JPH08185874A - Sealing method for solid high molecular fuel cell - Google Patents

Abstract

PURPOSE: To prevent a solid high molecular electrolytic film from expanding or deteriorating, due to humidification and heating at the time of power generation by specifying a moisture state and a heating condition for bonding and integrating the film with a packing by use of an adhesive. CONSTITUTION: Steam is fed to the internal space of both upper and lower dies 20 and 21 through steam introduction tubes 22 and 23. Thereafter, two packings 12 are arranged on the upper and lower peripheral sections of a high molecular electrolytic film 1 and set between the dies 20 and 21. Then, heat is applied thereto, while pressure being applied with the dies 20 and 21. Steam is used for this heating process. During an operation, steam is condensed and the condensation heat thereof is used to maintain hot water temperature equal to or above the glass transition point of the film 1 under pressure. As a result, the film 1 can be bonded to the packings 12 in a moisture state, without being dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing method for a polymer electrolyte fuel cell, and more specifically to a gas seal between a polymer electrolyte membrane of a polymer electrolyte fuel cell and a seal packing. -It is possible to improve the safety of the polymer electrolyte fuel cell effectively and significantly by eliminating the damage of the cell due to the expansion of the membrane during power generation and the deterioration of the membrane due to the heating during manufacturing. Polymer electrolyte fuel cell
Le method.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell is characterized in that an ionic conductor, that is, an electrolyte is a solid and a polymer. The solid polymer electrolyte is specifically an ion exchange resin or the like. Is used, and both electrodes of the negative electrode (anode) and the positive electrode (cathode) are arranged with the polymer electrolyte membrane sandwiched between them. For example, hydrogen gas as a fuel is placed on the negative electrode side, and on the positive electrode side. Electricity is generated by supplying oxygen or air to cause an electrochemical reaction.

Although there are various modes of this apparatus, FIG. 1 is a schematic diagram for explaining the principle or one mode of this polymer electrolyte fuel cell. In FIG. 1, 1 is a polymer electrolyte membrane, 2 is a cathode electrode (positive electrode), 3 is an anode electrode (negative electrode), and the polymer electrolyte membrane 1 is between the opposite positive and negative electrodes 2 and 3. It is arranged. Further, 4 is a cathode electrode side current collector, and 5 is an anode electrode side current collector, which are in contact with the positive and negative electrodes 2 and 3, respectively. Of these, a groove for oxygen or air supply is provided on the electrode 2 side of the cathode electrode side current collector 4, and a hydrogen supply groove is also provided on the electrode 3 side of the anode electrode side current collector 5. The groove of the positive electrode side current collector 4 is connected to the oxygen or air supply pipe 6, and the groove of the negative electrode side current collector 5 is connected to the hydrogen supply pipe 7.

Reference numeral 8 is a cathode terminal plate provided in contact with the positive electrode side current collector 4, and 9 is an anode terminal plate provided in contact with the negative electrode side current collector 5. Power is drawn through them during operation. Further, 10 is an upper frame, that is, an upper frame, 11 is a lower frame, that is, a lower frame. The battery main body up to the terminal plate 9 (this term is also used as referring to the one in which the electrode is in contact with the electrolyte membrane as described later) is fixed.

A packing (gasket) 12 is provided between the upper and lower frames 10 and 11 to surround the periphery of the battery main body from the polymer electrolyte membrane 1 to the cathode terminal plate 8 and the anode terminal plate 9. By this, the peripheral portion of the battery body is tightly fixed and sealed, and in particular, gas sealing is performed on the polymer electrolyte membrane 1 and the positive and negative electrodes 2 and 3. In FIG. 1, 13 and 14 are cooling water supply pipes, which communicate with grooves (closed passages) provided on the inner surfaces of the upper frame body 10 and the lower frame body 11, respectively, and are connected to the cathode terminal plate. 8
Is indirectly cooled from the back surface of the anode terminal board 9 and the back surface of the anode terminal board 9.

[0006] The above is the case of a single battery body,
It is also possible to stack two or more battery bodies. In this case, it is necessary to interpose a separator between each of the two or more battery bodies, and to provide a groove for cooling water, etc., as appropriate, but a packing is provided so as to surround the periphery of the battery body. The periphery of the battery body is tightly fixed and sealed, and gas seal is applied to the polymer electrolyte membrane 1 and the positive and negative electrodes 2 and 3.
This is basically the same as the case of the single battery main body described above, including the operation of the battery pack. In this case, in addition to the upper and lower frame members 10 and 11, the packing and the like should be tightened.
It is also performed via the target.

Even when the above-mentioned single battery main body or two or more battery main bodies are stacked, it is necessary to seal the edge portion tightly, particularly gas-tightly. As a sealing method, as described above, a packing is provided around the polymer electrolyte membrane so as to be in close contact (see packing 12, etc. in FIG. 1), an O-ring is interposed, and thereby a close contact is made. 2 is used and proposed, but FIG. 2 shows an example of a sealing method using an O-ring.

As shown in FIG. 2, the electrodes 2 (3) are arranged on both sides of the electrolyte membrane 1, and in the embodiment of FIG. 1, two or more battery bodies are stacked from above and below by the upper and lower frame bodies 10 (11). In the case of the configuration, both the upper and lower frames and the separator 1
6 and 17, the O-ring 15 is interposed between these and the peripheral portion of the electrolyte membrane 1 so as to be in close contact with each other, whereby sealing is achieved. In FIG. 2, reference numerals “16 (10)” and “17 (1
1) ”means that the separators 16 and 17 correspond to the upper frame body 10 or the lower frame body 11 when the separators 16 and 17 are the uppermost or lowermost portions.

However, in order to ensure the close contact and the seal by these methods, it is necessary to strongly press the packing or the O-ring, and therefore, the polymer electrolyte membrane itself with which they abut is contacted. Not only the battery will be damaged, but also the battery body will be tightened more than necessary, and the electrolyte membrane usually has the property of expanding and contracting depending on the temperature and the presence or absence of humidification. -Since the burden is apt to be placed on the seal portion, it is necessary to pay sufficient attention to this point even if any of the above sealing methods is adopted.

The present inventor fixes the peripheral portion (peripheral portion) of the battery main body and seals it, and gas seals the polymer electrolyte membrane 1 and the positive and negative electrodes 2 and 3. The above-mentioned drawbacks in the method of interposing packings or O-rings can be solved all at once, and the polymer electrolyte membrane can be sufficiently sealed by only lightly pressing it, and this also damages the polymer electrolyte membrane itself. It has previously developed and proposed a seal method having excellent advantages such as the fact that it does not occur (Japanese Patent Application No. 6-309936).

In the inventions according to the above developments and proposals, the seal of the polymer electrolyte fuel cell is surface-treated with a polymer electrolyte membrane and packing (gasket) of the polymer electrolyte fuel cell, preferably by sandblasting in advance. The packing (gasket) having fine irregularities is preliminarily joined by an adhesive to be integrated, as shown in FIG. 3 (a).
Shows the structure of the polymer electrolyte membrane in which the packing obtained above is integrated, and FIG. 3 (b) shows the structure of the fuel cell body in which the gas diffusion electrodes are joined to both sides of the packing-integrated polymer electrolyte membrane. Is.

In FIG. 3 (b), the arrangement of the polymer electrolyte membrane 1 and the positive and negative electrodes 2 and 3 is the same as in FIGS. 1 and 2, but the electrodes 2 and 3 obtained above are water repellent. Chemical Carbon Paper
Is the gas diffusion layer 18 and the deposited layer of catalyst particles is the catalyst layer 1
9 are formed. Therefore, both electrodes 2 and 3 are joined so that the catalyst layer 19 side is in contact with the polymer electrolyte membrane surface, thereby facilitating and ensuring gas seal between the electrolyte membrane and the packing, and thus the fuel cell. Not only can the safety be improved, but also the membrane can be sufficiently sealed by lightly pressing the membrane as compared with the conventional one, and thus the damage to the electrolyte membrane can be greatly reduced.

By the way, in carrying out this technique, after applying a solution of an adhesive to the packing, it is dried to remove the solvent, the applied surface is brought into contact with the polymer electrolyte membrane, and then the temperature is 120 ° C. or higher. , Especially 140-200 ℃
They are hot-pressed together to join the two. However, in this way, the adhesive is dried to remove the solvent, and at the time of hot pressing, the polymer electrolyte membrane is heated to such a high temperature that the membrane dries, resulting in a size different from that during power generation. It was observed that This has a risk of damaging the battery due to expansion of the membrane due to humidification during power generation, and there is a possibility that the membrane may be deteriorated by the above heating.

[0014]

Therefore, according to the present invention,
A polymer electrolyte membrane of a polymer electrolyte fuel cell and a packing (gasket) are preliminarily adhered to each other with an adhesive to form a seal. When the polymer electrolyte membrane and the packing are bonded and integrated with an adhesive, the water-containing state and heating conditions are specified and special measures are taken to make the seal of the solid polymer fuel cell free from the above-mentioned drawbacks. It provides a method.

[0015]

That is, the present invention relates to a sealing method for a solid polymer electrolyte fuel cell in which a solid polymer electrolyte membrane and packing are bonded and integrated with an adhesive in advance and sealed. To bond the polymer electrolyte membrane and the packing to each other in a water-containing state under pressure, at a hot water temperature above the glass transition point of the polymer electrolyte membrane, without drying the adhesive between them. And a sealing method for a polymer electrolyte fuel cell.

Here, as the above-mentioned polymer electrolyte membrane, any type can be applied, but a perfluorocarbon sulfonic acid type resin membrane can be preferably used because of its excellent characteristics. . In addition to its excellent electrical characteristics, this film is extremely stable chemically and physically, has high mechanical strength, and is used as a film with a thickness of 50 to 200 μm. It is known as a material having excellent characteristics such that its electric resistance is about 0.1 to 0.5Ω and is so small that it cannot be the main cause of the internal resistance of the battery.

The glass transition point varies depending on the type of solid polymer electrolyte membrane and the like (the glass transition point of the above-mentioned perfluorocarbon sulfonic acid type resin membrane is usually 100 to 1).
It is about 20 ° C., but is not limited to this range, and varies depending on the degree of polymerization thereof and the amount of sulfonic acid groups). In the present invention, the above-mentioned pressurization depending on the glass transition point of the solid polymer electrolyte membrane to be used, The hot water temperature during heating is adjusted to be higher than that.

As the material of the packing, fluororubber or the like is chemically stable in itself, does not deteriorate the material that comes into contact with the rubber, and the fluid such as hydrogen or air does not permeate. Any material can be used as long as it has various properties. In this case, in order to make the joining and integration by the adhesive more effective, a sand blast (steel) is applied to the surface of the packing itself that contacts the polymer electrolyte membrane (the surface that contacts the battery) prior to the bonding. It is especially effective to form fine irregularities by means of plasma etching, etc.). As a result, the packing can be tightly sealed and firmly fixed to the polymer electrolyte membrane.

Further, as the adhesive, any adhesive can be used as long as it can tightly adhere the polymer electrolyte membrane and the packing and gas seals. However, both of them, especially the polymer electrolyte membrane are deteriorated by chemical action or the like. It is necessary not to allow it to occur, and therefore, it is particularly desirable to use an adhesive composed of the same type of components as the polymer electrolyte membrane. In this respect, when the above-mentioned perfluorocarbonsulfonic acid resin film is used as the polymer electrolyte membrane, the same solution of the polymer electrolyte membrane is preferably used as the adhesive agent, for example, N
If afion-117 (R) membrane is used,
Nafion solution (Aldrich Chemical
(Registered trademark) manufactured by the company is used.

In addition, the above-mentioned method of adhering and integrating the polymer electrolyte membrane and the packing (gasket) in advance is, for example, one or both of the contact surfaces of the polymer electrolyte membrane and the packing. Apply an appropriate adhesive (preferably to the packing), remove the solvent if necessary, then bring the packing into contact with the polymer electrolyte membrane, and apply pressure and heat. In the present invention, this heating is performed at a hot water temperature equal to or higher than the glass transition point as described above, whereby the polymer electrolyte membrane can be bonded and integrated in a water-containing state.

FIG. 4 is a schematic diagram showing in principle the mode for carrying out the method of the present invention. In FIG. 4, 20 is an upper die, 21
Is a lower mold, and 22 and 23 are steam introducing pipes, and steam is supplied into the upper and lower molds through the steam introducing pipes 22 and 23. As shown in the figure, after arranging two packings 12 on the upper and lower peripheral portions of the polymer electrolyte membrane 1, the upper and lower molds 2
It is set between 0 and 21 and heated while pressure is applied by both molds 20 and 21.

This heating is carried out by the steam described above, and the steam is condensed during operation, and the heat of condensation is used so that the heating temperature is maintained at the temperature of hot water, that is, at 100 ° C. or higher. (Note that when the solid polymer electrolyte membrane has a glass transition point of 100 ° C. or higher, steam is correspondingly pressurized to 1 atm or higher). Further, in the present invention, as the heating source, hot water heated to a temperature of 100 ° C. or higher may be supplied instead of the steam,
In this case, the steam introduction pipes 22 and 23 are constructed as hot water supply conduits. In the present invention (in addition to the fact that the polymer electrolyte membrane 7 and the adhesive are not dried in advance), this allows the polymer electrolyte membrane to be used as a membrane in a wet state, that is, in a water-containing state without drying the polymer electrolyte membrane. The joining can be completed.

In this respect, in the method proposed above, the temperature of the film during hot pressing is 120 ° C. or higher, particularly 140 to
Since the polymer electrolyte membrane is heated to 200 ° C, it may be dried and have a different size from that during power generation. Therefore, there is a risk of battery damage due to expansion of the membrane during power generation. Also, the deterioration of the membrane due to heating was also a problem, but according to the present invention, those drawbacks could be solved all at once, and the polymer electrolyte membrane and the packing were joined in a water-containing state, thereby generating power. Since there is no stress on the membrane in the above, it is possible to perform safer power generation.

Next, an outline of one embodiment of the seal method according to the present invention will be described. (A) First, for example, a thickness of 1
Fine ruggedness is formed by sandblasting or plasma etching on the seal surface of the packing (the surface in contact with the battery = the surface in contact with the polymer electrolyte membrane) of about 5 mm.
A solution of a polymer electrolyte membrane as an adhesive (for example, Nafi) on the treated surface (the surface having fine irregularities) of (b) and (a)
on solution, manufactured by Aldrich Chemical Co., Ltd., is applied so that the electrolyte membrane has a concentration of about 0.1 to 5 mg / cm ² . In this case, as the coating method, a roll method, a method using a brush, or a method usually used as this kind of coating means can be applied.

(C) Then, the solvent in the coating solution of the above (b) is first dried at room temperature, and when the solvent cannot be confirmed from the surface (that is, when the solvent is no longer visible from the surface), vacuum drying is performed. At a temperature of about 80 ° C
Dry for about 3 hours to completely remove the solvent. The packing surface of the polymer electrolyte membrane is in contact with the polymer electrolyte membrane, and the packing is placed in a pressing die as shown in FIG. 4, for example.

(D) The pressure is about 1 by sandwiching the mold from above and below.
Water is heated at a temperature of 100 ° C. into a mold by pressing at a pressure of 00 to 200 kg / cm ² to bond the polymer electrolyte membrane and the packing. The fuel cell main body is obtained by joining the gas diffusion electrode to the electrolyte membrane obtained by the steps (e) and (a) to (d) and having the packing joined thereto in advance. Next, the fuel cell main body is sandwiched by a frame (and a separator) in which the packing fits in the seal portion, and the anode electrode, cathode electrode, and other necessary components are arranged as shown in FIG. 1, for example. By assembling, a fuel cell can be constructed.

The thickness and shape of the packing may be different from those shown in FIG. 1 depending on the mode and scale of the fuel cell structure.
It is not limited by the scale and the like, and is not limited to the case where the battery main body is a single body, and is similarly applicable to the case where two or more battery main bodies are stacked.

[0028]

EXAMPLES Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples. First, the seal surface (the surface that contacts the battery, that is, the electrolyte membrane) of a Viton packing (fluorine rubber) having a thickness of 3 mm was finely roughened by sandblasting. Then, apply Nafio on the uneven surface treated with
n film (perfluorocarbon sulfonic acid resin film, A
A solution of ldrich Chemical, registered trademark) was applied so that the electrolyte membrane had a concentration of 1 mg / cm ² .

Then, the solvent in the solution on the coated surface was dried at room temperature, and when the solvent could not be confirmed from the surface, it was dried at a temperature of 80 ° C. for about 3 hours by using a vacuum dryer to completely remove the solvent. I removed it. Obtained packing 2
With the coated surface (sealing surface) of the sheet facing inward, N
afion-117 film (perfluorocarbon-sulfonic acid resin film, manufactured by Du Pont, trade name) is sandwiched,
As shown in FIG.
It was put in the mold for the press shown in and set. Then, the mold is sandwiched from above and below, and the pressure is 150 kg / cm.
Pressing at ² and introducing water heated to a temperature of 100 ° C into the mold, the membrane and the packing are joined, and the packing as shown in Fig. 3 (a) is adhered and integrated into a solid polymer electrolyte membrane. Obtained.

A gas diffusion electrode is bonded to the packing-integrated solid polymer electrolyte membrane obtained in steps (1) and (2) in FIG.
A fuel cell body as shown in was obtained. The gas diffusion electrode used in this example is a carbon paper having a porosity of 80% and a thickness of 0.4 mm, made of neoflon (tetrafluoroethylene-hexafluoropropylene copolymer, manufactured by Daikin Industries, Ltd., trade name. ) On the carbon paper which was made water-repellent by the dispersion, coated with an alcohol solution of NAFION-117 (perfluorocarbon sulfonic acid resin, manufactured by Du Pont, trade name). It was obtained by depositing a suspension obtained by adding a dispersion of polytetrafluoroethylene to catalyst particles carrying 50% by weight of platinum (carrier: carbon black).

Then, by a conventional method, a current collector, a terminal plate, etc. are brought into close contact with the fuel cell body, hydrogen and oxygen inlets / outlets are installed, and the solid polymer fuel cell is set as shown in FIG. The change in the electrode characteristics and the performance as a battery was measured. This example was prepared separately as a comparative example, except that the packing was closely pressed and sealed by the conventional method without sealing and pre-bonding the polymer electrolyte membrane and the packing as in the present invention as in the present invention. The fuel cell obtained in the same manner as above was also measured.

Although both showed almost the same performance, in the conventional method, the damage of the membrane and the like occurred at a rate of 30% during power generation, whereas in the fuel cell obtained in the example, from the beginning of operation. No troubles such as breakage of the polymer electrolyte membrane occurred. In this respect, even if the same test was performed 10 times, it was exactly the same. Further, when the surface of the electrolyte membrane after sealing was visually observed, no damage to the membrane was observed in the example according to this example even after the disassembly.

[0033]

According to the seal method of the present invention, since the polymer electrolyte membrane and the packing are bonded together in a water-containing state and there is no stress on the membrane during power generation, safer power generation can be performed. it can. In addition, the gas seal between the electrolyte membrane and the packing can be easily and reliably ensured, and the safety of the fuel cell can be improved. Further, the membrane can be sufficiently sealed by simply pressing it lightly as compared with the conventional one, and therefore, the damage to the electrolyte membrane can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining one embodiment of a polymer electrolyte fuel cell.

FIG. 2 is a diagram showing an example of a conventional seal mode using an O-ring.

FIG. 3 is a view showing a structure of a polymer electrolyte membrane in which packing is integrated and a fuel cell main body in which a gas diffusion electrode is joined thereto.

FIG. 4 is a schematic diagram showing in principle the mode for carrying out the method of the present invention.

[Explanation of symbols]

 1 Polymer Electrolyte Membrane 2 Cathode Electrode (Positive Electrode) 3 Anode Electrode (Negative Electrode) 4, 5 Current Collector 6 Air Supply Pipe 7 Hydrogen Supply Pipe 8, 9 Terminal Plate 10 Upper Frame (Upper Frame) 11 Lower frame (lower frame) 12 Packing 13, 14 Cooling water supply pipe 15 O-ring 16, 17 Separator 18 Gas diffusion layer 19 Catalyst layer 20 Upper mold 21 Lower mold 22, 23 Introducing steam tube

Claims (3)

[Claims] 1. A sealing method for a solid polymer electrolyte fuel cell in which a solid polymer electrolyte membrane and a packing are preliminarily bonded and integrated with an adhesive to seal the solid polymer electrolyte membrane and the packing. The solid polymer electrolyte fuel cell is characterized in that the solid polymer electrolyte membrane is bonded in a water-containing state under pressure at a hot water temperature above the glass transition point of the solid polymer electrolyte membrane without drying the adhesive. Seal method. 2. The sealing method for a polymer electrolyte fuel cell according to claim 1, wherein the seal surface of the packing is provided with fine irregularities by sandblasting or plasma etching, and then an adhesive is applied to the irregular surface. 3. The solid polymer electrolyte according to claim 1, wherein the solid polymer electrolyte membrane is a perfluorocarbon-sulfonic acid resin-based membrane, and the adhesive is a perfluorocarbon-sulfonic acid-based resin solution. Molecular fuel cell seal method.