JP2003132905A - Electrolytic film/electrode structure and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic film/electrode structure and a fuel cell which enhance reliability and permanence by preventing the worn of the electrolytic film. SOLUTION: In the electrolytic film/electrode structure 20, a pair of electrode 24, 26 is put on the both side of a solid polymer electrolytic film 22. The electrode 24 is formed in the plane dimension larger than the other electrode 26, and the solid polymer electrolytic film 22 is formed in the plane dimension so as to protrude from the pair of electrode 24, 26. In the fuel cell 30, a paired separators 34, 36 which hold on the both side of the electrolytic film/electrode structure 20, are formed in the plane dimension the same as or larger than the solid polymer electrolytic film 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte membrane / electrode structure which is sandwiched between a pair of electrodes on both sides of a solid polymer electrolyte membrane, and a fuel cell in which the electrolyte membrane / electrode structure is sandwiched between a pair of separators. It is a thing.

[0002]

2. Description of the Related Art In a fuel cell, a fuel cell is constructed by sandwiching an electrolyte membrane / electrode structure composed of a solid polymer electrolyte membrane and anode electrodes and cathode electrodes on both sides thereof with a pair of separators. There is one in which a plurality of fuel cells are stacked to form a fuel cell stack.

An example of this will be described with reference to FIG. 5. In FIG. 5, reference numeral 1 denotes an electrolyte membrane / electrode structure. The electrolyte membrane / electrode structure 1 includes a solid polymer electrolyte membrane 2 and electrodes provided on both sides thereof. (Anode electrode and cathode electrode) 3,
It is composed of four. The solid polymer electrolyte membrane 2 is formed to have a larger plane size than the anode electrode 3 and the cathode electrode 4 on both sides of the solid polymer electrolyte membrane 2, and the solid polymer electrolyte membrane 2 protrudes from the outer periphery of these electrodes 3 and 4. ing. A pair of separators 5 and 6 are provided on both surfaces of the electrolyte membrane / electrode structure 1. A seal member 7 is arranged on the peripheral side of the facing surfaces of the separators 5 and 6, and the solid polymer electrolyte membrane 2 is sandwiched by the seal members 7. Further, in this state, the separators 5 and 6 sandwich the electrolyte membrane / electrode structure 1 to form the fuel cell 8, and the fuel cell stack 1 is formed by stacking a plurality of the fuel cells 8.
2 are configured. The separators 5 and 6 are provided with gas passage holes 9 and 10 for supplying a fuel gas, an oxidizing gas, and a cooling medium, and a cooling medium passage hole 11.

Fuel cell stack 1 constructed as described above
In No. 2, when a fuel gas (for example, hydrogen gas) is supplied to the reaction surface of the anode electrode 3 through the gas passage hole 9, hydrogen is ionized on this reaction surface (catalyst layer), and the hydrogen is ionized through the solid polymer electrolyte membrane 2. And moves to the cathode electrode 4 side. The electrons generated during this time are taken out to an external circuit and used as direct current electrical energy. In the cathode electrode 4, an oxidizing gas (for example, air containing oxygen) is supplied to the reaction surface of the cathode electrode 4 through the gas passage hole 10, so that hydrogen ions, electrons, and oxygen react to generate water. It It should be noted that cooling water is supplied to the cooling medium passage hole 11 to suppress the temperature of the fuel cell 8 to within a certain temperature and generate electric power.

[0005]

However, in the conventional electrolyte membrane / electrode structure 1, as shown in FIG. 5, the end faces of the electrodes 3 and 4 are arranged at the same position as seen from the stacking direction. Therefore, stress may be excessively concentrated on the solid polymer electrolyte membrane 2 in this portion. In particular, when the reaction gas supplied to the anode electrode 3 and the cathode electrode 4 has a pressure difference, stress may concentrate on the solid polymer electrolyte membrane 2.

Further, in the conventional fuel cell stack 12, the positions of the electrodes 3, 4 end faces and the seal member 7 are slightly apart from each other, and the anode side and the cathode side are located between the electrodes 3, 4 end face and the seal member 7. Was separated by the thin solid polymer electrolyte membrane 2 as shown in FIG. Therefore, when the solid polymer electrolyte membrane 2 in this partition portion is damaged, there is a risk that a gas leak is generated in the anode side and the cathode side, and a cross leak occurs, which lowers the power generation efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrolyte membrane / electrode structure and a fuel cell having improved reliability and durability.

[0008]

The invention described in claim 1 made in order to solve the above-mentioned problems, an electrolyte membrane (for example, the solid polymer electrolyte membrane 22 in the embodiment) is provided with a pair of electrodes (for example, Anode electrode 2 in the embodiment
4. The electrolyte membrane / electrode structure (for example, the electrolyte membrane / electrode structure 20 in the embodiment) sandwiched between the cathode electrode 26) and one of the pair of electrodes (for example, the embodiment). The anode electrode 24) in
While being formed to have a larger plane dimension than the other electrode (for example, the cathode electrode 26 in the embodiment),
The electrolyte membrane / electrode structure is characterized in that the electrolyte membrane is formed to have a planar dimension protruding from the pair of electrodes.

With the above structure, the end faces of the pair of electrodes sandwiching the electrolyte membrane can be provided at positions deviated from the stacking direction. This makes it possible to disperse the stress from each electrode end face without concentrating the stress on the same portion of the electrolyte membrane.

The invention according to claim 2 is characterized in that, of the pair of electrodes, a peripheral portion of an electrode having a large planar size is formed by a seal member (for example, the seal member 52 in the embodiment). Electrolyte membrane / electrode structure (for example, electrolyte membrane / electrode structure 50 in the embodiment)
Is.

With the above structure, the material of the electrode having the larger plane size can be reduced while maintaining the area of the power generation surface where the electrodes face each other, so that it is necessary for the electrode without lowering the power generation efficiency. It is possible to reduce expensive materials and reduce costs. Furthermore, it is possible to prevent the reaction gas from leaking from the end face of the larger electrode to the outside of the electrode.

According to a third aspect of the present invention, there is provided a fuel cell (for example, the fuel cell 30 according to the embodiment) in which the electrolyte membrane / electrode structure is sandwiched by a pair of separators (for example, the separators 34 and 36 according to the embodiment). ) And the pair of separators are formed to have the same plane dimension as or larger than that of the electrolyte membrane.

With the above structure, a seal member (for example, the seal member 3 in the embodiment) that sandwiches the portion of the electrolyte membrane protruding from the pair of electrodes from both sides.
40a side of 8, 40) can be provided, and
A seal member (for example, the 40b side of the seal member 40 in the embodiment) is also provided inside the seal member and on the outer side of the electrode end surface having the smaller plane size, and the seal member and the plane dimension facing the seal member are provided. The electrolyte membrane can be sandwiched between the electrode having the larger size. In this way, the electrolyte membrane is sandwiched between the inside (the portion in contact with the peripheral portion of the larger electrode) and the outside (the portion protruding from the pair of electrodes) by the seal members (sealing members 38, 40), whereby the sealing property is improved. Can be improved. That is, even if a problem occurs in the inner seal member and the reaction gas leaks to the outer side from the inner seal member, the outer anode side and the cathode side are partitioned by the electrolyte membrane, and the protruding portion of the electrolyte membrane Since the is sealed, it is possible to prevent the occurrence of cross leak. Also, a problem occurs in the outer sealing member that sandwiches the protruding portion of the electrolyte membrane,
Even if the reaction gas flows inward from the outer seal member, the inner portion is sandwiched between the inner seal member and the electrode, so that cross leak can be prevented.

In this case, since the seal member can be provided at the portion of the electrode having the larger plane size facing the inner seal member, the electrolyte membrane sandwiched between the seal member and the inner seal member can be provided. The sealing property can be further enhanced. That is, it is possible to more effectively prevent the reaction gas from flowing out from a portion of the electrolyte membrane sandwiched by the inner sealing member and the reaction gas from flowing into this portion. Therefore, the reliability of the fuel cell in terms of performance and the durability during operation can be further enhanced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an electrolyte membrane / electrode structure and a fuel cell according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of essential parts showing an electrolyte membrane / electrode structure and a fuel cell according to a first embodiment of the present invention. The electrolyte membrane / electrode structure 20 is a solid polymer electrolyte membrane 22.
And an anode electrode 24 and a cathode electrode 26 which are arranged with the solid polymer electrolyte membrane 22 interposed therebetween. The anode electrode 24 and the cathode electrode 26 are formed of a catalyst layer (not shown) that is in contact with the solid polymer electrolyte membrane 22 and a gas diffusion layer (not shown) outside the catalyst layer. The catalyst layer is formed of a material containing platinum as a main component, and the gas diffusion layer is formed of porous carbon cloth or porous carbon paper which is a porous layer. The solid polymer electrolyte membrane 22 is formed of perfluorosulfonic acid polymer (fluorine resin). As a material of the solid polymer electrolyte membrane film 22, a material containing a hydrocarbon-based resin as a main component may be used.

FIG. 2 is a plan view showing the electrolyte membrane / electrode structure 20 according to the present embodiment. As shown in FIG.
The anode electrode 24 is formed to have a larger plane size than the cathode electrode 26. Further, the solid polymer electrolyte membrane 22 is formed to have a larger plane size than the anode electrode 24 and the cathode electrode 26, and protrudes from these electrodes 24 and 26. In the present embodiment, as shown in FIG. 2, the end faces of the anode electrode 24 and the cathode electrode 26 are provided at positions displaced from each other in the stacking direction. As a result, the stress from the end faces of the electrodes 24 and 26 is applied to the solid polymer electrolyte membrane 22.
Distribute instead of concentrating in the same place. Therefore, the stress that the solid polymer electrolyte membrane 22 receives from the end faces of the electrodes 24 and 26 can be reduced, and the protection of the solid polymer electrolyte membrane 22 can be enhanced.

Further, the anode electrode 24 is replaced by the cathode electrode 2
By making the plane size larger than 6, it is possible to reduce the portion of the solid polymer electrolyte membrane 22 protruding from both electrodes 24, 26. As a result, the portion of the solid polymer electrolyte membrane 22 that is in contact with the anode electrode 24 can be reinforced by the anode electrode 24, so that the protection of the solid polymer electrolyte membrane 22 in the thickness direction can be enhanced. Further, since the respective electrodes 24 and 26 have a smaller plane size than the solid polymer electrolyte membrane 22, the materials of the expensive electrodes 24 and 26 can be reduced.

A fuel cell 30 using the above electrolyte membrane / electrode structure 20 will be described. As shown in FIG. 1, the fuel cell 30 includes the electrolyte membrane / electrode structure 20.
And a pair of separators 34 and 36 for sandwiching the same. A fuel cell stack 32 is formed by stacking a plurality of the fuel cells 30. The separator 3
Channels 4 and 36 are formed with flow passages for allowing the reaction gas (fuel gas, oxidant gas) to flow therethrough, but since they are almost the same as conventional ones, illustration and description thereof will be omitted. In addition, reference numeral 42 in FIG. 1 denotes a sealing member that seals the cooling flow path formed between the separators 34 and 36 that are adjacent to each other in the stacking direction, but description thereof will be omitted.

In the present embodiment, the separator 3
4, 36 are formed to have a plane dimension larger than that of the electrolyte membrane / electrode structure 20. Therefore, as described below, the seal member 40 can be provided outside the cathode electrode 26 and the seal member 38 can be provided outside the anode electrode 24. The seal member 38 is formed to have a convex cross section and has a convex portion 38a. Further, the seal member 40 has a convex portion 40a as with the seal member 38, and also has a convex portion 40b inside thereof.
The protrusions 38a and 40a of these seal members 38 and 40 are the protruding surfaces (electrodes 24 and 26) of the solid polymer electrolyte membrane 22.
The solid polymer electrolyte membrane 22 is sealed by pressure-contacting both sides (the surface protruding from the inside). Further, the convex portion 40b of the seal member 40 is further provided on the inner side of the solid polymer electrolyte membrane 2
Anode electrode 2 that is pressed against 2 and faces the convex portion 40b.
The solid polymer electrolyte membrane 22 is sandwiched between the peripheral edge of the solid polymer electrolyte membrane 22 and the peripheral edge of the solid polymer electrolyte membrane 22.

In this way, the solid polymer electrolyte membrane 22 is sandwiched between the inside (the portion in contact with the peripheral portion of the anode electrode 24) and the outside (the portion protruding from the anode electrode 24 and the cathode electrode 26) to improve the sealing property. Can be made. That is, even if a defect occurs in the convex portion 40b of the seal member 40 and the reaction gas leaks to the outside from the convex portion 40b, the anode side and the cathode side on the outside are the surfaces protruding from the solid polymer electrolyte membrane 22. Since the divided portion and the protruding portion of the solid polymer electrolyte membrane 22 are sealed by the convex portions 38a, 40a of the sealing members 38, 40, the occurrence of cross leak can be prevented.
Further, the convex portions 38a, 40a of the outer seal members 38, 40 sandwiching the protruding portion of the solid polymer electrolyte membrane 22.
Even if the reaction gas flows inward from the convex portions 38a and 40a, the inner portion is sandwiched between the convex portion 40b of the seal member 40 and the anode electrode 24, so that a cross leak occurs. Can be prevented.

Further, in the present embodiment, the convex portion 34a is provided on the electrode having the larger plane size, that is, the separator 34 on the anode electrode 24 side. This convex portion 34a
Contacting the peripheral edge of the anode electrode 24 supports and reinforces the peripheral edge of the anode electrode 24, and the height of the convex portion 38a of the seal member 38 (arrow P) and the height of the convex portion 40a of the seal member 40 are increased. (Arrow Q) is adjusted to be the same. Thus, the seal members 3 having the same height
By using Nos. 8 and 40, the contact areas of the seal members 38 and 40 that sandwich the solid polymer electrolyte membrane 22 can be equalized, and the sealing performance can be improved. in addition,
Since the solid polymer electrolyte membrane 22 is maintained flat without being bent by the convex portion 34a of the separator 34 and the seal member 38, the height of the convex portion 40a outside the seal member 40 (arrow Q), Height of inner convex portion 40b (arrow R)
Can be made the same, and the sealing property can be improved.

Further, as shown in FIG. 1, the plane dimensions of the anode electrode 24 and the cathode electrode 26 disposed on both sides of the solid polymer electrolyte membrane 22 are different, and the solid polymer electrolyte membrane 22 is formed between these electrodes. Since the electrodes 24 and 26 are protruded, the end faces of the electrodes 24 and 26 are provided at positions separated from each other via the solid polymer electrolyte membrane 22.
For this reason, the reaction gas (fuel gas, oxidant gas) supplied to the electrodes 24, 26 respectively is
It is possible to reduce the risk of mixing in the vicinity of the end surfaces of the electrodes and the risk of electrical short circuit between the end surfaces of the electrodes 24 and 26.

When the fuel cell 20 is caused to generate electric power, the pressure of the oxidant gas supplied to the electrode having the smaller plane dimension, that is, the cathode electrode 26 is adjusted to the electrode having the larger plane dimension, that is, the anode. It is preferable to set the pressure higher than that of the fuel gas supplied to the electrode 24. By doing so, the surface of the solid polymer electrolyte membrane 22 protruding from the cathode electrode 26 is supplied with an oxidizing gas having a high pressure, and this oxidizing gas protrudes from the cathode electrode 26 of the solid polymer electrolyte membrane 22. Press the surface. As a result, the solid polymer electrolyte membrane 22 and the anode electrode 24 act so as to be in close contact with each other, so that the solid polymer electrolyte membrane 22 can be reliably reinforced in the thickness direction by the anode electrode 24, and the solid polymer electrolyte membrane. 22 more protection. In the present embodiment, the seal member 4
Although 0 has an inner convex portion 40b and an outer convex portion 40a, the present invention is not limited to this, and the respective convex portions 40a and 40b may be formed by separate sealing members.

Next, the electrolyte membrane / electrode structure according to the second embodiment of the present invention will be described. FIG. 3 shows an electrolyte membrane / electrode structure 50 according to a second embodiment of the present invention.
3 is a cross-sectional view of a fuel cell 60. FIG. A fuel cell stack 61 is formed by stacking a plurality of the fuel cells 60. In the present embodiment, the peripheral edge portion of the electrode 24 having the larger plane dimension is formed into a frame-shaped seal member 52 made of, for example, a rubber material.
Is different from the first embodiment. Even in this case, the area of the portion (power generation surface) where the anode electrode 24 and the cathode electrode 26 that sandwich the solid polymer electrolyte membrane 22 face each other does not have to be reduced, so that the power generation efficiency is about the same as in the previous embodiment. In addition to maintaining the above, it is possible to reduce the cost of the material of the expensive electrode 24 and to reduce the cost. Further, since the inner portion of the solid polymer electrolyte membrane 22 is sandwiched by the seal member 52 and the convex portion 40b of the seal member 40, the portion of the solid polymer electrolyte membrane 22 sandwiched by the seal members 52, 40 is Outflow of the reaction gas and inflow of the reaction gas to this portion can be prevented more effectively. Therefore, the reliability of the performance of the fuel cell 60 and the durability during operation can be further improved. Further, also in the present embodiment, as in the first embodiment, the stress received by the solid polymer electrolyte membrane 22 from the end faces of the electrodes 24, 26 can be dispersed and reduced. Then, similarly to the first embodiment, the solid polymer electrolyte membrane 22 has a pair of electrodes 2
Since the portions protruding from 4, 26 can be made small, the protection of the solid polymer electrolyte membrane 22 in the thickness direction can be enhanced. Further, as in the first embodiment, each of the electrodes 24 and 26 has a solid polymer electrolyte membrane 2
Since the plane dimension is smaller than 2, the expensive electrodes 24, 26
The material can be reduced.

An electrolyte membrane / electrode structure and a fuel cell according to the third embodiment of the present invention will be described. FIG. 4 is a sectional view of the electrolyte membrane / electrode structure 20 and the fuel cell 70 according to the third embodiment of the present invention. A fuel cell stack 72 is formed by stacking a plurality of the fuel cells 70. In the present embodiment, the separators are metallic separators 62, 6 made of stainless steel or the like.
4 is different from the first embodiment. With this, the thickness of the separators 62 and 64 can be further reduced, and the fuel cell 70 can be downsized.

Further, the seal member 6 in the present embodiment.
6 has a convex portion 66a on the outer peripheral side.
The protruding portions 40a of the sealing member 40 press the protruding surfaces of the solid polymer electrolyte membrane 22 from both sides to seal the solid polymer electrolyte membrane 22. Further, the seal member 66 extends inward, and the inner peripheral side of the seal member 66 is brought into contact with the peripheral portion of the lower surface of the anode electrode 24. As a result, the peripheral edge of the anode electrode 24 is reinforced in the thickness direction by the seal member 66, and the seal member 66
The height of the convex portion 66a (arrow S) and the height of the convex portion 40a of the seal member 40 (arrow Q) can be adjusted to be the same. As described above, in the present embodiment, since the height of the convex portions 66a and 40a is adjusted by the seal member 66 which is easily formed without cutting the separators 62 and 64, the manufacturing process is It will be easy. Also,
The seal member 66 is the protrusion 40 of the seal member 40.
A slight convex portion 66b is provided at a position facing b. As a result, the solid polymer electrolyte membrane 22 is sealed with the sealing member 66,
When sandwiched by 40, the surface pressure can be made substantially uniform in the vicinity of the convex portion 66b. The convex portion 66b is preferable because it has the above-described effect, but it is not always necessary to provide it. Reference numeral 68 indicates a cooling surface sealing member.

Also in the present embodiment, as in the first embodiment, the solid polymer electrolyte membrane 22 has the electrodes 24,
It is possible to disperse and reduce the stress received from the end face. Then, as in the first embodiment, since the portion of the solid polymer electrolyte membrane 22 protruding from the pair of electrodes 24, 26 can be made small, the protection of the solid polymer electrolyte membrane 22 in the thickness direction is achieved. Can be increased. Furthermore, the first
Similar to the embodiment described above, since the respective electrodes 24 and 26 have a smaller plane size than the solid polymer electrolyte membrane 22, the materials of the expensive electrodes 24 and 26 can be reduced. The seal members 40 and 66 are preferably integrally molded with the separators 62 and 64, but the invention is not limited to this. Also in this embodiment, the peripheral portion of the electrode 24 having the larger plane size may be replaced with the frame-shaped seal member 52 as in the previous embodiment.

In the above embodiments, the case where the plane dimension of the anode electrode 24 is made larger than that of the cathode electrode 26 has been described, but the present invention is not limited to this, and the plane dimension of the anode electrode 24 is made smaller than that of the cathode electrode 26. May be. Further, although the case where a plurality of fuel cells are stacked to form a fuel cell stack has been described, the present invention is not limited to this, and the present invention can of course be applied to the case of using a single fuel cell.

[0029]

As described above, according to the invention described in claim 1, the stress received by the electrolyte membrane from the electrode end face can be reduced, and one electrode has a larger planar dimension than the other electrode. By doing so, it is possible to reduce the portion of the electrolyte membrane protruding from the pair of electrodes, because it is possible to reinforce the electrolyte membrane in the thickness direction,
The protection of the electrolyte membrane can be enhanced. Furthermore, since each electrode has a smaller plane size than the electrolyte membrane, the amount of expensive electrode material can be reduced.

According to the second aspect of the present invention, since the material of the electrode having the larger planar dimension can be reduced while maintaining the area of the power generation surface where the electrodes face each other, the power generation efficiency is reduced. It is possible to reduce the costly material required for the electrodes without increasing the cost. Further, the larger electrode can be sealed with a sealing member.

According to the third aspect of the invention, the electrolyte membrane is sealed by sandwiching the electrolyte membrane between the inside (the portion in contact with the peripheral portion of the larger electrode) and the outside (the portion of the electrolyte membrane protruding). It is possible to improve the sex. Further, when the peripheral portion of the electrode having the larger planar dimension is the sealing member, the sealing property with respect to the electrolyte membrane can be further enhanced, so that the reliability of the performance of the fuel cell and the durability during operation are improved. It can be further enhanced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an electrolyte membrane / electrode structure and a fuel cell according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an electrolyte membrane / electrode structure according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of essential parts showing an electrolyte membrane / electrode structure and a fuel cell according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of essential parts showing an electrolyte membrane / electrode structure and a fuel cell according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional electrolyte membrane / electrode structure and a fuel cell.

[Explanation of symbols]

20 Electrolyte Membrane / Electrode Structure 22 Solid polymer electrolyte membrane 24 Anode electrode 26 Cathode electrode 30 fuel cell 34, 36 separator 38, 40, 42 Seal member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tadashi Nishiyama             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory (72) Inventor Masaaki Nanami             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory (72) Inventor Naoki Mitsuda             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory F-term (reference) 5H026 AA06 CC10 CV00

Claims (3)

[Claims] 1. An electrolyte membrane / electrode structure in which an electrolyte membrane is sandwiched between a pair of electrodes, wherein one electrode of the pair of electrodes is formed to have a larger plane dimension than the other electrode, and An electrolyte membrane / electrode structure, wherein the electrolyte membrane is formed to have a planar dimension that protrudes from the pair of electrodes. 2. The electrolyte membrane / electrode structure according to claim 1, wherein a peripheral portion of one of the pair of electrodes having a larger plane size is formed of a seal member. 3. A fuel cell in which the electrolyte membrane / electrode structure according to claim 1 or 2 is sandwiched between a pair of separators, wherein the pair of separators is the same plane as or a larger plane than the electrolyte membrane. A fuel cell having a dimension.