Bipolar plate for a fuel cell
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- CELLCENTRIC GMBH & CO KG
- Filing Date
- 2024-08-27
- Publication Date
- 2026-07-08
Smart Images
Figure EP2024073947_06032025_PF_FP_ABST
Abstract
Description
[0001] BIPOLAR PLATE FOR A FUEL CELL
[0002] The present invention relates to a bipolar plate for fuel cells, a method for producing such a bipolar plate and a fuel cell stack with at least one such bipolar plate.
[0003] Various fuel cell systems are known, for example, polymer electrolyte membrane (PEM) fuel cells, which use hydrogen as fuel. A fuel cell consists of electrodes, an anode, and a cathode, between which an electrolyte (MEA - membrane electrode assembly) is located. In a PEM fuel cell, the electrolyte is in the form of a membrane made of an ion-conducting polymer (so-called ionomer), the so-called polymer electrolyte membrane (PEM). The PEM separates the two electrodes materially and electrically from each other, but allows a specific type of ion, in this case protons, to pass through. The protons migrate through the membrane to the cathode, while the electrons pass through an external circuit to generate electrical energy. At the cathode, the protons, electrons, and oxygen react to form water.
[0004] Since the electrical voltage of a single fuel cell is limited, several cells are connected in series to form a "stack" to achieve a correspondingly higher voltage. The individual MEAs are separated from each other by bipolar plates, with the bipolar plates connecting the anodes and cathodes of consecutive MEAs to form the series circuit. A bipolar plate is responsible for supplying hydrogen and oxygen, removing water, and cooling the fuel cell stack. Furthermore, the bipolar plate on the anode side (hydrogen side) absorbs the hydrogen released from the hydrogen and then returns it to the cathode side (oxygen side).
[0005] A bipolar plate can be manufactured from two sub-plates bonded together using a suitable adhesive. A coolant can be conducted through cavities, e.g., a channel structure, between the sub-plates. A surface structure can be formed on the outward-facing surfaces, i.e., the anode and cathode sides, respectively, to conduct the hydrogen or oxygen to the MEA (usually via a corresponding gas diffusion layer). The various fluids can be introduced via adjacent ports, with fluids or reaction products consumed after the reaction being discharged via corresponding ports.
[0006] The adhesive bond not only holds the two sub-plates of the bipolar plate together, but also acts as a seal to separate the different fluids during operation. Furthermore, the adhesive bond seals the interior of the bipolar plate from its surroundings.
[0007] For proper fuel cell operation, the sealing effect of the adhesive joint must be ensured, in particular to prevent mixing of the fluids within the bipolar plate and also to prevent fluid from escaping from the bipolar plate into the environment (adhesive seal). However, it can happen that an adhesive seal develops a defect, in particular a leak, due to unfavorable circumstances during production or develops a leak over the course of operation (e.g., over several years), allowing fluid to pass through the seal at this point, resulting in mixing or leakage. A fuel cell with such a defective bipolar plate cannot be operated safely, which can result in the affected fuel stack having to be completely replaced.
[0008] The present invention is based on the object of providing a bipolar plate with improved safety, durability, and robustness. In particular, the risk of mixing of fluids within the bipolar plate due to a damaged seal between the sub-plates is to be reduced.
[0009] This object is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.
[0010] A first aspect of the invention relates to a bipolar plate for fuel cells. The bipolar plate comprises a first and a second partial plate and an adhesive connection that sealingly connects the first and second partial plates. The first and second partial plates are joined together such that outwardly facing surfaces of the partial plates form a cathode side and an anode side of the bipolar plate, respectively, wherein the partial plates each have, on at least one of their surfaces, a surface structure with corresponding connections for conducting a fluid along the respective surface. The adhesive connection connects the partial plates to one another via their inwardly facing surfaces and has a plurality of webs.The adhesive connection seals the structures of the inward-facing surfaces against each other and has at least two webs spaced apart from each other by a gap as a multiple seal at least between two adjacent connections.
[0011] The invention is therefore based on proposing a special design for the adhesive connection between the partial plates of the bipolar plate. In particular, it is provided that the sealing connection between two adjacent connections is formed by spaced-apart webs, thereby forming a multiple seal with a gap between the webs of the multiple seal. The multiple sealing significantly reduces the risk of leakage. As long as only one web (or not all webs) of the multiple seal has a damaged area, in particular a leak, the seal is still guaranteed. The risk of fluid being exchanged between the connections is significantly reduced compared to a single seal, since this would require all webs of the multiple seal to have a damaged area.By providing the gap between the bars, the likelihood of a damage in one of the bars spreading to the other can be reduced. Furthermore, capillary action can be avoided or reduced, which, in the case of damage in both bars, would create a virtually direct connection between the adjacent terminals. Overall, this significantly improves the safety, durability, and robustness of the bipolar plate.
[0012] While the multiple seal may be particularly important for adjacent connections for introducing fluids, it is understood that it can also be provided for adjacent connections that discharge used fluids or reaction products from the bipolar plate. In particular, the multiple seal can be provided between adjacent connections designed to introduce the oxidant (particularly oxygen) or the fuel (particularly hydrogen), since mixing of the fluids (gases) in this case would be particularly damaging to a fuel cell with a correspondingly damaged bipolar plate. In particular, if such a mixture came into contact with the MEA, the damage to the fuel cell would be considerable. At the very least, however, the performance of the fuel cell would collapse and its service life would be significantly reduced.The term "subplate" used here refers in particular to a component of a bipolar plate that provides one of the two surfaces of the bipolar plate. Two subplates together (optionally with additional components such as seals, coatings, connections, etc.) form a bipolar plate. One subplate forms the anode side of the bipolar plate, while the other subplate forms the cathode side of the bipolar plate. The two subplates are accordingly also referred to as anode plate (or anode subplate) and cathode plate (or cathode subplate). The subplates are in particular essentially plate-shaped. To form the bipolar plate, they are joined together, in particular glued, whereby they can thereby also be connected in an electrically conductive manner.
[0013] The term "surface structure" used here refers in particular to a surface structure of a partial plate which is configured to conduct a fluid along the surface of the partial plate. The channels of the surface structure can accordingly have a course (continuous or branched) which allows a uniform distribution of the fluid over the surfaces of the bipolar plate. A gas diffusion layer (GDL) usually borders the surface structure on the anode side and cathode side. A hollow channel structure can be formed between the two partial plates, which is formed by a surface structure on the inward-facing surface of at least one of the partial plates (on one of the partial plates or on both). This hollow channel structure can be configured to conduct a coolant, which is then accordingly passed through the bipolar plate.Accordingly, the two partial plates can each have a surface structure on both surfaces.
[0014] The term "ports" used here refers specifically to the bipolar plate ports for introducing fluids or discharging used fluids or reaction products. Due to the flat design, the ports are typically arranged side by side and connected to the surface structures accordingly. The ports for introducing and discharging fluids can be located near opposite edges of the bipolar plate. The term "adjacent ports" used here therefore refers specifically to (adjacent) ports for different fluids.
[0015] The term "multiple seal" as used here refers specifically to a sealing design or sealing system in which areas to be sealed against each other are sealed against each other by more than one seal. A (single) seal can be formed by one web, whereby a multiple seal is then formed by several webs, for example, two ("double seal") or three or more. The individual webs of the multiple seal necessarily all extend between the two areas to be sealed against each other (in particular between two adjacent connections) to form the multiple seal, for example, all parallel to each other.
[0016] The term "web" used here refers specifically to a part of the adhesive joint, including the multiple seal. A web is formed in particular by a path along which the adhesive is applied (e.g., as a so-called adhesive bead). The adhesive joint forms a sealed connection between the two partial panels and can therefore also be referred to as an adhesive seal. A web can also be referred to as a "sealing lip," "sealing bead," "sealing rib," or similar.
[0017] As used herein, the terms "comprises," "includes," "includes," "has," "has," "with," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.
[0018] Furthermore, unless explicitly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).
[0019] The terms "a" or "an" as used herein are defined as "one or more." The terms "another" and "another," and any other variations thereof, are defined as "at least one other."
[0020] The term "plurality" as used here is to be understood in the sense of "two or more". The term "configured" or "set up" to perform a specific function (and respective variations thereof) is to be understood, within the meaning of the invention, that the corresponding device is already in a design or setting in which it can perform the function or is at least adjustable - i.e. configurable - so that it can perform the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that configuration can be carried out by selecting one of these configurations or operating modes.
[0021] Preferred embodiments of the bipolar plate are described below, which can each be combined with each other as well as with the other aspects of the invention described, unless this is expressly excluded or is technically impossible.
[0022] In some embodiments, the webs of the multiple seal, together with webs of the adhesive connection running transversely thereto, form at least one circumferentially closed barrier chamber as an intermediate space. The circumferentially closed barrier chamber thus not only provides a seal against each of the adjacent connections, but also a seal against the environment. If a fluid escapes from the relevant connection into the sealing chamber through a leak in one of the seals, this also prevents the fluid from escaping from the bipolar plate into the area surrounding the bipolar plate. This further improves safety, durability, and robustness. In order to achieve a further improved seal even in the event of damage to both webs, particularly if these occur offset along the length of the webs, it can be provided to divide the barrier chamber into two or more partial barrier chambers by at least one further transverse web.Furthermore, a suction device for the barrier chamber can be provided in order to suction the fluid entering the barrier chamber in the event of damage or - in the event of leaks in both webs - to suck the fluid mixture out of the barrier chamber. Alternatively, embodiments would also be conceivable in which the barrier chamber is filled with a barrier fluid, in particular a (viscous) liquid fluid, in order to prevent entry into the barrier chamber. In some alternative embodiments, the webs of the multiple seal, together with a web of the adhesive connection running transversely thereto, form the intermediate space, wherein the intermediate space has an opening on its circumference towards the area surrounding the bipolar plate. In contrast to the circumferentially closed barrier chamber just described, the opening does not prevent fluid from escaping through one of the webs, but the safety, durability, and robustness can nevertheless be increased, particularly compared to a single seal.In the event of damage to any of the webs of the multiple seal, the risk of fluids transferring between the two connections (and thus mixing between the two surface structures) can be reduced. By opening the gap to the environment, the two fluids can escape, so that the lower pressure in the gap compared to the connections reduces the risk of fluid (especially a "foreign" fluid) entering the area of the connections.
[0023] In some embodiments, the webs of the multiple seal run parallel to each other. This allows the multiple seal to be designed in a particularly space-saving manner. The width of the gap, i.e., the spacing of the webs, can be, for example, in the range of 0.75 mm to 8 mm, in particular in the range of 1.2 mm to 5 mm.
[0024] In some embodiments, the multiple seal is a double seal with two spaced-apart webs. This allows the above-described effect to be effectively achieved while requiring minimal space for the multiple seal. While this effect can be further enhanced, for example, with a triple seal, a double seal may still be more advantageous since this requires more space and the space on the sub-plates not occupied by the surface structure and connections is limited.
[0025] In some embodiments, the webs of the adhesive connection, in particular all webs, have a constant width. This can improve the production of the bipolar plate. The width of the webs can, for example, be in the range of 2.5 mm to 3.5 mm. While an improved seal could in principle be achieved simply by widening the webs at the desired locations, a pattern with different web widths can only be implemented with increased effort. By providing the multiple seal with several webs instead of widening one web, a manufacturing process can be realized in which the produced webs of the adhesive connection have the same width, which can increase the efficiency of the process. The shortest possible process time is particularly important for large batch sizes.
[0026] In some embodiments, the webs of the adhesive bond, in particular all webs, are connected. This also allows for improved production of the bipolar plate. The trajectory with which the webs are produced, i.e., the application of corresponding adhesive tracks (for example, as "adhesive beads") (see below), can be optimized such that interruptions in the application of the webs can be minimized, or the webs can possibly even be produced continuously without discontinuity. This can increase the efficiency of the production process. Combined with the previously described constant width of the webs, a further improved production process results.
[0027] In some embodiments, the adhesive bond is made from an adhesive material made of a plastic material with an electrically conductive additive. For example, two-component adhesives such as 2K polymer resins (e.g., 2K epoxy resins) can be used, wherein one component can be applied to one of the partial panels and the other component to the other of the partial panels, such that the components react with each other when the partial panels are joined. The components can also be provided in the form of a microencapsulated adhesive. The two different microencapsulated adhesives can form the two components of the two-component adhesive, with the microcapsules bursting when the partial panels are joined, so that the two components are mixed. Alternatively, various one-component adhesives can also be used.With an electrically conductive additive, such adhesives are also referred to as electrically conductive adhesives (EGAs). ECA formulations typically consist of a polymer resin component containing electrically conductive particulate fillers, such as metal particles. The particle size is typically in the micron range. Electrical conductivity of the adhesive bond can also be achieved by adding carbon fibers, graphite, or carbon black.
[0028] In some embodiments, the sub-plates are made of a metallic material (metallic bipolar plate). The metallic material can be stainless steel, aluminum, or titanium. Stainless steel is easy to process and cost-effective. In particular, stainless steel grade 1.4404 or 1.4435 (stainless steel 316L) can be used.
[0029] In some embodiments, the sub-plates are made of a non-metallic material. The non-metallic material can be a plastic material with an electrically conductive component, such as an epoxy resin-carbon mixture. For example, it can be a mixture of (thermoset) curing adhesives based on epoxy resin or phenolic resin (e.g., <25%) with a proportion of carbon black (carbon black conductive particles) (e.g., <5%), graphite (e.g., <85%), release agents (<5%), and stabilizers (e.g., <3%). Such a bipolar plate can be referred to as a carbon or carbon / composite bipolar plate.
[0030] In some embodiments, the sub-plates are made of both a metallic material described above as the core and a non-metallic material described above as the coating (hybrid bipolar plate).
[0031] A second aspect of the invention relates to a method for producing a bipolar plate, in particular a bipolar plate according to the first aspect. A first and a second partial plate are provided, each having a surface structure on at least one of their surfaces, with corresponding connections for conducting a fluid along the respective surfaces. An adhesive is then applied to a surface of at least one of the partial plates in webs (i.e., linearly), with two spaced-apart webs being applied at least between two adjacent connections. The partial plates are then joined together, for example, brought together and then pressed, in such a way that outward-facing surfaces of the partial plates form a cathode side and anode side, respectively, of the bipolar plate.The adhesive strips form an adhesive connection with a plurality of webs between the partial plates, which seals the surface structures against each other and has at least two webs spaced apart from each other by a gap as a multiple seal at least between the two adjacent connections.
[0032] In some embodiments, the adhesive is applied to at least one of the partial panels by screen printing or by means of a dispenser such that the webs have the same width. As explained above with regard to the webs, a constant width of the webs can increase the efficiency of the process, which is particularly advantageous for large quantities. This applies both to a screen printing process (provided the screen is produced using a laser beam) and to a dispensing process, as this makes it possible to apply all webs with the same nozzle, constant nozzle pressure, constant nozzle speed, etc. A constant width of the webs can also be advantageous for the bonding, as this ensures that the amount of adhesive and thus also the adhesive strength is constant along all webs, i.e. across the entire adhesive bond.In addition, the panel design can be simplified because the same adhesive bonding characteristics can be taken into account across the entire (partial) panel.
[0033] In screen printing, the adhesive is applied to the sub-panels through a fine-mesh screen. The screen has areas that are impermeable and areas that allow the adhesive to pass through. The sub-panel is positioned, the screen is placed over it, and the adhesive is applied over it. A squeegee forces the adhesive through the screen onto the sub-panel, creating the desired lines. With the dispensing method, the adhesive is applied to the sub-panel in a controlled manner from a nozzle (dispenser). This can be done using an automated system that meters the adhesive and precisely applies it to the desired lines. The metering and speed can be adjusted as needed to ensure accurate and even distribution.
[0034] A third aspect of the invention relates to a fuel cell stack comprising at least one fuel cell with at least one bipolar plate according to the first aspect or at least one bipolar plate produced according to the method according to the second aspect.
[0035] The features and advantages explained with respect to the first aspect of the invention also apply accordingly to the further aspects of the invention.
[0036] Further advantages, features and possible applications of the present invention will become apparent from the following detailed description in conjunction with the drawings.
[0037] It shows:
[0038] Fig. 1 is an exploded view of a bipolar plate according to a first embodiment;
[0039] Fig. 2 is a plan view of one of the partial plates of the bipolar plate from Fig. 1; Fig. 3 is a detailed view from Fig. 2;
[0040] Fig. 4a, 4b, 4c the detailed view from Fig. 3 with various damaged areas in the multiple seal;
[0041] Fig. 5 is a detailed view according to a second embodiment; and
[0042] Fig. 6a, 6b, 6c the detailed view from Fig. 5 with various damaged areas in the multiple seal.
[0043] Throughout the figures, the same reference numerals are used for the same or corresponding elements of the invention. The figures are schematic and therefore do not necessarily represent the actual objects to scale.
[0044] Fig. 1 shows a bipolar plate 10 according to a first embodiment in an exploded view. The bipolar plate 10 has a first partial plate 50, which forms, for example, the cathode side, and a second partial plate 60, which then correspondingly forms the anode side. During operation, an MEA is adjacent to the cathode side and the anode side, respectively, in a fuel cell stack. Corresponding connections 11, 12, 13, 14, 15, 16 are provided. A cathode gas (oxidizing agent, in particular oxygen) is supplied via the inlet 12 of the bipolar plate 10 and then flows over the cathode side of the bipolar plate 10 along a surface structure 51, which is formed, for example, by a plurality of corresponding channels. Corresponding reaction products (in particular water) leave the bipolar plate 10 via the outlet 15.An anode gas (fuel, in particular hydrogen) is supplied in a similar manner via inlet 11, flows over the anode side over a corresponding surface structure 61 (not visible in Fig. 1, but comparable to surface structure 51). Residues are discharged via outlet 14. A coolant is supplied via inlet 13, flows through hollow channels inside the bipolar plate 10, and finally leaves the bipolar plate 10 at outlet 16. The hollow channels inside the bipolar plate 10 are formed by surface structures 52, 62 on the inward-facing surfaces of the partial plates 50, 60. The invisible surface structure 52 corresponds in design to the surface structure 62.
[0045] The partial plates 50, 60 of the bipolar plate 10 are connected to one another by means of an adhesive connection 20, which simultaneously seals the various fluid regions from one another and from the environment 70 of the bipolar plate 10. The partial plate 60 with the adhesive connection 20 is shown in plan view in Fig. 2. In addition to the webs of the multiple seal(s) 28 described in more detail below, the adhesive connection comprises the webs 21, 22, 23, 24, which are all interconnected here. The webs 21, 22 on the circumference serve to seal against the environment 70, while the webs 23, 24 seal the connections to the inside. In the area of the outlets 14, 15, a single seal may be sufficient instead of the multiple seal 28', since any mixing of the fluids at the outlets is less critical.
[0046] In particular, an electrically conductive adhesive (EGA) can be used as the material for the adhesive bond to create an electrical connection between the two sub-plates 50, 60. ECA formulations typically consist of a polymer resin component with electrically conductive particle fillers.
[0047] A detailed view of the adhesive connection 20 of the bipolar plate 10 according to the first embodiment is shown in Fig. 3. In particular, the adhesive connection 20 is shown here in the region of the adjacent connections 11, 12. Sealing between these two connections is particularly important to prevent mixing of the anode gas and the cathode gas at the inlets. Therefore, a multiple seal 28 is provided, which is formed in particular from the webs 25, 26, which lie between the connections 11, 12 and are spaced from one another by a gap 40. According to this embodiment, the gap 40 is closed by the lateral webs 22, 24, so that a circumferentially closed barrier chamber is formed.
[0048] In Fig. 4a, 4b and 4c, different scenarios are shown in which the multiple seal 28 has different damaged areas 31, 32 in the webs 25, 26, which sever the respective web and thus can lead to a passage of fluid through the respective web (“leak”).
[0049] In Fig. 4a and 4b, only one of the webs 25, 26 exhibits a damaged area 31 or 32. Since the other web 25, 26 is still intact, fluid only leaks into the gap 40, thus ensuring the seal between the connections 11, 12. Furthermore, the circumferentially closed shape also prevents fluid from leaking into the surrounding area 70 of the bipolar plate 10.
[0050] In Fig. 4c, both webs 25, 26 each exhibit a damaged area 31, 32. While this can lead to mixing of the two fluids, the probability is significantly reduced. If the probability that only one of the webs 25, 26 exhibits a damaged area were, for example, 1%, the probability that the case shown in Fig. 4c would occur would be only 0.01%.
[0051] A detailed view of the adhesive connection 20 of the bipolar plate 10 according to a second embodiment with a multiple seal 29 is shown in Fig. 5. In contrast to the multiple seal 28 of the first embodiment, the web 22, which forms a seal against the environment 70 of the bipolar plate 10, has an opening (gap) 42 in the region of the intermediate space 41. The intermediate space 41 is thus not circumferentially closed as in the first embodiment, but is open toward the environment 70.
[0052] In Fig. 6a, 6b and 6c, analogous to Fig. 4a, 4b and 4c, different scenarios are shown in which the multiple seal 29 has different damaged areas 31, 32 in the webs 25, 26, which sever the respective web and thus can lead to a passage of fluid through the respective web.
[0053] In Fig. 6a and 6b, only one of the webs 25, 26 exhibits a damaged area 31 or 32. Since the other web 25, 26 is still intact, fluid only leaks into the gap 41, thus maintaining the seal between the connections 11, 12. However, fluid can escape from the gap 41 into the environment 70 (dashed arrows). This is less critical than mixing of the fluids within the fluids, so this risk can be accepted.
[0054] In Fig. 6c, both webs 25, 26 each have a damaged area 31, 32. Due to the open design of the intermediate space 41, the fluids can escape into the environment 70. This can reduce the risk of mixing of the fluids from the two connections 11, 12, since the outwardly open design means that the pressure in the intermediate space 41 is lower than in the area of the connections 11, 12. Therefore, the two fluids escaping through the damaged areas 31, 32 are more likely to escape through the opening 42 into the environment 70 (indicated by the dashed arrows) than to penetrate through the other damaged area 31, 32 into the area of the adjacent connection 11, 12.
[0055] While at least one exemplary embodiment has been described above, it should be appreciated that a wide variety of variations exist. It should also be understood that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide a guide to implementing at least one exemplary embodiment; it being understood that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the subject matter as defined in the appended claims, as well as their legal equivalents.
[0056] LIST OF REFERENCE SYMBOLS
[0057] 10 bipolar plate
[0058] 11 Connection (inlet)
[0059] 12 Connection (inlet)
[0060] 13 Connection (inlet)
[0061] 14 Connection (outlet)
[0062] 15 Connection (outlet)
[0063] 16 Connection (outlet)
[0064] 17 Surface structure
[0065] 20 Seal (adhesive joint)
[0066] 21 - 27 Bridge
[0067] 28, 29 Multiple seal
[0068] 31 , 32 Damaged area (leak)
[0069] 40 Intermediate space (barrier chamber)
[0070] 41 space
[0071] 42 Opening
[0072] 50 partial plates
[0073] 51 outward-facing surface structure
[0074] 52 inward-facing surface structure
[0075] 60 partial plate
[0076] 61 outward-facing surface structure
[0077] 62 inward-facing surface structure
[0078] 70 surroundings
Claims
CLAIMS 1. Bipolar plate (10) for fuel cells, comprising: a first and a second partial plate (50, 60) which are joined together in such a way that outwardly facing surfaces of the partial plates (50, 60) form a cathode side and anode side of the bipolar plate (10), wherein the partial plates (50, 60) each have on at least one of their surfaces a surface structure (51, 61) with corresponding connections (11; ..., 16) for conducting a fluid along the respective surface; and an adhesive connection (20) which connects the partial plates (50, 60) to one another via their inwardly facing surfaces and has a plurality of webs (21, ..., 27), wherein the adhesive connection (20) seals the surface structures (51, 61) against one another and has at least two webs (25, 26) spaced apart from one another by an intermediate space (40; 41) as a multiple seal (28; 29) at least between two adjacent connections (11; 12).
2. Bipolar plate according to claim 1, wherein the webs (25, 26) of the multiple seal (28) together with webs (22, 24) of the adhesive connection (20) extending transversely thereto form at least one circumferentially closed barrier chamber as an intermediate space (40).
3. Bipolar plate according to claim 1, wherein the webs (25, 26) of the multiple seal (29) together with a web (24) of the adhesive connection (20) extending transversely thereto form the intermediate space (41), wherein the intermediate space (41) has an opening (42) on its circumference towards an environment (70) of the bipolar plate (10).
4. Bipolar plate according to one of the preceding claims, wherein the webs (25; 26) of the multiple seal (28; 29) run parallel.
5. Bipolar plate according to one of the preceding claims, wherein the multiple seal (28; 29) is a double seal with two spaced-apart webs.
6. Bipolar plate according to one of the preceding claims, wherein the webs (21, ..., 27) of the adhesive connection (20) have the same width.
7. Bipolar plate according to one of the preceding claims, wherein the webs (21, ..., 27) of the adhesive connection are connected.
8. A method for producing a bipolar plate (10) for fuel cells, the method comprising: Providing a first and a second partial plate (50, 60) each having a surface structure (51, 61) on at least one of its surfaces with corresponding connections (11; ..., 16) for conducting a fluid along the respective surfaces; Applying an adhesive to a surface of at least one of the partial plates (50, 60) in strips, wherein two spaced-apart strips are applied at least between two adjacent connections (13, 14); Joining the partial plates (50, 60) together in such a way that outwardly facing surfaces of the partial plates (50, 60) form a cathode side or anode side of the bipolar plate (10), wherein an adhesive connection (20) with a plurality of webs (21, ..., 27) is formed between the partial plates (50; 60) by the adhesive strips, which seals the surface structures (51, 61) against one another and has at least two webs (25, 26) spaced apart from one another by an intermediate space (40; 41) as a multiple seal (28; 29) at least between the two adjacent connections (13, 14).
9. The method according to claim 8, wherein the adhesive is applied by screen printing or by means of a dispenser to at least one of the partial plates (50, 60) such that the webs have the same width.
10. A fuel cell stack comprising at least one bipolar plate (10) according to one of claims 1 to 7 or a bipolar plate (10) produced according to a method according to claim 8 or 9.