Bipolar plate with at least one layer and at least one insert

Abstract

Bipolar plate (1) for an electrochemical system, in particular for an electrolyzer, comprising at least one layer (2) and at least one insert (10), the layer (2) comprising - at least one through-opening (3, 4) as an inlet or outlet for a fluid, - a flow field (8) with an electrochemically active region, wherein the insert (10) is arranged at the through-opening (3, 4) and comprises a fluid guidance structure (12) for guiding the fluid, wherein the fluid guiding structure (12) of the insert (10) has several protrusions (14, 24) and is arranged in the flow direction of the fluid between the flow field (8) and the through-opening (3, 4), such that the fluid is guided from the through-opening (3, 4) through the fluid guiding structure (12) between the protrusions (14, 24) to the flow field (8) or vice versa, wherein the fluid guidance structure (12) comprises a first area (18) and a second area (19) which are arranged next to each other in the direction of fluid flow, wherein the elevations (14, 24) in the first area (18) and in the second area (19) each have different distances from each other and / or are arranged at different densities and / or are shaped differently, such that a flow cross-section in the first area (18) is smaller than a flow cross-section in the second area (19) and / or a flow resistance in the first area (18) is greater than a flow resistance in the second area (19).

Description

[0001] The present invention relates to a bipolar plate for an electrochemical system, comprising a layer and an insert. Furthermore, the present invention relates to an arrangement for an electrochemical system comprising the bipolar plate. Furthermore, the present invention relates to an electrochemical system comprising a plurality of stacked bipolar plates or a plurality of stacked arrangements.

[0002] The electrochemical system described in this document can be, for example, a fuel cell system, an electrochemical compressor, a redox flow battery or an electrolyzer.

[0003] In general, electrochemical systems typically comprise a stack of single electrochemical cells, each comprising a plurality of layers, including at least one bipolar plate and a membrane electrode assembly (MEA), with each single cell defined by two adjacent bipolar plates. The stack of single electrochemical cells may comprise two end plates that compress the single electrochemical cells together and provide stability to the stack. Furthermore, the single electrochemical cells may comprise gas diffusion layers (GDL) or porous transport layers (PTL) disposed between the bipolar plate and the membrane electrode assembly.The bipolar plate can fulfil several functions: indirect electrical contacting of electrodes of the membrane electrode assembly (MEA), separation of media such as water, oxygen or hydrogen and electrical connection of the neighbouring individual electrochemical cells.

[0004] The bipolar plate comprises at least one through-opening (port) as an inlet or outlet for conducting a fluid through the bipolar plate, a flow field with an electrochemically active region, and an intermediate fluid guide structure for guiding the fluid between the through-opening and the flow field. In particular, the fluid guide structure can form a fluidic connection between the through-opening and the flow field. The fluid guide structure is often formed by several elevations of the bipolar plate, so that respective passages are located between the adjacent elevations, through which the fluid flows.

[0005] The bipolar plate can, for example, be single- or multi-layered. While bipolar plates in fuel cells are often double-layered to allow cooling fluid to flow between the two individual layers, bipolar plates in electrolyzers are usually single-layered. The bipolar plate itself and each layer of a bipolar plate can be considered a separator plate, as this ensures the separation of media.

[0006] In addition to the aforementioned bipolar plates, MEA, GDL, or PTL, additional layers can be provided. For example, cell frames and / or cell seals can be arranged between adjacent bipolar plates to seal the cells. The stack of individual electrochemical cells must be sealed from the outside, as a fluid or medium within the individual electrochemical cells is often under excess pressure compared to the external pressure. Depending on the type of electrochemical system, the fluid can include, for example, hydrogen, air (oxygen), water, a cooling medium, and / or mixtures thereof. In an electrolyzer, the pressure difference between the environment and the interior of an electrochemical cell can even exceed 20 bar. For example, on the product side, for example the H2 side, the pressure can be up to 40 bar, while the pressure on the reactant side, for example the H2O side, is only up to 2 bar.It is therefore important to seal the fluid flow field from the environment and also within the electrochemical system. To this end, the electrochemical system can have at least one cell frame surrounding the outer edge of each electrochemical cell, particularly in electrolyzer applications, to achieve a sealing effect. Furthermore, the electrochemical system can include one or more sealing layers or cell seals for each of the electrochemical cells to enhance the sealing effect.

[0007] However, such conventional electrochemical systems have the following problems. The layer lying on top of the bipolar plate (i.e., the cell frame or cell seal) crosses the feedthroughs of the fluid guide structure and is not supported by the bipolar plate in this area. When the electrochemical cell is pressed together, the layer cannot transmit sufficient pressure or compression in this area. On the other hand, the area of ​​the fluid guide structure must be traversed in the case of a single-layer bipolar plate, since the anode and cathode sides of the bipolar plate, particularly of an electrolyzer, are made from a single sheet of metal. This means that when stacked or assembled, they essentially lie one above the other and can only transmit the force required for sealing via the strength and / or rigidity of the cell frame and / or the cell seal itself.Due to the required electrical insulation, the cell frame and / or cell seal are usually made of plastic, which, however, is often not strong and / or rigid enough, which can be problematic when pressing the stack together. This is because deformations in the direction of the feedthroughs can occur at the points where the cell frame and / or cell seal run over the fluid guidance structure. These deformations often lead to a loss of pressure or pressure in the sealing layer opposite the membrane and the cell frame and / or cell seal. When the medium is introduced into the port, the medium escapes from the sealing layer. The loss of pressure or pressure leads to leakage, which can cause a short circuit or even a total failure of the system.

[0008] To solve this problem, support elements are sometimes used in the prior art, which are arranged as a sealing support bridge above the fluid guide structure formed in the bipolar plate, see for example the publications DE 10 2014 202 775 A1 and DE 10 2020 215 014 A1.

[0009] There is a continuous need to further increase the tightness of the system, prevent or at least reduce pressure loss or fluid loss and / or increase the safety of the system.

[0010] The object of the present invention is therefore to provide a bipolar plate, an arrangement comprising the bipolar plate, and an electrochemical system comprising a plurality of the stacked bipolar plates or a plurality of the stacked arrangements, which at least partially solves the above-mentioned problems.

[0011] This problem is solved by the subject matter of the independent claims.

[0012] According to a first aspect, a bipolar plate for an electrochemical system, in particular for an electrolyzer, is provided. The bipolar plate comprises at least one layer and at least one insert. The layer comprises at least one through-opening as an inlet or outlet for a fluid and a flow field with an electrochemically active region.

[0013] The insert is arranged at the through-opening and comprises a fluid guide structure for guiding the fluid. The fluid guide structure of the insert has a plurality of elevations and is arranged between the flow field and the through-opening in the direction of fluid flow, so that the fluid is guided or can flow from the through-opening through the fluid guide structure between the elevations to the flow field, or vice versa.

[0014] Here, the fluid guide structure has a first region and a second region which are arranged next to one another in the flow direction of the fluid, wherein the elevations in the first region and in the second region each have different distances from one another and / or are arranged with different densities and / or are shaped differently, so that a flow cross-section in the first region is smaller than a flow cross-section in the second region and / or a flow resistance in the first region is greater than a flow resistance in the second region.

[0015] Due to the different flow cross-sections and flow resistances in the two areas of the fluid guidance structure of the insert, the fluid quantity and fluid velocity can be designed locally, which can have a positive influence on the tightness of the system. In addition, flow optimization can be achieved, which leads to a better even distribution of the fluid along the bipolar plate, which in turn has a positive effect on the tightness of the system. It has been found that the fluid flow is usually not constant along the fluid guidance structure with the same flow cross-sections and flow resistances. This is often due to the elements upstream or downstream of the fluid guidance structure. If the through-opening is rectangular, for example, the flow at its corners is usually lower than at the elongated edge of the through-opening due to the increased flow resistance in these areas.By locally increasing the flow resistance of the fluid guide structure at the elongated edge of the through-hole, the fluid flow can be homogenized. Homogenizing the fluid distribution, in turn, simplifies and standardizes the system's sealing elements. To compare the two areas, the areas of the fluid guide structure should be selected so that they have the same width laterally perpendicular to the flow direction.

[0016] The fluid-conducting structure of the insert often has multiple passages, each extending between adjacent elevations and designed to conduct the fluid along the layer. It can be provided that at least two of the passages have a different flow cross-section and / or a different flow resistance and / or a different width and / or a different length. The differently designed passages can be provided in the first and second regions of the fluid-conducting structure of the insert. The flow cross-sections of the passages can differ, for example, in terms of their shape and / or size.

[0017] The passages can have a first plurality of passages and a second plurality of passages, wherein the first plurality of passages and the second plurality of passages differ in terms of their flow cross-sections, widths and / or lengths. Thus, different groups of passages, each with different flow properties, can be provided. Instead of separate groups, the flow properties can also change continuously, for example, along an edge of the through-opening. For example, it can be provided that the flow cross-sections and / or widths of the passages change in a direction perpendicular to the flow direction of the fluid and / or remain constant in the flow direction of the fluid and preferably decrease towards the center of the fluid guide structure.

[0018] The elevations can form depressions on a first side of the insert facing away from the layer, wherein the depressions in the first region and in the second region each have the same diameter and / or a different diameter and / or the same width and / or a different width and / or the same cross-sectional area and / or a different cross-sectional area and / or the same cross-sectional shape and / or a different cross-sectional shape and / or the same length and / or a different length. It is therefore clear that several parameters can be varied in order to achieve the desired different flow properties in the first region and in the second region.

[0019] At least one, several, or all of the depressions can, in particular, be channel-shaped. In this case, the elevations are ridge-shaped. Channel-shaped or ridge-shaped does not necessarily mean that the structures are straight; curved channels or ridges are also possible. At least two or all of the elevations or depressions often extend essentially parallel to one another. In one embodiment, the fluid-conducting structure extends in a wave-like manner.

[0020] In some embodiments, at least one, several, or all elevations are knob-shaped. It can be provided that the density of the knob-shaped elevations is greater in the first region than in the second region. The density of the elevations or the density of the knob-shaped elevations is to be understood as referring to the relative area proportion in the area spanned by the elevations, and not necessarily just the number. The elevations can therefore also be of different sizes. A combination of elevations of different shapes, such as knob-shaped elevations and ridge-shaped elevations, is also possible.

[0021] The insert is often firmly connected to the layer, preferably by a material bond. Welded or adhesive joints are examples of possible solutions. Mechanical connections are also possible, preferably located outside the raised portion of the insert.

[0022] Sometimes, the insert is configured essentially as a flat surface in the region outside the fluid guidance structure. The elevations of the insert typically face the layer and, in particular, rest on the layer. The layer can have an essentially flat surface in the region of the fluid guidance structure of the insert. The elevations of the insert can, in particular, rest on the flat surface of the layer. Furthermore, the insert can be arranged around the through-opening and, in particular, at least partially enclose the through-opening. Furthermore, the flow field can be spaced from the fluid guidance structure or directly adjoin the fluid guidance structure.

[0023] It can be provided that the through-opening has an edge, wherein a longitudinal direction of first passages or elevations is aligned substantially perpendicular to a nearest region of the edge and / or a longitudinal direction of second passages or elevations is aligned at an angle between 0° and 90° to a nearest region of the edge.

[0024] Typically, the layer has at least two through-openings arranged side by side, which are separated from each other by a region of the layer. In some embodiments, the insert is arranged at the at least two through-openings and has a fluid-guiding structure for both through-openings. It can be provided that both through-openings are designed as fluid inlets or that both through-openings are designed as fluid outlets, in particular for the same fluid. The insert can extend further between the at least two through-openings. Optionally, the insert can extend in a frame-like, figure-8-shaped, or spectacle-like manner along the edges of the two through-openings.

[0025] In some embodiments, the layer has a bead arrangement formed into the layer, which partially surrounds the at least one through-opening. This can refer to the region of the through-opening that is arranged adjacent to the fluid-guiding structure. The insert can be arranged on the bead arrangement, in particular in the region outside the fluid-guiding structure. It can be provided that the bead arrangement runs between the through-openings. The bead arrangement can be designed as a half-bead or a full bead, wherein a height of the bead arrangement and a height of the elevations can be coordinated with one another, for example the heights are the same. In some embodiments, the insert can be arranged on the bead roof of the bead arrangement.

[0026] The flow field typically has channel structures for guiding a reaction or product medium along the separator plate. A bead roof of the bead arrangement and the channel structures of the flow field can be aligned in the same direction, preferably perpendicular to a plate plane of the layer, and formed into the separator plate, for example, by embossing such as roll embossing, stroke embossing, hydroforming, and / or deep drawing of the separator plate.

[0027] The bipolar plate can have an elastomer seal for sealing the through-opening, which is arranged on a first side of the insert facing away from the layer. The elastomer seal can be injection-molded onto the insert and / or the layer. For example, the elastomer seal is designed as an elastomer bead or coating and is arranged on the layer and / or the insert. In particular, an elastomer seal can be continuously applied to the insert and the layer. It can also be used to connect the insert and the layer—as an alternative to another connection between these two elements or in addition to another connection.

[0028] As already described above, the raised portions on the first side of the insert can form recesses, such as channels or nubs. In this case, the elastomer seal can be arranged at least in the recesses. On the back of the bipolar plate, i.e., on the side of the bipolar plate facing away from the insert, the bead arrangement can form a receptacle for another sealing element, for example, an elastomer sealing element.

[0029] The thickness of the insert is typically no more than 70%, preferably no more than 30%, of the thickness of the layer. The reduced thickness of the insert allows the elevations and penetrations to be structured more finely than if they were formed in the layer.

[0030] It can be provided that the insert is made of metal, e.g., titanium or stainless steel, and / or that the layer is made in sections, at least predominantly or entirely, of metal, e.g., titanium or stainless steel. Other materials such as alloys are also possible, and the invention is not limited to a specific material for the layer. Optionally, the insert and the layer are made of the same or different materials. Additionally or alternatively, the insert can be formed separately from the layer and made from a different material blank than the layer. The independent manufacturing option can increase the design freedom of both components.

[0031] According to a further aspect, a bipolar plate for an electrochemical system, in particular an electrolyzer, is proposed. The bipolar plate comprises at least one layer and at least one insert. The layer comprises at least one through-opening as an inlet or outlet for a fluid and a flow field with an electrochemically active region. The insert is arranged at the through-opening and comprises a fluid guide structure for guiding the fluid. The fluid guide structure of the insert is arranged in the flow direction of the fluid between the flow field and the through-opening, so that the fluid is guided or flows from the through-opening through the fluid guide structure to the flow field, or vice versa.The fluid guide structure of the insert has a plurality of elevations and passages, each of which extends between adjacent elevations and is designed to guide the fluid along the layer. At least two of the passages have a different flow cross-section and / or a different flow resistance and / or a different width and / or a different length.

[0032] The features described in connection with the bipolar plate according to the first aspect can be used individually or in combination with the bipolar plate of the second aspect without departing from the scope of the present specification.

[0033] According to a third aspect, an arrangement for an electrochemical system is proposed. The arrangement comprises a bipolar plate according to one of the two aspects described above, wherein the arrangement comprises a first cell frame and / or a membrane electrode unit and / or a second cell frame, and wherein the insert is arranged between the first cell frame and the layer and / or between the membrane electrode unit and the layer and / or between the second cell frame and the layer.

[0034] In one embodiment, the insert can be designed to support the first cell frame and / or the membrane electrode assembly and / or the second cell frame, particularly in the region of the fluid guide structure. The cell frames can be formed from a plastic and designed to seal areas of the bipolar plate, such as the flow field and / or the through-opening.

[0035] According to a fourth aspect of the invention, an electrochemical system is proposed. The electrochemical system comprises a plurality of stacked bipolar plates of the type described above and / or a plurality of stacked arrangements of the type described above.

[0036] In an embodiment where the electrochemical system is an electrolyzer, water can be the reaction medium, while hydrogen and oxygen are the product media. In a fuel cell system, hydrogen and oxygen, or air, are often the reaction media, while water is the product medium.

[0037] Examples of the bipolar plate, the assembly, and the electrochemical system are illustrated in the attached figures and explained in more detail in the following description. They show: Fig. 1 is a plan view of a bipolar plate according to one embodiment; Fig. 2 a perspective view of a section D of the bipolar plate according to Fig. 1; Fig. 3 a perspective view of a region of the bipolar plate according to Fig. 1; Fig. 4 a section through a part A of the bipolar plate of the Fig. 3; Fig. 5 a section through another part B of the bipolar plate of the Fig. 3; Fig. 6 a section through another part C of the bipolar plate of the Fig. 3; Fig. 7 a perspective view of a region of the bipolar plate according to Fig. 1; Fig. 8 a perspective view of a section along the line AA of the Fig. 7; Fig. 9 is a perspective view of a portion of a bipolar plate according to another embodiment; Fig. 10 is a plan view of a portion of an insert according to another embodiment; Fig. 11 is a perspective view of a portion of a bipolar plate according to another embodiment; and Fig. 12 is an exploded view of a single cell of an electrolyzer with a conventional bipolar plate according to the prior art.

[0038] Here and in the following, features that recur in various figures are designated by the same or similar reference symbols.

[0039] Fig. 12 shows an exploded view of a prior art electrochemical single cell 100, wherein the single cell 100 is a component of an electrolyzer in the example shown. Electrolyzers typically comprise a plurality of stacked single cells 100. The single cell 100 shown comprises two bipolar plates 1 and 1', two cell frames 42 and 44, a sealing layer 45, and a membrane electrode assembly 40 with media diffusion structures 41 and 43. Instead of the sealing layer 45, an elastomer seal can also be used, for example, on the surface of the bipolar plate 1' facing the cell frame 44; the cell frame 44 would thus be directly adjacent to the bipolar plate 1'. The media diffusion structure 43 comprises, for example, layers of carbon fleece, while the media diffusion structure 41 comprises metal, e.g., titanium. The bipolar plate 1 is arranged here, for example, on the anode side of the single cell 100.In the illustrated embodiment, the bipolar plate 1' is arranged on the cathode side of the individual cell 100. The individual layers are pressed together to form a single cell 100. The individual layers each have fluid passages 46, 47, 50 arranged flush with one another for the inflow and outflow of water, oxygen, and hydrogen, as well as positioning holes 48.

[0040] By projecting the cell frame 44 onto the separator plate 1', a flow field of the bipolar plate 1' is defined in the area enclosed by the cell frame 44. By projecting the cell frame 42 onto the bipolar plate 1, a flow field 8 of the bipolar plate 1 is defined in the area enclosed by the cell frame 42. The cell frame 42 has distribution channels (not shown) for distributing the introduced water. The through-openings 46, 47 are in fluid communication with the flow field 8 so that a medium can be conducted from the through-opening 46 to the flow field 8 or from the flow field 8 to the through-opening 47. When a potential is applied, hydrogen (or oxygen) can be generated in the electrolyzer from the supplied water. This can be discharged through the distribution channels 49 in the cell frame 44. It can then leave the cell through the through-openings 50. While the Fig. 12 have a round outer contour, other shapes are also possible. For example, the bipolar plates 1, 1' can have a rectangular outer contour, optionally with rounded corners (see also Fig. 1).

[0041] As already indicated above, the pressure difference between the environment and the interior of the electrochemical cell 100 can exceed 20 bar. Often, the pressure on the product side, for example, the hydrogen side, is up to 40 bar, while the pressure on the reactant side, for example, the water side, is only up to 2 bar. It is therefore important that the individual areas of the bipolar plates 1, 1' are sealed from other areas of the bipolar plates and / or the environment.

[0042] The Fig. Figure 1 shows a plan view of a highly schematic bipolar plate 1 according to the invention. The bipolar plate 1 has at least one layer 2 and at least one insert 10.

[0043] Layer 2 is typically configured as a sheet metal layer and has a plurality of through-openings 3, 4, 5, 6, wherein through-openings 4 and 6 are configured as inlets and through-openings 3 and 5 as outlets for a fluid, wherein the fluid can be, for example, water, hydrogen, or oxygen. Layer 2 further comprises a flow field 8 with an electrochemically active region. Flow field 8 has channel structures for guiding the fluid, such as a reaction or product medium, along bipolar plate 1. The channel structures of flow field 8 are typically, but not necessarily, configured as parallel elevations.

[0044] The insert 10 is arranged between the flow field 8 and the through-opening 3, 4. The insert 10 is arranged at the through-opening 3, 4 and has a fluid guide structure 12 for guiding the fluid.

[0045] The insert 10 and the layer 2 can be made of the same or different materials. For example, metals such as titanium or stainless steel are possible. Other materials such as alloys are also possible. Additionally or alternatively, the insert 10 can be formed separately from the layer 2 and made from a different material blank than the layer 2. The insert 10 can have a thickness of at most 70%, preferably at most 30% of the thickness of the layer 2. Furthermore, the insert 10 can be firmly connected to the layer 2, preferably by a material-to-material connection. Thus, the insert 10 can be connected to the layer 2 by a welded or adhesive connection. As shown in the Fig. As shown in Figures 1-9, the elevations 14, 24 of the insert 10 face the layer 2 and rest on the layer 2. The layer 2 can have a substantially flat surface in the region of the fluid guide structure 12 of the insert 10, wherein the elevations 14, 24 of the insert 10 rest on the flat surface of the layer 2.

[0046] In the examples of the Fig. 2-9, the insert 10 is arranged at the through-opening 3, 4 and further arranged around the through-opening 3, 4. The insert 10 often encloses the through-opening 3, 4 at least partially, preferably completely.

[0047] In order to clarify the structure of the insert 10, reference is also made to the Fig. 2-10, which show various sub-areas and aspects of the insert 10.

[0048] The fluid guide structure 12 of the insert 10 has a plurality of elevations 14, 24, 34 and is arranged in the direction of fluid flow between the flow field 8 and the through-opening 3, 4. This allows the fluid to flow from the through-opening 4 as an inlet through the elevations 14, 24, 34 of the fluid guide structure 12 to the flow field 8. Furthermore, the fluid can flow from the flow field 8 through the fluid guide structure 12 and between the elevations 14, 24, 34 of the insert 10 to the through-opening 3 as an outlet.

[0049] The fluid guide structure 12 comprises a first region 18 and a second region 19, which are arranged next to one another in the flow direction of the fluid. Optionally, a third region 21 can be provided, which is arranged next to the first region 18 or the second region 19 in the flow direction of the fluid. The regions 18, 19, 21 extend in the flow direction of the fluid from an end of the fluid guide structure 12 facing the through-opening 3, 4 to an end of the fluid guide structure 12 facing the flow field 8. The aforementioned regions 18, 19, 21 differ from one another with regard to their flow cross-sections and / or flow resistances.

[0050] The elevations 14, 24 are each at different distances from one another and / or are arranged with different densities, such that a flow cross-section in the first region 18 is smaller than a flow cross-section in the second region 19 and / or a flow resistance in the first region 18 is greater than a flow resistance in the second region 19. In addition, the elevations 24, 34 can each have different distances from one another and / or are arranged with different densities, such that a flow cross-section in the second region 19 is smaller than a flow cross-section in the third region 21 and / or a flow resistance in the second region 19 is greater than a flow resistance in the third region 21. In the exemplary embodiment shown, the elevations 14, 24, 34 have the same shape in the regions 18, 19, 21. Alternatively, they can also have a different shape in each of the regions 18, 19, 21.

[0051] In addition, the fluid guide structure 12 of the insert 10 has a plurality of passages 20, 30, 40, each extending between adjacent elevations 14, 24, 34 and designed to conduct the fluid along the layer 2. The passages 20 in the first region 18, the passages 30 in the second region 19, and the passages 40 in the third region 21 have different flow cross-sections and / or different flow resistances. Specifically, the flow cross-sections of the passages 40 are larger than those of the passages 30, with the flow cross-sections of the passages 30 in turn being larger than those of the passages 20. In addition, the passages 20, 30, 40 in the various regions 18, 19, 21 each have a different width and / or a different length.

[0052] By using the passages 20, 30, 40 or elevations 14, 24, 34 of the fluid guide structure 12, which vary in terms of flow resistance or flow cross-sections, the flow behavior of the fluid can be specifically influenced. Thus, the fluid flow resistance at the through-opening 3, 4 typically decreases from the corner region 39 toward the center of the through-opening or increases from its center toward the corner regions 39. If the flow resistance of the fluid guide structure 12 is greater in an area adjacent to the center of the through-opening 3, 4, namely the first region 18, than in the second region 19 and the third region 21, the flow distribution and fluid flow through the through-opening 3, 4 can be made more uniform.

[0053] The elevations 14, 24, 34 form depressions 15, 25, 35 on a first side 11 of the insert 10 facing away from layer 2, wherein the depressions 15 in the first region 18, the depressions 25 in the second region 19, and the depressions 35 in the third region 21 each have the same diameter, width, cross-sectional area, and cross-sectional shape. Alternatively, the dimensions mentioned can also differ from one another in the regions 18, 19, 21. Accordingly, the passages 20, 30, 40 form complementarily shaped webs 16, 26, 36 on the first side 11 of the insert 10 facing away from layer 2, which webs have different widths and / or lengths in the regions 18, 19, 21.

[0054] In some embodiments, it is provided that the flow cross sections and / or widths of the passages 20, 30, 40 change continuously in a direction perpendicular to the flow direction of the fluid and preferably decrease towards the center of the passage opening 3, 4 or the fluid guide structure 12, while they remain substantially constant in the flow direction of the fluid.

[0055] Surveys 14, 24, 34 of the Fig. 1-9 and 11 are all designed as elongated webs. Accordingly, the depressions 15, 25, 35 associated with the elevations 14, 24, 34 are designed as channel-shaped grooves. Through the web-shaped elevations 14, 24, 34 and the intermediate passages 20, 30, 40, the fluid guide structure 12 extends in a wave-like manner along the through-opening 3, 4. However, elevations or depressions of other shapes are also conceivable.

[0056] The Fig. Figure 10 shows an alternative embodiment of the insert 10, wherein the elevations 14, 24 are designed as knobs molded into the insert. Fig. 10 shows a plan view of the side of the insert facing layer 2 and arranged on layer 2. The density of the elevations 14 in the first region 18 of the insert 10 is higher than the density of the elevations 24 in the second region 19 of the insert. Specifically, this is achieved by a larger number of nubs. Additionally or alternatively, the nubs in the first region 18 can also be larger than the nubs in the second region, whereby the flow resistance in the first region 18 is greater than in the second region 19, or the flow cross-section in the second region 19 is larger than in the first region 18.

[0057] The channel structures of the flow field 8 are typically, but not necessarily, formed as parallel elevations whose length in the direction of fluid flow is often significantly longer, for example at least 5 times longer, than the length of the elevations 14, 24, 34 of the fluid guide structure 12. The layer 2 often has a bead arrangement 9 molded into the plate material of the layer 2, which partially surrounds the through-opening 3, 4, namely in the region outside the fluid guide structure 12. Together, the bead arrangement 9 and the fluid guide structure 12 surround the through-opening 3, 4. The bead arrangement 9 and the channel structures of the flow field 8 are generally molded into the layer 2 by embossing, deep drawing, or hydroforming and are aligned in the same direction, preferably perpendicular to a plate plane of the layer 2. Thus, the bead arrangement 9 and the channel structures of the flow field 8 are integrated components of the layer 2.The plate plane of layer 2 is an extended flat surface without embossing; the plate plane can, for example, extend adjacent to the insert 10.

[0058] In the Fig. 1, Fig. 3 and Fig. 9, the through-openings 3, 4 are rectangular with rounded corners. The through-opening 3, 4 has an edge 7, which delimits an edge region 17 of the layer 2 around the through-opening 3, 4, and a longitudinal direction of the feedthroughs 20, 30 is aligned substantially perpendicular to the edge 7 or a nearest region of the edge 7. In a corner region 39 of the through-opening 3, 4, a longitudinal direction of feedthroughs 30, 40 is aligned at an angle between 0° and 90° to a nearest region of the edge 7. The fluid guide structure 12 adjoins the through-opening 3, 4, more precisely, to the edge region 17 of the layer 2.

[0059] In the example of Fig. 1, a total of four inserts 10 are shown, each of which is arranged at a through-opening 3, 4 of the layer. The number of inserts 10 can be smaller than the number of through-openings 3, 4. In the embodiments of Fig. 3 and Fig. 9, at least two adjacent or adjacent through-openings 3, 4 share an insert 10. In this case, a single insert 10 is arranged at at least two through-openings 3, 4, wherein the insert has a fluid guiding structure 12 for both through-openings 3, 4.

[0060] It can be provided that the insert 10 extends between the at least two through openings 3; 4. In the Fig. 3 and Fig. 9, the insert part 10 extends in a frame-shaped, figure-8-shaped or eyeglass-shaped manner along the edges 7 of the two through openings 3.

[0061] The bead arrangement 9 can run between two adjacent through-openings 3, 4. The term bead or bead arrangement 9 is used here in particular to describe the bead shape; it can be connected to an element that has only a minimal or a significant elastic component, which depends in particular on the selected material and its material thickness. For example, the insert 10 can be arranged on the bead roof of the bead arrangement 9. One end face of the bead arrangement 9 faces the third region 21 of the fluid guide structure 12, wherein a fluid channel 37 is formed between the end face of the bead arrangement 9 and the elevations 34 of the third region 21, which fluid channel extends at an angle, e.g., perpendicular, to the elevations 34. The fluid channel 37 fluidically connects the through-opening 3, 4 to the feedthroughs 40 in the third region 21 of the fluid guide structure 12. In the Fig. 7, the fluid flow direction is indicated by arrows. As can be seen from the Fig. 7, the fluid channel 37 and the passages 40 in the third region 21 allow fluid flow in the region of layer 2 between the through-openings 3, 4, so that fluid can also flow there between the through-opening 3, 4 and the flow field 8. In the Fig. 8 also shows that the elevations 34 and the penetrations 40 in the third area 21 are longer than the elevations 24 and the penetrations 30 in the second area 19.

[0062] Typically, the bipolar plate 1 comprises an elastomer seal 22 for sealing the through-opening 3, 4, which is arranged on a first side 11 of the insert 10 facing away from the layer 2. The elastomer seal 22 can preferably be arranged in the recesses 15, 25 of the insert 10 or can be injection-molded onto the insert 10 there. The elastomer seal 22 can be designed such that it forms a flat surface on the side facing away from the layer 2. The elastomer seal 22 can be arranged as in Fig. 11, extend only over a portion of the first, second, and possibly third regions, particularly with respect to the fluid flow direction. However, it can also cover the entire region provided with elevations 14, 24, 34 or extend beyond it. The combination of insert 10 with elastomer seal 22 allows overlying components in this region of the fluid guide structure 12 to be supported, which improves the seal with the mating components such as the MEA, cell frame, etc. This ensures the main sealing function and increases the service life.

[0063] On the rear side of the bipolar plate 1, i.e. a side of the bipolar plate 1 facing away from the insert part 10, the bead arrangement 9 can form a receptacle for a further sealing element, for example an elastomeric sealing element 28.

[0064] Analogous to Fig.12, the bipolar plate 1 can be part of an arrangement for an electrochemical system. In addition to the bipolar plate 1, the arrangement comprises a first cell frame 42 and / or a membrane electrode assembly 40 and / or a second cell frame 44. The insert 10 is then arranged between the first cell frame 42 and layer 2 and / or between the membrane electrode assembly 40 and layer 2 and / or between the second cell frame 44 and layer 2. An electrochemical system according to the present document then comprises a plurality of stacked bipolar plates 1 and / or a plurality of the stacked assemblies. List of reference symbols: 1 bipolar plate 1' bipolar plate 2 layers 3 passage opening 4 passage opening 5 passage opening 6 passage opening 7 edge 8 Flow field 9 Bead arrangement 10 insert 11 first page 12 Fluid guide structure 13 second page 14 Survey in the first area 15 Deepening in the first area 16 Bridge in the first area 17 Marginal area 18 first area 19 second area 20 Implementation in the first area 21 third area 22 Elastomer seal 24 Survey in the second area 25 Deepening in the second area 26 Bridge in the second area 28 elastomeric sealing element 30 Implementation in the second area 34 Survey in the third area 35 Deepening in the third area 36 Bridge in the third area 37 Fluid channel 39 Corner area 40 Implementation in the third area 41 Media diffusion structure 42 cell frames 43 Media diffusion structure 44 cell frames 45 Sealing layer 46 Fluid passage opening 47 Fluid passage opening 48 positioning hole 49 hydrogen distribution channels 50 hydrogen through holes 60 membrane electrode array 100 electrochemical cells QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 202 775 A1

[0008] DE 10 2020 215 014 A1

[0008]

Claims

[1] Bipolar plate (1) for an electrochemical system, in particular for an electrolyzer, comprising at least one layer (2) and at least one insert (10), the layer (2) comprising - at least one through-opening (3, 4) as inlet or outlet for a fluid, - a flow field (8) with an electrochemically active region, wherein the insert part (10) is arranged at the through-opening (3, 4) and comprises a fluid guide structure (12) for guiding the fluid, wherein the fluid guide structure (12) of the insert part (10) has a plurality of elevations (14, 24) and is arranged in the flow direction of the fluid between the flow field (8) and the through-opening (3, 4), so that the fluid is guided from the through-opening (3, 4) through the fluid guide structure (12) between the elevations (14, 24) to the flow field (8) or vice versa, wherein the fluid guide structure (12) comprises a first region (18) and a second region (19) which are arranged next to one another in the flow direction of the fluid, wherein the elevations (14, 24) in the first region (18) and in the second region (19) each have different distances from one another and / or are arranged with different densities and / or are shaped differently, so that a flow cross-section in the first region (18) is smaller than a flow cross-section in the second region (19) and / or a flow resistance in the first region (18) is greater than a flow resistance in the second region (19). [2] Separator plate according to claim 1, wherein the fluid guide structure (12) of the insert part (10) has a plurality of passages (20, 30) which each extend between adjacent elevations (14, 24) and are designed to guide the fluid along the layer (2), wherein at least two of the passages (20, 30) have a different flow cross-section and / or a different flow resistance and / or a different width and / or a different length. [3] Bipolar plate (1) according to the preceding claim, wherein the flow cross-sections and / or widths of the passages (20, 30) change in a direction perpendicular to the flow direction of the fluid and / or remain constant in the flow direction of the fluid and preferably decrease towards the center of the fluid guide structure (12). [4] Bipolar plate (1) according to one of the preceding claims, wherein the elevations (14, 24) form depressions (15, 25), in particular channel-shaped grooves, on a first side (11) of the insert part (10) facing away from the layer (2), wherein the depressions (15, 25) in the first region (18) and in the second region (19) each have the same diameter and / or a different diameter and / or the same width and / or a different width and / or the same cross-sectional content and / or a different cross-sectional content and / or the same cross-sectional shape and / or a different cross-sectional shape and / or the same length and / or a different length. [5] Bipolar plate (1) according to one of the preceding claims, wherein the elevations (14, 24) are knob-shaped, wherein a density of the knob-shaped elevations (14, 24) in the first region (18) is greater than in the second region (19). [6] Bipolar plate (1) according to one of the preceding claims, wherein the insert part (10) is firmly connected to the layer (2), preferably by a material connection. [7] Bipolar plate (1) according to one of the preceding claims, wherein the elevations (14, 24) of the insert part (10) face the layer (2) and in particular rest on the layer (2). [8] Bipolar plate (1) according to one of the preceding claims, wherein the insert part (10) is arranged around the through-opening (3, 4) and at least partially encloses the through-opening (3, 4). [9] Bipolar plate (1) according to one of the preceding claims, wherein the layer (2) has a substantially flat surface in the region of the fluid guide structure (12) of the insert part (10), and the elevations (14, 24) of the insert part (10) rest on the flat surface of the layer (2). [10] Bipolar plate (1) according to one of the preceding claims, wherein the through-opening (3, 4) has an edge (7), and a longitudinal direction of first passages (20, 30) is aligned substantially perpendicular to a nearest region of the edge (7) and / or a longitudinal direction of second passages (20, 30) is aligned at an angle between 0° and 90° to a nearest region of the edge. [11] Bipolar plate (1) according to one of the preceding claims, wherein the layer (2) has a bead arrangement (9) formed into the layer (2) which partially surrounds the through opening (3, 4). [12] Bipolar plate (1) according to the preceding claim, wherein the layer (2) has at least two through-openings (3, 4) arranged next to one another, wherein the bead arrangement (9) runs between the through-openings (3, 4), wherein the insert part (10) is arranged on the at least two through-openings (3, 4) and has a fluid guide structure (12) for both through-openings (3, 4). [13] Bipolar plate (1) according to the preceding claim, wherein the insert part (10) extends between the at least two through-openings (3; 4) and is arranged on the bead arrangement (9), and preferably extends in a frame-shaped, figure-8-shaped or spectacle-shaped manner along the edges (7) of the two through-openings (3, 4). [14] Bipolar plate (1) according to one of the two preceding claims, wherein both through-openings (3; 4) are designed as fluid inlet or fluid outlet. [15] Bipolar plate (1) according to one of the preceding claims, comprising an elastomer seal (22) for sealing the through-opening (3, 4), which is arranged on a first side (11) of the insert part (10) facing away from the layer (2). [16] Bipolar plate (1) according to the preceding claim, wherein the elevations (14, 24) on the first side (11) of the insert part (10) form depressions (15, 25), in particular channel-shaped grooves, and the elastomer seal (22) is arranged at least in the depressions (15, 25). [17] Bipolar plate (1) according to one of the preceding claims, wherein a thickness of the insert (10) is at most 70%, preferably at most 30% of a thickness of the layer (2). [18] Bipolar plate (1) for an electrochemical system, in particular an electrolyzer, comprising at least one layer (2) and at least one insert, the layer (2) comprising - at least one through-opening (3, 4) as inlet or outlet for a fluid, - a flow field (8) with an electrochemically active region, wherein the insert part (10) is arranged at the through-opening (3, 4) and comprises a fluid guide structure (12) for guiding the fluid, wherein the fluid guide structure (12) of the insert part (10) is arranged in the flow direction of the fluid between the flow field (8) and the through-opening (3, 4), so that the fluid is guided from the through-opening (3, 4) through the fluid guide structure (12) to the flow field (8) or vice versa, wherein the fluid guide structure (12) of the insert (10) has a plurality of elevations (14, 24) and passages (20, 30), wherein the passages (20, 30) each extend between adjacent elevations (14, 24) and are designed to guide the fluid along the layer (2), wherein at least two of the passages (20, 30) have a different flow cross-section and / or a different flow resistance and / or a different width and / or a different length. [19] Arrangement for an electrochemical system, comprising a bipolar plate (1) according to one of the preceding claims, wherein the arrangement comprises a first cell frame and / or a membrane electrode unit and / or a second cell frame, and wherein the insert part (10) is arranged between the first cell frame and the layer (2) and / or between the membrane electrode unit and the layer (2) and / or between the second cell frame and the layer (2). [20] Electrochemical system, in particular electrolyzer, comprising a plurality of stacked bipolar plates (1) according to one of claims 1 to 18 and / or a plurality of stacked arrangements according to the preceding claim.

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