Fuel cell having an elastomeric layer and method of manufacturing a fuel cell
By employing a multilayer membrane composite structure in fuel cells, the issues of sealing and material selection have been resolved, resulting in better sealing performance and lower manufacturing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- AUDI AG
- Filing Date
- 2022-05-25
- Publication Date
- 2026-07-21
AI Technical Summary
Existing fuel cells have shortcomings in sealing and material selection, especially in the poor compensation for the roughness depth of the bipolar plates and the poor hydrodynamic sealing effect, which leads to complex manufacturing and high cost.
By employing a multilayer membrane composite structure, including a frame and different elastomer layers, and by changing the process and material selection, better sealing effect and material selection can be achieved, while reducing manufacturing complexity and cost.
It improves the sealing and manufacturing efficiency of fuel cells, expands the selection of materials, simplifies quality control and leak testing, and reduces manufacturing costs.
Smart Images
Figure CN117425987B_ABST
Abstract
Description
[0001] This invention relates to a fuel cell having a membrane electrode assembly (MEA) in a notch in an insert frame, wherein a first bipolar plate is arranged on a first side of the MEA and a second bipolar plate is arranged on a second side opposite to the first side. Furthermore, this invention relates to a method of manufacturing a fuel cell.
[0002] Fuel cells, such as those in fuel cell systems used in motor vehicles, include membrane electrode assemblies formed of a proton-conducting membrane, with an anode on one side and a cathode on the other. The electrodes are cast or sprayed onto the membrane or hot-pressed using a calendering process to achieve close contact. Reactant gases are supplied to these electrodes, specifically hydrogen on the anode side and oxygen or oxygen-containing gases, particularly air, on the cathode side. In the electrochemical reaction, hydrogen reacts with oxygen in the air to form water.
[0003] Bipolar plates are provided to supply reactant gases to the active region of the membrane electrode assembly. Typically, a composite of a metal slot and an elastomeric layer is used to hydrodynamically seal the fuel cell, particularly the bipolar plates. This results in the essential functions of the seal—elasticity and roughness depth compensation—being separated and assigned to materials suited for this purpose. Here, roughness depth compensation is entirely assigned to the elastomeric layer, while the primary elastic component of the seal is borne by the metal slot.
[0004] To adjust the uniform pressing feature line of the groove along the sealing line of the bipolar plate, the groove has a geometry that varies along the plane of the bipolar plate. The manufacturing process required for this geometric variation results in the groove top not being flat, but deformed during the molding process. This means that depressions and bulges will appear on the groove top, causing unevenness in the single-digit micrometer range. Typically, an elastomer layer with a thickness of less than 50 μm is used, which cannot adequately compensate for and / or seal this unevenness. To provide a sufficient seal, the height of the seal must correspond to the height of the flow field, i.e., the height of the bipolar plate and the gas diffusion layer disposed between the bipolar plate and the membrane electrode assembly. Therefore, the seal must have a height typically from 0.2 mm to 0.7 mm, preferably from 0.3 mm to 0.6 mm.
[0005] In the previous conventional manufacturing of fuel cells, particularly for the sealing systems used in fuel cells, metal grooves with elastomer layers were fabricated, for example, in discrete manufacturing processes. Pre-fabricated bipolar plates were fed into this process. The elastomer could be applied, for example, in a screen printing process or an injection molding process. For these processes, material selection is very limited due to processing and adhesion. While chemically very stable and expensive fluororubbers can meet these requirements well, they must be tuned to the necessary Shore hardness by foaming these materials. The result is long drying and crosslinking times. Furthermore, screen printing processes are prone to failure, requiring significant expenditure to ensure quality, especially for complex leak testing.
[0006] DE 102011105072 B3 discloses a method for manufacturing a membrane electrode unit for a fuel cell, wherein a thin sealing element is arranged on the frame of the membrane electrode unit. Here, the material used for the sealing element is not suitable for achieving roughness depth compensation of the bipolar plates and thus achieving adequate hydrodynamic sealing under the typical compressive forces of a fuel cell.
[0007] DE 102018217291 A1 describes a method for sealing a fuel cell, wherein a sealing membrane is also applied at at least one sealing point of the fuel cell.
[0008] DE 102012221730 A1 discloses a method for sealing the coolant space of a bipolar plate in a fuel cell. In this method, sealing elements are provided on both sides of the membrane electrode unit.
[0009] Therefore, the object of the present invention is to provide a fuel cell that reduces the above-mentioned disadvantages and a method for manufacturing a fuel cell.
[0010] This objective is achieved by a fuel cell having the features of claim 1 and a method having the features of claim 6. Advantageous embodiments with suitable extensions of the invention are described in the dependent claims.
[0011] Here, the fuel cell is particularly characterized in that the edge region of the frame has a first elastomer layer formed as a membrane on the side facing the first bipolar plate, and the edge region of the frame has a second elastomer layer formed as a membrane on the second side facing the second bipolar plate. The elastomer layers disposed on the frame are configured to hydrodynamically seal the bipolar plates through roughness depth compensation and the provided elasticity. This results in a fuel cell that is easier and therefore cheaper to manufacture and has a good seal. Furthermore, there are more options for materials suitable for the elastomer layers.
[0012] The materials used for the elastomeric layer are preferably selected from: acrylate rubber (ACM), acrylonitrile-butadiene rubber (NBA), ethylene-propylene-diene-(monomer) rubber (EPDM), fluororubber (FPM, XFPM), methyl- / vinyl-rubber (MVQ), hydrogenated acrylonitrile-butadiene rubber (HNBR), fluorosilicone rubber (FVMQ), polyester-polyurethane rubber (AU, PUR), styrene-butadiene rubber (SBR), natural rubber (NK), isobutylene-isoprene rubber (IIR), chlorosulfonated polyethylene (CSM), chloroprene rubber (CR), perfluororubber (FFPM), tetrafluoroethylene / propylene rubber (FEPM), or polytetrafluoroethylene (PTFE). Furthermore, it is advantageous that the elastomeric layer has a Shore hardness of less than 30°A. To achieve the desired Shore hardness, it is preferred that the elastomeric layer is formed of a foamed elastomeric material. It is also preferred that the thickness of the elastomeric layer is a maximum of 50 μm on each side and less than 30 μm in the compressed state.
[0013] In particular, preferably, the frame, the first elastomer layer, and the second elastomer layer form a membrane composite. Therefore, the membrane composite is a multilayer membrane composite.
[0014] To save materials, it is preferable that the first elastomer layer and / or the second elastomer layer only cover a portion of the edge region of the frame.
[0015] In this document, it is particularly advantageous that a first region on a first side of the edge region of the first elastomeric layer covering the frame, a second region on a second side of the edge region of the second elastomeric layer covering the frame, and the covered region are formed asymmetrically with respect to the longitudinal axis.
[0016] Furthermore, it is preferable that, in order to achieve the desired seal, the first elastomer layer differs from the second elastomer layer in terms of thickness and / or material.
[0017] Furthermore, it is advantageous that the fuel cell has a second frame including a second notch, the first and second frames stacked together, and one of the elastomer layers disposed as a membrane between the first and second frames and on their edge regions. In particular, one of the gas diffusion layers can be disposed in the second notch of the second frame. Preferably, the area of the second notch of the second frame is larger than that of the notch of the first frame. These frames are preferably formed of different materials to distribute different functions within the fuel cell structure. It is also preferred that the second frame is arranged radially outward relative to the first frame. Similarly, to improve sealing, it is preferred that a third elastomer layer formed as a membrane is disposed between the second frame and the bipolar plate adjacent to the second frame.
[0018] The method is particularly characterized by the following steps:
[0019] -Providing a framework material formed as a first membrane, a first elastomer layer formed as a second membrane, and a second elastomer layer formed as a third membrane.
[0020] These layers are stacked and joined to form a frame sealing functional layer, such that a first elastomer layer is disposed on a first side of the frame material, and a second elastomer layer is disposed on a second side of the frame material opposite to the first side.
[0021] - Cut the frame sealing functional layer into individual frame elements and cut notches from the frame elements.
[0022] - Position the membrane electrode assembly into the notch of the frame element.
[0023] - Two bipolar plates are provided, with the first bipolar plate positioned on a first side of the membrane electrode assembly and the second bipolar plate positioned on a second side of the membrane electrode assembly opposite to the first side.
[0024] - The membrane electrode assembly is joined to the frame elements and bipolar plates in a form-fit manner.
[0025] By offering more material options through changes in process and material adhesion preconditions, the manufacturing cost of fuel cells can be reduced. Due to process robustness, quality control can also be reduced, making simplified leak testing sufficient. The bonding can be achieved here using adhesives as a material-adaptive bonding method. However, it is preferred to achieve a detachable bonding between the frame elements, membrane electrode assembly, and bipolar plates. This can be achieved, for example, by pressing, i.e., by applying pressure perpendicular to the bipolar plates.
[0026] The expanded range of material choices here includes materials such as acrylate rubber (ACM), acrylonitrile-butadiene rubber (NBA), ethylene-propylene-diene-(monomer)-rubber (EPDM), fluororubber (FPM, XFPM), methyl- / vinyl-rubber (MVQ), hydrogenated acrylonitrile-butadiene rubber (HNBR), fluorosilicone rubber (FVMQ), polyester-polyurethane rubber (AU, PUR), styrene-butadiene rubber (SBR), natural rubber (NK), isobutylene-isoprene rubber (IIR), chlorosulfonated polyethylene (CSM), chloroprene rubber (CR), perfluororubber (FFPM), tetrafluoroethylene / propylene rubber (FEPM), or polytetrafluoroethylene (PTFE). To preferably adjust the Shore hardness to less than 30°A, it is preferable that the method further incorporates the foaming of the elastomer material.
[0027] In particular, in order to distribute the reactant gases over the active region of the membrane electrode assembly, it is preferable to provide two additional gas diffusion layers, arranged on both sides between the frame sealing functional layer and the bipolar plate, and joined to them in a shape- and material-adaptive manner.
[0028] Specifically, the steps of joining these layers to form a frame sealing functional layer are performed by transfer, spraying, casting, calendering, or transfer to produce the frame sealing functional layer.
[0029] Furthermore, it is advantageous that the first elastomer layer and / or the second elastomer layer are adhered to only a portion of the frame material via membrane transfer, so that the frame sealing functional layer has only a portion of the first elastomer layer and / or the second elastomer layer.
[0030] Specifically, it is preferred herein that the regions of the first elastomer layer and the second elastomer layer are applied asymmetrically with respect to the longitudinal axis of the membrane electrode assembly. It is also preferred herein that the first elastomer layer and the second elastomer layer have different thicknesses and / or different material compositions and / or different materials.
[0031] To further simplify the method, it is preferable that the frame material, the first elastomer layer, and the second elastomer layer are each provided in the form of being wound on a roll. Due to this roll manufacturing, the investment required for fuel cell manufacturing needs to be reduced. Furthermore, the roll process has the advantage that these layers are applied much faster compared to screen printing. Adjusting the adhesion of the elastomer layers to the frame material is easier, and the drying and cross-linking processes can be simplified.
[0032] The features and combinations of features mentioned above in the specification, as well as the features and combinations of features mentioned below in the description of the drawings and / or shown individually in the drawings, may be used not only in the form of the combinations shown in each case, but also in other combinations or individually, without departing from the scope of the invention. Therefore, embodiments not explicitly shown or explained in the drawings but which can be learned from the explained embodiments by individual combinations of features and are also considered to be included and disclosed by the invention.
[0033] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the accompanying drawings. These drawings illustrate:
[0034] Figure 1 A schematic diagram of a fuel cell with two elastomeric layers.
[0035] Figure 2 A schematic diagram of a framed membrane electrode assembly with a frame sealing functional layer.
[0036] Figure 3 Another schematic diagram of a framed membrane electrode assembly with a frame sealing functional layer.
[0037] Figure 4 Another schematic diagram of a framed membrane electrode assembly with a frame sealing functional layer, and
[0038] Figure 5 A schematic diagram of another fuel cell with three elastomeric layers and two frames.
[0039] Figure 1 A fuel cell with a membrane electrode assembly 4 inserted into a notch 2 of a frame 3 is shown. A first bipolar plate 5 is disposed on a first side of the membrane electrode assembly 4, and a second bipolar plate 6 is disposed on a second side opposite to the first side. The membrane electrode assembly 4 includes a proton-conducting membrane 16, an anode 12 disposed on its first side, and a cathode 13 disposed on its second side opposite to the first side. The anode 12 and cathode 13 may have a catalyst layer made of a noble metal such as platinum, palladium, ruthenium, or a mixture containing noble metals, which acts as a reaction promoter in the reaction of the fuel cell.
[0040] In this polymer electrolyte membrane fuel cell (PEM fuel cell), fuel, or fuel molecules, particularly hydrogen, split into protons and electrons at the anode 12. Membrane 16 allows protons (e.g., H+) to be released. + ) passes through, but electrons (e - It is impermeable. Membrane 16 is formed from an ionomer, preferably from sulfonated tetrafluoroethylene polymer (PTFE) or perfluorinated sulfonic acid polymer (PFSA). Alternatively, membrane 16 can also be formed as a sulfonated hydrocarbon membrane. At anode 12, the following reaction occurs: 2H₂ → 4H₂ + +4e - (Oxidation / Electron Release).
[0041] When protons pass through membrane 16 and reach cathode 13, electrons are conducted to cathode 13 or the energy storage device via an external circuit. Cathode gas, particularly oxygen or oxygen-containing air, is supplied at cathode 13 so that the following reaction occurs: O₂ + 4H₂O + +4e - →2H2O (reduction / electron absorption).
[0042] The two electrodes, namely anode 12 and cathode 13, are respectively provided with gas diffusion layers 14 and 15. Gas diffusion layers 14 and 15 are preferably formed of carbon fiber paper (CFP = "carbon fiber paper"). Other suitable fiber and / or nonwoven fabric layers may also be used as the substrate for the gas diffusion layers and the gas diffusion electrodes.
[0043] To improve fluid or gas flow within the fuel cell 1 and increase the water content in the membrane 16, the gas diffusion layers 14 and 15 may additionally be equipped with microporous layers (not shown in detail). The lateral dimensions of the microporous layers here substantially correspond to the lateral dimensions of the respective gas diffusion layers 14 and 15.
[0044] The edge region 7 of the frame 3 has a first elastomer layer 8 formed as a membrane on its side facing the first bipolar plate 5, while the edge region 7 of the frame 3 has a second elastomer layer 9 formed as a membrane on its second side facing the second bipolar plate 6. The elastomer layers 8 and 9 arranged on the frame 3 are configured to hydrodynamically seal the bipolar plates 5 and 6 through roughness depth compensation and the provided elasticity. Here, the frame 3, the first elastomer layer 8, and the second elastomer layer 9 form a membrane composite. This structure allows the bipolar plates 5 and 6 to be sealed, wherein the elastomer layers 8 and 9 perform both roughness depth compensation and the provided elasticity. Alternatively, the elastomer layers 8 and 9 may also be initially present as liquid materials, such as paint or paste, and printed or cast onto the frame 3 forming the membrane.
[0045] Figure 2 A framed membrane electrode assembly 4 with a frame sealing functional layer 11 is shown. The frame sealing functional layer 11 is here a membrane composite made of a frame material, namely a frame 3, a first elastomer layer 8, and a second elastomer layer 9. Figure 2 In this assembly, the first elastomer layer 8 is formed to be thicker than the second elastomer layer 9 compared to the other framed membrane electrode assemblies having the frame sealing functional layer 11.
[0046] Based on Figure 3 As can be seen from the embodiments, the first elastomer layer 8 and / or the second elastomer layer 9 only cover a portion of the edge region 7 of the frame 3.
[0047] Figure 4 Another embodiment is shown, wherein a first elastomer layer 8 covers a first region on a first side of an edge region 7 of a frame 3, and a second elastomer layer 9 covers a second region on a second side of an edge region 7 of a frame 3, wherein the covered regions are formed asymmetrically with respect to the longitudinal axis 10.
[0048] Furthermore, the first elastomer layer 8 may differ from the second elastomer layer 9 in its material and / or its material composition.
[0049] Figure 5 Another fuel cell was shown, according to Figure 1 Compared to other fuel cells, this one has a second frame 17 containing a second notch 18, in which a first gas diffusion layer 14 is housed. A third elastomeric layer 19, formed as a membrane, is disposed between the edge region of the second frame 17 and the first bipolar plate 5.
[0050] A method for manufacturing a fuel cell 1 includes the following steps: providing a frame material forming a first membrane, a first elastomer layer 8 forming a second membrane, and a second elastomer layer 9 forming a third membrane. These membranes are respectively wound onto rollers, thereby enabling a roll-to-roll process.
[0051] The layers, i.e. the films, are stacked and joined together to form a frame sealing functional layer 11, such that a first elastomer layer 8 is disposed on a first side of the frame material, i.e., the frame 3, and a second elastomer layer 9 is disposed on a second side of the frame material opposite to the first side. These layers can be applied and joined here by calendering, spraying, casting, printing, or transfer.
[0052] According to Figure 5 In the fuel cell 1, another membrane is provided as a second frame material for the second frame 17, and a third elastomer layer 19 is further formed as a membrane. The layers, i.e., the membranes, are stacked and bonded to form a frame sealing functional layer 11, such that a first elastomer layer 8 is disposed on a first side of the frame material, i.e., the frame 3; a second elastomer layer 9 is disposed on a second side of the frame material opposite to the first side; a second frame material is disposed on the side of the first elastomer layer 8 opposite to the membrane electrode assembly 4; and a third elastomer layer 19 is disposed on the side of the second frame material opposite to the first elastomer layer 8. These layers can be applied and bonded here by calendering, spraying, casting, printing, or transfer.
[0053] The frame sealing functional layer 11 is cut into individual frame elements, and notches 2 are cut out from the frame elements. Alternatively, notches 2 can be cut first, and then the frame elements are cut. The membrane electrode assembly 4 is positioned into the notches 2 of the frame elements and provides at least two bipolar plates 5, 6. A first bipolar plate 5 is positioned on a first side of the membrane electrode assembly 4, and a second bipolar plate 6 is positioned on a second side of the membrane electrode assembly 4 opposite to the first side. Gas diffusion layers 14, 15 are respectively arranged between the membrane electrode assembly 4 and the bipolar plates 5, 6. Finally, the membrane electrode assembly 4 is joined to the frame elements, bipolar plates 5, 6, and gas diffusion layers 14, 15 in a shape-fitting manner. This joining can be achieved here in a material-fitting manner, i.e., by adhesive. Alternatively and preferably, the joining is achieved by mechanical pressure orthogonal to the bipolar plates 5, 6, thereby achieving a detachable joining between the bipolar plates 5, 6 and the frame elements comprising the elastomer layers 8, 9. Additionally, heat can be applied to the frame elements or the composite of bipolar plates 5 and 6, and the frame elements and gas diffusion layers 14 and 15, i.e., at a temperature higher than the melting point of the elastomer, to melt the elastomer layers 8 and 9 and penetrate to the rough depth of the bipolar plates 5 and 6. This improves the sealing of the fuel cell 1.
[0054] In order to apply the elastomer layers 8 and 9 only to a local area of the frame material, a film transfer method is used to apply the first elastomer layer 8 and / or the second elastomer layer 9 only to a local area of the frame material and adhere them thereto.
[0055] List of reference numerals in the attached diagram:
[0056] 1 fuel cell
[0057] 2 gaps
[0058] 3-frame
[0059] 4-film electrode assembly
[0060] 5 First bipolar plate
[0061] 6 Second bipolar plate
[0062] 7. Edge area of the frame
[0063] 8 First Elastomer Layer
[0064] 9 Second Elastomer Layer
[0065] 10. Longitudinal axis
[0066] 11. Frame Sealing Functional Layer
[0067] 12 Anodes
[0068] 13 Cathode
[0069] 14 First Gas Diffusion Layer
[0070] 15 Second Gas Diffusion Layer
[0071] 16. Proton conduction membrane
[0072] 17 Second Framework
[0073] 18 Second Gap
[0074] 19 Third Elastomer Layer
Claims
1. A fuel cell (1) having a membrane electrode assembly (4) inserted into a notch (2) of a frame (3), wherein a first bipolar plate (5) is arranged on a first side of the membrane electrode assembly and a second bipolar plate (6) is arranged on a second side opposite to the first side, wherein an edge region (7) of the frame (3) has a first elastomer layer (8) formed as a second membrane on its side facing the first bipolar plate (5), and an edge region (7) of the frame (3) has a second elastomer layer (9) formed as a third membrane on its second side facing the second bipolar plate (6), characterized in that, The edge region (7) is formed as a first membrane, the frame (3), the first elastomer layer (8) and the second elastomer layer (9) form a membrane composite, and the elastomer layers (8, 9) arranged on the frame (3) are configured to hydrodynamically seal the bipolar plates (5, 6) by means of roughness depth compensation and the elasticity provided.
2. The fuel cell (1) according to claim 1, characterized in that, The first elastomer layer (8) and / or the second elastomer layer (9) only cover a portion of the edge region (7) of the frame.
3. The fuel cell (1) according to claim 1 or 2, characterized in that, The first elastomer layer (8) covers a first region on a first side of the edge region (7) of the frame (3), and the second elastomer layer (9) covers a second region on a second side of the edge region (7) of the frame (3), and the covered regions are formed to be asymmetrical with respect to the longitudinal axis (10).
4. The fuel cell (1) according to any one of claims 1 to 2, characterized in that, The first elastomer layer (8) differs from the second elastomer layer (9) in terms of thickness and / or the material used.
5. A method for manufacturing a fuel cell (1) according to any one of claims 1 to 4, comprising the following steps: - Provides a framework material formed as a first membrane, a first elastomer layer (8) formed as a second membrane, and a second elastomer layer (9) formed as a third membrane. - These layers are stacked and joined to form a frame sealing functional layer (11), such that a first elastomer layer (8) is disposed on a first side of the frame material, and a second elastomer layer (9) is disposed on a second side of the frame material opposite to the first side. - Cut the frame sealing functional layer (11) into individual frame elements and cut notches (2) from the frame elements. - Position the membrane electrode assembly (4) into the notch (2) of the frame element. - Two bipolar plates (5, 6) are provided, with the first bipolar plate (5) positioned on a first side of the membrane electrode assembly (4) and the second bipolar plate (6) positioned on a second side of the membrane electrode assembly (4) opposite to the first side. - The membrane electrode assembly (4) is joined to the frame elements and bipolar plates (5, 6) in a form-fit manner.
6. The method according to claim 5, characterized in that, The steps of joining these layers to form the frame sealing functional layer (11) are performed by printing, spraying, casting, calendering or transfer.
7. The method according to claim 6, characterized in that, The first elastomer layer (8) and / or the second elastomer layer (9) are adhered to only a portion of the frame material by membrane transfer, such that the frame sealing functional layer (11) has only a portion of the first elastomer layer and / or the second elastomer layer.
8. The method according to any one of claims 5 to 7, characterized in that, The first elastomer layer (8) and the second elastomer layer (9) have different thicknesses and / or different materials.
9. The method according to any one of claims 5 to 7, characterized in that, The frame material, the first elastomer layer (8), and the second elastomer layer (9) are provided in the form of being wound on a roller.