opening (4, 5) of the bipolar plate (1) on both sides of the bipolar plate (1) and / or the second sealing elements (32) of the sealing arrangements (15, 16) seal the electrochemically active region of the bipolar plate (1) on both sides of the bipolar plate (1). [19] Arrangement (100) according to one of claims 14-18, comprising at least one insulation layer, wherein the insulation layer is arranged between the frame-shaped layer (20) of the sealing arrangement (15, 16) and the bipolar plate (1) or wherein the frame-shaped layer (20) of the sealing arrangement (15, 16) is arranged between the insulation layer and the bipolar plate (1). [20] Electrochemical system, preferably electrolyzer or fuel cell stack, comprising a plurality of sealing arrangements (15, 16) according to any one of claims 1-11, a plurality of bipolar plates according to any one of claims 12-13 and / or a plurality of stacked arrangements (100, 9) according to any one of claims 14-19.

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