Bipolar plate with improved temperature distribution

Abstract

The invention relates to a bipolar plate with improved temperature distribution for use in an electrochemical system, and to an electrochemical system comprising a plurality of bipolar plates. The electrochemical system can for example be a fuel cell system, an electrochemical compressor, a redox flow battery or an electrolyser.

Description

Technical Field

[0001] This invention relates to bipolar plates for electrochemical systems, and to electrochemical systems comprising multiple bipolar plates. Such electrochemical systems may be, for example, fuel cell systems, electrochemical compressors, redox flow batteries, or electrolyzers. Background Technology

[0002] Known electrochemical systems typically comprise stacked electrochemical cells separated from each other by bipolar plates between two separators. Such bipolar plates can be used, for example, to indirectly electrically contact the electrodes of a single electrochemical cell (e.g., a fuel cell) and / or to electrically connect adjacent cells (cells in series). Bipolar plates are typically formed from two separate separators bonded together. The separators of the bipolar plates can be bonded together by material bonding, for example, through one or more weld joints, particularly through one or more laser-welded joints.

[0003] Bipolar plates and / or separators may each have or form structures such that they are configured, for example, to provide one or more media to and / or remove reaction products from an electrochemical cell defined by adjacent bipolar plates. The media may be a fuel (e.g., hydrogen or methanol) or a reactant gas (e.g., air or oxygen). Furthermore, bipolar plates and / or separators may include structures for guiding a cooling medium through the bipolar plates, particularly through cavities enclosed by the separators of the bipolar plates. Additionally, bipolar plates may be configured to transfer waste heat generated during the conversion of electrical and / or chemical energy in the electrochemical cell, and to seal various media channels and cooling channels relative to each other and / or relative to the outside.

[0004] Barrier elements may be disposed between the active region and the protruding edge that defines the active region to the outside, and the barrier elements are arranged and configured such that they reduce or prevent the passage of the reaction medium through the active region.

[0005] Furthermore, each bipolar plate typically has at least one or more through openings. Through these through openings, the dielectric and / or reaction products can be conducted into the electrochemical cell defined by the stacked adjacent bipolar plates or into the cavity formed by the separators of the bipolar plates, or can be conducted to the outside of the cell or the cavity. Each electrochemical cell also typically includes one or more membrane electrode assemblies (MEAs). MEAs may include one or more gas diffusion layers, which are typically oriented toward the bipolar plates and formed, for example, as a metal fabric or carbon fabric.

[0006] In some cases, it has been found problematic that, on the side of the separator facing away from the electrochemically active side, such as in a cavity enclosed by the two separators of a bipolar plate, the cooling medium is partially guided along an undesirable path. For example, it may happen that the cooling medium primarily intended for cooling the electrochemically active region of the separator or bipolar plate is at least partially guided through the active region and therefore does not contribute to cooling that active region, or only insufficiently does so.

[0007] This unintentional coolant bypass can lead to undesirable temperature spikes (concentrations) in regions of the electrochemical cell. Furthermore, increased pumping capacity is required to increase the amount of coolant directed through the active region. All these undesirable effects can negatively impact the efficiency of the electrochemical system.

[0008] The applicant’s following disclosures address the above-mentioned issues: DE 10 2007 048 184 B3, DE 20 2017 103 229U2, DE 20 2014 008 157 U1 and DE 20 2015 106 197 U1, and the purpose is to reduce coolant bypass. Summary of the Invention

[0009] The purpose of this invention is to achieve an improved temperature distribution in the bipolar plate, thereby further increasing efficiency.

[0010] According to the invention, this objective is achieved by a bipolar plate according to the main claim. Further developments form the subject matter of the dependent claims and the subject matter described below.

[0011] A bipolar plate for an electrochemical system is proposed, comprising:

[0012] - Two partitions

[0013] - At least one inlet opening for introducing the cooling medium.

[0014] - An outlet opening for discharging the cooling medium.

[0015] - In at least the first partition in the partition

[0016] The active region has a first structure for guiding the reaction medium along the outer side of the bipolar plate and a second structure for guiding the cooling medium along the inner side of the bipolar plate.

[0017] The essentially closed peripheral protrusion is used to seal and separate at least the active area. The peripheral protrusion extends around the active area and the outlet opening and defines the interior of the protrusion.

[0018] The outlet opening is sealed and separated from the inside of the outer peripheral protrusion to prevent the cooling fluid from flowing directly into the outlet opening from the inside of the protrusion, and / or to allow the cooling fluid to reach the outlet opening primarily through the second structure of the active region.

[0019] By sealing the outlet opening relative to the interior of the convex edge, the cooling fluid is thus forced to flow through the active region to the outlet opening. Since bipolar cooling is required only or primarily in the active region, the bypass flow is reduced, resulting in a comprehensive improvement in cooling performance. Better, more uniform temperature distribution means that more uniform and higher current densities can be achieved, and therefore, the efficiency of the electrochemical cell can be improved.

[0020] It can be provided that the outer peripheral flange seals the outlet opening relative to the interior of the flange. Specifically, the portion of the outer peripheral flange facing the outlet opening is responsible for the sealing function. In particular, the outer peripheral flange may have peripheral flange flanks facing the outlet opening, which seal the interior of the flange.

[0021] Each diaphragm typically has two longitudinal sides and two transverse sides. Furthermore, each diaphragm typically has an outer peripheral edge that laterally defines its respective diaphragm. This outer edge can be defined by the longitudinal and transverse sides of the corresponding diaphragm. A peripheral flange can be configured as the outermost sealing element, at least along the longitudinal sides of the respective diaphragm and in the region of the coolant outlet opening. In other words, the peripheral flange is a sealing element positioned closest to the outer edge of the respective diaphragm, at least along both longitudinal sides and in the region of the coolant outlet opening. Typically, each individual diaphragm is provided with at most a single, essentially closed peripheral flange enclosing the active area, i.e., the aforementioned peripheral flange. However, further peripheral flanges may also be provided, extending around the aforementioned peripheral flange and optional other elements, such as inlet openings. Another peripheral flange also extends around the element enclosed by the aforementioned peripheral flange.

[0022] According to another variation, the bipolar plate includes a first convex edge arranged around an outlet opening in at least the first of two diaphragms, wherein a portion of the convex edge facing outwards from the active region seals the outlet opening relative to the interior of the convex edge. Typically, the region of at least the first diaphragm between the outer convex edge and the aforementioned portion of the first convex edge arrangement is substantially unstructured and / or flat. In this region, the two individual plates typically abut and contact each other flatly. To ensure or facilitate this flat abutment, welded joints and / or welds, such as short welds, may be additionally provided in this region.

[0023] To seal the outlet opening relative to the interior of the flange, a weld or welded joint can be arranged between the outlet opening and the flange. The baffles are connected to each other in this area by the weld or welded joint. This weld can be configured, for example, as a stitched weld or a continuous weld. For example, the area between the outer peripheral flange and the outlet opening can have a sealing continuous weld, which additionally prevents any cross-flow of cooling media; this area is, for example, between the outer flank of the peripheral flange facing the outlet opening and the outlet opening, particularly between the outer peripheral flange and the flange facing the outer peripheral flange and surrounding the outlet opening.

[0024] Furthermore, the inlet opening is fluid-connected to the interior of the outer peripheral protrusion. While fluid connection between the inlet opening and the interior of the outer peripheral protrusion is avoided in the prior art, it is hereby proposed to connect the two.

[0025] This is because the inventors recognized that conventional bipolar plates exhibit a non-uniform temperature distribution during electrochemical system operation. In particular, the section of the bipolar plate near the inlet opening is typically cooler than the section near the outlet opening, as the cooling fluid heats up during its journey from the inlet to the outlet. If some of the coolant is now guided through a portion of the active region via the interior of the flange, this still relatively cool portion of the cooling fluid can be supplied to the warmer section of the active region. Since the outlet opening is sealed relative to the interior of the flange, as described above, the cooling fluid will pass through the active region to reach the outlet opening.

[0026] For example, the bipolar plate may include at least one third structure that is guided from the inlet opening to an outer peripheral protrusion in at least one of the two diaphragms in the first diaphragm, for guiding the cooling medium from the inlet opening into the interior of the protrusion. It may be provided that the third structure is formed as a single piece with the first diaphragm and / or with the second diaphragm. The third structure may also be formed partially by the first diaphragm and partially by the second diaphragm. Preferably, the third structure is configured as a raised protrusion. From a manufacturing perspective, the advantage provided by this last variation is that the third structure can be formed together with the first and second structures in a single manufacturing step, for example by convex forming, deep drawing, or hydroforming.

[0027] The bipolar plate may also include a second convex edge arrangement arranged to surround the inlet opening in at least one of the two partitions for sealing the through opening, and more specifically, for sealing the inlet opening.

[0028] The first convex edge arrangement of the outlet opening and / or the second convex edge arrangement of the inlet opening and / or the outer peripheral convex edge typically each include a convex edge top and convex edge flanks arranged on each side of the convex edge top. Here, a substantially straight convex edge top extending at an angle to the substantially straight convex edge flanks can be used, or a convex edge formed by a curved top that seamlessly merges with the similarly curved convex edge flanks can be used. Intermediate shapes are also possible. Furthermore, the first convex edge arrangement, the second convex edge arrangement, and / or the outer peripheral convex edge can protrude beyond the plane of the bipolar plate. Like the outer peripheral convex edge, the first convex edge arrangement and / or the second convex edge arrangement are typically essentially closed.

[0029] Provided, each of the two convex flanks of the second convex flank arrangement has at least one passage for conducting the cooling medium through the convex flank. In this case, the third structure is configured such a conduction channel, located outside the second convex flank arrangement, adjacent to the passage in the outer convex flank, and fluidly connected to the interior of the outer convex flank via another passage in the outer convex flank. According to different embodiments, the conduction channel can be arranged facing away from or towards the active region. Thus, some cooling fluid is preferably intentionally conducted from the inlet opening into the interior of the convex flank, such that a portion of the active region is bypassed.

[0030] To achieve a more uniform temperature distribution, it is also advantageous for the cooling fluid to be conducted from the interior of the convex edge to the warmer portion of the bipolar plate and / or the active region. On the one hand, it is possible that this portion of the cooling fluid reaches the active region uncontrolled via a leakage path. However, it is preferable that the bipolar plate is shaped such that the cooling fluid is conducted in a targeted manner from the interior of the convex edge to the active region. For example, the bipolar plate has a fourth structure that directs the cooling medium away from the outer peripheral convex edge to conduct the cooling medium from the interior of the convex edge to the active region. This fourth structure can be applied where more efficient cooling is required.

[0031] For example, at least the active region of the first septum includes:

[0032] - The first section faces the entrance opening and faces away from the exit opening, and

[0033] - The second section faces the exit opening and is away from the entrance opening.

[0034] The fourth structure, which guides the cooling medium away from the outer peripheral convex edge, can be arranged between the outer peripheral convex edge and the second section, such that at least part or most of the cooling medium flowing through the interior of the convex edge is guided through the first section of the active region and is laterally conducted into the second section.

[0035] For example, at least the active region of the first septum includes:

[0036] - The front section faces the inlet opening and faces away from the outlet opening.

[0037] - The rear section faces the exit opening and is away from the entrance opening, and

[0038] - The middle section is positioned between the front and rear sections.

[0039] In this embodiment, the fourth structure, which guides the cooling medium away from the outer peripheral protrusion, can be arranged between the outer peripheral protrusion and the middle section, such that at least part or most of the cooling medium flowing through the interior of the protrusion is guided through the front section of the active region and laterally conducted into the middle section.

[0040] As an alternative or supplementary approach, a fourth structure that guides the cooling medium away from the outer peripheral convex edge can be arranged between the outer peripheral convex edge and the rear section, such that the cooling medium flowing through the interior of the convex edge is guided through the front and / or middle sections of the active region and is laterally conducted into the rear section.

[0041] Furthermore, the fourth structure, which guides the cooling medium away from the outer peripheral convex edge, can be arranged between the outer peripheral convex edge and the front section, wherein only some of the cooling medium flowing through the interior of the convex edge is guided through the front section, and some of the cooling medium flowing through the interior of the convex edge is laterally introduced into the front section.

[0042] The second structure typically includes channel structures for guiding the cooling fluid, which define the longitudinal flow direction of the cooling medium. This longitudinal flow direction may be specifically given in the first or front section. In other words, these channel structures are arranged parallel to each other, particularly in the first or front section of the active region. It is also possible that at least a portion of the channel structures for guiding the cooling fluid is wavy. Nevertheless, the wavy channel structures have a macroscopic flow direction that defines the longitudinal flow direction. In this case, it is particularly preferred that the channel structures are formed in the two septa of the bipolar plate and, for example, have a phase offset relative to each other, such that cross-flow of fluid between adjacent channels is possible in these regions.

[0043] In the active region, connecting channels for the cooling medium can be provided, which fluidly connect adjacent channel structures to each other and cause the flow direction of the cooling medium to be at an angle to the longitudinal flow direction. These connecting channels can further improve the distribution of the cooling fluid. The connecting channels can be particularly located in the second section, middle section, or rear section. Alternatively, the connecting channel can be at least partially located in the first section or front section.

[0044] The first structure in the active region on the outer side of the bipolar plate typically includes a channel structure for guiding the reaction medium. It may be provided that this channel structure includes a cross-sectional contraction in certain regions, which forms a connecting channel for cooling the medium on the inner side of the bipolar plate.

[0045] In other variations, at least in the first partition, a constricting element is arranged between the active region and the outer peripheral convex edge. The constricting elements are typically configured to reduce or prevent the flow of the reaction medium along the outer peripheral convex edge and through the active region. The constricting element may form a fluid connection between the interior of the convex edge and the interior of the active region, or more specifically, between the interior of the convex edge and the second structure of the active region, allowing the cooling medium to flow from the interior of the convex edge to the second structure.

[0046] In some embodiments, the peripheral protrusion extends partially between the inlet opening and the active region. Alternatively, the inlet opening may be located within the area enclosed by the peripheral protrusion.

[0047] The inlet opening is typically fluidly connected to the distribution area, through which cooling fluid is conducted to the second structure and / or active area of ​​the bipolar plate.

[0048] In some embodiments, the bipolar plate includes at least one additional inlet opening for cooling fluid. This additional inlet opening may only be fluidly connected to the interior of the outer peripheral flange, that is, it is typically not connected to the distribution area. For example, the additional inlet opening is fluidly connected to the interior of the outer peripheral flange such that cooling fluid can be supplied from the additional inlet opening to at least the second or rear section via the interior of the flange. It may be possible to provide a greater number of inlet openings for the cooling medium than the number of outlet openings. In one embodiment, there is actually one outlet opening. It may be possible to provide multiple inlet openings. In some embodiments, the outer peripheral flange also encloses the at least one additional inlet opening for the cooling medium.

[0049] A common feature of all the foregoing embodiments of the present invention is that at least a portion of the cooling medium introduced via the inlet opening is conducted to the second structure via a distribution area without passing extensively through the interior of the outer peripheral convex edge. This portion of the cooling medium ensures basic cooling. The cooling medium conducted through the interior of the convex edge ensures targeted additional cooling for individual areas and can additionally, at least partially, compensate for the temperature rise of the cooling medium used for basic cooling. "Without passing extensively through the interior of the outer peripheral convex edge" means that although fluid flow within the interior of the convex edge can exist from a passage in one convex edge flank to a passage in another convex edge flank (deviating from the previous passage), the fluid flow within the interior of the convex edge cannot exceed the area of ​​the passage.

[0050] It should be noted that the cooling medium is understood as a coolant, which is not used as a reaction medium in electrochemical systems. Cooling media typically comprise liquid water and / or ethylene glycol or a mixture of water and antifreeze, or are composed of said substances. Cooling media are typically in liquid form at room temperature, while reaction media are typically in gaseous form at room temperature. Reaction media may include fuels such as molecules of hydrogen or methanol, reaction gases such as air or oxygen, and / or reaction products or consumed fuels such as water vapor.

[0051] The present invention also proposes an electrochemical system comprising a plurality of bipolar plates as described above, the bipolar plates being arranged in a stack, wherein a membrane electrode assembly is arranged between adjacent bipolar plates of the stack in each case.

[0052] The electrochemical system can be, for example, a fuel cell system, an electrochemical compressor, a redox flow battery, or an electrolyzer. Attached Figure Description

[0053] The accompanying drawings illustrate exemplary embodiments of the bipolar plate and electrochemical system, which will be explained in more detail below. In the drawings:

[0054] Figure 1 An electrochemical system is schematically illustrated in a three-dimensional diagram, comprising multiple bipolar plates arranged in a stacked configuration.

[0055] Figure 2 A three-dimensional diagram schematically illustrates the following based on Figure 1 The system has two bipolar plates, with the membrane electrode assembly (MEA) positioned between the bipolar plates.

[0056] Figure 3 A schematic plan view of the rear side of the separator, which is part of a bipolar plate, is shown.

[0057] Figure 4 A schematic plan view of the rear side of the partition, which is part of another bipolar plate, is shown.

[0058] Figure 5 A schematic plan view of the rear side of the partition, which is part of another bipolar plate, is shown.

[0059] Figure 6 A schematic diagram illustrating the coolant flow in another bipolar plate is shown.

[0060] Figure 7 A schematic diagram illustrating the coolant flow in another bipolar plate with yet another coolant inlet is shown.

[0061] Figure 8 A schematic diagram illustrating the coolant flow in another bipolar plate with yet another coolant inlet is shown.

[0062] Figure 9 A schematic diagram illustrating the coolant flow in another bipolar plate with yet another coolant inlet is shown.

[0063] Figure 10 A schematic diagram illustrating the coolant flow in another bipolar plate with yet another coolant inlet is shown.

[0064] Figure 11 The diagram schematically illustrates the flow of coolant in another bipolar plate.

[0065] Figure 12 The diagram schematically illustrates the flow of coolant in another bipolar plate.

[0066] Figure 13 The diagram schematically illustrates the coolant flow in a portion of a bipolar plate with coolant conduction channels.

[0067] Figure 14 The illustration schematically shows the coolant flow in a portion of a baffle having coolant conduction channels.

[0068] Figure 15 The passage cut along line AA is shown. Figure 14 The cross-section of the partition,

[0069] Figure 16 The passage cut along line BB is shown. Figure 14 The cross-section of the partition,

[0070] Figure 17 It shows according to Figure 14 A cross-sectional view taken along line AA of two interconnected partitions.

[0071] Figure 18 It shows according to Figure 14 A cross-sectional view taken along line BB of two interconnected partitions.

[0072] Features that appear repeatedly in different figures are indicated by the same or similar reference numerals in each case, both herein and hereinafter. Detailed Implementation

[0073] Figure 1An electrochemical system 1 is shown comprising multiple structurally identical metal bipolar plates 2 arranged in a stack 6 and stacked along a z-direction 7. The bipolar plates 2 of this stack 6 are typically sandwiched between two end plates 3, 4. The z-direction 7 is also referred to as the stacking direction. In this example, system 1 is a fuel cell stack. Therefore, each pair of adjacent bipolar plates 2 defines an electrochemical cell 20, which, for example, is used to convert chemical energy into electrical energy. To form the electrochemical cells of system 1, membrane electrode assemblies (MEAs) 10 are arranged between each pair of adjacent stacked bipolar plates 2 in each case (see, for example, [reference needed]). Figure 2 Each MEA10 typically contains at least one membrane, such as an electrolyte membrane. Additionally, a gas diffusion layer (GDL) may be disposed on one or both surfaces of the MEA.

[0074] In alternative embodiments, system 1 can also be configured as an electrolyzer, an electrochemical compressor, or a redox flow battery. Bipolar plates can also be used in these electrochemical systems. Thus, the structure of these bipolar plates can correspond to the structure of bipolar plate 2 described in detail herein, but in each case of an electrolyzer, electrochemical compressor, or redox flow battery, the medium conducted to and / or through the bipolar plates can differ from the medium used in fuel cell systems.

[0075] The z-axis 7, x-axis 8, and y-axis 9 form 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 end plates 4 typically have multiple medium ports 5 through which medium can be supplied to and discharged from system 1. The medium 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.

[0076] like Figure 2 The known bipolar plates shown are as follows: Figure 3 The bipolar plates shown according to the present invention can all be used for Figure 1 In an electrochemical system of the type shown.

[0077] Figure 2 A 3D diagram showing the relationship with Figure 1 The system 1 is an electrochemical system of the same type as the system in the prior art, consisting of two adjacent bipolar plates 2, and a membrane electrode assembly (MEA) arranged between the adjacent bipolar plates 2, which is also known in the prior art. Figure 2MEA 10 is largely obscured by bipolar plate 2 facing the observer. Bipolar plate 2 is constructed by bonding together materials (see also...). Figure 16 , Figure 17 It consists of two partitions 2a and 2b, in Figure 2 Only the first partition 2a facing the observer is visible, and the first partition obscures the second partition 2b. Partitions 2a and 2b can each be made of sheet metal, such as stainless steel. For example, partitions 2a and 2b can be welded together, for example, by laser welding. Partitions 2a and 2b typically have a rectangular shape. Each partition 2a and 2b typically has two longitudinal sides, the longitudinal sides being... Figure 2 Extending along the X direction in the middle, and on two lateral sides, the lateral sides are... Figure 2 It extends along the Y direction. In addition, each partition 2a, 2b typically has an outer periphery that laterally defines its respective partition 2a, 2b. This outer periphery can be defined by the longitudinal and transverse sides of the respective partition 2a, 2b.

[0078] Partitions 2a and 2b typically have through openings that are aligned with each other and form through openings 11a-11d of bipolar plate 2. When multiple bipolar plates of the same type as bipolar plate 2 are stacked, the through openings 11a-11d form conduits extending along the stacking direction 7 through the stack 6 (see...). Figure 1 Typically, each line formed by the through openings 11a-11d is fluidly connected to one of the ports 5 in the end plate 4 of system 1. For example, coolant can be introduced into the stack 6 via the line formed by through opening 11a, while coolant is discharged from the stack via through opening 11d. Through openings 11a and 11d can also be referred to as inlet opening 11a and outlet opening 11d, respectively. Conversely, lines formed by through openings 11b and 11c can be configured to supply fuel and reaction gases to the electrochemical cells of the fuel cell stack 6 of system 1 and to discharge reaction products from the stack. The medium-guided through openings 11a-11d are substantially parallel to the plate plane.

[0079] To seal the through openings 11a-11d relative to the interior of the stack 6 and relative to the surrounding environment, the first partition 2a typically has a sealing arrangement in the form of sealing beads 12a-12d, which are respectively arranged around the through openings 11a-11d and, in each case, completely surround the through openings 11a-11d. On the back side of the bipolar plate 2... Figure 2 On the rear side of the observer, the second partition 2b has corresponding sealing convex edges for sealing the through openings 11a-11d (not shown).

[0080] In the electrochemically active region 18, the first separator 2a faces its orientation Figure 2A flow field 17 is present on the front side of the observer, the flow field 17 having a first structure 14 for guiding the reaction medium along the outer side (or front side) of the partition 2a. Figure 2 In this configuration, the first structures 14 are defined by a plurality of 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 further has a dispensing or collecting region 20. This dispensing or collecting region 20 includes a structure 21 configured to dispense and / or collect or aggregate media on the active region 18, wherein the dispensed media is media already introduced into the dispensing or collecting region 20 from the first of two through openings 11b, and the collected or aggregated media is media flowing from the active region 18 to the second through opening 11b. Figure 2 In the distribution or collection area 20, the distribution structure 21 is also defined by the web and the channels extending between the webs and defined by the web.

[0081] The sealing flanges 12a-12d have passages 13a-13d, wherein passages 13a and 13d are formed on both the lower side of the upper partition 2a and the upper side of the lower partition 2b, while passage 13b is formed in the upper partition 2a and passage 13c is formed in the lower partition 2b. For example, passages 13a and 13d allow coolant to pass between the through openings 12a and 12d and the distribution or collection area 20, so that the coolant reaches and can be guided out of the distribution or collection area 20 between the partitions 2a and 2b.

[0082] Furthermore, passage 13b allows hydrogen gas to pass between the through opening 12b and the distribution area on the upper side of the upper partition 2a; these passages 13b are characterized by perforations facing the distribution or collection area and extending at an angle to the plate plane. Thus, hydrogen gas flows, for example, from the through opening 12c through the passage 13b to the distribution or collection area on the upper side of the upper partition 2a, or flows in the opposite direction. Passage 13c allows air to pass, for example, between the through opening 12c and the distribution or collection area, allowing air to reach and exit from the distribution or collection area on the lower side of the lower partition 2b. The associated perforations are not visible here.

[0083] The first baffle 2a also has an additional sealing arrangement in the form of a peripheral protrusion 12e, which extends around the flow field 17 of the active region 18, the distribution or collection region 20, and the through openings 11b, 11c, and seals these portions relative to the through openings 11a, 11d, i.e., relative to the coolant circuit and relative to the surrounding environment of the system 1. The second baffle 2b each includes a corresponding peripheral protrusion 12e. The structure of the active region 18, the distribution or collection structure of the distribution or collection region 20, and the sealing protrusions 12a-12e are each formed integrally with the baffle 2a, and are integrally formed in the baffle 2a, for example, by a stamping process, hydroforming process, or deep drawing process. The same applies to the corresponding distribution structure and sealing protrusions of the second baffle 2b. Each sealing protrusion 12a-12e may have at least one protrusion top and two protrusion side wings in cross-section. However, a substantially angular arrangement between these elements is unnecessary, and a curved transition can also be provided.

[0084] Although the sealing flanges 12a-12d have a generally circular outline, the outer peripheral flange 12e may have different sections with different shapes. For example, the outline of the outer peripheral flange 12e may have at least two wavy sections.

[0085] The two through openings 11b or the conduits formed by the through openings 11b passing through the plate stack of system 1 each pass through the passage 13b in the sealing flange 12b, through the distribution structure of the distribution or collection area 20, and through the facing Figure 2 The flow field 17 in the active region 18 of the first partition 2a 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 connected via corresponding convex edge passages, via corresponding distribution structures, and via the back-to-back Figure 2 The observers and the corresponding flow fields on the outside of the second partition 2b are fluidly connected to each other. For this purpose, a first structure 14, in particular a channel structure, is provided in each active region 18 for guiding the associated medium.

[0086] Conversely, the pipelines passing through the through openings 11a, 11d, or formed by the through openings 11a, 11d, and traversing the plate stack of system 1, are fluidly connected to each other via cavities 19 enclosed or surrounded by partitions 2a, 2b. In each case, the cavity 19 is used to guide the coolant through the bipolar plates 2, particularly for cooling the electrochemically active region 18 of the bipolar plates 2. Therefore, the coolant is primarily used to cool the electrochemically active region 18 of the bipolar plates 2. Starting from the inlet opening 11a, the coolant flows through the cavity 19 in the direction of the outlet opening 11d. A mixture of water and antifreeze is typically used as the coolant. However, other coolants are also conceivable. To better guide the coolant or cooling medium, a second structure 15 exists inside the bipolar plates 2. These structures... Figure 2 They are not visible because they extend, for example, on the surface of the partition 2a facing away from the observer; therefore, they are positioned opposite the first structure 14 described above, on another surface of the partition 2a. In the active region 18, the second structure 15 guides the cooling medium along the inner side of the bipolar plate in the direction of the outlet opening 11d. The second structure 15 typically includes channel structures for guiding the cooling fluid, which define the longitudinal flow direction of the cooling medium.

[0087] exist Figure 2 In this configuration, the two through openings 11a and 11d are located outside the area enclosed by the essentially closed peripheral protrusion 12e. The peripheral protrusion 12e of the partition plates 2a and 2b also forms a protrusion interior 22, which connects here to the cavity 19.

[0088] A common problem with the previous bipolar plate 2 is that, for example, coolant supplied through the through opening 11a is directed to the second structure 15 located on the rear side of the electrochemically active region 18. In principle, this is because the convex edge 12a again has passageways 13a in its flanks, allowing the coolant to be directed in the plate plane towards the second structure 15 on the rear side of the electrochemically active region 18. The problem here is that some of the coolant may also enter the interior 22 of the outer peripheral convex edge 12e, as the supplied coolant passes through the interior 22. Some of the coolant branches within the interior 22 instead of continuing to flow along the direction of the active region 18, and is thus directed through the active region 18 via the interior 22 to the outlet opening 11d. As a result, this portion of the coolant contributes little or no cooling to the active region 18.

[0089] Figure 2Another problem with the arrangement shown is that the coolant from the inlet opening 11a provides more cooling in the section of the active region 18 facing the inlet opening 11a and away from the outlet opening 11d than in the section of the active region 18 facing the outlet opening 11d and away from the inlet opening 11a, because the coolant was not initially heated by the active region 18. Due to the resulting spatially uneven temperature distribution, the active region 18 is cooled to varying degrees along the coolant flow direction, resulting in the fuel cell system 1 not operating at optimal efficiency.

[0090] The inventors have realized that the coolant bypass through the interior 22 of the convex edge can reduce the uneven temperature distribution in the active region 18 in a targeted manner.

[0091] The following will refer to Figures 3-17 The present invention will be described using exemplary embodiments shown.

[0092] Figure 3 A plan view of the rear side of the separators 2a and 2b of the bipolar plate 2 according to the present invention is shown. Figure 2 Compared to the bipolar plate 2, the essentially closed peripheral convex edge 12e extends not only around the flow field 17, distribution region 20, collection region 20', and through openings 11b, 11c of the active region 18, but also around the outlet opening 11d. This significantly reduces the possibility of cooling fluid flowing directly from the interior 22 of the peripheral convex edge 12e to the outlet opening 11d. Furthermore, the outlet opening 11d is additionally sealed off by the peripheral convex edge flanks facing the outlet opening 11d relative to the interior 22 of the peripheral convex edge 12e, thus preventing cooling fluid from flowing directly from the interior 22 of the convex edge to the outlet opening 11d. As a result, the cooling fluid reaches the outlet opening 11d essentially only via the second structure 15 of the active region 18. The fact that coolant can enter the interior 22 of the convex edge, but can only reach the outlet opening 11d from the interior 22 of the convex edge 22 via the second structure 15 due to the separation between the outlet opening 11d and the peripheral convex edge 12e, is actively utilized here.

[0093] Sealing the outlet opening 11d relative to the interior 22 of the convex edge can be achieved, for example, by means of the convex edge flank of the outer peripheral convex edge 12e facing the outlet opening. A first convex edge arrangement 12d arranged around the outlet opening 11d can also seal the outlet opening 11d relative to the interior 22 of the convex edge. In particular, a portion of the convex edge arrangement 12d facing the outer peripheral convex edge 12e and away from the active region 18 (such as the convex edge flank of the convex edge arrangement 12d) can seal the outlet opening 11d relative to the interior 22 of the convex edge.

[0094] The outer peripheral flange 12e can be configured as the outermost sealing element, which is located at least along the longitudinal side of the respective partitions 2a, 2b and in the region of the coolant outlet opening 11d. In other words, the outer peripheral flange 12e is a sealing element positioned closest to the outer edge of the respective partition, at least along the longitudinal side and in the region of the coolant outlet opening 11d. Typically, at most a single, essentially closed outer peripheral flange 12e is provided for each individual partition to enclose the active area. Figures 3-18 The aforementioned peripheral protrusion is shown. However, a further peripheral protrusion (not shown) may also be provided, extending around the aforementioned peripheral protrusion 12e and optional other elements, such as the inlet opening 11a. Thus, another peripheral protrusion extends around the element enclosed by the aforementioned peripheral protrusion 12e.

[0095] In addition, to seal the outlet opening relative to the interior 22 of the outer flange, one or more weld joints may be provided, which are arranged between the outlet opening 11d and the outer peripheral flange 12e.

[0096] Figure 4 This welded joint 27 is shown, which is partially constructed as a non-sealing welded joint (stitch weld). These welded joints ensure that the partitions 2a and 2b lie flat against each other within the intermediate space between the outlet opening 11d and the outer peripheral flange, thus enhancing the sealing effect of the flanges 12d and 12e. Figure 5 On the other hand, a sealed continuous welded joint 27 is provided, which is closely adjacent to another sealed welded joint between the partitions 2a, 2b. A welded joint 27' extending around the outside is also shown, and this can also exist in all other embodiments. The welded joint or weld is preferably configured as a laser-welded joint or laser-welded weld.

[0097] Depending on the embodiment, the coolant can flow along different paths from the inlet opening 11a to the outlet opening 11d.

[0098] Because the outlet opening 11d is sealed off from the interior 22 of the convex edge, the coolant is forced to flow through at least a portion of the active region 18 to the outlet opening 11d. As a result, a larger proportion of the coolant, i.e., all of the coolant, can be used for temperature control purposes.

[0099] Of particular advantage is that targeted measures can be taken to deliver cooling fluid into the interior 22 of the raised edge.

[0100] For example, in one variation, the inlet opening 11a may be specified to be fluidly connected to the interior 22 of the flange. For instance, at least one third structure 24 from the inlet opening 11a to the outer peripheral flange 12e is configured to guide the cooling medium from the inlet opening 11a into the interior 22 of the flange. The third structure 24 may in particular be configured as a conduction channel connecting the inlet opening 11a to the interior 22 of the flange, see reference. Figure 6 , 7 11, 12.

[0101] In a preferred variant, each of the two convex flanks of the second convex flank arrangement 12a has at least one passage for conducting the cooling medium through the convex flank. On the outer side of the second convex flank arrangement 12a, a third structure configured as a conduction channel may be adjacent to the passage in the convex flank. The third structure 24 configured as a conduction channel can be fluidly connected to the convex interior 22 of the outer convex flank 12e via another passage in the convex flank of the outer convex flank 12e.

[0102] Figure 6 , 7 11 and 12 indicate the flow direction of the coolant from the inlet opening 11a through the third structure 24 into the interior 22 of the raised edge. Figure 6 , 7 In 11 and 12, the third structure 24 points away from the active region 18 and is therefore opposite to the active region 18. In other embodiments, the third structure 24 may also face the active region 18, such as... Figures 3-5 As shown, or it can be enclosed at a 90° angle with the active region 18.

[0103] Although Figures 3-5 In the middle, the essentially closed peripheral convex edge 12e extends partially between the inlet opening 11a and the active region 18, and therefore does not completely seal off the inlet opening 11a, but... Figures 6 to 12 In this embodiment, the essentially closed peripheral convex edge 12e extends not only around the flow field 17, distribution region 20, collection region 20', and through openings 11b, 11c, and outlet opening 11d of the active region 18, but also around the inlet opening 11a. Figures 6-12 In the diagram, the flow direction of the cooling fluid is highlighted with arrows, and for clarity, some elements such as openings 11b and 11c have been omitted. Figure 6-12 In the figure, the positions of some components such as protruding edges 12a, 12d, and 12e are also indicated by the figure reference numerals.

[0104] The active region 18 can be divided into different sub-segments. For example, the active region 18 may have a front segment 31 facing the inlet opening 11a and away from the outlet opening 11d, and a rear segment 32 facing the outlet opening 11d and away from the inlet opening 11a. The front segment 31 and the rear segment 32 are sometimes referred to as the first segment and the second segment 31, 32, respectively. The front segment 31 may be adjacent to the rear segment 32 (see [link to relevant documentation]). Figure 3 In some cases, an intermediate segment 33 may exist, which is arranged between the front segment 31 and the rear segment 32 (see [reference]). Figure 4 , 5 And 9), and adjacent to two sections 31 and 32.

[0105] To further influence the flow direction of the coolant, the interior of the protrusion 22 can be connected to the active region 18 via at least one fourth structure 25. Specifically, a fourth structure 25 can be provided to guide the coolant away from the outer peripheral protrusion 12e to conduct the cooling medium from the interior of the protrusion 22 to the active region 18. Figures 13-18 Such a fourth structure 25 is shown. The fourth structure 25 can be arranged at different points between the outer peripheral protrusion 12e and the active region 18, and is preferably located where increased cooling is required. Depending on the requirements, the fourth structure 25 is arranged between the outer peripheral protrusion 12e on one hand, and the front section, rear section and / or middle section 31, 32, 33 on the other hand.

[0106] If the fourth structure 25 is provided only in the middle section and the rear section 33, 32, the cooling medium flowing through the interior 22 of the convex edge will be guided through the front section 31 of the active region 18 and will be transversely conducted to the middle section and the rear section 33, 32.

[0107] If the fourth structure is provided only in the rear section 32, for example, the cooling medium flowing through the interior 22 of the convex edge will be guided through the front section 31 and (if present) the middle section 33 of the active region 18, and will be laterally conducted into the rear section 32. This situation occurs in... Figures 6-8 and Figures 10-12 As shown in the image.

[0108] Figures 15-18 It shows along Figure 14 The segments intercepted by lines AA and BB are shown in the diagram. Although in Figure 15 and Figure 16 Only a single partition 2a is shown in the image, but Figure 17 and Figure 18 A cross-sectional view of bipolar plate 2 is shown.

[0109] exist Figure 15 and Figure 17As can be seen in the cross-sectional view, the interior 22 of the outer peripheral protrusion 12e is not fluidly connected to the active region 18. On the other hand, in Figure 16 and Figure 18 In the middle, the interior of the convex edge 22 and the active region 18 are fluidly connected to each other through the fourth structure 25.

[0110] If the fourth structure 25 is provided only in the middle section and the rear section 33, 32, the cooling medium flowing through the interior 22 of the convex edge will be guided through the front section 31 of the active area and will be transversely conducted to the middle section and the rear section 33, 32.

[0111] In some embodiments, the fourth structure 25 is present in each of the aforementioned segments 31, 32 and optionally 33, see reference. Figure 9 and Figure 12 Therefore, only some of the cooling medium flowing through the interior 22 of the convex edge will be guided through the front section 31, and some of the cooling medium flowing through the interior 22 of the convex edge has been laterally introduced into the front section 31.

[0112] like Figure 13 and Figure 14 As shown, the fourth structure 25 can be arranged at an angle to the main extension direction of the outer peripheral protrusion 12e. This main extension direction here originates from the line connecting the turning points of the neutral fibers at the top of the protrusion of the outer peripheral protrusion 12e.

[0113] To further improve the guidance of the coolant in the active region 18, a connecting channel 28 for the cooling medium may be provided in the active region 18. The connecting channel 28 fluidly connects adjacent channel structures 15 to each other. In particular, the connecting channel 28 makes the flow direction of the cooling medium at an angle to the longitudinal flow direction. As a result, the cooling medium can be directed to the warmer areas of the active region 18 in a targeted manner.

[0114] The channel structure of the first structure 14 mentioned above, that is, the channel structure on the surface of the partitions 2a and 2b facing away from the cavity 19, may include a contraction in cross-section in certain areas, forming a connecting channel 28 for the cooling medium on the inner side of the bipolar plate 2. The connecting channel 28... Figure 14 , Figure 16 and Figure 18 It is clearly visible in the middle.

[0115] The shape, number, orientation (angle), and size of the fourth structure 25 may be the same or different for each segment 31, 32, or 33.

[0116] In the first partition 2a and / or the second partition 2b, the limiting element 29 is preferably arranged between the active region 18 and the outer peripheral protrusion 12e. The limiting element 29 is configured such that it reduces or prevents the flow of the reaction medium on the outer side along the outer peripheral protrusion 12e and through the active region 18. In a preferred embodiment, the limiting element 29 forms a fluid connection between the interior 22 of the protrusion and the inner side, i.e., the cavity 19 of the active region, so that the cooling medium can flow from the interior 22 of the protrusion to the second structure 15. It can be configured such that the limiting element 29 and the fourth structure 25 are formed on opposite sides of the partitions 2a, 2b; in other words, the fourth structure 25 on the side of the bipolar plate 2, which conducts the cooling medium, forms the limiting element 29 on the side of the bipolar plate 2, which conducts the reaction medium.

[0117] The third structure 24 and / or the fourth structure 25 and / or the limiting element 29 may be formed as a single piece in at least one of the two partitions 2a, 2b, or partially in each of the two partitions 2a, 2b. In each case, the third structure 24 and / or the fourth structure 25 and / or the limiting element 29 may be configured as a raised structure. In particular, the third structure 24 and / or the fourth structure 25 and / or the limiting element 29 may be formed together with the first and second structures 14, 15 in a single manufacturing step, for example, by embossing, deep drawing, or hydroforming a metal layer.

[0118] Figures 3 to 6 , Figure 11 and Figure 12 Each of the embodiments shown has only one inlet opening 11a for the cooling medium. In contrast, Figures 7 to 10 The illustrated embodiment has at least one additional cooling inlet opening 40. Although in Figures 7 to 10 Two cooling inlet openings 40 are shown in each section, but the number of cooling inlet openings 40 may be more or less. Another cooling inlet opening 40 differs from inlet opening 11a in that it does not have a direct fluid connection to the active region 18 or the distribution region 20. Instead, the cooling inlet opening 40 is directly connected to the interior of the convex edge 22 only via the cooling channel 41. Each cooling inlet opening 40 is typically surrounded by a corresponding, essentially closed convex edge 42, and is sealed off from the surrounding environment by this convex edge 42. Another cooling inlet opening 40 may be located inside the area enclosed by the outer peripheral convex edge 12e (see reference). Figure 7 , Figure 8 Or located outside the area enclosed by the outer convex edge (see reference). Figure 9 , Figure 10 Furthermore, the cooling inlet opening 40 can be arranged upstream of the active area, see [reference needed]. Figure 7 , Figure 8 Alternatively, the cooling inlet opening 40 can be arranged in the front section 31 (see...). Figure 9) or the middle section 33 (see Figure 10 On the horizontal segment of ), by providing another cooling inlet opening 40, the cooling capacity of the cooling inlet opening 40 can be at least partially separated from the cooling capacity of the inlet opening 11a. As a result, the cooling capacity provided via the interior 22 of the outer peripheral protrusion 12e can be selectively controlled.

[0119] exist Figure 8 , Figure 9 and Figure 10 In one embodiment, the coolant enters the interior 22 of the protrusion only through another cooling inlet opening 40, while Figure 7 In one embodiment, the coolant flowing into the interior 22 of the convex edge originates from a combination of the inlet opening 11a and the cooling inlet opening 40.

[0120] It is obvious that, Figures 3-12 In all embodiments, some, and often even most, of the cooling medium does not enter the interior 22 of the convex edge from the inlet opening 11a to continue flowing therein along the path of the convex edge, but instead flows via the passage 13a to the distribution area 20 and outwards into the cavity 19 of the active area 18.

[0121] Figure 1 The electrochemical system shown can of course be used with the bipolar plate 2 according to the invention.

[0122] List of reference numerals in the attached diagram:

[0123] 1. Electrochemical System

[0124] 2 Bipolar plates

[0125] 2a Single board

[0126] 2b Single board

[0127] 3 end plates

[0128] 4 end plates

[0129] 5. Media Port

[0130] 6 stacking

[0131] 7 Z direction

[0132] 8 X direction

[0133] 9 Y direction

[0134] 10 Membrane Electrode Assembly

[0135] 11a-d Through opening

[0136] 12a-e Sealing convex edge

[0137] 13a-d pathway

[0138] 14 First Structure

[0139] 15 Second Structure

[0140] 17 Flow Field

[0141] 18 Electrochemical active regions

[0142] 19 cavities

[0143] 20. Allocation and / or collection areas

[0144] 20' Collection Area

[0145] 22. Inside the convex edge

[0146] 24 Third Structure

[0147] 25. Fourth Structure

[0148] 26 Pipeline from inlet opening 11a to inside the protruding edge 22

[0149] 27 Welded joints

[0150] 28 Connection Channels

[0151] 29. Limiting elements

[0152] 31 front section

[0153] 32 Rear Section

[0154] 33. Middle Section

[0155] 40. Entrance opening

[0156] 41 Fluid Channel

[0157] 42 Sealing convex edge

Claims

1. A bipolar plate (2) for an electrochemical system (1), the bipolar plate (2) comprising: - Two partitions (2a, 2b). - At least one inlet opening (11a) for introducing cooling medium, - Outlet opening (11d), said outlet opening (11d) is used to discharge the cooling medium. -In at least the first partition in the partitions (2a, 2b) o Active region (18), said active region (18) having a first structure (14) for guiding the reaction medium along the outer side of said bipolar plate (2) and a second structure (15) for guiding the cooling medium along the inner side of said bipolar plate (2). o Closed peripheral protrusion (12e), the peripheral protrusion (12e) is used to seal and separate at least the active region, the peripheral protrusion (12e) extends around the active region and the outlet opening (11d) and defines the interior (22) of the protrusion. The outlet opening (11d) is sealed off from the interior (22) of the outer peripheral protrusion (12e) to prevent the cooling medium from flowing directly into the outlet opening (11d) from the interior (22) of the protrusion, and / or to allow the cooling medium to reach the outlet opening (11d) only via the second structure (15) of the active region. The inlet opening (11a) is fluidly connected to the interior (22) of the outer peripheral protrusion (12e), and A fourth structure (25) is directed away from the outer peripheral protrusion (12e) to conduct the cooling medium from the interior (22) of the protrusion to the active region.

2. The bipolar plate (2) according to claim 1, characterized in that, Includes a first convex edge arrangement (12d) arranged in at least the first of the two partitions (2a, 2b) around the outlet opening (11d), wherein a portion of the convex edge arrangement (12d) facing the outer peripheral convex edge (12e) and away from the active region (18) seals the outlet opening (11d) relative to the interior (22) of the convex edge.

3. The bipolar plate (2) according to claim 1, characterized in that, The outer peripheral convex edge (12e) is configured as such an outermost sealing element that it extends at least along the longitudinal side of the respective partitions (2a, 2b) and in the region of the coolant outlet opening (11d).

4. The bipolar plate (2) according to claim 1, characterized in that, Includes at least one third structure (24) that is directed from the inlet opening (11a) to the outer peripheral protrusion (12e) in at least the first of the two partitions (2a, 2b) for guiding the cooling medium from the inlet opening (11a) into the interior (22) of the protrusion.

5. The bipolar plate (2) according to claim 4, characterized in that, The third structure (24) is constructed as a raised structure.

6. The bipolar plate (2) according to any one of claims 4 or 5, characterized in that, include - A second convex edge arrangement (12a) is arranged in at least one of the two partitions (2a, 2b) around the inlet opening (11a) for sealing the inlet opening (11a), and each of the two second convex edge wings of the second convex edge arrangement (12a) has at least one passage (13a) for guiding the cooling medium through the second convex edge wing. The third structure (24) is configured as a conduction channel that is located outside the second convex side arrangement (12a), adjacent to a passage in the side wing of the second convex side, and fluidly connected to the interior (22) of the convex side of the outer peripheral convex side (12e) via another passage in the side wing of the convex side of the outer peripheral convex side (12e).

7. The bipolar plate (2) according to claim 1, characterized in that, The active region (18) of at least the first partition (2a) includes: a front section (31) facing the inlet opening (11a) and away from the outlet opening (11d); and a rear section (32) facing the outlet opening (11d) and away from the inlet opening (11a), wherein the fourth structure (25), guided away from the outer peripheral convex edge (12e), is arranged between the outer peripheral convex edge (12e) and the rear section, such that at least part or most of the cooling medium flowing through the interior (22) of the convex edge is guided through the front section (31) of the active region and is laterally conducted into the rear section (32).

8. The bipolar plate (2) according to claim 7, characterized in that, The active region of at least the first partition includes: a front section (31) facing the inlet opening (11a) and away from the outlet opening (11d); a rear section (32) facing the outlet opening (11d) and away from the inlet opening (11a); and an intermediate section (33) disposed between the front section (31) and the rear section (32), wherein a fourth structure (25) guided away from the outer peripheral convex edge (12e) is also disposed between the outer peripheral convex edge (12e) and the intermediate section (33), such that at least part or most of the cooling medium flowing through the interior (22) of the convex edge is guided through the front section (31) of the active region (18) and is laterally conducted to the intermediate section (33).

9. The bipolar plate (2) according to claim 8, characterized in that, At least the active region (18) of the first partition (2a) includes: a front section (31) facing the inlet opening (11a) and away from the outlet opening (11d); a rear section (32) facing the outlet opening (11d) and away from the inlet opening (11a); and an intermediate section (33) disposed between the front section (31) and the rear section (32), wherein a fourth structure (25) guided away from the outer peripheral convex edge (12e) is also disposed between the outer peripheral convex edge (12e) and the front section (31), wherein only some of the cooling medium flowing through the interior (22) of the convex edge is guided through the front section (31) and some of the cooling medium flowing through the interior (22) of the convex edge is laterally introduced into the front section (31).

10. The bipolar plate (2) according to claim 1, characterized in that, The second structure (15) includes a channel structure for guiding the cooling medium, the channel structure defining the longitudinal flow direction of the cooling medium, wherein a connecting channel (28) for the cooling medium is provided in the active region (18), the connecting channel fluidly connecting adjacent channel structures to each other and making the flow direction of the cooling medium at an angle to the longitudinal flow direction.

11. The bipolar plate (2) according to claim 10, characterized in that, The first structure (14) includes a channel structure for guiding the reaction medium in the active region (18) on the outside of the bipolar plate (2), wherein the channel structure includes a cross-sectional contraction in some regions, and the cross-sectional contraction forms a connection channel (28) for the cooling medium on the inside of the bipolar plate (2).

12. The bipolar plate (2) according to claim 1, characterized in that, At least in the first partition (2a), restrictive elements are arranged between the active region and the outer peripheral protrusion (12e) and are configured such that they can reduce or prevent the reaction medium from flowing on the outside along the outer peripheral protrusion (12e) and through the active region.

13. The bipolar plate (2) according to claim 12, characterized in that, The limiting element (29) forms a fluid connection between the interior of the protruding edge (22) and the second structure (15) inside the active region (18), so that the cooling medium can flow from the interior of the protruding edge (22) to the second structure.

14. The bipolar plate (2) according to claim 1, characterized in that, The outer peripheral protrusion (12e) extends partially between the inlet opening (11a) and the active region (18).

15. The bipolar plate (2) according to claim 1, characterized in that, It includes another inlet opening (40) for the cooling medium, which is fluidly connected only to the interior (22) of the outer peripheral protrusion (12e).

16. The bipolar plate (2) according to claim 1, characterized in that, It includes at least one welded joint or weld seam that connects the partitions (2a, 2b) to each other and is arranged between the outlet opening (11d) and the outer peripheral protrusion (12e).

17. An electrochemical system (1) comprising a plurality of bipolar plates (2) according to any one of the preceding claims, the bipolar plates (2) being arranged in a stack (6), wherein, In each case, the membrane electrode assembly (10) is arranged between adjacent bipolar plates (2) of the stack (6).

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