JPS5968170A - Electrode base plate for fuel cell - Google Patents

Abstract

PURPOSE:To prevent such fetal defects of the conventional monopolar electrode base plate having a large contact resistance, an inhomogeneous intercellular temperature distribution and a decreased generation efficiency by using a three- layered electrode base plate consisting of a dense carbonaceous layer and porous carbonaceous layers placed on the surfaces of the dense carbonaceous layer, and providing each porous carbonaceous layer with a group of holes. CONSTITUTION:In a fuel cell constituted by stacking electrode base plates 11 with catalyst layers 2 and an electrolyte layer 3 interposed, the electrode base plate 11 having a three-layered construction is formed by unifying porous carbonaceous layers 7 over both surfaces of a dense carbonaceous layer 8. Each porous carbonaceous layer 7 is provided with a group of holes located preferably in the center of the thickness of the layer 7. These holes 9 extend from one end surface of the base plate 11 to its other end surface, are almost parallel to each other and almost parallel to the electrode surface of the base plate 11. In addition, hole groups 9 located over the surfaces of the dense carbonaceous layer 8 are perpendicular to each other. The sectional shape of the holes 9 may be arbitrarily chosen. When it is supposed to be a circle, the diameter of the circle is preferably 0.5-3mm..

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode substrate for fuel cells, and more specifically, to
The present invention relates to a positive electrode substrate for a carbonaceous fuel cell that has a three-layer structure and has hollow hole groups in porous carbonaceous layers on both sides of a dense carbonaceous layer.

Conventionally, pie-porase obtained by ribbing an impermeable graphite thin plate, and pie-7-no? using an e-lator. - Rana-nine-lator fuel cells are known.

On the other hand, it has a structure in which ribs are provided on one surface and the other surface is a flat electrode surface, so that the reaction gas flows from the ribbed surface into a flat r! A monopolar type tH electrode substrate with diffusion on the electrode surface has been developed.

Conventional mono Ij? - As shown in the attached FIG. 1, the L-type cell has an electrode substrate 1 having a rib 5 on one side and a flat structure on the other side. Abomination M2. It consists of a matrix 3 impregnated with an electrolyte and a separator sheet 4, and a reactive gas (oxygen or hydrogen) diffuses from the ribbed surface of the electrode substrate 1 to the flat electrode surface.

Traditionally, things, l? - As a manufacturing method for electrode substrates for R-type fuel cells, there is a press-forming method based on short carbon fibers (Japanese Patent Application No. 56-48700), a paper-making method in which carbon fibers are dispersed (% Komei 53-1.8603) , a method of chemical vapor deposition of pyrolytic carbon onto a web of carbon fibers (U.S. Pat. No. 3,8
No. 29,327) has been proposed. All of the electrode substrates produced by these conventional manufacturing methods consist of a single layer of 4fIt structure that is uniform throughout.

When the bulk density of such a homogeneous single-layer electrolyte substrate is large, the gas diffusion coefficient is small, so the flow density is at its limit, and the electrolyte retention is not sufficient, so there is a period when the performance deteriorates. It has the disadvantage of being faster and having a shorter lifespan. On the other hand, if the bulk density is small,
It has the disadvantages of high electrical resistance and high thermal resistance, and low mechanical strength such as bending strength.

! In addition, in the case of an electrode substrate having a rib structure, as shown in FIG. 1, since one side of the rib 5 is not flat, the section modulus is small. Therefore, in terms of strength as a whole, Atsunoko is a bit unreliable. Therefore, in order to maintain the strength of the molded plate, there is no choice but to increase the wall thickness of the flat plate part, so that when gas (oxygen or hydrogen) diffuses through the entire thickness of the electrode substrate from the rib side to the electrode surface side. The disadvantage was that the diffusion resistance of Moreover, it is necessary to perfect the flatness of the top surface of the rib with an internal angle IC, and the electrical and thermal contact resistance with the center plate is negligible. It is said that these contact resistances are several times as large as the transmission resistance within the substrate, and conventional monopolar electrode substrates and plates have large contact resistances, resulting in uneven temperature distribution between cells and a decrease in power generation efficiency. It had a decisive drawback.

An object of the present invention is to provide an electrode substrate for a fuel cell that eliminates the above-mentioned drawbacks.

The electrode substrate for a carbon fuel cell of the present invention has a three-layer structure having porous carbonaceous layers on both sides of a dense carbonaceous layer.
Each porous carbonaceous layer has a group of hollow pores.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Note that the same reference numerals are given to the middle portion of the drawings in FIGS. 1 and 2.

FIG. 2 shows a fuel cell structure using the electronic wide substrate of the present invention. The cell shown in FIG. 2 is obtained by laminating the electrode substrates 11 of the present invention with a catalyst layer 2 and an electrolyte layer 3 interposed therebetween, and the portion corresponding to the cell assembly shown in FIG. 1 is designated by the number 10.

The electrode substrate 11 of the present invention has a three-layer laminated structure in which a porous carbonaceous layer 7 is integrally formed on both sides of a dense carbonaceous layer 8, and this porous carbonaceous layer 7 includes: Preferably, a hollow hole group consisting of a plurality of hollow holes 9 is provided at the center of the thickness.

This hollow hole path 9 is continuous from one end surface of the electrode substrate 11 to the opposite end surface, and each hollow hole path 9 is separated from each other.
The holes are parallel to each other and substantially parallel to the electrodes of the electrode substrate 11, and the hollow hole groups 9 on both sides of the dense carbonaceous layer 8 are oriented at right angles to each other (see FIG. 2). .

The cross-sectional shape of the hollow hole 9 may be arbitrary, and may be circular as shown in FIG. 2, for example. This Hollow Hole Road 9-1! The dimension corresponding to the diameter when the Ji plane is considered to be circular (referred to as the equivalent diameter) is preferably between 0.5 and 3, and this equivalent diameter is 0.5 to 3.
If it is smaller than mine, the resistance to gas flow will be too large, and the height will be 3 m.
If m is larger, the porous carbonaceous layer becomes thicker: the capacity f+lt efficiency of a cell in which 1f4i electrode substrates are laminated decreases.

The porous carbonaceous layer 71d of the electrode substrate 11 of the present invention is composed of a homogeneous porous carbonaceous layer material, and has an average bulk density of 0.3 to 0.0 gI, preferably 0.4 to 0. ,
p at s 11/art, and gas permeability is 20rs
Da I Mitsu Aq.

It is good that the above is the case. A porous carbonaceous layer having an average density and gas permeability in the above ranges has good mechanical strength, such as bending strength, and has favorable gas diffusion resistance. In addition, it is preferable that the pores of the porous carbonaceous layer 7 are open pores, and that 60 or more of the pores have a diameter within the range of 10 to 100 microns.

The dense carbonaceous layer 8 of the electrode substrate 11 of the present invention has an average bulk density of 1.0 g or more and an average bulk density of 0.2 me/cm.door.A'1.
It is preferable to have the following gas permeability. Average bulk density is 1. , OgA, the desired density cannot be obtained. Also, dense carbon material J? 48 can function as a sheet with a small gas permeability (Fig. 1, 4), but if the gas permeability is Q, 2me/crn, juice, Aq, or thicker, it can function as a sheet. becomes unable to fulfill its role. The thickness of the dense carbonaceous layer 8 is preferably 1/2 or less of the total thickness of the electrode substrate J, and more preferably 0.1 to 3 mm.

The carbonaceous electrode substrate having a three-layer lining structure according to the present invention is manufactured as follows.

As the material for the porous carbonaceous layer, for example, 10 to 50% by weight of a filler (short flame fiber, 1 granular activated carbon, etc.) and a binder (
Phenol resin, epoxy resin 1 petroleum-based and/or coal-based pitch, etc.) for example 10 to 40 Door Jil q6, and pore Ti ladle #7 material (polyvinyl alcohol, polystyrene, 71?ripropylene, polyvinyl chloride, sugar, etc.) )
A mixture obtained by mixing, for example, 20 to 50% by weight is used.

For hollow holes, fJ? Liedylene, polypropylene 1. I? risky
Polymers such as chlorine, polyvinyl alcohol, and polyvinyl fluoride are used.

As materials for the dense carbonaceous layer, there are two methods: using graphite plates, compressed graphite paper, etc., and methods using short carbon fibers, fine carbon precursor powder (see Japanese Patent Publication No. 55-31116), phenol resins, etc. There is a method of integrally molding a powder mixture consisting of fine particles of activated carbon.

The molding is performed by a press molding method. The above porous carbon′
The R layer layer group mixture is supplied into a press molding die, a hollow hole material is placed thereon, a mixture for a porous carbonaceous layer is further supplied, and then a material for a dense carbonaceous layer is placed therein. Furthermore, a mixture for porous carbonaceous layer, a hollow hole layer, and a mixture for porous carbon V (for horses) are supplied in this order.

The press molding conditions are appropriately selected from the following ranges: mold heating temperature of 70 to 200 tr, molding pressure of 5 to 100 liters, and pressure holding time of 1 to 60 minutes.

After press molding, the obtained molded product is post-cured for at least 2 hours and then fired at 1000 to 3000 tons. It is preferable to raise the temperature slowly to prevent the generation of stress due to rapid contraction during gasification.If the temperature is raised rapidly at this low temperature of pyrolyzed overculm, it will cause peeling and cracking.

The electrode substrate of the present invention manufactured as described above has mechanical properties such as high bending strength, can be made into thin pieces, allows the diffusion layer of the reaction gas to be made thin, has low gas diffusion resistance, and has a current density. becomes larger. Furthermore, since the dense carbonaceous layer plays the role of a mono-Q layer, the conventional mono-Q layer is unnecessary, and the cost is reduced and contact resistance is completely eliminated. As a result, great effects such as a drastic reduction in electrical resistance as a whole when laminated are achieved. Thus, the electrode substrate of the present invention can be said to be ideal. By the way,
Compared to the carbon fiber P/Q-type produced by the carbon fiber papermaking method, the bending strength is increased and at the same time, a graphite plate with a lip is not required, and a reduction in price and electric resistance can be expected.

In order to further clarify the effects obtained by the electrode substrate of the present invention, we will discuss the electrode substrate of the present invention and the conventional lip-attached mono7-''?
Table 1 shows a comparative comparison of various physical properties of the R-type 'rk electrode substrate (see Figure 1). These physical property values are shown as 115'U for comparison, and were measured under similar disputes.

Table 1 (2 locations).

7) 200mA〆ff1T+7) ([,.

EXAMPLES The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

Example 1 Short-legged fiber (Kureha Chemical, MI O4S) 40wt
%, phenolic resin (manufactured by Asahi Corporation) 30wt
% and d? Rivinyl alcohol particles (manufactured by Nippon Gosei Kagaku)
A mixture (mixture for porous carbonaceous layer) consisting of 30wt-.

It was then placed into a press mold. Subsequently, a hollow pore material (sudare lattice-like molded product) was supplied, and a mixture for a porous carbonaceous layer was further supplied. Thereafter, a carbon plate (manufactured by Toyo Carbon Co., Ltd.) having a thickness of 0.6 mm was supplied. The above porous carbonaceous layer mixture, the hollow hole ladle, and the porous carbonaceous layer mixture were supplied to this 110.

After that, press molding was carried out for 20 minutes at 14 oc and 40% liter. After the molded product was post-cured for about 2 hours, the temperature was slowly raised to 700C at 100C/hour, and then fired at 2000C for 1 hour.

The obtained electrode substrate has a three-layer structure as shown in Figure 2, and the hollow holes have a nearly circular cross section and a diameter of approximately 0.
．． It was 8 friends. Table 2 shows the physical properties of this electrode substrate.

Table 2 Note 1) Excluding the hollow hole path part.

2) Value when the electrode substrate of the present invention (11 in Fig. 2) is integrated.

Example 2 Instead of the carbon plate used in Example 1, tempered plain fibers (
Kureha Chemical Co., Ltd., M2O2S) 20wt%, activated carbon fine particles (Kureha Chemical Co., Ltd.) 2Owt, carbon precursor fine powder (Kureha Chemical Co., Ltd., 1-1.) 1. ) 40wt% and phenolic resin (
An electrode substrate was manufactured in the same manner as in Example 1, except that a mixture consisting of Asahi Yuraku ff1zoil was used.

tlj, the physical property value of the polar substrate'? j: Shown in Table 3.

Table 3 2) The value of the whole.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a conventional mono-15-L type fuel cell structure, and FIG. 2 is a perspective view showing a cell structure using the electrode substrate of the present invention. Agent Benbushi Imamura Former 51-year-old Shinshin City 1. [Calendar-r-:flit fi
l 5 Pufferfish 11 December 11111rx'l Agency Director Name Sugiwa Daidono 1, Display of matter i'1 Showa j) Hui [Special h'1 application 178770th day? 3. Name of the invention: Electrode substrate for fuel cells 3, N + 1 ijr, connection with 11, Particularly a'l Applicant's name: (
IHI) Tsuiha Chemical, [] Industry Stock] (Delivery 4, Agent: Shinjuku 1-chome, Shinjuku-ku, Tokyo [11?f'r14 Yama LTJ Building 5.7 + Ii Stop Order [1 It 1 Voluntary 8] , Contents of the amendment (1) The scope of claims in the specification of the present application will be amended by attaching a separate sheet. (2) The phrase “lead paper, etc.” in the 6th line from the bottom of page 9 of the specification of the present application will be replaced with “Lead paper, etc.” "Lead paper (graphite sheet), etc." (3) Insert a separate sheet before "4. Brief explanation of drawings" on page 16 of the same. Example 3 In place of the carbon plate used in Example 1 An electrode substrate was manufactured in the same manner as in Example 1, except that a graphite sheet (UC (J4 Graph Oil)) having a thickness of 0.3 mm was used.The physical property values of this electrode substrate are shown in Table 4. The cross section of the hollow hole path was almost circular, and the diameter of the groove was approximately 0.8 mm. Show more. 2. Claims (1) A carbonaceous fuel having a three-layer 4-1-1 structure with porous carbonaceous layers on both sides of a dense carbonaceous layer, and having hollow holes in the porous carbonaceous layer. Electrode substrate for batteries. (2) Hollow hole path L''C1, located approximately in the center of the thickness of the porous carbonaceous layer, each hollow hole path is parallel to each other and to the electrode surface of the substrate, and the end surface facing from one end direction of the substrate The hollow holes on both sides of the dense carbonaceous layer are oriented at right angles to each other, and the equivalent diameter is 0.
．． 'y (L electrode substrate) according to claim 1, characterized in that the porous carbonaceous layer has a thickness of 0.3 to 1.OF!/α3
It has an average bulk density of 2Qmt/cm+r-imAq or more, and the dense carbonaceous layer has an average bulk density of 1. O
Average bulk density of g 7cm” or more and Q, 2me/cm−
The electrode substrate according to claim 1 or 2, having a gas permeability of hr-FmAq or less. (4) The pores of the porous carbonaceous layer are open pores, and 60 or more of the pores have a diameter within the range of 10 to 100μ. The electrode substrate according to any one of Item 3. (5) The thickness of the dense carbonaceous layer is less than V2 of the entire substrate υ
The electrode substrate according to any one of claims 1 to 4, characterized in that the electrode substrate is coated with 0.1 to 3 silk.

Claims (5)

[Claims] (1) An electrode substrate for a carbonaceous fuel cell, which has a three-layer structure having a porous carbonaceous layer on both sides of a dense carbonaceous layer, and has a group of hollow holes in the porous carbonaceous layer. (2) The hollow holes are located in the middle part of the porous carbonaceous layer, and the hollow holes are parallel to each other and to the electrode surface of the substrate, and extend from one end surface of the substrate to the opposite end surface. The hollow holes are continuous, sandwiching the dense carbonaceous layer, and the hollow holes on both sides are oriented at right angles to each other, and have an equivalent diameter of 0.5~
The electrode substrate according to claim 1, characterized in that the electrode substrate is made of three types. (3) The porous carbonaceous layer has an average bulk density of 0.3 to 1.0 and a gas permeability of 20 m1/cm・hr・mm A16 or more, and the dense carbonaceous layer has a gas permeability of 1.017 d or more. Average bulk density of 0.2 me/am・hr・ho A11. The electrode substrate according to claim 1 or 2, wherein the electrode substrate has the following gas permeability. (4) The pores of the porous carbonaceous layer are open pores, and 60% or more of the pores have a diameter within the range of 10 to 100μ. The electrode substrate according to any one of Item 3. (5) According to any one of claims 1 to 4, wherein the thickness of the dense carbonaceous layer is 1/2 or less of the entire substrate and has 0.1 to 3 sides. The electrode substrate described.