JPH11154525A - Solid electrolyte fuel cell and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the chemical stability and maintain the air tightness of a sealing part between a battery cell and a separator for a flat plate type solid electrolyte fuel cell. SOLUTION: In a solid electrolyte fuel cell having a battery cell provided with a solid electrolyte 10, an air electrode 12 placed on one surface of the solid electrolyte 10 and a fuel electrode 11 placed on the other surface of the solid electrolyte 10, a separator 13 placed opposite to at least one surface of the battery cell, and sealing parts 15 to seal the edges of the boundary surface between the battery cell and the separator 13, the sealing parts 15 include a sealing material formed from a sintered body obtained through a process where a sealing liquid containing, as a main constituent, an ultrafine particle oxide having a melting point higher than the operating temperature of the solid electrolyte fuel cell is applied and baked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell, and more particularly to a flat solid electrolyte fuel cell characterized by the structure of a sealing portion and a sealing method, and a method of manufacturing the same.

[0002]

2. Description of the Related Art The basic structure of a fuel cell comprises an electrolyte and two electrodes sandwiching both sides of the electrolyte. One of the two electrodes is called a fuel electrode, and the other is called an air electrode. A fuel gas such as hydrogen gas is supplied from the outside to the fuel electrode, and an oxidizing gas such as air is supplied from the outside to the air electrode. Fuel cells generate electrical energy by an electrochemical reaction of these gases.

[0003] Fuel cells are classified into several types depending on the type of electrolyte material used. A solid oxide fuel cell (SOFC) uses an oxide solid having ionic conductivity as an electrolyte. Since high-temperature conditions are necessary for this oxide solid, that is, the solid electrolyte to exhibit good ionic conductivity, the SOFC is usually 800 ° C. to 1200 ° C.
It is operated under the temperature condition of ° C.

FIG. 3 is an exploded perspective view showing a configuration example of a conventional flat-plate SOFC. FIG. 4A is a cross-sectional view showing a structure example of a conventional SOFC, and FIG. 4B is an enlarged cross-sectional view of a seal portion.

[0005] As shown in FIG.
When the fuel cell 1 is used as a support, the fuel electrode 1
02 is formed, and the air electrode 104 is formed on the back surface.

The solid electrolyte 10 on which the fuel electrode 102 is formed
Hydrogen, which is a fuel gas, is supplied on the front surface of the fuel cell 1, and air containing oxygen is supplied on the back surface of the solid electrolyte 101 on which the air electrode is formed. In order to obtain a desired current value, a plurality of cells are usually stacked and used via a separator 103.

As shown in FIG. 4A, between the one surface of the solid electrolyte 101 on which the fuel electrode 102 is formed and the separator 103 facing the same, both sides except for the gas supply path are sealed with a sealing material 105. Is sealed.

At the air electrode 104, oxygen ions are generated from the supplied oxygen. The oxygen ions reach the fuel electrode 102 through the solid electrolyte 101. At the fuel electrode 102, the oxygen ions react with the hydrogen gas supplied to the fuel electrode 102 to generate electrons. At the same time, water is produced as a by-product.

The solid electrolyte 101 is required to have high oxygen ion conductivity and to be chemically stable in an oxidizing and reducing atmosphere at a SOFC operating temperature of 800 ° C. to 1200 ° C. At the same time, it is also desired that the material has no electronic conductivity and is highly airtight so as not to pass gas. Generally, stabilized zirconia (YSZ) is selected as a material satisfying such requirements.

The fuel electrode 102 and the air electrode 104 are formed of a porous material so that gas can enter the inside. Neither of them has ionic conductivity and needs to exhibit high electronic conductivity. Also, it is desired that the thermal expansion coefficient of the adjacent solid electrolyte 101 is close to that of the adjacent solid electrolyte 101.

Since the fuel electrode 102 is exposed to hydrogen gas, it is necessary to be chemically stable in a high-temperature reducing atmosphere. The air electrode 104 is exposed to air, so that it is chemically stable in a high-temperature oxidizing atmosphere. Must be stable.

In general, the fuel electrode 102 is a cermet of nickel (Ni) and YSZ, etc., and the air electrode 104 is a perovskite-type oxide whose base material is lanthanum cobaltate (LaCoO ₃ ) or lanthanum manganate (LaMnO ₃ ). Is often selected.

Since the separator 103 has an air supply path on one side and a hydrogen gas supply path on the other side, it must be chemically stable in a high-temperature oxidizing and reducing atmosphere. Airtightness is also required to prevent air and hydrogen gas from leaking and coming into contact with each other. It is also desirable that the thermal expansion coefficient of the battery cell is similar to that of the battery cell.

On the other hand, since the separator 103 also serves as an interconnector for electrically connecting a plurality of battery cells, the separator 103 is required to have high electronic conductivity. As a material satisfying these conditions, lanthanum chromite-based oxide (LaCrO ₃ ) or the like is used as a separator material.

The solid electrolyte 10 on which the fuel electrode 102 is formed
The sealing material 105 that seals the gap between one surface of the first member and the separator needs to secure confidentiality so that hydrogen gas does not leak to the outside and ignite in contact with air. In order to secure a supply channel, the solid electrolyte 10
It is necessary to keep a certain distance between the first and the separator 103. Therefore, as shown in FIG.
It is necessary to use a considerable amount of glass so as to maintain a certain distance between the two and the solid electrolyte 101, and to seal the periphery thereof. Generally, borosilicate glass is often used as this glass.

[0016]

As described above, the sealing portion between the solid electrolyte 101 and the separator 103 is required to maintain a high sealing property in order to prevent contact ignition between hydrogen gas and air.

However, the melting point of borosilicate glass conventionally used as a sealing material is about 830 ° C.
The OFC is in a molten state at an operating temperature of 800 ° C to 1200 ° C. Therefore, when the cell size becomes large and it becomes necessary to supply the fuel gas at a high pressure, there is a risk that the fuel gas leaks from the sealing portion in a molten state due to a difference in gas pressure inside and outside the cell.

The sealing material is in a molten state during the operation of the SOFC, but solidifies as the cell temperature decreases after the operation is completed. That is, in the heat cycle of the battery, the sealing material has been switched between a molten state and a solidified state.

When the sealing material is in a molten state, the sealing portion often acts as a buffer for thermal stress. But,
When the cell temperature decreases and the sealing material solidifies, the difference in the coefficient of thermal expansion between the sealing material and the material to be sealed poses a problem. For example, the thermal expansion coefficients of the solid electrolyte 101 and the air electrode 104, which are the materials to be sealed, are about 10 × 10 ^{−6 to} 11 × 10 ⁻⁶ / ° C., whereas the thermal expansion coefficient of the solidified borosilicate glass is 3 × 10 ^-6
Since it is as small as about 4 × 10 ⁻⁶ / ° C., the generation of thermal stress due to the difference in the coefficient of thermal expansion may cause breakage of the cell.

Further, at the operating temperature, gases such as Si and SiO volatilize from the borosilicate glass containing SiO ₂ as a main component. Since a considerable amount of glass is used in the seal portion, the amount of volatile components generated also increases, and these forms a compound with the fuel electrode 102, which is a cermet of nickel and YSZ, which leads to deterioration of battery characteristics. There is.

An object of the present invention is to provide a solid oxide fuel cell having chemical stability and hermeticity of a seal between a battery cell and a separator, and a method of manufacturing the same.

[0022]

The first feature of the solid oxide fuel cell of the present invention is that the solid electrolyte, the air electrode provided on one surface of the solid electrolyte, and the other surface of the solid electrolyte are provided. A solid electrolyte type having a battery cell having a fuel electrode, a separator provided to face at least one surface of the battery cell, and a seal portion for sealing an end of a boundary surface between the battery cell and the separator. In the fuel cell, the seal portion is formed of a sintered body obtained through a step of applying and firing a sealing liquid agent containing an ultrafine oxide having a melting point higher than the operating temperature of the solid oxide fuel cell as a main component. It is to have a sealing material.

According to the first feature of the solid oxide fuel cell, the ultrafine oxide, which is the main component of the sealing material used, has higher reactivity than ordinary bulk oxide, and is fired at a low temperature. Can be tied. However, once sintered, it exhibits properties similar to bulk oxides, so that it can maintain a solid state at the operating temperature of the battery and maintain stable sealing properties during operation.

In the solid oxide fuel cell having the above-mentioned first characteristic, if a powder having an average particle diameter of 0.2 μm or less is used as the ultra-fine particle oxide, high reactivity which is an effect of the ultra-fine particles can be surely obtained. Can lower the sintering temperature.

In the solid oxide fuel cell having the first feature, if the sealing material partially includes a sintering aid contributing to lowering the firing temperature, the sintering temperature can be further reduced. can do.

Further, in the solid oxide fuel cell device having the first characteristic, the sealing material is 7 × 10 ^-6 /
A material having a coefficient of thermal expansion of not less than 11 ° ^C./° C. and not more than 11 × 10 ⁻⁶ / ° C. can reduce the difference in coefficient of thermal expansion between the sealing material and the material to be sealed. The generation of stress can be suppressed.

In the solid oxide fuel cell having the first feature, for example, the main component of the sealing material is
Either stabilized zirconia or spinel may be used.

According to a second feature of the solid oxide fuel cell of the present invention, in the solid oxide fuel cell having the first feature, in the solid electrolyte fuel cell, the seal portion has a seal supporting material and a seal material; The electrolyte and the separator face each other via the seal support material, and the seal material is provided on a contact surface between the solid electrolyte and the seal support material, and a contact surface between the separator and the seal support material, The seal supporting member has a melting point higher than the operating temperature of the solid oxide fuel cell, and does not transmit a fuel gas or an oxidizing gas.

According to the second feature of the solid oxide fuel cell, since the seal portion is composed of the seal supporting material and the seal material, the seal material may be provided only on the adhesive portion.
The amount of the sealing material used can be suppressed to a small amount.

A third feature of the solid oxide fuel cell of the present invention is that in the solid oxide fuel cell having the first feature, the seal portion is formed of a part of the solid electrolyte or a separator. Having a seal support material and a seal material, the seal material is provided on a contact surface between the seal support material and the solid electrolyte or the separator,
The seal supporting member has a melting point higher than the operating temperature of the solid oxide fuel cell, and does not transmit a used fuel gas.

According to the third feature of the solid oxide fuel cell, as in the case of the solid oxide fuel cell having the second feature, the seal portion is composed of a seal supporting material and a seal material. Therefore, the sealing material may be provided only at the bonding portion, and the amount of the sealing material used can be suppressed to a small amount.

[0032] In the solid oxide fuel cell having the second or third feature, the seal supporting material may be 7 × 1.
Using those having 0 ^-6 / ° C. or higher 11 × 10 ^-6 / ℃ or less coefficient of thermal expansion, since the thermal expansion coefficient difference between the constituent material and the separator of the fuel cell can be reduced, the repetitive operation In the accompanying heat cycle, generation of thermal stress can be suppressed.

A feature of the method for manufacturing a solid oxide fuel cell of the present invention is that a battery having a solid electrolyte, an air electrode formed on one surface of the solid electrolyte, and a fuel electrode formed on the other surface is provided. A step of producing a cell, a step of producing a separator provided to face at least one surface of the battery cell, and a step of producing a seal portion for sealing an end of a boundary surface between the battery cell and the separator. In the method for producing a solid oxide fuel cell having the above, the step of producing the seal portion includes mixing an ultrafine oxide having a melting point higher than the operating temperature of the solid oxide fuel cell, a binder and an additive. Producing a sealed sealing liquid, applying the sealing liquid to a boundary surface of a seal portion, and firing the sealing liquid at an operating temperature of the solid oxide fuel cell. It is to have a degree.

According to the characteristics of the method for manufacturing a solid oxide fuel cell, the ultrafine oxide, which is the main component of the sealing material used, has higher reactivity than ordinary bulk oxide, and is fired at a low temperature. Can be tied. However, once sintered, it exhibits properties similar to bulk oxides, so that it can maintain a solid state at the operating temperature of the battery and maintain stable sealing properties during operation.

[0035]

(First Embodiment) FIG. 1 (a)
FIG. 1 is a sectional view showing a structure of a solid oxide fuel cell according to a first embodiment of the present invention. FIG. 1B is a partially enlarged cross-sectional view illustrating a structure of a seal portion between the separator 13 and the solid electrolyte 10.

As shown in FIG. 1A, the structure of the solid oxide fuel cell according to the first embodiment other than the seal portion is substantially the same as the structure of the conventional SOFC shown in FIG. 4A. That is, a basic battery cell is composed of a plate-shaped solid electrolyte 10 as a support, a fuel electrode 11 formed on the central surface, and an air electrode 12 formed on the back surface. Separators 13 are provided above and below the battery cells.

For example, as shown in FIG.
3 is provided to face the surface of the solid electrolyte 10 on the side where the fuel electrode 11 is formed. A space between the separator 13 and the fuel electrode 11 is a supply path for hydrogen as a fuel gas.

Although not shown, the separator is also formed at a position facing the back surface of the solid electrolyte 10 where the air electrode is formed, and an air supply path is provided.

Each constituent material can be selected from the same materials as in the prior art. For example, stabilized zirconia (YSZ) is used as the solid electrolyte 10, nickel (Ni) and YSZ cermets are used as the fuel electrode 11, and lanthanum cobaltate (LaCoO ₃ ) and lanthanum manganate (LaMnO ₃ ) are used as the air electrode 12. A perovskite-type oxide serving as a base, and a lanthanum chromite-based oxide (LaCrO ₃ ) can be selected as the separator 13.

The SOFC according to the first embodiment has main features in the configuration of a seal portion provided between the solid electrolyte 10 and the separator 13 and the sealing method. That is, as shown in FIG. 1B, the left and right side surfaces of the separator 13 and the solid electrolyte 10 in the figure are bonded via a seal support member 14, and the seal member 15 serving as an adhesive is a seal support member. It is provided thinly on the bonding surface between the solid electrolyte 10 and the seal supporting material 14 and the separator 13.

The sealing material 15 is conventionally made of borosilicate glass, but instead has a coefficient of thermal expansion of 7 × 10
^It has a coefficient of thermal expansion of not less than ⁻⁶ / ° C. and not more than 11 × 10 ⁻⁶ / ° C.
A high melting point oxide such as YSZ or spinel is used. Further, these use ultrafine ceramic powder having a particle size of about 0.01 μm to 0.5 μm, and mix this with a binder and an additive aid to prepare a slurry as a sealing liquid. The slurry is applied to a predetermined adhesive surface and fired, thereby sealing the seal supporting member 14 and the separator 13 and the boundary surface between the seal supporting member 14 and the solid electrolyte.

The ultrafine ceramic particles have a higher reactivity than normal-sized particles and the like, and can be sintered at a low temperature. For example, when sintering normally used YSZ particles of several μm or more, a sintering temperature of 1300 ° C. to 1600 ° C. is required. When the ultrafine particles are used, the operating temperature of the SOFC is 800 ° C. to 1200 ° C. Sintering is possible in the above temperature range. Further, once sintered, it exhibits the same properties as a bulk sintered body, maintains a stable solid state at the operating temperature of the SOFC, and does not generate volatile gas and the like.

If a sintering aid such as Mn ₂ O ₃ or CuO ₂ is added to the sealing material, the temperature required for sintering can be further reduced.

The seal supporting member 14 has a temperature of 800.degree.
The solid state can be maintained even at the SOFC operating temperature of
A dense material is used so that fuel gas or oxidizing gas does not leak outside the cell. The thermal expansion coefficient of the solid electrolyte 10
And approx. 7 × 10 ^-6 / ° C.
A material having a coefficient of thermal expansion of 1 × 10 ⁻⁶ / ° C. or less and having no thermal stress due to a heat cycle is used for the seal material 15 that directly adheres the seal support 14 to the solid electrolyte 10 or the separator 13. Is preferred. For example, assuming that such conditions are satisfied, the solid electrolyte 1
YSZ or spinel (MgA)
l ₂ O ₄ ) can be used.

In the SOFC according to the first embodiment,
As shown in FIG. 1B, since the seal supporting member is provided, there is no need to maintain the distance between the surfaces to be sealed by the seal member itself. Therefore, the required amount of the sealing material can be made very small. For this reason, it is not necessary to use a clay-like sealing material, and the above-described sealing liquid can be used.

Since the amount of the sealing material used may be small, the amount of the SiO component volatilized from the sealing material during the operation of the cell can be reduced even if the borosilicate glass is used as the conventional sealing material. Can be. Therefore, glass may be mixed into the sealing material as an additive aid.

Hereinafter, an example of a method of manufacturing an SOFC according to the first embodiment will be briefly described with reference to FIG. For the basic part, a commonly used manufacturing method can be used.

First, a solid electrolyte 10, which is a support, is manufactured by an extrusion molding method. Zirconia (ZrO ₂ )
8 to 10 mol% yttria (Y
20 wt% of water as an additive agent and 1 part of methyl cellulose as a binder were added to a powder of stabilized zirconia (YSZ) having a solid solution of ₂ O ₃ ) having a mean particle size of 3 μm to 10 μm.
Mix with 0 wt% and knead the whole well to make a clay.
Next, this clay-like raw material is extruded and molded to about 5 cm x 5
It is processed into a plate having a thickness of 1 cm and a thickness of 1 mm. Furthermore, this plate-shaped Y
SZ is fired in an air atmosphere at a temperature of 1300 ° C. to 1500 ° C. to produce a dense sintered body.

Next, an air electrode 12 is formed on one surface of the solid electrolyte 10 by using a slurry coating method. The slurry used was a lanthanum strontium manganate (LaSrMnO ₃ ) powder having a perovskite crystal structure and a particle size of about 30 μm, 5 wt% of methylcellulose as a binder, and 20 parts of water as an additive.
A mixture of wt% is used. After applying the slurry, 13
It is fired at 00 ° C to 1500 ° C to form a porous sintered body having a thickness of about 200 µm.

Then, using the atmospheric pressure plasma spraying method,
On the surface of the solid electrolyte 10, a thickness of about 50 μm to 200 μm
The fuel electrode 11 made of m porous Ni and YSZ cermet is formed. The atmospheric pressure plasma spraying method is a method in which a raw material powder is melted by plasma and a film is formed by spraying the raw material in the molten state on a substrate, similarly to the low pressure plasma spraying method. However, by setting the atmospheric pressure to the atmospheric pressure, a porous film can be formed as compared with the case of the reduced pressure plasma spraying method.

The electrodes and the solid electrolyte may be formed by a conventional method such as electrochemical deposition (EVD) or acetylene spraying, in addition to the above-described methods.

The separator 13 provided on the battery cell is manufactured by the extrusion molding method in the same manner as the manufacturing process of the solid electrolyte 10 described above. Average particle size 0.1 μm to 25
μm lanthanum calcia chromite (LaCaCr
O ₃ ), 20 wt% of water and 10 wt% of a binder are added to produce a clay-like raw material, which is processed by extrusion molding, and further baked in the atmosphere at 1400 ° C. to 1600 ° C. for about 5 hours to produce a sintered body. I do.

Next, the battery cell 2 which is a characteristic part of the present invention is described.
A process of forming a seal portion between 0 and the separator 13 will be described.

The seal support material was extruded under the same conditions as in the above-described method for producing a solid electrolyte, and had a width of 50 m.
A YSZ sintered body having a thickness of 5 m, a thickness of 5 mm, and a length of 5 cm is prepared in advance.

The sealing material is a so-called ultrafine particle of YSZ having an average particle diameter of 0.5 μm or less, preferably 0.2 μm or less.
5 wt% of methylcellulose as a binder and 30 wt% of water as an additive are added to prepare a slurry as a liquid sealing material material.

This slurry is applied to the bonding portion between the plate-shaped solid electrolyte 10 and the separator 13 prepared in the previous step, and the seal supporting member 14 is sandwiched therebetween to be fixed. At this point, the assembly of the SOFC cell is temporarily completed. The final sintering of the liquid sealing material does not particularly require an independent firing step, and the temperature of the SOFC is set to 800 ° C. to 10 ° C. with the start of operation.
In the process of raising the operating temperature to 00 ° C., YSZ in the sealing material is simultaneously fired.

(Second Embodiment) FIG. 2A is a sectional view showing a structure of a solid oxide fuel cell according to a second embodiment of the present invention. FIG. 2B is a partially enlarged cross-sectional view illustrating a structure of a seal portion between the separator and the solid electrolyte.

In the SOFC seal portion according to the second embodiment, a side wall corresponding to the seal support member is provided on the separator without using an independent seal support member. When extruding the separator, the separator may be formed into a predetermined shape. In this case, the sealing material may be applied only to the opposing surfaces of the side walls of the solid electrolyte 10 and the separator 13.

Note that, instead of forming the seal supporting member with the separator 13, the sealing supporting member may be formed with the solid electrolyte 10.

In the case of the SOFC of the second embodiment, as in the case of the first embodiment, a sealing material is formed by applying and firing a sealing liquid agent. Ultrafine oxide ceramics is used as a main component of the sealing liquid. Therefore, in the SOFC operating temperature range, it is possible to form a sealing material by sintering, and after sintering once,
Like a normal sintered body, it has heat resistance and can maintain a solid state at an operating temperature.

In the SOFC according to the second embodiment,
As shown in FIG. 2B, since the seal supporting material is formed by the separator 13, there is no need to maintain the interval between the surfaces to be sealed by the sealing material itself. Therefore, the required amount of the sealing material can be made very small. Further, a sealing liquid can be used without using a clay-like sealing material.

Since the amount of the sealing material used is small, even if a volatile gas is contained in the sealing material, the influence on the surroundings can be slightly suppressed.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. In each of the slurries prepared in the examples, methylcellulose was used as a binder. However, the present invention is not limited to this, and another binder may be used. In this case, it is preferable to select the type of the additive aid according to the type of the binder.

[0064]

As described above, the solid oxide fuel cell of the present invention comprises a solid electrolyte, an air electrode provided on one surface of the solid electrolyte, and a fuel electrode provided on the other surface of the solid electrolyte. , A solid electrolyte fuel cell comprising: a separator provided to face at least one surface of the battery cell; and a sealing portion for sealing an end of a boundary surface between the battery cell and the separator. In the sealing part, a sealing material made of a sintered body obtained through a step of applying and sealing a sealing solution mainly composed of an ultra-fine particle oxide having a melting point higher than the operating temperature of the solid oxide fuel cell, and Have.

The ultrafine particle oxide, which is the main component of the sealing material, has a higher reactivity than ordinary bulk oxide, can be sintered at a low temperature, and, once sintered, has the same effect as bulk oxide. Because of its properties, the sealing material can be sintered at the operating temperature of the battery, and after sintering, a solid state can be maintained, and stable sealing properties can be maintained.

In the solid oxide fuel cell according to the present invention, since the seal portion is composed of a seal supporting material and a seal material, the seal material may be provided only at the bonding portion, and the amount of the seal material used may be reduced. Can be reduced to a small amount.

[Brief description of the drawings]

FIG. 1 is a sectional view of a battery cell and a partially enlarged sectional view showing a structure of an SOFC according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a battery cell and a partially enlarged sectional view showing a structure of an SOFC according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a battery cell showing a structure of a conventional SOFC.

FIG. 4 is a cross-sectional view of a battery cell showing the structure of a conventional SOFC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Solid electrolyte 11 ... Fuel electrode 12 ... Air electrode 13 ... Separator 14 ... Seal support material 15 ... Seal material

Continued on the front page (72) Inventor Namiko Kaneda Fujikura Co., Ltd. 1-5-1 Kiba, Koto-ku, Tokyo

Claims (9)

[Claims] 1. A battery cell having a solid electrolyte, an air electrode provided on one surface of the solid electrolyte, and a fuel electrode provided on the other surface of the solid electrolyte, and facing at least one surface of the battery cell. A solid electrolyte fuel cell having a separator sealing the end of the boundary surface between the battery cell and the separator, wherein the sealing portion is higher than the operating temperature of the solid electrolyte fuel cell. A solid oxide fuel cell comprising a sealing material made of a sintered body obtained by a step of applying and firing a sealing solution containing an ultrafine oxide having a high melting point as a main component. 2. The ultra-fine particle oxide has an average particle diameter of 0.2.
2. The solid oxide fuel cell according to claim 1, which is a powder having a size of not more than μm. 3. The solid oxide fuel cell according to claim 1, wherein the sealing material partially includes a sintering aid that contributes to lowering the firing temperature. 4. The solid oxide fuel cell according to claim 1, wherein the sealing material has a coefficient of thermal expansion of 7 × 10 ⁻⁶ / ° C. or more and 11 × 10 ⁻⁶ / ° C. or less. . 5. The solid oxide fuel cell according to claim 1, wherein a main component of the sealing material is one of stabilized zirconia, spinel, and magnesia. 6. The seal portion includes a seal support member and a seal member, wherein the solid electrolyte and the separator face each other via the seal support member, and wherein the seal member includes the seal member and the seal member. A contact surface with a support material, and a contact surface between the separator and the seal support material, wherein the seal support material has a melting point higher than the operating temperature of the solid oxide fuel cell, and contains a fuel gas or an oxidizing gas. The solid oxide fuel cell according to any one of claims 1 to 5, which does not permeate. 7. The seal portion has a seal support member and a seal member formed of the solid electrolyte or a part of the separator, and the seal member includes the seal support member and the solid electrolyte or the separator. The sealing support member has a melting point higher than the operating temperature of the solid oxide fuel cell, and does not transmit a fuel gas or an oxidizing gas. 3. The solid oxide fuel cell according to item 1. 8. The solid electrolyte fuel according to claim ⁶ , wherein said seal supporting member has a coefficient of thermal expansion of 7 × 10 ⁻⁶ / ° C. or more and 11 × 10 ⁻⁶ / ° C. or less. battery. 9. A step of producing a battery cell having a solid electrolyte, an air electrode formed on one surface of the solid electrolyte, and a fuel electrode formed on the other surface, and at least one of the battery cells A method for producing a solid oxide fuel cell, comprising: a step of producing a separator provided to face the surface; and a step of producing a seal portion that seals an end of a boundary surface between the battery cell and the separator. A step of preparing a seal portion, a step of preparing a seal liquid agent mixed with an ultrafine oxide having a melting point higher than the operating temperature of the solid oxide fuel cell, and a binder and an auxiliary additive; and sealing the seal liquid agent. A method of manufacturing a solid oxide fuel cell, comprising: applying the seal liquid to the boundary surface of a portion; and firing the seal liquid at an operating temperature of the solid oxide fuel cell.