Gas diffusion device for reducing head loss and method of manufacturing same

Abstract

To provide a gas diffusing device with reduced head loss, a method manufacturing thereof, and an electrochemical system including the device.SOLUTION: A gas diffusing device 6 provided with superposition cover a part of a composite material layer 62 containing a conductive fiber and a polymer resin coating the conductive fiber, and a first conductive layer 61 that includes open pores between a first surface and a second surface, and includes a first void 64 on the second surface 67, and in which the first surface 68 is in electrical contact with the conductive fibers of the composite material layer 62, and the polymer resin covers a part of the first conductive layer 61 on the first surface 68.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to the manufacture of electrochemical reactors, and more particularly to the manufacture of gas diffusion devices for electrochemical reactors. [Background technology]

[0002] Among electrochemical reactors, fuel cell stacks have undergone considerable development. They are especially envisioned as a power source for future mass-produced automobiles or as an auxiliary power source in aviation. A fuel cell stack is an electrochemical device that converts chemical energy directly into electrical energy. A fuel cell stack includes a stack of multiple cells in series. Each cell typically produces a voltage of about 1 volt, and these can be stacked to produce a power supply voltage of a higher level, for example, about 100 volts.

[0003] Among the known types of fuel cell stacks, mention may be made in particular of low-temperature proton exchange membrane (PEM) fuel cell stacks. Such fuel cell stacks have particularly advantageous properties in terms of compactness. Each cell comprises an electrolyte membrane that allows only protons to pass, but not electrons. The membrane comprises an anode on a first side and a cathode on a second side to form a membrane electrode assembly (MEA).

[0004] At the anode, dihydrogen, used as fuel, is oxidized to produce protons that pass through the membrane, thus forming an ionic conductor. Electrons produced in this reaction travel towards the flow plate and form an electric current through an electrical circuit outside the cell. At the cathode, oxygen is reduced and reacts with the protons to produce water.

[0005] A fuel cell stack may comprise a number of so-called bipolar plates stacked on top of each other, said plates being made, for example, of metal. The membrane is arranged between two bipolar plates.

[0006] The bipolar plates are conductive to collect the electrons generated at the anode. They also act as hermetic separators separating the anode and cathode currents. They also play a mechanical role in transmitting the force used to clamp the stack, which is essential for the quality of the electrical contact. Electronic conduction occurs through the bipolar plates, while ionic conduction is obtained through the membrane.

[0007] According to one design, the flow of the reagents is guided by channels in stamped metal sheets that are welded to form the bipolar plate. The metal sheets have good mechanical properties and form an effective barrier limiting the diffusion of dihydrogen. However, they have a low corrosion resistance. Furthermore, their degradation can form cations that foul the membrane and reduce the performance and lifespan of the fuel cell stack. To reduce these problems, the surface of the metal sheets is frequently treated. However, surface treatments do not improve the corrosion resistance sufficiently for certain applications and generate non-negligible additional costs. Furthermore, bipolar plates of this design, i.e. bipolar plates with channels defined by stamping, have the drawback that the dimensions of the channels are constrained by the stamping process. Thus, minimum dimensions must be respected for the width of the channels or the width of the ribs separating them. The uniformity of the current density in the fuel cell stack is therefore not optimal.

[0008] One of the factors slowing the widespread adoption of fuel cell technology is the cost of manufacturing and assembling the various components of a fuel cell stack. The manufacture of the bipolar plates in this design in particular represents a large portion of the cost of a fuel cell stack.

[0009] According to another design, the bipolar plate is smooth and the flow and diffusion of reagents is achieved through a gas diffusion layer interposed between the bipolar plate and the membrane electrode assembly. The reaction products and non-reacting species are exhausted where they exit the gas diffusion layer by entrainment with the flow. The gas diffusion layer takes the form of a porous layer with open pores, such as a layer of felt or carbon fabric. Summary of the Invention [Problem to be solved by the invention]

[0010] The gas diffusion layers must be thick enough to reduce head loss of the reagent flow, which increases the bulk of the fuel cell stack. Also, these bipolar plates are relatively heavy for certain applications. Furthermore, it proves desirable to fasten the gas diffusion layers to the bipolar plates. Furthermore, the electrical contact resistance between the gas diffusion layers and the bipolar plates remains relatively high. [Means for solving the problem]

[0011] The present invention aims to overcome one or more of these drawbacks.The present invention therefore relates to a gas diffusion device as defined in the appended claims.

[0012] The invention also relates to variants of the dependent claims. A person skilled in the art will understand that each feature of the specification or the dependent claims can be independently combined with the features of the independent claims without forming an intermediate generalization.

[0013] The invention also relates to a method for manufacturing a gas diffusion device as defined in the dependent claims.

[0014] Other characteristics and advantages of the invention will become more apparent from the description given below, given entirely by way of non-limiting indication, with reference to the attached drawings, in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is an exploded perspective view of an example stack of membrane electrode assemblies and bipolar plates of a fuel cell stack.

[0016] [Diagram 2]FIG. 2 is a cross-sectional view of a gas diffusion device with a conductive porous layer containing voids according to one exemplary embodiment, in which steps of the manufacturing process are detailed.

[0017] [Diagram 3] FIG. 2 is a cross-sectional view of a gas diffusion device with a conductive porous layer containing voids according to one exemplary embodiment, in which steps of the manufacturing process are detailed.

[0018] [Figure 4] 2 is a partial top view of a gas diffusion device having an electrically conductive porous layer including voids according to an exemplary embodiment;

[0019] [Diagram 5] FIG. 2 is a partial top view of a conductive porous layer including voids according to one variation of the example embodiment.

[0020] [Figure 6] FIG. 13 is a partial top view of a conductive porous layer including voids according to another variation of the example embodiment.

[0021] [Figure 7] FIG. 13 is a partial top view of a conductive porous layer including voids according to another variation of the example embodiment.

[0022] [Figure 8] FIG. 13 is a partial top view of a conductive porous layer including voids according to another variation of the example embodiment.

[0023] [Figure 9] 4 is a cross-sectional view of a gas diffusion device with a void-containing layer according to another exemplary embodiment, in which steps of the manufacturing process are detailed.

[0024] [Figure 10] 4 is a cross-sectional view of a gas diffusion device with a void-containing layer according to another exemplary embodiment, in which steps of the manufacturing process are detailed.

[0025] [Figure 11] 4 is a cross-sectional view of a gas diffusion device with a void-containing layer according to another exemplary embodiment, in which steps of the manufacturing process are detailed.

[0026] [Figure 12] 4 is a cross-sectional view of a gas diffusion device with a void-containing layer according to another exemplary embodiment, in which steps of the manufacturing process are detailed.

[0027] [Figure 13] 4 is a cross-sectional view of a gas diffusion device with a void-containing layer according to another exemplary embodiment, in which steps of the manufacturing process are detailed.

[0028] [Figure 14] FIG. 2 is a cross-sectional view of a gas diffusion device having a conductive porous layer containing two voids according to one embodiment of the present invention, and details various steps of the manufacturing process thereof.

[0029] [Figure 15] FIG. 2 is a cross-sectional view of a gas diffusion device having a conductive porous layer containing two voids according to one embodiment of the present invention, and details various steps of the manufacturing process thereof.

[0030] [Figure 16] FIG. 15 is a partial view from above of a gas diffusion device with two porous layers of FIG.

[0031] [Figure 17] FIG. 11 is a partial top view of a gas diffusion device according to a modified example of the third embodiment.

[0032] [Figure 18] 4 is a cross-sectional view of a gas diffusion device comprising a conductive porous layer containing three voids according to another embodiment of the present invention.

[0033] [Figure 19]1A-1D are partial cross-sectional views of an electrochemical system including a gas diffusion device according to the present invention at the end and during its manufacturing process.

[0034] [Figure 20] 1A-1D are partial cross-sectional views of an electrochemical system including a gas diffusion device according to the present invention at the end and during its manufacturing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] 1 is a schematic exploded perspective view of a stack of cells 1 of a fuel cell stack 4. The fuel cell stack 4 is formed by stacking a plurality of cells 1. The cells 1 are proton exchange membrane cells or polymer electrolyte membrane cells.

[0036] The fuel cell stack 4 comprises a fuel source 40, which supplies dihydrogen to the inlet of each cell 1. The fuel cell stack 4 also comprises an oxidant source 42, which supplies air to the inlet of each cell 1. Oxygen from the air is used as the oxidant. Each cell 1 also comprises an exhaust channel. One or more of the cells 1 have a cooling circuit.

[0037] Each cell 1 comprises a membrane electrode assembly 110 or MEA 110. The membrane electrode assembly 110 comprises an electrolyte 113, a cathode (not shown) and an anode 111, which are disposed on either side of the electrolyte and fixed to the electrolyte 113. The electrolyte layer 113 forms a semi-permeable membrane that allows proton conduction while being impermeable to gases present in the cell. The electrolyte layer also blocks the passage of electrons between the anode 111 and the cathode.

[0038] Between adjacent MEAs are arranged bipolar plates 5. Each bipolar plate 5 defines an anode flow passage and a cathode flow passage on its opposite outer face. Some bipolar plates 5 advantageously also define a flow passage for a coolant between two successive membrane electrode assemblies.

[0039] As is known, during operation of the fuel cell stack 4, air flows between the MEA and one bipolar plate, and dihydrogen flows between the MEA and the other bipolar plate. At the anode, the dihydrogen is oxidized to produce protons, which pass through the MEA. At the cathode, oxygen is reduced and reacts with the protons to produce water. Electrons generated by the oxidation of hydrogen are collected at the bipolar plate 5. Fuel Cell Stack 4 to generate an electric current. During its operation, one cell of the fuel cell stack typically produces a DC voltage of about 1 V between the anode and cathode.

[0040] The stack may also include peripheral seals and membrane reinforcements (not shown here). Each cell 1 may also include one gas diffusion layer (not shown) disposed between the anode and one of the bipolar plates, and another gas diffusion layer disposed between the cathode and the other of the bipolar plates.

[0041] Composite plies are often sold in the form of fibers pre-impregnated with a polymeric resin. These composite plies are often distributed in that form or on rolls or reels. Reinforcing fibers, such as carbon fiber, are electrically conductive.

[0042] Composite layers using pre-impregnated fibers have the advantage that they are easily deformable for shaping before the polymerization of the resin, which makes these layers very hard. The present invention aims to take advantage of certain properties of such pre-impregnated fibers in the formation of gas diffusion devices that can be combined with, for example, bipolar plates.

[0043] The present invention provides a gas diffusion device comprising a composite layer including conductive fibers and a polymeric resin impregnated with the fibers, superimposed with a conductive layer having open porosity between first and second opposing surfaces, where voids are created in the second surface, the first surface is in electrical contact with the conductive fibers of the composite layer, and the polymeric resin coats a portion of the conductive layer on the first surface.

[0044] In this way, a mechanical bond between the composite layer and the conductive layer is ensured, an optimal electrical connection between the conductive layer and the composite layer is ensured, and head losses in the flow in the plane of the conductive layer are reduced, since this flow can also occur through voids. Furthermore, the gas diffusion device thus formed benefits from the stiffness of the composite material.

[0045] 2 is a partial cross-sectional view of a gas diffusion device 2 according to an illustrative embodiment. Device 2 includes an open-pore conductive layer 20. The pores of layer 20 are open. Additionally, layer 20 is lower surface 202, A void 201 formed on the upper surface 200 of the layer 20 (here, the void 201 is a through void between the surfaces 200 and 202); a region 209 of less than the total thickness of layer 20 (whose lower surface is surface 202 and which comprises polymeric resin); It has. The porous layer 20 advantageously has a thickness of less than 0.5 mm.

[0046] The device 2 also includes a composite layer 23 including conductive fibers, advantageously made from carbon. The layer 23 has an upper surface 230 and a lower surface 232, and a polymerized resin coats the fibers. The polymerized resin is, for example, a phenolic resin. Such polymerized resin is impermeable to hydrogen, one of the reagents required for passage through the device 2. Once the resin is polymerized, the layer 23 forms a rigid composite layer. The composite layer 23 is conductive through its thickness.

[0047] The device 2 is rigid, conductive, and of unitary construction. The device 2 comprises a superposition of the elements described above. The porous layer 20 is located at the outer end of the stack and has open voids 201; A layer of composite material 23 is located at the opposite outer edge of the stack, with faces 202 and 230 in contact.

[0048] An open-pored conductive layer 20 is superimposed on a composite layer 23 (for example in the form of pre-impregnated fibers) comprising conductive fibers coated with a polymerizable resin. A uniform pressure is then applied to this superposition in a direction perpendicular to the faces 200 and 232, as shown in FIG. 3 (indicated by the white block arrows). The pressure applied is advantageously comprised between 0.5 and 1.5 MPa. This compression ensures the electrical interconnection of the fibers through the penetration of these fibers into the face 202 of the layer 20, guaranteeing both the mechanical and electrical contact between these fibers and the layer 20.

[0049] Compression allows flow of the polymerizable resin contained in layer 23 (indicated by the black block arrows) into porous layer 20 in a direction parallel to the direction of pressure. Resin flowing perpendicularly from layer 23 to layer 20 advantageously does not impregnate the entire volume of layer 20. Resin flowing perpendicularly from layer 23 to layer 20 passes through face 202 but does not reach the opposite outer face 200 of layer 20. Layer 20 can therefore participate in fluid flow through its open porosity in all areas not impregnated with resin.

[0050] For example, the volume of layer 20 may be greater than the volume of layer 23. Thus, layer 23 does not contain a sufficient amount of resin to flow and impregnate the entire volume of the conductive porous layer.

[0051] The overlap is maintained in compression and the flowed resin is polymerized. Initially, layer 23 containing the polymerizable resin forms a solidified conductive composite layer. Excess resin that flows from layer 23 through surface 202 onto layer 20 forms the conductive layer. 208 , which is solidified by the polymerizing resin after its flow. Layer 20 maintains its open porosity at the upper outer end of device 2. In particular, the resin does not reach face 200 of layer 20.

[0052] Voids 201 are then formed in face 200 of layer 20, in a direction perpendicular to the plane of the cross section shown. This step of forming voids 201 can be carried out, for example, by machining. Voids 201 are advantageously through voids between faces 200 and 202. In the example shown, a number of voids 201 are created in layer 20, distributed over its surface. Voids 201 may be created in layer 20 prior to superposition with layer 23.

[0053] FIG. 4 shows a partial view from above of a variant of the gas diffusion layer 2 described above. The voids 201 are formed in the face 200 of the layer 20. The voids 201 have a closed contour. The reagents are therefore forced to flow through the open pores of the layer 20, in order to avoid too large imbalances of head losses in the flow of the reagents through the layer 20. The voids 201 are advantageously through voids between the upper outer face 200 and the lower outer face (not shown) of the layer 20, so as to be able to obtain a large cross-sectional area for the flow of the reagents. The voids 201 are advantageously separated and take the form, for example, of parallel linear grooves of a certain length. The grooves can advantageously be obtained by a machining process or by laser ablation or by any other cutting process. Laser ablation in particular makes it possible to form a shell and to avoid an untimely subsequent flow of the resin. The grooves therefore form discontinuous flow paths. The discontinuous flow paths also allow the layer 20 to maintain a sufficient rigidity, in particular if these grooves are produced before the assembly of the layers 20 and 23. The variation in the dimensions of the grooves can also be small, so that the width of the grooves is typically less than 0.4 mm, and advantageously less than 0.2 mm.

[0054] The fluid passes partly through the formed voids 201 (as shown by the solid straight arrows in FIG. 4) and partly through the material of the porous layer 20 (as shown by the dashed straight arrows in FIG. 4). The layer 20 may be made of, for example, foam, felt or fabric.

[0055] 5 shows a partial view from above of an upper outer surface 200 of a conductive porous layer 20 according to another variant of the exemplary embodiment, which includes voids 201. The voids 201 each have a closed contour and may be, for example, through-voids between the upper outer surface 200 and a lower outer surface (not shown) of the layer 20.

[0056] In this variant, the voids 201 advantageously have a Z-shape, the Z angle adding up to 90°. The voids 201 thus formed are, for example, aligned with one another on the surface 200 in the vertical direction on the one hand and in the horizontal direction on the other hand.

[0057] 6 shows a partial view from above of an upper outer surface 200 of a conductive porous layer 20 according to another variation of an exemplary embodiment, the upper outer surface 200 includes voids 201. The voids 201 each have a closed contour and may be, for example, through-voids between the upper outer surface 200 and a lower outer surface (not shown) of the layer 20.

[0058] In this variant, the voids 201 advantageously have an L-shape. The voids 201 thus formed are, for example, grouped in pairs across an axis of symmetry. Each pair is advantageously aligned with one another on the surface 200, on the one hand longitudinally and on the other hand transversely.

[0059] 7 shows a partial view from above of the upper outer surface 200 of a conductive porous layer 20 according to another variant, which includes voids 201. The voids 201 each have a closed contour and may be, for example, through voids between the upper outer surface 200 and a lower outer surface (not shown) of the layer 20.

[0060] In this variant, the voids 201 advantageously have a T-shape. The voids 201 thus formed are, for example, grouped in pairs across an axis of symmetry. Each pair is advantageously aligned with one another on the surface 200, on the one hand longitudinally and on the other hand transversely.

[0061] 8 shows a partial view from above of the upper outer surface 200 of the conductive porous layer 20 including voids 201 according to another variant of the exemplary embodiment. The voids 201 each have a closed contour, e.g. 20 There may be a through void between the lower outer surface (not shown) of the inner casing.

[0062] In this variant, the voids 201 advantageously have a chevron shape. The voids 201 thus formed are now aligned vertically, with two adjacent rows being vertically offset.

[0063] 9 is a partial cross-sectional view of a gas diffusion device 6 according to another illustrative example. The device 6 includes an electrically conductive porous layer 61 having: lower surface 68, a void 64 formed in the upper surface 67; A region 619 that is thinner than the overall thickness of layer 61 and advantageously does not reach the surface of void 64 (the underside of region 619 is surface 68 that contains polymerized resin). The porous layer 61 advantageously has a thickness of less than 0.5 mm.

[0064] The device 6 also includes a composite layer 62 formed from conductive fibers. The resin and fibers may be of the same type as described in the first embodiment. When the resin is polymerized, the layer 62 forms a rigid composite layer. The composite layer 62 is conductive through its thickness.

[0065] The device 6 is rigid, conductive and of unitary construction. The device 6 is formed from a superposition of the elements described above. The porous layer 61 is located at the outer end of the stack and has free voids 64. A composite ply 62 is located at the opposite outer end of the stack.

[0066] To obtain the overlap, a conductive porous layer 61 may be provided in advance, the cross-section of which is shown in Figure 10. Between the faces 67 and 68, the layer 61 has open porosity.

[0067] 11 is obtained by forming voids 64 in the outer surface 67 of element 61. This step of forming voids 64 can be carried out, for example, by machining.

[0068] A composite ply 62 is then placed in contact with face 68 of ply 61, opposite void 64. Ply 62 contains conductive fibers. A polymerizable resin (not shown) infiltrates the fibers. The configuration shown in Figure 12 is obtained by superposing plies 61 and 62.

[0069] As shown in FIG. 13, a uniform pressure (indicated by the white block arrows) is applied in a direction perpendicular to the surfaces 67, 68 of the layer 61. This compression makes it possible to ensure the electrical interconnection of the fibers through their penetration into the surface 68 of the layer 61, and both the mechanical and electrical contact between these fibers and the layer 61 is guaranteed. The compression also makes it possible for the resin contained in the layer 62 to flow into the porous layer 61 (indicated by the black block arrows) in a direction parallel to the pressure direction. The resin flowing perpendicularly from the layer 62 to the layer 61 does not penetrate the entire volume of the layer 61. For example, the volume of the layer 61 can be made larger than the volume of the layer 62. In particular, the layer 62 will not contain a sufficient amount of resin to flow and penetrate the entire volume of the layer 61. The resin flowing perpendicularly from the layer 62 to the layer 61 will pass the surface 68 but will not reach the opposite outer surface 67 of the layer 61. Advantageously, the reagents pass through the voids 64, since the latter are not filled with resin. The overlap is maintained in compression and after flow the resin polymerizes.

[0070] 14 shows a partial cross-sectional view of a monolithic, rigid, electrically conductive gas diffusion device according to one embodiment of the present invention. The device includes an electrically conductive porous layer 20 including voids 201 formed in an upper outer surface 200, layer 20 also having a lower surface 202. Voids 201 are advantageously through voids between surfaces 200 and 202.

[0071] The device 2 also includes a composite layer 23 having a structure similar to that of the illustrative embodiment, with the layer 23 having an upper surface 230 and an opposite lower surface 232, with a polymeric resin coating the fibers.

[0072] Device 2 also includes a conductive layer 21 in its thickness, this layer 21 including a void 211 created in its upper surface 210. Layer 21 has the same structure and the same composition as layer 20. Layer 21 has a lower surface 212. Void 211 is filled with a polymeric resin that extends down to layer 20. Layer 21 is itself at least partially impregnated with the polymeric resin.

[0073] In the device 2, the faces 202 and 210 are in contact. The faces 212 and 230 are also in contact. The layer 21 is therefore interposed between the layers 20 and 23. The layer 20 perpendicular to the voids 211 filled with polymerized resin advantageously has areas 208 of polymerized and solidified resin. The resin flowing through the voids 211 can therefore ensure a mechanical bond between the layers 20 and 23. Moreover, the voids 211 promote the flow of the polymerizable resin, while the material of the layer 21 prevents this flow. The resin therefore only impregnates the areas 208 of the layer 20 and does not fill the voids 201. The flow of reagents through the layer 20 is therefore promoted through its open pores and the voids 201. Advantageously, only a part of the volume of the layer 21 is impregnated with resin, which layer 21 can also be passed by the flow of reagents.

[0074] To obtain the gas diffusion device 2 of this embodiment, an open-pore conductive layer 20 having voids 201, an open-pore conductive layer 21 having voids 211, and a composite material layer 23 including conductive fibers coated with a polymerizable resin are laminated.

[0075] Then, as shown in Figure 15, a uniform pressure is applied to this superposition in a direction perpendicular to the face 200 of layer 20 and to the face 232 of layer 23 (indicated by the arrows in white blocks). The pressure applied is advantageously comprised between 0.5 and 1.5 MPa. This compression ensures the electrical interconnection of the carbon fibres of layer 23 through the penetration of these fibres into face 212 of layer 21, guaranteeing both the mechanical and electrical contact between these fibres and layer 23. Compression also makes it possible to ensure an electrical interconnection through the contact of layers 21 and 20, through faces 210 and 202 respectively.

[0076] Compression also allows flow (indicated by black block arrows) of the polymerizable resin contained in layer 23 into the porous layers 20, 21 in a direction parallel to the direction of pressure. Resin flowing vertically from layer 23 to layer 20 through layer 21 advantageously does not impregnate the entire volume of layer 20. Resin flowing vertically from layer 23 to layer 21 passes through face 212 but does not reach the opposite outer face 210 of layer 21. Resin flowing vertically from layer 21 to layer 20 passes through face 202 but does not reach the opposite outer face 200 of layer 20.

[0077] The overlap is maintained in compression, and the flowed resin is allowed to polymerize. Layer 23, which initially contains the polymerizable resin, forms a solidified conductive composite layer. Any excess resin that flows from layer 23 onto layer 21 forms a solidified layer.

[0078] Excess resin that flows from layer 23 through layer 21 and into layer 20 concentrates at the interface of layer 20 and void 211 forming solidified region 208. Finally, layer 20 remains porous at the upper outer end of device 2.

[0079] 16 shows a partial view from above of an upper outer surface 200 of a conductive porous layer 20 according to one variation of this embodiment, the upper outer surface 200 including voids 201. The voids 201 each have a closed contour and may be, for example, through voids between the upper outer surface 200 and a lower outer surface (not shown) of the layer 20.

[0080] In this variant, the voids 201 are advantageously separated, so that the grooves form discontinuous flow paths, and therefore the width of these grooves is typically less than 0.4 mm, advantageously less than 0.2 mm.

[0081] The voids 211 are shown transparently in Fig. 16 and are, for example, parallel to the voids 201 described above. Here, the layers 20, 21 are arranged relative to each other such that the voids 201, 211 do not overlap. Thus, the resin flowing through the voids 211 forms a mechanical bond with the layer 20 without reducing the flow of reagents through the voids 201.

[0082] In another variation shown in Figure 17, the voids 201 and 211 are separate. Figure 17 is a partial view from above of the upper outer surface 200 of the conductive porous layer 20, in which the voids 201, 211 each have a closed contour and are through voids.

[0083] Here, voids 201 and 211 partially overlap each other. It is therefore possible to form a continuous but tortuous flow path for the flow of reagents through layers 20 and 21. Voids 201 and 211 may extend in the vertical direction.

[0084] The void structures described with reference to Figures 4 to 9 may also be used.

[0085] 18 shows a partial cross-sectional view of a rigid conductive gas diffusion device according to a second embodiment. The device includes a conductive porous layer 20 including voids 201 formed in an upper exterior surface 200, layer 20 having a lower surface 202. Voids 201 are through voids between surfaces 200 and 202.

[0086] The device also includes a composite layer 23 as described with reference to the previous embodiments and illustrative examples.

[0087] The device also includes layers 21 and 22 interposed between layers 20 and 23. Layers 21 and 22 can have the same structure and the same composition as layer 20. Layer 21 is conductive in its thickness and includes a void 211 created in its upper surface 210. Layer 21 also has a lower surface 212. Void 211 is advantageously filled with a polymeric resin. Layer 22 is conductive in its thickness and includes a void 221 created in its upper surface 220. Layer 22 also has a lower surface 222. Void 221 is advantageously filled with a polymeric resin. Void 221 at least partially overlaps with void 211 mentioned above. In this way, layers 20, 23 can be fixed to each other by the passage of resin through voids 211, 221.

[0088] The layer 20 perpendicular to the voids 211 filled with polymerized resin advantageously has an area 208 of polymerized and hardened resin. Outside this area 208, the layer 20 advantageously does not comprise an area containing polymerized resin.

[0089] 19 is a partial cross-sectional view of an electrochemical system 700 that may include a gas diffusion device according to the present invention. The electrochemical system 700 includes: - gas diffusion device 8, - gas diffusion device 9, - a membrane electrode assembly 7 arranged between the devices 8, 9.

[0090] Apparatus 8 is - a conductive porous layer 80 (including areas 812 impregnated with polymerized and hardened resin); - a conductive porous layer 82 (including areas 813 and 832 impregnated with polymerized and hardened resin); - a conductive porous layer 84 (including areas 833 impregnated with polymerized and hardened resin); a composite layer 81 arranged between layers 80 and 82; a composite layer 83 arranged between layers 82 and 84;

[0091] Composite layers 81 and 83 include conductive fibers coated with a polymeric resin.

[0092] Here, the gas diffusion device 8 forms a bipolar plate in connection with its use in a fuel cell stack.

[0093] Apparatus 9 is - a conductive porous layer 90 (including areas 912 impregnated with polymerized and hardened resin); - a conductive porous layer 92 (including areas 913 and 932 impregnated with polymerized and hardened resin); - a conductive porous layer 94 (including areas 933 impregnated with polymerized and hardened resin); a composite layer 91 arranged between layers 90 and 92; a composite layer 93 disposed between layers 92 and 94;

[0094] Composite layers 91 and 93 include conductive fibers coated with a polymeric resin.

[0095] Here, the gas diffusion device 9 forms a bipolar plate in connection with its use in a fuel cell stack.

[0096] The bipolar plates 8 and 9 allow different reagents to flow on their outer surfaces and a coolant to flow in their inner parts.

[0097] The membrane electrode assembly 7 is formed from: -Anode microporous layer 70, - cathode microporous layer 72, a proton exchange membrane 71 disposed between layers 70 and 72;

[0098] The assembly 7 may, in connection with its use in a fuel cell stack, ensure the flow of protons between two bipolar plates.

[0099] To obtain this configuration, after a suitable overlap of layers has been formed, a uniform pressure (indicated by the white block arrow) is applied to this overlap in a direction perpendicular to the outer faces, as shown in Figure 20. This compression ensures the electrical interconnection of the fibers present on the surface of the faces of layers 81, 83, 91 and 93, via the penetration of these fibers into the faces of porous layers 80, 82, 84, 90, 92 and 94, ensuring both mechanical and electrical contact between these fibers and the porous layers.

[0100] Compression may also cause the resin contained in layer 81 to flow vertically (indicated by black block arrows) toward porous layers 80 and 82 in a direction parallel to the direction of the applied pressure. The resin flowing vertically from layer 81 to layers 80 and 82 does not impregnate the entire volume of layers 80 and 82. For example, the volume of layers 80 and 82 may be greater than the volume of layer 81. Specifically, layer 81 does not contain a sufficient amount of resin to flow and impregnate the entire volume of conductive porous layers 80 and 82.

[0101] Compression may also cause the resin contained in layer 83 to flow vertically (indicated by black block arrows) in a direction parallel to the direction of the applied pressure toward porous layers 82 and 84. The resin flowing vertically from layer 83 to layers 82 and 84 does not impregnate the entire volume of layers 82 and 84. For example, the volume of layers 82 and 84 may be greater than the volume of layer 83. Specifically, layer 83 does not contain a sufficient amount of resin to flow and impregnate the entire volume of conductive porous layers 82 and 84.

[0102] Compression may also cause the resin contained in layer 91 to flow vertically (indicated by black block arrows) in a direction parallel to the direction of the applied pressure towards porous layers 90 and 92. The resin flowing vertically from layer 91 to layers 90 and 92 does not impregnate the entire volume of layers 90 and 92. For example, the volume of layers 90 and 92 may be greater than the volume of layer 91. Specifically, layer 91 does not contain a sufficient amount of resin to flow and impregnate the entire volume of conductive porous layers 90 and 92.

[0103] Compression finally causes the resin contained in layer 93 to flow (indicated by the black block arrows) towards the porous layers 92, 94 in a direction parallel to the direction of the applied pressure.

[0104] The compression is maintained and the resin is allowed to flow and then polymerize, resulting in the configuration described above.

[0105] Layer 81, which initially contains the polymerizable resin, forms a solidified conductive composite layer. Any excess resin that flows from layer 81 into layers 80, 82 subsequently forms solidified areas of polymerized resin.

[0106] Layer 83, which initially contains the polymerizable resin, forms a solidified conductive composite layer. Any excess resin that flows from layer 83 into layers 84, 82 subsequently forms solidified areas of polymerized resin.

[0107] Layer 91, which initially contains the polymerizable resin, forms the solidified conductive composite layer. Any excess resin that flows from layer 91 into layers 90, 92 subsequently forms solidified areas of polymerized resin.

[0108] Layer 93, which initially contains the polymerizable resin, forms a solidified conductive composite layer. Any excess resin that flows from layer 93 into layers 94, 92 subsequently forms solidified areas of polymerized resin.

[0109] This system can be advantageously used in the context of assemblies intended to form fuel cell stacks, as it allows both reagent fluids to flow through the gas diffusion device that constitutes it, allowing electrons to migrate through the membrane electrode assembly.

Claims

1. - A gas diffusion device (2) comprising a laminate of a composite material layer (23), a first conductive layer (20) and a second conductive layer (21), a composite layer (23) comprising conductive fibres and a polymeric resin coating said conductive fibres; a first conductive layer (20) having open porosity between a first side and a second side and containing first voids (201) in a second side (200), the first side (202) being in electrical contact with said conductive fibers of said composite layer (23), said polymeric resin coating a portion of said first conductive layer (20) on said first side (202); a second conductive layer (21) interposed between said first conductive layer (20) and said composite layer (23), said second conductive layer (21) having an open porosity between its first and second faces (212, 210) and comprising first through voids (211) between its first and second faces, said conductive fibres being in contact with the first face (212) of said second conductive layer (21); - the polymeric resin passes through the first through void (211) of the second conductive layer (21) and extends to the first surface (202) of the first conductive layer (20); Characterized in that Gas diffusion device (2).

2. the first void (201) of the first conductive layer (20) has a closed contour; A gas diffusion device (2) according to claim 1.

3. The first conductive layer (20) has other voids (201) on a second surface, the voids being separated. A gas diffusion device (2) according to claim 1 or 2.

4. The first void (201) of the first conductive layer (20) and the first through void (211) of the second conductive layer (21) do not overlap each other. A gas diffusion device (2) according to any one of claims 1 to 3.

5. the second conductive layer (21) includes a second void (211) that at least partially overlaps the first void (201) of the first conductive layer (20); A gas diffusion device (2) according to claim 4.

6. The laminate comprises a third conductive layer (22) having an open porosity between the first surface and the second surface and a second through void between the first surface and the second surface; The third conductive layer (22) is interposed between the second conductive layer (21) and the composite material layer (23), the third conductive layer (22) has a second through void (221) superimposed on the first through void (211) of the second conductive layer (21), and the polymeric resin extends through the second through void (221) of the third conductive layer (22) to the first surface (202) of the first conductive layer (20). A gas diffusion device (2) according to any one of the preceding claims.

7. The resin does not reach the second surface (200) of the first conductive layer (20). A gas diffusion device (2) according to any one of the preceding claims.

8. the first conductive layer (20) is a layer of foam, felt, or fabric; A gas diffusion device (2) according to any one of the preceding claims.

9. The resin is a phenol resin. A gas diffusion device (2) according to any one of the preceding claims.

10. The first void (201) of the first conductive layer (20) is a through void. A gas diffusion device (2) according to any one of the preceding claims.

11. The first void (201) of the first conductive layer (20) is a groove having a width of less than 0.4 mm. A gas diffusion device (2) according to any one of the preceding claims.

12. The thickness of the first conductive layer (20) is less than 0.5 mm. A gas diffusion device (2) according to any one of the preceding claims.

13. - first and second gas diffusion devices (8, 9) according to any one of claims 1 to 12, a membrane electrode assembly (7) comprising a proton exchange membrane (71), said membrane electrode assembly being arranged between said first and second gas diffusion devices (8, 9); Including, An electrochemical system (700).

14. - providing a laminate of a composite layer (23), a first conductive layer (20) and a second conductive layer (21), said second conductive layer (21) being interposed between said first conductive layer (20) and said composite layer (23), said composite layer (23) comprising conductive fibres and a polymerizable resin impregnated in said conductive fibres, said first conductive layer (20) having open pores between a first surface and a second surface (202, 200), said second conductive layer (21) having open pores between its first surface and a second surface (212, 210) and having a first through void (211) between its first surface and its second surface, - compressing said composite layer (23) to electrically contact said conductive fibers with the first side (202) of said first conductive layer (20), to cause said resin to flow through the first side (202) of said first conductive layer (20), to contact said conductive fibers with the first side (212) of said second conductive layer (21), and to cause said resin to flow through said first through voids (211) in said second conductive layer (21) to the first side of said first conductive layer (20); - polymerizing the flowed resin; - forming a first void (201) in the second surface (200) of said first conductive layer; A method for manufacturing a gas diffusion device (2).

15. The laminate is compressed at a pressure between 0.5 and 1.5 MPa. The method of claim 14.

16. The first void (201) formed is a through void between the first surface and the second surface of the first conductive layer (20); The method according to claim 14 or 15.

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