JP6735568B2 - Cell stack manufacturing method - Google Patents

Description

The present invention is a film forming process to wet a protective film material layer to the inorganic oxide particles containing a portion of Co and Mn components of the surface of the gold Shokumotozai main material, retaining Mamorumaku material layer and metallic A sintering process of sintering a base material to form a protective film on a metal base material, and providing a bonding layer made of a bonding material on the protective film to form a solid oxide fuel cell (hereinafter appropriately referred to as “SOFC”) And (b) a bonding step of bonding the single cells, and a stacking step of sintering and bonding the metal base material on which the protective film is formed, the bonding layer, and the single cells together , and to a method for manufacturing a cell stack .

In such a SOFC cell, a single cell in which an air electrode is joined to one surface side of the electrolyte membrane and a fuel electrode is joined to the other part side of the electrolyte membrane is used as an electron cell for the air electrode or the fuel electrode. It has a structure in which it is sandwiched between a pair of electron-conducting metallic base materials (inter-cell connecting members) that perform transfer.
Then, such a SOFC cell operates at an operating temperature of, for example, about 700 to 900° C., and the movement of oxide ions from the air electrode side to the fuel electrode side through the electrolyte membrane causes a gap between the pair of electrodes. Electromotive force is generated in the electromotive force, and the electromotive force can be taken out and used.

With the progress of development in recent years, the operating temperature of SOFC is decreasing. A conventional fuel cell has an operating temperature of about 1000° C., and a metal oxide represented by lanthanum chromite has been used from the viewpoint of heat resistance, but recently, the operating temperature has dropped to 700° C. to 800° C., Metal substrates have become available. The use of a metal base material can be expected to reduce costs and improve robustness.

Further, an n-type semiconductor protective film formed by doping a single oxide with impurities is formed on the surface of a metal base material used in a SOFC cell, and an alloy is formed by performing such a protective film forming treatment. There is a case where Cr contained therein is suppressed from being oxidized into a hexavalent oxide that easily scatters (for example, refer to Patent Document 1).

However, when forming a protective film on the surface of a metal substrate used in such a SOFC cell, it is necessary to form a conductive protective film on the side of the air electrode that is affected by Cr scattering from the above circumstances. However, there is a case where a structure in which a protective film is not formed on the fuel electrode side is adopted from the viewpoint of conductivity and the like. In such a case, when the protective film is formed on a part of the surface of the metal base material, if the sintering step is performed during the formation of the protective film, the other part of the metal base material is heated to a high sintering temperature. Since it is exposed, it may be oxidized to form an oxide film containing Cr such as Cr ₂ O ₃ or MnCr ₂ O ₄ . When such an oxide film is formed, since the oxide film has a high resistance, there is a problem in that the resistance in other portions of the metal base material becomes large and the power generation output as the SOFC greatly decreases.

Therefore, other parts to Rukoto as oxide coating (portions not forming the protective film) hardly occurs has been studied (for example, Patent Document metal substrate by various adjusting sintering conditions of the protective film 2).

International Publication No. 2007/083627 JP, 2009-152016, A

For example, there is a technology to sinter the protective film in an atmosphere of an inert gas such as argon or a low oxygen partial pressure atmosphere such as a high vacuum atmosphere, but argon is not an inexpensive gas and the process cost during mass production remains high. there's a possibility that.

According to the present inventors, it has been clarified that in the protective film thus formed, the spinel oxide of the protective film material may be reduced and converted into a composition having high resistance. ..

Therefore, in view of the above circumstances, the present invention can reliably sinter the protective film when forming the protective film on a part of the surface of the metal base material, and has a low-resistance spinel structure in use. An object of the present invention is to provide a simple cell stack manufacturing method.

[Configuration 1]
The characteristic configuration of the method for manufacturing the cell stack of the present invention for achieving the above object is
Deposition step of wet a protective film material layer to the inorganic oxide particles containing Co and Mn components in a portion of the surface of the gold Shokumotozai main material,
A sintering step of sintering the protective film material layer and the metal base material to form a protective film on the metal base material;
A bonding step of bonding a single layer of a solid oxide fuel cell by providing a bonding layer made of a bonding material to the protective film,
A stacking step of sequentially sintering and bonding the metal base material, the bonding layer, and the single cell on which the protective film is formed, which is a method of manufacturing a cell stack ,
The sintering step is a step of forming the protective film on the metal base material by sintering the protective film material layer and the metal base material under an inert gas atmosphere or a reducing atmosphere ,
In the bonding step, the unit cell is bonded to the protective film with the bonding layer in a state where a cobalt replenishing layer containing metallic cobalt is provided between the protective film and the bonding layer. It is a process.

[Operation effect 1]
For example, a flat plate type fuel battery cell in which a protective film is formed on one surface of a metal base material used for SOFC and an air electrode is bonded to the protective film is used when a fuel battery cell having a stack structure is formed. A protective film is formed on one surface of the metal base material, and even if the metal base material is heated by the operation of SOFC, a protective film is formed so that the components volatilized and scattered from the metal base material do not adversely affect the air electrode. A laminated structure of the air electrode, the solid electrolyte, and the fuel electrode can be formed with the interposition. Also, by connecting and stacking the stacked fuel electrode on another portion of the metal base material, the fuel electrode and the metal base material can be directly connected to each other in a conductive form. Further, the metal base material used for SOFC has a member that partially forms a protective film, and the present invention does not depend on the shape of the metal base material, and the air electrode is bonded to the protective film. Not only the formed fuel cells but also a member used to serve as a so-called separator for separating fuel and air, that is, a member used on one side in a fuel atmosphere and the other side in an air atmosphere. The present invention can be applied to a cell stack including a member having a protective film formed thereon.

By performing the film forming step of wet-forming the protective film material on a part of the surface of the metal base material, a coating can be formed on a part of the surface of the metal base material. This protective film material has inorganic oxide particles as a main material, but even if only the inorganic oxide particles are slurried to form a protective film, the adhesion between the inorganic oxide particles and the metal base material is high. Since it is insufficient and the sintering does not proceed sufficiently even after the subsequent sintering step and the adhesion is unlikely to increase, a protective film material containing a binder can be advantageously used.

When this coating is sintered, the protective film material layer is mainly composed of inorganic oxide particles containing Co and Mn components, and therefore is represented by Co _1.5 Mn _1.5 O ₄ and Co ₂ MnO _4. A protective film having a high spinel oxide structure and high resistance to Cr poisoning can be obtained. However, when sintering is performed in an inert gas atmosphere or a reducing atmosphere , the valences of the Co and Mn components change, and oxygen defects are generated, thereby performing charge compensation, but when the limit is exceeded, The crystal structure collapses and is reduced to a low valence oxide or metal to form a two-phase coexisting film. For example, it has been revealed that Co ₂ MnO ₄ is decomposed into Co and MnO in a high temperature reducing atmosphere. Further, according to the experimental findings of the present inventors, the phenomenon that an inorganic oxide containing Co and Mn components is decomposed into Co and MnO in a high-temperature reducing atmosphere is caused by the surface of the metal substrate in the protective film material layer. It has been found that this is a reaction that occurs preferentially on the surface side that is separated.

Here, MnO is an insulating material, and the environment in which the MnO phase is formed may significantly affect the power generation output. However, according to further studies by the present inventors, when the MnO phase contains a metallic Co component, it is heated in an oxygen atmosphere such as the air to regenerate the spinel oxide structure, and it is dense and sufficient. It has been found that it can be used as a protective film capable of ensuring excellent electrical conductivity, and has been experimentally confirmed.

Therefore, when a cobalt replenishment layer containing metallic cobalt is provided between the bonding layer and the protective film material layer that has been subjected to the sintering process in an inert gas atmosphere or a reducing atmosphere , the protection obtained can be obtained. In the film, a cobalt supplement layer containing metallic cobalt is arranged in a portion close to the bonding layer. Therefore, the obtained protective film contains metallic cobalt close to the surface of the protective film material when the MnO phase generated on the surface side separated from the metal substrate receives heat in an oxygen atmosphere such as the air. Can react with the cobalt supplementary layer to form a spinel oxide structure having a high electron conductivity and can be easily regenerated. Further, a MnO-deficient Co—Mn spinel oxide structure is formed on the metal substrate surface side of the protective film material layer which becomes the MnO-deficient layer of the protective film, but the electronic conductivity does not decrease and the power generation performance is adversely affected. It is possible to have a structure that can be maintained in a state where it is difficult to give.

Further, in the protective film obtained, the surface side portion separated from the metal base material in which the MnO phase is easily generated has a high-resistance crystal structure after the sintering step until the spinel oxide structure is regenerated. However, when integrated with the cobalt replenishment layer containing metallic cobalt, it reacts with metallic cobalt and reforms a low-resistance Co—Mn spinel phase, whereby the resistance gradually decreases. Regarding the bondability between the cobalt replenishment layer and the protective film material layer, Co and Co from the cobalt replenishment layer to the protective film material layer and Mn from the protective film material layer to the cobalt replenishment layer are electrically and mechanically dispersed. The bonding strength is increased, and the structure can have a low resistance and an improved adhesion strength. Regarding the bondability between the cobalt replenishment layer and the bonding layer, the inventors found that the electrical/mechanical bonding strength was sufficiently high without peeling or the like from the resistance value by the current application test and the cross-sectional SEM analysis result after the test. I'm confirming.

[Configuration 2]
Further, the joining step includes a cobalt supplement layer forming step of providing a cobalt supplement layer containing metallic cobalt on the surface of the protective film, the protective film formed of the cobalt supplement layer, and the unit cell . And a bonding layer forming step of forming the bonding layer therebetween.

[Function and effect 2]
The cobalt replenishing layer containing metallic cobalt, the bonding layer, may be prepared separately, when adjusting the bonding layer, the protective film material layer is disposed on the surface side away from the metal base material, You may heat-process simultaneously.

However, if the cobalt replenishment layer forming step of providing the cobalt replenishment layer containing metallic cobalt separately from the joining layer is performed by sequentially performing the replenishment layer forming step and the joining layer forming step, it is easy to perform. In addition, a cobalt replenishing layer having a uniform thickness is easily formed, which is preferable.

In short, in the step of performing the stacking step, if a layer containing a large amount of metallic cobalt as compared with the protective film material layer is located between the protective film material layer and the bonding layer, the metallic cobalt A layer containing a large amount of is called a cobalt supplement layer.

[Configuration 3]
The metal base material may be made of ferritic stainless steel.

[Operation effect 3]
As the metal base material, a material having high heat resistance and capable of withstanding an operating environment of SOFC is considered to be suitable, and austenite-based, ferritic-based stainless steel or Ni-based alloy such as Inconel is preferable, and ferritic stainless steel is SOFC. It has excellent thermal expansion coefficient matching with other components and heat resistance. However, ferritic stainless steel includes a Cr component, since it is preferable to bond the formed and air electrode protective layer to prevent scattering of the Cr component, the method of manufacturing the cell stack of the present invention By applying it, it is possible to suppress the oxidation of the metal base material and suppress the deterioration of the protective film, which leads to an increase in the use opportunities of the ferritic stainless steel metal base material, and the high-performance SOFC cell is inexpensive. It is advantageous to provide to.

[Configuration 4]
The inorganic oxide particles can be a metal oxide containing Co—Mn spinel oxide as a main component.

[Operation effect 4]
As the protective film, Co—Mn-based spinel oxide is known to have high conductivity and a coefficient of thermal expansion that matches that of the SOFC cell material, and is particularly effective for suppressing the scattering of Cr components. Therefore, by applying the cell stack manufacturing method of the present invention, it is possible to suppress the oxidation of the metal base material and the deterioration of the protective film, and further suppress the prevention of Cr scattering from the metal base material. Therefore, it is advantageous in providing a high-performance SOFC cell.

The metal oxide mainly composed of Co-Mn-based spinel oxide, such as cobalt-manganese oxide _{Co x Mn y O 4 (0} <x, y ≦ 3, x + y = 3) or zinc-cobalt-manganese-based oxide _{Zn z Co x Mn y O 4} (0 <x, y, z <3, x + y + z = 3) metal oxide fine particles made is used.

[Configuration 5]
It is particularly preferable that the inorganic oxide particles have at least one selected from Co _1.5 Mn _1.5 O ₄ and Co ₂ MnO ₄ as a main component.

[Function and effect 5]
As a metal oxide containing a Co—Mn-based spinel oxide as a main component, more specifically, Zn(Co,Mn)O ₄ , Co _1.5 Mn _1.5 O ₄ , CoMn ₂ O ₄ , MnCo ₂ O ₄ or the like is used. Those containing as the main component are preferably used. Among them, as the inorganic oxide particles, Co _1.5 Mn _1.5 O ₄ and Co ₂ MnO ₄ are highly conductive and have a thermal expansion coefficient matching that of the SOFC cell material, and Cr is one of the Co—Mn spinel oxides. It is particularly effective in suppressing the scattering of components.

[Configuration 6]
The sintering process may be performed at 500°C to 1050°C.

[Function and effect 6]
The sintering temperature in the sintering step varies depending on the composition of the metal base material and the protective film, but if it is generally 500° C. or higher, the acrylic binder and the like that are appropriately added to the protective film material layer are decomposed and disappeared. Can be made. On the other hand, if the temperature becomes too high, a high resistance film is likely to be formed on the surface of the metal base material, which may lead to deterioration, and problems such as easy peeling of the protective film material from the metal base material are likely to occur. To 1050° C. or lower is preferable.

In this way, when forming the protective film on a part of the surface of the metal base material, the protective film can be reliably sintered in a state in which it does not adversely affect other parts of the metal base material, It is possible to provide a simple cell stack manufacturing method capable of maintaining the conductivity of the film and increasing the bonding strength between the metal base material and the bonding layer, which can contribute to high-performance SOFC cell manufacturing. It became so.

Schematic of solid oxide fuel cell The figure which shows the usage form of the cell connecting member of a solid oxide fuel cell. Sectional view of inter-cell connection member test piece with protective film Sectional view of inter-cell connection member test piece with protective film SEM and EPMA diagram of cross section of protective film XRD diagram of protective film Graph showing resistance change of protective film Graph showing the temperature and pressure limit of the atmosphere in which cobalt oxide is reduced Graph showing resistance change of protective film SEM diagram of cross section of protective film SEM diagram of cross section of protective film

The method for manufacturing the cell stack according to the embodiment of the present invention will be described below. The preferred embodiments will be described below, but these embodiments are described for more specifically illustrating the present invention, and various modifications can be made without departing from the spirit of the present invention. However, the present invention is not limited to the following description.

<Solid oxide fuel cell (SOFC)>
The embodiment of the manufacturing method of the cell stack including the SOFC cell joined member as a member for fuel cell, it will be described with reference to the drawings. The fuel cell member is used in a cell stack of a solid oxide fuel cell. Not only when the air electrode is bonded to the protective film formed on the metal base material, but also widely applicable to the metal base material where the protective film is partially formed. It is called a member.
The SOFC cell C shown in FIGS. 1 and 2 has an air electrode made of a porous body having oxide ions and electron conductivity on one surface side of an electrolyte membrane 30 made of a dense body of oxide oxide conductive solid oxide. The unit cell 3 is formed by joining 31 and a fuel electrode 32 formed of an electron conductive porous body on the other surface side of the electrolyte membrane 30.
Further, the SOFC cell C has a pair of electron-conducting cells in which the single cell 3 is provided with a groove 2 for exchanging electrons with the air electrode 31 or the fuel electrode 32 and for supplying air and hydrogen. The inter-cell connecting member 1 serving as the metal base material 11 made of an alloy has a structure in which the gas seal body is sandwiched appropriately at the outer peripheral edge portion. The groove 2 on the side of the air electrode 31 functions as an air flow path 2a for supplying air to the air electrode 31 due to the air electrode 31 and the inter-cell connecting member 1 being arranged in close contact with each other. The groove 2 on the side of the fuel electrode 32 functions as a fuel flow path 2b for supplying hydrogen to the fuel electrode 32 by closely disposing the fuel electrode 32 and the inter-cell connecting member 1. The inter-cell connection member 1 may have a configuration in which a member that electrically connects the interconnector and the cell C is connected. Reference numeral 42 denotes a bonding layer 42 made of a bonding material 42a, which is used to secure the electrical connection between the inter-cell connecting member 1 and the air electrode 31.

In addition, when a general material used in each element constituting the SOFC cell C is added, for example, the material of the air electrode 31 is LaMO ₃ (for example, M=Mn, Fe, Co). The perovskite type oxide of (La,AE)MO ₃ in which a part of La of is substituted with an alkaline earth metal AE (AE=Sr,Ca) can be used, and the fuel electrode 32 is made of Ni. And yttria-stabilized zirconia (YSZ) can be used, and as the material of the electrolyte membrane 30, yttria-stabilized zirconia (YSZ) can be used. As the bonding material 42a, a perovskite type oxide or a spinel type oxide similar to the air electrode 31 can be used.

Further, in the SOFC cell C described so far, as the material of the inter-cell connecting member 1, a Fe-Cr alloy that is a ferritic stainless steel that is a material having excellent electronic conductivity and heat resistance, or an austenitic stainless steel. Alloys or oxides containing Cr such as Fe-Cr-Ni alloy which is steel and Ni-Cr alloy which is nickel-based alloy are used.

Then, in the state in which the plurality of SOFC cells C are stacked and arranged, a pressing force is applied in the stacking direction by the plurality of bolts and nuts so as to be sandwiched to form a cell stack.
In this cell stack, the inter-cell connecting members 1 arranged at both ends in the stacking direction may be those in which only one of the fuel flow passage 2b and the air flow passage 2a is formed, and are arranged in the middle of the other. As the inter-cell connecting member 1, it is possible to use one in which the fuel flow path 2b is formed on one surface and the air flow path 2a is formed on the other surface. In addition, in the cell stack having such a laminated structure, the inter-cell connection member 1 may be referred to as a separator.
An SOFC having such a cell stack structure is generally called a flat plate SOFC. In the present embodiment, a flat plate SOFC will be described as an example, but the present invention is also applicable to SOFCs having other structures.

Then, when the SOFC including the SOFC cell C is operated, as shown in FIG. 2, air is supplied through the air flow path 2a formed in the inter-cell connecting member 1 adjacent to the air electrode 31. While supplying the hydrogen, hydrogen is supplied to the fuel electrode 32 through the fuel flow path 2b formed in the inter-cell connecting member 1 adjacent to the fuel electrode 32, and operates at an operating temperature of, for example, about 800°C to 1000°C. Then, the air electrode 31 O ₂ electrons e ^- are reacting with O ^2- is generated, the O ^2- passes through the electrolyte membrane 30 to move to the fuel electrode 32, H ₂ supplied in the fuel electrode 32 React with the O ²⁻ to generate H ₂ O and e ⁻ , thereby generating an electromotive force E between the pair of inter-cell connecting members 1 and extracting the electromotive force E to the outside for use. be able to.

<Cell connecting member>
As shown in FIGS. 1 and 3, one of the inter-cell connecting members 1 is, for example, one of the metal base materials 11 (hereinafter sometimes simply referred to as the metal base material 11) for the inter-cell connecting members made of ferritic stainless alloy. A protective film 12 is provided on the surface on the side. Further, an air flow path 2a and a fuel flow path 2b are formed between each unit cell 3 and are formed in a groove plate shape which enables connection. An oxide film 13 is formed on the surface of the base material 11.

<Protective film>
As shown in FIG. 3, the protective film 12 is formed on one surface of the metal substrate 11 made of ferritic stainless steel containing 22% Cr and 0.1 to 0.5% Mn. An electrodeposition step (an example of a film forming step) of forming an electrodeposition coating film as the material layer 12a is performed, and the electrodeposition coating film as the protective film material layer 12a is sintered together with the metal base material 11 to remove metal oxide. The protective film 12 is formed by performing a sintering process for forming the protective film 12.

In this sintering step, it is preferable that the temperature is 500° C. or higher and 1050° C. or lower and the oxygen partial pressure at which Co ₃ O ₄ is thermodynamically reduced to Co or less is set. In such a reducing atmosphere, cobalt oxide (Co ₃ O ₄ or CoO) contained as an inorganic oxide is an atmosphere in which metal Co is reduced, and a temperature range of 500° C. to 1050° C. at which cobalt can be sintered. It is a pressure range that can be easily realized. (Refer to FIG. 8, for example, at 950° C., the oxygen partial pressure is 1.69×10 ⁻⁹ atm or less.) In the reducing atmosphere, the oxide film of the metal substrate 11 is formed on the other surface of the metal substrate 11. Perform under difficult conditions. The low oxygen partial pressure atmosphere can be adjusted by an ordinary method such as an inert gas atmosphere or a reducing atmosphere.

<Protective film material layer>
The protective film material layer 12a is formed of, for example, ZnCoMnO ₄ , Co ₁ . ₅ Mn ₁ . ₅ O ₄ , CoMn ₂ O ₄ , MnCo ₂ O ₄ and other metal oxides containing Co—Mn-based spinel oxide as a main component and polyacrylic acid and other anionic resins as acrylic binders in a mass ratio. (Metal oxide fine particles: anion-type resin)=(0.5:1) to (2:1) is used as a protective film material layer 12a by anion electrodeposition coating method using a mixed solution. It is formed by performing an electrodeposition step of forming an electrodeposition coating film (an example of a film forming step).

Hereinafter, a specific method for manufacturing the protective film 12 will be described in detail, but the present invention is not limited to the following examples.

<Example>
In the film forming step, a test piece of a metal base material 11 having a simple shape with a rectangular cross section is subjected to degreasing treatment, pickling treatment, electrolytic polishing, etc., if necessary, and then immersed in a mixed liquid of a protective film material. Then, by applying electricity, an electrodeposition coating film as the uncured protective film material layer 12a is formed on the surface of the metal substrate 11.
The obtained protective film material layer 12a is sintered together with the metal substrate 11 in a low oxygen partial pressure atmosphere.

[1] Pretreatment of Metal Substrate Prior to performing electrodeposition coating, each electrode was subjected to the following pretreatments in which 1 to 7 were sequentially performed.
1. Cathodic electrolysis with an electrolytic cleaner (Activator S (Shimizu) 100 g/L, 40° C., 10 A/dm2, 30 seconds)
2. Wash with water 3. Anodic electrolysis with electrolytic cleaning agent (Activator S (manufactured by Shimizu) 100 g/L, 40° C., 10 A/dm2, 30 seconds)
4. Washing with water 5. Acid neutralization (nitric acid 200 mL/L)
6. Washing with water 7. Wash with pure water

Further, the test piece of the metal base material 11 serving as the anode may be separately subjected to degreasing treatment, pickling treatment and the like.
The degreasing treatment is performed, for example, by supplying an alkaline aqueous solution to the surface of the metal base material 11. The alkaline aqueous solution is supplied, for example, by spraying the alkaline aqueous solution on the metal substrate 11 or by immersing the metallic substrate 11 in the alkaline aqueous solution. As the alkali, those commonly used for degreasing metals can be used, and examples thereof include alkali metal phosphates such as sodium phosphate and potassium phosphate. The alkali concentration in the alkaline aqueous solution is appropriately determined depending on, for example, the type of metal to be treated and the degree of contamination of the metal base material 11. Further, the alkaline aqueous solution may contain an appropriate amount of a surfactant such as an anionic surfactant or a nonionic surfactant. Degreasing is performed at a temperature of about 20 to 50° C. (liquid temperature of the alkaline aqueous solution), and is completed in about 1 to 5 minutes.

After degreasing, the metal substrate 11 is washed with water and subjected to the next pickling treatment. In addition, degreasing by dipping in an acidic bath, aerated dipping degreasing, electrolytic degreasing and the like can be appropriately combined and carried out. The pickling treatment is performed, for example, by supplying an aqueous acid solution to the surface of the metal substrate 11. The supply of the acid aqueous solution is performed by spraying the acid aqueous solution onto the metal base material 11 or immersing the metal base material 11 in the acid aqueous solution, as in the case of supplying the alkali aqueous solution in the degreasing treatment. As the acid, those commonly used for pickling metals can be used, and examples thereof include sulfuric acid, nitric acid and phosphoric acid. The acid concentration in the acid aqueous solution is appropriately determined depending on, for example, the type of the metal substrate 11. The pickling treatment is performed at a temperature of about 20 to 30° C. (liquid temperature of the aqueous acid solution) and is completed in about 15 to 60 seconds.

In addition to this, the metal substrate 11 may be subjected to scale removal treatment, rust prevention treatment, and the like. After these treatments, the metal base material 11 is dried at a temperature of about 70 to 120° C. and subjected to the next step.

[3] Film-forming step (3-1) Synthesis of anion type resin 50 parts of 1,4 dioxane were heated to about 82° C. in a four-necked flask equipped with a reflux condenser, a thermometer, a stirrer and a dropping funnel. While heating and stirring, the mixture shown in Table 1 below and 50 parts of 1,4 dioxane were continuously added dropwise over 3 hours from a dropping funnel.
After the dropping is completed, the reaction is continued at the same temperature for 3 hours to synthesize an anionic acrylic resin binder (solid content 50%). The Tg of the obtained anion-type resin was −27° C. (estimated value by calculation), and the molecular weight was MW 120,000 to 150,000.

Regarding the chemical properties of the anionic resin, Tg: −50° C. to +25° C. and molecular weight (MW mass average molecular weight): preferably in the range of 50,000 to 200,000. Generally, Tg of an anion type resin is around +20° C. and MW is about 30,000 to 70,000. In order to electrophoretically deposit a large amount of inorganic fine particles and locally generate an electrolytic gas to improve the eutectoid rate, it is preferable to use a high Tg high molecular weight anionic resin. When Tg is -50°C or less, the viscosity of the deposited film is too strong and the fluidity is large after bake hardening, and when it is +25°C or more, the fluidity decreases and the gas traces generated during the co-deposition of Co ₂ MnO ₄ fine particles may be erased. It cannot be formed and becomes a pinhole. When the MW is 50,000 or less, the dispersibility of Co ₂ MnO ₄ fine particles decreases. On the other hand, when it is 200,000 or more, the fluidity is lowered, the uniform dispersion of Co ₂ MnO ₄ fine particles in the coating film is deteriorated, and the appearance becomes nonuniform.

Further, when the anion-type resin and the metal oxide fine particles are subjected to a coupling reaction using a silane coupling agent described below, the deposition efficiency of the metal oxide fine particles typified by Co ₂ MnO ₄ fine particles is dramatically improved. be able to.

(3-2) as a mixture of creating a silane coupling agent, isocyanate-functional silane _{(OCN - C 3 H 6- Si} (OC 2 H 5) 3) used, the solvent nMP (n-methylpyrrolidone) 3 Weight Parts and 120 parts by mass of the anion-type resin prepared in (1) and 60 parts of solvent nMP (n-methylpyrrolidone) were mixed, and then a tin-based catalyst (DBTDL 0.2 part) was added and reacted at 60° C. for 1 hour. The isocyanate group of the silane coupling agent reacts with the OH group of the anion type resin to add the silane coupling agent to the anion type resin. (Table 2 first component)

100 parts by mass of Co ₂ MnO ₄ fine particles (average particle size 0.5 μm), 200 parts by mass of solvent nMP (n-methylpyrrolidone) and 750 parts by mass of zirconia beads having a diameter of 3 mm were mixed and wet-dispersed with a stirrer to form a slurry. Co ₂ MnO ₄ fine particles are obtained. (Table 3 second component)

The first component is added to the second component and mixed uniformly.
Further, 1.4 parts by mass of triethylamine, 10 parts by mass of a solvent nMP (n-methylpyrrolidone) and 10 parts by mass of an antifoaming agent (Surfynol 104) are added and stirred.
After uniform mixing, 500 parts by mass of ion-exchanged water is added little by little to prepare a mixed solution of Co ₂ MnO ₄ fine particles and anion type resin. After stirring for 24 hours to promote the hydrolysis reaction of the silane coupling agent, impurities are removed by ion exchange treatment to obtain a mixed solution having a pH of 9.0±0.2 bath conductivity of 200±50 μS/cm. The obtained dispersion liquid is used as a mixed liquid of Co ₂ MnO ₄ fine particles:resin=1:1 (mass ratio).

It should be noted that Co ₂ MnO ₄ fine particles:resin=0.5:1 (mass ratio) to 2:1 (mass ratio) can be prepared by changing the mixing ratio of the first component and the second component of the following formulation.

(3-3) Electrodeposition coating The anionic dispersant composition prepared in the above (3-2) is dispersed so that the dispersant particles therein will be 100 g per liter of the electrodeposition liquid, and the solution at 25° C. In the above, the electrodeposition coating was carried out at a DC voltage of 40 V for 30 seconds under stirring with a stirrer (20 rpm).
The electrodeposition coating was performed as follows.

The test piece of the pretreated metal base material 11 was placed in a solution at 25° C. with the metal base material 11 as a positive electrode and the electrode plate of SUS304 as a counter electrode with a negative polarity, and a stirrer stirring (20 rpm) at a DC voltage of 40 V for 30 seconds. ) And applying electricity, an uncured electrodeposition coating film is formed on the surface of the metal substrate 11.
The film thickness of the electrodeposition coating film can be controlled by changing the electrodeposition voltage and the electrodeposition time.

The metal base material 11 after the electrodeposition step is taken out from the energization bath and subjected to heat treatment. By heat-treating the metal base material 11 on which the uncured electrodeposition coating film is formed, the inter-cell connecting member 1 having the cured electrodeposition coating film on the surface of the metal base material 11 is obtained.

The electrodeposition coating is carried out according to a known method, for example, by immersing the metal substrate 11 completely or partially in an energizing tank filled with a mixed solution to form an anode, and energizing.
The conditions for electrodeposition coating are not particularly limited, and are wide according to various conditions such as the type of metal that is the metal base material 11, the type of mixed solution, the size and shape of the energizing tank, the intended use of the inter-cell connecting member 1. The temperature can be appropriately selected from the range, but usually, the bath temperature (mixed solution temperature) is about 10 to 50° C., the applied voltage is about 10 to 450 V, the voltage application time is about 1 to 10 minutes, and the mixed solution temperature is about 10 to 45° C. Good.

The heat treatment includes preliminary drying for drying the electrodeposition coating film and curing heating for curing the electrodeposition coating film, and curing heating is performed after the preliminary drying. The preliminary drying is performed under heating at about 60 to 140° C. and is completed in about 3 to 30 minutes. Curing heating is performed under heating at about 150 to 220° C., and is completed in about 10 to 60 minutes. In this way, an electrodeposition coating film with the mixed liquid is obtained.

[4] Sintering Step An electrodeposition coating film formed by using Co ₂ MnO ₄ fine particles (particle diameter 0.5 μm):resin=2:1 (mass ratio) as a mixed liquid was added with 5% H ₂ /N. ₂ Under the low oxygen partial pressure atmosphere of oxygen partial pressure of 1.69×10 ⁻⁹ atm (1 atm=980 hPa) or less, the acrylic resin is decomposed by keeping at about 500° C. to 1050° C. in an electric furnace. Make it disappear. Specifically, the acrylic resin is held at 950° C. for 2 hours to decompose and disappear the acrylic resin, and the sintering step of sintering the Co ₂ MnO ₄ particles and reacting with the surface of the test piece of the metal substrate 11 is performed. As a result, a dense protective film 12 having an adhesive force to the metal base material 11 was formed (see FIG. 4A). When the protective film 12 thus obtained was cooled to room temperature and taken out under the condition of flowing 5% H ₂ /N ₂ gas, it had a good appearance with no defects such as cracking or peeling.

In order to evaluate the oxidation state of the back surface of the metal base material 11 on which the protective film 12 was formed, the electrical resistance was measured with a tester. As a result, it was confirmed that the resistance was 1 Ω or less (0.21 to 0.23 Ω), which was low, and that most of the metal gloss remained.

A SEM photograph of the protective film 12 formed on the metal substrate 11 is shown in FIG.
From the figure, it can be seen that in the protective film 12, the cobalt component is contained in a high concentration on the surface portion close to the metal base material 11, and the manganese component is contained in a high concentration on the surface side separated from the metal base material 11. .. Further, the cobalt supplied as the cobalt replenishment layer 41 to the surface side of the protective film 12 separated from the metal base material 11 reacts with the manganese component and contributes to regenerate the Co—Mn-based spinel structure. Conceivable.

It was found that a dense protective film 12 was formed in the cross section of the obtained protective film 12. When this protective film 12 is observed, a cobalt component is contained in a high concentration in the surface portion of the protective film 12 close to the metal base material 11, and MnO is contained in a high concentration on the surface side separated from the metal base material 11. Was considered to be present. Further, when the XRD of the structure of the protective film 12 in the vicinity of the metal substrate 11 is measured, the result is as shown in FIG. 6, and in the reducing atmosphere used for the previous sintering of the protective film 12, the protective film 12 once exhibits a reducing action. Therefore, it is considered that cobalt oxide (Co ₃ O ₄ or CoO) was sintered in the state of being reduced to metallic cobalt and Mn ₃ O ₄ was reduced to MnO.

[Joining process]
A bonding step is performed in which the bonding layer 42 made of the bonding material 42a is provided on the protective film 12 and the bonding layer 42 is bonded to the air electrode 31 provided in the adjacent single cell 3.
The bonding step includes a cobalt supplement layer forming step of providing a cobalt supplement layer 41 containing metallic cobalt on the surface of the protective layer 12, and the protective layer 12 formed of the cobalt supplement layer 41 and another cell. The bonding layer forming step of forming the bonding layer 42 between the air electrodes 31 of the adjacent single cells 3 is sequentially performed.

<Cobalt supplement layer>
The cobalt replenishment layer 41 is formed by applying a metallic cobalt paste, which is composed of metallic cobalt particles 41a as a main component and is dispersed in a solvent 41b such as glycerin to form a paste, on the surface of the protective film 12 fired at a low oxygen partial pressure according to a conventional method. After that, the solvent 41b is volatilized and removed to form a coating film (see FIG. 4B).

[Cobalt supplement layer forming step]
Specifically, as the cobalt paste, a mixture of metal cobalt particles 41a as a starting material and glycerin as a solvent 41b at a weight ratio of 1:1 was used as the cobalt paste. A cobalt paste having a uniform thickness of 0.5 mm was applied on the surface of the metal base material 11 and dried at room temperature to form the cobalt replenishment layer 41.

The cobalt replenishment layer forming step may be performed by spraying, sputtering, CVD method, AD method, thermal spraying, PLD method, dip coating, electrodeposition coating, or plating instead of applying paste. Further, the metallic cobalt paste or the dip coating by dip coating may contain other components, for example, the same or similar components as the protective film material other than cobalt, and the protective film material layer 12a. A composition containing an inorganic material having a higher content rate of metallic cobalt than the main component can also be used.

<Joining layer>
On the surface side of the obtained cobalt replenishment layer 41, a bonding layer 42 made of a bonding material paste, which is mainly composed of the bonding material 42a and is dispersed in a solvent 42b such as glycerin to form a paste, is provided. (See FIG. 4C) As the bonding material 42a, a perovskite type oxide or a spinel type oxide similar to the air electrode 31 can be used. Specifically, as the bonding material 42a forming the bonding layer 42, the air electrode 31 mainly composed of a perovskite type oxide containing a metal selected from La, Sr, Pr, Sm, Fe, Co, Mn, and Ni. A conductive ceramic material having a composition similar to that is preferably used.

[Joining layer forming step]
After the cobalt replenishment layer 41 was dried at room temperature, the bonding material paste was applied to the surface of the cobalt replenishment layer 41 to form the bonding layer 42. A state in which a plurality of single cells 3 are connected in a form in which the air electrode 31 of an adjacent single cell 3 as another cell is bonded to the bonding layer 42 in a state where the bonding layer 42 is maintained in a paste state. To be done.

[Stacking process]
The plurality of single cells 3 are sintered as a whole to form a cell stack (SOFC cell 3). The cell C is sintered at 1000° C. to 1150° C. for 2 hours, whereby the bonding layer 42 is sintered and the plurality of unit cells 3 are integrally bonded (FIG. 4(d). )reference).

Generally, in the stacking process of SOFC, the inter-cell connecting member 1 and the single cell 3 whose coating is sintered are alternately laminated, the conductive bonding layer 42 is sandwiched between them, and the gas is added to a necessary portion. After applying a sealing material (such as glass), heat treatment is performed to increase the adhesion strength between the bonding layer 42 and the unit cell 3/inter-cell connecting member 1 or to sinter the sealing material to ensure gas leakage.
Although this step depends on the structure and design concept of the stack, it is generally performed at 500° C. or higher and 1050° C. or lower (when it exceeds 1050° C., the inter-cell connecting member 1 of the alloy deteriorates). Therefore, when the obtained inter-cell connecting member 1 was placed in the environment of 800° C. in the atmosphere and the resistance change of the protective film 12 was measured, the result was as shown in FIG. 7. As a comparison, instead of the inter-cell connection member 1 (Example) in the above-described embodiment, the cobalt replenishment layer 41 was not provided on the surface side of the protective film 12, and the protective film 12 having the same thickness after sintering was formed. The resistance change of the protective film 12 was similarly measured for the product (comparative example).

From FIG. 7, the protective film 12 of the comparative example shows a high resistance value at the initial stage and does not change significantly with time. On the other hand, the protective film 12 of the example shows a low resistance value due to metallic cobalt in the initial stage, and although the resistance value gradually increases in the use environment, it is stabilized at a resistance value of about 150 mΩcm ² . The high-resistance component of MnO generated in the protective film 12 of the comparative example remains as it is without being reconfigured into the spinel structure due to the diffusion of the Co component during sintering, so that the entire protective film 12 has a high resistance. There is. On the other hand, in the examples, although the resistance value is initially increased by converting MnO to the Co—Mn-based spinel oxide structure while consuming metallic cobalt, the resistance value is stable at a low resistance value. Can be explained.

That is, by providing the cobalt replenishment layer 41 containing metallic cobalt between the protective film 12 and the bonding layer 42, which are sintered under a low oxygen partial pressure atmosphere, in the use environment of the fuel cell member, It is clear that MnO which is initially formed in the protective film 12 by sintering is converted into a Co—Mn-based spinel oxide structure and can be used as the protective film 12 which is dense and has low resistance and can suppress stable scattering of Cr components. Became.

[Another embodiment]
In the above described embodiment, the Co ₂ MnO ₄ as the inorganic oxide particles, Co _{1. 5} Mn ₁ . It has been experimentally shown that even if ₅ O ₄ is used, MnO initially formed in the protective film 12 by sintering can be converted into a Co—Mn-based spinel oxide structure in the use environment of the fuel cell member. It has been clarified that if the metal oxide contains Co—Mn-based spinel oxide as the main component, the dense protective film 12 can similarly suppress the scattering of the Cr component as the protective film 12 that is dense and has low resistance and is stable. It is thought that it can be used as. Such CoMn spinel oxides, using _{Zn (Co, Mn) O 4} , Co 1.5 Mn 1.5 O 4, CoMn 2 O 4, MnCo 2 O , etc. suitably those containing as a main component ₄ To be

In the above embodiment, the cobalt replenishment layer 41 was formed by applying a paste material containing metallic cobalt to the metal base material 11. However, dip coating or electrodeposition using a metallic cobalt dispersion liquid in which metallic cobalt is dispersed. The cobalt supplement layer 41 can also be formed by painting. For example, as a dip solution used for dip coating, metal cobalt powder, methoxypropanol, and hydroxypropyl cellulose are mixed at a weight ratio of 5:10:1, and the dip coating is performed once or twice on the protective film 12. The cobalt replenishment layer 41 may be dried at room temperature.
In addition, when the cobalt replenishment layer 41 is formed on the protective film 12 by dip coating using the metallic cobalt dispersion liquid having the following composition and the sintered protective film 12 is formed, when the protective film 12 is initially formed in the vicinity of the metal substrate 11, The resistance value is about 90 mΩcm ^2, and it is clear that the resistance value is lower than that of the above-mentioned example (125.6 mΩcm ² ) coated with the paste.

Further, the protective film 12 layer may be plated with cobalt, or the cobalt replenishment layer 41 containing metallic cobalt as a main component may be formed by spraying, sputtering, CVD method, AD method, thermal spraying, PLD method, dip coating or electrodeposition coating. Can also

[Measurement of long-term resistance change]
FIG. 9 is a graph showing the results of measuring the resistance change of the example and the comparative example shown in FIG. 7 over 4000 hours. In FIG. 9, the results of the same sample as the inter-cell connecting member 1 used in the measurement of FIG. 7 are shown as “Example 1st sample” and “Comparative example sample”, and the results of the samples of other examples described above are “ The second sample of the example" is also shown.

In the sample of the comparative example and the first sample of the example, the resistance value suddenly increased near 1300 hours and 2700 hours. This is because the measurement of the resistance change was interrupted and the probe for measuring the resistance value was attached and detached. It depends. The resistance value of the comparative sample gradually decreased until 1000 hours, but after 1000 hours, the change in resistance value converged, and after 4000 hours, the resistance value remained at about 160 mΩcm ² . The resistance value of the first sample of the embodiment tended to decrease after 1000 hours, and the resistance value was about 120 mΩcm ^{2 at} around 3800 hours. The resistance value of the second sample of the example increased like that of the first sample of the example until about 500 hours, but after that, the resistance value consistently decreased, and after the lapse of 4000 hours, the resistance value changed to about 100 mΩcm ^2. doing. From the above results, the resistance value of the first sample and the second sample of the embodiment is smaller than that of the comparative sample, and the resistance value does not increase even when placed in a SOFC use environment for a long period of time. It was confirmed that it can be used stably.

[SEM observation of cross section of protective film]
After measuring the long-term resistance change described above, the second sample of the example and the sample of the comparative example were cut, and the cross section was observed with an SEM (electron microscope). The result of the second example sample is shown in FIG. 10, and the result of the comparative example sample is shown in FIG. In the second sample of the example shown in FIG. 10, cracks and the like were not seen between the base material 11 and the protective film 12, and even if the inter-cell connecting member 1 was used for a long period of time, the base material 11 and the protective film 12 were not used. It was shown that the bond between and was kept strong. The boundary between the cobalt replenishing layer 41 and the bonding layer 42 is in an indistinguishable state, and it can be seen that element diffusion has occurred between the cobalt replenishing layer 41 and the bonding layer 42. When comparing the oxide film 13 between the comparative example sample of FIG. 11 and the example second sample of FIG. 10, the oxide film 13 of the example second sample is thinner than that of the comparative example sample. The reason why the oxide film 13 is thin is that cobalt is elementally diffused from the cobalt replenishment layer 41 to the protective film 12 side, and the protective film 12 is formed as a denser film, thus suppressing the growth of the oxide film 13. It is thought to be because. It can be said that the second sample of the example is more suitable as the inter-cell connecting member 1 because the electric resistance is reduced due to the thin oxide film 13.

1: Cell connecting member 2: Groove 2a: Air flow path 2b: Fuel flow path 3: Single cell 11: Metal substrate 12: Protective film 30: Electrolyte film 31: Air electrode 32: Fuel electrode C: Cell

Claims (6)

Deposition step of wet a protective film material layer to the inorganic oxide particles containing Co and Mn components in a portion of the surface of the gold Shokumotozai main material,
A sintering step of sintering the protective film material layer and the metal base material to form a protective film on the metal base material;
A bonding step of bonding a single layer of a solid oxide fuel cell by providing a bonding layer made of a bonding material to the protective film,
A stacking step of sequentially sintering and bonding the metal base material, the bonding layer, and the single cell on which the protective film is formed, which is a method of manufacturing a cell stack ,
The sintering step is a step of forming the protective film on the metal base material by sintering the protective film material layer and the metal base material under an inert gas atmosphere or a reducing atmosphere ,
In the bonding step, the unit cell is bonded to the protective film with the bonding layer in a state where a cobalt replenishing layer containing metallic cobalt is provided between the protective film and the bonding layer. A method of manufacturing a cell stack , which is a step. A step of forming a cobalt supplement layer containing a cobalt supplement layer containing metallic cobalt on the surface of the protective layer; and a step of forming the cobalt supplement layer with the protective film and the unit cell. The method for manufacturing a cell stack according to claim 1, further comprising: a bonding layer forming step of forming the bonding layer on the substrate. The method for manufacturing a cell stack according to claim 1, wherein the metal base material is made of ferritic stainless steel. The method for producing a cell stack according to claim 1, wherein the inorganic oxide particles are a metal oxide containing a Co—Mn spinel oxide as a main component. The method for producing a cell stack according to claim 4, wherein the inorganic oxide particles have at least one selected from Co _1.5 Mn _1.5 O ₄ and Co ₂ MnO ₄ as a main component. The method for manufacturing a cell stack according to claim 1, wherein the sintering step is performed at 500° C. to 1050° C. 6.