JP2021153017A - Cell-cell connection member, solid oxide fuel cell, sofc monogeneration system, sofc cogeneration system, and manufacturing method of cell-cell connection member - Google Patents

Abstract

To provide a cell-cell connection member that exhibits good performance on both the fuel electrode side and the air electrode side while a procedure for forming the coating is simple.SOLUTION: A cell-to-cell connection member used for a solid oxide fuel cell 1 includes a metal base material 11 made of stainless steel, a substrate coating layer 13 formed of Ni and Co, which is formed on a surface on the side joined to a fuel pole 32 of a single cell 3 constituting the cell for the solid oxide fuel cell and a surface on the side joined to the air electrode 31 of the single cell 3 on the surface of the metal base material, and a protective film 12 formed of an oxide containing Mn, which is formed on the surface of the base material coating layer 13 on the side bonded to the air electrode 31 of the single cell 3.SELECTED DRAWING: Figure 3

Description

The present invention relates to an inter-cell connecting member used in a cell for a solid oxide fuel cell, a solid oxide fuel cell, an SOFC monogeneration system, an SOFC cogeneration system, and an inter-cell connecting member. Regarding the manufacturing method.

A cell for a solid oxide fuel cell (hereinafter, appropriately referred to as “SOFC”) is configured to include a single cell having an air electrode and a fuel electrode and an inter-cell connecting member. Then, a part of the cell-cell connecting member is joined to the fuel electrode, and the other part of the cell-cell connecting member is joined to the air electrode. The cell-to-cell connecting member used in such an SOFC cell is manufactured by using a metal base material made of stainless steel having excellent electron conductivity and heat resistance.

In the part of the cell-to-cell connecting member used on the fuel electrode side, phosphorus volatilized from the stainless steel constituting the cell-cell connecting member reacts with Ni, which is the main component of the fuel electrode of the SOFC cell, to react with the fuel electrode. It may cause deterioration such as inducing volatilization of Ni from. As an example, Ni used for the fuel electrode of SOFC cells generally has a vapor pressure with respect to Ni in a metallic state when it reacts with impurities such as phosphorus volatilized from the cell-cell connection member under high temperature operating conditions. Rise. Therefore, Ni volatilizes from the fuel electrode material (mainly Ni and the cermet of the oxide of the electrolyte material), the Ni metal network in the fuel electrode is divided, the electron conductivity decreases, and the cell performance deteriorates (deteriorates). Occurs. In this case, phosphorus contained in the stainless steel of the metal base material constituting the cell-cell connecting member has a low concentration of, for example, about several hundred ppm, but it has been reported that it causes deterioration of the fuel electrode.

Patent Document 1 (Patent No. 3855043) describes a method for producing ultra-low phosphorus stainless steel. By using the stainless steel manufactured by this manufacturing method as the metal base material of the cell-cell connecting member, there is a possibility that the deterioration of the fuel electrode as described above can be suppressed.

Another problem arises in the portion of the cell-to-cell connecting member that is used on the air electrode side. Specifically, since the stainless steel constituting the cell-cell connecting member contains Cr, an oxidation-resistant film Cr ₂ O ₃ is formed in the portion used on the air electrode side under high temperature operating conditions. .. This oxide film is a high-resistance layer, and has durability such as reducing the power generation output of the fuel cell and reacting with the air electrode of the SOFC cell due to the evaporation of Cr from stainless steel to significantly reduce the electrode performance. There is a problem with sexuality.

Patent Document 2 (International Publication No. 2007/083627) describes a firing process in which a cell-cell connecting member manufactured using a metal base material such as a stainless alloy containing Cr and an air electrode are bonded to each other. It is described that the alloy or oxide is in a Cr (VI) oxide-suppressed state in which the formation of Cr (VI) oxide is suppressed. In order to bring the Cr (VI) oxide to the suppressed state, an n-type semiconductor film made of an oxide having _{a standard free energy of WO 3 or less is formed on the surface of the alloy or oxide before the firing treatment.} It is described that the film forming treatment is performed.
In this way, in order _{to suppress the formation of high-resistance Cr 2} O ₃ and prevent scattering of Cr due to evaporation from stainless steel, the surface of the metal substrate has high electron conductivity. A ceramic coating is formed as a protective film. By applying such a ceramic coating, it has become possible to use an inexpensive stainless steel material as a material for a metal base material.

Japanese Patent No. 3855043 International Publication No. 2007/083627

As described in Patent Document 1, a method for producing stainless steel having a low phosphorus concentration has been proposed, but there is a problem that the cost of the cell-to-cell connecting member increases when such stainless steel is used. Moreover, phosphorus contained in stainless steel cannot be completely eliminated.

The method described in Patent Document 2 is a countermeasure for the surface of the metal base material constituting the cell-to-cell connecting member on the side bonded to the air electrode of the single cell constituting the solid oxide fuel cell. However, it is not a measure for the surface on the side joined to the fuel electrode.

As described above, the conventional countermeasures are a countermeasure for the surface of the metal base material constituting the cell-cell connecting member on the side bonded to the air electrode and a countermeasure for the surface bonded to the fuel electrode. Have been discussed separately. That is, the coating design is not performed in consideration of both the side bonded to the fuel electrode and the side bonded to the air electrode on the surface of the cell-cell connecting member.

The present invention has been made in view of the above problems, and an object of the present invention is an inter-cell connecting member that exhibits good performance on both the fuel electrode side and the air electrode side while the procedure for forming a coating is simple. , And, a solid oxide fuel cell, an SOFC monogeneration system, an SOFC cogeneration system, and a method for manufacturing an inter-cell connection member.

The characteristic configuration of the cell-to-cell connecting member according to the present invention for achieving the above object is an inter-cell connecting member used in a cell for a solid oxide fuel cell.
A metal base material made of stainless steel and
On the surface of the metal base material, the surface on the side bonded to the fuel electrode of the single cell constituting the solid oxide fuel cell and the surface on the side bonded to the air electrode of the single cell. A base material coating layer composed of Ni and Co, which is formed,
The point is that the surface of the base material coating layer is provided with a protective film formed of an oxide containing Mn, which is formed on the surface of the single cell on the side bonded to the air electrode.
Here, the protective film can be formed by using any one of Mn oxide, Co-Mn-based oxide, Ni-Mn-based oxide, and Cu-Mn-based oxide.

According to the above characteristic configuration, among the surfaces of the metal base material constituting the cell-cell connecting member, the surface on the side joined to the fuel electrode of the single cell constituting the solid oxide fuel cell, and the air electrode. Since the same base material coating layer is attached to both surfaces on the side to be joined to, it is not necessary to cover the metal base material with a mask or the like when forming the base material coating layer. As a result, there is an advantage that the procedure for forming the base material coating layer on the surface of the metal base material is simplified and the manufacturing cost of the cell-to-cell connecting member is low.
Further, among the surfaces of the metal base material constituting the cell-cell connecting member, the surface on the side bonded to the fuel electrode of the single cell constituting the solid oxide fuel cell is formed by using Ni and Co. The base material coating layer to be formed is formed. As a result, even if phosphorus is contained in the metal base material, the phosphorus is suppressed from volatilizing from the metal base material. As a result, when the cell-cell connecting member is joined to the fuel electrode of the solid oxide fuel cell, it is possible to prevent phosphorus from adversely affecting the fuel electrode. In addition, since Ni and Co in the base material coating layer on the fuel electrode side are exposed to a reduced state during power generation operation, they exist in a metallic state and have sufficient electronic conductivity, so an increase in electrical resistance is taken into consideration. It doesn't have to be.
Furthermore, on the surface of the metal base material of the cell-to-cell connecting member, the surface on the side joined to the air electrode of the single cell constituting the solid oxide fuel cell is formed by using Ni and Co. A base material coating layer is formed, and a protective film formed by using an oxide containing Mn is formed on the surface of the base material coating layer. That is, on the surface of the metal base material of the cell-to-cell connecting member, the surface on the side bonded to the air electrode of the single cell constituting the solid oxide fuel cell is formed with a base material coating layer and a protective film. Since a layer made of a ternary material containing Ni, Co, and Mn is formed, the formation of highly resistant Cr ₂ O ₃ is suppressed and the scattering of Cr from the metal substrate due to evaporation is prevented. NS.

In this way, the base material coating layer formed on both the surface of the metal base material of the cell-cell connecting member on the side bonded to the fuel electrode and the surface on the side bonded to the air electrode is bonded to the fuel electrode. On the surface on the side to be bonded, the effect of suppressing the volatilization of phosphorus from the metal base material is exhibited, and on the surface on the side bonded to the air electrode, high resistance Cr ₂ O ₃ is formed together with the protective film. It is suppressed and exerts the effect of preventing scattering of Cr due to evaporation from the metal substrate. That is, in this feature configuration, the procedure for forming the coating is performed by considering both the side bonded to the fuel electrode and the side bonded to the air electrode on the surface of the cell-cell connecting member. It is possible to provide an inter-cell connecting member that is simple but exhibits good performance on both the fuel electrode side and the air electrode side.

The characteristic configuration of the solid oxide fuel cell according to the present invention is that a plurality of cells for a solid oxide fuel cell including the cell-to-cell connecting member and the single cell are laminated.

According to the above characteristic configuration, it is possible to obtain a solid oxide fuel cell capable of suppressing phosphorus poisoning of the fuel electrode and suppressing Cr poisoning of the air electrode.

The characteristic configuration of the SOFC monogeneration system according to the present invention is that the solid oxide fuel cell is provided and the electric power generated by the solid oxide fuel cell is supplied to the electric power load.

According to the above characteristic configuration, it is possible to realize an SOFC monogeneration system that supplies the electric power generated by the solid oxide fuel cell to the electric power load by using the solid oxide fuel cell having high power generation performance.

The characteristic configuration of the SOFC cogeneration system according to the present invention is that the solid oxide fuel cell is provided and the power and heat generated by the solid oxide fuel cell are supplied to the power load and the heat load.

According to the above characteristic configuration, it is possible to realize an SOFC cogeneration system that supplies the power and heat generated by the solid oxide fuel cell to the power load and the heat load by using the solid oxide fuel cell having high power generation performance. ..

The characteristic configuration of the method for manufacturing an inter-cell connecting member according to the present invention is a method for manufacturing an inter-cell connecting member used in a cell for a solid oxide fuel cell.
Of the surface of the metal base material made of stainless steel, the surface on the side to be joined to the fuel electrode of the single cell constituting the solid oxide fuel cell and the air electrode of the single cell are joined. A film forming step of forming a substrate coating layer composed of Ni and Co on the surface on the side to be formed.
A point having a protective film forming step of forming a protective film formed by using an oxide containing Mn on the surface of the base material coating layer on the side of the single cell to be joined to the air electrode. It is in.

According to the above characteristic configuration, both the surface of the metal base material constituting the cell-cell connecting member and the surface of the side bonded to the fuel electrode and the surface of the side bonded to the air electrode are formed by the film forming process. Since the same base material coating layer is attached to the base material coating layer, it is not necessary to cover the metal base material with a mask or the like when forming the base material coating layer. As a result, there is an advantage that the procedure for forming the base material coating layer on the surface of the metal base material is simplified and the manufacturing cost of the cell-to-cell connecting member is low.
Further, in the film forming step, Ni And Co are used to form a substrate coating layer. As a result, even if phosphorus is contained in the metal base material, the phosphorus is suppressed from volatilizing from the metal base material. As a result, when the cell-cell connecting member is joined to the fuel electrode of the solid oxide fuel cell, it is possible to prevent phosphorus from adversely affecting the fuel electrode. In addition, since Ni and Co in the base material coating layer on the fuel electrode side are exposed to a reduced state during power generation operation, they exist in a metallic state and have sufficient electronic conductivity, so an increase in electrical resistance is taken into consideration. It doesn't have to be.
Furthermore, on the surface of the metal base material of the cell-to-cell connecting member, the surface on the side joined to the air electrode of the single cell constituting the solid oxide fuel cell is formed by using Ni and Co. A base material coating layer is formed, and a protective film formed by using an oxide containing Mn is formed on the surface of the base material coating layer. That is, on the surface of the metal base material of the cell-to-cell connecting member, the surface on the side bonded to the air electrode of the single cell constituting the solid oxide fuel cell is formed with a base material coating layer and a protective film. Since a layer made of a ternary material containing Ni, Co, and Mn is formed, the formation of highly resistant Cr ₂ O ₃ is suppressed and the scattering of Cr from the metal substrate due to evaporation is prevented. NS.

In this way, the base material coating layer formed on both the surface of the metal base material of the cell-cell connecting member on the side bonded to the fuel electrode and the surface on the side bonded to the air electrode is bonded to the fuel electrode. On the surface on the side to be bonded, the effect of suppressing the volatilization of phosphorus from the metal base material is exhibited, and on the surface on the side bonded to the air electrode, high resistance Cr ₂ O ₃ is formed together with the protective film. It is suppressed and exerts the effect of preventing scattering of Cr due to evaporation from the metal substrate. That is, in this feature configuration, the procedure for forming the coating is performed by considering both the side bonded to the fuel electrode and the side bonded to the air electrode on the surface of the cell-cell connecting member. It is possible to provide a method for manufacturing an inter-cell connecting member which is simple but exhibits good performance on both the fuel electrode side and the air electrode side.

It is a schematic diagram of a solid oxide fuel cell. It is explanatory drawing of the reaction at the time of operation of a solid oxide fuel cell. It is sectional drawing which shows the structure of the cell-cell connecting member. It is a figure which shows the structure of the system including the solid oxide fuel cell.

Hereinafter, the cell-to-cell connecting member 1 used in the solid oxide fuel cell (SOFC) cell according to the embodiment of the present invention, its manufacturing method, and the solid oxide fuel cell will be described with reference to the drawings.
FIG. 1 is a schematic view of a solid oxide fuel cell. FIG. 2 is an explanatory diagram of the reaction during operation of the solid oxide fuel cell. As shown in FIGS. 1 and 2, the SOFC cell (solid oxide fuel cell) C includes a single cell 3 and an inter-cell connecting member 1. The single cell 3 includes an air electrode 31 and a fuel electrode 32. Specifically, oxygen ions and electrons are conducted on one side of an electrolyte membrane 30 made of a dense body of an oxygen ion conductive solid oxide. The air electrode 31 made of a porous body is bonded, and the fuel electrode 32 made of an electron-conducting porous body is bonded to the other surface side of the electrolyte membrane 30.

In the SOFC cell C, the single cell 3 is used between a pair of electron-conducting cells in which a groove 2 is formed for transferring electrons to and from the air electrode 31 or the fuel electrode 32 and supplying air and hydrogen. The connecting member 1 has a structure in which the gas seal body is sandwiched between the outer peripheral edges as appropriate. By arranging the air electrode 31 and the cell-cell connecting member 1 in close contact with each other, 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. By arranging the fuel electrode 32 and the cell-cell connecting member 1 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.

To add a description of the general material used in each element constituting the single cell 3, for example, as the material of the air electrode 31, La in LaMO ₃ (for example, M = Mn, Fe, Co, Ni) A perovskite-type oxide of _{(La, AE) MO 3} in which a part of the metalloid AE (AE = Sr, Ca) is substituted can be used. As the material of the fuel electrode 32, for example, a cermet of Ni and yttria-stabilized zirconia (YSZ) can be used, and as the material of the electrolyte membrane 30, for example, yttria-stabilized zirconia (YSZ) or the like can be used.

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 way, a solid oxide fuel cell (cell stack) in which a plurality of SOFC cells C including the cell-to-cell connecting member 1 and the single cell 3 are laminated can be obtained. In this cell stack, the cell-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. A solid oxide fuel cell having such a cell stack structure is generally called a flat plate solid oxide fuel cell. In the present embodiment, a flat plate type solid oxide fuel cell will be described as an example, but the present invention is also applicable to a solid oxide fuel cell having another structure.

When the solid oxide fuel cell (cell stack) provided with the SOFC cell C is operated, as shown in FIG. 2, the air flow formed in the cell-to-cell connecting member 1 adjacent to the air electrode 31 is formed. Air is supplied through the passage 2a, and hydrogen is supplied through the fuel flow path 2b formed in the cell-to-cell connecting member 1 adjacent to the fuel electrode 32, and operates at an operating temperature of, for example, about 800 ° C. .. Then, the oxygen molecule O ₂ reacts with the electron e ^{− at} the air electrode 31 to generate an oxygen ion O ^2- , and the O ^2- moves to the fuel electrode 32 through the electrolyte membrane 30 and is supplied 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 1>
FIG. 3 is a cross-sectional view showing the structure of the cell-to-cell connecting member 1. As shown in the figure, the cell-to-cell connecting member 1 is formed on a metal base material 11 made of stainless steel and a fuel electrode 32 of a single cell 3 forming the SOFC cell C on the surface of the metal base material 11. A base material coating layer 13 made of Ni and Co, and a base material coating layer 13 formed on the surface on the side to be joined and the surface on the side to be joined to the air electrode 31 of the single cell 3. A protective film 12 formed of an oxide containing Mn, which is formed on the surface of the surface on the side bonded to the air electrode 31 of the single cell 3, is provided.

That is, in the method for manufacturing the cell-to-cell connecting member 1 of the present embodiment, the surface of the metal base material 11 made of stainless steel is joined to the fuel electrode 32 of the single cell 3 constituting the SOFC cell C. A base material composed of Ni and Co on the surface on the side to be joined to the air electrode 31 of the single cell 3 (in the case of FIG. 3, the entire surface of the metal base material 11). The film forming step of forming the coating layer 13 and the protection formed by using an oxide containing Mn on the surface of the surface of the base material coating layer 13 on the side bonded to the air electrode 31 of the single cell 3. It has a protective film forming step of forming the film 12.

Ferrite-based stainless steel is often used as the metal base material 11 of the cell-cell connecting member 1, but Fe-Cr-Ni alloy, which is an austenite-based stainless steel having excellent heat resistance, and Ni, which is a nickel-based alloy. -Cr alloy etc. may be used. Further, instead of an alloy, _{a metal oxide typified by (La, Ca) CrO 3} (calcium doprantan chromite) may be used. As will be described later, the stainless steel constituting the metal base material 11 contains a trace amount of phosphorus.

<Base coating layer 13>
As described above, on both the surface of the metal base material 11 on the side bonded to the fuel electrode 32 of the single cell 3 constituting the SOFC cell C and the surface bonded to the air electrode 31. Is formed with a base material coating layer 13. As in the example shown in FIG. 3, the base material coating layer 13 may be formed on the entire surface of the metal base material 11. The base material coating layer 13 is formed by coating the metal base material 11 with Ni (nickel) and Co (cobalt). The film thickness of the base material coating layer 13 can be appropriately set, for example, 5 μm. As a film forming method for the base material coating layer 13, a plating method, an electrodeposition coating method, a sputtering method, or the like can be used.

<Protective film 12>
As described above, the protective film 12 is formed on the surface of the metal base material 11 on the side of the single cell 3 constituting the SOFC cell C that is joined to the air electrode 31. The protective film 12 is formed as a thick film by coating a metal base material 11 with a coating film forming material containing a conductive ceramic material. The thickness of the thick film is preferably 0.1 μm to 100 μm.

Examples of the film forming method for the protective film 12 include the following.
For example, it can be formed by a wet coating method or a dry coating method. Examples of the wet coating method include a screen printing method, a doctor blade method, a spray coating method, an inkjet method, a spin coating method, a dip coating method, an electroplating method, an electroless plating method, and an electrodeposition coating method. Examples of the dry coating method include a vapor deposition method, a sputtering method, an ion plating method, a chemical vapor deposition (CVD) method, an electrochemical vapor deposition (EVD) method, an ion beam method, a laser ablation method, and an atmospheric pressure plasma. Examples thereof include a film forming method, a reduced pressure plasma film forming method, and a thermal spraying method.

However, as the dry coating method, the CVD / EVD method, the thermal spraying method, etc. have drawbacks such as the complicated process for forming the protective film and the unstable composition of the protective film 12, so that they can be replaced with these methods. It is also considered to form the protective film 12 by the laser ablation method. Further, when the laser ablation method is adopted, the manufacturing cost is higher than that of the CVD / EVD method and the thermal spraying method. Therefore, in reality, the wet coating method is adopted as a technique capable of manufacturing the protective film 12 at low cost. In many cases.

For example, if the electrodeposition coating method is applied, the protective film 12 can be formed by the following method.
The metal oxide fine particles were dispersed so as to be 100 g per liter of the electrodeposition solution, and electrodeposition coating was performed using a mixed solution containing an anionic resin such as polyacrylic acid. Here, (metal oxide fine particles: anionic resin) = (1: 1) (mass ratio). By using a mixed liquid and energizing the electrode plate of SUS304 with the metal base material 11 as a positive and the counter electrode as a negative polarity, the air of the single cell 3 constituting the SOFC cell C on the surface of the metal base material 11 is applied. An uncured electrodeposition coating film is formed on the surface of the side bonded to the pole 31. Electrodeposition coating is carried out according to a known method, for example, by immersing the metal base material 11 completely or partially in an energizing tank filled with a mixed liquid to form an anode and energizing. The electrodeposition coating conditions are also not particularly limited, and are wide depending on various conditions such as the type of metal as the metal base material 11, the type of mixed liquid, the size and shape of the energizing tank, and the application of the obtained inter-cell connecting member 1. It can be appropriately selected from the range, but usually, the bath temperature (mixed liquid temperature) is about 10 to 40 ° C., the applied voltage is about 10 to 450 V, the voltage application time is about 1 to 10 minutes, and the liquid temperature of the mixed liquid is 10 to 40 ° C. And it is sufficient. The film thickness of the electrodeposited coating film can be controlled by changing the electrodeposition voltage and the electrodeposition time. Further, various pretreatments can be performed on the metal base material 11. By heat-treating the metal base material 11 on which the uncured electrodeposition coating film is formed, a cured electrodeposition coating film is formed on the surface of the metal base material 11. The heat treatment includes pre-drying to dry the electrodeposition coating film and curing heating to cure the electrodeposition coating film, and the curing heating is performed after the pre-drying. Then, it was fired at 1000 ° C. for 2 hours using an electric furnace, and then slowly cooled to obtain an inter-cell connecting member 1.

As the fine particles of the metal oxide used as the material for forming the protective film, metal oxide fine particles made of an oxide containing Mn are used. Specifically, the fine particles of the metal oxide used as the material for forming the protective film include Mn (manganese) oxide, Co-Mn-based (cobalt-manganese-based) oxide, and Ni-Mn-based (nickel-manganese-based) oxidation. Any one of a substance and a Cu-Mn-based (copper-manganese-based) oxide is used.

As described above, among the surfaces of the metal base material 11, the surface of the single cell 3 constituting the SOFC cell C on the side joined to the fuel electrode 32 and the surface on the side joined to the air pole 31 are base materials. Between cells in which the coating layer 13 is formed and a protective film 12 is formed on the surface of the base material coating layer 13 on the side of the surface of the base material coating layer 13 that is joined to the air electrode 31 of the single cell 3 constituting the SOFC cell C. The connecting member 1 is obtained. As described above, in the cell-cell connecting member 1 of the present embodiment, on both the surface of the metal base material 11 on the side bonded to the fuel electrode 32 and the surface bonded to the air electrode 31. Since the base material coating layer 13 may adhere, that is, it is not necessary to cover the metal base material 11 with a mask or the like when forming the base material coating layer 13, it is based on the surface of the metal base material 11 in the film forming process. The procedure for forming the material coating layer 13 is simplified. As a result, there is an advantage that the manufacturing cost of the cell-to-cell connecting member 1 is lowered.

<Adhesion / joining with joining materials>
The cell stack of the fuel cell is formed by sequentially joining the cell-to-cell connecting member 1 and the single cell 3 produced as described above in series. Specifically, the surface of the cell-to-cell connecting member 1 on which the protective film 12 is formed on the side of the air electrode 31 is adhesively bonded to the air electrode 31 of the single cell 3 constituting the SOFC cell C by using the bonding material 4. do.

As the bonding material 4, Co-Mn-based oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) with respect to the protective film 12 made of, Co-Mn-based oxide _Co x Mn _y When _{the bonding material of O 4} (0 ≦ x, y ≦ 3, x + y = 3), more specifically, the material for forming the protective film 12 is (Co, Mn) O ₄ , the bonding material 4 is Co _{1 .5 Mn 1.5 O 4, Co 2} MnO 4, Co 3 O 4 such as an oxide material can be used for forming the material of the protective film 12 is _{Co x Mn y O 4 (0} <x, y <3 , X + y = 3), the bonding material is Co _{x +} αMn _y− αO ₄ (0 ≦ x, y, α ≦ 3, x + y = 3), and more specifically, the material for forming the protective film 12 is Co. If it is _1.5 Mn _1.5 O _4, as the bonding material _4, it is possible to use an oxide material such as _{Co 2 MnO 4, Co 3 O} 4. From the experimental examples described later, these materials are protective films in which element diffusion occurs between the protective film 12 and the air electrode 31 under the energizing conditions of the fuel cell, and diffusion bonding occurs between the protective film 12 and the material forming the protective film 12. It is preferable to select so that the bonding material 4 made of the forming material 12 and the oxide material of the same type is used for adhesive bonding.
That is, it is considered that if the bonding material 4 is selected, element diffusion occurs under the energizing conditions of the fuel cell, and diffusion bonding occurs between the bonding material 4 and the material forming the protective film 12.
Further, while firing the protective film 12 requires heating at, for example, 1000 ° C., bonding / joining with the bonding material 4 can be performed at a low temperature such as the operating temperature of the fuel cell to 950 ° C. This is because the bonding between the metal base material 11 and the protective film 12 requires a relatively high temperature (a temperature slightly higher than the operating temperature of the fuel cell), whereas the air electrode 31, the bonding material 4, and the bonding material are required. It is considered that the adhesive bonding between 4 and the protective film 12 can be performed at a relatively low temperature because diffusion bonding can be expected.

<Effect of providing the base material coating layer 13 on the surface on the side joined to the fuel electrode 32>
Below, of the surface of the metal base material 11 used in manufacturing the cell-to-cell connecting member 1, the base material coating layer 13 is formed on the surface of the single cell 3 constituting the SOFC cell C on the side to be joined to the fuel electrode 32. Describe the effect of providing. Here, the sample (Example 1) in which the base material coating layer 13 is formed on the surface of the metal base material 11 and then heat-treated, and the metal base material 11 in which the base material coating layer 13 is not formed are heat-treated. A sample (Comparative Example 1) and a sample (Comparative Example 2) in which the metal base material 11 on which the base material coating layer 13 was not formed was heat-treated were prepared and subjected to ICP analysis.

The heat treatment for the samples of Example 1 and Comparative Example 2 was performed in order to simulate the heat history received by the cell-to-cell connecting member 1 during the production of the cell stack and the operation of the fuel cell. Specifically, the influence of heat received when the cell stack is formed by using the cell-to-cell connecting member 1 and the single cell 3 (heat history during manufacturing) and the heat received when power generation operation is performed using the cell stack. Considering the effect (heat history during operation). Then, as a simulation of the heat history during manufacturing, the samples of Example 1 and Comparative Example 2 are heated at 800 ° C. in the atmosphere to simulate firing for forming the protective film 12 on the cell-to-cell connecting member 1. A treatment was performed in which heating and heating at 700 ° C. in a reducing atmosphere (hydrogen atmosphere) simulating the reduction of the cell stack were performed for 2 hours each. As a simulation of the heat history during operation, treatment was performed in a hydrogen / steam atmosphere under the temperature and time conditions described later.

[Sample of Example 1: With base material coating layer 13]
A general-purpose stainless steel material (corresponding to SUS445J1) was used as the metal base material 11, and Ni was formed on the surface of the metal base material 11 by a plating method to form a base material coating layer 13. Then, as a simulation of the heat history during production, a process of firing in the air at 800 ° C. and a reducing atmosphere (hydrogen atmosphere) at 700 ° C. for 2 hours each was performed. Further, as a simulation of the heat history during operation, heat treatment was performed for a predetermined time (24 hours, 48 hours, 300 hours) in a hydrogen / steam atmosphere. The temperature during this heat treatment is 850 ° C or 900 ° C.

Since the base material coating layer 13 used in Example 1 does not contain Co, it is not composed of Ni and Co, but in principle, there is a problem if Ni is present. It is considered that there is no (Co has no adverse effect). That is, the effect obtained when the base material coating layer 13 is composed of Ni is considered to be the same as the effect obtained when the base material coating layer 13 is composed of Ni and Co. In this Example 1, the result of using the base material coating layer 13 composed of Ni is shown.

[Sample of Comparative Example 1: No base material coating layer 13]
A general-purpose stainless steel material (corresponding to SUS445J1) was used as the metal base material 11. Ni is not formed on the surface (the base material coating layer 13 is not formed). The sample of Comparative Example 1 was not subjected to any heat treatment of simulating the heat history during production and heat treatment simulating the heat history during operation.

[Sample of Comparative Example 2: No base material coating layer 13]
A general-purpose stainless steel material (corresponding to SUS445J1) was used as the metal base material 11. Ni is not formed on the surface (the base material coating layer 13 is not formed). Then, as a simulation of the heat history during production, a process of firing in the air at 800 ° C. and a reducing atmosphere (hydrogen atmosphere) at 700 ° C. for 2 hours each was performed. Further, as a simulation of the heat history during operation, heat treatment was performed for a predetermined time (24 hours, 300 hours) in a hydrogen / steam atmosphere. The temperature during this heat treatment is 850 ° C or 900 ° C.

In the ICP analysis, a test piece having a thickness of 5 mm square and 0.4 mm was prepared for each sample, and the whole amount was dissolved to detect the concentration of phosphorus (P) contained in each test piece. Tables 1 and 2 below show the results of ICP analysis.

First, the difference between the sample of Comparative Example 1 and the heat treatment time of the samples of Example 1 and Comparative Example 2 in a hydrogen / steam atmosphere of 0 hours is that the samples of Example 1 and Comparative Example 2 are manufactured. While the heat treatment that simulates the thermal history is performed, the sample of Comparative Example 1 is not subjected to the heat treatment. Then, as can be seen from Tables 1 and 2, the phosphorus concentration of the sample of Comparative Example 2 is compared with the phosphorus concentration (280 ppm) of the sample of Comparative Example 1 when the heat treatment time in the hydrogen / steam atmosphere is 0 hour. The concentration is as low as 220 ppm. That is, it was found that the heat treatment simulating the heat history during production causes a large amount of phosphorus volatilization from the surface of the metal base material 11.

Focusing on the sample of Example 1, as can be seen from Tables 1 and 2, the heat treatment time in the hydrogen / steam atmosphere is 0 hours as compared with the phosphorus concentration (280 ppm) of the sample of Comparative Example 1. The phosphorus concentration of the sample of Example 1 in the case is as low as 190 ppm. It is considered that this is because, among the heat treatments simulating the heat history during production, phosphorus chemically bonded to Ni slightly disappeared from the surface of the metal base material 11 during the heat treatment in the atmosphere. However, among the heat treatments that simulate the heat history during manufacturing, the heat treatment in the atmosphere is a process that simulates firing for forming the protective film 12 on the cell-cell connecting member 1, that is, the cell-cell connecting member. Since the process is performed in a state where 1 and the single cell 3 are not joined, phosphorus does not adversely affect the fuel electrode 32.

In the sample in which the base material coating layer 13 of Example 1 was formed, the difference in phosphorus concentration before and after the heat treatment in the hydrogen / steam atmosphere was almost the same regardless of the heat treatment temperature in the hydrogen / steam atmosphere simulating the heat history during operation. There wasn't. That is, it was found that in the sample in which the base material coating layer 13 of Example 1 was formed, it can be said that the volatilization of phosphorus from the metal base material 11 hardly occurs by the heat treatment simulating the heat history during operation.

On the other hand, in the sample of Comparative Example 2, when the heat treatment temperature in the hydrogen / steam atmosphere was 850 ° C., the phosphorus concentration was reduced from 220 ppm to 120 ppm by the heat treatment for 300 hours, and the heat treatment temperature in the hydrogen / steam atmosphere was increased. At 900 ° C., the phosphorus concentration was reduced from 220 ppm to 100 ppm by heat treatment for 24 hours. That is, it was found that in the sample in which the base material coating layer 13 of Comparative Example 2 was not formed, the volatilization of phosphorus from the metal base material 11 was larger than that in the heat treatment simulating the heat history during operation.

As described above, in the sample of Example 1, as shown in Tables 1 and 2, it is considered that phosphorus is volatilized from the metal base material 11 by the heat treatment simulating the heat history during production, but during operation. The volatilization of phosphorus from the metal base material 11 by the heat treatment simulating the heat treatment is effectively prevented. Therefore, by using the cell-to-cell connecting member 1 in which the base material coating layer 13 is formed on at least the surface of the surface of the metal base material 11 that is joined to the fuel electrode 32 of the single cell 3, the actual solid oxide oxidation is performed. It is considered that the phosphorus poisoning of the fuel electrode 32 can be suppressed even with a physical fuel cell.

<Effect of providing the base material coating layer 13 and the protective film 12 on the surface on the side bonded to the air electrode 31>
Below, of the surface of the metal base material 11 used in manufacturing the cell-to-cell connecting member 1, the base material coating layer 13 is on the surface of the single cell 3 constituting the SOFC cell C on the side to be joined to the air electrode 31. The effect of providing the protective film 12 on the surface of the base material coating layer 13 will be described. Here, as shown in Table 3 below, a sample (Examples 3 and 4) in which the base material coating layer 13 and the protective film 12 are formed on the surface of the metal base material 11, and the base material coating layer 13 are formed and protected. A sample in which the film 12 was not formed (Comparative Example 3) and a sample in which the substrate coating layer 13 was not formed and a film corresponding to the protective film 12 was formed (Comparative Example 4) were prepared, and the electrical resistance was measured. ..

[Sample of Example 2]
A general-purpose stainless steel material (equivalent to SUS445J1) is used as the metal base material 11, _{and a material containing NiCO 2} O ₄ is formed on the surface by dip coating and heat-treated in a reducing atmosphere (1000 ° C.) to obtain Ni in a metallic state and The base material coating layer 13 composed of Co was formed. _{Further, a material containing Ni 2} MnO ₄ is formed on the surface of the base material coating layer 13 by dip coating and heat-treated in an atmospheric atmosphere (1000 ° C.) to obtain a Ni—Mn-based oxide (Ni ₂ MnO ₄ ). A protective film 12 was formed using the above.

[Sample of Example 3]
A general-purpose stainless steel material (equivalent to SUS445J1) is used as the metal base material 11, _{and a material containing NiCO 2} O ₄ is formed on the surface by dip coating and heat-treated in a reducing atmosphere (1000 ° C.) to obtain Ni in a metallic state and The base material coating layer 13 composed of Co was formed. _{Further, a material containing Cu 2} MnO ₄ is formed on the surface of the base material coating layer 13 by dip coating and heat-treated in an atmospheric atmosphere (1000 ° C.) to obtain a Cu-Mn-based oxide (Cu ₂ MnO ₄ ). A protective film 12 was formed using the above.

[Sample of Comparative Example 3]
A general-purpose stainless steel material (equivalent to SUS445J1) is used as the metal base material 11, _{and a material containing NiCO 2} O ₄ is formed on the surface by dip coating and heat-treated in a reducing atmosphere (1000 ° C.) to obtain Ni in a metallic state and The base material coating layer 13 composed of Co was formed. In the sample of Comparative Example 3, the protective film 12 was not formed on the surface of the base material coating layer 13.

[Sample of Comparative Example 4]
A general-purpose stainless steel material (equivalent to SUS445J1) is used as the metal base material 11 _{, a material containing Co 2} MnO ₄ is formed on the surface by dip coating, and heat treatment is performed in an atmospheric atmosphere (1000 ° C.) to oxidize Cu-Mn. A protective film 12 composed of a material (Cu ₂ MnO _{4) was formed.} In the sample of Comparative Example 4, the base material coating layer 13 was not formed.

Table 4 shows the temperature-dependent results of the resistance values of Examples and Comparative Examples at 600 to 900 ° C.
The sample of Example 2 showed a low resistance result as compared with the sample of Comparative Example 3 and Comparative Example 4. The sample of Example 2 has a low resistance value even though two thick films (base material coating layer 13 and protective film 12) are formed on the surface of the metal base material 11 through two heat treatments. Shown. That is, a layer made of a ternary material containing Ni, Co, and Mn composed of the base material coating layer 13 and the protective film 12 is formed on the surface of the metal base material 11 of the cell-to-cell connecting member 1. In addition to the advantage of being able to suppress the formation of high-resistance Cr ₂ O ₃ and the advantage of being able to prevent scattering of Cr from the metal substrate 11 due to evaporation, the advantage of low resistance can be obtained. In consideration of the above, it can be said that the sample of Example 2 has much higher performance than the samples of Comparative Examples 3 and 4.
The resistance value of the sample of Example 3 was slightly increased as compared with the samples of Comparative Examples 3 and 4. However, considering that the sample of Example 3 also has _{an advantage that the formation of high-resistance Cr 2} O ₃ can be suppressed and an advantage that the scattering of Cr due to evaporation from the metal base material 11 can be prevented can be obtained. It cannot be said that the performance is low as compared with the samples of Comparative Examples 3 and 4.

As described above, in the present embodiment, among the surfaces of the metal base material 11 constituting the cell-to-cell connecting member 1, the surface on the side bonded to the fuel electrode 32 and the surface on the side bonded to the air electrode 31. Since the same base material coating layer 13 is attached to both of the above, it is not necessary to cover the metal base material 11 with a mask or the like when forming the base material coating layer 13. As a result, the procedure for forming the base material coating layer 13 on the surface of the metal base material 11 is simplified, and there is an advantage that the manufacturing cost of the cell-to-cell connecting member 1 is lowered. In addition, the base material coating layer 13 formed on both the surface of the metal base material 11 of the cell-to-cell connecting member 1 on the side joined to the fuel pole 32 and the surface on the side joined to the air pole 31 is On the surface bonded to the fuel electrode 32, the effect of suppressing volatilization of phosphorus from the metal base material 11 is exhibited, and on the surface bonded to the air electrode 31, high resistance together with the protective film 12. The formation of Cr ₂ O ₃ is suppressed, and the effect of preventing scattering of Cr due to evaporation from the metal base material 11 is exhibited.

If only the performance of the surface of the cell-cell connecting member 1 on the side joined to the air electrode 31 is considered, Ni—Co—Mn is applied to the surface on the side joined to the air electrode 31. There is also a method of forming a film of the ternary material containing the material at one time (in one layer). However, when that method is adopted, a material containing Ni—Co—Mn is also formed on the surface of the cell-to-cell connecting member 1 on the side bonded to the fuel electrode 32, so that the cell is formed. Since Mn is deposited on the surface of the interconnecting member 1 on the fuel electrode side and Mn exists as an oxide in the reducing atmosphere on the fuel electrode side in the SOFC operating temperature range, there is a problem that it exhibits high resistance.
Therefore, in the present embodiment, Ni—Co (base material coating layer 13) having good performance and durability as a coating on the fuel electrode side is formed on the surface of the metal base material 11 as a coating on the fuel electrode side, and on the air electrode side. An oxide containing Mn (protective film 12) was formed on the second layer of the surface of the first base material coating layer 13. That is, the procedure for forming the coating is simple because the coating design is performed in consideration of both the side joined to the fuel pole 32 and the side joined to the air pole 31 on the surface of the cell-cell connecting member 1. However, it is possible to provide the cell-to-cell connecting member 1 that exhibits good performance on both the fuel electrode side and the air electrode side.

FIG. 4 is a diagram showing a configuration of a system including a solid oxide fuel cell (cell stack) equipped with a SOFC cell C manufactured by the above method. In particular, FIG. 4 shows an SOFC cogeneration system including a solid oxide fuel cell (SOFC) 20 and supplying the electric power and heat generated by the solid oxide fuel cell 20 to the electric power load and the heat load. It is a figure which shows the structure. The solid oxide fuel cell 20 has a cell stack in which a plurality of SOFC cells C manufactured as described above are stacked. Although not shown, the solid oxide fuel cell 20 is a reformer for producing a fuel gas such as hydrogen supplied to the fuel electrode 32 by reforming a hydrocarbon such as city gas. May be added.

The electric power output from the solid oxide fuel cell 20 is supplied to the electric power line 22 connected to the commercial electric power system 21 via a electric power converter 24 such as an inverter. Various power load devices 23 such as lighting equipment and air conditioning equipment used in the facility where the solid oxide fuel cell 20 is installed are connected to the power line 22. That is, power is supplied from at least one of the commercial power system 21 and the solid oxide fuel cell 20 with respect to the power load in the power load device 23.

The heat discharged from the solid oxide fuel cell 20 is applied to the heat load of various heat load devices 26 such as a hot water supply device and a heating device installed in the facility where the solid oxide fuel cell 20 is installed. Will be supplied. Further, as shown in the figure, if a heat storage device 25 for storing the heat storage medium is provided, the heat discharged from the solid oxide fuel cell 20 can be recovered by the heat storage medium and stored in the heat storage device 25. Then, when heat demand is generated in the heat load device 26, heat can be supplied from the heat storage device 25 to the heat load device 26.

<Another Embodiment>
<1>
In the above embodiment, the cell-cell connecting member 1, the solid oxide fuel cell, the SOFC cogeneration system, and the method for manufacturing the cell-cell connecting member 1 of the present invention have been described with reference to specific examples. The configuration can be changed as appropriate.
For example, the composition of each material can be changed as appropriate.
Further, the film forming method of the base material coating layer 13 and the protective film 12 can be appropriately selected. For example, Ni-Co as the base material coating layer 13 is formed on the surface of the metal base material 11 made of stainless steel by a plating method, and then a Co-Mn-based oxide as the protective film 12 is formed, for example. A film may be formed by electrodeposition coating or the like. In this case, since the electronic conductivity of the metal base material 11 is not lost even if Ni-Co is plated on the metal base material 11, the second layer of the protective film 12 is also electrochemically coated or electroplated. It is possible to form a film by a specific method.

<2>
In the above embodiment, an example of constructing a cogeneration system including a solid oxide fuel cell (cell stack) has been described, but a monogeneration system including a solid oxide fuel cell can also be constructed. That is, it is also possible to construct an SOFC monogeneration system including a solid oxide fuel cell and supplying the electric power generated by the solid oxide fuel cell to the electric power load.

<3>
The configurations disclosed in the above embodiment (including other embodiments, the same shall apply hereinafter) can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction, and are disclosed in the present specification. The embodiment is an example, and the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

According to the present invention, a cell-cell connection member, a solid oxide fuel cell, and an SOFC monogeneration system that exhibit good performance on both the fuel electrode side and the air electrode side while the procedure for forming a coating is simple. , And SOFC cogeneration system, and can be used for manufacturing methods of cell-cell connecting members.

1 Cell-to-cell connection member 3 Single cell 11 Metal base material 12 Protective film 13 Base material coating layer 20 Solid oxide fuel cell (cell stack)
31 Air pole 32 Fuel pole C Solid oxide fuel cell cell (SOFC cell)

Claims (6)

An inter-cell connection member used in solid oxide fuel cell cells.
A metal base material made of stainless steel and
On the surface of the metal base material, the surface on the side bonded to the fuel electrode of the single cell constituting the solid oxide fuel cell and the surface on the side bonded to the air electrode of the single cell. A base material coating layer composed of Ni and Co, which is formed,
An inter-cell connection member including a protective film formed of an oxide containing Mn, which is formed on the surface of the base material coating layer on the side of the single cell to be joined to the air electrode. The cell-to-cell structure according to claim 1, wherein the protective film is formed by using any one of Mn oxide, Co-Mn-based oxide, Ni-Mn-based oxide, and Cu-Mn-based oxide. Connecting member. A solid oxide fuel cell in which a plurality of cells for a solid oxide fuel cell including the cell-to-cell connecting member according to claim 1 or 2 and the single cell are laminated. An SOFC monogeneration system comprising the solid oxide fuel cell according to claim 3 and supplying the electric power generated by the solid oxide fuel cell to an electric power load. A SOFC cogeneration system comprising the solid oxide fuel cell according to claim 3 and supplying the electric power and heat generated by the solid oxide fuel cell to the electric power load and the heat load. A method for manufacturing an inter-cell connection member used in a cell for a solid oxide fuel cell.
Of the surface of the metal base material made of stainless steel, the surface on the side to be joined to the fuel electrode of the single cell constituting the solid oxide fuel cell and the air electrode of the single cell are joined. A film forming step of forming a substrate coating layer composed of Ni and Co on the surface on the side to be formed.
A cell having a protective film forming step of forming a protective film formed by using an oxide containing Mn on the surface of the base material coating layer on the side of the single cell to be joined to the air electrode. Manufacturing method of connecting member.

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