Method for manufacturing a fuel cell stack

Abstract

The invention relates to a method for manufacturing a fuel cell stack (10), wherein an insulating material (15) is applied to edge regions (6) of bipolar plates (1) of a provided fuel cell stack (10). For this purpose, the insulating material (15) is sprayed onto at least one side surface (11) of the fuel cell stack (10) by means of a spraying device (21). In particular, the insulating material may be sprayed so that it penetrates at least partially between adjacent bipolar plates (1) and thereby at least partially covers the edge regions (6) of the surfaces of the bipolar plates (1) with the insulating material (15).

Description

[0001] 120096P1348PC

[0002] METHOD FOR PRODUCING A STACK OF FUEL CELLS

[0003] The present invention relates to a method for manufacturing a fuel cell stack, wherein in particular electrical insulation is produced between bipolar plates in their edge regions.

[0004] 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 is located (the membrane electrode assembly (MEA)). 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). In particular, catalyst layers are applied to both sides of the PEM, resulting in a catalyst-coated membrane (CCM). A gas diffusion layer (GDL) is then applied to each side of the CCM, ultimately forming an MEA. The PEM separates the two electrodes both materially and electrically, 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 travel through an external circuit to generate electrical energy. At the cathode, the protons, electrons, and oxygen react to form water.

[0005] Since the electrical voltage of a single fuel cell is limited, several cells are connected in series in a fuel cell stack to obtain a correspondingly higher voltage. The individual MEAs are separated from each other by bipolar plates, which connect the anodes and cathodes of successive MEAs to form the series connection. A bipolar plate performs the functions of supplying hydrogen and oxygen, removing water, and cooling the fuel cell stack. Additionally, the bipolar plate receives the hydrogen-emitting electrodes on the anode side (hydrogen side) and returns them to the cathode side (oxygen side).

[0006] For the fuel cell to operate correctly, a seal must be present between the MEA and the bipolar plates adjacent to the MEA to prevent the fluids within the fuel cell from mixing and also to prevent fluid from escaping the fuel cell into the environment. The seals, or possibly other structures, also serve to electrically insulate two adjacent bipolar plates in a fuel cell stack.

[0007] These seals or insulation components are often applied to, or even integrated into, a frame substrate of the MEA. Such a frame substrate reinforces the MEA and provides the assembly with structural support and stability. The MEA with the frame substrate, i.e., the framed MEA, is also called a MEFA (membrane electrode frame assembly). Finally, the frame substrate prevents (electrical) contact between two adjacent bipolar plates in a fuel cell stack under load, which would lead to a short circuit.

[0008] In other designs with frameless MEAs, the sealing and insulation functions must be achieved differently. In particular, insulation can be applied directly to the bipolar plates themselves. These insulating layers can be applied using processes such as inkjet or spray printing. However, if the insulating layer is to be applied to the edge of the bipolar plate, the pressure must be over-engineered due to positional tolerances in these processes. This results in overflow at at least some of the edges, requiring a complex print cavity design and a cleaning process for the print cavity. To potentially avoid this problem, the edges of the bipolar plates must remain clear for technical reasons, for example, by reducing the size of the printed image. Even when using screen printing, a small edge area must remain clear due to the printing process.In these areas, which are not insulated, an electrical short circuit can occur in a fuel cell stack, especially under load, i.e., mechanical stress or strain, for example further promoted by particle ingress, contamination, burrs, etc.

[0009] The present invention is based on the objective of providing a method for manufacturing a fuel cell stack, in particular with frameless membrane electrode arrangements, which makes it possible to apply an insulating material in a simple and efficient manner even in the edge regions of the bipolar plates, in order to ultimately further improve the safety and performance during operation of the fuel cell stack. 120096P1348PC

[0010] The solution to this problem 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.

[0011] A first aspect of the invention relates to a method for manufacturing a fuel cell stack. An insulating material is applied to the edge regions of bipolar plates of a provided fuel cell stack. For this purpose, the insulating material is sprayed onto at least one side surface of the fuel cell stack using a spray device.

[0012] The method described in the first aspect thus relates in particular to the application of an insulating material to, especially, exposed edge areas of the bipolar plates. However, the insulating material is not applied individually to the edges of the bipolar plates, particularly before they are connected to form a stack. Instead, it is sprayed laterally, i.e., sprayed onto at least one side surface, preferably all side surfaces of the entire fuel cell stack. The application of the insulating material can therefore be carried out in a single operation directly on the prepared fuel cell stack, without having to handle each bipolar plate individually. The fuel cell stack is thus protected against short circuits between two bipolar plates in a simple and efficient manner.

[0013] The term "insulating material" used here refers specifically to a material for electrical insulation. An insulating material typically has a very high electrical resistance and very low (or even no) electrical conductivity. This can be, in particular, a plastic material with suitable properties. For the present process, it is advantageous that this material can be processed in liquid form by spraying. It is understood that, for the safe operation of a fuel cell system, the insulating material should be resistant, in particular, to the reaction gases used or generated, if it comes into contact with them. This is especially important if the insulating material is also applied to the inside of the ports (through-openings).

[0014] The terms “comprises”, “includes”, “includes”, “has”, “with”, or any other variant thereof, as used herein, 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 120096P1348PC, but may include other elements not expressly listed or inherent in such method or apparatus.

[0015] Furthermore, unless explicitly stated otherwise, "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: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0016] The terms "ein" or "eine," as used here, are defined as "one or more." The terms "ein anderer" and "ein Weitere," as well as any other variant thereof, are to be understood as "at least one more."

[0017] The term "plural", as used here, is to be understood in the sense of "two or more".

[0018] For the purposes of this invention, the terms "configured" or "set up" to perform a specific function (and their respective variations) mean that the device is already in a configuration or setting in which it can perform the function, or at least that it is adjustable—i.e., configurable—so that it can perform the function after appropriate adjustment. Configuration can be achieved, for example, by adjusting parameters of a process sequence or by using switches or similar devices to activate or deactivate functionalities or settings. In particular, the device can have several predetermined configurations or operating modes, allowing configuration by selecting one of these configurations or operating modes.

[0019] Preferred embodiments are described below, which, unless expressly excluded or technically impossible, can be combined with each other as desired and, if necessary, with further aspects of the invention.

[0020] In some embodiments, the insulating material is applied directly to the edge areas of the bipolar plates.

[0021] In some embodiments, the insulating material is applied over the entire surface of the bipolar plates' edges. 120096P1348PC

[0022] In some embodiments, the insulating material is sprayed onto at least one side surface of the fuel cell stack, at least in certain areas, using the spray device.

[0023] In some embodiments, the insulating material is sprayed onto at least one side surface of the fuel cell stack by means of the spray device in such a way that the insulating material penetrates at least partially between adjacent bipolar plates and thereby covers the edge areas of the surfaces of the bipolar plates at least partially, in particular directly, with the insulating material.

[0024] In some embodiments, the insulating material is applied to the edge regions of the bipolar plates in such a way that a layer of the insulating material is formed on the edge regions of the bipolar plate, which at a first location with a highest layer thickness differs by a maximum of 50%, 30% or 10% of the layer thickness at the first location from a second location with a lowest layer thickness.

[0025] In some embodiments, the insulating material is applied to the edge regions of the bipolar plates in such a way that the thickness of the insulating material layer on the edge regions of the bipolar plate is less than the thickness of the bipolar plate.

[0026] In some embodiments, the provided fuel cell stack comprises a plurality of bipolar plates and a plurality of membrane electrode arrangements, which are arranged alternately along a vertical direction of the fuel stack to form the fuel cell stack, wherein adjacent bipolar plates in the fuel cell stack are spaced apart from each other and wherein at least a peripheral region of a surface of each of the bipolar plates is at least partially free of an insulating material.

[0027] The membrane electrode arrangements allow the bipolar plates to be spaced apart. This spacing can be less than 1 mm, for example, 0.5 mm or 0.3 mm. A coating of insulating material in the edge regions can be less than 0.1 mm thick, for example, at a spacing of 0.5 mm or 0.3 mm. Since the bipolar plates in the stack are spaced slightly apart, particularly due to the MEAs positioned between them, the insulating material can penetrate these gaps and thus create electrical insulation between two adjacent bipolar plates in the stack. However, the gaps are preferably not completely filled with the insulating material; rather, the applied layer of insulating material is thinner, particularly significantly thinner, than the height of the gap.

[0028] In some embodiments, the method includes providing the fuel cell stack, in particular for applying the insulating material to the edge areas of the bipolar plates of the fuel cell stack.

[0029] In some embodiments, the membrane electrode arrangements are frameless membrane electrode arrangements.

[0030] In some embodiments, the insulating material is applied by means of the spray device by spraying at a spray angle of less than 90 degrees relative to the vertical direction of the fuel cell stack. In other words, the application is not carried out in a spray direction perpendicular to the side surface(s) of the fuel cell stack. With perpendicular application, the insulating material could penetrate too deeply between the bipolar plates in the fuel cell stack and potentially touch the edges of the MEA or its seals, which could lead to undesirable material reactions. Instead, the application is advantageously carried out at an angle, such as a "shallow" angle relative to the surfaces of the bipolar plates, for example, at an angle of 10 to 70 degrees, preferably 20 to 60 degrees, such as 45 degrees (correspondingly analogous angles if defined relative to the vertical direction). By appropriately selecting the spray angle (and, if necessary, theBy adjusting other process parameters, a desired distribution of the insulating material in the edge areas of the bipolar plates can be achieved.

[0031] In some embodiments, the spraying device has at least one spray nozzle with a directed and flat spray pattern for applying the insulating material by spraying it onto a target area on the side surface of the fuel cell stack, which is elongated along a circumferential direction. On the one hand, the spray nozzles are thus configured to spray in a specific direction, in particular at the spray angle described above towards the side surfaces of the fuel cell stack. On the other hand, they produce a flat, i.e., essentially linear or band-shaped, spray pattern, as opposed, for example, to round, more planar spray patterns. The spray pattern is advantageously aligned parallel to the surfaces of the bipolar plates, so that controlled application of the insulating material can be achieved. 120096P1348PC

[0032] In some embodiments, the spraying device has a plurality of spray nozzles arranged side by side in a circumferential direction of the fuel cell stack, with the spraying device being moved along the vertical direction of the fuel cell stack during the application of the insulating material. In this way, the circumferential side surfaces of the fuel cell stack can be sprayed with the insulating material together in a single operation, which simplifies the process and reduces the process time, particularly compared to methods in which each side surface of the fuel cell stack would have to be sprayed individually. The spraying device is therefore dimensioned and designed to surround a fuel cell stack such that all spray nozzles are at substantially the same distance from the side surfaces of the fuel cell stack. The spraying device can be moved in any direction, i.e.,The spray pattern can be either from bottom to top or from top to bottom. The spray nozzles can all be arranged side by side at the same height, with a continuous row of spray nozzles being possible. However, it is understood that other arrangements of the spray nozzles, for example, staggered arrangements or multiple rows, could be provided.

[0033] In some related embodiments, the majority of spray nozzles are arranged and configured such that, at least in a target area on the side surface (or in a circumferential target area on the side surfaces) of the fuel cell stack, a substantially uniform spray pattern and thus a substantially uniform distribution of the insulating material is achieved. The target area can, in particular, be a band-shaped area extending around the fuel cell stack if all side surfaces are treated simultaneously. The target areas of individual spray nozzles can overlap or adjoin one another, so that no gaps are created.

[0034] In some embodiments, the insulating material is also applied, at least partially, to the edge surfaces of the bipolar plates. Particularly in the case of the described application at a specific spray angle, a coating of the edges can also be achieved. This not only provides insulation between the bipolar plates but also, depending on the application of the fuel cell stack manufactured in this way, insulation from surrounding parts. 120096P1348PC

[0035] In some embodiments, the bipolar plates each have at least one through-opening, with corresponding through-openings in the fuel cell stack each forming a passage through the fuel cell stack along the vertical direction. The fuel cell stack is arranged such that the edge regions of the surface of each bipolar plate surrounding the through-openings are at least partially free of insulating material. Such through-openings or passages are known in principle. For example, six passages can be provided, each with an inlet and an outlet for hydrogen, oxygen (or air), and a cooling medium during the operation of a corresponding fuel cell system.The insulating material is applied to the perimeter areas of the bipolar plate surfaces surrounding the through-holes. This is achieved by spraying the insulating material, at least partially, onto an inner surface of the through-holes using at least one additional spraying device, such that it penetrates at least partially between adjacent bipolar plates, thereby at least partially covering the perimeter areas of the bipolar plate surfaces surrounding the through-holes with the insulating material. In this way, the inner perimeter areas of the bipolar plates can also be coated with the insulating material in essentially the same manner as described above.

[0036] In some embodiments, the insulating material is applied directly to the edge areas of the bipolar plate surfaces that run around the through-holes.

[0037] In some embodiments, the insulating material is applied over a flat area to the edge regions of the bipolar plate surfaces that run around the through-holes.

[0038] In some related embodiments, the at least one further spray device has at least one spray nozzle with a circumferential and flat spray pattern for applying the insulating material by spraying it onto a circumferential target area on the side surface of a corresponding passage, which is elongated along a circumferential direction. As described above, this advantageously produces a flat, i.e., linear or band-shaped, spray pattern. This pattern extends from the spray nozzle in all directions (360 degrees), so that the inner surfaces of the passages can be easily sprayed. 120096P1348PC

[0039] In some embodiments, the additional spraying device has one spray nozzle per pass, and the additional spraying device is moved along the vertical direction during the application of the insulating material. The movement of the additional spraying device can be coupled to the movement of the spraying device described above, particularly with regard to direction and speed. In this way, both the side surfaces and the inner surfaces of the fuel cell stack can be sprayed with the insulating material in a single operation.

[0040] In some embodiments, the insulating material is applied such that it is only applied to a predetermined portion of the surface of the bipolar plates surrounding the through-holes. In particular, it may be possible to leave a portion of the inner surfaces of the through-holes, such as a strip running vertically, uncoated with the insulating material. This may be necessary, for example, to prevent the insulating material from clogging conductors leading from the through-holes or individual openings in the bipolar plates towards the MEA. While this does not achieve complete coating with the insulating material, excluding a portion is typically not critical.

[0041] The spray nozzles can be masked in one area (or possibly several areas) so that, for example, they no longer have a 360-degree spray pattern, but rather a less than 360 degrees, such as only 300 degrees, depending on the design of the bipolar plates and corresponding cables. The area that should remain free of insulating material is advantageously kept as small as possible. Instead of masking or modifying the spray nozzle to avoid covering this area, the described area of ​​the through-holes can also be covered. For this purpose, an adhesive strip, a protective plate, a metal rod, or similar material could be temporarily inserted into the respective through-hole.

[0042] In some embodiments, the insulating material is applied in such a way that it is only applied to a predetermined sub-area on the edge regions of the bipolar plate surfaces. Similar to the procedure described above, where certain sub-areas are omitted when spraying the inner surfaces of the passages, this may also be necessary on the side surfaces, for example, if connections for cell voltage monitoring (CVM) are provided. Similar to 120096P1348PC described above, the spray nozzles can be masked to keep desired sub-areas of the side surfaces free of insulating material. However, since the side surfaces are external, a cover can also simply be applied to the relevant area of ​​a side surface, for example, adhesive tape along the vertical direction, a protective plate, or the like.Here too, it is generally acceptable with regard to the risk of a short circuit if small areas of the edges of the bipolar plates remain free of insulating material.

[0043] In some embodiments, the application of the insulating material, in particular in the step of providing the fuel cell stack before arranging the bipolar plates and membrane electrode assemblies to form the fuel cell stack, may be preceded by further processes, as explained below.

[0044] In some embodiments, an insulating material is applied to at least one surface of the bipolar plates, at least in areas of the respective surface surrounding the membrane electrode assembly, while at least one edge region of each bipolar plate surface remains free. The insulating material can be applied to the surfaces of the bipolar plates by a printing process, such as screen printing or inkjet printing, or by spraying. By providing a uniform distribution of the insulating material across the surfaces of the bipolar plates, the electrical insulation of adjacent bipolar plates can be further improved. This edge insulation, as described above, can overlap or adjoin the uniform insulation, thus achieving a substantially complete coating of the surfaces of the bipolar plates (excluding the area of ​​the membrane electrode assembly) with the insulating material.However, under certain circumstances, the full insulating coating can be dispensed with, as the insulation of the particularly critical edge areas described above may already be sufficient to prevent a short circuit.

[0045] In some embodiments, the circumferential edges of the bipolar plates are chamfered on at least one surface of the respective bipolar plate. This increases the distance between the edges of the bipolar plates, which can also reduce the risk of short circuits. Furthermore, the sprayed insulating material can penetrate between the bipolar plates more easily, and, depending on the arrangement, any excess material can run off during spraying to prevent droplet formation. 120096P1348PC

[0046] In some embodiments, the insulating material (especially printed or sprayed onto the surface of a bipolar plate) overlaps at least partially with a chamfered area. Together with the insulating material sprayed laterally, this allows for the particularly effective production of a continuous insulating layer on the surfaces of the bipolar plates.

[0047] In some embodiments, the insulating material is applied to the edge areas of the bipolar plates and / or to the edge areas of the surfaces of the bipolar plates extending around the through-holes by means of an uninterrupted and / or single and / or common and / or continuous spraying process.

[0048] In some embodiments, the bipolar plates have chamfers on at least one of their surfaces along their circumferential edges.

[0049] A second aspect of the invention relates to a fuel cell stack manufactured according to a method according to the first aspect. In some embodiments, the fuel cell stack and / or the membrane electrode arrangements are frameless, in particular housing-free.

[0050] A third aspect of the invention relates to a manufacturing system comprising means for carrying out a method according to the first aspect.

[0051] In some embodiments of the manufacturing system, the means for carrying out the process include at least one spraying device with at least one nozzle.

[0052] A fourth aspect of the invention relates to a computer program comprising commands that cause the manufacturing system according to the third aspect to execute the process steps of the inventive method described above.

[0053] A fifth aspect of the invention relates to a computer-readable medium comprising the computer program according to the fourth aspect for carrying out the method according to the first aspect.

[0054] The computer program can be stored, in particular, on a non-volatile data carrier. Preferably, this is a data carrier in the form of an optical data carrier or a flash memory module. This can be advantageous if the computer program is to be traded as such, independent of a processor platform on which the one or more programs are to be executed. In another implementation, the computer program can exist as a file on a data processing unit, in particular on a server, and be downloadable via a data connection, for example, the Internet or a dedicated data connection, such as a proprietary or local network. Furthermore, the computer program can comprise a plurality of interacting individual program modules.

[0055] The manufacturing system according to the third aspect can accordingly have a program memory in which the computer program is stored. Alternatively, the system can also be configured to access an external computer program, for example on one or more servers or other data processing units, via a communication link, in particular to exchange data with it that is used during the execution of the process or computer program or represents outputs of the computer program.

[0056] The features and advantages explained in relation to the first aspect of the solution also apply accordingly to the other aspects of the solution.

[0057] Further advantages, features and possible applications of the present invention will become apparent from the following detailed description in conjunction with the drawings.

[0058] This shows:

[0059] Fig. 1 shows a top view of a bipolar plate;

[0060] Fig. 2 shows a top view of the bipolar plate with insulating material applied to the surface, leaving the edges uncovered;

[0061] Fig. 3 schematically shows a section through a fuel cell stack before the application of insulating material in the edge areas;

[0062] Fig. 4 schematically shows a process for applying insulating material to the edge regions of the bipolar plates; 120096P1348PC

[0063] Fig. 5 schematically shows a spraying device with several spray nozzles for spraying the outer side surfaces of a fuel cell stack;

[0064] Fig. 6 schematically shows an example of a spray nozzle with a directed, flat spray pattern;

[0065] Fig. 7 schematically shows an example of a spray nozzle with a circumferential, flat spray pattern;

[0066] Fig. 8 schematically shows a spraying device with several spray nozzles, including spray nozzles for spraying the passages through the fuel cell stack;

[0067] Fig. 9 schematically shows a process for applying insulating material to the edge areas of the bipolar plates;

[0068] Fig. 10 schematically shows bipolar plates in section with chamfered upper edges; and

[0069] Fig. 11 schematically shows bipolar plates in section with chamfered lower edges.

[0070] The same reference numerals are used throughout the figures for the same or corresponding elements of the invention. The figures are schematic and therefore do not necessarily represent reality to scale.

[0071] Fig. 1 shows a top view of a bipolar plate 1. This plate has a circumferential edge 4 and a central area 2 in which a membrane electrode assembly (MEA) 9 can be placed. Channels for supplying reaction gases (not shown) for the operation of a fuel cell run through this area; these gases are supplied and discharged via connections (see through-hole 7 in Fig. 2). Several bipolar plates 1 and MEAs 9 are stacked to form a fuel cell stack 10 (see Fig. 3). In the case of a framed MEA (MEFA), the frame substrate of such an MEA is located in area 3, which electrically insulates adjacent bipolar plates 1 from each other. In this case, however, a frameless MEA 9 is assumed, so electrical insulation must be provided in area 3 by other means.An insulating material 5 can be applied to the surface of the bipolar plate 1 using contactless methods such as inkjet printing, spraying, or screen printing. However, for technical reasons, it is unlikely that a complete coating of the entire area 3 with insulating material 5 can be achieved in this way. As explained in section 120096P1348PC, the printing pressure for a complete coating would have to be excessively high with the aforementioned methods, which could lead to overflow at least at some of the edges and potentially result in a significant cleaning effort for the print area.

[0072] Therefore, as shown in Fig. 2, the surface of the bipolar plate 3 remains free of insulating material 5 in edge regions 6, 8. This includes a circumferential edge region 6 along the circumferential edge 4, as well as an edge region 8 that extends around each of the through-holes 7 (see in particular the enlarged detail in Fig. 2). The edge regions 6, 8 typically have a width of approximately 0.1 to 1.0 mm.

[0073] Fig. 3 schematically shows a fuel cell stack 10 with bipolar plates 1 and MEA 9. An exemplary simplified structure of an MEA 9 with membrane (PEM) 9a and electrodes 9b, 9c, e.g., cathode 9b and anode 9c, is shown in Fig. 4. The MEA 9 could also be configured in reverse order with the cathode at the top and the anode at the bottom. For the sake of simplicity, other structures, such as any seals, are not shown. The bipolar plates 1 are spaced apart from each other by the MEA 9. The spacing 14 can be less than 1 mm, for example, 0.5 mm or 0.3 mm. Particularly under load, short circuits can occur in a fuel cell stack 10, especially in the exposed edge regions 6, due to pressure and any deformations, and possibly exacerbated by contamination, burrs, manufacturing tolerances, and the like.

[0074] Figures 4 and 5 illustrate a process for applying insulating material 15 to the edge regions 6. Using a spray device 21 with spray nozzles 12, the insulating material 15 is sprayed against the side surfaces 11 of the fuel cell stack 10. The spray device 21 moves along the vertical direction 13 of the fuel cell stack 10 to spray the entire side surfaces 11 with insulating material 15. In this example, the spray device 21 moves from bottom to top. However, the reverse direction is also possible. The insulating material 15 is sprayed at a spray angle, for example, in the range of 20 to 45 degrees relative to the surfaces of the bipolar plates 1. In this way, due to the gaps 14 between the bipolar plates 1, it reaches the exposed edge regions 6, overlapping here with the previously applied coating of insulating material 5.The outward-facing surfaces of the edges 4 are also coated with insulating material 15. 120096P1348PC.

[0075] Droplet formation must be avoided, for example, by appropriately selecting process parameters such as spray angle, spray quantity, spray pressure, travel speed and direction, distance, and the like. Droplet formation must be avoided because, although the edge regions 6 of the bipolar plates 1 should be sufficiently covered for electrical insulation, the spaces 14 between the bipolar plates 1 should not be completely filled vertically, as this could, for example, impair the necessary compression of seals during operation of the fuel cell stack 10. Therefore, a coating of insulating material 15 in the edge regions 6 should be less than approximately 0.1 mm thick, assuming a spacing 14 of approximately 0.3 mm.

[0076] For a uniform result, the spray nozzles 12 of the spraying device are arranged side by side around the fuel cell stack 10, or conversely, the spraying device 21 with its spray nozzles 12 is designed such that it can accommodate a fuel cell stack 10, whereby the distance between the side surfaces 11 and the spray nozzles 12 should be approximately the same at every point. In this way, a uniform coating of the edge areas 6 with the insulating material 15 can be achieved in a single operation.

[0077] Advantageously, the spray nozzles 12 have a directed and flat spray pattern ("flat jet nozzles"), the target areas of which form a continuous, band-shaped target area around the side surfaces 11 of the fuel cell stack, ensuring uniform material distribution. Such a spray nozzle 16 is also shown by way of example in Fig. 6.

[0078] Fig. 7, in contrast, shows a spray nozzle 17 with a similarly flat but circumferential spray pattern. Its target area is therefore essentially a ring. These nozzles are used to apply insulating material to the edge regions 8 of the through-openings 7.

[0079] This procedure is schematically illustrated in Fig. 8. Fig. 8 shows a fuel cell stack 10 in section. One of the spray nozzles 17 is moved along a passage 19 formed by the through-openings 7 in the fuel cell stack 10 in a similar manner along the vertical direction 13 as described in connection with Fig. 5. In this respect, essentially the same applies to the coating of the edge regions 8 as to the coating of the edge regions 6. 120096P1348PC

[0080] However, it may be necessary to protect certain areas from the insulating material. In particular, connections between the through-openings 7 and the aforementioned channel structures in the bipolar plates 1 must not be blocked. Therefore, a suitable mask 18 can be provided for the spray nozzle 17 to exclude this area. In this case, the insulating material 19 will no longer be applied completely around the perimeter areas 8. However, such a cutout is typically not critical. Instead of the mask 18, the area to be protected can also be covered, for example, by means of adhesive tape, a protective plate, a metal rod, or the like. A similar solution can also be provided for the coating of the perimeter areas 6, for example, if connections for cell voltage monitoring (CVM) must remain accessible.However, a protective device can simply be attached to the side surface 11 of the fuel cell stack 10 at appropriate locations.

[0081] It is understood that all spray nozzles for coating all edge areas 6, 8 can be moved together in a spray device 21, which represents a simple and efficient method for coating the edge areas 6, 8 of bipolar plates 1.

[0082] Figure 9 shows an embodiment that is essentially the same as that shown in Figures 2 and 4. Reference is therefore made to the description above. Only the preceding surface coating with the insulating material 5 has been omitted. It may be sufficient to apply the insulating material 15, 19 only to the edge regions 6, 8, as this is where the risk of a short circuit is highest.

[0083] To further reduce the risk of short circuits, it can be advantageous to increase the distance between the edges 4 of the bipolar plates 1. This can be achieved by chamfering the edges 4. In Fig. 10, the chamfered areas 20 are located on the surface where the insulating material 5 is also applied. This material overlaps the chamfered areas 20. The insulating material 15 is then applied by spraying as described. The chamfered areas 20 also reduce droplet formation, as any droplets can run off. Alternatively (or additionally), the chamfered area 20 could be located on the other surface of the bipolar plate 1, i.e., the surface opposite the one coated with insulating material 5, as illustrated in Fig. 11. In both cases, the penetration of the sprayed material is facilitated. 120096P1348PC

[0084] While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist. It should also be noted that the described exemplary embodiments are only non-limiting examples, and it is not intended to restrict the scope, applicability, or configuration of the devices and methods described herein.

[0085] Rather, the preceding description will provide the person skilled in the art with guidance for implementing at least one exemplary embodiment, whereby it is understood that various changes can be made to the function and arrangement of the elements described in an exemplary embodiment without deviating from the one specified in the appended claims.

[0086] The subject matter and its legal equivalents are not affected.

[0087] 120096P1348PC

[0088] REFERENCE MARK LIST

[0089] 1 Bipolar plate

[0090] 2 Area for membrane electrode assembly (MEA)

[0091] 3 areas to be isolated

[0092] 4-edge

[0093] 5 Insulation material

[0094] 6 Edge area (all around)

[0095] 7 Passage opening

[0096] 8 Edge area (passage opening)

[0097] 9 membrane electrode assembly (MEA)

[0098] 9a Membrane (PEM)

[0099] 9b electrode (cathode / anode)

[0100] 9c electrode (anode / cathode)

[0101] 10 fuel cell stacks

[0102] 11 side surface

[0103] 12 spray nozzles

[0104] 13 Altitude

[0105] 14 distance

[0106] 15 Insulation material

[0107] 16 Spray nozzle (directed, flat)

[0108] 17 spray nozzles (360 degrees)

[0109] 18 Masking for spray nozzle

[0110] 19th round

[0111] 20 chamfered area

[0112] 21 Spray device

Claims

120096P1348PC REQUIREMENTS 1. Method for producing a fuel cell stack (10), comprising applying an insulating material (15) to edge areas (6) of bipolar plates (1) of a provided fuel cell stack (10), wherein the insulating material (15) is sprayed onto at least one side surface (11) of the fuel cell stack (10) by means of a spray device (21).

2. Method according to claim 1, wherein the insulating material is applied directly to the edge regions of the bipolar plates (1).

3. Method according to claim 1 or 2, wherein the insulating material is applied over a flat area to the edge regions of the bipolar plates (1).

4. Method according to one of the preceding claims, wherein the spraying of the insulating material (15) by means of the spraying device (21) onto at least one side surface (11) of the fuel cell stack (10) is carried out at least partially.

5. Method according to one of the preceding claims, wherein the spraying of the insulating material (15) by means of the spraying device (21) onto the at least one side surface (11) of the fuel cell stack (10) is carried out in such a way that the insulating material (15) penetrates at least partially between adjacent bipolar plates (1) and thereby covers the edge areas (6) of the surfaces of the bipolar plates (1) at least partially, in particular directly, with the insulating material (15).

6. Method according to one of the preceding claims, wherein the insulating material is applied to the edge regions of the bipolar plates (1) in such a way that a layer of the insulating material is formed on the edge regions of the bipolar plate (1) which at a first location with a maximum layer thickness differs by a maximum of 50%, 30% or 10% of the layer thickness at the first location from a second location with a minimum layer thickness.

7. Method according to one of the preceding claims, wherein the insulating material is applied to the edge regions of the bipolar plates (1) such that the layer thickness of the insulating material on the edge regions of the bipolar plate is less than the thickness of the bipolar plate. 120096P1348PC 8. A method according to any of the preceding claims, wherein the provided fuel cell stack (10) comprises a plurality of bipolar plates (1) and a plurality of membrane electrode arrangements (9) which are alternately arranged along a height direction (13) of the fuel stack (10) to form the fuel cell stack (10), wherein adjacent bipolar plates (1) in the fuel cell stack (10) are spaced apart from each other (14) and wherein at least one edge region (6) of a surface of each of the bipolar plates (1) is at least partially free of an insulating material.

9. Method according to one of the preceding claims, wherein the method comprises providing the fuel cell stacks, in particular for applying the insulating material (15) to the edge regions (6) of the bipolar plates (1) of the fuel cell stack (10).

10. Method according to any of the preceding claims, wherein the membrane electrode arrangements (9) are frameless membrane electrode arrangements (9).

11. Method according to one of the preceding claims, wherein the application of the insulating material (15) by means of the spray device (21) is carried out by spraying at a spray angle of less than 90 degrees with respect to the vertical direction (13) of the fuel cell stack (10).

12. Method according to one of the preceding claims, wherein the spray device (21) has at least one spray nozzle (12; 16) with a directed and flat spray characteristic to apply the insulating material (15) by spraying onto a target area on the side surface (11) of the fuel cell stack (10), which is elongated along a circumferential direction.

13. Method according to one of the preceding claims, wherein the spraying device (21) has a plurality of spray nozzles (12) arranged side by side in a circumferential direction of the fuel cell stack (10), wherein the spraying device (21) is moved along the vertical direction (13) of the fuel cell stack (10) during the application of the insulating material (15). 120096P1348PC 14. Method according to claim 13, wherein the plurality of spray nozzles (12) are arranged and configured such that a substantially uniform spray pattern is obtained at least partially in a target area on at least one side surface (11) of the fuel cell stack.

15. Method according to one of the preceding claims, wherein the insulating material (15) is also applied at least partially to edge surfaces of the bipolar plates (1).

16. A method according to any of the preceding claims, wherein the bipolar plates (1) each have at least one through-opening (7), wherein the through-openings (7) in the provided fuel cell stack (10) each form a passage through the fuel cell stack (10) along the vertical direction (13), wherein the fuel cell stack (10) is provided or is provided such that the edge regions (8) of the surface of each of the bipolar plates (1) extending around the through-openings (7) are, in particular at least partially, free of an insulating material, wherein the method further comprises: Applying the insulating material (19) to the edge regions (8) of the surfaces of the bipolar plates (1) extending around the through-holes (7), wherein the insulating material is sprayed at least partially onto an inner surface of the through-holes by means of at least one further spraying device in such a way that it penetrates at least partially between adjacent bipolar plates (1) and thereby at least partially covers the edge regions (8) of the surfaces of the bipolar plates (1) extending around the through-holes (7) with the insulating material.

17. Method according to claim 16, wherein the insulating material (19) is applied directly to the edge regions (8) of the surfaces of the bipolar plates (1) extending around the through-holes (7).

18. Method according to claim 16 or 17, wherein the insulating material (19) is applied over a flat area to the edge regions (8) of the surfaces of the bipolar plates (1) extending around the through-holes (7).

19. Method according to one of claims 16 to 18, wherein the at least one further spraying device comprises at least one spray nozzle (17) with a circumferential and flat 120096P1348PC exhibits spray characteristics for applying the insulating material by spraying onto a circumferential target area on the side surface of a corresponding passage, which is elongated along a circumferential direction.

20. Method according to one of claims 16 to 19, wherein the further spraying device has one spray nozzle (17) per pass, wherein the further spraying device is moved along the vertical direction during the application of the insulating material.

21. Method according to one of claims 16 to 20, wherein the insulating material is applied in such a way that the insulating material is applied only in a predetermined partial area to the edge regions (8) of the surfaces of the bipolar plates (1) extending around through-holes (7).

22. Method according to one of the preceding claims, wherein the application of the insulating material (15, 19) is carried out in such a way that the insulating material is applied only in a predetermined partial area to the edge areas (6, 8) of the surfaces of the bipolar plates (1).

23. A method according to any of the preceding claims, wherein the step of providing the fuel cell stack (10) prior to arranging the bipolar plates (1) and membrane electrode assemblies (9) to form the fuel cell stack (10) further comprises: Applying an insulating material (5) to at least one surface of the bipolar plates (1) at least in areas of the respective surface which surround the membrane electrode arrangement (9), wherein the at least one edge region (6, 8) of the surfaces of each of the bipolar plates (1) remains free.

24. Method according to claim 23, wherein the application of the insulating material (5) to the surfaces of the bipolar plates (1) is carried out by means of a printing process.

25. Method according to any of the preceding claims, wherein the step of providing the fuel cell stack (10) prior to arranging the bipolar plates (1) and membrane electrode assemblies (9) to form the fuel cell stack (10) further comprises: 120096P1348PC Chamfering the circumferential edges (4) of the bipolar plates (1) on at least one of the surfaces of the respective bipolar plate (1).

26. Method according to one of the preceding claims, wherein the bipolar plates (1) have chamfers on their circumferential edges on at least one of the surfaces.

27. Method according to one of the preceding claims, wherein the insulating material (5) on the surfaces of the bipolar plates (1) overlaps at least partially with a chamfered area (20).

28. Method according to one of the preceding claims, wherein the application of the insulating material to the edge regions (6) of the bipolar plates (1) and / or to the edge regions (8) of the surfaces of the bipolar plates (1) extending around the through-holes (7) is carried out by means of an uninterrupted and / or single and / or common and / or continuous spraying process.

29. Fuel cell stack manufactured according to a method according to one of the preceding claims, wherein the fuel cell stack and / or the membrane electrode arrangements are frameless, in particular housing-free.

30. Manufacturing system comprising means for carrying out a method according to any one of claims 1 to 28.

31. Manufacturing system according to claim 30, wherein the means for carrying out the method comprises at least one spray device with at least one nozzle.

32. Computer program comprising instructions which, when executed, cause the manufacturing system according to claim 30 or 31 to perform the process steps of a method according to any one of claims 1 to 28.

33. Computer-readable medium comprising the computer program according to claim 32.

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