JP2000058085A - Electrolyte film and manufacture thereof, solid high molecular electrolyte fuel cell using the electrolyte film and operating method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the moisture content of an electrolyte film by forming a multiple- layered electrolyte film of the porous electrolyte formed with at least one electrolyte film having three-dimensional communication holes except for both sides electrolyte films. SOLUTION: After adjusting the concentration of the electrolyte solution obtained by dissolving the solvent containing alcohol, the electrolyte solution is coated on one surface of an electrolyte film into the layered-structure for porous treatment, and an electrolyte solution coated layer is formed into the porous electrolyte having three-dimensional communication holes. Continuously, this electrolyte is laminated on a perfluorosulfonic acid resin film, so that the porous electrolyte film contacts with the resin film. This film is heated at 125 deg.C and pressurized at 50-500 kg/cm2 for integral bonding. A three-layered multiple-layered electrolyte film forming with the perfluorosulfonic acid resin film in both sides thereof and the three-dimensional communication holes between them is formed. This multiple-layered electrolyte film holds water in holes parts of the porous electrolyte having the three-dimensional holes for raising the moisture content of the electrolyte film, and increase in the resistance of the electrolyte due to the lowering of the moisture content is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell having an electrolyte membrane.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is an electrochemical device that supplies electric power, for example, hydrogen as an anode, and oxygen, for example, as an oxidant to an anode and electrochemically reacts them to produce electric power. The anode and the cathode are gas diffusion electrodes, and the anode is joined to one surface of the electrolyte membrane and the cathode is joined to the other surface to form a gas diffusion electrode.
Construct an electrolyte membrane assembly. The gas diffusion electrode is composed of a gas diffusion layer and a reaction layer, and the anode and cathode catalyst layers are provided with catalysts such as metal particles of platinum group metals or carbon particles carrying these particles, and the gas diffusion layers are water repellent. For example, a porous carbon paper having the following is used.

[0003] The gas diffusion electrode-electrolyte membrane assembly is sandwiched between a pair of gas-impermeable separators having a gas supply channel formed therein to form a unit cell as a basic unit. A plurality of such unit cells are stacked to form a solid polymer electrolyte fuel cell.

When a solid polymer electrolyte fuel cell is operated, an electrochemical reaction of 2H2.fwdarw.4H ++ 4e- at the anode and O2 + 4H ++ 4e-.fwdarw.2H2O at the cathode proceeds.

In a solid polymer electrolyte fuel cell, the electrolyte is a polymer membrane, for example, a membrane having proton conductivity such as a perfluorosulfonic acid resin membrane, which is a kind of ion exchange resin membrane. These electrolyte membranes show proton conductivity in a water-containing state, and protons generated from hydrogen at the anode are transmitted to the cathode through the electrolyte membrane with some hydration water, and react with oxygen to produce water. . However, these electrolyte membranes do not show proton conductivity in a dry state, and when the water content of the electrolyte membrane is reduced, the proton conductivity is reduced, thereby increasing the membrane resistance.

When a solid polymer electrolyte fuel cell is operated, the water content of the electrolyte membrane on the anode side decreases due to the movement of hydration water, which causes an increase in the resistance of the electrolyte membrane. In order to prevent this, the fuel gas supplied to the anode is humidified and supplied to a state containing moisture. In a solid polymer electrolyte fuel cell, an increase in resistance due to a decrease in the water content of the electrolyte membrane significantly increases the resistance overvoltage and causes a decrease in output characteristics. It is important to maintain the amount of water.

In order to maintain the water content of the electrolyte membrane, a water management method for maintaining the water content of the electrolyte membrane has been proposed in addition to the method of supplying a humidified fuel gas. For example, there is a method using an electrolyte membrane having a small thickness. On the cathode side of the electrolyte membrane, the water content becomes excessive with respect to the anode side due to movement of water generated by the electrode reaction and hydration water accompanying the movement of protons. That is, a gradient of the water content occurs in the electrolyte membrane. At this time, the concentration gradient of water in the electrolyte membrane serves as a driving force, and reverse diffusion of water from the cathode side to the anode side occurs. Since the concentration gradient becomes steeper as the electrolyte membrane becomes thinner, the reverse diffusion of water occurs more frequently, and the contribution to suppressing the decrease in the water content on the cathode side increases.

Further, in order to maintain the water content of the electrolyte membrane, a method of supplying water by bringing one end or a part of the electrolyte membrane into contact with water or embedding a water-absorbing fiber or the like in the electrolyte membrane to form one end of the fiber There is a method relating to a method of supplying water to the electrolyte membrane, such as a method of bringing water into contact with water and supplying water by a wick. Alternatively, a method of improving water retention by dispersing fine particles such as titanium oxide in the electrolyte membrane, or water from oxygen and hydrogen permeating the electrolyte membrane by dispersing fine particles of platinum in the electrolyte membrane. Methods for improving the water content of the electrolyte membrane, such as a method for producing the same, have been proposed.

[0009]

However, in the method of reducing the thickness of the electrolyte membrane, the strength of the electrolyte membrane is reduced if the thickness is reduced. For this reason, there is a limit in reducing the film thickness in order to maintain the strength that can constitute a solid polymer electrolyte fuel cell. On the other hand, in order to maintain the water content of the electrolyte membrane, it is necessary to increase the water retention capacity of the electrolyte membrane itself.
However, it is difficult to supply a sufficient amount of water by a method using a wick such as a fiber that is in contact with water and water-absorbing fibers.

[0010] The method of dispersing titanium oxide in the electrolyte membrane is insufficient for improving the water retention of the electrolyte membrane.
In addition, the method of dispersing platinum in the electrolyte membrane complicates the manufacturing process and increases the cost because expensive platinum is used. Therefore, in order to increase the output of a solid polymer electrolyte fuel cell, it is necessary to improve the water retention of the electrolyte membrane to reduce the membrane resistance, and to provide a simple and low-cost manufacturing method of the electrolyte membrane.

[0011]

Means for Solving the Problems At least one of the electrolyte layers other than the electrolyte layers on both sides forms a multilayer electrolyte membrane which is a porous electrolyte having three-dimensionally communicating pores, and the pores of this porous electrolyte layer are formed. The water content of the electrolyte membrane is increased by holding water. By integrating an electrolyte membrane formed with a porous electrolyte layer having three-dimensionally communicating pores on at least one surface thereof with the electrolyte membrane so that the porous electrolyte layer contacts, at least one electrolyte excluding the electrolyte layers on both sides The present invention provides a method for producing a multilayer electrolyte membrane in which the layer is a porous electrolyte layer having three-dimensionally connected pores.

[0012] A solid polymer electrolyte fuel cell comprising a multilayer electrolyte membrane in which at least one of the electrolyte layers except for the electrolyte layers on both sides is a porous electrolyte having three-dimensionally communicating pores is formed. In order to improve the membrane resistance and suppress the increase in membrane resistance, thereby reducing the resistance overvoltage caused by the membrane resistance to increase the output of the polymer electrolyte fuel cell and supplying the fuel and oxidant without humidification However, the output is stabilized by maintaining the water content of the electrolyte membrane.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing a multilayer electrolyte membrane of the present invention comprises the following two steps.

In step 1, a porous electrolyte layer having three-dimensionally connected pores on at least one surface of the electrolyte membrane is formed.

In the step 2, the electrolyte membrane provided with the porous electrolyte layer having the three-dimensionally connected pores is arranged on the electrolyte membrane so that the porous electrolyte layer is in contact with the electrolyte membrane and integrated to form the composite membrane of the present invention. A layer electrolyte membrane is produced.

First, step 1 will be described.

A porous electrolyte layer having three-dimensionally connected pores can be prepared as follows. That is, after adjusting the concentration of the solution of the electrolyte dissolved in the solvent containing alcohols, at least one surface of the electrolyte membrane is applied in a layer form and subjected to a porous treatment, and the coating layer of the electrolyte solution is three-dimensionally connected. A porous electrolyte having pores of The porosity treatment is immersion in an organic solvent having a polar group other than the alcoholic hydroxyl group, and the dissolved electrolyte is solidified to form a porous electrolyte having three-dimensionally connected pores.

Next, an example of a method for producing a porous electrolyte layer having three-dimensionally communicating pores will be specifically described.

As a solution obtained by dissolving the electrolyte in a solvent containing alcohols, for example, a 5 wt% Nafion solution (Aldrich, USA) which is a commercially available solution of perfluorosulfonic acid resin can be used. By concentrating this Nafion solution, Nafion solutions of various concentrations are prepared.

As the electrolyte membrane, for example, a commercially available perfluorosulfonic acid resin membrane, Nafion 112 membrane (US,
DuPont) can be used. The electrolyte membrane is boiled with purified water for one hour and stored in purified water at room temperature. Thereafter, the electrolyte membrane is further swelled by immersion in ethanol such as ethanol. The swollen electrolyte membrane is taken out of ethanol, excess ethanol on the surface of the membrane is wiped off with a paper towel or the like, and at least one side of the surface is coated with a Nafion solution having the above-mentioned concentration by spraying or the like. After forming the solution-coated body, the above-mentioned electrolyte membrane-electrolyte solution-coated body is immersed in an organic solvent having a polar group other than the alcoholic hydroxyl group, for example, butyl acetate, and left as it is.

Thereafter, the electrolyte membrane-electrolyte solution coated body is taken out of the butyl acetate and dried at room temperature to produce an electrolyte membrane having a porous electrolyte layer having three-dimensionally connected pores on at least one surface of the electrolyte membrane. it can. Nafion is a registered trademark of DuPont.

Although a 5 wt% Nafion solution which is a commercially available solution of perfluorosulfonic acid resin is used as a solution in which the electrolyte is dissolved in a solvent containing alcohols, the present invention is not limited to this solution. Instead, a solution of a perfluorosulfonic acid resin may be used. For example, a solution of another perfluorosulfonic acid resin such as Flemion (trade name of Asahi Glass) can be used, and the concentration of the electrolyte solution is diluted or concentrated. It can be arbitrarily changed by such a method.

The electrolyte is diluted with methanol, ethanol,
An alcohol having 4 or less carbon atoms, such as 1-propanol, 2-propanol, 1-butanol or 2-butanol, water or a mixture thereof can be used. In the concentration, a part of the solvent of the electrolyte solution can be removed by a method such as heating or vacuum drying.

Although the description has been made using Nafion 112 as the electrolyte membrane, other hydrofluoric electrolyte membranes such as perfluorosulfonic acid membranes and perfluorocarboxylic acid membranes and hydrocarbon-based electrolyte membranes such as styrene vinylbenzene sulfonic acid can be used. If it is a polymer membrane that shows proton conductivity,
Either film may be used. In addition to a commercially available electrolyte membrane in the form of a membrane, a casting membrane prepared from an electrolyte solution can also be used. However, among these polymer films, a fluorine-based electrolyte film such as a perfluorosulfonic acid film or a perfluorocarboxylic acid film having excellent heat resistance is preferable.

The application of the electrolyte solution to the electrolyte membrane includes, for example, a doctor blade method and a screen printing method as methods other than spraying, and a conventionally known method can be used.

Alcohol which wets the electrolyte membrane in a water-containing state is methanol having 4 or less carbon atoms in addition to ethanol.
1-propanol, 2-propanol, 1-butanol or 2-butanol can also be used.

The organic solvent having a polar group other than the alcoholic hydroxyl group is not limited to butyl acetate, and the number of carbon atoms in the carbon chain having an alkoxycarbonyl group in the molecule is one.
To 7 organic solvents, for example, propyl formate, butyl formate, isobutyl formate, ethyl acetate, propyl acetate, isopropyl acetate, allyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, propionic acid Ethyl, propyl propionate, methyl acrylate, butyl acrylate, isobutyl acrylate, methyl butyrate, methyl isobutyrate, ethyl butyrate, ethyl isobutyrate, methyl methacrylate, propyl butyrate, isopropyl isobutyrate, 2-ethoxyethyl acetate, acetic acid 2-
(2ethoxyethoxy) ethyl or the like alone or as a mixture, or an organic solvent having 3 to 5 carbon atoms in the carbon chain having an ether bond in the molecule, for example, dipropyl ether;
Dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tripropylene glycol monomethyl ether, alone or a mixture of tetrahydrofuran, or an organic solvent having 4 to 8 carbon atoms in the carbon chain having a carbonyl group in the molecule, for example, methyl butyl Ketone, methyl isobutyl ketone, methyl hexyl ketone, dipropyl ketone, etc., alone or in a mixture, or an organic solvent having 1 to 5 carbon atoms in the carbon chain having an amino group in the molecule, for example, isopropylamine, isobutylamine, tertial Butylamine, isopentylamine, diethylamine, etc., alone or in a mixture, or an organic solvent having 1 to 6 carbon atoms in the carbon chain having a carboxyl group in the molecule, for example, propionic acid, valeric acid, caproic acid, heptonic acid Alone or a mixture of such phosphate,
Alternatively, a material obtained from a combination thereof can be used.

FIG. 2 shows an example of a view (electron micrograph) showing the appearance of the surface of the porous electrolyte layer having three-dimensionally interconnected pores thus produced. The pores are in communication with each other and are formed three-dimensionally, and the electrolytes are continuous in a network and are formed three-dimensionally.

FIG. 3 is a schematic diagram showing the basic structure of the surface of the porous electrolyte layer having three-dimensionally communicating pores. 1 is an electrolyte part of a porous electrolyte layer having three-dimensionally communicating pores, 2 is a pore part of a porous electrolyte layer having three-dimensionally communicating pores, and 3 is a porous part having three-dimensionally communicating pores. The opening diameter of the pore portion of the porous electrolyte layer is indicated by 4, and the diameter of the electrolyte portion of the porous electrolyte layer having three-dimensionally communicating pores is indicated by 4.

FIG. 2 shows a porous electrolyte layer having three-dimensionally communicating pores when a 16 wt% Nafion solution is used. The opening diameter of the pore portion of the porous electrolyte layer having three-dimensionally communicating pores is as follows. The diameter of the electrolyte portion of the porous electrolyte layer having pores of 0.3 to 5.0 μm and three-dimensional communication is 0.2 to 1.0.
0 μm, porosity is 70%.

Depending on the concentration of the Nafion solution applied to the electrolyte membrane, the opening diameter of the mesh portion of the network skeleton structure of the porous electrolyte layer having three-dimensionally communicating pores is in the range of 0.1 to 10 μm, and the skeleton of the network skeleton structure is formed. The diameter of the part is 0.1-30 μm
And the porosity can be adjusted in the range of 10 to 90%. The thickness of the porous electrolyte layer having three-dimensionally connected pores formed on the surface of the electrolyte membrane can be adjusted in the range of 1 to 50 μm depending on the amount of the Nafion solution to be applied.

Next, step 2 will be described.

A multilayer electrolyte membrane in which at least one electrolyte layer other than the electrolyte layers on both sides is a porous electrolyte having three-dimensionally connected pores can be produced, for example, as follows. That is, the electrolyte membrane provided with the porous electrolyte layer having pores of three-dimensional communication on at least one surface prepared in Step 1 is integrated with the electrolyte membrane so that the porous electrolyte layer is in contact with the electrolyte membrane.

Next, an example of a method for producing a multilayer electrolyte membrane in which at least one electrolyte layer except for the electrolyte layers on both sides is a porous electrolyte having three-dimensionally communicating pores will be specifically described.

An electrolyte having a porous electrolyte layer having three-dimensionally connected pores on one surface prepared in step 1 is laminated on Nafion 112 so that the porous electrolyte layer is in contact with the electrolyte. For example, this laminated body is set at 50 kg / cm ^{2 to} 500 kg /
C. for ² minutes at 125.degree. On both sides, a Nafion 112 membrane is formed, and a multilayer electrolyte membrane of the present invention comprising three layers in which a porous electrolyte having three-dimensionally communicating pores is formed therebetween is formed. FIG. 1 is a schematic view of the multilayer electrolyte membrane of the present invention.

In this description, the electrolyte membrane provided with the porous electrolyte having the three-dimensionally connected pores prepared in the step 1 has the porous electrolyte only on one side, but may have the porous electrolyte on both sides. In this case, the multilayer electrolyte membrane of the present invention having a porous electrolyte having three-dimensionally connected pores also on the surface composed of four layers is formed.

Although the description has been made using Nafion 112 as an electrolyte membrane to be joined to the electrolyte membrane having a porous electrolyte having three-dimensionally interconnected pores prepared in Step 1, other perfluorosulfonic acid membranes and perfluorocarboxylic acid Any membrane may be used as long as it is a polymer membrane that exhibits proton conductivity in a water-containing state, such as a fluorine-based electrolyte membrane such as a membrane or a hydrocarbon-based electrolyte membrane such as styrene-vinylbenzenesulfonic acid. In addition to the electrolyte membrane that is commercially available in the form of a membrane,
A casting film made from an electrolyte solution can also be used.

The pressure, temperature and time when the above-mentioned electrolyte membrane is heated and pressed are determined by balancing these factors. Depending on the case, the pressure, the temperature and the time may be 50 kg / cm ^{2 to} 500 kg / cm ² ,
Conditions are determined in the range of 100 ° C to 175 ° C.

Further, an electrolyte having a porous electrolyte layer having three-dimensionally communicating pores on one surface is laminated on the three-layered multilayer electrolyte membrane of the present invention so that the porous electrolyte layer is in contact with the electrolyte. Then, they are integrally joined by heating and pressure welding to form a multi-layer electrolyte membrane in which a non-porous electrolyte layer and a porous electrolyte layer have a repeating structure as shown in FIG.

By repeating joining of the electrolyte provided with the porous electrolyte layer having three-dimensionally connected pores on one surface as described above an arbitrary number of times, the non-porous electrolyte layer and the porous electrolyte layer are repeatedly bonded. Can constitute the multilayer electrolyte membrane of the present invention having a repeating structure of an arbitrary number of times.

[0041]

Next, a preferred embodiment of the present invention will be described with reference to the drawings.

Example 1 An example of an embodiment of the method for producing a multilayer electrolyte membrane of the present invention will be described. FIG. 5 is a float view showing an example of the embodiment of the production process of the multilayer electrolyte membrane of the present invention. The production of the multilayer electrolyte membrane of the present invention comprises six steps, and each step will be specifically described with reference to FIG.

In the first step, the concentration of the electrolyte solution was adjusted. A commercially available 5 wt% Nafion solution was placed in a sample bottle, and heated to 60 ° C with stirring to concentrate the solution to 16 wt%.

In the second step, an electrolyte casting film was formed from the concentrated Nafion solution. Set the interval to 0.
16wt using a doctor blade adjusted to 33mm
The Nafion solution was applied to an aluminum foil and dried to form a casting film of Nafion on the aluminum foil. When the thickness of this film was measured, it was about 22 μm, which was used as the electrolyte film A1.

In the third step, a porous electrolyte layer having three-dimensionally communicating pores was formed on the electrolyte membrane A1. 16 using a doctor blade with the spacing adjusted to 0.16 mm.
A wt% Nafion solution is applied to the electrolyte membrane A1 on the aluminum foil prepared in the second step, immersed in butyl acetate for 10 minutes as a porous treatment, and then dried at room temperature to obtain a surface of the electrolyte membrane A1 on the aluminum foil. Then, a porous electrolyte layer having three-dimensionally connected pores was formed. This is referred to as an electrolyte membrane A2. The thickness of the formed porous electrolyte layer was about 17 μm.

In the fourth step, the electrolyte membrane A2 was joined to form a multilayer electrolyte membrane. Two electrolyte membranes A2 formed on an aluminum foil are laminated such that the porous electrolyte layers face each other. This laminate was placed on a press jig, and 100 kg /
The ^two electrolyte membranes A were heated and pressed at 125 ° C. for 3 minutes in cm ² .
2 were integrally joined to form a multilayer electrolyte membrane of the present invention in a state where aluminum foil was adhered to both surfaces.

In the fifth step, the aluminum foil was removed from the produced multilayer electrolyte membrane. The aluminum foil is adhered to both surfaces of the prepared multilayer electrolyte membrane. 0.5M
Of dilute sulfuric acid to dissolve and remove the aluminum foil to obtain a multilayer electrolyte membrane of the present invention. The thickness of the multilayer electrolyte membrane of the present invention was about 59 μm in a water-containing state.

In the sixth step, the prepared multilayer electrolyte membrane of the present invention was subjected to a pretreatment. The prepared multilayer electrolyte membrane was transferred to another 0.5 M diluted sulfuric acid, boiled for 1 hour, washed 5 times with purified water to convert the electrolyte membrane into a proton type, and stored in purified water.

The multilayer electrolyte membrane of the present invention thus manufactured is referred to as multilayer electrolyte membrane A.

A solid polymer electrolyte fuel cell provided with the multilayer electrolyte membrane A according to the present invention was manufactured. The fabrication method is described below. First, catalyst layers were formed on both surfaces of the multilayer electrolyte membrane A of the present invention as follows. That is, 3
2.6 g of a carbon catalyst loaded with 0 wt% and 45 m of purified water
Then, 45 ml of 2-propanol is added while gradually diffusing to disperse the platinum-supported carbon catalyst in a mixed solvent of water / 2-propanol, and further mixed using a stirrer for 30 minutes. A PTFE dispersion solution (manufactured by Mitsui DuPont Fluorochemicals, PTFE solid component: 6) is added to this mixture.
0%) 0.5 ml was slowly added with stirring, and 3
After stirring for 0 minutes, 17.5 ml of a 5 wt% Nafion solution (manufactured by Aldrich, USA) was gradually added with stirring, and further stirred for 30 minutes to prepare a catalyst dispersion.

The catalyst dispersion was sprayed with a diameter of 3c by spraying.
m was applied to both surfaces of the multilayer electrolyte membrane A in a circular shape and dried to form catalyst layers on both surfaces of the multilayer electrolyte membrane A. The catalyst dispersion was applied so that the content of the platinum catalyst in this catalyst layer was about 0.5 mg / cm ² .

Next, water-repellent carbon paper cut to a diameter of 3 cm as a gas diffusion layer was placed on both sides of the multilayer electrolyte membrane A having a catalyst layer formed on both surfaces thereof, and heated and pressed (120 kg / cm ² , 135 kg). (5 ° C., 5 minutes) to form a gas diffusion electrode-multilayer electrolyte membrane assembly A.

The solid polymer electrolyte fuel cell A of the present invention was constructed by sandwiching the gas diffusion electrode-multilayer electrolyte membrane assembly A thus produced between metal separators having gas supply passages formed therebetween. .

This solid polymer electrolyte fuel cell was operated under the following conditions, and the current-voltage characteristics were measured. Pure hydrogen was used as a fuel gas and supplied to the battery at a flow rate at which the utilization factor became 70%. Pure oxygen was used as the oxidizing gas and supplied to the battery at a flow rate at which the utilization factor became 50%. Oxygen and hydrogen reactant gases were each supplied at atmospheric pressure and none of the reactant gases was humidified. Coolant at 65 ° C. was circulated through the battery to keep the battery temperature constant.

Example 2 A commercially available Nafion 112 membrane was washed three times with purified water and then washed with a 3% hydrogen peroxide solution.
After boiling for 1 hour and washing with purified water twice, then boiling for 1 hour with 0.5 M diluted sulfuric acid to replace the proton type, then purify with purified water for 5 hours.
Washed twice. This is referred to as an electrolyte membrane B.

A solid polymer electrolyte fuel cell equipped with the electrolyte membrane B was manufactured as follows.

First, the catalyst dispersion prepared in Example 1 was applied to both sides of the electrolyte membrane B in a circular shape having a diameter of 3 cm by spraying, and dried to form catalyst layers on both sides of the electrolyte membrane B. The platinum layer content of this catalyst layer was about 0.5 mg /
cm ² of the catalyst dispersion was applied.

Next, water-repellent carbon paper cut to a diameter of 3 cm as a gas diffusion layer was placed on both sides of the electrolyte membrane B having a catalyst layer formed on both sides thereof, and heated and pressed (120 kg / cm ² , 135 ° C., (5 minutes) to form a gas diffusion electrode-electrolyte membrane assembly B.

The solid polymer electrolyte fuel cell B of the present invention was constructed by sandwiching the gas diffusion electrode-electrolyte membrane assembly B thus produced between metal separators provided with gas supply passages.

This solid polymer electrolyte fuel cell B was operated under the same conditions as in Example 1, and the current-voltage characteristics were measured.

FIG. 6 shows the current-voltage characteristics of the solid polymer electrolyte fuel cells produced in Examples 1 and 2. As is clear from FIG. 6, the solid polymer electrolyte fuel cell A including the multilayer electrolyte membrane A of the present invention has a higher cell voltage than the solid polymer electrolyte fuel cell B including the ordinary electrolyte membrane. Despite operating the reaction gas in a non-humidifying operation, the solid polymer electrolyte fuel cell including the multilayer electrolyte membrane of the present invention has a high output.

Internal resistance meter (TSURUGA MODE)
L 3562), the internal resistance of these solid polymer electrolyte fuel cells in the operating state was measured.
FIG. 7 shows the relationship between the current and the internal resistance. Although the internal resistance of the solid polymer electrolyte fuel cell B increases as the current increases, the internal resistance of the solid polymer electrolyte fuel cell A hardly increases even when the current increases. In the multi-layer electrolyte membrane provided in the polymer electrolyte fuel cell A, water is retained in pores of the porous electrolyte having three-dimensionally connected pores, and the water content of the electrolyte membrane is increased. Therefore, it is considered that the increase in the resistance of the electrolyte membrane due to the decrease in the water content of the electrolyte membrane is suppressed.

That is, when the multilayer electrolyte membrane of the present invention is used, the water retention of the electrolyte membrane is improved, so that the resistance overvoltage caused by the increase in the membrane resistance of the electrolyte membrane is reduced, and the fuel or oxidant gas is humidified. Thus, a solid polymer electrolyte fuel cell that operates stably even when supplied without supply can be provided.

[0064]

According to the multilayer electrolyte membrane of the present invention, the water retention of the electrolyte is increased by forming a porous electrolyte having three-dimensionally connected pores. For this reason, when this multilayer electrolyte membrane is used in a solid polymer electrolyte fuel cell, it is possible to suppress an increase in membrane resistance due to a decrease in the water content of the electrolyte membrane even when operated with a non-humidified reaction gas. As a result, high output can be achieved by reducing the resistance overvoltage of the polymer electrolyte fuel cell.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross section of a multilayer electrolyte membrane provided with a porous electrolyte layer having three-dimensionally communicating pores in an intermediate layer of the present invention.

FIG. 2 is a view showing the surface properties of a porous electrolyte layer having three-dimensionally connected pores of the present invention. (Electron micrograph)

FIG. 3 is a schematic diagram showing a unit cell of a porous electrolyte having three-dimensionally connected pores of the present invention.

FIG. 4 is a schematic view showing a cross section of a multilayer electrolyte membrane having a structure in which a nonporous electrolyte layer and a porous electrolyte layer having three-dimensionally communicating pores of the present invention are alternately repeated.

FIG. 5 is a diagram illustrating a process for producing a multilayer electrolyte membrane including a porous electrolyte layer having three-dimensionally communicating pores in an intermediate layer according to the present invention.

FIG. 6 is a diagram showing current-voltage characteristics of a solid polymer electrolyte fuel cell A having a multilayer electrolyte membrane A of the present invention and a solid polymer electrolyte fuel cell B having a known electrolyte membrane B. .

FIG. 7 is a diagram showing a current-internal resistance relationship between a solid polymer electrolyte fuel cell A having a multilayer electrolyte membrane A of the present invention and a solid polymer electrolyte fuel cell B having a known electrolyte membrane B. It is.

[Explanation of symbols]

1 electrolyte portion of porous electrolyte layer having three-dimensionally communicating pores 2 pore portion of porous electrolyte layer having three-dimensionally communicating pores 3 pore portion of porous electrolyte layer having three-dimensionally communicating pores 4 Diameter of electrolyte part of porous electrolyte layer having three-dimensionally communicating pores 5 Porous electrolyte layer having three-dimensionally communicating pores 6 Nonporous electrolyte layer 7 Multilayer electrolyte membrane of the present invention

Claims (4)

[Claims] 1. A multi-layer electrolyte membrane, characterized in that at least one electrolyte layer except for the electrolyte layers on both sides is a porous electrolyte having three-dimensionally communicating pores. 2. An electrolyte membrane having a porous electrolyte layer having three-dimensionally communicating pores formed on at least one surface thereof is arranged on the electrolyte membrane so that the porous electrolyte layer is in contact with the electrolyte membrane, and is integrally formed. A method for producing a multilayer electrolyte membrane, characterized in that at least one electrolyte layer other than the electrolyte layer is a porous electrolyte having three-dimensionally connected pores. 3. A solid polymer electrolyte fuel cell comprising the multilayer electrolyte membrane according to claim 1. 4. The method for operating a solid polymer electrolyte fuel cell according to claim 3, wherein the fuel and / or the oxidizing agent are supplied without humidification.