JP7108476B2 - MEMBRANE ELECTRODE ASSEMBLY AND METHOD FOR MANUFACTURING FUEL CELL - Google Patents

Description

The present invention relates to a method for manufacturing a membrane electrode assembly and a fuel cell.

A polymer electrolyte fuel cell is a fuel cell that includes an ion-conducting solid polymer electrolyte membrane between two electrodes. An electrolyte membrane and two electrodes provided on both sides thereof is called a membrane electrode assembly.

In a polymer electrolyte fuel cell, hydrogen gas is supplied to one electrode as source gas, and oxygen gas is supplied to the other electrode. At the electrode supplied with hydrogen gas, a reaction occurs in which the hydrogen gas is separated into protons and electrons. Current is generated by the movement of these electrons to the other electrode via an external circuit. At the electrodes supplied with oxygen gas, protons and electrons transferred from one electrode via the electrolyte membrane react with the oxygen gas to produce water. Each electrode includes a catalyst layer in which reactions of source gases occur. The catalyst layer generally contains an ion-conducting polymer electrolyte similar to the electrolyte membrane for enhanced catalytic action.

A membrane electrode assembly is generally manufactured by a wet process. Specifically, the electrolyte membrane is prepared by mixing a raw material for the membrane such as a polymer electrolyte with a solvent such as water or alcohol to prepare an ink, coating or casting the prepared ink on a substrate, and drying the ink. formed by A catalyst layer is also formed by a similar wet process (see Patent Document 1, for example).

JP 2017-126514 A

A wet process that uses a solvent requires processes such as drying, cooling, recovery of the solvent, reuse, and treatment for detoxification at the time of disposal. Since not only the required equipment but also the labor and time required for manufacturing increase, the overall manufacturing cost tends to increase.

An object of the present invention is to reduce the manufacturing costs of membrane electrode assemblies and fuel cells.

According to one aspect of the present invention, there is provided a method for manufacturing a membrane electrode assembly (4) comprising an electrolyte membrane (1) between two electrodes (2) including a catalyst layer (21), comprising: 2) comprising steps (S2 to S4) of forming one or more of the catalyst layer (21) and the electrolyte membrane (1) by a dry process, wherein the catalyst layer (21) formed by the dry process or There is provided a method for producing a membrane electrode assembly, wherein the electrolyte membrane (1) is in the form of nanometer-sized particles and contains polymer electrolytes with different particle shapes .

According to another aspect of the present invention, there is provided a method of manufacturing a fuel cell comprising a membrane electrode assembly (4), wherein the membrane electrode assembly (4) comprises two electrodes (2 ) and an electrolyte membrane (1) provided between the two electrodes (2), wherein one or more of the catalyst layer (21) of the two electrodes (2) and the electrolyte membrane (1) is formed by a dry process (S2 to S4), and the catalyst layer (21) or the electrolyte membrane (1) formed by the dry process is in the form of nanometer-sized particles, A method of making a fuel cell is provided that includes polymer electrolytes of different shapes .

According to the present invention, manufacturing costs of membrane electrode assemblies and fuel cells can be reduced.

1 is a cross-sectional view showing the configuration of a fuel cell according to one embodiment; FIG. 1 is a front view showing an example of a manufacturing apparatus for a membrane electrode assembly; FIG. 4 is a flow chart showing an example of a procedure for manufacturing a membrane electrode assembly by a dry process; FIG. 4 is a cross-sectional view showing a catalyst layer laminated on a gas diffusion layer; 4 is a cross-sectional view showing a catalyst layer and an electrolyte membrane laminated on a gas diffusion layer; FIG. FIG. 3 is a cross-sectional view showing a catalyst layer, an electrolyte membrane, and a catalyst layer laminated on a gas diffusion layer; 1 is a cross-sectional view showing a membrane electrode assembly; FIG. 4 is a flow chart showing an example of a procedure for manufacturing a membrane electrode assembly by a wet process;

An embodiment of the method for manufacturing a membrane electrode assembly and a fuel cell according to the present invention will be described below with reference to the drawings. The configuration described below is an example (representative example) as one embodiment of the present invention, and the present invention is not limited to the configuration described below.

(Fuel cell)
The fuel cell manufactured by the manufacturing method of the present invention may be a fuel cell having a single cell structure or a fuel cell having a stack structure.
FIG. 1 shows a configuration example of a fuel cell, which is a basic unit of a fuel cell.

A fuel cell 10 shown in FIG. 1 is a solid polymer electrolyte fuel cell (PEFC: Polymer Electrolyte Fuel Cell) that generates power by receiving supply of hydrogen gas and oxygen gas. The fuel cell 10 includes two separators 3 and a membrane electrode assembly (MEA) 4 provided between the two separators 3, as shown in FIG. The separator 3 is provided with a channel through which the raw material gas supplied to the fuel cell 10 flows to the membrane electrode assembly 4 . When the fuel cells 10 have a stack structure, the separators 3 electrically connect adjacent cells.

(Membrane electrode assembly)
The membrane electrode assembly 4 includes an electrolyte membrane 1 and two electrodes 2, as shown in FIG. One or more of the electrolyte membrane 1 and the two electrodes 2 are formed by a dry process.

An electrolyte membrane 1 is provided between two electrodes 2 . The electrolyte membrane 1 is a polymer electrolyte membrane having ionic conductivity.
Polymer electrolytes that can be used for the electrolyte membrane 1 include proton-donating organic polymers, inorganic polymers, and ceramics. Among them, organic polymers are preferable from the viewpoint of improving ion conductivity. Examples of organic polymer electrolytes that can be used for the electrolyte membrane 1 include fluorine-based polymers and hydrocarbon-based polymers having acidic functional groups such as sulfonic acid groups, phosphoric acid groups, and carboxylic acid groups. Examples of fluorine-based polymers include perfluorosulfonic acid polymers. Examples of hydrocarbon-based polymers include sulfonated polyetheretherketone (SPEEK), sulfonated polyethersulfone (SPES), sulfonated polyphenylsulfone (SPPSU), sulfonated polyimide, sulfonated polyetherimide, sulfonated polysulfone, Examples include aromatic polymers such as sulfonated polystyrene, and aliphatic polymers such as polyvinylsulfonic acid and polyvinylphosphoric acid.

When the electrolyte membrane 1 is formed by a dry process, a nanometer-sized particulate polymer electrolyte is used as the polymer electrolyte for the electrolyte membrane 1 . The ionic conduction on the surface of the polymer electrolyte is faster than the ionic conduction on the bulk part, and the conduction distance is also long. That is, the larger the surface area of the polymer electrolyte, the higher the ionic conductivity. A polymer electrolyte of nanometer-sized particles has a larger surface area as a whole than a granular polymer electrolyte having a size larger than the nanometer unit, so that an electrolyte membrane 1 having excellent ion conductivity can be obtained. In addition, by forming the electrolyte membrane 1 by a dry process that does not require a drying step, it is possible to avoid a decrease in the overall surface area and a change in the shape of the particles due to fusion of the nanometer-sized particles during drying. be able to. Even after film formation, a large surface area can be maintained and high ionic conductivity can be exhibited.

The average particle size of the polymer electrolyte particles may be any nanometer size, and can be selected within the range of 1 to 999 nm, for example. From the viewpoint of improving ion conductivity, the average particle size of the polymer electrolyte is preferably 5 to 500 nm.

The average particle size of the polymer electrolyte can be obtained as the average value of the particle sizes of n particles observed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). can. When the shape of the particles is spherical, the diameter is determined as the particle size. When the shape of the particles is non-spherical such as elliptical, cylindrical, fibrous, etc., the average value of the major axis and the minor axis may be determined as the particle size. n can be 200-300, for example.

The shape of the polymer electrolyte is not particularly limited as long as the average particle size is nanometer size, and is spherical, star-shaped (spherical with protrusions on the surface), ellipsoidal, cylindrical, fibrous, needle-shaped, and plate-shaped. etc. can be used. From the viewpoint of expanding the surface area and further increasing the ion conductivity, the polymer electrolyte preferably has a shape having unevenness on the surface. From the same point of view, the polymer electrolyte having a fibrous shape preferably has a long particle size. Moreover, when the granular polymer electrolyte has a shape other than a spherical shape, the particles are preferably randomly oriented in order to suppress the anisotropy of the electrolyte membrane 1 .

A nanometer-sized granular polymer electrolyte can be obtained by a self-assembly method, a phase separation method, an electrospinning method, or the like. Also, the nanometer-sized granular polymer electrolyte can be obtained by pulverization by a miller, ultrasonic waves, or the like, pelletization by a pelletizer (manufactured by Gala Industries, for example), or the like.
Commercially available products can also be used as nanometer-sized granular polymer electrolytes. Examples of commercially available products include Trepearl (registered trademark) (manufactured by Toray Industries, Inc.).

The electrolyte membrane 1 can contain additives such as a binder and a radical quencher in the polymer electrolyte membrane, if necessary. In particular, the electrolyte membrane 1 using a nanometer-sized granular polymer electrolyte preferably further contains a binder. The binder in the electrolyte membrane 1 is interposed between the particles of the polymer electrolyte, shields the raw material gas flowing between the particles from one electrode 2 to the other electrode 2, and can reduce leakage of the raw material gas.

Binders that can be used for the electrolyte membrane 1 include, for example, polyolefins such as polypropylene and polyethylene, and general-purpose polymers such as polycarbonate and polyvinylidene fluoride. Moreover, the polymer electrolyte mentioned above can also be used as a binder. By using a polymer electrolyte having a melting point or glass transition point different from that of a nanometer-sized polymer electrolyte as a binder, only the binder can be melted as described later. The binder may or may not be nanometer-sized particulate similar to the polyelectrolyte.

The melting point or glass transition temperature of the polymer electrolyte is preferably higher than the melting point or glass transition temperature of the binder. This makes it easy to melt only the binder by pressurization or heating.

A radical quencher captures radicals to suppress deterioration of the polymer electrolyte. Radical quenchers include, for example, cesium, cerium oxides, polyphenyl sulfides, and the like.

The content of the polymer electrolyte in the electrolyte membrane 1 is preferably 90 to 100% by mass from the viewpoint of obtaining sufficient ionic conductivity.

(electrode)
Two electrodes 2 are provided on both sides of the electrolyte membrane 1 respectively. One electrode 2 is an anode and is also called a fuel electrode. The other electrode 2 is the cathode, also called air electrode. At the electrode 2 which is the anode, a reaction occurs to generate electrons (e ⁻ ) and protons (H ⁺ ) from hydrogen gas (H ₂ ) supplied through the separator 3 . The electrons move through an external circuit to electrode 2, which is the cathode. This movement of electrons generates a current in an external circuit. Protons move through the electrolyte membrane 1 to the electrode 2 which is the cathode. Oxygen gas (O ₂ ) is supplied through the separator 3 to the electrode 2 which is the cathode, and oxygen ions (O ²⁻ ) are generated by electrons transferred from the external circuit. Oxygen ions combine with protons (2H ⁺ ) transferred from the electrolyte membrane 1 to form water (H ₂ O).

The electrode 2 comprises a catalyst layer 21 and a gas diffusion layer 22, as shown in FIG.
The gas diffusion layer 22 can be provided as necessary for the purpose of uniformly diffusing the supplied raw material gas to each electrode 2 . As the gas diffusion layer 22, for example, a conductive, gas-permeable, and gas-diffusible porous fiber sheet such as carbon fiber, or a porous metal plate such as foam metal or expanded metal can be used.

As shown in FIG. 1, the fuel cell 10 can have a sealing material 5 around the electrode 2 . The sealing material 5 seals the outer periphery of the electrode 2 to reduce leakage of the raw material gas from the electrode 2 to the outside.

(catalyst layer)
Catalyst layer 21 is provided adjacent to electrolyte membrane 1 . The catalyst layer 21 contains a catalyst, a carrier, and a polymer electrolyte, and accelerates the reaction of the raw material gas with the catalyst. In the catalyst layer 21, a particulate catalyst is supported on a carrier, and the carrier and catalyst are coated with a polymer electrolyte.

(catalyst)
The catalyst is not particularly limited as long as it has a catalytic action for the reaction of hydrogen gas or oxygen gas. Osmium (Os), Tungsten (W), Lead (Pb), Iron (Fe), Chromium (Cr), Cobalt (Co), Nickel (Ni), Manganese (Mn), Vanadium (V), Molybdenum (Mo), Metals such as gallium (Ga) and aluminum (Al), mixtures and alloys of these metals, and the like. Among them, platinum and mixtures or alloys containing platinum are preferable from the viewpoint of improving catalytic activity, poisoning resistance to carbon monoxide and the like, and heat resistance. When the catalyst is made of an alloy, the composition of the alloy is, for example, 30 to 90 atomic percent of platinum and 10 to 70 atomic percent of other metals, depending on the type of metals to be alloyed. be able to.

Although the average particle size of the catalyst is not particularly limited, it is preferably 1 to 30 nm, more preferably 1 to 20 nm, from the viewpoint of improving the catalyst utilization rate and supportability on the carrier.
The average particle size of the catalyst can be determined as the crystallite size obtained from the half width of the diffraction peak of the catalyst particles in X-ray diffraction. The average particle size of the catalyst can also be determined as the average value of the particle sizes of n catalyst particles observed by TEM or SEM. n can be 200-300, for example.

(Carrier)
A conductive porous metal compound having pores can be used as the support. Examples of porous metal compounds include mesoporous carbon. Examples of mesoporous carbon include carbon black such as Ketjenblack (registered trademark), acetylene black, and Vulcan (registered trademark), and carbon having a structure in which multiple layers of graphene sheets are laminated to form a mesoporous carbon. Examples of porous metal compounds include Pt black, Pd black, fractal-precipitated Pt metal, oxides, nitrides, carbides, oxynitrides of Ti, Zr, Nb, Mo, Hf, Ta, W, etc. substances, carbonitrides, and the like. Among them, mesoporous carbon is preferable from the viewpoint of good dispersibility, large surface area, and little particle growth at high temperatures even when a large amount of catalyst is supported.

Although the average particle size of the carrier is not particularly limited, it is preferably 10 to 100 nm from the viewpoint of enhancing the supportability of the catalyst particles.
The average particle size of the carrier can be determined by TEM or SEM in the same manner as the average particle size of the catalyst.

From the viewpoint of supporting many catalyst particles, the BET specific surface area of the carrier is preferably 50 m ² /g or more, more preferably 500 m ² /g or more, and even more preferably 700 m ² /g or more. On the other hand, the BET specific surface area of the carrier is preferably 1500 m ² /g or less, more preferably 1300 m ² /g or less, and even more preferably 1000 m ² /g or less, from the viewpoint of uniformly supporting the catalyst particles. Therefore, the BET specific surface area of the carrier is preferably 50 to 1500 m ² /g, more preferably 500 to 1300 m ² /g, even more preferably 700 to 1000 m ² /g.
The BET specific surface area of the carrier is measured by a nitrogen adsorption method.

The mass of the catalyst supported on the carrier can be usually 1 to 99% by mass with respect to the combined mass of the catalyst and the carrier (100% by mass). 10 to 90% by mass is preferred, and 20 to 80% by mass is more preferred.

(polymer electrolyte)
Polymer electrolytes that can be used for the catalyst layer 21 include the same polymer electrolytes as those used for the electrolyte membrane 1 described above.
When the catalyst layer 21 is formed by a dry process, a nanometer-sized particle-like polymer electrolyte is used as the polymer electrolyte for the catalyst layer 21 , as in the electrolyte membrane 1 .

As with the electrolyte membrane 1, the catalyst layer 21 containing nanometer-sized particulate polymer electrolyte preferably further contains a binder. The binder in the catalyst layer 21 binds the particles of the polymer electrolyte together and enhances the ionic conductivity between the particles. As with the electrolyte membrane 1, the melting point or glass transition temperature of the polymer electrolyte is preferably higher than the melting point or glass transition temperature of the binder.

(Manufacturing method of membrane electrode assembly)
The membrane electrode assembly 4 described above is manufactured by forming one or more of the electrolyte membrane 1 and the two electrodes 2 by a dry process. Manufacturing by a dry process can reduce steps such as a drying step for removing the solvent from the membrane, recovery of the removed solvent, reuse, and disposal. The overall manufacturing cost can be reduced because the manufacturing facility can be reduced and the labor and time required for manufacturing can be reduced. From the viewpoint of further reducing manufacturing costs, it is preferable that the electrolyte membrane 1 and the two electrodes 2 are all formed by a dry process.

The electrolyte membrane 1 or electrode 2 formed by the dry process contains nanometer-sized particulate polymer electrolyte. By forming the particulate polymer electrolyte membrane by a dry process, the size and shape of the particles can be maintained even after membrane formation, and high ionic conductivity can be exhibited due to the large surface area.

FIG. 2 shows an example of a manufacturing apparatus for forming all the films of the membrane electrode assembly 4 by a dry process.
As shown in FIG. 2, the manufacturing apparatus 100 includes a transport mechanism 50, sealing units 61 and 65, stacking units 62 to 64, and a stabilization processing unit 66. As shown in FIG. The manufacturing apparatus 100 manufactures the membrane electrode assembly 4 by roll-to-roll.

The conveying mechanism 50 includes an unwinding roller 51 , a winding roller 52 and a plurality of conveying rollers 53 . The conveying mechanism 50 unwinds the roll-shaped base material W by the unwinding roller 51 and conveys the unwound sheet of the base material W by each of the conveying rollers 53 . The conveying mechanism 50 also winds up the sheet of the membrane electrode assembly 4 obtained by laminating the electrolyte membrane 1 and the electrodes 2 on the base material W with the winding roller 52 .

As the base material W, a carbon fiber sheet or the like used as the gas diffusion layer 22 of the electrode 2 can be used. When forming the electrode 2 with only the catalyst layer 21, a protective film or the like may be used as the base material W, and the gas diffusion layer 22 may be provided by peeling off the protective film and laminating a carbon fiber sheet later. A case where the gas diffusion layer 22 is used as the base material W will be described below.

In the sealing portion 61, the sealing material 5 is adhered onto the gas diffusion layer 22 which is the base material W. As shown in FIG.

In the laminated parts 62 and 64, the catalyst layer 21 is formed by depositing each particle of the catalyst, the carrier, and the polymer electrolyte, which are the materials of the catalyst layer 21, by a dry process. Dry processes that can be used to form the catalyst layer 21 include, for example, a powder jet deposition method, an electrospinning method, an electrostatic spray method, and the like. In addition, in the laminated portions 62 and 64, the catalyst layer 21 is formed inside the sealing material 5 by using a mask or the like. Here, an example of manufacturing the membrane electrode assembly 4 including the sealing material 5 is described, but when manufacturing the membrane electrode assembly 4 without the sealing material 5, such pattern formation is unnecessary. be.

In the case of the powder jet deposition method, the material of the catalyst layer 21, for example, a platinum-supported carbon carrier and nanometer-sized particulate polymer electrolyte are mixed using a Henschel mixer or the like, and the resulting powder mixture is jetted. A film is formed by depositing the If the catalyst layer 21 contains a binder and the binder has a high viscosity and is difficult to mix uniformly with other materials, the binder may be dried by freeze-drying or the like to be powdered, and then mixed.

In the case of the electrospinning method, a mixture of the material of the catalyst layer 21 and the solvent is put into a syringe, and the mixture is injected while applying a high voltage between the needle of the syringe and the gas diffusion layer 22 . When the voltage exceeds a threshold, the repulsive force of the charge overcomes the surface tension of the droplet, creating a charged jet. The jet is elongated in the electric field to form very fine nanometer-sized fibrous particles, which deposit on the gas diffusion layer 22 to form a film. The film formed is dry because the solvent evaporates from the droplets during jetting. Electrospinning allows the formation of nanometer-sized polyelectrolytes in parallel with the formation of membranes.

In the electrostatic spray method, a mixed liquid of the material of the catalyst layer 21 and a solvent is contained in a capillary to which a voltage is applied, and the charged mixed liquid is jetted (sprayed) from the tip of the capillary. When the solvent evaporates from the ejected droplet and the repulsive forces of the charges within the droplet exceed the surface tension of the droplet, the droplet breaks up. Evaporation and splitting of the solvent are repeated, and the droplets turn into fine nanometer-sized particles, which are attracted to the gas diffusion layer 22 side by electrostatic force and deposited to form a film.

According to the powder jet deposition method, since no solvent is used, processes such as drying, solvent recovery, recycling, and disposal are not required, and the production cost can be reduced. According to the electrospinning method and the electrostatic spraying method, a solvent is used, but since it evaporates, a drying process is unnecessary, and the manufacturing cost can be reduced. Solvents that can be used include, for example, polar solvents with low boiling points such as water and alcohols.

When the catalyst layer 21 is formed by a wet process, the wet process that can be used is not particularly limited. A casting method, roll coating method, flow coating method, ink jet method, spray coating method, dip coating method, bar coating method, gravure printing method, etc. using an ink obtained by mixing the material of No. 21 with a solvent can be used. Protic polar solvents such as water and alcohol are usually used as the solvent for the ink. It is preferable to select a solvent that does not swell or dissolve the polymer electrolyte in order to avoid deformation of the particle size and shape due to swelling or dissolution of the polymer electrolyte by the solvent.

When a binder is used in a wet process, the lowest temperature T1 among the melting point Tm, glass transition point Tg and decomposition temperature Td of the polymer electrolyte is higher than the plasticizing temperature T2 of the composite resin combining the polymer electrolyte and the binder. is preferred. The plasticizing temperature T2 is the temperature at which the composite resin starts to flow. In the wet process, the temperature T1 of the polymer electrolyte is higher than the temperature T2. easier to suppress. Depending on the type of polymer electrolyte, any one of the melting point Tm, glass transition point Tg, and decomposition temperature Td may not exist. In this case, the temperature may be determined from existing temperatures. For example, in the case of a polymer electrolyte having a glass transition temperature of 300°C, a decomposition temperature of 450°C, and no melting point, the temperature T1 is 300°C.

When the composite resin is amorphous, it generally starts to flow when the glass transition point Tg is exceeded, so the plasticizing temperature T2 satisfies the relationship of T2>Tg. When the composite resin is crystalline, it starts to flow when the melting point Tm is exceeded, so the plasticizing temperature T2 satisfies the relationship of T2>Tm. From the viewpoint of further suppressing changes in the size and shape of the polymer electrolyte particles, the plasticizing temperature T2 of the amorphous composite resin is preferably Tg+5° C. or higher. Moreover, the plasticizing temperature T2 of the crystalline composite resin is preferably Tm+5°C.

When the composite resin satisfying the above temperature conditions is melt-kneaded, the binder is fluidized by the melt-kneading, but the polymer electrolyte is not fluidized. In order that the temperature t of the composite resin during melt kneading satisfies the relationship of T2≦t<T1, the temperature of the cylinder of the extruder is set to T2 or higher, or the temperature of the heat generated by shearing during kneading is added. The temperature of the cylinder may be set so that the temperature of the cylinder is equal to or higher than T2. Moreover, since the temperature of the melt changes depending on the residence time, the residence time in the cylinder should be adjusted so that the temperature t does not exceed the temperature T1. The temperature t can be obtained by measuring the temperature of the melt immediately after being extruded from the die with a radiation thermometer or the like.

In the laminated portion 63, the electrolyte membrane 1 is formed by depositing particles of polymer electrolyte, which is the material of the electrolyte membrane 1, by a dry process. As a method for forming the electrolyte membrane 1 by a dry process, the same method as for the catalyst layer 21 described above can be used. Also, when the electrolyte membrane 1 is formed by a wet process, the same wet process method as that for the catalyst layer 21 described above can be used.

In the sealing portion 65 , the gas diffusion layer 22 is adhered onto the sealing material 5 and the catalyst layer 21 after the sealing material 5 is arranged on the outer periphery of the catalyst layer 21 . Thus, a laminate of the gas diffusion layer 22, the catalyst layer 21, the electrolyte membrane 1, the catalyst layer 21 and the gas diffusion layer 22, that is, the membrane electrode assembly 4 is obtained.

In the stabilization processing section 66 , at least one of pressure processing and heat processing is performed on the membrane electrode assembly 4 . By pressurizing or heating, the strength of each layer of the membrane electrode assembly 4 can be increased and stabilized.

FIG. 3 shows the manufacturing procedure of the membrane electrode assembly 4 in the manufacturing apparatus 100. As shown in FIG. The manufacturing procedure shown in FIG. 3 is an example in which all of the catalyst layer 21 and the electrolyte membrane 1 formed by the lamination parts 62 to 64 are formed by a dry process.
4A to 4D are cross-sectional views schematically showing each film of the membrane electrode assembly 4 formed by the dry process.

As shown in FIG. 3 , in the manufacturing apparatus 100 , the sheet of the roll-shaped gas diffusion layer 22 is sequentially unwound and transported by the transport mechanism 50 . The sealing material 5 is adhered to one surface of the transported gas diffusion layer 22 at the sealing portion 61 (step S1).

In the laminated portion 62, as shown in FIG. 4A, the catalyst layer 21 of one electrode 2 is formed inside the sealing material 5 on one surface of the gas diffusion layer 22 (step S2). Next, in the laminated portion 63, as shown in FIG. 4B, the electrolyte membrane 1 is formed on the catalyst layer 21 (step S3).

Further, in the laminated portion 64, as shown in FIG. 4C, the catalyst layer 21 of the other electrode 2 is formed on the electrolyte membrane 1 (step S4). The catalyst layer 21 is formed so as to be positioned inside the sealing material 5 provided in a later step. After the formation of the catalyst layer 21, the sealing material 5 is adhered at the sealing portion 65, and the sheet of the gas diffusion layer 22 is further laminated (step S5), whereby the membrane electrode assembly 4 is obtained. FIG. 4D shows a membrane electrode assembly 4 obtained by stacking gas diffusion layers 22 .

The catalyst layer 21 or the electrolyte membrane 1 formed by the dry process contains nanometer-sized particulate polymer electrolyte. The catalyst layer 21 or the electrolyte membrane 1 containing nanometer-sized particulate polymer electrolyte preferably further contains a binder. When the catalyst layer 21 contains a binder, it is possible to bind particles of the polymer electrolyte and suppress collapse of the particle structure due to wind pressure during supply of the raw material gas. In addition, since the electrolyte membrane 1 contains a binder, the raw material gas flowing between the particles of the polymer electrolyte in the electrolyte membrane 1 from each electrode 2 can be shielded, and gas leakage between the electrodes 2 can be reduced.

The size of the polymer electrolyte particles is preferably selected depending on whether the membrane in which the polymer electrolyte is used is the catalyst layer 21 or the electrolyte membrane 1 . For example, since the electrolyte membrane 1 contains a large amount of polymer electrolyte, the ionic conductivity of the electrolyte membrane 1 can be increased by selecting a polymer electrolyte having a small size among the nanometer sizes. On the other hand, since the catalyst layer 21 also contains a catalyst and a support, a high particle size of approximately the same size is selected according to the particle size of the catalyst (eg, 1 to 30 nm) or the particle size of the support (eg, 10 to 100 nm). A molecular electrolyte may be selected. As a result, gaps are formed between the particles of the catalyst or carrier and the particles of the polymer electrolyte, making it easier to diffuse the raw material gas over the entire catalyst layer 21 .

The shape of the polymer electrolyte particles is preferably selected depending on whether the membrane in which the polymer electrolyte is used is the catalyst layer 21 or the electrolyte membrane 1 . For example, when the membrane using a polymer electrolyte is the electrolyte membrane 1, from the viewpoint of obtaining a high-density membrane, it is possible to select a shape such as a fibrous shape, a plate-like shape, or the like, in which particles overlap frequently. In addition, when the catalyst layer 21 is a membrane using a polymer electrolyte, a shape such as a spherical shape, a star shape, or the like that facilitates the formation of gaps between particles can be selected from the viewpoint of improving the permeability of the supplied raw material gas.

The catalyst layer 21 and the electrolyte membrane 1 can also contain polymer electrolytes with different particle shapes. For example, by combining fibrous particles with spherical particles, the gaps between the fibrous particles can be filled with the spherical particles to obtain a membrane with high density and high ion conductivity. In particular, the catalyst layer 21 to which the raw material gas is supplied preferably contains polymer electrolytes with different particle shapes. For example, by combining spherical particles with star-shaped particles, gaps can be provided between the particles even if the particles are adjacent to each other, and both ion conductivity and raw material gas permeability can be achieved.

The catalyst layer 21 and the electrolyte membrane 1 can also contain polymer electrolytes with different particle sizes. For example, by combining a polymer electrolyte with a size of 1-30 nm and a polymer electrolyte with a larger size of 100-200 nm, the spaces between the larger particles are filled with the smaller particles to form a high-density membrane with high ion conductivity. Obtainable.

When the membrane electrode assembly 4 is obtained, at least one of pressure treatment and heat treatment is performed in the stabilization treatment section 66 (step S6). The particles of the polymer electrolyte are densified by pressurization and partially fused by heating, thereby improving the durability against the wind pressure of the source gas and the strength of the membrane. Therefore, a stable electrolyte membrane 1 and catalyst layer 21 are obtained. When the film contains a binder, it can be heated at a temperature higher than the melting point or glass transition point of the binder and lower than the melting point or glass transition point of the polymer electrolyte, from the viewpoint of avoiding changes in shape and size due to melting of the polymer electrolyte. preferable.

FIG. 5 shows a manufacturing procedure when both the catalyst layer 21 and the electrolyte membrane 1 are formed by a wet process.
In the case of the wet process, as shown in FIG. 5, pellet-shaped polymer electrolyte is melted and kneaded to be plasticized, and then extruded onto a substrate by a die to form an electrolyte membrane 1 (step S11). After the obtained electrolyte membrane 1 is cooled, it is stretched (step S12). The stretched long sheet of the electrolyte membrane 1 is wound into a roll (step S13).

Next, the catalyst, carrier and polymer electrolyte are mixed with a solvent to prepare a catalyst ink (step S14). The roll-shaped electrolyte membrane 1 is unwound and conveyed, and the prepared catalyst ink is applied onto one surface of the conveyed electrolyte membrane 1 to form a membrane (step S15). By drying the formed film, the catalyst layer 21 is obtained (step S16).

Next, the sheet surface of the electrolyte membrane 1 is reversed (step S17), and catalyst ink is applied to the other surface opposite to the one surface on which the catalyst layer 21 is formed to form a membrane (step S18). . By drying the formed membrane, an electrolyte membrane 1 (CCM: Catalyst Coated Membrane) having catalyst layers 21 on both sides is obtained (step S19). The obtained CCM is wound into a roll by a winding roller (step S20).

A roll-shaped CCM is set on another line, unwound by an unwinding roller, and conveyed. A carbon fiber sheet or the like is adhered to one surface of the conveyed CCM to form the gas diffusion layer 22 of one electrode 2 (step S21). Then, the CCM with the gas diffusion layer 22 formed thereon is subjected to pressure treatment or heat treatment (step S22). The sheet surface of the CCM is reversed (step S23), and a carbon fiber sheet or the like is adhered to the other surface opposite to the one surface on which the gas diffusion layer 22 is formed to form the gas diffusion layer of the other electrode 2. 22 is formed (step S24). Next, pressure treatment or heat treatment is performed (step S25) to obtain the membrane electrode assembly 4 having the electrodes 2 on both surfaces of the electrolyte membrane 1 . Finally, the obtained sheet of the membrane electrode assembly 4 is rolled up (step S26).

Thus, when manufacturing the membrane electrode assembly 4 by the wet process, the number of steps such as drying and cooling is increased compared to the case of the dry process. Further, in the wet process, in order to form the electrodes 2 on both surfaces of the electrolyte membrane 1, it is necessary to reverse the sheet surface of the electrolyte membrane 1. FIG. Therefore, the sheet is wound once at the stage of forming the electrolyte membrane 1 and at the stage of forming the catalyst layer 21 . Since each production line is required, the production equipment becomes large. On the other hand, in the dry process, the electrode 2, the electrolyte membrane 1, and the electrode 2 may be laminated in this order, and as illustrated in FIG. 2, continuous production is possible on one production line. It is possible to reduce the size of facilities and shorten the time required for manufacturing, thereby reducing manufacturing costs.

Also, if a nanometer-sized granular polymer electrolyte is used for the catalyst layer 21 and the electrolyte membrane 1, excellent ion conductivity can be obtained. and may change shape. However, according to the dry process, since there is no drying step, the size and shape of the particles can be maintained, and excellent ionic conductivity can be exhibited by the nanometer-sized granular polymer electrolyte.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.
For example, the present invention can be applied to manufacture of electrodes for storage batteries such as lithium batteries, in which positive electrodes and negative electrodes are alternately laminated with separators interposed therebetween.

DESCRIPTION OF SYMBOLS 10... Fuel cell, 3... Separator, 4... Membrane electrode assembly, 1... Electrolyte membrane, 2... Electrode, 21... Catalyst layer, 22... Gas diffusion layer , 100... manufacturing apparatus, 50... conveying mechanism, 61, 65... sealing section, 62 to 64... stacking section

Claims (5)

A method for manufacturing a membrane electrode assembly (4) comprising an electrolyte membrane (1) between two electrodes (2) including a catalyst layer (21),
Forming one or more of the catalyst layer (21) and the electrolyte membrane (1) of the two electrodes (2) by a dry process (S2 to S4),
The catalyst layer (21) or the electrolyte membrane (1) formed by the dry process contains polymer electrolytes in the form of nanometer-sized particles having different particle shapes ,
A method for manufacturing a membrane electrode assembly. The catalyst layer (21) or the electrolyte membrane (1) containing the nanometer-sized particulate polymer electrolyte further contains a binder,
The manufacturing method of the membrane electrode assembly according to claim 1. The size of the particles of the polymer electrolyte is selected depending on whether the membrane in which the polymer electrolyte is used is the catalyst layer (21) or the electrolyte membrane (1).
The method for manufacturing the membrane electrode assembly according to claim 1 or 2. The shape of the particles of the polymer electrolyte is selected depending on whether the membrane in which the polymer electrolyte is used is the catalyst layer or the electrolyte membrane.
A method for manufacturing a membrane electrode assembly according to any one of claims 1 to 3. A method for manufacturing a fuel cell comprising a membrane electrode assembly (4),
The membrane electrode assembly (4) comprises two electrodes (2) including a catalyst layer (21) and an electrolyte membrane (1) provided between the two electrodes (2),
Forming one or more of the catalyst layer (21) and the electrolyte membrane (1) of the two electrodes (2) by a dry process (S2 to S4),
The catalyst layer (21) or the electrolyte membrane (1) formed by the dry process is
Containing polymer electrolytes in the form of nanometer-sized particles with different particle shapes ,
A method for manufacturing a fuel cell.

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