Bipolar plate for an electrochemical unit of an electrochemical apparatus, and electrochemical apparatus

Abstract

The invention relates to a bipolar plate for an electrochemical unit of an electrochemical apparatus, which comprises a plurality of electrochemical units which follow one another along a stacking direction, wherein the bipolar plate comprises the following: - at least one medium through-opening, which forms a part of a medium channel which extends along the stacking direction through the electrochemical apparatus; - a sealing bead, which extends around the medium through-opening; - a plurality of medium inlets, which are arranged on an inner side of the sealing bead facing the medium through-opening and enable medium to flow into the interior of the sealing bead; and - a plurality of medium outlets, which are arranged on an outer side of the sealing bead facing away from the medium through-opening and enable medium to flow out from the interior of the sealing bead, in which the pressure loss which occurs when the medium flows from the medium through-opening through the medium inlets, the interior of the sealing bead and the medium outlets, is as low as possible and wherein, preferably, the medium flows out of the medium outlets as evenly as possible via a medium inlet region of a medium distribution region, to which end it is proposed that the total through-flow cross-section of the medium inlets is at least 10% larger than the total through-flow cross-section of the medium outlets.

Description

[0001] Bipolar plate for an electrochemical unit of an electrochemical device and electrochemical device

[0002] The present invention relates to a bipolar plate for an electrochemical unit of an electrochemical device, comprising a plurality of electrochemical units arranged one after the other along a stacking direction, wherein the bipolar plate comprises the following: at least one medium passage opening, which forms a component of a medium channel extending through the electrochemical device along the stacking direction; a sealing bead extending around the medium passage opening; a plurality of medium inlets arranged on an inner side of the sealing bead facing the medium passage opening and allowing medium to flow into the interior of the sealing bead; and a plurality of medium outlets arranged on an outer side of the sealing bead facing away from the medium passage opening and allowing medium to flow out of the interior of the sealing bead.

[0003] The medium inlets and the medium outlets, through which the interior of the sealing bead is in fluid communication with the medium passage opening or with the exterior space surrounding the sealing bead, are also referred to as gas ports.

[0004] These medium inlets and outlets, or gas ports, are located on the flanks of the sealing bead and allow the respective medium to pass from the respective medium channel into a medium distribution area and from there into a medium flow field of the bipolar plate. Known bipolar plates of the type mentioned above have the same number of medium inlets as medium outlets.

[0005] Based on this prior art, the present invention is based on the object of creating a bipolar plate of the type mentioned at the outset, in which the pressure loss occurring during the flow of the medium from the medium passage opening through the medium inlets, the interior of the sealing bead and the medium outlets is as low as possible, wherein the medium preferably flows out of the medium outlets distributed as evenly as possible over a medium inlet area of ​​a medium distribution area.

[0006] This object is achieved according to the invention in a bipolar plate for an electrochemical unit of an electrochemical device having the features of the preamble of claim 1 in that the total flow-through cross section of the medium inlets is at least 10% larger than the total flow-through cross section of the medium outlets.

[0007] The flowable cross sections of the medium inlets and the medium outlets are taken along a plane which is aligned parallel to the stacking direction and perpendicular to the mean flow direction of the medium through the respective medium inlet or medium outlet.

[0008] The inventive solution is based on the concept of overfilling the interior of the sealing bead with the relevant medium. Since the flow-through cross-section of the interior of the sealing bead itself is significantly larger than the flow-through cross-section of the medium inlets and outlets, the flow resistance within the sealing bead contributes hardly to the pressure drop in the medium as it flows from the medium passage opening to the outside of the sealing bead. By enlarging the total flow-through cross-section of the medium inlets, a maximum medium flow is achieved at the medium outlets on the outside of the sealing bead. The average flow velocity when flowing through the medium inlets is lower, which reduces the pressure drop in the medium at the medium inlets and also reduces the total pressure drop as the medium passes from the medium passage opening to the outside of the sealing bead.The total pressure drop is then essentially determined by the flow resistance of the medium outlets.

[0009] It is particularly advantageous if the total flow-through cross-section of the medium inlets is at least 15%, particularly preferably at least 20%, larger than the total flow-through cross-section of the medium outlets.

[0010] In principle, the flowable cross-section of the medium inlets can be influenced by selecting the number of medium inlets and by selecting the size of the flowable cross-sectional area of ​​the medium inlets.

[0011] Likewise, the total flow-through cross-section of the medium outlets can be influenced by selecting the number of medium outlets and by selecting the size of the flow-through cross-sectional area of ​​the medium outlets.

[0012] In a preferred embodiment of the invention, it is provided that the number of medium inlets is greater than the number of medium outlets, each on the same sealing bead.

[0013] In this case, the mean flow-through cross-section of a medium inlet can, for example, be substantially the same size as the mean flow-through cross-section of a medium outlet.

[0014] It is particularly advantageous if the number of medium inlets exceeds the number of medium outlets by two or more. The medium inlets are preferably arranged offset from the medium outlets along the circumference of the sealing bead.

[0015] In a preferred embodiment of the invention, it is provided that the bipolar plate comprises an electrochemically active region, which comprises an anode gas flow field through which an anode gas can flow, a cathode gas flow field through which a cathode gas can flow, and a coolant flow field through which a coolant can flow, wherein the bipolar plate comprises a medium distribution region via which the medium passage opening is in fluid communication with the electrochemically active region of the bipolar plate.

[0016] From the anode gas flow field of the electrochemically active region, the anode gas flows—optionally through a gas diffusion layer on the anode side—to an anode of a membrane-electrode assembly. From the cathode gas flow field of the electrochemically active region, the cathode gas flows—optionally through a gas diffusion layer on the cathode side—to a cathode of a membrane-electrode assembly. The region of the bipolar plate comprising the anode gas flow field and the cathode gas flow field is therefore referred to as its electrochemically active region, even though no electrochemical reactions take place at the bipolar plate itself.

[0017] Preferably, at least one medium outlet is arranged and aligned on the sealing bead such that the medium flows out of the medium outlet directed toward a medium inlet area of ​​the medium distribution area.

[0018] For example, it can be provided that several medium outlets are arranged in a distribution area section of the sealing bead, which is opposite a medium inlet area of ​​the medium distribution area. It is particularly advantageous if all medium outlets of a sealing bead are arranged in the distribution area section of the sealing bead, which is opposite the medium inlet area of ​​the medium distribution area.

[0019] Furthermore, at least one medium inlet is preferably arranged on the sealing bead outside the distribution area section of the sealing bead.

[0020] It is particularly favorable if at least two medium inlets, in particular at least three medium inlets, particularly preferably at least four medium inlets, are arranged on the sealing bead outside the distribution area section of the sealing bead.

[0021] In a preferred embodiment of the invention, all medium outlets are arranged at a medium outlet section of the sealing bead, which begins at a first outer medium outlet and ends at a second outer medium outlet. All other medium outlets are then located, distributed along the circumference of the sealing bead, between the first outer medium outlet and the second outer medium outlet.

[0022] In this case, it is advantageous if at least one medium inlet is arranged on the sealing bead outside the medium outlet section of the sealing bead.

[0023] Preferably, at least two medium inlets, in particular at least three medium inlets, particularly preferably at least four medium inlets, are arranged on the sealing bead outside the medium outlet section of the sealing bead.

[0024] A longitudinal direction of the bipolar plate preferably runs parallel to a main flow direction of the medium through a medium flow field of the bipolar plate associated with the medium. Preferably, at least one medium inlet is arranged and aligned on the sealing bead such that the medium flows through the medium inlet into the interior of the sealing bead substantially perpendicular to the longitudinal direction of the bipolar plate.

[0025] The longitudinal direction of the bipolar plate is preferably aligned parallel to the long sides of a bipolar plate which is essentially rectangular when viewed in a plan view along the stacking direction.

[0026] In order not to negatively influence the mechanical stability and the spring properties of the sealing bead in the curved sections of the sealing bead, it is advantageous if no medium inlet is arranged on a curved section of an edge of the medium passage opening.

[0027] This ensures a homogeneous pressing of the sealing bead.

[0028] The flow-through cross section of the sealing bead is preferably larger than the mean flow-through cross section of a medium flow channel of a medium flow field of the bipolar plate assigned to the medium.

[0029] The medium passage opening, for whose associated sealing bead the total flowable cross section of the medium inlets is at least 10% larger than the total flowable cross section of the medium outlets, can be an anode gas passage opening, a cathode gas passage opening or a coolant passage opening of the bipolar plate.

[0030] It is particularly advantageous if, for all sealing beads on the anode gas passage opening, on the cathode gas passage opening, and on the coolant passage opening, the total flow-through cross-section of the medium inlets on the respectively assigned sealing bead is at least 10% larger than the total flow-through cross-section of the medium outlets. In a preferred embodiment of the invention, it is therefore provided that an anode gas passage opening, a cathode gas passage opening, and a coolant passage opening of the bipolar plate are each surrounded by a sealing bead on which medium inlets and medium outlets are arranged, wherein the total flow-through cross-section of the medium inlets on each of these sealing beads is at least 10%, in particular by at least 15%, particularly preferably by at least 20% larger than the total flow-through cross-section of the medium outlets on the respective sealing bead.

[0031] The bipolar plate according to the invention is particularly suitable for use as a component of an electrochemical device comprising a plurality of electrochemical units which follow one another along a stacking direction and each comprise a bipolar plate according to the invention.

[0032] Such an electrochemical device may, for example, be a fuel cell device or an electrolyzer.

[0033] In a preferred embodiment of the invention, the electrochemical device is designed as a polymer electrolyte membrane (PEM) fuel cell device.

[0034] Further features and advantages of the invention are the subject of the following description and the drawing of an embodiment.

[0035] The drawings show:

[0036] Fig. 1 is a plan view of an end region of a bipolar plate for an electrochemical unit of an electrochemical device comprising a plurality of electrochemical units arranged one after the other along a stacking direction, wherein the bipolar plate comprises a plurality of medium passage openings, each of which forms a component of a medium channel extending through the electrochemical device along the stacking direction, a sealing bead extending around the medium passage opening, a plurality of medium inlets arranged on an inner side of the sealing bead facing the medium passage opening and allowing medium to flow into the interior of the sealing bead, and a plurality of medium outlets arranged on an outer side of the sealing bead facing away from the medium passage opening and allowing medium to flow out of the interior of the sealing bead.wherein the total flow-through cross-section of the medium inlets at a sealing bead is at least 10% larger than the total flow-through cross-section of the medium outlets at the same sealing bead, looking towards the cathode side of the bipolar plate;

[0037] Fig. 2 is a plan view of the end region of the bipolar plate from Fig. 1, looking towards the anode side of the bipolar plate;

[0038] Fig. 3 is a plan view of the inside of the end region of an anode-side bipolar plate layer of the bipolar plate of Figs. 1 and 2; and

[0039] Fig. 4 is a plan view of the inside of the end region of a cathode-side bipolar plate layer of the bipolar plate from Figs. 1 and 2.

[0040] Identical or functionally equivalent elements are designated by the same reference numerals throughout the figures. A bipolar plate, shown in detail in Figs. 1 to 4 and 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 comprise a membrane-electrode assembly, gas diffusion layers, and a sealing assembly.

[0041] A plurality of 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.

[0042] The bipolar plate 100 has a substantially rectangular shape, with long sides 107 of the bipolar plate 100 extending along a longitudinal direction 108 and short sides 109 of the bipolar plate 100 extending along a transverse direction 110 of the bipolar plate 100.

[0043] The longitudinal direction 108 and the transverse direction 110 are preferably aligned perpendicular to each other and perpendicular to the stacking direction 104.

[0044] The longitudinal direction 108 is also referred to as the x-direction, the transverse direction 110 is referred to as the y-direction, and the stacking direction 104 is referred to as the z-direction.

[0045] The x-direction, the y-direction and the z-direction form a rectangular coordinate system.

[0046] The bipolar plate 100 has two end regions 112 and an electrochemically active region 114 located between the end regions 112. The electrochemically active region 114 of the bipolar plate 100 comprises an anode gas flow field 116 through which an anode gas can flow, a cathode gas flow field 118 through which a cathode gas can flow, and a coolant flow field 120 through which a coolant can flow.

[0047] In the embodiment described here, the bipolar plate 100 is formed in two layers and comprises an anode-side bipolar plate layer 122, on which the anode gas flow field 116 is formed, and a cathode-side bipolar plate layer 124, on which the cathode gas flow field 118 is formed.

[0048] The bipolar plate layers 122 and 124 consist of a material with good electrical conductivity, preferably a metallic material.

[0049] The bipolar plate layers 122 and 124 are materially connected to one another along joining lines (not shown in the drawing), preferably welded, in particular by laser welding.

[0050] The anode flow field 116 of the bipolar plate 100 is in fluid communication with an anode-side electrode of a membrane electrode arrangement, optionally via an anode-side gas diffusion layer.

[0051] The cathode flow field 118 of the bipolar plate 100 is in fluid communication with a cathode-side electrode of a membrane-electrode arrangement, optionally via a cathode-side gas diffusion layer.

[0052] Thus, anode gas and cathode gas can flow from the electrochemically active region 114 of the bipolar plate 100 to the electrochemically active regions of each membrane electrode assembly. Therefore, the region of the bipolar plate 100 provided with the anode gas flow field 116 and the cathode gas flow field 118 is referred to as its electrochemically active region 114, even though no electrochemical reactions take place at the bipolar plate 100 itself.

[0053] The anode gas flow field 116 comprises anode gas flow channels 126 whose main flow direction is aligned parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100.

[0054] The cathode gas flow field 118 comprises cathode gas flow channels 128 whose main flow direction extends parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100.

[0055] In its end regions 112, of which a first end region 112a is shown in Figs. 1 to 4, the bipolar plate 100 has a plurality of medium passage openings 130 through which a fluid medium to be supplied to the electrochemical device 106 (an anode gas (fuel gas, for example, hydrogen), a cathode gas (oxidizing agent, for example, oxygen or air), or a coolant (for example, water)) can pass through the bipolar plate 100. The medium passage openings 130 of the bipolar plates 100 arranged consecutively in the stack of electrochemical units 102 and the spaces located between the medium passage openings 130 in the stacking direction 104 together form a medium channel 132.

[0056] Each of the medium channels 132 in one of the end regions 112 of the bipolar plate 100, through which a fluid medium can be supplied to the electrochemical device 100, is assigned a different medium channel 132 in the respective opposite end region 112, through which the respective fluid medium can be discharged from the electrochemical device 106. The fluid media pass through the anode gas flow field 116, the cathode gas flow field 118, or the coolant flow field 120 in the electrochemically active region 114 of the bipolar plate 100 from one end region 112 to the other end region 112.

[0057] In the first end region 112a of the bipolar plate 100 shown in Figs. 1 to 4, an anode gas passage opening 134, a cathode gas passage opening 136 and a coolant passage opening 138 are arranged.

[0058] In principle, each of these passage openings 134, 136 and 138 can serve either to supply the respective medium to the electrochemical device 106 or to remove the respective medium from the electrochemical device 106.

[0059] In principle, each of the three media, anode gas, cathode gas and coolant, can flow through the electrochemically active region 114 parallel to the other media or with an opposite main flow direction with respect to the main flow directions of one or two of the other media.

[0060] In a preferred embodiment of the invention, it is provided that all passage openings 134, 136 and 138 arranged in the first end region 112a of the bipolar plate 100 serve to supply the respective medium to the electrochemical device 106 and the passage openings 134, 136 and 138 arranged in the second end region 112 of the bipolar plate 100 serve to remove the respective medium from the electrochemical device 106.

[0061] To prevent unwanted leakage of fluid media from the respective passages 134, 136, and 138, each of these passages is provided with a sealing bead 140. The anode gas passage 134 is surrounded by an anode gas sealing bead 142.

[0062] In order to be able to supply the anode gas from the anode gas passage opening 134 to the anode gas flow field 136, the anode gas sealing bead 142 is provided on its inner side facing the anode gas passage opening 134 with a plurality of anode gas inlets 144 through which anode gas can flow from the anode gas passage opening 134 into the interior of the anode gas sealing bead 142 (see Fig. 2).

[0063] The anode gas inlets 144 each open at an edge 146 of the anode gas passage opening 134.

[0064] Preferably, the anode gas inlets 144 each open at a straight edge section 148, 150 or 152 of the anode gas passage opening 134.

[0065] The straight edge section 148 runs obliquely to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and obliquely to the transverse direction 110 (y-direction) of the bipolar plate 100 and preferably faces the electrochemically active region 114 of the bipolar plate 100.

[0066] At the edge section 148, a plurality of anode gas inlets, preferably at least three, in the illustrated embodiment four, are arranged, through which the anode gas flows preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100 into the interior of the anode gas sealing bead 142.

[0067] The rectilinear edge section 150 preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and preferably faces the coolant passage opening 138. One or more anode gas inlets 144, two anode gas inlets 144 in the illustrated embodiment, open at the edge section 150.

[0068] The straight edge section 152 preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and is preferably facing away from the coolant passage opening 138.

[0069] At the edge section 152, one or more anode gas inlets 144, in the illustrated embodiment two anode gas inlets 144, preferably open, through which the anode gas flows preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100 into the interior of the anode gas sealing bead 142.

[0070] Furthermore, the edge 146 of the anode gas passage opening 134 comprises a straight edge section 153, which is preferably aligned obliquely to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and obliquely to the transverse direction 110 (y-direction) of the bipolar plate 100 and preferably faces away from the electrochemically active region 114 of the bipolar plate 100.

[0071] Preferably, no anode gas inlet 144 opens at the edge section 153.

[0072] Together, the edge sections 148, 150, 152 and 153 form a polygonal edge 146 of the anode gas passage opening 134.

[0073] In the illustrated embodiment, the edge 146 of the anode gas passage opening 134 is square; however, the polygonal edge 146 of the anode gas passage opening 134 can also have more or fewer than four corners.

[0074] The corners of the anode gas passage opening 134 are preferably rounded to prevent tearing of the bipolar plate layers 122 and 124 in the region of these corners. To allow the anode gas to escape from the interior of the anode gas sealing bead 142, the anode gas sealing bead 142 is provided with a plurality of anode gas outlets 154 on its outer side facing away from the anode gas passage opening 134.

[0075] The anode gas outlets 154 are preferably arranged on a portion 156 of the anode gas sealing bead 142 which faces the electrochemically active region 114 of the bipolar plate 100.

[0076] The portion 156 of the anode gas sealing bead 142 preferably runs substantially parallel to the straight edge portion 148 of the edge 146 of the anode gas passage opening 134 and substantially parallel to the rounded corner regions 157a and 157b of the edge 146, which connect the straight edge portion 148 to the edge portion 150 and to the edge portion 152, respectively.

[0077] In this case, several, preferably at least four, in the illustrated embodiment six, anode gas outlets 154 are preferably arranged on the section 156.

[0078] The anode gas inlets 144, which are arranged on the same portion 156 of the anode gas sealing bead 142, are preferably offset from the anode gas outlets 154 along the circumferential direction of the anode gas sealing bead 142.

[0079] Furthermore, the anode gas sealing bead 142 comprises further sections 158a, 158b, and 160, which are each aligned substantially parallel to the rectilinear edge sections 150 and 152 running parallel to the longitudinal direction 108 of the bipolar plate 100, or substantially parallel to the rectilinear edge section 153 of the edge 146 of the anode gas passage opening 134 facing away from the electrochemically active region 114. The anode gas flows through the anode gas outlets 154 at the section 156 of the anode gas sealing bead 142 into an anode gas distribution region 170, which serves to distribute the anode gas as evenly as possible among the anode gas flow channels 126 of the anode gas flow field 116.

[0080] The anode gas distribution region 170 comprises a plurality of directed distribution structures 172 and a plurality of non-directed distribution structures 174, which serve to deflect the anode gas from its original flow direction.

[0081] The directed distribution structures 172 are designed, for example, as essentially linearly extending distribution webs 176.

[0082] The non-directional distribution structures 174 are formed, for example, as essentially cup-shaped distribution knobs 178.

[0083] The distributor structures 172 and 174, like all other structures of the bipolar plate 100 described above and below, are preferably formed integrally with the material of the bipolar plate layers 122 or 124 and are introduced into the respective bipolar plate layer 122 or 124 by a forming process, for example by a stamping process or a deep-drawing process.

[0084] The cathode gas passage opening 136 is surrounded by a cathode gas sealing bead 162.

[0085] The coolant passage opening 138 is surrounded by a coolant sealing bead 164. A closed, annular edge bead 182 extends near the outer edge 180 of the bipolar plate 100.

[0086] The edge bead 182 encloses the electrochemically active region 114 of the bipolar plate 100, the anode gas passage openings 134 and the anode gas sealing beads 142 in both end regions 112, the cathode gas passage openings 136 and the cathode gas sealing beads 162 in both end regions 112, and the coolant passage openings 138 and the coolant sealing beads 164 in both end regions 112 of the bipolar plate 100.

[0087] The edge bead 182 serves to prevent the media to be supplied to the electrochemical device 106, in particular the anode gas, the cathode gas and the coolant, from escaping from the electrochemical units 102 into the outer space 184 of the electrochemical device 106.

[0088] In order to allow the cathode gas to flow out of the cathode gas passage opening 136 through the cathode gas sealing bead 162, the cathode gas sealing bead 162 is provided with a plurality of cathode gas inlets 194 on its inner side facing the cathode gas passage opening 136 (see in particular Fig. 1).

[0089] Through the cathode gas inlets 194, cathode gas passes from the cathode gas passage opening 136 into the interior of the cathode gas sealing bead 162.

[0090] The cathode gas inlets 194 preferably open at rectilinear edge sections 196, 202, and 204 of the edge 198 of the cathode gas passage opening 136. The rectilinear edge section 196 preferably runs obliquely to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and obliquely to the transverse direction 110 (y-direction) of the bipolar plate 100 and preferably faces the electrochemically active region 114 of the bipolar plate 100. Preferably, several cathode gas inlets 194 open at the edge section 196, in particular at least four, six in the illustrated embodiment.

[0091] The rectilinear edge section 202 preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and preferably faces the coolant passage opening 138. One or more cathode gas inlets 194, two cathode gas inlets 194 in the illustrated embodiment, preferably open at the edge section 202, through which the cathode gas flows into the interior of the cathode gas sealing bead 162, preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100.

[0092] The straight edge section 204 preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and preferably faces the edge bead 182.

[0093] At the edge section 204, one or more cathode gas inlets 194, in the illustrated embodiment two cathode gas inlets 194, preferably open, through which the cathode gas flows preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100 into the interior of the cathode gas sealing bead 162.

[0094] Furthermore, the edge 198 of the cathode gas passage opening 136 can comprise a rectilinear edge section 206 extending substantially parallel to the transverse direction 110 (y-direction) of the bipolar plate 100, preferably facing away from the electrochemically active region 114 of the bipolar plate 100. Together, the edge sections 196, 202, 204, and 206 form a polygonal edge 198 of the cathode gas passage opening 136.

[0095] In the embodiment illustrated in the drawing, the edge 198 of the cathode gas passage opening 136 is rectangular. However, the number of corners of the polygonal edge 198 can also be fewer or larger than four.

[0096] Several, for example four or more, preferably six or more, in the illustrated embodiment eight, cathode gas outlets 214 are arranged on the outside of a section 200 of the cathode gas sealing bead 162, which runs substantially parallel to the rectilinear edge section 196 of the edge 198 of the cathode gas passage opening 136 and substantially parallel to the rounded corner regions 201a and 201b of the edge 198, which connect the rectilinear edge section 196 to the edge section 202 and to the edge section 204, respectively.

[0097] Furthermore, the cathode gas sealing bead 162 comprises further sections 208, 210 and 212, which are each aligned substantially parallel to the straight edge sections 202 and 204 running parallel to the longitudinal direction 108 of the bipolar plate 100 or substantially parallel to the straight edge section 206 of the edge 198 of the cathode gas passage opening 136 facing away from the electrochemically active region 114.

[0098] The cathode gas outlets 214 are preferably all arranged on the section 200 of the cathode gas sealing bead 162 that faces the electrochemically active region 114 of the bipolar plate 100. Preferably, the cathode gas inlets 194, which are arranged on the same section 200 of the cathode gas sealing bead 162, are offset from the cathode gas outlets 214 along the circumferential direction of the cathode gas sealing bead 162.

[0099] Preferably, a total of two or more, in particular four or more, particularly preferably six or more, in the illustrated embodiment eight, cathode gas outlets 214 are provided on the cathode gas sealing bead 162.

[0100] The cathode gas flows through the cathode gas outlets 214 into a cathode gas distribution region 216 of the bipolar plate 100, which serves to distribute the cathode gas as evenly as possible to the cathode gas flow channels 128 of the cathode gas flow field 118.

[0101] For this purpose, the cathode gas distribution region comprises distribution structures 218, which are designed as directional distribution structures 220 or as non-directional distribution structures 221.

[0102] The directional distribution structures 220 are preferably formed as linearly extending distribution webs 222.

[0103] The non-directional distribution structures 221 are formed, for example, as essentially cup-shaped distribution knobs 223.

[0104] In order to allow the coolant to flow out of the coolant passage opening 138 into the coolant flow field 120 of the bipolar plate 100, the coolant sealing bead 164 is provided with a plurality of coolant inlets 224 on its inner side facing the coolant passage opening 138 (see in particular Fig. 1).

[0105] The coolant passes through the coolant inlets 224 from the coolant passage opening 138 into the interior of the coolant sealing bead 164. The coolant inlets 224 preferably open at straight edge sections 226, 232a and 232b of the edge 228 of the coolant passage opening 138.

[0106] The rectilinear edge section 226 preferably runs substantially parallel to the transverse direction 110 (y-direction) of the bipolar plate 100 and preferably faces the electrochemically active region 114 of the bipolar plate 100. Preferably, several, in particular at least three, four in the illustrated embodiment, coolant inlets 224 open at the edge section 226.

[0107] The rectilinear edge section 232a preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and preferably faces the anode gas passage opening 134. One or more coolant inlets 224, two in the illustrated embodiment, preferably open at the edge section 232a, through which the coolant flows into the interior of the coolant sealing bead 164, preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100.

[0108] The rectilinear edge section 232b preferably runs substantially parallel to the longitudinal direction 108 (x-direction) of the bipolar plate 100 and preferably faces the cathode gas passage opening 136. One or more coolant inlets 224, two in the illustrated embodiment, preferably open at the edge section 232b, through which the coolant flows into the interior of the coolant sealing bead 164, preferably perpendicular to the longitudinal direction 108 (x-direction) of the bipolar plate 100. Furthermore, the edge 228 of the coolant passage opening 138 can comprise a rectilinear edge section 234 running substantially parallel to the transverse direction 110 (y-direction) of the bipolar plate 100 and preferably facing away from the electrochemically active region 114 of the bipolar plate 100. Preferably, no coolant inlet 224 opens into the edge section 234.

[0109] The edge sections 226, 232a, 232b, and 234 together form a polygonal edge 228 of the coolant passage opening 138, which is rectangular in the embodiment illustrated in the drawing. However, the number of corners of the polygonal edge 228 of the coolant passage opening 138 can also be greater or less than four.

[0110] Several, for example, three or more, preferably five or more, in the illustrated embodiment, seven, coolant outlets 225 are arranged on a section 230 of the coolant sealing bead 164, which runs substantially parallel to the rectilinear edge section 226 of the edge 228 of the coolant passage opening 138 and substantially parallel to the rounded corner regions 231a and 231b of the edge 228, which connect the rectilinear edge section 226 to the edge section 232a and the edge section 232b, respectively. The section 200 of the coolant sealing bead 164 preferably faces the electrochemically active region 114 of the bipolar plate 100.

[0111] Preferably, the coolant inlets 224, which are arranged on the same section 230 of the coolant sealing bead 164, are offset from the coolant outlets 225 along the circumferential direction of the coolant sealing bead 164. In addition to the section 230 provided with the coolant outlets 225, the coolant sealing bead 164 preferably comprises further sections 238a, 238b, and 240, which are each aligned substantially parallel to the edge sections 232a, 232b, and 234, respectively, of the edge 228 of the coolant passage opening 138.

[0112] These further sections 238a, 238b and 240 of the coolant sealing bead 164 are preferably not provided with coolant outlets 225.

[0113] The coolant flows through the coolant outlets 225 into a coolant distribution area 242 of the bipolar plate 100, which serves to distribute the coolant as evenly as possible to the coolant flow channels of the coolant flow field.

[0114] In this coolant distribution region 242, the anode-side bipolar plate layer 122 and the cathode-side bipolar plate layer 124 are offset in opposite directions along the stacking direction 104 with respect to a longitudinal center plane of the bipolar plate 100 oriented perpendicular to the stacking direction 104, such that a large flow-through cross-section is available for the flow of the coolant through the coolant distribution region 242.

[0115] The bipolar plate 100 is preferably rotationally symmetrical with respect to a rotation of 180° about an axis of rotation extending through the center of the electrochemically active region 114 of the bipolar plate 100 and parallel to the stacking direction 104 (z-direction).

[0116] The medium passage openings 130 arranged in the second end region 112, in particular the anode gas passage opening 134 arranged there, the cathode gas passage opening 136 arranged there and the coolant passage opening 138 arranged there, are therefore preferably constructed and arranged essentially in the same way as the anode gas passage opening 134, the cathode gas passage opening 136 and the coolant passage opening 138 in the first end region 112a, which have been described above.

[0117] The anode gas inlets 144 form medium inlets 272 at the anode gas sealing bead 142. The anode gas outlets 154 form medium outlets 274 at the anode gas sealing bead 142.

[0118] The cathode gas inlets 194 form medium inlets 272 at the cathode gas sealing bead 162. The cathode gas outlets 214 form medium outlets 274 at the cathode gas sealing bead 162.

[0119] The coolant inlets 224 form medium inlets 272 on the coolant sealing bead 164. The coolant outlets 225 form medium outlets 274 on the coolant sealing bead 164.

[0120] The bipolar plate 100 shown in Figs. 1 to 4 and described above aims to reduce the pressure drop in the media supplied to the electrochemical device 106 as they pass through the respective associated sealing beads 140. For this purpose, it is advantageous if the total flow-through cross-section of the respective medium inlets 272 at the respective sealing bead 140 is at least 10%, in particular at least 15%, particularly preferably at least 20%, larger than the total flow-through cross-section of the medium outlets 274 at the same sealing bead 140.

[0121] This can be achieved in particular by the flowable cross section of a medium inlet 272 on a sealing bead 140 being substantially the same size as the flowable cross section of a medium outlet 274 on the same sealing bead 140, but the number of medium inlets 272 on the sealing bead 140 being greater than the number of medium outlets 274. Preferably, the number of medium inlets 272 is two or more times greater than the number of medium outlets 274.

[0122] Thus, in the exemplary embodiment shown in the drawing, eight anode gas inlets 144 are arranged on the anode gas sealing bead 142 on the inside of the anode gas sealing bead 142 facing the anode gas passage opening 134, while six anode gas outlets 154 are arranged on the outside of the anode gas sealing bead 142 facing away from the anode gas passage opening 134.

[0123] As a result, the pressure drop in the anode gas as the anode gas flows from the anode gas passage opening 134 through the anode gas sealing bead 142 into the anode gas distribution area 170 is significantly reduced.

[0124] Furthermore, in the exemplary embodiment of a bipolar plate 100 shown in the drawing, it is provided that ten cathode gas inlets 194 are arranged on the inside of the cathode gas sealing bead 162 facing the cathode gas passage opening 136, while eight cathode gas outlets 214 are arranged on the outside of the cathode gas sealing bead 162 facing away from the cathode gas passage opening 136.

[0125] As a result, the pressure drop in the cathode gas when the cathode gas flows from the cathode gas passage opening 136 through the cathode gas sealing bead 162 into the cathode gas distribution area 216 is significantly reduced.

[0126] Furthermore, in the exemplary embodiment illustrated in the drawing, eight coolant inlets 224 are arranged on the inside of the coolant sealing bead 164 facing the coolant passage opening 138, while seven coolant outlets 225 are arranged on the outside of the coolant sealing bead 164 facing away from the coolant passage opening 138. This significantly reduces the pressure drop in the coolant as the coolant flows from the coolant passage opening 138 through the coolant sealing bead 164 into the coolant distribution area 242.

[0127] The anode gas distribution area 170 forms a medium distribution area 276 for the anode gas.

[0128] The cathode gas distribution area 216 forms a medium distribution area 276 for the cathode gas.

[0129] The coolant distribution area 242 forms a medium distribution area 276 for the coolant.

[0130] Each of the medium distribution areas 276 comprises a medium inlet area 278 through which the respective medium enters the respective medium distribution area 276.

[0131] The section of a sealing bead 140 which faces the electrochemically active region 114 of the bipolar plate 100 forms a distribution region section 280 of the respective sealing bead 140.

[0132] The anode gas flow field 116 forms a medium flow field 282 for the anode gas.

[0133] The cathode gas flow field 118 forms a medium flow field 282 for the cathode gas.

[0134] The coolant flow field 120 forms a medium flow field 282 for the coolant. Each of the medium flow fields 282 of the bipolar plate 100 comprises medium flow channels 284 that extend along a main flow direction of the medium through the respective medium flow field 282.

[0135] For all medium inlets 272, it applies that they are preferably arranged offset from the respective medium outlets 274 along the circumference of the respective sealing bead 140.

[0136] Each of the medium outlets 274 is preferably arranged and aligned on the respective sealing bead 140 such that the medium flowing through the medium outlet 274 flows out of the medium outlet 274 directed toward a medium inlet region 278 of the respectively associated medium distribution region 276.

[0137] Preferably, all medium outlets 274 are arranged on the distribution area section 280 of the respective sealing bead 140, which is opposite the medium inlet area 278 of the respectively assigned medium distribution area 276.

[0138] For each of the medium passage openings 130, at least one medium inlet 272 is preferably arranged outside the distribution area section 280 of the respective sealing bead 140 on the respective sealing bead 140.

[0139] Preferably, at each medium passage opening 130, at least two, in particular at least three, particularly preferably at least four, medium inlets 272 are arranged outside the distribution area section 280 of the respective sealing bead 140 on the respective sealing bead 140. At each of the sealing bead 140, a medium outlet section 286 of the respective sealing bead 140 is defined by beginning at a first outer medium outlet 274a and ending at a second outer medium outlet 274b.

[0140] Preferably, for each sealing bead 140, at least one medium inlet 272 is arranged outside the medium outlet section 286 of the respective sealing bead 140 on the respective sealing bead 140.

[0141] The longitudinal direction 108 (x-direction) of the bipolar plate 100 runs parallel to a main flow direction of the media through the medium flow fields 282 assigned to the media.

[0142] Preferably, at least one medium inlet 272 is arranged and aligned on each sealing bead 140 such that the medium flows substantially perpendicular to the longitudinal direction 108, i.e. substantially parallel to the transverse direction 110, of the bipolar plate 100 through the respective medium inlet 272 into the interior of the respective sealing bead 140.

[0143] In order not to negatively influence the mechanical stability and the spring properties of the sealing beads 140 in their curved sections, it is preferably provided that no medium inlet 272 is arranged on a curved section of the edge of the respective medium passage opening 130.

[0144] For each of the sealing beads 140, the flow-through cross section of the respective sealing bead 140 is preferably larger than the average flow-through cross section of a medium flow channel 284 of the medium flow field 282 of the bipolar plate 100 associated with the respective medium.

Claims

Patent claims Bipolar plate for an electrochemical unit (102) of an electrochemical device (106), which comprises a plurality of electrochemical units (102) which follow one another along a stacking direction (104), wherein the bipolar plate (100) comprises the following: at least one medium passage opening (130), which forms a component of a medium channel (132) which extends along the stacking direction (104) through the electrochemical device (106); a sealing bead (140), which extends around the medium passage opening (130); a plurality of medium inlets (272), which are arranged on an inner side of the sealing bead (140) facing the medium passage opening (130) and which enable medium to flow into the interior of the sealing bead (140);and a plurality of medium outlets (274) arranged on an outer side of the sealing bead (140) facing away from the medium passage opening (130) and allowing medium to flow out of the interior of the sealing bead (140); characterized in that the total flow-through cross-section of the medium inlets (272) is at least 10% larger than the total flow-through cross-section of the medium outlets (274). Bipolar plate according to claim 1, characterized in that the number of medium inlets (272) is greater than the number of medium outlets (274). Bipolar plate according to one of claims 1 or 2, characterized in that the medium inlets (272) are arranged offset from the medium outlets (274) along the circumference of the sealing bead (140). Bipolar plate according to one of claims 1 to 3, characterized in that the bipolar plate (100) comprises an electrochemically active region (114) which comprises an anode gas flow field (116) through which an anode gas can flow, a cathode gas flow field (118) through which a cathode gas can flow, and a coolant flow field (120) through which a coolant can flow, wherein the bipolar plate (100) comprises a medium distribution region (276) via which the medium passage opening (130) is in fluid communication with the electrochemically active region (114) of the bipolar plate (100).Bipolar plate according to claim 4, characterized in that at least one medium outlet (274) is arranged and aligned on the sealing bead (140) such that the medium flows out of the medium outlet (274) in a direction directed toward a medium inlet region (278) of the medium distribution region (276). Bipolar plate according to one of claims 4 or 5, characterized in that a plurality of medium outlets (274) are arranged on a distribution region section (280) of the sealing bead (140), which lies opposite a medium inlet region (278) of the medium distribution region (276). Bipolar plate according to claim 6, characterized in that at least one medium inlet (272) is arranged on the sealing bead (140) outside the distribution region section (280) of the sealing bead (140). Bipolar plate according to one of claims 1 to 7, characterized in that all medium outlets (274) are arranged at a medium outlet section (286) of the sealing bead (140), which begins at a first outer medium outlet (274a) and ends at a second outer medium outlet (274b). Bipolar plate according to claim 8, characterized in that at least one medium inlet (272) is arranged outside the medium outlet section (286) of the sealing bead (240) on the sealing bead (140).Bipolar plate according to one of claims 1 to 9, characterized in that a longitudinal direction (108) of the bipolar plate (100) runs parallel to a main flow direction of the medium through a medium flow field (282) of the bipolar plate (100) assigned to the medium, wherein at least one medium inlet (272) is arranged and aligned on the sealing bead (140) such that the medium flows through the medium inlet (272) into the interior of the sealing bead (140) essentially perpendicular to the longitudinal direction (108) of the bipolar plate (100). Bipolar plate according to one of claims 1 to 10, characterized in that no medium inlet (272) is arranged on a curved section of an edge (146, 198, 228) of the medium passage opening (130).Bipolar plate according to one of claims 1 to 11, characterized in that the flow-through cross section of the sealing bead (140) is larger than the mean flow-through cross section of a medium flow channel (284) of a medium flow field (282) of the bipolar plate (100) associated with the medium. Bipolar plate according to one of claims 1 to 12, characterized in that the medium passage opening (130) is an anode gas passage opening (134), a cathode gas passage opening (136) or a coolant passage opening (138). Bipolar plate according to one of claims 1 to 13, characterized in that an anode gas passage opening (134), a cathode gas passage opening (136) and a coolant passage opening (138) of the bipolar plate (100) are all surrounded by a respective sealing bead (140) on which medium inlets (272) and medium outlets (274) are arranged, wherein the total flow-through cross section of the medium inlets (272) at each of these sealing bead (140) is at least 10% larger than the total flow-through cross section of the medium outlets (274) at the respective sealing bead (140).Electrochemical device comprising a plurality of electrochemical units (102) which follow one another along a stacking direction (104) and each comprise a bipolar plate (100) according to one of claims 1 to 14.

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