Fuel cell assembly and method of manufacturing such an assembly

Abstract

Fuel cell assembly and method for manufacturing such an assembly Fuel cell assembly, comprising a stack comprising a first gas diffusion layer (2); first and second reinforcements (4, 5); and a second gas diffusion layer (3); the first and second gas diffusion layers (2, 3) respectively having two first and second faces turned respectively towards the first and second reinforcements (4, 5); the first and second faces respectively having first and second zones; the first zone is fixed on the first reinforcement (4), the fixing having a first weld with fusion of the first zone with the first reinforcement (4), without fusion of the first reinforcement (4); and the second zone is fixed on the second reinforcement (5), the fixing having a second weld with fusion of the second zone with the second reinforcement (5), without fusion of the second reinforcement (5).Figure for abstract: Fig.1.

Description

Title of the invention: Fuel cell assembly and method of manufacturing such an assembly Technical field

[0001] The present invention relates to fuel cell assemblies, in particular to cells comprising fuel cells using proton exchange membranes, and more particularly to the manner of assembling the various components of the fuel cell assemblies. STATE OF THE ART

[0002] Generally speaking, fuel cells using proton exchange membranes, called PEMFC (which corresponds to the acronym for "Proton Exchange Membrane Fuel Cell" in English), comprise a membrane electrode assembly, called AME. An AME contains different components, such as a membrane, two electrodes and two gas diffusion layers, called GDL (which corresponds to the acronym for "Gas Diffusion Layer" in English). The assembly comprising the membrane and the two electrodes is called the electrode-membrane assembly, or CCM (which corresponds to the acronym for "Catalyst Coated Membrane" in English, i.e. a membrane coated with a catalyst on either side of it). Some AMEs comprise reinforcements located on either side of the CCM.In this case, the MEAs are called 7-layer, because they include a membrane, an anode electrode and a cathode electrode on either side of the membrane, a reinforcement on either side of the CCM (formed by the membrane and the two electrodes), and a GDL on either side of the reinforcement and the CCM. A reinforcement is used to stiffen the MEA, it can be made of plastic material.

[0003] The components of an AME can be assembled by a bonding step. For example, the reinforcements are bonded to the edges of the CCM and the GDLs are bonded to the CCM and the edge of the reinforcements. But the bonding step is long (for example, more than a minute), and requires the materials of the components to be heated by an external temperature input with the addition of a bonding material at room temperature or at a temperature higher than room temperature. The bonding step is also generally associated with a constraint, i.e. hot pressing of the GDLs onto the CCM and the edge of the reinforcements. But to carry out the hot pressing step, a press and molds or templates must be used to position the components. This involves: an external temperature input (from 130°C to 160°C and more); a long time for pressing (from 1 minute to more); and to maintain the components of the AME under the temperature between 130°C and 160°C or more, and under stress. Furthermore, to assemble the GDLs, it is necessary to add a glue or adhesive system to hold the GDL on the reinforcement, this involves adding an additional material that bonds the GDLs with the reinforcements. Furthermore, the positioning of the different components must be very precise. In addition, hot pressing extends over the entire surface of the FAME components, which can damage the CCM.

[0004] For example, patent application US2009169946 discloses a method for manufacturing an AME, comprising the use of a thermoplastic polymer film between the GDL and an electrode placed in contact with a membrane. All of the components are compressed between a holding device and an anvil, and the components are heated by ultrasonic vibrations to melt the thermoplastic polymer film so that the polymer film impregnates the GDL layer and the electrode. However, the resulting FAME is not sufficiently rigid for prior storage before being assembled with bipolar plates to form a fuel cell.

[0005] Also citeable is patent application DE102005058370, which discloses a method using a support frame assembled to a CCM via roller conveyors. The method comprises ultrasonic welding of the support frame to the CCM and ultrasonic welding of the GDL to the CCM. But ultrasonic welding of the GDL to the CCM can damage the CCM and decreases the durability of FAME.

[0006] An object of the present invention is therefore to propose means for overcoming the drawbacks mentioned above, and in particular, to propose means for providing an AME having good performance, while limiting the quantity of materials used.

[0007] Another object is to provide a method of manufacturing an AME which is simple and rapid.

[0008] Another object is to propose means for providing an AME whose rigidity is improved in order, in particular, to be more easily stored before being assembled to the bipolar plates.

[0009] Other objects, features and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0010] To achieve this objective, a method for manufacturing a fuel cell assembly is proposed, comprising providing a stack, the stack successively comprising, in a direction, called the stacking direction, at least: - a first gas diffusion layer; - a first reinforcement; - a second reinforcement; and - a second gas diffusion layer; the method comprising: - a placement of the first and second gas diffusion layers such that the gas diffusion layers respectively have two first and second faces facing respectively the first and second reinforcements; the first and second faces respectively having first and second zones.

[0011] The method comprises: - a primary adhesion comprising a first ultrasonic adhesion such that the first area bonds to the first reinforcement to secure the first area to the first reinforcement, and a second ultrasonic adhesion such that the second area bonds to the second reinforcement to secure the second area to the second reinforcement, the first and second reinforcements retaining physical integrity in that the first and second reinforcements do not melt during the primary adhesion.

[0012] Such a method makes it possible to considerably reduce the time for fixing the various components of a membrane-electrode assembly for a fuel cell, and thus reduce manufacturing costs. The method is simplified in that it does not require the use of an adhesive material to fix the gas diffusion layers on the reinforcements.

[0013] According to another aspect, there is provided an assembly for a fuel cell, comprising a stack comprising successively in a direction, called stacking, at least: - a first gas diffusion layer; - a first reinforcement; - a second reinforcement; and - a second gas diffusion layer; the first and second gas diffusion layers respectively having two first and second faces facing respectively the first and second reinforcements; the first and second faces respectively having first and second zones.

[0014] The first zone is fixed to the first reinforcement, the fixing having a first adhesion with bonding of the first zone to the first reinforcement, without fusion of the first reinforcement; and the second zone is fixed to the second reinforcement, the fixing having a second adhesion with bonding of the second zone to the second reinforcement, without fusion of the second reinforcement. BRIEF DESCRIPTION OF THE FIGURES

[0015] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0016] [Fig.l] [Fig.l] schematically illustrates an exploded perspective view of an embodiment of a fuel cell assembly;

[0017] [Fig.2] [Fig.2] schematically illustrates the main stages of a process of manufacturing of a fuel cell assembly;

[0018] [Fig.3]

[0019] [Fig.4]

[0020] [Fig.5] Figures 3 to 5 schematically illustrate different embodiments of a fuel cell assembly;

[0021] [Fig.6] [Fig.6] schematically illustrates a top view of a layer of gas diffusion fixed to a reinforcement;

[0022] [Fig.7] [Fig.7] is an image illustrating a sectional view of an embodiment of an ultrasonic assembly for fuel cell.

[0023] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. DETAILED DESCRIPTION

[0024] Before beginning a detailed review of embodiments and implementations of the invention, optional features which may possibly be used in combination or alternatively are set out below.

[0025] According to one example, the stack comprises, according to the stacking direction, a membrane located between the first and second reinforcements.

[0026] According to one example, the membrane comprises an upper face facing the first reinforcement and a lower face facing the second reinforcement, the method comprising a secondary adhesion comprising a third ultrasonic adhesion such that a portion of the upper face of the membrane sticks to the first reinforcement and to the upper face and a fixing of the second adhesive to the second reinforcement and to the lower face a fourth ultrasonic adhesion such that a portion of the lower face of the membrane sticks to the second reinforcement, the first and second reinforcements retaining physical integrity in that the first and second reinforcements do not melt during the secondary adhesion.

[0027] According to one example, the stack comprises, according to the stacking direction: - a first electrode located between the first reinforcement and the membrane; and - a second electrode located between the membrane and the second reinforcement.

[0028] According to one example, the first electrode comprises an upper face facing the first reinforcement and the second electrode comprises a lower face facing the second reinforcement, the method comprising an additional adhesion comprising an adhesion of the first electrode by ultrasound so that a portion of the upper face of the first electrode sticks to the first reinforcement and an adhesion of the second electrode by ultrasound so that a portion of the lower face of the second electrode sticks to the second reinforcement, the first and second reinforcements retaining physical integrity in that the first and second reinforcements do not melt during the additional adhesion.

[0029] According to one example, the primary membership is carried out after or simultaneously with the secondary membership.

[0030] According to one example, the primary membership is performed after or simultaneously with the additional membership.

[0031] According to one example, the primary, secondary and additional memberships are performed simultaneously.

[0032] According to one example, the first membership is carried out before or simultaneously with the second membership.

[0033] According to one example, the first reinforcement has an external face facing the first gas diffusion layer and an internal face facing the second reinforcement, the second reinforcement has an internal face facing the first reinforcement and an external face facing the second gas diffusion layer, and the stack comprises first and second thermally activatable adhesive elements located respectively on the internal faces of the first and second reinforcements.

[0034] According to one example, the method includes attaching the first and second reinforcements comprising ultrasonic welding such that the first thermally activatable adhesive fuses with the second thermally activatable adhesive to attach the first reinforcement to the second reinforcement, and the first and second reinforcements retain their physical integrity in that the first and second reinforcements do not melt during the ultrasonic welding.

[0035] According to one example, the membrane comprises an upper face facing the first reinforcement and a lower face facing the second reinforcement, a portion of the upper face of the membrane is glued to the first reinforcement, and a portion of the lower face of the membrane is glued to the second reinforcement.

[0036] According to one example, the stack comprises first and second thermally activatable adhesive elements located respectively on the internal faces of the first and second reinforcements.

[0037] According to one example, the first thermally activatable adhesive is fused with the second thermally activatable adhesive, without fusing the first and second reinforcements.

[0038] It is specified that, in the context of the present invention, the terms "on", "overcomes", "covers", "underlying", "facing", "facing" and their equivalents do not necessarily mean "in contact with". Thus, for example, the deposition, transfer, bonding, assembly or application of a first layer on a second layer does not necessarily mean that the two layers are in direct contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it or by being separated from it by at least one other layer or at least one other element.

[0039] A layer may also be composed of several sub-layers of the same material or of different materials.

[0040] In [Fig. 1], a method for manufacturing a fuel cell assembly is shown. The fuel cell assembly is also referred to as a membrane-electrode assembly, called an AME. The method is particularly suitable for manufacturing AMEs intended for PEMFC type fuel cells. The method comprises providing a stack 1, the stack 1 successively comprising, in a direction Z, called the stacking direction, at least: a first gas diffusion layer 2; a first reinforcement 4; a second reinforcement 5; and a second gas diffusion layer 3.

[0041] The first and second gas diffusion layers 2, 3 are also called GDLs. Generally, the GDLs are intended to be placed in contact with the bipolar plates of the fuel cells. The bipolar plates comprise channels for the diffusion of gases which penetrate the GDLs in order to reach the electrodes E1, E2 of FAME. The GDLs are porous. Some GDLs may comprise a macroporous layer facing the bipolar plates, also called a substrate, and a microporous layer called an MPL (Micro Porous Layer in English, i.e. microporous layer). Generally, the GDLs 2, 3 comprise a PTFE-type polymer (i.e. polytetrafluoroethylene). PTFE is a thermoplastic polymer. In particular, the macroporous layer and the MPL comprise a PTFE-type polymer.

[0042] The reinforcements make it possible to stiffen the stack 1. The reinforcements 4, 5 are generally made from a thermoplastic polymer. For example, the reinforcements 4, 5 can be made of PET (i.e. Polyethylene terephthalate) or PEN (i.e. Poly(ethylene naphtha)). PET and PEN are thermoplastic polymers.

[0043] In particular, the method comprises placing the first and second gas diffusion layers 2, 3 such that the gas diffusion layers 2, 3 respectively have two first and second faces F1, F2 facing respectively the first and second reinforcements 4, 5. Furthermore, the first and second faces F1, F2 respectively have first and second zones Z1, Z2, as illustrated in [Fig.6].

[0044] In order to fix the first and second gas diffusion layers 2, 3 on the first and second reinforcements 4, 5 respectively, the method comprises a main adhesion.

[0045] The main adhesion comprises a first ultrasonic adhesion such that the first zone Z1 bonds to the first reinforcement 4. The first adhesion makes it possible to fix the first zone Z1 to the first reinforcement 4. In addition, the main adhesion comprises a second ultrasonic adhesion such that the second zone Z2 bonds to the second reinforcement 5. The second adhesion makes it possible to fix the second zone Z2 to the second reinforcement 5. More particularly, the first and second reinforcements 4, 5 retain physical integrity in that the first and second reinforcements 4, 5 do not melt during the main adhesion, that is to say during the first and second ultrasonic adhesion. The fact that the reinforcements do not melt is also understood to mean that the reinforcements 4, 5 do not melt over their entire thickness. The thickness of the reinforcements 4, 5 is measured along the stacking direction Z.It is also said that the reinforcements 4, 5 do not melt over more than 90%, preferably not more than 95%, of their total thickness. In other words, the adhesion of the GDLs to the reinforcements 4, 5 takes place mainly, or even only, on the surface of the GDLs 2, 3, that is to say on the first and second zones Z1, Z2.

[0046] In other words, the main adhesion comprises a first ultrasonic adhesion such that only the first zone Z1 bonds to the first reinforcement 4 and a second ultrasonic adhesion such that only the second zone Z2 bonds to the second reinforcement 5. The main adhesion comprises a first ultrasonic adhesion configured such that the first zone bonds to the first reinforcement 4 and a second ultrasonic adhesion configured such that the second zone Z2 bonds to the second reinforcement 5.

[0047] To achieve the main adhesion, an ultrasonic device 10 configured to achieve the first and second adhesions may be used. For example, the ultrasonic device 10 comprises an ultrasonic generator 11 connected to a sonotrode head 12. Two separate ultrasonic devices may be used to achieve the first and second welds respectively. Preferably, a single ultrasonic device 10 is used to achieve the main adhesion, i.e., the first and second adhesions. Based on ultrasonic technology, the frequency for adhesion varies between 20 and 70 kHz, the adhesion of the GDL 2, 3 on the reinforcements 4, 5 is achieved thanks to the sonotrode head 12. The head 12 is preferably brought into contact with the materials with a certain stress remaining lower than 3 MPa, and then causes mechanical vibrations (ultrasound). These vibrations propagate in the components and generate frictional heat which causes the materials to melt. Generally speaking, ultrasound can melt most thermoplastic materials (plastics malleable under heat).

[0048] The main adhesion makes it possible to melt the PTFE-type polymer (which melts under the vibrations caused by ultrasound) of the GDLs 2, 3 onto the reinforcements 4, 5 which comprise a thermoplastic polymer. That is to say that the PTFE-type polymer of the GDLs 2, 3 sticks to the thermoplastic polymer reinforcements. In particular, during the main adhesion, the reinforcements 4, 5 retain their physical integrity in that the first and second reinforcements 4, 5 do not melt during the first and second adhesions. The difference in ultrasonic behavior between the reinforcements 4, 5 and the GDLs 2, 3, comes mainly from the fact that the GDLs 2, 3 and the reinforcements 4, 5 are not manufactured from the same materials. More particularly, the GDLs 2, 3 and the reinforcements 4, 5 are of a different physicochemical nature.

[0049] Generally speaking, bonding means that a first material A melts and sticks to a second material B which does not melt. Thus, ultrasonic bonding is obtained when the first and second materials A, B are of different physicochemical nature. Furthermore, fusion means that first and second materials A, B melt to fuse with each other. Thus, ultrasonic fusion is obtained when the first and second materials A, B are of the same physicochemical nature.

[0050] Thus, the zones Z1, Z2 of the GDLs 2, 3 are bonded to the reinforcements 4, 5 in a simple, rapid, localized manner and without the addition of external temperature.

[0051] Furthermore, the first reinforcement 4 has an external face FRE1 facing the first gas diffusion layer 2 and an internal face FRI1 facing the second reinforcement 5, the second reinforcement 5 has an internal face FRI2 facing the first reinforcement 4 and an external face FRE2 facing the second gas diffusion layer 3.

[0052] Advantageously, the stack comprises first and second thermally activatable adhesive elements 6, 7 located respectively on the internal faces FRI1, FRI2 of the first and second reinforcements 4, 5.

[0053] According to one embodiment, the method comprises fixing the first and second reinforcements 4, 5 comprising ultrasonic welding so that the first thermally activatable adhesive 6 fuses with the second thermally activatable adhesive 7 to fix the first reinforcement 4 to the second reinforcement 5, as illustrated in the [Fig. 3]. In particular, the first and second reinforcements 4, 5 retain their physical integrity in that the first and second reinforcements 4, 5 do not melt during ultrasonic welding. Thus, a so-called four-layer AME is obtained, comprising two reinforcements 4, 5 and two GDLs 2, 3.

[0054] According to another embodiment, the stack 1 comprises, in the stacking direction Z, a membrane 8 located between the first and second reinforcements 4, 5. The membrane 8 comprises an upper face facing the first reinforcement 4 and a lower face facing the second reinforcement 5.

[0055] Advantageously, the method comprises fixing the first and second reinforcements 4, 5 comprising a secondary adhesion comprising a third adhesion by ultrasound so that a portion of the upper face of the membrane 8 sticks to the first reinforcement 4, and a fourth adhesion by ultrasound so that a portion of the lower face of the membrane 8 sticks to the second reinforcement 4, the first and second reinforcements 4, 5 retaining physical integrity in that the first and second reinforcements 4, 5 do not melt during the secondary adhesion, as illustrated in [Fig. 4]. Thus, an AME, called five layers, is obtained comprising two reinforcements 4, 5, two GDLs 2, 3 and a membrane 8. In particular, the membrane 8 comprises PFSA (Perfluorosulfonated acid), which melts during vibrations caused by ultrasound, and which makes it possible to stick the membrane 8 to the reinforcements 4, 5.The membrane retains its physical integrity, its thickness not being altered by more than 10%, or even less than 5%.

[0056] According to another embodiment, the stack 1 comprises, in the stacking direction Z: a ​​first electrode E1 located between the first reinforcement 4 and the membrane 8; and a second electrode E2 located between the membrane 8 and the second reinforcement 5. The electrodes E1, E2 may be catalytic layers. The electrodes E1, E2 preferably comprise PFSA in their composition.

[0057] Furthermore, the first electrode E1 comprises an upper face facing the first reinforcement 4 and the second electrode E2 comprises a lower face facing the second reinforcement 5. For example, the method comprises an additional adhesion comprising an adhesion of the first electrode E1 by ultrasound so that a portion of the upper face of the first electrode E1 sticks to the first reinforcement 4 and an adhesion of the second electrode E2 by ultrasound so that a portion of the lower face of the second electrode E2 sticks to the second reinforcement 4, the first and second reinforcements 4, 5 retaining physical integrity in that the first and second reinforcements 4, 5 do not melt during the additional adhesion.

[0058] Advantageously, the method comprises ultrasonic welding of the first thermally activatable adhesive 6 to the second thermally activatable adhesive 7. Thus we obtain an AME, said to be seven layers comprising two reinforcements 4, 5, two GDL 2, 3, a membrane 8, and two electrodes El, E2.

[0059] For example, the first and second electrodes E1, E2 may be pre-assembled with the membrane 8 to form an electrode-membrane assembly, called a CCM. Thus, the CCM may be formed before the main adhesion. In other words, the main adhesion may be carried out after the assembly of the reinforcements 4, 5 with the CCM or at the same time. The two GDLs 2, 3, present on either side of the stack 1, may be assembled at the same time on the reinforcements 4, 5.

[0060] For example, the primary membership is performed after or simultaneously with the secondary membership.

[0061] For example, the primary membership is made after or simultaneously with the additional membership.

[0062] Advantageously, the primary, secondary and additional memberships are carried out simultaneously. Thus, a simple and rapid method is provided.

[0063] The first weld may be performed before or simultaneously with the second weld.

[0064] In [Fig. 1], an embodiment of the reinforcements 4, 5 is shown. The reinforcements 4, 5 may have the form of a frame provided with an opening 40 to allow contact of the GDLs 2, 3 with the electrodes E1, E2.

[0065] In [Fig. 6] there is shown a top view of a GDL 2, 3 in the foreground glued to a reinforcement 4, 5 in the background. Reference 41 represents the edges of the GDL 2, 3 and reference 42 represents the edges of the opening 40 of the reinforcement 4, 5. The first and second zones Z1, Z2 are delimited by the edges of the GDL and the edges of the opening 40 of the reinforcement 4, 5.

[0066] [Fig. 7] shows an image of an example of an AME, seen in section, obtained using the method described above. In this example, the bonding of the first and second GDL 2, 3 to the first and second reinforcements 4, 5 respectively was done simultaneously with the ultrasonic bonding of the first and second reinforcements 4, 5 to the membrane 8 and the two GDL 2, 3 were bonded at the same time to each reinforcement 4, 5 (on either side of the membrane 8). The ultrasound frequency used in the case presented is 35 kHz. The ultrasound amplitude was set at 22.4 pm and the approach force at 80 N. To control the approach force, an anvil 50 can be used, as illustrated in [Fig. 2]. The operating range for obtaining ultrasonic adhesion that allows effective fixing of the different components and prevents their degradation is 0.25 to 1.25 MPa with an energy of 25 to 250 J / cm2. The time of ultrasound is less than 3 seconds.

[0067] Advantageously, the GDLs 2, 3 can be glued to the reinforcements 4, 5 after or at the same time as the fixing of the reinforcements 4, 5 to the CCM. Such a manufacturing method is different from what is done "traditionally" by hot pressing or adding an adhesive material or glue. Moreover, the process is faster: on the order of a second (or even a "fraction" of a second) regardless of the surface to be bonded, compared to hot pressing which takes at least more than a minute.

[0068] Furthermore, the method is simple because it does not require any additional equipment necessary to carry out the primary, secondary and additional adhesions. Indeed, it is not necessary to use a mold or waffle iron; nor positioning templates; nor specific tools, other than the ultrasonic device 10 and the sonotrode head 12.

[0069] The method is even simpler because it does not require the addition of glue, nor the addition of an adhesive material to fix the GDL 2, 3 on the reinforcements 4, 5. The method also does not use an external temperature input (i.e. it is not necessary to heat plates for hot presses, the temperature is generated naturally by the fact that the ultrasound sets the molecules in motion). The method advantageously allows the different components (4, 5 or 7 layers) of the AME to be fixed simultaneously. By fixing, we mean welding, bonding or holding by adhesive, so as to mechanically connect two parts together so that their separation results in destruction of material.

[0070] By using an ultrasonic device 10 to carry out the main, secondary and additional adhesions, the assembly of the different constituents of the AME can be put online; which offers the possibility of obtaining significant production rates.

Claims

Claims

1. A method of manufacturing a fuel cell assembly, comprising providing a stack (1), the stack successively comprising, in a direction (Z), called the stacking direction, at least: • a first gas diffusion layer (2); • a first reinforcement (4); • a second reinforcement (5); and • a second gas diffusion layer (3); the method comprising: • placing the first and second gas diffusion layers (2, 3) so that the gas diffusion layers (2, 3) respectively have two first and second faces facing the first and second reinforcements (4, 5) respectively; the first and second faces respectively having first and second zones;characterized in that the method comprises: • a main adhesion comprising a first ultrasonic adhesion such that the first zone sticks to the first reinforcement (4) to fix the first zone to the first reinforcement (4), and a second ultrasonic adhesion such that the second zone sticks to the second reinforcement (5) to fix the second zone to the second reinforcement (5), the first and second reinforcements (4, 5) retaining physical integrity in that the first and second reinforcements (4, 5) do not melt during the main adhesion.;

2. Method according to the preceding claim, in which the stack comprises, according to the stacking direction, a membrane (8) located between the first and second reinforcements (4, 5).

3. Method according to the preceding claim, in which the membrane (8) comprises an upper face facing the first reinforcement (4) and a lower face facing the second reinforcement (5), the method comprising a secondary adhesion comprising a third ultrasonic adhesion such that a portion of the upper face of the membrane (8) sticks to the first reinforcement (4) and a fourth ultrasonic adhesion such that a portion of the lower face of the membrane (8) sticks to the second reinforcement (4), the first and second reinforcements (4, 5) retaining physical integrity in that the first and second reinforcements (4, 5) do not melt during the secondary adhesion.

4. Method according to any one of the preceding claims, in which the stack comprises, according to the stacking direction: • a first electrode (El) located between the first reinforcement (4) and the membrane (8); and • a second electrode (E2) located between the membrane (8) and the second reinforcement (5).

5. Method according to the preceding claim, in which the first electrode (El) comprises an upper face facing the first reinforcement (4) and the second electrode (E2) comprises a lower face facing the second reinforcement (5), the method comprising an additional adhesion comprising an adhesion of the first electrode (El) by ultrasound so that a part of the upper face of the first electrode (El) sticks to the first reinforcement (4) and an adhesion of the second electrode (E2) by ultrasound so that a part of the lower face of the second electrode (E2) sticks to the second reinforcement (4), the first and second reinforcements (4, 5) retaining physical integrity in that the first and second reinforcements (4, 5) do not melt during the additional adhesion.

6. The method of claim 3, wherein the primary adhesion is performed after or simultaneously with the secondary adhesion.

7. The method of claim 5, wherein the primary membership is performed after or simultaneously with the supplemental membership.

8. A method according to claims 6 and 7 in combination, wherein the primary, secondary and additional memberships are performed simultaneously.

9. A method according to any preceding claim, wherein the first adhesion is performed before or simultaneously with the second adhesion.

10. Method according to any one of the preceding claims, in which the first reinforcement (4) has an external face facing the first gas diffusion layer (2) and an internal face facing the second reinforcement (5), the second reinforcement (5) has an internal face facing the first reinforcement (4) and an external face facing the second gas diffusion layer (3), and the stack (1) comprises first and second thermally activatable adhesive elements (6, 7) located respectively on the internal faces of the first and second reinforcements (4, 5).

11. A method according to the preceding claim, comprising fixing the first and second reinforcements (4, 5) by ultrasonic welding such that the first thermally activatable adhesive (6) fuses with the second thermally activatable adhesive (7) to fix the first reinforcement (4) to the second reinforcement (5), and the first and second reinforcements (4, 5) retain their physical integrity in that the first and second reinforcements (4, 5) do not melt during the ultrasonic welding.

12. Fuel cell assembly, comprising a stack comprising successively in a direction, called stacking, at least: • a first gas diffusion layer (2); • a first reinforcement (4); • a second reinforcement (5); and • a second gas diffusion layer (3); the first and second gas diffusion layers (2, 3) respectively having two first and second faces turned respectively towards the first and second reinforcements (4, 5); the first and second faces respectively having first and second zones; characterized in that: • the first zone is fixed on the first reinforcement (4), the fixing having a first adhesion with bonding of the first zone on the first reinforcement (4), without melting of the first reinforcement (4); and • the second zone is fixed on the second reinforcement (5), the fixing having a second adhesion with bonding of the second zone on the second reinforcement (5), without fusion of the second reinforcement (5).

13. Assembly according to claim 12, in which the stack comprises, in the stacking direction, a membrane (8) located between the first and second reinforcements (4, 5).

14. Assembly according to the preceding claim, in which the membrane (8) comprises an upper face facing the first reinforcement (4) and a lower face facing the second reinforcement (5), a part of the upper face of the membrane (8) is glued to the first reinforcement (4), and a part of the lower face of the membrane (8) is glued to the second reinforcement (5).

15. Assembly according to claim 13, in which the stack comprises, according to the stacking direction: • a first electrode (El) located between the first reinforcement (4) and the membrane (8); and • a second electrode (E2) located between the membrane (8) and the second reinforcement (5).

16. Assembly according to the preceding claim, in which the first electrode (El) comprises an upper face facing the first reinforcement (4) and the second electrode (E2) comprises a lower face facing the second reinforcement (5), a part of the upper face of the first electrode (El) is glued to the first reinforcement (4) and a part of the lower face of the second electrode (E2) is glued to the second reinforcement (5).

17. Assembly according to any one of claims 12 to 16, in which the first reinforcement (4) has an external face facing the first gas diffusion layer (2) and an internal face facing the second reinforcement (5), the second reinforcement (5) has an internal face facing the first reinforcement (4) and an external face facing the second gas diffusion layer (3), and the stack comprises first and second thermally activatable adhesive elements (6, 7) located respectively on the internal faces of the first and second reinforcements (4, 5).

18. Assembly according to the preceding claim, in which the first thermally activatable adhesive (6) is fused with the second thermally activatable adhesive (7), without fusing the first and second reinforcements (4, 5).

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