Bipolar plate, bipolar plate system, end plate and fuel cell

Abstract

A bipolar plate (210) for a fuel cell (1), wherein the bipolar plate (210) extends in a width direction (B) and a longitudinal direction (L), the longitudinal direction (L) and the width direction (B) being particularly perpendicular to each other, the bipolar plate (210) has a plurality of openings (240), the openings (240) having an outer contour, the outer contour of the openings (240) being formed in each case by a mounting opening (242) and at least one flow opening (244), the mounting openings (242) forming a circular segment-shaped portion of the outer contour of the openings (240), and the mounting openings (242) being designed to accommodate fasteners (9).

Description

[Technical Field]

[0001] The present invention relates to a bipolar plate, a bipolar plate system, an end plate and / or a fuel cell.

[0002] Fuel cells are already known from the state of the art. They are used to generate an electric current or to supply energy, in particular by a reaction that releases electrons. Various fluids can be used as fuel, for example hydrogen. However, a problem with known systems is that a fuel cell consists of several cells separated from each other by bipolar plates. To achieve a compact design, these cells are usually arranged in a stack and covered at the ends by end plates. The cells are usually fixed to each other and to the end plates using external fasteners. However, this exposes the bipolar plates and end plates to high bending stresses and / or results in high installation space requirements.

[0003] It is therefore an object of the present invention to provide a space-saving arrangement that allows the components of a fuel cell to be securely fixed.

[0004] This problem is solved by a bipolar plate according to claim 1, a bipolar plate system according to claim 4, an end plate according to claim 8 and a fuel cell according to claim 10. Further advantages, features and embodiments are shown in the dependent claims, the embodiments and the figures.

[0005] The present invention relates to a bipolar plate. The bipolar plate forms or can be used to form part of a fuel cell. The bipolar plate extends in a width direction and a longitudinal direction, the longitudinal direction and the width direction being particularly perpendicular to each other. The bipolar plate has a plurality of openings, the openings having an outer contour, the outer contour of the openings in each case being formed by a mounting opening and at least one flow opening, the mounting opening forming a circular segment-shaped portion of the outer contour of the opening, and the mounting opening is designed to hold a fastener or connector. The bipolar plate can be part of and / or arranged or used in a fuel cell. In particular, an MEA is arranged between two bipolar plates. The MEA is a membrane electrode assembly within the meaning of the present invention. Therefore, to limit the suction volume of the MEA, the bipolar plate functions to at least partially simultaneously supply fuel, in particular hydrogen, and / or oxygen and / or combustion products, in particular fluids such as water or water vapor, from and / or to the MEA. Furthermore, the bipolar plate can be used in particular to conduct electrons. In particular, the bipolar plates are made at least partially of a conductive material and / or plastic and / or at least partially of an insulating material. The bipolar plates can therefore form part of a stack or "bag" of a fuel cell. The bipolar plates extend in particular in a width direction and a longitudinal direction. The longitudinal direction is in particular the direction in which the bipolar plate has its largest main dimension. The width direction, on the other hand, can in particular be the direction in which the width of the bipolar plate is measured. The direction perpendicular to the length and / or width direction is the height direction. In particular, the height direction can be the direction in which the material thickness of the bipolar plate is measured. It is particularly advantageous for the length and width directions to be perpendicular to one another. The length, width, and height directions can also be perpendicular to one another. In other words, the length, width, and height directions can form a rectangular coordinate system. The bipolar plates have a number of openings. These openings pass completely through the bipolar plate, and the main direction of the openings is in particular the height direction. In other words, the openings extend vertically through the bipolar plate.This allows for the guiding of joints, in particular fasteners and / or connectors, and / or fluids through the bipolar plate. In other words, the openings can therefore function to allow fluids to flow from one side of the bipolar plate to the other side of the bipolar plate and at the same time provide space for accommodating fasteners or clamps. The flow openings of the openings are particularly intended to guide fluids. The openings themselves are formed by one component, which is the flow opening, and by at least one other component, called the mounting opening. The mounting openings function to accommodate fasteners or connectors, which can also be clamps or connectors that allow clamping of the bipolar plate and / or stacking of fuel cells. In other words, the openings can therefore be formed by a combination of a mounting opening and at least one flow opening. The bipolar plate is advantageously provided with a number of openings, each having at least one flow opening and one mounting opening. The openings are arranged or designed so that they form an outer contour in the bipolar plate. The outer contour is the outer edge of the opening, in particular in the vertical direction, in particular on the surface adjacent to the bipolar plate. The outer contour of the opening or openings is formed at least in part by the flow opening and at least in part by the mounting opening. In other words, the edge of the opening is formed at least in part by the mounting opening and at least in part by the flow opening. In particular, the mounting opening forms a circular segment-shaped portion of the outer contour of the opening. In other words, at least a part of the outer opening is therefore also formed by the circular portion that defines the mounting opening. Alternatively, the opening may have a portion in the shape of a semicircular segment formed by the mounting opening. This makes it possible to achieve a particularly low fatigue notch coefficient and a compact design of the mounting opening that is suitable for production, in particular for fasteners or connectors, in particular fasteners and / or connectors in the form of screws. A screw in the sense of the present invention may in particular be a fastener and / or connector having an operating head and / or an operating portion, and further having an external and / or internal thread, in particular in the shank portion.

[0006] In a preferred embodiment, the bipolar plate has a flow region, which in particular subsequently / later serves to define a fluid volume, which is or can be fluidly connected with at least two openings. The flow region is in particular a region or outer surface or a surface of the bipolar plate in the vertical direction, which is or can be fluidly connected later with an MEA. The flow region can therefore form or include a surface on the bipolar plate. Advantageously, the bipolar plate has both a flow region formed by adjacent surfaces in the positive height direction and a flow region formed by adjacent surfaces in the negative height direction. In particular, the fluid region is used to limit a fluid volume that will later communicate with the MEA and / or to at least partially provide a volume in which the MEA will be located. The fluid region is therefore adjacent to a fluid volume that is or can be fluidly connected with at least two openings in the bipolar plate. This is particularly important if a sealing element is or will be subsequently placed on the bipolar plate, allowing fluid to flow from an opening to a fluid region and from a fluid region to another opening. In this way, a fluid inlet, in particular an opening in fluid communication with a fluid region or fluid volume, can be used to achieve fluid inflow and outflow into the fluid volume.

[0007] Advantageously, the mounting openings and the flow openings or apertures of the openings pass through the bipolar plate, which makes it particularly easy to supply flow fluid to the fasteners and / or connectors through the bipolar plate.

[0008] Advantageously, the flow opening is designed such that it extends from the mounting opening to the fluid field in a plane spanned by the longitudinal and width directions. In this way, a particularly favorable fluid design of the flow opening can be achieved.

[0009] Advantageously, the circular segment-shaped portion of the mounting opening forms at least 51%, preferably at least 65%, and particularly preferably at least 75% of a circle. In other words, the circular segment-shaped portion may form at least 51%, preferably at least 65%, and particularly preferably at least 75% of a complete circle. A design in which at least 51% is formed by the circular segment-shaped portion of the mounting opening may ensure the position of the fastener / connector accommodated in the circular segment-shaped portion or the mounting opening. In other words, such a design may ensure, or at least provide in an emergency, secure locking of the fastener / connector in the mounting opening, so that slippage of the bipolar plate relative to the fastener / connector, especially in the longitudinal and lateral planes, is prevented or prevented by the secure locking. To further improve this secure locking, the circular segment-shaped portion should form at least 65%, preferably at least 75%, of a complete circle. This allows for a further improvement in the secure locking between the bipolar plate and the fastener / connector to achieve better positional accuracy. This type of positive locking of the bipolar plates to the fasteners / connectors makes installation particularly easy, as it in particular allows individual bipolar plates to be screwed onto the fasteners / connectors at a later stage, thus simplifying mounting.

[0010] Preferably, however, the circular segment-shaped portion of the mounting opening forms a maximum of 98%, preferably a maximum of 90%, and particularly preferably a maximum of 80% of the circle. The portion missing to form a complete circle belongs specifically to the flow opening. In other words, such a design can ensure that there is enough space for the flow opening in the opening so that a sufficient flow area or flow options are provided.

[0011] Preferably, the bipolar plate has flow grooves, especially in one flow region of the bipolar plate, especially flow grooves that end and / or start at an opening. In other words, the bipolar plate may have grooves that can support and / or achieve a fluid flow, especially in the surface that defines the bipolar plate in the height direction. These grooves are especially called flow grooves. Advantageously, these flow grooves extend along the bipolar plate or are arranged on the bipolar plate so that they end and / or start at an opening, especially a flow opening. In other words, the grooves extend into the flow opening or openings. This makes it possible to achieve a particularly favorable fluid connection of the flow grooves. By providing flow grooves, a blockage and a uniform supply of fluid to the MEA can be achieved.

[0012] In preferred embodiments, the flow grooves are formed by straight and rectangular sections and / or the flow grooves are serpentine. By using only straight and / or rectangular or right-angled sections and / or serpentine designs, the flow grooves have a particularly large extension. This allows for a particularly effective and uniform fluid supply and / or drainage to and / or from the MEA into the flow grooves. Due to the serpentine design of the flow grooves, a particularly long flow length of the grooves can also be achieved, and therefore a particularly uniform fluid supply or drainage to and / or from the MEA is achieved.

[0013] Advantageously, the portion of the outer contour of the opening formed by the flow opening is further away from the center of gravity of the opening or the center of the circular segment-shaped portion than the portion of the outer contour of the opening formed by the mounting opening. In other words, the flow opening may extend away from the otherwise circular mounting opening, like an extension. Alternatively or even more preferably, the mounting opening forms all of the circular segment-shaped portion of the opening and / or is formed only by circular segment-shaped portions, in particular all having the same center point. These types of designs of the opening, some of the openings, a majority of the openings and / or all of the openings may create particularly good fluid path options. The center of the circular segment-shaped portion is in particular the point from which the radius of the circular segment-shaped portion is determined or the point that is the same distance from all points of the circular segment-shaped portion.

[0014] Preferably, the bipolar plate has a width-to-length ratio of 1 to 3 or less, and the bipolar plate has an opening, in particular a plurality of openings, in its central region in the longitudinal direction. In other words, the ratio of the bipolar plate's dimension in the width direction to its dimension in the length direction can be 1 to 3 or less. If such a ratio exists, the opening, in particular a plurality of openings, can be provided in the central region in the longitudinal direction. The central region in the longitudinal direction is in particular a region of the bipolar plate in the longitudinal direction extending from the ideal center point in the longitudinal direction by + / - 25%, preferably + / - 15%, particularly preferably + / - 10%, and most preferably + / - 5% of the maximum length of the bipolar plate in the longitudinal direction. The center of the bipolar plate is in particular the volumetric center or center of gravity of the bipolar plate. The arrangement of the openings, in particular the arrangement of a plurality of openings as also described above and below, in the central region makes it possible to achieve particularly good reinforcement of the bipolar plate. In particular, bending moments due to the reinforcement can be avoided or reduced by the arrangement of openings in the central region, all of which are advantageously designed as described above and below, in particular so that the openings thus comprise mounting openings and flow openings, and fasteners / connectors are or can be guided in particular through the flow openings.

[0015] A further aspect of the invention may relate to the use of a bipolar plate in / for a fuel cell.

[0016] A further aspect of the present invention may relate to a bipolar plate system. In particular, the bipolar plate system comprises a bipolar plate as described above and / or below, and a sealing element, in particular a sealing ring. It is advantageous if the sealing element is arranged relative to the bipolar plate, so that the sealing element follows or can follow, at least in part, a circular segment-shaped portion of the outer contour of the opening. The bipolar plate system therefore comprises at least one sealing element, which may in particular be designed as a sealing ring. The sealing ring is a self-contained sealing element. In other words, the sealing ring is therefore a sealing element without ends. In particular, the sealing element contacts the bipolar plate. This can in particular be achieved by direct contact between the sealing element and the bipolar plate. Ideally, this contact or contact area between the sealing element and the bipolar plate forms a closed contour. In other words, the sealing element can therefore always be in contact with the bipolar plate along its length. Advantageously, the sealing element follows, at least in part, a circular segment-shaped portion of the outer contour of the opening. The following should be understood to mean in particular that the projections of the sealing element and the projections of the outer contour in the plane spanned by the longitudinal and transverse directions overlap, that the course and the outer contour of the sealing element are the same at least in the following regions and / or that the sealing element abuts at least in part against the circular segment-shaped part of the outer contour.Since the sealing element follows the outer contour of the opening in the circular segment-shaped part, it is possible to achieve a particularly short length of the sealing element and also a strong sealing effect.

[0017] In an advantageous embodiment, the sealing element follows at least 40%, preferably at least 60%, particularly preferably at least 80%, particularly preferably at least 90%, and most preferably at least 97% of the circular segment-shaped portion of the outer contour of the opening. Alternatively or even more preferably, the sealing element follows at least 40%, preferably at least 60%, particularly preferably at least 80%, particularly preferably at least 90%, and most preferably at least 97% of the outer contour of the opening. By following at least 40% of the circular segment-shaped portion and / or the entire outer contour of the opening, particularly simple installation can be achieved. However, a particularly good sealing effect can be achieved if at least 60% or at least 80% of the circular segment-shaped portion of the outer contour and / or the entire outer contour of the opening is followed by the sealing element. However, if 90% of the outer contour or circular portion is followed by the sealing element, this can provide particularly good mechanical support around the periphery of the opening. This capability is particularly noteworthy when the bipolar plate is reinforced by fasteners / connectors guided through the openings, since contact or tension forces can be safely dissipated directly via the sealing element.Following the circular segment-shaped portion of the outer contour of the opening or the outer contour of the opening by at least X percent should be understood to mean in particular that at least X percent of the projections of the outer contour of the circular segment-shaped portion or of the entire outer contour in the plane spanned by the longitudinal and width directions overlap with the projections of the sealing element in this plane, and / or that the sealing element abuts at least X percent of the circular segment-shaped portion of the outer contour or the outer contour.

[0018] Advantageously, a sealing element projects into the or one opening and / or into at least two openings. In particular, only openings having a mounting opening and a flow opening and / or through which a fastener / connector is guided and / or which function or are designed to accommodate a fastener are relevant. By projecting inward, in particular, a seal is arranged between the fastener / connector and the edge of the opening, preventing a connection between the fastener / connector and the opening. In other words, the sealing element can thus be used to create an electronic insulation between the fastener / connector and the bipolar plate.

[0019] Advantageously, the sealing element is made of an especially insulating material.

[0020] Advantageously, the bipolar plate system comprises a plurality of sealing elements, the sealing elements at least partially following the course of the outer contour of at least one opening and / or each opening being surrounded by the outer contour of the sealing element. This is particularly relevant for openings having mounting and flow openings and / or designed to accommodate fasteners / connectors. The use of a design in which the openings and / or at least one of the openings is surrounded by the outer contour of the sealing element means that the opening can be used to guide fluid into and / or out of a fluid volume. Surrounding an opening by the outer contour of the sealing element means that the outer contour of the protrusion of the sealing element or the outer edge of this contour surrounds and / or includes the outer contour of the opening, in particular in a protrusion in the plane formed by the longitudinal direction and the width direction surrounding the sealing element and the opening.

[0021] Preferably, the sealing elements are fixed to the bipolar plates in a particularly material-bonded and / or irreversible manner and / or the sealing elements are formed by a screen printing process. The advantage of using a screen printing process is the cost-effective production of bipolar plate systems, particularly those with sealing elements. By fixing the sealing elements to the bipolar plates, the bipolar plate system can be easily installed. To achieve this fixing, a material bond is used, for example, by gluing and / or screen printing. Advantageously, the sealing elements are fixed to the bipolar plates irreversibly, such that the connection between the sealing elements and the bipolar plates can only be achieved by breaking the connection. This allows a particularly high sealing effect to be achieved.

[0022] Advantageously, the sealing elements are arranged on the bipolar plate so that they form a closed contour on the bipolar plate, and at least two flow openings, in particular different openings, and / or flow fields of the bipolar plate are advantageously arranged within the closed contour. By providing a closed contour of the sealing elements on the bipolar plate, a particularly strong sealing effect can be achieved. The arrangement of at least two flow openings within a closed contour allows particularly good supply and discharge of fluid into the sealed region. In particular, the flow region of the bipolar plate and / or at least the contours of the outlets or flow openings (in particular at different openings) are also arranged within this closed region or within a closed contour. This allows particularly uniform or targeted supply and discharge of fluid into the flow field of the bipolar plate.

[0023] In a preferred embodiment, the bipolar plate system includes fasteners / connectors, which are guided through openings, in particular mounting openings, and which contact the sealing elements. The contact between the sealing elements and the fasteners / connectors can provide insulation between the fasteners / connectors and the bipolar plate. By guiding the fasteners / connectors through openings, in particular mounting openings, a simple and space-saving method of reinforcing and mounting the bipolar plate can be achieved. Advantageously, the fasteners / connectors have an actuation area, in particular a head, and a mounting area, which forms a thread. Advantageously, the mounting area is formed in and / or around the shank area of the fasteners / connectors. The fasteners / connectors extend in a vertical direction, in other words, the main direction of extension of the fasteners / connectors is therefore advantageously parallel to the height direction. The fasteners / connectors are particularly preferably guided through respective openings in the bipolar plate, which have mounting openings and flow openings. This allows a particularly uniform reinforcement of the bipolar plate to be achieved.

[0024] In a preferred embodiment, the fastener / connector has a flow channel extending in one height direction or along said height direction, the fluid channel being fluidly connected to a flow opening that also forms an opening through which the fastener / connector is guided. For example, the fastener / connector can be a banjo, whereby the flow channel can be formed in the banjo. Alternatively and preferably, the flow channel can also be formed externally in the fastener / connector, for example by an external groove. The fluid channel extends in a particular vertical direction. In other words, the flow channel can thus provide a fluid transport capacity in the vertical direction. This flow channel of the fastener / connector is fluidly connected in particular with the flow opening, so that the fluid can flow from the flow channel to the flow opening. This can provide a particularly effective flow option.

[0025] Alternatively or in a further preferred embodiment, the bipolar plate system comprises a plurality of fasteners / connectors, each of which is guided through an opening, which in particular comprises a mounting opening and / or a flow opening, which allows a particularly uniform tension distribution to be achieved and ultimately a particularly high sealing effect to be achieved, while at the same time saving valuable installation space.

[0026] Another aspect of the invention may relate to the use of fasteners / connectors in / for bipolar plate systems and / or fuel cells.

[0027] Another aspect of the present invention may relate to an end plate for a fuel cell, the end plate extending in a longitudinal direction and a width direction, the end plate having two mounting areas, particularly spaced apart from each other in the longitudinal direction, and the bending stiffness of the end plate between the mounting areas being variable, advantageously decreasing in the direction toward the mounting areas. In particular, the end plate extending in a longitudinal direction and a width direction, the longitudinal direction of the end plate may correspond to the longitudinal direction described above and below, and / or the width direction may correspond to the width direction described above and below. The longitudinal direction of the end plate is particularly the direction along which the end plate has its largest main dimension and / or along which the length of the end plate is determined. Meanwhile, the width direction is particularly the direction along which the width of the end plate is determined and / or along which the end plate has its second largest main dimension. The longitudinal direction and the width direction may be perpendicular to the height direction, particularly the height direction being parallel and / or coincident with the height direction already described above and below. The end plate is used in particular in a fuel cell arrangement, particularly in a vertical direction, to form one end of the fuel cell. To mount the end plate, it has two mounting areas spaced apart from each other. The mounting areas are areas that function, in particular, to provide force transmission to the end plate. Advantageously, the end plate has a region with variable bending stiffness between these two mounting areas. In particular, this region with variable bending stiffness extends so that it includes and / or forms a central region in the longitudinal direction of the end plate. The central region of the end plate is similarly determined as the central region of the bipolar plate. Advantageously, the bending stiffness of the region located between the mounting areas is designed so that its bending stiffness decreases in the direction of the mounting areas. Thus, the bending stiffness is greatest, in particular in the region farthest longitudinally from the mounting areas. Essentially, the end plate may also be referred to as a head plate for the purposes of the present invention.

[0028] In an advantageous embodiment, the end plates have curved reinforcing ribs, which extend particularly parallel to the longitudinal direction. Advantageously, these curved reinforcing ribs have a variable height in the longitudinal direction. The curved reinforcing ribs are designed such that they have their largest major dimension parallel to the longitudinal direction in order to provide particularly good bending stress absorption.

[0029] The end plates, in particular the mounting areas of the end plates, have fastening openings. Particularly preferably, fasteners / connectors extend through these fastening openings, which fasteners / connectors may also extend through openings in particular or in some bipolar plates.

[0030] A further aspect of the invention may relate to the use of end plates in / for fuel cells.

[0031] A further aspect of the present invention may relate to a fuel cell. Advantageously, the fuel cell comprises at least one bipolar plate, preferably a plurality of bipolar plates, in particular as described above and / or below. Alternatively or more preferably, the fuel cell may also relate to a bipolar plate system, preferably a plurality of bipolar plate systems, and / or a bipolar plate system comprising a plurality of bipolar plates and / or fasteners / connectors and / or sealing elements, in particular as described above and / or below. Furthermore, alternatively or more preferably, the fuel cell may also have at least one end plate or two end plates, in particular as described above and / or below.

[0032] In a preferred embodiment of the fuel cell, a cavity is formed between and / or in two bipolar plates, said cavity being partially bordered by a flow field of one or both bipolar plates, and fluid can enter or leave the cavity through one of the openings, in particular through a flow opening of a bipolar plate. In other words, a flow field of a bipolar plate can thus be in fluid communication with a flow opening of one opening and with a flow opening of another opening. This provides a particularly effective and simple way of bringing fluid into contact with the flow field through the flow opening.

[0033] In a preferred further development, an MEA is arranged in the cavity. The MEA is a membrane electrode assembly. This allows a particularly compact design of the fuel cell to be achieved. [Brief explanation of the drawings]

[0034] Further advantages and features of the present invention are set forth in the following description with reference to the drawings. Individual features of the illustrated embodiments can also be used in other embodiments, unless expressly excluded. The figure includes: [Figure 1] Figure 1: Bipolar plate; [Figure 2] Figure 2: Bipolar plate system and / or bipolar plate; [Figure 3] Figure 3: Selective design diagram of bipolar plate; [Figure 4] Figure 4: Bipolar plate system with bipolar plates and fasteners; [Figure 5] FIG. 5: Fuel cell with end plates and multiple bipolar plates and bipolar plate systems; and [Figure 6] Figure 6. Isometric view of the end plate.

[0035] FIG. 1 shows an isometric view of a bipolar plate 210. The bipolar plate 210 has a plurality of openings 240 extending in a height direction H. The openings 240 each include a mounting opening 242 and a flow opening 244. The mounting openings 242 each have a circular segment-shaped portion and / or form a circular segment-shaped portion of the outer contour of the opening 240. The mounting openings 242 are designed to accommodate fasteners or connectors. The bipolar plate has a width-to-length ratio of 1 to 3 or less, and the plurality of openings 240 are arranged in the bipolar plate 210 in a central region in the longitudinal direction L. This allows for particularly uniform distribution of stress across the bipolar plate 210.

[0036] FIG. 2 shows an isometric view of bipolar plates 210 arranged one above the other in the height direction H. A sealing element 310 is arranged between each bipolar plate 210. In other words, FIG. 2 shows a bipolar plate system 300. As seen from the highest bipolar plate 210 in the height direction H, multiple sealing elements 310 are fixed to it. These sealing elements 310 each surround an opening 240. Each opening 240 includes at least one mounting opening 242 and one flow opening 244. The sealing elements 310 follow at least 60% of the circular segment-shaped portion of the outer contour of each opening 240. The circular segment-shaped portion of the mounting opening 242 forms at least 65% of the circle of each opening 240. The flow openings 244 are formed so that they face toward the flow field 252. The flow field 252 is also surrounded by the sealing elements 310. Each sealing element 310 protrudes at least partially into the opening 240 or into both openings 240, i.e., at least partially into the mounting opening 242. This may create a particularly good insulation option for a fastener 9 that may be received in the mounting opening 244, as shown in FIG.

[0037] 3 shows a diagram of a bipolar plate 210 having six openings 240 extending in a height direction H. A width direction B and a length direction L are perpendicular to the height direction H. Flow grooves 250 leading through a flow region 252 extend from the opening 240 located at the lower left to the opening 240 located at the upper right. The flow grooves 250 are arranged in a serpentine pattern.

[0038] The flow region 252 is surrounded by a sealing element 310 , which also surrounds the two openings 240 .

[0039] 4 shows a bipolar plate system 300. The bipolar plate system 300 includes a plurality of sealing elements 310, a plurality of bipolar plates 210, and fasteners 9. The fasteners 9, which may also be called connectors, extend in a height direction H. As can be seen in FIG. 4, the plurality of sealing elements 310 contact the bipolar plates 210 and the fasteners 9. The fasteners 9 are designed such that they have flow channels extending in the height direction H, which are fluidly connected to the flow openings 244 of each opening 240. This allows for particularly good and advantageous flow supply and / or discharge through the fasteners 9.

[0040] 5 shows a fuel cell 1 including a plurality of fasteners 9, which may also be called connectors, and a plurality of bipolar plates 210 and / or bipolar plate systems 300. The fuel cell 1 is at least partially limited in height direction H by end plates 500.

[0041] 6 shows an end plate 500. The end plate 500 extends in a longitudinal direction L and a width direction B, and has mounting regions 502 spaced apart from one another in the longitudinal direction L, with fastening openings 510 disposed in the mounting regions 502. The mounting regions 502 are arranged such that they each have at least three fastening openings 510. Between the mounting regions 502, particularly as viewed in the longitudinal direction L, the end plate 500 has a variable bending stiffness that decreases in the direction toward the mounting regions 502. This variable bending stiffness can be achieved by stiffening ribs 520 extending parallel to the longitudinal direction L.

[0042] List of reference numbers: 1 - fuel cell 9 - Fasteners or connectors 210 - Bipolar Plate 240 - aperture 242 - Mounting opening 244 - Flow opening 250 - Flow groove 252 - Flow Region 300-Bipolar Plate System 310 - Sealing element 500 - End Plate 502 - Wearing Area 510 - fixed aperture 520 - Reinforcement rib B - Width direction L - Longitudinal H - Height

Claims

1. A bipolar plate (210) for a fuel cell (1), comprising: The bipolar plate (210) extends in a longitudinal direction (L) and a width direction (B), The longitudinal direction (L) and the width direction (B) are particularly perpendicular to each other, The bipolar plate (210) has a plurality of openings (240); the opening (240) has an outer contour; the outer contours of the openings (240) are each defined by a mounting opening (242) and at least one flow opening (244); the mounting opening (242) forms a circular segment-shaped portion of the outer contour of the opening (240); and The mounting opening (242) is designed to accommodate a fastener (9), A bipolar plate (210) for a fuel cell (1).

2. the circular segment-shaped portion of the mounting opening (242) forms at least 51%, preferably at least 65% and particularly preferably at least 75% of a circle; The bipolar plate (210) of claim 1.

3. the circular segment-shaped portion of the mounting opening (242) forms a maximum of 98%, preferably a maximum of 90%, and particularly preferably a maximum of 80% of a circle; The bipolar plate (210) of claim 1 or 2.

4. The bipolar plate (210) has flow grooves (250), particularly in the fluid region (252) of the bipolar plate (210), the flow grooves (250) end and / or start, in particular at the openings (240); The bipolar plate (210) according to any one of claims 1 to 3.

5. the flow grooves (250) are formed by straight and rectangular sections; and / or the flow grooves (250) describe a serpentine pattern; A bipolar plate (210) according to any one of claims 1 to 4, in particular claim 5.

6. A bipolar plate system (300) comprising a bipolar plate (210) according to any one of claims 1 to 5 and a sealing element (310), in particular a sealing ring, The sealing element (310) is placed against the bipolar plate (210), the sealing element (310) at least partially follows the circular segment-shaped portion of the outer contour of the opening (240); Bipolar plate system (300).

7. The sealing element (310) protrudes into the opening (240) or into at least two of the openings (240). The bipolar plate system (300) of claim 6.

8. The bipolar plate system (300) has a plurality of the sealing elements (310), the sealing element (310) at least partially follows the course of the outer contour of the opening (240); and / or Each opening (240) is surrounded by the outer contour of said sealing element (310); A bipolar plate system (300) according to claim 6 or 7.

9. the sealing element (310) is fixed to the bipolar plate (210), in particular in a materially bonded and / or irreversibly manner, and / or The sealing element (310) is manufactured by a screen printing process or a mold-in-place process. A bipolar plate system (300) according to any one of claims 6 to 8.

10. The sealing element (310) is disposed on the bipolar plate (210) such that the sealing element (310) forms a self-contained contour on the bipolar plate (210); In particular, the different openings (240), preferably at least two flow openings (244), and / or the fluid fields (252) of said bipolar plate (210) are arranged within a closed contour, A bipolar plate system (300) according to any one of claims 6 to 9.

11. Use of a bipolar plate (210) according to any one of claims 1 to 5 and / or a bipolar plate system (300) according to any one of claims 6 to 10 in / for a fuel cell (1).

12. An end plate (500) for a fuel cell (1), comprising: The end plate (500) extends in a longitudinal direction (L) and a width direction (B), the end plate (500) has two mounting areas (502) spaced apart from each other, in particular in the longitudinal direction (L), the bending stiffness of the end plates (500) is variable, in particular between the mounting areas (502), and advantageously decreases in the direction towards the mounting areas (502); End plate (500).

13. the end plate (500) has curved reinforcing ribs (520); curved reinforcing ribs (520) extending in particular parallel to the longitudinal direction (L); The end plate (500) of claim 12.

14. Use of an end plate (500) according to any one of claims 12-13 in / for a fuel cell (1).

15. A fuel cell (1) comprising a bipolar plate (210) according to any one of claims 1 to 5 and / or a bipolar plate system (300) according to any one of claims 6 to 10 and / or an end plate (500) according to any one of claims 12 to 13.

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