JPH0817096B2 - Method for manufacturing carbonaceous composite member for fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to carbon for a phosphoric acid fuel cell in which a porous electrode plate composed of a carbonaceous material and a dense separator plate are integrally formed. To a method for manufacturing a quality composite member.

[Prior Art] Materials such as electrode plates and separator plates that make up phosphoric acid fuel cells are made of carbonaceous materials that meet the required properties such as heat resistance, chemical resistance, good electrical conductivity, and easy processability. The material has been useful.

However, since the carbonaceous material inherently has low mechanical strength, it may be damaged during handling or cell assembly. In recent years, in order to reduce the resistance and the stack thickness, the electrode plate has been thinned to about 2 mm and the separator plate has been thinned to about 0.8 to 1.0 mm, and the degree of breakage tends to further increase. Further, in the conventional method in which the electrode plate and the separator plate are laminated, it is difficult to obtain a sufficiently even close contact between both surfaces, and therefore there is a limit in reducing the internal resistance of the battery.

In order to eliminate such inconvenience, improve mechanical strength, reduce electrical / thermal resistance, and simplify cell assembly, both members of the electrode plate and the separator plate are integrally formed in advance to form a composite structure. Attempts are proceeding rapidly.

The simplest and most practical means for producing such a composite member is disclosed in JP-A-60-20471 and JP-A-60-1.
This is a joining firing method in which an electrode base material and a separator base material are bonded with an adhesive and then fired as disclosed in Japanese Patent No. 5759.

[Problems to be Solved by the Invention]

The above-mentioned joining and firing method is a method of joining and firing the carbonaceous electrode plate and the carbonaceous separator plate, which have been carbonized, and an electrode plate and a separator plate at the stage of precursor (form) before firing. However, the latter method is more advantageous than the former method in that the firing carbonization step is performed only once and the joint strength is increased.

However, when the latter joining method in the precursor stage is adopted, if the difference in shrinkage in the firing process of the electrode material and the separator plate to be combined is large, defect phenomena such as interfacial peeling, member warpage, and cracking occur during firing. This tendency becomes more remarkable as the size of the member becomes larger, which is a major impediment to practical use.

The present inventor has conducted multifaceted research on the shrinkage behavior of members in the firing process, and as a result, controls the plane direction dimensional shrinkage of the separator plate precursor to approximate it to the electrode plate shrinkage, and specifies the difference in the shrinkage. The present invention has been completed by finding that, when the content is within the range, the above-mentioned defect phenomenon can be effectively reduced and a composite structure suitable for phosphoric acid fuel cells can be obtained.

[Means for solving the problem]

That is, the method for producing a carbonaceous composite member for a fuel cell according to the present invention is a method in which a carbonaceous electrode plate and a separator plate are bonded at a precursor stage before firing and then subjected to a firing treatment, in which a carbonaceous powder filler and thermosetting are used. By controlling the compounding ratio of the resin binder to control the dimensional shrinkage of the separator plate precursor in the surface direction, the difference from the dimensional shrinkage ratio of the electrode plate precursor in the surface direction is set within ± 1.0%, and the bonding is performed. This is a constitutional feature.

The precursor of the electrode plate, carbon fiber or polyacrylonitrile, organic fibers such as cellulose and the like with a thermosetting resin such as a phenol resin molding method, a thin plate shape using a means such as papermaking method, 150 ~ It is manufactured by a process of heat curing in the temperature range of 250 ° C.

The precursor of the separator plate is a thin plate-like kneaded product of at least one filler selected from powders of graphite, glassy carbon, coke and the like, and a binder made of a carbonized thermosetting resin such as phenol or furan. Molded into
It is manufactured by a process of heat curing at 50 to 120 ° C. for 10 hours or more.

The electrode plate precursor and the separator plate precursor manufactured in this way have a difference in the in-plane dimensional shrinkage ratio of ± 1.
Join with adjusting within 0%. The plane direction dimensional shrinkage ratio in the present invention means that the rectangular plate member is 1000
The average value of the heat shrinkage ratios that occur in the horizontal and vertical directions when baked at ℃, and when this value is within ± 1.0% between the electrode plate precursor and the separator plate precursor to be joined, it is normal. Firing is done, but the difference is ± 1.0
If it exceeds%, phenomena such as interfacial peeling, warpage, and cracking frequently occur during the firing process.

The planar dimensional shrinkage of the electrode plate precursor is in the range of 8 to 30% in the manufacturing process described above. This shrinkage ratio can be controlled to a desired value by changing the compounding ratio of the fibrous base material and the thermosetting resin, but the change of the manufacturing conditions also changes the pore structure of the electrode itself. It is not preferable because it will happen. Therefore, the adjustment of the surface direction dimensional shrinkage is performed exclusively in the process of manufacturing the separator plate precursor,
For the electrode plate precursor, it is a good idea to keep the heat treatment (250 to 400 ° C), which can control the decrease within the range of several percent without changing the pore structure.

The dimensional shrinkage in the plane direction of the separator plate precursor can be controlled within the range of 3 to 18% by changing the blending ratio of the carbonaceous powder filler and the thermosetting resin binder without impairing the denseness.

The in-plane dimensional shrinkage ratio of both members can be grasped at the precursor stage by calibrating the relationship with the manufacturing conditions in advance, and the combination of ± 1.0% difference between inside and outside can be confirmed in the joining process.

To bond the electrode plate precursor and the separator plate precursor, both members are directly contacted with each other and press-hardened in a temperature range of 170 to 250 ° C. for 1 hour or more, or a thermosetting resin or graphite on the bonding interface is used. It is carried out by a method of adhesively hardening via an adhesive agent in which fine powder is mixed.

After joining, the members should be welded in a non-oxidizing atmosphere at 1000
Baking is performed at a temperature of ℃ or more.

[Work]

By the above process, a carbonaceous composite member for a fuel cell in which a porous electrode plate and a separator plate are integrally formed is obtained, but in the present invention, a carbonaceous powder filler and a thermosetting resin binder are manufactured during the production of the separator plate precursor. The dimensional shrinkage of the electrode plate precursor is controlled by adjusting the compounding ratio of the electrode plate, and the difference from the dimensional shrinkage of the electrode plate precursor in the plane direction is ± 1.0%.
Since it is set within the range, decrease in the pore production of the electrode plate precursor,
Fluctuation is suppressed. As a result, it is possible to effectively prevent the peeling of the bonding interface, the warp and the crack of the member, etc. due to the difference in heat shrinkage during the firing process without deteriorating the porosity of the porous electrode plate. Therefore, a good quality composite member can always be manufactured.

〔Example〕

(1) Production example of electrode plate precursor To 70 parts by weight of chopped strands of carbon fiber, 10 parts by weight of a water-soluble phenolic resin [“PRIOFEN J303” manufactured by Nippon Reichhold Co., Ltd.] and 20 parts by weight of water were added and mixed by stirring. Then, a uniform slurry dispersion liquid was prepared. This slurry was formed into a thin plate by a papermaking method, and then heat-cured at a temperature of 250 ° C. to produce an electrode plate precursor. The dimensional shrinkage of this product is 13.2%, and the apparent specific gravity after firing is
The porous structure was 0.63 g / cc and the porosity was 66.1%.

Further, this electrode plate precursor was heat-treated at 350 ° C. for 3 hours. The dimensional shrinkage of this product was reduced to 11.1%, but there was no difference in the pore characteristics after firing.

(2) Example of producing separator plate precursor Graphite powder having an average particle size of 4 μm was used as a filler, and powdered phenol resin [Sumilite Resin PR1078] manufactured by Sumitomo Dures Co., Ltd., liquid phenol resin [Sumitomo Dures Co., Ltd.]. "Sumilite Resin PR940"] and carboxymethyl cellulose were blended in a ratio of parts by weight shown in Table 1.

The mixture was kneaded with a screw type kneader and then formed into a thin plate having a thickness of 1 mm using a roll pressure device. Next, the molded body was heat-cured under conditions of 50 ° C. for 24 hours and 80 ° C. for 24 hours to produce a separator plate precursor.

Table 2 shows the dimensional shrinkage ratio of each of the obtained separator plate precursors in the surface direction.

(3) Production Example and Evaluation of Composite Member The electrode plate precursor and the separator plate precursor produced in the above (1) and (2) were pressed and joined at 190 ° C. for 2 hours, and subsequently transferred to a firing furnace and nitrogen gas was introduced. A carbonaceous composite member was manufactured by firing at a temperature of 1000 ° C. in an atmosphere.

Table 3 shows the status of the obtained carbonaceous composite members after the firing treatment.
And shown in Table 4. In addition, the displayed numerical value is the number of outbreaks in 10 pastures.

From the results of Table 3 and Table 4, in the case of the present invention in which the difference in the in-plane dimensional shrinkage ratio between the electrode plate precursor and the separator plate precursor is adjusted within ± 1.0%, interfacial peeling, warpage of the member, Although no phenomenon such as cracking occurred, it was confirmed that any defect phenomenon occurred when the difference exceeded ± 1.0%.

〔The invention's effect〕

As described above, according to the present invention, it becomes possible to mass-produce a good quality carbonaceous composite member that does not cause a property defect in the firing process. Therefore, it can always be stably supplied as a high performance composite member for a fuel cell.

Claims (1)

[Claims] 1. A method of joining a carbonaceous electrode plate and a separator plate at a precursor stage before firing and then performing a firing treatment, by adjusting a blending ratio of a carbonaceous powder filler and a thermosetting resin binder. A carbonaceous composite member for a fuel cell, which is characterized in that the dimensional shrinkage of the plate precursor in the plane direction is controlled, and the difference from the dimensional shrinkage of the electrode plate precursor in the plane direction is set to within ± 1.0% to perform the joining. Manufacturing method.