BIPOLAR PLATE FOR A FUEL CELL OR ELECTROLYSER TYPE STACK

Description

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

[0002] As is known per se, a fuel cell is an electrochemical device which converts 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 the release of heat and the production of electricity.

[0003] An electrolyser is based on the opposite principle, namely an input of electrical energy for the production of chemical reactions, for example for the production of 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 electrolyser.

[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 stack of cells is carried out, at the time of stacking of each bipolar plate, either from the inside, by means of guides arranged in openings of the bipolar plates (either dedicated openings, or by exploiting one or more collectors), or from the outside, by means of at least three guide pins coming into contact with respective edges of the bipolar plate.

[0005] Document DE 10 2017 125903 A1 discloses a bipolar plate comprising a seal forming a metal sealing rib, and embossments in the plate, the embossments forming channels substantially perpendicular to the seal. The embossments, formed inside the plate and not on the periphery, do not form a shoulder, and even less so a shoulder at a peripheral end of the plate.

[0006] US 2008 / 311461 A1 discloses a proton exchange membrane fuel cell (PEMFC) but focuses on the relative location of the fuel supply, oxidizer supply, and coolant discharge manifolds. The apertures are offset in the direction perpendicular to the plane of the fuel cells.

[0007] Aligning the components of a stack of several dozen or even several hundred cells is tricky. The various components of the stack (particularly the bipolar plates and the MEA) can tend to slide on each other, causing an aesthetic defect, a loss of performance, a lack of sealing, and reduced vibration resistance. Poor alignment of the bipolar plates and the MEA 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 space (metal shavings, dust, etc.).

[0008] When manufacturing a fuel cell or an electrolyser, 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 stack.

[0009] The present invention aims to effectively overcome these drawbacks by proposing a bipolar plate for a fuel cell type stack or for an electrolyzer type stack, the bipolar plate comprising an anode plate and a cathode plate assembled together, face to face, the face of the anode plate facing the face of the cathode plate delimiting an internal space forming a circuit for the distribution of a first fluid, the anode plate comprising a first opening, the cathode plate comprising a second opening,the first opening and the second opening being opposite each other 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 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 forming a shoulder at the peripheral end of the collector.,

[0010] Such a configuration ensures good guidance of the bipolar plates during the manufacture of a stack and prevents any short circuit formation between the anode plates and the cathode plates.

[0011] According to one embodiment, the respective dimensions of the first opening and the second opening are arranged so that at least on a portion of the peripheral end of the bipolar plate, the peripheral end of the first opening and the peripheral end of the second opening are not opposite each other.

[0012] 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.

[0013] According to one embodiment, the peripheral end of the first opening and the peripheral end of the second opening each have a straight edge extending perpendicular to the plane of the bipolar plate.

[0014] Depending on one embodiment, the shoulder forms a step or a crenel.

[0015] According to one embodiment, the plate comprises at least one guide zone for guiding the bipolar plate during the manufacture of a stack, the guide zone being arranged at the shoulder, the guide zone comprising an external edge of the bipolar plate.

[0016] According to one embodiment, the shoulder extends over at least 90% of the circumference of the peripheral end of the collector.

[0017] According to one embodiment, the shoulder comprises an obtuse angle, in particular between 92° and 100°.

[0018] According to one embodiment, the anode plate and the cathode plate have distinct dimensions such that at least a portion of the peripheral end of the anode plate and at least a portion of the peripheral end of the cathode plate are offset from each other in the plane of the bipolar plate forming a second shoulder at a peripheral end of the bipolar plate.

[0019] According to one embodiment, the second shoulder is considered perpendicular to the plane of the bipolar plate.

[0020] According to one embodiment, the first fluid is a cooling fluid.

[0021] According to one embodiment, the second fluid is a fuel or an oxidizer.

[0022] According to one embodiment, the anodic plate is produced by molding and at least one of its edges comprises a first draft angle, the first draft angle being distinct from the shoulder.

[0023] According to one embodiment, the cathode plate is produced by molding and at least one of its edges comprises a second draft angle, the second draft angle being distinct from the shoulder.

[0024] 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.

[0025] According to one embodiment, the membrane electrode assembly comprises a third opening intended to come opposite the first and second openings, the membrane electrode assembly having dimensions allowing alignment of the peripheral end of the third opening and the peripheral end of one of the first opening and the second opening closest to the center of the third opening, at the shoulder.

[0026] According to one embodiment, the bipolar plate comprises a portion of the peripheral end of the collector which is devoid of a shoulder, the membrane electrode assembly protruding from the peripheral end of the collector in said portion, projecting relative to the bipolar plate in the direction of the plane of the bipolar plate.

[0027] The invention further relates to a fuel cell or electrolyser, in particular with a proton exchange membrane, comprising a stack of cells as described above.

[0028] The invention will be better understood by reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention. [ Fig.1 ] There [ Fig.1 ] is a schematic representation of a prior art cell; [ Fig.2 ] there [ Fig.2 ] is a representation along the II-II axis of the cell of the [ Fig.1 ] ; [ Fig.3 ] there [ Fig.3 ] is a schematic elevational representation of a bipolar plate according to the invention; [ Fig.4 ] there [ Fig.4 ] is a schematic cross-sectional representation of a cell according to the invention; and [ Fig.5 ] there [ Fig.5 ] is a schematic cross-sectional representation of another embodiment of the cell according to the invention.

[0029] Identical, similar, or analogous elements retain the same reference from one figure to another.

[0030] With reference to the [ Fig.1 ] which represents a fuel cell 1 of the prior art, it can be observed that such a cell 1 comprises a proton-conducting electrolyte 2 which is sandwiched between two porous cathodic 3 and anodic 4 electrodes and which ensures the proton transfer between these two electrodes 3, 4.

[0031] For this purpose, the electrolyte 2 may be a proton exchange polymer membrane, in particular with a thickness of between 5 and 200 µm, the resulting cell being a PEM (for “Proton Exchange Membrane”) or PEMFC (for “Proton Exchange Membrane Fuel Cell”) type cell.

[0032] 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 the current, the distribution of the oxidant and the fuel in the electrodes 3, 4 and the circulation of the heat transfer fluid.

[0033] Commonly used 6,7 bipolar plates are made of materials with good corrosion resistance and electrical conductivity properties, such as carbonaceous materials like graphite, polymer-impregnated graphite, or soft graphite sheets shaped by machining or molding.

[0034] It is also possible, to produce the bipolar plates 6, 7, to use metallic materials such as titanium, aluminum and iron-based alloys including stainless steels. In this case, the shaping of the bipolar plate 6, 7 can be obtained by stamping or drawing thin sheets.

[0035] In order to ensure the distribution of the oxidizer, fuel and heat transfer fluid in all the constituent cells of the cell, the second bipolar plate 7 has six openings 7a-7f.

[0036] The first bipolar plate 6 has the same openings arranged in the same places as on the bipolar plate 7, the [ Fig.1 ] only revealing four openings 6a-6d.

[0037] 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 battery.

[0038] At each of these openings 7a-7f, 6a-6d, a conduit (not shown) makes it possible to supply or collect the heat transfer fluid, the fuel or the oxidant circulating on the surface of the plate 6,7 or in the plate 6,7 or in fluid circulation channels provided for this purpose.

[0039] With reference to the [ Fig.2 ] which is a section along line II-II of the [ Fig.1 ], the cathodic 3 and anodic 4 electrodes each comprise a respective active layer 10, 11 which are the seat of the cathodic and anodic reactions respectively and a respective diffusion layer 12, 13 interposed between the active layer 10, 11 and the corresponding bipolar plate 6, 7, this diffusion layer 12, 13 being able for example to be a paper substrate or a carbon fabric.

[0040] 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.

[0041] In this way, the active layer 11 of the anode electrode 4 is supplied with dihydrogen via the diffusion layer 13 and the reaction which occurs in this active layer 11 is as follows: H 2 → 2e + 2H +< . In the same way, the active layer 10 of the cathode electrode 3 is supplied with oxygen via the diffusion layer 12 and the reaction which occurs at this active layer 10 is as follows: ½ O 2 + 2H +< + 2e -< → H 2 O. These reactions are made possible by the presence of the membrane 2 which ensures the proton transfer from the active layer 11 of the anode 4 to the active layer 10 of the cathode 3.

[0042] 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.

[0043] 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 the fuel in the electrodes and the circulation of the heat transfer fluid.

[0044] With reference to the [ Fig.3 ], the bipolar plate 6, 7 comprises an anode plate 16 and a cathode plate 17 glued or welded face to face, delimiting an internal space forming a circuit for the distribution of a first fluid. The anode plate 16 and the cathode plate 17 are each rectangular in section (in the thickness, the edge is straight, that is to say it extends in a direction perpendicular to the plane of the plate).

[0045] The anode plate 16 has a first opening for the inlet or outlet of a second fluid and the cathode plate 17 has a second opening for the inlet or outlet of the second fluid. The first opening and the second opening are opposite each other to form a collector 18 to allow the passage of the second fluid through the bipolar plate 6, 7.

[0046] The first opening and the second opening have 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 shoulder at the peripheral end of the collector 18, the shoulder being considered perpendicular to the plane of the bipolar plate 6, 7.

[0047] In other words, on at least a portion of the end opening into the collector 18 of the bipolar plate 6, 7, the anode plate 16 or the cathode plate 17 projects relative to the other.

[0048] The shoulder forms a step or crenel.

[0049] The bipolar plate 6, 7 comprises a guide zone for guiding the bipolar plate 6, 7 during the manufacture of a stack, the guide zone being arranged at the shoulder, the guide zone comprising an outer edge of the bipolar plate. The guide zone is thus the portion of the end of the anode plate 16 or the cathode plate 17 which projects relative to the other.

[0050] In the example of the [ Fig.3 ], the shoulder extends around the entire circumference of the peripheral end of the bipolar plate 6, 7. In other words, the shoulder is continuous around the entire periphery of the collector 18. Thus, guidance can be carried out using a shaft passing through the collector 18.

[0051] In the example of the [ Fig.3 ], the anode plate 16 and the cathode plate 17 have distinct dimensions such that at least a portion of the peripheral end of the anode plate 16 and at least a portion of the peripheral end of the cathode plate 17 are offset from each other in the plane of the bipolar plate 6, 7, forming a second shoulder at a peripheral end of the bipolar plate 6, 7, the second shoulder being considered perpendicular to the plane of the bipolar plate 6, 7.

[0052] In the example of the [ Fig.3 ], all of the outer 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 circumference of the edge in question.

[0053] There [ Fig.4 ] represents a fuel cell or electrolyzer cell 1 comprising two bipolar plates 6, 7 as described above in connection with the [ Fig.3 ], the bipolar plates 6, 7 sandwiching a membrane electrode assembly 5.

[0054] The membrane electrode assembly 5 has dimensions allowing alignment of the peripheral end of the membrane electrode assembly 5 and the peripheral end of one of the anode plate 16 and the cathode plate 17 furthest from the internal space, at the shoulder. In the example considered, the MEA 5 and the anode plate 16 are aligned edge to edge, at the shoulder.

[0055] Thus the guide zones, at the shoulder, are produced by the peripheral edges of the anode plates 16 which protrude relative to the cathode plates 17. It is possible to carry out an assembly according to the reverse configuration in which the AME 5 is aligned edge to edge with the cathode plate 17.

[0056] There [ Fig.5 ] represents a fuel cell or electrolyzer cell 1 according to another embodiment. The difference compared to cell 1 of the [ Fig.4 ] is that in this embodiment, the anode plate 16 is produced by molding. The peripheral end of the anode plate 16 comprises a first draft angle. In the example of the [ Fig.5 ], the draft angle is located in the thickness of the plate.

[0057] The cathode plate 17 is also produced by molding. The peripheral end of the cathode plate 17 comprises a second draft angle. The second draft angle is located in the plane in which the cathode plate 17 lies.

[0058] In the example of the [ Fig.5 ], the shoulder includes at least one obtuse angle, due to the clearance angles. In the example considered, the shoulder includes an angle between 92° and 100°.

Claims

1. Bipolar plate (6, 7) for a fuel cell stack or for an electrolyser stack, the bipolar plate (6, 7) having an anode plate (16) and a cathode plate (17) which are joined to one another face-to-face, the face of the anode plate (16) that faces the face of the cathode plate (17) delimiting an internal space that forms a circuit for the distribution of a first fluid, the anode plate (16) having a first opening, the cathode plate (17) having a second opening, the first opening and the second opening facing one another so as to form a collector (18) for enabling the passage of the first fluid or a second fluid through the bipolar plate (6, 7), the first opening and the second opening having distinct dimensions such that at least part of the peripheral end of the first opening and at least part of the peripheral end of the second opening are offset in relation to one another in the plane of the bipolar plate (6, 7), forming a shoulder at the peripheral end of the collector (18).

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

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

4. Bipolar plate (6, 7) according to one of the preceding claims, having 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 including an outer edge of the bipolar plate (6, 7).

5. Bipolar plate (6, 7) according to one of the preceding claims, the shoulder extending over at least 90% of the perimeter of the peripheral end of the collector (18).

6. Bipolar plate (6, 7) according to one of the preceding claims, the anode plate (16) and the cathode plate (17) having distinct dimensions such that at least part of the peripheral end of the anode plate (16) and at least part of the peripheral end of the cathode plate (17) are offset in relation to one another in the plane of the bipolar plate (6, 7), forming a second shoulder at a peripheral end of the bipolar plate (6, 7).

7. Cell (1) for a fuel cell stack or an electrolyser, having two bipolar plates (6, 7) according to any one of the preceding claims, wherein the bipolar plates (6, 7) sandwich a membrane electrode assembly (5).

8. Cell (1) according to the preceding claim, the membrane electrode assembly (5) having a third opening intended to face the first and second openings, the membrane electrode assembly (5) having dimensions which make it possible to align the peripheral end of the third opening and the peripheral end of that one of the first opening and the second opening that is closest to the centre of the third opening, at the shoulder.

9. Cell (1) according to either of Claims 7 and 8, the bipolar plate (6, 7) having a portion of the peripheral end of the collector (18) which does not have a shoulder, the membrane electrode assembly (5) projecting from the peripheral end of the collector (18) in this portion by protruding beyond the bipolar plate (6, 7) in the direction of the plane of the bipolar plate (6, 7).

10. Fuel cell stack or electrolyser, notably with a proton exchange membrane, having a stack of cells (1) according to one of Claims 7 to 9.