Bipolar plate arrangement and electrochemical unit

Abstract

To provide a bipolar plate arrangement for an electrochemical unit that achieves optimized supply and / or discharge of a fluid medium to and / or from a membrane electrode unit, it is proposed that at least two bipolar plates arranged in a stack be provided, forming a plurality of flow channels for a fluid medium, wherein the flow channels are bounded at least partially by webs, and the webs are designed such that the at least two adjacent bipolar plates are supported at least partially by the webs relative to each other, and that a gas diffusion layer is provided, arranged between the at least two bipolar plates, wherein the gas diffusion layer comprises at least one section having a thickness different from the base thickness of the gas diffusion layer.and at least one recess is provided on the upper sides of the webs to receive the section of the gas diffusion layer that differs from the base thickness.

Description

[0001] The present invention relates to a bipolar plate arrangement for an electrochemical unit and an electrochemical unit.

[0002] The core component of a fuel cell consists of the membrane electrode assemblies, which are separated from each other on the cathode and anode sides by bipolar plates. The bipolar plates have a channel structure that creates a flow field, through which reaction media are supplied uniformly to the membrane electrode assemblies and reaction products are removed.

[0003] The present invention is based on the objective of providing a bipolar plate arrangement by which an optimized supply and / or discharge of a fluid medium to and / or from a membrane electrode assembly is achieved. Furthermore, it is an objective of the invention to provide an electrochemical unit that exhibits an optimized performance potential.

[0004] This problem is solved according to the invention by a bipolar plate arrangement for an electrochemical unit comprising at least two bipolar plates arranged in a stack, wherein each bipolar plate is formed by at least one plate body on which a plurality of flow channels are provided, which form at least one flow field for a fluid medium, wherein the plurality of flow channels are at least partially bounded by webs, and the webs are designed in such a way that the at least two adjacent bipolar plates are supported at least partially via the webs to one another, wherein a gas diffusion layer is provided which is arranged between the at least two bipolar plates, and wherein the gas diffusion layer comprises at least one section which has a thickness that differs from a base thickness of the gas diffusion layer.and wherein at least one depression is provided on the upper sides of the webs for receiving the section of the gas diffusion layer that differs from the base thickness.

[0005] The electrochemical unit is in particular a fuel cell unit or an electrolysis unit.

[0006] In particular, a membrane electrode assembly (MEA) is provided between the at least two bipolar plates arranged in the stack.

[0007] In a fuel cell unit, the at least two bipolar plates arranged in a stack, together with the membrane electrode unit arranged between them, form a fuel cell.

[0008] Several such fuel cells arranged in a stack form a fuel cell stack.

[0009] A fuel cell unit can comprise one or more such fuel cell stacks.

[0010] The bipolar plates can preferably be formed from one layer of the plate body or from several layers of the plate body.

[0011] The at least one plate body can be made of metal, graphite, a graphite-polymer compound or ceramic.

[0012] The at least one plate body can be provided with a coating, in particular with a conductive and / or corrosion-resistant coating.

[0013] For example, at least one plate body may be coated with or made from gold, titanium, titanium nitride, carbon, chromium nitride and / or a ceramic material.

[0014] The webs forming the flow field for the fluid medium can in particular be formed from the at least one plate body, preferably formed from it, molded onto it or inserted into it.

[0015] The flow channels preferably extend in the flow direction from an inlet-side end of the bipolar plate to an outlet-side end of the bipolar plate.

[0016] The flow channels can provide both a flow in the same direction and a flow in opposite directions, preferably for different fluid media.

[0017] In particular, the recesses provided on the upper sides of the webs are designed to correspond to the at least one section of the gas diffusion layer that differs from the base thickness, so that this section is included in the recesses in an assembly state of the fuel cell.

[0018] Preferably, the recesses on the upper sides of the webs are aligned to each other in such a way that at least one section of the gas diffusion layer that differs from the base thickness can be arranged in the recesses.

[0019] In particular, the recesses on the upper sides of the webs are arranged in alignment with each other in order to accommodate at least one section of the gas diffusion layer that differs from the base thickness.

[0020] The depressions can preferably extend over the entire width of a rib on its upper side.

[0021] A further development of the bipolar plate arrangement can provide that the gas diffusion layer comprises at least two diffusion areas that have different properties, and that the at least one section of the gas diffusion layer that deviates from the base thickness is formed by an overlap section between the diffusion areas.

[0022] Preferably, the at least two diffusion areas have different diffusion properties.

[0023] The different diffusion properties of the at least two diffusion areas can be physical and / or chemical diffusion properties.

[0024] In particular, to achieve adapted diffusion characteristics during the operation of the fuel cell, i.e., during the flow of the fluid medium through the flow field, due to the changing moisture content, oxygen partial pressure, and the like of the fluid medium.

[0025] Due to the different diffusion properties of the at least two diffusion areas, uniform functional properties of the gas diffusion layer can be achieved in fuel cell operation.

[0026] Due to manufacturing processes, clear boundaries cannot be formed between the diffusion areas, so that in an area where the diffusion areas border each other, an overlap of the diffusion areas occurs, through which at least one section deviating from the base thickness is formed.

[0027] The overlap section, for example, is a superposition of the microporous layers in the area where the diffusion zones border each other.

[0028] In an assembled state of the bipolar plate arrangement, i.e., in a pressed state of the bipolar plate arrangement, it is particularly intended that the thickness of the fuel cell is essentially constant. Due to the overlapping sections, local variations in the thickness of the respective layer can occur within the individual fuel cell components, which are preferably compensated for by another layer.

[0029] One embodiment of the bipolar plate arrangement can also provide that the at least two diffusion areas are each formed by a microporous layer on the gas diffusion layer.

[0030] Preferably, the microporous layer has a thickness between 5-20 µm.

[0031] The at least two diffusion zones can either have the same thickness or different thicknesses. In this way, for example, different diffusion properties can be achieved.

[0032] In order to set defined diffusion properties of the at least two diffusion areas, the at least two diffusion areas can also be formed by physically and / or chemically different microporous layers.

[0033] In an advantageous further development of the bipolar plate arrangement, the at least one overlap section formed by the microporous layer between the diffusion areas can have a thickness that is greater than the thickness of the microporous layer in the at least two diffusion areas.

[0034] Preferably, the overlap section between the diffusion areas can have a thickness between 40 µm and 5 µm, more preferably between 40 µm and 7 µm, and particularly preferably between 40 µm and 10 µm.

[0035] The overlap section can have a width of approximately 10 mm or less, preferably 4 mm or less, and particularly preferably 2 mm or less.

[0036] In a further development of the bipolar plate arrangement, the at least one recess on the upper sides of the webs can have a length in an extension direction of the webs of 10 mm or less, preferably 4 mm or less, particularly preferably 2 mm or less.

[0037] Preferably, the depressions each have essentially the same length.

[0038] Similarly, the depressions can each have different lengths.

[0039] In particular, the lengths of the depressions correspond to the width of the overlap section between the at least two diffusion areas of the gas diffusion layer.

[0040] Another advantageous embodiment of the bipolar plate arrangement can provide that the at least one recess has a depth with respect to the top of the webs which corresponds to the thickness of the at least one section of the gas diffusion layer that differs from the base thickness, preferably the overlap section between the diffusion areas.

[0041] Preferably, the recesses are designed in such a way that they have essentially the same depth with respect to the upper surfaces of the webs.

[0042] In a preferred embodiment of the bipolar plate arrangement, the at least one recess can have a depth relative to the top of the web of 20 µm or less, preferably 10 µm or less, particularly preferably 5 µm or less.

[0043] Advantageously, in the bipolar plate arrangement, it can be provided that the at least one recess has a depth with respect to the top of the webs which is designed in such a way that, in the assembly state of the bipolar plate arrangement, a pressure of 50 bar or less, preferably 30 bar or less, particularly preferably 20 bar or less, is applied to the at least one section of the gas diffusion layer that deviates from the base thickness, preferably the overlap section between the diffusion areas.

[0044] In this way, it can preferably be achieved that, in the assembled state of the fuel cell, a locally adapted surface load, i.e., in the area of ​​the at least one recess, acts on the membrane electrode assembly or on the at least one section of the gas diffusion layer that deviates from the base thickness. Local impairments of the diffusion properties of the membrane electrode assembly due to excessive local loading on the gas diffusion layer can thus be avoided.

[0045] In one embodiment of the bipolar plate arrangement, the at least one section of the gas diffusion layer that differs from the base thickness, preferably the overlap section between the diffusion areas, can be arranged in a direction transverse to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0046] Advantageously, at least two diffusion areas on the gas diffusion layer are formed in a strip shape and are oriented in a direction perpendicular to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0047] The formation of at least two diffusion areas on the gas diffusion layer can be carried out both in a continuous manufacturing process, in particular a roll-to-roll manufacturing process, and in a discontinuous manufacturing process, i.e., a batch manufacturing process.

[0048] In roll-to-roll manufacturing, the gas diffusion layer can be unrolled from a roll in one manufacturing step, and then the microporous layer in the form of at least two diffusion areas can be applied to the gas diffusion layer during the unrolling process.

[0049] The at least two diffusion zones can be provided in strip form on the gas diffusion layer in one unwinding direction from the roll, i.e., in one machine direction of a production machine. Such continuous roll production enables fast and cost-optimized manufacturing of the gas diffusion layer.

[0050] The gas diffusion layer can then be cut to size for placement between at least two bipolar plates, either in a direction perpendicular to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0051] In batch production, the microporous layer, in the form of at least two diffusion zones, can be applied to the gas diffusion layer in a customizable production step. The gas diffusion layer can be pre-cut to size before or after the microporous layer is applied.

[0052] By such an alignment of the diffusion areas, the area between the at least two diffusion areas, in which the microporous layer is provided to overlap, i.e. the overlap section, is also aligned in this direction transversely to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0053] Another embodiment of the bipolar plate arrangement can provide that several recesses corresponding to each other are formed on the upper sides of adjacent webs, so that the recesses together form a recess section for receiving the section of the gas diffusion layer that differs from the base thickness, preferably the overlap section between the diffusion areas.

[0054] In other words, the recesses are arranged on the upper surfaces of the webs in such a way that the recesses together form the recessed section which extends over the bipolar plate and is designed to receive the section of the gas diffusion layer that differs from the base thickness, preferably the overlapping section between the diffusion areas.

[0055] In a further development of the bipolar plate arrangement, the depressions can be arranged in such a way that the depression section formed jointly by the depressions is oriented in a direction transverse to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0056] By orienting the recessed section perpendicular to the main flow direction of the bipolar plates or at an angle other than 90° to the main flow direction of the bipolar plates, the diffusion zones of the gas diffusion layer can be adapted to differently configured flow regions within the flow field of the bipolar plate. In this way, different diffusion properties of the gas diffusion layer can be provided in different flow regions of the flow field.

[0057] In a further development of the bipolar plate arrangement, at least one section of the gas diffusion layer that deviates from the base thickness, preferably the overlap section between the diffusion areas, can be included in the depression section in a direction transverse to the main flow direction of the bipolar plates or at an angle to the main flow direction of the bipolar plates that deviates from 90°.

[0058] Advantageously, the corresponding depressions are arranged in such a way that the respective depression section formed by the depressions is oriented in the same direction as the overlap section formed between the diffusion areas, so that the overlap section is arranged in the depression section formed by the depressions.

[0059] Furthermore, an advantageous further development of the bipolar plate arrangement can provide that several recessed sections are formed on the upper sides of the webs, which are spaced apart from each other in the main flow direction of the bipolar plates, and that the gas diffusion layer has a corresponding number of overlapping sections between several diffusion areas, wherein the overlapping sections are included in the respective recessed sections.

[0060] In this way, the gas diffusion layer can have more than two different diffusion areas, so that several sections deviating from the base thickness, preferably overlapping sections, are formed on the gas diffusion layer, which are received in the respective recessed sections arranged at a distance from each other.

[0061] The multiple recessed sections can be aligned in directions corresponding to each other, i.e., parallel to each other, or in directions diverging from each other.

[0062] Another embodiment of the bipolar plate arrangement can provide that the ribs are designed along a longitudinal extension in such a way that the ribs have a gradually or continuously increasing or decreasing rib height, and the diffusion areas of the gas diffusion layer have a correspondingly gradually or continuously decreasing or increasing thickness.

[0063] By having the diffusion zones of the gas diffusion layer exhibit a gradually or continuously decreasing or increasing thickness, defined physical and / or chemical diffusion properties of the gas diffusion layer can be formed along the main extension direction of the bipolar plates or in the flow direction of the fluid medium.

[0064] A particularly advantageous application of the bipolar plate arrangement according to the invention is, according to a further development of the invention, an electrochemical unit comprising at least one bipolar plate arrangement according to one of the embodiments described above.

[0065] The electrochemical unit is in particular a fuel cell unit or an electrolysis unit.

[0066] The fuel cell unit comprises any fuel cell that has bipolar plates for forming a fuel cell stack. For example, the fuel cell unit can include a polymer electrolyte fuel cell (PMFC), alkaline fuel cell (AFC), direct methanol fuel cell (DMFC), or phosphoric acid fuel cell (PAFC).

[0067] In particular, the fuel cell unit comprised a plurality of membrane electrode assemblies stacked in a stacking direction to form a fuel cell stack, with the membrane electrode assemblies being provided between the bipolar plates.

[0068] In particular, a bipolar plate is arranged on both an anode side and a cathode side of the membrane electrode assembly.

[0069] The bipolar plate arrangement creates an anode compartment on the anode side and a cathode compartment on the cathode side, through which the fluid medium (e.g. process gases) is supplied and / or removed for the fuel cell reaction.

[0070] A fuel cell unit with such a bipolar plate arrangement allows for improved supply and removal of the fluid medium to the membrane electrode assembly, thereby optimizing the fuel cell unit's performance potential. The bipolar plate arrangement thus maximizes the power density of the membrane electrode assembly, resulting in improved efficiency for the fuel cell unit.

[0071] Further preferred features and / or advantages of the invention are the subject of the following description and the graphic representation of exemplary embodiments.

[0072] The figures show: Fig. 1 a schematic sectional view of a bipolar plate arrangement according to an embodiment as disclosed; Fig. 2 a schematic sectional view of a gas diffusion layer of the bipolar plate arrangement; Fig. 3 a schematic perspective view of an exemplary process for producing the gas diffusion layer in a roll manufacturing process; Fig. 4 a schematic top view of a bipolar plate with a gas diffusion layer according to Fig. 2 of the bipolar plate arrangement; Fig. 5 a schematic sectional view of the bipolar plate with the gas diffusion layer according to section AA in Fig. 4; Fig. 6 a schematic top view of a bipolar plate with a gas diffusion layer according to an alternative embodiment of the bipolar plate arrangement; Fig. 7 a schematic top view of a bipolar plate with a gas diffusion layer according to a further alternative embodiment of the bipolar plate arrangement; Fig. 8 a schematic top view of a starting material for producing the gas diffusion layer according to Fig. 7; Fig. 9 a schematic side view of a bipolar plate according to a further alternative embodiment of the bipolar plate arrangement; Fig. 10 a schematic side view of a bipolar plate according to another alternative embodiment of the bipolar plate arrangement.

[0073] Identical or functionally equivalent elements are provided with the same reference symbols in all figures.

[0074] Fig. Figure 1 shows a schematic sectional view of a bipolar plate arrangement, designated as a whole by 100, for an electrochemical unit not shown in detail, in particular for a fuel cell unit or an electrolysis unit. The representation in Fig. Figure 1 illustrates the basic structure of the bipolar plate arrangement 100 according to an embodiment as disclosed.

[0075] The fuel cell unit comprises one or more fuel cell stacks, each formed by several fuel cells arranged in a stack. The fuel cell stacks are also referred to as fuel cell stacks, which comprise a plurality of such bipolar plate arrangements.

[0076] The fuel cell can be any type of fuel cell that includes bipolar plates to form the fuel cell stack, for example a polymer electrolyte fuel cell (PMFC), alkaline fuel cell (AFC), direct methanol fuel cell (DMFC) or phosphoric acid fuel cell (PAFC).

[0077] The fuel cell comprises a feed system for supplying a fluid medium to the fuel cell, in particular a fuel, fuel mixture (fuel-exhaust gas mixture), oxidizer and / or coolant. The exhaust gas, fuel, oxidizer and / or coolant are discharged from the fuel cell via an exhaust system.

[0078] The fuel cell stack comprises a plurality of membrane electrode assemblies 102, which are stacked in a single stacking direction. The membrane electrode assemblies 102 are each arranged between bipolar plates 104. That is, one bipolar plate 104 is arranged on one anode side and one cathode side of each membrane electrode assembly 102.

[0079] In other words, the bipolar plate 104 forms the anode side of a membrane electrode assembly 102 and the cathode side of an adjacent membrane electrode assembly 102.

[0080] The bipolar plate arrangement 100 is designed to provide a uniform distribution and supply of the fluid medium to the membrane electrode units 102 and to ensure optimal drainage of the fluid medium.

[0081] The bipolar plates 104 of the bipolar plate arrangement 100 are formed from one or more plate bodies 106, on which a flow field 108 for the fluid medium is formed.

[0082] The plate body 106 can be made of metal, graphite, a graphite-polymer compound or ceramic.

[0083] The surface of the plate body 106 can be provided with a coating, in particular with a conductive and / or corrosion-resistant coating. For example, the plate body 106 can be coated with or formed from gold, titanium, titanium nitride, carbon, chromium nitride and / or a ceramic material.

[0084] The flow field 108 is formed by a multitude of flow channels 110 through which the fluid medium can flow.

[0085] The flow channels 110 are preferably formed from the plate body 106, in particular they are formed from it, molded onto it or introduced into it.

[0086] The flow channels 110 are each bounded from one another by webs 112. The webs 112 are preferably formed from the plate body 106, in particular they are formed from it, molded onto it or inserted into it.

[0087] The adjacent bipolar plates 104 are collapsed towards each other via the webs 112. Preferably, the webs 112 are flattened on their upper surfaces 114 for this purpose, so that planar support sections are formed on these upper surfaces 114.

[0088] If the bipolar plates 104 are stacked on top of each other in a stack, corresponding webs 112 of the bipolar plates 104 lie at least partially against each other, causing adjacent bipolar plates 104 to crash into each other.

[0089] The webs 112 can have a width of 0.8 mm or less, preferably 0.5 mm or less, particularly preferably 0.3 mm or less.

[0090] The membrane electrode units 102 comprise a catalyst-coated membrane 116 with an anode-side gas diffusion layer 118 and a cathode-side gas diffusion layer 118.

[0091] The anode-side and cathode-side gas diffusion layer 118 are each provided with an anode-side and cathode-side microporous layer 120 towards the catalyst-coated membrane 116.

[0092] Fig. Figure 2 shows a schematic cross-sectional view of the gas diffusion layer 118 with the microporous layer 120 provided thereon.

[0093] The gas diffusion layer 118 comprises three diffusion zones 122, each formed by the microporous layer 120 and each exhibiting different diffusion properties.

[0094] Alternatively, the gas diffusion layer 118 can also have fewer or more than three diffusion areas 122.

[0095] These diffusion zones 122 are designed to provide different diffusion properties along a main flow direction H (main flow direction) of the bipolar plates 104. In particular, this is to achieve defined diffusion characteristics during the operation of the fuel cell due to the changing moisture content, oxygen partial pressure, and the like of the fluid medium as it flows through the flow channels 110.

[0096] In other words, the diffusion areas 122 each exhibit different diffusion properties with respect to at least one chemical and / or physical property.

[0097] In particular, the diffusion areas 122, which have different diffusion properties, are provided in a strip shape on the gas diffusion layer 118.

[0098] Preferably, the diffusion areas 122 are arranged transversely to the main flow direction H of the bipolar plates 104 or at an angle deviating from 90° to the main flow direction H of the bipolar plates 104 ( Fig. 3 and Fig. 5).

[0099] The microporous layer 120 preferably has a thickness between 5-20 µm in the respective diffusion areas 122.

[0100] Additionally, the gas diffusion layer 118 can be provided with a perforation, at least in certain areas, which penetrates the gas diffusion layer 118 completely or partially. For example, a defined perforation of the gas diffusion layer 118 can be assigned to the respective diffusion areas 122. The perforation can penetrate the gas diffusion layer 118, for example, by at least 25%, preferably by at least 50%, and particularly preferably by at least 75%.

[0101] By having the perforation completely or partially penetrate the gas diffusion layer 118 and / or depending on a density distribution of such a perforation, the diffusion properties of the gas diffusion layer 118 can also be defined and adjusted.

[0102] As in Fig. As can be seen in Figure 2, due to manufacturing reasons, a clear demarcation cannot be formed between the diffusion areas 122, so that sections 124 are formed between the diffusion areas 122, which have a thickness that differs from a base thickness B of the gas diffusion layer 118.

[0103] These sections 124 are each formed by overlapping sections 126 of the microporous layer 120 provided at the gas diffusion layer 118.

[0104] These overlapping sections 126 are formed because, during the production of the microporous layer 120, clearly defined areas between the diffusion regions 122 cannot be formed. Instead, in the overlapping sections 126, the microporous layers 120 of the different diffusion regions 122 overlap.

[0105] As a result, the gas diffusion layer 118 has a thickness greater than the base thickness B of the gas diffusion layer 118 in the diffusion areas 122 due to the overlap sections 126 formed by the microporous layer 120.

[0106] Preferably, the overlap sections 126 have a thickness between 40 µm and 5 µm, more preferably between 40 µm and 7 µm, and particularly preferably between 40 µm and 10 µm.

[0107] The overlap sections 126 extend between the diffusion areas 122, essentially in a strip-like fashion, along the gas diffusion layer 118.

[0108] Fig. Figure 3 is a perspective view that schematically illustrates an exemplary procedure for producing the gas diffusion layer 118 in a roll manufacturing process.

[0109] This roll manufacturing process forms a continuous manufacturing process for forming the diffusion areas 122 on the gas diffusion layer 118.

[0110] The manufacturing process takes place in one manufacturing step in which the coiled gas diffusion layer 118 is first unwound in a rolling direction A, and then, during the unwinding process, the microporous layer 120 in the form of the diffusion areas 122 is applied to the gas diffusion layer 118 by an application device not shown in detail.

[0111] In particular, the diffusion areas 122 in the rolling direction A, which preferably represents a machine direction of the manufacturing machine, are applied in strip form to the gas diffusion layer 118.

[0112] In this way, the overlap sections 126 are formed parallel to the rolling direction A, preferably the machine direction. The sections 124, which have a thickness differing from the base thickness B of the gas diffusion layer 118, are also formed parallel to the rolling direction A, preferably the machine direction.

[0113] As an alternative to this roll-to-roll manufacturing process, the microporous layer 120 can also be applied to the gas diffusion layer 118 by batch manufacturing.

[0114] Fig. Figure 4 shows a schematic top view of a bipolar plate 104 with a gas diffusion layer 118 according to Fig. 2, i.e. a gas diffusion layer 118 which has three diffusion areas 122.

[0115] This top view of the bipolar plate 104 illustrates the flow field 108 for the fluid medium, which is formed by the multitude of flow channels 110, each of which is limited to the others by the webs 112.

[0116] According to the in Fig. In the embodiment of the bipolar plate arrangement 100 shown in Figure 4, the flow field 108 is formed by flow channels 110 which extend in a straight line in the main flow direction H of the bipolar plate 104.

[0117] The flow field 108 has an inlet-side end 128 for supplying and an outlet-side end 130 for discharging the fluid medium.

[0118] It is understood that the embodiment of the bipolar plate arrangement 100 as disclosed is not limited to such a configuration of the flow field 108; rather, the flow channels 110 can have any course on the bipolar plate 104 and form any flow characteristic of the flow field 108, as shown below with reference to the Fig. 6 and Fig. 7 is described.

[0119] The gas diffusion layer 118 is provided on the bipolar plate 104 in such a way that the gas diffusion layer 118 rests essentially on the upper surfaces 114 of the webs 112.

[0120] The three diffusion areas 122 of the gas diffusion layer 118 are arranged one behind the other along the main flow direction H (flow direction of the fluid medium) of the bipolar plate 104.

[0121] Between the diffusion areas 122 of the gas diffusion layer 118, the two overlap sections 126 are formed, each having a thickness greater than the base thickness B of the gas diffusion layer 118 in the diffusion areas 122, as previously described with respect to Fig. 2 was described.

[0122] The overlap sections 126 extend essentially transversely to the main flow direction H of the bipolar plate 104.

[0123] Fig. Figure 5 shows a sectional view of the bipolar plate arrangement 100 according to section AA in Fig. 4, where the sectional view represents a longitudinal section in the area of ​​the overlap section 126. It should be noted that the representation in Fig. Figure 5 is exaggerated for illustrative purposes and not shown to scale.

[0124] The sectional view shows that recesses 132 are formed on the upper surfaces 114 of the webs 112, which are intended to receive the overlap section 126 of the gas diffusion layer 118.

[0125] The recesses 132 are provided on the upper surfaces 114 of the webs 112 corresponding to the overlap sections 126, so that the overlap sections 126 of the gas diffusion layer 118 are each received in the corresponding recesses 132.

[0126] Preferably the recesses 132 on the webs 12 extend transversely to a longitudinal extension of the webs 112 (transverse to the main flow direction H of the bipolar plate 104).

[0127] The recesses 132 are preferably formed over the entire width of the corresponding web 112.

[0128] Preferably, the recesses 132 can be designed in a trough shape transverse to the longitudinal extent of the webs 112.

[0129] In particular, the recesses 132 of adjacent webs 112 are arranged in alignment with each other, so that the corresponding recesses 132 form a continuous recess section transverse to the main extension direction H of the bipolar plate 104, in which the respective overlap section 126 is received.

[0130] The recesses 132 on the upper surfaces 114 of the webs 112 have a length in the longitudinal direction of the webs 112 of 10 mm or less.

[0131] Preferably the recesses 132 can have a length in the longitudinal direction of the webs 112 of 4 mm or less.

[0132] The recesses 132 are particularly preferably able to have a length in the longitudinal direction of the webs 112 of 2 mm or less.

[0133] Correspondingly, the overlap sections 126 of the gas diffusion layer 118 can have a width of 10 mm or less, preferably 4 mm or less, particularly preferably 2 mm or less.

[0134] The recesses 132 preferably each have a depth with respect to the upper surface 114 of the webs 112 which corresponds essentially to the thickness of the overlap section 126 between the diffusion areas 122 of the gas diffusion layer 118.

[0135] Preferably, the correspondingly arranged recesses 132 can have a substantially equal depth with respect to the upper surface 114 of the webs 112.

[0136] The recesses 132 can have a depth relative to the top surface 114 of the webs 112 of 20 µm or less, preferably 10 µm or less, particularly preferably 5 µm or less.

[0137] Advantageously, the recesses 132 can have a depth that depends on the thickness of the respective overlap section 126 and in which, in an assembly state of the bipolar plate arrangement 100, a pressure is applied to the overlap section 126 that does not exceed a defined limit.

[0138] In particular, the recesses 132 can have a depth depending on the thickness of the respective overlap section 126, at which, in the assembled state of the bipolar plate arrangement 100, a pressure of 50 bar or less, preferably 30 bar or less, and particularly preferably 20 bar or less, is applied to the overlap section 126. It is understood that the specified pressure ranges are preferably locally occurring pressures.

[0139] As in Fig. As shown in Figure 5, the gas diffusion layer 118 can be formed into the respective recesses 132 in the assembly state of the bipolar plate arrangement 100 in the area of ​​the overlap section 126.

[0140] Fig. Figure 6 shows a schematic top view of a bipolar plate 104 with a gas diffusion layer 118 according to an alternative embodiment of the bipolar plate arrangement 100.

[0141] In this alternative embodiment of the bipolar plate arrangement 100, the flow field 108 has a different appearance compared to the embodiment according to Fig. 3 other flow characteristics.

[0142] The webs 112 are designed in such a way that the flow channels 110 meander from the inlet-side end 128 to the outlet-side end 130 along the main flow direction H of the bipolar plate 104.

[0143] This meandering design of the flow field 108 creates four flow areas, to which corresponding four diffusion areas 122 are provided on the gas diffusion layer 118.

[0144] The embodiment according to Fig. Figure 6 is merely intended to illustrate that the bipolar plate arrangement 100 is not limited to a specific configuration of the flow field 108. Rather, the flow field 108 can exhibit any flow characteristic, and the gas diffusion layer 118 can be adapted to the configuration or flow characteristic of the flow field 108 by means of a corresponding number, configuration, and / or arrangement of the diffusion zones 122.

[0145] As regarding Fig. As described in section 5, in this embodiment of the bipolar plate arrangement 100, recesses 132 are provided on the webs 112 in the same way to accommodate the overlap sections 126 between the diffusion areas 122.

[0146] Fig. Figure 7 shows a schematic top view of a bipolar plate 104 with a gas diffusion layer 118 according to a further alternative embodiment of the bipolar plate arrangement 100.

[0147] The webs 112 are designed in such a way that the flow channels 110 run in a labyrinthine manner from the inlet-side end 128 to the outlet-side end 130.

[0148] Due to the labyrinthine course of the flow channels 110, the flow field 108 has three flow areas which are arranged adjacent to each other in the main flow direction H of the bipolar plate 104 and are provided at an angle to the bipolar plate 104 that deviates from 90° to the main flow direction H (to the rolling direction A and / or to the machine direction).

[0149] Alternatively, the labyrinthine design of the flow field 108 can also be configured in such a way that more or fewer than three such flow areas are formed.

[0150] Likewise, the orientation of the flow regions of flow field 108 is not on the one in Fig. The angle shown in section 7 is limited, but it can alternatively have any other angle that deviates from it.

[0151] The recesses 132 on the upper surfaces 114 of the webs 112 are arranged correspondingly to each other, such that the recessed section formed jointly by the recesses 132 is aligned at an angle to the main flow direction H of the bipolar plate 104, corresponding to the orientation of the flow areas of the flow field 108, which deviates from 90°.

[0152] In this embodiment of the bipolar plate arrangement 100, the overlap sections 126 between the diffusion areas 122 are taken up in the corresponding recess sections formed by the recesses 132 at an angle to the main flow direction H of the bipolar plate 104 that deviates from 90°.

[0153] In other words, the corresponding recesses 132 are arranged in such a way that the respective recess section formed by the recesses 132 is oriented at the same angle deviating from 90° as the overlap sections 126 formed between the diffusion areas 122, so that the respective overlap sections 126 are received in the corresponding recess sections formed by the recesses 132.

[0154] Fig. Figure 8 shows a schematic top view of how the gas diffusion layer 118 for the bipolar plate arrangement 100 is arranged according to Fig. 7 can be produced from a single starting material.

[0155] For this purpose, a gas diffusion layer as starting material 134 is first provided with the microporous layer 120 in such a way that several diffusion areas 122 arranged adjacent to each other are formed.

[0156] The diffusion areas 122 are arranged parallel to each other and perpendicular to a direction of extension of the gas diffusion layer serving as the starting material 134.

[0157] This starting material 134 has a larger surface area than the gas diffusion layer 118 to be produced.

[0158] This allows the gas diffusion layer 118 to be cut out from this starting material at the required angle, i.e., at the corresponding angle deviating from 90°, whereby the gas diffusion layer 118 is formed as shown in Fig. 7 is shown to be trainable.

[0159] It is understood that the gas diffusion layer 118 can also be cut out parallel or orthogonally from the starting material 134.

[0160] The Fig. 9 and Fig. Figure 10 shows schematic side views of bipolar plates 104 according to two further alternative embodiments of the bipolar plate arrangement 100.

[0161] In the embodiment according to Fig. 9 the webs 112 along the longitudinal extent of the webs 112, i.e. along the main flow direction H of the bipolar plate 104, are designed in such a way that the webs 112 have a gradually or stepwise increasing web height.

[0162] In this case, the gas diffusion layer 118 is designed in such a way that the diffusion areas 122 have a corresponding gradually or stepwise decreasing thickness.

[0163] Alternatively, it can also be provided that the webs 112 have a gradually or stepwise decreasing web height along the longitudinal extent and that the diffusion areas 122 of the gas diffusion layer 118 have a correspondingly gradually or stepwise increasing thickness.

[0164] In the embodiment according to Fig. 10 the webs 112 along the longitudinal extent of the webs 112, i.e. along the main flow direction H of the bipolar plate 104, are designed in such a way that the webs 112 have a continuously increasing web height.

[0165] Here, the gas diffusion layer 118 is designed in such a way that the diffusion areas 122 have a corresponding continuously decreasing thickness.

[0166] Alternatively, it can also be provided that the webs 112 have a continuously decreasing web height along the longitudinal extent and that the diffusion areas 122 of the gas diffusion layer 118 have a corresponding continuously increasing thickness.

[0167] In the two embodiments of the bipolar plate arrangement 100 according to the Fig. 9 and Fig.10 It may also be provided that the recesses 132 are provided on the upper surfaces 114 of the webs 112 in the manner described above in order to accommodate overlap sections 126 between the diffusion areas 122 of the gas diffusion layer 118.

[0168] It is understood that the features of the various embodiments described above can also be combined arbitrarily in an embodiment of a bipolar plate arrangement 100. Reference symbol list 100 Bipolar plate arrangement 102 Membrane Electrode Unit 104 Bipolar plate 106 plate bodies 108 Flow field 110 flow channels 112 Bridge 114 Top 116 catalyst-coated membrane 118 Gas diffusion layer 120 microporous layers 122 diffusion areas 124 Section with varying thickness 126 Overlap section 128 Inlet-side end 130 Outlet end 132 In-depth study 134 Starting material H Main flow direction A Rolling direction

Claims

[1] Bipolar plate arrangement (100) for an electrochemical unit, comprising at least two bipolar plates (104) arranged in a stack, wherein each bipolar plate (104) is formed by at least one plate body (106) on which a plurality of flow channels (110) are provided, which form at least one flow field (108) for a fluid medium, wherein the plurality of flow channels (110) are delimited at least in regions by webs (112), and the webs (112) are designed in such a way that the at least two adjacent bipolar plates (104) are supported relative to one another at least in sections via the webs (112), and comprising a gas diffusion layer (118) arranged between the at least two bipolar plates (104), wherein the gas diffusion layer (118) comprises at least one section (124) which has a thickness deviating from a base thickness (B) of the gas diffusion layer (118). has,and wherein at least one recess (132) is provided on upper sides (114) of the webs (112) for receiving the portion (124) of the gas diffusion layer (118) deviating from the base thickness (B). [2] Bipolar plate arrangement according to claim 1, characterized by in that the gas diffusion layer (118) comprises at least two diffusion regions (122) which have different properties, preferably different diffusion properties, and the at least one section (124) of the gas diffusion layer (118) which deviates from the base thickness (B) is formed by an overlap section (126) between the diffusion regions (122). [3] Bipolar plate arrangement according to claim 2, characterized by that the at least two diffusion regions (122) are each formed by a microporous layer (120) on the gas diffusion layer (118), which preferably has a thickness between 5-20 µm. [4] Bipolar plate arrangement according to claim 3, characterized bythat the at least one overlap section (126) formed by the microporous layer (120) between the diffusion regions (122) has a thickness which is greater than the thickness of the microporous layer (120) in the at least two diffusion regions (122), preferably a thickness between 40 µm and 5 µm, further preferably between 40 µm and 7 µm, particularly preferably between 40 µm and 10 µm. [5] Bipolar plate arrangement according to one of the preceding claims, characterized by that the at least one recess (132) on the upper sides (114) of the webs (112) has a length in an extension direction of the webs (112) of 10 mm or less, preferably 4 mm or less, particularly preferably 2 mm or less. [6] Bipolar plate arrangement according to one of the preceding claims, characterized byin that the at least one depression (132) has a depth with respect to the upper side (114) of the webs (112) which corresponds to the thickness of the at least one section (124) of the gas diffusion layer (118) deviating from the base thickness (B), preferably the overlap section (126) between the diffusion regions (122). [7] Bipolar plate arrangement according to one of the preceding claims, characterized by that the at least one recess (132) has a depth with respect to the upper side (114) of the webs (112) of 20 µm or less, preferably 10 µm or less, particularly preferably 5 µm or less. [8] Bipolar plate arrangement according to one of the preceding claims, characterized byin that the at least one depression (132) has a depth with respect to the upper side (114) of the webs (112) which is designed in such a way that, in an assembly state of the bipolar plate arrangement (100), a pressure of 50 bar or less, preferably 30 bar or less, particularly preferably 20 bar or less, is applied to the at least one section (124) of the gas diffusion layer (118) deviating from the base thickness (B), preferably the overlap section (126) between the diffusion regions (122). [9] Bipolar plate arrangement according to one of the preceding claims, characterized bythat the at least one section (124) of the gas diffusion layer (118) deviating from the base thickness (B), preferably the overlap section (126) between the diffusion regions (122), is arranged in a direction transverse to the main flow direction (H) of the bipolar plates (104) or at an angle deviating from 90° to the main flow direction (H) of the bipolar plates (104). [10] Bipolar plate arrangement according to one of the preceding claims, characterized by that a plurality of recesses (132) are formed corresponding to one another on the upper sides (114) of adjacent webs (112), so that the recesses (132) together form a recess section for receiving the section (124) of the gas diffusion layer (118) deviating from the base thickness (B), preferably the overlap section (126) between the diffusion regions (122). [11] Bipolar plate arrangement according to claim 10, characterized bythat the depressions (132) are arranged corresponding to one another in such a way that the depression section formed jointly by the depressions (132) is oriented in a direction transverse to the main flow direction (H) of the bipolar plates (104) or at an angle deviating from 90° to the main flow direction (H) of the bipolar plates (104). [12] Bipolar plate arrangement according to claim 10 or 11, characterized by that the at least one section (124) of the gas diffusion layer (118) deviating from the base thickness (B), preferably the overlap section (126) between the diffusion regions (122), is received in the recess section in a direction transverse to the main flow direction (H) of the bipolar plates (104) or at an angle deviating from 90° to the main flow direction (H) of the bipolar plates (104). [13] Bipolar plate arrangement according to one of claims 10 to 12, characterized bythat a plurality of recessed sections are formed on the upper sides (114) of the webs (112), which recessed sections are provided at a distance from one another in the main flow direction (H) of the bipolar plates (104), and the gas diffusion layer (118) has a corresponding number of overlapping sections (126) between a plurality of diffusion regions (122), the overlapping sections (126) being received in the respective recessed sections. [14] Bipolar plate arrangement according to one of the preceding claims, characterized by that the webs (112) are formed along a longitudinal extent in such a way that the webs (112) have a gradually or continuously increasing or decreasing web height, and the diffusion regions (122) of the gas diffusion layer (118) have a gradually or continuously decreasing or increasing thickness corresponding thereto. [15] Electrochemical unit comprising at least one bipolar plate arrangement (100) according to one of the preceding claims.

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