Plate for cell stack and method for mounting seal on plate

Abstract

A plate (2, 8, 25) of a stack (1) of electrochemical cells (3), in particular an electrolytic cell stack or a fuel cell stack, has a lower side (12), an upper side (11) and at least one end face (10), a strip-shaped seal (9) having at least one sealing lip (9a) being mounted on the at least one end face (10) only in an integral manner.

Description

Technical Field

[0001] The invention relates to a plate which is arranged for use in a stack of electrochemical cells, such as fuel cells or electrolytic cells, and which interacts in a sealed manner with other components of the stack. In addition, the invention relates to a method for mounting a seal on such a plate for a stack of electrochemical cells. Background Art

[0002] For example, a sealing device for a fuel cell is known from DE 101 60 905 B4. The known sealing device is designed for an assembly formed by two battery separators, wherein a deformable membrane electrode unit is arranged between the battery separators. The side surface of the membrane electrode unit is recessed relative to the side surface of the battery separator to leave a sealing gap. According to DE 101 60 905 B4, the sealing gap should be sealed in an airtight manner by means of an elastic sealing element. The sealing element is made of a polymer and encloses the aforementioned assembly in the form of a circumferential sealing strip. In addition, the porous gas-permeable plate as part of the membrane electrode unit is impregnated and / or coated with a second polymer on one or both sides.

[0003] Another sealed membrane electrode assembly for a fuel cell is disclosed in EP 3 257 097 B1. In this case, it is proposed that the edges of the membrane electrode assembly are fluid-sealed by using a frame. For this purpose, the device described in EP 3 257 097 B1 includes a reservoir of a flowable sealing material. During the production of the sealed membrane electrode assembly, the flowable sealing material is hardened. A thermosetting liquid injection molding compound is proposed as a sealing material.

[0004] A method for mounting a seal on 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 a positive effect on the corrosion properties of the fuel cell component. Summary of the invention

[0005] The invention is based on the object of describing the possibilities for further development of the prior art, in particular with regard to aspects of production and sealing technology, for sealing components for fuel cells, electrolysis cells, redox flow batteries or other electrochemical cells.

[0006] According to the invention, this object is achieved by a plate arranged for use in a stack of electrochemical cells, having the features of claim 1. The object is also achieved by a method for mounting a seal on a plate for a cell stack according to claim 8. The embodiments and advantages of the invention described below in conjunction with the method apply mutatis mutandis to the device, i.e. the plate arranged for sealing installation in a cell stack, and the embodiments and advantages of the invention described below in conjunction with the device, i.e. the plate arranged for sealing installation in a cell stack, apply mutatis mutandis to the method.

[0007] In addition to the types of electrochemical cells already mentioned, so-called electrochemical hydrogen compressors are also suitable, for example, for the installation of the sealing plate according to the present application. With regard to electrochemical hydrogen compressors, reference is made to document US 2004 / 0211679 A1 as an example.

[0008] The plates according to the present application can be made, for example, of metal, in particular steel, plastic or a mixture of materials. In the case of metal plates, the plates can in particular be stamped or laser-cut sheets. Likewise, porous, for example sintered, flat parts are included 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 plates can be single-layer or multi-layer textile plates, foam-like plates or other porous plate-like structures.

[0009] In any case, the plate has two sides which, without loss of generality, are referred to as upper and lower sides, but the terms front and rear sides will also be suitable. Between the upper and lower sides of the plate, narrow end faces are formed at least at the outer edges of the plate and possibly also at openings provided in the plate. At least on one of these end faces and indeed only on at least one of them, a strip-type seal having at least one sealing lip is integrally mounted. This seal is generally used to seal the plate against at least one other component also mounted in the battery stack.

[0010] According to various possible embodiments, the seal contacts only the end face or a contour area of ​​the end face. In the case where the seal contacts only the contour area of ​​the end face, the contour surface on the end face contacted by the seal is generally narrower than the wall thickness of the plate contacted by the seal. In the simplest case, the width of the end face or the contour front face is the same as the wall thickness of the plate. In a variant in which the contour end face is formed with steps to the upper side and / or the lower side of the plate, wherein the seal extends to these steps, the seal contacts only the area of ​​the plate located between the upper side and the lower side of the plate. The following variant can also be envisaged: in the variant, the seal engages in at least one groove extending parallel to the end face or engages in a separate recess in the end face of the plate in order to provide a form-fitting connection.

[0011] In all cases, the plate can be constructed in one or more layers. The multilayer structure of the plate is particularly suitable if the plate is designed as a bipolar plate for a fuel cell or other electrochemical cell. In this case, a coolant channel can be formed, for example, between the two half sheets of the bipolar plate, wherein the coolant channel is spaced apart from the seal in a plan view of the plate. The seal, which is held on the plate at least in a form-fitting manner, is joined around the construction plate, i.e. the two half sheets of the bipolar plate, at the edge of the plate in a clamp-like manner.

[0012] In a variant, for example, the seal has a completely or at least approximately circular cross-sectional shape. This forms a sealing lip. Different shapes of seals, for example with a rectangular basic shape or with one or more molded sealing lips, are also possible. In particular, the seal can be designed as a flat or shaped seal, which is essentially located in the same plane as the plate on which the seal is mounted. Such a flat seal can have two or more thickened portions as sealing lips, which are connected to each other by one or more bridges. The individual thickened portions have, for example, a circular, oval or polygonal cross-sectional shape.

[0013] In all variants of the method for mounting the seal on the plate, the seal is integrally fastened to one end face of the plate, optionally producing an additional form-fitting connection. The seal can be mounted using auxiliary materials such as adhesion promoters. When selecting such auxiliary materials, care must be taken to ensure that the corresponding substance is not dissolved or washed off during the subsequent operation of the electrochemical cell, which could otherwise impair operation at another location in the cell stack.

[0014] In any case, the plate including the molded seal can be provided as a prefabricated intermediate product for the further production of the cell stack. This eliminates the step of installing the seal during assembly, which not only streamlines the process but also increases process reliability. Among other things, it is no longer necessary to check the correct position of the seal when assembling the cell stack. A variety of known materials, in particular elastomers, are suitable for producing the seal. In any case, the material of the seal is different from the material from which the rest of the plate is made.

[0015] The seal can be molded onto the plate in particular by injection molding, ie in particular plastic injection molding. It is also possible to mount different seals made of different materials on the same plate.

[0016] In an advantageous process, the end face of the plate is roughened before the seal is molded thereon, in order to create particularly good conditions for permanently and stably holding the seal on the plate. The roughening of the end face can be performed in particular by particle blasting, for example with metal blasting abrasives. The end face can also be roughened by etching, brushing or other chemical or physical pretreatments.

[0017] Instead of molding the seal thereon, a prefabricated seal can also be adhesively bonded to the end face of the plate. Likewise, a seal can be created directly on at least one end face of the plate using known additive processes, ie 3D printing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Several exemplary embodiments of the present invention are described in more detail below with the aid of the accompanying drawings, in which, in a partly oversimplified manner:

[0019] Figure 1 A stack of electrochemical cells, i.e. electrolytic cells, is schematically shown;

[0020] Figure 2 Shown according to Figure 1 plates of a battery stack;

[0021] Figure 3 A plate designed as a plastic insert for a stack of electrochemical cells is shown;

[0022] Figure 4 and Figure 5 Different design options for plates with seals mounted on the end faces are shown;

[0023] Figure 6 A symbolic representation of the steps of a method for installing a seal on a plate configured for use in a battery stack is shown;

[0024] Figures 7 to 9 Other design options are shown for plates with seals mounted on the end faces, which in these cases are in the form of flat seals. DETAILED DESCRIPTION

[0025] Unless otherwise stated, the following description relates to all exemplary embodiments. In all figures, parts that correspond to each other or have substantially the same function are denoted by the same reference numerals.

[0026] In the exemplary embodiment, the stack of electrochemical cells generally indicated by reference numeral 1 is a cell stack of an electrolysis plant for producing hydrogen from water. Alternatively, the cell stack 1 may be, for example, a fuel cell stack. With regard to the basic structure of the stack of electrochemical cells 1, reference is made to the cited prior art.

[0027] The cell stack 1 comprises, among other things, plates 2 designed as bipolar plates, which separate a first electrochemical cell 3 from a further electrochemical cell 3. Each electrochemical cell 3, ie an electrolysis cell or a fuel cell, is constructed from two half cells 4, 5, between which a membrane 6 is arranged. Instead of a membrane 6, a separator can also be arranged at a corresponding position.

[0028] In the present case, the bipolar plate 2 has an embossed structure, denoted by 7, which is Figure 1 In the example indicated. Alternatively, bipolar plates without embossed structures, ie flat plates without shaped elements, can be used. Figure 1 Frames 8 can be seen in FIG. 1 , which are arranged between bipolar plates 2 which are arranged parallel to one another and are often also referred to as plates.

[0029] Seals 9 are mounted on the end faces of each plate 2, 8 made of metal, in particular stainless steel or titanium, or plastic. The end faces of the plates 2, 8, generally indicated by 10, establish a connection between the upper side 11 and the lower side 12 of the plates 2, 8, and the use of the terms "upper side" and "lower side" does not imply any statement about the actual orientation of the plates 2, 8 in space.

[0030] In an exemplary embodiment, the plate 2 ( Figure 1 , Figure 2 , Figure 4 , Figure 5 and Figure 6 ) is a metal plate, and the frame 8 of the battery stack 1 is also mainly made of metal. Alternatively, the frame 8 can be designed as a plastic component. Figure 3 The plastic insert 25, which is outlined in the figure and has a rectangular basic shape in this case, also constitutes a plate provided for installation in the battery stack 1. As can be seen from the figure, the seal 9 can be arranged on the outer edge of the plate 2, 8, 25 or on the edge of the recess 13, 14 provided in the plate 2, 8, 25.

[0031] Figure 4 and Figure 5 Different design options are shown for the seals 9, each of which covers an end face 10 of a plate 2. Figure 4 In the case of the plate 2, the plate 2 is profiled on the end face 10 such that a step 15 is formed towards the upper side 11 and towards the lower side 12. Figure 4 The one shown in FIG has a circular basic shape in cross section, i.e. the shape of an O-ring seal, and extends over the step 15, but does not exceed the wall thickness of the plate 2 to contact the upper side 11 and the lower side 12. This means that the plate 2 slightly penetrates the seal 9 at the end face.

[0032] In contrast, according to Figure 5 In the design according to , the plate 2 has no contour on the end face, and the seal 9 only contacts the end face 10 due to the wall thickness and is held integrally on the end face. Figure 4 Variations and bases Figure 5 In both variants, the diameter of the seal 9 is significantly greater than the wall thickness of the plate 2 due to the spherical cross-sectional shape.

[0033] Figure 6 The diagram shows the Figure 4 The invention relates to a method for mounting a seal 9 on a plate 2. The production facility for this purpose is generally indicated by 16. In a first step, the plate 2 is cut by means of a laser 17 in order to produce an end face 10. The end face 10 is then roughened by means of a particle blasting device 18. The particle blasting device 18 emits, for example, metal particles, in particular in the form of steel balls, and comprises, among other things, a compressed air supply 19 and a shut-off valve 20.

[0034] 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, which shape can be Figure 4 After the plate 2 together with the seal 9 has been removed from the injection molding tool 21 , the plate 2 can in the present case be installed in the cell stack 1 , ie in the electrolysis system.

[0035] exist Figure 7 and Figure 8 In the embodiments outlined in , 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 of which forms a sealing lip 9a and which are connected to each other by a bridge 28. The function of the sealing lip 9a is thus fulfilled by the thickened portions 26, 27, which are connected to each other by a bridge 28. Figure 7 In the case of having a square cross-section inclined at 45 degrees relative to the plane in which the plate 8 lies, and Figure 8 The case has a circular cross section. Fig. 9 , four truncated cone-shaped thickened portions 26, 27 are arranged adjacent to one another and form four sealing lips 9a. Instead of truncated cone-shaped thickened portions 26, 27, truncated pyramid-shaped thickened portions having a rectangular basic shape of a pyramid can also be used here. Figures 7 to 9 In all cases, one of the thickened portions 26, 27 is integrally connected to the end face 10 of the plate 8, with the Figure 1 and Figure 5 The implementation method is similar.

[0036] Reference numerals list

[0037] 1 Stack of electrochemical cells

[0038] 2 plates, bipolar plates

[0039] 3 Electrochemical cells

[0040] 4 Half-cell

[0041] 5 Half Cell

[0042] 6 Membrane

[0043] 7 Imprinted structure

[0044] 8 boards, frame

[0045] 9 Seals

[0046] 9a Sealing lip

[0047] 10 End face

[0048] 11 Upper side

[0049] 12 Lower side

[0050] 13 recess

[0051] 14 recess

[0052] 15 Steps

[0053] 16 Production Facilities

[0054] 17 Laser

[0055] 18 Particle injection device

[0056] 19 Compressed air supply

[0057] 20 Stop valve

[0058] 21 Injection molding tools

[0059] 22 Tools section

[0060] 23 Tools section

[0061] 24 chambers

[0062] 25 Plates, plastic inserts

[0063] 26 Thickening part

[0064] 27 Thickening part

[0065] 28 Bridge piece.

Claims

1. A plate (2, 8, 25) of a stack (1) of electrochemical cells (3), the plate having an upper side (11), a lower side (12) and at least one end face (10), wherein: A strip-type seal (9) having at least one sealing lip (9a) is integrally mounted only on at least one of the end faces (10).

2. The plate (2, 8, 25) according to claim 1, characterized in that The seal (9) is arranged circumferentially on the edge of the recess (13, 14) in the plate (2, 8, 25).

3. A plate (2, 8, 25) according to claim 1 or 2, characterized in that The plates are made of metal or plastic.

4. A plate (2, 8, 25) according to any one of claims 1 to 3, characterised in that The plate has two or more sealing lips (9a).

5. The plate (2, 8, 25) according to any 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.

6. A plate (2, 8, 25) according to any one of claims 1 to 4, characterised in that The seal (9) is designed as a flat or shaped seal.

7. A plate (2, 8, 25) according to any one of claims 1 to 6, characterised in that At least one of the end faces (10) is designed in a contoured manner.

8. The plate (2, 8, 25) according to claim 7, characterized in that The sealing member (9) covers a step portion (15) formed on the end surface (10) toward the upper side portion (11) and / or the lower side portion (12).

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

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 blasting before the seal (9) is molded onto the at least one end face.

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