JP2003217611A - Separator for fuel cell, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve excellent mechanical strength, corrosion resistance and electric conductivity, and to reduce the manufacturing cost. <P>SOLUTION: This separator 1 for a fuel cell is formed of a laminated body comprising graphite material 5, a thin film layer 6, metal material 7, a thin film layer 6, and graphite material 5 laminated in this order. The thin film layer 6 for a fuel cell is formed of an adhesion layer comprising a resin thin layer. This separator 1 is obtained by forming a close contact layers comprising the thin film layers 6 of resin on both surfaces of a metal plate as the metal material 7, and directly compression-molding graphite powder on them. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell separator, a method for producing the same, and a fuel cell, and more particularly to a polymer electrolyte fuel cell separator.

[0002]

2. Description of the Related Art A fuel cell that continuously supplies a fuel (reducing agent) and oxygen (oxidizing agent) from the outside to extract electric energy has excellent power generation efficiency and can generate power without using fossil fuel and emit it. Since gas is only water, it is being developed as an energy source that is kind to the global environment. Especially about
A polymer electrolyte fuel cell, which can operate at a low temperature of about 80 ° C and can discharge a relatively large current, has been drawing attention as a power source for households and electric vehicles. In a polymer electrolyte fuel cell, an anode and a cathode are arranged on both sides of a polymer membrane to form a membrane / electrode assembly, and an anode-side flow path substrate for supplying hydrogen as fuel to both outer sides of the assembly and A cathode side channel substrate that supplies oxygen is arranged to form a unit cell,
These unit cells are stacked with a separator interposed therebetween. Alternatively, the separator is laminated so as to also serve as the flow path substrate. The separator is a plate with a thickness of about 2 mm, and grooves on both sides are formed as gas channels. Usually, the voltage generated in a unit cell is about 0.7 V, so a plurality of unit cells are stacked in series to obtain a desired voltage.

The separator material has a conductivity of about 100 S / cm,
Since gas impermeability and corrosion resistance are required, metals and graphite materials that satisfy these characteristics are used. As a material using a metal material, a method for improving corrosion resistance such as stainless steel (for example, JP-A-2000-239806) or a method for forming a corrosion-resistant film on a metal material (for example, JP-A 2000-32)
3531) is disclosed. Further, a method of coating a noble metal (for example, Japanese Patent Laid-Open No. 2001-96538) and a method of forming a corrosion resistant coating of carbon, resin, etc. (for example, Japanese Patent Laid-Open No. 2001-76740) are known. On the other hand, as the one using graphite or a resin material, a separator in which a flow path is formed by cutting a graphite block, a separator in which an expanded graphite sheet or the like is molded under high pressure, and the like are known.
As a fuel cell separator using a resin material, a fuel cell separator (International Publication No. W097 / 02612) in which expanded graphite powder having a specific particle diameter is dispersed in a thermoplastic resin or a thermosetting resin, ring-opening polymerization A separator for a fuel cell in which a carbon material such as expanded graphite powder is dispersed in a cured phenol resin cured product (JP-A-11-3541).
35) is known.

[0004]

However, in the method of improving the corrosion resistance of a metal material or forming a corrosion-resistant coating, poisoning of the electrode-supported catalyst by eluted metal ions and deterioration of the conductivity over time due to passivation of the surface can be avoided. There is a problem that there is no.
The method of forming a corrosion-resistant coating of noble metal, carbon, resin or the like has a problem in that it is difficult to form a coating that does not cause pinholes or the coating material is expensive, resulting in high manufacturing cost. Separator made by cutting a graphite block to form a flow path or using a resin material does not have sufficient separator properties such as conductivity, gas impermeability, acid resistance, corrosion resistance, and mechanical strength. In addition, since the raw materials are expensive, the manufacturing cost is high.

Further, even if the resin composition has improved moldability, when a groove is formed by molding, the pressure distribution in the mold is non-uniform and cracks occur in the groove or the separator plate There is a problem of warping.

The present invention has been made to solve the above problems, and is excellent in mechanical strength, corrosion resistance, and electrical conductivity, and can efficiently manufacture a separator plate for a fuel cell. An object of the present invention is to provide a separator, a manufacturing method thereof, and a fuel cell using the separator.

[0007]

A fuel cell separator according to the present invention comprises a laminate of a metal material and a graphite material, and the metal material and the graphite material are electrically connected to each other. It is characterized by being laminated via thin film layers which are in close contact with each other. Here, being electrically conductive means
Volume resistivity (hereinafter referred to as resistivity) is 1 × 10 ^-2 Ω ・
It is less than or equal to cm. The thin film layer is a thin film layer formed on the surface of the metal material. Further, the thin film layer is a resin layer,
In particular, it is characterized by being a layer of a fluororesin which is soluble in a solvent. The thin film layer is a composite layer of a resin layer and a conductive layer. Further, the fuel cell separator is characterized in that the graphite material is closely adhered to both main surfaces of the metal material via the thin film layer, that is, the metal material is sandwiched between the graphite materials. And

In another fuel cell separator, a first graphite material and two second graphite materials are laminated with the graphite material sandwiched therebetween. 3
A fuel cell separator comprising a layered graphite material laminate, wherein the first and second graphite materials are expanded graphite materials, and the two second graphite materials are provided with gas flow paths containing the graphite material. It is characterized by being formed by being hollowed out. Further, it is characterized in that a through hole penetrating the first graphite material is formed at a position in contact with the gas flow path end of the second graphite material. Further, the gas flow path or the through hole is formed by compression molding or machining. The first graphite material and the second graphite material are electrically connected to each other,
In addition, it is characterized in that they are laminated through a resin thin film layer which is in close contact with each other.

The method for producing a fuel cell separator of the present invention comprises a step of forming a thin film layer on the surface of a metal material and a step of compression-molding graphite powder on the surface of the metal material on which the thin film layer is formed. It is characterized by

The fuel cell of the present invention is characterized by being a polymer electrolyte fuel cell using the above-mentioned fuel cell separator.

The fuel cell separator is required to have conductivity, gas impermeability, acid resistance, corrosion resistance, mechanical strength and the like. It has been found that the above characteristics are sufficiently satisfied by bringing the metal material and the graphite material into close contact with each other via the thin film layer. In particular, conventionally used as a water repellent or a mold release agent, etc., it has a good film forming ability, and if a fluororesin that dissolves in a solvent is used, the adhesion between the metal material and the graphite material is improved, and the electrical conductivity is improved. As a result of the experiment, it was found that The present invention is based on such findings. Moreover, by sandwiching both sides of the metal material with the graphite material and performing compression molding, it becomes easy to integrally mold the flow path such as the flow path substrate / separator. Therefore, even a fuel cell separator having a complicated channel groove can be manufactured with high production efficiency.

In another fuel cell separator, a first graphite material made of expanded graphite material and a second graphite material in which a gas flow path is formed are laminated and pressure-bonded to each other to form an interlayer between expanded graphite material layers. Sufficient adhesion can be obtained without using an adhesive.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a fuel cell separator is shown in FIG. FIG. 1 is a perspective view showing a structure concept of a separator that also serves as a flow path substrate used in a solid polymer electrolyte fuel cell and a solid polymer electrolyte fuel cell using the separator. A membrane / electrode assembly (MEA) in which an anode 3 and a cathode 4 are arranged on both sides of the solid polymer electrolyte membrane 2;
A plurality of fuel cell separators 1 are alternately laminated to obtain a cell stack as an assembly. The fuel cell separators 1 and 1 are arranged so as to sandwich the membrane / electrode assembly (MEA) from both sides. On the surface of the fuel cell separator 1,
The groove portion 1a is formed to secure a flow path for hydrogen gas or air.

The structure of the fuel cell separator 1 will be described with reference to FIG. 2A, 2B, and 2C are enlarged cross-sectional views of the portion A in FIG. The fuel cell separator 1 shown in FIG. 2A is formed of a laminated body in which a graphite material 5, a thin film layer 6, a metal material 7, a thin film layer 6 and a graphite material 5 are laminated in this order. The thin film layer 6 is formed of a resin thin layer. In this case, the thin film layer 6 forms an adhesion layer.

The fuel cell separator 1 shown in FIG. 2 (b).
The thin film layer 6 is composed of a conductive layer 6a and an adhesion layer 6b, and a graphite material 5, a conductive layer 6a, an adhesion layer 6b, a metal material 7, an adhesion layer 6b, a conductive layer 6a and a graphite material 5 are laminated in this order. It is formed of a laminated body. In the fuel cell separator 1 shown in FIG. 2 (c), the thin film layer 6 is composed of the conductive layer 6a alone,
The graphite material 5, the conductive layer 6a, the metal material 7, the conductive layer 6a, and the graphite material 5 are laminated in this order to form a laminated body.

In the fuel cell separator 1 shown in FIGS. 2 (a), 2 (b) and 2 (c), a thin film layer 6 is formed on both main surfaces of a metal plate, which is a metal material 7, and graphite powder is formed on the thin film layer 6. It is obtained by a method of forming the graphite material 5 by direct compression molding. By forming a thin film layer that firmly adheres both the metal plate and the graphite material, we manufacture a solid polymer fuel cell separator with excellent adhesion, mechanical strength, corrosion resistance and electrical conductivity. it can. Further, by providing a conductive layer for reducing the contact resistance between the metal plate and the graphite material, the electrical conductivity can be further improved.

There is no particular restriction on the type, size and thickness of the metal material 7, as long as it is electrically conductive and has the strength required for the separator. Specifically, a plate material such as iron, steel, stainless steel, aluminum or an alloy thereof is a metal material 7.
Can be used as

The graphite material 5 is not only a corrosion-resistant layer that protects the surface of the metal plate, but also a current-carrying layer through which electricity flows.
Expanded graphite, artificial graphite, natural graphite, conductive carbon black such as acetylene black and Ketjen black,
Coke powder, glassy carbon obtained by carbonizing a phenol resin or furan resin, mesocarbon graphite obtained by heat-treating pitch, carbonaceous powder such as carbon fiber, or a mixture thereof can be used. In order to form the graphite material of the fuel cell separator 1 only by compression molding, it is preferable to use expanded graphite or expanded graphite that is mainly excellent in moldability. At this time, if the density of the graphite material is low, the corrosion resistance is deteriorated, so that the molding density is preferably 1.6 g / cm ³ or more. Further, the thickness of the graphite material is poor corrosion resistance if it is too thin, the conductivity will be reduced if it is too thick,
Since a large amount of expensive graphite raw material is used, 20 μm-150
The range is preferably 0 μm, and more preferably 50 μm to 800 μm.

The thin film layer 6 is formed of a material that allows the graphite material 5 and the metal material 7 to be in close contact with each other and to be electrically connected to each other. A resin material is mentioned as such a material. The resin material may be solid, semi-solid, or liquid. Specific resin materials include polyethylene, polypropylene, polymethylpentene, polystyrene, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyether sulfone, polycarbonate, polyoxymethylene, polyamide, polyimide, poly. Ether imide, polyamide imide, polybenzimidazole, polyether ketone, polyether ether ketone, polyarylate, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, ethylene-tetrafluoroethylene copolymer, ethylene -Chlorotrifluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene-fluorinated Vinylidene copolymer,
Polyvinylidene fluoride, polytetrafluoroethylene,
ABS resin, AS resin, syndiotactic polystyrene, phenol resin, melamine resin, silicone resin,
Examples thereof include epoxy resin, urea resin, alkyd resin, furan resin, polyurethane resin, polycarbodiimide resin and the like. The above resin materials can be used alone or as a mixture.

Although the above resin material is an insulating material, the thin film layer 6 is formed on the surface of the metal material 7, and the graphite material 5 is compression-molded on the surface of the metal material 7, so that the metal material 7 and the graphite material 5 adhere to each other. Property is improved, and the resistivity required for a fuel cell separator is obtained. It is considered that the metal material and the graphite material come into contact with each other due to appropriate deformation and breakage of the thin film layer during compression molding, so that electrical conductivity can be obtained. Therefore, if the thickness of the adhesion layer is too thin, the metal material and the graphite material do not adhere, and if the thickness is too thick, the conductivity of the metal material and the graphite material is poor, so the thickness of the thin film layer is 0.005. The thickness is preferably in the range of μm or more and less than 5 μm, more preferably 1 μm or less.

In the present invention, the adhesive strength between the metal material 7 and the graphite material 5 is improved by increasing the compressive strength during compression molding with the thin film layer 6 having a thickness of less than 5 μm. Also, with the improvement of the adhesive force, the resistivity of 1 × 10 ⁻² Ω · cm or less, which is the resistivity required for the fuel cell separator, was obtained. Therefore, the degree of adhesion can be judged by the magnitude of the resistivity.

A suitable resin material for the thin film layer 6 is a fluororesin which is soluble in a solvent. This is because a thin film layer having a predetermined thickness can be formed on the surface of the metal material by coating. Copolymerized fluororesin is mentioned as a preferable fluororesin which melt | dissolves in a solvent. In particular, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer is preferable. This copolymerized fluororesin is soluble in a ketone-based or ester-based solvent and has excellent adhesiveness to the surface of the metal material. Commercially available products of tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer include T
HV200, THV400, THV500 etc. (Sumitomo 3M product name) are mentioned.

A conductive resin material can also be used as the thin film layer 6. For example, polyacetylene, polyaniline, polyphenylene-based resin such as polypyrrole, etc. to which conductivity is imparted can be used. In this case, the thin film layer may have a thickness of 5 μm or more.

The thin film layer 6 may be an adhesion layer made of the above resin material alone, or may be a thin film layer in which a conductive layer is further laminated. Providing the conductive layer further improves the electrical conductivity. The conductive layer may be any layer as long as it reduces the contact resistance between the metal material layer and the graphite material layer, and specifically, a noble metal coating such as gold, platinum, palladium, silver, copper, or IT.
Conductive oxide coatings such as O (indium tin composite oxide), tin oxide, and zinc oxide are included. If the thickness of these conductive layers is too thin, it does not contribute to the reduction of contact resistance between the metal material and the graphite material, and if they are too thick, a large amount of expensive conductive layer materials are used, and the film formation time becomes long, so it is manufactured. This leads to increased costs. Specifically, it is preferably 1 nm to 500 nm, more preferably 2 nm to 50 nm.

Next, a method of manufacturing a fuel cell separator using the above material will be described. (1) Prepare a metal plate to be a metal material. A conductive layer is formed on the surface of the metal plate as needed. (2) For forming the conductive layer, a known thin film forming method can be adopted. For example, a wet plating method, an electroless plating method, a vacuum deposition method, an ion plating method, a sputtering method and the like P
The VD method and the CVD method are exemplified. (3) A thin film layer is formed on the surface of the metal plate alone or on the surface of the metal plate on which the conductive layer is formed. The thin film forming method may be any method as long as it can form a thickness of less than 5 μm.
For example, a dipping method using a resin solution or a resin dispersion, a spin coating method, a coating or spraying method, a powder press molding method, a vacuum vapor deposition method, a sputtering method and the like can be mentioned. (4) A metal plate having a conductive layer formed on the surface thereof, a metal plate having a conductive layer and a thin film layer formed on the surface in order, or a metal plate having a thin film layer formed on the surface thereof, and a graphite material Form the layers. As a compression molding method, a hydraulic press or CIP (cold isotropic pressure molding) can be adopted.

Further, during compression molding, a mold having a shape corresponding to a gas flow path in advance may be used to mold the flow path substrate integrated separator. An example of the mold is shown in FIGS. 3 and 4. 3 and 4 are sectional views of the mold. In FIG. 3, the powder of the graphite material 5 is held between the upper die 9 and the lower die 10 held by the die die 8, the metal material 7 having the thin film layer 6 formed on the surface, and the powder of the graphite material 5 are laminated in this order. Then, the mold is clamped by a hydraulic press or the like to mold the flow path substrate integrated separator. FIG. 4 shows an example in which the metal plate is formed at the same time when the mold is clamped.

In the fuel cell separator of the present invention, the mechanical strength and gas impermeability are maintained by the metal material, and the corrosion resistance and the acid resistance are maintained by the graphite material formed on the surface, and the adhesion between the metal material and the graphite material is maintained. It is sufficiently retained by forming a thin film layer having excellent adhesion. Since the graphite material is thinly formed on the metal material, it has excellent electrical conductivity. Further, by using a metal material having high mechanical strength and gas impermeability, a thinner structure can be obtained as compared with a graphite-only or resin-only separator. For this reason, performance equal to or higher than that of the graphite-only or resin-only separator is obtained. Further, by forming a conductive layer that suppresses contact resistance, electrical conductivity can be further improved.

Further, it is not necessary to use expensive stainless steel or the like as the metal material, and since the graphite material layer and the conductive layer, which are expensive materials, are thin, the amount used is small,
Excellent in industrial productivity. Since the graphite layer is formed by simple compression molding, heating / cooling is unnecessary when molding the resin material, the cycle time can be shortened, and the groove part corresponding to the gas flow path can be molded once. Therefore, post-processing such as a cutting process is unnecessary. Therefore, the manufacturing process can be shortened and a fuel cell separator having excellent manufacturability can be obtained.

The obtained fuel cell separator is a composite of a metal material and a graphite material, and is excellent in conductivity, gas impermeability, acid resistance, corrosion resistance, mechanical strength, and can be miniaturized. . Therefore, a high performance polymer electrolyte fuel cell can be obtained by using this separator.

A method for manufacturing a fuel cell separator obtained by compression-molding expanded graphite powder without using a metal material will be described below with reference to FIG. FIG. 5 is an exploded perspective view of the fuel cell separator. This method is suitable as a method for preventing cracks and warpage of the separator plate that occur when forming the flow channel by resin molding. As shown in FIG. 5, the expanded graphite powder is compression-molded to obtain three plate-shaped molded bodies. Upper plate 11 and lower plate 13 which are second graphite plates
The holes 11a serving as fuel gas and oxidant gas flow paths, respectively.
And 13a are formed. Further, through holes 11b and 13b for supplying gas or discharging gas from the flow paths are formed at the ends of the respective flow paths. Further, through holes 11c and 13c for supplying gas to or discharging gas from the gas flow path are formed in the gas flow path on the opposite surface. These through holes 11c and 13c are provided in the holes 11a and 13a, which are flow paths. It is independent without being linked. The middle plate 12 serving as the first graphite plate has through holes 12a for supplying gas to the gas passages of the upper plate 11 and the lower plate 13 or for discharging gas from the gas passages. The fuel cell separator includes an upper plate 11, a middle plate 12, and a lower plate 13 stacked one on top of the other.
It can be obtained by pressure bonding from above and below.
At that time, it is preferable to insert a structure having a flow channel shape into the gas flow channel holes 11a and 13a of the upper plate 11 and the lower plate 13 in order to prevent the grooves from collapsing. This structure may be integrated with the pressing jig. It is also preferable to provide a structure for restraining the shape on the side surface of the plate in order to maintain the shape. The gas flow path can be designed arbitrarily according to the size and efficiency of the fuel cell. For example, in order to increase the efficiency of gas supply / discharge, a plurality of gas flow path systems can be used, and in this case, there are a plurality of supply / discharge holes. It is also possible to provide a flow path for cooling water of the fuel cell.

Further, the upper plate 11, the middle plate 12 and the lower plate 13
Can be laminated via resin thin film layers that are electrically connected to each other and are in close contact with each other. Further, in order to impart water repellency to this separator, a substance having a small surface energy can be applied, or a small amount (8% by weight or less) of these substances can be added to the expanded graphite powder to be molded. On the contrary, hydrophilicity can be imparted by changing the substance to be applied or added. In addition, a part of the expanded graphite can be replaced with flaky graphite, or can be reinforced with a filler such as carbon fiber. Further, it is possible to adopt a structure in which the middle plate 12 is made of a metal having good corrosion resistance, or a metal plate is arranged in the center to increase the strength.

[0032]

[Examples] Examples 1 to 10 and Comparative Examples 1 to 4 Table 1 was prepared on a metal (iron) plate having a length of 80 mm, a width of 50 mm and a thickness of 1 mm.
A conductive layer, a thin film layer, and a graphite material were formed under the conditions shown in. The conductive layer was formed using a vacuum evaporation method (Au) and a magnetron sputtering method (ITO). The thin film layer was formed by dipping the THV200P (Sumitomo 3M), which is a ketone-based solvent-soluble fluororesin, in acetone. The film thickness of the thin film layer was controlled by the concentration of the dipping liquid, the pulling rate, and the like. Graphite material is expanded graphite powder KE
X (manufactured by Nippon Graphite Industry Co., Ltd.) was molded by a hydraulic press. The molding density of the graphite material was controlled by the molding pressure. The obtained fuel cell separator was evaluated by a resistivity measurement and a corrosion resistance test. The resistivity was measured by applying an applied current of 100 by the 4-probe method
Measured in mA. For the corrosion resistance test, an H ₂ SO ₄ aqueous solution adjusted to PH 2 was sprayed on the surface of the molded product in a saturated steam atmosphere at 90 ° C., and a durability test was conducted for 250 hours. After the durability test, the case where no corrosion was visually observed is indicated by ◯, and the case where corrosion was observed is indicated by x. The results are shown in Table 1.

[0033]

[Table 1]

Each of the examples has a resistivity of 1 × 10 ⁻² Ω.
・ Low as cm or less and excellent in corrosion resistance. Although the conductive layer was provided in Example 7, the resistivity was equivalent to those in Examples 1 to 6 because the conductive layer was thin. In Comparative Example 1, the iron plate and the graphite material did not adhere because there was no thin film layer. Comparative example 2
Then the thin film layer is too thick and is required for the separator 1
A resistivity below × 10 ^-2 Ω · cm could not be obtained. Comparative Example 3
However, since the molding density of the graphite layer was too low, sufficient corrosion resistance could not be obtained. In Comparative Example 4, the graphite material was too thin to obtain sufficient corrosion resistance.

Example 11 A fuel cell separator was produced by compression molding using the mold shown in FIG. The shape of the separator is 100mm x 100mm in length x width, and the thickness of the metal (iron) plate is 0.3mm.
The groove depth is 0.7 mm, and the thickness of the graphite material at the groove bottom is 0.15
mm, the total thickness is 2 mm. As a result of evaluating the resistivity and the corrosion resistance of the obtained fuel cell separator, the resistivity was 6 to 7 × 10 ⁻³ Ω · cm, and the corrosion resistance measured under the conditions of Example 1 was also good. As a result, even the separator with the gas passage groove could be produced by compression molding.

Example 12 A fuel cell separator was produced by a compression molding method using the mold shown in FIG. The shape of the separator is 100mm x 100mm in length x width, and the thickness of the metal (iron) plate is 0.2mm.
The groove depth is 0.7 mm, the thickness of the graphite material is 0.3 mm, and the total thickness is 1.5 mm. The obtained fuel cell separator was evaluated for resistivity and corrosion resistance, and the resistivity was 6 to 7
It was × 10 ^-3 Ω · cm, and the corrosion resistance measured under the conditions of Example 1 was also good. By compression-molding the metal plate at the same time, a thinner separator with gas channel grooves was obtained.

Example 13 Expanded graphite powder (Nippon Graphite Industry Co., Ltd .: KEX, average particle size)
16 μm) was filled in a mold and compressed at room temperature under a pressure of 100 MPa to form three 50 mm square, 3 mm thick plate materials. As shown in FIG. 5, holes 11a and 13a corresponding to the gas passages in the upper and middle plates and a hole 12a corresponding to the gas supply / discharge holes were formed by machining, respectively. The width w of the flow path is 3 mm
And Laminate these 3 plates and crimp them at 200MPa,
An integrated separator having different gas flow paths on both sides and having holes for supplying or discharging gas was obtained.

Comparative Example 5 Expanded graphite powder was converted into flake graphite (KS44, manufactured by Lonza Co., Ltd.).
The molding was performed in the same manner as in Example 13 except that the average particle size was changed to 18 μm). The molded product taken out of the mold was brittle and could not maintain the shape of the separator.

Comparative Example 6 A graphite molded body (graphite block) was subjected to a cutting process to prepare the same three plates as in Example 13. This 3
When the sheets were laminated and pressure-bonded at 200 MPa, they seemed to be in close contact with each other once, but when a force in the direction perpendicular to the lamination was applied, they were easily delaminated and separated.

[0040]

The fuel cell separator of the present invention comprises a laminate of a metal material and a graphite material, and the metal material and the graphite material are electrically connected to each other and adhere to each other. Since they are laminated via a thin film layer, they have excellent mechanical strength, corrosion resistance and electrical conductivity. In addition, by using a metal material having high mechanical strength and gas impermeability, graphite alone,
A thinner structure can be achieved as compared to a resin-based separator.

Further, in the fuel cell separator, since the thin film layer is a thin film layer formed on the surface of the metal material, the adhesion between the metal material and the graphite material is excellent. In particular, since the thin film layer is a resin layer, the resin layer is a layer of a fluororesin that is soluble in a solvent, and therefore the adhesiveness is more excellent. Furthermore, since the thin film layer is a composite layer of the resin layer and the conductive layer, the metal material and the graphite material are excellent in adhesiveness and the electrical conductivity between them is also excellent.

In addition, the first graphite material and the graphite material are sandwiched between the two.
A fuel cell separator comprising a three-layer graphite material laminate in which a plurality of second graphite materials are laminated, wherein the first and second graphite materials are expanded graphite materials, and the two second Since the gas flow path is formed by penetrating the graphite material in the graphite material,
It is possible to easily and inexpensively form the groove serving as the gas flow path. Further, by using expanded graphite as a raw material, molding and lamination pressure bonding can be performed only by pressurization without heating, and cost reduction of the separator can be realized.

In the method for manufacturing a fuel cell separator of the present invention, since graphite powder is compression-molded on the metal surface on which the thin film layer is formed, post-processing such as a cutting step is unnecessary, and the manufacturing process can be shortened and manufacturability is improved. Excel.

Since the fuel cell of the present invention is a polymer electrolyte fuel cell using the above separator, it is excellent in conductivity, gas impermeability, acid resistance, corrosion resistance, mechanical strength, etc. It becomes a high performance fuel cell.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structural concept of a polymer electrolyte fuel cell.

FIG. 2 is an enlarged cross-sectional view of a fuel cell separator.

FIG. 3 is a diagram showing an example of a mold.

FIG. 4 is a diagram showing another example of a mold.

FIG. 5 is an exploded perspective view of a fuel cell separator.

[Explanation of symbols]

1 Fuel cell separator 2 Solid polymer electrolyte membrane 3 anode 4 cathode 5 Graphite material 6 thin film layers 7 metal materials 8 die 9 Upper mold 10 Lower mold 11 Upper plate 12 Middle plate 13 Lower plate

Claims (12)

[Claims] 1. A fuel cell separator comprising a laminate of a metal material and a graphite material, wherein the metal material and the graphite material are electrically connected to each other and are in close contact with each other. A fuel cell separator, wherein the fuel cell separator is laminated by interposing layers. 2. The fuel cell separator according to claim 1, wherein the thin film layer is a thin film layer formed on the surface of the metal material. 3. The fuel cell separator according to claim 1, wherein the thin film layer is a resin layer. 4. The fuel cell separator according to claim 3, wherein the resin layer is a fluororesin layer which is soluble in a solvent. 5. The fuel cell separator according to claim 1, wherein the thin film layer is a composite layer of a resin layer and a conductive layer. 6. The fuel cell separator according to claim 1, wherein the graphite material is adhered to both main surfaces of the metal material via the thin film layer. 7. A fuel cell separator comprising a first graphite material and a three-layer graphite material laminate in which two second graphite materials are laminated with the graphite material sandwiched between the first graphite material and the first and second graphite materials. 2. The fuel cell separator, wherein the graphite material of 2 is an expanded graphite material, and a gas flow path is formed in the two second graphite materials by hollowing the graphite material. 8. The fuel cell separator according to claim 7, wherein a through hole penetrating through the first graphite material is formed at a position in contact with an end of the gas flow path of the second graphite material. . 9. The fuel cell separator according to claim 7, wherein the gas flow path or the through hole is formed by compression molding or machining. 10. The first graphite material and the second graphite material are laminated via a resin thin film layer that electrically conducts them and makes them adhere to each other. The fuel cell separator according to claim 7. 11. A fuel cell separator comprising: a step of forming a thin film layer on the surface of a metal material; and a step of compression-molding graphite powder on the surface of the metal material on which the thin film layer is formed. Production method. 12. The fuel cell is a polymer electrolyte fuel cell, and the separator used in the fuel cell is the fuel cell separator according to any one of claims 1 to 10. Fuel cell.