JP2004087490A - Solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell which is excellent in output performance and durability performance by forming an electrolyte membrane having no gas permeability with SSZ / YSZ material having high oxygen ion conductivity. .
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 other side; and an interconnector having a role of electrical connection. The electrolyte membrane is composed of at least a layer made of zirconia in which scandia and yttria are dissolved, and the 3% diameter in the particle size distribution of the particles on the membrane surface in the electrolyte membrane is 3 μm or more and the 97% diameter is 50 μm or less. A solid oxide fuel cell is provided.
[Selection diagram] None

Description

The present invention relates to a solid oxide fuel cell having excellent output performance and durability 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.

(4) As an electrolyte membrane of a conventional solid oxide fuel cell, a layer made of zirconia in which yttria is dissolved (hereinafter referred to as YSZ) has been proposed (for example, see Patent Document 1). In this case, there has been a problem that the oxygen ion conductivity of the electrolyte membrane decreases at a low temperature of 900 ° C. or lower, and the output performance decreases.

も Some have proposed a layer made of zirconia in which scandia is dissolved (hereinafter, referred to as SSZ) as an electrolyte membrane of a solid oxide fuel cell (for example, see Patent Document 2). However, there was a problem that it was difficult to produce an electrolyte membrane having low sinterability and no gas permeability.

As an electrolyte membrane of a solid oxide fuel cell, there is one that proposes a layer made of zirconia in which scandia and yttria are dissolved (hereinafter, referred to as SSZ / YSZ) (for example, see Patent Document 3). . However, when an attempt was made to produce an electrolyte membrane using the material of Patent Document 3, it was found that there were cases where an electrolyte membrane without gas permeability could not be produced, and cases where the output performance was reduced.
JP-A-10-158894 (page 1-6, FIG. 1-12) JP-A-7-6774 (page 1-5, FIG. 1-5) JP-A-2000-340240 (pages 1-8, FIG. 1-4)

The present invention has been made in order to solve the above-mentioned problems, and in the present invention, a solid electrolyte having excellent output performance and durability performance is formed by forming an electrolyte membrane having no gas permeability with a high oxygen ion conductive SSZ / YSZ material. An oxide fuel cell is provided.

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 is composed of at least a layer made of zirconia in which scandia and yttria are dissolved, and 3% or more of the crystal grain size on the membrane surface of the electrolyte membrane is 3 μm or more and 97% or more. A solid oxide fuel cell having a thickness of 50 μm or less is provided.

According to the present invention, since the electrolyte membrane is made of SSZ / YSZ, it is possible to provide an electrolyte membrane having high oxygen ion conductivity and excellent sinterability. Further, since the 3% diameter in the particle size distribution of the particles on the membrane surface in the electrolyte membrane is 3 μm or more and the 97% diameter is 50 μm or less, a solid oxide fuel cell excellent in output performance can be provided.

The reason is that the electrolyte membrane contains SSZ, which has higher oxygen ion conductivity than YSZ, and the oxygen ion conductivity of the electrolyte membrane is higher. This is because a film can be manufactured. If the 3% diameter in the particle size distribution of the particles on the membrane surface in the electrolyte membrane is less than 3 μm, the electrolyte membrane becomes a membrane having open pores communicating with each other. On the other hand, when the 97% diameter is larger than 50 μm, contamination from the air electrode and / or the fuel electrode is included, so that the electrolyte membrane has electronic conductivity and the output performance is reduced.

少 な く と も The zirconia in which at least scandia and yttria are solid-solved as shown here may be zirconia in which at least two types of scandia and yttria are solid-solved, and other compositions may be solid-dissolved. For example, zirconia, in which scandia, yttria, and ceria are dissolved, corresponds to this.

The electrolyte membrane without gas permeability shown here is evaluated by the amount of gas permeated therethrough when a pressure difference is provided between one side and the opposite side of the electrolyte membrane, and the gas permeation amount Q ≦ 2.8 × 10 ^-9 ms ^-1 Pa ^-1 (more preferably, Q ≦ 2.8 × 10 ^-10 ms ^-1 Pa ^-1 ).

The particle size distribution of the particles on the film surface shown here is the particle size distribution of the particles obtained by the following planimetric method. First, take pictures of the electrolyte membrane surface in SEM, draw a known circular area (A) on this picture, by the spent grains the number n _i the number of particles n _c and the circumference of the circle (1) The number of particles _NG per unit area is determined.
N _G = (n _c + 1 / 2n _i ) / (A / m ² )… (1)
Here, m is the magnification of the photograph. Since 1 / N _G is an area occupied by one particle, the particle size equivalent circle diameter of the membrane surface is obtained in 2 / √ (πN _G), when the side of the square 1 / √N _G.

The 3% diameter in the particle size distribution of the particles on the film surface shown here is the third equivalent particle size when the crystal particle diameters are measured in 100 places by the planimetric method and arranged in ascending order of particle diameter. , And the 97% diameter refers to a particle diameter corresponding to the 97th. In addition, even if it seems that particles are joined by sintering, if a grain boundary is observed, it is considered as a separate particle and measured.

In a preferred embodiment of the present invention, the 3% diameter in the particle size distribution of the particles on the membrane surface of the electrolyte membrane is 3 μm or more, and the 97% diameter is 20 μm or less.

When the 3% diameter in the particle size distribution of the particles on the membrane surface of the electrolyte membrane is 3 μm or more and the 97% diameter is 20 μm or less, a solid oxide fuel cell excellent in durability performance can be provided.

The reason for this is that the SSZ / YSZ film composed of particles having a 3% diameter of 3 μm or more and a 97% diameter of 20 μm or less has a large number of grain boundaries and has a fuel gas side formed thereon by an anchor effect. This is because the adhesion to the electrode can be further improved.

In a preferred embodiment of the present invention, the total solid solution amount of scandia and yttria in the SSZ / YSZ is 3 to 12 mol%.

(4) 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 and durability performance can be provided.

The reason for this is that if the total solid solution amount of scandia and yttria is less than 3 mol%, the oxygen ion conductivity of the material will be low and the output performance will be reduced, whereas if it exceeds 12 mol%, the crystal phase will be cubic. In addition, a rhombohedral crystal is generated to lower the oxygen ion conductivity, and the stability of the crystal phase is lowered to lower the durability.

In a preferred embodiment of the present invention, the total solid solution amount of scandia and yttria in the SSZ / YSZ is 8 to 12 mol%.

By setting the total solid solution amount of scandia and yttria to 8 to 12 mol%, a solid oxide fuel cell having more excellent output performance can be provided.

This is because oxygen ion conductivity is highest when the total solid solution amount of scandia and yttria is 8 to 12 mol%.

In a preferred embodiment of the present invention, the solid solution ratio of scandia in the layer composed of SSZ / YSZ is 20 to 90% based on the total solid solution amount of scandia and yttria.

(4) By setting the scandia solid solution ratio in SSZ / YSZ to 20 to 90%, an electrolyte membrane having high oxygen ion conductivity and no gas permeability can be easily produced.

The reason is that if the solid solution ratio of scandia is less than 20%, it is almost the same as the oxygen ion conductivity of YSZ, so the solid oxide fuel cell with better output performance than the solid oxide fuel cell whose electrolyte membrane is YSZ On the other hand, if it is more than 90%, oxygen ion conductivity is high, but sinterability is reduced, and it is difficult to produce an electrolyte membrane having no gas permeability.

In a preferred embodiment of the present invention, 5 mol% or less of ceria is further dissolved in the SSZ / YSZ layer.

According to this embodiment, a solid oxide fuel cell having excellent output performance and durability can be provided by further dissolving an appropriate amount of ceria in solid solution.

The reason for this is that the solid solution of ceria has the effect of improving oxygen ion conductivity and the effect of stabilizing the crystal phase. On the other hand, since ceria has electronic conductivity in the fuel atmosphere of the solid oxide fuel cell, the output performance is conversely reduced when a large amount of ceria is dissolved in the electrolyte membrane. The ceria solid solution amount is preferably 5 mol% or less, which has little effect on electronic conductivity.

In a preferred embodiment of the present invention, it is provided that the layer comprising SSZ / YSZ further contains bismuth in a solid solution of 5 mol% or less.

According to this aspect, by dissolving an appropriate amount of bismuth in a solid solution, the sinterability of the SSZ / YSZ layer is improved, and an electrolyte membrane having no gas permeability at a lower temperature can be formed.

The reason why bismuth is preferably dissolved as a solid solution is that bismuth has a low melting point of about 820 ° C. and a high boiling point of about 1900 ° C., so that sintering of SSZ can be performed at a low temperature. On the other hand, when a large amount of bismuth forms a solid solution, the bismuth component is removed from the SSZ material in the step of sintering the interconnector and the fuel electrode of the solid oxide fuel cell, and an electrolyte without gas permeability cannot be obtained. . The solid solution amount of bismuth is preferably 5 mol% or less.

In a preferred embodiment of the present invention, ceria and bismuth are further dissolved in the layer composed of SSZ / YSZ in a total amount of 5 mol% or less.

According to this aspect, by dissolving a proper amount of ceria and bismuth in a solid solution, an electrolyte membrane having no gas permeability at lower temperature can be formed, and a solid oxide fuel cell excellent in output performance can be provided.

The reason that it is preferable to form a solid solution of ceria and bismuth is because the solid solution of ceria improves the oxygen ion conductivity of the electrolyte membrane, and the solid solution of bismuth improves the sintering property, thereby improving gas permeability at lower temperatures. This is because it is possible to form an electrolyte membrane free from defects. On the other hand, if the content is more than 5 mol%, bismuth is likely to escape from the electrolyte membrane, and the electronic conductivity of ceria is more likely to be exerted, so that the output performance of the solid oxide fuel cell is reduced.

In a preferred embodiment of the present invention, an air-side electrode reaction layer that promotes a reaction for generating oxygen ions from oxygen gas and electrons is interposed between the electrolyte membrane and the air electrode.

According to this aspect, a solid oxide fuel cell having excellent output performance can be provided by providing a layer that promotes the reaction of the formula (2) between the electrolyte membrane and the air electrode.
^{_{1 / 2O 2 + 2e - →}} O 2- ... (2)

The reason is that when the reaction of the formula (2) is promoted, oxygen ions are efficiently sent to the electrolyte membrane.

In a preferred embodiment of the present invention, the air-side electrode reaction layer uniformly mixes lanthanum manganite and SSZ represented by (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr). (Hereinafter referred to as LaAMnO ₃ / SSZ).

According to this embodiment, by using a mixture of (La _1-x A _x ) _y MnO ₃ and SSZ having high oxygen ion conductivity as the air-side electrode reaction layer, at a power generation temperature of about 700 ° C. Also, a solid oxide fuel cell having excellent output performance can be provided.

The reason is that LaAMnO ₃ / SSZ has high electron conductivity and oxygen ion conductivity, so that the reaction of formula (2) occurring between the air electrode and the electrolyte membrane can efficiently proceed even at a low temperature of about 700 ° C. This is because the oxygen ion conductivity of the electrolyte membrane of the present invention is high, so that 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.

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 is made of lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr).

According to this aspect, it is possible to provide a solid oxide fuel cell having excellent output performance by using (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr) for the air electrode. Can be.

The reason is that lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A is either Ca or Sr) has an electron conductivity under the air atmosphere of a solid oxide fuel cell. This is because it is expensive and stable as a material.

In a preferred embodiment of the present invention, between the electrolyte membrane and the fuel electrode, at least hydrogen gas (H ₂ ) and / or carbon monoxide gas (CO) contained in the fuel gas, and oxygen ions (O ²⁻ ) , A fuel-side electrode reaction layer that promotes a reaction to generate electrons with H ₂ O and / or CO ₂ is interposed.

According to this aspect, a solid oxide fuel cell having excellent output performance can be provided by providing a layer that promotes the reactions of formulas (3) and (4) between the electrolyte membrane and the fuel electrode.
^{_{H 2 + O 2- → H 2}} O + 2e - ... (3)
_{^{CO + O 2- → CO 2 +}} 2e - ... (4)

 The reason for this is that the electrons reacted in the equations (3) and (4) can be efficiently sent to the fuel electrode.

In a preferred embodiment of the present invention, it is provided that the layer comprises a layer (hereinafter, referred to as NiO / SSZ or Ni / SSZ) in which NiO or Ni and zirconia in which scandia is dissolved are uniformly mixed.

According to this aspect, a solid oxide fuel cell having excellent output performance even at a power generation temperature of about 700 ° C. can be provided by using NiO / SSZ or Ni / SSZ as the electrode reaction layer.

The reason for this is that NiO / SSZ or Ni / SSZ has high electron conductivity and oxygen ion conductivity even at a low temperature of about 700 ° C, so that the reactions of equations (3) and (4) that occur between the electrolyte membrane and the fuel electrode can be efficiently performed. This is because the oxygen ion conductivity 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. is there.

NiNiO shown here is reduced to Ni in a fuel gas atmosphere, and this layer becomes Ni / SSZ.

In a preferred embodiment of the present invention, it is provided that the fuel electrode is composed of a layer (hereinafter, referred to as NiO / YSZ or Ni / YSZ) in which zirconia in which NiO or Ni and yttria are dissolved is uniformly mixed. .

According to this aspect, a solid oxide fuel cell having excellent output performance can be provided by using NiO / YSZ or Ni / YSZ for the fuel electrode.

This is because Ni / YSZ has high electronic conductivity, excellent durability, and is stable under the fuel gas atmosphere of the solid oxide fuel cell.

NiNiO shown here is reduced to Ni under fuel gas atmosphere, and this layer becomes Ni / YSZ.

In a preferred embodiment of the present invention, the interconnector is lanthanum chromite in which Ca is dissolved.

According to this aspect, by using lanthanum chromite in which Ca is dissolved as a solid solution, it is easy to produce a film having no gas permeability and an interconnector having high electronic conductivity can be produced.

The reason for this is that lanthanum chromite in which a solid solution other than Ca is dissolved requires firing at a temperature higher than 1500 ° C in order to produce an interconnector membrane with no gas permeability. When baking is performed, a reaction occurs between other constituent materials, and the output performance is reduced. On the other hand, lanthanum chromite in which Ca is dissolved is preferable because the sintering aid component Ca _m Cr _n O ₄ is generated at a temperature lower than the sintering temperature of other materials of the solid oxide fuel cell, and gas permeation is caused. This is because an interconnector having no property can be easily manufactured. In addition, a lanthanum chromite film in which Ca having no gas permeability is formed into a solid solution has a high electron conductivity.

The interconnector having no gas permeability shown here means that a pressure difference is provided between one side and the opposite side of the interconnector, and the gas permeation passing therethrough is evaluated. The gas permeation Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ (more preferably, Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ ).

In a solid oxide fuel cell, the electrolyte membrane is composed of a layer composed of SSZ / YSZ, and the 3% diameter in the particle size distribution of the particles on the membrane surface of the electrolyte membrane is 3 μm or more and the 97% diameter is 50 μm or less. As a result, the obtained electrolyte membrane has no gas permeability, and a solid oxide fuel cell having excellent output performance can be provided.

Further, when the 3% diameter in the particle size distribution of the particles on the membrane surface in the electrolyte membrane is 3 μm or more and the 97% diameter is 20 μm or less, the adhesion to the fuel gas side electrode is improved, and the durability is improved. An excellent solid oxide fuel cell can be provided.

Further, by optimizing the air-side electrode reaction layer and the fuel-side electrode reaction layer, a solid oxide fuel cell having high output performance even at a low temperature of about 700 ° C. 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 (3) and (4). By connecting the fuel electrode 4 and the interconnector 2, electricity can be taken out.
^{_{H 2 + O 2- → H 2}} O + 2e - ... (3)
_{^{CO + O 2- → CO 2 +}} 2e - ... (4)

FIG. 2 is a cross-sectional view showing a type in which an air-side electrode reaction layer 1b is provided between the air electrode 1 and the electrolyte membrane 3 and a fuel-side electrode reaction layer 4b is provided between the electrolyte membrane 3 and the fuel electrode 4. . The air-side electrode reaction layer 1b is a layer provided to promote the reaction of the formula (2) in which oxygen gas is generated from oxygen gas and electrons from the air electrode, and the oxygen generated in the air-side electrode reaction layer 1b is provided. The ions move to the fuel electrode side through the electrolyte membrane 3. Then, the reactions shown in the equations (3) and (4) are performed in the fuel-side electrode reaction layer 4b, and electricity can be extracted to the outside by connecting the fuel electrode 4a and the interconnector 2. Therefore, by optimizing the air-side 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- ... (2)

The electrolyte membrane in the present invention, in an air atmosphere and a fuel gas atmosphere at the power generation temperature of the solid oxide fuel cell, has a higher oxygen ion conductivity than the conventionally used YSZ, and has no gas permeability. Preferably, it has no electronic conductivity.

SSSSZ is preferred from the viewpoint of higher oxygen ion conductivity than YSZ and no electronic conductivity. However, SSZ has a problem that a film having no gas permeability cannot be easily produced due to low sinterability. Therefore, the present invention uses SSZ / YSZ, which includes SSZ having high oxygen ion conductivity and YSZ having excellent sinterability and can easily produce a film having no gas permeability.

In the solid oxide fuel cell having the SSZ / YSZ electrolyte membrane according to the present invention, it is more preferable to optimize the particle size distribution of the particles on the electrolyte membrane surface in order to improve output performance and durability. The particle size distribution of the particles on the film surface is preferably such that the 3% diameter is 3 μm or more and the 97% diameter is 50 μm or less, more preferably the 3% diameter is 3 μm or more and the 97% diameter is 20 μm or less. . The reason is that if there are many particles smaller than 3 μm, the SSZ / YSZ film is a film with open pores communicating with each other, so the fuel electrode is exposed to a small amount of oxygen, and the air electrode is exposed to a small amount of fuel. This is because the fuel electrode and the air electrode may be degraded by power generation.On the other hand, if there are many particles larger than 50 μm, the pores between the particles are large, and the gas permeability in the electrolyte membrane increases, and the output performance decreases. . Further, when there are many particles larger than 50 μm, the grain boundary is small, so that the anchor effect is small, and the adhesion to the fuel gas side electrode is low, so that the durability by the thermal cycle is reduced. The SSZ / YSZ film, which has a particle size distribution of particles having a 3% diameter of 3 μm or more and a 97% diameter of about 20 μm or less, has appropriate closed pores and therefore has low gas permeability without passing oxygen gas and fuel gas. In addition, since there are many grain boundaries, the adhesion to the fuel-side electrode is improved by the anchor effect, so that the thermal cycle characteristics are excellent and the durability is more preferable.

The raw material powder in the SSZ / YSZ in the present invention is not particularly limited as long as it has no gas permeability and can form an appropriate particle size distribution of the film particles. It is more preferable that the raw material powder has a BET value of 0.5 to ²⁰ m ² g ⁻¹ , a particle size distribution of 0.1 to 2 μm, and an average particle size of about 0.3 to ¹ μm.

B The BET value shown here is a value obtained by measurement using a flow-type specific surface area measurement device 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.

In the layer made of SSZ / YSZ in the present invention, Sm ₂ O ₃ , Gd ₂ O ₃ or the like may be used as a solid solution in addition to CeO ₂ to improve oxygen ion conductivity. The amount of solid solution is preferably 5 mol% or less. It may be a solid solution of Sm ₂ O ₃ and Gd ₂ O ₃ alone or a solid solution of a plurality of oxides such as a solid solution of two types of Sm ₂ O ₃ and Gd ₂ O _3. May be. Further, a mixed material of CeO _{2 in} which Sm ₂ O ₃ is dissolved and SSZ / YSZ may be used. The ratio of CeO ₂ in which Sm ₂ O ₃ is dissolved in the mixed material is preferably 5 mol% or less.

Further, in order to enable low-temperature sintering, Al ₂ O ₃ , SiO ₂ or the like may be added in addition to Bi ₂ O ₃ .

作 製 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 preferred from the viewpoint of excellent mass productivity and low cost.

法 The method of producing the electrolyte membrane raw material in the present invention is not particularly limited as long as it is a method capable of uniformly dissolving yttria and scandia. The coprecipitation method is common.

It is preferable that the air electrode in the present invention 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 (2). From this viewpoint, a preferred material is lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr).

From the viewpoint that the reaction of the formula (2) can be performed efficiently and the output performance is improved, it is preferable to interpose an air-side electrode reaction layer between the air electrode and the electrolyte membrane.

The air-side electrode reaction layer is a layer provided for efficiently performing the reaction of the formula (2) and improving the output performance, and thus preferably has high oxygen ion conductivity. Further, it is more preferable that the air-side electrode reaction layer further has electron conductivity because the reaction of the formula (2) 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. Preferred materials from the above viewpoint include LaAMnO ₃ / SSZ.

In the present invention, the composition of LaAMnO ₃ in the air-side electrode reaction layer LaAMnO ₃ (A = Ca or Sr) / SSZ is selected from (La _{1 -xA x} ) _{y When} expressed as 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 cell in order to generate an insulating layer represented by La ₂ Zr ₂ O ₇ .

Lanthanum manganite in the air-side electrode reaction layer, in addition to Sr or Ca, may be a solid solution of Ce, Sm, Gd, Pr, Nd, Co, Al, Fe, Cr, Ni, etc. . In particular, it is preferable to form a solid solution of Ni because formation of an insulating layer called lanthanum zirconate represented by La ₂ Zr ₂ O ₇ can be suppressed.

In the SSZ of the air-side electrode reaction layer in the present invention, CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O _{3, and the} like may be further dissolved as 5 mol% or less. Also, two or more solid solutions may be used. 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 increase the electrode activity of the air-side electrode reaction layer made of LaAMnO ₃ / SSZ in the present invention, a structure in which the average particle diameter and 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 carrying out the reaction of the formula (2), it is preferable to use a material having a gradient of the average particle diameter or the BET value.

A structure in which the composition is inclined to enhance the electrode activity of the air-side electrode reaction layer made 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 (2) can be performed efficiently, it is preferable that the composition is inclined.

The solid solution amount of scandia in the SSZ of the air-side electrode reaction layer composed of LaAMnO ₃ / SSZ in the present invention 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.

Cerium oxide may be further dissolved in SSZ in LaAMnO ₃ / SSZ in the present invention. The reason for this is that a solid solution of cerium oxide in SSZ has higher oxygen ion conductivity. The solid solution amount of cerium oxide is preferably about 0.5 to 5 mol%. The reason for this is that if it is less than 0.5 mol%, the effect of increasing the oxygen ion conductivity than SSZ does not appear, while if it is more than 5 mol%, the oxygen ion conductivity decreases.

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 air-side electrode reaction layer. Examples include a coprecipitation method, a powder mixing method, a spray pyrolysis method, and a sol-gel method.

In the present invention, the composition of the lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr) of the air electrode includes electronic conductivity at 700 ° C. or higher, From the viewpoint of material stability and the like, 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. Then, an insulating layer represented by La ₂ Zr ₂ O ₇ is generated to lower the output performance of the cell.

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

法 The method for producing the cathode material in the present invention is not particularly limited. Examples include 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 and high fuel gas permeability in a fuel gas atmosphere of a solid oxide fuel cell, and can efficiently perform the reactions of the formulas (3) and (4). . From this viewpoint, preferable materials include NiO / YSZ and the like. NiO is reduced to Ni in the fuel gas atmosphere of the solid oxide fuel cell, and the layer becomes Ni / YSZ.

It is preferable to provide a fuel-side electrode reaction layer between the electrolyte membrane and the fuel electrode from the viewpoint that the reactions of the formulas (3) and (4) can be performed efficiently and the output performance is improved.

NiNiO / SSZ or Ni / SSZ, which is excellent in both electron conductivity and oxygen ion conductivity, is preferable as the fuel-side electrode reaction layer in the present invention. 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.

SS The preferred amount of scandia SSSS in NiO / SSZ or Ni / SSZ of the present invention is 3 to 12 mol%. The reason is that within this range, the oxygen ion conductivity is high and the reactions of (3) and (4) can be promoted. Further, since 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.

CeO ₂ , Sm ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O _3, etc. may be further dissolved in the NiO / SSZ or the SSZ in the Ni / SSZ of the present invention in a solid solution of 5 mol% or less. Also, two or more solid solutions may be used. 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 a fuel gas atmosphere, a layer in which NiO, SSZ, and cerium oxide are uniformly mixed at a predetermined weight ratio (hereinafter, NiO / SSZ / cerium oxide) from the viewpoint of high oxygen ion conductivity and high electron conductivity May be indicated.). NiO is reduced to Ni under the fuel gas atmosphere of the solid oxide fuel cell, and the layer becomes Ni / SSZ / cerium oxide.

The cerium 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.

燃料 The fuel electrode in the present invention preferably has high electron conductivity in order to reduce IR loss. From this viewpoint, the ratio of NiO / YSZ 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 exceeds 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 / SSZ as a composition other than NiO / YSZ, and a mixture of NiO and zirconia in which calcium is dissolved as a solid solution (hereinafter, referred to as NiO / CSZ) Can be mentioned. 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 solid oxide fuel cell.

法 The method for 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.

イ ン タ ー 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 produce 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 amount of lanthanum chromite in which Ca is used as a 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%.

形状 The shape of the solid oxide fuel cell of 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 metal such as heat-resistant 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. That is, a strip-shaped interconnector 2, an electrolyte membrane 3 on a cylindrical air electrode support 1, and a fuel electrode 4 on the electrolyte membrane so as not to contact the interconnector, as shown in FIG. An air-side electrode reaction layer 1b was provided between the air electrode and the electrolyte membrane, and a fuel-side electrode reaction layer 4b was provided between the fuel electrode and the electrolyte membrane.

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

(2) the composition of Preparation air-side electrode reaction layer on the air side electrode reaction layer, using _{La 0.75 Sr 0.25 MnO 3/90} mol% ZrO 2 -10mol% Sc 2 O 3 = 50/50. Using the aqueous nitrate solutions of La, Sr, Mn, Zr and Sc, each was prepared to have the above-mentioned composition, and then coprecipitated with oxalic acid. Further heat treatment was performed to obtain a raw material powder having a controlled particle size. The average particle size was 2 μm. 40 parts by weight of the raw material powder for the air-side electrode reaction layer 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 (polyoxyethalene alkylsonate), and an antifoaming agent (sorbitan). After mixing with 1 part by weight of sesquiolate), the mixture was sufficiently stirred to prepare a slurry. The viscosity of this slurry 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:
The composition of the electrolyte membrane was 90 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ , and after being prepared to have the above-mentioned composition by using the respective nitrate aqueous solutions of Zr, Sc and Y. And coprecipitation with oxalic acid. Further heat treatment was performed to obtain a raw material powder having a controlled particle size. The average particle size was 0.5 μm. 40 parts by weight of the 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 (polyoxyetalene alkylsonate), 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 Electrolyte Membrane A film was formed on the air-side electrode reaction layer by a slurry coating method and fired at 1400 ° C. The thickness of the obtained electrolyte was 30 μm. The portion where the interconnector is to be formed in a later step was masked so that the film was not applied.

(5) Slurry preparation of fuel-side electrode reaction layer The fuel-side electrode reaction layer was NiO / 90 mol% ZrO ₂ -10 mol% Sc ₂ O _3, and the above composition was prepared using nitrate aqueous solutions of Ni, Zr and Sc. After the preparation, coprecipitation with oxalic acid was performed. Further, after heat treatment was performed to control the particle size, a raw material was obtained. The composition of the fuel-side 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. . 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 (polyoxyetalene alkyl phosphate), 1 part by weight of an antifoaming agent (sorbitanses oxolate) And 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.

(6) Slurry preparation of fuel electrode:
The fuel electrode is composed of NiO / 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ = 70/30, and mixed with the nitric acid aqueous solution of each of Ni, Zr and Y so as to have the composition described above, and then oxalic acid is used. Coprecipitation was performed. Further, after heat treatment was performed to control the particle size, a raw material was obtained. 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 (polyoxyetalene alkyl phosphate), 1 part by weight of an antifoaming agent (sorbitanes sesquiolate) And 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.

(7) Preparation of Fuel Electrode Mask the battery so that the area of the fuel electrode becomes 150 cm ² , and first apply the NiO / 90 mol% ZrO ₂ -10 mol% Sc on the electrolyte by the slurry coating method on the electrolyte. Films were formed in the order of ₂ O ₃ = 20/80 (average particle diameter 0.5 μm) and 50/50 (0.5 μm). The thickness (after firing) was 10 μm. A fuel electrode was formed thereon by a slurry coating method. The film thickness (after firing) was 90 μm. Further, firing was performed at 1400 ° C.

(8) 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 as a solid solution, produced by spray pyrolysis, and then heat-treated. The average particle size of the obtained powder was 1 μm. 40 parts by weight of the 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 (polyoxyethalene alkylsonate), 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 fired at 1400 ° C. The thickness after firing was 40 μm.

(9) Power generation test A power generation test was performed using the obtained battery (fuel electrode effective area: 150 cm 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

(10) Gas leak test Before the power generation test, a nitrogen gas was flowed 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.

(11) Measurement of particle size distribution of particles on the surface of the electrolyte membrane The surface of the electrolyte membrane of the battery prepared by the above method was observed by SEM using S-4100 manufactured by Hitachi, Ltd., and the surface of the electrolyte membrane was magnified 300 times. Taken. Further, the crystal grain size was calculated by a planimetric method from the photographed image.

(Example 2)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1350 ° C.

(Example 3)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1500 ° C.

(Example 4)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1420 ° C.

(Example 5)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1430 ° C.

(Example 6)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1450 ° C.

(Example 7)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1470 ° C.

(Comparative Example 1)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1300 ° C.

(Comparative Example 2)
Example 1 was the same as Example 1 except that the sintering temperature of the electrolyte membrane was 1520 ° C.

(Comparative Example 3)
Example 1 was repeated except that the composition of the electrolyte membrane was 92 mol% ZrO ₂ -8 mol% Y ₂ O ₃ .

Table 1 shows the results of 3% diameter, 97% diameter, average crystal grain diameter, potential at 800 ° C. current density of 0.3 Acm ⁻² and gas permeation amount of the electrolyte membrane. In practical use of a fuel cell, in consideration of the balance between the output density and the power generation efficiency, for example, when the current density is 0.3 Acm ^-2 , the potential of the cell is preferably 0.6 V or more. It can be seen that in Examples 1 to 7, the gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ was achieved under any conditions at a potential of 0.6 V or more. On the other hand, in Comparative Example 1, the potential was 0.45 V and the gas permeation amount was 28 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ , which was insufficient, and in Comparative Example 2, the gas permeation amount was Q ≦ 2.8 × 10 ⁻⁹ ms. ^{Although -1} Pa ^-1 is satisfied, the potential is as low as 0.55 V. In Comparative Example 3, even though the more preferable gas permeation amount Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ is satisfied, and the 3% diameter is 3 μm and the 97% diameter is 13 μm, the potentials in Examples 1 to 3 are not changed. Low compared to 3. In the YSZ material, when the power generation temperature is further lowered, the oxygen ion conductivity is greatly reduced, and the potential drop is increased. Therefore, it is considered that the potential drop is larger than that of SSZ / YSZ including SSZ, which is not preferable. From the above results, it was found that the electrolyte membrane was composed of SSZ / YSZ, and the 3% diameter in the particle size distribution of the membrane was preferably 3 μm or more, and the 97% diameter was preferably 50 μm or less.

The average crystal grain size shown here is a particle size of a particle corresponding to 50% in a particle size distribution of film surface particles measured by the above-mentioned planimetric method.

(12) Endurance Test The batteries of Examples 1 to 7 and Comparative Examples 1 and 2 were held for 1000 hours under the conditions of the power generation test. After the temperature was lowered to room temperature, the temperature was raised again to 800 ° C. and maintained for 500 hours under the same conditions. After the temperature was lowered again to room temperature, the temperature was raised to 800 ° C., and kept under the same conditions for 500 hours. As described above, a durability test for a total of 2000 hours including two heat cycles was performed.
Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2
Oxidizing agent: Air
Power generation temperature: 800 ° C
Current density: 0.3Acm ^-2

Table 2 shows potential changes in endurance tests of Examples 1 to 7 and Comparative Examples 1 and 2. In the first 1000 hour endurance, no potential drop was observed in Examples 1 to 7, but in Comparative Examples 1 and 2, a potential drop was observed. Further, when an endurance test was performed after the heat cycle, no potential change was observed in Examples 1, 2 and 4, but in Examples 3, 5, and 6, the potential tended to decrease gradually. Compared with Comparative Examples 1 and 2, the rate of decrease is low, which is preferable. From the above results, it was confirmed that considering the durability, it is more preferable that the 3% diameter in the particle size distribution of the SSZ / YSZ film particles be 3 μm or more and the 97% diameter be 20 μm or less. In Comparative Example 2, although the potential drop was large, there was peeling of the fuel electrode, which was considered to be the cause of the large drop in potential. For other batteries, no change such as peeling of the fuel electrode was found after the test.

About the composition of SSZ / YSZ
(Example 8)
Example 1 was repeated except that the composition of the electrolyte membrane was 97 mol% ZrO ₂ -1.5 mol% Sc ₂ O ₃ -1.5 mol% Y ₂ O ₃ .

(Example 9)
Example 1 was repeated except that the composition of the electrolyte membrane was 94 mol% ZrO ₂ -3 mol% Sc ₂ O ₃ -3 mol% Y ₂ O ₃ .

(Example 10)
Example 1 was repeated except that the composition of the electrolyte membrane was 92 mol% ZrO ₂ -4 mol% Sc ₂ O ₃ -4 mol% Y ₂ O ₃ .

(Example 11)
Example 1 was repeated except that the composition of the electrolyte membrane was 88 mol% ZrO ₂ -6 mol% Sc ₂ O ₃ -6 mol% Y ₂ O ₃ .

(Example 12)
Example 1 was repeated except that the composition of the electrolyte membrane was 98 mol% ZrO ₂ -1 mol% Sc ₂ O ₃ -1 mol% Y ₂ O ₃ .

(Example 13)
Example 1 was repeated except that the composition of the electrolyte membrane was 85 mol% ZrO ₂ -7.5 mol% Sc ₂ O ₃ -7.5 mol% Y ₂ O ₃ .

Table 3 shows the results of the potential and the gas permeation amount of the electrolyte membrane at the current density of 0.3 Acm ^-2 at 800 ° C. In the gas permeation of the electrolyte membrane, the gas permeation amount Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ required for the electrolyte membrane is achieved under any conditions, but is more preferable in Examples 12 and 13. It can be seen that the gas permeation amount Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ is not satisfied. The potential is higher than 0.6 V in Examples 1 and 8 to 11, whereas it is slightly lower than 0.6 V in Examples 12 and 13. From the above results, it was found that Examples 1 and 8 to 11 were more preferable than Examples 12 and 13. Regarding the particle size distribution of the particles on the film surface, it was confirmed that the 3% diameter was 3 μm or more and the 97% diameter was 50 μm or less in all Examples. From the above results, it was confirmed that the electrolyte membrane was preferably composed of SSZ / YSZ, and the total amount of solid solution of scandia and yttria was preferably in the range of 3 to 12 mol%. Further, in Examples 1, 10 and 11, since the potential was higher than the results of Examples 8 and 9, the total amount of solid solution of scandia and yttria was 8 to 12 mol%. And more preferred.

On the solid solution ratio of scandia in SSZ / YSZ
(Example 14)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 90 mol% ZrO ₂ -2 mol% Sc ₂ O ₃ -8 mol% Y ₂ O ₃ (20%).

(Example 15)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 90 mol% ZrO ₂ -7 mol% Sc ₂ O ₃ -3 mol% Y ₂ O ₃ (70%).

(Example 16)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 90 mol% ZrO ₂ -9 mol% Sc ₂ O ₃ -1 mol% Y ₂ O ₃ (90%).

(Example 17)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 90 mol% ZrO ₂ -1.5 mol% Sc ₂ O ₃ -8.5 mol% Y ₂ O ₃ (15%).

(Example 18)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 90 mol% ZrO ₂ -9.5 mol% Sc ₂ O ₃ -0.5 mol% Y ₂ O ₃ (95%).

Table 4 shows the results of the potential at 800 ° C. current density of 0.3 Acm ⁻² , the gas permeation amount of the electrolyte membrane, and the particle size distribution of the particles on the surface of the electrolyte membrane. In Examples 1, 14, 15 and 16, the electric potential was high, and the gas permeation amount was more preferable as the electrolyte membrane Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ . On the other hand, in Example 17, the gas permeation amount is a more preferable gas permeation amount Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ , but the potential is lower than those of the other examples. Although the gas permeation amount is high, the gas permeation amount is Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ , but is worse than the more preferable gas permeation amount Q ≦ 2.8 × 10 ⁻¹⁰ ms ⁻¹ Pa ⁻¹ . Regarding the particle size distribution of the particles on the film surface, it was confirmed that the 3% diameter was 3 μm or more and the 97% diameter was 50 μm or less in all Examples. From the above results, it was confirmed that the scandia solid solution ratio in SSZ / YSZ is preferably 20 to 90%.

<About solid solution of ceria and bismuth>
(Example 19)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 89 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -1 mol% CeO ₂ .

(Example 20)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 85 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -5 mol% CeO ₂ .

(Example 21)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 84 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -6 mol% CeO ₂ .

(Example 22)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 89 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -1 mol% Bi ₂ O ₃ .

(Example 23)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 85 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -5 mol% Bi ₂ O ₃ .

(Example 24)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 84 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -6 mol% Bi ₂ O ₃ .

(Example 25)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 89 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -0.5 mol% CeO ₂ -0.5 mol% Bi ₂ O ₃ did.

(Example 26)
The composition of the electrolyte membrane was the same as in Example 1 except that the composition was 88 mol% ZrO ₂ -5 mol% Sc ₂ O ₃ -5 mol% Y ₂ O ₃ -3 mol% CeO ₂ -3 mol% Bi ₂ O ₃ .

Table 5 shows the results of the potential at 800 ° C. current density of 0.3 Acm ⁻² , the gas permeation amount of the electrolyte membrane, and the crystal grain size on the electrolyte membrane surface. First, comparing the amounts of ceria dissolved from Examples 1, 19, 20, and 21, the potentials of Examples 19 and 20 in which ceria was added up to 5 mol% were higher than those of Example 1 in which ceria was not dissolved. However, it can be seen that in Example 21, it was lower. Regarding the gas permeation amount of the electrolyte membrane, the larger the solid solution amount of ceria is, the larger the value is. However, Q ≦ 2.8 × 10 ⁻⁹ ms ⁻¹ Pa ⁻¹ does not cause any problem. Regarding the particle size distribution of the particles on the film surface, it was confirmed that the 3% diameter was 3 μm or more and the 97% diameter was within 50 μm in all Examples. From the above results, it was confirmed that the solid solution amount of ceria is preferably 5 mol% or less from the viewpoint of output performance.

か ら Comparing Examples 1, 22, 23 and 24 with respect to the bismuth solid solution amount, it can be seen that the gas permeation amount of the electrolyte membrane decreases when bismuth is dissolved. It can be seen that the potential hardly changed up to 5 mol% solid solution, but decreased when 6 mol% was dissolved. It was observed that the 97% diameter in the particle size distribution of the particles on the film surface tended to increase depending on the bismuth solid solution amount. From the above results, it was found that sintering can be performed at a lower temperature by dissolving bismuth. However, when the solid solution exceeds 5 mol%, the output tends to decrease. Therefore, the solid solution amount of bismuth is 5 mol. % Was found to be preferable.

Examples 25 and 26 are the results of solid solution of ceria and bismuth. Compared to the results of solid solution of only ceria and bismuth, the results of electric potential, gas permeation amount and particle size distribution of particles on membrane surface are all between the results of ceria solid solution and bismuth solid solution. You can see that it is in. From the above results, it was confirmed that the total solid solution amount of ceria and bismuth is also preferably 5 mol% or less.

<Effect of power generation temperature>
A power generation test was performed on Example 1 and Comparative Example 1 at a power generation temperature of 700 to 1000 ° C. The operating conditions are shown below.
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 potentials at 700 to 1000 ° C. of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. In Comparative Example 3, the temperature at 1000 ° C. is almost the same as that of the example, but the potential drop is large at 900 ° C. or lower. In Comparative Example 1 and Comparative Example 2, the potential was low at 1000 ° C., and as the temperature became lower, the potential decreased similarly to Comparative Example 3. On the other hand, in Example 1, it can be seen that the potential drop is small at 700 to 1000 ° C., and that it has a potential of 0.6 V or more even at 700 ° C. From the above results, it was confirmed that the high output performance was obtained even at a low temperature of about 700 ° C. by using the electrolyte membrane of SSZ / YSZ and optimizing the crystal grain size of the electrolyte membrane.

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
1b: Air side electrode reaction layer
4b: Fuel-side electrode reaction layer

Claims (15)

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 solid comprising a layer made of zirconia in which scandia and yttria are dissolved, wherein the 3% diameter in the particle size distribution of particles on the membrane surface of the electrolyte membrane is 3 μm or more and the 97% diameter is 50 μm or less. Oxide fuel cells. 2. The solid oxide fuel cell according to claim 1, wherein the 3% diameter in the particle size distribution of the particles on the membrane surface of the electrolyte membrane is 3 μm or more and the 97% diameter is 20 μm or less. 3. The solid oxide fuel cell according to claim 1, 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%. 4. 3. The solid oxide fuel cell according to claim 1, wherein the total amount of scandia and yttria in the layer made of zirconia in which scandia and yttria are dissolved is 8 to 12 mol%. 4. The ratio of the amount of solid solution of scandia in the layer made of zirconia in which scandia and yttria are dissolved is 20 to 90% with respect to the total amount of solid solution of scandia and yttria. The solid oxide fuel cell according to any one of the above. The solid oxide fuel according to any one of claims 1 to 5, wherein ceria is further dissolved in the layer of zirconia in which scandia and yttria are dissolved in a solid solution of 5 mol% or less. battery. The solid oxide fuel according to any one of claims 1 to 5, wherein bismuth is further dissolved in a solid solution of scandia and yttria in a layer made of zirconia in an amount of 5 mol% or less. battery. The solid oxide according to any one of claims 1 to 5, wherein ceria and bismuth are further dissolved in the layer made of zirconia in which scandia and yttria are dissolved in a total amount of 5 mol% or less. Shaped fuel cell. 9. The air-side electrode reaction layer that promotes a reaction for generating oxygen ions from oxygen gas and electrons is interposed between the electrolyte membrane and the air electrode. The solid oxide fuel cell according to claim 1. In the air-side electrode reaction layer, lanthanum manganite represented by (La _1-x A _x ) _y MnO ₃ (where A = Ca or Sr) and zirconia in which scandia is dissolved are uniform. 10. The solid oxide fuel cell according to claim 9, wherein the solid oxide fuel cell comprises a layer mixed with: The air _{electrode, (La 1-x A x} ) y MnO 3 ( where, either A = Ca or Sr) any of claims 1 to 10, comprising the lanthanum manganite represented by A solid oxide fuel cell according to claim 1. Between the electrolyte membrane and the fuel electrode, at least hydrogen gas (H ₂ ) and / or carbon monoxide gas (CO) contained in the fuel gas, oxygen ions (O ²⁻ ), and H ₂ O and / or or a CO _2, the solid oxide fuel cell according to any one of claims 1 to 11, the fuel-side electrode reaction layer to accelerate the reaction to produce electrons, characterized in that it is interposed. 13. The solid oxide fuel cell according to claim 12, wherein the fuel-side electrode reaction layer is a layer in which NiO or Ni and zirconia in which scandia is dissolved are uniformly mixed. The solid oxide fuel cell according to any one of claims 1 to 13, wherein the fuel electrode comprises a layer in which NiO or Ni and zirconia in which yttria is dissolved are uniformly mixed. . The solid oxide fuel cell according to any one of claims 1 to 14, wherein the interconnector is made of lanthanum chromite in which Ca is dissolved.

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