MEMBRANE ELECTRODE UNIT FOR AN ELECTROCHEMICAL CELL AND METHOD FOR MANUFACTURING A MEMBRANE ELECTRODE UNIT - Patent application

Abstract

The membrane electrode unit (1) for an electrochemical cell (100) has a frame structure (10) for housing a membrane (2) coated with electrodes (3, 4). The frame structure (10) includes a first film (11) and a second film (12) with an adhesive (13) interposed therebetween. The first film (11) is welded to the second film (12) at a bonding area (15).

Description

[Technical field]

[0001] The present invention relates to a membrane electrode unit for an electrochemical cell and to a method for manufacturing the membrane electrode unit. [Background technology]

[0002] A fuel cell is an electrochemical cell that has two electrodes separated by an ionically conductive electrolyte. Fuel cells convert the energy of a chemical reaction between an oxidant and a fuel directly into electricity. There are many different types of fuel cells.

[0003] One particular type of fuel cell is the polymer electrolyte membrane fuel cell (PEM-FC). In the active area of ​​the PEM-FC, two porous electrodes with a catalyst layer adjoin a polymer electrolyte membrane (PEM). The PEM-FC further comprises gas diffusion layers (GDLs) in the active area, which separate the polymer electrolyte membrane (PEM) and the two porous electrodes with a catalyst layer on either side. The PEM and both electrodes with a catalyst layer, and optionally both GDLs, form a so-called membrane electrode unit (MEA) in the active area of ​​the PEM-FC. The MEA is further separated on either side by two bipolar plates (bipolar half plates) facing each other. The MEAs and bipolar plates, which are arranged one above the other, form a fuel cell stack. The anode plate of the bipolar plate provides the distribution of the fuel, in particular hydrogen, and the cathode plate of the bipolar plate provides the distribution of the oxidant, in particular air / oxygen. For electrical insulation of adjacent bipolar plates, for stabilization of the MEA and for prevention of accidental leakage of fuel or oxidant, the MEA can be surrounded by a frame-like opening of two films arranged next to each other. Usually, both films of such a frame structure are made of the same material, for example polyethylene naphthalate (PEN). Both films made of the same material have non-essential redundant properties, for example the electrical insulation capacity (insulation) and / or oxygen tightness of each of both films.

[0004] Patent Document 1 discloses a membrane electrode unit for a fuel cell, which includes a layer structure consisting of an anode electrode, a cathode electrode, and a membrane disposed therebetween, and a polymer material is applied to the upper and lower surfaces of the layer structure.

[0005] Patent Document 2 shows a membrane electrode unit having a frame structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 10140684 A1 [Patent Document 2] German Patent Application Publication No. 102018131092A1 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the invention is to prevent the glue from being squeezed out of the frame structure and preferably to ensure a defined height of the frame structure. [Means for solving the problem]

[0008] For this purpose, the membrane electrode unit comprises a frame structure for receiving the membrane coated with electrodes. The frame structure has a first film and a second film with an adhesive therebetween. In the bonding region, the first film is welded to the second film, i.e., in the bonding region, both films are bonded to one another in a material-bonding manner.

[0009] For this purpose, both films preferably consist of the same material, particularly preferably of a thermoplastic polymer such as PEN, so that they can be welded together in a very simple manner, for example by hot stamping.

[0010] The welding of both films creates a barrier for the adhesive, which prevents the adhesive from being squeezed out of the frame structure, especially when the electrochemical cells are stacked and pressed. The adhesive is, as it were, trapped in the frame structure. The volume of relatively incompressible adhesive defined in this way adjusts a defined uniform height of the membrane electrode units. The cell stack can accordingly be pressed with a more uniform contact pressure distribution, with the stack height tolerances being within tighter limits.

[0011] The membrane electrode unit may include a membrane, in particular a polymer electrolyte membrane (PEM). The membrane electrode unit may further include two porous electrodes each having a catalyst layer, which are in particular arranged on the PEM and bound both sides. In particular the name MEA-3 may be used here. In addition to this, the membrane electrode unit may include two gas diffusion layers, which in particular may bound the MEA-3 on both sides. In particular the name MEA-5 may be used here.

[0012] The electrochemical cell may be, for example, a fuel cell, an electrolytic cell or a battery cell. The battery cell is in particular a PEM-FC (Polymer Electrolyte Membrane Fuel Cell). A cell stack in particular comprises a number of electrochemical cells arranged one above the other.

[0013] The frame structure in particular has a frame shape. The frame structure is preferably manufactured in a circumferential manner. In that way, the membrane and both electrodes can be particularly preferably surrounded by the frame structure. Furthermore, the frame structure is configured in particular U-shaped or Y-shaped in cross section and accommodates the membrane and both electrodes between the respective legs of the U or Y.

[0014] When both films are bonded together, they are preferably bonded only at the central leg of the Y, with a membrane being placed between each film between the other two legs, which may then be bonded to both films.

[0015] The adhesive preferably seals the membrane electrode unit towards the outside, bonds both films together and fixes the membrane together with both electrodes in a framework.

[0016] Furthermore, the adhesive may preferably be electrically insulating, so that the frame structure may be particularly preferably electrically insulating and inadvertent current flow in non-active areas of the electrochemical cell may be particularly preferably low, and in particular prevented.

[0017] In a preferred development, both films are welded to one another around the periphery of the active area, so that the adhesive seals the edge of the active area, and this sealing function can be significantly improved and ensured if extrusion of the adhesive is prevented.

[0018] In a preferred embodiment, both films are welded to each other around the circumference of the distribution area, so that the adhesive seals the edges of the distribution area, and such a sealing function can be significantly improved and ensured if extrusion of the adhesive is prevented.

[0019] The present invention also includes a method for manufacturing a membrane electrode unit according to one of the above embodiments, the method comprising the following method steps: The first film is fused to the second film in the bonding area by hot stamping.

[0020] The hot stamp is then preferably produced in two parts, so that each film can be brought into direct contact with the heated stamp, and this process is particularly preferably carried out with the application of a holding pressure during the welding process and especially during the cooling process, so that both films can be well bonded to one another in a material-bonding manner.

[0021] Other ways of improving the invention will become apparent from the following description of some embodiments of the invention, which are illustrated diagrammatically in the drawings. Any features and / or advantages that become apparent from the claims, the specification, or the drawings, including design specifics, spatial arrangements, and method steps, may be part of the invention either alone or in various combinations, with the understanding that the drawings are merely illustrative in nature and are not intended to limit the invention in any way.

[0022] The drawings show diagrammatically: [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a membrane electrode unit according to the prior art, only the main areas are shown. [Diagram 2] 1 is a membrane electrode unit according to the invention, only the main areas are shown. [Diagram 3] FIG. 2 is a perspective view showing a schematic membrane electrode unit, with only the main area being shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] FIG. 1 shows a membrane electrode unit 1 of an electrochemical cell 100, in particular of a fuel cell, according to the prior art in vertical section, of which only the essential areas are shown.

[0025] The membrane electrode unit 1 comprises a membrane 2, which is by way of example a polymer electrolyte membrane (PEM), and two porous electrodes 3 to 4, each with a catalyst layer, each arranged on one side of the membrane 2. Furthermore, the electrochemical cell 100 in particular comprises two gas diffusion layers 5 to 6, which may also belong to the membrane electrode unit 1 in some embodiments.

[0026] The membrane electrode unit 1 is surrounded on its periphery by a framework 10, also referred to herein as a subgasket. The framework 10 serves to provide rigidity and sealing for the membrane electrode unit 1 and is the inactive area of ​​the electrochemical cell 100.

[0027] The frame structure 10 is configured in particular U- or Y-shaped in cross section, with a first leg of the U-shaped frame section being formed by a first film 11 made of a first material W1 and a second leg of the U-shaped frame section being formed by a second film 12 made of a second material W2. In addition to this, the first film 11 and the second film 12 are bonded together by means of an adhesive 13 made of a third material W3. Frequently, the first material W1 and the second material W2 are identical.

[0028] Both gas diffusion layers 5-6 are also respectively arranged on one side of the frame structure 10 by means of another adhesive 14 and are normally adapted to contact one electrode 3, 4 respectively in the active area of ​​the electrochemical cell 100.

[0029] When pressing several electrochemical cells 100 into a cell stack, there is a risk that the adhesive 13 will be squeezed out of the frame structure 10. This can lead to non-hermeticity of the membrane electrode units 1 and even to total failure of the entire cell stack.

[0030] Therefore, in the present invention, both films 11, 12 are welded to each other in the bonding area 15 or are sealed in such a way that the adhesive 13 is prevented from escaping.

[0031] In this respect, Figure 2 shows in cross section a membrane electrode unit 1 in which the first film 11 and the second film 12 are welded together in the joining area 15, thereby sealing in the adhesive 13. No escape of the adhesive 13 towards the left hand side as viewed in the drawing of Figure 2 is possible even when both films 11, 12 are pressed against one another.

[0032] Furthermore, such shielding of the volume of adhesive 13 ensures a defined height of the adhesive 13 and thus of the position of the entire membrane electrode unit 1 in the stacking direction of the electrochemical cell 100, since a defined mutual distance of both films 11, 12 is ensured.

[0033] 2 further shows a schematic representation of a corresponding manufacturing method for the membrane electrode unit 1. The welding or material-bonding bond of the two films 11, 12 is preferably produced by means of a hot stamp 40. In the diagrammatic embodiment shown, the hot stamp 40 for this purpose comprises a first stamp 41 and a second stamp 42. Both stamps 41, 42 are heated during the manufacturing step and brought close to each other in the bonding area 15, so that the first stamp 41 acts on the first film 11 and the second stamp 42 acts on the second film 12. The two stamps 41, 42 move close to each other until the first film 11 comes into contact with the second film 12 in the bonding area 15. The high temperature of the two stamps 41, 42 melts the two films 11, 12 at least in the bonding area 15, so that the polymer chains belonging to them can be bonded to each other. That is to say, after the two films 11, 12 have cooled, a material-bonding bond between the two films 11, 12 is formed in the bonding area 15.

[0034] This manufacturing step for welding both films 11, 12 can preferably be combined with further manufacturing steps, such as for example a punching process at the membrane electrode unit 1 or cutting of the frame structure 10.

[0035] FIG. 3 shows a schematic diagram of a perspective view of a membrane electrode unit 1. In the center of the membrane electrode unit 1 there is preferably a rectangular active area 35 with a coated membrane. The coated membrane is surrounded on its periphery by a framework 10. In the embodiment of FIG. 3, the framework 10 has three distribution openings 30 at its narrow end faces for the supply and discharge of the media fuel, oxidant and coolant, respectively. Between the distribution openings 30 and the active area 35 there is formed a so-called distribution area 31, which serves to distribute (supply side) or withdraw (discharge side) the media from the relatively narrow distribution openings 30 to the relatively wide active area 35.

[0036] In a preferred embodiment of the invention, both films 11, 12 of the framework 10 are welded to one another at the periphery 36 of the active area 35 and / or at the periphery 32 of the distribution area 31, so that the volume of adhesive 13 is defined in the corresponding areas 31, 35 and cannot be squeezed out, so that a uniform thickness of the membrane electrode unit 1 is adjusted with high robustness and the respective areas 31, 35 are sealed very well. [Explanation of symbols]

[0037] 1. Membrane electrode unit 2 membrane 3,4 electrodes 10 Frame structure 11 First Film 12 Second Film 13. Glue 15 Combined area 31 Distribution area 32 Distribution Area Circumference 35 Active area 36 Around the active region 40 Hot stamping 100 Electrochemical Cells

Claims

1. A membrane electrode unit (1) for an electrochemical cell (100), said membrane electrode unit (1) having a frame structure (10) for accommodating a membrane (2) coated with electrodes (3, 4), said frame structure (10) including a first film (11) and a second film (12) with an adhesive (13) interposed therebetween, The first film (11) is welded to the second film (12) in a bonding region (15); One gas diffusion layer (5) is disposed on one side of the frame structure (10) by another adhesive (14), and another gas diffusion layer (6) is disposed on the other side of the frame structure (10) by the other adhesive (14); The bonding area (15) is provided at a position protruding outward from the other adhesive (14), A membrane electrode unit, characterized in that the bonding area (15) has a recess formed by welding.

2. 2. A membrane electrode unit (1) according to claim 1, characterized in that both films (11, 12) are made of the same material.

3. 3. A membrane electrode unit (1) according to claim 1 or 2, characterized in that both films (11, 12) consist of a thermoplastic polymer.

4. 3. A membrane electrode unit (1) according to claim 1 or 2, characterized in that both films (11, 12) consist of PEN.

5. 5. The membrane electrode unit (1) according to claim 1, wherein the two films (11, 12) are welded to one another over the periphery (36) of the active area (35).

6. 6. A membrane electrode unit (1) according to claim 1, characterized in that the two films (11, 12) are welded to one another over the periphery (32) of the distribution area (31).

7. 7. A method for producing a membrane electrode unit (1) according to claim 1, the membrane electrode unit (1) having a frame structure (10) for accommodating a membrane (2) coated with electrodes (3, 4), the frame structure (10) including a first film (11) and a second film (12) with an adhesive (13) interposed therebetween, the method comprising: The method comprises the following steps: - A method, characterized in that said first film (11) is welded to said second film (12) in a bonding area (15) by hot stamping (40), forming a recess in said bonding area (15).

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