JP2003346838A - Direct fuel cell and method of manufacturing the fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mass-production direct fuel cell and a method of manufacturing the fuel cell at an advantageous cost. <P>SOLUTION: In this direct fuel cell, a fuel electrode 10 and an air electrode 12 are formed on the front and rear of a proton conductive part 6 opposite to each other by arranging a plurality of cells adjacent to each other, and the cells are electrically connected to each other. The proton conductive part 6 is formed by providing a proton conductivity thereto by graft-polymerizing monomer with ion-exchange groups after reaction active point is produced with a synthetic resin film 3 partially being irradiated with electron beam or radioactive ray. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct fuel cell for directly generating an electric power by supplying an organic solvent and water to a proton conductor and a method for producing the same, and more particularly to a portable fuel cell such as a portable telephone or a portable information terminal. The present invention relates to a small direct fuel cell optimal for a power supply of an electronic device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, measures against environmental problems and resource problems have become important, and as one of the measures, a direct fuel cell has been developed. In particular, direct methanol fuel cells, which use methanol as fuel and generate electricity directly without reforming or gasification, have a simple structure, are easily reduced in size and weight, and are easily used in mobile phones and portable computers. Promising as a small consumer power supply.

In a direct methanol fuel cell, when an aqueous methanol solution having a concentration of about 3% is supplied to the fuel electrode side, carbon dioxide gas is generated by a cell reaction, and waste fuel and carbon dioxide gas are discharged on the fuel exhaust side. On the other hand, on the air electrode side, when air is supplied as an oxidant, water is generated by a battery reaction and is discharged from the air outlet. When such a direct methanol fuel cell is used as a small power source for a mobile phone or the like, the operating voltage of the direct methanol fuel cell is as low as about 0.5 to 0.4 V per cell. It was necessary to connect these cells in series and boost the voltage.

[0004]

As such a series connection of batteries, a bipolar series connection in which a number of small cells are stacked, and a fuel electrode and an air electrode are formed on the front and back of a single solid electrolyte membrane. A sheet-type series connection in which a plurality of unit cells are formed adjacent to each other and electrically connected to each other has been proposed.

[0005] However, in the bipolar series connection, cells need to be stacked using a separator having a fuel flow path and an air flow path, and it is difficult to reduce the size of the cells. Take it.

On the other hand, in the sheet type series connection,
Since it is necessary to prepare a portion where a unit cell is formed by the solid electrolyte membrane and a portion where the unit cell is not formed, the portion where the unit cell is formed is provided with proton conductivity (proton conductivity) which is an original function of the solid electrolyte membrane. Conductivity of 10 ^-2 S / cm ²
Above, and the portion where no single cell is formed is insulative to proton conductivity (proton conductivity is 10 ⁻³ S / c).
m ² or less) must be so impart a, as an example, U.S. Patent No. 4,673,624, discloses impregnating sulfuric acid to small holes in the cross-section of the insulating polymer, in U.S. Patent No. 5,759,712 is It is disclosed that similar holes are impregnated with a proton conductive substance such as Nafion (registered trademark). Further, in such a series connection, a wiring for connection is provided in the solid electrolyte membrane to make an in-membrane connection in which the front and back surfaces of the solid electrolyte membrane are penetrated, or as shown in FIG. Using a mask 56, a portion where proton conductivity is to be left is masked with a mask 57, this portion is used as a proton conductive portion 6, and other portions are impregnated with an insulating synthetic resin or the like, so that the hydrophilicity in the proton conductor film is reduced. It is necessary to block the conductive region and insulate it with respect to proton conductivity to form the insulating portion 8.

However, as described above, making a minute hole in the cross section of the insulating polymer and impregnating the hole with a proton conductive material is complicated in processing and has a problem in mass production. There was a cost problem. Also,
Although the use of Nafion (registered trademark) as a proton conductive material contributes to a reduction in internal resistance, the impregnation with Nafion (registered trademark) alone implies that the Nafion (registered trademark) impregnated from the perspective of the entire part where the unit cells are formed. Was not enough, and there was a problem in performance. In the case of an intra-membrane connection in which wiring for connection is provided in the solid electrolyte membrane to penetrate both the front and back surfaces of the solid electrolyte membrane, it is necessary to perform wiring so as to penetrate the solid electrolyte membrane, which complicates the manufacturing process. . In the embodiment shown in FIG. 5, a solid polymer electrolyte membrane such as a Nafion (registered trademark) membrane having a thickness of 20 to 200 μm is used as the material film 56 of the proton conductor. There is.

[0008]

The basic object of the present invention is to provide:
A plurality of cells can be formed by facing the fuel electrode and the air electrode on the front and back of the proton conductive portion,
It is an object of the present invention to obtain a method for manufacturing a membrane suitable for mass production and to obtain a direct fuel cell using the membrane.

According to the first aspect of the present invention, a unit cell of a direct fuel cell in which a plurality of unit cells are formed adjacent to each other and the unit cells are electrically connected to each other, has a fuel electrode and an air electrode. In addition, it is characterized in that it is formed so as to be opposed to the front and back sides of the proton conductive portion provided with proton conductivity by graft polymerization of an ion exchange group.

According to the first aspect of the present invention, a plurality of cells are formed by opposing the fuel electrode and the air electrode on the front and back of the proton conductive portion provided with proton conductivity, and each cell is insulated with respect to proton conductivity. Therefore, it is possible to obtain a direct fuel cell in which the leakage current between the cells can be reduced.

According to a second aspect of the present invention, a plurality of cells are formed adjacent to each other with the fuel electrode and the air electrode facing each other on the front and back of the proton conductive portion, and the cells are electrically connected. A method for manufacturing a direct fuel cell, comprising:
After partially irradiating an electron beam or radiation to generate a reactive active site, the proton-conductive portion is formed by graft-polymerizing a monomer having an ion-exchange group to impart proton conductivity, and forming a remaining portion. It is characterized by being insulative with respect to proton conduction.

According to the second aspect of the present invention, the synthetic resin film is continuously irradiated with an electron beam or radiation to generate reactive active points (radicals), which are then immersed in a monomer solution having an ion exchange group. Alternatively, since the graft polymerization is performed by immersion in a precursor monomer solution into which an ion exchange group can be introduced by a substitution reaction or the like, mass production becomes possible by continuously supplying a synthetic resin film. In addition, since a step of providing a minute hole or impregnating the hole with a proton conductive substance can be omitted, the process can be simplified. In addition, since the proton conductivity can be uniformly applied to the unit cell, the internal resistance of the unit cell can be reduced. In addition, since a synthetic resin film is used as the material film without using a solid polymer electrolyte membrane of a proton conductor such as a Nafion (registered trademark) film, it is advantageous in terms of cost.

The synthetic resin film is preferably made of a chemically stable, high mechanical strength polyolefin resin such as polyethylene or polypropylene, or a fluorine resin such as polytetrafluoroethylene.

The monomer solution having an ion exchange group includes a styrene sulfonic acid solution such as a sodium vinyl sulfonate solution having an unsaturated bond and further having a sulfone group for imparting proton conductivity. Examples of the precursor monomer solution into which an exchange group can be introduced include styrene solutions such as styrene, allylbenzene, 2-phenyl-2-butene, vinylnaphthalene, vinylpyridine, vinylbenzoic acid, and vinyl biphenyl which can impart proton conductivity by sulfonation. Can be used.

According to a third aspect of the present invention, in the method for manufacturing a direct fuel cell according to the second aspect, a plurality of unit cells are arranged adjacent to each other by alternately opposing a fuel electrode and an air electrode on the front and back of the proton conductive portion. And each of the cells is electrically connected.

The invention according to claim 4 is the invention according to claim 2 or 3.
In the method for manufacturing a direct fuel cell described above, a plurality of cells formed with the fuel electrode and the air electrode facing each other on the front and back of the proton conductive portion are arranged in a row.

The invention according to claim 5 is the invention according to claim 2 or 3.
The method for manufacturing a direct fuel cell described above is characterized in that a plurality of cells formed by opposing a fuel electrode and an air electrode on the front and back of the proton conductive portion are arranged in a plurality of rows.

According to a sixth aspect of the present invention, in the method for manufacturing a direct fuel cell according to any one of the second to fifth aspects, the synthetic resin film in which a plurality of cells are formed adjacent to each other is rolled. It is characterized by the following.

According to the third to sixth aspects of the present invention, the direct fuel cell manufactured by the manufacturing method of the second aspect has various shapes suitable for a power supply of a portable electronic device such as a mobile phone or a portable information terminal. This can contribute to expanding the use of small direct fuel cells.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

According to the present invention, a plurality of cells are formed by a fuel electrode and an air electrode which are opposed to each other on both front and back surfaces of a proton conductive portion,
Connecting the fuel electrode and the air electrode of two adjacent unit cells in a predetermined direction determined by the arrangement direction of the fuel electrode and the air electrode,
This is a direct fuel cell in which each unit cell is connected in series and a method for manufacturing the same. According to the direct fuel cell of the present invention and the method of manufacturing the same, an MEA (composite of a proton conductive portion and an electrode) in which a plurality of cells are connected in series can be configured.
It is possible to obtain a voltage that can be easily used in a portable information terminal such as a mobile phone or a portable personal computer such as 12V. In addition, in the series connection of the unit cells, the structure of the separator is simplified, unlike the bipolar system. In the following description, a methanol-water system is shown as a fuel for a direct fuel cell, but an organic substance such as ethyl alcohol, isopropyl alcohol, butanol, or dimethyl ether, or a mixture thereof with water or the like can be used. .

That is, FIG. 3 is a sectional view of a direct fuel cell according to the present invention. As shown in FIG. 3, the proton conductive portion 6 of the film 4 having the proton conductive portion 6 having proton conductivity and the insulating portion 8 having insulation with respect to proton conductivity.
A plurality of cells are formed by alternately arranging the fuel electrodes 10 and the air electrodes 12 on both front and back surfaces of the MEA 2 to constitute the MEA 2. The fuel electrode 10 is made of, for example, C (carbon) -Pt-
Nafion (registered trademark) and PTFE as Ru conductive catalyst
(Polytetrafluoroethylene),
In addition, a backing layer such as carbon paper is provided on the fuel flow path side. The air electrode 12 is C (carbon) -Pt-
Instead of Ru conductive catalyst, preferably C (carbon)
It is preferable to use a conductive catalyst of -Pt and to make the same as the fuel electrode 10 in other points, and to similarly provide a backing layer such as carbon paper. In this embodiment, the thickness of the proton conductive portion 6 provided on the membrane 4 is 180 μm,
And the thickness of the air electrode 12 was set to 200 μm.
And the air electrode 12 having the thickness of 1
A catalyst layer of 00 to 500 μm can be provided. In FIG. 3, reference numeral 14 denotes a connection portion between the fuel electrode 10 and the air electrode 12, which may be made of a metal plate, a metal film, carbon paper, a conductive polymer, or the like, as long as it has electron conductivity. . In the case of FIG. 3, the fuel electrode 10 and the air electrode 1 are provided between the fuel electrode 10 and the adjacent air electrode 12 on the left side thereof.
The fuel electrode 10 in a predetermined direction with respect to the
And the air electrode 12 are electronically connected. Also, 16,
Reference numeral 17 denotes an output terminal which is connected to an output terminal provided on a casing of a direct fuel cell (hereinafter sometimes simply referred to as "fuel cell"). As a result, a plurality of cells are MEA2
The upper part is linearly arranged in series, and an electromotive force proportional to the number of cells can be obtained between the output terminals 16 and 17.

FIG. 1 shows an example of a process diagram of a method for manufacturing a direct fuel cell according to the present invention in which a proton conductive portion 6 and an insulating portion 8 are provided on a membrane 4 as shown in FIG. That is,
As shown in FIG. 1, a film 3 is sent from a material roll 1 on which a polyethylene film as a material of a film 4 is wound to an electron beam irradiation device 5 in a batch system. The shutter 57 of the mask plate 58 provided with the shutter 57, which is located between the film 3 and the electron beam irradiation device 5, is opened, and is irradiated with an electron beam so that a predetermined irradiation pattern is formed. A corresponding reaction active site (radical) is generated. After a predetermined irradiation pattern is formed, the shutter 57 is closed, and the film 3 continuing from the shutter 57 is sent from the material roll 1 to the electron beam irradiation device 5 and similarly irradiated with the electron beam. The film 3a that has generated the reaction active points (radicals)
About 30% sodium vinyl sulfonate solution is sent to the graft reaction tank 7 in which benzene sulfonic acid groups are introduced into the reaction active points (radicals). The film 3b into which the benzenesulfonic acid group is introduced is placed in a washing tank 9
And dried in a drying chamber 11 to form a film 3c having a proton conductive portion 6 and an insulating portion 8 as a product roll 1.
It is wound around 3.

As shown in FIG. 2A, a mask plate 58 having a shutter 57 made of heavy metal such as lead and having a shutter 57 is arranged on the film 3 as shown in FIG. A predetermined irradiation pattern is formed. In this way, as shown in FIG.
The proton conductive portion 6 can be formed in a portion not covered by the mask plate 58, and the insulating portion 8 can be formed in a portion covered by the mask plate 58. The fuel electrode 10 and the air electrode 12 are formed on both front and back surfaces through the proton conductive portion 6 thus obtained.
Are opposed to each other to form a series connection of unit cells as shown in FIG. In the graft reaction tank 7, the amount of benzenesulfonic acid groups introduced can be changed depending on the concentration and temperature of the sodium vinylsulfonate solution while the film 3a is immersed in the sodium vinylsulfonate solution. It may be determined based on the proton conductivity and the required stability at the operating temperature at which the conductor film is used.

In the above-described embodiment, the film 3 is fed to the electron beam irradiation device 5 in a batch system to impart proton conductivity by graft polymerization of the ion exchange group, and this is detected, Although the radiation is performed, the method is not limited to such a method. For example, an endless mask plate (not shown) may be sent to the electron beam irradiation device 5 while being superposed on the film 3 so that a predetermined irradiation pattern is formed. In addition, the method of irradiating the film 3 with an electron beam is such that a reactive active point (radical) is formed by irradiating the film 3 with an electron beam in advance, and then the film 3 is brought into contact with the monomer in addition to pre-irradiation with the monomer. Simultaneous irradiation with electron beam irradiation may be performed, and which method may be selected as appropriate.

The irradiation pattern can be defined in various shapes. That is, in the direct fuel cell shown in FIG. 3, although the fuel electrode 10 and the air electrode 12 are alternately opposed to each other on the front and back sides of the proton conductive portion 6, a plurality of unit cells are provided adjacently in a line. On the other hand, in the direct fuel cell shown in FIG. 4, the fuel electrode 10 and the air electrode 12 are alternately opposed to each other on the front and back of a proton conductive portion (not shown), and a plurality of unit cells are provided adjacently in a plurality of rows. I have. That is, FIG.
The air electrode is provided on the back surface facing the fuel electrode 10, and the fuel electrode is provided on the back surface facing the air electrode 12. 26 is the fuel electrode 10
A connecting portion between the fuel electrode 10 and the air electrode 12, a connecting portion 28 with the output terminals 16 and 17, and a metal plate, a metal film, carbon paper, or the like are used for these, and a carbon paper is used for the connecting portion 26. When the air electrode 12 is applied in a predetermined pattern on carbon paper and cut, the fuel electrode 10
And a composite of the air electrode 12 and the connecting portion 26 can be easily obtained. As described above, when the fuel electrode 10 and the air electrode 12 are arranged in two rows, the output terminals 16 and 17 are connected to one end of the MEA 22.
Can be aligned. When the fuel electrode 12b and the air electrode 10b at the ends opposite to the output terminals 16 and 17 are both air electrodes or both fuel electrodes, a direction perpendicular to the longitudinal direction of the MEA 22 in FIG. ), The electrodes have the same polarity, and the formation of the air flow path and the fuel flow path is facilitated. In FIG. 4, two rows of fuel electrodes 10 and air electrodes 12
Are arranged in series, but these may be arranged in parallel.

In the shape of FIG. 3, the aspect ratio (aspect ratio)
It is easy to form an MEA having a large aspect ratio. With the shape of FIG. 4, an MEA having a small aspect ratio can be obtained. Such a shape depends on the outer shape of the direct fuel cell and the mounting structure of the MEA in the cell, and the anode 10 and the cathode 1
It is good to determine the number of columns with 2, but in addition to the illustration, M
A direct fuel cell in which the EA is wound in a roll can also be realized. In this way, a direct fuel cell having a cylindrical outer shape is obtained, and both output terminals can be arranged near the center and the circumference of the cylinder.

In the embodiment described above, the fuel electrode 10 and the air electrode 12 are alternately opposed to each other on the front and back of the proton conductive portion 6 to form a plurality of unit cells adjacent to each other. The air electrode 12 and the air electrode 12 can also be applied to ones having the same polarity on the front and back of the proton conductive portion 6 and adjacent to each other. Further, the present invention can be applied to an arrangement other than a row such as a concentric circle.

[0029]

As described above, in the direct fuel cell according to the embodiment of the present invention, the plurality of cells have proton conductivity provided between the fuel electrode and the air electrode by graft polymerization of ion exchange groups. It is formed by opposing the proton conductive portion on the front and back sides, and since each cell is made to be insulative with respect to proton conductivity, it can contribute to reduction of leak current between the cells and has a membrane having such a proton conductive portion. By using, direct fuel cells having various shapes such as a stick shape, a square plate shape, and a cylindrical shape can be obtained.

In the method for manufacturing a direct fuel cell according to the embodiment of the present invention, the synthetic resin film is partially irradiated with an electron beam or radiation to generate a reaction active site, and then the ion exchange group is formed. The proton conductive portion is formed by graft polymerization of a monomer having the following formula to impart proton conductivity, and the remaining portion is made insulative with respect to proton conductivity. Therefore, a solid electrolyte membrane such as a Nafion (registered trademark) membrane is used. By continuously supplying a synthetic resin film without using it, mass production becomes possible, which is advantageous in terms of cost.

Further, in the method for manufacturing a direct fuel cell according to the embodiment of the present invention, a step of providing minute holes in a synthetic resin film or impregnating the holes with a proton conductive substance can be omitted. Thus, the process can be simplified.

[Brief description of the drawings]

FIG. 1 is a view showing a process chart according to a manufacturing method of the present invention.

FIG. 2 is a diagram showing an example of the manufacturing method of the present invention.

FIG. 3 is a sectional view of a direct fuel cell according to the present invention.

FIG. 4 is a perspective view of another direct fuel cell according to the present invention.

FIG. 5 is a view showing a conventional manufacturing method.

[Explanation of symbols]

1 Material roll 2,22 MEA 3 film 4,24 membrane 5 Electron beam irradiation device 6 Proton conductive part 7 Graft reaction tank 8 insulation 9 Rinse tank 10,10b fuel electrode 11 Drying room 12,12b air electrode 13 Product Roll 14, 26, 28 connection 16, 17 output terminal 58 Mask plate

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shirou Tanso             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation (72) Inventor Kenichi Saito             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation F term (reference) 5H026 AA08 CV06 CX05 EE18

Claims (6)

[Claims] 1. A direct fuel cell comprising a plurality of unit cells formed adjacent to each other and electrically connecting the unit cells, wherein a fuel electrode and an air electrode are grafted with an ion exchange group. A direct fuel cell, wherein a proton conductive portion provided with proton conductivity by polymerization is opposed to the front and back sides thereof. 2. Production of a direct fuel cell in which a plurality of cells are formed adjacent to each other with a fuel electrode and an air electrode facing each other on the front and back sides of a proton conductive portion, and the cells are electrically connected to each other. The method, by partially irradiating a synthetic resin film with an electron beam or radiation to generate reactive active sites, and then graft-polymerizing a monomer having an ion exchange group to impart proton conductivity. A method for manufacturing a direct fuel cell, comprising forming a proton conductive portion and making the remaining portion insulative with respect to proton conductivity. 3. A method of manufacturing a direct fuel cell according to claim 2, wherein a plurality of cells are formed adjacent to each other by alternately opposing a fuel electrode and an air electrode on the front and back of the proton conductive portion. A method for manufacturing a direct fuel cell in which cells are electrically connected. 4. A method for manufacturing a direct fuel cell according to claim 2, wherein a plurality of cells are formed in a single row in which a fuel electrode and an air electrode are opposed to each other on both sides of the proton conductive portion. A method for manufacturing a direct fuel cell, comprising: 5. The method for manufacturing a direct fuel cell according to claim 2, wherein a plurality of cells formed by opposing a fuel electrode and an air electrode on the front and back of the proton conductive portion are arranged in a plurality of rows. A method for manufacturing a direct fuel cell, comprising: 6. The method for producing a direct fuel cell according to claim 2, wherein the synthetic resin film formed adjacent to the plurality of cells is formed into a roll shape. Manufacturing method of a solid fuel cell.