JPH11162478A - Fuel cell separator - Google Patents

Abstract

(57) [Problem] To provide a low-cost fuel cell separator having high electric conductivity, high corrosion resistance and low cost. SOLUTION: In a fuel cell stack in which a plurality of fuel cells 100 having electrodes arranged on both sides of a solid electrolyte are stacked, the fuel cells are interposed between the fuel cells and used on one side. An oxidant gas passage for supplying a fuel gas to one fuel cell; and an oxidant gas passage for supplying an oxidant gas to the other adjacent fuel cell on the other side. A fuel cell separator 200 having a groove 201, wherein the metal plate 203 serving as a base material of the separator is selected from the group consisting of silver, chromium nitride, a complex oxide of a platinum group, or a compound of boron carbide and nickel. A separator for a fuel cell, which has been subjected to plating surface treatment with a different material.

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.

[0002]

2. Description of the Related Art Various types of fuel cells, such as a solid polymer electrolyte type, a phosphoric acid type, a molten carbonate type, and a solid oxide type, are known depending on the type of electrolyte used. Among them, the solid polymer electrolyte fuel cell is a fuel cell utilizing the fact that a polymer resin membrane having a proton exchange group in a molecule functions as a proton conductive electrolyte when saturated with water.
It operates in a relatively low temperature range and has excellent power generation efficiency.
Various applications are expected, including those mounted on electric vehicles.

In a polymer electrolyte fuel cell, a mixed gas of hydrogen, carbon dioxide, nitrogen and water vapor is supplied to an anode (fuel electrode) side, and air and water vapor are supplied to a cathode (oxidant electrode) side.

[0004] Each gas is in a high temperature state of 80 to 90 ° C, and the separator is required to have high heat resistance by being exposed to each gas.

[0005] Further, since the separator electrically connects the cells, high electrical conductivity and low contact resistance with the constituent materials are required.

As a prior art, Japanese Patent Publication No. Hei 8-222237
As disclosed in Japanese Unexamined Patent Application Publication No. HEI 9-115, a metal plate coated with dense carbon graphite having good electric conductivity is disclosed. Japanese Patent Application Laid-Open No. 6-349508 discloses that a metal plate is provided with a coating of a conductive material such as chromium, a platinum group metal or an oxide thereof, or a conductive polymer.

[0007]

However, the former is a technique coated with carbon graphite, but there is a manufacturing method such as sputtering in the coating of carbon graphite. However, such a technique has a low productivity and is expensive. Become.

In the latter case, chromium or a conductive polymer does not have sufficient corrosion resistance in a high-temperature and high-humidity environment. Platinum group metals and their oxides have relatively high corrosion resistance, but do not have sufficient stability over a long period of time. Surface treatment is required for stabilization, which is disadvantageous in terms of productivity and cost.

Further, when used for a fuel cell, a potential of about 1 V due to an electrode reaction, and the supplied air and hydrogen are exposed to the separator as a gas at about 80 ° C. including water vapor, and environmental conditions are severe. There is something.

[0010] As a surface treatment method for a metal plate made of SUS, titanium, aluminum or the like having electrical conductivity and excellent corrosion resistance, gold plating can be used, but the cost is high.

The present invention has solved the above-mentioned problems, and provides a fuel cell separator having high electric conductivity, high corrosion resistance, and low cost.

[0012]

Means for Solving the Problems In order to solve the above technical problems, the technical measures taken in claim 1 of the present invention (hereinafter, referred to as first technical means) are provided on both sides of the solid electrolyte. In a fuel cell stack in which a plurality of fuel cells having electrodes arranged thereon are stacked, the fuel cells are used by being interposed between the fuel cells, and one side is provided with fuel gas in one adjacent fuel cell. A fuel cell separator having a fuel gas flow channel for supplying and an oxidizing gas flow channel for supplying an oxidizing gas to the other adjacent fuel cell on the other side surface. A silver plate, a chromium nitride, a composite oxide of the platinum group, or a plating surface treatment with a material selected from the group consisting of a composite of boron carbide and nickel, Do It is a separator for a fee battery.

The effects of the first technical means are as follows.

That is, the electric conductivity is high, the corrosion resistance is high,
It has the effect of a low-cost fuel cell separator.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings.

FIG. 1 is an exploded view of the fuel cell of the present invention.
A battery cell 100 having a structure in which an electrolyte layer 101 formed of a solid polymer electrolyte is sandwiched between a fuel electrode 103 and an oxidant electrode 105, and a battery cell 100 having a structure in which the battery cell 100 is sandwiched between separators 200. 100 are sandwiched between separators 200 and stacked.

On one surface of the separator 200, a passage 201 through which an oxidizing gas supplied to the oxidizing electrode 105 passes is formed. The other side of the separator 200 has a passage 20 through which the fuel gas supplied to the fuel cell 103 passes.
2 are formed.

The separator 200 includes the electrodes 103 and 105
And has a current collecting function and a partition function of preventing mixing of the oxidizing gas and the fuel gas. As the metal plate 203 serving as a base, an aluminum plate, a titanium plate, SUS (stainless steel plate) or the like is used. Particularly, aluminum, which is a low-cost material, is preferable.

(Example 1) A silver plating process is performed on a metal plate 203 to form a silver plating surface coating. The silver plating on the metal plate 203 is performed by a conventional electrolytic plating method or an electroless plating method to a thickness of 10 μm. Although silver plating is a noble metal, it is inexpensive and allows low-cost surface treatment.

Table 1 is a graph showing the relationship between surface pressure and contact resistance. The test conditions at this time were 45 mm × 5
Using a 2 mm SUS304 (stainless steel) substrate with a test piece by electroplating, a 1.0 mm thick mating material
Was contacted with a contact area of 10 cm ² .

As a result, as can be seen from this graph,
The contact resistance of a silver-plated test specimen as in the present invention is:
It shows a value almost as low as the contact resistance of a test piece obtained by subjecting SUS to gold plating, and satisfies the required performance as a fuel cell separator.

Table 2 is a graph showing the relationship between the corrosion test days of silver-plated test pieces and the contact resistance. The corrosive environmental conditions are performed in an air / water vapor atmosphere at 75 ° C. As can be seen from this graph, the contact resistance obtained by the silver plating treatment as in the present invention is low even under corrosive environmental conditions, and the corrosion resistance is good. In this test, the corrosion environment test
Although it was performed only for 50 days, the contact resistance seems to be around 5 mΩ × cm ² even after 50 days.

(Example 2) A chromium nitride plating (CrN) treatment is performed on the metal plate 203 to form a chromium nitride plating surface film. The chromium nitride plating on the metal plate 203 is performed to a thickness of 5 μm by sputtering or PDV.

In this embodiment, the chromium nitride is directly coated on the metal surface by the PVD method. This chromium nitride was excellent in chemical stability and could realize a separator excellent in electric conductivity.

Table 3 is a graph showing the relationship between the surface pressure and the contact resistance of the test piece coated with nitride. The test conditions at this time are the same as those in Example 1.

As can be seen from this graph, the contact resistance of the chromium nitride plated test piece according to the present invention is S
It shows a value close to the contact resistance of a test piece gold-plated to US, and satisfies the required performance as a fuel cell separator. Instead of chromium nitride plating, titanium nitride may be used. In the case of titanium nitride, it is also possible to perform nitriding directly on the titanium plate.

As a comparative example, as can be seen from the graph, the zinc nitride plating treatment has a large contact resistance and does not satisfy the required performance as a fuel cell separator.

Example 3 A platinum group composite plating process for forming a platinum group composite plating surface film is performed on the metal plate 203. The platinum group composite plating on the metal plate 203 is performed up to a thickness of 5 μm.

Table 4 is a graph showing the relationship between the surface pressure and the contact resistance of a palladium (Pd) composite oxide plating test piece. The test conditions at this time are the same as those in Example 1.

As can be seen from this graph, the present embodiment 3
The contact resistance of the test piece plated with palladium composite oxide is as low as the contact resistance of the test piece plated with SUS gold, satisfying the required performance as a fuel cell separator. Is what you do.

Table 5 is a graph showing the relationship between the corrosion test days and the contact resistance of the test piece subjected to the palladium composite oxide plating treatment. Corrosion environment conditions are air at 75 ° C
It is performed in a steam atmosphere. As can be seen from this graph, the contact resistance obtained by the silver plating treatment as in the present invention is low even under corrosive environmental conditions, and the corrosion resistance is good. In this test, the corrosion environment test was performed only for 35 days.
Even after 5 days, the contact resistance seems to be around 5 mΩ × cm ² .

In addition to palladium composite oxide plating, chromium nitride plating and ruthenium (Ru) and iridium (Ir) composite oxide plating may be performed. This plating is formed by performing electrolytic composite plating of ruthenium and iridium and then performing anodic oxidation.

The composite oxide plating of ruthenium and tantalum is formed in a similar manner. Further, RuO ₂ / Zr
O ₂ , RuO ₂ / TiO ₂ , RuO ₂ / Al ₂ O ₃ , R
A platinum group composite oxide such as uO ₂ / LaO ₃ may be used.

(Embodiment 4) A composite plating process of boron carbide and nickel (B ₄ C / Ni) is performed on the metal plate 203. The composite plating of boron carbide and nickel on the metal plate 203 is performed to a thickness of 5 μm by sputtering or PDV.

Table 6 is a graph showing the relationship between the surface pressure and the contact resistance of a composite plated test piece of boron carbide and nickel. As can be seen from this graph, the contact resistance of the test piece subjected to the composite plating of boron carbide and nickel as in Example 4 is as low as the contact resistance of the SUS plated with gold, and the fuel This satisfies the required performance as a battery separator.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

[Table 7]

[0043]

The invention of claim 1 has the following effects.

That is, the electric conductivity is high, the corrosion resistance is high,
It has the effect of a low-cost fuel cell separator.

[Brief description of the drawings]

FIG. 1 is an exploded view of a fuel cell including a separator and the like of the present invention.

[Description of Signs] 100: fuel cell 202: fuel gas flow groove 201: oxidizing gas flow groove 200: fuel cell separator

Claims (1)

[Claims] 1. A fuel cell stack comprising a plurality of fuel cells in which electrodes are arranged on both sides of a solid electrolyte. The fuel cell stack is used by being interposed between the fuel cells. One side is adjacent to one side. A fuel gas passage groove for supplying fuel gas to one fuel cell is provided, and an oxidant gas passage groove for supplying oxidant gas to the other adjacent fuel cell is provided on the other side surface. A fuel cell separator comprising: a metal plate serving as a base material of the separator; a surface plated with a material selected from the group consisting of silver, chromium nitride, a complex oxide of a platinum group, or a complex of boron carbide and nickel; A separator for a fuel cell, which has been subjected to a treatment.