JP2003036867A - Separator for water electrolysis cell or fuel cell using solid polymer type electrolyte film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cheaply provide a separator for a water electrolysis cell or a fuel cell using a solid polymer type electrolyte film, in which the separator is precisely manufactured not by mechanical processing of titanium but by molding a synthetic resin as a material. SOLUTION: A synthetic resinous separator material molded in the shape of a separator is provided. A metal layer is formed on the outer face of the separator using electroless plating to give conductivity between one face and another face of the outer face. It is preferable to provide a metal frame at the circumference of the separator material to raise the conductivity from one face to another at the circumference or to provide a metal conductor through the separator material to raise the direct conductivity between one face to another.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water electrolysis cell or a fuel cell separator using a solid polymer electrolyte membrane. The present invention also relates to a method for manufacturing the separator and a water electrolysis cell or a fuel cell using the separator.

[0002]

2. Description of the Related Art In recent years, an electrolyte using a solid polymer electrolyte membrane as an electrolyte in a water electrolysis cell has been attracting attention because of its high efficiency. A fuel cell using a solid polymer electrolyte membrane is also expected to be useful. The water electrolysis cell and the fuel cell are devices that perform opposite reactions in terms of electrochemical reaction.
That is, in the concept of a battery, water electrolysis is equivalent to charging,
Power generation by a fuel cell corresponds to discharge. For this reason, both the water electrolysis cell using the solid polymer electrolyte membrane and the fuel cell are basically composed of the parts shown in FIG.

In FIG. 1, reference numeral (1) is a fluororesin (PTFE) type cation exchange membrane, the surface of which is
Electroless plating of platinum group metals such as platinum, iridium, ruthenium, etc., or oxides thereof, or PTFE and carbon and platinum group metals (or oxides)
There is a reaction layer (2) formed by coating a mixture obtained by kneading, drying and baking. This reaction layer is also called an electrode assembly. Reference numeral (3) is a component made of an electrically conductive porous material, specifically, metal or porous graphite, which is a “power supply body” in a water electrolysis cell and a “current collector” in a fuel cell. "It is called.

The parts (1) to (3) are gathered together as shown in FIG. 1, and are laminated while being partitioned by a metal plate having irregularities, that is, a plate called a separator (4), and are end plate (5). A water electrolysis cell or a fuel cell is constructed by tightening from both sides.

When water electrolysis is performed, the separator (4) provides a passage for supplying water to the surface of the electrode assembly, and at the same time, acts as a partition plate for separating hydrogen gas and oxygen gas generated by electrolysis. . At the same time, it is a current-carrying body that transfers electricity to the electrode assembly. In the fuel cell, it is a gas flow path that separately supplies hydrogen gas and oxygen gas to the fuel electrode side and the oxygen electrode side, and is also a current-carrying body for transmitting electrons generated by the oxidation reaction of hydrogen gas.

Currently, this separator has a thickness of 10
A titanium plate having a depth of up to 20 mm, which is provided with irregularities having a depth of several mm by machining, and the surface of which is plated with platinum to enhance the electrical conductivity, is mainly used.

However, the unit cell composed of the components (1) to (3) is laminated by several tens to several hundreds with the separator (4) sandwiched therebetween to form an electrolytic cell or a fuel cell.
If the separators are not processed with high precision and are not evenly manufactured, the tightening pressure on each electrode assembly will not be uniform, and there will be local deviation in the surface pressure at which the power supply or current collector contacts the electrode assembly. Occurs. The uneven surface pressure causes problems such as promoting local deterioration of the polymer film and deteriorating current / voltage characteristics due to the uneven current.

Therefore, the separators must be processed into the same shape with high accuracy. In processing the same shape with high accuracy, it is necessary to consider the problem that the plate is distorted by the heat generated during the grinding of the concave and convex grooves. As is well known, titanium is a poorly workable material. For this reason, a titanium plate as thick as 10 to 20 mm must be used in consideration of heat dissipation and mechanical strength of the separator. Needless to say, titanium is an expensive material, and the product yield is low due to cutting, so the separator is a costly part.

The reason why titanium is used as the material of the separator is that titanium having a high corrosion resistance is selected so as not to cause anodic dissolution when placed in an anode environment where oxygen is generated during water electrolysis. Platinum plating on the surface of the separator means that when titanium undergoes anodic oxidation,
This is because it is easy to form an electrically insulating anodic oxide film on the surface.

On the other hand, the separator in the fuel cell does not necessarily need to use titanium because the environment on the oxygen electrode side resulting from the oxidation reaction of hydrogen is not higher in oxidation potential than the environment on the anode side of water electrolysis. Therefore, it has been proposed to manufacture a separator by using stainless steel which is cheaper than titanium (Japanese Patent Laid-Open Nos. 2001-32056, 2001-6703, 2000-328205,
JP-A-2000-328200, JP-A-2000-3098
54, JP 2000-303151 A, JP 2000-2 A.
65248, JP 2000-260439 A, JP 200 JP
0-256808, JP-A-2000-243409, etc.).

Regarding the separator for water electrolysis, Japanese Patent Application Laid-Open No. HEI 7-187
No. 252682 proposes a method of superplasticizing a thin plate of a titanium alloy to ensure the same shape of each separator, reduce the amount of titanium material used, and reduce the cost.

Regarding the separator of the fuel cell, JP-A-2
000-164228, on the surface of a metal base material, two or more layers of a low electric resistance layer, a corrosion resistant layer and a peeling resistant layer selected from various metals or metal compounds, vapor deposition, plating, thermal spraying, etc. It is proposed to provide it by the method of.

It has also been devised to provide an inexpensive separator using synthetic resin as a material rather than metal. For example, in Japanese Patent Laid-Open No. 2000-77079, graphite powder 85-87.
% And a thermosetting resin of 3 to 15% are kneaded, filled in a mold and molded into a predetermined shape. Similar methods are disclosed in JP-A-2000-77081 and JP-A-2000-48.
830, JP-A-11-354138, JP-A-11-3541
37, JP-A 11-354136, JP-A 11-35413.
5, JP-A-11-297337, JP-A-10-33492
7, JP-A-11-354135 and the like.
These measures are based on the idea that the synthetic resin plays a role as a separator for separating oxygen gas and hydrogen gas, and the role of energization is played by graphite powder kneaded and dispersed in the synthetic resin. .

However, since the separator formed by kneading graphite and synthetic resin uses graphite having a lower electric conductivity than the metallic separator, it has a large amount of electric conductivity in order to ensure the electric conductivity. It is necessary to knead the above graphite with a synthetic resin. A high black smoke filling rate lowers the mechanical strength originally possessed by synthetic resins. There is also a problem that the gas adsorbed to the graphite powder appears as bubbles during molding, which prevents the graphite particles from contacting each other inside the separator molded product, and consequently obstructs the current flow.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems encountered in a separator which constitutes a water electrolysis tank or a fuel cell using a solid polymer electrolyte membrane, is inexpensive, and has a high shape accuracy. To provide a high separator. Providing a method for manufacturing this separator,
It is also included in the object of the present invention to provide a water electrolysis cell and a fuel cell using this separator.

[0016]

A separator for a water electrolysis cell or a fuel cell using a solid polymer electrolyte membrane of the present invention has a metal layer on the entire outer surface of a synthetic resin separator material molded in the shape of the separator. Is formed to give conductivity between one surface and the other surface.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION
A synthetic resin separator material having an appropriate cross-sectional shape is prepared as a separator by injection molding, extrusion molding or press molding of a synthetic resin, and electroless metal plating is applied to the entire surface of the separator material to impart conductivity.

The water electrolysis cell of the present invention is a water electrolysis cell using a solid polymer electrolyte membrane obtained by combining the above separator with an anode and a cathode.

The fuel cell of the present invention is a fuel cell using a solid polymer electrolyte membrane in which the above separator is combined with an anode and a cathode.

The method for producing the separator of the present invention will be described with reference to FIG.
First, as shown in FIG. 2A, a mold (6) processed to have a desired separator shape.
2 is filled with synthetic resin, and the synthetic resin is molded by pressurizing or pressurizing to obtain a separator material (7) as shown in FIG. 2B. The separator material taken out from the mold is cleaned and removed of impurities such as a release agent adhering to the surface and subjected to surface roughening treatment such as blast treatment, and then, as shown in FIG. 2C.
Immerse in the electroless plating bath (8).

The synthetic resin used for producing the separator material should be selected according to the environment in which the water electrolysis cell or the fuel cell is used. For example, when the temperature is 100 ° C. or less and the environment is mild, the environment is mild. , Polyethylene, polyvinyl chloride, polypropylene, polystyrene,
It can be arbitrarily selected from commonly used synthetic resins such as polyvinyl acetate, ABS resin, AS resin and acrylic resin.

When the temperature is 100 ° C. or higher and the pressure is 0.2 to 0.
When used in an environment of medium temperature and pressure of 5 MPa, polyacetal, polyimide, polycarbonate, modified polyphenylene ether (PPE), polybutylene terephthalate (PPB, polyester of terephthalic acid and 1,4-butanediol), urea resin, phenol resin Unsaturated polyester resin is suitable.

At higher temperatures, polyarylate, polysulfone, polyphenylene sulfide, polyether ether ketone, polyimide resin, fluororesin, etc. may be used. In particular, polyamideimide, polyetheretherketone, and the like have heat resistance of 250 ° C. or higher, and can withstand long-term use, and are therefore suitable as synthetic resins for producing the raw material of separators used under severe conditions.

For the purpose of reinforcing the mechanical strength, FRP prepared by adding glass fiber, carbon fiber, aramid fiber or the like to thermoplastic resin such as polypropylene, nylon or polycarbonate is also useful, and unsaturated polyester resin, epoxy resin, phenol It is also effective to use a thermosetting resin such as resin as a material.

For the operation of electroless plating the surface of a synthetic resin molded product in the shape of a separator to give conductivity to the surface of the separator, silver coating known as a silver mirror reaction or electroless plating of nickel-phosphorus is recommended. To be done. In particular, silver coating is useful because it is simple and has high conductivity. The resistivity of silver is 1.96 × 10 ⁻⁶ Ω
・ Cm, which is 5.5 × 10 ^-5 Ω ・ cm of titanium
The conductivity of silver is 28 times higher than that of. When considered as a flow path for an electric current, it means that for a titanium plate having a cross section of 1 mm, only 1/28 of 36 μm is necessary for silver.

However, when a conductive material is applied only to the surface such as a silver coating, electric current is passed along the surface of the separator around the flow edge and reaches the back surface. Is disadvantageous to
In order to cope with high current density, as shown in FIG. 3, a frame (9) made of metal, especially titanium, should be placed on the edge of the separator material made of synthetic resin to reduce the electric resistance at the edge. But that is one measure. The layout of the metal frame is
Although it can be performed after the electroless plating, it is also possible to previously form the separator material by integrating the synthetic resin and the metal frame, and then apply the coating by the electroless plating.

As an alternative method, as shown in FIG. 4, a conductive material (10) made of a metal such as titanium penetrating a separator material made of synthetic resin is embedded, and the separator is directly penetrated without passing through an edge to generate a current. Is effective. In this case, it is preferable that the separator material of synthetic resin is embedded by a method such as insert injection molding so that the metal is exposed on the surface, and then electroless plating is performed. In any case, such a method can reduce the IR drop at high current density.

The environment in which the anode in water electrolysis and the oxygen electrode in the fuel cell are placed depends on the operating conditions.
Due to the oxidizing environment, it may be necessary to improve the corrosion resistance of silver. In this case, another coating may be applied on the silver coating by another method. If the main purpose is to improve corrosion resistance, platinum plating is effective, but chemical or physical surface coating such as ion plating and sputtering is also useful for reinforcing corrosion resistance. .

The surface of the separator is easily scratched when the water electrolysis cell or the fuel cell is assembled. Especially, since silver is a soft metal, defects are likely to occur during handling. To deal with this problem, it is effective to apply nickel-phosphorus electroless plating. The electroless nickel-phosphorus plating layer has a Vickers hardness of Hv500 or more, and a uniform coating layer is easily obtained. The hard chrome plating (electrolytic plating) layer also has a hardness of Hv1000 or more, which is effective from the viewpoint of surface protection, but the electric current concentration on the edge portion in electroplating tends to increase the plating thickness at the end portion. Therefore, it is necessary to plate with appropriate masking.

In addition to the above-mentioned method, the conductive material can be coated on the surface of the synthetic resin separator material by a method such as sputtering, ion plating, vapor deposition, etc., although the cost is high. Particularly, sputtering is effective because it is easy to form an amorphous alloy layer having excellent corrosion resistance.

[0031]

EFFECTS OF THE INVENTION Since the separator of the present invention can manufacture the separator material with high precision, the product separator can be obtained with high dimensional accuracy, and the surface pressure of the separator can be obtained even in a water electrolysis cell or a fuel cell in which many units are stacked. There is no concern about variations.

Since most of the materials are synthetic resins and inexpensive materials are sufficient, the cost can be much lower than that of the prior art in which expensive materials such as titanium plates are machined and used at a low product yield. . Electroless plating, such as silver mirror reaction, is an operation that can be easily performed according to established techniques.

A preferred embodiment of the separator, in which a separator material is provided with a frame or a conductive material, effectively reduces the resistance associated with creeping surface conductivity and helps to keep the efficiency of the water electrolysis cell or fuel cell high.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a water electrolysis cell and a fuel cell using a solid polymer electrolyte membrane.

FIG. 2 is a diagram for explaining an example of a method for producing a separator of the present invention, where A is a stage in which a synthetic resin is press-molded with a mold to prepare a separator material, and B is the obtained separator. The cross section of the material, C, shows the step of immersing it in the electroless plating bath.

FIG. 3 is a plan view of a separator material for explaining what is manufactured by a method different from the manufacturing method of FIG. 2 of the separator of the present invention.

FIG. 4 is a plan view of a separator material for explaining what is manufactured by a method different from the manufacturing method of FIGS. 2 and 3 of the separator of the present invention.

[Explanation of symbols]

1 Cation exchange membrane 2 reaction layers 3 Power supply or current collector 4 separator 5 End plate 6 mold 7 Separator material 8 Electroless plating bath 9 frames 10 Conductive material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor K. Inazumi             1-89 South Kohoku, Suminoe-ku, Osaka-shi, Osaka             Issue Hitachi Shipbuilding Co., Ltd. (72) Inventor Masayoshi Kondo             1-89 South Kohoku, Suminoe-ku, Osaka-shi, Osaka             Issue Hitachi Shipbuilding Co., Ltd. (72) Inventor Hitoshi Ojira             1-89 South Kohoku, Suminoe-ku, Osaka-shi, Osaka             Issue Hitachi Shipbuilding Co., Ltd. (72) Inventor Hiroshi Tatsumi             1-89 South Kohoku, Suminoe-ku, Osaka-shi, Osaka             Issue Hitachi Shipbuilding Co., Ltd. F-term (reference) 5H026 AA06 BB01 BB02 BB04 CC05                       EE02 EE18

Claims (7)

[Claims] 1. A metal layer is formed on the entire outer surface of a separator material made of a synthetic resin molded in the shape of a separator,
A water electrolysis cell or a fuel cell separator using a solid polymer electrolyte membrane having conductivity between one surface and the other surface. 2. The separator according to claim 1, wherein a metal frame is provided on the peripheral edge of the synthetic resin separator material to enhance conductivity from one surface to the other surface of the peripheral edge. 3. A conductive material made of metal, which penetrates through the synthetic resin separator material and connects one surface to the other surface, to enhance direct conductivity from one surface to the other surface. 1
Separator. 4. A synthetic resin separator material having an appropriate cross-sectional shape as a separator is prepared by injection molding, extrusion molding or press molding of synthetic resin, and electroless metal plating is applied to the entire surface thereof. 1. The method for manufacturing the separator according to 1. 5. The separator according to claim 2 or 3, wherein when a synthetic resin separator material is prepared by injection molding, insert molding is performed in which a metal frame or a conductive material is placed in a mold in advance. Method. 6. A water electrolysis cell using a solid polymer electrolyte membrane obtained by combining the separator according to claim 1 with an anode and a cathode. 7. A fuel cell using a solid polymer electrolyte membrane obtained by combining the separator according to claim 1 with an anode and a cathode.