Patent Application
20240186536
The present invention relates to a bipolar plate for a fuel cell stack or for an electrolyzer stack, to a cell for a fuel cell stack or electrolyzer having such a plate, and to a fuel cell stack or an electrolyzer having such a cell.
In a manner known per se, a fuel cell stack is an electrochemical device that makes it possible to convert chemical energy into electrical energy using a fuel, generally dihydrogen, and an oxidant, generally dioxygen or a gas containing it, such as air, the product of the reaction being water together with a release of heat and generation of electricity.
An electrolyzer is based on the reverse principle, specifically the input of electrical energy to generate chemical reactions, for example to produce a fuel such as dihydrogen and an oxidant such as oxygen. The following description more particularly concerns the fuel cell stack, but could be applied to the electrolyzer.
A fuel cell stack or an electrolyzer is a stack of multiple cells, each cell having two bipolar plates that sandwich a membrane electrode assembly (MEA). The components of a stack of cells are aligned, when each bipolar plate is being added to the stack, either from the inside, by means of guides disposed in the openings in the bipolar plates (either dedicated openings or by utilizing one or more collectors), or from the outside, by means of at least three guide pins that come into contact with respective edges of the bipolar plate.
The alignment of the components of a stack of several tens of cells or even several hundred cells is tricky. The various components of the stack (notably the bipolar plates and the MEA) can specifically tend to slide on one another, thus causing an aesthetic defect, a loss in performance, a leak and reduced resistance to vibrations. A poor alignment of the bipolar plates and of the MEA can also increase the risk of a short circuit. The risk is all the greater if there is a short distance, even locally, between two points of different potentials and if a conductor element fills this space (metal chips, dust, etc.)
During the manufacture of a fuel cell stack or an electrolyzer, it is therefore necessary to stack bipolar plates correctly, that is to say to align them correctly along the stacking axis.
In certain embodiments, the present invention aims to effectively overcome these drawbacks by proposing a bipolar plate for a fuel cell stack or for an electrolyzer stack, the bipolar plate having an anode plate and a cathode plate which are joined to one another face-to-face, the face of the anode plate that faces the face of the cathode plate delimiting an internal space that forms a circuit for the distribution of a first fluid, the anode plate and the cathode plate having distinct dimensions such that at least part of the peripheral end of the anode plate and at least part of the peripheral end of the cathode plate are offset in relation to one another in the plane of the bipolar plate, forming a shoulder at a peripheral end of the bipolar plate.
Such a configuration makes it possible to ensure proper guidance of the bipolar plates during the manufacture of a stack and to prevent any formation of a short circuit between the anode plates and the cathode plates.
According to one embodiment, the respective dimensions of the anode plate and of the cathode plate are disposed such that, at least over part of the peripheral end of the bipolar plate, the peripheral end of the cathode plate and the peripheral end of the anode plate do not face one another.
According to one embodiment, the shoulder is considered perpendicularly to the plane of the bipolar plate. In other words, the shoulder extends on the edge of the bipolar plate over its thickness.
According to one embodiment, the peripheral end of the anode plate and the peripheral end of the cathode plate each have a straight edge extending perpendicularly to the plane of the bipolar plate.
According to one embodiment, the shoulder forms a step or a crenelation.
According to one embodiment, the bipolar plate has at least one guide zone for guiding the bipolar plate 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.
According to one embodiment, the shoulder extends over at least 90% of the perimeter of the peripheral end of the bipolar plate.
According to one embodiment, the shoulder comprises an obtuse angle, notably of between 92° and 100°.
According to one embodiment, the anode plate has a first opening and the cathode plate has a second opening, the first opening and the second opening facing one another so as to form a collector for allowing 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 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, forming a second shoulder at the peripheral end of the collector.
According to one embodiment, the second shoulder is considered perpendicularly to the plane of the bipolar plate.
According to one embodiment, the first fluid is a cooling fluid.
According to one embodiment, the second fluid is a fuel or an oxidant.
According to one embodiment, the anode plate is produced by molding and at least one of its edges comprises a first rake angle, the first rake angle being separate from the shoulder.
According to one embodiment, the cathode plate is produced by molding and at least one of its edges comprises a second rake angle, the second rake angle being separate from the shoulder.
The invention moreover comprises a cell for a fuel cell stack or an electrolyzer, having two bipolar plates as described above, wherein the bipolar plates sandwich a membrane electrode assembly.
According to one embodiment, the membrane electrode assembly has dimensions which make it possible to align the peripheral end of the membrane electrode assembly and the peripheral end of that one of the anode plate and the cathode plate that is furthest away from the internal space, at the shoulder.
According to one embodiment, the bipolar plate has a portion of the peripheral end which does not have a shoulder, the membrane electrode assembly projecting from the peripheral end of the bipolar plate in this portion by protruding beyond the bipolar plate in the direction of the plane of the bipolar plate.
The invention also relates to a fuel cell stack or electrolyzer, notably with a proton exchange membrane, having a stack of cells as described above.
The invention will be understood better from reading the following description and from studying the accompanying figures. These figures are given only by way of illustration and do not in any way limit the invention.
Those elements which are identical, similar or analogous keep the same reference from one figure to the next.
With reference to
To this end, the electrolyte 2 may be a polymer proton exchange membrane in particular with a thickness of between 5 and 200 μm, the resulting stack being a PEM (for “proton exchange membrane”) or PEMFC (for “proton exchange membrane fuel cell”) stack.
The assembly made up 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 collect current, distribute the oxidant and the fuel to the electrodes 3, 4 and circulate heat transfer fluid.
The bipolar plates 6, 7 that are typically used are made of materials that provide good corrosion resistance and electrical conductivity properties, like carbon-based materials such as graphite, polymer-impregnated graphite or flexible graphite sheets shaped by machining or by molding.
It is also possible, to produce the bipolar plates 6, 7, to use metal materials such as alloys based on titanium, on aluminum and on iron, including stainless steels. In this case, the bipolar plate 6, 7 may be shaped by pressing or stamping sheets of low thickness.
In order to ensure the distribution of the oxidant, the fuel and the heat transfer fluid in all the constituent cells of the stack, the second bipolar plate 7 has six openings 7a-7f.
The first bipolar plate 6 has the same openings disposed in the same places as on the bipolar plate 7, with
The openings 6a-6d in the first bipolar plate 6 and the openings 7a-7f in the second bipolar plate 7 are aligned so as to form collectors ensuring the circulation of fluids through all the constituent cells of the stack.
At each of these openings 7a-7f, 6a-6d, a duct, which is not shown, makes it possible to supply them with 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 the fluid circulation channels provided to that end.
With reference to
The diffusion layer 12, 13 ensures the diffusion of the reactants, such as the dihydrogen and dioxygen which circulate in the respective channels 14, 15 formed by grooves made in the respective bipolar plates 6, 7.
In this way, the active layer 11 of the anode electrode 4 is supplied with dihydrogen via the diffusion layer 13 and the reaction that takes place in this active layer 11 is as follows: H2→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 that takes place in this active layer 10 is as follows: ½ 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.
In a manner known per se, a fuel cell stack or electrolyzer stack has 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.
A fuel cell stack according to the invention has a stack of cells 1 as described above. The cells 1 ensure collection of the current, distribution of the oxidant and the fuel to the electrodes, and circulation of the heat transfer fluid.
With reference to
That face of the anode plate 16 that faces the face of the cathode plate 17 has 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 shoulder at a peripheral end of the bipolar plate 6, 7, the shoulder being considered perpendicularly to the plane of the bipolar plate 6, 7.
In other words, over at least one portion of the end of the bipolar plate 6, 7, the anode plate 16 or the cathode plate 17 protrudes beyond the other.
The shoulder forms a step or crenelation.
The bipolar plate 6, 7 has a 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. The guide zone is thus that portion of the end of the anode plate 16 or of the cathode plate 17 that protrudes beyond the other.
In the example of
In the example of
In the example of
The membrane electrode assembly 5 has dimensions which make it possible to align the peripheral end of the membrane electrode assembly 5 and the peripheral end of that one of the anode plate 16 and the cathode plate 17 that is furthest away from the internal space, at the shoulder. In the example in question, the MEA 5 and the anode plate 16 are aligned edge-to-edge at the shoulder.
As a result, the guide zones, at the shoulder, are realized by those peripheral edges of the anode plates 16 that project beyond the cathode plates 17. It is possible to perform assembly in the reverse configuration, in which the MEA 5 is aligned edge-to-edge with the cathode plate 17.
The cathode plate 17 is also produced by molding. The terminal edge of the second opening in the cathode plate 17 comprises a second rake angle. The second rake angle is located in the plane of the cathode plate 17.
In the example in
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.
“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2103579 | Apr 2021 | FR | national |
This application is a § 371 of International PCT Application PCT/EP2022/055472, filed Mar. 3, 2022, which claims the benefit of FR2103579, filed Apr. 8, 2021, both of which are herein incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/055472 | 4/8/2021 | WO |
