JP6967894B2 - Manufacturing method of cell-to-cell connection member - Google Patents

Description

The present invention relates to a method for manufacturing an intercell connection member used in a cell for a solid oxide fuel cell.

In a cell for a solid oxide fuel cell (hereinafter, appropriately referred to as "SOFC"), an air electrode is bonded to one surface side of the electrolyte layer, and a fuel electrode is bonded to the other surface side of the electrolyte layer. It has a structure in which a single cell is sandwiched between a pair of electron-conducting cell-to-cell connecting members that transfer electrons to and from an air electrode or a fuel electrode. In such an SOFC cell, for example, the SOFC cell operates at an operating temperature of about 700 ° C. to 900 ° C., and a pair of electrodes are moved along with the movement of oxide ions from the air electrode side to the fuel electrode side via the electrolyte membrane. An electromotive force is generated during this period, and the electromotive force can be taken out and used.

The cell-to-cell connection member used in such an SOFC cell is manufactured by using a metal base material such as a stainless alloy containing Cr, which is excellent in electron conductivity and heat resistance. _{However, Cr 2} O ₃ which is an oxidation resistant film is formed on the metal base material used for the SOFC cell under high temperature operating conditions. This oxide film is a high-resistance layer, and has problems with durability such as reducing the power generation output of the fuel cell and reacting with the air electrode of the fuel cell due to the evaporation of Cr to significantly reduce the electrode performance. be.

As described above, in order _{to suppress the formation of Cr 2} O ₃ and prevent scattering due to evaporation of Cr, a ceramic coating having high electron conductivity is used as a protective film on the surface of the metal substrate. Forming is being done. 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.

Patent Document 1 describes a firing process for firing a cell-to-cell connecting member manufactured using a metal base material such as a stainless alloy containing Cr in a state where the air electrode is joined, in the alloy or oxide. It is described that the Cr (VI) oxide is suppressed to suppress the formation of Cr (VI) oxide. In order to suppress the Cr (VI) oxide, 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.

International Publication No. 2007/083627

Hideto Kurokawa et al., “Oxidation behavior of Fe-16Cr alloy interconnect for SOFC under hydrogen potential gradient”, Solid State Ionics 168 (2004) 13-21

In addition to the main components Fe and Cr, various elements are added to the stainless alloy used as a metal base material in order to impart heat resistance and corrosion resistance. It has been reported that these trace amounts of additive elements form a film-like region of oxide inside the metal substrate due to the oxygen potential near the interface between the metal substrate and the protective film formed on the surface thereof. (Non-Patent Document 1). In this document, it is reported that a composite oxide (spinel compound) of Mn and Cr is formed inside a metal substrate and exists as a highly resistant layer in a Cr-rich composition.

When the metal base material is made of stainless steel containing Si and Al and Ti, Al, Si, Ti and the like contained in the metal base material are oxidized inside the metal with high insulating properties according to the Eringham diagram. It is formed as a film, and there is a concern that the electron conductivity in the metal substrate is lowered, that is, the power generation performance is lowered.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing an cell-to-cell connection member of a solid oxide fuel cell for a 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 for achieving the above object is a method for manufacturing an inter-cell connecting member used in a cell for a solid oxide fuel cell.
A film formation in which a protective film material layer containing a spinel-type metal oxide containing Mn and Co as a main material is wet-deposited on the surface of a metal base material composed of stainless steel containing Si and Al and Ti. Process and
The protective film material layer is sintered by subjecting the metal substrate on which the protective film material layer is formed by the film forming step to a heat treatment at a temperature higher than 1000 ° C. in an atmospheric atmosphere. The point is that it has a sintering step of forming a protective film on a metal base material.

The inventors of the present application perform a film forming step and a sintering step for forming a protective film on the surface of a metal base material composed of stainless steel containing Si and Al and Ti under an air atmosphere. We have found a phenomenon in which the magnitude of the electrical resistance of the cell-to-cell connecting member changes depending on the heat treatment temperature in the sintering process. Then, the metal substrate on which the protective film material layer is formed by the film forming step is heat-treated at a temperature higher than 1000 ° C. in an atmospheric atmosphere, whereby Si, Ti, which has high insulating properties, is applied to the metal substrate. It was confirmed that even if an oxide of Al is formed, the oxide has a distribution form that does not cause an increase in electrical resistance, and the present invention has been completed.
That is, according to this characteristic configuration, it is possible to provide a cell for SOFC having high power generation performance by allowing the oxides of Si, Ti, and Al having high insulating properties to have a distribution form that does not bring about an increase in electrical resistance. ..

Another characteristic feature of the manufacturing method of intercell connecting member according to the present invention, a main material of the protective layer is comprised of cobalt manganese oxide _{Co x Mn y O 4 (0} <x, y <3, x + y = 3) , Or zinc cobalt manganese-based oxide Zn _z Co _x Mn _y O ₄ (0 <x, y, z <3, x + y + z = 3). Here, the main material of the protective film may be a Co _1.5 Mn _1.5 O ₄ or Co ₂ MnO _4.

According to the above-mentioned characteristic configuration, the discrepancy between the coefficient of thermal expansion of the protective film and the coefficient of thermal expansion of the metal substrate or the air electrode can be reduced, and the durability of the SOFC cell can be enhanced.

Yet another characteristic configuration of the method for manufacturing a cell-to-cell connecting member according to the present invention is that the protective film material layer is formed by electrodeposition coating in the film forming step.

According to the above characteristic configuration, a dense and strong protective film can be realized.

It is a schematic diagram of the cell for 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 of the structure of the cell-to-cell connecting member. It is a schematic diagram of the energization test jig. It is a graph of the energization test result which shows the time-dependent change of electric resistance. FIG. 3 is an SEM image and an EPMA diagram of a cross section of a solid oxide fuel cell. FIG. 3 is an SEM image and an EPMA diagram of a cross section of a solid oxide fuel cell. It is a graph of the energization test result which shows the time-dependent change of electric resistance.

Hereinafter, a method for manufacturing an cell-to-cell connection member used in a solid oxide fuel cell (SOFC) cell according to an embodiment of the present invention 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 of the solid oxide fuel cell during operation. As shown in FIGS. 1 and 2, in the SOFC cell C, air 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. A single cell 3 formed by joining a pole 31 and joining a fuel pole 32 made of an electron-conducting porous body is provided on the other 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 transferring electrons to and from 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-to-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-to-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-to-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 connection member 1 may have a configuration in which a member that electrically connects the interconnector and the cell C is connected.

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, in LaMO ₃ (for example, M = Mn, Fe, Co, Ni). A perovskite-type oxide of _{(La, AE) MO 3 in which a part} of La is replaced with an alkaline earth metal AE (AE = Sr, Ca) can be used. As the material of the fuel electrode 32, a cermet of Ni and yttria-stabilized zirconia (YSZ) can be used, and further, as the material of the electrolyte membrane 30, yttria-stabilized zirconia (YSZ) 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 cell stack, the cell-to-cell connecting members 1 arranged at both ends in the stacking direction may be such that 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-to-cell connection 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-to-cell connecting member 1 may be referred to as 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. SOFCs having such a cell stack structure are generally called flat plate type SOFCs. 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.

When the SOFC provided with the SOFC cell C is operated, as shown in FIG. 2, air is supplied 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 via 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, 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]
FIG. 3 is a cross-sectional view of the structure of the cell-to-cell connecting member. The cell-to-cell connection member 1 has a structure in which a protective film 12 described later is formed on the surface of the metal base material 11. Then, the cell-to-cell connecting member 1 is joined to the single cell 3 with the adhesive layer 4 in between. As described above, by providing the protective film 12 on the surface of the metal base material 11, Cr poisoning can be suppressed, which is suitable as a cell for a solid oxide fuel cell. Further, an oxide film 13 described later is formed on the surface of the metal base material 11.

As the material of the metal base material 11, stainless steel containing Si, Al, and Ti, which is a material having excellent electronic conductivity and heat resistance, is used.

[Oxide film]
An oxide film 13 is formed on the surface of the metal base material 11. The oxide film 13 is formed by oxidizing the surface of the alloy of the metal base material 11 by oxygen in the ambient atmosphere. In the case of a stainless alloy containing Cr as in the present embodiment, the oxide film 13 is mainly chromium (Cr ₂ O ₃ ) and is formed as a dense film. The oxide film 13 is formed by heat treatment in the manufacturing process of the SOFC cell C, such as the sintering step of the protective film 12 and the baking of the adhesive layer 4, which will be described later.

〔Protective film〕
A protective film 12 is formed on the surface of the metal base material 11 in order to suppress Cr poisoning. The protective film 12 is mainly made of a spinel-type metal oxide containing Mn and Co. For example, the main material of the protective film 12 is cobalt-manganese-based oxide Co _x Mn _y O ₄ (0 <x, y <3, x + y = 3) or zinc-cobalt-manganese-based oxide Zn _z Co _x Mn _y O _4. It may be (0 <x, y, z <3, x + y + z = 3). Co _1.5 Mn _1.5 O ₄ or Co ₂ may be MnO _4. The "main material" means that it is the main material, and it is also possible to use a mixture of a plurality of types of metal oxides or a mixture of other components. By using such a protective film 12, the discrepancy between the coefficient of thermal expansion of the protective film 12 and the coefficient of thermal expansion of the metal base material 11 and the air electrode 31 can be reduced, and the durability of the SOFC cell C can be improved. .. Further, in an experiment using a sample in which the main material of the protective film 12 is Co ₂ MnO _{4 , it has been confirmed that the formation of MnCr 2} O ₄ is suppressed, and it is a spinel-type metal oxide of the same type. It is strongly inferred that the same result will be obtained for Co _1.5 Mn _1.5 O _4. Therefore, by using such a protective film 12, it is _{possible to suppress the formation of MnCr 2} O ₄ having a large electric resistance inside the metal base material 11 of the cell-to-cell connection member 1, and the SOFC cell having high power generation performance is suppressed. C can be provided.

As a method for forming the protective film 12 on the metal substrate 11, a screen printing method, a doctor blade method, a spray coating method, an inkjet method, a spin coating method, a dip coating, an electroplating method, an electroless plating method, and an electrodeposition coating method. Wet film formation such as, etc. can be exemplified.

For example, if the electrodeposition coating method is applied, the protective film 12 can be formed by the following method.
Metal oxide fine particles are dispersed so as to be 100 g per liter of electrodeposition liquid, and electrodeposition coating is performed using a mixed solution containing an anionic resin such as polyacrylic acid. Here, (metal oxide fine particles: anionic resin) = (1: 1) (mass ratio). An uncured electrodeposition coating film is formed on the surface of the metal substrate 11 by energizing the electrode plate of SUS304 with the metal substrate 11 as a positive polarity and a negative polarity as a counter electrode using a mixed solution. Electrodeposition coating is carried out, for example, by immersing the metal substrate 11 completely or partially in an energizing tank filled with a mixed solution to form an anode and energizing. The electrodeposition coating conditions are also not particularly limited, and are wide depending on various conditions such as the type of the metal as the metal base material 11, the type of the mixed liquid, the size and shape of the energizing tank, and the application of the obtained cell-to-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 V to 450 V, the voltage application time is about 1 minute to 10 minutes, and the liquid temperature of the mixed liquid is about 10 ° C. 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, using an electric furnace, heat treatment (for example, firing for 2 hours) is performed in an atmospheric atmosphere at a temperature higher than, for example, 1000 ° C., and then slowly cooled.

[Adhesive layer]
The adhesive layer 4 joins the cell-to-cell connecting member 1 and the air electrode 31 of the single cell 3. Specifically, the protective film 12 formed on the surface of the metal base material 11 of the cell-to-cell connecting member 1 and the air electrode 31 of the single cell 3 are bonded and bonded by the adhesive layer 4. As the main material of the adhesive layer 4, a perovskite-type oxide similar to the air electrode 31 or a spinel-type oxide is used. For example, LSCF6428 (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ ) is used.

[Manufacturing method of solid oxide fuel cell]
Next, a method for manufacturing the solid oxide fuel cell C will be described. The method for manufacturing the cell C for a solid oxide fuel cell includes a process of manufacturing the cell-to-cell connecting member 1 (hereinafter, "protective film forming step") and the cell-cell connecting member 1 with an air electrode 31 and a fuel electrode 32. The process of joining (hereinafter referred to as "joining process") is included.

[Protective film forming process]
The protective film forming step, which is the method for manufacturing the cell-to-cell connecting member 1 of the present invention, includes a film forming step and a sintering step. In the protective film forming step, the protective film 12 is formed on the surface of the metal base material 11 of the cell-to-cell connecting member 1.

In the film forming step, a protective film material layer containing a spinel-type metal oxide containing Mn and Co as a main material is formed on the surface of a metal base material 11 made of stainless steel containing Si and Al and Ti. Wet film formation. For example, a coating film (protective film material layer) is wet-formed on the metal base material 11 of the cell-to-cell connection member 1 using a slurry containing a fine powder of a metal oxide. The wet film formation may be carried out by immersing the metal base material 11 in the slurry and pulling it up (dip), by an electrodeposition coating method, or by using any of the methods exemplified above. .. The wet film formation may be performed on the entire metal substrate 11 or on only one surface of the flat metal substrate 11. In the latter case, the surface on which the protective film 12 is formed by wet film formation is joined to the air electrode 31 of the single cell 3. The surface on which the material of the metal base material 11 is exposed without wet film formation is joined to the fuel electrode 32 of the single cell 3.

In the sintering step, the metal base material 11 on which the coating film (protective film material layer) is formed by the film forming step is heat-treated at a temperature higher than 1000 ° C. in an atmospheric atmosphere to form the coating film. The protective film 12 is formed on the metal base material 11 by sintering. For example, the metal base material 11 on which the coating film is wet-formed is heat-treated to sintered the fine powder of the metal oxide to form the protective film 12 on the surface of the metal base material 11. The heat treatment is performed in an atmospheric atmosphere, for example, at a temperature higher than 1000 ° C. for 2 hours. As described above, the heat treatment in the sintering step of the protective film forming step is performed in a state where the single cell 3 of the SOFC cell C and the metal base material 11 are not bonded. That is, after performing this sintering step to form the protective film 12, a joining step described later is performed.

[Joining process]
In the joining step, the cell-to-cell connecting member 1 obtained in the protective film forming step (film forming step and sintering step) is joined to the air electrode 31 and the fuel electrode 32 via the adhesive layer 4. Specifically, the paste containing the material of the adhesive layer 4 described above is applied to the cell-to-cell connecting member 1 to be bonded to the single cell 3, and the adhesive layer 4 is formed by heat treatment and baking. Normally, the heat treatment is performed at a low temperature of the operating temperature of the fuel cell to 950 ° C., but the heat treatment is not limited to this temperature.

[Changes in electrical resistance and element distribution of cell-to-cell connection members due to the temperature of the adhesive layer baking]
Experimental samples were prepared according to the method for producing SOFC cell C described above, and changes in electrical resistance over time, SEM observation of cross sections, and EPMA elemental analysis were performed.

[Creation of experimental sample]
[Experimental Example 1 (1000 ° C.): Comparative Example]
A coating film (protective film material layer) was formed on the surface of a stainless steel plate containing Si, Al, and Ti by an anionic electrodeposition coating method using a slurry containing a fine powder of _{Co 2} MnO _4. Membrane process). The plate was subjected to a sintering step of heating the plate in an air atmosphere of 1000 ° C. for 2 hours to form a protective film containing _{Co 2} MnO _{4 as a main material.} LSCF6428 was applied to both sides of the plate, dried, and baked at 1000 ° C. for 2 hours to form a layer simulating the adhesive layer 4. As described above, a sample of Experimental Example 1 simulating the cell-to-cell connection member 1 of the solid oxide fuel cell cell was prepared.

[Experimental Example 2 (1050 ° C.): Example]
The processing temperature of the sintering step was changed to 1050 ° C., and the other conditions were the same as in Experimental Example 1 to prepare a sample of Experimental Example 2.

[Experimental Example 3 (1075 ° C.): Example]
The processing temperature of the sintering step was changed to 1075 ° C., and the other conditions were the same as in Experimental Example 1 to prepare a sample of Experimental Example 3.

[Changes in electrical resistance over time]
The changes over time in the electrical resistance values of the samples of Experimental Examples 1 to 3 were measured. The result of this energization test is shown in the graph of FIG. The measurement was carried out by setting each sample on the energization test jig 5 shown in FIG. 4 and measuring the electric resistance over time in an environment of 800 ° C. under a constant current state. The energization test jig 5 has a structure in which a sample is sandwiched between a pair of metal plates 51 and fixed with screws 52. The Pt mesh 53 was in contact with the adhesive layer 4, and the resistance value between the pair of Pt meshes 53 was measured to measure the resistance value of the sample.

If the heat treatment temperature in the sintering step, which is one of the protective film forming steps described above, is raised, it is expected that the resistance value will differ due to the densification of the protective film 12 and the increase of the oxide film 13. According to the results shown in (1), there was almost no difference in the initial resistance values of the samples having the heat treatment temperatures of 1000 ° C. and 1050 ° C., and the initial resistance values of the samples having the heat treatment temperature of 1075 ° C. were relatively high. Focusing on the change over time in the resistance value, the sample in which the sintering process was performed at 1000 ° C. showed an increase in the resistance value over time, and the sample at 1050 ° C. and 1075 ° C. showed an increase in the resistance value compared to the initial value. It was not confirmed and the result was relatively good. It is considered that this result is due to the fact that the formation of the oxide film 13 had a large effect on the resistance value in the sample obtained by performing the sintering step at 1000 ° C.

FIG. 6 is an SEM image of a cross section of the solid oxide fuel cell cell before the above-mentioned energization test and an EPMA element mapping diagram (hereinafter referred to as “EPMA diagram”). FIG. 7 is an SEM image and an EPMA diagram of a cross section of a solid oxide fuel cell cell after an energization test.

The leftmost column of each figure shows the SEM image, and the other 6 columns show the EPMA diagram (Cr, Si, Ti, Al, Mn, Co). In the SEM image and the EPMA diagram, the metal base material 11, the oxide film 13, the protective film 12, and the bonding layer are shown in this order from the upper side of the image. In the EPMA diagram, the positions where the concentration of elements is high are shown in light color. It should be noted that the concentration scales of the four elements are different, and even if the same dark color appears between different elements, it does not mean that they have the same concentration.

The field of view of the SEM image and the field of view of the EPMA diagram are in agreement. For example, in the EPMA diagram of Cr of the 1000 ° C. sample (Experimental Example 1) of FIG. 6, a light-colored Cr distribution region exists at the lower part of the diagram, but this region coincides with the region of the oxide film 13 in the SEM image. There is. _{This is because Cr contained in chromia (Cr 2} O ₃ ), which is the main component of the oxide film 13, appears in the EPMA diagram.

Looking at the EPMA diagram before the energization test in FIG. 6, by setting the heat treatment temperature in the sintering step to 1050 ° C., the density of the protective film 12 clearly increased, and an almost porous region existed. It turns out that there is no such thing. On the other hand, when the heat treatment temperature in the sintering step was increased to 1075 ° C., the oxide film 13 became thicker. Regarding the oxide film 13 formed inside the metal substrate 11, in the sample at 1000 ° C., the high concentration region of the highly insulating Si, Ti, Al oxide spreads in a relatively continuous layer in the plane direction. Formed, in the samples at 1050 ° C and 1075 ° C, relatively discontinuous in the plane direction and extended in the thickness direction (that is, the high concentration region of the oxide is thin when viewed in the cross section along the thickness direction). It was confirmed that the metal was formed in a striped state extending in the thickness direction. That is, although it is called the oxide film 13, it seems that the region has a relatively low resistance except for the striped portion.

Looking at the EPMA diagram after the energization test in FIG. 7, in the sample at 1000 ° C., the layer of the insulating oxide (oxide of Si, Ti, Al) constituting the oxide film 13 is thick in the high concentration region. It is shown that it has become. As a result, the resistance value of the oxide film 13 in the thickness direction increased, and it is considered that the resistance value increased as shown in FIG.
On the other hand, when the heat treatment temperature in the sintering step is set to 1050 ° C. or higher, the high concentration region of the insulating oxide constituting the oxide film 13 is discretely striped and has low resistance even after the energization test. Regions also exist discretely. As a result, it is considered that the increase in the resistance value in the thickness direction is suppressed inside the oxide film 13.

As described above, when the film forming step and the sintering step for forming the protective film 12 on the surface of the metal base material 11 made of stainless steel containing Si and Al and Ti are performed, the atmosphere is atmospheric. We have found a phenomenon in which the magnitude of the electrical resistance of the cell-to-cell connecting member 1 changes depending on the heat treatment temperature in the sintering step performed in 1. Then, by heat-treating the metal base material 11 on which the protective film material layer is formed by the film forming step at a temperature higher than 1000 ° C. in an atmospheric atmosphere, the metal base material 11 is subjected to highly insulating Si. It was confirmed that even if the oxides of Ti and Al are formed, the oxides have a distribution form that does not cause an increase in electrical resistance. In addition, the state in which the oxide was distributed so as not to increase the electric resistance was maintained even after a long-term energization test. In this way, in order to reduce the resistance at the interface between the metal base material 11 and the protective film 12, high resistance oxides should not be formed in a layered form that continuously spreads in the plane direction inside the metal base material 11. , And it is considered preferable to make the protective film 12 dense. It was possible to achieve this by performing the heat treatment of the sintering step in an atmospheric atmosphere at a temperature higher than 1000 ° C., and further at a temperature higher than 1000 ° C. and 1075 ° C. or lower.

FIG. 8 is a graph showing the results of measuring the change over time in the electrical resistance values of three types of samples subjected to the sintering steps at 1000 ° C., 1050 ° C., and 1075 ° C. in the same manner as in Experimental Examples 1 to 3 described above. be. Specifically, in the graph shown in FIG. 8, each sample was set in the energization test jig 5 shown in FIG. 4, and the electric resistance was measured over time in a constant current state in an environment of 900 ° C. The result is shown. That is, the conditions other than the temperature during the measurement of the electric resistance value are the same as those in FIG. 5, and only the temperature during the measurement of the electric resistance value is different between FIG. 5 (800 ° C.) and FIG. 8 (900 ° C.). In the graph of FIG. 8, around 7300 hours and around 9200 hours, the data is missing because the sample was temporarily set to a temperature other than 900 ° C. and another test was performed, and the data is discontinuous. .. Further, the hunting of the resistance value around 3900 hours appearing in the samples subjected to the sintering process at 1050 ° C and 1075 ° C is an influence of the test equipment, and the resistance change of the sample does not occur.

As shown in FIG. 8, the initial resistance is lowest in the sample subjected to the sintering step at 1050 ° C, and increases in the order of the sample at 1075 ° C and the sample at 1000 ° C. Therefore, focusing on the initial resistance value, the sample at 1050 ° C. is the best. Focusing on the change over time in the resistance value, it is confirmed that the resistance value of each sample increases after 2000 hours. The amount of increase in resistance value with the passage of time, that is, the deterioration rate, was the largest in the sample subjected to the sintering step at 1000 ° C., and the sample subjected to the sintering step at 1050 ° C. was subjected to the sintering step at 1075 ° C. It becomes smaller in the order of the sample. Therefore, focusing on the deterioration rate, the samples subjected to the sintering step at 1050 ° C and 1075 ° C are the best. In addition, the samples subjected to the sintering steps at 1050 ° C and 1075 ° C show good resistance values even when the elapsed time exceeds 9000 hours. The sample subjected to the sintering process at 1000 ° C. has an inflection point where the inclination (deterioration rate) becomes large in the vicinity of about 4000 hours, which is due to the progress of abnormal oxidation of the stainless steel material as the metal substrate 11. It is thought that this is because the resistance increase rate has increased.

In Table 1 below, the deterioration rate (increase in resistance value) of each sample that can be read from the graph of FIG. 8 shows the deterioration rate between 2000 hours and 4000 hours and the elapsed time of 5000 hours. Shows the rate of deterioration between ~ 7000 hours. In the sample subjected to the sintering step at 1000 ° C., the amount of increase in resistance value (per 1000 hours) between 2000 and 4000 hours is 5 ^{mΩcm 2} , but the elapsed time thereafter is between 5000 and 7000 hours. It can be seen that the amount of increase in the resistance value of ^{the above increases to 8.5 mΩcm 2} , and the deterioration rate suddenly increases at the above-mentioned turning point. On the other hand, in the samples subjected to the sintering steps at 1050 ° C and 1075 ° C, the deterioration rate remains consistently low, and the deterioration rate does not suddenly increase.

As described above, it was found that it is desirable to perform the sintering process at a temperature higher than 1000 ° C from the viewpoint of initial performance and durability even when the change over time of the electrical resistance value is measured in an environment of 900 ° C. rice field.

Supplementally, when the protective film 12 is sintered at a high temperature, the protective film 12 is sintered and a dense protective film 12 can be obtained. Therefore, the adhesion of the protective film 12 to the metal substrate 11 is improved. It can be expected that the protective film 12 enhances the ability to suppress Cr scattering from the metal base material 11 and improves the electron conductivity of the protective film 12 itself (improves the electron conductivity due to densification). However, in the case of performing the sintering step of the protective film 12 at high temperature, with respect to the oxide film 13 formed on the inside of the metal substrate 11, Cr ₂ O ₃ (oxidation of Fe) increases and abnormal oxidation of the thickness of the oxide layer, There is a concern that abnormal growth of insulating oxides (oxides of Si, Ti, Al) may occur and the electron conductivity may decrease.

On the other hand, in the case of performing the sintering step of the protective film 12 at a low temperature, the growth of a high-resistance oxide film 13 _(Cr 2 _{O 3} and an insulating oxide (including Si, Ti, oxides of Al) of) the By limiting the thickness of the high-resistance layer and reducing the thickness, the effect of reducing the deterioration of power generation performance can be expected. However, when the protective film 12 is sintered at a low temperature, the adhesion of the protective film 12 to the metal base material 11 cannot be sufficiently ensured, and the contact resistance between the protective film 12 and the metal base material 11 increases. , The protective film 12 may deteriorate the ability to suppress Cr scattering from the metal base material 11, and the protective film 12 may peel off from the metal base material 11 to cause a rapid increase in resistance.

As described above, the temperature condition in the sintering process of the protective film 12 is a very important factor, and while there is a trade-off relationship between performance and durability, in the present invention, stainless steel containing Si and Al and Ti is used. The temperature condition of the sintering step of the protective film material layer containing a spinel-type metal oxide containing Mn and Co, which is wet-deposited on the surface of the metal base material 11 configured to be used as a main material, is set to a temperature higher than 1000 ° C. By doing so, it was clarified that the above-mentioned trade-off can be solved and a cell-to-cell connection member for a solid oxide fuel cell cell having high power generation performance can be provided. In particular, even if an oxide of Si, Ti, Al having high insulating properties is formed on the metal base material 11, it is confirmed that the oxide has a distribution form that does not cause an increase in electrical resistance. The invention was completed.

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 also disclosed herein. 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.

INDUSTRIAL APPLICABILITY The present invention can be used to provide a method for manufacturing a cell-to-cell connection member of a cell for a solid oxide fuel cell having high power generation performance.

1 Cell-to-cell connection member 3 Single cell 11 Metal substrate 12 Protective film C Solid oxide fuel cell cell (SOFC cell)

Claims (4)

A method for manufacturing a cell-to-cell connection member used in a cell for a solid oxide fuel cell.
A film formation in which a protective film material layer containing a spinel-type metal oxide containing Mn and Co as a main material is wet-deposited on the surface of a metal base material composed of stainless steel containing Si and Al and Ti. Process and
The protective film material layer is sintered by subjecting the metal substrate on which the protective film material layer is formed by the film forming step to a heat treatment at a temperature higher than 1000 ° C. in an atmospheric atmosphere. A method for manufacturing an intercell connection member having a sintering step of forming a protective film on a metal substrate. The main material of the protective film is cobalt manganese oxide Co _x Mn _y O ₄ (0 <x, y <3, x + y = 3) or zinc cobalt manganese manganese oxide Zn _z Co _x Mn _y O ₄ (0 <x, y <3, x + y = 3). The method for manufacturing an intercell connecting member according to claim 1, wherein 0 <x, y, z <3, x + y + z = 3). The main material of the protective film, Co _1.5 Mn _1.5 O ₄ or manufacturing method of the intercell connection member according to claim 2 Co ₂ is MnO _4. The method for manufacturing an inter-cell connecting member according to any one of claims 1 to 3, wherein the protective film material layer is formed by electrodeposition coating in the film forming step.

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