Bipolar plate and electrochemical device comprising a bipolar plate

Abstract

Disclosed is a bipolar plate for an electrochemical unit of an electrochemical device comprising multiple successive electrochemical units in a stacking direction, wherein the bipolar plate comprises an anode gas passage opening, a cathode gas passage opening, an electrochemically active region, an anode gas distribution region and a cathode gas distribution region, wherein the anode gas distribution region comprises anode gas flow channels through which an anode gas can flow, and the cathode gas distribution region comprises cathode gas flow channels through which a cathode gas can flow, wherein the anode gas flow channels and the cathode gas flow channels are arranged relative to one another such that a projection of at least one anode gas flow channel onto a cathode-side bipolar plate layer perpendicular to the planar surface of a cathode-side bipolar plate layer intersects a cathode gas flow channel in an intersection region. In order to create a bipolar plate of said type in which a weld seam can have a greater longitudinal extent in an intersection region without a support frame of a membrane-electrode assembly of an electrochemical unit bulging too far into the anode gas flow channel, according to the invention, at least one anode gas flow channel is widened locally to such an extent that at least one anode-side ridge that bounds the anode gas flow channel is shifted in at least one section in a transverse direction of the anode gas flow channel which is perpendicular to a local longitudinal direction of the anode gas flow channel and perpendicular to the stacking direction.

Description

[0001] Bipolar plate and an electrochemical device comprising a bipolar plate

[0002] The present invention relates to a bipolar plate for an electrochemical unit of an electrochemical device comprising several electrochemical units arranged one after the other along a stacking direction, the bipolar plate comprising: an anode gas passage opening forming part of an anode gas channel extending along the stacking direction through the electrochemical device; a cathode gas passage opening forming part of a cathode gas channel extending along the stacking direction through the electrochemical device; an electrochemically active area comprising an anode gas flow field through which an anode gas can flow transversely to the stacking direction and a cathode gas flow field through which a cathode gas can flow transversely to the stacking direction; an anode gas distribution area,above which the anode gas passage opening is in fluid communication with the anode gas flow field; and a cathode gas distribution area above which the cathode gas passage opening is in fluid communication with the cathode gas flow field; wherein the anode gas distribution area comprises anode gas flow channels through which the anode gas flows, and the cathode gas distribution area comprises cathode gas flow channels through which the cathode gas flows, wherein the anode gas distribution area is formed on an anode-side bipolar plate layer and the cathode gas distribution area is formed on a cathode-side bipolar plate layer, wherein an anode gas flow channel is separated at least partially by an anode-side bridge from an adjacent anode gas flow channel, and wherein a cathode gas flow channel is separated at least partially by a cathode-side bridge from an adjacent cathode gas flow channel.wherein the anode gas flow channels and the cathode gas flow channels are arranged relative to each other such that a projection of at least one anode gas flow channel onto the cathode-side bipolar plate layer perpendicular to the plane of the cathode-side bipolar plate layer intersects a cathode gas flow channel at a crossing point.

[0003] The bipolar plate layers are preferably made of a metallic material and are gas-tightly connected to each other by a joining process, for example a welding process, preferably a laser welding process.

[0004] For example, the anode-side bipolar plate layer and / or the cathode-side bipolar plate layer can be made of a non-rusting, austenitic steel, preferably a steel with the material number 1.4404.

[0005] A bipolar plate layer forms part of an electrochemical unit, which, in addition to the bipolar plate, may include a membrane electrode arrangement comprising a support frame, gas diffusion layers, and a sealing arrangement.

[0006] Several such electrochemical units are stacked one after the other along a single direction to form a stack of electrochemical units, which is a component of an electrochemical device, for example, a fuel cell device, an electrolyzer, or an electrochemical compressor. The bipolar plate, which comprises an anode-side bipolar plate layer and a cathode-side bipolar plate layer, must have very good electrical conductivity to ensure the electrical functionality of the electrochemical device.

[0007] To ensure the required electrical conductivity between the bipolar plate layers of the bipolar plate, the inner surfaces facing each other of the bipolar plate layers must be bonded together.

[0008] Such a material-bonded connection can be produced, for example, by a weld, whereby the weld may be interrupted and may include separate weld sections (stitch seams) or weld spots.

[0009] Such a welded joint can be produced in particular by laser welding.

[0010] For welding such a weld joint, a connection area is necessary in which the anode-side bipolar plate layer and the cathode-side bipolar plate layer lie flat against each other.

[0011] In particular, welding the area where the anode gas distribution area of ​​the anode-side bipolar plate layer and the cathode gas distribution area of ​​the cathode-side bipolar plate layer are adjacent is necessary to improve the electrical conductivity and the mechanical load-bearing capacity of the bipolar plate.

[0012] In the adjacent distribution areas, due to the longitudinal direction of each anode gas flow channel being aligned at an acute angle to the local longitudinal direction of each cathode gas flow channel, diamond-shaped intersection areas result, in which the channel base of an anode gas flow channel and the channel base of a cathode gas flow channel lie flat against each other, the diamond-shaped intersection areas being each bounded by the anode-side webs and the cathode-side webs respectively.

[0013] The connection area, in which a material-bonded connection, preferably a weld, is made, must lie within the intersection area. It follows that the area available for arranging the connection area is limited by the boundaries of the intersection area and, in particular, by the anode-side and cathode-side webs adjacent to the intersection area.

[0014] However, due to the accumulation of manufacturing tolerances, which result, for example, from the tolerance of the width of the weld seam, the tolerance in the positioning of the weld seam relative to the bipolar plate layers, and the tolerance of the relative positioning of the bipolar plate layers to each other, an area where the welding is to be carried out must have a minimum length and a minimum width.

[0015] However, recent developments in bipolar plate technology tend towards increasingly narrower channel structures in order to improve gas distribution dynamics and to ensure sufficient support of neighboring components, especially the support frame of the membrane electrode assemblies.

[0016] However, narrower anode gas flow channels and / or cathode gas flow channels reduce the weldability of the bipolar plate layers in the anode gas distribution area and in the cathode gas distribution area, or at least the process capability, which inevitably leads to more scrap in larger production runs. In the bipolar plate according to DE 20 2015 104 300, the anode-side webs formed between the anode gas flow channels and / or the cathode-side webs formed between the cathode gas flow channels are locally interrupted in a section to create the largest possible surface area where the anode-side bipolar plate lies flat against the cathode-side bipolar plate.

[0017] Due to the considerable size of the anode-side and / or cathode-side channel interruptions, a relatively large area of ​​the membrane assembly's support frame is not supported by the bipolar plate. This allows the support frame to bulge into the channel structure in the stacking direction, reducing the available cross-section of the anode gas flow channel and / or the cathode gas flow channel. This results in flow losses of the anode gas and / or the cathode gas.

[0018] The present invention is based on the objective of creating a bipolar plate in which a connection area, in particular a weld seam, can have a greater longitudinal extent at a crossing area without a support frame of a membrane electrode arrangement of an electrochemical unit bulging too far into the anode gas flow channel or into the cathode gas flow channel.

[0019] This problem is solved in a bipolar plate according to the preamble of claim 1 according to a first alternative of the present invention by locally widening at least one anode gas flow channel by displacing at least one anode-side web limiting the anode gas flow channel in at least one section along a transverse direction of the anode gas flow channel perpendicular to a local longitudinal direction of the anode gas flow channel and perpendicular to the stacking direction, wherein the anode-side bipolar plate layer and the cathode-side bipolar plate layer are materially bonded to each other at at least one connection area within the locally widened section of the anode gas flow channel.

[0020] Furthermore, the problem underlying the present invention is solved in a bipolar plate according to the preamble of claim 1 according to a second alternative of claim 1 in that at least one cathode gas flow channel is locally widened by displacing at least one cathode-side web limiting the cathode gas flow channel in at least one section along a transverse direction of the cathode gas flow channel perpendicular to a local longitudinal direction of the cathode gas flow channel and perpendicular to the stacking direction, wherein the anode-side bipolar plate layer and the cathode-side bipolar plate layer are materially bonded to each other at at least one connection area within the locally widened section of the cathode gas flow channel.

[0021] When the anode gas flow channel and / or the cathode gas flow channel is locally displaced within a section, it is preferably provided that the extent of the displacement varies along the anode gas flow channel or the cathode gas flow channel, respectively. This displacement is therefore not a shape-preserving parallel displacement of a section of an anode gas flow channel or a cathode gas flow channel, but rather a shape-changing displacement of a section of an anode gas flow channel or a shape-changing displacement of a section of a cathode gas flow channel.In this process, the side of the anode-side web facing the anode gas flow channel, which limits the anode gas flow channel, is shifted by sections of different lengths that are aligned perpendicular to the longitudinal direction of the anode gas flow channel and perpendicular to the stacking direction, and that are parallel to each other.

[0022] Alternatively or additionally, the side of the cathode-side web facing the cathode gas flow channel, which limits the cathode gas flow channel, is shifted by distances of different lengths perpendicular to the longitudinal direction of the cathode gas flow channel and perpendicular to the stacking direction, as well as parallel sections to each other.

[0023] Preferably, the displacement of the locally displaced section increases monotonically from a first end, where the displacement is preferably zero, to a maximum along the anode gas flow channel and / or along the cathode gas flow channel, and the displacement decreases monotonically after the maximum along the anode gas flow channel or along the cathode gas flow channel to a second end, where the displacement is preferably zero, wherein the maximum displacement of the anode gas flow channel is referred to as the maximum local displacement Vo.

[0024] This shape-changing displacement preferably forms a concave side and a convex side of the anode-side rib that bounds the anode gas flow channel, wherein the concave side of the anode-side rib faces the locally widened anode gas flow channel and wherein the convex side of the anode-side rib faces away from the locally widened anode gas flow channel.

[0025] Alternatively or additionally, this shape-changing displacement forms a concave side and a convex side of the cathode-side rib that bounds the cathode gas flow channel, wherein the concave side of the cathode-side rib faces the locally widened cathode gas flow channel and wherein the convex side of the cathode-side rib faces away from the locally widened cathode gas flow channel.

[0026] In a particular embodiment of the invention, it is provided that a first-order anode gas neighboring flow channel adjacent to the anode gas flow channel, which is at least partially bounded by the locally transversely displaced anode-side web and by a first-order anode-side neighboring web adjacent to the anode-side web, is in fluid communication with a second-order anode gas neighboring flow channel following in the transverse direction, in that the first-order anode-side neighboring web is at least partially lowered in the section adjacent to the locally displaced section of the anode-side web, and / or that a first-order cathode gas neighboring flow channel adjacent to the cathode gas flow channel, which is at least partially bounded by the locally transversely displaced cathode-side web and by a first-order cathode-side neighboring web adjacent to the cathode-side web,in fluid communication with a second-order cathode gas neighboring flow channel following in the transverse direction, by virtue of the fact that the first-order cathode-side neighboring web is at least partially lowered in the section adjacent to the locally displaced section of the cathode-side web.

[0027] It is advantageous that, by lowering the anode gas neighboring flow channel of the first order, which is narrowed by the local displacement of the anode-side bridge, it is in fluid communication with the anode gas neighboring flow channel of the second order, and / or that, by lowering the cathode gas neighboring flow channel of the first order, which is narrowed by the local displacement of the cathode-side bridge, it is in fluid communication with the cathode gas neighboring flow channel of the second order, thereby ensuring overall better flow properties of the anode gas or better flow properties of the cathode gas.

[0028] Preferably, the anode-side adjacent first-order web and / or the cathode-side adjacent first-order web is completely lowered in the section adjacent to the locally displaced section of the anode-side or cathode-side web, respectively, and is particularly preferably interrupted.

[0029] Preferably, the smallest distance between the transversely displaced anode-side web and the anode-side adjacent second-order web and / or the smallest distance between the transversely displaced cathode-side web and the cathode-side adjacent second-order web in the locally displaced section of the anode-side web or the cathode-side web is at most 2.2 times, in particular at most 2.0 times, and most preferably at most 1.9 times, the channel width k of a non-locally widened section of the anode gas flow channel or the channel width k of a non-locally widened section of the cathode gas flow channel.

[0030] Preferably, a first-order anode-side adjacent web that is adjacent in the transverse direction to the locally displaced anode-side web and / or a first-order cathode-side adjacent web that is adjacent in the transverse direction to the locally displaced cathode-side web is also locally displaced along the transverse direction.

[0031] In particular, an anode-side neighboring web of the first order adjacent in the transverse direction to the locally displaced anode-side web and an anode-side neighboring web of the second order following in the transverse direction and / or a cathode-side neighboring web of the first order adjacent in the transverse direction to the locally displaced cathode-side web and a cathode-side neighboring web of the second order following in the transverse direction are also locally displaced along the transverse direction.Particularly preferably, on a side of the anode-side web of the anode gas flow channel facing away from the anode gas flow channel, anode-side neighboring webs follow one another in the transverse direction, the order of which increases by one from one anode-side neighboring web to the next anode-side neighboring web following in the transverse direction, wherein the anode-side neighboring webs in a section that is assigned to the locally displaced section of the anode-side web each have a maximum local displacement, wherein the maximum local displacement V. n +i of the anode-side neighboring bridge (n + l)-th order is at most as large as the maximum local displacement V n of the anode-side neighboring bridge of the nth order.

[0032] Alternatively or additionally, on a side of the cathode-side rib of the cathode-gas flow channel facing away from the cathode-gas flow channel, cathode-side neighboring ribs follow one another in the transverse direction, their order increasing by one from one cathode-side neighboring rib to the next in the transverse direction, wherein the cathode-side neighboring ribs each have a maximum local displacement in a section that corresponds to the locally displaced section of the cathode-side rib, where the maximum local displacement V n +i of the cathode-side neighboring bridge of the (n + l)-th order is at most as large as the maximum local displacement V n of the cathode-side neighboring bridge of the nth order.

[0033] In a particular embodiment of the invention, the locally displaced anode-side web and / or the locally displaced cathode-side web has a web width s which extends perpendicular to the local longitudinal direction of the respective web and perpendicular to the stacking direction, wherein the web width in the locally displaced section of the web is not constant along the web. The flexible design of the web width s makes it possible to further widen the local boundary at the intersection area. Alternatively or additionally, it can also be provided that the anode gas flow channel and / or the cathode gas flow channel is locally widened by displacing both anode-side webs or cathode-side webs that bound the anode gas flow channel or the cathode gas flow channel, respectively, locally along the transverse direction.

[0034] The local displacement of both anode-side webs and / or cathode-side webs along the transverse direction (but preferably in opposite directions) results in a local mirror symmetry with respect to a plane of symmetry which runs along the local longitudinal direction of the anode gas flow channel or along the local longitudinal direction of the cathode gas flow channel and parallel to the stacking direction.

[0035] In principle, however, if both anode-side webs or both cathode-side webs are shifted in the transverse direction, there must be no mirror symmetry with respect to a plane of symmetry which runs along the local longitudinal direction of the anode gas flow channel or along the local longitudinal direction of the cathode gas flow channel (but preferably in opposite directions).

[0036] For example, it may be provided that the maxima of the displacement of the two anode-side ribs and / or the two cathode-side ribs are arranged relative to each other in such a way that they are not mapped onto each other when reflected across a plane which runs along the local longitudinal direction of the anode gas flow channel or along the local longitudinal direction of the cathode gas flow channel and parallel to the stacking direction, resulting in a local asymmetry with respect to the plane which runs along the local longitudinal direction of the anode gas flow channel or along the local longitudinal direction of the cathode gas flow channel and parallel to the stacking direction.Preferably, the first-order anode-side adjacent webs and / or the first-order cathode-side adjacent webs adjacent to the transversely displaced anode-side webs are at least partially lowered, in particular completely lowered, and especially preferably interrupted, in a section adjacent to the locally displaced section of the respective adjacent anode-side web or the respective adjacent cathode-side web.

[0037] It is advantageous if the anode-side bipolar plate layer and the cathode-side bipolar plate layer are welded together at the connection area by means of a weld seam.

[0038] Particularly preferred is the extent of the weld seam at the connection area in its longitudinal direction at least as large as the greatest width, i.e. the greatest extent perpendicular to the longitudinal direction of the flow channel and perpendicular to the stacking direction, of the locally widened section of the anode gas flow channel or of the locally widened section of the cathode gas flow channel.

[0039] Preferably, the greatest width of the locally expanded section of the anode gas flow channel and / or the greatest width of the locally expanded section of the cathode gas flow channel is at most 3.2 times, in particular at most 3.0 times, and especially preferably at most 2.9 times, the width of the anode gas flow channel in a non-locally expanded section or the width of the cathode gas flow channel in a non-locally expanded section.

[0040] In principle, it can be provided that a support frame (sometimes also referred to as a "subgasket") of a membrane electrode assembly of an electrochemical unit rests against the locally displaced section of the anode-side bridge and / or the locally displaced section of the cathode-side bridge. Preferably, an angle α between at least one local longitudinal direction of an anode gas flow channel and at least one local longitudinal direction of a cathode gas flow channel is greater than 5 degrees, in particular greater than 15 degrees, and particularly preferably greater than 20 degrees, and is, for example, 24 degrees.

[0041] Preferably, the angle α between the local longitudinal direction of the anode gas flow channel and the local longitudinal direction of the cathode gas flow channel is less than 85 degrees, in particular less than 65 degrees, particularly preferably less than 40 degrees, and is for example 24 degrees.

[0042] In a particular embodiment of the bipolar plate according to the invention, it is provided that one of the two anode-side webs bounding the locally expanded anode gas flow channel is neither displaced nor at least partially lowered in any section along the transverse direction of the anode gas flow channel, which is oriented perpendicular to the local longitudinal direction of the anode gas flow channel and perpendicular to the stacking direction, and / or that one of the two cathode-side webs bounding the locally expanded cathode gas flow channel is neither displaced nor at least partially lowered in any section along the transverse direction of the cathode gas flow channel, which is oriented perpendicular to the local longitudinal direction of the cathode gas flow channel and perpendicular to the stacking direction. In this embodiment of the invention, the design of the locally expanded anode gas flow channel is...The cathode gas flow channel is modified only on one side, which simplifies the manufacture of the bipolar plate and results in minimal interference with the spatial distribution of contact pressures in the electrochemical unit of the electrochemical device. The bipolar plate according to the invention is particularly suitable for use in an electrochemical device comprising several electrochemical units arranged along a stacking direction, each comprising a bipolar plate according to the invention.

[0043] Such an electrochemical device could be, for example, a fuel cell device, an electrolyzer, or an electrochemical compressor.

[0044] The electrochemical unit in which the bipolar plate according to the invention is used preferably comprises a polymer electrolyte membrane.

[0045] Further features and advantages of the invention are the subject of the following description and the graphic representation of exemplary embodiments.

[0046] The drawings show:

[0047] Fig. 1 shows a top view of a bipolar plate for an electrochemical unit of an electrochemical device comprising several electrochemical units arranged one after the other along a stacking direction, with the view towards the anode side of the bipolar plate, wherein the bipolar plate has an anode gas passage opening forming part of an anode gas channel extending along the stacking direction through the electrochemical device, a cathode gas passage opening forming part of a cathode gas channel extending along the stacking direction through the electrochemical device, an electrochemically active area of ​​the bipolar plate comprising an anode gas flow field and a cathode gas flow field, and an anode gas distribution area.comprising an anode gas passage opening above which the anode gas flow field is in fluid communication with the anode gas flow field, and a cathode gas distribution area above which the cathode gas passage opening is in fluid communication with the cathode gas flow field;

[0048] Fig. 2 shows a top view of the bipolar plate from Fig. 1 along the stacking direction, with the view towards the cathode side of the bipolar plate;

[0049] Fig. 3 shows a partial schematic representation of an anode gas distribution area and a cathode gas distribution area of ​​a bipolar plate according to the prior art, viewed along the stacking direction, wherein the anode gas distribution area comprises anode gas flow channels through which the anode gas flows, and the cathode gas distribution area comprises cathode gas flow channels through which the cathode gas flows, wherein the anode gas distribution area is formed on an anode-side bipolar plate layer and the cathode gas distribution area on a cathode-side bipolar plate layer, wherein an anode gas flow channel is separated at least partially by an anode-side rib from an adjacent anode gas flow channel, and wherein a cathode gas flow channel is separated at least partially by a cathode-side rib from an adjacent cathode gas flow channel.wherein the anode gas flow channels and the cathode gas flow channels are arranged relative to each other such that a projection of at least one anode gas flow channel onto the cathode-side bipolar plate layer perpendicular to the plane of the cathode-side bipolar plate layer intersects a cathode gas flow channel at a crossing point, wherein the anode-side bipolar plate layer and the cathode-side bipolar plate layer are metallurgically connected to each other at at least one connection point within the anode gas flow channel and / or the cathode gas flow channel;

[0050] Fig. 4 shows a partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​a bipolar plate according to another prior art, corresponding to Fig. 3, wherein an anode-side web is interrupted in a section and wherein in the interrupted section of the anode-side web the anode-side bipolar plate layer and the cathode-side bipolar plate layer are materially bonded to each other at a connection area;

[0051] Fig. 5 shows a partial schematic representation of an anode gas distribution area and a cathode gas distribution area in a first embodiment of a bipolar plate of an electrochemical unit according to the invention, viewed along the stacking direction, wherein at least one anode gas flow channel is locally widened by displacing at least one anode-side web limiting the anode gas flow channel in at least one section along a transverse direction of the anode gas flow channel perpendicular to a local longitudinal direction of the anode gas flow channel and perpendicular to the stacking direction, wherein the anode-side bipolar plate layer and the cathode-side bipolar plate layer are metallurgically connected to each other at at least one connection area within the locally widened section of the anode gas flow channel; Fig. 6 shows one of the figures.5 corresponding partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​the first embodiment according to the invention of a bipolar plate of an electrochemical unit, wherein the maximum local displacement V. o of the anode-side bridge;

[0052] Fig. 7 shows a partial schematic representation of an anode gas distribution area and a cathode gas distribution area corresponding to Fig. 5 in a second embodiment of a bipolar plate of an electrochemical unit according to the invention, wherein the anode gas flow channel is locally widened by the fact that both anode-side webs limiting the anode gas flow channel are locally displaced along the transverse direction;

[0053] Fig. 8 shows a partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​the second embodiment of the bipolar plate of an electrochemical unit according to the invention, corresponding to Fig. 7, wherein the maximum local displacements Vo and Vo' of the two anode-side webs are shown.

[0054] Fig. 9 shows a partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​a third embodiment of a bipolar plate of an electrochemical unit according to the invention, wherein the locally displaced anode-side web has a web width s which extends perpendicular to the local longitudinal direction of the web and perpendicular to the stacking direction, which is not constant along the web in the locally displaced section; Fig. 10 shows a partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​the third embodiment of a bipolar plate according to the invention, corresponding to Fig. 9, wherein the maximum local displacement Vo of the anode-side web is shown;

[0055] Fig. 11 shows a partial schematic representation of the anode gas distribution area and the cathode gas distribution area of ​​a fourth embodiment of a bipolar plate of an electrochemical unit according to the invention, wherein, on a side of the anode-side web of the anode gas flow channel facing away from the anode gas flow channel, anode-side neighboring webs follow one another in the transverse direction, the order of which increases by one from one anode-side neighboring web to the next anode-side neighboring web following in the transverse direction, wherein the anode-side neighboring webs each have a maximum local displacement in a section that is associated with the locally displaced section of the anode-side web, wherein the maximum local displacement Vn+i of the anode-side neighboring web of the (n + l)th order is at most as large as the maximum local displacement V n of the anode-side adjacent bridge of the nth order; and

[0056] Fig. 12 shows a partial schematic representation, corresponding to Fig. 11, of the anode gas distribution area and the cathode gas distribution area of ​​the fourth embodiment of a bipolar plate of an electrochemical unit according to the invention, wherein the maximum local displacements V n the anode-side adjacent bridges are shown.

[0057] Identical or functionally equivalent elements are designated with the same reference numerals in all figures. A bipolar plate shown in Figures 1 and 2, designated as a whole by 100, forms a component of an electrochemical unit 102 (not shown as a whole), which, in addition to the bipolar plate 100, may include a membrane electrode arrangement 103 (not shown) comprising a support frame 105, gas diffusion layers, and a sealing arrangement.

[0058] Several such electrochemical units 102 follow one another along a stacking direction 104 to form a stack of electrochemical units 102, which is a component of an electrochemical device 106, for example a fuel cell device, an electrolyzer or an electrochemical compressor.

[0059] The bipolar plate 100 comprises an anode gas passage opening 108, which forms part of an anode gas channel 111 extending along the stacking direction 104 through the electrochemical device 106; a cathode gas passage opening 110, which forms part of a cathode gas channel 113 extending along the stacking direction 104 through the electrochemical device 106; an electrochemically active area 112, which comprises an anode gas flow field 114 through which an anode gas can flow transversely to the stacking direction 104 and a cathode gas flow field 116 through which a cathode gas can flow transversely to the stacking direction 104; and an anode gas distribution area 118, through which the anode gas passage opening 108 is in fluid communication with the anode gas Flow field 114 is located, and a cathode gas distribution area 120, above which the cathode gas passage opening 110 is in fluid communication with the cathode gas flow field 116.

[0060] The bipolar plate 100 further preferably comprises at least one coolant passage opening 107, which forms part of a coolant channel 109. The anode gas distribution area 118 comprises anode gas flow channels 122 through which the anode gas flows, and the cathode gas distribution area 118 comprises cathode gas flow channels 124 through which the cathode gas flows, wherein the anode gas distribution area 118 is formed on an anode-side bipolar plate layer 126 and the cathode gas distribution area 120 on a cathode-side bipolar plate layer 128, wherein an anode gas flow channel 122 is separated at least partially by an anode-side web 130 from an adjacent anode gas flow channel 150, and wherein a cathode gas flow channel 124 is separated at least partially by a cathode-side web 134 from another cathode gas flow channel 124.wherein the anode gas flow channels 122 and the cathode gas flow channels 124 are arranged relative to each other such that a projection of at least one anode gas flow channel 122 onto the cathode-side bipolar plate layer 128 perpendicular to the plane of the cathode-side bipolar plate layer 128 intersects a cathode gas flow channel 124 at a crossing area 138.

[0061] An angle α between the local longitudinal direction 146 of the anode gas flow channel 122 and the local longitudinal direction 147 of the cathode gas flow channel 124 is preferably an acute angle and preferably greater than 5 degrees, in particular greater than 15 degrees, particularly preferably greater than 20 degrees, and is for example 24 degrees.

[0062] Preferably, the angle α between the local longitudinal direction 146 of the anode gas flow channel 122 and the local longitudinal direction 147 of the cathode gas flow channel 124 is less than 85 degrees, in particular less than 65 degrees, particularly preferably less than 40 degrees, and is for example 24 degrees.

[0063] As can best be seen from Fig. 3, due to the longitudinal direction 146 of each anode gas flow channel 122 being oriented at an acute angle a to the local longitudinal direction 147 of each cathode gas flow channel 124, diamond-shaped intersection areas 138 result, at which the channel base of an anode gas flow channel 122 and the channel base of a cathode gas flow channel 124 lie flat against each other, the diamond-shaped intersection areas 138 being bounded by the anode-side webs 130 and the cathode-side webs 134.

[0064] In the prior art shown in Fig. 3, a connection area 140, in which a material-bonded connection is produced taking into account manufacturing tolerances, lies within a diamond-shaped intersection area 138.

[0065] It is preferably provided that the material-bonded connection is formed in the form of a weld 142, which has an extent a in the longitudinal direction of the weld 142.

[0066] The weld seam 142 ensures a fluid-tight and electrically conductive connection between the anode-side bipolar plate layer 126 and the cathode-side bipolar plate layer 128.

[0067] In order to achieve the best possible electrical conductivity of the bipolar plate 100, it is advantageous if the extent a of the weld seam 142 is as large as possible.

[0068] As can best be seen from Fig. 4, in the further prior art shown therein, to satisfy this requirement, an anode-side web 130 is interrupted section by section, so that the channel base of a cathode gas flow channel 124 and two channel bases of adjacent anode gas flow channels 122 lie flat against each other without interruption by the anode-side web 130, thereby providing the largest possible area for the expansion of the weld seam 142 for the metallurgical connection of the anode-side bipolar plate layer 126 and the cathode-side bipolar plate layer 128.The problem here is that, due to the large distance A2 of the anode-side webs 130' adjacent to the interrupted anode-side web 130, the (not shown) support frame 105 of the (not shown) membrane electrode arrangement 103 bulges in the stacking direction 104 into the anode gas flow channels 122, thereby reducing the available cross-sectional area of ​​the anode gas flow channel 122, which leads to flow losses of the anode gas.

[0069] As can best be seen from Fig. 5 and Fig. 6, in a first embodiment of a bipolar plate 100 according to the invention, at least one anode gas flow channel 122 in the anode gas distribution area 118 is locally widened by means that an anode-side web 130 limiting the anode gas flow channel 122 is displaced in a section 144 along a transverse direction 148 of the anode gas flow channel 122 which is oriented perpendicular to a local longitudinal direction 146 of the anode gas flow channel 122 and perpendicular to the stacking direction 104.

[0070] In the local displacement of the anode gas flow channel 122 in a section 144, it is provided that the displacement of the anode gas flow channel 122 varies along the anode gas flow channel 122. Preferably, it is provided that the displacement increases monotonically from a first end 139 of the locally displaced section 144 to a maximum along the anode gas flow channel 122, and that after the maximum, the displacement decreases monotonically along the anode gas flow channel 122 to a second end 139 of the locally displaced section 144, the maximum displacement of the anode gas flow channel 122 being referred to as the maximum local displacement Vo.

[0071] This shape-changing displacement results in a concave side of the anode-side bridge 130, which faces the anode gas flow channel 122, and a convex side of the anode-side bridge 130, which faces away from the anode gas flow channel 122. Thus, there is a displacement corresponding to the side of the anode-side bridge 130 that is concave after the displacement, and a displacement corresponding to the side of the anode-side bridge 130 that is convex after the displacement.

[0072] If the extent of the displacement associated with the concave side is greater than the extent of the displacement associated with the convex side, then the width s of the displaced anode-side web 130 is at least sectionally smaller than the original width of the anode-side web 130.

[0073] If the extent of the displacement associated with the convex side is greater than the extent of the displacement associated with the concave side, then the width s of the displaced anode-side web 130 is at least section by section greater than the original width of the anode-side web 130.

[0074] Provided that both displacements along the anode gas flow channel 122 are of the same size, the width s of the displaced anode-side web 130 remains unchanged.

[0075] If the description and the attached claims refer to the displacement, the extent of the displacement and / or the maximum local displacement V n When referring to a jetty or a neighboring jetty, this always refers to the displacement of the concave side of the jetty in question (see, for example, the maximum local displacement Vo in Fig. 6), unless otherwise specified.

[0076] In the first embodiment according to the invention shown in Figs. 5 and 6, a first-order anode gas neighboring flow channel 150i adjacent to the anode gas flow channel 122, which is at least partially limited by the locally displaced anode-side web 130 and by an anode-side neighboring web 152i adjacent to the anode-side web 130, is in fluid communication with a second-order anode gas neighboring flow channel 1502 following in the transverse direction 148, insofar as the anode-side neighboring web 152i is at least partially lowered in the section adjacent to the locally displaced section 144 of the anode-side web 130.

[0077] Preferably, the anode-side adjacent first-order web 152i is completely lowered, in particular interrupted, in the section adjacent to the locally displaced section 144 of the anode-side web 130.

[0078] It is advantageous that the greatest width A6 of the locally widened section 154 of the anode gas flow channel 122 and the smallest distance A3 between the anode-side web 130 displaced in the transverse direction 148 and the adjacent anode-side web of the second order 1522 are each smaller in this first embodiment of a bipolar plate 100 according to the invention than the distance A2 of the anode-side webs 130 adjacent to the interrupted anode-side web 130 in the prior art according to Fig. 4, thereby reducing a bulging of the (not shown) support frame 105 into the anode gas flow channels 122.

[0079] Preferably, the smallest distance A3 between the anode-side web 130, which is displaced in the transverse direction 148, and the adjacent second-order anode-side web 1522 at the locally displaced section 144 of the anode-side web 130 is at most 2.2 times, in particular at most 2.0 times, and most preferably at most 1.9 times, the channel width k of a non-locally widened section 154 of the anode gas flow channel 122. The anode-side bipolar plate layer 126 and the cathode-side bipolar plate layer 128 are metallurgically bonded to each other at the connection area 140.

[0080] Preferably, the anode-side bipolar plate layer 126 and the cathode-side bipolar plate layer 128 are connected to each other by a weld seam at the connection area 140.

[0081] Particularly preferred is the extent a of the weld in the longitudinal direction of the weld being at least as large as the greatest width A6 of the locally widened section 154 of the anode gas flow channel 122.

[0082] A second embodiment of a bipolar plate 100 according to the invention, shown in Figs. 7 and 8, differs from the first embodiment according to the invention shown in Figs. 5 and 6 in that the anode gas flow channel 122 is locally widened by the fact that both anode-side webs 130 and 130' limiting the anode gas flow channel 122 are locally displaced along the transverse direction 148.

[0083] Preferably, the anode-side adjacent first-order adjacent webs 150i and 150i' to the anode-side webs 130, 130' which are displaced in the transverse direction 148 are at least partially lowered, preferably completely lowered, and particularly preferably interrupted in a section adjacent to the locally displaced section 144 of the respective adjacent anode-side web 130 and 130'.

[0084] Preferably, the maximum width A6 of the locally widened section 154 of the anode gas flow channel 122 is at most 3.2 times, in particular at most 3.0 times, and most preferably 2.9 times, the width k of the anode gas flow channel 122 in a non-locally widened section. As can be seen, for example, in Fig. 7, this embodiment of a bipolar plate 100 results in a local mirror symmetry of the anode-side bipolar plate arrangement with respect to a plane of symmetry 151, which runs along the local longitudinal direction 146 of the anode gas flow channel 122 and parallel to the stacking direction 104.

[0085] In an alternative embodiment of the second embodiment according to the invention, it can also be provided that the maxima V o, Vo' of the displacements of the anode-side web 130 and the anode-side web 130' are arranged offset from each other along the local longitudinal direction 146, in which case there is no local mirror symmetry with respect to a plane of symmetry which runs along the local longitudinal direction 146 of the anode gas flow channel 122 and perpendicular to the stacking direction 104.

[0086] Preferably, in this alternative embodiment, the local interruption of the anode-side adjacent first-order bridge 150i' is adjacent to the maximum Vo' of the displacement of the anode-side bridge 130'.

[0087] Furthermore, the second embodiment of a bipolar plate 100 shown in Figs. 7 and 8 corresponds with regard to structure, function and method of manufacture to the first embodiment shown in Figs. 5 and 6, to the preceding description of which reference is made in this respect.

[0088] A third embodiment of a bipolar plate 100 shown in Figs. 9 and 10 differs from the first embodiment shown in Figs. 5 and 6 in that the locally displaced anode-side web 130 has a web width s which extends perpendicular to the local longitudinal direction 146 of the respective web 130 and perpendicular to the stacking direction 104, wherein the web width s is not constant in the locally displaced section 144 of the web 130 along the web 130. By narrowing the web width s of the locally displaced anode-side web 130, the anode gas flow channel 122, which is locally widened in one section, can be further widened, whereby by widening the web width s at another location along the anode-side web 130 the support frame 105 of the membrane electrode arrangement 103, which abuts the anode-side web 130, can be better supported.

[0089] Furthermore, the third embodiment of a bipolar plate 100 shown in Figs. 9 and 10 corresponds in terms of structure, function and method of manufacture to the first embodiment shown in Figs. 5 and 6, to the preceding description of which reference is made in this respect.

[0090] A fourth embodiment of a bipolar plate 100 according to the invention, shown in Figures 11 and 12, differs from the first embodiment shown in Figures 5 and 6 in that, on a side of the anode-side web 130 of the anode gas flow channel 122 facing away from the anode gas flow channel 122, adjacent anode-side webs 150 follow one another in the transverse direction 148, the order of which increases by one from one adjacent anode-side web 150n to the next adjacent anode-side web 150n+i following in the transverse direction 148, wherein the adjacent anode-side webs 150 each have a maximum local displacement V in a section that is associated with the locally displaced section 144 of the anode-side web 130. n exhibit. The maximum local displacement is V. n+i of the anode-side neighboring bridge 150n+i of the (n + l)-th order at most as large as the maximum local displacement V n of the anode-side neighboring web 150n of the nth order. In the fourth embodiment shown in Figs. 11 and 12, the anode-side neighboring web of the first order 152i and the anode-side neighboring web of the second order 1522 have the maximum displacement Vi and V2 respectively in the transverse direction 148, wherein the displacement Vi is at most as large as the displacement Vo of the locally displaced anode-side web 130 and wherein the displacement V2 of the anode-side neighboring web of the second order 1502 is at most as large as the displacement Vi of the anode-side neighboring web of the first order 152i.

[0091] Preferably, the maximum displacement V2 is smaller than the maximum displacement Vi, and the maximum displacement Vi is smaller than the maximum displacement Vo.

[0092] In the fourth embodiment, the anode-side neighboring web of the third order 1523 does not exhibit any displacement, although it is conceivable that the anode-side neighboring web of the third order 1523 and further neighboring webs of higher order 152 may also exhibit displacement. n >3 are additionally shifted locally, with the maximum shift V n with increasing order, at least remaining the same or becoming smaller.

[0093] Alternatively, it is also conceivable that only the anode-side neighboring first-order bridge 152i exhibits a local displacement Vi, while all other neighboring higher-order bridges 152 n >i are not moved locally.

[0094] In contrast to the first embodiment shown in Figs. 5 and 6, the fourth embodiment shown in Figs. 11 and 12 does not have a local lowering and / or interruption of the anode-side adjacent first-order web 150i.

[0095] As can best be seen from Fig. 11, the anode-side neighboring flow channel of the first order 150i, the anode-side neighboring flow channel of the second order 1502 and the anode-side neighboring flow channel of the third order 1503 each have a minimum channel width Ni, N2 and N3 respectively in the region of the local displacement, wherein their minimum channel width Ni, N2 and N3 is preferably at most 30 percent, in particular at most 25 percent, and most preferably at most 20 percent, smaller than the channel width k in an undisplaced section of the respective anode-side neighboring flow channel 150i, 1502 and 1503.

[0096] Furthermore, the fourth embodiment of a bipolar plate 100 shown in Figs. 11 and 12 corresponds in terms of structure, function and manufacturing method to the first embodiment shown in Figs. 5 and 6, to whose preceding description reference is made in this respect.

[0097] The described features of the embodiments according to the invention only describe the inventive design of the anode-side bipolar plate layer 126, but this design is also applicable to the cathode-side bipolar plate layer 128.

[0098] Thus, it is possible that the anode-side bipolar plate layer 126 and / or the cathode-side bipolar plate layer 128 can be designed according to the features of the described embodiments.

[0099] An embodiment according to the invention can be extended in such a way that it can be locally symmetrical with respect to a plane of symmetry which runs essentially along the local longitudinal direction of the anode gas flow channel 150 or along the local longitudinal direction of the cathode gas flow channel 136 and parallel to the stacking direction 104.

Claims

1. Patent claims 1. Bipolar plate for an electrochemical unit (102) of an electrochemical device comprising several electrochemical units (102) arranged along a stacking direction (104), the bipolar plate (100) comprising: an anode gas passage opening (108) forming part of an anode gas channel (111) extending along the stacking direction (104) through the electrochemical device (106); a cathode gas passage opening (110) forming part of a cathode gas channel (113) extending along the stacking direction (104) through the electrochemical device (106); an electrochemically active region (112) comprising an anode gas flow field (114) through which an anode gas can flow transversely to the stacking direction (104) and a cathode gas flow field (116) through which a cathode gas can flow transversely to the stacking direction (104);an anode gas distribution area (118) through which the anode gas passage opening (108) is in fluid communication with the anode gas flow field (114); and a cathode gas distribution area (120) through which the cathode gas passage opening (110) is in fluid communication with the cathode gas flow field (116); wherein the anode gas distribution area (118) comprises anode gas flow channels (122) through which the anode gas can flow and the cathode gas distribution area (120) comprises cathode gas flow channels (124) through which the cathode gas can flow; wherein the anode gas distribution area (118) is formed on an anode-side bipolar plate layer (126) and the cathode gas distribution area (120) is formed on a cathode-side bipolar plate layer (128), wherein an anode gas flow channel (122) is separated at least partially by an anode-side bridge (130) from an adjacent anode gas flow channel (150) and wherein a cathode gas flow channel (124) is separated at least partially by a cathode-side bridge (134) from an adjacent cathode gas flow channel, wherein the anode gas flow channels (122) and the cathode gas flow channels (124) are arranged relative to each other such that a projection of at least one anode gas flow channel (122) onto the cathode-side The bipolar plate position (128) perpendicular to the plane of the cathode-side bipolar plate position (128) intersects a cathode gas flow channel (124) at a crossing area (138), characterized by this,a) that at least one anode gas flow channel (122) is locally widened by the fact that at least one anode-side web (130) bounding the anode gas flow channel (122) is displaced in at least one section (144) along a transverse direction (148) of the anode gas flow channel (122) perpendicular to a local longitudinal direction (146) of the anode gas flow channel (122) and perpendicular to the stacking direction (104), and / or b) that at least one cathode gas flow channel (124) is locally widened by the fact that at least one cathode-side web (134) bounding the cathode gas flow channel (124) is displaced in, at least one section is displaced along a transverse direction of the cathode gas flow channel (124) perpendicular to a local longitudinal direction (147) of the cathode gas flow channel (124) and perpendicular to the stacking direction (104); wherein the anode-side bipolar plate layer (126) and the cathode-side bipolar plate layer (128) are metallurgically connected to each other at at least one connection area (140) within the locally widened section (154) of the anode gas flow channel (122) and / or the cathode gas flow channel (124).

2. Bipolar plate according to claim 1, characterized in that a first-order anode gas neighboring flow channel (150i) adjacent to the anode gas flow channel (122), which is at least partially bounded by the locally displaced anode-side web (130) in the transverse direction (148) and by a first-order anode-side neighboring web (152i) adjacent to the anode-side web (130), is in fluid communication with a second-order anode gas neighboring flow channel (1502) following in the transverse direction (148), in that the first-order anode-side neighboring web (152i) is at least partially lowered in the section adjacent to the locally displaced section (144) of the anode-side web (130).and / or that a first-order cathode gas neighboring flow channel adjacent to the cathode gas flow channel (124), which is at least partially bounded by the locally transversely displaced cathode-side web (134) and by a first-order cathode-side neighboring web adjacent to the cathode-side web (134), is in fluid connection with one following in the transverse direction. The second-order cathode gas neighboring flow channel is created by the fact that the first-order cathode-side neighboring bridge is at least partially lowered in the section adjacent to the locally displaced section of the cathode-side bridge.

3. Bipolar plate according to claim 2, characterized in that the anode-side neighboring first-order rib (152i) and / or the cathode-side neighboring first-order rib is completely lowered in the section adjacent to the locally displaced section (144) of the anode-side rib (130) or the cathode-side rib (134).

4. Bipolar plate according to one of claims 2 or 3, characterized in that the smallest distance (A3) between the anode-side web (130) displaced in the transverse direction (148) and the anode-side adjacent web of the second order (1522) and / or the smallest distance between the cathode-side web (134) displaced in the transverse direction and the cathode-side adjacent web of the second order in the locally displaced section of the anode-side web (130) or the cathode-side web (134) is at most 2.2 times the channel width (k) of a non-locally expanded section of the anode gas flow channel (122) or of a non-locally expanded section of the cathode gas flow channel (124).

5. Bipolar plate according to one of claims 1 to 4, characterized in that an anode-side neighboring rib (152i) adjacent in the transverse direction (148) to the locally displaced anode-side rib (130) and / or a cathode-side neighboring rib (134) adjacent in the transverse direction is also locally displaced along the transverse direction.

6. Bipolar plate according to one of claims 1 to 5, characterized in that on a side of the anode-side web (130) of the anode gas flow channel (122) facing away from the anode gas flow channel (122) anode-side adjacent webs (152) are arranged in the transverse direction (148). n ) follow one another, the order of which begins with order one from an anode-side neighboring bridge (152 n ) to an anode-side adjacent bridge following in the transverse direction (148) (152 n+i) increases by one in each case, wherein the anode-side neighboring webs (152) in a section associated with the locally displaced section (144) of the anode-side web (130) each have a maximum local displacement, wherein the maximum local displacement (V n +i) of the anode-side adjacent bridge (152 n+ i) of the (n + l)th order is at most as large as the maximum local displacement (V n ) of the anode-side adjacent bridge (152 n) of the nth order, and / or that on a side of the cathode-side web (134) of the cathode-side flow channel (124) facing away from the cathode-gas flow channel (124), cathode-side neighboring webs follow one another in the transverse direction, the order of which increases by one from one cathode-side neighboring web to the next cathode-side neighboring web following in the transverse direction, wherein the cathode-side neighboring webs in a section that is associated with the locally displaced section of the cathode-side web (134) each have a maximum local displacement, wherein the maximum local displacement (V n +i)of the cathode-side neighboring bridge of the (n + l)th order is at most as large as the maximum local displacement (V n ) of the cathode-side neighboring bridge of the nth order.

7. Bipolar plate according to one of claims 1 to 6, characterized in that the locally displaced anode-side rib (130) or the locally displaced cathode-side rib (134) has a rib width (s) which is perpendicular to the local longitudinal direction (146) of the respective rib (130) and extends perpendicular to the stacking direction (104), wherein the web width (s) in the locally displaced section (144) of the web (130) along the web (130) is not constant.

8. Bipolar plate according to one of claims 1 to 7, characterized in that the anode gas flow channel (122) and / or the cathode gas flow channel (124) is locally widened by the fact that both anode-side webs (130) and cathode-side webs (134) limiting the anode gas flow channel (122) and the cathode gas flow channel (124) respectively are locally displaced along the transverse direction (148).

9. Bipolar plate according to claim 8, characterized in that adjacent anode-side ribs (130, 130') and / or adjacent cathode-side ribs (134) are at least partially lowered in a section adjacent to the locally displaced section (144) of the respective adjacent anode-side rib (130, 130') or cathode-side rib (134, 134').

10. Bipolar plate according to one of claims 1 to 9, characterized in that the anode-side bipolar plate layer (126) and the cathode-side bipolar plate layer (128) are welded together at the connection area (140) by means of a weld seam (142).

11. Bipolar plate according to claim 10, characterized in that the extent of the weld seam (142) at the connection area (140) in its longitudinal direction is at least as large as the greatest width of the locally expanded section (154) of the anode gas flow channel (122) or of the locally expanded section (154) of the cathode gas flow channel (124).

12. Bipolar plate according to one of claims 1 to 11, characterized in that the greatest width (A6) of the locally expanded section (154) of the anode gas flow channel (122) and / or the greatest width of the locally expanded section of the cathode gas flow channel (124) is at most 3.2 times the width (k) of the anode gas flow channel (122) in a non-locally expanded section or the width of the cathode gas flow channel (124) in a non-locally expanded section.

13. Bipolar plate according to one of claims 1 to 12, characterized in that a support frame of a membrane electrode arrangement of an electrochemical unit (102) is located on the locally displaced section (144) of the anode-side bridge (130) and / or on the locally displaced section of the cathode-side bridge (134).

14. Bipolar plate according to one of claims 1 to 13, characterized in that an angle (a) between the local longitudinal direction of the anode gas flow channel (122) and the local longitudinal direction of the cathode gas flow channel (124) is greater than 5° and / or less than 85°.

15. Bipolar plate according to one of claims 1 to 14, characterized in that one of the two anode-side webs (130) bounding the locally widened anode gas flow channel (122) is neither displaced nor at least partially lowered in a section along the transverse direction (148) of the anode gas flow channel (122) perpendicular to the local longitudinal direction (146) of the anode gas flow channel (122) and perpendicular to the stacking direction (104). that one of the two cathode-side webs (134) limiting the locally widened cathode gas flow channel (124) is neither displaced nor at least partially lowered in a section along the transverse direction of the cathode gas flow channel (124) oriented perpendicular to the local longitudinal direction (147) of the cathode gas flow channel (124) in question and perpendicular to the stacking direction (104).

16. Electrochemical device comprising several electrochemical units (102) arranged along a stacking direction (104) and each comprising a bipolar plate (100) according to any one of claims 1 to 15.

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