JP2000173629A - Separator for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator, having high electrical conductivity without losing dominance over the use of a resin material by penetratingly arranging a conductive member to a facing surface from a surface for forming a reaction gas flowing channel of a base material. SOLUTION: In a separator, plural metallic pins 302 penetrate through a partition wall 301a to form a reaction gas flowing channel of a base material 301 composed of resin. The length of the metallic pins 302 is set longer than a thickness D of the base material 301, and both ends are exposed from the surface and the rear surface of the base material 301. The more the number of metallic pins 302 increases, the lower the electrical resistivity becomes, so that gold, silver and nickel are used. In the separator, a metallic film 303 is desirably formed on at least a surface, more desirably, on the whole surface of the rear surface, and platinum and gold of a material hardly corroded by reaction gas are used. The separator is arranged as a cathode side separator 1 or an anode side separator 5, so that channels cross at a right angle to each other when constituting a fuel cell, and the metallic pins 302 of adjacent separators make contact with each other to be electrically continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator structure required for a fuel cell having a structure in which unit cells are connected in series.

More specifically, the present invention relates to a structure of a separator required for separating unit cells from each other so that gas is not mixed and connecting adjacent unit cells in series.

[0003]

2. Description of the Related Art There is known a so-called fuel cell which directly converts chemical energy of a fuel material into electric energy.

FIG. 4 is a schematic diagram showing a basic structure of a phosphoric acid type fuel cell. FIG. 5 schematically shows the outline of the operation principle.

In general, a fuel cell has a structure in which a plurality (usually several tens or more) of unit cells are stacked in series as shown in FIG.

FIG. 4 mainly shows the n-th unit cell.

First, the unit cell will be described. The unit cell has a structure as a minimum unit for performing power generation.

[0008] As shown in FIG.
And a structure in which the polymer film 3 is sandwiched between the anodes 4. The cathode 2 and the anode 4 are made of, for example, carbon paper containing platinum.

In the battery, the anode 4 functions as a negative electrode and the cathode 2 functions as a positive electrode.

[0010] It functions as cathode 2 or asode 4
The difference between the two functions is determined by the type of gas in contact. The one that contacts oxygen gas (generally air) is the cathode 2 and the one that contacts hydrogen gas is the anode 4.

A cathode-side separator 1 is arranged outside the cathode 2. A large number of channels (grooves) are provided on the cathode 2 side of the cathode side separator 1.

Oxygen gas is supplied to the cathode side separator 1.
Flows in the channel provided in the. The oxygen gas comes into contact with the cathode 2 when flowing through the channel portion of the cathode-side separator 1.

On the other hand, on the anode 4 side, an anode-side separator 5 is arranged outside the anode 4.
A large number of channels (grooves) are provided on the anode 4 side of the anode-side separator 5.

The hydrogen gas is supplied to the anode-side separator 5.
Flows in the channel. The hydrogen gas contacts the anode 4 when flowing through the channel portion of the anode-side separator 5.

As can be seen from FIG. 4, the cathode side separator 1 and the anode side separator 5 are arranged so that their channels are orthogonal to each other, and the flowing directions of the oxygen gas and the hydrogen gas are different from each other by 90 degrees. It has become. This is a device for separating and easily supplying both gases.

Power generation is performed by a mechanism as shown in FIG. Here, for simplicity of description, it is assumed that the anode-side separator 5 and the cathode-side separator 1 are electrically connected via a load (not shown) (indicated by a dashed line in the figure).

First, when hydrogen gas comes into contact with the anode 4, the catalytic action of the platinum component contained in the anode 4 causes
Hydrogen molecules separate into hydrogen ions (cations) and electrons. The former moves into the polymer film 3, and the latter moves to the anode-side separator 5.

On the other hand, in the cathode 2, oxygen molecules receive electrons generated from hydrogen at the anode 4 by the catalytic action of the platinum component contained therein and moved from the anode-side separator 5 via a load, and the oxygen molecules receive the electrons. Oxygen ions (anions) are generated. The negative oxygen ions are combined with hydrogen ions (cations) that have moved from the cathode 4 side into the polymer membrane 3 to synthesize water.

By repeating this cycle, electrons continue to flow from the anode-side separator 5 to the cathode-side separator 1, and power is generated. Thus, a battery in which the cathode-side separator 1 is an anode (plus electrode) and the anode-side separator 5 is a cathode (minus electrode) is obtained.

Generally, a fuel cell has a structure in which a number of unit cells are stacked in series. In this case, in the n-th unit cell, the anode-side separator 7 of the (n-1) -th unit cell is used. , And the operation of emitting electrons to the cathode-side separator 6 of the (n + 1) th unit cell is performed in unit cells other than the unit cells at both ends, and one of the unit cells at both ends receives electrons from the load, The other performs the operation of emitting electrons to the load, so that the fuel cell in which many cells are connected in series generates power.

In such a structure, the separator is required to have properties as shown in Table 1 below.

[0022]

[Table 1]

Each of the materials used so far has advantages and disadvantages as shown in the table.

As is evident from the table, as the separator, a resin molded article is most excellent overall. Although the corrosion resistance problem can be avoided by plating the surface of the metal material with a corrosion resistant metal material, there is a problem that the weight increases. There is also a problem in terms of cost.

In particular, it is necessary to form a gas flow channel in the separator. For this purpose, the separator needs to have a certain thickness. Therefore, when the whole is made of metal, its weight increases. In addition, the amount of metal used increases, which is disadvantageous in terms of cost.

As described above, it is generally desirable to use a resin material for the separator. However, the resin material has a fundamentally difficult problem of high electric resistance.

In particular, when employing a structure in which several tens of unit cells are stacked (connected in series), the high electrical resistance of the resin material poses a serious problem.

Techniques for using a resin material as a separator include those disclosed in JP-A-60-37670 and JP-A-Heisei 1-3.
What is described in 11570 gazette is publicly known.

For example, JP-A-60-37670 discloses a separator made of a thermosetting resin such as a phenol resin and carbon paper. The technique described in this publication is to impregnate a resin into conductive carbon paper.

JP-A-1-31570 discloses a separator comprising a thermosetting resin such as a phenol resin and a furan resin mixed with expanded graphite and carbon black.

In these known techniques, the conductivity of the separator is ensured by the carbon component.

[0032]

However, in the above-described technique, in order to obtain a required low electrical resistivity, a large amount of a carbon component must be blended, and the workability deteriorates. In addition, there is a problem that the cost increases. Particularly in the case of a fuel cell having a large number of stacks, a very low resistivity is required, but it is very difficult to satisfy the requirement without sacrificing other requirements.

In order to reduce the electrical resistivity by using a resin material, a complicated composition or a delicate composition must be pursued, and a high-cost material must be used. The problem that cost increases arises. Generally, when a resin material is used, a separator can be obtained at extremely low cost unless low electrical resistivity is pursued.

Accordingly, an object of the present invention is to provide a fuel cell separator having high conductivity (low electric resistivity) without losing the advantage of using a resin material.

[0035]

In order to achieve the above object, the present invention provides a fuel cell separator comprising a resin as a base material, wherein the conductive member is used for flowing a reaction gas through the base material. A fuel cell separator is provided so as to penetrate from a surface where a channel is formed to a surface facing the surface.

In this structure, it is not necessary to pursue low electrical resistivity by the resin itself. Therefore, the superiority of the resin material as shown in Table 1 can be obtained to the maximum.

[0037] Since the lowering of the electrical resistivity required for the separator is realized by a conductive member arranged to penetrate a base material made of a resin, a satisfactory one can be obtained. As the conductive member, a metal plate having a metal pin or a protrusion can be used.

Further, by coating at least the surface on the channel forming side with a corrosion-resistant metal, more reliable and stable conduction can be ensured, and corrosion by a reaction gas such as oxygen gas or hydrogen gas can be suppressed. .

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to preferred embodiments. (First Embodiment) FIGS. 1A and 1B are sectional views showing a first embodiment of a fuel cell separator of the present invention.

As shown in FIG. 1A, the separator has a structure in which a plurality of metal pins 302 penetrate a partition wall 301a forming a channel for reacting gas flow of a base material 301 made of resin. Both ends of the metal pin 302 are exposed on the front surface (the side on which the tunel is formed) and the back surface of the substrate 301.

The greater the number of metal pins 302, the lower the electrical resistivity. Although the size of the metal pin 302 is not particularly limited, its length needs to be equal to or more than the thickness (D) of the base material 301, and is set to, for example, 2 mm in a general separator.
The diameter is equal to or less than the width of the partition wall 301a forming the channel, for example, about 1.6 mm. Note that the metal pin 302 is not limited to a columnar shape, and may be a prismatic shape.

The material of the metal pin 302 is gold, silver,
Copper, nickel, zinc, stainless steel, brass, or alloys thereof can be used. Although a carbon material can be used in addition to metal, it is preferable to use a metal material in order to obtain a low electric resistivity.

The resin material for forming the base material 301 is not particularly limited, and a known resin for a separator can be used. For example, one or a plurality of thermosetting resins such as an epoxy resin, a phenol resin, and a melanin resin, and a thermoplastic resin such as a liquid crystal polyester and a polyphenylene sulfide can be used. Of these, epoxy resins are particularly preferred because of their good fluidity during molding.

According to the present invention, it is not necessary to obtain a low electrical resistivity for the resin material serving as the base material 301. Therefore, a resin material pursuing specifications other than the electrical resistivity shown in Table 1 may be selected. .

The above-described separator is obtained by disposing a metal pin 302 in an injection molding die, injecting a molten resin material into the metal pin 302, and integrally molding the same.

Further, it is preferable that the metal film 303 is formed on the entire surface of the separator, at least on the front surface (channel forming side), and preferably also on the rear surface. The thickness of the metal film 303 may be about 1 to 20 μm. Thus, the state shown in FIG. 1B is obtained.

As a film forming method, a vapor deposition method, a plating method, a sputtering method, or the like can be used. Alternatively, a method of attaching a separately obtained thin film may be employed.

For the metal film 303, it is necessary to use a material that is not or hardly corroded by the reaction gas. Examples of such materials include platinum and gold. Since the metal pins 302 are covered at both ends with the metal film 303, there is no need to consider corrosion.

The metal film 303 may be formed on the side surface in addition to the front and back surfaces of the base material 301 to cover the entire exposed surface.

This metal film has the following functions: (1) an action of increasing the electrical contact area on the front and back surfaces of the separator; and (2) an action of preventing the metal pins 302 from being corroded by contact with the reaction gas. I have.

Therefore, the separator shown in FIG.
In addition to the metal pins 302, the front and back metal films 303
As a result, conduction can be ensured, so that a low electrical resistivity required for the separator can be completely ensured.

Further, as the resin material constituting the base material 301, a material pursuing other required properties can be employed at the expense of lowering the electrical resistivity. Can be obtained.

The metal film 303 may be formed only on the surface of the metal pin 302 exposed from the base material 301. In this case, corrosion resistance that does not cause any practical problem can be imparted. In this case, the above-described injection molding may be performed using the metal pins 302 whose both end surfaces are coated with the metal films 303 in advance, or the exposed portions of the metal pins 302 may be formed by a suitable member when the metal films 303 are formed. Other than the above may be masked.

As shown in FIG. 3, the above-described separators are arranged as a cathode-side separator 1 or an anode-side separator 5 so that their respective channels are orthogonal to each other when a fuel cell is constructed. At this time, the metal pins 302 of the adjacent separators come into contact with each other, and conduction between the two separators is ensured.

(Embodiment 2) In the present embodiment, a metal plate having a projection is used instead of the metal pin 302 of the first embodiment. With this projection, the same effect as when the metal pin 302 is used can be obtained. This embodiment will be described with reference to FIG.

As shown in FIG. 2A, first, the metal plate 4
A hole 403 is made by punching in 01 to produce an annular projection 402 formed in that portion. The protrusions 402 are formed so as to alternately protrude from both sides of the metal plate 401. The material of the metal plate 401 is selected from the same materials as the metal pins 302.

The shape of the hole 403 of the protrusion 402 can be selected arbitrarily. The protruding height (H) over both sides of the metal plate 401 is the thickness (D) of the base material 404.
Above.

Next, as in the first embodiment, the above-mentioned metal plate 401 is placed in an injection molding die, and thereafter, a molten resin material is injected to be integrally molded. At this time, the alignment is performed so that the channel forming partition 404a of the base material 404 and the protrusion 402 of the metal plate 401 coincide with each other. Thus, FIG.
The state shown in is obtained. As a result, the protruding portions 402 of the metal plate 401 are exposed from the front and back surfaces of the base material 404, and conduction can be achieved on both surfaces.

Further, as in the first embodiment, the metal film 40
5 was formed by vapor deposition or sputtering, etc.
The state shown in (C) is obtained.

In this structure, the metal plate 401 having the protrusion 402 ensures conduction on the front and back surfaces of the base material 404, further increases the contact area for conduction by the metal film 405, and prevents corrosion of the protrusion 402. Is given.

In this structure, since the metal plate 401 spreads in the plane direction in the base material 404 and functions as a reinforcing material, a separator excellent in strength can be obtained.

The method of forming the protrusion 402 is not limited to the method of punching, but may employ a burring process, a cut-and-raise process, or the like. Further, the protrusion 402 does not need to have the hole 403 opened at the upper end thereof.

As in the first embodiment, the separator
When constituting a fuel cell, the respective channels are arranged orthogonally as a cathode-side separator or an anode-side separator (see FIG. 3).

[0064]

As described above, according to the present invention, (1) moldability of a complicated uneven shape (2) gas impermeability (3) corrosion resistance (low pH) (4) low electric resistance (high (Conductivity) (5) High compressive strength / high resistance to mechanical stress (6) Low cost A fuel cell separator having the following characteristics can be obtained. Further, since the amount of the metal material used can be minimized, a lightweight separator having low resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a separator according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the separator according to the present invention.

FIG. 3 is a schematic diagram showing a schematic structure of a fuel cell including a separator according to the present invention.

FIG. 4 is a schematic diagram showing a schematic structure of a fuel cell.

FIG. 5 is a schematic diagram for explaining the power generation principle of a fuel cell.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Cathode side separator 2 Cathode 3 Polymer film 4 Anode 5 Anode side separator 6 Cathode side separator of the next cell 7 Anode side separator of the next cell 301 Base material 301a Partition wall 302 Metal pin 303 Metal film 401 Metal plate 402 Projection 403 Hole 404 Base material 404a Partition wall 405 Metal film

Claims (4)

[Claims] 1. A fuel cell separator comprising a resin as a base material, wherein a conductive member penetrates from a surface of the base material where a reaction gas flow channel is formed to a surface facing the surface. A fuel cell separator, which is disposed. 2. The fuel cell separator according to claim 1, wherein the conductive member is a metal pin. 3. The fuel cell separator according to claim 1, wherein the conductive member is a metal plate having a protrusion. 4. A metal film having corrosion resistance in contact with the conductive member is formed on at least a surface of the substrate on which a channel for reacting gas flow is formed. The fuel cell separator according to any one of claims 1 to 3.