JP2001118590A - High conductivity solid electrolyte film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high conductivity solid electrolyte film with economy, mass productivity, and ease in large area application, and a homogeneous and elaborated thin film by a slurry coat method. SOLUTION: In a solid electrolyte film of zirconia (ZrO2) system, etc., a high conductivity solid electrolyte film is made to include at least one of Si, Na, Ba, Al, Nd, Ce, Pr, Ti, Sm, Fe elements and also to include one of La, Mn, Co, Sr, Ca, Ni elements. Also, the solid electrolyte film is manufactured by a slurry coat method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition of a highly conductive material formed on a porous ceramic, such as a solid electrolyte membrane of a solid oxide fuel cell (hereinafter also referred to as SOFC).

[0002]

2. Description of the Related Art A conventional technique of an electrolyte material and a method of forming an electrolyte film will be described by taking a solid electrolyte thin film for SOFC as an example. In an SOFC, a solid electrolyte thin film having oxygen ion (O ²⁻ ) permeability and no gas permeability is required. In order to satisfy both of these characteristics, a thin and dense film is generally produced using a high-purity material obtained by adding Y ₂ O ₃ to ZrO ₂ as the solid electrolyte film. Furthermore, it is also required that a large-area thin film can be formed economically. In the power generation cell of this SOFC, the thickness is generally 0.1 mm.
On a porous substrate having a thickness of 3 to 5.0 mm, a thickness of 30 to 20
A solid electrolyte membrane of 00 μm is formed. Further, a fuel electrode (Ni-based cermet or the like) is formed thereon.

[0003]

[Problems that the Invention is to Solve As a conventional solid electrolyte material, had a high-purity materials with the addition of Y ₂ O ₃ in ZrO _2, in the material obtained by adding only Y ₂ O ₃ in ZrO ₂ However, sufficient conductivity cannot be obtained, and the use of a high-purity material increases the cost. Therefore, when a solid electrolyte material or a solid electrolyte membrane is put into practical use, it is required to improve the conductivity and to manufacture the solid electrolyte at a low cost by reducing the purity.

[0004] The present invention provides a solid oxide fuel cell device having a high output density, which is economical, mass-producible, and easily applicable to a large area.
In order to form a uniform and dense thin film, an object is to form the thin film using a highly conductive solid electrolyte material.

[0005]

Means for Solving the Problems and Actions / Effects Therefor, in order to achieve the above object, a solid electrolyte material contains Si,
Na, Ba, Al, Nd, Ce, Pr, Ti, Sm, F
It is intended to provide a highly conductive film by producing a solid electrolyte membrane containing at least one or more of the elements e.

In the production of the above-mentioned highly conductive solid electrolyte membrane, Si, Na, Ba, Al, Nd, Ce, Pr, T
A solid electrolyte film is formed on an electrode (air electrode or fuel electrode) containing at least one of i, Sm, and Fe elements, and Si, Na, Ba,
Of the Al, Nd, Ce, Pr, Ti, Sm, and Fe elements,
By including at least one or more elements, it is possible to use a low-purity electrode material, and a low-cost SOF
C can be provided.

Further, Si, Na, Ba, Al, Nd, C
LaMnO ₃ -based or LaCoO ₃ containing at least one or more of e, Pr, Ti, Sm, and Fe elements
By forming a solid electrolyte membrane on an air electrode in which part of La of the system air electrode is replaced with Sr or Ca, or on a NiO / YSZ-based fuel electrode, Si,
Na, Ba, Al, Nd, Ce, Pr, Ti, Sm, F
e, at least one element, La, M
By including at least one or more of n, Co, Sr, Ca, and Ni elements, a solid electrolyte membrane with higher conductivity can be provided.

The preparation of the solid electrolyte membrane includes a step of preparing a slurry and a step of laminating the solid electrolyte slurry on an electrode substrate.

A feature of the present invention is to form a highly conductive solid electrolyte membrane. Its characteristic is that, as a solid electrolyte film, a solid electrolyte material that is stable at high temperatures as a solid electrolyte membrane and yttria is dissolved in zirconia to be a highly conductive material,
Si, Na, Ba, Al, Nd, Ce, Pr, Ti, S
A solid electrolyte membrane containing at least one or more of m and Fe elements.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, Si, Na, B
The ionic conductivity of the solid electrolyte itself can be improved by including at least one or more of a, Al, Nd, Ce, Pr, Ti, Sm, and Fe elements in the solid electrolyte membrane.

Further, Si, Na, Ba, Al, Nd, C
e, Pr, Ti, Sm, and at least one element of Fe, and La, Mn, Co, Sr, Ca, Ni
By including at least one of the elements in the solid electrolyte membrane, the ionic conductivity of the solid electrolyte itself can be further improved.

In the present invention, Si, Na, Ba, Al, Nd, Ce, Pr, Ti, S
The reason for including at least one or more of the elements m and Fe is to improve the conductivity of the solid electrolyte membrane by diffusing it into the solid electrolyte membrane when firing the solid electrolyte on the electrode. is there.

In the present invention, Si, Na, Ba, Al, Nd, Ce, and the like are contained in the solid electrolyte material or the solid electrolyte.
The reason that at least one or more of the elements Pr, Ti, Sm, and Fe is contained in a range of less than 10 atomic% is that if the content is more than 10 atomic%, the conductivity is significantly reduced.

The thickness of the solid electrolyte membrane in the present invention is desirably 5 to 150 μm. If it is less than 5 μm, a sufficiently dense film cannot be obtained, while if it exceeds 150 μm, the internal resistance becomes too large. Preferably, it is 100 μm or less, more preferably 50 μm
It is as follows.

The firing temperature of the solid electrolyte membrane is 120
0 ° C to 1700 ° C is desirable. At a temperature lower than 1200 ° C., sintering of the solid electrolyte powder does not proceed sufficiently, so that a dense solid electrolyte membrane cannot be obtained.
At a temperature higher than 0 ° C., the porosity of the electrode substrate is lost.

In the case where the solid electrolyte slurry is formed on the air electrode substrate, La (Sr, Ca) M
nO ₃ perovskite oxide (LSCM) or L
a (Sr, Ca) CoO ₃ perovskite oxide (L
Composite powder (LSCM / YSZ or LSCC / YS) of SCC) and yttria-doped zirconia (YSZ)
It is preferable to include a step of forming a film containing the slurry containing Z) on the cathode base. The reason is that the interface conductivity between the air electrode and the solid electrolyte can be increased.

In an electrolyte material obtained by dissolving yttria in zirconia, ionic conductivity can be improved by dissolving yttria in a concentration of 3 to 20 mol%, preferably 8 to 12 mol%.

In the present invention, the content of the solid electrolyte powder in the slurry is from 10 parts to 100 parts of the slurry solution.
50 parts are preferred. The composition of the slurry solution in the present invention is not particularly limited. The slurry may include a solvent, a binder, a dispersant, an antifoaming agent, and the like. In addition, a non-volatile solvent is used as a solvent,
It is desirable to contain about 80 wt%. The effect of the hardly volatile solvent is to suppress a change in viscosity of the slurry during preparation and storage of the slurry, and to suppress the occurrence of cracks due to drying after film formation (for example, dipping) using the slurry. It is. Here, the degree of low volatility is desirably 1 or less when the volatility of butyl acetate is 100, for example. For example, α-terpineol and the like can be mentioned.

The slurry solution may contain a general volatile solvent in addition to the non-volatile solvent. The action of the solvent contained in the solution is to improve the dispersibility of the solid electrolyte powder and the defoaming property. As an example of such a solvent, ethyl alcohol is suitable. Its desirable content is 20-90 wt% of the slurry solution.

The function of the binder contained in the slurry solution is to improve the coating property (adhesion) of the solid electrolyte powder on the substrate. The amount of the binder is preferably 0.1 to 10 parts based on 100 parts of the solvent. The reason is that if the concentration is low (for example, less than 0.1 wt%), the coating property is low, and if the concentration is high (for example, more than 10 wt%), the dispersibility of the solid electrolyte powder is deteriorated. As a specific example of the binder, ethyl cellulose is suitable.

The action of the dispersant contained in the slurry solution is as follows:
This is an improvement in the dispersibility of the solid electrolyte powder. The amount of dispersant is
0.1 to 4 parts is preferable for 100 parts of the solvent. The reason is that if the concentration is low (less than 0.1 wt%), the dispersibility is low,
If the concentration is high (over 4 wt%), the slurry is likely to be denatured. Specific examples of the dispersant include polyoxyethylene alkyl phosphate.

The defoaming agent contained in the slurry solution has a function of eliminating bubbles in the slurry. The amount of defoaming agent should be
0.1 to 4 parts is preferable for 00 parts. The reason is,
If the concentration is low (for example, less than 0.1 wt%), the effect is not so expected. If the concentration is high (for example, more than 4 wt%), the slurry is likely to be denatured. Specific examples of the antifoaming agent include sorbitan sesquioleate.
A method such as a ball mill can be adopted as a mixing method of each agent and the solid electrolyte powder.

The method for applying the slurry to the substrate in the production method of the present invention is not particularly limited. A dipping method, a spray method, a brush coating, a sheet bonding method, or the like may be used. Among them, the dipping method is preferred. This is because it is simple, rich in mass productivity, and low in cost. As the dipping method, besides a normal dipping method in which a substrate is immersed in a slurry in the air, a dipping method in a pressurized gas or a vacuum can be adopted. In that case, the number of times of dipping can be selected according to the required film thickness and the slurry composition to be used.

[0024]

Example 1 10 mol% of commercially available solid electrolyte powder
Si, Na, Ba, A to yttria-added zirconia powder
l, Nd, Ce, Pr, Ti, Sm, and Fe elements were each weighed in the range of 0 atomic% to 10 atomic%, and wet-mixed using ceramic balls.
After the mixed powder was dried, it was press-molded in a mold and fired at 1500 ° C. for 5 hours to obtain a press-fired body. The obtained fired body was polished so as to have a thickness of about 1 mm, and then a platinum electrode was attached to both sides, and a reference electrode was attached to a side surface having a thickness of 1 mm, to prepare a conductivity measurement sample. 1000 ° C,
The ionic conductivity of the electrolyte was measured by an AC impedance method in an air atmosphere. As a result, as shown in Table 1, 1
Si, Na, Ba, A in a range of less than 0 atomic%
It has been found that the conductivity can be improved by including at least one or more of l, Nd, Ce, Pr, Ti, Sm, and Fe elements.

[Table 1]

[0025]

Example 2 Similarly to Example 1, a commercially available 10 mol% yttria-added zirconia powder as a solid electrolyte powder was added with L
a, Mn, Co, Sr, Ca and Ni elements are each 1a
Atomic% and 1 atomic% of Si element were weighed and wet-mixed using a ceramic ball. After the mixed powder is dried, press molding is performed using a mold.
By sintering at 00 ° C. for 5 hours, a pressed sinter was obtained. The obtained fired body was polished so as to have a thickness of about 1 mm, and then a platinum electrode was attached to both sides, and a reference electrode was attached to a side surface having a thickness of 1 mm, to prepare a conductivity measurement sample. For these samples, the ionic conductivity of the electrolyte was measured at 1000 ° C. in an air atmosphere by an alternating current impedance method. As a result, as shown in Table 2, La,
It can be seen that the conductivity can be further improved by including one element of Mn, Co, Sr, Ca, and Ni elements and the Si element as compared with the case where only the Si element is included. Was.

[Table 2]

[0026]

As described above, according to the present invention, Si, Na, Ba, Al, Nd, Ce, P
A highly conductive solid electrolyte membrane can be formed by including at least one or more of the elements r, Ti, Sm, and Fe in a range of less than 10 atomic%.
Further, by further containing one kind of element among La, Mn, Co, Sr, Ca, and Ni elements, a more highly conductive solid electrolyte membrane can be formed.

Further, by forming the solid electrolyte membrane by a slurry coating method, it is possible to form a solid electrolyte thin film on the entire surface of a substrate of various shapes (a flat plate, the inner and outer surfaces of a pipe, etc.) or any part thereof. . Also, CVD / EV
Compared with D, the plasma spraying method or the like, an expensive manufacturing apparatus is unnecessary, and application to a large-sized product is easy.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int. Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 13/00 H01B 13/00 Z H01M 4/86 H01M 4/86 T 8/12 8/12 F term ( Reference) 4G048 AA03 AB02 AC04 AC06 AD02 AE05 5G301 CA30 CD01 5H018 AA06 BB01 EE02 EE12 EE13 5H026 AA06 BB00 BB01 BB04 EE13 HH05

Claims (9)

[Claims] 1. The method according to claim 1, wherein the elements are Si, Na, Ba, Al, Nd, Ce,
A highly conductive solid electrolyte membrane comprising at least one element among Pr, Ti, Sm, and Fe elements. 2. Si, Na, Ba, Al, Nd, Ce,
High conductivity comprising at least one or more of Pr, Ti, Sm and Fe elements and at least one or more of La, Mn, Co, Sr, Ca and Ni elements Solid electrolyte membrane. 3. An air electrode material in which a part of La of a LaMnO ₃ -based or LaCoO ₃ -based air electrode is partially substituted with Sr or Ca, Si, Na, Ba, Al, Nd, Ce, P
An air electrode comprising at least one or more of r, Ti, Sm, and Fe elements. 4. The NiO / YSZ-based fuel electrode material contains S
i, Na, Ba, Al, Nd, Ce, Pr, Ti, S
A fuel electrode comprising at least one or more of m and Fe elements. 5. A method for sintering a solid electrolyte on the air electrode or the fuel electrode to obtain Si, Na, Ba, Al,
A method for producing a solid electrolyte membrane, characterized by including at least one or more of Nd, Ce, Pr, Ti, Sm, and Fe elements in a solid electrolyte membrane. 6. The method of sintering a solid electrolyte on the air electrode or the fuel electrode to obtain Si, Na, Ba, Al,
At least one of Nd, Ce, Pr, Ti, Sm, and Fe elements, and La, Mn, Co, Sr, and C;
a. A method for producing a solid electrolyte membrane, characterized by including at least one or more of Ni elements in a solid electrolyte membrane. 7. The method for producing a solid electrolyte membrane according to claim 1, wherein the solid electrolyte membrane is formed on the air electrode or the fuel electrode by a slurry coating method. . 8. Si, Na, Ba, Al, Nd, Ce,
8. The solid electrolyte membrane according to claim 1, wherein at least one or more of Pr, Ti, Sm, and Fe elements are contained in a range of less than 10 atomic%. Method. 9. The zirconia (ZrO)
9. The method for producing a solid electrolyte membrane according to claim 1, wherein yttrium (Y ₂ O ₃ ) is dissolved in ₂ ).