JP5243285B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell using an air electrode comprising a perovskite-type metal oxide and cerium oxide to which praseodymium is added.

  There is a growing interest in solid oxide fuel cells using zirconia-based oxygen ion conductors, which are excellent electrolyte materials. In particular, from the viewpoint of effective use of energy, solid fuel cells have essentially high energy conversion efficiency because they are not restricted by Carnot efficiency, and have excellent features such as good environmental conservation. have.

  The solid oxide fuel cell initially had a high operating temperature of 900 to 1000 ° C., and all members were made of ceramic. For this reason, it was not easy to reduce the manufacturing cost of the cell stack. Here, if the operating temperature can be lowered to 800 ° C. or less, a heat-resistant alloy material can be used for the interconnector, and the manufacturing cost can be reduced. However, as the operating temperature decreases, the electrochemical resistance at the air electrode, that is, the overvoltage, suddenly increases and the output voltage decreases.

In order to solve the problem of the air electrode due to such a decrease in operating temperature, La _1-X Sr _X Fe _1-Y Co _Y O ₃ (LSFC: X = 0.1 to 0.3, Y = 0.1 ~0.6, X + Y <0.7) , La 1-X Sr X CoO 3 (X = 0.1~0.5), LaNi 1-X Fe X O 3 (LNF: X = 0.3~0 There is a technique using a perovskite type metal oxide (perovskite type oxide) having high electrode activity (electrochemical reaction performance). These materials are perovskite oxides containing La and Sr at the A site and Ni, Co, and Fe at the B site. Some of the A sites contain La and Ca. These materials are suitable for an air electrode for low temperature operation.

However, since the air electrode is manufactured by firing in contact with an electrolyte containing zirconia, an insulator such as La ₂ Zr ₂ O ₇ is generated in a portion in contact with the electrolyte, and this product is This is one of the causes of deteriorating characteristics in the air electrode. In order to prevent this problem, a ceria layer made of a cerium oxide (ceria compound) added with rare earths such as Ce _0.9 Gd _0.1 O ₂ and Ce _0.8 Sm _0.2 O ₂ is provided between the air electrode and the electrolyte. A method of breaking the contact between the pole-side perovskite oxide and the electrolyte-side zirconia has been studied (Non-Patent Document 1). The ceria layer thus provided has high oxygen ion conductivity, and a reaction that generates an insulator with the perovskite oxide is less likely to occur.

  In addition, in order to further improve the low-temperature characteristics of a solid oxide fuel cell using an air electrode composed of the above-mentioned materials, a method of providing a mixture of perovskite oxide particles and ceria compounds in the vicinity of an electrolyte is known. (See Non-Patent Document 2). By forming the air electrode in a state where the perovskite oxide powder (powder) and the fine powder of the ceria compound are mixed, the active area of the electrode generated at the junction between the electrolyte and the air electrode is increased, and the electrode It is possible to reduce the interface resistance.

The ceria compound is suitable as a material to be mixed with the air electrode because the reaction deterioration with the Co-based and Fe-based air electrode materials described above hardly occurs. In the air electrode composed of this mixture, the perovskite oxide particles are covered with ceria compound particles, and the direct contact between the perovskite oxide material and the zirconia material constituting the electrolyte is suppressed. In addition, formation of reaction products with harmful zirconia such as La ₂ Zr ₂ O ₇ is suppressed.

  In addition, the output voltage may be improved by using cerium oxide to which praseodymium (Pr) is added as the above-described ceria compound.

A. Mai, et al., "Ferrite-based perovskites as cathode materials for anode-suported solid oxide fuel cells Part II influence of the CGO recycling", Solid State Ionics 177, pp.2103-2107, 2006. Y. Matsuzaki, et al., "Electrochemical properties of reduced-temperature SOFCs with mixed ionic-electronic conductors in electrodes and / or ables", Solid State Ionics 152-153, pp.463-468, 2002.

  However, when Pr is added, if the amount added exceeds 5 at%, the thermal expansion coefficient becomes very large, and the cell may be cracked or peeled off due to a temperature change caused by an operation stop or the like. There's a problem.

  The present invention has been made to solve the above problems, and even if Pr is added to the air electrode material in excess of 5 at%, the occurrence of problems such as cracks and peeling can be suppressed. The purpose is to do.

Solid oxide fuel cell according to the present invention, a fuel electrode, an electrolyte, and the solid oxide fuel cell comprising an air electrode, air electrode, is disposed on the side of the electrolyte _{(Ce 1-y Ln y)} 1 _-xz Pr _x M _z O ₂ (Ln = Sm, Gd, Y, M = Nb, Ta, 0.05 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.5, x / 20 ≦ z ≦ x / 5 And a second layer that is disposed in contact with the first layer and is made of a perovskite-type metal oxide.

In the solid oxide fuel cell, the first layer may be constituted by mixed _{(Ce 1-y Ln y)} 1-xz Pr x M z in addition to O ₂ metal oxide having a perovskite . In addition, you may make it provide the intermediate | middle layer comprised from the cerium oxide which is arrange | positioned between electrolyte and an air electrode, and added rare earths other than praseodymium.

As described above, according to the present invention, the air electrode _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 (Ln = Sm, Gd, Y, M = Nb, Ta, 0.05 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.5, x / 20 ≤ z ≤ x / 5), so even if Pr exceeds 5 at%, problems such as cracks and peeling It is possible to obtain an excellent effect that the generation of water can be suppressed.

It is sectional drawing which shows typically the structural example of the solid oxide fuel cell in Embodiment 1 of this invention. It is a perspective view which shows the structure of a single cell. It is sectional drawing which shows typically the structural example of the solid oxide fuel cell in Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a configuration example of a solid oxide fuel cell according to Embodiment 1 of the present invention. This solid oxide fuel cell includes an electrolyte 101 made of a zirconia-based material and a fuel electrode 102 formed on one surface of the electrolyte 101. The solid oxide fuel cell of the present embodiment includes an air electrode 103 formed on the other side of the electrolyte 101, and the air electrode 103 is opposite to the first layer 103 a on the electrolyte 101 side and the electrolyte 101. And a second layer 103b formed on the first layer 103a on the side. Further, in the present embodiment, the intermediate layer 104 is provided between the electrolyte 101 and the air electrode 103 and is made of cerium oxide to which a rare earth other than Pr is added.

In this embodiment, first, the first layer 103a is composed of a _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2. Here, Ln is any one of samarium (Sm), gadolinium (Gd), and yttrium (Y), M is niobium (Nb) or tantalum (Ta), and 0.05 ≦ x ≦ 1. 0, 0 ≦ y ≦ 0.5, and x / 20 ≦ z ≦ x / 5.

Next, the second layer 103b is composed of LaNi _0.6 Fe _0.4 O ₃ (LNF), La _0.5 Sr _0.5 CoO ₃ (LSC), La _0.8 Sr _0.2 Fe _0.8 Co _0.2 O ₃ (LSCF), La _0.8 Sr _0.2 FeO ₃ ( LSF), La _0.8 Sr _0.2 Mn (LSM), and Sm _0.5 Sr _0.5 CoO ₃ (SSC) and other perovskite oxides. Thus, when using cerium oxide with praseodymium (Pr) added to the air electrode 103 (first layer 103a), by adding Nb to this cerium oxide, Pr is added in excess of 5 at%. Even so, the thermal expansion coefficient can be reduced.

The electrolyte 101 is made of, for example, scandium oxide (Sc ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) stabilized ZrO ₂ (SASZ), yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), and the like. What is necessary is just to be comprised from the sintered compact of the powder (powder) of the zirconia material. In the fuel electrode 102, for example, nickel metal is mixed with an oxide material constituting the electrolyte 101 such as nickel-yttria stabilized zirconia cermet (Ni-YSZ), nickel-scandia stabilized zirconia (Ni-ScSZ). It is only necessary to be composed of a sintered body of a powder of a metal-oxide mixture (cermet) having electron conductivity.

The intermediate layer 104 is made of Ce _0.9 Gd _0.1 O ₂ (GdDC). The intermediate layer 104 may be made of, for example, a sintered body of GdDC (Ce _0.9 Gd _0.1 O ₂ ) powder. By providing the intermediate layer 104 in this way, the reaction at the time of firing between zirconia constituting the electrolyte 101 and La or Pr constituting the air electrode 103 can be efficiently suppressed. The interface resistance in the fuel cell (air electrode / electrolyte) can be further suppressed. In addition, it can also be considered that the entire air electrode 103 including the intermediate layer 104 functions as an air electrode.

  In addition, as is well known, each of these layers produces a slurry of powder or mixed powder, and forms a slurry film (layer) by molding by a doctor blade method or application by a screen printing method, This can be produced by firing at 1000 to 1200 ° C. In addition, fuel gas containing hydrogen obtained by reforming hydrocarbon gas such as city gas is supplied to the fuel electrode 102, and air containing oxygen as oxidant gas is supplied to the air electrode 103, A power generation operation is performed.

  Next, the characteristic measurement result in the single cell of the actually produced solid oxide fuel cell will be described below.

[Measuring method]
First, measurement will be described. As will be described later, in each of the fabricated sample cells, the interfacial resistance, which is an index of electrode performance, is measured by an AC impedance method. At the time of measurement, it is performed under the condition of an open circuit voltage, a minute AC signal is applied between the air electrode and the fuel electrode, and a minute electric potential change between the air electrode and the reference electrode (fuel electrode) is measured. The impedance is obtained from the result (3-terminal AC impedance method). In the measurement, each sample was heated to 800 ° C. in an electric furnace, humidified hydrogen gas was supplied as a fuel gas to the fuel electrode, and air was supplied to the reference electrode and the air electrode. Moreover, as an open electromotive force, the value of 1.13V or more is obtained at 800 degreeC.

[Production of cell]
Next, production of a single cell of a solid oxide fuel cell serving as a sample will be described. First, well known Sc ₂ O ₃ obtained by firing molded into a sheet by a doctor blade method, Al ₂ O ₃ doped zirconia _{(0.89ZrO 2 -0.10Sc 2 O 3 -0.01Al} 2 O 3: SASZ An electrolyte substrate is prepared. The electrolyte substrate is formed to a thickness of 0.2 mm. Next, a mixture of zirconia powder (40 wt%) with an average particle diameter of about 0.3 μm added with 8 mol% Y ₂ O ₃ and NiO powder (60 wt%) with an average particle diameter of 0.8 μm was mixed. A slurry of powder is prepared, and this slurry is applied to one surface of the above-described electrolyte substrate by a well-known screen printing method to form a fuel electrode coating film. In addition, a current collector made of platinum mesh is disposed on the fuel electrode coating film, and these are fired in air under a heat treatment condition of 1400 ° C. for 4 hours. It is assumed that a fuel electrode having a thickness of 60 μm is formed.

  Next, a slurry of GdDC powder having an average particle size of 0.2 μm is prepared, and this slurry is applied to the other surface of the above-described electrolyte substrate by a screen printing method to form an intermediate layer coating film. This is fired under heat treatment conditions of 1200 ° C. to form an intermediate layer having a thickness of 4 μm. This is an intermediate layer made of cerium oxide (GdDC) to which a rare earth other than Pr is added.

Then, the average particle diameter is 0.2μm in the _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 to produce a powder slurry, screen the slurry, on the other surface of the electrolyte substrate as described above The first layer coating film is formed by applying and drying by a printing method. Next, a slurry of LaNi _0.6 Fe _0.4 O ₃ (LNF) powder having an average particle diameter of 1.0 μm is prepared, and this slurry is applied on the first layer coating film by the screen printing method and dried. The second layer coating film is formed. Instead of LNF, any one of LSC, LSCF, LSF, LSM, and SSC may be used. Thereafter, the electrolyte substrate on which the first layer coating film and the second layer coating film are formed is baked under heat treatment conditions of 1100 ° C. for 2 hours, and an air electrode made of a sintered body of the powder is formed. And A Pt paste is applied on the air electrode, a Pt mesh current collector is placed on the Pt paste, and fired under heat treatment conditions of 1000 ° C. for 2 hours.

  As shown in the perspective view of FIG. 2, the unit cell formed in this way is formed on a disk having a diameter of 10 mm on an electrolyte substrate 201 formed in a square plate shape with a side of 30 mm. Has been placed. In FIG. 2, the fuel electrode disposed below the electrolyte substrate 201 is omitted from illustration. In addition, this single cell includes the reference electrode 203 made of platinum around the electrolyte substrate 201, and performs the above-described measurement in a state where it is connected thereto. In addition, each sample is subjected to a thermal cycle resistance test before the test, and a thermal cycle is performed 10 times between 20 ° C./min.

[Example 1]
Next, as Example 1, sample solid oxide fuel cells (sample cells: # -1-1-0 to # -1-1-3, # -1-2-0 to # -1- 2-3, #-1-3-0 to # -1-3-3, #-2-1-0 to # -2-1-3, #-2-2-0 to # -2-2- 3, # -2-3-0 to # -2-3-3, # -3-1-0 to # -3-1-3, # -3-2-0 to # -3-2-3, Production of # -3-3-0 to # -3-3-3) will be described. What the sample cell, the air electrode of the above sample cell used in the (first layer) prepared _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 and Ln = Gd, and the M = Nb (NbPrGdDC). Further, the composition ratio of Nb and Pr is changed. The composition ratio is shown as a ratio of NbO _5/2 , PrO _11/6 , GdO _3/2, and CeO ₂ .

Here, sample cells (# -1-1-0, #-1-2-0, #-1-3-0, #-2-1-0, #-2-2-0, #-2- 3-0, # -3-1-0, # -3-2-0, # -3-3-0) are comparative samples prepared without adding Nb. The unit cell of Example 1, from the side of the electrolyte, "intermediate layer _{/ (Ce 1-y Gd y} ) 1-xz Pr x Nb z O 2 consisting of a first layer / LNF composed of a second layer of GdDC" It becomes the composition of.

  When the above-described measurement is performed in these sample cells, as shown in Table 1-1, Table-1-2, and Table 1-3, the comparative sample cells (# -1-1-0, # -1-2-0, #-1-3-0, #-2-1-0, #-2-2-0, #-2-3-0, #-3-1-0, #-3 -2-0, #-3-3-0) is a fairly large interface except for # -1-1-0, #-2-1-0, #-3-1-0, where the amount of Pr added is small The resistance value is shown. This is considered to be a deterioration due to the occurrence of cracks or the like in the air electrode by the heat cycle resistance test described above.

  Any sample cell (# -1-1-1 to # -1-1-3, # -1-2-1 to # -1-2-3, # -1-3) -1 to # -1-3-3, # -2-1-1 to # -2-1-3, # -2-2-1 to # -2-2-3, # -2-3-1 ~ # -2-3-3, #-3-1-1 ~ # -3-1-3, #-3-2-1 ~ # -3-2-3, #-3-3-1 ~ # Also in -3-3-3), good results have been obtained with low interface resistance.

[Example 2]
Next, as Example 2, a solid oxide fuel cell as a sample (sample cells: # -4-1-0 to # -4-1-3, # -4-2-0 to # -4- 2-3, #-4-3-0 to # -4-3-3, #-5-1-0 to # -5-1-3, #-5-2-0 to # -5-2- 3, #-5-3-0 ~ # -5-3-3, #-6-1-0 ~ # -6-1-3, #-6-2-0 ~ # -6-2-3, Production of # -6-3-0 to # -6-3-3) will be described. What the sample cell, the air electrode of the above sample cell used in the (first layer) prepared _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 and Ln = Gd, and the M = Ta (TaPrGdDC). Further, the composition ratio of Ta and Pr is changed. The composition ratio is shown by the ratio of TaO _5/2 , PrO _11/6 , GdO _3/2 and CeO ₂ .

Here, sample cells (# -4-1-0, #-4-2-0, #-4-3-0, #-5-1-0, #-5-2-0, #-5- 3-0, # -6-1-0, # -6-2-0, # -6-3-0) are comparative samples prepared without adding Ta. The single cell of Example 2, from the side of the electrolyte, "intermediate layer _{/ (Ce 1-y Gd y} ) 1-xz Pr x Ta z O 2 consisting of a first layer / LNF composed of a second layer of GdDC" It becomes the composition of.

  When the above-described measurement was performed in these sample cells, as shown in Table 2-1-1, Table 2-2, and Table 2-3-3, the comparative sample cells (# -4-1-0, # -4-2-0, #-4-3-0, #-5-1-0, #-5-2-0, #-5-3-0, #-6-1-0, #-6 -2-0, #-6-3-0) is a fairly large interface except for # -4-1-0, #-5-1-0, #-6-1-0 where the amount of Pr added is small The resistance value is shown. This is considered to be a deterioration due to the occurrence of cracks or the like in the air electrode by the heat cycle resistance test described above.

  Any sample cell (# -4-1-1 to # -4-1-3, # -4-2-1 to # -4-2-3, # -4-3) -1 to # -4-3-3, # -5-1-1 to # -5-1-3, # -5-2-1 to # -5-2-3, # -5-3-1 ~ # -5-3-3, #-6-1-1 ~ # -6-1-3, #-6-2-1 ~ # -6-2-3, #-6-3-1 ~ # -6-3-3) also shows good results with low interface resistance.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a configuration example of the solid oxide fuel cell according to Embodiment 2 of the present invention. This solid oxide fuel cell includes an electrolyte 101 made of a zirconia-based material and a fuel electrode 102 formed on one surface of the electrolyte 101. These are the same as those in the first embodiment. The solid oxide fuel cell according to the present embodiment includes an air electrode 303 formed on the other side of the electrolyte 101, and the air electrode 303 is opposite to the first layer 303 a on the electrolyte 101 side and the electrolyte 101. And a second layer 303b formed on the first layer 303a on the side. In the present embodiment, the intermediate layer 104 is provided between the electrolyte 101 and the air electrode 303 and is made of cerium oxide to which a rare earth other than Pr is added.

In this embodiment, first, the first layer 303a is composed of a perovskite oxide such as _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 , and LNF. Here, Ln is any one of Sm, Gd, and Y, M is Nb or Ta, 0.05 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.5, and x / 20 ≦ z ≦ x / 5. The perovskite oxide is not limited to LNF, and may be any of LSC, LSCF, LSF, LSM, and SSC. The second layer 303b is made of a perovskite oxide such as LNF, LSC, LSCF, LSF, LSM, and SSC.

  Thus, when using the cerium oxide which added praseodymium (Pr) to the air electrode 303 (1st layer 303a), by adding Nb to this cerium oxide and using it, Pr is added exceeding 5 at% Even so, the thermal expansion coefficient can be reduced.

  As is well known, each of these layers produces a slurry of powder or mixed powder, and forms a slurry film (layer) by molding by the doctor blade method or application by the screen printing method. It can produce by baking at 1000-1200 degreeC. A fuel gas containing hydrogen obtained by reforming a hydrocarbon gas such as city gas is supplied to the fuel electrode 102, and air containing oxygen as an oxidant gas is supplied to the air electrode 303. A power generation operation is performed.

  Next, the characteristic measurement result in the single cell of the actually produced solid oxide fuel cell will be described below.

[Measuring method]
First, the measurement will be described. As will be described later, in each of the fabricated sample cells, the interfacial resistance, which is an index of electrode performance, is measured by an AC impedance method. At the time of measurement, it is performed under the condition of an open circuit voltage, a minute AC signal is applied between the air electrode and the fuel electrode, and a minute electric potential change between the air electrode and the reference electrode (fuel electrode) is measured. The impedance is obtained from the result (3-terminal AC impedance method). In the measurement, each sample was heated to 800 ° C. in an electric furnace, humidified hydrogen gas was supplied as a fuel gas to the fuel electrode, and air was supplied to the reference electrode and the air electrode. Moreover, as an open electromotive force, the value of 1.13V or more is obtained at 800 degreeC.

[Production of cell]
Next, production of a single cell of a solid oxide fuel cell serving as a sample will be described. First, well known Sc ₂ O ₃ obtained by firing molded into a sheet by a doctor blade method, Al ₂ O ₃ doped zirconia _{(0.89ZrO 2 -0.10Sc 2 O 3 -0.01Al} 2 O 3: SASZ An electrolyte substrate is prepared. The electrolyte substrate is formed to a thickness of 0.2 mm. Next, a mixture of zirconia powder (40 wt%) with an average particle diameter of about 0.3 μm added with 8 mol% Y ₂ O ₃ and NiO powder (60 wt%) with an average particle diameter of 0.8 μm was mixed. A slurry of powder is prepared, and this slurry is applied to one surface of the above-described electrolyte substrate by a well-known screen printing method to form a fuel electrode coating film. In addition, a current collector made of platinum mesh is disposed on the fuel electrode coating film, and these are fired in air under a heat treatment condition of 1400 ° C. for 4 hours. It is assumed that a fuel electrode having a thickness of 60 μm is formed.

  Next, a slurry of GdDC powder having an average particle size of 0.2 μm is prepared, and this slurry is applied to the other surface of the above-described electrolyte substrate by a screen printing method to form an intermediate layer coating film. This is fired under heat treatment conditions of 1200 ° C. to form an intermediate layer having a thickness of 4 μm. This is an intermediate layer made of cerium oxide (GdDC) to which a rare earth other than Pr is added.

Then, the average particle diameter is _{0.2μm (Ce 1-y Ln y} ) 1-xz Pr x M z O 2 powder and mixed powder having an average particle size of the 1.0 .mu.m LNF powder (mixing ratio Is preferably 30 wt%: 70 wt% to 70 wt%: 30 wt%), and this slurry is applied to the other surface of the electrolyte substrate by the screen printing method and dried to form the first layer. A coating film is formed. Instead of LNF, any one of LSC, LSCF, LSF, LSM, and SSC may be used.

  Next, a slurry of LNF powder having an average particle diameter of 1.0 μm is prepared, and this slurry is applied on the first layer coating film by the screen printing method and dried to form a second layer coating film. State. Instead of LNF, any one of LSC, LSCF, LSF, LSM, and SSC may be used. Thereafter, the electrolyte substrate on which the first layer coating film and the second layer coating film are formed is baked under heat treatment conditions of 1100 ° C. for 2 hours, and an air electrode made of a sintered body of the powder is formed. And A Pt paste is applied on the air electrode, a Pt mesh current collector is placed on the Pt paste, and fired under heat treatment conditions of 1000 ° C. for 2 hours.

  As shown in the perspective view of FIG. 2, the unit cell formed in this way is formed on a disk having a diameter of 10 mm on an electrolyte substrate 201 formed in a square plate shape with a side of 30 mm. Has been placed. In FIG. 2, the fuel electrode disposed below the electrolyte substrate 201 is omitted from illustration. In addition, this single cell includes the reference electrode 203 made of platinum around the electrolyte substrate 201, and performs the above-described measurement in a state where it is connected thereto. In addition, each sample is subjected to a thermal cycle resistance test before the test, and a thermal cycle is performed 10 times between 20 ° C./min.

[Example 3]
Next, as Example 3, a solid oxide fuel cell as a sample (sample cells: # -7-1-0 to # -7-1-3, # -7-2-0 to # -7- 2-3, #-7-3-0 to # -7-3-3, #-8-1-0 to # -8-1-3, #-8-2-0 to # -8-2- 3, #-8-3-0 ~ # -8-3-3, #-9-1-0 ~ # -9-1-3, #-9-2-0 ~ # -9-2-3, Production of # -9-3-0 to # -9-3-3) will be described. What the sample cell, the air electrode of the above sample cell used in the (first layer) prepared _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 and Ln = Gd, and the M = Nb (NbPrGdDC). Further, the composition ratio of Nb and Pr is changed. The composition ratio is shown as a ratio of NbO _5/2 , PrO _11/6 , GdO _3/2, and CeO ₂ .

Here, the sample cells (# -7-1-0, #-7-2-0, #-7-3-0, #-8-1-0, #-8-2-0, #-8- 3-0, # -9-1-0, # -9-2-0, # -9-3-0) are comparative samples prepared without adding Nb. The single cell of Example 3 is, from the electrolyte side, “an intermediate layer made of GdDC / (Ce _1-y Gd _y ) _1-xz Pr _x Nb _z O ₂ and _second layer made of LNF / second made of LNF. It has a “layer” configuration.

  When the above-described measurement is performed in these sample cells, as shown in Tables 3-1 to 3-2 and Tables 3-3 below, comparative sample cells (# -7-1-0, # -7-2-0, #-7-3-0, #-8-1-0, #-8-2-0, #-8-3-0, #-9-1-0, #-9 -2-0, # -9-3-0) is relatively large except for # -7-1-0, # -8-1-0, # -9-1-0, where the amount of Pr added is small The interface resistance value is shown. This is considered to be a deterioration due to the occurrence of cracks or the like in the air electrode by the heat cycle resistance test described above.

  Any sample cell (# -7-1-1 to # -7-1-3, # -7-2-1 to # -7-2-3, # -7-3) -1 to # -7-3-3, # -8-1-1 to # -8-1-3, # -8-2-1 to # -8-2-3, # -8-3-1 ~ # -8-3-3, #-9-1-1 ~ # -9-1-3, #-9-2-1 ~ # -9-2-3, #-9-3-1 ~ # -9-3-3) shows good results with low interface resistance. In Table-3-1, Table-3-2, and Table-3-3, the mixing ratio of NbPrGdDC and LNF is 50 wt%: 50 wt%.

[Example 4]
Next, as Example 4, a solid oxide fuel cell as a sample (sample cells: # -10-1-0 to # -10-1-3, # -10-2-0 to # -10- 2-3, #-10-3-0 to # -10-3-3, #-11-1-0 to # -11-1-3, #-11-2-0 to # -11-2- 3, #-11-3-0 to # -11-3-3, #-12-1-0 to # -12-1-3, #-12-2-0 to # -12-2-3, The production of # -12-3-0 to # -12-3-3) will be described. What the sample cell, the air electrode of the above sample cell used in the (first layer) prepared _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 and Ln = Gd, and the M = Ta (TaPrGdDC). Further, the composition ratio of Ta and Pr is changed. The composition ratio is shown by the ratio of TaO _5/2 , PrO _11/6 , GdO _3/2 and CeO ₂ .

Here, sample cells (# -10-1-0, #-10-2-0, #-10-3-0, #-11-1-0, #-11-2-0, #-11- 3-0, # -12-1-0, # -12-2-0, # -12-3-0) are comparative samples prepared without adding Ta. The unit cell of Example 4, from the side of the electrolyte, "intermediate layer _{/ (Ce 1-y Gd y} ) 1-xz Pr x Ta z O 2 and the second consisting of a first layer / LNF consisting LNF consisting GdDC It has a “layer” configuration.

  When the above-described measurements were performed on these sample cells, as shown in the following Table-4-1, Table-4-2, and Table-4-3, the comparative sample cells (# -10-1-0, # -10-2-0, #-10-3-0, #-11-1-0, #-11-2-0, #-11-3-0, #-12-1-0, #-12 -2-0, #-12-3-0) is relatively large except for # -10-1-0, #-11-1-0, #-12-1-0 where the amount of Pr added is small The interface resistance value is shown. This is considered to be a deterioration due to the occurrence of cracks or the like in the air electrode by the heat cycle resistance test described above.

  Any sample cell (# -10-1-1 to # -10-1-3, # -10-2-1 to # -10-2-3, # -10-3) -1 to # -10-3-3, # -11-1-1 to # -11-1-3, # -11-2-1 to # -11-2-3, # -11-3-1 ~ # -11-3-3, #-12-1-1 ~ # -12-1-3, #-12-2-1 ~ # -12-2-3, #-12-3-1 ~ # -12-3-3) also shows good results with low interface resistance. In Table-4-1, Table-4-2, and Table-4-3, the mixing ratio of TaPrGdDC and LNF is 50 wt%: 50 wt%.

  Next, another example in the first embodiment will be described.

[Example 5]
Hereinafter, as Example 5, a solid oxide fuel cell as a sample (sample cells: # -13-1-0 to # -13-5-0, # -13-1-1 to # -13-5 -1) will be described. These sample cells are manufactured by changing the material of the second layer 103b in Embodiment 1 to LSC, SSC, LSCF, LSF, and LSM. Further, the composition ratio of Nb and Pr is changed. The composition ratio is shown by the ratio of NbO _5/2 , PrO _11/6, and GdO _3/2 .

Here, the sample cells (# -13-1-0 to # -13-5-0) are comparative samples prepared without adding Nb. The unit cell of Example 5, from the side of the electrolyte, "consisting GdDC intermediate layer _{/ (Ce 1-y Gd y} ) 1-xz Pr x Nb z O 2 consisting of the first layer / LSC, SSC, LSCF, LSF , LSM, or a second layer composed of LSM ”.

  When the measurement described above was performed in these sample cells, the sample was compared with the comparative sample cells (# -13-1-0 to # -13-5-0) as shown in Table-5-1 below. The cells (# -13-1-1 to # -13-5-1) have good results with low interface resistance.

[Example 6]
Hereinafter, as Example 6, solid oxide fuel cells (sample cells: # -14-1-0 to # -14-5-0, # -14-1-1 to # -14-5 as samples) -1) will be described. These sample cells are manufactured by changing the material of the second layer 103b in Embodiment 1 to LSC, SSC, LSCF, LSF, and LSM. Moreover, the composition ratio of Ta and Pr is changed. The composition ratio is shown as a ratio of TaO _5/2 , PrO _11/6, and GdO _3/2 .

Here, the sample cells (# -14-1-0 to # -14-5-0) are comparative samples prepared without adding Ta. The unit cell of Example 6, from the side of the electrolyte, "consisting GdDC intermediate layer _{/ (Ce 1-y Gd y} ) 1-xz Pr x Ta z O 2 consisting of the first layer / LSC, SSC, LSCF, LSF , LSM, or a second layer composed of LSM ”.

  When the measurement described above was performed in these sample cells, as shown in Table-6-1 below, the sample was compared with the comparative sample cells (# -14-1-0 to # -14-5-0). The cells (# -14-1-1 to # -14-5-1) have good results with low interface resistance.

From the above examples, the case of adding Pr to the air electrode, an air electrode _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 (Ln = Sm, Gd, Y, M = Nb, Ta, 0.05 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.5, x / 20 ≦ z ≦ x / 5), it can be seen that the characteristics of the air electrode are improved. As described above, when the cerium oxide with Pr added to the air electrode is used, the thermal expansion coefficient increases as the temperature rises, and there is a large amount of oxygen vacancies in the oxide (cerium oxide with Pr added). It is considered that a phase transition or dissociation of association of oxygen ion vacancies is involved. Therefore, it is considered that an additive having greatly different valence and ion radius from Pr and Ce ions is effective in suppressing increase in thermal expansion coefficient. Further, the effect cannot be obtained unless the additive is dissolved in the cerium oxide to which Pr is added. In addition, if the amount added is too large, the ionic conductivity in the air electrode is lowered and the characteristics of the air electrode are deteriorated. Here, when Nb and Ta were examined, it was found that they were dissolved in the range of the addition amount described above, and an effect was obtained, which was effective in reducing the thermal expansion coefficient.

In the above description, the intermediate layer 104 made of cerium oxide to which a rare earth other than Pr is added is provided between the electrolyte and the electrolyte, but this is not necessary. However, by providing the intermediate layer 104, contact between the perovskite oxide on the air electrode side and zirconia on the electrolyte side is avoided, and an insulator such as La ₂ Zr ₂ O ₇ is formed in the portion in contact with the electrolyte. Can be suppressed.

  In addition, the particle diameter mentioned above is an average particle diameter obtained from the measurement of the light intensity distribution pattern by the well-known laser diffraction scattering method. For example, the particle size can be measured by using a laser diffraction / scattering particle size distribution measuring device LA-910 manufactured by HORIBA, Ltd.

  DESCRIPTION OF SYMBOLS 101 ... Electrolyte, 102 ... Fuel electrode, 103 ... Air electrode, 103a ... 1st layer, 103b ... 2nd layer, 104 ... Intermediate | middle layer.

Claims (3)

In a solid oxide fuel cell comprising a fuel electrode, an electrolyte, and an air electrode,
The air electrode, wherein disposed on the side of the electrolyte _{(Ce 1-y Ln y)} 1-xz Pr x M z O 2 (Ln = Sm, Gd, Y, M = Nb, Ta, 0.05 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.5, x / 20 ≦ z ≦ x / 5),
A solid oxide fuel cell comprising: a second layer made of a perovskite metal oxide, disposed in contact with the first layer. The solid oxide fuel cell according to claim 1, wherein
The first layer, wherein the _{(Ce 1-y Ln y)} 1-xz Pr x M z in addition to O _2, wherein a metal oxide having a perovskite type is constituted by mixed solid oxide Fuel cell. The solid oxide fuel cell according to claim 1 or 2,
A solid oxide fuel cell comprising an intermediate layer made of cerium oxide, which is disposed between the electrolyte and the air electrode and to which a rare earth other than praseodymium is added.

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