Bipolar plate for an electrochemical system

Abstract

Bipolar plate (2) for an electrochemical system (1), comprising a first separator plate (2a) and a second separator plate (2b) arranged adjacent to each other in a direction perpendicular to the plane (39a, 39b) of the first and / or the second separator plate (2a, 2b), wherein the first and the second separator plate (2a, 2b) are each adjacent to each other in a direction perpendicular to the plane (39a, 39b) of the plate. - a first through-opening (11b, 11c) for passing a reaction medium through the separator plate and a second through-opening (11a) adjacent to the first through-opening in the plane of the plate (39a, 39b) for passing a temperature control medium through the separator plate (2a, 2b) ; - an active area (18) with first structures (17) for guiding reaction medium along an outer flat side of the separator plate and second structures for guiding the temperature control medium along the inner side of the bipolar plate (2); and - at least one distribution or collection area (20) with first structures for guiding the reaction medium between the first through-hole (11b, 11c) and the active area and second structures for guiding the temperature control medium between the second through-hole (11a) and the active area, wherein the structures for guiding the temperature control medium in the distribution or collection area (20) have temperature control medium flow channels (22a, 22b) which are separated from each other by webs (21a, 21b), characterized by the fact that the distribution or collection area (20) of the first separator plate (2a) and / or the distribution or collection area (20) of the second separator plate (2b) shall have at least one equalization area (35, 35a, 35b), wherein, in the unmounted state of the bipolar plate (2), in one, several or all of the at least one compensation area (35), the webs (21a, 21b) facing the respective adjacent separator plate (2a, 2b) are spaced apart from the adjacent separator plate in a direction perpendicular to the plate plane (39a, 39b) between mutually adjacent temperature control medium flow channels (22a, 22b), with the exception that the compensation area (35, 35a, 35b) has at least one freestanding elastic contact area (44) spaced apart from its outer edge (30), in which a section of a web (21a, 21b) projects outwards in such a way that this section forms a contact surface (42) with the adjacent separator plate (2a, 2b).

Description

[0001] The invention relates to a bipolar plate for an electrochemical system. The electrochemical system can, in particular, be a fuel cell system, an electrochemical compressor, an electrolyzer, or a redox flow battery. It can comprise a plurality of such bipolar plates. An electrochemical system comprising a plurality of such bipolar plates is also disclosed.

[0002] Known electrochemical systems of this type typically comprise a stack of electrochemical cells, each separated from the other by bipolar plates. Such bipolar plates can serve, for example, to electrically contact the electrodes of the individual electrochemical cells (e.g., fuel cells) and / or to electrically connect neighboring cells (series connection of the cells). Typically, the bipolar plates are formed from two joined individual plates, which are also referred to as separator plates in this document. The individual plates can be joined together in a materially bonded manner, e.g., by one or more welded joints, in particular by one or more laser-welded joints.

[0003] The bipolar plates or the individual plates can each have or form structures of the type explained below, which are designed, for example, to supply the electrochemical cells arranged between adjacent bipolar plates with one or more media and / or to transport reaction products away. The media can be fuels (e.g., hydrogen or methanol), reaction gases (e.g., air or oxygen), or a temperature control medium. Furthermore, the bipolar plates can be designed to conduct the waste heat generated during the conversion of electrical or chemical energy in the electrochemical cell and to seal the various media or temperature control medium channels from one another and / or from the outside.

[0004] Furthermore, the bipolar plates typically each have at least one through-opening through which the media and / or reaction products can be conducted to or from the electrochemical cells arranged between adjacent bipolar plates of the stack. The electrochemical cells typically also each comprise one or more membrane electrode assemblies (MEAs). The MEAs can have one or more gas diffusion layers, which are usually oriented toward the bipolar plates and are formed, for example, as a metal or carbon fleece.

[0005] As structures for media supply and / or media guidance, channels can be provided within the separator plates and thus the bipolar plate, separated from each other by webs. The channels, which can be embossed, for example, in the form of grooves, can provide flow paths for the typically liquid or gaseous media.

[0006] Typically, each separator plate has an active region with channels for guiding a reaction medium and / or reaction products along the outside of the bipolar plate. This active region faces an MEA. The active region can also be referred to as a flow field or comprise a flow field.

[0007] The active area is fluidically connected to one of the through-openings via a so-called distribution area and is fed through this. From the active area, reaction media and / or reaction products can be fed to another through-opening for removal via a further distribution area, which can also be referred to as a collection area.

[0008] On the facing inner sides of two separator plates encompassed by a respective bipolar plate, the aforementioned channel-web structures of the flow field and the at least one distribution area form complementarily shaped web-channel structures. These define a flow area for conducting the temperature control medium in the interior of the bipolar plate.

[0009] The distribution areas also typically have separate channels. In the following, the channels on the outer sides of the bipolar plate in a distribution area are referred to as gas flow channels, and the channels in the interior of the bipolar plate are referred to as temperature control medium flow channels.

[0010] When forming a functional stack, a membrane electrode assembly is provided between adjacent bipolar plates. This assembly separates the channels for the passage of the reaction medium in a first bipolar plate from the channels for the passage of another reaction medium in a second bipolar plate, separated from the first bipolar plate only by the membrane electrode assembly. The membrane electrode assembly, typically abbreviated as MEA, typically extends beyond the active region into the distribution region(s).

[0011] The active region of an MEA typically comprises the actual proton-conducting membrane, electrodes applied to it, and catalyst layers, on which conductive and gas-permeable layers, so-called gas diffusion layers (GDLs), are applied. In its peripheral region, the MEA typically comprises a polymer-based film material that encloses the active region in a frame-like manner and overlaps with the materials forming the active region, or a portion of them, in a narrow overlap area. In a stack of an electrochemical system, the MEA defines the distance between the separator plates. At the same time, the gas diffusion layers (GDLs) of the MEA exhibit relatively large variations in their thickness.

[0012] Therefore, just enough space is usually provided between bipolar plates in the thickness direction of the stack to ensure that there is sufficient room in the active area to accommodate the relevant section of the MEA, while at the same time, there is just enough space for this section of the MEA to be compressed in a defined manner. This results in more space being provided in the distribution areas than is absolutely necessary for its proper function. An above-average thick MEA in the active area will result in a large gap in the distribution areas, while an below-average thin active area of ​​the MEA will result in a small or no gap in the distribution areas.

[0013] In conventional electrochemical systems, the bipolar plates are designed so that their separator plates partially overlap, both in the active region and in the distribution regions, and are at least partially welded together in these regions. However, pressure fluctuations in the temperature control medium flowing between the separator plates of a bipolar plate cause the separator plates to move relative to each other and subject the connections between the separator plates of a bipolar plate, particularly welded connections in the distribution regions, to dynamic pressure fluctuations and stresses. These can lead to fracture of the welded connection. This is especially true if the connections are already subjected to increased stress due to variations in the thickness of the MEAs.

[0014] As a result, undefined flow of the temperature control media through the interior of the bipolar plate can occur, leading to pressure losses and thus efficiency losses. Furthermore, the separator plates themselves can also become perforated in the area of ​​the welded joints, jeopardizing the operability and, in particular, the operational reliability of the bipolar plate and the underlying electrochemical system.

[0015] Other previously known solutions provide the necessary height tolerance in the distribution area in the form of a gap between the two separator plates of a bipolar plate, but this results in no or insufficient control of the temperature control medium, so that poorly cooled zones can arise in the active area of ​​the bipolar plate, which can lead to damage to the MEA and also result in efficiency losses.

[0016] An object of the present invention is therefore to provide a bipolar plate with which thickness variations of an MEA can be compensated in an electrochemical system while ensuring improved efficiency and improved operational reliability, wherein preferably at the same time a defined distribution of the temperature control medium over the active area of ​​the bipolar plate is achieved.

[0017] This object is at least partially achieved by the subject matter of the independent claims. Advantageous further developments are specified in the dependent claims, in this description, and in the figures.

[0018] Accordingly, a bipolar plate for an electrochemical system is proposed. The bipolar plate comprises a first separator plate and a second separator plate, which are arranged adjacent to one another in a direction perpendicular to the plate plane of the first and / or the second separator plate. The first and the second separator plates each have, adjacent to one another in a direction perpendicular to the plate plane, a first through-opening for passing a reaction medium through the separator plate and a second through-opening adjacent to the first through-opening in the plate plane for passing a temperature control medium through the separator plate. The first and second separator plates further each comprise an active region with first structures for guiding reaction medium along an outer flat side of the separator plate and second structures for guiding the temperature control medium along the inner side of the bipolar plate.These are also arranged adjacent to each other in the vertical direction or overlap with each other when projected orthogonally into the plane of the plate.

[0019] Furthermore, the first and second separator plates each have at least one distribution or collection region adjacent to one another in a direction perpendicular to the plate plane, with first structures for guiding the reaction medium between the first through-opening and the active region and second structures for guiding the temperature control medium between the second through-opening and the active region. The structures for guiding the temperature control medium in the distribution or collection region have temperature control medium flow channels that are separated from one another by webs pointing toward the respective other separator plate.

[0020] Furthermore, the at least one distribution or collection region of the first separator plate and / or the distribution or collection region of the second separator plate has at least one compensation region. In the unassembled state of the bipolar plate, in one, several, or all of the at least one compensation region, those webs facing the respective adjacent separator plate are spaced from the adjacent separator plate in the regions between adjacent temperature control medium flow channels in a direction perpendicular to the plate plane. This applies with the exception that the compensation region has at least one freestanding elastic contact region spaced from its outer edge, in which a section of a web projects such that this section forms a contact surface with the adjacent separator plate.

[0021] The predominant spacing of the webs of a separator plate from the adjacent separator plate in the compensation area serves to compensate for height fluctuations of the MEA or GDLs. If an MEA or MEAs are installed with above-average thickness GDLs, a gap remains even after the bipolar plate and MEA have been installed and clamped in a stack of an electrochemical system. If an MEA is installed with below-average thickness GDLs, at least part of the gap is compressed during the installation and clamping of the bipolar plate and MEA in a stack of an electrochemical system. The gap is typically designed to accommodate even very thin GDLs.

[0022] However, at a distance from its outer edge, the compensation region also has at least one free-standing elastic contact region in which a section of a web projects in such a way that this section forms a contact surface with the adjacent separator plate. The at least one elastic contact region is usually designed such that it has at least an elastic compression component so that, after installation and clamping, it can deform reversibly under normal operating pulsation of the temperature control medium. After installation and clamping of the bipolar plate and a relatively thinner MEA in a stack of an electrochemical system, the at least one elastic contact region exhibits both plastic and elastic deformation. If, on the other hand, a very thick MEA is also installed, only elastic deformation may be present.However, the elasticity of the contact areas not only allows height compensation for different MEA or GDL thicknesses, but also adaptation to pressure pulsation.

[0023] Preferably, the contact surfaces of the elastic contact regions of one separator plate contact web sections of the other separator plate such that the contact surfaces of the elastic contact regions and the web sections of the other separator plate contacting the contact surfaces form a fluid barrier inside the bipolar plate, around which the temperature control medium must flow. This can result in a steering effect for the temperature control medium, so that, through a suitable arrangement of the contact surfaces, the temperature control medium can be guided in a defined manner into the areas that would experience inadequate temperature control during operation without such guidance, thereby improving the efficiency of the electrochemical system.

[0024] The contact surfaces project from the web surface towards the other separator plate and, before the bipolar plate is installed and clamped in a stack of an electrochemical system, lie against the other separator plate. This contact is also usually present under normal operating conditions, i.e. after installation and clamping. Very strong temperature control medium pressure pulses can temporarily cause the contact surfaces to lift off briefly. It is advantageous if, within a compensation area, the webs of one of the separator plates are free of any material connections to the other separator plate. The elastic contact elements therefore even make it possible to dispense with weld seams connecting the separator plates. These seams cannot therefore tear, especially if the separator plates are locally perforated. This increases operational reliability.

[0025] The elastic contact area can have an elongated shape, an elongated-rounded shape, a round shape, or a free-form shape for one, several, or all of the elastic contact areas when viewed from the plane of one of the separator plates. If multiple elastic contact areas are present in a distribution or collection area, these can have different shapes. In particular, the choice of a specific shape for the elastic contact area can be adapted to the available installation space; moreover, the specific shape can also influence the elasticity of an elastic contact area. For example, round elastic contact areas can be used in areas where less fluid guidance is required, while the other shapes mentioned, in particular the elongated shapes, can preferably be used for guidance.

[0026] In a top view of the plate plane of a separator plate, one compensation area or one of several or all compensation areas together - including the elastic contact areas contained therein - occupies an area FA. The total area of ​​all contact areas contained therein is denoted by FKges. The ratio of these two areas is FKges ≤ 0.2 FA, in particular FKges ≤ 0.1 FA. The elastic contact areas therefore only take up a fraction of the compensation area. This results in a large area of ​​the compensation area in which temperature control medium is present or can flow between the two separator plates, in particular also between the mutually facing webs.

[0027] The contact surfaces of the elastic contact areas typically only make up a portion of the total area of ​​the elastic contact areas. Viewed from the plane of a separator plate, the total area of ​​the contact surfaces contained in one, a specific one of several, or all of the compensation areas can be determined as FBges. The ratio of the area of ​​the one, one of several, or all of the compensation areas FA, as defined above, and the contact surfaces enclosed therein is FBges ≤ 0.05 FA, in particular FBges ≤ 0.03 FA. This applies to both the uninstalled and installed state.

[0028] It has been found that particularly good fluid guidance of the temperature control medium can be achieved if one, several or all of the elastic contact areas have / have an elongated or elongated-rounded shape when viewed onto the plate plane of one of the separator plates and run / run in their / their longitudinal axis at an angle α other than zero to the longitudinal axis of the webs from which they project in the respective elastic contact area. Angles α with 15° ≤ α ≤ 90°, in particular 20° ≤ α ≤ 60°, are particularly advantageous. In the case of non-rectilinear webs, the longitudinal axis can be understood as the center line of two tangents, whereby the tangents touch the straight flank sections or turning points of the web flanks on both sides of the web where a web flank is at the shortest distance from the respective elastic contact area.

[0029] While in the active region of a bipolar plate, the channels of both separator plates usually run essentially parallel, it is advantageous for targeted media distribution across the entire width of the active region if, in the distribution and / or collection region, the gas channels of one separator plate run at an angle to the gas channels of the other separator plate of the bipolar plate. As a result, the temperature control medium flow channels of both separator plates do not run parallel to each other inside a bipolar plate. For example, the temperature control medium flow channels of one of the separator plates and the temperature control medium flow channels of the other separator plate can run, at least in sections, at an angle of 15° ≤ δ ≤ 90°, preferably 20° ≤ δ ≤ 60°. This already contributes significantly to distributing the temperature control medium across the entire width of the active region.For both sufficient support of the contact surface(s) of the at least one elastic contact region on the other separator plate and defined guidance of the temperature control medium, it is advantageous if one, several, or all of the elastic contact regions of one of the separator plates and a web of the distribution or collection region of the other separator plate extend at a very acute or even negligible angle to one another in orthogonal projection onto the plate plane of the first and / or second separator plate. Particularly advantageous are angles γ for which γ ≤ 30°, preferably γ ≤ 20°, in particular γ ≤ 10°. The angle is determined on the side of the elastic contact region along its longest extent, both in the case of an elongated elastic contact region and in the case of an elastic contact region that corresponds to a free form.On the side of the web, the longitudinal axis of the web is used, which is determined as before the longitudinal axis of the web of the separator plates containing the elastic contact area, whereby the elastic contact area is projected orthogonally onto the other separator plate.

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

[0031] In embodiments, the web width is constant in the region of the elastic contact area. Alternatively, the web width increases in the elastic contact area. Thus, the maximum web width in the region of the elastic contact area can be at least 30%, preferably at least 50%, in particular at least 100%, and particularly preferably at least 200% larger than the web width of this web outside of an elastic contact area, for example, in the region of the web profile that does not have an elastic contact area and in which the web otherwise has its maximum width.

[0032] The elastic contact area can have a spring surface that extends at least partially around the contact surface. The spring surface is preferably designed to impart elasticity to the elastic contact area. For example, the spring surface can have a smaller gradient than the average gradient of the flank of the web in which the elastic contact area is arranged. For example, the gradient of the spring surface can form an angle β relative to the contact surface of the elastic contact area, for which β ≤ 30°, preferably β ≤ 20°, in particular β ≤ 15° applies.

[0033] The spring surface can completely surround a contact surface. This is particularly preferred for rounded, elongated, or round contact areas, or for contact areas with a free form. Alternatively, particularly 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 sections, in a plan view of the plate plane of one of the separator plates, and its longitudinal axis can run essentially parallel to a web, in particular to the longitudinal axis of a web, in the adjacent separator plate. It is preferred if a corresponding elongated spring surface extends on both sides of each elongated contact surface.

[0034] In particular, an elongated or elongated-rounded spring surface can extend between two adjacent tempering medium flow channels in such a way that it connects their facing flank ends. This allows the entire width of the web to be provided with a barrier element.

[0035] Furthermore, it is possible for a spring region of an elastic contact region to consist of more than just one uniformly designed region. A spring region can also have at least two regions which have a different pitch relative to the contact surface delimited by the spring region. On the one hand, such regions of different pitch can follow one another in a circumferential manner, for example in order to achieve different elasticities in different regions. For this purpose, the width of the corresponding regions of the spring region is preferably also adapted to avoid height steps. On the other hand, but not excluding the previous arrangement, these different regions can also be arranged relative to one another in such a way that one of these two regions preferably surrounds the other region, in particular completely surrounds it.For example, a contact surface can be surrounded by a first of these spring regions, particularly over its entire circumference. This first spring region can then, in turn, be partially or completely surrounded by the second spring region. These series-connected spring regions can create a progressive spring characteristic, especially if both spring regions have different maximum deflections.

[0036] Furthermore, one of the two separator plates of a bipolar plate in the compensation area(s) can have the temperature control medium flow channels, with the exception of the elastic contact areas, less deep than the outer flank of one or both of the two outermost temperature control medium flow channels. This makes it particularly easy to create the gap between the webs in the compensation area.

[0037] The invention also relates to an electrochemical system comprising a plurality of bipolar plates according to any aspect described herein and MEAs, in particular a plurality of stacked bipolar plates and MEAs arranged therebetween.

[0038] Embodiments of the invention are explained below with reference to the accompanying schematic figures. Similar reference numerals may be used throughout the figures for comparable features. They show: Fig. 1 an electrochemical system with conventional bipolar plates or bipolar plates according to the invention; Fig. 2 a section of the electrochemical system from Fig. 1 with conventional bipolar plates; Fig. 3 in three Fig. 3A-3C show 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; Fig. 4 in five Fig. 4A-4E show a partial plan view, three partial cross-sectional views and a temperature control medium distribution of a bipolar plate according to the invention; Fig. 5 in two Fig. 5A and Fig. 5B is an oblique view of a portion of a distribution region of a bipolar plate according to the invention and a corresponding detailed view; Fig. 6 in two Fig. 6A and Fig. 6B is an oblique view of a portion of a distribution region of another bipolar plate according to the invention and a corresponding detailed view; Fig. 7 a partial plan view of a distribution area of ​​another bipolar plate according to the invention; Fig. 8 In three Fig. 8A-8C show three partial plan views of distribution regions of bipolar plates according to the invention; and. Fig. 9 an oblique view of a section of a distribution area of ​​another bipolar plate according to the invention

[0039] Fig. 1 shows an electrochemical system 1 with a plurality of identical bipolar plates 2. The bipolar plates 2 are arranged as an array in a stack 6 and stacked along a z-direction 7. The bipolar plates 2 of the stack 6 are clamped between two end plates 3, 4. The z-direction 7 is also called the stacking direction. In the present example, the system 1 is a fuel cell stack. Each two adjacent bipolar plates 2 of the stack 6 enclose an electrochemical cell between them, which serves, for example, to convert chemical energy into electrical energy. To form the electrochemical cells of the system 1, a membrane electrode assembly (MEA) is arranged between each adjacent bipolar plates 2 of the stack 6 (see, for example, Fig. 2). MEAs typically contain a membrane, e.g., an electrolyte membrane. Furthermore, a gas diffusion layer (GDL) can be arranged on one or both surfaces of the MEA.

[0040] Alternatively, this can be Fig. 1 and Fig. The system 1 shown in Figure 2 can also be designed as an electrolyzer, an electrochemical compressor, or a redox flow battery. Bipolar plates 2 can also be used in these electrochemical systems. The structure of these bipolar plates 2 can correspond to the structure of the bipolar plates 2 explained in more detail here, even if the media flowing on or through the bipolar plates 2 in an electrolyzer, an electrochemical compressor, or a redox flow battery can differ from the media used in a fuel cell system.

[0041] The z-axis 7, together with an x-axis 8 and a y-axis 9, forms a right-handed Cartesian coordinate system. The bipolar plates 2 each define a plate plane E (see Fig. 3B and Fig. 4B), in which separator plates 2a, 2b (see Fig. 2), which form metallic layers of the bipolar plates 2. The separator plates 2a, 2b also form their own plate plane 39a, 39b in their non-formed areas (cf. Fig. 3B, Fig. 4B, Fig. 5B and Fig. 6B), wherein the plate planes of both the bipolar plates 2 and the separator plates 2a, 2b are each aligned parallel to the xy-plane and thus perpendicular to the stacking direction or to the z-axis 7. The end plate 4 has a plurality of media connections 5, via which media can be supplied to the system 1 and via which media can be removed from the system 1. These media that can be supplied to the system 1 and removed from the system 1 can include, for example, fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or depleted fuels, or possibly a temperature control medium such as water and / or glycol. In an electrolyzer, water is supplied to the stack and oxygen and hydrogen are removed from it.

[0042] Fig. 2 shows in perspective two adjacent bipolar plates 2 of the system 1 from Fig. 1 and a membrane electrode assembly (MEA) 10 arranged between these adjacent bipolar plates 2 and known in principle from the prior art. The MEA 10 is in Fig. 2 is largely covered by the bipolar plate 2 facing the viewer. The bipolar plate 2 is formed from two materially joined separator plates 2a, 2b, of which Fig. 2, only the first separator plate 2a facing the viewer is visible over a large area, which obscures the second separator plate 2b. The separator plates 2a, 2b can each be made of a metal sheet, e.g., a stainless steel sheet or a sheet made of a titanium alloy. The sheets can be coated or plated in sections or over their entire surface, for example, by means of a corrosion-inhibiting and / or conductivity-enhancing coating. The separator plates 2a, 2b can, for example, be connected to one another in a materially bonded manner, for example, welded, soldered, or adhesively bonded, and can in particular be connected by laser welding. The MEA 10 has a reinforcing edge along its outer edge, at which edge the MEA is clamped in a fluid-tight manner between the two bipolar plates 2.

[0043] The separator plates 2a, 2b have mutually aligned through-openings, which form through-openings 11a-c of the bipolar plate 2. When stacking a plurality of bipolar plates of the type of bipolar plate 2, the through-openings 11a-c, together with aligned through-openings in the reinforcement edges of the MEAs 10, form lines that extend in the stacking direction 7 through the stack 6 (see Fig. 1). Typically, each of the lines formed by the through-openings 11a-c is in fluid communication with one of the ports 5 in the end plate 4 of the system 1. For example, temperature control medium can be introduced into or discharged from the stack via the lines formed by the through-openings 11a. The lines formed by the through-openings 11b, 11c, on the other hand, can be designed to supply the electrochemical cells of the fuel cell stack 6 of the system 1 with fuel and reaction gas, as well as to discharge the reaction products from the stack 6. The media-carrying through-openings 11a-11c are each formed essentially parallel to the plate plane.

[0044] To seal the through-openings 11a-c from the interior of the stack 6 and from the environment, the first separator plates 2a each have sealing arrangements in the form of port beads 12a-c, which are each arranged around the through-openings 11a-c and which completely enclose the through-openings 11a-c. The second separator plates 2b have, on the side visible from the viewer of the Fig. 2 opposite the rear side of the bipolar plates 2 corresponding port beads for sealing the through openings 11a-c (not shown).

[0045] In an electrochemically active area 18, the first separator plates 2a have, at their side facing the observer, Fig. 2 facing front side, a flow field 17 with structures for guiding a reaction medium along the front side of the separator plate 2a. These structures are shown in Fig. 2 by a multitude of bridges and channels running between the bridges and defined by the bridges. At the point where the viewer sees the Fig. 2, the first separator plates 2a each have at least one distribution region 20, which, depending on the flow direction, can also be referred to as a collection region in the manner described above. The distribution or collection region 20 comprises structures configured to distribute a medium introduced into the distribution or collection region 20 from a first of the two through-openings 11b over the active region 18 and / or to collect or bundle a medium flowing from the active region 18 to the second of the through-openings 11b. In Fig. 2, the respective corresponding passage openings, which serve for the inlet or outlet of the same fluid, possibly modified during the electrochemical reaction, are designated with and without apostrophes, e.g. 11a and 11a'. The distribution structures of the distribution or collection area 20 are shown in Fig. 2, also defined by webs 26a, 26b and gas flow channels 27a, 27b extending between the webs 26a, 26b and delimited by the webs 26a, 26b. In general, the elements 17, 18, 20 can therefore be considered media-conducting embossed structures.

[0046] With a conventional bipolar plate in Fig. 2, the separator plates lie directly on top of one another in the area of ​​the rear sides of the bottoms of the gas flow channels 27a, 27b in the distribution areas and support one another. Typically, the two separator plates are connected to one another at contact points in the distribution areas, in particular welded, for example by means of short weld seams 38, as shown in Fig. 2 shown.

[0047] The port beads 12a-12c of the example from Fig. 2 have passages 13a-13c, which serve to allow media to pass through these sealing beads. For example, the passages 13a enable the temperature control medium to pass between the passage opening 12a and the distribution area 20, so that the temperature control medium enters the distribution area between the separator plates 2a, 2b or is led out of it. Furthermore, the passages 13b enable hydrogen to pass between the passage opening 12b and the distribution area 20 on the upper side of the upper separator plate 2a. The passages 13c enable the passage of air, for example, between the passage opening 12c and the distribution area 20, so that air enters the distribution area 20 on the underside of the lower separator plate 2b or is led out of this distribution area 20. The passage openings 11a andThe lines formed by the through-openings 11a through the plate stack of system 1 are each fluidically connected to one another via a cavity 19 enclosed or surrounded by the separator plates 2a, 2b. This cavity 19 can, if necessary, serve to guide a temperature control medium through the bipolar plate 2, in particular for temperature control such as cooling, heating, or maintaining a constant temperature of the electrochemically active region 18 of the bipolar plate 2.

[0048] The first separator plates 2a of the bipolar plates 2 of the stack 6 further each have a further sealing arrangement in the form of a perimeter bead 12d, which surrounds the flow field 17 of the active region 18, the distribution or collection region 20, and the through-openings 11b, 11c and seals them from the through-opening 11a, i.e., from the temperature control medium circuit, and from the environment of the system 1. The second separator plates 2b each comprise corresponding perimeter bead 12d. In alternative plate designs, the perimeter bead can also enclose the temperature control medium openings and thus the entire temperature control medium circuit. The structures of the active region 18, the webs 21 and channels 22 of the distribution or collection region 20 and the sealing beads 12a-d are each formed integrally with the separator plates 2a and molded into the separator plates 2a, e.g., in a stroke stamping, roll stamping, deep drawing, or hydroforming process.The same applies to the corresponding distribution structures and sealing beads of the second separator plates 2b.

[0049] The separator plates 2a, 2b of the bipolar plate 2 can, for example, each be formed from a stainless steel sheet with a thickness of less than 100 µm, particularly in the case of a fuel cell. In the case of an electrolyzer, the use of sheets made of a titanium alloy as well as fully coated stainless steel is possible. The sheet thicknesses are typically greater for electrolyzers, for example, they can be 100-800 µm, 150-500 µm, or in particular 200-300 µm. The bipolar plate 2 generally has a substantially rectangular shape, but can also be round or oval, particularly in electrolyzers.

[0050] The Fig. 3 shows in Fig. 3A a partial plan view of a bipolar plate 2 or its separator plate 2a according to an example of the prior art in the region of the through openings 11a-11c, a distribution region 20, and a short section of the active region 18. The example differs from that of Fig. 2 in that there are no welded joints 38 in the distribution area 20 and the backs of the bottoms of the channels 27a, 27b do not rest on each other in the distribution area, but are arranged at a distance from each other within the boundary line 30.

[0051] In Fig. Figure 3A shows an example of a section plane AA with multiple bends. The section plane AA is generally orthogonal to the Fig. 3B registered plate planes E of the bipolar plate 2 or 39a, 39b of the separator plates 2a, 2b and thus in the z-direction of the stack of Fig. 1. It then runs in an area where there is also a distribution area 20 of the Fig. 3A extends from the second separator plate 2b hidden by the separator plate 2a. Thus, in the section plane AA, the distribution areas 20 of the separator plates 2a, 2b overlap Fig. 3A. In addition, the rear sides or inner sides of the separator plates 2a, 2b, which are shaped complementarily to the respective distribution areas 20, are opposite each other, as can be seen from the partial cross-sectional view of Fig. 3B becomes clear.

[0052] The identical bipolar plates 2 of the stack each comprise, as in the example of Fig. 2 a first metallic separator plate 2a and a second metallic separator plate 2b. Structures for media conduction along the outer surfaces of the bipolar plates 2 can be seen, here in particular in the form of webs 26a, 26b and gas flow channels 27a, 27b separated by the webs 26a, 26b. In particular, temperature control flow channels 22a, 22b are shown in the cavity 19 between adjacent separator plates 2a, 2b. Between the temperature control flow channels 22a, 22b, the two separator plates 2a, 2b have webs 21a, 21b, which, however, unlike in the example of Fig. 2 are not in contact with each other. Rather, a gap 23 is defined between the planes 32a, 32b, in which the closest regions of the webs 21a, 21b extend, in which the temperature control medium can flow freely. Flanks 29a, 29b and 28a, 28b extend between the webs or web roofs and channels or channel bottoms.

[0053] Between adjacent bipolar plates 2 of the stack, a membrane electrode assembly (MEA) 10, known from the prior art, is arranged. The MEA 10 typically comprises a membrane 14, e.g., a catalyst-coated electrolyte membrane, and an edge section 15 connected to the membrane, as well as at least one, here two, gas diffusion layers (GDL) 16. For example, the edge section 15 can be integrally connected to the membrane, e.g., by an adhesive bond or by lamination. The gas diffusion layers 16 enable flow to the membrane over the largest possible area of ​​the membrane's surface and can thus improve proton transfer across the membrane. The gas diffusion layers 16 can, for example, be arranged on both sides of the membrane in the active region 18 between the adjacent bipolar plates 2. The gas diffusion layers 16 can, for example, be formed from a fiber fleece or comprise a fiber fleece.

[0054] The membrane of the MEA 10 extends at least over the active region 18 of the adjacent bipolar plates 2 and enables proton transfer over or through the membrane. However, the membrane does not extend into the distribution or collection region 20. The edge section 15 of the MEA 10 serves to position, fix, and seal the membrane between the adjacent bipolar plates 2. When the bipolar plates 2 of the system 1 are clamped in the stacking direction between the end plates 3, 4 (see Fig. 1), the edge section 15 of the MEA 10 can, for example, be pressed between the port beads 12a-c of the respective adjacent bipolar plates 2 and / or at least between the perimeter beads 12d of the adjacent bipolar plates 2 in order to fix the membrane 14 of the MEA 10 between the adjacent bipolar plates 2 in this way.

[0055] Only around the sealing beads, for example around the port bead 12b and along the outer edge 24, the two separator plates 2a, 2b are tightly welded to one another by means of weld seams 38', as can be seen from the sectional view of the Fig. 3B becomes clear.

[0056] From the Fig. 3C schematically depicted tempering medium distribution of the bipolar plate from Fig. However, Figure 3A clearly shows that the centrally located areas are very well supplied with temperature control medium, while the lateral edge areas, which are roughly an extension of the through openings 11b, 11c, are supplied with only very little temperature control medium, as illustrated by the lines of different thicknesses.

[0057] The present invention has been conceived to at least partially solve the above problems. The invention will be further described with reference to Fig. 4 to 7 explained.

[0058] Fig. 4 represents in four Fig. 4A-4E show a partial plan view, three partial cross-sectional views and a temperature control medium distribution of a bipolar plate 2 according to the invention.

[0059] As in the prior art examples from Fig. 2 and Fig. 3, the bipolar plate 2 is also formed with a first separator plate 2a and a second separator plate 2b, which are arranged adjacent to one another in a direction perpendicular to the plate plane 39a, 39b of the first and / or the second separator plate 2a, 2b, as shown in the sectional view of Fig. 4B, which extends along the section line BB from Fig. 4A. An explicit representation of the MEA or its reinforcement edge was omitted in Fig. 4B, but the arrangement of the MEA relative to a bipolar plate basically corresponds to that shown in Fig. 3B. In both separator plates 2a, 2b, in the section shown, two first through-openings 11b, 11c are adjacent to each other in a direction perpendicular to the plate plane 39a, 39b for passing a reaction medium through the separator plates and a second through-opening 11a, adjacent to the first through-opening in the plate plane 39a, 39b, for passing a temperature control medium through the separator plate 2a, 2b are present and shown at least in sections. As in Fig. 2, corresponding through-openings are also present adjacent to the opposite short end of the bipolar plate 2, but not shown here.

[0060] From the active area 18, both in the top view of the Fig. 4A and the partial cross-sectional view of the Fig. 4B only a short section with first structures 17 for guiding reaction medium along an outer flat side of the separator plate 2a is shown, the second structures for guiding the temperature control medium along the inside of the bipolar plate 2 are shown in the partial cross-sectional view of Fig. 4B.

[0061] The separator plates 2a, 2b again have at least one distribution or collection region 20 with first structures for guiding the reaction medium between the first through-opening 11b or 11c and the active region 18 and with second structures for guiding the temperature control medium between the second through-opening 11a and the active region 18, wherein the second structures for guiding the temperature control medium in the distribution or collection region 20 on the inner sides of the separator plates 2a, 2b have temperature control medium flow channels 22a, 22b, which are separated from one another by webs 21a, 21b, and span a cavity 19 for guiding the temperature control medium in the interior of the bipolar plate 2. Both the distribution or collection area 20 of the first separator plate 2a and the distribution or collection area 20 of the second separator plate 2b have a compensation area 35a, 35b, the outer boundary of which corresponds to the dashed boundary line 30 in Fig. 4A.

[0062] The cross-sectional view of the Fig. Figure 4B shows the state in which the two separator plates 2a, 2b are already connected to each other, but not yet assembled in a stack of electrochemical cells. In the compensation area 35, the webs 21a, 21b facing the respective adjacent separator plate 2a, 2b are spaced apart from the adjacent separator plate between adjacent temperature control medium flow channels 22a, 22b in a direction perpendicular to the plate plane 39a, 39b. As shown in Fig. 3, there is therefore a distance 23 in the z-direction, which allows crossing of the webs 21a, 21b.

[0063] Excepted from this, however, is at least one freestanding elastic contact region 44, which is arranged at a distance from the outer edge 30 of the compensation region 35 and in which a section of a web, here a web 21a in the upper separator plate 2a, projects such that it forms a contact surface 42 with the adjacent separator plate 2b. Thus, contact surfaces 42 are formed at some of the intersection points of the webs 21a, 21b of both separator plates 2a, 2b. The elasticity of the contact regions 44 enables height compensation for different MEA or GDL thicknesses, and furthermore, it enables adaptation to pressure pulsation, as will be described below.

[0064] These elastic contact areas 44 allow, under normal operating conditions, a better distribution of the temperature control medium across the width of the active area 18, as shown in Fig. 4C is illustrated by the equally wide lines distributed across the entire width. Due to their elasticity, the elastic contact areas 44 spring back upon pulsation, so that the area of ​​the respective contact surfaces 42 can change. Only in the case of extremely high temperature medium impacts can the contact surfaces 42 lose contact. Unlike the welded solutions of the prior art, this results in only a brief lifting, without causing damage to the separator plates or even tearing of the plate material.

[0065] The contact surfaces 42 of the elastic contact regions 44 of the separator plate 2a touch web sections 21k of the other separator plate 2b, wherein the contact surfaces 42 of the elastic contact regions 44 and the web sections 21k of the other separator plate 2b touching the contact surfaces 42 preferably form a fluid barrier 31 inside the bipolar plate 2. In this case, the temperature control medium must flow laterally past the contact surfaces 42 and through the flow spaces spanned by the distance 23 adjacent to the fluid barrier.

[0066] In the present example, the area limited by the outer edge 30 is the entire area FA of the considered compensation area 35. In the example of Fig. 4, the distribution area 20 or compensation area 35 has two areas 201, 202 with different fluid flow paths, in which the elastic contact areas 44 are also designed differently, for example. The different designs of the elastic contact areas could also originate from different bipolar plates.

[0067] Fig. 4D shows a partial cross-sectional view along section line CC from Fig. 4A. Fig. 4E finally shows the enlarged area V Fig. 4E, where, to clarify the height relationships, the magnification in the z-direction is greater than that in the plate plane. This detailed view clearly shows the distance 23 between the web 21a, or its surface facing the lower separator plate 2b, and the surface of the web 21b facing it, even if the view here intersects the webs offset from one another in the plate plane. In particular, this surface of the web 21a is spaced from the plate plane E of the bipolar plate 2. The channel flank 28a' facing the outer edge 30 of the compensation region 35 is higher than the channel flank 28a arranged in the interior of the compensation region 35. In this compensation region 35, the temperature control medium flow channels 22a, with the exception of the elastic contact regions 44, are therefore less deep than the outer flank 28a' of at least the shown one of the two outermost temperature control medium flow channels 22a.

[0068] Fig. 5 shows in two Fig. 5A and Fig. 5B shows an oblique view of section 201 of a distribution area 20 of a bipolar plate 2 according to the invention, as well as a corresponding detailed view. While in the separator plate 2b arranged at the bottom, the flow cross sections of the temperature control medium flow channels 22b and the gas flow channels 27b are comparable, the separator plate 2a arranged at the top spans considerably more flow space for the gas conduction on the outer surface in the gas flow channels 27a than for the temperature control medium conduction in the flow channels 22a. Fig. 5, the temperature control medium flow channels 22a and 22b in both separator plates 2a, 2b run at an angle to one another, the temperature control medium flow channels 22a of the first separator plate 2a are significantly narrower than the temperature control medium flow channels 22b of the second separator plate 2b. Between the mutually facing webs 21a, 21b between adjacent temperature control medium flow channels 22a, 22b, a distance 23 remains in large sections of the compensation region 35 in the direction perpendicular to the plate plane 39a, 39b. Although this distance is less than a quarter of the height of a temperature control medium flow channel 22a, 22b, it nevertheless allows crossing of the webs 21a, 21b and a wide variety of flow paths for the temperature control medium.Also to direct the flow of the temperature control medium, several elastic contact areas 44 are provided in those sections of a separator plate that form a bottom of a gas flow channel 27a on one surface and the web 21a between two temperature control medium flow channels 22a on their other surface. In these areas, a section 21k of a web 21a projects out in such a way that it forms a contact surface 42 with the adjacent separator plate, here separator plate 2b.

[0069] The Fig. The elastic contact regions 44 shown in Figure 5A all have an elongated, rounded shape. The longitudinal axis Lo of an exemplary contact region 44 runs at an angle α to the longitudinal axis Lsa of the web 21a in the corresponding elastic contact region 44, where α here—in a plan view of the plate plane 39—is approximately 30°. This oblique arrangement forces the temperature control medium to be directed in a targeted manner in addition to the barrier effect of the elastic contact regions 44. Unlike in the example shown here, not all elastic contact regions 44 need to span the same angle α with their longitudinal axes with the longitudinal axis of the associated webs; rather, it may be preferable for fluid guidance if different elastic contact regions 44 have different orientations.

[0070] In Fig. In the section of the compensation region 35 shown in Figure 5A, 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. As a result of this and the only small height of the elastic contact region 44, the cross section of the respective gas flow channels 27a changes only slightly, so that the elastic contact regions 44 do not cause any significant pressure losses.

[0071] The elastic contact areas 44, which all belong to the same compensation area, each have an area FK. The areas FK can be summed for an entire compensation area to form a total area FKtotal. Compared to the area of ​​the respective compensation area 35 (cf. Fig. 4A), however, this total area is very small, amounting to less than 10%. Likewise, the areas FB of the contact surfaces 42 of the contact regions 44 of a compensation region can be summed to form a total area FBtotal. This results in an even smaller area share of the area FA of the respective compensation region 35, amounting to less than 3%. The aforementioned values ​​can refer to the state of an uninstalled bipolar plate 2 or to a bipolar plate 2 installed in a stack 6 of an electrochemical system 1.

[0072] In Fig. 5B shows that the elastic contact area 44 has a spring surface 46 extending around the contact surface 42. This spring surface 46 has a slope sk, with a slope angle relative to the contact surface β of approximately 10°, and a smaller slope sk than the average slope of the flank of the adjacent web sf in the same separator plate 2a, with a slope angle φ of approximately 32° relative to the contact surface. However, the slope of the flank or the straight flank section 29a is significantly steeper and amounts to approximately ε=60°.

[0073] In Fig. 6A of the Fig. 6 shows an oblique view of another section 202 of a distribution region 20, which could also belong to another bipolar plate 2 according to the invention. Fig. 6B shows a corresponding detailed view. The elastic contact areas 44, which are Fig. 6A, each have a round shape, as do the contact surfaces 42. The spring surfaces 46 enclose the latter essentially in a circular ring. The gas flow channels 27a of the upper separator plate 2a have, compared to the webs 26a separating them, in the areas where no elastic contact areas 44 are arranged, a width that is only approximately 1 / 4 of the width of the webs 27a separating them. Accordingly, the temperature control medium flow channels 22a are approximately four times as wide as the webs 21a separating them. However, the webs 21a widen in the area of ​​the elastic contact area 44. There, they have a maximum web width Bk that is almost 5 times as large as the web width Bs outside of an elastic contact area 44, as in Fig. 6B is particularly evident. In Fig. In Figure 6B, the width Bk is only symbolically shown in the widest web area shown; in fact, it should extend orthogonally to the longitudinal axis of the web and thus parallel to Bk, which, however, is difficult to represent due to the oblique view.

[0074] The angle β that the spring surface 46 forms with the plane of the separator plate or the contact surface 42 is again approximately 10°, whereas the angle that the flank 29a forms with the contact surface 42 is approximately 25° and is thus somewhat smaller than in the previous example.

[0075] Fig. 7 shows a partial plan view of a distribution region 20 of a further bipolar plate 2 according to the invention. It shows, on the one hand, various forms of elastic contact regions 44 as viewed from above onto the plate plane E or viewed through the separator plate 2a. Reference numerals are provided for both the elements located on the surface facing the viewer and those arranged in the cavity 19 or on the underside. On the one hand, a group of elastic contact regions 44l is shown, which extends in an elongated shape from the bottom left to the top right and each merges directly into the webs 21a separating the temperature control medium flow channels 22a.Both on the far right and in the center, groups of elastic contact areas 44o with an elongated, rounded shape are shown, which also extend from the bottom left to the top right, but maintain a small distance from the webs 21a separating the temperature control medium flow channels 22a. To the left of the center, a group of elastic contact areas 44r is shown, which have a round shape and are significantly spaced from the webs 21a separating the temperature control medium flow channels 22a. Finally, at the top left, an embodiment of an elastic contact area 44f with a free form is shown.

[0076] In all examples shown of the Fig. 7, the elastic contact region 44 has a contact surface 42 and a spring surface 46 that extends at least partially around the contact surface 42. The spring surface 46o, 46r, 46f is each designed such that the spring surface 46o, 46r, 46f completely surrounds the contact surface 42o, 42r, 42f. In the group of elastic contact regions 44l with an elongated shape, the spring surfaces 42l also have an elongated shape, at least in sections. These elongated spring surfaces 42l extend between two closest tempering medium flow channels 22a in such a way that they connect their mutually facing flank ends.

[0077] The gas flow channels 27a of the upper separator plate 2a run in Fig. 7 parallel to each other and from top left to bottom right, with the inclination relative to the horizontal being less than 10°. On the rear side of the webs 26a separating the gas flow channels 27a, which also run parallel and at the same inclination, the temperature control medium flow channels 22a extend in the same direction. The flanks between the webs and channels are each indicated by the reference numeral 28a - on the inside of the bipolar plate 2 carrying the temperature control medium - or 29a - on the gas-carrying outer surface of the bipolar plate 2.

[0078] On the other hand, Fig. 7 also shows the courses of the temperature control medium flow channels 22b in the separator plate 2b, which is located at the bottom in this illustration, with dashed lines. The temperature control medium flow channels 22b (or webs 26b between the gas flow channels 27b) each extend between the areas delimited by longer dashed lines, the corresponding webs 21b (or gas flow channels 27b) between the areas delimited by shorter dashed lines, and the flanks 28b and 29b each extend between a longer dashed line and a shorter dashed line. These structures each run from bottom left to top right. The temperature control medium flow channels 22a of the first separator plate 2a form an angle δ of approximately 150° with the temperature control medium flow channels 22b of the second separator plate 2b.

[0079] The elastic contact regions 44l run with their longitudinal axis LI essentially parallel to the longitudinal axis Lsb of a web in the adjacent separator plate 2b, here both to the webs 21b separating the temperature control medium flow channels and to the webs 26b separating the gas flow channels. The longitudinal axis Lsb is only explicitly shown for a web of the latter type. In principle, however, an acute angle between the two webs is also possible, although this should not exceed 30°. A comparable parallelism is also given here for the longitudinal axes Lo and Lf of the elastic contact regions 44o and 44f and the longitudinal axis Lsb. The longitudinal axes Lt of the spring surfaces 46 arranged on both sides of the contact regions 42f also run parallel to the longitudinal axes Lsb of the webs 21b and 26b.

[0080] Fig. Figure 8 shows in three partial figures further embodiments of bipolar plates according to the invention, wherein the elastic contact areas 44 in Fig. 8A and Fig. 8B differs from the aforementioned embodiments, in order to emphasize this different form, the relevant reference numerals are provided with dashes for differentiation. Both in Fig. 8A as well as Fig. 8B, elastic contact areas 44', 44'', 44''' are formed in keyhole shape. In Fig. 8A, all elastic contact areas 44', 44'' have in common that the contact surfaces 42', 42'' have a rounded, 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. While the corresponding sections of the contact area 44' initially have a narrow area 48', which widens into a wide area 47' and then tapers essentially symmetrically back to a narrow area 48', the arrangement of the wide areas 47'' and the narrow area 48'' in the elastic contact area 44'' is opposite. Thus, in the elastic contact area 44', a particularly high elasticity is achieved in the central area, i.e.in the area with the narrow sections of the spring surface 44', so the elasticity increases from one end to the middle, before increasing again towards the opposite end. With the spring surface 46'', on the other hand, a more uniform elasticity is achieved across the entire elastic contact area 44'. The changing width of the elastic contact area 44', 44'', with its projections or recesses, can further contribute to the guidance of the temperature control medium. The differently wide areas 47, 48, since they connect planes of equal distance, are associated with different gradients. Fig. 8A thus shows two different elastic contact regions 44', 44'', in each of which a spring region 46 has at least two regions 47, 48 which have a different gradient relative to the contact surface 42 delimited by the spring region 46, wherein the at least two regions 47, 48 follow one another circumferentially.

[0081] In the elastic contact area 44''', the contact surface 42''' also has an approximately keyhole shape. The spring surface 46''' surrounds the contact surface 42''' with a substantially constant width. However, the curved areas 49 have somewhat less elasticity than the straight sections. The overall shape of the elastic contact area 44''', with its projections and recesses, serves, on the one hand, to ensure good utilization of the installation space within a temperature control medium web 21 and, at the same time, to additionally guide the temperature control medium around the elastic contact area 44'''.

[0082] In the Fig. 8B are still with the same line patterns as in Fig. 7 shows the different areas of the separator plate hidden by the visible separator plate of the bipolar plate 2. Unlike, for example, in Fig. 7, the webs and channels of the concealed separator plate do not run parallel to the longitudinal axis Lf of the elastic contact areas 44''', but at an acute angle γ, which here is approximately 5°.

[0083] In the Fig. 8C shows that the distribution area can also be designed with at least one intermediate temperature control channel 220, which is arranged, for example, in sections in a web 21 between two temperature control flow channels 22. The dashed lines indicate, as in Fig. 7 shows the various regions of the separator plate concealed by the visible separator plate of the bipolar plate 2. The intermediate channel 220 runs correspondingly in a region in which a temperature control medium flow channel also extends in the other separator plate, or rather the flanks that delimit it. The intermediate channel 220 thus expands the flow cross-section available for the temperature control medium in the corresponding region. At the same time, the structures of the intermediate channel 220 can also form additional flow guidance elements on the surface facing the viewer, i.e., an intermediate web or an additional barrier in the region of a gas flow channel 270. This additionally allows the direction of the gas flowing in this gas flow channel 270 to be influenced. The reference numerals in Fig. 8C are shown without reference to the first or second separator plate to emphasize that the elastic contact regions 44 can, in principle, be arranged in an anode and / or cathode plate of a bipolar plate. However, if they are arranged in both separator plates, it is preferred if they are arranged in non-overlapping sections of the bipolar plate.

[0084] Fig. 9 shows an oblique view of a section of a distribution area of ​​another bipolar plate according to the invention, which is a variant of Fig. 5. Here, the spring surface 46 is designed in a stepped manner around the contact surface 42 and has an outer region 46a with a constant pitch sk and an inner region 46b with a pitch defined as a radius r1. The cutting edge of the region 46b facing the viewer, including the short straight section in which the cutting edge runs along the contact surface 42, is shown dotted in both its lower boundary line and its upper boundary line to emphasize this radius r1.

[0085] All of the examples of Fig. 4 to 9 show that within a compensation area 35 the webs of one of the separator plates 2a, 2b are each free of material connections 38 with the second separator plate 2b.

Claims

[1] Bipolar plate (2) for an electrochemical system (1), comprising a first separator plate (2a) and a second separator plate (2b) which are arranged adjacent to one another in a direction perpendicular to the plate plane (39a, 39b) of the first and / or the second separator plate (2a, 2b), wherein the first and the second separator plate (2a, 2b) each have a direction perpendicular to the plate plane (39a, 39b) - a first through-opening (11b, 11c) for passing a reaction medium through the separator plate and a second through-opening (11a) adjacent to the first through-opening in the plate plane (39a, 39b) for passing a temperature control medium through the separator plate (2a, 2b); - an active region (18) with first structures (17) for guiding reaction medium along an outer flat side of the separator plate and second structures for guiding the temperature control medium along the inner side of the bipolar plate (2); and - at least one distribution or collection area (20) with first structures for guiding the reaction medium between the first through-opening (11b, 11c) and the active area and second structures for guiding the temperature control medium between the second through-opening (11a) and the active area, wherein the structures for guiding the temperature control medium in the distribution or collection area (20) have temperature control medium flow channels (22a, 22b) which are separated from one another by webs (21a, 21b), characterized by , that the distribution or collection area (20) of the first separator plate (2a) and / or the distribution or collection area (20) of the second separator plate (2b) have at least one compensation area (35, 35a, 35b), wherein, in the unassembled state of the bipolar plate (2), in one, several or all of the at least one compensating regions (35), the webs (21a, 21b) facing the respective adjacent separator plate (2a, 2b) are spaced apart from the adjacent separator plate between mutually adjacent temperature control medium flow channels (22a, 22b) in a direction perpendicular to the plate plane (39a, 39b), with the exception that the compensating region (35, 35a, 35b) has, at a distance from its outer edge (30), at least one free-standing elastic contact region (44), in which a section of a web (21a, 21b) projects in such a way that this section forms a contact surface (42) with the adjacent separator plate (2a, 2b). [2] Bipolar plate according to the preceding claim, characterized by that the contact surfaces (42) of the elastic contact regions (44) of one separator plate (2a, 2b) touch web sections (21k) of the other separator plate (2b, 2a), wherein the contact surfaces (42) of the elastic contact regions (44) and the web sections (21k) of the other separator plate (2b, 2a) touching the contact surfaces (42) form a fluid barrier (31) in the interior of the bipolar plate (2). [3] Bipolar plate according to one of the preceding claims, characterized by that for one, several or all of the elastic contact areas (44), the elastic contact area (44) in plan view onto the plate plane of one of the separator plates has an elongated shape (44l), an elongated-rounded shape (44o), a round shape (44r) or a free form (44f). [4] Bipolar plate according to one of the preceding claims, characterized bythat for one, several or all of the compensation areas (35) in a plan view of the plate plane (39a, 39b) of one of the separator plates (2a, 2b), the compensation area (35) has an area FA and the elastic contact areas (44) of this compensation area (35) have a total area FKges, where FKges ≤ 0.2FA, in particular FKges ≤ 0.1 FA. [5] Bipolar plate according to one of the preceding claims, characterized by that for one, several or all of the compensation areas (35) in a plan view of the plate plane (39a, 39b) of one of the separator plates (2a, 2b), the compensation area (35) has an area FA and the contact surfaces (42) of the elastic contact areas (44) of this compensation area (35) have a total area FBges, wherein in the pressed state FBges ≤ 0.05 FA, in particular Fbges ≤ 0.03 FA. [6] Bipolar plate according to one of the preceding claims, characterized bythat for one, several or all of the elastic contact regions (44) in a plan view of the plate plane (39a, 39b) of one of the separator plates (2a, 2b), the elastic contact region (44) has an elongated shape (44l) or an elongated-rounded shape (44o) and runs in its longitudinal axis (Ll, Lo) at an angle α ≠ 0° to the longitudinal axis (Ls, Lsa, Lsb) of the web (21a, 21b) in the respective elastic contact region (44), wherein advantageously 15° ≤ α ≤ 90°, in particular 20° ≤ α ≤ 60°. [7] Bipolar plate according to one of the preceding claims, characterized by that one, several or all elastic contact areas of one of the separator plates (2a, 2b) and a web of the distribution or collection area (20) of the other separator plate (2b, 2a) extend in orthogonal projection onto the plate plane (39a, 39b) of the first and / or the second separator plate (2a, 2b) at an angle γ ≤ 30°, preferably γ ≤ 20°, in particular γ ≤ 10° relative to one another. [8] Bipolar plate according to one of the preceding claims, characterized by that for one, several or all of the elastic contact regions (35) in a plan view of the plate plane (39a, 39b) of one of the separator plates (2a, 2b), the elastic contact region (44) has an elongated shape or an elongated-rounded shape and runs in its longitudinal axis (L) substantially parallel to a longitudinal axis (Ls, Lsa, Lsb) of a web (21) in the adjacent separator plate. [9] Bipolar plate according to one of the preceding claims, characterized by that the web width (Bs) is constant in the region of the elastic contact area (44). [10] Bipolar plate according to one of the preceding claims, characterized bythat the maximum web width (Bk) in the region of the elastic contact region (44) is at least 30%, preferably at least 50%, in particular at least 100% and particularly preferably at least 200% greater than the web width (Bs) outside an elastic contact region (44). [11] Bipolar plate according to one of the preceding claims, characterized by that the elastic contact region (44) has a spring surface (46) which at least partially surrounds the contact surface (42) and has a smaller gradient (sk) than the average gradient of the flank of the adjacent web (sf) in the same separator plate. [12] Bipolar plate according to one of the preceding claims, characterized by that the elastic contact area (44) has a spring surface (46) which runs at least partially around the contact surface (42) and which has a gradient (sb) of β ≤ 30°, preferably β ≤ 20°, in particular β ≤ 15° relative to the contact surface. [13] Bipolar plate according to one of the two preceding claims, characterized by that the spring surface (46) completely surrounds the contact surface (42). [14] Bipolar plate according to one of claims 11-13, characterized by that the spring surface (46) has an elongated shape at least in sections when viewed onto the plate plane (39a, 39b) of one of the separator plates (2a, 2b) and runs with its longitudinal axis (Lt) substantially parallel to the longitudinal axis (Ls, Lsa, Lsb) of a web (21) in the adjacent separator plate. [15] Bipolar plate according to one of claims 11-14, characterized by that the spring surface (46) extends between two tempering medium flow channels (26) located closest to one another in such a way that it connects their flank ends facing one another. [16] Bipolar plate according to one of the preceding claims, characterized bythat the temperature control medium flow channels (22a) of one of the separator plates (2a, 2b) and the temperature control medium flow channels (22b) of the other separator plate (2b, 2a) run at least in sections at an angle of 15° ≤ δ ≤ 90°, preferably 20° ≤ δ ≤ 60°. [17] Bipolar plate (2) according to one of the preceding claims, characterized by that within a compensation area (35) the webs (21) of one of the separator plates (2a, 2b) are each free of material connections with the other separator plate (2b, 2a). [18] Bipolar plate (2) according to one of the preceding claims, characterized byin that a spring region (46) has at least two regions (46a, 46b, 47, 48, 49) which have a different gradient relative to the contact surface (42) delimited by the spring region (46), wherein one of these two regions preferably surrounds the other region, in particular completely surrounds it and / or the at least two regions (47, 48, 49) follow one another in a circumferential manner. [19] Bipolar plate (2) according to one of the preceding claims, characterized by that for one, several or all of the compensation regions (35, 35a, 35b) of the first and / or the second separator plate (2a, 2b) in the compensation region (35, 35a, 35b), the temperature control medium flow channels (22a, 22b), with the exception of the elastic contact regions, are less deep than the outer flank (28a') of one or both of the two outermost temperature control medium flow channels. [20] Electrochemical system (1) comprising at least one separator plate (2) according to one of the preceding claims and at least one MEA.

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