JPS61288381A - Manufacture of fuel cell composing element - Google Patents

Abstract

PURPOSE:To easily obtain a flat formed body having an uniform thickness distribution or a regular thickness distribution, by extruding slurry together with a support body and drying it up on the support body. CONSTITUTION:Slurry 31 is supplied into an inclined slot 30 through a slurry supply port 23 and extruded out through a gap 29 and a mouth die 24 by the turning movement of a sleeve, and a support body 28 in the sleeve is also extruded coaxially with the mouth die. This results in obtaining the support body with the slurry sticking on it and having a cross section corresponding to that of the mouth die. The slurry is dried by heat to obtain a circular green body, and after letting it be a flat plate by cutting it on the support body in the direction of extrusion with succeeding baking, a flat formed body 13 having an uniform thickness distribution or a predetermined cross section due to a regular thickness distribution is obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing components for fuel cells, in particular as electrode plates or electrolyte plates for molten carbonate fuel cells. The present invention relates to a method for manufacturing a plate-shaped battery component having a uniform thickness distribution, or a plate-shaped battery component having a predetermined cross-sectional shape with a regular thickness distribution, which can be suitably used.

(Prior art) In recent years, molten carbonate fuel cells, which use molten carbonate as an electrolyte and operate at high temperatures, have high power generation efficiency and can be used with many types of fuel, such as platinum. It is attracting attention because it does not require a precious metal catalyst, and high-quality waste heat is recovered for high-temperature operation, and its practical application is progressing.

Conventionally, in such molten carbonate fuel cells, a single cell is constructed by stacking a positive electrode plate and a negative electrode plate with an electrolyte plate containing molten carbonate in between, and this single cell is made up of a current collector plate and a separator. A fuel cell is constructed by stacking a large number of them with each other in between. The separator and/or the electrode plate may be provided with grooves as passages for fuel gas or oxidizing gas, the fuel gas being e.g. hydrogen and/or carbon oxide, and the oxidizing agent being e.g. air. and carbon dioxide gas are supplied, and predetermined electrochemical reactions are performed at the electrodes, respectively.

In any case, in the conventional molten carbonate fuel cell described above, the positive electrode is typically a porous sheet made by sintering nickel powder in hydrogen at high temperature and having a porosity of about 60%. A porous nickel plate whose surface is oxidized to give it conductivity is used. As the negative electrode, a porous body made of a nickel alloy such as nickel-chromium or nickel-cobalt is used. Furthermore, since the separator is required to have high conductivity, gas impermeability, and corrosion resistance, stainless steel or a nickel-clad plate thereof has been conventionally used.

Among the constituent elements of the fuel cell as described above, the electrode plate and the electrolyte plate in particular are conventionally manufactured by being formed into a flat plate shape from the beginning by an extrusion method, a press method, etc., respectively. Even in the case of a molded product having grooves on its surface, it is manufactured into a flat plate shape having such grooves from the beginning using an appropriate mold.

In order to reduce the battery capacity, these components are generally thin plate-shaped with a thickness of several days and dimensions ranging from tens of marks to 1 mm angle, but there is a uniform gap between adjacent plate-shaped components. In order to maintain contact, molding and manufacturing are required with high manufacturing precision, and in particular, the larger the area of the component, the more
Or, the thinner the material, the higher the requirement for a uniform flat plate shape. In other words, when the constituent elements lack uniform flatness, the contact resistance between the constituent elements is large, the battery output decreases, and sufficient battery performance cannot be obtained, and the battery cannot be used continuously for long periods of time. In this case, each component undergoes more non-uniform shape changes due to mechanical and thermal causes, such as expansion and contraction, which further increases the contact resistance between the components, thus reducing battery performance. It is from.

However, when molding into a flat plate from the beginning as in the conventional method, it is not easy to produce a plate-shaped molded product having uniform flatness. For example, when using an extrusion method, conventionally the extrusion speed of the slurry and the feeding speed of the extruded plate-shaped product are strictly controlled, but the larger the area or the thinner the plate-shaped product, the more difficult it is to extrude. Sometimes, the extruded slurry causes a waving phenomenon, making it difficult to obtain a plate-like product having a uniform thickness or a regular thickness distribution and a predetermined cross-sectional shape. Moreover, in the step of heating and drying such an extrudate, further bending and deformation are unavoidable. Furthermore, as described above, it is necessary to strictly control the extrusion speed of the slurry and the feeding speed of the extruded plate-like material, making the equipment complex and expensive.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned problems in the production of molded components for molten carbonate fuel cells, in particular electrode plates and electrolyte plates.
As a plate-like molded product having a uniform thickness distribution or having a predetermined cross-sectional shape due to a regular thickness distribution, which can be suitably used as an electrode plate or an electrolyte plate for a molten carbonate fuel cell. It is an object of the present invention to provide a method of manufacturing a battery component.

(Structure of the Invention) The present invention provides a method for manufacturing a plate-shaped molded article as a fuel cell component, in which a support made of a tube or a rod is formed into a predetermined shape together with a slurry containing component powder for the fuel cell component. The slurry is coaxially extruded from a mouth die having a predetermined cross-sectional shape to obtain a support, and this slurry is dried on this support to obtain an annular green body on the support. The method is characterized in that the annular green body is cut in the extrusion direction on the support to form a flat plate, and then heated and fired.

In the present invention, battery components refer to electrode plates and electrolyte plates as molded articles, and therefore, component powders for battery components include, for example, when the component is an electrode of a molten carbonate fuel cell. For example, in addition to nickel, powders of nickel-chromium alloys, nickel-cobalt alloys, etc. are preferably used. Furthermore, if the component is, for example, an electrolyte plate for a molten carbonate fuel cell, the component powder therefor may be carbonate powder, which may of course contain appropriate additives. .

In addition to a binder and a solvent, the component powders for these components are mixed with other necessary auxiliary agents such as a plasticizer and a deflocculant, if necessary, to form a slurry. As the solvent, water is usually preferably used, and therefore, as the binder, water-soluble resins such as polyvinyl alcohol, polyethylene glycol, etc. are usually preferably used, but are not limited thereto.

In addition, the plasticizer is added to give the slurry the required viscosity, and the deflocculant is added to obtain a uniform slurry, but they are not particularly limited.
As the plasticizer, for example, a polyol resin or the like is used, and as the deflocculant, for example, ammonium salt of a high-molecular polycarboxylic acid is used.

The method for preparing slurry of inorganic compounds and fine metal powder is as follows:
These conventional techniques are already widely known in various technical fields, and in the present invention, a slurry having an appropriate viscosity can be obtained according to these conventional techniques. Therefore, the blending amounts of component powders, binders, plasticizers, peptizers, etc. in the slurry are not necessarily limited, but for example, in the slurry, 40 to 80% by weight of component powders and 1 part solvent.
0-500-50 weight under 3-30% by weight, plasticizer 0
~10% by weight and peptizer O~5% by weight are appropriate. In addition, the slurry viscosity is 2000 to 2000 at 25°C.
Approximately 0 cps is suitable.

In the present invention, the support is preferably a heat-resistant round rod or a tube with both ends sealed, and for example, a round rod or tube made of stainless steel is preferable.

In the present invention, the slurry and support are charged into a container or extruder equipped with a mouth mold having a predetermined shape, and while the slurry is attached to the support, the support is formed into a predetermined shape together with the slurry. The slurry is coaxially extruded from a mold having a mouth to obtain a support having a predetermined cross-sectional shape on the peripheral surface of the slurry.

That is, when the mouth shape is a uniform circular hole, it is possible to obtain a support to which the slurry is attached in an annular shape having a clearly uniform thickness distribution. In addition, when the mouth shape is formed of a circular hole whose periphery is formed by regular uneven shapes, for example, as shown in FIG. It is possible to obtain a support 12 which is attached in an annular manner so as to have a uniform thickness distribution.

Next, according to the present invention, the slurry attached in an annular shape on the support is heated to remove the solvent, thereby obtaining an annular green body on the support. Since this green body still contains a binder and is flexible, a flat green body can be obtained by cutting it in the extrusion direction on a support and rolling it out. This is heated and fired to a required temperature depending on the ingredients for the fuel cell component, and the binder is removed to create a plate-shaped molded product with a uniform thickness distribution.
Or, as mentioned above, if the mouth mold has a predetermined cross-sectional shape, according to the shape of the mouth mold, as shown in FIG. The object 13 can be obtained as an electrode plate or an electrolyte plate.

Depending on the type, molding aids such as plasticizers and peptizers may remain in the molded product even after the above-mentioned firing, but they may also serve as sintering aids, so they must be removed by firing. Not necessarily.

The heating and firing temperature of the green body depends on the components, but for example, in the case of metal powder for electrodes, 1000° C. or higher is usually suitable.

FIG. 3 shows an example of an extruder that can be suitably used to carry out the method of the present invention. That is, the extruder 21 is
The body wall 22 has a slurry supply port 23, and the tip thereof is provided with a mouth mold 24 having a predetermined cross-sectional shape. A nipple 26 having a lip 25 coaxially with the body and a sleeve 27 integral with the nipple 26 are rotatably (and forwardly) accommodated in the body, facing the date mold, and a sleeve 27 is supported within the sleeve and nipple. A body 28 is inserted and coaxially extruded through the nipple and the mouth mold into the mouth mold. The nipple has a gap 29 between it and the body wall at its tip, and also has an annular inclined groove 30 inclined with respect to the axial direction of the slurry supply port, and the gap is communicated with the inclined groove. There is.

Therefore, slurry is supplied from the slurry supply port to the inclined groove, and as the sleeve rotates (and moves forward), the slurry is pushed out through the gap and the mouth mold, and the support inside the sleeve is also pushed out coaxially with the mouth mold. By doing so, it is possible to obtain the support 28 on which the slurry 31 is adhered on the support in a cross-sectional shape corresponding to the cross-sectional shape of the mouth mold. The annular slurry on the support is heated and dried as described above to obtain an annular green body, which is cut in the extrusion direction on the support to form a flat plate, and then heated and baked to form a mouth-shaped green body. Depending on the cross-sectional shape, a plate-shaped molded product having a uniform thickness distribution or a plate-shaped molded product having a predetermined cross-sectional shape with a regular thickness distribution can be obtained.

(Effects of the Invention) As described above, according to the method of the present invention, a flat molded product having a uniform thickness distribution or a regular thickness distribution can be easily and easily produced regardless of its area or thickness. You can definitely get it. In particular, according to the conventional method, it is first formed into a plate shape, then heated and dried, and then heated and fired.
For example, when using an extrusion method, the slurry not only becomes wavy during extrusion, but also bends and deforms during the heating and drying stage, but according to the method of the present invention, the slurry is supported. extruded with the body, and
Since it is heated and dried on the support, no bending or deformation occurs at this stage. Furthermore, in the method of the present invention,
Since the extruder used has a simple structure, the manufacturing cost is also low.

(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way. still,
In the following, parts indicate parts by weight.

Example 1 Fine nickel powder (average particle size 2.5 μm) 60 parts water
30 parts deflocculating agent 1 part deflocculant
A mixture of 3 parts polyvinyl alcohol and 6 parts polyethylene glycol (binder) was thoroughly mixed and stirred to prepare a slurry having a viscosity of 5000 cps at 25°C.

This slurry is extruded coaxially with a stainless steel support rod through a circumferential mouth mold whose periphery is formed with regular uneven shapes using an extruder as shown in Fig. 3, and the slurry is applied to the surface. A support rod was obtained which was attached so as to have a regular uneven thickness distribution. The slurry on this support rod was heated together with the support rod in air at a temperature of 60° C. for 2 hours to remove water and obtain an annular green body.

Next, this annular green body is cut in the extrusion direction, expanded to form a plate shape, and then fired in air at a temperature of 1000°C to form a shape with dimensions of about 315 mm in length and width, a height of 3 convex parts, and a height of concave parts. A molded plate as an electrode plate was obtained, with a length of 11 m and a width of each of the convex portion and the concave portion of 2 m.

For comparison, an electrode plate having a cross-sectional shape similar to that described above was manufactured using a conventional extraction method.

Next, in order to examine the thermal strength of each of the five electrode plates produced by the method of the present invention and the conventional method, they were tested in air at 300°C using a fluidized bed thermal fatigue tester. and 650° C. for 10 thermal cycles. Heating time from 350℃ to 600℃ 1
The holding time at 600°C was 15 minutes, and the cooling time from 600'C to 350°C was 10 minutes.

After such a thermal fatigue test, whether or not cracks had occurred on the surface of the electrode plate was visually inspected. The results are shown in the table.

It is clear that the electrode plate produced by the method of the present invention has excellent thermal strength.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the cross-sectional shape of the slurry deposited on the support, FIG. 2 is a cross-sectional view showing an example of the negative electrode plate obtained by the method of the present invention, and FIG. FIG. 2 is a cross-sectional view showing an example of an extruder that can be suitably used to carry out the method. DESCRIPTION OF SYMBOLS 11... Slurry, 12... Support body, 13... Plate-shaped molded product, 21... Extruder, 23... Slurry supply port, 24... Mold, 25... Lip, 26...Nipple, 28...Support, 29...Gap, 30...
- Inclined groove, 31...Slurry. Figure 1 Figure 2

Claims (3)

[Claims] (1) In a method for manufacturing a plate-shaped molded product as a fuel cell component, a support made of a tube or a rod is coaxially moved from a mouth mold having a predetermined shape together with a slurry containing component powder for the fuel cell component. Extrusion to obtain a support to which the slurry is adhered in a predetermined cross-sectional shape, dry this slurry on this support to obtain an annular green body on the support, and then support this annular green body. 1. A method for manufacturing a fuel cell component, which comprises cutting the body in the extrusion direction to form a flat plate, and then heating and firing the plate. (2) The method for manufacturing a fuel cell component according to claim 1, wherein the fuel cell component is an electrode plate, and the component therefor is a metal powder for the electrode. (3) The method for manufacturing a fuel cell component according to claim 1, wherein the fuel cell component is an electrolyte plate, and the component therefor is carbonate powder for the electrolyte.