Plate of a cell stack, and method for mounting a seal on a plate

Abstract

A plate (2, 8, 25) of a stack (1) of electrochemical cells (3), in particular an electrolysis cell stack or a fuel cell stack, has an underside (12), an upper side (11) and at least one end face (10), wherein a strip-type seal (9) having at least one sealing lip (9a) is integrally bondingly mounted only on the at least one end face (10).

Description

[0001] Plate of a cell stack and

[0002] Method for attaching a seal to a plate

[0003] The invention relates to a plate intended for use in a stack of electrochemical cells, for example, fuel cells or electrolysis cells, which interacts in a sealed manner with other components of the cell stack. Furthermore, the invention relates to a method for applying a seal to such a plate for a stack of electrochemical cells.

[0004] A sealing arrangement for fuel cells is known, for example, from DE 101 60 905 B4. The known sealing arrangement is designed for a composite formed from two cell separator plates, with a deformable membrane electrode assembly placed between the cell separator plates. The side surfaces of the membrane electrode assembly are recessed relative to the side surfaces of the cell separator plates to leave a sealing gap. According to DE 101 60 905 B4, the sealing gap is to be sealed gas-tight by means of an elastic sealing element. The sealing element is made of a polymer and encloses the composite like a continuous sealing strip. In addition, porous, gas-permeable plates, which are part of the membrane electrode assembly, are impregnated and / or coated on one or both sides with a second polymer.

[0005] Another sealed membrane electrode assembly for a fuel cell is disclosed in EP 3 257 097 B1. In this case, it is proposed to liquid-seal the edge of a membrane electrode assembly using a frame. For this purpose, a device described in EP 3 257 097 B1 comprises a reservoir of flowable sealing material. During the production of the sealed membrane electrode assembly, the flowable sealing material is cured. A thermosetting liquid injection-moldable compound is proposed as the sealing material. A method for applying a seal to a component of a fuel cell is also described in US 2012 / 0077110 A1. The described method, which includes an injection molding process, is also said to have positive effects on the corrosion properties of fuel cell components.

[0006] The invention is based on the object of providing more advanced possibilities for sealing components of fuel cells, electrolysis cells, redox flow cells or other electrochemical cells compared to the prior art, in particular with regard to manufacturing and sealing technology.

[0007] This object is achieved according to the invention by a plate intended for use in a stack of electrochemical cells having the features of claim 1. The object is also achieved by a method for attaching a seal to a plate for a cell stack according to claim 8. Embodiments and advantages of the invention explained below in connection with the method also apply mutatis mutandis to the device, i.e. the plate intended for sealed installation in a cell stack, and vice versa.

[0008] In addition to the types of electrochemical cells already mentioned, so-called electrochemical hydrogen compressors, for example, are also suitable for the installation of sealed plates according to the application. In connection with electrochemical hydrogen compressors, reference is made to document US 2004 / 0211679 A1 as an example.

[0009] The plate according to the application can be made, for example, of metal, in particular steel, plastic, or a material mix. In the case of a metallic plate, it can, in particular, be a punched or laser-cut sheet. Porous, for example, sintered, flat components are also subsumed under the general term "plate." In electrochemical cells, such plates are present, for example, in the form of porous transport layers (PTL) and gas diffusion layers (GDL). These can be single- or multi-layer fabric plates, foam-like plates, or other porous plate-like structures.

[0010] In any case, the plate has two sides, which, without loss of generality, are referred to as the top and bottom, although the terms front and back would also be suitable. Between the top and bottom of the plate, narrow end faces are formed at least at the outer edge of the plate, and possibly also at openings located in the plate. At least on one of these end faces, and indeed only on at least one of the end faces, a strip-shaped seal with at least one sealing lip is materially bonded. This seal generally serves to seal the plate against at least one other component that is also installed in the cell stack.

[0011] According to various possible designs, the seal only contacts the end face or contoured areas of the end face. In the latter case, the contoured areas on the end face which are contacted by the seal are typically narrower than the wall thickness of the plate contacted by the seal. In the simplest case, the width of the end face or contoured end face is identical to the wall thickness of the plate. In variants in which a contoured end face is formed with steps towards the top and / or bottom of the plate, with the seal extending up to these steps, the seal only contacts areas of the plate between the top and bottom of the plate. Variants are also conceivable in which the seal engages in at least one groove running parallel to the end face or individual recesses in the end face of the plate, thus creating a positive fit.

[0012] In all cases, the plate can be constructed in one or more layers. A multi-layer plate structure is particularly suitable if the plate is designed as a bipolar plate for a fuel cell or other electrochemical cell. In this case, coolant channels, for example, can be formed between two half-sheets from which the bipolar plate is constructed, wherein the coolant channels - in a plan view of the plate - are spaced from the seal. The seal, which is held at least positively to the plate, engages around the edge of the plate in a clamp-like manner between both half-sheets from which the plate, i.e. the bipolar plate, is constructed.

[0013] In variants, the seal has, for example, a completely or at least approximately circular cross-sectional shape. This forms a sealing lip. Other seal shapes are also possible, for example with a rectangular basic shape or with one or more molded sealing lips. In particular, the seal can be designed as a flat or shaped seal, which lies essentially in the same plane as the plate to which the seal is attached. Such a flat seal can have two or more thickened portions as sealing lips, which are connected to one another by a web or a plurality of webs. The individual thickened portions have, for example, a circular, oval, or polygonal cross-sectional shape.

[0014] In all variants of the process for attaching the seal to the plate, the seal is firmly attached to one end of the plate, optionally providing an additional form fit. The seal can be attached using auxiliary materials such as adhesion promoters. When selecting such auxiliary materials, care must be taken to ensure that the corresponding materials cannot be detached or washed out during subsequent operation of the electrochemical cell, which could impair operation at other points in the cell stack.

[0015] In any case, the plate, including the molded-on seal, can be provided as a prefabricated intermediate product for the further production of the cell stack. This eliminates the step of attaching a seal during assembly, which not only streamlines processes but also increases process reliability. Among other things, there is no longer any need to check the correct position of the seal during assembly of the cell stack. A wide variety of known materials, particularly elastomers, are suitable for manufacturing the seal. In any case, the material of the seal differs from the material from which the rest of the plate is made. The seal can be molded onto the plate using injection molding, i.e., in particular, plastic injection molding. It is also possible to attach various seals made of different materials to one and the same plate.

[0016] In an advantageous process, the end face of the plate is roughened before the seal is formed, creating particularly good conditions for a permanently stable attachment of the seal to the plate. Roughening the end face can be achieved, in particular, by particle blast, for example, with a metallic blasting agent. Roughening the end face by etching, brushing, or other chemical or physical pretreatment is also possible.

[0017] Instead of injection-molding the seal, it is also possible to glue a prefabricated seal to the end face of the plate. Likewise, known additive processes, i.e., 3D printing processes, can be used to directly build the seal onto at least one end face of the plate.

[0018] Several embodiments of the invention are explained in more detail below with reference to a drawing. These show, in some cases in a simplified form:

[0019] Fig. 1 shows a stack of electrochemical cells, namely electrolysis cells, in a schematic representation,

[0020] Fig. 2 a plate of the cell stack according to Fig. 1 ,

[0021] Fig. 3 shows a plate designed as a plastic insert for a stack of electrochemical cells, Fig. 4 and 5 show various design options for plates with a seal attached to the front,

[0022] Fig. 6 shows in symbolic representation steps of a method for attaching a seal to a plate intended for use in a cell stack,

[0023] Fig. 7 to 9 show further design options for panels with a seal attached to the front, in these cases in the form of a flat seal.

[0024] Unless otherwise stated, the following explanations refer to all embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in all figures.

[0025] In the exemplary embodiments, a stack of electrochemical cells, designated overall by reference numeral 1, is a cell stack of an electrolysis system for producing hydrogen from water. Alternatively, the cell stack 1 could be, for example, a fuel cell stack. Regarding the basic structure of the stack 1 of electrochemical cells, reference is made to the cited prior art.

[0026] The cell stack 1 comprises, among other things, plates 2 designed as bipolar plates, which separate a first electrochemical cell 3 from another electrochemical cell 3. Each electrochemical cell 3, i.e., an electrolysis cell or fuel cell, is composed of two half-cells 4, 5, between which a membrane 6 is arranged. Instead of a membrane 6, a diaphragm could also be arranged at the corresponding location.

[0027] In the present case, the bipolar plates 2 have an embossed structure, designated 7, shown by way of example in Fig. 1. Alternatively, bipolar plates without an embossed structure, i.e., flat plates without shaped elements, can be used. Furthermore, frames 8 can be seen in Fig. 1, which are placed between bipolar plates 2 arranged parallel to one another and are also generally referred to as plates.

[0028] Seals 9 are attached to the front faces of the various plates 2, 8, which are made of metal, in particular stainless steel or titanium, or plastic. The end faces of the plates 2, 8, generally designated 10, establish the connection between an upper side 11 and a lower side 12 of the respective plate 2, 8. The use of the terms "upper side" and "lower side" does not imply any statement about the actual orientation of the plate 2, 8 in space.

[0029] In the exemplary embodiments, the plates 2 (Figs. 1, 2, 4, 5, 6) are metal plates, whereby the frames 8 of the cell stack 1 are also predominantly made of metal. Alternatively, the frames 8 could be designed as plastic components. A plastic insert 25 sketched in Fig. 3, which in this case has a rectangular basic shape, also represents a plate intended for installation in the cell stack 1. As can be seen from the figures, seals 9 can be arranged either on the outer edge of a plate 2, 8, 25 or on the edge of recesses 13, 14 which are located in a plate 2, 8, 25.

[0030] 4 and 5 show various design options for seals 9, each covering an end face 10 of a plate 2. In the case of Fig. 4, the plate 2 is contoured on the end face 10 so that a step 15 is formed towards the top side 11 and the bottom side 12. In cross-section, as can be seen from Fig. 4, the seal 9 has a circular basic shape, i.e. the shape of an O-ring seal, and extends over the steps 15, but does not contact the top and bottom sides 11, 12 beyond the wall thickness of the plate 2. This is equivalent to the plate 2 being slightly immersed in the seal 9 at the end.

[0031] In contrast, in the design shown in Fig. 5, the plate 2 has no contouring on its end face, with the seal 9 only touching the end face 10 according to the wall thickness and held there firmly. In both the variant shown in Fig. 4 and the variant shown in Fig. 5, the diameter of the seal 9 is significantly larger than the wall thickness of the plate 2 due to the spherical cross-sectional shape.

[0032] Fig. 6 illustrates a method for attaching the seal 9 according to Fig. 4 to the plate 2. The production system used for this purpose is generally designated 16. In a first step, the plate 2 is cut to size using a laser 17 to create the end face 10. The end face 10 is then roughened using a particle irradiation device 18. The particle irradiation device 18 emits, for example, metallic particles, particularly in the form of steel balls, and includes, among other things, a compressed air supply 19 and a shut-off valve 20.

[0033] After roughening the end face 10, the plate 2 is inserted into an injection molding tool 21 comprising tool parts 22, 23. The tool parts 22, 23 form a cavity 24, the shape of which determines the shape of the seal 9 to be molded, visible in Fig. 4. After removing the plate 2 together with the seal 9 from the injection molding tool 21, the plate 2 can be installed into the cell stack 1, that is, in this case, into the electrolysis system.

[0034] In the embodiments outlined in Figures 7 and 8, the seal 9 is designed as a flat seal. In each of these cases, the seal 9 has two or more thickened portions 26, 27, each forming a sealing lip 9a and connected to one another by a web 28. The function of sealing lips 9a is thus realized by the thickened portions 26, 27, which in the case of Fig. 7 have a square cross-section tilted by 45 degrees relative to the plane in which the plate 8 lies, and in the case of Fig. 8 have a circular cross-section. According to Figure 9, four frustoconical thickened portions 26, 27 are arranged in a row and form four sealing lips 9a. Instead of the frustoconical thickened portions 26, 27, truncated pyramid-shaped thickened portions with a rectangular basic pyramid shape can also be used here.In all cases of Figures 7 to 9, one of the thickened portions 26, 27 is connected in a material-to-material manner to the end face 10 of the plate 8, comparable to the embodiments according to Figures 1 and 5.

[0035] List of reference symbols

[0036] Stack of electrochemical cells Plate, bipolar plate Electrochemical cell Half-cell Half-cell Membrane Embossed structure Plate, frame Seal a Sealing lip 0 End face 1 Top side 2 Bottom side 3 Recess 4 Recess 5 Step 6 Production system 7 Laser 8 Particle irradiation device 9 Compressed air supply 0 Shut-off valve 1 Injection mold 2 Mold part 3 Mold part 4 Cavity 5 Plate, plastic insert 6 Thickening 7 Thickening 8 Web

Claims

Patent claims Plate (2, 8, 25) of a stack (1) of electrochemical cells (3), having a top side (11), a bottom side (12) and at least one end face (10), wherein a strip-shaped seal (9) with at least one sealing lip (9a) is attached in a materially bonded manner to at least one of the end faces (10). Plate (2, 8, 25) according to claim 1, characterized in that the seal (9) is located circumferentially on the edge of a recess (13, 14) in the plate (2, 8, 25). Plate (2, 8, 25) according to claim 1 or 2, characterized in that it is made of metal or plastic. Plate (2, 8, 25) according to one of claims 1 to 3, characterized in that it has two or more sealing lips (9a). Plate (2, 8, 25) according to one of claims 1 to 4, characterized in that the seal (9) has a sealing lip (9a) and an at least approximately circular cross-section.Plate (2, 8, 25) according to one of claims 1 to 4, characterized in that the seal (9) is designed as a flat or shaped seal. Plate (2, 8, 25) according to one of claims 1 to 6, characterized in that the at least one end face (10) is contoured.

8. Plate (2, 8, 25) according to claim 7, characterized in that the seal (9) covers a step (15) formed on the end face (10) towards the top and / or bottom side (11, 12).

9. Method for attaching a seal (9) to a plate (2, 8, 25) for a A stack (1) of electrochemical cells (3) according to one of claims 1 to 8, wherein the seal (9) is molded in a form-fitting manner only onto at least one end face (10) of the plate (2, 8, 25).

10. The method according to claim 9, characterized in that the at least one end face (10) of the plate (2, 8, 25) is roughened by particle irradiation before the seal (9) is molded onto it.

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