JPH11354136A - Fuel cell, separator for fuel cell, and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a separator, excellent in electrical resistance, gas permeability, liquid swelling properties, and mechanical strength, and satisfactory in moldability, by molding expanded graphite powder having a specific average grain size and mixed with a resin. SOLUTION: Expanded graphite powder having an average grain size of 50 μm or more is previously manufactured and mixed with a resin, and the mixture is molded into a separator. If the average size of the expanded graphite powder is less than 50 μm, the separator is larger in electrical resistivity and inferior in mechanical characteristics, and therefore 80 to 500 μm is preferable. As the expanded graphite powder, expanded graphite having worm-like shapes and compression characteristics, can be obtained, for example, by immersing graphite in a solution with an acid constituent, thereby producing a graphite interlayer compound, rinsing the graphite, and rapidly heating it so as to cause graphite crystals to extend in the C axis direction. This graphite is worked into a sheet-like shape and then pulverized. As the resin, a non-solvent liquid epoxy resin, a solid epoxy resin, a melamine resin, an acryl resin, a phenol resin, a polyamide resin, and the like are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell, a fuel cell separator, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a fuel cell separator is produced by shaving a graphite block, treating natural flaky graphite with a strong acid and an oxidizing agent, and then subjecting the expanded graphite and expanded graphite sheet obtained by heat treatment to high pressure. And a method of impregnating and curing the molded article with a liquid thermosetting resin.

However, each of the above-mentioned manufacturing methods has a drawback that a separator having sufficient performance cannot be obtained, the number of manufacturing steps increases, the cost increases, and the weight increases. As a solution to these problems, International Publication No. WO97 / 02612 describes that the average particle size is 5 to 5.
A fuel cell separator in which expanded graphite powder having a specific particle size of 12 μm is dispersed in a thermoplastic resin or a thermosetting resin is described. However, when the expanded graphite powder having the fine particle diameter as described above is used, there is still a defect that the electrical resistivity and the mechanical characteristics are inferior, and a fuel cell separator satisfying the required characteristics cannot be supplied.

[0004]

In view of the above problems, the inventions according to claims 1 and 2 are excellent in separator characteristics such as electric resistance, gas permeability, liquid swelling property and mechanical strength, and are also excellent in economic efficiency. An object of the present invention is to provide a fuel cell separator. Further, the invention according to claims 3 and 4 provides an electric resistance,
Provided is a method for producing a fuel cell separator which is excellent in separator properties such as gas permeability, liquid swelling property and mechanical strength, and which can produce a fuel cell separator having good moldability in a simple process at low cost and stably. Things. further,
The invention according to claims 5 and 6 provides an electric resistance of the separator,
An object of the present invention is to provide a high-performance fuel cell having excellent properties such as gas permeability, liquid swelling property and mechanical strength.

[0005]

According to the present invention, the average particle size is 5%.
The present invention relates to a fuel cell separator in which expanded graphite powder of 0 μm or more and μm is dispersed in a resin. Further, the present invention relates to the above fuel cell separator, wherein the fuel cell is a solid polymer type.

The present invention also relates to a method for producing a separator for a fuel cell, comprising molding a mixture containing expanded graphite powder having an average particle size of 50 μm or more and a thermosetting resin or a thermoplastic resin. The present invention also relates to the above-described method for producing a fuel cell separator, wherein the resin used is a phenolic resin. The present invention also relates to a fuel cell having the separator. Furthermore, the present invention relates to the fuel cell, which is a solid polymer type.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the average particle size is 5
By preparing an expanded graphite powder of 0 μm or more in advance, mixing this with a resin, and molding, it is possible to manufacture a fuel cell separator in which an expanded graphite powder having an average particle size of 50 μm or more is dispersed in a resin. . The average particle size is a number average particle size, for example, SALD-30 manufactured by Shimadzu Corporation.
It can be measured by various particle size distribution measuring devices such as 00J.

The expanded graphite powder has an average particle size of 50 μm.
If it is less than 1, the electrical resistivity of the separator is large and the mechanical properties are inferior. The average particle size of the expanded graphite powder used in the present invention is preferably from 80 μm to 500 μm,
More preferably, the thickness is from 00 μm to 300 μm,
0 μm to 280 μm, more preferably 15 μm to 280 μm.
Most preferably, it is 0 μm to 250 μm.

Such expanded graphite powder is manufactured, for example, as follows. Preferred examples of graphite used as a raw material of the expanded graphite powder include graphite in which crystals are highly developed, such as natural graphite, cachet graphite, and pyrolytic graphite.
Natural graphite is preferred from the viewpoint of the balance between the obtained properties and economy. The natural graphite to be used is not particularly limited.
8C (trade name, manufactured by Nippon Graphite Co., Ltd.), H-50 (Chuetsu Graphite)
Commercial products such as (trade name, manufactured by Co., Ltd.) can be used.

The acid component used for the treatment of graphite includes sulfuric acid, nitric acid, a mixed solution of sulfuric acid and nitric acid, and the like.
These can be treated by adding hydrogen peroxide.
As a treatment method for forming expanded graphite, for example, the graphite is immersed in a solution of the acid component to generate a graphite intercalation compound, and then washed with water and then rapidly heated to obtain a C-axis of graphite crystal. There is a method of expanding the direction. This makes it possible to obtain an insect-like expanded graphite having compressive properties.

The expanded graphite obtained in the above process can be processed into a sheet by compression molding, rolls or the like, adjusted to an optimum density, and then pulverized to obtain expanded graphite powder. If necessary, the obtained expanded graphite powder can be classified and used.

In the present invention, the properties (liquid or powdery) and structure of the thermosetting resin or thermoplastic resin used together with the expanded graphite powder are not particularly limited. Various phenol resins such as an epoxy resin, a melamine resin, an acrylic resin, a resol type and a novolak type, a polyamide resin, a powdery polyamideimide resin, and a phenoxy resin are used. These resins may be used in combination with a curing agent, a curing accelerator, a curing catalyst, and the like, if necessary. For example, an epoxy resin is used in combination with a curing agent and a curing accelerator. Among these resins, it shows an excellent balance of properties,
Phenolic resins are preferred because they are also economical and workable.

The mixing ratio of the expanded graphite powder having an average particle diameter of 50 μm or more to the thermosetting resin or the thermoplastic resin is not particularly limited. However, considering the moldability and characteristics, the expanded graphite powder / resin = 95/5 to 5/5. A range of 20/80 (weight ratio) is preferable,
Particularly, the range of 10/90 to 30/70 is preferable. Here, when the amount of the expanded graphite powder to be mixed exceeds 95/5, the moldability tends to decrease, and the mechanical strength tends to sharply decrease due to insufficient matrix. On the other hand, 20/8
If it is less than 0, the conductivity tends to decrease.

The method of mixing the expanded graphite powder having an average particle size of 50 μm or more with a thermosetting resin or a thermoplastic resin is not limited. When using a solution in which a liquid resin and a solid resin are dissolved in a solvent, a predetermined amount of the expanded graphite powder having an average particle size of 50 μm or more and a resin solution are blended and uniformly stirred using a stirrer. Can be. Here, the mixture produced using a resin containing a solvent is usually used after removing the solvent with a reduced-pressure drier or the like and pulverizing. Further, a method of dry-blending the expanded graphite powder and the powdery resin (a method of mixing without using a solvent with a shaker or a mixer) can also be used. In consideration of cost and workability, a dry blending method is preferable, and a dry blending (dry mixing) method of a powdered phenol resin is particularly preferred because of excellent moldability and characteristics of a molded article.

The method of forming the fuel cell separator is not particularly limited, and a compression molding method, an extrusion molding method, a transfer molding method and the like can be used. The molding conditions can be selected according to the type of the resin, and a temperature of normal temperature to 400 ° C. can be usually used. In addition, a step of degassing unnecessary substances such as condensation water generated at the time of curing can be provided according to the type of the resin. Further, a heat treatment may be performed after molding in order to further advance the curing of the obtained molded article.

As a molding method, a method using a mold or the like having a desired separator shape is preferable since the separator can be directly molded. However, a large molded body is prepared in advance, and this is cut to obtain a desired shape. It can also be a separator of a size.

The size, thickness, shape, and the like of the fuel cell separator of the present invention are not particularly limited. FIG. 1 shows a perspective view of an example of the fuel cell separator of the present invention. In general, the fuel cell separator 1 is provided with ribs as shown in FIG. 1 in order to secure a flow path of a reaction gas. 2 is a rib, and 3 is a groove. FIG. 1A shows a configuration in which ribs are provided on both surfaces, and FIG. 1B shows a configuration in which ribs are provided on one surface.

The fuel cell separator according to the present invention comprises:
It can be used as a fuel cell separator of various types such as a solid polymer type, a solid oxide type, a molten carbonate type, an alkaline aqueous solution type and an acid aqueous solution type. In general, a fuel cell has a fuel electrode and an air electrode sandwiching an electrolyte layer,
Includes cells in units of separators sandwiched from both sides.
As the electrolyte, potassium hydroxide or the like is used for an alkaline aqueous solution type, phosphoric acid or the like is used for an acid aqueous solution type, and an ion exchange membrane or the like is used for a solid polymer type, and a molten carbonate type is used. In the case of, lithium carbonate or the like is used,
In the case of a solid oxide type, stabilized zirconia or the like is used. Examples of the base material of the electrode include a carbon material such as carbon fiber, and, if necessary, platinum, palladium,
What provided the catalyst layer of silver, nickel, etc. on the surface is used. Hydrogen, which is a fuel gas, is supplied by reacting raw materials such as decomposition products of water, natural gas, petroleum, coal, and methanol with water, etc., as necessary, to extract hydrogen-rich reformed gas, and using it. You. Among others, the separator of the present invention is particularly suitable for a polymer electrolyte fuel cell.

FIG. 2 is a perspective view showing a cell structure of an example of the polymer electrolyte fuel cell. The minimum unit cell 4 that causes a battery reaction is composed of a three-layer membrane 8 composed of a solid polymer electrolyte membrane 5, a fuel electrode 6, and an air electrode 7, and separators 9a and 9b sandwiching the membrane 8 from both sides. ing. The cells 3 configured as described above are stacked in several stages as shown in FIG. 1, and a cell stack 10 as an aggregate is obtained.

[0020]

Next, embodiments of the present invention will be described. Hereinafter,% means% by weight. Example 1 (1) Production of expanded graphite powder 600 g of sulfuric acid (concentration 99%) and nitric acid (concentration 99%) 20
0 g was placed in a 3 liter glass beaker. The graphite F48C (fixed carbon number 99% or more, Nippon Graphite Co., Ltd.)
(Trade name), 400 g was mixed, and the mixture was stirred for 5 minutes with a stirring motor (60 rpm) equipped with a glass blade, and then 32 g of hydrogen peroxide (concentration: 35%) was added and stirred for 15 minutes.
After the stirring, the graphite oxide and the acid component were separated by filtration under reduced pressure, the obtained graphite oxide was transferred to another container, and 5 liters of water was added thereto.
The mixture was stirred for 0 minute, and the graphite oxide washed by filtration under reduced pressure and washing water were separated.

The obtained washed graphite oxide was transferred to an enamel vat, leveled, and left in a dryer heated to 110 ° C. for 1 hour to remove water. This was further heat-treated in a heating furnace heated to 800 ° C. for 5 minutes to obtain expanded graphite. The expanded graphite is rolled with a roll and processed into a sheet having a density of 1.0 g / cm ³ , and the obtained sheet is pulverized with a coarse pulverizer (Rosoplex (trade name) manufactured by Hosokawa Micron Corporation). Crusher (Nara Machinery Co., Ltd., free crusher M-
3 (trade name)) to obtain 90 g of expanded graphite powder having an average particle size of 150 μm.

(2) Production of fuel cell separator 56 g of expanded graphite powder produced in Example 1 (1) and resol type phenol resin powder (TD2040C, trade name of Dainippon Ink KK, trade name) 24 g (ratio 70 / 30) is measured in a plastic bag and air is injected into the bag to inflate the bag.
Dry blending was performed for 0 seconds.

The above blended powder is uniformly filled in a separator molding die for a fuel cell heated to 180 ° C., and molded by a compression molding machine heated to the above temperature at a pressure of 50 kgf / cm ² (gauge pressure). Molding was performed for 10 minutes (three times of degassing), and 2 mm was applied to one side of the shape shown in FIG.
(Height) 140 mm long and 18 wide with rib-shaped protrusions formed
A 0 mm fuel cell separator was produced. This was sandwiched between two 3 mm-thick iron plates, placed in a dryer heated to 200 ° C., and heat-treated for 30 minutes.

Example 2 (1) Production of Expanded Graphite Powder A part of the expanded graphite sheet obtained in Example 1 (1) was pulverized by the same pulverizer so as to have an average particle size of 250 μm, and 90 g of expanded graphite was obtained. A powder was produced. (2) Production of Fuel Cell Separator Except that 56 g of the expanded graphite powder obtained in Example 2 (1) was used, molding was performed by the same composition and method as in Example 1 to form rib-like projections having good appearance. A separator for a fuel cell was manufactured.

Example 3 (1) Production of Expanded Graphite Powder A part of the expanded graphite sheet obtained in Example 1 (1) was pulverized by the same pulverizer so as to have an average particle size of 400 μm, and 90 g of expanded graphite was obtained. A powder was produced. (2) Production of Fuel Cell Separator Except that 56 g of the expanded graphite powder obtained in Example 3 (1) was used, the same composition and method as in Example 1 were used to form a rib-like projection having a good appearance. A separator for a fuel cell was manufactured.

Comparative Example 1 (1) Production of Expanded Graphite Powder A part of the expanded graphite sheet obtained in Example 1 (1) was pulverized by the same pulverizer so as to have an average particle diameter of 20 μm, and 90 g of expanded graphite was obtained. A powder was produced. (2) Production of Fuel Cell Separator Except that 56 g of the expanded graphite powder obtained in Comparative Example 1 (1) was used, a rib-like projection having a good appearance was formed by the same composition and method as in Example 1. A separator for a fuel cell was manufactured.

The appearance of the fuel cell separators produced in Examples 1, 2, and 3 and Comparative Example 1, and the ribs of each separator were polished flat to produce a 1.5 mm thick flat plate, and the bending strength was measured. And the electrical resistance was measured. Table 1 shows the results.

[0028]

[Table 1]

[0029]

The fuel cell separator according to the first and second aspects is excellent in separator characteristics such as electric resistance, gas permeability, liquid swelling property and mechanical strength, and is also excellent in economic efficiency.
According to the method for manufacturing a fuel cell separator according to the third and fourth aspects, a separator for a fuel cell which is excellent in separator characteristics such as electric resistance, gas permeability, liquid swelling property and mechanical strength and has good moldability can be easily prepared. Inexpensive and stable production with simple processes. The fuel cell according to claims 5 and 6 has excellent properties such as electrical resistance, gas permeability, liquid swelling property, and mechanical strength of the separator, and has high performance.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a fuel cell separator of the present invention, wherein (a) shows a separator having ribs on both surfaces;
(B) has a rib on one side.

FIG. 2 is a perspective view showing an example of the fuel cell of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separator 2 Rib part 3 Groove part 4 Cell 5 Solid polymer electrolyte membrane 6 Fuel electrode 7 Air electrode 8 Three-layer membrane 9a, 9b Separator 10 Cell stack

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jun Fujita 3-3-1 Ayukawacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Chemical Co., Ltd. Yamazaki Plant

Claims (6)

[Claims] 1. A fuel cell separator in which expanded graphite powder having an average particle size of 50 μm or more is dispersed in a resin. 2. The fuel cell separator according to claim 1, wherein the fuel cell is a solid polymer type. 3. A method for producing a fuel cell separator, comprising molding a mixture containing expanded graphite powder having an average particle size of 50 μm or more and a thermosetting resin or a thermoplastic resin. 4. The method for producing a fuel cell separator according to claim 3, wherein the resin used is a phenol resin. 5. A fuel cell comprising a separator according to claim 1 or 2, or a separator obtained by the production method according to claim 3. 6. The fuel cell according to claim 5, wherein the fuel cell is a solid polymer type.