Electrolysis cell and method for producing the electrolysis cell

Abstract

The invention relates to an electrolysis cell with a cell frame and to a method for producing an electrolysis cell. The cell frame has a stepped inner profile. The inner profile comprises at least one support surface for receiving a planar component in the cell frame, and the support surface has a recess for a seal. A seal is first placed in the recess, and a membrane-electrode unit, a first gas diffusion layer, and an electrically conductive top layer are then introduced into the cell frame. The cell frame is then rotated, and a second gas diffusion layer is applied. The electrolysis cell produced in this manner comprises the cell frame with the seal and the different layers.

Description

[0001] Description

[0002] Electrolysis cell and method for manufacturing the electrolysis cell

[0003] The invention relates to an electrolysis cell and a method for manufacturing the electrolysis cell.

[0004] An electrolyzer is a device that uses electric current to bring about a chemical reaction (electrolysis). Corresponding to the variety of different electrolysis processes, there are also many different types of electrolyzers, such as an electrolyzer for hydrogen electrolysis.

[0005] Current considerations focus on storing surplus energy from renewable energy sources during periods of high sunshine and wind, i.e., with above-average solar or wind power generation. Storage is particularly feasible with electrochemical cells, especially fuel cells or electrolysis cells. Energy can also be stored through the production of valuable materials. One such valuable material is hydrogen, which is produced using water electrolyzers. This hydrogen can then be used, for example, to produce so-called renewable energy gas.

[0006] In this process, a (hydrogen electrolysis) electrolyzer uses electrical energy, primarily from wind or solar power, to first produce hydrogen. This hydrogen can then be combined with carbon dioxide in a Sabatier process to produce methane. The methane can then be fed into an existing natural gas network, enabling energy storage and transport to consumers, thus relieving pressure on the electrical grid. Alternatively, the hydrogen produced by the electrolyzer can be used directly, for example, in a fuel cell.

[0007] In a hydrogen electrolyzer, water is split into hydrogen and oxygen. In a PEM electrolyzer, distilled water is typically supplied as a reactant at the anode and split into hydrogen and oxygen across a proton-exchange membrane (PEM). The water is oxidized to oxygen at the anode. The protons pass through the permeable membrane. At the cathode, the protons recombine to form hydrogen.

[0008] A typical PEM electrolyzer setup comprises a first gas diffusion layer and a second gas diffusion layer. The proton exchange membrane (PEM) is positioned between these layers. All layers are arranged within a cell frame. Currently, the precise arrangement of the gas diffusion layers within the cell frame is a disadvantage, as it requires a high degree of accuracy to produce a reliably functioning electrolysis cell. This makes the manufacturing of the components and their assembly complex.

[0009] German patent DE 25 33 728 discloses an electrolysis cell for the electrolysis of a solution of alkali salts. The electrolysis cell comprises two bipolar electrodes arranged side by side and at least one outer frame enclosing at least one chamber of the electrolysis zone.

[0010] Further electrochemical cells with sealed cell frames are described, for example, in US 6,117,287 A and US 2002 / 068208 A. A manufacturing process for a PEM membrane electrode assembly is described in CN 107 881 528 A.

[0011] The object of the invention is to provide an electrolysis cell with a cell frame and a method for manufacturing the electrolysis cell, which simplifies the construction of the electrolysis cell and the method for manufacturing the electrolysis cell, especially for large cell areas, and enables high reliability in the operation of the electrochemical cell.

[0012] The problem is solved with an electrolysis cell according to claim 1 and a method according to claim 10.

[0013] The cell frame for an electrochemical cell according to the invention, in particular for a fuel cell or an electrolysis cell, has a stepped inner profile. The stepped inner profile comprises at least one support surface for receiving a planar component in the cell frame. The support surface has a recess for a seal.

[0014] An electrolysis cell according to the invention has a cell frame with a stepped inner profile. The stepped inner profile comprises at least one contact surface for receiving a planar component in the cell frame. The contact surface has a recess for a seal. The electrolysis cell further comprises a seal which is arranged in the recess of the contact surface. The electrolysis cell further comprises a membrane electrode assembly which covers the contact surface of the cell frame and the seal. It also has a first gas diffusion layer which adjoins a first side of the membrane electrode assembly. It also has a second gas diffusion layer which adjoins a second side of the membrane electrode assembly. The electrolysis cell also has a

[0015] electrically conductive final layer, which rests on the first gas diffusion layer and is firmly connected to the cell frame.

[0016] Due to the stepped internal profile, the first gas diffusion layer protrudes beyond the boundaries of the second gas diffusion layer. The gap dimensions between the cell frame and the membranes, or gas diffusion layers, can therefore be advantageously larger. This simplifies and shortens the assembly process. Furthermore, the outer contours of the membranes and / or gas diffusion layers can be freely selected. It is only necessary that the outer contours of the membranes and the first gas diffusion layer extend beyond the seal to ensure sufficient support for the seal. The seal also advantageously provides a seal between the cathode and anode sides of the electrolysis cell.

[0017] In an advantageous embodiment and further development of the invention, the contact surface is essentially planar. In other words, the contact surface is flat, i.e., not curved. The flat surface is interrupted only by the recess. Advantageously, the membranes, particularly as an MEA (membrane-electrode assembly), and the gas diffusion layers can lie flat and thus form-fittingly on the contact surface. This advantageously achieves a high degree of tightness.

[0018] In a further advantageous embodiment and development of the invention, the cell frame consists of a single workpiece. In other words, it is not composed of several components, but is manufactured from a single workpiece. The cell frame can, in particular, comprise a polymer. It can, in particular, be cast from this polymer. Alternatively, it is also conceivable to manufacture the cell frame from sheet-shaped raw materials by mechanical processing.

[0019] The cell frame preferably comprises an electrically insulating material.

[0020] In a further advantageous embodiment and development of the invention, the cell frame encloses an area of ​​at least 3000 cm². 2 .

[0021] In a further advantageous embodiment and development of the invention, the membrane electrode unit, the first gas diffusion layer, and the second gas diffusion layer each have a size smaller than the area enclosed by the inner profile of the cell frame. Particularly preferably, one of the gas diffusion layers has a larger area than the other. They are therefore of different sizes. These layers can be placed within the inner profile of the cell frame. They do not rest on top of the cell frame, but are arranged within the area enclosed by the inner profile of the cell frame. Advantageously, these layers can thus be arranged within the inner profile of the cell frame in such a way that their height does not exceed the height of the cell frame. In other words, arranging the layers within the cell frame fills the interior of the cell frame, but the layers do not protrude from the cell frame.

[0022] In a further advantageous embodiment and development of the invention, the electrically conductive end layer has a size that is larger than the area enclosed by the inner profile of the cell frame. In other words, the electrically conductive end layer thus rests on the cell frame. Advantageously, this end layer can therefore be easily mechanically attached to a top or bottom surface of the cell frame. Attaching this layer to the inner profile of the cell frame is advantageously unnecessary.

[0023] The fact that the contact surface has a recess for a seal means, in other words, that the recess for the seal is not located at the edge of the contact surface. The recess therefore has no lateral boundaries shared with the contact surface. It is located within the contact surface. This advantageously achieves that a seal cannot be displaced, i.e., it can be fixed in place within the contact surface. A first seal is particularly preferably firmly connected to the cell frame. Thus, sealing is not achieved, as before, via small gaps between the cell frame and membranes and / or gas diffusion layers, but rather via a seal located in the contact surface of the cell frame.

[0024] The inventive method for manufacturing electrolysis cells comprises several steps. First, a cell frame is provided. The cell frame has a stepped inner profile. The stepped inner profile has at least one contact surface for receiving a planar component in the cell frame. The contact surface includes a recess for a seal. In a next step, a seal is placed in the recess of the contact surface. If a cell frame with a permanently attached first seal is used, this step can be omitted. Subsequently, a membrane electrode assembly is placed on the contact surface, the membrane electrode assembly covering the contact surface of the cell frame and the seal. Subsequently, a first gas diffusion layer is placed on a first side of the membrane electrode assembly. Finally, an electrically conductive finishing layer is placed on the first gas diffusion layer and the cell frame.The sealing layer is mechanically fixed to the cell frame. The cell frame, along with the seal, the membrane electrode assembly of the first gas diffusion layer, and the sealing layer, is then rotated so that the sealing layer is now at the bottom and the membrane catalyst layer is at the top. "Top" and "bottom" here refer to the Earth's gravitational field. Thus, "bottom" means that this layer is closer to the Earth than a layer positioned at the top. A second gas diffusion layer is then placed on the other side of the membrane electrode assembly within the cell frame.

[0025] The stepped inner profile of the cell frame offers the advantage of allowing the seal, membrane electrode assembly, first gas diffusion layer, and electrically conductive top layer to be easily positioned within the frame. The subsequent rotation significantly simplifies the installation of the second gas diffusion layer onto the membrane electrode assembly. During rotation, the membrane electrode assembly is supported and clamped within the cell frame by the first gas diffusion layer and the top layer. This support prevents the membrane electrode assembly from shifting, ensuring it remains positioned so that the seals are covered. The second gas diffusion layer can then be easily placed onto the membrane electrode assembly. This rotation allows for the simple and efficient installation of the layers within the cell frame, even for very large cell areas.

[0026] In an advantageous embodiment of the invention, the cell frame and the electrically conductive finishing layer are sealed to each other.

[0027] To obtain a cell stack, several electrolysis cells are stacked on top of each other, sealed and pressed together.

[0028] In an advantageous embodiment and further development of the invention, the mechanical fixing of the end layer to the cell frame is carried out by means of a screw connection, a rivet connection or by a clamping device.

[0029] Further features, properties and advantages of the present invention will become apparent from the following description with reference to the accompanying figures. These schematically depict:

[0030] Figure 1 shows a section of a cell frame for an electrolysis cell;

[0031] Figure 2 shows a top view of a cell frame for an electrolysis cell;

[0032] Figure 3 shows a section of a cell frame with layers and mechanical fixation during assembly; Figure 4 shows a section of an electrolysis cell with the cell frame;

[0033] Figure 5 shows a flow diagram of the manufacturing process of an electrolysis cell.

[0034] Figure 1 shows a section of a cell frame 100 for an electrochemical cell, in particular a fuel cell or an electrolysis cell, with a stepped inner profile 101. The stepped inner profile 101 has a support surface 102. A recess is provided in the support surface 102.

[0035] 103 arranged. The cell frame 100 has a frame top.

[0036] 104 and a frame underside 105.

[0037] Figure 2 shows a top view of the cell frame 100 with a stepped internal profile 101. In this example, the cell frame 100 is rectangular. However, it is equally conceivable that it could have a round or oval shape, or other technically advantageous shapes.

[0038] This embodiment describes the construction of an electrolysis cell. However, it is also possible to use the cell frame 100 for the construction of a fuel cell.

[0039] At the start of the electrolysis cell assembly, the cell frame 100 is positioned in the Earth's gravitational field such that the upper frame surface 104 faces upwards, away from the Earth, and the lower frame surface 105 faces downwards, towards the Earth. This is shown in Figure 1. The cell frame 100 is manufactured from a single workpiece. In a first assembly step, a seal 6 is placed in the recess 103. This seal 6 can be designed as a sealing strip, a bonded seal, or a sealing ring. The seal 6 typically comprises materials such as PTFE, silicone, fluororubber, or other materials from the group of

[0040] Elastomers. Figure 3 shows the cell frame 100 in an intermediate assembly stage. The seal 6 is positioned in the recess 103. A membrane electrode assembly 7 is then placed on the support surface 102. The membrane electrode assembly 7 is large enough to almost completely fill the cell frame. Ideally, the size of the membrane electrode assembly 7 should be such that it extends beyond the seal 6 reliably and within tolerance, as shown in Figure 3. A first gas diffusion layer 8 is then placed on top of the membrane electrode assembly 7. The size of the first gas diffusion layer 8 should be such that it extends beyond the area enclosed by the seal. In other words, the gas diffusion layer 8 rests indirectly on the step of the stepped inner profile 101.Both the size of the membrane electrode assembly 7 and the first gas diffusion layer 8 should be selected such that they are no larger than the area enclosed by the cell frame 100. Advantageously, a seal is then inserted to seal between the cell frame 100 and the electrically conductive end layer 9. Optionally, the seal can already be part of the cell frame 100 or the electrically conductive end layer 9. An electrically conductive end layer 9 is then placed on top of the first gas diffusion layer 8. This electrically conductive end layer 9 is firmly fixed to the cell frame 100 with a mechanical fixing device, in this example with a screw 10. Figure 3 shows how the cell frame with the different layers 7 is arranged at this assembly point.

[0041] 8, 9, the seal 6 and the screw connection 10. In a next step, the cell frame 100 is rotated with the seal 6, the membrane electrode unit 7, the first gas diffusion layer 8 and the final layer 9.

[0042] Figure 4 shows the cell frame 100 after it has been rotated.

[0043] The upper frame surface 104 is now positioned at the bottom, and the lower frame surface 105 is now positioned at the top. In other words, in the Earth's gravitational field, the lower frame surface 105 is now located farther from the Earth than the upper frame surface 104. In the next step, a second gas diffusion layer 11 is placed on the membrane electrode assembly 7. The membrane electrode assembly 7 now directly abuts the second gas diffusion layer 11 on one side. On the other side, the membrane electrode assembly 7 directly abuts the first gas diffusion layer 8. The electrolysis cell 1 assembled in this way can now be stacked with several other electrolysis cells 1 to form a stack. The electrolysis cells are sealed against each other during this process. Advantageously, rotating the partially assembled cell according to the assembly intermediate stage in Figure 3 allows for easy assembly of the second gas diffusion layer 11 for large cell frame areas of at least 3000 cm². 2The size of the membrane electrode assembly 7 should be chosen such that it at least covers the seal 6 but is smaller than the inner surface area of ​​the cell frame. The membrane electrode assembly 7 is supported by the first gas diffusion layer 8 and secured against slippage by clamping. This allows for faster and more efficient assembly of the membrane electrode assembly 7, while simultaneously ensuring a reliable seal between the first cell half, in which the first gas diffusion layer 8 is located, and the second cell half, in which the second gas diffusion layer 11 is located.

[0044] Figure 5 schematically shows a flow diagram of the assembly process with its different steps. First, the cell frame 100 is prepared 50. Then, the seal 6 is inserted into the recess 103 51. Step 51 can be omitted if the seal is already part of the cell frame. Next, the membrane electrode assembly is placed into the cell frame 52. Then, the first gas diffusion layer 8 is placed onto the membrane electrode assembly 7 in a single step 53. A seal can now be inserted into the cell frame. This step can be omitted if the seal is already part of the cell frame 100 or the final layer 9. In the following step 55, a final layer 9 is placed onto the first gas diffusion layer 8. In step 56, the final layer 9 is mechanically fixed to the cell frame 100. Then, in step 57, the cell frame 100 with layers 7, 8, and 9 is rotated.Subsequently, in step 58, a second gas diffusion layer 11 is applied to the membrane electrode unit 7.

Claims

1.         An electrolysis cell (1) comprising: -      a cell frame (100), wherein the cell frame (100) has a step-like interior profile (101), wherein the step-like interior profile (101) comprises at least one support surface (102) for accommodating a planar component in the cell frame (100), wherein the support surface (102) comprises a recess (103) for a seal (6), -      a first seal (6) which is arranged in the recess (103) of the support surface (102), -      a membrane electrode assembly (7) which covers the support surface (102) of the cell frame (100) and the seal (6), -      a first gas diffusion layer (8) which adjoins a first side of the membrane electrode assembly (7), -      a second gas diffusion layer (11) which adjoins a second side of the membrane electrode assembly (7) and -      an electrically conductive closure layer (9) which lies on the first gas diffusion layer (8) and is fixed to the cell frame (100), wherein the exterior contours of the membrane electrode assembly (7) and the first gas diffusion layer (8) project beyond the seal (6). 2.         The electrolysis cell (1) as claimed in claim 1, wherein the membrane electrode assembly (7), the first gas diffu­sion layer (8) and the second gas diffusion layer (11) have a size which is smaller than the area enclosed by the interior profile (101) of the cell frame (100). 3.         The electrolysis cell (1) as claimed in either claim 1 or 2, wherein the electrically conductive closure layer (9) has a size which is greater than the area enclosed by the interior profile (101) of the cell frame (100). 4.         The electrolysis cell (1) as claimed in either claim 1 or 2, wherein the cell frame (100) consists of one workpiece. 5.         The electrolysis cell (1) as claimed in either claim 1 or 2, wherein the cell frame (100) encloses an area of at least 3000 cm 2 . 6.         The electrolysis cell (1) as claimed in either claim 1 or 2, wherein the cell frame (100) is electrically insulating. 7.         The electrolysis cell (1) as claimed in claim 5, wherein the cell frame (100) comprises an electrically insulating material. 8.         The electrolysis cell (1) as claimed in any of the preceding claims, wherein a first seal is connected to the cell frame in the recess. 9.         The electrolysis cell (1) as claimed in either claim 1 or 2, wherein a second seal is arranged between a frame upper side (104) and the electrically conductive closure layer (9). 10.       A process for producing an electrolysis cell (1), compris­ing the following steps: -      provision of a cell frame (100), where the cell frame (100) has a step-like interior profile (101), the step-like interior profile (101) has at least one support surface (102) for accommodating a planar component in the cell frame (100) and the support surface (102) comprises a recess (103) for a seal (6), -      laying of a seal (6) into the recess (103) of the support surface (102), -      laying of a membrane electrode assembly (7) on the support surface (102), where the membrane electrode assembly (7) covers the support surface (102) of the cell frame (100) and the seal (6), -      laying of a first gas diffusion layer (8) on a first side of the membrane electrode assembly (7), where the exterior contours of the membrane electrode assembly (7) and the first gas diffusion layer (8) project beyond the seal (6), -      laying of an electrically conductive closure layer (9) on the first gas diffusion layer (8) and the cell frame (100), -      mechanical fixing of the closure layer (9) to the cell frame (100), -      rotation of the cell frame (100) together with the seal (6), the membrane electrode assembly (7), the first gas diffusion layer (8) and the closure layer (9) in such a way that the closure layer (9) is arranged at the bottom and the membrane electrode assembly (7) is arranged at the top, -      application of a second gas diffusion layer (11) to a second side of the membrane electrode assembly (7) in the cell frame (100), -      clamping of the layers in the cell frame. 11.       The process as claimed in claim 10, wherein the mechanical fixing of the closure layer (9) to the cell frame (100) is effected by means of a screw connection (10), riveting or by a clamp.

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