Bipolar plate for electrochemical system

Abstract

The invention relates to a bipolar plate for an electrochemical system. The electrochemical system may in particular be a fuel cell system, an electrochemical compressor, an electrolyzer, or a redox flow battery. It may comprise a large number of such bipolar plates. Also disclosed is an electrochemical system comprising a plurality of such bipolar plates.

Description

Technical Field

[0001] The present invention relates to a bipolar plate for an electrochemical system. The electrochemical system may be a fuel cell monomer system, an electrochemical compressor, an electrolyzer, or a redox flow battery. It may include a large number of such bipolar plates. An electrochemical system including a plurality of such bipolar plates is also disclosed. Background Art

[0002] Known electrochemical systems of the above-mentioned type usually include stacked electrochemical cells separated from each other by bipolar plates. Such bipolar plates can be used, for example, to establish electrical contact with the electrodes of individual electrochemical cells (e.g. fuel cells) and / or to electrically connect adjacent cells (series connection of cells). Usually, the bipolar plate is formed by two adjacent individual plates, which are also referred to as separators within the scope of the present application. The individual plates can be combined together in a material connection, for example by one or more welded joints, in particular by one or more laser welded joints.

[0003] The bipolar plates or individual plates may each have or form a structure of the type explained below, which is provided, for example, for supplying one or more media to the electrochemical cells arranged between adjacent bipolar plates and / or for removing reaction products. The medium may be a fuel (e.g., hydrogen or methanol), a reaction gas (e.g., air or oxygen), or a temperature control medium. In addition, the bipolar plates may be designed to conduct waste heat generated during the conversion of electrical or chemical energy in the electrochemical cells, and to seal the various media or temperature control medium channels from each other and / or from the external environment.

[0004] In addition, the bipolar plates generally include at least one corresponding through-opening, through which the medium and / or the reaction products can be conducted to or away from the electrochemical cells arranged between the adjacent bipolar plates of the stack. The electrochemical cells generally also each include one or more membrane electrode assemblies (MEAs). The MEA may have one or more gas diffusion layers, which are generally oriented toward the bipolar plates and are formed, for example, as metal felt or carbon felt.

[0005] In particular, channels in the separator and in the bipolar plate separated from each other by webs can provide structures for medium supply and / or medium guidance. These channels can be embossed in the form of grooves, for example, can provide flow paths for typical liquid or gaseous media.

[0006] Typically, each separator has an active area with channels for directing the reaction medium and / or reaction products along the outside of the bipolar plate. The active area is opposite the MEA. The active area may also be referred to as a flow field or include a flow field.

[0007] The active area is connected to one of the through-openings in a fluid-conducting manner via a so-called distribution area and is fed through the through-opening. Via a further distribution area, which can also be referred to as a collection area, the reaction medium and / or reaction products can be fed from the active area to a further through-opening for removal.

[0008] On the inner sides of two mutually facing separators surrounded by the respective bipolar plates, the above-mentioned channel-web structures of the flow field and at least one distribution region form complementary web-channel structures that span the flow area for guiding the temperature control medium in the interior of the bipolar plates.

[0009] The distribution area also typically has defined, separated channels. In the following, the channels on the outside of the bipolar plates in the distribution area are referred to as gas flow channels, and the channels in the inside of the bipolar plates are referred to as temperature control medium flow channels.

[0010] When forming a ready-to-use stack, a membrane electrode assembly is provided between adjacent bipolar plates, which membrane electrode assembly separates in the flow region the channels for the passage of a reaction medium in a first bipolar plate from the channels for the passage of another reaction medium in a second bipolar plate, the second bipolar plate being separated from the first bipolar plate only by the membrane electrode assembly. The membrane electrode assembly, often abbreviated as MEA, usually extends beyond the active area and into the distribution area(s).

[0011] In their active area, MEAs usually comprise the actual proton-conducting membrane, electrodes applied thereto, and a catalyst layer, on which a conductive layer and a gas-permeable layer, the so-called gas diffusion layer (GDL), are applied. In their edge region, MEAs usually comprise a polymer-based thin film material which encloses the active area in a frame shape and overlaps in a narrow overlapping region with a material forming the active area or a part of the active area. In the stack of electrochemical systems, MEAs define the spacing between the separators. At the same time, the gas diffusion layer (GDL) of the MEA exhibits relatively large fluctuations in thickness.

[0012] Therefore, the space between the bipolar plates is usually provided in the thickness direction of the stack so that, on the one hand, there is enough space in the active area to accommodate the relevant section of the MEA and, on the other hand, there is just enough space for a predefined compression of this section of the MEA. As a result, sometimes there is more space in the distribution area than is absolutely necessary for their function. Thus, an MEA with a thickness in the active area greater than average results in large gaps in the distribution area, while an MEA with a thickness in the active area less than average results in very small gaps or no gaps in the distribution area.

[0013] In conventional electrochemical systems, bipolar plates are designed so that their separators are placed on top of each other in sections both in the active area and in the distribution area and are welded together in sections at least in these areas. However, pressure fluctuations of the temperature control medium passing between the separators of the bipolar plates can lead to movements of the separators relative to each other and expose the connections between the separators of the bipolar plates, in particular the welded connections in the distribution area, to the effects of dynamic pressure fluctuations and loads. These can lead to fractures in the welded joints. This applies in particular if the connections are already exposed to the effects of increased loads due to changes in the thickness of the MEA.

[0014] As a result, undefined temperature control medium flows can occur within the bipolar plates, which leads to pressure losses and thus efficiency losses. In addition, such separators can also have perforations in the area of ​​the welded joints, which endangers the operating capability and, in particular, the operating safety of the bipolar plates and higher-level electrochemical systems.

[0015] Other previously known solutions maintain the necessary height tolerances in the distribution area in the form of a gap between the two separators of the bipolar plate, but this means that no or only poor control of the temperature control medium is possible. This means that particularly poorly cooled areas may occur in the active area of ​​the bipolar plate, which can lead to damage to the MEA and also to efficiency losses. Summary of the invention

[0016] An object of the present invention is therefore to provide a bipolar plate with which fluctuations in the thickness of an MEA in an electrochemical system can be compensated while ensuring increased efficiency and operating reliability, preferably while achieving a defined distribution of a temperature control medium over the active area of ​​the bipolar plate.

[0017] This object is at least partially solved by the subject matter of the independent claims. Advantageous further embodiments are given in the dependent claims, the description and the drawings.

[0018] Based on this, a bipolar plate for an electrochemical system is proposed. The bipolar plate includes a first separator and a second separator, and the first separator and the second separator are arranged adjacent to each other in a direction perpendicular to the plate plane of the first separator and / or the second separator. The first separator and the second separator each have a first through opening for allowing the reaction medium to pass through the separator, wherein the first through openings are adjacent to each other in a direction perpendicular to the plate plane for allowing the reaction medium to pass through the separator; and a second through opening, the second through opening is adjacent to the first through opening in the plate plane for allowing the temperature control medium to pass through the separator. In addition, the first separator and the second separator each include an active area with a first structure for guiding the reaction medium along the outer flat side of the separator and a second structure for guiding the temperature control medium along the inner side of the bipolar plate. They are also arranged adjacent to each other in the vertical direction, or overlap each other when orthogonally projected onto the plate plane.

[0019] Furthermore, the first and second partitions each have at least one distribution or collection area, wherein the distribution or collection area(s) of the first and second partitions are adjacent to each other in a direction perpendicular to the plate plane, with a first structure for guiding the reaction medium between the first through-opening and the active area and a second structure for guiding the temperature control medium between the second through-opening and the active area. The structure for guiding the temperature control medium in the distribution or collection area comprises temperature control medium flow channels, which are separated from each other by webs pointing in the direction of the other partition.

[0020] Furthermore, at least one distribution or collection area of ​​the first separator and / or the distribution or collection area of ​​the second separator has at least one compensation area. In the unassembled state of the bipolar plate, in one, several or all of the at least one compensation area, the webs facing the corresponding adjacent separators are spaced apart from the adjacent separators in a direction perpendicular to the plate plane in the area between mutually adjacent temperature control medium flow channels. This applies, but with the exception that the compensation area has at least one free-standing elastic contact area at a distance from its outer edge, in which a section of the web protrudes so that the section forms a contact surface with the adjacent separator.

[0021] The main spacing of the web of one separator to the adjacent separator is used in the compensation area to compensate for height fluctuations of the MEA or GDL. If one or more MEAs with a GDL thicker than average are installed, a gap remains in the stack of the electrochemical system even after the bipolar plates and MEAs have been installed and tensioned; if MEAs with a GDL thicker than average have been installed, at least a portion of the remaining gap is pressed into the stack of the electrochemical system when the bipolar plates and MEAs are installed and tensioned. The gap is usually designed so that it can also compensate for very thin GDLs.

[0022] However, at a certain distance from its outer edge, the compensation area also has at least one independent elastic contact area, in which a section of the web protrudes so that the section forms a contact surface with the adjacent partition. At least one elastic contact area is generally designed so that it has at least one elastic compression component, so that after installation and tensioning it can be reversibly deformed with the normal operating pulsation of the temperature control medium. After the bipolar plates and the thinner MEA are installed and tensioned in the stack of the electrochemical system, at least one elastic contact area exhibits both plastic and elastic deformation. On the other hand, if a very thick MEA is installed, only elastic deformation may occur. However, the elasticity of the contact area not only enables a high compensation for different MEA or GDL thicknesses, but also adapts to pressure pulsations.

[0023] Preferably, the contact surface of the elastic contact area of ​​one separator touches the web section of the other separator, so that the contact surface of the elastic contact area and the web section of the other separator form a fluid barrier inside the bipolar plate, around which the temperature control medium must flow. This can lead to a deflection effect on the temperature control medium, so that by appropriately arranging the contact surfaces, the temperature control medium can be guided in a defined manner into areas that would experience insufficient temperature control during operation without such guidance, thereby increasing the efficiency of the electrochemical system.

[0024] The contact surface protrudes from the web surface in the direction of the other separator and contacts the other separator before the bipolar plate is installed and tensioned in the stack of the electrochemical system. This contact usually exists even under normal operating conditions, that is, after installation and tensioning. In the case of very strong pressure pulses of the temperature control medium, the contact surfaces can also rise away from each other in a short time. It is advantageous if the webs of one of the separators are not each connected to the material of the other separator in the compensation area. The elastic contact element can therefore even save welds connecting the separators. As a result, these cannot be torn apart, especially if the separator is locally perforated. This improves operational safety.

[0025] When viewed from the plate plane of one of the partitions, one, several or all of the elastic contact areas may have an elongated shape, a rounded elongated shape, a rounded shape or a free form. If there are several elastic contact areas in the distribution or collection area, these elastic contact areas may have different shapes. In particular, the choice of the specific shape of the elastic contact area can be adapted to the available installation space, and the specific shape can also influence the elasticity of the elastic contact area. For example, a rounded elastic contact area can be used in areas where less fluid diversion is required, while the other shapes mentioned, in particular the elongated shape, can be preferably used for diversion.

[0026] When viewed from above the plate plane of the partition, a compensation area or one of several or all compensation areas as a whole - including the elastic contact area contained therein - occupies an area FA. The total area of ​​all contact areas contained therein is denoted as FKges. The ratio of these two areas is FKges≤0.2FA, in particular FKges≤0.1FA. The elastic contact area thus occupies only a fraction of the compensation area. This results in a larger area in the compensation area in which the temperature control medium is present or can flow between the two partitions, in particular also between the webs facing each other.

[0027] The contact surface of the elastic contact area usually only constitutes a part of the surface of the elastic contact area. When viewed from above the plate plane of the partition, the total area of ​​the contact surface contained by a compensation area or a specific one of several or all compensation areas can be determined as FBges. The ratio of the area FA of the one compensation area or one of several or all compensation areas to the area of ​​the contact surface is FBges≤0.05FA, in particular FBges≤0.03FA, as defined above. This applies to the non-mounted and mounted state.

[0028] It has been found that a particularly good flow deflection of the temperature control medium can be achieved if one, several or all of the elastic contact areas have an elongated or bluntly elongated shape when viewed from above the plate plane of one of the partitions and their longitudinal axes form a non-zero angle α with the longitudinal axis of the web from which they protrude in the respective elastic contact area. An angle α of 15°≤α≤90° is particularly advantageous, in particular 20°≤α≤60°. In the case of a non-rectilinear web, the longitudinal axis can be understood as the center line of two tangents, wherein the tangents touch the inflection point of the straight flank section or the web flank on both sides of the web, where the web flank has the smallest distance from the respective elastic contact area.

[0029] Although in the active area of ​​the bipolar plate, the channels of the two separators usually run essentially parallel, it is advantageous to distribute the medium in a targeted manner over the entire width of the active area if the gas channels of one separator extend at an angle to the gas channels of the other separator of the bipolar plate in the distribution and / or collection area, with the result that the temperature control medium flow channels of the two separators inside the bipolar plate do not run parallel to each other. For example, the temperature control medium flow channels of one separator and the temperature control medium flow channels of the other separator can extend at least in some sections at an angle of 15°≤δ≤90° to each other, preferably at 20°≤δ≤60°. This already significantly contributes to the distribution of the temperature control medium over the entire width of the active area. In order to adequately support the contact surface(s) of at least one elastic contact area on the other partition and to guide the temperature control medium in a defined manner, it is advantageous if one, several or all of the elastic contact areas of one of the partitions and the web of the distribution or collecting area of ​​the other partition are positioned at a very acute or even vanishing angle to each other in the orthogonal projection to the plate plane of the first and / or second partition. A particularly advantageous angle γ is γ≤30°, preferably γ≤20°, in particular γ≤10°. In the case of elongated elastic contact areas and in the case of elastic contact areas corresponding to free forms, the angle is determined along the longest extension of the elastic contact area. On the side of the web, the longitudinal axis of the web is used, which is determined in the same way as the longitudinal axis of the web of the partition containing the elastic contact area, wherein the elastic contact area is projected orthogonally onto the other partition.

[0030] It can be particularly advantageous if for one, several or all of the elastic contact areas the elastic contact area has an elongated or bluntly elongated shape when viewed from the plate plane of one of the partitions and its longitudinal axis runs essentially parallel to the web in the adjacent partition. This results in a particularly large contact surface.

[0031] In an embodiment, the web width is constant in the elastic contact area. Alternatively, the web width increases in the elastic contact area. The maximum web width in the area of ​​the elastic contact area can therefore be at least 30%, preferably at least 50%, in particular at least 100%, particularly preferably at least 200% greater than the web width of the web outside the elastic contact area, for example in the area of ​​the web's run, which area has no elastic contact area and in which the web has its maximum width.

[0032] The elastic contact area may have a spring surface which runs around the contact surface at least in some sections. The spring surface is preferably designed such that it gives the elastic contact area its elasticity. For example, the spring surface may have a pitch smaller than the average pitch of the flanks of the web in which the elastic contact area is arranged. For example, the pitch of the spring surface relative to the contact surface of the elastic contact area may span an angle β, wherein β≤30°, preferably β≤20°, in particular β≤15°.

[0033] The spring surface can completely surround the contact surface. This is particularly preferred for rounded elongated or rounded contact areas or for contact areas with a free shape. Alternatively, in particular in the case of an elongated contact surface or an elongated elastic contact area, the spring surface can have an elongated shape at least in some sections when viewed from above the plate plane of one of the partitions and extend with its longitudinal axis essentially parallel to the longitudinal axis of the web, in particular of the web, in the adjacent partition. It is preferred if the corresponding elongated spring surface extends on both sides of the elongated contact surface.

[0034] In particular, the elongated or bluntly elongated spring surface can extend between the two closest temperature control medium flow channels so that it connects their mutually facing flank ends. This allows the entire web width to be provided with the barrier element.

[0035] It is possible that the spring area of ​​the elastic contact area is not only composed of uniformly designed areas. The spring area can also have at least two areas, and these at least two areas have different pitches relative to the contact surface defined by the spring area. On the one hand, such areas with different pitches can follow each other in a continuous order, for example to achieve different elasticities in different areas. For this reason, it is also preferred to adjust the width of the corresponding area of ​​the spring area to avoid height steps. On the other hand, but not excluding the aforementioned arrangement, these different areas can also be arranged relative to each other so that one area in these two areas preferably encircles other areas, particularly completely encircles it. For example, the contact surface can be surrounded by the first area in these areas of the spring area, particularly around its entire periphery. Then, this first area of ​​the spring area is then surrounded in some sections or completely by the second area of ​​the spring area. When these spring areas are connected in series, a progressive spring characteristic can be achieved, particularly if the two spring areas have different maximum deflections.

[0036] Furthermore, the depth of one of the two separators of the bipolar plate in one or more compensation regions of the temperature control medium flow channel can be smaller than the depth of one of the two outermost temperature control medium flow channels or the outer flanks of both flow channels, excluding the elastic contact region. This makes it particularly easy to create gaps between the webs in the compensation region.

[0037] The present invention also relates to an electrochemical system comprising a plurality of bipolar plates according to any aspect described herein and an MEA, in particular a plurality of stacked bipolar plates and an MEA arranged therebetween. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Exemplary embodiments of the present invention will be explained below with reference to the accompanying drawings. In all figures, comparable features may be indicated using similar reference numerals. In the accompanying drawings:

[0039] Figure 1 An electrochemical system with a conventional bipolar plate or a bipolar plate according to the present invention is shown;

[0040] Figure 2 shows a conventional bipolar plate, Figure 1 A cross section of the electrochemical system shown in;

[0041] In three Figure 3A-3C A partial plan view, a partial cross-sectional view and a temperature control medium distribution of a bipolar plate according to an example of the prior art are shown;

[0042] In five Figure 4A-4E A partial plan view, three partial cross-sectional views and temperature control medium distribution of a bipolar plate according to the present invention are shown;

[0043] In two Figure 5A and Figure 5B An oblique view of a cross section of a distribution area of ​​a bipolar plate according to the invention and a related detailed view are shown;

[0044] In two Fig. 6A and Figure 6B : shows an oblique view of a cross section of a distribution region of a further bipolar plate according to the invention and a related detailed view;

[0045] Figure 7 A partial top view showing a distribution area of ​​a further bipolar plate according to the invention;

[0046] In three Figure 8A-8C , three partial plan views of the distribution area of ​​the bipolar plate according to the invention are shown; and

[0047] Fig. 9 An oblique view of a cross section through a distribution region of another bipolar plate according to the invention is shown. DETAILED DESCRIPTION

[0048] Figure 1An electrochemical system 1 is shown with a plurality of identical bipolar plates 2. The bipolar plates 2 are arranged as an assembly in a stack 6 and are stacked in a z-direction 7. The bipolar plates 2 of the stack 6 are sandwiched between two end plates 3, 4. The z-direction 7 is also referred to as the stacking direction. In the present example, the system 1 is a stack of fuel cell cells. Therefore, each two adjacent bipolar plates 2 of the stack 6 enclose an electrochemical cell cell between them, which is used, for example, to convert chemical energy into electrical energy. In order to form the electrochemical cell cells of the system 1, a membrane electrode unit (MEA) is arranged between adjacent bipolar plates 2 of the stack 6 (see, for example, Figure 2 ). Each MEA generally includes a membrane, such as an electrolyte membrane. In addition, a gas diffusion layer (GDL) may be arranged on one or both surfaces of the MEA.

[0049] Alternatively, Figure 1 and Figure 2 The system 1 shown in can also be designed as an electrolyzer, an electrochemical compressor or a redox flow battery. The bipolar plates 2 can also be used in these electrochemical systems. The structure of these bipolar plates 2 can then correspond to the structure of the bipolar plates 2 described in detail herein, although in the electrolyzer, the electrochemical compressor or the redox flow battery, the medium fed to and / or passing through the bipolar plates 2 can in each case differ from the medium used for the fuel cell monomer system.

[0050] The z-axis 7 together with the x-axis 8 and the y-axis 9 define a right-handed Cartesian coordinate system. The bipolar plates 2 each define a plate plane E (see Figure 3B and 4B ), wherein the separators 2a, 2b (see Figure 2 ) touch each other. The partitions 2a, 2b also form their own plate planes 39a, 39b in the areas where they are not formed (see Figure 3B , Figure 4B , Figure 5B and Figure 6B ), wherein the plate planes of both the bipolar plates 2 and the separators 2a, 2b are each aligned parallel to the xy plane and thus perpendicular to the stacking direction or z-axis 7. The end plate 4 comprises a plurality of media connections 5 via which media can be fed to the system 1 and via which media can be discharged from the system 1. These media that can be supplied to and discharged from the system 1 can, for example, include fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or exhausted fuel, or, if applicable, temperature control media such as water and / or ethylene glycol. In the case of an electrolyzer, water is supplied to the stack and oxygen and hydrogen are discharged from it.

[0051] Figure 2 Shows Figure 11 and a membrane electrode assembly (MEA) 10 which is arranged between the adjacent bipolar plates 2 and is known in principle from the prior art. Figure 2 The MEA 10 in the image is mostly obscured by the bipolar plate 2 facing the viewer. The bipolar plate 2 is formed by two separators 2a and 2b joined together by a material connection. Figure 2 In the figure, only the first separator 2a facing the observer is visible over a large area, and the first separator 2a covers the second separator 2b. The separators 2a, 2b can each be made of a metal sheet, for example a sheet made of a stainless steel sheet or a titanium alloy. The sheets can be coated or covered in some sections or on their entire surface, for example, with a coating that prevents corrosion and / or enhances conductivity. The separators 2a, 2b can be connected to each other, for example, by material bonding, such as welding, brazing or gluing, and can be connected in particular by laser welded joints. The MEA 10 has a reinforced edge along its outer edge, at which the MEA is clamped between the two bipolar plates 2 in a fluid-tight manner.

[0052] The separators 2a, 2b have through-openings which form through-openings 11a-11c of the bipolar plate 2 and are aligned with each other. When a plurality of bipolar plates of the bipolar plate 2 type are stacked, the through-openings 11a-11c and the aligned through-openings in the reinforced edge of the MEA 10 form lines extending through the stack 6 in the stacking direction 7 (see Figure 1 ). Typically, each of the through-openings formed by the channel openings 11a-11c is fluidically connected to one of the ports 5 in the end plate 4 of the system 1. The pipeline formed by the through-opening 11a can be used, for example, to introduce a temperature control medium into the stack or to discharge it from the stack. Conversely, the pipeline formed by the through-openings 11b, 11c can be designed to supply fuel and reaction gases to the electrochemical cells of the fuel cell cell stack 6 of the system 1 and to discharge reaction products from the stack 6. The through-openings 11a-11c for medium conduction are each substantially parallel to the plate plane.

[0053] In order to seal the through-openings 11a-11c with respect to the interior of the stack 6 and with respect to the surroundings, the first partition plates 2a each have a sealing arrangement in the form of a sealing bead 12a-12c which is arranged in each case around the through-openings 11a-11c and in each case completely surrounds the through-openings 11a-11c. Figure 2 On the rear side of the viewer, there are corresponding port flanges (not shown) for sealing the through openings 11a-11c.

[0054] In the electrochemically active region 18, the first separators 2a are disposed on their facing sides. Figure 2On the front side of the observer, there is a flow field 17 with structures for guiding the reaction medium along the front side of the partition 2a. These structures are Figure 2 The bipolar plate 2 is shown as a plurality of webs and channels running between and defined by these webs. Figure 2 On the front side of the observer, the first partitions 2a also each have at least one distribution area 20, which distribution area 20 can also be called a collection area in the above manner depending on the flow direction. The distribution or collection area 20 includes a structure configured to distribute the medium and / or collect or gather the medium on the active area 18, the distributed medium is the medium that has been transported from the first of the two through openings 11b to the distribution or collection area 20, and the collected or gathered medium is the medium that flows from the active area 18 toward the second through opening of the through openings 11b. Figure 2 In the example, corresponding through openings for the inlet or outlet of the same fluid that may have been changed during the electrochemical reaction are marked with or without a prime, for example 11a and 11a'. The distribution structure of the distribution or collection area 20 is also Figure 2 26a, 26b and gas flow channels 27a, 27b extending between and delimited by the webs 26a, 26b. In general, the elements 17, 18, 20 can therefore be interpreted as convex structures for media guidance.

[0055] exist Figure 2 In conventional bipolar plates, the separators arranged in the region of the rear side of the base of the gas flow channels 27a, 27b are placed directly on top of each other in the distribution region and bear against each other. The two separators are usually connected to each other at the contact point in the distribution region, in particular welded together, for example by means of a short weld seam 38, such as Figure 2 shown.

[0056] Figure 2The port flanges 12a-12c of the example in the embodiment have passages 13a-13c for passing a medium through these sealing flanges. For example, passage 13a allows a temperature control medium to pass between the through-opening 12a and the distribution area 20, so that the temperature control medium enters or is guided out of the distribution area between the partitions 2a, 2b. In addition, passage 13b allows hydrogen to pass between the through-opening 12b and the distribution area 20 on the upper side of the partition 2a. Passage 13c enables air to pass, for example, between the through-opening 12c and the distribution area 20, so that air enters the distribution area 20 on the lower side of the lower partition 2b and is guided out of the distribution area 20. The through-opening 11a or the pipelines formed by the through-opening 11a through the plate stack of the system 1 are each fluidly connected to each other via a cavity 19 enclosed by the partitions 2a, 2b. If necessary, this cavity 19 can be used to conduct a temperature control medium through the bipolar plate 2 , in particular for temperature control, such as cooling, heating or keeping the temperature of the electrochemically active region 18 of the bipolar plate 2 constant.

[0057] The first separators 2a of the bipolar plates 2 of the stack 6 also each have an additional sealing arrangement in the form of a peripheral ridge 12d, which surrounds the flow field 17 of the active area 18, the distribution and collection area 20 and the through openings 11b, 11c, and seals them with the through opening 11a, that is, with the temperature control medium circuit, and with the environment of the system 1. The second separators 2b each include a corresponding peripheral ridge 12d. In an alternative plate design, the peripheral ridge can also include a temperature control medium opening and therefore the entire temperature control medium circuit. The structure of the active area 18, the web 21 and the channel 22 of the distribution or collection area 20, and the sealing ridges 12a-12d are each formed as one piece with the separator 2a and molded into the separator 2a, for example, by a raised stamping, roller stamping, deep drawing or hydraulic forming process. The same applies to the corresponding distribution structure and sealing ridge of the second separator 2b.

[0058] In particular in the case of fuel cell monomers, the separators 2a, 2b of the bipolar plate 2 can each be formed, for example, from a stainless steel sheet having a thickness of less than 100 μm. In the case of an electrolyzer, sheets made of a titanium alloy or sheets made of fully coated stainless steel can be used. The thickness of the sheets in an electrolyzer is generally greater; for example, they can be 100-800 μm, 150-500 μm, in particular 200-300 μm. The bipolar plate 2 generally has a substantially rectangular shape, but it can also be rounded or oval, in particular in the case of an electrolyzer.

[0059] exist Figure 3A 2 shows a partial top view of a bipolar plate 2 or its separator 2a in the region of the through-openings 11a - 11c, in the distribution region 20 and in a short section of the active region 18 according to an example of the prior art. Figure 2The example in FIG. 2 differs in that there is no weld joint 38 in the dispensing area 20 and the rear sides of the bottoms of the channels 27 a , 27 b do not rest on each other in the dispensing area but are arranged at a distance from each other within the boundary line 30 .

[0060] Figure 3A An example of the position of the cross-sectional plane AA with multiple bends is shown. The cross-sectional plane AA is generally aligned with the plate plane E of the bipolar plate 2 and Figure 3B The plate planes 39a, 39b of the partitions 2a, 2b shown in FIG. 1 are orthogonal, and thus in FIG. Figure 1 It also extends in the region in which the distribution area 20 of the second partition 2b also extends, the distribution area 20 being in the z direction of the stack. Figure 3A is hidden by the partition 2a. Figure 3A The distribution areas 20 of the partitions 2a, 2b overlap in the cross-sectional plane AA. In addition, the rear sides or inner sides of the partitions 2a, 2b also face each other at this location, and the partitions 2a, 2b are shaped to complement the corresponding distribution areas 20, such as from Figure 3B This can be seen in the partial cross-sectional view.

[0061] The stacked identical bipolar plates 2 each include a first metal separator 2a and a second metal separator 2b, such as Figure 2 . The structure for medium conduction can be seen along the outer surface of the bipolar plate 2, here in particular in the form of webs 26a, 26b and gas flow channels 27a, 27b separated by the webs 26a, 26b. In particular, the temperature control medium flow channels 22a, 22b are shown in the cavity 19 between adjacent separators 2a, 2b. Between the temperature control medium flow channels 22a, 22b, the two separators 2a, 2b have webs 21a, 21b, which are connected to the bipolar plate 2. Figure 2 Unlike the example of the embodiment of the present invention, the webs 21a, 21b do not touch each other. Between the planes 32a, 32b extending in the region where the webs 21a, 21b are closest to each other there is a gap 23, in which the temperature control medium can flow freely. The side wings 29a, 29b and 28a, 28b extend between the web or web roof and the channel or channel floor.

[0062] A membrane electrode assembly (MEA) 10, such as is known from the prior art, is arranged in each case between stacked adjacent bipolar plates 2. The MEA 10 typically comprises a membrane 14, such as a catalyst-coated electrolyte membrane and an edge section 15 connected to the membrane, and at least one, in the present case two, gas diffusion layers (GDL) 16. For example, the edge section 15 can be connected to the membrane in a materially bonded manner, such as by an adhesive connection or by lamination. The gas diffusion layer 16 is able to guide the flow to the membrane over as large an area as possible of the surface of the membrane and can thus improve the proton transfer via the membrane. The gas diffusion layer 16 can, for example, be arranged on both sides of the membrane in an active area 18 between adjacent bipolar plates 2. The gas diffusion layer 16 can, for example, be formed by a fiber felt or include a fiber felt.

[0063] The membrane of the MEA 10 in each case extends at least over the active area 18 of the adjacent bipolar plates 2 and at this location a proton transfer is possible via or through the membrane. However, the membrane does not extend into the distribution or collection area 20. The edge sections 15 of the MEA 10 in each case serve to position, attach and seal the membrane between the adjacent bipolar plates 2. If the bipolar plates 2 of the system 1 are sandwiched between the end plates 3, 4 in the stacking direction (see Figure 1 ), the edge section 15 of the MEA 10 can, for example, be pressed in each case between the port flanges 12a-12c of the corresponding adjacent bipolar plates 2 and / or in each case at least between the peripheral flanges 12d of the adjacent bipolar plates 2, so as to fix the membrane 14 of the MEA 10 between the adjacent bipolar plates 2.

[0064] The two partitions 2a, 2b are tightly welded together by means of a weld 38' only around the sealing flange, for example around the port flange 12b and along the outer edge 24, as shown in FIG. Figure 3B The cross-section view can be seen in .

[0065] However, in Figure 3C The temperature control medium distribution of the bipolar plate schematically shown in Figure 3A It is clearly shown in FIG. 1 that the centrally located region is supplied very adequately with temperature-control medium, whereas the lateral edge regions, which are situated approximately in the extension of the through-openings 11 b , 11 c , are supplied only very little with temperature-control medium, as indicated by the lines of different thicknesses.

[0066] The present invention has been designed to at least partially address the above-mentioned problems. FIG. 4A to FIG. 7 The present invention is further explained.

[0067] In four Figure 4A-4E Detailed description of the drawings is given in FIG. 1 , showing a partial plan view, three partial cross-sectional views and the distribution of the temperature control medium of the bipolar plate 2 according to the present invention.

[0068] as from Figure 2 In the prior art example of 3, the bipolar plate 2 is also formed with a first separator 2a and a second separator 2b, which are arranged adjacent to each other in a direction perpendicular to the plate planes 39a, 39b of the first separator and / or the second separator 2a, 2b, such as along Figure 4A The section line BB extends Figure 4B The MEA or its reinforced edges are clearly shown in the cross-sectional view. Figure 4B Omitted in, but the arrangement of MEA relative to the bipolar plate basically corresponds to Figure 3B In the two partitions 2a, 2b, two first through-openings 11b, 11c and a second through-opening 11a are present and at least partially shown in the cross section shown in the direction perpendicular to the plate planes 39a, 39b, the two first through-openings 11b, 11c are used to allow the reaction medium to pass through each of the partitions, and the second through-opening 11a is adjacent to the first through-openings in the plate planes 39a, 39b and is used to allow the temperature control medium to pass through the two partitions 2a, 2b. Figure 2 As shown in , corresponding through-openings also exist adjacent to the opposite short ends of the bipolar plates 2 , but are not shown here.

[0069] exist Figure 4A Floor plan and Figure 4B In the partial cross-sectional view of FIG. 1 , only a short section of the active area 18 with the first structure 17 is shown, which is used to guide the reaction medium along the outer flat side of the partition 2a; Figure 4B The second structure is shown in the partial cross-sectional view of , and the second structure is used to guide the temperature control medium along the inner side of the bipolar plate 2.

[0070] The separators 2a, 2b in turn have at least one distribution or collection area 20 with a first structure for guiding the reaction medium between the first through-opening 11b or 11c and the active area 18 and a second structure for guiding the temperature control medium between the second through-opening 11a and the active area 18, wherein the second structure for guiding the temperature control medium in the distribution or collection area 20 has temperature control medium flow channels 22a, 22b on the inner side of the separators 2a, 2b, which are separated from each other by webs 21a, 21b and span the cavity 19 for guiding the temperature control medium in the interior of the guide bipolar plate 2. Both the distribution or collection area 20 of the first separator 2a and the distribution or collection area 20 of the second separator 2b have compensation areas 35a, 35b, the outer boundaries of which correspond to Figure 4A The dashed boundary line 30 in FIG.

[0071] Figure 4BThe partial cross-sectional view of shows a state in which the two separators 2a, 2b are connected to each other but have not yet been assembled into a stacked electrochemical cell. In the compensation area 35, the webs 21a, 21b between the adjacent temperature control medium flow channels 22a, 22b, facing the corresponding adjacent separators 2a, 2b, are spaced apart from the adjacent separators in a direction perpendicular to the plate planes 39a, 39b. Figures 3A-3C As shown in FIG. 4 , there is therefore a gap 23 in the z-direction which allows the webs 21 a , 21 b to cross.

[0072] In addition, however, there is at least one freestanding elastic contact area 44, which is arranged at a distance from the outer edge 30 of the compensation area 35 and in which a web, here a section of the web 21a placed on top in the separator 2a, protrudes so that it forms a contact surface 42 with the adjacent separator 2b. Thus, at some intersections of the webs 21a, 21b of both separators 2a, 2b, there are contact surfaces 42. The elasticity of the contact area 44 enables a high degree of compensation for different MEA or GDL thicknesses and also enables adaptation to pressure pulsations, as described below.

[0073] Under normal operating conditions, these elastic contact areas 44 enable a better distribution of the temperature control medium over the width of the active area 18, such as Figure 4C 4 is shown in FIG. 4 by lines of equal width distributed over the entire width. Due to the elasticity, the elastic contact area 44 springs up during the pulsation, so that the area of ​​the corresponding contact surface 42 can change. Only in the case of extremely high surges of the temperature control medium does the contact surface 42 lose contact. Compared to the welding solutions of the prior art, this only results in a brief lifting away without damaging the separator or even tearing the plate material.

[0074] The contact surface 42 of the elastic contact area 44 of the separator 2a touches the web section 21k of the other separator 2b, wherein the contact surface 42 of the elastic contact area 44 and the web section 21k of the other separator 2b touching the contact surface 42 preferably form a fluid barrier 31 inside the bipolar plate 2. The temperature control medium must flow laterally through the contact surface 42 and through the flow space spanned by the gap 23 to the fluid barrier.

[0075] In this example, the area bounded by the outer edge 30 is the entire area FA of the compensation area 35 under consideration. Figure 4A-4E In the example of , the distribution region 20 or the compensation region 35 has two regions 201 , 202 with different fluid paths, wherein the elastic contact region 44 is also designed differently as an example. The different designs of the elastic contact regions can also result from different bipolar plates.

[0076] Figure 4D shows the Figure 4A Finally, Figure 4E Shown from Figure 4E , in which the enlargement in the z direction is greater than in the plate plane, in order to clarify the height ratio. This detailed view clearly shows the gap 23 between the web 21a or its surface facing the lower partition 2b and the surface of the web 21b facing it, even if the view here shows that the webs intersect and deviate from each other in the plate plane. In particular, this surface of the web 21a is spaced apart from the plate plane E of the bipolar plate 2. The channel flank 28a' facing the outer edge 30 of the compensation area 35 is higher than the channel flank 28a arranged inside the compensation area 35. Therefore, in this compensation area 35, the depth of the temperature control medium flow channel 22a, excluding the elastic contact area 44, is less than the depth of the outer flank 28a' of the at least two outermost temperature control medium flow channels 22a shown.

[0077] In two Figure 5A and Figure 5B An oblique view of a section 201 of the distribution area 20 of the bipolar plate 2 according to the present invention and a related detailed view are shown; although the flow cross-sectional areas of the temperature control medium flow channel 22b and the gas flow channel 27b in the partition 2b arranged at the bottom are comparable, for the partition 2a arranged at the top bridge portion, the flow space for guiding the gas on the outer surface in the gas flow channel 27a is significantly larger than the flow space for guiding the temperature control medium in the flow channel 22a. Figure 5A and Figure 5B In the embodiment of the present invention, the temperature control medium flow channels 22a, 22b in both the partitions 2a, 2b run at an angle to each other, and the temperature control medium flow channel 22a of the first partition 2a is significantly narrower than the temperature control medium flow channel 22b of the second partition 2b. A gap 23 is retained in a direction perpendicular to the plate planes 39a, 39b, in a large section of the compensation area 35, between mutually adjacent temperature control medium flow channels 22a, 22b, and between mutually facing webs 21a, 21b. Although this gap is less than one-quarter of the height of the temperature control medium flow channels 22a, 22b, it still allows the webs 21a, 21b to cross and provide multiple flow paths for the temperature control medium. Likewise, in order to direct the flow of the temperature control medium, a plurality of elastic contact areas 44 are provided in those sections of the partitions, which form the bottom of the gas flow channel 27a on one surface of the partition and form the web 21a between two temperature control medium flow channels 22a on the other surface of the partition. In these areas, the section 21 k of the web 21 a protrudes so that it forms a contact surface 42 with the adjacent web, in this case the web 2 b .

[0078] Figure 5AThe elastic contact areas 44 shown in all have a rounded and elongated shape. The longitudinal axis Lo of the exemplary contact area 44 runs at an angle α to the longitudinal axis Lsa of the web 21a in the corresponding elastic contact area 44, wherein α here in the plan view of the plate plane 39 is about 30°. In addition to the barrier effect of the elastic contact area 44, this angled arrangement also forces the temperature control medium to turn in a targeted manner. In contrast to the example shown here, not all elastic contact areas 44 must have a longitudinal axis at the same angle α to the longitudinal axis of the associated web; on the contrary, it may be better for fluid guidance if different elastic contact areas 44 have different orientations.

[0079] exist Figure 5A In the cross section of the compensation region 35 shown in , the web width Bs in the region of the elastic contact region 44 is constant and corresponds to the web width outside the elastic contact region 44. Due to this and as a result of the only small height of the elastic contact region 44, the cross section of the associated gas flow channel 27a changes only slightly, so that the elastic contact region 44 does not cause any significant pressure losses.

[0080] All elastic contact areas 44 belonging to the same compensation area each have an area FK. For the entire compensation area, the areas FK can be added up to a total area FKges. However, in relation to the associated compensation area 35 (see Figure 4A ), this total area is very small, less than 10%. Similarly, the areas FB of the contact surfaces 42 of the contact areas 44 of the compensation region can add up to a total area FBges. This results in an even smaller proportion of the area FA of the associated compensation region 35, less than 3%. The aforementioned values ​​can refer to the state of the bipolar plate 2 not installed, or to the state of the bipolar plate 2 installed in the stack 6 of the electrochemical system 1.

[0081] Figure 5B The resilient contact area 44 is shown with a spring surface 46 running around the contact surface 42. With an inclination of about 10° relative to the contact surface β, the spring surface 46 has a pitch sk which is lower than the average pitch of the flanks of adjacent webs sf in the same diaphragm 2a with an inclination φ of about 32° relative to the contact surface. However, the inclination of the flanks, i.e. the inclination of the straight flank section 29a, is significantly steeper and is about ε=60°.

[0082] exist Fig. 6A In FIG. 1 , an oblique view of another section 202 of the distribution region 20 is shown, which section 202 may, however, also belong to another bipolar plate 2 according to the invention. Figure 6B A detailed view of the association is shown. Fig. 6AThe elastic contact areas 44 shown in each have a blunt shape, as do the contact surfaces 42. The spring surface 46 surrounds the latter in a substantially circular shape. Compared to the webs 26a that separate them, the width of the gas flow channel 27a of the upper partition 2a in the area in which the elastic contact areas 44 are not arranged is only about a quarter of the width of the webs 27a that separate them. Therefore, the width of the temperature control medium flow channel 22a is about four times the width of the partitions 21a that separate them. However, the webs 21a widen in the area of ​​the elastic contact areas 44. There, they have a maximum web width Bk, which is almost 5 times the web width Bs outside the elastic contact areas 44, which is Figure 6B This is particularly evident in Figure 6B , the width Bk is only shown symbolically in the widest web region; it should actually extend orthogonally to the longitudinal axis of the web and therefore parallel to Bk, but this is difficult to depict due to the oblique view.

[0083] The angle β that the spring surface 46 makes with the plane of the diaphragm or the plane of the contact surface 42 is again approximately 10°, whereas the angle that the flank 29a makes with the contact surface 42 is approximately 25° and is therefore somewhat smaller than in the previous examples.

[0084] Figure 7 A partial top view of the distribution area 20 of another bipolar plate 2 according to the invention is shown. On the one hand, various forms of elastic contact areas 44 are exemplarily shown in a top view of the plate plane E or a view through the partition 2a. On the one hand, various forms of elastic contact areas 44 are exemplarily shown in a top view of the plate plane E or a view through the partition 2a. Elements located on the surface facing the observer and elements arranged in the cavity 19 or on the bottom side are provided with reference numerals. On the one hand, a group of elastic contact areas 44l is provided, which extend from the lower left to the upper right in an elongated shape and merge directly into the web 21a separating the temperature control medium flow channel 22a in each case. A group of elastic contact areas 44o with a rounded elongated shape is shown as the far right and in the center, which also extends from the lower left to the upper right, but is a short distance away from the web 21a separating the temperature control medium flow channel 22a. To the left of the center, a group of elastic contact areas 44r is shown, which have a rounded shape and a clear distance from the webs 21a separating the temperature control medium flow channels 22a. Finally, an exemplary embodiment of an elastic contact area 44f is shown at the upper left corner, which has a free form.

[0085] exist Figure 7In all the examples shown in the drawings, the elastic contact area 44 has a contact surface 42 and a spring surface 46 extending around the contact surface 42 at least in some sections. The spring surfaces 46o, 46r, 46f are designed so that the spring surfaces 46o, 46r, 46f completely encircle the contact surfaces 42o, 42r, 42f. In the elastic contact area 44l with a group of elongated shapes, the spring surface 42l also has an elongated shape, at least in some sections. These elongated spring surfaces 42l extend between the two most proximal temperature control medium flow channels 22a so that they connect their mutually facing flank ends.

[0086] Figure 7 , the gas flow channels 27a of the upper separator 2a are parallel to each other and run from the upper left to the lower right with an inclination of less than 10° to the horizontal plane. The temperature control medium flow channels 22a extend in the same direction on the rear side of the webs 26a separating the gas flow channels 27a and also run parallel and with the same inclination. The flanks between the webs and the channels are each indicated by reference numeral 28a on the inner side of the bipolar plate 2 carrying the temperature control medium, or by reference numeral 29a on the outer surface of the bipolar plate 2 carrying the gas.

[0087] on the other hand, Figure 7 Also shown is the direction of the temperature control medium flow channel 22b in the partition 2b, which is shown at the bottom of the illustration with a dotted line. The temperature control medium flow channel 22b (or the partition 26b between the gas flow channels 27b) extends between the areas bounded by the longer dotted lines, the corresponding partition 21b (or the gas flow channel 27b) extends between the areas bounded by the shorter dotted lines, and the flank 28b or 29b extends between the longer dotted lines and the shorter dotted lines. These structures run from the lower left to the upper right. The temperature control medium flow channel 22a of the first partition 2a forms an angle δ of about 150° with the temperature control medium flow channel 22b of the second partition 2b.

[0088] The elastic contact areas 44l run in such a way that their longitudinal axes Ll are substantially parallel to the longitudinal axes Lsb of the webs in the adjacent partitions 2b, in this case parallel to the webs 21b separating the flow channels for the temperature control medium and parallel to the webs 26b separating the flow channels for the gas. The longitudinal axis Lsb is only explicitly drawn for the webs of the latter type. In principle, however, there can also be an acute angle between the two webs, but it should not exceed 30°. For the longitudinal axes Lo and Lf of the elastic contact areas 44o and 44f and the longitudinal axis Lsb, a considerable degree of parallelism is also given here. The longitudinal axes Lt of the spring surfaces 46 arranged on both sides of the contact area 42f also run parallel to the longitudinal axes Lsb of the webs 21b and 26b.

[0089] Fig. 8A , Figure 8B , Figure 8C Three figures show further embodiments of the bipolar plate according to the invention, wherein Fig. 8A and Figure 8B The elastic contact area 44 in the embodiment is different from that in the previous embodiment; in order to emphasize this different form, the relevant reference numerals are provided with a prime to distinguish them. Fig. 8A and Figure 8B In both cases, the elastic contact areas 44', 44", 44'" are formed in the shape of keyholes. Fig. 8A In the embodiment, all elastic contact areas 44', 44" have in common that the contact surfaces 42', 42" have a rounded and elongated shape. The spring surfaces 46', 46' surrounding the contact surfaces 42', 42" each have a constant width along their rounded end areas. The elongated lateral sections are designed differently. Although the corresponding section of the contact area 44' initially forms a narrow area 48', which widens into a wide area 47' and then narrows again essentially symmetrically into a narrow area 48', the arrangement of the wide area 47" and the narrow area 48" is reversed in the elastic contact area 44". Therefore, in the elastic contact area 44', a particularly high elasticity is achieved in the middle area, that is, in the narrow area of ​​the spring surface 44', so that the elasticity increases from one end towards the middle and only increases again towards the opposite end. On the other hand, the uniformity of the elasticity is achieved over the entire elastic contact area 44' by means of the spring surface 46". The varying width of the elastic contact areas 44', 44" and their protrusions or depressions can further contribute to the deflection of the temperature control medium. The regions 47, 48 with different widths have different pitches because they connect planes with the same distance. Fig. 8A Two different elastic contact areas 44 ′, 44 ″ are shown, in each of which the elastic area 46 has at least two areas 47 , 48 with different pitches relative to the contact surface 42 delimited by the elastic area 46 , which at least two areas 47 , 48 follow one another circumferentially.

[0090] In the elastic contact area 44'", the contact surface 42'" also has a roughly keyhole shape. The spring surface 46'" runs around the contact surface 42'" with a substantially constant width. However, the curved area 49 has slightly less elasticity than the straight section. The elastic contact area 44'" and its convex or concave overall shape serve, on the one hand, to better utilize the installation space in the temperature control medium web 21 and at the same time to additionally guide the temperature control medium around the elastic contact area 44'".

[0091] exist Figure 8B In the example, different areas of the separator covered by the visible separator of the bipolar plate 2 are also shown in the same manner as Figure 7 The same line pattern is shown. For example, Figure 7In contrast, the webs and channels of the covered diaphragm do not run parallel to the longitudinal axis Lf of the elastic contact region 44 ′″, but rather at an acute angle γ, which here amounts to approximately 5°.

[0092] Figure 8C The distribution area can also be designed with at least one intermediate temperature control medium channel 220, which is, for example, partially arranged in the web 21 between two temperature control medium flow channels 22. Figure 7 As shown in , the dotted lines represent different areas of the partitions covered by the visible partitions of the bipolar plate 2. Thus, the intermediate channel 220 runs in an area in which the temperature control medium flow channel, i.e., the flanks that bound the channel, also extend in another partition. Thus, the intermediate channel 220 extends the flow cross section available to the temperature control medium in the corresponding area. At the same time, the structure of the intermediate channel 220 can also form additional flow guiding elements on the surface facing the observer, i.e., an intermediate web or an additional barrier in the area of ​​the gas flow channel 270. This also allows the direction of the gas flow in the gas flow channel 270 to be affected. Figure 8C The given reference numerals in do not specify the first separator or the second separator, thereby emphasizing that the elastic contact area 44 can in principle be arranged in the anode plate and / or the cathode plate of the bipolar plate. However, if they are arranged in two separators, it is preferred to arrange them in non-overlapping sections in the bipolar plate.

[0093] Fig. 9 An oblique view of a cross section of a distribution area of ​​another bipolar plate according to the invention is shown, which is a variation of FIG. 5 . Here, the spring surface 46 is stepped around the contact surface 42 and has an outer region 46a with a constant pitch sk and an inner region 46b with a pitch designed to be a radius r1. The cutting edge of the region 46b facing the observer, including the short straight section where the cutting edge runs along the contact surface 42, is shown in dashed lines in its lower and upper boundary lines, thereby emphasizing the radius r1.

[0094] FIG. 4A to FIG. 9 All examples in FIG. 3 show that, in the compensation region 35 , the web of one of the webs 2 a , 2 b each has no materially bonded connection 38 to the second web 2 b .

Claims

1. A bipolar plate (2) for an electrochemical system (1), comprising a first separator (2a) and a second separator (2b), wherein the first separator (2a) and the second separator (2b) are arranged adjacent to each other in a direction perpendicular to a plate plane (39, 39b) of the first separator and / or the second separator (2a, 2b), wherein the first separator and the second separator (2a, 2b) each have, a first through opening (11b, 11c) for allowing a reaction medium to pass through the partition plate, and a second through opening (11a), the first through opening being used for allowing a reaction medium to pass through the partition plate, the second through opening being adjacent to the first through opening in the plate plane (39a, 39b) for allowing a temperature control medium to pass through the partition plate (2a, 2b); - an active area (18) with first structures (17) for directing the reaction medium along the outer flat side of the separator and second structures for directing the temperature control medium along the inner side of the bipolar plate (2); and - at least one distribution or collection area (20) with a first structure for guiding the reaction medium between the first through-opening (11b, 11c) and the active area and a second structure for guiding the temperature control medium between the second through-opening (11a) and the active area, wherein The structure for guiding the temperature control medium in the distribution or collection area (20) has temperature control medium flow channels (22a, 22b) separated from each other by webs (21a, 21b), It is characterized in that The distribution or collection area (20) of the first partition (2a) and / or the distribution or collection area (20) of the second partition (2b) has at least one compensation area (35, 35a, 35b), Wherein, in a state where the bipolar plate (2) is not assembled, in one, several or all of the at least one compensation area (35), the webs (21a, 21b) facing the corresponding adjacent partitions (2a, 2b) between the mutually adjacent temperature control medium flow channels (22a, 22b) are spaced apart from the adjacent partitions in a direction perpendicular to the plate planes (39a, 39b), but the compensation area (35, 35a, 35b) has at least one independent elastic contact area (44) spaced apart from its outer edge (30), in which a section of the web (21a, 21b) protrudes so that the section forms a contact surface (42) with the adjacent partitions (2a, 2b).

2. The bipolar plate according to the preceding claim, characterized in that The contact surface (42) of the elastic contact area (44) of one of the separators (2a, 2b) touches the web section (21k) of another of the separators (2b, 2a), wherein the contact surface (42) of the elastic contact area (44) and the web section (21k) of the other separator (2b, 2a) that touches the contact surface (42) form a fluid barrier (31) inside the bipolar plate (2).

3. A bipolar plate according to any one of the preceding claims, characterized in that For one, several or all of the elastic contact areas (44), the elastic contact area (44) has an elongated shape (44l), an elongated blunt shape (44o), a blunt shape (44r) or a free shape (44f) in a top view of the plate plane of one of the partitions.

4. A bipolar plate according to any one of the preceding claims, characterized in that For one, several or all of the compensation areas (35), in a top view of the plate plane (39a, 39b) of one of the partitions (2a, 2b), the compensation area (35) has a compensation area area (FA), and the elastic contact area (44) of the compensation area (35) has a total elastic contact area area (FKges), wherein FKges≤0.2FA, in particular FKges≤0.1FA.

5. A bipolar plate according to any one of the preceding claims, characterized in that For one, several or all of the compensation areas (35), in a top view of the plate plane (39a, 39b) of one of the partitions (2a, 2b), the compensation area (35) has a compensation area area (FA), and the contact surface (42) of the elastic contact area (44) of the compensation area (35) has a total contact surface area (FBges), wherein in the pressed state FBges≤0.05FA, in particular Fbges≤0.03FA.

6. A bipolar plate according to any one of the preceding claims, characterized in that For one, several or all of the elastic contact areas (44), in a top view of the plate plane of one of the partitions (2a, 2b), the elastic contact area (44) has an elongated shape (44l) or a blunt elongated shape (44o), and extends on its longitudinal axis (Ll, Lo) at an angle α≠0° to the longitudinal axis (Ls, Lsa, Lsb) of the web (21a, 21b) in the corresponding elastic contact area (44), wherein advantageously 15°≤α≤90°, in particular 20°≤α≤60°.

7. A bipolar plate according to any one of the preceding claims, characterized in that The orthogonal projections of one, several or all of the elastic contact areas of one of the partitions (2a, 2b) and the web of the distribution or collecting area (20) of the other partition (2b, 2a) onto the plate plane (39a, 39b) of the first partition and / or the second partition (2a, 2b) extend at an angle γ≤30°, preferably γ≤20°, in particular γ≤10° relative to each other.

8. A bipolar plate according to any one of the preceding claims, characterised in that For one, several or all of the elastic contact areas (35), in a top view of the plate plane (39a, 39b) of one of the partitions (2a, 2b), the elastic contact area (44) has an elongated shape or a blunt elongated shape, and its longitudinal axis (L) extends basically parallel to the longitudinal axis (Ls, Lsa, Lsb) of the web (21) in the adjacent partition.

9. A bipolar plate according to any one of the preceding claims, characterized in that The web width (Bs) is constant in the region of the elastic contact region (44).

10. A bipolar plate according to any one of the preceding claims, characterised in that The maximum web width (Bk) in the region of the elastic contact area (44) is at least 30%, preferably at least 50%, in particular at least 100%, particularly preferably at least 200% greater than the web width (Bs) outside the elastic contact area (44).

11. A bipolar plate according to any one of the preceding claims, characterized in that The resilient contact area (44) has a spring surface (46) which extends around the contact surface (42) at least in some sections and has a pitch (sk) which is smaller than the average pitch of the flanks of adjacent webs (sf) in the same diaphragm.

12. A bipolar plate according to any one of the preceding claims, characterised in that The elastic contact area (44) has a spring surface (46) which extends around the contact surface (42) at least in sections and has a pitch (sb) of β≤30°, preferably β≤20°, in particular β≤15° relative to the contact surface.

13. A bipolar plate according to any one of the two preceding claims, characterised in that The spring surface (46) completely encircles the contact surface (42).

14. The separator according to any one of claims 11 to 13, characterized in that: The spring surface (46) has an elongated shape at least in some sections in a top view of the plate plane (39a, 39b) of one of the partitions (2a, 2b), and its longitudinal axis (Lt) extends substantially parallel to the longitudinal axis (Ls, Lsa, Lsb) of the web (21) of the adjacent partition.

15. The separator according to any one of claims 11 to 14, characterized in that: The spring surface (46) extends between two temperature control medium flow channels (26) that are closest to each other, so that the spring surface connects the flank ends of the two temperature control medium flow channels that face each other.

16. A bipolar plate according to any one of the preceding claims, characterised in that The temperature control medium flow channel (22a) of one of the partitions (2a, 2b) and the temperature control medium flow channel (22b) of the other partition (2b, 2a) extend at an angle of 15°≤δ≤90°, preferably 20°≤δ≤60°, at least in some sections.

17. The bipolar plate (2) according to any one of the preceding claims, It is characterized in that In the compensation region (35), the webs (21) of one of the webs (2a, 2b) are each connected to the other web (2b, 2a) without a material bond.

18. The bipolar plate (2) according to any one of the preceding claims, It is characterized in that The spring area (46) has at least two areas (46a, 46b, 47, 48, 49), which have different pitches relative to the contact surface (42) defined by the spring area (46), wherein one of the two areas preferably encloses the other area, in particular completely encloses the other area and / or the at least two areas (47, 48, 49) follow each other in a circumferential manner.

19. A bipolar plate according to any one of the preceding claims, characterised in that For one, several or all of the compensation areas (35, 35a, 35b) of the first partition and / or the second partition (2a, 2b), in the compensation area (35, 35a, 35b), except for the elastic contact area, the depth of the temperature control medium flow channel (22a, 22b) is less than the depth of the outer side wings (28a') of one or both of the two outermost temperature control medium flow channels.

20. Electrochemical system (1) comprising at least one separator (2) according to one of the preceding claims and at least one MEA.

Images