Cell for an electrochemical energy converter

Abstract

The present invention relates to a method (100) for producing a cell (200) for an electrochemical energy converter (300), the method (100) comprising: - arranging (101) a terrace seal (201) in a recess (203) formed by a frame terrace (205) of a frame (207) for encompassing a membrane electrode assembly (MEA) (209) of the cell (200), wherein the frame (207) comprises a frame body (211) and the frame terrace (205), wherein a height of the frame terrace (205) is smaller than a height of the frame body (211), wherein the terrace seal (201) comprises a first part (213) and a second part (215), wherein a height of the second part (215) of the terrace seal (201) is smaller than a height of the first part (213) of the terrace seal (201), wherein the first part (213) of the terrace seal (201) protrudes in height direction over an upper level (217) of the recess (203), and wherein the second part (215) of the terrace seal (201) protrudes in height direction beneath the upper level (217) of the recess, - combining (103) the MEA (209) and the frame (207), thereby pressing the first part (213) of the terrace seal (201) in the recess (203) using the MEA (209), - arranging (105) a first bipolarplate (219) on an upper side of the MEA (209) and the frame (207), - arranging (107) a second bipolarplate (221) on a lower side of the MEA (209) and the frame (207).

Description

[0001] R.414900

[0002] - 1 -

[0003] Description

[0004] Title

[0005] Cell for an electrochemical energy converter

[0006] The present invention relates to a method for producing a cell for an electrochemical energy converter, a cell for an electrochemical energy converter, and an electrochemical energy converter.

[0007] State of the art

[0008] A stack (series arrangement) of electrochemical cells, such as a fuel cell or an electrolysis stack, is well known in the art

[0009] Each cell in the stack has a layered construction, typically comprising an electrically insulating and chemically separating but ion conducting composite polymer membrane with a respective cathode and anode electrode with a catalyst layer provided on either side thereof, at which the actual electrochemical reaction occurs, such as H2O oxidation (OER: oxygen evolution reaction) at the anode and IT reduction (HER: hydrogen evolution reaction) at the cathode in case of electrolysis of water.

[0010] The anode and cathode catalyst layers comprise catalyst nano particles mixed with binder and support materials, typically an ionomer. This layered assembly of the membrane and the electrodes is often referred to as a catalyst coated membrane (CCM), which latter naming refers to the conventional production process of coating the membrane with the electrode catalyst mixture dissolved in a volatile solvent.

[0011] Further, the layered construction comprises a porous transport or gas diffusion layer (PTL / GDL) on either (i.e. anode & cathode) side of the CCM for R.414900

[0012] - 2 - carrying electric current to or away from the electrodes, while allowing electrolyte and / or the electrochemical reactants and products to be supplied to or carried away from a respective electrode of the CCM.

[0013] The PTL / GDL can be provided as a metal (open-celled) foam, sintered metal powder or pellets or fibres or whiskers, woven or non-woven carbon fibres and the like.

[0014] Further, the layered construction comprises a metal “bipolar” plate (BPP) shared between and mutually chemically separating adjacent cells for coupling electric current out of, resp. into these cells, which plate can be corrugated such that it defines a fluid supply and distribution area and a fluid flow-field for the transport of the electrolyte, the reactant, the product and / or a cooling medium across the active area of the cell.

[0015] Disclosure of the invention

[0016] According to a first aspect, the present invention relates to a method for producing a cell for an electrochemical energy converter.

[0017] The method comprises arranging a terrace seal in a recess formed by a frame terrace of a frame for encompassing a membrane electrode assembly (MEA) of the cell, wherein the frame comprises a frame body and the frame terrace, wherein a height of the frame terrace is smaller than a height of the frame body, wherein the terrace seal comprises a first part and a second part, wherein a height of the second part of the terrace seal is smaller than a height of the first part of the terrace seal, wherein the first part of the terrace seal protrudes in height direction over an upper level of the recess, and wherein the second part of the terrace seal protrudes in height direction beneath the upper level of the recess.

[0018] The method further comprises combining the MEA and the frame, thereby pressing the first part of the terrace seal in the recess using the MEA, arranging a first bipolarplate on an upper side of the MEA and the frame, and arranging a second bipolarplate on a lower side of the MEA and the frame. R.414900

[0019] - 3 -

[0020] The present invention is based on a construction of a cell that includes a frame, in particular a single, i.e. one piece frame that encompasses the MEA. The frame is provided with an inner section of reduced thickness, denoted frame terrace.

[0021] In a recessed part of the frame terrace, a terrace seal is provided between the frame and the MEA, in particular the CCM of the MEA. This terrace seal prevents leakage of gas on the opposite side, in particular the cathode side of the unit cell to the anode side.

[0022] The terrace seal may comprise elastic material, such as an elastomer containing polyurethane, for example.

[0023] The terrace seal performs the essential function of preventing leakage of gas, in particular hydrogen, from one side, typically a higher pressure cathode side of the cell to its other side.

[0024] According to the present invention, the terrace seal is shaped in relation to the recess of the frame terrace with a thicker first part or bulge that protrudes in height direction outside the recessed part, i.e. that protrudes beyond the level of the recess and with a second thinner part to at least one side of the first part. The second part remains inside the recess, i.e. lies below the upper level of the recess.

[0025] The frame terrace is a first part of the frame that is smaller in height than a second part of the frame, wherein the frame terrace is arranged in a direction pointing towards a center of the cell. Thus, the second part of frame body is arranged on an outer side, encompassing the first part and the MEA arranged in part on the frame terrace.

[0026] The first part of the terrace seal may form a bulge in an uncompressed state. Thus, upon compression of the terrace seal, i.e. upon assembly of the cell, the first part thereof is compressed in height direction and expands in width direction, thus, at least partly, filling the free space in the recess between the frame terrace and the MEA by the expansion of the second part in height direction. R.414900

[0027] - 4 -

[0028] Hereby, a contact area between the terrace seal and the MEA, in particular the membrane, favourably increases. Further, the contact between the terrace seal and the MEA is very tight, in particular tight against leakage of hydrogen.

[0029] According to an embodiment, the recess encompasses the terrace seal on a side facing towards the active area of the cell, or the recess forms a step that is open and has a side facing towards the active area of the cell.

[0030] The recess may form a channel that receives the terrace seal, which supports the terrace seal from three sides and therefore provides for a high pressure pressing the terrace seal against the MEA.

[0031] The recess may also form a step that is open on a side facing towards the active area of the cell, such that a movement of the MEA compressing the terrace sealing is not limited by the recess.

[0032] According to an embodiment, the terrace seal further comprises a third part, wherein, before combining the MEA and the frame, a height of the third part is greater than the height of the second part and smaller than the height of the first part, and wherein the second part is located between the first part and the third part.

[0033] By using a third part of the terrace sealing that has a height greater than the height of the second part and smaller than the height of the first part, wherein the second part is located between the first part and the third part, the free space in the recess may be fully filled by combining the MEA and the frame or at least filled at the edges, such that leakage of gas through the recess and the terrace seal is minimized.

[0034] According to another embodiment, the third part is essentially flush with the upper level of the recess.

[0035] A third part of the terrace seal that is essentially flush with the upper level of the recess results in very gas-tight sealing and to the possibility of choosing the R.414900

[0036] - 5 - dimension of the second part of the terrace sealing such that the free space in the recess is fully filled up by the terrace seal, when the terrace seal is under compression by the MEA.

[0037] According to another embodiment, the first part of the terrace seal is located off- center, relative to a width of the terrace seal, on the side facing towards a center of the cell.

[0038] By locating the first part off-center, the path between the MEA and the frame is sealed by the terrace sealing. Thus, a space in which gas may be streaming between the MEA and the frame is minimized.

[0039] According to another embodiment, a bottom of the recess is inclined downwards in a direction towards the center of the cell.

[0040] An inclined shape of the recess is giving the terrace seal more volume on the location where it is compressed the most and thus reduces internal stress in the cell.

[0041] According to another embodiment, the height for which the first part of the terrace seal protrudes over the upper level of the recess is such that the terrace seal provides for a counter force to a compression force applied during pressing of the first bipolarplate against the MEA and the frame, wherein the counter force is greater than the compression force.

[0042] Preferably, i.e. for optimum sealing, the terrace seal may be shaped such that its first, thicker part protrudes in height direction outside the recessed part, for more than a compression amount of a bipolarplate-seal, in particular an anode-side bipolarplate-seal upon assembly of the cell, which bipolarplate-seal is provided between the frame and the particular bipolarplate, in particular the anode-side bipolarplate of the cell.

[0043] Since the anode-side bipolarplate-seal is typically provided in its own recess in the frame, its compression amount upon assembly is equal to its protruding amount beyond the frame in unassembled condition. R.414900

[0044] - 6 -

[0045] Thus, according to another embodiment, the counter force is such that it corresponds to a sum of a first force corresponding to a protruding amount of a first bipolarplate-seal between the MEA and the first bipolarplate and a second force corresponding to a protruding amount of a second bipolarplate-seal between the MEA and the second bipolarplate, in an uncompressed state.

[0046] The protruding amount of the first part of terrace seal may correspond to the sum of the protruding amount of both the anode-side bipolaplate-seal and the cathode-side bipolarplate-seal in the unassembled / uncompressed condition of all three seals.

[0047] According to a second aspect, the present invention relates to a cell for an electrochemical energy converter, wherein the cell is obtainable by an embodiment of the method disclosed herein.

[0048] By using the method disclosed herein for obtaining a cell, a very gas-tight, in particular hydrogen-tight sealing is formed between a MEA and a frame encompassing the MEA of the cell. This sealing is formed by the terrace seal arranged in the recess.

[0049] According to an embodiment, the second part of the terrace seal is spaced apart from the MEA.

[0050] A second part of the terrace seal that is spaced apart from the MEA results from a first of the terrace seal pressing against the MEA hard and, therefore, very gastight.

[0051] Thus, according to another embodiment, the first part of the terrace seal provides for a pressing force that presses against the MEA.

[0052] The high pressing force leads to an out-levelling of small differences in height between the MEA and the terrace seal, resulting in a very gas-tight connection. R.414900

[0053] - 7 -

[0054] According to a third aspect, the present invention relates to an electrochemical energy converter, wherein the electrochemical energy converter comprises a stack of a number of possible embodiments of the cells disclosed herein.

[0055] Because of the cells disclosed herein, the electrochemical energy converter disclosed herein is very gas-tight and, therefore, very energy efficient.

[0056] According to an embodiment, the electrochemical energy converter, is a fuel-cell system or an electrolysis system.

[0057] BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The foregoing and other features and advantages of the invention will become further apparent from the following detailed description read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.

[0059] Figure 1 shows a method for producing a cell for an electrochemical energy converter, according to an embodiment of the invention disclosed herein.

[0060] Figure 2 shows a detail of the method according to Fig. 1 ,

[0061] Figure 3 shows a first embodiment of the cell disclosed herein,

[0062] Figure 4 shows a second embodiment of the cell disclosed herein,

[0063] Figure 5 shows a special design of a frame and a terrace seal according to an embodiment of the cell disclosed herein,

[0064] Figure 6 shows an embodiment of the electrochemical energy converter disclosed herein.

[0065] In Fig. 1 , a method 100 for producing a cell 200 for an electrochemical energy converter 300 is shown. R.414900

[0066] - 8 -

[0067] The method 100 comprises a first arranging step 101 , in which a terrace seal 201 (shown in Fig. 2) is arranged in a recess 203 formed by a frame terrace 205 of a frame 207 for encompassing a membrane electrode assembly (MEA) 209 of the cell 200.

[0068] The frame 207 comprises a frame body 211 and the frame terrace 205, wherein a height of the frame terrace 205 is smaller than a height of the frame body 211 .

[0069] The terrace seal 201 comprises a first part 213 and a second part 215, wherein a height of the second part 215 is smaller than a height of the first part 213.

[0070] The first part 213 protrudes in height direction over an upper level 217 of the recess 203, and the second part 215 protrudes in height direction beneath the upper level 217 but further in width of the recess 203 than the first part 213.

[0071] The method 100 further comprises a combining step 103, in which the MEA 209 (shown in Fig. 3) and the frame 207 are combined, thereby pressing the first part 213 of the terrace seal 201 in the recess 203 using the MEA 209.

[0072] The method 100 further comprises a second arranging step 105, in which a first bipolarplate 219 is arranged on an upper side of the MEA 209 and the frame 207, and a third arranging step 107, in which a second bipolarplate 221 is arranged on a lower side of the MEA 209 and the frame 207.

[0073] In Fig. 2 the terrace seal 201 is shown in a state during the method 100 before the MEA 209 is arranged on the frame 207. Thus, the first part 213 of the terrace seal 201 is greater in its height than a height of the recess 203, whereas the second part 215 is smaller in its height than the height of the recess 203.

[0074] Upon compression of the terrace seal 201 the first part 213 is compressed in height direction and expands in width direction, thus at least partly filling the free space between the second part 215 of the terrace seal 201 and the upper level of the recess 201 by the expansion thereof in height direction. R.414900

[0075] - 9 -

[0076] Hereby, a surface area of the sealing contact between the terrace seal 201 and the ME A 209 favorably increases, as shown in Fig. 3

[0077] In Fig. 3 a cell 200 for an electrochemical energy converter 300 is shown.

[0078] In the cell 200 the terrace seal 201 is arranged in the recess 203 between the frame terrace 205 of the frame 207 and the MEA 209. The first bipolarplate 219 is arranged on the upper side of the frame body 211 and the MEA 209, and the second bipolarplate 221 is arranged on the lower side of the frame 207 and the MEA 209.

[0079] In the cell 200, the first part 213 is compressed by the MEA 209, such that the height of the first part 213 equals, in essence the height of the recess 203 but is increased in its width and the second part 215 is reduced in its width, compared to Fig. 2

[0080] In Fig. 4 the terrace seal 201 is shown in a configuration having an additional third part 223, which is greater in height than the second part 215 and lower in height than the first part 213, at least in an uncompressed state. The third part 223 is essentially flush with the upper level of the recess 203.

[0081] Further, the terrace seal 201 shown in Fig. 4 comprises an optional fourth part 225, which is also thinner than the first part 213, such that the first part 213 is arranged between thin parts 225 and 215.

[0082] In Fig. 5, the frame terrace 205 is shown in a configuration in which the recess 203 is inclined downwards in the direction towards the active area of the cell 200 and left open on the side towards the active area of the cell 200.

[0083] In Fig. 6, an electrochemical energy converter 300 in form of a fuel-cell system is shown. The energy converter 300 comprises a stack 301 of fuel-cells 200 according to Fig. 3, for example.

[0084] Claims

Claims

R.414900- 10 -1 . Method (100) for producing a cell (200) for an electrochemical energy converter (300), the method (100) comprising: arranging (101) a terrace seal (201) in a recess (203) formed by a frame terrace (205) of a frame (207) for encompassing a membrane electrode assembly (MEA) (209) of the cell (200), wherein the frame (207) comprises a frame body (211) and the frame terrace (205), wherein a height of the frame terrace (205) is smaller than a height of the frame body (211), wherein the terrace seal (201) comprises a first part (213) and a second part (215), wherein a height of the second part (215) of the terrace seal (201) is smaller than a height of the first part (213) of the terrace seal (201), wherein the first part (213) of the terrace seal (201) protrudes in height direction over an upper level (217) of the recess (203), and wherein the second part (215) of the terrace seal (201) protrudes in height direction beneath the upper level (217) of the recess, combining (103) the MEA (209) and the frame (207), thereby pressing the first part (213) of the terrace seal (201) in the recess (203) using the MEA (209), arranging (105) a first bipolarplate (219) on an upper side of the M EA (209) and the frame (207), arranging (107) a second bipolarplate (221) on a lower side of the MEA (209) and the frame (207).

2. Method (100) according to claim 1 , characterized in that, the recess (203) encompasses the terrace seal (201) on a side facing towards the active area of the cell (200), or the recess (203) forms a step that is open and has a side facing towards the active area of the cell (200).

3. Method (100) according to claim 2, characterized in that,R.414900- 11 - the terrace seal (201) further comprises a third part (223), wherein, before combining the MEA (209) and the frame (207), a height of the third part (223) is greater than the height of the second part (215) and smaller than the height of the first part (213), and wherein the second part (215) is located between the first part (213) and the third part (223).

4. Method (100) according to claim 3, characterized in that, the third part (223) is essentially flush with the upper level (217) of the recess (203).

5. Method (100) according to any of the previous claims, characterized in that, the first part (213) of the terrace seal (201) is located off-center, relative to a width of the terrace seal (201), on the side facing towards a center of the cell (200).

6. Method (100) according to any of the previous claims, characterized in that, a bottom of the recess (203) is inclined downwards in a direction towards the center of the cell (200).

7. Method (100) according to any of the previous claims, characterized in that, the height for which the first part (213) of the terrace seal (201) protrudes over the upper level (217) of the recess (203) is such that the terrace seal (201) provides for a counter force to a compression force applied during pressing of the first bipolarplate (219) against the MEA (209) and the frame (207), wherein the counter force is greater than the compression force.R.414900- 12 -8. Method (100) according to claim 7, characterized in that, the counter force is such that it corresponds to a sum of a first force corresponding to a protruding amount of a first bipolarplate-seal between the MEA (209) and the first bipolarplate (219) and a second force corresponding to a protruding amount of a second bipolarplate-seal between the MEA (209) and the second bipolarplate (221), in an uncompressed state.

9. Cell (200) for an electrochemical energy converter (300), wherein the cell (200) is obtainable by a method (100) according to any of claims 1 to 8.

10. Cell (200) according to claim 9, characterized in that, the second part (215) of the terrace seal (201) is spaced apart from the MEA (209).11 . Cell (200) according to claim 9 or 10, characterized in that, the first part (213) of the terrace seal (201) provides for a pressing force that presses against the MEA (209).

12. Electrochemical energy converter (300), wherein the electrochemical energy converter (300) comprises a stack of a number of cells according to claim 10 or 11 .

13. Electrochemical energy converter (300) according to claim 12, characterized in that, the electrochemical energy converter (300), is a fuel-cell system or an electrolysis system.

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