Proton exchange membrane fuel cell with improved contact between gas diffusion layer and polymer electrolyte membrane

Abstract

The present invention relates to a proton exchange membrane fuel cell having improved contact properties between a gas diffusion layer (GDL) and a catalyst-coated polymer electrolyte membrane (CCM), and a gas diffusion layer, a method of manufacturing a gas diffusion layer and a method of manufacturing a proton exchange membrane fuel cell having improved contact at the interface between a gas diffusion layer and a catalyst-coated polymer electrolyte membrane. The gas diffusion layer comprises a carbon fiber non-woven material or a carbon fiber paper comprising carbon fibers having a main orientation direction with respect to the base plane of the non-woven material or paper, which main orientation direction is not parallel to the main orientation direction of the flow channels of an adjacent flow distribution plate.

Description

Technical Field

[0001] This invention relates to a proton exchange membrane fuel cell (PEMFC) exhibiting improved contact performance between a gas diffusion layer (GDL) and a catalyst-coated polymer electrolyte membrane (CCM). The invention also relates to a method for manufacturing the gas diffusion layer and a method for manufacturing a PEMFC that provides improved contact at the interface between the gas diffusion layer and the catalyst-coated polymer electrolyte membrane. Furthermore, the invention relates to gas diffusion layers, PEMFCs, and fuel cell stacks obtainable by these methods. The invention further relates to the use of such a gas diffusion layer in a PEMFC to improve the contact between the catalyst-coated polymer electrolyte membrane and the gas diffusion layer. Background Technology

[0002] Fuel cells generate electricity by reacting fuel (particularly hydrogen) with oxygen to produce water. In a hydrogen-oxygen fuel cell, hydrogen or a hydrogen-containing gas mixture is fed to the anode, where electrochemical oxidation occurs, releasing electrons (H2 → 2H+). + + 2 e - Protons are transported from the anode chamber to the cathode chamber through a membrane that hermetically separates and electrically insulates the reaction spaces. Electrons provided at the anode are guided to the cathode via an external circuit. Oxygen or a mixture of oxygen-containing gases is supplied to the cathode, where the oxygen undergoes a reduction reaction after absorbing electrons. The oxygen anions formed in this process react with the protons transported through the membrane to produce water (1 / 2 O₂ + 2 H₂). + + 2 e - → H2O).

[0003] Proton exchange membrane fuel cells (PEMFCs), also known as polymer electrolyte fuel cells or polymer electrolyte membrane fuel cells, are used in many applications, particularly automotive powertrains. A specific implementation is a hydrogen-oxygen fuel cell in the form of a low-temperature proton exchange membrane fuel cell (LT-PEMFC). The core component of this PEMFC is the polymer electrolyte membrane (PEM), which only reacts to protons (or oxonium ions H3O). +The membrane is permeable to water molecules, allowing the oxidant (usually oxygen from the air) to be spatially separated from the reductant. A catalyst layer is coated on the anode and cathode sides of this hermetically tight, electrically insulating, and proton-conducting membrane. This catalyst layer forms the electrode and typically contains platinum as the catalytically active metal. The actual redox reaction and charge separation occur within these catalyst layers. This membrane and these catalyst layers constitute a unit, also known as a CCM (catalyst-coated membrane).

[0004] Typically, a gas diffusion layer (GDL) is located on each side of the CCM (Chemical Cell Module). These layers stabilize the battery structure and facilitate the transport and distribution of reactant gases, water, heat, and electricity. The gas diffusion layer of a fuel cell is usually constructed from a carbon fiber substrate, which is typically hydrophobized using a fluoropolymer (e.g., PTFE) and subsequently coated with a microporous layer (MPL). The MPL usually consists of a polymer binder (usually a fluoropolymer, such as PTFE) and at least one porous, conductive carbon material (e.g., carbon black, graphite). Currently, the three materials used as the carbon fiber substrate for the GDL include: - Carbon fiber fabrics (e.g., made from polyacrylonitrile fiber yarns that have been oxidized but not yet carbonized, which are then carbonized or graphitized after weaving). - Carbon fiber paper (wet-laid and chemically bonded carbon fiber nonwoven fabric, wherein the chemical binder is carbonized). - Carbon fiber nonwoven fabric (e.g., nonwoven fabric made from oxidized polyacrylonitrile through dry laying, carding, hydroentangling and consolidation, followed by thickness calibration and carbonization).

[0005] In conventional designs, the gas diffusion layer for proton exchange membrane fuel cells has a fiber side (= substrate side) and a side coated with MPL (MPL side).

[0006] The membrane electrode assembly (MEA) of this proton exchange membrane fuel cell consists of a membrane, electrodes, and a gas diffusion layer. Flow distribution plates are located at the ends of the fuel cell stack and between the individual MEAs. These flow distribution plates have channels for supplying process gases to adjacent cathodes and anodes, and typically also incorporate cooling channels. The flow distribution plates at the ends are called end plates, while those between the individual MEAs are called bipolar plates. These flow distribution plates are typically stamped metal plates or stamped graphite carbon fiber pads. In a proton exchange membrane fuel cell (PEM fuel cell), the gas diffusion layer is typically in direct contact with these flow distribution plates (bipolar plates). In this case, the ridges of these bipolar plates are typically placed directly on the fiber side (substrate side) of the gas diffusion layer, forming direct contact points with the gas diffusion layer, thereby achieving conductivity. In this arrangement, the MPL side of the GDL (Glass Diffusion Layer) is in contact with the catalyst-coated membrane (CCM). The material flow (reacting gases oxygen and hydrogen, and water) flows through the flow channels of the flow distribution plate and the porous structure of the gas diffusion layer, from the flow channels to the membrane and then from the membrane back to the flow channels.

[0007] Therefore, the gas diffusion layer (GDL) located between the bipolar plates and these catalyst layers is crucial to the function and performance of the fuel cell. The reaction media consumed and generated in the electrode reactions must be transported through this GDL and uniformly distributed from the macroscopic structure of the bipolar plates to the microscopic structure of the catalyst layers. Electrons generated and consumed in the half-cell reaction must be conducted to the bipolar plates with the lowest possible voltage loss. The heat generated in the reaction must be dissipated into the coolant of the bipolar plates; therefore, the material of the GDL must also possess sufficient thermal conductivity. Furthermore, the GDL must also provide mechanical balance between the macroscopically structured flow distribution plates and the catalyst layers. To this end, component tolerances must be compensated and compression pressure distributed. This GDL also provides mechanical protection for the ultrathin films subjected to high loads in the fuel cell. Therefore, this places particularly stringent requirements on the mechanical properties of the GDL.

[0008] During production, fuel cell components are typically assembled under high pressure. Due to the ridge and channel surface structure of the flow distribution plate, different regions on the fiber side of the gas diffusion layer in contact with it experience varying pressure loads. This differentiated mechanical load causes the fiber layer to deform under pressure, for example, at the contact point between the ridge and the gas diffusion layer fiber layer, by passing through the ridge and compressing the gas diffusion layer, or by the gas diffusion layer undergoing bending or wavy deformation in the channel region of the flow distribution plate. The degree of these two deformations depends on the mechanical properties of the gas diffusion layer, such as strength, elasticity, or plasticity. Conversely, the mechanical properties of the gas diffusion layer largely depend on the type of carbon fiber substrate, which, as mentioned earlier, can be carbon fiber fabric, carbon fiber paper, or carbon fiber nonwoven fabric. In carbon fiber fabric and dry-laid carbonized nonwoven fabric, the fibers are mechanically interwoven or entangled by water jets. In carbon fiber paper or wet-laid nonwoven fabric, these fibers are chemically bonded by adding resin, followed by integral carbonization. Fabrics are typically ordered structures made of continuous fibers, while nonwovens and carbon fiber paper use chopped fibers that are disordered and randomly oriented.

[0009] Therefore, the differentiated pressure loads inside the fuel cell stack perpendicular to the base planes (x, y planes) of these gas diffusion layers have a significant impact on the application performance of the fuel cell, such as drainage efficiency, electrical contact, current density distribution, achievable total cell voltage, and fuel cell stack lifespan.

[0010] Uneven distribution of mechanical compressive stress on the stack assembly surface can also affect the contact between the gas diffusion layer (GDL) on the MPL side and the catalyst-coated polymer electrolyte membrane (CCM). For example, if wavy deformation and / or bending of the GDL into the flow channel structure occurs in the flow channel region of these flow distribution plates, it may cause partial or complete delamination of the GDL from the CCM on the MPL side, resulting in increased contact resistance with the CCM. This negatively impacts the current density distribution over the basal plane and can significantly reduce the performance and lifespan of the fuel cell (especially when the delamination extends to the ridge). In the worst case, reducing the contact area between the GDL and the CCM can lead to the formation of water bubbles between the two layers, potentially causing so-called "flooding" of the fuel cell. The contact resistance between the CCM and the gas diffusion layer largely determines the performance of the fuel cell.

[0011] Because the spacing, width, angle, and curvature of the bipolar plate ridges are individually designed according to requirements, gas diffusion layers with specific (mechanical) properties may exhibit different operating performance depending on the ridge profile. Particularly at the transition from the ridge to the flow channel, the substrate of the gas diffusion layer experiences exceptionally high stress. This location is particularly vulnerable to damage to the microporous layer due to fiber breakage or other injuries, depending on the radius and angle of the ridge. Broken fibers have particularly sharp edges at the break point, which may pierce the microporous layer and membrane, causing a short circuit. This significantly reduces the performance and lifespan of the fuel cell or fuel cell stack.

[0012] For fuel cell stacks, there is still a general need for proton exchange membrane fuel cells that can avoid the aforementioned drawbacks. In existing technologies, solutions to the problem of insufficient contact between the gas diffusion layer and the catalyst coating film, especially the problem of excessively high contact resistance, are mostly focused on the structural design of the flow distribution plate.

[0013] JP 2021 125356 A relates to a fuel cell separator with improved corrosion resistance and conductivity, the separator comprising a coated substrate that contacts the electrodes of the fuel cell. This fuel cell is, for example, a solid polymer fuel cell. The separator may have channels for gas supply. The coating comprises Fe3O4. The separator has an electrode-side surface roughness (Sa) of 5 to 100 μm, preferably 10 to 50 μm. The coating is, for example, an electroplated layer or a sintered layer. The substrate is, for example, stainless steel, titanium-based material, or aluminum-based material. The electrode surface in contact with the coating is, for example, composed of a carbon-based material. A gas-displacement layer (GDL) may be arranged between the catalyst coating and the separator. The contact surface pressure acting between the coating and the electrode surface is 5 MPa or less, preferably 3 MPa or less.

[0014] JP 2021 026909 A describes a fuel cell that avoids pressure loss on the cathode side. The fuel cell includes a laminate comprising a separator, a gas diffusion layer, and a catalyst-containing electrode layer on the cathode side, followed by an electrolyte layer, and on the anode side, a catalyst-containing electrode layer, a gas diffusion layer, and a separator in sequence. Both separators have gas channels. The cathode gas diffusion layer has higher flexural strength and permeability relative to its thickness than the anode gas diffusion layer.

[0015] US 2021 / 0005905 A1 (DE 10 2018 202 561 A1) relates to a fuel cell having an ion-selective membrane, a gas diffusion layer, and a separator. The separator and the gas diffusion layer together form at least one flow field. At least one channel ridge of the separator has an end with a top surface and an end face. The end face is used to divide fluid impinging on the end face of the channel ridge in a first direction into two parts. The end face is used to deflect liquid in the fluid impinging on the end face near the top surface, such that the liquid is farther from the top surface after deflection than before deflection.

[0016] WO 2022129533 A1 (DE 10 2020 216 101 A1) relates to an electrochemical battery assembly comprising at least one gas diffusion layer (preferably having a microporous layer), a catalyst-coated membrane with a frame, and a bipolar plate, wherein the gas diffusion layer is connected to the catalyst-coated membrane and / or the bipolar plate respectively by a preferred conductive adhesive, the conductive adhesive being disposed on the surface of the frame of the catalyst-coated membrane, the bipolar plate, and / or optionally the microporous layer of the gas diffusion layer, and the surface being plasma-functionalized. Furthermore, the present invention relates to a vehicle including the electrochemical battery assembly and a method for manufacturing the electrochemical battery assembly. Covalent bonding of the conductive adhesive to the frame, bipolar plate, or microporous layer of the gas diffusion layer is achieved through plasma functionalization of the surface or pretreatment of the surface by plasma, representing a stronger material bond, thereby more firmly fixing the gas diffusion layer to the bipolar plate or catalyst-coated membrane. Furthermore, the conductive adhesive can be used to better wet the surface. Using conductive binders can significantly reduce the clamping forces typically required in electrochemical cell assemblies (which can negatively impact the gas diffusion layer), thereby improving gas distribution within the electrochemical cell. Conductive binders also improve the electrical contact between the bipolar plates and the gas diffusion layer, reducing contact resistance. Furthermore, during stacking, conductive binders prevent displacement of the gas diffusion layer or the chemically coated film on the bipolar plates.

[0017] WO 2022 / 094717 A1 relates to a fuel cell assembly with improved contact pressure distribution. The fuel cell assembly includes a single cell having a proton exchange membrane coated with a catalyst, and first and second electrodes and first and second gas diffusion layers on opposite sides of the proton exchange membrane, respectively. A first flow field plate has a surface adjacent to the first gas diffusion layers, the first flow field plate including a plurality of first channels separated by ridges, and wherein the first channels have a first channel length and a width, the width varying along at least a portion of the first channel length. A second flow field plate has a surface adjacent to a second gas diffusion layer. This design with different channel widths results in a substantially uniform contact pressure distribution between the first gas diffusion layer and the ridges of the first flow field plate in the active region of the single cell when a substantially uniform pressure is applied to the single cell (or when a non-uniform pressure is applied to the active region of the single cell).

[0018] WO 2022 / 028998 A1 (DE 10 2020 209 811 A1) relates to a method for reducing the contact resistance between a metal separator (e.g., a monopolar or bipolar plate) and a gas diffusion layer of a fuel cell, wherein the separator is at least partially provided with a carbon-based coating. According to the invention, at least one elastomer is added to the carbon as a binder to form the coating.

[0019] US 2018 / 0006314 A1 describes a bipolar plate that can improve battery efficiency by reducing the contact resistance of the electrodes in contact with the bipolar plate. For this purpose, a bipolar plate with a surface at least partially coated with a conductive thermoplastic is used, the conductive thermoplastic morphologically adapting the bipolar plate to the electrodes. In one specific embodiment, the present invention relates to a fuel cell stack having at least one battery as described above, wherein the thermoplastic is melted by applying a voltage, thereby morphologically adapting the bipolar plate to the electrodes.

[0020] US 2010 / 0291464 A1 (DE 10 2010 020 168 A1) relates to a stainless steel-based bipolar plate that makes conductive contact with a gas diffusion layer of a fuel cell. To reduce the contact resistance between the plate and the gas diffusion layer, this contact is at least partially achieved via a nickel-based alloy.

[0021] KR 101320786 B1 relates to an apparatus and method for measuring the contact resistance of bipolar plates in a fuel cell.

[0022] It is well known that adapting the properties of the gas diffusion layer to the water management of a PEM fuel cell is crucial to avoid flooding and achieve uniform high current density under various operating conditions, such as fluctuating operating temperatures. Here, the issue of contact resistance, particularly the GDL-CCM contact, is only mentioned briefly.

[0023] US 2023 / 0163314 A1 relates to a gas diffusion layer for use in electrochemical devices, such as PEM fuel cells, the gas diffusion layer having a side with an enlarged surface for containing a catalyst or contacting a catalyst layer. It is described that a gas diffusion layer having a mechanically machined surface roughness, thereby having an enlarged surface, can improve the effective diffusion capability of gaseous reactants in electrochemical devices, such as polymer electrolyte membrane fuel cells.

[0024] WO 2023 / 190153 A1 discloses a gas diffusion layer having a microporous layer on at least one side of a conductive porous substrate, wherein the microporous layer comprises carbon black and graphite particles with an aspect ratio of 10 or more, and the conductive porous substrate is characterized in that the thickness of the portion of the conductive porous substrate impregnated by the microporous layer is 5% or more, and 20% or less, the thickness of the portion of the conductive porous substrate not impregnated by the microporous layer. Therefore, the resistance of the gas diffusion layer is reduced, while the permeability is not affected. Using such a gas diffusion layer in a fuel cell can improve its power generation performance.

[0025] DE 10 2020 202 433 A1 proposes a gas diffusion layer for improving the contact resistance of a fuel cell. This gas diffusion layer includes a conductive network comprising conductive fibers wrapped in an electrically insulating and hydrophobic material, and at least partially removes the electrically insulating material in the bipolar region. Specifically, the conductive network may consist of carbon fibers wrapped in a hydrophobic material (such as PTFE), and the removal may be performed, for example, by laser.

[0026] DE 10 2016 200 802 A1 relates to a flow channel-gas diffusion layer unit for a fuel cell, wherein the flow channel and the gas diffusion layer are formed by a porous body, and the unit is arranged between a membrane electrode assembly and a bipolar plate, wherein the porosity of the porous body in the region where it forms the flow channel is greater than the porosity of the region where it forms the gas diffusion layer. This provides a layered structure for a fuel cell designed to reduce contact resistance between components.

[0027] A member of patent family KR 20110062552 A (US 10,431,838 B2; US 10,511,043 B2; DE 102010 002 392 A1) describes a gas diffusion layer for a fuel cell that prevents gas diffusion from penetrating into the flow channels of a flow distribution plate (bipolar plate). To address this issue, the rolled fabric of the gas diffusion layer is cut such that the machine direction of the high-stiffness GDL material is not parallel to the mainstream direction of the flow distribution plate, thereby increasing the stiffness of the gas diffusion layer in the direction transverse to the mainstream direction. In one embodiment, the gas diffusion layer comprises a bilayer structure having a microporous layer and a macroporous layer.

[0028] A member of patent family KR 20120061232 A (US 9,847,535 B2; US 10,629,918 B2; DE 102011 006 651 A1) describes a fuel cell stack with improved freeze-thaw stability. This fuel cell stack includes a gas diffusion layer between a membrane electrode assembly and a flow distribution plate (bipolar plate), wherein the structure of the gas diffusion layer (GDL) reduces the contact resistance at transition points in the fuel cell, and the stiffness of the GDL material in the width direction perpendicular to the flow distribution plate is improved by cutting the GDL material at a specific angle so that the machine direction (i.e., the high-stiffness direction) of the GDL material is not parallel to the main flow channel direction of the flow distribution plate.

[0029] It has been found that by appropriately optimizing the mechanical properties of the gas diffusion layer, different pressure loads on the gas diffusion layer within the fuel cell stack can be reduced or avoided, thereby significantly improving the application performance of the fuel cell. In particular, by reducing the contact resistance between the GDL and CCM, electrical contact is improved, and the current density distribution, achievable total cell voltage, lifespan, and other performance characteristics of the fuel cell stack are significantly enhanced. Summary of the Invention

[0030] The first subject of this invention is a proton exchange membrane fuel cell, comprising: - A proton exchange membrane, wherein both sides of the proton exchange membrane are coated with catalytically active electrodes. A gas diffusion layer is disposed on each side of the catalyst coating film, and the inner side of the gas diffusion layer is in contact with the catalytically active electrode. - Flow distribution plates are respectively disposed on each side of the catalyst-coated film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer. The gas diffusion layer comprises a planar conductive fiber material A) selected from carbon fiber nonwoven fabric, carbon fiber paper, and combinations thereof, wherein the fiber material A) comprises one or more fiber layers. One of the fiber layers has oriented fibers, or in the case where the fiber material comprises multiple fiber layers, at least one of the multiple fiber layers has oriented fibers with a principal orientation direction relative to the basal plane (x, y plane) of the fiber layer. Furthermore, the flow channel of the flow distribution plate has a main orientation direction, and the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channel.

[0031] A preferred embodiment of the present invention is a proton exchange membrane fuel cell, comprising: - A proton exchange membrane, wherein both sides of the proton exchange membrane are coated with catalytically active electrodes. A gas diffusion layer is disposed on each side of the catalyst coating film, and the inner side of the gas diffusion layer is in contact with the catalytically active electrode. - Flow distribution plates are respectively disposed on each side of the catalyst-coated film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer. The gas diffusion layer comprises carbon fiber nonwoven fabric or a planar conductive fiber material A composed of carbon fiber nonwoven fabric, wherein the carbon fiber nonwoven fabric comprises one or more bonded fiber web layers. Wherein, the fibers of one fiber web layer are oriented, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, the fibers of at least one of the multiple fiber web layers are oriented and have a principal orientation direction relative to the base plane (x, y plane) of the fiber web layer. Furthermore, the flow channel of the flow distribution plate has a main orientation direction, and the main orientation directions of the fibers and the main orientation directions of the flow channel are not parallel.

[0032] In a preferred embodiment, the planar conductive fiber material A) is selected from carbon fiber nonwoven fabric, carbon fiber paper and combinations thereof, and the main orientation direction of the fiber forms an angle of 30° to 90°, preferably 45° to 90°, and particularly 60° to 90° with the main orientation direction of the flow distribution plate in contact with the gas diffusion layer.

[0033] In one specific embodiment, the planar conductive fiber material A) is composed of a carbon fiber nonwoven fabric.

[0034] In one specific embodiment, the carbon fiber nonwoven fabric has multiple fiber web layers, particularly 2, 3, 4, 5 or more fiber web layers.

[0035] In one embodiment, the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, wherein the fibers of the fiber web layers facing the flow distribution plate (i.e., the fibers of the fiber web layers in contact with the flow distribution plate) are oriented, and the main orientation direction of the fibers of the fiber web layers is not parallel to the main orientation direction of the flow channels of the flow distribution plate. Preferably, the main orientation direction of the fibers of the fiber web layers facing the flow distribution plate and the main orientation direction of the flow channels of the flow distribution plate form an angle of 30° to 90°, particularly preferably 45° to 90°, and especially 60° to 90°.

[0036] Another subject of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises: A) Planar conductive fiber material, wherein the planar conductive fiber material is selected from carbon fiber nonwoven fabric, carbon fiber paper and their combinations, and B) A microporous layer on the side facing the catalytically active electrode, wherein the microporous layer contains conductive particles in a matrix composed of a polymer binder.

[0037] One specific embodiment is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises: A) Planar conductive fiber material, said planar conductive fiber material comprising or composed of carbon fiber nonwoven fabric, and B) A microporous layer on the side facing the catalytically active electrode, wherein the microporous layer contains conductive particles in a matrix composed of a polymer binder.

[0038] Another subject of the present invention is a method for manufacturing a gas diffusion layer for a fuel cell, as defined above and below, in which: i) Provide a planar conductive fiber material A), said planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, said carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of at least one of said fiber web layers are oriented and have a principal orientation direction relative to the basal plane (x, y plane) of said fiber web layer. ii) Coating the precursor for forming the microporous layer onto the dimensional material provided in step i). iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature.

[0039] Another subject of the present invention is a method for manufacturing a proton exchange membrane fuel cell, as defined above and below, in which: i) Provides a planar conductive fiber material A), said planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, said carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of at least one of said fiber web layers are oriented and have a principal orientation direction relative to the base plane (x, y plane) of said fiber web layer. ii) Coating the precursor for forming the microporous layer onto the fibrous material provided in step i). iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature. iv) The coated fiber material obtained in step ii) or iii) is placed as a gas diffusion layer on both sides of a proton exchange membrane coated with catalytically active electrodes, wherein the microporous layer is located on the side of the gas diffusion layer facing the catalytically active electrodes. v) Flow distribution plates with flow channels are placed on the outer side of the gas diffusion layer. These flow channels supply reactant gases and discharge battery reaction products, and are in contact with the outer side of the gas diffusion layer. vi) Press the flow distribution plate and the components located between the flow distribution plates together.

[0040] Preferably, in the methods for manufacturing the gas diffusion layer and the method for manufacturing the proton exchange membrane fuel cell described above and below, in order to manufacture the planar conductive fiber material A): i-1) Provides a fiber composition comprising carbon fibers and / or carbon fiber precursors. i-2) The fiber composition provided in step i-1) is combed to increase the parallel orientation in the fiber length direction. i-3) Lay the fiber composition obtained in step i-2) into a fiber web. i-4) Optionally, at least one additional fiber web layer may be laid on the first fiber web layer. i-5) Consolidate the one or more fiber web layers obtained in step i-3) or i-4) into a nonwoven fabric. i-6) Optionally treat the nonwoven fabric obtained in step i-5) with at least one additive. i-7) Optionally, the nonwoven fabric obtained in step i-5) or the treated nonwoven fabric obtained in step i-6) is subjected to post-treatment under increased pressure and optionally increased temperature. i-8) If the fiber composition used in step i-1) includes a carbon fiber precursor, the nonwoven fabric obtained in step i-5), the treated nonwoven fabric obtained in step i-6), or the post-treated nonwoven fabric obtained in step i-7) is subjected to thermal pyrolysis at a temperature of at least 1000°C.

[0041] Specifically, in order to manufacture the planar conductive fiber material A), in step i-4), at least one additional fiber web layer is laid on the first fiber web layer, wherein at least one of the additional web layers has a main orientation direction of the fibers, the main orientation direction being substantially transverse to the main orientation direction of the fibers of the first fiber web layer.

[0042] Specifically, in order to manufacture the planar conductive fiber material A), in step i-5), the one or more fiber web layers obtained in step i-3) or i-4) are consolidated to form a nonwoven fabric by the action of an aqueous fluid jet.

[0043] Another subject of the present invention is a gas diffusion layer, which can be obtained by methods as defined above and below.

[0044] Another subject of the present invention is a proton exchange membrane fuel cell, which can be obtained by methods as defined above and below.

[0045] Another subject of the present invention is a fuel cell stack comprising a plurality of proton exchange membrane fuel cells as defined above and below.

[0046] Another subject of the invention is the use of at least one gas diffusion layer, which can be obtained by the methods defined above and below, in a proton exchange membrane fuel cell for improving the contact between a catalyst-coated polymer electrolyte membrane and the microporous layer of the gas diffusion layer.

[0047] Invention Description The proton exchange membrane fuel cell and the gas diffusion layer used therein according to the present invention have the following advantages: - The proton exchange membrane fuel cell according to the present invention has improved contact characteristics between the gas diffusion layer (GDL) and the catalyst-coated polymer electrolyte membrane (CCM).

[0048] The gas diffusion layer comprises one or more fiber web layers, wherein the fibers have a principal orientation relative to the basal plane (x, y plane), which causes the fibers in the one or more fiber web layers of the gas diffusion layer (GDL) in the fuel cell to be non-parallel to the principal orientation of the flow channel of the flow distribution plate. Surprisingly, this reduces the contact resistance at the interface between the gas diffusion layer and the CCM compared to prior art fuel cells. Specifically, a microporous layer (MPL) is provided on the side of the gas diffusion layer facing the catalytic active electrode. This reduces the contact resistance at the interface between the microporous layer of the gas diffusion layer and the catalytic layer applied to the polymer electrolyte membrane of the proton exchange membrane fuel cell, especially in the flow channel region of the flow distribution plate of the fuel cell, particularly in the central region of the flow channel.

[0049] - By optimizing mechanical properties, the differential pressure load on the gas diffusion layer within the fuel cell stack can be reduced or avoided. This can significantly improve electrical contact, particularly by reducing the contact resistance between the gas diffusion layer and the CCM, thereby significantly improving current density distribution, achievable total cell voltage, lifespan, and other performance characteristics of the fuel cell stack.

[0050] In particular, the use of multilayer nonwoven fabrics with fiber orientation can help avoid uneven pressure loads on the gas diffusion layer within the fuel cell stack and improve the contact between the gas diffusion layer and the CCM.

[0051] - The gas diffusion layer exhibits excellent tensile properties in both the x-axis direction (machine orientation, MD) and the y-axis direction (machine transverse, CD or CMD). Consequently, its maximum tensile force and maximum elongation at break are very good according to EN 29073-3:1992 standard.

[0052] Materials with high compressive stiffness will bend inward along the z-direction into the bipolar plate channel while maintaining their thickness. This can cause the gas diffusion layer (which typically has an MPL coating) facing the CCM side to at least partially lose contact with the CCM or undergo delamination. Specifically, for materials with high compressive stiffness, increased contact resistance is observed in the flow distribution plate channel region. A further consequence may be a decrease in current density. Delamination at the channel location may also extend to the entire surface, leading to a further accelerated performance degradation and a shorter fuel cell lifespan. Furthermore, the wavy deformation of gas diffusion within the flow distribution plate channel reduces the contact area between the flow distribution plate and the gas diffusion layer, potentially increasing the contact resistance between the two components.

[0053] In contrast, the pressure-sensitive, compressible, and flexible gas diffusion layer can flexibly respond to different pressure conditions on its surface. Although it is also compressed at the contact point with the ridge of the flow distribution plate and may bend towards the substrate side into the flow channel, it has sufficient flexibility to maintain contact with the CCM on the MPL side and prevent delamination at that location. This ensures a sufficiently low contact resistance.

[0054] Besides fiber orientation, other properties, particularly those of the gas diffusion layer, can be modified to optimize its mechanical properties for specific applications. Adjustable properties include the components used in manufacturing the gas diffusion layer, specifically the yarn thickness or fineness (weight per unit length), fineness or meters (length per unit mass) of the carbon fiber nonwoven fabric, basis weight, and the type of chemical binder used in the carbon fiber nonwoven fabric. The characteristics of the microporous layer of the gas diffusion layer substrate can also significantly affect the interaction between the CCM and the gas diffusion layer (particularly between the CCM and the MPL). Furthermore, the manufacturing process of the gas diffusion layer can significantly influence the mechanical properties of the GDL in specific applications. This includes, in particular, the type of fiber orientation (e.g., in fiber preparation and web laying, and in nonwoven fabric consolidation), the type of layup of different layers of the nonwoven fabric (e.g., using a cross-laying machine or a transverse layup machine), compaction, etc.

[0055] For the purposes of this invention, the term flow distribution plate includes both bipolar plates disposed between two membrane electrode assemblies in a fuel cell stack and end plates located at the ends of the fuel cell stack.

[0056] The function of the flow distribution plate is to ensure that the reactant gases are supplied as uniformly as possible to the membrane electrode assembly (MEA) of a proton exchange membrane fuel cell, and to discharge the reaction products, specifically the water formed in the cathode reaction in a hydrogen-oxygen fuel cell. The flow distribution plate has a one-sided open flow channel structure between the supply and discharge ports, known as the flow field. This flow field macroscopically distributes the reactant gases to adjacent GDLs, which in turn microscopically distribute them to the catalytically active regions of the membrane. The flow field also discharges the gaseous and liquid product water.

[0057] The flow field consists of ridges and channels, and its design is characteristic. Preferably, the width of the channels is in the range of 0.1 to 3.5 mm, particularly preferably 0.2 to 1.5 mm. Preferably, the width of the mesh is in the range of 0.1 to 2.5 mm, particularly preferably 0.2 to 1.5 mm. Preferably, the depth of the channels is in the range of 0.1 to 2.0 mm, particularly preferably 0.15 to 0.5 mm.

[0058] In a preferred embodiment, the transition from the ridge to the flow channel is not a sharp edge, but rather designed with rounded corners. Specifically, the transition from the ridge to the flow channel is designed as an arc segment. The central angle of the arc segment is preferably in the range of 60° to 120°, more preferably 75° to 105°, and particularly about 90° (a quarter-circle arc segment). Within the scope of the invention, the radius of the arc segment is included in the width portion of the ridge. Figure 1 The image shows a cross-section of a flow distribution plate with an arc transition section between the ridge and the channel. Here, "B" represents the width of the channel, "R" represents the radius of the arc segment, and the ridge S connects to the arc segment on both sides.

[0059] In the flow distribution plate used according to the invention, the flow field may have fixed values ​​regarding the width of the channel, the width of the ridge, the fillet radius of the transition from the ridge to the channel, and the depth of the channel. Alternatively, at least one of these values ​​may vary. For example, the width of the channel may vary along its length, and / or the flow field may have multiple channels of different widths. This similarly applies to the other parameters. Furthermore, in a fuel cell stack, the geometries of the individual flow distribution plates may be the same or different. In a particular embodiment, the flow field for the MEA anode side has a different geometry than the flow field for the MEA cathode side.

[0060] The primary orientation direction of the flow channels refers to the direction in which the proportion of the length of each flow channel in the flow distribution plate is largest relative to the total length of the flow channels, pointing in the same direction. Preferably, the flow channels of the flow distribution plate have at least 25%, particularly preferably at least 40%, and especially at least 50% of their orientation relative to the total length, corresponding to the primary orientation direction. In particular, the flow channels of the flow distribution plate have at least 60%, more particularly at least 75% of their orientation relative to the total length, corresponding to the primary orientation direction.

[0061] In principle, the flow channels of a flow distribution plate may have two main orientation directions. For example, in a pin-type flow field (see...). Figure 2 In E), the flow channels may have two orientation directions at approximately 90° angles to each other, wherein the flow channel lengths in the two orientation directions are equal. More generally, a mesh (needle-type or grid-type) flow distribution plate may have two main orientation directions. These designs have two sets of orthogonal parallel flow channel groups, which allow flow in both directions. According to the invention, the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channels. For a flow distribution plate with two main orientation directions, the carbon fiber nonwoven fabric preferably comprises at least two fiber web layers, wherein the main orientation direction of the fibers in each fiber web layer is not parallel to the main orientation direction of the flow channels.

[0062] The primary orientation direction refers to the spatial arrangement of the flow channels, not the flow direction within the channels. Therefore, parallel-oriented flow channels have the same primary orientation direction, even if they (e.g., in a serpentine flow field) flow in opposite directions along a portion of their length.

[0063] The following four flow field designs are preferred, wherein the flow channels have a clearly defined main flow direction: parallel flowfield with a straight channel, serpentine flowfield with a single channel or multiple parallel channels in the same direction, interdigitated flowfield with discontinuous channels, and pin-type flowfield. These flow field types are shown in... Figure 2 In the middle. A simple flow field design with a single flow channel is a single-channel serpentine flow field. In particular, the flow distribution plate used according to the present invention has a flow field selected from parallel flow fields, serpentine flow fields, interdigitated flow fields, and cylindrical flow fields.

[0064] The paper, fiber web, carbon fiber nonwoven fabric, and gas diffusion layer used in this invention are all planar structures with a basic two-dimensional planar extension and a smaller thickness. These structures can be described using an orthogonal coordinate system, where the base planes of the paper, fiber web, carbon fiber nonwoven fabric, and gas diffusion layer lie in a plane formed by the x-axis and y-axis (also called the x, y plane), and the z-axis, orthogonal to it, is used to describe the material thickness. Following the common descriptive method for fiber composite materials, the x-axis is also called the winding direction (machine direction, MD), and the y-axis is called the cross-machine direction (CD). Material transport between the flow distribution plate and the membrane mainly occurs in the z-axis direction.

[0065] Within the scope of this invention, a fiber web (also known as a nonwoven fabric) generally refers to a planar structure composed of single fibers, the bonding of which is primarily achieved through their inherent adhesion. A fiber web (nonwoven fabric) can be transformed into a nonwoven fabric by creating a stronger bond between the fibers than the web itself; this is achieved through nonwoven bonding processes, which are generally categorized as mechanical, chemical, and thermal processes. Fiber webs, webs, nonwoven fabrics, and methods of their manufacture are described in the 2nd edition of Vliesstoffe (Nonwoven Fabrics) by H. Fuchs and W. Albrecht (Wiley-VCH, Weinheim, Germany).

[0066] The gas diffusion layer is also referred to as GDL below, and the microporous layer is also referred to as MPL below.

[0067] The gas diffusion layer used according to the present invention has a base surface, which typically corresponds to the base surface of an adjacent membrane with a catalyst layer and the base surface of an adjacent flow distribution plate. The shape of the base surface of the gas diffusion layer can be polygonal (n-sided, where n ≥ 3, e.g., triangle, quadrilateral, pentagon, hexagon, etc.), circular, arc-shaped (e.g., semicircular), elliptical, or elliptical arc. Preferably, the base surface is rectangular or circular.

[0068] According to the present invention, a bonded fiber web layer is used in the GDL, wherein the fibers in the fiber web layer are oriented and have a main orientation direction relative to the base plane (x, y plane) of the fiber web layer, wherein the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channel.

[0069] The principles of manufacturing fiber-oriented webs (nonwoven fabrics) and methods for manufacturing fiber-oriented nonwoven fabrics (i.e., parallel fiber arrangement) are known. The principles of manufacturing fiber-oriented paper are also known. Fiber orientation affects the material properties of nonwoven fabrics or paper, and the gas diffusion layer produced therefrom, such as strength, stiffness, and tensile properties. The characteristics of the gas diffusion layer itself influence the extent to which the gas diffusion layer (GDL) penetrates the flow distribution plate channels and the contact between the GDL and the MEA. Specifically, the fiber orientation relative to the flow distribution plate channels affects electrical contact, contact resistance, and the current density distribution of the fuel cell.

[0070] Fiber orientation can be determined using known optical or mechanical measurement methods. For example, cross-sectional images of fiber webs and nonwoven fabrics or paper can be prepared and optical analysis performed using an optical microscope or scanning electron microscope. Fibers are visible as circular or elliptical in cross-section, and their position (angle of inclination Θ with respect to the normal) and orientation angle Φ can be evaluated using image analysis methods.

[0071] In the papermaking process, fiber orientation is significantly affected by headbox operating parameters. The fiber suspension supplied from the feed system is ejected from the headbox nozzles, creating a fiber feed jet in the machine direction. The orientation and velocity of this fiber feed jet affect the orientation of the fibers laid on the screen. If a velocity difference exists between the jet and the screen (so-called lead or lag), the fibers are oriented in the machine's direction of travel. The greater the velocity difference, the stronger the longitudinal orientation of the fibers, resulting in higher strength in the longitudinal direction. Crossflow in the jet can affect the transverse profile of the fiber orientation. Such crossflow can be generated by nozzles at appropriate locations or by using baffles in the headbox nozzles.

[0072] In longitudinally laid nonwoven fabrics, the vast majority of fibers are located in the longitudinal direction (machine direction of the production line) of the produced nonwoven fabric. In transversely laid nonwoven fabrics, the vast majority of fibers are located in the transverse direction (perpendicular to the machine direction of the production line) of the produced nonwoven fabric.

[0073] For higher basis weights or larger surface areas, multiple fiber webs can be laid overlapping or parallel to each other. So-called cross-laid nonwovens are made by repositioning individual fiber filaments or nonwoven fabrics with different fiber orientations onto each other. For this purpose, a so-called cross-laying machine (also known as a transverse lay-up machine) can be used in nonwoven fabric manufacturing.

[0074] Multilayer nonwoven fabrics and nonwoven fabrics obtained therefrom therefore have different fiber layers, and the orientation of the fibers in each layer may be the same or different. Multilayer nonwoven fabrics with multiple orientations are preferred, wherein at least two fiber web layers have different main orientation directions. One specific embodiment is a multilayer nonwoven fabric with multiple orientations, wherein at least two adjacent fiber web layers have different main orientation directions.

[0075] To manufacture fibrous fabrics with oriented fibers, the fiber material can first be carded and laid on a carding machine. The carding process determines the orientation of the fibers in the web, such as parallel orientation, random orientation, compaction orientation, or a combination thereof. For example, during carding, the fibers can be oriented in a parallel manner, and the carded fiber web can be removed and laid along the machine direction of the production line to obtain a longitudinal fiber web in which the main orientation direction of the fibers is located in the machine direction (MD) in which the nonwoven fabric is produced. These fiber webs are anisotropic, for example, having high strength in the machine direction and lower strength in the machine transverse (CD) direction. If the fiber web removed from the carding machine is laid on a vertical conveyor belt, a transverse fiber web is obtained in which the main orientation direction of the fibers is located in the machine transverse (CD) direction in which the nonwoven fabric is produced. To obtain higher quality per unit area, multiple fiber webs can be stacked and laid. For this purpose, two or more carding machines can be connected in parallel, and the fiber webs can be laid on a common conveyor belt. To manufacture multi-layer fiber webs (nonwoven fabrics) with fiber layers of different orientations, a cross-laying machine (transverse laying machine) can be used. The fibers in an unconsolidated nonwoven fabric can be made isotropic by using a suitable adjustment device. Subsequently, the fiber web can be consolidated using conventional methods such as thermal consolidation, mechanical consolidation, or chemical consolidation to produce a nonwoven fabric. Thermal consolidation is preferably carried out by calendering or by hot air without applying pressure, for example in a drum dryer or belt dryer. Mechanical consolidation is preferably carried out by water jet consolidation or by needle punching.

[0076] During the nonwoven fabric consolidation process, the fibers can be further oriented. In a preferred embodiment, for consolidation, the fiber web layer (one or more) is treated with a hydroentanglement (spunlacing) process. In this process, the loose fiber web passes through a series of high-pressure water nozzles that spray water onto the fiber material. As the fibers pass through these water jets, the fiber web consolidates and simultaneously undergoes longitudinal orientation of the fibers within the web. After hydroentanglement, residual moisture is removed from the resulting nonwoven fabric. Studies have found that if the water jet pattern generated by hydroentanglement is not parallel to the flow channel of the flow distribution plate, it is advantageous for the mechanical properties of the gas diffusion layer and the resulting fuel cell. Therefore, according to the invention, it is more advantageous when the main orientation direction of the fibers and the main orientation direction of the water jet pattern are not parallel to the main orientation direction of the flow channel.

[0077] The degree of fiber orientation in longitudinal nonwoven fabrics can be characterized by the MD / CD ratio. Similarly, the degree of fiber orientation in transverse nonwoven fabrics can be characterized by the CD / MD ratio.

[0078] The gas diffusion layer used according to the present invention may comprise a carbon fiber nonwoven fabric having a single bonded fiber web layer (single-layer nonwoven fabric) or multiple bonded fiber web layers (multi-layer nonwoven fabric). Studies have found that using multi-layer nonwoven fabrics is beneficial for improving the mechanical properties of the gas diffusion layer. For example, using multi-layer nonwoven fabrics helps avoid uneven pressure loading on the gas diffusion layer within the fuel cell stack. Specifically, it can improve the GDL-CCM contact and reduce the contact resistance between the GDL and CCM. Studies have found that using multi-layer nonwoven fabrics with fiber orientation of the fiber web layers is particularly advantageous.

[0079] Preferred is a proton exchange membrane fuel cell, wherein the carbon fiber nonwoven fabric comprises 2, 3, 4, 5 or more fiber web layers.

[0080] A particularly preferred embodiment is a proton exchange membrane fuel cell according to one of the foregoing embodiments, wherein the carbon fiber nonwoven fabric has a plurality of fiber web layers, and at least two of the fiber web layers, preferably at least three of the fiber web layers, and in particular all of the fiber web layers have fiber orientation.

[0081] One specific embodiment is a proton exchange membrane fuel cell, wherein the carbon fiber nonwoven fabric has multiple fiber web layers, and at least two fiber web layers have fiber orientations with two different principal orientation directions. Preferably, the principal orientation directions of the fibers in the fiber web layers are at an angle of 30° to 90° to each other, particularly preferably 45° to 90°, and especially 60° to 90°.

[0082] A more specific embodiment is a proton exchange membrane fuel cell, wherein the carbon fiber nonwoven fabric has multiple fiber webs, and at least two adjacent fiber webs have two different principal orientation directions. Preferably, the principal orientation directions of the fibers in two adjacent fiber webs with different principal orientation directions form an angle of 30° to 90°, particularly preferably 45° to 90°, and especially 60° to 90° with each other.

[0083] A preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the main orientation direction of the fibers of one fiber web layer, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, facing the flow distribution plate, is not parallel to the main orientation direction of the flow channel of the flow distribution plate.

[0084] Preferably, the main orientation direction of the fibers in at least one of the fiber web layers forms an angle of 30° to 90° with the main orientation direction of the flow channel, particularly preferably 45° to 90°, and especially 60° to 90°.

[0085] A first preferred embodiment is a gas diffusion layer comprising a carbon fiber nonwoven fabric having a bonded fiber web layer (single-layer nonwoven fabric), wherein the main orientation direction of the fibers of the fiber web layer forms an angle of 30° to 90°, particularly preferably 45° to 90°, and especially 60° to 90° with respect to the main orientation direction of the flow channel of the flow distribution plate in contact with the gas diffusion layer.

[0086] A second preferred embodiment is a gas diffusion layer comprising a carbon fiber nonwoven fabric having 2, 3, 4, 5 or more 5 fiber web layers (multilayer nonwoven fabric), wherein the main orientation direction of the fibers of at least one of the fiber web layers forms an angle of 30° to 90° with the main orientation direction of the flow channel of the flow distribution plate in contact with the gas diffusion layer, particularly preferably 45° to 90°, and especially 60° to 90°.

[0087] A particularly preferred embodiment is a gas diffusion layer comprising a carbon fiber nonwoven fabric having 2, 3, 4, 5 or more fiber web layers (multilayer nonwoven fabric), wherein the main orientation direction of the fibers of the fiber web layers in contact with the flow distribution plate forms an angle of 30° to 90° with the main orientation direction of the flow channel of the flow distribution plate, particularly preferably 45° to 90°, and especially 60° to 90°.

[0088] A preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, and the method for manufacturing the carbon fiber nonwoven fabric includes providing carbon fibers, combing the provided carbon fibers to increase the parallel orientation in the fiber length direction, laying the combed fibers into a fiber web, optionally laying at least one additional fiber web layer on a first fiber web layer, and consolidating the fiber web layer into a nonwoven fabric.

[0089] Preferred is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the principal orientation direction of the fibers of one fiber web layer, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, is such that the principal orientation direction of the fibers of at least one fiber web layer corresponds to the machine direction (MD) or corresponds to a transverse direction perpendicular to the machine direction (CD).

[0090] A particularly preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the principal orientation direction of the fibers of one fiber web layer, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, corresponds to the machine direction (MD) or the transverse direction (CD) perpendicular to the machine direction.

[0091] A preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the MD / CD ratio of at least one of the fiber web layers, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, is in the range of at least 2.0:1, preferably at least 5.0:1, and particularly at least 10.0:1.

[0092] Another preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the CD / MD ratio of at least one of the fiber web layers, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, is in the range of at least 2.0:1, preferably at least 5.0:1, and especially at least 10.0:1.

[0093] A particularly preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric comprising a plurality of bonded fiber web layers, wherein the MD / CD ratio of the fiber web layers facing the flow distribution plate is in the range of at least 2.0:1, preferably at least 5.0:1, and especially at least 10.0:1.

[0094] A particularly preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric comprising a plurality of bonded fiber web layers, wherein the CD / MD ratio of the fiber web layers facing the flow distribution plate is in the range of at least 2.0:1, preferably at least 5.0:1, and especially at least 10.0:1.

[0095] Another particularly preferred embodiment of the present invention is a proton exchange membrane fuel cell, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric comprising a plurality of bonded fiber web layers, wherein at least one of the fiber web layers is oriented in the machine direction (MD) and at least one other of the fiber web layers is oriented in a transverse direction (CD) perpendicular to the machine direction.

[0096] Planar conductive material A) According to the present invention, a planar conductive fiber material A selected from carbon fiber nonwoven fabric, carbon fiber paper, and combinations thereof is used. Preferably, a planar conductive fiber material A comprising or composed of carbon fiber nonwoven fabric is used. Particularly preferred is a planar conductive fiber material A composed of carbon fiber nonwoven fabric. The carbon fiber nonwoven fabric may include one or more bonded fiber web layers. According to the present invention, the fibers of at least one fiber web layer are oriented and have a principal orientation direction relative to the base plane (x, y plane) of the fiber web layer, the carbon fiber nonwoven fabric, or the planar conductive fiber material A.

[0097] Preferably, the planar conductive fiber material A) has a basis weight of 15 to 400 g / m³. 2 Preferred concentration: 20 to 300 g / m 2 More preferably 30 to 150 g / m 2 And especially 40 to 120 g / m 2 For example, 50 to 100 g / m 2 In g / m 2 The basis weight (also known as areal density or weight in grams) can be determined according to ISO 9073-1 or EN 29073-1:1992. Within the scope of this invention, basis weight refers to untreated fibrous materials, i.e., those free from any components such as polymer binders or other additives.

[0098] The thickness of the planar conductive fiber material A) is preferably in the range of 50 to 500 µm, and particularly preferably 100 to 400 µm. Thickness refers to the thickness of the fiber material in its untreated, uncompressed state, i.e., before the GDL is assembled into the fuel cell. The thicknesses of the planar conductive fiber material A) and the gas diffusion layer can be determined according to DIN 53855-1:1993-08 "Determination of the thickness of planar textile structures".

[0099] The fibers in fiber material A) include carbon fibers and fibers that are optionally different from them, preferably selected from glass fibers, fibers of organic polymers, such as polypropylene, polyester, polyphenylene sulfide, polyetherketone and mixtures thereof.

[0100] Specifically, the fibers contained in fiber material A) consist only of carbon fibers.

[0101] Carbon fibers can be manufactured in a conventional manner, with polyacrylonitrile fibers (PAN fibers) preferably used as the starting material. PAN fibers are obtained by free radical polymerization of a monomer composition, which preferably contains at least 90% by mass of acrylonitrile based on the total weight of the monomers used in the polymerization. The resulting polymer solution is spun into filaments and bundled into tows by, for example, wet spinning and coagulation. Before converting the PAN precursor into carbon fibers at high temperatures, it is typically subjected to an oxidative cyclization treatment (also simply called oxidation) in an oxygen-containing environment at a high temperature of about 180 to 300°C. The resulting chemical crosslinking improves the dimensional stability of the fibers. Subsequently, actual pyrolysis is performed at a temperature of at least 1000°C (preferably at least 1200°C) to obtain carbon fibers. For the pyrolysis treatment, starting fibers or shaped planar fiber materials can be used depending on the desired shape of the fiber material. Depending on the temperature during the pyrolysis treatment, it can be classified as carbonization or graphitization. Carbonization refers to a material treatment carried out at about 1200 to 1500°C in an inert gas atmosphere, which results in the release of volatile products. Graphitization involves heating materials in an inert gas atmosphere to approximately 2000 to 3000°C, resulting in so-called high-modulus or graphite fibers. These fibers are highly pure, lightweight, strong, and possess excellent electrical and thermal conductivity.

[0102] According to the present invention, the planar conductive fiber material A) comprises or is composed of carbon fiber nonwoven fabric. Preferably, the planar conductive fiber material A) is composed of carbon fiber nonwoven fabric. In an alternative embodiment, the planar conductive fiber material A) comprises carbon fiber nonwoven fabric and at least one other planar conductive material, which is preferably selected from carbon fiber fabric, carbon fiber paper, and combinations thereof.

[0103] Carbon fiber fabrics are made by interlacing two sets of yarn systems: warp yarns and weft yarns. Similar to textiles, the fiber bundles are flexibly and permanently interconnected. PAN fibers that have been oxidized but not yet carbonized or graphitized are preferred for manufacturing carbon fiber fabrics. The carbonization or graphitization process, which imparts electrical conductivity to planar fiber materials, occurs after weaving.

[0104] Carbon fiber paper is typically manufactured using oxidized PAN fibers. These fibers are pulverized into fiber fragments using existing known processes and suspended in pulp. The fibers are then separated from the pulp bath using a screen, similar to papermaking, to form a fiber layup and subsequent drying. In a preferred embodiment, at least one binder is additionally introduced into the paper. Suitable binders include phenolic resins, furan resins, polyimide resins, etc. To incorporate the binder, the paper can be impregnated with it, and subsequently optionally, the binder can be hardened. After impregnation and hardening, the carbon fiber paper is further subjected to carbonization / graphitization to convert the binder into a compound with better electrical conductivity. In another suitable embodiment, filled carbon fiber paper is used as the fiber material A). A filler consisting of carbon material from the polymer binder is incorporated into the still-wet paper. In particular, a carbon-PTFE filler is used for this purpose. This filler improves both thermal and electrical conductivity, making the carbonization / graphitization step unnecessary.

[0105] To manufacture carbon fiber nonwoven fabrics, unoxidized or oxidized PAN fibers can be used. In a preferred embodiment, the fibers are carded and then dry-laid into a fiber web, which is subsequently consolidated into a nonwoven fabric. The nonwoven fabric consolidation can be performed by conventional methods, preferably by hydroentanglement (spunlacing). The loose fiber web is passed through a series of high-pressure water nozzles to compact the nonwoven fabric, while the fibers in the nonwoven fabric are oriented longitudinally. Optionally, the nonwoven fabric can be treated with at least one additive. By treating under high pressure and / or high temperature, the nonwoven fabric can be compacted, and the thickness of the consolidated nonwoven fabric can be calibrated to a desired value. Fiber webs based on unoxidized PAN fibers are first oxidized at high temperature in an oxygen atmosphere after laying and consolidation, followed by carbonization / graphitization in an inert gas atmosphere. Fiber webs based on oxidized PAN fibers are only carbonized / graphitized after laying and consolidation. In the manufacturing process of carbon fiber nonwoven fabric, the fibers are dry-laid into a fiber web in the first step, which is a preferred embodiment of the present invention.

[0106] In a preferred embodiment, the conductive fiber material A) comprises at least one additive coated on and / or incorporated therein. For this purpose, the fiber material can be treated with a polymer component and optionally other additives using conventional coating and impregnation processes. Preferably, the additive is selected from: a1) at least one polymer additive, a2) Optionally, at least one conductivity-enhancing additive, a3) Optionally at least one additional additive and composition thereof that are different from a1) and a2).

[0107] In a preferred embodiment, the conductive fiber material A) comprises at least one polymer additive a1 coated on and / or incorporated therein. The polymer additive a1) is preferably selected from fluoropolymer a11), fluorine-free high-temperature resistant polymer a12), polymer a13 different therefrom, and mixtures thereof.

[0108] Preferably, the polymer additive a1) comprises at least one fluoropolymer a11), which is preferably selected from polytetrafluoroethylene (PTFE), polytetrafluoroethylene-hexafluoropropylene copolymer (FEP), perfluoroalkoxy polymer (PFA), and mixtures thereof. For example, a perfluoroalkoxy polymer is a copolymer of tetrafluoroethylene (TFE) and perfluoroalkoxy vinyl ether (such as perfluorovinyl propyl ether). Particularly preferably, the fluoropolymer a11) comprises polytetrafluoroethylene. Component a11) can be used to improve the hydrophobicity of fibrous materials.

[0109] Preferably, the mass fraction of the fluoropolymer a11) is 0.5 to 40% relative to the mass of the conductive fiber material A), more preferably 1 to 20%, and particularly 1 to 10%.

[0110] In one particular embodiment, the fluoropolymer (a11) is PTFE, and the mass fraction of PTFE is 0.5 to 40% relative to the mass of the fiber material, preferably 1 to 20%, particularly 1 to 10%.

[0111] Also preferably, polymer additive a1) includes at least one polymer a12) different from a11), polymer a12) selected from fluorine-free, high-temperature resistant polymers. More preferably, polymer a12) is selected from so-called high-performance plastics, characterized by properties such as high glass transition temperature, high melting point, good temperature resistance, good chemical resistance, and good mechanical properties. More preferably, polymer a12) has a continuous operating temperature (continuous use temperature) of at least 150°C. More preferably, polymer a12) is a semi-aromatic or aromatic polymer. More preferably, polymer a12) is a thermoplastic.

[0112] Particularly preferred, the polymer (a12) is selected from polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyethersulfone (PES), semi-aromatic (co)polyamide (high temperature polyamide, HTPA), polyimide (PI), polyamide-imide (PAI), polyetherimide (PEI) and mixtures thereof (blenders).

[0113] Using component a12) in the conductive fiber material A) of the gas diffusion layer can reduce the contact resistance at the interface between the gas diffusion layer and the catalyst layer applied to the polymer electrolyte membrane of the polymer electrolyte membrane fuel cell, especially in the flow channel region of the flow distribution plate of the fuel cell, particularly in the central region of the flow channel.

[0114] Specifically, polymer component a12) comprises at least one polyaryletherketone. Polyaryletherketones are semi-crystalline thermoplastics having an alternating structure in which each aryl group is followed by a ketone (carbonyl) or ether group, wherein the ratio of ketone to ether groups is variable and may differ in terms of the substitution pattern on the aromatic ring. Suitable polyaryletherketones a12 include polyetherketones (PEK), polyetheretherketones (PEEK), polyetherketoneketones (PEKK), etc. Preferably, polymer component a1) comprises at least one polyetheretherketone, and in particular, polymer component a1) is composed of at least one polyetheretherketone.

[0115] Suitable semi-aromatic (co)polyamides (a12) particularly refer to polymers known as high-temperature polyamides (HTPA). These are semi-crystalline or amorphous and thermoplastic semi-aromatic polyamides. Preferably, these polymers are copolymerized with at least one aromatic dicarboxylic acid, particularly selected from terephthalic acid, isophthalic acid, and mixtures of terephthalic acid and isophthalic acid. Preferred semi-aromatic (co)polyamides (a12) are selected from PA 6.T, PA 10.T, PA 12.T, PA 6.I, PA 10.I, PA 12.I, PA 6.T / 6.I, PA 6.T / 6, PA 6.T / 10T, PA 10.T / 6.T, PA 6.T / 12.T, PA 12.T / 6.T, and mixtures thereof.

[0116] Another particular embodiment of polyamide a12 is polyphthalamide (PPA).

[0117] Suitable polyimides (a12) include polysuccinimide (PSI), polybismaleimide (PBMI), polyimide sulfone (PISO), and polymethacrylimide (PMI).

[0118] Suitable polymers include (semi)aromatic polyesters, such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polycarbonate (PC), and heat-resistant melamine, such as melamine foam filled with nanoporous SiO2 aerogel.

[0119] Preferably, the mass fraction of polymer a12) is 0.5% to 40%, more preferably 1% to 20%, relative to the mass of the conductive fiber material A). In a particular embodiment, polymer a12) is PEEK, and the mass fraction of PEEK a12) is 0.5% to 40%, more preferably 1% to 20%, relative to the mass of the fiber material.

[0120] In a particularly preferred embodiment, polymer a1) comprises at least one fluoropolymer a11) and at least one polymer a12) different from a11) (as defined above respectively) in order to simultaneously achieve suitable hydrophobicity of the fibrous material and the reduced contact resistance as described above.

[0121] Preferably, the weight percentage of the fluoropolymer a11) is 10 to 100% relative to the total weight of polymers a11) and a12), preferably 20 to 90%, more preferably 30 to 80%, and even more preferably 40 to 75%, for example, particularly 40 to 60% or 60 to 75%.

[0122] Suitable polymers (a13) are selected, for example, from phenolic resins, furan resins, polyimide resins, and mixtures thereof. Specifically, relative to the total weight of the conductive fiber material A), the conductive fiber material A) coated on its surface and / or incorporated therein comprises other polymers (a13) not used in the fluoropolymer (a11) and the fluorine-free high-temperature resistant polymer (a12), at a weight percentage of up to 5%, preferably up to 1%, particularly preferably up to 0.5%, and especially up to 0.1%. More specifically, the fiber material does not contain additives of other polymers (a13) different from the fluoropolymer (a11) and polymer (a12). This is particularly applicable to polymer binders (a13) that carbonize under the manufacturing conditions of the conductive material A).

[0123] If bonded fiber materials are used, the fiber materials are specifically selected from mechanically bonded fiber materials. Chemical bonding, especially chemical bonding using carbonizable polymer binders, may adversely affect the flexural properties of the gas diffusion layer. Specifically, the fiber materials used according to the present invention do not contain any other polymers as binders besides polymers a11) and a12).

[0124] In a particular embodiment of the invention, the fibers are wet-laid in the first step. In this embodiment, the term carbon fiber nonwoven fabric will subsequently also include, for example, a wet-laid material composed of chopped carbon fibers, carbon black, at least one polymer (a11) (particularly PTFE), and at least one fluorine-free, high-temperature resistant polymer (a12) (particularly PEEK). Unlike carbon fiber paper known in the prior art, the wet-laid fiber material used in this invention has little or no phenolic resin as a binder. The mass fraction of phenolic resin relative to the weight of the fiber material is preferably 0 to 10%, more preferably 0 to 5%, particularly 0 to 1%.

[0125] In many cases, even without conductive reinforcing additives, the fibrous material already possesses good electrical and thermal conductivity due to the carbon fibers used. However, to improve electrical and thermal conductivity, the fibrous material can be additionally treated with at least one conductive reinforcing additive (a2). The conductive reinforcing additive (a2) is preferably selected from metal particles, carbon black, graphite, graphene, carbon nanotubes (CNTs), carbon nanofibers, and mixtures thereof. A particular embodiment is graphite carbon nanofibers (GCNF). The conductive reinforcing additive (a2) preferably comprises or is composed of carbon black. The fibrous material can be treated simultaneously with at least one conductive reinforcing additive (a2) and at least one polymer additive (a1) and / or other additives (a3). It is preferred to treat the fibrous material with an aqueous dispersion.

[0126] The mass fraction of the conductivity-enhancing additive a2) in the conductive fiber material A) is preferably 0 to 50% relative to the total weight of the conductive fiber material A). If the conductive fiber material A) contains the conductivity-enhancing additive a2), its mass fraction relative to the mass of the fiber material is preferably 0.5 to 45%, particularly preferably 1 to 25%. In one specific embodiment, the conductivity-enhancing additive a2) comprises or is composed of carbon black, and its mass fraction relative to the mass of the conductive fiber material A) is 0.5 to 45%, preferably 1 to 25%.

[0127] In one embodiment, the planar conductive fiber material A) further comprises at least one additive a3) coated on and / or incorporated therein, said additive a3) being, for example, selected from surfactants other than polymer additive a1) and conductivity-enhancing additive a2), as well as other additives and auxiliary substances. The fiber material may be treated with at least one additional additive, for example, together with a3) and a1) and / or a2).

[0128] The total mass fraction of the further additive a3) relative to the mass of the conductive fiber material A) is preferably 0 to 80%, more preferably 0 to 50%. As long as the fiber material also contains at least one additional additive a3), the total mass fraction of the further additive a3) relative to the mass of the conductive fiber material A) is 0.1 to 80%, preferably 0.5 to 50%.

[0129] In one specific embodiment, the conductive fiber material A) is heat-treated (dried and / or sintered), which optionally has components a1), a2) and / or a3). The heat treatment is preferably carried out at a temperature of at least 250°C, more preferably at least 300°C, and particularly in the range of 250 to 500°C. As described in more detail below, the heat treatment may also be carried out after the application of the microporous layer B).

[0130] The fibrous material can be treated using common methods with polymer additives a1), conductivity-enhancing additives a2), and optionally other additives a3), which will be described in more detail below. Suitable coating and impregnation processes are also described in more detail below. A method for manufacturing the conductive material A) according to the invention is further described below using subsequent drying and / or sintering (preferably drying and sintering) of the coated and / or impregnated fibrous material. Polymer bonding is achieved through sintering. The sintering step can also be performed without a pre-drying step. However, a pre-drying step is preferred to promote a more uniform distribution of the binder in the sintered product of the conductive material A).

[0131] Manufacturing planar conductive materials A) The present invention also relates to a method for manufacturing a planar conductive fiber material A), wherein the fibers of at least one fiber web layer are combed to increase the parallel orientation along the fiber length direction. The planar conductive fiber material A) obtained in this manner is particularly suitable for manufacturing a gas diffusion layer for a proton exchange membrane fuel cell according to the present invention.

[0132] Preferred for manufacturing planar conductive fiber materials: A) i-1) Provides a fiber composition, wherein the carbon fiber composition comprises carbon fibers and / or carbon fiber precursors; i-2) The fiber composition provided in step i-1) is combed to increase the parallel orientation in the fiber length direction; i-3) Lay the fiber composition obtained in step i-2) into a fiber web; i-4) Optionally, at least one additional fiber web layer is laid on the first fiber web layer; i-5) The fiber web obtained in step i-3) or i-4) is consolidated to form a nonwoven fabric; i-6) Optionally treat the nonwoven fabric obtained in step i-5) with at least one additive; i-7) Optionally, the nonwoven fabric obtained in step i-5) or the treated nonwoven fabric obtained in step i-6) is post-treated under increased pressure and optional increased temperature. i-8) If the fiber composition used in step i-1) includes a carbon fiber precursor, the nonwoven fabric obtained in step i-5), the treated nonwoven fabric obtained in step i-6), or the post-treated nonwoven fabric obtained in step i-7) is subjected to thermal pyrolysis at a temperature of at least 1000°C.

[0133] In steps i-1) to i-5) of the method according to the invention, a planar conductive fiber material A) is provided, comprising or composed of carbon fiber nonwoven fabric, wherein the carbon fiber nonwoven fabric comprises one or more bonded fiber web layers. Preferably, at least one planar conductive fiber material A composed of carbon fiber nonwoven fabric is provided. For suitable and preferred fiber materials and methods applicable to nonwoven fabric production, please refer to the foregoing description. Here, carbon fiber nonwoven fabric also includes nonwoven fabric comprising carbon fiber precursors.

[0134] Preferably, in step i-4), at least one additional fiber web layer is laid on the first fiber web layer, wherein at least one of the additional fiber web layers has a main fiber orientation direction, which is substantially transverse to the main fiber orientation direction of the first web layer.

[0135] Preferably, in step i-5), one or more fiber web layers obtained in step i-3) or i-4) are consolidated into a nonwoven fabric by the action of an aqueous fluid jet.

[0136] In step i-6), the provided conductive fiber material A) is preferably coated and / or impregnated using an aqueous composition comprising at least one polymer additive a1), optionally at least one conductivity-enhancing additive a2), and optionally at least one other additive a3 different from a1) and a2), and combinations thereof.

[0137] Aqueous compositions can exist in the form of dispersions or solutions. Typically, they exist in the form of aqueous dispersions.

[0138] The coating and / or impregnation of the fibrous material is performed using conventional application methods known to those skilled in the art. Preferably, the fibrous material is coated and / or impregnated using methods selected from padding, scraping, spraying, smearing, and combinations thereof.

[0139] In the padding process, the fibrous material passes through a padding mill (impregnation tank) containing a solution or dispersion of additives, and is subsequently extruded to the desired amount of additives by rollers with adjustable pressure and optionally adjustable gap.

[0140] The squeegee process can be divided into gravure printing and screen printing. In gravure printing, a blade-shaped steel strip, with or without a support, is used as the squeegee. It is used to scrape (scrape off) excess additive-containing solution or dispersion from the ridge of the printing cylinder. On the other hand, in screen printing, the squeegee is usually made of rubber or plastic and has a pointed or rounded edge.

[0141] In the spray coating process, a solution or dispersion containing additives is applied to the fiber material to be treated through a slit nozzle.

[0142] The kiss-roll process is used to coat the underside of a horizontally running strip of material. The coating medium can be applied to the strip material in either the reverse or forward direction. Indirect coating with small amounts of coating can be achieved using a transfer roller.

[0143] In one specific embodiment, the cleaning product according to the invention is finished using a padding method.

[0144] In step i-7) of the method according to the invention, the coated and / or impregnated fibrous material is dried and / or sintered, preferably dried and sintered. Methods for drying fibrous materials (such as nonwovens or fabrics) coated and / or impregnated by a solution or dispersion containing additives are known in principle. After application, at least a portion of the solvent (particularly water) can be drawn out of the fibrous material, for example, by passing the fibrous material through a suction opening and draining the liquid from the suction opening by applying negative pressure. Alternatively or additionally, the fibrous material can be dried at a high temperature. Furthermore, drying can be carried out under reduced pressure. Drying of the fibrous material is preferably carried out at a temperature in the range of 20 to 250°C, particularly preferably 40 to 200°C. Furthermore, after drying, or as an alternative to drying, the coated and / or impregnated fibrous material can be sintered. Sintering is preferably carried out as a heat treatment at a temperature of 250°C to 500°C, more preferably 300°C to 450°C, particularly 350°C to 450°C.

[0145] Alternatively or additionally, a compaction / thickness calibration process may be performed in step i-7), preferably using an apparatus selected from single-layer presses, multi-layer presses, continuous belt presses, calenders, and combinations thereof, particularly a double-belt press, calender, and combinations thereof. A particularly suitable calender is a felt belt calender.

[0146] In particular, in order to perform the processing in step i-7), the nonwoven fabric obtained in step i-5) by the action of the aqueous fluid jet is post-treated under high pressure and optionally high temperature, wherein it is preferred to use the nonwoven fabric that is still wet after being consolidated by the aqueous fluid jet.

[0147] If the fiber composition used in step i-1) includes a carbon fiber precursor, the nonwoven fabric is subjected to pyrolysis treatment at a temperature of at least 1000°C in step i-8). Depending on the temperature at which the pyrolysis treatment occurs, it can be classified as carbonization or graphitization. Carbonization refers to treating the material at approximately 1000 to 1500°C in an inert gas atmosphere, resulting in the release of volatile products. Graphitization involves heating the material in an inert gas atmosphere to approximately 2000 to 3000°C to obtain so-called high-modulus or graphite fibers. During the pyrolysis treatment, the carbon content gradually increases, for example, its mass fraction increasing from approximately 67% when treated at temperatures below 1000°C to approximately 99% when treated at temperatures above 2000°C. The fibers obtained through graphitization are particularly characterized by high purity, lightweight, high strength, and very good electrical and thermal conductivity.

[0148] Manufacturing gas diffusion layer and proton exchange membrane fuel cells This invention relates to a method for manufacturing a gas diffusion layer for a fuel cell, wherein: i) Provides a planar conductive fiber material A), the planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of at least one fiber web layer are oriented and have a principal orientation direction relative to the basal plane (x, y plane) of the fiber web layer. ii) Coat the fibrous material provided in step i) with the precursor for forming the microporous layer B). iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature.

[0149] The present invention also relates to a method for manufacturing a proton exchange membrane fuel cell, wherein, in addition to steps i) to iii) described above: iv) The coated fiber material obtained in step ii) or iii) is placed as a gas diffusion layer on both sides of a proton exchange membrane coated with catalytically active electrodes, wherein the microporous layer is located on the side of the gas diffusion layer facing the catalytically active electrodes. v) A flow distribution plate is placed on the outside of the gas diffusion layer. The flow distribution plate has flow channels for supplying reactant gases and discharging battery reaction products. The flow channels are in contact with the outside of the gas diffusion layer. vi) Press the flow distribution plate and the components located therebetween together.

[0150] Regarding the provision of planar conductive fiber material A) in step i) of the method of the present invention, referring entirely to the foregoing statement regarding planar conductive fiber material A), planar conductive fiber material A) comprises or is composed of carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more consolidated fiber web layers having fiber orientation.

[0151] In step ii) of the method of the present invention, the fibrous material provided in step i) is coated with a precursor for forming the microporous layer B). The microporous layer B) preferably contains conductive particles in a matrix composed of a polymer binder. The conductive particles are preferably selected from conductive carbon particles, particularly carbon black, graphite, graphene, carbon nanotubes (CNTs), carbon nanofibers, and mixtures thereof, with carbon black, graphite, or mixtures thereof being preferred.

[0152] In particular, the polymer binder comprises at least one fluoropolymer. The fluoropolymer is preferably selected from polytetrafluoroethylene (PTFE), PTFE-hexafluoropropylene copolymer, perfluoroalkoxy polymers, and mixtures thereof. PTFE is preferred.

[0153] Preferably, in order to manufacture the microporous layer B), the amount of polymer binder used is 0.5% to 50% by mass relative to the total weight of the polymer binder and conductive particles, particularly preferably 1.0% to 40%, especially 10% to 25%.

[0154] In contrast to macroporous fibrous materials A), MPL B) is microporous, with pore sizes typically much smaller than 5 micrometers, preferably much smaller than 1 micrometer. Preferably, the pore size of the MPL is at most 900 nm, particularly preferably at most 500 nm, and especially at most 300 nm. The average pore size of the MPL is preferably in the range of 5 to 200 nm, particularly preferably in the range of 10 to 100 nm. The porosity and pore size distribution are determined using mercury porosimetry, as described in DIN ISO 15901-1:2019-03: "Mercury Porosimetry". The above-mentioned average pore size is mainly applicable to the use of carbon black as the conductive particle in the MPL. Significantly larger MPL pores can also be formed by using graphite as the conductive particle or by using a pore-forming agent. Depending on the composition, the average pore size is, for example, greater than 1 µm. When using different conductive particles, the pore size can have a bimodal or multimodal distribution curve.

[0155] In one specific embodiment, the precursor used in step ii) for forming the MPL comprises at least one pore-forming agent. A suitable pore-forming agent is commercially available plastic granules, such as those made of polymethyl methacrylate (PMMA). A suitable particle size is in the range of 10 to 100 μm.

[0156] The thickness of the microporous layer B) is preferably in the range of 5 to 150 µm, and particularly preferably in the range of 10 to 100 µm. This thickness refers to the uncompressed state of the microporous layer B), i.e., before the GDL is installed into the fuel cell.

[0157] Arithmetic mean roughness R of the microporous layer a Preferably, the maximum roughness depth R, as determined according to DIN 4768-1:1974-08, is 10 μm, and more preferably, it is 5 µm. z Preferably, the maximum value is 60 μm, as determined according to DIN 4768-1:1974-08, and more preferably, the maximum value is 30 µm.

[0158] The presence of the microporous layer has a significant impact on the water balance of fuel cells. Due to the high proportion of PTFE and small pore size in the MPL, the MPL acts as a liquid water barrier, thereby inhibiting flooding of the GDL and electrodes and promoting the transport of gaseous reactants to the catalyst.

[0159] In step ii), the precursor for forming the MPL B) can be applied to the planar conductive fiber material A) in different ways. While spraying, screen printing, or Meyer-Rod processes are frequently used in batch manufacturing, doctor blade coating, slit nozzle, and gravure roller processes are preferred in continuous coating. Here, the MPL layer thickness and embedding depth can be influenced by the coating process parameters and the viscosity of the coating.

[0160] In step iii) of the method of the present invention, the coated fiber material obtained in step ii) is optionally post-treated under increased pressure and / or increased temperature. In one specific embodiment, the treatment in step iii) is carried out under a pressure of at least 0.5 MPa and a temperature increase of at least 100°C.

[0161] Preferably, the treatment in step iii) is carried out at a pressure ranging from 0.5 to 10.0 MPa (5 to 100 bar), and particularly preferably at a pressure ranging from 1.5 to 8.0 MPa.

[0162] Preferably, the treatment in step iii) is carried out at a temperature in the range of 100 to 400°C, and particularly preferably at a temperature in the range of 120 to 370°C.

[0163] Preferably, the processing in step iii) is carried out in the press for a period of 5 seconds to 5 minutes, more preferably 10 seconds to 2 minutes.

[0164] Preferably, the processing in step iii) is carried out in a calender for a period of more than 0 to 10 seconds, preferably 0.1 to 5 seconds.

[0165] For the post-processing in step iii), conventional equipment can be used, such as single-layer presses, multi-layer presses, continuous belt presses, or calenders.

[0166] In the method for manufacturing a proton exchange membrane fuel cell according to the present invention, the GDL obtained by the aforementioned steps i), ii) and optionally iii) is further subjected to steps iv), v) and vi).

[0167] Fuel cells and fuel cell stacks A further subject of the present invention is a proton exchange membrane fuel cell, comprising: - A proton exchange membrane, with catalytically active electrodes coated on both sides. - Gas diffusion layers are respectively disposed on each side of the catalyst-coated film, with the inner side of the gas diffusion layer in contact with the catalytically active electrode. - Flow distribution plates are respectively disposed on each side of the catalyst coating film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer.

[0168] In principle, the gas diffusion layer comprising the planar conductive fiber material A) according to the present invention is applicable to all conventional proton exchange membrane fuel cell types, wherein the planar conductive fiber material A) comprises or is composed of a carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising at least one fiber web layer having fiber orientation. See the foregoing statements regarding the structure of proton exchange membrane fuel cells for complete reference.

[0169] As described above, compared to prior art gas diffusion layers, the gas diffusion layer according to the present invention is suitable for reducing the contact resistance at the interface between the microporous layer of the gas diffusion layer and the catalyst layer applied to the proton exchange membrane in a proton exchange membrane fuel cell, particularly in the flow channel region of the flow distribution plate of the fuel cell, such as especially in the central region of the flow channel. The contact resistance of the GDL applied to the flow distribution plate at its interface with the catalyst layer applied to the proton exchange membrane can be simulated by using the strip measurement described below. This applies both to the flow channel region of the flow distribution plate of the fuel cell (such as especially in the central region of the flow channel) and the ridge region of the flow distribution plate of the fuel cell. Here, the contact resistance is simulated by alternatively determining the contact resistance of the GDL applied to the flow distribution plate at the interface with the measuring electrode in the corresponding region. For details regarding the strip measurement (including the measuring device), refer to the subsequent measurement method section. Since the pressure experienced by the GDL in the flow channel region of the flow distribution plate, and particularly in the central region of the flow channel, is reduced relative to the ridge region after the individual components of the fuel cell are compressed, the contact resistance at the interface with the catalyst layer is relatively high therein. Surprisingly, it was found that, compared to gas diffusion layers in the prior art, the GDL according to the invention resulted in a significant reduction in contact resistance at the interface with the catalyst layer in the compressed fuel cell. This is particularly effective in the flow channel region, especially its center.

[0170] Another subject of the present invention is the use of at least one gas diffusion layer obtained by the aforementioned method in a proton exchange membrane fuel cell to improve the contact between the catalyst-coated polymer electrolyte membrane and the microporous layer of the gas diffusion layer.

[0171] In one specific embodiment of the invention, in the region opposite to the flow channel of the flow distribution plate, particularly in the region opposite to the center of the flow channel, at least one gas diffusion layer according to the invention is used to prevent a reduction in the contact area between the catalyst-coated polymer electrolyte membrane and the gas diffusion layer.

[0172] Another particular embodiment of the invention is that in the region opposite to the flow channel of the flow distribution plate, particularly in the region opposite to the center of the flow channel, at least one gas diffusion layer according to the invention is used to prevent an increase in the contact resistance between the catalyst coating film and the gas diffusion layer.

[0173] Measurement methods The test methods used as the basis for evaluating this application, and in particular as the (comparative) examples, are explained in detail below: Basis weight In g / m 2 The unit area mass (area-related mass, gram weight) is determined according to ISO 9073-1.

[0174] thickness The thickness in the uncompressed state can be determined according to DIN 53855-1:1993-08 "Determination of thickness of planar textile structures". DIN also describes methods for determining the thickness under specific pressures (e.g., at 0.025 MPa or 6.0 MPa).

[0175] roughness Roughness (e.g., microporous layers) can be determined using conventional stylus methods known to those skilled in the art, for example, in DIN 4768-1:1974-08 standard "Determination of roughness measurement variable R by an electric stylus instrument". a R z R max As described in "Basic Knowledge".

[0176] The arithmetic mean roughness R was determined using a Mahrsurf XCR20 measuring instrument and an MFW-250 free stylus. a (Average distance from the measurement point on the surface to the centerline) and average roughness depth R z These values ​​are the average of 6 measurements: 3 in the machine direction (MD) and 3 perpendicular to the machine direction (CD).

[0177] Simulated contact resistance through strip measurement The contact resistance at the interface between the GDL applied to the bipolar plate and the catalyst layer on the polymer electrolyte membrane can be simulated by strip measurement. This applies to both the flow channel region (especially the central region of the flow channel) and the ridge region of the bipolar plate of a fuel cell. The corresponding contact resistance is simulated by determining the contact resistance at the interface between a circular GDL sample applied to the flow channel structure of the corresponding bipolar plate and the measuring electrode (specifically in the desired region, such as the central region of the flow channel and / or the ridge region). For this purpose, a circular GDL sample is clamped between the corresponding flow channel structure (top) and measuring electrodes 1-20 (bottom) at a specified angle to the main flow channel direction of the flow channel structure, with a compression pressure of 1.0 MPa. Here, the wiring of the 20 measuring electrodes is arranged in the device perpendicular to the main flow channel direction. The flow channel can be, for example, having the geometry defined above (B1, R1), (B1, R2), (B2, R1), or (B2, R2). The circular GDL sample is large enough that it covers at least one flow channel and two adjacent ridges at its maximum width. Measuring electrodes 1 and 2, and 19 and 20, are arranged in the ridge region of the GDL sample; measuring electrodes 10 and 11 are also arranged in the central region of the flow channel of the GDL sample. Further details of the measurement method (including the measuring apparatus) can be found in the *Journal of The Electrochemical Society*, 159 (6) B709-B713 (2012), which is incorporated herein by reference. The experimental portion of that publication, including the figures referenced therein (such as, in particular, Figure 1 (And the statement under “measuring contact resistance” in particular here also applies.)

[0178] Maximum tensile force (HZK) (in Newtons) and elongation at maximum tensile force (HZD) According to EN 29073-3:1992, the maximum tensile force (HZK) and elongation at the maximum tensile force (HZD) were determined on 200 mm x 50 mm specimens. The tensile force / elongation behavior was measured on dry material along both the longitudinal (winding direction, MD) and transverse (cross-winding direction, CD) directions. Three specimens were measured for each stamping, and the average value was calculated. Attached Figure Description

[0179] Figure 1 A partial view of a prior art bipolar plate is schematically shown, which can also be applied to the fuel cell of the present invention (cross-sectional view). Here, "B" represents the width, "R" represents the fillet radius of the shown flow channel K, and the two sides of the flow channel K are connected by ridges S.

[0180] Figure 2The flow field design of the flow distribution plate suitable for a proton exchange membrane fuel cell according to the present invention is shown. Figure 2 A illustrates a single-channel serpentine flow field. Figure 2 B illustrates a five-channel serpentine flow field. Figure 2 C illustrates the interdigitated flow field. Figure 2 D illustrates a parallel flow field with a direct current path. Figure 2 D illustrates the columnar flow field. Detailed Implementation

[0181] 1. A proton exchange membrane fuel cell, comprising: - A proton exchange membrane, wherein both sides of the proton exchange membrane are coated with catalytically active electrodes. - A gas diffusion layer is disposed on each side of the catalyst coating film, and the inner side of the gas diffusion layer is in contact with the catalytic active electrode; - Flow distribution plates are respectively disposed on each side of the catalyst-coated film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer. The gas diffusion layer comprises a planar conductive fiber material A consisting of carbon fiber nonwoven fabric or carbon fiber nonwoven fabric, wherein the carbon fiber nonwoven fabric comprises one or more bonded fiber web layers. In this embodiment, the fibers of one fiber web layer are oriented, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, the fibers of at least one fiber web layer are oriented and have a principal orientation direction relative to the base plane (x, y plane) of the fiber web layer. Furthermore, the flow channel of the flow distribution plate has a main orientation direction, and the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channel.

[0182] 2. The proton exchange membrane fuel cell according to Embodiment 1, wherein the flow distribution plate has a flow field, the flow field being selected from a parallel flow field, a serpentine flow field, an interdigitated flow field, and a columnar flow field.

[0183] 3. The proton exchange membrane fuel cell according to embodiment 1 or 2, wherein the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, and the fibers of the fiber web layers facing the flow distribution plate side are oriented, and the main orientation direction of the fibers of the fiber web layers is not parallel to the main orientation direction of the flow channel of the flow distribution plate.

[0184] 4. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the carbon fiber nonwoven fabric comprises 2, 3, 4, 5 or more fiber web layers.

[0185] 5. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the carbon fiber nonwoven fabric has a plurality of fiber web layers, and at least two of the fiber web layers, preferably at least three of the fiber web layers, and in particular all of the fiber web layers have fiber orientation.

[0186] 6. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the carbon fiber nonwoven fabric has a plurality of fiber web layers, and at least two of the fiber web layers have fiber orientations with two different main orientation directions, preferably at least two adjacent fiber web layers have fiber orientations with two different main orientation directions.

[0187] 7. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the main orientation direction of the fibers of the at least one fiber web layer forms an angle of 30° to 90° with the main orientation direction of the flow channel of the flow distribution plate in contact with the gas diffusion layer, preferably 45° to 90°, and particularly preferably 60° to 90°.

[0188] 8. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, and the method for manufacturing the carbon fiber nonwoven fabric comprises: providing carbon fibers, combing the provided carbon fibers to increase the parallel orientation in the fiber length direction, laying the combed fibers into a fiber web, optionally laying at least one additional fiber web layer on a first fiber web layer, and consolidating the one or more fiber web layers into a nonwoven fabric.

[0189] 9. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein, The main orientation direction of the fibers in the fiber web layer, or in the case where the carbon fiber nonwoven fabric includes multiple fiber web layers, is such that the main orientation direction of the fibers in at least one fiber web layer corresponds to the machine direction (MD) or the machine transverse direction (CD) of the machine direction. Preferably, the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, and the main orientation direction of the fibers of at least the fiber web layer facing the flow distribution plate corresponds to the machine direction (MD) or the machine transverse direction (CD).

[0190] 10. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein, The carbon fiber nonwoven fabric has a density of at least 20 g / m². 2 The base weight, and the maximum tensile force in the machine direction is at least 5 N, preferably at least 7 N; and / or The carbon fiber nonwoven fabric has a density of at least 20 g / m².2 The base weight, and the maximum tensile force in the transverse direction of the machine perpendicular to the machine direction is at least 5 N, preferably at least 7 N.

[0191] 11. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the gas diffusion layer comprises: A) A planar conductive fiber material comprising or composed of carbon fiber nonwoven fabric, and B) A microporous layer facing the side of the catalytically active electrode, wherein the microporous layer contains conductive particles in a matrix composed of a polymer binder.

[0192] 12. The proton exchange membrane fuel cell according to any one of the foregoing embodiments, wherein the flow distribution plate has at least one of the following properties: The width of the flow channel is in the range of 0.1 to 3.5 mm, preferably in the range of 0.2 to 1.5 mm. The width of the ridge is in the range of 0.1 to 2.5 mm, preferably in the range of 0.2 to 1.5 mm. - The depth of the flow channel is in the range of 0.1 to 2.0 mm, and particularly preferably in the range of 0.15 to 0.5 mm.

[0193] 13. A method for manufacturing a gas diffusion layer for a proton exchange membrane fuel cell as defined in any one of embodiments 1 to 12, wherein: i) Provide a planar conductive fiber material A), said planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, said carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of said at least one fiber web layer are oriented and have a principal orientation direction relative to the basal plane (x, y plane) of said fiber web layer. ii) The precursor for forming the microporous layer is coated onto the planar conductive fiber material A) provided in step i). iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature.

[0194] 14. A method for manufacturing a proton exchange membrane fuel cell as defined in any one of embodiments 1 to 12, wherein: i) Provide a planar conductive fiber material A), said planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, said carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of said at least one fiber web layer are oriented and have a principal orientation direction relative to the basal plane (x, y plane) of said fiber web layer. ii) The precursor for forming the microporous layer is coated onto the planar conductive fiber material A) provided in step i). iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature. iv) The coated fiber material obtained in step ii) or iii) is placed as a gas diffusion layer on both sides of a proton exchange membrane coated with catalytically active electrodes, wherein the microporous layer is located on the side of the gas diffusion layer facing the catalytically active electrodes. v) Flow distribution plates are placed on the outer side of the gas diffusion layer, each flow distribution plate having channels for supplying reactant gases and discharging battery reaction products, the channels being in contact with the outer side of the gas diffusion layer. vi) Press the flow distribution plate and the components located therebetween together.

[0195] 15. The method according to embodiment 13 or 14, wherein, in order to manufacture the planar conductive fiber material A): i-1) Provides a fiber composition comprising carbon fibers and / or carbon fiber precursors. i-2) The fiber composition provided in step i-1) is combed to increase the parallel orientation in the fiber length direction. i-3) Lay the fiber composition obtained in step i-2) into a fiber web. i-4) Optionally, at least one additional fiber web layer is laid on the first fiber web layer. i-5) Consolidate the fiber web obtained in step i-3) or i-4) to form a nonwoven fabric. i-6) Optionally, the nonwoven fabric obtained in step i-5) is treated with at least one additive. i-7) Optionally, the nonwoven fabric obtained in step i-5), or the treated nonwoven fabric obtained in step i-6), is subjected to post-treatment under increased pressure and optionally increased temperature. i-8) If the fiber composition used in step i-1) includes a carbon fiber precursor, the nonwoven fabric obtained in step i-5), or the treated nonwoven fabric obtained in step i-6), or the post-treated nonwoven fabric obtained in step i-7) is subjected to thermal pyrolysis at a temperature of at least 1000°C.

[0196] 16. The method according to embodiment 15, wherein, in step i-4), at least one additional fiber web layer is laid on the first fiber web layer, wherein the at least one additional web layer has a main fiber orientation direction, the main fiber orientation direction being substantially transverse to the main fiber orientation direction of the first web layer.

[0197] 17. The method according to embodiment 15 or 16, wherein, in step i-5), the one or more fiber web layers obtained in step i-3) or i-4) are consolidated into a nonwoven fabric by an aqueous fluid jet.

[0198] 18. The method according to any one of embodiments 15 to 17, wherein the apparatus for processing in step i-7) is selected from a single-layer press, a multi-layer press, a continuous belt press, a calender, and combinations thereof, preferably selected from a double-belt press, a calender, and combinations thereof.

[0199] 19. The method according to any one of embodiments 15 to 18, wherein the nonwoven fabric obtained by the action of an aqueous fluid jet in step i-5) is used for the treatment in step i-7), and is post-treated under increased pressure and optionally increased temperature, wherein the nonwoven fabric obtained by consolidation by the use of an aqueous fluid jet is preferably used.

[0200] 20. A gas diffusion layer, which can be obtained by a method as defined in any one of embodiments 13 or 15 to 18.

[0201] 21. A proton exchange membrane fuel cell, which can be obtained by a method as defined in any one of embodiments 15 to 20.

[0202] 22. A fuel cell stack comprising a plurality of proton exchange membrane fuel cells as defined in any one of embodiments 1 to 11 and 20.

[0203] 23. The application of at least one gas diffusion layer obtained by a method as defined in any one of embodiments 12 or 14 to 18 in a proton exchange membrane fuel cell for improving the contact between the catalyst-coated polymer electrolyte membrane and the microporous layer of the gas diffusion layer.

[0204] 24. The application according to embodiment 22 is used to prevent a reduction in the contact area between the catalyst-coated polymer electrolyte membrane and the gas diffusion layer in the region opposite to the flow channel of the flow distribution plate, particularly in the region opposite to the center of the flow channel.

[0205] 25. The application according to embodiment 22 or 23, which is used to prevent an increase in contact resistance between the catalyst coating film and the gas diffusion layer in the region opposite to the flow channel of the flow distribution plate, particularly in the region opposite to the center of the flow channel.

[0206] The present invention will be described in detail below with the aid of embodiments.

[0207] Example Example 1: Planar conductive fiber materials are manufactured from single-layer fiber webs with oriented fibers. Pre-oxidized PAN fibers with a fineness of 1.2 dtex and a length of 60 mm were laid laterally on a carding machine to form a basis weight of 50 g / m². 2 The fiber web is conveyed to a consolidation unit, where the fibers are entangled and interwoven on both sides by a high-energy water jet, with a pressure of approximately 100 bar in the first stage and approximately 170 bar in the second stage. The nonwoven fabric is dried to a residual moisture content of 1% to 15% and undergoes thickness calibration, thereby reducing the thickness of the water-jet-consolidated nonwoven fabric. Subsequently, the consolidated nonwoven fabric is conveyed to a carbonization unit and carbonized at approximately 1000 to 1400°C under a nitrogen atmosphere. After carbonization, the nonwoven fabric has a thickness of 100 µm.

[0208] Example 2: Planar conductive fiber materials are manufactured from double-layer fiber webs with oriented fibers. The double-layer fiber web is conveyed to the consolidation unit. The double-layer fiber web consists of a first transversely laid web layer and a second longitudinally oriented web layer. The first transversely laid web layer has a density of 40 g / m. 2 The basis weight is composed of pre-oxidized PAN fibers with a fiber fineness of 1.2 dtex and a fiber length of 52 mm, and the second longitudinally oriented web layer has a weight of 20 g / m. 2 The nonwoven fabric is composed of pre-oxidized PAN fibers with a fiber fineness of 1.2 dtex and a fiber length of 52 mm, and is laid longitudinally on a carding machine. The fibers are entangled and interwoven on both sides by high-energy water jets at a pressure of approximately 120 bar in the first stage and approximately 190 bar in the second stage. The nonwoven fabric is dried to a residual moisture content of approximately 5% and thickness calibration is performed to reduce the thickness of the water-jet-bonded nonwoven fabric. Subsequently, the nonwoven fabric is conveyed to a carbonization unit and carbonized at approximately 1000 to 1400°C under a nitrogen atmosphere. After carbonization, the nonwoven fabric has a thickness of 114 µm.

[0209] Example 3: The preparation of Example 3 was similar to that of Example 2. However, the fiber fineness of both web layers was 2.2 dtex. The transversely laid fiber web layer had a density of 63 g / m². 2 The base weight of the longitudinally laid fiber web is 32 g / m. 2 The basis weight. After carbonization, the nonwoven fabric has a thickness of 151 µm.

[0210] Example 4: The preparation of Example 4 was similar to that of Example 2. However, the fiber fineness of both web layers was 2.2 dtex. The transversely laid fiber web layer had a density of 110 g / m². 2 The base weight, with the longitudinally laid fiber web having a density of 40 g / m², is [not specified]. 2 The basis weight. After carbonization, the nonwoven fabric has a thickness of 211 µm.

[0211] Example 5: Use fiber-oriented materials with a basis weight of 44.5 g / m 2 A single-layer carbonized carbon fiber paper. After carbonization, the carbon fiber paper substrate had a thickness of 192 µm, measured at 0.25 bar.

[0212] Examples I to IV: To process the nonwoven fabrics (base nonwoven fabrics) from Examples 1 to 4, an impregnation composition comprising 70% by mass of carbon black and 30% by mass of PTFE was mixed relative to the total solid mass. Pulping impregnation was performed using an aqueous dispersion containing 15% by mass of finishing agent (relative to the mass of the GDL substrate). The mixture was then dried at 160°C for 5 minutes and sintered at 400°C for 10 minutes. MPL was then coated. The composition of the slurry is shown in Table 1. In another method, PTFE, various carbons, and plastic particles as pore-forming agents were dispersed in distilled water and coated onto a fiber nonwoven fabric by scraping. The sheet was then dried at 160°C and sintered at 400°C. The resulting MPL loading was 15 g / m². 2 .

[0213] Example V: The finishing process involved impregnating the nonwoven fabric (carbon fiber paper-based nonwoven fabric) from Example 5 with a PTFE aqueous dispersion containing 10% by weight of the finishing agent (relative to the mass of the GDL substrate). It was then dried at 160°C for 5 minutes and sintered at 400°C for 10 minutes. MPL was subsequently coated onto the surface. The composition of the slurry is shown in Table 1. The preparation method involved dispersing PTFE, various carbons, and plastic particles as pore-forming agents in distilled water and coating them onto carbon fiber paper by blade coating. The sheets were then dried at 160°C and sintered at 400°C. The resulting MPL loading was 15 g / m². 2 .

[0214] Table 1 Application technology performance Contact resistance was determined by strip measurement, as previously described. Measurements were performed under a compression pressure of 1.0 MPa. The GDL sample was oriented on the flow distribution plate with its transverse direction (CD) parallel to the main orientation direction of the flow channel (i.e., the GDL was arranged on the flow distribution plate such that the machine direction (MD) of the GDL formed a 90° angle with the main flow channel direction of the flow distribution plate). For the double-layer base nonwoven fabric, the longitudinally laid fiber web always faced the bipolar plate, while the transversely laid fiber web always faced the electrode. During measurement, the flow channels had the following geometries: (B1, R1), (B1, R2), (B2, R1), and (B2, R2). Here, "B1" represents a flow channel width of 0.3 mm, and "B2" represents a flow channel width of 0.6 mm. "R1" represents a flow channel fillet radius of 0.13 mm, and "R2" represents a flow channel fillet radius of 0.26 mm. Measurements were performed at the center of the gas flow channel. The results are given in Table 2.

[0215] As previously stated, the maximum tensile force (HZK) and elongation at the maximum tensile force (HZD) were determined in Newtons according to EN 29073-3:1992. The results are given in Table 3. Table 3

Claims

1. A proton exchange membrane fuel cell, comprising: - A proton exchange membrane, wherein both sides of the proton exchange membrane are coated with catalytically active electrodes; - A gas diffusion layer is disposed on each side of the catalyst coating film, and the inner side of the gas diffusion layer is in contact with the catalytic active electrode; - Flow distribution plates are respectively disposed on each side of the catalyst-coated film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer. The gas diffusion layer comprises a planar conductive fiber material A) selected from carbon fiber nonwoven fabric, carbon fiber paper, and combinations thereof, wherein the fiber material A) comprises one or more fiber layers. One of the fiber layers has oriented fibers, or in the case where the fiber material comprises multiple fiber layers, at least one of the multiple fiber layers has oriented fibers with a principal orientation direction relative to the basal plane (x, y plane) of the fiber layer. Furthermore, the flow channel of the flow distribution plate has a main orientation direction, and the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channel.

2. A proton exchange membrane fuel cell, comprising: - A proton exchange membrane, wherein both sides of the proton exchange membrane are coated with catalytically active electrodes; - A gas diffusion layer is disposed on each side of the catalyst coating film, and the inner side of the gas diffusion layer is in contact with the catalytic active electrode; - Flow distribution plates are respectively disposed on each side of the catalyst-coated film. The flow distribution plates have channels for supplying reactant gases and discharging battery reaction products, wherein the channels are in contact with the outer side of the gas diffusion layer. The gas diffusion layer comprises a planar conductive fiber material A) consisting of carbon fiber nonwoven fabric or carbon fiber nonwoven fabric, wherein the carbon fiber nonwoven fabric comprises one or more bonded fiber web layers. The fibers of one of the fiber web layers are oriented, or in the case where the carbon fiber nonwoven fabric comprises multiple fiber web layers, at least one of the multiple fiber web layers has oriented fibers with a principal orientation direction relative to the base plane (x, y plane) of the fiber web layer. Furthermore, the flow channel of the flow distribution plate has a main orientation direction, and the main orientation direction of the fibers is not parallel to the main orientation direction of the flow channel.

3. The proton exchange membrane fuel cell according to claim 1 or 2, wherein the flow distribution plate has a flow field selected from parallel flow field, serpentine flow field, interdigitated flow field and columnar flow field.

4. The proton exchange membrane fuel cell according to claim 2, wherein the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, and the fibers of the fiber web layers on the side facing the flow distribution plate are oriented, and the main orientation direction of the fibers of the fiber web layers is not parallel to the main orientation direction of the flow channels of the flow distribution plate.

5. The proton exchange membrane fuel cell according to any one of claims 2 to 4, wherein the carbon fiber nonwoven fabric comprises 2, 3, 4, 5 or more than 5 fiber web layers.

6. The proton exchange membrane fuel cell according to any one of claims 2 to 5, wherein the carbon fiber nonwoven fabric has a plurality of fiber web layers, and at least two of the fiber web layers, preferably at least three of the fiber web layers, and in particular all of the fiber web layers are fiber-oriented.

7. The proton exchange membrane fuel cell according to any one of claims 2 to 6, wherein the carbon fiber nonwoven fabric has a plurality of fiber web layers, and at least two fiber web layers have fiber orientations with two different main orientation directions, particularly at least two adjacent fiber web layers have fiber orientations with two different main orientation directions.

8. The proton exchange membrane fuel cell according to claim 1, wherein the main orientation direction of the fibers is at an angle of 30° to 90°, preferably 45° to 90°, and particularly 60° to 90° to the main orientation direction of the flow distribution plate in contact with the gas diffusion layer.

9. The proton exchange membrane fuel cell according to any one of claims 2 to 7, wherein the main orientation direction of the fibers of at least one fiber web layer is at an angle of 30° to 90°, preferably 45° to 90°, and particularly 60° to 90° to the main orientation direction of the flow channel of the flow distribution plate in contact with the gas diffusion layer.

10. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the gas diffusion layer comprises a carbon fiber nonwoven fabric, and the method of manufacturing the carbon fiber nonwoven fabric comprises providing carbon fibers, combing the provided carbon fibers to increase the parallel orientation in the fiber length direction, laying the combed fibers into a fiber web, optionally laying at least one additional fiber web layer on a first fiber web layer, and consolidating the fiber web layer into a nonwoven fabric.

11. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the main orientation direction of the fibers of the one fiber web layer, or, in the case where the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, the main orientation direction of the fibers of at least one of the plurality of fiber web layers corresponds to the machine direction (MD) or corresponds to the transverse direction (CD) perpendicular to the machine direction.

12. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the carbon fiber nonwoven fabric comprises a plurality of fiber web layers, and the main orientation direction of the fibers of the fiber web layers on at least one side toward the flow distribution plate corresponds to the machine direction (MD) or to a transverse direction (CD) perpendicular to the machine direction.

13. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the carbon fiber nonwoven fabric has a density of at least 20 g / m³. 2 The base weight, and the maximum tensile force in the machine direction is at least 5 N, preferably at least 7 N.

14. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the carbon fiber nonwoven fabric has a density of at least 20 g / m³. 2 The base weight, and the maximum tensile force in the transverse direction perpendicular to the machine direction is at least 5 N, preferably at least 7 N.

15. The proton exchange membrane fuel cell according to claim 1 or 8, wherein the gas diffusion layer comprises A) Planar conductive fiber material, wherein the planar conductive fiber material is selected from carbon fiber nonwoven fabric, carbon fiber paper and their combinations, and B) A microporous layer on the side facing the catalytically active electrode, wherein the microporous layer contains conductive particles in a matrix composed of a polymer binder.

16. The proton exchange membrane fuel cell according to any one of claims 2 to 7 and 9 to 14, wherein the gas diffusion layer comprises A) Planar conductive fiber material, said planar conductive fiber material comprising or composed of carbon fiber nonwoven fabric, and B) A microporous layer on the side facing the catalytically active electrode, wherein the microporous layer contains conductive particles in a matrix composed of a polymer binder.

17. The proton exchange membrane fuel cell according to any one of the preceding claims, wherein the flow distribution plate has at least one of the following features: - The width of the flow channel is in the range of 0.1 to 3.5 mm, preferably 0.2 to 1.5 mm; - The width of the ridge is in the range of 0.1 to 2.5 mm, preferably 0.2 to 1.5 mm; - The depth of the flow channel is in the range of 0.1 to 2.0 mm, and is particularly preferred to be 0.15 to 0.5 mm.

18. A method for manufacturing a gas diffusion layer for a proton exchange membrane fuel cell as defined in any one of claims 2 to 7 and 9 to 17, comprising: i) Provide a planar conductive fiber material A), the planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of at least one of the plurality of fiber web layers are oriented and have a main orientation direction relative to the base plane (x, y plane) of the fiber web layer. ii) Coating the fibrous material provided in step i) with a precursor for forming the microporous layer; iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature.

19. A method for manufacturing a proton exchange membrane fuel cell as defined in any one of claims 2 to 7 and 9 to 17, comprising: i) Provide a planar conductive fiber material A), the planar conductive fiber material A) comprising or composed of carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric comprising one or more bonded fiber web layers, wherein the fibers of at least one of the plurality of fiber web layers are oriented and have a main orientation direction relative to the base plane (x, y plane) of the fiber web layer. ii) Coating the fibrous material provided in step i) with a precursor for forming the microporous layer; iii) Optionally, the coated fiber material obtained in step ii) is post-treated under increased pressure and / or increased temperature; iv) Place the coated fiber material obtained in step ii) or iii) as a gas diffusion layer on both sides of a proton exchange membrane coated with catalytic active electrodes, wherein the microporous layer is located on the side of the gas diffusion layer facing the catalytic active electrodes. v) Place flow distribution plates with flow channels on the outer side of the gas diffusion layer, the flow channels being used to supply reactant gases and discharge battery reaction products, and the flow channels being in contact with the outer side of the gas diffusion layer; vi) Press the flow distribution plate and the components located between the flow distribution plates together.

20. The method according to claim 18 or 19, wherein in order to manufacture the planar conductive fiber material A): i-1) Provides a fiber composition comprising carbon fibers and / or carbon fiber precursors; i-2) The fiber composition provided in step i-1) is combed to increase the parallel orientation in the fiber length direction; i-3) Lay the fiber composition obtained in step i-2) into a fiber web; i-4) Optionally, at least one additional fiber web layer is laid on the first fiber web layer; i-5) Consolidate the one or more fiber web layers obtained in step i-3) or i-4) into a nonwoven fabric; i-6) Optionally treat the nonwoven fabric obtained in step i-5) with at least one additive; i-7) Optionally, the nonwoven fabric obtained in step i-5) or the treated nonwoven fabric obtained in step i-6) is post-treated under increased pressure and optionally increased temperature. i-8) If the fiber composition used in step i-1) includes a carbon fiber precursor, then the nonwoven fabric obtained in step i-5), the treated nonwoven fabric obtained in step i-6), or the post-treated nonwoven fabric obtained in step i-7) is subjected to thermal pyrolysis at a temperature of at least 1000°C.

21. The method of claim 20, wherein in step i-4), at least one additional fiber web layer is laid on the first fiber web layer, wherein at least one of the plurality of additional web layers has a main fiber orientation direction, the main fiber orientation direction being substantially transverse to the main fiber orientation direction of the first web layer.

22. The method according to claim 20 or 21, wherein in step i-5), the one or more fiber web layers obtained in step i-3) or i-4) are consolidated into a nonwoven fabric by the action of an aqueous fluid jet.

23. The method according to any one of claims 20 to 22, wherein the apparatus for processing in step i-7) is selected from a single-layer press, a multi-layer press, a continuous belt press, a calender, and combinations thereof, preferably selected from a double-belt press, a calender, and combinations thereof.

24. The method according to any one of claims 20 to 23, wherein, The nonwoven fabric obtained in step i-5) by the action of an aqueous fluid jet is used for the treatment in step i-7), and is post-treated under increased pressure and optionally increased temperature, wherein the nonwoven fabric obtained by compaction by an aqueous fluid jet is preferably used.

25. A gas diffusion layer, which can be obtained by the method defined in any one of claims 18 or 20 to 24.

26. A proton exchange membrane fuel cell, which can be obtained by the method defined in any one of claims 19 to 24.

27. A fuel cell stack comprising a plurality of proton exchange membrane fuel cells as defined in any one of claims 1 to 17 and 26.

28. Use of at least one gas diffusion layer in a proton exchange membrane fuel cell, which can be obtained by the method defined in any one of claims 18 or 20 to 24, for improving the contact between a catalyst-coated polymer electrolyte membrane and the microporous layer of the gas diffusion layer.

29. The use according to claim 28, which is used to prevent a reduction in the contact area between the catalyst-coated proton exchange membrane and the gas diffusion layer in the region of the flow channel relative to the flow distribution plate, particularly in the region relative to the center of the flow channel.

30. The use according to claim 28 or 29, which is used to prevent an increase in contact resistance between the catalyst coating and the gas diffusion layer in the region of the flow channel relative to the flow distribution plate, particularly in the region relative to the center of the flow channel.

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