JP2005044789A - Porous fuel cell separator, manufacturing method for porous fuel cell separator and solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous fuel cell separator wherein water permeating and staying in a pore is hard to freeze even when exposed to the cold temperatures below a freezing point, and capable of suppressing degradation of generation efficiency in restarting. <P>SOLUTION: This porous fuel cell separator wherein a groove part for gas circulation is formed in a surface of a porous plate comprising a conductive material and a resin comprises a far-infrared radiating material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a porous fuel cell separator, a method for producing a porous fuel cell separator, and a polymer electrolyte fuel cell.

  A fuel cell is a device that directly generates electricity by supplying water, such as hydrogen, and oxygen in the atmosphere to the cell and reacting them electrochemically to produce water, enabling high energy conversion and environmental friendliness. Therefore, development is progressing for various applications such as small-scale regional power generation, household power generation, simple power supply in campsites, mobile power supplies for automobiles, small ships, etc., artificial satellites, and space development power supplies. It has been.

  Such a fuel cell, in particular, a polymer electrolyte fuel cell, includes two separators having convex and concave portions for forming a plurality of passages for hydrogen, oxygen, etc. on both side surfaces of the plate-like body, and between these separators. Consists of a battery body (module) in which dozens or more of unit cells (unit cells) interposing a solid polymer electrolyte membrane and a gas diffusion electrode (carbon paper) in parallel (this is called a stack) Has been.

  In this case, the fuel cell separator has conductivity for each unit cell, ensures passage of fuel and air (oxygen) supplied to the unit cell, and serves as a separation boundary film. Various properties such as high gas impermeability, (electro) chemical stability and hydrophilicity are required.

In recent years, porous separators for fuel cells have been developed and started to be used (Patent Document 1: Austrian Patent No. 389,020, Patent Document 2: US Pat. No. 6,197,442). ).
In a fuel cell using this porous separator, a phenomenon hardly seen in a dense separator occurs in which water generated during power generation penetrates into the pores of the separator and remains in the separator as it is after stopping.
Therefore, when a fuel cell used in a cold district or the like is exposed to a low-temperature environment such as below freezing after use, there is a problem that it penetrates into the pores and the remaining water freezes to close the pores. Further, due to the blockage of the pores, there is a problem that water generated by power generation is accumulated inside the battery at the time of restart, and power generation efficiency is remarkably lowered.

Austrian Patent No. 389,020 US Pat. No. 6,197,442

  The present invention has been made in view of the above circumstances, and even when exposed to a low temperature such as below freezing point, it penetrates into the pores and the remaining water is difficult to freeze, and suppresses a decrease in power generation efficiency at restart. It is an object of the present invention to provide a porous fuel cell separator, a method for producing the same, and a polymer electrolyte fuel cell.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have made the porous fuel cell separator contain a far-infrared radiation material so that the fuel cell equipped with this separator can be cooled to a low temperature such as below freezing point. Even when exposed, it was found that it could penetrate into the pores and prevent the remaining water from freezing, and suppress the decrease in power generation efficiency at the time of restart, and thus the present invention was completed.

That is, the present invention
1. A porous fuel cell separator in which a groove for gas flow is formed on at least one surface of a porous plate comprising a conductive material and a resin, the porous fuel cell separator comprising a far-infrared radiation material Quality fuel cell separator,
2. A porous fuel cell separator in which a groove for gas flow is formed on at least one surface of a calcined plate obtained by calcining a porous plate comprising a conductive material and a resin, and a far-infrared radiation material A porous fuel cell separator, comprising:
3. 1 or 2 porous fuel cell separators, wherein the far infrared radiation material is present on at least the pore inner surface of the porous fuel cell separator;
4). A method for producing a porous fuel cell separator, characterized by forming a raw material composition obtained by mixing a conductive material, a resin and a far-infrared radiation material into a mold, and then molding the raw material composition,
5. A raw material composition obtained by mixing a conductive material and a resin is put into a mold, and then the raw material composition is molded to produce a porous plate, and the resulting porous plate is coated with a paint containing a far-infrared radiation material. A method for producing a porous fuel cell separator, characterized by being impregnated,
6). A solid polymer fuel cell comprising a large number of unit cells arranged in parallel with a pair of electrodes sandwiching a solid polymer membrane and a pair of separators forming a gas supply / discharge channel sandwiching the electrodes, A solid polymer fuel cell is provided, wherein a part or all of the separator is any one of 1 to 3 porous fuel cell separators.

  According to the porous fuel cell separator of the present invention, even when exposed to a low temperature such as below freezing, it can penetrate into the pores and prevent freezing of the remaining water, and suppress a decrease in power generation efficiency at restart. be able to.

Hereinafter, the present invention will be described in more detail.
The porous fuel cell separator according to the present invention has a gas distribution groove formed on at least one surface of a porous plate comprising a conductive material and a resin, or a fired plate obtained by firing the porous plate. A porous fuel cell separator comprising a far-infrared radiation material.
In the present invention, the conductive material constituting the porous plate is not particularly limited, and a conductive material usually used for a porous fuel cell separator can be used. For example, natural graphite, artificial graphite, expanded graphite, Carbonaceous materials such as carbon black, highly conductive carbon black (Ketjen Black, manufactured by Lion Corporation), and coke can be used.

  Also, as the resin, it can be appropriately selected from thermosetting resins, thermoplastic resins and the like that are usually used for porous fuel cell separators, for example, phenol resins, epoxy resins, unsaturated polyester resins, acrylic resins, melamine resins, Polyamide resin, polyimide resin, polyamideimide resin, polyetherimide resin, phenoxy resin, or the like can be used. In addition, you may heat-process these resins as needed.

The far-infrared radiation material in the present invention is not particularly limited as long as it has a far-infrared radiation action. For example, titanium oxide, silica, alumina, silicon carbide, silicon nitride, zirconia, iron oxide, oxidation Manganese, aluminum titanate, and a mixture thereof may be mentioned, and it is particularly preferable to use silica, alumina, silicon carbide, and a mixture thereof. Examples of commercially available far-infrared radiation materials include Seragit (manufactured by OK Trading Co., Ltd.), Seraheat (manufactured by Supply Control Co., Ltd.), and the like.
The content of the far-infrared radiation material in the separator is not particularly limited. However, the far-infrared radiation is sufficiently radiated to effectively prevent freezing of water remaining in the separator, and thus the entire separator. The content is preferably 0.1 to 20% by mass, particularly 1 to 10% by mass.

  The far-infrared radiation material only needs to be contained in the separator, and the containing site in the separator is not particularly limited, but is preferably present on at least the pore inner surface of the porous fuel cell separator. Thus, since the far-infrared radiation material is present on the inner surface of the pores, the far-infrared radiation material is present in the vicinity of the water remaining in the pores, so that the antifreezing effect can be sufficiently exhibited. .

In the present invention, the porosity of the porous plate is preferably 1 to 50%, particularly preferably 10 to 30%. Here, if the porosity is less than 1%, the absorbability of water generated during power generation is reduced, and as a result, there is a possibility of closing the groove serving as the gas flow path. If the porosity exceeds 50%, the shape of the groove is precise. In addition, there is a risk that the strength may be reduced.
Moreover, it is preferable that the pore diameter of a porous plate is 0.01-50 micrometers, especially 0.1-10 micrometers. Here, when the pore diameter is less than 0.01 μm, the permeability of the generated water is lowered, and as a result, there is a possibility that the groove portion serving as a gas flow path may be blocked. When the pore diameter exceeds 50 μm, the shape of the groove portion is precisely set. It cannot be formed and the strength may be reduced.

  In addition to the conductive material, resin and infrared radiation material, the porous fuel cell separator of the present invention includes various fibers such as organic fibers such as carbon fibers and cellulose fibers, inorganic fibers, alumina, silica and silicon carbide. Other additives such as inorganic fillers may be included.

The method for producing the porous fuel cell separator containing the far-infrared radiation material described above is not particularly limited as long as the method can contain the far-infrared radiation material in the separator. It is preferable to use these methods.
As a first method, a raw material composition obtained by mixing the above-described conductive material, resin, and far infrared radiation material is put into a mold, and then this raw material composition is molded to provide a separator containing the far infrared radiation material. Is what you get.

In this case, the blending ratio of the conductive material, the resin and the far infrared radiation material is not particularly limited. For example, the total composition is 100 parts by mass, and the conductive material is 50 to 99 parts by mass, particularly 65 to 90 parts by mass. What is necessary is just to mix | blend 1-50 mass parts of resin, especially 10-20 mass parts, 0.1-20 mass parts of far-infrared radiation materials, especially 1-10 mass parts.
For the purpose of improving the strength, the raw material composition contains various fibers such as organic fibers such as carbon fibers and cellulose fibers, inorganic fibers, and inorganic fillers such as alumina, silica, and silicon carbide. 1 to 20 parts by mass, preferably 1 to 10 parts by mass.

  The raw material composition is preferably used after being compounded. There is no restriction | limiting in particular as a compounding method, The thing stirred, granulated, and dried by the well-known method can be used. In particular, it is preferable to use one having a uniform particle size by sieving so as not to agglomerate, and the particle size is preferably an average particle size of 60 μm or more, although it depends on the particle size of the conductive material used. The distribution is preferably 10 μm to 2.0 mm, preferably 30 μm to 1.5 mm, particularly 50 μm to 1.0 mm.

The method of molding the raw material composition with a mold is not particularly limited as long as it is a molding method capable of producing a porous plate, and compression molding, injection molding, extrusion molding, sheet molding and the like can be employed. It is preferable to employ compression molding because uniform pore formation is possible.
The pressure at the time of compression molding is not particularly limited, and may be appropriately set according to the required porous plate (fuel cell separator), but is usually 0.098 to 19.6 MPa, preferably 0.8. 98 to 14.7 MPa, more preferably 1.96 to 9.8 MPa. Here, if the molding pressure is less than 0.098 MPa, there is a possibility that the strength sufficient to maintain the shape of the porous plate may not be obtained. On the other hand, if the molding pressure exceeds 19.6 MPa, the molding machine and the mold may be distorted. It may occur, and the surface and dimensional accuracy of the porous plate may be lowered, and the pores of the porous plate may be filled.

  As a second method, a raw material composition obtained by mixing the above-described conductive material and resin is put into a mold, and then the raw material composition is molded to produce a porous plate. A separator containing a far-infrared radiation material is obtained by impregnating a paint containing a far-infrared radiation material. Thus, by impregnating the paint containing the far-infrared radiation material, the far-infrared radiation material can be efficiently present in the vicinity of the pore surface of the porous plate.

  Moreover, when using the coating material containing this far-infrared radiation material, after shape | molding a porous plate, this can be once baked and the method of impregnating the said coating material to the porous plate after baking can also be employ | adopted. When firing, the temperature and time are not particularly limited, but the firing is usually performed at 1200 to 1500 ° C., particularly 1200 to 1400 ° C., for 12 to 24 hours, particularly 12 to 18 hours.

  In the case of the second method, the blending ratio of the conductive material and the resin is not particularly limited. For example, the total composition is 100 parts by mass, and the conductive material is 50 to 99 parts by mass, particularly 65 to 90 parts by mass, the resin. What is necessary is just to mix | blend by 1-50 mass parts, especially 5-20 mass parts. Also in this case, it is preferable to use the raw material composition after compounding, as in the above-described method. Moreover, the said fiber and an inorganic filler can also be mix | blended with the above-mentioned ratio in a raw material composition as needed. Furthermore, the method for forming the raw material composition is the same as the first method, and it is preferable to use compression molding in the second method.

As a paint containing a far-infrared radiation material, 20-99 mass parts of the far-infrared radiation material mentioned above, especially 40-70 mass parts, and 1-80 mass parts of thermosetting resins, especially 30-60 mass parts are arbitrary. A paint obtained by mixing by the above method can be used.
The amount of impregnation of the paint into the porous plate is such that the far-infrared radiation material is 0.01 to 10 parts by mass, particularly 0.05 to 5 parts by mass with respect to the raw material composition comprising the conductive material and the resin. It is preferable that the amount is as follows. As described above, when the impregnation method is used, the far-infrared radiation material is likely to be present in the vicinity of the pore surface of the porous plate. Therefore, the amount of the far-infrared radiation material used is reduced as compared with the first method. In addition, the antifreezing effect can be efficiently exhibited.
The impregnation method of the paint is not particularly limited, and can be performed, for example, under a reduced pressure of -0.01 to -0.1 MPa.

In the first and second methods, the gas flow groove may be formed at the same time as the mold clamping using a mold corresponding to the groove shape. May be. Moreover, a groove part may be formed only in one surface of a porous plate (separator), and may be formed in both surfaces.
Furthermore, the mold to be used is not particularly limited, and can be appropriately selected from known molds generally used for molding a separator according to the shape of the groove portion of the porous separator. .

  Moreover, the porous fuel cell separator obtained by each manufacturing method described above can be subjected to a hydrophilic treatment as necessary. In this hydrophilic treatment, the fuel cell separator is treated with a known hydrophilic substance using an appropriate method such as an impregnation method, a spray method, or a dip method. Among these treatment methods, it is preferable to use an impregnation method from the viewpoint of further infiltrating a hydrophilic substance into the pores of the porous fuel cell separator, and in this case, a reduced pressure of -0.06 to -0.1 MPa is used. It is preferable to perform the impregnation treatment below.

  The hydrophilic substance that can be used for the hydrophilic treatment is not particularly limited, but Denacol EX-1310, Denacol EX-1610, Denacol EX861 (manufactured by Nagase ChemteX Corporation), Dick Fine EN-0270 ( Dainippon Ink Chemical Co., Ltd.), SR-8EG, SR-4PG (Sakamoto Yakuhin Kogyo Co., Ltd.) and the like can be suitably used. What is necessary is just to melt | dissolve -99 mass% and use it as aqueous solution.

  As described above, since the porous fuel cell separator of the present invention contains a far-infrared radiation material, the far-infrared radiation radiated from this material prevents water remaining in the pores from freezing. be able to. Therefore, when the fuel cell equipped with the fuel cell separator of the present invention is restarted at a low temperature such as below freezing point, it is possible to prevent a decrease in power generation efficiency seen in the past.

  A polymer electrolyte fuel cell according to the present invention comprises a large number of unit cells each composed of a pair of electrodes sandwiching a polymer electrolyte membrane and a pair of separators forming a gas supply / discharge channel sandwiching the electrodes. In the solid polymer fuel cell provided, a porous fuel cell separator including the above-described far-infrared radiation material is used as a part or all of the separator.

  Here, the part or all of the separator specifically means 50% or more of the total separator in the fuel cell, preferably 50 to 100%, more preferably 70 to 100%, and still more preferably 80 to 100%. Is preferably the fuel cell separator of the present invention. If the ratio of the fuel cell separator of the present invention to the total separator in the fuel cell is too small, the water remaining in the pores of the separator not containing the far-infrared radiation material is frozen, and the battery output is reduced at the time of restart. There is a fear. In addition, as a separator other than the fuel cell separator of the present invention, a separator generally used for a fuel cell can be used.

  In addition, as the solid polymer electrolyte membrane, those generally used for solid polymer fuel cells can be used. For example, polytrifluorostyrene sulfonic acid, perfluorocarbon sulfonic acid (trade name: Nafion), which is a proton conductive ion exchange membrane formed of a fluorine-based resin, can be used. On the surface of this electrolyte membrane, carbon powder carrying platinum or an alloy composed of platinum and other metals as a catalyst is prepared, and this carbon powder is mixed with a lower fatty acid alcohol containing perfluorocarbon sulfonic acid and water. A paste dispersed in an organic solvent such as a solution (Nafion 117 solution) is applied.

The pair of electrodes sandwiching the solid polymer electrolyte membrane can be formed by, for example, carbon paper, carbon felt, carbon cloth woven with yarn made of carbon fiber, or the like.
These electrolyte membrane and electrode are integrated by interposing an electrolyte membrane between a pair of electrodes and thermocompression bonding at 120 to 130 ° C.
Note that the electrolyte membrane and the pair of electrodes can be joined and integrated using an adhesive.
The unit membrane is obtained by attaching the electrolyte membrane and the electrode integrated in this way so as to form a flow path capable of supplying and discharging the fuel gas between the pair of separators. In this case, a method of applying an adhesive to the portion (rib) in contact with the electrode of the separator can be employed.

  Since the polymer electrolyte fuel cell of the present invention uses the porous fuel cell separator of the present invention as a part (preferably 50% or more) or all of all separators in the fuel cell, water generated during power generation is used. Even if it is exposed to below freezing while remaining in the pores of the separator, it is difficult for the residual water to freeze, and it is possible to prevent the power generation efficiency from being reduced at the time of restart. In particular, automobiles and small vessels used in cold regions, etc. It is suitable as a power source for movement.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to a following example.
In the following description, the average particle size is a value measured by a particle size measuring device (manufactured by Microtrak).

[Example 1]
Artificial graphite as the conductive material, phenol resin as the resin, and far-infrared radiation material (far-infrared radiation ceramics: Ceraheat, average particle size 80 μm, manufactured by Supply Control Co., Ltd.) in the proportions shown in Table 1 and mixed Further, after a raw material composition having a particle size distribution of 10 to 1000 μm (average particle size of 500 μm) obtained by granulation, drying and sieving (compounding) is introduced into a mold having grooves, a surface pressure of 10 MPa, 170 The porous fuel cell separator having a concavo-convex groove was molded by compression molding at 5 ° C. for 5 minutes.

[Example 2]
Artificial graphite as a conductive material and phenol resin as a resin are mixed and stirred in the proportions shown in Table 1, and further granulated, dried, and sieved (compounded) to a particle size distribution of 10 to 1000 μm (average particle size of 500 μm) ) Was injected into a mold having grooves formed thereon, and then compression molded at a surface pressure of 10 MPa and 170 ° C. for 5 minutes to form a porous plate having uneven grooves.
Subsequently, 7 parts by mass of artificial graphite, 6 parts by mass of phenol resin, 7 parts by mass of far-infrared radiation material (far-infrared radiation ceramics: Ceraheat, average particle size 0.3 μm, manufactured by Supply Control Co., Ltd.) and 80 parts by mass of water Was added to a ball mill and mixed for 24 hours to prepare a paint.
This paint was impregnated into the previously prepared porous plate under a reduced pressure of −0.09 MPa, and then heated at 150 ° C. for 1 hour to cure the resin to obtain a fuel cell separator.

[Comparative Example 1]
A fuel cell separator was obtained in the same manner as in Example 1 except that no far-infrared radiation material was used.

  The fuel cell separators obtained in each Example and Comparative Example were measured and evaluated for the porosity, bending strength, bending elastic modulus, specific resistance and freezing point of water, and the results are shown in Table 2.

In Table 2, each evaluation item was measured and evaluated as follows.
[1] Porosity Measured by mercury porosimetry.
[2] Flexural strength, flexural modulus Measured by a method based on ASTM D790.
[3] Resistivity Measured by a four-probe method described in JIS H-0602.
[4] Freezing point of water A sample cut into a 3 mm square cube was impregnated with ion-exchanged water, and then measured by using DSC and cooling at 5 ° C./min in a nitrogen atmosphere.

As shown in Table 2, since the fuel cell separators obtained in Examples 1 and 2 contain a far-infrared radiation material, freezing of water that has permeated into the separator as in the separator of Comparative Example 1 is prevented. It turns out that it can prevent. Moreover, it turns out that intensity | strength and electroconductivity are also favorable.

Claims (6)

A porous fuel cell separator in which a groove for gas circulation is formed on at least one surface of a porous plate comprising a conductive material and a resin,
A porous fuel cell separator comprising a far-infrared radiation material. A porous fuel cell separator in which a groove for gas circulation is formed on at least one surface of a fired plate formed by firing a porous plate comprising a conductive material and a resin,
A porous fuel cell separator comprising a far-infrared radiation material.   3. The porous fuel cell separator according to claim 1, wherein the far-infrared radiation material is present on at least a pore inner surface of the porous fuel cell separator.   A method for producing a porous fuel cell separator, wherein a raw material composition obtained by mixing a conductive material, a resin and a far-infrared radiation material is put into a mold and then the raw material composition is molded.   A raw material composition obtained by mixing a conductive material and a resin is put into a mold, and then the raw material composition is molded to produce a porous plate, and the resulting porous plate is coated with a paint containing a far-infrared radiation material. A method for producing a porous fuel cell separator, comprising impregnation.   A solid polymer fuel cell comprising a large number of unit cells arranged in parallel with a pair of electrodes sandwiching a solid polymer membrane and a pair of separators forming a gas supply / discharge channel sandwiching the electrodes, A polymer electrolyte fuel cell, wherein a part or all of the separator is the porous fuel cell separator according to any one of claims 1 to 3.