JPH02112161A - Manufacture of carbon component for fuel cell - Google Patents

Abstract

PURPOSE:To increase reliability in a component bonding part and to simplify a manufacturing process by selecting material characteristics of a separator combined with side seals. CONSTITUTION:A material having such carbon characteristics that thermal expansion coefficient is 3X10<-6> deg.C<-1> or less, flexural strength is 900kg/cm<3> or more, gas permeability is 10<-5>cc/cm<3>.min. or less, and corrosion current density is 5mumA/cm<2> or less is selected as a separator 2 combined with side seals 1. Bonding is conducted by applying a thermosetting resin adhesive to the recess of the separator. Since the side seal 1 and the separator 2 are formed with the same material, airtightness in the bonded part is increased and interface separation is prevented. By selecting material characteristics of the separator, separation between components and wear caused by heat cycles are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a carbon member for a phosphoric acid fuel cell, in which an electrode, a separator, and a zide seal are integrally formed.

[Prior Art] In recent years, in carbon components that constitute fuel cells, electrodes and separators have been integrated in advance in order to improve mechanical strength, reduce electrical and thermal resistance, and simplify cell assembly. Attempts to form composite structures are actively underway.

As a means of manufacturing such a composite member, for example, an electrode material, a separator material, and a side seal material as disclosed in Japanese Patent Application Laid-Open No. 60-20471 and Japanese Utility Model Application Publication No. 60-15759 are bonded with an adhesive. The bonding and firing method, in which the electrodes, separators, and side seals made of carbon materials are bonded and fired, is highly practical. There is a method in which the electrodes, separators, and side seals at the green precursor stage, which are the previous molding base materials, are bonded and fired.

In general, the points required in manufacturing the above-mentioned composite members for fuel cells are ensuring performance as a composite structure,
The aim is to ensure the reliability of the joint parts (especially the side seal parts) and to shorten and simplify the process, and among the above-mentioned joint firing methods, the latter green precursor joining method can be said to meet these requirements. .

However, in the case of the green precursor bonding method, it is difficult to install the side seal portion and simultaneous bonding is not possible, resulting in a complicated process in which bonding must be performed separately after the electrode base material bonding process.

[Problem to be solved by the invention]

As a measure to eliminate the above-mentioned drawbacks, a fuel cell separator in which a gas isolation separator part having a specific property and a gas leakage prevention edge part (side seal part) are integrated by carbonization firing and its manufacturing method (Japanese Patent Laid-Open No. 61-19071 Publication No.)
, by forming recessed portions on both sides of the gas-impermeable carbonaceous plate in directions perpendicular to each other except for the edge portions, the side seal portion and the separator material are formed into a body, and in the recessed portions. A method for manufacturing a composite electrode for a fuel cell (Japanese Patent Application Laid-Open No. 188173/1983) has been proposed, in which electrode materials are bonded via a resin-impregnated porous sheet and then fired.

However, the method disclosed in JP-A No. 61-19071, in which the separator material and the side seal portion are integrated by carbonization firing, has the problem that sufficient airtightness cannot be provided at the bonding interface between the two members. Although the method of No. 73 completely maintains the airtightness between the separator material and the side seal, there is room for improvement in the performance of the composite structure as a whole, such as peeling, wear, and damage of parts during the practical process. It was not possible to dispel this phenomenon.

An object of the present invention is to provide a manufacturing method that improves the performance of a composite structure, improves the reliability of joining parts, and simplifies the manufacturing process.

[Means to solve the problem]

In order to achieve the above object, the method for producing a carbon member for fuel cells according to the present invention includes a separator base material formed into a concave shape leaving the edge portion forming the side seal portion at the green precursor stage, or In a method of obtaining a carbon member with a composite structure by inserting a green precursor base material constituting a porous carbon electrode or an electrode material obtained by firing and carbonizing this into a fired and carbonized separator material, bonding them together, and then firing them. , thermal expansion coefficient 3X10-6 as separator material
゛C-1 or less, bending strength of 900 kg/c/ or more, gas permeation of 10-'cc/c+It min or less, and g-line current density of 5/7 A/d or less. The structural feature is that a thermosetting resin adhesive is applied to the concave surface.

The green precursor of the separator with the side seal part is preferably a mixture of carbonaceous fine powder such as graphite and highly carbonizable thermosetting resin such as phenol type or furan type, and is formed into a concave surface with the edges remaining. It is formed by placing it in a mold of a predetermined shape that can be molded into a shape and pressing it under heat. The separator base material made of the formed green precursor can also be made into a carbon separator material by heat-treating it at a temperature of 800° C. or higher in a non-oxidizing atmosphere to sinter and carbonize the resin component.

In the above process, by adjusting and controlling the particle size of the graphite fine powder used as the feller, the blending ratio of the thermosetting resin binder, the kneading conditions, etc., the thermal expansion coefficient specified in the present invention is 3 Strength 900kg/c
+f1 or more, gas permeation amount 10-'cc/c+fl ・m
in and corrosive current density 5 ha/c+! The following carbon properties are imparted.

Of these carbon properties, the gas permeation amount is the gas used: nitrogen, pressure crab] kg/c+fl, the temperature: the value measured at room temperature, and the corrosion current density here is the value measured at 200°C.
Anode potential 0.8 VRHE in phosphoric acid.

Refers to the measured value 500 minutes after the start of energization.Furthermore, the bending strength is JIS K6911, and the thermal expansion coefficient is the Carbon Society Standard JC.
The value obtained by applying AS-18-1978 shall be used. However, the coefficient of thermal expansion is from room temperature to 200°C.

The above-mentioned carbon properties are necessary for improving the performance of composite structures, and if these limits are exceeded, the occurrence of peeling, wear, damage, etc. of members due to heat cycling increases significantly.

The concave surface can be formed on one or both sides of the separator material, but if it is formed on both sides, the direction of the edge portion that will become the side seal part 1 and the concave surface that will become the separator material 2 is upward, as shown in Figure 1. They are formed so that they are perpendicular to each other on the lower surface.

Porous carbon electrodes are produced by molding carbon fibers or organic fibers such as polyacrylonitrile or cellulose together with thermosetting resins such as phenol resin into a thin plate using methods such as molding or papermaking, and then heating and curing the electrodes. A green precursor substrate was obtained, which was heated at 800 °C in a non-oxidizing atmosphere.
A carbonized electrode material is formed by firing and carbonizing the material to a temperature higher than 'C.

To join the separator base material or separator material having a side seal portion to the electrode substrate or electrode material, apply a thermosetting resin adhesive to the concave surface of the separator, fit the electrode member, and heat at approximately 50 to 200°C. Temperature and 1kg/c++T
This is done by applying the above pressure and applying heat.

The thermosetting resin adhesive to be used is preferably a mixture of an initial condensate of phenol or furan resin with an appropriate hardening agent. Uniform mixing in the range of ~70% by weight is effective for lowering the resistivity.

Moreover, by polishing the concave surface in advance to a surface roughness of 10 μmRZ or more during bonding, the bonding strength is significantly improved.

The composite member after bonding is fired and carbonized in a non-oxidizing atmosphere at a temperature range of 1000 to 2000°C according to a conventional method, and further graphitized at a temperature of 3000°C if necessary. FIG. 2 shows the form after the firing process, in which 1 is a side seal part, 2 is a separator material, and 3 is an electrode material integrally joined to the upper and lower concave surfaces of the separator material.

The carbon member having the composite structure thus obtained is made into a fuel cell by cutting a predetermined groove 4 into the electrode material and finishing the outer shape as shown in FIG.

[For production]

As described above, in the carbon member for fuel cells having a composite structure manufactured according to the present invention, since the side seal portion and the separator material are integrally formed of the same material, the airtightness of this portion and interfacial peeling are limited. Moreover, since the material properties of the separator material are selected to improve practical performance, the occurrence of phenomena such as peeling, wear, and damage of members due to heat cycles is effectively reduced.

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 3, Comparative Examples 1 to 2 Fine graphite powder with an average particle size of 5 μm and liquid phenol resin (manufactured by Sumitomo Durez ■, "PR940") were homogeneously kneaded in a Ni-Goo, and then kneaded at a temperature of 150 using a concave mold. It was hot-pressed for 15 minutes at 100 kg/cdl at 1°C. The molded green precursor has a thickness of Ⅲ, leaving edge portions forming side seals on the top and bottom surfaces.
It was a square thin plate with a side of 150 mm and a concave surface of 150 mm perpendicular to each other. Next, the molded products were transferred to an electric furnace and fired and carbonized at a temperature up to 1300''C in a nitrogen gas atmosphere to obtain five types of carbon separator materials (shaped in FIG. 1) having different characteristics.

Carbon fiber chop (average diameter 15 denier, average length 8mm)
) 70 parts by weight, water-soluble phenol resin [manufactured by Nippon Reichhold ■, "Pryophen J303"] 110
A uniform slurry-like dispersion was prepared by stirring and mixing 20 parts by weight of water. This slurry was formed into a thin plate shape using a papermaking method, heated and hardened at 170°C, and then fired and carbonized at a temperature of 1000°C in an electric furnace kept in a nitrogen atmosphere to form a sheet with a length of 150m+n, a width of 100mm, and a thickness of 1 mm.
A porous carbon electrode material was created. The characteristics of the obtained electrode material were that the apparent specific gravity was 0.56 g/cc and the porosity was 68.1%.

Next, the upper and lower concave surfaces of the separator material were polished with sandpaper to a surface roughness of 20 μm RZ, and this surface was coated with 100 parts by weight of a phenolic resin initial condensate and fine graphite powder (average particle size 2
An adhesive containing 80 parts by weight of 0fm) and 5 parts by weight of para-toluenesulfonic acid chloride was uniformly applied. Subsequently, electrode materials were fitted on the upper and lower concave surfaces, and heated at a temperature of 80°C and 5k.
Bonding was carried out by holding at a pressure of g/ci for 1 hour.

The joining members were transferred to an electric furnace and heated at 1300°C under a nitrogen atmosphere.
After firing at a temperature of , the electrode material was subjected to grooving and other finishing processes to produce a carbon member for a fuel cell having a composite structure as shown in FIG. 3.

Power generation test (200°C10,8
VRHE, 100Ohr, l kg/c+fl)
was carried out.

The results are shown in the table below in comparison with the characteristics of the separator material.

As shown in the above table, no abnormality was observed in any of the examples satisfying the separator material'+h property requirements of the present invention.

(Effects of the Invention) As unusual, according to the present invention, carbon for fuel cells has improved performance as a composite structure, reliability of member joints, etc. by selecting the material properties of the separator material integrated with the zyte seal part. Since the parts can be manufactured using a simple process, safe heat-generating operations are always guaranteed.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the separator material of the present invention, FIG. 2 is a perspective view showing a form in which an electrode material is bonded to the separator material and fired, and FIG. 3 is a perspective view showing the final form. 1... Zyde seal part, 2... Separator material, 3
...electrode material, 4...groove.

Claims (1)

[Scope of Claims] 1. A porous carbon electrode is formed on a separator base material formed into a concave shape leaving the edge part forming the side seal part at the green precursor stage, or on a separator material obtained by firing and carbonizing this separator base material. In the method of obtaining a carbon member with a composite structure by inserting a green precursor base material or an electrode material obtained by firing and carbonizing the green precursor base material, bonding them together, and then firing the same, a thermal expansion coefficient of 3 × 10^-^ is used as a separator material. Below 6℃＾-＾1,
Bending strength 900kg/cm^2 or more, gas permeation rate 10^
- A material with carbon properties of less than 5 cc/cm^2 min and a corrosion current density of less than 5 μA/cm^2 is selected, and a thermosetting resin adhesive is applied to the concave surface during bonding. A method for manufacturing a carbon member for a fuel cell. 2. The method for manufacturing a carbon member for a fuel cell according to claim 1, wherein the concave surface is treated in advance to a surface roughness of 10 μm RZ or more during bonding.