Electrochemical system

Abstract

Electrochemical system (100; 200; 300), comprising: an end plate (2); a stack end plate (50) adjacent to the end plate (2); and at least one metallic electrical conductor (19a, 19b, 19c); wherein the stack end plate (50) has an electrically conductive contact plate (51) adjacent to the end plate (2) and an electrically conductive separator plate half (52) facing away from the end plate (2), wherein the contact plate (51) and the separator plate half (52) are connected to each other in a materially bonded, electrically and media-tight manner; wherein the metallic electrical conductor (19a, 19b, 19c) extends to an outer surface (8) of the electrochemical system (100; 200; 300); and wherein the metallic electrical conductor (19a, 19b, 19c) and the contact plate (51) are formed in one piece or the metallic electrical conductor (19a, 19b, 19c) directly contacts the contact plate (51); characterized by that the separator plate half (52) has at least one opening (52') for passing through a coolant, wherein the separator plate half (52) has on its rear side (52b) facing away from the contact plate (51) a sealing arrangement designed as a bead (54) for sealing the opening (52'), wherein the bead (54) has openings (55) which are configured to direct a coolant passed through the opening (52') of the separator plate half (52) into a space (56) arranged between the separator plate half (52) and the contact plate (51).

Description

[0001] The invention relates to an electrochemical system, e.g. a fuel cell system, an electrochemical compressor or an electrolyzer, comprising an end plate and a stack end plate according to the preambles of the independent claims.

[0002] Known electrochemical systems typically have two end plates between which a stack of multiple metallic separator plates or bipolar plates is arranged. Adjacent separator plates usually enclose electrochemical cells in which chemical energy is converted into electrical energy, or vice versa. These electrochemical cells can also be used to increase the pressure in a hydrogen system electrochemically. For this to work, the system needs electrical conductors that connect the electrodes of the electrochemical cells to an external surface of the system, allowing an electrical voltage to be applied to or drawn from the electrodes. These conductors are then typically connected to, or connectable to, an electrical load or a voltage source.

[0003] Typically, the supply or removal of electrical energy, or the application or removal of electrical voltage to the electrochemical system, occurs via at least one of the end plates and the separator plate adjacent to that end plate. This separator plate is also called the end plate, end separator plate, or, if applicable, the end bipolar plate, as it terminates the plate stack towards the respective end plate. The electrical connection between the end plate and the outside of the electrochemical system is typically established via a metallic current collector on the side of the end plate facing the end plate and via an electrically conductive gas diffusion layer (GDL) located between the current collector and the end plate, with both in electrical contact. The current collector is connected to the outside of the system, for example, via an electrical cable.The gas diffusion layer is usually formed as graphite-containing tissue or the like.

[0004] However, it has been repeatedly shown that high ohmic losses occur with this type of electrical contacting of the electrodes of the electrochemical cells of the plate stack.

[0005] Typically, both the end plate and the sealing plate have through-holes for reaction media and coolant, which are each sealed. If, as is common practice, the end plate is made of a polymer material and the sealing plate of metal, then heating and cooling of the electrochemical system leads to different degrees of expansion and contraction, which destroys the sealing devices used so far, thus compromising the long-term sealing of the electrochemical system.

[0006] For example, US patent 8,173,320 B2 relates to a fuel cell stack. This stack comprises a membrane electrode assembly with an electrolyte membrane and electrode catalyst layers sandwiching the electrolyte membrane; metal separators defining gas channels, the metal separators being arranged on both surfaces of the membrane electrode assembly; a current collector from which the electromotive force is derived, the current collector being in contact with at least one of the metal separators; and

[0007] Connecting parts that connect the metal separator to the current collector at sections where the metal separator touches the current collector.

[0008] The present invention is therefore based on the objective of creating an electrochemical system with an improved electrical connection between the cell stack and the outside of the system. Alternatively, The present invention is based on the objective of creating an electrochemical system with a sealing device arranged between a cover plate and an end plate, wherein the sealing device should be as durable as possible even under strong temperature fluctuations. Preferably, the system should also be as simple and cost-effective to manufacture as possible.

[0009] An electrochemical system is therefore proposed, comprising an end plate, a stack end plate adjacent to the end plate, and at least one metallic electrical conductor. The stack end plate has an electrically conductive contact plate adjacent to the end plate and an electrically conductive separator plate half facing away from the end plate. The contact plate and the separator plate half are electrically and media-tightly connected to each other. The metallic electrical conductor extends to an outer surface of the electrochemical system.

[0010] The metallic electrical conductor and the contact plate are formed as a single unit, or the metallic electrical conductor contacts the contact plate directly.

[0011] The separator plate half has at least one opening for the passage of a coolant, wherein the separator plate half has a sealing arrangement formed as a bead on its rear side facing away from the contact plate for sealing the opening. The bead has perforations that are configured to direct a coolant passed through the opening of the separator plate half into a space arranged between the separator plate half and the contact plate.

[0012] By forming the metallic electrical conductor, which extends to the outside of the system, and the contact plate as a single unit, or by making direct contact with the contact plate, ohmic losses occurring along the electrical connection between the contact plate and the outside of the system, caused, for example, by contact voltages and / or frictional voltages, are significantly reduced compared to known systems.

[0013] The metallic electrical conductor can be in the form of an electrical cable, e.g., a copper cable. However, any metallic electrical conductor can be used. Preferably, the metallic electrical conductor is formed in one piece.

[0014] The metallic electrical conductor should preferably be considered a single piece even if it has a cable lug or plug at its end that contacts the contact plate.

[0015] The electrochemical system can be, for example, a fuel cell system, an electrochemical compressor, or an electrolyzer. Such systems typically have two end plates with multiple separator plates positioned between them. An electrochemical cell is typically located between adjacent separator plates or bipolar plates. Thus, the electrochemical system usually contains a large number of electrochemical cells. These cells can be used to convert chemical energy into electrical energy or vice versa, or to increase the pressure in a hydrogen system electrochemically.

[0016] In one embodiment of the electrochemical system, the contact plate and the separator plate half are bonded together, for example by a weld or a solder joint. This ensures good mechanical stability and media tightness.

[0017] In a further embodiment, the at least one metallic electrical conductor and the end plate are designed such that the metallic electrical conductor extends completely or at least partially through the end plate. This thus enables electrical contact of the electrochemical system through the end plate.

[0018] Another embodiment is characterized in that the contact plate has at least one projection on its front surface facing the end plate, projecting beyond the rest of the surface of this front surface. The projection is normally also made of a metallic material. The projection and the contact plate are in electrical contact with each other. The projection and the contact plate can be formed as a single piece. The projection can be welded or soldered to the contact plate; this also counts as direct contact within the scope of the present invention. The projection can extend through the end plate to form the electrical conductor. The projection can thus extend from the contact plate to the outside of the electrochemical system. Alternatively or additionally, the projection can engage at least partially in a first recess of the end plate.The metallic electrical conductor can then contact the contact plate, for example, within the recess on the projection. The projection extending through the end plate, or at least partially engaging with the end plate, provides the end plate and the contact plate, or the stack termination, with additional mechanical stability.

[0019] The projection can be in the form of a dome or a bolt. The contact plate and the projection can be formed as a single piece. The contact plate and the projection can be made of the same material, e.g., stainless steel. This can completely or largely prevent corrosion in the contact area between the contact plate and the projection. The projection can be metallurgically bonded to the contact plate, e.g., via a soldered or welded joint. The contact plate and the projection can also be made of different materials. For example, the projection can comprise a nickel or copper sheet, or be formed from nickel or copper sheet. The projection can have a gold coating. Nickel, copper, and gold each have a particularly low specific electrical resistance.

[0020] The metallic electrical conductor and the contact plate can be bonded together, in particular by a weld or solder joint. The metallic electrical conductor and the contact plate can also be connected by a positive or force-fit connection. For example, the end of the metallic electrical conductor contacting the contact plate can be designed as a plug that is inserted into a corresponding recess or socket in the contact plate. The end of the metallic electrical conductor contacting the contact plate can also have a compression spring that presses the metallic electrical conductor against the contact plate.

[0021] In another embodiment, the contact plate can have a projection that extends, at least partially, beyond the contour of the end plate in a lateral direction to form the metallic electrical conductor. This projection typically extends beyond the outer surface of the electrochemical system. However, it can also extend into an area that aligns with a recess in the end plate, thus protruding beyond an inner contour of the end plate. In both solutions, the projection, when not bent, extends parallel to the plane of the end plate or parallel to the plane of the contact plate. The projection can, for example, be designed as a bendable tab. In this case, the projection is typically bent towards the end plate on the outer surface of the electrochemical system.To increase the flexibility of the extension, it can be thinner than the rest of the contact plate. Normally, the contact plate and extension are formed as a single piece; however, they can also be separate components. In this case, the contact plate and extension can be made of the same material or different materials. The contact plate and extension can be metallurgically bonded, for example, by soldering or welding. The extension can be made of a metal sheet, such as nickel or copper. To improve electrical conductivity, the extension can have a metallic coating, such as a gold plating.

[0022] If the at least one metallic electrical conductor and the contact plate are not formed as a single unit, it is advantageous if there is only one contact point to the contact plate for each metallic electrical conductor. However, the electrochemical system according to the invention can, in both this embodiment and the one-piece embodiment, have several contact points on a contact plate, at each of which exactly one conductor draws the current.

[0023] In another embodiment, the contact plate is made of sheet metal. This makes it particularly easy and cost-effective to manufacture. The material thickness of the contact plate, determined perpendicular to its plane, can be between 0.1 mm and 8.0 mm, preferably between 0.2 mm and 3.0 mm, and most preferably between 0.5 mm and 1.0 mm. The direction perpendicular to the plane of the contact plate and the end plate is hereinafter also referred to as the stacking direction.

[0024] In a further embodiment, at least one sealing arrangement is provided between the contact plate and the end plate. The sealing arrangement preferably comprises a second recess in the side of the end plate facing the contact plate and a sealing ring at least partially enclosed in the second recess. The sealing ring preferably forms a closed loop. The sealing ring can be annular, oval, or rectangular in shape. However, it can also be shaped in any other way. Typically, the sealing ring is made of an elastic material, e.g., an elastomer. The hardness of the material from which the sealing ring is made is preferably between 30 Shore A and 80 Shore A. The depth of the second recess, determined along the stacking direction, can be up to 10 mm, preferably up to 5 mm, and particularly preferably up to 3 mm.The dimensions of the sealing ring are normally chosen such that, in the uncompressed state, the sealing ring extends beyond the second recess by at least 0.1 mm and / or up to 5.0 mm or up to 2.0 mm along the stacking direction.

[0025] The end plate and the contact plate typically have openings for the passage of a medium, in particular a process gas, a reaction product, or a coolant. Normally, the sealing arrangement(s) is arranged around these openings to seal them. However, the plates of the electrochemical system according to the invention do not necessarily need to have a seal at their outer edge. It may, however, be advantageous to have a sectioned or circumferential support device along the outer edge, which may correspond in its design to the aforementioned sealing arrangement.

[0026] In another embodiment, one side of the contact plate facing the end plate is flat, at least in the area of ​​the sealing arrangement. This allows the sealing ring to slide or roll off the contact plate when the contact plate and the end plate are displaced laterally relative to each other. This can occur particularly during temperature changes if the end plate and the contact plate have different coefficients of thermal expansion.

[0027] In another embodiment, at least 80 percent, preferably at least 90 percent, of the surface of the contact plate facing the end plate is flat. These are preferably contiguous flat areas of the surface. The surface of the contact plate facing the end plate can also be completely flat. This simplifies the manufacture of the contact plate and reduces manufacturing costs.

[0028] In a further embodiment, the end plate and the contact plate each have contact areas on their facing sides, along which the contact plate and the end plate are in contact with each other when pressed together. When the contact plate and the end plate are pressed against each other along the stacking direction by a clamping force, this clamping force is preferably introduced primarily into the end plate and the contact plate along these contact areas. Thus, the clamping force is preferably not, or primarily not, introduced into the end plate and the contact plate via the sealing arrangement. In this way, the sealing arrangement can be relieved of stress. This, in particular, prevents damage to the sealing arrangement when the end plate and the contact plate are laterally displaced relative to each other due to temperature changes.

[0029] The force exerted on the sealing assembly during the compression of the end plate with the contact plate along the stacking direction is limited to the force necessary to compress the sealing assembly along the stacking direction just enough to bring the end plate and contact plate into contact along the contact areas. This maximum force exerted on the sealing assembly during compression is hereinafter referred to as the maximum force. The magnitude of the maximum force can be adjusted by appropriately selecting the depth of the second recess along the stacking direction, the thickness of the sealing ring along the stacking direction, the elasticity or hardness of the sealing ring material, and the geometry of the contact areas.For example, the contact areas of the end plate and / or the contacting plate can be designed, at least in sections, as projections extending from the respective plate along the stacking direction. Alternatively or additionally, the contact areas of the end plate and / or the contacting plate can be designed, at least in sections, as recesses or indentations. The geometry of the contact areas is then defined, in particular, by the height of the projections and the depths of the recesses / indentations along the stacking direction.

[0030] In a further embodiment, the depth of the second recess along the stacking direction, the thickness of the sealing ring along the stacking direction, the elasticity or hardness of the sealing ring material, and the geometry of the contact areas are adjusted such that the contact force during operation of the electrochemical system is at least twice, preferably at least five times, and particularly preferably at least ten times the maximum force. The contact force is then primarily transferred via the contact areas into the end plate and the contacting plate, thus significantly relieving stress on the sealing arrangement and extending its service life.

[0031] A contact area between the end plate and the contacting plate, defined along the contact regions in the compressed state, is hereinafter referred to as the first contact area. In contrast, a contact area between the sealing arrangement and the end plate, or between the sealing arrangement and the contacting plate, defined along the sealing arrangement in the compressed state, shall be referred to as the second contact area. The contact regions and the sealing arrangement can be designed such that the first contact area is at least five times, preferably at least ten times, and particularly preferably at least twenty times the size of the second contact area. This also contributes to relieving stress on the sealing arrangement and extends its service life.

[0032] In another embodiment, the separator plate half has channels on its rear side, facing away from the contact plate, for guiding a medium, in particular a process gas or a reaction product. The process gas can, for example, be supplied to a chemically active area of ​​the electrochemical system where chemical energy is converted into electrical energy. The separator plate half can be formed as a stamped part into which the channels are embossed on the rear side. The separator plate half can be formed from a sheet, e.g., a stainless steel sheet. Typically, the separator plate half has a material thickness of at most 0.2 mm or at most 0.1 mm, but at least 0.025 mm.

[0033] Normally, such a conversion of chemical energy into electrical energy also generates reaction heat, which is then at least partially dissipated via the separator plate half of the stack end plate. Therefore, to cool the separator plate half of the stack end plate, the contact plate can have channels on its side facing the separator plate half for conveying a coolant.

[0034] The contact plate can, for example, be designed as an embossed part with pre-formed initial deformations. Alternatively, these initial deformations can be introduced into the contact plate by chemical etching. On the side of the contact plate facing the separator plate half, these initial deformations can form the aforementioned channels for coolant flow. The channels formed by the initial deformations in the contact plate can have a different cross-section than those of the channels in the separator plate half. The cross-section of the channels formed by the initial deformations, available for coolant flow, can be smaller than the cross-section of the channels formed for coolant flow through the separator plates of the rest of the electrochemical system.Alternatively or additionally, the cross-section of the channels formed by the initial deformations, available for guiding the coolant, can be larger than the cross-section formed by the channels of the separator plate half alone. Thus, the cross-section available for coolant guidance can be adjusted by dimensioning the channels formed by the initial deformations.

[0035] If the first deformations are pressed through the contact plate, deformations also form on its surface facing the end plate; these are subsequently referred to as second deformations. The side of the end plate facing the contact plate can have third deformations. These third deformations can be designed such that the second and third deformations accommodate each other when the end plate and the contact plate are pressed together. In particular, the end plate has a single third deformation, which is designed as a recess relative to the first contact surface and accommodates all second deformations. The second and third deformations are preferably designed such that, in the pressed state, they allow movement of the end plate and the contact plate relative to each other during temperature changes.

[0036] The separator plate half can be essentially the same as the plate halves of the bipolar plates of the electrochemical system with regard to its thickness, the depth of its embossing and / or the diameter of its through-holes, but these parameters can also all differ from those of the bipolar plates of the electrochemical system.

[0037] The separator plate half of the stack end plate has at least one opening for the passage of a coolant. On its side facing away from the contact plate, the separator plate half has a sealing arrangement designed as a bead for sealing the opening in the separator plate half. This bead has perforations that are configured to direct the coolant passing through the opening of the separator plate half into a space arranged between the separator plate half and the contact plate. Thus, the material-bonded connection between the contact plate and the separator plate half preferably allows for the formation of a space between the contact plate and the separator plate half for the passage of a coolant.

[0038] The proposed electrochemical system can comprise a plurality of electrochemical cells, each separated from the others by separator plates. These separator plates can each have a cavity for the passage of a coolant. However, if the gap between the contact plate and the separator plate half and the cavities of the separator plates within the stack each have identical volumes, excessive cooling of the separator plate half of the stack end plate may occur during operation. To prevent this and to achieve a uniform temperature distribution both within and at the edge of the stack during operation, it is therefore advantageous if the volume of the gap formed between the contact plate and the separator plate half of the stack end plate is smaller than the volume of the cavity of one of the separator plates.

[0039] Preferably, therefore, the volume Vz of the space formed between the contacting plate and the separator plate half of the stack end plate and the volume V are given. H of the cavity of one of the separator plates: 0.5·V H < V Z < V H , especially preferably 0.5·V H < V Z < 0.75·V H .

[0040] A rear side of the separator plate half, facing away from the contact plate, can define an electrochemical cell, which may include, for example, gas diffusion layers and a membrane electrode assembly. The electrochemical cell is thus directly adjacent to the separator plate half.

[0041] The end plate is advantageously formed as an injection-molded part from PPS (phenylene sulfide), PI (polyimide), PAI (polyamide-imide), PPA (polyphthalamide), PA (polyamide), or GFRP (glass fiber reinforced plastic). To reduce weight, it can be designed with reinforcing ribs and recesses between the reinforcing ribs on its outer surface.

[0042] The invention further relates to an electrochemical system with an end plate and a stack end plate adjacent to the end plate. The stack end plate comprises an electrically conductive contact plate adjacent to the end plate and an electrically conductive separator plate half facing away from the end plate. The contact plate and the separator plate half are electrically and media-tightly connected to each other. The end plate has at least one sealing arrangement. The sealing arrangement can be arranged wholly or at least partially in or on the side of the end plate facing the contact plate. The contact plate is flat on its side facing the end plate.To compensate for expansions or contractions of the end plate and contact plate, particularly those caused by thermal expansion and varying degrees due to the different materials used, the sealing arrangement can slide or roll along the surface of the contact plate. The sealing arrangement serves primarily to seal a media passage for reagents or coolants that extends through the separator plate half, the contact plate, and the end plate.

[0043] In this electrochemical system, the separator plate half also has at least one opening for the passage of a coolant, wherein the separator plate half has a sealing arrangement designed as a bead on its rear side facing away from the contact plate for sealing the opening, wherein the bead has openings which are designed to direct a coolant passed through the opening of the separator plate half into an intermediate space arranged between the separator plate half and the contact plate.

[0044] Advantageously, the electrochemical system comprises a multitude of separator plates or bipolar plates whose surface area essentially corresponds to the surface area of ​​the separator plate half or the contacting plate. The plates of the stack end plates thus extend to the outer edge of the separator plates or bipolar plates of the electrochemical system and are clamped together with them.

[0045] The above description of the sealing arrangement, its arrangement and the first to third projections can also apply analogously to this embodiment of the invention.

[0046] The embodiments of the proposed electrochemical system described so far, as well as individual features of the embodiments described so far, can be combined with each other in any way.

[0047] Specific embodiments of the electrochemical system proposed here are shown in the figures and are explained in more detail below. It shows: Fig. 1 schematically an electrochemical system according to the prior art with an end plate, a termination bipolar plate and with an electrical connection between the termination bipolar plate and an outside of the system; Fig. 2 schematically a first embodiment of an electrochemical system according to the invention with a stack end plate adjacent to an end plate, which has a contact plate and a separator plate half; Fig. 3 schematically a second embodiment of the contact plate according to Fig. 2; Fig. 4 schematically a third embodiment of the contact plate according to Fig. 2; Fig. 5 schematically a perspective view of the electrochemical system according to Fig. 2; Fig. 6 schematically a second embodiment of the electrochemical system according to the invention, wherein the contact plate has channels for guiding a medium; Fig. 7 schematically a detailed view of the contact plate and the separator plate half according to Fig. 6 in perspective view; Fig. 8 schematically a third embodiment of the electrochemical system according to the invention, wherein the contact plate is designed as an embossed part; and Fig. 9 schematically a detailed view of the contact plate and the separator plate half according to Fig. 8 in perspective view.

[0048] Fig. Figure 1 shows a schematic representation of an electrochemical system 1 according to the prior art in the region of an end plate and the elements immediately adjacent to it. The electrochemical system 1 comprises an end plate 2, a terminal bipolar plate 3 immediately adjacent to the end plate 2, and a separator plate 4 in the form of a bipolar plate. The plates 3 and 4 are made of stainless steel. An electrochemical cell 5 is arranged between the terminal bipolar plate 3 and the separator plate 4. This cell comprises gas diffusion layers 6a and 6b as well as a membrane electrode assembly (MEA) 7 and serves, for example, to convert chemical energy into electrical energy.

[0049] An electrical connection between the termination bipolar plate 3 and an outer surface of the system 1 is established via a gas diffusion layer 9, a copper current collector 10 integrated into the end plate 2, and an electrical copper cable 11. The gas diffusion layer 9 is designed as a graphite-containing fabric. The gas diffusion layer 9 is in electrical contact with the termination bipolar plate 3 and with the current collector 10. The copper cable 11 is in electrical contact with the current collector 10 and extends from the current collector 10 to the outer surface 8 of the system 1. There, it is connected, for example, to an electrical load (not shown). High ohmic losses can occur at a first contact point 9a between the gas diffusion layer 9 and the current collector 10, and at a second contact point 9b between the gas diffusion layer 9 and the termination bipolar plate 3.Such losses reduce the efficiency of system 1 when used as a voltage source, electrolyzer, or the like.

[0050] Fig. Figure 2 shows an embodiment of an electrochemical system 100 according to the invention. Recurring features are designated by the same reference numerals in this and the following. The system 100 is a fuel cell arrangement. The system 100 comprises an end plate 2, a stacking end plate 50 immediately adjacent to the end plate 2, and a separator plate 4, here in the form of a bipolar plate. The stacking end plate 50 comprises a contact plate 51 facing the end plate 2 and adjacent to it, and a separator plate half 52 facing away from the end plate 2. The plates 51 and 52 are made of metal, here each of stainless steel, and are welded together multiple times or at least once in a media-tight manner. In particular, the plates 51 and 52 are in electrical contact with each other. The contact plate 51 is a sheet metal plate.Along a stacking direction 17, which is oriented perpendicular to the planar surfaces of plates 2, 51, 52, 4, the contact plate 51 has a material thickness 70 of, for example, 0.9 mm. A lateral direction 18 runs perpendicular to the stacking direction 17 and parallel to the planar surfaces of plates 2, 51, 52, 4. The end plate 2 is made of a plastic. The end plate 2 and the contact plate 51 therefore have different coefficients of thermal expansion.

[0051] System 100 further comprises an electrochemical cell 5 enclosed between separator plate half 52 and separator plate 4, with gas diffusion layers 6a, 6b and a MEA 7. Cell 5 serves to convert chemical energy into electrical energy. Plates 52 and 4 serve to supply process gas and remove reaction products to and from cell 5, respectively, to electrically connect the electrodes of cell 5, to dissipate heat generated during the conversion of chemical energy into electrical energy in cell 5, and to separate the respective media. System 100 comprises a plurality of further separator plates (not shown) stacked along the stacking direction 17, with further electrochemical cells arranged between each stack.

[0052] The electrodes of the electrochemical cells of system 100 are electrically connected to one another; here, they are connected in series. An electrical voltage generated by the electrochemical cells of system 100 relative to zero potential can be tapped at the contact plate 51. An electrical connection between the contact plate 51 and an outer surface 8 of system 100 is established via a metallic electrical conductor 19a. The conductor 19a and the contact plate 51 are in electrical contact with each other at a front face 51a of the contact plate 51 facing the end plate 2. There, the conductor 19a and the contact plate 51 are welded together. The conductor 19a is formed in one piece, e.g., as a one-piece molded part, here as a bolt.The conductor 19a extends from the front face 51a of the contact plate 51 to the outer surface 8 of the system, specifically to an outer surface 2a of the end plate 2 facing away from the stack end plate 50. The conductor 19a passes through a through-opening 22 in the end plate 2. The through-opening 22 extends from the outer surface 2a of the end plate 2 to an inner surface 2b of the end plate 2 facing the contact plate 51. The conductor 19a is made of stainless steel and forms a bolt-shaped projection on the front face 51a of the contact plate 51. The end of the conductor 19a facing away from the contact plate 51 is in electrical contact with an electrical cable 11, which is connected, for example, to an electrical load.

[0053] In a modified embodiment of system 100, not explicitly shown here, the contact plate 51 and the metallic electrical conductor 19a can also be formed as a single unit, e.g., as a one-piece molded part. The electrical connection according to the invention between the contact plate 51 and the outer surface 8 of system 100 is thus different from that of system 1. Fig. 1 significantly improved, where high ohmic losses can occur at contact points 9a and 9b.

[0054] The Fig. 3 and Fig. 4 show modified embodiments of the in Fig. 2 shown contact plate 51 and separator plate half 52. Also those in the Fig. 3 and Fig. The 4 embodiments of the stack end plate shown each have material-bonded connections between the contacting plate 51 and the separator plate half 52 according to the material-bonded connections 63 and 64. Fig. 2. A representation of the materially bonded compound 63 or 64 was shown in the Fig. 3 and Fig. However, for the sake of clarity, point 4 has been omitted. The contact plate 51 in Fig. 3 shows, in addition to the one already in Fig. The metallic electrical conductor 19a shown in Figure 2 is joined by further metallic electrical conductors 19b and 19c. Conductor 19b contacts the contact plate 51, as does conductor 19a, at its front face 51a facing the end plate 2, and is welded to the contact plate 51 there. Metallic conductor 19c forms a lateral extension of the contact plate 51. Metallic conductor 19c and contact plate 51 are formed as a single unit. Fig. 3 corresponds to a thickness 19c' of the conductor 19c determined along the stacking direction 17 of the material thickness 70 of the contact plate 51. The conductor 19c extends laterally to the outer surface 8 of the system 100 (not shown), where it can be, for example, soldered or welded to a cable. The separator plate half 52 is, in the embodiment according to Fig. 3 to at least 90 percent are properly trained.

[0055] On the one hand, the conductors 19a, 19b, and 19c shown here can be used side-by-side in a single contact plate 51 to tap the current. On the other hand, the conductors 19a, 19b, and 19c also represent different types of electrical conductors, of which only one or more of each of the three different types 19a, 19b, and 19c shown may be present in a contact plate 51. In principle, voltage can therefore be tapped at different points on a contact plate 51 using several conductors, but each conductor has only one contact point. If the contact plate has only a single conductor 19a, 19b formed as a projection, this is advantageously arranged in the region of the centroid of the contact plate or aligned with the centroid of the end plate.

[0056] Fig. Figure 4 shows a modified embodiment of conductor 19c. Fig. 3. The manager 19c according to Fig. 4 differs from conductor 19c according to Fig. 3 by a thickness 19c' reduced compared to the material thickness 70 of the contact plate 51. For example, the thickness 19c' of the conductor 19c in Fig. 3 less than 50 percent or less than 20 percent of the material thickness 70 of the contact plate 51. The conductor 19c in Fig. In this way, 4 forms a tab that can be easily bent over on the outside of the system 100, e.g. in the stacking direction 17 towards the end plate 2.

[0057] In system 100 according to Fig. The plates 2, 51, 52, and 4 have aligned openings 2', 51', 52', and 4' that form a channel 13 for conveying a medium 14. The medium 14 can be a process gas, e.g., molecular hydrogen or molecular oxygen, a reaction product, e.g., water vapor, or a coolant. To seal the channel 13 against a gap 15 between the end plate 2 and the contact plate 51, the system 100 has a sealing arrangement 16. The sealing arrangement 16 is arranged around the channel 13 between the end plate 2 and the contact plate 51. The sealing arrangement 16 laterally surrounds the opening 2' in the end plate 2 and the opening 51' in the contact plate 51 and extends in a plane parallel to the planar surfaces of the end plate 2 and the contact plate 51.

[0058] The sealing arrangement 16 comprises, for example, an annular recess 24 on the inner side 2b of the end plate 2 and an elastic sealing ring 25 arranged in the recess 24. The hardness of the elastomer from which the sealing ring 25 is formed is, for example, 60 Shore A. Along the stacking direction 17, the dimensions of the recess 24 and the sealing ring 25 are selected such that, in the uncompressed state, the sealing ring 25 projects beyond the inner side 2b of the end plate 2 along the stacking direction 17, for example, by at least 10 percent or at least 20 percent of a depth of the recess 24 determined along the stacking direction 17.

[0059] Here, the depth of the recess 24, the thickness of the sealing ring 25 determined along the stacking direction 17, and the hardness of the sealing ring 25 are selected such that the force that must be exerted on the sealing ring 25 parallel to the stacking direction 17 via the end plate 2 and the contact plate 51 to compress the sealing ring 25 until the end plate 2 and the contact plate 51 touch each other is at most 10 percent or at most 5 percent of the contact force typically exerted to compress the system 100 along the stacking direction. This ensures that the contact force acting between the end plate 2 and the contact plate 51 is primarily introduced into the end plate 2 and the contact plate 51 via the inner surface 2a of the end plate 2 and the front surface 51a of the contact plate 51, and not via the sealing arrangement 16.

[0060] In the System 100 of the Fig. The inner surface 2a of the end plate 2 is completely flat. Likewise, the front surface 51a of the contact plate 51 is completely flat. The rear surface 51b of the contact plate 51, facing the separator plate half 52, is also completely flat. The inner surface 2b of the end plate 2 and the front surface 51a of the contact plate 51 thus each form contact areas of the end plate 2 and the contact plate 51, which are brought into contact with each other when the system 100 is pressed together. The front surface 51a of the contact plate 51 is particularly flat in the area of ​​the sealing arrangement 16.Thus, during temperature changes, when the end plate 2 and the contact plate 51 shift relative to each other perpendicular to the stacking direction 17 due to their different coefficients of thermal expansion, the sealing ring 25 can slide or roll off the flat or smooth front surface 51a of the contact plate in the area of ​​the sealing arrangement 16. The dimensions of the flat area of ​​the front surface 51a of the contact plate 51 in the area of ​​the sealing arrangement 16 can be selected depending on the expected displacement of the end plate 2 and the contact plate 51. This usually depends on the coefficients of thermal expansion of the end plate 2 and the contact plate 51, as well as the temperature range in which the system 100 is to be used. The system 100 is typically designed for use at temperatures between -40°C and 100°C. The sealing arrangement 16 is particularly durable.In particular, the sealing arrangement 16 can be easily reused when the system 100 is disassembled.

[0061] The separator plate half 52 is designed as an embossed part. On its rear side 52b, facing away from the contact plate 51, the separator plate half 52 has channels 53 for guiding a process gas that is supplied to the electrochemical cell 5. Here, the channels 53 were embossed into the separator plate half 52 in an embossing process. The thickness of the separator plate half 52, perpendicular to the plane of the separator plate, is, for example, less than 0.2 mm or less than 0.1 mm.

[0062] To seal the electrochemical cell 5 from the channel 13, the separator plate half 52 additionally has a sealing arrangement on its rear side 52b that surrounds the channel 13 and has an annular bead 54 extending beyond the channels 53 along the stacking direction 17. The bead 54 has openings 55 (see also Fig. 7 and Fig. 9), through which a coolant can be directed into an intermediate space 56. The intermediate space 56 is located between the contact plate 51 and the separator plate half 52 and is enclosed by the plates 51 and 52. For this purpose, the contact plate 51 and the separator plate half 52 are welded together on both sides of the groove 54, circumferentially and in a media-tight manner along the weld seams 63. The weld sections 64, which are visible in the area of ​​the outer edges of the plates 51 and 52, are only provided in sections and serve to stabilize the overall system.

[0063] Fig. Figure 5 schematically shows a perspective representation of System 100 according to Fig. 2, which in particular illustrates the structure of the channel 13 formed by the aligned openings 2', 51', 52' in the plates 2, 51, 52. For clarity only, the metallic electrical conductor 19a and the channels 53 on the rear side 52b of the separator plate half 52 are shown in Fig. 5 not shown.

[0064] Fig. Figure 6 shows an electrochemical system 200, which is a slightly modified embodiment of the electrochemical system 100. Fig. 2. System 200 differs from system 100 in that the contact plate 51 is not flat on its rear side 51b facing the separator plate half 52, but has channels 57 for guiding a coolant. This enables or improves the cooling of the separator plate half 52, through which at least some of the reaction heat generated in the electrochemical cell 5 is normally dissipated. The channels 57 can be formed, for example, by an etching process. A representation of possible corrugation penetrations or plate connections was omitted in Fig. 6. Omitted for the sake of clarity.

[0065] Fig. Figure 7 schematically shows a detailed view of a section of the contact plate 51 and the separator plate half 52 of the system 200 according to Fig. Figure 6 is shown in perspective. Clearly visible are the completely smooth or flat front surface 51a and the structured back surface 51b of the contact plate 51 with the channels 57 formed by the structuring. Also visible is the separator plate half 52, which is formed as an embossed part, with the channels 53, the groove 54, and a perforation 55 formed on the back surface 52b, through which coolant can flow from the channel 13 into the space 56 between the contact plate 51 and the separator plate half 52 to cool the separator plate half 52.

[0066] Fig. Figure 8 shows an electrochemical system 300, which is a modified embodiment of system 200 according to the Fig. 6 and Fig. 7 is. System 300 differs from System 200 according to the Fig. 6 and Fig. 7 by the fact that the contact plate 51 is designed as an embossed part with embossed first and second deformations, wherein the first deformations on the rear side 51b of the contact plate 51 facing the separator plate half 52 form the previously described channels 57 for guiding a coolant. The channels 57 of the contact plate 51 have a cross-section that differs from that of the channels 56 of the separator plate half 52, so that the cross-section available for guiding the coolant is, on the one hand, smaller than that for guiding the coolant through the bipolar plate 4, but, on the other hand, larger than the cross-section that the channels 56 have in the exemplary embodiment of the Fig. 2. By dimensioning the channels 57, the cross-section available for coolant flow can be adjusted.

[0067] The second deformations project in contact areas 58 in the stacking direction 17 towards the end plate 2 by a length 59 beyond a flat area 60 of the front surface 51a of the contact plate in the area of ​​the sealing arrangement 16. The end plate 2 has a third deformation on its inner surface 2b in the form of a recess 61. The recess 61 has a depth relative to a flat area 62 of the inner surface 2b of the end plate 2 in the area of ​​the sealing arrangement 16, which is determined along the stacking direction 17 and corresponds exactly to the aforementioned length 59. This results in the inner surface 2b of the end plate 2 and the front surface 51a of the contact plate 51 being brought into contact both along the flat areas 60, 62 in the area of ​​the sealing arrangement 16 and along the contact areas 58 projecting into the recess 61 when the end plate 2 and the contact plate 51 are pressed together in the stacking direction 17, so that the sealing arrangement is relieved.Further indications . Fig. Figure 8 indicates that the sealing element 16 does not necessarily have to have a round cross-section; the diamond-shaped cross-section is only an example. Here too, possible corrugation penetrations or plate connections have been omitted for the sake of clarity.

[0068] Fig. Figure 9 schematically shows a detailed view of a section of the contact plate 51 and the separator plate half 52 of the system 300 according to Fig. Figure 8 in perspective view. The first and second deformations embossed into the contact plate 51, which is designed as an embossing part, are clearly visible.

Claims

[1] Electrochemical system (100; 200; 300) comprising: an end plate (2); a stack end plate (50) adjacent to the end plate (2); and at least one metallic electrical conductor (19a, 19b, 19c); wherein the stack end plate (50) has an electrically conductive contacting plate (51) adjacent to the end plate (2) and an electrically conductive separator plate half (52) facing away from the end plate (2), wherein the contacting plate (51) and the separator plate half (52) are connected to one another in a materially bonded, electrically bonded and media-tight manner; wherein the metallic electrical conductor (19a, 19b, 19c) extends to an outer side (8) of the electrochemical system (100; 200; 300); and wherein the metallic electrical conductor (19a, 19b, 19c) and the contacting plate (51) are formed in one piece or the metallic electrical conductor (19a, 19b, 19c) directly contacts the contacting plate (51); characterized by , that the separator plate half (52) has at least one opening (52') for the passage of a coolant, wherein the separator plate half (52) has, on its rear side (52b) facing away from the contacting plate (51), a sealing arrangement designed as a bead (54) for sealing the opening (52'), wherein the bead (54) has openings (55) which are designed to guide a coolant guided through the opening (52') of the separator plate half (52) into an intermediate space (56) arranged between the separator plate half (52) and the contacting plate (51). [2] Electrochemical system (100; 200; 300) according to claim 1, characterized bythat the material connection between the contact plate (51) and the separator plate half (52) is a welded connection or an adhesive connection. [3] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the contacting plate (51) has channels (57) for guiding a coolant on its rear side (51b) facing the separator plate half (52). [4] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized byin that the contacting plate (51) is designed as a stamped part with stamped second deformations, wherein the second deformations form channels (57) for guiding a coolant on a rear side (51b) of the contacting plate (51) facing the separator plate half (52), and wherein the inner side (2b) of the end plate (2) facing the contacting plate (51) has at least one third deformation (61) which is designed such that the at least one third deformation (61) absorbs the second deformations when the end plate (2) and the contacting plate (51) are pressed together. [5] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the separator plate half (52) has channels (53) for guiding a process gas or a reaction product on its rear side (52b) facing away from the contacting plate (51). [6] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the material connection between the contact plate (51) and the separator plate half (52) forms an intermediate space (56) arranged between the contact plate (51) and the separator plate half (52) for the passage of a coolant. [7] Electrochemical system (100; 200; 300) according to claim 6, characterized by a plurality of electrochemical cells, each separated from one another by separator plates (4), wherein the separator plates (4) each have a cavity for the passage of a coolant and wherein a volume of the intermediate space (56) formed between the contacting plate (51) and the separator plate half (52) of the stack end plate (50) is smaller than a volume of the cavity of one of the separator plates (4). [8] Electrochemical system (100; 200; 300) according to claim 7, characterized bythat for the volume V Z of the intermediate space (56) formed between the contact plate (51) and the separator plate half (52) of the stack end plate (50) and for the volume V H of the cavity of one of the separator plates (4) is: 0.5·V H < V Z < V H . [9] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that a rear side (52b) of the separator plate half (52) facing away from the contacting plate (21) delimits an electrochemical cell (5), wherein the electrochemical cell (5) comprises gas diffusion layers (6a, 6b) and a membrane electrode unit (7). [10] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the electrical conductor (19a, 19b, 19c) extends completely or at least partially through the end plate (2). [11] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the contacting plate (51) has a projection on its side facing the end plate (2), wherein the projection extends through the end plate (2) to form the electrical conductor (19a, 19b, 19c) or wherein the projection at least partially extends into a first recess of the end plate (2) and the electrical conductor (19a, 19b, 19c) contacts the contacting plate (51) within the recess on the projection. [12] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the electrical conductor (19a, 19b, 19c) and the contact plate (51) are materially connected, in particular by a welded connection or by a soldered connection. [13] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized bythat the contacting plate (51) has an extension which projects beyond the end plate (2) parallel to the flat surface plane of the end plate (2) to form the electrical conductor (19a, 19b, 19c), wherein the extension is preferably designed as a bendable tab. [14] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the contact plate (51) is designed as a sheet metal, wherein a material thickness (70) of the contact plate (51) determined perpendicular to the flat surface plane of the contact plate (51) is between 0.1 mm and 8.0 mm, preferably between 0.2 mm and 3.0 mm, particularly preferably between 0.5 mm and 1.0 mm. [15] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized bya sealing arrangement (16) arranged between the contacting plate (51) and the end plate (2), wherein the sealing arrangement (16) has a second recess (24) in the end plate (2) and a sealing ring (25) at least partially received in the second recess (24). [16] Electrochemical system (100; 200; 300) according to claim 15, characterized by that a front side (51a) of the contacting plate (51) facing the end plate (2) is flat at least in the region of the sealing arrangement (16), so that the sealing ring (25) is designed to slide or roll on the contacting plate (51) when the end plate (2) is displaced relative to the contacting plate (51) in a direction parallel to the flat surface plane of the contacting plate (51). [17] Electrochemical system (100; 200; 300) according to one of claims 15 or 16, characterized bythat the end plate (2) and the contacting plate (51) have mutually facing contact regions which are designed such that the contact regions are in contact with one another during operation of the electrochemical system when the end plate (2) and the contacting plate (51) are pressed together along a pressing direction oriented perpendicular to the flat surface plane of the end plate (2) and the contacting plate (51), so that a pressing force acting along the pressing direction is introduced primarily via the contact regions and is not introduced primarily via the sealing arrangement (16). [18] Electrochemical system (100; 200; 300) according to one of claims 15 to 17, characterized bythat the end plate (2) and the contacting plate (51) have openings (2', 51') for passing through a medium, in particular for passing through at least one process gas, a reaction product or a coolant, wherein the sealing arrangement (16) for sealing the openings (2', 51') is arranged around the openings (2', 51'). [19] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that at least 80 percent, preferably at least 90 percent of a front side (51a) of the contacting plate (51) facing the end plate (2) is flat. [20] Electrochemical system (100; 200; 300) comprising: an end plate (2); and a stack end plate (50) adjacent to the end plate (2); wherein the stack end plate (50) has an electrically conductive contacting plate (51) adjacent to the end plate (2) and an electrically conductive separator plate half (52) facing away from the end plate (2), wherein the contacting plate (51) and the separator plate half (52) are electrically and media-tightly connected to one another; wherein the end plate (2) has at least one sealing device (16); and wherein the contact plate (51) is flat on its side facing the end plate (2) at least in the region of the sealing arrangement (16) and the sealing device (16) can slide or roll on the contact plate (51) to compensate for expansions or contractions; characterized byin that the separator plate half (52) has at least one opening (52') for the passage of a coolant, wherein the separator plate half (52) has, on its rear side (52b) facing away from the contacting plate (51), a sealing arrangement designed as a bead (54) for sealing the opening (52'), wherein the bead (54) has openings (55) which are designed to guide a coolant guided through the opening (52') of the separator plate half (52) into an intermediate space (56) arranged between the separator plate half (52) and the contacting plate (51). [21] Electrochemical system (100; 200; 300) according to claim 20, characterized by a plurality of separator plates (4), wherein the surface area of the contacting plate (51), the separator plate half (52) and the separator plates (4) is substantially the same. [22] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized bytwo end plates (2), adjacent stack end plates (50) and a plurality of separator plates (4) lying between the stack end plates (50). [23] Electrochemical system (100; 200; 300) according to one of the preceding claims, characterized by that the electrochemical system (100; 200; 300) is a fuel cell system, an electrochemical compressor or an electrolyzer.

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