METHOD FOR MANUFACTURING GAS DIFFUSION DEVICE WITH IMPROVED ELECTRICAL CHARACTERISTICS

Abstract

The present invention relates to a method for manufacturing a gas diffusion device (3), comprising the steps of: - providing a superposition of a composite material layer (31) and a conductive member (30), wherein the composite material layer (31) comprises conductive fibers and a polymeric resin impregnating the conductive fibers, and the conductive member (30) has openings between a first surface (33) and a second surface; - compressing the overlapping portion of the composite material layer (31) and the conductive member (30) to bring the conductive fibers into contact with the first surface (33) of the member (30) and to allow the resin to flow into the member (30) without impregnating the entire volume of the conductive member (30) with the resin; -The process of polymerizing the flowed resin.

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 cells (fuel cell stacks) have made great progress. In particular, fuel cells are being considered as a power source for future large automobiles and as an auxiliary power source for aircraft. A fuel cell is an electrochemical device that converts chemical energy directly into electrical energy. A fuel cell is a stack of multiple cells in series. Each cell typically generates a voltage on the order of 1 volt, and by stacking them, it is possible to generate a high-level power supply voltage, for example, on the order of 100 volts.

[0003] Among the known types of fuel cells, there is the proton exchange membrane fuel cell, known as PEM, which operates at low temperatures. Such fuel cells have the advantage of being particularly compact. Each cell consists of an electrolyte membrane that only allows the passage of protons and not electrons. On one side of the membrane, a positive electrode (anode) and on the second side, a negative electrode (cathode) are formed, forming a membrane / electrode assembly called AME (French: assemblage membrane / electrodes).

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

[0005] The fuel cell may be constructed by stacking so-called bipolar plates, for example made of metal. The membrane is placed between two bipolar plates. The bipolar plates may contain channels or openings for the continuous conduction of reactants and products to and from the membrane. The bipolar plates continuously supply the reaction areas of the electrodes with reagents as they are consumed. The bipolar plates are also provided with channels for the conduction of a coolant for the removal of the generated heat. The reaction products and unreacted species are carried by the flow to the outlet of the channel network. The channels for the different flows are separated by the bipolar plates.

[0006] The bipolar plates are also electrically conductive to collect the electrons generated at the anode. They also act as impermeable separators between the anode and cathode circuits. They also perform a mechanical function by transmitting the stack clamping force required to ensure good electrical contact. Gas diffusion layers are typically interposed between the electrodes and the bipolar plates and are in contact with the bipolar plates. Gas diffusion layers are placed on both sides of the membrane / electrode assembly and ensure electrical conduction, uniform delivery of reagent gases, and removal of produced water. Gas diffusion layers can be in the form of felt or carbon cloth, for example.

[0007] Electronic conduction occurs through the bipolar plates and ionic conduction occurs through the membrane.

[0008] One of the obstacles to widespread adoption of fuel cell technology is the cost of manufacturing and assembling the various components, particularly the bipolar plates, which account for a large portion of the cost of a fuel cell.

[0009] US2007 / 0154779 describes a method for manufacturing resin-impregnated fibers to form porous electrodes, which creates gaps in the resin to make it porous.

[0010] US2006 / 078784 describes a method for manufacturing a gas diffusion device.

[0011] US2019 / 027761 describes a gas diffusion device that is composed of a stack of porous layers.

[0012] US2019 / 123359 describes a conductive fibrous structure impregnated with a hydrophobic resin. Summary of the Invention [Problem to be solved by the invention]

[0013] A known manufacturing technique for bipolar plates is the deep drawing of metal sheets (emboutir). Two deep drawn metal sheets (toles metalliques embouties) are typically welded to the outer faces of the assembly to form the coolant channels between the plates. Seals (joints) are placed in the appropriate positions to ensure the flow of the various fluids is leak-proof. Metal sheets have good mechanical properties and provide an effective barrier to limit the diffusion of dihydrogen. However, they have a low resistance to corrosion. Their degradation can also lead to the formation of cations that pollute the membrane and impair the performance and lifespan of the fuel cell. To mitigate these problems, surface treatments of the metal sheets are often used. However, these surface treatments do not sufficiently improve the resistance for some applications and involve significant additional costs.

[0014] Another known technique for making bipolar plates is to mold composite plates to define the geometry of the different flow channels. The composite plate comprises a matrix of fiber-reinforced resin. Resins are generally highly electrically insulating and require a high content of conductive fillers to make the plate conductive. The high content of conductive fillers in the resin significantly reduces the mechanical properties of the resulting composite plate. [Means for solving the problem]

[0015] The present invention aims to overcome one or more of these drawbacks.The present invention therefore relates to a method for manufacturing a gas diffusion device as claimed in claim 1 attached hereto.

[0016] The invention also relates to variants of the dependent claims. It will be understood by those skilled in the art that each feature of the present specification and the dependent claims can be independently combined with the features of the independent claims without forming an intermediate generalization.

[0017] The invention also relates to a gas diffusion device as defined in the accompanying claims. Effect of the Invention

[0018] Other characteristics and advantages of the present invention will become apparent from the following description, by way of indication and in no way of limitation, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is an exploded perspective view showing an example of a membrane / electrode assembly and a stack of bipolar plates for a fuel cell.

[0020] [Diagram 2] 2, 3 and 4 are cross-sectional views of a gas diffusion device according to a first embodiment, called lateral flow, at different stages in the manufacturing process.

[0021] [Diagram 3] 2, 3 and 4 are cross-sectional views of a gas diffusion device according to a first embodiment, called lateral flow, at different stages in the manufacturing process.

[0022] [Figure 4] 2, 3 and 4 are cross-sectional views of a gas diffusion device according to a first embodiment, called lateral flow, at different stages in the manufacturing process.

[0023] [Diagram 5] 5, 6 and 7 are cross-sectional views of a gas diffusion device according to a second embodiment, called vertical flow, at different stages in the manufacturing process.

[0024] [Figure 6] 5, 6 and 7 are cross-sectional views of a gas diffusion device according to a second embodiment, called Vertical Flow, at different stages in the manufacturing process.

[0025] [Figure 7] 5, 6 and 7 are cross-sectional views of a gas diffusion device according to a second embodiment, called Vertical Flow, at different stages in the manufacturing process.

[0026] [Figure 8] 8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0027] [Figure 9] 8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0028] [Figure 10] 8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0029] [Figure 11] 8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0030] [Figure 12]8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0031] [Figure 13] 8, 9, 10, 11, 12 and 13 are cross-sectional views of a rainure solidification type gas diffusion device according to a third embodiment at different stages in the manufacturing process.

[0032] [Figure 14] 14, 15, 16, 17 and 18 are cross-sectional views of a rainure non solidification groove gas diffusion device according to a fourth embodiment at different stages in the manufacturing process.

[0033] [Figure 15] 14, 15, 16, 17 and 18 are cross-sectional views of a rainure non solidification groove gas diffusion device according to a fourth embodiment at different stages in the manufacturing process.

[0034] [Figure 16] 14, 15, 16, 17 and 18 are cross-sectional views of a rainure non solidification groove gas diffusion device according to a fourth embodiment at different stages in the manufacturing process.

[0035] [Figure 17] 14, 15, 16, 17 and 18 are cross-sectional views of a rainure non solidification groove gas diffusion device according to a fourth embodiment at different stages in the manufacturing process.

[0036] [Figure 18] 14, 15, 16, 17 and 18 are cross-sectional views of a rainure non solidification groove gas diffusion device according to a fourth embodiment at different stages in the manufacturing process.

[0037] [Figure 19] 19 and 20 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device according to an embodiment of the invention at different stages in the manufacturing process.

[0038] [Figure 20] 19 and 20 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device according to an embodiment of the invention at different stages in the manufacturing process.

[0039] [Figure 21] 21 and 22 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device at different stages in a manufacturing process according to an embodiment of the invention.

[0040] [Figure 22] 21 and 22 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device according to an embodiment of the invention at different stages in the manufacturing process.

[0041] [Diagram 23] 23 and 24 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device according to an embodiment of the invention at different stages in the manufacturing process.

[0042] [Figure 24] 23 and 24 are partial cross-sectional views illustrating an example of a bipolar plate using a gas diffusion device according to an embodiment of the invention at different stages in the manufacturing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] 1 is a schematic exploded perspective view of a stack of cells 1 of a fuel cell 4. The fuel cell 4 is constructed by stacking a large number of cells 1. The cells 1 are of a proton exchange membrane type or a polymer electrolyte membrane type.

[0044] The fuel cell 4 is configured to include a fuel source 40. Here, the fuel source 40 supplies dihydrogen to the inlet of each cell 1. The fuel cell 4 also includes an oxidant source 42. The oxidant source 42 supplies air to the inlet of each cell 1, and oxygen in the air is used as an oxidant. Each cell 1 is provided with an exhaust path. One or more cells 1 also have a cooling circuit.

[0045] Each cell 1 is comprised of a membrane / electrode assembly 110 or AME 110. The membrane / electrode assembly 110 is comprised of an electrolyte 113 and a cathode (not shown) and an anode 111 disposed on either side of and attached to the electrolyte 113. The electrolyte layer 113 forms a semi-permeable membrane that is impermeable to gases within the cell, but allows proton conduction, and also prevents the flow of electrons between the positive electrode (anode) 111 and the negative electrode (cathode).

[0046] Disposed between each adjacent pair of AMEs is a bipolar plate 5. Each bipolar plate 5 defines an anode flow passage and a cathode flow passage on opposing outer surfaces. The bipolar plate 5 may also preferably provide a coolant flow passage between two successive membrane / electrode assemblies.

[0047] In a manner known per se, during operation of the fuel cell 4, air flows between the AME and a bipolar plate, and dihydrogen flows between the AME and another bipolar plate. At the anode, the dihydrogen is oxidized to produce protons, which pass through the AME. At the cathode, oxygen is reduced and reacts with the protons to form water. Electrons produced by the oxidation of hydrogen are collected by the bipolar plate 5. The electrons are then applied to an electrical load connected to the fuel cell 1 to generate an electric current. During operation, the fuel cell typically produces a direct current voltage of around 1 V between the anode and the cathode.

[0048] Each bipolar plate 5 may be formed in a manner known per se from two electrically conductive metal sheets, for example stainless steel or a titanium, aluminum, nickel or tantalum alloy, joined together, each sheet having a respective outer surface. The bipolar plate 5 may also be obtained by any other process, for example by moulding or injection moulding from a carbon-polymer composite. In this way, the bipolar plate 5 may also be formed in one piece, and the outer surface of the bipolar plate 5 is then defined by such an integral part.

[0049] The stack may also include perimeter seals and membrane stiffeners, not shown here.

[0050] Each cell 1 may further include a gas diffusion layer (not shown) arranged between the anode and the bipolar plate, and a further gas diffusion layer arranged between the cathode and a further bipolar plate.

[0051] Composite plies are often sold in the form of fibers pre-impregnated with a polymerizable resin. These composite plies are often distributed in rolls or reels. The reinforcing fibers, such as carbon fibers, are electrically conductive. The reinforcing fibers may also be a combination of non-conductive and conductive reinforcing fibers.

[0052] Composite layers using prepreg fibers have the advantage that they are easy to shape and deform before the resin polymerizes, and once the resin polymerizes, these layers become very stiff. The present invention aims to take advantage of many of the properties of such prepreg fibers in the formation of gas diffusion devices, which can be associated with bipolar plates, for example.

[0053] The present invention proposes to form a gas diffusion device by compressing a layer of a composite material comprising conductive fibers and a polymerizable resin impregnating the fibers against a conductive member having an opening between two opposing faces, bringing the conductive fibers into contact with a first face of the conductive member and allowing the resin to flow without impregnating the entire volume of the conductive member with the resin. The flowed resin is then polymerized.

[0054] After the resin is polymerized, the conductive member retains its gas diffusion function, provides an optimal electrical connection between the stiff composite layer and the conductive member, provides a mechanical connection between the composite layer and the conductive member, and the gas diffusion device thus formed can benefit from the stiffness of the composite material after the resin is polymerized.

[0055] 2 is a cross-sectional view showing an example of a manufacturing process of the gas diffusion device 2 according to the first embodiment at one stage. The device 2 is formed by sandwiching a porous conductive member 21 between layers 20 and 22 of a composite material. The layer 20 is arranged so as to contact an outer side portion 23 of the member 21. The layer 22 is arranged so as to contact an opposite outer side surface 24 of the member 21. The first embodiment can also be implemented by bonding only one of the layers 20 and 22 to the conductive member 21. Here, the layer 20, the member 21, and the layer 22 are overlapped horizontally.

[0056] The member 21 serves, for example, as a gas diffusion layer in a bipolar plate. The member 21 is, for example, made of foam, felt, cloth, etc. Each of the layers 20 and 22 includes conductive fibers, preferably carbon fibers. Carbon fibers have high stiffness and high electrical conductivity. Those skilled in the art will understand that other types of conductive fibers can be used. The fibers are preferably impregnated with a polymerizable resin (not shown). Polymerized resins are highly gas-tight to hydrogen. Thus, the layers 20 and 22 can function as a seal or channel boundary that allows the flow of hydrogen. The polymerizable resin is, for example, a phenolic resin, which, once polymerized, can easily increase its hydrogen gas-tightness. Moreover, such resins are not very hydrolyzable. Thus, at the end of the manufacturing process, the layers 20, 22 are impermeable to hydrogen. Those skilled in the art will understand that other resins can also be used in the context of the present invention. Furthermore, the layers 20, 22 become dimensional shims when compressed, and the resulting Component 21 Control the thickness.

[0057] According to the second aspect of the invention, particularly in combination with the manufacturing process according to the second embodiment, one of the composite layers may only comprise electrically non-conductive fibers. According to the second aspect of the invention, particularly in combination with the manufacturing process according to the second embodiment, the member 21 may be electrically insulating. According to the second aspect of the invention, particularly in combination with the manufacturing method according to the second embodiment, the member 21 may be free of open holes. In this way, a sealing function can be formed with the member 21.

[0058] As shown in FIG. 3, a uniform pressure (shown by an open arrow) is applied to the device 2 in a direction perpendicular to the upper and lower outer surfaces of the member 21. The applied pressure is, for example, 0.5 to 1.5 MPa. This compression makes it possible, on the one hand, to make the height of the layers 20, 22 and the member 21 uniform, and on the other hand, to ensure electrical interconnection of the carbon fibers by permeating the respective faces 23 and 24 of the member 21, thus ensuring both mechanical and electrical contact between the fibers and the member 21. In addition, the compression allows the resin (shown by a solid arrow) contained in the layers 20, 22 to flow laterally toward the porous member 21 in the longitudinal direction perpendicular to the direction in which the pressure is applied. The resin flowing laterally from the layers 20, 22 toward the member 21 does not permeate the entire volume of the member 21. The flowed resin permeates a maximum of 30% of the volume of the conductive member 21. For example, the volume of the conductive member 21 may be larger than the volumes of the layers 20 and 22. This is because layers 20, 22 do not have enough flowable resin to penetrate the entire volume of conductive member 20. Resin flowing laterally from layer 22 to member 21 now passes through face 24 but does not reach face 23. Similarly, resin flowing laterally from layer 20 to member 21 now passes through side 23 but does not reach side 24.

[0059] Preferably, the compression is maintained and the resin flows and then polymerizes. After polymerization, the configuration shown in FIG. 4 is obtained. The layers 20, 22, initially containing unpolymerized resin, solidify to form conductive composite layers 201, 221, respectively. The excess resin that flows from layers 20, 22 into member 21 forms regions 202, 222, respectively, which are solidified by the polymerized resin. Finally, the intermediate region 211 obtained from member 21 is not impregnated with resin and preserves the porosity in the center of device 2.

[0060] As mentioned above, this first embodiment can also be implemented by simply adhering layer 20 to conductive member 21. In this case (not shown), surface 24 of conductive member 21 will maintain its open porosity.

[0061] Thus, at the end of the manufacturing process step according to the first embodiment, called lateral flow, a rigid, electrically conductive, one-piece gas diffusion device 2 is obtained, having a porous region 211 in its center and two solidified rigid composite layers 201 and 221 at either end. The composite layers 201, 221 are electrically conductive throughout their thickness.

[0062] 5 is a cross-sectional view showing an example of a gas diffusion device 3 at one stage of a manufacturing process according to the second embodiment. The device 3 is formed by a layer 31 of a composite material sandwiched on both sides by porous conductive members 30, 32. Member 30, layer 31, and member 32 are stacked vertically. Component 30 teeth, layer 31 3. The axial extension 32 is disposed so as to contact the outer apex surface 33 of the axial extension 32. Item 32 teeth, layer 31 The second embodiment is arranged so as to contact the outer lower surface 34 of the composite material layer 31. Component 30 , 32 may be implemented by overlapping only one of them.

[0063] The layer 31 comprises conductive fibres, preferably fibres of carbon, and a polymerisable resin (not shown) preferably impregnates the fibres. The polymerisable resin is for example a phenolic resin, which once polymerised is gas-tight to hydrogen. For this reason, after the manufacturing process, Component 30 , 32 is impermeable to hydrogen.

[0064] As shown in Figure 6, layer 31 A uniform pressure (indicated by the white arrows) is applied to the device 3 in a direction perpendicular to the faces 33 and 34 of the device. This compression causes these fibers to layer 31 By penetrating the respective faces 33 and 34 of the carbon fibers, electrical interconnection of the carbon fibers is ensured and therefore layer 31 The compression ensures mechanical and electrical contact between the layers 30, 32 and 33. The compression also allows the resin contained in layer 31 (indicated by the black arrows) to flow vertically towards the porous members 30, 32 in a direction parallel to the direction of the applied pressure. layer 31 from Component 30, 32, the resin flows perpendicular to Component 30 , but does not penetrate all 32 volumes. For example, Component 30 , 32 volume is conductive layer 31 This can be larger than the volume of the conductive layer 31 But conductive Component 30 , 32 does not have a sufficient amount of flowable resin to penetrate the entire volume of component 32. Resin flowing perpendicularly from layer 31 into component 32 will now pass through face 34 but will not reach the opposite outer surface of the component. Similarly, resin flowing perpendicularly from layer 31 in component 30 will now pass through face 33 but will not reach the opposite outer circumferential surface of the component.

[0065] The compression is maintained, the resin is allowed to flow and then polymerized. The configuration shown in Figure 7 is obtained. The layer 31, which initially contains unpolymerized resin, solidifies to form the conductive composite layer 311. The excess resin that flows from the layer 31 into the members 30, 32 forms regions 302, 322, respectively, which are solidified by the polymerized resin that flows in. Finally, the regions 301 and 321 obtained from the members 30 and 32, respectively, remain porous at the vertical ends of the device 3.

[0066] Thus, at the end of the second embodiment manufacturing process step known as Vertical Flow, there is a rigid, conductive, one-piece gas diffusion device 3 having porous regions 301 and 321 at its vertical edges, and a solidified, rigid composite layer 311 at its center. Composite layer 31 is conductive throughout its thickness.

[0067] 8 is a cross-sectional view of a composite layer 61 used in a method for manufacturing a gas diffusion device 6 according to a third embodiment. The layer 61 comprises conductive fibers, preferably carbon fibers, which are preferably impregnated with a polymerizable resin (not shown). The polymerizable resin is, for example, a phenolic resin, which becomes gas-tight to hydrogen once polymerized.

[0068] The configuration shown in FIG. 9 is obtained by forming a groove 64 in an outer surface 67 of the member 61. The groove 64 extends in a direction perpendicular to the cross-section shown. The step of forming the groove 64 can be performed, for example, by laser etching. The groove 64 is preferably formed by locally heating the surface formed by the groove 64, thereby polymerizing the resin on this surface. Such local heating can be achieved, for example, by laser etching or laser processing. By locally heating, it is possible to prevent the remaining resin from polymerizing and to allow the resin to flow in a subsequent step.

[0069] 10, a layer 65 of resin is formed which polymerizes to form a seal. Layer 65 thus forms a shell on the surfaces of groove 64.

[0070] A porous, conductive member 60 is then placed in contact with the surface 67 of layer 61 in which grooves 64 are formed. A second porous, conductive member 62 is placed on the opposite side of member 60 in contact with an outer surface 68 of layer 61 opposite surface 67. The configuration shown in Figure 11 is obtained, which forms device 6 with superimposed members 60, 62 and layer 61. Members 60 and 62 preferably have a thickness of between 40 and 350 micrometers.

[0071] As shown in FIG. 12, a uniform pressure is then applied to the device 6 in a direction perpendicular to the surfaces 67 and 68 of the layer 61 (illustrated by white arrows). This compression electrically interconnects the carbon fibers, as they penetrate the respective surfaces 67 and 68 of the layer 61, and ensures both mechanical and electrical contact between the fibers and the layer 61. The compression also causes the resin in the layer 61 (illustrated by black arrows) to flow vertically toward the porous members 60, 62 in a direction parallel to the direction of the applied pressure. The resin flowing perpendicularly from the layer 61 to the members 60, 62 does not penetrate the entire volume of these layers 60, 62. For example, the volume of the members 60, 62 may be larger than the volume of the layer 61. This is because the layer 61 cannot allow a sufficient amount of resin to flow to penetrate the entire volume of the conductive members 60, 62. Resin flowing vertically from layer 61 into member 62 passes through face 68 but does not reach the outer peripheral face on the opposite side. Similarly, resin flowing vertically from layer 61 of member 60 passes through face 67 but does not reach the outer surface on the opposite side of the member. Because layer 65 of resin, which has become a seal by polymerization, exists on the face of groove 64, the resin of layer 61 cannot flow into groove 64.

[0072] The compression is maintained, allowing the resin to flow and then polymerize. The result is the configuration shown in Figure 13. Layer 61, which initially contains unpolymerized resin, solidifies to form conductive composite layer 611. Excess resin that flows from layer 61 into components 60, 62 forms regions 602, 622, respectively, which are solidified by the polymerized resin that flows in. Regions 601, 621 obtained from components 60, 62, respectively, remain porous at the ends of device 6.

[0073] Thus, at the end of the steps of the manufacturing process according to the third embodiment, a rigid, electrically conductive one-piece gas diffusion device 6 is provided having porous regions 601 and 621 at its edges, a layer of solidified composite material 611 at its center, and a channel 64 sealed at its bottom and walls to allow the flow of reactant fluids. The layer of composite material 611 is electrically conductive throughout its thickness.

[0074] 14 is a cross-sectional view of a composite layer 61 used in a method for manufacturing a gas diffusion device 6 according to the fourth embodiment. The layer 61 comprises conductive fibers, preferably carbon fibers, which are preferably impregnated with a polymerizable resin (not shown). The polymerizable resin is, for example, a phenolic resin, which becomes gas-tight to hydrogen once polymerized.

[0075] 15 is obtained by forming a groove 64 in the outer surface 67 of the member 61 in a direction perpendicular to the plane of the cross section shown. The step of forming the groove 64 can be carried out, for example, by machining. By forming the groove 64, excessive heating of the resin at the groove 64 is avoided so as not to polymerize the resin at the surface of the groove 64.

[0076] A porous, conductive member 60 is then placed in contact with the surface 67 of layer 61 in which grooves 64 are formed. A second porous, conductive member 62 is placed on the opposite side of member 60 in contact with an outer surface 68 of layer 61 opposite surface 67. The result is the configuration shown in Figure 16, where the superposition of members 60, 62 and layer 61 forms device 6.

[0077] As shown in FIG. 17, the device 6 then applies uniform pressure (illustrated by white arrows) in a direction perpendicular to the surfaces 67 and 68 of the layer 61. This compression electrically interconnects the carbon fibers as they penetrate the respective surfaces 67 and 68 of the layer 61, thereby ensuring both mechanical and electrical contact between the fibers and the layer 61. This also ensures both mechanical and electrical contact between the fibers and the layer 61. The compression also causes the resin in the layer 61 (illustrated by black arrows) to flow towards the porous members 60, 62 in a direction parallel to the direction of the applied pressure, as well as towards the grooves 64. The resin flowing perpendicular to the members 60, 62 from the layer 61 causes these Item 60, 62. For example, the volume of members 60 and 62 may be greater than the volume of layer 61, because layer 61 would not allow a sufficient amount of resin to flow to penetrate the entire volume of conductive members 60, 62. Resin flowing perpendicularly from layer 61 into member 62 would now pass through face 68, but would not reach the opposite outer peripheral face. Similarly, resin flowing perpendicularly from layer 61 into member 60 would now pass through face 67, but would not reach the opposite outer face of the member. Groove 64 is completely filled with resin.

[0078] The compression is maintained, the resin is allowed to flow and then polymerized. The configuration shown in FIG. 18 is obtained. The layer 61, which initially contains unpolymerized resin, forms a layer 611 of composite material of solidified composite conductive material. The grooves 64 form insertions 641 of polymerized resin. The excess resin that flows from the layer 61 into the members 60, 62 forms areas 602, 622, respectively, which are solidified by the polymerized resin that flows in. Finally, the areas 601 and 621 obtained from the members 60 and 62, respectively, are kept porous at the end of the device 6.

[0079] Thus, at the end of the steps of the manufacturing process according to the fourth embodiment, a rigid, electrically conductive, one-piece gas diffusion device 6 is provided having porous regions 601 and 621 at its edges and a consolidated composite layer 611 at its center, which is electrically conductive throughout its thickness.

[0080] 19 is a partial cross-sectional view of a bipolar plate 7 obtained by a manufacturing process implementing some of the embodiments described above. The bipolar plate 7 includes porous, electrically conductive members 70 and 78, which can, for example, provide the function of gas diffusion layers on each of the outer surfaces of the bipolar plate.

[0081] The bipolar plate 7 also includes layers 790, 791 and 792 formed from pieces of composite material with the following distribution:

[0082] - elements 721, 722, 723, 724 and 725 form a layer 790, which is arranged between the porous element 70 and the element 73 of composite material. Element 725, arranged at the outer edge of layer 790, is completed by element 71, also of composite material, arranged in the lateral extension of the porous element 70. Layer 790 thus delimited can be considered, for example, as a gas diffuser, and preferably assumes the role of the anode circuit in the bipolar plate 7. This layer 790 is therefore also called gas diffuser 790. The distance between elements 721, 722, 723, 724, 725 is configured in such a way that the recesses between them are not filled with resin;

[0083] - elements 741, 742, 743, 744 and 745 form a layer 791, which is arranged between element 73 and element 75, also made of composite material. Layer 791 thus delimited preferably serves as a cooling circuit within the bipolar plate 7. To enhance the sealing while ensuring the mechanical strength of layer 791 and its role as electrical conductor and heat exchanger, layer 791 is preferably made gas-tight by introducing a metal layer (not shown) therein. Such a metal layer could also be replaced by a graphene layer, deposited for example by chemical vapor deposition. The distances between elements 741, 742, 743, 744, 745 are configured such that the recesses between them are not filled with resin;

[0084] - Elements 761, 762, 763, 764, 765, 766, 767, 768 and 769 form a layer 792, which is arranged between element 75 and porous element 78. Element 769, arranged at the outer end of layer 792, is completed by element 77, also made of composite material, arranged in the lateral extension of porous element 78. Layer 792 thus delimited can be considered, for example, as a gas diffuser, preferably ensuring the role of the cathode circuit in the bipolar plate 7 (the channels are wider here to facilitate the flow of the more viscous reactive fluid). For this reason, this layer 792 is also called gas diffuser 792. The distances between elements 761, 762, 763, 764, 765, 766, 767, 768, 769 are configured in such a way that the recesses between them are not filled with resin.

[0085] Each of the members 71, 721-725, 73, 741-745, 75, 761-769, 77 comprises conductive fibers, preferably of carbon; a polymerizable resin (not shown) preferably impregnates the fibers. When the resin is polymerized, the members 71, 721-725, 73, 741-745, 75, 761-769, 77 become gas-tight to hydrogen. The polymerizable resin is, for example, a phenolic resin, which can be easily polymerized to become gas-tight to hydrogen. The skilled person will understand that other resins can also be used in the context of the present invention. Therefore, it is advantageous to use different resins for the manufacture of the gas diffusion devices 790, 792, depending on the desired properties in terms of mechanical strength and gas-tightness to the fluids used in the fuel cell.

[0086] According to the manufacturing process of the third embodiment described above, uniform pressure (illustrated by white arrows) is applied in a direction perpendicular to the upper outer surface of member 70 and the lower outer surface of member 78. Resin (illustrated by black arrows) is then caused to flow from the composite members into the porous conductive members 70, 78. The resin is then polymerized. This results in the configuration shown in Figure 20 (for simplicity, the resin overflow into the formed channels is not shown), where:

[0087] Member 71 forms member 710 of polymerized composite material;

[0088] - the elements 721 to 725 form on the one hand polymerized elements 7210, 7220, 7230, 7240, 7250 of resin that has polymerized after flowing into the porous element 70, and also elements 7001, 7002, 7003, 7004, 7251;

[0089] In this way, the member 70 forms an electrically conductive porous member 700;

[0090] - member 73 forms a polymerized composite member 730;

[0091] - members 741-745 form polymeric members 7410, 7420, 7430, 7440 and 7450;

[0092] - member 75 is polymerized to form a composite member 750;

[0093] - members 761 to 769 form polymerized members 7610, 7620, 7630, 7640, 7650, 7660, 7670, 7680, 7690, and members 7801, 7802, 7803, 7804, 7805, 7806, 7807, 7808 and 7691 of resin that has flowed through the porous member 78 and then polymerized;

[0094] - In this way, the member 78 forms an electrically conductive porous member 780;

[0095] The members 77 form a polymerized composite member 770 .

[0096] Conductive bonds as described above are formed between layer 790 and layers 70 and 73, between layer 791 and layers 73 and 75, and between layer 792 and layers 78 and 73.

[0097] Thus, at the end of the steps of the manufacturing process according to the third embodiment previously described, a bipolar plate 7 is obtained:

[0098] - the anode circuit function is preferably carried by layer 790;

[0099] The cooling circuit function is preferably provided by layer 791;

[0100] The cathode circuit function is preferably provided by layer 792.

[0101] These circuits are formed by mechanically bonding polymerized composite and porous components, making the entire structure electrically conductive while simultaneously being impermeable to the various reactive fluids used in fuel cells.

[0102] The polymerization operation can be carried out, for example, by applying a gas flow in the channel, preferably at a temperature above 35°C.

[0103] Figure 21 shows a partial cross-sectional view of a bipolar plate 7 obtained by a manufacturing process implementing some of the embodiments previously described. The configuration illustrated in Figure 21 is based on the configuration illustrated in Figure 19 and previously described, and adds to it:

[0104] - a rigid mold 711 arranged on the upper outer surface of the member 70;

[0105] - A rigid mold 771 disposed under the lower outer surface of member 78.

[0106] The manufacturing process according to the third embodiment previously described for the bipolar plate 7 is carried out. The steps of the manufacturing process are the same as those described with reference to Fig. 19, the only difference being the use of moulds 711 and 771. The moulds 711, 771 are used to fix the members for forming the bipolar plate 7 while constraining the shape obtained from the members 70, 78 during compression and polymerization.

[0107] In this manner, through molding, compression, and polymerization, part 70 provides part 701. Similarly, through molding, compression, and polymerization, part 78 provides part 781. The result is the configuration shown in Figure 22. The geometry of moulds 711 and 771 allows for precise and independent control of the final thicknesses of parts 710 and 701, and parts 770 and 781.

[0108] Thus, at the end of the steps of the manufacturing process according to the third embodiment previously described, a bipolar plate 7 is obtained:

[0109] - the anode circuit function is preferably carried by layer 790;

[0110] The cooling circuit function is preferably provided by layer 791;

[0111] The cathode circuit function is preferably occupied by layer 792.

[0112] These circuits are formed by mechanically bonding polymerized composite and porous members, making the entire structure electrically conductive while remaining impermeable to the various reactive fluids used in fuel cells.

[0113] The polymerization operation can be carried out, for example, by applying a gas flow in the channel, preferably at a temperature above 35°C.

[0114] Figure 23 is a partial cross-sectional view of a bipolar plate 7 resulting from a manufacturing process implementing some of the embodiments previously described. The configuration shown in Figure 23 is based on the configuration shown in Figure 19 and previously described, with the addition of a sealing membrane / electrode assembly 772 disposed under the outer lower surface of member 78.

[0115] The manufacturing process according to the third embodiment described above is carried out to manufacture the bipolar plate 7. The steps of this manufacturing process are the same as those described with reference to FIG. 19, here using plate 772. Eventually several bipolar plates 7 will be stacked to create a fuel cell. Plate 772 is intended to form the external underside of the future fuel cell: it ensures the rigidity and sealing of the stack.

[0116] Thus, after molding, compression and polymerization, the structure shown in FIG. 24 is obtained.

[0117] Thus, at the end of the steps of the manufacturing process according to the third embodiment described above, a bipolar plate 7 is obtained:

[0118] - the anode circuit function is preferably carried by layer 790;

[0119] - the cooling circuit function is preferably provided by layer 791;

[0120] The cathode circuit function is preferably provided by layer 792.

[0121] These circuits are formed from polymeric composite elements mechanically bonded with porous elements, making the entire structure electrically conductive yet impermeable to the various reactive fluids used in fuel cells, particularly hydrogen.

[0122] The polymerization operation can be carried out, for example, by applying a gas flow in the channel, preferably at a temperature above 35°C.

Claims

1. A method for manufacturing a gas diffusion device, comprising the steps of: providing a composite layer and an electrically conductive member superimposed on each other, the composite layer comprising electrically conductive fibers and a polymerizable resin impregnating the electrically conductive fibers, the electrically conductive member having a porosity between a first surface, which is a contact surface between the composite layer and the electrically conductive member, and a second surface opposite the first surface, - compressing the overlapping portion of the composite material layer and the conductive member in a direction perpendicular to the first surface, so that the conductive fibers come into contact with the first surface of the conductive member, and the polymerizable resin flows into the conductive member without impregnating the entire volume of the conductive member with the polymerizable resin; - polymerizing the flowed polymerizable resin and polymerizing the polymerizable resin of the composite layer so that the composite layer becomes hydrogen impermeable; A manufacturing method comprising:

2. A method for manufacturing a gas diffusion device, comprising: providing a composite layer and an electrically conductive member superimposed on each other, the composite layer comprising electrically conductive fibers and a polymerizable resin impregnating the electrically conductive fibers, the electrically conductive member having a porosity between a first surface, which is a contact surface between the composite layer and the electrically conductive member, and a second surface opposite the first surface, - compressing the composite layer and the conductive member in a direction parallel to the first surface to bring the conductive fibers into contact with the first surface of the conductive member and to allow the polymerizable resin to flow into the conductive member without impregnating the entire volume of the conductive member with the polymerizable resin; - polymerizing the flowed polymerizable resin and polymerizing the polymerizable resin of the composite layer so that the composite layer becomes hydrogen impermeable; Equipped with the conductive member is plate-shaped having a first side edge and a second side edge that respectively define the first surface and the second surface of the conductive member; Manufacturing method.

3. The conductive member is compressible, and the compressing step includes compressing the conductive member in a direction perpendicular to an outer surface extending between the first side edge and the second side edge. The method according to claim 2 .

4. The conductive member and the composite layer have different thicknesses in a resting state, and the compression of the conductive member is performed along a direction perpendicular to its outer surface such that the conductive member and the composite layer have the same thickness during compression. The method according to claim 3.

5. The composite material layer overlaid on the conductive member has a groove covered by the conductive member. The method of claim 1 .

6. a preliminary step of forming the groove in the composite material layer, and a step of polymerizing the polymerizable resin on a surface of the groove, The method according to claim 5 .

7. The step of forming the groove and the step of polymerizing are performed by laser etching of the composite material layer. The method according to claim 6.

8. The step of polymerizing includes directing a gas stream into the channel at a temperature greater than 35° C. The method according to claim 6 or 7.

9. The conductive member superimposed on the composite material layer has a thickness of 40 to 350 μm. The method according to any one of claims 1 to 8.

10. The conductive member is a layer of foam, felt or cloth. The method according to any one of claims 1 to 9.

11. The polymerizable resin is a phenolic resin. The method according to any one of claims 1 to 10.

12. The stack is compressed at a pressure of 0.5 to 1.5 MPa. The method according to any one of claims 1 to 11.

13. The compression is performed such that the polymerizable resin flows into the conductive member without reaching the second surface. The method according to any one of claims 1 to 12.

14. The compression is performed so that the polymerizable resin impregnates the conductive member to a maximum of 30% of its volume. The method according to any one of claims 1 to 13.

15. forming a first gas diffusion device (790) by the manufacturing method according to any one of claims 1 to 14; forming a second gas diffusion device (792) by the manufacturing method according to any one of claims 1 to 14; and further comprising a step of overlapping the first gas diffusion device (790) and the second gas diffusion device (792). A method for manufacturing a bipolar plate (7).

16. The polymerizable resin used to form the first gas diffusion device (790) and the polymerizable resin used to form the second gas diffusion device (792) have different chemical compositions.

16. A method for manufacturing a bipolar plate according to claim 15.

17. introducing a metal layer between the stacked first gas diffusion device (790) and the second gas diffusion device (792); 17. A method for manufacturing a bipolar plate according to claim 15 or 16.

18. a composite layer which is impermeable to hydrogen and which comprises conductive fibers coated with a polymeric resin; the conductive member having a first surface which is a contact surface between the composite material layer and the conductive member and a second surface opposite to the first surface, the conductive fiber being in contact with the first surface of the conductive member, the conductive member having voids filled with the polymerizable resin on the first surface, and the conductive member having openings not containing the polymerizable resin on the second surface; A gas diffusion device comprising a superposition of

Images