Bipolar Plates and Electrochemical Cells

Abstract

The present invention relates to a bipolar plate (1) and an electrochemical cell (12) comprising a plurality of such bipolar plates (1, 1'). The bipolar plate (1) comprises a first half-plate (1a) and a second half-plate (1b) fixedly connected to each other, the bipolar plate (1) having a plurality of fluid passage openings (2) including fluid inlet openings (2a, 2c, 2e) and fluid outlet openings (2b, 2d, 2f), a first distributor field (3) for distributing fluid, an active field (4), and a second distributor field (5) for distributing fluid, arranged on both sides of the bipolar plate (1). Also, at least one sealing portion (6, 6') is present on each side of the bipolar plate (1), and in at least one transition region (7) between a fluid passage opening (2) and an adjacent distributor field (3, 5), the sealing portions (6, 6') are positioned so that they coincide one above the other when viewed perpendicular to a plane spanning the bipolar plate (1) and are reinforced by embossed structures (9a, 9b).

Description

[Technical Field]

[0001] The present invention relates to a bipolar plate comprising a first half-sheet and a second half-sheet fixedly connected to each other, the bipolar plate having a plurality of fluid passage openings including fluid inlet openings and fluid outlet openings, a first distributor field for distributing fluid, an active field, and a second distributor field for distributing fluid arranged on both sides of the bipolar plate, each side of the bipolar plate having at least one seal, and a transition region formed between the fluid passage openings and adjacent distributor fields. [Background technology]

[0002] German Patent Application Publication No. 102014225160 describes a metal separator, i.e., a bipolar plate, for a fuel cell stack having an anode separator and a cathode separator. In particular, German Patent Application Publication No. 102014225160 describes an embodiment in which a transition region is formed in the metal separator between the fluid passage openings and the active area (not shown in detail) where the electrochemical reaction takes place. The metal separator has seals on both sides, which are arranged offset from each other. Support elements embossed into the separator are also located at the inlet and outlet of the metal separator, forming channels for the fluids that drive the fuel cell stack.

[0003] Chinese Utility Model No. 208722997 discloses a bipolar plate for a fuel cell having an anode plate and a cathode plate, and a configuration of the bipolar plate in the transition region between the fluid passage opening and the reaction region where the electrochemical reaction occurs. The sealing portions arranged on both sides of the bipolar plate are offset from each other and are respectively arranged in elongated recesses or bead portions.

[0004] DE 10 2020 202 075 A1 describes an electrochemical cell with a supply device or bipolar plate including a first circuit board and a second circuit board for supplying a working medium to a supply region through fluid passage openings, referred to in the document as port connections. The circuit boards are configured with bead sections that accommodate seals that are arranged offset from one another. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to optimize a bipolar plate of the above-mentioned type with respect to the pressure losses occurring in the transition region and the sealing effect of the seals. Another object of the present invention is to provide an electrochemical cell comprising a bipolar plate improved in this way. [Means for solving the problem]

[0006] The object is achieved with respect to a bipolar plate comprising a first half-sheet and a second half-sheet fixedly connected to each other, the bipolar plate having a plurality of fluid passage openings including a fluid inlet opening and a fluid outlet opening, a first distributor field for distributing a fluid, an active field, and a second distributor field for distributing a fluid, arranged on both sides of the bipolar plate, with at least one seal on both sides of the bipolar plate, and in at least one transition area between a fluid passage opening and an adjacent distributor field: the first half-sheet has a first step and a second step, starting from the fluid inlet opening towards the second half-sheet; the second half-sheet is provided with a third step in the region of the first step, starting from the fluid inlet opening towards the first half-sheet, and a fourth step in the region of the second step, directed away from the first half-sheet; the first half-sheet has, in the region between the first and second steps, elongated three-dimensional first embossed structures oriented parallel to one another and curved in the direction of the second half-sheet; the second half-sheet has, in the region between the third and fourth steps, elongated three-dimensional second embossed structures oriented parallel to each other, curved towards the first half-sheet, and aligned with and supported against the first embossed structures; the first half-sheet has a first sealing area formed in the area of ​​the first embossed structure on a side of the first half-sheet facing away from the second half-sheet and positioned to extend across and close the first embossed structure; the second half-sheet has a second sealing region that extends across and closes the second embossed structure on a side of the second half-sheet facing away from the first half-sheet, the first sealing region and the second sealing region being aligned one above the other when viewed perpendicular to a plane spanning the bipolar plate; the second half-sheet has an opening slot, the opening slot being positioned between the fourth step and the adjacent distributor field, and there is a three-dimensional third embossed structure curved toward the first half-sheet and aligned with the second embossed structure in the fluid flow direction and supported relative to the first half-sheet, the opening slot being positioned such that the third embossed structure positioned on the second half-sheet intersects with the second half-sheet;

[0007] Because the sealing portions on the two half sheets extend congruently above one another in the transition region between the distributor field and the fluid passage opening, the first and second embossed structures are filled with sealing material and hardened, significantly increasing the sealing effect on the components adjacent to the bipolar plate in the region of the fluid passage opening. The term "congruent" means that the centerlines of the first and second sealing regions are above one another when viewed perpendicular to the plane spanning the bipolar plate. However, the widths of the first and second sealing regions may be slightly different. Thus, a cell stack of an electrochemical cell can be constructed with defined compression of the sealing portions. The sealing material can also be applied more precisely to the half sheets in the transition region due to the introduced first and second embossed structures and improved support of the half sheets. The first embossed structure and the second embossed structure provide a distance between the first half-sheet and the second half-sheet that is large enough to guide the flow with little pressure loss.

[0008] In at least one transition region between the fluid passage opening and an adjacent distributor field, the first half-sheet has a third step and a fourth step, starting from the fluid outlet opening towards the second half-sheet; the second half-sheet is provided with a first step in the region of the third step of the first half-sheet, starting from the fluid outlet opening and directed towards the first half-sheet, and a second step in the region of the fourth step of the first half-sheet, directed away from the first half-sheet; the first half-sheet has, in the region between its third step and its fourth step, further first embossed structures of elongated three-dimensional shape which are oriented parallel to one another and curved in the direction of the second half-sheet, the second half-sheet has, in the region between its first step and its second step, elongated three-dimensional further second embossed structures which are oriented parallel to one another, curved in the direction of the first half-sheet, and arranged in alignment with and supported against the further first embossed structures; the first half-sheet has a third sealing area formed in the area of ​​the further first embossed structure on the side of the first half-sheet facing away from the second half-sheet and arranged to extend across and close the further first embossed structure; the second half-sheet has a fourth sealing region that is arranged to extend across and close the second embossed structure to an area of ​​the second embossed structure on a side of the second half-sheet facing away from the first half-sheet, and the third sealing region and the fourth sealing region are arranged one above the other when viewed perpendicular to a plane spanning the bipolar plate; - The second half-sheet has a further opening slot, which is arranged between the second step of the second half-sheet and the adjacent distributor field, and there is a three-dimensional further third embossed structure curved towards the first half-sheet and aligned with the further second embossed structure in the fluid flow direction and supported against the first half-sheet, and the further opening slot has proven useful when the further third embossed structure arranged on the second half-sheet is arranged so as to intersect with the second half-sheet.

[0009] The advantages of this arrangement in the region of the fluid outlet openings are similar to those described above for the fluid inlet openings. In this case, the term "coincident" also means that the centerlines of the third and fourth sealing regions are one above the other when viewed perpendicular to the plane spanning the bipolar plate. However, the widths of the third and fourth sealing regions may be slightly different.

[0010] The transition region between the distributor field and the fluid passage openings has an opening slot on each side of the bipolar plate, through which fluid is guided from the fluid inlet openings through the opening slot toward the distributor field and the active field. Furthermore, the transition region between the distributor field and the fluid passage openings on the same side of the bipolar plate has another opening slot, through which fluid coming from the active field is guided through another distributor field toward the fluid outlet opening. Oxidant is supplied to the active field on a first side of the bipolar plate, and fuel is supplied to a further active field on the opposite second side of the bipolar plate.

[0011] It has proven particularly effective if the first and third sealing regions are each configured as flat sealing sections, while the second and fourth sealing regions preferably each have two parallel sealing ridges. This improves the sealing seal and optimizes the compression of the sealing sections of the stacked bipolar plates when assembling the cell stack.

[0012] The first and second embossed structures are preferably aligned with their longitudinal axes in the fluid flow direction between the fluid passage opening and the adjacent distributor field, and are preferably linearly elongated and have a constant width and length to optimally support each other.

[0013] A first fluid inlet opening for supplying an oxidizing gas and a first fluid outlet opening for discharging the oxidizing gas are preferably configured on a first side of the bipolar plate, and a second fluid inlet opening for supplying a fuel gas and a second fluid outlet opening for discharging the fuel gas are preferably configured on a second side of the bipolar plate.

[0014] In particular, each half sheet of the bipolar plate is three-dimensionally structured in the regions of the first distributor field, the active field, and the second distributor field to form fluid-guiding paths. Such structuring is achieved, in particular, by embossing the half sheets. The structuring can be achieved by forming channels, locally separated ridges or recesses, etc.

[0015] A fluid guide path for the coolant is preferably formed between the first and second half sheets of the bipolar plate, the coolant being supplied through the fluid inlet openings, and the fluid outlet openings being used to discharge the coolant.

[0016] The object is further achieved with respect to an electrochemical cell comprising a plurality of bipolar plates according to the invention and in each case a membrane electrode unit arranged between two bipolar plates, the membrane electrode unit being covered on both sides by a fluid transport layer in each case.

[0017] The electrochemical cell is preferably an electrolysis cell for the electrolysis of water or a polymer electrolyte fuel cell for the decomposition of water into hydrogen as fuel and oxygen as oxidizing gas.

[0018] In electrolysis cells, the fluid transport layer is also called a porous transport layer, or PTL for short. In fuel cells, the fluid transport layer is also called a gas diffusion layer, or GDL for short.

[0019] Stacked devices containing multiple fuel cells or electrolysis cells can also be formed.

[0020] 1-9 are intended to illustrate the invention by way of example. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a plan view of a bipolar plate viewed from one side. [Figure 2]2 is a view of a cross section II-II' through the bipolar plate according to FIG. 1 in the region of the fluid inlet opening. [Figure 3] FIG. 3 is a plan view of a section of the bipolar plate according to FIG. 2; [Figure 4] 3 shows a side view of a section of the bipolar plate according to FIG. 2 when viewed from the fluid inlet opening side. [Figure 5] 3 is a side view of a section of the bipolar plate according to FIG. 2 when viewed from the distributor field side. [Figure 6] 3 is a three-dimensional view of a section of the bipolar plate according to FIG. 2 without showing the seal 6'. [Figure 7] 3 shows a three-dimensional view of a section of the bipolar plate according to FIG. 2 showing the seal 6'. [Figure 8] 3 is a view of a cross section III-III' through the bipolar plate according to FIG. 1 in the region of the fluid outlet opening. [Figure 9] FIG. 1 is a three-dimensional schematic diagram of a stacked arrangement of electrochemical cells. DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 shows a rectangular bipolar plate 1 in a plan view from one side B. The bipolar plate 1 comprises a first half sheet 1a and a second half sheet 1b (see FIG. 2) fixedly connected to each other, for example, by welding, adhesive bonding, or the like. The bipolar plate 1 further comprises a plurality of fluid passage openings 2 arranged at both ends of the rectangular bipolar plate 1. The fluid passage openings 2 include fluid inlet openings 2a, 2c, and 2e and fluid outlet openings 2b, 2d, and 2f. Between the fluid passage openings 2 are a first distributor field 3 for distributing fluid, an active field 4, and a second distributor field 5 for distributing fluid. This arrangement of the fluid passage openings 2, distributor fields 3, 5, and active field 4 is also aligned on the second side A of the bipolar plate 1. The bipolar plate 1 has at least one seal 6, 6' on each side A, B (see FIG. 2), the outline of which is shown here with a dotted line for clarity. The seals 6, 6' extend around the periphery of each half-plate 1a, 1b and also around each of the fluid passage openings 2.

[0023] Cross section II-II' is located in the transition area 7 between the fluid inlet opening 2c for the fuel and the adjacent distributor field 5 and is shown in FIG.

[0024] 2, it can be seen that the first half-sheet 1a has a first step 8a and a second step 8b, starting from the fluid inlet opening 2c and extending towards the second half-sheet 1b. The second half-sheet 1b has a third step 8c in the region of the first step 8a, starting from the fluid inlet opening 2c and extending towards the first half-sheet 1a, and a fourth step 8c in the region of the second step 8b, directed away from the first half-sheet 1a. In the region between the first step 8a and the second step 8b, the first half-sheet 1a has an elongated three-dimensional first embossed structure 9a oriented parallel to one another and curved towards the second half-sheet 1b. In the region between the third and fourth steps 8c and 8d, the second half-sheet 1b has an elongated, three-dimensional second embossing structure 9b oriented parallel to each other, curved toward the first half-sheet 1a, and aligned with and supported against the first embossing structure 9a. The first half-sheet 1a has a first sealing area 6a in the form of a planar seal formed in the region of the first embossing structure 9a on the side of the first half-sheet 1a facing away from the second half-sheet 1b, extending across and sealing the first embossing structure 9a. The first embossing structure 9a is suitably sealed and rigidified with a sealing compound.

[0025] The second half-sheet 1b has a second sealing region 6b with two parallel sealing ridges 10a, 10b extending across and sealing the second embossed structure 9b in the region of the second embossed structure 9b on the side of the second half-sheet 1b facing away from the first half-sheet 1a, which is also suitably sealed and stiffened with a sealing compound.

[0026] The first sealing area 6a and the second sealing area 6b are arranged so that one is coincident above the other when viewed perpendicular to a plane spanning the bipolar plate 1, and therefore extend parallel over side A and side B of the bipolar plate 1.

[0027] The second half-sheet 1b has an opening slot 11, which is positioned between the fourth step 8d and the adjacent distributor field 5, and a three-dimensional third embossed structure 9c that curves toward the first half-sheet 1a. The third embossed structure 9c is aligned with the second embossed structure 9b in the fluid flow direction S and is supported against the first half-sheet 1a. The opening slot 11 is positioned so that the third embossed structure 9c positioned on the second half-sheet 1b intersects with the second half-sheet 1b. Thus, during the formation of the opening slot 11, a portion of the second half-sheet 1b is separated from a previously formed portion including a portion of the third embossed structure 9c.

[0028] Figure 3 shows a plan view of a section of the bipolar plate 1 according to figure 2. The same reference symbols in figure 2 denote identical elements.

[0029] Figure 4 shows a side view of the section of the bipolar plate 1 according to Figure 2 when viewed from the side of the fluid inlet opening 2c. The same reference numerals as in Figure 2 indicate identical elements. It can be clearly seen in this view that the first embossed structure 9a and the second embossed structure 9b support each other and form a flow channel for the fluid between the two half-sheets 1a and 1b. The flow channel extends towards the opening slot 11.

[0030] Figure 5 shows a side view of a section of the bipolar plate 1 according to Figure 2 when viewed from the side of the distributor field 5. The same reference symbols as in Figure 2 indicate identical elements. The third embossed structure 9c and the opening slot 11, which allow fluid flow between the two half-sheets 1a and 1b, are clearly visible in this view.

[0031] Figure 6 shows a three-dimensional view of a section of the bipolar plate 1 according to Figure 2, without showing the sealing portion 6' or the second sealing area 6b. In the second half-sheet 1b, the elongated second embossed structure 9b and the third embossed structure 9c can be seen to be arranged longitudinally aligned with each other in the fluid flow direction S. The first embossed structure 9a of the first half-sheet 1a is not visible in this view. The same reference symbols as in Figure 2 indicate identical elements.

[0032] Figure 7 shows a three-dimensional view of a section of the bipolar plate 1 according to Figure 2, showing the sealing portion 6' or the second sealing portion 6b. The first embossed structure 9a of the first half-sheet 1a and the third embossed structure 9c of the second half-sheet 1b are visible in this view. The second embossed structure 9b of the second half-sheet 1b is not visible in this view and is covered by the sealing portion 6'. The same reference symbols as in Figure 2 indicate identical elements.

[0033] 8 shows a cross section III-III' through the bipolar plate 1 according to FIG. 1 in the region of the fluid outlet opening 2d for unused fuel. In the transition region 7 between the fluid outlet opening 2d and the adjacent distributor field 3, the first half-sheet 1a has a third step 8c' and a fourth step 8d', starting from the fluid outlet opening 2d towards the second half-sheet 1b. The second half-sheet 1b has a first step 8a' in the region of the third step 8c' of the first half-sheet 1a, starting from the fluid outlet opening 2d towards the first half-sheet 1a, and a second step 8b', directed away from the first half-sheet 1a, in the region of the fourth step 8d' of the first half-sheet 1a. The first half-sheet 1a has, in the region between its third step 8c' and its fourth step 8d', elongated three-dimensional further first embossed structures 9a' that are oriented parallel to one another and curved towards the second half-sheet 1b. The second half-sheet 1b has, in the region between its first step 8a' and its second step 8b', elongated three-dimensional further second embossed structures 9b' that are oriented parallel to one another and curved towards the first half-sheet 1a and are arranged in alignment with and supported against the further first embossed structures 9a'. The first half-sheet 1a has a third sealing area 6c formed in the area of ​​the further first embossed structure 9a' on the side of the first half-sheet 1a facing away from the second half-sheet 1b and arranged to extend across and seal the further first embossed structure 9a', which is suitably sealed and stiffened with a sealing compound.

[0034] The second half-sheet 1b has a fourth sealing area 6d arranged to extend across and seal the further second embossed structure 9b' in the area of ​​the further second embossed structure 9b' on the side of the second half-sheet 1b facing away from the first half-sheet 1a, which further second embossed structure 9b' is also suitably sealed and stiffened with a sealing compound.

[0035] The third sealing area 6c in the form of a planar seal and the fourth sealing area 6d comprising two sealing ridges 10a, 10b extending parallel to each other extend one above the other when viewed perpendicular to the plane spanning the bipolar plate 1, and therefore extend parallel over side A and side B of the bipolar plate 1.

[0036] The second half-sheet 1b has a further opening slot 11', which is disposed between the second step 8b' of the second half-sheet 1b and the adjacent distributor field 3, and a three-dimensional further third embossed structure 9c' that curves toward the first half-sheet 1a. The further second embossed structure 9b' and the further third embossed structure 9c' are disposed aligned with the fluid flow direction S and supported relative to the first half-sheet 1a. The further opening slot 11' is disposed so that the further third embossed structure 9c' disposed on the second half-sheet 1b intersects with the second half-sheet 1b.

[0037] Thus, during the formation of the further opening slot 11', a portion of the second half-sheet 1b was separated from the previously formed portion including part of the further third embossed structure 9c'.

[0038] Thus, on side B of the bipolar plate 1 there are inlets and outlets for fuel gas, in particular in the form of hydrogen, as described above and shown in FIGS.

[0039] Also on side A of the bipolar plate 1 according to FIG. 1 there is an arrangement for the inlet and outlet of a fluid, in particular in the form of an oxidizer, such as air or oxygen. The oxidizer flows into side A of the bipolar plate 1 through the fluid inlet opening 2a, and thus through an arrangement similar to that in the transition region 7, to side B of the bipolar plate 1, and then through the opening slots in the first half-plate 1a in the direction of the fluid outlet openings 2b to the distributor field, the active field, the further distributor field, and the further opening slots in the first half-plate 1a. For the arrangement of the transition region on side A of the bipolar plate 1, only the indications of the half-plates are used in reverse. The basic design for the oxidizer inlet and outlet corresponds to the basic design for the fuel inlet and outlet on side B of the bipolar plate 1.

[0040] The fluid inlet openings 2e (see FIG. 1) are configured to feed the coolant into a fluid guiding channel or flow space (not shown in detail) between the two half plates 1a and 1b of the bipolar plate 1. The coolant flows along the rectangular bipolar plate 1 to the fluid outlet openings 2f, the geometry of which is predetermined by the two structured half sheets 1a, 1b. The area between the fluid outlet openings 2f at the transition to the fluid guiding channel between the half plates 1a and 1b is not subject to any design specifications and can be configured as desired.

[0041] The geometric configuration of the fluid passage openings 2, distributor fields 3, 5 and active fields 4 may vary within the limits of breadth and need not be configured as shown in Figures 1-8.

[0042] 9 shows a three-dimensional schematic diagram of a stacking arrangement 20 of several electrochemical cells 12. The electrochemical cells 12 comprise several bipolar plates 1, 1' and membrane electrode units 13, which are in each case arranged between two bipolar plates 1 and 1' and are covered on both sides by fluid transport layers (not shown separately here). For ease of overview, the distributor fields between the fluid passage openings 2 and the active fields 4 have also been omitted. In contrast to FIG. 1, the cross section of the fluid passage openings 2 is configured circular. [Explanation of symbols]

[0043] 1, 1' Bipolar Plate 1a, 1b half seat 2 Fluid passage opening 2a, 2c, 2e fluid inlet openings 2b, 2d, 2f fluid outlet openings 3. First distributor station 4 Active field 5 Second distributor station 6, 6' sealing part 6a First sealing region 6b Second sealing region 6c Third sealing area 6d Fourth sealing area 7. Transition Zone 8a, 8a' First step 8b, 8b' Second step 8c, 8c' Third step 8d, 8d' Fourth step 9a, 9a' First embossed structure 9b, 9b' Second embossed structure 9c, 9c' Third embossed structure 10a, 10b Sealing ridges 11, 11' Opening Slot 12 Electrochemical Cell 13 Membrane electrode unit 20 Stacking device A First side of the bipolar plate B Second side of the bipolar plate S Fluid flow direction

Claims

1. A bipolar plate (1) comprising a first half-sheet (1a) and a second half-sheet (1b) fixedly connected to each other, the bipolar plate (1) comprising a plurality of fluid passage openings (2) including fluid inlet openings (2a, 2c, 2e) and fluid outlet openings (2b, 2d, 2f), a first distributor field (3) for distributing fluids, an active field (4) and a second distributor field (5) for distributing the fluids are arranged on both sides of the bipolar plate (1), the bipolar plate (1) has at least one sealing portion (6, 6') on both sides, and in at least one transition region (7) between a fluid passage opening (2) and an adjacent distributor field (3, 5), - said first half-sheet (1a) is provided with a first step (8a) and a second step (8b) starting from the fluid inlet openings (2a, 2c, 2e) towards said second half-sheet (1b); - said second half-sheet (1b) is provided with a third step (8c) in the region of said first step (8a), starting from said fluid inlet opening (2a, 2c, 2e) towards said first half-sheet (1a), and with a fourth step (8c) in the region of said second step (8b) directed away from said first half-sheet (1a); - said first half-sheet (1a) has, in the region between said first step (8a) and said second step (8b), elongated three-dimensional first embossed structures (9a) oriented parallel to one another and curved in the direction of said second half-sheet (1b); - said second half-sheet (1b) has, in the region between said third step (8c) and said fourth step (8d), elongated three-dimensional second embossing structures (9b) oriented parallel to one another, curved towards said first half-sheet (1a), arranged in alignment with said first embossing structures (9a) and supported against said first embossing structures (9a); - said first half-sheet (1a) has a first sealing area (6a) formed in the area of ​​said first embossing structure (9a) on the side of said first half-sheet (1a) facing away from said second half-sheet (1b) and arranged so as to extend across said first embossing structure (9a) and to close said first embossing structure (9a); the second half-sheet (1b) has a second sealing area (6b) which is arranged so as to extend across and close the second embossing structure (9b) in the area of ​​the second embossing structure (9b) on the side of the second half-sheet (1b) facing away from the first half-sheet (1a), the first sealing area (6a) and the second sealing area (6b) being arranged so as to coincide one above the other when viewed perpendicularly to a plane spanning the bipolar plate (1); the second half-sheet (1b) has an opening slot (11) arranged between the fourth step (8d) and the adjacent distributor field (5), a three-dimensional third embossed structure (9c) curved towards the first half-sheet (1a) and arranged aligned with the second embossed structure (9b) in the fluid flow direction (S) and supported against the first half-sheet (1a), the opening slot (11) being arranged so that the third embossed structure (9c) arranged in the second half-sheet (1b) intersects with the second half-sheet (1b), Bipolar plate (1).

2. In at least one transition region (7) between the fluid passage opening (2) and an adjacent distributor field (3, 5), - said first half-sheet (1a) is provided with a third step (8c') and a fourth step (8d') starting from the fluid outlet openings (2b, 2d, 2f) towards said second half-sheet (1b); - the second half-sheet (1b) is provided with a first step (8a') in the region of the third step (8c') of the first half-sheet (1a), starting from the fluid outlet opening (2b, 2d, 2f) and directed towards the first half-sheet (1a), and a second step (8b') directed away from the first half-sheet (1a) in the region of the fourth step (8d') of the first half-sheet (1a); - said first half-sheet (1a) has, in the region between its third step (8c') and its fourth step (8d'), further elongated three-dimensional first embossed structures (9a') oriented parallel to one another and curved in the direction of said second half-sheet (1b); - said second half-sheet (1b) has, in the region between its first step (8a') and its second step (8b'), elongated three-dimensional further second embossing structures (9b') oriented parallel to one another, curved in the direction of said first half-sheet (1a), arranged in alignment with said further first embossing structure (9a') and supported against said further first embossing structure (9a'); - said first half-sheet (1a) has a third sealing area (6c) formed in the area of ​​said further first embossed structure (9a') on the side of said first half-sheet (1a) facing away from said second half-sheet (1b) and arranged to extend across said further first embossed structure (9a') and to close said further first embossed structure (9a'); the second half-sheet (1b) has a fourth sealing area (6d) which is arranged to extend across and close the further second embossed structure (9b') in the area of ​​the further second embossed structure (9b') on the side of the second half-sheet (1b) facing away from the first half-sheet (1a), and the third sealing area (6c) and the fourth sealing area (6d) are arranged so as to coincide one above the other when viewed perpendicularly to a plane spanning the bipolar plate (1); the second half-sheet (1b) has a further opening slot (11'), the further opening slot (11') being arranged between the second step (8b') of the second half-sheet (1b) and the adjacent distributor field (3), a three-dimensional further third embossed structure (9c') being curved towards the first half-sheet (1a) and arranged in alignment with the further second embossed structure (9b') in the fluid flow direction (S) and supported against the first half-sheet (1a), the further opening slot (11') being arranged so that the further third embossed structure (9c') arranged in the second half-sheet (1b) intersects with the second half-sheet (1b); A bipolar plate (1) according to claim 1.

3. 3. The bipolar plate (1) according to claim 1 or 2, wherein the first sealing area (6a) and the third sealing area (6c) are each configured as a planar seal.

4. 4. The bipolar plate (1) according to any one of claims 1 to 3, wherein the second sealing area (6b) and the fourth sealing area (6d) each have two parallel sealing ridges (10a, 10b).

5. 5. The bipolar plate (1) according to claim 1, wherein the first embossed structure (9a, 9a') and the second embossed structure (9b, 9b') are oriented in a fluid flow direction (S) between the fluid passage opening (2) and the adjacent distributor field (3, 5) with their longitudinal axes aligned.

6. 6. A bipolar plate (1) according to any one of claims 1 to 5, wherein a first fluid inlet opening (2a) for supplying an oxidizing gas and a first fluid outlet opening (2b) for discharging the oxidizing gas are configured on a first side (A) of the bipolar plate (1).

7. 7. A bipolar plate (1) according to any one of claims 1 to 6, wherein a second fluid inlet opening (2c) for supplying fuel gas and a second fluid outlet opening (2d) for discharging fuel gas are configured on a second side (B) of the bipolar plate (1).

8. 8. A bipolar plate (1) according to any one of claims 1 to 7, wherein each half-sheet (1a, 1b) is three-dimensionally structured in the region of the first distributor field (3), the active field (4) and the second distributor field (5) to form fluid-guiding channels.

9. 9. A bipolar plate (1) according to any one of the preceding claims, wherein fluid conducting channels for a coolant are formed between the first half-sheet (1a) and the second half-sheet (1b).

10. 10. An electrochemical cell (12) comprising a plurality of bipolar plates (1, 1') according to any one of claims 1 to 9 and a membrane electrode unit (13) arranged in each case between two bipolar plates (1, 1') and covered on both sides with a fluid transport layer in each case.

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