JP2002050365A - Separator for fuel cell and fuel cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell separator that is easy to manufacture and is equipped with good balance of conduction, gas impermeability and strength. SOLUTION: A conductive resin composite made of a resin and a metal fiber having a diameter of 5-30 μm and a length of 50-1000 μm is formed and a fuel cell separator having on at least one surface a gas passage for supplying fuel gas or oxidant gas to the electrode is obtained. A rib for forming a gas passage is formed on the sheet-form metal substrate by a conductive resin composite having a volume resistivity of 0.05 Ω/cm or less. A ground rib is formed on the sheet-form metal substrate and a rib is formed on top of the ground rib.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell separator and a fuel cell using the same, and more particularly, to a polymer electrolyte fuel cell separator.

[0002]

2. Description of the Related Art A fuel cell which generates electric energy and heat by reacting a fuel gas with an oxidizing gas generally includes a pair of porous electrodes opposed to each other via an electrolyte membrane and the porous electrode. It consists of a separator having a gas flow path for supplying gas. Generally, an electrode having a conductive sheet as the separator and an electrode having a gas diffusion layer made of carbon paper or the like and a catalyst layer made of carbon powder or the like supporting a metal catalyst is used as the porous electrode. It is. Here, in the polymer electrolyte fuel cell, a polymer electrolyte membrane or an ion exchange membrane is used as the electrolyte membrane. A desired fuel cell is constructed by laminating an electrolyte membrane / electrode assembly obtained by joining a pair of porous electrodes to this membrane via the separator.

[0003] There are various types of fuel cell separators. For example, as a separator provided with gas channels on both surfaces of a single conductive sheet, it has a plate-shaped gas channel on both front and back surfaces, and the gas channel is formed by a plurality of parallel ribs. Examples include fuel cell separators. In this case, the fuel gas and the oxidizing gas can be supplied to the adjacent cells on both sides, respectively. On the other hand, when a plurality of separators are stacked and used, a gas flow path may be provided on at least the side of the separator that contacts the unit cell. If gas flow paths are provided on both sides of the separator at this time, the gas flow path on the side where the separators that are not in contact with the unit cell are in contact with each other can be used as the cooling water flow path.

[0004] The separator serves to supply gas to the electrode and to carry out a reaction product, generally water, out of the battery system. In addition, the separator supports the porous electrode and functions as a current collector for the porous electrode, and also has a role of electrically connecting adjacent unit cells. Therefore, the fuel cell separator needs to have high conductivity and excellent gas impermeability and strength.

Here, as a fuel cell separator,
Conventionally, carbon material impregnated with resin, glassy carbon processed into a separator shape and fired, molded product obtained by pressing sheet-like graphite, molded product of a composition comprising carbon powder and resin, etc. Used.

However, it is difficult to say that these conventional separators have a good balance of manufacturing cost, conductivity, gas impermeability and strength. For example, a carbon material impregnated with a resin requires cutting, which increases the manufacturing cost. In addition, the glassy carbon shrinks at the time of firing, so that the accuracy is low and the gas impermeability is poor. Further, a composition comprising carbon powder and a resin is easy to mold, but is inferior in conductivity.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel cell separator which is easy to manufacture and has a good balance of conductivity, gas impermeability and strength, and a fuel cell using the same. With the goal.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface thereof. 5 to 30 μm and length 50
The present invention relates to a separator for a fuel cell, which is a molded article of a conductive resin composition composed of metal fibers having a thickness of about 1000 μm.

The resin is preferably made of at least one selected from the group consisting of polystyrene, polyethylene, polypropylene, polyphenylene ether, polybutylene terephthalate and polyamide. Stainless steel is effective as the metal fiber. As the separator, those having a volume resistivity of 0.05 Ω · cm or less and a surface resistance of 0.5 Ω / cm ² or less are effective.

[0010] The present invention also provides a fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface thereof. The present invention relates to a fuel cell separator comprising a plurality of parallel ribs provided on a substrate, wherein the ribs are made of a conductive resin composition having a volume resistivity of 0.05 Ω · cm or less. It is preferable that the sheet-shaped metal substrate has a plurality of through holes in the plane.

The present invention further provides a fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface, comprising a sheet-shaped metal substrate and the metal sheet. The sheet-shaped metal substrate includes a plurality of parallel ribs provided on a substrate, and the sheet-shaped metal substrate has a base rib, and the rib is a conductive resin composition having a volume resistivity of 0.05 Ω · cm or less. A fuel cell separator comprising: In order to obtain this separator, it is effective to form base ribs on the sheet-shaped metal substrate in advance corresponding to the portions where the ribs are formed.

The present invention also relates to a fuel cell in which an electrolyte membrane / electrode assembly in which a pair of porous electrodes are bonded to both sides of an electrolyte membrane is laminated via any of the above fuel cell separators. As the electrolyte membrane, a polymer electrolyte membrane or an ion exchange membrane conventionally used generally in fuel cells can be used. As the porous electrode,
Conventionally used fuel cells can be used without particular limitation. Conventionally used porous electrodes include, for example, those in which carbon paper is used as a gas diffusion layer and carbon powder supporting a metal catalyst is used as a catalyst layer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 In this embodiment, among fuel cell separators comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface, A fuel cell separator, which is a molded article of a conductive resin composition made of a resin and metal fibers having a diameter of 5 to 30 μm and a length of 50 to 1000 μm, will be described. The entirety of the separator according to the present embodiment, including the gas flow path and the portion other than the gas flow path, is made of resin and has a diameter of 5 to 30 μm and a length of 50 to 100 μm.
It is a molded article of a conductive resin composition comprising 0 μm metal fibers. Such a separator can be manufactured by, for example, injection molding a conductive resin composition.

The separator has a cross section perpendicular to the gas flow direction, for example, as shown in FIG. in this case,
The thickness d of the separator obtained by molding the conductive resin composition 1 is 1 to 2.5 mm, and the pitch w of the rib 2 is 1
And the height h (depth of the groove) h of the rib 2 is 0.2 mm.
It is generally set to 〜1 mm.

Since the separator is manufactured by integrally molding the gas flow path and parts other than the gas flow path, the manufacturing cost is advantageously reduced. Further, since the resin is used, the resin has elasticity, and is not easily chipped or cracked at the top of the rib, and is easily thinned. Furthermore, since the resin composition contains the metal fiber having a predetermined shape, the conductivity is extremely high and the volume resistivity can be significantly reduced as compared with the resin composition containing the carbon powder.

As the conductive resin composition, a composition in which 5 to 30 parts by volume of a metal fiber is blended with 100 parts by volume of the resin is preferable in terms of a good balance between moldability and conductivity.
When the amount of the metal fiber exceeds 30 parts by volume, the moldability decreases,
If it is less than 5 parts by volume, the conductivity will be insufficient.

The diameter of the metal fiber may be 5 to 30 μm, preferably 7 to 15 μm, and the length is 50 to 1 μm.
000 μm, preferably 100-500
μm. However, the average value of each of the diameter and the length may be within the above range. Metal fiber diameter is 5μ
When it is less than m, the production cost of the metal fiber itself increases, and when it exceeds 30 μm, the aspect ratio decreases and the conductivity of the separator decreases. When the length of the metal fiber is less than 50 μm, the conductivity becomes low, and
If it exceeds μm, the conductivity of the separator may be uneven, or the metal fibers may be easily protruded from the surface of the separator, and the metal fibers may be detached from the separator.

As the material of the metal fiber, stainless steel,
Nickel, copper and the like are preferred. These may be used alone or in combination of two or more. Among these, stainless steel is particularly preferable because it has excellent corrosion resistance and the decrease in the conductivity of the separator with time is extremely small.

Among them, a curved fiber containing a large amount of fine fibers obtained by cutting stainless steel is preferable. In this case, the fibers easily contact each other in the separator to form a uniform network structure, and a separator having sufficient conductivity can be obtained even at a low filling rate.

As the resin, at least one selected from the group consisting of polystyrene, polyethylene, polypropylene, polyphenylene ether, polybutylene terephthalate, and polyamide can be used. These may be used alone or in combination of two or more. Among them, polystyrene, polyethylene and polyphenylene ether are preferred from the viewpoint of heat resistance, moisture resistance, acid resistance and the like. As the polyamide, for example, nylon-6 can be used.

Preferably, the resin is a thermoplastic elastomer comprising at least one selected from the group consisting of polystyrene, polyethylene, polypropylene, polyphenylene ether, polybutylene terephthalate and polyamide. In this case, rubber elasticity is imparted to the separator, so that the contact resistance between the separator and the gas diffusion layer of the porous electrode is reduced, and chipping and cracking of the rib top are less likely to occur.

The separator according to the present embodiment has a volume resistivity of 0.05 Ω. cm or less, and the surface resistance is 0.1 cm.
It can be reduced to 5 Ω / cm ² or less and has excellent conductivity. Here, the method for measuring the volume resistivity is not particularly limited. For example, a four-terminal method (SRIS 230) at 25 ° C.
1). The method of measuring the surface resistivity is not particularly limited, but can be determined, for example, at 25 ° C. by the following method. First, the conductive resin composition used for the separator is formed into a plate having a smooth surface. In this case, the molding is performed under the same heating conditions as used for producing the separator. Then, the obtained plate-like molded body is placed horizontally, and two brass columnar electrodes of the same height having a rectangular end surface of 5 mm × 15 mm for contacting the surface of the plate-like molded body are placed thereon. They are installed parallel to each other. At this time, the distance between the electrodes is set at 15 mm.
Next, a total of 5 kg of weight is placed on the two electrodes via an insulating plate, and the measurement may be performed.

Embodiment 2 In this embodiment, a sheet-like metal substrate of a fuel cell separator composed of a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface is described. And a plurality of parallel ribs provided on the metal substrate, wherein the rib has a volume resistivity of 0.05Ω ·
A fuel cell separator made of a conductive resin composition having a diameter of not more than 1 cm will be described. Since the ribs of the separator according to the present embodiment are formed on the sheet-like metal substrate with a conductive resin composition having a volume resistivity of 0.05 Ω · cm or less, the strength is particularly high, and thinning is easy. is there. It is also excellent in gas impermeability.

The separator has a cross section perpendicular to the gas flow direction, for example, as shown in FIG. In FIG. 2, 3
Indicates a sheet-like metal substrate inside the separator. The separator thickness, rib pitch, and rib height (groove depth) are the same as in the first embodiment.

The separator can be obtained, for example, by screen-printing a conductive resin composition on a sheet-like metal substrate in the shape of a flow path and then curing the composition. Alternatively, the bulk molding compound of the conductive resin composition may be press-formed on a sheet-shaped metal substrate in a flow path shape. Further, the conductive resin composition may be injection-molded in a flow path shape on a sheet-like metal substrate.

The thickness of the sheet-like metal substrate is from 100 to
Preferably it is 1000 μm. Thickness 1000μ
m, the lightness of the separator is impaired and 100
If it is less than μm, the strength of the separator will be insufficient.

As the material of the sheet-shaped metal substrate, stainless steel which is excellent in corrosion resistance and inexpensive is preferable. Also,
If a thin film of gold, carbon material, titanium nitride, or the like is applied to the surface of the sheet-like metal substrate, the corrosion resistance can be further improved.

As the conductive resin composition, a resin
Powdered or fibrous materials containing a conductive filler such as carbon, silver, nickel, or copper can be used. Further, the same conductive resin composition as used in Embodiment 1 may be used. On the other hand, a conductive resin such as polypyrrole may be used as the resin. When using conductive resin,
It is not always necessary to use a conductive filler. The compounding ratio of the filler and the resin may be the same as the compounding ratio of the resin and the metal fiber in the conductive resin composition of the first embodiment. However,
In order for the separator to have sufficient conductivity, the volume resistivity of the conductive resin composition is 0.05 Ω. cm or less.

As the resin, a phenol resin, an epoxy resin, coal tar or the like may be used. These may be used alone or in combination of two or more. Among these, from the viewpoint of heat resistance and chemical resistance,
Phenolic resins are preferred.

Embodiment 3 The separator of the present embodiment is different from the separator of Embodiment 2 in that the sheet metal substrate used in Embodiment 2 is replaced with a sheet metal substrate having a plurality of through holes in the plane. 2 has the same configuration as that of FIG. The separator according to the present embodiment has a cross section perpendicular to the gas flow direction, for example, as shown in FIG.

As shown in FIG. 3, when a sheet-like metal substrate having a plurality of through-holes in the plane is used, the conductive resin composition on both the front and back surfaces of the sheet-like metal substrate 3 is passed through the through-holes 4. The molded articles can be adhered to each other. Therefore,
The strength of the separator is further improved than the separator according to the second embodiment. Further, the separator according to the present embodiment is easily thinned and excellent in gas impermeability, similarly to the separator according to the second embodiment.

The separator is formed, for example, by sandwiching a sheet-like metal substrate having a plurality of through-holes in a plane with a bulk molding compound of a conductive resin composition and press-forming the bulk molding compound so as to have a flow path shape. Obtainable. Alternatively, the conductive resin composition may be injection-molded in a flow path shape on a sheet-like metal substrate having a plurality of through holes in a plane.

Examples of the sheet metal substrate having a plurality of through holes in the plane include a punching metal, a lath plate, and an expanded metal. In addition, as the material,
It is the same as the sheet-shaped metal substrate used in the second embodiment,
Stainless steel is preferred. Also, gold,
A thin film of a carbon material, titanium nitride, or the like may be applied to improve corrosion resistance. The aperture ratio may be, for example, 60 to 85%.

Embodiment 4 In this embodiment, a sheet-like metal substrate of a fuel cell separator made of a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface. And a plurality of parallel ribs provided on the metal substrate, wherein the sheet-shaped metal substrate has a base rib, and the rib has the base rib and the volume resistivity of 0.0.
A fuel cell separator made of a conductive resin composition of 5 Ω · cm or less will be described.

In order to obtain a sheet-like metal substrate having base ribs, the sheet-like metal substrate used in Embodiment 2 or 3 may be pressed, for example. In addition, the same conductive resin composition as that used in Embodiment 1 or 2 can be used for the separator according to this embodiment, such as injection molding, screen printing, press molding using a bulk molding compound, and the like. Thereby, a rib can be formed on the base rib.

The cross section of the separator according to the present embodiment, which is perpendicular to the gas flow direction, is as shown in FIG. 4, for example. The pitch w of the base rib 5 is the same as the pitch of the rib 1 to 4
In general, the height h ′ of the base rib is 0.1 to 1 mm, and the bending angle r is 0 to 45 degrees.

In the separator, the rib is formed on the base rib of the metal substrate, and the portion of the conductive resin composition is thinner by the base rib. Accordingly, the strength of the separator is improved and the conductivity is also improved. Further, since the metal substrate is used, the thickness can be easily reduced and the gas impermeability is excellent as in the separator of the second embodiment.

[0038]

Next, the present invention will be described more specifically based on examples. << Example 1 >> An example of the separator according to Embodiment 1 was manufactured. Here, as the conductive resin composition, a thermoplastic elastomer made of polystyrene (Asahi Kasei Corporation)
100 parts by weight of SUS304 fiber having a diameter of 10 μm and a length of 300 μm were mixed with 100 parts by weight of Tuftec E2044 (trade name) manufactured by Toshiba Corporation.

Resin composition temperature 200 ° C., mold temperature 50
The resin composition is injection-molded at a temperature of 500 ° C. and a pressure of 500 kg / cm ² , and has a length of 100 mm having a predetermined gas flow path as shown in FIG.
A separator having a size of 100 mm x 100 mm x 1.5 mm was prepared. The volume resistivity of this separator is 0.07Ω ·
cm, and the surface resistance was 0.5 Ω / cm ² . Further, the gas permeability was extremely low.

Example 2 An example of the separator of Embodiment 2 was manufactured. Here, as a sheet-like metal substrate,
A SUS304 plate having a thickness of 0.1 mm was used. In addition, a phenol resin (PR50607B (trade name) manufactured by Sumitomo Durres Co., Ltd.) is used as the conductive resin composition for forming the gas flow path.
A composition comprising 50 parts by volume of artificial graphite powder having 50 parts by volume and an average particle size of 150 μm was used.

The composition was screen-printed on the substrate. At this time, a gas flow pattern having a predetermined shape with a height of 0.3 mm and a pitch of 1 mm as shown in FIG. 2 was formed. Then, 200 is applied to cure the gas flow path pattern portion.
Heated at ° C. The thickness of the obtained separator is 0.7 mm
And the volume resistivity of the gas flow path is 0.05Ω · cm.
Met.

Example 3 An example of the separator of Embodiment 3 was manufactured. Here, as a sheet-like metal substrate,
A SUS304 lath plate having a thickness of 0.5 mm and an aperture ratio of 78% was used. Phenol resin (PR50 manufactured by Sumitomo Durres Co., Ltd.) may be used as the conductive resin composition for forming the gas flow path.
607B (trade name)) 50 parts by volume and average particle size 150
Thickness 1 of composition consisting of 50 parts by volume of artificial graphite powder of μm
mm bulk molding compound was used. 2
The lath plate was sandwiched between two bulk molding compounds and pressed at a temperature of 140 ° C. and a pressure of 100 kg / cm ² to form a gas flow path. The thickness of the obtained separator is 1.5 mm, and the volume resistivity of the gas passage portion is 0.0
It was 3 Ω · cm.

Example 4 An example of the separator of Embodiment 4 was manufactured. Here, as a sheet-like metal substrate,
A SUS304 plate having a thickness of 0.2 mm and a base rib having a pitch of 2.5 mm, a height of 0.5 mm and a bending angle of 10 ° formed at a position corresponding to the gas flow path was used. This metal substrate was pressed between two sheets made of the conductive resin composition used in Example 2, and the entire surface of the metal substrate was covered with the conductive resin composition having a thickness of 0.1 mm. The thickness of the obtained separator was 0.9 mm, and the volume resistivity of the gas channel portion was 0.05 Ω · cm.

[0044]

According to the present invention, it is possible to provide a fuel cell separator which is easy to manufacture and has a good balance of conductivity, gas impermeability and strength, thereby reducing the cost of the fuel cell. , Thinning and high performance can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a fuel cell separator according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of an example of a fuel cell separator according to Embodiment 2 of the present invention.

FIG. 3 is a cross-sectional view of an example of a fuel cell separator according to Embodiment 3 of the present invention.

FIG. 4 is a sectional view of an example of a fuel cell separator according to Embodiment 4 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive resin composition 2 rib 3 sheet metal substrate 4 through hole 5 base rib d separator thickness w rib pitch h rib height h ′ base rib height r bending angle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Matsumoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 5H026 AA06 CC03 CX02 CX04 EE02 EE18 HH01 HH03 HH06

Claims (8)

[Claims] 1. A fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface, comprising a resin and a diameter of 5 to 30 μm and a length of 50 to 50 μm. A separator for a fuel cell, which is a molded article of a conductive resin composition comprising 1000 μm metal fibers. 2. The fuel cell separator according to claim 1, wherein the resin is at least one selected from the group consisting of polystyrene, polyethylene, polypropylene, polyphenylene ether, polybutylene terephthalate, and polyamide. 3. The fuel cell separator according to claim 1, wherein the metal fibers are made of stainless steel. 4. The method according to claim 1, wherein the volume resistivity is 0.05 Ω · cm or less and the surface resistance is 0.5 Ω / cm ² or less.
The fuel cell separator according to any one of the above. 5. A fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface, provided on a sheet-shaped metal substrate and on the metal substrate. A plurality of parallel ribs having a volume resistivity of 0.05 Ω ·
A separator for a fuel cell, comprising a conductive resin composition having a size of not more than 1 cm. 6. The fuel cell separator according to claim 5, wherein the sheet-shaped metal substrate has a plurality of through holes in a plane thereof. 7. A fuel cell separator comprising a conductive sheet having a gas flow path for supplying a fuel gas or an oxidizing gas to an electrode on at least one surface, provided on a sheet-shaped metal substrate and on the metal substrate. A plurality of parallel ribs, wherein the sheet-shaped metal substrate has a base rib, and the rib has a volume resistivity equal to that of the base rib.
A separator for a fuel cell, comprising a conductive resin composition having a resistance of not more than 05 Ω · cm. 8. A fuel cell comprising an electrolyte membrane and an electrode assembly in which a pair of porous electrodes are joined on both sides of an electrolyte membrane via the fuel cell separator according to claim 1.