JPH1050331A - Solid electrolyte fuel cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of thermal stress in a sealing part, increase chemical stability in the sealing part, and keep airtightness by sealing a gap between a cylindrical cell and a ceramic block fit to an opening on each side of the cylindrical cell with the same material as a solid electrolyte. SOLUTION: Gaps S1, S2 between a cylindrical cell formed by concentrically arranging from the inside an air electrode 11, a solid electrolyte 14 and a fuel electrode 15 in order and ceramic blocks 12a, 12b, fit to the openings on both sides of the cylindrical cell are sealed with the same material as the solid electrolyte 14. The material of the solid electrolyte 14 and the sealing material is preferably stabilized zirconia. Sealing is preferably performed by a reduced pressure plasma spraying method, for example.

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 seal portion for filling a gap between a cylindrical battery cell and a ceramic block fitted into openings at both ends thereof in a battery cell having a cylindrical structure. The present invention relates to a solid oxide fuel cell having features and a method for 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 required for the oxide solid, that is, the solid electrolyte to exhibit good ionic conductivity, the SOFC is usually used at 800 ° C. to 120 ° C.
It is operated under a temperature condition of 0 ° C.

[0004] Further, SOFCs are classified into flat type SOFCs and cylindrical type SOFCs according to their shapes. FIG. 6 (A)
FIG. 2 is a schematic sectional view showing an example of a battery cell constituting a cylindrical SOFC. As shown in the drawing, a cylindrical battery cell 105 generally has a cylindrical air electrode 101 as a support tube, a solid electrolyte 102 formed on the outer surface thereof, and a fuel electrode 104 formed on the outer surface thereof. In order to electrically connect a plurality of battery cells, an interconnector 103 is arranged in a certain area of the cylindrical air electrode 101.

Air or oxidizing gas is supplied inside the cylindrical air electrode 101 in the direction of the arrow, and fuel gas such as hydrogen gas is supplied outside the cylindrical battery cell having the fuel electrode in the direction of the arrow. You.

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

The solid electrolyte 102 is required to have high oxygen ion conductivity and to be chemically stable in an oxidizing and reducing atmosphere at a battery 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 104 and the air electrode 101 are porous so that gas can penetrate into 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 102 is close to that of the adjacent solid electrolyte 102.

Since the anode 104 is exposed to hydrogen gas, it needs to be chemically stable in a high-temperature reducing atmosphere. Since the cathode 101 is exposed to air, it is chemically stable in a high-temperature oxidizing atmosphere. Must be stable.

In general, the fuel electrode 104 is a cermet of nickel (Ni) and YSZ or the like, and the air electrode 101 is a perovskite-type oxide based on lanthanum cobaltate (LaCoO ₃ ) or lanthanum manganate (LaMnO ₃ ). Things are often selected.

The interconnector 103 is a connection area for electrically connecting a plurality of cylindrical battery cells. Therefore, it is necessary that the electronic conductivity is high. In addition, since the outer surface is exposed to hydrogen gas or the like, it must be chemically stable in a high-temperature oxidizing and reducing atmosphere. Airtightness is also required so that air and hydrogen gas do not leak into and out of each other. In addition, it is desirable that the thermal expansion coefficient is close to that of the cylindrical battery cell. As a material satisfying these conditions, a lanthanum chromite oxide (LaC
rO ₃ ) or the like is often used as an interconnector material.

As shown in FIG. 6B, the cylindrical battery cell 105 has openings on both sides of YSZ or alumina (Al).
It is sealed in a ceramic block 106 such as ₂ O ₃ ) and installed in an outer cylinder 108 to avoid mixing of the outside air and the fuel gas.

On one ceramic block 106,
A gas inlet tube 113 is provided, from which air is introduced into the cylindrical battery cell. The opening at the tip of the introduction tube is taken out of the outer cylinder 108. Gas inlet pipe 11
3 also serves as an outlet at the same time.

The outer cylinder 108 has a fuel gas supply port 109 and a discharge port 110. Fuel gas is supplied from the supply port 110 into the outer cylinder 108, and excess fuel gas is discharged from the discharge port 109.

Usually, a gap is formed between the cylindrical battery cell and the ceramic blocks 106 provided at both ends of the cylindrical battery cell. In this state, gas leakage occurs inside and outside the cylindrical battery cell in the outer cylinder, and there are many safety and efficiency problems.
The gap is sealed by the glass sealing material 107.

As a method of sealing the gap, first, a cylindrical battery cell 105 is manufactured, and a ceramic block 106 having annular grooves at both left and right ends thereof is inserted into an end of the cylindrical battery cell 105. Fit so that it enters. After that, the end of the cylindrical battery cell is immersed in a molten glass reservoir, and the inside of the groove of the ceramic block 106 is filled with glass to seal. Generally, borosilicate glass is often used as this glass.

[0017]

As described above, when gas leaks between the inside and outside of the cylindrical battery cell 105, the utilization efficiency of the fuel is reduced. It is necessary to seal the gap between the ceramic block and the ceramic block.

However, the melting point of borosilicate glass conventionally used as a sealing material is about 830 ° C.
It is in a molten state at the operating temperature of the OFC. The problem is small when the gas pressure difference between the air supplied to the inside of the cylindrical battery cell and the hydrogen supplied to the outside is small, but when the gas pressure difference is large, gas leaks from the sealing portion in a molten state. There is danger.

On the other hand, the sealing material using borosilicate glass is in a molten state during the operation of the SOFC, but solidifies as the temperature of the cylindrical battery cell decreases after the operation is completed. That is, in the heat cycle of the battery, the sealing material goes back and forth between a molten state and a solidified state.

When the sealing material is in a molten state, the sealing portion often serves as a buffer for thermal stress. But,
When the temperature of the cylindrical battery cell decreases and the sealing material solidifies, a difference in the coefficient of thermal expansion between the sealing material and the material to be sealed becomes a problem. For example, the thermal expansion coefficient of the cylindrical battery cell and the ceramic block is about 8 to 12 × 10 ⁻⁶ / ° C., while the thermal expansion coefficient of the solidified borosilicate glass is 3 to 4 × 1
It is as small as 0 ^-6 / ° C. Therefore, the generation of thermal stress due to the difference in the coefficient of thermal expansion between the cylindrical battery cell 105 and the sealing material may cause the cell to break.

At the operating temperature, gases such as Si and SiO volatilize from the borosilicate glass containing SiO ₂ as a main component. These volatile components may form a compound with the fuel electrode 104, which is a cermet of nickel and YSZ, and may cause deterioration of battery characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a solid electrolyte fuel cell capable of improving the characteristics of a sealing portion for filling a gap between a cylindrical battery cell and a ceramic block fitted into openings at both ends thereof. And a method for manufacturing the same.

[0023]

The solid electrolyte fuel cell of the present invention is characterized by a cylindrical battery cell in which an air electrode, a solid electrolyte, and a fuel electrode are concentrically arranged in this order from the inside.
A ceramic block fitted into both side openings of the cylindrical battery cell, made of the same material as the solid electrolyte,
A sealing material for filling a gap between the cylindrical battery cell and the ceramic block.

According to the above feature, since the material of the sealing material is the same as that of the solid electrolyte, the sealing portion is chemically stable and can maintain a solid state even during the operation of the battery. In addition, since the thermal expansion coefficient is substantially equal to the constituent material of the battery cell, it is possible to reduce the thermal stress generated in the sealing portion during the operation of the battery.

[0025] The material of the solid electrolyte and the sealing material may be stabilized zirconia. This material is
It has good characteristics as a solid electrolyte.

The method of manufacturing a solid oxide fuel cell according to the present invention is characterized in that a step of manufacturing a cylindrical air electrode support tube, a step of fitting a ceramic block into both end openings of the cylindrical air electrode support tube, The method includes a step of forming a solid electrolyte on the outer surface of the cylindrical air electrode support tube, the ceramic block, and the fitting portion thereof, and a step of forming a fuel electrode on the solid electrolyte.

According to the features of the above manufacturing method, the gap between the cylindrical battery cell and the ceramic block can be simultaneously sealed with the same solid electrolyte material when forming the solid electrolyte.

The material of the solid electrolyte may be stabilized zirconia. A solid electrolyte having good characteristics can be obtained, a solid state can be maintained at the battery operating temperature, and a seal portion that is chemically stable and has a thermal expansion coefficient substantially equal to that of the material constituting the cylindrical battery cell can be formed.

Further, the step of forming the solid electrolyte comprises:
The solid electrolyte may be formed by using a low pressure plasma spraying method. The solid electrolyte can be formed at a high speed.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A process for manufacturing a solid oxide fuel cell according to an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1A to 1D are cross-sectional views of the apparatus in each manufacturing process of a cylindrical battery cell. The left side of each drawing shows a cut surface in the cell long axis direction, and the right side shows a cut surface in the cell short axis direction. Note that the cut surface on the right side corresponds to the cut surface along the dashed-dotted line A1-A2 shown in the drawing on the left side.

A cylindrical air electrode 11 shown in FIG. 1A is manufactured by the following procedure. The air electrode 11 also serves as a support tube for the cylindrical battery cell.

A lanthanum strontium manganate (LaSrMnO ₃ ) powder having an average particle diameter of 3 to 10 μm and having a perovskite crystal structure is mixed with water at 20 wt% and a binder such as methyl cellulose at 10 wt%. The whole is kneaded well to form a clay, which is processed into a cylindrical shape using an extrusion molding method.

Next, the temperature of the cylindrical tube obtained by the extrusion molding method is increased at a rate of about 100 ° C./hr in the atmosphere. On the way, after evaporating the moisture and the binder at a certain temperature, the temperature is further raised. When the temperature reaches 1300 ° C. to 1500 ° C., firing is performed at this temperature for about 5 hours. Under these conditions, LaSrMnO
_The air electrode support tube 11 made of the porous sintered body of No. ₃ is formed. The size of the air electrode 11 after sintering is about 1 to 3 m in thickness.
m, the outer diameter is about 20 mm, and the length is about 1500 mm.

Next, as shown in FIG. 1B, ceramic blocks 12a and 12b are formed, and the air electrode supporting tube 1 is formed.
1 is fitted into the openings at both left and right ends. The ceramic blocks 12a and 12b are manufactured by the following method.

YSZ powder having an average particle size of 15 to 50 μm
20 wt% water, 1 binder such as methylcellulose
Mix so as to be 0% by weight, and knead the whole well to form a clay. The clay-like raw material is formed into a block having a shape adapted to the cylindrical shape of the cathode support tube 11 by using an extrusion molding method. Alternatively, a press molding or slip casting method may be used.

As shown in FIG. 1B, one of the ceramic blocks 12b is provided with a gas introduction pipe 13 for introducing air into the cylinder of the air electrode support pipe. The other ceramic block 12a does not include a gas introduction tube and has a shape of a sealing stopper. As described above, when only one of the ceramic blocks is provided with the gas introduction pipe, this introduction pipe also serves as the gas discharge pipe. The ceramic block 12a may be provided with a gas discharge pipe having the same shape as the gas introduction pipe 13.

The temperature of the block obtained by extrusion molding, press working, or slip casting is raised at a rate of about 100 ° C./hr in the air atmosphere. On the way, the moisture and binder are evaporated at a constant temperature, and the temperature is further increased to about 16
When the temperature reaches 00 ° C, bake at this temperature for about 5 hours,
Sinter the YSZ powder.

Thereafter, the sintered ceramic blocks 12a and 12b are fitted into the openings at both ends of the cathode support tube 11. It is preferable that no gap is formed between the ceramic blocks 12a, 12b and the cathode support tube 11, but as shown in the left diagram of FIG.
1, S2 can be done.

Next, as shown in FIG. 1C, a solid electrolyte 14 is formed on the outer surface of the cathode support tube 11. The feature of the present embodiment is that at this time, the gaps S1, S between the cathode support tube 11 and the ceramic blocks 12a, 12b are simultaneously formed.
2 is filled or sealed with a solid electrolyte 14.

Various methods can be used for forming the solid electrolyte 14. Here, a method for forming the solid electrolyte 14 by using a low pressure plasma spraying method will be described with reference to FIG.

FIG. 3 is a schematic configuration diagram of a reduced pressure plasma spraying apparatus. The inside of the chamber 37 is evacuated from the exhaust port 38 using a vacuum pump, and is maintained at a reduced pressure of about 100 Torr. In the chamber 37, a rod-shaped tungsten electrode 31 serving as a cathode and a copper nozzle-shaped electrode 32 serving as an anode are provided around the outside thereof. In the nozzle between both electrodes,
A mixed gas of argon (Ar) and hydrogen (H ₂ ) is supplied as a working gas.

When a voltage is applied between the electrode 31 and the electrode 32 to perform a discharge, the working gas flowing between the electrodes is ionized and ejected from the nozzle opening of the electrode 32 as a high-temperature plasma flame 35. A nozzle 34 for supplying the thermal spraying powder is provided on a side portion of the plasma flame 35.
From 4 YSZ powder is supplied into the plasma flame 35.
The YSZ powder is melted by the high-temperature plasma flame 35 and is injected in the same direction as the jetting direction of the plasma flame. The YSZ used here is 8 to 10 in the zirconia (ZrO ₂ ) base material.
It is assumed that mol% yttria (Y ₂ O ₃ ) is dissolved.

A cylindrical air electrode support tube 36 in which a ceramic block is fitted is installed in the YSZ ejection direction. On the cylindrical air electrode support tube 36, a region where an interconnector is to be formed in a later step is formed by a thin copper plate strip-shaped mask 3.
Cover with 9 The interconnector is a cathode support tube 1
1 are formed inside both ends.

As shown by the arrow in the figure, the cylinder is rotated around the central axis of the cylinder, and YSZ is sprayed on the outer surface of the cathode support tube 36 except for the portion covered with the mask 39.

As shown in FIG. 1C, about 100 μm to 200 μm of YSZ is formed on the outer surface including the air electrode support tube 11 in the area not covered with the mask 39 and the ceramic blocks 12 a and 12 b at both ends. A thermal spray coating, ie, solid electrolyte 14, is formed.

FIG. 2 is an enlarged sectional view of the gap S2 between the ceramic block 12a and the cathode support tube 11 in FIG. The thermal spray coating of YSZ fills at least the gap S2 near the outer surface. The gaps S1 and S2 are sealed by the YSZ thermal spray coating.

Next, a fuel electrode 15 made of porous Ni and YSZ cermets having a film thickness of about 50 to 150 μm is formed on the surface of the solid electrolyte 14 by atmospheric pressure plasma spraying. The atmospheric pressure plasma spraying uses an apparatus having substantially the same configuration as the above-described low pressure plasma spraying. However, since the spraying atmosphere is at atmospheric pressure, the size of the plasma flame formed is slightly smaller, the melting state of the sprayed powder tends to be insufficient, and the porous film is more porous than when using the low pressure plasma spraying method. Can be formed.

As shown in FIG. 1D, by using a copper plate mask, the fuel electrode 15 is formed only on both sides of the cylindrical battery cell and on the outer surface excluding the interconnector formation region.

Thereafter, an interconnector 16 having a thickness of about 100 to 500 μm is formed in the exposed region of the cathode support tube 11 exposed on the outer surface by using the same atmospheric pressure plasma spraying method as described above. As the material of the interconnector,
Lanthanum calcia chromite (LaCaCrO ₃ ) is used.

As shown in FIG. 1D, the interconnector 16 is a strip-shaped electrode that is long in the longitudinal direction of the cylindrical battery cell, and is formed directly on the surface of the cathode support tube 11. The entire outer surface of the cathode support tube 11 where the interconnector is not formed is covered with the solid electrolyte 14,
Make sure that no exposed areas remain. FIG. 4 shows a perspective view of the cylindrical battery cell 40 formed by the above-described method.

As shown in FIG. 5, the cylindrical battery cell is provided in an outer cylinder 51 having a gas supply port 52 and a gas exhaust port 53. The material of the outer cylinder 51 may be alumina, magnesia, or a composite material thereof. Note that, as shown in FIG.
b, one end of the cylindrical battery cell 40 has an outer cylinder 51.
The boundary between the outer cylinder 51 and the cylindrical battery cell 40 is filled with a ceramic adhesive 54.

Although FIG. 5 shows a single battery cell, a plurality of cylindrical battery cells are usually electrically connected via an interconnector to obtain higher power.
It is housed in the same outer cylinder 51.

As described above, in this embodiment, the gap between the air electrode support tube and the ceramic block fitted into the openings on both sides thereof is sealed with YSZ, which is the same material as the solid electrolyte. Since the solid electrolyte and the sealing material are the same material,
When the solid electrolyte is formed on the cathode support tube, the gap can be sealed at the same time. Since an independent sealing process is not required, the manufacturing process can be simplified.

In general, the material constituting the battery cell approximates the coefficient of thermal expansion of the solid electrolyte. Therefore, by using the same material as the solid electrolyte as the sealant, it is possible to suppress the thermal stress generated in the gap, that is, the seal, of the air electrode support tube. Further, even in a heat cycle accompanying repetition of battery operation, breakage of the seal portion due to thermal stress is less likely to occur.

At the operating temperature of the battery cell of 800 ° C. to 1200 ° C., since the conventional sealing material made of borosilicate glass was in a molten state, gas leakage from the sealing portion could occur. In the case of the above-described embodiment, YSZ, which is a sealing material, maintains a solid state during battery operation, so that good sealing performance can be ensured even when a gas pressure difference exists inside and outside the cylindrical cell.

Further, when a sealing material made of borosilicate glass is used, Si which is volatilized from the glass during operation of the battery is used.
There has been a problem that the fuel electrode and the SiO component react with the fuel electrode to lower the battery performance. However, when YSZ is used as a sealing material, such a volatile component hardly occurs.

When the material of the ceramic block is YSZ as in the embodiment, since the ceramic block and the seal portion are formed of the same material, the generation of thermal stress in the seal portion can be further suppressed.

In the above-described embodiment, a low pressure plasma spraying method is used as a method for forming a solid electrolyte. However, in addition to this method, a slurry coating method, an electrochemical vapor deposition method (EVD method), or an electrophoresis method may be used. Can be.

Although the dense YSZ can be obtained by using the EVD method, when the low-pressure plasma spraying method is used,
The film can be formed at a higher speed as compared with the case where the VD method or the like is used. In the above-described embodiment, the ceramic block made of YSZ is used. However, other than YSZ, alumina (Al ₂ O ₃ ), spinel (MgAl ₂ O ₄ ), or the like has an expansion coefficient similar to that of the solid electrolyte, A ceramic material that is chemically stable in an oxidation-reduction atmosphere at a battery operating temperature of 800 ° C. to 1200 ° C. may be used.

In the above embodiment, only one of the ceramic blocks has a gas supply pipe and the other ceramic block seals the opening of the air electrode support pipe. Also, a supply pipe or an exhaust pipe may be provided. The shape is not particularly limited.

[0062]

As described above, according to the solid oxide fuel cell of the present invention, the solid state can be maintained without melting the sealing material even at the operating temperature. The airtightness of the seal portion is easily maintained without being performed.

In the operating state, since the seal portion is chemically stable, the deterioration of the characteristics of the battery cell constituent material is less likely to be induced.

Further, by selecting a sealing material having a coefficient of thermal expansion close to that of the battery cell, the generation of thermal stress in the sealing portion can be suppressed, and the durability of the battery to heat cycles can be improved. it can.

According to the method for manufacturing a solid oxide fuel cell of the present invention, when forming a solid electrolyte on the cathode support tube,
At the same time, the gap between the air electrode support tube and the ceramic blocks provided at both ends of the air electrode support tube can be sealed with the solid electrolyte, so that a cylindrical SOFC can be manufactured by a simpler process.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylindrical battery cell in each step for explaining a method of manufacturing an SOFC according to an embodiment of the present invention.

FIG. 2 is a part of a cross section of a cylindrical battery cell showing a seal portion of the SOFC according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of a reduced pressure plasma spraying apparatus used in the embodiment of the present invention.

FIG. 4 is a perspective view of a cylindrical battery cell according to the embodiment of the present invention.

FIG. 5 is a sectional view of an apparatus showing a structure of a cylindrical SOFC according to an embodiment of the present invention.

FIG. 6 is a sectional view of an apparatus showing a structure of a conventional cylindrical SOFC.

[Explanation of symbols]

 11 ... Air electrode support tubes 12a, 12b ... Ceramic block 13 ... Gas introduction tube 14 ... Solid electrolyte 15 ... Fuel electrode 16 ... Interconnector

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

Claims (5)

[Claims] 1. A cylindrical battery cell in which an air electrode, a solid electrolyte, and a fuel electrode are concentrically arranged in this order from the inside, a ceramic block fitted into openings on both sides of the cylindrical battery cell, A solid electrolyte fuel cell comprising the same material as the solid electrolyte and having a sealing material filling a gap between the cylindrical battery cell and the ceramic block. 2. The solid oxide fuel cell according to claim 1, wherein the materials of the solid electrolyte and the sealing material are stabilized zirconia. 3. A step of manufacturing a cylindrical air electrode support tube; a step of fitting a ceramic block into both ends of the cylindrical air electrode support tube;
A method for manufacturing a solid oxide fuel cell, comprising: a step of forming a solid electrolyte on the outer surface of these fitting portions; and a step of forming a fuel electrode on the solid electrolyte. 4. The method for manufacturing a solid oxide fuel cell according to claim 3, wherein the material of the solid electrolyte is stabilized zirconia. 5. The method for manufacturing a solid oxide fuel cell according to claim 4, wherein the step of forming the solid electrolyte forms the solid electrolyte using a low pressure plasma spraying method.