JP2002313406A - Solid electrolytic type fuel cell and method of manufacturing electrode for solid electrolytic type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic type fuel cell having a durability for long period under high temperature conditions. SOLUTION: In this solid electrolytic type fuel cell 10 having a pair of electrodes 16 holding the both faces of a solid electrolytic layer 17, a material layer 14 facing the boundary face of the electrodes 16 with the solid electrolytic layer 17 has a porous structure and is formed by mixing material particles 12 with a melting point higher than that the main material of the electrodes 16. Thus the solid electrolytic type fuel cell having such a durability that makes hard sintering even under high temperature conditions can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell and a method for manufacturing an electrode for a solid oxide fuel cell, and more particularly to a solid oxide fuel cell provided with an electrode having excellent heat resistance. Get involved.

[0002]

2. Description of the Related Art A solid oxide fuel cell is provided with an oxide or metal electrode on both sides of an oxide oxygen conductor, one of which supplies an oxidizing gas and the other of which supplies a fuel. As a result, power is generated by the progress of the electrochemical reaction.

It is important that the function of the electrode is (1) to have conductivity, (2) to allow gas to permeate, and (3) to allow the electrochemical reaction to proceed. In order to achieve both conductivity and gas permeability, the electrode usually needs to be a porous body. Further, in order to have sufficient gas diffusivity, sufficient porous properties (pore diameter, porosity) are required. Also,
The electrochemical reaction of (3) is usually performed using a solid electrolyte material (solid phase).
3 where the electrode, the electrode material (solid phase) and the pores (gas phase) are in contact.
Although it occurs at the phase interface, there is a trade-off relationship in that, if the diameter of the electrode particles is increased in order to secure the gas diffusibility of (2), the three-phase interface is reduced in the reaction field.

Therefore, as a technique for achieving both the gas permeability of (2) and the electrochemical reactivity of (3), electrodes near the three-phase interface are formed of fine electrode material, and the other portions are rough. An electrode for a solid oxide fuel cell formed of a granular electrode material has been proposed (for example, Japanese Patent Application Laid-Open No. 1-227362). According to this method, since the electrode layer existing at the interface with the solid electrolyte (hereinafter, referred to as the first electrode layer) is composed of fine particles, many three-phase interfaces exist, and the electrode reaction proceeds smoothly. I do. Further, since the thickness of this portion (first electrode layer) is several tens μm or less, there is little adverse effect on gas diffusion. Since an electrode layer made of coarse particles (hereinafter, referred to as a second electrode layer) is formed outside the first electrode layer, the reaction smoothly diffuses and reaches the three-phase interface as a reaction field. can do. Further, in this electrode material, since particles constituting the electrode are in contact with each other, if the material itself has electronic conductivity, electrons can be exchanged through the electrode layer. Therefore, if such a conventional configuration is used, the electrodes can fulfill the functions (1), (2), and (3) described above.

[0005]

However, in the above-described conventional configuration, as shown in FIG. 4, the second electrode layer made of coarse particles is composed of relatively large particles 1 and relatively small particles 2, Each particle tends to be finer. Even in this case, the gas does not completely collapse and the gas diffusibility can be ensured, but the gas diffusion holes gradually shrink due to the progress of sintering between particles due to prolonged exposure to high temperature conditions, There is a problem in that gas diffusivity is reduced and power generation capacity is further reduced.

Accordingly, an object of the present invention is to provide a solid oxide fuel cell having long-term durability under high temperature conditions and an electrode used for the same.

[0007]

SUMMARY OF THE INVENTION Therefore, the invention according to claim 1 is a solid electrolyte fuel cell having a pair of electrodes sandwiching both surfaces of a solid electrolyte layer, wherein an interface between the electrodes and the solid electrolyte layer is provided. Has a porous structure, and the material layer is mixed with a sub-material having a different composition or a different particle shape from the main material of the electrode.

According to a second aspect of the present invention, there is provided the solid oxide fuel cell according to the first aspect, wherein the surface of the material layer on the side of the solid electrolyte layer is made of fine particles and has pores narrower than the material layer. Wherein a surface material layer having a porous structure having the following structure is formed.

According to a third aspect of the present invention, there is provided a solid oxide fuel cell according to the first or second aspect, wherein the electrode comprises a mixture of the main material having electron conductivity and a high melting point material. It is characterized by being composed of a body.

A fourth aspect of the present invention is the solid oxide fuel cell according to the third aspect, wherein the high melting point material has a melting point of 1900 ° C. or more.

According to a fifth aspect of the present invention, there is provided the solid oxide fuel cell according to the third or fourth aspect, wherein one of the pair of electrodes is an air electrode and the other is an air electrode. A fuel electrode, wherein the main material of the one electrode is La-
Mn-based perovskite-type composite oxide, La-Co-based perovskite-type composite oxide, La-Fe-based perovskite-type composite oxide and their element-substituted perovskite-type composite oxide, silver, at least one of platinum,
The main material of the other electrode is iron, cobalt, nickel,
It contains at least one of copper, silver, platinum and palladium, and the high melting point material is aluminum oxide, calcium oxide, magnesium oxide, silicon oxide, zirconium oxide, cerium oxide, boron nitride, silicon nitride, boron carbide, carbonized It is characterized by containing at least one of titanium and its derivatives.

According to a sixth aspect of the present invention, in the solid oxide fuel cell according to any one of the third to fifth aspects, the mixing ratio of the high melting point material mixed in the material layer is as follows:
It is characterized by being at most 20 wt%.

According to a seventh aspect of the present invention, there is provided a solid oxide fuel cell device according to any one of the second to sixth aspects, wherein the surface material layer is formed of an acicular crystal electrode material and a spherical crystal. It is characterized by being composed of a mixture with an electrode material.

The invention according to claim 8 is the solid oxide fuel cell according to claim 7, wherein the ratio of the minor axis to the major axis of the electrode material of the spherical crystal is 3 or less, and The ratio of the minor axis to the major axis of the material is 3 to 20.

According to a ninth aspect of the present invention, there is provided the solid oxide fuel cell according to the eighth aspect, wherein the electric conductivity of the electrode material of the needle-shaped crystal is 10 ² S · cm ⁻¹ or more in an operating temperature range. In the case where the ratio of the electrode material of the needle-like crystal contained in the material layer is 50 wt% or less and the conductivity of the electrode material of the needle-like crystal is 10 ² S · cm ⁻¹ or less in an operating temperature range, The ratio of the electrode material of the needle-like crystals contained in the material layer is not more than 20 wt%.

According to a tenth aspect of the present invention, there is provided a method of manufacturing an electrode for a solid oxide fuel cell sandwiching both sides of a solid electrolyte layer, wherein the porous material layer having gas diffusion holes has A surface material layer having a porous structure, which is made of fine particles and has pores narrower than the gas diffusion pores, which is bonded to the solid electrolyte layer, is formed by any one of PVD, CVD, EVD, and sol-gel methods. And

According to an eleventh aspect of the present invention, there is provided the method of manufacturing an electrode for a solid oxide fuel cell according to the tenth aspect, wherein after forming the surface material layer, a slurry or paste is printed on the surface material layer. It is characterized by being applied by a method or a spray method.

According to a twelfth aspect of the present invention, there is provided a method for manufacturing an electrode for a solid oxide fuel cell according to the eleventh aspect, wherein the material layer is formed by a thermal spraying method.

[0019]

According to the first to ninth aspects of the present invention, it is possible to suppress the sintering of the material layer of the electrode layer which should have gas diffusibility from progressing. It has the effect of exhibiting power generation capacity.

According to the tenth to twelfth aspects of the invention, there is an effect that an electrode having a good reaction diffusion property can be easily manufactured.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a solid oxide fuel cell and an electrode for a solid oxide fuel cell according to the present invention will be described based on embodiments.

In the solid oxide fuel cell according to the present invention, in order to prevent the gas diffusion holes of the electrode from narrowing due to sintering under high temperature conditions, a material having a different composition from the main material of the electrode or a material having a different composition is used. It is characterized by being formed by mixing particles having a crystal shape.

Although the sintering of the electrode material is an unavoidable problem in terms of thermodynamic function, it can be reduced to a practically acceptable level by reducing the speed. In the present embodiment, a material having a property different from that of the main material of the electrode is mixed with the main material. As a specific property of the mixed material, a material having a high melting point is effective. Generally, in the case of a perovskite oxide used for an air electrode of a solid oxide fuel cell,
The melting point is approximately 1800 ° C. In order to prevent such sintering of the perovskite oxide, an effect can be obtained by mixing a material having a melting point higher than this material. That is, the melting point of the material mixed with the perovskite oxide is preferably 1900 ° C. or higher. The presence of materials having different compositions between the electrode main materials suppresses aggregation of the electrode main materials. Further, since a material having a higher melting point tends to be less likely to cause sintering, a material having a higher melting point has a greater effect. FIG. 2 shows a material layer of an electrode formed by mixing high melting point material particles 12 with perovskite type oxide particles 11 which are an electrode main material.

As another electrode structure for preventing such sintering, as shown in FIG. 3, a crystal shape different from that of the perovskite-type oxide particles 11 as a main electrode material (in this embodiment, a needle-shaped oxide particle 11). It is effective to mix particles having (crystal). In an electrode made of a perovskite oxide formed by an ordinary method, spherical particles are gathered as shown in FIG. In such a collection of spherical particles, the particles tend to be stacked without gaps. As a result, there are too many contact points between the particles, and the contact points serve as starting points, and sintering is likely to occur. However, as shown in FIG. 3, when particles 13 having needle-like crystals are mixed, for example, as in the present embodiment, the gaps are forcibly increased, and the number of contact points between the particles is appropriately reduced. Rings can be suppressed.

Therefore, as shown in FIG. 1, the solid oxide fuel cell 10 according to the present embodiment is made by mixing perovskite oxide particles 11 with high melting point material particles 12 as shown in FIG. An electrode 16 having a two-layer structure of a material layer 14 and a surface material layer 15 made of fine particles bonded to a solid electrolyte layer 17 and having a narrow pore structure is provided.

When one of the electrodes 16 is used as an air electrode, the main material of the material layer 14 is La-Mn-based perovskite-type composite oxide, La-Co-based perovskite-type composite oxide, or La-Fe-based perovskite. -Type composite oxides and their element-substituted perovskite-type composite oxides, silver, including at least one of platinum, the main material of the other electrode is iron, cobalt, nickel, copper, silver, platinum,
Containing at least one of palladium,
Aluminum oxide, calcium oxide,
It is preferable to include at least one of magnesium oxide, silicon oxide, zirconium oxide, cerium oxide, boron nitride, silicon nitride, boron carbide, titanium carbide and derivatives thereof.

The high melting point material preferably has a melting point of 1900 ° C. or higher. Furthermore, the high melting point material particles are 20 wt%
% Is preferable. Further, the ratio of the minor axis to the major axis of the perovskite oxide particles is preferably 3 or less, and the ratio of the minor axis to the major axis of the acicular crystal particles is preferably 3 to 20. Further, when the conductivity of the material particles having needle-like crystals is 10 ² S · cm ⁻¹ or more in the operating temperature range, the ratio of the needle-like particles 13 including the material layer 15 is 50%.
wt% or less, and when the conductivity is 10 ² S · cm ⁻¹ or less, it is preferably 20 wt% or less.

As a method for forming the material layer 14, a PVD method, a CVD method, an EVD method, a sol-gel method,
It can be formed using a thermal spraying method. Further, a slurry or paste may be applied to the surface of the surface material layer 15 by a printing method or a spray method.

(Example) A sintered disk of yttrium-stabilized zirconia (hereinafter referred to as YSZ) (diameter 15 mm, thickness 1 mm) has La _0.8 Sr _0.2 MnO on one surface.
_3. Ni is vapor-deposited on the other surface by sputtering to a thickness of 1 μm. Thereafter, baking was performed at 1000 ° C. for 10 minutes. Then, alumina particles 10w
air and calcined t% and La _0.8 Sr _0.2 MnO ₃ powder mixture of 90 wt% were mixed well in a mixed solution of terpineol and ethanol was coated on La _0.8 Sr _0.2 MnO ₃ side of the YSZ disc at 1200 ° C. 20 min A pole was formed. Thereafter, alumina particles were reduced to 10 using a commercially available Ni paste.
It was blended so as to be wt% and applied to the Ni surface of the YSZ disk to form a fuel electrode. Thus Ni · Al ₂ O ₃
/ Ni / YSZ / La _0.8 Sr _0.2 MnO ₃ / La _0.8 Sr
_0.2 MnO ₃ .Al ₂ O ₃ was obtained. The final thicknesses of the air electrode and the fuel electrode were 25 μm and 20 μm, respectively.

(Comparative Example) Ni.Al ₂ O ₃ / Ni was the same as in the above embodiment except that alumina was mixed with the electrode material.
/ YSZ / La _0.8 Sr _0.2 MnO ₃ / La _0.8 Sr _0.2 M
nO ₃ was obtained.

As a result of performing a power generation test using a solid oxide fuel cell using such an example and a comparative example, no sintering progress was observed in the electrode in the example, and good power generation characteristics were obtained for a long period of time. As shown, in the comparative example, sintering of the electrode progressed, and a decrease in reaction diffusion was observed.

As described above, it should not be understood that the description and drawings forming part of the disclosure of the embodiments of the present invention limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art. For example, as a perovskite oxide, L
Although a _0.8 Sr _0.2 MnO ₃ has been described, La-Mn
In addition to the perovskite-based composite oxides, La-Co-based perovskite-based composite oxides, La-Fe-based perovskite-based composite oxides, and element-substituted perovskite-based composite oxides can of course be used.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part of a solid oxide fuel cell according to the present invention.

FIG. 2 is an explanatory diagram showing a fine structure of a material layer of an electrode according to an embodiment.

FIG. 3 is an explanatory diagram showing another fine structure of a material layer of an electrode according to the embodiment.

FIG. 4 is an explanatory view showing a fine structure of a conventional electrode.

[Explanation of symbols]

 Reference Signs List 10 solid oxide fuel cell 11 perovskite oxide particles 12 high melting point material particles 14 material layer 15 surface material layer 16 electrode 17 solid electrolyte layer

Continued on the front page (72) Inventor Keiko Kushibiki 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. Naoki Hara 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Nissan Motor Co., Ltd. Nissan Motor Co., Ltd., Nissan Motor Co., Ltd. (72) Inventor Makoto Uchiyama 2nd Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. F-term (reference) 5H018 AA06 AS01 BB01 BB07 BB08 BB12 DD10 EE12 EE13 HH01 HH04 HH05 HH06 5H026 AA06 BB01 BB04 BB08 CC01 CC10 EE12 EE13 HH01 HH03 HH04 HH05 HH06

Claims (12)

[Claims] 1. A solid electrolyte fuel cell having a pair of electrodes sandwiching both sides of a solid electrolyte layer, wherein a material layer facing an interface between the electrode and the solid electrolyte layer has a porous structure, A solid oxide fuel cell, wherein a layer above the layer is mixed with a sub-material having a different composition or a different particle shape from the main material of the electrode. 2. A surface material layer made of fine particles and having a porous structure having pores narrower than the material layer is formed on a surface of the material layer on the side of the solid electrolyte layer. The solid oxide fuel cell according to claim 1. 3. The solid oxide fuel cell according to claim 1, wherein the electrode is made of a mixture of the main material having electron conductivity and a high melting point material. 4. The solid oxide fuel cell according to claim 3, wherein the high melting point material has a melting point of 1900 ° C. or higher. 5. One of the pair of electrodes is an air electrode, the other electrode is a fuel electrode, and the main material of the one electrode is a La—Mn-based perovskite composite oxide, La—Co. -Based perovskite-type composite oxide, La-Fe-based perovskite-type composite oxide and their element-substituted perovskite-type composite oxide, silver, at least one of platinum, the main material of the other electrode is iron, cobalt, nickel,
It contains at least one of copper, silver, platinum and palladium, and the high melting point material is aluminum oxide, calcium oxide, magnesium oxide, silicon oxide, zirconium oxide, cerium oxide, boron nitride, silicon nitride, boron carbide, carbonized 5. The composition according to claim 3, comprising at least one of titanium and its derivatives.
2. A solid oxide fuel cell according to claim 1. 6. The solid oxide fuel cell according to claim 3, wherein a mixing ratio of the high melting point material mixed in the material layer is 20 wt% or less. 7. The solid electrolyte according to claim 2, wherein the surface material layer is made of a mixture of an electrode material of a needle crystal and an electrode material of a spherical crystal. Type fuel cell. 8. The ratio of the minor axis to the major axis of the electrode material of the spherical crystal is 3 or less, and the ratio of the minor axis to the major axis of the electrode material of the acicular crystal is 3 to 20. Item 7. A solid oxide fuel cell according to Item 7. 9. The electric conductivity of the electrode material of the acicular crystal is activated.
10 in the temperature range ^TwoS ・ cm^-1In the above case, the material
The ratio of the electrode material of the needle crystals contained in the material layer is 50 w
t% or less, and the electrical conductivity of the electrode material of the needle-shaped crystal is within an operating temperature range.
10^TwoS ・ cm^-1Included in the material layer in the following cases
The ratio of the electrode material of the needle-like crystal is 20% by weight or less.
9. The solid oxide fuel cell according to claim 8, wherein
pond. 10. A method for producing an electrode for a solid oxide fuel cell sandwiching both surfaces of a solid electrolyte layer, wherein a surface of a porous structure material layer having gas diffusion holes is provided.
Forming a surface material layer of a porous structure having fine pores made of fine particles and narrower than the gas diffusion pores, which is bonded to the solid electrolyte layer, by any of PVD, CVD, EVD, and sol-gel methods. A method for producing an electrode for a solid oxide fuel cell, comprising: 11. The electrode for a solid oxide fuel cell according to claim 10, wherein after forming the surface material layer, a slurry or a paste is applied on the surface material layer by a printing method or a spraying method. Manufacturing method. 12. The method for manufacturing an electrode for a solid oxide fuel cell according to claim 10, wherein the material layer is formed by a thermal spraying method.