JP2002190304A - Fuel cell separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell separator, composed mainly of a metal plate which is superior in conductivity and corrosion resistance, and can be produced at a relatively low cost. SOLUTION: A fuel cell separator has a coated resin layer which includes a conductive filler on at least one side of a metal substrate, and the metal substrate and the resin layer is bonded directly without an adhesive layer or a primer layer in between.

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, and more particularly, to a fuel cell formed by stacking a plurality of single cells, provided between adjacent single cells. The present invention relates to a fuel cell separator that forms an oxidizing gas flow path and separates a fuel gas and an oxidizing gas, and particularly relates to a fuel cell separator excellent in moldability, strength, and corrosion resistance.

[0002]

2. Description of the Related Art A separator constituting a fuel cell, especially a polymer electrolyte fuel cell, is disposed in contact with each electrode sandwiching a solid electrolyte membrane from both sides, and a fuel gas, an oxidizing agent and the like are interposed between the electrodes. It is required to form a supply gas passage for gas or the like, and to have excellent current collection performance for contacting an electrode to derive a current.

[0003] Generally, a fuel cell separator is made of a dense carbon graphite excellent in strength and conductivity as a base material, or a metal material such as stainless steel (SUS), titanium, and aluminum.

[0004]

Usually, a large number of projections, grooves, etc. for forming a gas flow path are formed on the surface of the separator facing the electrode. Therefore, in the separator composed of the dense carbon graphite, the electric conductivity is high, and the high current collecting performance is maintained even when used for a long period of time. It is not easy to perform machining such as cutting in order to form a large number of projections and grooves, which increases the processing cost and makes mass production difficult.

On the other hand, a separator made of the above-mentioned metal material is superior in strength and ductility as compared with dense carbon graphite, so that a large number of projections, grooves and the like for forming a gas flow path are formed. Has the advantages that press working is possible, processing cost is low, and mass production is easy. However, such a metal material is liable to form an oxide film due to corrosion on the surface thereof in a use environment of the separator, and the contact resistance between the generated oxide film and the electrode increases, thereby lowering the current collecting performance of the separator. There is a problem.

[0006] Therefore, as a constituent material of the separator, a material in which the surface of a metal material having excellent workability is coated with a noble metal material such as gold having excellent corrosion resistance has been studied. However, there is a problem that such a material is extremely expensive and thus lacks versatility.

Further, a material in which at least one surface of the metal substrate is coated with a resin layer mixed with a conductive filler has been studied. However, usually, there is a problem that the conductivity is hindered due to the presence of the adhesive layer or the primer layer between the metal substrate and the resin layer, and the resistance value of the separator increases.

The present invention has been made to solve the above-mentioned problem, and mainly comprises a metal substrate which has high conductivity, has excellent corrosion resistance and can be produced at a relatively low cost even if it is coated with a resin layer mixed with a conductive filler. The present invention relates to a fuel cell separator.

[0009]

SUMMARY OF THE INVENTION The present invention has found a fuel cell separator which can solve the above-mentioned problems. The gist of the present invention is to provide a resin layer containing a conductive filler on at least one surface of a metal substrate. Which is a fuel cell separator which is directly joined without interposing an adhesive layer or a primer layer between a metal substrate and a resin layer. On the surface of the metal substrate bonded to the resin layer, includes a fuel cell separator provided with a fine rough surface layer, the fine rough surface layer is formed by a mechanical etching method, a chemical etching method, or an electrolytic etching method It is included.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the metal substrate used in the separator of the present invention, a thin plate made of stainless steel, titanium, aluminum, copper, nickel, or steel can be suitably used, and has a thickness of 0.1 mm to 1.0 mm.
A range of 5 mm is desirable.

As the material used for the resin layer, a fluororesin and a fluororubber can be suitably used from the viewpoint of chemical resistance. Specifically, PTFE (polytetrafluoroethylene), P
FA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), EPE
(Tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer), E
TFE (tetrafluoroethylene-ethylene copolymer), PCTFE (polychlorotrifluoroethylene), ECTFE (chlorotrifluoroethylene-ethylene copolymer), PVDF (polyvinylidene fluoride),
PVF (polyvinyl fluoride), THV (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer), VDF-HFP (vinylidene fluoride-hexafluoropropylene copolymer), TFE-P
(Vinylidene fluoride-propylene copolymer), fluorine-containing silicone rubber, fluorine-containing vinyl ether rubber, fluorine-containing phosphazene rubber, at least one or more fluorine-containing resin and fluorine-containing thermoplastic elastomer can be used. In the resins exemplified above, PVDF and TH containing vinylidene fluoride are particularly preferable from the viewpoint of moldability.
V, VDF-HFP and TFE-P are preferred.

It is necessary to mix a conductive filler with the above-mentioned fluororesin and fluororubber. As the conductive filler, carbon, metal carbide, metal oxide, metal nitride and metal powder can be suitably used.

As carbon, graphite, carbon black, expanded graphite, and as metal carbide, tungsten carbide, silicon carbide, calcium carbide, zirconium carbide, tantalum carbide, titanium carbide, niobium carbide, molybdenum carbide, vanadium carbide, metal oxide as,
Titanium oxide, ruthenium oxide, indium oxide, metal nitrides such as chromium nitride, aluminum nitride, molybdenum nitride, zirconium nitride, tantalum nitride, titanium nitride, gallium nitride, niobium nitride, vanadium nitride, vanadium nitride, boron nitride, and metal powder titanium Powder, nickel powder, tin powder, tantalum powder, and niobium powder. Among the above-mentioned conductive fillers, use of a metal carbide is particularly preferable from the viewpoint of conductivity and acid resistance.

The mixing ratio of the conductive filler is 40% by weight or less.
The volume resistivity of the resin layer may be appropriately determined so as to be 1.0 Ω · cm or less at 95% by weight, and the mixing ratio is 40% by weight.
If it is less than 1.0, the volume resistivity exceeds 1.0 Ω · cm, resulting in poor conductivity. If it exceeds 95% by weight, molding tends to be difficult.

[0015] The thickness of the resin layer is preferably in the range of 10 to 300 µm, and if it is less than 10 µm, the corrosion resistance to the metal substrate is small, and if it exceeds 300 µm, the problem that the separator becomes thick and the stacked fuel cell becomes large tends to occur. .

As the etching method for providing a fine rough surface layer on the surface of the metal substrate to be joined to the resin layer, a mechanical etching method using an abrasive, a chemical etching method using a chemical, and electric energy are used. An electrolytic etching method using anodic dissolution may be mentioned, and may be appropriately determined depending on the type of the metal substrate.

The thickness of the fine rough layer provided by the etching method is in the range of 5 to 50 μm, preferably 10 to 30 μm.
Good range. When the thickness of the fine rough surface layer is less than 5 μm,
It becomes difficult to coat the resin layer containing the conductive filler. Further, there is a problem that it takes a long time to form a fine rough surface layer exceeding 50 μm on a metal substrate, so that productivity is poor.

The method for producing the separator of the present invention is not particularly limited, but a pre-formed fluororesin sheet having the above-mentioned composition is placed on one or both sides of a metal substrate and laminated and integrated by a hot press method. Thereafter, a method of forming a projection or a groove is preferable in terms of productivity and the like. The sheet may be formed by a conventional extrusion or roll forming method, and the hot pressing method may be performed under normal pressing conditions and a heating temperature of 120 ° C. to 300 ° C.
° C., a pressure ^{2.9 × 10 6 Pa~9.8 × 10 6} Pa (3
^{0kgf / cm 2 ~100kgf / cm 2} ) may be carried out at about.

Hereinafter, embodiments will be described, but the present invention is not limited thereto.

EXAMPLE 15 parts by weight of a fluororesin (THV) and 85 parts by weight of a conductive filler (tungsten carbide) were mixed by a twin screw extruder. The mixture was roll-formed (roll temperature 240 ° C.) to form a 200 μm thick sheet.
As the metal substrate, an aluminum 5052 plate (thickness: 5 mm) having an etching layer of 20 μm formed by an electrolytic etching method is used.
The sheets were placed in the order of 052 plate / fluororesin sheet, and laminated and integrated by hot press processing. The hot pressing condition is temperature 200 ° C,
10 minutes, pressure 3.5 × 10 ⁶ Pa (36 kgf / c
m ² ). Using the above laminate, press processing was again performed to form a gas flow path, and a fuel cell separator was obtained.
Pressing conditions are room temperature, 1 minute, and pressure 1.8 × 10 ⁷ Pa (1
80 kgf / cm ² ).

The resulting fuel cell separator has good adhesion between the fluororesin layer containing the conductive filler and the aluminum plate, does not peel off, has excellent volume resistivity of 0.005 Ω · cm, and has excellent conductivity. There was no problem in performance as a separator.

[0021]

As described above, the fuel cell separator of the present invention has high conductivity, excellent corrosion resistance, and can be produced at a relatively low cost. Great availability.

Claims (7)

[Claims] 1. A fuel cell separator comprising a metal substrate coated on at least one side with a resin layer containing a conductive filler, wherein the separator is directly bonded without interposing an adhesive layer or a primer layer between the metal substrate and the resin layer. Fuel cell separator. 2. The fuel cell separator according to claim 1, wherein a fine rough surface layer is provided on the surface of the metal substrate bonded to the resin layer. 3. The fuel cell separator according to claim 2, wherein the fine rough surface layer is formed by a mechanical etching method, a chemical etching method, or an electrolytic etching method. 4. The fuel cell separator according to claim 2, wherein the thickness of the fine rough surface layer is in the range of 5 to 50 μm. 5. The method according to claim 1, wherein the metal substrate is made of stainless steel, titanium,
5. The fuel cell separator according to claim 1, wherein the separator is selected from aluminum, copper, nickel, and steel. 6. The fuel cell separator according to claim 1, wherein the conductive filler is selected from carbon, metal carbide, metal oxide, metal nitride, and metal powder. 7. The fuel cell separator according to claim 1, wherein the resin layer is selected from a fluororesin and a fluororubber.