Method for manufacturing edge-to-frame catalyst-free membrane electrode assembly (MEA) for fuel cell, MEA and MEA fuel cell

Abstract

The invention relates to a manufacturing method for a membrane electrode assembly for a fuel cell, the membrane electrode assembly comprising a membrane (2) with a catalyst layer (3) and a frame (6) arranged on the same face of the membrane (2) and a gap (5) between the catalyst layer (3) and the frame (6). In order to allow manufacturing such a membrane assembly in a simple and cost-saving manner, the manufacturing method comprises the following steps: • positioning a first decal layer (10, 13) made of the same material as the first catalyst layer (3) on a first face of the membrane (2) in such a way that the first decal layer (10, 13) overlaps the frame (6), • positioning a second decal layer (10, 14) made of the same material as the second catalyst layer (4) on a second face of the membrane (2), • pressing the first decal layer (10, 13) and the second decal layer (10, 14) against each other, the membrane (2) and the frame (6) being positioned therebetween.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for manufacturing a membrane assembly for a fuel cell, the membrane assembly comprising a membrane having a first face and a second face, a first catalyst layer arranged on the first face of the membrane and a second catalyst layer arranged on the second face of the membrane, a frame arranged at least on the first face of the membrane, wherein the frame encloses the first catalyst layer in the plane of the main extension of the first catalyst layer, and a gap between the first catalyst layer and the frame. Another aspect of the invention relates to a membrane assembly for a fuel cell manufactured by the above-mentioned method. Yet another aspect of the invention relates to a fuel cell having the membrane assembly. BACKGROUND

[0002] Membrane assemblies, also commonly known as membrane electrode assemblies (MEA), are well known for use in fuel cells. If such a membrane assembly comprises a frame, it is also known as a membrane electrode frame assembly (MEFA). A fuel cell is configured to convert a fuel, such as hydrogen, into electrical energy, in particular a voltage generating electric current, when a power circuit is closed.

[0003] A membrane assembly for a fuel cell comprises a membrane, also known as electrolyte, and first and second catalyst layers, also known as electrodes. A number of fuel cells can be combined into a fuel cell stack. Each fuel cell of the stack can comprise a respective membrane assembly.

[0004] Current membrane assemblies, in particular membrane electrode frame assemblies, are prone to failure at the edges between the frame and the catalyst layers. Such failures can be caused by chemical degradation in the area where the catalyst layers and the frame face each other. In this area where the frame and the catalyst layers face each other, there can be a gas diffusion layer that goes over the frame. This gas diffusion layer can be attached on both surfaces of the membrane assembly. The chemical degradation can be caused by so-called “local OCV (open circuit voltage)” type conditions in this area. OCV type degradation occurs when hydrogen diffusing through the membrane and reacting with oxygen at the cathode or oxygen diffusing through the membrane and reacting with hydrogen at the anode form hydrogen peroxide and associated free radicals.

[0005] Document EP1876666B1 discloses a polymer electrolyte fuel cell comprising a stack of one or more cells, each cell having a MEA and anode and cathode separators sandwiching the MEA. The electrode layers of the fuel cell have a peripheral region.

[0006] The present invention aims to overcome the above-mentioned chemical degradation problem. SUMMARY

[0007] This object is solved by the membrane assembly, the method for manufacturing a membrane assembly and the fuel cell of the independent claims. Advantageous embodiments and practical improvements are subject of the dependent claims.

[0008] The present invention is based on the idea that the above degradation is eliminated when no catalyst layer is present in the frame region. In other words, part of the idea is to form the membrane assembly in such a way that the first catalyst layer and the frame are completely separated by a gap between them. In other words, the gap should separate the frame from the first catalyst layer. The gap can have a width that is at least approximately constant. Again, in other words, the width can be the distance by which the frame and the catalyst layer are separated from each other, in particular the distance by which the first catalyst layer and the frame are separated from each other.

[0009] The present method is suitable for manufacturing a membrane assembly for a fuel cell, the membrane assembly comprising a membrane having a first face and a second face, a first catalyst layer arranged on the first face of the membrane and a second catalyst layer arranged on the second face of the membrane, a frame arranged at least on the first face of the membrane, wherein the frame encloses the first catalyst layer in the plane of the main extension direction of the first catalyst layer, and a gap between the first catalyst layer and the frame.

[0010] In order to allow the manufacture of such a membrane assembly in a simple and cost-saving manner, it is envisaged that the manufacturing method comprises the following steps:

[0011] - positioning a first decal layer made of the same material as the first catalyst layer on the first face of the membrane in such a way that the first decal layer overlaps the frame positioned on the first face of the membrane,

[0012] - positioning a second decal layer made of the same material as the second catalyst layer on the second face of the membrane, and

[0013] - pressing the first decal layer and the second decal layer against each other, wherein the membrane and the frame are positioned therebetween.

[0014] When the frame and the first catalyst layer are both arranged on the first face of the membrane, the frame can form a closed loop around the first catalyst layer. In some embodiments, it can be envisaged that the frame is arranged on both the first face and the second face of the membrane. In these embodiments, the frame can comprise two parts which are arranged on different faces of the membrane, respectively. In this case, the first face of the membrane can be enclosed by a first part of the frame and the second catalyst layer can be enclosed by a second part of the frame. Within the scope of the present invention, "enclosed" means in particular completely enclosed. In other words, the first face of the membrane can be completely surrounded or enclosed by the frame in the plane of the main extension direction of the first catalyst layer. There is a free area between the first catalyst layer and the frame which forms the gap. In other words, in this gap, no part of the frame and no part of the first catalyst layer are arranged on the membrane. As mentioned above, the gap can have a constant value between the first catalyst layer and the frame.

[0015] The first catalyst layer is made from the first decal layer in a decal transfer process. The second catalyst layer is made from the second decal layer in a decal transfer process. This decal layer process can comprise the steps of positioning the first decal layer and the second decal layer and pressing the first decal layer and the second decal layer against each other. The manufacturing method of the present application makes use of the fact that the thickness of the film and the frame is not constant when positioned between the first and second decal layer while pressing them against each other. The combination of the film and the frame has a greater thickness in the area of the film where parts of the frame are arranged on the film. In other words, the film and the frame have a greater thickness in the area where the frame extends. Similarly, in the area where the frame does not extend, the thickness is equal to the thickness of the film. In the area where the frame extends, the thickness is equal to the thickness of the film plus the thickness of the frame. Therefore, in the area of the film where the frame is arranged, a higher pressure is automatically applied compared to the area of the film that is not covered by the frame. This is further ensured when the press with two corresponding pressing surfaces to press the first and second decal layer against each other is flat. The pressure applied during pressing increases with the distance to the frame. In other words, the lowest pressure is applied where the gap is presumed to be. Therefore, the first decal layer is not attached to the first face of the film next to the frame. On the first side of the gap where the frame is presumed to be, the first decal layer is likewise not attached when the frame is made of a suitable material. In other words, the frame can be made of a material to which the first decal layer is not attached. On the second side of the gap where the first catalyst layer is presumed to be formed, the pressure is sufficient for the first decal layer to be attached to the film. Therefore, the attached part of the decal layer forms the first catalyst layer.

[0016] The two decal layers are positioned before pressing the first decal layer and the second decal layer against each other. It is conceivable that the first decal layer overlaps the frame. Advantageously, the first decal layer has a larger size than the area of the film that is covered by the frame, the gap and the first catalyst layer together. Said area can be completely overlapped by the first decal layer. The second decal layer can have the same, at least approximately the same size as the first decal layer. The second decal layer can be positioned similarly to the first decal layer, but on the second face of the film. For example, the second decal layer can be positioned in such a way that its projection in the plane of the film is equal to the projection of the first decal layer in that plane.

[0017] In a next step, the two decal layers are pressed against each other. This is done when positioning the membrane with the frame positioned on the first face of the membrane between the first and second decal layers. The decal layers can be arranged on the respective substrates while positioning the first and second decal layers and / or pressing them against each other. The substrates can help to handle the decal layers and stabilize them while pressing and / or positioning. The pressing can be done by a hot press. For example, by pressing two pressing surfaces against each other with the first decal layer and the second decal layer and the membrane and the frame in between. Due to the pressing, both decal layers are partially attached to the first face or the second face of the membrane. The part of the decal layer attached to the first face of the membrane can form the first catalyst layer. The part of the second decal layer attached to the second face of the membrane can at least substantially form the second catalyst layer.

[0018] Sometimes, another part of the second decal layer can be attached to the membrane on the second face of the membrane opposite the area where the membrane contacts the frame on the first face. This can be referred to as an additional catalyst layer. The additional catalyst layer does not affect the performance of the membrane assembly or of a fuel cell made of the membrane assembly. An additional gap can be formed on the second face of the membrane exactly at the opposite position of the gap on the first face of the membrane. This is because the first and second catalyst layers can have the same extent on the respective face of the membrane.

[0019] The manufacturing method provides a simple method of manufacturing a membrane assembly with a frame and catalyst layers and a gap between the frame and the catalyst layers. The first and second decal layers can have a much larger extent than the resulting membrane assembly. A careful alignment of the first catalyst layer and the frame relative to each other is not necessary to provide the gap. A careful alignment of the first catalyst layer and the second catalyst layer relative to each other is also not necessary. Instead, the gap is formed automatically during the manufacturing method without the need to precisely or accurately position the frame and the first catalyst layer relative to each other.

[0020] According to yet another development of the application, it is envisaged that the positioning of the second decal layer is done in such a way that the decal layer overlaps with the projection of the frame in the plane of the second decal layer. In other words, the second decal layer can overlap with the frame or its projection in the plane of the second decal layer. Advantageously, this overlap is the same as the overlap of the first decal layer relative to the frame. In particular, the second decal layer can overlap with the frame or its projection in each direction, respectively. In particular, the second decal layer can overlap with the frame, the gap and the first catalyst layer in the projection in the plane of the second decal layer. Thereby, it is ensured that the first and second catalyst layers are arranged on the membrane on different faces but directly opposite each other. In other words, the projections of the first and second catalyst layers in the plane of the membrane can be at least approximately equal.

[0021] According to yet another development, the pressing is carried out using two pressing surfaces which both overlap the frame. In other words, the two pressing surfaces can overlap the frame, the gap and the first or second catalyst layer, respectively. Thereby it is ensured that a proper pressure is applied to form the gap, the first and second catalyst layer.

[0022] According to yet another development, it is envisaged that the frame is arranged on the membrane by a separate pressing procedure before positioning the first catalyst layer and the second decal layer. The separate pressing procedure can be carried out using the same press and / or the same two pressing surfaces as the pressing of the first decal layer and the second decal layer against each other. In particular, the separate pressing procedure can be a hot pressing using a hot press. An advantage of the separate pressing procedure is that the frame is already fixed to the membrane when the positioning of the first and second decal layer is carried out.

[0023] According to another development, it is envisaged that the frame is already positioned on the membrane before positioning the first decal layer and the second decal layer to be fixed to the membrane when subsequently pressing the first decal layer and the second decal layer against each other. In other words, only one pressing procedure is envisaged for fixing the frame to the membrane and forming the first and second catalyst layer from the respective decal layer. This can make the manufacturing of the membrane assembly more cost-effective.

[0024] According to yet another development, it is envisaged to vary the thickness of the frame to adjust the width of the gap. For example, frames of different thicknesses can be used as they can cause different widths of the gap. Other factors which can be used to adjust the gap width are the compliance of the press or the material being calendered. All these parameters can be adjusted to ensure in a simple way that the gap is free of catalyst.

[0025] Another aspect of the present invention relates to a membrane assembly for a fuel cell, comprising:

[0026] - a membrane having a first face and a second face,

[0027] - a first catalyst layer arranged on the first face of the membrane and a second catalyst layer arranged on the second face of the membrane,

[0028] - a frame arranged at least on the first face of the membrane, wherein the frame encloses the first catalyst layer in the plane of the main extension of the catalyst layers, and

[0029] - a gap between the first catalyst layer and the frame.

[0030] In order to allow the manufacturing of such a membrane assembly in a simple and cost-saving way, the membrane assembly is characterized in that

[0031] - the first catalyst layer is formed from a first decal layer by decal transfer, the first decal layer being made of the same material as the first catalyst layer, the second catalyst layer is formed from a second decal layer by decal transfer, the second decal layer being made of the same material as the second catalyst layer, and

[0032] - the gap between the first catalyst layer and the frame is formed by pressing the first and second decal layers overlapping the frame against each other by means of decal transfer, the membrane and the frame being positioned therebetween.

[0033] As a result of being formed from the respective decal layers, the membrane assembly can be distinguished from any other membrane assembly due to the different properties of the first and second catalyst layers. The gap also causes different properties of the gap compared to other membrane assemblies by means of being formed by pressing. In particular, the edges of the first catalyst layer facing the gap can be different, and the width of the gap is rarely constant.

[0034] The resulting membrane assembly has been discussed in the context of the manufacturing method. The first catalyst layer and the second catalyst layer can be made of the same material. In this case, the first and second decal layers can also be made of the same material. The first and second catalyst layers can be configured to enhance the conversion of fuel into electrical energy. The first and / or second catalyst layers can be made of an electrically conductive material. They can thus also be referred to as electrodes. When the membrane assembly is part of a fuel cell, the electrodes or catalyst layers can be configured to conduct electrical energy or current to the electrodes of the membrane assembly or fuel cell, respectively.

[0035] According to yet another development, it is envisaged that the first catalyst layer and the second catalyst layer (at least approximately) completely overlap with respect to their extension parallel to the membrane. In other words, the first and second decal layers can have (at least approximately) the same projection in the plane of the membrane. For example, the first and second decal layers can have (at least approximately) the same size, extension, and position parallel to the membrane. Precise equivalent positioning of the two catalyst layers on both sides of the membrane is thereby ensured, and this can be crucial for the advantageous operation of the membrane assembly or the fuel cell of which the membrane assembly is a part.

[0036] A third aspect of the present invention relates to a fuel cell having the above-described membrane assembly. In other words, the fuel cell can comprise the above-described membrane assembly. Again in other words, the fuel cell can comprise a membrane assembly manufactured using the above-described manufacturing method.

[0037] The fuel cell can comprise one or more such membrane assemblies. The fuel cell can be stacked with other fuel cells into a fuel cell stack. The fuel cells of the fuel cell stack can / may not be mechanically and electrically connected. The fuel that is converted into electrical energy can flow through all fuel cells of the fuel cell stack. The exhaust gas resulting from said conversion can also be discharged through the same exhaust pipe. The fuel cells of the fuel cell stack can be electrically connected in parallel or in series or in a combination.

[0038] The fuel cell can further comprise a housing at least partially surrounding the membrane assembly. The fuel cell can comprise one or more gas diffusion layers for allowing fusion of the fuel. For example, a first gas diffusion layer can be arranged on the first catalyst layer. The first gas diffusion layer can also extend over the gap and / or the frame. In other words, the first gas diffusion layer can cover the first catalyst layer, the gap and the frame. A second gas diffusion layer can be arranged on the second catalyst layer. The second gas diffusion layer can extend over the entire second face of the membrane. It can thus extend over the additional gap and / or the additional catalyst layer of the second face of the membrane.

[0039] Further advantages, features and details of the present application result from the following description of preferred embodiments and the attached drawings. The features and combinations of features mentioned in the description above and in the description of the figures below and / or shown only in the figures can be used not only in the respective combinations indicated, but also in any other combination or alone without departing from the scope of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] The drawings show:

[0041] Figure 1 is a schematic cross-section of a membrane assembly with additional gas diffusion layers;

[0042] Figure 2 is an exemplary step of a manufacturing process of a membrane assembly using one pressing procedure;

[0043] Figure 3 is a method of manufacturing a membrane assembly using two separate pressing procedures;

[0044] Figure 4 is a technical device for performing a manufacturing method with two pressing steps; and

[0045] Figure 5 is a schematic representation of a cross-section of a membrane assembly prototype.

[0046] In the drawings, identical elements or elements with identical functions are provided with the same reference signs. DETAILED DESCRIPTION

[0047] Figure 1 A membrane assembly 1 is shown, which comprises a membrane 2, a frame 6 arranged on the membrane 2 and catalyst layers 3, 4 on both sides of the membrane. Gas diffusion layers 8, 9 are applied on both sides of the membrane assembly 1. The respective gas diffusion layers 8, 9 can be considered as part of the membrane assembly 1 or not.

[0048] The membrane 2, which can also be referred to as an electrolyte, has a first side 18 and a second side 19. The membrane 2 can be permeable or semi-permeable to enable ions and / or molecules to exchange between the first side 18 and the second side 19. A first catalyst layer 3 is arranged on the first side 18 of the membrane 2. A second catalyst layer 4 is arranged on the second side 19 of the membrane 2. The frame 6 is arranged on the first side 18 of the membrane 2. The first catalyst layer 3 and the second catalyst layer 4 can be formed as electrodes. In other words, the catalyst layers 3, 4 can be configured to conduct an electric current. The catalyst layers 3, 4 can be made of different or the same material. Both catalyst layers 3, 4 can be configured to catalyze a conversion of fuel to electrical energy. For example, fuel and ambient air or oxygen can be converted to energy and exhaust gas by the catalyst layers 3, 4. When arranged in a fuel cell, the membrane assembly 1 can be arranged to perform the conversion. The fuel cell can comprise one or more membrane assemblies 1 and a housing (not shown in the figures).

[0049] The catalytic reactions within and around the first catalyst layer 3 can cause a degradation process at the frame 6. This can especially occur when the first catalyst layer 3 and the frame 6 directly face each other. In other words, the degradation especially occurs when the first catalyst layer 3 and the frame 6 are in contact with each other or at least very close to each other. The degradation can be a chemical degradation caused by a local open-circuit-voltage type condition in this area. The open-circuit-voltage type degradation occurs when hydrogen diffusing through the membrane 2 and reacting with oxygen at the cathode or oxygen diffusing through the membrane 2 and reacting with hydrogen at the anode form hydrogen peroxide and associated free radicals. This degradation pathway is cut off when there is no catalyst layer 3, 4 in this area. Therefore, there is a gap 5 between the frame 6 and the first catalyst layer 3. In other embodiments not shown in the figures, the frame 6 can be arranged on both sides 18, 19 of the membrane 2. For example, the frame 6 can consist of at least two parts, wherein a first part is arranged on the first side 18 and a second part is arranged on the second side 19. The frame 6 can also unfold the counterpart of the membrane 2 and thus contact both sides 18, 19 of the membrane 2. If this is the case, the above applies to the second catalyst layer 4 and the frame 6 as well. In any case, there is an additional gap 12 between the second catalyst layer 4 and the projection of the frame 6 in the plane of the second catalyst layer 4. In the current case, there is an additional catalyst layer 11 in the area of the projection of the frame 6 in the plane of the second catalyst layer 4.

[0050] The first gas diffusion layer 8 covers the first catalyst layer 3, the gap 5 and the frame 6. The thought triangle area above the gap 5 is also called the triangle area 7. In other words, all the arrangement on the first face 18 is completely covered by the gas diffusion layer 8. In the absence of the gap 5, the triangle area would be located between the first catalyst layer 3, the first gas diffusion layer 8 and the frame 6. The second gas diffusion layer 9 is arranged on the second catalyst layer 4 and the additional catalyst layer 11. The second gas diffusion layer 9 also covers the additional gap 12. Similarly, the gap 5 is covered by the first gas diffusion layer 8.

[0051] Reference will now be made to Figure 2 a first possibility to manufacture the membrane assembly 1 is shown. In a first step S1.1 of the exemplary method, the membrane 2, the frame 6, the first decal layer 13 and the second decal layer 14 are positioned relative to each other. More precisely, the second decal layer 14 is positioned on the second face 19 of the membrane 2. The frame 6 is positioned on the first face 18 of the membrane 2. The first decal layer 13 is also positioned on the first face 18 of the membrane 2. The positioning of the first decal layer 13 is done in such a way that the first decal layer 13 overlaps the frame 6. In other words, the frame 6 is positioned between the membrane 2 and the first decal layer 13. Thus, the frame 6 contacts the first face 18 of the membrane 2 with its first face and the frame 6 contacts the first decal layer 13 with its second face. The first face and the second face of the frame 6 can be at least approximately parallel to each other. Both decal layers 13, 14 are arranged on a respective backing layer 10. The backing layer 10 or substrate makes it easier to handle the respective decal 13, 14. In other words, the backing layer 10 facilitates handling of the decal layers 13, 14. In a next step S1.2, the whole arrangement of the decal layers 13, 14, the membrane 2 and the frame 6 is pressed in a pressing procedure 20. By the pressing procedure 20, the frame 6 is firmly connected to the membrane 2. A portion of the decal layers 13, 14 is also firmly connected to the membrane 2. In particular, the first decal layer 13 is partially attached to the first face 18 of the membrane 2. The portion of the first decal layer 13 that is attached to the membrane 2 forms the first catalyst layer 3. In particular, the second decal layer 14 is partially attached to the second face 19 of the membrane 2. The portion of the second decal layer 14 that is attached to the membrane 2 forms the second catalyst layer 4. This can be seen in step S1.3. Thus, the first decal layer 13 is made of the same material as the first catalyst layer 3. Similarly, the second decal layer 14 is made of the same material as the second catalyst layer 4. If both catalyst layers 3, 4 are composed of the same material, both decal layers 13, 14 can be identical.

[0052] In step S1.2, due to the frame 6 present in the triangular area 7, a lower pressure is applied compared to the areas in which the respective catalyst layers 3, 4 are formed. Of course, a relatively high pressure is also applied at the location of the frame 6. Because the first decal layer 13 is not properly connected to the frame 6 there, in the area in which the frame 6 and the first decal layer 13 face each other, the decal layer remains on the backing layer 10. On the second face 19 of the membrane 2, the decal layer is also attached to the membrane 2 opposite the frame 6. This results in the formation of an additional catalyst layer 11. This additional catalyst layer 11 is not necessary for operation, but does not harm the fuel cell or the membrane assembly 1. Due to the lower pressure during the pressing procedure 20, neither the first decal layer 13 nor the second decal layer 14 is attached to the membrane 2 in the area of the gap 5 and the additional gap 12. This is a desired effect of the present manufacturing method.

[0053] In another possible manufacturing method, two pressing procedures 21, 24 are envisaged as opposed to a single pressing procedure 20. Figure 3 A step-by-step diagram is shown in Fig. 2. In a first step S2.1, the frame 6 is positioned on the membrane 2 and pressing is performed in a first separate pressing procedure 21. During the first separate pressing procedure 21, the frame 6 is attached to the first face 18 of the membrane 2. During the first pressing procedure 21, the membrane 2 can be attached to a backing layer 30 or a substrate. Similar to the backing layer 10 of the decal layers 13, 14, the backing layer 30 can facilitate handling of the membrane 2. After the first pressing procedure 21, the backing layer 30 is removed from the membrane 2. This can occur in step S2.2. In the following step S2.3, the two decal layers 13, 14 are positioned on the membrane 2. This step can be understood similar to step S1.1, as the decal layers 13, 14 have to be positioned in the same way with respect to the membrane 2 and the frame 6. In particular, the first decal layer 13 is positioned on the first face 18 of the membrane 2 in such a way that the first decal layer 13 overlaps the frame 6. In particular, the second decal layer 14 is positioned on the second face 19 of the membrane. Advantageously, the second decal layer 14 is positioned in such a way that the projection of the second decal layer 14 into the plane of the second decal layer 14 overlaps the frame 6.

[0054] In step S2.4, a second pressing procedure 24 is performed. By this pressing procedure 24, the first catalyst layer 3 and the second catalyst layer 4 are formed. In step S2.5, the pressure is released and the backing layer 10 is removed. The result is exactly the same as described above according to steps S1.2 and S1.3. The pressing surfaces 22 and 23 for the respective pressing procedures 21 and 24 can be identical or different. The pressing surfaces 22 and / or 23 can be part of a hot press or a respective hot press. Accordingly, the pressing procedures 21 and 24 can be hot pressing procedures. Similarly, the pressing procedure 20 can be a hot pressing procedure.

[0055] Figure 4 A step-by-step diagram is shown in Fig. 2. In a first step S2.1, the frame 6 is positioned on the membrane 2 and pressing is performed in a first separate pressing procedure 21. During the first separate pressing procedure 21, the frame 6 is attached to the first face 18 of the membrane 2. During the first pressing procedure 21, the membrane 2 can be attached to a backing layer 30 or a substrate. Similar to the backing layer 10 of the decal layers 13, 14, the backing layer 30 can facilitate handling of the membrane 2. After the first pressing procedure 21, the backing layer 30 is removed from the membrane 2. This can occur in step S2.2. In the following step S2.3, the two decal layers 13, 14 are positioned on the membrane 2. This step can be understood similar to step S1.1, as the decal layers 13, 14 have to be positioned in the same way with respect to the membrane 2 and the frame 6. In particular, the first decal layer 13 is positioned on the first face 18 of the membrane 2 in such a way that the first decal layer 13 overlaps the frame 6. In particular, the second decal layer 14 is positioned on the second face 19 of the membrane. Advantageously, the second decal layer 14 is positioned in such a way that the projection of the second decal layer 14 into the plane of the second decal layer 14 overlaps the frame 6.Figure 3 One example of an apparatus for the manufacturing method of the preamble of claim 1. The pressing surfaces 22 can be provided by rollers 25, respectively. Similarly, the pressing surfaces 23 can be provided by corresponding rollers 26. The apparatus shall be briefly described below:

[0056] The film 2 with its liner 30 enters the rollers 25 together with the frame 6. The rollers 25 perform the first pressing procedure 21. Due to the film 2 according to Figure 1 The rollers 25 provide a unique effect similar to a planar pressing surface 22 in a continuous process moving to the right. After the first pressing procedure 21 between the two rollers 25, the liner 30 is removed from the film 2. The result is a framed film 16 as an intermediate product. For the second pressing procedure 24 realized by the rollers 26, the decal layers 13, 14 are arranged on their respective liners on the respective faces / sides of the film or framed film 16, respectively. Thus, step S2.3 is performed just before the rollers 26. Between the rollers 26, step S2.4 or the second pressing procedure 24 is performed. When leaving the rollers 26, the two liners 10 are removed. This equals step S2.5. The result is an endless role of membrane assemblies / continuous roll of membrane assemblies 17.

[0057] Finally, Figure 5 A cross-sectional view showing a portion of the membrane assembly 1. Figure 5 is a prototype manufactured using the present manufacturing method according to Figure 2 or Figure 3 A photograph of a prototype manufactured using the present manufacturing method according to Figure 5 In the photograph, it can be seen that the two catalyst layers 3 and 4 are well aligned with each other. The difference d1 in size and / or linearity (positioning / alignment) is about 10 pm. In other words, the two catalyst layers 3, 4 are positioned relative to each other within a negligible tolerance of 10 pm. The width d2 of the intermediate gap 5 in the prototype equals 500 pm. It should be mentioned that the given measurement values for d1 and width d2 are only exemplary. However, both measures have proven useful in practical examples.

[0058] Reference signs

[0059] 1 membrane assembly

[0060] 2 film

[0061] 3 first catalyst layer

[0062] 4 second catalyst layer

[0063] 5 intermediate gap

[0064] 6 frame

[0065] 7 triangular area

[0066] 8 first diffusion layer

[0067] 9 second diffusion layer

[0068] 10 backing layer

[0069] 11 additional catalyst layer

[0070] 12 additional gap

[0071] 13 first decal layer

[0072] 14 second decal layer

[0073] 16 frame film

[0074] 17 film assembly

[0075] 18 first side

[0076] 19 second side

[0077] 20 pressing procedure

[0078] 21 pressing procedure

[0079] 22 pressing surface

[0080] 23 pressing surface

[0081] 24 pressing procedure

[0082] 25 roller

[0083] 26 roller

[0084] 30 backing layer

[0085] S1.1...S1.3 steps

[0086] S2.1...S2.5 steps

Claims

1. A method for manufacturing a membrane assembly for a fuel cell, the membrane assembly comprising: - a membrane having a first face and a second face, - a first catalyst layer arranged on the first face of the membrane and a second catalyst layer arranged on the second face of the membrane, - a frame arranged at least on the first face of the membrane, wherein the frame encloses the first catalyst layer in the plane of the main extension of the first catalyst layer, and - a gap between the first catalyst layer and the frame, the method being characterized by the steps of: - positioning a first decal layer made of the same material as the first catalyst layer on the first face of the membrane relative to the frame in such a way that the first decal layer overlaps the frame positioned on the first face of the membrane, - positioning a second decal layer made of the same material as the second catalyst layer on the second face of the membrane, - pressing the first decal layer and the second decal layer against each other with the membrane and the frame positioned therebetween, the method comprising changing the thickness of the frame to adjust the width of the gap.

2. The method according to claim 1, characterized in that the positioning of the second decal layer is performed in such a way that the second decal layer overlaps the projection of the frame in the plane of the second decal layer.

3. The method according to claim 1 or 2, characterized in that the pressing is performed using two pressing surfaces that both overlap the frame.

4. The method according to claim 1 or 2, characterized in that the frame is arranged on the membrane by a separate pressing procedure before positioning the first decal layer and the second decal layer.

5. The method according to claim 1 or 2, characterized in that the frame is positioned on the membrane before positioning the first decal layer and the second decal layer to be fixed to the membrane in the subsequent step of pressing the first decal layer and the second decal layer against each other.

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