Terminal bipolar plate, plate assembly and electrochemical system for an electrochemical system

Abstract

The invention relates to a plate assembly (50) for an electrochemical system (1), comprising: an end plate (52); a first separator plate (31) which adjoins the end plate (52) and has a plate plane; a second separator plate (32) which adjoins the first separator plate (31), the second separator plate (32) having at least one media-guided second through-opening (42), wherein an orthogonal projection of the second through-opening (42) onto the plate plane of the first separator plate (31) defines a projection area (40), wherein the first separator plate (31) has no through-openings in the area of the projection area (40) or has first through-openings (41) which have an area which is less than 20% of the area of the second through-openings (42). The invention also relates to an electrochemical system (1) comprising such a plate assembly (50) and a terminal bipolar plate (30) for the electrochemical system (1).

Description

Technical Field

[0001] This invention relates to a terminal bipolar plate for an electrochemical system, and to a plate assembly. The invention also relates to an electrochemical system comprising such a plate assembly and such a terminal bipolar plate. Specifically, the electrochemical system may be a fuel cell cell system, an electrochemical compressor, an electrolyzer, a humidifier for an electrochemical system, or a redox flow battery. Background Technology

[0002] Known electrochemical systems of the above types typically comprise stacked electrochemical cell units (cells), each separated from the others by bipolar plates or monopolar plates. Such bipolar plates or monopolar plates can be used, for example, to indirectly electrically contact the electrodes of a single electrochemical cell (e.g., a fuel cell unit) and / or to electrically connect adjacent cells (cells in series). Bipolar plates or monopolar plates are typically formed of two layers bonded together, each individual layer being referred to as a separator. The separators (individual plates) of a bipolar or monopolar plate can be bonded together by means of material bonding (material joining), for example, through one or more weld joints, particularly through one or more laser weld joints. The terms "bipolar plate" or "monopolar plate" arise from the arrangement of the plates relative to a medium, which consists of two separators. In the case of a bipolar plate, different media flow on two surfaces; in the case of a monopolar plate, the same media flows on two surfaces. The following references to multiple bipolar plates or a single bipolar plate may also refer to multiple monopolar plates or a single monopolar plate, unless otherwise stated.

[0003] The separators or layers may each have or form structures designed, for example, to provide one or more media to and / or remove reaction products from an electrochemical cell perimetered by adjacent separators. This media may be a fuel (e.g., hydrogen or methanol) or a reactant gas (e.g., air or oxygen). Furthermore, the separators may have structures designed to guide cooling media through a bipolar plate composed of two separators, particularly through a cavity enclosed by the separators. Additionally, the separators may be designed to transfer waste heat generated during the conversion of electrical and / or chemical energy within the electrochemical cell, and also to seal various media channels and cooling channels relative to each other and / or relative to the outside.

[0004] In addition, each separator typically has multiple through openings. Through these through openings, the medium and / or reaction products can be conducted to the electrochemical cell bounded by the stacked adjacent separators or into the cavity formed by the individual plates of the separators, or they can be conducted to the outside of the cell or the cavity.

[0005] Each electrochemical cell also includes one or more membrane electrode assemblies (MEAs). MEAs may have one or more gas diffusion layers, which are typically oriented toward a separator and constructed, for example, as a metal felt or carbon felt. Furthermore, each MEA has a framework-like reinforcing layer surrounding the electrochemically active region of the MEA and is typically made of an electrically insulating material.

[0006] A stack consisting of bipolar plates and electrochemical cells typically terminates at each end of the stack with end plates or terminal plates. Here, a terminal plate should be understood as a combination of an end plate and at least one outer plate. In this case, at least one outer plate may be arranged on the plate surface of the end plate facing away from the stack. Therefore, when using terminal plates, the end plates typically serve primarily as insulation, while the outer plates are used for force absorption. At least one of the end plates or at least one of the terminal plates typically has one or more dielectric ports. Lines for supplying dielectric and / or removing reaction products can be connected to said ports. Furthermore, at least one of the end plates or at least one of the terminal plates typically has an electrical connection via which the cell stack can be electrically connected to a power-consuming device, or, particularly, to a voltage source in the case of an electrolyzer. Corresponding other end plates and / or terminal plates may also be used only for compressing and / or sealing the stack, and therefore may not have dielectric ports. The bipolar plate positioned closest to or adjacent to the end plate or terminal plate of the stack will also be referred to as a terminal bipolar plate.

[0007] A sealing device is typically arranged between the terminal bipolar plate and the end plate. This sealing device is used to seal various lines or sections of the electrochemical system relative to the outside and / or relative to each other. In known systems, the seal between the terminal bipolar plate and the end plate is achieved by means of a metal protrusion applied as a coating through screen printing. However, this screen printing tends to adhere primarily to the machined, or at least slightly roughened, plastic surface of the end plate. The terminal bipolar plate and the end plate are typically made of different materials and therefore have different coefficients of thermal expansion. If the terminal bipolar plate and the end plate shift relative to each other under temperature changes, particularly in the lateral direction, i.e., orthogonal to the stacking direction, the sealing device may also detach or be damaged. The bipolar plate, and therefore the terminal bipolar plate, is typically made of metal such as stainless steel, while the end plate is typically made of plastic or primarily plastic.

[0008] In some applications, the sealing device must function equally reliably across a temperature range between a minimum (e.g., -40°C) and a maximum (e.g., +100°C). Such temperature variations can occur when a fuel cell unit system begins operation at ambient temperature, or during a cold start in winter, moving from sub-zero temperatures to the stack's maximum operating temperature. The effects of coating detachment and adhesion become particularly noticeable during stack disassembly, where the coating is pulled away from the terminal bipolar plates due to prior detachment.

[0009] To prevent or at least reduce this relative displacement under temperature variations, the end plates can also be made of metal. However, this increases the manufacturing cost and weight of the system, which is undesirable for many applications. On the other hand, sealing the boundary layer between the end plates and the terminal bipolar plates by means of rubber seals (O-rings or soft seals) partially embedded in at least one plate may lead to difficulties in coordinating the height and force of the sealing system due to the high compressibility of such seals.

[0010] This problem is also known from publication DE 20 2014 002 512 U1. That document proposes a sealing device between one of the two end plates and the terminal bipolar plate, designed such that, under temperature variations, the sealing function occurs solely by means of sliding of the end plate and / or the terminal bipolar plate on the sealing device, or at least also by means of this sliding. However, this requires additional surface machining and / or special coatings. Summary of the Invention

[0011] The object of this invention is to provide a plate assembly, a terminal bipolar plate, and an electrochemical system with good sealing. Preferably, the plate assembly, the terminal bipolar plate, and the electrochemical system should also be as easy and inexpensive to manufacture as possible.

[0012] This objective is achieved through the terminal bipolar plate, plate assembly, and electrochemical system according to the present invention. Specific embodiments are disclosed in other technical solutions and in the following description.

[0013] Therefore, a plate assembly for an electrochemical system is proposed. The plate assembly includes: - End plate, - A first partition, which is adjacent to the end plate and has a plate plane, and - A second partition, which is adjacent to the first partition, has at least one medium-guided second through opening.

[0014] The orthogonal projection of the second through opening onto the first partition plate, perpendicular to the plate plane, defines the projection area, wherein the first partition plate is located within the projection area. - No through opening, or - It has a first through opening, the area of ​​which is 20% smaller than the area of ​​a second through opening.

[0015] Therefore, in the first case, there is no through opening in the projection area of ​​the first partition. Thus, the entire projection area is closed and formed by the plate material of the first partition. This eliminates the need for a separate seal made of elastomer or screen-printed coating, which in the prior art is arranged between the end plate and the first partition. Instead, the plate material of the first partition fluidly seals the projection area. Therefore, the relative movement between the end plate and the first partition, as described above, is not a problem and has no negative impact on the sealing performance of the plate assembly. Furthermore, the surface quality of the end plate does not need to correspond to the quality of the sealing surface, but is only used to abut against the first partition. Therefore, the surface finishing step for the end plate, whether as part of actual production or as post-processing, can be omitted, and costs can be reduced.

[0016] The solution described will not incur any additional costs, because the first and second partitions can, in principle, be manufactured in the same manufacturing tool or by means of the same manufacturing tool, wherein when manufacturing the first partition, the step of providing a through opening contained in the second partition is omitted.

[0017] Preferably, the end plate adjacent to the first partition is an end plate that does not have a medium port, or at least does not have a medium port for the medium being conducted through the second through opening. Furthermore, in some embodiments, at least one outer plate may be provided, which is combined with the end plate to form a terminal plate. In this case, at least one outer plate may be disposed on the surface of the end plate facing away from the first partition.

[0018] If a first through-opening exists, its difference from a second through-opening is a significant reduction in area, specifically less than 20%. The area of ​​the first through-opening is typically less than 10% of the area of ​​the second through-opening, preferably less than 7%, and particularly less than 5%. Therefore, the first through-opening is much smaller than the second through-opening. As a result, the corresponding seal for sealing the first through-opening relative to the surrounding environment can be made much smaller than previously known seals, simplifying its manufacture. In this case, a spiral insert can also be used, which can be applied to many different product ranges, regardless of the typically complex geometry of the second through-opening and other special features of the corresponding plate assembly.

[0019] The first through opening is designed, for example, as a vent opening. Furthermore, the first through opening can be designed to compensate for pressure differences inside and / or outside the plate assembly. For this purpose, a corresponding valve can be fluidly connected to the first through opening. The end plate can have an outlet opening fluidly connected to the first through opening. If a terminal plate is present, comprising an end plate and at least one outer plate, it is advantageous that the entire terminal plate, i.e., the end plate and at least one outer plate, has such an outlet opening valve that can be arranged at either the outlet opening or the first through opening. A flow path can be formed from the first through opening to the outlet opening. The valve can be located in the flow path between the first through opening and the outlet opening. Alternatively, or in addition to a valve, the first through opening can also be provided with a closure element, such as a sealing cap, which seals the first through opening closed. As a supplement or alternative, the outlet opening can have such a closure element.

[0020] The second through opening of the second partition is designed as a passage for, for example, cooling fluid. When the assembly is filled with cooling fluid, such as during initial filling (i.e., the first filling), the first through opening can remain open, for example, by removing the sealing cap or because the sealing cap has not yet been attached to the first through opening. As a result, air retained in the plate assembly can escape through the first through opening, and preferably subsequently be vented out through the outlet opening. After filling, the first through opening and / or the outlet opening is closed by a corresponding sealing cap or closure. Venting is also conceivable before the plate assembly or electrochemical system is put into service. A permanently open mode for the first through opening and / or the outlet opening is also conceivable in principle and generally depends on other operating conditions.

[0021] Such a permanently open first through opening and / or outlet opening can be positioned adjacent to a second through opening for a gaseous medium. This can be advantageous, for example, for a hydrogen or oxygen supply opening or a hydrogen or oxygen discharge opening serving as the second through opening, in which case condensate can be discharged via the first through opening and / or outlet opening. However, it is also possible to provide a temporary interruption of discharge, rather than continuous discharge of condensate, for example via a valve or—if the plate assembly is installed in a vehicle—depending on road conditions.

[0022] The second partition typically has multiple second through openings, for example, for supplying and removing reaction media or cooling fluids. The first partition has multiple projection zones corresponding to the number of second through openings. It can be specified that the first partition has no through opening in at least one projection zone. Furthermore, in at least one of the other projection zones, the first partition may have a first through opening with an area less than 20% of the area of ​​the second through openings.

[0023] It can be stipulated that the first partition has a first through opening only when the second through opening of the second partition is designed for the passage of a selected medium, particularly coolant. If the second through opening is designed for the passage of a reaction medium, then the first partition can be closed in the projected area. However, as mentioned above, it may also be advantageous to design the second through opening of the second partition for the passage of a medium, wherein, preferably, this medium is not the actual medium being conducted through or away, but rather condensates within the medium.

[0024] Optionally, the outer contour of the first through opening may differ from that of the second through opening. In other words, each through opening in this embodiment has a different shape. Although the through openings are different in size, the first and second through openings may optionally have the same shape, such as a circle.

[0025] As described above, one side consists of end plates and the other of partitions, which can be made of materials with different coefficients of thermal expansion. Typically, the plate body of the end plate is at least partially or primarily made of polymer material; this usually applies even when the end plate is part of a terminal plate, which may also include an outer plate made of a different material. Furthermore, the plate bodies of the first partition and the second partition can each be made of metallic material.

[0026] It can be specified that the first partition has at least one raised structure in the projection area. The raised structure can be produced, for example, by means of hydroforming, deep drawing, or embossing. In this case, the raised structure can perform various functions, such as guiding the medium and / or reinforcing the rigidity of the first partition in the projection area and / or supporting the first partition against the end plate.

[0027] In some embodiments, at least one media guiding structure is arranged in the region of the projection area. This media guiding structure is typically part of the first partition, but it can also be provided as a separate element. Alternatively, the media guiding structure is part of the end plate. In the second partition, passageways or guiding through-structures may be arranged around a second through-opening. The media guiding structure may be tilted such that fluid is directed toward these passageways or toward the outlet opening of the end plate. The media guiding structure typically extends into the second through-opening, or into the outlet opening, or through the second through-opening or the outlet opening. The raised structure may be or may include the media guiding structure.

[0028] The plate assembly may have at least one support element for supporting the first partition against the end plate. The support element may be arranged in the region of the projection area. The support element may be integrally formed with the first partition or the end plate, or it may be designed as a separate element. The raised structure may be or may include the support element.

[0029] In some embodiments, at least one reinforcing structure is arranged in the projection area of ​​the first partition to reinforce that area. The raised structure may be or may include reinforcing elements.

[0030] The first and second septa are typically connected to each other by material bonding, preferably by means of welded joints, laser-welded joints, or other welding joints. Generally, the first and second septa together constitute a terminal bipolar plate. This terminal bipolar plate is sometimes also referred to as a unipolar plate.

[0031] According to some embodiments, the second partition has a second sealing element surrounding the second through opening. Additionally, the first partition may have a spring element surrounding the projection area of ​​the second through opening on the first partition. The spring element typically abuts the end plate and supports the first partition against the end plate. The spring element of the first partition and the sealing element of the second partition can be formed from structurally identical elements, such as protrusions (convexities) pressed into or applied to the respective partitions by an elastomer. In particular, the sealing element and the spring element can have the same shape, the same dimensions, and / or the same material. Thus, due to structural similarity, the spring element can be referred to as the first sealing element, but it does not have a sealing function because the sealing material of the first partition in the projection area is not required. Instead, the spring element is provided to maintain as constant as possible the compressive force along the stack. The spring element is subjected to pressure in the installed stack or electrochemical system. The second sealing element may have a coating for micro-sealing, such as a screen-printed coating. The spring element may also have such a coating.

[0032] The second sealing element may define a sealing line along which it extends around the second through opening. The spring element may define a line along which it extends around the projection area or the second through opening. The sealing line of the second sealing element and the line of the spring element may coincide in parallel projections.

[0033] The present invention also proposes a stack, particularly for use in electrochemical systems. The stack comprises a plate assembly of the type described above. Furthermore, the stack includes another end plate having a plurality of dielectric ports. Each dielectric port of the other end plate is fluidly connected to a second through-opening of a second separator. Additionally, a separator is arranged between the two end plates. Therefore, the other end plate differs from the aforementioned end plates in the dielectric ports. Another bipolar plate is typically adjacent to another terminal bipolar plate, which includes two separators having aligned through-openings that are fluidly connected to the dielectric ports of the other end plate. This other terminal bipolar plate differs from the terminal bipolar plate described above. The stack typically comprises a plurality of bipolar plates arranged between the end plates and / or the terminal bipolar plates.

[0034] An electrochemical system comprising a plate assembly of the type described above is also proposed.

[0035] A terminal bipolar plate for an electrochemical system is also provided. The terminal bipolar plate includes: - A first partition, the first partition having a plate surface. - A second partition, adjacent to the first partition, having at least one medium-guided second through-opening. The second through-opening defines a projection area by an orthogonal projection perpendicular to the plane of the first partition, wherein the first partition is located within the projection area. - No through opening, or - It has a first through opening, the area of ​​which is 20% smaller than the area of ​​a second through opening.

[0036] The features of the aforementioned plate assembly related to the first and / or second partitions can also be combined with the terminal bipolar plate. Attached Figure Description

[0037] The invention will be explained in more detail with reference to the accompanying drawings. In the drawings: Figure 1 An electrochemical system is schematically illustrated in a three-dimensional view, comprising a plurality of separators or bipolar plates arranged in a stacked manner; Figure 2 A three-dimensional diagram schematically illustrates the following based on Figure 1 The system has two bipolar plates, with a membrane electrode assembly (MEA) arranged between the bipolar plates; Figure 3 schematically illustrates the cross-section according to the prior art. Figure 1 A cross-section of a portion of a plate stack of an electrochemical system; Figure 4 A cross-section according to one embodiment is schematically shown. Figure 1 A cross-section of a portion of a plate stack of an electrochemical system; Figure 5A A schematic plan view of a terminal bipolar plate according to one embodiment is shown; Figure 5B The schematic diagram shows the cross-section including Figure 5A A cross-section of a portion of the plate assembly of the terminal bipolar plate; Figure 6A A schematic plan view of a terminal bipolar plate according to one embodiment is shown; Figure 6B The diagram schematically illustrates a section along the cutting line BB, including... Figure 6A A cross-section of a portion of the plate assembly of the terminal bipolar plate; Figure 7AA schematic plan view of a terminal bipolar plate according to one embodiment is shown; Figure 7B The schematic diagram shows the section along the cutting line CC, passing through... Figure 7A A cross-section of a portion of the plate assembly of the terminal bipolar plate; Figure 8 A cross-section of a portion of a plate assembly according to one embodiment is schematically shown; and Figure 9 A cross-sectional view schematically showing a portion of a plate assembly according to one embodiment is shown; and Figure 10 A cross-section of a portion of a plate assembly according to one embodiment is shown schematically. Detailed Implementation

[0038] In the following description and figures, features that appear repeatedly and have the same function have the same reference numerals. For clarity, reference numerals are not always indicated in every example; however, related elements may be present in the relevant examples.

[0039] Figure 1 An electrochemical system 1, of the type proposed herein, is shown, comprising multiple identical metal separators or bipolar plates 2 arranged in a stacked configuration along the z-direction 7. To form the electrochemical cell of system 1, a membrane electrode assembly (MEA) is arranged between adjacent bipolar plates 2 in each case of the stack (see, for example, [link to relevant documentation]). Figure 2 Each MEA typically contains at least one membrane, such as an electrolyte membrane. Additionally, a gas diffusion layer (GDL) may be arranged on one or both surfaces of the MEA. The bipolar plates 2 of the stack 6 and the MEA 10 are sandwiched between the first end plate 3 and the second end plate 4. The z-direction 7 is also referred to as the stacking direction. In this example, system 1 is a fuel cell cell stack 6. Therefore, each pair of adjacent bipolar plates 2 in the stack 6 encloses an electrochemical cell between them, which is used, for example, to convert chemical energy into electrical energy.

[0040] In alternative embodiments, system 1 can also be designed as an electrolyzer, compressor, humidifier for an electrochemical system, or redox flow battery. Separators, particularly bipolar or monopolar plates constructed from two separate plates, can also be used in these electrochemical systems. Thus, the structure of these bipolar or monopolar plates can correspond to the structure of bipolar plate 2 described in detail herein, but in the case of an electrolyzer, electrochemical compressor, or redox flow battery, the medium conducted on and / or through the bipolar or monopolar plates can differ in each case from the medium used for a fuel cell cell system.

[0041] The z-axis 7, together with the x-axis 8 and y-axis 9, forms a right-handed Cartesian coordinate system. Each bipolar plate 2 defines a plate plane, and each plate plane of the partition is oriented parallel to the xy plane and therefore perpendicular to the stacking direction or z-axis 7. The second end plate 4 has multiple medium ports 5 through which medium can be supplied to and discharged from system 1. The medium that can be supplied to and discharged from system 1 may 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 fuel, or coolants such as water and / or ethylene glycol. In the case of a humidifier, temperature control is typically not required here, and therefore there are only four medium ports, instead of... Figure 1 The six media ports 5 shown are illustrated.

[0042] Figure 1 It can refer to both the prior art electrochemical system 1 and the electrochemical system 1 according to the present invention.

[0043] Figure 2 Showing the relationship with a 3D diagram Figure 1 The system 1 consists of two adjacent separators 2a, 2b or bipolar plates 2 of the same type as the electrochemical system, and a membrane electrode assembly (MEA) 10, known from the prior art, arranged between the adjacent separators 2. Figure 2 MEA 10 is largely obscured by the observer-facing partition 2. The partition 2 is formed by two separate plates 2a and 2b joined together by material bonding (e.g., see Figure 3). Figure 2 Only the first individual plate 2a facing the observer is visible, and the first individual plate obscures the second individual plate 2b. The individual plates 2a and 2b can be made of metal plates, such as stainless steel. For example, the individual plates 2a and 2b can be welded together, for example, by laser welding joints.

[0044] Partitions 2a and 2b have through openings that are aligned with each other to form through openings 11a-11c of bipolar plate 2. MEA 10 also has corresponding aligned through openings; for clarity, the description of individual reference numerals is omitted here. When multiple bipolar plates of the same type as bipolar plate 2 and MEA 10 are stacked, the through openings 11a-11c, together with the corresponding through openings of MEA 10 and / or the electrically insulating edge regions of MEA 10', form conduits extending along the stacking direction 7 through the stack 6 (see, for example...). Figure 1(3 and 4). Typically, each line formed by through openings 11a-11c is fluidly connected to one port 5 of the second end plate 4 of system 1. For example, coolant can be introduced into or discharged from the stack 6 via the line formed by through opening 11a. Conversely, the lines formed by through openings 11b, 11c can be designed to supply fuel and reaction gases to the electrochemical cells of the fuel cell stack of system 1 and to discharge reaction products from the stack. Figure 1 Not shown is the electrical connection also arranged on the second end plate 4, through which power-consuming devices can be connected to the fuel cell cell stack 6.

[0045] To seal the through openings 11a-11c relative to the interior of the stack 6, and at least relative to the surrounding environment in the case of through opening 11a, the first partition 2a may in each case have a sealing arrangement in the form of sealing flanges (beaded edges) 12a-12c, which in each case are arranged around the through openings 11a-11c and completely surround the through openings 11a-11c. The back of the bipolar plate 2 Figure 2 On the rear side of the observer, the second partition 2b may have a corresponding sealing convex edge (not shown) for sealing the through openings 11a-11c.

[0046] In region 18, opposite the electrochemically active region of MEA 10, the first partition 2a is typically positioned on its facing side. Figure 2 A flow field 17 is present on the front side of the observer, the flow field having a structure for guiding the reaction medium along the front side of the partition 2a. Figure 2 In this structure, these structures are defined by multiple webs and channels extending between and defined by these webs. In the bipolar plate 2 facing... Figure 2 On the observer's front side, the first partition 2a typically also has a distribution or collection area 20 with a distribution channel 29. This distribution or collection area 20 includes structures designed to distribute and / or collect or aggregate media on the flow field 17, the distributed media being the media introduced into the distribution or collection area 20 from the first of two through openings 11b, and the collected or aggregated media being the media flowing from the flow field 17 to the second through opening 11b. Figure 2 In this configuration, the distribution structure of the distribution or collection region 20 is also defined by webs and channels 29 extending between and defined by the webs. At the transition between the distribution and collection region 20 and the flow field 17, transition regions 21 are located on each side of the flow field 17, each of which is oriented parallel to the flow field 17. Figure 2 9 in the y-direction. In the transition region 21, the medium guiding structure can have a reduced height compared to the adjacent regions 17 and 20 (see Figure 3).

[0047] In the exemplary embodiment shown, each of the first baffles 2a also has an additional sealing arrangement in the form of a peripheral protrusion 12d extending around the flow field 17 opposite the active region 18, and also around the distribution or collection region 20 and the through openings 11b, 11c, sealing these with respect to the through openings 11a, i.e., sealing these with respect to the coolant circuit and with respect to the surrounding environment of system 1. Each of the second baffles 2b includes a corresponding peripheral protrusion. The structure of the flow field 17, the distribution structure of the distribution or collection region 20, and each of the sealing protrusions 12a-12d are formed integrally with the baffles 2a, and are integrally formed in the baffles 2a, for example by a relief process or deep drawing process and / or by means of hydroforming. This also applies to the corresponding structure of the second baffles 2b.

[0048] The conduits passing through the plate stack 6 of system 1 via the two through openings 11b or formed by the through openings 11b typically pass through the passage 13b in the sealing flange 12b, through the distribution structure of the distribution or collection area 20 and the transition area 21, and through the direction towards Figure 2 The flow field 17 of the first partition 2a of the observer is fluidly connected to each other. Similarly, the two through openings 11c or the pipelines formed by the through openings 11c through the plate stack of the system 1 are respectively via corresponding convex edge passages, via corresponding distribution structures, transition regions, and via opposite sides. Figure 2 The observers are fluidly connected to each other through the corresponding flow fields on the outside of the second partition 2b. Conversely, the through-opening 11a or the tubing formed by the through-opening 11a through the plate stack of the system 1 is generally fluidly connected to each other via a cavity 19 enclosed or surrounded by partitions 2a, 2b. In each case, the cavity 19 is used to guide coolant through the bipolar plates 2, particularly to cool the flow field 17 of the bipolar plates 2, and thus indirectly to cool the electrochemically active region 18 of the MEA 10.

[0049] Figure 3 shows a cross-section of the system 1 according to the prior art in the region of the through opening 11b. Specifically, the first end plate 3 and a plurality of bipolar plates 2 including partitions 2a, 2b can be seen here. The bipolar plates 30 adjacent to the end plates 3, 4 are generally referred to as… Terminal bipolar plate or monopolar plate The bipolar plates 2 of the fuel cell cell stack 6, particularly the terminal bipolar plates 30, are typically raised metal components made of stainless steel, with a diameter of 1.6 mm. 10 -5 K -1 The longitudinal coefficient of thermal expansion. Conversely, end plates 3 and 4 are primarily made of plastic, with a coefficient of thermal expansion of, for example, approximately 5.0. 10 -5 K -1The longitudinal coefficient of thermal expansion is much greater between different plastics than between different steel materials. Therefore, the terminal bipolar plate 30 has a lower longitudinal coefficient of thermal expansion than its adjacent end plates 3 and 4 in every case. Thus, for example, when the temperature of the first end plate 3 and the terminal bipolar plate 30 increases or decreases by the same amount, the degree of lateral expansion of the first end plate 3 and the adjacent terminal bipolar plate 30, particularly in the xy plane perpendicular to the stacking axis 7, differs. This different thermal expansion of the terminal bipolar plate 30 and the first end plate 3 results in a relative displacement between the regions of the two plates 3 and 30. This is not an absolute displacement, but rather, from a simplified perspective, an increasingly larger lateral displacement occurs between the regions of the two plates 3 and 30 as the distance of the plate region from the center of gravity of the terminal bipolar plate 30 increases. Furthermore, this displacement is also affected by, for example, different temperature distributions and temperature variations depending on the material thickness. Such temperature changes may be caused by variations in ambient temperature, cold starts of the fuel cell unit system at low ambient temperatures, or increases or decreases in the internal temperature of the fuel cell unit stack 6, for example, as a result of waste heat generated when converting chemical energy into electrical energy. These relative movements may adversely affect the elastomeric seal or coating 28 of system 1, which is disposed between one of the convex edge arrangements 12a-12d of the terminal bipolar plate 30 and the first end plate 3. Furthermore, in practice, it has been found that end plates 3 made of plastic materials respond more slowly to temperature changes than separators made of steel materials, which at least temporarily enhances the difference and relative displacement. Moreover, metal separators are subjected to direct cooling in at least certain areas without providing active cooling or temperature control to the end plates.

[0050] The present invention is conceived to solve or at least mitigate the above-mentioned problems.

[0051] Figure 4 , 5A 5B, 6A, 6B, 7A, 7B, 8, 9, and 10 show various terminal bipolar plates 30 and plate assemblies 50, which can be installed in the electrochemical system 1 or Figure 1 In the stack 6. Each of the illustrated plate assemblies 50 includes an end plate 52 and a first partition 31 and a second partition 32, the first partition being adjacent to the end plate 52 and having a plate plane, and the second partition being adjacent to the first partition 31, these plates together forming a terminal bipolar plate 30 or a monopolar plate 30. Figure 4 , 5A As shown in 5B, 6A, 6B, 7A, 7B, 8, 9, and 10, the second partition 32 has at least one medium-guided second through opening 42 with an edge 43, the second through opening corresponding to... Figure 2 One of the through openings 11a-11c of 3. In other words, the second partition 32 can have the same as... Figure 2The partition 2b shown in Figure 3 has the same through openings 11a-11c.

[0052] The second through opening 42 extends onto the first partition 31, and its orthogonal projection perpendicular to the plane of the partition defines a projection area 40. The first partition 31 has no through opening within the projection area 40 (see [reference]). Figure 4 , 5A 5B, 7A, 7B, 8, 10) or having a first through opening 41 (see Figure 6A , 6B (9), whose area is less than 20% of the area of ​​the second through opening 42, preferably less than 10% or less than 5%.

[0053] The second partition 32 can be designed to be substantially identical to the partition 2b described above. However, unlike the first partition 2a, the first partition 31, at the position where the second partition 32 has the second through opening 42, has no through opening or has a first through opening 41 that is much smaller than the second through opening 42.

[0054] therefore, Figure 4 , 5A The first partition 31 of 5B, 7A, 7B, 8, and 10 is closed in the region of projection area 40, so the plate material of partition 31 is adjacent to the second through opening 42. The advantage of this is that this region is already sealed by the material of the first partition 31. Therefore, no sealing arrangement is required between the first partition 31 and the end plate 52. To ensure that the compressive force along the stacking direction 7 in the stack 6 has a similar magnitude in the region of the terminal bipolar plate 30 as in other regions of the stack 6, a spring element 48 can be provided, which is adjacent to the end plate 52 and supports the first partition 31 against the end plate 52. This spring element 48 can have the same convex edge structure as the convex edge arrangements 12a-12c mentioned above. Furthermore, the second partition includes a sealing element 49, which is configured the same as the convex edge arrangements 12a-12c. Therefore, referring to the above description, the spring element 48 and the sealing element 49 are thus positioned on opposite sides of the terminal bipolar plate 30. Spring element 48 and / or sealing element 49 may additionally have a coating 28 for micro-sealing, such as a screen-printed coating, which can also be applied to the convex edge arrangements 12a-12d and corresponds to the coating 28 shown in FIG. 3. Here, coating 28 may be applied to the top and / or sides of the convex edge arrangements. Thus, spring element 48 and coating 28 together can have the effect that the terminal bipolar plate 30 and end plate 52 are compressed in the same way as the other bipolar plates 2 of the stack 6 are compressed against each other. The resulting very uniform force distribution across the entire stack 6 and across all spring elements and sealing elements 48, 49, 12a-12d is advantageous for the durability of these elements.

[0055] exist Figure 5A, 5B In embodiments 6A, 6B, 7A, and 7B, the first partition 31 has at least one raised structure 44 in the region of the projection area 40. In this case, the raised structure 44 can be formed in the first partition 31 by deep drawing, hydroforming, or convex forming (bore forming) in a manner similar to the raised structures described above. As described below, at least one raised structure 44 can perform various functions and can be designed, for example, as a medium guiding structure 45, a support element 46, or a reinforcing element 47. For clarity, regarding the raised structure 44, Figure 5A The plan view deliberately only shows the section view located in the context of the section. Figure 5B Those lines outside the plane E of the middle plate.

[0056] Figures 5A to 6B The raised structure 44 has a substantially the same circumferential shape as the second through opening 32 and is arranged coaxially with each other. Figure 5A and Figure 5B In the illustrated embodiment, the circumferential shape of the raised structure 44 and the second through opening 32 is annular, and particularly circular. Figure 6A and Figure 6B In the illustrated embodiment, the circumferential shape of the raised structure 44 and the second through opening 32 is trapezoidal. However, other circumferential shapes of the raised structure 44 and the second through opening 32 are also conceivable, such as elliptical, rectangular, square, or free-form shapes.

[0057] exist Figure 5A , 5B In the middle, the internal raised structure 44 is designed as a support element 46, which is designed to support the first partition 31 against the end plate 52. In addition, the external raised structure 44 is designed as a reinforcing element 47, and reinforces the first partition 31 in the region of the projection area 40. Figure 5A , 5B The raised structures 44 point in the same direction and face the end plate 52. From Figure 5B It can also be clearly seen that the first partition 31 has no passage, while in the partition 2a located closest to the terminal bipolar plate 30, the passage 13b is formed on or stamped on both sides of the protrusion 12b.

[0058] exist Figure 6A and 6B The plate assembly 50 may also provide a raised structure 44, wherein both the outer and middle raised structures 44 are designed as reinforcing elements 47. The two raised structures 44 point in different directions and face and turn away from the end plate 52.

[0059] and Figure 5A and 5B The opposite of the embodiments, Figure 6A , 6BThe first partition 31 has a first through opening 41, which is centrally located in the region defined by the projection area 40 of the first partition 31. Other locations besides the central location shown are also conceivable. The first through opening 41 is fluidly connected to an outlet opening 54 formed in the end plate 52.

[0060] exist Figure 6B In this embodiment, the first through opening 41 is designed as a venting opening. In its function as a venting opening, the first through opening 41 can remain open, for example, when the electrochemical system 1 is filled with a cooling fluid or reaction medium, allowing air in the system 1 to escape via the first through opening 41 and the outlet opening 54. After filling, the through opening 41 and / or the outlet opening 54 can be sealed shut by a closure, such as a sealing cap. Ventilation of the system 1, stack 6, or plate assembly 50 can also be performed immediately before commissioning of the stack 6 or system 1. A permanently open configuration of the first through opening 41 and the outlet opening 54 is also conceivable and typically depends on other operating conditions.

[0061] The fluid guiding structure 45 can be arranged annularly around the first through opening 41. This fluid guiding structure can be designed, for example, as a conical protrusion 44, and preferably faces the end plate 52 and the outlet opening 54 of the end plate 52. Due to its orientation and conical shape, the fluid guiding structure 45 guides the fluid along the direction of the outlet opening 54. Figure 6B As shown, the fluid guiding structure 45 can extend into the outlet opening 54. In some embodiments (not shown), the fluid guiding structure 45 even extends through the outlet opening 54. For venting purposes, a valve 60 may optionally be provided, for example at the outlet opening 54, at the first through opening 41, or in the fluid path between the outlet opening and the first through opening 41. For example, Figure 9 Such a valve 60 is shown in the figure.

[0062] and Figure 2 and Figure 5A compared to, Figure 6A The fundamentally different arrangements of the medium-through openings 11a-11c, the associated port protrusions 12a-12c, and the outer peripheral protrusion 12d are shown. For further details, refer to WO 2019 / 229138 A1, the contents of which are fully incorporated herein by reference. Specifically, refer to WO 2019 / 229138 A1... Figure 4 The partition shown is the one of the present application. Figure 6A The partition shown is based on this. However, regardless of this different arrangement, the fundamental problems of different coefficients of thermal expansion between the end plates and the terminal bipolar plates, and the displacement of the sealing lines relative to each other, still exist.

[0063] exist Figure 7A , 7B In the embodiment, a medium guiding structure 45 is also provided, which serves as a raised structure 44 and is integrally formed with the first partition 31.

[0064] Figure 7A , 7B The medium guiding structure 45 and Figure 6A , 6B The medium guiding structure 45 differs in that it faces away from the end plate 52 and extends into or through the second through opening 42. Figure 7A , 7B The medium guiding structure 45 is designed to guide fluid, for example, along the direction of the passages 33, which are formed on one hand between the partitions 31 and 32 and on the convex side wing 34 of the second partition 32. Therefore, for example, hydrogen or other fluids can be conducted into the space formed between the partitions 31 and 32. To emphasize the asymmetrical shape of the projection area 40, in Figure 7A Several circular lines are shown in the middle.

[0065] exist Figure 5A , 5B In 6A, 6B, 7A, and 7B, the fluid guiding structure 45, the support element 46, and the reinforcing element 47 are each designed as a raised structure 44 and are integrally formed with the first partition 31. In alternative embodiments, elements 45, 46, and 47 may also be in the form of independent elements, or may be formed by end plates 52 (e.g., see reference 6A, 6B, 7A, and 7B). Figure 9 (and related descriptions below).

[0066] Instead of using a similar method of protruding edges into the corresponding partitions as convex edges arranged 12a-12c, the spring element 48 and / or sealing element 49 can be alternatively formed of an elastomeric material, such as an O-ring. Such embodiments... Figure 8 and Figure 9 As shown in the diagram, spring element 48 is arranged between and abuts against the first partition 31 and end plate 52. Furthermore, sealing element 49 is arranged on the second partition 32. Spring element 48 and sealing element 49 can be connected to partitions 31 and 32 by means of known methods, such as adhesive bonding.

[0067] In addition to end plate 52 Figure 8 The plate assembly 50 additionally includes at least one outer plate 57, which, together with the end plate 52, forms a terminal plate 58. The end plate 52 is located between the outer plate 57 and the first partition 31 and primarily serves an insulating function, while the outer plate 57 is primarily configured for compressing the stack 6. Although the configuration with the outer plate 57 and the terminal plate 58 is only... Figure 8 As shown, but it can also be set in... Figure 5B ,6B In the embodiments of 7B, 9, and 10.

[0068] Apart from Figure 8 In addition to the 50 board components, Figure 9 The plate assembly 50 also includes at least one elastomeric support element 56 or a single elastomeric annular support element 56, which is arranged between the end plate 52 and the first partition 31. A fluid line 55 formed by the end plate 52 is also provided, which is fluidly connected to a first through opening 41 in the first partition 31. The fluid line 55 may also advantageously have a supporting function. An exhaust valve 60 is arranged in the fluid line 55. Alternatively, the fluid line 55 may be in the form of a separate element and may be arranged between the first partition 31 and the end plate 52.

[0069] on the contrary, Figure 10 The plate assembly 50 is shown, which includes only the end plate 52 and does not have the multi-part terminal plate 58. In this case, the end plate 52 directly abuts against the terminal bipolar plate 30, so no spring element 48 is arranged between the terminal bipolar plate 30 and the end plate 52.

[0070] exist Figure 4 , 5A In the plate assembly 50 shown in 5B, 6A, 6B, 7A, 7B, 8, 9, and 10, the plate body of the end plate 52 may be at least partially or primarily made of plastic, such as a polymer material. Furthermore, the plate bodies of the first partition 31 and the second partition 32 are typically each made of a metallic material, wherein the latter may be coated at least in certain areas.

[0071] It should be pointed out that, Figure 4 , 5A The embodiments 5B, 6A, 6B, 7A, 7B, 8, 9, and 10 can be combined with each other, particularly since the second partition 32 typically has six, or four second through openings 11a-11c in systems without cooling, see also Figure 1 Subsequently, there are also six projection areas 40 on the first partition 31. Therefore, the first partition 31 may not have a through opening in at least one of the projection areas 40. In addition, the first partition 31 may have a first through opening 41 in at least one of the remaining projection areas 40, the area of ​​which is smaller than 20% of the area of ​​the corresponding second through opening 42.

[0072] Except for the area and features of the first partition 31 inside the projection area 40 (e.g., the first through opening 41, the raised structure 44, the medium guiding structure 45, the support element 46, and the reinforcing element 47), the first partition 31 can be the same as the individual plate 2a. Figure 4 , 5BEnd plates 52 shown in 7B, 8, and 10 can be designed to be substantially the same as the first end plate 3 described above, while Figure 6B and 9 The end plate additionally includes an outlet opening 54 and a fluid line 55. The second partition 32 and the individual plate 2b preferably have the same design.

[0073] List of reference numerals in the attached diagram: 1. Electrochemical System 2 partitions 2' partition 2a Individual board 2b Separate board 3 First end plate 4 Second end plate 5. Media Port 6 stacking 7 z direction 8 x directions 9 y direction 10 Membrane Electrode Assembly 10' MEA reinforced edge 11a-d Through opening 12a-d Convex edge arrangement 13a-c pathway 14 Membrane 15. Edge section 15a Thin film layer 15b thin film layer 16 Gas diffusion layer 17 Flow Field 18 Electrochemically Active Regions 19 cavities 20. Allocation and / or collection areas 21 Transition Zone 28 Coating 29. Allocation Channel 30. Terminal bipolar or monopolar plates 31 First partition 32 Second partition 33 access 34 Convex side wings 40 Projection Area 41 First through opening 42 Second through opening 43. Edge of the second through opening 44. Raised / Underlined Structure 45. Medium-guided structure 46 Support elements 47 Reinforcing Components 48 Spring elements 49 Sealing elements 50-board assembly 52 end plate 54. Exit opening 55 Fluid Piping 56 Support elements 57 outer panel 58. Terminal board.

Claims

1. A plate assembly (50) for an electrochemical system (1), comprising: End plate (52). A first partition (31) is adjacent to the end plate (52) and has a plate plane. The first partition has a flow field with a structure for guiding the reaction medium along the front side of the first partition. A second partition (32) is adjacent to the first partition (31) and has a flow field with a structure for guiding the reaction medium. The second partition (32) has at least one second through opening (42) for medium guidance. The first and second partitions enclose a cavity for guiding the coolant. Wherein, the second through opening (42) to the first partition plate (31) and the orthogonal projection perpendicular to the plane of the plate define a projection area (40), wherein the first partition plate (31) is in the region of the projection area (40). There is no through opening, or It has a first through opening (41), the area of ​​which is 20% smaller than the area of ​​the second through opening (42).

2. The board assembly (50) according to claim 1, characterized in that, The plate body of the end plate (52) is at least partially made of polymer material, and the plate bodies of the first partition (31) and the second partition (32) are respectively made of metal material.

3. The board assembly (50) according to claim 1, characterized in that, The plate body of the end plate (52) is mainly made of polymer material, while the plate bodies of the first partition (31) and the second partition (32) are respectively made of metal material.

4. The board assembly (50) according to claim 1, characterized in that, The first partition (31) has at least one raised structure (44) in the projection area (40).

5. The board assembly (50) according to claim 1, characterized in that, At least one medium guiding structure (45) is arranged in the projection area (40).

6. The plate assembly (50) according to claim 5, characterized in that, The medium guiding structure (45) extends into or through the second through opening (42).

7. The plate assembly (50) according to claim 1, characterized in that, It includes at least one support element (46) for supporting the first partition (31) against the end plate (52), the support element (46) being arranged in the projection area (40).

8. The plate assembly (50) according to claim 7, characterized in that, The support element (46) is integrally formed with the first partition (31) or the end plate (52).

9. The plate assembly (50) according to claim 7, characterized in that, The support element (46) is a separate element that is not integrally formed with the first partition (31) or the end plate (52).

10. The plate assembly (50) according to claim 1, characterized in that, The first through opening (41) is designed as a ventilation opening.

11. The plate assembly (50) according to claim 10, characterized in that, The projection area has a first through opening, and the end plate (52) has an outlet opening (54) which is fluidly connected to the first through opening (41).

12. The plate assembly (50) according to claim 1, characterized in that, The first partition (31) and the second partition (32) are connected to each other by means of material bonding.

13. The plate assembly (50) according to claim 12, characterized in that, The first partition (31) and the second partition (32) are connected to each other by means of a welded joint.

14. The plate assembly (50) according to claim 12, characterized in that, The first partition (31) and the second partition (32) are connected to each other by means of laser welding joints or brazing joints.

15. The plate assembly (50) according to claim 1, characterized in that, The second partition (32) has a second sealing element (49) surrounding the second through opening (42), while the first partition (31) has a first spring element (48) surrounding the projection area (40) of the second through opening (42) on the first partition (31).

16. An electrochemical system (1) comprising a plate assembly (50) according to any one of claims 1-15 and a second end plate (4), the second end plate (4) having a plurality of medium ports (5), wherein the medium ports (5) of the second end plate (4) are fluidly connected to a second through opening (42) of a second partition (32), the first partition (31) and the second partition (32) being arranged between the two end plates (52; 4).

17. A terminal bipolar plate (30) for an electrochemical system (1), comprising: A first partition (31) has a plate plane and a flow field, the flow field having a structure for guiding the reaction medium along the front side of the first partition. A second partition (32) is adjacent to the first partition (31), the second partition having a flow field having a structure for guiding the reaction medium, and the second partition (32) having at least one second through opening (42) for medium guidance. The first and second partitions enclose a cavity for guiding the coolant. Wherein, the second through opening (42) to the first partition plate (31) and the orthogonal projection perpendicular to the plane of the plate define a projection area (40), wherein the first partition plate (31) is in the region of the projection area (40). There is no through opening, or It has a first through opening (41), the area of ​​which is 20% smaller than the area of ​​the second through opening (42).

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