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

Abstract

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 area in a frame-shaped manner, wherein the recess (23) extends over this area 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 guiding a fluid through it, and - a first elastomeric sealing element (31, 33) which rests against the inner edge (27, 28) of the passage opening (24, 25) and projects laterally into the passage opening (24, 25) to seal the passage opening (24, 25) and / or - 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).

Description

The present invention relates to a sealing arrangement, a bipolar plate and an arrangement for an electrochemical system and an electrochemical system. The electrochemical system can be, for example, a fuel cell stack, an electrolyser or a redox flow battery.Generally, electrochemical systems such as electrolysers or fuel cell stacks typically comprise a stack of individual electrochemical cells each having a plurality of layers including at least one separator plate and a membrane electrode assembly (MEA), each individual cell being bounded by two adjacent separator plates. The stack of electrochemical single cells may have two end plates that compress the electrochemical single cells together and provide stability to the stack. Furthermore, the electrochemical single cells may comprise gas diffusion layers (GDL) or porous transport layers (PTL) arranged between the separator plate and the membrane electrode assembly. The separator plate can fulfil several functions: indirect electrical contacting of electrodes of the membrane electrode arrangement (MEA), separation of media such as water, oxygen or hydrogen and electrical connection of the adjacent electrochemical individual cells. The separator plate is often also referred to as a bipolar plate.The separator plate comprises at least one through-opening, sometimes also called a port, as inlet or outlet for passing a fluid through the separator plate, a flow field having an electrochemically active region, and a fluid guiding structure lying therebetween for guiding the fluid between the through-opening and the flow field.The separator plate can be formed, for example, in one or more layers. While separator plates in fuel cells are often two-ply, so that cooling fluid can flow between the two individual plies, separator plates in electrolysers are generally single-ply, since additional cooling is not necessary. Two-layer separator plates sometimes also exist in electrolyser applications. In this case, for example, the flow field can be configured as an additional metallic layer which is mounted on a metallic base plate in order to form the bipolar plate.In addition to the separator plates, MEA, GDL or PTL mentioned, further layers can also be provided. Thus, cell frames and / or cell seals may be disposed between adjacent separator plates to seal the cells. The stack of electrochemical individual cells must namely be sealed with respect to an outer space, since a fluid or medium within the electrochemical individual cells is often under overpressure compared to the external pressure. The fluid may comprise, for example, hydrogen, air or oxygen, water and / or mixture(s) thereof. In an electrolyser, a pressure difference between the environment and the interior of an electrochemical cell can frequently be more than 20 bar. Thus, on the product side, for example the H 2- side, the pressure can be, for example, up to 40 bar, while the pressure on the reactant side, for example the H 2 O side, is only up to 2 bar. It is therefore important to seal the flow field of the fluid from the environment and also within the electrochemical system. For this purpose, the electrochemical system can have for each of the electrochemical individual cells at least one cell frame running around the outer edge of the electrochemical individual cell in order to achieve a sealing effect. In addition, the electrolyser can comprise one or more sealing layers or cell seals for each of the electrochemical individual cells in order to reinforce the sealing effect.For sealing the flow field and / or the through-openings, sealing beads molded into the separator plates, elastomer seals injection-molded onto a metallic layer of the separator plate, or combinations thereof are often used. In order to avoid leaks, it is important here that the elastomer seal is connected as firmly as possible to the metallic layer. If the elastomer seal no longer seals well, the separator plate including the elastomer seal and the metallic layer must be replaced in the event of repair or maintenance. If the separator plate is to be reused, the elastomer seal must be removed very laboriously and a new elastomer seal must be applied.The elastomer seals or sealing beads mentioned are in a force-fit connection, i.e. along the pressing force used to press the stack of separator plates together. Secure pressing of the seals over the complete stack is thus usually highly dependent on manufacturing tolerances and operating situations. The operating pressures of modern electrolysers of up to 40 bar or even more can therefore quickly become a problem with the seals currently used.In conventional sealing concepts, a groove formed in the metallic layer is often provided for receiving an elastomeric seal, wherein the elastomeric seal is generally sprayed into the groove. Due to the groove and the injected elastomer seal, the space requirement in the pressing direction is relatively large. In addition, in such sealing concepts, the metallic layer is in contact with the fluid, which has an influence on the material selection of the metallic layer.There is thus a continuous need to further increase the tightness of the system, to prevent or at least to reduce a pressure loss or a fluid loss and / or to increase the safety of the system. The present invention has been devised to meet this need and at least partially solve the above problems.The present invention is defined by the subject matter of the independent claims. Further developments are described in the dependent claims and in the following description.According to a first aspect, a sealing arrangement for an electrochemical system is proposed. The sealing arrangement comprises:a frame-shaped layer having a cutout, wherein the layer surrounds an electrochemically active region in a frame-shaped manner, wherein the cutout extends over this region and has an inner edge, wherein the layer additionally has at least one passage opening having an inner edge for passing a fluid through, anda first elastomeric sealing element which abuts the inner edge of the passage opening and projects laterally into the passage opening in order to seal and / or seal the passage openinga second elastomeric sealing element which abuts the inner edge of the recess and extends laterally into the recess to seal the recess.Thus, only the first sealing element or only the second sealing element or the combination of the two sealing elements can be provided. Such a sealing arrangement is sometimes also known as a cell frame, since the sealing arrangement extends in the form of a frame and is suitable for use in an electrochemical cell, in particular for sealing the electrochemical cell. The sealing arrangement can be provided, for example, on the cathode side and / or on the anode side in an electrochemical cell.In intended use, the sealing arrangement is pressed together with further elements or layers. During the pressing of the sealing arrangement, the first sealing element and / or the second sealing element are typically in force bypass and are pressed laterally or radially in the direction of the regions to be sealed, i.e. the through opening or recess. This has the advantage that manufacturing tolerances and operating parameters with respect to the sealing potential play a lesser role.It can be provided that the first sealing element abuts circumferentially on the inner edge of the through-opening and / or that the second sealing element abuts circumferentially on the inner edge of the recess. In the intended use of the sealing arrangement, the first sealing element and / or the second sealing element are usually in contact with the fluid. The sealing arrangement is usually designed in such a way that the layer does not come into contact with the fluid, cf. the description further below. As a result, materials can be used for the layer which are normally not suitable for use in the electrochemical system on account of the contact with the fluid. Thus, plastics, metals or combinations thereof can be used for the layer, which plastics are more cost-effective and / or easier to process than materials conventionally used for the cell frame, such as stainless steel or titanium.The layer often has a first side (first flat side) and a second side (second flat side), which are arranged opposite one another and generally extend in a planar manner. It can be provided that the first sealing element and / or the second sealing element, in an uncompressed state of the sealing arrangement, project beyond the first side of the layer and / or the second side of the layer in the vertical direction-i.e. the compression direction which is oriented parallel to a surface normal of the layer, for example the z direction. The horizontal direction is parallel to the layer or to the layer plane. During the pressing of the sealing arrangement, the vertical protrusion is pressed laterally in the direction of the recess or the through-opening, so that the corresponding sealing element in the pressed state ends substantially flush with the layer.In many embodiments, the first sealing element is injection-molded onto the inner edge of the through-opening and / or the second sealing element is injection-molded onto the inner edge of the recess. In these embodiments, the first sealing element and / or the second sealing element can be designed in particular as "edge-moulded" sealing profiles.The sealing arrangement may comprise an elastomeric fluid guiding structure having a plurality of fluid passages for passing a fluid from the passage opening to the recess or vice versa. The fluid-guiding structure is usually formed integrally with the first sealing element and / or the second sealing element. In some examples, the fluid guiding structure connects the first sealing element to the second sealing element, in particular in a materially bonded manner. It can thus 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 guiding structure in the direction perpendicular to a flow direction of the fluid.In some embodiments, the recess and the through opening form a common opening in the frame-shaped layer. In this case, the cutout and the passage opening can be spatially separated from one another by the elastomeric fluid guide structure, in particular separated from one another only by the elastomeric fluid guide structure. Thus, only the material of the fluid guiding structure can run between the recess and the through-opening, without material of the layer being present here.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 of the fluid, while the other of the through-openings can be designed as a fluid outlet for the same fluid and a further fluid. On the cathode side, both through-openings can be designed as a fluid outlet. The cutout is then arranged in each case between the two through-openings, in particular arranged between the two through-openings in the fluid flow direction.The layer may be made of a metallic material such as aluminum, steel, titanium or 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 manufactured from a material which does not have to be corrosion-resistant, such as aluminum or (stainless) steel.For example, the first sealing element and / or the second sealing element are made of fluororubber, FKM, and / or ethylene-propylene-diene rubbers, EPDM and / or a silicone. The first sealing element and the second sealing element can be made of the same material or of 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 component of a single sealing element.According to another aspect of the present specification, a bipolar plate for an electrochemical system is provided. The bipolar plate comprises a flow field having an electrochemically active region and at least one through opening for passing a fluid. The bipolar plate is substantially flat between the flow field and the through hole. 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 the stated areas, the bipolar plate has in particular no sealing elements such as sealing beads, elastomer seals and / or depressions for receiving elastomer seals. The sealing of the through-opening and / or of the flow field and the fluid line between the through-opening and the flow field are therefore taken over by the sealing arrangement described above, while the bipolar plate is designed for the electrical contacting and separation or distribution of the media. Because the bipolar plate itself does not have an elastomer seal around the through-openings and the flow field, the bipolar plate can be removed relatively easily in the event of service, serviced, possibly cleaned, possibly recoating and reused.The bipolar plate mentioned can be used in particular with the sealing arrangement described above. The sealing arrangement takes over sealing functions 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 takes over the fluid line function between the passage opening and the flow field via the elastomeric material of the fluid guide structure. The flow field usually has a multiplicity of channels which are formed into the bipolar plate, for example by means of stamping, hydroforming and / or deep drawing. The bipolar plate can be, for example, single-layer or two-layer. The bipolar plate may be made of titanium or stainless steel, for example.According to a third aspect, an arrangement for an electrochemical system is provided. The sealing arrangement and the bipolar plate are positioned relative to one another in such a way that the through-openings of the bipolar plate and of 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 configured to seal the through-opening of the bipolar plate. Alternatively or additionally, the second sealing element is configured to seal the electrochemically active region of the bipolar plate.It can be provided that the through-opening formed in the bipolar plate is smaller than the through-opening formed in the layer. In this case, 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 consist of different or of the same materials. Because preferably only the sealing elements of the layer are in contact with the fluid, the layer can be manufactured from a different material than the bipolar plate, in particular from a material other than the relatively expensive titanium.Two sealing arrangements of the type described above can be provided for each bipolar plate. The arrangement may have two sealing arrangements which are arranged on opposite sides of the bipolar plate, wherein the first sealing elements of the sealing arrangements seal the passage 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 assemblies may be provided on a cathode side of the bipolar plate, while the second of the two sealing assemblies may 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 in such a way that their fluid-conducting structures face the bipolar plate and in particular lie on the bipolar plate.In addition, the arrangement can also have at least one insulation layer and / or insulation coating for electrical insulation. The insulation layer and / or insulation coating can be arranged on one side or on both sides of the sealing arrangement. The insulation layer and / or insulation coating can be arranged between the frame-shaped layer of the sealing arrangement and the bipolar plate. Alternatively, the frame-shaped layer of the sealing arrangement can be arranged between the insulation layer and the bipolar plate. Preferably, no additional layer or coating is located 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 configured to seal the insulation layer with respect to 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 the intended use of the arrangement. The first sealing element and / or the second sealing element are often likewise designed to be electrically insulating.The assembly may further include a membrane electrode assembly (MEA) disposed between two sealing assemblies and / or a porous transport layer (PTL) or gas diffusion layer (GDL) disposed between the MEA and the flow field of the bipolar plate.According to a further aspect, an electrochemical system is proposed, preferably an electrolyser or fuel cell stack. The system includes 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.The electrochemical system can be, for example, an electrolyser. However, the present specification is not limited to an electrolyser. Alternatively, the electrochemical system can also be a fuel cell system or a redox flow battery. In an embodiment where the electrochemical system is an electrolyser, water is often the reaction medium, while hydrogen or oxygen may be the product medium or media. In a fuel cell system, hydrogen and oxygen are often the reaction media, while water is the product medium.Exemplary embodiments of the sealing arrangement, the bipolar plate, the arrangement and the electrochemical system are illustrated in the appended figures and are explained in more detail with reference to the following description. The following are shown: FIG. 1 shows an exploded illustration of a single cell of an electrolyser according to the prior art; FIG. 2 shows a plan view of a bipolar plate according to the prior art; FIG. 3 schematically illustrates 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 illustration of a detail from 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 illustration of a detail from FIG. 6 ; FIG. 8 schematically shows a perspective view of a composite of bipolar plate and anode-side and cathode-side sealing arrangement, viewed on the anode side; FIG. 9 schematically shows an enlarged illustration of a detail from FIG. 8 ; FIG. 10 schematically shows a perspective view of a composite of bipolar plate and cathode-side and anode-side sealing arrangement, viewed on the cathode side; FIG. 11 schematically shows an enlarged illustration of a detail from FIG. 10 ; FIG. 12 shows the composite of FIG. 8 with marked lines A-A and B-B; FIG. 13 is a sectional view taken along section A-A of FIG. 12 ; FIG. 14 is a sectional view taken along section B-B of FIG. 12 ; and FIG. 15 shows, in two partial figures, a sectional illustration through a composite of bipolar plate and cathode-side and anode-side sealing arrangement in the region of a through-opening in the uncompressed state and in the compressed state.Here and in the following, recurring features in different figures are each denoted by the same or similar reference numerals.FIG. 1 shows an exploded view of an electrochemical single cell 9, wherein the single cell 9 is part of an electrolyser. Electrolysers typically comprise a multiplicity of stacked individual cells 9. the individual cell 9 comprises two separator plates 1 and 2, two cell frames 42 and 44, a sealing layer 45 and a membrane electrode arrangement 40 having media diffusion structures 41 and 43. the media diffusion structure 43 comprises, for example, layers of carbon nonwoven, while the media diffusion structure 41 comprises metal, for example. Titanium is included in the titanium. The separator plate 1 is arranged here, for example, on the anode side of the individual cell 9. In the exemplary embodiment shown, the separator plate 2 is arranged on the cathode side of the individual cell 9. The individual layers are pressed together to form an individual cell. The individual layers each have fluid passages 46, 47, 50 arranged in alignment one above the other for introducing or discharging water, oxygen and hydrogen and positioning holes 48.A flow field of the separator plate 2 is defined by a projection of the cell frame 44 onto the separator plate 2. A projection of the cell frame 42 onto the separator plate 1 defines a flow field 3 of the separator plate 1. The cell frame 42 has not-shown distribution channels 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 from the supplied water in the electrolyser. 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 separator plates 1 shown in FIG. 1 have a round outer contour, other shapes are also possible. For example, the separator plates 1, 2 can have a rectangular outer contour, cf. FIG. 2.The separator plates 1, 2 from FIGS. 1 and 2 are exemplary separator plates according to the prior art.As already indicated above, a pressure difference between the environment and the interior of the electrochemical cell 9 can be more than 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 in order to seal the individual regions from one another.For example, elastomer seals are used which are arranged around the regions to be sealed, e.g. flow field 3 or through-openings 46, 47, 50. The elastomer seal is usually not provided over the full surface, but only on the regions of the separator plate 1, 2 to be sealed and is firmly connected to the plate body of the respective separator plate 1, 2.FIG. 2 schematically shows a plan view of a separator plate 1 for an electrolyser. The separator plate 1 comprises a metallic layer 10, which consists, for example, at least predominantly or completely of titanium or stainless steel or alloys thereof. The metallic layer 10 may 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 passage openings 4 as flat as possible. For this purpose, channel structures 6 are optionally provided in the flow field 3. The through-openings 5 are designed for discharging 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 that, on the one hand, the water cannot escape and, on the other hand, that hydrogen or ambient air cannot enter.Separator plates of fuel cells are often formed in two layers, so that each layer can be individually processed, such as embossed, surface-treated, injection-molded, etc. Separator plates 1, 2 of electrolysers, on the other hand, are often of single-layer configuration. For this reason, sealing elements 7 of separator plates in electrolyzers must be provided on both sides of an individual layer 10. In addition, the arrangement of sealing elements in a separator plate of an electrolyser results in the accumulation of different sealing elements in a narrow space. The seal members are also mutually arranged to seal both sides of the separator plate. The separator plate thus exhibits a high complexity when sealing the passage openings 4, 5 or the flow field 3 both due to the small spacing of the sealing elements and due to the mutual arrangement.As mentioned at the beginning, there is thus a constant need to improve the tightness of electrolyzers and fuel cell stacks.Figures 3-14 relate to various aspects and embodiments of the present invention.FIG. 3 shows a plan view of a bipolar plate 1 according to one embodiment of the invention. Like the bipolar plate 1 of FIGS. 1 and 2, the bipolar plate of FIG. 3 also has a flow field 3 with an electrochemically active region and a plurality of through-openings 4, 5 for passing a fluid. The flow field 3 has a multiplicity of channels 6, which are formed into the bipolar plate 1, for example by hydroforming, stamping and / or deep drawing. The bipolar plate 1 is generally single-layer, but can also be two-layer, 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.In comparison and in contrast to the bipolar plate 1 of FIGS. 1 and 2, it is evident that the bipolar plate 1 is substantially flat between the flow field 3 and the through-opening 4, 5, i.e. is configured there as a planar surface. The bipolar plate is designed as a flat, planar plate 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 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 adjoins the through opening 4, 5 and completely surrounds the through opening 4, 5. The second flat region 13 adjoins the flow field 3 and runs completely around it. In the regions 11, 12, 13 mentioned, the bipolar plate does not have sealing elements or other elevations or depressions. Thus, these regions 11, 12, 13 are free of sealing beads, elastomer seals, elastomer beads and / or depressions for receiving sealing elements.The bipolar plate 1 has two opposite sides 17, 19, wherein in FIG. 3 only the first side 17 (front side of the bipolar plate 1) is visible and the second side 19 (rear side of the bipolar plate 1) is concealed for the observer. Due to the absence of sealing elements in the bipolar plate 1, both sides 17, 19 of the bipolar plate 1 can be configured identically or identically, so that the bipolar plate 1 has a rotational symmetry axis running through the plane of the bipolar plate 1 and running parallel to the plane of the bipolar plate 1. A rotation by 180° about this axis of rotational symmetry results in the same arrangement of the bipolar plate 1, except at most for the channels 6 in the flow field 3 being oriented the other way round. In the exemplary embodiment shown, the bipolar plate 1 is single-layer and made of titanium.The sealing of the flow field 3 and the sealing of the fluid feedthroughs 4, 5 are realized by a sealing arrangement 15, 16 separate from the bipolar plate, which is described below.FIGS. 4-7 show perspective views of a sealing arrangement 15, 16 for an electrochemical system, wherein the sealing arrangement 15, 16 is configured in particular for sealing the regions 3, 4, 5 of the bipolar plate 1 of FIG. 3.The sealing arrangement 15, 16 has a frame-shaped layer 20, which can be made of metal and / or plastic. The frame-shaped layer 20 comprises a cutout 23 with an inner edge 26. the layer 20 or the inner edge 26 of the cutout 23 surrounds an electrochemically active region in a frame-shaped manner, wherein the cutout 23 extends over this region. The cutout 23 is preferably brought into alignment with the electrochemically active region of the flow field 3 of the bipolar plate 1 of FIG. 3, such that the cutout 23 of the layer 2 and the electrochemically active region of the bipolar plate 1 overlap.The layer 20 additionally has at least one through-opening 24, 25 with an inner edge 27, 28 for passing a fluid through. The through-openings 24, 25 of the layer 20 are typically brought into alignment with the through-openings 4, 5 of the bipolar plate 1 of FIG. 3. The passage openings 4, 24 and passage 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 have, for example, at least two through-openings 24, 25. In the figures, the through-openings 24, 25 of the sealing arrangement 15, 16 and the through-openings 4, 5 of the bipolar plate are provided with the same reference sign when transporting fluid(s) which flows / flow on the anode side or the cathode side of the bipolar plate 1. For example, in the case of an electrolyser, the passage openings 5, 25 are designed for transporting away 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.The sealing arrangement 15, 16 also has a first elastomeric sealing element 31, 33, which abuts the inner edge 27, 28 of the through-opening 4, 5 and projects laterally into the through-opening 24, 25 in order to seal the through-opening 24, 25. The first sealing element 31, 33 abuts in particular circumferentially on the inner edge 27, 28 of the through-opening 24, 25. The first sealing element 31, 33 is usually injection-molded in an edge-molding process onto the inner edge 27, 28 of the through-opening 24, 25.In addition, the sealing arrangement 15, 16 has a second elastomeric sealing element 32 which abuts the inner edge 26 of the recess 23 and projects laterally into the recess 23 in order to seal the recess 23. The second sealing element 32 abuts in particular circumferentially on the inner edge 26 of the recess 23. The second sealing element 32 is usually injection-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 likewise designed to be electrically insulating.In the intended use of the sealing arrangement 15, 16, the first sealing element 31 and the second sealing element 32 are preferably in contact with the respective fluid which flows through the through-opening 24, 25 or through the recess 23. The layer 20 or the material of the layer 20 cannot be in contact with the fluid (or fluids) due to the sealing of the sealing elements 31, 32. As a result, materials can be used for the layer 20 which may not be chemically resistant to the fluids used or incompatible with the fluids used, such as H 2, O 2 and H 2 O, under the operating conditions of the electrochemical cell. 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 layer 20 comes into contact with the fluids.In order that the fluid can pass from the passage opening 24, 25 to the cutout 23 and thus to the electrochemically active region, a fluid guidance structure 34 having a plurality of fluid feedthroughs 35 can be provided. The fluid guiding structure 34 is preferably likewise formed from an elastomer and is designed for the passage of the fluid from the through-opening 24, 25 to the cutout 23 or vice versa. The fluid guiding 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 by the electrochemically active region and guided to the through-opening. It can be provided that the fluid guiding structure 34 is formed integrally with the first sealing element 31, 33 and / or the second sealing element 32. Furthermore, the fluid guiding structure 34 can connect the first sealing element 31, 33 to the second sealing element 32, in particular in a materially bonded manner. It can also be provided that the first sealing element 31, the second sealing element 32 and the fluid guiding structure 34 are formed by the same element, cf. one-piece sealing element 30 in FIGS. 4-5. Similarly, the first sealing member 33, the second sealing member 32, and the fluid guiding structure 34 may be formed by the same member, see the one-piece sealing member 30 in FIGS. 6-7.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 passage opening 24, 25 of the layer 20 merge into one another before the sealing elements 31, 32, 33 are injection-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 takes place only by the provision of the fluid guiding structure 34, wherein 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 one another only by the elastomeric fluid guiding structure 34. Thus, in particular in FIGS. 8-12 the second side 22 of the layer 20 and thus also the rear side of the fluid guiding structure 34 is shown, while in FIGS. 4-7 the first side 21 of the layer 20 and the front side of the fluid guiding structure 34 is shown. In the direction of fluid flow between the through-openings 24 and the recess 23 of the anode-side sealing arrangement 16 (FIGS. 8, 9 ) or between the through-openings 25 and the recess 23 of the cathode-side sealing arrangement 15 (FIGS. 10, 11 ), therefore, no material of the metallic layer 20 runs.Separating elements 39 such as finger-shaped webs can be provided in the layer 20 in order to fluidically separate adjacent through-openings 24, 25 which can pass identical fluids from one another. The fluid guiding structure 34 is preferably connected to end sections of the finger-shaped separating elements 39, or rests on the layer 20 in the region of the end sections of the separating elements 39. The optional separators 39 additionally provide mechanical stability to the seal assembly 15, 16 by shortening the distance to be bridged by the fluid guiding structure 34.Alternatively, the fluid guiding structure 34 can rest on the layer 20, i.e. in the flow direction of the fluid, in the region between the recess 23 and the through-opening 24, 25. In this case, the recess 23 and the through-opening 24, 25 of the layer 20 are spatially separated from one another in the fluid flow direction by both the material of the layer 20 and the fluid guiding structure 34.Exemplary materials for the first sealing element 31, 33, the second sealing element 32, the fluid guiding structure 34 and the one-piece sealing element 30 are fluororubber, FKM and / or ethylene-propylene-diene rubbers, EPDM and / or silicone.FIGS. 8-12 each show an arrangement 100 for an electrochemical system. When stacking a plurality of arrangements 100, the electrochemical system can thus be realized. The arrangement 100 comprises the sealing arrangements 15, 16 of FIGS. 4-7 and the bipolar plate 1 of FIG. 3 In this case, the sealing arrangements 15, 16 are arranged on both sides of the bipolar plate 1, that is to say on opposite sides 17, 19 of the bipolar plate 1, such that a sandwich arrangement of the elements 15, 1, 16 is formed. Here, the first side 21 of the respective sealing arrangement 15, 16 usually faces the bipolar plate 1, so that the second side 22 of the sealing arrangement 15, 16 becomes visible in FIGS. 8-12. Furthermore, each sealing arrangement 15, 16 and the bipolar plate 1 are positioned relative to one another in such a way 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 with respect 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 configured to seal the through-opening 4, 5 of the bipolar plate 1. Furthermore, the second sealing element 32 is configured to seal the electrochemically active region of the flow field 3 of the bipolar plate 1. The sealing arrangement 15 thus seals the regions 3, 4, 5 on the front side 17 of the bipolar plate 1, while the sealing arrangement 16 seals the regions 3, 4, 5 on the rear side 19 of the bipolar plate.The sealing arrangements 15, 16 are generally positioned such that their fluid guidance structures 34 face the bipolar plate 1. The fluid feedthroughs 35, which are formed as channel-shaped depressions, are thus covered by the bipolar plate 1.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.For sealing the regions 3, 4, 5 of the bipolar plate 1 as well as possible, it is advantageous if the first sealing element 31, 33 and / or the second sealing element 32 of the layer 20 contact the bipolar plate 1. This also ensures that the layer 20 does not come into contact with the fluid during operation of the electrochemical cell. In this way, it can be provided that a plate body of the layer 20 and a plate body of the bipolar plate 1 consist of different materials. In addition, it can be provided that the plate body of the layer 20 is composed of a plurality of parts, i.e. is segmented using methods from the prior art.In an uncompressed state of the sealing arrangement 15, 16, the first sealing element 31, 33 and the second sealing element 32 project in the vertical direction beyond the first side 21 of the layer 20 and / or the second side 22 of the layer 20, cf. FIGS. 14A, 15A. The vertical direction is defined here such that it is parallel to the pressing force and perpendicular to the surface normal of the sealing arrangement 15, 16, cf. z-direction in FIGS. 13-15. The protrusion 51 of the respective sealing element 31, 32, 33, which thus protrudes beyond the flat sides 21, 22 of the layer 20 in the uncompressed state of the sealing arrangements 15, 16, is clearly visible here in particular in FIGS. 13-15. When pressing the sealing arrangement 15, 16 together with the bipolar plate 1, the protrusion 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 ends substantially flush with the layer 20, cf. FIGS. 14B and 15B. The sealing elements 31, 32, 33 can be dimensioned or configured here such that their lateral extension 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 in the compressed state of the sealing arrangement 15, 16.Optionally, a gap 36 can run on the surface between the fluid guiding structure 35 and the closest sealing element 31, 32, in order to offer space for the fluid guiding structure 35 to escape during compression, cf. FIGS. 9 and 11.According to the figures shown, the sealing arrangement 15 is designed to be arranged in a cathode space of the electrolyser, while the sealing arrangement 16 is arranged in an anode space of the electrolyser. However, the invention is not limited to this. The sealing assemblies 15, 16 may also find use in a fuel cell stack or other electrochemical systems.It can further be seen in FIGS. 4-14 that in the cathode-side sealing arrangement 15 the through-openings 4, 24 for the passage of water and / or oxygen through the first sealing element 31 are completely sealed in a circumferential manner, while hydrogen generated in the electrochemically active region can pass through the fluid guiding structure 34 to the through-openings 5, 25 and the fluid line 29.Accordingly, in the anode-side sealing arrangement 16, the through-openings 5, 25 for the passage of hydrogen are completely sealed by the first sealing element 31, while water can pass from the through-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 unconverted water through the fluid guidance structure 34 to the passage openings 4, 24.In the sandwich arrangement 100 of FIGS. 14, 15, one sealing arrangement 15, 16 thus completely seals the through-openings all around, while the other sealing arrangement 16, 15 allows a fluid flow from or to the electrochemically active region of the bipolar plate.The arrangement 100 can comprise further layers. For example, the arrangement 100 also 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 can 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 bear directly on the bipolar plate 1, even if further layers are present. Further additional elements are shown in FIG. 1, which can be combined with the arrangement 100 of FIGS. 8-14. Thus, the arrangement can further comprise a membrane electrode unit (MEA) which is arranged on the side of the flow field 3 of the bipolar plate 1 and / or a porous transport layer (PTL) or gas diffusion layer (GDL) which is arranged between the MEA and flow field 3 of the bipolar plate 1.It will be apparent to those skilled in the art that the features of Figures 1-15 described above may be combined, unless otherwise conflicting, and individually claimed.List of reference characters1 Separator plate 2 Separator plate 3 Flow field 4 Fluid passage opening 5 Fluid passage opening 6 Channel structures 7 Elastomer seal 8 Centring opening 9 Electrochemical cell 10 Metallic layer of the bipolar plate 11 Flat region 12 Flat region 13 Flat region 15 Sealing arrangement 16 Sealing arrangement 17 First side 18 Centring opening 19 Second side 20 Frame-shaped layer 21 First side 22 Second side 23 Cutout 24 Passage opening 25 Passage opening 26 Inner edge of the cutout 27 Inner edge of the passage opening 28 Inner edge of the passage opening 29 Fluid line 30 One-piece sealing element 31 First elastomer sealing element 32 Second elastomer sealing element 33 First elastomer sealing element 34 Fluid guiding structure 35 Fluid passage 36 Gap 37 Inner edge of the fluid passage opening 38 Inner edge of the fluid passage opening 39 Separating element 40 Membrane electrode arrangement 41 Media diffusion structure 42 Cell frame 43 media diffusion structure 44 cell frame 45 sealing layer 46 fluid passage opening 47 fluid passage opening 48 positioning hole 49 manifold channels hydrogen 50 passage openings hydrogen 51 protrusion 100 arrangement

Claims

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 passing a fluid through, and - a first elastomeric sealing element (31, 33), which abuts 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 abuts against the inner edge (26) of the recess (23) and projects laterally into the recess (23) in order to seal the recess (23).Sealing arrangement (15, 16) according to claim 1, wherein the first sealing element (31, 33) abuts circumferentially on the inner edge (27, 28) of the through-opening (24, 25) and / or wherein the second sealing element (32) abuts 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).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 beyond the first side of the layer (20) and / or the second side of the layer (20) in the vertical direction in an uncompressed state of the sealing arrangement (15, 16).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).Sealing arrangement (15, 16) according to one of the preceding claims, comprising an elastomeric fluid guiding structure (34) with a plurality of fluid passages (35) for passing a fluid from the passage opening (24, 25) to the recess (23) or vice versa.Sealing arrangement (15, 16) according to the preceding claim, wherein the fluid guiding structure (34) is formed integrally with the first sealing element (31, 33) and / or the second sealing element (32).Sealing arrangement (15, 16) according to one of the two preceding claims, wherein the fluid guiding structure (34) connects the first sealing element (31, 33) to the second sealing element (32), in particular in a materially bonded manner.The sealing arrangement (15, 16) according to any one of the three 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 each other by the elastomeric fluid guiding structure (34).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).Sealing arrangement (15, 16) according to one of the preceding claims, wherein the layer (20) is manufactured from a metallic material such as aluminium, titanium or stainless steel, plastic and / or combinations thereof, wherein the first sealing element (31, 33) and the second sealing element (32) are manufactured from the same material, in particular from fluororubber, FKM, and / or ethylene propylene diene rubbers, EPDM and / or a silicone.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 formed as an integral component of a single sealing element (30).Bipolar plate (1) for an electrochemical system, comprising: - a flow field (3) having an electrochemically active region and - at least one through-opening (4, 5) for passing a fluid, wherein the bipolar plate (1) is substantially flat between the flow field (3) and the through-opening (4, 5), wherein the bipolar plate (1) is substantially flat in a first region (12) adjoining the through-opening (4, 5) and circumferentially around the through-opening (4, 5) and / or in a second region (13) adjoining the flow field (3) and circumferentially around the flow field (3), and the bipolar plate (1) has in particular no sealing elements such as sealing beads, elastomer seals and / or depressions for accommodating elastomer seals in the said regions (12, 13).The bipolar plate (1) of the preceding claim, wherein the flow field (3) comprises a plurality of channels (6) formed in the bipolar plate (1).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 with respect to one another in such a way that the passage openings (4, 5) of the bipolar plate and the passage 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 configured to seal the passage opening (4, 5) of the bipolar plate (1) and / or wherein the second sealing element (32) is configured to seal the electrochemically active region of the bipolar plate (1).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).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).The assembly (100) according to the preceding claim, wherein a plate body of the layer (20) and a plate body of the bipolar plate (1) are made of different materials.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 passage 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).The assembly (100) according to any 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 assembly (15, 16) and the bipolar plate (1) or wherein the frame-shaped layer (20) of the sealing assembly (15, 16) is arranged between the insulation layer and the bipolar plate (1).Electrochemical system, preferably electrolyser or fuel cell stack, comprising a plurality of sealing arrangements (15, 16) according to any of claims 1-11, a plurality of bipolar plates according to any of claims 12-13 and / or a plurality of stacked arrangements (100, 9) according to any of claims 14-19.

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