Subassembly for a fuel cell stack, fuel cell comprising such a subassembly and method for manufacturing such a subassembly

Abstract

The invention relates to a subassembly for a fuel cell stack comprising at least a first bipolar half-plate (42) and a membrane-electrode assembly including a membrane and a bipartite frame (30) formed by a first half-frame (32) and a second half-frame (34). At least the second half-frame (34) is coated, on a first surface (S34) opposite a first surface (S32) of the first half-frame, with a layer of securing glue. First apertures (320) through the first half-frame (32) are each arranged opposite a solid portion (42A) of the first bipolar half-plate and opposite a solid portion (34A) of the second half-frame in a direction perpendicular to a main plane of the membrane (TT22). The first bipolar half-plate (42) is rigidly attached to the frame (30) by a quantity (Q2) of glue which extends through the first apertures (320) and which comes from the glue coated on the first surface (S34) of the second half-frame (34).

Description

[0001] TITLE: Subassembly for fuel cell stack, fuel cell comprising such a subassembly and method of manufacturing such a subassembly

[0002] The present invention relates to a subassembly intended to be integrated into a stack of electrochemical cells, within a fuel cell. The invention also relates to a fuel cell comprising a stack of electrochemical cells, at least one of which comprises, or is constituted by, such a subassembly. The invention finally relates to a method for manufacturing a subassembly as mentioned above.

[0003] In the field of fuel cells, it is known to insert a stack of electrochemical cells between two end plates, located on either side of this stack in a stacking direction, and possibly to arrange this stack in a casing. Electrochemical cells are formed by membrane-electrode assemblies and bipolar plates. A membrane-electrode assembly is sometimes called MEA, from the English "Membrane-Electrode Assembly", and generally comprises a base membrane, which can be coated on one or both of its faces, with a catalytic layer comprising a catalyst, as well as a frame which supports this membrane. The frame can comprise openings which, in the stack, define fluid flow galleries within the stack of electrochemical cells for the distribution and recovery of these fluids in the corresponding fluid compartments of each cell.This frame is most often associated with at least one seal, sometimes called a "gasket", with which it also provides a sealing function to the flow of fluids within the stack.

[0004] The membrane, when coated with layers comprising a catalyst, is sometimes called CCM, from the English “Catalyst Coated Membrane” and in this case comprises three layers, namely, a membrane itself, a catalytic layer on the anode side and a catalytic layer on the cathode side.

[0005] In the stack, a membrane-electrode assembly is interposed between two bipolar plates and thus delimits an anode compartment and a cathode compartment. On each side, the catalyst-coated membrane is covered by a gas diffusion layer which is therefore received in the corresponding anode or cathode compartment and promotes contact between the chemical species present in the corresponding anode or cathode compartment and the membrane. Each gas diffusion layer also has an electron conduction role. These diffusion layers are sometimes called GDL, from the English "Gas Diffusion Layer".

[0006] It is known to manufacture a membrane-electrode assembly by attaching the catalyst-coated membrane to the frame, which in particular makes it possible to stiffen this membrane and facilitate its handling. This is done by tightly gluing the membrane to the frame.

[0007] It is known to produce, during the manufacture of a fuel cell, bipolar plates formed from two half-plates or sheet metal strips which belong to two adjacent electrochemical cells. This requires handling separately the membrane-electrode assemblies, on the one hand, and the bipolar plates, on the other hand, when they are placed within the stack of a fuel cell. This solution requires the two half-plates or strips of a bipolar plate to be joined together. This joining can be carried out by laser welding or brazing, in particular point by point, by plastic deformation of the strips, in particular by means of an electric tool creating an impact, or by gluing.However, we also know the possibility of having bipolar plates formed from two half-plates or sheet metal strips which belong to two adjacent electrochemical cells, the two half-plates being only kept in contact with each other, by the compression of the stack, with generally the interposition of one or more sealing joints, which can be free joints or joints integrated into one or other of the half-plates.

[0008] Once the membrane-electrode assemblies, on the one hand, and the bipolar plates, on the other hand, are formed, they must be arranged alternately along the stacking direction, which in practice proves to be long and delicate to implement.

[0009] It is known from WO-A-2014 / 1 11745 and US-B-8399150 to bond an electrochemical cell frame to a bipolar plate, by means of a layer of adhesive inserted between these parts. This approach requires securing the strips of the bipolar plates using one of the techniques mentioned above and providing a quantity of adhesive dedicated to creating the connection between the frame and the bipolar plate. This approach imposes the way in which the stack of electrochemical cells of the fuel cell is then formed and increases its cost price, on the one hand in terms of investment for the means of removing the adhesive and on the other hand in terms of the cost of this added adhesive.

[0010] It is also known from JP2008084707A to distribute glue dots between the two half-frames of a frame surrounding an electrochemical cell membrane and to drill through holes in these half-frames which are aligned in a direction perpendicular to the plane of the membrane. A bipolar half-plate is attached to each half-frame by means of other glue dots. This assembly technique with glue dots requires a relatively large quantity of glue. Each bipolar half-plate is directly secured only to the adjacent half-frame. In addition, the glue placed between the two half-frames risks overflowing onto one side of the subassembly thus produced.

[0011] It is these drawbacks that the invention more particularly intends to remedy by proposing a new subassembly for a fuel cell stack, the manufacture of which is simplified and the cost price of which can be reduced compared to previous equipment.

[0012] To this end, the invention relates to a subassembly for a fuel cell stack comprising a membrane-electrode assembly including a membrane and a bipartite frame formed by a first half-frame arranged on a first side of the membrane and a second half-frame arranged on a second side of the membrane. The membrane-electrode assembly also includes at least one first bipolar half-plate. At least the second half-frame is coated, on a first surface facing a first surface of the first half-frame, with a layer of adhesive for securing the half-frames.

[0013] According to the invention, first orifices arranged through the first half-frame are each arranged opposite a solid portion of the first bipolar half-plate and opposite a solid portion of the second half-frame, in a direction perpendicular to a main plane of the membrane. In addition, the first bipolar half-plate is secured to the frame by a quantity of glue which extends through the first orifices and which comes from the glue coated on the first surface of the second half-frame.

[0014] Thanks to the invention, the structure of the subassembly makes it possible to use the layer of glue provided primarily to secure the two frames of the membrane-electrode assembly together to provide an additional function of immobilizing the first bipolar half-plate. This makes it possible to handle this subassembly as a unit during the manufacture of a fuel cell incorporating it, which facilitates the work of an operator or a robot and makes it possible to increase production rates, therefore reducing the cost price of the fuel cell. In addition, the method of securing the first bipolar half-plate and the frame is precise since the quantity of glue which extends through the first orifices is well positioned in space, thanks to these first orifices. In particular, this quantity of glue does not risk flowing outside the subassembly of the invention.Furthermore, in the case where the subassembly comprises a second bipolar half-plate, it constitutes a unitary electrochemical cell which can be tested, or even pre-activated, before its incorporation into a stack of cells, which makes a manufacturing process for such a battery more reliable.

[0015] According to advantageous but not mandatory aspects of the invention, such a subassembly may incorporate one or more of the following features, taken in any technically admissible combination:

[0016] - The subassembly comprises a second bipolar half-plate arranged, relative to the membrane, opposite the first bipolar plate. The first half-frame is coated, on its first surface, with a layer of glue for securing the half-frames. Second orifices arranged through the second half-frame are each arranged opposite a solid portion of the second bipolar half-plate and opposite a solid portion of the first half-frame, in the direction perpendicular to a main plane of the membrane. In addition, the second bipolar plate is secured to the frame by a quantity of glue which extends through the second orifices and which comes from the glue coated on the first surface of the first half-frame.

[0017] - The first and second orifices are offset from each other in at least one direction parallel to the main plane of the membrane, so that there is no overlap between these orifices in the direction perpendicular to the main plane of the membrane.

[0018] - The first bipolar half-plate is provided with cutouts aligned with the second orifices and / or in that the second bipolar half-plate is provided with cutouts aligned with the first orifices, in the direction perpendicular to the main plane of the membrane.

[0019] - A cutout opens onto at least one longitudinal edge of the bipolar plate in which it is made.

[0020] - Each hole made through a half-frame has a section whose area is greater than or equal to 5 mm 2 , preferably 10 mm 2 , with a preferably circular, rectangular or oblong shape.

[0021] - The glue is heat-activated and based on thermoplastic polymer, in particular EVA copolymer.

[0022] - At least one of the first orifices provided through the first half-frame is arranged in a peripheral external zone of the sub-assembly which is located outwards relative to a peripheral seal of the sub-assembly.

[0023] - The membrane electrode assembly comprises four corners, while the sub-assembly comprises at least four first orifices arranged through the first half-frame and arranged in a peripheral external zone of the sub-assembly which is located outwards relative to a peripheral seal of the sub-assembly, each in a corner of the membrane electrode assembly.

[0024] - At least one of the first orifices arranged through the first half-frame and the facing solid portion belonging to the first bipolar half-plate are arranged in a gallery framing zone, arranged around an opening of the first bipolar half-plate, and fluidically isolated from at least one anodic or cathodic fluidic compartment delimited in the sub-assembly, between the membrane electrode assembly and the first bipolar half-plate.

[0025] According to another aspect, the invention relates to a fuel cell comprising a stack of electrochemical cells, each with a membrane-electrode assembly and two bipolar half-plates, at least one of these cells comprising, or being constituted by, a subassembly as mentioned above.

[0026] This fuel cell has the same advantages as those mentioned above.

[0027] According to a third aspect, the invention relates to a method for manufacturing a subassembly, in particular a subassembly as mentioned above, comprising a membrane-electrode assembly including a membrane and a bipartite frame formed by a first half-frame arranged on a first side of the membrane and a second half-frame arranged on a second side of the membrane. The membrane-electrode assembly also includes at least one first bipolar half-plate. This method comprises at least one prior step of coating at least one first surface of the second half-frame with an adhesive and a step of securing the frame and the membrane by applying the first surface of the second half-frame, coated with adhesive, against the first surface of the first half-frame.

[0028] According to the invention, this method comprises at least one step of applying the first bipolar half-plate against a second surface of the first half-frame opposite the first surface of this first half-frame and a step of securing the first bipolar half-plate and the frame by migration of the glue coated on the first surface of the second half-frame, towards a surface of the first bipolar half-plate, through first orifices arranged in the first half-frame, between its first and second surfaces.

[0029] This method makes it possible to form electrochemical cells or parts of electrochemical cells which can be easily integrated into a stack of fuel cell cells, according to a technique which can be well mastered, with high production rates. Advantageously, the subassembly comprises a second bipolar half-plate and the method comprises at least one preliminary step of coating at least a first surface of the first half-frame with an adhesive, a step of applying the second bipolar half-plate against a second surface of the second half-frame opposite the first surface of this second half-frame and a step of securing the second bipolar half-plate and the frame by migrating the adhesive coated on the first surface of the first half-frame, towards a surface of the second bipolar half-plate, through first orifices arranged in the second half-frame, between its first and second surfaces.

[0030] It can further be provided that, during the joining step, the glue coated on the first surface of the second half-frame, and possibly on the first surface of the first half-frame, is heated at least in the vicinity of the first orifices, and possibly at the level of the second orifices.

[0031] The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of four embodiments of a subassembly, of a fuel cell and of a method in accordance with its principle, given solely by way of example and with reference to the appended drawings in which:

[0032] [Fig.1] Figure 1 is a partially exploded perspective view of a subassembly according to a first embodiment of the invention, this subassembly constituting an electrochemical cell belonging to a stack of a fuel cell;

[0033] [Fig.2] Figure 2 is an exploded perspective view of a membrane-electrode assembly belonging to the subassembly shown in Figure 1;

[0034] [Fig. 3] Figure 3 is a front view of the subassembly shown in Figure 1;

[0035] [Fig.4] Figure 4 is a longitudinal section of the subassembly shown in Figures 1 and 3, along line IV-IV in Figure 3, during a step of manufacturing a fuel cell including this subassembly;

[0036] [Fig. 5] Figure 5 is a partial view, similar to Figure 4, for a subassembly according to a second embodiment of the invention.

[0037] [Fig.6] Figure 6 is a simplified front view, similar to Figure 3, for a subassembly according to a third embodiment of the invention;

[0038] [Fig.7] Figure 7 represents, on two inserts A) and B) and on a larger scale, partial sections at the level of the cutting lines AA and BB in Figure 6 in the case where the subassembly is integrated into a stack of electrochemical cells; and

[0039] [Fig.8] Figure 8 is a simplified front view, similar to Figure 6, for a subassembly according to a fourth embodiment of the invention. In order to clearly show the characteristics of the invention, the proportions are not necessarily respected between the objects represented in the figures.

[0040] A membrane-electrode assembly 2 is shown in a partially exploded view in Figure 1. This assembly 2 is associated with a first bipolar half-plate 42 and a second bipolar half-plate 44 to form a subassembly 6 intended to constitute an electrochemical cell, intended to be part of a stack, this stack constituting a part of a fuel cell. Such a stack is shown with the reference 60, in Figure 7, within a partially visible fuel cell 8, for the third embodiment of the invention.

[0041] The bipolar half-plates 42 and 44 may also be referred to as polar plates.

[0042] We note A2 a longitudinal axis of the membrane-electrode assembly 2, which is coincident with a longitudinal axis A6 of the subassembly 6.

[0043] The membrane-electrode assembly 2 may be referred to as MEA and comprises a base membrane 22 which, in the example described below, is coated with catalyst. More specifically, the base membrane 22 is a proton exchange polymer membrane. The structure of the membrane-electrode assembly 2 is the same as that visible in FIG. 7 for the third embodiment. It is described with reference to this FIG. 7. The base membrane 22 is therefore, in the example, coated, on a first side facing upwards in FIGS. 1, 2 and 7, with a first catalytic layer 23 forming a cathode and, on a second side opposite the first side and facing downwards in FIGS. 1, 2 and 7, with a second catalytic layer 24 forming an anode. The membrane 22 and the catalytic layers 23 and 24 together form a catalyst-coated membrane 25, otherwise referred to as CCM. In the remainder of this description, this catalyst-coated membrane 25 is referred to as a CCM membrane.

[0044] Here, the base membrane 22 is made of polymer material, in particular of the NAFION type (registered trademark), and has a thickness of the order of 0.005 to 0.050 mm, preferably 0.008 to 0.015 mm. The catalytic layers 23 and 24 are made from a platinum base and each have a thickness of the order of 0.001 to 0.010 mm, preferably 0.002 to 0.005 mm. The thickness of the CCM membrane 25 is preferably between 0.008 and 0.050 mm, preferably of the order of 0.017 mm.

[0045] We denote TT22 a median plane of the basal membrane 22, which is also a median plane of the CCM membrane 25. The longitudinal axis A2 is included in the median plane TT22.

[0046] The CCM 25 membrane is mounted on a frame 30 made up of two half-frames

[0047] 32 and 34 which are intended to come into plane support against each other which are, for example, made of polymer film, for example of poly(ethylene terephthalate) or PET or of poly(ethylene naphthalate) or PEN.

[0048] TT30 denotes a plane for supporting the two half-frames 32 and 34 against each other. The plane TT30 is also a median plane of the frame 30 and it includes the longitudinal axis A2. The two half-frames 32 and 34 are configured to trap between them a peripheral edge 22a of the membrane 22 when they are supported against each other along the plane TT30. In this configuration, the half-frames 32 and 34 form a zone, also called an “overlap”, between the membrane 22 and the two half-frames 32, 34. Along each longitudinal edge or each transverse edge of the frame, the overlap has a width for example included in the range from 1 to 5 mm, preferably in the range from 2 to 4 mm.

[0049] The half-frame 32 is arranged on a first side of the CCM membrane 25, in the example above the membrane in FIGS. 1, 2 and 7, while the half-frame 34 is arranged on a second side of the CCM membrane 25, in the example below the membrane in FIGS. 1, 2 and 7. This has the effect of immobilizing the membrane 22, that is to say in practice the CCM membrane 25, by pinching it between the half-frames 32 and 34, within the frame 30.

[0050] Advantageously, the thickness of each of the half-frames 32 and 34 is between 0.020 and 0.030 mm, preferably of the order of 0.025 mm.

[0051] The frame 30 makes it possible to stiffen the CCM 25 membrane and hold it in position within the stack.

[0052] In practice, the half-frames 32 and 34 are secured to each other at the level of the support plane TT30, preferably by means of glue.

[0053] Preferably, as can be seen in Figure 4 for example, the glue is not deformed and remains parallel to the TT30 plane.

[0054] We denote S32 the surface of the half-frame 32 facing the half-frame 34. We denote S34 the surface of the half-frame 34 facing the half-frame 32. In the mounted configuration of the frame 30 around the membrane 22, the surfaces S32 and S34 are in surface contact with each other, aligned on the plane TT30 and secured to each other by means of the glue.

[0055] In this configuration, the median plane TT22 of the membrane 22 is also aligned with the plane TT30.

[0056] The glue used to assemble the half-frames 32 and 34 is preferably a thermo-activatable glue based on thermoplastic polymer, for example an EVA copolymer-based glue, such as the glue sold under the reference AP12 by the company Micel. Advantageously, the thickness of the layer of glue coated, that is to say deposited, on the surface S32 or S34 of each of the half-frames is between 0.01 and 0.02 mm, preferably of the order of 0.013 mm, before application of the surfaces S32 and S34 against each other.

[0057] Advantageously, the frame 30 defines openings 36 intended to form circulation and fluid distribution / collection galleries within the stack, when several sub-assemblies 6 are juxtaposed within the stack, in a direction perpendicular to their median planes TT30.

[0058] The openings 36 are formed by aligning, in directions parallel to the axis A30, individual openings 36s and 364 formed respectively in the half-frames 32 and 34.

[0059] Alternatively, particularly in the case of a fuel cell with “external manifolds”, the frame 30 is devoid of openings of the type of openings 36.

[0060] We note A30 an axis perpendicular to the plane TT30 and passing through the geometric center of the frame 30. The axis A30 is perpendicular to the base membrane 22, as well as to the CCM membrane 25, therefore to their median plane TT22.

[0061] Within the stack, the axes A30 of the different frames 30 are merged and the frames 30 are oriented around this axis so that the openings 36 together constitute galleries for circulation and distribution / collection of fluid, in particular hydrogen, air or heat transfer fluid, within the stack.

[0062] Each bipolar half-plate 42 or 44 is equipped with openings 46 of the same geometry as the openings 36 and which also participate in the definition of these galleries.

[0063] The longitudinal ends of the half-frame 32 are denoted 32A and 32B respectively. The longitudinal ends of the half-frame 34 are denoted 34A and 34B respectively.

[0064] A32 and A34 denote respectively a longitudinal axis of the half-frame 32 and a longitudinal axis of the half-frame 34. In the assembled configuration of the membrane-electrode assembly 2, the axes A2, A32 and A34 are perpendicular to the axis A30, parallel to each other and, preferably almost coincident, within the thickness of the half-frames. B32 and B34 denote respectively a transverse axis of the half-frame 32 and a transverse axis of the half-frame 34, respectively perpendicular to the axes A32 and A34. In the assembled configuration of the membrane-electrode assembly 2, the axes B32 and B34 are perpendicular to the axis A30, parallel to each other and, preferably almost coincident, within the thickness of the half-frames.

[0065] The half-frames 32 and 34 each define a central opening 32C, respectively 34C, which passes through them from one side to the other and opposite which the CCM membrane 25 is arranged in the mounted configuration of this membrane on the frame 30. The central openings 32C and 34C of the half-frames 32 and 34 are therefore delimited by internal edges of these half-frames. The meeting of the central openings 32C and 34C defines a central opening 30C of the frame 30, which is closed by the CCM membrane in the mounted configuration of the membrane-electrode assembly 2. The half-frames 32 and 34, and therefore the frame 30 which they constitute, have a closed contour around the corresponding central opening.

[0066] We denote 32D the transverse edges of the central opening 32C of the half-frame 32, each transverse edge being parallel to the axis B32. We denote 34D the transverse edges of the central opening 34C of the half-frame 34, each transverse edge being parallel to the axis B32.

[0067] Advantageously, the membrane-electrode assembly 2 also comprises a first gas diffusion layer 28 and a second gas diffusion layer 29 which can be called GDL and which have the function of promoting exchanges between the CCM membrane 25 and the fluids circulating between the two bipolar half-plates 42 and 44 of a subassembly 6 to which this membrane-electrode assembly belongs.

[0068] Advantageously, the thickness of the diffusion layers 28 and 29 is between 0.050 and 0.320 mm, preferably of the order of 0.250 mm.

[0069] In the mounted configuration of the membrane-electrode assembly 2, the diffusion layers 28 and 29 cover the CCM membrane 25 and a part of the frame 30, in the vicinity of the central opening 30C, each on one side of the CCM membrane25.

[0070] To allow the immobilization of the bipolar half-plates 42 and 44 on the frame 30 equipped with the CCM membrane 25, each of the half-frames 32 and 34 is equipped with first orifices 320, respectively second orifices 340, which are arranged on either side of its central opening 32C or 34C, along its longitudinal axis A32 or A34, and on either side of its individual openings 36s or 364 along its transverse axis B32 or B34. The first orifices 320 are intended to be covered by the bipolar half-plate 42, while the second orifices 340 are intended to be covered by the bipolar half-plate 44, in the mounted configuration of the subassembly 6. Thus, in the mounted configuration of the subassembly 6, the orifices 320 and 340 are arranged opposite the bipolar half-plates 42 and 44, in a direction parallel to the axis A30, that is to say in a direction perpendicular to the planes TT22 and TT30.

[0071] In the example, the orifices 320 of the half-frame 32 are 4 in number, as are the orifices 340 of the half-frame 34.

[0072] In a variant not shown, a different number of orifices 320 and 340 may be provided, or even different numbers of orifices on the two half-frames. The half-frame 32 comprises two rows of two orifices 320 which extend respectively near the ends 32A and 32B of the half-frame 32, on either side of the individual openings 362, and which connect the surface S32 of the half-frame 32 to a surface S'32 of the half-frame 32 which is opposite the surface S32 and on which the first bipolar half-plate 42 and the diffusion layer 28 bear. The orifices 320 therefore pass through the thickness of the half-frame 32.

[0073] In the same way, the half-frame 34 comprises two rows of two orifices 340 which extend respectively near the ends 34A and 34B of the half-frame 34, on either side of the individual openings 364, and which connect the surface S34 of the half-frame 34 to a surface S'34 of the half-frame 34 which is opposite the surface S34 and on which the second bipolar half-plate 42 and the diffusion layer 28 bear. The orifices 340 therefore pass through the thickness of the half-frame 34.

[0074] Advantageously, the orifices 320 are distributed on the first half-frame 32 symmetrically with respect to the axes A32 and B32. In the same way, the orifices 340 are distributed on the first half-frame 34 symmetrically with respect to the axes A34 and B34.

[0075] Advantageously, the orifices 320 are further away from the transverse edges 32D than the orifices 340 are from the transverse edges 34D. Thus, the orifices 320 and 340 are offset from each other, in a direction parallel to the longitudinal axes A32 and A34, so that there is no overlap between these orifices in the direction of the axis A30.

[0076] We denote d32 a distance measured parallel to the axis A32 between the axis B32 and a straight line passing through the geometric centers of the orifices 320. We denote d34 a distance measured parallel to the axis A34 between the axis B34 and a straight line passing through the geometric centers of the orifices 340. The distances d32 and d34 are different. In the example, the distance d32 is greater, by a non-zero difference A24, compared to the distance d34 and this difference A24 induces an offset between the orifices 320 and 340, parallel to the longitudinal axes A32 and A34, such that there is no superposition between them.

[0077] According to a variant of the invention not shown, in addition to or instead of the offset in a direction parallel to the longitudinal axes A32 and A34, the orifices 320 and 340 are offset relative to each other, in a direction parallel to the transverse axes B32 and B34, which also avoids superposition between these orifices in a direction parallel to the axis A30.

[0078] We denote S42 the surface of the first bipolar half-plate 42 facing the frame 30 in the assembled configuration of the subassembly 6. We denote S44 the surface of the second bipolar plate 44 facing the frame 30 in the assembled configuration of the subassembly 6. In the assembled configuration of the subassembly 6, each orifice 320 extends, through the half-frame 32, between the surfaces S34 and S42, while each orifice 340 extends, through the half-frame 34, between the surfaces S32 and S44.

[0079] In the vicinity of two of its opposite corners, the first bipolar half-plate 42 is provided with two cutouts 48 which open onto two opposite longitudinal edges of this half-plate and which give access, from above in figure 1, to two zones Z2 of the first half-frame 32 which are opposite with respect to the axes A32 and B32 and which cover from above the orifices 340 of the second half-frame 34, when the subassembly 6 is mounted. Likewise, the second bipolar half-plate 44 is provided, at two of its opposite corners, with two cutouts 49 which open onto two longitudinal edges and two opposite transverse edges of this half-plate and which give access, from below in figure 1, to two zones Z4 of the second half-frame 34 which are opposite with respect to the axes A34 and B34 and which cover from below the orifices 320 of the first half-frame 32, when the subassembly 6 is mounted.

[0080] A system of peripheral seals 50 is arranged between the frame 30 and the bipolar half-plates 42 and 44, on each side of the frame. In practice, two peripheral seals 50 are provided, one on the surface S'32, the other on the surface S'34. These seals 50 surround both the central opening 30C and the openings 36 of the frame, so that they ensure sealing, with respect to the exterior of the subassembly 6, for each of the operational fluids of the cell, namely hydrogen, oxygen, air and the possible cooling fluid. These peripheral seals 50 therefore fluidically isolate the cathode compartment from the exterior and the anode compartment from the exterior.

[0081] Each of the openings 36, 46 is also surrounded by a system of opening seals 51 which allow, for a given fluid compartment, namely one of the anode compartment, the cathode compartment and possibly a cooling compartment between two adjacent cells, the fluid communication of this given compartment only with the openings 36, 46 which allow the entry and exit of the fluid in this compartment. In practice, two series of opening seals 51 are provided, one on the surface S'32, the other on the surface S'34.

[0082] In Figure 3, the joints 50 and 51 are shown in dotted lines, seen through the bipolar half-plate 42. The joints 50 surround an internal zone Z int of the subassembly 6 in which the CCM membrane 25, the gas diffusion layers 28 and 29 and the gallery portions formed by the openings 36 and 46 are located. A peripheral external zone Zext of the subassembly 6 is defined around the joints 50, between these joints and the external edges of the subassembly. The joints 50 surround the different joints 51 which connect to the joints 50. In other words, the joints 51 are located in the internal zone Z int .

[0083] We define an external peripheral zone Z ext3 o of frame 30 as the area of ​​this frame which belongs to the peripheral external zone Z ext of subassembly 6 in the assembled configuration of this cell. The peripheral external zone Z ext3 o therefore surrounds the joints 50, on each of the half-frames 32 and 34.

[0084] In order not to break the seal provided by the seals 50, and as visible in Figures 1 to 3, the first and second orifices 320 and 340 are preferably provided in the peripheral external zone Z ext3 o of frame 30, therefore in the peripheral external zone Z ext of subset 6.

[0085] A method of manufacturing a subassembly 6 as mentioned above is described below.

[0086] In a first preliminary step, the surfaces S32 and S34 are coated with glue. This preliminary step can be carried out at the site where the membrane-electrode assembly 2 is manufactured, just before the following steps or in advance. Alternatively, this preliminary step can be carried out at a remote site, from which the half-frames coated with glue are transported to the site where the membrane-electrode assembly is manufactured. The operation of coating the surfaces S32 and S34 with the glue can therefore be carried out by a manufacturer other than the one manufacturing the membrane-electrode assembly. In such a case, a protective film can be provided on the layer of glue for transporting it, this protective film then being removed before the second step described below.

[0087] In a second step, the two half-frames 32 and 34 are pressed by their surfaces S32 and S34 along the plane TT30, while the membrane 22 is arranged between them, which has the effect of pinching the edge 22a of the membrane 22 and securing the frame 30 and the membrane 22, that is to say the frame 30 and the CCM membrane 25. The frame 30 is formed by the adhesion of the surfaces S32 and S34 thanks to the glue which is coated there.

[0088] Advantageously, during the second step, the assembly of the two half-frames 32 and 34, by trapping the edges of the membrane 25, is carried out by activating the glue by applying ultrasound. Typically, the assembly of the two half-frames 32 and 34 trapping the membrane 25 is clamped between a sonotrode and an anvil, and the ultrasound transmitted by the sonotrode to the two half-frames 32 and 34 ensures the activation of the glue, therefore the bonding of the two half-frames 32 and 34 together and, in the overlapping zone, the bonding of the two half-frames 32 and 34 with the membrane. Conventionally, the application of ultrasound can be implemented in particular by means of a ridged sonotrode, such as those known for example from US-B-10981245 or US-A-2013 / 213552.Typically, as illustrated in US-A-2013 / 213552, the ribbing may for example be formed of two or three networks of grooves formed on the surface of the sonotrode, each network comprising grooves parallel to each other in a direction specific to each network. The grooves of the networks thus delimit between them projecting pins which are the preferred contact zones with the frame during the application of ultrasound. It is noted that the use of a ribbed sonotrode may form, at least on the surface of the half-frame with which the sonotrode is in contact, a texturing of the surface of the half-frame which is substantially the reverse image of the ribbing of the sonotrode. This texturing may have a depth less than the depth of the ribbing of the sonotrode. The sonotrode may be ribbed over its entire surface in contact with the two half-frames 32 and 34, or over only part of its surface.Preferably, the entire surface of the two half-frames 32 and 34 is assembled by ultrasound. In other words, the bonding zone of the two half-frames, which corresponds to the zone where the ultrasound is applied, then corresponds to the entire surface area of ​​the frame 30. In certain embodiments, the entire bonding zone of the two half-frames, which corresponds to the zone where the ultrasound is applied, has a texturing of the surface of the half-frame which is substantially the reverse image of the striation of the sonotrode. In other embodiments, only one or more portions of the bonding zone of the two half-frames, which corresponds to the zone where the ultrasound is applied, has such a texturing, other portions of the bonding zone resulting from the activation of the glue by means of a smooth sonotrode or a smooth portion of a sonotrode.In the overlapping zone of the frame 30 with the membrane 25, the ultrasound causes the assembly by bonding of each of the two half-frames 32 and 34 on the corresponding face of the membrane. Preferably, it is avoided that the sonotrode comes into contact with the membrane 25 inside the window delimited inside each half-frame, to avoid heating and compressing the membrane 25 in its actually active part which will be exposed to the reagents. The sonotrode implemented can be in the form of a frame, possibly allowing the complete assembly of the frame 30 on the membrane 25 in a single operation. Alternatively, it is possible to provide the implementation of a sonotrode covering only a part of the desired bonding zone, the complete assembly of the frame 30 on the membrane 25 can then be carried out in several successive operations.Alternatively, it is possible to provide for the implementation of several sonotrodes each covering only a part of the bonding zone, the complete assembly of the frame 30 on the membrane 25 then being able to be carried out in a single operation for all the sonotrodes simultaneously, or in several successive operations with one or more sonotrodes implemented in each operation. During a third step, the diffusion layers 28 and 29 are deposited on the frame 30 then assembled thereon by any appropriate technique, for example by bonding.

[0089] In a fourth step, the two bipolar half-plates 42 and 44 are applied on either side of the frame 30 equipped with the CCM membrane 25 and the GDL layers 28 and 29, more precisely on the external surfaces S'32 and S'34 of the half-frames 32 and 34. The locations and dimensions of the cutouts 48 and 49 are chosen such that, at the end of the fourth step, the bipolar half-plate 42 covers the orifices 320 and the cutouts 48 are aligned, parallel to the axis A30, with the orifices 340, while the bipolar half-plate 44 covers the orifices 340 and the cutouts 49 are aligned, parallel to the axis A30, with the orifices 320.Thus, in a direction parallel to the axis A30, each orifice 320 is arranged between a solid portion 42A of the bipolar half-plate 42 and a solid portion 34A or 34B of the half-frame 34, opposite a cutout 49, and each orifice 340 is arranged between a solid portion 44A of the bipolar half-plate 44 and a solid portion 32A or 32B of the half-frame 32, opposite a cutout 48. The solid portions 32A and 34A of the half-frames 32 and 34 are formed, in this embodiment, at their longitudinal ends 32A and 34A. The solid portions 32A and 34A of the half-frames 32 and 34 are constituted by zones respectively devoid of openings 36 and orifices 320 or 340. At the level of these solid portions 32A and 34A, the surfaces S32 and S34 are not interrupted. The solid portions 42A and 44A of the bipolar half-plates 42 and 44 are constituted by zones respectively devoid of openings 46 or other orifice or cutout.At the level of these solid portions 42A and 44A, the surfaces S42 and S44 are not interrupted.

[0090] The geometry of the GDL 28 is such that it does not interpose between the first orifices 320 and the solid portions 42A of the bipolar half-plate 42 which are opposite the orifices 320, so as to allow direct contact, through a given first orifice 320, of the solid portion 34A, corresponding to this given first orifice 320, of the half-frame 34, with the solid portion 42A corresponding to this given first orifice 320, of the bipolar half-plate 44. Similarly, the geometry of the GDL 29 is such that it does not interpose between the second orifices 340 and the solid portions 44A of the bipolar half-plate 44 which are opposite the orifices 340, so as to allow direct contact, through a given second orifice 340, of the solid portion 32A, corresponding to this second given orifice 340, of the half-frame 32, with the solid portion 44A corresponding to this first given orifice 340, of the bipolar half-plate 42.In both cases, such relative positioning may be achieved by the geometry of the external contour of the GDL 28, 29, as in the illustrated example, or perhaps achieved by the presence of an orifice in the GDL 28, 29. A solid portion of a half-frame or a half-bipolar plate corresponds to a first or second orifice when it is aligned with, in other words opposite, this orifice, in a direction parallel to the axis A30.

[0091] A nine-layer structure is thus formed, namely the three layers 22, 23 and 24 of the CCM membrane 25, the two half-frames 32 and 34, the two GDLs 28 and 29 and the two bipolar half-plates 42 and 44. This multi-layer structure is intended to form the sub-assembly 6, at the end of the method of the invention.

[0092] A fifth step of securing the first and second bipolar half-plates 42 and 44 with the frame 30 is implemented by activating, for example by heating, the glue present on the surfaces S32 and S34, at least over the extent of the solid portions 34A of the half-frame 34 which are opposite the first orifices 320, and over the extent of the solid portions 32A of the half-frame 32 which are opposite the second orifices 340. This activation can optionally be completed by a pressing operation to ensure contact, through first and second orifices 320 and 340, of the glue thus activated with the corresponding solid portion 44A, 42A of the bipolar half-plate 44, 42. The optional pressing can be concomitant, at least in part, with the activation. Pressing may follow activation, or may begin before or during activation and continue beyond activation.Thus, through a first given orifice 320, the solid portion 34A of the half-frame 34, which is opposite this first given orifice 320, is secured to the corresponding solid portion 42A of the bipolar half-plate 42, which is also opposite this first given orifice 320, this in particular by the glue initially carried by the solid portion 34A of the half-frame 34. It can therefore be considered that at least a part of the glue initially carried by the half-frame 34 migrates, through the first given orifice 320, to reach the surface S42 of the polar half-plate 42. Similarly, through a second given orifice 340, the solid portion 32A of the half-frame 32, which is opposite this second given orifice 340, is secured to the corresponding solid portion 44A of the bipolar half-plate 44, which is opposite this second orifice 340 given, this in particular by the glue initially carried by the solid portion 32A of the half-frame 32.It can therefore be considered that at least part of the glue initially carried by the half-frame 32 migrates through the second given orifice 340 to reach the surface S44 of the polar half-plate 44.

[0093] Furthermore, the activation of the glue may, in particular in the case of thermoplastic glues activated by heating, have the effect of fluidizing this glue and of allowing a portion of this glue, in particular that located in the vicinity around a given first and / or second orifice 320 and 340, to then migrate into this orifice 320 and 340, respectively in the direction of the surfaces S44 and S42. In particular, the heating of the glue present on the surface S34 may also have the effect of causing a portion of the glue present between the half-frames 32 and 34 to flow into the orifices 320. Similarly, the heating of the glue present on the surface S32 may also have the effect of causing a portion of the glue present between the half-frames 32 and 34 to flow into the orifices 340.Thus, during the fifth step, the glue previously coated on the surfaces S32 and S34 can flow between these surfaces and migrate into the nearest hollow volumes which are constituted by the orifices 320 and 340. From there, the glue flows, in these orifices, towards the edges of these orifices which adjoin the surfaces S42 and S44 of the bipolar half-plates 42 and 44 which it reaches at the end of the fifth step.

[0094] The above assumes such migration of the glue "in the vicinity and around" the first and / or second orifices. This implies that the glue is activated, in particular by heating, on an area which covers these orifices and whose area is strictly greater than that of these orifices.

[0095] During the fifth step, the first bipolar half-plate 42 is secured to the frame 30 using the glue present in the orifices 320, while the second bipolar half-plate 44 is secured to the frame 30 using the glue present in the orifices 340.

[0096] The fifth step is advantageously carried out by applying a localized heat source 82 to the half-frame 34, located in alignment with each orifice 320 in a direction parallel to the axis A30, and by applying a localized heat source 84 to the half-frame 32, located in alignment with each orifice 340 in a direction parallel to the axis A30, as shown in FIG. 4. The application of the heat source 82 or 84 makes it possible to locally raise the temperature of the glue, in order to ensure its activation and, possibly, to facilitate its flow in the orifices 320 and 340.

[0097] The heat source is advantageously a heating rod that can be manipulated manually by an operator or by a robot and that includes a heating resistor. The heating rod can notably be of the type of a hand-held soldering station stylus. The heating rod can also be a system operating by impulse.

[0098] Optionally, a mechanical force, i.e. pressure from the heat source towards the frame, is exerted in conjunction with the heat input, which makes it possible to secure the activation of the glue and the assembly of the frame 30 with the bipolar half-plate 42.

[0099] Here the heating bar 82 is inserted, in a direction parallel to the axis A30, into a cutout 49 and / or the heating bar 84 is inserted, in a direction parallel to the axis A30, into a cutout 48, to provide heat as close as possible to the glue coated on the surface S34 or S32, by direct application to the zone Z4 or Z2 of the half-frame 34 or 32 accessible through the cutout in question.

[0100] Alternatively, only one of the bipolar half-plates 42 or 44 is equipped with cutouts.

[0101] The fact that the cutouts 48 and 49 each open onto at least one longitudinal edge of the bipolar half-plates 42 and 44 facilitates contact between the heating bar 82 or 84 and the half-frame 32 or 34.

[0102] Alternatively, in the fifth step, the glue is heated by radiation, convection, especially with blown hot air, or by applying ultrasound or ultraviolet rays. The choice of heating method, and therefore of the heat source used, depends on the type of glue used and the geometry of the bipolar half-plates and the frame.

[0103] Additionally and advantageously, as already mentioned above, a step of pressing the multilayer structure, in a direction parallel to the axis A30, can be implemented, as well as a step of applying vibrations to the glue present in the multilayer structure. This pressing and this vibration facilitate the migration of the glue, from the surfaces S34 and S32 respectively towards the surfaces S42 and S44, within the orifices 320 and 340 and / or can facilitate the contacting of this glue with the surface S42 and S44 through the orifices 320 and 340. The pressing can be localized, for example concentrated on the extent of the first and second orifices, or can be extended to a larger area of ​​the multilayer structure, possibly to the entire surface of the multilayer structure or to the entire portion of the surface of the multilayer structure which is located outside the perimeter of the GDLs 28 and 29.

[0104] Following the fifth step, a quantity Q2 of glue initially located on the surface S34 is present in each orifice 320, such that it connects the surface S42 to the portion of the surface S34 located opposite this orifice 320 and possibly to the edge of this orifice which adjoins the surface S34, that is to say at the level of the solid portion 34A of the half-frame 34 which is opposite the orifice 320. In addition, a quantity Q4 of glue initially located on the surface S32 is present in each orifice 340, such that it connects the surface S44 to the portion of the surface S32 located opposite this orifice 340 and possibly to the edge of this orifice which adjoins the surface S32, that is to say at the level of the solid portion 32A of the half-frame 32 which is opposite the orifice 340.In other words, the quantity of glue Q2 generally comes essentially from the glue initially coated on the surface S34, while the quantity of glue Q4 generally comes essentially from the glue initially coated on the surface S32. In this respect, the fact that there is no overlap between the orifices 320 and 340 ensures that a solid portion of a half-frame, coated with glue, is exposed, through each orifice 320 or 340, opposite a solid portion of the opposite half-plate. Thus, the quantities of glue Q2 and Q4 which extend respectively into the orifices 320 and 340 ensure the bonding, either of the first bipolar half-plate 42, or of the second bipolar plate 44, on the frame 30, without direct connection between these two half-plates 42, 44 through the frame 30.

[0105] The glue constituting a quantity Q2 can be formed by the sole quantity of glue present on the portion of the surface S34 facing an orifice 320, while glue constituting a quantity Q4 can be formed by the sole quantity of glue present on the portion of the surface S32 facing an orifice 340.

[0106] Alternatively and as explained above, the glue constituting a quantity Q2 may be formed from the glue which was, before the fifth step, on the surface S34, both at and around an orifice 320, whereas the glue constituting the quantity Q4 is formed from the glue which was, before the fourth step, on the surface S32, both at and around an orifice 340.

[0107] Preferably, the quantity Q2 of glue extends, within the first orifices 320, parallel to the plane TT30. In other words, the quantity Q2 of glue is not deformed during the assembly process, so that the quantity Q2 of glue is, on the finished product, not deformed, but on the contrary parallel to the plane TT30.

[0108] In other words, the method of manufacturing the subassembly 6 of the invention takes advantage of the fact that an adhesive is applied to the surfaces S32 and S34 to use it, on the one hand, to secure the half-frames 32 and 34 to each other and around the CCM membrane 25 and, on the other hand, to secure the bipolar half-plates 42 and 44 to the frame 30, without using an additional adhesive, welding or other assembly means.

[0109] The section of the orifices 320 and 340 can be chosen with a relatively small area, less than or equal to 50 mm 2 , preferably 20 mm 2This avoids weakening the frame 30, while allowing effective securing of the bipolar half-plates 42 and 44 to the frame. In addition, the section of the orifices 320 and 340 can be chosen with an area greater than or equal to 5 mm. 2 , preferably 10 mm 2 This allows the glue surface in contact with a surface S42 or S44 to be sufficient to ensure effective immobilization of the bipolar half-plate 42 or 44.

[0110] For example, the orifices 320 and 340 may be circular in shape, with a diameter of between 3 and 8 mm, preferably of the order of 5 mm, as shown in the figures. Alternatively, they may be of any other shape, for example polygonal (triangle, rectangle, pentagon, hexagon, etc.) or oblong in shape, with a length in the range of 5 to 10 mm, for example 7 mm, and a width in the range of 2 to 5 mm. Of course, a larger size of the orifices is also possible, making it possible in particular to increase the adhesion strength, but with potential repercussions on the total size, or on the positioning with respect to the plate.

[0111] At the end of the fifth step of the method of the invention, the subassembly 6 constitutes an electrochemical cell and can be handled, by a human operator or a robot, without risk of seeing its different layers separate from each other, because these are effectively held in relation to each other thanks to the glue coated on the surfaces S32 and S3 during the first preliminary step and part of which is in the orifices 320 and 340.

[0112] When several electrochemical cells have thus been created, in the form of subassemblies 6, by repeating the first to fifth steps mentioned above, it is possible to continue the manufacture of the fuel cell 8 by forming, during a subsequent step, a stack, by juxtaposition of the different cells, as shown in Figure 7 for the third embodiment. This subsequent step is easy and quick to implement, by handling the electrochemical cells each individually.

[0113] The first five steps mentioned above make it possible to constitute cells which have all their main components, including the CCM membrane 25 and the two bipolar half-plates 42 and 44, and which, in the context of normal handling, do not risk separating or accidentally shifting, which makes it possible to test them, or even to pre-activate them. Indeed, creating an individual electrochemical cell in this way offers the opportunity to test it subsequently with suitable tooling, tooling ensuring the various seals and making it possible to supply the reagents and possibly the cooling fluid. Such test tooling is advantageously capable of, and designed to, measure the efficiency of the cell. Advantageously, the same tooling, or a separate tooling makes it possible to carry out, at least partially, the electrochemical running-in which is usually carried out after the stacking of the cells, when the battery is assembled.Such activation, at least partial, makes it possible to bring the electrochemical performances to the level or close to the expected level of initial performances. Such testing and / or pre-activation operations make it possible to validate the operation and performances of the cell thus pre-assembled, before integrating them into the stack.

[0114] In the first embodiment, the sealing of the anode compartment, between the membrane-electrode assembly 2 and the anode bipolar half-plate, and of the cathode compartment, between the membrane-electrode assembly 2 and the cathode bipolar half-plate, is ensured by the peripheral sealing gaskets 50 and the opening gaskets 51, and not by the pre-assembly of the membrane-electrode assembly 2 with one and / or the other of the bipolar half-plates, as described above. Indeed, this pre-assembly by the quantities Q2, Q4 of glue which extend through the first and / or second orifices 320, 340 and which come from the glue coated on the first surface S34 of the second half-frame 34 or from the glue coated on the second surface S32 of the first half-frame 32, only form a pre-assembly at the level of point zones. This pre-assembly is therefore unable to ensure fluid tightness of the compartment concerned with respect to the exterior.

[0115] In the second to fourth embodiments shown in Figures 5 and following, the elements similar to those of the first embodiment bear the same references. In the following, we mainly describe what distinguishes these embodiments from the first. If a reference is mentioned in the remainder of the description without being shown in one of Figures 6 to 8 or if a reference is shown in one of Figures 6 to 8 without being mentioned in the remainder of the description, it designates the same object as that bearing the same reference in the first embodiment.

[0116] In the second embodiment, the bipolar half-plates 42 and 44 are devoid, for at least one orifice 320 and / or 340, of a cutout comparable to the cutouts 48 and 49 of the first embodiment. More particularly, in certain variants of this second embodiment, the bipolar half-plates 42 and 44 are entirely devoid of cutouts comparable to the cutouts 48 and 49 of the first embodiment, so that each second orifice 340 is arranged between a solid portion 44A of the second bipolar half-plate 44 and a solid portion 32A of the half-frame 32 which is itself arranged opposite a solid portion 42A of the first bipolar half-plate 42. In other words, at the level of the second orifices, the frame 30 is covered, on its two opposite sides, by the bipolar half-plates 42 and 44. Thus, the bipolar half-plates are simpler to manufacture than in the first embodiment and are interchangeable.

[0117] In this second embodiment, the heating of the glue is obtained by applying a heat source 84 not directly to the frame 30, as in the first embodiment, but to the portion 44A of the second half-plate 44, in the area where it is desired to be secured to the frame 30, that is to say opposite an orifice 340. A quantity Q2 of glue, which has migrated from the layer of glue previously coated on the surface S32 of the half-frame 32, then ensures the connection between the frame 30 and the bipolar half-plate 44 through the orifice 320.

[0118] In a variant not shown, the heat source can be applied to the portion 42A of the first half-plate 42. At each orifice 320, the situation is symmetrical with respect to the plane TT30, with respect to that shown in figure 5.

[0119] This method is simpler to implement than the previous one, at the cost of potentially less efficient heating of the glue.

[0120] In Figures 6 and 8, the areas where it is preferable to provide the first and second orifices 320 and 340 are identified with single-line hatching and the exclusion areas, where these orifices are preferably not provided, are identified with cross-hatching.

[0121] In the third embodiment of Figures 6 and 7, the subassembly 6 comprises a peripheral seal system 50, which is formed of peripheral seals providing the same function as the peripheral seal system 50 of the first embodiment. An opening seal system 51 is also provided, with the same function as the opening seal system 51 of the first embodiment.

[0122] In the third embodiment of Figures 6 and 7, the peripheral seals 50 partly provide the sealing function of the openings, with the opening sealing seals 51 which connect with the peripheral seal 50.

[0123] Compared to the first embodiment, an additional peripheral seal 50 is arranged on the surface of the bipolar half-plate 42 opposite the frame 30, as visible in the upper part of the inserts A) and B) of figure 7. According to a variant of the invention not shown, the same is true at the level of the opening sealing joints 51.

[0124] As can be seen in Figure 7, the stack 60 of electrochemical cells 6, produced within a fuel cell 8 according to the invention, comprises several electrochemical cells, formed by subassemblies 6 also according to the invention, which are separated by bipolar plates 4 each constituted by a first bipolar half-plate 42 belonging to a cell 6 and by a second bipolar half-plate 44 belonging to an adjacent cell 6, the frames 30 of these subassemblies being held tightly in a sealed manner relative to the bipolar plates 4, with peripheral seals 50, arranged in particular along the longitudinal edges of the electrochemical cells and opening seals 51 which each surround one of the openings 36, 46 forming the fluid flow galleries within the stack of electrochemical cells.

[0125] The peripheral seals 50 delimit the inner limit of a peripheral external zone Z ext of subassembly 6 which is delimited in a sealed manner with respect to the anodic, cathodic and cooling fluid compartments. The peripheral external zone Z ext of the subassembly 6 is therefore located towards the outside with respect to at least one peripheral seal 50 of the subassembly 6. It is in this peripheral external zone Z ext , external, in particular with respect to the peripheral seal 50 provided between the frame 30 and the first bipolar half-plate 42, that it is preferably chosen to place the first orifices 320 arranged through the first half-frame 32 and the solid portions 42A of the first bipolar half-plate 42. It is also in this external peripheral zone Z ext, external, in particular with respect to the peripheral seal 50 provided between the frame 30 and the second bipolar half-plate 42, that it is preferably chosen to place the second orifices 340 arranged through the second half-frame 34 and the solid portions 44A of the second bipolar half-plate 44. For each electrochemical cell 6, the peripheral seals 50 are generally arranged radially set back inwards with respect to the external edges of the bipolar half-plates and the external edges of the frame of the membrane-electrode assembly, so that it is actually possible to use this peripheral external zone Z ext to place there the first orifices 320 arranged through the first half-frame 32 and the solid portions 42A of the first bipolar half-plate 42, and / or the second orifices 340 arranged through the second half-frame 34 and the solid portions 44A of the second bipolar half-plate 44. It is noted that it is possible to provide that the contour of the peripheral sealing joints 50 can be adapted, to locally present a detour towards the interior, in order to increase the peripheral external surface Z ext available around the first orifices 320 and / or the second orifices 340.

[0126] Furthermore, on each side of the frame 30, the opening seals 51 delimit, in combination with the corresponding peripheral seal 50 and around the openings 36, 46, gallery framing zones Z eg . Six Z gallery framing areas egare therefore visible in Figure 6. Each of the Z gallery framing zones eg is fluidically isolated from the anode, cathode and cooling fluid compartments. Each of the Z gallery framing zones eg can also accommodate at least some of the first orifices 320, arranged through the first half-frame 32 opposite a solid portion 42A of the first bipolar half-plate 42, and / or at least some of the second orifices 340, arranged through the second half-frame 34 opposite a solid portion 44A of the second bipolar half-plate 44. It should be noted, however, that each gallery framing zone Z eg is likely to be fluidly connected with the gallery it surrounds.

[0127] Such zones may also be defined in the first and second embodiments, even if they are not formally identified in Figures 1 to 6. In Figures 6 and 7, the presence of the bonding zones Z2, Z4 has been illustrated, which correspond respectively to the position of the first orifices 320 and the second orifices 340, along the longitudinal edges of the subassembly 6, at the height of the active zone corresponding to the presence of the CCM membrane 25. However, these bonding zones Z2, Z4 could be, as in the example of Figure 3, located near the longitudinal ends of the subassembly 6, for example longitudinally at the height of the openings 36, 46 of the subassembly 6, or even beyond the openings 36, 46 of the subassembly 6 in the longitudinal direction starting from the center of the subassembly 6.Alternatively, and as envisaged above, these bonding zones Z2, Z4 may be located in one or other of the gallery framing zones Z. eg .

[0128] More specifically, it is particularly advantageous, as illustrated in FIG. 3, to provide at least four first orifices 320 and, where appropriate, at least four second orifices 340, each located at one of the four corners of the membrane electrode assembly, a corner being defined as being a portion of the membrane electrode assembly which is included in the peripheral external zone Z ext and which is:

[0129] - longitudinally at the height of the openings 36 of the frame 36 forming galleries for reactive or cooling fluid of the sub-assembly 6, or beyond these openings 36, 46 in the longitudinal direction starting from the center of the sub-assembly 6;

[0130] - and / or transversely at the height of that of the openings 36 of the frame 36, forming a gallery of reactive or cooling fluid of the sub-assembly 6, which is the closest transversely to the longitudinal edge considered, or beyond this opening 36 in the transverse direction starting from the center of the sub-assembly 6.

[0131] In Figure 7, but also in Figure 4, it has been illustrated that it is advantageous to provide that the solid portion 42A of the first bipolar half-plate 42, which is opposite a first orifice 320 of the first half-frame 32, and / or the solid portion 44A of the second bipolar half-plate 44, which is opposite a second orifice 340 of the second half-frame 34, is folded down to be arranged, along the axis A30, at a position equal to the position of the median plane TT30 of the frame 30 along the axis A30, or close to it, this in order to minimize the deformation of the frame along the axis A30 at the location of the junction of the frame 30 with the corresponding bipolar half-plate 42.This position can be exactly that of the median plane TT30 of the frame 30 along the axis A30, or be offset from that of the median plane TT30 of the frame 30 by a value less than or equal to the thickness of the frame 30 along the axis A30, ideally offset from that of the median plane TT30 of the frame 30 by a value equal to the thickness, along the axis A30, of the half-frame 32, 34 in which the orifice 320, 340 is formed. In the example of FIGS. 6 and 7, the bipolar half-plates 42, 44 have reliefs along the axis A30, these reliefs corresponding to bottoms of reactive fluid circulation channels, to separation teeth between two channels, to bearing surfaces for sealing joints 50, 51. These reliefs can be moved away from the median plane TT30 of the frame 30 along the axis A30.It can however be seen that, just as in the example of FIG. 4, the first bipolar half-plate 42 is formed in such a way that the solid portion 42A opposite a first orifice 320 is arranged in a position which, along the axis A30, is offset from that of the median plane TT30 of the frame 30 by a value equal to the thickness, along the axis A30, of the half-frame 32 in which the first orifice 320 is formed.

[0132] Thus, in the case of a bipolar half-plate formed from a stamped metal sheet, the solid portion 42A of the first bipolar half-plate 42, which is opposite a first orifice 320 of the first half-frame 32, may correspond to a stamped shape of the sheet forming the first bipolar half-plate 42 and / or the solid portion 44A of the second bipolar half-plate 44, which is opposite a second orifice 340 of the second half-frame 34, may correspond to a stamped shape of the sheet forming the second bipolar half-plate 44.

[0133] In the embodiment of Figure 8, the opening seals 51 are separate from the peripheral seals 50 and therefore have a closed contour ensuring by themselves the sealing function, for each anodic, cathodic or cooling fluid compartment, between the compartment concerned and at least those of the openings 36 and 46 which do not communicate with this given compartment. In the embodiment of Figure 8, the opening seals 51 each delimit by themselves a gallery framing zone Z eg and portions of the internal area lie between two Z gallery framing areas eg , as represented by the cross-hatched areas disposed between two opening seals 51 in Figure 8.

[0134] In this embodiment also, the first and second orifices 320 and 340 are preferably provided in the peripheral external zone Z extof subset 6.

[0135] According to a variant not shown of the fourth embodiment, some or all of the gluing zones Z2, Z4 may be provided in one or more gallery framing zones Z eg ..

[0136] According to another variant of the invention, not shown, applicable to all embodiments, only one of the first orifices 320 or only some of them is / are provided in the peripheral external zone Z ext or in one or more Z gallery framing areas eg . Similarly, it can be provided that only one of the second orifices 340 or only some of them is / are provided in the peripheral external zone Z e xt or in one or more Z gallery framing areas eg .

[0137] Whatever the embodiment, in the stack, such as the stack 60 shown in FIG. 7, at least one electrochemical cell 6 is in accordance with the invention. Preferably, for the sake of homogeneity, all the electrochemical cells 6 are in accordance with the invention.

[0138] According to a variant not shown of the invention, applicable to all embodiments, the subassembly 6 comprises a first polar half-plate 42 on one side only and this is joined to a second polar half-plate 44 to form a pre-assembled polar plate 4, before joining the frame 30 and the polar half-plate 42, with the bonding technique using, for example, the first orifices 320. In this case, the subassembly 6 is a multilayer structure which is not symmetrical with respect to the plane TT30, since the two joined polar half-plates are located on the side of the half-frame 32. This subassembly 6 can be integrated into a stack of the type of stack 60 shown in FIG. 7, in one operation because it can be handled individually by an operator or a robot.Each subassembly 6 then constitutes a part of an electrochemical cell, since it must be associated with the second bipolar half-plate 44 which is itself part of another pre-assembled bipolar plate 4 of an adjacent subassembly to constitute a complete cell. In this case, only the first orifices 320 are provided through the first half-frame 32, without the need to provide second orifices through the second half-frame 34, only the component of the fifth step shown in the upper part of Figure 4, or a symmetrical component of that shown in Figure 6, is implemented and the glue may only be coated on the first surface S34 of the second half-frame 34. This embodiment does not allow testing or pre-activating a cell before the stack is formed.

[0139] The invention is shown in the figures in the case where the membrane 25 is of the CCM type, the catalytic layers 23, 24 being carried by the base membrane 22. It is also applicable to the case where the catalytic layers 23, 24 are carried by the diffusion layers 28 and 29, according to the CCB technology, from the English “Catalyst Coated Baking” or even in the case of a mixed assembly, with one of the catalytic layers 23, 24 which is carried by the base membrane 22, and the other of the catalytic layers 23, 24 which is carried by the corresponding diffusion layer 28 or 29.

[0140] Alternatively, the subassembly 6 does not include the diffusion layers 28 and 29, which can moreover be omitted, and / or replaced by structures integrated into the bipolar plates 4. Whatever the embodiment or variant considered, the quantity of glue Q2 or Q4 present in an orifice 320 or 340 does not necessarily fill the entire volume of this orifice.

[0141] In the embodiments mentioned above, the orifices 320 and 340 have the same geometry, as shown in the figures. In a variant not shown, one or more of the orifices of a half-frame has a geometry different from that of the other orifices of this half-frame and / or one or more of the orifices of a half-frame has a geometry different from that of one or more orifices of the other half-frame.

[0142] The embodiments and variations contemplated above may be combined to generate new embodiments of the invention.

Claims

CLAIMS 1. Subassembly (6) for fuel cell stack (8) comprising - a membrane-electrode assembly (2) including o a membrane (22, 25) o a bipartite frame (30) formed by ■ a first half-frame (32) arranged on a first side of the membrane; ■ a second half-frame (34) arranged on a second side of the membrane; - and at least one first bipolar half-plate (42), in which at least the second half-frame (34) is coated, on a first surface (S34) opposite a first surface (S32) of the first half-frame (32), with a layer of glue for securing the half-frames, characterized in that - first orifices (320) arranged through the first half-frame (32) are each arranged opposite a solid portion (42A) of the first bipolar half-plate (42) and opposite a solid portion (34A) of the second half-frame (34), in a direction (A30) perpendicular to a main plane of the membrane (TT22); and - the first bipolar half-plate (42) is secured to the frame (30) by a quantity (Q2) of glue which extends through the first orifices (320) and which comes from the glue coated on the first surface (S34) of the second half-frame (34).

2. Subassembly for fuel cell stack according to claim 1, characterized in that - it comprises a second bipolar half-plate (44) arranged, relative to the membrane (22, 25), opposite the first bipolar plate (4A); the first half-frame (32) is coated, on its first surface (S32), with a layer of glue for securing the half-frames (32, 34); - second orifices (340) arranged through the second half-frame (34) are each arranged opposite a solid portion (44A) of the second bipolar half-plate (44) and opposite a solid portion (32A) of the first half-frame (32), in the direction (A30) perpendicular to a main plane of the membrane (TT22); and - the second bipolar plate (44) is secured to the frame (30) by a quantity (Q4) of glue which extends through the second orifices (340) and which comes from the glue coated on the first surface (S32) of the first half-frame (34).

3. Subassembly for fuel cell stack according to claim 2, characterized in that the first and second orifices (320, 340) are offset (A24) relative to each other in at least one direction parallel to the main plane (TT22) of the membrane (22, 25), so that there is no overlap between these orifices in the direction (A30) perpendicular to the main plane of the membrane.

4. Subassembly for fuel cell stack according to one of claims 2 and 3, characterized in that the first bipolar half-plate (42) is provided with cutouts (48) aligned with the second orifices (340) and / or in that the second bipolar half-plate (44) is provided with cutouts (49) aligned with the first orifices (320), in the direction (A30) perpendicular to the main plane of the membrane.

5. Subassembly for fuel cell stack according to claim 4, characterized in that a cutout (48, 49) opens onto at least one longitudinal edge of the bipolar plate in which it is formed.

6. Subassembly for fuel cell stack according to one of the preceding claims, characterized in that each orifice (320, 340) arranged through a half-frame (32, 34) has a section whose area is greater than or equal to 5 mm 2 , preferably 10 mm 2 , with a preferably circular, rectangular or oblong shape.

7. Subassembly for fuel cell stack according to one of the preceding claims, characterized in that the glue is heat-activatable and based on thermoplastic polymer, in particular EVA copolymer.

8. Subassembly for fuel cell stack according to one of the preceding claims, characterized in that at least one of the first orifices (320) arranged through the first half-frame (32) is arranged in a peripheral external zone (Z ext ) of the subassembly (6) which is located outwards relative to a peripheral seal (50) of the subassembly (6).

9. Subassembly for fuel cell stack according to one of the preceding claims, characterized in that the membrane electrode assembly (2) comprises four corners, and in that the subassembly (6) comprises at least four first orifices (320) arranged through the first half-frame (32) and arranged in a peripheral external zone (Z ext ) of the subassembly (6) which is located towards the outside relative to a peripheral seal (50) of the subassembly (6), each in a corner of the membrane electrode assembly.

10. Subassembly for fuel cell stack according to one of the preceding claims, characterized in that at least one of the first orifices (320) arranged through the first half-frame (32) and the facing solid portion (42A) belonging to the first bipolar half-plate (42) are arranged in a gallery framing zone (Z eg ), arranged around an opening 46 of the first bipolar half-plate (42), and fluidically isolated from at least one anodic or cathodic fluidic compartment delimited in the sub-assembly, between the membrane electrode assembly (2) and the first bipolar half-plate (42).

11. Fuel cell (8) comprising a stack (60) of electrochemical cells, each with a membrane-electrode assembly (2) and two bipolar half-plates (42, 44), characterized in that at least one of the cells comprises, or is constituted by, a subassembly (6) according to one of the preceding claims.

12. Method of manufacturing a subassembly (6) comprising - a membrane-electrode assembly (2) including o a membrane (22, 25) o a bipartite frame (30) formed by ■ a first half-frame (32) arranged on a first side of the membrane ■ a second half-frame (34) arranged on a second side of the membrane - and at least one first bipolar half-plate (42), this method comprising at least one prior step of coating at least one first surface (S34) of the second half-frame (34) with an adhesive; and - a step of securing the frame (30) and the membrane (22, 25) by applying the first surface (S34) of the second half-frame, coated with glue, against the first surface (S32) of the first half-frame (32); this method being characterized in that it comprises at least one step of applying the first bipolar half-plate (42) against a second surface (S'32) of the first half-frame (32) opposite the first surface (S32) of this first half-frame; - a step of securing the first bipolar half-plate (42) and the frame (30) by migration of the glue coated on the first surface (S34) of the second half-frame (34), towards a surface (S42) of the first bipolar half-plate, through first orifices (320) arranged in the first half-frame (32), between its first and second surfaces (S32, S'32).

13. Method according to claim 12, characterized in that the subassembly comprises a second bipolar half-plate (44) and in that the method comprises at least one prior step of coating at least a first surface (S32) of the first half-frame (32) with an adhesive; a step of applying the second bipolar half-plate (44) against a second surface (S'34) of the second half-frame (34) opposite the first surface (S34) of this second half-frame; - a step of securing the second bipolar half-plate (44) and the frame (30) by migration of the glue coated on the first surface (S32) of the first half-frame (32), towards a surface (S44) of the second bipolar half-plate, through first orifices (340) arranged in the second half-frame, between its first and second surfaces (S34, S'34).

14. Method according to one of claims 12 or 13, characterized in that, during the joining step, the glue coated on the first surface (S34) of the second half-frame (34), and possibly on the first surface (S32) of the first half-frame (32), is heated at least in the vicinity of the first orifices (320), and possibly at the level of the second orifices (340).

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