JP2007250468A - Electrolyte film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte film in which there is no dimension change due to swelling and contraction, and no performance reduction due to creep in which performance and durability of a fuel cell are improved and which has higher performance than a conventional electrolyte. <P>SOLUTION: Regarding the electrolyte film for the fuel cell, this is the reinforced electrolyte film in which polymer electrolyte covers a metallic base material surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane, particularly an electrolyte membrane for a fuel cell, and more particularly to an electrolyte membrane excellent in durability, particularly an electrolyte membrane for a fuel cell.

  Currently, as means for solving environmental problems, the remaining amount of fossil fuel, and the like, there are means using a clean fuel cell that does not release carbon dioxide. There are various types of fuel cells, and none of them can be returned to perfection, but there is no problem of electrolyte dissipation, and it is easy to control the pressure difference between the two electrodes and pressurize the battery. The polymer electrolyte fuel cell sets a different line from other fuel cells in that it can be started up in a short period of time, the startup time is short, and the size and weight can be reduced. Therefore, improving the conventional polymer electrolyte fuel cell so that it can withstand practical use is nothing other than changing the energy society.

  In the prior art, a polymer-only electrolyte thin film, such as Nafion (manufactured by Dupont), was used for CCM. Therefore, the moisture content in the film changed depending on the usage environment, and it repeatedly swelled and contracted. There was a problem of breaking. In addition, because of the same configuration, the film creeps due to the surface pressure after stacking, and the surface pressure between each member, for example, between the separators and between the separator and the GDL decreases, resulting in an increase in contact resistance and a decrease in power generation performance. On the other hand, there was a problem that hydrogen was not effectively used due to a decrease in hermeticity. Furthermore, since the membrane is compressed by the surface pressure after stacking and the water in the membrane is discharged from the membrane, there is a problem that the proton conduction resistance is increased and the performance is lowered.

  In order to alleviate the above problems, a membrane in which a porous resin metal base material is impregnated with an electrolyte, for example, a Gore-Tex electrolyte membrane has been developed. However, since the metal substrate is a porous resin body, it cannot be a fundamental solution to the above problem.

  Patent Document 1 proposes a method for solving the above problem using a metal sintered thin film. However, unlike the present invention, the metal base material is porous to a metal sintered body. There was a problem that polymer electrolyte injection was difficult, gaps remained, gas leaked, and performance deteriorated.

Further, in the process of manufacturing the fuel cell, there is a problem that part of the air remains in the fine holes of the reinforcing plate, and a gap is generated between the reinforcing material and the polymer electrolyte, resulting in a decrease in power generation performance and gas leakage. It was. Further, when water enters the generated gap, the interface between the reinforcing material and the polymer electrolyte is peeled off, and further, there is a problem that performance is lowered and gas leakage is increased.
JP 2004-063249 A

  Therefore, the present invention aims to improve the performance and durability of the fuel cell by using a metal sheet as a reinforcing material, without the above-mentioned problems of dimensional change due to swelling and shrinkage, and deterioration in performance due to creep. Furthermore, it aims at providing the electrolyte of higher performance than the conventional electrolyte.

  Further, the present invention eliminates the gap between the reinforcing material and the polymer electrolyte in the manufacturing process of the fuel cell, thereby preventing performance deterioration and gas leakage, and preventing interfacial peeling between the reinforcing material and the polymer electrolyte to improve durability. .

  In order to achieve the above object, the inventors have found a reinforced electrolyte membrane characterized in that a polymer electrolyte coats the surface of a metal substrate.

  According to the present invention, it is possible to provide a fuel cell electrolyte membrane that can maintain not only the durability of the membrane but also the amount of water in the membrane and is excellent in proton conductivity.

  The first aspect of the present invention is a reinforced electrolyte membrane in which a polymer electrolyte covers the surface of a metal substrate. The present invention exhibits the following characteristics.

  (1) Since the metal base material for reinforcement is a metal (metal base material), shrinkage and expansion of the film are reduced by changes in the use environment, for example, drying and wetting, so the stress applied to the film is reduced. This increases the fatigue life of the film.

  (2) Since the base material for reinforcement is a metal (metal base material), there is almost no compression creep due to a reduction in surface pressure. As a result, there is almost no increase in resistance and a decrease in hermeticity due to an increase in the surface roughness of the film.

  (3) Since the metal base material is a metal and the compression elastic modulus is increased, the membrane is not compressed even if a surface pressure is applied, and thus the amount of water in the membrane can be maintained. Performance improvement is possible.

  The polymer electrolyte used in the present invention is not particularly limited, and a known one can be used. Examples thereof include the same materials as those used for the electrode catalyst layer, and at least those materials having high proton conductivity. That's fine. The polymer electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte containing fluorine atoms in the whole or a part of the polymer skeleton and a hydrocarbon-based electrolyte not containing fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene Preferred examples include polymers and polyvinylidene fluoride-perfluorocarbon sulfonic acid polymers.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polyaryl ether sulfone sulfonic acid, sulfonated polyphenoxybenzoylphenylene, polybenzimidazole alkyl sulfonic acid, and polybenzimidazole alkyl phosphonic acid. Polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl sulfonic acid and the like are preferable examples. The polymer electrolyte preferably contains a fluorine atom because of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred.

  When the reinforced electrolyte membrane according to the present invention is used for MEA (hereinafter also referred to as a reinforced electrolyte membrane composite), the solid polymer electrolyte used in the polymer electrolyte membrane and the electrode catalyst layer (hereinafter also referred to as the catalyst layer) is Although it may be different, it is preferable to use a fluorine system having a lower Tg in consideration of the bonding property between the membrane and the electrode.

  The material of the metal substrate used in the present invention is preferably Ti, stainless steel, aluminum, zirconia, iron, copper, Ni—Ti alloy, alloys thereof, and the like, and more preferably stainless steel.

  The metal substrate according to the present invention is preferably a flat plate, a metal fiber fabric, a metal foam, or a metal sintered body, and more preferably a flat plate.

  The thickness of the metal base material according to the present invention is preferably 5 to 100 μm, more preferably 10 to 50 μm, and most preferably 15 to 30 μm.

  In the present invention, the metal substrate is preferably a metal thin film having a through hole.

  When the through-hole is processed in the metal thin film, the polymer electrolyte can be easily injected, so that the voids can be eliminated and gas leakage and performance degradation can be prevented. That is, if the material to be reinforced is made of a metal porous body, the surface area becomes very large, so that the polymer electrolyte does not completely penetrate to the inside of the metal porous body due to surface tension, and voids are generated, thereby causing gas leakage, Proton conductivity and electron movement are hindered, resulting in battery performance degradation. Furthermore, since the metal porous body is very brittle, it is difficult to reduce the stress applied to the film. However, such a problem can be overcome in the case of a reinforced electrolyte membrane in which a metal thin film having a through hole is embedded as in the present invention.

  The “through-hole” according to the present specification means that it can pass through the electrolyte from end to end when viewed from the thickness direction. The shape of the through hole is not limited to those shown in FIGS. 1-1 to 1-5, and when viewed from the thickness direction, hydrogen atoms, protons, water molecules, and electrons are sufficiently contained in the electrolyte from end to end. The object of the present invention can be achieved without any problem as long as the shape can be moved to, but as shown in FIGS. 1-1 to 1-5, polygons such as rectangles, squares, hexagons, circles, ellipses, etc. Is more preferably a rectangle, a square, a hexagon, or a circle, and the most preferred shape is a regular hexagon. This is because when the shape of the through hole is a regular hexagon, the portions of the metal thin film other than the through hole have substantially the same width, and the force is uniformly applied to the compression in the vertical direction, which significantly improves the durability of the film. It is because it can improve.

  Also, the arrangement of the holes is not particularly limited, and the holes may be arranged in the same row as in FIG. 1-2 left and FIG. 1-3 left, or in FIG. 1-2 right and FIG. 1-3 right. As described above, the positions of the holes may be shifted in each row. That is, when circular holes are arranged as shown in FIG. 1-3 left, the rib strength is relatively maintained even if the radius of the circular hole is increased and the rib is reduced and the porosity is increased. If hexagonal holes are arranged as shown in FIG. 1-4 and the porosity is similarly increased, the rib width is constant at any position, and the rib strength is maintained. Furthermore, since the rib width is constant, there is an advantage that it is difficult to buckle and break even by stresses such as bending and bending of the entire metal base.

  Porosity = (volume of through hole) / (volume of metal base material without holes) is preferably 30 to 99%, more preferably 60 to 95%, most preferably 75 to 90%. It is.

  The thickness of the metal thin film is preferably 5 to 100 μm, more preferably 10 to 50 μm, and most preferably 15 to 30 μm.

  In the present invention, the metal base material is preferably a reinforced electrolyte membrane formed by laminating a plurality of through holes of the metal thin film in communication with each other. That is, the metal substrate according to the present invention may be formed by laminating a metal thin film having a plurality of through holes. In this case, a metal in which metal thin films are laminated so as to communicate through holes of adjacent metal thin films. A base material is preferred. By connecting through-holes of adjacent metal thin films, a path through which protons, water, gas, etc. can pass from end to end when viewed from the thickness direction of the reinforced electrolyte membrane is secured. The method of laminating in a connected state is not limited as long as the passage of protons, water, gas, etc. can be secured, but most preferably, as shown in FIG. This is a method of stacking in alignment.

  When a plurality of metal thin films are used, any metal thin film may be made of a different material, or all may be made of the same material.

  Further, the number of laminated metal thin films is preferably 2 to 3 sheets. If it is 2 or 3 sheets, it has sufficient durability as a reinforced electrolyte membrane, and can also suppress discharge due to the pressure of moisture in the electrolyte. Furthermore, the thickness of the entire reinforced electrolyte membrane is also appropriate.

  The thickness of the metal thin film in the case where the plurality of through holes of the metal thin film are stacked in communication with each other is preferably a value obtained by dividing the thickness of the metal thin film by the number.

  The metal substrate is preferably surface-treated. By surface-treating the metal base material, the electrical resistance between the anode and the cathode can be increased, and performance degradation due to conduction can be prevented.

  As the surface treatment method according to the present invention, a known method can be used as long as it is a surface treatment method capable of suppressing / preventing corrosion of the base material and elution of metal ions. As the surface treatment method, a metal base is previously plated with metal, chemical plating, hot dipping, anodizing, chromate treatment, chemical conversion treatment, phosphate treatment, lining, CVD chemical vapor phase method, ion plating, Examples include surface sintering. In addition, after the surface treatment, surface modification may be performed with the polymer material on the metal base material further surface-treated with the polymer material.

  The surface treatment is preferably performed by coating the surface of a metal substrate with a metal oxide. Thereby, since a metal oxide layer is formed on the surface of the metal substrate, metal ion elution from the substrate and corrosion of the substrate can be prevented.

  The metal oxide coated on the surface of the metal substrate according to the present invention is preferably a metal oxide that has high electrical insulation, such as silica, titania, alumina, zirconia, and is stable in water and acid, preferably silica, zirconia, titania. Particularly preferred are titania and silica.

  The thickness of the oxide film should be such that the metal ions are prevented from leaching from the base material, corrosion of the base material, and the strength of the metal oxide itself is not easily cracked or peeled off. The film thickness is preferably 1 to 10 μm. In this specification, “coating the surface of a metal substrate with a metal oxide” means not only laminating a metal oxide on the surface of the metal substrate, but also the surface of the metal substrate. It also includes oxidizing the metal.

  Or in this invention, it is also preferable that the said surface treatment is performed by coating a metal base material with a polymer. Since the coating material is a polymer, the affinity between the metal substrate surface and the electrolyte is improved, the adhesive strength between the metal substrate and the electrolyte is enhanced, and the durability is improved. In the present invention, the surface of the metal substrate, that is, the surface of the metal thin film may be subjected to a surface treatment such as bonding a metal atom on the surface of the metal thin film directly with an atom in the polymer by plasma treatment or the like. After the oxide is formed on the surface of the metal substrate, the polymer may be modified on the metal oxide layer. In this case, both chemically and physically modified modifications are within the scope of the present invention.

  In addition, the thickness of the polymer when the polymer is formed on the metal oxide layer is preferably 1 to 10 μm, and when the polymer is directly formed on the metal substrate, 1 to 10 μm is preferable.

The present invention is the reinforced electrolyte membrane, wherein the polymer is a hydrophobic polymer.
Since the polymer coating material is hydrophobic, there is no ingress of moisture between the coating and the metal substrate, preventing peeling between the coating and the metal substrate due to invasion of water, and improving durability. I can do it.

  The hydrophobic polymer according to the present invention includes fluororesins such as PTFE, PVDF, and PFA, polyolefins such as PP (polypropylene) and PE (polyethylene), PES (polyethersulfone), PFS (polysulfone), and PEA (polyether). Polyarylenes such as amide), PI (polyimide), and aramid are preferred.

  In the present invention, the polymer is preferably a polymer having the same main chain or the same side chain as the polymer electrolyte membrane and having no sulfone group.

  The polymer is a polymer having a structure similar to that of the electrolyte, that is, the same main chain or the same side chain as that of the polymer electrolyte membrane, and is not sulfonated. When the polymer is hydrophobic, there is no ingress of moisture between the coating and the metal substrate, and the infiltration of water. The peeling between the coating and the metal substrate can be prevented, and the durability can be enhanced.

  The interface between the injected polyelectrolyte and the coating on the metal substrate is bonded by hydrogen bonding and anchoring effects. For this reason, the polymer electrolyte swells and shrinks in the through hole, so that the anchor effect is removed, and the interface may peel off. In addition, when water enters the interface, the hydrogen bond is broken (the hydrogen bond between the coating OH group and water is stronger than the hydrogen bond between the OH group and polymer electrolyte on the surface of the coating ceramic). Concerned. If a part of the film is peeled off, the peeling point may be a starting point and the peeling may be spread. If the peeling is spread, hydrogen or air leaks, and the performance and efficiency as a fuel cell are lowered.

  For this reason, it is good to provide a coating with a hydrophobic polymer on a metal substrate or a metal oxide film. In addition, after injecting a polymer electrolyte into a metal substrate provided with this polymer coating, it is preferable to soften the polymer by applying heat. By doing so, the polymer coating and the polymer electrolyte are mixed at the interface and are difficult to peel off. Since this polymer coating is hydrophobic, water can be prevented from entering, and peeling of the polymer coating from the metal base metal or metal oxide film can be prevented.

  In addition, it is desirable that the polymer coating is formed using a polymer electrolyte non-sulfonated polymer. If the polymer electrolyte is Nafion, the polymer is PTFE, and if the polymer electrolyte is S-PES (sulfonated polyethersulfone), the polymer is PES (polyethersulfone). In this case, the coating is hydrophobic, and the interaction between the polymer electrolyte and the coating is increased, so that the interfacial peeling is further difficult and durability, performance, and efficiency are improved. These coatings are preferably polymerized in a thin film on the surface of the base material using a monomer as a raw material for the polymer. By doing so, the coating can be made thinner, uniformly dense, and the performance can be improved without being reduced by the volume coating that can be impregnated with the electrolyte.

  In the present invention, the surface treatment with the polymer is preferably performed by polymerizing the polymer into a thin film on the surface of the metal substrate.

  Since the polymer coating is polymerized in a thin film on the surface of the substrate using the monomer that is the raw material of the polymer, the coating can be made thinner and uniformly dense, and the volume that can be impregnated with the electrolyte is reduced. You can increase the performance.

  Even when the polymer is polymerized in a thin film on the surface of the metal substrate, the polymer and the surface of the metal substrate may be chemically adsorbed or physically adsorbed. . Furthermore, after coating the surface of the metal substrate with a metal oxide, the polymer may be polymerized in a thin film on the surface of the metal oxide. Also in this case, the polymer and the metal oxide surface may be chemically adsorbed and polymerized, or may be physically adsorbed and polymerized.

  The thickness of the polymer film when polymerizing the polymer into a thin film is preferably 1 to 5 μm.

In the present invention, it is preferable that a polymer electrolyte is applied in a thin film on at least one of the side surfaces of the reinforced electrolyte membrane. Since the electrolyte is applied in a thin film on the upper and lower surfaces of the polymer electrolyte membrane reinforced with a metal base material, the bondability with the catalyst layer is improved and the catalyst bonding area increases, so that the performance can be improved. it can. In addition, when the side surface of the metal base material is exposed, metal elution occurs from there, but this can be suppressed / prevented. When the polymer electrolyte is applied in a thin film on at least one side surface of the reinforced electrolyte membrane, The thickness of the polymer electrolyte is preferably 1 to 5 μm.

  The present invention is preferably a reinforced electrolyte membrane laminate in which at least two of the above reinforced electrolyte membranes are laminated, and an electrolyte is applied to the joint surface between the reinforced electrolyte membrane and another layer. Since at least two polymer electrolyte membranes reinforced with a metal base material are stacked and the electrolyte is applied to the joining surface and the upper and lower surfaces, the joining property with the catalyst layer is improved and the entire region of the membrane is applied to the fuel cell. Such catalytic reactions can occur.

  Moreover, when laminating at least two or more of the above-mentioned reinforcing electrolyte membranes, the polymer electrolyte membrane used for each reinforcing electrolyte membrane may be covered with a different polymer electrolyte, and the metal oxide used for the reinforcing electrolyte membrane , And the polymer may also be different for each reinforced electrolyte membrane.

  In other words, for example, in an electrolyte membrane used in a battery or the like, ion conductivity, particularly in a fuel cell, proton conductivity has a great influence on energy efficiency. Therefore, when laminating at least two reinforced electrolyte membranes and changing the type of polymer electrolyte membrane used for each reinforced electrolyte membrane, the electrolyte is selected by paying attention to the value of proton conductivity. It is more preferable to produce a laminate.

However, in general, a polymer electrolyte membrane having high ion conductivity 1.1 to 4 meq / g (hereinafter also referred to as a high IEC polymer electrolyte) has high performance (1.0 × 10 ^{−3 to} 1.0 × 10 ⁻² S / cm 30 ° C.), a polymer electrolyte membrane having low durability and normal ion conductivity of 0.2 to 1.1 meq / g (hereinafter also referred to as IEC polymer electrolyte) has durability. High (1.0 × 10 ^{−4 to} 1.0 × 10 ⁻³ S / cm 30 ° C.). Therefore, when a membrane / electrode assembly is produced using only a high IEC polymer electrolyte membrane in order to obtain a battery with excellent energy efficiency, the high IEC polymer electrolyte membrane is damaged due to swelling shrinkage or the like. However, as in the present invention, a so-called sandwich in which a reinforced electrolyte membrane in which a metal substrate such as a metal thin film is inserted into a high IEC polymer electrolyte is supported by a normal IEC polymer electrolyte having excellent durability. With this structure, a reinforced electrolyte membrane (laminate) having higher ionic conductivity and superior durability can be obtained.

  In addition, a normal IEC polymer electrolyte membrane coated with a metal substrate may be sandwiched between high IEC polymer electrolyte membranes not coated with a metal substrate, and these combinations are also within the scope of the present invention. Needless to say.

Examples of the high IEC polymer electrolyte according to the present invention include sulfonated polyarylethersulfone (S-PES), sulfonated polyphenoxybenzoylphenylene (S-PPBP), and the like.
Examples of the normal IEC polymer electrolyte according to the present invention include sulfonated ether-etherketone. The IEC of these materials may be adjusted to provide a high IEC electrolyte or a low IEC electrolyte.

  In addition, as for the thickness of the reinforcement electrolyte membrane laminated body which concerns on this invention, 20-50 mm is preferable.

  Further, as shown in FIG. 12, the present invention may be a reinforced electrolyte membrane composite in which a polymer electrolyte membrane is sandwiched between a pair of the reinforced electrolyte membrane or the reinforced electrolyte membrane laminate, as shown in FIG. Alternatively, a reinforced electrolyte membrane composite in which the reinforced electrolyte membrane or the reinforced electrolyte membrane laminate is sandwiched between a pair of the polymer electrolyte membranes may be used.

  In any of the above cases, it goes without saying that the type of polymer electrolyte is the same or different and is within the scope of the present invention.

    The first embodiment of the present invention will be described below with reference to FIGS.

    A metal substrate 1 is formed by processing through-holes 2 using a metal thin film such as Ti, stainless steel, aluminum or the like by etching, photoresist or the like.

    “Etching” as used herein refers to a chemical precision processing technology that uses a photoengraving process on a metal thin film to form a corrosion-resistant film in the required pattern and partially corrode it. Shape patterns are possible.

    When this technique is used, the through hole may be slit-shaped, circular, or the like. For example, in the case of a slit, the slit width depends on the plate pressure, but 1 to 100 μm and the porosity is preferably about 30 to 90%. When the porosity is increased, the porosity is increased and the usable electrolyte area is increased, so that the performance is improved. However, if the slit width is increased and the remaining portion (rib) is narrowed, the rib becomes elongated, so that the bending moment of the rib increases when stress is applied, and there is a possibility that the rib breaks. In addition, since the area where the electrolyte is continuous increases, the amount of swelling and shrinkage increases, making it difficult to obtain a reinforcing effect.

    When circular holes are arranged as shown in the left side of FIG. 1-3, even if the radius of the circular hole is increased and the rib is reduced and the porosity is increased, the rib strength is relatively maintained. If hexagonal holes are arranged as shown in FIG. 1-4 and the porosity is similarly increased, the rib width is constant at any position, and the rib strength is maintained. Furthermore, since the rib width is constant, there is an advantage that it is difficult to buckle and break even by stresses such as bending and bending of the entire metal base.

    2 to 3 show schematic views of the reinforced electrolyte membrane. The surface of the metal thin film, which is a metal substrate, is coated with a coating 3 made of an oxide of the substrate metal or other metal oxide. At this time, when a metal oxide is formed on the substrate surface, the substrate surface may be oxidized by an anodic oxidation method or the like. In the case of a base metal oxide or other metal oxides, surface coating by CVD (chemical vapor deposition), ion plating, or surface sintering may be used. Silica, titania, alumina, zirconia, and the like are preferable because they have a high electrical insulating property and are stable in moisture and acid. A polymer electrolyte 4 is injected into the through hole 2 as described above to create a reinforced electrolyte membrane 5 shown in FIG. The polymer electrolyte 4 may be, for example, Dupont Nafion or the like, and may be injected in a molten state or may be injected in a state dissolved in a solvent. Here, a slurry of carbon particles carrying a catalyst such as Pt and a polymer electrolyte, for example, a Nafion solution, is applied to a gas diffusion sheet such as carbon paper to form a catalyst layer 6 and a gas diffusion layer 7, and this and a reinforced electrolyte membrane 5 is joined by applying heat to form MEA 8 (Membrane & electroassembled) (also referred to as a reinforced electrolyte membrane composite in this specification) shown in FIG.

  Such an MEA contains a metal in a reinforced electrolyte membrane, and the membrane is not shrunk or expanded due to changes in the use environment, for example, drying and wetting, so that the stress applied to the membrane is reduced and the fatigue life of the membrane is extended. In addition, since compression creep is almost eliminated, there is almost no increase in resistance and airtightness due to a decrease in surface pressure. Further, since the metal base material is metal and the compression elastic modulus is increased, the membrane is not compressed even when surface pressure is applied, the water in the membrane is retained, and the performance of the fuel cell can be improved.

  However, even if power generation is performed using such an MEA, the electrolyte area is reduced as compared with an electrolyte membrane without a metal base material, so that the performance is considered to be reduced. For this reason, performance degradation is eliminated by the method of multilayering the reinforced electrolyte membrane 5 prepared by the above method. Hereinafter, the second and third embodiments will be described.

  The second embodiment will be described with reference to FIG.

  A high IEC polymer electrolyte 10 having a low mechanical strength alone is injected into the through hole 2 of the metal substrate 1. The IEC is preferably 1.1 to 4 meq / g. The IEC polymer electrolyte 11 is usually thinly applied to the upper and lower sides to form a multilayer reinforcing film 12. In this case, the IEC is preferably 0.2 to 1.1 meq / g. By doing so, the high IEC polymer electrolyte 10 can be retained and the strength as a multilayer can be maintained. The coating thickness of the polymer electrolyte 11 is preferably 1 to 20 μm.

  Thereafter, the catalyst layer 6 and the gas diffusion layer 7 are attached to form an MEA. As described above, by using two types of the high IEC polymer electrolyte 10 and the normal IEC polymer electrolyte 11, it is possible to improve the performance degradation without reducing the durability. In addition, it is possible to form a high IEC polymer electrolyte that has not been able to obtain strength by itself. This high IEC electrolyte has a high water holding capacity and can easily form a channel of a proton conduction path, so that high performance can be exhibited even with low humidification. In addition, the bondability between the catalyst layer 6 and the reinforcing membrane is improved, and performance deterioration is prevented.

  However, since these MEAs use the high IEC polymer electrolyte 10, there is a concern that cracking and peeling at the interface of the metal substrate 1 are caused by repeating swelling and shrinkage in the through-hole 2. The high IEC polymer electrolyte 10 originally has large swelling and shrinkage and low mechanical strength.

  Embodiment 3 will be described with reference to FIG.

  As in the second embodiment, the high IEC polymer electrolyte 10 is injected into the through hole 2 of the metal substrate 1 to obtain a high IEC reinforced electrolyte membrane 15. A high IEC polymer electrolyte 10 or a normal IEC polymer electrolyte 1 is applied to the upper and lower sides thereof. Next, it is sandwiched from above and below by a normal IEC reinforced electrolyte membrane 14 in which a normal IEC polymer electrolyte 11 is separately injected into the through-hole 2 of the metal substrate 1 and thermocompression-bonded. At this time, the applied polymer electrolytes 10 and 11 function as an adhesive and prevent the proton conduction path channel from being disconnected. Thereafter, the IEC polymer electrolyte 11 is thinly applied to the upper and lower surfaces in the same manner as in the second embodiment to obtain a reinforced electrolyte membrane laminate 16.

  Depending on the environment used, the high IEC electrolyte has a large swelling and shrinkage. By using a low to normal IEC electrolyte on both sides, the high ICEC polymer electrolyte 10 with low mechanical strength is less susceptible to the cell environment and the swelling shrinkage is reduced. Separation from the interface of the material 1 is reduced and durability is improved. Further, the thickness of the high IEC reinforced electrolyte membrane 15 and the normal IEC reinforced electrolyte membrane 14 may be changed according to the environment to be used. If the high IEC reinforced electrolyte membrane 15 is thickened in a low humidified environment and has water retention, higher performance is obtained. Further, the thickness and IEC of the normal IEC reinforcing electrolyte membrane 14 may be changed on the anode side and the cathode side. On the cathode side, water is generated by the reaction of protons, but in order to reduce the proton conduction resistance and improve the performance by taking this generated water into the membrane, the thickness of the normal IEC reinforced electrolyte membrane 14 on the cathode side is reduced. However, increasing the IEC improves performance.

  The present invention is a method for producing a reinforced polymer electrolyte membrane comprising a step of thermocompression bonding the polymer electrolyte membrane (a) from one side of a metal substrate having a through hole in the step of reinforced polymer electrolyte membrane.

  According to the method for producing a reinforced electrolyte membrane, since thermocompression bonding is performed from one side, the polymer electrolyte can be introduced while air is being released from the micropores in the metal reinforcing material, so that there is no gap between the reinforcing material and the polymer electrolyte. In addition, it is possible to prevent performance degradation and gas leakage, and to prevent interfacial peeling between the reinforcing material and the polymer electrolyte, thereby improving durability.

  Examples of the polymer electrolyte membrane (a) according to the present invention include the same materials as those of the polymer electrolyte, and are not particularly limited, and known materials can be used as long as the materials have at least high proton conductivity. .

  The present invention is a method for producing a reinforced electrolyte membrane, comprising the step of thermocompression bonding a metal substrate having a through hole from both sides of the polymer electrolyte membrane (a) in the step of the reinforced polymer electrolyte membrane.

  According to the method for manufacturing a reinforced electrolyte membrane, since the metal reinforcing material processed with micropores from both sides of the polymer electrolyte membrane is subjected to thermocompression bonding, air and gaps are eliminated in the reinforcing material micropores. In addition to preventing the interfacial separation between the reinforcing material and the polymer electrolyte and improving the durability, the two reinforcing materials can further improve the strength and durability.

  The present invention is a method for producing a reinforced electrolyte membrane, further comprising the step of applying a solution or melt of the polymer electrolyte (b) over the entire surface of the reinforced polymer electrolyte membrane.

  Examples of the polymer electrolyte membrane (b) according to the present invention include the same materials as the above polymer electrolyte, and are not particularly limited, and known materials can be used as long as they have at least high proton conductivity. .

  According to the method for manufacturing the reinforced electrolyte membrane, the polymer electrolyte is spread on the surface of the reinforcing material on the opposite side of the thermocompression bonding by applying the polymer electrolyte (b) solution or melt after the pressure bonding, thereby further reducing the performance degradation. In addition to reducing leakage, it is possible to improve electronic insulation and reduce elution.

  The present invention is a method for producing a reinforced electrolyte membrane, wherein the thermocompression bonding is performed under vacuum or under reduced pressure.

  According to the method for producing a reinforced electrolyte membrane, since thermocompression bonding is performed under vacuum or reduced pressure, air in the reinforcing material micropores does not remain, and further, there is no gap between the reinforcing material and the polymer electrolyte, resulting in performance degradation. Gas leaks can be further prevented, and interfacial delamination between the reinforcing material and the polymer electrolyte can be further prevented to improve durability.

The pressure for thermocompression bonding is preferably 0.5 to 10 MPa, more preferably 1 to 7 MPa, and the pressure bonding temperature is preferably 100 to 200 ° C., more preferably 120 to 180 ° C.
The degree of vacuum of the system at the time of thermocompression bonding is preferably 10 ⁻¹ to 10 ⁻³ Torr.

  In the present invention, the polymer electrolyte membrane (a) preferably has a higher ion exchange capacity than the polymer electrolyte (b).

  According to the method for manufacturing a reinforced electrolyte membrane, since the polymer electrolyte to be thermocompression bonded has a higher IEC than the polymer electrolyte to be applied, the softening point of the polymer electrolyte during thermocompression is lowered and the thermocompression bonding temperature is reduced. The polymer electrolyte can be easily introduced without causing thermal deterioration of the polymer electrolyte.

  The difference in ion exchange capacity between the polymer electrolyte membrane (a) and the polymer electrolyte (b) is preferably 0.1 to 3.0 meq / g, more preferably 0.3 to 2.0 meq / g. Particularly preferably, 0.5 to 1.0 meq / g and (a)> (b).

  The ion exchange capacity of the polymer electrolyte membrane (a) is preferably 1.1 to 4.0 meq / g, more preferably 1.5 to 3.0 meq / g, and particularly preferably 1.8 to 2.5 meq / g.

  The ion exchange capacity of the polymer electrolyte (b) is preferably 0.5 to 2.5 meq / g, more preferably 1.0 to 2.0 meq / g, and particularly preferably 1.5 to 1. 8 meq / g.

  Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS. A reinforcing material 1 is formed by processing the through hole 2 in a metal thin film made of, for example, Ti, stainless steel, aluminum, or the like, using etching, photoresist, or the like. The through hole may be slit-shaped, circular, or the like. For example, in the case of a slit, the slit width depends on the plate pressure, but 1 to 100 μm and the porosity is preferably about 30 to 90%.

  7-10 show schematic views of the reinforced electrolyte membrane and the manufacturing method thereof. A metal substrate (FIGS. 1 and 6) is coated on the thin film surface with a coating 3 made of an oxide of a substrate metal or other metal oxide. At this time, in the case of the base metal oxide, the base surface is oxidized by an anodic oxidation method or the like. In the case of a base metal oxide or other metal oxides, surface coating by CVD (chemical vapor deposition), ion plating, or surface sintering may be used. Silica, titania, alumina, zirconia, and the like are preferable because they have a high electrical insulating property and are stable in moisture and acid.

  A method for introducing the polymer electrolyte 44 into the through-hole 2 will be described with reference to FIG. The polymer electrolyte 44 is thermocompression-bonded from one side of the metal substrate 1 using a hot press machine 55 or the like with a built-in heater 66. The polymer electrolyte 44 may be, for example, Nafion (manufactured by Dupont). The thermocompression bonding temperature is preferably about 5 to 50 ° C. on the high temperature side of the Tg (glass transition temperature) of the polymer electrolyte 44. In the case of Nafion, since the Tg is about 130 ° C., the thermocompression bonding temperature is desirably 100 ° C. to 180 ° C. In the case of Nafion, the thermocompression bonding pressure is preferably in the range of 1 to 7 MPa.

    Here, an air vent groove 77 is processed on the metal substrate 1 side of the hot press machine 55. For this reason, since air escapes from the through-hole 2 in the metal substrate 1 during thermocompression bonding, the polymer electrolyte 44 is introduced without a gap between the metal substrate and the polymer electrolyte. Further, this step may be performed in a vacuum or in a reduced pressure. Since air does not remain in the through-hole 2 of the metal substrate 1, the polymer electrolyte 44 can be introduced without a gap.

    When the gap is formed, the polymer electrolyte 44 is interrupted in the thickness direction and does not exhibit good proton conductivity. However, when thermocompression bonding is performed in this manner, the polymer electrolyte 44 is not interrupted in the middle and good proton Shows conductivity and almost no performance degradation. Further, gas leakage from the anode to the cathode or from the cathode to the anode, which can occur due to the gap, can be prevented. Furthermore, since it is possible to prevent water from entering the interface between the reinforcing material and the polymer electrolyte, it is possible to prevent peeling of the reinforcing material and the polymer electrolyte and to improve durability.

    The polymer electrolyte 44 to be thermocompression bonded may be in the form of a film or particles. In order to uniformly introduce the polymer electrolyte 44, a membrane is preferable. In this way, a reinforced electrolyte membrane 88 as shown in FIG. 8 is obtained.

    However, the polymer electrolyte 44 may not be introduced into the surface of the metal substrate 1 opposite to the polymer electrolyte 44 (B surface). Further, the polymer electrolyte 44 may not be introduced into the outer peripheral portion (C surface) of the metal substrate 1. For this reason, the polymer electrolyte solution 9A or the polymer electrolyte melt 9B may be separately applied to the surface and the outer periphery. By doing so, the polymer electrolyte 44 exhibits good proton conductivity without interruption, and performance degradation can be prevented. In addition, by reliably coating the metal substrate 1 with a polymer, gas leakage to the outside can be reduced, electronic insulation can be improved, current leakage can be eliminated, and performance degradation can be prevented. Furthermore, catalyst poisoning can be prevented by reducing the elution of ions and the like from the metal substrate 1.

    In general, the polymer electrolyte 44 has a lower Tg at a high IEC, and therefore, the polymer electrolyte 44 can have a lower thermocompression bonding temperature and can be easily operated. In addition, there is an effect of preventing thermal deterioration of the polymer electrolyte 44. Here, as shown in FIG. 9, the case where the high IEC polymer electrolyte 10 is introduced from the A surface by thermocompression bonding will be described. In this case, since the high IEC polymer electrolyte 10 exhibits higher proton conductivity, a high-performance reinforced electrolyte membrane 111 is obtained. However, since the high IEC polymer electrolyte 10 has a low Tg as described above, it can be easily softened, causing deformation, cracks, or the like, or a problem that the electrolyte flows out under high temperature and high humidity. For this reason, the low IEC polymer electrolyte solution 12A or the polymer electrolyte melt 12B is preferably applied to the B surface and the C surface. Further, the low IEC polymer electrolyte solution 12A or the polymer electrolyte melt 12B may be applied to the A surface. By doing so, it is possible to prevent the deformation, cracks, and electrolyte outflow.

  The creation of MEA 13 (Membrane & electroassembly) using such a reinforced electrolyte membrane 88 will be described with reference to FIG. A slurry of carbon particles carrying a catalyst such as Pt and a polymer electrolyte, for example, a Nafion solution, is applied to a gas diffusion sheet such as carbon paper to form a catalyst layer 140 and a gas diffusion layer 150, and a reinforcing electrolyte membrane 88. Are heated and joined to form MEA13.

  Next, a fifth embodiment of the present invention will be described with reference to FIG. The metal substrate 1 is thermocompression bonded from both sides of the polymer electrolyte 44 using a hot press machine 55. At this time, an air vent groove 77 is provided on the surface of the hot press machine 55, the end surface on the D surface side of the metal substrate 1, and the end surface on the E surface side so that air can escape from the through hole 2 of the metal substrate 1 during thermocompression bonding. To do. The thermocompression bonding conditions, materials, etc. may be the same as in the fourth embodiment. In this way, the reinforced electrolyte membrane 16 is obtained. Further, as shown in FIG. 12, the polymer electrolyte solution 9A or the polymer electrolyte melt 9B may be applied to both surfaces (E and D surfaces) and the periphery (F surface) of the metal substrate 1 after thermocompression bonding. As for the IEC of these electrolytes, the polymer electrolyte to be thermocompression bonded may be high IEC, and the polymer electrolyte to be applied may be low IEC as in the first embodiment.

By providing a metal base on both sides of the polymer electrolyte in this way, higher strength can be achieved than in the fourth embodiment, and thus durability can be further improved.
The production of MEA using this reinforced electrolyte 16 is the same as in the first embodiment.

  The present invention is a membrane electrode assembly (also referred to as a reinforced electrolyte membrane composite in the present specification) using the reinforced electrolyte membrane and the reinforced electrolyte membrane laminate, and is characterized by using the membrane electrode assembly. This is a fuel cell.

  The preferable aspect of the manufacturing method of MEA of this invention is demonstrated. In addition, the following aspects show the preferable aspect of this invention, and the manufacturing method of MEA of this invention is not limited to the following method.

  First, the catalyst ink of the present invention is applied and dried on a transfer mount to form an electrode catalyst layer.

  In this case, as the transfer mount, a known sheet such as a PTFE (polytetrafluoroethylene) sheet, a PET (polyethylene terephthalate) sheet, or a polyester sheet can be used. The transfer mount is appropriately selected according to the type of catalyst ink to be used. In the above process, the thickness of the electrode catalyst layer is not particularly limited as long as it can sufficiently exhibit the catalytic action of the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). Thickness can be used. Specifically, the thickness of the electrode catalyst layer is 5 to 30 μm, more preferably 10 to 20 μm.

  The method for applying the catalyst ink onto the transfer mount is not particularly limited, and a known method such as a screen printing method, a deposition method, or a spray method can be similarly applied. Also, the drying conditions of the applied electrode catalyst layer are not particularly limited as long as the polar solvent can be completely removed from the electrode catalyst layer. Specifically, the coating layer of the catalyst ink coating layer (electrode catalyst layer) is dried in a vacuum dryer at room temperature to 100 ° C., more preferably 50 to 80 ° C., for 30 to 60 minutes. At this time, if the thickness of the catalyst layer is not sufficient, the coating and drying process is repeated until a desired thickness is obtained. Next, after sandwiching the reinforcing electrolyte membrane (laminated body) with the catalyst layer thus produced, hot pressing is performed on the laminated layer. At this time, the hot press conditions are not particularly limited as long as the electrode catalyst layer and the reinforced electrolyte membrane (laminated body) can be joined sufficiently closely, but are 100 to 200 ° C., more preferably 120 to 180 ° C. The pressure is preferably 1 to 7 MPa. Thereby, bondability with a reinforced electrolyte membrane (laminated body) and an electrode catalyst layer can be improved.

  After performing the hot pressing, the reinforced electrolyte membrane composite including the electrode catalyst layer and the reinforced electrolyte membrane (laminated body) can be obtained by peeling off the transfer mount. The membrane electrode assembly according to the present invention generally further includes a gas diffusion layer as described in detail below. At this time, the gas diffusion layer peels off the transfer mount in the above method. It is preferable that the obtained joined body is further sandwiched between gas diffusion layers to further join each electrode catalyst layer after joining the electrode catalyst layer and the reinforcing electrolyte membrane (laminated body). Alternatively, an electrode catalyst layer is formed on the surface of the gas diffusion layer in advance to produce an electrode catalyst layer-gas diffusion layer assembly, and then reinforced with the electrode catalyst layer-gas diffusion layer assembly in the same manner as described above. It is also preferable to sandwich and bond the electrolyte membrane (laminated body) by hot pressing.

  In addition to the hot pressing method described above, a method of laminating an electrode catalyst layer, a reinforced electrolyte membrane (laminated body), an electrode catalyst layer, and a gas diffusion layer by sequential coating on the gas diffusion layer may be used.

  As the catalyst component used in the electrode catalyst layer according to the present invention, the cathode catalyst layer is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. Further, the catalyst component used in the anode catalyst layer is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. Is done. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like.

  The composition of the alloy is preferably 30 to 90 atomic% for platinum and 10 to 70 atomic% for the metal to be alloyed, depending on the type of metal to be alloyed. The composition of the alloy when the alloy is used as a cathode catalyst varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art, but platinum is 30 to 90 atomic%, and other metals to be alloyed are 10 It is preferable to set it to -70 atomic%. In general, an alloy is a generic term for an element obtained by adding one or more metal elements or non-metal elements to a metal element and having metallic properties.

  The alloy structure consists of a eutectic alloy, which is a mixture of component elements that form separate crystals, a component element that completely dissolves into a solid solution, and a component element that is an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the cathode catalyst layer and the catalyst component used for the anode catalyst layer can be appropriately selected from the above. In the following description, unless otherwise specified, the description of the catalyst component for the cathode catalyst layer and the anode catalyst layer has the same definition for both, and is collectively referred to as “catalyst component”. However, the catalyst components for the cathode catalyst layer and the anode catalyst layer do not need to be the same, and are appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used, but the catalyst component is preferably granular. At this time, the smaller the average particle size of the catalyst component used in the catalyst slurry, the higher the effective electrode area where the electrochemical reaction proceeds, and thus the higher the oxygen reduction activity, but in reality the average particle size is too small. On the other hand, a phenomenon in which the oxygen reduction activity decreases is observed. Therefore, the average particle diameter of the catalyst component contained in the catalyst slurry is preferably 1 to 30 nm, more preferably 1.5 to 20 nm, even more preferably 2 to 10 nm, and particularly preferably 2 to 5 nm. It is preferably 1 nm or more from the viewpoint of easy loading, and preferably 30 nm or less from the viewpoint of catalyst utilization. The “average particle diameter of the catalyst component” in the present invention is the average value of the particle diameter of the catalyst component determined from the crystallite diameter or transmission electron microscope image obtained from the half width of the diffraction peak of the catalyst component in X-ray diffraction. Can be measured.

  The electrode catalyst used in the catalyst layer according to the present invention is formed by supporting a catalyst component on a conductive material.

  The conductive material may be any material that has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electronic conductivity as a current collector. The main component is carbon. Preferably there is. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

The BET specific surface area of the conductive material may be a specific surface area sufficient to support the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Is good. If the specific surface area is less than 20 m ² / g, the dispersibility of the catalyst component and the polymer electrolyte in the conductive material may be reduced, and sufficient power generation performance may not be obtained, and the specific surface area exceeds 1600 m ² / g. In addition, the effective utilization rate of the catalyst component and the polymer electrolyte may decrease instead.

  In addition, the size of the conductive material is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the electrode catalyst layer within an appropriate range, the average particle size is 5 to 200 nm. The thickness is preferably about 10 to 100 nm.

  In the electrode catalyst in which the catalyst component is supported on the conductive material, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. Good. When the loading amount exceeds 80% by mass, the degree of dispersion of the catalyst component on the conductive material is lowered, and although the loading amount is increased, the improvement in power generation performance is small and the economic advantage may be lowered. On the other hand, if the loading amount is less than 10% by mass, the catalytic activity per unit mass is lowered, and a large amount of electrode catalyst is required to obtain the desired power generation performance, which is not preferable. The amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  The ion conductive polymer in the electrode catalyst layer according to the present invention is not particularly limited and known ones can be used, but the same materials as those used for the polymer electrolyte can be used, and at least high proton conductivity can be used. Any material that has The cathode catalyst layer / anode catalyst layer (hereinafter also simply referred to as “catalyst layer”) of the present invention contains a polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte containing fluorine atoms in the whole or a part of the polymer skeleton and a hydrocarbon-based electrolyte not containing fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene Preferred examples include polymers and polyvinylidene fluoride-perfluorocarbon sulfonic acid polymers.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl. A suitable example is sulfonic acid.

  The polymer electrolyte preferably contains a fluorine atom because of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred.

  The catalyst component can be supported on the conductive material by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used. Alternatively, a commercially available electrode catalyst may be used.

  The polymer electrolyte used in the polymer electrolyte membrane and the electrode layer may be different, but it is preferable to use the same polymer electrolyte considering the contact resistance between the membrane and the electrode.

  The polymer electrolyte is preferably coated with an electrode catalyst as a polymer that functions as an adhesive. Thereby, while being able to maintain the structure of an electrode stably, the sufficient three-phase interface where an electrode reaction advances can be ensured, and high catalyst activity can be obtained. Although content of the said solid polymer electrolyte contained in an electrode is not specifically limited, It is good to set it as 25-35 mass% with respect to the whole quantity of a catalyst component.

  As a material used for the gas diffusion layer (hereinafter referred to as GDL) according to the present invention, a sheet-like material made of carbon paper, non-woven fabric, carbon woven fabric, paper-like paper body, felt or the like has been proposed. When GDL has excellent electron conductivity, efficient transport of electrons generated by a power generation reaction is achieved, and the performance of the fuel cell is improved. Further, if the GDL has an excellent water repellency, the generated water is efficiently discharged.

  In order to ensure high water repellency, a technique for water repellency treatment of a material constituting the GDL has also been proposed. For example, a solution containing a fluorine-based resin such as polytetrafluoroethylene (PTFE) is impregnated with a material constituting GDL such as carbon paper, and dried in the air or an inert gas such as nitrogen. Depending on the case, the hydrophilization treatment may be performed on the material constituting the GDL.

  In addition, carbon particles and a binder may be disposed on a sheet-like GDL made of carbon paper, nonwoven fabric, carbon fabric, paper-like paper body, felt, etc., and both may be used as a gas diffusion layer. You may use the film itself which consists of particle | grains and a binder as a gas diffusion layer. As a result, since the water repellent material and the carbon particles are uniformly formed on the film itself, the water repellent efficiency is increased as compared with the above application.

Examples of the water repellent material include fluorine resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene, polyethylene, and the like. Is mentioned. Of these, fluororesins are preferred because they are excellent in water repellency and corrosion resistance during electrode reaction.
Incidentally, the “binder” refers to a substance having a role of adhesion, and in the examples according to the present invention, a fluororesin having both a role of a binder and a role of water repellency is used, but it is not necessarily limited thereto. Alternatively, the binder and the water repellent material may be mixed and used as independent substances.

  The anode side electrode catalyst layer and the cathode side electrode catalyst layer according to the present invention include a catalyst metal, a proton conductive polymer, and a water repellent material.

  The porosity of the electrode catalyst layer is preferably 30 to 70%, more preferably 40 to 60%. If the porosity is less than 30%, gas diffusion is not sufficient, and the cell voltage in the high current region decreases. On the other hand, when the porosity exceeds 70%, the strength of the electrode catalyst layer is not sufficient, and the porosity decreases in the transfer process.

  In the present invention, MEA (membrane-electrode assembly (also referred to as membrane electrode assembly or reinforced electrolyte membrane composite)) can be produced by a method similar to a conventionally known method. For example, by applying and drying the prepared catalyst slurry on a transfer mount with a desired thickness, an electrode catalyst layer on the cathode side and the anode side is formed, and the electrode catalyst layer is placed so that the electrode catalyst layer is on the inside. After the molecular electrolyte membrane is sandwiched between the electrode catalyst layers and bonded by hot pressing or the like, the transfer mount is peeled off to obtain a membrane / electrode assembly.

  In the catalyst slurry of the present invention, the electrode catalyst may be used in any amount as long as it can sufficiently exhibit the desired action, that is, the action of catalyzing the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). , May be used. The electrode catalyst is preferably present in the catalyst slurry in an amount of 0.5 to 3% by mass, more preferably 1 to 2% by mass.

  The catalyst slurry of the present invention may contain a water-repellent polymer such as polytetrafluoroethylene, polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer in addition to the electrode catalyst, the electrolyte, and the solvent. . Thereby, the water repellency of the obtained electrode catalyst layer can be increased, and water generated at the time of power generation can be quickly discharged. The amount of the water-repellent polymer added when the water-repellent polymer is used is not particularly limited as long as it is an amount that does not interfere with the effects of the present invention.

  Instead of the water-repellent polymer or in addition to the water-repellent polymer, the catalyst slurry of the present invention may contain a thickener. The use of a thickener is effective when the catalyst slurry or the like cannot be successfully applied onto the transfer mount. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. Examples thereof include glycerin, (EG (ethylene glycol), PVA (polyvinyl alcohol)), and the like. The amount of the thickener added when the thickener is used is not particularly limited as long as it does not interfere with the above-described effect of the present invention.

  The catalyst slurry of the present invention is not particularly limited in its preparation method as long as an electrode catalyst, an electrolyte and a solvent, and if necessary, a water-repellent polymer and / or a thickener are appropriately mixed. The solvent constituting the catalyst slurry used in the present invention is not particularly limited, and ordinary solvents used for forming the catalyst layer can be used in the same manner. Specifically, water, lower alcohols such as cyclohexanol, ethanol and 2-propanol can be used.

  The amount of the solvent used in the present invention is not particularly limited as long as it can dissolve the electrolyte completely.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell has been described as an example, but in addition to this, a representative example is an alkaline fuel cell and a phosphoric acid fuel cell. Examples thereof include an acid electrolyte fuel cell, a direct methanol fuel cell, and a micro fuel cell. Among them, a solid polymer electrolyte fuel cell is preferable because it is small in size and can achieve high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. However, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be particularly preferably used.

  The polymer electrolyte fuel cell is useful not only as a stationary power source but also as a power source for a moving body such as an automobile having a limited mounting space. In particular, moving bodies such as automobiles that are susceptible to corrosion of the carbon support due to the high output voltage required after a relatively long shutdown, and deterioration of the polymer electrolyte due to the high output voltage being taken out during operation. It is particularly preferred to be used as a power source.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be appropriately used. Generally, the fuel cell has a structure in which a membrane electrode assembly is sandwiched between separators.

  The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Further, in order to prevent the gas supplied to each catalyst layer from leaking to the outside, a gas seal portion may be further provided at a portion where the catalyst layer is not formed on the gasket layer. Examples of the material constituting the gas seal portion include rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoro. Fluorine polymer materials such as propylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. The thickness of the gas seal portion may be 2 mm to 50 μm, preferably about 1 mm to 100 μm.

  Furthermore, a stack in which a plurality of membrane electrode assemblies are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  The method of applying the catalyst slurry containing the catalyst component, the conductive material, and the polymer electrolyte on the transfer sheet is not limited to the application method such as the screen printing method, the spray method, and the doctor blade method.

  Hereinafter, the present invention will be specifically described based on examples. The following example shows only one preferred embodiment of the present invention, and it goes without saying that the present invention is not limited thereto.

Example 1
Polymer electrolyte membrane (1)
Vertical x horizontal 70mm x 70mm, thickness 30μm, material is etched with a stainless steel metal thin film, and hexagonal shape (circumscribed radius 300μm), leaving the remaining width (rib width 30μm) through hole, porosity An 80% metal substrate was used.

  Next, a silica coating was applied to the thin film surface and the through-hole cross section. In this case, the coating method was performed using an ion plating method. A sulfonated polyarylethersulfone (IEC 1.9 meq / g) as a high IEC polymer electrolyte was injected as a 20% MNP solution into such a through-hole to produce a reinforced electrolyte membrane. Here, this solution was cast on a base metal. Thereafter, the temperature was raised from room temperature to 120 ° C. at a rate of 0.5 ° C./min in a nitrogen atmosphere, and maintained at 120 ° C. for 6 hours to remove NMP to obtain a reinforced electrolyte membrane.

  A thin 20% NMP solution of IEC polyelectrolyte sulfonated polyarylether sulfone (IEC is 1.1 meq / g) is applied thinly to the upper and lower surfaces, and from room temperature at a rate of 0.5 ° C./min in a nitrogen atmosphere. The temperature was raised to 120 ° C. and held at 120 ° C. for 6 hours to remove NMP to obtain a multilayer reinforced electrolyte membrane. Since the coating thickness of the polymer electrolyte was 10 μm, the film thickness of the multilayer reinforced electrolyte membrane was 50 μm.

The proton conductivity of the obtained multilayer reinforced electrolyte membrane was measured in the range of 30 ° C to 80 ° C. For the humidification, steam generated by a steam generator was used. Moreover, the film thickness required for calculation of ionic conductivity was measured using a micrometer in a dry state.
The proton conductivity of the multilayer reinforced electrolyte thus obtained was 2.0 × 10 ⁻³ S / cm (60 ° C.).

Electrocatalyst layer (2)
A gas diffusion layer with a catalyst layer (commercially available) manufactured by Johnson Matthey Fuel Cells was used. The multilayer reinforcing electrolyte thus obtained was sandwiched between GDLs with a catalyst layer from both sides and hot pressed at 130 ° C. and 10 Mpa for 10 minutes to obtain an MEA (active area 25 cm ² ) as shown in FIG.

The power generation performance of this MEA was evaluated in a single cell (active area 25 cm ² ) manufactured by Electrochem. The cell temperature is constant at 70 ° C., and 70 ° C. hydrogen and 70 ° C. air are supplied to the hydrogen electrode and the air electrode.

Similarly, this MEA was repeatedly subjected to a wet-dry durability test using a single cell (model number: EFC25-02SP active area 25 cm ² ) manufactured by Electrochem. The cell temperature was constant at 70 ° C. After flowing wet hydrogen (70 ° C. RH 90%) and wet air (70 ° C. RH 90%) for a fixed time (5 minutes) at normal pressure into a hydrogen electrode and an air electrode, dry hydrogen (70 ° C.) for a fixed time (5 minutes) was passed. The mode in which RH 5%) and dry air (70 ° C. RH 5%) are supplied is one cycle, and the cycle is repeated until the multilayer reinforced electrolyte membrane breaks. Breakage of the multilayer reinforced electrolyte membrane was detected by hydrogen leak current. As a result, when a predetermined number of cycles is repeated, an increase in hydrogen leakage current is observed due to an increase in hydrogen leakage in the multilayer reinforced electrolyte membrane, the multilayer reinforced electrolyte membrane breaks, and this cycle number is set to 100.

(Comparative Example 1)
As a comparison of the examples, an electrolyte membrane that does not use a reinforcing base material was converted to MEA, and power generation performance and durability performance were measured. For the electrolyte membrane, a 20% NMP solution of an IEC polyelectrolyte sulfonated polyarylethersulfone (IEC is 1.1 meq / g) is usually cast on a glass substrate at a rate of 0.5 ° C./min in a nitrogen atmosphere. NMP was removed by raising the temperature from room temperature to 120 ° C. and holding at 120 ° C. for 6 hours to obtain an electrolyte membrane. The obtained electrolyte membrane was 50 μm. Using the same method as in the example, MEA was performed, and using the same single cell as in the example, power generation performance and wet-dry durability performance were obtained under the same conditions as in the example.
The obtained power generation performance was 115 as compared with 100 of the example.
The obtained wet-dry durability was 40 compared to the case where the cycle number of the example was 100.

(Comparative Example 2)
As a comparison of the examples, an electrolyte membrane that does not use a reinforcing base material was converted to MEA, and power generation performance and durability performance were measured. As the electrolyte membrane, a 20% NMP solution of high IEC polyelectrolyte sulfonated polyarylethersulfone (IEC is 1.9 meq / g) was cast on a glass substrate, and the nitrogen membrane was at a rate of 0.5 ° C / min NMP was removed by raising the temperature from room temperature to 120 ° C. and holding at 120 ° C. for 6 hours to obtain an electrolyte membrane. The obtained electrolyte membrane was 50 μm. Using the same method as in Example 1 and Comparative Example 2, MEA was performed, and using the same single cell as in Example and Comparative Example 2, power generation performance and wet-dry durability performance were obtained under the same conditions as in Example and Comparative Example 2. did.
The power generation performance obtained was 130 compared with 100 in the example.
The resulting wet-dry durability was 15 compared to 100 in the example.

  As described above, since the swelling of the reinforced electrolyte membrane using the reinforced substrate of the present invention, particularly the multilayer reinforced electrolyte membrane, is suppressed, the wet-dry durability is greatly improved. By suppressing the extrusion of moisture due to the surface pressure while suppressing the swelling with the reinforcing base material, it was possible to suppress the performance degradation due to the suppression of the swelling.

  Moreover, even if the external environment is in a dry state due to multilayering (usually IEC electrolyte applied to the surface), the water inside the reinforced electrolyte membrane is hard to dry and the amount of swelling shrinkage is reduced, and a high IEC electrolyte is added inside. By using it, it was considered that the decrease in water retention and proton conduction resistance was suppressed, and the durability was greatly improved while minimizing the decrease in performance.

It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane composite (MEA) which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane laminated body which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane laminated body which concerns on this invention. It is explanatory drawing which showed the shape of the metal base material which concerns on this invention typically. It is explanatory drawing which showed typically the process of the single-sided thermocompression bonding which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane laminated body which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane composite which concerns on this invention. It is explanatory drawing which showed typically the process of the double-sided thermocompression bonding which concerns on this invention. It is explanatory drawing which showed typically the cross section of the reinforced electrolyte membrane laminated body which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal base material 2 Through-hole 3 Coating 4 Polymer electrolyte 5 Reinforcement electrolyte membrane 6 Catalyst layer 7 Gas diffusion layer 8 MEA (reinforcement electrolyte membrane composite)
10 High IEC polymer electrolyte 11 Normal IEC polymer electrolyte 13 MEA (Reinforced electrolyte membrane composite)
12 Reinforced electrolyte membrane laminate 14 Normal IEC reinforced electrolyte membrane 15 High IEC reinforced electrolyte membrane 16 Reinforced electrolyte membrane laminate 33 Coating 44 Polymer electrolyte 55 Hot press machine 66 Heater 77 Air vent groove 88 Reinforced electrolyte membrane 9A Polymer electrolyte solution 9B High Molecular electrolyte melt 111 Reinforced electrolyte membrane 12A Low IEC polymer electrolyte solution 12B Low IEC polymer electrolyte melt 140 Catalyst layer 150 Gas diffusion layer

Claims (21)

  A reinforced electrolyte membrane comprising a polymer electrolyte covering a surface of a metal substrate.   The reinforced electrolyte membrane according to claim 1, wherein the metal substrate is a metal thin film having a through hole.   The reinforced electrolyte membrane according to claim 2, wherein the metal substrate is laminated in a state where a plurality of through-holes of the metal thin film are in communication with each other.   The reinforced electrolyte membrane according to claim 1, wherein the metal substrate is surface-treated.   The reinforced electrolyte membrane according to claim 4, wherein the surface treatment is performed by coating a surface of a metal substrate with a metal oxide.   The reinforced electrolyte membrane according to claim 4 or 5, wherein the surface treatment is performed by coating a surface of a metal substrate with a polymer.   The reinforced electrolyte membrane according to claim 6, wherein the polymer is a hydrophobic polymer.   The reinforced electrolyte membrane according to claim 7, wherein the polymer is a polymer having the same main chain or the same side chain as that of the polymer electrolyte and having no sulfone group.   The reinforced electrolyte membrane according to any one of claims 6 to 8, wherein the surface treatment with the polymer is performed by polymerizing the polymer into a thin film on the surface of the metal substrate.   Furthermore, the reinforced electrolyte membrane of any one of Claims 1-9 which apply | coats a polymer electrolyte in the shape of a thin film to at least one surface of the said reinforced electrolyte membrane.   A reinforced electrolyte membrane comprising at least two or more reinforced electrolyte membranes according to any one of claims 1 to 10, and an electrolyte applied to a joint surface between the reinforced electrolyte membrane and another layer. Laminated body.   The reinforced electrolyte membrane according to any one of claims 3 to 11, wherein the plurality of reinforced electrolyte membranes are covered with different polymer electrolytes.   The reinforced electrolyte membrane composite according to any one of claims 1 to 12, wherein a polymer electrolyte membrane is sandwiched between the pair of reinforced electrolyte membranes. Thermocompression bonding the polymer electrolyte membrane (a) from one side of a metal substrate having a through-hole,
The manufacturing method of the reinforced electrolyte membrane which has this. Thermocompression bonding a metal substrate having a through hole from both sides of the polymer electrolyte membrane (a),
The manufacturing method of the reinforced electrolyte membrane which has this.   The method for producing a reinforced electrolyte membrane according to claim 15 or 16, further comprising a step of applying a solution or melt of the polymer electrolyte (b) to at least a part of the surface portion of the reinforced polymer electrolyte membrane.   The method for producing a reinforced electrolyte membrane according to any one of claims 15 to 17, wherein the thermocompression bonding is performed under vacuum or under reduced pressure.   The method for producing a reinforced electrolyte membrane according to claims 15 to 18, wherein the polymer electrolyte membrane (a) has a higher ion exchange capacity than the polymer electrolyte (b).   The reinforced electrolyte membrane manufactured by the method of any one of Claims 14-18.   The membrane electrode assembly using the reinforced electrolyte membrane of any one of Claims 1-14, or the reinforced electrolyte membrane manufactured by the method of any one of Claims 14-18.   21. A fuel cell comprising the membrane electrode assembly according to claim 20.

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