Frame-like holding plate for an electrolysis cell, electrolysis cell and electrolysis cell stack

Abstract

The invention relates to a frame-like holding plate (1, 1.1) for an electrolysis cell with a rectangular opening (2) which is bordered on two opposite sides by plates (3) inserted into the holding plate (1, 1.1), in which the inserted plates (3) form media ports (4) and in-plane media channels (5) and they have a greater rigidity than the holding plate (1). The invention further relates to an electrolysis cell and an electrolysis cell stack.

Description

[0001] Description

[0002] Frame-like for an electrolysis cell is cell and cell stack

[0003] The present invention relates to a frame-like holding plate for an electrolysis cell. Furthermore, the present invention relates to an electrolysis cell and an electrolysis cell stack.

[0004] Background

[0005] An electrolysis cell has a layered construction, typically comprising:

[0006] An electrically insulating and chemically separating, but ion conducting membrane with a respective catalyst layer provided on either side thereof, forming an anode and a cathode, often referred to as catalyst coated membrane (CCM).

[0007] A porous transport layer (PTL) on either side of the CCM for carrying electric current to the electrodes, while allowing electrolyte to be supplied to and products carried away from a respective electrode of the CCM. The PTL can be provided as a metal foam, (sintered) metal powder, metal fibers / whiskers felt or mesh, (woven or non-woven) carbon fibers and the like. Effective porosity, average pore size, tortuosity, as well as electric conductance are all relevant characteristics of the PTL.

[0008] A frame-like holding plate on either side of the CCM for sealing and supporting the CCM. The holding plates have a central opening for receiving the respective PTL. Besides, they are provided with media ports and in-plane media channels which extend from the media ports to a central opening. Seals on both sides of the holding plate separate the different media from each other. A metal bipolar plate (BPP) shared between and mutually separating adjacent cells for coupling electric current into these cells.

[0009] A large number of identical electrolysis cells are stacked and braced together to form an electrolysis cell stack. In such a stack, the seals on the outside of the holding plates of two adjacent electrolysis cells press against the bipolar plate between them. As the bipolar plate is not supported in the area of the media channels, there is a risk that the bipolar plate will bend and bulge into the recesses formed by the media channels. As a result, the bending of the bipolar plate may lead to leakage of media from the inside to the outside.

[0010] The object of the present invention is preventing leakage caused by bending of a bipolar plate arranged between two electrolysis cells in an electrolysis cell stack. The object is solved by the holding plate according to claim 1 . The dependent claims relate to preferable embodiments of the invention. The object is further solved by the proposed electrolysis cell and the proposed electrolysis cell stack.

[0011] Disclosure of the invention

[0012] Proposed is a frame-like holding plate for an electrolysis cell. The frame-like holding plate has a rectangular opening which is bordered on two opposite sides by plates inserted into the holding plate. The inserted plates form media ports and in-plane media channels and they have a greater rigidity than the holding plate.

[0013] According to the invention, the holding plate is made in several parts, preferably in at least three parts, i.e. a frame-like part forming the rectangular opening and two other parts forming the media ports with the in-plane media channels. The latter are inserted into the frame-like part such that they border the rectangular opening at two opposite sides, which sides depends on whether the holding plate is an anode-side or cathode-side holding plate. As the inserted plates are stiffer than the frame-like part of the holding plate, they can better support an adjacent bipolar plate. Preferably, the inserted plates project beyond the adjacent area of the holding plate on both sides. This measure helps to ensure that a bipolar plate arranged between two holding plates comes into contact with the inserted plates in order to be optimally supported. In particular, the projecting plates level out a tolerance- related unevenness of the holding plate. Furthermore, the heights of intermediate seals can be bridged by the projecting plates.

[0014] According to a preferred embodiment of the invention the holding plate has seals on both sides, such that the overall height of the holding plate is larger than the height of the inserted plates. This ensures that the seals are compressed when at least two electrolysis cells are stacked and braced together. As a result, a high sealing pressure is achieved.

[0015] Preferably, the height of the inserted plates corresponds to the height of the holding plate including the height of the seals in the compressed state. A bipolar plate supported by the holding plate thus lies flat on the inserted plates and the seals, so that there is no longer any risk of bending or bulging.

[0016] It is further proposed that the inserted plates have at least one edge forming a step via which the plate is supported on a corresponding step of the holding plate. This means that the inserted plates and the holding plate, i.e., the framelike part of the holding plate, are connected by a positive fit. The positive fit prevents the inserted plates from moving relative to the holding plate when they are subjected to pressure, especially if the compressive force is aligned perpendicular to the plane of the holding plate. The step along the edge of the inserted plates can also form a tongue or a groove. In this case, the edge of the holding plate is formed in the opposite direction, i.e., as a groove or tongue.

[0017] Further preferably, each media port is connected to the rectangular opening of the holding plate via at least one in-plane media channel, preferably via several in-plane media channels. If the holding plate is arranged on the anode side, a medium can be supplied via the media ports, which is then fed via the media channels to a PTL accommodated in the rectangular opening of the holding plate. The medium then reaches the membrane via the PTL, which separates the anode side from the cathode side. If the holding plate is arranged on the cathode side, the product can be picked up via the PTL accommodated in the rectangular opening of the holding plate and fed to the media ports via the media channels, through which the product is then discharged.

[0018] Outside the areas in which the plates with the media ports and the in-plane media channels are inserted, the holding plate can have additional media ports. However, these are then only used to feed a medium or product between electrolysis cells in a stack.

[0019] According to a preferred embodiment of the invention each of the inserted plates consists of at least two parts of which a first part forms the media channels, and a second part forms a cover extending over the media channels. By covering the in-plane media channels the inserted plates provide a full-faced support for a bipolar plate. Thus, because of the full-faced support, the bipolar plate cannot bend or bulge. The two-part design of the inserted plates facilitates the manufacturing of the in-plane media channels. The connection of the two parts can be a simple plug-in connection, e.g., via a pin that is inserted into a corresponding opening provided in the respective other part.

[0020] Further preferably, the holding plate, i.e., the frame-like part of the holding plate, has a metal core, preferably a stainless-steel core, that is fully covered by an elastomeric material, preferably rubber, for example ethylene propylene diene monomer (EPDM), fluorocarbon-based materials (FKM) or hydrogenated nitrilebutadiene rubber (HNBR). The metal core can be overmoulded with the elastomeric material, whereby the seals can be formed at the same time, so that the seals are made of the same elastomeric material as the holding plate. The metal core inside ensures a certain basic rigidity. Still, due to the elastomeric material around the metal core, the rigidity of the holding plate is less than the rigidity of the inserted plates.

[0021] The inserted plates can be made of plastics, preferably a thermoset resin, for example epoxide, or a thermoplastic, like polyether ether ketone (PEEK) or polyphenylene sulfide (PPS). The rigidity of these materials is high enough. According to a further preferred embodiment of the invention the inserted plates only partly extend along the two opposite sides of the rectangular opening of the holding plate. In particular, the inserted plates do not extend from one end to the other end of one side of the opening. With other words, they maintain a distance from both ends. The distance serves to prevent an overlap in the case that a first holding plate according to the invention is placed on the anode side of a first electrolysis cell and a second holding plate according to the invention is placed on the cathode side of a second electrolysis cell, separated only by a bipolar plate in between. In this case the two holding plates are arranged at 90° to each other, which means that the plates inserted into the two holding plates may overlap due to tolerances. The rigidity of the inserted plates that overlap may then damage the bipolar plate in between. This can be prevented by maintaining a distance to both ends along the side of the opening.

[0022] For further improving the support of a bipolar plate in contact with the holding plate it is suggested that at least some of the seals arranged on both sides of the holding plate are led up to the inserted plates. Accordingly, there is no gap between the seals and the inserted plates into which the bipolar plate could bulge.

[0023] Alternatively or additionally, it is proposed that the seals on both sides of the holding plate are designed as double or triple seals. The seals are routed in strands around the media ports of a certain medium, whereby either two strands or three strands are routed in parallel. In this way, the tightness of the seals can be improved. If a double or triple seal is extended to an inserted plate, then the extended section, which only serves to support the bipolar plate and does not fulfil a sealing function, is preferably cut off from the seal. This prevents that medium present in the media channels enters the seal between two strands thereby increasing the risk of a leak.

[0024] Besides, an electrolysis cell is proposed with at least one holding plate according to the invention. The holding plate may serve as an anode holding plate or a cathode holding plate. Preferably, the electrolysis cell has a holding plate according to the present invention on both sides, i.e., the anode side and the cathode side. In this case, the two holding plates are arranged at 90° to each other. Each holding plate has further media ports that can be brought into overlap with the media ports of the other holding plate for leading the respective medium to the cell or away from the cell.

[0025] Since the proposed electrolysis cell is preferably used in an electrolysis cell stack, an electrolysis cell stack comprising at least two electrolysis cells according to the invention is further proposed, wherein the two cells are separated by a bipolar plate. The cells are stacked and braced together.

[0026] Preferred embodiments of the invention are explained in conjunction with the enclosed figures. The figures show:

[0027] Figure 1 a top view on a first holding plate according to the present invention,

[0028] Figure 2 a top view on a second holding plate according to the present invention,

[0029] Figure 3 a cross section through the holding plates of two adjacent electrolysis cells with a bipolar plate in between, according to a first preferred embodiment of an electrolysis cell according to the present invention,

[0030] Figure 4 a cross section through the holding plates of two adjacent electrolysis cells with a bipolar plate in between, according to a second preferred embodiment of an electrolysis cell according to the present invention,

[0031] Figure 5 a cross section through the holding plates of two adjacent electrolysis cells with a bipolar plate in between, according to a third preferred embodiment of an electrolysis cell according to the present invention,

[0032] Figure 6 a) an enlarged cut-out of figure 1 and b) an enlarged cut-out of figure 2,

[0033] Figure 7 a) an enlarged cut-out of figure 1 and b) an enlarged cut-out of a top view of a modified holding plate, Figure 8 an enlarged cut-out of figure 1 in the area of intersecting seals that are carried out as double seals and

[0034] Figure 9 an enlarged cut-out of figure 1 in the area if intersecting seals that are carried out as triple seals.

[0035] Detailed description of the figures

[0036] Figures 1 shows a first holding plate 1 according to the present invention which serves as an anode holding plate 1.1. With other words, the holding plate 1 shown in figure 1 is positioned on the anode side of an electrolysis cell 10. The holding plate 1 comprises a frame-like first part forming a rectangular opening 2. At two opposite sides the opening 2 is bordered by plates 3 that are inserted into the frame-like part of the holding plate 1. These two sides are the top and the bottom side. The inserted plates 3 extend over the whole length of the sides.

[0037] Each of the inserted plates 3 forms media ports 4 and in-plane media channels 5 via which the media ports 4 are connected to the rectangular opening 2. Via the media ports 4 and the media channels 5 the anode side of the electrolysis cell 10 is fed with water as medium. Further media ports 4 arranged along the rectangular opening 2 on the two other sides serve for discharging hydrogen from the cathode side of the electrolysis cell 10. For separating the different media, seals 6 are provided on the top of the holding plate 1.

[0038] Figure 2 shows a second holding plate 1 according to the present invention which serves as a cathode holding plate 1 .2. Accordingly, the media ports 4 provided on the left and right side are connected via media channels 5 to the rectangular opening 2 of the holding plate 1 , while the media ports 4 on the top and bottom side are only extending through the holding plate 1 . Seals 6 are provided on top of the holding plate 1 for separating the different media transported through the media ports 4 and media channels 5.

[0039] An electrolysis cell 10 according to the present invention comprises at least one holding plate 1 according to the present invention. This can be an anode holding plate 1 .1 and / or a cathode holding plate 1 .2. If both holding plates 1 .1 , 1 .2 are carried out according to the present invention, then the holding plates 1.1 , 1.2 are orientated when stacked so that the inserted plates 3 are arranged at 90° to each other.

[0040] Figure 3 shows a configuration of two electrolysis cells 10 according to the present invention on top of each with a bipolar plate 12 in between. Thus, figure 3 shows a cut-out of an electrolysis cell stack 11 according to the present invention. The lower holding plate 1 is an anode holding plate 1 .1 of a first electrolysis cell 10 and the top holding plate 1 is a cathode holding plate 1 .2 of a second electrolysis cell 10 within the stack 11 . Both holding plates 1 .1 , 1 .2 have a metal core 9 that is overmoulded with rubber. The rubber forms seals 6 on both sides of each holding plate 1.1 , 1.2. The seals 6 are carried out as double seals 6. The position of the seals 6 is such that the bipolar plate 12 in between is supported by the seals 6. However, in the area of the media channels 5 of the anode holding plate 1 .1 there is no seal 6 on the anode side, but on the cathode side. Thus, the bipolar plate 12 in between is pressed by the seal 6 on the cathode side into the media channels 5 on the anode side. For preventing the bipolar plate 12 from bending and bulging, the media channels 5 are formed by a plate 3 inserted into the anode holding plate 1 .1. The inserted plate 3 is made of a material that has a higher rigidity compared to the rigidity of the rubber of which the holding plate 1 is made. Besides, the height of the inserted plate 3 equals the height of the holding plate 1 including the height of the seals 6 in their compressed state. Thus, the bipolar plate 12 is optimally supported by the inserted plate 3.

[0041] Figure 4 shows a modification of a holding plate 1 according to the present invention. In the modified embodiment shown, the inserted plate 3 forms a step 7 along its edge via which the inserted plate 3 is supported on a corresponding step 8 formed by the holding plate 1. In this configuration, the inserted plate 3 and the holding plate 1 are form-fitted, such that the inserted plate 3 can not move relative to the holding plate 1 when the bipolar plate 12 is pressed against it.

[0042] Figure 5 shows another advantageous modification. Here, the inserted plate 3 consists of at least two parts. A first part 3.1 which forms the in-plane media channels 5 and a second part 3.2 which forms a cover extending over the media channels 5. The two parts 3.1 , 3.2 are connected by a plug-in connection via a pin 13 that is inserted into a corresponding opening of the respective other part of the inserted plate 3. In figure 5 the pin 13 is provided at the second part 3.2 and the opening is provided in the first part 3.1. Optionally, the arrangement can be vice-versa. The second part 3.2 that covers the media channels 5 serves as a full-faced support for the bipolar plate 12, thereby preventing the bipolar plate 12 from bending and bulging.

[0043] Each of figures 6a) and 6b) shows a cut-out of a holding plate 1 according to the present invention. The holding plate 1 of figure 6a) is an anode holding plate 1.1 and the holding plate 1 of figure 6b) is a cathode holding plate 1 .2. Due to tolerances, the inserted plates 3 of both holding plates 1 .1 , 1 .2 may overlap when arranged on top of each other with a bipolar plate 12 in between. As a result, the bipolar plate 12 in between may be damaged by the two plates 3 in the area where they overlap (see marked area in figures 6a) and 6b)). To prevent this, the inserted plate 3 of at least one holding plate 1 can maintain a distance a to the end of the opening 2 as shown in figure 7b). The distance a corresponds to the distance between the inserted plates 3 of the two holding plates 1.1 , 1.2 when stacked (see figures 7a) and 7b)).

[0044] In the embodiment shown in figures 7a) and 7b), the seals 6 for separating the different media are extended to the inserted plates 3. This prevents a gap between the seal 6 and the respective plate 3, thereby improving the support of the bipolar plate 12 in between. The extended portions 14 of the seals 6 have no sealing function only a supporting function. Therefore, when carried out as double or triple seals, the extended portions 14 of the seals 6 are preferably cut off from the seals 6 as shown in figures 8 and 9.

Claims

Claims1 . Frame-like holding plate (1 ) for an electrolysis cell (10) with a rectangular opening (2) which is bordered on two opposite sides by plates (3) inserted into the holding plate (1), in which the inserted plates (3) form media ports(4) and in-plane media channels (5) and they have a greater rigidity than the holding plate (1).

2. Holding plate (1) according to claim 1 , characterized in that the inserted plates (3) project beyond the adjacent area of the holding plate (1) on both sides.

3. Holding plate (1) according to claim 1 or 2, characterized in that the holding plate (1) has seals (6) on both sides, such that the overall height of the holding plate (1) is larger than the height of the inserted plates (3), preferably the height of the inserted plates (3) corresponds to the height of the holding plate (1) including the height of the seals (6) in the compressed state.

4. Holding plate (1) according to any one of the preceding claims, characterized in that the inserted plates (3) have at least one edge forming a step (7) via which the plate (3) is supported on a corresponding step (8) of the holding plate (1).

5. Holding plate (1) according to any one of the preceding claims, characterized in that each media port (4) is connected to the rectangular opening (2) of the holding plate (1) via at least one in-plane media channel(5), preferably via several in-plane media channels (5).

6. Holding plate (1) according to any one of the preceding claims,characterized in that each of the inserted plates (3) consists of at least two parts (3.1 , 3.2) of which a first part (3.1) forms the media channels (5), and a second part (3.2) forms a cover extending over the media channels (5).

7. Holding plate (1) according to any one of the preceding claims, characterized in that the holding plate (1) has a metal core (9), preferably a stainless-steel core, that is fully covered by an elastomeric material, preferably rubber, for example ethylene propylene diene monomer (EPDM), fluorocarbon-based materials (FKM) or hydrogenated nitrile-butadiene rubber (HNBR).

8. Holding plate (1) according to any one of the preceding claims, characterized in that the inserted plates (3) are made of plastics, preferably a thermoset resin, for example epoxide, or a thermoplastic, like polyether ether ketone (PEEK) or polyphenylene sulfide (PPS).

9. Holding plate (1) according to any one of the preceding claims, characterized in that the inserted plates (3) only partly extend along the two opposite sides of the rectangular opening (2) of the holding plate (1).

10. Holding plate (1) according to any one of claims 3 to 9, characterized in that at least some of the seals (6) arranged on both sides of the holding plate (1) are led up to the inserted plates (3) and / or are designed as double or triple seals.11 . Electrolysis cell (10) with at least one holding plate (1) according to any one of the preceding claims serving as an anode holding plate (1 .1) or a cathode holding plate (1.2).

12. Electrolysis cell stack (11 ) comprising at least two electrolysis cells (10) according to claim 11 , which are separated by a bipolar plate (12)

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