CN106463738B

CN106463738B - Metallic bipolar plate and electrochemical system with elastomeric seal assembly

Info

Publication number: CN106463738B
Application number: CN201580026703.4A
Authority: CN
Inventors: B·高格勒; A·欧鲁克
Original assignee: Rheinz Gasket Co Ltd
Current assignee: Rheinz Gasket Co Ltd
Priority date: 2014-05-23
Filing date: 2015-05-22
Publication date: 2020-01-10
Anticipated expiration: 2035-05-22
Also published as: CA2949586C; DE112015002427T5; CA2949586A1; WO2015177365A1; DE202014004456U1; CN106463738A; WO2015177365A8

Abstract

The present subject matter relates to a metallic bipolar plate (9) for an electrochemical system (1), comprising an elastic sealing assembly (11) with at least one bead (20) extending in a direction parallel to the plate plane of the bipolar plate (9); wherein the flange members (20) perpendicular to the trajectory (course) of the flange members (20) each comprise an M-shaped cross-section with lateral projections (30a,30b) and recesses (31) formed between the lateral projections (30a,30 b); wherein the lateral protrusions (30a,30b) comprise inner side faces (38a,38b) directed towards the groove (31), the inner side faces (38a,38b) having a side height (t1) extending perpendicularly to the plate plane from a vertex (35) of the groove (31), which is the deepest point of the groove (31), to a top (32a,32b) of each lateral protrusion (30a,30b), which is the highest point of the lateral protrusion (30a,30 b); and wherein the groove (31) is filled with an elastomer (21); wherein the elastomer body (21) of the entire track of the bead (20) perpendicular to the plate plane is higher than the tops (32a,32b) of the lateral projections (30a,30b) and the elastomer body (21) of the entire track of the bead (20) along the apex (35) of the groove (31) of the M-shaped cross-section of the bead (20) and at least over 50% of the side height (t1) reaches and covers the inner side faces (38a,38b) of the lateral projections (30a,30b), so that during a compression of the bipolar plate (9) perpendicular to the plate plane, the compression force applied to the elastomer body (21) is guided into the bead (20) by the elastomer body (21). Further, the present subject matter also relates to electrochemical systems.

Description

Metallic bipolar plate and electrochemical system with elastomeric seal assembly

Technical Field

The present invention relates to a metallic bipolar plate with an elastomeric seal assembly, and an electrochemical system having a plurality of such bipolar plates.

Background

Known electrochemical systems, such as fuel cell systems or electrochemical compression systems (e.g., electrolyzers), typically include a stack of electrochemical cells separated from each other by bipolar plates. Such bipolar plates may be used, for example, for electrical contact between the electrodes of individual electrochemical cells (e.g., fuel cells), and/or for electrical connection of adjacent cells, such as a series connection of cells. The bipolar plate may also comprise or form a channel structure, which is formed to supply one or more media to the cell and/or to remove reaction products. The medium may be, for example, a fuel such as hydrogen or methanol and a reactant gas such as air, oxygen or a coolant. Such channel structures are typically arranged in the electrochemically active area and thus in the gas distribution structure (also called flow field). Further, the bipolar plates may be designed for conducting heat generated during the conversion of electrical or chemical energy in an electrochemical cell, and for sealing the different media or coolant channels from each other and/or from the outside. Typically, the bipolar plates of the stack include mutually aligned via openings. Which then form channels in which media and/or reaction products can be directed to or removed from the electrochemical cells between adjacent bipolar plates of the stack. The electrochemical cells may, for example, each comprise one or more membrane-electrode assemblies, abbreviated to MEA, having a polymer-electrolyte membrane, abbreviated to PEM. The MEA may include one or more gas diffusion layers that are generally oriented toward the bipolar plates and may take the form of, for example, metal or carbon felts.

With regard to the sealing of the mentioned passage openings in the bipolar plates in the stack and/or the sealing of the channel structures in the electrochemically active regions, known bipolar plates comprise a sealing assembly with at least one bead extending parallel to the plate plane of the bipolar plate. In order to reduce the material and weight of the system, the flange members used have as little material strength or material thickness as possible. During assembly of the stack, the flange members are compressed in a first step. In a second step, compression and relaxation of the flange members occurs during operation of the bipolar stack. However, known flange members of the type described have a great limit when relaxed. This is why the bipolar plates in the stack are often irreversibly plastically deformed during their compression, in particular during the assembly of the stack. Bipolar plates generally have a longer life expectancy than polymer-electrolyte membranes or MEAs. Thus, the used bipolar plate can be assembled with a new MEA. Existing bipolar plates can usually only be reused to a very limited extent with new MEAs in a stack of other bipolar plates, whose sealing function is not satisfactory due to plastic deformation.

It is therefore an object of the present invention to provide a bipolar plate with a seal based on a bead having better spring properties and as little material strength as possible, while ensuring the sealing properties as well as possible.

This object is solved by a metallic bipolar plate with a sealing assembly. Specific embodiments are shown below.

Disclosure of Invention

To this end, a metallic bipolar plate for an electrochemical system is proposed, which comprises an elastic sealing assembly with at least one bead extending parallel to the plate plane of the bipolar plate;

wherein, in a direction perpendicular to the extending direction of each flange member, the flange member includes an M-shaped cross section having lateral projections and a groove formed between the two lateral projections;

wherein the transverse protrusions have inner side faces facing the grooves, the side heights of the inner side faces are perpendicular to the plate plane and extend from the top points of the grooves to the top points of the transverse protrusions, the top points are the deepest points of the grooves, the top points are the highest points of the transverse protrusions, and

wherein the grooves are filled with an elastomer.

In contrast to the known bipolar plates of the type mentioned above, the bipolar plate is characterized in that the elastomer extends perpendicularly to the plate plane and over the top point of the transverse projections in the entire extension direction of the bead, and that the elastomer on the entire course of the bead, starting from the top point of the groove of the M-shaped cross section of the bead and at least 50% of the height of the flank, reaches the inner flanks of the longitudinal projections and covers them, so that during compression of the bipolar plate perpendicularly to the plate plane, the pressure applied to the elastomer is introduced into the bead via the elastomer.

Further, electrochemical systems, in particular fuel cell stacks or electrolysers, having a plurality of metallic bipolar plates of the above-mentioned type and a plurality of electrochemical cells arranged between the bipolar plates, respectively, are proposed. In the electrochemical system, the bipolar plate and the electrochemical cell are stacked in the stacking direction, and mechanical pressure in the stacking direction may be applied or mechanical pressure in the stacking direction may be applied.

The elastomer bodies are thus each along a portion of the inner side corresponding to at least 50% of the side height of the respective inner side, the elastomer bodies being in direct contact with the inner side, i.e. along a section perpendicular to the respective track of the flange part and on both sides of the groove apex at the groove bottom. The inner side surface preferably extends from the apex of the groove to the apex of each lateral projection. The two inner sides of this form preferably comprise the bottom of the groove and the sides of the groove.

The extent of the seal assembly and the flange member trace may be expressed with reference to the centerline of the flange member, respectively, and the same applies to the flange member, extending parallel to the plane of the plate. If it is mentioned that a cross section of the flange member at a particular position along the trace of the flange member is oriented perpendicularly with respect to the trace of the flange member, it preferably means that the cross section intersects tangentially at various positions on the centerline of the flange member. Therefore, the cross-section is preferably oriented perpendicularly with respect to the plane of the plate. The terms "section of the seal assembly", "section of the flange member" or "section" herein, if not otherwise stated, refer to a section along the plane of the plate, oriented perpendicular to the respective traces of the plane and perpendicular to the plane of the plate, respectively.

The cross-sectional geometry of the flange member may remain the same throughout the trace, but may also vary. For example, the inclination of the side of the flange part in the region remote from the bolt position can be greater than the inclination in the region close to the bolt position, in order to achieve a regular (regular) force introduction. The side of the flange member remote from the bolt hole area may also be smaller and/or higher than the side closer to the bolt hole area. Likewise, the flange members of the curved regions may be lower or wider, or have more gradual sides, than the linearly extending regions. If the geometry of the projections of the flange member varies along its trajectory, the cross-section of the elastomer body may vary as well as the flange member, or to a different extent, or remain the same.

In the region of the flange member having a constant direction of extension in macroscopic viewing, it may also extend in a macroscopically straight line, but may also alternate around the direction of extension and extend in a wavy shape in top viewing. The last variant with a similar cross-sectional geometry can lead to a higher stiffness.

The plate plane of the bipolar plate is then also referred to as the x-y plane. The direction in which bipolar plates in an electrochemical system with a plurality of such bipolar plates can be stacked or the stacked stacking direction is also referred to hereinafter as the z-direction. The x-, y-, and z-directions of this form the axes of a right-handed cartesian coordinate system. The height of the flange member therefore extends generally in the z-direction.

Since the cross-section of the flange has an M-shaped geometry, particularly in the z-direction, at least one of the two properties, stiffness and resilience, of the flange is improved without significantly compromising the other property. Since the elastomer on the entire track of the flange element projects perpendicularly to the plate plane over the entire plate plane track of the flange element and beyond the top of the transverse projection, and the elastomer on the entire track of the flange element, starting from the apex of the groove of the M-shaped cross-section of the flange element and at least over 50% of the height of the side face, reaches the inner side face of the longitudinal projection and covers said inner side face, the elastomer is configured or fixed sufficiently stably in the groove at the top of the flange element so that it does not deviate in the transverse direction, meaning that it is perpendicular to the individual tracks of the flange element and parallel to and outwardly of the x-y plane so that it does not flow away. Thereby avoiding creep of the elastomer during compression of the bipolar plate.

In the process of compressing the bipolar plate along the z direction, the flange part can be elastically deformed, namely reversely deformed; thereby, for example, the width of the groove at the top of the flange perpendicular to the flange trace is reduced. The elastomer body may then be compressed during deformation of the flange member, for example in a direction perpendicular to the respective tracks of the flange member. Thereby, plastic deformation, i.e., irreversible deformation, of the flange member can be prevented to the maximum extent. When the bead is relieved of load again, for example during removal of the bipolar plate from the stack, the elastomer generally returns to its original uncompressed shape and thereby causes a favorable spring back of the bead. Thereby, the characteristic curve of the flange member can be adjusted by the hardness or elasticity of the elastomer used, thereby adjusting the elastic deformation (mm) depending on the compression force per unit length (N/mm) applied to the flange member along the trace of the flange member. The sealing effect of the sealing assembly of the bipolar plate compressed in the stack is also improved due to the enhanced resilience.

By having the elastomer, along the entire trajectory of the bead, starting from the apex of the groove of the M-shaped cross section of the bead and reaching the inner side of the lateral projection and covering at least 80% of the height of the side of said inner side, it is possible to fix the elastomer in particular in the depression at the top of the bead, to introduce in particular a force for compressing the bipolar plate perpendicular to the plate plane into the bead, and to increase the rigidity of the seal assembly.

The stiffness and resilience properties of the seal assembly can be set and controlled in particular if the elastomer fills the groove of the M-shaped cross-section of the flange and covers everywhere over the entire side height, practically preferably along the trace of the flange. This includes that the region defined in cross section and thus perpendicularly to the respective course of the flange element, which is enclosed by the inner side of the transverse projection and the straight line connecting the two vertices of the transverse projection, is in each case completely filled with elastomer. In other words, the recess is void-free below the line, i.e. between the line and the plane of the plate.

The elastomer of the M-shaped cross-section along a part of the bead extends from the apex of the first transverse projection to the apex of the second transverse projection, projects perpendicularly to the plate plane and beyond the apex of the curved transverse projection, preferably over the entire course of the bead, whereby a compressive force applied to the bead can be introduced particularly regularly during compression of the bipolar plate in the z-direction. With respect to the predefined straight line, which is defined by the two vertices of the lateral projection of the flange member, this means that the elastomer body protrudes continuously in the z-direction and above the straight line. Whereby the outer side or surface of the resilient body extending from the apex of the first transverse projection to the apex of the second transverse projection and facing away from the flange member may continue to curve and bulge outwardly to extend in a direction away from the apex of the groove.

If the elastomer does not completely cover the inner side faces, it still rises from the interface with one of these inner side faces towards the perpendicular through the apex of the groove and falls again on the other side of the perpendicular through the apex of the groove. The rise and fall here are preferably continuous, but in the region of the perpendicular through the apex of the groove, a platform without height variations can also be formed.

If the flange member extends linearly, the seal assembly in its cross-section is typically mirror-symmetrical or substantially mirror-symmetrical with respect to an axis of symmetry of the seal assembly. The axis of symmetry extends generally into the respective cross-section and perpendicular to the plane of the plate and intersects the apex of the groove. This strict symmetry is deviated if the flange member extends non-linearly, for example forming a corner, or if it extends substantially in a wave shape.

The height of the elastomer body measured in the z-direction may reach a maximum at the centre or middle part of the flange member along its cross-section and decrease monotonically towards the lateral projection of the flange member. The elastomer of the central portion is then the furthest distance in the z-direction beyond the laterally projecting portion of the flange member. This is consistent with the elastomer also having a maximum thickness in the region where it extends the furthest distance relative to the projection of the metal flange member.

To improve the resilient properties of the seal assembly, the elastomer may be compressible. The elastomer may be a thermoplastic elastomer, a fluoropolymer, such as a fluoropolymer rubber, a perfluororubber, a perfluoro-alkoxy polymer, a butadiene rubber, an acrylonitrile-butadiene rubber, a styrene-butadiene rubber, a hydrated acrylonitrile-butadiene rubber, an ethylene-propylene-diene rubber, an ethylene-propylene rubber, a silicone rubber, a fluorosilicone rubber, a polyacrylate rubber, an ethylene-acrylate rubber, or a polyurethane, or one or more of the foregoing materials. The elastomer may be applied to the groove of the flange member using a screen printing method.

The seal assembly provides sufficient resiliency even with a small thickness of material of the flange member. The material thickness of the flange part can therefore be less than 0.15mm, preferably less than 0.1mm, particularly advantageously less than 0.08 mm. Therefore, for the same number of plates or fuel cells, a smaller build height is required in the fuel cell stack. Thereby, material cost and weight can be reduced. Alternatively, a stack with more individual cells can be constructed with a constant construction height.

Typically, the depth of the flange member recess is less than the height of the flange member lateral projection. The grooves in the z-direction do not usually reach the plane of the plate. In this case, then, there is a distance between the groove apex and the plate plane. This can also help to increase the spring back properties of the seal assembly because during compression of the pocket area of the bipolar plate in the z-axis direction toward the plane of the plate, the bead can spring back and not push up into the pocket area. The plate plane can be defined, for example, by a straight portion of the bipolar plate which adjoins the outer side of the bead transverse projection and faces away from the bead groove. Typically, the distance between the apex of the groove and the plane of the plate is no more than 50%, preferably no more than 40%, of the height of the flange member from the top of the lateral projection of the flange member in the z-direction to the plane of the plate.

In order to adequately fix the elastomer body in the recess of the flange part, it is advantageous if the lateral height of the inner lateral surface of the lateral projection of the flange part corresponds to at least 15%, preferably at least 20%, particularly preferably at least 30%, of the height of the flange part. The flange height is typically less than 0.7mm, preferably less than 0.55 mm.

In order to increase the resilience of the seal assembly, the laterally projecting outer side of the flange member is inclined only slightly away from the groove. The angle between the outer side and the z-direction along the cross-section of the flange part may be, for example, at least 30 °, preferably at least 45 °, particularly preferably at least 50 °.

The cross section of the transverse projection of the flange element preferably exhibits a bulge away from the plane of the plate, which connects the inner side of the transverse projection with the outer side of the transverse projection in each case. The resilient properties of the seal assembly may also be improved if the radius of curvature of the ridge is at least 6%, preferably at least 9%, of the width between the bottom corners of the flange member. The width between the bottom corners of the flange member is for example less than 3mm, preferably less than 2.5 mm.

Further, to improve the resiliency of the seal assembly, the flange member may be curved along a cross-section of the flange member in the region of the groove, at least partially, or at least at a center or middle portion of the cross-section of the flange member. The radius of curvature of the curve in this region of the groove is for example less than 50%, preferably less than 40%, relative to the width between the two bottom corners of the flange member. The cross-section of the flange member in the region of the recess may also be wavy in order to increase the rigidity of the seal assembly.

In order to form the channels for the liquid and/or gaseous medium, the bipolar plate can comprise one or more channel openings perpendicular to the plane of the plate. In an electrochemical system having a plurality of bipolar plates as described herein, the passage openings of adjacent bipolar plates are, for example, arranged at least partially in alignment to form one or more channels for the supply and/or removal of liquid and/or gaseous media. These channels then typically extend in the stacking direction through the stack of plates, or through the entire electrochemical system. The sealing assembly of the bipolar plate may then be configured such that it radially surrounds the opening of the bipolar plate and seals off from the surroundings and/or from the interior of the electrochemical system. The sealing assembly of the bipolar plate may be at least partially designed in the form of an electrochemically active area of an electrochemical cell for sealing the system.

In order to form a guide path for the liquid and/or gaseous medium through the flange member, in particular a path perpendicular to the track of the flange member, the outer side of the flange member may comprise one or more through-going locations or perforations. The liquid and/or gaseous medium can be conducted to the electroactive areas of the electrochemical cell, for example adjacent to the bipolar plates, or transported away from the cell through these through-going locations.

The bipolar plate may comprise two partial plates which are arranged parallel to one another and which are mechanically connected to one another. The partial plates serve, for example, for contacting the electrodes of two adjacent electrochemical cells of an electrochemical system, which are each arranged on different sides of the bipolar plate. The flange member of the seal assembly may then be formed integrally with the partial plate. In this case the flange member is formed by the respective partial plate itself.

In a particular embodiment, the first partial plate may comprise a first sealing assembly of the type described, and the first flange member and the first partial plate form one piece. The second part plate in this embodiment thus comprises a second sealing assembly and a second flange part of the kind described, wherein the second flange part and the second part plate also form one piece. The first partial flange of the first partial flange and the second partial flange of the second partial plate can then enclose a cavity for conducting a liquid and/or gaseous medium between the first and the second flange.

The two partial plates of the bipolar plate are joined to one another at least outside the bead. Preferably, a continuous weld seam, in particular a laser weld seam, is used to connect the two partial plates. In particular, if the flange piece is also used for conducting a liquid and/or gaseous medium, it is preferred to arrange a continuous weld seam on both sides of the flange piece. Alternatively, nail welds or spot welds may be used. Thus, the weld is preferably located at the bottom corner region of the flange member or away from the flange member so as to be adjacent to the bottom corner of the flange member.

Drawings

Embodiments of the invention are illustrated in the drawings and will be further explained using the description that follows. It is shown in:

FIG. 1 is a schematic perspective view of an electrochemical system having a plurality of bipolar plates and an electrochemical cell disposed between the bipolar plates;

FIG. 2 is a schematic top view of one of the bipolar plates of the electrochemical system depicted in FIG. 1;

FIG. 3 is a schematic view of two adjacent bipolar plates and an electrochemical cell disposed between the bipolar plates of an electrochemical system similar to that of FIG. 1;

FIG. 4 is a schematic cross-sectional view of a first embodiment of a seal assembly according to the present invention;

FIG. 5a is a schematic view of the seal assembly of FIG. 4 in an unloaded state;

FIG. 5b is a schematic view of the seal assembly of FIG. 4 under load;

FIG. 6 is a schematic cross-sectional view of a second embodiment of a seal assembly according to the present invention;

FIG. 7 is a schematic cross-sectional view of a third embodiment of a seal assembly according to the present invention;

FIG. 8 is a schematic cross-sectional view of a fourth embodiment of a seal assembly according to the present invention;

figure 9 is a schematic view of a bipolar plate and a seal assembly for sealing the passage openings in the bipolar plate according to the present invention;

figure 10 is a schematic view of a bipolar plate and a seal assembly for sealing the passage openings in the bipolar plate according to the invention, wherein the outer side of the flange of the seal assembly comprises perforations for conducting a liquid and/or gaseous medium.

Fig. 11 shows a bipolar plate according to the invention with a first and a second partial plate, wherein a first bead of the first partial plate and a second bead of the second partial plate enclose a cavity for guiding a gaseous and/or liquid medium;

figure 12 is a comparison of the load-deflection curves of a bead of a bipolar plate according to the present invention and a bead of a bipolar plate according to the prior art; and

fig. 13 is an explanatory cross section of fig. 12.

Detailed Description

Fig. 1 shows an electrochemical system 1 comprising hydrogen fuel cells electrically connected in series. In an alternative embodiment, the system 1 may also be an electrochemical compressor or an electrolysis device. They do not differ from each other in structural design, but differ significantly in the generation or supply of fluids and electrical energy directed to and from the MEA.

The electrochemical system 1 comprises a stack 2 having a plurality of metallic bipolar plates and electrochemical cells each arranged between adjacent bipolar plates for converting chemical energy into electrical energy. The cells are connected in series. The bipolar plates and cells of the stack are stacked in the z-direction 5 and arranged between the

end plates

3 and 4. The plate planes of the bipolar plates of the stack 2 are arranged parallel to the x-y plane, respectively. The x-direction 6 and the y-direction 7 together with the z-direction form a right-handed cartesian coordinate system. The bipolar plates and the cells of the stack 2 are mechanically pressed and held together by the

end plates

3 and 4 in the z-direction 5, for example using screws or bolts not shown here.

The end plate 4 comprises a plurality of ports 8 through which liquid and/or gaseous medium can be supplied to the electrochemical system 1 and/or removed from the electrochemical system 1. For example, a fuel (e.g., hydrogen) and a reactant gas (e.g., oxygen) may be supplied to the system 1 through the port 8. Further, the reaction products (e.g., water and air), reduced oxygen species, and heated coolant may be exhausted from the system 1.

Figure 2 shows a top view of a metallic bipolar plate 9 of the stack 2 of figure 1, said bipolar plate being oriented parallel to the x-y plane. The bipolar plate 9 comprises two mechanically connected

partial plates

9a and 9b, of which only the first partial plate 9a is shown in fig. 2, the second partial plate 9b being covered. The bipolar plate 9 includes via openings 10 a-h. The remaining bipolar plates in the stack 2 of the electrochemical system 1 in fig. 1 have via openings corresponding to the via openings 10a-h of the bipolar plate 9. These passage openings of the bipolar plates of the stack 2 of the system 1 in fig. 1 are aligned in the z-direction, so that conduits for conducting the above-mentioned liquid and/or gaseous medium are formed. These conduits then extend perpendicular to the plate planes of the bipolar plates and through the stack 2 of the system 1. The conduit is in fluid communication with a port 8 of the end plate 4 of the system 1.

The partial plates 9a of the bipolar plate 9 also comprise an elastic sealing assembly 11 which extends parallel to the plate plane of the bipolar plate 9, so as to be shown parallel to the x-y plane in fig. 2. Here and hereinafter, the same numerical references are used to denote repetitive features. The seal assembly is formed to seal the region 28 from the environment of the system 1. The seal assembly 11 forms a closed arc and completely encloses the region 28. Here the sealing assembly extends along the oval passage opening and has an oval basic shape. In this case, the extension region thereof does not extend straight but undulates back and forth to provide a substantially constant stiffness to the entire trace of the flange member. In a central rectangular partial region 29 of the region 28, the partial plate 9a comprises a plurality of projections which project perpendicularly to the plate plane. A partial region 29 is formed between adjacent

bipolar plates

9 and 13 of the stack 2 to accommodate the electrochemical cell 14, as shown in figure 3. Here, the electrochemical cell 14 is a bipolar plate for converting chemical energy into electrical energy. The channels formed between the projections of the subregion 29 serve to deliver a fuel or reactant gas supply to the electrochemically active regions of the electrochemical cells 14 disposed in the subregion 29 between the

bipolar plates

9 and 13, as shown in figure 3.

In addition to the sealing assembly 11, the partial plate 9a of the bipolar plate 9 comprises a plurality of further elastic sealing assemblies 12a-h, which each serve to seal the channel formed by the passage openings 10a-h from the area 28 or from the environment of the system 1. The sealing assemblies 12a-h each also extend parallel to the plate plane of the bipolar plate 9, form separate (self-contained) tracks, and completely radially enclose the passage openings 10a-h of the bipolar plate 9. The sealing assemblies 11 and 12a-h each project from the partial plate 9a perpendicularly to the plate plane of the partial plate 9 a. The features of the elastomeric seal assemblies 11 and 12a-h will be further described below.

Figure 3 shows a cross-section in the y-z plane of a stack 1 similar to that of figure 1. FIG. 3 shows a view similar to

The bipolar plate 9 of the bipolar plate 9 in fig. 2, which has metal part-

plates

9a and 9b, the second bipolar plate 13 in the stack 2 is adjacent to the first bipolar plate 9. The

bipolar plates

9 and 13 have the same structure. The bipolar plate 13 also comprises two mechanically connected metal part-

plates

13a and 13 b. The

partial plates

9a,9b, 13a, 13b are each made of stainless steel and the material thickness perpendicular to the plate plane is 0.075 mm. In the partial region 29, the aforementioned electrochemical cells 14 are arranged between adjacent

bipolar plates

9 and 13. Electrochemical cell 14 includes an electrolyte membrane 15, an anode 16, a cathode 17, and gas diffusion layers 18 and 19. Electrically conductive gas diffusion membranes 18 and 19 are arranged between the electrode 16 and the bipolar plate 9 and between the

bipolar plates

9,13, respectively.

Fig. 3 shows a section through the sealing element 11 of the partial plate 9 a. The seal assembly 11 includes a metal flange member 20 and an elastomer 21. The flange 20 of the bipolar plate 9 and the partial plate 9a form one piece. The bead 20 extends parallel to the plate plane of the bipolar plate 9 and rises perpendicularly from the plate plane of the bipolar plate 9. As shown in fig. 3, the flange member 20 extends in the x-direction 6 perpendicularly to the plane of the picture and the picture is perpendicular to its direction of extension, so as to have an M-shaped cross section on the picture of fig. 3, i.e. on the y-z plane, with lateral protrusions and grooves formed between the lateral protrusions, which are filled with an elastic body 21, as shown in fig. 4.

The second partial plate 9b of the bipolar plate 9 comprises a sealing arrangement 22 of the same construction as the sealing arrangement 11 of the first partial plate 9a, said arrangement 22 having a metal collar 24 and an elastomer 25, and the sealing arrangement 22 extends parallel to the plate plane of the bipolar plate 9, identical to the sealing arrangement 11. The flange member 24 and the second partial plate 9a are formed as one piece. The sealing

assemblies

11 and 22 project away from the respective bipolar plate 9 in opposite directions perpendicular to the plate plane of the bipolar plate 9. In this respect, the

seal assemblies

11 and 22 are designed in the following manner: the cavity 26 formed between the

seal assemblies

11 and 22 is also suitable as a conduit or passage for one of said gaseous and/or liquid media.

The cavity 26 formed by the

flange members

20 and 24 between the

partial plates

9a and 9b is sealed transversely (thus in the y-direction in fig. 3) by

weld lines

27a and 27b which extend continuously along the

flange members

20 and 24.

Bipolar plate 13 includes a seal assembly 52 having the same construction as seal assembly 11 of bipolar plate 9. To seal the region 28 between the

bipolar plates

9 and 13, the

seal assemblies

11 and 52 cooperate to enclose the electrolyte membrane 15 of the cell 14 between them and face against the membrane 15.

Fig. 4 schematically shows a detailed cross-sectional view of the sealing assembly 11 of the partial plate 9 a. The cross-section is oriented along a plane perpendicular to the plate plane of the bipolar plate 9 or of a part 9a thereof and perpendicular to the trajectory of the seal assembly 11, i.e. in the region where there are no flange-side perforations.

The cross section of the seal assembly in fig. 4 shows a metal flange member 20 having

lateral protrusions

30a and 30b and a groove 31 formed between the

lateral regions

30a and 30b, which is filled with an elastomer 21. At the tops 32a and 32b of the

transverse projections

30a and 30b, the maximum height t2 of the

transverse projections

30a and 30b is measured in the z direction 5 and perpendicular to the plate plane of the partial plate 9 a. The plate plane of the partial plate 9a is defined by

straight portions

33a and 33b of the partial plate 9b, which extend in the y-direction 7 and meet the flange members 20 at bottom corner points 34a and 34b of the flange members 20 on both sides of the flange members 20. At the apex 35 of the groove, the lowest height t1 of the flange member in the region of the groove 31 is measured perpendicular to the plane of the plate. The seal assembly 11 is symmetrical in its cross-section with respect to an axis of symmetry which extends perpendicular to the plane of the plate and intersects the flange member 20 at the apex 35 of the groove 31.

The flange member 20 has a flange member width b between its two bottom corners extending from a bottom corner point 34a parallel to the plate plane to a bottom corner point 34b with a length of 2.2 mm. The height t2 of the flange member 20 in the embodiment shown is 0.5 mm. The height of the apex 35 of the groove 31 is approximately 0.25mm and thus equal to 50% of the height t2 of the flange member. In various embodiments, the height t1 may also be less than 50% or less than 40% of the flange member height t 2. The apex therefore does not reach into the plane of the plate and is at a distance from the plane of the plate. Typically, the height t1 of the flange member 20 at the apex 35 of the groove 31 is equal to at least 20% or at least 30% of the flange member height t 2.

The

lateral projections

30a and 30b of the flange member 20 include

lateral sides

37a and 37b facing away from the groove 31, the lateral sides extending from the bottom corner point 34a to the top 32a and from the bottom corner point 34b to the top 32 b. In order to increase the resilience of the seal assembly 11, in particular perpendicular to the plane of the plate, the outer side faces 37a and 37b of the flange member 20 are designed in a flat form. Here, the angle between the outer side face and the z-direction extending perpendicular to the plate plane is, at least in some parts, greater than 30 °. The angle between the outer side face and the z direction is greater than 30 ° over at least 30% of the height t2 of the flange member.

The flange member 20 also includes inner side surfaces 38a and 38b facing the recess 31. The lateral projection medial side 38a extends from the top 32a of the lateral projection 30a to the apex 35 of the groove 31 and from the medial side 38b of the lateral projection 30b to the apex 35 of the groove 31. So that the inner side faces 38a and 38b form the bottom or base and the sides of the recess 31. The height t1 of the inner side surfaces 38a and 38b extends perpendicular to the plane of the plate from the plane of the apex 35 of the groove 31 to the plane of the tops 32a and 32b of the

lateral projections

30a and 30 b. The height t1 of the inner side surfaces 38a and 38b is also the depth of the groove 31. Here, the height t1 of the inner side surfaces 38a and 38b is equal to 50% of the flange member height t 2. In modified embodiments, the height t1 of the inner side surfaces 38 and 38b is preferably equal to at least 15%, at least 20%, or at least 30% of the flange member height t 2. This enables the elastomer body 21 to be secured in particular in the groove 31 of the bead 20, so that a deflection of the elastomer body 21 (in particular a deflection parallel to the plate plane and perpendicular to the individual tracks of the bead 20) or of the seal assembly 11 can be avoided as effectively as possible if, during the compression of the bipolar plate of the stack 2 (see fig. 1), a pressure acts on the seal assembly perpendicular to the plate plane of the bipolar plate or in the z direction 5.

In the example described here, the distance between the top 32a of the transverse projection 30a and the top 32b of the transverse projection 30b, measured parallel to the plate plane, is equal to 1 mm. The distance between the

top portions

32a and 32b parallel to the plane of the plate is thus approximately 45% of the width b between the bottom corners of the flange member 20. In a modified embodiment, the distance between the

top portions

32a and 32b parallel to the plane of the plate is preferably less than 50% of the width b between the bottom corners of the flange member 20.

In the region of the

top portions

32a and 32b, the

transverse projections

30a and 30b of the flange members each comprise a bulge facing away from the plane of the plate. The ridge of the flange member 20 in the region of the top portion 32a connects the outer side surface 37a of the lateral projection 30a with the inner side surface 38a, and the ridge of the flange member 20 in the region of the top portion 32b connects the outer side surface 37b of the lateral projection 30b with the inner side surface 38 b. In the region of the apex 35 of the groove, the flange piece comprises a bulge in the direction of the plane of the plate. This also has a positive effect on the resilience of the seal assembly 11. The groove 31 is then bent into the central part of the cross-section of the flange. The central curved portion of the flange member 20 here extends for a length of about 0.25 mm. The length of the curved portion of the flange member 20 in the region of the apex 35 of the groove 31 is then at least 10% of the width b between the two base corners of the flange member 20. In the example illustrated here, the central curved portion along the cross-section of the flange member is symmetrical with respect to the apex 35 of the groove 31. The radius of curvature (not explicitly indicated) of the flange member 20 in the region of the apex 35 of the groove 31 is 0.2 mm. In a modified embodiment, the radius of curvature of the flange member 20 in the region of the apex 35 of the groove 31 is preferably less than 50%, less than 40% or less than 30% of the width b between the two base corners of the flange member 20.

The elastomer 21 is a compressible elastomer, such as a silicon-based elastomer. The elastomer 21 is printed on the surface of the recess 31 in the top of the flange, here in particular using a screen printing method. The elastomer 21 fills the groove 31 of the flange member 20 along the entire trace of the seal assembly shown in fig. 2. In particular, the elastomer body 21 fills the surface 39 completely along the flange section, said surface 39 being defined by the inner lateral surfaces 38a and 38b of the

lateral projections

30a and 30b and by the straight line connecting the

top portions

32a and 32 b. The resilient body 21 thus extends from the apex 35 of the recess 31 and over the entire height t1 of the inner side surfaces 38a and 38b of the

lateral projections

30a and 30b, covering the inner side surfaces 38a and 38 b. In other words, the elastic body 21 is in direct contact with the inner side faces 38a and 38b, which, starting from the apex 35 of the groove 31 and going up to the tops 32a and 32b of the

lateral projections

30a and 30b, completely cover the inner side faces 38a and 38 b. This helps to secure the elastomer in the groove 31 and to regularly introduce compressive forces acting on the sealing system 11 into the flange member 20 during compression of the stack 2 perpendicularly with respect to the plane of the plate, thereby preventing lateral deflection and creep of the elastomer 21 during compression of the stack 2. In the example shown in fig. 2, this effect is achieved along the entire sealing curve of the sealing assembly 11, even in the region where the flange

outer sides

37a and 37b have perforations 50.

In a modified embodiment, the resilient body 21, starting from the apex 35 of the groove and projecting to at least 50% or at least 80% of the height t1 of the inner side faces 38a and 38b, is in direct contact with the inner side faces 38a and 38b and completely covers the inner side faces 38a and 38b, respectively, in this portion. This effect can also be achieved along the entire hermetic trace of the seal assembly shown in fig. 2. Fig. 8 shows a modified embodiment of such a sealing assembly 11, in which the elastomer extends over 85% of the height t1, directly to the inner side faces 38a and 38b and completely covers the inner side faces 38a and 38b in this section, respectively. In the 15% portion of the uppermost portion of the height t1, the medial side is exposed.

Furthermore, the elastomer body 21 projects perpendicularly to the plate plane of the bipolar plate 9 or of the partial plate 9a and, in practice, along the entire sealing curve of the seal assembly 11 shown in fig. 2, beyond the

tips

32a and 32b of the

transverse projections

30a and 30 b. In particular, the elastomer body 21 projects perpendicularly to the plate plane of the bipolar plate 9 or of the partial plate 9a and over the

top sections

32a and 32b in the entire cross section, wherein the entire section is the section extending in the cross section from the top section 32a of the transverse projection 30a to the top section 32b of the transverse projection 30 b. At the top 42 of the elastomer body 21 (the highest point of the elastomer body 21 with respect to the plate plane of the partial plate 9a), the elastomer body projects perpendicularly to the plate plane and over the top 32a and 32b by a height h. The height h here is 0.05 mm. Thus, the height of the elastomer beyond the flange member 20 is here at least 10% of the flange member height t 2. The top 42 of the elastomer 21 is located on the axis of symmetry 36. The elastomer then reaches a maximum height in the central part of the cross-section of the flange.

The maximum thickness of the elastomer body 21, measured perpendicular to the plane of the plate, along the axis of symmetry 36 of the seal assembly 11 or the flange member 20, is 43mm, which here is about 50% of the height t2 of the flange member. In varying embodiments, the maximum thickness 43 of the resilient body 21 is equal to at least 10% or at least 30% of the flange member height t 2. The thickness of the elastomer decreases monotonically, preferably continuously and/or strictly monotonically, in cross-section from the top 42 of the elastomer 21 to the

sides

38a and 38b of the

lateral projections

30a and 30 b.

Along the portion 41, the outer surface of the elastic body 21 facing away from the flange member 20 is continuously curved and bulges outward, facing away from the plate plane. The radius of curvature of the outer surface of the elastomer body 21 in the region of the top 42 of the elastomer body (said radius not being explicitly shown here) amounts in this case to 0.3mm and is thus at least 50% of the width b between the two bottom corners of the flange part 20. This also contributes to a particular pressure guidance towards the flange part 20.

Fig. 5a again shows a cross section of the elastic sealing assembly 11 shown in fig. 4, i.e. in an unloaded state, in which no pressure is acting on the sealing assembly 11. This state is, for example, the case before the bipolar plate 9 and the seal assembly 11 are mounted to the stack 2 (refer to fig. 1), to which pressure is to be applied in the z direction 5.

Fig. 5b shows the elastic sealing arrangement 11 of fig. 4 and 5a again in cross section, but in this case in a loaded state, in which a pressure acts on the sealing arrangement perpendicular to the plate plane of the bipolar plate 9 and is conducted through the elastomer body 21 into the flange 20. This state is then, for example, the case when the bipolar plate 9 and the seal assembly 11 are mounted to the stack 2 of the electrochemical system 1, with the pressure acting in the stacking direction. Fig. 5b thus shows, for example, the situation schematically illustrated in fig. 3, in which the sealing assembly is pressed against the electrolyte membrane 15 and between the

bipolar plates

9 and 13 to seal the region 28, so that a pressure 45 acts on the sealing assembly 11 via the electrolyte membrane arranged parallel to the plate planes of the bipolar plates 9.

The pressure 45 in fig. 5b causes a deformation of the seal assembly 11. In particular, the pressure 45 causes deformation of the flange member 20 and the elastic body 21. First, the pressure 45 presses the compressible resilient body 21 in the z-direction 5, thereby pressing the compressible resilient body 21 perpendicular to the plate plane of the partial plate 9a of the bipolar plate. By applying a pressure force 45 to the flange member 20, the flange member 20 is also subjected to a pressure force in the z-direction 5 perpendicular to the plate plane of the partial plate 9a, so that the flange member 20 in the state shown in fig. 5b exhibits a reduced height t2 compared to the non-loaded state in fig. 5 a. The height t2 of the seal assembly 11 in the loaded state is reduced by, for example, 5% compared to the seal assembly 11 in the unloaded state.

As a result of the form of the flange members 20, compression of the flange members 20 perpendicular to the plane of the plate also results in deformation of the flange members 20 parallel to the plane of the plate, and in particular compression of the flange members 20 parallel to the plane of the plate. Therefore, the outer side surfaces 37a and 37 of the

lateral projections

30a and 30b in the loaded state are crushed as compared with the unloaded state. Likewise, the distance 41 (parallel to the plane of the plate and thus parallel to the x-y plane) between the top 32a of the lateral projection 30a and the top 32b of the lateral projection 30b is reduced in the loaded state compared to the unloaded state. Similarly, the inner side faces 38a and 38b are also moved toward each other parallel to the plate plane and press the elastic body 21 arranged between the inner side faces 38a and 38b of the groove 31 parallel to the plate plane. This situation is illustrated in fig. 5b by arrow 46.

The deformation of the flange member 20 and the resilient body 21 shown in fig. 5b is entirely elastic and thus reversibly compressible. If pressure is no longer applied to the seal assembly 11, as shown in figure 5b, the seal assembly will substantially return to the unloaded position shown in figures 4 and 5a when the compression assembly holding the stack together is removed. Thereby, the deformation energy stored in the compressible resilient body 21 in the loaded state supports the flange member 20 to be deformed again to the non-loaded position. The reversibility of deformation of the seal assembly 11 as referred to herein is a decisive advantage over prior art seal assemblies in which compression of the bipolar plates in a prior art bipolar plate stack results in plastic deformation, i.e. irreversible deformation, of the seal assembly. Such known bipolar plates, once assembled to a stack and irreversibly deformed in their sealing assembly, are generally not reusable. In contrast, the bipolar plates presented herein can generally be reused as desired.

In fig. 6 and 7, a second and a third embodiment of the first embodiment of the sealing assembly 11 according to the invention shown in fig. 4 and 5 are shown. The outer side faces 37a and 37b of the

lateral projections

30a and 30b of the second embodiment shown in fig. 6, which, unlike the first embodiment, are inclined almost continuously and form an angle of 40 ° to 50 ° with the z direction 5 perpendicular to the plate plane of the partial plate 9a, are more gradual. In addition, the radius of curvature of the flange member 20 in the region of the laterally projecting

crests

32a and 32b is smaller than in the first embodiment.

The flange member 20 of the third embodiment of the seal assembly 11 shown in figure 7 differs from the first embodiment of figures 4 and 5 in that there is an additional undulating deformation in the central portion 47 of the groove along the cross-section of the flange member. The central portion 47 of the groove 31 of the flange member 20 extends between the two

top portions

35a and 35b of the groove 31 and is bulged away from the plane of the plate. The portion 47 extends parallel to the plane of the plate over a length of about 10% or at least 5% of the width b between the two bottom corners of the flange member. The raised height of the portion 47, measured perpendicular to the plane of the plate, is at least 10% of the height t1 of the inner side faces 38a and 38b of the

transverse projections

30a and 30b of the flange member 20.

As explained above, fig. 8 shows a fourth embodiment of seal assembly 11, which differs from the other embodiments in that the elastomer does not completely cover

inner faces

38a and 38b of flange member 20 over the entire height t1, covering height t3 being only 85% of t 1. At the central portion 47 of the groove, as in the other embodiments, the elastomer protrudes to a height exceeding the height of the two tops 32a and 32 b.

A perspective view of a pair of

bipolar plates

9 and 13 and an electrolyte membrane 15 disposed therebetween is shown in fig. 9. The other elements of the MEA detailed in figure 3 are not shown in this figure. The bipolar plate 9 shown in this section comprises passage openings 10b through which, for example, reaction gases are transported in the z direction, i.e. in the direction of the plate stack. The region communicating with the outside is sealed by the sealing assembly 11, and the sides of the

flange members

20 and 24 of the bipolar plate 9 facing the outer edges are continuously and tightly joined to each other by a weld 27 b. The bipolar plate 13 also has similar welds.

A perspective view of the

bipolar plates

9 and 13 of figure 3 and the electrolyte membrane 15 disposed between the

bipolar plates

9 and 13 is shown in figure 10. The figure further illustrates the passage openings 10b in the bipolar plate 9, which are arranged in alignment with corresponding passage openings in the electrolyte membrane 14 and the bipolar plate 13 in the z-direction, so that these aligned passage openings form channels 48 for conducting a liquid and/or gaseous medium, such as fuel or reaction gas. The

outer sides

49a and 49b of the flange 24 of the seal assembly 20 include perforations 50 that serve as defined passages (deliberatepassways) for media flowing into the channels 48 through the seal assembly 22 of the bipolar plate 9. The medium introduced into the channels 48 can thereby be removed via the perforations 50 and the cavities 26 to the electrochemically active region of an electrochemical cell (not shown in fig. 9), which is arranged, for example, between a bipolar plate 9 of the stack 2 and another bipolar plate adjacent to the bipolar plate 9. The seal arrangement 22 of the partial plate 9b of the bipolar plate and the seal arrangement 11 of the partial plate 9a of the bipolar plate 9 are identical in construction. The outer side faces 37a and 37b of the flange member 20 of the seal assembly 11 do not include through holes. The

bead parts

20 and 24 of the bipolar plate 9 are connected to one another in the bead base corner regions on both sides of the bead part by a continuously extending, tight weld seam, so that the medium can only enter or leave the cavity through the through-openings 50 of the bead part. The weld lines facing the channels 48 may also be nail welds or spot welds, which also applies in the case of the bipolar plates 13.

Fig. 11 is an enlarged view of the cavity 26 shown in fig. 3, 9 and 11, which is enclosed by the

bead elements

20 and 24 between the partial plate 9a and the partial plate 9b of the bipolar plate 9. The bead 20 of the seal assembly 11 is formed integrally with the first partial plate 9a of the bipolar plate 9, and the bead 24 of the seal assembly 22 is formed integrally with the second partial plate 9b of the bipolar plate 9. The portion 22 in fig. 10 extends between the flange member through holes 50. A possible connection between the two

partial plates

9a and 9b is not shown here.

Fig. 12 shows a comparison of the load deflection curves between the sealing

arrangements

11 and 22 according to the invention of a bipolar plate 9 and a sealing arrangement according to the prior art, i.e. the

bead elements

61 and 62 of the bipolar plate 63 according to DE10158772a 1. The

bead elements

61 and 62 of the

sealing assemblies

11 and 22 according to the invention of the bipolar plate 9 and of the bipolar plate 63 of DE10158772a1 are shown in fig. 13. In fig. 12, the pressure force 45 acting in the z direction on the seal assemblies 11 and 12 or on the

flange members

61 and 62 is plotted against the offset (see fig. 13). The offset corresponds to the deformation of the seal assemblies 11 and 12 or the

flange members

61 and 62 caused by the pressure 45 in the z-direction 5. Thus, the deflection in the case of the

seal assemblies

11 and 22 according to the invention involves deformation of the

elastomer bodies

21 and 25 and the

flange members

20 and 24 in the z-direction. The prior art flange members are each formed integrally with a respective partial plate of the bipolar plate. The characteristic curves of the prior art flange pieces with different sheet metal thicknesses are recorded. In the case of the uninterrupted characteristic curve, the sheet metal thickness is 0.1 mm. In the case of the point-like characteristic curve, the sheet metal thickness is 0.075 mm. In addition, the two flange pieces of DE10158772a1 present the same geometry. The flange member with the greater sheet metal thickness (characteristic curve 64) is less resilient than the flange member with the smaller sheet metal thickness (characteristic curve 65) at the same level of force. A flange member with a smaller sheet metal thickness (characteristic curve 65) can withstand less force than a flange member with a larger sheet metal thickness (characteristic curve 64), as shown by the lower positioned characteristic curve 65. It follows that if the bipolar plate is made of a very thin material, the conventional geometry of the bead is not sufficient for a permanent seal.

The shape of the flange member of the present invention is reversed. The dotted line characteristic curve 66 and dotted line characteristic curve 67 of fig. 12 show the load-deflection curve of the flange member according to the present invention, wherein the elastic body 21 of the seal assembly 22 and the elastic body 25 of the seal assembly 22 are 50 μm higher in the z-direction 5 than the

top portions

32a,32b,62a,62b of the

lateral protrusions

30a,30b,60a,60b, respectively, in the uncompressed and unmounted state, as shown in fig. 13. The height of the lateral protrusions is selected according to the compressibility of the elastic body 21. Thereby standardizing the bending, only a compression of the two

flange parts

20,24 with the groove and the elastomer occurs in the first 0.1mm of the bending. In this region, compression of the

elastomer body

21 or 25, respectively, mainly occurs, and the leg (leg) of the flange element is only slightly compressed, as shown by the gentle dotted-line characteristic curve 66 and the dotted-line characteristic curve 67 of this region. In the assembly measurements, the two flange members of the prior art, which did not include elastomeric protrusions, were also compressed only after 0.1mm, as shown in FIG. 13.

It was found that the proportion of the load deflection curve of the bipolar plate according to the invention corresponds substantially to the bulge of the elastomer which, during the assembly of the fuel cell stack, is subjected to an initial stage of compression and is therefore not suitable for the actual sealing effect in the assembled state. In fig. 12, this corresponds to an offset of 0mm to 0.1 mm. In this region, during the compression process, only the protruding

elastic bodies

21 and 25 are initially deformed, and the

flange members

20 and 24 are still hardly compressed. Only the area with a load deflection of more than 0.1mm contributes to the actual sealing in the assembled state, which is why the comparison of the two sealing systems is concentrated in this area.

The two

characteristic curves

66 and 67 of the bipolar plate according to the invention differ from one another, the dotted-line characteristic curve 66 originating from the bipolar plate 9, in which the

partial plates

9a and 9b are connected to one another only on one side of the seal assemblies 11 and 12 by means of a weld seam, which is the case in fig. 9, and the dotted-line characteristic curve 67 originating from the bipolar plate 9, in which the

partial plates

9a and 9b are connected to one another on both sides of the seal assemblies 11 and 12 by means of a weld seam, which is the case in fig. 3 and 10. It is apparent here that the pair of flange pieces welded on both sides can withstand greater forces than the pair of flange pieces welded on only one side, as the dash-dot characteristic curve 67 has a higher height relative to the dot-segment line characteristic curve 66. The resilience of the two pairs of flange members is comparable because the

characteristic curves

66 and 67 have a similar degree of inclination.

The branches shown on the right of both

characteristic curves

66 and 67 of the bipolar plate according to the invention each comprise at least one

bend

68 or 69, which respectively represent a simultaneous compression of the metal plate and of the filled elastomer into a compression of the metal sheet only. The

characteristic curves

66 and 67 in the region of the right side of the

bends

68 and 69, which is compressed almost exclusively against the metal sheet, are significantly more inclined than the region of the left side of the

bends

68 and 69, which is compressed against the metal sheet and the elastomer at the same time. In the leftmost region, i.e. the region compressed by 0-0.1mm, the branches of the

characteristic curves

66 and 67 are very flat, which corresponds to a compression of the elastomer mainly.

A comparison of the two

characteristic curves

66 and 67 of the elastomer-filled flange with the broken-line characteristic curve 65 of the unfilled flange of the same sheet metal thickness shows that the flange according to the invention is able to withstand greater forces, since the inflection point in both cases is higher than the broken line 65 and more elastic, the slope of the rise of which is less than the broken line 65 when the entire branch is considered, i.e. also in the case of both sides including the

bends

68 and 69.

At least by welding both sides of the flange member according to the invention and reducing the sheet metal thickness by a quarter, it is possible to withstand substantially the same forces as the prior art flange member. The resulting bipolar plates according to the invention have all the characteristics of higher elasticity than the bipolar plates of the prior art.

Claims

1. Metallic bipolar plate (9) for an electrochemical system (1), comprising an elastic sealing assembly (11) having at least one bead (20) extending parallel to the plate plane of the bipolar plate (9);

wherein the cross-sections of the flange members (20) perpendicular to the trajectory of the flange members (20) each comprise an M-shaped cross-section with lateral projections (30a,30b) and recesses (31) formed between the lateral projections (30a,30 b);

wherein the lateral protrusions (30a,30b) comprise an inner side face (38a,38b) facing the groove (31), and the side height (t1) of the inner side face (38a,38b) extends perpendicular to the plate plane from a vertex (35) of the groove (31), which is the deepest point of the groove (31), to a top (32a,32b) of each lateral protrusion (30a,30b), which top (32a,32b) is the highest point of the lateral protrusion (30a,30 b); and is

Wherein the groove (31) is filled with an elastomer (21);

characterized in that the elastomer body (21) on the entire track of the bead (20) projects in a direction perpendicular to the plane of the plate and above the tops (32a,32b) of the transverse projections (30a,30b), and the elastomer body (21) along the entire track of the bead (20) projects from the apex (35) of the groove (31) of the M-shaped cross-section of the bead (20) to the inner side (38a,38b) of the transverse projections (30a,30b) and covers a part of the inner side (38a,38b) of the transverse projections (30a,30b), said elastomer body (21) exceeding at least 50% of the side height (t1), so that during compression of the bipolar plate (9) perpendicular to the plane of the plate, the pressure applied to the elastomer body (21) is introduced into the bead (20) through the elastomer body (21).

2. Metallic bipolar plate (9) according to claim 1, wherein the elastomer (21) on the entire track of the bead (20) starts from the apex (20) of the groove (31) of the M-shaped cross-section of the bead (20) to the inner side (38a,38b) of the lateral projection (30a,30b) and covers at least 80% of the side height (t 1).

3. Metallic bipolar plate (9) according to claim 1 or 2, wherein the elastomer (21) fills the M-section groove (31) of the bead (20) above the entire lateral height (t 1).

4. Metallic bipolar plate (9) according to claim 3, wherein the elastomer (21) fills the M-section groove (31) of the bead (20) above the entire track of the bead (20).

5. Metallic bipolar plate (9) according to claim 2, wherein the elastomer body (21) along the M-shaped cross section of the bead (20) in a section (41) projects continuously perpendicular to the plate plane beyond the top (32a,32b) of the transverse projections (30a,30b), which section (41) extends from the top (32a) of a first transverse projection (30a) to the top (32b) of a second transverse projection (30 b).

6. Metallic bipolar plate (9) according to claim 5, wherein the elastomer is raised over the entire track of the bead (20).

7. Metallic bipolar plate (9) according to claim 1 or 2, wherein the outer surface of the elastomer body (21) facing away from the bead (20) is continuously curved and bulges outwards in order to introduce a uniform pressure into the bead (20).

8. Metallic bipolar plate (9) according to claim 1 or 2, wherein the height of the elastomer body (21) in cross section reaches a maximum in a central region of the bead (20) and decreases monotonically towards the lateral projections (30a,30b) of the bead (20).

9. Metallic bipolar plate (9) according to claim 1 or 2, wherein the elastomer (21) is compressible.

10. Metallic bipolar plate (9) according to claim 1 or 2, wherein the seal assembly (11) in cross-section is substantially mirror-symmetrical with respect to an axis of symmetry (36) of the seal assembly (11).

11. Metallic bipolar plate (9) according to claim 1 or 2, wherein the material thickness of the bead (20) is less than 0.15 mm.

12. Metallic bipolar plate (9) according to claim 11, wherein the material thickness of the bead (20) is less than 0.1 mm.

13. Metallic bipolar plate (9) according to claim 11, wherein the material thickness of the bead (20) is less than 0.08 mm.

14. Metallic bipolar plate (9) according to claim 1 or 2, wherein straight portions (33a,33b) of the bipolar plate (9) which adjoin the outer flanks (37a,37b) of the transverse projections (30a,30b) of the bead (20) and face away from the recess (31) define a plate plane of the bipolar plate (9), and wherein the apex (35) of the recess (31) closest to the plate plane is at a distance from the plate plane.

15. Metallic bipolar plate (9) according to claim 1 or 2, wherein the lateral height (t1) of the inner side faces (38a,38b) is equal to at least 15% of the height (t2) of the bead (20) relative to the plate plane.

16. Metallic bipolar plate (9) according to claim 15, wherein the lateral height (t1) of the inner lateral faces (38a,38b) is equal to at least 20% of the height (t2) of the bead (20) relative to the plate plane.

17. Metallic bipolar plate (9) according to claim 15, wherein the lateral height (t1) of the inner lateral faces (38a,38b) is equal to at least 30% of the height (t2) of the bead (20) relative to the plate plane.

18. Metallic bipolar plate (9) according to claim 1 or 2, wherein straight portions (33a,33b) of the bipolar plate (9) which adjoin the outer flanks (37a,37b) of the transverse projections (30a,30b) of the bead (20) and face away from the recess (31) define a plate plane of the bipolar plate (9), and wherein the height (t2) of the bead (20) relative to this plate plane is less than 0.7 mm.

19. Metallic bipolar plate (9) according to claim 18, wherein the height (t2) of the bead (20) relative to the plate plane is below 0.55 mm.

20. Metallic bipolar plate (9) according to claim 1 or 2, wherein the lateral projections (30a,30b) of the bead (20) comprise inclined outer flanks (37a,37b) facing away from the recess (31), which outer flanks at least in sections form an angle of at least 30 ° with a perpendicular direction extending perpendicular to the plate plane of the bipolar plate (9).

21. Metallic bipolar plate (9) according to claim 20, wherein at least some parts of the outer side faces are at an angle of at least 40 ° to a vertical direction extending perpendicular to the plate plane of the bipolar plate (9).

22. Metallic bipolar plate (9) according to claim 20, wherein at least some parts of the outer side faces are at an angle of at least 50 ° to a vertical direction extending perpendicular to the plate plane of the bipolar plate (9).

23. Metallic bipolar plate (9) according to claim 1 or 2, wherein the bead (20) is at least partially curved in cross section in the region of the groove (31).

24. Metallic bipolar plate (9) according to claim 23, wherein the bead (20) is curved in cross section in a central region of the bead (20).

25. Metallic bipolar plate (9) according to claim 23, wherein the bead (20) is corrugated in cross section in the region of the groove (31).

26. Metallic bipolar plate (9) according to claim 1, wherein the radius of curvature of the curvature in the region of the groove (31) is less than 50% of the width between the two base corners of the bead (20).

27. Metallic bipolar plate (9) according to claim 26, wherein the radius of curvature of the curvature in the region of the groove (31) is less than 40% relative to the width between the two base corners of the bead (20).

28. Metallic bipolar plate (9) according to claim 1 or 2, wherein the width (b) between the base corners of the bead (20) is less than 3 mm.

29. Metallic bipolar plate (9) according to claim 28, wherein the width (b) between the base corners of the bead (20) is less than 2.5 mm.

30. Metallic bipolar plate (9) according to claim 1 or 2, having a passage opening (10a) for the passage of a liquid and/or gaseous medium, wherein the sealing assembly (12a) radially surrounds the passage opening (10 a).

31. Metallic bipolar plate (9) according to claim 20, wherein at least one of the outer sides (37a,37b) of the bead (20) comprises perforations (51) for the passage of a liquid and/or gaseous medium.

32. Metallic bipolar plate (9) according to claim 1 or 2, wherein the bead (20) and the partial plate (9a) of the bipolar plate (9) form one piece.

33. Metallic bipolar plate (9) according to claim 1 or 2, having a first partial plate (9a) comprising a first sealing assembly (11) with a first bead (20), wherein the first bead (20) and the first partial plate (9a) are formed in one piece, and having a second partial plate (9b) comprising a second sealing assembly (22) with a second bead (24), wherein the second bead (24) and the second partial plate (9b) are formed in one piece, wherein a cavity (26) is formed between the first bead (20) and the second bead (24) as a passage for a liquid and/or gaseous medium.

34. Metallic bipolar plate (9) according to claim 1 or 2, having a first partial plate (9a) which comprises a first sealing assembly (11) having a first bead (20), wherein the first bead (20) and the first partial plate (9a) are formed in one piece, and having a second partial plate (9b) which comprises a second sealing assembly (22) having a second bead (24), wherein the second bead (24) and the second partial plate (9b) are formed in one piece, wherein the two partial plates (9a,9b) are connected at least on one side of the beads (20, 24).

35. Metallic bipolar plate (9) according to claim 34, wherein the two partial plates (9a,9b) are connected at least on the side of the bead (20,24) facing the outer edge of the bipolar plate (9).

36. Metallic bipolar plate (9) according to claim 34, wherein the two partial plates (9a,9b) are connected tightly by a continuously extending weld seam.

37. Electrochemical system (1) having a plurality of bipolar plates (9,13) according to one of the preceding claims and a plurality of electrochemical cells which are each arranged between the bipolar plates (9,13), wherein the bipolar plates (9,13) and the electrochemical cells are stacked in the stacking direction and a mechanical compression can be applied to the bipolar plates (9,13) and the electrochemical cells in the stacking direction.

38. The electrochemical system (1) according to claim 37, wherein the electrochemical system is a fuel cell stack or an electrolyser.

39. Electrochemical system (1) according to claim 37, with a plurality of metallic bipolar plates (9,13) according to claim 31, wherein the passage openings of the metallic bipolar plates (9,13) are arranged at least partially in alignment to form one or more channels (48) for the supply and/or removal of a liquid and/or gaseous medium.

40. Electrochemical system (1) according to claim 37 or 39, wherein a sealing assembly of metallic bipolar plates is provided at least partly to seal the electrochemically active area of the electrochemical cell.