JP2001236969A - Cell for solid electrolyte fuel cell and method of producing the same as well as fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell of a solid electrolyte fuel cell having a good generating performance and possible durability improved and a method of producing the same as well as a fuel cell. SOLUTION: A cell of a solid electrolyte fuel cell 59 has a solid electrolyte 31 containing zirconia as a main component and a fuel electrode 33 laminated in sequence on the surface of an air electrode 32 containing Mn. The cell has a low porosity layer 43 whose porosity is smaller than that of the other area 45 of the air electrode 32 on the solid electrolyte 31 side of the air electrode 32.

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 having a solid electrolyte and a fuel electrode on the surface of an air electrode, a method for producing the same, and a fuel cell.

[0002]

2. Description of the Related Art Conventionally, a solid oxide fuel cell has a high power generation efficiency because its operating temperature is as high as 900 to 1100 ° C., and is expected as a third generation power generation system.

[0003] In general, a cylindrical type and a flat type are known as solid oxide fuel cells. Flat fuel cells are
Although it has the feature that the power density per unit volume of power generation is high, there are problems such as incomplete gas sealing and non-uniformity of temperature distribution in the cell in practical use. On the other hand,
Cylindrical fuel cells are characterized by low mechanical strength of the cells, while maintaining a uniform temperature within the cells, although the output density is low. Both types of solid oxide fuel cells are being actively researched and developed utilizing their respective characteristics.

A single cell of a cylindrical fuel cell is, for example, shown in FIG.
As shown in the figure, LaMnO having an open porosity of about 30 to 40%
Porous form an air electrode support tube 2 made of ₃ based material, coating the solid electrolyte 3 made of Y ₂ O ₃ stabilized ZrO ₂ on the surface thereof, further a porous fuel Ni-ZrO ₂ on the surface It is configured with poles 4.

In the fuel cell module, each single cell is connected via a LaCrO ₃ -based current collector (interconnector) 5. In the power generation, air (oxygen) 6 flows inside the cathode support tube 2 and fuel (hydrogen) 7 flows outside, and 900 to
It is performed at a temperature of 1100 ° C. Further, as a material of the cathode support tube 2 having a function as an cathode, for example, L
A solid solution material in which a is substituted with 20 at% by Ca or 10 to 15 at% by Sr is used.

In recent years, a so-called co-sintering method has been proposed, in which at least two of the constituent materials are simultaneously fired in order to simplify the manufacturing process of the cell and reduce the manufacturing cost. This co-sintering method is, for example, a method in which a solid electrolyte molded body and a current collector molded body are wound around a cylindrical air electrode molded body in a roll shape and fired simultaneously, and then a fuel electrode is formed on the solid electrolyte surface. is there. Also, to simplify the process,
A co-sintering method has also been proposed in which a fuel electrode molded body is further laminated on the surface of the solid electrolyte molded body, and the air electrode, the solid electrolyte, the fuel electrode, and the current collector are simultaneously fired.

This co-sintering method is a very simple process with a small number of manufacturing steps, and is advantageous in improving the yield and cost reduction in manufacturing cells. In such a fuel cell by the co-sintering method, a solid electrolyte composed of Y ₂ O ₃ stabilized or partially stabilized ZrO ₂ is used, and the coefficient of thermal expansion matches the solid electrolyte. , LaMnO
_The perovskite-type composite oxide of No. _{3 in} which a part of La is substituted with Y and Ca is used (see Japanese Patent Application Laid-Open No. 10-162847). In addition, a LaCrO ₃ material is used as a current collector material.

[0008]

However, when a cylindrical fuel cell is manufactured using the above-described co-sintering method,
During co-sintering, the Mn element, which is a component of the air electrode, evaporates into the atmosphere around the solid oxide fuel cell, and the evaporated Mn diffuses inside the fuel electrode. The Mn content in the fuel cell increases, the polarization value of the fuel electrode site and the actual resistance value of the cell constituent components increase, and as a result, there is a problem that the power density in the initial stage is low.

Particularly, LaCrO ₃ -based materials have been known to be difficult to sinter. However, when a fuel cell is manufactured using the above-described co-sintering method, LaCrO ₃ -based materials are used. If the sintering temperature is increased to sinter the current collector, or sintering is performed for a long time, Mn in the air electrode diffuses into the atmosphere, and the Mn easily diffuses from the surface of the fuel electrode to the inside, and the fuel There is a problem that the polarization value of the pole site increases and the output density in the initial stage is low.

Therefore, in order to suppress the diffusion of Mn into the inside of the fuel electrode, it is necessary to lower the firing temperature and perform firing in a short time. It cannot be sufficiently densified, or the adhesion strength between the solid electrolyte and the air electrode interface is weak. In the operating environment of 900 to 1100 ° C in which the solid electrolyte fuel cell operates, the durability is poor, and the output performance decreases with time. Further, when the temperature is cooled from 1000 ° C. to room temperature, cracks occur at the interface between the solid electrolyte and the air electrode, and when power is generated again, there is a problem that the output performance is significantly reduced.

[0011] Therefore, it is very difficult for fuel cells manufactured by the co-sintering method, which are excellent in cost reduction, to have excellent power generation performance and satisfy durability at the same time. Has become a major obstacle in the transformation.

An object of the present invention is to provide a solid oxide fuel cell having excellent output performance and improved durability, a method for producing the same, and a fuel cell.

[0013]

The solid electrolyte fuel cell according to the present invention is a solid electrolyte fuel cell comprising a manganese-containing air electrode and a zirconia-based solid electrolyte and a fuel electrode laminated in that order on the surface of the Mn-containing air electrode. A fuel cell, comprising a low porosity layer having a porosity smaller than other regions of the air electrode on the solid electrolyte side of the air electrode.

In order to form the low porosity layer on the solid electrolyte side of the air electrode as described above, zirconia is mainly applied to the surface of the Mn-containing air electrode formed body (including the air electrode calcined body). The laminated molded body formed by forming the solid electrolyte molded body as a component (including the solid electrolyte calcined body) is subjected to a frequency 1
It is obtained by sintering by irradiating microwaves of up to 30 GHz. The laminated molded body in which the fuel electrode molded body is formed on the surface of the solid electrolyte molded body may be subjected to microwave firing.

In the solid oxide fuel cell according to the present invention,
Since the low porosity layer is provided on the solid electrolyte side of the air electrode, although the reason is not clear, the adhesion can be improved, and the durability can be improved while maintaining high output performance. That is, by using a microwave heating method of directly heating the laminated molded body itself, and by using a material having a smaller microwave absorption characteristic than the solid electrolyte for the air electrode, co-sintering can be performed at a low temperature and in a short time, and at the same time, the fuel is discharged from the air electrode. It is possible to obtain a solid oxide fuel cell cell in which diffusion of Mn into the electrode is suppressed and the durability is excellent, that is, the power generation efficiency is excellent even when used repeatedly.

More specifically, in order to improve durability while maintaining high output performance, first, a portion (low porosity layer) of the air electrode in contact with the solid electrolyte has a higher porosity than other portions. Needs to be low.

Here, the durability means that the output performance does not deteriorate during a long-term output at a high temperature, for example, at 1000 ° C. for 1000 hours, and after the power is cooled down to room temperature, the power is again generated. Indicates that high output performance can be demonstrated again. When the durability deteriorated, most of the deterioration was due to cracks at the interface between the air electrode and the solid electrolyte. Therefore, in order to improve the durability, it was necessary to increase the adhesion between the air electrode and the solid electrolyte. However, as described above, in the present invention, a low porosity layer is formed on the solid electrolyte side of the air electrode. Thereby, generation of cracks at the interface between the air electrode and the solid electrolyte can be suppressed, high adhesion can be obtained, and durability can be improved.

Although the mechanism by which the low porosity layer significantly improves durability is not clearly understood, the thermal expansion coefficient of a solid electrolyte such as ZrO ₂ is generally smaller than that of a LaMnO ₃ -based air electrode. Therefore, a large stress acts on the cell itself in the air electrode circumferential direction (in the case of a cylindrical cell) or in the horizontal direction (in the case of a planar cell), and this stress causes long-term use or repeated thermal history. Although it is considered that a crack is generated at the interface between the cathode and the solid electrolyte, in the present invention, stress caused by a difference in thermal expansion coefficient due to a change in porosity of the cathode is reduced,
At the same time, it is considered that the generation of cracks at the interface is suppressed due to the high adhesion.

Further, since sintering can be performed at a low temperature in a short time, Mn
On the surface of the air electrode molded body containing, a solid electrolyte molded body,
Even when co-sintering a laminated compact in which the anode compacts are sequentially laminated, the amount of Mn in the air electrode evaporating and diffusing into the anode can be reduced, and the polarization value in the anode can be reduced. Can,
The power density in the initial stage can be improved.

In the solid oxide fuel cell according to the present invention,
It is desirable that the difference in porosity between the low porosity layer formed on the solid electrolyte side of the air electrode and other regions is 0.5% or more. As a result, the output performance can be further improved, and the adhesion between the air electrode and the solid electrolyte can be improved to further improve the durability.

It is desirable that the amount of Mn in the fuel electrode be 0.1% by weight or less. Thereby, the polarization value of the fuel electrode site can be reduced, and the power density in the initial stage can be improved.

Further, in the solid oxide fuel cell of the present invention, the dielectric loss factor of the air electrode at room temperature of 1 to 30 GHz is smaller than the dielectric loss factor of the solid electrolyte,
It is desirable that a perovskite-type composite oxide containing at least La and Mn be used as a main component.

Further, the fuel cell of the present invention comprises a plurality of the above-mentioned solid oxide fuel cells in a reaction vessel.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a typical solid oxide fuel cell of the present invention has a cylindrical solid electrolyte 31 having an air electrode 32 on the inner surface and a fuel electrode 33 on the outer surface.
Is formed to form a cell body 34, and a current collector 35 (interconnector) is electrically connected to the air electrode 32.

That is, the notch 36 is formed in a part of the solid electrolyte 31.
Is formed, a part of the air electrode 32 formed on the inner surface of the solid electrolyte 31 is exposed, and the surface of the solid electrolyte 31 near the exposed surface 37 and the notch 36 is covered with the current collector 35, Current collectors 35 are joined to the surfaces of both ends of the solid electrolyte 31 and the surface of the air electrode 32 exposed from the notch 36 of the solid electrolyte 31.

Current collector 35 electrically connected to air electrode 32
Are formed on the outer surface of the cell body 34 so as to cover the continuous same surface 39 having almost no level difference.
And are not electrically connected. The current collector 35 is electrically connected to the fuel electrode of another cell via Ni felt or the like when connecting the cells, thereby forming a fuel cell module. The continuous same surface 39 is formed by polishing between both ends of the solid electrolyte until both ends of the solid electrolyte and a part of the air electrode become continuous and almost the same surface.

The solid electrolyte 31 is, for example, 3 to 15 mol%
Of partially stabilized or stabilized ZrO ₂ containing Y ₂ O ₃
Is used. With such a composition, 1 to 30 GHz
Has a sufficiently large dielectric loss factor to efficiently absorb microwaves.

As the air electrode 32, La and Mn are used.
By using LaMnO ₃ as a main component, the perovskite-type composite oxide contains a sufficiently low dielectric loss factor as compared with the solid electrolyte, and allows the solid electrolyte to selectively absorb microwaves. At this time, in order to reduce the thermal expansion difference from the solid electrolyte, for example, La of LaMnO ₃ is 10 to 30 atomic% in Ca or Sr, and 5 to 20 atomic% in Y.
Atomic% may be substituted. As the current collector 35, for example,
LaC in which Cr is mainly substituted with 10 to 30 atomic% of Mg
rO ₃ porcelain is used.

As the fuel electrode 33, for example, 50 to 80
A ZrO ₂ (containing Y ₂ O ₃ ) cermet containing wt% Ni is used. Both the current collector and the fuel electrode need to have a sufficiently small dielectric loss factor as compared with the solid electrolyte.

The magnitude of the dielectric loss factor in the present invention can be measured by a known cavity resonator method, cylindrical dielectric resonator method, or the like. Alternatively, it can be simply estimated by irradiating a sample of the same volume with a microwave having a constant output in a microwave heating furnace, and the temperature at which equilibrium is reached. A material having a large temperature rise at that time can be approximately regarded as having a large dielectric loss factor.

In the solid oxide fuel cell of the present invention, the low porosity layer 4 is provided on the solid electrolyte 31 side of the air electrode 32.
3 are formed. This low porosity layer 43 is
The porosity is smaller than that of the other region 45, that is, the portion on the inner surface side of the air electrode 32.

The porosity of the porous air electrode 32 is about 20 to 50%, and preferably 30 to 40% in order to enhance the performance of the fuel cell. The porosity difference between the low porosity layer 43 and the other region 45 is 0.1% for improving durability.
The above is necessary. Particularly, from the viewpoint of improving adhesion and improving durability, 0.5% or more, and further, 0.5 to
Desirably, it is 2.0%.

The thickness of the low porosity layer 43 is desirably 20 μm or more, and desirably 1 to 20% of the thickness of the air electrode 32. Further, it is desirable that the porosity of the low porosity layer 43 gradually increases toward the other region 45 side of the air electrode 32 from the viewpoint of reducing the difference in thermal expansion between the solid electrolyte and the air electrode. Further, most of the pores in the air electrode are open pores.

The dielectric loss factor of the air electrode at room temperature of 1 to 30 GHz is smaller than the dielectric loss factor of the solid electrolyte, and the air electrode is preferably composed mainly of a perovskite-type composite oxide containing at least La and Mn. desirable. The air electrode is not limited to the above example as long as it is mainly composed of a perovskite-type composite oxide containing at least La and Mn.

In the present invention, it is desirable that the amount of Mn in the fuel electrode be 0.1% by weight or less, particularly 0.05% by weight or less, from the viewpoint of reducing the polarization value in the fuel electrode.

The solid oxide fuel cell of the present invention comprises a laminate molded article having a solid electrolyte molded article mainly composed of zirconia on the surface of an air electrode molded article mainly composed of a perovskite composite oxide. It is formed by sintering by irradiating a microwave having a frequency of 1 to 30 GHz.

Specifically, first, a cylindrical air electrode molded body is formed. The cylindrical air electrode molded body is made of, for example, La ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ , Mn according to a predetermined composition.
The raw material of O ₂ is weighed and mixed. At this time, the A / B ratio of the perovskite-type composite oxide constituting the air electrode molded body is:
0.95 to 0.99 is desirable.

Thereafter, for example, the mixture is calcined at a temperature of about 1500 ° C. for 2 to 10 hours, and then pulverized to a particle size of 4 to 8 μm. A binder is mixed and kneaded with the prepared powder to produce a cylindrical air electrode molded body by an extrusion molding method, further debindered, and calcined at 1200 to 1250 ° C. to form a cylindrical air electrode temporary body. Prepare a fired body.

As a sheet-like first solid electrolyte molded body,
A slurry obtained by adding toluene, a binder, and a commercially available dispersant to ZrO ₂ powder containing ₃ to 15 mol% of Y ₂ O ₃ is prepared, for example, by a doctor blade method, for example, to obtain 1 slurry.
Using a molded body having a thickness of 100 to 120 μm, a solid electrolyte molded body is adhered to the surface of the cylindrical air electrode calcined body and calcined, and the first solid electrolyte Form a fired body.

Next, a sheet-shaped fuel electrode molded body is manufactured. First, for example, a slurry prepared by adding toluene and a binder to a Ni / YSZ mixed powder prepared at a predetermined ratio is prepared. Similarly to the production of the first solid electrolyte molded body, the molded body is dried and formed into a sheet-shaped second solid electrolyte molded body having a thickness of, for example, 15 μm.

After printing and drying the fuel electrode layer formed body on the second solid electrolyte formed body, the fuel electrode layer formed body is dried on the first solid electrolyte calcined body.
The second solid electrolyte molded body on which the fuel electrode layer molded body is formed,
The first solid electrolyte calcined body is wound and laminated so that the second solid electrolyte molded body is in contact with the first solid electrolyte calcined body.

The Ni / YSZ mixed powder constituting the fuel electrode layer compact has an average particle diameter of the Ni powder of 0.2 to 0.4 μm,
The raw material powder having an average particle size of YSZ powder of 0.4 to 0.8 μm is used.
The slurry was formed by wet pulverization and mixing using rO ₂ balls.

Next, as in the preparation of the solid electrolyte molded body,
Of LaCrO _{3, which is} substituted with 10 to 30 atomic% of Mg, and molded to a thickness of 100 to 120 μm, is attached to a predetermined position.

Thereafter, the first molded body of the solid electrolyte, the second molded body of the solid electrolyte, the molded body of the fuel electrode, and the molded body of the current collector were laminated on the surface of the calcined body of the cylindrical air electrode in a micro form. Irradiate waves and heat and sinter. As a microwave source,
An oscillation tube such as a magnetron, a klystron, and a gyrotron that can obtain an output of about several kW is used.

The frequency of the microwave used at this time may be 1 to 30 GHz.
It is preferable to use a heating furnace having a 45 GHz or 28 GHz magnetron or gyrotron as an oscillation tube. The frequency is preferably 1 to 30 GHz, and if it is higher than this, it is difficult to control the output, and if it is lower than 1 GHz, the sample itself becomes difficult to be heated. The mechanism of microwave heating is such that dipoles in dielectrics such as ceramics vibrate and rotate with microwaves, and the frictional heat at that time is converted into thermal energy. When the electric field intensity is constant, it depends on the dielectric loss factor (the product of the dielectric constant and the dielectric loss) of the sample.

The laminated molded product is placed in a microwave heating furnace applicator. At this time, it is preferable to use an alumina or magnesia crucible from the viewpoint of suppressing the escape of heat from the surface.

Further, the crucible uses a molded body of alumina fiber having a low thermal conductivity as a heat insulating material. The sample was measured with a thermocouple, and firing conditions were 1300 to 160
Sintering is performed at 0 ° C. for a holding time of 10 minutes to 60 minutes. At this time, if microwave irradiation is continued, the amount of Mn in the fuel electrode tends to increase. Therefore, the condition of microwave heating varies depending on the composition, but the holding time at 1300 to 1600 ° C. is particularly set to 2 hours or less. It is desirable to
It is preferably at 300 to 1500 ° C. for 10 to 60 minutes. In the air electrode heated under such conditions, a low porosity layer is formed from the vicinity of the solid electrolyte, and the porosity becomes inclined, so that high durability is obtained.

Therefore, a material containing zirconia having a large dielectric loss factor as a main component is used for the solid electrolyte, and a material having a smaller dielectric loss factor than the solid electrolyte for the air electrode, that is, a material that is less heated by microwaves, specifically, At least La, Mn
By using a material containing a perovskite-type composite oxide containing as a main component, the solid electrolyte is preferentially heated, and as a result, the temperature of the portion of the air electrode that is in contact with the solid electrolyte is higher than that of the portion that is not in contact For high density,
Adhesion can be improved.

In the above example, a first solid electrolyte calcined body, a second solid electrolyte molded body,
Although the example in which the laminated body obtained by laminating the fuel electrode molded body and the current collector molded body is microwave-fired has been described, in the present invention, the solid electrolyte molded body, the fuel electrode molded body and the current collector are formed on the surface of the air electrode molded body. The laminated molded body obtained by laminating the molded bodies may be subjected to microwave firing.

Further, in the present invention, it is sufficient that the laminate formed by laminating the solid electrolyte molded body on at least the surface of the air electrode molded body is subjected to microwave firing, and the fuel electrode molded body and the current collector molded body are necessarily fired simultaneously. Although it is not necessary, it is desirable to fire four layers of the air electrode, the solid electrolyte, the fuel electrode, and the current collector simultaneously from the viewpoint of cost and reduction in the number of steps.

In the above example, the cylindrical type is described, but the present invention may be a flat type.

For example, as shown in FIG. 2, the fuel cell according to the present invention comprises an oxygen-containing gas chamber partition plate 5 in a reaction vessel 51.
3. Oxygen-containing gas chamber A, combustion chamber B, reaction chamber C, fuel gas chamber D using combustion chamber partition plate 55 and fuel gas chamber partition plate 57.
Are formed.

A plurality of the above-described bottomed cylindrical solid oxide fuel cells 59 are housed in the reaction vessel 51, and these solid oxide fuel cells 59 are formed on the combustion chamber partition plate 55. The opening 61 protrudes from the combustion chamber partition plate 55 into the combustion chamber B, and contains therein the oxygen-containing gas chamber partition plate 53 fixed to the oxygen-containing gas chamber partition plate 53. One end of the gas introduction pipe 63 is inserted.

The combustion chamber partition plate 55 is provided with a plurality of exhaust holes 64 for discharging excess unreacted fuel gas from the reaction chamber C to the combustion chamber B. The fuel gas chamber partition plate 57 has In addition, a supply hole for supplying from the fuel gas chamber D into the reaction chamber C is formed.

The reaction vessel 51 has a fuel gas inlet 65 for introducing a fuel gas made of, for example, hydrogen.
An oxygen-containing gas inlet 67 for introducing air and an outlet 69 for discharging gas burned in the combustion chamber B are formed.

In such a solid oxide fuel cell, the oxygen-containing gas, for example, air from the oxygen-containing gas chamber A is supplied into the solid oxide fuel cell 59 via the oxygen-containing gas introducing pipe 63, respectively. In addition, the fuel gas from the fuel gas chamber D is supplied between the plurality of solid oxide fuel cells 59 and reacted in the reaction chamber C to generate power, and excess air and unreacted fuel gas are burned in the combustion chamber B. Then, the burned gas is discharged to the outside through the exhaust port 69.

The fuel cell of the present invention is not limited to the fuel cell shown in FIG. 2, but it is sufficient that a plurality of the above-mentioned fuel cells are accommodated in a reaction vessel.

[0058]

EXAMPLE A cylindrical air electrode calcined body was molded by extrusion and calcined (La _0.56 Y _0.14 Ca _0.3 ) _0.98 MnO _3.
Was prepared. Using a stabilized zirconia containing Y ₂ O ₃ at a rate of 8 mol% as a solid electrolyte, a 100 μm-thick sheet-shaped first solid electrolyte molded body was further formed by a doctor blade method, and further a 15 μm-thick sheet-shaped. The second solid electrolyte molded bodies were produced.

Next, the production of the fuel electrode molded body will be described. Zr containing 8 mol% of Y ₂ O ₃ having an average particle diameter of 0.6 μm with respect to Ni powder having an average particle diameter of 0.4 μm.
O ₂ powder was prepared and the Ni / YSZ ratio (weight fraction) was 6
The mixture was prepared to be 5/35, crushed and mixed, and slurried. Thereafter, the prepared slurry was printed on the entire surface of the second solid electrolyte molded body so as to have a thickness of 30 μm.

Next, commercially available La _{2 having} a purity of 99.9% or more is used.
Starting from O ₃ , Cr ₂ O ₃ , and MgO, this
(Mg _0.3 Cr _0.7 ) After weighing and mixing to a composition of _0.97 O ₃ , the mixture was calcined and pulverized at 1500 ° C. for 3 hours, a slurry was prepared using the solid solution powder, and a 100 μm-thick current collector was obtained by a doctor blade method. A molded body was produced.

First, the first solid electrolyte molded body was wound around the air electrode calcined body in a roll shape so that both ends were opened, and calcined at 1150 ° C. for 5 hours. After calcining, the first solid electrolyte calcined body was polished flat so as to expose the air electrode calcined body and worked so as to form a continuous same surface.

Next, the second solid electrolyte molded body having the fuel electrode molded body formed thereon is placed on the surface of the first solid electrolyte calcined body so that the first solid electrolyte calcined body and the second solid electrolyte molded body come into contact with each other. After drying, a current collector molded body was attached to the same continuous surface to produce a laminated molded body.

The obtained laminate was placed in an alumina tube crucible, placed in a microwave firing furnace (A, B, C) and a resistance heating furnace (R). And fired. In addition, the temperature measurement of microwave heating
A W-Re thermocouple sheathed with platinum was brought into direct contact with the sample, and was used as a microwave source at a frequency of 2.45 GHz.
z, magnetron (A) with output 5 kW, 6 GHz, 10
Different waveguides were used using a kW klystron (B), 28 GHz, and a 10 kW gyrotron (C).

At the time of heating, only the sample in which 200 first solid electrolyte molded bodies were laminated in advance and the air electrode molded body alone were heated at a constant output of 1.0 kW at a frequency of 28 GHz and heated to 1000 ° C., and the temperature rise at that time The curve is shown in FIG. From FIG. 3, it can be seen that the dielectric loss factor of the solid electrolyte zirconia is larger than that of the LaMnO ₃ air electrode.

The thickness of the air electrode of the obtained cell was 2 mm, and the thickness of the solid electrolyte was 100 μm. A part of this sintered body is cut, and a section thereof is taken with a scanning electron microscope (SE).
M) The porosity of the photograph was calculated using an image analyzer. The measurement was performed over a portion of 0.1 mm from the surface of the air electrode on the solid electrolyte side and a portion of 0.1 to 0.2 mm from the inner surface of the air electrode over a width of 0.1 mm. The results are shown in Table 1. FIG. FIG. 4 (b) shows an SEM photograph in the vicinity of a range of 0.1 mm from the surface on the solid electrolyte side of the air electrode of FIG.
An SEM photograph near the range of 1 to 0.2 mm was shown.

Using the above co-sintered body, the amount of Mn diffusion in the fuel electrode was evaluated. The evaluation was performed using X
Using a line microanalyzer (EPMA), all the constituent components were quantified, and from this, the concentration of the Mn component with respect to all the fuel electrode components was calculated, and the results are shown in Table 1.

Further, from the SEM photograph of the sample of the present invention,
When the porosity was measured at a pitch of 0.1 mm from the surface of the cathode on the solid electrolyte side, the thickness of the low porosity layer was 20 μm or more, and the porosity of the low porosity layer gradually increased toward the inner surface of the cathode. Had become. In Table 1, the sample No. The porosity at 12 is shown in FIG. 5 that the thickness of the low porosity layer is 0.4 mm, which is 20% of the thickness of the air electrode.

Next, in order to manufacture a cylindrical cell for power generation, a sealing member was joined to one end of the co-sintered body. The joining of the sealing member was performed in the following procedure. ZrO containing Y ₂ O ₃ at a ratio of 8 mol% and having an average particle size of 1 μm
_{(2) A} slurry was prepared by adding water to the powder as a solvent, and one end of the co-sintered body was immersed in the slurry to a thickness of 100
It was applied to the outer peripheral surface at one end to a thickness of μm and dried. A molded body having a cap shape as a sealing member was subjected to isostatic pressing (rubber pressing) using a powder having the same composition as the slurry composition, and was cut. Thereafter, one end of the co-sintered body coated with the slurry was inserted into a molding for a sealing member, and baked at a temperature of 1300 ° C. for 1 hour in the atmosphere.

For power generation, air was flowed inside the cell and hydrogen was flown outside at 1000 ° C., and the performance was measured and evaluated based on the initial value when the output value was stabilized and the value after holding for 1000 hours. The sample whose output value was stabilized after further holding for 1000 hours was then cooled to room temperature, and then again generated to measure the output density. Table 1 shows the measurement results.

[0070]

[Table 1]

As shown in Table 1, in the conventional firing method using the resistance heating furnace, the sample No. 60 at 1450 ° C as in 1.
In the case of baking for 0 minutes, the current collector was insufficiently densified, and the air electrode was accelerated, and the re-output value was reduced.

The sample No. In the case of baking at 1550 ° C. for 360 minutes as in 2, Mn in the air electrode diffuses as much as 0.49% by weight in the fuel electrode, the polarization value of the fuel electrode increases, the initial performance is low, and It can be seen that the deterioration also occurs.

On the other hand, in the sample of the present invention fired by microwave, a low porosity layer having a smaller porosity than other regions of the air electrode is formed on the solid electrolyte side of the air electrode, and Mn in the fuel electrode is formed. Since the amount is as small as 0.1% by weight or less, the polarization value of the fuel electrode is low. As a result, a high output density is obtained at the initial value, and a high output is obtained even after 1000 hours and at the time of re-generation. Density was obtained.

[0074]

The solid oxide fuel cell of the present invention can be co-sintered in a short time at a low temperature by using a microwave heating method and using a material having a smaller microwave absorption characteristic than the solid electrolyte for the air electrode. , On the solid electrolyte side of the air electrode,
A low porosity layer having a smaller porosity than other regions of the cathode is formed, the amount of Mn diffused into the anode can be reduced, the polarization value of the anode can be reduced, and the initial performance can be improved. Even when used repeatedly, a solid oxide fuel cell having excellent power generation efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a cylindrical solid oxide fuel cell according to the present invention.

FIG. 2 is a conceptual diagram showing a fuel cell of the present invention.

FIG. 3 is a graph showing a temperature rise when microwaves are constantly irradiated to a solid electrolyte and an air electrode.

FIG. 3 shows an SEM photograph.

FIG. 12 is a diagram showing porosity with respect to distance from the surface of the air electrode 12 on the solid electrolyte side. FIG.

FIG. 6 is a perspective view showing a conventional cylindrical solid oxide fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel electrode 43 ... Low porosity layer 45 ... Other area of an air electrode 51 ... Reaction vessel 59 ... Solid electrolyte type fuel Battery cell

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H018 AA06 AS02 AS03 BB01 CC03 EE13 HH04 HH05 HH06 5H026 AA06 BB00 BB01 CV02 EE13 HH04 HH05 HH06

Claims (6)

[Claims] 1. A solid electrolyte fuel cell comprising a manganese-containing air electrode and a zirconia-based solid electrolyte and a fuel electrode sequentially laminated on the surface of the Mn-containing air electrode, wherein the solid electrolyte side of the air electrode is on the solid electrolyte side. And a low porosity layer having a lower porosity than other regions of the air electrode. 2. The porosity difference between the low porosity layer formed on the solid electrolyte side of the air electrode and other regions of the air electrode is 0.5%.
2. The solid oxide fuel cell according to claim 1, wherein: 3. The solid oxide fuel cell according to claim 1, wherein the amount of Mn in the fuel electrode is 0.1% by weight or less. 4. The solid oxide fuel cell according to claim 1, wherein the air electrode mainly comprises a perovskite-type composite oxide containing at least La and Mn. 5. A laminated molded article comprising a solid electrolyte molded article containing zirconia as a main component is irradiated on a surface of an air electrode molded article containing Mn by irradiating a microwave having a frequency of 1 to 30 GHz. A method for producing a solid oxide fuel cell unit, comprising: 6. A fuel cell comprising a plurality of solid oxide fuel cells according to claim 1 in a reaction vessel.