JP6948791B2 - Manufacturing method of cell-to-cell connection member and manufacturing method of cell for solid oxide fuel cell - Google Patents

Description

The present invention relates to a method for manufacturing a cell-to-cell connecting member and a method for manufacturing a cell for a solid oxide fuel cell.

A cell for a solid oxide fuel cell (hereinafter sometimes referred to as a "cell for SOFC") has an air electrode bonded to one side of an electrolyte membrane and a fuel electrode to the other side of the electrolyte membrane. It has a structure in which a single cell formed by joining is sandwiched between an electron conductive base material (cell-to-cell connecting member). Such an SOFC cell operates at an operating temperature of about 700 to 900 ° C., and generates an electromotive force between the electrodes as the oxide ions move from the air electrode side to the fuel electrode side via the electrolyte membrane. generate. The cell-cell connection member is a member that electrically connects single cells to each other, and is also a member that serves as a partition wall between fuel and air.

With the progress of development in recent years, the operating temperature of SOFCs has been decreasing. The conventional operating temperature is about 1000 ° C., and a metal oxide typified by lanthanum chromite has been used from the viewpoint of heat resistance. Recently, the operating temperature has dropped to 700 ° C to 800 ° C, and alloys can be used as constituent members of SOFC cells. The use of alloys can be expected to reduce the cost of SOFCs and improve robustness.

As the alloy, ferritic stainless steel is often used because of its consistency with the coefficient of thermal expansion of the metal oxide to be bonded. On the other hand, Fe-Cr-Ni alloy, which is an austenitic stainless steel having excellent heat resistance, Ni-Cr alloy, which is a nickel-based alloy, and the like may be used. In addition, metal oxides typified by (La, Ca) CrO ₃ (calcium doprantan chromite) may be used.

These alloys contain Cr almost without exception, and form an oxide film _{of Cr 2} O ₃ or _{Mn Cr 2} O _{4 on} the surface in a high temperature atmospheric atmosphere which is an operating environment. It is known that this oxide film becomes thicker with time, the electrical resistance increases, and it evaporates as a hexavalent chromium compound in the high-temperature atmospheric atmosphere, which is the operating environment, and deteriorates the air electrode (). Cr poisoning). Further, even when (La, Ca) CrO ₃ is used, Cr poisoning may occur, although it is less than that of the alloy. Therefore, attempts have been made to suppress deterioration of the air electrode by coating the surface of the alloy or (La, Ca) CrO _{3 with a metal oxide material having excellent heat resistance.}

The solid oxide fuel cell of Patent Document 1, the base material of the intercell connection member is made of ferritic stainless steel alloy, a metal oxide material on the surface of the substrate _{(Zn x (Co y Mn (} 1- A protective film containing _(y) ) _(3-x) O _{4) is formed.} For the formation of the protective film, more specifically, a slurry-like coating film-forming material containing a fine powder of a metal oxide material is applied to a base material by a dipping method, dried, and then fired at 1000 ° C. for 2 hours to oxidize the metal. It is done by sintering the material.

Japanese Unexamined Patent Publication No. 2013-229317

Heating the substrate to a high temperature during the formation of the protective film by sintering may damage the substrate. As described above, the operating temperature of the SOFC has been lowered to about 700 to 800 ° C., and an alloy has been used as the base material. It is considered that there is no problem even if the temperature of the base material is raised to 1000 ° C. if it is heated for a short time when sintering the protective film, but the protective film can be sintered at a lower temperature. If so, there is a possibility that the durability and reliability of the solid oxide fuel cell can be improved.

In addition, for the purpose of cost reduction by improving the manufacturing process, heat treatment for firing the protective film of the base material and subsequent heat treatment (bonding of a single cell and the base material, sealing using a glass seal member, etc.) Is required to be done at once. However, for example, the glass seal member has a low upper limit of the heat resistant temperature, and when the temperature is raised to 1000 ° C., there is a risk that the sealed portion may be damaged. Therefore, there has been a demand for the realization of a protective film that can be sintered at a lower temperature.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is a method for manufacturing an inter-cell connecting member capable of sintering a protective film at a lower temperature than before, and for a solid oxide fuel cell. The purpose is to provide a method for manufacturing a cell.

The characteristic configuration of the method for manufacturing the cell-to-cell connection member used in the solid oxide fuel cell for achieving the above object is as follows.
Cobalt-manganese-based oxide Co _x Mn _y O ₄ with a slurry containing a fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc, the cell A film forming step in which a coating film is wet-deposited on the base material of the connecting member,
The point is that the base material on which the coating film is wet-formed is heat-treated at a temperature of 900 ° C. or lower, and the metal oxide fine powder is sintered to form a protective film on the surface of the base material.

Ordinarily, cobalt-manganese-based oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) protective film composed mainly of, it to properly sintered at a temperature below 1000 ° C. I can't. However, after diligent studies, the inventors have studied diligently, and by mixing the fine metal powder with the slurry containing the fine powder of cobalt-manganese-based metal oxide, which is the material of the protective film, the sintering of the protective film is promoted. I found that there are cases. Then, it was confirmed by experiments that the temperature required for sintering the protective film could be lowered by containing fine powder of metallic zinc in the slurry, and the present invention was completed.

That is, according to the above characteristic structure, cobalt-manganese-based oxide Co _x Mn _y O ₄ and fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc using a slurry containing performs the film formation step of wet deposition a coating film, the heat treatment of the coating film at a temperature of 900 ° C. or less to a substrate which is wet-formed substrate of the intercell connection member, metal oxides By having a sintering step of sintering fine powder to form a protective film on the surface of the base material, it is possible to sinter the protective film at a lower temperature than before. As a result, it is possible to reduce the thermal damage given to the base material when the protective film is sintered. It is also possible to join the single cell and the base material, seal using a glass sealing member, or the like at the same time as sintering the protective film.

The reason why the sintering temperature is lowered by the inclusion of the fine powder of metallic zinc is that when the cobalt manganese metal oxide is sintered in the sintering step, the zinc and the cobalt manganese metal are between the fine powder of the metal oxide. It is considered that the metal oxide having a spinel structure is generated by the oxide to promote the sintering of the metal oxide fine powder, and as a result, the sintering of the protective film is realized at a temperature lower than the conventional one.

In general, it is conceivable to add a low melting point sintering aid (lithium, aluminum, glass, etc.) in order to densely sinter the metal oxide at a low temperature. However, when a conventional sintering aid is used for the SOFC cell, impurities (for example, Si and B in the case of glass) volatilize at the operating temperature and inspiration of the SOFC and react at the air electrode and fuel electrode to form an electrode. It may cause so-called impurity poisoning, which greatly reduces the performance of the fuel cell. Therefore, as a sintering aid for the constituent material of SOFC, one containing an element that causes deterioration cannot be used. Further, the element contained in the sintering aid has high insulating property, and even if sintering can be promoted, the electric resistance is increased, and the element cannot be used for a material requiring electron conductivity. However, metallic zinc can react with other elements in the protective film to sinter the protective film at a low temperature, and the tightness and adhesion of the protective film are sufficient. In addition, since the electron conductivity of the protective film and the like is also maintained, it is considered that the protective film has an action / effect different from that of the conventional sintering aid.

Another characteristic configuration of the method for manufacturing the cell-cell connecting member according to the present invention is that the metal oxide fine powder contains Co _1.5 Mn _1.5 O ₄ as a main component.

It has been experimentally confirmed that the protective film can be sintered at a lower temperature than before by combining the metal oxide fine powder containing Co _1.5 Mn _1.5 O _{4 as a main component and metallic zinc.}

Another characteristic configuration of the method for producing an inter-cell connecting member according to the present invention is that the content of the fine powder of metallic zinc contained in the slurry is the same as that of the fine powder of metal oxide and the fine powder of zinc. The point is that it is 5% by weight or more and 50% by weight or less with respect to the total amount.

As described in the above characteristic configuration, the content of the fine powder of metallic zinc contained in the slurry shall be 5% by weight or more and 50% by weight or less with respect to the total amount of the fine powder of metal oxide and the fine powder of metallic zinc. Therefore, it is possible to form a protective film having good adhesion to the base material.

Another characteristic configuration of the method for producing an inter-cell connecting member according to the present invention is that the content of the fine powder of metallic zinc contained in the slurry is the same as that of the fine powder of metal oxide and the fine powder of zinc. The point is that it is 20% by weight or more and 50% by weight or less with respect to the total amount.

As described in the above characteristic configuration, the content of the fine powder of metallic zinc contained in the slurry is 20% by weight or more and 50% by weight or less with respect to the total amount of the fine powder of metal oxide and the fine powder of metallic zinc. Therefore, the heat treatment temperature of the sintering step can be further lowered, which is preferable.

Another characteristic configuration of the method for manufacturing an cell-cell connecting member according to the present invention is that the heat treatment in the sintering step is performed at a temperature of 875 ° C. or lower.

Cobalt-manganese-based oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) By using a slurry containing a fine powder of metal oxide fine powder and metallic zinc as a main component, The protective film can be sintered at a heat treatment temperature of 875 ° C. or lower. Sintering of the protective film at a relatively low temperature of 875 ° C. or lower was impossible by the conventional method without using fine powder of metallic zinc.

Another characteristic configuration of the method for manufacturing an cell-cell connecting member according to the present invention is that the heat treatment in the sintering step is performed at a temperature of 800 ° C. or higher.

Cobalt-manganese-based oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) By using a slurry containing a fine powder of metal oxide fine powder and metallic zinc as a main component, It has been experimentally confirmed that the temperature of the heat treatment in the sintering step can be lowered to 800 ° C.

In the method for manufacturing the cell-to-cell connecting member described above, the heat treatment in the sintering step can be preferably performed in a state where the single cell of the solid oxide fuel cell and the base material are not bonded.

Further, in the method for manufacturing the cell-to-cell connecting member described above, the heat treatment in the sintering step is suitable in a state where the single cell of the solid oxide fuel cell and the base material are joined to form a cell stack. Can be done. By performing the heat treatment at a temperature of 875 ° C. or lower, sealing using a glass sealing member or the like in the state of the cell stack can be performed at the same time as sintering the protective film, so that the heat treatment process can be reduced. It is possible to reduce the manufacturing cost. Further, if the cell stack is formed, the heat treatment can be performed in an air atmosphere, and the manufacturing cost can be further reduced, which is preferable.

The characteristic configuration of the manufacturing method of the solid oxide fuel cell for achieving the above object is as follows.
Cobalt-manganese-based oxide Co _x Mn _y O ₄ with a slurry containing a fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc, the cell A film forming step in which a coating film is wet-deposited on the base material of the connecting member,
A joining step of joining a single cell of a solid oxide fuel cell and the base material on which a coating film is wet-deposited to form a cell stack.
The cell stack is heat-treated at a temperature of 900 ° C. or lower to have a sintering step of sintering the metal oxide fine powder to form a protective film on the surface of the base material.

According to the above characteristic structure, cobalt-manganese-based oxide Co _x Mn _y O ₄ and fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc Using the contained slurry, a film forming step of wet-forming a coating film on the base material of the cell-to-cell connection member, and a single cell of a solid oxide fuel cell and a base material on which a coating film is wet-deposited are formed. A joining step of joining to form a cell stack and a sintering step of subjecting the cell stack to a heat treatment at a temperature of 900 ° C. or lower and sintering metal oxide fine powder to form a protective film on the surface of the base material. By having it, it becomes possible to sinter the protective film at a lower temperature than before. As a result, it is possible to reduce the thermal damage given to the base material when the protective film is sintered. Then, heat treatment is performed in a state where the single cell and the base material are joined to form a cell stack, and the protective film is sintered. Therefore, the heat treatment process is reduced and the manufacturing cost of the solid oxide fuel cell is reduced. can do.

Another characteristic configuration of the method for producing a solid oxide fuel cell according to the present invention is that the heat treatment in the sintering step is performed at a temperature of 875 ° C. or lower.

According to the above characteristic configuration, since the heat treatment in the state of the cell stack is performed at a temperature of 875 ° C. or lower, for example, sealing using a glass sealing member or the like can be performed at the same time as sintering the protective film. The heat treatment process can be further reduced to reduce the manufacturing cost of the solid oxide fuel cell. Further, if the cell stack is formed, the heat treatment can be performed in an air atmosphere, and the manufacturing cost can be further reduced, which is preferable.

Schematic diagram of solid oxide fuel cell cell Explanatory drawing of reaction at the time of operation of solid oxide fuel cell Cross-sectional view of cell-to-cell connecting member Table showing the results of the tape peeling test Graph showing the measurement result of the change of resistance value with time Image showing the cross section of the created sample Image showing the cross section of the created sample Graph showing the measurement result of the change of resistance value with time

Hereinafter, the solid oxide fuel cell cell and the cell-to-cell connection member will be described, and a manufacturing method and an experimental example will be shown. Preferable examples of the present invention will be described below, and each of these examples has been described in order to more specifically exemplify the present invention, and various changes may be made without departing from the spirit of the present invention. It is possible, and the present invention is not limited to the following description.

[Solid oxide fuel cell (SOFC)]
In the SOFC cell C shown in FIGS. 1 and 2, an air electrode 31 made of an oxygen ion-conducting porous body is provided on one side of an electrolyte membrane 30 made of a dense body of an oxygen ion-conducting solid oxide. In addition to joining, a single cell 3 formed by joining a fuel electrode 32 made of an electron-conducting porous body is provided on the other surface side of the electrolyte membrane 30.
Further, the SOFC cell C is a pair of electron conductive cells in which the single cell 3 is formed with a groove 2 for transmitting and receiving electrons to the air electrode 31 or the fuel electrode 32 and supplying air and hydrogen. It has a structure in which a gas-sealed body is appropriately sandwiched between cell-cell connecting members 1 made of an alloy or an oxide at an outer peripheral edge portion. By arranging the air electrode 31 and the cell-cell connecting member 1 in close contact with each other, the groove 2 on the air electrode 31 side functions as an air flow path 2a for supplying air to the air electrode 31. By arranging the fuel electrode 32 and the cell-cell connecting member 1 in close contact with each other, the groove 2 on the fuel electrode 32 side functions as a fuel flow path 2b for supplying hydrogen to the fuel electrode 32. The cell-to-cell connecting member 1 may have a configuration in which a member that electrically connects the interconnector and the cell C is connected.

If a general material used in each element constituting the SOFC cell C is described, for example, the material of the air electrode 31 is LaMO ₃ (for example, M = Mn, Fe, Co, Ni). _{A perovskite-type oxide of (La, AE) MO 3} in which a part of La in) is replaced with an alkaline earth metal AE (AE = Sr, Ca) can be used, and the material of the fuel electrode 32 can be used. , Ni and yttria-stabilized zirconia (YSZ) can be used, and yttria-stabilized zirconia (YSZ) can be used as the material of the electrolyte membrane 30.

Further, in the SOFC cell C described so far, as the material of the cell-to-cell connecting member 1, a perovskite-type oxide such as _{LaCrO 3 type, which is a material having excellent electron conductivity and heat resistance, or a ferrite type stainless steel} Cr-containing alloys or oxides are used, such as Fe-Cr alloys, Fe-Cr-Ni alloys, which are austenite-based stainless steels, and Ni-Cr alloys, which are nickel-based alloys.

Then, in a state where the plurality of SOFC cells C are stacked and arranged, the cells are sandwiched by applying a pressing force in the stacking direction by a plurality of bolts and nuts to form a cell stack.
In this cell stack, the cell-to-cell connecting members 1 arranged at both ends in the stacking direction need only be one in which only one of the fuel flow path 2b and the air flow path 2a is formed, and are arranged in the middle of the other. As the cell-cell connecting member 1, a member in which a fuel flow path 2b is formed on one surface and an air flow path 2a is formed on the other surface can be used. In a cell stack having such a laminated structure, the cell-cell connecting member 1 may be called a separator.
The cell stack is attached to a manifold that supplies fuel gas (hydrogen) with an adhesive such as a glass sealant. As the glass sealing material, for example, crystallized glass is used. The glass sealing material is used in places where sealing is required, such as between the single cell 3 and the cell-to-cell connecting member 1, in addition to adhering the manifold.
An SOFC having such a cell stack structure is generally called a flat plate type SOFC. In the present embodiment, the flat plate type SOFC will be described as an example, but the present invention can also be applied to SOFCs having other structures.

Then, when the SOFC provided with the SOFC cell C is operated, as shown in FIG. 2, air is introduced through the air flow path 2a formed in the cell-to-cell connecting member 1 adjacent to the air electrode 31. At the same time, hydrogen is supplied 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. Then, oxygen molecules O ₂ in the air electrode 31 is an electron e ^- is reacted with oxygen ions O ^2- is generated, the O ^2- passes through the electrolyte membrane 30 to move to the fuel electrode 32, provided at the fuel electrode 32 been H ₂ reacts with the O ^2-H ₂ O and e ^- and that is generated, the electromotive force E is generated between the pair of cell connecting member 1, outside the electromotive force E Can be taken out and used.

[Cell-to-cell connection member]
As shown in FIGS. 1 and 3, the cell-cell connecting member 1 is formed in a groove plate shape that enables connection while forming an air flow path 2a and a fuel flow path 2b with the single cell 3. As the material of the base material 11, a Cr-containing alloy or metal oxide is used as described above. An oxide film 13 is formed on the surface of the base material 11. Further, by providing the protective film 12 described below on the surface of the base material 11, Cr poisoning can be suppressed, which is suitable as a cell for a solid oxide fuel cell.

〔Protective film〕
In intercell connection member 1 according to the present embodiment, on the surface of the substrate 11, cobalt-manganese-based oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) metal oxide mainly composed of The protective film 12 is formed by using the fine powder and the fine metal powder containing metallic zinc as a main component.

The protective film 12 is formed on the base material 11 as follows. First, the above-mentioned metal oxide fine powder and metal fine powder are mixed with a solvent, a binder resin, or the like to prepare a slurry. A coating film is wet-deposited on the surface of the base material 11 using the slurry, and the coating film is cured by drying, heating, or the like. Then, the base material 11 on which the coating film is formed is heat-treated at a high temperature to burn off components such as resin in the coating film, and the metal oxide fine powder is sintered. The heat treatment can be performed not only in an atmospheric atmosphere, but also in an atmosphere in which the partial pressures of oxygen and hydrogen are controlled, in a reducing atmosphere, in an inert atmosphere, and the like.

Examples of the method for forming a coating film by wet film formation include a screen printing method, a doctor blade method, a spray coating method, an inkjet method, a spin coating method, and a dip coating method.

[Manufacturing method of cell-to-cell connecting member]
Next, a method of manufacturing the cell-cell connecting member will be described. The method for manufacturing the cell-cell connecting member includes a film forming step and a sintering step.

[Film formation step]
In the film forming step, a coating film is wet-deposited on the base material 11 of the cell-to-cell connection member 1 using a slurry containing the metal oxide fine powder and the metal fine powder. In the present embodiment, as a fine powder metal oxides, cobalt-manganese-based oxide Co _x Mn _y O ₄ a (0 <x, y <3 , x + y = 3) used as a main component, a metallic powder, Use one containing metallic zinc as the main component. It is more preferable to use a metal oxide fine powder containing Co _1.5 Mn _1.5 O _{4 as a main component.}

In the present embodiment, the content of the metal fine powder contained in the slurry is 5% by weight or more and 50% by weight or less with respect to the total amount of the metal oxide fine powder and the metal fine powder. It is more preferable that the content of the metal fine powder contained in the slurry is 20% by weight or more and 50% by weight or less with respect to the total amount of the metal oxide fine powder and the metal fine powder. It is more preferably 25% by weight or more and 50% by weight or less.

The wet film formation may be carried out by immersing the base material 11 in the slurry (dip) and pulling it up, or may use any of the methods exemplified above. The wet film formation may be performed on the entire base material 11, or may be performed on only one surface of the flat plate-shaped base material 11. In the latter case, the surface on which the protective film 12 is formed by the wet film formation is joined to the air electrode 31 of the single cell 3. The surface where the material of the base material 11 is exposed without the wet film formation is joined to the fuel electrode 32 of the single cell 3.

[Sintering step]
In the sintering step, the base material 11 on which the coating film is wet-deposited is heat-treated, and the fine powder is sintered to form the protective film 12 on the surface of the base material 11. The heat treatment is preferably performed at 900 ° C. or lower, more preferably below 900 ° C., and even more preferably at 875 ° C. or lower. The heat treatment is preferably performed at 850 ° C. or higher, more preferably at 825 ° C. or higher, and even more preferably at 800 ° C. or higher.

The heat treatment in the sintering step may be performed in a state where the single cell 3 of the solid oxide fuel cell and the base material 11 are not bonded. Various choices can be made as the atmosphere during the heat treatment. When the slurry containing the fine particles is applied to one surface of the base material 11 and the material of the base material 11 is exposed on the other surface, the heat treatment is performed under the atmosphere of an inert gas or a reducing gas. It is preferable that the material of the base material 11 can suppress the oxidation of the exposed surface.

[Manufacturing method of solid oxide fuel cell]
Subsequently, a method for manufacturing a cell for a solid oxide fuel cell will be described. A method for manufacturing a cell for a solid oxide fuel cell includes a film forming step, a joining step, and a sintering step. In the above-mentioned manufacturing method of the cell-to-cell connecting member, the protective film 12 is sintered by heat treatment in a state where the base material of the cell-to-cell connecting member 1 and the single cell 3 are not bonded, whereas the solid oxide described below is used. In the method for manufacturing a cell for a physical fuel cell, after joining the base material of the cell-to-cell connecting member 1 and the single cell 3 in a joining step, heat treatment is performed in a sintering step to sinter the protective film 12. .. Since the film forming step is the same as the method for manufacturing the cell-cell connecting member described above, the description thereof will be omitted.

[Joining step]
In the joining step, the single cell 3 of the solid oxide fuel cell and the base material 11 coated with the slurry are joined to form a cell stack. The cell stack is formed, for example, as follows. A bonding material is sandwiched (or applied) between the single cell 3 and the base material 11, and the single cell 3 and the base material 11 are alternately stacked. A slurry containing crystallized glass is applied to a part that needs to be sealed with a glass sealing material (for example, a joint part with a manifold or between a single cell 3 and a base material 11). You may. Then, the entire laminated single cell 3 and the base material 11 are fixed with bolts or the like.

[Sintering step]
In the sintering step, the cell stack is heat-treated and the fine powder is sintered to form the protective film 12 on the surface of the base material 11. The heat treatment is preferably performed at 900 ° C. or lower, more preferably below 900 ° C., and even more preferably at 875 ° C. or lower, as in the method for manufacturing the cell-cell connecting member. The heat treatment is preferably performed at 850 ° C. or higher, more preferably at 825 ° C. or higher, and even more preferably at 800 ° C. or higher.

The heat treatment is performed in a state where air is passed through the air flow path 2a and hydrogen (fuel gas) is passed through the fuel flow path 2b. Then, the surface of the base material 11 in contact with hydrogen (fuel gas) is suitable because the formation of an oxide film can be suppressed. When the cell stack is sealed using a glass sealing material, it is preferable to perform the heat treatment at a temperature lower than the heat resistant temperature of the glass sealing material. For example, when the heat resistant temperature of the glass sealing material is 950 ° C., it is preferable to perform the heat treatment at 900 ° C. because the thermal damage to the glass sealing material can be reduced. Further, in the heat treatment of the sintering step, the reduction treatment of the fuel electrode 32 may be performed at the same time.

When the slurry is mixed with fine powder of metallic zinc (Experimental Examples 1 to 6) and when not mixed (Experimental Examples 7 to 9), a protective film 12 is formed on the base material 11 of the cell-to-cell connecting member 1 to perform performance. Evaluation (tape peeling test, change in resistance value with time) and cross-sectional observation were performed.

[Experimental example 1: Formation of protective film with _{Co 1.5} Mn _1.5 O _{4 and metallic zinc]}
A SUS445J1 (ferritic stainless steel) member was used as the base material 11 of the cell-cell connecting member 1. _{Co 1.5} Mn _1.5 O ₄ was used as the metal oxide fine powder. Metallic zinc was used as the metal fine powder. 30 g of alcohol (1-methoxy-2-propanol) as a solvent, 2.7 g of hydroxypropyl cellulose as a binder resin, and the above-mentioned metal oxide fine powder and metal oxide fine powder were mixed with a paint shaker. A slurry was prepared.

In Experimental Example 1, the content of the metal fine powder contained in the slurry was set to 50% by weight with respect to the total amount of the metal oxide fine powder and the metal fine powder. Using this slurry, a coating film was formed on the base material 11 by a general dipping method. Specifically, after the first coating, drying was performed, and then the second coating was performed to form a coating film.

Subsequently, the base material 11 was heated in an atmospheric atmosphere in a box-shaped electric furnace to decompose and desorb the solvent and binder resin, and the protective film 12 was sintered. In Experimental Example 1, five types of samples were prepared at five types of heat treatment temperatures of 800 ° C., 825 ° C., 850 ° C., 875 ° C., and 900 ° C.

[Experimental Examples 2 to 6: Change in content of fine metal powder]
As Experimental Examples 2 to 6, samples were prepared by changing the content of the fine metal powder. The content of the fine metal powder is 25% by weight in Experimental Example 2, 20% by weight in Experimental Example 3, 15% by weight in Experimental Example 4, 10% by weight in Experimental Example 5, and 5% by weight in Experimental Example 6. Other conditions are the same as in Experimental Example 1. That is, for each of Experimental Examples 2 to 6, five types of samples were prepared at five types of heat treatment temperatures of 800 ° C., 825 ° C., 850 ° C., 875 ° C., and 900 ° C., respectively.

[Experimental Examples 7-9: No metal fine powder used]
As Experimental Examples 7 to 9, samples were prepared without mixing the fine metal powder with the slurry. As the metal oxide powder, Example 7 In ZnCoMnO _4, Experiment 8, Co ₂ MnO _4, using Co _1.5 Mn _1.5 O ₄ In Example 9. Regarding the heat treatment temperature, samples were prepared at 8 types in which 950 ° C, 975 ° C, and 1000 ° C were added to 5 types of Experimental Examples 1 to 6. In Experimental Example 7 (ZnCMnO ₄ ), a sample at 875 ° C. was not prepared.

[Tape peeling test]
A tape peeling test was performed on the samples of Experimental Examples 1 to 9. The tape peeling test is performed by attaching a tape (made by Diatex, adhesive tape for curing Piolan Y-09-GR) to the protective film 12, peeling off the tape, and checking whether or not a piece of the protective film 12 is attached to the tape. Was visually confirmed. When the piece of the protective film 12 was not attached to the tape, it was determined that the protective film 12 was properly formed (passed). When a piece of the protective film 12 was attached to the tape, it was determined that the protective film 12 was not properly formed (failed).

The results of the tape peeling test are shown in the table of FIG. Passes are indicated by "○" and failures are indicated by "×". The "-" column indicates that a sample has not been created.

In Experimental Examples 1 to 3, all samples at 800 ° C. to 900 ° C. passed. In Experimental Examples 4 and 5, samples at 825 ° C to 900 ° C passed, but samples at 800 ° C failed. In Experimental Example 6, samples at 850 ° C. to 900 ° C. passed, but samples at 800 ° C. and 825 ° C. failed.

In Experimental Examples 7 to 9 in which metallic zinc was not added to the slurry, all the samples below 875 ° C. were rejected. In Experimental Examples 7 and 9, samples at 900 ° C to 1000 ° C passed. In Experimental Example 8, only the sample at 1000 ° C. passed.

Considering from the above experimental results, Experimental Examples 7 to 9 in which metallic zinc was not added to the slurry did not pass the temperature below 875 ° C, whereas Experimental Examples 1 to 6 in which metallic zinc was added to the slurry did not pass the temperature of 875 ° C or lower. Since the peeling test was passed below, by adding metallic zinc to the slurry, the protective film 12 can be sintered at a lower temperature (875 ° C or lower) than when it is not added, and the protective film can be sintered. An improvement in the adhesion strength between the 12 and the base material 11 is observed. The content of metallic zinc was rejected at 800 ° C. and 825 ° C. in Experimental Example 6 of 5% by weight, 800 ° C. in Experimental Example 5 of 10% by weight, and 800 ° C. in Experimental Example 4 of 15% by weight. On the other hand, in Experimental Examples 1 to 3 having a content of 20% by weight or more, all the samples passed. From this result, there is a correlation between the lower limit temperature at which the protective film 12 can be formed and the content of metallic zinc, and the higher the content, the lower the temperature at which the protective film 12 can be sintered. Is recognized.

[Measurement of change over time in resistance value under SOFC usage environment]
The cell-cell connecting member 1 (heat treatment temperature: 800 ° C.) prepared in Experimental Examples 2, 6 and 7 was placed in an SOFC usage environment, and the change in resistance value with time was measured. Specifically, a conductive ceramic paste was applied to both sides of the cell-cell connecting member 1, a platinum mesh current collector was attached, and the mixture was installed in an electric furnace at 850 ° C., and the resistance value was measured. Table 1 shows the values of the surface resistance (unit: mΩ · cm ^{2) at the initial stage of measurement.} Further, FIG. 5 shows a graph of the transition of the surface resistance up to 300 hours.

Regarding the surface resistance at the initial stage of measurement, the surface resistance was smaller in Experimental Examples 2 and 6 in which metallic zinc was added to the slurry than in Experimental Example 7 in which metallic zinc was not added to the slurry. Therefore, it is recognized that the cell-cell connecting member 1 having a smaller surface resistance was obtained by adding metallic zinc to the slurry to form the protective film 12.

Further, as shown in the graph of FIG. 5, in Experimental Example 7 in which metallic zinc was not added to the slurry, the surface resistance increased and exceeded 100 mΩ · cm ^{2 in the} vicinity of 300 hours. On the other hand, in Experimental Examples 2 and 6 in which metallic zinc was added to the slurry, the surface resistance ^{did not exceed 100 mΩ · cm 2} even after 300 hours, although the surface resistance increased with time, which was higher than that of Experimental Example 7. The surface resistance is small. Therefore, it is recognized that by adding metallic zinc to the slurry to form the protective film 12, the cell-cell connecting member 1 in which the increase in surface resistance with time is further suppressed is obtained.

FIG. 8 shows a graph of the transition of the surface resistance up to 4500 hours. Table 2 shows the deterioration rate (change amount of resistance value per 1000 hours) from 3500 hours to 4500 hours.

As shown in the graph of FIG. 8, in Experimental Examples 2 and 6 in which metallic zinc was added to the slurry, the resistance value was stable for a long period of time, and no problematic behavior such as a rapid increase in the resistance value was observed. Was confirmed. Further, as shown in Table 2, in Experimental Examples 2 and 6 in which metallic zinc was added to the slurry, the deterioration rate was smaller than that in Experimental Example 7 in which metallic zinc was not added to the slurry. In particular, in Experimental Example 2 (25% by weight added), the deterioration rate could be reduced to 1/5 or less as compared with Experimental Example 7 (without addition). From the above results, it is recognized that by adding metallic zinc to the slurry to form the protective film 12, the cell-cell connecting member 1 in which the increase in electrical resistance with time is suppressed for a long period of time was obtained. ..

[Cross-section observation with an electron microscope]
6 and 7 show images of the cross section of the prepared sample observed with an electron microscope. FIG. 6 is a sample of Experimental Example 2 and FIG. 7 is a sample of Experimental Example 6, both of which have a heat treatment temperature of 800 ° C. From the images of FIGS. 6 and 7, it is recognized that the protective film 12 is appropriately formed on the substrate 11 in any of the samples of Experimental Examples 7 and 8.

From the above experimental examples, performance evaluation, and cross-sectional observation results, it was confirmed that a good protective film 12 can be formed by adding metallic zinc to the slurry to form the protective film 12. It was also confirmed that when metallic zinc was added to the slurry, the temperature of the heat treatment could be lowered as compared with the case where it was not added.

According to the method for manufacturing a cell-to-cell connecting member and the method for manufacturing a cell for a solid oxide fuel cell of the present invention, it is possible to sinter the protective film at a lower temperature than before.

1: Cell-to-cell connecting member 2: Groove 2a: Air flow path 2b: Fuel flow path 3: Single cell 4: Bonding material 11: Base material 12: Protective film 30: Electrolyte film 31: Air electrode 32: Fuel electrode C: Solid Oxide fuel cell cell

Claims (12)

A method for manufacturing an inter-cell connection member used in a cell for a solid oxide fuel cell.
Cobalt-manganese-based oxide Co _x Mn _y O ₄ with a slurry containing a fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc, the cell A film forming step in which a coating film is wet-deposited on the base material of the connecting member,
Cell-to-cell connection having a sintering step in which the base material on which the coating film is wet-formed is heat-treated at a temperature of 900 ° C. or lower and the metal oxide fine powder is sintered to form a protective film on the surface of the base material. Manufacturing method of parts. The method for manufacturing an inter-cell connecting member according to claim 1, wherein the metal oxide fine powder contains Co _1.5 Mn _1.5 O _{4 as a main component.} Claim 1 or that the content of the fine powder of metallic zinc contained in the slurry is 5% by weight or more and 50% by weight or less with respect to the total amount of the fine powder of metal oxide and the fine powder of zinc metal. 2. The method for manufacturing an inter-cell connecting member according to 2. Claim 1 or that the content of the fine powder of metallic zinc contained in the slurry is 20% by weight or more and 50% by weight or less with respect to the total amount of the fine powder of metal oxide and the fine powder of zinc metal. 2. The method for manufacturing an inter-cell connecting member according to 2. The method for manufacturing an inter-cell connecting member according to any one of claims 1 to 4, wherein the heat treatment in the sintering step is performed at a temperature of 875 ° C. or lower. The method for manufacturing an inter-cell connecting member according to any one of claims 1 to 5, wherein the heat treatment in the sintering step is performed at a temperature of 800 ° C. or higher. The cell-to-cell connecting member according to any one of claims 1 to 6, wherein the heat treatment in the sintering step is performed in a state where the single cell of the solid oxide fuel cell and the base material are not bonded. Production method. Claims 1 to 1 that the heat treatment in the sintering step is performed at a temperature of 875 ° C. or lower in a state where a single cell of a solid oxide fuel cell and the base material are joined to form a cell stack. The method for manufacturing an inter-cell connecting member according to any one of 6. The method for manufacturing an inter-cell connecting member according to claim 8, wherein the heat treatment in the sintering step is performed in an air atmosphere. A method for manufacturing solid oxide fuel cell cells.
Cobalt-manganese-based oxide Co _x Mn _y O ₄ with a slurry containing a fine powder (0 <x, y <3 , x + y = 3) metal oxide as a main component powder and metallic zinc, the cell A film forming step in which a coating film is wet-deposited on the base material of the connecting member,
A joining step of joining a single cell of a solid oxide fuel cell and the base material on which a coating film is wet-deposited to form a cell stack.
A cell for a solid oxide fuel cell having a sintering step in which the cell stack is heat-treated at a temperature of 900 ° C. or lower and the metal oxide fine powder is sintered to form a protective film on the surface of a base material. Production method. The method for producing a solid oxide fuel cell according to claim 10, wherein the heat treatment in the sintering step is performed at a temperature of 875 ° C. or lower. The method for producing a solid oxide fuel cell according to claim 10 or 11, wherein the heat treatment in the sintering step is performed in an air atmosphere.

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