JP7836655B2 - Solid oxide fuel cell and method for manufacturing the same - Google Patents

Description

This invention relates to a solid oxide fuel cell and a method for manufacturing the same.

To develop solid oxide fuel cell systems usable in automobiles and other applications, it is desirable to develop cells that can withstand vibration and do not crack even during rapid heating. Therefore, metal-supported solid oxide fuel cells, supported by a metal support, are being developed (see, for example, Patent Documents 1-3).

Japanese Patent Publication No. 2020-124704 Japanese Patent Publication No. 2021-026947 Japanese Patent Publication No. 2017-195193

In systems that generate electricity by producing reformed gas (gas containing _H₂ , CO, _CO₂ , etc.) in a reformer, the presence of the reformer makes it difficult to miniaturize the entire system. One proposed solution to this problem is to add a catalyst to a solid oxide fuel cell to realize an internal reforming function that simultaneously reforms the gas and generates electricity. However, catalysts used in conventional solid oxide fuel cells have large particle sizes and small specific surface areas, making it difficult to achieve sufficient reforming function. On the other hand, increasing the amount of catalyst added improves reforming performance, but it reduces the porosity of the porous part, making it difficult for the gas to diffuse, and as a result, the power generation performance deteriorates. For example, in the technology described in Patent Document 3, when the fuel gas passes from the second electrode to the first electrode, if the particle size of the second electrode is larger than the particle size of the first electrode, the reforming reaction cannot be carried out sufficiently, and the power generation characteristics are thought to deteriorate.

This invention has been made in view of the above-mentioned problems, and aims to provide a solid oxide fuel cell and a method for manufacturing the same that can achieve both highly efficient internal reforming and high power generation characteristics.

The solid oxide fuel cell according to the present invention comprises: a solid electrolyte layer containing a solid oxide having oxide ion conductivity; an anode provided on the solid electrolyte layer and having a porous body containing electron-conducting ceramics and oxide ion-conducting ceramics, with an anode catalyst in the porous body; a mixed layer provided on the side of the anode opposite to the solid electrolyte layer and having a porous body with a structure in which a metal material and a ceramic material are mixed, with a reforming catalyst in the porous body; and a support provided on the side of the mixed layer opposite to the solid electrolyte layer and mainly composed of metal. In the pore size distribution of each void in the cross-section of the mixed layer, a first peak of occurrence frequency and a second peak of pore size larger than the first peak appear, and the D10% diameter of voids larger than the minimum frequency pore size between the first and second peaks is greater than or equal to the D90% diameter of voids smaller than the minimum frequency pore size.

In the above-described solid oxide fuel cell, the ratio of the D50% particle size of the ceramic particles constituting the porous body of the anode to the D50% particle size of the ceramic particles in the mixed layer may be 1.1:1 to 1:1.1.

In the above-described solid oxide fuel cell, the particle size of the ceramic particles in the solid electrolyte layer may be larger than the D50% particle size of the ceramic particles constituting the porous body of the anode and the D50% particle size of the ceramic particles constituting the porous body of the mixed layer.

In the above-described solid oxide fuel cell, the D50% particle size of the ceramic particles constituting the porous body of the mixed layer may be 0.5 μm or more and 3 μm or less.

In the above-described solid oxide fuel cell, the D50% diameter of the small voids in the mixed layer may be 0.5 times or more and 2 times or less the D50% particle size of the ceramic particles constituting the porous body of the mixed layer.

In the above-described solid oxide fuel cell, the porosity of the entire anode may be 40% or more and 80% or less.

In the above-described solid oxide fuel cell, the thickness of the anode may be 1 μm or more and 15 μm or less.

In the above-described solid oxide fuel cell, the D50% particle size of the metal particles constituting the porous body in the mixed layer may be 2 μm or more and 10 μm or less.

In the above-described solid oxide fuel cell, the D50% diameter of the large voids in the mixed layer may be 0.5 times or more and 2 times or less the D50% particle size of the metal particles constituting the porous body of the mixed layer.

In the above-described solid oxide fuel cell, the porosity of the entire mixed layer may be 40% or more and 80% or less.

In the above-described solid oxide fuel cell, the thickness of the mixed layer may be 5 μm or more and 50 μm or less.

In the above-described solid oxide fuel cell, the anode catalyst may contain Ni and a mixture of one or more of the following: Y-doped BaCe 1 _{- x} Zr _x O ₃ (BCZY, x=0 to 1), Y-doped SrCe 1-x Zr _x O ₃ (SCZY, x=0 to 1), Sr-doped LaScO ₃ (LSS), and Gd-doped ceria.

In the above-described solid oxide fuel cell, the D50% particle size of the anode catalyst may be 10 nm or larger and 1 μm or smaller.

The present invention relates to a method for manufacturing a solid oxide fuel cell, comprising the steps of: firing a laminate in which an electrode green sheet containing electron-conducting ceramic material powder and oxide-ion-conducting ceramic material powder, a mixed layer green sheet containing ceramic material powder and metal material powder, and a support green sheet containing metal powder are laminated on both sides of an electrolyte green sheet containing solid oxide material powder having oxide ion conductivity; and impregnating the mixed layer obtained by firing the mixed layer green sheet with a reforming catalyst, wherein the particle size of the lost material added to the mixed layer green sheet is adjusted so that, in the pore size distribution of each void in the cross-section of the mixed layer, a first peak of occurrence frequency and a second peak of pore size larger than the first peak appear, and the D10% diameter of voids larger than the minimum frequency pore size between the first and second peaks is 90% or greater than the D90% diameter of voids smaller than the minimum frequency pore size.

According to the present invention, it is possible to provide a solid oxide fuel cell and a method for manufacturing the same that can achieve both highly efficient internal reforming and high power generation characteristics.

This is a schematic cross-sectional view illustrating the layered structure of a solid oxide fuel cell. This is an enlarged cross-sectional view illustrating details of the first support, the first mixed layer, the anode, the cathode, the second mixed layer, and the second support. This figure illustrates the pore size distribution for each void observed in the cross-section of the first mixed layer. This diagram illustrates a flow chart of a fuel cell manufacturing method.

The embodiments will be described below with reference to the drawings.

(First Embodiment)
Figure 1 is a schematic cross-sectional view illustrating a stacked structure of a solid oxide type fuel cell 100 according to the first embodiment. As illustrated in Figure 1, the fuel cell 100 has a structure comprising an anode 30 on the first surface (bottom surface) of a solid electrolyte layer 40, a first mixed layer 20 on the surface of the anode 30 opposite to the solid electrolyte layer 40, a first support 10 on the surface of the first mixed layer 20 opposite to the solid electrolyte layer 40, a cathode 50 on the second surface (top surface) of the solid electrolyte layer 40, a second mixed layer 60 on the surface of the cathode 50 opposite to the solid electrolyte layer 40, and a second support 70 on the surface of the second mixed layer 60 opposite to the solid electrolyte layer 40. Multiple fuel cells 100 may be stacked to form a fuel cell stack.

The solid electrolyte layer 40 is a dense solid layer with gas impermeability, mainly composed of a solid oxide having oxide ion conductivity. Preferably, the solid electrolyte layer 40 is mainly composed of _scandia -yttria stabilized zirconium oxide (ScYSZ). The oxide ion conductivity is highest when the concentration of _Y₂O₃ + _Sc₂O₃ is between 6 _mol % and 15 mol%, and it is desirable to use a material with this composition. Furthermore, the thickness of the solid electrolyte layer 40 is preferably 20 μm or less, and more preferably 10 μm or less. While a thinner electrolyte is preferable, a thickness of 1 μm or more is desirable to prevent gas leakage from both sides during manufacturing.

Figure 2 is an enlarged cross-sectional view illustrating the details of the first support 10, the first mixed layer 20, the anode 30, the cathode 50, the second mixed layer 60, and the second support 70.

The first support 10 is a gas-permeable member capable of supporting the first mixed layer 20, anode 30, solid electrolyte layer 40, cathode 50, and second mixed layer 60. The first support 10 is a porous metal, such as a porous Fe-Cr alloy.

The anode 30 is an electrode possessing electrode activity as an anode, and has a porous ceramic material (electrode skeleton). The porous material does not contain any metal components. In this configuration, the decrease in the anode's porosity due to the coarsening of metal components during firing in a high-temperature reducing atmosphere is suppressed. Furthermore, alloying with the metal components of the first support 10 is suppressed, thereby preventing a decrease in catalytic function.

The porous material of the anode 30 has both electronic conductivity and oxide ion conductivity. The porous material of the anode 30 contains an electronically conductive ceramic 31. As the electronically conductive ceramic 31, for example, a perovskite-type oxide represented by the compositional formula _ABO3 can be used, in which the A site is at least one selected from the group Ca, Sr, Ba, and La, and the B site is at least one selected from Ti and Cr. The molar ratio of the A site to the B site may be B ≥ A. Specifically, as the electronically conductive ceramic 31, materials such as LaCrO3 _- based materials and _SrTiO3- based materials can be used.

Furthermore, the porous body of the anode 30 contains oxide ion conductive ceramics 32. The oxide ion conductive ceramics 32 are such as ScYSZ. For example, it is preferable to use ScYSZ having a composition range of 5 mol% to 16 mol% of scandia _{( Sc2O3} ) and 1 mol% to 3 mol% of yttria ( _{Y2O3 )} . ScYSZ with a combined amount of scandia and yttria of 6 mol% to 15 mol% is even more preferable, because the oxide ion conductivity is highest in this composition range. The oxide ion conductive ceramics 32 are, for example, materials with an oxide ion transport fraction of 99% or more. GDC may also be used as the oxide ion conductive ceramics 32. In the example in Figure 2, the same solid oxide contained in the solid electrolyte layer 40 is used as the oxide ion conductive ceramics 32.

As illustrated in Figure 2, in the anode 30, for example, an electron-conducting ceramic 31 and an oxide ion-conducting ceramic 32 form a porous body. Multiple voids are formed by this porous body. The anode catalyst is supported on the surface of the porous body in the void portions. Therefore, multiple anode catalysts are spatially dispersed in the spatially continuous porous body. It is preferable to use a composite catalyst as the anode catalyst. For example, it is preferable that an oxide ion-conducting ceramic 33 and a catalyst metal 34 are supported on the surface of the porous body as a composite catalyst. As the oxide ion-conducting ceramic 33, for example, Y-doped BaCe _1-x Zr _x O ₃ (BCZY, x=0 to 1), Y-doped SrCe _1-x Zr _x O ₃ (SCZY, x=0 to 1), Sr-doped LaScO ₃ (LSS), GDC, etc. can be used. Ni or the like can be used as the catalyst metal 34. The oxide ion conductive ceramic 33 may have the same composition as the oxide ion conductive ceramic 32, or it may have a different composition. The metal that functions as the catalyst metal 34 may be in the form of a compound when no power is being generated. For example, Ni may be in the form of NiO (nickel oxide). During power generation, these compounds are reduced by the reducing fuel gas supplied to the anode 30 and take the form of a metal that functions as an anode catalyst. For example, the D50% particle size of the anode catalyst is 10 nm or more and 1 μm or less.

Furthermore, since the fuel cell 100 generates electricity at high temperatures, for example, 600°C to 900°C, if the ceramic particles constituting the porous body of the anode 30 are too small, the ceramic particles may sinter at the power generation temperature, potentially reducing the void space for gas flow. Therefore, it is preferable to set a lower limit on the D50% diameter of the ceramic particles constituting the porous body of the anode 30 in the cross-section. For example, the D50% diameter of the ceramic particles constituting the porous body of the anode 30 is preferably 0.5 μm or larger, more preferably 0.8 μm or larger, and even more preferably 1 μm or larger. The ceramic particles constituting the porous body of the anode 30 refer to the electron-conducting ceramics 31 and the oxide ion-conducting ceramics 32.

On the other hand, if the ceramic particles constituting the porous body of the anode 30 are too large, the specific surface area decreases, reducing the three-phase interface that contributes to the electrode reaction, which may degrade the power generation characteristics. Therefore, it is preferable to set an upper limit on the D50% diameter of the ceramic particles constituting the porous body of the anode 30 in cross-section. For example, the D50% diameter of the ceramic particles constituting the porous body of the anode 30 is preferably 3 μm or less, more preferably 2.5 μm or less, and even more preferably 2 μm or less.

If the anode 30 is too thin, the three-phase interface contributing to the electrode reaction will decrease, potentially degrading the power generation characteristics. Therefore, it is preferable to set a lower limit on the thickness of the anode 30. For example, the thickness of the anode 30 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.

On the other hand, if the anode 30 is too thick, the gas used in the power generation reaction must diffuse over a longer distance. To suppress this gas diffusion resistance, it is preferable to set an upper limit on the thickness of the anode 30. For example, the thickness of the anode 30 is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less.

The thickness of anode 30 can be obtained, for example, by calculating the average thickness of 10 different points.

If the porosity of the anode 30 as a whole is too low, the fuel gas may not react sufficiently, potentially leading to a decrease in power generation performance. Therefore, it is preferable to set a lower limit on the porosity of the anode 30 as a whole. For example, the porosity of the anode 30 as a whole is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more.

On the other hand, if the porosity of the anode 30 as a whole is too high, the adhesion between layers will decrease, and there is a risk of delamination. Therefore, it is preferable to set an upper limit on the porosity of the anode 30 as a whole. For example, the porosity of the anode 30 as a whole is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less.

The overall porosity of the anode 30 can be obtained by calculating the ratio of the total area of each void to the total area of the anode 30 in a cross-sectional photograph.

The first mixed layer 20 contains a metal material 21 and a ceramic material 22. In the first mixed layer 20, the metal material 21 and the ceramic material 22 are randomly mixed. Therefore, a structure in which layers of metal material 21 and layers of ceramic material 22 are stacked is not formed. Multiple voids are also formed in the first mixed layer 20. The metal material 21 is not particularly limited as long as it is a metal. In the example in Figure 2, the same metal material as the first support 10 is used as the metal material 21. As the ceramic material 22, an electronically conductive ceramic 31, an oxide ion conductive ceramic 32, etc., can be used. For example, as the ceramic material 22, ScYSZ, GDC, _SrTiO3 -based material, _LaCrO3 -based material, etc., can be used. Since _SrTiO3- based material and _LaCrO3- based material have high electronic conductivity, the ohmic resistance in the first mixed layer 20 can be reduced.

As illustrated in Figure 2, in the first mixed layer 20, for example, a metal material 21 and a ceramic material 22 form a porous body. This porous body creates multiple voids. Multiple reforming catalysts are supported on the surface of the porous body in the void portions. It is preferable to use a composite catalyst as the reforming catalyst. For example, as a composite catalyst, oxide ion conductive ceramics 23 and a catalyst metal 24 are supported on the surface of the porous body. Therefore, in the porous body formed spatially continuous by the metal material 21 and the ceramic material 22, multiple oxide ion conductive ceramics 23 and catalyst metals 24 are spatially dispersed. The reforming catalyst is not particularly limited as long as it can reform hydrocarbon gas into hydrogen gas. As combinations of catalyst metal 24 and oxide ion conductive ceramics 23, for example, a combination of Ni and GDC, a combination of Ni and YSZ, or a combination of Ni and SDC (Samaria-doped ceria) can be used. Ni may also be in the form of NiO (nickel oxide). During power generation, these compounds are reduced by the reducing fuel gas supplied to the anode 30, and become metals that function as reforming catalysts. It is preferable that the oxide ion conductive ceramic 23 is made of the same material as the oxide ion conductive ceramic 33. It is preferable that the catalyst metal 24 is made of the same material as the catalyst metal 34.

The cathode 50 is an electrode having electrode activity as a cathode and has a porous body (electrode skeleton) made of ceramic material. The porous body does not contain any metal components. The porous body of the cathode 50 has electron conductivity and oxide ion conductivity. The cathode 50 contains electron-conductive ceramics 51. As the electron-conductive ceramics 51, for example, a perovskite-type oxide represented by the compositional formula _ABO3 can be used, in which the A site is at least one selected from the group Ca, Sr, Ba, and La, and the B site is at least one selected from Ti and Cr. The molar ratio of the A site to the B site may be B ≥ A. Specifically, as the electron-conductive ceramics 51, _LaCrO3 -based materials, _SrTiO3 -based materials, etc., can be used. Preferably, the electron-conductive ceramics 51 contains the same components as the electron-conductive ceramics 31 and preferably has the same composition ratio.

Furthermore, the porous body of the cathode 50 contains oxide ion conductive ceramics 52. The oxide ion conductive ceramics 52 are such as ScYSZ. For example, it is preferable to use ScYSZ having a composition range of 5 mol% to 16 mol% of scandia _{( Sc2O3} ) and 1 mol% to 3 mol% of yttria ( _{Y2O3 )} . ScYSZ with a combined amount of scandia and yttria of 6 mol% to 15 mol% is even more preferable, as this composition range provides the highest oxide ion conductivity. The oxide ion conductive ceramics 52 are, for example, materials with an oxide ion transport rate of 99% or more. GDC may be used as the oxide ion conductive ceramics 52. It is preferable that the oxide ion conductive ceramics 52 contain the same components as the oxide ion conductive ceramics 32 and have the same composition ratio. In the example shown in Figure 2, the same solid oxide contained in the solid electrolyte layer 40 is used as the oxide ion conductive ceramic 52.

As illustrated in Figure 2, in the cathode 50, for example, an electron-conducting ceramic 51 and an oxide ion-conducting ceramic 52 form a porous body. Multiple voids are formed by this porous body. A cathode catalyst 53 is supported on the surface of the porous body in the void portions. Therefore, multiple cathode catalysts 53 are spatially dispersed in the spatially continuous porous body. As the cathode catalyst 53, materials such as praseodymium oxide ( _ProOx ), LSM (lanthanum strontium manganite), and LSC (lanthanum strontium cobaltite) can be used. LSM is a Sr-doped LaMnO3 _- based material. LSM is a Sr-doped LaCoO3 _- based material.

The second mixed layer 60 contains a metal material 61 and a ceramic material 62. In the second mixed layer 60, the metal material 61 and the ceramic material 62 are randomly mixed. Therefore, a structure is not formed in which layers of metal material 61 and layers of ceramic material 62 are stacked. Multiple voids are also formed in the second mixed layer 60. The metal material 61 is not particularly limited as long as it is a metal. In the example in Figure 2, the same metal material as the second support 70 is used as the metal material 61. As the ceramic material 62, electron conductive ceramics 51, oxide ion conductive ceramics 52, etc. can be used. For example, as the ceramic material 62, ScYSZ, GDC, _SrTiO3 -based material, _LaCrO3- based material, etc. can be used. _SrTiO3 -based material and _LaCrO3 -based material have high electron conductivity, so the ohmic resistance in the second mixed layer 60 can be reduced.

The second support 70 is a gas-permeable member capable of supporting the second mixed layer 60, the cathode 50, the solid electrolyte layer 40, the anode 30, and the first mixed layer 20. The second support 70 is a porous metal, such as a porous Fe-Cr alloy.

The fuel cell 100 generates electricity through the following process: An oxidizing gas containing oxygen, such as air, is supplied to the second support 70. The oxidizing gas reaches the cathode 50 via the second support 70 and the second mixing layer 60. At the cathode 50, the oxygen that reaches the cathode 50 reacts with electrons supplied from an external electrical circuit to form oxide ions. These oxide ions then conduct through the solid electrolyte layer 40 to the anode 30.

Meanwhile, fuel gas containing hydrocarbon gas, water vapor, etc., is supplied to the first support 10. The fuel gas reaches the first mixing layer 20 through the voids in the first support 10. The fuel gas is reformed into a reformed gas containing hydrogen gas by the catalytic action of the reforming catalyst in the first mixing layer 20. The reforming reaction can be represented, for example, by the following formula.
2CH ₄ + 2H ₂ O → CO + 6H ₂ + CO ₂

The reformed gas reaches the anode 30 through the voids in the first mixing layer 20. The hydrogen that reaches the anode 30 releases electrons and reacts with oxide ions that conduct through the solid electrolyte layer 40 from the cathode 50 side to form water ( _H₂O ). The released electrons are extracted to the outside by an external electrical circuit. The extracted electrons perform electrical work before being supplied to the cathode 50. Electricity is generated through the above process.

In the above power generation reaction, catalyst metal 24 functions as a catalyst for the reforming reaction. Catalyst metal 34 functions as a catalyst in the reaction between hydrogen and oxide ions. Electronically conductive ceramics 31 are responsible for the conduction of electrons obtained from the reaction between hydrogen and oxide ions. Oxide ion conductive ceramics 32 are responsible for the conduction of oxide ions that have reached the anode 30 from the solid electrolyte layer 40. Cathode catalyst 53 functions as a catalyst in the reaction in which oxide ions are generated from oxygen gas and electrons. Electronically conductive ceramics 51 are responsible for the conduction of electrons from the external electrical circuit. Oxide ion conductive ceramics 52 are responsible for the conduction of oxide ions to the solid electrolyte layer 40.

As described above, in the fuel cell 100 according to this embodiment, fuel gas reforming and power generation are performed inside the fuel cell 100. However, if the amount of reforming catalyst added is increased to obtain sufficient reforming action, the porosity of the first mixing layer 20 decreases, making it difficult for the gas to diffuse, which may reduce power generation performance. Therefore, the first mixing layer 20 according to this embodiment has a structure that can achieve both highly efficient internal reforming and high power generation characteristics.

Specifically, the first mixed layer 20 has both small and large voids. The 10% diameter of the large voids is greater than or equal to the 90% diameter of the small voids. Figure 3 illustrates the pore size distribution for each void observed in the cross-section of the first mixed layer 20. In Figure 3, the horizontal axis represents the pore size of each void on a logarithmic scale, and the vertical axis represents the frequency of occurrence (%). As illustrated in Figure 3, for the small voids, a first peak in the frequency of occurrence appears at relatively small pore sizes. Similarly, for the large voids, a second peak in the frequency of occurrence appears at relatively large pore sizes. Therefore, the relationship between the pore size of the first peak and the pore size of the second peak is obtained.

The smaller the voids in which the catalyst metal 24 is positioned, the more sufficiently the gas and catalyst metal 24 can come into contact, and the easier it is for the reforming reaction to proceed. Therefore, by creating many small voids so that the first peak appears, highly efficient internal reforming can be achieved.

Next, if large voids are provided in the first mixing layer 20, the diffusion of the reformed gas obtained by the reforming reaction can be promoted. Therefore, by providing many large voids so that the second peak appears, high power generation characteristics can be achieved.

As described above, the configuration of the first mixed layer 20 according to this embodiment makes it possible to achieve both highly efficient internal reforming and high power generation characteristics.

The voids in the first mixed layer 20 can be confirmed by cross-sectional photographs (for example, cross-sections along the stacking direction of each layer). The diameter of each void can be calculated by, for example, obtaining five or more cross-sectional photographs at a magnification of 5000x and performing image processing. For example, image processing is performed to calculate the area of each void. Next, the diameter of a circle equal to the area of each void is defined as the void diameter.

The boundary between small and large voids can be defined, for example, as the minimum frequency void size between the first and second peaks in the pore size distribution illustrated in Figure 3.

Furthermore, if the pore diameter of the small voids in the first mixing layer 20 is too small, gas flow will be hindered, potentially reducing power generation performance due to increased gas diffusion resistance. Therefore, it is preferable to set a lower limit on the pore diameter of the first peak of the small voids. For example, the pore diameter of the first peak is preferably 0.3 μm or larger, more preferably 0.5 μm or larger, and even more preferably 1 μm or larger. Also, the D10% diameter of the small voids is preferably 1 μm or larger, more preferably 1.5 μm or larger, and even more preferably 2 μm or larger.

On the other hand, if the pore size of the small voids in the first mixing layer 20 is too large, there is a risk that the gas and the reforming catalyst may not be able to come into sufficient contact. Therefore, it is preferable to set an upper limit on the pore size of the first peak. For example, the pore size of the first peak is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. Furthermore, the D90% diameter of the small voids is preferably 3 μm or less, more preferably 2.5 μm or less, and even more preferably 2 μm or less.

If the pore size of the large voids in the first mixing layer 20 is too small, the reformed gas may not be able to diffuse sufficiently. Therefore, it is preferable to set a lower limit for the pore size of the second peak. For example, the pore size of the second peak is preferably 1 μm or larger, more preferably 2 μm or larger, and even more preferably 3 μm or larger. Furthermore, the D10% diameter of the large voids is preferably 8 μm or larger, more preferably 10 μm or larger, and even more preferably 12 μm or larger.

On the other hand, if the pore diameter of the large voids in the first mixed layer 20 is too large, the adhesion of the layer will decrease, and there is a risk of delamination. Therefore, it is preferable to set an upper limit on the pore diameter of the second peak. For example, the pore diameter of the second peak is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 15 μm or less. Furthermore, the D90% diameter of the large voids is preferably 30 μm or less, more preferably 28 μm or less, and even more preferably 25 μm or less.

In the example shown in Figure 3, the D10% diameter of the small void is approximately 0.2 μm, the D50% diameter is approximately 1 μm, and the D90% diameter is approximately 5 μm. Similarly, the D10% diameter of the large void is approximately 5 μm, the D50% diameter is approximately 10 μm, and the D90% diameter is approximately 30 μm.

If the porosity of the entire first mixed layer 20 is too low, the reforming reaction may not proceed sufficiently, potentially leading to a decrease in power generation performance. Therefore, it is preferable to set a lower limit on the porosity of the entire first mixed layer 20. For example, the porosity of the entire first mixed layer 20 is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more.

On the other hand, if the porosity of the entire first mixed layer 20 is too high, the adhesion between layers will decrease, and there is a risk of delamination. Therefore, it is preferable to set an upper limit on the porosity of the entire first mixed layer 20. For example, the porosity of the entire first mixed layer 20 is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less.

The porosity of the entire first mixed layer 20 can be obtained by calculating the ratio of the total area of each void to the total area of the first mixed layer 20 in a cross-sectional photograph.

The small and large voids in the first mixed layer 20 are formed by the metal particles and ceramic particles that constitute the porous body of the first mixed layer 20. In the cross-section of the first mixed layer 20, the D50% particle size of the metal particles constituting the porous body of the first mixed layer 20 is, for example, 2 μm or more and 10 μm or less. In the cross-section of the first mixed layer 20, the D50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20 is, for example, 0.5 μm or more and 3 μm or less. For example, the D50% particle size of the metal particles constituting the porous body of the first mixed layer 20 is larger than the D50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20. For example, the small voids are formed by ceramic particles constituting the porous body of the first mixed layer 20, and it is preferable that the D50% diameter of the small voids is approximately 0.5 times or more and 2 times or less the D50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20. For example, the large voids are formed by metal particles constituting the porous body of the first mixed layer 20, and it is preferable that the D50% diameter of the large voids is approximately 0.5 times or more and 2 times or less the D50% particle size of the metal particles constituting the porous body of the first mixed layer 20. Note that the metal particles constituting the porous body of the first mixed layer 20 refer to the metal material 21. The ceramic particles constituting the porous body of the first mixed layer 20 refer to the ceramic material 22.

If the first mixed layer 20 is too thin, the particles of the metal material 21 may break through the anode 30, potentially reducing the effective electrode area that contributes to power generation. Therefore, to ensure the first mixed layer 20 is flat, it is preferable to set a lower limit on its thickness. For example, the thickness of the first mixed layer 20 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, if the first mixed layer 20 is too thick, the diffusion of the reformed gas may be inhibited, potentially reducing power generation characteristics. Therefore, it is preferable to set an upper limit on the thickness of the first mixed layer 20. For example, the thickness of the first mixed layer 20 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The thickness of the first mixed layer 20 can be obtained, for example, by calculating the average value of the thicknesses at 10 different points.

If the difference between the 50% particle size of the ceramic particles constituting the porous body of the anode 30 and the 50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20 is large, thermal expansion stress is likely to occur, potentially causing the solid electrolyte layer 40 to crack. Therefore, it is preferable that the difference between the average 50% particle size of the ceramic particles constituting the porous body of the anode 30 and the 50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20 be small. For example, in this embodiment, the ratio of the 50% particle size of the ceramic particles constituting the porous body of the anode 30 to the 50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20 is preferably 1:1.1 to 1.1:1.

The particle size of the ceramic particles contained in the solid electrolyte layer 40 is preferably larger than the 50% particle size of the ceramic particles constituting the porous body of the anode 30 and the 50% particle size of the ceramic particles constituting the porous body of the first mixed layer 20. This is because the grain boundary resistance is small when oxide ions move.

Furthermore, since the fuel cell 100 comprises a first support 10 and a second support 70, both primarily composed of metal, it has a structure that is resistant to thermal shock, mechanical shock, and the like. Also, since the first mixed layer 20 contains a metal material 21 and a ceramic material 22, it possesses the material properties of both metal and ceramic. Therefore, the first mixed layer 20 has high adhesion to the first support 10 and also high adhesion to the anode 30. As a result, delamination between the first support 10 and the anode 30 can be suppressed. Since the second mixed layer 60 contains a metal material 61 and a ceramic material 62, it possesses the material properties of both metal and ceramic. Therefore, the second mixed layer 60 has high adhesion to the second support 70 and also high adhesion to the cathode 50. As a result, delamination between the second support 70 and the cathode 50 can be suppressed.

Furthermore, in the fuel cell 100, oxide ion-conducting ceramics 33 are supported on the porous body of the anode 30. This structure allows for the formation of the porous body by firing first, followed by impregnation with the oxide ion-conducting ceramics 33 and firing at a low temperature. Therefore, even if the oxide ion-conducting ceramics 32 and 33 do not have the same composition, the reaction between oxides is suppressed. Consequently, there is greater flexibility in selecting an oxide suitable for the composite catalyst as the oxide ion-conducting ceramics 33.

Similarly, in the fuel cell 100, the cathode catalyst 53 is supported on the porous body of the cathode 50. This structure allows the porous body to be formed first by firing, and then the cathode catalyst 53 to be impregnated and fired at a low temperature. Therefore, even if the oxide ion conductive ceramic 52 and the cathode catalyst 53 do not have the same composition, the reaction between oxides is suppressed. Consequently, there is greater freedom in selecting a preferred oxide for the cathode catalyst 53.

Similarly, in the fuel cell 100, oxide ion conductive ceramics 23 and catalyst metal 24 are supported on the porous body of the first mixed layer 20. This structure allows for the formation of the porous body by firing first, followed by impregnation with the oxide ion conductive ceramics 23 and catalyst metal 24, and then firing at a low temperature.

Furthermore, it is preferable that the following relationship holds between the porosity of the first support 10, the porosity of the first mixed layer 20, and the porosity of the anode 30: (first support 10 > first mixed layer 20 > anode 30). Similarly, it is preferable that the following relationship holds between the porosity of the second support 70, the porosity of the second mixed layer 60, and the porosity of the cathode 50: (second support 70 > second mixed layer 60 > cathode 50). This relationship ensures sufficient gas permeability in the support. In the electrodes, relatively low porosity allows for high electronic conductivity and high oxide ion conductivity while maintaining gas permeability. In the mixed layer, gas permeability is achieved, and a contact area with the support is obtained, resulting in good adhesion to the support.

Furthermore, it is preferable that the following relationship holds between the thicknesses of the first support 10, the first mixed layer 20, and the anode 30: first support 10 > first mixed layer 20 > anode 30. Similarly, it is preferable that the following relationship holds between the thicknesses of the second support 70, the second mixed layer 60, and the cathode 50: second support 70 > second mixed layer 60 > cathode 50. When these relationships are met, a large portion (e.g., 80% or more) of the fuel cell 100 is composed of metal material, resulting in improved mechanical strength, such as rapid temperature rise/fall and flexibility.

From the perspective of facilitating gas flow during power generation, that is, suppressing gas diffusion resistance, it is preferable that the crystal grain size of the metal components in the first support 10 and the second support 70 is larger than that of the metal components in the first mixed layer 20 and the second mixed layer 60. Larger crystal grain sizes result in larger gaps between particles, allowing gas to pass through more easily. For example, the crystal grain size of the metal components in the first support 10 and the second support 70 is preferably 10 μm or larger, and more preferably 20 μm or larger. Furthermore, when manufacturing the green sheet, if the metal crystal grain size is too large, the metal powder will settle during coating, resulting in an uneven distribution of the material in the thickness direction of the green sheet. From the perspective of maintaining the quality of the green sheet, it is preferable that the crystal grain size of the metal components in the first support 10 and the second support 70 is 100 μm or smaller, and more preferably 80 μm or smaller.

The manufacturing method of the fuel cell 100 will be described below. Figure 4 is a diagram illustrating the flow of the manufacturing method of the fuel cell 100.

(Process for manufacturing the material for the first support and the material for the second support)
As a support material, metal powder (e.g., particle size 10 μm to 100 μm), plasticizer (e.g., adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), solvent (toluene, 2-propanol (IPA), 1-butanol, terpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity), loss agent (organic matter), and binder (PVB, acrylic resin, ethylcellulose, etc.) are mixed to form a slurry. The support material is used as the material for forming the support. The volume ratio of organic components (loss agent, binder solids, plasticizer) to metal powder is, for example, in the range of 1:1 to 20:1, and the amount of organic components is adjusted according to the porosity.

(Process for manufacturing the material for the first mixed layer and the material for the second mixed layer)
As a material for the mixed layer, ceramic material powder (e.g., particle size 100 nm to 10 μm), which is the raw material for ceramic materials 22 and 62; small particle size metal material powder (e.g., particle size 1 μm to 10 μm), which is the raw material for metal materials 21 and 61; solvent (toluene, 2-propanol (IPA), 1-butanol, terpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity); plasticizer (e.g., adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet); waste material (organic matter); and binder (PVB, acrylic resin, ethyl cellulose, etc.) are mixed to form a slurry. The volume ratio of organic components (waste material, binder solids, plasticizer) to ceramic material powder and metal material powder is, for example, in the range of 1:1 to 5:1, and the amount of organic components is adjusted according to the porosity. The pore size of the voids is controlled by adjusting the particle size of the waste material. The ceramic material powder may contain both an electronically conductive material powder and an oxide ion conductive material powder. In this case, the volume ratio of the electronically conductive material powder to the oxide ion conductive material powder is preferably in the range of 1:9 to 9:1. Furthermore, even if an electrolyte material such as ScYSZ or GDC is used instead of the electronically conductive material, there is no delamination at the interface, and the cell can be fabricated. However, from the viewpoint of reducing ohmic resistance, it is preferable to mix the electronically conductive material with metal powder. In the material for the first mixed layer, in order to simultaneously form small and large voids, it is preferable to mix a loss material with a small particle size and a loss material with a large particle size in a range of 1:9 to 9:1.

(Process for preparing materials for the anode)
As the anode material, a slurry is prepared by mixing ceramic material powder constituting the porous body, a solvent (toluene, 2-propanol (IPA), 1-butanol, terpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity), a plasticizer (for example, adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), a waste material (organic substance), and a binder (PVB, acrylic resin, ethylcellulose, etc.). As the ceramic material powder constituting the porous body, an electronically conductive material powder (for example, with a particle size of 100 nm to 10 μm), which is the raw material for electronically conductive ceramics 31, or an oxide ion conductive material powder (for example, with a particle size of 100 nm to 10 μm), which is the raw material for oxide ion conductive ceramics 32, may be used. The volume ratio of the organic component (waste material, binder solids, plasticizer) to the electronically conductive material powder is, for example, in the range of 1:1 to 5:1, and the amount of the organic component is adjusted according to the porosity. Furthermore, the pore size of the voids is controlled by adjusting the particle size of the lost material. The volume ratio of the electronically conductive material powder to the oxide ion conductive material powder is, for example, in the range of 1:9 to 9:1.

(Process for preparing materials for the cathode)
As a cathode material, a slurry is prepared by mixing ceramic material powder constituting the porous body, a solvent (toluene, 2-propanol (IPA), 1-butanol, terpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity), a plasticizer (for example, adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), a waste material (organic substance), and a binder (PVB, acrylic resin, ethylcellulose, etc.). As the ceramic material powder constituting the porous body, an electronically conductive material powder (for example, with a particle size of 100 nm to 10 μm), which is the raw material for electronically conductive ceramics 51, or an oxide ion conductive material powder (for example, with a particle size of 100 nm to 10 μm), which is the raw material for oxide ion conductive ceramics 52, may be used. The volume ratio of the organic component (waste material, binder solids, plasticizer) to the electronically conductive material powder is, for example, in the range of 1:1 to 5:1, and the amount of the organic component is adjusted according to the porosity. Furthermore, the pore size of the voids is controlled by adjusting the particle size of the lost material. The volume ratio of the electron-conducting material powder to the oxide ion-conducting material powder is, for example, in the range of 1:9 to 9:1. In cases where the anode material and the cathode material are common, the anode material may be used as the cathode material.

(Process for manufacturing materials for the electrolyte layer)
As a material for the electrolyte layer, an oxide ion conductive material powder (e.g., ScYSZ, YSZ, GDC, etc., with a particle size of 10 nm to 1000 nm), a solvent (toluene, 2-propanol (IPA), 1-butanol, terpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity), a plasticizer (e.g., adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), and a binder (PVB, acrylic resin, ethyl cellulose, etc.) are mixed to form a slurry. The volume ratio of organic components (binder solids, plasticizer) to oxide ion conductive material powder is, for example, in the range of 6:4 to 3:4.

(Firing process)
First, a first support green sheet is prepared by coating a PET (polyethylene terephthalate) film with a first support material. A first mixed layer green sheet is prepared by coating another PET film with a first mixed layer material. An anode green sheet is prepared by coating another PET film with an anode material. An electrolyte layer green sheet is prepared by coating another PET film with an electrolyte layer material. A cathode green sheet is prepared by coating another PET film with a cathode material. A second mixed layer green sheet is prepared by coating another PET film with a second mixed layer material. A second support green sheet is prepared by coating another PET film with a second support material. For example, multiple first support green sheets, one first mixed layer green sheet, one anode green sheet, one electrolyte layer green sheet, one cathode green sheet, one second mixed layer green sheet, and multiple second support green sheets are stacked in that order and cut to a predetermined size. Then, the assembly is fired in a reducing atmosphere with an oxygen partial pressure of ^10⁻²⁰ atm or less at a temperature range of approximately 1100°C to 1300°C. This yields a cell comprising a first support 10, a first mixed layer 20, a porous anode 30, a porous solid electrolyte layer 40, a porous cathode 50, a second mixed layer 60, and a second support 70. The reducing gas flowing into the furnace may be a gas in which _H₂ (hydrogen) is diluted with a non-combustible gas (such as Ar (argon), He (helium), _N₂ (nitrogen)), or it may be a gas of 100% _H₂ . For safety reasons, it is preferable to set an upper limit up to the explosion limit. For example, in the case of a mixed gas of _H₂ and Ar, the concentration of _H₂ is preferably 4% by volume or less.

(Impregnation process of the anode and the first mixed layer)
Next, the raw materials for the oxide ion conductive ceramic 33 and the catalyst metal 34 are impregnated into the porous body of the anode 30, and the raw materials for the oxide ion conductive ceramic 23 and the catalyst metal 24 are impregnated into the porous body of the first mixed layer 20. For example, nitrates or chlorides of Zr, Y, Sc, Ce, Gd, and Ni are dissolved in water or alcohols (ethanol, 2-propanol, methanol, etc.) so that Gd-doped ceria or Sc,Y-doped zirconia and Ni are produced when fired at a predetermined temperature in a reducing atmosphere. These solutions are then impregnated into the porous bodies of the anode 30 and the first mixed layer 20, dried, and the heat treatment is repeated the required number of times.

(Cathode impregnation process)
Next, a cathode catalyst 53 such as _PrOx is impregnated into the porous body of the cathode 50. When _PrOx is used as the cathode catalyst 53, for example, a nitrate or chloride of Pr is dissolved in water or an alcohol (ethanol, 2-propanol, methanol, etc.), impregnated into the porous body of the cathode 50, dried, and the heat treatment is repeated the required number of times. When LSM is used as the cathode catalyst 53, for example, a nitrate or chloride of Sr, a nitrate or chloride of La, or a nitrate or chloride of Mn is dissolved in water or an alcohol (ethanol, 2-propanol, methanol, etc.), impregnated into the half cell, dried, and the heat treatment is repeated the required number of times. When using LSC as the cathode catalyst 53, for example, dissolve Sr nitrate or chloride, La nitrate or chloride, or Co nitrate or chloride in water or alcohol (ethanol, 2-propanol, methanol, etc.), impregnate the half-cell with the solution, dry it, and repeat the heat treatment the required number of times.

In the above embodiment, the anode 30 and cathode 50 are fired simultaneously, but this is not the only option. For example, the cathode 50 may be formed after firing the first support 10, the first mixed layer 20, the anode 30, and the solid electrolyte layer 40.

A fuel cell was manufactured according to the manufacturing method described in the above embodiment.

(Example 1)
When preparing the material for the first mixed layer, a fuel cell was fabricated by mixing a lost material with an average particle size of 10 μm and a lost material with an average particle size of 1 μm in a volume ratio of 1:3. Upon examining the cross-section of the fuel cell, a first peak appeared in the pore size distribution for each void in the first mixed layer, and a second peak appeared in the voids with larger voids. For the small voids, the D10% diameter was 0.1 μm, the pore size of the first peak was 0.5 μm, and the D90% diameter was 1 μm. For the large voids, the D10% diameter was 5 μm, the pore size of the second peak was 15 μm, and the D90% diameter was 40 μm. The ratio of the D50% particle size of the ceramic particles contained in the first mixed layer to the D50% particle size of the ceramic particles contained in the anode was 1:1.1. When power generation was evaluated using methane ( _CH₄ ) as the fuel gas, a power generation characteristic of 0.7 W/ ^cm² was obtained.

(Example 2)
When preparing the material for the first mixed layer, a lost material with an average particle size of 5 μm and a lost material with an average particle size of 1 μm were mixed in a volume ratio of 1:1 to produce a fuel cell. Other conditions were the same as in Example 1. When the cross-section of the fuel cell was examined, a first peak appeared in the pore size distribution for small voids and a second peak appeared in the large voids. For the small voids, the D10% diameter was 0.3 μm, the pore size of the first peak was 1 μm, and the D90% diameter was 3 μm. For the large voids, the D10% diameter was 3 μm, the pore size of the second peak was 10 μm, and the D90% diameter was 30 μm. The ratio of the D50% particle size of the ceramic particles contained in the first mixed layer to the D50% particle size of the ceramic particles contained in the anode was 1:1. When power generation was evaluated using methane ( _CH₄ ) as the fuel gas, a power generation characteristic of 1.0 W/ ^cm² was obtained.

(Example 3)
When preparing the material for the first mixed layer, a waste material with an average particle size of 5 μm and a waste material with an average particle size of 1 μm were mixed in a volume ratio of 3:1 to fabricate a fuel cell. Other conditions were the same as in Example 1. When the cross-section of the fuel cell was examined, a first peak appeared in the pore size distribution for small voids and a second peak appeared in the large voids. For the small voids, the D10% diameter was 0.5 μm, the pore size of the first peak was 1.5 μm, and the D90% diameter was 3.5 μm. For the large voids, the D10% diameter was 1 μm, the pore size of the second peak was 6 μm, and the D90% diameter was 10 μm. The ratio of the D50% particle size of the ceramic particles contained in the first mixed layer to the D50% particle size of the ceramic particles contained in the anode was 1.1:1. Thus, the D50% particle size of the ceramic particles contained in the first mixed layer was slightly larger than the D50% particle size of the ceramic particles contained in the anode. This is thought to be because, due to the small amount of 1 μm lost material, the aggregated ceramic particles grew larger through sintering. Furthermore, it was confirmed that the number of small voids in the first mixed layer was reduced compared to Examples 1 and 2. When power generation was evaluated using methane ( _CH4 ) as the fuel gas, a power generation characteristic of 0.5 W/ ^cm² was obtained.

(Comparative Example 1)
When preparing the material for the first mixed layer, a fuel cell was fabricated using only waste material with an average particle size of 1 μm. Other conditions were the same as in Example 1. Upon examining the cross-section of the fuel cell, no two types of peaks were observed in the pore size distribution for each void in the first mixed layer. The ratio of the D50% particle size of ceramic particles contained in the first mixed layer to the D50% particle size of ceramic particles contained in the anode was 1:1. Since there was no 5 μm waste material, no large voids were observed. The size of the voids was approximately 0.5 to 2 μm. When power generation was evaluated using methane ( _CH₄ ), a power generation characteristic of 0.2 W/ ^cm² was obtained. The power generation characteristic decreased because the gas diffusion resistance was greater than in Example 1.

(Comparative Example 2)
In preparing the material for the first mixed layer, a fuel cell was fabricated using only the waste material with an average particle size of 5 μm. Other conditions were the same as in Example 1. Upon examining the cross-section of the fuel cell, no two types of peaks were observed in the pore size distribution for each void in the first mixed layer. The ceramic particles in the first mixed layer had grown considerably. This is thought to be because, since there was no 1 μm waste material, there were many aggregates of ceramic particles. In addition, no small voids were observed, and the size of the voids was about 3 to 10 μm. When power generation was evaluated using methane ( _CH₄ ), a power generation characteristic of 0.05 W/ ^cm² was obtained. The reforming reaction proceeded only slightly, and since there was little reacting gas, almost no electricity could be extracted.

In Example 1, although the reforming reaction proceeded sufficiently due to the addition of a larger amount of small lost material, the power generation characteristics were likely reduced due to an increase in gas diffusion resistance because there were fewer large voids created by the 5 μm lost material. In Example 3, the opposite was true; the reforming reaction did not proceed sufficiently because there were fewer small voids, and the amount of CO and _H₂ contributing to the reaction decreased, which is likely why the power generation characteristics were reduced.

Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

10 First support 20 First mixed layer 21 Metal material 22 Ceramic material 23 Oxide ion conductive ceramic 24 Catalyst metal 30 Anode 31 Electronically conductive ceramic 32 Oxide ion conductive ceramic 33 Oxide ion conductive ceramic 34 Catalyst metal 40 Solid electrolyte layer 50 Cathode 51 Electronically conductive ceramic 52 Oxide ion conductive ceramic 53 Cathode catalyst 60 Second mixed layer 70 Second support 100 Fuel cell

Claims (14)

A solid electrolyte layer containing a solid oxide having oxide ion conductivity,
An anode is provided on the solid electrolyte layer and has a porous body containing electron-conducting ceramics and oxide ion-conducting ceramics, the porous body having an anode catalyst,
A mixed layer is provided on the side of the anode opposite to the solid electrolyte layer, having a porous structure in which a metal material and a ceramic material are mixed, and the porous structure has a modifying catalyst.
The mixed layer comprises a support made mainly of metal, provided on the side opposite to the solid electrolyte layer of the mixed layer,
A solid oxide fuel cell in which, in the pore size distribution of each void in the cross-section of the mixed layer, a first peak of occurrence frequency and a second peak of pore size larger than the first peak appear, and the D10% diameter of voids larger than the minimum frequency pore size between the first and second peaks is greater than or equal to the D90% diameter of voids smaller than the minimum frequency pore size. The solid oxide fuel cell according to claim 1, wherein the ratio of the D50% particle size of the ceramic particles constituting the porous body of the anode to the D50% particle size of the ceramic particles constituting the porous body of the mixed layer is 1:1.1 to 1.1:1. The solid oxide fuel cell according to claim 1 or 2, wherein the particle size of the ceramic particles in the solid electrolyte layer is larger than the D50% particle size of the ceramic particles constituting the porous body of the anode and the D50% particle size of the ceramic particles constituting the porous body of the mixed layer. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the D50% particle size of the ceramic particles constituting the porous body of the mixed layer is 0.5 μm or more and 3 μm or less. The solid oxide fuel cell according to any one of claims 1 to 4, characterized in that the D50% diameter of the small voids in the mixed layer is 0.5 times or more and 2 times or less the D50% particle size of the ceramic particles constituting the porous body of the mixed layer. The solid oxide fuel cell according to any one of claims 1 to 5, wherein the porosity of the entire anode is 40% or more and 80% or less. The solid oxide fuel cell according to any one of claims 1 to 6, wherein the thickness of the anode is 1 μm or more and 15 μm or less. The solid oxide fuel cell according to any one of claims 1 to 7, wherein the D50% particle size of the metal particles constituting the porous body of the mixed layer is 2 μm or more and 10 μm or less. The solid oxide fuel cell according to any one of claims 1 to 8, wherein the D50% diameter of the large voids in the mixed layer is 0.5 times or more and 2 times or less the D50% particle size of the metal particles constituting the porous body of the mixed layer. The solid oxide fuel cell according to any one of claims 1 to 9, wherein the porosity in the entire mixed layer is 40% or more and 80% or less. The solid oxide fuel cell according to any one of claims 1 to 10, wherein the thickness of the mixed layer is 5 μm or more and 50 μm or less. The solid oxide fuel cell according to any one of claims 1 to 11, wherein the anode catalyst comprises a mixture of one or more of the following: Y-doped BaCe _{1-x Zr x O 3} (BCZY, x=0 to 1), Y-doped SrCe 1-x Zr x O ₃ (SCZY, x=0 to 1), Sr-doped LaScO ₃ (LSS), and Gd-doped ceria, and Ni. The solid oxide fuel cell according to any one of claims 1 to 12, wherein the D50% particle size of the anode catalyst is 10 nm or more and 1 μm or less. A process of firing a laminate in which an electrolyte green sheet containing oxide ion conductive solid oxide material powder is laminated on both sides, an electrode green sheet containing electron conductive ceramic material powder and oxide ion conductive ceramic material powder, a mixed layer green sheet containing ceramic material powder and metal material powder, and a support green sheet containing metal powder are laminated together,
The process includes impregnating the mixed layer obtained by firing the mixed layer green sheet with a modifying catalyst,
A method for manufacturing a solid oxide fuel cell, comprising adjusting the particle size of the lost material added to the mixed layer green sheet such that, in the pore size distribution of each void in the cross-section of the mixed layer, a first peak of occurrence frequency and a second peak of pore size larger than the first peak appear, and the D10% diameter of voids larger than the minimum frequency pore size between the first and second peaks is greater than or equal to the D90% diameter of voids smaller than the minimum frequency pore size.