Electrochemical cell

Abstract

The present invention relates to an electrochemical cell (1), in particular an electrolysis cell. The electrochemical cell (1) comprises a catalyst-coated membrane (100), diffusion layers (5, 6) arranged on both sides of the membrane, and a sealing frame (40). The sealing frame (40) surrounds the catalyst-coated membrane (100) and the diffusion layers (5, 6). The sealing frame (40) has a step (45) on which the catalyst-coated membrane (100) rests. The catalyst-coated membrane (100) is positioned within the sealing frame (40) by means of at least one positioning pin (50) arranged on the step (45).

Description

[0001] The present invention relates to an electrochemical cell. State of the art

[0002] Electrochemical cells, such as fuel cells or electrolysis cells, with membrane electrode arrangements and bipolar plates arranged on both sides are known from the prior art, for example from EP3969640B1. The electrochemical cell comprises a catalyst-coated membrane, diffusion layers arranged on both sides of this membrane, and a sealing frame. The sealing frame surrounds the catalyst-coated membrane and the diffusion layers. The sealing frame has a step on which the catalyst-coated membrane is placed.

[0003] The sealing concept of such an electrochemical cell is subject to constant development, particularly with regard to sealing function, positioning accuracy and handling. Disclosure of the invention

[0004] The present invention relates to an electrochemical cell, in particular an electrolysis cell. The electrochemical cell comprises a catalyst-coated membrane, diffusion layers arranged on both sides of the membrane, and a sealing frame. The sealing frame surrounds the catalyst-coated membrane and the diffusion layers. The sealing frame has a step on which the catalyst-coated membrane rests. The catalyst-coated membrane is positioned within the sealing frame by means of at least one positioning pin arranged on the step.

[0005] This increases the positional accuracy of the catalyst-coated membrane relative to the sealing frame and thus to the rest of the electrochemical cell. Furthermore, the handling of the catalyst-coated membrane during assembly is improved when it is fixed in the sealing frame.

[0006] Advantageously, the positioning pin interacts with a recess formed in the catalyst-coated membrane. The positioning pin can, for example, be cylindrical and the recess a bore. When the positioning pin protrudes through the recess, it forms an undercut with the catalyst-coated membrane in the xy-plane, thus fixing it positively in the xy-plane.

[0007] In preferred embodiments, the catalyst-coated membrane comprises a membrane and electrode layers arranged on both sides thereof. The electrode layers are positioned on the membrane only over an active area, the active area being defined by the inner circumference of the sealing frame. The positioning pins thus allow the electrode layer to be positioned very precisely relative to the sealing frame and therefore to the intended active area. The present invention is therefore particularly well suited for membranes that are not fully coated, but rather for electrode layers that have a smaller area than the membrane.

[0008] In advantageous further developments, at least two positioning pins, each with a recess, interact. The two positioning pins are essentially cylindrical. The two recesses have an essentially oval shape. The ovality of the first recess is orthogonal to the ovality of the second recess. This allows the positioning of the catalyst-coated membrane within the xy-plane to be carried out with very tight tolerances.

[0009] The ovality of the first recess runs, for example, in the x-direction, and the ovality of the second recess in the y-direction. The first positioning pin in the first recess then serves to fix the catalyst-coated membrane in the y-direction; and the second positioning pin in the second recess serves to fix the catalyst-coated membrane in the x-direction. The ovalities compensate for the tolerances in the direction that is not intended for positioning.

[0010] In advantageous designs, the positioning pins are bonded to the sealing frame by means of a material connection, for example by gluing or welding.

[0011] In preferred embodiments, one of the diffusion layers is positioned within the sealing frame by means of the positioning pin. This is the larger of the two diffusion layers, which also indirectly rests on the step of the sealing frame. In the case of an electrolysis cell, this is preferably the anode-side diffusion layer. Thus, the positioning pin serves both to position the catalyst-coated membrane and a diffusion layer. This is particularly advantageous if the diffusion layer has a flow structure pointing towards the catalyst-coated membrane. This ensures that the flow structure is aligned very precisely with the catalyst-coated membrane, and especially with the corresponding electrode layer.

[0012] In advantageous embodiments, the electrochemical cell is an electrolysis cell, particularly preferably a PEM electrolysis cell. The PEM membrane (proton exchange membrane) is comparatively thin and difficult to handle. However, if it is robustly arranged in the sealing frame, its handling improves, especially if the subsequent assembly is further stabilized by a diffusion layer.

[0013] Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description. They show: Fig. 1 Schematic cross-section of a state-of-the-art electrochemical cell, showing only the essential areas. Fig. 2 schematically another electrochemical cell with a sealing frame from the prior art in cross-section, showing only the essential areas. Fig. 3 schematically a cross-section of an electrochemical cell according to the invention, wherein only the essential areas are shown. Fig. 4 schematically a top view of an electrochemical cell according to the invention, wherein only the essential areas are shown.

[0014] Fig. Figure 1 schematically shows a cross-section of an electrochemical cell 1 known from the prior art, in the form of an electrolysis cell, with only the essential areas depicted. The electrolysis cell 1 has an electrolyte 2, for example a membrane, in particular a polymer electrolyte membrane, so that the electrolysis cell 1 is preferably designed as a PEM electrolysis cell. Viewed in the stacking direction z, a cathode compartment 1a is formed on one side of the membrane 2 and an anode compartment 1b on the other side.

[0015] In the cathode compartment 1a, an electrode layer 3, a diffusion layer 5, and a distribution plate 7 are arranged pointing outwards from the membrane 2 – i.e., in the normal direction z. Similarly, in the anode compartment 1b, an electrode layer 4, a diffusion layer 6, and a distribution plate 8 are arranged pointing outwards from the membrane 2.

[0016] The assembly of membrane 2 and the two electrode layers 3, 4 constitutes a catalyst-coated membrane 100. Alternatively, membrane 2 can also be coated with only one of the two electrode layers 3, 4; the other electrode layer 3, 4 is then arranged on the membrane-side surface of the associated diffusion layer 5, 6.

[0017] The catalyst-coated membrane 100 and the two diffusion layers 5, 6 form a membrane electrode unit 10. The diffusion layers 5, 6 can each also have a multilayer structure.

[0018] The distribution plates 7, 8 have channels 11 for the supply and discharge of media – for example, hydrogen in the cathode compartment 1a and water in the anode compartment 1b – to the diffusion layers 5, 6. The diffusion layers 5, 6 can consist, for example, of fiber fleeces and / or porous metal layers.

[0019] The distribution plates 7, 8 have channels 11 and thus implicitly also webs 12 that delimit the channels 11. The undersides of these webs 12 therefore form a contact surface 7a, 8a of the respective distribution plate 7, 8 to the corresponding contact surface 5a, 6a of the underlying diffusion layer 5, 6.

[0020] The cathode-side distribution plate 7 of an electrochemical cell 1 and the anode-side distribution plate 8 of the adjacent electrochemical cell can be rigidly connected at their connecting surfaces 20b, for example by welds, and thus combined to form a bipolar plate 20. The distribution plates 7, 8 can also be manufactured as a single piece, so that the second distribution plate 8 is omitted. Particularly in the latter case, the distribution plate 7 can also be manufactured without channels 11; the bipolar plate 20 would then be a distribution plate 7 manufactured as a flat sheet, and the actual media distribution would then take place entirely in the diffusion layers 5, 6.

[0021] Fig. Figure 2 shows a cross-sectional view of an electrochemical cell 1 known from EP3969640B1, in the form of an electrolysis cell, with only the essential areas depicted. The electrolysis cell 1 is enclosed around its circumference by a sealing frame 40. A seal 41 is arranged in a recess 42 formed in the sealing frame 40 and interacts with the catalyst-coated membrane 100, thus functionally sealing the cathode compartment 1a from the anode compartment 1b.

[0022] The sealing frame 40 has a step 45 with a contact surface for the catalyst-coated membrane 100. The recess 42 is arranged in this contact surface. The step 45 results in the windows formed in the sealing frame 40 for the cathode-side diffusion layer 5 and for the anode-side diffusion layer 6 being of different sizes; preferably, the window for the anode-side diffusion layer 6 is larger. With its smaller window, the sealing frame 40 defines the active area 120 of the electrochemical cell 1, i.e., the area in which both electrode layers 3, 4 are virtually freely accessible to ions or reaction fluids; in other words, within the tolerances, the active area 120 corresponds to the area of ​​the smaller diffusion layer 5 or also to the smallest inner circumference 49 of the sealing frame 40.

[0023] Ideally, the size of the catalyst-coated membrane 100 should be chosen such that it reliably extends beyond the seal 41 in every tolerance case, as shown in Fig. 2 can be seen. Subsequently, a first gas diffusion layer 6 is placed on top of the catalyst-coated membrane 100. The size of the anode-side diffusion layer 6 should be chosen such that it extends beyond the area enclosed by the seal 41, so that it can transfer the sealing force to the seal 41 as a contact partner with the catalyst-coated membrane 100. In other words, the anode-side diffusion layer 6 indirectly rests on the step 45 of the sealing frame 40.

[0024] In order to better position the catalyst-coated membrane 100 within the sealing frame 40, at least one positioning pin is now arranged on the sealing frame 40 according to the invention. This is shown in the figure. Fig. 3 an electrochemical cell 1 according to the invention in the form of an electrolysis cell in cross-section, wherein only the essential areas are shown.

[0025] The catalyst-coated membrane 100 rests on the step 45 of the sealing frame 40 and is clamped between the anode-side diffusion layer 6 and the step 45. The positioning pin 50 is located on the step 45 and penetrates the catalyst-coated membrane 100 in a recess 110 formed in it. The positioning pin 50 thus forms an undercut or a positive-locking connection with the catalyst-coated membrane 100 in the xy-plane within the recess 110, so that it positions the catalyst-coated membrane 100 within the tolerances in the xy-plane. The positioning pin 50 can be permanently connected to the sealing frame 40, for example by gluing or welding, or it can be integrated with it during assembly.

[0026] Fig. Figure 4 shows a top view of an electrochemical cell 1 according to the invention, showing only the essential areas. In the embodiment of the Fig.The catalyst-coated membrane 100 is positioned relative to the sealing frame 40 by means of five positioning pins 50 arranged on the sealing frame 40. The positioning pins 50 are formed on the step 45 of the sealing frame 40. This also aligns the active area 120 of the catalyst-coated membrane 100 with the sealing frame 40. This is particularly advantageous when the electrode layers 3, 4 are not applied to the entire surface of the membrane 2, but only to the active area 120. The electrode layers 3, 4 are therefore preferably only formed up to the inner circumference 49 of the sealing frame 40, which encloses the smaller of the two diffusion layers 5. Similarly, the electrode layers 3, 4 can be applied to the diffusion layers 5, 6, but only to the extent of the area of ​​the smaller of the two diffusion layers 5, 6.

[0027] By placing positioning pins 50 on the step 45 of the sealing frame 40, the catalyst-coated membrane 100 can be aligned with the sealing frame 40 and thus also with the active surface 120 of the electrochemical cell 1 by means of the recesses 110 corresponding to the positioning pins 50. The positioning pins 50 can be arranged in any number at any position on the step 45. The positioning pins 50 can, for example, be cylindrical or conical. The positioning pins 50 are fixedly connected to the sealing frame 40.

[0028] The positioning pins 50 can also be used to position other components of the electrochemical cell 1, for example the corresponding diffusion layer 6 or any stabilizing films for stabilizing the membrane 2. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3969640B1 [0002, 0021]

Claims

[1] Electrochemical cell (1) with a catalyst-coated membrane (100), diffusion layers (5, 6) arranged on both sides of it and a sealing frame (40), wherein the sealing frame (40) is arranged surrounding the catalyst-coated membrane (100) and the diffusion layers (5, 6), wherein the sealing frame (40) has a step (45), wherein the catalyst-coated membrane (100) rests on the step (45), characterized by , that the catalyst-coated membrane (100) is positioned within the sealing frame (40) by means of at least one positioning pin (50) arranged on the step (45). [2] Electrochemical cell (1) according to claim 1 characterized by , that the positioning pin (50) interacts with a recess (110) formed in the catalyst-coated membrane (100). [3] Electrochemical cell (1) according to claim 1 or 2 characterized by, that the catalyst-coated membrane (100) comprises a membrane (2) and electrode layers (3, 4) arranged on both sides thereof, wherein the electrode layers (3, 4) are arranged on the membrane (2) only via an active area (120), wherein the active area (120) is determined by an inner circumference (49) of the sealing frame (40). [4] Electrochemical cell (1) according to any one of claims 1 to 3 characterized by , that at least two positioning pins (50) interact with each a recess (110), wherein the two positioning pins (50) are substantially cylindrical, wherein the two recesses (110a, 110b) have a substantially oval shape, wherein the ovality of the first recess (110a) is orthogonal to the ovality of the second recess (110b). [5] Electrochemical cell (1) according to any one of claims 1 to 4 characterized by that the positioning pins (50) are materially bonded to the sealing frame (40). [6] Electrochemical cell (1) according to any one of claims 1 to 5 characterized by , that one of the diffusion layers (6) is still positioned within the sealing frame (40) by means of the positioning pin (50). [7] Electrochemical cell (1) according to claim 6 characterized by , that the diffusion layer (6) has a flow structure pointing towards the catalyst-coated membrane (100). [8] Electrochemical cell (1) according to any one of the preceding claims characterized by , that the electrochemical cell (1) is an electrolysis cell (1), in particular a PEM electrolysis cell.

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