JPH0678177B2 - Sealing material for solid oxide fuel cell and sealing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material for a solid oxide fuel cell and a sealing method thereof. More specifically, according to the present invention, a gas passage manifold can be melt-sealed in a unit cell of a solid oxide fuel cell at a relatively low temperature, and a sealing portion that withstands the operating temperature of the fuel cell is formed. The present invention relates to a sealing material that can be used and a sealing method.

[0002]

2. Description of the Related Art Recently, solid electrolyte fuel cells, for example,
A unit cell composed of a (La, Sr) MnO ₃ air electrode layer, 8 mol% Y ₂ O ₃ -ZrO ₂ solid electrolyte layer and a Ni / ZrO ₂ cermet fuel electrode layer, which are sequentially laminated, and L battery
Fuel cells that are electrically connected by a (Cr, Mg) O ₃ separator are being actively developed.

The solid oxide fuel cell is superior in efficiency and durability to other types of fuel cells, but its practical temperature is as high as 1000 to 1050 ° C.,
In addition, the fuel electrode side forms a reducing atmosphere, but the air electrode side forms an acidic atmosphere, and the operating conditions are extremely severe.Therefore, in order to achieve the practical application of the solid oxide fuel cell, there is a solution. There are a number of issues to be addressed.

As a solid oxide fuel cell, as shown in FIG. 1, a tubular air electrode layer 2 is formed on the outer side of a porous tubular support layer 1, and a part of the tubular air electrode layer is opened on the outer side in a band shape. There is known a cylindrical fuel cell in which the tubular solid electrolyte layer 3 is further formed, a tubular fuel electrode layer 4 is further provided outside the tubular solid electrolyte layer 3, and a strip-shaped interconnector 5 is sequentially arranged in an opening portion of the tubular fuel electrode layer 4.
In this cylindrical fuel cell, air is supplied from the hollow portion of the porous tubular support layer 1 in the direction of arrow 6 and fuel gas is supplied to the outside of the tubular fuel electrode layer in the direction of arrow 7. Such a cylindrical fuel cell has a problem that the space utilization efficiency is low when it is multi-staged with one unit.

In order to solve this problem, a flat plate-type solid electrolyte fuel cell is proposed in which an air electrode layer, a solid electrolyte layer, and a fuel electrode layer are each formed in a flat plate shape and are laminated. Has been done. The main body of the flat plate-type solid oxide fuel cell is composed of one unit cell or a laminate of two or more unit cells, and each unit cell is a pair of separators, as will be described later in detail. Sandwiched between
Further, it is composed of a flat plate air electrode layer, a flat plate solid electrolyte layer and a fuel electrode layer which are sequentially laminated.

In the flat plate-type solid oxide fuel cell as described above, gas (fuel gas,
Alternatively, it is necessary to seal and connect a gas passage manifold for supplying or discharging an oxygen-containing gas (air) with a sealing material to integrate them. As the sealing / connecting method, conventionally, a brazing method and a diffusion bonding method have been known, but there are many problems to be solved in sealing / connecting these.

[0007]

A solid oxide fuel cell generally utilizes an oxidation / reduction reaction at a high temperature of 1000 ° C to 1050 ° C. Normal operating temperature is 1000 ℃ ~ 1050
In the case of ℃, under these conditions of use, in order to form a sealed part that does not cause melting, deterioration, deterioration, etc., it is necessary to perform melt sealing at a temperature considerably higher than the above temperature, for example 1500 ° C. It was considered necessary to use a high temperature sealing material.

However, when the fuel cell unit cell is heated to the above-mentioned high temperature for its sealing, the material (La, Sr) MnO ₃ forming the air electrode layer is sintered and shrinks. , It becomes difficult for air to pass through, and especially when heated to a temperature of 1150 ° C or higher, the air electrode layer forming material is solid electrolyte layer forming material (8 mol% Y ₂ O ₃ -ZrO ₂ ) and solid phase. This causes a problem that it reacts to form an electrically defective conductor.

Therefore, the sealing material can be sealed at a relatively low temperature without degrading the fuel cell components, and after sealing, the sealing material is melted or melted at the operating temperature of the fuel cell. Should not deteriorate and deteriorate, and shall not be damaged by thermal expansion of the material to be sealed. Furthermore, the sealing material has a good adhesiveness to the material to be sealed, and is completely airtight to form a sealed portion that blocks gas flow and has good electrical insulation. Must be something that

However, a sealing material that can satisfy all the above requirements has not been provided yet.

The present invention is capable of sealingly connecting a unit cell of a solid oxide fuel cell to a gas passage manifold at a relatively low temperature that does not adversely affect the material and performance of the solid electrolyte fuel cell. Does not melt, deteriorate or deteriorate under the conditions of use of the fuel cell, has excellent adhesiveness to the material to be sealed, and is completely airtight and cuts off gas flow. Another object of the present invention is to provide a sealing material capable of forming a sealing portion having excellent electrical insulation and a sealing method.

[0012]

The present invention comprises a mixture of a specific composition aluminosilicate glass granules having a relatively low glass softening temperature and a specific composition high silica glass granules having a relatively high glass softening temperature. The above-mentioned problems have been successfully solved by using the sealing material.

That is, the sealing material for a solid oxide fuel cell of the present invention is a sealing material for hermetically connecting a gas passage manifold to the main body of a solid oxide fuel cell, and includes the following elements: (A) Contains silica and alumina, and 770 ℃ ~ 9
1450 ° C. to 1550, containing at least one low softening point glass granules made of aluminosilicate glass having a glass softening temperature of 50 ° C., and (B) silica and alumina.
It is characterized by comprising a mixture with at least one high softening point glass granules made of high silica glass having a glass softening temperature of ° C. In the above solid electrolyte fuel cell sealing material, the aluminosilicate of the low softening point glass particles preferably contains 52 to 58% by weight of silica and 20 to 22% by weight of alumina, and also high. High-silica glass with softening point glass granules contains 94-98% by weight silica and 0.
2 to 0.8% by weight of aluminum is preferable, and the ratio of the total weight of the low softening point glass particles to the total weight of the high softening point glass particles is 50:50 to 35:65. It is preferably within the range.

Further, the method for sealing a solid oxide fuel cell of the present invention comprises at least one solid electrolyte type fuel cell comprising a fuel electrode layer, a solid electrolyte layer, an air electrode layer and a separator, which are sequentially laminated. In order to hermetically connect the gas passage manifold to each fuel cell unit cell, the joint between the unit cell and the manifold is sealed while softening the sealing material, and the softened seal portion is cooled. A method for solidifying, wherein the sealing material contains the following elements: (A) silica and alumina, and 770 ° C to 9 ° C.
1450 ° C. to 1550, containing at least one low softening point glass granules made of aluminosilicate glass having a glass softening temperature of 50 ° C., and (B) silica and alumina.
Characterized in that it comprises a laminate with at least one high softening point glass granules made of high silica glass having a glass softening temperature of 0 ° C., and said softening and sealing operation is carried out at a temperature of 1000 ° C. to 1150 ° C. It is what In the above solid oxide fuel cell sealing method, the low softening point glass particles of aluminosilicate are 52 to 58% by weight of silica and 20
~ 22 wt% alumina and preferably,
High silica glass with high softening point glass granules is 94-98% by weight
Silica and 0.2 to 0.8% by weight of Alnami, and further, the total weight of the low softening point glass particles,
The ratio of the high softening point glass particles to the total weight is 50:50 ~
It is preferably within the range of 35:65.

[0015]

FIG. 2 shows the structure of a flat plate-type solid electrolyte fuel cell unit cell to which the sealing material and the sealing method of the present invention are applied. That is, in FIG. 2, a flat plate-shaped air electrode layer 9, a flat plate-shaped solid electrolyte layer 10 and a flat plate-shaped fuel electrode layer 11 are sequentially laminated and combined between a pair of flat plate-shaped separators 8 to form a flat plate-shaped fuel cell unit cell. Is formed. The flat air electrode layer 9 and the flat fuel electrode layer 11 have grooves extending in the directions of arrows 12 and 13, respectively, and allow air or fuel gas to flow along these grooves in the direction of the arrow. You can

The air electrode layer is made of, for example, (La, Sr) MnO ₃ , the solid electrolyte layer is made of 8 mol% Y ₂ O ₃ -ZrO ₂ system material, and the fuel electrode layer is made of Ni-ZrO ₂ material. And the separator layer is formed of a La (Cr.Mg) O ₃ material.

These element layers are integrally laminated in a flat plate shape, and a manifold is sealed on each side surface of the unit cell to form a gas passage thereof. In FIG. 3, a fuel cell unit cell 14 is composed of a separator 8a, a fuel electrode layer 11, a solid electrolyte layer 10, an air electrode layer 9 and a separator 8b, which are sequentially stacked and combined, and a side surface A among the four side surfaces thereof.
Is an air supply surface and is connected to an air supply manifold (not shown), side B is a fuel gas supply surface and is connected to a fuel gas supply manifold (not shown), and side C is a fuel gas The discharge surface is connected to the fuel gas discharge manifold 15a, and the side surface D is an air discharge surface and is connected to the air discharge manifold 15b.
Although only one fuel cell unit cell and the manifold connected to it are shown in FIG. 3, the manifold may be connected to a stack of two or more unit cells in this way.

Each fuel cell unit cell and manifold are
The sealing material of the present invention is used to hermetically connect by the sealing method of the present invention.

The sealing material of the present invention comprises silica (preferably 52
~ 58 wt%) and alumina (preferably 20-22 wt%)
And at least one low softening point glass granules (A) made of aluminosilicate glass having a glass softening temperature of 770 ° C to 950 ° C, for example 870 ° C, and silica (preferably 94 to 98% by weight). And alumina (preferably 0.2 to 0.2.
8% by weight) and 1450 ° C to 1550 ° C, for example 1530
(C) and at least one type of high softening point glass particles (B) made of high silica glass. The mixing ratio of the total weight of the low softening point glass particles (A) to the total weight of the high softening point glass particles (B) is preferably 50:50 to 35:65, and 40:
More preferably, it is 60 to 35:65.

As described above, the low softening point glass particles (A)
And a high-softening point glass granule (B) are mixed to obtain a low-softening-point glass granule at the initial stage when the sealing material is heated and sealed at 1000 ° C to 1150 ° C. The softening (melting) of the body wets the sealing part to seal it, and the high softening point glass particles are immersed in the softened (melting) low softening point glass. The softening point glass and the high softening point glass are melt-mixed with each other to form a glass having a softening temperature higher than 1050 ° C and lower than 1150 ° C.

The softening temperature is about 1000 at the operating temperature of the fuel cell.
C. to above 1050.degree. C., and therefore the sealing portion does not soften or melt at the operating temperature of the fuel cell. The composition of the glass that constitutes such a sealed portion is determined by the composition and weight ratio of the low softening point glass granules (A) and the high softening point glass granules (B), and is generally 79.2 to 81.3 wt% silica ( S
iO ₂ ) and 7.6 to 8.6% by weight of alumina (Al ₂ O ₃ ) are preferable.

The low softening point glass particles preferably have a particle size of 1 to 40 μm, and the high softening point glass particles preferably have a particle size in the range of 1 to 80 μm. Also,
The total weight ratio ((A) / (B)) of the low softening point glass particles to the high softening point glass particles is preferably 50:50 to 35:65, and 40:60 to 35:65. Is more preferable.
If the total weight ratio ((A) / (B)) exceeds 50/50, the softening point of the sealing glass portion formed by the sealing operation is 10 or less.
The temperature may be lower than 00 ° C, and therefore the disadvantage that the sealing glass part is softened / melted at the operating temperature of the fuel cell may occur. Further, if the weight ratio ((A) / (B)) is less than 35/65, the temperature required for the sealing operation becomes higher than 1150 ° C, and at such sealing temperature, the components of the fuel cell, In particular, the air electrode layer ((La · Sr) MnO ₃ ) may sinter and shrink, and may undergo solid phase reaction with the solid electrolyte (stabilized zirconia) to change its properties.

In the method of the present invention, the softening and sealing operation is 1000
It is carried out at a temperature from ℃ to 1150 ℃. This sealing temperature is 10
If the temperature is lower than 00 ° C, the soft and mixed glass particles having low and high softening points are not sufficiently softened and mixed, and a uniform glass sealing part having a desired composition and a softening temperature cannot be formed.
When the sealing temperature rises above 1150 ° C, the fuel cell components, especially the air electrode layer, sinter and shrink as described above, and a solid-state reaction with the solid electrolyte (stabilized zirconia) occurs. As a result, its performance is reduced.

In the method of the present invention, the portion of the fuel cell body to be sealed and the sealing portion of the manifold are butted against each other,
A predetermined amount of the sealing material of the present invention is placed on the abutting portion, and the sealing material is heated by an appropriate heating means such as N ₂
Atmosphere It is heated by an electric furnace, etc. to soften and mix the low and high softening point glass particles in the sealing material, and perform sealing.
Next, this is cooled and solidified to form a glass sealing part.

[0025]

EXAMPLES The present invention will be specifically described with reference to the following examples. Examples 1 and 2 and Comparative Examples 1 to 3 (1) Production of low softening point glass granules 54% by weight of SiO ₂ , 21% by weight of Al ₂ O ₃ , and residual amount of Na
Aluminosilicate glass containing O, CaO and other oxides (glass softening point: 870 ° C.) was crushed and sifted to produce low softening point glass particles having a particle size of 1 to 40 μm.

(2) Production of high softening point glass granules 98% by weight of SiO ₂ , 0.4% by weight of Al ₂ O ₃ and the balance of NaO,
High silica glass (glass softening point: 1530 ° C. or higher) containing CaO and other oxides was crushed and sifted to obtain glass particles having a high softening point of 1 to 40 μm.

(3) Preparation of Sealing Material The low softening point glass granules and the high softening point glass granules were mixed in a weight mixing ratio shown in Table 1 to prepare a sealing material. did.

An aqueous paste of the above-mentioned sealing material was applied on a yttria-stabilized zirconia membrane (solid electrolyte) (thickness 150 μm) and dried at a temperature of 150 ° C. to prepare a test piece. The two test pieces are stacked so that the coating layers adhere to each other,
Heat this to 1100 ℃ at a heating rate of 20 ℃ / min,
After holding for 1000 minutes, the two solid electrolyte membranes were sealed and cooled to room temperature. The bonding state of the obtained sealed product was observed and evaluated.

Further, the above-mentioned sealing material was heated under the same conditions as above, cooled and solidified to prepare a softened mixture, and its glass softening temperature was measured.

Further, using the above-mentioned sealed material, a ZrO ₂ manifold was sealed to the side surface of the flat plate solid oxide fuel cell body under the same sealing heating conditions as above, and the bonding state of the sealed portion was observed. The fuel cell was evaluated and further discharged at 1000 ° C. The results of the above tests are shown in Table 1.

[Table 1]

As is apparent from Table 1, the plate-shaped solid oxide fuel cell body and the manifold were easily sealed at a temperature of 1000 ° C. to 1150 ° C. by using the sealing material and the sealing method of the present invention. , At the operating temperature of 1000 ℃ ~ 1050 ℃,
It was possible to obtain a fuel cell that could be put to practical use without any inconvenience.

[0032]

According to the sealing material and sealing method of the present invention, the flat plate solid oxide fuel cell main body and the manifold are sealed at a relatively low temperature which does not change the constituent elements, and It has become possible to manufacture a fuel cell that can be used without inconvenience at a practical temperature of 1000 ° C to 1050 ° C.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a conventional cylindrical solid oxide fuel cell.

FIG. 2 is an explanatory diagram showing constituent elements of a flat plate solid oxide fuel cell single cell to which the sealing material and the sealing method of the present invention are applied, and a laminated structure thereof.

FIG. 3 is an explanatory view showing a sealing connection state of a flat plate solid oxide fuel cell single cell to which a sealing material and a sealing method of the present invention are applied and a gas passage manifold.

[Explanation of symbols]

 1 ... Porous tubular support layer 2 ... Tubular air electrode layer 3 ... Tubular solid electrolyte layer 4 ... Tubular fuel electrode layer 5 ... Interconnector 6, 12 ... Air flow direction 7, 13 ... Fuel gas flow direction 8, 8a, 8b ... Separator 9 ... Flat air electrode layer 10 ... Flat solid electrolyte layer 11 ... Flat fuel electrode layer 14 ... Fuel cell unit cell 15a, 15b ... Manifold A, B, C, D ... Flat fuel cell unit cell side

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Hayashi 585 Tomimachi, Funabashi, Chiba Sumitomo Cement Co., Ltd. New Business Headquarters (72) Ken Ken Kato 585 Tomicho, Funabashi, Chiba Sumitomo Cement Shares Company New Business Headquarters (72) Inventor Isamu Yasuda 1-1625 Shibaura, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Toshihiko Koyama 1-16-25 Shibaura, Minato-ku, Tokyo Tokyo Gas Co., Ltd. Within

Claims (8)

[Claims] 1. A sealing material for hermetically connecting a gas passage manifold to a main body of a solid oxide fuel cell, comprising: (A) silica and alumina; 9
1450 ° C. to 1550, containing at least one low softening point glass granules made of aluminosilicate glass having a glass softening temperature of 50 ° C., and (B) silica and alumina.
A sealing material for a solid oxide fuel cell, comprising a mixture of at least one high softening point glass granules made of high silica glass having a glass softening temperature of ° C. 2. The solid electrolyte fuel cell sealing material according to claim 1, wherein the low softening point glass aluminosilicate glass contains 52 to 58% by weight of silica and 20 to 22% by weight of alumina. Material. 3. The solid electrolyte type according to claim 1, wherein the high-silica glass of the high softening point glass granules contains 94 to 98% by weight of silica and 0.2 to 0.8% by weight of alumina. Sealant for fuel cells. 4. The total weight of the low softening point glass particles,
The ratio to the total weight of the high softening point glass particles is 50:
The sealing material for a solid oxide fuel cell according to claim 1, which is in a range of 50 to 35:65. 5. A gas passage manifold is hermetically sealed in each of at least one layer of a solid oxide fuel cell main unit including a fuel electrode layer, a solid electrolyte layer, an air electrode layer, and a separator, which are sequentially stacked. In order to connect, the battery main body unit, the joint portion of the manifold, is sealed while softening the sealing material, a method of cooling and solidifying the softened sealing portion, the sealing material, The following elements: (A) Contains silica and alumina, and 770 ° C to 9
1450 ° C. to 1550, containing at least one low softening point glass granules made of aluminosilicate glass having a glass softening temperature of 50 ° C., and (B) silica and alumina.
Solid electrolyte type, which comprises a mixture with at least one high softening point glass granules made of high silica glass having a glass softening temperature of 0 ° C., and the softening and sealing operation is performed at a temperature of 1000 ° C. to 1150 ° C. Sealing method for fuel cells. 6. The solid electrolyte fuel cell sealing method according to claim 5, wherein the low softening point glass aluminosilicate glass contains 52 to 58% by weight of silica and 20 to 22% by weight of alumina. . 7. The solid electrolyte type of claim 5, wherein the high-silica glass of the high softening point glass granules contains 94 to 98% by weight of silica and 0.2 to 0.8% by weight of alumina. Fuel cell sealing method. 8. The total weight of the low softening point glass particles,
The ratio to the total weight of the high softening point glass particles is 50:
The method for sealing a solid oxide fuel cell according to claim 5, which is in the range of 50 to 35:65.