JPH1186885A - Cell of solid electrolyte fuel cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell of a solid electrolyte fuel cell, having a solid electrolyte which does not generate an insulating material while having high denseness, and a manufacturing method therefor. SOLUTION: A fuel electrode 2 is arranged by applying slurry of a material of the fuel electrode 2 on an outer peripheral surface of a base body 1, and after a fuel electrode side solid electrolyte 3a is arranged by applying slurry of a material mainly composed of zirconia on an outer peripheral surface of the fuel electrode 2, an intermediate solid electrolyte 3b is arranged by applying slurry by adding 3 to 5 wt.% of an oxidizing agent, composed of at least either one of Al2 O3 or Bi2 O3 to a material composed mainly of zirconia on an outer peripheral surface of the fuel electrode side solid electrolyte 3a. Then, an air electrode 4 is arranged by applying slurry of a material of the air electrode 4 and is baked at a temperature of less than 1400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cell of a solid oxide fuel cell and a method for producing the same.

[0002]

2. Description of the Related Art A solid electrolyte fuel cell includes a cell in which a solid electrolyte made of a material containing zirconia as a main component is disposed on a porous substrate sandwiched between a porous air electrode and a fuel electrode. Has become.

Such a cell comprises an anode, a solid electrolyte,
It is manufactured by applying a slurry of each raw material such as an air electrode on a substrate and then sintering (1400 to 1500 ° C.) to form a film (slurry integrated sintering method).

In a solid oxide fuel cell using such a cell, for example, when a fuel electrode side is provided on a substrate, an oxidizing gas such as air or oxygen flows through the outside of the substrate, and hydrogen flows inside the substrate. When the temperature is increased to about 800 to 1000 ° C. while flowing a fuel gas such as methane or methane, the fuel gas passes through the base and the fuel electrode, and the oxidizing gas passes through the air electrode. React electrochemically to generate electric power.

[0005]

In the solid oxide fuel cell as described above, the higher the operating voltage at the rated current value, the better. The operating voltage E is a value obtained by subtracting the voltage drop ΔV due to the internal resistance of the cell from the open circuit voltage V _oc as shown in the following equation (1).

[0006]

E = V _oc −ΔV (1)

Therefore, the operating voltage, that is, the operation of the cell
To improve the voltage, reduce the above-mentioned voltage drop
In addition, it is necessary to increase the open circuit voltage. This opening
The circuit voltage (OCV) is expressed by the following equation (2).
And the oxygen partial pressure P in the oxidizing gas _O1(Atm) and in fuel gas
Oxygen partial pressure P_o2(Atm) and operating temperature T
(K).

[0008]

V _oc = (RT / 4F) × ln (P _O1 / P _o2 ) (2) where R is a gas constant and F is a Faraday constant.

Therefore, for example, if the oxidizing gas on the oxidizing electrode side of the cell leaks into the fuel gas on the fuel electrode side, the oxygen partial pressure in the fuel gas increases, and the open circuit voltage decreases. I will. In such a cell, since the gas is most likely to leak in the solid electrolyte portion having the largest occupied area, it is necessary to reduce the amount of gas leakage by making the solid electrolyte dense.

Therefore, as described above, one solid electrolyte made of a hardly sinterable material containing zirconia as a main component is used.
Although the solid electrolyte is densified by firing at a high temperature of 400 ° C. or higher,
When firing at the above high temperature, there is a possibility that a chemical reaction occurs with other materials such as a fuel electrode and an air electrode to generate an insulator.

In view of the above, an object of the present invention is to provide a cell of a solid oxide fuel cell having a solid electrolyte which has high density and does not generate an insulator, and a method of manufacturing the same. did.

[0012]

Means for Solving the Problems To solve the above-mentioned problems, a solid oxide fuel cell according to the present invention comprises:
A cell of a solid oxide fuel cell having a solid electrolyte sandwiched between a fuel electrode and an air electrode and provided on a substrate, wherein an oxidizing agent comprising at least one of Al ₂ O _{3 and} Bi ₂ O ₃ is used as the solid electrolyte. It is characterized by being contained in.

[0013] In the above-mentioned cell of the solid oxide fuel cell, the solid electrolyte is provided on the fuel electrode side on the fuel electrode side, the air electrode side solid electrolyte provided on the air electrode side, and It comprises an intermediate solid electrolyte provided between the electrode-side solid electrolyte and the air electrode-side solid electrolyte, wherein the intermediate solid electrolyte contains the oxidizing agent.

In the above-mentioned solid oxide fuel cell, the oxidizing agent is contained in an amount of 3 to 5% by weight.

[0015] Further, a method for manufacturing a cell of a solid oxide fuel cell according to the present invention, which solves the above-mentioned problems, comprises:
A cell of a solid oxide fuel cell in which the solid electrolyte, the fuel electrode, and the slurry of the air electrode are applied to the substrate and sintered integrally so that the solid electrolyte is provided on the substrate sandwiched between the fuel electrode and the air electrode. The method for producing Al ₂ O ₃ or B
A slurry of the solid electrolyte to which an oxidizing agent composed of at least one of i ₂ O ₃ is added is applied and sintered integrally at a temperature of less than 1400 ° C.

In the above-mentioned method for manufacturing a cell of a solid oxide fuel cell, before and after applying the slurry of the solid electrolyte to which the oxidizing agent is added, the slurry of the solid electrolyte to which the oxidizing agent is not added is applied. It is characterized by.

In the above-described method for manufacturing a cell of a solid oxide fuel cell, the amount of the oxidizing agent is 3 to 5 wt%.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a solid oxide fuel cell according to the present invention and a method for manufacturing the same will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of the cell.

As shown in FIG. 1, a porous material having a cylindrical shape
A porous fuel electrode 2 is formed on the outer peripheral surface of the base 1.
ing. Zirconia is the main component on the outer peripheral surface of the fuel electrode 2.
Of the fuel electrode side solid electrolyte 3a made of
ing. Zircon is provided on the outer peripheral surface of the fuel electrode side solid electrolyte 3a.
Al as a material mainly containing near_TwoO_ThreeOr Bi_TwoO _Three
An oxidizing agent consisting of at least one of
The added intermediate solid electrolyte 3b is deposited. Intermediate solid
On the outer peripheral surface of the electrolyte 3b, the fuel electrode side solid electrolyte 3a
The air electrode side solid electrolyte 3c made of the same material as
Have been. On the outer peripheral surface of the air electrode side solid electrolyte 3c, air
The pole 4 is formed.

That is, a solid electrolyte comprising the intermediate solid electrolyte 3b sandwiched between the fuel electrode side solid electrolyte 3a and the air electrode side solid electrolyte 3c is sandwiched between the fuel electrode 2 and the air electrode 4, and the fuel electrode 2 is placed on the substrate 1 side. It was provided so as to be positioned.

In such a cell, a slurry of a material for the fuel electrode 2 is applied on the outer circumferential surface of the base 1 to provide the fuel electrode 2, and a slurry of a material containing zirconia as a main component is coated on the outer circumferential surface of the fuel electrode 2. The solid electrolyte 3a provided on the anode is coated with a slurry obtained by adding 3 to 5% by weight of the oxidizing agent to a material containing zirconia as a main component. After the electrolyte 3b is provided, a slurry of a material containing zirconia as a main component is applied on the outer peripheral surface of the intermediate solid electrolyte 3b to provide the cathode-side solid electrolyte 3c, and then, a slurry of the material of the cathode 4 is applied. And the air electrode 4 is provided.
It can be easily obtained by firing at a temperature lower than 00 ° C.

That is, before and after the slurry of the solid electrolyte to which the oxidizing agent is added (the intermediate solid electrolyte 3b), the solid electrolyte to which the oxidizing agent is not added (the fuel electrode side solid electrolyte 3a and the air electrode side solid electrolyte 3c) is formed. The solid electrolyte is formed by applying the slurry.

Here, since the oxidizing agent is added to the intermediate solid electrolyte 3b, sintering of the material containing zirconia as a main component can be promoted. Densification of the solid electrolyte 3b can be achieved. Further, a fuel electrode-side solid electrolyte 3a to which no oxidizing agent is added is provided between the fuel electrode 2 and the intermediate solid electrolyte 3b, and an air electrode-side solid electrolyte 3c to which no oxidizing agent is added is provided between the fuel electrode 2 and the air electrode 4. Since it is provided between the solid electrolyte 3b, the flow and volatilization of the oxidizing agent during firing can be suppressed, and a decrease in sinterability can be prevented.

Therefore, it is possible to obtain a cell having a high density and a solid electrolyte in which the generation of an insulator is suppressed, so that the oxidizing gas on the oxidation electrode side leaks into the fuel gas on the fuel electrode side. Can be prevented, and the open circuit voltage (OCV) can be increased to improve the operating voltage.

In the present embodiment, the cell of the solid electrolyte type fuel cell in which the fuel electrode 2 is provided on the base 1 side has been described. However, the solid electrolyte type fuel cell in which the air electrode 4 is provided on the base 1 side. The same effect as in the above case can be obtained in the fuel cell.

[0026]

EXAMPLES In order to confirm the effects of the cells of the solid oxide fuel cell according to the present invention and the method of manufacturing the same, a confirmation test based on the above-described embodiment was performed as follows.

<< Adjustment of Cell Materials >> [Base Tube] A porous tube made of ZrO ₂ -13 mol% CaO and having a length of 50 mm, an outer diameter of 21 mm and an inner diameter of 17 mm was prepared.

[Slurry of fuel electrode] NiO and YSZ (Zr
O ₂ -8 mol% Y ₂ O ₃ ) is mixed at a weight ratio of 60:40, and the mixed powder is mixed with ethanol and ethylene glycol at a weight ratio of 80:10:10 to form a paste. Shape.

[Slurry of air electrode] Lanthanum oxide, strontium carbonate and manganese carbonate are mixed at a predetermined ratio and fired at 1400 ° C. for 5 hours, and then pulverized with a ball mill to have a center particle diameter of 0.3 to 0.5 μm. La _0.9 Sr _0.1 MnO
After powder ₃ was obtained, the powder and turpentine oil were mixed at a weight ratio of 80:20.

[Slurry of Fuel Electrode Side Solid Electrolyte and Air Electrode Side Solid Electrolyte] YSZ (ZrO ₂ -8 mol% Y ₂ O)
₃ ) and ethanol were mixed at a weight ratio of 60:40.

[Slurry of Intermediate Solid Electrolyte] YSZ (Zr
An oxidizing agent (two kinds of Al ₂ O ₃ or Bi ₂ O ₃ ) is added to O ₂ -8 mol% Y ₂ O ₃ ) at a predetermined ratio (0, 1, ₃ , 5 w).
(four types of t%) (total eight types), distilled water was added and mixed with a ball mill. After the distilled water was evaporated with a dryer, the powder and ethanol were mixed at a weight ratio of 60:40. Mix in proportions.

<< Production of Cell >> A slurry of a fuel electrode is applied on the outer peripheral surface of the base tube in a thickness of about 100 μm and a length of 30 mm,
After drying at 100 ° C. for 2 hours to provide the fuel electrode, a slurry of the fuel electrode side solid electrolyte is sprayed on the fuel electrode by air spray using compressed air to provide a fuel electrode side solid electrolyte having a thickness of about 20 μm and a length of 10 mm, Spray the slurry of the intermediate solid electrolyte on the fuel electrode side solid electrolyte in the same manner as described above to provide an intermediate solid electrolyte having the same size as the above, and on the intermediate solid electrolyte, slurry the air electrode side solid electrolyte on the intermediate solid electrolyte as described above. After providing an air electrode side solid electrolyte having the same size as the above, a slurry of an air electrode was applied on the air electrode side solid electrolyte with a metal spatula to a thickness of about 300 μm and a length of 10 mm. Then, by firing at 1350 ° C. for 5 hours in the air and integrating them, cells having different types and amounts of oxidizing agents of the intermediate solid electrolyte were manufactured (eight types in total).

<< Test Method >> The gas leakage characteristics of each cell (eight kinds in total) manufactured as described above were evaluated by measuring the open circuit voltage (OCV). OC
FIG. 2 shows a schematic configuration of the test apparatus used for the measurement of V.

As shown in FIG. 2, around the cylindrical container 11, an electric furnace 12 for heating the inside of the container 11 is provided. Below the inside of the cylindrical container 11, a cylindrical support 13 is inserted penetrating coaxially with the container 11.
On the cylindrical support 13, a zirconia support tube 14 stands upright coaxially with the support 13. Cylindrical support 1
An introduction tube 15 is inserted through the lower portion of the cylindrical support 13 into the zirconia support tube 3 and the zirconia support tube 14. An air mass flow 16 for supplying dry air into the container 11 is connected to an upper portion of the cylindrical container 11. Introductory pipe 1
5, a hydrogen gas mass flow 17 for supplying hydrogen gas and a nitrogen gas mass flow 18 for supplying nitrogen gas are provided.
Are connected via a humidifier 19. One end of an exhaust pipe 20 is connected near the lower peripheral edge of the cylindrical container 11. The other end of the exhaust pipe 20 communicates with the outside via a drain pot 22 and a water seal pot 24. One end of an exhaust pipe 21 is connected to the lower side of the introduction pipe 15. The other end of the exhaust pipe 21 communicates with the outside via a drain pot 23 and a water seal pot 25.

In such a test apparatus, the cell 10 is mounted on the zirconia support tube 14 with the fixture 2 made of Pyrex glass.
6 and a platinum wire is attached to the air electrode and the fuel electrode of the cell 10 and connected to a voltage measuring device (not shown). Then, the electric furnace 12 is operated to heat the inside of the cylindrical container 11 at a predetermined speed (100 ° C. / h) Then, when the temperature reaches a predetermined temperature (1000 ° C.), the air mass flow 16 is operated to supply dry air into the cylindrical container 11 at a predetermined flow rate (500 cc / min), so that the outer peripheral surface of the cell 10, that is, While the air is circulated to the air electrode side, the hydrogen gas mass flow 16 and the nitrogen gas mass flow 17 are operated to dilute the hydrogen gas into a humidifier 19.
A predetermined flow rate (100 cc)
/ Min) to allow hydrogen gas to flow through the inner peripheral surface of the cell 10, that is, the fuel electrode side, and cause oxygen and hydrogen gas in the air to undergo an electrochemical reaction in the cell 10 portion. The open circuit voltage (OCV) is measured, and the magnitude thereof allows the gas leak characteristics of the cell 10 to be evaluated. The air used for power generation in the cell 10 is discharged from the exhaust pipe 20 to the outside via the drain pot 22 and the water sealing pot 24. The hydrogen gas and the nitrogen gas used for power generation in the cell 10 are discharged from the exhaust pipe 20. 21 to drain pot 23
And the water is discharged to the outside through the water seal pot 25.

Based on the test apparatus and test method as described above, the OCV of each cell was measured. The result is shown in FIG.
Shown in

As can be seen from FIG. 3, in the cell where the oxidizing agent is not added to the intermediate solid electrolyte, the OCV value is about 1.0.
9V, which was about 91% of the theoretical OCV value (about 1.195 V). On the other hand, in the cell in which the oxidizing agent was added to the intermediate solid electrolyte at 1 wt%, the OCV value was 1.11 to 11.
1.13 V, which is about 93 to 9 with respect to the theoretical OCV value.
Up to 5%, 3 ~ 5wt% oxidizing agent in the intermediate solid electrolyte
In the added cell, the OCV value was 1.17 to 1.19, which was about 98 to 99.6% of the theoretical OCV value.

From the above results, it was confirmed that when the oxidizing agent was added in an amount of 3 to 5% by weight, the theoretical OCV value could be made almost equal to the theoretical OCV value, so that the solid electrolyte could be densified to prevent gas leakage.

[0039]

Solid oxide fuel cell of the cell according to the present invention exhibits, a solid electrolyte or a solid electrolyte fuel cell of a cell provided on a substrate by being sandwiched between a fuel electrode and an air electrode, Al ₂ O
_{Since the} solid electrolyte contains an oxidizing agent consisting of at least one of _{3 and} Bi ₂ O _3, the cell has a solid electrolyte that has high density and suppresses generation of an insulator. Therefore, it is possible to prevent the oxidizing gas on the oxidizing electrode side from leaking into the fuel gas on the fuel electrode side, and it is possible to increase the open circuit voltage (OCV) and improve the operating voltage. .

Further, the solid electrolyte is provided on the fuel electrode side, the fuel electrode side solid electrolyte, the air electrode side solid electrolyte provided on the air electrode side, the fuel electrode side solid electrolyte, and the air electrode side. It is composed of an intermediate solid electrolyte provided between the solid electrolyte and the solid electrolyte, and the intermediate solid electrolyte contains the oxidizing agent. Since the lowering is prevented, the above-described effects can be obtained more reliably.

Further, if the oxidizing agent is contained at 3 to 5 wt%, the above-mentioned effects can be more reliably obtained.

The method of manufacturing a cell of a solid oxide fuel cell according to the present invention is characterized in that the solid electrolyte, the fuel electrode, and the slurry of the air electrode are provided on a substrate sandwiched between the fuel electrode and the air electrode. Is applied to the substrate and integrally sintered, the method comprising the steps of:
₂ O ₃ or Bi ₂ O ₃ slurry of the solid electrolyte which is added an oxidizing agent consisting of at least one of the coating, since the integrally sintered at a temperature below 1400 ° C., the solid electrolyte by an oxidant baked Can promote
Even if firing is performed at a temperature of less than 400 ° C., the solid electrolyte can be densified, so that a cell having a solid electrolyte with high density and suppressed generation of an insulator can be obtained. As a result, the oxidizing gas on the oxidizing electrode side can be prevented from leaking into the fuel gas on the fuel electrode side, and the operating voltage can be improved by increasing the open circuit voltage (OCV).

Further, before and after applying the slurry of the solid electrolyte to which the oxidizing agent is added, the slurry of the solid electrolyte to which the oxidizing agent is not added is applied. Thus, the sinterability can be prevented from lowering.

When the amount of the oxidizing agent is 3 to 5% by weight, the above-described effects can be obtained more reliably.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a cell of a solid oxide fuel cell according to the present invention.

FIG. 2 is a schematic configuration diagram of a test device used for a confirmation test.

FIG. 3 is a graph showing a confirmation test result.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Fuel electrode 3a Fuel electrode side solid electrolyte 3b Intermediate solid electrolyte 3c Air electrode side solid electrolyte 4 Air electrode 10 Cell 11 Cylindrical container 12 Electric furnace 13 Cylindrical support stand 14 Zirconia support pipe 15 Introducing pipe 16 Air mass flow 17 Hydrogen gas mass flow 18 Nitrogen gas mass flow 19 Humidifier 20, 21 Exhaust pipe 22, 23 Drain pot 24, 25 Water seal pot 26 Fixture

Claims (6)

[Claims] 1. A cell of a solid oxide fuel cell having a solid electrolyte sandwiched between a fuel electrode and an air electrode and provided on a substrate,
Al ₂ O ₃ or Bi ₂ solid oxide fuel cell of a cell made of at least one oxidizing agent, characterized in that it is contained in the solid electrolyte of the O _3. 2. The solid electrolyte fuel cell according to claim 1, wherein the solid electrolyte is provided on the fuel electrode side and the fuel electrode side solid electrolyte is provided on the air electrode side. A solid electrolyte comprising: a solid electrolyte; an intermediate solid electrolyte provided between the fuel electrode-side solid electrolyte and the air electrode-side solid electrolyte, wherein the intermediate solid electrolyte contains the oxidizing agent. Electrolyte fuel cell. 3. The cell of a solid oxide fuel cell according to claim 1, wherein the oxidizing agent is contained in an amount of 3 to 5% by weight. 4. A solid electrolyte in which the solid electrolyte, the fuel electrode, and the slurry of the air electrode are applied to the substrate and sintered integrally so that the solid electrolyte is provided on the substrate sandwiched between the fuel electrode and the air electrode. A method of manufacturing a cell of a fuel cell, comprising:
₂ O ₃ or Bi ₂ O ₃ slurry of the solid electrolyte which is added an oxidizing agent consisting of at least one of the coating, the solid electrolyte type fuel cell, characterized by integrally sintering at temperatures below 1400 ° C. Cell manufacturing method. 5. The method for producing a cell of a solid oxide fuel cell according to claim 4, wherein the solid electrolyte to which the oxidizing agent is not added before and after applying the slurry of the solid electrolyte to which the oxidizing agent is added. A method for producing a cell of a solid oxide fuel cell, comprising applying a slurry. 6. The cell for a solid oxide fuel cell according to claim 4, wherein the amount of the oxidizing agent is 3 to 5 wt%. Manufacturing method.