Membrane-electrode arrangement for an electrochemical cell, and electrochemical cell
Patent Information
- Application Number
- EP2024703964
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-21
- Filing Date
- 2024-02-07
- Publication Date
- 2025-12-31
AI Technical Summary
Electrochemical cells face membrane damage due to pressure differences between the anode and cathode sides, leading to reduced robustness and service life.
A membrane-electrode arrangement with a relief space formed by flattened, beveled, rounded, or arcuate edge geometries between the transport layers and frame parts allows membrane deformation, preventing sharp edges and increasing robustness.
The solution enhances membrane robustness and extends the lifespan of electrochemical cells by distributing pressure loads effectively and preventing membrane damage.
Smart Images
Figure EP2024052964_29082024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title:
[0003] Membrane electrode assembly for an electrochemical cell and electrochemical cell
[0004] The invention relates to a membrane-electrode assembly for an electrochemical cell, in particular for a fuel cell or an electrolysis cell. Furthermore, the invention relates to an electrochemical cell with a membrane-electrode assembly according to the invention.
[0005] In practice, a large number of electrochemical cells are combined to form a cell stack, in particular a fuel cell stack or an electrolyzer. The preferred application areas are therefore fuel cell stacks and / or electrolyzers. The electrolyzer can, in particular, be a PEM or AEM electrolyzer for producing hydrogen, or a CO2 electrolyzer.
[0006] State of the art
[0007] Electrochemical cells have a multi-layered structure. The central layer forms a membrane, which is usually coated on both sides with a catalytically active material to form an anode and a cathode. A transport layer, through which the respective reaction medium is fed to the membrane, is attached to both the anode and cathode sides of the membrane. Typically, the membrane is enclosed in at least one edge region extending beyond the transport layers by a frame structure. This frame structure supports the membrane and can also function as a seal. The frame structure, which usually consists of two frame sections, is also called a gasket or subgasket.
[0008] During operation of an electrochemical cell, different pressures prevail on the anode and cathode sides. Typically, the pressure on the cathode side is higher than on the anode side. This leads to compressive loading of the membrane perpendicular to the membrane plane, causing the membrane on the side with the lower pressure, usually the anode side, to be pressed against the transport layer and the adjacent frame part. The edges of the transport layer and the frame part can thus cause damage to the membrane.
[0009] The present invention aims to increase the robustness and thus the service life of the membrane. As a result, the service life of the electrochemical cell containing the membrane should be increased.
[0010] To achieve this objective, the membrane electrode assembly having the features of claim 1 is proposed. Advantageous further developments of the invention are set forth in the subclaims. Furthermore, an electrochemical cell having a membrane electrode assembly according to the invention is proposed.
[0011] Disclosure of the invention
[0012] Proposed is a membrane-electrode assembly for an electrochemical cell, in particular for a fuel cell or an electrolysis cell, comprising a membrane arranged between two transport layers and, in at least one edge region, between two frame parts of a frame. The transport layer and the frame part of at least one side have a common connection region over which the membrane extends. According to the invention, in at least one connection region, preferably in an anode-side connection region, the transport layer and the frame part each have a flattened, beveled, rounded and / or arcuate edge geometry on their side facing the membrane to form a relief space for the membrane.
[0013] If different pressures prevail on either side of the membrane, the relief chamber enables deformation of the membrane. The membrane is pressed into the relief chamber against the flattened, beveled, rounded and / or curved edge geometries. The relief chamber is therefore preferably formed on the side of the membrane where the lower pressure prevails. This is usually the anode side. The flattened, beveled, rounded and / or curved edge geometries that form the relief chamber prevent the formation of sharp edges and thus damage to the membrane. The robustness of the membrane increases accordingly, which has a positive effect on its service life. At the same time, the service life of the electrochemical cell increases.
[0014] According to a preferred embodiment of the invention, the relief space has a width B and a height H. The width B is greater than the height H, preferably 1.1 to 10 times greater than the height H, further preferably 1.5 to 9.5 times greater than the height H. The specified size ratio of the width B to the height H enables an obtuse-angled transition of a flattened and / or bevelled edge geometry into the surface of the transport layer and / or the frame part that is in contact with the membrane. The more obtuse the angle in the transition area, the lower the risk of damage to the membrane if it is pressed against it. With a rounded and / or curved edge geometry, the transition area can even be designed completely free of edges.
[0015] Furthermore, the membrane preferably has a thickness D, and the height H of the relief chamber corresponds to up to 100%, preferably up to 75%, and further preferably up to 50%, of the thickness D. The height H of the relief chamber is therefore not greater than the thickness D of the membrane. In this way, the maximum deformation of the membrane is kept within limits and adapted to the respective membrane thickness. The stress on the membrane caused by the deformation is therefore correspondingly low, which further increases the robustness of the membrane.
[0016] Furthermore, the relief chamber is preferably arranged asymmetrically with respect to the connection region, so that the edge geometries of the transport layer and the frame part that delimit the relief chamber have different widths a, b. This is particularly advantageous if the two frame parts of the frame are designed with different widths, so that one connection region, preferably the anode-side connection region, is arranged offset outwards relative to the other connection region. The pressure acting on the membrane, which presses the membrane against the flattened, beveled, rounded and / or curved edge geometries, is thus greater in the region of the transport layer than in the region of the frame part.The larger width a of the edge geometry of the transport layer can be used to create a larger contact surface for the membrane, which can also transition into the surface of the transport layer that is in contact with the membrane at an obtuse angle or even without edges.
[0017] In a preferred embodiment, at least one of the two edge geometries has the shape of a partial ellipse extending from a secondary vertex SN to a primary vertex SH, with the secondary vertex SN being located on the membrane and the primary vertex SH being located in the connection area. The partially elliptical edge geometry represents a special form of an arcuate edge geometry that enables completely angle-free transitions. If the partial ellipse is also oriented such that the secondary vertex SN is located on the membrane, a relief space can be easily created whose width B is greater than its height H.
[0018] Furthermore, the two edge geometries are preferably substantially mirrored. This means that both edge geometries have substantially the same shape. If the two edge geometries are not exactly mirrored, they may differ, in particular with regard to their widths a and b.
[0019] As already mentioned, the frame parts of the frame can also have different widths x, y. The connection areas formed on both sides of the membrane between the respective transport layer and the respective frame part are then arranged offset from one another in the plane of the membrane. This has the advantage that one connection area, preferably the anode-side connection area, is covered by the frame part arranged on the other side of the membrane, preferably the cathode-side frame part, so that the membrane is subjected to less stress in this area. This measure also contributes to increasing the robustness of the membrane. It follows that the width x of the anode-side frame part is preferably smaller than the width y of the cathode-side frame part. Advantageously, the frame parts of the frame form sealing surfaces that lie directly against the membrane.The frame can then also be used to seal the membrane electrode assembly.
[0020] Preferably, the membrane and / or the transport layers are coated with a catalytically active material. The membrane can be coated on one or both sides. If one side is uncoated, a transport layer coated with a catalytically active material is preferably present at least on this side. Preferably, both sides of the membrane are coated with a catalytically active material, so that coating the transport layers with a catalytically active material is unnecessary.
[0021] Furthermore, an electrochemical cell, in particular a fuel cell or an electrolysis cell, with a membrane-electrode assembly according to the invention is proposed. The increased robustness of the membrane-electrode assembly according to the invention has a positive effect on the robustness of the electrochemical cell, resulting in a longer service life.
[0022] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:
[0023] Fig. 1 is a schematic longitudinal section through a first membrane electrode arrangement according to the invention,
[0024] Fig. 2 shows a schematic longitudinal section through a second membrane electrode arrangement according to the invention and
[0025] Fig. 3 a partial ellipse extending from a secondary vertex SN to a primary vertex SH.
[0026] Detailed description of the drawings
[0027] Figure 1 shows a membrane electrode assembly 1 with a membrane 2, which is arranged between two transport layers 3, 4 and in an edge region 5 between two frame parts 6.1, 6.2 of a frame 6. The upper frame part 6.2, which in this case is the cathode-side frame part 6.2, has a width y that is greater than a width x of the lower frame part 6.1 or the anode-side frame part 6.1. This means that connection regions 7, 8 are formed between the transport layers 3, 4 and the frame parts 6.1, 6.2, which connection regions are arranged offset from one another in the plane of the membrane 2. The upper frame part 6.2 thus covers the connection region 7 between the lower frame part 6.1 and the lower transport layer 3. Since there is generally a higher pressure on the cathode side than on the anode side, a force acts on the membrane 2, which presses the membrane 2 against the lower connection area 7.Since the connection area 7 is offset outwards, the force does not act directly on the membrane 2 in the connection area 7, so that the pressure load in the connection area 7 is reduced.
[0028] To further relieve the pressure on the membrane 2, the lower transport layer 3 and the lower frame part 6.1 each have an edge geometry 9, 10 in the connection area 7 on their side facing the membrane 2, which is flattened or beveled, respectively, so that a relief chamber 11 is formed. The relief chamber 11 enables deformation of the membrane 2 under compressive load. The membrane 2 is pressed against the flattened or beveled edge geometries 9, 10. Since these each transition via an obtuse angle into the surface of the transport layer 3 or the frame part 6.1 resting against the membrane 2, sharp edges are avoided, which could lead to damage to the membrane 2.
[0029] The relief chamber 11 in the present case has a width B and a height H, wherein the width B corresponds to a multiple of the height H. The height H is also slightly smaller than a thickness D of the membrane 2. The two edge geometries 9, 10 also have different widths a, b, wherein the width a of the edge geometry 9 of the transport layer 3 is greater than the width b of the edge geometry 10 of the frame part 6.1, since in the area of the transport layer 3 the pressure applied to the membrane 2 is greater than in the area of the frame part 6.1.
[0030] As shown by way of example in Figure 2, the edge geometries 9, 10 can also have an arcuate shape. In Figure 2, an arcuate shape in the form of a partial ellipse is selected, with the edge geometries 9, 10 each extending from a secondary vertex SN1, SN2 adjacent to the membrane 2 to a main vertex SHI, SH2, which is respectively arranged in the connection region 7. The transition of the edge geometries 9, 10 into the respective surface adjacent to the membrane 2 is thus completely edge-free. Figure 3 shows an example of a partial ellipse with a secondary vertex SN and a main vertex SH ZU.
Claims
Claims 1. Membrane electrode assembly (1) for an electrochemical cell, in particular for a fuel cell or an electrolysis cell, comprising a membrane (2) which is arranged between two transport layers (3, 4) and in at least one edge region (5) between two frame parts (6.1, 6.2) of a frame (6), wherein the transport layer (3, 4) and the frame part (6.1, 6.2) have a common connection region (7, 8) on at least one side, over which the membrane (2) extends, characterized in that in at least one connection region (7, 8), preferably in an anode-side connection region (7), the transport layer (3) and the frame part (6.1) each have a flattened, beveled, rounded and / or arcuate edge geometry (9, 10) on their side facing the membrane (2) to form a relief space (11) for the membrane (2).
2. Membrane electrode assembly (1) according to claim 1, characterized in that the relief space (11) has a width (B) and a height (H), wherein the width (B) is greater than the height (H), preferably 1.1 to 10 times greater than the height (H), further preferably 1.5 to 9.5 times greater than the height (H).
3. Membrane electrode assembly (1) according to claim 2, characterized in that the membrane (2) has a thickness (D) and the height (H) of the relief space (11) corresponds to up to 100%, preferably up to 75%, further preferably up to 50%, of the thickness (D).
4. Membrane electrode assembly (1) according to one of the preceding claims, characterized in that the relief space (11) is arranged asymmetrically with respect to the connection region (7), so that the edge geometries (9, 10) of the transport layer (3) and the frame part (6.1) delimiting the relief space (11) have different widths (a, b).
5. Membrane electrode arrangement (1) according to one of the preceding claims, characterized in that at least one of the two edge geometries (9, 10) has the shape of a partial ellipse which runs from a secondary vertex (SN) TO a main vertex (SH), wherein the secondary vertex (SN) is arranged on the membrane and the main vertex (SH) is arranged in the connection region (7).
6. Membrane electrode assembly (1) according to one of the preceding claims, characterized in that the two edge geometries (9, 10) are substantially mirrored.
7. Membrane electrode assembly (1) according to one of the preceding claims, characterized in that the frame parts (6.1, 6.2) of the frame (6) have different widths (x, y), wherein preferably the width (x) of the anode-side frame part (6.1) is smaller than the width (y) of the cathode-side frame part (6.2).
8. Membrane electrode assembly (1) according to one of the preceding claims, characterized in that the frame parts (6.1, 6.2) of the frame (6) form sealing surfaces (12) which bear directly against the membrane (2).
9. Membrane electrode assembly (1) according to one of the preceding claims, characterized in that the membrane (2), preferably on both sides, and / or the transport layers (3, 4) is / are coated with a catalytically active material.
10. Electrochemical cell, in particular fuel cell or electrolysis cell, with a membrane electrode arrangement (1) according to one of the preceding claims.