Sealed membrane electrode assembly
By embedding planar sealing elements in the membrane electrode assembly and using through-hole anchoring, the problem of seal detachment during roll-to-roll manufacturing is solved, mechanical stability and airtightness are improved, and the processing flow is simplified.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CARL FREUDENBERG KG
- Filing Date
- 2024-10-22
- Publication Date
- 2026-06-16
AI Technical Summary
In the prior art, during the roll-to-roll manufacturing process, the sealing components of the membrane electrode assembly are prone to detachment due to mechanical stress, which affects the sealing performance of the medium and results in insufficient processing stability.
A planar sealing element is embedded in the membrane at the edge and anchored by a shape fit. The sealing element has through holes to improve mechanical stability and avoid the use of adhesives or adhesion promoters.
This technology improves the stability of seals during roll-to-roll manufacturing, ensuring airtightness and mechanical stability, simplifying the processing, and avoiding the negative effects of adhesives.
Smart Images
Figure CN122228569A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a membrane electrode assembly (MEA) comprising a membrane made of a polymeric ion-conducting material disposed between two electrodes and a sealing element surrounding the outer peripheral edge, the sealing element being embedded in the membrane at least in the edge region. The invention also relates to a method for preparing such a MEA. Background Technology
[0002] The membrane electrode assembly (MEA), hereinafter referred to as MEA, is the core component of a so-called polymer electrolyte membrane (PEM) fuel cell. Electrochemical reactions and other electrochemical reactions (such as electrolysis) occur within the MEA. Therefore, the MEA is composed of a variety of different functional active materials.
[0003] In its simplest form, the MEA comprises a composite consisting of two electrodes (anode and cathode) and a membrane made of a polymeric ion-conducting material disposed between these electrodes, wherein each electrode is composed of a porous, permeable layer (Lage) (GDL) coated with a catalyst on the membrane side.
[0004] GDLs with a catalyst layer are also known as gas diffusion electrodes (GDEs). GDLs typically also have a microporous layer (Schicht) (MPL) on the catalyst side.
[0005] The electrode typically comprises a (supported) catalyst, which is associated with a so-called ionomer. At the catalyst surface, hydrogen oxidation at the anolyte and oxygen reduction at the cathode occur. These reactions generate a subsequently usable electric current from the chemical energy of the fuel. The ionomer performs the electrolytic conduction function, while the catalyst support or the catalyst itself performs the electrical conduction.
[0006] The membrane separates the electrodes from each other. The membrane not only prevents the flow of electrons but also prevents gas exchange between the two electrodes. In addition to its separating function, the membrane also allows protons (the product of the hydrogen oxidation reaction at the anode) to diffuse from the anode to the cathode. These protons react at the cathode to produce water.
[0007] The GDL and the MPL applied to them have the following functions: to deliver the reactants (hydrogen and oxygen from the air) of the electrochemical reaction, as well as the water produced in the reaction, to the electrode.
[0008] For the MEA to operate, the two electrodes must be equally hermetically separated from their surroundings at the interface; this is ensured by gaskets (sometimes also called internal seals). Gaskets separate the dielectrics of the anode and cathode at the interface of the active materials (electrode, membrane, GDL / MPL).
[0009] A method for preparing a membrane element (MEA) is known from EP 3 807 946 A1, which forms the prior art according to the preamble. In this method, two gas chromatography-mass spectrometers (GDLs) are provided for preparing two gas chromatography-mass spectrometers (GDEs), each having a catalyst coating. A thin film is then applied to at least one of these GDEs. Finally, the two GDEs are arranged and pressed together, thereby surrounding the one or more membrane sheets. It is also known from EP 3 807 946 A1 that the MEA thus prepared is provided with a surrounding sealing frame. Here, another sealing element can be provided, extending parallel to the plane of the MEA and interlocking in the edge region at the joint position between the two membrane sheets of the MEA.
[0010] In the further processing of MEAs, the roll-to-roll method, commonly used in fuel cell manufacturing, is generally employed. When the MEA is tensioned onto the roll and the material web is transported at high speed, mechanical stress may occur within the material web, especially at the joints between the sealing elements and the layers, where these stresses must be withstood. However, reliable media sealing must be guaranteed in the case of MEAs. Therefore, improving the mechanical stability of the material web is desirable. Summary of the Invention
[0011] Therefore, an object of the present invention is to further develop a membrane electrode assembly of the type mentioned at the outset, which can withstand high mechanical loads and thus can be further processed in roll-to-roll manufacturing without problems, without the seals falling off. Another object is to provide a method for preparing such a MEA.
[0012] This objective is achieved by the membrane electrode assembly (MEA) according to claim 1. Claim 14 describes a method for preparing such a MEA. Advantageous designs of the invention are described in the dependent claims.
[0013] According to the present invention, for a membrane electrode assembly (MEA) comprising a membrane made of a polymeric ion-conducting material disposed between two electrodes and a sealing element surrounding the outer peripheral edge, the sealing element being embedded in the membrane at least in the edge region, a design is proposed in which the sealing element is formed such that it is anchored in the membrane by means of form fit.
[0014] It has been surprisingly shown that mechanically anchoring the sealing element in the membrane does not adversely affect the membrane's function, but on the other hand, it can improve the mechanical stability of the joint between the seal and the layer, allowing the material web to be further processed in the fuel cell manufacturing process using a roll-to-roll method without any problems.
[0015] According to a preferred embodiment of the invention, the sealing element is formed in a planar shape and the shape is produced by a through-hole in the planar sealing element, the through-hole being at least partially penetrated by the membrane material.
[0016] The through-hole can be fabricated in a simple manner by perforating the planar sealing element. For example, the perforation can be introduced into the planar sealing element by means of laser processing or punching. Here, the perforation can have a regular or irregular hole pattern.
[0017] Advantageously, the diameter of the through-hole should be greater than or equal to 5 µm. With a diameter less than 5 µm, the ionomer can no longer fully engage the sealing position, and therefore the airtightness at the junction between the MEA and the gasket is no longer present. According to another preferred embodiment of the invention, the diameter should be less than or equal to 15 cm, particularly preferably less than 5 cm, and more preferably less than 3 cm. A diameter greater than 15 cm results in the loss of advantageous mechanical anchorage. That is, the improved mechanical stability at the junction between the MEA and the gasket is no longer present. Very good mechanical stability is achieved with a diameter less than or equal to 5 cm, and even better mechanical stability is achieved with a diameter less than or equal to 3 cm.
[0018] According to a preferred embodiment of the invention, the distance between the through holes relative to each other is between 1 µm and 5 cm. When the distance between the through holes is less than 1 µm, the bridging portion between the through holes becomes mechanically unstable and no longer guarantees favorable mechanical anchoring. If the distance between the through holes exceeds 5 cm, favorable mechanical anchoring is also no longer guaranteed. That is, the improved mechanical stability at the junction between the MEA and the washer is no longer present.
[0019] According to another preferred embodiment of the invention, the thickness of the planar sealing element is between 1 µm and 1000 µm. When the thickness of the sealing element (or gasket) is less than 1 µm, the sealing element itself becomes too mechanically and chemically unstable to be further processed under typical fabrication conditions for fuel cells, and also fails to meet the required lifespan of the fuel cell. If the sealing element (or gasket) is thicker than 1000 µm, the subsequent function of the MEA is negatively affected.
[0020] Surprisingly, it has been shown that planar sealing elements with through-holes can also be used as planar reinforcing layers for MEAs. For this purpose, the planar sealing element can extend either partially or completely over the planar extension of the membrane. Planar reinforcing layers are known. They are typically introduced into the layered composites of MEAs to impart mechanical strength to the composite. This is particularly important when the material is subjected to mechanical loads during further processing, such as when using a roll-to-roll method.
[0021] Porous materials, often ePTFE, are typically used as planar reinforcing layers in membranes. This requires impregnating the porous material with a material in which it is embedded. This process can be very costly due to the small pore size of commonly used materials (typically <0.2 µm). When using a planar sealing element with relatively large through-holes as the planar reinforcing layer, the impregnation step is omitted. The through-holes of the planar sealing element are simply filled during pressing with a polymeric material that conducts ions within the membrane.
[0022] MEA can be provided with a sealing frame surrounding the outer periphery, the sealing frame extending substantially perpendicular to the planar extensions of the layers and covering and sealing the edges of the individual layers on the outer periphery.
[0023] When the planar sealing element is connected to the sealing frame at its outer periphery, a particularly good sealing effect can be achieved.
[0024] The following materials may be used for the planar sealing element and the sealing frame: thermoplastics (PET, PEN, LDPE, MDPE, HDPE, LLDPE, PP, polyester, nylon, PTFE, PEEK, PEEKK, etc.), fiber-reinforced thermoplastics (e.g., glass fiber), bioplastics (hydrated cellulose and / or other cellulose-based polymers), thermoplastic elastomers, and / or coated metal foils.
[0025] A preferred method for preparing a membrane electrode assembly with a sealing element according to the present invention includes the following steps:
[0026] i) Provide two gas diffusion layers (GDLs), optionally having microporous layers (MPLs).
[0027] ii) Coating GDL / MPL onto the MPL side having a catalyst paste and drying the paste to prepare a gas diffusion electrode (GDE).
[0028] iii) Coating at least one of the GDEs onto the surface of a catalyst having an ionomer paste,
[0029] iv) Provide a planar sealing element with a through hole,
[0030] v) Cut two GDEs coated with ionomer or one GDE coated with ionomer and one uncoated GDE.
[0031] vi) Position the two GDEs from step v) such that the plurality of ionomer layers, or the ionomer layer and catalyst layer, are in contact with each other, and
[0032] vii) Joining is performed by hot pressing, wherein the planar sealing element is introduced into the joining gap prior to the joining.
[0033] In the case where a sealing frame is provided, step vi) also includes positioning the sealing frame.
[0034] Because, according to the present invention, the electrode (as is common in other cases) is not pressed together with a separately prepared membrane, but rather an ionomer layer is applied, the GDE needs to be constructed stepwise.
[0035] GDLs are known. They are typically composed of planar porous, breathable materials, such as carbon fibers with PTFE hydrophobication.
[0036] MPL is also known in itself. According to the present invention, MPL formed of carbon (graphite, carbon black) and binder (e.g., PTFE) is preferred.
[0037] According to the present invention, the GDL / MPL sheet is equipped with a catalyst layer, firstly equipped with an industrially commonly used first catalyst layer and selectively additionally equipped with a second catalyst / ionomer layer with advanced sensitivity, the second catalyst / ionomer layer preventing the infiltration of the ionomer solution in the subsequent step iii) "applying the ionomer paste to the GDE". Direct coating, decal transfer, or similar methods can be used as the coating method.
[0038] The catalyst layer is preferably prepared using a paste containing catalyst components, which is commonly used in industry.
[0039] The layer is dried after the paste is applied.
[0040] To prepare an ionomer layer on at least one GDE, a paste having an ionomer is also applied according to the invention and then dried. Suitable ionomer paste components are commercially available ionomers (e.g., Nafion®), solvents such as methanol, ethanol, propanol, acetone, DMAc, DMF, butanol, etc., and water.
[0041] In the next step, the two ionomer-coated GDEs or the one ionomer-coated GDE and an uncoated GDE are cut and positioned such that multiple ionomer layers, or ionomer layers and catalyst layers, are in contact with each other. These layers are then joined to the planar sealing element by means of hot pressing. This involves a standard hot pressing process known in the art. When the ionomer-coated electrode is pressed together with the sealing element having through-holes, the ionomer / film material penetrates the through-holes and thereby creates anchorage.
[0042] The method according to the invention not only has the advantage of firmly anchoring the seal in the membrane in a simple manner, but also achieves this firm connection purely mechanically. No adhesives or adhesion promoters are used, which in some cases have a negative impact on the MEA.
[0043] The present invention will now be described in detail with reference to the accompanying drawings: Attached Figure Description
[0044] In the attached diagram:
[0045] Figure 1 A schematic side-section view illustrates a symmetrically constructed MEA according to a preferred embodiment of the invention.
[0046] Figure 2 A schematic side-section view illustrates an asymmetric MEA according to another preferred embodiment of the invention.
[0047] Figure 3 Electron micrographs showing a longitudinal section of the MEA through an anchored sealing element (relative to...) Figure 1 , 2 (and 4 rotated 90°).
[0048] Figure 4 The MEA is shown in a schematic side cross-section, wherein the sealing element is formed in the form of a reinforcing sheet. Detailed Implementation
[0049] exist Figure 1 The membrane electrode assembly (MEA) 10 can be seen, including a membrane 4 made of a polymeric ion-conducting material disposed between two electrodes. These electrodes are formed by a gas diffusion layer 1, a microporous layer 2 disposed thereon, and a catalyst layer 3 deposited thereon.
[0050] A sealing element 5 can also be seen, which is embedded in the membrane 4 in the edge region of the membrane 4. According to the invention, the sealing element 5 is anchored in the membrane 4. For this purpose, the sealing element has through holes 6, which are penetrated by the membrane material and thus create a form fit.
[0051] exist Figure 1 In the middle, the sealing element 5 is arranged in the middle of the membrane 4.
[0052] Figure 2 Showing something similar to Figure 1 The MEA shown is provided, but in another preferred embodiment of the invention, the seal 5 is arranged at the edge of the membrane, adjacent to the catalyst layer 3.
[0053] exist Figure 3 The image shows an electron microscope photograph of a longitudinal section through the MEA according to the invention. The gas diffusion layer is indicated by reference numeral 1, and the microporous layers and catalyst layers, indistinguishable from each other in this photograph, are indicated by 2 and 3. The membrane 4 and the sealing element 5 are visible in the photograph, extending into and embedded within the membrane 4 in the edge region (from right to left). The section passes through a through-hole 6 in the sealing element 5. The through-hole 6 is filled with membrane material. This creates a form fit, and the sealing element 5 is anchored within the membrane 4.
[0054] Figure 4 A schematic longitudinal cross-sectional view illustrates another embodiment of the MEA according to the invention, wherein a perforated sealing element 5 extends along the entire planar extension of the membrane as a reinforcing sheet. This eliminates the need for additional reinforcing sheets. The through-holes 6 of the perforated sealing element are simply filled with membrane material during the heat-pressing of the sheets. This forms an anchorage through the sealing element 5.
Claims
1. A membrane electrode assembly (MEA) comprising a membrane (4) made of a polymeric ion-conducting material disposed between two electrodes and a planar sealing element (5) surrounding its outer peripheral edge, the sealing element being embedded in the membrane (4) at least in the edge region, characterized in that, The sealing element (5) is formed such that it is anchored in the membrane (4) by means of shape fit.
2. The membrane electrode assembly according to claim 1, characterized in that, The shape fit is formed through a through hole (6) in the planar sealing element (5), the through hole being at least partially penetrated by the membrane material.
3. The membrane electrode assembly according to claim 1 or 2, characterized in that, The through hole (6) is formed by perforation.
4. The membrane electrode assembly according to at least one of claims 1 to 3, characterized in that, The diameter of the through hole (6) is between 5 µm and 15 cm.
5. The membrane electrode assembly according to at least one of claims 1 to 4, characterized in that, The distance between the through holes (6) and each other is between 1 µm and 5 cm.
6. The membrane electrode assembly according to at least one of claims 1 to 5, characterized in that, The thickness of the planar sealing element (5) is between 1 µm and 1000 µm.
7. The membrane electrode assembly according to at least one of claims 1 to 6, characterized in that, The planar sealing element (5) extends over the entire planar extension of the membrane (4) in a reinforced layer manner.
8. The membrane electrode assembly according to at least one of claims 1 to 7, characterized in that, In order to seal the edge of the layer on the outer periphery of the MEA (10), a sealing frame is provided that extends substantially perpendicular to the layer.
9. The membrane electrode assembly according to claim 8, characterized in that, The planar sealing element (5) is connected to the sealing frame at its outer periphery.
10. The membrane electrode assembly according to at least one of claims 1 to 9, characterized in that, The planar sealing element (5) is composed of thermoplastics (PET, PEN, LDPE, MDPE, HDPE, LLDPE, PP, polyester, nylon, PTFE, PEEK, PEEKK, etc.), fiber-reinforced thermoplastics (e.g., glass fiber), bioplastics (hydrated cellulose and / or other cellulose-based polymers), thermoplastic elastomers, and / or coated metal foils.
11. The membrane electrode assembly according to at least one of claims 1 to 10, characterized in that, The sealing frame is composed of thermoplastics (PET, PEN, LDPE, MDPE, HDPE, LLDPE, PP, polyester, nylon, PTFE, PEEK, PEEKK, etc.), fiber-reinforced thermoplastics (e.g., glass fiber), bioplastics (hydrated cellulose and / or other cellulose-based polymers), thermoplastic elastomers, and / or coated metal foil.
12. The membrane electrode assembly according to any one of claims 1 to 8, characterized in that, The electrode is formed as a gas diffusion electrode.
13. The membrane electrode assembly according to any one of claims 1 to 9, characterized in that, The gas diffusion layer (1) is provided with a microporous layer (2).
14. A method for preparing a membrane electrode assembly according to any one of claims 1 to 13, the method comprising the following steps: i) Provide two gas diffusion layers (GDLs), which optionally have microporous layers (MPLs). ii) Coating GDL / MPL onto the MPL side having a catalyst paste and drying the paste to prepare a gas diffusion electrode (GDE). iii) Coating at least one of the GDEs onto the surface of a catalyst having an ionomer paste, iv) Provide a planar sealing element with a through hole, v) Cut two GDEs coated with ionomers, or one GDE coated with ionomers and one uncoated GDE. vi) Position the two GDEs from step v) such that the plurality of ionomer layers, or the ionomer layers and catalyst layers, are in contact with each other, and vii) Joining is performed by hot pressing, wherein the planar sealing element is introduced into the joining gap prior to the joining.
15. The method according to claim 14, characterized in that, Step vi) also includes positioning the sealing frame.