JP2004259691A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte film of a solid oxide fuel cell superior in output performance. <P>SOLUTION: This is the solid oxide fuel cell provided with a single cell in which an air electrode is arranged on one face and in which a fuel electrode is arranged on the opposite face of the electrolyte film, and an interconnector having a role of electric connection. The electrolyte film has two layers composed of a first layer composed of a material having an oxygen ion conductivity S1 on the air electrode side, and a second layer composed of a material having an oxygen ion conductivity S2 on the fuel electrode side and containing at least zirconium, and the oxygen ion conductivity S1 of the air electrode side and the oxygen ion conductivity S2 of the fuel electrode side S2 have a relationship S1>S2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a solid oxide fuel cell having excellent output performance. In particular, the present invention relates to a solid oxide fuel cell having an electrolyte membrane having excellent oxygen ion conductivity and having no gas permeability and having high output performance even at a power generation temperature of 900 ° C. or lower.

A layer made of zirconia in which yttria is dissolved (hereinafter, referred to as YSZ) has been proposed as an electrolyte membrane of a conventional solid oxide fuel cell. (For example, see Patent Document 1). Since YSZ has excellent sinterability, it is possible to easily produce an electrolyte membrane without gas permeability.However, the output performance of a solid oxide fuel cell using this material for the electrolyte membrane is 900 ° C or less. At low temperatures, the oxygen ion conductivity of the electrolyte membrane is reduced, and the reaction of the formula (1) between the air electrode and the electrolyte membrane does not proceed efficiently, so that there is a problem that the output performance is reduced.
^{_{1 / 2O 2 + 2e - →}} O 2- ... (1)

In addition, the electrolyte membrane having no gas permeability shown here is evaluated by a gas permeation amount passing therethrough when a pressure difference is provided between one side and the opposite side of the electrolyte membrane, and a gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ (more preferably, Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ ).

  As an electrolyte membrane of a solid oxide fuel cell, a layer made of zirconia (hereinafter, referred to as SSZ) in which scandia is dissolved has been proposed. (For example, see Patent Document 2). SSZ has higher oxygen ion conductivity than YSZ, and it is expected that the use of this material for the electrolyte membrane will increase the output performance of the solid oxide fuel cell. However, although an electrolyte membrane was manufactured using the material disclosed in Patent Document 2, it was difficult to manufacture an electrolyte membrane having no gas permeability according to the results of tests performed by us.

As an electrolyte membrane of a solid oxide fuel cell, a layer made of a cerium-containing oxide obtained by dissolving samarium, gadria, or the like in ceria has been proposed. (For example, see Patent Documents 3 and 4). The materials proposed in Patent Literature 3 and Patent Literature 4 have electronic conductivity under a fuel gas atmosphere of a solid oxide fuel cell, so that when an electrolyte membrane is formed using only the proposed materials, output performance is reduced. There was a problem.

A layer made of lanthanum gallate has been proposed as an electrolyte membrane for a solid oxide fuel cell. (See, for example, Patent Documents 5 and 6). The materials proposed in Patent Documents 5 and 6 use an oxide containing manganese, such as lanthanum manganite, as the air electrode of a solid oxide fuel cell. Therefore, there is a problem that when the electrolyte membrane is composed of only the proposed materials, the output performance is reduced.
JP-A-10-158894 (pages 1-6, FIGS. 1-12) JP-A-7-6774 (pages 1-5, FIGS. 1-5) JP-A-11-273451 (pages 1-8, FIGS. 1-5) Patent Publication No. 2813355 (Pages 1-5, FIGS. 1-5) JP-A-2002-15756 (pages 1-9, FIGS. 1-9) JP-A-11-335164 (pages 1-12, FIGS. 1-12)

  The present invention has been made in order to solve the above problems, and provides a solid oxide fuel cell having excellent output performance by optimizing the material on the air electrode side and the material on the fuel electrode side in the electrolyte membrane. The purpose is to:

  In order to achieve the above object, the present invention provides a solid oxide type comprising: a cell having an air electrode on one side of an electrolyte membrane and a fuel electrode on the other side; and an interconnector having a role of electrical connection. In a fuel cell, the electrolyte membrane has a first layer made of a material having an oxygen ion conductivity S1 on the air electrode side and a second layer made of a material containing at least zirconia having an oxygen ion conductivity S2 on the fuel electrode side. And wherein the oxygen ion conductivity S1 on the air electrode side and the oxygen ion conductivity S2 on the fuel electrode side are S1> S2. .

  According to the present invention, a solid layer having excellent output performance is provided by providing a first layer made of an electrolyte material having high oxygen ion conductivity on the air electrode side and a second layer made of a material containing at least zirconia on the fuel electrode side. An oxide fuel cell can be provided.

  The reason for this is that the high oxygen ion conductivity of the electrolyte membrane in the first layer allows the reaction of the formula (1) occurring between the air electrode and the electrolyte membrane to proceed efficiently, and This is because the zirconia is contained in the electrolyte membrane in the layer (1), so that an electrolyte membrane having no gas permeability can be easily produced.

In a preferred embodiment of the present invention, the thickness of the first layer in the electrolyte membrane is 5 to 90% based on the total thickness of the electrolyte membrane.

By setting the thickness of the first layer in the electrolyte membrane in the above range, an electrolyte membrane having high oxygen ion conductivity and having no gas permeability can be easily produced.

The reason for this is that if the thickness of the first layer is less than 5% of the total thickness of the electrolyte membrane, the oxygen ion conductivity of the electrolyte membrane decreases, and the reaction of equation (1) can proceed efficiently. On the other hand, if it is more than 90%, there is a problem that the cost of the electrolyte membrane material is high and impractical, or that the electrolyte membrane without gas permeability cannot be easily produced. That's why.

In a preferred embodiment of the present invention, the thickness of the first layer is 30 to 80% with respect to the total thickness of the electrolyte membrane.

By setting the thickness of the first layer in the above-described range, the solid oxide fuel cell having high oxygen ion conductivity, facilitating the production of an electrolyte membrane having no gas permeability, and having excellent output performance. Can be provided.

  The reason for this is that if it is less than 30%, the oxygen ion conductivity of the entire electrolyte membrane is slightly low, and the output performance may be reduced in power generation at 900 ° C or lower. This is because there is a possibility that the cost is slightly high or that it is difficult to produce an electrolyte membrane having no gas permeability at a low temperature.

In a preferred embodiment of the present invention, the second layer in the electrolyte membrane is a YSZ material.

By including the YSZ material in the electrolyte membrane, an electrolyte membrane having no gas permeability can be easily manufactured.

The reason for this is that the YSZ material has a high sintering property and is a preferable material for forming an electrolyte membrane having no gas permeability.

In a preferred embodiment of the present invention, the first layer in the electrolyte membrane is an SSZ material.

By providing the SSZ on the air electrode side of the electrolyte membrane, an electrolyte membrane having excellent oxygen ion conductivity and no gas permeability can be manufactured, so that a solid oxide fuel cell having excellent output performance can be provided.

The reason is that the SSZ material with high oxygen ion conductivity is provided on the air electrode side, so that the reaction of the formula (1) that occurs between the air electrode and the electrolyte membrane can be performed efficiently, and YSZ is laminated. Therefore, an electrolyte membrane having no gas permeability can be easily manufactured.

In a preferred embodiment of the present invention, the amount of scandia in the SSZ is 3 to 12 mol%.

When the solid solution amount of scandia is 3 to 12 mol%, the reaction of formula (1) can proceed more efficiently, and a solid oxide fuel cell having excellent output performance can be provided.

The reason for this is that if the solid solution amount is less than 3 mol%, the oxygen ion conductivity of the material is lowered, and the output performance is lowered. On the other hand, if it exceeds 12 mol%, the crystal phase is cubic and rhombohedral. This is because crystals are formed and oxygen ion conductivity is reduced.

In a preferred embodiment of the present invention, the amount of scandia dissolved in the SSZ material is 8 to 12 mol%.

Since the solid solution amount of scandia is set to 8 to 12 mol%, the reaction of the formula (1) can proceed more efficiently, and a solid oxide fuel cell having excellent output performance can be provided.

  The reason for this is that the oxygen ion conductivity is the highest in the range of 8 to 12 mol%, and the resistance loss in the electrolyte membrane is the smallest.

In a preferred embodiment of the present invention, the SSZ material, further _{CeO 2, Sm 2 O 3,} Gd 2 O 3, Yb 2 O 3, at least one oxide of selected from Er ₂ O ₃ and Bi ₂ O ₃ 5 mol% or less is dissolved.

According to the present invention, at least one oxide selected from CeO ₂ , Sm ₂ O ₃ , Gd ₂ O _3, Yb ₂ O _3, Er ₂ O ₃ and Bi ₂ O ₃ forms a solid solution of 5 mol% or less. A solid oxide fuel cell having excellent output performance can be provided.

  It is preferable that the oxide be contained in an amount of 5 mol% or less, because the oxygen ion conductivity is increased, the sinterability of the material is improved, or at least one of the effects is produced. That is, if the oxygen ion conductivity is improved, the output performance is improved, and if the sinterability is improved, it is possible to form an electrolyte membrane having no gas permeability at low temperatures. It is preferable to use two or more kinds of solid solutions since both effects of oxygen ion conductivity and sinterability may be obtained. On the other hand, when the content is more than 5 mol%, a rhombohedral crystal phase other than a cubic crystal is precipitated as a crystal phase, and oxygen ion conductivity is reduced.

In a preferred embodiment of the present invention, the amount of yttria in the YSZ material is 3 to 12 mol%.

When the solid solution amount of yttria is in the above range, an electrolyte membrane having no gas permeability can be easily produced, and a solid oxide fuel cell having excellent output performance can be provided.

The reason why the solid solution range of yttria is preferably 3 to 12 mol% is that if it is less than 3 mol%, the oxygen ion conductivity is low and the stability of the crystal phase is reduced. This is because the rhombohedral phase precipitates in addition to the cubic phase, and the oxygen ion conductivity is reduced.

In a preferred embodiment of the present invention, both the first layer and the second layer in the electrolyte membrane are made of zirconia in which at least scandia and yttria are dissolved, and the scandia solid solution amount Sc1 in the first layer and The scandia solid solution amount Sc2 in the second layer is Sc1> Sc2.

According to the present invention, a solid oxide fuel cell having excellent output performance is provided by providing a zirconia layer having a large amount of scandia solid solution on the air electrode side and a zirconia layer having a small amount of scandia solid solution on the fuel electrode side. Can be.

The reason for this is that the zirconia layer on the air electrode side has high oxygen ion conductivity because it contains a large amount of scandia, and the reaction of the formula (1) can proceed efficiently, and the zirconia layer on the fuel electrode side has a small amount of scandia. This is because an electrolyte membrane having excellent sinterability and no gas permeability can be easily produced.

In a preferred embodiment of the present invention, in a two-layer electrolyte membrane made of at least scandia and yttria in a solid solution of zirconia, the total solid solution of scandia and yttria in any layer made of zirconia in which scandia and yttria are made a solid solution The amount is between 3 and 12 mol%.

According to the present invention, by setting the total solid solution amount of scandia and yttria to 3 to 12 mol%, a solid oxide fuel cell excellent in output performance can be provided.

The reason is that if the total solid solution amount of scandia and yttria is less than 3 mol%, the oxygen ion conductivity is lowered and the output performance is reduced, while if it contains more than 12 mol%, This is because a rhombohedral crystal is formed in addition to a cubic crystal phase, and oxygen ion conductivity is reduced.

The zirconia in which at least scandia and yttria are dissolved as shown here may be any zirconia in which at least two types of scandia and yttria are dissolved, and other components may be dissolved. For example, zirconia, in which scandia, yttria, and ceria are dissolved, corresponds to this.

In a preferred embodiment of the present invention, the layer consisting of zirconia is solid-solved scandia and yttria, further _{CeO 2, Sm 2 O 3,} Gd 2 O 3, Yb 2 O 3, Er 2 O 3 and Bi ₂ O _At least one oxide selected from ₃ is dissolved in a solid solution of 5 mol% or less.

According to the present invention, the layer consisting of zirconia is solid-solved scandia and yttria, further from _{CeO 2, Sm 2 O 3,} Gd 2 O 3, Yb 2 O 3, Er 2 O 3 and Bi ₂ O ₃ When at least one oxide selected is dissolved in a solid solution of 5 mol% or less, a solid oxide fuel cell having excellent output performance can be provided.

  The content of 5 mol% or less is preferable because the oxygen ion conductivity increases, the sinterability of the material improves, and at least one of the effects is produced. That is, if the oxygen ion conductivity is improved, the output performance is improved, and if the sinterability is improved, it is possible to form an electrolyte membrane having no gas permeability at low temperatures. It is preferable to use two or more kinds of solid solutions since both effects of oxygen ion conductivity and sinterability may be obtained. On the other hand, when the content is more than 5 mol%, a rhombohedral crystal phase other than a cubic crystal is precipitated as a crystal phase, and oxygen ion conductivity is reduced.

In a preferred embodiment of the present invention, the first layer in the electrolyte membrane general formula _{La 1-a A a Ga 1} -b B b O 3 or _{La 1-a A a Ga 1} -bc B b C c O 3 ( However, A is one or more of Sr, Ca, Ba, B is one or more of Mg, Al, In, and C is one or more of Co, Fe, Ni, Cr) The lantern gallate represented.

By providing a layer made of a lanthanum gallate material on the air electrode side, a solid oxide fuel cell having excellent output performance can be provided.

  The reason for this is that the lanthanum gallate material has a high oxygen ion conductivity and can efficiently promote the reaction of the formula (1) occurring between the air electrode and the electrolyte membrane.

In a preferred embodiment of the present invention, the first layer in the electrolyte membrane is a general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B is any one of Sm, Gd, Y, 0.05 ≦ X ≦ 0.15) is a cerium-containing oxide.

According to the present invention, (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B = Sm, one of Gd, Y, 0.05 ≦ X ≦ 0.15) is _expressed on the air electrode side of the electrolyte membrane. By providing the layer made of the cerium-containing oxide described above, a solid oxide fuel cell having excellent output performance can be provided.

The reason is that oxygen ion conductivity is high on the air electrode side (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (However, B is one of Sm, Gd, Y, 0.05 ≤ X ≤ 0.15) By providing the cerium oxide represented, oxygen ions generated by the reaction of the formula (1) generated between the air electrode and the electrolyte membrane can be efficiently supplied to the electrolyte membrane.

In addition, by providing an electrolyte layer made of a material containing zirconia on the fuel electrode side, the cerium-containing oxide is not exposed to the fuel gas atmosphere and has no electronic conductivity, so that a solid oxide fuel excellent in output performance is provided. A battery can be provided.

In another aspect of the present invention, a solid oxide fuel cell comprising: a unit cell having an air electrode on one side of an electrolyte membrane and a fuel electrode on the opposite side; and an interconnector serving as an electrical connection The electrolyte membrane has a first layer made of a zirconia material in which scandia is dissolved at least on the air electrode side and an oxygen ion conductivity S2 on the fuel electrode side. A second layer made of a material containing the contained oxide, and the oxygen ion conductivity S1 on the air electrode side and the oxygen ion conductivity S2 on the fuel electrode side are S1> S2.

According to the present invention, the output is provided by providing a first layer made of a zirconia material in which at least scandia is dissolved in the air electrode side and a second layer made of a material containing at least a cerium-containing oxide on the fuel electrode side. A solid oxide fuel cell having excellent performance can be provided.

  The reason for this is that since the zirconia material in which at least scandia is dissolved as a solid solution is laminated on the air electrode side, the electronic conductivity of the cerium-containing oxide provided on the fuel electrode side can be suppressed, and the oxygen ion conductivity can be reduced. This is because the zirconia layer in which scandia having a high solubility is dissolved is on the air electrode side, so that the reaction of the formula (1) occurring between the air electrode and the electrolyte membrane can be efficiently advanced.

In a preferred embodiment of the present invention, the thickness of the first layer is 10 to 90% based on the total thickness of the electrolyte membrane.

According to the present invention, by setting the thickness of the first layer within the above range, a solid oxide fuel cell having excellent output performance can be provided.

The reason for this is that if it is less than 10%, the electronic conductivity of the second layer containing the cerium-containing oxide becomes larger than the oxygen ion conductivity, and the output performance is reduced. This is because there is a problem either when the cost is too high to be practical or when an electrolyte membrane without gas permeability cannot be easily produced.

In a preferred embodiment of the present invention, the thickness of the first layer is 30 to 80% with respect to the total thickness of the electrolyte membrane.

By setting the thickness of the first layer in the above-described range, which is further limited, a solid oxide fuel cell having more excellent output performance can be provided.

  The reason for this is that if it is less than 30%, the output performance is somewhat reduced due to the effect of the electronic conductivity of the cerium-containing oxide provided on the fuel electrode side, whereas if it is more than 80%, the cost of the electrolyte membrane material is slightly increased. This is because there is a possibility that the temperature is high or a case where it is difficult to produce an electrolyte membrane having no gas permeability at a low temperature.

In a preferred embodiment of the present invention, the second layer in the electrolyte membrane has a general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B = Sm, Gd, any one of Y, 0.05 ≦ X ≦ 0.15).

According to the present invention, (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B is any one of Sm, Gd, Y, 0.05 ≦ X ≦ 0.15) is provided on the fuel electrode side of the electrolyte membrane. By providing the layer made of the cerium-containing oxide described above, a solid oxide fuel cell having excellent output performance can be provided.

The reason for this is that on the fuel electrode side, oxygen ion conductivity is high (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (however, B = Sm, Gd, any one of Y, 0.05 ≦ X ≦ 0.15) By providing the cerium-containing oxide represented, it is possible to efficiently promote the reaction of the formulas (2) and (3) that occur between the electrolyte membrane and the fuel electrode, and to have at least a high oxygen ion conductivity on the air electrode side. This is because the zirconia material in which scandia is dissolved is constituted, so that the reaction of the formula (1) occurring between the air electrode and the electrolyte membrane can be efficiently advanced.
^{_{H 2 + O 2- → H 2}} O + 2e - ... (2)
_{^{CO + O 2- → CO 2 +}} 2e - ... (3)

In a preferred embodiment of the present invention, an electrode reaction layer having an open pore communicating therewith is provided between the electrolyte membrane and the air electrode to promote a reaction of generating oxygen ions from oxygen gas and electrons.

By promoting the reaction of generating oxygen ions between the electrolyte membrane and the air electrode and providing a layer having connected open pores, a solid oxide fuel cell having excellent output performance can be provided.

The reason for this is that the oxygen gas is easily introduced and has a function of generating oxygen ions, so that the reaction of the formula (1) is promoted and oxygen ions can be efficiently supplied to the electrolyte membrane.

In a preferred embodiment of the present invention, the electrode reaction layer is made of lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (however, either Ca or Sr) and zirconia in which scandia is dissolved. It is a uniformly mixed layer (hereinafter referred to as LaAMnO ₃ / SSZ).

According to the present invention, a solid oxide fuel cell having excellent output performance even at a power generation temperature of about 700 ° C. is provided by providing an electrode reaction layer made of LaAMnO ₃ / SSZ between an air electrode and an electrolyte membrane. Can be.

The reason is that LaAMnO ₃ / SSZ has high electron conductivity and oxygen ion conductivity even at a low temperature of about 700 ° C., so that the reaction of equation (1) that occurs between the air electrode and the electrolyte membrane can be efficiently advanced. Since the oxygen ion conductivity of the electrolyte membrane material on the air electrode side of the electrolyte membrane of the present invention is high, oxygen ions can be efficiently sent to the fuel electrode, and high output performance can be obtained even at a low temperature of about 700 ° C. That's why.

The layer of (La _1-x A _x ) _y MnO ₃ (where A = either Ca or Sr) shown here, in which lanthanum manganite and SSZ are uniformly mixed, is formed by a co-precipitation method. It can be obtained by using a raw material produced by a phase method. That is, the uniformity shown here means that the raw material obtained by the coprecipitation method is sufficiently uniform if there is uniformity.

In a preferred embodiment of the present invention, the air electrode shows a _{(La 1-x A x)} y MnO 3 ( where, A is either Ca or Sr) lanthanum manganite represented by (hereinafter, LaAMnO _3. ).

According to the present invention, a solid oxide fuel cell having excellent output performance can be provided by setting the composition of the air electrode in the above range.

The reason for this is that the solid oxide fuel cell has high electron conductivity under an air atmosphere and is stable as a material.

In a preferred embodiment of the present invention, the electrolyte membrane is formed on the surface of the electrode reaction layer and then sintered at 1350 to 1500 ° C.

According to the present invention, since the electrolyte membrane is formed on the surface of the electrode reaction layer and then sintered at an appropriate temperature, the reaction of the formula (1) occurring between the air electrode and the electrolyte membrane proceeds efficiently, and gas An electrolyte membrane having no permeability can be formed.

  The reason for this is that sintering at a temperature lower than 1350 ° C. results in a low sintering temperature, making it difficult to produce an electrolyte membrane having no gas permeability. This is because the reactivity with the electrolyte increases, the oxygen ion conductivity of the electrolyte membrane decreases, and the output performance decreases.

  In a solid oxide fuel cell including a unit cell having an air electrode on one side of an electrolyte membrane and a fuel electrode on the opposite side thereof, and an interconnector having a role of electrical connection, the electrolyte membrane is located on the air electrode side. A first layer made of a material having an oxygen ion conductivity S1 and a second layer made of a material containing at least zirconia having an oxygen ion conductivity S2 on the fuel electrode side. Since the oxygen ion conductivity S1 of the fuel cell and the oxygen ion conductivity S2 of the fuel electrode side satisfy S1> S2, a solid oxide fuel cell having excellent output performance can be provided.

The solid oxide fuel cell according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a cross section of a cylindrical solid oxide fuel cell. A strip-shaped interconnector 2 and an electrolyte membrane 3 are formed on a cylindrical air electrode support 1, and a fuel electrode 4 is formed on the electrolyte membrane 3 so as not to contact the interconnector 2. When air is flowed inside the air electrode support and fuel gas is flown outside, oxygen in the air is changed into oxygen ions at the interface between the air electrode and the electrolyte membrane, and the oxygen ions reach the fuel electrode through the electrolyte membrane. Then, the fuel gas and oxygen ions react to form water and carbon dioxide. These reactions are represented by equations (2) and (3). By connecting the fuel electrode 4 and the interconnector 2, electricity can be taken out.
^{_{H 2 + O 2- → H 2}} O + 2e - ... (2)
_{^{CO + O 2- → CO 2 +}} 2e - ... (3)

FIG. 2 shows that an electrode reaction layer 1a is provided between the air electrode 1 and the electrolyte membrane 3, and a fuel-side electrode reaction layer 4a is provided between the electrolyte membrane 3 and the fuel electrode 4. Further, the electrolyte membrane is provided as a first layer 3a. FIG. 9 is a cross-sectional view showing a type having two layers of a second layer 3b. The electrode reaction layer 1a is a layer provided to promote the reaction of the formula (1) in which oxygen gas is generated from oxygen gas and electrons from the air electrode, and the oxygen ions generated in the electrode reaction layer 1a are electrolyte membranes. It moves to the fuel electrode side through 3a and 3b. Then, the reactions shown in the formulas (2) and (3) are performed in the fuel-side electrode reaction layer 4a, and electricity can be extracted to the outside by connecting the fuel electrode 4 and the interconnector 2. Therefore, by optimizing the electrode reaction layer, the electrolyte membrane, and the fuel-side electrode reaction layer, it is possible to provide a solid oxide fuel cell having excellent output performance up to a low temperature of about 700 ° C.
^{_{1 / 2O 2 + 2e - →}} O 2- ... (1)

  The electrolyte membrane in the present invention is a membrane that has high oxygen ion conductivity, is a gas-impermeable membrane, and has no electronic conductivity at the power generation temperature of a solid oxide fuel cell in an air atmosphere and a fuel gas atmosphere. Preferably, there is. In particular, it is preferable that at least the material of the electrolyte membrane on the air electrode side is made of a material having high oxygen ion conductivity in order to efficiently advance the reaction of the formula (1).

  Materials with high oxygen ion conductivity, such as SSZ and lanthanum gallate, which have been developed to date, have problems such as high material cost and low sinterability. Considering this, it is preferable to stack materials having a low material cost, high sinterability, and a certain degree of oxygen ion conductivity. From this viewpoint, as the electrolyte membrane, a first layer made of a material having high oxygen ion conductivity is stacked on the air electrode side, and a second layer made of a material containing at least zirconia is laminated on the fuel electrode side with excellent sinterability. The electrolyte membrane having the above configuration is used in the present invention.

As the first layer in the electrolyte membrane of the present invention, a material having high oxygen ion conductivity is preferable. From this viewpoint, as the first layer, SSZ, cerium-containing oxide, a mixed layer of SSZ and cerium-containing oxide, (La _1-x Sr _x Ga _1-y Mg _y O ₃ ) and (La _1-x Sr Lanthanum gallate represented by _x Ga _1-yz Mg _y Co _z O ₃ ). Further, at least a zirconia-based material in which scandia and yttria are dissolved (hereinafter, referred to as ScYSZ), a zirconia material in which SSZ and YSZ are mixed (hereinafter, referred to as SSZ / YSZ), and SSZ and lanthanum gallate are mixed. These materials and those obtained by dissolving CeO ₂ or Bi ₂ O _{3 in} SSZ also correspond to these.

The cerium-containing oxide shown here is not particularly limited as long as it is an oxide containing cerium, but from the viewpoint of high oxygen ion conductivity, the general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (however, any one of B = Sm, Gd, Y, 0.05 ≦ X ≦ 0.15) is preferable.

The oxygen ion conductivity is high material shown here is a 0.1Scm ^-1 or more at 1000 ° C., further preferably those preferably 0.02Scm ^-1 or more materials even at 700 ° C.. The reason is that if a material having an oxygen ion conductivity of 0.1 Scm ^-1 or more at 1000 ° C. is used for the electrolyte membrane, a solid oxide fuel cell having high output performance at 900 to 1000 ° C. can be provided. This is because if it is 0.02 Scm ⁻¹ or more at 700 ° C., it is possible to provide a solid oxide fuel cell having high output performance even at a low temperature of about 700 ° C.

  Here, a method for measuring the oxygen ion conductivity will be described. A binder such as PVA is mixed with the electrolyte membrane material, press-formed with a disk-shaped mold, and sintered to produce a sample having no gas permeability. After mounting a platinum electrode on the sample, the temperature was raised to 1000 ° C., and the oxygen ion conductivity was measured by an AC impedance measurement method. Further, the oxygen ion conductivity was measured at 700 ° C. in the same manner.

Here, data at 1000 ° C. and 700 ° C. are described, but the relationship between the oxygen ion conductivity S1 and S2 in the present invention is a relationship when compared with the value of the oxygen ion conductivity at 1000 ° C. It indicates that the material having the oxygen ion conductivity S1 and the material having the oxygen ion conductivity S2 on the fuel electrode side satisfy S1> S2. Table 1 shows an example of the result of the oxygen ion conductivity obtained by the above method.

The second layer in the electrolyte membrane of the present invention is not particularly limited as long as it has a certain degree of oxygen ion conductivity (for example, 0.01 Scm ^-1 or more at 1000 ° C.) and contains at least zirconia. Zirconia in which a rare earth oxide other than yttria and scandia is dissolved may be used. However, in order to obtain better performance than an electrolyte membrane formed only of a material having high oxygen ion conductivity, a material having excellent sinterability is more preferable. The reason for this is that if the material has excellent sinterability, the electrolyte membrane without gas permeability can be sintered at a low temperature.For example, when LaAMnO ₃ is used as the air electrode material, the manganese to the electrolyte membrane can be reduced. This is because it is possible to suppress the diffusion of, and to suppress a decrease in output performance. From this point of view, YSZ, SSZ, a material in which Bi ₂ O ₃ is further dissolved, ScYSZ, SSZ / YSZ, or zirconia in which erbia is dissolved may be used.

  Examples of the combination of the first layer and the second layer in the electrolyte membrane according to the present invention are shown in Table 2 with reference to the data in Table 1.

As the raw material powder for the electrolyte membrane in the present invention, it is preferable that a membrane having no gas permeability can be produced. When the BET value is 0.5 to ²⁰ m ² g ⁻¹ , the particle size distribution is more than 0.1% for 3% diameter, 2% or less for 97% diameter, and the average particle diameter is controlled to be about 0.3 to 1 μm. preferable. By using a raw material powder controlled in this range, it is possible to produce an electrolyte membrane having no gas permeability even with a combination of electrolyte materials having low sinterability. For example, when the first layer shown in the twelfth of Table 2 is (CeO ₂ ) _0.8 (Gd ₂ O ₃ ) _0.1 , and the second layer is 85 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -5 mol CeO ₂ However, it is possible to produce an electrolyte membrane having no gas permeability.

  The BET value shown here is a value obtained by measurement using a flow type specific surface area measuring apparatus Flowsorb II2300 manufactured by Shimadzu Corporation. The particle size distribution is a value obtained by measurement using a laser diffraction type particle size distribution analyzer SALD-2000 manufactured by Shimadzu Corporation. Further, the average particle diameter is a value of a median diameter (50% diameter) obtained by using a laser diffraction type particle size distribution analyzer SALD-2000 manufactured by Shimadzu Corporation.

  The method for producing the electrolyte membrane in the present invention is not particularly limited, but a slurry coating method, a screen printing method, and a sheet bonding method are preferable from the viewpoint of excellent mass productivity and low cost.

  The method for producing the electrolyte membrane raw material in the present invention is not particularly limited. The coprecipitation method is common.

The air electrode in the present invention preferably has high electron conductivity and high oxygen gas permeability in an air atmosphere of a solid oxide fuel cell, and can efficiently perform the reaction of the formula (1). From this viewpoint, a preferable material is LaAMnO ₃ .

  From the viewpoint that the reaction of the formula (1) can be performed efficiently and the output performance is improved, it is preferable that an electrode reaction layer is interposed between the air electrode and the electrolyte membrane.

Since the electrode reaction layer is a layer provided for efficiently performing the reaction of the formula (1) and improving the output performance, the electrode reaction layer preferably has high oxygen ion conductivity. Further, it is more preferable that the electrode reaction layer further has electronic conductivity because the reaction of the formula (1) can be further promoted. Further, it is preferable that the material has a coefficient of thermal expansion close to that of the electrolyte membrane material, low reactivity with the electrolyte membrane and the air electrode, and good adhesion. If the material is good for all these characteristics, high output characteristics can be obtained even at a low temperature of about 700 ° C. From the above viewpoint, a preferable material is LaAMnO ₃ / SSZ.

In the present invention, the composition of lanthanum manganite represented by LaAMnO ₃ (A = Ca or Sr) in LaAMnO ₃ / SSZ of the electrode reaction layer includes electronic conductivity at 700 ° C. or higher, material stability, etc. Therefore, when expressed as (La _1-x A _x ) _y MnO ₃ , the values of x and y are more preferably in the range of 0.15 ≦ x ≦ 0.3 and 0.97 ≦ y ≦ 1.

The reason is that the electron conductivity decreases in the range of x <0.15 and x> 0.3, and the reactivity increases and the activity of the electrode reaction layer decreases in the case of y <0.97. This is to lower the output performance of the battery in order to generate an insulating layer represented by La ₂ Zr ₂ O ₇ .

In the SSZ of the electrode reaction layer in the present invention, any one or more oxides of CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O ₃ , and Y ₂ O ₃ are further dissolved in 5 mol% or less. May be. When these materials are dissolved, it is preferable to include them because an improvement in oxygen ion conductivity and / or an improvement in sinterability can be expected.

In order to enhance the electrode activity of the electrode reaction layer composed of LaAMnO ₃ / SSZ in the present invention, a structure in which the average particle diameter and the BET value of the raw material powder used are inclined may be used. For example, the average particle diameter may be 5 μm, 3 μm, 1 μm from the air electrode side toward the electrolyte membrane, or the BET value may be 1 m ² g ⁻¹ , 3 m ² g ⁻¹ , 5 m ² g ⁻¹ . From the viewpoint of efficiently performing the reaction of the formula (1), those composed of those having inclined average particle diameters or BET values are more preferable.

A structure in which the composition is inclined in order to enhance the electrode activity of the electrode reaction layer composed of LaAMnO ₃ / SSZ in the present invention may be used. For example, LaAMnO ₃ / SSZ: 80/20, 50/50, 20/80 from the air electrode side toward the electrolyte membrane may be used. From the viewpoint that the difference in thermal expansion between the air electrode and the electrolyte membrane can be reduced and the reaction of the formula (1) can be performed efficiently, it is preferable to make the composition gradient.

LaAMnO ₃ of the electrode reaction layer made of LaAMnO ₃ / SSZ in the present invention, Ce from the viewpoint of suppression of diffusion of the Mn component into the electron conductivity enhancing or electrolyte membrane, Sm, Pr, Nd, Co , Al, Fe, A solid solution of Ni, Cr or the like may be used. In particular, it is preferable to make Ni a solid solution.

In the present invention, the solid solution amount of scandia in the SSZ of the electrode reaction layer composed of LaAMnO ₃ / SSZ is preferably 3 to 12 mol%. The reason for this is that the composition in this range has high oxygen ion conductivity. From the viewpoint of high oxygen ion conductivity, 8 to 12 mol% is more preferable.

LaAMnO ₃ / SSZ in the present invention may be a solid solution or mixed cerium-containing oxide. The reason is that the use of a solid solution or a mixture of cerium-containing oxides can suppress the diffusion of the Mn component into the electrolyte membrane, and is a solid oxide fuel excellent in output performance and durability performance. This is because a battery can be provided.

From the viewpoint of suppressing the diffusion of the Mn component into the electrolyte membrane, a layer in which LaAMnO ₃ and the cerium-containing oxide are uniformly mixed (hereinafter, LaAMnO ₃ / cerium-containing oxide) is preferable.

As the first layer in the electrolyte membrane, a general formula La _1-a A _a Ga _1-b B _b O ₃ or La _1-a A _a Ga _1-bc B _b C _c O ₃ (where A is Sr, Ca, When using lanthanum gallate represented by one or more of Ba, B is one or more of Mg, Al, In, and C is one or more of Co, Fe, Ni, Cr) In particular, since the diffusion of the Mn component is particularly large, the diffusion of the Mn component such as a solid solution or a mixture of the cerium-containing oxide in the LaAMnO ₃ / SSZ or the LaAMnO ₃ / cerium-containing oxide is preferable. It is preferable to use an electrode reaction layer capable of suppressing the occurrence of the reaction.

The cerium-containing oxide shown here is not particularly limited as long as it is an oxide containing cerium. _{Those represented by the} general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B is any one of Sm, Gd, and Y, 0.05 ≦ X ≦ 0.15) have high oxygen ion conductivity, preferable.

The method for producing the raw material of LaAMnO ₃ / SSZ in the present invention is not particularly limited as long as it can satisfy the preferable characteristics as the electrode reaction layer. Co-precipitation method, powder mixing method, spray pyrolysis method, sol-gel method and the like.

In the present invention, the composition of lanthanum manganite represented by LaAMnO ₃ (A = Ca or Sr) of the air electrode may be (La _{1− When} expressed as _x Ax) _y MnO ₃ , the values of x and y are preferably in the range of 0.15 ≦ x ≦ 0.3 and 0.97 ≦ y ≦ 1.

The reason is that the electron conductivity decreases in the range of x <0.15 and x> 0.3, and the reactivity increases and the activity of the electrode reaction layer decreases in the case of y <0.97. This is to lower the output performance of the cell in order to generate an insulating layer represented by La ₂ Zr ₂ O ₇ .

  Lanthanum manganite at the air electrode may be a solid solution of Ce, Sm, Gd, Pr, Nd, Co, Al, Fe, Cr, Ni, etc. in addition to Sr or Ca.

  The method for producing the cathode material in the present invention is not particularly limited. Examples of the method include a method using a powder mixing method, a coprecipitation method, a spray pyrolysis method, and a sol-gel method.

  It is preferable that the fuel electrode in the present invention has high electron conductivity in a fuel gas atmosphere of a solid oxide fuel cell, high fuel gas permeability, and can efficiently perform the reaction of formulas (2) and (3). . From this viewpoint, a preferable material is a layer in which NiO and zirconia in which yttria is dissolved are uniformly mixed (hereinafter, referred to as NiO / YSZ) or a layer in which NiO and cerium-containing oxide are uniformly mixed. (Hereinafter, referred to as NiO / cerium-containing oxide). NiO is reduced to Ni in the fuel gas atmosphere of the solid oxide fuel cell, and the layer becomes Ni / YSZ or Ni / cerium-containing oxide.

The cerium-containing oxide shown here is not particularly limited as long as it is an oxide containing cerium. What is represented by the general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B = Sm, one of Gd, Y, 0.05 ≦ X ≦ 0.15) has high oxygen ion conductivity, preferable.

  From the viewpoint that the reactions of the formulas (2) and (3) can be performed efficiently and the output performance is improved, it is preferable to provide a fuel-side electrode reaction layer between the electrolyte membrane and the fuel electrode.

  In the present invention, when a zirconia-based material such as zirconia in which yttria is dissolved as a second layer of the electrolyte membrane is used, the fuel-side electrode reaction layer is NiO which is excellent in both electronic conductivity and oxygen ion conductivity. And a layer (hereinafter, referred to as NiO / SSZ) in which zirconia in which scandia is dissolved is uniformly mixed. NiO is reduced to Ni under the fuel atmosphere of the solid oxide fuel cell, and the layer becomes Ni / SSZ. Further, the ratio of NiO / SSZ is preferably 10/90 to 50/50 by weight. The reason is that if it is less than 10/90, the electronic conductivity is too low, while if it is more than 50/50, the oxygen ion conductivity is too low.

  The scandia solid solution amount of SSZ in the NiO / SSZ of the present invention is preferably 3 to 12 mol%. The reason is that within this range, the oxygen ion conductivity is high and the reactions of (2) and (3) can be promoted. Further, since the oxygen ion conductivity is high even at a low temperature of about 700 ° C., a solid oxide fuel cell having high output performance up to a low temperature of about 700 ° C. can be provided.

In the SSZ in the NiO / SSZ of the present invention, at least one selected from CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Er ₂ O ₃ , Y ₂ O ₃ , and Bi ₂ O ₃ is further dissolved in 5 mol% or less. May be. When these materials are dissolved, not only oxygen ion conductivity but also electron conductivity can be expected to be improved in a fuel gas atmosphere.

  In the present invention, when the cerium-containing oxide is used as the second layer of the electrolyte membrane, NiO and the cerium-containing oxide excellent in both electronic conductivity and oxygen ion conductivity are uniformly used as the fuel-side electrode reaction layer. A mixed layer (hereinafter, referred to as NiO / cerium-containing oxide) is preferable. NiO is reduced to Ni under the fuel atmosphere of the solid oxide fuel cell, and the layer becomes Ni / cerium-containing oxide. Further, the ratio of NiO / cerium-containing oxide is preferably 10/90 to 50/50 by weight. The reason is that if it is less than 10/90, the electronic conductivity is too low, while if it is more than 50/50, the oxygen ion conductivity is too low.

The cerium-containing oxide shown here is not particularly limited as long as it is an oxide containing cerium. A compound represented by the general formula (CeO ₂ ) _1-2X (C ₂ O ₃ ) _X (however, C = Sm, Gd, Y, or La, one of 0.05 ≦ X ≦ 0.15) is preferable.

  It is preferable that the fuel electrode in the present invention has high electron conductivity in order to reduce IR loss. From this viewpoint, the ratio of NiO / YSZ and NiO / cerium-containing oxide is preferably 50/50 to 90/10 by weight. The reason is that if it is less than 50/50, the electronic conductivity is low, while if it is more than 90/10, the output performance is reduced due to aggregation of Ni particles.

  Regarding the composition of the fuel electrode in the present invention, NiO / YSZ, NiO / SSZ as a composition other than the cerium-containing oxide, a layer in which zirconia in which NiO and calcium are dissolved in a solid solution are uniformly mixed (hereinafter, NiO / CSZ Shown). YSZ is preferred because YSZ is cheaper than SSZ, but NiO / CSZ is most preferred from the viewpoint of cost because CSZ is cheaper than YSZ. Note that NiO / CSZ also becomes Ni / CSZ under the fuel gas atmosphere of the fuel cell.

  The method of synthesizing the fuel electrode raw material in the present invention is not particularly limited as long as the fuel electrode materials such as NiO / SSZ and NiO / YSZ are uniformly mixed. Examples include a coprecipitation method and a spray drying method.

  The interconnector in the present invention is preferably one having high electron conductivity, no gas permeability, and stable in an oxidation-reduction atmosphere in an air atmosphere and a fuel gas atmosphere at the power generation temperature of the solid oxide fuel cell. From this viewpoint, lanthanum chromite is most preferred.

  Since lanthanum chromite is difficult to sinter, it is difficult to manufacture an interconnector having no gas permeability at the firing temperature (1500 ° C. or lower) of a solid oxide fuel cell. In order to improve sinterability, Ca, Sr, and Mg are preferably used as a solid solution. A solid solution of Ca is most preferable because it has the highest sinterability and can produce a membrane having no gas permeability at the same temperature as other materials of the solid oxide fuel cell.

  There is no particular limitation on the solid solution amount of lanthanum chromite in which Ca is used as the solid solution for the interconnector. Although the electronic conductivity increases as the amount of Ca solid solution increases, the stability of the material decreases, so the amount of Ca solid solution is preferably about 10 to 40 mol%.

  The shape of the solid oxide fuel cell in the present invention is not particularly limited, and may be a flat plate type or a cylindrical type. In the flat type, the interconnector is called a separator, and the role is the same as that of the interconnector. In the case of a separator, a heat-resistant metal such as ferritic stainless steel may be used.

The solid oxide fuel cell according to the present invention is applicable to a microtube type (outer diameter of 10 mm or less, more preferably 5 mm or less).

(Example 1)
The cylindrical solid oxide fuel cell shown in FIG. 1 was used as a basic configuration. In other words, a strip-shaped interconnector 2 and an electrolyte membrane 3 are formed on a cylindrical air electrode support 1, and a fuel electrode 4 is formed on the electrolyte membrane so as not to contact the interconnector. In this embodiment, as shown in FIG. 2, an electrode reaction layer is provided between the air electrode and the electrolyte membrane, and a fuel-side electrode reaction layer is provided between the electrolyte membrane and the fuel electrode. Was used.

(1) Preparation of air electrode support The composition of the air electrode is a lanthanum manganite in which Sr represented by the composition of La _0.75 Sr _0.25 MnO ₃ is dissolved as a solid solution. A powder was obtained. The average particle size was 30 μm. A cylindrical molded body was produced by an extrusion molding method. Further, sintering was performed at 1500 ° C. to obtain an air electrode support.

(2) As a manufacturing electrode reaction layer of the electrode reaction layer, and LaAMnO ₃ / SSZ, the composition and the weight _{ratio, La 0.75 Sr 0.25 MnO 3/} 90 mol% ZrO 2 -10mol% Sc 2 O 3 = 50 / 50 was set. The aqueous solution of La, Sr, Mn, Zr and Sc was mixed to have the above-mentioned composition using the respective nitrate aqueous solutions, and then oxalic acid was added to precipitate. The precipitate and the supernatant were dried and further heat-treated to obtain a raw material powder after controlling the particle size. The average particle size was 2 μm. 40 parts by weight of the electrode reaction layer powder were 100 parts by weight of a solvent (ethanol), 2 parts by weight of a binder (ethyl cellulose), 1 part by weight of a dispersant (polyoxyethylene alkyl phosphate), and 1 part by weight of an antifoaming agent (sorbitan sesquiolate). After mixing, the slurry was sufficiently stirred to prepare a slurry. The slurry viscosity was 100 mPas. The slurry was formed on an air electrode support (outside diameter: 15 mm, wall thickness: 1.5 mm, effective length: 400 mm) by a slurry coating method, and then sintered at 1400 ° C. The thickness was 20 μm.

(3) Preparation of slurry for electrolyte membrane (first layer):
The material of the first layer was SSZ, and the composition was 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ . ZrO ₂ was dissolved in concentrated nitric acid of 3N or more heated at 100 ° C. and diluted with distilled water to obtain a nitrate aqueous solution. For Sc ₂ O ₃ , a nitrate aqueous solution was obtained in the same manner. Each nitrate aqueous solution was prepared so as to have the above-mentioned composition, and an oxalic acid aqueous solution was added thereto for coprecipitation. The precipitate and the supernatant obtained by co-precipitation were dried at about 200 ° C., thermally decomposed at 500 ° C., and further heat-treated at 800 ° C. for 10 hours to obtain a raw material powder. The average particle size was 0.5 μm. 40 parts by weight of the raw material powder, 100 parts by weight of a solvent (ethanol), 2 parts by weight of a binder (ethyl cellulose), 1 part by weight of a dispersant (polyoxyethylene alkyl phosphate), and 1 part by weight of an antifoaming agent (sorbitan sesquiolate) After mixing, the slurry was sufficiently stirred to prepare a slurry. The slurry viscosity was 140 mPas.

(4) Preparation of slurry for electrolyte membrane (second layer):
The material of the second layer is YSZ, and the composition is 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ . ZrO ₂ was dissolved in concentrated nitric acid of 3N or more heated at 100 ° C. and diluted with distilled water to obtain a nitrate aqueous solution. A nitrate aqueous solution was obtained from Y ₂ O _{3 by} the same method. Each nitrate aqueous solution was prepared so as to have the above-mentioned composition, and an oxalic acid aqueous solution was added thereto for coprecipitation. The precipitate and the supernatant obtained by co-precipitation were dried at about 200 ° C., thermally decomposed at 500 ° C., and further heat-treated at 800 ° C. for 10 hours to obtain a raw material powder. The average particle size was 0.5 μm. 40 parts by weight of the powder were mixed with 100 parts by weight of a solvent (ethanol), 2 parts by weight of a binder (ethyl cellulose), 1 part by weight of a dispersant (polyoxyethylene alkyl phosphate), and 1 part by weight of an antifoaming agent (sorbitan sesquiolate). After mixing, the slurry was sufficiently stirred to prepare a slurry. The slurry viscosity was 140 mPas.

(5) Preparation of Electrolyte Membrane First, a first layer was formed on the electrode reaction layer by a slurry coating method. Further, a second layer was formed by a slurry coating method and sintered at 1400 ° C. The thickness of the obtained electrolyte membrane was 30 μm (first layer: 15 μm, second layer: 15 μm). The portion where the interconnector is to be formed in a later step was masked so that the film was not applied.

(6) As the material of the slurry produced fuel-side electrode reaction layer of a fuel-side electrode reaction layer and NiO / SSZ, the composition was the _{NiO / 90 mol% ZrO 2 -10mol} % Sc 2 O 3. After using the aqueous nitrate solutions of Ni, Zr and Sc to prepare the above composition, oxalic acid was added for precipitation. After drying the precipitate and the supernatant, it was further subjected to a heat treatment to control the particle size to obtain a raw material. The weight ratio of the electrode reaction layer was Ni / 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ = 20/80 and 50/50, and the average particle diameter was 0.5 μm in each case. 100 parts by weight of the powder, 500 parts by weight of an organic solvent (ethanol), 10 parts by weight of a binder (ethyl cellulose), 5 parts by weight of a dispersant (polyoxyethylene alkyl phosphate), 1 part by weight of an antifoaming agent (sorbitanses oxolate) After mixing 5 parts by weight of a plasticizer (DBP), the mixture was sufficiently stirred to prepare a slurry. The viscosity of this slurry was 70 mPas.

(7) Preparation of Fuel-Side Electrode Reaction Layer Mask the battery so that the surface area of the fuel-side electrode reaction layer becomes 150 cm ² , and place NiO / 90 mol% ZrO ₂ -10 mol% Sc ₂ on the electrolyte membrane by the slurry coating method. O ₃ (average particle diameter) = 20/80 (0.5 μm) and 50/50 (0.5 μm) in this order. The film thickness (after sintering) was 10 μm.

(8) Slurry preparation of fuel electrode:
The material of the fuel electrode was NiO / YSZ, and the composition was NiO / 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ . After using the aqueous nitrate solutions of Ni, Zr and Y to prepare the above composition, oxalic acid was added for precipitation. After drying the precipitate and the supernatant, the mixture was further subjected to a heat treatment to control the particle size, thereby obtaining a raw material. The composition and the weight ratio were NiO / 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ = 70/30, and the average particle size was 2 μm. 100 parts by weight of the powder, 500 parts by weight of an organic solvent (ethanol), 20 parts by weight of a binder (ethyl cellulose), 5 parts by weight of a dispersant (polyoxyethylene alkyl phosphate), 1 part by weight of an antifoaming agent (sorbitanses oxolate) After mixing 5 parts by weight of a plasticizer (DBP), the mixture was sufficiently stirred to prepare a slurry. The viscosity of this slurry was 250 mPas.

(9) Preparation of fuel electrode A fuel electrode was formed on the fuel-side electrode reaction layer by a slurry coating method. The thickness (after sintering) was 90 μm. Further, the fuel-side electrode reaction layer and the fuel electrode were co-sintered at 1400 ° C.

(10) Fabrication of interconnectors:
The composition of the interconnector was lanthanum chromite in which Ca represented by La _0.80 Ca _0.20 CrO ₃ was dissolved. After being produced by the spray pyrolysis method, it was obtained by performing a heat treatment. The average particle diameter of the obtained powder was 1 μm. 40 parts by weight of the powder were mixed with 100 parts by weight of a solvent (ethanol), 2 parts by weight of a binder (ethyl cellulose), 1 part by weight of a dispersant (polyoxyethylene alkyl phosphate), and 1 part by weight of an antifoaming agent (sorbitan sesquiolate). After mixing, the slurry was sufficiently stirred to prepare a slurry. The slurry viscosity was 100 mPas. An interconnector was formed by a slurry coating method and sintered at 1400 ° C. The thickness after sintering was 40 μm.

(Example 2)
Example 1 was repeated except that the material of the first layer was ScYSZ and the composition was 90 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ .

(Example 3)
The material of the first layer and SSZ / YSZ, the composition is _{90mol% ZrO 2 -10mol% Sc 2} O 3 / 90mol% ZrO 2 -10mol% Y 2 O 3 = 50/50. 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ is prepared by the coprecipitation method, powder having an average particle diameter of 0.5 μm and 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ are prepared by the coprecipitation method, Example 1 was repeated except that 20 parts by weight of powder having an average particle diameter of 0.5 μm was added to prepare a slurry.

(Example 4)
Example 1 was repeated except that the material of the first layer was SSZ and the composition was 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -1 mol% CeO ₂ .

(Example 5)
The same as Example 1 except that the material of the first layer was SSZ and the composition was 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -0.5 mol% Bi ₂ O ₃ -0.5 mol% CeO ₂ did.

(Example 6)
Example 2 was repeated except that the material of the second layer was ScYSZ and the composition was 90 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ .

(Example 7)
The material of the first layer is ScYSZ, the composition is 90 mol% ZrO ₂ -8 mol% Sc ₂ O ₃ -2 mol% Y ₂ O ₃ , the material of the second layer is ScYSZ, and the composition is 90 mol% ZrO ₂ Same as Example 1 except that -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ was used.

(Comparative Example 1)
The electrolyte membrane was the same as in Example 1 except that the electrolyte membrane was composed only of the first layer, 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ , and the film thickness was 30 μm.

(Power generation test)
A power generation test was performed using the cells (effective fuel electrode area: 150 cm ² ) obtained in Examples 1 to 7 and Comparative Example 1. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
For the batteries obtained in Examples 1 to 7 and Comparative Example 1, nitrogen gas was flown into the inside of the air electrode support, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the amount of gas permeated through the electrolyte membrane was measured. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 3 shows the results of the potential and the gas permeation amount of the electrolyte membrane in the power generation test. In Examples 1 to 7 and Comparative Example 1, the more preferable gas permeation amount for the electrolyte membrane was Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ , which confirmed that there was no problem with the gas permeability of the electrolyte membrane. Was done. Further, the generated potential was 0.6 V or more in Examples 1 to 7, but was clearly 0.57 V in Comparative Example 1. From the above results, the first layer and the second layer in the electrolyte membrane, SSZ and YSZ, ScYSZ and YSZ, SSZ / YSZ and YSZ, SSZ and ScYSZ and ScYSZ and ScYSZ the amount of scandia of the first layer It has been confirmed that a solid oxide fuel cell having excellent output performance can be provided by adopting such a configuration that the number is larger.

Example 4, of at least one selected from Examples 5 and further CeO ₂ to the SSZ as shown in Table _{1, Sm 2 O 3, Gd} 2 O 3, Yb 2 O 3, Er 2 O 3 and Bi ₂ O ₃ It was confirmed that the use of an oxide in which the oxide was dissolved in an amount of 5 mol% or less improved the power generation performance or reduced the gas permeation amount of the electrolyte membrane, and was more preferable.

(Example 8)
The material of the second layer in the electrolyte membrane is ScYSZ, the composition is 90 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O _3, and the material of the first layer is (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 . (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 was prepared in the same manner as in Example 1 except that the average particle diameter was 0.5 μm and the sintering temperature was 1430 ° C. by the above-mentioned coprecipitation method.

(Example 9)
Example 2 was the same as Example 1 except that the material of the second layer in the electrolyte membrane was YSZ and the composition was 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ .

(Example 10)
The material of the second layer was YSZ, the composition was 90 mol% ZrO ₂ -10 mol% Y ₂ O _3, and the material of the first layer was La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ . La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ is a mixture of La ₂ O ₃ , SrCO ₃ , Ga ₂ O ₃ , MgO so as to have the above composition, mixed in a ball mill, heat treated at 1200 ° C., and pulverized. Powder having an average particle diameter of 0.5 μm was used as a raw material. For the electrode reaction layer, La _0.75 Sr _0.25 MnO ₃ , 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ and each powder of (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 were mixed, and heat treatment was performed. After crushing and controlling the particle size, a raw material powder was obtained. The average particle size was 2 μm. Mixing composition of the raw material was _{La 0.75 Sr 0.25 MnO 3/90} mol% ZrO 2 -10mol% Sc 2 O 3 / (CeO 2) 0.8 (Sm 2 O 3) 0.1 = 40/40/20 in weight ratio Except for this, the procedure was the same as in Example 1.

(Example 11)
Example 10 was the same as Example 10 except that the material of the second layer was SSZ, and the composition was 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -1 mol% CeO ₂ .

(Example 12)
The material of the second layer is SSZ, the composition is 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -1 mol% CeO _2, and the material of the first layer is La _0.8 Sr _0.2 Ga _0.8 Mg _0.115 Co _0.085 O ₃ The procedure was the same as in Example 10, except that

(Comparative Example 2)
The electrolyte membrane was made up of only (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 and sintered at 1430 ° C. The film thickness was 30 μm. Subsequently, the material of the fuel-side electrode reaction layer and the fuel electrode was NiO / cerium-containing oxide, and the composition was NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 . Ni, Ce and Sm were each prepared using the respective nitrate aqueous solutions so as to have the above-mentioned composition, and then oxalic acid was added for precipitation. After drying the precipitate and the supernatant, it was further subjected to a heat treatment to control the particle size to obtain a raw material. The composition of the fuel-side electrode reaction layer and its weight ratio were NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 20/80 and 50/50, and the average particle diameter was 0.5 μm for both. did. The composition of the fuel electrode and its weight ratio were NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 70/30. Except for these, the procedure was the same as in Example 1.

(Comparative Example 3)
The electrolyte membrane was composed of only La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ and the film thickness was 30 μm. For the electrode reaction layer, La _0.75 Sr _0.25 MnO ₃ , 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ and each powder of (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 were mixed, and heat treatment was performed. After crushing and controlling the particle size, a raw material powder was obtained. The average particle size was 2 μm. Mixing composition of the raw material was _{La 0.75 Sr 0.25 MnO 3/90} mol% ZrO 2 -10mol% Sc 2 O 3 / (CeO 2) 0.8 (Sm 2 O 3) 0.1 = 40/40/20 by weight. The material of the fuel-side electrode reaction layer and the fuel electrode was NiO / cerium-containing oxide, and the composition was NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 . Ni, Ce and Sm were each prepared using the respective nitrate aqueous solutions so as to have the above-mentioned composition, and then oxalic acid was added for precipitation. After drying the precipitate and the supernatant, it was further subjected to a heat treatment to control the particle size to obtain a raw material. The composition of the fuel-side electrode reaction layer and its weight ratio were NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 20/80 and 50/50, and the average particle diameter was 0.5 μm for both. did. The composition of the fuel electrode and its weight ratio were NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 70/30, except that the fuel electrode reaction layer and the fuel electrode were co-sintered at 1350 ° C. As in Example 1.

(Power generation test)
A power generation test was performed using the cells (effective fuel electrode area: 150 cm ² ) obtained in Examples 8 to 12 and Comparative Examples 2 and 3. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
For the batteries obtained in Examples 8 to 12 and Comparative Examples 2 and 3, nitrogen gas was allowed to flow inside the air electrode support, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the amount of gas permeated through the electrolyte membrane was measured. did. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 4 shows the results of the potential and the gas permeation amount of the electrolyte membrane in the power generation test. In Examples 8, 10, 12 and Comparative Example 3, the gas permeation amount Q which is more preferable as the electrolyte membrane is within the range of Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ , and in Examples 9, 11, and Comparative Example 2, Is within a preferable gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ as an electrolyte membrane, and it was confirmed that there was no problem in gas permeability as an electrolyte membrane in any case. On the other hand, the generated electric potential was extremely low at 0.1 V in Comparative Example 2 and 0.3 V in Comparative Example 3, while the electric potential was 0.6 V or more in Examples 8 to 12. This is because, only (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 , the cerium-containing oxide has electronic conductivity due to exposure to an oxidation-reduction atmosphere, and the electromotive force is greatly reduced. _This is because, when only _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ is used, Mn from the air-side electrode reaction layer and the air electrode enters La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ and has electron conductivity, and the electromotive force is reduced. On the other hand, by providing a second electrolyte layer containing at least zirconia on the fuel electrode side as shown in Examples 8 to 12, a reduction in electromotive force can be suppressed, and a solid oxide fuel excellent in output performance can be suppressed. It was confirmed that a battery could be provided.

From the results of Examples 1 to 12 and Comparative Examples 1 to 3, the second layer made of a material containing at least zirconia on the fuel electrode side of the electrolyte membrane, and a material having a higher oxygen ion conductivity than the second layer It was confirmed that a solid oxide fuel cell having excellent output performance can be provided by being composed of the first layer made of.

(Example 13)
The material of the second layer is (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 , the material of the first layer is SSZ, and the composition is 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -1 mol% CeO ₂ And baked at 1420 ° C. The composition of the fuel-side electrode reaction layer was NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1, and Ni, Ce and Sm were each used to prepare the above composition using the nitrate aqueous solution. Added and precipitated. After drying the precipitate and the supernatant, it was further subjected to a heat treatment to control the particle size to obtain a raw material. The weight ratio of the fuel-side electrode reaction layer was NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 20/80 and 50/50, and the average particle size was 0.5 μm. Was. Further, the fuel electrode was NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1, and after using Ni, Ce and Sm each nitrate aqueous solution to prepare the composition described above, oxalic acid was added and precipitated. Was. After drying the precipitate and the supernatant, the mixture was further subjected to a heat treatment to control the particle size, thereby obtaining a raw material. The composition and the weight ratio were NiO / (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 = 70/30, and the average particle size was 2 μm. Except for these, the procedure was the same as in Example 1.

(Example 14)
The material of the second layer is (CeO ₂ ) _0.8 (Y ₂ O ₃ ) _0.1, and the material of the first layer is 89 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ -0.5 mol% Bi ₂ O ₃ -0.5 mol % Y ₂ O ₃ and baked at 1420 ° C. in the same manner as in Example 13.

(Example 15)
Conducted except that the material of the second layer was (CeO ₂ ) _0.8 (Y ₂ O ₃ ) _0.1 and the material of the first layer was 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ and baked at 1420 ° C. Same as Example 13.

(Power generation test)
A power generation test was performed using the batteries (effective fuel electrode area: 150 cm ² ) obtained in Examples 13 to 15 and Comparative Example 2. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
For the batteries obtained in Examples 13 to 15 and Comparative Example 2, nitrogen gas was flown into the inside of the air electrode support, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the amount of gas permeated through the electrolyte membrane was measured. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 5 shows the results of the potential and the gas permeation amount of the electrolyte membrane in the power generation test. In Example 14, the more preferable gas permeation amount for the electrolyte membrane was Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ , and in Examples 13, 15 and Comparative Example 2, the preferable gas permeation amount for the electrolyte membrane was Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ , and it was confirmed that there was no problem in gas permeability as an electrolyte membrane in each case. On the other hand, the generated potential was 0.6 V or more in Examples 13 to 15, whereas it was 0.10 V in Comparative Example 2, which was an extremely low potential. This is because when only (CeO ₂ ) _0.8 (Sm ₂ O ₃ ) _0.1 was used, the cerium-containing oxide was exposed to an oxidation-reduction atmosphere, had electronic conductivity, and the electromotive force was greatly reduced. On the other hand, as shown in Examples 13 to 15, the output performance was significantly improved by using a material made of zirconia in which at least scandia was dissolved in the air electrode side and having a higher oxygen ion conductivity than the cerium-containing oxide. Was confirmed to be improved. From the above results, (CeO ₂ ) _0.9 (Gd ₂ O ₃ ) _0.05 , (CeO ₂ ) _0.8 (Gd ₂ O ₃ ) _0.1 , (CeO ₂ ) _0.7 (Gd ₂ O ₃ ) It was considered that good performance was obtained with _0.15 . Therefore, the second layer of the electrolyte membrane is represented by the general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B is one of Sm, Gd, and Y, 0.05 ≦ X ≦ 0.15). It was confirmed that the cerium-containing oxide and the first layer to be formed were more preferably SSZ materials.

(About the ratio of the thickness of the electrolyte membrane of the first layer (when the air electrode side is a material containing zirconia such as SSZ))
(Example 16)
Example 1 was repeated except that the thickness of the first layer was 1 μm and the thickness of the second layer was 29 μm.

(Example 17)
Example 1 was repeated except that the thickness of the first layer was 1.5 μm and the thickness of the second layer was 28.5 μm.

(Example 18)
Example 1 was repeated except that the thickness of the first layer was 6 μm and the thickness of the second layer was 24 μm.

(Example 19)
Example 1 was repeated except that the thickness of the first layer was 9 μm and the thickness of the first layer was 21 μm.

(Example 20)
Example 1 was repeated except that the thickness of the first layer was 24 μm and the thickness of the first layer was 6 μm.

(Example 21)
Example 1 was repeated except that the thickness of the first layer was 27 μm and the thickness of the first layer was 3 μm.

(Example 22)
Example 1 was repeated except that the thickness of the first layer was 28 μm and the thickness of the first layer was 2 μm.

(Comparative Example 4)
The procedure was the same as that of Example 1 except that the electrolyte membrane was composed only of 90 mol% ZrO ₂ -10 mol% Sc ₂ O ₃ , the film thickness was 30 μm, and sintering was performed at 1420 ° C.

(Power generation test)
A power generation test was performed using the cells (effective area of fuel electrode: 150 cm ² ) obtained in Examples 1, 16 to 22 and Comparative Examples 1 and 4. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
Nitrogen gas was flowed into the air electrode support inside the batteries obtained in Examples 1, 16 to 22 and Comparative Examples 1 and 4, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the gas permeation amount passing through the electrolyte membrane was applied. Was measured. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 6 shows the results of the power generation potential and the gas permeation amount of the electrolyte membrane of the battery in which the thickness of the first layer was changed. Regarding the generated potential, the potential was higher than that of Comparative Example 1, and it was confirmed that the output performance was improved by laminating the first layer. Looking at the generated potential, Example 16 is almost the same as Comparative Example 1, but the potential rapidly increases when increasing to 5% of Example 17, and the potential increases as the thickness of the first layer increases up to 80%. Although it increased, no potential improvement was observed at 80% or more. On the other hand, when looking at the gas permeation amount, the gas permeation amount is preferably in the range of Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ which is preferable as the electrolyte membrane, but the gas permeation amount increases as the first layer becomes thicker. There is a tendency. From the above results, if less than 5%, the effect of improving the potential is small, and if it is more than 90%, the potential does not improve any more, so that an expensive SSZ material is used more than necessary. It was confirmed that the thickness is preferably 5 to 90% of the entire electrolyte membrane. Further, it was confirmed from the result of the electric power generation potential and the result of the gas permeation amount that the thickness of the first layer was more preferably 30 to 80%.

(About the ratio of the thickness of the electrolyte membrane of the first layer (when the air electrode side is a cerium-containing oxide))
(Example 23)
Example 13 was repeated except that the thickness of the first layer was 1.5 μm and the thickness of the second layer was 28.5 μm.

(Example 24)
Example 13 was the same as Example 13 except that the thickness of the first layer was 3 μm and the thickness of the second layer was 27 μm.

(Example 25)
Example 13 was carried out in the same manner as in Example 13, except that the thickness of the first layer was 6 µm and the thickness of the second layer was 24 µm.

(Example 26)
Example 13 was the same as Example 13 except that the thickness of the first layer was 9 μm and the thickness of the second layer was 21 μm.

(Example 27)
Example 13 was carried out in the same manner as in Example 13 except that the thickness of the first layer was set to 24 µm and the thickness of the second layer was set to 6 µm.

(Example 28)
Example 13 was the same as Example 13 except that the thickness of the first layer was 27 μm and the thickness of the second layer was 3 μm.

(Example 29)
Example 13 was carried out in the same manner as in Example 13, except that the thickness of the first layer was 28 µm and the thickness of the second layer was 2 µm.

(Power generation test)
A power generation test was performed using the batteries (effective fuel electrode area: 150 cm ² ) obtained in Examples 13, 23 to 29 and Comparative Examples 2 and 4. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
For the batteries obtained in Examples 13, 23 to 29 and Comparative Examples 2 and 4, nitrogen gas was allowed to flow inside the air electrode support, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the amount of gas permeating the electrolyte membrane was applied. Was measured. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 7 shows the results of the power generation potential and the gas permeation amount of the electrolyte membrane of the battery in which the thickness of the first layer was changed. Regarding the generated potential, the potential was higher than that of Comparative Example 2, and it was confirmed that the output performance was improved by laminating the first layer. Looking at the generated potential, the potential was low in Example 23, but increased to 10% of Example 24, the potential rapidly increased, and up to 80%, the potential increased as the thickness of the first layer increased. , 80% or more, no improvement in potential was observed. On the other hand, when looking at the gas permeation amount, each is in the range of gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ which is preferable as the electrolyte membrane. × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ , which means that the gas permeability is higher than when the YSZ material is included. From the above results, if less than 10%, the effect of improving the potential is small, and if it is more than 90%, the potential is not further improved, so that an expensive SSZ material is used more than necessary. It was confirmed that the thickness is preferably 10 to 90% of the entire electrolyte membrane. Furthermore, it was confirmed from the results of the power generation potential and the result of the gas permeation amount that the thickness of the first layer was more preferably 30 to 80%.

(Power generation test)
A power generation test was performed using the batteries (effective electrode area: 150 cm ² ) obtained in Examples 1, 2, 4, 7, 8 and Comparative Example 1. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 700-1000 ℃
Current density: 0.3Acm ^-2

Fig. 3 shows the power generation potential at 700 to 1000 ° C. At 900 to 1000 ° C., little difference was observed compared to Comparative Example 1, but when the temperature was 900 ° C. or less, the potential difference from the comparative example increased, and at 700 ° C., a difference of about 0.2 V was confirmed. . From the above results, it is confirmed that the solid oxide fuel cell having excellent output performance even at a low temperature of about 700 ° C. can be provided by using the electrolyte membrane configuration represented by Examples 1, 2, 4, 7, and 8. I was able to. In particular, it was confirmed that the configurations of Examples 4 and 8 were preferable.

(Effect of sintering temperature)
(Example 30)
It was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1340 ° C.

(Example 31)
It was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1350 ° C.

(Example 32)
It was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1450 ° C.

(Example 33)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1500 ° C.

(Example 34)
Example 1 was repeated except that the sintering temperature of the electrolyte membrane was changed to 1510 ° C.

(Power generation test)
A power generation test was performed using the batteries (fuel electrode effective area: 150 cm ² ) obtained in Examples 1 and 30 to 34. The operating conditions at this time were as follows.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

(Gas leak test)
For the batteries obtained in Examples 1, 30 to 34 and Comparative Example 1, nitrogen gas was flown inside the air electrode support, a pressure of 0.1 MPa was applied from the inside of the air electrode, and the amount of gas permeating the electrolyte membrane was measured. did. Thereby, it was evaluated whether the electrolyte membrane was a membrane having no gas permeability.

Table 8 shows the results of the power generation potential and the gas permeation amount with respect to the sintering temperature of the electrolyte membrane. Regarding the power generation potential, it can be seen that the sintering at 1340 ° C. in Example 30 and the sintering at 1510 ° C. in Example 34 had higher potentials than Comparative Example 1 but lower potentials than the other Examples. Further, the gas permeation amount is in the range of gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ which is preferable for the electrolyte membrane. From the above results, it was confirmed that the sintering temperature of the electrolyte membrane was more preferably in the range of 1350 to 1500 ° C.

It is a figure which shows the cross section of a cylindrical type solid oxide fuel cell. FIG. 2 is a cross-sectional view showing in detail an air electrode, an electrolyte membrane, and a fuel electrode configuration of the solid oxide fuel cell shown in FIG. 1. 4 is a graph showing a relationship between a power generation temperature (horizontal axis) and a power generation potential (vertical axis) of a test battery.

Explanation of reference numerals

1: Air electrode support
2: Interconnector
3: Electrolyte membrane
4: Fuel electrode
1a: Electrode reaction layer
3a: First layer
3b: Second layer
4a: Fuel-side electrode reaction layer

Claims (22)

An air electrode on one side of the electrolyte membrane, a unit cell having a fuel electrode disposed on the opposite side thereof, and an interconnector having a role of electrical connection, a solid oxide fuel cell comprising: A first layer made of a material having oxygen ion conductivity S1 on the air electrode side, and a second layer made of a material containing at least zirconia with oxygen ion conductivity S2 on the fuel electrode side, A solid oxide fuel cell, wherein the oxygen ion conductivity S1 on the air electrode side and the oxygen ion conductivity S2 on the fuel electrode side are S1> S2. 2. The solid oxide fuel cell according to claim 1, wherein the thickness of the first layer is 5 to 90% of the total thickness of the electrolyte membrane. 3. The solid oxide fuel cell according to claim 2, wherein the thickness of the first layer is 30% to 80% of the total thickness of the electrolyte membrane. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the second layer is a zirconia material in which yttria is dissolved. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the first layer is a zirconia material in which scandia is dissolved. 6. The solid oxide fuel cell according to claim 5, wherein the amount of scandia dissolved in the zirconia in which scandia is dissolved is 3 to 12 mol%. 6. The solid oxide fuel cell according to claim 5, wherein the amount of scandia dissolved in the zirconia in which scandia is dissolved is 8 to 12 mol%. 7. In the zirconia in which the scandia is dissolved, at least one oxide selected from CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O _3, Er ₂ O ₃ and Bi ₂ O ₃ is 5 mol% or less. The solid oxide fuel cell according to any one of claims 5 to 7, which is solid-dissolved. 5. The solid oxide fuel cell according to claim 4, wherein the amount of yttria in zirconia in which yttria is dissolved is 3 to 12 mol%. Both the first layer and the second layer are made of zirconia in which scandia and yttria are dissolved, and the scandia solid solution Sc1 in the first layer and the scandia solid solution Sc2 in the second layer are both formed. The solid oxide fuel cell according to any one of claims 1 to 3, wherein Sc1> Sc2. The solid oxide fuel cell according to claim 10, wherein the total amount of scandia and yttria in the layer made of zirconia in which scandia and yttria are dissolved is 3 to 12 mol%. In the layer made of zirconia in which scandia and yttria are dissolved, at least one of CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O _3, Er ₂ O ₃ and Bi ₂ O ₃ The solid oxide fuel cell according to claim 10, wherein the oxide is dissolved in a solid solution of 5 mol% or less. The first layer has the general formula La _1-a A _a Ga _1-b B _b O ₃ or La _1-a A _a Ga _1-b-c B _b C _c O ₃ (where A is Sr, Ca, Ba is lanthanum gallate represented by one or more of Ba, B is one or more of Mg, Al, In, and C is one or more of Co, Fe, Ni, Cr) The solid oxide fuel cell according to claim 1, wherein: The first layer is a cerium-containing oxide represented by the general formula (CeO ₂ ) _1-2X (B ₂ O ₃ ) _X (where B is any one of Sm, Gd, and Y, 0.05 ≦ X ≦ 0.15). The solid oxide fuel cell according to any one of claims 1 to 4, wherein the solid oxide fuel cell is a product. An air electrode on one side of the electrolyte membrane, a unit cell having a fuel electrode disposed on the opposite side thereof, and an interconnector having a role of electrical connection, a solid oxide fuel cell comprising: A first layer made of a zirconia material in which at least scandia is dissolved as a solid solution with oxygen ion conductivity S1 on the air electrode side, and a first layer made of a material containing at least cerium-containing oxide with oxygen ion conductivity S2 on the fuel electrode side. A solid oxide fuel cell, wherein the oxygen ion conductivity S1 on the air electrode side and the oxygen ion conductivity S2 on the fuel electrode side are S1> S2. . The solid oxide fuel cell according to claim 15, wherein the thickness of the first layer is 10 to 90% of the total thickness of the electrolyte membrane. The solid oxide fuel cell according to claim 15, wherein the thickness of the first layer is 30 to 80% of the total thickness of the electrolyte membrane. The second layer is a cerium-containing oxide represented by the general formula (CeO ₂ ) _{1-2 X} (B ₂ O ₃ ) _X (where B is any one of Sm, Gd, and Y, 0.05 ≦ X ≦ 0.15). The solid oxide fuel cell according to any one of claims 15 to 17, which is a product. An electrode reaction layer having an open pore communicating therewith is provided between the electrolyte membrane and the air electrode, which promotes a reaction for generating oxygen ions from oxygen gas and electrons. 19. The solid oxide fuel cell according to any one of claims 18 to 18. The electrode reaction layer is a layer in which lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A is either Ca or Sr) and zirconia in which scandia is dissolved are uniformly mixed. 20. The solid oxide fuel cell according to claim 19, wherein: The air electrode is made of lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A is either Ca or Sr). A solid oxide fuel cell according to claim 1. The solid oxide fuel cell according to any one of claims 1 to 21, wherein the electrolyte membrane is formed on the surface of the electrode reaction layer and then sintered at 1350 to 1500 ° C.

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