JP3502012B2 - Solid oxide fuel cell and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supporting membrane type solid oxide fuel cell having a low temperature active electrode and a method for producing the fuel cell.

[0002]

2. Description of the Related Art Recently, a fuel cell which directly converts the chemical energy of the fuel into electric energy by using, for example, air and hydrogen as an oxidant gas and a fuel gas, respectively, has attracted attention from the viewpoint of resource saving and environmental protection. In particular, solid electrolyte fuel cells have many advantages such as high power generation efficiency and effective utilization of waste heat, and thus research and development are progressing.

Solid oxide fuel cells are broadly classified into a self-supporting membrane type in which the thickness of the electrolyte is increased and a supporting membrane type in which an electrolyte film is formed on the electrode plate by making the electrode plate strong. A self-supporting membrane type solid oxide fuel cell has an electrolyte thickness of 100 μm.
Since the thickness is about m and the resistance of the electrolyte is high, in order to obtain sufficient power generation characteristics, the operating temperature of the battery is 900 to 1000.
It is necessary to raise the temperature to about 0 ° C, and the high temperature may adversely affect the long-term stability of the constituent materials.

On the other hand, the supporting membrane type solid oxide fuel cell is
For example, a fuel electrode of Ni / YSZ cermet is used as a substrate, and an electrolyte film having a thickness of about 20 μm made of a zirconia sintered body (YSZ) doped with yttria is formed on the fuel electrode, and an air electrode is formed on the electrolyte film. A single cell is formed by forming a film, and an electromotive force is generated by bringing a fuel gas and an oxidant gas into contact with each electrode surface of the single cell. It has the advantage that the operating temperature can be reduced.

[0005]

As an air electrode material of a conventional solid oxide fuel cell, (La, Sr) MnO ₃ (L
A material (referred to as SM) has been used. However, the air electrode of LSM has excellent characteristics at high temperatures, but when the operating temperature is lowered, mass transfer resistance such as dissociative adsorption of oxygen on the air electrode and surface diffusion of adsorbed oxygen increases, which causes polarization. It has the disadvantage of increasing. In order to solve this problem, an air electrode having excellent characteristics at low temperature and a method for producing the same have been invented and already filed (application number: Japanese Patent Application No. 10-16014). Only the performance was evaluated, and in an actual single cell, a method of adapting to a support membrane type solid oxide fuel cell capable of low temperature operation is required.

The present invention has been made in view of the above points, and a support membrane type solid oxide fuel cell having improved performance in low temperature operation by changing the cathode material to a material having high activity at low temperature is provided. The purpose is to provide.

[0007]

In order to achieve the above object, the present invention has a fuel electrode as a substrate, an electrolyte membrane formed on the fuel electrode, and an air electrode formed on the electrolyte membrane. In a solid oxide fuel cell having a unit cell composed of Ce _{1 -X} F _X O ( _2-
δ) (F is Ca, Y, Sm, Gd, La, Mg, Sc,
Nd, Yb, Pr, Pb, Sr, Eu, Dy, Ba, B
any one of e or a combination of two or more, and 0 ≦ x
≦ 0.50), and the air electrode has an average particle size of 0.1 to 20 μm (A _1-x B _x ) (C _1-y
And particles having a composition of _{D y) O (3+ δ)} , the average particle size surrounding the periphery of the particles is 0.1 to 5 [mu] m, 0.5 to
A solid oxide fuel cell was constructed by using particles having a composition of Ce _1-X E _X O ( _2- δ) contained in the range of 60 wt%.

Here, A is most preferably La in terms of performance, but Y, Sm, Gd, Pr, and Ca can be used as alternatives, and any one or a combination of two or more thereof may be used. B is most preferably Sr in terms of performance, but as an alternative, B
a and Ca are possible, and any one of them or a combination of two or more thereof may be used.

C is most preferably Co in terms of performance, but as an alternative, Mn and Ce are possible, and any one or a combination of two or more thereof may be used. Fe is most preferable in terms of performance as D, but as an alternative, Ni, Mg, Zr, Ce, C
r and Al are possible, and any one or a combination of two or more thereof may be used. E is most preferably Sm or Gd in terms of performance, but as an alternative, Y, Ca, La, Mg,
Sc, Nd, Yb, Pr, Pb, Sr, Eu, Dy, B
a and Be are possible, and any one of them or a combination of two or more thereof may be used. Also, 0 ≦ x ≦ 0.50, 0 ≦
y ≦ 0.50.

In the particles of (A _1-x B _x ) (C _1-y D _y ) O ( _{3 +} δ), the durability is low when the average particle size is 0.1 μm or less, and the performance is low when the average particle size is 20 μm or more. Become. Also (A _1-x
In B _x) composition of _{(C 1-y D y)} O (3+ δ) of particles surrounding the particles having the composition _{(Ce 1-X E X O} (2- δ)), an average particle diameter When the thickness is 0.1 μm or less, the durability is low,
If it is 5 μm or more, the performance is poor and the content ratio is 0.5 wt.
% Or less, there is almost no effect, and if it is 60 wt% or more, the conductivity of the electrode decreases.

The most preferable combination of the whole is as follows.
A is La, B is Sr, C is Co, and D is Fe.
And E is Sm.

The metal organic compound is any one of octylates, naphthenates and acetylacetonate complexes or a combination of two or more.

Further, A is La, B is Sr, C is Co, D
Is Fe and E is Sm, and the starting material of Ce _1-X E _X O ( _2- δ) is the octylate salt of Ce and E.

Further, the present invention uses a fuel electrode as a substrate, a solid electrolyte fuel having a unit cell comprising an electrolyte film formed on the fuel electrode and an air electrode formed on the electrolyte film. A battery, such as an SDC (samaria-doped ceria) film or the like on the electrolyte film, Ce _1-X F _X O ( _2- δ) (F is Ca,
Y, Sm, Gd, La, Mg, Sc, Nd, Yb, P
Any one of r, Pb, Sr, Eu, Dy, Ba, Be
One or a combination of two or more, and a film of 0 ≦ x ≦ 0.50) is formed, and (A _1-x B _x ) (C _1-y D _y ) O ( ₃₊
δ) oxide powder (A is La, Y, S
Any one or a combination of two or more of m, Gd, Pr and Ca, B is any one or a combination of two or more of Sr, Ba and Ca, and C is any one of Mn, Co and Ce. Or a combination of two or more, D is Cr, Ni, Mg, Zr, C
Any one of e, Fe and Al, or a combination of two or more thereof,
0 ≦ x ≦ 0.50, 0 ≦ y ≦ 0.50) and E (E is C
a, Y, Sm, Gd, La, Mg, Sc, Nd, Yb,
Any one of Pr, Pb, Sr, Eu, Dy, Ba, and Be or a combination of two or more, and 0 ≦ x ≦ 0.50)
A solution of a metal organic compound of Ce and Ce is added to form a slurry, E and Ce are hydrolyzed in the slurry, and a polycondensation reaction is allowed to proceed. Then, the slurry is applied onto the SDC film and heated. The thermal decomposition reaction of the slurry is carried out by
_1-x B _x ) (C _1-y D) O ( ₃₊ δ) particles and Ce _1-x E _x O (
_2- δ) fine particles are mixed with good dispersibility, and Ce _1-X E _X O
An air electrode containing ( _2- δ) in the range of 0.5 to 60 wt% was formed.

As described above, the components of the air electrode and the like are specified, and the ceria-based material film such as the SDC film is formed between the electrolyte membrane and the air electrode, so that the solid electrolyte fuel cell having a high power generation performance can be obtained. You can get a battery.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A unit cell of a support membrane type solid oxide fuel cell according to the present invention will be described.

FIG. 1 shows a unit cell 2. In the unit cell 2, the electrolyte membrane 6 has a thickness of 20 μm on the surface of the fuel electrode 4 as a support.
Formed on the surface of the electrolyte membrane 6, and SDC on the surface of the electrolyte membrane 6.
An air electrode 8 is formed with the film 7 interposed. As shown in FIG. 10, the unit cell 2 is sandwiched between an alloy separator 30 and a separator 34 including a ceramic manifold 32,
The solid oxide fuel cell 1 is configured by appropriately stacking the separator 34 and the unit cell 2. Solid oxide fuel cell 1
Generates an electromotive force by supplying the fuel gas to the fuel electrode 4 and the oxidant gas to the air electrode 8 under a predetermined condition.

Next, a method of manufacturing the unit cell 2 will be described with reference to FIG.

First, a powdery raw material is pressed into a predetermined shape to form a fuel electrode 4 as a support (S1). The raw material of the fuel electrode 4 is, for example, a cermet of nickel and yttria-stabilized zirconia (YSZ),
The raw material is kneaded with a water-soluble binder, such as polyvinyl alcohol, and pressed by a pressing device (not shown) or the like,
Mold. The fuel electrode 4 formed into a predetermined shape is shown in FIG. The raw material of the fuel electrode 4 contains a predetermined amount of a pore-forming agent such as graphite powder, and when the pore-forming agent is burned off by firing described later, a large number of holes are formed inside the fuel electrode 4.

The unfired fuel electrode 4 formed by the pressing device is placed in the coating device 18 (see FIG. 2) as it is, and the electrolyte slurry 24 is coated on the surface (S).
2). The electrolyte slurry 24 is prepared by kneading a raw material of an electrolyte (electrolyte film 6) made of yttria-doped zirconia sintered body (YSZ) and a water-insoluble binder, for example, polyvinyl butyral, and set to a predetermined viscosity. I am doing it. In addition to the above, as the binder, there are methyl cellulose, polyethylene, sodium polyacrylate, gum arabic and the like.

As shown in FIG. 2, the coating device 18 is a printing machine for performing printing by a so-called screen printing method, and a mold having the same shape as the electrolyte membrane 6 is formed on the screen plate 20. When the fuel electrode 4 is arranged at a predetermined position of the coating device 18, the electrolyte slurry 24 is coated on the upper surface of the fuel electrode 4 through the mold by moving the squeegee 22 along the screen plate 20 (S2). Electrolyte slurry 2
When No. 4 is applied in a predetermined shape, the surface of the electrolyte is appropriately dried. It is not necessary to completely dry the electrolyte slurry 24 in the drying operation, and it is sufficient that the electrolyte slurry 24 can be applied over the applied electrolyte slurry 24.
FIG. 4 shows the fuel electrode 4 having the electrolyte membrane 6 formed on its surface.

After the electrolyte slurry 24 has been appropriately dried, the electrolyte slurry 24 is coated and dried in the same manner as above. Then, the application of the electrolyte slurry 24 is repeated until the electrolyte slurry 24 has a predetermined thickness. When the electrolyte slurry 24 is laminated to a predetermined thickness, it is co-sintered with the fuel electrode 4 (the electrolyte membrane 6 and the fuel electrode 4 are fired together) (S3).

Then, the SDC slurry is applied to the electrolyte membrane 6 to form the SDC membrane 7 (S4). The SDC is ceria (Ce _1-x Sm _x O _(2-
δ ₎ ), the particle size is 0.1 to 5 μm, and x = 0 to 0.5.
Then, the slurry dispersed and mixed in Ce sol is applied to at least the entire surface of the electrolyte membrane 6 by a dipping method or the like. The applied state is shown in FIG. The applied SDC film 7 is fired (S5), and the air electrode 8 is formed on the electrolyte film 6 via the SDC film 7 (S6).

The air electrode 8 is composed of La _0.6 Sr _0.4 Co _0.8 Fe.
_A predetermined amount of air electrode slurry (air electrode slurry) made of _0.2 O ₃ -Ce _0.8 Sm _0.2 O _1.9 (LSCF-SDC) and compounded to have such a component after sintering was formed on the electrolyte membrane 6 by screen printing. It is applied to a thickness, and the whole is baked to complete (S7). FIG. 6 shows the entire unit cell 2 in which the air electrode 8 is formed on the electrolyte membrane 6.

In this way, the air electrode 8 is set to La _0.6 Sr _{0.4.
Co 0.8 Fe 0.2 O 3 -Ce 0.8} Sm 0 .2 O 1.9 (LSCF
-SDC) makes it possible to operate at a low temperature by forming a thin film, and by providing an SDC film 7 having an electric resistance smaller than that of the electrolyte film 6 between the electrolyte film 6 and the air electrode 8, Conductivity is improved, and the La of the air electrode 8 is further improved.
It is possible to prevent YSZ of the electrolyte membrane 6 from reacting with each other to generate La ₂ Zr ₂ O ₇ , prevent deterioration of the air electrode, prevent conduction failure, and realize high power generation performance.

Further, by screen printing, the electrolyte membrane 6,
Since the air electrode 8 is formed, and the electrolyte slurry 24 and the like is applied through the screen plate 20 to form the appropriate unevenness, the fuel electrode 4 and the electrolyte membrane 6, and the electrolyte film 6 and the air electrode are formed. It is possible to improve the adhesiveness with 8.

Furthermore, the electrolyte membrane 6 and the air electrode 8 having a predetermined shape and thickness are applied to the fuel electrode 4 as a support simply and quickly,
In addition, the electrolyte slurry 24 can be directly formed after molding the raw material of the fuel electrode 4 without calcining the fuel electrode 4.
Since it can be applied to the fuel electrode 4, labor and cost can be significantly reduced.

When the electrolyte slurry 24 is applied to the fuel electrode 4 by properly selecting the properties of the binders of the fuel electrode 4 and the electrolyte slurry 24, that is, the combination of water-soluble and water-insoluble binders. It is possible to adjust the interface state generated between them, and it is possible to form a good electrolyte membrane 6 that is dense after firing and has few impurities. Furthermore, the electrolyte membrane 6 and the fuel electrode 4 (SD) can be selected by appropriately selecting the binders of both types from combinations other than water-soluble or water-insoluble combinations.
The interface of the C film 7) can have a desired structure.

The SDC membrane 7 is applied not to the entire surface of the electrolyte membrane 6 but to the entire surfaces of the fuel electrode 4 and the electrolyte membrane 6, that is, the surface of the fuel electrode 4, as shown in FIGS. 8 and 9. May be. Further, between the electrolyte membrane 6 and the air electrode 8, instead of the SDC membrane 7, Ce _1-X F _X O ( _2- δ) (F is Ca, Y, S
m, Gd, La, Mg, Sc, Nd, Yb, Pr, P
A film of 0 ≦ x ≦ 0.50, which is one or a combination of two or more of b, Sr, Eu, Dy, Ba, and Be, may be provided.

In the above example, the electrolyte slurry 24 is applied by the screen printing method to form the electrolyte membrane 6. However, the present invention is not limited to the screen printing, and other printing methods may be used. A film may be formed.

The properties of the binder are not limited to the above examples, and other properties and types may be combined.

Experimental Example In the experiment, a power generation test was conducted with a unit cell having an air electrode according to the present invention and a unit cell having a conventional air electrode as a comparative example.

The fuel electrode in both unit cells was a cermet in which NiO powder and yttria-stabilized zirconia powder (YSZ) were mixed at a weight ratio of 60:40, and graphite powder and a water-soluble binder were added as a pore-forming material. It was granulated by the spray dry method and molded by pressing. The electrolyte membrane is made of yttria-stabilized zirconia (Y
SZ), the binder was made water-insoluble and was applied on the fuel electrode by screen printing.

The unit cell according to the present invention uses SDC as the electrolyte.
Through the _{membrane, La 0.6 Sr 0.4 Co 0. 8} Fe 0.2 O 3 -Ce
_An air electrode made of _0.8 Sm _0.2 O _1.9 (LSCF-SDC) was applied by screen printing and baked to prepare a single cell of a support membrane type solid oxide fuel cell. On the other hand, the air electrode of a single cell as a conventional example has Pr _0.6 Sr _0.4 MnO ₃ -C
e _0.8 Sm _0.2 O _1.9 (PSM-SDC).

The cell size is 5 cm square, and the area of the air electrode is 4 cm ² . The operating temperature of the experiment was 750 ° C., humidified H ₂ was used as the fuel, and air was used as the oxidant.

The results are shown in FIG. FIG. 11 shows the current densities (A / c) of the unit cell according to the present invention and the conventional unit cell.
7 is a graph showing changes in voltage (V) with respect to m ² ).
It can be seen from the graph of FIG. 11 that the unit cell of the present invention does not show a voltage drop up to a high current density and has excellent characteristics as compared with the unit cell of the conventional example.

As described above, according to the present invention, the electrolyte membrane is thinned to obtain a high power density, and the lowering of the operating temperature improves the durability and reliability of each constituent member and alleviates restrictions on material selection. In particular, by configuring the air electrode as described above, it is possible to provide a support membrane type solid oxide fuel cell having high power generation performance.

[0038]

According to the unit cell of the solid oxide fuel cell of the present invention, the air electrode has small polarization and high stability even when the operating temperature is low, and accordingly, the low operating temperature is used. However, it is possible to provide a solid oxide fuel cell having good cell performance.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a screen printing method.

FIG. 3 is a diagram showing a fuel electrode.

FIG. 4 is a diagram showing a fuel electrode on which an electrolyte membrane is formed.

FIG. 5 is a view showing a fuel electrode on which an SDC film is formed.

FIG. 6 is a view showing a fuel electrode having an air electrode.

FIG. 7 is a diagram showing a procedure of a manufacturing method according to the present invention.

FIG. 8 is a cross-sectional view of a fuel electrode having an electrolyte membrane.

FIG. 9 is a view showing a cross section of a unit cell.

FIG. 10 is a sectional view showing a solid oxide fuel cell.

FIG. 11 is a diagram showing experimental results.

[Explanation of symbols]

1 Solid oxide fuel cell 2 cells 4 fuel pole 6 electrolyte membrane 7 SDC film 8 air poles 18 Coating device 20 screen version 22 Squeegee 24 Electrolyte slurry 25 Fuel electrode slurry 30 alloy separator 32 ceramic manifold 34 Separator

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-129252 (JP, A) JP-A-11-214014 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 8 / 02,8 / 12 H01M 4/86-4/88

Claims (5)

(57) [Claims] 1. A solid electrolyte fuel cell comprising a unit cell comprising a fuel electrode as a substrate, an electrolyte film formed on the fuel electrode, and an air electrode formed on the electrolyte film, The air electrode includes particles having a composition of (A _1-x B _x ) (C _1-y D _y ) O _{(3 + δ)} having an average particle size of 0.1 to 20 μm, and the particles. Surrounding average particle size is 0.1-5μ
consists of a particle having a composition of _{Ce 1-x E x O (} 2-δ) in the range of m, the Ce _1-x E x O a _(2-δ) 0.5
-60% by weight, where A is
Any one or more of La, Y, Gd, Pr, Ca
The above combination, B is any one of Sr, Ba, Ca or
Combination of two or more, C is Mn, Co, or Ce 1
One or a combination of two or more, D is Cr, Ni, Mg, Z
Any one or more of r, Mg, Ce, Fe and Al
The above combination, E is Ca, Y, Sm, Gd, La, Mg,
Sc, Nd, Yb, Pr, Pb, Sr, Eu, Dy, B
one or a combination of two or more of a and Be,
0 ≦ X ≦ 0.50, 0 ≦ Y ≦ 0.50) Electrolysis
Between Shitsumaku and the air electrode, or _{Ce (1-x) F x} O (2-δ)
Solid electrolyte fuel cell characterized by having a membrane made of
pond. (Where F is Ca, Y, Sm, Gd, La, M
g, Sc, Nd, Yb, Pr, Pb, Sr, Eu, D
Any one of y, Ba, Be or a combination of two or more
And X is 0 ≦ X ≦ 0.50) 2. The solid electrolyte according to claim 1, wherein A is La, B is Sr, C is Co, D is Fe, and E and F are Sm. Type fuel cell. 3. The solid electrolyte type according to claim 1, wherein the starting material of Ce _(1-x) E _x O _(2-δ) is Ce and the metal organic compound of E. Fuel cell. 4. The metal organic compound is one or a combination of two or more of an octylate salt, a naphthenate salt, and an acetylacetonate complex.
The solid oxide fuel cell according to 1. 5. A film is formed on the fuel electrode by using the fuel electrode as a substrate.
Electrolyte and an air electrode formed on the electrolyte membrane
Membrane-type solid electrolyte fuel cell including single cell
pondThe manufacturing method of Ce on the electrolyte membrane_(1-x) F_x O_(2-δ)Membrane consisting of
(Where F is Ca, Y, Sm, Gd, L
a, Mg, Sc, Nd, Yb, Pr, Pb, Sr, E
Any one or more of u, Dy, Ba, and Be
And X is 0 ≦ X ≦ 0.50) The film formed above
above,The average particle size is in the range of 0.1 to 20 μm(A
_1-x B_x) (C_1-y D_y) O_{(3 + δ)} (Where A is L
Any one or more of a, Y, Gd, Pr, Ca
, B is any one of Sr, Ba, and Ca or 2
More than two, C is any one of Mn, Co, Ce
Or a combination of two or more, D is Cr, Ni, Mg, Zr,
Any one or more of Mg, Ce, Fe, Al
Combination, 0 ≦ X ≦ 0.50, 0 ≦ Y ≦ 0.50)
E (E is Ca, Y, S
m, Gd, La, Mg, Sc, Nd, Yb, Pr, P
Any one of b, Sr, Eu, Dy, Ba, Be or
Combination of two or moreIs), And metal organic compounds of Ce
The above solution is added to form a slurry, and the above E
And Ce are hydrolyzed and the condensation reaction is further advanced.
After applying it, apply it on the electrolyte membrane and apply heat to decompose the pyrolysis reaction.
Then, by baking at a high temperature,
(A_1-x B_x) (C_1-y D_y) O_{(3 + δ)}Fine particles and 0.
Included in the range of 5 to 60 wt%With a particle size of 0.1-5 μm
Ce _1-x  E _x  O _(2-δ)  Of fine particlesMix well with dispersibility
Characterized by forming a closed air electrodeClaim 1
didMethod of manufacturing solid oxide fuel cell.