JPH03205764A - Gas seal method for side end part of gas transmissive carbon base for fuel battery - Google Patents

Abstract

PURPOSE:To enable gas seal of side end part of carbon base easily by bringing a seal part covered with thermoplastic resin into contact with a side end part of gas transmissive carbon base, and jointing the seal member to the side end part with heat. CONSTITUTION:On a gas nontransmissive conductive board 6 a gas transmissive carbon base 14 having a narrower width than that of the board 6 and having a plurality of grooves 14a formed thereon is arranged. In this case a film made of thermoplastic resin 115 is interposed therebetween. Seal members 11 each having the same size with that of stepped parts 15, 15 are placed to be abutted on opposed side end faces of a gas transmissive carbon base 12, and thereafter the whole thereof is pressurized under a specified temperature. Then thermo plastic resin is partially melted together with the termoplastic film. By cooling them gradually, the base 14, the board 6 and the seal member 11 are integrated by the resin 11b. It is thus possible to easily gas seal the side ends of porous electrode or gas diffusion board.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a gas sealing method for the side edges of a gas-permeable carbonaceous substrate for fuel electrical devices, and more specifically, it relates to a gas sealing method for gas-sealing the side edges of a gas-permeable carbonaceous substrate for fuel electrical devices. It relates to a method by which the ends can be gas-sealed.

(Prior Art) Research and development efforts are underway to develop fuel cells because they can directly convert the chemical energy of fuel into electrical energy and have high power generation efficiency. Various types of fuel cells have been developed, including phosphoric acid fuel cells, fuel cells that use an ion exchange membrane as the electrolyte (membrane fuel cells), and fuel cells that use acid or alkali as the electrolyte.

An example of a single cell for a fuel cell is shown in FIG. 6 as a partial perspective view. In this single cell, first, the fuel electrode 1 which is the substrate
and an air electrode 2 are stacked on top of each other with an electrolyte matrix 3 in between.

Both the fuel electrode 1 and the air electrode 2 are porous plates made of a gas-permeable and conductive material such as carbon or graphite, and in the single cell having the structure shown in FIG. , serves as both a gas diffusion plate and an electrode. These poles are generally made from porous carbon material.

As shown in FIG. 7, a plurality of grooves 1a or 2a are drilled in one surface of the fuel electrode 1 and the air electrode 2 in parallel with each other, and the other surface, that is, the electrolyte matrix 3
Catalyst layers 4 and 5 made of platinum or a platinum-based catalyst are respectively formed on the surface that comes into contact with. The fuel electrode 1 and the air electrode 2 are both so-called ribbed electrodes, and are stacked so that their respective grooves 1a and 2a are perpendicular to each other (cross-flow method). On the one surface of the air electrode 2, gas-impermeable conductive plates (separators) 6, 6 made of a gas-impermeable and conductive material maintain conduction with the fuel electrode 1 and the air electrode 2, respectively. It is connected in a state.

A plurality of such single cells are stacked in the vertical direction, and manifolds for supplying fuel gas and oxidizing gas through gaskets are placed facing each other on the side surfaces of the resulting stacked body. A fuel cell is configured.

In this cell, fuel gas such as hydrogen gas is flowed into the groove 1a of the fuel electrode 1, and the groove 2 of the air electrode 2 is
An oxidizing gas such as air is normally flowed through a. The fuel gas diffuses within the fuel electrode 1 and is ionized at the catalyst layer 4, and the oxidizing component of the oxidizing gas (eg, oxygen) diffuses within the air electrode 2 and is ionized at the catalyst layer 5. As a result, ion movement occurs through the electrolyte matrix 3, and electrical energy is extracted from each pole.

By the way, the gases supplied to the grooves 1a and 2a not only diffuse in the direction of the plate thickness where the catalyst layers 4 and 5 are present, but also in the direction of the plate surfaces of the respective poles 1 and 2. Therefore, as shown by the arrow p in FIG. 7, there is a risk of leakage to the outside from the side end portion 1b (or 2b) along the groove 1a (or 2a). Conversely, another gas may flow in from the side end portion 1b (or 2b) and a direct reaction between the fuel gas and the oxidizing gas may occur. Therefore, it is necessary to provide a gas seal to the side end of each unit cell to prevent the above-mentioned problems from occurring.

In this case, the gas seal part is used to maintain electrical contact between the fuel electrode 1 (or air electrode 2) and the gas-impermeable conductive plates 6, 6, and to utilize the heat generated in the single cell. In order to dissipate to the fuel electrode 1 (or air electrode 2)
It is necessary that the plate surface and the surface of the gas seal part be formed on the same plane.

In addition, since the side end 1b (or 2b) of a single cell will come into contact with the manifold, if this side end 1b (or 2b) is conductive, it will not connect to other stacked single cells. The gas seals that form the side ends of the single cell must be electrically insulating, since the gas seals that form the side ends of the single cell must be electrically insulative because the gas seals that form the side ends of the single cell must be electrically insulative because the gas seals that form the side ends of the single cell become electrically insulating.

In the case of a single cell with the structure shown in Figure 6, the gas seal part is
A gas-impermeable sealing material 7 is disposed along the side edge of the electrolyte matrix 3, and a gas-impermeable sealing material 7 is sandwiched between the gas-impermeable sealing material 7 and the side edges 1b and 2b of the fuel electrode 1 and the air electrode 2. It is composed of seal members 8, 8 disposed along the line. The surfaces of the sealing members 8, 8 are usually coated with a resin such as polytetrafluoroethylene, and as shown in the figure, the sealing members 8, 8 are coated with the side end surfaces of the fuel electrode 1 and the air electrode 2, and the gas-impermeable conductive plate 6. , and 6, respectively.

FIG. 8 is a partial perspective view illustrating a unit cell having another structure. In the case of this single cell, both the fuel electrode 1 and the air electrode 2 are conductive porous plates, and their respective catalyst layers 4 and 5 sides are overlapped with an electrolyte matrix 3 in between.

The other surfaces of the fuel electrode 1 and the air electrode 2 are made of a conductive and porous material, and have a plurality of parallel grooves 9 on one surface.
Gas diffusion plates 9 and IO in which grooves a and 10a are formed are arranged with their grooves facing each other. These gas diffusion plates are also generally manufactured from porous carbon materials.

A gas impermeable conductive plate (separator) 6, 6 is provided on the other surface of each gas diffusion plate 9, 1O.
, 10 while maintaining continuity. Power generation progresses as the fuel gas flows through the grooves 9a and the oxidizing gas flows through the grooves 10a.

In the case of a single cell with this structure, the side edges of each component also have
As with the single cell in Figure 6, the gas-impermeable sealing material 7
, seal members 8, 8 are arranged to prevent leakage of each gas flowing in the groove.

Figure 9 is a partial perspective view showing yet another single cell structure, which is the same as the single cell shown in Figure 8, except that the electrolyte matrix is a 3° ion exchange membrane. It has a structure.

By the way, seal members 8, 8 are arranged at the side ends of the fuel electrode 1 and the air electrode 2 (FIG. 6), or a gas diffusion plate 9.
As a method for gas sealing by arranging the seal members 8, 8 (FIGS. 8 and 9) at the side end portions of 10, there are the following methods.

For example, JP-A-63-155563 and JP-A-6
3-48767 discloses a method of wrapping and sealing the side end portions of a porous electrode in a U-shape with a fluororesin film. Also, JP-A-61-
Publication No. 114476 discloses a method in which a groove is formed in the side end of a porous electrode, a sealing member is inserted into the groove, and the entire side end is further wrapped in a U-shape with a fluororesin film for sealing. has been done.

However, in any of the above-mentioned methods, since a long and narrow sealing film is adhered to the side end portion of a porous electrode, the sealing film is likely to be twisted or cut during the operation. Furthermore, in order to prevent the formation of a step in the sealed portion, it is necessary to make the thickness of the sealing film as thin as possible, which makes handling the sealing film even more difficult.

For this reason, the work of uniformly adhering a sealing film to the electrode side end portion and gas-sealing it by the method described above was a difficult work that required an extremely large amount of labor.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems and provides a method for extremely easily gas-sealing the side edges of a porous electrode or gas diffusion plate made of a carbonaceous material. With the goal.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a gas-impermeable conductive plate and a gas-permeable carbonaceous substrate having a width narrower than that of the gas-impermeable conductive plate. The gas-impermeable conductive plate and the gas-permeable carbonaceous substrate are overlapped with each other via a thermoplastic resin, and a sealing member coated with the thermoplastic resin is placed on the stepped portion formed by the gas-impermeable conductive plate and the gas-permeable carbonaceous substrate. The gas impermeable conductive plate, the gas permeable carbonaceous substrate, and the sealing member are bonded by the thermoplastic resin by placing the plate in contact with the side end surface, and then heating and pressurizing the entire body. Provided is a method for gas sealing a side end of a gas-permeable carbonaceous substrate for a fuel cell, characterized in that:
A gas-impermeable conductive plate and a gas-permeable carbonaceous substrate having a width narrower than the gas-impermeable conductive plate are bonded together using a thermoplastic resin. A sealing member coated with a thermoplastic resin is placed on the step portion to be formed so as to come into contact with the side end surface of the gas-permeable carbonaceous substrate, and then the whole is heated and pressurized, and the thermoplastic resin is used to Provided is a method for gas sealing a side end of a gas-permeable carbonaceous substrate for a fuel cell, the method comprising joining the sealing member to the gas-impermeable conductive plate and the gas-permeable carbonaceous plate. .

The present invention is a gas sealing method in a single cell when the fuel electrode, air electrode, and gas diffusion plate are made of porous carbon material. In this invention, these fuel electrodes, air electrodes, and gas diffusion plates are collectively referred to as a gas-permeable carbonaceous substrate.

This gas-permeable carbonaceous substrate has, for example, a single fiber diameter of 4 to 4.
Short carbon fibers with a diameter of 15 μm and a fiber length of 2 to 20 mm are randomly dispersed in a two-dimensional plane, and each short carbon fiber is bonded with carbon. It allows fuel gas and oxidizing gas to permeate in the surface direction.

This type of gas-permeable carbonaceous substrate can be manufactured, for example, by the method described in Japanese Patent Publication No. 53-18603 and Japanese Patent Publication No. 53-43920.

Other types of gas-permeable carbonaceous substrates include, for example, a single fiber diameter of 4 to 15 μm and a fiber length of 0.5 μm. 1 =
It may be manufactured by mixing short carbon fibers having a diameter of 1 mm with a carbonizable substance such as a phenolic resin, forming the resulting mixture into a plate shape, and then firing the mixture. In this type of substrate, short carbon fibers are randomly oriented three-dimensionally.

This type of board is, for example, Japanese Patent Publication No. 61-5091
It can be produced by the method described in Japanese Patent Publication No. 2-29-207.

Further, depending on the application, a combination of the former type of substrate and the latter type of substrate may be used.

The average pore diameter and porosity of these gas-permeable substrates are
Although it varies depending on the single fiber diameter and content of the carbon short fibers used, the amount of matrix carbon, etc., considering both gas permeability and conductivity, the average pore diameter is 20 to 150 μm, and the porosity is 40 to 80. % is preferable. Average pore diameter 2
It is particularly preferable to have a porosity of 0 to 60 μm and a porosity of 50 to 80%.

As illustrated in FIGS. 2 to 5, the member disposed at the side end portion of the gas-permeable carbonaceous substrate described above to seal that portion includes a member main body 11a and a thermoplastic resin covering the member main body 11a. It consists of 1 lb.

The member main body 11a is preferably made of a carbonaceous material having compression properties equivalent to those of the above-mentioned gas-permeable carbonaceous substrate, and is particularly preferably made of the same material as the above-described gas-permeable carbonaceous plate.

Figure 2 shows a sealing member 1 in which the member main body 11a is inserted into a thermoplastic resin tube and covered with 1 lb of thermoplastic resin.
1 and FIG. 3 shows a sealing member in which the member body 11a is covered with a thermoplastic resin 1lb by wrapping the member body 11a with a thermoplastic resin film and heat-sealing the overlapping portion.

In these cases, it is useful to use, for example, a heat shrink tube as the tube, since 1 lb of thermoplastic resin can be formed extremely easily just by heating.

FIG. 4 shows the sealing member 1l shown in FIG. 2 or 3.
FIG. 2 is a perspective view showing a sealing member 12 in which both ends in the longitudinal direction are further wrapped in a U-shape with a thermoplastic resin film, and both ends are also covered with a thermoplastic resin 11b. Also,
FIG. 5 shows the member main body 11a in FIG. 2 or 3.
FIG. 3 is a perspective view showing the sealing member 13 in a case where the entire surface of the member body is coated with 1 lb of thermoplastic resin by, for example, coating or impregnating the thermoplastic resin.

This thermoplastic resin acts as a barrier to prevent gas leakage in the direction of the plate surface of the gas-permeable carbonaceous substrate, but at the same time, the sealing member is connected to the side edges of the gas-permeable carbonaceous substrate and the gas-impermeable conductive plate. During heating during fixation, a portion of the sealing member melts and adheres the sealing member to the substrate and the conductive plate.

If the fuel cell is a phosphoric acid fuel cell that operates at high altitudes and uses a corrosive electrolyte, the thermoplastic resin used may be, for example, a fluororesin or polyether sulfone resin that has excellent corrosion resistance. It is preferable that

Examples of the fluororesin include polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and hexafluoropropylene (PFEP), a copolymer of tetrafluoroethylene and hexafluoropropylene (PETFE), and a copolymer of tetrafluoroethylene and hexafluoropropylene (PETFE). Copolymer of ethylene and perfluoroalkyl vinyl ether (PFA).
Copolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether (E
PE), etc. can be mentioned.

In addition, when the fuel cell is a fuel cell that operates at a relatively low temperature and uses acid or alkali as an electrolyte, or a membrane fuel cell, the thermoplastic resin used is
In addition to the above-mentioned fluororesins and polyethersulfone resins, for example, polyvinyl chloride, polyvinylidene chloride,
Examples include polystyrene, polyethylene, polypropylene, polyamide, polycarbonate, polyphenylene oxide, polysulfone, polyester, polyamideimide, polyphenylene sulfide, polyether sulfone, and polyether ether ketone.

Next, the gas-impermeable conductive plate is a plate made of a material that does not allow gas to pass therethrough and has conductivity, such as a gas-impermeable carbonaceous material or a metal material.

Examples of carbonaceous materials include high-density carbon plates, glassy carbon plates, plastic plates in which carbon powder or carbon fibers are dispersed, or compressed vermicular graphite powder obtained by treating graphite powder with strong acid. A molded graphite plate or the like can be used. Further, as the metal material, an electrolytic copper plate or stainless steel is used. These may be coated with a conductive resin. These thicknesses may be appropriately selected depending on the application.

In the method of the present invention, for example, as shown in FIG. 1, first, a gas-impermeable conductive plate 6 having a required size and shape is prepared. Next, a gas-permeable carbonaceous substrate 14 having a width narrower than that of the gas-impermeable conductive plate 6 and having a plurality of grooves 14a cut on its surface is mounted. At this time, a film made of thermoplastic resin as described above is interposed between the substrate l4 and the conductive plate 6, depending on the type of unit cell to be assembled.

Thus, two step portions 15 are formed between the side end portions of the gas-permeable carbonaceous substrate 14 and the gas-impermeable conductive plate 6.

For each of the stepped portions 15.15, a sealing member l1 shown in FIG.
The whole body is placed under pressure at a predetermined temperature.

A portion of 1 lb of thermoplastic resin of the sealing member 11 is melted,
The thermoplastic film interposed between the gas-permeable carbonaceous substrate 14 and the gas-impermeable conductive plate 6 is also melted. The molten thermoplastic resin seeps into a very small portion of the communicating holes of the gas-permeable carbonaceous substrate l4.

By continuing to cool slowly, the gas-permeable carbonaceous substrate l4, the gas-impermeable conductive plate 6, and the sealing member l1 are integrally joined by the thermoplastic resin.

Therefore, the side edges of the gas-permeable carbonaceous substrate 14 are sealed with gas in the direction of the mask.

In addition, when arranging the sealing member 1l on the stepped portion l5, it may be adhered with a thermoplastic resin adhesive.

Further, the substrate l4 and the conductive plate 6 may be bonded in advance with thermoplastic resin.

(Example) Polyacrylonitrile carbon fiber "Torayca" T300 (average single yarn diameter: 7 μm) manufactured by Toray Industries, Inc. was cut into 12 lengths, and this was paper-formed by a conventional method to obtain a carbon fiber mat. Next, the carbon fiber mat was impregnated with a 10% by weight methanol solution of phenolic resin to adhere 125 parts by weight of phenolic resin to 80 parts by weight of carbon fibers,
After drying at 90'C for 3 minutes, the phenolic resin was cured by hot pressing at 170°C for about 15 minutes under a pressure of 5 kg/cnf, and then heated at 250 °C in a nitrogen atmosphere.
The phenolic resin is carbonized by firing at 0'C, and the vertical 26
A porous carbon plate having a size of 0 mm, a width of 300 mm, and a thickness of 1.8+ nm was obtained.

The average pore diameter and porosity of this porous carbon plate were 40 μm and 71%, respectively.

On one side of this porous carbon plate, a width of 1.5 mm and a depth of 1 mm
25 grooves for gas distribution were excavated at equal intervals.

In addition, from a porous carbon plate obtained in the same manner as above, a length of 3
00mm, width 20m, thickness 1. Cut out a 3 mm long thin plate, insert this plate into a PTFE heat shrink tube (film thickness: 0.3 mm), and then heat the plate with hot air using a hair dryer to adhere the PTFE to the surface of the plate. At least it was used as a sealing member.

Next, the length is 300 mm, the width is 300 mm, and the thickness is 0. 8
A PFA film with a thickness of 25 μm was placed on a glass-like carbon plate (GCR-101, manufactured by Kobe Steel, Ltd.) of m+++, and the side on which the groove was not drilled was in contact with the PFA film. The above porous carbon plate was placed in this manner. As a result, there are 300 mm in length, 20 mm in width,
Thickness 1. A step of 8 mm is formed.

Next, the sealing member described above is placed on the two stepped portions so as to contact the side end surface of the porous carbonaceous plate,
In this state, temperature 350℃, pressure 5kg/crl
PT of PFA film and sealing member by heating and pressurizing.
A portion of the FE coating was melted and then slowly cooled to a permanent state.

The sealing member was adhered to the side end portion of the porous carbon plate and the glassy carbon plate at the stepped portion.

(Effects of the Invention) As is clear from the above explanation, according to the method of the present invention, a sealing member coated with a thermoplastic resin is brought into contact with the side edge of a gas-permeable carbonaceous substrate and heated. Since it is only necessary to join the sealing member to the side end portion, the gas sealing method is extremely simple compared to the conventional method.

In addition, if a thermoplastic resin film is interposed between the gas-permeable carbonaceous substrate and the gas-impermeable conductive plate, the gas-permeable carbonaceous substrate, the gas-impermeable conductive plate, and the sealing member can be bonded simultaneously in one heat treatment. Therefore, the manufacturing process of the single cell can be further simplified and the manufacturing cost can be reduced.

Furthermore, if the main body of the sealing member is made of the same material as the gas-permeable carbonaceous substrate, the compression characteristics of the two will be almost the same, so when the fuel cell is assembled by tightening the stack of single cells, the sealing The plate surfaces of the member and the gas-permeable carbonaceous substrate are on the same plane, eliminating uneven tightening and improving electrical and thermal conduction.4. The conductivity becomes uniform and the insulation performance improves.

Further, since the surface of the sealing member is coated with thermoplastic resin and has electrical insulation properties, electrical short circuit between each unit cell when the manifold is arranged is also prevented.

Furthermore, since the side edges of the gas-permeable carbonaceous substrate are shielded with a chemical-resistant thermoplastic resin, for example, in a phosphoric acid fuel cell, the side edges may be corroded by phosphoric acid and deteriorate over time. Situations such as gas leakage and scattering due to leakage of electrolyte (phosphoric acid) are suppressed, and battery life is extended.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state in which a sealing member is arranged at the side end of a gas-permeable carbonaceous substrate, FIGS. 2 to 5 are perspective views of the sealing member used in the present invention, and FIG. 6 is a partial perspective view of a single cell example, FIG. 7 is a perspective view of a fuel electrode (or air electrode), FIG. 8 is a partial perspective view of another single cell example, and FIG. 9 is a partial perspective view of yet another single cell example. FIG. l...Fuel electrode, la, 9a...Groove for fuel gas, 1
b...Side end portion, 2...Air electrode, 2a, 10a...
Groove for oxidizing gas, 2b... Side end portion, 3... Electrolyte matrix, 3'... Ion exchange membrane, 4, 5... Catalyst layer, 6... Gas impermeable conductive plate (Separator), 7
...Gas-impermeable sealing material, 8...Sealing member, 9
．． 10... Gas diffusion plate, 1 1, 1 2. 1
3--Seal member, lla--Member body, llb
...Thermoplastic resin, l4... Gas permeable carbonaceous substrate (fuel electrode, air electrode or gas diffusion plate), 14a... Groove, l5... Step portion.

Claims (2)

[Claims] (1) A gas-impermeable conductive plate and a gas-permeable carbonaceous substrate whose width is narrower than that of the gas-impermeable conductive plate are stacked together via a thermoplastic resin, and the gas-impermeable conductive plate and the gas-permeable A sealing member coated with a thermoplastic resin is placed on the stepped portion formed by the carbonaceous substrate so as to be in contact with the side end surface of the gas-permeable carbonaceous substrate, and then the whole is heated and pressurized. The gas-impermeable conductive plate, the gas-permeable carbonaceous substrate, and the sealing member are bonded to each other by a thermoplastic resin, and the side end portion of the gas-permeable carbonaceous substrate for a fuel cell is characterized in that: Gas seal method. (2) A gas-impermeable conductive plate and a gas-permeable carbonaceous substrate whose width is narrower than that of the gas-impermeable conductive plate and the gas-permeable carbonaceous substrate bonded by thermoplastic resin. A sealing member coated with a thermoplastic resin is placed on the stepped portion formed with the substrate so as to be in contact with the side end surface of the gas-permeable carbonaceous substrate, and then the whole is heated and pressurized to remove the thermoplastic resin. A method for gas sealing a side end of a gas-permeable carbonaceous substrate for a fuel cell, characterized in that the sealing member is joined to the gas-impermeable conductive plate and the gas-permeable carbonaceous plate with a resin.