Separator plate for an electrochemical system

Abstract

Separator plate (10) for an electrochemical system, in particular for an electrolyzer, comprising: • a first layer (34) having a first outer side (38) and a first inner side (40), wherein a first channel-web structure (14) with a plurality of channels (24) and webs (22) separating the channels (24) is formed on the first outer side (38), wherein the first channel-web structure (14) forms a complementarily shaped second channel-web structure (32) on the first inner side (40), • a second layer (36) having a second outer side (42) and a second inner side (44), wherein the second inner side (44) lies opposite the complementarily shaped second channel-web structure (32) and defines with it a plurality of internal channels (24'), • a plurality of openings (50) per inner channel (24'), wherein the openings (50) each define a fluid connection between a respective inner channel (24') and the first channel-web structure (14) on the first outer side (38), wherein the number of openings (50) within a first half (H1) of a total channel length of a respective inner channel (24') is less than within a second half (H2) of the total channel length.

Description

[0001] The invention relates to a separator plate for an electrochemical system, in particular for an electrolyzer.

[0002] Electrolyzers typically comprise a stack of individual electrochemical cells, each of which has a plurality of layers, including at least one separator plate and a membrane electrode assembly (MEA), with each individual cell being defined by two adjacent separator plates. The stack of individual electrochemical cells may have two end plates that press the individual electrochemical cells together and provide stability to the stack. Furthermore, the individual electrochemical cells may comprise gas diffusion layers (GDL) and / or porous transport layers (PTL) arranged between the separator plate and the membrane electrode assembly. The separator plate can fulfill 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 adjacent individual electrochemical cells.The separator plate itself and each layer of a separator plate typically separate the media. The separator plate is often referred to as a bipolar plate.

[0003] The separator plate comprises at least one through-opening (port) as an inlet or outlet for passing a fluid through the separator 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 principle, it is possible to provide all the functions of a separator plate within the plate itself, but it is also possible to divide some of the functions between the actual separator plate and a cell frame.

[0004] Separator plates in electrolyzers are usually single-layer, i.e. they are made from a single layer of a typically sheet material, in particular by means of embossing, punching and / or deep drawing.

[0005] An important parameter of electrochemical systems is the achieved efficiency. This depends largely on how efficiently the electrochemical reaction is implemented. For example, the efficiency of an electrochemical system decreases if the available reaction surface is supplied with reactants in a very uneven manner. On the other hand, it is often not possible to arbitrarily change the reaction surface or make other geometric adjustments within the area of ​​the separator plate.

[0006] The present invention is directed to the task of improving the efficiency of an electrochemical system.

[0007] This object is achieved by the subject matter of the independent claims. Advantageous further developments are specified in the dependent claims as well as in this description and the accompanying figures.

[0008] Accordingly, a separator plate for an electrochemical system is proposed, in particular for an electrolyzer, comprising: • a first layer having a first outer side and a first inner side, wherein a first channel-web structure having a plurality of channels and webs separating the channels is formed on the first outer side, wherein the channel-web structure forms a complementarily shaped second channel-web structure on the first inner side, • a second layer having a second outer side and a second inner side, wherein the second inner side is opposite the complementarily shaped second channel-web structure and defines with it a plurality of internal channels, • a plurality of openings per inner channel, wherein the openings each define a fluid connection between a respective inner channel and the first channel-web structure on the first outer side, wherein the number of openings, which may also be zero, is less within a first half of a total channel length of a respective inner channel than within a second half of the total channel length.

[0009] For example, the number of openings within the second half of the total channel length may be at least 20% or at least one-third higher than in the first half. If the number within the first half is zero, the number of openings within the second half may be at least one. In general, the number of openings within the second half may be at least two, at least three, at least four, or at least five.

[0010] According to the invention, it was recognized that the efficiencies of existing electrochemical systems can be impaired, particularly by the fact that the resulting reaction products, on the one hand, dilute the reactants and, on the other hand, can accumulate in areas that are subsequently no longer sufficiently accessible for the desired electrochemical reaction to occur. In both cases, incoming reaction media can only reach these areas in too low a concentration, no longer reach them, or only reach them to a limited extent, so that the desired electrochemical reaction cannot be realized to the desired extent.

[0011] In the case of electrolyzers, it has been recognized that, for example, catalyst layers in the anode region of an electrochemical cell can be obscured by oxygen produced during the electrochemical reaction. Since water is typically used as the reaction medium along the anode, the oxygen concentration increases along the flow path and the achievable local efficiency decreases increasingly. The more oxygen is produced, or in other words, the higher the gas content, the more difficult it becomes for the supplied water to remove the oxygen. Likewise, it becomes more difficult for the water to penetrate a typically provided porous transport layer (PTL) on its way to the anode or the catalyst layer there. The increasing gas content also impairs the local viscosity of the water-oxygen mixture and thus its local flow behavior.In principle, the water content in the water-oxygen mixture decreases without further measures.

[0012] The invention therefore proposes structural adaptations to separator plates with which such disadvantages can be at least partially reduced. In particular, it is proposed to use the internal channels to specifically supply a reaction medium, and in particular water, or in other words, to locally replenish it, especially in downstream regions. Viewed along the first web-channel structure, the reaction medium can thus be locally reintroduced, particularly after a certain channel length has already been covered. This can increase the probability that resulting reaction products can be sufficiently transported away or, figuratively speaking, flushed away. In other words, the concentration of the reaction medium can be increased again after a significant amount of flow through the first web-channel structure has already taken place, and the proportion of reaction products can be reduced.

[0013] More specifically, the fact that the openings defining a fluid connection are unevenly distributed along the entire length of the channels allows for the fact that, viewed in a flow direction along a channel's longitudinal axis, the concentration of reaction products to be transported away is expected to increase. When the reaction medium flows along the separator plate from the first half toward the second half of a channel's total length, the reaction products, which are expected to be present in greater numbers there, can be reliably transported away due to the higher number of openings defining a fluid connection in the second half. Thus, a catalyst layer can still be achieved to a sufficient extent.

[0014] The inventive solution enables an increase in the flow-through cross-sectional area on the anode side of the separator plate without requiring an increase in the active area. Furthermore, the required installation space in the stacking direction is not significantly increased.

[0015] The first channel-web structure can comprise or form a flow field. The flow field can define or be comprised by an active region of an electrochemical cell, wherein the separator plate is part of this electrochemical cell. The electrochemical reaction can take place in the active region. The second channel-web structure can be formed complementarily to the first channel-web structure in such a way that channels of the corresponding first structure form webs of the corresponding second structure, and webs of the corresponding first structure form channels of the corresponding second structure.

[0016] Both the first and the second layer can each be made of a similar material, in particular a sheet metal material. For example, they can be sheets coated at least on one side, at least in sections, in particular over the entire surface, for example made of titanium, stainless steel, or other metals or metal alloys. They can therefore be plate-shaped components in which the respective channel-web structures are formed, for example, by forming and, in particular, embossing processes. The first and the second layer can be fastened to one another, in particular by means of a material-to-material connection and, furthermore, in particular, by means of one or more welded joints.

[0017] In general, features of the first channel-web structure can be referred to as external features, and features of the second channel-web structure can be referred to as internal features. For example, the openings of a respective internal channel can also form openings in a respective external channel and / or external web, i.e., they can open into or originate from them. Consequently, the fluid connections established by the openings can be present, in particular, within an active region of the separator plate.

[0018] When reference is made herein to a total channel length, this can be understood in particular as the length of a flow path specified or defined by the channel. For example, the channel paths may not necessarily be straight, but may also be curved, in particular with multiple curves and, for example, wave-shaped. The total channel length can therefore correspond to the unwound length of a non-straight channel.

[0019] According to one embodiment, the internal channels each comprise a channel base that merges into a respective side flank on both sides, wherein at least one of the openings of a respective internal channel is formed at least partially in one of the side flanks. In particular, at least a portion of the opening cross-section can extend within one of the side flanks and / or overlap with it or, in other words, locally interrupt it. As a result of the complementary formation, the channel base of an internal channel can form a web crest of the first channel-web structure on the first outer side. In this way, the fluid from the internal channels can merge directly into a fluid flow within the channels of the first channel-web structure.

[0020] Alternatively or additionally, the internal channels can each comprise a channel base which merges into a respective side flank on both sides, wherein at least one of the openings of a respective internal channel is formed at least partially in the channel base. In particular, at least a portion of the opening cross-section can extend within the channel base and / or overlap with it or, to put it another way, locally interrupt it. In this way, it can be achieved that the fluid from the internal channels reaches the outside via the web crests on the outside and thus in increased proximity to elements lying on the outside of the separator plate. For example, these lying elements, such as a permeable PTL, can lie directly against the web crests on the outside.In particular, it is also possible for at least one of the openings to extend in sections into the channel bottom and at least one side flank.

[0021] The at least one opening in the channel base and / or in the side flank can have a first dimension along a longitudinal channel axis of the inner channel and a second dimension that runs transversely to the longitudinal channel axis. The first dimension can be at least one and a half times and in particular at least twice the second dimension. In this way, an outflow direction of the fluid from the inner channels in a direction along the longitudinal channel axis can be supported. If several openings are arranged along a channel, they can have different shapes. The longitudinal channel axis can generally correspond to a flow path of a fluid along a channel. Accordingly, depending on the extent of the channel, the longitudinal channel axis can also be curved and / or wavy, for example.

[0022] By enlarging one of the second and first dimensions relative to the corresponding other dimension, an oval opening shape can be defined, for example. Alternatively, other elongated shapes are also possible, such as crescent or lens shapes. According to an alternative embodiment, the second dimension can be approximately the same size as or equal to the first dimension. This corresponds to a substantially or completely circular opening shape.

[0023] Likewise, the edges of the opening do not have to be arranged in a plane, for example, parallel to or in the plane of the plate. For example, an edge region of the opening, in particular the downstream edge, can form a scoop-shaped projection that extends into the flow path, i.e., an inner channel, and thus facilitates the discharge from the inner channel into the outer channel.

[0024] According to a further embodiment, the second layer is substantially planar, in particular at least in a region opposite the second channel-web structure. For example, the second layer can be formed as a smooth sheet, at least in said region. In this way, an increase in the thickness of the separator plate can be limited compared to known single-layer configurations. With appropriate selection of other parameters, it is even possible for a design according to the invention to be implemented without requiring a greater amount of installation space.

[0025] According to one variant, the first layer has a recessed receiving area for the second layer. This is particularly advantageous when the second layer spans a smaller area than the first. The receiving area can be configured to receive the second layer in such a way that it does not protrude from adjacent areas of the first layer and, in particular, is flush with them. Thus, the separator plate can have a largely or even completely flat outer side despite its two-layer design, wherein this outer side faces away from the first web-channel structure. It has been shown that a flat outer side - when combined with suitable sealing elements - is well suited for conducting the produced hydrogen on the cathode side.

[0026] According to a further embodiment, one of the first layer and the second layer has a plurality of through-openings, each of which is fluidically connected to the first and / or the second channel-web structure. In particular, the channels of the first channel-web structure and optionally also the internal channels can fluidically connect the through-openings within the separator plate. In particular, at least the channels of the first channel-web structure can extend between two through-openings and fluidically connect them. In a manner known per se, a reaction medium can be passed through a through-opening, which can pass into the channels and be guided by them in the direction of the corresponding other through-opening, in particular after passing through the active region.In general, the through-openings can be configured to pass a fluid through the separator plate and / or through a stack of separator plates, for which purpose the through-openings of the individual separator plates can be arranged in alignment with one another.

[0027] Accordingly, a further development provides that the part of the first and second layer which does not have the through-openings has a smaller area than the corresponding other part of the first and second layer. The area can be a base area of ​​the corresponding layer and / or a surface size of the outside and / or inside of the corresponding layer. By reducing the area accordingly, the layer can, for example, be dimensioned only such that it can sufficiently delimit the internal channels. This makes it possible to limit the material consumption and the weight of this layer and thus also of the entire separator plate. On the one hand, it is possible for the first and second layers to have the same sheet thickness.On the other hand, for example, if the smaller layer is received in a ledge and / or a recessed receiving area of ​​the larger layer, the smaller layer may be formed from a thinner sheet than the larger layer.

[0028] According to a further development, the first layer has the through-openings and an area of ​​the second layer is less than one and a half times as large as an area of ​​the first layer in which the first channel-web structure extends.

[0029] One embodiment provides that the second layer is connected to the first layer in a materially bonded or otherwise fluid-tight manner in a region that surrounds the second channel-web structure, in particular in a frame-like manner. Furthermore, web crests of this second channel-web structure can also be connected to the second layer, for example in sections or along short connecting lines. The web crests can, at least locally, form regions of the second channel-web structure that protrude furthest in the direction of the second layer. For example, these web crests lie in the same plane as the frame-like region of the first layer surrounding the second channel-web structure.

[0030] In particular, in this way, a web crest and a web flank of the second channel-web structure can continuously delimit a respective internal channel with an inner side of the second layer and, furthermore, the next web flank. Figuratively speaking, the inner side of the second layer can thus form one side or side wall of, for example, four sides or side walls of a cross-sectional profile of a respective internal channel. The remaining sides or side walls can be formed by the second channel-web structure. This represents a space-saving solution for forming the internal channels, while also reliably producing material-to-material connections in the area of ​​the web crests.

[0031] A further development provides that the first half of the total channel length of each internal channel lies upstream of the second half. This can apply, for example, during intended use and / or intended operation of the separator plate and the electrochemical system. In such a case, a fluid can initially be guided proportionally along the first half of each internal channel and along the first half of each channel of the first channel-web structure, i.e. the external channels, for example after emerging from a through-opening. It can then proportionally flow into the second half of the total channel length of the internal channels or into the second half of the channels of the first channel-web structure.

[0032] According to a further embodiment, the number of openings within the first half or within the first at least 30% or within the first at least 20% of the total channel length of each internal channel is zero. In other words, no openings can be formed there and consequently no direct fluid connection enabled thereby can exist between an internal channel and the outside. This can take into account the fact that in these regions the electrochemical reaction has not yet taken place to such an extent that a proportion of reaction products is present that may reduce the efficiency. This can only apply when the channel length is correspondingly advanced, so that the openings and fluid connections can only be provided there.In this way, pressure losses and / or flow resistances, which inevitably arise from the openings and fluid connections, can be limited.

[0033] On the other hand, the number of openings, in particular per internal channel, within the second half of the total channel length of each internal channel can be at least two and in particular at least three.

[0034] According to a further embodiment, the number of openings within the second half of the total channel length is at least 50% higher than within the first half of the total channel length, and in particular at least 100% higher. If the number of openings within the first half is zero, the number within the second half can be at least 1.

[0035] Additionally or alternatively, at least within the second half of the total channel length, the distance between successive openings may be inhomogeneous. In particular, the distance between successive openings may decrease at least in sections in a direction from the first to the second half of the total channel length. This may take into account the fact that the concentration of the reaction products increases successively along the total channel length, and in particular in the direction and along the second half. Accordingly, the distance between the openings in the direction from the first to the second half (and along the second half) may decrease at least in sections and / or continuously.

[0036] According to a further embodiment, the internal channels each have a first end at the beginning of the first half of the total channel length and a second end at the end of the second half of the total channel length, wherein a flow cross-section of the second end is between at least 50% smaller and up to and including 100% smaller than an average flow cross-section within the first and / or second half of the total channel length and is thus closed. The first and second halves of the total channel length can merge into one another or adjoin one another in a central position of the total channel length. The first and second ends of a respective internal channel can each be spaced from this central position by one half of the total channel length. For non-rectilinear channels, a distance in the developed length and / or a distance along a non-rectilinear longitudinal channel axis can be considered.

[0037] The reduced flow cross-section of the second end allows a targeted dynamic pressure to be generated within a respective internal channel, which can force a fluid conveyed therein out through the opening toward the outside. In particular, this dynamic pressure can allow the fluid to exit the openings even in the presence of corresponding counterpressure on the outside and / or prevent a reverse inflow of fluid from the outside into the internal channels. The average flow cross-section within one half of the total channel length is advantageously determined over those sections that are free of openings.

[0038] In contrast, the first end of a respective internal channel can be open and, in particular, have a flow cross-section that is at least as large as the average flow cross-section within the first and / or second half of the total channel length. This can enable a reliable inflow of fluid into the internal channels. Additionally or alternatively, the first end can generally have a larger flow cross-section than the second end, provided the latter is not completely closed, in particular a flow cross-section that is at least 50% or at least 100% larger.

[0039] According to a further development, the openings of a respective inner channel have different cross-sectional sizes and / or cross-sectional shapes. Generally, these can be configured differently from one another. This allows the openings to be adapted, for example, to the respective locally present concentrations of reaction products and / or flow and pressure conditions, particularly on the first outer side, for example to enable effective inflow of fluid from the inner channels to the first outer side. For example, the cross-sectional sizes can increase with increasing distance from an aforementioned first end of the inner channels.

[0040] According to a further development, at least one of the openings has a radially inner circumferential section and a radially outer circumferential section, viewed in a flow direction that runs along a channel longitudinal axis and from the first half of the total channel length towards the second half and / or that runs from the above-explained first to the second end of a respective inner channel. The radial positioning can refer to a positioning transverse to the channel longitudinal axis and, for example, the radially inner circumferential section can be correspondingly radially indented relative to the radially outer circumferential section. The circumferential sections can each comprise or form edge regions of the opening or edge lengths of the separator plate that delimit the opening. The radially inner circumferential section is preferably arranged downstream of the radially outer circumferential section.This can mean that, viewed from a top view and / or a sectional view including the channel's longitudinal axis, at least one opening has a radially stepped edge. This can facilitate the escape of fluid from the inner channel to the outside.

[0041] One embodiment provides that, in the region of at least one of the openings of a respective internal channel, a flow cross-section of the internal channel is reduced at least in sections. Again, it can be provided that this narrows at least in sections, viewed in the flow direction.

[0042] According to a further development, at least one of the openings of a respective internal channel is designed to define or, in other words, to generate a fluid flow in a direction directed away from the first outer side, i.e. the opening area. This can be equivalent to a vector component of the flow direction in the orthogonal direction to the first outer side in the region of the opening being at least as large as a vector component in a direction parallel to the first outer side in the region of the opening. In this way, the fluid flow can be directed in a targeted manner in the direction of a component adjacent to the first outer side in the region of the opening, such as in particular a PTL.

[0043] Exemplary embodiments of the separator plate are illustrated in the attached schematic figures and explained in more detail in the following description. Recurring features can be designated by the same or similar reference symbols across the figures. Only selected instances of a feature shown multiple times within a figure can be provided with a reference symbol associated with that feature. They show: Fig. 1 an exploded view of a single cell of an electrolyzer with two separator plates according to the prior art; Fig. 2 is a perspective view of a single separator plate according to an embodiment of this disclosure; Fig. 3 a detailed view of the separator plate from Fig. 2; Fig. 4 a partial sectional view of the separator plate from Fig. 2; Fig. 5 another detailed view of the separator plate from Fig. 2; Fig. 6a & 6b sectional views of a single internal channel, as can be formed in separator plates according to embodiments of the invention, in a non-flow ( Fig. 6a) and in a flow-through state ( Fig. 6b); Fig. 7a & 7b sectional views of a single internal channel, as can be formed in separator plates according to embodiments of the invention, in a non-flow ( Fig. 7a) and in a flow-through state ( Fig. 7b); Fig. 8a & 8b sectional views of a single internal channel, as can be formed in separator plates according to embodiments of the invention, in a non-flow ( Fig. 8a) and in a flow-through state ( Fig. 8b); Fig. 9 - 11 each show a cross-sectional view of a single internal channel as it can be formed in separator plates according to embodiments of the invention; Fig. 12 & 13 each show a cross-sectional view of a single internal channel as may be formed in separator plates according to embodiments of the invention; Fig. 14 is a schematic representation of a separator plate according to a further embodiment of the invention; and Fig. 15 a schematic plan view of several internal and external channels along their course, as they can be formed in separator plates according to embodiments of the invention.

[0044] Fig. 1 shows an exploded view of a prior art electrochemical single cell 9, wherein the single cell 9 is a component of an electrolyzer. Electrolyzers typically comprise a plurality of stacked single cells 9. The single cell 9 comprises two separator plates 1 and 2, two cell frames 142 and 144, a sealing layer 145, a membrane-electrode assembly 140 with catalyst materials, and media diffusion structures 141 and 143. The media diffusion structure 143 comprises, for example, layers of carbon fleece, while the media diffusion structure 141, which forms a previously mentioned PTL, comprises metal, e.g., titanium. The separator plate 1 is arranged here, for example, on the anode side of the single cell 9. The separator plate 2 is arranged on the cathode side of the single cell 9 in the illustrated embodiment. The individual components are pressed together to form a single cell.The individual components each have fluid passages 146, 147, 150 (also referred to as through holes) arranged in alignment one above the other for the inflow and outflow of water, oxygen and hydrogen as well as positioning holes 148.

[0045] By projecting the cell frame 144 onto the separator plate 2, a flow field 3-2 and the active region of the separator plate 2 are defined. By projecting the cell frame 142 onto the separator plate 1, a flow field 3-1 and the active region of the separator plate 1 are defined.

[0046] In the area of ​​the flow fields 3, the separator plates 1, 2 each have channel-web structures with fluid-carrying channels and webs separating these channels. The separator plates 1, 2 made of Fig. 1 are single-layer components formed from a thin sheet material. The channel-web structures are complementarily formed on the back and front sides of each separator plate 1, 2. This means that webs on a respective back side form channels on a respective front side (and vice versa), and channels on a respective back side form webs on a respective front side (and vice versa). A back side can be understood, for example, as a side facing the interior of a respective cell.

[0047] The cell frame 142 has distribution channels (not shown) for distributing the introduced water. The through-openings 146, 147 are in fluid communication with the flow field 3-2 so that a medium can be conducted from the through-opening 146 to the flow field 3-2 or from the flow field 3-2 to the through-opening 147. 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 149 in the cell frame 144. It can then leave the cell through the through-openings 150. While the Fig. 1 have a round outer contour, other shapes are also possible. For example, the separator plates 1, 2 can have a rectangular outer contour (see also Fig. 2).

[0048] If water flows along the visible side of the flow field 3-1 of the separator plate 1, the resulting oxygen may make it increasingly difficult for the water to reach the adjacent MEA 140 to the desired extent as the flow path progresses. This reduces the extent of the electrochemical reaction taking place and thus the efficiency of the electrolyzer.

[0049] Based on the Fig. 2-15 illustrate embodiments of the invention that can be used to limit such problems. Fig. 2 shows an exemplary rectangular separator plate 10. This is a component of a basically Fig. 1 constructed electrochemical cell of an electrolyzer. The separator plate 10 shown can be arranged on an anode side, analogous to the separator plate 1 of Fig. 1. One side of the separator plate 10, which can be brought into contact with a PTL, is in Fig. 2 facing the viewer. On this side, a flow field 12 with a first channel-web structure 14 is formed. The separator plate 10 of the Fig. 2 can be combined with one or more cell frames and / or with sealing layers, as shown in Fig. 1, however, different arrangements - without cell frames and / or without sealing layers - are also possible; the corresponding details of the periphery of the separator plate 10 are not considered here.

[0050] The separator plate 10, in turn, comprises a plurality of through-holes 16, 16', 18, and mounting holes 20. The through-holes 16 serve to supply water, and the through-holes 16' serve to remove oxygen and water. The through-holes 18 serve to remove hydrogen. They are fluidically sealed from the first channel-web structure 14 and the fluids conveyed therein by sealing structures (not shown).

[0051] Fig. 3 shows an enlarged view of a part A of Fig. 1. The individual webs 22 and channels 24 of the first channel-web structure 14 are visible. Each channel 24 comprises a channel base 26, which transitions on both sides into a respective side flank 28. The webs 22 comprise web crests 30, which also transition on both sides into adjacent side flanks 28. The webs 22 and channels 24 are each rectilinear, although this is not mandatory, and extend along mutually parallel longitudinal axes L1, L2.

[0052] It is further clear that the first channel-web structure 14 forms a complementary second channel-web structure 32 on the side facing away from the viewer. This comprises a correspondingly complementary arrangement of internal channels 24' and internal webs 22'.

[0053] The end 33 of the webs 22 of the first channel-web structure 14 facing the viewer, which also forms a first end 33 of the inner channels 24', is open. As indicated by arrows SA, SI, supplied water can thus flow both along the outer channels 24 and along the inner channels 24'.

[0054] This connection is further illustrated by Fig. 4, which is a sectional view along a part of a section axis S of Fig. 2. More precisely, this cutting axis S runs centrally through one of the webs 22 of the first channel-web structure 14 and along its longitudinal axis L1, cf. Fig. 3.

[0055] Out of Fig. Figure 4 clearly shows that, in contrast to known solutions of the prior art, the separator plate 10 is formed in two layers, specifically in the area of ​​the flow field 12 and extending slightly beyond. More precisely, it comprises a first layer 34 and a second layer 36. These are each made of single-layer sheet metal and are secured to one another, in particular by welding. The layers 34, 36, and in particular at least their center planes and / or flat surface planes, which comprise undeformed regions of the respective layers 34, 36, run essentially parallel to one another.

[0056] The first layer 34 comprises a first outer side 38 and a first inner side 40 facing away from it. These form a correspondingly opposite first and second surface of the first layer 34. The second layer 36 comprises a second outer side 42 and a first inner side 44 facing away from it. These form a correspondingly opposite first and second surface of the second layer 36. The first outer side 38 and the second outer side 42 face away from one another. They form at least partially opposite surfaces or outer sides of the separator plate 10, for example a front and a back side. The first inner side 40 and the second inner side 44 lie opposite one another. Together they delimit the inner channels 24'. Such inner channels 24' are not present in known single-layer separator plates according to the prior art, since no comparable second layer 36 is provided there.

[0057] In the example shown, the first layer 34 has a larger surface area than the second layer 36. The first layer 34 comprises, for example, all of the through-openings 16, 16', 18 and fastening holes 20 from Fig. 2.

[0058] In the example shown, the second layer 36 extends opposite the flow field 12 of the first layer 34, but only slightly beyond it. As an optional feature, the first layer 34 has a step 60 in the area bordering the outer edge of the second layer 36, which forms a recessed receiving area 46 for the second layer 36. This recessed receiving area 46 surrounds the flow field 12 in a frame-like manner, see Fig. 2 & 3. The second layer 36, however, is flat and inserted into the recessed receiving area 46. The Fig. 4 downwardly facing rear side of the separator plate 10 is therefore substantially flat, since the second outer side 42 of the second layer 36 is aligned with an adjacent region of the first outer side 40 of the first layer 34. This adjacent region 40 surrounds the second layer 36 in a frame-like manner and includes the through-openings 16, 16', 18 and fastening holes 20 made of Fig. 2. The flatness of the back of the separator plate 10 improves the compressibility of a stack of multiple electrochemical cells and helps to reduce the resulting stack height.

[0059] Further shows Fig. 4 a weld seam 62, which connects the two layers 34, 36 in a fluid-tight manner around the flow field 12. This ensures that the anode chamber and the cathode chamber are fluidically separated from each other. The weld seam 62 runs adjacent to and spaced from the outer edge of the second layer 36 and the step 60 of the first layer 34. A representation of the weld seam 62 was omitted in Fig. 2, Fig. 3 and Fig. 5 has been omitted for reasons of clarity.

[0060] As a further optional feature, the first layer 34 is at least 1.5 times or at least twice as thick as the second layer 36, or, in other words, has a correspondingly increased material thickness. The second layer 36 is well supported by a flat support, for example, on a GDL, while the first layer 34 must withstand the pressure of the media in the channel-web structures 14, 32, so a greater material thickness is advantageous.

[0061] In Fig. 4 it is not separately apparent that the second inner side 44 of the second layer 36 rests against inner webs 22' of the second web-channel structures 32 and is optionally also fastened there at least locally, in particular fastened by a material bond and furthermore in particular by welding.

[0062] In Fig. 4 again shows the open end 33 of the webs 22 and internal channels 24', through which water flows into the internal channels 24'.

[0063] Fig. 5 shows an enlarged view of a partial area B from Fig. 1. This partial area B contains the second ends 35 of the webs 22 of the first channel-web structure 14, which are opposite the first open ends 33 and also form second ends 35 of the inner channels 24'. These second ends 35 are closed, which means that the inner channels 24' are also closed at their second ends 35. This creates a dynamic pressure within the inner channels 24', which forces the water conveyed in the inner channels 24' out of the same to the first outer side 38. For this purpose, the first layer 34 has a plurality of openings 50, which establish fluid connections between its first inner side 40 and first outer side 38.

[0064] By way of example only, these openings 50 are arranged in the side flanks 28 of the first channel-web structure 14 and thus also of the second channel-web structure 32. The openings 50 are thus arranged in the region of the inner channels 24' and connect them to an adjacent channel 24 on the first outer side 38 of the separator plate 10. In Fig. 5, openings 50 are visible only on the side flanks 28 facing the viewer. Openings could also be formed in the side flanks facing away from the viewer, or there could also be no openings at all.

[0065] From a summary of Fig. 3, Fig. 2 and Fig. 5 shows that the number of openings 50 near the second end 35 of a respective web 22 is higher than near the open first end 33, where no openings 50 are present. Accordingly, the number of openings 50 per internal channel 24' increases along its extension from the first end 33 to the second end 35. More specific examples of possible numbers and / or distributions of openings 50 along the total channel length of a respective internal channel 24' have already been mentioned above and are also detailed in the claims. What these examples have in common is that the number of openings 50 in a second half H2 of the total channel length, which extends to the second end 35, is higher than in a first half H1 of the total channel length, which extends from the first end 33. The halves H1 and H2 are shown by way of example in Fig. 2. In the present exemplary embodiment, the first half H1 has one opening 50 per inner channel 14' and visible side flank 28, while in the second half there are three openings 50 per inner channel 14' and visible side flank 28. In particular, no openings 50 can be present within this first half H1, and accordingly, no targeted fluid outlet from the inner channels 24' to the first outer side 38 of the separator plate 10 or from its first layer 34 can take place there, see Fig. 15. As previously described, such a fluid outlet is only made possible with increasing flow length of the water entering the open end 33 and is increasingly forced by a correspondingly increasing number of openings 50, since the oxygen concentration at the first outer side 38 also increases along this flow direction (ie increases from the first end 33 to the second end 35).

[0066] The Fig. 6a-8b each show sectional views of a section of a single internal channel 24' in the region of one of the openings 50. The respective sectional plane contains the longitudinal axis L1 of the Fig. 3 and Fig. 4 or runs parallel thereto. In addition, the cutting plane runs parallel to the second and / or first layer 34, 36. The examples of Fig. 6a-8b may be provided for at least individual openings 50 and alone or in any combination in a respective internal channel 24' of the examples disclosed here.

[0067] The Fig. 6a, Fig. 7a and Fig. 8a each show an unfilled inner channel 24' in which no water flows. Fig. 6b, Fig. 7b and Fig. 8b show the corresponding internal channels 24' in a filled state, ie with water flowing therein. In Fig. 6a, a flow direction is marked with an arrow F, with the same flow direction also being used for the remaining Fig. 6b-8b applies.

[0068] In the example of Fig. 6a-6b, a channel section located upstream of the opening 50 has a flow cross-section-narrowing region 52, the flow cross-section of which gradually decreases as viewed in the flow direction F. Downstream of the opening 50, however, the inner channel 24' has a flow cross-section-increasing region 54, the flow cross-section of which is initially constant as viewed in the flow direction F before gradually increasing again. The smallest flow cross-section 53 of the flow cross-section-narrowing region 52, which in the example shown is located directly adjacent to the opening 50, is larger (for example, at least 5% larger) than the smallest flow cross-section 55 of the flow cross-section-increasing region 54, which also directly borders the opening 50.

[0069] The edges of the regions 52, 54 adjacent to the opening 50 can form circumferential sections that are located at radially different levels relative to the longitudinal axis L1. More precisely, a radially wider outer circumferential section can be located upstream of the opening 50 than downstream. Viewed in the flow direction, the circumference or edge of the opening 50 is thus radially stepped and, in particular, radially indented downstream.

[0070] The above configuration enables the water emerging from the flow cross-section narrowing region 52 to exit in a defined manner from the opening 50 into the adjacent channels 24 of the first web-channel structure 14 and to pass into the flow cross-section increasing region 54 only to a correspondingly reduced extent.

[0071] The example of Fig. 7a-7b is largely analogous to the example of Fig. 6a-6b, with the difference that a smallest cross section 55 of the flow cross section increasing region 54 is located at an axial distance from the opening 50. Starting from the opening 50, the flow cross section of the flow cross section increasing region 54 initially decreases successively to the smallest cross section 55, before subsequently increasing again. This cross-sectional change is reflected in a limited dynamic pressure. The edge 59 of the opening 50, which represents the beginning of the region 54, also protrudes more into the inner channel 24' than is the case in Fig. 6a-6b is the case. In addition, the flow cross-section narrowing region 52 has a more pronounced taper than in Fig. 6a-6b. These factors together cause a higher proportion of water to escape from an inner channel 24' into the adjacent channels 24 of the first web-channel structure 14

[0072] The example of Fig. 8a-8b is largely analogous to the example of Fig. 7a-7b, with the difference that an axial opening width of the opening 50 is smaller than in Fig. 7a. The area of ​​the inner channels 24' located to the left, ie upstream with respect to the outer channels 24, also ends at the closed second end 35 of the webs 30, so that a large back pressure develops in this area, which in summary leads to all water flowing in the inner channels 24' from the right to the openings 50 exiting through these openings.

[0073] The Fig. 9-11 show further sectional views of selected webs 22 of the first web-channel structure 14. Webs 22 formed in this way can be provided in combination with all of the previously explained embodiments. The sectional plane is perpendicular to the longitudinal axes L1, L2 of the previous figures, see in particular Fig. 3. Compared to the view from, for example, Fig. 4, however, the orientation is changed such that the first outer side 38 of the separator plate 10 points downwards. Accordingly, the inner channels 24' point upwards. The extension of the second layer 36 is only in Fig. 9 indicated.

[0074] In Fig. 9 shows an example in which openings 50 are formed in the side flanks 28. This corresponds to the variant of the Fig. 2-5.

[0075] In Fig. 10, the openings 50 are formed in a transition region between the side flanks 28 and the web crest 30 or a channel bottom 26' of the inner channel 24' shown. An exit direction R of the water from the inner channel 24 is thus inclined more strongly in the direction of a PTL adjacent to the web crest 22, i.e., more strongly in an orthogonal direction to a plane of the separator plate 10. This can support a type of flushing of the PTL and thus bring more water into contact with the catalyst materials of the adjacent MEA.

[0076] In Fig. 11, an opening 50 is formed in the web tip 30 or the channel bottom 26' of the inner channel 24' shown. In Fig. 11, as well as in all of the Fig. 9 and Fig. 10, several of the illustrated openings 50 can be distributed along the channel or web lengths.

[0077] From the Fig. 11 positioned openings 50, the fluid exits essentially orthogonally to the surrounding surfaces of the web crest 30 and the channel bottom 26'. Fig. Figure 11 also shows a top view of the opening 50 tilted toward the viewer, including its cross-sectional dimensions. The cross-section is oval here. A first dimension D1, which runs along the longitudinal axis and thus in the flow direction, is larger than a second dimension D2, which runs perpendicular to the longitudinal axis and thus the flow direction. This increases the volume flow of the escaping water.

[0078] Also shown is a section of a PTL or, more generally, a media guide structure 41, which rests against the web tip 22 in the region of the opening 50. It can be seen that the opening 50 is significantly larger than granular, solid regions of the PTL and thus overlaps with several porous regions or pore sizes of the PTL, shown in black. In particular, an opening area of ​​the opening 50 is larger than an average pore size of the PTL, for example, at least four times as large.

[0079] Fig. 12 and Fig. 13 show two alternative designs of a separator plate 10 according to further embodiments. While the cross sections of the Fig. 9-11 show cross sections orthogonal to the channel longitudinal axis L1, the cross sections of the Fig. 12 and Fig. 13 parallel to the channel longitudinal axis L1. Fig. 12 shows an opening 50 in which the surrounding edge regions run in the same plane, parallel to the plate plane or to the channel bottom 26'. Fig. 13, however, shows an opening into which a scoop 56 projects on the downstream side. This scoop enables targeted drainage of water from an internal channel 24' to the outside, ie, into the first channel-web structure 14, in order to increase the water content there.

[0080] Fig. 14 shows an alternative design of a separator plate 10 according to a further exemplary embodiment. The separator plate 10 is fundamentally similar to the preceding examples, including two layers. Facing the viewer is the first outer side 38 of a first layer 34, which in turn has a first channel-web structure 14. A plurality of openings 50 are formed in the webs 22 of this first channel-web structure 14, which establish fluid connections to concealed internal channels 24'. Furthermore, first ends 33 of the webs 22 of the first channel-web structure 14, and thus also of the internal channels 24', are open. These first ends 33 are located close to a through-opening 16, from which water flows into the channel-web structure 14 and, through the open ends 33, also into the internal channels 24'.

[0081] The water flows along the channel-web structure 14 to an opposite through-opening 16'. Furthermore, it is shown that the separator plate 10, and specifically its first layer 34, also has further through-openings 18, which, however, are fluidically sealed from the first channel-web structure 14 and the through-openings 16, 16' by a seal 19.

[0082] The webs 22, and thus also the internal channels 24', extend in a curved and, for example, asymmetrical S-shape to their second ends 35, which in turn are closed. The total channel length of the internal channels 24' is measured as the flow path of the water along the internal channels 24 and not as a straight-line distance between their first and second ends 33, 35. This can also be understood as a consideration of the developed length of a respective internal channel 24'.

[0083] A line M is drawn connecting the approximate center positions of a respective total channel length of each inner channel 24' and thus also of each land 22—except for optional outermost lands 23. A first half H1 of the total channel length extends from a respective first end 33 to a center position indicated by the line M. A second half H2 of the total channel length, downstream of the first half, extends from this center position to a respective second end 35.

[0084] It can be seen that the openings 50 are positioned differently for each web 22 and thus for each internal channel 24'. Several of the internal channels 24' have no openings 50 along their first half H1. Others have only one opening 50 or only a portion of an opening 50. In contrast, all internal channels 24' have multiple openings 50 along their second half H2 of the total channel length. Thus, along a flow path along the first channel-web structure 14, with increasing proximity to the second end 35, more water can be supplied or refilled from the internal channels 24' in order to achieve the efficiency increases explained above.

[0085] Only by way of example, two outermost and comparatively short webs 23 are also shown, which have no openings 50 along their entire length.

[0086] Fig. 15 shows a split top and through view of first and second channel-web structures 14, 32. The crests 30 of the second channel-web structure 32 are only indicated by their first and second ends 33, 35 and the openings 50. While the first ends 33 are open and essentially correspond to the central channel cross-section, the second ends 35 are closed. In the first half H1—it is intentionally drawn smaller to provide sufficient space for a clear representation of the second half—of an internal channel 24', there are no openings in the web crests 30. In the second half H2, however, the web crests 30 have openings 50 that allow water to flow out of an internal channel 24'. In the present embodiment, the openings 50 within a web tip 30 are equidistant, but are offset from the openings 50 of the nearest web tip 30.This allows for a uniform water supply to the intermediate channels 24 of the first channel-web structure 14, with the material of the webs having sufficient stability. In terms of the shape of the openings, the openings 50 essentially correspond to those of FIG. Fig. 11 and are arranged in the area of ​​the web crests 30.

Claims

[1] Separator plate (10) for an electrochemical system, in particular for an electrolyzer, comprising: • a first layer (34) having a first outer side (38) and a first inner side (40), wherein a first channel-web structure (14) with a plurality of channels (24) and webs (22) separating the channels (24) is formed on the first outer side (38), wherein the first channel-web structure (14) forms a complementarily shaped second channel-web structure (32) on the first inner side (40), • a second layer (36) having a second outer side (42) and a second inner side (44), wherein the second inner side (44) lies opposite the complementarily shaped second channel-web structure (32) and defines with it a plurality of internal channels (24'), • a plurality of openings (50) per inner channel (24'), wherein the openings (50) each define a fluid connection between a respective inner channel (24') and the first channel-web structure (14) on the first outer side (38), wherein the number of openings (50) within a first half (H1) of a total channel length of a respective inner channel (24') is less than within a second half (H2) of the total channel length. [2] Separator plate (10) according to claim 1, wherein the inner channels (24') each comprise a channel bottom (26') which merges on both sides into a respective side flank (28), wherein at least one of the openings (50) of a respective inner channel (24') is formed at least in sections in one of the side flanks (28). [3] Separator plate (10) according to claim 1 or 2, wherein the inner channels (24') each comprise a channel bottom (26') which merges on both sides into a respective side flank (28), wherein at least one of the openings (50) of a respective inner channel (24') is formed at least in sections in the channel bottom (26'). [4] Separator plate (10) according to claim 2 or 3, wherein the at least one opening (50) in the channel bottom (26') and / or in a side flank (28) has a first dimension (D1) along a channel longitudinal axis (L1) of the inner channel (24'), which has a second dimension (D2) of the opening (50) which runs transversely to the channel longitudinal axis (L1), wherein the first dimension (D1) is at least one and a half times and in particular at least twice the second dimension (D2). [5] Separator plate (10) according to one of the preceding claims, wherein the second layer (36) is substantially planar, in particular at least in a region which lies opposite the second channel-web structure (32). [6] Separator plate (10) according to one of the preceding claims, wherein one of the first layer (34) and the second layer (36) has a plurality of through-openings (16, 16', 18) which are each fluidically connected to the first and / or the second channel-web structure (14, 32). [7] Separator plate (10) according to claim 6, wherein the one of the first and second layers (36) which does not have the through-openings (16, 16', 18) has a smaller area than the corresponding other of the first and second layers (36). [8] Separator plate (10) according to one of the preceding claims, wherein the second layer (36) is integrally or otherwise fluid-tightly connected to the first layer (34) in a region surrounding the second channel-web structure (32). [9] Separator plate (10) according to one of the preceding claims, wherein the first half (H1) of the total channel length of each internal channel (24') is upstream of the second half (H2). [10] Separator plate (10) according to one of the preceding claims, wherein the number of openings (50), in particular per internal channel (24'), within the second half (H2) is at least two and in particular at least three. [11] Separator plate (10) according to one of the preceding claims, wherein the internal channels (24') each have a first end (33) at the beginning of the first half (H1) of the total channel length and a second end (35) at the end of the second half (H2) of the total channel length, wherein a flow cross-section of the second end is between at least 50% smaller and up to and including 100% smaller and thus closed than an average flow cross-section within the first and / or second half of the total channel length. [12] Separator plate (10) according to claim 11, wherein the first end (33) is open and in particular has a flow cross-section which is at least as large as the average flow cross-section within the first and / or second half of the total channel length. [13] Separator plate (10) according to one of the preceding claims, wherein the openings (50) of a respective internal channel (24') have different cross-sectional sizes and / or cross-sectional shapes from one another and / or are otherwise designed differently from one another. [14] Separator plate (10) according to one of the preceding claims, wherein in the region of at least one of the openings (50) of a respective inner channel (24') a flow cross-section of the inner channel (24') is reduced at least in sections. [15] Separator plate (10) according to one of the preceding claims, wherein at least one of the openings (50) of a respective internal channel (24') is adapted to define a fluid flow in a direction away from the first outer side (38).

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