Bipolar plate for an electrochemical device

Abstract

To create a bipolar plate for an electrochemical unit of an electrochemical device, wherein the bipolar plate comprises at least one reactant gas passage opening, an electrochemically active region and at least one reactant gas distribution region, wherein the electrochemically active region and / or the reactant gas distribution region comprises at least one primary flow channel through which the reactant gas flows, which is in fluid communication with at least one secondary flow channel of a first type and at least one secondary flow channel of a second type via a distribution section comprising one or more transition channels, in which the reactant gas flow is distributed as evenly as possible onto the secondary flow channels during operation of the electrochemical device, it is proposed thatthat the at least one transition channel comprises at least one deflection device for diverting a flow component of the reactant gas towards a secondary flow channel of the first type assigned to the same transition channel, and / or that the at least one transition channel comprises at least one deflection device for diverting a flow component of the reactant gas towards a secondary flow channel of the first type assigned to another transition channel.

Description

[0001] The present invention relates to a bipolar plate for an electrochemical unit of an electrochemical device comprising several electrochemical units which follow one another along a stacking direction, wherein the bipolar plate comprises the following: - at least one reactant gas passage opening, which forms part of a reactant gas channel extending along the stacking direction through the electrochemical device; - an electrochemically active area which includes at least one reactant gas flow field through which a reactant gas can flow transversely to the stacking direction; and - at least one reactant gas distribution area, above which the at least one reactant gas passage opening is in fluid communication with the at least one reactant gas flow field; wherein the electrochemically active area and / or the reactant gas distribution area comprises at least one primary flow channel through which the reactant gas can flow, which is in fluid communication via a distribution section comprising one or more transition channels with at least one secondary flow channel of a first type and at least one secondary flow channel of a second type, wherein each transition channel comprises an end region of the primary flow channel and an initial region of the at least one secondary flow channel of the first type and an initial region of the at least one secondary flow channel of the second type.

[0002] Preferably, the bipolar plate comprises an anode-side bipolar plate layer and a cathode-side bipolar plate layer, wherein these two bipolar plate layers are joined together. The bipolar plate layers are preferably joined together by a material bond, in particular by welding, for example by laser welding.

[0003] The bipolar plate is preferably made of a metallic material, in particular of a non-rusting, austenitic steel, especially preferably of a steel with the material number 1.4404.

[0004] The bipolar plate 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.

[0005] Several such electrochemical units follow one another along a stacking 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.

[0006] Due to the design of bipolar plates, the number of primary flow channels, which preferably form part of the reactant gas distribution area, is lower than the number of secondary flow channels, which preferably form part of the electrochemically active area.

[0007] When the reactant gas flow is divided from a primary flow channel into several secondary flow channels via a distribution section, different reactant gas flow rates result in the secondary flow channels according to the state of the art.

[0008] This may be due, for example, to a different flow resistance of the secondary flow channel of the first kind compared to the flow resistance of the secondary flow channel of the second kind.

[0009] If the at least one transition channel is curved, a difference in reactant gas flow rate in the secondary flow channels can result from the curvature of the at least one transition channel in conjunction with the inertia of the reactant gas. Due to the curvature and the inertia, for example, a relative overpressure of the reactant gas occurs in the initial region of the at least one secondary flow channel of the second type, into which a radially outer region of the transition channel opens and which is also referred to as the outer secondary flow channel, compared to the pressure of the reactant gas in the initial region of the at least one secondary flow channel of the first type, into which a radially inner region of the transition channel opens and which is also referred to as the inner secondary flow channel.

[0010] This pressure difference in the initial regions of the secondary flow channels can lead to different reactant gas flow rates within the secondary flow channels.

[0011] However, for efficient operation of the electrochemical device, it is advantageous if the reactant gas flow of the at least one primary flow channel is distributed as evenly as possible onto the secondary flow channels, in order to supply the electrochemically active area as homogeneously as possible with the at least one reactant gas.

[0012] The present invention is based on the objective of creating a bipolar plate in which the reactant gas flow is distributed as evenly as possible onto the secondary flow channels during operation of the electrochemical device.

[0013] This problem is solved in a bipolar plate according to the preamble of claim 1 according to the invention in that the at least one transition channel comprises at least one deflection device for deflecting a flow component of the reactant gas towards a secondary flow channel of the first type associated with the same transition channel. and / or that the at least one transition channel includes at least one deflection device for deflecting a flow component of the reactant gas towards a secondary flow channel of the first type assigned to another transition channel.

[0014] If the transition channel has a curvature, wherein the at least one transition channel has a curvature, wherein the at least one secondary flow channel of the first type is designed as an inner secondary flow channel into which a radially inner region of the transition channel opens, and wherein the at least one secondary flow channel of the second type is designed as an outer secondary flow channel into which a radially outer region of the transition channel opens, it is preferably provided that the at least one transition channel comprises a deflection device for deflecting a flow component of the reactant gas towards an inner secondary flow channel associated with the same transition channel and / or that the at least one transition channel comprises a deflection device for deflecting a flow component of the reactant gas towards an inner secondary flow channel associated with another transition channel.

[0015] In a preferred embodiment of the invention, the deflection device comprises at least a local elevation of a channel base of the at least one transition channel along the stacking direction.

[0016] It is particularly advantageous if at least one section of a contour line running perpendicular to the stacking direction leads from a bridge bounding the transition channel away from the local uplift of a channel bottom of the at least one transition channel and towards a bridge bounding the secondary flow channel of the first type.

[0017] Such a local elevation of a channel bottom of the at least one transition channel is advantageous because this design achieves a guiding of the reactant gas flow which has a relatively low flow resistance.

[0018] It is particularly advantageous if the contour line running perpendicular to the stacking direction of the local elevation of the channel bottom of the at least one transition channel begins at the web bounding the transition channel and ends at the web bounding the secondary flow channel of the first type.

[0019] The local elevation has a maximum height H maxA which extends along the stacking direction, preferably at least 10%, in particular at least 20%, and most preferably at least 30% of the maximum height H maxU of the transition channel, which extends along the stacking direction.

[0020] Alternatively or in addition to the local raising of a channel bed of the transition channel, it may also be provided that the diversion device includes at least a local lowering of a bridge bounding the transition channel.

[0021] In this process, a flow component of the reactant gas from the at least one transition channel is preferably deflected towards a secondary flow channel of the first type assigned to another transition channel.

[0022] Such a local lowering of a bridge bounding the transition channel in the distribution section is different from a possible lowering of bridges bounding the secondary flow channels in the electrochemically active area of ​​the bipolar plate, which can serve to compensate for a height difference of a membrane electrode arrangement adjacent to the bipolar plate along the stacking direction.

[0023] It is particularly advantageous if the maximum longitudinal extent L maxSthe local depression, which is aligned parallel to a local longitudinal direction of the web bounding the transition channel and perpendicular to the stacking direction, at least 2.5 times, in particular at least 5.0 times, most preferably at least 10 times, a maximum height h maxAb the local subsidence of the bridge bounding the transition channel, where the maximum height h maxAb the local subsidence of the bridge bordering the transition channel extends along the stacking direction.

[0024] In a particular embodiment of the invention, the minimum height of the web bounding the transition channel is h minS in the area of ​​local subsidence at most 98%, in particular at most 95%, most preferably at most 92%, of the maximum height h maxS of the bridge bounding the transition channel outside the area of ​​local subsidence, wherein the minimum height h minS and the maximum height h maxSextend along the stacking direction.

[0025] The minimum height h minS The thickness of the web bounding the transition channel is preferably at least 30%, in particular at least 60%, and most preferably at least 90% of the maximum height h in the area of ​​local depression. maxS of the bridge 150 bounding the transition channel 130 outside the area of ​​the local subsidence 148.

[0026] Regardless of the dimensioning of the local lowering, it can be provided that the local lowering is arranged in such a way that, by means of it, the at least one transition channel assigned to the primary flow channel and a transition channel assigned to another primary flow channel are in fluid communication with each other.

[0027] This can be particularly advantageous when differences in reactant gas flow rates between two or more primary flow channels need to be compensated for.

[0028] In a particular embodiment of the invention, the deflection device comprises at least one local bulge of a web bounding the transition channel, which extends perpendicularly to the stacking direction into the transition channel.

[0029] It is particularly advantageous if a maximum width B maxW of the web bounding the transition channel in the area of ​​the local bulge at least 1.2 times, in particular at least 1.4 times, particularly preferably at least 1.6 times, the maximum width b maxS of the bridge bounding the transition channel outside the area of ​​the local bulge, wherein the maximum width B maxW and the maximum width b maxS each extend perpendicular to the stacking direction and perpendicular to the local longitudinal direction of the web bounding the transition channel.

[0030] Such a local bulge of the web bounding the transition channel does not necessarily have to be symmetrical with respect to a mirror plane which is oriented perpendicular to the local longitudinal direction of the web bounding the transition channel.

[0031] The local bulge can, for example, extend wedge-shaped into the transition channel. This means that the width of the web bounding the transition channel in the area of ​​the bulge increases along the course of the local bulge from its beginning to a point of maximum width B. maxWThe width of the rib bounding the transition channel increases monotonically, and its width decreases monotonically along the local longitudinal direction towards one end of the local bulge. The decrease in width of the rib bounding the transition channel in the decreasing section can be greater than the increase in width in the increasing section, and vice versa.

[0032] Furthermore, this local bulge does not necessarily have to extend over the entire height of the transition channel, from the channel floor of the transition channel up to the maximum height H. maxU of the transition channel.

[0033] The maximum height of the bulge can lie within a height interval, the lower limit of which is preferably at least 10%, in particular at least 20%, and most preferably at least 25% of the maximum height H. maxUof the transition channel and its upper limit preferably at most 90%, in particular at most 80%, most preferably at most 75%, of the maximum height H maxU of the transition channel.

[0034] To ensure particularly efficient manufacturing, it is advantageous if the deflection device is formed as a single piece with the bipolar plate.

[0035] This allows the deflection device and the bipolar plate to be manufactured in a single manufacturing step, for example by embossing and / or deep drawing from a flat starting material.

[0036] Preferably, at least two transition channels are assigned to the at least one primary flow channel.

[0037] It is advantageous if at least one transition channel is assigned exactly one secondary flow channel of the first type and / or exactly one secondary flow channel of the second type.

[0038] Preferably, at least one secondary flow channel forms part of the electrochemically active area of ​​the bipolar plate.

[0039] In a preferred embodiment of the invention, the at least one primary flow channel forms a component of the reactant gas distribution area of ​​the bipolar plate.

[0040] Preferably, the angle α between a local longitudinal direction of a secondary flow channel and a local longitudinal direction of a primary flow channel is greater than 40°, in particular greater than 50°, and especially preferably greater than 60°.

[0041] The bipolar plate according to the invention is particularly suitable for use in an electrochemical device which comprises several electrochemical units that follow one another along a stacking direction and each comprise a bipolar plate according to the invention.

[0042] Such an electrochemical device could be, for example, a fuel cell device, an electrolyzer, or an electrochemical compressor.

[0043] The electrochemical unit in which the bipolar plate according to the invention is used preferably comprises a polymer electrolyte membrane.

[0044] Further features and advantages of the invention are the subject of the following description and the graphic representation of exemplary embodiments.

[0045] The drawings show: Fig. 1. A top view of a bipolar plate for an electrochemical unit of an electrochemical device comprising several electrochemical units arranged in a stacking direction, with the view along the stacking direction towards one side of the bipolar plate, wherein the bipolar plate comprises a reactant gas passage opening forming part of a reactant gas channel extending along the stacking direction through the electrochemical device, an electrochemically active region comprising at least one reactant gas flow field through which a reactant gas can flow transversely to the stacking direction, and at least one reactant gas distribution region above which the at least one reactant gas passage opening is in fluid communication with the at least one reactant gas flow field.wherein the electrochemically active area and / or the reactant gas distribution area comprises at least one primary flow channel through which the reactant gas flows, which is connected via a distribution section to at least one secondary flow channel of a first type and at least one secondary flow channel of a second type; Fig. 2. A perspective view of a distribution section of a bipolar plate for an electrochemical unit of an electrochemical device according to the prior art, wherein the reactant gas distribution area comprises at least one primary flow channel through which a reactant gas flows, which is in fluid communication with three secondary flow channels of a first type and three secondary flow channels of a second type via a distribution section comprising three transition channels, wherein each transition channel comprises an end region of the secondary flow channel of the first type and each an initial region of a secondary flow channel of the second type, wherein each transition channel has a curvature, wherein the secondary flow channels of the first type are designed as inner secondary flow channels into which a radially inner region of each transition channel opens.and wherein the secondary flow channels of the second type are designed as outer secondary flow channels, into which a radially outer region of each transition channel opens; Fig. 3 a top view along the stacking direction of the distribution section, the end region of the primary flow channel and the starting regions of the three inner secondary flow channels as well as the starting regions of the three outer secondary flow channels from Fig. 2; Fig. 4 one of the Fig. 2. A corresponding perspective view of the distribution section in a first embodiment according to the invention of a bipolar plate of an electrochemical unit, wherein the transition channels of the distribution section each comprise a deflection device for deflecting a flow component of the reactant gas towards an inner secondary flow channel assigned to another transition channel; Fig. 5 a top view along the stacking direction of the distribution section, the end region of the primary flow channel and the starting regions of the three inner secondary flow channels as well as the starting regions of the three outer secondary flow channels in the first embodiment according to the invention of a bipolar plate of an electrochemical unit made of Fig. 4; Fig. 6 a partial longitudinal section through a bridge bounding a transition channel, along line 6 - 6 in Fig. 5, wherein a maximum longitudinal extent L maxS a local depression, which is aligned parallel to a local longitudinal direction of the web bounding the transition channel and perpendicular to the stacking direction, at least 2.5 times a maximum height h maxAb the local subsidence of the bridge bounding the transition channel, where the maximum height h maxABthe lowering of the bridge bordering the transition channel extends along the stacking direction; Fig. 7 a perspective view of the distribution section, the end region of the primary flow channel and the initial regions of the inner secondary flow channels as well as the initial regions of the outer secondary flow channels in a second embodiment according to the invention of a bipolar plate of an electrochemical unit, wherein the deflection device in this embodiment comprises a local bulge of the web bounding the respective transition channel, which extends perpendicular to the stacking direction into the respective transition channel; Fig. 8 a top view along the stacking direction of the distribution section, the end region of the primary flow channel and the starting regions of the inner secondary flow channels as well as the starting regions of the outer secondary flow channels of a bipolar plate of an electrochemical unit made of Fig. 7; Fig. 9 an enlarged representation of the area marked I from Fig. 8, where the maximum width B maxW of a bridge bounding the transition channel in the area of ​​local bulging at least 1.2 times the maximum width b maxS of the bridge bounding the transition channel outside the area of ​​the local bulge, wherein the maximum width B maxW and the maximum width b maxS each extend perpendicular to the stacking direction and perpendicular to the local longitudinal direction of the web bounding the transition channel; Fig. 10 a perspective view of the distribution section, the end region of the primary flow channel and the initial regions of the inner secondary flow channels as well as the initial regions of the outer secondary flow channels in a third embodiment according to the invention of a bipolar plate of an electrochemical unit, wherein the deflection device of a transition channel comprises a local elevation of a channel base of the transition channel along the stacking direction; Fig. 11 a top view along the stacking direction of the distribution section, the end region of the primary flow channel and the beginning regions of the inner secondary flow channels as well as the beginning regions of the outer secondary flow channels of a bipolar plate of an electrochemical unit made of Fig. 10; Fig. 12 a partial cross-section through two transition channels and their limiting webs made of Fig. 11, along line 12 - 12 in Fig. 11, where each local elevation has a maximum height h maxA exhibits a length extending along the stacking direction and which is at least 10% of the maximum height H maxU of the transition channel, which extends along the stacking direction; and Fig. 13 an enlarged representation of the area marked II from Fig. 11, wherein a section of a contour line of the local uplift of the transition channel leads away from a bridge bounding the transition channel and towards a bridge bounding the secondary flow channel of the first type.

[0046] Identical or functionally equivalent elements are designated with the same reference symbols in all figures.

[0047] One in the Fig. The bipolar plate shown in 100, as a whole designated as 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 (not shown), which may include a support frame and gas diffusion layers, and a sealing arrangement.

[0048] Several such electrochemical units 102 follow one another along a stacking direction 108 to form a stack of electrochemical units 102, which is a component of an electrochemical device 110, for example a fuel cell device, an electrolyzer or an electrochemical compressor.

[0049] The bipolar plate 100 comprises an anode-side bipolar plate layer 104 and a cathode-side bipolar plate layer, wherein the two bipolar plate layers are joined together, preferably by material bonding, in particular by welding, for example by laser welding.

[0050] The features of the embodiments described below can be implemented in both the anode-side and cathode-side bipolar plate arrangements of the bipolar plate. For the sake of simplicity, only the anode-side bipolar plate arrangement 104 is described below and illustrated in the figures.

[0051] The bipolar plate 100 also comprises at least one reactant gas passage opening 112, which forms a component of a reactant gas channel 114 extending along the stacking direction 108 through the electrochemical device 110, an electrochemically active area 116, which comprises at least one reactant gas flow field 118 through which a reactant gas can flow transversely to the stacking direction 108, and at least one reactant gas distribution area 120, above which the at least one reactant gas passage opening 112 is in fluid communication with the at least one reactant gas flow field 118.

[0052] The bipolar plate 100 further preferably comprises at least one coolant passage opening 122, which forms part of a coolant channel 124.

[0053] The reactant gas distribution area 120 comprises at least one primary flow channel 126 through which the reactant gas flows, which is in fluid communication with at least one secondary flow channel 132 of a first type and with at least one secondary flow channel 134 of a second type via a distribution section 128, which comprises one or more transition channels 130.

[0054] Here, each transition channel 130 comprises an end region 136 of the primary flow channel 126 and an initial region 138 of the at least one secondary flow channel 132 of the first type and an initial region 140 of the at least one secondary flow channel 134 of the second type.

[0055] How best to derive from the perspective representation of a distribution section 128 of a bipolar plate 100 for an electrochemical unit 102 according to the prior art Fig. As can be seen in Figure 2, the curvature of the transition channels 130 in conjunction with the inertia of the flowing reactant gas results in a different distribution of the reactant gas flow 145 of the primary flow channel 126 onto the secondary flow channels 132, 134.

[0056] In the secondary flow channels 134 of the second type, a reactant gas flow 145a flows with high flow rate (shown as thick arrows in Fig. 2) and in the secondary flow channels 132 of the first type flows a reactant gas flow 145b (shown as thin arrows in Fig. 2) with a correspondingly lower flow rate.

[0057] If at least one transition channel 130 has a curvature, as is evident from Fig. As can be seen from Figure 2, it follows that the at least one secondary flow channel 134 of the second type is designed as an outer secondary flow channel 144 into which a radially outer region of the transition channel 130 opens, and that the secondary flow channel 132 of the first type is designed as an inner secondary flow channel 142 into which a radially inner region of the transition channel 130 opens.

[0058] However, in order to create the most homogeneous supply possible to the electrochemically active area 116 with reactant gas, it is advantageous if the mass flow of the reactant gas is distributed as evenly as possible onto the secondary flow channels 132, 134.

[0059] During a session in the Fig. 4, Fig. 5 to Fig. In the first embodiment of a bipolar plate 100 according to the invention, shown in partial detail in Figure 6, for an electrochemical unit 102, the at least one transition channel 130 comprises a deflection device 146 for deflecting a flow component of the reactant gas towards a secondary flow channel 132 of the first type assigned to another transition channel 130.

[0060] The deflection device 146 preferably comprises at least one local lowering 148 of a web 150 bounding the transition channel 130.

[0061] This local lowering 148 causes compensating flows 153 between the transition channels 130 in the area of ​​the local lowering 148 during the operation of the electrochemical device 110. These compensating flows 153 flow transversely to the local longitudinal directions 152a of the transition channels 130 which are in fluid communication with each other by means of the local lowering 148.

[0062] How best to Fig. As can be seen in section 6, the maximum longitudinal extent L is maxS the local depression 148, which is aligned parallel to the local longitudinal direction 152b of the web 150 bounding the transition channel 130 and perpendicular to the stacking direction 108, preferably at least 2.5 times, in particular at least 5.0 times, most preferably at least 10 times, a maximum height h maxAb the local subsidence 148 of the bridge 150 bounding the transition channel 130, wherein the maximum height h maxAb the local depression 148 of the bridge 150 bounding the transition channel 130 extends along the stacking direction 108.

[0063] In a particular embodiment of the invention, the minimum height h is minS of the bridge 150 bounding the transition channel 130 in the area of ​​the local depression 148 at most 98%, in particular at most 95%, particularly preferably at most 92% of the maximum height h maxSof the bridge 150 bounding the transition channel 130 outside the area of ​​the local subsidence 148, wherein the minimum height h minS , and the maximum height h maxS extend along the stacking direction 108.

[0064] The minimum height h minS The thickness of the web 150 bounding the transition channel 130 is preferably at least 30%, in particular at least 60%, and especially preferably at least 90% of the maximum height h in the area of ​​the local depression 148. maxS of the bridge 150 bounding the transition channel 130 outside the area of ​​the local subsidence 148.

[0065] In the electrochemically active area 116, a different lowering of the webs 143 delimiting the secondary flow channels 142, 144 is provided (compare, for example, the perspective view in the Fig. 2 and Fig. 4), which compensates for a height difference of the (not shown) membrane electrode arrangement, which is located at the electrochemically active area 116, in the stacking direction 108.

[0066] This lowering of the secondary flow channels 132, 134 therefore does not have the function of a deflection device 146, since adjacent secondary flow channels 132, 134 are not locally in fluid contact with each other due to this lowering and the compensating flows 153 described above cannot occur in this area.

[0067] Preferably, the angle α between a local longitudinal direction 152c of a secondary flow channel 132, 134 and a local longitudinal direction 152d of a primary flow channel is greater than 40°, in particular greater than 50°, and especially preferably greater than 60°.

[0068] One in the Fig. 7, Fig. 8 to Fig. Figure 9 shows a second embodiment of a bipolar plate 100 of an electrochemical unit 102, which differs from the one shown in the Fig. 4, Fig. 5 to Fig. 6 first embodiment according to the invention in that the deflection device 146 does not comprise a local depression 148, but a local bulge 154 of the web 150 bounding the transition channel 130, wherein the local bulge 154 extends perpendicular to the stacking direction 108 into the transition channel 130 in question.

[0069] The transition channels 130 of this second embodiment according to the invention thus comprise a deflection device 146 for deflecting a flow component of the reactant gas towards a secondary flow channel 132 of the first type assigned to the same transition channel 130.

[0070] How best to view the enlarged representation of the local bulge 154 of the web 150 bounding the transition channel 130 in Fig. As can be seen in Figure 9, the maximum width B is maxW of the web 150 bounding the transition channel 130 in the area of ​​the local bulge 154 preferably at least 1.2 times, in particular at least 1.4 times, most preferably at least 1.6 times, the maximum width b maxS of the bridge 150 bounding the transition channel 130 outside the area of ​​the local bulge 154, wherein the maximum width B maxW and the maximum width b maxS each extend perpendicular to the stacking direction 108 and perpendicular to the local longitudinal direction 152b of the bridge 150 bounding the transition channel 130.

[0071] Moreover, the one in the Fig. 7, Fig. 8 to Fig. 9 shown second embodiment of a bipolar plate 100 according to the invention with regard to structure, function and method of manufacture with the one shown in the Fig. 4, Fig. 5 to Fig. 6 shown in the first embodiment according to the invention, to the preceding description of which reference is made in this respect.

[0072] One in the Fig. 10, Fig. 11, Fig. 12 to Fig. 13. The third embodiment of a bipolar plate 100 of an electrochemical unit 102, shown in partial detail, differs from the one shown in the Fig. 4, Fig. 5 to Fig. 6 shown first embodiment according to the invention in that the deflection device 146 does not comprise a local lowering 148, but a local raising 156 of a channel bottom 158 of the at least one transition channel 130 along the stacking direction 108.

[0073] How best to Fig. As can be seen in section 12, the local elevation 156 has a maximum height h maxA on, which extends along the stacking direction 108 and which preferably comprises at least 10%, in particular at least 20%, and especially preferably at least 30% of the maximum height H maxU of the transition channel 130, which extends along the stacking direction 108.

[0074] How best to Fig. 13 to be obtained, the local elevation 156 of the channel bottom 158 is designed such that at least one section 160 of a contour line 162 perpendicular to the stacking direction 108 of the local elevation 156 of the channel bottom 158 of the transition channel 130 leads away from a web 150 bounding the transition channel 130 and to a web 164 bounding an inner secondary flow channel 142.

[0075] Moreover, the one in the Fig. 10, Fig. 11, Fig. 12 to Fig. 13 third embodiment of a bipolar plate 100 according to the invention with regard to structure, function and method of manufacture with the one shown in the Fig. 4, Fig. 5 to Fig. 6 shown in the first embodiment according to the invention, to the preceding description of which reference is made in this respect.

[0076] For the sake of completeness, it should be mentioned that a local bulging 154 of a rib 150 bounding the transition channel 130, a local lowering 148 of a rib 150 bounding the same transition channel 130 and / or a local raising 156 of the channel floor 158 of the same transition channel 130 can be combined with each other.

[0077] For example, it may be provided that a transition channel 130 includes all three of the features of a deflection device 146 described above.

[0078] Alternatively or additionally, it may also be provided that the features of the embodiments of the invention described above are combined within a distribution section 128.

[0079] For example, a transition channel 130 of the distribution section 128 may include a local bulge 154 of the web 150 bounding the transition channel 130, wherein another transition channel 130 of the same distribution section 128 may include a local raising 156 of the channel floor 158 of this other transition channel 130.

Claims

[1] Bipolar plate for an electrochemical unit (102) of an electrochemical device (110) comprising several electrochemical units (102) which follow one another along a stacking direction (108), wherein the bipolar plate (100) comprises: - at least one reactant gas passage opening (112) which forms part of a reactant gas channel (114) which extends along the stacking direction (108) through the electrochemical device (110); - an electrochemically active area (116) comprising at least one reactant gas flow field (118) through which a reactant gas can flow transversely to the stacking direction (108); and - at least one reactant gas distribution area (120) above which the at least one reactant gas passage opening (112) is in fluid communication with the at least one reactant gas flow field (118); wherein the electrochemically active region (116) and / or the reactant gas distribution region (120) comprises at least one primary flow channel (126) through which the reactant gas flows, which is in fluid communication via a distribution section (128) comprising one or more transition channels (130) with at least one secondary flow channel (132) of a first type and at least one secondary flow channel (134) of a second type, wherein each transition channel (130) comprises an end region (136) of the primary flow channel (126) and an initial region (138) of the at least one secondary flow channel (132) of the first type and an initial region (140) of the at least one secondary flow channel (134) of the second type, characterized by , that the at least one transition channel (130) comprises at least one deflection device (146) for deflecting a flow component of the reactant gas towards a secondary flow channel (132) of the first type associated with the same transition channel (130) and / or that the at least one transition channel (130) comprises at least one deflection device (146) for deflecting a flow component of the reactant gas towards a secondary flow channel (132) of the first type assigned to another transition channel (130). [2] Bipolar plate according to claim 1, characterized by, that the at least one transition channel (130) has a curvature, wherein the at least one secondary flow channel (132) of the first type is designed as an inner secondary flow channel (142) into which a radially inner region of the transition channel (130) opens, and wherein the at least one secondary flow channel (134) of the second type is designed as an outer secondary flow channel (144) into which a radially outer region of the transition channel (130) opens. [3] Bipolar plate according to one of claims 1 or 2, characterized by , that the deflection device (146) comprises at least a local elevation (156) of a channel bottom (158) of the at least one transition channel (130) along the stacking direction (108). [4] Bipolar plate according to claim 3, characterized by, that at least one section (160) of a contour line perpendicular to the stacking direction (108) of the local elevation (156) of a channel bottom (158) of the at least one transition channel (130) leads away from a bridge (150) bounding the transition channel (130) and towards a bridge (164) bounding the secondary flow channel (132) of the first type. [5] Bipolar plate according to one of claims 3 or 4, characterized by , that the local elevation (156) has a maximum height (h maxA ), which extends along the stacking direction (108), which has at least 10% of the maximum height (H maxU ) of the transition channel (130), which extends along the stacking direction (108). [6] Bipolar plate according to any one of claims 1 to 5, characterized by that the deflection device (146) includes at least a local lowering (148) of a bridge (150) bounding the transition channel (130). [7] Bipolar plate according to claim 6, characterized by, that a maximum longitudinal extent (L maxS ) the local depression (148), which is aligned parallel to a local longitudinal direction (152b) of the web (150) bounding the transition channel (130) and perpendicular to the stacking direction (108), at least 2.5 times a maximum height (h maxAB ) the local subsidence (148) of the bridge (150) bounding the transition channel (130), wherein the maximum height (h maxAB ) the local depression (148) of the bridge (150) limiting the transition channel (130) extends along the stacking direction (108). [8] Bipolar plate according to one of claims 6 or 7, characterized by , that the local lowering (148) is arranged such that by means of it the at least one transition channel (130) associated with the primary flow channel (126) and a transition channel (130) associated with another primary flow channel (126) are in fluid communication with each other. [9] Bipolar plate according to any one of claims 1 to 8, characterized by , that the deflection device (146) comprises at least one local bulge (154) of a web (150) bounding the transition channel (130), which extends perpendicularly to the stacking direction (108) into the transition channel (130). [10] Bipolar plate according to claim 9, characterized by that a maximum width (B maxW ) of the web (150) bounding the transition channel (130) in the area of ​​the local bulge (154) at least 1.2 times the maximum width (b maxS ) of the web (150) bounding the transition channel (130) outside the area of ​​the local bulge (154), wherein the maximum width (B maxW ) and the maximum width (b maxS ) extend perpendicular to the stacking direction (108) and perpendicular to the local longitudinal direction (152b) of the bridge (150) bounding the transition channel (130). [11] Bipolar plate according to any one of claims 1 to 10, characterized by , that the deflection device (146) is formed in one piece with the bipolar plate (100). [12] Bipolar plate according to any one of claims 1 to 11, characterized by , that at least one primary flow channel (126) is assigned at least two transition channels (130). [13] Bipolar plate according to any one of claims 1 to 11, characterized by , that at least one transition channel (130) is assigned exactly one secondary flow channel (132) of the first type and / or exactly one secondary flow channel (134) of the second type. [14] Bipolar plate according to any one of claims 1 to 13, characterized by , that at least one secondary flow channel (132, 134) forms a component of the electrochemically active area (116) of the bipolar plate (100). [15] Bipolar plate according to any one of claims 1 to 14, characterized by , that the at least one primary flow channel (126) forms a component of the reactant gas distribution area (120). [16] Bipolar plate according to any one of claims 1 to 15, characterized by , that an angle (α) between a local longitudinal direction (152c) of a secondary flow channel (132, 134) and a local longitudinal direction (152d) of a primary flow channel (126) is greater than 40°.

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