Electrochemical cell

Abstract

The present invention relates to an electrochemical cell (1), in particular an electrolytic cell. The electrochemical cell (1) comprises: a catalyst-coated membrane (100); diffusion layers (5, 6) arranged on both sides thereof; and a sealing frame (40). The sealing frame (40) is arranged so as to surround the catalyst-coated membrane (100) and the diffusion layers (5, 6). The periphery of the catalyst-coated membrane (100) is enclosed by a membrane frame (110). The sealing frame (40) has a step (45). The membrane frame (110) interacts with a seal (41) of the sealing frame (40), which seal is arranged on the step (45).

Description

[0001] R.414451

[0002] - 1 -

[0003] Description

[0004] Title:

[0005] Electrochemical cell

[0006] The present invention relates to an electrochemical cell.

[0007] State of the art

[0008] 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.

[0009] The sealing concept of such an electrochemical cell is subject to constant development, particularly with regard to sealing function, positioning accuracy and handling.

[0010] Disclosure of the invention

[0011] 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. R.414451

[0012] - 2 - arranged. The catalyst-coated membrane is enclosed around its circumference by a membrane frame. The sealing frame has a step. The membrane frame interacts with a seal of the sealing frame arranged at the step.

[0013] The membrane frame can, for example, consist of two films that enclose the catalyst-coated membrane and are bonded together, extending further outwards. This improves the sealing effect between the anode and cathode compartments of the electrochemical cell, preventing leakage. The membrane frame also seals against a gasket in the sealing frame; this connection ultimately contributes to the improved seal between the anode and cathode compartments.

[0014] In advantageous further developments, the membrane frame also features a step. One of the diffusion layers is fixed within the membrane frame by means of this step. This diffusion layer thus rests on the step. Additionally, the diffusion layer can be pressed into the step of the membrane frame. This fixes the diffusion layer within the membrane frame, improving positioning accuracy. Furthermore, it improves handling during the manufacturing process of the electrochemical cell.

[0015] Preferably, the anode-side diffusion layer is fixed within the membrane frame. The anode-side diffusion layer is most preferably made of sintered titanium. This is a material that can be easily pressed into the membrane frame.

[0016] In advantageous embodiments, the diffusion layer is made up of at least two parts. It comprises a first layer and a second layer, with only the first layer being fixed in the membrane frame. The second layer can thus cover the membrane frame; various manufacturing processes are possible here, for example, molding the second layer when the first layer is already fixed in the membrane frame.

[0017] In preferred further developments, the first layer consists of sintered titanium, which can be easily pressed into the membrane frame. R.414451

[0018] - 3 -

[0019] In advantageous embodiments, the diffusion layer is positively fixed to the step of the membrane frame. For this purpose, cutouts or recesses can be provided in the catalyst-coated membrane, into which an adhesive from the membrane frame penetrates, thereby anchoring the membrane frame within the catalyst-coated membrane. The membrane frame can consist of two films, each coated with adhesive on its facing side. This ensures the positioning of the catalyst-coated membrane within the membrane frame.

[0020] 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 encased in a membrane frame, its handling improves, especially if the membrane frame is itself encased in the sealing frame and the subsequent assembly is further stabilized by a diffusion layer.

[0021] Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description. They show:

[0022] Figure 1 schematically shows a cross-section of a prior art electrochemical cell, with only the essential areas depicted.

[0023] Figure 2 schematically shows another electrochemical cell with a sealing frame from the prior art in cross-section, with only the essential areas shown.

[0024] Figure 3 schematically shows a cross-section of an electrochemical cell according to the invention, with only the essential areas being shown.

[0025] Figure 1 schematically shows a cross-section of an electrochemical cell 1 known from the prior art in the form of an electrolysis cell, wherein R.414451

[0026] - 4 - only the essential areas are shown. 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 1 a is formed on one side of the membrane 2, and an anode compartment 1 b on the other side.

[0027] 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.

[0028] The assembly of membrane 2 and the two electrode layers 3, 4 constitutes a catalyst-coated membrane 100. 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 multilayered structure.

[0029] 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.

[0030] 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.

[0031] 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 welded joints, 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. Distribution plate 7 R.414451

[0032] - 5 - can also be implemented without channels 11, especially in the last case; the bipolar plate 20 would thus be a distribution plate 7 designed as a flat sheet metal, the actual media distribution would then take place entirely in the diffusion layers 5, 6.

[0033] 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.

[0034] 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.

[0035] Ideally, the size of the catalyst-coated membrane 100 should be chosen such that it reliably extends beyond the seal 41 in all tolerance cases, as shown in Figure 2. A first gas diffusion layer 6 is then 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 45.

[0036] According to the invention, the catalyst-coated membrane 100 now has a membrane frame 110 so that it can be installed in the sealing frame 40 in a positionally and centrally secure manner. Figure 3 shows an R.414451

[0037] - 6 - electrochemical cell 1 according to the invention in the form of an electrolysis cell in cross-section, wherein only the essential areas are shown.

[0038] The catalyst-coated membrane 100 is enclosed around its circumference in the membrane frame 110, which in turn rests on the step 45 of the sealing frame 40 and is clamped between the sealing frame 40 and the anode-side diffusion layer 6. The membrane frame 110 acts as a seal together with the gasket 41 of the sealing frame 40. The catalyst-coated membrane 100 can, for example, be glued into the membrane frame 110 and / or fixed in the membrane frame 110 via undercuts. Advantageously, the catalyst-coated membrane 100 has several holes or recesses by means of which the undercuts or positive-locking connections to the membrane frame 110 are formed.

[0039] In preferred embodiments, the anode-side diffusion layer 6 is made in two parts, with a first layer 61 and a second layer 62. The first layer

[0040] 61 is arranged adjacent to the catalyst-coated membrane 100 and the second layer 62 adjacent to the distributor plate 8. The first layer 61 preferably consists of sintered titanium, and the second layer 62 preferably consists of a metallic expanded metal mesh.

[0041] Preferably, the membrane frame 110 also has a step 111 on which the first layer 61 rests or by means of which the first layer 61 is embedded in the membrane frame 110. The membrane frame 110 thus secures both the catalyst-coated membrane 100 and the first layer 61. In advantageous embodiments, a portion of the first layer 61 projects beyond the membrane frame 110—that is, towards the sealing frame 40—so that the second layer 62 is not in direct contact with the membrane frame 110. The second layer 62 is in contact with the sealing frame 40 or forms a small gap with it.

[0042] The first layer 61 is essentially smaller in circumference than the second layer.

[0043] 62 is shaped and thereby positioned in the membrane frame 110. The second layer 62 transmits a surface pressure caused by the tensioning of the electrochemical cell 1 to the first layer 61 and presses it R.414451

[0044] - 7 - thus against the catalyst-coated membrane 100. This minimizes the electrical contact resistance between the catalyst-coated membrane 100 and the first layer 61. To seal the electrochemical cell 1 to the outside, the following are attached to the

[0045] Sealing frame 40 circumferential seals 49 formed, which interact with the distributor plates 7, 8 and seal the cathode chamber 1a or anode chamber 1b to the outside.

Claims

R.414451 - 8 - 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 catalyst-coated membrane (100) is enclosed at its circumference by a membrane frame (110), wherein the sealing frame (40) has a step (45), characterized in that the membrane frame (110) interacts with a seal (41) of the sealing frame (40) arranged at the step (45).

2. Electrochemical cell (1) according to claim 1 characterized in that the membrane frame (110) also has a step (111), wherein one of the diffusion layers (5, 6) is fixed in the membrane frame (110) by means of the step (111).

3. Electrochemical cell (1) according to claim 2 characterized in that the anode-side diffusion layer (6) is fixed in the membrane frame (110).

4. Electrochemical cell (1) according to claim 2 or 3 characterized in that the diffusion layer (5, 6) is designed in at least two parts, with a first layer (61) and a second layer (62), wherein only the first layer (61) is fixed in the membrane frame (110).

5. Electrochemical cell (1) according to claim 4 characterized in that the first layer (61) consists of a sintered titanium.

6. Electrochemical cell (1) according to one of claims 2 to 5 R.414451 - 9 - characterized in that the diffusion layer (5, 6) is positively fixed to the step (111) of the membrane frame (110).

7. Electrochemical cell (1) according to one of the preceding claims characterized in that the electrochemical cell (1) is an electrolysis cell (1), in particular a PEM electrolysis cell.

Images