Sub-gasket for a membrane electrode assembly of an electrochemical cell

Abstract

Sub-gasket (1) for a membrane electrode assembly (10) of an electrochemical cell (20), wherein the sub-gasket (1) is formed from at least one plastic film (1a, 1b) and has a thickness in the range of 30 to 200 µm, wherein an opening (1c) arranged centrally in the sub-gasket (1), viewed perpendicular to a plane of the sub-gasket (1), is provided for receiving a polymer electrolyte membrane (2) of the membrane electrode assembly (10), and a microstructure (3) is present on at least one side of the sub-gasket (1), wherein the microstructure (3) is formed into a free surface area of ​​the plastic film (1a, 1b) or of at least one of the plastic films (1a, 1b), and a depth of the microstructure (3) is at least 2.5 to a maximum of 15% of the thickness of the sub-gasket (1), wherein the microstructure (3) comprises channel-shaped structures (31), and wherein the sub-gasket (1) has channel-shaped structures (31) on both sides Each side has a sealing arrangement (4,4') and first channel-shaped structures (311) are arranged in an edge region of the sub-gasket (1), viewed perpendicular to the plane of the sub-gasket (1), outside the respective sealing arrangement (4, 4').

Description

[0001] The invention relates to a sub-gasket for a membrane electrode assembly of an electrochemical cell, wherein the sub-gasket is formed from at least one plastic film and has a thickness in the range of 30 to 200 µm. An opening arranged centrally in the sub-gasket, viewed perpendicular to a plane of the sub-gasket, is provided for receiving a polymer electrolyte membrane of the membrane electrode assembly, and a microstructure is present on at least one side of the sub-gasket. The invention further relates to a membrane electrode assembly and an electrochemical cell.

[0002] US 2006 / 0078781 A1 describes a membrane electrode assembly for a polymer electrolyte fuel cell, comprising a polymer electrolyte membrane, a gas diffusion layer, a catalyst layer between the polymer electrolyte membrane and the gas diffusion layer, and a subgasket. The subgasket is made, for example, of a thermoplastic material. One surface of the subgasket has a sealing surface, which can be microstructured or adhesive to improve the sealing effect on the membrane electrode assembly.

[0003] KR 10 2020 0 086 833 A discloses an apparatus for manufacturing a membrane electrode assembly for a fuel cell. A subgasket in a specific shape is formed by applying heat to a 5-layer membrane electrode assembly with a thermocompression frame, utilizing gas expansion properties within the subgasket.

[0004] US 2010 / 0 062 320 A1 describes a sub-gasket with a thickness that decreases towards the electrolyte membrane and a sealing area arranged in the edge area.

[0005] Such a membrane electrode assembly is typically held between two electrically conductive flow guide plates, which have three-dimensional flow guide and support structures on their surface to ensure fluid distribution during operation of the electrochemical cell and its mechanical stability. Local areas often exist where inadequate fluid distribution occurs due to insufficient channel depth. Furthermore, membrane electrode assemblies are usually pliable, making them difficult to handle when constructing a cell stack of electrochemical cells. Automated stacking repeatedly leads to misalignment of the membrane electrode assembly or leaks in the cell stack.

[0006] It is an object of the present invention to further improve the structure of an electrochemical cell and a fluid distribution in an electrochemical cell.

[0007] The object is achieved by a sub-gasket for a membrane electrode assembly of an electrochemical cell, wherein the sub-gasket is formed from at least one plastic film and has a thickness in the range 30 to 200 µm, wherein an opening arranged centrally in the sub-gasket, viewed perpendicular to a plane of the sub-gasket, is provided for receiving a polymer electrolyte membrane of the membrane electrode assembly, and a microstructure is present on at least one side of the sub-gasket in that the microstructure is formed into a free surface area of ​​the plastic film or of at least one of the plastic films, and a depth of the microstructure is at least 2.5 to a maximum of 15% of the thickness of the sub-gasket, wherein the microstructure comprises channel-shaped structures.The sub-gasket has a sealing arrangement on each side and first channel-shaped structures are arranged in an edge region of the sub-gasket, seen perpendicular to the plane of the sub-gasket, outside the respective sealing arrangement.

[0008] Such a subgasket exhibits improved mechanical stability compared to conventional subgaskets and is therefore characterized by significantly improved handling. It can be gripped much more precisely by automated grippers and used to construct a membrane electrode assembly. Furthermore, the microstructure provides a fluid distribution system that further supports the function of adjacent electrically conductive flow guide plates in electrochemical cells, which also have fluid-conducting structures on their surfaces.

[0009] The first channel-shaped structures serve primarily to increase the mechanical strength of the sub-gasket and thus contribute significantly to stiffening a membrane electrode assembly, enabling automated gripping and placement during cell stack formation. When a plastic film is used as the sub-gasket, the sealing arrangements are applied to both sides of this plastic film. When multiple plastic films are used as the sub-gasket, the sealing arrangements are arranged on the plastic films of the sub-gasket, which form the free surfaces on both sides of the sub-gasket.

[0010] Particularly preferably, the sub-gasket comprises at least two interconnected plastic films, which are provided for accommodating the polymer electrolyte membrane of the membrane-electrode assembly between the plastic films, and wherein the sub-gasket has the microstructure on both sides. This further improves the mechanical stability of the sub-gasket.

[0011] The polymer electrolyte membrane is typically bonded between two plastic films. However, several plastic films can also be bonded to the polymer electrolyte membrane on one or both sides as a sub-gasket.

[0012] The plastic films are preferably provided with microstructures by rolling them into the surface of the plastic film. However, microstructures can also be introduced by pressing a heated stamp onto the plastic film or during the calendering process, thus forming the plastic film.

[0013] The sub-gasket preferably has a plurality of fluid passages, with second channel-shaped structures arranged in an edge region of the fluid passages within a region enclosed by the respective sealing arrangement, viewed perpendicular to the plane of the sub-gasket. The second channel-shaped structures have both a supporting and a fluid-conducting function.

[0014] Preferably, third channel-shaped structures are arranged adjacent to the opening for receiving the polymer electrolyte membrane of the membrane electrode assembly and within an area enclosed by the sealing arrangement, viewed perpendicular to the plane of the sub-gasket.

[0015] The third channel-shaped structures preferably form a fan-out distribution structure starting from a fluid passage opening in the direction of the opening.

[0016] The third channel-shaped structures preferably continue to run alongside the opening between two distributor structures and form a fluid conducting structure.

[0017] Thus, the third channel-shaped structures also have a supporting as well as a fluid conducting function.

[0018] The first channel-shaped structures form in particular a stiffening structure that increases the mechanical strength of the sub-gasket.

[0019] Other microstructures other than channel-like or distributor structures can be incorporated into the plastic films. For example, nub-, lens-, or ring-like structures can also be present, which serve a supporting function with respect to an adjacent flow guide plate in an electrochemical cell.

[0020] The object is further achieved for a membrane electrode assembly for an electrochemical cell, comprising a polymer electrolyte membrane which is coated on both sides with at least one electrode and catalyst layer, and with a gas diffusion layer on the electrode and catalyst layers, wherein the polymer electrolyte membrane is held fixed on one side by the at least one plastic film of the sub-gasket or between at least two plastic films of the sub-gasket according to the invention in the opening thereof.

[0021] Due to the sub-gasket used, such a membrane electrode assembly exhibits improved mechanical stability compared to conventional membrane electrode assemblies and is therefore characterized by significantly improved handling. It can be gripped much more precisely using automatic grippers and used to construct an electrochemical cell. Furthermore, the microstructure provides a fluid distribution system that further supports the function of adjacent electrically conductive flow guide plates in electrochemical cells, which also have fluid-conducting structures on their surfaces.

[0022] An electrochemical cell, in particular a fuel cell or an electrolyzer, comprising at least one membrane electrode unit according to the invention between two electrically conductive flow guide plates has proven successful, wherein the electrically conductive flow guide plates are designed as metallic bipolar plates or carbon-polymer composite plates.

[0023] The fuel cell is, in particular, a polymer electrolyte fuel cell. The electrolyzer is preferably one for electrolyzing water.

[0024] The Fig. Figures 1 to 6 are intended to illustrate the invention by way of example. Thus, Fig. 1 a sub-gasket for a membrane electrode assembly, Fig. 2 the sub-sealing from Fig. 1 on the back, Fig. 3 a membrane electrode assembly with a sub-gasket according to the Fig. 1 and Fig. 2, Fig. 4 a cross section IV-IV through the membrane electrode assembly according to Fig. 3, Fig. 5 a three-dimensional view of an electrically conductive flow guide plate, and Fig. 6 schematically shows a cell stack of electrochemical cells comprising alternately arranged electrically conductive flow guide plates and membrane electrode assemblies.

[0025] Fig. 1 showed a sub-gasket 1 for a membrane electrode assembly 10 (compare Fig. 3) an electrochemical cell 20 (compare Fig. 6). The sub-seal 1 is made of two interconnected plastic films 1a, 1b (compare Fig. 2) and has a thickness in the range of 30 to 200 µm. Alternatively, a single plastic film 1a can be used. Fig. 1 shows the sub-gasket 1 with a view of the plastic film 1a. An opening 1c arranged centrally in the sub-gasket 1, viewed perpendicular to a plane of the sub-gasket 1, is intended to accommodate a polymer electrolyte membrane 2 of the membrane electrode assembly 10 (cf. Fig. 3) between the plastic films 1a, 1b. Furthermore, fluid passage openings 5, 5', 5'' are provided, which serve for the supply or discharge of fluids. The peripheral shape of the fluid passage openings 5, 5', 5'' is rectangular here, but can also have a different shape, for example, round (see Fig. 6).

[0026] On at least one side of the sub-gasket 1, a microstructure 3 is present, wherein the microstructure 3 is formed into a free surface area of ​​at least one of the plastic films 1a, 1b. The depth of the microstructure 3 is at least 2.5 to a maximum of 15% of the thickness of the sub-gasket 1, wherein the microstructure 3 comprises channel-shaped structures 31. The channel-shaped structures 31 serve for the targeted guidance and distribution of fluids in an electrochemical cell 20. They support the flow of fluids on an adjacent electrically conductive flow guide plate 9 (see Fig. 5) intended three-dimensional surface structures for the guidance and distribution of fluids.

[0027] The sub-seal 1 has a sealing arrangement 4, 4' on both sides, compare Fig. 1 and Fig. 2. The channel-shaped structures 3 here comprise first channel-shaped structures 311 in an edge region of the sub-gasket 1, which, viewed perpendicular to the plane of the sub-gasket 1, are arranged outside the respective sealing arrangement 4, 4'. The first channel-shaped structures 311 form a stiffening structure that increases the mechanical strength of the sub-gasket 1.

[0028] The channel-shaped structures 3 further comprise second channel-shaped structures 312, which are arranged in an edge region of the fluid passage openings 5, 5', 5'' within a region enclosed by the respective sealing arrangement 4, 4', seen perpendicular to the plane of the sub-gasket 1.

[0029] The channel-shaped structures 3 further comprise third channel-shaped structures 313, which are arranged adjacent to the opening 1c for receiving the polymer electrolyte membrane 2 of the membrane-electrode assembly 10 and within an area enclosed by the sealing arrangement 4, 4', viewed perpendicularly to the plane of the sub-gasket 1. Starting from a fluid passage opening 5, 5'' in the direction of the opening 1c, the third channel-shaped structures 313 form a fan-out distributor structure 6 for the fluid flowing in or out through the fluid passage opening 5, 5''. The third channel-shaped structures 313 also run alongside the opening 1c between two distributor structures 6a, 6b. The third channel-shaped structures 313 form a fluid conduction structure. The fluid passage opening 5' is used here merely as an opening for conducting a coolant in a direction perpendicular to the plane of the sub-gasket 1.

[0030] The plastic films 1a, 1b are preferably provided with the microstructures 3 by rolling them into the surfaces of the plastic films 1a, 1b. However, microstructures 3 can also be introduced into the plastic film by pressing a heated stamp onto it or during calendering and thus forming the plastic film.

[0031] Fig. 2 shows the sub-gasket 1 from Fig. 1 on its back, i.e. looking at the plastic film 1b. The sealing arrangement 4' is aligned with the sealing arrangement 4 on the front (see Fig. 1) arranged.

[0032] Fig. 3 shows a membrane electrode assembly 10 with a sub-gasket 1 according to the Fig. 1 and Fig. 2. Same reference numerals as in the Fig. 1 and Fig. 2 denote identical elements. A polymer electrolyte membrane 2 is located in the opening 1c of the sub-gasket 1. It is fixedly arranged between the plastic films 1a, 1b of the sub-gasket 1 and fills the opening 1c. The polymer electrolyte membrane 2 is coated on both sides with at least one electrode and catalyst layer 7a, 7b. Furthermore, a gas diffusion layer 8a, 8b is arranged on the electrode and catalyst layers 7a, 7b.

[0033] Fig. 4 shows a cross section IV-IV through the membrane electrode assembly 10 according to Fig. 3. Same reference numerals as in the Fig. 1 to 3 indicate the same elements. The polymer electrolyte membrane 2 held between the two plastic films 1a, 1b is clearly visible, which is located on each side in the area of ​​the opening 1c (compare Fig. 1 and Fig. 2) each has an electrode and catalyst layer 7a, 7b. Furthermore, the gas diffusion layers 8, 8a, 8b present on each side of the polymer electrolyte membrane 2 in the region of the opening 1c are visible. Furthermore, the sealing arrangements 4, 4' and their arrangement on both sides of the sub-gasket 1 can be seen. Section IV-IV also shows the position and arrangement of the existing microstructures 3, 311, 313.

[0034] Fig. 5 shows a three-dimensional view of an electrically conductive flow guide plate 9. The flow guide plate 9, in turn, has fluid passage openings 50, 50', 50''. Furthermore, an electrochemically active field 9' is present on both sides of the flow guide plate 9, which field has a fluid conducting structure and with which the opening 1c of the membrane electrode assembly 10 is arranged in alignment. The electrically conductive flow guide plate 9 can be in the form of a monopolar plate or a bipolar plate. In particular, an electrically conductive flow guide plate 9 is designed as a metallic bipolar plate or a carbon-polymer composite plate. Typically, two distribution fields (not shown in detail here) are located on each side of the flow guide plate 9, with one distribution field each being arranged between the fluid passage openings 50, 50', 50'' and the electrochemically active field 9'.Such distribution fields are realized by three-dimensional structures on the surface of the electrically conductive flow guide plate 9 and serve, on the one hand, to distribute fluids starting from a fluid passage opening 50, 50', 50'', here synonymous with a fluid inflow opening, in the direction of the electrochemically active field 9', or to collect a fluid which, after flowing along the electrochemically active field 9', leaves the area of ​​the electrochemically active field 9' again, in the direction of the fluid passage opening 50, 50', 50'', here synonymous with a fluid outlet opening.

[0035] Fig.6 schematically shows a cell stack 100 of electrochemical cells 20 comprising alternatingly arranged electrically conductive flow guide plates 9 and membrane electrode assemblies 10. Such an electrochemical cell 20 is, in particular, a cell of a fuel cell, in particular a polymer electrolyte fuel cell, or of an electrolyzer for the electrolysis of water. Each electrochemical cell 20 comprises at least one membrane electrode assembly 10 between two electrically conductive flow guide plates 9. The fluid passage openings 5, 5', 5'' of the sub-gasket 1 of the membrane electrode assembly 10 are arranged in alignment with the fluid passage openings 50, 50', 50'' of the electrically conductive flow guide plates 9. List of reference symbols 1 sub-sealing 1a, 1b plastic film 1c Opening for the polymer electrolyte membrane 2 polymer electrolyte membrane 3 Microstructure 31 channel-shaped structure 311 first channel-shaped structure 312 second channel-shaped structure 313 third channel-shaped structure 4, 4' sealing arrangement 5, 5', 5'' Fluid passage opening in sub-seal 6, 6a, 6b distribution structure 7, 7a, 7b Electrode and catalyst layer 8, 8a, 8b Gas diffusion layer 9 electrically conductive flow guide plate 9' electrochemically active field 10 Membrane electrode assembly 20 electrochemical cell 50, 50', 50'' Fluid passage opening in flow guide plate 100 cell stacks

Claims

[1] Sub-gasket (1) for a membrane electrode assembly (10) of an electrochemical cell (20), wherein the sub-gasket (1) is formed from at least one plastic film (1a, 1b) and has a thickness in the range of 30 to 200 µm, wherein an opening (1c) arranged centrally in the sub-gasket (1), viewed perpendicular to a plane of the sub-gasket (1), is provided for receiving a polymer electrolyte membrane (2) of the membrane electrode assembly (10), and a microstructure (3) is present on at least one side of the sub-gasket (1), wherein the microstructure (3) is formed into a free surface area of ​​the plastic film (1a, 1b) or of at least one of the plastic films (1a, 1b), and a depth of the microstructure (3) is at least 2.5 to a maximum of 15% of the thickness of the sub-gasket (1), wherein the microstructure (3) comprises channel-shaped structures (31), and wherein the sub-gasket (1) on both sides a sealing arrangement (4,4') and first channel-shaped structures (311) are arranged in an edge region of the sub-gasket (1), viewed perpendicular to the plane of the sub-gasket (1), outside the respective sealing arrangement (4, 4'). [2] Sub-gasket (1) according to claim 1, characterized by that the sub-gasket (1) comprises at least two interconnected plastic films (1a, 1b) which are provided for receiving the polymer electrolyte membrane (2) of the membrane electrode unit (10) between the plastic films (1a, 1b), and that the sub-gasket (1) has the microstructure (3) on both sides. [3] Sub-gasket (1) according to one of claims 1 or 2, characterized bythat the sub-seal (1) has a plurality of fluid passage openings (5, 5', 5'') and that second channel-shaped structures (312) are arranged in an edge region of the fluid passage openings (5, 5', 5'') within a region enclosed by the respective sealing arrangement (4), seen perpendicular to the plane of the sub-seal (1). [4] Sub-gasket (1) according to one of claims 1 to 3, characterized by that third channel-shaped structures (313) are arranged adjacent to the opening (1c) for receiving the polymer electrolyte membrane (2) of the membrane electrode unit (10) and within an area enclosed by the sealing arrangement (4, 4'), seen perpendicular to the plane of the sub-gasket (1). [5] Sub-gasket (1) according to claim 4, characterized by that the third channel-shaped structures (313) form a fan-out distributor structure (6) starting from a fluid passage opening (5, 5', 5'') in the direction of the opening (1c). [6] Sub-gasket (1) according to claim 5, characterized by that the third channel-shaped structures (313) continue to run alongside the opening (1c) between two distributor structures (6a, 6b) and form a fluid conducting structure. [7] Sub-gasket (1) according to claim 1 or claim 1 in conjunction with any one of claims 3 to 6, characterized by that the first channel-shaped structures (311) form a stiffening structure which increases the mechanical strength of the sub-gasket (1). [8] Membrane electrode unit (10) for an electrochemical cell (20), comprising a polymer electrolyte membrane (2) which is coated on both sides with at least one electrode and catalyst layer (7a, 7b), and with a gas diffusion layer (8a, 8b) on the electrode and catalyst layers (7a, 7b), wherein the polymer electrolyte membrane (2) is held fixed on one side by the at least one plastic film (1a, 1b) of the sub-gasket (1) or between at least two plastic films (1a, 1b) of the sub-gasket (1) according to one of claims 1 to 7 in the opening (1c). [9] Electrochemical cell (20), in particular fuel cell or electrolyzer, comprising at least one membrane electrode unit (10) according to claim 8 between two electrically conductive flow guide plates (9), wherein the electrically conductive flow guide plates (9) are designed as metallic bipolar plates or carbon-polymer composite plates.

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