Method for producing multi-layer, in particular five-layer or six-layer membrane electrode assembly

Abstract

The invention relates to a method for producing a multi-layer, in particular five-layer or six-layer membrane electrode assembly (1), comprising a polymer membrane (2), which has catalyst layers (5, 6) and gas diffusion layers (7, 8) on both sides, respectively, for forming an anode (3) and a cathode (4). According to the invention, the anode-side catalyst layer (5) is applied in a wet chemical coating process on the anode-side gas diffusion layer (7), dried and bonded to the polymer film (2) before complete drying.

Description

Field of the Invention

[0001] The present invention relates to a method for manufacturing a multi-layer, especially a five-layer or six-layer, membrane electrode assembly. A membrane electrode assembly is required for manufacturing an electrochemical cell (such as a fuel cell or an electrolytic cell).

[0002] Therefore, an electrochemical cell is a preferred application field for the membrane electrode assembly manufactured by the method according to the present invention. Background Art

[0003] A membrane electrode assembly for an electrochemical cell is constructed in multiple layers. A polymer membrane forms the core, and the polymer membrane has a catalyst layer and a gas diffusion layer on both sides respectively for constructing an anode and a cathode. Therefore, the membrane electrode assembly includes at least five layers. At least one thin film used as a gasket or a sub-gasket can be added as an additional layer, and the additional layer is usually arranged between the catalyst layer and the gas diffusion layer.

[0004] The manufacture of the layer or coating can be carried out especially by a wet chemical coating process. Here, an ionic polymer dispersion with or without a catalyst is applied to a carrier membrane and dried. Then, the coatings manufactured in this way are connected to each other in a lamination step.

[0005] In fact, the direct coating of a polymer membrane with an electrode ink to construct a catalyst layer has been mature. In this way, the lamination step can be bypassed. However, here, a solvent-sensitive polymer membrane is coated with an electrode ink that usually contains a solvent, and it is a challenge to remember to dry the electrode ink applied as a wet layer. Summary of the Invention

[0006] The task of the present invention is to simplify the manufacture of the membrane electrode assembly, especially considering the solvent sensitivity of the polymer membrane.

[0007] To solve this task, a method with the features of claim 1 is proposed. Preferred expansion schemes of the present invention are shown in the dependent claims.

[0008] The present invention proposes a method for manufacturing a multi-layer (especially a five-layer or six-layer) membrane electrode assembly, which includes a polymer membrane having a catalyst layer and a gas diffusion layer on both sides for constructing an anode and a cathode. According to the present invention, the anode-side catalyst layer is applied, dried on the anode-side gas diffusion layer in a wet chemical coating process, and joined to the polymer membrane before being completely dried.

[0009] Different from the direct coating of the above-mentioned polymer membrane, in the proposed method, the anode-side catalyst layer is not applied to the polymer membrane, but to the anode-side gas diffusion layer. This anode-side gas diffusion layer is usually composed of a carbon fiber felt, and the carbon fiber felt is coated with a coating on one side for constructing a microporous layer. However, the microporous layer can also be omitted ("low-cost GDL"). In any case, the gas diffusion layer is less sensitive to solvents than the polymer membrane, so it is more problem-free to apply the anode-side catalyst layer to the anode-side gas diffusion layer than to directly coat the polymer membrane. The anode-side catalyst layer applied on the anode-side gas diffusion layer is first dried before it contacts the polymer membrane, whereby the solvent content and the load on the polymer membrane can be reduced.

[0010] In the proposed method, the anode-side catalyst layer is applied to the anode-side gas diffusion layer by means of a wet chemical coating process, and the gas diffusion layer also serves as a carrier membrane at the same time. Since the gas diffusion layer constitutes one layer in the multilayer membrane electrode assembly, in this case, the carrier membrane remains in the product. This means that less material is required and less waste is generated.

[0011] The anode-side catalyst layer is preferably applied to the side of the anode-side gas diffusion layer facing the polymer membrane after bonding. This means that, in the case where the gas diffusion layer has a microporous layer on one side, the anode-side catalyst layer is applied to the microporous layer. In a single-layer gas diffusion layer, the gas diffusion layer is oriented after the anode-side catalyst layer is coated so that the catalyst layer contacts the polymer membrane. Otherwise, the anode-side catalyst layer cannot be bonded to the polymer membrane.

[0012] Furthermore, it is proposed that the anode-side catalyst layer is dried through the side of the anode-side catalyst layer facing the polymer membrane after bonding. This means that the anode-side catalyst layer is dried through its free side so that the solvent contained in the catalyst layer can be better removed. The drying of the anode-side catalyst layer can be supported by means of convection and / or heating. For example, infrared radiation can be used as a heat source.

[0013] In addition, the anode-side catalyst layer is preferably completely dried after bonding to the polymer membrane. This means that at the time of bonding, the anode-side catalyst layer applied to the anode-side gas diffusion layer is not yet solid, but is, for example, only thickened or gelled, so that the anode-side catalyst layer can be used to bond two bonding pairs. The anode-side catalyst layer is preferably dried through the side of the anode-side catalyst layer facing the anode-side gas diffusion layer. This means that the residual solvent in the catalyst layer is removed through the gas diffusion layer. Different from the polymer membrane, the gas diffusion layer is permeable to solvent vapor, so the drying can be accelerated in this way. At the same time, the contact between the polymer membrane and the solvent will also be prevented or at least reduced. The complete drying of the anode-side catalyst layer can also be supported by means of convection and / or heating.

[0014] Advantageously, the anode-side gas diffusion layer is provided as a web product and fed in by rollers and / or belts. In this way, membrane electrode assemblies can be produced cost-effectively in large quantities. Then, the anode-side catalyst layer is preferably applied continuously as a wet layer along the web direction of the gas diffusion layer.

[0015] According to a preferred embodiment of the invention, when applying the anode-side catalyst layer, a marginal distance is maintained from each of the two side edges of the anode-side gas diffusion layer. This means that the side edges of the gas diffusion layer remain uncoated or free. The gas diffusion layer can be joined to at least one other layer via the free side edges. The marginal distance is preferably 1 to 100 mm, more preferably 2 to 5 mm.

[0016] In an expansion of the invention, it is proposed to provide the polymer membrane as a web product and feed it in by rollers for connection to the anode-side catalyst layer. This further simplifies the manufacturing process, especially in cases where large quantities are to be produced. Preferably, the two joining partners are joined under the influence of pressure and / or temperature. For example, the required pressure can be applied by means of the rollers for feeding the polymer membrane. If the polymer membrane has a protective film, the protective film can be removed with the same or another roller during feeding.

[0017] Preferably, after the anode-side catalyst layer is joined to the polymer membrane, the cathode-side catalyst layer is applied to the polymer membrane. The cathode-side catalyst layer can be applied here as a wet layer by a wet chemical coating method or as individual patches by means of conveying rollers. The advantage of the latter is that the polymer membrane on the cathode side can also come into contact with the solvent as little as possible. In addition, drying of the cathode-side catalyst layer applied to the polymer membrane can be dispensed with, or at least significantly shortened.

[0018] Furthermore, preferably, the cathode-side catalyst layer is applied intermittently. In the intermittent application, the cathode-side catalyst layer is applied as regions or patches spaced apart from each other. In this way, material can be saved because the catalyst layer is only required in the region of the active surface of the membrane electrode assembly. The intermittent application can be carried out both in a wet chemical coating process and by means of conveying rollers.

[0019] Alternatively or additionally, it is proposed to apply the cathode-side catalyst layer while maintaining a distance from the two side edges of the polymer membrane. In this way, additional material can be saved. At the same time, the free side edges of the polymer membrane can be used to join at least one other layer. The marginal distance is preferably 1 to 10 mm.

[0020] The result of these method steps is an intermediate product comprising four layers, namely the anode-side gas diffusion layer, the anode-side catalyst layer, the polymer membrane, and the cathode-side catalyst layer. The last layer is preferably not continuous but interrupted multiple times in the web direction, so that in these areas only three layers are stacked on top of each other. The intermediate product can be wound onto a roll (with or without a separator film) and then temporarily stored or immediately further processed.

[0021] The expansion variant can in particular include applying a film with window-shaped openings as a subliner on the cathode-side catalyst layer. The window-shaped openings are used to expose the active surface of the membrane electrode assembly. The size of the window-shaped openings is preferably adapted here to the area or patch size of the cathode-side catalyst layer. The distance between the areas or patches and the edge distance maintained by the catalyst layer and the side edges of the polymer membrane can be used to fix the film to the polymer membrane. For example, the film can be applied by means of a hot melt adhesive bonding process or an ultrasonic welding process, so that the film is fixed by means of said application.

[0022] In order to expose the active surface of the membrane electrode assembly, the film used as a subliner is preferably applied in such a way that window-shaped openings are arranged within the area of the cathode-side catalyst layer. In order to fix the film to the polymer membrane, the film used as a subliner is also preferably applied in such a way that the two side edges of the film protrude beyond the side edges of the cathode-side catalyst layer.

[0023] Subsequently, the cathode-side gas diffusion layer can be applied, preferably pasted, onto the cathode-side catalyst layer and / or the film used as a subliner.

[0024] If a film used as a subliner is arranged between the cathode-side catalyst layer and the cathode-side gas diffusion layer, the membrane electrode assembly manufactured according to the proposed method has a six-layer structure. If the film is omitted, the membrane electrode assembly has only a five-layer structure. Description of the Drawings

[0025] A preferred embodiment of the method according to the invention will be explained in more detail below with reference to the drawings. It shows:

[0026] Figure 1 A schematic cross-section of an electrochemical cell with a membrane electrode assembly,

[0027] Figure 2 A schematic view of a device for manufacturing a membrane electrode end assembly according to the method of the invention,

[0028] Figure 3 A top view of a four-layer composite as an intermediate product during the manufacture of a membrane electrode assembly, Figure 4 Top view of a four-layer composite, including a subliner and

[0029] Figure 5Top view of the completed membrane electrode assembly. Detailed description of the invention

[0030] Figure 1 It can be seen that the conventional membrane electrode assembly 1 includes five layers and is surrounded on the outside by embossed plates 15 and 16, which are configured for gas distribution structures for the respective reaction gases.

[0031] The polymer membrane 2 forms the core of the membrane electrode assembly 1. Catalyst layers 5 and 6 are respectively arranged on both sides of the polymer membrane to form the anode 3 and the cathode 4. Gas diffusion layers 7 and 8 are respectively arranged on the catalyst layers 5 and 6, and the corresponding reaction gases are fed into the cathode layers 5 and 6 through the gas diffusion layers.

[0032] The method according to the invention can be used to manufacture such a five-layer membrane electrode assembly 1. However, a six-layer membrane electrode assembly 1 can also be manufactured by means of the method according to the invention. In this case, the sixth layer is a thin film 13 configured as a subliner. Hereinafter, the method according to the invention will be described by taking the manufacture of the six-layer membrane electrode assembly 1 as an example.

[0033] Figure 2 It can be seen a device for manufacturing a multi-layer membrane electrode assembly 1 according to the invention. The device includes a plurality of rollers 9, 10, 11, 12 for applying and / or transporting layers respectively.

[0034] The anode-side gas diffusion layer 7 configured as a web product is fed in through the first roller 9. The anode-side gas diffusion layer serves as a carrier layer for the other layers. In the wet chemical coating process, the anode-side catalyst layer 5 is applied to the anode-side gas diffusion layer 7 here. This forms a wet layer on the anode-side gas diffusion layer 7, which is dried by means of a heating device 17. During drying, the solvent contained in the wet layer volatilizes. Before the anode-side catalyst layer 5 is completely dried, the polymer membrane 2 is applied by means of the second roller 10. The protective film 18 arranged on the polymer membrane is removed by means of the third roller 11. Another heating device 17 is also arranged between the two rollers 10 and 11 to support the complete drying of the anode-side catalyst layer 5 after the application of the polymer membrane 2. Since the anode-side catalyst layer 5 is already dry when joined to the polymer membrane 2, the solvent content is reduced, thereby protecting the solvent-sensitive polymer membrane 2.

[0035] Then, the cathode-side catalyst layer 6 is applied to the polymer membrane 2 by means of the conveying roller 12. The application is carried out in the form of individual patches arranged at a distance on the polymer membrane 2. The cathode-side catalyst layer 6 can be dried with the support of the heating device 17. With the application of the cathode-side catalyst layer 6, a four-layer composite is formed, that is, at least one layer is still missing.

[0036] Figure 3A top view of a four-layer composite is shown. The gas diffusion layer 7 on the anode side is located at the bottom and has protruding side edges 7.1, 7.2. Behind it is the anode-side catalyst layer 5, which is continuously constructed in the width direction of the gas diffusion layer 7, but maintains a marginal distance a from the two side edges 7.1, 7.2 of the anode-side gas diffusion layer 7 respectively. The polymer membrane 2 is applied on the anode-side catalyst layer 5, and the polymer membrane is also continuously constructed in the width direction. The cathode-side catalyst layer 6 constructed in the form of individual patches is arranged on the polymer membrane 2. They are not only arranged at intervals from each other, but also maintain a marginal distance b from the side edges 2.1, 2.2 of the polymer membrane 2. Therefore, the side edges 6.1, 6.2 of the cathode-side catalyst layer 6 are arranged at a distance from the side edges 2.1, 2.2 of the polymer membrane 2.

[0037] The thin film 13 can be arranged as a fifth layer on the four-layer composite for constructing a subliner. The five-layer composite is shown, for example, in a top view in Figure 4 The thin film 13 protrudes beyond all other layers, with its side edges 13.1, 13.2 protruding laterally. The thin film 13 has a window-like opening 14 that exposes the cathode-side catalyst layer 6. Other layers arranged below the cathode-side catalyst layer 6 can also be seen through the thin film 13.

[0038] Finally, Figure 4 the cathode-side gas diffusion layer 8 is applied on the five-layer composite of Figure 5 so that there is a six-layer composite or a six-layer membrane electrode assembly 1 with a subliner. This is shown, for example, in a top view in

Claims

1. A method for manufacturing a membrane electrode assembly (1) having multiple layers, in particular five or six layers, the membrane electrode assembly comprising a polymer membrane (2) which has catalyst layers (5, 6) and gas diffusion layers (7, 8) on both sides respectively for constructing an anode (3) and a cathode (4). It is characterized in that The anode-side catalyst layer (5) is applied, dried on the anode-side gas diffusion layer (7) by a wet chemical coating process, and joined to the polymer membrane (2) before being completely dried.

2. The method according to claim 1. It is characterized in that The anode-side catalyst layer (5) is applied to the side of the anode-side gas diffusion layer (7) that faces the polymer membrane (2) after the joining.

3. The method according to claim 1 or 2. It is characterized in that The anode-side catalyst layer (5) is dried through the side of the anode-side catalyst layer (5) that faces the polymer membrane (2) after the joining, wherein preferably the drying is assisted by convection and / or heating.

4. The method according to any one of the preceding claims. Characterized in that, The anode-side catalyst layer (5) is completely dried after the joining with the polymer membrane (2), preferably by drying through the side of the anode-side catalyst layer (5) that faces the anode-side gas diffusion layer (7).

5. The method according to any one of the preceding claims. It is characterized in that The anode-side gas diffusion layer (7) is provided as a web product and fed in by a roller (9) and / or a belt, wherein preferably the anode-side catalyst layer (5) is continuously applied as a wet layer in the web direction of the gas diffusion layer (7).

6. The method according to any one of the preceding claims. It is characterized in that When applying the anode-side catalyst layer (5), an edge distance (a) is maintained respectively from two side edges (7.1, 7.2) of the anode-side gas diffusion layer (7), and the edge distance is preferably 1 to 100 millimeters, more preferably 2 to 5 millimeters.

7. The method according to any one of the preceding claims. It is characterized in that The polymer membrane (2) is provided as a web product and fed in by a roller (10) for joining with the anode-side catalyst layer (5), wherein preferably the joining is carried out under the influence of pressure and / or temperature.

8. The method according to any one of the preceding claims. It is characterized in that After joining the anode-side catalyst layer (5) with the polymer membrane (2), the cathode-side catalyst layer (6) is applied to the polymer membrane (2), preferably as a wet layer by a wet chemical coating process, or applied as individual patches by means of a conveying roller (12).

9. The method according to claim 8. It is characterized in that The cathode-side catalyst layer (6) is applied intermittently and / or with an edge distance (b) maintained from two side edges (2.1, 2.2) of the polymer membrane (2), wherein preferably the edge distance (b) is 1 to 10 millimeters.

10. The method according to any one of the preceding claims. It is characterized in that Preferably by means of a hot melt bonding process or an ultrasonic welding process, a film (13) with a window-shaped opening (14) is applied as a subliner to the cathode-side catalyst layer (6).

11. The method according to claim 10, It is characterized in that The film (13) used as a subliner is applied in such a way that the window-shaped opening (14) is arranged in the region of the cathode-side catalyst layer (6) and / or the two side edges (13.1, 13.2) of the film (13) project beyond the side edges (6.1, 6.2) of the cathode-side catalyst layer (6).

12. The method according to any one of the preceding claims, It is characterized in that The cathode-side gas diffusion layer (8) is applied, preferably adhered, to the cathode-side catalyst layer (6) and / or the film (13) used as a subliner.

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