JP2012209105A - Method of manufacturing fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a fuel cell capable of performing ion exchanging in an electrolyte layer efficiently and securing workability during manufacturing of the fuel cell.SOLUTION: There is provided a method of manufacturing a fuel cell 1 comprising a unit cell 16 including: a membrane electrode assembly 2 including an electrolyte layer 5 and an anode electrode 6 and a cathode electrode 7 stacked on the electrolyte layer 5; and an anode-side diffusion layer 8 and a cathode-side diffusion layer 9 stacked on the membrane electrode assembly 2. After the anode-side diffusion layer 8 and the cathode-side diffusion layer 9 are stacked on the membrane electrode assembly 2, the membrane electrode assembly 2 is immersed in alkaline solution. Since the electrolyte layer 5 is supported by the anode-side diffusion layer 8 and the cathode-side diffusion layer 9, favorable workability can be secured. As a result, according to the method of manufacturing the fuel cell 1, ion exchanging can be efficiently performed in the electrolyte layer 5, and workability can be secured during manufacturing the fuel cell 1.

Description

  The present invention relates to a method for manufacturing a fuel cell, and more particularly to a method for manufacturing a fuel cell using liquid fuel.

  Conventionally, as a fuel cell using liquid fuel, for example, a direct methanol fuel cell, a direct dimethyl ether fuel cell, a hydrazine fuel cell, and the like are known.

  Specifically, a fuel cell using a liquid fuel includes a membrane / electrode assembly (MEA) including an electrolyte layer made of a polymer electrolyte membrane, a fuel side electrode and an oxygen side electrode arranged opposite to each other with the electrolyte layer interposed therebetween. And a unit cell comprising a fuel side separator disposed opposite to the fuel side electrode and an oxygen side separator disposed opposite to the oxygen side electrode. In the fuel cell, a plurality of such unit cells are stacked.

  In order to smoothly diffuse the fuel and air and to smoothly discharge the generated water, between the membrane / electrode assembly and the fuel side separator, and between the membrane / electrode assembly and the oxygen side separator. There are gas diffusion layers interposed between them.

  In such a fuel cell, the anion-type polymer electrolyte membrane is ion-exchanged by immersing it in an alkaline solution when the MEA is produced (for example, see Patent Document 1).

International Publication WO2006 / 028190 Pamphlet

  However, when the electrolyte layer is immersed in an alkaline solution, it becomes excessively flexible. For this reason, there is a problem that the workability at the time of manufacturing the unit cell, and hence the workability at the time of manufacturing the fuel cell, is inferior.

  The objective of this invention is providing the manufacturing method of a fuel cell which can ensure workability | operativity at the time of preparation of a fuel cell, while being able to implement ion exchange of an electrolyte layer efficiently.

  In order to achieve the above object, a method for producing a fuel cell of the present invention includes an electrolyte layer made of an anion exchange type polymer electrolyte membrane, a fuel side electrode and an oxygen side electrode laminated so as to sandwich the electrolyte layer. A first step of preparing a membrane / electrode assembly, a second step of laminating a gas diffusion layer so as to come into contact with the membrane / electrode assembly after the first step, and after the second step, A third step of fabricating a unit cell by assembling a separator so as to be in contact with the gas diffusion layer, and a fourth step of fabricating a fuel cell stack by stacking the unit cell after the third step. And a step of immersing the membrane / electrode assembly on which the gas diffusion layer is laminated in an alkaline solution at least after the second step.

  In the fuel cell manufacturing method of the present invention, at least after the gas diffusion layer is laminated on the membrane / electrode assembly, the membrane / electrode assembly on which the gas diffusion layer is laminated is immersed in an alkaline solution. Therefore, even if the electrolyte layer becomes excessively soft due to the immersion of the alkaline solution, the electrolyte layer (membrane / electrode assembly) is supported by the gas diffusion layer, so that good workability can be ensured. .

  As a result, in the fuel cell manufacturing method of the present invention, ion exchange of the electrolyte layer can be efficiently performed, and workability at the time of manufacturing the fuel cell can be ensured. Therefore, the manufacturing cost of the fuel cell can be reduced.

1 is a schematic configuration diagram showing a fuel cell according to an embodiment of the present invention. FIG. 2 is a process diagram illustrating a method of manufacturing the fuel cell shown in FIG. 1, wherein (a) is a process of preparing a membrane / electrode assembly including a fuel side electrode and an oxygen side electrode, and (b) is a membrane / electrode joint. A step of laminating a gas diffusion layer on the body, (c) a step of immersing the membrane / electrode assembly in which the gas diffusion layer is laminated in an alkaline solution, and (d) a fuel supply member and an air supply to the gas diffusion layer The step of laminating the members, (e) shows the unit cell obtained thereby.

1. 1 is a schematic configuration diagram showing a fuel cell according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a method for manufacturing the fuel cell shown in FIG. .

  1 and 2, a fuel cell 1 is an anion exchange type fuel cell to which a liquid fuel component is directly supplied.

  Examples of the fuel component supplied to the fuel cell 1 include methanol, dimethyl ether, hydrazine (including hydrated hydrazine, anhydrous hydrazine, and the like).

  The fuel cell 1 includes a membrane / electrode assembly 2, an anode side diffusion layer 8 as a gas diffusion layer laminated on one side (anode side) of the membrane / electrode assembly 2, and a membrane / electrode junction in the anode side diffusion layer 8. A fuel supply member 3 laminated on the other side of the body 2, a cathode side diffusion layer 9 as a gas diffusion layer laminated on the other side (cathode side) of the membrane-electrode assembly 2, and a cathode side diffusion layer 9 A unit cell 16 (fuel cell) having an air supply member 4 stacked on the other side of the membrane-electrode assembly 2 is formed as a stacked fuel cell stack.

  In FIG. 1, only one of the plurality of unit cells 16 is taken out and disassembled, and the other unit cells 16 are shown in a stacked state. In FIG. 2, only one of the plurality of unit cells 16 is taken out to show the manufacturing method, and the other unit cells 16 are omitted.

  As shown in FIG. 2A, the membrane-electrode assembly 2 is a fuel-side electrode laminated on the electrolyte layer 5 and one surface in the thickness direction of the electrolyte layer 5 (hereinafter simply referred to as one surface). And a cathode electrode 7 as an oxygen side electrode laminated on the other surface in the thickness direction of the electrolyte layer 5 (hereinafter simply referred to as the other surface).

  The electrolyte layer 5 is formed of an anion exchange type polymer electrolyte membrane (hereinafter referred to as an anion exchange membrane) in which an anion component can move.

The anion exchange membrane is not particularly limited as long as it is a medium in which an anion component (for example, hydroxide ion (OH ⁻ )) can move, and for example, an anion exchange group such as a quaternary ammonium group or a pyridinium group can be used. And a solid polymer membrane (anion exchange resin).

  Examples of the solid polymer forming the anion exchange membrane include hydrocarbon-based solid polymer membranes such as polystyrene and modified products thereof.

  The solid polymer forming the anion exchange membrane may have a cross-linked structure in its molecular structure.

  Moreover, an anion exchange membrane is available as a commercial item, for example, Selemion (made by Asahi Glass Co., Ltd.), Neoceptor (made by Astom Corp.), etc. are mentioned.

  Moreover, the film thickness of the electrolyte layer 5 is 10-100 micrometers, for example.

  The anode electrode 6 is formed of, for example, a catalyst carrier that supports a catalyst. Further, the catalyst may be directly formed as the anode electrode 6 without using the catalyst carrier.

  The catalyst is not particularly limited, and examples thereof include platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt)), iron group elements ( Periodic table 8-10 (VIII) group elements such as iron (Fe), cobalt (Co), nickel (Ni)), for example, periodic table such as copper (Cu), silver (Ag), gold (Au) 11th (IB) group element etc. are mentioned. Of these, nickel is preferable. These may be used alone or in combination of two or more.

  Examples of the catalyst carrier include porous substances such as carbon.

  The thickness of the anode electrode 6 is, for example, 10 to 200 μm, preferably 20 to 100 μm.

  The cathode electrode 7 is formed of, for example, a catalyst carrier that supports a catalyst, similarly to the anode electrode 6.

  The cathode electrode 7 has a transition metal supported on, for example, a complex composed of a complex-forming organic compound and / or a conductive polymer and carbon (hereinafter, this complex is referred to as “carbon composite”). It may be formed of a material.

  Examples of the transition metal include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu ), Yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), lanthanum (La) ), Hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and the like. Among these, Preferably, silver and cobalt are mentioned. These may be used alone or in combination of two or more.

  The complex-forming organic compound is an organic compound that forms a complex with the metal atom by coordinating with the metal atom. For example, pyrrole, porphyrin, tetramethoxyphenylporphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin And complex-forming organic compounds such as these or polymers thereof. Among these, Preferably, the polypyrrole which is a polymer of pyrrole is mentioned. These may be used alone or in combination of two or more.

  As the conductive polymer, there is a compound overlapping with the above complex-forming organic compound, for example, polyaniline, polypyrrole, polythiophene, polyacetylene, polyvinylcarbazole, polytriphenylamine, polypyridine, polypyrimidine, polyquinoxaline, polyphenylquinoxaline, Examples include polyisothianaphthene, polypyridinediyl, polythienylene, polyparaphenylene, polyflurane, polyacene, polyfuran, polyazulene, polyindole, and polydiaminoanthraquinone. Among these, Preferably, a polypyrrole is mentioned. These may be used alone or in combination of two or more.

  The thickness of the cathode electrode 7 is, for example, 10 to 300 μm, preferably 20 to 150 μm.

  As the anode side diffusion layer 8, for example, a hard gas permeable material in which carbon paper or carbon cloth or the like is fluorine-treated as necessary can be used. The anode side diffusion layer 8 also functions as a current collector.

  The anode side diffusion layer 8 is available as a commercial product, for example, B-1 Carbon Close Type A No wet profiling (manufactured by BASF), ELAT (registered trademark), LT 1400-W (manufactured by BASF) and the like. Can be mentioned.

  The anode side diffusion layer may be hydrophilized in order to improve the permeability of the liquid fuel.

  The fuel supply member 3 is made of a gas impermeable conductive member, and supplies liquid fuel to the anode electrode 6 via the anode side diffusion layer 8. The fuel supply member 3 is also used as a separator. The fuel supply member 3 is formed with a groove that is recessed from the surface thereof, for example, a distorted shape. The surface of the fuel supply member 3 where the groove is formed is opposed to the anode electrode 6. As a result, a fuel supply path 10 is formed between the one surface of the anode electrode 6 and the other surface (the surface on which the groove is formed) of the fuel supply member 3 so that the fuel component contacts the entire anode electrode 6. (See FIG. 2 (e)).

  A fuel supply port 11 for allowing the fuel component to flow into the fuel supply member 3 is formed in the fuel supply path 10 on one end side (the upper side in the drawing in FIG. 2E), and the fuel component is discharged from the fuel supply member 3. A fuel discharge port 12 is formed on the other end side (the lower side in FIG. 2E).

  Examples of the cathode side diffusion layer 9 include hard gas permeable materials exemplified as the anode side diffusion layer 8. Similarly to the anode side diffusion layer 8, the cathode side diffusion layer 9 also functions as a current collector.

  The air supply member 4 is made of a gas impermeable conductive member, and supplies air to the cathode electrode 7 via the cathode side diffusion layer 9. The air supply member 4 is also used as a separator. The air supply member 4 is formed with a groove having a concave shape, for example, a twisted shape. The air supply member 4 has a grooved surface facing the cathode electrode 7. As a result, an air supply path 13 is formed between the other surface of the cathode electrode 7 and one surface of the air supply member 4 (the surface on which the groove is formed) for bringing air into contact with the entire cathode electrode 7. (See FIG. 2 (e)).

In the air supply path 13, an air supply port 14 for allowing air to flow into the air supply member 4 is formed on one end side (the upper side in the drawing in FIG. 2 (e)), and the air is discharged from the air supply member 4. The air discharge port 15 is formed on the other end side (the lower side of the drawing in FIG. 2E).
(1-2) Power Generation by Fuel Cell In the fuel cell 1 described above, the fuel component is supplied from the fuel supply port 11 to the anode electrode 6. On the other hand, air is supplied from the air supply port 14 to the cathode electrode 7.

  On the anode side, the liquid fuel passes through the fuel supply path 10 while being in contact with the anode electrode 6. On the other hand, on the cathode side, air passes through the air supply path 13 while being in contact with the cathode electrode 7.

Then, an electrochemical reaction occurs in each electrode (the anode electrode 6 and the cathode electrode 7), and an electromotive force is generated. For example, when the liquid fuel is methanol, the following formulas (1) to (3) are obtained.
(1) CH ₃ OH + 6OH ⁻ → CO ₂ + 5H ₂ O + 6e ⁻ (reaction at anode electrode 6)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at cathode electrode 7)
(3) CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O (reaction in the entire fuel cell 1)
That is, at the anode electrode 6 supplied with methanol, methanol (CH ₃ OH) reacts with hydroxide ions (OH ⁻ ) generated by the reaction at the cathode electrode 7 to react with carbon dioxide (CO ₂ ) and water. (H ₂ O) is generated and electrons (e ⁻ ) are generated (see the above formula (1)).

Electrons (e ⁻ ) generated at the anode electrode 6 reach the cathode electrode 7 via an external circuit (not shown). That is, electrons (e ⁻ ) passing through the external circuit become current.

On the other hand, in the cathode electrode 7, electrons (e ⁻ ), water (H ₂ O) generated by external supply or reaction in the fuel cell 1, and oxygen (O ₂ ) in the air flowing through the air supply path 13. React with each other to produce hydroxide ions (OH ⁻ ) (see the above formula (2)).

And the produced | generated hydroxide ion (OH < ^- >) passes the electrolyte layer 5, reaches the anode electrode 6, and reaction (refer said Formula (1)) similar to the above arises.

  When the electrochemical reaction at the anode electrode 6 and the cathode electrode 7 continuously occurs, the reaction represented by the above formula (3) occurs in the fuel cell 1 as a whole, and an electromotive force is generated in the fuel cell 1. To do. That is, the fuel cell 1 consumes the fuel component to generate power.

For example, when the fuel component is hydrazine, the electrochemical reaction is represented by the following formulas (4) to (6).
(4) N ₂ H ₄ + 4OH ⁻ → N ₂ + 4H ₂ O + 4e ⁻ (reaction at anode electrode 6)
(5) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at cathode electrode 7)
(6) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O (reaction in the entire fuel cell 1)
2. 2. Fuel Cell Manufacturing Method Next, a fuel cell manufacturing method of the present embodiment will be described with reference to FIG.

  First, in this method, as shown in FIG. 2A, a membrane / electrode assembly 2 including an electrolyte layer 5 and an anode electrode 6 and a cathode electrode 7 stacked so as to sandwich the electrolyte layer 5 is prepared. (First step).

  In order to form the anode electrode 6 and the cathode electrode 7, first, a catalyst ink for the anode electrode 6 and a catalyst ink for the cathode electrode 7 are prepared.

  In preparation of the catalyst ink for the anode electrode 6, first, 5 to 50 parts by mass of an electrolyte resin (ionomer) and 100 to 10,000 parts by mass of a solvent are added to 100 parts by mass of the catalyst described above and stirred. Then, a catalyst ink for the anode electrode 6 is prepared.

  Examples of the electrolyte resin (ionomer) include the same anion conductive resin as that of the electrolyte layer 5. As the electrolyte resin (ionomer), a resin previously dissolved in a known solvent such as, for example, a lower alcohol such as methanol, ethanol or propanol, or water may be used.

  The catalyst ink for the cathode electrode 7 is prepared in the same manner as the catalyst ink for the anode electrode 6, for example.

  The catalyst ink for the anode electrode 6 and the catalyst ink for the cathode electrode 7 may be prepared, for example, by forming a carbon composite by a known method and then supporting a transition metal on the carbon composite.

  Next, for example, a catalyst ink for the anode electrode 6 is applied to one surface of the electrolyte layer 5 by a known coating method such as a spray method, a die coater method, or an ink jet method, and the cathode electrode 7 is applied to the other surface of the electrolyte layer 5. The catalyst ink is applied, dried at, for example, 10 to 40 ° C., and pressurized if necessary. Thereby, the membrane / electrode assembly 2 in which the anode electrode 6 and the cathode electrode 7 are laminated on the electrolyte layer 5 is formed.

  Next, in this method, as shown in FIG. 2B, the anode side diffusion layer 8 and the cathode side diffusion layer 9 are laminated so as to be in contact with the membrane-electrode assembly 2 (second step).

  In order to laminate the anode side diffusion layer 8 and the cathode side diffusion layer 9 on the membrane / electrode assembly 2, the anode side diffusion layer 8 covers the surface of the anode electrode 6 on both sides of the membrane / electrode assembly 2, and the cathode The anode side diffusion layer 8 and the cathode side diffusion layer 9 are arranged so that the side diffusion layer 9 covers the surface of the cathode electrode 7 and, if necessary, fixed with a gasket (not shown) or the like.

  In order to laminate the anode side diffusion layer 8 and the cathode side diffusion layer 9 on the membrane / electrode assembly 2, the anode side diffusion layer 8 covers the surface of the anode electrode 6 on both sides of the electrolyte layer 5, and the cathode side The anode-side diffusion layer 8 and the cathode-side diffusion layer 9 are arranged so that the diffusion layer 9 covers the surface of the cathode electrode 7, for example, 0.5 to 30 MPa from both sides in the thickness direction of the membrane-electrode assembly 2. The pressure (compression molding) may be preferably performed at a pressure of 1 to 20 MPa.

  Next, in this method, as shown in FIG. 2C, the membrane / electrode assembly 2 in which the anode side diffusion layer 8 and the cathode side diffusion layer 9 are laminated is immersed in an alkaline solution (immersion step).

  As an alkaline solution, for example, water is used as a solvent, 1 to 20% by weight, preferably a potassium hydroxide aqueous solution containing 5 to 15% by weight of potassium hydroxide as a solute, or water as a solvent and 1 to 20% by weight. Preferably, an aqueous sodium hydroxide solution containing 5 to 15% by weight of sodium hydroxide as a solute can be used.

  Further, the immersion conditions are not particularly limited, but the liquid temperature of the alkaline solution is, for example, 10 to 80 ° C., preferably 20 to 40 ° C., and the immersion time is, for example, 1 minute to 48 hours, preferably 12 to 36 hours.

  The membrane / electrode assembly 2 in which the anode side diffusion layer 8 and the cathode side diffusion layer 9 are laminated is subjected to an alkaline solution under a pressure condition of 0.01 to 0.1 MPa, preferably 0.03 to 0.05 kPa. It can also be impregnated under pressure.

  Next, in this method, as shown in FIG. 2 (d), the fuel supply member 3 is assembled to the membrane / electrode assembly 2 so as to be in contact with the anode side diffusion layer 8 and is in contact with the cathode side diffusion layer 9. Thus, the air supply member 4 is assembled to the membrane / electrode assembly 2 (third step).

  In assembling the fuel supply member 3 and the air supply member 4, for example, the fuel supply member 3 covers the anode side diffusion layer 8 on both sides of the membrane-electrode assembly 2, and the air supply member 4 is the cathode side diffusion layer 9. The fuel supply member 3 and the air supply member 4 are arranged so as to cover them, and are fixed so as to sandwich the membrane-electrode assembly 2.

  In the case where the fuel supply member 4 and the air supply member 5 are integrally formed and form a single separator that divides each of the stacked unit cells 16, for example, it contacts the anode side diffusion layer 8. The fuel supply member 3 side of the separator is assembled to the membrane / electrode assembly 2, and the air supply member 4 side of the separator is assembled to the membrane / electrode assembly 2 so as to contact the cathode side diffusion layer 9. wear.

  Thereby, as shown in FIG.2 (e), the unit cell 16 can be produced.

Next, in this method, a plurality of unit cells 16 are stacked to produce a fuel cell stack (fuel cell 1) (fourth step) (see FIG. 1). The method for stacking the unit cells 16 is not particularly limited and conforms to a known method.
3. Effects In this method of manufacturing the fuel cell 1, after the anode-side diffusion layer 8 and the cathode-side diffusion layer 9 are laminated on the membrane-electrode assembly 2, the membrane-electrode assembly 2 is immersed in an alkaline solution. Therefore, even if the electrolyte layer 5 becomes excessively soft due to the immersion of the alkaline solution, the electrolyte layer 5 (membrane / electrode assembly 2) is supported by the anode side diffusion layer 8 and the cathode side diffusion layer 9. Good workability can be ensured.

  Specifically, for example, what is required for the conventional dipping process for about 3 days can be shortened to about 1 day. That is, the time required for the dipping process can be reduced to about 1/3 of the conventional time.

  As a result, according to such a manufacturing method of the fuel cell 1, ion exchange of the electrolyte layer 5 can be performed efficiently, and workability at the time of manufacturing the fuel cell 1 can be ensured. Therefore, the manufacturing cost of the fuel cell can be reduced.

  In the above embodiment, the anode-side diffusion layer 8 and the cathode-side diffusion layer 9 are also immersed in the alkaline solution together with the membrane / electrode assembly 2. Therefore, the affinity of the anode side diffusion layer 8 to the liquid fuel can be ensured from the initial operation, and excellent fuel diffusibility can be ensured.

  In the above-described embodiment, the anode-side diffusion layer 8 and the cathode-side diffusion layer 9 are laminated on the membrane-electrode assembly 2 and then the membrane-electrode assembly 2 is immersed in an alkaline solution. As shown in e), after the step of assembling the fuel supply member 3 to the anode side diffusion layer 8 and the air supply member 4 to the cathode side diffusion layer 9, the fuel supply member 3 and the air supply member 4 are assembled. The attached membrane / electrode assembly 2, that is, the unit cell 16, may be immersed in an alkaline solution. In such a method, as in the above embodiment, ion exchange of the electrolyte layer 5 can be performed efficiently, and workability at the time of manufacturing the fuel cell 1 can be ensured.

  Further, as shown in FIG. 1, after the step of stacking a plurality of unit cells 16 to produce a fuel cell stack, the fuel cell stack may be immersed in an alkaline solution. In such a method, as in the above embodiment, ion exchange of the electrolyte layer 5 can be performed efficiently, and workability at the time of manufacturing the fuel cell 1 can be ensured.

  In addition, the anode-side diffusion layer 8 and / or the cathode-side diffusion layer 9 may be formed with an operation grip 20 (see the dotted line in FIG. 1) using a gasket or a seal rubber. Thereby, the handleability of the membrane-electrode assembly 2 in which the anode side diffusion layer 8 and the cathode side diffusion layer 9 are laminated can be further improved.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Membrane / electrode assembly 3 Fuel supply member 4 Air supply member 5 Electrolyte layer 6 Anode electrode 7 Cathode electrode 8 Anode side diffusion layer 9 Cathode side diffusion layer 16 Unit cell

Claims (1)

A first step of preparing a membrane / electrode assembly including an electrolyte layer composed of an anion exchange type polymer electrolyte membrane, a fuel side electrode and an oxygen side electrode laminated so as to sandwich the electrolyte layer;
After the first step, a second step of laminating a gas diffusion layer so as to come into contact with the membrane-electrode assembly,
After the second step, a third step of fabricating a unit cell by assembling a separator so as to be in contact with the gas diffusion layer;
After the third step, a fourth step of fabricating a fuel cell stack by stacking the unit cells;
And a step of immersing the membrane-electrode assembly on which the gas diffusion layer is laminated in an alkaline solution after at least the second step.

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