Bipolar plate for a fuel cell or electrolyzer type stack

Abstract

The invention relates to a bipolar plate (6, 7) for a fuel cell type stack or for an electrolyzer type stack, the bipolar plate (6, 7) comprising an anodic plate (16) and a cathodic plate (17) assembled face to face, the face of the anodic plate (16) opposite the face of the cathodic plate (17) delimiting an internal space forming a circuit for the distribution of a first fluid, the anodic plate (16) and the cathodic plate (17) having distinct dimensions such that at least a part of the peripheral end of the anodic plate (16) and at least a part of the peripheral end of the cathodic plate (17) are offset from each other in the plane of the bipolar plate (6, 7), forming a shoulder at the level of a peripheral end of the bipolar plate (6, 7). Abbreviated figure: Fig. 3

Description

Title of the invention: Bipolar plate for a fuel cell or electrolyzer type stack

[0001] The present invention relates to a bipolar plate for a fuel cell type stack or for an electrolyzer type stack, a fuel cell or electrolyzer cell comprising such a plate and a fuel cell or electrolyzer comprising such a cell.

[0002] In a manner known per se, a fuel cell is an electrochemical device which makes it possible to convert chemical energy into electrical energy from a fuel, generally dihydrogen, and an oxidant, generally dioxygen or a gas containing it such as air, the product of the reaction being water accompanied by a release of heat and a production of electricity.

[0003] An electrolyzer is based on the reverse principle, namely the input of electrical energy to produce chemical reactions, for example, to produce a fuel such as dihydrogen and an oxidant such as oxygen. The following description relates more specifically to the fuel cell, but could be applied to the electrolyzer.

[0004] A fuel cell or electrolyzer is a stack of several cells, each cell comprising two bipolar plates sandwiching a Membrane Electrode Assembly (MEA). The alignment of the components of a cell stack is achieved, at the time of stacking each bipolar plate, either internally, by means of guides arranged in openings in the bipolar plates (either dedicated openings or by using one or more collectors), or externally, by means of at least three guide axes coming into contact with respective edges of the bipolar plate.

[0005] Aligning the components of a stack of several dozen or even several hundred cells is a delicate process. The various components of the stack (particularly the bipolar plates and the AME) can tend to slip against each other, causing an aesthetic defect, a loss of performance, a leak, and reduced vibration resistance. Misalignment of the bipolar plates and the AME can also increase the risk of short circuits. The risk is even greater when there is, even locally, a short distance between two points of different potentials and a conductive element fills this gap (metal shavings, dust, etc.).

[0006] When manufacturing a fuel cell or an electrolyzer, it is therefore necessary to carry out a correct stacking of bipolar plates, that is to say to align them correctly along the axis of the stacking.

[0007] The present invention aims to effectively remedy these drawbacks by proposing a bipolar plate for a fuel cell type stack or for an electrolyzer type stack, the bipolar plate comprising an anodic plate and a cathodic plate assembled face to face, the face of the anodic plate opposite the face of the cathodic plate delimiting an internal space forming a circuit for the distribution of a first fluid, the anodic plate and the cathodic plate having distinct dimensions such that at least a part of the peripheral end of the anodic plate and at least a part of the peripheral end of the cathodic plate are offset from each other in the plane of the bipolar plate, forming a shoulder at the level of a peripheral end of the bipolar plate.

[0008] Such a configuration ensures good guidance of the bipolar plates during the manufacture of a stack and prevents any short circuit formation between the anodic plates and the cathodic plates.

[0009] According to one embodiment, the respective dimensions of the anodic plate and the cathodic plate are arranged so that at least on a part of the peripheral end of the bipolar plate, the peripheral end of the cathodic plate and the peripheral end of the anodic plate are not opposite each other.

[0010] According to one embodiment, the shoulder is considered perpendicular to the plane of the bipolar plate. In other words, the shoulder extends along the edge of the bipolar plate, at the level of its thickness.

[0011] According to one embodiment, the peripheral end of the anodic plate and the peripheral end of the cathodic plate each have a straight edge extending perpendicularly to the plane of the bipolar plate.

[0012] According to one embodiment, the shoulder forms a step or crenellation.

[0013] According to one embodiment, the bipolar plate comprises at least one guide zone for guiding the bipolar plate during the manufacture of a stack, the guide area being disposed at the shoulder, the guide area having an external edge of the bipolar plate.

[0014] According to one embodiment, the shoulder extends over at least 90% of the perimeter of the peripheral end of the bipolar plate.

[0015] According to one embodiment, the shoulder includes an obtuse angle, in particular between 92° and 100°.

[0016] According to one embodiment, the anodic plate has a first opening and the cathodic plate has a second opening, the first opening and the second opening being opposite to form a collector to allow the passage of the first fluid or a second fluid through the bipolar plate, the first opening and the second opening having distinct dimensions such that at least a part of the peripheral end of the first opening and at least a part of the peripheral end of the second opening are offset from each other in the plane of the bipolar plate, forming a second shoulder at the peripheral end of the collector.

[0017] According to one embodiment, the second shoulder is considered perpendicular to the plane of the bipolar plate.

[0018] According to one embodiment, the first fluid is a cooling fluid.

[0019] According to one embodiment, the second fluid is a fuel or an oxidizer.

[0020] According to one embodiment, the anodic plate is produced by molding and at least one of its edges include a first draft angle, the first draft angle being distinct from the shoulder.

[0021] According to one embodiment, the cathode plate is produced by molding and at least one of its edges includes a second draft angle, the second draft angle being distinct from the shoulder.

[0022] The invention further relates to a fuel cell or electrolyzer cell comprising two bipolar plates as described above, the bipolar plates sandwiching a membrane electrode assembly.

[0023] According to one embodiment, the membrane electrode assembly has dimensions allowing alignment of the peripheral end of the membrane electrode assembly and the peripheral end of one of the anodic plate and the cathodic plate furthest from the internal space, at the shoulder.

[0024] According to one embodiment, the bipolar plate has a portion of the peripheral end which is devoid of a shoulder, the membrane-electrode assembly protruding from the peripheral end of the bipolar plate in said portion, projecting out from the bipolar plate in the direction of the plane of the bipolar plate.

[0025] The invention further relates to a fuel cell or electrolyzer, in particular with a proton exchange membrane, comprising a stack of cells as described above.

[0026] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only to illustrate, but in no way limit, the invention.

[0027] [Fig-1] The [Fig.1] is a schematic representation of a cell from the prior art;

[0028] [Fig.2] [Fig.2] is a representation along axis II-II of the cell of [Fig.1];

[0029] [Fig.3] [Fig.3] is a schematic elevation representation of a plate bipolar according to the invention;

[0030] [Fig.4] [Fig.4] is a schematic cross-sectional representation of a cell according to the invention; and

[0031] [Fig. 5] [Fig. 5] is a schematic cross-sectional representation of another mode of realization of the cell according to the invention.

[0032] Identical, similar, or analogous elements retain the same reference from one figure to another.

[0033] With reference to [Fig.1] which represents a prior art fuel cell 1, it can be observed that such a cell 1 comprises a proton-conducting electrolyte 2 which is sandwiched between two porous cathodic electrodes 3 and anodic electrodes 4 and which ensures proton transfer between these two electrodes 3, 4.

[0034] For this purpose, the electrolyte 2 can be a proton exchange polymer membrane in particular with a thickness between 5 and 200 pm, the resulting cell being a PEM (for "Proton Exchange Membrane") or PEMFC (for "Proton Exchange Membrane Fuel Cell") type cell.

[0035] The assembly consisting of the electrolyte 2 and the two electrodes 3, 4 forms a Membrane Electrode Assembly (MEA) 5 which is itself sandwiched between first 6 and second 7 bipolar plates which ensure the collection of current, the distribution of oxidant and fuel in the electrodes 3, 4 and the circulation of the heat transfer fluid.

[0036] The commonly used bipolar plates 6,7 are made of materials offering good corrosion resistance and electrical conductivity properties, such as carbon materials like graphite, polymer-impregnated graphite or flexible graphite sheets shaped by machining or molding.

[0037] It is also possible to use metallic materials such as titanium, aluminum, and iron-based alloys, including stainless steels, to produce the bipolar plates 6, 7. In this case, the bipolar plate 6, 7 can be shaped by deep drawing or stamping thin sheets.

[0038] In order to ensure the distribution of the oxidizer, fuel and heat transfer fluid in all the constituent cells of the fuel cell, the second bipolar plate 7 has six openings 7a-7f.

[0039] The first bipolar plate 6 has the same openings arranged in the same places as on the bipolar plate 7, [Fig.1] showing only four openings 6a-6d.

[0040] The openings 6a-6d of the first bipolar plate 6 and the openings 7a-7f of the second bipolar plate 7 are aligned to form collectors ensuring the circulation of fluids through all the constituent cells of the stack.

[0041] At each of these openings 7a-7f, 6a-6d, a conduit not shown allows the heat transfer fluid, fuel or oxidizer circulating on the surface of the plate 6,7 or in the plate 6,7 or in fluid circulation channels provided for this purpose to be supplied with or collected.

[0042] With reference to [Fig.2], which is a section along line II-II of [Fig. 1], the cathodic electrode 3 and anodic electrode 4 each have a respective active layer 10, 11 which are the site of the cathodic and anodic reactions respectively and a respective diffusion layer 12, 13 intercalated between the active layer 10, 11 and the corresponding bipolar plate 6, 7, this diffusion layer 12, 13 being for example a paper substrate or a carbon fabric.

[0043] The diffusion layer 12, 13 ensures the diffusion of reactants such as dihydrogen and dioxygen which circulate in the respective channels 14, 15 formed by grooves made in the respective bipolar plates 6, 7.

[0044] In this way, the active layer 11 of the anodic electrode 4 is supplied with dihydrogen via the diffusion layer 13, and the reaction that occurs in this active layer 11 is as follows: H2 → 2e- + 2H+. Similarly, the active layer 10 of the cathodic electrode 3 is supplied with oxygen via the diffusion layer 12, and the reaction that occurs in this active layer 10 is as follows: O2 + 2H+ + 2e- → H2O. These reactions are made possible by the presence of the membrane 2, which ensures the transfer of protons from the active layer 11 of the anode 4 to the active layer 10 of the cathode 3.

[0045] In a manner known per se, a fuel cell or electrolyzer type stack comprises a stack of cells 1, a first end plate and a second end plate, the stack of cells 1 being mounted between the first and second end plates.

[0046] A fuel cell according to the invention comprises a stack of cells 1 as described above. The cells 1 ensure the collection of current, the distribution of the oxidant and fuel to the electrodes and the circulation of the heat transfer fluid.

[0047] With reference to [Fig. 3], the bipolar plate 6, 7 comprises an anodic plate 16 and a cathodic plate 17 bonded or welded face to face, defining an internal space forming a circuit for the distribution of a first fluid. The anodic plate 16 and the cathodic plate 17 are each rectangular in cross-section (in thickness, the edge is straight, i.e., it extends in a direction perpendicular to the plane of the plate).

[0048] The face of the anodic plate 16 opposite the face of the cathode plate 17 has distinct dimensions such that at least a portion of the peripheral end of the anodic plate 16 and at least part of the peripheral end of the cathodic plate 17 are offset from each other in the plane of the bipolar plate 6, 7, forming a shoulder at the level of a peripheral end of the bipolar plate 6, 7, the shoulder being considered perpendicular to the plane of the bipolar plate 6, 7.

[0049] In other words, on at least a portion of the end of the bipolar plate 6, 7, the anodic plate 16 or the cathodic plate 17 protrudes relative to the other.

[0050] The shoulder forms a step or crenellation.

[0051] The bipolar plate 6, 7 includes a guide zone for guiding the bipolar plate 6, 7 during the manufacturing of a stack, the guide zone being located at the shoulder, the guide zone having an outer edge of the bipolar plate. The guide zone is thus the portion of the end of the anodic plate 16 or the cathodic plate 17 that protrudes relative to the other.

[0052] In the example of [Fig.3], the shoulder extends over the entire perimeter of the peripheral end of the bipolar plate 6, 7. In other words, the shoulder is continuous over the entire periphery of the bipolar plate 6, 7. Thus, guidance can be carried out on any portion of the periphery of the plate.

[0053] In the example of [Fig.3], the anodic plate 16 has a first opening for the inlet or outlet of a second fluid, the cathodic plate 17 has a second opening for the inlet or outlet of the second fluid, the first opening and the second opening being opposite each other to form a collector 18 to allow the passage of the second fluid through the bipolar plate 6, 7. The first opening and the second opening have distinct dimensions such that at least a part of the peripheral end of the first opening and at least a part of the peripheral end of the second opening are offset from each other in the plane of the bipolar plate 6, 7, forming a second shoulder at the peripheral end of the collector 18, the second shoulder being considered perpendicular to the plane of the bipolar plate 6, 7.

[0054] In the example of [Fig.3], all the external edges of the bipolar plate 6, 7 (the peripheral ends of the plate 6, 7 and the peripheral ends of the collectors 18) have a shoulder and each shoulder is continuous around the entire perimeter of the edge considered.

[0055] Fig. 4 represents a fuel cell or electrolyzer cell 1 comprising two bipolar plates 6, 7 as described above in relation to Fig. 3, the bipolar plates 6, 7 sandwiching a membrane electrode assembly 5.

[0056] The membrane electrode assembly 5 has dimensions that allow the peripheral end of the membrane electrode assembly 5 to be aligned with the peripheral end of one of the anodic plates 16 and the cathodic plate 17 furthest from the internal space, at the shoulder. In the example considered, the membrane electrode assembly 5 and the anodic plate 16 are aligned edge to edge at the shoulder.

[0057] Thus the guide zones, at the level of the shoulder, are made by the peripheral edges of the anodic plates 16 which protrude in relation to the cathodic plates 17. It is possible to proceed with an assembly according to the reverse configuration in which the AME 5 is aligned edge to edge with the cathodic plate 17.

[0058] Figure 5 represents a fuel cell or electrolyzer cell 1 according to another embodiment. The difference compared to cell 1 of Figure 4 is that in this embodiment, the anodic plate 16 is molded. The end edge of the first opening of the anodic plate 16 includes a first draft angle. In the example of Figure 5, the draft angle is located within the thickness of the plate.

[0059] The cathode plate 17 is also produced by molding. The end edge of the second opening of the cathode plate 17 includes a second draft angle. The second draft angle is located in the plane in which the cathode plate 17 lies.

[0060] In the example in [Fig. 5], the shoulder includes at least one obtuse angle, due to the draft angles. In the example considered, the shoulder includes an angle between 92° and 100°.

Claims

Demands

1. Bipolar plate (6, 7) for a fuel cell stack or for an electrolyzer stack, the bipolar plate (6, 7) comprising an anodic plate (16) and a cathodic plate (17) assembled face to face, the face of the anodic plate (16) opposite the face of the cathodic plate (17) delimiting an internal space forming a circuit for the distribution of a first fluid, the anodic plate (16) and the cathodic plate (17) having distinct dimensions such that at least a portion of the peripheral end of the anodic plate (16) and at least a portion of the peripheral end of the cathodic plate (17) are offset from each other in the plane of the bipolar plate (6, 7), forming a shoulder at a peripheral end of the bipolar plate (6, 7). 7).

2. Bipolar plate (6, 7) according to the preceding claim, the peripheral end of the anodic plate (16) and the peripheral end of the cathodic plate each having a straight edge extending perpendicularly to the plane of the bipolar plate.

3. Bipolar plate (6, 7) according to any one of the preceding claims, the shoulder forming a step or a crenellation.

4. Bipolar plate (6, 7) according to any one of the preceding claims, comprising at least one guide zone for guiding the bipolar plate (6, 7) during the manufacture of a stack, the guide zone being disposed at the shoulder, the guide zone comprising an external edge of the bipolar plate (6, 7).

5. Bipolar plate (6, 7) according to any one of the preceding claims, the shoulder extending over at least 90% of the perimeter of the peripheral end of the bipolar plate (6, 7).

6. Bipolar plate (6, 7) according to any one of the preceding claims, the anodic plate (16) having a first opening, the cathodic plate (17) having a second opening, the first and second openings being opposite each other to form a collector (18) for allowing the passage of the first fluid or a second fluid through the bipolar plate (6, 7), the first and second openings having distinct dimensions such that at least a portion of the peripheral end of the first opening and at least a portion of the peripheral end of the second opening are offset from each other in the plane of the bipolar plate (6, 7), forming a second shoulder at the peripheral end of the collector (18).

7. Fuel cell or electrolyzer cell (1) comprising two bipolar plates (6, 7) according to any one of the preceding claims, the bipolar plates (6, 7) sandwiching a membrane electrode assembly (5).

8. Cell (1) according to the preceding claim, the membrane electrode assembly (5) having dimensions allowing alignment of the peripheral end of the membrane electrode assembly (5) and the peripheral end of one of the anodic plate (16) and the cathodic plate (17) furthest from the internal space, at the shoulder.

9. Cell (1) according to any one of claims 7 to 8, the bipolar plate (6, 7) having a portion of the peripheral end which is devoid of a shoulder, the membrane electrode assembly (5) protruding from the peripheral end of the bipolar plate (6, 7) in said portion, projecting out from the bipolar plate (6, 7) in the direction of the plane of the bipolar plate (6, 7).

10. Fuel cell or electrolyzer, in particular with a proton exchange membrane, comprising a stack of cells (1) according to any one of claims 7 to 9.

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