Fuel cell with compression device

Abstract

The invention relates to a fuel cell comprising a body (1) produced in the form of a stack of plates (P0, P1, P2), comprising several cells and a first end plate (P1) and a second end plate (P2) applied on either side of the cells, and a compression device arranged to compress the cells stacked between the two end plates, characterized in that said compression device comprises at least one link (2) formed of a loop of flexible material wound around said stack, said loop comprising an intermediate portion (20) composed of two strands (200, 201) and two end portions, forming a first attachment elbow (21) and a second attachment elbow (22) and in that the first end plate (P1) comprises a first attachment member on which said first attachment elbow (21) is attached and a second attachment member on which said second attachment elbow (22) is attached.Figure to be published with the abstract: Figure 3B.

Description

Title of the invention: Fuel cell equipped with a compression device Technical field of the invention

[0001] The present invention relates to a fuel cell provided with a compression device. State of the art

[0002] A fuel cell consists of a stack of plates forming a "stack", comprising several cells connected in series and / or parallel and two terminal plates applied on either side of the cells.

[0003] The cell of a fuel cell is a generator in which the production of electricity is done by the oxidation on one electrode (anode) of a reducing fuel, for example dihydrogen, coupled with the reduction on the other electrode (cathode) of an oxidant, such as dioxygen from the air. The hydrogen oxidation reaction is accelerated by a catalyst which is generally platinum. If other combinations are possible, the most commonly studied and used cell is the dihydrogen-dioxygen or dihydrogen-air cell (this is explained in particular by the abundance of hydrogen resources on Earth and the ease of production of dihydrogen).

[0004] Each cell is composed of a pair of plates, called bipolar plates, and a membrane interposed between the two plates. The cells are stacked to form a fuel cell of the desired capacity.

[0005] The electrical potential of a pair of bipolar plates is typically between 0.6 V and 1.2 V for a battery in normal operation.

[0006] The best known and most commonly used fuel cell is the PEM (Polymer Exchange Membrane) type. It operates with hydrogen and transforms the chemical energy released by the reaction between hydrogen (H2) and oxygen (O2) into electrical energy (electrons e-), thus forming water molecules (H2O).

[0007] For the assembly and operation of a PEM type fuel cell, it is necessary to maintain the stack of plates in position and under certain constraints. The multitude of materials and fluids used generate significant differential expansions due to thermal and hygrometric variations. The use of seals between each plate, and between the plates and the membranes, ensures the sealing of the stack.

[0008] This sealing is ensured by a homogeneous compression of the stack.

[0009] To compress the stack and ensure the sealing of the assembly, it is known to use a compression device. Different solutions have already been proposed in the state of the art. Patent application US2011 / 244355A1 describes, for example, the use of a metal cover enclosing the stack. Patent application CN214378524 describes the use of metal strips extending laterally over the height of the stack and being fixed to the two end plates. Patent US8257879B2 describes the use of several straps supplemented by metal plates.

[0010] Previous solutions are often bulky, heavy and not always easy to install, requiring tools. The compression level is not always easily adjustable.

[0011] The aim of the invention is to propose a fuel cell equipped with a compression device which is: - Easy to install; - Reliable to achieve suitable stack compression; - High mechanical resistance to withstand any deformation; - Slightly degradable over time; - Advantageously electrically insulating; - Space-saving, with respect to the exterior of the battery, and also allowing fluid circuits to be fitted on the terminal plates; Statement of the invention

[0012] According to a first embodiment, this aim is achieved by a fuel cell comprising a body produced in the form of a stack of plates in a stacking direction, comprising several cells and a first end plate and a second end plate applied on either side of the cells, and a compression device arranged to compress the cells stacked between the two end plates, said compression device comprising at least one link formed from a loop of flexible material wound around said stack, said loop comprising an intermediate portion composed of two strands and two end portions, forming a first attachment bend and a second attachment bend, the first end plate comprising a first attachment member on which said first attachment bend is attached and a second attachment member on which said second attachment bend is attached.

[0013] According to one embodiment, the first attachment member and the second attachment member are each formed from a groove made in the first end plate.

[0014] According to another embodiment, the first attachment member and the second attachment member produced on the first end plate are each formed from a recess completed by a removable locking insert.

[0015] According to a particular feature of this first embodiment, the second terminal plate comprises at least two grooves arranged in parallel, receiving the two strands of the intermediate portion.

[0016] According to another feature of this first embodiment, said at least one link is made of a textile, metallic or composite material.

[0017] According to another feature of this first embodiment, said at least one link has a circular cross-section.

[0018] According to another feature of this first embodiment, the cells are of the PEMFC type.

[0019] The invention also relates to a method of mounting the fuel cell according to this first embodiment, the compression of the fuel cell being implemented works in: - Imposing an initial compression stress on the fuel cell in the stacking direction so that the distance between the first attachment member and the second attachment member is less than or equal to the total length of the link between the first attachment elbow and the second attachment elbow, - Positioning the first attachment elbow in the first attachment member, - Positioning the second attachment elbow in the second attachment member, - Removing the initial compressive stress, the link extending by its intermediate portion around the stack of plates to maintain by the link the compression of the fuel cell in the direction of the stack.

[0020] According to a second embodiment, the object of the invention is also achieved by a fuel cell comprising a body produced in the form of a stack of plates in a stacking direction, comprising several cells and a first end plate and a second end plate applied on either side of the cells, and a compression device arranged to compress the cells stacked between the two end plates, said compression device comprising at least two links each formed from a loop of flexible material each positioned on either side of the stack, each loop comprising an intermediate portion composed of two strands and two end portions, forming a first attachment elbow and a second attachment elbow,the first end plate comprising a first attachment member on which said first attachment elbow of the first link is attached and a second attachment member on which said first attachment elbow of the second link is attached and the second end plate comprising a first attachment member on which the second attachment elbow of the first link is attached and a second attachment member on which, comes to hook the second attachment elbow of the second link.

[0021] According to one embodiment, the first attachment member and the second attachment member produced on the one hand on the first end plate and on the other hand on the second end plate are each formed from a groove hollowed out in the plate.

[0022] According to another embodiment, the first attachment member and the second attachment member produced on the one hand on the first end plate and on the other hand on the second end plate are each formed from a recess completed by a removable locking insert.

[0023] According to a particular feature of this second embodiment, each link is made from a textile, metallic or composite material.

[0024] According to another feature, each link has a circular cross-section.

[0025] According to another particularity, the cells are of the PEMFC type.

[0026] The invention also relates to a method for mounting a fuel cell of this second embodiment, the compression of the cell being implemented by: - ​​Imposing an initial compressive stress on the cell in the stacking direction so that the distance between the first attachment member of the first end plate and the first attachment member of the second end plate is less than or equal to the total length between the first attachment bend and the second attachment bend of the first link, and that the distance between the second attachment member of the first end plate and the second attachment member of the second end plate is less than or equal to the total length between the first attachment bend and the second attachment bend of the second link, - Positioning the first attachment elbow of the first link in the first attachment member of the first end plate and the first attachment elbow of the second link in the second attachment member of the first end plate, - Positioning the second attachment elbow of the first link in the first attachment member of the second end plate and the second attachment elbow of the second link in the second attachment member of the second end plate, - Removing the initial compressive stress, each link extending by its intermediate portion, between its two attachment members, along a surface of the stack of plates to maintain the compression of the fuel cell by said two links in the direction of the stack. Brief description of the figures

[0027] Other features and advantages will become apparent in the detailed description which following is made with regard to the attached drawings in which: - [Fig.l] schematically represents a fuel cell composed of a stack of several cells; - [Fig.2] schematically represents a cell of a fuel cell and illustrates its operating principle; - Figures 3A and 3B represent the body of the fuel cell receiving a compression device, according to a preferred variant of the invention; - Figures 4A and 4B represent, according to an alternative embodiment, the body of the fuel cell receiving its compression device; - Figures 5A and 5B represent, according to another variant embodiment, the body of the fuel cell receiving its compression device; - Figures 6A and 6B show, according to another variant embodiment, the body of the fuel cell receiving its compression device; - Figures 7A to 7F illustrate the different stages of mounting the compression device on the fuel cell, according to the variant of Figures 3A and 3B;

[0028] Detailed description of at least one embodiment

[0029] [Fig.l] represents a stack of several cells between two terminal plates PI, P2, forming the body 1 of a fuel cell, and intended for supplying an electrical load C.

[0030] As an example, the fuel cell shown is of the PEMFC type (for "Polymer Exchange Membrane Fuel Cells"). It operates with hydrogen and transforms the chemical energy, released by the reaction between hydrogen (H2) and oxygen (O2), into electrical energy (electrons e-), thus forming water molecules (H2O). The cells are connected in series between a first terminal B1 (its anode) and a second terminal B2 (its cathode). The stack can comprise N cells, with N greater than or equal to 2. Each cell can be referenced with a rank i, with i ranging from 1 to N. In [Fig.l], the fuel cell comprises three cells Cell_l, Cell_2, Cell_3 connected in series.

[0031] For the remainder of the description, a designated axis (A) is defined corresponding to the axis along which the plates and therefore cells of the stack are stacked. The terms "upper", "lower", "above", "below" or equivalent are defined along this vertical axis (A) and directed upwards.

[0032] With reference to [Fig.2], in a known manner, a cell used in a stack assembly of a fuel cell conventionally comprises: - Bipolar plates (not shown in [Fig.2]): Their purpose is to allow the reagents to be transported to the diffusion layers (see below). It is therefore necessary that they be im permeable to prevent any leakage of gases to the outside and to adjacent compartments. They must also act as a current collector to the external circuit or to the neighboring cell in the case of a stack of several cells (a stack called a "stack") and allow the heat generated by the reaction to escape. Finally, they also provide the mechanical support for the cell. They are, most of the time, made of graphite, composite materials or metal (such as stainless steel, aluminum, titanium or nickel). - Diffusion layers 10a, 10b: These are called GDL in English for "Gas Diffusion Layer". They have several objectives to fulfill: they must be permeable to gases and therefore porous in order to bring the reactants from the channels to the electrodes, they also ensure the conduction of electrons and heat. They are generally made of carbon fibers in the form of paper or woven together. - The Membrane Electrode Assembly (MEA): This assembly includes a first active layer called the anode A, which allows the dissociation of the dihydrogen molecule H2 into electrons and protons. The generated electrons then go to the diffusion layer 10a while the protons cross the membrane 11 to join the oxygen O2 and other electrons coming from the external circuit. These three elements combine at the level of the second active layer, the cathode C, to form water H2O. Thus, the role of the MEA is to catalyze chemical reactions at the electrodes and to be a good ionic conductor at the membrane. The main materials used in the design of MEAs are first of all sulfonated perfluorinated polymers, such as Nafion (registered trademark), which form the membrane with a thin thickness ranging from 10 to 100 μm depending on the applications.The electrodes are composed mainly of Platinum for the catalyst, carbon serving as a support for the catalyst, and a polymer facilitating proton percolation within the electrode.

[0033] In a non-limiting manner, the body 1 of a fuel cell is therefore formed from a stack of plates, delimiting cells, as described above in connection with [Fig.l].

[0034] With reference to the attached figures, the body 1 of the fuel cell may have a right prism-type shape, for example parallelepiped. The upper end plate PI defines the upper face of the body 1 of the cell and the lower end plate P2 defines the lower face of the body 1 of the fuel cell. The body 1 of the fuel cell comprises several lateral faces, for example four faces lateral, opposite two by two. The lateral faces are oriented parallel to the axis (A) of the stack. The upper end plate PI and the lower end plate P2 each have a so-called external face oriented outwards and a so-called internal face oriented inwards. The intermediate plates PO of the fuel cell cells are stacked, the joints between the PO plates, and between the PO plates and the membranes, being intended to be compressed by exerting pressure against the two end plates PI, P2, using the compression device. As such, the end plates PI and P2 generally have greater mechanical rigidity than the intermediate PO plates.

[0035] The invention aims in fact to provide the body 1 of the fuel cell with a compression device, making it possible to compress the seals of the cells along the axis (A) of the stack in order to both ensure the sealing of the assembly and gain in compactness.

[0036] The compression device uses at least one tie 2 or strap, formed from a loop of flexible material, said loop comprising an intermediate portion 20 composed of two strands 200, 201 and two end portions, forming a first attachment elbow 21 and a second attachment elbow 22.

[0037] We then distinguish two main possible configurations.

[0038] In a first configuration illustrated by [Fig.3A] and [Fig.3B], a link 2 is used which is attached by its first attachment bend 21 to the first terminal plate PI and by its second attachment bend 22 to this same first terminal plate, after having surrounded the stack of plates of the body 1 of the fuel cell, along a first lateral face, the lower face and a second lateral face, opposite the first lateral face. Each attachment point of the link 2 is made on the external face of the first terminal plate PL

[0039] In a second configuration illustrated by [Fig.4A] and [Fig.4B], at least two links 2_1, 2_2 are used, attached on either side along two opposite lateral faces of the stack (four links are shown in FIGS. 4A and 4B). The first link 2_1 is attached, by its first attachment elbow 21_1 to the first end plate PI and by its second attachment elbow 22_1 to the second end plate P2, running along its intermediate portion 20_1 along a first lateral face of the stack. The second link 2_2 is attached, by its first attachment elbow 21_2 to the first end plate PI and by its second attachment elbow 22_2 to the second end plate P2, running along its intermediate portion 20_2 along a second lateral face of the stack, opposite the first lateral face. Each attachment point is made on the external face of each terminal plate PI, P2.

[0040] The first configuration of Figures 3A and 3B can be declined by multiplying the number of links used. Depending on the size of the body 1 of the fuel cell, it may be useful to use several links in parallel to ensure uniform compression. and well distributed throughout the body 1 of the fuel cell. In [Fig.5A] and [Fig.5B], for example, two links 2_1, 2_2 are used in parallel, each arranged according to the first configuration described above.

[0041] In Figures 4A and 4B, four links are shown, but two links would be sufficient, arranged along two opposite lateral faces of the body 1 of the fuel cell.

[0042] Similarly, it is possible to multiply the number of links used in the second configuration, to take into account the size of the body 1 of the fuel cell and the distribution of the tightening.

[0043] To attach each attachment elbow of a link to the terminal plate PI, P2, the body 1 of the fuel cell has a attachment member.

[0044] According to a first particular embodiment used in the embodiments of Figures 3A to 5B, the attachment member is made in the form of a groove 3 hollowed out on the external face of the end plate on which the link is attached. The link is placed in the groove 3, via its attachment elbow. The groove 3 may have a U shape to form a guide for the link. It may extend to the edge of the plate so as to house the entire attachment elbow of the link and guide it. In the embodiments of Figures 3A to 5B, the link is positioned in the groove 3 by taking advantage of the elastic compressibility of the stack according to (A), a combination of the elastic compressibility of the joint system and the elastic compressibility of certain layers of the stack such as, for example, bipolar plates made of stamped thin sheets.

[0045] According to a second particular embodiment illustrated by [Fig.6A] and [Fig.6B], the attachment member can be produced by a recess 30 produced on the external face of the terminal plate, close to the edge, completed by a removable locking insert 31. The shape of the insert can be chosen to adjust the level of compression produced by the link when it is attached by its two ends. Each insert is fixed in a removable manner to the plate, via fixing means such as rivets, screws or equivalent.

[0046] Depending on the configuration chosen, the terminal plate PI, P2 may have one or more attachment members produced according to the first embodiment and / or the second embodiment.

[0047] In the case of the first configuration described above in connection with Figures 3A and 3B, the second end plate P2 advantageously does not include any attachment member. However, it may include grooves 32, advantageously parallel, to accommodate the two strands of the intermediate portion of each link, and thus guide the strands along the second end plate. This feature is visible in [Fig.7F] described below.

[0048] The principle of positioning the link 2 on the body 1 of the fuel cell is described below in connection with FIGS. 7 A to 7F.

[0049] [Fig.7A] shows the body 1 of the fuel cell intended to receive its compression link 2. The body 1 of the cell is not yet compressed.

[0050] [Fig.7B] shows the two strands of the intermediate portion of the link placed in the two grooves of the lower end plate. The body of the battery is not yet compressed.

[0051] [Fig.7C] shows the body 1 of the compressed fuel cell, awaiting attachment of the link to the two attachment members of the upper end plate.

[0052] [Fig.7D] shows the link attached, by its two attachment elbows, to each attachment member present on the upper end plate, compressing the plates of the body of the fuel cell.

[0053] [Fig.7E] shows the body of the fuel cell, in side view, compressed by the link of the compression device in place on the body 1 of the cell.

[0054] [Fig.7F] shows the body of the fuel cell, lower side, and illustrates the passage of the two strands of the intermediate portion in the two grooves made on the lower face of the lower end plate P2.

[0055] In a non-limiting manner: - Each link is for example made from a textile, metallic or composite material. - Each link has, for example, a circular cross-section.

[0056] Of course, it should be noted that the length of each link must be adapted to allow compression of the pile. In other words, the total length of the link between its two attachment elbows must advantageously be less than the distance between its two attachment members when the pile is not compressed.

[0057] The solution of the invention thus takes advantage of the elastic compressibility of the fuel cell.

[0058] The solution of the invention makes it possible in particular to easily obtain the so-called nominal compression, that is to say the minimum level of compression to obtain the sealing of the fuel cell.

[0059] It should be noted that it is entirely possible to adapt the diameter of the section of the link and therefore the size of the attachment groove in the plate.

[0060] The invention has numerous advantages, including: - A simple solution for compressing a fuel cell; - An easy-to-install solution, requiring at least one link; - A solution that allows you to obtain a suitable level of compression, by adjusting the size of the link or by using an insert hook;

Claims

Claims

1. Fuel cell comprising a body (1) produced in the form of a stack of plates (PO, PI, P2) in a stacking direction (A), comprising several cells and a first end plate (PI) and a second end plate (P2) applied on either side of the cells, and a compression device arranged to compress the cells stacked between the two end plates, characterized in that said compression device comprises at least one link (2) formed of a loop of flexible material wound around said stack, said loop comprising an intermediate portion (20) composed of two strands (200, 201) and two end portions,forming a first attachment elbow (21) and a second attachment elbow (22) and in that the first end plate (PI) comprises a first attachment member on which said first attachment elbow (21) is attached and a second attachment member on which said second attachment elbow (22) is attached.,

2. Fuel cell according to claim 1, characterized in that the first attachment member and the second attachment member are each formed from a groove (3) made in the first end plate.

3. Fuel cell according to claim 1, characterized in that the first attachment member and the second attachment member produced on the first end plate are each formed from a recess (30) completed by a removable locking insert (31).

4. Fuel cell according to one of claims 1 to 3, characterized in that the second end plate comprises at least two grooves (32) arranged in parallel, receiving the two strands (200, 201) of the intermediate portion (20).

5. Fuel cell according to one of claims 1 to 4, characterized in that said at least one link (2) is made of a textile, metallic or composite material.

6. Fuel cell according to one of claims 1 to 5, characterized in that said at least one link has a circular cross section.

7. Fuel cell according to one of claims 1 to 6, characterized in that the cells are of the PEMFC type.

8. Method for mounting a fuel cell as defined in one of claims 1 to 7, characterized in that the compression of the fuel cell is implemented by: - Imposing an initial compressive stress on the fuel cell in the stacking direction (A) so that the distance between the first attachment member and the second attachment member is less than or equal to the total length of the link between the first attachment elbow and the second attachment elbow, - Positioning the first attachment elbow (21) in the first attachment member, - Positioning the second attachment elbow (22) in the second attachment member, - Removing the initial compressive stress, the link extending by its intermediate portion (20) around the stack of plates to maintain by the link the compression of the fuel cell in the stacking direction.

9. Fuel cell comprising a body (1) produced in the form of a stack of plates in a stacking direction (A), comprising several cells and a first end plate (PI) and a second end plate (P2) applied on either side of the cells, and a compression device arranged to compress the cells stacked between the two end plates, characterized in that said compression device comprises at least two links (2_1, 2_2) each formed from a loop of flexible material each positioned on either side of the stack, each loop comprising an intermediate portion composed of two strands and two end portions, forming a first attachment elbow (21_1, 21_2) and a second attachment elbow (22_1,22_2) and in that the first end plate (PI) comprises a first attachment member on which said first attachment elbow (21_1) of the first link is attached and a second attachment member on which said first attachment elbow (21_2) of the second link is attached and in that the second end plate (P2) comprises a first attachment member on which the second attachment elbow (22_1) of the first link is attached and a second attachment member on which the second attachment elbow (22_2) of the second link is attached.,

10. Fuel cell according to claim 9, characterized in that the first attachment member and the second attachment member made on the one hand on the first end plate (PI) and on the other hand on the second end plate (P2) are each formed from a groove (3) hollowed out in the plate.

11. Fuel cell according to claim 9, characterized in that the first attachment member and the second attachment member produced on the one hand on the first end plate and on the other hand on the second end plate are each formed of a recess (30) completed by a removable locking insert (31).

12. Fuel cell according to one of claims 9 to 11, characterized in that each link is made of a textile, metallic or composite material.

13. Fuel cell according to one of claims 9 to 12, characterized in that each link has a circular cross section.

14. Fuel cell according to one of claims 9 to 13, characterized in that the cells are of the PEMFC type.

15. Method for mounting a fuel cell as defined in one of claims 9 to 14, characterized in that the compression of the cell is implemented by: - ​​Imposing an initial compressive stress on the cell in the stacking direction (A) so that the distance between the first attachment member of the first end plate (PI) and the first attachment member of the second end plate (P2) is less than or equal to the total length between the first attachment elbow (21_1) and the second attachment elbow (22_1) of the first link, and that the distance between the second attachment member of the first end plate (PI) and the second attachment member of the second end plate (P2) is less than or equal to the total length between the first attachment elbow (21_2) and the second attachment elbow (22_2) of the second link,- Positioning the first attachment elbow (21_1) of the first link in the first attachment member of the first end plate (PI) and the first attachment elbow (21_2) of the second link in the second attachment member of the first end plate (PI), - Positioning the second attachment elbow (22_1) of the first link in the first attachment member of the second plate, terminal (P2) and the second attachment elbow (22_2) of the second link in the second attachment member of the second terminal plate (P2), Removing the initial compressive stress, each link extending by its intermediate portion (20), between its two attachment members, along a surface of the stack of plates to maintain the compression of the fuel cell by said two links in the direction of the stack.

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