JP2006244715A - Bipolar membrane and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar membrane on which respective element cells of a flat type fuel cell can be connected in series in a simple way, and to provide the fuel cell using the bipolar membrane which can output the current and the voltage of given values. <P>SOLUTION: The bipolar membrane 10 has a plurality of regions with different properties. The membrane comprises a plurality of first regions 14 having proton conductivity between a first and a second main surfaces of the bipolar membrane 10, and second regions 16 having electron conductivity between the first and the second main surfaces of the bipolar membrane 10. The fuel cell 30 using the bipolar membrane 10 comprises a plurality of first electrodes 32, a plurality of second electrodes 34, a first electron conduction member 38b which connects a first electrode 32b on one side with a second region 16α, and a second electron conduction member 40a which connects a second electrode 34a on another side with the second region 16α. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite membrane and a fuel cell using the composite membrane, and more specifically, a composite membrane capable of connecting cells on a planar fuel cell with a simple structure and a fuel using the composite membrane It relates to batteries.

  A fuel cell is a device that generates electrical energy from hydrogen and oxygen, and can achieve high power generation efficiency. The main feature of the fuel cell is direct power generation that does not go through the process of thermal energy and kinetic energy as in the conventional power generation method, so high power generation efficiency can be expected even on a small scale, and there is little emission of nitrogen compounds, etc. Noise and vibration are also small, so the environmental performance is good. In this way, fuel cells can effectively use the chemical energy of fuels and have environmentally friendly characteristics, so they are expected to be energy supply systems for the 21st century, and are used on a large scale from space use to automobiles and portable devices. It is attracting attention as a promising new power generation system that can be used in various applications from power generation to small-scale power generation, and technological development is in full swing toward practical application.

  Among them, solid polymer fuel cells are characterized by low operating temperature and high power density compared to other types of fuel cells. In particular, as a form of solid polymer fuel cells, direct methanol A fuel cell (Direct Methanol Fuel Cell: DMFC) is attracting attention. In DMFC, an aqueous methanol solution as a fuel is directly supplied to the anode without modification, and electric power is obtained by an electrochemical reaction between the aqueous methanol solution and oxygen, and carbon dioxide is emitted from the anode to the cathode by this electrochemical reaction. The product water is discharged as a reaction product. Aqueous methanol solution has higher energy per unit volume than hydrogen, and is suitable for storage and has a low risk of explosion, so it can be used in automobiles and mobile devices (cell phones, notebook personal computers, PDAs, MP3 players, Use for power sources such as digital cameras or electronic dictionaries (books) is expected.

A fuel cell generally has a stack structure in which the electromotive force is increased in accordance with the purpose. However, a DMFC for a portable device that does not require electromotive force and is required to be as thin as possible has a planar configuration. Taken.
JP 2003-197225 A

  However, it is difficult to connect a planar fuel cell in series as compared to a stag structure. On the other hand, Patent Document 1 adopts a method of penetrating the connection wiring through the solid polymer film, but in this case, a problem that concentrated stress is applied to a portion of the solid polymer film through which the connection wiring is penetrated. was there.

  The present invention has been made in view of the above problems, and is a composite membrane capable of connecting cells on a planar fuel cell with a simple structure, and an arbitrary current value using the composite membrane. It is another object of the present invention to provide a fuel cell that can output a voltage value.

  In order to achieve the above object, the present invention provides a composite membrane having a plurality of regions having different properties, wherein the composite membrane has a proton conductivity between the first main surface and the second main surface of the composite membrane. And a second region having electron conductivity between the first main surface and the second main surface of the composite film. Thereby, when producing a planar fuel cell using this composite membrane, each cell on the planar fuel cell can be connected with a simple structure.

  The invention according to claim 2 is characterized in that, in the composite film according to claim 1, each first region is separated and a third region having an insulating property is provided. The composite membrane according to claim 1 or 2, further comprising an insulating and porous base material, wherein the first region is filled with a proton conductive material, and the second region is a base material. It is filled with an electron conductive material. Thereby, a composite film can be easily produced.

  According to a fourth aspect of the present invention, there is provided a fuel cell, wherein the composite membrane according to any one of the first to third aspects and the first main surface are disposed so as to face the first region. A plurality of first electrodes, a plurality of second electrodes provided on the second main surface and arranged to face the first region, one first electrode and the first main electrode A first electron-conducting member that connects the second region of the surface, a second electrode that connects the other second electrode that does not oppose one of the first electrodes, and a second region of the second main surface. And an electron conducting member. Thereby, each cell on a planar fuel cell can be connected with a simple structure, and an arbitrary current value and voltage value can be output depending on how the cells are arranged or connected.

  Finally, the invention according to claim 5 is the fuel cell according to claim 4, wherein regions other than the first region and the second region of the composite membrane do not transmit fluid other than water. Features. Thereby, cross leak can be reduced and the battery efficiency of a fuel cell can be improved.

  According to the present invention, each cell on a planar fuel cell can be connected with a simple structure, whereby an arbitrary current value and voltage value can be output.

  A method for producing the composite film 10 of the present invention will be described in detail with reference to the drawings.

  The base material 12 of the composite film 10 is a material obtained by processing a fibrous fluororesin into a non-woven fabric having a thickness of about 50 μm (hereinafter referred to as “porous fluorine film”). As shown in FIG. 1, the insulating portion 18 other than the portion that becomes the connecting portion 16 is filled with the insulating material 20, in this embodiment, the fluororesin 20 so as to fill the holes of the porous fluorine film 12. By first filling the base material 12 with the insulating material 20 so as to separate the power generation unit 14 and the connection unit 16 from each other, the proton conductive material 22 and the electron conductive material 24 to be filled in the power generation unit 14 and the connection unit 16 later. Can be prevented from being short-circuited, particularly in the power generation unit 14.

  Next, as shown in FIG. 2, the electronic conductive material 24, in the present embodiment, powdered carbon black (Vulcan XC-72: manufactured by CABOT) 24 is formed in the connection portion 16 with holes in the porous fluorine film 12. Fill to fill. Instead of using connection wiring as in the prior art, by arranging the connection portion 16 that is rectangular on the base material 12, the connection area (cross-sectional area of the electron flow path) can be increased, and each power generation unit 14 The electric resistance between them can be reduced, and the power generation efficiency can be improved. Further, it is possible to prevent the fuel or the oxidant from leaking from the portion through which the connecting wiring of the membrane is passed, or the membrane is cracked and the fuel cell is damaged. Finally, the proton conductive material 22, in this embodiment, a 5 wt% Nafion solution (manufactured by DuPont) 22 is filled in the pores of the porous fluorine film 12 in the power generation unit 14 to evaporate the solvent component.

  The configuration of the planar fuel cell 30 using the composite membrane 10 produced by the above method will be described in detail with reference to FIGS. 3 is a schematic perspective view showing the configuration of the planar fuel cell 30, and FIG. 4 is a cross-sectional view taken along the line A-A 'of FIG.

  4 in FIG. 4 is an anode side electrode. The anode side electrode 32 is made of carbon paper subjected to water repellent treatment as a base material, and Pt-Ru black and 5 wt% Nafion solution (manufactured by DuPont) are provided on one side thereof. A catalyst paste mixed with and is applied. The anode side electrode 32 is not shown in FIG. 3 because it is located on the lower surface of the composite membrane 10, but the surface coated with the catalyst paste is the power generation unit 14 of the composite membrane 10, that is, the portion filled with the proton conducting material 22. Arrange to touch. 34 is a cathode side electrode, and the cathode side electrode 34 is filled with carbon black (Vulcan XC-72: manufactured by CABOT) in a carbon paper subjected to water repellent treatment, and Pt black and 5 wt% are formed on one surface thereof. A catalyst paste mixed with a Nafion solution (manufactured by DuPont) is applied and prepared. In this embodiment, only the cathode side electrode 34 is filled with carbon black. However, when carbon black is filled into the carbon paper of both the anode side electrode 32 and the cathode side electrode 34, the amount of carbon black filled into the carbon paper is When the cathode side is larger than the anode side, the generated water generated from the cathode side is easily discharged, and even in a fuel cell system that does not have an air supply means for forcibly supplying air to the cathode side. Water can be discharged and air can be supplied smoothly. The cathode side electrode 34 is disposed on the upper surface of the composite membrane 10 so that the surface coated with the catalyst paste is in contact with the power generation unit 14 of the composite membrane 10, that is, the portion filled with the proton conducting material 22.

  Current collectors 38 and 40 are provided outside the cell 36 including the anode side electrode 32, the power generation unit 14 of the composite membrane 10, and the cathode side electrode 34. A thin and porous member using a material excellent in electronic conductivity and oxidation resistance is suitable for the current collectors 38 and 40 so that a fuel and an oxidant can be supplied to the cell 36. In the present embodiment, the current collectors 38 and 40 are made of gold mesh. The anode-side current collector 38 covers the anode-side electrode 32 and has one end (left end in FIG. 4) larger than the anode-side electrode 32 so that it can be connected to the connecting portion 16 of the composite film 10. To do. On the other hand, the cathode-side current collector 40 covers the cathode-side electrode 34 and has one end portion (the right end in FIG. 4) larger than the cathode-side electrode 34 and can be connected to the connection portion 16 of the composite film 10. Make dimensions.

  A cathode-side current collector 40a provided in the cell 36a and an anode-side current collector 38b provided in the cell 36b are connected via the connecting portion 16α. Similarly, the cathode-side current collector provided in the cell 36b. Since 40b and the anode side current collector 38c provided in the cell 36c are connected via the connecting portion 16β, the cells 36a, 36b, 36c and 36d are connected in series.

  In the present embodiment, the case where the eight cells 36 are arranged in a 2 × 4 manner and the four cells are connected in series has been described. However, the number or arrangement of the cells 36 in FIG. It is easy for those skilled in the art that the current value and the voltage value output from the planar fuel cell 30 using one composite membrane 10 can be arbitrarily set by changing the arrangement and the shape of the current collectors 38 and 40. I can understand. In addition, the catalyst layer was produced by applying a catalyst paste on an electrode substrate such as carbon paper, but it may be formed on a current collector by omitting the electrode substrate, and further on the composite film. You may take the preparation process which forms and clamps with an electrode base material or a collector. As the catalyst, particles composed of Pt—Ru or Pt (Pt—Ru black or Pt black) are used, but catalyst supporting carbon in which the catalyst is supported on carbon black may be used.

  The present invention does not require so much electromotive force, and can be used not only in a planar DMFC for portable equipment that is required to be as thin as possible, but also in a fuel cell for home use or automobile.

It is a schematic diagram which shows the preparation process of the insulation part of the composite film which concerns on this invention. It is a schematic diagram which shows the manufacturing process of the connection part and power generation part of the composite film which concern on this invention. 1 is a perspective view showing a configuration of a fuel cell according to the present invention. It is sectional drawing which shows the cross-sectional structure of the fuel cell which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Composite film 12 Base material 14 Electric power generation part 16 Connection part 18 Insulation part 20 Insulation substance 22 Proton conduction substance 24 Electron conduction substance 30 Planar fuel cell 32 Anode side electrode 34 Cathode side electrode 36 Cell 38 Anode side collector 40 Cathode side Current collector

Claims (5)

A composite film having a plurality of regions having different properties,
A plurality of first regions having proton conductivity between the first main surface and the second main surface of the composite membrane;
A second region having electron conductivity between the first main surface and the second main surface of the composite film;
A composite membrane characterized by comprising: The composite membrane according to claim 1,
The composite film according to claim 1, further comprising a third region that separates the first regions and has an insulating property. The composite film has an insulating property and a porous base material,
3. The composite membrane according to claim 1, wherein the first region is filled with a proton conductive material in the base material, and the second region is filled with an electron conductive material in the base material. . A composite membrane according to any one of claims 1 to 3,
A plurality of first electrodes provided on the first main surface and arranged to face the first region;
A plurality of second electrodes provided on the second main surface and arranged to face the first region;
A first electron conducting member that connects one of the first electrodes and the second region of the first main surface;
A second electron-conducting member that connects the other second electrode that does not face the one first electrode and the second region of the second main surface;
A fuel cell comprising: 5. The fuel cell according to claim 4, wherein a region other than the first region and the second region of the composite membrane has a property of not transmitting fluid other than water.

Images