JP7291838B1 - Electrolyte membrane for electrochemical cell and electrochemical cell - Google Patents

Abstract

An electrolyte membrane for an electrochemical cell capable of suppressing damage, and an electrochemical cell capable of suppressing damage to the electrolyte membrane are provided. An electrolyte membrane (10) for an electrochemical cell includes an electrolyte body (11) and a plurality of coarse pores (12). The electrolyte main body 11 has a first main surface A and a second main surface B. As shown in FIG. The second major surface B is arranged on the opposite side of the first major surface A. As shown in FIG. A plurality of coarse pores 12 are arranged in the electrolyte body 11 . The coarse pores 12 have a cross-sectional area of 1.5 μm 2 or more. More coarse pores 12 are arranged in the first main-surface-side region R1 than in the second main-surface-side region R2. [Selection drawing] Fig. 2

Description

The present invention relates to an electrolyte membrane for an electrochemical cell and an electrochemical cell.

Conventionally, in electrochemical cells such as alkaline fuel cells, alkaline secondary batteries, and electrolytic cells, ion conductors having ion conductivity are used as electrolytes (see, for example, Patent Document 1).

JP 2019-220463 A

Since an electrochemical cell uses an electrolyte in the presence of water (or water vapor), the volume of the electrolyte may change depending on the water content in the electrolyte, which may damage the inside of the electrolyte. Electrolyte membranes for electrochemical cells are required to suppress damage while maintaining strength.

An object of the present invention is to provide an electrochemical cell electrolyte membrane capable of suppressing damage, and an electrochemical cell capable of suppressing damage to the electrolyte membrane.

An electrolyte membrane for an electrochemical cell according to one aspect of the present invention includes an electrolyte body and a plurality of coarse pores. The electrolyte body has a first principal surface and a second principal surface. The second major surface is arranged opposite the first major surface. A coarse pore is disposed in the electrolyte body. More coarse pores are arranged in the first main surface side area than in the second main surface side area.

According to this configuration, more coarse pores are arranged in the first main surface side area than in the second main surface side area. Here, for example, when a large amount of water is supplied on the anode side, the volume change is likely to occur in the region of the electrolyte membrane on the anode side, that is, in the region on the first main surface side. In this case, by arranging the electrolyte membrane so that the first main surface faces the anode side, the stress can be relieved by the coarse pores in the first main surface side region where the volume change is likely to occur. Furthermore, by reducing or eliminating the number of coarse pores in the second main surface side region, which is less prone to volume change than in the first main surface side region, than the number of coarse pores in the first main surface side region, electricity The strength of the electrolyte membrane for chemical cells can be maintained. As a result, damage to the electrochemical cell electrolyte membrane can be suppressed while maintaining the strength of the electrochemical cell electrolyte membrane as a whole.

Preferably, at least one coarse pore is flattened.

Preferably, at least one coarse pore is inclined with respect to the direction of the first major surface. In this case, stress relaxation in the thickness direction can be further improved.

Preferably, an ion-conducting material is further provided, the ion-conducting material being disposed within the coarse pores.

Preferably, the ion-conducting substance is liquid.

Preferably, the ion-conducting material is phosphoric acid.

Preferably, the electrolyte body includes a substrate and ceramics. Ceramics are dispersed in the substrate.

Preferably, the substrate is resin.

Preferably, the substrate is polybenzimidazole. The ceramic is tin pyrophosphate.

An electrochemical cell of the present invention includes any of the fuel cell electrolyte membranes described above, an anode, and a cathode.

Preferably, the first main surface faces the anode side.

Preferably, the first main surface faces the cathode side.

ADVANTAGE OF THE INVENTION According to this invention, the electrolyte membrane for electrochemical cells which can suppress damage, and the electrochemical cell which can suppress damage to an electrolyte membrane can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of the configuration of a direct methanol fuel cell using an electrochemical cell electrolyte membrane according to an embodiment; 1 is an enlarged schematic cross-sectional view of an electrolyte membrane for an electrochemical cell according to an embodiment; FIG. FIG. 3 is an enlarged schematic cross-sectional view of an electrolyte membrane for an electrochemical cell according to an embodiment different from that of FIG. 2 ; BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed the electrolyte membrane for electrochemical cells which concerns on embodiment with a chemical formula.

Hereinafter, a direct methanol fuel cell (DMFC) 100, which is a type of electrochemical cell including an electrolyte membrane for an electrochemical cell (hereinafter simply referred to as an electrolyte membrane) 10 according to the present embodiment, will be described with reference to the drawings.

[DMFC100]
As shown in FIG. 1, DMFC 100 is a type of fuel cell that uses protons as carriers. DMFC 100 comprises electrolyte membrane 10 , anode 20 and cathode 30 . Electrolyte membrane 10 is positioned between anode 20 and cathode 30 . The DMFC 100 further has a fuel supply section 21 and an oxidant supply section 22 .

DMFC 100 preferably generates power at a relatively low temperature (eg, 50° C. to 250° C.) based on the following electrochemical reaction formula. Methanol is used as the fuel in the electrochemical equations below.

Anode 20: _CH3OH + _H2O → _CO2 +6H ^{++ 6e-}
Cathode 30: 6H ⁺ +3/2O ₂ +6e ⁻ →3H ₂ O
・ Overall: CH ₃ OH + 3/2O ₂ →CO ₂ + 2H ₂ O

The fuel supply unit 21 supplies fuel containing methanol (CH ₃ OH) to the anode 20 to be described later during operation of the DMFC 100 . The methanol contained in the fuel may be in a gaseous phase, a liquid phase, or a mixture of gaseous and liquid phases. The fuel supply section 21 has a supply pipe 21a, a supply space 21b and a discharge pipe 21c. Fuel introduced from the supply pipe 21a is supplied to the anode 20 in the supply space 21b. Fuel not consumed in the anode 20 and carbon dioxide (CO ₂ ) and water (H ₂ O) generated in the anode 20 are discharged to the outside through the discharge pipe 21c.

The oxidant supply unit 22 supplies an oxidant containing oxygen (O ₂ ) to the cathode 30 . Air is preferably used as the oxidizing agent, and the air is more preferably humidified. The oxidant supply section 22 has a supply pipe 22a, a supply space 22b and a discharge pipe 22c. The oxidant introduced from the supply pipe 22a is supplied to the cathode 30 in the supply space 22b. The oxidant not consumed at the cathode 30 is discharged to the outside through the discharge pipe 22c.

[Anode 20]
Anode 20 is a cathode commonly referred to as an anode. During the power generation of the DMFC 100 , fuel containing methanol is supplied from the fuel supply section 21 to the anode 20 . The anode 20 is a porous body in which methanol can diffuse. The porosity of anode 20 is not particularly limited. Although the thickness of the anode 20 is not particularly limited, it can be, for example, 10 to 500 μm.

The anode 20 is not particularly limited as long as it contains a known anode catalyst. Examples of anode catalysts include metal catalysts such as Pt, Ni, Co, Fe, Ru, Sn, and Pd. The metal catalyst is preferably supported on a carrier such as carbon, but may be in the form of an organometallic complex having the metal atom of the metal catalyst as the central metal, and may be supported using this organometallic complex as a carrier. Also, a diffusion layer made of a porous material or the like may be arranged on the surface of the anode catalyst. Preferred examples of the anode 20 include nickel, cobalt, silver, platinum on carbon (Pt/C), platinum on ruthenium on carbon (PtRu/C), palladium on carbon (Pd/C), and rhodium on carbon (Rh/C). , nickel on carbon (Ni/C), copper on carbon (Cu/C), and silver on carbon (Ag/C).

The method for producing the anode 20 is not particularly limited, but for example, the anode catalyst and, if desired, a carrier are mixed with a binder to prepare a paste mixture, and the paste mixture is applied to the anode-side surface of the electrolyte membrane 10. can do.

[Cathode 30]
Cathode 30 is an anode commonly referred to as a cathode. During power generation of the DMFC 100 , an oxidant containing oxygen (O ₂ ) is supplied from the oxidant supply section 22 to the cathode 30 . The cathode 30 is a porous body in which an oxidant can be diffused. The porosity of cathode 30 is not particularly limited. Although the thickness of the cathode 30 is not particularly limited, it can be, for example, 10 to 200 μm.

The cathode 30 is not particularly limited as long as it contains a known air electrode catalyst. Examples of cathode catalysts include platinum group elements (Ru, Rh, Pd, Ir, Pt), iron group elements (Fe, Co, Ni) and other Group 8 to 10 elements (8th in the IUPAC periodic table). Group 11 elements such as Cu, Ag, and Au (elements belonging to Group 11 in the IUPAC periodic table), rhodium phthalocyanine, tetraphenylporphyrin, Co salen, Ni salen (salen = N,N'-bis(salicylidene)ethylenediamine), silver nitrate, and any combination thereof. The amount of catalyst supported on the cathode 30 is not particularly limited, but is preferably 0.05 to 10 mg/cm ² , more preferably 0.05 to 5 mg/cm ² . The cathode catalyst is preferably supported on carbon. Preferred examples of the cathode 30 include platinum-on-carbon (Pt/C), platinum-cobalt-on-carbon (PtCo/C), palladium-on-carbon (Pd/C), rhodium-on-carbon (Rh/C), nickel-on-carbon (Ni /C), copper on carbon (Cu/C), and silver on carbon (Ag/C).

The method for producing the cathode 30 is not particularly limited. can be formed.

[Electrolyte membrane 10]
The electrolyte membrane 10 is formed in the shape of a film, a layer, or a sheet. Electrolyte membrane 10 is positioned between anode 20 and cathode 30 . Electrolyte membrane 10 is connected to each of anode 20 and cathode 30 . Although the thickness of the electrolyte membrane 10 is not particularly limited, it is, for example, 5 to 100 μm. Preferably, the thickness of electrolyte membrane 10 is 20 μm or more.

As shown in FIG. 2 , the electrolyte membrane 10 includes an electrolyte body 11 and a plurality of coarse pores 12 .

[Electrolyte body 11]
The electrolyte main body 11 has a first main surface A and a second main surface B. As shown in FIG. The first main surface A faces the anode 20 side. The second major surface B is arranged on the opposite side of the first major surface A. As shown in FIG. The second main surface B faces the cathode 30 side.

The electrolyte body portion 11 further has a first main surface side region R1 and a second main surface side region R2. The first main-surface-side region R1 is a region arranged on the first main surface A side when the electrolyte main body 11 is divided into two regions by bisected by a virtual plane parallel to the first main surface A. is. The second main surface side region R2 is a region arranged on the second main surface B side when the electrolyte main body portion 11 is divided into two regions by a virtual plane parallel to the first main surface A. As shown in FIG.

The electrolyte main body 11 includes a base material 13 and ceramics 14 .

[Base material 13]
The base material 13 maintains the shape of the electrolyte membrane 10 .

The base material 13 is resin. Specifically, it is made of a resin having a glass transition temperature (Tg) of 200° C. or higher.

Preferably, substrate 13 is a basic polymer. A basic polymer is a polymer having proton-accepting groups. When the base material 13 is composed of a basic polymer, it can hold the ion-conductive substance 15 (phosphoric acid), which will be described later, by an acid-base reaction. More preferably, the basic polymer has amino groups.

The material forming the base material 13 is, for example, at least one or more selected from polybenzimidazole (PBI), polyaramid, polyimide, polyamideimide, polyvinylidene fluoride, and polyvinylidene fluoride. Preferably, substrate 13 is polybenzimidazole (PBI).

[Ceramics 14]
Ceramics 14 are dispersed in base material 13 . The ceramics 14 suppresses so-called crossover in which methanol supplied to the anode 20 side permeates the electrolyte membrane 10 and reaches the cathode 30 side to directly react with oxygen.

The ceramics 14 are ionically conductive. Specifically, the ceramics 14 are proton-conducting. During power generation of the DMFC 100 , the electrolyte membrane 10 conducts protons (H ⁺ ) from the anode 20 to the cathode 30 side through the ceramics 14 .

When the ceramics 14 conducts protons, the proton conductivity of the ceramics 14 is not particularly limited, but is preferably 0.1 mS/cm or more, more preferably 0.5 mS/cm or more, and still more preferably 1.0 mS/cm or more. be. The proton conductivity of the ceramics 14 is preferably as high as possible, and its upper limit is not particularly limited, but is, for example, 10 mS/cm.

The ceramics 14 are ceramic particles. A well-known ceramic material having proton conductivity can be used as the ceramics 14 . For example, a metal oxide having proton conductivity can be used as such a ceramic material. Examples of such metal oxides include phosphoric acid compounds. The phosphoric acid compound is preferably at least one or more selected from the group consisting of tin pyrophosphate, lanthanum pyrophosphate zirconium phosphate, tin phosphate, and zirconium phosphate.

The content of the ceramics 14 in the electrolyte membrane 10 can be 35 to 65% by volume. The electrolyte membrane 10 is substantially composed only of the base material 13 and the ceramics 14, and other substances are negligible. The content of the ceramics 14 in the electrolyte membrane 10 is preferably 40% by volume or more, more preferably 50% by volume or more.

The content of the ceramics 14 can be obtained by observing the cross section of the electrolyte membrane 10 with a SEM (scanning electron microscope) and calculating the cross-sectional area ratio of the ceramics 14, which appears brighter than the resin on the SEM image, by image analysis. obtained by More specifically, the cross-sectional area ratio of the ceramics 14 is calculated by specifying the ceramics 14 on the SEM image and dividing the cross-sectional area of the ceramics 14 in the field of view by the cross-sectional area of the entire electrolyte membrane 10 within the field of view. . In this specification, the cross-sectional area ratio of the ceramics 14 calculated by image analysis is considered as the volume ratio of the ceramics 14 .

The average particle diameter of the ceramic particles constituting the ceramics 14 can be 0.5 to 5.0 μm in circle equivalent diameter. The specific surface cross-sectional area of the ceramic particles forming the ceramics 14 can be 1 to 200 m ² /cm ³ .

The average particle diameter of the ceramics 14 is obtained by observing the cross section of the electrolyte membrane 10 with a SEM or TEM (transmission electron microscope) and arithmetically averaging the circle equivalent diameters of 20 randomly selected ceramics 14 on the observed image. obtained by The equivalent circle diameter is calculated from the cross-sectional area obtained by obtaining the cross-sectional area of each particle of the ceramics 14 .

The specific surface area of the ceramics 14 is calculated by calculating the average surface area and the average volume from the average particle size of the ceramics 14 and dividing the average surface area by the average volume.

[Coarse pores 12]
A plurality of coarse pores 12 are arranged in the electrolyte body 11 . Specifically, the coarse pores 12 are located within the substrate 13 and between the substrate 13 and the ceramics 14 .

The coarse pores 12 mean pores having a cross-sectional area of 1.5 μm ² or more. The cross-sectional area of the coarse pores 12 is preferably 3.0 μm ² or more, more preferably 5.0 μm ² or more.

The cross-sectional area of the coarse pores 12 is preferably 30 μm ² or less, more preferably 20 μm ² or less. This can prevent the fuel supplied to the anode 20 from permeating to the cathode 30 side.

The cross-sectional area of coarse pores 12 is measured by the following method. A cross section of the electrolyte membrane 10 is observed with an SEM. The cross-sectional area of the coarse pores 12 is obtained by calculating, by image analysis, the cross-sectional area of a portion displayed with lower luminance than the ceramics 14 and the resin on the SEM image.

The coarse pores 12 relieve stress due to volumetric changes in the electrolyte membrane 10 due to changes in the water content of the electrolyte body 11 during operation of the DMFC 100 .

More coarse pores 12 are arranged in the first main-surface-side region R1 than in the second main-surface-side region R2. That is, the number of coarse pores 12 in the first main surface side region R1 is greater than the number of coarse pores 12 in the second main surface side region R2. In this embodiment, the coarse pores 12 are not formed in the second main surface region R2. Note that the coarse pores 12 may be formed in the second main surface region R2.

The number of coarse pores 12 is measured by the following method. A sample is taken from the electrolyte membrane 10 . Specifically, the electrolyte membrane 10 is cut perpendicularly to the first main surface A from the position where the electrolyte membrane 10 is equally divided in the longitudinal direction. The region from the half position in the thickness direction of the electrolyte membrane 10 to the first main surface A is defined as a first main surface side region R1, and the region from the half position in the thickness direction of the electrolyte membrane 10 to the second main surface B. is defined as a second main-surface-side region R2. A sample including the cross section of the first main surface side region R1 and a sample including the cross section of the second main surface side region R2 are produced. After washing the sample with water, dry it. Polish the observation surface of the dried sample. After polishing, backscattered electron images of arbitrary 3 fields of view (100 μm×100 μm) are acquired for each polished observation surface at a magnification of 3000 using SEM.

In the acquired backscattered electron image, the difference in brightness between the electrolyte main body 11 and the coarse pores 12 is different, and the electrolyte main body 11 is displayed as an aggregate of fine particles of “grey white”, “gray” and “black”. be done. The coarse pores 12 are “black” and appear as areas larger than the grains that make up the electrolyte body 11 . The brightness of the image is classified into 256 gradations and binarized using image analysis software HALCON manufactured by MVTec (Germany) to distinguish between the electrolyte body 11 and the coarse pores 12 . However, as long as similar results can be obtained, the type of image analysis software does not matter. In each field, the number of coarse pores 12 is measured. The total number of coarse pores 12 in a total of 12 views (3 views each for 4 samples) for each region is defined as the number of coarse pores 12 for each region.

As described above, the following chemical reactions occur on the anode 20 side.

Anode 20: _CH3OH + _H2O → _CO2 +6H ^{++ 6e-}
That is, a large amount of water is supplied to the anode 20 side. Therefore, in the first main surface region R1 located on the anode 20 side, the electrolyte membrane 10 contains a large amount of water. A volume change occurs in the electrolyte membrane 10 due to hydration. Here, the coarse pores 12 relieve the stress due to the volume change of the electrolyte membrane 10 caused by the change in the moisture content of the electrolyte body 11 during operation of the DMFC 100 . Thereby, it is possible to suppress the generation of stress at the interface between the anode 20 and the electrolyte membrane 10 . In the electrolyte membrane 10 of the present embodiment, more coarse pores 12 are arranged in the first main surface side region R1 than in the second main surface side region R2. Stress can be relieved efficiently. As a result, damage to electrolyte membrane 10 can be suppressed.

At least one coarse pore 12 is flattened. In addition, the longitudinal direction of the coarse pores 12 is along the surface direction of the first main surface A. As shown in FIG. The coarse pores 12 have rounded corners at both ends in the longitudinal direction. The planar direction of the first main surface A means the horizontal direction of the first main surface A. As shown in FIG.

The coarse pores 12 extend parallel to the surface direction of the first main surface A. As shown in FIG. In addition, as shown in FIG. 3, the coarse pores 12 may be inclined with respect to the surface direction of the first main surface A. As shown in FIG. That is, the longitudinal direction of the coarse pores 12 may be inclined with respect to the surface direction of the first main surface A. For example, the longitudinal direction of the coarse pores 12 may be inclined with respect to the planar direction of the first main surface A by about 10 degrees or less. Thereby, stress relaxation in the thickness direction can be further improved. The coarse pores 12 may extend in the longitudinal direction of the electrolyte membrane 10 .

[Ion-conductive substance 15]
An ionically conductive material 15 is disposed within the coarse pores 12 . The ion conductive material 15 is liquid. The ion-conducting material 15 is phosphoric acid. As shown in FIG. 4, when the base material 13 of the electrolyte membrane 10 is a basic polymer, phosphoric acid can be retained by an acid-base reaction. Therefore, the outflow of phosphoric acid from the electrolyte membrane 10 can be suppressed. In addition, in FIG. 4, the base material 13 is polybenzimidazole.

The ion conductive material 15 conducts protons (H ⁺ ) from the anode 20 side to the cathode 30 side during power generation of the DMFC 100 . The proton conductivity of the ion conductive material 15 is not particularly limited, but is preferably 0.1 mS/cm or more, more preferably 0.5 mS/cm or more, and still more preferably 1.0 mS/cm or more. The proton conductivity of the ion conductive material 15 is preferably as high as possible, and its upper limit is not particularly limited, but is, for example, 100 mS/cm.

[Manufacturing Method of Electrolyte Membrane 10]
Next, a method for manufacturing the electrolyte membrane 10 will be described. The method for manufacturing the electrolyte membrane 10 described below is an example of the method for manufacturing the electrolyte membrane 10 of the present embodiment. Therefore, the electrolyte membrane 10 having the configuration described above may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of the manufacturing method of the electrolyte membrane 10 of the present embodiment.

The electrolyte membrane 10 of this embodiment is manufactured by bonding two types of electrolyte membranes 10, a first electrolyte membrane and a second electrolyte membrane. The first electrolyte membrane is porous and contains coarse pores 12 . The second electrolyte membrane is a dense membrane and does not contain coarse pores 12 .

The method for manufacturing the first electrolyte membrane includes a mixing step, an intermediate manufacturing step, and a densifying step. Each step will be described below.

[Mixing process]
In the mixing step, ceramics, resin and organic solvent are mixed to prepare a mixture. Although the method of preparing the mixture is not particularly limited, for example, the simple dispersion method described below can be used.

First, a varnish is prepared by dissolving an organic polymer as the base material 13 in a solvent. Any solvent may be used as long as it can dissolve the organic polymer and can be evaporated after film formation. Examples of solvents include aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethylsulfoxide, or ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and propylene glycol. Alkylene glycol monoalkyl ethers such as monomethyl ether and propylene glycol monoethyl ether, halogen solvents such as dichloromethane and trichloroethane, and alcohols such as i-propyl alcohol and t-butyl alcohol can be used.

Next, a mixture is prepared by mixing ceramics 14 into the prepared varnish. As a method for mixing the varnish and the ceramics 14, for example, a stirrer method, a ball mill method, a jet mill method, a nanomill method, ultrasonic waves, or the like can be used.

[Intermediate manufacturing process]
In the intermediate production step, the mixture is dried to produce an intermediate. The intermediate has pores, and the porosity, which is the existence ratio of pores, is 35% or more. Specifically, a pore former is added to the mixture of the varnish and the ceramics 14 . An intermediate is obtained by forming a film on a substrate from the mixture to which the pore-forming material has been added. Any substrate can be used as long as the mixture can be peeled off after forming a film, and for example, a glass plate, a polytetrafluoroethylene sheet, a polyimide sheet, or the like can be used. As a method for forming the mixture into a film, for example, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, or the like can be used.

The porosity is calculated as follows. The intermediate body after drying is punched to φ10 mm, and the film thickness is measured with a micrometer. A film volume b is calculated from the measured film thickness. Also, the membrane weight is measured. The film weight is divided into the ceramics weight and the resin weight from the mixing ratio, and the ceramics volume d and the resin volume e are calculated from the respective specific gravities. The porosity is defined by the following formula (2).

(Membrane volume b-Ceramics volume d-Resin volume e)/Membrane volume b×100 (2)

When producing the intermediate, the porosity of the intermediate may be adjusted to 35% or more by mechanically mixing gas or by chemically decomposing the pore-forming material.

Preferably, the porosity of the intermediate is 80% or less. In this case, densification in the next step is facilitated.

[Densification step]
In the densification step, the first electrolyte membrane is formed by densifying the intermediate with a compressibility of 100% or more. The densification step is performed at a temperature of 80-130°C. When the intermediate body is densified at a temperature of 130° C. or less, the resistance of the electrolyte membrane 10 does not increase, and a decrease in conductivity can be prevented. In addition, when the intermediate is placed between two lumirrors (registered trademark) and the two lumirrors in the densification equipment, the compression rate is the intermediate film thickness before the densification process, a, and the lumirror thickness, b. , is defined by the following formula (3), where c is the dimension of the gap that sandwiches the intermediate in the densification equipment.

Compression rate = (Intermediate film thickness a before densification step + Lumirror thickness b × 2 - Dimension c of the gap sandwiching the intermediate in the densification equipment) / Intermediate film thickness before densification step a × 100 (3)

The compression rate defined by Equation (3) indicates the compression conditions in the densification process. By setting the compressibility to 100% or more, the intermediate can be sufficiently compressed as described below.

First, since the intermediate is porous, it deforms more easily than Lumirror. Therefore, when the intermediate body sandwiched between the lumirrors is densified by the densification equipment, the intermediate body is first compressed, and after the intermediate body is sufficiently compressed, the lumirror elastically deforms. That is, elastic deformation of the lumirror means that the intermediate is sufficiently compressed. Here, a compression rate of 100% means that the dimension c of the gap sandwiching the intermediate body in the densification equipment and the thickness 2b of two lumirrors are the same value. Therefore, if the compression rate is 100% or more, the lumirror is elastically deformed, that is, the intermediate body is sufficiently compressed. Therefore, by densifying the intermediate with a compressibility of 100% or more, the intermediate can be sufficiently compressed.

Although the method of densification is not particularly limited, it is, for example, roll press. In the case of roll pressing, the dimension c of the gap between the intermediates of the densification equipment is the gap between the two rolls. Since the intermediate is porous and easily deformable, roll pressing can be performed even if the thickness of the laminate sandwiching the intermediate between lumirrors is five times or more the gap between the rolls. Moreover, the densification step is not limited to the above method as long as the method can sufficiently compress the intermediate.

The method for manufacturing the second electrolyte membrane includes a mixing step, an intermediate manufacturing step, and a densifying step. The mixing step is the same as the mixing step for the first electrolyte membrane.

No pore-forming material is added in the intermediate manufacturing process. Therefore, the porosity of the intermediate is less than 35%. Since the porosity of the intermediate is low, the compressibility in the densification step may be 100% or more. Other than that, it is the same as the intermediate production process and the densification process of the first electrolyte membrane.

The first electrolyte membrane and the second electrolyte membrane prepared as described above are bonded together. A known method may be used for the bonding method. For example, there are a method of bonding two electrolyte membranes 10 together using a known adhesive, a method of bonding together with a solution of the same kind of polymer as that of the electrolyte membrane 10, a hot press method, and the like. In the case of the hot press method, specifically, the stacked first electrolyte membrane and second electrolyte membrane are sandwiched between Lumirror (registered trademark) and placed between pressure plates of a hot press machine. After heating the pressure plate to a predetermined temperature, the stacked electrolyte membranes are pressed. After holding for a predetermined time, the pressure plate is opened and the electrolyte membrane 10 is taken out and cooled to room temperature. The electrolyte membrane 10 can be formed by the above steps.

The electrolyte membrane 10 obtained by bonding is impregnated with phosphoric acid. This places the phosphoric acid in the coarse pores 12 . The phosphoric acid is preferably 85% aqueous phosphoric acid. Moreover, when the base material 13 is a basic polymer, the basic polymer is doped with phosphoric acid by impregnating the electrolyte membrane 10 with phosphoric acid. The phosphoric acid is set so that 2-10 molecules are doped per repeating unit of the basic polymer.

[Modification of Embodiment]
The present invention is not limited to the embodiments described above, and various modifications and changes are possible without departing from the scope of the present invention.

[Modification 1]
Although the ceramics 14 are ion conductive in the above embodiment, the present invention is not limited to this. Ceramics 14 need not be ionically conductive. In this case, a porous base material 13 can be used and the pores of the base material 13 can be impregnated with the ion conductive material 15 . Here, pores mean pores having a cross-sectional area of 0.1 to 1.0 μm ² . In addition, since the pores are 1.0 μm ² or less, the strength of the electrolyte membrane 10 does not decrease. The cross-sectional area of the pore is obtained by calculating the cross-sectional area of the portion displayed with lower luminance than the ceramics 14 and the resin in the SEM observation image by image analysis. The porous substrate 13 can be manufactured by using a pore-forming material.

[Modification 2]
In the above embodiment, the first main surface A faces the anode 20 side and the second main surface B faces the cathode 30 side, but the present invention is not limited to this. For example, when the electrolyte membrane 10 is used in a polymer electrolyte fuel cell (PEFC), the first main surface A may face the cathode 30 side and the second main surface B may face the anode 20 side. PEFC generates power based on the following chemical reaction formula.

Anode 20: H ₂ →2H ⁺ +2e ⁻
Cathode 30: O ₂ +4H ⁺ +4e ⁻ →2H ₂ O

As shown in the above chemical reaction formula, in PEFC, water does not exist on the anode side. On the other hand, water is produced on the cathode side. If the first main surface A faces the cathode 30 side, the volume change of the electrolyte membrane 10 due to the water generated on the cathode 30 side being contained in the electrolyte membrane 10 can be efficiently mitigated.

[Modification 3]
In the above embodiment, the electrolyte membrane 10 is applied to DMFC, which is a type of fuel cell, but the present invention is not limited to this. The electrolyte membrane 10 can be applied to electrochemical cells in general. For example, the electrolyte membrane 10 can be applied to electrolytic cells.

Examples of the present invention are described below. However, the present invention is not limited to the examples described below.

[Preparation of sample]
In Test No. 1, the first electrolyte membrane was produced as follows. As shown in Table 1, the ceramic particles (average particle diameter of 1.0 μm or more) and the base raw material were compounded and mixed. The mixture was added to 50 mL of dimethylacetamide (DMAc) to form a slurry. Techpolymer BM30X-5 was added as a pore former. This slurry was applied onto a PET film by a printing method and heat-treated (30 minutes, 90° C.) to form an intermediate. By adjusting the coating amount of the slurry, the film thickness of the intermediate was set to 80 μm. The intermediate was peeled off from the PET film. The porosity of the intermediate was 60-80%. A roll press was applied to the intermediate at 180° C. and a compression rate of 200%.

Next, a second electrolyte membrane was produced. The second electrolyte membrane was prepared in the same manner as the first electrolyte membrane except for the following points. No pore former was added. The porosity of the intermediate was 35% or less. The film thickness of the intermediate was 50 μm. The compression ratio during roll pressing was 200%.

An electrolyte membrane 10 was produced by hot-pressing the first electrolyte membrane and the second electrolyte membrane (1 hour, 60° C., 3 MPa). The thickness of the electrolyte membrane 10 was 60 μm. The first electrolyte membrane and the second electrolyte membrane have substantially the same size in plan view. The electrolyte membrane 10 was impregnated with an 85% phosphoric acid aqueous solution. As a result, phosphoric acid, which is an ion conductive material, was placed in the coarse pores of the first electrolyte membrane.

Test No. 2 was prepared in the same manner as the second electrolyte membrane of Test No. 1, except for the following points. The film thickness of the intermediate was 80 μm. The compression ratio during roll pressing was 200%. The first electrolyte membrane was not attached, and only the second electrolyte membrane was used as the electrolyte membrane. The thickness of the electrolyte membrane was 60 μm.

Test No. 3 was prepared in the same manner as the first electrolyte membrane of Test No. 1, except for the following points. The film thickness of the intermediate was 120 μm. The compression ratio during roll pressing was 200%. The second electrolyte membrane was not attached, and only the first electrolyte membrane was used as the electrolyte membrane. The thickness of the electrolyte membrane was 60 μm.

[Measurement of number of coarse pores]
The number of coarse pores was measured in the first main surface side region and the second main surface side region.

[Evaluation of electrolyte membrane damage]
A carbon-supported cathode catalyst (Pt/C) (50 wt% Pt supported (TEC10E50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and PVDF powder as a binder were prepared. Cathode catalyst: PVDF powder: water A cathode paste was prepared by mixing in a weight ratio of 9 wt%: 0.9 wt%: 90 wt% The prepared cathode paste was applied to a PET film and dried to form a cathode transfer film. In addition, an anode catalyst supported on carbon (Pt--Ru/C) with a Pt--Ru supported amount of 54 wt % (TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and PVDF powder as a binder were prepared. The anode paste was prepared by mixing the anode catalyst: PVDF powder: water in a weight ratio of 9 wt%: 0.9 wt%: 90 wt%.The prepared anode paste was applied to the PET film. It was then dried to produce an anode transfer film.

A cathode transfer film and an anode transfer film were arranged so as to sandwich each electrolyte membrane. At this time, in Test Nos. 1 and 2, the first electrolyte membrane was arranged on the anode side. Then, hot pressing (120° C., 1 minute, 3 MPa) is performed from the cathode transfer film side and the anode transfer film side to transfer the cathode of the cathode transfer film onto the electrolyte membrane and form the anode of the anode transfer film. A fuel cell was fabricated by transfer forming on an electrolyte membrane. In addition, in each example, the configuration was basically the same except for the configuration of the electrolyte membrane.

First, while supplying a fuel containing methanol to the anode and supplying air to the cathode, the alkaline fuel cell is heated to 120° C. in 1 hour, held for 1 hour, and then cooled to room temperature, which is repeated 100 times. A thermal cycle test was performed. For each example, the test was performed using five electrolyte membranes.

The presence or absence of breakage in each electrolyte membrane after the thermal cycle test was confirmed with an optical microscope, and the results are shown in Table 1. In Table 1, "○" means that none of the five electrolyte membranes tested was damaged, and "X" means that even one of the five electrolyte membranes was damaged. means that

[Measurement of Strength of Electrolyte Membrane 10]
The strength of the electrolyte membrane 10 was evaluated as follows. In accordance with the test method of JISZ1707, the electrolyte membrane was sandwiched between plates with a φ10 mm hole, and the maximum breaking load when the plate was broken by piercing the center of the hole with a φ0.5 mm needle was measured.

[Test results]
According to Table 1, the coarse pores 12 having a cross-sectional area of 1.5 μm ² or more are arranged in the first main-surface-side region R1 more than in the second main-surface-side region R2. It was found that breakage can be suppressed.

10 Electrolyte membrane 11 Electrolyte main body 12 Coarse pores 13 Base material 14 Particles 15 Ion conductive material 20 Anode 30 Cathode A First main surface B Second main surface R1 First main surface side region R2 Second main surface side region

Claims (10)

an electrolyte body having a first major surface and a second major surface located opposite the first major surface;
a plurality of coarse pores disposed in the electrolyte body;
an ion-conducting substance;
with
The coarse pores are arranged more in the first main surface side region than in the second main surface side region,
said ionically conductive material disposed within said coarse pores;
The ion-conducting substance is phosphoric acid,
Electrolyte membrane for electrochemical cells.
an electrolyte body having a first major surface and a second major surface located opposite the first major surface;
a plurality of coarse pores disposed in the electrolyte body;
an ion-conducting substance;
with
The coarse pores are arranged more in the first main surface side region than in the second main surface side region,
said ionically conductive material disposed within said coarse pores;
The electrolyte main body is
a base material;
ceramics dispersed in the substrate;
including,
Electrolyte membrane for electrochemical cells.
at least one of said coarse pores is flattened;
The electrolyte membrane for an electrochemical cell according to claim 1 or 2 .
at least one of the coarse pores is inclined with respect to the direction of the first major surface;
The electrolyte membrane for an electrochemical cell according to claim 3 .
The ion-conducting substance is liquid,
The electrolyte membrane for an electrochemical cell according to claim 1 or 2 .
The base material is a resin,
The electrolyte membrane for an electrochemical cell according to claim 2 .
The base material is polybenzimidazole,
The ceramic is tin pyrophosphate,
The electrolyte membrane for electrochemical cells according to claim 2 or 6 .
The electrolyte membrane for an electrochemical cell according to claim 1 or 2 ;
an anode;
a cathode;
an electrochemical cell.
the first main surface faces the anode side;
9. Electrochemical cell according to claim 8 .
the first main surface faces the cathode side;
9. Electrochemical cell according to claim 8 .

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