JP6317710B2 - Solid oxide electrochemical cell, method for producing solid oxide electrochemical cell, solid oxide fuel cell, and high-temperature steam electrolysis apparatus - Google Patents

Description

  The present invention relates to a solid oxide electrochemical cell, a method for producing a solid oxide electrochemical cell, a solid oxide fuel cell, and a high-temperature steam electrolysis apparatus, and more particularly, a short circuit in a solid electrolyte layer. Solid oxide electrochemical cell having excellent power generation capability while suppressing, method for producing solid oxide electrochemical cell, solid oxide fuel cell including the solid oxide electrochemical cell, and high-temperature steam electrolysis Relates to the device.

  Solid oxide electrochemical cell capable of generating power using hydrogen and oxygen, or a solid oxide electrochemical cell as a member of a high-temperature steam electrolysis apparatus that decomposes water to generate hydrogen and oxygen Is used. The solid oxide electrochemical cell has an oxygen electrode, a solid electrolyte layer, and a fuel electrode. The solid electrolyte layer may be made of a perovskite oxide for the purpose of high performance. The fuel electrode contains a transition element such as Ni in order to obtain a catalytic function and electronic conductivity. The air electrode contains transition elements such as Co and Fe in order to obtain a catalytic function and electronic conductivity.

  When producing a solid oxide electrochemical cell, a method of firing after laminating a firing precursor of a solid electrolyte layer and a firing precursor of a fuel electrode may be used. In the firing process, Ni or the like contained in the fuel electrode firing precursor diffuses into the solid electrolyte layer firing precursor. The air electrode may be fired after the air electrode firing precursor is laminated on the surface of the solid electrolyte layer of the co-fired body of the fuel electrode and the solid electrolyte layer. In the air electrode firing process, Co or the like contained in the air electrode firing precursor diffuses into the solid electrolyte layer firing precursor. When these Ni and Co and the like diffuse and penetrate deeply into the solid electrolyte layer, an electron conduction path from the fuel electrode to the air electrode of the solid electrolyte layer is formed, and an electrical connection between the air electrode and the fuel electrode is formed. An internal short circuit may occur, which may cause a decrease in electromotive force or performance of the solid oxide electrochemical cell. In particular, when the solid electrolyte layer has a perovskite oxide containing Ga, the thickness of the solid electrolyte layer is designed to be reduced in order to reduce the amount of relatively expensive Ga used. As the thickness of the solid electrolyte layer is reduced, there is a problem that the problem of short circuit due to diffusion of Ni or the like from the fuel electrode and diffusion of Co or the like from the air electrode is more likely to occur.

  Conventionally, a technique for suppressing diffusion of Ni in the fuel electrode toward the solid electrolyte layer is known. For example, Patent Document 1 states that “the fuel electrode includes at least one of Ni and NiO, the solid electrolyte layer includes a perovskite complex oxide including at least La and Ga, and MgO, and the solid electrolyte layer includes The solid oxide fuel cell is characterized in that the MgO becomes particulate MgO particles and is unevenly distributed on the one side surface side (see claim 1 of Patent Document 1). According to the invention disclosed in Patent Document 1, it is possible to prevent Ni from reacting with the perovskite oxide in the solid electrolyte layer by reacting MgO and Ni that are unevenly distributed on the fuel electrode side of the solid electrolyte layer. it can.

  On the other hand, a technique for suppressing the element contained in the air electrode from diffusing toward the solid electrolyte layer is known. For example, Patent Document 2 states that “an intermediate layer made of a sintered body containing a ceria-based oxide is interposed between the solid electrolyte and at least one of the anode side electrode and the cathode side electrode. The intermediate layer further contains a total of 0.5 to 5 mol% of at least one member selected from the group consisting of Al, Ca, Co, Cr, Cu, Fe, Mn, Ni, and Zn derived from a sintering aid. In addition, an “electrolyte / electrode assembly having a thickness of 0.5 to 3 μm and a relative density of 70 to 100%” (see claim 1 of Patent Document 2) is disclosed. In Patent Document 2, the intermediate layer is densified by firing an intermediate layer containing a ceria-based oxide at a relatively low temperature in the presence of a sintering aid, whereby the cathode side electrode (air electrode) and the solid layer are solidified. It is disclosed that element diffusion with the electrolyte is avoided (column 0028 to column 0040 of Patent Document 2, etc.).

JP 2012-156007 A JP 2008-258064 A

  In the invention disclosed in Patent Document 1, MgO is an insulator and reduces the electrical characteristics of the solid electrolyte layer. Therefore, the power generation performance of the solid oxide fuel cell disclosed in Patent Document 1 decreases. There is a problem.

  Further, in the invention disclosed in Patent Document 2, the means for providing the intermediate layer between the air electrode and the solid electrolyte layer has a problem that the electrical resistance is increased, and that the structure is complicated and the cost is increased. There is.

An object of the present invention is to provide a solid oxide electrochemical cell having a high electromotive force and excellent power generation capability by suppressing a short circuit in the solid electrolyte layer.
Another object of the present invention is to provide a method for producing a solid oxide electrochemical cell having a high electromotive force and an excellent power generation capability by suppressing a short circuit in the solid electrolyte layer.
Another object of the present invention is to provide a solid oxide fuel cell having a high electromotive force and an excellent power generation capability by suppressing a short circuit in the solid electrolyte layer.
Still another object of the present invention is to provide a high-temperature steam electrolysis apparatus that is excellent in water decomposition capability by suppressing short-circuiting in the solid electrolyte layer.

Means for solving the problems are as follows:
(1) A solid oxide electrochemical cell having a solid electrolyte layer, a fuel electrode formed on one side of the solid electrolyte layer, and an air electrode formed on the other side of the solid electrolyte layer Because
The fuel electrode contains nickel oxide and yttria-stabilized zirconia ,
The air electrode contains La _0.6 Sr _0.4 CoO _3-δ ,
The solid electrolyte layer contains La _0.9 Sr _0.1 Ga _x Mg _y O _3-δ (x: 0.8 to 0.95, y: 0.05 to 0.2), and has its own thickness. Having a perovskite type oxide a containing Ga and having a perovskite type oxide a containing Ga, and by performing point analysis on the cut surface of the solid electrolyte layer with a wavelength dispersive X-ray spectrometer attached to an electron beam probe microanalyzer, The ratio of the total mass of transition elements of the same type as the transition elements contained in the fuel electrode to the total mass of the elements excluding the elements having atomic numbers 1 to 8 among all the detected elements is 0.5% by mass or less. And the 1st area | region whose ratio of the total mass of the transition element of the same kind as the transition element contained in the said air electrode is 0.5 mass% or less, and said 1st in the film thickness direction of the said solid electrolyte layer The thickness of the region is 5 μm or more A solid oxide electrochemical cell.

Preferred embodiments of the solid oxide electrochemical cell (1) are as follows.
(2) When the solid electrolyte layer is point-analyzed by a wavelength dispersive X-ray spectrometer attached to an electron beam probe microanalyzer, the solid electrolyte layer has atomic numbers 1 to The ratio of the total mass of transition elements of the same type as the transition elements contained in the fuel electrode to the total mass of elements excluding the 8 elements is a second region exceeding 0.5 mass%, and the solid electrolyte layer The solid oxide electrochemical cell according to (1), wherein the thickness of the second region in the film thickness direction is 20 μm or less .
(3) before SL solid electrolyte layer, the cut surfaces of the solid electrolyte layer when point analyzed by wavelength-dispersive X-ray spectrometer supplied with the electron probe microanalyzer, atomic number among the detected total elements 1 The solid electrolyte layer has a third region in which the ratio of the total mass of transition elements of the same type as the transition elements contained in the air electrode to the total mass of elements excluding ˜8 elements exceeds 0.5 mass%. The solid oxide electrochemical cell according to (1) or (2), wherein the thickness of the third region in the film thickness direction is 20 μm or less.

Means for solving the another problem is as follows.
(4) The method for producing a solid oxide electrochemical cell according to any one of (1) to (3) , wherein the solid electrolyte layer is formed on a surface of an unfired fuel electrode serving as the fuel electrode. And forming a co-fired body by forming an unsintered solid electrolyte layer and firing at a temperature of 1320 ° C. or lower.

A preferred embodiment of the method for producing a solid oxide electrochemical cell (4) is as follows:
(5) The method for producing a solid oxide electrochemical cell according to any one of (1) to (3) , wherein an unsintered air electrode serving as the air electrode is provided on a surface of the co-fired body. The method for producing a solid oxide electrochemical cell according to (4) , comprising a step of forming and firing at a temperature of 1100 ° C. or lower.

Means for solving the another problem is as follows.
(6) A solid oxide fuel cell comprising the solid oxide electrochemical cell according to any one of (1) to (3) .

Means for solving the another problem is as follows.
(7) A high-temperature steam decomposition apparatus comprising the solid oxide electrochemical cell according to any one of (1) to (3) .

(1) The perovskite oxide a containing Ga is a solid electrolyte material having high conductivity of oxide ions. On the other hand, since the solid electrolyte layer has a high element diffusibility of the transition element, when the thickness of the solid electrolyte layer is thin and 100 μm or less, it diffuses from the transition electrode such as Ni diffused from the fuel electrode and the air electrode during firing. The transition element such as Co may form an electron conduction path from the fuel electrode to the air electrode in the solid electrolyte layer, which may cause a short circuit in the solid electrolyte layer. However, according to the present invention, even when the thickness of the solid electrolyte layer containing the perovskite oxide a is 100 μm or less, the ratio of the total mass of transition elements of the same type as the transition elements contained in the fuel electrode is 0. The thickness of the solid electrolyte layer is 5% by mass or less and has a first region in which the ratio of the total mass of transition elements of the same type as the transition element contained in the air electrode is 0.5% by mass or less. Since the thickness of the first region in the direction is 5 μm or more, an electrical short circuit can be suppressed, and a solid oxide electrochemical cell having high electromotive force and excellent power generation capability can be provided. .
(2) (La1- [ _alpha] Sr [ _alpha] ) (Ga1- [ _beta] Mg [ _beta] ) O3- [ _delta] (0.05 ≦ α <0.2, 0.05 ≦ β <0.2) contains Ga. Among the perovskite oxides, the conductivity of oxide ions is particularly high. Further, as β decreases, the segregation of MgO in the solid electrolyte decreases. When MgO is segregated in the solid electrolyte layer, MgO easily reacts with the transition element contained in the fuel electrode and the air electrode to form a solid solution. Therefore, the transition element from the fuel electrode and the air electrode to the solid electrolyte layer. Becomes easy to diffuse. However, since the perovskite oxide a represented by the general formula described above has a β smaller than 0.2, the segregation of MgO is small, so that the diffusion of transition elements from the fuel electrode and the air electrode to the solid electrolyte layer is further increased. It is suppressed. Therefore, according to the present invention, it is possible to suppress a short circuit while forming a thin thickness of the solid electrolyte layer, and it is excellent in oxide ion conductivity in the solid electrolyte layer, and as a result, has a high electromotive force. It is possible to provide a solid oxide electrochemical cell excellent in power generation capacity.
(3) The solid electrolyte layer in the present invention has a second region in which the ratio of the total mass of transition elements of the same type as the transition element contained in the fuel electrode exceeds 0.5% by mass, and the thickness of the solid electrolyte layer The thickness of the second region in the direction is 20 μm or less. Therefore, according to the present invention, an electrical short circuit in the solid electrolyte layer can be further suppressed, and a solid oxide electrochemical cell excellent in high electromotive force and power generation capability can be provided.
(4) According to the present invention, since at least one of the transition elements contained in the fuel electrode is Ni, a high-performance solid oxide electrochemical cell having a fuel electrode having high reaction activity and electronic conductivity Can be provided.
(5) The solid electrolyte layer in the present invention has a third region in which the ratio of the total mass of transition elements of the same type as the transition elements contained in the air electrode exceeds 0.5% by mass, and the thickness of the solid electrolyte layer The thickness of the third region in the direction is 20 μm or less. Therefore, according to the present invention, an electrical short circuit in the solid electrolyte layer can be further suppressed, and a solid oxide electrochemical cell excellent in high electromotive force and power generation capability can be provided.
(6) According to the present invention, since at least one of the transition elements contained in the air electrode is Co, a high-performance solid oxide electricity having an air electrode having high reaction activity and oxide ion conductivity. A chemical cell can be provided.
(7) According to the method for producing a solid oxide electrochemical cell described in (7) above, an unsintered solid electrolyte layer to be a solid electrolyte layer is formed on the surface of an unsintered fuel electrode to be a fuel electrode, Since the co-fired body is formed by firing at the following temperature, diffusion of transition elements such as Ni from the fuel electrode to the solid electrolyte layer can be reduced, thereby suppressing an electrical short circuit, A solid oxide electrochemical cell having a high electromotive force and excellent power generation capability can be produced.
(8) According to the method for producing a solid oxide electrochemical cell described in (8) above, an unsintered air electrode serving as an air electrode is formed on the surface of the co-fired body and fired at a temperature of 1100 ° C. or lower. Therefore, it is possible to reduce diffusion of transition elements such as Co from the air electrode to the solid electrolyte layer, thereby suppressing an electrical short circuit, and having a high electromotive force and excellent power generation capability. A physical electrochemical cell can be manufactured.
(9) According to the invention according to (9), it is possible to provide a solid oxide fuel cell that hardly causes an electrical short circuit, has a high electromotive force, and is excellent in power generation capability.

(10) According to the invention according to (10), it is possible to provide a high-temperature steam electrolysis apparatus that is less likely to cause an electrical short circuit and is excellent in water decomposition ability.

FIG. 1 is a cross-sectional view of a cylindrical solid oxide electrochemical cell showing an example of a solid oxide electrochemical cell according to the present invention. FIG. 2 is a perspective view showing an example of a solid oxide fuel cell stack including a solid oxide electrochemical cell according to the present invention. FIG. 3 is a schematic cross-sectional view taken along the line AA ′ of FIG. 2, and is substantially perpendicular to the longitudinal axis direction of the solid oxide electrochemical cell at a substantially central portion in the longitudinal axis direction of the solid oxide electrochemical cell. It is the cross-sectional schematic of the solid oxide fuel cell stack at the time of cut | disconnecting. FIG. 4 is a cross-sectional view of the solid oxide fuel cell stack shown in FIG. 2 taken along the line BB ′ and observed when the solid oxide electrochemical cell is taken out and observed. FIG. 5 is a perspective view showing an example of the insulating porous body shown in FIG. 6 is a cross-sectional view of the solid oxide fuel cell stack shown in FIG. 2 taken along the line BB ′. FIG. 7 is a cross-sectional explanatory view showing the measurement positions of the thicknesses of the first region and the second region on the cut surface of the solid oxide electrochemical cell.

  A solid oxide electrochemical cell (hereinafter sometimes referred to as “single cell”) includes a solid electrolyte layer, a fuel electrode formed on one side of the solid electrolyte layer, and the other of the solid electrolyte layer. And an air electrode formed on the side.

The fuel electrode is provided on the surface of the solid electrolyte layer opposite to the surface on which the air electrode is formed. The fuel electrode may be formed of a material having a catalytic function for redox reaction, electron conductivity, gas permeability, stability under high temperature conditions, and the like. The fuel electrode contains at least one transition element of Mn, Fe, Co, Ni, and Cu. Among these, Ni and Cu are preferable, and Ni is more preferable. When the fuel electrode contains Ni, a high-performance solid oxide electrochemical cell having a fuel electrode having high reaction activity and electronic conductivity can be provided. The fuel electrode includes at least one of a ZrO ₂ -containing ceramic such as zirconia stabilized by at least one kind of rare earth elements such as Sc and Y, and a ceramic such as CeO ₂ -containing ceramic in addition to the transition element. Contains one. The air electrode may contain the transition element as a metal, may be contained as two or more kinds of alloys, or may be contained as a metal oxide or a composite oxide. The fuel electrode may be formed of a cermet that is a mixture of the transition element and the ceramic.

The air electrode is provided on the surface opposite to the surface on which the fuel electrode of the solid electrolyte layer is formed. The air electrode may be formed of a material having a catalytic function, electronic conductivity, oxide ion conductivity, gas permeability, stability under high temperature conditions, and the like. The air electrode contains at least one transition element of Mn, Fe, Co, Ni, and Cu. Among these, Mn, Fe, and Co are preferable, and Fe and Co are more preferable. When the air electrode contains Co, a high-performance solid oxide electrochemical cell including the air electrode having high reaction activity and oxide ion conductivity can be provided. The air electrode may contain the transition element as a metal, may be contained as two or more kinds of alloys, or may be contained as a metal oxide or a composite oxide. As a material for forming the air electrode, for example, La _1-x Sr _x Co _y Fe _1-y O _3-δ (0 <x <0.5, 0 <y <0.4), La _1-x Sr _x MnO _3-δ (0 <x <0.3), La _1-x Sr _x CoO _3-δ (0 <x <0.5) (hereinafter sometimes referred to as “LSC”), Sm _1-x Sr _x CoO _3-δ (0 <x <0.6), Ba _1-x La _x CoO _3-δ (0 <x <0.6), and the like. Further, the air electrode may contain other materials such as Ag as required.

The solid electrolyte layer is provided between the fuel electrode and the air electrode. The solid electrolyte layer has a perovskite type crystal structure and contains a perovskite type oxide a containing at least Ga. The perovskite oxide a is a solid electrolyte having oxide ion conductivity. Examples of the perovskite oxide a include a perovskite oxide containing La and Ga. In the perovskite oxide a containing La and Ga, a part of La and a part of Ga are preferably substituted with another element such as Ca, Sr, or Mg. Although the substitution rate by Ca, Sr, and Mg contained in the perovskite oxide a is not particularly limited, for example, when La and Ga are substituted by an A element and a B element, respectively (the A element is one of Ca and Sr When at least one element B is Mg) and the number of A-site atoms in the perovskite type crystal structure (the sum of the number of La atoms and the number of A element atoms) is 0.05 or more and 0.2 When La of less than the number of atoms is substituted with the A element and the number of atoms at the B site (the sum of the number of Ga atoms and the number of B element atoms) is 1, 0.05 or more and less than 0.2 atoms It is preferable that the number Ga is substituted with the B element. A preferred example of the perovskite oxide a can be represented by the following general formula (I).
(La _1−α Sr _α ) (Ga _1−β Mg _β ) O _3−δ (0.05 ≦ α <0.2, 0.05 ≦ β <0.2) General Formula (I)

The perovskite oxide a represented by the general formula (I) has a particularly high oxide ion conductivity among the perovskite oxides a, so that the solid electrolyte layer is represented by the general formula (I). When a is contained, a solid oxide electrochemical cell excellent in power generation capability can be provided.
In general formula (I), as β becomes smaller than 0.2, the segregation of MgO in the solid electrolyte decreases. When MgO is segregated in the solid electrolyte layer, MgO easily reacts with the transition element contained in the fuel electrode and the air electrode to form a solid solution. Therefore, the transition element from the fuel electrode and the air electrode to the solid electrolyte layer. Becomes easy to diffuse. However, the perovskite oxide a represented by the general formula (I) has less segregation of MgO because β is smaller than 0.2, so that the diffusion of transition elements from the fuel electrode and the air electrode to the solid electrolyte layer is further reduced. It is further suppressed. Therefore, when the solid electrolyte layer is formed of the perovskite oxide a represented by the general formula (I), a short circuit can be suppressed even if the thickness of the solid electrolyte layer is reduced, and the solid electrolyte As a result, it is possible to provide a solid oxide electrochemical cell that is excellent in conductivity of oxide ions in the layer and has high electromotive force and excellent power generation capacity.

  The fact that the solid electrolyte layer has the perovskite oxide a is analyzed by an X-ray diffractometer (XRD) on the cut surface when the fuel electrode, the solid electrolyte layer, and the air electrode are cut in the arrangement direction. It can be confirmed by identifying the substances contained in the layer. Further, the atomic ratio of the elements contained in the perovskite oxide a is determined by the wavelength dispersive X-ray spectrometer (WDS) attached to the electron probe microanalyzer (EPMA) near the center of the cut surface of the solid electrolyte layer. ) To perform elemental analysis.

  The thickness of the solid electrolyte layer is 100 μm or less. The thinner the solid electrolyte layer, the lower the internal resistance, thereby providing a solid oxide electrochemical cell with excellent power generation capability. On the other hand, if the thickness of the solid electrolyte layer is too thin, the solid electrolyte layer is easily damaged, and a short circuit is likely to occur inside the solid electrolyte layer. Therefore, the thickness of the solid electrolyte layer is preferably 20 μm or more. When the solid electrolyte layer containing the perovskite oxide a is thin and has a thickness of 100 μm or less, a transition element such as Ni diffused from the fuel electrode during firing and a transition element such as Co diffused from the air electrode during firing, An electron conduction path from the fuel electrode to the air electrode is formed in the solid electrolyte layer, and a short circuit may occur in the solid electrolyte layer. Therefore, in the solid oxide electrochemical cell including the solid electrolyte layer containing the perovskite oxide a, the electromotive force and the power generation capacity may be reduced. However, even if the thickness of the solid electrolyte layer in the present invention is as thin as 100 μm or less, since the thickness of the first region is 5 μm or more as will be described later, an electrical short circuit can be suppressed, and the solid electrolyte layer is high. A solid oxide electrochemical cell having an electromotive force and excellent power generation capability can be provided.

  When the solid electrolyte layer is point-analyzed by a wavelength dispersive X-ray spectrometer (WDS) attached to an electron beam probe microanalyzer (EPMA), the solid electrolyte layer has atomic numbers 1 to 8 among all detected elements. The ratio of the total mass of the transition element of the same type as the transition element contained in the fuel electrode to the total mass of the elements excluding the above elements is 0.5% by mass or less, and the transition element contained in the air electrode It has the 1st field where the ratio of the total mass of the transition element of the same kind is 0.5 mass% or less, and the thickness of the 1st field in the film thickness direction of a solid electrolyte layer is 5 micrometers or more. That is, in the solid electrolyte layer, even if the transition elements contained in the solid electrolyte layer diffuse from the fuel electrode and the air electrode during firing, there is a region where the transition element is hardly diffused in the central portion of the solid electrolyte layer. And the thickness of the area | region is 5 micrometers or more. Although the thickness of the first region is preferably as large as possible, the upper limit is the thickness of the solid electrolyte layer. Since the thickness of the first region of the solid electrolyte layer is 5 μm or more, a short circuit in the solid electrolyte layer can be suppressed.

  When the solid electrolyte layer is point-analyzed by the WDS attached to EPMA, the solid electrolyte layer includes transitions included in the fuel electrode with respect to the total mass of elements other than the elements having atomic numbers 1 to 8 among all the detected elements. It is preferable that the ratio Rf of the total mass of transition elements of the same type as the element has a second region exceeding 0.5% by mass, and the thickness of the second region in the film thickness direction of the solid electrolyte layer is 20 μm or less. . That is, in the solid electrolyte layer, even if the transition element diffuses from the fuel electrode to the solid electrolyte layer during firing, the thickness of the diffusion region of the transition element is preferably 20 μm or less. When the thickness of the second region is 20 μm or less, the solid electrolyte layer can further suppress an electrical short circuit in the solid electrolyte layer. In addition, as the diffusion of the transition element proceeds, the oxide ion conductivity of the perovskite oxide a tends to decrease, but if the thickness of the second region is 20 μm or less, the decrease in oxide ion conductivity is suppressed. It is possible to provide a solid oxide electrochemical cell having a higher electromotive force and an excellent power generation capability.

  When the solid electrolyte layer is subjected to point analysis on its own cut surface by WDS attached to EPMA, the transition included in the air electrode with respect to the total mass of the elements excluding the elements having atomic numbers 1 to 8 among all the detected elements It is preferable that the ratio Ra of the total mass of transition elements of the same type as the element has a third region that exceeds 0.5% by mass, and the thickness of the third region in the film thickness direction of the solid electrolyte layer is 20 μm or less. . That is, in the solid electrolyte layer, even if the transition element diffuses from the air electrode to the solid electrolyte layer during firing, the thickness of the diffusion region of the transition element is preferably 20 μm or less. When the thickness of the second region is 20 μm or less, the solid electrolyte layer can further suppress an electrical short circuit in the solid electrolyte layer, and also suppress a decrease in oxide ion conductivity. Therefore, it is possible to provide a solid oxide electrochemical cell having a higher electromotive force and excellent power generation capability.

The thickness of the solid electrolyte layer is determined by polishing the cut surface when the unit cell is cut in the direction in which the fuel electrode, the solid electrolyte layer, and the air electrode are arranged. as shown in 7, the interface F ₁ between the solid electrolyte layer 2 and the fuel electrode 3, the distance d between the interface F ₂ between the solid electrolyte layer 2 and the air electrode 4 be determined by measuring with an electron microscope or the like it can.

The thickness of the second region can be obtained as follows. A polished surface is formed in the same manner as when the thickness of the solid electrolyte layer 2 is obtained, and on this polished surface, an interface F ₁ between the fuel electrode 3 and the solid electrolyte layer 2 to an interface F between the air electrode 4 and the solid electrolyte 2 is formed. ₂ , point analysis is performed on the straight line L perpendicular to the interface F ₁ at regular intervals, for example, 1 μm. When a transition element such as Ni contained in the fuel electrode 3 diffuses into the solid electrolyte layer, as the point analysis proceeds from the analysis point on the interface F ₁ to the interface F ₂ on the straight line L, Ni The ratio Rf of the total mass of transition elements such as is small. When the analysis point at which the ratio Rf is 0.5 mass% or less is reached, the distance from the analysis point before the analysis point to the analysis point on the interface F ₁ is measured, and this is determined as the thickness of the second region. and d _2. Similarly to the thickness of the second region, the thickness of the third region can be obtained by performing point analysis on the straight line L toward the interface F ₁ with the analysis point on the interface F ₂ as a starting point. The thickness d ₁ of the first region is the difference between the distance d between the interface F ₁ and the interface F ₂ and the sum of the thickness d ₂ of the _second region and the thickness d ₃ of the third region (d− (d ₂ + d ₃ )).
The point analysis is performed with an acceleration voltage of 15 kV, an irradiation current of 50 nA, and a spot diameter of 1 μm using the WDS attached to the EPMA. In addition, since the analysis accuracy of light elements is low in the WDS analysis of EPMA, the total mass of transition elements such as Ni is based on the total mass of elements excluding the elements with atomic numbers 1 to 8 among all detected elements. The ratios Rf and Ra are calculated.

  Next, an example of a single cell according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the single cell 1 of this embodiment is cylindrical. The unit cell 1 has a circular cross-sectional shape when cut by a plane perpendicular to the longitudinal direction of the axis of the cylindrical body. In the cross-sectional shape of the single cell 1, a cylindrical fuel electrode 3 is provided on the innermost side in the radial direction. On the outer side of the fuel electrode 3 in the radial direction, a cylindrical solid electrolyte layer 2 and a cylindrical air electrode 4 are provided in this order concentrically. In the unit cell 1, the outer surface of the fuel electrode 3 and the inner surface of the solid electrolyte layer 2 are surface bonded, and the outer surface of the solid electrolyte layer 2 and the inner surface of the air electrode 4 are surface bonded. The fuel electrode 3 is formed in a thicker shape in the radial direction than the other layers in the single cell 1 and has a function as a support that mechanically supports the single cell 1.
The cross-sectional shape of the cylindrical single cell is not limited to a circle, and may be an ellipse, a polygon, or the like. In addition, the shape of the single cell in the present invention is not limited to a cylindrical shape, and may be a flat plate shape. In the flat plate type single cell, a fuel electrode is provided on one surface of a plate-shaped solid electrolyte layer, and an air electrode is provided on the surface opposite to the surface on which the fuel electrode is provided.

  Next, an example of a method for manufacturing a single cell according to the present invention will be described.

  In the method for producing a single cell according to the present invention, an unsintered solid electrolyte layer to be a solid electrolyte layer is formed on the surface of an unsintered fuel electrode to be a fuel electrode and fired at a temperature of 1320 ° C. or less to form a co-fired body And a step of forming an unfired air electrode to be an air electrode on the surface of the co-fired body and firing at a temperature of 1100 ° C. or lower.

(1) Production of unsintered fuel electrode Clay-like by adding water after adding binder and pore former powder to a mixed powder of nickel oxide and ceramic such as ZrO ₂ -containing ceramic. To obtain a mixture of The clay-like mixture is put into an extruder and formed into a predetermined shape, whereby an unfired fuel electrode is obtained.

(2) Preparation of slurry for forming a solid electrolyte layer In a mixture of perovskite oxide a powder or various oxide powders blended so that perovskite oxide a is formed by firing, such as polyvinyl butyral The solid electrolyte layer forming slurry is obtained by mixing the binder, dispersant, plasticizer, and solvent.

(3) Preparation of unsintered solid electrolyte layer Next, after masking the surface of the unsintered fuel electrode as necessary, the unsintered fuel electrode is immersed in the slurry for forming a solid electrolyte layer, and slowly pulled up, A green electrolyte molded body in which a film of the green solid electrolyte layer is formed on the surface of the green fuel electrode is obtained.

(4) Production of co-fired body Thereafter, the unfired electrolyte molded body is simultaneously fired at 1320 ° C. or less, preferably 1300 ° C. to 1320 ° C., with the unfired solid electrolyte layer and the unfired fuel electrode. After firing, a co-fired body comprising a solid electrolyte layer and a fuel electrode is obtained.

  When the unsintered electrolyte molded body is simultaneously fired, a transition element such as Ni contained in the unsintered fuel electrode diffuses toward the solid electrolyte layer. However, in the method for producing a single cell of the present invention, the unfired electrolyte molded body is fired at a relatively low temperature of 1320 ° C. or less to form a co-fired body, so that the diffusion of transition elements is suppressed.

  Further, when the perovskite oxide a powder is the perovskite oxide represented by the general formula (I), or the perovskite oxide a represented by the general formula (I) is formed by firing. In the case of a mixture of various oxide powders blended, the oxide ion conductivity is increased, so that a solid oxide electrochemical cell having a more excellent power generation capability can be provided. In addition, β in the general formula (I) is smaller than 0.2, so that MgO hardly segregates in the solid electrolyte layer during firing, and a transition element such as Ni that is easily dissolved in MgO diffuses into the solid electrolyte layer. Is further suppressed.

(5) Production of air electrode forming slurry Other materials such as Ag are mixed with the material forming the air electrode such as LSC, if necessary, and a binder, a dispersant, a plasticizer, and a solvent are mixed, and air is mixed. An electrode forming slurry is prepared.

(6) Production of unsintered air electrode After the surface of the co-fired body is masked as necessary, the co-fired body is immersed in the slurry for forming the air electrode, and then slowly pulled up. A green air electrode molded body in which a film of the green air electrode is formed on the surface of the solid electrolyte layer is obtained.

(7) Production of air electrode Thereafter, the green air electrode molded body was baked with a film of the green air electrode under conditions of 1100 ° C. or lower, preferably 900 ° C. to 1100 ° C. It is formed. Thereby, the single cell which has an air electrode, a solid electrolyte layer, and a fuel electrode is obtained.

  When the green air electrode compact is fired, a transition element such as Co contained in the green air electrode diffuses toward the solid electrolyte layer. However, in the method for producing a single cell of the present invention, since the unfired air electrode molded body is fired at a relatively low temperature of 1100 ° C. or lower to form a single cell, diffusion of transition elements is suppressed.

  Further, when the perovskite oxide a powder is the perovskite oxide represented by the general formula (I), or the perovskite oxide a represented by the general formula (I) is formed by firing. In the case of a mixture of various oxide powders blended, the oxide ion conductivity is increased, so that a solid oxide electrochemical cell having a more excellent power generation capability can be provided. In addition, β in the general formula (I) is smaller than 0.2, so that MgO is not easily segregated in the solid electrolyte layer during firing, and a transition element such as Co that is easily dissolved in MgO diffuses into the solid electrolyte layer. Is further suppressed.

  According to the method for manufacturing the single cell, as described above, since diffusion from the fuel electrode and the air electrode to the solid electrolyte layer can be suppressed, formation of an electron conduction path from the fuel electrode to the air electrode is suppressed, A single cell in which the thickness of the first region in the solid electrolyte layer is 5 μm or more can be manufactured. Therefore, a single cell in which a short circuit is suppressed can be manufactured. Further, in the method for producing a single cell, the oxide ion conductivity of the solid electrolyte layer is improved by using the perovskite oxide represented by the general formula (I) as the powder of the perovskite oxide a, Further, by further suppressing the diffusion from the fuel electrode and the air electrode to the solid electrolyte layer, it is possible to manufacture a single cell in which the formation of a highly conductive region with high electron conductivity is suppressed.

  Next, an example of the solid oxide fuel cell of the present invention will be described.

  As shown in FIG. 2, the solid oxide fuel cell stack 31 (hereinafter sometimes simply referred to as “fuel cell stack”) of this embodiment is a rectangular parallelepiped block. A large number of cylindrical unit cells 1 are arranged so as to be parallel to the axial direction. For example, in FIG. 2, three single cells 1 are arranged in the horizontal direction and eight in the vertical direction. As shown in FIG. 3, the reactor cell layer portion 43 includes three unit cells 1 arranged in the horizontal direction, an insulating porous body 34, and a part of a conductive accumulation material layer 35 made of a conductive accumulation material. Is formed. In addition, gas seal layers 33 that prevent gas leakage are formed on both sides of the unit cell 1 in the axial direction.

  As shown in FIG. 3, a plurality of the reactor cell layer portions 43 are formed in parallel in the vertical direction of the figure. The single cells 1 in the reactor cell layer part 43 of FIG. 3 are electrically connected and integrated by a conductive accumulation material layer 35 disposed around the unit cell 1. Further, a plurality of conductive accumulation material layers 35 are arranged in the vertical direction with the insulating porous layer 34 interposed therebetween.

  As shown in FIGS. 2 and 3, the single cell 1 is a thin and long cylindrical member, and a fuel gas conduction hole 39 through which fuel gas flows is formed at the center. The size of the cross-sectional shape of the single cell 1 is not particularly limited, and may be a circle having an outer diameter of 0.5 mm or more and 2.0 mm or less, for example.

  At one end of the unit cell 1, for example, on the right side of the unit cell 1 shown in FIG. 4, a part of the solid electrolyte layer 2 is removed in a strip shape until the fuel electrode 3 is exposed. A metal seal layer 41 is formed on the portion where the solid electrolyte layer 2 is removed so as to cover the exposed portion of the fuel electrode 3. The metal seal layer 41 is a dense metal layer that blocks gas flow and serves as a current collecting terminal of the fuel electrode 3 and is formed in a strip shape from a conductive seal material.

  As shown in FIG. 5, the insulating porous body 34 is a plate-shaped porous ceramic member capable of air flow. On the upper surface of this insulating porous body 34, a large number of array grooves 25 into which the single cells 1 are fitted are formed in parallel, and on the lower surface thereof, they are fitted into the array grooves 25 of other insulating porous bodies 34 and positioned. A positioning convex portion 27 is formed. Each array groove 25 is formed with a communication hole 32 provided with the electrical connection path 42 shown in FIG. 6 in order to conduct electricity through the upper and lower surfaces of the insulating porous body. The uppermost insulating porous body 34 of the fuel cell stack 31 does not have the alignment groove 25, and the lowermost insulating porous body 34 does not have the positioning projection 27.

  As indicated by an arrow FG in FIG. 2, when power generation of the solid oxide fuel cell is performed using the fuel cell stack 31, a fuel gas containing hydrogen is conducted through the fuel gas conduction hole 39. In the fuel gas conduction hole 39, the fuel gas contacts the fuel electrode 3, and hydrogen in the fuel gas reacts with oxide ions carried from the solid electrolyte layer to generate water. Further, as indicated by an arrow AG in FIG. 2, during power generation by the fuel cell stack 31, air gas containing oxygen is supplied from the outside of the insulating porous body 34 in a direction perpendicular to the stacking direction of the single cells 1. Is done. The air gas passes through the insulating porous body 34 and the conductive accumulation material layer 35 and comes into contact with the air electrode 4. In the air electrode 4, oxide ions are generated from oxygen molecules contained in the oxygen gas.

  As shown in FIG. 6, in the fuel cell stack 31, the reactor cell layer portion 43 is assembled in the vertical direction so that the upper side of the figure is a negative electrode and the lower side is a positive electrode. Specifically, the single cell 1 is accommodated in the array groove 25 of the insulating porous body 34, a conductive integration material layer 35 is formed around the single cell 1, and the conductive integration material layer 35 is further formed. Are separated in the left-right direction in FIG. 6 by the insulating material layer 40. A first conductive integration material layer 35a is formed in the left direction of FIG. 6, and a second conductive integration material layer 35b is formed in the right direction of FIG.

  As shown in FIG. 6, the conductive integration material layer 35 is disposed around the metal seal layer 41 to electrically connect the metal seal layer 41 and the electrical connection path 42 of the other insulating porous body 34. Connected. The first conductive accumulation material layer 35a disposed on the left side in FIG. 6 is disposed around the air electrode 4, and in the downward direction of the single cell 1 in FIG. 6, the air electrode 4 and the other insulating porous body 34. The electrical connection path 42 is electrically connected. As indicated by the arrows in FIG. 6, electrons are transmitted from the fuel electrode 3 to the air electrode 4 in each single cell 1, and further electrons flow to the adjacent single cell 1 through the electrical connection path 42. Become.

  The above-described fuel cell stack 31 can be used as the solid oxide fuel cell according to the present invention. More specifically, a current collecting member is provided on the positive electrode side and the negative electrode side of the fuel cell stack 31, and electric power is taken out through a conducting wire or the like connected to the current collecting member. A solid oxide fuel cell module in which a plurality of fuel cell stacks 31 are electrically connected by arranging them in a predetermined direction can also be used as the solid oxide fuel cell according to the present invention.

  As described above, in the single cell of the present invention, diffusion of transition elements such as Ni and Co into the solid electrolyte layer is suppressed, and the thickness of the first region in the solid electrolyte layer is 5 μm or more, and has electronic conductivity. Formation of the region is suppressed. Therefore, when power generation is performed by the fuel cell stack having the single cell, occurrence of a short circuit between the air electrode and the fuel electrode is suppressed, and an electromotive force of the fuel cell stack and a decrease in power generation capacity due to the short circuit are suppressed. .

  Next, an example of a method for manufacturing the fuel cell stack 31 will be described.

(1) Production of insulating porous body 34 For example, a magnesium oxide powder, a cellulose-based binder, and a pore former are mixed, and water is added and mixed to obtain a clay-like body. This clay-like body is put into an extrusion molding machine, and a sheet is formed so that the insulating porous body 34 is formed with portions that become the alignment grooves and the positioning convex portions 27. After firing this sheet at a temperature of about 1500 ° C., the insulating porous body 34 having a shape suitable for manufacturing the fuel cell stack 31 is formed by cutting the sheet into predetermined dimensions and opening the communication holes. The

(2) Production of conductive accumulation material layer molding paste For example, a conductive accumulation material layer molding paste is obtained by mixing LSCF powder, α-terpineol, and an amine-based dispersant.

(3) Production of insulating material layer forming paste For example, an insulating material layer forming paste is obtained by mixing magnesium oxide, α-terpineol, and an amine-based dispersant.

(4) Assembly of fuel cell stack 31 An insulating material layer forming paste is applied to a predetermined position in the insulating porous body 34. Next, the conductive material layer molding paste is applied to a predetermined position on the surface of the insulating material layer molding paste. Further, the single cell 1 is disposed in the array groove 25 of the insulating porous body 34. Specifically, the single cell 1 is provided with a metal seal layer 41 at a predetermined position, and the position of the metal seal layer 41 and the position of the communication hole 32 in the insulating porous body 34 correspond to each other. Cell 1 may be arranged. A laminated body is obtained by laminating many insulating porous bodies 34 in which the single cells 1 are embedded. The stack is obtained by firing the laminated body in the atmosphere at about 1000 ° C. for 2 hours.

(5) Formation of gas seal layer 33 For example, an appropriate amount of polyvinyl butyral, amine dispersant, and plasticizer is added to a borosilicate glass powder having a softening point of 700 ° C. and an average particle diameter of 4 μm. A slurry is obtained using toluene as a solvent. A glass sheet having a thickness of about 300 μm is formed by the doctor blade method using the obtained slurry. This glass sheet is punched to form a large number of through-holes through which single cells are inserted.

  In addition, an appropriate amount of ethyl cellulose and an amine-based dispersant is added to the glass powder and a predetermined amount, for example, 10% by volume of the magnesia powder with respect to the glass, and a paste is prepared using butyl carbitol as a solvent. This paste is applied to one plane of the glass sheet to form a paste layer. The glass sheet provided with the paste layer is bonded to the end face of the stack body through a single cell through the through hole while the paste layer faces the stack body side. Thereafter, the stack body is heated at a temperature higher than the softening point of the glass for about 2 hours, the paste layer is softened, and the glass sheet is firmly bonded to the stack body. Can be obtained.

  Next, an example of the high temperature steam cracking apparatus of this invention is demonstrated.

  In the solid oxide fuel cell of the present invention, by connecting an external power source capable of supplying a current in the opposite direction to the time of power generation of the cell to the positive electrode of the fuel cell and the negative electrode of the fuel cell, the high-temperature steam electrolysis apparatus Obtained and function as an anode and a cathode, respectively. In the high-temperature steam electrolysis apparatus, water molecules are decomposed by energizing the fuel electrode and the air electrode with an external power supply while blowing steam under a high temperature condition of about 900 ° C. Specifically, hydrogen gas derived from water molecules is extracted from the fuel electrode, and oxygen gas derived from water molecules is extracted from the air electrode.

  Since the high-temperature steam electrolysis apparatus according to the present invention has a single cell including a solid electrolyte layer having a thickness of the first region of 5 μm or more, the hydrogen production loss of the high-temperature steam electrolysis apparatus due to a short circuit during steam decomposition Etc. are suppressed, and the resolution of water vapor is excellent.

Example 1
<Preparation of specimen>
A mixed powder of nickel oxide and yttria-stabilized zirconia (hereinafter sometimes referred to as “YSZ”) has a ratio of Ni: YSZ = 50: 50 (volume%) in a state where the fuel electrode after production is reduced. Thus, nickel oxide and YSZ were weighed and prepared by mixing. Cellulose binder and polymethyl methacrylate (PMMA) bead powder as a pore former were added to the weighed mixed powder and mixed well, and then water was added to obtain a clay body. The addition amount of the bead powder was adjusted so that the pore volume was 60% with respect to the volume of NiO and YSZ in the fuel electrode after production. The clay body was put into an extruder to produce a cylindrical unfired fuel electrode having an outer diameter of 12.5 mm.

  On the other hand, in order to form a solid electrolyte layer, a powder of perovskite oxide a shown in Table 1, polyvinyl butyral, an amine-based dispersant, a plasticizer, and a mixture of methyl ethyl ketone and ethanol as solvents are mixed. A slurry for layer formation was prepared.

  After cutting the unburned fuel electrode to a predetermined length and performing masking at a position where a solid electrolyte layer is not formed, the surface of the unburned fuel electrode is immersed in a slurry for forming a solid electrolyte layer and slowly pulled up. A film of an unfired solid electrolyte layer was formed. Thereafter, the co-fired body comprising the fuel electrode and the solid electrolyte layer is obtained by co-firing the unfired fuel electrode and the unfired solid electrolyte layer at a predetermined temperature in the temperature range of 1320 ° C. to 1350 ° C. shown in Table 1. Obtained.

Next, in order to form an air electrode, a powder of La _0.6 Sr _0.4 CoO _3-δ (hereinafter sometimes referred to as “LSC”) is added to polyvinyl butyral, an amine-based dispersant, The plasticizer was mixed with methyl ethyl ketone and ethanol as a solvent to prepare an air electrode forming slurry.

  After masking the position where the air electrode is not formed, the film was immersed in the air electrode forming slurry and slowly pulled up to form a film of the unfired air electrode on the surface of the solid electrolyte layer in the co-fired body. Then, the unit cell which has a fuel electrode, a solid electrolyte layer, and an air electrode was obtained by baking the film of a non-baking air electrode at the predetermined temperature of the temperature range of 1100 degreeC-1150 degreeC shown in Table 1. FIG.

  A silver wire was wound around the exposed portion of the fuel electrode of the obtained single cell to form an anode terminal. Next, only the air electrode of a single cell is covered with a platinum mesh, a silver wire is connected on the platinum mesh, a conductive paste for current collection is applied on the platinum mesh and baked in an electric furnace to form a cathode terminal. Then, a power generation evaluation type test specimen was produced.

<Measurement of electromotive force and power generation capacity of specimen>
The produced test specimen of the power generation evaluation form was installed in an electric furnace, and then the anode terminal and the cathode terminal were connected to a voltmeter and an impedance measuring device (SI1287, 1255B manufactured by solartron). Next, in a state where nitrogen gas is continuously supplied to the fuel electrode side and air is continuously supplied to the air electrode side, the temperature inside the electric furnace is raised to 700 ° C., and then the nitrogen gas on the fuel electrode side is switched to hydrogen gas. The fuel electrode was reduced. After the reduction treatment, the temperature in the furnace was lowered to 500 ° C., and the power generation output when an open circuit electromotive force and a current at 500 ° C. were applied at 50 mA / cm ² was measured. These results are shown in Table 1.
After measuring the open circuit electromotive force and the power generation output, the furnace temperature was lowered to room temperature with hydrogen gas flowing in the fuel electrode side.

<Identification of perovskite oxide a>
The specimen taken out from the electric furnace was embedded in an epoxy resin and cut in a direction perpendicular to the axis of the single cell to form a cut surface from which the fuel electrode, the solid electrolyte layer, and the air electrode were exposed. After this machined surface was mechanically polished, a smooth surface was formed by cross polisher processing. When the solid electrolyte layer was analyzed with an X-ray diffractometer (XRD) on the obtained smooth surface, the perovskite oxide a was identified.

<Measurement of thickness of solid electrolyte layer and first region to third region>
An analysis surface for elemental analysis was obtained by performing carbon deposition on the smooth surface. For elemental analysis, an electron probe microanalyzer (FE-EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDS) is used (JXA-8500F, manufactured by JEOL Ltd.), acceleration voltage is 15 kV, irradiation current is 50 nA. Elemental analysis was performed.
When elemental analysis was performed on the specimens of test numbers 3 to 6 near the center of the solid electrolyte layer on the analysis surface, the atomic ratio of the elements contained in the perovskite oxide a used as a raw material was almost the same. It was.

The thickness d ₂ of the second region indicating the diffusion distance of Ni from the fuel electrode to the solid electrolyte layer is, as described above, from the interface F ₁ between the fuel electrode and the solid electrolyte layer to the interface between the air electrode and the solid electrolyte layer. Point analysis was performed by WDS on the straight line L perpendicular to the interface F ₁ toward the F ₂ at intervals of 1 μm. The mass ratio Rf of Ni decreases as the analysis proceeds on the straight line L from the interface F ₁ toward the interface F ₂ , and when the analysis point reaches 0.5% by mass or less, The distance from the analysis point to the analysis point on the interface F ₁ was measured, and this was defined as the thickness d ₂ of the second region.

The thickness d ₃ of the third region showing the diffusion distance of Co from the air electrode to the solid electrolyte layer, the interface on the straight line L from the analysis point on the interface F ₂ in the same manner as the thickness d ₂ of the second region F Point analysis was performed toward ₁ . When the analysis point where the mass ratio Ra of Co is 0.5% by mass or less is reached, the distance from the analysis point before the analysis point to the analysis point on the interface F ₂ is measured, and this is measured in the third region. of a thickness of _{d 3.}
The ratios Rf and Ra were calculated based on the total mass of the elements excluding the elements having atomic numbers 1 to 8 among all the detected elements.

The thickness d ₁ of the first region is the difference between the distance d between the interface F ₁ and the interface F ₂ and the sum of the thickness d ₂ of the first region and the thickness d ₃ of the second region (d ₁ = d - it was determined by _{(d 2 + d 3))} . These results are shown in Table 1.

As shown in Table 1, the test bodies of test numbers 1 to 7 within the scope of the present invention can obtain a normally required open circuit electromotive force of 1.00 V or higher and a power generation output of 10 mW / cm ² or higher. was gotten.

  On the other hand, the test body of test number 8 outside the scope of the present invention had an open circuit electromotive force lower than 1.00 V, and the power generation output could not be measured. Since the test body of test number 8 has a co-firing temperature higher than 1320 ° C., Ni diffuses from the fuel electrode and the thickness of the second region increases, and the air electrode firing temperature is higher than 1100 ° C. Since the thickness of the third region increased due to diffusion of Co from the pole, the thickness of the first region became 0 μm, and a short circuit occurred in the solid electrolyte layer, thereby reducing the open circuit electromotive force. I understand that. Further, the generation output cannot be measured due to the occurrence of a short circuit in the solid electrolyte layer.

  In addition, the test body of test number 9 outside the scope of the present invention had an open circuit electromotive force of 1.00 V or higher, while the power generation output was smaller than other test bodies. As for the test body of test number 9, the thickness of the second region and the third region is large as in the case of the test body of test number 8, but the thickness of the first region is larger because the thickness of the solid electrolyte layer is larger than that. Is 5 μm or more. Therefore, a high open circuit electromotive force is obtained without causing a short circuit in the solid electrolyte layer. On the other hand, the test body of test number 9 has a solid electrolyte layer thickness greater than 100 μm, a higher resistance than the other test bodies, and the second and third regions have a greater thickness and oxide ion conduction. It can be seen that the power generation output is reduced due to the decrease in performance.

  In the test bodies of test number 1 and test number 2, the number of Mg atoms in the perovskite oxide a constituting the solid electrolyte layer is 0.2 when the total number of atoms of Ga and Mg is 1. The general formula (I) is not satisfied. Since Ni and Co are solid-dissolved with MgO under the heat treatment conditions, the specimens of Test No. 1 and Test No. 2 having a high Mg content tend to segregate MgO in the solid electrolyte layer and attract Ni and Co. Becomes larger. Therefore, it is considered that the thicknesses of the second region and the third region are larger than those of test numbers 3 to 6 that satisfy the general formula (I).

  In the test body of test number 7, since the perovskite oxide a constituting the solid electrolyte layer does not contain Mg, the force for attracting Ni and Co is small, and the thickness of each of the second region and the third region is small. On the other hand, since the perovskite oxide a does not contain Mg, the oxide ion conductivity is lowered, and as a result, the power generation output is smaller than those of test numbers 1 to 6.

  In the test bodies of Test Nos. 3 to 6, since the perovskite oxide a constituting the solid electrolyte layer satisfies the general formula (I), the diffusion of Ni and Co is suppressed, and the second region and the third region Each thickness is 20 μm or less. Therefore, the test bodies of test numbers 3 to 6 can form a thin solid electrolyte layer while suppressing a short circuit, and can obtain high open circuit electromotive force and power generation output.

  When test numbers 1 and 2 are compared, since the temperature at the time of simultaneous firing of test number 1 is lower than that of test number 2, the diffusion of Ni is suppressed and the thickness of the second region is reduced. Therefore, the test body of Test No. 1 having a low temperature at the time of co-firing can form a thin solid electrolyte layer while suppressing a short circuit, and also suppresses formation of a highly conductive region having high electron conductivity. And high power output can be obtained.

  When test numbers 4 and 5 are compared, since the temperature at the time of firing the air electrode of test number 4 is lower than that of test number 5, the diffusion of Co is suppressed and the thickness of the third region is reduced. Therefore, the test body of test number 4 having a low temperature at the time of air electrode firing can form a solid electrolyte layer thinner while suppressing a short circuit, and can form a highly conductive region with high electron conductivity. It can be suppressed and high power generation output can be obtained.

DESCRIPTION OF SYMBOLS 1 Single cell 2 Solid electrolyte layer 3 Fuel electrode 4 Air electrode 25 Arrangement groove 27 Positioning convex part 31 Solid oxide fuel cell stack 32 Communication hole 33 Gas seal layer 34 Insulating porous body 35 Conductive integration material layer 35a 1 conductive material layer 35b second conductive material layer 39 fuel gas conduction hole 40 insulating material layer 41 metal seal layer 42 electrical connection path 43 reactor cell layered portion

Claims (7)

A solid oxide electrochemical cell having a solid electrolyte layer, a fuel electrode formed on one side of the solid electrolyte layer, and an air electrode formed on the other side of the solid electrolyte layer, ,
The fuel electrode contains nickel oxide and yttria-stabilized zirconia ,
The air electrode contains La _0.6 Sr _0.4 CoO _3-δ ,
The solid electrolyte layer contains La _0.9 Sr _0.1 Ga _x Mg _y O _3-δ (x: 0.8 to 0.95, y: 0.05 to 0.2), and has its own thickness. Having a perovskite type oxide a containing Ga and having a perovskite type oxide a containing Ga, and by performing point analysis on the cut surface of the solid electrolyte layer with a wavelength dispersive X-ray spectrometer attached to an electron beam probe microanalyzer, The ratio of the total mass of transition elements of the same type as the transition elements contained in the fuel electrode to the total mass of the elements excluding the elements having atomic numbers 1 to 8 among all the detected elements is 0.5% by mass or less. And the 1st area | region whose ratio of the total mass of the transition element of the same kind as the transition element contained in the said air electrode is 0.5 mass% or less, and said 1st in the film thickness direction of the said solid electrolyte layer The thickness of the region is 5 μm or more The solid oxide electrochemical cell.   The solid electrolyte layer is an element having atomic numbers 1 to 8 among all the elements detected when the cut surface of the solid electrolyte layer is point-analyzed by a wavelength dispersive X-ray spectrometer attached to an electron beam probe microanalyzer. The ratio of the total mass of transition elements of the same type as the transition elements contained in the fuel electrode to the total mass of the elements excluding the second region exceeds 0.5% by mass, and the film thickness direction of the solid electrolyte layer 2. The solid oxide electrochemical cell according to claim 1, wherein the second region has a thickness of 20 μm or less. The solid electrolyte layer is an element having atomic numbers 1 to 8 among all the elements detected when the cut surface of the solid electrolyte layer is point-analyzed by a wavelength dispersive X-ray spectrometer attached to an electron beam probe microanalyzer. The ratio of the total mass of transition elements of the same type as the transition element contained in the air electrode to the total mass of elements excluding the third region has a third region exceeding 0.5% by mass, and the film thickness direction of the solid electrolyte layer 3. The solid oxide electrochemical cell according to claim 1, wherein the third region has a thickness of 20 μm or less. It is a manufacturing method of the solid oxide type electrochemical cell as described in any one of Claims 1-3 , Comprising: The unbaking solid electrolyte layer used as the said solid electrolyte layer on the surface of the unburned fuel electrode used as the said fuel electrode And a step of forming a co-fired body by firing at a temperature of 1320 ° C. or lower, and a method for producing a solid oxide electrochemical cell. It is a manufacturing method of the solid oxide type electrochemical cell as described in any one of Claims 1-3, Comprising: The unbaking air electrode used as the said air electrode is formed in the surface of the said co-fired body, 1100 degrees C or less The method for producing a solid oxide electrochemical cell according to claim 4 , further comprising a step of firing at a temperature of 5 ° C. A solid oxide fuel cell comprising the solid oxide electrochemical cell according to claim 1 . A high-temperature steam decomposition apparatus comprising the solid oxide electrochemical cell according to any one of claims 1 to 3 .

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