Electrochemical cell, and electrochemical cell stack
The innovative sealing frame design with a keyway and distributor plate interaction addresses sealing robustness and mechanical stability issues, enhancing the performance and longevity of electrochemical cells under differential pressure conditions.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-12-22
- Publication Date
- 2026-07-02
Smart Images
Figure EP2025088663_02072026_PF_FP_ABST
Abstract
Description
[0001] R.415638
[0002] - 1 -
[0003] Description
[0004] Title:
[0005] Electrochemical cell and electrochemical cell stack
[0006] The present invention relates to an electrochemical cell and an electrochemical cell stack.
[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 and distribution plates arranged on both sides of the membrane, and a sealing frame. The sealing frame surrounds the catalyst-coated membrane and the diffusion layers. In one stacking direction of the cell, the frame and the membrane with the diffusion layers are enclosed on both sides by the distribution plates.
[0009] The sealing concept of such an electrochemical cell is subject to constant further development, particularly with regard to sealing function, positioning accuracy and robustness over its lifetime.
[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, with R.415638 arranged on both sides of it.
[0012] - 2 -
[0013] The system consists of diffusion layers, distributor plates arranged on the diffusion layers, and a sealing frame. The sealing frame surrounds the catalyst-coated membrane and the diffusion layers. The sealing frame interacts with a distributor plate at each of its end faces. A keyway is formed on the sealing frame, which engages with a recess in one of the distributor plates.
[0014] The invention further relates to a cell stack comprising a plurality of electrochemical cells. The electrochemical cells include a catalyst-coated membrane, diffusion layers arranged on both sides of the membrane, distributor plates arranged on the diffusion layers, and a sealing frame. The sealing frame surrounds the catalyst-coated membrane and the diffusion layers. The sealing frame interacts with a distributor plate at each of its end faces. A key is formed on the sealing frame of a first electrochemical cell, which projects through a recess formed in the distributor plate and interacts with a bore formed in the sealing frame of a second electrochemical cell.
[0015] The sealing frame is thereby stiffened by the distributor plate and / or the next sealing frame. A clamping force acting on the electrochemical cell, perpendicular to the cell plane, can thus be transmitted by the sealing frame with less compression. Consequently, relative displacements in the sealing areas are reduced, and the sealing effect can be robustly maintained over a longer service life. Alternatively or additionally, the clamping force can be increased; this is particularly advantageous for a differential pressure electrolyzer. Specifically, a differential pressure electrolyzer should have a pressure difference of at least 20 bar between the cathode and anode.
[0016] In advantageous further developments, the clearance between the key and the recess of the distributor plate is designed asymmetrically. The asymmetry is such that the clearance towards the outside of the cell is smaller than the clearance towards the inside of the cell. This means that expansion of the sealing frame due to the interaction of the key with the distributor plate R.415638
[0017] - 3 -
[0018] The movement is primarily restricted outwards; in this direction, only friction-induced holding forces typically act. In the opposite inwards direction, however, there are usually positive locking mechanisms provided by additional components such as the diffusion layers. This means that the described asymmetry essentially supplements the radial inner support of the sealing frame through the usual cell structure with an additional outer support.
[0019] In advantageous embodiments, the clearance between the keyway of the first cell and the bore of the sealing frame of the second cell is designed asymmetrically. The asymmetry is such that the clearance facing the outside of the cells is larger (fit_1) than the clearance facing the inside of the cells (fit_0). Particularly preferably, the asymmetry in the clearances between the two sealing frames is thus the opposite of the asymmetry of the clearances between the sealing frame and the intermediate distributor plate. This results in further stiffening of the two sealing frames, especially in the area of the keyway, which lies close to the actual sealing line between the sealing frame and the distributor plate.
[0020] In further developed versions, a burr is formed at the recess of the distributor plate. A groove is formed in the sealing frame at the base of the keyway. The burr of the distributor plate engages in the groove of the sealing frame. This allows for improved dimensional accuracy, particularly in the stacking direction. The assembly of the sealing frame and distributor plate is further stiffened, especially in the cell plane.
[0021] If the keyway engages in the bore of the adjacent sealing frame, a burr can also be preferably formed there: a groove is formed at the base of the bore of the sealing frame of the adjacent cell, and a burr is formed at the recess of the distributor plate. The burr of the distributor plate engages in the groove of the adjacent sealing frame. Here, too, improved dimensional accuracy, especially in the stacking direction, can be achieved. The assembly of both sealing frames and the intermediate distributor plate is further stiffened, particularly in the cell plane. R.415638
[0022] - 4 -
[0023] 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 mechanically unstable. However, if it is robustly arranged in the sealing frame, its load-bearing capacity improves, especially when it is part of a differential pressure electrolyzer.
[0024] Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description. They show:
[0025] Figure 1 schematically shows a cross-section of a prior art electrochemical cell, with only the essential areas depicted.
[0026] Figure 2 schematically shows another electrochemical cell with a sealing frame from the prior art in cross-section, with only the essential areas shown.
[0027] Figure 3 schematically shows a cross-section of an electrochemical cell according to the invention, with only the essential areas being shown.
[0028] Figure 4 shows a section of a cell stack according to the invention with a plurality of electrochemical cells in a perspective view, showing only the essential areas.
[0029] Figure 5 shows the cell stack of Figure 4 with preferred games, with only the essential areas depicted.
[0030] Figure 6 shows a section of another cell stack according to the invention, with only the essential areas being shown.
[0031] 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 comprises an electrolyte 2, for example a membrane, in particular an R.415638
[0032] - 5 -
[0033] A polymer electrolyte membrane is used, such 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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 firmly connected at their connecting surfaces 20b, for example by welded connections, and thus form a bipolar plate 20R.415638
[0040] - 6 -
[0041] The distribution plates 7 and 8 can also be manufactured as a single piece, thus eliminating the need for the second distribution plate 8. Particularly in this latter case, the distribution plate 7 can also be manufactured without channels 11; the bipolar plate 20 would then be a distribution plate 7 designed as a flat sheet metal piece, with the actual media distribution taking place entirely in the diffusion layers 5 and 6.
[0042] 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. The sealing frame 40 interacts with the distributor plates 7, 8 in the z-direction at both of its end faces 40a, 40b; typically, the sealing frame 40 seals against the distributor plates 7, 8, for example by means of an inserted seal (not shown), which then defines the sealing line between the sealing frame 40 and the distributor plates 7, 8.
[0043] 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. The sealing frame 40, with its smaller window, defines the active area 120 of the electrochemical cell 1, i.e., the area in which both electrode layers 3, 4 are 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.
[0044] Ideally, the size of the catalyst-coated membrane 100 should be chosen such that it reliably exceeds the tolerances specified in R.415638 in every case.
[0045] - 7 -
[0046] The seal 41 extends beyond the surface, as shown in Figure 2. A first diffusion layer 6 is then placed from above onto 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.
[0047] According to the invention, the electrochemical cell 1 is now designed to be stiffer by means of a key 50 formed on the sealing frame 40, which interacts with the distributor plate 7, 8 and / or with the sealing frame 40 of the adjacent electrochemical cell 1; advantageously, the key 50 is arranged on the outside of the inserted seal between the sealing frame 40 and the distributor plate 7, 8.
[0048] Figure 3 shows an electrochemical cell 1 according to the invention in the form of an electrolysis cell in cross-section, with only the essential areas shown.
[0049] The sealing frame 40 has a key 50 on its upper end face 40a, for example in the form of a pin or a rib. In the embodiment shown in Fig. 3, a recess 70 is formed in the anode-side distributor plate 8. The key 50 interacts with the recess 70 and forms a positive-locking connection with it in the xy-plane. In alternative embodiments, corresponding recesses 70 can also be formed in the cathode-side distributor plate 7 or in both distributor plates 7 and 8. The sealing frame 40 can have a plurality of keys 50, which can also point towards both distributor plates 7 and 8. Furthermore, the keys 50 can, in principle, have any shape; they must then correspond to appropriately adapted geometries of the recesses 70. R.415638
[0050] - 8 -
[0051] In the embodiment of Fig. 3, a preferred clearance between the key 50 and the recess 70 can be in the range of 0.2 mm to 0.3 mm; this ensures good mountability of the electrochemical cell 1.
[0052] In another embodiment, the key 50 can also be designed as a single circumferential key 50, thus forming a closed contour in the xy-plane. Here, too, different cross-sectional geometries are conceivable for the key 50, for example rectangular, trapezoidal, triangular, or elliptical.
[0053] The positive fit between the key 50 and the distributor plate 7, 8 effectively stiffens the sealing frame 40 in the xy-plane by means of the distributor plate 7, 8. This allows the sealing frame 40 to transmit higher clamping forces in a cell stack of several cells 1 without falling below the permissible compression in the z-direction.
[0054] The sealing frame 40 is typically made of a plastic, for example a thermoplastic, and has a higher coefficient of thermal expansion than the distribution plates 7, 8 and the diffusion layers 5, 6, which can be made of metal or carbon, for example. The anode-side diffusion layer 6 is preferably made of titanium or a titanium alloy. When the electrochemical cell 1 heats up, the gap at the smallest inner circumference 49 of the sealing frame 40 to the diffusion layer 5 embedded therein would increase. This gap can become detrimentally large for the catalyst-coated membrane 100 placed there. Furthermore, the different coefficients of thermal expansion can lead to detrimental relative movement between the catalyst-coated membrane 100 and the seal 41.The stiffening of the sealing frame 40 by means of the assembly of distributor plate 7, 8 and keyway 50 leads to a reduction in relative displacements and / or a reduced gap widening; this results in reduced wear of the catalyst-coated diaphragm 100 and the seal 41. The service life of both the catalyst-coated diaphragm 100 and the seal 41 is increased by the proposed stiffening, as it counteracts thermal relative displacement. R.415638.
[0055] - 9 -
[0056] The entire sealing concept is therefore more robust against temperature differences, which in electrochemical cells 1, especially in P EM design, can range between 10°C and 70°C, for example.
[0057] Figure 4 shows a perspective view of a section of a cell stack 200 according to the invention, comprising a plurality of electrochemical cells 1, with only the essential areas depicted. A first electrochemical cell 11 and a second electrochemical cell 12 are visible. In the embodiment of Figure 4, the distribution plates 7, 8 are configured as bipolar plates 20; the anode-side distribution plate 8 of one electrochemical cell 1 thus corresponds to the cathode-side distribution plate 7 of the adjacent electrochemical cell 1. However, for the invention, the number of parts comprising the distribution plates 7, 8 or bipolar plates 20 is irrelevant.
[0058] On the sealing frames 40 of the electrochemical cells 1 1, 1_2, a keyway 50 is formed on the first end face 40a and a bore 80 on the second end face 40b. The keyway 50 is designed to be higher than the thickness of the distributor plate 7, 8, so that the keyway 50 projects through the recess 70 of the distributor plate 7, 8 and into the bore 80 of the next sealing frame 40.
[0059] The key 50 can interact with both the recess 70 of the distributor plate 7, 8 and the bore 80 of the next sealing frame 40. Here, too, the connection of several sealing frames 40 can be stiffened by the positive locking of the key 50 with the intermediate distributor plates 7, 8. This allows for an increase in the permissible clamping forces for the cell stack 200. This is particularly advantageous when the cell stack 200 is designed as a differential pressure electrolyzer, for example, with a pressure difference between cathode compartment 1a and anode compartment 1b of more than 20 bar.
[0060] In further embodiments, an electrochemical cell 1 can also have two sealing frames 40, one each for the cathode compartment 1a and the anode compartment 1b. Both sealing frames 40 then preferably interact by means of a key 50 and a bore 80. R.415638
[0061] - 10 -
[0062] Advantageously, the key 50 and the receiving recess 70 or receiving bore 80 have some play, particularly in the xy-plane. The play in the xy-plane can be asymmetrical, with less play towards the outside of the electrochemical cell 1. Figure 5 shows the embodiment of the cell stack 200 from Figure 4 with the play of the key 50 to the recess 70 and the bore 80.
[0063] The areas marked "fit_1" advantageously have a clearance of 0.2 mm to 0.3 mm. The areas marked "fit_O" advantageously have a clearance of 0 mm or 0.0 mm to 0.1 mm. With respect to the key 50 and the recess 70 in the distributor plate 7, 8, 20, the clearance is "fit_O" pointing outwards and "fit_1" pointing inwards. With respect to the key 50 and the bore 80 of the adjacent cell 1_2, the clearances are designed in the opposite asymmetrical way: "fit_1" pointing outwards and "fit_O" pointing inwards. This results in very good tension and stiffening between the two cells 1_1, 1_2 and the distributor plate 7, 8, 20 arranged between them. "Pointing inwards" can also be interpreted as "pointing inwards towards the cell," i.e., towards the active surface 120. This prevents, in particular, the sealing frame 40 from expanding outwards; the sealing frame 40 is thus clamped almost radially by the distributor plate 7, 8.
[0064] Figure 6 shows a cross-sectional section of another cell stack 200 according to the invention, with only the essential areas shown. Similar to the embodiments shown in Figures 4 and 5, this embodiment demonstrates the interaction of the key 50 of cell 11 with the recess 70 of the distributor plate 7, 8, 20 and the bore 80 of the adjacent cell 1_2.
[0065] In the embodiment of Figure 6, the distributor plate 7, 8, 20 now has one or more ridges 77 at its recess 70, which engage in a corresponding groove 51, 81 of the sealing frame 40.
[0066] The image on the right shows a groove 51 formed at the base of the key 50 in the sealing frame 40 of the first cell 1_1, into which the downwardly pointing ridge 77 of the distributor plate 7, 8, 20 engages. This results in, among other things, in R.415638
[0067] - 11 -
[0068] Stacking direction z keeps the dimensional accuracies of the cell stack 200 small because the burr 77 can be absorbed by the sealing frame 40 without additional contact pressure; secondly, a further undercut is created in the xy direction, which further stiffens the assembly of sealing frame 40 and distributor plate 7, 8, 20.
[0069] The image on the left shows a groove 81 formed at the base of the bore 80 in the sealing frame 40 of the second cell 1_2, into which the upwardly pointing ridge 77 of the distributor plate 7, 8, 20 engages. The groove 81 is essentially an extension of the bore 80 towards the distributor plate 7, 8, 20. Firstly, this design keeps the dimensional tolerances of the cell stack 200 low in the stacking direction z, because the ridge 77 can be received by the sealing frame 40 of the adjacent cell 1_2 without additional contact pressure; secondly, it creates a further undercut in the xy direction, which further stiffens the assembly of the two cells 1_1, 1_2.
Claims
R.415638 - 12 - Claims 1. Electrochemical cell (1) with a catalyst-coated membrane (100), diffusion layers (5, 6) arranged on both sides of this membrane, distributor plates (7, 8) arranged on the diffusion layers (5, 6) 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) interacts with a distributor plate (7, 8) at each of its end faces (40a, 40b), characterized in that a key (50) is formed on the sealing frame (40) which interacts with a recess (70) formed in one of the distributor plates (7, 8).
2. Electrochemical cell (1) according to claim 1 , characterized in that the clearance between the key (50) and the recess (70) is asymmetrically designed, such that the clearance pointing towards the outside of the cell (1) is smaller (fit_O) than the clearance pointing towards the inside of the cell (fit_1).
3. Electrochemical cell (1) according to claim 1 or 2, characterized in that a burr (77) is formed on the recess (70) and that a groove (51) is formed at the base of the key (50), wherein the burr (77) engages in the groove (51).
4. Cell stack (200) with a plurality of electrochemical cells (1), wherein the electrochemical cells (1) comprise a catalyst-coated membrane (100), diffusion layers (5, 6) arranged on both sides of the membrane, distributor plates (7, 8) arranged on the diffusion layers (5, 6) and a sealing frame (40), wherein the sealing frame (40) contains the catalyst-coated membrane (100) and the diffusion layers (5, 6). - 13 - is arranged surrounding, wherein the sealing frame (40) interacts with a distribution plate (7, 8) at each of its end faces (40a, 40b), characterized in that a key (50) is formed on the sealing frame (40) of a first electrochemical cell (1_1), which projects through a recess (70) formed in the distributor plate (7, 8) and interacts with a bore (80) formed in the sealing frame (40) of a second electrochemical cell (1_2).
5. Stack of cells (200) according to claim 4, characterized in that the clearance between the key (50) and the recess (70) is asymmetrically designed, such that the clearance pointing towards the outside of the cell (1) is smaller (fit_O) than the clearance pointing towards the inside of the cell (fit_1).
6. Stack of cells (200) according to claim 4 or 5, characterized in that the clearance between the key (50) and the bore (70) is asymmetrically designed, such that the clearance pointing towards the outside of the cell (1) is greater (fit_1) than the clearance pointing towards the inside of the cell (fit_O).
7. Stack of cells (200) according to one of claims 4 to 6, characterized in that the cell stack (200) is designed as a differential pressure electrolyzer, preferably with a pressure difference from a cathode compartment (1a) to an anode compartment (1b) of more than 20 bar.
8. Stack of cells (200) according to one of claims 4 to 7, characterized in that a burr (77) is formed on the recess (70) and that a groove (51) is formed at the base of the key (50), wherein the burr (77) engages in the groove (51).
9. Stack of cells (200) according to any one of claims 4 to 8, characterized in that a burr (77) is formed at the recess (70) and that a groove (81) is formed at the base of the bore (80), wherein the burr (77) engages in the groove (81).