JP2011165652A - Method of manufacturing interconnector for fuel cell, and interconnector for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for inexpensively manufacturing an interconnector including a further uniform protective film with high productivity by a dip coat method. <P>SOLUTION: In this method of manufacturing an interconnector for a fuel cell which forms a protective film 12 by dip-coating a slurry-like coating film formation material on a base material 11 for an interconnector, after a coating film formation process of dip-coating a coating film of a coating film formation material on the base material 11 for an interconnector, a recoating process of performing dip-coating by superposing a new coating film on the coating film is repeated before perfect drying time passage for perfectly drying the coating film, and the coating film dip-coated by being superposed a plurality of times are dried, whereby a protective film 12 is formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a fuel cell interconnector and a fuel cell interconnector.

  The production of an interconnector is one of the most important and difficult processes in fuel cell manufacturing technology. In addition, the interconnector of the fuel cell has stable and sufficient electronic conductivity under a wide range of oxygen partial pressure from the air electrode side to the fuel electrode side, the thermal expansion coefficient is almost equal to the electrolyte material, and other It must be non-reactive with battery constituents at 1,273K.

Therefore, a technique is known in which a protective film made of a semiconductor material that hardly oxidizes and deteriorates even at high temperatures is provided on an interconnector base material.
The protective film of the interconnector can be formed by, for example, a wet coating method or a dry coating method. Examples of the wet coating method include a screen printing method, an electrophoresis (EPD) method, a doctor blade method, a spray coating method, an ink jet method, a spin coating method, and a dip coating method. Examples of the dry coating method include vapor deposition, sputtering, ion plating, chemical vapor deposition (CVD), electrochemical vapor deposition (EVD), ion beam, laser ablation, and atmospheric pressure plasma. Examples thereof include a film forming method, a low pressure plasma film forming method, and a thermal spraying method.

  However, as a dry coating method, the CVD / EVD method, the thermal spraying method, and the like have a drawback that the process for forming the protective film is complicated or the composition of the protective film is not stable. It is also considered to form a protective film by a laser ablation method. (Patent Document 1)

  In addition, when the laser ablation method is employed, the manufacturing cost is higher than that of the CVD / EVD method or the thermal spraying method. Therefore, the wet coating method is practically employed as a technique capable of producing a protective film at a low cost. There are many cases.

Japanese Patent Laid-Open No. 05-174853

  However, when a typical dip coating method is adopted as the wet coating method, it is difficult to control the thickness of the protective film with respect to the substrate for an interconnector to be constant as will be shown later. If the thickness of the protective film of the interconnector is not uniform, its durability is lowered, and there is a concern that the performance of the fuel cell itself may be adversely affected.

  Accordingly, the present invention is to provide a technique for manufacturing an interconnector having a more uniform protective film with good productivity and low cost by the dip coating method.

  The present inventors have found that the coating film formed on the interconnector substrate by the dip coating method has a large film thickness on the surface of the interconnector substrate, slow drying, and a small film thickness on the sides and corners. As a result of diligent research on the dip coating method based on the empirical rule that drying is fast, when forming a protective film by overcoating the coating film, when a new coating film is applied to a part on the sufficiently dried coating film The film thickness of the paint film increases, but when a new paint film is applied to a part of the paint film that is not sufficiently dry, the film thickness of the paint film does not increase so much. I found.

  This is because the new coating film tends to flow with the underlying coating that is not sufficiently dry, so that the new coating-forming material that is retained on the coating that is not sufficiently dried is sufficiently dried. This is because it is less than the new film-forming material that is retained on the film. Further, the coating film is dried faster as the film thickness is thinner, and the drying is slower as the film is thicker. Therefore, as the number of times of overcoating is increased, the ratio of the thin part to the thick part decreases (approaching 1), and the film thickness approaches a more uniform film thickness.

  This invention is made | formed based on the said knowledge, Comprising: The following characteristic structures are provided.

[Configuration 1]
When the protective film is formed by dip-coating the slurry-like film forming material on the interconnector base material, the characteristic configuration of the present invention is:
After the coating film forming step of dip-coating the coating film forming material on the interconnector substrate, a new coating is applied on the coating film before the complete drying time elapses when the coating film is completely dried. The overcoating step of dip-coating the film repeatedly is repeated, and the protective film is formed by drying the coating film that has been dip-coated multiple times.

[Operation effect 1]
That is, based on the above knowledge, the coating film formed on the interconnector base material is firstly thickly attached to both sides of the interconnector base material (this thickness is assumed to be d1), and the side part. And adheres thinly to the corners (this thickness is assumed to be d2). The closer this ratio (r, r = d1 / d2) is to 1, the more the coating film forms a protective film having a uniform thickness as an interconnector.

When the coating film is formed by dip coating the slurry-like film forming material once again after the complete drying time for completely drying the coating film, the thickness of the coating film simply increases evenly (d1). / D2 hardly changes). On the other hand, when the coating film is formed again by dip coating the slurry-like film forming material before the complete drying time for completely drying this coating film, Then, since the drying is progressing, the coating film increases by a thickness close to d2 (a * d2 (a≈1)). On the other hand, since it is difficult for drying to proceed on the surface portion where the thickness of the coating film is thick, the coating film with low dryness is thinned with the flow of the coating film forming material. The film increases in thickness by an amount less than d1 (b * d1 (b <a)). Then, as the coating film is repeatedly applied (k times), the film thicknesses D1 and D2 are:
Corner: D2 = d2 + (a * d2) * (k-1)
Surface portion: D1 = d1 + (b * d1) * (k−1) where (d2 <d1), (b <a)
It becomes.

Therefore, their ratio (R) is
R = D1 / D2 = (d1 * (1 + b (k-1))) / (d2 * (1 + a (k-1)))
And as k increases,
R = (d1 / d2) * (b / a)
Get closer to. That is, since b <a, R decreases monotonously and approaches a value smaller than r.

  Therefore, the coating film formed on the substrate for the interconnector by repeating the overcoating step of dip-coating a new coating film on the coating film before the complete drying time elapses. As a result, a uniform protective film is formed, so that a suitable fuel cell interconnector can be manufactured.

[Configuration 2]
Moreover, it is preferable that the coating film-forming material contains a conductive ceramic material as a main component, and contains a binder and a solvent.

[Operation effect 2]
As a coating film forming material, if a binder and a solvent are contained, it can be made into the physical property which can form a slurry-like coating film. Moreover, in order to make the coating film forming material easy to form a coating film, it is desirable to have an appropriate viscosity and solvent volatility.

  As a solvent for forming the slurry, various solvents such as water, ethanol, propanol, isopropanol, methoxypropanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and butyl acetate can be used alone or in combination.

  As the binder, acrylic resin, ethyl cellulose, hydroxypropyl cellulose, polyvinyl pyrrolidone, or the like can be used.

[Configuration 3]
It is preferable that the conductive ceramic material contains at least one selected from a spinel oxide and a perovskite oxide as a main component.

Specific examples of these include spinel-based oxides such as NiCo ₂ 0 ₄ , ZnCo ₂ O ₄ , FeMn ₂ 0 ₄ , NiMn ₂ 0 ₄ , CoMn ₂ 0 ₄ , MnFe ₂ 0 ₄ , MnNi ₂ 0 ₄ , Perovskite series, such as MnCo ₂ 0 ₄ , TiCo ₂ 0 ₄ , ZnFe ₂ 0 ₄ , FeCo ₂ 0 ₄ , CoFe ₂ 0 ₄ , MgCo ₂ 0 ₄ , Co ₃ 0 ₄ , ZnMn ₂ O ₄ , Co _1.5 Mn _1.5 O ₄ As an oxide, LaM
nO ₃ , LaFeO ₃ , LaCoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ ,
(La, Sr) FeO ₃ , (La, Sr) (Co, Fe) O _{3 and the} like can be mentioned.

[Operation effect 3]
As a coating film forming material, if the main component is a conductive ceramic material, the conductivity of the fuel cell interconnector can be secured, and this should be of a physical property capable of forming a slurry-like coating film. it can.

The conductive ceramic material can be formed of a spinel oxide, a perovskite oxide, or the like. One of these may be used alone, or a mixture of two or more may be used. May be. These conductive ceramic materials are preferable because they are excellent in handling during coating film formation, are relatively versatile and inexpensive, and have excellent physical properties such as high heat durability and conductivity.
[Configuration 4]
The conductive ceramic material preferably has a particle size of 0.2 μm to 1.0 μm.

[Operation effect 4]
If the particle size of the conductive ceramic material is too fine, cracks are likely to occur when the formed coating film is dried to form a protective film, and if it is too large, it will be difficult to prepare a suitable viscosity. 0.2 μm to 1.0 μm is preferable.

[Configuration 5]
Furthermore, the viscosity of the coating film forming material is preferably 25 mPa · s or more and 80 mPa · s or less.

[Operation effect 5]
In addition, if the viscosity of the coating film forming material is too low, the coating film thickness becomes too thin, the number of repeated coatings must be increased, workability decreases, and even if the coating is repeated, the coating film at the corners Does not reach a sufficient thickness. On the other hand, if the viscosity is too high, the coating film becomes too thick and defects such as cracks are likely to occur during drying. Therefore, it is preferably 25 mPa · s or more and 80 mPa · s or less.

[Configuration 6]
Moreover, it is preferable that the said solvent has as a main component at least 1 type chosen from isopropanol and methoxypropanol.

[Operation effect 6]
In order to make the coating film forming material easy to form a coating film, it is desirable to have an appropriate viscosity and volatility of the solvent. However, the amount and type of the binder and the particle size of the conductive ceramic material are selected. Thus, the viscosity can be adjusted, and the volatility can be adjusted by selecting the solvent. Therefore, as the solvent, a solvent having at least one selected from isopropanol and methoxypropanol as a main component is particularly preferable.

[Configuration 7]
Moreover, it is preferable that the binder contains at least one selected from hydroxypropylcellulose, polyvinylpyrrolidone, and ethylcellulose as a main component.

[Operation effect 7]
As the binder, acrylic resin, ethyl cellulose, hydroxypropyl cellulose, polyvinyl pyrrolidone, or the like can be used. In particular, when hydroxypropyl cellulose, polyvinyl pyrrolidone, or ethyl cellulose is used, forming a suitable protective film will be described later. It has been confirmed from the examples.

[Configuration 8]
Moreover, it is preferable that the binder is hydroxypropyl cellulose, the solvent is isopropanol, and the complete drying time is adjusted to 300 seconds to 1200 seconds under an open air condition.

[Operation effect 8]
The complete drying time is preferably the time when the coating film forming material is formed in a moderately dried state and a film having an appropriate film thickness is formed, and the next coating film is repeatedly applied in anticipation of a certain period of time. It is preferable to dry and cure with sufficient margin. In other words, in order to make it easy to properly set the drying time for overcoating the coating, it needs to be long to some extent, and conversely, if it is too long, workability for forming the coating is reduced, so it is also preferable that it is too long. Absent. Therefore, for example, when the binder is hydroxypropyl cellulose and the solvent is isopropanol, the complete drying time is preferably adjusted to 300 seconds to 1200 seconds.

[Configuration 9]
In addition, the coating film was dried by 1/30 to 1/8 of the complete drying time required for completely drying the coating film before the drying time until the coating film was completely dried. The state is preferable.

[Effect 9]
The state before the complete drying time elapses when the coating film is completely dried is set at a time when the thick part of the coating film is not so dry and the drying of the thin part of the coating film is being completed. Therefore, it can be said that a state in which the coating film is dried by 1/30 to 1/8 of a complete drying time required for completely drying the coating film is preferable. Specifically, when the binder is hydroxypropyl cellulose and the solvent is isopropanol, and the complete drying time is 600 seconds, a suitable state can be obtained in about 20 seconds to 80 seconds.

[Configuration 10]
The binder is mainly composed of at least one selected from hydroxypropylcellulose, ethylcellulose, and polyvinylpyrrolidone, the solvent is methoxypropanol, and the complete drying time is adjusted to 300 seconds to 1400 seconds under an open air condition. It is preferable.

[Operation effect 10]
The complete drying time is preferably set to an appropriate length as described above. Therefore, when the binder is mainly composed of at least one selected from hydroxypropylcellulose, ethylcellulose, and polyvinylpyrrolidone, and the solvent is methoxypropanol, the complete drying time is adjusted to 300 seconds to 1400 seconds. Preferably it is.

[Configuration 11]
The state before the complete drying time when the coating film is completely dried is a state where the coating film is dried by 1/70 to 1/8 of the complete drying time required for completely drying the coating film. Preferably there is.

[Effect 11]
As described above, it is desirable that the state before the complete drying time elapses when the coating film is completely dried is set at an appropriate time. Specifically, when the binder is mainly composed of at least one selected from hydroxypropylcellulose, ethylcellulose, and polyvinylpyrrolidone, and the solvent is methoxypropanol, and the complete drying time is 1400 seconds A suitable state can be obtained in about 20 seconds to 180 seconds.

[Configuration 12]
Further, the fuel cell interconnector manufactured by the method for manufacturing a fuel cell interconnector has a thickness ratio between the thickest part and the thinnest part of the protective film (thickest part thickness / thinnest part). The (thickness) is preferably 3 or less.

[Operation effect 12]
In other words, since the fuel cell interconnector manufactured by the method for manufacturing the fuel cell interconnector can easily form a uniform film thickness on the interconnector base material, the productivity is high and the physical properties are uniform. It can be set as the interconnector for fuel cells. The thickness of the protective film is desired to be uniform and appropriate, but the thickness ratio of the thickest part to the thinnest part of the protective film (thickness of the thickest part / thinnest By setting the thickness of the portion to 3 or less, it has become possible to provide a high-quality interconnector for a fuel cell that can be said to be practically sufficiently homogeneous at low cost.

Schematic diagram of solid oxide fuel cell The figure which shows the usage form of the interconnector of a solid oxide fuel cell Cross section of interconnector test piece with protective film Graph showing change in coating weight over time when drying the coating formed on the interconnector

  Below, the manufacturing method of the interconnector for solid oxide fuel cells (SOFC) of this invention and the interconnector for SOFC are demonstrated. Preferred examples are described below, but these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

<Solid oxide fuel cell>
DESCRIPTION OF EMBODIMENTS Embodiments of an SOFC interconnector and a method for manufacturing the same according to the present invention will be described with reference to the drawings.
The SOFC cell C shown in FIGS. 1 and 2 has an air electrode made of an oxide ion and an electron conductive porous body on one side of an electrolyte membrane 30 made of a dense oxide oxide conductive solid oxide. 31 and a single cell 3 formed by joining a fuel electrode 32 made of an electron conductive porous body to the other surface side of the electrolyte membrane 30.
Further, the SOFC cell C exchanges electrons with the single cell 3 with respect to the air electrode 31 or the fuel electrode 32, and at the same time, a pair of electronically conductive elements in which grooves 2 for supplying air and hydrogen are formed. The interconnector 1 made of an alloy or oxide has a structure in which the gas seal body is appropriately sandwiched between outer peripheral edges. And the said groove | channel 2 by the side of the air electrode 31 functions as the air flow path 2a for supplying air to the air electrode 31 because the air electrode 31 and the interconnector 1 are closely_contact | adhered, on the other hand, a fuel electrode The groove 2 on the 32 side functions as a fuel flow path 2 b for supplying hydrogen to the fuel electrode 32 by arranging the fuel electrode 32 and the interconnector 1 in close contact with each other.

  In addition, when a general material used in each element constituting the SOFC cell C is described, for example, the material of the air electrode 31 is LaMO3 (for example, M = Mn, Fe, Co). A perovskite oxide of (La, AE) MO3 in which a part of La is replaced with an alkaline earth metal AE (AE = Sr, Ca) can be used. As the material of the fuel electrode 32, Ni and yttria are used. Cermet with stabilized zirconia (YSZ) can be used, and yttria stabilized zirconia (YSZ) can be used as the material of the electrolyte membrane 30.

  Furthermore, in the SOFC cell C described so far, the material of the interconnector 1 is a perovskite oxide such as LaCrO3, which is a material excellent in electronic conductivity and heat resistance, or Fe ferritic stainless steel. Alloys or oxides containing Cr are used, such as —Cr alloys, Fe—Cr—Ni alloys that are austenitic stainless steels, and Ni—Cr alloys that are nickel-based alloys.

Then, in a state where the plurality of SOFC cells C are arranged in a stacked manner, a pressing force is applied in the stacking direction by a plurality of bolts and nuts to form a cell stack.
In this cell stack, the interconnector 1 disposed at both ends in the stacking direction may be any one in which only one of the fuel flow path 2b or the air flow path 2a is formed, and the other interconnector disposed in the middle. 1 may use a fuel channel 2b formed on one surface and an air channel 2a formed on the other surface. In such a stacked cell stack, the interconnector 1 may be called a separator.
An SOFC having such a cell stack structure is generally called a flat-plate SOFC. In the present embodiment, a flat SOFC will be described as an example. However, the present invention is applicable to SOFCs having other structures.

  When the SOFC having the SOFC cell C is operated, air is supplied through an air flow path 2a formed in the interconnector 1 adjacent to the air electrode 31, as shown in FIG. At the same time, hydrogen is supplied through the fuel flow path 2b formed in the interconnector 1 adjacent to the fuel electrode 32, and operates at an operating temperature of, for example, about 800 ° C. Then, O2 reacts with the electron e- in the air electrode 31 to generate O2-, and the O2- moves through the electrolyte membrane 30 to the fuel electrode 32, and H2 supplied in the fuel electrode 32 becomes the O2-. As a result, H 2 O and e − are generated to generate an electromotive force E between the pair of interconnectors 1, and the electromotive force E can be taken out and used.

<Interconnector>
As shown in FIGS. 1 and 3, the interconnector 1 is configured by providing a protective film 12 on the surface of a substrate 11 for an interconnector. And it forms in the shape of a groove plate which can be connected, forming the air flow path 2a and the fuel flow path 2b between the cells 3.

  The protective film 12 is formed as a thick film by dip-coating the base material for interconnector 11 with a film-forming material containing a conductive ceramic material.

<Protective film>
The conductive ceramic material powder is dispersed in a solvent together with a binder to form a slurry-like film forming material. The coating film forming material is subjected to a coating film forming step of dip-coating the coating film of the coating film forming material on the interconnector base material. After that, before the complete drying time until the coating film is completely dried, a repeated coating process is repeated to dip coat a new coating film on the coating film, and the coating film that has been dip coated multiple times is dried. Thus, the protective film 12 is formed.

  Although the specific manufacturing method of the said protective film 12 is explained in full detail below, this invention is not limited to a following example.

[Examples 1 to 5]
<Coating material>
The conductive ceramic material powder is dispersed in a solvent together with a binder to form a slurry-like film forming material. Specifically, a slurry was prepared by dispersing 15 g of spinel oxide powder having a particle size of 1.0 μm as conductive ceramic material powder in 50 ml of isopropanol as a solvent and adding hydroxypropylcellulose as a binder. The slurry had a viscosity of 40 mPa · s at room temperature (25 ° C.).

<Base materials for interconnectors>
Forming a coating using a stainless-steel comb-shaped test piece comprising a plurality of combs having a surface portion length of 0.5 to 2 mm and a side portion length of half as the interconnector base material 11 The process was performed.

<Coating film formation process>
The coating film forming step was performed at room temperature using a dip coater (DC4200 manufactured by Aiden Co., Ltd.). The test piece was suspended and held, immersed in the slurry, and then pulled up at a pulling speed of 36 mm / s to form a coating film. The obtained coating film required about 600 seconds (complete drying time) in an open air state (25 ° C., 62% RH) to be completely dried. In the present invention, complete drying means that the coating film weight reduction rate is based on the relationship between the weight m1 of the coating film shown in FIG. 4 held on the substrate and the weight m2 of the coating film upon firing. Is sufficiently slow and can be regarded as a substantially constant weight. In the present invention, the time for giving w = m3 such that (m3−m2) / (m1−m2) <0.05 t was determined as the complete drying time.

  The coating film obtained in the above-mentioned coating film forming step is repeatedly coated with a new coating film on the coating film before dip coating, and repeated dip coating is repeated 10 times. A protective film was formed on the sample piece by drying the film. The obtained protective film was heated in an electric furnace at 1000 ° C. for 2 hours to completely remove the solvent and the binder and baked. As the drying time before the complete drying time, the results of tests conducted in 10 seconds, 20 seconds, 40 seconds, 60 seconds, and 80 seconds (referred to as Examples 1 to 5 in this order) in order are shown in Table 1 (1) to 1 Shown in (5). As a comparative example, Table 1 (10) shows the result of applying the completely dried coating film 5 times.

  As shown in FIG. 3, the thickness of the protective film 12 crosses the test piece of the interconnector substrate 11 on which the protective film 12 is formed, and the protective film 12 in FIGS. The average thickness (x) is the thickness of the rolled surface, and the average thickness (y) of the c and d protective films 12 corresponding to the side portions is the side thickness, and e, f, g, and h corresponding to the corner portions. The average thickness (z) of the protective film 12 was evaluated as the edge film thickness.

Example 6
Table 1 (6) shows the results of forming the protective film by changing the particle size of the conductive ceramic material powder in Example 3 to 0.2 μm.

Example 7
Table 1 (7) shows the results of changing the solvent in Example 4 to methoxypropanol and forming a protective film in the same manner. In addition, the slurry used here requires about 1400 seconds (complete drying time) in an air-released state (25 ° C., 62% RH) to completely dry the obtained coating film when the coating film is formed. It was a thing.

Example 8
Table 1 (8) shows the results of changing the binder in Example 2 to ethyl cellulose and forming a protective film in the same manner. In addition, the slurry used here requires about 1400 seconds (complete drying time) in an air-released state (25 ° C., 62% RH) to completely dry the obtained coating film when the coating film is formed. It was a thing.

Example 9
Table 1 (9) shows the results of changing the binder in Example 2 to polyvinyl pyrrolidone, changing the particle size of the conductive ceramic material powder to 0.5 μm, and similarly forming a protective film. In addition, the slurry used here requires about 1400 seconds (complete drying time) in an air-released state (25 ° C., 62% RH) to completely dry the obtained coating film when the coating film is formed. It was a thing.

〔result〕
From Examples 1 to 5 and Comparative Example, before the complete drying time until the coating film was completely dried, the overcoating step of dip coating a new coating film on the coating film was repeated, and the dip was repeated several times. It was found that when the coated film was obtained, the thin and strong protective film 12 could be formed in a state where the film thickness ratio was not so great as compared with the case where the overcoating process was performed by completely drying. In the case where the drying time is 20 seconds, the edge film thickness is not sufficiently increased even after 10 times of overcoating, so that it is understood that further overcoating is necessary, and the protective film 12 is formed more easily. It is understood that it is preferable to perform drying for 20 seconds or longer. Moreover, in the example of 80 seconds, it turns out that the rolling surface film thickness is also increasing by the initial ratio, and since the effect of reducing the ratio is not sufficient, it is understood that it is preferable to keep the drying for 80 seconds or less. This is because when the edge part has been dried more than the other parts, all parts are not dried immediately after the sample piece is pulled up in the coating film forming process. In addition, even in a sufficiently dry state, there is no difference in the dryness of all parts, so it is considered that there is no difference in the degree of formation of the coating film. The ratio decreases each time the overcoating is repeated (the thickness ratio (x / z) between the thickest portion (rolled surface) and the thinnest portion (edge) of the protective film 12 is 4.5). It is thought that it has fallen to 3 or less.

  In Examples 1 to 5 described above, it was preferable to repeatedly coat the coating film that completely dried in about 600 seconds with a drying time of 20 seconds to 80 seconds. Moreover, as a standard at this time, from the above-mentioned result, it is considered that the state in which the coating film is dried for 1/30 to 1/8 of the complete drying time required to completely dry the coating film is preferable. . In addition, when forming a coating film using the slurry which has the same drying characteristic, a protective film can be formed on the same time conditions.

  In addition, from Examples 2, 6, and 9, even if the particle size of the conductive ceramic material is 0.2 μm, 0.5 μm, or 1.0 μm, if the solvent is the same, the complete drying time can be reduced. It was almost the same, and it was found that the workability at the time of forming the coating film and the strength at the time of drying were also good. In addition, since it becomes easy to generate | occur | produce a crack, so that a particle size becomes fine and it will become difficult to adjust to a suitable viscosity when it is too large, 0.2 micrometer-1.0 micrometer are preferable.

  Furthermore, from Examples 4 and 7, the solvent for preparing the film-forming material is either isopropanol or methoxypropanol, and there is no significant difference in the film thickness ratio of the protective film obtained. It was confirmed that can be used well. Therefore, it can be seen that various solvents such as water, ethanol, propanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and butyl acetate can be used alone or in combination as long as they are equivalent solvents.

  Furthermore, from Examples 7 to 9, the binder for preparing the coating film forming material is hydroxypropyl cellulose, ethyl cellulose, or polyvinyl pyrrolidone. It was confirmed that any of them can be used satisfactorily. Therefore, it can be seen that any binder such as an acrylic resin having the same physical properties as these can be suitably used.

1: Interconnector 11: Interconnector base material 12: Protective film 2: Groove 2a: Air flow path 2b: Fuel flow path 3: Single cell 30: Electrolyte film 31: Air electrode 32: Fuel electrode C: Cell for SOFC

Claims (12)

A method for producing an interconnector for a fuel cell, wherein a protective film is formed by dip-coating a slurry-like film forming material on a substrate for an interconnector,
After the coating film forming step of dip-coating the coating film forming material on the interconnector substrate, a new coating is applied on the coating film before the complete drying time elapses when the coating film is completely dried. A method of manufacturing an interconnector for a fuel cell, wherein the protective film is formed by repeating a multi-coating process of dip coating with overlapping films and drying a coating film that has been dip coated by multiple times.   The manufacturing method of the interconnector for fuel cells of Claim 1 with which the said coating-film formation material has a conductive ceramic material as a main component and contains a binder and a solvent.   The method for producing an interconnector for a fuel cell according to claim 2, wherein the conductive ceramic material contains at least one selected from a spinel oxide and a perovskite oxide as a main component.   The method for manufacturing an interconnector for a fuel cell according to claim 2 or 3, wherein the conductive ceramic material has a particle size of 0.2 µm to 1.0 µm.   The method for producing an interconnector for a fuel cell according to any one of claims 2 to 4, wherein the viscosity of the coating film forming material is 25 mPa · s or more and 80 mPa · s or less.   The method for producing an interconnector for a fuel cell according to any one of claims 2 to 5, wherein the solvent contains at least one selected from isopropanol and methoxypropanol as a main component.   The method for producing an interconnector for a fuel cell according to any one of claims 2 to 6, wherein the binder is mainly composed of at least one selected from hydroxypropylcellulose, polyvinylpyrrolidone, and ethylcellulose.   The fuel cell according to any one of claims 2 to 5, wherein the binder is hydroxypropylcellulose, the solvent is isopropanol, and the complete drying time is adjusted to 300 seconds to 1200 seconds under an open air condition. Method of manufacturing an interconnector.   In a state where the coating film is dried by 1/30 to 1/8 of the complete drying time required to completely dry the coating film before the complete drying time has elapsed. A method for producing an interconnector for a fuel cell according to claim 8.   The binder is mainly composed of at least one selected from hydroxypropylcellulose, ethylcellulose, and polyvinylpyrrolidone, the solvent is methoxypropanol, and the complete drying time is adjusted to 300 seconds to 1400 seconds under an open air condition. A method for producing an interconnector for a fuel cell according to any one of claims 2 to 5.   The state before the complete drying time when the coating film is completely dried is a state where the coating film is dried by 1/70 to 1/8 of the complete drying time required for completely drying the coating film. A method for manufacturing an interconnector for a fuel cell according to claim 10.   It is manufactured by the manufacturing method of the fuel cell interconnector according to any one of claims 1 to 11, wherein a thickness ratio between the thickest part and the thinnest part of the protective film (thickness of the thickest part / maximum thickness). A fuel cell interconnector having a thickness of a thin portion of 3 or less.

Images