Method of producing a membrane-electrode assembly using an adhesive film in order to dimensionally stabilize the polymer membrane

Abstract

The invention relates to a method of producing a membrane-electrode assembly for a fuel cell and / or electrolysis cell. This involves providing a polymer membrane based on hydrocarbon ionomers and comprising a front side and reverse side. There is a carrier film on the reverse side of the polymer membrane, and a first catalyst layer has been applied to the front side. The carrier film is removed, such that the reverse side of the polymer membrane is freely accessible. An adhesive film is applied to the first catalyst layer, so as to enable stabilization for the coating of the reverse side with a second catalyst layer. The invention further relates to a membrane-electrode assembly producible by the method of the invention.

Description

[0001] Manufacturing method of a membrane-electrode unit using an adhesive film for dimension stabilization of the polymer membrane

[0002] DESCRIPTION

[0003] The invention relates to a method for producing a membrane electrode assembly for a fuel cell and / or electrolysis cell.

[0004] A polymer membrane based on hydrocarbon ionomers is provided, comprising a front and back side. A carrier film is applied to the back of the polymer membrane, and a first catalyst layer is applied to the front side. The carrier film is removed, leaving the back of the polymer membrane freely accessible. An adhesive film is applied to the first catalyst layer, providing stabilization for the coating of the back with a second catalyst layer.

[0005] Furthermore, the invention relates to a membrane electrode assembly which can be produced by the method according to the invention.

[0006] Background and state of the art

[0007] In membrane-based hydrogen technologies, ^-fuel cells, and / or water electrolysis, so-called CCMs (catalyst-coated membranes), also known as membrane electrode assemblies (MEAs), are used as a central component. These membranes also find application in other technologies, such as Power-to-X applications. A CCM or MEA is a membrane coated with electrodes on both sides. The membrane separates the anode and cathode sides of the CCM or MEA and is selectively permeable (in the case of anion exchange membranes, AEMs) to only negatively charged anions or (in the case of proton exchange membranes, PEMs) to protons. The respective chemical redox reactions take place in the electrode layers.Essential for efficient operation of the fuel cell and / or electrolysis cell is a low resistance at the respective boundary layers, i.e. a close connection of the two electrode layers to the membrane.

[0008] Due to the high importance of CCM for the operation of a fuel cell, there are also a variety of approaches in the state of the art to offer advantageous process technologies for their production. These technologies must consider several factors to ensure safe production and reliable functionality. For example, the low layer thickness of the polymer membrane is a relevant parameter, which must provide the necessary stability for use in a fuel cell or electrolysis cell. However, coating a polymer membrane with catalyst layers of such a low thickness is not trivial. Applying the catalyst layer can lead to deformation and / or swelling of the membrane, which in turn would be disadvantageous for use in the fuel cell, as an inhomogeneous design would result.Furthermore, the catalyst layer is usually liquid during coating, which makes adhesion of the catalyst layer to the membrane more difficult. A proven manufacturing process for a CCM in the state of the art is the so-called decal process. In the decal process, a catalyst dispersion is usually coated onto a carrier film or decal film (or just decal) and dried. This creates an anode electrode or ACD (anode coated decal) and a cathode electrode. Using a pressing process, e.g., lamination, a composite comprising a polymer membrane and a cathode is applied to the anode electrode. After pressing, the decal film is removed. After the decal film has been removed, the result is a polymer membrane or CCM coated on both sides with catalyst or electrode material.

[0009] In the state of the art, both different variants of a basic decal process and alternative approaches, for example by means of a direct coating of catalyst material on polymer membranes, are known in order to be able to produce catalyst-coated membranes.

[0010] EP 3529845 B1 discloses a method for providing a catalyst-coated membrane for a fuel cell by direct coating in a roll-to-roll process. A first side is coated with a catalyst layer, while a carrier film supports the membrane. After removal of the carrier film, the polymer membrane is transported through a vacuum conveyor to prevent or minimize potential swelling caused by the coating of a further catalyst layer.

[0011] US 2002 / 0064593 A1 describes a method for producing a membrane electrode assembly, which also involves direct coating of the membrane with the catalyst layers. During this process, the opposite sides of the membrane are constantly supported. When the polymer membrane is coated with a first catalyst layer, a support film is present on the opposite side. A gas distribution layer is then applied as a web to the (still) moist first catalyst layer. The support film is then removed, and the second side of the membrane can be coated with a catalyst material, while the gas distribution layer serves as a support structure to prevent swelling.

[0012] US 2022 / 0069325 A1 relates to a method for producing a polymer membrane coated with a catalyst layer. During the coating of a first side of the polymer membrane with the catalyst layer, a base material serves as a support. For the coating of the second side, the first electrode or catalyst layer itself serves as the support material and comprises a binder material for this purpose.

[0013] US 10,118,374 B2 teaches the use of a roll-to-roll process for coating a polymer membrane on both sides with a catalyst layer. A catalyst layer is coated on the front side of the polymer membrane, while a first protective layer is applied to the back side. After the catalyst layer has dried, a second protective layer is applied. The first protective layer is then removed in order to coat the exposed back side of the polymer membrane with a second catalyst layer. DE 102016224398 A1, a family member of US 10,118,374 B2, also teaches such a roll-to-roll process for coating a polymer membrane on both sides. Specific membrane materials are not disclosed in DE 102016224398 A1.

[0014] EP 2654112 B1 discloses a method for coating both sides of a polymer membrane with a catalyst layer or catalyst ink. Regarding the problem of potential swelling of the polymer membrane when coated with a catalyst ink, it is explained that the polymer membrane is provided with a shape-retaining film and that this composite is passed through a system. The catalyst ink is then coated on the other side. The shape-retaining film has a longer width than the polymer membrane. After the catalyst ink has dried, a second shape-retaining film is applied to the dried catalyst layer, which also has a greater width than the membrane. The first shape-retaining film applied to the other side is then removed and coated with another catalyst ink.Such a process is also disclosed in US 2012 / 0315571 A1, a member of EP 2654112 B1. The membrane material used is perfluorosulfonic acid (PFSA).

[0015] EP 1645001 B1 also relates to a method for producing a polymer membrane coated with a catalyst on both sides. A polymer membrane is supported with its back side on a first support film. The corresponding front side is coated with a catalyst material and dried. A second support film is then applied to the front side, and the first support film is removed from the back side. The back side of the membrane is then coated.

[0016] EP 1492184 A1, a family member of EP 1645001 B1, also describes a process for producing a polymer membrane coated with a catalyst on both sides. The key concept described is that at least one support film rests on the membrane throughout the entire process. This is said to have the advantageous technical effect of producing smooth and wrinkle-free CCMs. Furthermore, it describes the possibility of applying adhesion promoters in the edge region of the coated membrane side between the support film and the membrane. For the proposed catalyst-coated polymer membrane, perfluorosulfonic acid (PFSA)-based nitrile is used as the membrane material.While direct coating of a polymer membrane using catalyst material is well known in the art, the decal process continues to be a standard, particularly due to the difficulty of stabilizing the membrane during coating.

[0017] For the polymer membranes themselves, the current state of the art is to use perfluorosulfonic acid (PFSA)-based membranes. However, PFSA-based membranes have several disadvantages. Perfluorinated chemicals, which include PFSAs, are considered particularly bioaccumulative because they are resistant to thermal, chemical, and / or microbiological degradation. Perfluorinated chemicals therefore accumulate along the food chain in plants and animals, including humans. Unlike other organic contaminants, organic fluorine compounds bind to serum proteins. Perfluorinated acids are toxic to the liver, can be carcinogenic and reproductively toxic, and could lead to developmental disorders. They have a residence time of up to nine years in the human organism. For these reasons, the release of perfluorinated chemicals into the environment should be prevented as far as possible, and their use minimized.

[0018] In addition, there are currently very few suppliers of PFSA-based polymer membranes. Current suppliers distribute PFSA-based materials at high costs. The best-known PFSA-based ionomer is Nation (a registered trademark of Chemours), which sells for up to €1,000 per kilogram. When the costs of the catalyst material for the catalyst layer, such as platinum, are also considered, it becomes clear that a significant economic disadvantage currently exists, which also has a detrimental impact on mass application.

[0019] Furthermore, PFSA-based polymer membranes pose several challenges from a technical perspective. PFSA-based materials require complex syntheses, making their availability cost- and time-sensitive. Furthermore, they are only functional at a very limited operating temperature (up to approximately 120°C). Furthermore, PFSA-based polymer membranes exhibit high permeability to reactants such as hydrogen and / or oxygen, which could lead to inefficiencies and failures.

[0020] Therefore, the current state of the art is striving to avoid PFSA-based polymer membranes and to use an alternative material. Hydrocarbon-based polymer membranes are considered to have great potential in this regard, as hydrocarbons offer better environmental compatibility, are more cost-effective, and can also be more effective for operation within a fuel cell.

[0021] However, the current state-of-the-art methods for applying catalyst layers to PFSA-based polymer membranes cannot be readily transferred to hydrocarbon-based polymer membranes. In particular, the decal process used in conventional CCMs is not suitable for hydrocarbon-based polymer membranes. While a PFSA-based polymer membrane typically exhibits a thermal transition between 100°C and 150°C, allowing electrodes to be laminated to the membrane using pressure and elevated temperature, hydrocarbon-based polymer membranes do not exhibit flow behavior in these temperature ranges. However, if the membranes are directly coated with a catalyst layer, swelling and / or shrinkage may occur.This effect, which must be avoided, occurs more frequently in polymer membranes based on hydrocarbon ionomers, as they generally exhibit greater swelling behavior than PFSA polymer membranes.

[0022] For these reasons, known methods for the direct coating of polymer membranes cannot be readily adapted for the provision of membrane electrode assemblies with polymer membranes based on hydrocarbon ionomers. As explained above, polymer membranes based on hydrocarbon ionomers differ from PFSA-based polymer membranes not only in their swelling behavior, but also in their mechanical stability and thermal behavior. Therefore, there is a need in the art to provide alternative manufacturing processes that allow for the reliable and robust production of membrane electrode assemblies using a polymer membrane based on hydrocarbon ionomers.

[0023] The object of the invention is to eliminate the disadvantages of the prior art. In particular, one object of the invention is to provide a method for producing a membrane electrode assembly in which the electrode or catalyst layers can be applied simply, with high precision and efficiency, without exposing the polymer membrane to deformation or stress.

[0024] Summary of the invention

[0025] The object of the invention is achieved by the independent claims. Advantageous embodiments of the invention are disclosed in the dependent claims.

[0026] In a first aspect, the invention relates to a method for producing a membrane electrode unit for a fuel cell and / or an electrolysis cell, comprising the following steps: a) providing a polymer membrane based on hydrocarbon ionomers comprising a front side and a back side, wherein a carrier film is present on the back side and a first catalyst layer is present on the front side, b) removing the carrier film so that the back side of the polymer membrane is freely accessible, c) applying an adhesive film to the front-side, first catalyst layer, d) coating a second catalyst layer on the back side of the polymer membrane.

[0027] The method according to the invention has proven to be particularly advantageous in several aspects.

[0028] The process, in particular, allows for the continuous production of membrane electrode assemblies by directly coating a second catalyst layer to provide the polymer membrane. Advantageously, the coating can be used to obtain a stable membrane-electrode assembly, particularly for membranes based on hydrocarbon ionomers, which, as explained above, are not suitable for a decal transfer process. By providing the adhesive film, any disadvantages that may arise during the coating process with regard to membrane deformation are effectively avoided.

[0029] Thus, by applying an adhesive film to the front-side first catalyst layer, a sufficiently stabilized effect is achieved for the coating of a second catalyst layer on the back of the polymer membrane, which is based on hydrocarbon ionomers. The adhesive film therefore acts as a stabilizer for the polymer membrane while the coating of the second catalyst layer takes place. The stabilizing effect is particularly pronounced due to the adhesive film, since its adhesive property offers sufficient mechanical resistance during the coating of the second catalyst layer, so that deformation, swelling and / or expansion and / or shrinkage of the polymer membrane is prevented. This advantageously results in a homogeneous, i.e.a smooth and wrinkle-free membrane electrode assembly is provided, which ensures reliable functionality when used in a fuel cell and / or electrolysis cell.

[0030] The approaches known in the prior art for coating an additional catalyst layer are advantageous in themselves, but they had the disadvantage that applying the catalyst layer in liquid form resulted in deformations of the polymer membrane, for example, due to swelling and / or shrinkage. This adverse effect is particularly pronounced in the case of polymer membranes based on hydrocarbon ionomers. The inventive use of an adhesive film, which is applied to the first catalyst layer prior to the application of the second catalyst layer, thus reveals its advantages particularly in the production of membrane-electrode assemblies comprising a polymer membrane based on hydrocarbon ionomers.

[0031] A further advantage of the process according to the invention is that it can be used as a film-based manufacturing process within a roll-to-roll process on an industrial scale. This allows for the cost-effective and mass-producible production of membrane electrode assemblies that can be used in a fuel cell and / or electrolysis cell.

[0032] Furthermore, the process steps in the roll-to-roll process can be carried out essentially at room temperature. Higher temperatures can optionally be used only during drying steps to accelerate the process. Consequently, the conditions for the process steps can be well controlled. Furthermore, the process advantageously features high process efficiency. For example, the process according to the invention allows for a continuous process thanks to the continuously feedable adhesive film and the smooth integration of the coating, without interruptions or pauses reducing the effectiveness of the production process.

[0033] The method according to the invention serves in particular to produce a membrane electrode assembly for a fuel cell and / or an electrolysis cell. As explained above, a membrane electrode assembly preferably refers to an essential component for the operation of a fuel cell or an electrolysis cell. The membrane electrode assembly comprises the polymer membrane and two catalyst layers, which in the context of the invention are referred to as the first and second catalyst layers. The polymer membrane has a front side and a back side. The first catalyst layer is applied to the front side of the polymer membrane, and the second catalyst layer is located on the back side of the polymer membrane. The membrane electrode assembly is given particular importance because it is jointly responsible for several functions during the operation of a fuel cell and / or electrolysis cell.They enable the partial electrochemical reactions that lead to the overall reaction process. Furthermore, they must possess a certain degree of ionic and electronic conductivity to enable transfer through the membrane-electrode assembly. Furthermore, they fulfill a sealing and insulating function with respect to other components that can also be used for the fuel cell and / or electrolysis cells, such as bipolar plates. The basic structure and function of a fuel cell are known to those skilled in the art. A fuel cell preferably comprises an anode, a cathode, and a polymer membrane. Between the electrodes is an electrolyte that acts as an ion conductor between the anode and cathode. The polymer membrane lies between the anode and cathode. An electrolysis cell has a fundamentally identical structure to a fuel cell; however, the reaction and function are reversed.For example, in hydrogen electrolysis in an electrolysis cell, water is converted into hydrogen with the help of electrical current, which can then be stored. In a fuel cell, this process is reversed and electrical current is generated.

[0034] According to the invention, the polymer membrane is based on hydrocarbon ionomers. An ionomer is known in the art as a polymer having recurring side chains bonded to the polymer backbone and comprising electrically charged or ionic and electrically neutral functional groups. Side chains comprising ionic functional groups are referred to as ionic side chains. An ionomer preferably has a proportion of at least 10% ionic side chains (preferably in relation to the total number of ionic and non-ionic side chains), particularly preferably a proportion of more than 30% ionic side chains.

[0035] In one embodiment, the ionomer has a proportion of at least 10% (of the side chains) of ionic side chains, for example, at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% ionic side chains. In another embodiment, the ionomer has a proportion of 30% to 70% ionic side chains.

[0036] For proton-conducting polymer membranes, ionomers or polymers with negatively charged ionic side chains can generally be used, while anion-conducting membranes generally comprise ionomers or polymers with positively charged ionic side chains. Negatively charged ionic side chains include, but are not limited to, anionic functional groups such as sulfonate -SO3'X. + , Phosphoryl - PO3'X + 2 and / or carboxyl -COO X -, where X is a proton (H +) or another cation, for example a potassium or sodium cation. Positively charged ionic side groups include, but are not limited to, cationic functional groups such as sulfonium -R1 R2R3S + Y', Phosphonium -R1 R2R3P + Y', and / or a quaternary amine - R1 R2R3N + Y where R1, R2 and R3 are alkyl or aryl and Y is an anion, for example a chloride, iodide, bromide or fluoride anion.

[0037] An ionomer may further comprise side chains which comprise non-ionic or neutral functional groups, such as, but not limited to, alkyl, halogen, nitro and / or cyano.

[0038] A hydrocarbon ionomer means an ionomer having a polymer backbone essentially comprising carbon and hydrogen. The polymer backbone of a hydrocarbon ionomer may further comprise heteroatoms such as nitrogen, sulfur, oxygen, and / or phosphorus. A hydrocarbon ionomer may further comprise a linker that forms a covalent bond between the backbone of the hydrocarbon ionomer and a side chain and / or between the individual units of the polymer backbone, for example, but not limited to, sulfonyl, ester, ether, amide, secondary amine, tertiary amine, and / or ammonium.

[0039] Examples of a polymer backbone of a hydrocarbon ionomer include, but are not limited to, polyarylene such as polyphenylene, polysulfone, polyester, polyether, polyketone, polyimide, polyamide, polyimidazole, polyurethane, and polyalkylene. In one embodiment, the polymer backbone of a hydrocarbon ionomer of the present invention is a polyarylene, preferably selected from the group consisting of polyphenylene, polysulfone, polyester, polyimide, polyamide, polyurethane, and polyalkylene, with polyphenylene being particularly preferred.

[0040] In one embodiment, a hydrocarbon ionomer preferably comprises a polymer backbone formed by a chain comprising carbon atoms and hydrogen atoms. Preferably, the polymer backbone comprises aryl groups such as phenyl groups. Preferably, a hydrocarbon ionomer comprises an ionic side chain which is sulfonate SO3-X. +, Phosphoryl PÜ3-X + 2 and / or carboxyl COO-X + wherein X is a proton or another cation, such as a potassium or a sodium ion. Preferred hydrocarbon ionomers can be found in WO 2018 / 187864 A1. A hydrocarbon ionomer comprising an ionic side chain which is sulfonate SOa-X + is referred to as a sulfonated hydrocarbon ionomer in the sense of the invention.

[0041] In one embodiment, the hydrocarbon ionomer is a sulfonated polyarylene, preferably selected from the group consisting of sulfonated polyphenylene, sulfonated polysulfone, sulfonated polyester, sulfonated polyimide, sulfonated polyamide, sulfonated polyurethane, and sulfonated polyalkylene. The hydrocarbon ionomer is particularly preferably a sulfinated polyphenylene. The fact that the polymer membrane is based on hydrocarbon ionomers means, in particular, that the polymer membrane has a higher proportion of hydrocarbon ionomers than other optional chemical compounds that could be used to construct the polymer membrane. In particular, the polymer membrane can essentially comprise hydrocarbon ionomers, preferably a proportion of more than 80% by weight, more than 90% by weight, more than 95% by weight, more than 99% by weight.

[0042] The polymer membrane serves in particular to allow the passage of protons or anions, while the first and second catalyst layers are involved in the partial chemical reactions for the anode and cathode.

[0043] First, the polymer membrane based on hydrocarbon ionomers is provided. A carrier film is located on the back of the polymer membrane, and the first catalyst layer is located on the front. In the context of the invention, it is preferably provided to provide the following layer sequence at the beginning of the process: a carrier film, on which the polymer membrane is positioned, and on the front of the polymer membrane, the first catalyst layer, with the carrier film initially being applied to the back of the polymer membrane. The carrier film refers to a film that acts as a carrier and thus also as a support for the polymer membrane and first catalyst layer. The layer sequence comprising carrier film, polymer membrane, and catalyst layer can preferably be provided as a holistic unit and used for the further process steps.It may also be preferable to provide such a layer sequence within the scope of the process in which the polymer membrane is applied to a carrier film and the first catalyst layer is applied to the front side of the polymer membrane.

[0044] In order to expose the back of the polymer membrane, the carrier film is removed. The back of the polymer membrane is therefore freely accessible, i.e. in particular freely accessible for application of a further layer, in particular the second catalyst layer. Before coating the second catalyst layer, the adhesive film is applied to the first catalyst layer in order to give the layer system the stability required to obtain a polymer membrane coated on both sides with catalyst layers that is as smooth and wrinkle-free as possible. It may be preferable for the adhesive film to be applied to the first catalyst layer after the carrier film has been removed, i.e. that step b) takes place before step c). In other words, it may be preferable for the carrier film to be removed first before the adhesive film is applied.Although the polymer membrane in this embodiment is preferably not temporarily stabilized by a carrier film or an adhesive film, it has been recognized that this advantageously enables, particularly in a roll-to-roll process, easy application of the adhesive film to one or the same roll or cylinder (see Fig. 1) on which the second catalyst layer is coated. This ensures a particularly rapid process flow for carrying out the process steps, particularly with regard to the coating of the second catalyst layer.

[0045] A short-term guidance of the polymer membrane preferably means a distance of less than 20 cm, preferably less than 10 cm, particularly preferably 1 cm - 10 cm, most preferably approximately 3 - 5 cm. The distance refers in particular to a length of the polymer film between a position of removal of the carrier film (for example by means of a wedge) and the application of the adhesive film (for example on a roller or cylinder), as is shown by way of example for a preferred embodiment in Fig. 1. In other words, in preferred embodiments of the method, the polymer membrane with coated first catalyst layer can be guided over the above-mentioned distances essentially freely, i.e. in particular without the support of a further carrier or adhesive film. In this embodiment too, application of the second catalyst layer to the polymer membrane preferably takes place after stabilization by the adhesive film.The above-mentioned embodiment advantageously offers greater spatial flexibility, particularly for a roll-to-roll process, with regard to the positioning of components used for removing the carrier film and applying the adhesive film, and thus ensures greater process reliability and speed.

[0046] It may also be preferable for the adhesive film to be applied to the first catalyst layer first, followed by the removal of the carrier film, so that step c) can take place before step b). Therefore, the listing of steps a)-d) does not specify a restrictive order. Rather, the process can also be carried out using a different order of the listed process steps.For example, the method can preferably also be characterized by the following sequence of process steps: a) providing a polymer membrane based on hydrocarbon ionomers comprising a front side and a back side, wherein a carrier film is present on the back side and a first catalyst layer is present on the front side, b) applying an adhesive film to the front-side, first catalyst layer, c) removing the carrier film so that the back side of the polymer membrane is freely accessible, d) coating a second catalyst layer onto the back side of the polymer membrane.

[0047] In a preferred embodiment, the adhesive film has a continuous surface and preferably, in particular, comprises essentially no perforations. Essentially no perforations means, in particular, that the area ratio of perforations to the total area of ​​the adhesive film is less than 1%, preferably less than 0.1%, 0.01%, 0.001%, or less. The adhesive film particularly preferably has no perforations.

[0048] In a preferred embodiment, the adhesive film is applied to the first catalyst layer essentially over its entire surface. Full-surface application of the adhesive film to the first catalyst layer preferably means that the adhesive film is applied to the first catalyst layer over at least 80%, preferably at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99%, or completely (100%) the surface of the first catalyst layer. Thus, in particular, the essentially complete application also achieves essentially complete contact between the adhesive film and the first catalyst layer to form a uniform adhesive force.

[0049] In particular, this ensures essentially full-surface and uniform adhesion of the adhesive film to the first catalyst layer. Adhesion, for example, only along an edge area is not present. This further reduces the risk of possible deformation of the polymer membrane during the coating of the second catalyst layer.

[0050] After the adhesive film is applied to the front-side first catalyst layer, the second catalyst layer is coated on the back of the polymer membrane. The adhesive film advantageously prevents swelling and / or shrinkage while the second catalyst layer is coated onto the polymer membrane. This is ensured in particular by the adhesive effect of the adhesive film, which prevents unwanted deformation by stabilizing the polymer membrane.

[0051] In a further preferred embodiment, the method is characterized in that the adhesive film contacts the polymer membrane with an adhesive force of 0.1 - 10 cN / mm (centinewtons per millimeter), preferably of 0.5 - 5 cN / mm, particularly preferably of 1 - 3 cN / mm.

[0052] The adhesive force preferably refers to the bonding force between the adhesive film and the polymer membrane. In the context of the invention, it is preferably specified in newtons per millimeter or centinewtons per millimeter. The adhesive force preferably indicates how much force must be applied to separate the adhesive film from the polymer membrane over an area of ​​1 mm. With regard to the design of the components to be used in the process, in particular with regard to the thickness of the polymer membrane and the pressure applied during the coating of the second catalyst layer, the stated value ranges for the adhesive force have proven advantageous in order to reliably maintain the homogeneity of the polymer membrane without adverse effects occurring due to excessive adhesive force.The aforementioned values ​​represent an optimal range that reliably prevents swelling and / or deformation for a wide variety of polymer membranes while simultaneously enabling residue-free removal of the adhesive film. This ensures high repeatability of the manufacturing process and reproducible high performance of the membrane electrode assembly in a fuel cell and / or electrolysis cell.

[0053] The adhesive strength can be measured, for example, using a so-called peel test. This preferably involves a force gauge, a sample holder, and a mechanism through which the adhesive film is peeled off at a continuous speed and at a specific angle. The adhesive film, which is attached to an object that is in turn attached to the sample holder, is peeled off by the mechanism. The force gauge measures the force applied to remove the adhesive film, taking the angle into account. A peel test can be performed using a suitable peel test device. The peel test can be carried out, for example, according to DIN 55529 and / or using a T-peel test.

[0054] In order to ensure that the shape of the polymer membrane is maintained by the adhesive effect of the adhesive film, it is preferred that the adhesive film comprises a portion and / or a component that enables adhesion as such.

[0055] The use of the adhesive film advantageously eliminates the need for additional adhesion promoters, which are used in the prior art, such as in EP 1492184 A1, to enable the necessary adhesion. Thus, the adhesive film can advantageously achieve sufficient adhesion and stability without additional materials, such as adhesion promoters, and without the need for further processing steps. In the manufactured membrane-electrode assembly as such, the use of the adhesive film can also result in a higher degree of compactness and / or avoid adhesive residues when the adhesive film is removed. Furthermore, a particularly uniform distribution of a supporting adhesive force can be achieved, whereby the adhesive film serves as a robust stabilizer for the polymer membrane and effectively prevents deformation, swelling, and / or expansion and / or shrinkage of the polymer membrane.

[0056] In a preferred embodiment, the method is characterized in that the adhesive film has a multi-layer structure and comprises a substrate and an adhesive layer, wherein, during application of the adhesive film, its adhesive layer is contacted with the first catalyst layer.

[0057] The adhesive layer preferably refers to an area of ​​the adhesive film through which, in particular, the adhesion between the adhesive film and the polymer membrane is enabled.

[0058] Accordingly, the adhesive layer can be considered an adhesive layer or adhesive-capable layer of the adhesive film. In the process, it is the adhesive layer that contacts the polymer membrane when the adhesive film is applied to the front-side, first catalyst layer.

[0059] The substrate refers to a component of the adhesive film that acts as the carrier of the adhesive layer and is particularly responsible for the mechanical stability of the adhesive film. The substrate provides the adhesive film with the stability it needs to provide the mechanical resistance needed for the coating of the second catalyst layer, preventing or significantly reducing swelling and / or shrinkage caused by the membrane.

[0060] In preferred embodiments, the substrate of the carrier film is formed by a material whose modulus of elasticity (E-modulus) of 1000 N / mm 2 up to 10,000 N / mm 2 , preferably 2000 N / mm 2 up to 8 000 N / mm 2 , particularly preferably 3000 N / mm 2 up to 6000 N / mm 2 amounts.

[0061] The adhesive film preferably has a strength, preferably a tensile strength in the longitudinal and / or transverse direction, between 10 - 1400 N / mm 2, preferably between 20 - 500 N / mm 2 , particularly preferably 50 - 300 N / mm 2 on.

[0062] The stated preferred strength ranges for the adhesive film have proven advantageous in ensuring sufficient stability to counteract possible deformations, such as swelling and / or shrinkage of the polymer membrane, during the coating of the second catalyst layer. At the same time, the stated preferred strength ranges are advantageous in that the adhesive film has sufficient flexibility to be used, in particular, in a roll-to-roll process. The preferred strength values ​​can be determined, in particular, by the choice of material and the thickness of the substrate to which the preferred adhesive layer is applied.

[0063] Preferably, the adhesive layer and the substrate are designed to be substantially congruent, so that the surface of the adhesive layer substantially covers the surface of the substrate. Therefore, it is preferred that the adhesive layer and the substrate substantially match each other in terms of length and / or width. The design of the adhesive layer and the substrate can thus also predetermine the design of the adhesive film. This can serve, for example, to optimize the adhesive properties to the polymer membrane and / or to save material.

[0064] It may also be preferred for a partial area of ​​the substrate to be coated with the adhesive layer. For example, it may be preferred to coat only an edge area of ​​the substrate with the adhesive layer, so that a central area of ​​the substrate is free of the adhesive layer. In particular, the adhesive layer may surround a surface of the substrate, so that the adhesive layer is not applied flatly to the substrate.

[0065] In preferred embodiments, the adhesive film has one or more perforations. This can preferably be specified by applying one or more perforations to the adhesive layer and / or the substrate. The one or more perforations can preferably be semicircular, circular, elliptical, triangular, square, pentagonal, hexagonal, and / or polygonal. The perforations can have different sizes; for example, it can be preferred for the one or more perforations to have dimensions between 0.1 and 1000 μm, preferably between 1 and 500 μm, particularly preferably between 10 and 200 μm.

[0066] By applying perforations, the achieved mechanical resistance to the coating of the second catalyst layer can be optimized. In particular, the perforations can increase the adhesive film's flexibility, allowing, for example, higher pressure to be applied to the second catalyst layer while simultaneously ensuring a homogeneous polymer membrane geometry. Furthermore, a faster feed rate can be set within a roll-to-roll process without increasing the risk of cracking.

[0067] In a further preferred embodiment, the method is characterized in that an adhesive force exists between the adhesive layer and the substrate which is greater than the adhesive force between the adhesive layer and the polymer membrane. Preferably, the adhesive force between the adhesive layer and the substrate is greater by a factor of 1, 5, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more than the adhesive force between the adhesive layer and the polymer membrane. The greater adhesive force, which is preferably present between the adhesive layer and the substrate, advantageously ensures that the structural design of the adhesive film is retained, while the adhesive film can be reliably removed from the second catalyst layer in order to be able to use it in a fuel and / or electrolysis cell.

[0068] In a further preferred embodiment, the process is characterized in that the substrate is selected from a group consisting of polyesters, preferably polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene, polypropylene, polyvinyl chloride (PVC), polyimide, and polyvinyl chloride. Likewise, the substrate can also be formed, for example, by a paper to which the adhesive layer is applied.

[0069] In a further preferred embodiment, the method is characterized in that the adhesive layer is formed by an adhesive material selected from a group comprising an acrylate and / or silicone. Hot-melt pressure-sensitive adhesives, such as rubber, can also be used with preference.

[0070] These preferred materials for the substrate and the adhesive layer allow the stability properties and / or adhesiveness of the adhesive film to be easily optimized, both to provide sufficient adhesive strength to stabilize the membrane and to avoid residues when removing the adhesive film. In particular, the materials mentioned are suitable for a substantially homogeneous distribution of the adhesive strength on the polymer membrane, so that no distortion occurs during the manufacturing process, thus maintaining the shape of the polymembrane, including the applied first catalyst layer.

[0071] The materials mentioned have also proven reliable in that they provide a sufficiently strong adhesive bond between the adhesive layer and the substrate to enable the adhesive film to be applied as a whole to the first catalyst layer on the polymer membrane. The adhesive strength between the adhesive layer and the substrate is preferably sufficiently high to prevent the adhesive layer from detaching from the substrate when removing the adhesive film from the first catalyst layer, as well as to withstand any shear forces that may occur when passing over rollers and / or rolls, particularly in a roll-to-roll process. The resulting adhesive film can thus be reliably used in a roll-to-roll process and is suitable for cost-effective mass production on an industrial scale.

[0072] Furthermore, the aforementioned materials offer a variety of advantages due to standardized processes for processing the adhesive film, for example the application of perforations and / or the modification of thickness values ​​of the adhesive layer and / or the substrate.

[0073] In a preferred embodiment, the method is characterized in that the adhesive film has a thickness of 10 μm - 1 mm, preferably 20 μm - 500 μm, further preferably 50 μm - 500 μm, particularly preferably 40 μm - 200 μm, very particularly preferably 100 μm - 200 μm. Preferred thicknesses of the adhesive films are in the aforementioned range, although intermediate ranges may also be preferred, such as, for example, 10 - 100 μm, 100 - 200 μm, 200 - 300 μm, 300 - 400 μm, 400 - 500 μm, 500 - 600 μm, 600 - 700 μm, 700 - 800 μm, 800 - 900 μm or 900 - 1000 μm or 1 mm. A person skilled in the art will recognize that other of the aforementioned preferred range limits can also be combined to obtain further preferred ranges, such as 100 pm to 500 pm, 400 pm to 1000 pm or even 200 pm to 600 pm.

[0074] The specified thickness values ​​for the adhesive film, on the one hand, promote mechanical resistance to stabilize the polymer membrane while the second catalyst layer is applied to the polymer membrane. On the other hand, the thicknesses are not so high that they would complicate processing in a roll-to-roll process. The preferred ranges thus represent an optimal range for producing an electrode-membrane unit reliably and without deformation in a roll-to-roll process.

[0075] One of ordinary skill in the art will recognize that in the preferred embodiment in which the adhesive film comprises a substrate and an adhesive layer, the sum of their individual thicknesses results in the total thickness of the adhesive film.

[0076] In a preferred embodiment, the thickness of the substrate can be, for example, from 5 pm - 900 pm, preferably from 15 pm - 400 pm, particularly preferably between 30 - 150 pm, while the adhesive layer can have, for example, a thickness of 1 pm - 100 pm, preferably between 5 - 50 pm, particularly preferably between 10 - 30 pm.

[0077] In a further preferred embodiment, the method is characterized in that the adhesive film is removed after coating the second catalyst layer and / or wound up on a winding roll for recycling.

[0078] Removing the adhesive film exposes the first catalyst layer, allowing the membrane electrode assembly to be integrated into a fuel cell and / or electrolysis cell to which it was previously applied. For operation in a fuel cell and / or electrolysis cell, it is important that the adhesive film is no longer attached for the corresponding partial reaction of the overall reaction. The adhesive film can preferably be removed immediately before integration into a fuel cell and / or electrolysis cell.

[0079] For example, it may be preferable to transport the manufactured membrane electrode assembly to the site of integration into a fuel cell and / or electrolysis cell with the protective adhesive film still in place. Advantageously, the membrane electrode assembly, together with the adhesive film, already represents a transportable individual product that can be brought to the site of integration into a fuel cell and / or electrolysis cell without any loss of quality.

[0080] In preferred embodiments, the adhesive film can also be removed and replaced with another carrier film. The membrane electrode assembly can be transported together with the other carrier film to the site of integration into a fuel cell and / or electrolysis cell. For example, the carrier film can be selected to be more cost-effective than the adhesive film, thereby further increasing cost-effectiveness. The other carrier film then preferably corresponds to a transport film and fulfills a protective function, particularly during transport. The requirements with regard to material selection for such a transport or protective film are lower than for the adhesive film, the adhesive strength of which, as explained, is preferably matched to the polymer membrane.

[0081] It may also be preferable to transport the membrane electrode assembly without any additional foil directly to a location where the integration in a fuel cell and / or electrolysis is to be carried out.

[0082] It may also be preferred for the adhesive film to be wound onto a winding roll, so that the wound adhesive film can advantageously be reused for recycling. This is particularly preferred if the adhesive film is to be removed and / or replaced, for example, with another carrier film or transport film.

[0083] Winding the adhesive film onto the winding roll can, for example, also be carried out as an additional step of the method according to the invention. This can take place, in particular, after the application of the second catalyst layer, i.e., after the essential purpose of the adhesive film has been fulfilled. Preferably, a corresponding operative connection can be present so that after coating (and / or optional drying of the second catalyst layer), the adhesive film is wound back onto a winding roll for reuse in a continuous process. This advantageously results in material savings for the adhesive film, which proves particularly advantageous with regard to mass production.Furthermore, recycling the adhesive film is also advantageous for the process itself, as it ensures a continuous production process that can run essentially uninterrupted, and factors such as the reinsertion of adhesive film, should it run out, can be disregarded. In a further preferred embodiment, the process is characterized in that the adhesive film has a protective film, wherein the protective film is removed before the adhesive film is applied to the first catalyst layer.

[0084] The protective film refers to a component applied to the adhesive film to prevent the adhesive film from sticking to itself or to other (undesired) components. In particular, the protective film also prevents unwanted sticking to a take-up roll to which the adhesive film might be attached. Advantageously, this makes the feeding of the adhesive film more reliable, enabling uniform contact with the first catalyst layer. In alternative embodiments, the adhesive film does not have a protective film, but is present on a take-up roll, for example, analogous to an adhesive strip without a separate protective film.

[0085] In the preferred embodiment, in which the adhesive film comprises a substrate and an adhesive layer, the protective film is present on the adhesive layer. The protective film is preferably present in a substantially precisely fitted manner on the adhesive film and is held in place by the adhesive effect of the adhesive layer. In this case, it is preferred that the adhesive force between the protective film and the adhesive film is, on the one hand, sufficient to ensure reliable processing in a roll-to-roll process and, on the other hand, not too great to cause partial detachment of the adhesive layer from the substrate when the protective film is removed. To attach the adhesive film to the first catalyst layer, the protective film is first removed, which can be done, for example, using a roller designed for this purpose. The protective film can, for example, comprise a material selected from a group comprising polyesters, for example polyethylene terephthalate (PET).

[0086] In a further preferred embodiment, the method is characterized in that the method is carried out via a roll-to-roll process, wherein the adhesive film is preferably applied to the first catalyst layer via a coating roll and a coating of the second catalyst layer is subsequently carried out while the polymer membrane is still guided along the coating roll.

[0087] The roll-to-roll process refers to a manufacturing process in which one or more rolls and / or cylinders are used to perform process steps such as coating, application, and / or lamination. The number of rolls and / or cylinders is referred to as the web run and can be determined by one skilled in the art.

[0088] In the context of the invention, the carrier film, the polymer membrane, and the first catalyst layer are preferably continuously fed into the process via a first roll. It is preferred that the composite comprising the carrier film, polymer membrane, and first catalyst layer be wound along the first roll. Furthermore, it may be preferred to allow a deflection of the composite used at the beginning of the process via a second roll, which can also be referred to as a deflection roll, by which the adhesive film can be applied to the first catalyst layer and / or the carrier film can be removed.

[0089] The adhesive film is preferably provided by a further roller, which according to the invention can also be referred to as an unwinding roller for the adhesive film. The adhesive film is, however, preferably applied to the first catalyst layer using a coating roller, with the second catalyst layer being coated subsequently while the polymer membrane is still being guided along the coating roller. In other words, the adhesive film is preferably provided by the unwinding roller, while the coating roller pulls the adhesive film off the unwinding roller and enables coating with the second catalyst layer. In order to ensure reliable adhesion of the adhesive film, the adhesive film is preferably applied in such a way that the application as such is essentially parallel to the surface normal vector and therefore perpendicular to the section plane of the first catalyst layer orthe polymer membrane. Thus, the application of the adhesive film to the first catalyst layer can preferably be carried out using both compressive stress and tensile stress. If the force for applying the adhesive film, from which the stress results, acts in such a way that the polymer membrane or first catalyst layer is pulled at the cutting plane, this is referred to as tensile stress. However, if the acting stress exerts pressure against the cutting plane, it is preferably referred to as compressive stress. In the embodiment in which the adhesive film is present with a protective film, the removal of the protective film is preferably carried out using an unwinding roll for the protective film before the application of the adhesive film to the first catalyst layer can take place.

[0090] The carrier film can preferably be removed via a winding roll for the carrier film, onto which the carrier film used at the beginning of the process is wound. It may be preferred that the rolls be configured such that the adhesive film is applied before the carrier film is removed. It may also be preferred that the adhesive film is applied after the carrier film has been removed. The winding roll for removing the carrier film can preferably be in the form of a wedge, so that the carrier film is removed via the wedge. This ensures that the removal of the carrier film does not disrupt the subsequent production process.

[0091] Preferably, the composite comprising adhesive film, first catalyst layer, and polymer membrane is guided along a coating roll. While still being guided along the coating roll, the back of the polymer membrane is coated with the second catalyst layer. The coating roll refers to a roll configured to peel the adhesive film from the unwinding roll for the adhesive film and apply it to the first catalyst layer, as well as to position the polymer membrane such that the second catalyst layer can be coated onto the back of the polymer membrane. This advantageously achieves considerable efficiency, as it ensures a continuous process flow to enable the stability required for the coating to maintain the shape of the polymer membrane.

[0092] The use of a roll-to-roll process advantageously allows the web speed to be precisely determined, particularly with regard to the process steps to be performed. Thus, it may be preferred that the process steps run continuously at a substantially equal and constant speed. It may also be preferred that the web speed be intermittent, so that, depending on the production step, a faster or slower web speed is preferred.

[0093] Preferably, the size, in particular the diameter, of the coating roller can be used to define a time window within which the coating of the second catalyst layer is to take place. Typically, a larger time window exists if the coating roller has larger dimensions. The rolling speed of the coating roller can also (co-)determine the time window for coating with the second catalyst layer. The coating of the second catalyst layer preferably takes place at the outlet of the slot die. The size of the roller thus determines the time window over which the adhesive film is applied or pressed onto the first catalyst layer.

[0094] In a further preferred embodiment, the method is characterized in that the coating of a second catalyst layer is carried out using a coating method selected from a group comprising slot die coating, spray coating, screen printing method, doctor blade coating, and / or gravure printing method, wherein a slot die coating is particularly preferably used.

[0095] The listed methods are known to those skilled in the art. In the context of the invention, the mentioned process options have proven reliable for coating the second catalyst layer onto the back of the polymer membrane. In particular, the mentioned processes can be easily integrated into a roll-to-roll process, thereby improving the efficiency of the manufacturing process. To carry out a preferred process for coating the second catalyst layer, a corresponding coating component is preferably used. The preferred coating component is designed to carry out a selected coating process.

[0096] The use of a slot-die coating is particularly advantageous in that it allows for the precise predetermination of the amount of the second catalyst layer to be applied. Furthermore, a uniform distribution of the catalyst layer on the back of the polymer membrane is achieved, so that the second catalyst layer is homogeneously distributed or can spread when applied in the liquid phase. In particular, no or only insignificant variations in the thickness of the second catalyst layer are advantageously achieved when using a slot-die coating, which is particularly advantageous for operation in a fuel cell and / or electrolysis cell. With a slot-die coating, a slot-die coating component comprising a nozzle and a pouring head is preferably used. The material for the second catalyst layer is preferably introduced into the pouring head and is applied to the polymer membrane via the nozzle.

[0097] In a further preferred embodiment, the process is characterized in that the second catalyst layer is dried after coating onto the polymer membrane using a drying process, wherein the drying process is preferably selected from a group comprising hot air drying, infrared drying, plasma drying, and / or contact drying (e.g. via a heating cylinder or a heating roller), wherein preferably a drying time between 1 - 30 min, preferably between 1 - 5 min, particularly preferably between 1 - 4 min and / or a temperature between 20°C - 150°C, preferably between 20°C - 100°C or 40° - 100°C is used.

[0098] Drying can solidify the second catalyst layer, which can then enable use in a fuel cell and / or electrolysis cell. During drying, moisture is removed from the second catalyst layer, particularly by evaporation or vaporization. This can be achieved by applying one or more of the drying methods mentioned above. Preferably, the second catalyst layer is in a dry state when the moisture content is approximately 30% or less.

[0099] The drying time can be varied depending on the drying method and / or temperature used. Typically, the drying time can be shortened if a higher temperature is applied. For example, it is preferred that the drying time is approximately 30 minutes if drying takes place at room temperature (i.e., at approximately 20°C). At higher temperatures of, for example, approximately 150°C, the drying time can be shortened to, for example, 4 minutes. The drying time can, for example, be set over a distance that is defined between the coating roll and a take-up roll in a roll-to-roll process. Within the distance, which can also be referred to as the drying section, a drying method for drying the second catalyst layer can preferably be used.

[0100] In a further preferred embodiment, the process is characterized in that the polymer membrane based on the hydrocarbon ionomers is free of perfluorinated sulfonic acids, preferably substantially fluorine-free.

[0101] Sulfonic acids are known as organic sulfur compounds with the general structure R-SO2-OH, where R represents an organic residue, SO2 represents sulfur dioxide and OH represents the hydroxy group.

[0102] Perfluorinated means that at least one carbon atom of the carbon skeleton of the sulfonic acid, to which hydrogen atoms are bonded, has its hydrogen atoms completely replaced by fluorine atoms. Preferably, the hydrogen atoms of several carbon atoms or of all carbon atoms of the carbon skeleton can also be replaced by fluorine atoms.

[0103] Free of perfluorinated sulfonic acids preferably means that the polymer membrane has a proportion of up to 5 mol percent at most, particularly preferably up to 2.5 mol percent at most, most preferably up to 1 mol percent at most.

[0104] Essentially fluorine-free preferably means that fluorine content is up to 5 mol percent, up to 2.5 mol percent, or up to 1 mol percent. Essentially fluorine-free polymer membranes can particularly preferably mean that the polymer membrane is completely free of fluorine.

[0105] The polymer membrane preferably comprises sulfophenylated polyarylene (sPPX), in particular sulfophenylated polyphenylene (sPPP), i.e., sulfophenylated polyarylene containing a phenylene linker in the main chain of the ionomer. Sulfophenylated polyphenylene provides the polymer membrane with high mechanical robustness and high ionic (protonic) conductivity, which is particularly advantageous for operation in a fuel cell and / or electrolysis cell. The sulfophenylated polyphenylene can preferably have the structure disclosed in Fig. 1 of the paper Nguyen, Hien, et al., “Hydrocarbon-based Pemion™ proton exchange membrane fuel cells with state-of-the-art performance.” Sustainable Energy & Fuels 5.14 (2021): 3687-3699, or in Fig. 1 of patent application WO 2018 / 187864 A1.

[0106] In a further preferred embodiment, the method is characterized in that the polymer membrane has a thickness between 10 - 500 pm, preferably between 10 - 350 pm, particularly preferably between 10 - 250 pm, most particularly preferably between 10 - 50 pm.

[0107] The mentioned ranges for the thickness of the polymer membrane have proven to be advantageous in order to have a high ionic and at the same time low electrical conductivity as well as a high chemical resistance, for example against peroxides, hydrolysis and / or redox reactions, as well as a high mechanical stability in order to ensure safe and long-lasting operational suitability in a fuel cell and / or electrolysis cell.

[0108] In a further preferred embodiment, the process is characterized in that the first and / or second catalyst layer is coated as a disperse liquid onto the polymer membrane.

[0109] A disperse liquid, or dispersion, is a heterogeneous mixture of substances containing two or more substances that are insoluble or only slightly soluble in one another. Typically, the catalyst layer comprises several components. These can serve different functions to ensure secure bonding to the polymer membrane and / or optimal performance during operation of the fuel cell and / or electrolysis cell.

[0110] In a further preferred embodiment, the method is characterized in that a catalyst ink is provided for coating the first and / or second catalyst layer, wherein the catalyst ink preferably comprises a catalyst material, a carrier material, a solvent and / or a binder material.

[0111] The catalyst material is preferably a material selected from a group comprising platinum, ruthenium, rhodium, iridium, palladium, gold, silver, chromium, manganese, copper, cobalt, nickel, iron, molybdenum, and / or yttrium. The catalyst material serves the actual catalytic effect during the chemical reaction during operation of the fuel cell and / or electrolysis cell. The catalyst material can be in powder or particle form, which gives the catalyst ink its dispersed character.

[0112] The support material preferably comprises carbon, preferably in graphite form. The support material serves in particular to advantageously distribute the catalyst material. Furthermore, the support material can increase the active surface area of ​​the catalyst material used. Furthermore, the support material can promote stability and charge transport. The solvent preferably comprises a material selected from a group comprising water, an organic solvent, preferably ethanol, propanol and / or butanol, and / or solvent mixtures. The solvent imparts its dispersive behavior to the catalyst layer and is essentially evaporated or vaporized during an optional drying step.

[0113] A hydrocarbon-based ionomer is preferably used as the binder material. The binder preferably serves to enable both a long-lasting, stable bond between the catalyst material and the polymer membrane and protonic conductivity within the catalyst layer.

[0114] In a further preferred embodiment, the method is characterized in that the carrier film comprises a material selected from a group comprising polyesters (such as

[0115] B. Polyethylene terephthalate (PET) and / or polyethylene naphthalate (PEN)), polyethylene, polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate, polyamide, polyimide and / or polyurethane.

[0116] In a further preferred embodiment, the method is characterized in that the carrier film has a thickness between 0.01 - 2 mm, preferably between 0.1 - 0.5 mm, particularly preferably between 0.1 - 0.3 mm.

[0117] The listed materials and / or thickness ranges for the carrier film have proven advantageous, on the one hand, to provide stable and long-lasting support for the polymer membrane and first catalyst layer at the beginning of the process, and, on the other hand, to be easily removed from the back of the polymer membrane without leaving residues on the polymer membrane. This can improve the homogeneity of the second catalyst layer to be coated on the back of the polymer membrane and thus also the performance of a fuel cell and / or electrolysis cell.

[0118] In a further aspect, the invention relates to a membrane electrode assembly that can be produced by a method according to the above-described method.

[0119] The average person skilled in the art recognizes that technical features, definitions and advantages of embodiments that apply to the method for producing the membrane electrode assembly equally apply to the membrane electrode assembly, and vice versa.

[0120] As explained above, the membrane electrode assembly comprises the polymer membrane as well as the front-side first catalyst layer and the back-side second catalyst layer.

[0121] After the membrane electrode assembly has been produced, the adhesive film can be located on the first catalyst layer, so that the end product can comprise the membrane electrode assembly and the adhesive film. Furthermore, it can be preferred for a separating film to be applied to the second catalyst layer. Advantageously, this can provide a stack of membrane electrode assemblies that are positioned and / or stacked on top of one another without one of the catalyst layers being in direct contact with another catalyst layer of a different membrane electrode assembly. This provides reliable protection for the catalyst layers of the membrane electrode assemblies. Thus, the end product of the production process can comprise the adhesive film and / or protective film together with the membrane electrode assembly. At a minimum, the end product comprises the manufactured membrane electrode assembly.

[0122] It may also be preferred for the membrane electrode assembly to be provided with an additional carrier film, which has previously been replaced with the adhesive film. The membrane electrode assembly can be transported with the additional carrier film to the site of integration into a fuel cell and / or electrolysis cell. The additional carrier film then preferably corresponds to a transport film and fulfills a protective function, particularly during transport.

[0123] It may also be preferred to integrate the membrane electrode assembly directly into a fuel cell and / or electrolysis cell without any additional foil.

[0124] In a further aspect, the invention relates to the use of the membrane electrode assembly producible by means of the described method for electrochemical applications, preferably selected from a group comprising hydrogen fuel cells, electrolysis cells, power-to-X applications, in particular for CO2 electrolysis and / or ammonia electrolysis.

[0125] The average person skilled in the art recognizes that technical features, definitions and advantages of embodiments which apply to the method for producing the membrane electrode assembly and / or to the membrane electrode assembly as such equally apply to the use of the membrane electrode assembly, and vice versa.

[0126] When used in a fuel and / or electrolysis cell, the membrane electrode assembly acts as a separator between the anode and cathode sides of the CCM and is selectively permeable. The respective chemical redox reactions or partial reactions take place in the electrode layers, which add up to an overall reaction and are responsible for the reaction sequence within the fuel cell and / or electrolysis cell.

[0127] Power-to-X applications primarily refer to technologies in which excess electrical power is converted into chemical energy sources for electricity storage, into electricity-based fuels for mobility, and / or into raw materials for the chemical industry. The term "power" refers to temporary surplus electricity production above demand, and "X" stands for the energy form or intended use. Power-to-X applications are therefore divided according to intended use (e.g., power-to-fuel, power-to-chemicals, or power-to-ammonia) or energy form (power-to-gas, power-to-heat, power-to-liquid). The membrane electrode assembly can also be advantageously used in such applications, thus opening up a wide range of energy-related applications for the membrane electrode assembly.

[0128] The aspects of the invention will be explained in more detail below with reference to figures, without being limited to these figures.

[0129] FIGURES

[0130] Brief description of the figures Fig. 1 Schematic representation for carrying out a preferred embodiment of the method according to the invention for producing a membrane electrode assembly

[0131] Detailed description of the characters

[0132] Fig. 1 schematically illustrates the steps for carrying out the method to manufacture the membrane electrode assembly.

[0133] First, a polymer membrane 1 based on hydrocarbon ionomers is provided, comprising a front side and a back side. A carrier film 5 is present on the back side, while the first catalyst layer 3 is present on the front side. The carrier film 5 is removed, leaving the back side of the polymer membrane 1 freely accessible. An adhesive film 7 is applied to the front-side first catalyst layer 3. A second catalyst layer 9 is then coated onto the back side of the polymer membrane 1.

[0134] The application of the adhesive film 7 to the front-side first catalyst layer 3 advantageously achieves a stabilizing effect for the coating of the second catalyst layer 9 on the back of the polymer membrane 1. The adhesive film 7 therefore acts as a stabilizer for the polymer membrane 1 while the coating of the second catalyst layer 9 is taking place. The stabilizing effect is particularly pronounced due to the adhesive film 7, since its adhesive properties offer sufficient mechanical resistance when the second catalyst layer 9 is coated, thus preventing deformation, swelling, and / or expansion and / or contraction of the polymer membrane 1. This advantageously produces a homogeneous, in particular smooth and wrinkle-free, membrane-electrode assembly, thereby ensuring reliable functionality when used in a fuel cell and / or electrolysis cell.

[0135] A further advantage is that the method can be applied in mass production, so that it can also be used on an industrial scale. This allows membrane electrode assemblies to be produced both cost-effectively and in a mass-producible manner, which can be used in particular in a fuel cell and / or electrolysis cell. A further advantage of the method according to the invention is that it can be used as a film-based manufacturing process in a roll-to-roll process on an industrial scale. This allows membrane electrode assemblies to be produced both cost-effectively and in a mass-producible manner, which can be used in a fuel cell and / or electrolysis cell. An embodiment of the method in a roll-to-roll process is shown in Fig. 1, which will be described in more detail below.

[0136] In the roll-to-roll process, the composite comprising the carrier film 5, the polymer membrane 1, and the first catalyst layer 3 is continuously fed via a first roll (not shown). A second roll or deflection roll 11 can enable deflection of the composite used at the beginning of the process, by means of which the adhesive film 7 can be applied to the first catalyst layer 3 and / or the carrier film 5 can be removed. The adhesive film 7 is applied to the first catalyst layer 3 by a coating roll 17. The coating roll 17 pulls the adhesive film 7 from a pay-off roll 13, which provides the adhesive film 7. To enable reliable adhesion of the adhesive film 7, the adhesive film 7 is applied such that it is directed essentially parallel to the surface normal vector and thus perpendicular to the section plane of the first catalyst layer 3 or the polymer membrane 1.Thus, the adhesive film 7 can be applied to the first catalyst layer 3 using both compressive and tensile stress. Preferably, a protective film is present on the adhesive film 7, which can be removed by a protective film winding roll 15 before the adhesive film 7 is applied to the first catalyst layer 3.

[0137] The removal of the carrier film 5 can be achieved via a wedge 19 or a take-up roll for the carrier film, onto which the carrier film 5, which is inserted at the beginning of the process, is wound. In the illustration in Fig. 1, the adhesive film 7 is applied after the carrier film 5 has been removed. A wedge 19 can be used to remove the carrier film 5, as shown in Fig. 1, with the carrier film 5 being wound up via a take-up roll at a different position (indicated by a dashed arrow).

[0138] The composite comprising adhesive film 7, first catalyst layer 3, and polymer membrane 1 is guided along the coating roll 17. While still being guided along the coating roll 17, the back of the polymer membrane is coated with the second catalyst layer 9. The coating roll 17 denotes a roll configured to peel the adhesive film 7 from the unwinding roll 13 for the adhesive film and apply it to the first catalyst layer, as well as to position the polymer membrane such that the second catalyst layer 9 can be applied or coated to the back of the polymer membrane 1. The coating of the second catalyst layer is carried out using a coating process carried out by a corresponding coating component 21.This advantageously achieves considerable efficiency, as it ensures a continuous process flow in order to enable the stability required for the coating to maintain the shape of the polymer membrane 1.

[0139] REFERENCE SYMBOL LIST

[0140] 1 polymer membrane

[0141] 3 First catalyst layer

[0142] 5 Carrier film

[0143] 7 Adhesive film

[0144] 9 Second catalyst layer

[0145] 11 pulley

[0146] 13 Unwinding roll for adhesive film

[0147] 15 Take-up roll for protective film

[0148] 17 Coating roller

[0149] 19 Wedge or take-up roll for carrier film

[0150] 21 Coating component

Claims

PATENT CLAIMS 1 . A method for producing a membrane electrode assembly for a fuel cell and / or an electrolysis cell, comprising the following steps: a) providing a polymer membrane (1) based on hydrocarbon ionomers, comprising a front side and a back side, wherein a carrier film (5) is present on the back side and a first catalyst layer (3) is present on the front side, b) removing the carrier film (5 so that the back side of the polymer membrane (1) is freely accessible, c) applying an adhesive film (7) to the front-side, first catalyst layer (3), d) coating a second catalyst layer (9) on the back side of the polymer membrane (1).

2. Method according to the preceding claim, characterized in that the adhesive film (7) contacts the polymer membrane (1) with an adhesive force of 0.1 - 10 cN / mm, preferably of 0.5 - 5 cN / mm, particularly preferably of 1 - 3 cN / mm.

3. Method according to one or more of the preceding claims, characterized in that the adhesive film (7) has a multi-layer structure and comprises a substrate and an adhesive layer, wherein during the application of the adhesive film (7) the adhesive layer thereof comes into contact with the first catalyst layer (3).

4. Method according to the preceding claim, characterized in that the substrate is selected from a group of polyesters - preferably polyethylene terephthalate, polyethylene naphthalate - or from a group of polyolefins, preferably polyethylene, polypropylene or a group of polyimides and / or polyamides, polyvinyl chloride and / or the adhesive layer is formed by an adhesive material selected from a group comprising an acrylate, rubber and / or silicone.

5. Method according to one or more of the preceding claims, characterized in that the adhesive film (7) has a thickness of 10 pm - 1 mm, preferably of 20 pm - 500 pm, particularly preferably of 40 pm - 200 pm.

6. Method according to one or more of the preceding claims, characterized in that the adhesive film (7) is removed after coating the second catalyst layer (9) and / or is wound up on a winding roll for recycling.

7. Method according to one or more of the preceding claims, characterized in that TI the adhesive film (7) has a protective film, wherein the protective film is removed before the adhesive film is applied to the first catalyst layer.

8. Method according to one or more of the preceding claims, characterized in that the method is carried out via a roll-to-roll process, wherein the adhesive film (7) is preferably applied to the first catalyst layer (3) via a coating roll and a coating of the second catalyst layer (9) is subsequently carried out while the polymer membrane (1) is still being guided along the coating roll.

9. Method according to one or more of the preceding claims, characterized in that the coating of a second catalyst layer (9) is carried out using a coating method selected from a group comprising slot die coating, spray coating, screen printing method, doctor blade coating, and / or gravure printing method, wherein a slot die coating is particularly preferably used.

10. The method according to one or more of the preceding claims, characterized in that the second catalyst layer (9) is dried after coating onto the polymer membrane (1) using a drying method, wherein the drying method is preferably selected from a group comprising hot air drying, infrared drying, plasma drying and / or contact drying, wherein preferably a drying time between 1 - 30 min, preferably between 1 - 5 min, particularly preferably between 1 - 4 min and / or a temperature between 20°C - 150°C, preferably between 20°C - 100°C is used.

11. Method according to one or more of the preceding claims, characterized in that the polymer membrane (1) based on the hydrocarbon ionomers is free of perfluorinated sulfonic acids, preferably substantially fluorine-free.

12. Method according to one or more of the preceding claims, characterized in that the first and / or second catalyst layer (9) is coated as a disperse liquid onto the polymer membrane (1).

13. Method according to one or more of the preceding claims, characterized in that a catalyst ink is provided for coating the first and / or second catalyst layer (9), wherein the catalyst ink preferably comprises a Catalyst material which is bound to a support material, comprises a solvent and / or a binder material, wherein preferably the catalyst material comprises a material selected from a Group comprising platinum, ruthenium, rhodium, iridium, palladium, gold, silver, chromium, manganese, copper, cobalt, nickel, iron, molybdenum and / or yttrium, wherein preferably the solvent comprises a material selected from a group comprising water, an organic solvent, preferably ethanol, propanol and / or butanol as well as solvent mixtures, wherein preferably the carrier material comprises carbon, preferably in graphite form.

14. Membrane electrode assembly producible by a method according to one or more of the preceding claims.

15. Use of a membrane electrode assembly according to the preceding claim for electrochemical applications, preferably selected from a group comprising Hydrogen fuel cells, electrolysis cells, power-to-X applications, especially for CO2 electrolysis and / or ammonia electrolysis.

Images