Bipolar plate for a fuel cell and fuel cell stack

Abstract

The invention relates to a bipolar plate (10) for a fuel cell, comprising a channel structure (12) formed by recesses (20) extending in a vertical direction (18) for flow with a reaction gas, a sealing area (26) laterally surrounding the channel structure (12) at its edge, which has a sealing surface (28) that can be abutted against a sealing element (66) to seal the channel structure (12) to the outside, a support area (30) with a support surface (32) for laterally supporting a membrane electrode assembly (50) spanning the channel structure (12), and a barrier element (34) having a barrier surface (69) for limiting a bypass flow of the reaction gas laterally outside the channel structure (12), wherein, with respect to the vertical direction (18), a height (72) of the sealing surface (28) is greater than a height (74) of the support surface (32).wherein a height (70) of the barrier surface (69) is equal to or greater than a height (72) of the sealing surface (28). The invention further relates to a fuel cell stack (46) with such a bipolar plate (10).

Description

[0001] The invention relates to a bipolar plate according to the preamble of claim 1. Furthermore, the invention relates to a fuel cell stack with such a bipolar plate. State of the art

[0002] US patent 2019 / 214655 A1 describes a fuel cell with a metal separator that has a circumferential sealing rim and bypass blocking means around a channel structure to reduce bypass of the channel structure between the sealing rim and the contact areas for a membrane electrode assembly. The bypass blocking means are located at a lower height than the sealing rim. Disclosure of the invention

[0003] According to the present invention, a bipolar plate with the features of claim 1 is proposed. This allows for a more efficient and reliable reduction of bypass of reaction gases outside the active field.

[0004] The lateral direction, or the reference given as lateral, refers to a direction perpendicular to the vertical direction. This direction can be a longitudinal or transverse direction. Both the longitudinal and transverse directions are lateral directions. The longitudinal direction is perpendicular to the transverse direction.

[0005] The fuel cell can be arranged in a mobile device, in particular a vehicle. The vehicle can be an electric vehicle. The fuel cell can provide drive energy for propelling the vehicle.

[0006] The reaction gas can be a fuel, in particular hydrogen or containing hydrogen. The reaction gas can be an oxidizing agent, in particular oxygen, preferably from air.

[0007] The bipolar plate can be made of metal, graphite, or a composite material. The bipolar plate may have cooling fluid openings for the passage of cooling fluid. The bipolar plate may have an active field located laterally within the contact area and encompassing at least a portion of the channel structure. The active field is the area of ​​the bipolar plate in which the reaction gas is guided vertically from the channel structure to the electrodes of the membrane electrode assembly.

[0008] The membrane electrode assembly can comprise at least one anode, in particular coated with a catalyst layer, one cathode, in particular coated with a catalyst layer, one proton exchange membrane, in particular coated with a catalyst layer and / or one gas diffusion layer.

[0009] The sealing area can be laterally spaced from the support area. The support area can be arranged laterally between the channel structure, in particular the active field, and the sealing area. The sealing area and the support area can be separated from each other by a recess. The barrier elements can be arranged in the recess. The gas diffusion layer can be inserted laterally spaced from the sealing area, in particular to prevent the gas diffusion layer from resting on the sealing surface.

[0010] The sealing element can be a component or a coating. The sealing element can be made of an elastomer, in particular silicone or EPDM.

[0011] The bearing surface, the sealing surface and / or the barrier surface can be parallel to each other.

[0012] Limiting the bypass flow can involve reducing or preventing the bypass flow.

[0013] The vertical position refers to a position, particularly one facing away from the channel structure in the direction of the membrane-electrode assembly. A different vertical position signifies a difference in height. Height, in turn, is a length extending in the vertical direction.

[0014] In a preferred embodiment of the invention, it is advantageous if the locking means are arranged laterally between the sealing area and the bearing area. The locking means can be arranged transversely between the sealing area and the bearing area.

[0015] In a particular embodiment of the invention, it is advantageous if the locking means comprise several locking elements arranged laterally offset from one another in a longitudinal direction perpendicular to the vertical direction. The locking elements can be arranged transversely between the bearing area and the sealing area.

[0016] In a particular embodiment of the invention, it is advantageous if the locking means comprise support elements formed integrally with the channel structure and sealing elements arranged separately on them in the vertical direction. The sealing elements can be made of an elastomer, in particular a fluoroelastomer. The sealing elements can be made of the same material as the sealing element. The sealing elements and the sealing element can be formed in one piece.

[0017] The sealants can have a vertical height between 10 µm and 100 µm, preferably between 10 µm and 40 µm. The sealants can occupy a height between 20% and 60% of the total height of the barrier elements. The height of the sealants can be less than the height of the support elements.

[0018] The sealants can be a component or a coating. The sealants can be bonded to the support materials.

[0019] The sealing elements can include support elements integrated as a single unit with the channel structure and sealing elements arranged separately on them in the vertical direction. Some of the sealing elements may not have any sealing elements. The support elements and the sealing elements arranged on them may be spaced apart from other support elements and the sealing elements arranged on them.

[0020] In a specific embodiment of the invention, it is advantageous if the barrier surface is a surface of the sealant. The barrier surface can have larger dimensions in the transverse direction than in the longitudinal direction. The barrier surface can be in contact with the sealing element. This allows a bypass opening to be completely sealed.

[0021] According to the present invention, a fuel cell stack with the features of claim 6 is further proposed. This reduces bypass flows of the reaction gas around the active field and increases the efficiency of the fuel cell stack. Furthermore, backflow from a lateral edge region outside the support area into the active field can be reduced or prevented.

[0022] The fuel cell stack can comprise at least one proton exchange membrane, in particular with a catalyst layer, an anode, in particular with a catalyst layer, a cathode, in particular with a catalyst layer and a gas diffusion layer.

[0023] The sealing element can be connected to the membrane electrode assembly. The sealing element can be bonded to the membrane electrode assembly by a material-bonded connection, in particular by adhesive bonding.

[0024] In an advantageous embodiment of the invention, the barrier means are provided that they overlap at least partially in the vertical direction at least one gas diffusion layer of the membrane electrode assembly. The barrier means can also abut a gas diffusion layer of the membrane electrode assembly in the transverse direction.

[0025] In a preferred embodiment of the invention, it is advantageous if the barrier means overlap at least partially, in a transverse direction perpendicular to the vertical direction, at least one gas diffusion layer of the membrane electrode assembly. The barrier means can have an edge surface inclined in the vertical direction, which overlaps with the gas diffusion layer. This allows bypass flow from an edge region of the membrane electrode assembly to the active field to be limited. Furthermore, the limitation can be less dependent on tolerances with respect to the dimensions and / or positions of the membrane electrode assembly, the bipolar plate, and / or the sealing element.

[0026] In an advantageous embodiment of the invention, a free area is formed on one side of the sealing element opposite the barrier surface in the vertical direction. This allows for reliable contact between the barrier surface and the sealing surface while minimizing the impact on the sealing function of the sealing element, which is dependent on contact pressure.

[0027] The sealing element can be deflected, at least in the lateral area of ​​the barrier surface, in a vertical direction away from it into the free area. This reduces the contact pressure between the barrier surface and the sealing surface and thus has less of an impact on the sealing function of the sealing area.

[0028] In a preferred embodiment of the invention, the further bipolar plate has a further channel structure formed by vertically extending depressions for the flow of the reaction gas, and further barrier elements for limiting a bypass flow of the reaction gas laterally outside the further channel structure. The barrier elements comprise several barrier elements arranged offset with respect to a longitudinal direction perpendicular to the vertical direction, and the further barrier elements comprise several further barrier elements arranged offset with respect to the longitudinal direction. The barrier elements and the further barrier elements are arranged without overlap in the longitudinal direction and are alternately offset. This allows the bypass flow to be limited on both sides of the sealing element with respect to the vertical direction, while still minimizing the impact on the sealing function of the sealing element.

[0029] The invention further relates to a fuel cell with at least one fuel cell stack as previously described. The fuel cell can include a cooling system for cooling the fuel cell stack, a humidity control system for adjusting the conductivity of a membrane of the membrane electrode assembly, control electronics, a fuel supply, and / or an air supply.

[0030] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations. Character description

[0031] The invention is described in detail below with reference to the illustrations. These show, in detail: Fig. 1: A top view of a bipolar plate in a special embodiment of the invention. Fig. 2: Excerpt A from Fig. 1 in an enlarged view. Fig. 3: A section of a cross-section of a fuel cell stack in a special embodiment of the invention. Fig. 4: A section of a cross-section of a fuel cell stack in a special embodiment of the invention. Fig. 5: A section of a cross-section of a fuel cell stack in a special embodiment of the invention.

[0032] Fig. Figure 1 shows a top view of a bipolar plate in a particular embodiment of the invention. The bipolar plate 10 for a fuel cell comprises a channel structure 12 for flow with a reaction gas, an inlet opening 14 for introducing the reaction gas into the channel structure 12, and an outlet opening 16 for removing the remaining reaction gas and / or reaction products from the channel structure 12. The channel structure 12 is formed by recesses extending in a vertical direction 18 and through which the reaction gas can flow in a longitudinal direction 22 perpendicular to the vertical direction 18.

[0033] The channel structure 12 comprises an active field 24 in which the reaction gas is guided from the channel structure 12 in the vertical direction 18 to electrodes of a membrane electrode assembly to be arranged on the bipolar plate 10. The channel structure 12 is laterally surrounded at its edge by a sealing area 26, which has a sealing surface 28 for contact with a sealing element that seals the channel structure 12 to the outside. The sealing surface 28 has a normal parallel to the vertical direction 18.

[0034] Between the channel structure 12 and the sealing area 26, a support area 30 with a support surface 32 is arranged for the lateral edge support of the membrane electrode assembly that can span the channel structure 12.

[0035] Fig. Figure 2 shows section A from Fig. 1 in an enlarged view. The bipolar plate 10 includes, laterally between the support area 30 and the sealing area 26, barrier means 34 for limiting a bypass flow of the reaction gas laterally outside of the active field 24 of the channel structure 12. The barrier means 34 comprise several barrier elements 36 arranged laterally offset from one another in the longitudinal direction 22.

[0036] The support area 30 comprises several support sections 40 by means of segmental subdivisions 38 in the longitudinal direction 22, from which the locking elements 36 extend in a transverse direction 42 perpendicular to the vertical direction 18 and the longitudinal direction 22, and extend in the transverse direction 42 to the wave-shaped sealing area 26. The locking elements 36 extend, in particular with respect to the longitudinal direction 22, centrally from the respective support sections 40.

[0037] The subdivision of the support sections 40 in the longitudinal direction 22 and the wave shape of the sealing area 26 are coordinated. Specifically, this means that a support section 40 is assigned to each wave crest 44 of the sealing area 26 facing the channel structure 12 in the transverse direction 42.

[0038] Fig. Figure 3 shows a section of a cross-section of a fuel cell stack in a special embodiment of the invention. The fuel cell stack 46 has a stacked layer structure 48 in the vertical direction 18, consisting at least of a layer as shown in Figure 3. Fig. 1 described bipolar plate 10 with the channel structure 12 formed by recesses 20, at least one membrane electrode assembly 50 arranged on the bipolar plate 10 and a further bipolar plate 52, which, for example, is arranged as a mirror axis in relation to the transverse direction 42 and, like the latter, has a further channel structure 54 adapted to the channel structure 12.

[0039] The bipolar plate 10, together with the channel structure 12 and the membrane electrode assembly 50 arranged thereon, forms flow channels 56 for longitudinal flow 22 of the reaction gas, for example a gaseous fuel, in particular hydrogen, and the further bipolar plate 52, together with the further channel structure 54 and the membrane electrode assembly 50 arranged thereon, forms further flow channels 58 for longitudinal flow 22 of another reaction gas, for example an oxidizing agent, in particular air.

[0040] The membrane electrode assembly 50 comprises a gas diffusion layer 60 facing the channel structure 12 and a further gas diffusion layer 62 facing the other channel structure 54. A proton exchange membrane 64 and electrodes mounted on it are arranged vertically 18 between the gas diffusion layer 60 and the further gas diffusion layer 62. The membrane electrode assembly 50 is bonded to a sealing element 66 at a lateral edge. The membrane electrode assembly 50 extends transversely 42 to the barrier elements 36, which are arranged transversely 42 between the support area 30 and a further sealing area 68 of the further bipolar plate 52. The sealing element 66 is clamped in the vertical direction 18 between the sealing area 26 and the further sealing area 68 in order to seal the channel structure 12 as well as the further channel structure 54 to the outside.

[0041] A barrier surface 69 of the barrier elements 36 has a height 70 with respect to the vertical direction 18 and, in particular, with respect to a first direction 19 extending away from the flow channels 56 towards the membrane electrode assembly 50. This height 70 is equal to or greater than a height 72 of the sealing surface 28, which in turn is greater than a height 74 of the bearing surface 32. As a result, the barrier surface 69 rests against the sealing element 66 in the vertical direction 18, thereby limiting the bypass flow laterally at the edge of the membrane electrode assembly 50, at least along the longitudinal direction 22.

[0042] The barrier means 34 with the barrier elements 36 are arranged overlapping at least partially with the gas diffusion layer 60 of the membrane-electrode assembly 50 in the vertical direction 18 and in the transverse direction 42. A free area 76 is formed on one side of the sealing element 66 opposite the barrier surface 69 in the vertical direction 18. The sealing element 66 can be deflected into the free area 76, at least in the lateral region of the barrier surface 69, away from it in the vertical direction 18. This allows the sealing element 66 to deflect into the free area 76, away from the barrier surface 69, and reduce the contact pressure between the barrier surface 69 and the sealing element 66. This, in turn, reduces the influence on the contact pressure between the sealing element 66 on the one hand and the sealing surface 28 and another sealing surface 78 of the further sealing area 68 on the other.

[0043] The additional locking elements 79, which are arranged offset in the longitudinal direction 22 on the further bipolar plate 52 and are not visible here but can be seen on the lower bipolar plate 52' of the layer structure 48, which is identical to the further bipolar plate, are arranged without overlap with the locking elements 36 in the longitudinal direction 22 and are alternately offset. This prevents an overlap in the longitudinal direction 22 between the locking elements 36 and the further locking elements 79, which would lead to an increased contact pressure between the sealing element 66 on the one hand and the locking surface 69 and the further locking surface on the other.

[0044] Fig. Figure 4 shows a section of a cross-section of a fuel cell stack in a specific embodiment of the invention. The locking elements 36 of the locking means 34 have support means 80 integrated with the channel structure 12 and sealing means 81 arranged separately thereon in the vertical direction 18. The locking surface 69 is a surface of the sealing means 81. The sealing means 81 are preferably made of an elastomer, in particular a fluoroelastomer, and can consist of the same material as the sealing element 66.

[0045] The sealing materials 81 have in particular a height 82 which is less than a height 84 of the support materials 80.

[0046] Fig.Figure 5 shows a section of a cross-section of a fuel cell stack in a special embodiment of the invention. The barrier means 34 are arranged overlapping at least partially in the vertical direction 18 and the transverse direction 42 with a gas diffusion layer 60 of the membrane electrode assembly 50, thereby limiting even a bypass flow originating from a lateral edge region 86 of the membrane electrode assembly 50 via the adhesive joint 88 of the membrane electrode assembly 50 with the sealing element 66 to the active field 24. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2019 / 214655 A1

[0002]

Claims

[1] Bipolar plate (10) for a fuel cell, comprising a channel structure (12) formed by depressions (20) extending in a vertical direction (18) for flow with a reaction gas, a sealing area (26) laterally surrounding the channel structure (12) at its edge, which has a sealing surface (28) that can be applied to the outside of a sealing element (66) to seal the channel structure (12), a support area (30) with a support surface (32) for the lateral edge support of a membrane electrode assembly (50) spanning the channel structure (12), a barrier surface (69) barrier means (34) for limiting a bypass flow of the reaction gas laterally outside the channel structure (12), wherein with respect to the vertical direction (18) a height level (72) of the sealing surface (28) is greater than a height level (74) of the bearing surface (32), characterized by , that a height (70) of the barrier surface (69) is equal to or greater than a height (72) of the sealing surface (28). [2] Bipolar plate (10) according to claim 1, characterized by , that the locking means (34) are arranged laterally between the sealing area (26) and the support area (30). [3] Bipolar plate (10) according to claim 1 or 2, characterized by , that the locking means (34) comprise several locking elements (36) arranged laterally offset to each other in a longitudinal direction (22) perpendicular to the vertical direction (18). [4] Bipolar plate (10) according to any one of the preceding claims, characterized by , that the locking means (34) include support means (80) formed in one piece with the channel structure (12) and sealing means (81) arranged separately on them in the vertical direction (18). [5] Bipolar plate (10) according to claim 4, characterized by , that the barrier surface (69) is a surface of the sealant (81). [6] fuel cell stack (46) a layered structure (48) stacked in a vertical direction (18) consisting of at least one bipolar plate (10) according to one of the preceding claims, at least one membrane electrode assembly (50) arranged on the bipolar plate (10), at least one further bipolar plate (52) arranged on the membrane electrode assembly (50) with at least one further sealing surface (78) opposite the sealing surface (28) in the vertical direction (18) and at least one sealing element (66) clamped in the vertical direction (18) between the sealing surface (28) and the further sealing surface (78). [7] Fuel cell stack (46) according to claim 6, characterized by , that the barrier means (34) overlap at least partially in the vertical direction (18) at least one gas diffusion layer (60) of the membrane electrode assembly (50). [8] Fuel cell stack (46) according to claim 6 or 7, characterized by , that the barrier means (34) overlap at least partially at least one gas diffusion layer (60) of the membrane electrode assembly (50) in a transverse direction (42) perpendicular to the vertical direction (18). [9] Fuel cell stack (46) according to any one of claims 6 to 8, characterized by , that a free area (76) is formed on one side of the sealing element (66) opposite the barrier surface (69) in the vertical direction (18). [10] Fuel cell stack (46) according to any one of claims 6 to 9, characterized by, that the further bipolar plate (52) has a further channel structure (54) formed by recesses extending in the vertical direction (18) for flow through with the reaction gas and further barrier means for limiting a bypass flow of the reaction gas laterally outside the further channel structure (54), wherein the barrier means (34) has several barrier elements (36) arranged offset with respect to a longitudinal direction (22) perpendicular to the vertical direction (18) and the further barrier means has several further barrier elements (79) arranged offset with respect to the longitudinal direction (22), wherein the barrier elements (36) and the further barrier elements (79) are arranged without overlap and alternately offset in the longitudinal direction (22).

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