JP2004087318A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily enable downsizing as well as surely form a reaction gas passage with a simple and economical structure. <P>SOLUTION: A fuel cell 10 has an electrolyte film/electrode structure 12 and a first and a second metallic separators 14, 16. An anode side electrode 28 and a cathode side electrode 30 composing the structure 12 is provided with gas diffusion layers 32a, 32b composed of a foam made from metallic material such as stainless steel, and passage walls 36a, 36b, 36c, 36d made from a resin for forming the reaction gas passage are installed by impregnation in the foam. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell in which an electrolyte membrane / electrode structure having electrodes provided on both sides of an electrolyte membrane and a separator are stacked.
[0002]
[Prior art]
In general, a polymer electrolyte fuel cell has an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode are provided on both sides of an electrolyte membrane composed of a polymer ion exchange membrane (cation exchange membrane). , And a separator. This type of fuel cell is generally used as a fuel cell stack by alternately stacking a predetermined number of electrolyte membrane / electrode structures and separators.
[0003]
In this fuel cell, a fuel gas supplied to the anode electrode, for example, a gas mainly containing hydrogen (hereinafter, also referred to as a hydrogen-containing gas) is obtained by ionizing hydrogen on the electrode catalyst and passing through the electrolyte to the cathode side. Move to the electrode side. The electrons generated during that time are taken out to an external circuit and used as DC electric energy. Since an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas) is supplied to the cathode side electrode, hydrogen ions, electrons, And oxygen react to produce water.
[0004]
In this case, the anode-side electrode and the cathode-side electrode usually have a gas diffusion layer made of a porous carbon member, and porous carbon particles having a platinum alloy supported on the surface are uniformly coated on the surface of the gas diffusion layer. Electrode catalyst layers. At that time, in order to improve the diffusion characteristics of the reaction gas into the electrode catalyst layer of the gas diffusion layer, for example, a polymer electrolyte fuel cell disclosed in Japanese Patent No. 311278 is known.
[0005]
In this conventional technique, a polymer electrolyte membrane, a carbon porous body supporting a catalyst, disposed so as to sandwich both sides of the polymer electrolyte membrane, and at least a portion disposed outside the carbon porous body, The foamed metal has a water-repellent metal foam and a bulk electrode disposed outside the foamed metal.
[0006]
In the prior art configured as described above, the diffusion characteristics of the reaction gas into the catalyst layer of the carbon porous body can be improved through the foam metal, and the water generated inside the carbon porous body can be foamed. It can be discharged smoothly through metal.
[0007]
[Problems to be solved by the invention]
By the way, as shown in FIG. 9, this type of fuel cell is usually constituted by sandwiching an electrolyte membrane / electrode structure 1 between a pair of separators 2a and 2b. The electrolyte membrane / electrode structure 1 is provided such that both sides of the polymer electrolyte membrane 3 are sandwiched between an anode 4 and a cathode 5. A fuel gas flow path 6 for supplying a fuel gas to the anode 4 is formed in the separator 2a, while an oxidant gas for supplying an oxidant gas to the cathode 5 is formed in the separator 2b. A channel 7 is formed.
[0008]
However, in the above configuration, in order to provide the fuel gas flow path 6 and the oxidizing gas flow path 7, grooves are formed in the separators 2a and 2b, or the separators 2a and 2b are formed of a metal plate and press-formed. It is necessary to form grooves on the diffusion layers constituting the anode-side electrode 4 and the cathode-side electrode 5. For this reason, the manufacturing cost of the entire fuel cell increases, and the dimension in the stacking direction (the direction of the arrow X) becomes longer. Particularly, when a fuel cell stack is formed by stacking a plurality of fuel cells in the direction of arrow X, a problem has been pointed out that the dimension of the entire fuel cell stack in the stacking direction becomes considerably long.
[0009]
Further, in the above-described fuel cell stack, a reaction gas communication hole for supplying and discharging a reaction gas such as an oxidizing gas or a fuel gas in a stacking direction is usually provided to constitute an internal manifold. As a result, a seal structure is required to reliably prevent gas leakage from the reaction gas communication hole, and this type of seal structure is complicated and is not economical.
[0010]
The present invention is to solve this kind of problem, and to provide a fuel cell that has a simple and economical configuration, reliably forms a reaction gas flow path, and can easily be downsized. Aim.
[0011]
Another object of the present invention is to provide a fuel cell capable of reliably forming a reaction gas communication hole and a seal with a simple and economical structure and capable of easily reducing the size.
[0012]
[Means for Solving the Problems]
The fuel cell according to claim 1 of the present invention includes a diffusion member that comes into contact with the electrolyte membrane or the electrolyte membrane / electrode structure. Here, when the diffusion member is provided with an electrode to form a diffusion electrode, the diffusion member contacts the electrolyte membrane, while the electrode is provided on the electrolyte membrane to form an electrolyte membrane / electrode structure. The diffusion member comes into contact with the electrolyte membrane / electrode structure. A diffusion member is provided with a foam made of a metal material, and a resin flow path wall that is incorporated in the foam and forms a reaction gas flow path for flowing a reaction gas along an electrode in the foam. ing.
[0013]
Therefore, since the reaction gas flow path is formed directly in the foam, there is no need to form a flow path groove in the separator or the diffusion member, and the manufacturing cost of the entire fuel cell can be effectively reduced, and the fuel cell can be easily miniaturized. be able to. Furthermore, when a metal plate separator is used, press working is not required, the degree of freedom in designing the reaction gas flow path is improved, and the separator can be made as thin as possible. In addition, since the separator is laminated on the electrolyte membrane / electrode structure by surface contact, reduction of electric resistance in the thickness direction and improvement of impact resistance can be achieved.
[0014]
In the fuel cell according to claim 2 of the present invention, the fuel cell further includes a diffusion member that comes into contact with the electrolyte membrane or the electrolyte membrane / electrode structure, and the diffusion member includes a foam made of a metal material, and is incorporated in the foam. And a resin flow path wall for forming a reaction gas communication hole for flowing a reaction gas in the stacking direction. Thus, gas communication holes having various shapes can be easily formed at arbitrary positions only by setting the shape and position of the resin flow path wall.
[0015]
Further, in the fuel cell according to claim 3 of the present invention, the resin flow path wall is formed by impregnating a foam with a resin. Therefore, it is possible to easily and surely form the reaction gas passages and the reaction gas communication holes having various shapes.
[0016]
Furthermore, in the fuel cell according to claim 4 of the present invention, the fuel cell further includes a diffusion member that comes into contact with the electrolyte membrane or the electrolyte membrane / electrode structure, and the diffusion member includes a foam made of a metal material; And a resin seal portion for integrally forming a reaction gas communication hole for flowing a reaction gas in the stacking direction and a seal for the reaction gas communication hole. That is, when the resin seal portion is incorporated in the foam, a reaction gas communication hole is formed in the resin seal portion, and the reaction gas communication hole is sealed through the sealing function of the resin seal portion. The reaction gas communication hole seal is formed.
[0017]
Thereby, the reaction gas communication hole and the seal for the reaction gas communication hole are integrally formed by merely incorporating the resin seal portion, and a complicated sealing structure is not required, and the configuration can be easily simplified. . Moreover, since the resin sealing portion is incorporated in the foam, the sealing performance is effectively improved, and the leakage of the reaction gas can be reliably prevented.
[0018]
Further, in the fuel cell according to claim 5 of the present invention, the resin seal portion is configured by impregnating the foam with the resin. For this reason, various shapes of reaction gas communication holes can be easily and reliably formed, and good sealing performance can be ensured.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an exploded perspective view of a main part of a fuel cell 10 according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the main part of the fuel cell 10.
[0020]
The fuel cell 10 includes an electrolyte membrane / electrode structure 12, and first and second metal plate separators 14 and 16 sandwiching the electrolyte membrane / electrode structure 12. A sealing member, such as a gasket, is provided between the electrolyte membrane / electrode structure 12 and the first and second metal plate separators 14 and 16 to cover a periphery of a communication hole described later and an outer periphery of an electrode surface (power generation surface). 18 are interposed.
[0021]
One end of the fuel cell 10 in the direction of arrow B communicates with each other in the direction of arrow A, which is the stacking direction, to form an oxidant gas supply passage 20a for supplying an oxidant gas, for example, an oxygen-containing gas. A cooling medium discharge communication hole 22b for discharging a medium and a fuel gas discharge communication hole 24b for discharging a fuel gas, for example, a hydrogen-containing gas, are provided in an arrow C direction (vertical direction).
[0022]
At the other end of the fuel cell 10 in the direction of the arrow B, a fuel gas supply communication hole 24a for supplying a fuel gas and a cooling medium supply communication hole for supplying a cooling medium are communicated with each other in the direction of the arrow A. 22a, and an oxidizing gas discharge communication hole 20b for discharging the oxidizing gas are arranged in the arrow C direction.
[0023]
The electrolyte membrane / electrode structure 12 includes, for example, a solid polymer electrolyte membrane 26 in which a thin film of perfluorosulfonic acid is impregnated with water, an anode electrode 28 and a cathode electrode sandwiching the solid polymer electrolyte membrane 26. 30.
[0024]
As shown in FIG. 2, the anode electrode 28 and the cathode electrode 30 are composed of gas diffusion layers (diffusion members) 32a and 32b and porous carbon particles having a platinum alloy supported on the surfaces thereof. And the electrode catalyst layers 34a and 34b uniformly applied to the surface of the substrate. The electrode catalyst layers 34a and 34b are joined to both surfaces of the solid polymer electrolyte membrane 26 so as to face each other with the solid polymer electrolyte membrane 26 interposed therebetween.
[0025]
The gas diffusion layer 32a is formed of, for example, a foam made of a metal material such as stainless steel, titanium, or nickel that is highly conductive, does not generate rust due to moisture, and does not corrode under strong acidity. Is formed by impregnating resin flow path walls 36a, 36b, 36c and 36d which are thermoplastic resin or thermosetting resin. As shown in FIG. 1, the resin flow path walls 36a to 36d extend in the direction of arrow B inside the gas diffusion layer 32a, and are arranged in a staggered manner. A fuel gas passage 38 meandering through the resin passage walls 36a to 36d is formed. The fuel gas passage 38 communicates with the fuel gas supply passage 24a and the fuel gas discharge passage 24b.
[0026]
As shown in FIGS. 2 and 3, the gas diffusion layer 32b is formed of, for example, a foam made of the same metal material as the gas diffusion layer 32a described above. 40a, 40b, 40c and 40d are formed by impregnation. The resin flow path walls 40a to 40d extend in the direction of arrow B and are arranged in a staggered manner, and a meandering oxidant gas flow path 42 is formed in the gas diffusion layer 32b. The oxidizing gas passage 42 communicates with the oxidizing gas supply communication hole 20a and the oxidizing gas discharge communication hole 20b.
[0027]
As shown in FIG. 1, an opening 44 is formed in the center of the seal member 18 so as to correspond to the anode 28 and the cathode 30. Although not shown, for example, when the fuel cells 10 are stacked, a cooling medium flow path for supplying a cooling medium between the adjacent fuel cells 10 is provided. The cooling medium passage communicates with the cooling medium supply communication hole 22a and the cooling medium discharge communication hole 22b.
[0028]
The operation of the fuel cell 10 configured as described above will be described below.
[0029]
As shown in FIG. 1, a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply passage 24a, and an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas supply passage 20a.
[0030]
The fuel gas is supplied to the anode 28 from the fuel gas supply passage 24 a of the electrolyte membrane / electrode assembly 12. In the anode 28, a fuel gas flow path 38 is formed in a gas diffusion layer 32a formed of a foam through resin flow path walls 36a to 36d. Therefore, the fuel gas moves in the surface direction of the electrode catalyst layer 34a while meandering inside the gas diffusion layer 32a along the fuel gas flow path 38.
[0031]
On the other hand, the oxidizing gas is supplied to the cathode 30 from the oxidizing gas supply passage 20 a of the electrolyte membrane / electrode structure 12. In the cathode 30, as shown in FIG. 3, an oxidizing gas channel 42 is formed in a gas diffusion layer 32 b formed of a foam via resin channel walls 40 a to 40 d. Therefore, the oxidizing gas moves in the surface direction of the electrode catalyst layer 34b while meandering inside the gas diffusion layer 32b along the oxidizing gas flow path 42.
[0032]
Thus, in the electrolyte membrane / electrode structure 12, the oxidizing gas supplied to the cathode 30 and the fuel gas supplied to the anode 28 are consumed by the electrochemical reaction in the electrode catalyst layer 34b. , Electricity is generated.
[0033]
Next, the fuel gas supplied to the anode 28 and consumed is discharged in the direction of arrow A along the fuel gas discharge communication hole 24b. Similarly, the oxidizing gas supplied to and consumed by the cathode 30 is discharged in the direction of arrow A along the oxidizing gas discharge communication hole 20b.
[0034]
In this case, in the first embodiment, the gas diffusion layers 32a and 32b constituting the anode 28 and the cathode 30 are formed of a foam made of a metal material, and the foam is impregnated with a resin. Thereby, resin flow passage walls 36a to 36d and 40a to 40d are provided. Therefore, inside the gas diffusion layers 32a and 32b, the meandering fuel gas passage 38 and the oxidizing gas passage 42 are formed directly by being partitioned by the resin passage walls 36a to 36d and 40a to 40d. ing.
[0035]
Therefore, there is no need to form a groove for a reaction gas flow passage in the first and second metal plate separators 14, 16 or the gas diffusion layers 32a, 32b, and the manufacturing cost of the entire fuel cell 10 can be effectively reduced. Can be. Moreover, it is not necessary to provide grooves in the first and second metal plate separators 14 and 16 by press working, so that the cost of the press die can be reduced, and the first and second metal plate separators 14 and 16 can be provided. It becomes possible to make it thinner. As a result, an effect is obtained that the dimension of the entire fuel cell 10 in the stacking direction can be significantly reduced.
[0036]
Furthermore, since the press working of the first and second metal plate separators 14 and 16 is not required, the degree of freedom in designing the fuel gas flow path 38 and the oxidizing gas flow path 42 is improved.
[0037]
Furthermore, the first and second metal plate separators 14 and 16 are formed in a flat plate shape, and have a greater resistance to external force when compared with a conventional metal plate separator having an uneven shape for forming a reaction gas flow path. It is possible to effectively reduce the increase in the surface pressure and to reduce the electric resistance in the thickness direction.
[0038]
That is, FIG. 4 shows the relationship between the electrical resistance in the thickness direction due to the contact between a metal plate separator having a normal irregular shape and carbon paper (conventional example) and the surface pressure, and the metal plate separator of the first embodiment. The relationship between the electrical resistance in the thickness direction and the surface pressure due to the contact between the metal foams 14 and 16 and the foam made of a metal material is shown. As is apparent from FIG. 4, the first embodiment has an advantage that the electric resistance in the thickness direction is significantly reduced as compared with the conventional example.
[0039]
Further, in the first embodiment, the resin flow passage walls 36a to 36d and 40a to 40d are formed in the foam constituting the gas diffusion layers 32a and 32b by resin impregnation. Therefore, the fuel gas flow path 38 and the oxidizing gas flow path 42 having various shapes can be easily and reliably formed.
[0040]
As shown in FIG. 5, a predetermined opening 46 is provided in the foam constituting the gas diffusion layers 32a and 32b, and resin flow path walls 36a to 36d and 40a formed in advance in the opening 46 are formed. ~ 40d may be inserted and fixed.
[0041]
In the first embodiment, the fuel gas flow path 38 and the oxidizing gas flow path 42 are configured in a meandering flow path shape. For example, as shown in FIG. 38a and the oxidizing gas channel 42a may be employed. At this time, the fuel gas flow path 38a and the oxidizing gas flow path 42a are impregnated or inserted into the foams constituting the gas diffusion layers 32a and 32b, and a plurality of resin flow path walls 48 extending in various directions. , 50.
[0042]
Therefore, the fuel gas flow path 38a and the oxidizing gas flow path 42a having various flow path shapes can be easily formed only by incorporating the resin flow path walls 48 and 50 in the anode 28 and the cathode 30. The advantage is that it can be used.
[0043]
FIG. 7 is an exploded perspective view of a main part of a fuel cell 60 according to a second embodiment of the present invention, and FIG. 8 is a cross-sectional view of the main part of the fuel cell 60. The same components as those of the fuel cell 10 according to the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.
[0044]
The fuel cell 60 includes an electrolyte membrane / electrode structure 62. As shown in FIG. 8, the electrolyte membrane / electrode structure 62 includes gas diffusion layers 63a and 63b constituting the anode 28 and the cathode 30. Is provided. The gas diffusion layers 63a and 63b are limited to substantially the same dimensions as the solid polymer electrolyte membrane 26 in a planar shape. 64a to 64f are provided.
[0045]
The resin-made flow path walls 64a to 64f are formed in a substantially ring shape, and the oxidant gas supply communication hole 20a, the cooling medium discharge communication hole 22b, the fuel gas discharge communication hole 24b, A fuel gas supply passage 24a, a cooling medium supply passage 22a, and an oxidant gas discharge passage 20b are formed.
[0046]
On the resin flow path walls 64a to 64f, a resin seal portion 66 constituting a seal for a reaction gas communication hole is formed as required by, for example, coin injection molding (two-color molding).
[0047]
Resin channel walls 68 and 70 are incorporated in the anode 28 and the cathode 30 in order to regulate the ranges of the fuel gas channel 38 and the oxidizing gas channel 42.
[0048]
In the fuel cell 60 configured as described above, the leakage of the fuel gas and the oxidizing gas can be reliably prevented and a good sealing function can be achieved only by incorporating the resin sealing portion 66, and the sealing structure can be simplified. Can be achieved. Moreover, as compared with the case where an individual seal structure is provided, an alignment operation or the like is not required, and an effect that the workability of assembling the entire fuel cell 60 is improved at once.
[0049]
In the second embodiment, the resin sealing portion 66 is formed by coin injection molding on the resin channel walls 64a to 64f as needed. It is also possible to form a reaction gas communication hole such as the oxidizing gas supply communication hole 20a by directly impregnating or attaching the foam into the foam.
[0050]
【The invention's effect】
In the fuel cell according to the present invention, since the reaction gas flow path is formed directly in the foam, it is not necessary to form a flow path groove in the separator or the diffusion member, thereby effectively reducing the manufacturing cost of the entire fuel cell. , And can be easily reduced in size. Furthermore, when a metal plate separator is used, press working is not required, the degree of freedom in designing the reaction gas flow path is improved, and the thickness of the separator material can be reduced as much as possible. In addition, since the separator is laminated on the electrolyte membrane / electrode structure by surface contact, the electric resistance in the thickness direction can be reduced.
[0051]
Also, in the present invention, gas communication holes having various shapes can be easily formed at arbitrary positions simply by setting the shape and position of the resin flow path wall.
[0052]
Further, in the present invention, by incorporating the resin seal portion in the foam, the reaction gas communication hole and the seal for the reaction gas communication hole are integrally formed, so that a complicated sealing structure is not required and the configuration is simplified. Can be easily achieved. Moreover, since the resin sealing portion is incorporated in the foam, the sealing performance is effectively improved, and the leakage of the reaction gas can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a main part of a fuel cell according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a main part of the fuel cell.
FIG. 3 is an explanatory front view of an electrolyte membrane / electrode structure constituting the fuel cell.
FIG. 4 is a diagram illustrating the relationship between surface pressure and electric resistance in the thickness direction in the conventional example and the first embodiment.
FIG. 5 is an explanatory view when a resin channel wall is incorporated as a separate body in a foam.
FIG. 6 is an explanatory front view of the electrolyte membrane / electrode structure when the resin flow path walls are randomly arranged.
FIG. 7 is an exploded perspective view of a main part of a fuel cell according to a second embodiment of the present invention.
FIG. 8 is a sectional view of a main part of the fuel cell.
FIG. 9 is a partial cross-sectional explanatory view of a fuel cell according to a conventional technique.
[Explanation of symbols]
10, 60 ... fuel cell 12, 62 ... electrolyte membrane / electrode structure 14, 16 ... metal plate separator 26 ... solid polymer electrolyte membrane 28 ... anode side electrode 30 ... cathode side electrodes 32a, 32b ... gas diffusion layer 34a, 34b: Electrode catalyst layers 36a to 36d, 40a to 40d, 48, 50, 64a to 64f, 68, 70: Resin flow path walls 38, 38a: Fuel gas flow paths 42, 42a: Oxidant gas flow path 66: Resin Seal part

Claims (5)

An electrolyte membrane / electrode structure provided with electrodes on both sides of the electrolyte membrane, and a fuel cell in which a separator is laminated,
A diffusion member that contacts the electrolyte membrane or the electrolyte membrane / electrode structure,
The diffusion member, a foam made of a metal material,
A resin flow path wall incorporated in the foam, forming a reaction gas flow path for flowing a reaction gas along the electrode in the foam,
A fuel cell, comprising: An electrolyte membrane / electrode structure provided with electrodes on both sides of the electrolyte membrane, and a fuel cell in which a separator is laminated,
A diffusion member that contacts the electrolyte membrane or the electrolyte membrane / electrode structure,
The diffusion member, a foam made of a metal material,
A resin flow path wall that is incorporated in the foam and forms a reaction gas communication hole for flowing a reaction gas in the stacking direction,
A fuel cell, comprising: 3. The fuel cell according to claim 1, wherein the resin channel wall is formed by impregnating the foam with a resin. 4. An electrolyte membrane / electrode structure provided with electrodes on both sides of the electrolyte membrane, and a fuel cell in which a separator is laminated,
A diffusion member that contacts the electrolyte membrane or the electrolyte membrane / electrode structure,
The diffusion member, a foam made of a metal material,
A resin seal portion that is incorporated in the foam and integrally forms a reaction gas communication hole for flowing a reaction gas in the stacking direction and a seal for the reaction gas communication hole,
A fuel cell, comprising: The fuel cell according to claim 4, wherein the resin seal portion is configured by impregnating the foam with a resin.

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