JPS59132572A - Fuel cell - Google Patents

Abstract

PURPOSE:To increase reliability of a seal structure of a phosphoric acid type fuel cell by heating and pressing a resin film to the periphery of an electrode with rib in a fuel cell obtained by stacking a plurality of unit cells having a set of electrodes with ribs. CONSTITUTION:A film 21 comprising resin which easily makes fiber is heated and pressed to the periphery 20 of an electrode 19 with rib and pushed in gaps of the periphery 20 to form a fitting layer 22. The rest of it forms a residual layer 23. A set of faced electrodes 19 are arranged with a matrix 1 impregnated with electrolyte placed in between to form a unit cell. A plurality to unit cells are stacked with separators 18 interposed to form a stacked fuel cell. Thereby, internal heat generation caused by combustion of reaction gas due to a defective seal structure of the periphery of the electrode 19 is prevented. Decrease of current efficiency caused by electrical short in the periphery is also prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fuel cell, and in particular to a lip-equipped electrode. I'm being beaten.

This fuel cell usually has a pair of porous electrodes sandwiching an electrolyte between them, and a fluid fuel such as hydrogen is brought into contact with the back surface of one electrode, and a fluid oxidizer such as oxygen is brought into contact with the back surface of the other electrode. Electrical energy is extracted from between the electrodes by utilizing the electrochemical reaction that occurs when It is something that can be taken out.

By the way, a unit cell of a fuel cell based on the above principle, especially using phosphoric acid as an electrolyte, is shown in FIG. 1(a) or (b).
), and by stacking a plurality of unit cells, a fuel cell as shown in FIG. 2 is constructed.

That is, in FIG. 1(a), the unit cell has electrodes 2.3 (usually made of carbonaceous material) formed of a porous material and provided with a catalyst on both sides of a matrix 1 impregnated with an electrolyte. In addition, a plate 6 with a lip 4.5 on the back side opposite to the IJ sock (generally composed of a mixed bond of graphite and thermosetting resin. It is called an ink connector.

) are placed. Each electrode 2 of the interconnector 6.
A plurality of grooves 7.8 are regularly provided in parallel in the directions perpendicular to each other by means of lips 4.5 on the surface located on the 3 side, and these grooves 7.8 are respectively provided with fluid fuel and Forms a flow path for fluid oxidizer. Also, on the opposite side of the intercopter 260, grooves 7.8 are provided to flow paths for fluid fuel and fluid oxidizer in the unit cells that are in contact with each other in directions perpendicular to each other by grooves 4.5.
is formed. In this way, matrix 1, electrode 2
．． 3 and the interconnector 6 are stacked, and in this state, only the openings at both ends of the six grooves 7 and 8 of the ink connector 6 are left open, and the end faces of each stack are hermetically sealed to form a unit cell.

A plurality of unit cells configured as shown in FIG. 1(a) are stacked together, and as shown in FIG. , a manifold 12 having a fuel outlet 11 on the other hand, and a manifold 14 having an oxidizer supply port 13 on one of the opposite end faces and a manifold with an oxidizer outlet 15 on the other side. 16 are applied, and these manifolds 10, 12, 14, 16 are tightened with bolts or the like to maintain airtightness, thereby constructing a fuel cell 17.

Therefore, according to this fuel cell 17, when fluid fuel is supplied from the fuel supply port 9, this fuel flows through the plurality of grooves that are the flow paths of each unit cell and flows while being in contact with the back surface of the porous electrode 2. Then, the fuel is discharged from the fuel discharge port 11.

Further, when a fluid oxidant is supplied through the oxidizer supply port 13, this oxidant flows through the plurality of grooves 8, which are the flow paths of each unit cell, and flows while contacting the back surface of the porous electrode 3. The fluid fuel and the fluid oxidant are then discharged through the outlet 15, and the fluid fuel and the fluid oxidant are then supplied by diffusion into the porous electrode 2.3 to generate electrical energy as a fuel cell.

Note that the output terminal is omitted in the figure.

However, the conventional fuel cylinder configured as above,
There were the following problems with the pond.

(1) Since the thickness of the interconnector is large, the calculation resistance is large, the pressure drop outside is large, and the +0 loss of output electrical energy is large.

(2) Since the ink connector is thick and has a high density (about 1.8 g/crit), the fuel cell is heavy.

(3) The lifespan is short due to the use of interconnectors made of phenolic resin binder.

(4) Since it has a large own weight, its own weight accelerates deterioration.

A fuel cell unit cell configured as shown in FIG. 2(b) has been considered as an improved type to solve the above problems.

That is, in FIG. 1(b), 18 is a separator;
19 is an electrode with a lip. Components having the same effect as in FIG. 1(a) are designated by the same numbers. In other words, Figure 1 (a
) shows an ink connector 6 with a separator 18 and a lip 4.
The grass lips 4.5 are each integrated with the electrodes 2.3 to form an electrode with lips 19.

A feature of this improved type is that the separator 18 prevents mixing of the fluid fuel and fluid oxidizer, and serves as a current collector for unit cell stacking. The weight of this improved fuel cell is reduced by half compared to the fuel cell using the interconnector shown in FIG. 1(a).

By the way, the lip-equipped electrode 19 must have sufficient reaction fluid permeability for the reaction fluids of fluid fuel and fluid oxidizer to reach the catalyst layer, and the electrode 19 must have sufficient conductivity.
In addition, the electrode 19 with lips is usually made of a material such as carbon fiber or graphite particles, and has a porosity of 7.
It is designed to be between 0 and 80%.

The conventional manufacturing method for the lipped electrode 19 is to use materials such as carbon fiber or graphite particles, add a thermosetting resin such as phenolic resin, or tar pitch as a binder to the material, and then hot-press the material. The sheet is formed into a sheet, and this sheet is then burned in a graphitization furnace to convert the carbon component of the binder into graphite and increase the porosity.The sheet is then machined to create grooves for the reaction fluid flow path. It is manufactured by.

By the way, since the ribbed electrode 1b is a porous material with an average pore diameter of several tens of microns, a gas seal is applied to prevent gas diffusion and leakage from the end perpendicular to the flow path. ing. This seal has the function of preventing a decrease in the actual amount of reactant gas due to leakage of reactant gas, and also prevents deterioration of battery performance due to overheating of the battery body due to combustion reaction on the catalyst surface caused by mixing of leaked gas. As this sealing method, a wet sealing method, an impregnation sealing method, and a method using a film are generally used.

In the wet seal method, microparticles such as silicon carbide that are resistant to high temperatures and high concentration phosphoric acid are buried in the sealing surface of the end of the ribbed electrode, and an electrolyte is applied to the electrode to seal the gaps between the particles. This method uses the surface tension of the electrolyte to prevent gas diffusion. The impregnating sealing method is a method for preventing gas diffusion by impregnating and solidifying the sealing portion of the lipped electrode with a liquid such as fluororubber paint that is resistant to high temperatures and high concentration phosphoric acid.

However, since lipped electrodes are generally porous with a thickness of about 2 m and small pores of 10 microns, it is difficult to uniformly fill the entire sealing area with particles using the wet seal method. It is difficult to fill only the surface layer and cannot completely fill the inside.

Also, even if the impregnated seal is impregnated, only the surface layer is impregnated in the same way,
The inside is not impregnated.

As described above, in the conventional seal structure, the effective seal portion is small and there is a problem in maintaining a stable sealing function for a long period of time.Therefore, a more reliable seal structure has been desired.

[Purpose of the invention]

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a phosphoric acid fuel cell in which the peripheral end sealing structure of the electrode with a lip is improved.

[Summary of the invention]

To achieve this object, the present invention provides a fuel cell in which a plurality of unit cells are stacked, each having a pair of lipped electrodes impregnated with an electrolyte and arranged opposite to each other with a matrix interposed therebetween. It is characterized in that a film made of resin is heat-pressed to the peripheral edge.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a perspective view of a main part of an electrode with a lip according to an embodiment of the present invention. This lipped electrode is constructed as follows.

After binding and solidifying carbon fiber with phenolic resin,
A 12m thick carbon fiber porous plate obtained by carbonizing the resin (density 0.5gk, average pore diameter 20-50μ)
A plurality of grooves 7 forming gas flow passages are provided in parallel with each other by means of lips 4. A film made of a resin that easily turns into fibers is heat-pressed onto the peripheral end 20 of the lipped electrode 19. Ethylenetetrafluoroethylene (
E T F E ) Using film 21, with ribs'! *
19 peripheral end plus 2000c, 31cq/crA
By heating and pressurizing at a temperature and pressure of This thickness is about 0.2++ m.The thickness of the residual layer is 0.05 mm or less.The heating temperature is preferably 1708C to 200C in order to give a carved shape to the thickness of the fixed layer and the residual layer.

In this way, a fuel cell is assembled as shown in FIGS. 1(b) and 2 using the rib-covered electrode 19 with the resin film 21 heat-pressed onto the peripheral edge thereof.

That is, a unit cell is formed by arranging a pair of lipped electrodes 19 facing each other with the matrix 1 impregnated with an electrolyte interposed therebetween. A fuel cell stack is constructed by layering a plurality of these unit cells via separators 18, and manifolds are attached to opposite sides of the stack to construct a fuel cell.

By the way, the ETFE film mentioned above was heated at 190°C for 10
A sealing structure for the peripheral edge of the ribbed electrode is achieved which is stable even in 5% phosphoric acid and has good airtightness and has a long life even when exposed to high temperature and high concentration phosphoric acid.

Moreover, since the thickness of the residual layer 22 can be set to 0.05 mm or less, there is almost no unevenness in the tightening pressure during lamination, and the entire surface contact between the separator and the ribbed electrode is impaired. It won't happen.

The same concentration can be obtained by using an FEP film instead of the ETFE film.

Incidentally, it is also possible to heat and press the film before cutting into the porous carbon plate having a thickness of 2 mm.

〔Effect of the invention〕

According to the present invention, it is possible to prevent internal heat generation in the combustion chamber of the reaction gas due to a defective sealing structure at the peripheral end of the ribbed electrode, thereby making it possible to effectively utilize the reaction gas. It is also possible to prevent a decrease in current efficiency due to electrical short circuits that are likely to occur. In this way, a fuel cell with significantly improved reliability can be provided.

[Brief explanation of the drawing]

Fig. 1 (at, (b) is an exploded perspective view showing a unit cell of a conventional fuel cell, Fig. 2 is a perspective view of a fuel cell incorporating the same cell, and Fig. 3 (a) is an exploded perspective view showing a unit cell of a conventional fuel cell. A perspective view of the main part of the ribbed electrode, and FIG. 3(b) is a sectional view of the peripheral end of the ribbed electrode. 1... Matrix 2.3... Electrode 19...
・Ribbed electrode”...Peripheral end 21...Film agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1

Claims (1)

[Claims] 1. In a fuel cell in which a plurality of unit cells each having a pair of lipped electrodes are stacked, each having a pair of lipped electrodes facing each other with an electrolyte-impregnated matrix interposed therebetween, a peripheral edge of the lipped electrode is provided. A fuel cell characterized in that a film made of resin is bonded under heat and pressure. 2. The fuel cell according to claim 1, wherein the resin is a Teflon resin. 3. The fuel cell according to claim 1, wherein the thermocompression bonding is carried out at 1706C to 200C. 4. The fuel cell according to claim 2, wherein the Teflon resin is ethylenetetrafluoroethylene (ETFZ). 5. The fuel cell according to claim 2, wherein the Teflon resin is tetrafluoroethylene or hexafluoropropylene (FEP).