JP2001351646A - LaGaO3 SOLID ELECTROLYTE FUEL CELL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell that has a high generating performance and a longtime stability using LaGaO3 material in the solid electrolyte layer of the solid electrolyte fuel cell. SOLUTION: The solid electrolyte layer 6 is made of a sintered body of La0.9Sr0.1Ga0.8Mg0.2O2.85 of a thickness of 0.2 mm and is formed of SDC film 10 having a composition of Ce0.8Sm0.2O1.90 on its surface. On one face of the solid electrolyte layer 6, a fuel pole 4 made of Ni/CeYSZ/SDC (Ce0.9Sm0.1O1.95) is formed through SDC film 10 and on the other face an air pole made of La0.6 Sr0.4Co0.2Fe0.8O3 is made through SDC film 10. Even if a LaGaO3 material is used for the solid electrolyte layer, reaction between the solid electrolyte and the fuel pole or the air pole do not occur and a high performance and long time stabilized generation is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a solid oxide fuel cell, particularly to high LaGaO ₃ based solid electrolyte fuel cell power generation performance using LaGaO ₃ type material in the solid electrolyte layer.

[0002]

2. Description of the Related Art A solid oxide fuel cell has a relatively high operating temperature of 700 to 1000 ° C. among fuel cells, so that various fuels can be used, power generation efficiency is high, and all are made of solid materials. Therefore, it has advantages such as easy handling, and is attracting attention as a new energy source from the viewpoint of resource saving and the impact on the environment, and research and development for practical use are being promoted.

[0003] A solid oxide fuel cell is a unit cell comprising a solid electrolyte layer, a fuel electrode provided on one surface of the solid electrolyte layer, and an air electrode provided on the opposite surface.
An electric power supply is generated by supplying a fuel gas such as hydrogen to the fuel electrode and an oxidizing gas such as air to the air electrode.

The solid electrolyte layer is mainly composed of 8YSZ (YSZ:
Stabilized zirconia doped with 8 mol% of yttria),
Alternatively, the air electrode is made of LaYSr or the like.
MnO ₃ (referred to as LSM) is used as a typical material, and a material in which La in the LSM is replaced by another element or a Co-based material in which Mn is replaced by Co has been proposed. The fuel electrode is made of a material typified by Ni / YSZ cermet or the like.

[0005] For the air electrode or the fuel electrode, for example, a material to be a fuel electrode is first applied to one surface of the solid electrolyte layer, baked at a high temperature of about 1450 ° C, and then the material for the air electrode is applied to the opposite surface. And formed by firing at a low temperature of about 1150 ° C.
Thus, an interface is formed between the air electrode and the solid electrolyte layer, and between the fuel electrode and the solid electrolyte layer.

In recent years, using materials LaGaO ₃ based on the solid electrolyte layer, LaGaO ₃ aimed at realization of low-temperature activation
Attention has been focused on the development of a solid oxide fuel cell.

[0007]

However, a solid electrolyte fuel cell using a LaGaO ₃ -based oxide for the solid electrolyte layer has the following disadvantages.

That is, since the LaGaO ₃ -based electrolyte material has a high reactivity with a commonly used fuel electrode material such as NiO or YSZ, a reaction layer is formed at the interface between the fuel electrode and the solid electrolyte layer during firing of the fuel electrode. Performance is reduced.

When metallic Ni is used as a fuel electrode raw material in order to prevent reaction with NiO or YSZ, N
It is necessary to sinter in a reducing atmosphere so as not to produce iO, which increases the production cost and also causes sintering of Ni to progress with time during power generation, resulting in a problem of deterioration of the fuel electrode.

The present invention has been made in view of the above points, and provides a LaGaO ₃ -based solid electrolyte fuel cell having improved performance and durability using a LaGaO ₃ -based material for a solid electrolyte layer. The purpose is to:

[0011]

Accordingly, in the present invention, a LaGaO ₃ -based solid oxide fuel cell is constructed as follows in order to solve the above-mentioned problems. That is, a LaGaO ₃ material is used for a solid electrolyte layer of a solid oxide fuel cell,
A doped ceria film was formed between the solid electrolyte layer and the fuel electrode.

By providing the doped ceria film between the solid electrolyte layer and the fuel electrode, the LaGaO
_{Even when a three-} system material is used for the solid electrolyte layer, no reaction occurs between the solid electrolyte layer and YSZ or NiO as a fuel electrode raw material, so that high performance and stable performance over a long period of time can be maintained, and the solid electrolyte layer can be maintained. High performance due to the use of a LaGaO ₃ -based material.

Specifically, La is used as a solid electrolyte layer.
_1-x Sr _x Ga _1-y Mg _y O ₃ (0.05 <x <
0.5, 0.05 <y <0.5), preferably La
_0.9 Sr _{0. 1} Ga _0.8 Mg _0.2 O ₃ is used.
When x is 0.05 or less, the effect of doping Sr is small,
If it is more than 0.5, the characteristics will deteriorate. When y is 0.05 or less, the effect of doping with Mg is small, and when y is 0.5 or more, the characteristics deteriorate.

As the doped ceria film, Ce
_1-zM_zO_d(M is trivalent rare earth, 0.05 ≦ z ≦
0.5, d = 2-0.5z), M is the most ion
Highly conductive Ce_1-zM_zO_dGd or
Sm, for example, Ce_0.8Sm _0.2O_1.9age
Was. When z is 0.05 or less, the effect of doping M is small.
Above 0.5, oxygen ion conductivity decreases.
U.

In the case of such a configuration, the fuel electrode
The commonly used Ni (O) -YSZ cermet can be selected. To further improve low-temperature performance, N
It is composed of iO, CeYSZ, and ceria oxide doped with Samaria, for example, Ce _0.9 Sm _0.1 O _1.95 . Further, for example, Gd may be used instead of Sm. At this time, the particle size of the Ni particles is preferably about 2 μm, and the volume ratio of the Ni particles to the entire cermet is preferably about 0.6.

The cathode is made of a known electrode material, for example, La.
_0.6 Sr _0.4 Co _0.2 Fe _{0 . 8} O ₃ (LSC
F) can be used, and a doped ceria oxide may be dispersed in the air electrode.

In the present invention, a doped ceria film is formed between the solid electrolyte layer and the air electrode. As a result, the polarization resistance of the air electrode can be reduced, and the performance of the battery can be further improved. As a doped ceria film, Ce _1-z M _z O _d (M
Is a trivalent rare earth element, 0.05 ≦ z ≦ 0.5, d = 2-0.
5z) As M, Ce has the highest ionic conductivity.
A _1-z M _{z O d} give Gd or Sm, such as _Ce 0.8 _Sm 0.2 _{O 1.9.}

[0018]

Next, the LaGaO according to the present invention will be described.
An embodiment of a _three- system solid oxide fuel cell (flat solid electrolyte fuel cell) will be described.

The solid oxide fuel cell comprises a separator (not shown) as an interconnector and a unit cell 2. The unit cell 2 has a fuel electrode 4 as shown in FIG.
, A solid electrolyte layer 6 and an air electrode 8, and a fuel electrode 4 and an air electrode 8 are formed on the front and back of the solid electrolyte layer 6, respectively. The solid electrolyte layer 6 is made of a LaGaO ₃ -based material, and SDC (Ce _0.8 Sm _0.2 O
_1.9 ) The film 10 is formed.

The solid electrolyte layer 6 is made of, for example, La_0.9Sr
_0.1Ga_0.8Mg_0.2O_{2. 85}Alumina 2
It is a sintered body obtained by adding W% and sintering. The SDC film 10
Ce _0.8Sm_0.2O_1.9Powder (1-2 μm)
The solid electrolyte layer 6 is dispersed in ethanol and the solution is dispersed in the ethanol.
After dipping and lifting, it is formed by firing at about 1250 ° C.
You.

One surface of the solid electrolyte layer 6 is Ni / CeYS.
The fuel electrode 4 made of Z / SDC (Ce _0.9 Sm _0.1 O _1.95 ) is formed via the SDC film 10.

The fuel electrode 4 is prepared by, for example, crushing and mixing SDC powder and NiO powder to a predetermined size with a ball mill, further adding a toluene solution of octylic acid of Ce, Zr and Y, hydrolyzing, and screen A predetermined thickness is applied on the SDC film 10 by a printing method or the like, and after being applied, it is formed by firing at about 1350 ° C. With such a configuration, the oxide component in the fuel electrode 4 has high ionic conductivity and electronic conductivity.

The air electrode 8 is made of La _0.6 Sr _0.4 Co
_0.2 Fe _0.8 O ₃ and is formed on the surface of the solid electrolyte layer 6 opposite to the fuel electrode 4 via the SDC film 10.

The air electrode 8 is, for example, La _0.6 Sr
A powder of _0.4 Co _0.2 Fe _0.8 O ₃ (LSCF) is dispersed in hexylene glycol, and the solution is applied on the SDC film 10 by a screen printing method or the like, and 1100 ° C.
For 4 hours.

The Ce of the fuel electrode 4_0.9Sm_0.1O
_1.95To Ce_0.8Sm_0.2O _1.9As well
And the air electrode 8 is Pr_0.6Sr_0.4MnO₃When
Ce_{0 . 8}Sm_0.2O_1.90Formed of composite
May be.

By constituting the cell 2 in this manner, the solid electrolyte layer 6 is formed from a LaGaO ₃ -based material having high performance, and the fuel electrode 4 and the solid electrolyte layer 6 and the air electrode 8 and the solid electrolyte layer 6 are formed. Is formed between the solid electrolyte layer 6 and the raw material of the fuel electrode 4 or the air electrode 8 without causing a reaction between the solid electrolyte layer 6 and the LaGaO layer that can maintain stable and high performance for a long time. _{A three-} system solid oxide fuel cell can be formed.

The SDC film 10 is formed at least between the fuel electrode 4 and the solid electrolyte layer 6 so that the fuel electrode 4
The reaction with metal oxides and the like in the inside can be prevented, and high performance and long-term stable performance can be maintained.

Further, by appropriately mixing the SDC powder into the fuel electrode 4 and the air electrode 8, improvement in long-term stability and improvement in electrode performance can be expected.

(Experimental Example) Hereinafter, an experimental example of a LaGaO ₃ -based solid oxide fuel cell will be described.

In the experiment, a unit cell was manufactured as follows.

That is, the solid electrolyte layer is made of La _0.9 S
r _0.1 Ga _0.8 Mg _0.2 O _{2 .} Sintered ₈₅ 6
cm sintered body, SDC film on both sides 0.2μ
m. The SDC membrane is made of Ce in ethanol.
A powder of _0.8 Sm _0.2 O _1.90 (1-2 μm) was dispersed, the solid electrolyte layer was immersed in the solution, pulled up, and then fired at about 1250 ° C.

The fuel electrode is obtained by grinding and mixing SDC powder and NiO powder to a predetermined size with a ball mill, and further mixing Ce and Z
A toluene solution of octylic acid of r and Y is added, hydrolyzed, applied on an SDC film by a screen printing method or the like, baked at about 1350 ° C., and Ce _0.9 Sm _0.1 O by volume ratio.
_1.95 40%, Ni 50%, CeYSZ ((Ce
0 ₂ ) _0.1 ((Y ₂ O ₃ ) _0.2 (Zr
O ₂ ) _0.8 ) _0.9 ) was _adjusted to 10%.

The air electrode is La _0.6 Sr _0.4 Co
_0.2 Fe _0.8 O ₃ (LSCF) powder is dispersed in hexylene glycol, the solution is applied on the SDC film on the opposite side of the fuel electrode by a screen printing method or the like, and baked at 1100 ° C. for 4 hours. Formed.

FIGS. 2 to 4 show electron micrographs of the surfaces of the solid electrolyte layer and the SDC layer and their cross sections.

FIG. 2 shows La_0.9Sr_0.1Ga_0.8
Mg_0.2O_2.85Electron microscope of the surface of the solid electrolyte layer
A photograph is shown. As shown in FIG._0.9Sr_0.1
Ga _0.8Mg_0.2O_2.85Surface crystal grains appear
I have. FIG._0.9Sr_0.1Ga_0.8Mg
_0.2O_2.85On the surface of the solid electrolyte layer (shown in Fig. 2)
5 is an electron micrograph of the surface when an SDC film is formed.
You. By comparing FIG. 2 and FIG. 3, the solid electrolyte
That the entire surface of the layer was evenly covered with a dense SDC film
Understand.

FIG. 4 is a cross section of a solid electrolyte layer having an SDC film formed on the surface. As shown in FIG. 4, it can be seen that the SDC film is formed with a uniform thickness on the surface of the solid electrolyte layer.

FIG. 5 is a graph showing a current density and a voltage when a solid oxide fuel cell is constructed using the above-mentioned unit cells and the solid oxide fuel cell is operated. As shown in FIG. 5, the maximum power density is 800 per square cm.
0.67 at 750 ° C, 700 ° C, and 650 ° C
W, 0.58 W, 0.46 W, and 0.29 W, indicating that the solid oxide fuel cell of the present invention has high power generation capability and sufficient power generation characteristics even at low temperature operation. When the solid oxide fuel cell was continuously operated, a stable operation for a long time was observed.

[0038]

According to LaGaO ₃ based solid electrolyte fuel cell of the present invention, using a LaGaO ₃ type material in the solid electrolyte layer, since the formation of the ceria film doped at least between the fuel electrode, the fuel Even if NiO or YSZ-based material is used for the pole, LaGa that does not cause a reaction between the materials, has high power generation performance, and performs stable power generation operation for a long time
O ₃ based solid electrolyte fuel cell can be provided.

Further, since the doped ceria film is formed between the air electrode and the solid electrolyte layer, the power generation performance can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a unit cell according to the present invention.

FIG. 2 is an electron micrograph showing experimental results.

FIG. 3 is an electron micrograph showing experimental results.

FIG. 4 is an electron micrograph showing experimental results.

FIG. 5 is a graph showing experimental results.

[Explanation of symbols]

 2 unit cell 4 fuel electrode 6 solid electrolyte layer 8 air electrode 10 SDC membrane

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // C01F 17/00 C01F 17/00 BF term (reference) 4G076 AA02 AA18 AB02 BA37 BF02 CA10 DA04 5G301 CA02 CD01 5H026 AA06 EE13

Claims (5)

[Claims] 1. A LaGaO ₃ -based solid electrolyte fuel cell including an air electrode, a solid electrolyte layer made of a LaGaO ₃ -based material, and a fuel electrode, wherein a dope is provided between the fuel electrode and the solid electrolyte layer. A LaGaO ₃ -based solid oxide fuel cell comprising a ceria film formed as described above. 2. A LaGaO ₃ -based solid electrolyte fuel cell including an air electrode, a solid electrolyte layer made of a LaGaO ₃ -based material, and a fuel electrode, wherein the air between the fuel electrode and the solid electrolyte layer and the air between pole to the solid electrolyte layer, LaGaO ₃ based solid electrolyte fuel cell is characterized in that the formation of the film of doped ceria. 3. The LaGaO ₃ -based material is La _1-x
Sr _x Ga _1-y Mg _y O ₃ (0.05 <x <0.5,
_3. The LaGaO3-based solid oxide fuel cell according to claim 1, wherein 0.05 <y <0.5). 4. The doped ceria film is made of Ce
_1-z M _z O _d (M is a trivalent rare earth, 0.05 ≦ z ≦
0.5, d = 2-0.5z) LaGaO ₃ based solid electrolyte fuel cell according to any one of claims 1 to 3 characterized in that a. 5. The LaGaO ₃ -based solid oxide fuel cell according to claim 4, wherein M is Gd or Sm.