FR3060211A1 - METHOD FOR MANUFACTURING AN ELEMENTARY CELL FOR A FUEL CELL - Google Patents

Abstract

The invention relates to a method for manufacturing a fuel cell elementary cell comprising two identical bipolar plates surrounding an electrode membrane assembly. The invention also relates to a fuel cell elementary cell cutting and breaking machine and a fuel cell assembly line.

Description

Holder (s): COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN Limited partnership with shares, MICHELIN RECHERCHE ET TECHNIQUE S.A. Limited company.

Extension request (s)

Agent (s): MANUF FSE PNEUMATIQUES MICHELIN Limited partnership with shares.

METHOD FOR MANUFACTURING AN ELEMENTARY CELL FOR A FUEL CELL.

The invention relates to a method for manufacturing an elementary cell for a fuel cell comprising two identical bipolar plates surrounding an electrode membrane assembly. The invention also relates to a seal cutting and pause machine for a fuel cell elementary cell and a fuel cell assembly line.

FR 3 060 211 - A1

Field of the Invention The present invention relates to the field of fuel cells, and more particularly to the field of manufacturing and assembly of fuel cells.

A fuel cell allows the generation of electrical energy by an electrochemical reaction from a fuel, generally hydrogen, and an oxidizer, generally oxygen.

A fuel cell of the proton exchange membrane type with solid electrolyte (PEMFC) usually comprises a stack of elementary cells, in the form of plates, constituting electrochemical generators, each of the cells being separated from the adjacent cells by bipolar plates. . Each cell comprises an anode element and a cathode element, separated by a solid electrolyte in the form of an ion exchange membrane, made for example of a perfluorinated sulfurized polymer material. This assembly comprising the cathode element, the anode element and the solid electrolyte forms a membrane-electrode assembly, also called AME.

In addition, these assemblies are regularly supplemented by the addition of reinforcements, as described in document US2008 / 0105354, formed from polymer films, and which prevent the deterioration of MEAs by facilitating the handling of assemblies, or by limiting the dimensional variations of the membrane as a function of temperature and humidity. These reinforcements are generally superimposed on the periphery of the electrodes. In addition, gas diffusion layers are interposed between the electrodes and the bipolar plates.

According to a usual variant, each bipolar plate ensures on one side the supply of fuel to the cell adjacent to this side and on the other side to supply the oxidant to the cell adjacent to this other side, the supplies provided by the bipolar plates being carried out in parallel. Gas diffusion layers, for example made of carbon fabric, are installed on either side of the MEAs to ensure electrical conduction and the homogeneous arrival of the reactive gases supplied via the bipolar plates.

-2 [0006] The successive stacking of the bipolar plates, of the gas diffusion layers and of the MEAs is maintained under support pressures which must guarantee good electrical contact and good sealing. However, maintaining pressure is not enough to guarantee a perfect seal. It is useful to have a seal between the electrode membrane assembly and the bipolar plate, made for example of silicone or EPDM.

Several methods are known for making such a seal, using molding or cutting steps. However, these methods have various drawbacks. Thus, the manufacturing by cutting presents a technical difficulty for the implementation since the joints are flexible elements which it is difficult to hold in place for a precise cutting. Manufacturing by molding, on the other hand, is complex to set up, and requires the use of expensive tools. In addition, manufacturing by molding does not allow a joint to be directly deposited on a reinforcement.

The present invention therefore aims to provide a method of manufacturing a fuel cell to overcome these drawbacks.

BRIEF DESCRIPTION OF THE INVENTION Thus, the invention relates to a method for manufacturing an elementary cell for a fuel cell comprising two identical bipolar plates surrounding a membrane assembly, the method comprising the following steps:

A sheet of a material used for the formation of fuel cell seals is placed on a cutting anvil,

We install two clamps to position the sheet on the cutting anvil, so that the sheet is held on the anvil by adhesion,

- A first cut is made with a tool, the size of which depends on the shape of the bipolar plates of the elementary cell, this first cut aimed at defining the internal shape of the joint,

-3 We eliminate the waste from the first cut while keeping the joint in place thanks to the pliers and adhesion,

We install a membrane-electrode assembly on the joint,

A second cutting is carried out with a tool making it possible to define the external shape of the joint,

The waste from the second cutting is eliminated.

During the first cutting phase, the sheet of material intended to form the seal is held by adhesion to the cutting tool itself. In fact, this first cutting phase aims to perform the central, or internal, cutting of the joint, which allows the shapes corresponding to the active surface of an elementary cell, and the supply orifices of the fuel cell to be released. Thus, during this phase, the periphery of the seal is absolutely not impacted, and it is therefore possible to keep the seal in place by pressing on this periphery, for example in positioning, on the cutting tool, foams allowing apply holding pressure without damaging the seal. This cutting tool will be described later using figures.

However, in the second cutting phase, which aims to cut the periphery of the joint, the holding by the cutting tool is no longer possible, and the joint is then held in place thanks to the membrane assembly -electrode installed between the two cutting phases. These advantages will be illustrated below using figures showing the different stages of the process;

In a preferred embodiment, the material used for the formation of seals is silicone in the form of a sheet having a smooth and non-talc surface, allowing adhesion to the membrane-electrode assembly.

In order to meet the constraints of the manufacturing process, the silicone must have sufficient adhesion so that the seal remains in place during the various stages. Thus, preferably, the silicone has an adhesion between 0.0010 N / mm ² and 0.020N / mm ² .

[0014]

To measure this adhesion, the following method is used:

-4 A silicone disc is glued on a turned part, allowing the hanging of a weight,

The turned part is then applied to a glass plate, the silicone being in contact with the glass, with a force of 60 N.,

We hang a weight and determine what load is bearable by the silicone without the part coming off. We will determine that a load is "bearable" when the part remains at least 10 seconds without picking up under the effect of this load,

When the maximum bearable load has been determined, this load is converted into a force expressed in Newton, using the known formula force = mass x g where g is the finding of gravitation,

- We then divide this force by the surface of the disc, to obtain the adhesion of the silicone.

According to the embodiments, a method according to the invention can also comprise one or the other of the following characteristics, considered alone or in combination:

the two clamps used to position the sheet include a fixed clamp and a movable clamp.

which the step of eliminating the waste of the second cut includes the step of moving the movable clamp by taking away the external waste from the joint.

the silicone is initially sandwiched between two spacers, and the method comprises a prior step of separation of the silicone and the spacers.

- the membrane-electrode assembly comprises a face bearing a seal, and in which the membrane-electrode assembly is positioned so that the free face is installed in contact with the new seal.

The invention also relates to a seal cutting and pausing machine for an elementary fuel cell cell comprising two identical bipolar plates surrounding an electrode membrane assembly, the material intended to form the seal being presented between two spacers, the whole in the form of a roll, the machine comprising:

-5 An unrolling and separation station for the material forming the joint and spacers,

Means for positioning the material unrolled on a cutting anvil,

Means for securing the material with the cutting anvil,

A cutting tool with a predetermined template depending on the format of the bipolar plate for the central cutting of the joint,

Means for ejecting waste after cutting

Means for installing a membrane-electrode assembly on the cut joint and holding it in place and

A cutting tool for the peripheral cutting of the joint.

In a particular embodiment, the cutting anvil has a mixed upper surface, comprising a finely sanded inner part and a polished outer part.

The finely sanded interior part corresponds to the interior cuts of the joint during the first cutting phase. In fact, fine sanding makes it possible to reduce the adhesion of this surface, and therefore makes it possible to ensure that the parts which must be removed at the end of the first cutting phase do not adhere to the cutting anvil . On the other hand, the polished part is used so that the periphery of the joint, not cut during the first cutting phase, adheres to the anvil, and therefore allow the joint to be held in position when the cutting tool is withdrawn. the outcome of the first cutting phase.

The invention also relates to a machine comprising two cutting and parallel manufacturing lines:

A first line on which we cut a first joint, and we install a membrane-electrode assembly on it,

A second line on which a second seal is cut, and a membrane-electrode assembly from the first production line is installed.

Advantageously, such a machine further comprises a transfer element making it possible to recover the membrane-electrode assembly at the outlet of the first line, and to turn it over before positioning it in the second machine.

BRIEF DESCRIPTION OF THE FIGURES Other objectives and advantages of the invention will appear clearly in the description which follows of a preferred but nonlimiting embodiment, illustrated by the following figures in which:

• Figure 1 shows a partial view of a machine according to the invention, • Figure 2 shows a cutting tool implemented in a machine according to the invention, • Figures 3 to 7 illustrate the different steps of a method according to the invention.

DESCRIPTION OF THE BEST MODE FOR CARRYING OUT THE INVENTION On the machine shown in FIG. 1, there is seen a first station for unwinding a roll 1 comprising silicone inserted between two spacers. This station includes three sets of rollers allowing the simultaneous unwinding, and therefore the separation, of the three products, namely the silicone and the two spacers.

Thus, the rollers 2 and 3 allow the evacuation of the upper and lower tabs, when the roller 4 allows the silicone to be evacuated in the direction of the next machine station.

The next station is the cutting station itself. This station includes a cutting tool 10, shown in Figure 2, and a cutting anvil 11. The cutting anvil has a mixed surface previously described. The station also includes ejectors for removing waste after cutting, and a vacuum tray for transporting and positioning a membrane-electrode assembly.

-7 This station includes different actuators for setting in motion the different elements involved in the manufacturing process:

Two clamp cylinders allow you to catch the silicone from the unwinding station to position it correctly at the cutting anvil,

- A cutting cylinder, allowing the cutting tool to be moved in vertical translation,

An ejection cylinder, allowing the ejectors to be moved in vertical translation.

U ’cutting tool 10 has a template suitable for cutting that one wishes to do depending on the shape of the bipolar plate used in the elementary cell intended to accommodate the membrane-electrode assembly. Indeed, a fuel cell seal must leave free the active surfaces of the cell and the various gas circulation orifices, while providing a seal between the various gas circuits, so that the fuel and the oxidant do not enter contact elsewhere than at the ion exchange membrane, seat of the electrochemical reaction.

Thus, on the cutting tool shown in Figure 2, we can clearly see a central part 20, corresponds to the active surfaces of the stack, and peripheral parts 21, 22, 23, 24, 25, 26, corresponding to the gas supply ports. The fine lines appearing in the figure around each of these parts are actually knives cutting the interior parts of the joint.

Similarly, the lateral lines 27 and 28 are the knives performing the cutting of the periphery of the joint.

Ues different stages of cutting will now be described using Figures 3 to 7.

When the silicone arrives in the cutting station, it is installed on the cutting anvil 11, and it is fixed by a fixed clamp 30 and a movable clamp 31. The cutting tool is then lowered, to come cut the joint according to the pattern shown in figure 3.

An ejector is then lowered vertically to eject the waste from this first cutting phase. The joint then has the form shown in FIG. 4.

-8 Then an electrode membrane assembly 32 is installed on the joint, as shown in Figure 5. Advantageously, for this installation step, the membrane is held on one arm by a vacuum plate which also includes side knives intended to finish the peripheral cutting of the joint.

After lowering this plate, the periphery of the joint is cut according to the pattern shown in FIG. 6.

The last step of eliminating peripheral waste 33 is carried out by a horizontal translation of the movable clamp.

Thus, at the end of this last step, there is a membrane10 electrode assembly carrying a seal on one of these faces. In one embodiment of the invention, this assembly is then turned over and transferred by a manipulation arm towards a second machine, in order to allow the affixing of a seal on the second face of the membrane electrode assembly. .

Claims (5)

E Method for manufacturing an elementary cell for a fuel cell comprising two identical bipolar plates surrounding an electrode membrane assembly, the method comprising the following steps: A sheet of a material used for the formation of fuel cell seals is placed on a cutting anvil, We install two clamps to position the sheet on the cutting anvil, so that the sheet is held on the anvil by adhesion, A first cut is made with a tool, the size of which depends on the shape of the bipolar plates of the elementary cell, this first cut aiming to delimit the internal shape of the joint, We eliminate the waste from the first cut while keeping the joint in place thanks to the pliers and adhesion, We install a membrane-electrode assembly on the joint, A second cutting is carried out with a tool making it possible to define the external shape of the joint, The waste from the second cutting is eliminated. 2. The manufacturing method according to claim 1, wherein the two clamps used to secure the sheet comprise a fixed clamp and a movable clamp. 3. The manufacturing method according to claim 2, wherein the step of eliminating the waste of the second cut comprises the step of moving the movable clamp by taking away the external waste from the joint. 4. The manufacturing method according to one of the preceding claims, wherein the material used for the formation of joints is silicone in the form of a sheet having a smooth and non-talc surface, allowing adhesion to the membrane-electrode assembly. -25. Manufacturing process according to one of the preceding claims, in which the silicone is initially sandwiched between two spacers, the process comprising a prior step of separation of the silicone and the spacers. 6. The manufacturing method as claimed in claim 1, in which the membrane-electrode assembly comprises a face bearing a seal, and in which the membrane-electrode assembly is positioned so that the free face is installed at the contact of the new seal. 7. Joint cutting and pause machine for an elementary fuel cell cell comprising two identical bipolar plates surrounding an electrode membrane assembly, the material intended to form the joint being presented between two spacers, all in the form of a roll, the machine including: A station for unwinding and separating the material forming the joint and the spacers, Means for positioning the material unrolled on a cutting anvil, Means for securing the material with the cutting anvil, A cutting tool with a predetermined template depending on the format of the bipolar plate for the central cutting of the joint, Means for ejecting waste after cutting Means for installing a membrane-electrode assembly on the cut joint and holding it in place and A cutting tool for the peripheral cutting of the joint. 8. Machine according to claim 7, wherein the cutting anvil has a mixed upper surface, comprising a finely sanded inner part and a polished outer part. -39. Fuel cell assembly line comprising a first machine according to one of claims 7 and 8 for depositing a seal on a first face of a membrane-electrode assembly, means for turning the membrane-electrode assembly at the leaving the 5 first machine, and a second machine according to one of claims 7 and 8 for depositing a seal on the second face of the membrane-electrode assembly. 1/3