WO2024256509A1 - Separator plate for an electrochemical system - Google Patents

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

REINZ-Dichtungs-GmbH, Robert Bosch GmbH

1

separator plate for an electrochemical system

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 with a plurality of such separator plates is also disclosed.

Known electrochemical systems of the type mentioned normally comprise a stack of electrochemical cells, each of which is 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 adjacent cells (series connection of the cells). The separator plates are typically 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.

The separator plates or the individual plates can each have or form structures which are designed, for example, to supply the electrochemical cells arranged between adjacent separator plates with one or more media and/or to transport away reaction products. In particular, these structures can be used to guide a cooling fluid through a gap 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.

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. 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 Ul.

It is known to guide a first fluid, e.g. a fuel, on a first outer side of the separator plate, i.e. an outer side of a first individual plate, and to guide a second fluid, e.g. a reaction gas, on a second outer side of the separator plate facing away from it, i.e. an outer side of a second individual plate. In contrast, a cooling fluid is usually guided in an interior space delimited by the inner sides of the individual plates. The fluid-conducting structures on the respective outer sides of the individual plates form complementary shaped structures on their inner sides, which guide the cooling fluid.

However, it has been shown that the performance of such electrochemical systems can still be optimized. For example, the fluid guides between the through holes and a flow field still take up a significant amount of surface area on the respective sides of a separator plate. This surface area is not available as an active area of the cell and therefore does not directly contribute to its performance.

An object of the present invention is therefore to improve a performance of an electrochemical system with a plurality of such separator plates.

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 in the figures.

Accordingly, a separator plate for an electrochemical system is proposed, the system comprising:

- a first single plate and a second single plate, the inner sides of which face each other,

- at least one first passage opening for passing air or oxygen through the separator plate, - at least one second through-opening for passing hydrogen through the separator plate, wherein the first individual plate has a first flow field on its outside and at least one first distribution region which connects the first flow field and the first through-opening in a fluid-conducting manner, wherein the second individual plate has a second flow field on its outside and at least one second distribution region which connects the second flow field and the second through-opening in a fluid-conducting manner, wherein the first and second distribution regions each have a plurality of fluid-conducting channels, wherein the first and second flow fields each have a flow field main flow axis along which the respective fluid can flow through them, and a length dimension of the first and second distribution regions extends parallel to the respective flow field main flow axis, ie to the flow field main flow axis of the flow field to which a distribution region under consideration is connected in a fluid-conducting manner, wherein the first and second distribution regions each have a width dimension orthogonal to the respective flow field main flow axis where:

- a maximum length of the first distribution area is less than 28% of a maximum width of the first distribution area; and

- a channel length of the first distribution area averaged over the number of channels is less than 30%, in particular less than 28% of the maximum width of the first distribution area.

It was recognized that by setting the appropriate length and width and in comparison to existing solutions, the surface area of the first distribution area on the outside of the first individual plate can be significantly reduced without significantly impairing the function of the separator plate. In return, the surface area of the first flow field can be increased, which improves the performance of an electrochemical system comprising the separator plate. The second distribution area can also be reduced accordingly, whereas the proportion of the second flow field can be increased.

In the prior art, such length and width specifications are not provided for. This is usually omitted because reductions in the size of a distribution area along one dimension would require compensating enlargements in another dimension in order to provide sufficient flow cross-sections for the fluid to be supplied. According to the invention, Instead, it was recognized that the various parameters of the distribution area can be varied and combined in such a way that the area share of the distribution area in the total plate can be reduced without significantly impairing the fluid distribution.

The aim was to reduce the length of the distribution field for a fixed flow field without substantially changing the width of the distribution field. Instead, an average channel length was reduced. As a result, the required proportions were maintained.

Any distribution area disclosed here can be designed to have a guided fluid flow through it, in particular continuously and/or simultaneously in all channels included in the distribution area. Preferably, none of the distribution areas has channels or areas in which fluid can accumulate standing. The channels of each distribution area can be embossed into the respective plate. Each channel can be elongated and/or delimited by webs. Any two adjacent channels can be separated from one another by a web between them.

Furthermore, any distribution region disclosed here can be spatially positioned between the through-opening, in particular a center of gravity thereof, and the flow field which the distribution region connects to one another in a fluid-conducting manner. This intermediate positioning can in particular be present along the flow field main flow axis of the flow field connected to the distribution region in a fluid-conducting manner.

Usually, in addition to the through-openings for oxygen and hydrogen, the separator plate also has a through-opening for coolant, whereby the through-opening for coolant is preferably arranged between the through-opening for oxygen and the through-opening for hydrogen in a direction perpendicular to the flow field main flow axis. The end of the distribution area facing away from the flow field can be defined by the furthest point of a distribution area, from which the medium guided on the outer surface of the individual plate is guided between the coolant through-opening and the distribution area in the direction of the flow field past the coolant through-opening. The width of a distribution area can be defined so that it corresponds to the width of the associated flow field. The latter can be determined as the distance between the points that are most deflected from the plane of the plane, i.e. the channel base, of the outermost channel of the flow field. If one or both of these outermost channels not only have a line of maximum deflection from the plane of the plane, but also a bottom surface of maximum deflection from the plane of the plane, the center line of this bottom surface, i.e. the center orthogonal to the flow field main flow axis, is considered. If the flow field is formed by periodically deflected, for example wave-shaped, channels and webs, the width of the flow field and thus also the width of the distribution area can result from the width of the center lines of the lowest points of the outermost channels or the corresponding bottom surfaces.

If the flow field does not only have straight, parallel or periodically deflected channels and webs, the average width on the last 10% of the length of the flow field adjacent to the distribution area in question can be considered as the width of the flow field.

The end of the flow field towards the distribution area can be defined at the point at which, on an outer side of the flow field, which forms an outer side or an outer edge of the flow field when viewed transversely to the flow field main flow axis, for example, the center line of the outermost channel experiences a first change in direction relative to the flow field main flow axis, which is at least 0.5% of the width of the flow field. This can mean that the center line changes its direction relative to the flow field main flow axis, so that a distance of the center line to this flow field main flow axis changes by at least 0.5% of the width of the flow field. The location at which this change in distance first occurs can define the end of the flow field towards the distribution area.

If the changes occur at different locations on both outer sides, the location that is closer to the outer edge of the single plate that is at least substantially orthogonal to the flow field main flow axis and that lies beyond the nearest through openings can be considered.

In the case of wave-shaped flow fields, only those changes that do not follow the wave pattern should be considered. The separator plate can have regions with differing heights, e.g. a region that is lowered relative to another region. For example, average, minimum or maximum heights of the respective regions can be considered. Alternatively, one can speak of differences in the thickness of the separator plate. The regions with differing heights can each extend over a large part of the width of the separator plate, in particular over the region in which fluid-carrying channels are formed, whereby this width can run transversely to any of the flow field main axes. Preferably, the differences in thickness are not formed in the regions in which the sealing elements are formed.

Additionally or alternatively, these areas can be distributed along any of the flow field main axes and/or follow one another. As explained below, the distribution area and the flow field can be arranged in areas that differ from one another, with a height, in particular a mean or maximum height, of these areas differing from one another. Locations of maximum height can, for example, comprise web crests, with a respective web running between adjacent channels and separating them from one another. At the transition between a distribution area and the flow field, a further area of different height can be arranged, which has a lower height than both the other flow field and the other distribution area. This transition area can be allocated proportionately to both with regard to the aforementioned demarcation between flow field and distribution area, or belong to only one of the two; the aforementioned width definition should be the only decisive factor for this.

The height and the thickness can be measured orthogonally to a plane of the separator plate and in particular to a plane of any of its individual plates. In a manner known per se, the plane 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 here. On the one hand, the planes of the planes of the corresponding sections of the plates 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 planes of the planes of the plates. With the latter approach, however, it must be ensured that when considering distances or the like, the material thickness of only one of the two plates considered is taken into account. As a result of the provision of areas with different heights, for example, a first area can be lowered relative to the plane of the flat surface, whereas a further area can be lowered more or less significantly relative to the plane of the flat surface. Alternatively, the further area can lie in the plane of the flat surface or be raised relative to it. Raising relative to the plane of the flat surface can be equivalent to removing opposing areas of the individual plates, whereas lowering can reduce the distance between these opposing areas.

According to one variant, the separator plate comprises a height-reduced and/or lowered first region, which is preferably designed to be covered by a gas diffusion layer (GDL). The first region can be height-reduced or lowered, for example, compared to a flat surface plane and/or compared to a second region explained below. The first region can comprise the flow fields of the separator plate. As is known, a GDL can be arranged on one or both surfaces of an MEA, which is supported by the separator plate and is arranged in particular between two adjacent separator plates of a stack. The first region can be used as an active region by covering it with the GDL and the MEA.

Additionally or alternatively, the separator plate comprises at least one second region which is raised and/or not reduced in height. This can apply, for example, in comparison to a flat surface plane and/or the first region explained above. When comparing the heights of the first and second regions, locations of maximum height of these regions can be compared with one another, in particular web crests of these regions. Any distribution region disclosed here can be comprised of a raised second region.

In summary, a further development provides that the separator plate has a first region, which in particular comprises the flow fields, and which has a lower, in particular maximum, height compared to at least one second region, wherein the second region comprises at least one first and at least one second distribution region of the type explained above. These first and second regions can therefore be defined in such a way that they comprise parts of the outer sides of both individual plates, i.e. complete sections and in particular complete cross sections of the assembled separator plate. The aforementioned transition region can in this sense represent a third region in terms of height, but in terms of width it can either be completely the first region, completely the second area or partly to the first and partly to the second area, according to the width of the outermost channels on both sides.

Any flow field disclosed here can be characterized, for example, in that all webs and channels included thereby are straight over at least a large part of their length and run parallel to one another and parallel to a flow field main flow direction of this flow field.

Alternatively, the webs and channels of a respective flow field can also be wave-shaped and run next to each other and along the main flow axis with a similar wave shape.

The flow field main flow axis can correspond to a longitudinal axis and/or an axis of symmetry, in particular a mirror symmetry axis, of a respective flow field or run parallel thereto. The separator plate can have two outer edges or also longitudinal sides that lie opposite one another and run at least in sections along at least one of the flow field main flow axes. The flow field main flow axes of the first and second flow fields can run parallel to one another or coincide with one another, in particular in an orthogonal projection into a common plane.

To achieve low flow resistance, it is advantageous if the channel lengths, as well as the total and average channel length in a distribution area, are short. The average channel length can be determined by adding up all the individual channel lengths of a distribution area on the outside of a single plate and then dividing by the number of these channels.

According to a further development, a maximum length of the second distribution area is less than 65%, preferably less than 55%, in particular less than 50%, of the maximum length of the first distribution area. A corresponding reduction in the size of the second distribution area creates additional degrees of freedom in order to provide flow spaces for the cooling fluid, in particular by means of the second individual plates. In particular, this makes it possible to reduce flow resistances of the cooling fluid in the first distribution area. A reduced length of the second distribution area compared to the first distribution area is also acceptable because the second distribution area carries hydrogen, for which this reduction in size results in only partially relevant flow resistances. However, it can also be provided that the maximum length of the second distribution area is greater than 35%, in particular greater than 40%, of the maximum length of the first distribution area.

A further development provides that the first and second flow fields are lowered relative to the respective first and second distribution areas connected thereto. The connection relates to the fluid-conducting connection of the distribution area and the flow field. In particular, the lowering can apply in relation to locations of maximum height encompassed by the distribution areas and flow fields. These can be, for example, web crests and preferably not channel bottoms. This further development can be implemented in particular by and/or can in particular include the flow fields being encompassed by a first area of the type discussed above and the distribution areas being encompassed by a second area of the type discussed above, wherein the first area is lowered relative to the second area.

In a further embodiment, the maximum length of the first and second distribution region lies between a transition from the respective distribution region and (or to) an associated flow field and a point of the respective distribution region that is at a maximum distance from this transition.

Additionally or alternatively, a maximum dimension of the first and second distribution region can be orthogonal to one of the flow field main flow axes in each case in an edge region of the first and second distribution region, in which fluid from the correspondingly connected one of the first and second flow fields is fed into the distribution regions or in which fluid from the distribution regions is fed into the correspondingly connected one of the first and second flow fields. In particular, the maximum dimension can run orthogonal to the flow field main flow axis of the flow field that is fluidly connected to the distribution region in question.

The invention also relates to an electrochemical system comprising a plurality of separator plates according to any aspect disclosed herein.

The invention is explained below with reference to the attached schematic figures. The same reference numerals can be used across the figures for similar or equivalent features. Figure 1 shows a perspective view of an electrochemical system with a plurality of stacked separator plates with membrane electrode units arranged between them.

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 is an illustration of a portion of a separator plate according to an example of the prior art.

Figure 4 is a simplified schematic representation of the fluid flow in the separator plate from Figure 3.

Figure 5 is an illustration of a portion of a separator plate according to a first embodiment of the invention.

Figure 6 is a schematically simplified representation of the fluid flow in the separator plate from Fig. 5.

Figure 7 is a schematically simplified representation of the fluid guide in a separator plate according to a further embodiment of the invention

Figure 1 shows an electrochemical system 1 of the type proposed here with 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 called the stack direction. In the present example, the system 1 is a fuel cell stack. 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 unit (MEA) 10 is arranged between 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. In alternative embodiments, the 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 guided on or through the separator plates in an electrolyzer, an electrochemical compressor or a redox flow battery can differ from the media used for a fuel cell system.

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 x-y plane and thus perpendicular to the stacking direction (z-axis 7). The end plate 4 has a plurality of media connections 5 via which media can be fed to the system 1 and via which media can be removed from the system 1. These media that can be fed 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.

Figure 2 shows in perspective two adjacent separator plates 2 or bipolar plates, which can be included in an electrochemical system of the type of system 1 from Figure 1. The separator plates 2 correspond to an example from the prior art. However, the properties and features explained below in relation to this can also apply to the separator plates 2 according to the invention disclosed here or can be provided for them, unless otherwise mentioned or apparent.

Fig. 2 also shows a known membrane electrode unit (MEA) 10 arranged between these adjacent separator plates 2, wherein the MEA 10 in Figure 2 is largely covered 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 covers the other individual plate 2b. The individual plates 2a, 2b can each be made from a metal sheet, e.g. from a stainless steel sheet. The individual plates 2a, 2b can be welded to one another, e.g. by laser welding or only connected when the stack is stacked. In particular In particular, the design of fluid-conducting structures on the outside of the individual plate 2a facing the viewer in Fig. 2 may differ from the structures according to the invention in the further figures below.

The individual plates 2a, 2b have through-openings which are aligned with one another and 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 which 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. A cooling fluid can be introduced into the stack 6 or drained from the stack 6 via the lines formed by the through-openings 11a, for example. 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 with reaction gas and to drain the reaction products from the stack 6.

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.

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 20a. The distribution regions 20a 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 20a by means of the flow field 17a over the active region 18 or to distribute a medium introduced from the active region 18 or from the flow field 17a to the second of the through openings 11b to collect or bundle the medium flowing. In the latter case, the collecting distribution region 20a can also be referred to as a collection region. The fluid-conducting structures of the distribution regions 20a are also provided in Figure 2 by webs and channels running between the webs and delimited by the webs.

Without this being shown separately in Figure 2, a cooling fluid distribution structure 19 formed and/or enclosed between the individual plates 2a, 2b also has distribution areas 20c which overlap with the distribution areas 20a, b of the individual plates 2a, 2b. This cooling fluid distribution structure 19 is fluidically connected to a flow field 17c which overlaps with the flow fields 17a, b of the outer sides of the individual plates 2a, 2b or is enclosed between them, or comprises this flow field 17c. 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.

The two through-openings 11b or the lines formed by the through-openings 11b through the plate stack of the system 1 are each in fluid communication with one another via passages 13b in sealing beads 12b, via the distribution structures of the distribution areas 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 in the sense of this disclosure. A fluid guided along the outside 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.

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 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 in the sense 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 is particularly evident from the fact that, compared to the other through openings 11a, 11b largest cross-section of the air or oxygen through openings 11c.

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

Figure 3 shows a partial area of a separator plate 2 according to the prior art that is analogous to the separator plate 2 from Figure 2. The partial area corresponds to an end area comprising three of the through openings 11a-c. The positioning of these through openings 11a-c makes it clear that the view is rotated by 90° compared to Figure 2.

In Figure 3, one looks at the outside of the second individual plate 2a (anode plate), as can be seen from the distribution area 20a shown and its indicated extension of channels 36a. These channels 36a are spaced from each other by material webs that are not separately marked and extend from the through-opening 11b in the direction of the flow field 17a.

An extension of the distribution area 20b is also indicated by hatching. In this area of the outside of the second individual plate 2a, there are preferably only those web-channel structures that provide a flow space inside the assembled separator plate for cooling fluid, but no web-channel structures that are accessible on the outside for gas, for example hydrogen, escaping from the through-opening 11b. The cooling fluid can reach this area via a left-hand and angled part of the passages 13a on the through-opening 11a in Figure 3. Cooling fluid can flow along a part of the inside of the distribution area 20a via the right-hand and oppositely angled part of the passages 13a on the through-opening 11a in Figure 3. This is further illustrated in Figure 4, in which fluid flows in the separator plate 2 from Figure 3 are shown in a simplified schematic. Figure 4 again shows the through openings 11a-c and an extension of the distribution areas 20a, b. These are shown in a superimposed form, for example resulting from an orthogonal projection in a common plane. The representation in Figure 4 therefore corresponds to a view through the separator plate 2 from Figure 3, whereby the hatching only represents hatching and not channels or webs as such.

The fluids exiting from the through openings 11a-c are marked by different types of arrows. The flow fields 17a-c are also shown superimposed, as can be seen from the fact that all types of arrows are shown in their area. A flow field main flow axis S is entered, the orientation of which is the same for each of the flow fields 17a-c in Figure 4.

Firstly, in the case of the through-opening 11a, one can see the exit of cooling fluid via the passages 13a (not shown separately). This exit essentially takes place in the two different directions described above, which are angled relative to one another. The cooling fluid thus initially flows backwards along parts of both distribution areas 20a, b, before entering an overlap area in which sections of both distribution areas 20a, b lie opposite one another and overlap. This overlap area corresponds to the area shown in cross-hatched form in Figure 3. From this overlap area, the cooling fluid finally passes into the flow field 17c of the cooling fluid distribution structure.

For the distribution areas 20a, b, the basically parallel flow directions present therein are marked by corresponding arrows. Channels 36a, b within the distribution areas 20a, b, which are not shown in detail, run along these arrows.

As further quantities or parameters of the distribution areas 20a, b, an average channel length klvquer is entered, but as an example only for one of the distribution areas 20a, b.

Also shown is a length hk, ha of the distribution areas 20a, b. This is measured along and/or parallel to the flow field main flow axis S. It extends between a first location of the distribution area 20a, b, which is closest to the fluid-conducting area 20a, b in question. tend connected flow field 17a, b, and a second location of the distribution region 20a, b, which is furthest away from the corresponding flow field 17a, b. This second location corresponds to an end of the distribution region 20a, b facing away from the associated flow field 17a, b. The second location or the facing away end is defined by the furthest point of the distribution region 20a, b, from which on the outer surface of the corresponding individual plate 2a, 2b the medium guided on this outer surface is guided between the coolant passage opening 11a and the distribution region 20a, b in the direction of the flow field 17a, b past the coolant passage opening 11a. In other words, it is the point of the distribution region 20a, b which is furthest away from the flow field 17a, b along the flow field main flow axis S, from which point on the outer surface of the corresponding individual plate 2a, 2b the medium guided on this outer surface is guided from the associated through-opening 11b, 11c through the distribution region 20a, b in the direction of the flow field 17a, b.

Finally, a width bactive of the flow fields 17a-c is also entered, which in the example shown is aligned and dimensioned in the same way for all flow fields 17a-c. In particular, a maximum width bactive of the flow fields 17a-c can be considered which, as shown, is present at the transition between the distribution areas 20a, b and flow fields 17a-c. A dimension of the distribution areas 20a, b orthogonal to the flow field main flow axis S at this transition has the same amount as the flow field width bactive. At this transition, the distribution areas 20a, b and flow fields 17a, b, which are each connected in a fluid-conducting manner, exchange fluid with one another. However, the width of the distribution area changes immediately after entering or immediately before exiting one of the distribution areas 20a, 20b, since the outermost channels run at an angle to the flow field main flow axis S.

Figure 4 also shows a first and second region 40, 42 of the separator plate, which have different heights relative to one another or, in other words, define different height levels of the separator plate. The first region 40 comprises the flow fields 17a-c. The second region 42 comprises the distribution regions 20a, b. The first region 40 is lowered relative to the second region 42, ie lowered into the image plane of Figure 4. This applies in particular to web crests that are present between channels of the flow fields 17a and 17b and the distribution regions 20a, b. A maximum or average position of these web crests, for example, is in the first region. 40 lower than in the second region 42. A height axis along which these positions are viewed is perpendicular to the image plane of Fig. 4. A transition region 41 is given in Fig. 4 by means of a rectangle framed with dashed lines. In this transition region, the height of the webs on the outside of the second individual plate 2a can be even lower than in the aforementioned first and second regions 40, 42. Whether this transition region is counted completely or partially as part of the distribution region 20a and/or the flow field 17a is preferably determined not by the height, but by the width. This means that preferably at most such a portion of the transition region 41 can be assigned to the flow field 17a that lies in a region in which the outermost channels of the flow field 17a do not yet have a change in direction of more than 0.5% of the width of the flow field 17a. Remaining portions of the transition region 41, in particular those which extend in the direction of an adjacent distribution region 20a following the aforementioned changes in direction, can preferably be assigned to this distribution region 20a.

Fig. 5 is a view analogous to Fig. 3, but for a separator plate 2 according to an embodiment of the invention, wherein, however, sections of the through openings 11a-c as well as the upper outer edge of the separator plate 2 are omitted. One difference from Fig. 3 can be seen in that the passages 13a in the region of the through opening 11a are aligned in such a way that they allow the cooling fluid to flow in essentially in only one direction, namely along an inner side of a part of the first distribution region 20b of the first individual plate 2b. Thus, with the illustrated and explained in more detail below with reference to Fig. 6 inventive design of the distribution regions 20a, b, it is not possible and also not desired to allow cooling fluid to flow along part of the inner side of the second distribution region 20a of the second individual plate 2a.

This is clear from the schematic representation of Figure 6, whereby the type of representation is basically comparable to Figure 4. Since there is no projection 46 (see Figure 4) of the second distribution area 20a relative to the first distribution area 20b comparable to Figure 4, no cooling fluid can be guided along the inside of the second distribution area 20a starting from the through-opening 11a. Such a relative projection 46 is formed in the variant of Figure 4 in that the second distribution area 20a, in contrast to Figure 6, does not completely overlap with the first distribution area 20b, see the simply hatched portion of the second distribution area 20a. Another significant difference between the embodiment according to the invention and the previously known variant of Figures 3 & 4, explained below, relates to the size ratios of the distribution area parameters. These are selected in such a way that a respective area of the distribution areas 20a, b is smaller than in Figures 3 & 4. This area-reducing definition of the distribution area parameters is favored by the cooling fluid guide described above along the rear of only one of the distribution areas 20b, since, for example, no overhang 46 comparable to Figure 4 needs to be maintained. However, this cooling fluid guide including the elimination of the overhang 46 is not a mandatory requirement in order to be able to define the distribution area parameters in the manner described below, as is also made clear in the context of Figure 7.

Compared to the variant of Figures 3 and 4, in Fig. 6 the area of the first distribution region 20b on the outside of the first individual plates 2b has been reduced in particular. The previous area 48 of the first distribution region 20b or its previous outline according to the variant of Figures 3 and 4 is marked with a dashed line. It can be seen that in particular the maximum length hk of the first distribution region 20b has been reduced compared to this previous area 48, since the corresponding point of maximum length has moved in the direction of the flow field 17b connected to the first distribution region 20b in a fluid-conducting manner. At the same time, the maximum width baktiv of the first distribution region 20b or of the flow field 17b has been left essentially unchanged. The position of the axis along which hk is maximum shifts to the right in comparison from Figures 3 and 4 to Figures 5 and 6, which on the one hand enables sufficient flow cross-sections for the fluid guided by the distribution region 20b and at the same time results in a reduction of the average channel length klvquer relative to the variant of Figures 3 and 4.

For the second distribution area 20a, the height ha was also reduced relative to the width bactive. The height reduction in the present example is smaller than in the case of the first distribution area 20b. Here, too, the position of the maximum height ha is shifted compared to Figures 3 and 4. In the case of the second distribution area 20a, this is acceptable, since only very large reductions in the flow cross-section would lead to significant flow resistances for the hydrogen carried by it.

Specifically, the parameters are defined as follows:

- The maximum length hk of the first distribution area 20b is less than 28% of a maximum width baktiv of the first distribution area 20b; - The channel length klvquer of the first distribution area 20b averaged over the number of channels 36b is less than 30%, in particular less than 28% of the maximum width baktiv of the first distribution area 20b; and preferably:

- The maximum length ha of the second distribution region 20a is less than at least 55% of the maximum length hk of the first distribution region 20b and/or greater than at least 35% of the maximum length hk of the first distribution region 20b.

In this way, the indicated reductions in the area of the distribution areas 20a, b could be achieved without an inadmissible increase in the flow resistances for the fluids guided by the distribution areas 20a, b.

Figure 7 is a view of a separator plate 2 according to a further embodiment of the invention, analogous to Figure 6. As in Figure 4 and in contrast to Figure 6, it can be seen that the passages 13a in the area of the through opening 11a are aligned in such a way that they allow the cooling fluid to flow in at an angle in order to allow cooling fluid to flow both along a part of the inside of the first distribution area 20b of the first individual plate 2b and along a part of the inside of the second distribution area 20a of the second individual plate 2a. As in Figure 4, there is a projection 46 of the second distribution area 20a relative to the first distribution area 20b.

On the other hand, the embodiment according to the invention in Figure 7 has similar differences as the embodiment according to the invention in Figures 5 and 6 compared to the previously known variant in Figures 3 and 4 with regard to the size ratios of the distribution area parameters. These are again selected in such a way that a respective area of the distribution areas 20a, b is smaller than in Figures 3 and 4, although there is now even a projection 46.

Again, the previous outline 48 of the first distribution area 20b is marked with dashed lines according to the variant of Figure 4. The reduction in size of the distribution area 20b is not quite as clear as in the example according to the invention shown in Figures 5 and 6. Nevertheless, the maximum length hk of the first distribution area 20b is also reduced here compared to this previous area 48. The position of the axis along which hk is maximum is also shifted to the right in the latter when comparing Figure 4 with Figure 7, which, as in Figure 6, on the one hand enables sufficient flow cross-sections for the fluid guided by the distribution area 20b and at the same time a reduction in the average channel length klvquer relative to the variant of Figure 4.

In addition, the previous outline 48' of the second distribution area 20a is shown in dashed lines according to the variant of Figure 4. This distribution area 20a is also reduced in size in Figure 7 compared to the original size in Figure 4. Furthermore, the position of the maximum height ha is shifted slightly towards the middle, i.e. to the left, compared to Figure 4.

Again, the parameters are set as follows:

- The maximum length hk of the first distribution area 20b is less than 28% of a maximum width baktiv of the first distribution area 20b;

- The channel length klvquer of the first distribution area 20b averaged over the number of channels 36b is less than 30%, in particular less than 28% of the maximum width baktiv of the first distribution area 20b; and preferably:

- The maximum length ha of the second distribution area 20a is greater than at least 35% of the maximum length hk of the first distribution area 20b.

Here too, the area reductions shown for the distribution areas 20a, b could be achieved without an unacceptable increase in the flow resistance for the fluids carried by the distribution areas 20a, b.

Claims

patent claims 1. Separator plate (2) for an electrochemical system (1), comprising: - a first single plate (2b) and a second single plate (2a), the inner sides of which face each other, - at least one first passage opening (11c) for passing air or oxygen through the separator plate (2), - at least one second through-opening (11b) for passing hydrogen through the separator plate (2), wherein the first individual plate (2b) has on its outside a first flow field (17b) and at least one first distribution region (20b) which connects the first flow field (17b) and the first through-opening in a fluid-conducting manner, wherein the second individual plate (2a) has on its outside a second flow field (17a) and at least one second distribution region (20a) which connects the second flow field (17a) and the second through-opening (11b) in a fluid-conducting manner, wherein the first and second distribution regions (20a, 20b) each have a plurality of fluid-conducting channels (36a, 36b), wherein the first and second flow fields (17a, 17b) each have a flow field main flow axis (S) along which they can be flowed through by the respective fluid, and a length dimension (hk, ha) of the first and second distribution regions (20a, 20b) extend parallel to the respective flow field main flow axis (S), wherein the first and second distribution regions (20a, 20b) each have a width dimension (baktiv) orthogonal to the respective flow field main flow axis, wherein: - a maximum length (hk) of the first distribution area (20b) is less than 28% of a maximum width (baktiv) of the first distribution area (20b); and - a channel length (klvquer) of the first distribution area (20b) averaged over the number of channels (36b) is less than 30%, in particular less than 28% of the maximum width (baktiv) of the first distribution area (20b). 2. Separator plate (2) according to one of the preceding claims, a maximum length (ha) of the second distribution region (20a) is less than 65%, in particular less than 55%, in particular less than 50% of the maximum length (hk) of the first distribution region (20b). 3. Separator plate (2) according to one of the preceding claims, wherein the maximum length (ha) of the second distribution region (20a) is greater than 35%, in particular greater than 40%, of the maximum length (hk) of the first distribution region (20b). 4. Separator plate (2) according to one of the preceding claims, wherein the first and second flow fields (17a, b) are lowered relative to the respective first and second distribution regions (20a, b) connected thereto. 5. Separator plate (2) according to one of the preceding claims, wherein the maximum length (ha, hk) of the first and second distribution region (20a, b) is between a transition from the respective distribution region (20a, b) and associated flow field (17a, b) and a point of the respective distribution region (20a, b) at the maximum distance from this transition. 6. Separator plate (2) according to one of the preceding claims, wherein a maximum dimension of the first and second distribution region (20a, b) orthogonal to one of the flow field main flow axes (S) is present in an edge region of the first and second distribution region (20a, b) in which fluid is fed from the correspondingly connected one of the first and second flow fields (17a, b) or in which fluid is fed into the correspondingly connected one of the first and second flow fields (17a, b). 7. Electrochemical system (1) containing a plurality of separator plates (2) according to one of the preceding claims.