JP5511875B2 - Solid oxide fuel cell and method for producing the same - Google Patents

Description

  The present invention relates to a solid oxide fuel cell and a method for manufacturing the same, and more specifically to an electrode-supported solid oxide fuel cell having a tubular structure (tube type) and having a gas flow path therein. .

Conventionally, as a solid oxide fuel cell (hereinafter sometimes simply referred to as a fuel cell), a tube-type solid electrolyte body (solid oxide body) provided with electrodes inside and outside is known.
As for the electrode of this fuel cell, the electrode that bears the structure support portion needs to be thick in order to maintain the structure. Further, in order to obtain a fuel cell having high power generation efficiency, a structure is required in which the gas supplied to the electrode is made as small as possible and the gas can be used as efficiently as possible inside the fuel cell.

  For that purpose, it is necessary to make it the electrode structure which can diffuse gas efficiently inside the electrode which has a thick structure. On the other hand, in order to promote the electrode reaction, it is necessary to reduce the internal resistance of the fuel cell by forming a fine structure and increasing the electrode surface area.

  As a countermeasure against the latter, the following patent document 1 realizes very good electrode performance (low electric resistance between the fuel electrode and the electrolyte interface) by controlling the raw material particle diameter, the mixing ratio of the electrode material, and the like. Technology has been proposed.

  As a study for realizing both, as shown in Patent Document 2 below, the electrode has a two-layer structure, and the structure support portion has an electrode structure mainly focusing on gas diffusivity. As for the reaction field in the vicinity, a technique for ensuring electrode performance by adopting a fine electrode structure has been proposed.

JP 2009-266713 A JP 2007-165143 A

  However, in a fuel cell of a type in which the electrode is a structure support portion and a gas flow path is formed inside the structure support portion, that is, the above-described tube-type solid oxide fuel cell, the current is a solid electrolyte body. In this structure, electricity does not flow in the direction of the gas flow path (ie, in the radial direction), and electricity is taken out when current flows in the length direction of the electrode (ie, in the axial direction). Therefore, in such a fuel cell, in addition to the internal resistance (reaction resistance) and gas diffusivity of the above fuel cell intended for electrode reaction, the resistance of movement of electrons flowing in the electrode (in the axial direction) Need to be small.

  In other words, in the fuel cell having such a structure, the electrode formed inside the solid electrolyte body plays a role of collecting the current obtained by power generation, and at the same time, diffuses the gas to the reaction activation field near the solid electrolyte body. Therefore, the characteristics have a great influence on the fuel cell performance, but the examination is not sufficient.

In addition, in the case of an electrode having a two-layer structure as in Patent Document 2, the number of steps increases and the cost may be increased, which is not preferable.
The present invention has been made in order to solve the above-described problems. The object of the present invention is a tube type that can be easily manufactured, has good electrical characteristics and gas diffusibility, and has excellent power generation characteristics. To provide a solid oxide fuel cell and a method for manufacturing the same.

(1) The present invention provides, as a first aspect, a tubular solid electrolyte body having an inner side and an outer side, a first electrode layer disposed inside the solid electrolyte body and serving as a structural support, and the solid electrolyte body In a tube-type solid oxide fuel cell comprising a second electrode layer disposed outside the gas, a gas from an inner surface of the first electrode layer to an interface between the first electrode layer and the solid electrolyte body The transmittance is 1 × 10 ⁻⁴ ml / cm ² secPa or more, and the first electrode layer has an electric conductivity of 3000 S / cm or more at 25 ° C.

In the present invention, the gas permeability from the inner surface of the first electrode layer (that is, the surface on the through hole side of the tube) to the interface between the first electrode layer and the solid electrolyte body is 1 × 10 ⁻⁴ ml / cm ² secPa. As described above, gas diffusibility is good, and excellent power generation characteristics can be obtained by efficiently supplying the gas to the vicinity of the solid electrolyte body serving as a reaction field.

  In addition, since the first electrode layer has an electric conductivity of 3000 S / cm or more at 25 ° C., the electric resistance is sufficient for taking out electricity (especially in the axial direction) obtained by power generation from the first electrode layer. Low power generation loss can be reduced.

Therefore, in the present invention, it is possible to realize a solid oxide fuel cell having good electrical characteristics and gas diffusibility and having excellent power generation characteristics.
This is clear from the relationship among the electrical conductivity, gas permeability, and power generation output in Table 1 described later.

The upper limit of the gas permeability is preferably, for example, 9.5 × 10 ⁻⁴ ml / cm ² secPa or less in consideration of electrical conductivity.
The “tubular shape” of the present invention is a cylindrical shape having a through-hole in the axial direction, and includes a flat cylindrical shape and a columnar cylindrical shape in addition to a true cylindrical shape.

(2) As a second aspect, the present invention is characterized in that 8 to 60% by volume of the material particles constituting the first electrode layer is composed of particles having a particle diameter of 2 μm or more.
In this way, the presence of 8% by volume or more of particles having a particle diameter of 2 μm or more dramatically improves the gas diffusibility of the electrode and makes it easy to obtain good power generation performance. Here, the reason why the ratio of the particles is set to 60% by volume or less is that the surface area of the particles having a particle diameter of 2 μm or more is small, and if the ratio is large, the performance of the electrode is decreased due to the decrease in the electrode surface area.

  In other words, when forming the first electrode layer, there is a method of improving the gas permeability by forming pores with a pore former or the like. However, when the pore former is used, the introduced structure in the electrode structure is used. Since the volume fraction of the pore material remains as pores, the abundance ratio of the electrode material itself having an electrode catalytic ability is lowered. On the other hand, when the gas permeability is improved by introducing coarse particles of 2 μm or more, the amount of the pore former can be reduced, so that the ratio of the electrode material in the electrode structure can be improved. . Thereby, good gas permeability, low electrode reaction resistance (radial electrical conductivity), and further resistance related to electronic conduction in the electrode (axial electrical conductivity) can be realized simultaneously.

This is clear from the relationship between the measured coarse particle ratio and power generation output in Table 1 described later.
Here, the particle diameter indicates the maximum diameter of each particle (the same applies hereinafter).
Hereinafter, particles having a particle diameter of 2 μm or more are referred to as coarse particles, and particles having a particle diameter of 1 μm or less are referred to as fine particles. The material constituting the coarse particles is preferably a material that does not undergo structural change in use.

(3) As a third aspect, the present invention is characterized in that the first electrode layer has a single-layer structure having a homogeneous structure.
Thus, by making the first electrode layer have a uniform single layer structure, the manufacturing process can be simplified and the manufacturing cost can be reduced. Further, the shape accuracy can be increased.

The term “homogeneous” means that the first electrode layer does not have a structure composed of a plurality of layers with clearly different electrode structures in the direction from the inner surface to the outer surface.
(4) As a fourth aspect of the present invention, the first electrode layer is a fuel electrode.

  Here, a preferable first electrode layer is illustrated. The fuel electrode material is generally required to be sintered at a high temperature in the production stage, and a more excellent fuel cell can be obtained from the viewpoint of securing a larger electrode surface area. In the present invention, the first electrode layer has a high electrical conductivity, and when used as a fuel electrode, a better fuel cell is obtained.

(5) As a fifth aspect of the present invention, the porosity of the first electrode layer is 30 to 60% by volume.
The reason why the porosity of the first electrode layer is set to 30% by volume or more is that when the porosity is lower than 30% by volume, the gas diffusibility is lowered and the gas is efficiently supplied to the reaction field in the vicinity of the solid electrolyte body. This is because the power generation performance is reduced.

  In addition, the porosity of the first electrode layer is set to 60% by volume or less because when the porosity exceeds 60% by volume, the abundance of the electrode material itself responsible for electrical conduction decreases due to an increase in the number of pores. This is because it is not easy to obtain high electrical conductivity (5000 S / cm or more).

This is clear from the relationship among the porosity, power generation output, and electrical conductivity in Table 1 described later.
(6) As a sixth aspect of the present invention, the shortest distance from the flow path of the gas supplied to the first electrode layer to the solid electrolyte body is 500 μm or less.

  Here, the shortest distance from the gas flow path (the gas flow path extending in the axial direction inside the tube) to the solid electrolyte body is set to 500 μm or less. When the shortest distance exceeds 500 μm, the gas diffusion distance This is because the gas supply to the vicinity of the solid electrolyte body becomes difficult and the power generation performance decreases.

This is apparent from the relationship between the thickness of the fuel electrode, the power generation output, and the electrical conductivity in Table 1 described later.
(7) In the seventh aspect, the present invention is characterized in that zirconia-based particles have the highest content among particles having a particle diameter of 2 μm or more constituting the first electrode layer.

  Here, among the particles having a particle diameter of 2 μm or more constituting the first electrode layer, the zirconia-based particles have the highest content (for example, molar ratio) because zirconia is the operating temperature among the materials used as the electrode material. This is because an electrode having excellent long-term durability can be obtained by forming a large skeleton from a material having excellent chemical stability in the vicinity and having excellent stability.

The zirconia-based particles are particles containing zirconia as a main component or all components (the same applies hereinafter).
(8) In the eighth aspect, the present invention is characterized in that, among the material particles constituting the first electrode layer, 30% by volume or more is composed of particles having a particle diameter of 1 μm or less.

  Here, among the material particles constituting the first electrode layer, 30% by volume or more is composed of particles having a particle diameter of 1 μm or less. By introducing 30% by volume or more of fine particles having a particle diameter of 1 μm or less, the electrode This is because more specific reaction fields can be introduced because the specific surface area increases.

This is clear from the relationship between the actually measured fine particle ratio and power generation output in Table 1 described later.
(9) According to the ninth aspect of the present invention, in the ninth aspect, among the material particles constituting the first electrode layer, 50 to 90% by volume of particles having a particle diameter of 1 μm or less (for example, measured Ni fine particle ratio in Table 2 described later + The measured YSZ fine particle ratio, or the measured Ni fine particle ratio + the measured ScSZ fine particle ratio).

  Of the material particles constituting the first electrode layer, 50 to 90% by volume are composed of fine particles having a particle diameter of 1 μm or less. In order to obtain high performance and high durability, fine particles having a particle diameter of 1 μm or less. This is because it is necessary to introduce.

  That is, if less than 50% by volume is introduced, the effect of suppressing the sintering of metal particles (for example, Ni, Cu, Fe, etc.) in the first electrode layer cannot be obtained sufficiently, and performance deterioration easily occurs. The reason why the sintering suppression effect is obtained when there are many fine particles is that the contact between metal particles (for example, Ni, Cu, Fe, etc.) can be reduced.

  Moreover, when it introduce | transduces more than 90 volume%, gas diffusibility is impaired and it becomes difficult to obtain favorable electric power generation performance. That is, when the content is 50 to 90% by volume, particularly good fuel cell performance can be obtained.

  This is apparent from the relationship between “measured Ni fine particle ratio + actually measured YSZ fine particle ratio” or “actually measured Ni fine particle ratio + measured ScSZ fine particle ratio” and power generation output and deterioration rate in Table 2 described later.

  (10) In the tenth aspect of the present invention, at least a part of the particles having a particle diameter of 1 μm or less constituting the first electrode layer is composed mainly of nickel, copper, iron, silver, platinum, ruthenium, rhodium, It is a metal or alloy particle made of at least one of cobalt.

Such a material has excellent catalytic ability as an electrode material of a solid oxide fuel cell.
(11) In the eleventh aspect of the present invention, in the eleventh aspect, zirconia-based particles having a particle diameter of 1 μm or less (for example, the actually measured YSZ fine particle ratio in Table 2) of the material particles constituting the first electrode layer. It is characterized by comprising.

  Of the material particles constituting the first electrode layer, 20 to 50% by volume is composed of zirconia-based particles having a particle diameter of 1 μm or less. The main cause of deterioration of the fuel cell is the metal during power generation (eg, Ni, Cu , Fe, etc.) or alloy particles (for example, Ni-Fe, Ni-Cu, etc.), but when the amount is less than 20% by volume, the sintering inhibiting effect is not sufficient, and when the amount is more than 50% by volume. This is because the gas permeability of the first electrode layer is low and it becomes difficult to obtain sufficient fuel cell performance. That is, when the content is 20 to 50% by volume, an electrode having excellent long-term durability and good performance can be obtained.

This is apparent from the relationship between “actually measured fine particle ratio” in Table 2 described later, the power generation output, and the deterioration rate.
(12) The twelfth aspect of the present invention is characterized in that the zirconia-based particles contain scandium-stabilized zirconia or yttrium-stabilized zirconia as a main component.

  The reason why the zirconia-based particles are composed of scandium-stabilized zirconia (ScSZ) or yttrium-stabilized zirconia (YSZ) is that these materials are excellent in ionic conductivity, and an electrode having excellent electrical properties can be obtained. Because.

  (13) In the thirteenth aspect of the present invention, the proportion of the zirconia-based particles (for example, YSZ mixing ratio in Table 2) in the material particles constituting the first electrode layer is 50 to 60% by volume. Features.

  Of the material particles constituting the first electrode layer, the proportion of the zirconia-based particles is 50 to 60% by volume. When the ratio is less than 50% by volume, the metal particles (for example, Ni, Cu, Fe, etc.) contact each other. Since the number of zirconia-based particles necessary to reduce the amount is insufficient, sintering or aggregation of metal or alloy particles in the electrode is likely to occur. When the amount is more than 60% by volume, the abundance ratio of metal or alloy particles serving as a catalyst is high. This is because it becomes less and it becomes difficult to obtain high fuel cell performance.

This is apparent from the relationship among the YSZ mixing ratio, the power generation output, and the deterioration rate in Table 2 described later. The YSZ mixing ratio and the ratio of the material particles of the first electrode layer are substantially the same.
(14) In the fourteenth aspect of the present invention, the permeation amount of helium gas from the outer surface of the solid electrolyte body to the inner surface of the first electrode layer (for example, the helium gas permeation amount in Table 3) per cm ² 5.0 × 10 ⁻⁵ Pa · m ³ / sec or less.

The permeation amount of helium gas was set to 5.0 × 10 ⁻⁵ Pa · m ³ / sec or less per 1 cm ^{2 because the} solid electrolyte body exceeding this permeation amount is not a dense structure. When fuel gas and air leak from the solid electrolyte body, particularly when power generation is performed at a high fuel utilization rate, the fuel gas necessary for the reaction becomes insufficient, and there is excess air in the reaction field of the first electrode layer. This is because the first electrode layer is oxidized and the durability performance is lowered.

  (15) The present invention provides, as a fifteenth aspect, a method for producing the above-described solid oxide fuel cell, the step of mixing powder into a clay state, and the step of extruding the clay-like mixture And the first electrode layer is formed by extrusion molding.

  Here, the first electrode layer is formed by extrusion molding in a form having a gas flow path (extending in the axial direction) inside the first electrode layer of the tube-shaped solid oxide fuel cell. This is because it is the most convenient and accurate manufacturing method.

  (16) As a sixteenth aspect, the present invention provides a raw material having an average particle diameter of 2 μm or more as a raw material of the first electrode layer, and a volume ratio of a portion excluding a component (for example, pore former) that disappears in a firing stage. It mixes and manufactures in the ratio of 8-60 volume% in conversion, It is characterized by the above-mentioned.

Here, the raw material having an average particle diameter of 2 μm or more is mixed because the first electrode layer having good gas diffusibility can be easily realized.
(17) In the seventeenth aspect of the present invention, as a seventeenth aspect, a raw material having an average particle diameter of 1 μm or less is used as a raw material for the first electrode layer, and a volume ratio of a portion excluding a component (for example, pore former) that disappears in the firing stage It is characterized by being manufactured by mixing at a ratio of 30% by volume or more in terms of conversion.

Here, the raw material having an average particle diameter of 1 μm or less is mixed because the first electrode layer having a large electrode surface area can be easily realized.
(18) The present invention is characterized in that, as an eighteenth aspect, the pore former is produced by adding 20 to 40% by volume with respect to the volume of the raw material of the first electrode layer.

Here, the reason why 20-40% by volume of the pore former is added is that the porosity of the first electrode for obtaining a solid oxide fuel cell having high performance can be easily realized.
(19) In the nineteenth aspect of the present invention, the pore former is a spherical pore former or a pore former obtained by combining the spherical particles, and the particle diameter of the pore former is 1. 10 to 10 μm.

  Here, the spherical pore former is used because the packing density of the electrode material powder hardly changes during the molding stage, and the shape accuracy of the product is easily obtained. Moreover, the particle diameter of the pore former was set to 1 to 10 μm. In the case of a pore former less than 1 μm, the strength of the sintered body tends to be low, and in the case of a pore former more than 10 μm This is because pores due to the pore former are sparsely scattered in the electrode structure, and the effect of improving the electrode performance is lost.

  (20) According to the twentieth aspect of the present invention, in the twentieth aspect, a raw material having an average particle diameter of 1 μm or less (for example, a mixing ratio of fine particles in Table 2) is excluded as a raw material for the first electrode layer It is characterized by being manufactured by mixing at a ratio of 55 to 95% by volume in terms of volume ratio.

  As a raw material for the first electrode layer, a raw material having an average particle diameter of 1 μm or less is mixed at a ratio of 55 to 95% by volume in terms of the volume ratio of the portion excluding components (for example, pore former) that disappear in the firing stage. The reason for manufacturing is that the mixing ratio is most suitable for manufacturing in order to obtain an electrode structure as set forth in claim 9.

(21) In the twenty-first aspect, the present invention is characterized in that nickel oxide (NiO) having an average particle diameter of 1 μm or less is mixed as a raw material for the first electrode layer.
When this nickel oxide (NiO) is used, sintering can be kept low at the time of firing, and it is reduced to nickel during power generation and has excellent catalytic activity.

(22) In the twenty-second aspect, the present invention is characterized in that the first electrode layer and the solid electrolyte body are simultaneously fired at a temperature of 1350 ° C. or lower (for example, the firing temperature in Table 3).
The co-firing temperature of the first electrode layer and the solid electrolyte body is set to 1350 ° C. or lower. The lower the firing temperature, the easier it is to obtain a structure with a large surface area of the first electrode layer, while obtaining the density of the solid electrolyte body. This is because a firing temperature of 1350 ° C. or lower is preferable in order to obtain good fuel cell performance.

The firing temperature is preferably 1300 ° C. or higher from the viewpoint of obtaining the density of the solid electrolyte body.
<Hereinafter, each configuration of the present invention will be described>
The first electrode layer (for example, the inner electrode) and the second electrode layer (for the outer electrode) are, for example, a fuel electrode that is in contact with a fuel gas and an air electrode that is in contact with a combustion-supporting gas such as air that is an oxygen source. Can be used.

  Among these, in the case of the “fuel electrode”, the fuel electrode is in contact with the hydrogen gas and functions as a negative electrode in the single cell. As the fuel electrode, a cermet made of metal (particularly Ni) particles and ceramic particles can be employed.

In addition to Ni, Cu, Fe, Co, Ag, Pt, Pd, W, Mo, and alloys thereof can be used as the metal.
Examples of ceramics include zirconia, YSZ (yttrium stabilized zirconia), ScSZ (scandium stabilized zirconia), SDC (ceria doped with samarium), GDC (ceria doped with gadolinium), alumina, silica, titania, and the like. It is done. In particular, YSZ, ScSZ, SDC, and GDC are desirable.

On the other hand, in the case of an “air electrode”, it comes into contact with a combustion-supporting gas serving as an oxygen source and functions as a positive electrode in a single cell.
The material of the air electrode can be appropriately selected depending on, for example, the use conditions of the solid oxide fuel cell. As this material, for example, a metal, a metal oxide, a metal composite oxide, or the like can be used. Examples of the metal include metals such as Pt, Au, Ag, Pd, Ir, Ru, Rh, and alloys containing two or more metals.

Furthermore, examples of the metal oxide include oxides such as La, Sr, Ce, Co, Mn, and Fe (for example, La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , FeO). Etc.). Further, as the complex oxide, various complex oxides containing at least one of La, Pr, Sm, Sr, Ba, Co, Fe, Mn, etc. (for example, La _1-x Sr _x CoO ₃ series) Complex oxides, La _1-x Sr _x FeO ₃ complex oxides, La _1-x Sr _x Co _1-y Fe _y O ₃ complex oxides, La _1-x Sr _x MnO ₃ complex oxides, Pr _1-x Ba _x CoO ₃ composite oxide, Sm _1-x Sr _x CoO ₃ composite oxide, and the like.

  Furthermore, examples of the “solid electrolyte body” include solid electrolytes (solid oxides) such as YSZ, ScSZ, SDC, GDC, and perovskite oxides. These may be a single film or a multilayer film in which two or more kinds of compositions have a laminated structure. Examples of the multilayer film include a YSZ + SDC film and a YSZ + GDC film.

In the case of a fuel cell, for example, this solid electrolyte body can move at least a part of one of the fuel gas introduced into the fuel electrode or the combustion-supporting gas introduced into the air electrode during operation as ions. It has ionic conductivity. Although what kind of ion can be conducted is not particularly limited, examples of the ion include oxide ion O ²⁻ and proton H ⁺ .

1 is a perspective view of a solid oxide fuel cell according to an embodiment. It is sectional drawing which fractured | ruptured some solid oxide fuel cells along the axis. It is a perspective view showing a solid oxide fuel cell stack in which a plurality of solid oxide fuel cells are arranged. It is explanatory drawing which shows the manufacturing method of a solid oxide fuel cell. 6 is an explanatory diagram showing an experimental method of Experimental Example 1. FIG. It is explanatory drawing which shows the experimental method of Experimental example 2. FIG. It is explanatory drawing which shows the experimental method of Experimental example 5. FIG. It is explanatory drawing which shows the experimental method of Experimental example 6. FIG. It is explanatory drawing which shows the experimental method of Experimental example 7. FIG.

Hereinafter, embodiments of the present invention will be described.
[Embodiment]
a) First, the configuration of the solid oxide fuel cell according to the present embodiment will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the solid oxide fuel cell 1 has a cylindrical shape (tube shape) having a small diameter (for example, a diameter of 0.5 to 2.0 mm) and a long length (for example, a length of 10 to 50 mm). A through hole 3 through which fuel gas flows is formed at the center of the shaft.

  The solid oxide fuel cell 1 includes a cylindrical fuel electrode (inner electrode: first electrode) 5 serving as a support at the center, and the fuel electrode 5 is disposed on the outer peripheral surface of the fuel electrode 5. A solid electrolyte layer (solid oxide layer) 7 which is a thin solid electrolyte body is formed so as to cover the entire circumference. The solid electrolyte layer 7 is formed to have a smaller axial dimension than the fuel electrode 5 so that the fuel electrode 5 is slightly exposed from both axial sides of the solid oxide layer 7.

  Further, a thin reaction prevention layer 9 (which prevents reaction between the solid oxide material and the air electrode material) is formed on the outer peripheral surface of the solid electrolyte layer 7 so as to cover the entire circumference of the solid electrolyte layer 7. Yes. The reaction preventing layer 9 is formed to have a smaller axial dimension than the solid electrolyte layer 7 so that the solid electrolyte layer 7 is slightly exposed from both axial sides of the reaction preventing layer 9.

  Further, a thin air electrode (outside electrode: second electrode) 11 is formed on the outer peripheral surface of the reaction preventing layer 9 so as to cover the entire reaction preventing layer 9. The air electrode 11 is formed to have a smaller axial dimension than the reaction preventing layer 9 so that the reaction preventing layer 9 is slightly exposed from both axial sides of the air electrode 11.

Each configuration will be described below.
The fuel electrode 5 is mainly composed of nickel and yttrium-stabilized zirconia (YSZ) and has a single layer structure having a homogeneous structure, and the thickness thereof is 500 μm or less.

Further, the gas permeability (in the thickness direction) of the fuel electrode 5 is 1 × 10 ⁻⁴ ml / cm ² secPa or more, and its electric conductivity is 3000 S / cm or more at 25 ° C. The porosity of the fuel electrode 5 is 30 to 60% by volume.

  Further, among the material particles constituting the fuel electrode 5, 8 to 60% by volume is composed of particles (coarse particles) having a particle diameter of 2 μm or more, and among the coarse particles having a particle diameter of 2 μm or more, zirconia-based particles ( Here, YSZ particles) has the highest content (molar ratio). In addition, as this content, 50% is mentioned, for example.

Moreover, among the material particles constituting the fuel electrode 5, 30% by volume or more (particularly 50 to 90% by volume) is composed of particles having a particle diameter of 1 μm or less.
In addition, at least a part of the particles having a particle diameter of 1 μm or less is mainly composed of nickel. In addition to nickel, metal or alloy particles composed of at least one of copper, iron, silver, platinum, ruthenium, rhodium, and cobalt can also be employed.

  Furthermore, the proportion of zirconia-based particles in the material particles constituting the fuel electrode 5 is 50 to 60% by volume, and among the material particles constituting the fuel electrode 5, 20 to 50% by volume has a particle diameter of 1 μm. It is composed of the following zirconia-based particles.

The zirconia-based particles are particles mainly composed of YSZ (here, particles composed only of YSZ), but may be composed mainly of ScSZ.
Further, the permeation amount of helium gas from the outer surface of the solid electrolyte layer 7 to the inner surface of the fuel electrode 5 is 5.0 × 10 ⁻⁵ Pa · m ³ / sec or less per 1 cm ² .

The solid electrolyte layer 7 is a thin film having a thickness of, for example, 5 μm, and is mainly made of, for example, yttrium-stabilized zirconia (YSZ).
The reaction preventing layer 9 is a thin film having a thickness of 3 μm, for example, and is mainly made of gadolinium solid solution type ceria (GDC), for example.

The air electrode 11 is a thin film having a thickness of, for example, 20 μm, and is mainly composed of, for example, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-x (LSCF) and GDC.
In the solid oxide fuel cell 1 having the above-described configuration, as shown in FIG. 2, hydrogen is supplied to the through hole 3 of the fuel electrode 5 under a predetermined temperature condition (for example, 650 ° C.), and the air electrode By supplying air to the outside of 11, the output (electric power) can be taken out between the fuel electrode 5 and the air electrode 11.

  In addition, as shown in FIG. 3, this kind of tube-shaped solid oxide fuel cell 1 can be used as the solid oxide fuel cell stack 15 by aligning a plurality of columns in the vertical and horizontal directions. it can.

b) Next, the manufacturing method of the solid oxide fuel cell 1 of this embodiment is demonstrated based on FIG.
As shown in FIG. 4A, first, in order to produce the fuel electrode 5, a mixed powder of nickel oxide (NiO) and yttrium-stabilized zirconia (YSZ) is mixed with a cellulosic binder and a pore former ( For example, spherical polymethyl methacrylate (PMMA) bead powder having a particle diameter of 1 to 10 μm (for example) having a diameter of 5 μm was added, mixed well, and then mixed until it became clayy by adding water.

  Here, as the mixed powder composed of nickel oxide and YSZ, as illustrated in Table 1 below, coarse particles having an average particle diameter of 2 μm or more (in terms of the volume ratio of the portion excluding the pore former) are 8 to A mixed powder containing 60% by volume or more and 30% by volume or more of fine particles having an average particle diameter of 1 μm or less (in terms of the volume ratio of the portion excluding the pore former) is used. The ratio of particles having an average particle diameter in nickel oxide and the ratio of particles having an average particle diameter in YSZ are the same as those in the mixed powder.

  Further, as this mixed powder, in addition to the above conditions, for example, a mixed powder containing 55 to 95% by volume of fine particles having an average particle diameter of 1 μm or less (in terms of the volume ratio of the portion excluding the pore former) is used.

Moreover, the addition rate of a pore making material shall be the range of 20-40 outer volume% with respect to the said mixed powder, for example.
The mixing ratio of nickel oxide and YSZ is, for example, 50% by volume: 50% by volume. The mixed powder is mainly composed of coarse particles having an average particle diameter of 2 μm or more and fine particles having an average particle diameter of 1 μm or less. The coarse particles are composed of zirconia (YSZ), and the fine particles are composed of nickel oxide and zirconia (YSZ). It is configured.

The ratio (volume%) between the coarse particles and the fine particles is a predetermined ratio (within the scope of the present invention) as described in Tables 1 and 2 below, for example.
Next, the clay was put into an extrusion molding machine to produce a cylindrical (tube) fuel electrode molded body 21 having an outer diameter of 2.5 mm. The fuel electrode molded body 21 was cut to a predetermined length.

  Next, as shown in FIG. 4 (b), in order to form the solid electrolyte layer 7, YSZ powder, polyvinyl butyral, amine dispersant, plasticizer, methyl ethyl ketone and ethanol are mixed as a solvent, A slurry for coating was prepared.

  Next, after performing masking with a predetermined width on the outer peripheral surface of the fuel electrode molded body 21 at a position where the solid electrolyte layer 7 is not formed, that is, on the outer peripheral surfaces on both sides in the axial direction of the fuel electrode molded body 21. The solid electrolyte layer coating 23 was formed on the surface of the fuel electrode molded body 21 by dipping in the coating slurry and slowly pulling it up.

Thereafter, the fuel electrode molded body 21 and the solid electrolyte layer forming film 23 were simultaneously fired at 1350 ° C. to obtain a co-fired body 25 of the fuel electrode 5 and the solid electrolyte layer 7.
Next, as shown in FIG. 4C, gadolinium solid solution type ceria (GDC) powder and polyvinyl chloride are used to form a reaction preventing layer 9 for the purpose of preventing the reaction between the solid electrolyte layer 7 and the air electrode 11. Butyral, an amine-based dispersant, and a plasticizer were mixed with methyl ethyl ketone and ethanol as a solvent to prepare a coating slurry.

  Next, the outer peripheral surface of the co-fired body 25 of the fuel electrode 5 and the solid electrolyte layer 7 is masked at a position where the reaction preventing layer 9 is not formed, that is, the outer peripheral surfaces on both sides in the axial direction of the solid electrolyte layer 7 with a predetermined width. Then, the reaction prevention layer coating 27 was formed on the surface of the co-fired body 25 by dipping in the coating slurry and slowly pulling it up.

Thereafter, the reaction preventing layer 9 was formed on the surface of the co-fired body 25 by heat treatment at 1200 ° C.
Next, as shown in FIG. 4D, in order to form the air electrode 11, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-x (LSCF) powder, GDC powder, polyvinyl butyral, amine-based A dispersing agent and a plasticizer were mixed with methyl ethyl ketone and ethanol as a solvent to prepare an air electrode slurry.

  Next, after masking with a predetermined width on the outer peripheral surfaces of the reaction preventing layer 9 in the axial direction at a position where the air electrode 11 is not formed, the co-fired body 25 having the reaction preventing layer 9 formed thereon is air A film 29 for the air electrode was formed on the surface of the reaction preventing layer 9 by dipping in the electrode slurry and then slowly pulling it up.

Thereafter, baking treatment was performed at 1000 ° C. to produce the air electrode 11, and the solid oxide fuel cell 1 of the present embodiment was completed.
c) Next, the effect of this embodiment will be described.

In this embodiment, the gas permeability from the inner surface of the fuel electrode 5 to the interface between the fuel electrode 5 and the solid electrolyte layer 7 is 1 × 10 ⁻⁴ ml / cm ² secPa or more. The gas is efficiently supplied to the vicinity of the solid electrolyte layer 7 serving as a reaction field, whereby excellent power generation characteristics can be obtained. In addition, since the fuel electrode 5 has an electric conductivity of 3000 S / cm or more at 25 ° C., the electric resistance is sufficiently low for taking out the electricity obtained from the power generation from the fuel electrode 5, and the power generation loss can be reduced.

  Therefore, in this embodiment, high gas permeability, low electric resistance related to electrode reaction, and low electronic resistance flowing inside the electrode can be compatible, and the solid oxide fuel cell 1 having high performance can be realized with a simple electrode structure. . That is, in this embodiment, the solid oxide fuel cell 1 having excellent electric characteristics and gas diffusibility and excellent power generation characteristics can be realized.

  In the present embodiment, among the material particles constituting the fuel electrode 5, 8 to 60% by volume is composed of particles having a particle diameter of 2 μm or more. Therefore, good gas permeability and low electrode reaction resistance (radial direction) Electrical conductivity), and furthermore, low electrical resistance (electrical conductivity in the axial direction) related to electronic conduction in the electrode can be realized simultaneously.

-In this embodiment, since the fuel electrode 5 is a uniform 1 layer structure, a manufacturing process can be simplified and manufacturing cost can be reduced. Further, the shape accuracy can be increased.
-In this embodiment, since the porosity of the fuel electrode 5 is 30-60 volume%, gas diffusivity is high, gas is efficiently supplied to the reaction field of the solid electrolyte body vicinity, and electric power generation performance improves. In addition, the abundance of the electrode material itself responsible for electrical conduction is large, and sufficient electrical conductivity (3000 S / cm or more) can be obtained.

  In this embodiment, since the shortest distance from the flow path (through hole 3) of the gas supplied to the fuel electrode 5 to the solid electrolyte layer 7 is 500 μm or less, the gas diffusion distance is short, and the solid electrolyte layer The gas supply to the vicinity of 7 becomes easy, and the power generation performance is improved.

  In the present embodiment, since the zirconia-based particles have the highest content among the particles having a particle diameter of 2 μm or more constituting the fuel electrode 5, a large skeleton can be formed with a material having excellent stability. An electrode having excellent long-term durability can be obtained.

  In this embodiment, among the material particles constituting the fuel electrode 5, 30% by volume or more is composed of particles having a particle diameter of 1 μm or less, so that the specific surface area of the electrode is increased, so that more reaction fields are generated. Can be introduced.

  -In this embodiment, 50-90 volume% is comprised by the particle | grains with a particle diameter of 1 micrometer or less among the material particles which comprise the fuel electrode 5. FIG. Therefore, the effect of suppressing the sintering of the metal particles in the fuel electrode 5 is high, the deterioration of performance can be suppressed, and the gas diffusibility is excellent, so that good power generation performance can be obtained.

  -In this embodiment, 20-50 volume% is comprised with the zirconia-type particle | grains with a particle diameter of 1 micrometer or less among the material particles which comprise the fuel electrode 5. FIG. Therefore, it is possible to suppress sintering and aggregation of metal or alloy particles during power generation, which is a main cause of deterioration of the solid oxide fuel cell 1, and to ensure high gas permeability. That is, the fuel electrode 5 having excellent long-term durability and good performance can be realized.

-In this embodiment, the zirconia-type particle | grains in the fuel electrode 5 are comprised from YSZ. This YSZ is excellent in ionic conductivity, and an excellent fuel electrode 5 can be realized.
-In this embodiment, the ratio for which a zirconia-type particle accounts among the material particles which comprise the fuel electrode 5 is 50-60 volume%. Therefore, sintering or aggregation of metal or alloy particles in the fuel electrode 5 hardly occurs, and high fuel cell performance can be obtained (since the abundance ratio of metal or alloy particles serving as a catalyst is sufficient).

In this embodiment, the permeation amount of helium gas from the outer surface of the solid electrolyte layer 7 to the inner surface of the fuel electrode 5 is 5.0 × 10 ⁻⁵ Pa · m ³ / sec or less per 1 cm ² .
Therefore, since the solid electrolyte layer 7 has a moderately dense structure, the fuel gas and air can be prevented from leaking from the solid electrolyte layer 7, and the oxidation of the fuel electrode 5 can be suppressed, resulting in high durability. Performance can be realized.

-In this embodiment, since the fuel electrode 5 is manufactured by extrusion molding, the fuel electrode 5 can be manufactured most simply and accurately.
-In this embodiment, it manufactures by mixing the powder which has an average particle diameter of 2 micrometers or more as a raw material of the fuel electrode 5 in the ratio of 8-60 volume% (in the volume ratio conversion of the part except a pore making material). Therefore, the fuel electrode 5 with good gas diffusibility can be easily realized.

  -In this embodiment, as a raw material of the fuel electrode 5, since it mixes and manufactures the powder which has an average particle diameter of 1 micrometer or less (in the volume ratio conversion of the part except a pore making material) in the ratio of 30 volume% or more. The fuel electrode 5 having a large electrode surface area can be easily realized.

  In this embodiment, since the pore former is manufactured by adding 20 to 40% by volume to the mixed powder of the fuel electrode 5, the fuel electrode 5 for obtaining the solid oxide fuel cell 1 having high performance is obtained. The porosity can be easily realized.

  In this embodiment, since a spherical pore former having a particle size of 1 to 10 μm is used, the packing density of the electrode material powder hardly changes during the molding stage, and the shape accuracy of the product is easily obtained. Moreover, there exists an advantage that the intensity | strength of a sintered compact is high and electrode performance improves.

  In this embodiment, nickel oxide (NiO) having an average particle size of 1 μm or less is mixed and used as a raw material for the fuel electrode 5, so that sintering can be kept low during firing, and reduced and nickel is generated during power generation. And has excellent catalytic activity.

d) Next, experimental examples conducted to confirm the effects of the present invention will be described.
<Experimental example 1>
(Measurement of gas permeability of fuel electrode tube)
As shown in FIG. 5, as the sample 31 used in this experimental example, the materials shown in the following Table 1 (pore forming material [volume%], coarse particles [volume%], fine particles [volume%]) are used, and the fuel electrode After firing the molded body for use at a predetermined temperature without coating the solid electrolyte layer, a sample of a fuel electrode tube reduced in hydrogen at 800 ° C. was prepared. In addition, the content of the manufacturing process etc. which are not described in the following experiment examples are the same as that of the said embodiment.

  And as shown in the figure, while the outer peripheral surface of the both ends of the sample 31 was airtight with the packing 33, the lower end side (of the figure) of the sample 31 was obstruct | occluded. Next, air whose pressure is adjusted by a regulator 38 is supplied from a cylinder 37 to the through hole 35 at the center of the shaft from the upper end side (in the figure) of the sample 31, and the flow rate is measured by a soap film flow meter 39. did. Specifically, a gas pressure was applied from the inner surface of the sample 31, and the amount of gas permeated to the opposite surface was measured with a soap film flow meter 39.

The obtained gas flow rate is F (ml / min), the outer surface area of the sample 31 (the surface area corresponding to the length L between the packings 33) is the gas permeation area A (cm ² ), and the gas pressure applied from the inner surface is As P (Pa), gas permeability C (ml / cm ² secPa) was determined by the following formula (1).
The results are shown in Table 1 below.

In Table 1, examples are samples within the scope of the present invention, and comparative examples are samples outside the scope of the present invention (the same applies to other tables below).
C = F / 60AP (1)
<Experimental example 2>
(Measurement of electric conductivity of fuel electrode tube)
As shown in FIG. 6, as the sample 41 used in this experimental example, the material shown in Table 1 below was used, and the fuel electrode molded body was fired at a predetermined temperature without being coated with a solid electrolyte layer, and then in hydrogen. A sample of a fuel electrode tube reduced at 800 ° C. was prepared.

  Then, as shown in the figure, two voltage terminals 43 and 45 used at the time of measurement are formed by winding an Ag wire at a position 10 mm from the center in the longitudinal direction of the sample 41 and baking and fixing with Ag paste. did.

Furthermore, current terminals 47 and 49 were formed in the same manner as the voltage terminals 43 and 45 at positions 5 mm outward from the voltage terminals 43 and 45, respectively.
The measurement was performed at room temperature (25 ° C.) in an air atmosphere by using a DC power source 51, an ammeter 53, and a voltmeter 55, and applying a DC current from the current terminals 47 and 49 at both ends of the sample 41. By recording the voltage between the voltage terminals 43 and 45, the electric conductivity κ (() is obtained from the current I (A), the voltage E (V), the sample cross-sectional area A (cm ² ), and the distance L (cm) between the voltage terminals. S / cm) was determined by the following equation (2). The results are shown in Table 1 below.

κ = IL / EA (2)
Here, evaluation results at room temperature (25 ° C.) different from the operating temperature at which power is actually generated are used. However, when the operating temperature is reached, the numerical value of electrical conductivity changes, but between each sample 41. The superiority or inferiority of the evaluation did not change, and therefore, the evaluation was performed at room temperature at which it can be measured efficiently.

<Experimental example 3>
(Measurement of porosity of fuel electrode tube)
Although not shown in the figure, as a sample used in this experimental example, the material shown in Table 1 below was used, and the molded article for a fuel electrode was fired at a predetermined temperature without being coated with a solid electrolyte layer. A sample of the fuel electrode tube subjected to reduction treatment was prepared.

Using this sample, the porosity was measured with a mercury porosimeter. The results are shown in Table 1 below.
<Experimental example 4>
(Confirmation of anode thickness and anode structure)
Although not shown in the figure, as a sample used in this experimental example, the material shown in Table 1 below was used, and the molded article for a fuel electrode was fired at a predetermined temperature without being coated with a solid electrolyte layer. A sample of the fuel electrode tube subjected to reduction treatment was prepared.

This sample was embedded and fixed in an epoxy resin, then cut perpendicular to the axial direction, mirror-polished, and the tube cross section was confirmed with a scanning electron microscope (SEM).
The fuel electrode thickness was calculated by measuring the distance in a field of view where the entire thickness of the fuel electrode could be confirmed.

The particle diameter was determined by measuring the long diagonal length in the particle image obtained by SEM observation of the tube cross section.
Further, the abundance ratio of coarse particles (having a particle diameter of 2 μm or more) and fine particles (having a particle diameter of 1 μm or less) was determined. This abundance ratio is the ratio of the area occupied by the particles within the corresponding particle diameter to the total area of the particles present in the image at a magnification at which the size of the particles can be confirmed. The ratio was investigated for 10 images, the average value was taken as the area ratio S of the sample, and further converted into the volume ratio V. After calculating by formula (3), the volume ratio is shown in Table 1. As described.

  In Table 1, the volume ratio (volume%) of the coarse particles is shown as “actually measured coarse particle ratio [%]”, and the volume ratio (volume%) of the fine particles is shown as “actually measured fine particle ratio [%]”.

In addition, the material corresponding to which material of the mixed powder is clarified by examining by elemental analysis.
<Experimental example 5>
(Power generation evaluation)
As shown in FIG. 7, the tube-type solid oxide fuel cell 63 described above is used as the sample 61 used in this experimental example, and the fuel electrode 67 that is not coated with the solid electrolyte layer 65 is exposed to the exposed portion. A terminal for collecting current from the fuel electrode 67 was formed by winding a silver wire 69 and applying a silver paste.

  In addition, the Pt net 73 is wound around the portion where the air electrode 71 is formed and fixed with a silver wire 75, and then a paste produced by LSCF is applied to collect current from the air electrode 71. The silver wire 75 used for fixing the Pt net 73 was used as a current collecting terminal for the air electrode 71.

  Further, as shown in the figure, both ends of the solid oxide fuel cell 63 (exposed portions of the solid electrolyte layer 77 and the reaction preventing layer 79) are gas-sealed and fixed with a glass material 81, and a power generation jig 83 and did.

  The power generation jig 83 is set so that the solid oxide fuel cell 63 is positioned at the center of the electric furnace 85, and hydrogen humidified at room temperature is supplied to the inside of the tube at a flow rate of 25 cc / min. Configured. The air electrode 71 side was left open to the atmosphere.

  Then, in order to measure the temperature of the solid oxide fuel cell 63, a thermocouple 87 is set at a position 2 mm away from the outer surface of the air electrode 71 of the solid oxide fuel cell 63, and a program temperature controller is used. Electric power was generated by adjusting the solid oxide fuel cell 63 to 650 ° C.

  And the power generation output at that time (power generation output at 0.6 V) was measured. The results are shown in Table 1 below.

(Consideration of results)
As is apparent from Table 1, all the samples within the range of the present invention (Examples 1 to 14) satisfy Claim 1 and are out of the range of the present invention (Comparative Examples 1 to 7). It can be seen that a high power output density of 0.5 W / cm ² or more is obtained.

  Compared to each comparative example, in each example, the gas permeability is high, the gas supplied to the electrode is effectively diffused into the electrode reaction field, and the electric conductivity is high. It is thought that there is.

  In Comparative Examples 1, 2, and 4, gas permeability is low because coarse particles of 2 μm or more are not mixed. In Comparative Examples 3 and 7, the gas permeability is lowered when the thickness of the fuel electrode is as thick as 600 μm.

  When Example 3 and Example 4 are compared, the performance of Example 4 with a smaller amount of pore-forming material is obtained. This is considered to be a result obtained by the effect of increasing the electrode reaction field by the amount of the pores in the electrode structure decreased.

  Moreover, when Example 4 and Example 5 are compared, in Example 5, since the pore former is not introduced, the porosity is lowered and the gas permeability is lowered. This is thought to be due to a decrease in performance compared to Example 4 due to insufficient gas diffusion.

  Furthermore, in Examples 1-14, the ratio of the coarse particle of 2 micrometers or more is changed. Here, it is considered that the sample having more coarse particles has a higher gas permeability than that of Comparative Example 3, and high performance was obtained due to the effect.

  About Example 13 and Comparative Example 5, compared with Examples 1-12 and 14, a lot of pore formers are introduced. In Example 11, the coarse particle mixing ratio (and thus the measured coarse particle ratio) is high. Therefore, although the gas permeability is high, the number of pores in the electrode structure is reduced, so that the number of electron conduction paths is reduced and the electrical conductivity is lowered. That is, since the electrode reaction field corresponding to the increase in pores is impaired, it is considered that only a low output was obtained as a result as compared with Examples 1 to 10, 12, and 14.

  In Comparative Example 6, compared with Examples 1 to 14, the mixing ratio of fine particles of 1 μm or less is small. In other words, as the measured fine particle ratio decreased, the electrode surface area decreased and the electrode reaction field was impaired. As a result, only a low output was obtained as compared with Examples 1-14.

In Examples 11 and 14, the measured fine particle ratio is lower than in the other examples, and therefore, it is considered that the output is lower than in the other examples.
In Examples 1 to 14, since only zirconia-based particles (YSZ particles) are added as coarse particles, zirconia-based particles have the highest content among particles having a particle diameter of 2 μm or more constituting the fuel electrode. is there. For example, in Example 1, the content of zirconia-based particles having a particle diameter of 2 μm or more was 48% by volume.
<Experimental example 6>
(Durability performance evaluation by continuous energization)
As shown in FIG. 8, a power generation jig 93 using the tube-type solid oxide fuel cell 91 described above was produced in the same manner as in Experimental Example 5.

  Then, the solid oxide fuel cell 91 of the power generation jig 93 was set in an electric furnace 95, and hydrogen humidified at room temperature was supplied to the inside of the tube at a flow rate of 25 cc / min. Further, the air electrode 97 side was left open to the atmosphere.

Further, as in Experimental Example 5, the first silver wire 101 of the current collector terminal was connected to the exposed portion of the fuel electrode 99, and the second silver wire 103 of the current collector terminal was also connected to the surface of the air electrode 97.
For use in other experiments described later, a third silver wire 105 (electrically connected to the fuel electrode 99) is arranged in parallel with the first silver wire 101, and in parallel with the second silver wire 103. A fourth silver wire 107 (electrically connected to the air electrode 97) was disposed.

  Then, in order to measure the temperature of the solid oxide fuel cell 91, the thermocouple 109 is set in the same manner as in Experimental Example 5, and the solid oxide fuel cell 91 is set to 650 ° C. using a programmed temperature controller. The power was generated after adjusting.

Then, using the first silver wire 101 and the second silver wire 103, the power generation output at that time (power generation output at 0.6V) was measured. The results are shown in Table 2 below.
In addition, in this experimental example, when the cell voltage at the start of energization was V0 and the cell voltage after 1000 hours elapsed was V1, the durability performance was evaluated based on the deterioration rate expressed by the following equation (4).

Deterioration rate [%] = (V0−V1) / V0 × 100 (4)
As shown in FIG. 8, the voltage is measured by connecting the third silver wire 105 and the fourth silver wire 107 for flowing current to an electronic load device (variable resistor in FIG. 8) 111 and measuring the voltage. For this purpose, the first silver wire 101 and the second silver wire 103 were connected to a voltmeter 113 by a four-terminal method.

  That is, a current (for example, 0.4 A) is passed between the third silver wire 105 and the fourth silver wire 107 in the initial stage and after the endurance, and the voltage (V0, V1) measured by the voltmeter 113 at that time. From this, the deterioration rate was determined. The results are shown in Table 2 below.

  In addition to the results of this experimental example (power generation output, deterioration rate), Table 2 shows the composition of the materials of each sample (various mixing ratios and proportions of fine particles) and the samples obtained in the above-described experimental examples. Characteristics (electrical conductivity, gas permeability) are described.

  Moreover, the YSZ mixing ratio in Table 2 is a ratio at the raw material powder preparation stage, and the ratio becomes metal Ni and YSZ at the stage of reduction of the sintered body obtained from the preparation composition. , Calculated and written.

  That is, when the sintered body is reduced and reduced, the total volume of the metal Ni and YSZ is set to 100%, and the ratio of YSZ in the volume is described. The Ni ratio is the remainder of the YSZ mixing ratio in Table 2.

  In the evaluation stage in this experimental example, NiO is reduced to Ni, but in general, the volume ratio obtained by calculation at the time of sample preparation is almost the same as the volume ratio of Ni: YSZ in the state of the sintered body. It becomes equivalent. In addition, in order to know the ratio of Ni: YSZ from an actual sample, for example, there is a method of measuring the mass by ICP-MS or the like and dividing the specific gravity to calculate the volume.

(Consideration of results)
As is apparent from Table 2, Examples 1, 6, 15, 16, 17, 8, 20, and 21 satisfy the scope of claim 1 and therefore have a favorable value of 0.5 W / cm ² or more. It can be confirmed that it has power generation characteristics.

  In Example 1, the actually measured fine particle ratio is 47% by volume even when Ni and YSZ are added together, and does not satisfy the condition of 50% by volume or more in claim 9. In other words, Example 1 is considered to have a large deterioration rate of 8.2% because the proportion of fine particles is small and the effect of suppressing the sintering of Ni is insufficient.

On the other hand, in Comparative Example 2, the measured fine particle ratio is 92% by volume when Ni and YSZ are added together, and does not satisfy the condition of 90% by volume or less of claim 9, so that the gas diffusibility is insufficient. It can be seen that the power generation output is as low as 0.45 W / cm ² .

  In Examples 1, 6, 15, and 16, the actually measured YSZ fine particle ratio is less than 20% by volume, and does not satisfy the condition of 20% by volume or more of claim 11. That is, since the presence ratio of YSZ which is a fine particle is small, the effect of suppressing the sintering of Ni cannot be sufficiently obtained, and the deterioration rate is relatively large at 8.2, 6.7, 12.3, 5.4%. I understand that.

On the other hand, in Comparative Example 9, the actually measured YSZ fine particle ratio is 51% by volume and does not satisfy the condition of 50% by volume or less of claim 11. Therefore, it can be understood that the power generation output is as low as 0.38 W / cm ² because sufficient gas permeability cannot be obtained.

  -About Example 15, YSZ mixing rate is 45 volume% and does not satisfy | fill the conditions of 50 volume% or more of Claim 13. That is, it can be understood that since the YSZ ratio is small, the effect of suppressing the sintering of Ni is not sufficient and the deterioration rate is as large as 12.3%.

On the other hand, in Comparative Example 8, the YSZ mixing ratio is as high as 65%, and the ratio of Ni particles is small, so that the electric conductivity does not satisfy the condition of claim 1 and the power generation performance is as small as 0.37 W / cm ^2. I understand that.

In Example 1, the fine particle mixing ratio in the manufacturing stage is 50%, and does not satisfy the condition of 55% or more of Claim 20.
Therefore, the condition of claim 9 is not satisfied and the deterioration rate is large.

  On the other hand, in Comparative Example 2, the fine particle mixing ratio in the manufacturing stage is 100%, and does not satisfy the condition of 95% or less of claim 20. Thereby, since the structure | tissue of Claim 9 is not obtained, it can be understood that a power generation output is low.

-Since Example 21 uses ScSZ particle | grains as a zirconia-type particle | grain, the high electric power generation output is obtained. Thereby, it is understood that ScSZ has excellent ionic conductivity and high electrode performance like YSZ.
<Experimental example 7>
(Measurement of helium gas permeation)
As shown in FIG. 9, a tube-shaped sample 121 in which a fuel electrode and a solid electrolyte layer similar to those in the above-described embodiment were simultaneously fired was set in a helium leak detector 123 (manufactured by Canon Anelva Technics).

The reason why helium gas is used for the measurement of the gas permeation amount is that there is no danger of an explosion like hydrogen gas, so that an exhaust device is unnecessary and a safe and easy measurement environment can be constructed.
Then, helium gas was directly injected from a position 15 mm from the outer surface of the sample 121 at a pressure of 0.3 MPa, and the amount of helium gas per cm ² was measured. The results are shown in Table 3 below.

  In addition to the results of this experimental example (helium gas permeation amount), Table 3 shows the characteristics of each sample obtained in each of the above experimental examples (electric conductivity, gas permeability, firing temperature, power generation output, degradation) Rate).

(Consideration of results)
As is apparent from Table 3, Examples 17, 18, and 19 satisfy the conditions of Claim 1.

The firing temperatures of Examples 17, 18, and 19 satisfy the temperature condition of the firing temperature of claim 22 (1350 [° C.] or lower) and have a high power generation output. At the same time, the helium gas permeation condition of claim 14 (5.0 × 10 ⁻⁵ Pa · m ³ / sec or less) is satisfied, and a dense solid electrolyte layer can be obtained.

Thereby, it turns out that high power generation capability (power generation output: 0.57 [W / cm < ² >] or more) and durability performance (deterioration rate: 4.9% or less) are compatible.
On the other hand, since Comparative Example 10 exceeds the temperature condition of Claim 22, the deterioration rate is low by obtaining a dense solid electrolyte layer, but the gas permeability satisfies the condition of Claim 1, There is a problem that power generation output is low.

  In Comparative Example 11, since the helium gas permeation amount does not satisfy the helium gas permeation amount condition of claim 14, the deterioration rate is as large as 12.9%, so that a dense solid electrolyte layer is obtained. Therefore, it can be understood that the fuel gas leaks, the fuel gas required for power generation is insufficient, and the fuel electrode is oxidized and deteriorated.

In addition, this invention is not limited to the said embodiment at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from this invention.
(1) For example, in the above-described embodiment, the fuel electrode is a support, but another configuration may be a support (for example, an air electrode).

(2) In the above embodiment, the inside of the tube is the fuel electrode and the outside is the air electrode. However, the inside of the tube may be the air electrode and the outside may be the fuel electrode.
(3) Furthermore, the reaction preventing layer can be omitted.

DESCRIPTION OF SYMBOLS 1, 63, 91 ... Solid oxide fuel cell 3, 35 ... Through-hole 5, 67, 99 ... Fuel electrode (1st electrode layer)
7, 65, 77 ... Solid electrolyte layer 9 ... Reaction prevention layer 11, 71, 97 ... Air electrode (second electrode layer)

Claims (22)

A tubular solid electrolyte body having an inner side and an outer side;
A first electrode layer disposed inside the solid electrolyte body and serving as a structural support;
A second electrode layer disposed outside the solid electrolyte body;
In a tube type solid oxide fuel cell comprising:
The gas permeability from the inner surface of the first electrode layer to the interface between the first electrode layer and the solid electrolyte body is 1 × 10 ⁻⁴ ml / cm ² secPa or more,
The first electrode layer has an electric conductivity of 3000 S / cm or more at 25 ° C. The solid oxide fuel cell according to claim 1,
8 to 60% by volume of the material particles constituting the first electrode layer is composed of particles having a particle diameter of 2 μm or more. The solid oxide fuel cell according to claim 1 or 2,
The solid oxide fuel cell, wherein the first electrode layer has a single layer structure having a homogeneous structure. The solid oxide fuel cell according to any one of claims 1 to 3,
The solid oxide fuel cell, wherein the first electrode layer is a fuel electrode. The solid oxide fuel cell according to any one of claims 1 to 4,
A solid oxide fuel cell, wherein the porosity of the first electrode layer is 30 to 60% by volume. A solid oxide fuel cell according to any one of claims 1 to 5,
A solid oxide fuel cell, wherein a shortest distance from a flow path of a gas supplied to the first electrode layer to the solid electrolyte body is 500 μm or less. The solid oxide fuel cell according to any one of claims 2 to 6,
A solid oxide fuel cell characterized in that zirconia-based particles have the highest content among particles having a particle diameter of 2 μm or more constituting the first electrode layer. The solid oxide fuel cell according to any one of claims 2 to 7,
30% by volume or more of material particles constituting the first electrode layer is composed of particles having a particle diameter of 1 μm or less. The solid oxide fuel cell according to claim 8, wherein
50 to 90% by volume of the material particles constituting the first electrode layer are composed of particles having a particle diameter of 1 μm or less. The solid oxide fuel cell according to claim 8 or 9, wherein
At least a part of particles having a particle diameter of 1 μm or less constituting the first electrode layer is a metal or alloy particle whose main component is at least one of nickel, copper, iron, silver, platinum, ruthenium, rhodium, and cobalt. A solid oxide fuel cell characterized by the above. It is a solid oxide fuel cell given in any 1 paragraph of Claims 1-10,
A solid oxide fuel cell comprising 20 to 50% by volume of zirconia-based particles having a particle diameter of 1 μm or less among the material particles constituting the first electrode layer. The solid oxide fuel cell according to claim 11,
The solid oxide fuel cell, wherein the zirconia-based particles contain scandium-stabilized zirconia or yttrium-stabilized zirconia as a main component. The solid oxide fuel cell according to any one of claims 1 to 12,
A solid oxide fuel cell, wherein the proportion of the zirconia-based particles in the material particles constituting the first electrode layer is 50 to 60% by volume. The solid oxide fuel cell according to any one of claims 1 to 13,
The permeation amount of helium gas from the outer surface of the solid electrolyte body to the inner surface of the first electrode layer is 5.0 × 10 ⁻⁵ Pa · m ³ / sec or less per 1 cm ^2. Solid oxide fuel cell. A method for producing a solid oxide fuel cell according to any one of claims 1 to 14,
Mixing the powder into a clay,
Extruding the clay-like mixture;
Have
A method for producing a solid oxide fuel cell, wherein the first electrode layer is formed by extrusion molding. A method for producing a solid oxide fuel cell according to claim 15,
As a raw material for the first electrode layer, a raw material having an average particle diameter of 2 μm or more is mixed and produced at a ratio of 8 to 60% by volume in terms of the volume ratio of the portion excluding components that disappear in the firing stage. A method for producing a solid oxide fuel cell. A method for producing a solid oxide fuel cell according to claim 16,
As a raw material for the first electrode layer, a raw material having an average particle diameter of 1 μm or less is produced by mixing at a ratio of 30% by volume or more in terms of the volume ratio of the portion excluding components that disappear in the firing stage. A method for manufacturing a solid oxide fuel cell. A method for producing a solid oxide fuel cell according to claim 17,
A method for producing a solid oxide fuel cell, comprising producing a pore former by adding 20 to 40% by volume with respect to the volume of the raw material of the first electrode layer. A method for producing a solid oxide fuel cell according to claim 18,
The pore former is a spherical pore former or a pore former in which the spherical particles are combined, and the pore diameter of the pore former is 1 to 10 μm. Of manufacturing a fuel cell. A method for producing a solid oxide fuel cell according to any one of claims 15 to 19, comprising:
As a raw material for the first electrode layer, a raw material having an average particle diameter of 1 μm or less is mixed and manufactured at a ratio of 55 to 95% by volume in terms of the volume ratio of the portion excluding components that disappear in the firing stage. A method for producing a solid oxide fuel cell. A method for producing a solid oxide fuel cell according to any one of claims 15 to 20, comprising:
A method for producing a solid oxide fuel cell, wherein nickel oxide (NiO) having an average particle diameter of 1 μm or less is mixed as a raw material for the first electrode layer. A method for producing a solid oxide fuel cell according to any one of claims 15 to 21,
A method for producing a solid oxide fuel cell, wherein the first electrode layer and the solid electrolyte body are co-fired at a temperature of 1350 ° C. or lower.