JPH0888012A - Fuel cell and manufacture thereof - Google Patents

Abstract

PURPOSE: To make a system compact, prevent the damage on an electrolyte film caused by contact of an atmosphere on an anode side with an atmosphere on a cathode side, and moisten a fuel gas. CONSTITUTION: A plurality of through holes 12 are formed in the direction of the film thickness of an electrolyte film 10. A gas shut-off layer 70 is formed between the electrolyte film 10 and an anode 20. Water produced in a cathode 30 is sent to the anode 20 side by a capillary action through the through holes 12 of the electrolyte film 10. Although an oxidizing gas taken in the cathode 30 passes through the through holes 12 together with the produced water, the oxidizing gas is completely shut out by the gas shut-out layer 70 and does not reach the anode 20. A fuel gas taken in the anode 20 is completely shut out by the gas shut-out layer 70 and does not enter the through holes 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell for supplying gas to an electrode to obtain electromotive force from a chemical reaction of the gas, and a method for manufacturing the fuel cell.

[0002]

2. Description of the Related Art For example, in a polymer electrolyte fuel cell, which is one of the fuel cells, a reaction of converting hydrogen gas into hydrogen ions and electrons at the anode and oxygen gas and hydrogen ions at the cathode are performed as shown in the following equation. And the reaction of producing water from the electrons takes place. Anode reaction: H ₂ → 2H ⁺ + 2e ⁻ Cathode reaction: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O

The hydrogen ions generated at the anode become hydrated (H ⁺ · xH ₂ O) and move to the cathode in the electrolyte membrane. For this reason, water becomes insufficient in the vicinity of the surface of the electrolyte membrane on the anode side, and in order to continuously carry out the above-mentioned reaction, it is necessary to replenish this insufficient water. The electrolyte membrane used in the polymer electrolyte fuel cell has good electric conductivity in a wet state, but when the water content decreases, the electric resistance of the electrolyte membrane increases and the electrolyte membrane does not sufficiently function as an electrolyte. Will stop the electrode reaction.

Replenishment of this water is generally performed by humidifying the fuel gas. As a device for humidifying the fuel gas, for example, there is a device for bubbling the fuel gas to humidify the fuel gas, and the fuel gas humidified by this device is supplied into the main body of the polymer electrolyte fuel cell. However, in such a technique, since the humidifying device is separately provided outside the stack that houses the polymer electrolyte fuel cell main body, there is a problem that the device becomes large.

On the other hand, a technique has been proposed in which a water-absorbing or water-retaining substance is held in an electrolyte membrane so that the substance serves as a water passage to communicate between the anode side and the cathode side (Japanese Patent Laid-Open No. H05-53242). -2830944).
According to this technique, the water generated on the cathode side can be supplied to the anode side through the water passage in the electrolyte membrane,
It was possible to humidify the anode side of the electrolyte membrane without using a large-scale device such as the above-mentioned humidifier, and it was possible to make the entire device compact.

[0006]

SUMMARY OF THE INVENTION In the above conventional technique,
As the water-absorbing or water-retaining substance, for example, monofilament is used, but a gap is formed in the boundary between the monofilament and the base material of the electrolyte membrane. The gap can be almost ignored when the single fiber is sufficiently wet, but the gap becomes large when the single fiber is in a dry state such as at the start of operation. Therefore, the atmosphere on the anode side and the atmosphere on the cathode side come into contact with each other through the gap, and a combustion reaction occurs between the fuel gas on the anode side and the oxygen gas on the cathode side, and as a result, the electrolyte membrane is damaged. Such a problem occurred.

Even when a substance other than single fiber is used as the water-absorbing or water-retaining substance, contact between the atmosphere on the anode side and the atmosphere on the cathode side cannot be avoided, and the same problem occurs. .

The fuel cell of the present invention has been made in view of these problems, and the size of the entire device is reduced, and the electrolyte membrane formed by the contact between the atmosphere on the anode side and the atmosphere on the cathode side is improved. The purpose is to realize humidification of fuel gas while preventing damage.

[0009]

In order to achieve such an object, the following constitution is adopted as a means for solving the above problems.

That is, the fuel cell of the present invention has two electrolyte membranes.
A fuel cell, which is sandwiched by two electrodes to obtain an electromotive force by supplying a reaction gas to each electrode, wherein a water passage extending from one electrode side to the other electrode side is formed in the electrolyte membrane. In addition, a blocking layer made of an electrolyte and blocking the passage is formed between the electrolyte membrane and at least one of the electrodes.

As a first method for manufacturing such a fuel cell, a step of forming a through hole as a passage for the water in an electrolyte membrane having a predetermined thickness, and an electrolyte membrane body thinner than the thickness of the electrolyte membrane are used. As the blocking layer, a step of thermocompression-bonding to the electrolyte membrane was adopted.

As a second manufacturing method, a step of forming a through hole as a passage for the water in an electrolyte membrane having a predetermined thickness, and applying an electrolyte solution in a film form on the surface of the electrolyte membrane. Thus, a configuration including a step of forming the blocking layer is adopted.

As a third manufacturing method, a step of forming a through hole as a passage for the water in the electrolyte membrane having a predetermined thickness and an electrolyte membrane body thinner than the thickness of the electrolyte membrane are used as the blocking layer. As a result, a step of thermocompression bonding to at least one of the electrodes is adopted.

As a fourth manufacturing method, a step of forming a through hole as a passage for the water in the electrolyte membrane having a predetermined thickness, and applying a solution of the electrolyte in a film form to at least one of the electrodes. By so doing, a structure including a step of forming the blocking layer was adopted.

[0015]

According to the fuel cell of the present invention configured as described above, the water generated at one electrode is transmitted to the other electrode side through the water passage in the electrolyte membrane. If the blocking layer is formed between the electrode on the other side and the electrolyte membrane, the water transmitted to the other electrode side reaches the blocking layer, diffuses into the blocking layer made of the electrolyte, and Reach the electrode. Therefore, it works to supply the water generated by one electrode to the other electrode.

Further, the water passage connecting the two electrodes transmits gas in no small amount, but the gas is completely blocked by the blocking layer made of the electrolyte. Therefore, it works to prevent contact between the atmosphere of one electrode and the atmosphere of the other electrode.

Even when the blocking layer is formed between the electrode on one side (the electrode for generating water) and the electrolyte membrane, the blocking layer allows the generated water to pass therethrough and blocks the gas. Therefore, it works the same as the above case.

The first and second aspects of the present invention (claim 2)
According to the fuel cell manufacturing method of 3) and 3), the barrier layer is formed on the electrolyte membrane to manufacture the fuel cell. On the other hand, according to the third and fourth methods for manufacturing a fuel cell of the present invention (claims 4 and 5), the barrier layer is formed on at least one of the electrodes to manufacture the fuel cell. It In either case, the manufacture of the main part of the polymer electrolyte fuel cell 1 is facilitated.

[0019]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above.

FIG. 1 is a schematic view of a cell structure of a polymer electrolyte fuel cell 1 to which the first embodiment of the present invention is applied, and FIG. 2 is an exploded perspective view of a main part of the cell structure. As shown in both figures, the cell has an electrolyte membrane 10, an anode 20 and a cathode 30 as gas diffusion electrodes that sandwich the electrolyte membrane 10 from both sides to form a sandwich structure, and a fuel gas while sandwiching the sandwich structure from both sides. And a channel groove for oxidizing gas is formed, and the anode 20 and the cathode 3 are formed.
Collector electrodes 40 and 50 for exchanging electrons with 0, and collector electrode 4
Separator 6 placed outside 0, 50 to partition each cell
With 0 and. Further, this cell includes a gas barrier layer 70 between the electrolyte membrane 10 and the anode 20. If the electrode 50 is gas impermeable, the separator 60 may be
It may be omitted.

The electrolyte membrane 10 is made of a polymer material, for example, a fluorine-based sulfonic acid polymer resin, and has a thickness of 100.
It is an ion-exchange membrane having a thickness of μm to 200 μm and exhibits good electric conductivity in a wet state. Furthermore, this electrolyte membrane 10
Has a plurality of through holes 12 as water passages in the film thickness direction. The diameter of the through hole 12 is several tens to several hundreds of μm in a wet state.

The anode 20 and the cathode 30 are made of carbon cloth woven from yarns of carbon fibers, and the carbon cloth carries carbon or platinum carrying platinum as a catalyst or an alloy of other metals. The powder is kneaded into the cloth gap.

The collector electrodes 40 and 50 are made of porous carbon having gas permeability and have a porosity of 40 to 80%. Further, a plurality of ribs 42 are formed on the collector electrode 40, and the ribs 42 and the surface of the anode 20 form a flow channel groove 45 for a mixed gas of fuel gas and water vapor. The channel groove 45 is connected at one end thereof to a fuel gas intake manifold (not shown) and at the other port thereof to a fuel gas exhaust manifold (not shown). On the other hand, collector electrode 5
0 also has a plurality of ribs 52 formed thereon.
Channel groove 55 that forms a channel for the oxidizing gas between the cathode 2 and the cathode 30
Is formed. The channel groove 55 is connected at one end to an oxidizing gas intake manifold (not shown) and at the other port to an oxidizing gas exhaust manifold (not shown).

The gas barrier layer 70 is made of the same fluorocarbon sulfonic acid polymer resin as the electrolyte membrane 10 and has a thickness of several μm.
It is a film body of m. The gas barrier layer 70 is used as the electrolyte membrane 10.
Covering the entire surface of the anode 20 side of the electrolyte membrane 10
All the through holes 12 formed in the above are closed.

The separator 60 is made of gas-impermeable carbon that is made gas-impermeable by compressing carbon, and is composed of an electrolyte membrane 10, an anode 20, a cathode 30, a gas blocking layer 70, and collecting electrodes 40, 50. Forming a partition wall when the cells are stacked in the thickness direction. The respective members thus formed are used as a separator 60, a collecting electrode 40, an anode 20, a gas blocking layer 70, an electrolyte membrane 10, a cathode 30,
A plurality of collector electrodes 50 and separators 60 are stacked in this order to form the polymer electrolyte fuel cell 1.

A method for manufacturing the polymer electrolyte fuel cell 1 thus constructed will be described below. FIG. 3 is a flowchart showing the steps of the manufacturing method. As shown in FIG. 3, when manufacturing the polymer electrolyte fuel cell 1, first, a step of forming the through holes 12 in the electrolyte membrane 10 made of a fluorosulfonic acid polymer resin having a thickness of 100 μm to 200 μm is performed. (Step S100). In this step, specifically, the through holes 12 are formed in the electrolyte membrane 10 by pressing a flat plate on which a plurality of needles are stood up at equal intervals against the electrolyte membrane 10. The needle is 100-500
The diameter is about μm, and the diameter of the through hole 12 is considered to be several tens to several hundreds μm when the electrolyte membrane 10 is in a wet state.

Next, a fluorine-based sulfonic acid polymer resin (same as the electrolyte membrane 10) having a thickness of several μm, which is sufficiently thinner than the thickness of the electrolyte membrane 10, is prepared, and the electrolyte membrane having the through holes 12 formed in step S100. A process of joining the prepared resin to 10 is executed (step S110). This joining is performed at a temperature of 100 ° C. to 160 ° C., preferably 120 ° C. to 155 ° C., and 1 MPa {10.2 kgf / cm ² }.
To 10 MPa {102 kgf / cm ² }, preferably 3
MPa {31 kgf / cm ² } to 7 MPa {71 kgf / c
It is carried out by a hot pressing method in which a pressure of m ² } is applied to bond. The fluorine-based sulfonic acid polymer resin bonded to the electrolyte membrane 10 in this way becomes the gas barrier layer 70.

Subsequently, in step S110, the gas barrier layer 7 is formed.
A step of sandwiching the electrolyte membrane 10 having 0 bonded thereto with the anode 20 and the cathode 30 and then joining the anode 20 and the cathode 30 on both sides of the electrolyte membrane 10 by the same method as the hot pressing method described above. Is executed (step S120).

Thus, the anode 20, the gas barrier layer 70,
Electrolyte membrane 10 composed of electrolyte membrane 10 and cathode 30
Is manufactured. After that, steps of forming the collecting electrodes 40, 50, the separator 60, and the like are performed, but since these steps are not directly related to the present invention, description thereof is omitted here.

The polymer electrolyte fuel cell 1 described in detail above
The gas flow in the above will be described below. The fuel gas sent from a fuel gas source (not shown) flows through the intake manifold of the fuel gas and flows into the flow passage groove 45 on the anode 20 side.
Sent to The fuel gas is taken into the anode 20 through the flow channel groove 45, and the remainder is sent from the fuel gas exhaust manifold to the outside. On the other hand, the oxidizing gas stored in the oxidizing gas source (not shown) flows through the intake manifold of the oxidizing gas and is sent to the channel groove 55 on the cathode 30 side. This oxidizing gas is transmitted through the flow channel 55 and the cathode 3
While being taken up by 0, the remainder is sent to the outside from the oxidizing gas exhaust manifold. Although water is generated at the cathode 30 by receiving the oxidizing gas, a part of this water is discharged to the outside together with the remaining oxidizing gas.

The water generated in the cathode 30 also has the following flow. As shown in FIG. 4, the produced water W is sent to the gas blocking layer 70 through the through holes 12 of the electrolyte membrane 10 by the action of capillarity. Since the gas barrier layer 70 is made of an electrolyte, the produced water W diffuses into the gas barrier layer 70 and reaches the anode 20. Therefore, the water generated at the cathode 30 is
0 is supplied.

In the polymer electrolyte fuel cell 1 having such a configuration, the oxidizing gas taken into the cathode 30 leaks through the through holes 12 in the electrolyte membrane 10 together with the generated water W, and the oxidizing gas is emitted from the electrolyte. It is completely blocked by the gas blocking layer 70 and does not reach the anode 20. Further, the fuel gas taken into the anode 20 is completely blocked by the gas blocking layer 70, and therefore does not enter the through holes 12 in the electrolyte membrane 10. Therefore,
Fuel gas as the atmosphere on the anode 20 side and the cathode 30
There is no contact with the oxidizing gas that is the atmosphere on the side.

As described above in detail, in the polymer electrolyte fuel cell 1 of the first embodiment, the water generated at the cathode 30 is supplied to the anode 20 through the through holes 12 of the electrolyte membrane 10, Humidification on the anode 20 side of the electrolyte membrane 10 can be realized without providing a large-scale humidifier. Further, the through hole 1 which is a water passage in the electrolyte membrane 10.
Since the fuel gas and the oxidizing gas do not come into contact with each other via the electrode 2, damage to the electrolyte membrane 10 can be prevented.

Also, the polymer electrolyte fuel cell 1 can be manufactured with its main part extremely easily by the manufacturing method described above.

Another method for producing the polymer electrolyte fuel cell 1 (hereinafter referred to as the second production method) will be described below. FIG. 5 is a flowchart showing the steps of the second manufacturing method. This second manufacturing method is different from the above-described manufacturing method (first manufacturing method) in step S210.
The other steps are different only in the process in step S2.
00 and S220 are step S in the process of the manufacturing method described above.
100, same as S120.

As shown in FIG. 5, in this second manufacturing method, through holes 12 are formed in the electrolyte membrane 10 (step S200) in the same manner as in step S100, and then a solution of a fluorine resin is applied to the electrolyte membrane 10. Is applied in a film form (step S210). In this step, specifically, the gas blocking layer 70 is applied by spraying a fluorine resin on the surface of the electrolyte membrane 10 by spraying. It should be noted that instead of this spray-type coating method, a cast film as the gas blocking layer 70 may be generated by flowing a solution of a fluororesin on the surface of the electrolyte membrane 10.

Then, similarly to step S120,
A process of joining the anode 20 and the cathode 30 to both sides of the electrolyte membrane 10 is performed (step S220). The main part of the polymer electrolyte fuel cell 1 can be manufactured very easily by the second manufacturing method having such a configuration.

A third manufacturing method for manufacturing the polymer electrolyte fuel cell 1 will be described below. FIG. 6 is a flowchart showing the steps of the manufacturing method. The third manufacturing method is different from the first manufacturing method described above only in the step S310, and the other steps S300 and S320 are the same as the steps S100 and S120 of the first manufacturing method. Is the same.

As shown in FIG. 6, in the third manufacturing method, through holes 12 are formed in the electrolyte membrane 10 (step S300) in the same manner as in step S100, and then a solution of a fluororesin is applied to the anode 20. A process of applying in a film shape is executed (step S210). The solution may be applied in this step by a spray method or by flowing a solution, as in the step S210 of applying the gas barrier layer 70 to the electrolyte membrane 10 described above. Good.

Then, the anode 2 is formed on both sides of the electrolyte membrane 10.
The process of joining 0 and the cathode 30 is performed (step S320). Here, the joining is performed so that the surface of the gas blocking layer 70 applied to the anode 20 is in contact with the electrolyte membrane 10.

The main part of the polymer electrolyte fuel cell 1 can be manufactured very easily by the third manufacturing method having such a structure.

In this manufacturing method, step S
You may replace 310 with the following processes. That is, the gas blocking layer 70 is bonded to the anode 20 by a hot pressing method, and the bonding in this step is step S11 of bonding the gas blocking layer 70 to the electrolyte membrane 10 described above.
Bonding is performed in the same manner as in the step 0. With such a configuration, the main part of the polymer electrolyte fuel cell 1 can be manufactured very easily in the same manner.

The second embodiment of the present invention will be described below. FIG. 7 is a schematic diagram of a cell structure of a polymer electrolyte fuel cell 500 to which the second embodiment is applied. The polymer electrolyte fuel cell 500 of the second embodiment is different from the polymer electrolyte fuel cell 1 of the first embodiment in the disposition position of the gas blocking layer 570, and other configurations are the same. Is.
That is, in the polymer electrolyte fuel cell 500 of this example,
The gas barrier layer 570 may include the electrolyte membrane 510 and the cathode 530.
It is arranged between and.

A polymer electrolyte fuel cell 50 having such a structure
At 0, the water generated in the cathode 530 diffuses in the gas barrier layer 570, and then passes through the through holes 512 of the electrolyte membrane 510 and is sent to the anode 520 by the action of capillarity. Therefore, the water generated at the cathode 530 is supplied to the anode 520. At this time, the cathode 5
The oxidizing gas taken in by 30 does not enter the through holes 512 in the electrolyte membrane 510 by the gas blocking layer 570, and the fuel gas from the anode 520 leaking through the through holes 512 of the electrolyte membrane 510 is , Gas barrier layer 5
70 reaches the cathode 530 but is blocked.

Therefore, the polymer electrolyte fuel cell 500 of the second embodiment can realize humidification without providing a large-sized humidifier, as in the first embodiment, and further, the anode 20 Of the fuel gas, which is the atmosphere on the side of the cathode, and the oxidizing gas, which is the atmosphere on the side of the cathode 30,
It is possible to prevent damage to the electrolyte membrane 10.

A modified example of the present invention will be described below. In the first and second embodiments, the gas barrier layer 70
(570) is the electrolyte membrane 10 (510) and the anode 20.
It is arranged either between (520) or between the electrolyte membrane 10 (510) and the cathode 30 (530), but instead, it may be arranged on both. With this configuration, contact between the fuel gas on the anode 20 (520) side and the oxidizing gas on the cathode 30 (530) side can be more reliably prevented.

Further, in the first and second embodiments, the through holes 12 are formed as the water passages in the electrolyte membrane, but instead of this, water-absorbing monofilaments are contained in the electrolyte membrane 10. It may be configured to be held. According to this configuration,
The produced water on the cathode 30 side is transmitted along the single fiber to the anode 20.
Can be fed to the side.

Alternatively, the water passage in the electrolyte membrane 10 may be configured such that the electrolyte membrane 10 is impregnated with a water-absorbing or water-retaining substance such as an aqueous solution of polyvinyl alcohol. According to this configuration, the generated water on the cathode 30 side can be supplied to the anode 20 side via the water absorbing or water retaining substance.

Further, in the first and second embodiments, the gas barrier layer 70 is made of the same material as the electrolyte membrane 10, but instead of this, the gas barrier layer 70 and the electrolyte membrane 10 are replaced. , Containing sulfonic acid groups (ion exchange groups) mo
It may be configured to be made of materials having different l numbers. That is, the electrolyte membrane 10 is made of a material having a large mol number of ion exchange groups, and the gas blocking layer 70 is made of a material having a small mol number of ion exchange groups.

Since the ionic conductivity of the electrolyte is higher as the number of mols of ion-exchange groups contained in hydrogen ions is higher, the electrolyte membrane 10 has a higher number of mols of ion-exchange groups in order to improve battery performance. Is used. On the other hand, the gas barrier layer 70 has a thickness of several μm.
Since it is as thin as m, it is possible to obtain a sufficient ionic conductivity even if the number of mols of ion-exchange groups is reduced,
An electrolyte having a small mol number of ion exchange groups may be used. With this configuration, the gas barrier layer 70
As the ionic conductivity is lowered, the strength thereof can be increased, and as a result, the life of the polymer electrolyte fuel cell 1 can be increased.

Although some embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be implemented in various modes without departing from the scope of the present invention. Of course.

[0052]

As described above, in the fuel cell of the present invention, the water generated in one electrode is supplied to the other electrode side through the passage of water in the electrolyte membrane, thereby providing a large humidifier. Humidification can be realized without providing. Further, since the blocking layer can prevent the fuel gas and the oxidizing gas from coming into contact with each other through the water passage in the electrolyte membrane, damage to the electrolyte membrane can be prevented.

Further, according to the method of manufacturing the fuel cell of the present invention, the main part of the fuel cell can be manufactured very easily.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a cell structure of a polymer electrolyte fuel cell 1 to which a first embodiment of the present invention is applied.

FIG. 2 is an exploded perspective view of a main part of the cell structure.

FIG. 3 is a flowchart showing steps of a first manufacturing method of the polymer electrolyte fuel cell 1.

FIG. 4 is an explanatory diagram showing a flow of water generated in the cathode 30 of the polymer electrolyte fuel cell 1.

FIG. 5 is a flow chart showing steps of a second manufacturing method.

FIG. 6 is a flowchart showing steps of a third manufacturing method.

FIG. 7 is a schematic diagram of a cell structure of a polymer electrolyte fuel cell 500 to which a second embodiment of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid polymer fuel cell 10 ... Electrolyte membrane 12 ... Through hole 20 ... Anode 30 ... Cathode 40 ... Collection electrode 42 ... Rib 45 ... Flow channel 50 ... Collection electrode 52 ... Rib 55 ... Flow channel 60 ... Separator 70 Gas barrier layer 500 Solid polymer fuel cell 510 Electrolyte membrane 512 Through hole 520 Anode 530 Cathode 570 Gas barrier layer

Claims (5)

[Claims] 1. A fuel cell in which an electrolyte membrane is sandwiched between two electrodes and an electromotive force is obtained by supplying a reaction gas to each electrode, wherein one electrode side to the other electrode are provided in the electrolyte membrane. A fuel cell in which a water passage reaching the side is formed and a blocking layer made of an electrolyte and blocking the passage is formed between the electrolyte membrane and at least one of the electrodes. 2. The method of manufacturing a fuel cell according to claim 1, wherein a step of forming a through hole as a passage for the water in an electrolyte membrane having a predetermined thickness, and an electrolyte thinner than the thickness of the electrolyte membrane. And a step of thermocompression-bonding the membrane body to the electrolyte membrane as the barrier layer. 3. The method of manufacturing a fuel cell according to claim 1, wherein a step of forming a through hole as a passage for the water in an electrolyte membrane having a predetermined thickness, and a step of forming an electrolyte on the surface of the electrolyte membrane. Forming a barrier layer by applying a solution in the form of a film. 4. The method for manufacturing a fuel cell according to claim 1, wherein a step of forming a through hole as the passage for the water in the electrolyte membrane having a predetermined thickness, and a thickness smaller than the thickness of the electrolyte membrane. A method of manufacturing a fuel cell, comprising a step of thermocompression bonding to at least one of the electrodes using the electrolyte membrane as the blocking layer. 5. The method of manufacturing a fuel cell according to claim 1, wherein a step of forming a through hole as the passage for the water in the electrolyte membrane having a predetermined thickness, and at least one of the electrodes Forming a barrier layer by applying an electrolyte solution in the form of a film.