Separator plate for an electrochemical system

Abstract

The invention relates to a separator plate for an electrochemical system. The electrochemical system can in particular be a fuel cell system, an electrochemical compressor, an electrolyzer or a redox flow battery. The invention also discloses an electrochemical system comprising multiple separator plates of this type.

Description

[0001] for an electrochemical m

[0002] The invention relates to a separator plate for an electrochemical system. The electrochemical system can, in particular, be a fuel cell system, an electrochemical compressor, an electrolyzer, or a redox flow battery. An electrochemical system comprising a plurality of such separator plates is also disclosed.

[0003] Known electrochemical systems of this type typically comprise a stack of electrochemical cells, each separated from one another by separator plates. In the context of such stacks, the separator plates are also referred to as bipolar plates. The separator plates can serve, for example, to electrically contact the electrodes of the individual electrochemical cells (e.g., fuel cells) and / or to electrically connect neighboring cells (series connection of the cells). Typically, the separator plates are formed from two individual plates, in particular joined together. The individual plates can be joined together in a materially bonded manner, e.g., by one or more welded joints, in particular by one or more laser-welded joints.

[0004] The separator plates or the individual plates can each have or form structures that are designed, for example, to supply the electrochemical cells arranged between adjacent separator plates with one or more media and / or to transport reaction products away. In particular, these structures can be used to guide a cooling fluid through a space between the individual plates of a separator plate. The structures can, for example, comprise sequences of webs and channels. The media can therefore be fuels (e.g., hydrogen or methanol), reaction gases (e.g., air or oxygen), or coolants. In the context of this disclosure, the terms medium and fluid can be used synonymously.

[0005] Furthermore, the separator plates usually each have at least one through-opening through which the media can be guided to or away from the electrochemical cells or membrane electrode assemblies (MEAs) arranged between adjacent separator plates of the stack.

[0006] From such a through-opening, a respective fluid is guided by means of the structures described above into a respective first distribution area and from there into a flow field opposite the active area of ​​the cell or MEA. After flowing through the active area, the fluid is fed back to an outlet through-opening via a second distribution area, also called a collection area. An example of this can be found in DE 20 2016 107 302 U1.

[0007] It is known to conduct a first fluid, e.g., a fuel, on a first outer side of the separator plate, ie, an outer side of a first individual plate, and to conduct a second fluid, e.g., a reaction gas, on a second outer side of the separator plate facing away from the first outer side, ie, an outer side of a second individual plate. In contrast, a cooling fluid is usually conducted in an interior space defined by the inner sides of the individual plates.

[0008] The fluid-conducting structures on the respective outer sides of the individual plates form complementary structures on their inner sides, which guide the cooling fluid. However, it has been shown that with previous solutions, the cooling fluid flow is sometimes only possible with increased flow resistance. This correspondingly reduces the cooling capacity of the separator plate and can therefore limit the performance of the electrochemical system.

[0009] An object of the present invention is therefore to improve the cooling capacity of a separator plate and thus a performance of an electrochemical system having a plurality of such separator plates.

[0010] This object is achieved by the subject matter of claim 1. Advantageous further developments are specified in the dependent claims as well as in this description and in the figures.

[0011] Accordingly, a separator plate for an electrochemical system is proposed, wherein the separator plate comprises:

[0012] - a first individual plate and a second individual plate which define an interior of the separator plate with a cooling fluid distribution structure, - a first overlap region in which a first section of the cooling fluid distribution structure and a first section of a first fluid distribution region overlap each other, wherein the first fluid distribution region is formed on an outer side of the first individual plate,

[0013] - a second overlap region in which a second section of the cooling fluid distribution structure, a second section of the first fluid distribution region, and a section of a second fluid distribution region overlap one another, wherein the second fluid distribution region is formed on an outer side of the second individual plate, wherein the cooling fluid distribution structure has a first web-channel structure which has a plurality of webs and channels formed between each two webs and which forms a complementarily shaped web-channel structure of the first fluid distribution region, wherein the first web-channel structure has at least one change of direction in a transition region from the first to the second overlap region; wherein the second individual plate is formed opposite this change of direction so as to deviate from the first web-channel structure.

[0014] The first single plate may form a cathode plate and / or may carry oxygen or air as the first fluid.

[0015] The second single plate can form an anode plate and / or can carry hydrogen as the second fluid.

[0016] In the first overlap region, preferably only the first and third fluids are conducted without mixing. In the second overlap region, preferably the first to third fluids are conducted in separate flow spaces.

[0017] Likewise, the overlap areas can define overlaps that also exist in an orthogonal projection of the respective sections, structures, and features onto a plane surface of the separator plate. An overlap can mean that the corresponding sections, structures, and features are intersected by a common axis that runs perpendicular to the plane surface of the separator plate.

[0018] By providing at least one change in direction, flow resistance during a transition of the cooling fluid from the first to the second overlap region can be reduced compared to a variant without a change in direction. Thus, on its way through the first overlap region, the cooling fluid typically flows, and also according to embodiments of this disclosure, along a boundary line that extends in the transition region between the first and second overlap regions. A transition over this boundary line into the second overlap region may require a deflection, so that the cooling fluid flows at a larger angle to this boundary line, for example, substantially orthogonal thereto. This angle and / or generally the flow guidance during this transition can be significantly predetermined by the first web-channel structure on the inside of the first individual plate.Without a change in direction of the first web-channel structure, the flow guidance at this transition would correspond to a sharp-edged bend, which would mean increased flow resistance.

[0019] In contrast to known and typically completely rectilinear web-channel structures, a change in direction within the web-channel structure is proposed here, specifically in the transition region. This change in direction can be implemented in such a way that the flow resistance of the cooling fluid at the transition from the first to the second overlap region is reduced compared to a variant without a change in direction. For example, the curve radius of the change in flow direction can be increased, which enables a more uniform flow pattern with less resistance. Thus, the overall cooling fluid flow through the cooling fluid distribution structure can be achieved with lower flow resistance.

[0020] A further factor reducing flow resistance is a local enlargement of the flow cross-section for the cooling fluid in the transition region, which is made possible according to the invention. This enlargement is made possible by the change in direction. This means that more space is available in a direction transverse to the direction of the webs and channels. In the present case, this is preferably used to widen the channels of the first web-channel structure in the transition region. On the outer side of the first individual plate, this can result in an increased distance between adjacent channels of the complementarily shaped web-channel structure there. Alternatively, the webs of the first web-channel structure could also be widened in the transition region. The additional installation space could also be divided between webs and channels.Furthermore, it was recognized that the change in direction of the web-channel structure does not significantly impair the fluid flow within the first fluid distribution region. Furthermore, the fact that the second individual plate is designed opposite the change in direction and deviates from the first web-channel structure provides a further degree of freedom for improving the fluid transition from the first to the second overlap region. For example, the second individual plate can have a step, explained below, opposite the transition region. By means of the step, the cooling fluid can be transferred into the second overlap region in a targeted manner and with an optional change of plane, explained later.

[0021] Thus, an optional development provides that the second individual plate, opposite the change in direction, has a step extending in the direction of the first individual plate, in particular wherein the step is formed along a longitudinal axis that runs at an angle (in particular orthogonally) to a respective longitudinal axis of the channels and webs of the first web-channel structure. For example, the longitudinal axes of the step and of the webs and channels can run substantially transversely or at an angle of at least 60° to one another (relative to a smallest intersection angle between the longitudinal axes). The step can at least partially delimit the first section of the cooling fluid distribution structure.

[0022] The step preferably results in the second individual plate running immediately adjacent to the step in the second overlap region in the plane of the second individual plate, while immediately adjacent to the step in the first overlap region it is spaced from this plane of the plane.

[0023] Additionally or alternatively, the step may extend along a boundary line between the first and second overlapping areas and in particular along a predominant length portion or even along the entire length of this boundary line.

[0024] In general, it should be noted that the channels and webs can be elongated and their main extension can run along a corresponding longitudinal axis. However, this longitudinal axis is not necessarily straight, particularly due to the change in direction disclosed here in the transition region, but can, for example, be curved once or multiple times at least in sections. A change in the plane of the cooling fluid guidance can occur when transitioning from the first to the second overlap region. In particular, a change in flow planes of the cooling fluid distribution structure can occur in such a way that, in the first overlap region, a flow cross-section of the cooling fluid distribution structure extends significantly into a flow space for the cooling fluid spanned by the second individual plate.A section of the first individual plate within the first overlap area, however, can lie to a greater extent in the plane of the first individual plate, thus providing a comparatively insignificant and / or smaller flow space for the cooling fluid. In the second overlap area, however, the flow space can also be spanned by the first individual plate, at least to a significant extent (e.g., approximately the same size).

[0025] In a manner known per se, the plane of the flat surface of a respective individual plate can be defined, for example, by an edge of the individual plate or by those flat areas of the individual plate that are not deformed as a result of an embossing or deep-drawing process to form the web-channel structures or beads described herein. On the one hand, the planes of the flat surface can run in the neutral fibers of the corresponding sections of the plates; on the other hand, it is also possible to consider the surfaces of the relevant sections of the plates as planes of the flat surface. However, with the latter approach, it is important to note that when considering distances, etc., the material thickness of only one of two plates under consideration is taken into account.

[0026] In a further optional variant a), the webs and channels of the first web-channel structure each have a first segment that extends in the first overlap region and a second segment that extends in the transition region, wherein the first and second segments are angled relative to one another. This angulation can correspond to and / or result in the change in direction in the transition region. The first and second segments can merge directly into one another. The first segment can extend from the edge of the transition region towards and optionally up to a through-opening that is fluidically connected to the first fluid distribution region and / or up to openings explained below that are fluidically connected to this through-opening.

[0027] Alternatively or additionally, in a further variant b), the webs and channels of the first web-channel structure can each have a third segment extending into the second overlap region and a second segment extending into the transition region, wherein the second and third segments are angled relative to one another. This angle can also correspond to or result from the change in direction in the transition region. The third segment can extend from the edge of the transition region to a flow field of the first individual plate.

[0028] Particularly when both variants a) and b) above are provided, a multiple change of direction can occur in the transition area. This allows the flow resistance for the cooling fluid to be reduced particularly effectively compared to a variant without a change of direction. In particular, this enables a particularly pronounced increase in the flow cross-sections for the cooling fluid in the transition area, which can significantly reduce pressure losses of the cooling fluid in the transition area.

[0029] It can further be provided that the first and third segments (but preferably not the second segment) of a respective web and channel run parallel to each other. In this case, the change in direction in the transition area can, for example, occur in such a way that an initial change in direction is canceled again in order to establish parallelism between the first and third segments.

[0030] As an alternative to parallelism, the first and third segments can run at an angle relative to one another that is smaller than a respective angle between the second segment and one of the first and third segments. For example, an angle between the first and second segment and an angle between the second and third segment can each be more than 90°, e.g., more than 120° or more than 140°. An angle at which the first and third segments run relative to one another, on the other hand, can be smaller than these respective angles, e.g., less than half or less than a quarter as large and / or less than 45°.

[0031] In particular, it can be provided that the angle by which the first and second segments are angled relative to each other is between 90° and 170° and / or the angle by which the second and third segments are angled relative to each other is between 90° and 170°. In each case, the largest possible cutting angle that can be entered can be considered.

[0032] According to a further aspect, the first segment and the second segment merge into one another, in particular directly into one another and / or without interruption by a fluid connection formed by these segments. Alternatively or additionally, the separator plate is designed according to the above variant b), and the second segment and the third segment merge into one another, in particular directly into one another and / or without interruption by a fluid connection formed by these segments.

[0033] A further embodiment comprises the first segment being at least twice as long as the second segment. Alternatively or additionally, the separator plate is designed according to variant b) above, and the third segment is at least twice as long as the second segment. In both cases, the second segment is deliberately designed to be short in order to limit the associated change in direction locally and / or to the transition region. This enables the aforementioned less sharp-edged deflection of the cooling fluid guided on the inside, as well as a local or section-wise enlargement of flow cross-sections in the transition region.

[0034] The lower limit of the above length ratios can, for example (and in particular only) be present in edge regions of the first fluid distribution region, in which the length of the webs and channels is significantly reduced compared to an average length of the webs and channels in the fluid distribution region. Accordingly, the above length ratios can be significantly different in a large part of the area of ​​the first fluid distribution region and in particular in central regions thereof, in particular in such a way that the first and / or third segment is significantly longer than the second segment (for example, at least six times as long). In summary, the first and / or third segment can be at least six times longer than the second segment, in particular at half the width of the first fluid distribution region.This width dimension can, for example, be orthogonal to a main flow axis of a flow field that is fluidly connected to the first fluid distribution region.

[0035] The flow field can be characterized, for example, in that all of the webs and channels encompassed thereby are rectilinear and run parallel to one another and parallel to the main flow direction. Alternatively, the webs and channels of the flow field could also be wave-shaped and run alongside one another with a similar wave shape and along a main flow direction of the flow field. The wave shape can oscillate uniformly around the main flow axis and / or the main flow axis can define a central axis of the wave shape around which it oscillates in a wave-like manner. Additionally or alternatively, the flow field can be characterized in that it lies within an MEA reinforcement edge, at least with respect to a direction perpendicular to the flow field's main flow axis, and in particular is surrounded and / or framed by this edge at least in sections.However, the flow field itself is not opposed to the MEA reinforcement edge, but rather to the actual active region of the MEA, particularly in the form of its electrolyte membrane. Reference is made to DE 20 2020 106 459 U1 as an example, and in particular to Figure 3B, which shows an MEA with a reinforcement edge framing an active region of the MEA. However, the situation may be different with regard to the less deeply formed region associated with the flow field, where the MEA reinforcement edge and the GDL overlap.

[0036] Alternatively or additionally, the second segment may have a length that corresponds to one to seven times, preferably one and a half times to five times, a channel width of the channels of the first web-channel structure.

[0037] The channel width can extend transversely to a longitudinal axis of the channel. In particular, the channel width can extend between the highest points of the webs closest to one another, with respect to a plane of the separator plate (and / or the first individual plate), between which a respective channel is arranged and / or enclosed.

[0038] According to a further embodiment, the first segment and the third segment have the same flow cross-section. Alternatively, any deviations in the flow cross-sections of these segments can be no more than 20% or no more than 10%. Due to the small deviation or even identity of the flow cross-sections, uniform fluid guidance can occur on both the inside and the outside of the first individual plate. This advantageously contributes to reducing flow resistance. The second segment, on the other hand, can have a larger flow cross-section in the transition region and in particular limited to this region compared to the first and / or third segment. This increase can, for example, be at least 20% or at least 50%.

[0039] A further development provides that the first and / or third segment is essentially or completely rectilinear. A substantially rectilinear extension can be understood as extensions with a slight curvature and / or curvature present only in sections. In particular, the first and / or third segment are each essentially or completely rectilinear, at least over a length corresponding to the length of the second segment.

[0040] In a further development, the first fluid distribution region is fluidly connected to a first flow field of the separator plate, and the second fluid distribution region is fluidly connected to a second flow field of the separator plate. In particular, the first flow field is fluidly connected to a first through-opening formed in the separator plate via the first fluid distribution region, the second flow field is fluidly connected to a second through-opening formed in the separator plate via the second fluid distribution region, and the cooling fluid distribution structure is fluidly connected to a third through-opening formed in the separator plate.

[0041] According to one embodiment, a change of flow planes of the cooling fluid distribution structure takes place in the transition region in such a way that in the first overlap region, a flow cross-section of the cooling fluid distribution structure extends primarily in a flow space spanned by the second individual plate, and in the second overlap region, a flow cross-section of the cooling fluid distribution structure extends primarily in a flow space spanned by the first individual plate. In the complementary regions, i.e., in the flow space spanned by the second individual plate in the first overlap region and in the flow space spanned by the first individual plate in the second overlap region, cooling fluid is present between the individual plates; however, this either does not flow or flows only to a significantly lesser extent than in the aforementioned flow spaces.

[0042] The invention is explained below with reference to the accompanying schematic figures. The same reference numerals may be used throughout the figures for similar or equivalent features.

[0043] Figure 1 shows a perspective view of an electrochemical system with a plurality of stacked separator plates with membrane electrode units arranged between them.

[0044] Figure 2 shows a perspective view of two separator plates of a system similar to Figure 1 with a membrane electrode assembly (MEA) arranged between the separator plates. Figure 3 shows a highly simplified schematic representation of a coolant guide within a separator plate, which is designed according to a first embodiment of this disclosure.

[0045] Figure 4 shows a perspective partial view of the separator plate of the first embodiment in the region of a first fluid distribution region of a first individual plate, in particular cathode plate, of the separator plate.

[0046] Figure 5 shows an enlarged detail from Fig. 4.

[0047] Figure 6 shows a perspective partial view of a separator plate according to a further embodiment in the region of a second fluid distribution region of a second individual plate, in particular anode plate, of the separator plate.

[0048] Figure 7 shows a schematic simplified view of the partial view of Figure 4.

[0049] Figure 8 shows a further schematically simplified representation of a coolant guide within a separator plate.

[0050] Figure 9 shows a partial view analogous to Fig. 4 in transparent form with several sectional planes.

[0051] Figures 10-12 each show sectional views according to one of the sectional planes of Figure 9.

[0052] Figure 1 shows an electrochemical system 1 of the type proposed here, comprising a plurality of identical metallic separator plates 2 (or bipolar plates). These are arranged in a stack 6 and stacked along a z-direction 7. The separator plates 2 of the stack 6 are clamped between two end plates 3, 4. The z-direction 7 is also referred to as the stacking direction. In the present example, the system 1 is a fuel cell stack. Each two adjacent separator plates 2 of the stack 6 enclose an electrochemical cell between them, which serves, for example, to convert chemical energy into electrical energy. To form the electrochemical cells of the system 1, a membrane electrode assembly (MEA) 10 is arranged between each adjacent separator plates 2 of the stack 6 (see Figure 2 below). The MEAs typically each contain at least one membrane, e.g., an electrolyte membrane.Furthermore, a gas diffusion layer (GDL) can be arranged on one or both surfaces of the MEA.

[0053] In alternative embodiments, system 1 can also be designed as an electrolyzer, compressor, or redox flow battery. Separator plates can also be used in these electrochemical systems. The structure of these separator plates can correspond to the structure of the separator plates 2 explained in more detail here, even if the media flowing onto or through the separator plates in an electrolyzer, an electrochemical compressor, or a redox flow battery can differ from the media used in a fuel cell system.

[0054] The z-axis 7, together with an x-axis 8 and a y-axis 9, spans a right-handed Cartesian coordinate system. The separator plates 2 each define a plate plane, wherein the plate planes of the separator plates 2 are each aligned parallel to the xy-plane and thus perpendicular to the stacking direction (z-axis 7). The end plate 4 has a plurality of media connections 5 through which media can be supplied to the system 1 and through which media can be removed from the system 1. These media that can be supplied to the system 1 and removed from the system 1 can 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 fuels, or a cooling fluid such as water and / or glycol.

[0055] Figure 2 shows a perspective view of two adjacent separator plates 2 or bipolar plates that may be comprised of an electrochemical system of the type of system 1 shown in Figure 1. The separator plates 2 correspond to an example from the prior art. However, the properties and features explained below with reference to them may also apply to the separator plates 2 according to the invention disclosed here or be provided in them, unless otherwise stated or apparent.

[0056] Fig. 2 also shows a known membrane electrode assembly (MEA) 10 arranged between these adjacent separator plates 2, wherein the MEA 10 in Figure 2 is largely concealed by the separator plate 2 facing the viewer. The separator plate 2 is formed from two materially joined individual plates 2a, 2b, of which in Figure 2 only the individual plate 2a facing the viewer is visible, which conceals the other individual plate 2b. The individual plates 2a, 2b can each be made of a metal sheet, e.g., a stainless steel sheet. The individual plates 2a, 2b can, for example, be welded to one another, e.g., by laser welding, or can be connected only when the stack is stacked. In particular, the design of fluid-conducting structures on the outer side of the individual plate 2a facing the viewer can deviate from the inventive structures of the further Figures 3 to 12 below.

[0057] The individual plates 2a, 2b have aligned through-openings, which form through-openings 11a-c of the separator plate 2. When a plurality of separator plates 2 are stacked, the through-openings 11a-c form lines that extend through the stack 6 in the stacking direction 7 (see Figure 1). Typically, each of the lines formed by the through-openings 11a-c is in fluid communication with one of the ports 5 in the end plate 4 of the system 1. For example, a cooling fluid can be introduced into the stack 6 or discharged from the stack 6 via the lines formed by the through-openings 11a. The lines formed by the through-openings 11b, 11c, on the other hand, can be designed to supply the electrochemical cells of the fuel cell stack of the system 1 with fuel and reaction gas, and to discharge the reaction products from the stack 6.

[0058] To seal the through-openings 11a-c from the interior of the stack 6 and from the environment, the individual plate 2a facing the viewer has sealing arrangements in the form of sealing beads 12a-c. These are arranged around the through-openings 11a-c and completely enclose the through-openings 11a-c. The second individual plate 2b also has corresponding sealing beads 12a-c on the rear side of the separator plate 2 facing away from the viewer in Figure 2 for sealing the through-openings 11a-c (not shown). Alternative sealing systems, such as elastomer seals, can also be used.

[0059] Adjacent to the electrochemically active region 18 of the MEA, the individual plate 2a facing the viewer has, on its outer side facing the viewer, a flow field 17a with structures for guiding a reaction medium along the outer side of the individual plate 2a. These structures are designed in Figure 2 in the form of a plurality of webs and channels running between the webs and delimited by the webs. On the outer side of the separator plate 2 facing the viewer, the individual plate 2a facing the viewer also has two distribution regions 20. The distribution regions 20 each comprise structures which are designed to distribute a medium introduced from a first of the two through-openings 11b into one of the distribution regions 20 by means of the flow field 17a over the active region 18 or to guide a medium introduced from the active region 18 orto collect or concentrate the medium flowing from the flow field 17a to the second of the through-openings 11b. In the latter case, the collecting distribution region 20 can also be referred to as a collection region. The fluid-conducting structures of the distribution regions 20 are also represented in Figure 2 by webs and channels extending between the webs and delimited by the webs.

[0060] Without this being specifically shown in Figure 2, a cooling fluid distribution structure 19 formed and / or enclosed between the individual plates 2a, 2b also has distribution regions that overlap with the distribution regions 20 of the individual plates 2a, 2b. This cooling fluid distribution structure 19 is fluidically connected to or encompasses a flow field, wherein this flow field overlaps with the flow fields 17a, b of the outer sides of the individual plates 2a, 2b or is enclosed between them. The web-channel structures on the outer sides of the individual plates 2a, 2b form complementarily shaped web-channel structures on the corresponding inner sides and thus complementarily shaped web-channel structures of the cooling fluid distribution structure 19 (see also Figures 10-12 discussed below).

[0061] The two through-openings 11b, or the lines formed by the through-openings 11b through the plate stack of system 1, are each fluidically connected to one another via passages 13b in sealing beads 12b, via the distribution structures of the distribution regions 20, and via the flow field 17a of the individual plate 2a facing the viewer of Figure 2. This individual plate 2a is a second individual plate 2a within the meaning of this disclosure. A fluid guided along the outer side of this individual plate 2a is preferably hydrogen, so that the through-openings 11b are preferably hydrogen through-openings 11b. This results in particular from the smallest cross-section of the hydrogen through-openings 11b compared to the other through-openings 11a, 11c.

[0062] In an analogous manner, the two through-openings 11c or the lines formed by the through-openings 11c through the plate stack of the system 1 are each in fluid communication with one another via corresponding bead feedthroughs 13c, via corresponding distribution structures, and via a corresponding flow field on an outer side of the individual plate 2b facing away from the viewer of Figure 2. This individual plate 2b is a first individual plate 2b within the meaning of this disclosure. A fluid guided along the outer side of this individual plate 2b is preferably air or oxygen, so that the through-openings 11c are preferably air or oxygen through-openings 11c. This results in particular from the largest cross-section of the air or oxygen through-openings 11c compared to the other through-openings 11a, 11b.

[0063] The through-openings 11a, or the lines formed by the through-openings 11a through the plate stack of the system 1, are each fluidly connected to one another via a cavity enclosed or surrounded by the individual plates 2a, 2b, which forms the cooling fluid distribution structure 19. This is achieved, for example, again via feedthroughs 13a. This cavity or this cooling fluid distribution structure 19 serves to guide a cooling fluid through the separator plate 2, in particular for cooling the electrochemically active region 18 of the MEA. The through-openings 11a are therefore cooling fluid through-openings, which is particularly evident from their average cross-sectional size compared to the other through-openings 11b, 11c.

[0064] In the following, fluid guides in a separator plate 2 according to one embodiment of the invention are explained with reference to Figures 3 to 12. The separator plate 2 is designed in principle analogous to Figures 1 and 2 and additionally has the features and special features explained below with regard to the fluid guides. In Figures 3 and 4 as well as 6 to 9, an area of ​​a separator plate 2 outlined in dashed lines in Fig. 2 is considered, although reference is also made in part to the outer side of the first individual plate 2b facing away from the viewer or to the internal cooling fluid structure.

[0065] Figure 3 shows a highly simplified schematic representation of a coolant guide within a separator plate 2 according to the invention. More precisely, an extension of the cooling fluid distribution structure 19 is schematically shown in an area analogous to the dashed area in Figure 2. The illustrated area corresponds to a distribution area of ​​the cooling fluid distribution structure 19, i.e., an electrochemically non-active area. It is understood that the cooling fluid distribution structure 19 is not visible from the outside when the separator plate 2 is joined together due to its position between the individual plates 2a, 2b.

[0066] The perspective of Figure 3 is rotated relative to Figure 2, as can be seen from the schematically illustrated positions of the through-openings 11a-c. Furthermore, the arrangement of these through-openings 11a-c corresponds to a viewing angle on the outside of the first individual plate 2b from Figure 2. The through-openings 11a-c again have the size ratios explained above.

[0067] The cooling fluid distribution structure 19 is delimited by the mutually facing inner sides of the individual plates 2a, 2b. More precisely, opposing regions of these inner sides are spaced apart from one another to varying degrees in sections, so that fluid-absorbing free spaces (i.e., flow spaces) are formed in the cooling fluid distribution structure 19. The cooling fluid distribution structure 19 also has web-channel structures (not shown), which form complementarily shaped web-channel structures on the outer sides of the individual plates 2a, 2b, as explained above with reference to Figure 2. In the following, webs or channels on the outer side of the first individual plate 2b are referred to as 27b and 29b, webs or channels on the outer side of the second individual plate as 27a and 29a, and webs or channels on the inner sides of the individual plates as 27c and 29c. 27 and 29 generally refer to bridges and channels, respectively.

[0068] The cooling fluid distribution structure 19 has three sections A, B, and C. The first section A and the third section C, which is merely optional, are each fluidly connected to the cooling fluid passage 11a. If a section C is present, the cooling fluid distribution structures there preferably run at an obtuse angle to the cooling fluid distribution structures of section A. The fluid-connecting openings through sealing beads near the cooling fluid passage 11a, as explained above, are not shown separately in Figure 3, but are nevertheless present. Two arrows 1A and 1C each represent a fluid inflow from the cooling fluid passage 11a into the first and third sections A and C. The size of the arrows illustrates the proportionality of these flows.It is thus evident that the fluid inflow 1A into the first section A is significantly larger (for example, at least three times, at least five times, or at least ten times as large) than the fluid inflow 1C into the optional third section C. It is understood that a reversal of the flow directions is also possible.

[0069] The first section A of the cooling fluid distribution structure 19 runs in a first overlap region 15 of the separator plate 2. In this region, the first section A overlaps with a first section of a distribution region 20 of the first individual plate 2b, which is also referred to below as the first fluid distribution region 21 (not shown in Fig. 3). Consequently, the section A is delimited by a section of the inner side of the first individual plate 2b, which faces away from this fluid distribution region 21 or forms its opposite side, as well as by an opposite inner side of the second individual plate 2a. The crests of the webs of the first individual plate 2b run essentially on a flat surface plane of this individual plate 2b, specifically transversely to the fluid inflow direction 1A of the cooling fluid.The correspondingly delimiting section 30 of the second individual plate 2a (see Figure 6 discussed below), however, is formed predominantly opposite the flat surface plane of this individual plate 2a and in a direction pointing away from the first individual plate 2b. The webs take up a smaller area proportion on the cooling fluid side than the channels. The delimiting section 30 of the second individual plate 2a essentially forms a flow space of the first section A of the cooling fluid distribution structure 19. In the first section A, advantageously no fluid inflow from the through-opening 11b takes place on the corresponding rear side, i.e., the outer side; the fluid inflow from the through-opening 11b advantageously occurs only through section B and possibly through section C.This means that in the first overlap region 15, in which a first section A of the cooling fluid distribution structure 19 and a first section of a first fluid distribution region 21 overlap each other, these advantageously do not overlap with a section of the second fluid distribution region 23.

[0070] The second section B of the cooling fluid distribution structure 19 extends in a second overlap region 22, in which the first fluid distribution region 21 and a second fluid distribution region 23 (not shown in Fig. 3) overlap, which is a distribution region 20 of the second individual plate 2a. The fluid distribution regions 21, 23 are formed on the outer sides of the respective individual plates 2a, 2b (see Figs. 4 and 6). In this second overlap region 22, sections of the inner sides of the individual plates 2a, 2b are located opposite one another, having first web-channel structures that are complementary to the web-channel structures of the respective fluid distribution regions 21, 23. The first web-channel structures of these opposing inner sides extend in intersecting directions, which means an increased flow resistance for the cooling fluid. An example of such an inside first web-channel structure 47 is shown in Fig.11 removable.

[0071] A transition region 58 between the first and second overlap regions comprises a step 33 explained below.

[0072] The optional third section C of the cooling fluid distribution structure 19 extends in a likewise optional third overlap region 24, in which a section of the second fluid distribution region 23 and a section of an inner side of the first individual plate 2b overlap each other. The structural configurations of the sections AC and the overlap regions 15, 22, 24 are explained in more detail below with reference to Figures 4-12. The following assumes a case in which the optional third section C of the cooling fluid distribution structure 19, as well as the optional third overlap region 24, are omitted.

[0073] Figure 4 shows a section of the outer side of the bipolar plate 2 with a view of the first individual plate 2b, in particular a cathode plate, in the area outlined in dashed lines from Figure 2 according to one embodiment. The viewing angle is rotated in particular compared to Figure 3, as can be seen from the indicated position of the through-opening 11c in Figure 4. Only a cut-off part of the flow field 17b is shown. In this, a fluid is guided from the through-opening 11c via the first fluid distribution region 21 and through a web-channel structure 46 on the outer side of the first individual plate 2b. The web-channel structure 46 has a plurality of outwardly projecting webs 27b and channels 29b enclosed therebetween, selected ones of which are each provided with a corresponding reference symbol. With the exception of the webs 27b, the first fluid distribution region 21 runs in the plane of the first individual plate 2b.

[0074] The following explains features of the web-channel structure 46, and in particular of the segments 60-64 encompassed thereby. These explanations and features apply equally to the complementarily shaped first web-channel structure 47 on the inside (see Figures 10-12), without this being repeated separately below.

[0075] The webs 27c each comprise a continuous sequence of a first segment 60, a second segment 62, and a third segment 64. In Figure 4, regions comprising these segments 60, 62, 64 are marked with a corresponding reference numeral. The first segment 60 of each web 27c extends from an edge of the first fluid distribution region 21 near the through-opening 11c to the transition region 58. The second segment 62 of each web 27c extends into the transition region 58. The third segment 64 of each web 27c extends from the transition region 58 to the flow field 17b. It is understood that the channels 29c are also divided into similarly extending first to third segments 60, 62, 64 and all properties of the segments 60, 62, 64 of the webs 27c also apply to the segments of the channels 29c, without this always being mentioned separately below.The first and third segments 60, 64 each run straight and parallel to each other. The second segment 62, however, runs at an angle to both the first and third segments 64.

[0076] This relationship is illustrated in Figure 5, which is an enlarged detailed view of Figure 4. Figure 5 shows the angular relationships of the segments 60, 62, and 64 of one of the webs 27c. Longitudinal axes LI, L3 are entered for the first and third segments 60, 64 of this web, and a longitudinal axis L2 is also shown for the second segment 62. The angles W12 and W23 between the longitudinal axis L2 of the second segment 62 and a respective longitudinal axis LI, L3 of the first and third segments are identical and amount to approximately 120°. The largest possible enterable intersection angle W12 or W23 of the longitudinal axes LI, L2 or L2, L3 is considered.

[0077] Figure 5 further shows a longitudinal axis A of the transition region 58, which extends transversely through the fluid distribution region 21 and along the transition region 58. This longitudinal axis A also corresponds to a longitudinal axis of the step 33 explained below (see Fig. 3). It is shown that the longitudinal axis A of the transition region 58 and step 33 runs at an angle to all longitudinal axes LI, L2, L3 of the webs 27, in particular to the longitudinal axes LI, L3 outside the second segment 62.

[0078] As a result, Figures 4 and 5 show that the webs 27 (and analogously the channels 29) each run completely straight outside the transition region 58, but experience a change in direction in the transition region 58, which is reflected in the angle W12 or W23 shown and different from 0°. In the example shown, the change in direction occurs such that at the boundary between the first segment 60 and the transition region 58, there is initially a curvature or bend in a first direction (right in Fig. 5) and at the boundary between the third segment 64 and the transition region 58, there is a curvature or bend in a second direction (left in Fig. 5). This twofold change in direction cancels each other out in the example shown, resulting in the parallelism of the first and third segments 60, 64. Alternatively, only one of the shown changes in direction could occur.

[0079] The distribution of the fluid distributed by the first fluid distribution region 21 is not significantly affected by the changes in direction. On the other hand, the web-channel structure 46 forms a complementarily shaped first web-channel structure 47 (see Figures 10-12) on the inner side of the first individual plate 2b, which guides the cooling fluid and, more precisely, directs a flow thereof through the cooling fluid distribution structure 19. Consequently, the cooling fluid undergoes similar changes in direction in the transition region 58 and thus upon transition into the second overlap region 22, as explained above.

[0080] Fig. 5 also shows that in the transition region 58, the distances between adjacent webs 27 and channels 29 change compared to outside the transition region 58, and more precisely, the channels 29c on the inside, i.e., the webs 27b on the outside, increase. By way of example, Fig. 5 considers a distance D, D1, D2 between the highest points of two adjacent webs 27c. The distance runs perpendicular to a web longitudinal axis and / or to a tangent to a local circle of curvature (not shown) of a web 27c. It can be seen that the webs 27c outside the transition region 58 are spaced at a comparatively small distance D from one another. This distance D is preferably essentially identical between all webs 27c. Within the transition region 58, the distance increases, for example, to at least 1.25 times (see distance D1), or at least twice (see distance D2), compared to the distance D outside the transition region 58.In the example of Fig. 5, the change in the web spacing shown only affects the width of the channels on the inside, ie the coolant channels 29c and the webs 27b between the channels on the outside, but the division could also be designed differently.

[0081] The increased web spacings D1, D2 in the transition region 58 result in a corresponding channel widening of the first channel-web structure 47 on the inner side of the first individual plate 2b. Thus, the cooling fluid, which is guided in these inner channels, has an enlarged flow cross-section available in the transition region 58, which can limit pressure losses.

[0082] Figure 6 shows a section of the bipolar plate 2 with a view of the outer side of the second individual plate 2a, preferably an anode plate, in the area outlined in dashed lines in Figure 2. The viewing angle is rotated compared to Figure 3, as can be seen from the indicated position of the through-opening 11b in Figure 6. Only a cut-off part of the flow field 17a is shown. In this, a fluid is guided from the through-opening 11b via the second fluid distribution region 23 and through a web-channel structure 40 on the outer side of the second individual plate 2a. By way of example only, the web-channel structure 40 has a plurality of outwardly projecting webs 27a and channels 29a enclosed therebetween, selected ones of which are provided with a corresponding reference symbol.As shown, the webs 27a are optionally interrupted in sections along their longitudinal extent, but can also extend continuously in the direction of the flow field 17a. With the exception of the webs 27a, the second fluid distribution area 23 runs in the plane of the second individual plate 2a.

[0083] The second fluid distribution region 23 is delimited by an elongated step 32, which is directed away from the opposite first individual plate 2b and extends toward a side of the flow field 17a remote from the through-opening 11b. Adjoining the step 32 in the first fluid distribution region 21 is a section 42 of the second individual plate 2a that is raised relative to the plane of the flat surface of the second individual plate 2a and that significantly delimits, or in other words, spans, a flow space of the first section A of the cooling fluid distribution structure 19. The raised section 42 forms the aforementioned section 30 of the second individual plate 2a, which partially delimits the first section A of the cooling fluid distribution structure 19. An optionally shown plurality of stiffening beads 44 in this section 42 can also be omitted.

[0084] The step 32 forms a complementarily shaped inner step 33 within the first section A of the cooling fluid distribution structure 19, which extends toward the first individual plate 2b. This inner step 33 consequently promotes the above-described change of level during the transition of the cooling fluid from the first to the second overlap region 15, 22. The inner step 33 further overlaps with the transition region 58 and runs along it.

[0085] Returning to Figure 4, one can also see the raised section 42 of the second individual plate 2a, which is lowered in Figure 4, as well as the first section A of the cooling fluid distribution structure 19 formed therefrom (see Figure 6). A portion of the second fluid distribution region 23 is also visible.

[0086] The fluid flows occurring in the embodiment under consideration are explained separately with reference to the further figures 7 and 8. Figure 7 is a schematically highly simplified partial view of the first fluid distribution region 21, wherein the viewing angle, as evident from the position of the through-opening 11c, is rotated compared to Figure 4 and essentially corresponds to that of Figure 3. A plurality of flow arrows show the course of the fluid flow through the first fluid distribution region 21 in the direction of the flow field 17b on the outer side of the first individual plate 2b. The flow arrows are curved according to the twofold change of direction explained above.

[0087] Fig. 8 is a representation of the cooling fluid distribution structure 19 that is essentially analogous to Fig. 3, omitting the optional third overlap region 24. Figure 8 is a highly simplified schematic. A slightly different position of the transition region 58 compared to Fig. 3 and Fig. 7 is due to this schematic simplification and is of no particular significance.

[0088] Fig. 8 shows a fluid inflow from the through-opening 11a into the first section A of the cooling fluid distribution structure 19. The cooling fluid flows along the first section A (see main flow arrow 66) and successively enters the transition region 58 at several positions and, via this, into the second overlap region 22 (see curved arrows 67). In doing so, it undergoes the above-described plane change and flows primarily along the first web-channel structure 47 on the inside of the first individual plate 2b (see Figures 10-12).

[0089] In addition, the cooling fluid flow changes direction from the main flow arrow 66 to the arrows 68 of the second overlap region 22, which point toward the flow field 17. In the transition region 58, the cooling fluid follows the change in direction of the web-channel structure 46 of the first fluid distribution region 21, which is analogously reflected in the first web-channel structure 47 on the inside of the first individual plate 2b. The curved ends of the arrows 68 represent at least part of this change in direction.

[0090] This makes it clear that the cooling fluid flow is deflected by approximately 90° relative to the main flow arrow 66 when it crosses into the second overlap region 22 and flows further there according to the arrows 68. However, this means a gentler deflection with a larger curve radius compared to a hypothetical absence of the described change of direction in the transition region 58. In such a hypothetical case, the change of direction would occur more narrowly and would require a sharp-edged bend in the cooling fluid flow relative to the main flow arrow 66. A hypothetical flow arrow 70, which would be generated in such a case in the second overlap region 22, is indicated by dashed lines in Fig. 8. As a result, the solution presented sustainably reduces the flow resistance for the cooling fluid in the transition region 58. To further clarify the explained relationships, Figure 9 shows a diagram related to Fig.Figure 4 shows an analog partial view of a view through the bipolar plate 2 with several sectional planes AA (along the transition region), BB (through the second overlap region 22), and CC (through the first overlap region 15). The sectional views clearly show that the various regions are simultaneously optimized for all media, and that the inner and outer surfaces of the two individual plates 2a, 2b, formed from a single sheet with a thickness of less than 100 μm, are in a positive-negative relationship to each other.

[0091] Figure 10 is a sectional view along section plane AA of Figure 9. In the correspondingly sectioned transition region 58, the inner side of the second individual plate 2a is guided by the step 33 into partial contact with the inner side of the first individual plate 2b. Consequently, the cooling fluid flows via the illustrated first web-channel structure 47 on the inner side of the first individual plate 2b, which decisively defines a flow space 72 of the cooling fluid structure 19 in the transition region 58, into the second overlap region 22 outside the plane of the drawing. In doing so, it undergoes the change of plane discussed above. Furthermore, it is redirected by the inner first web-channel structure 47 into the second overlap region 22 with reduced flow resistance as a result of the explained less sharp-edged change in direction and the increase in flow cross-section in the transition region 58.

[0092] Fig. 10 as well as Figures 11 and 12 also show the relationship between the web-channel structure 46 on the outside of the first individual plate 2b and the complementarily shaped first web-channel structure 47 on its inside. The webs 27b of the web-channel structure 46 form channels 29c of the first web-channel structure 47 on the inside, and vice versa. The channels 29b of the web-channel structure 46 form webs 27c of the first web-channel structure 47 on the inside, and vice versa. Figure 10 also shows a distance D2 between two webs 27c analogous to the distance D2 shown in Figure 5. This makes it clear that the distance between two webs 27 always spans an intermediate channel 29.

[0093] Figure 11 is a sectional view along section plane BB of Figure 9. In the correspondingly sectioned second overlap region 22, first web-channel structures are located opposite each other on the respective inner sides of the individual plates 2a, 2b. This leads to non-uniform and multiply intersecting flow paths within the overlap region 22. Figure 12 is a sectional view along section plane CC of Figure 9. In the correspondingly sectioned first overlap region 15, a flow space 72 of the cooling fluid distribution structure 19 is substantially limited by the raised section 42 of the second individual plate 2a, which overlaps with a section of the first fluid distribution region 21. The first web-channel

[0094] However, structure 47 on the inner side of the first individual plate 2b runs essentially transversely to a main flow direction of the cooling fluid (cf. Figures 3 and 4) and therefore does not provide any significant flow space for the cooling fluid.

Claims

Patent claims 1. Separator plate (2) for an electrochemical system (1), wherein the separator plate (2) comprises: - a first individual plate (2b) and a second individual plate (2a) which define an interior of the separator plate (2) with a cooling fluid distribution structure (19), - a first overlap region (15) in which a first section (A) of the cooling fluid distribution structure (19) and a first section of a first fluid distribution region (21) overlap each other, wherein the first fluid distribution region (21) is formed on an outer side of the first individual plate (2b), - a second overlap region (22) in which a second section (B) of the cooling fluid distribution structure (19), a second section (B) of the first fluid distribution region (21) and a section of a second fluid distribution region (23) overlap one another, wherein the second fluid distribution region (23) is formed on an outer side of the second individual plate (2a), wherein the cooling fluid distribution structure (19) has a first web-channel structure (47) which has a plurality of webs (27c) and channels (29c) formed between each two webs (24) and which forms a complementarily shaped web-channel structure (46) of the first fluid distribution region (21), wherein the first web-channel structure (47) has at least one change of direction in a transition region (58) from the first to the second overlap region (15, 22); wherein the second individual plate (2a) is formed opposite this change in direction deviating from the first web-channel structure (47).

2. Separator plate (2) according to claim 1, wherein the second individual plate (2a) has a step (33) extending in the direction of the first individual plate (2b) opposite the change in direction.

3. Separator plate (2) according to claim 1 or 2, wherein a) the webs (27c) and channels (29c) of the first web-channel structure (47) each have a first segment (60) extending in the first overlap region (15) and a second segment (62) extending in the transition region (58), wherein the first and second segments (60, 62) are angled relative to one another; and / or wherein b) the webs (27c) and channels (29c) of the first web-channel structure (47) each have a third segment (64) extending in the second overlap region (22) and a second segment (60) extending in the transition region (58), wherein the second and third segments (62, 64) are angled relative to one another.

4. Separator plate (2) according to claim 3 with a) and b) in combination, wherein the first and third segments (60, 64) of a respective web (27c) and channel (29c) run parallel to each other or run at an angle relative to each other which is less than a respective angle (W12, W23) between the second segment (62) and one of the first and third segments (60, 64).

5. Separator plate (2) according to one of claims 3 to 4, wherein the angle (W12) by which the first and second segments (60, 62) are angled relative to one another is between 90° and 170°; and / or wherein the separator plate (2) is designed according to variant b) of claim 3 and the angle (W23) by which the second and third segments (62, 64) are angled relative to one another is between 90° and 170°.

6. Separator plate (2) according to one of claims 3 to 5, wherein the first segment (60) and the second segment (62) merge into one another; and / or wherein the separator plate (2) is designed according to variant b) of claim 3 and the second segment (62) and the third segment (64) merge into one another.

7. Separator plate (2) according to one of claims 3 to 6, wherein the first segment (60) is at least twice as long as the second segment (62); and / or wherein the separator plate (2) is designed according to variant b) of claim 3 and the third segment (64) is at least twice as long as the second segment (62). TI 8. Separator plate (2) according to one of claims 3 to 7, wherein the second segment (62) has a length which corresponds to one to seven times, preferably one and a half times to five times, a channel width of the channels (29c) of the first web-channel structure (47), wherein the channel width extends between the highest points, with respect to a planar surface plane of the separator plate (2), of those webs (27c) which are closest to one another and between which a respective channel (29c) is arranged.

9. Separator plate (2) according to one of claims 3 to 8, wherein the first segment (60) is substantially or completely rectilinear; and / or wherein the separator plate (2) is formed according to variant b) of claim 3 and the third segment (64) is substantially or completely rectilinear.

10. Separator plate (2) according to one of the preceding claims, wherein in the transition region a change of flow planes of the cooling fluid distribution structure (19) takes place in such a way that in the first overlap region (15) a flow cross-section of the cooling fluid distribution structure (19) extends substantially in a flow space (72) spanned by the second individual plate (2a) and in the second overlap region (22) extends substantially in a flow space (72) spanned by the first individual plate (2b).

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