JP2002280015A - Single room type solid electrolyte fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single room type solid electrolyte fuel cell stably providing relatively high current at 600 deg.C or lower without thinning an electrolyte and to provide the manufacturing method of the single room type solid electrolyte fuel cell. SOLUTION: This single room type solid electrolyte fuel cell has a single room type cell structure in which a positive electrode 2 and a negative electrode 3 are installed on the same surface of an oxygen ion conductive solid electrolyte 1, the positive electrode 2 is strontium-doped Ln1-x Srx CoO3-δ (wherein Ln is a rare-earth element), and the negative electrode 3 contains nickel and a composite oxide mainly comprising cerium oxide. The single room type solid electrolyte fuel cell uses the oxygen ion conductive solid electrolyte of thickness having sufficient mechanical strength at of 600 deg.C or lower and can stably generate power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is a single-chamber type solid electrolyte type which does not require the use of a gas seal material and a separator material which have been required since the single-chamber type and the device structure are simple. Related to fuel cells. More specifically, the present invention relates to a single-chamber solid electrolyte fuel cell capable of outputting a stable and large current even at a lower temperature than before, without requiring a thin electrolyte.

[0002]

2. Description of the Related Art A conventional solid oxide fuel cell is capable of generating power unless it is a two-chamber system in which a fuel gas such as hydrogen or methane is supplied to a nickel-zirconia cermet negative electrode and air is separately supplied to a manganese lanthanum positive electrode. I couldn't do it. For this reason, not only the device becomes complicated due to the necessity of a gas seal material and a separator material, but also a deterioration is caused by a solid phase reaction between the zirconia electrolyte, the positive electrode and the negative electrode, and the life of the battery is shortened.

In order to solve this drawback, a single-chamber solid electrolyte fuel cell has been developed in which a fuel gas and air are mixed in advance and power can be generated in this gas. Palladium or platinum on the electrode of
An impractical electrode member such as gold had to be used (see Japanese Patent No. 2810977).

Further, the power generation starting temperature of a single-chamber solid oxide fuel cell can shorten the time until startup, and can reduce the thermal stress at the time of repeated startup and shutdown and the accompanying deterioration. Lower values are preferred because of the merit. In addition, since methane is a main component of general city gas, it is easily available and suitable as a gas source for a single-chamber solid oxide fuel cell.

[0005] For this reason, research on operating a single-chamber solid oxide fuel cell at a relatively low temperature of 700 ° C. or lower has recently been active. For example, the inventors of the Journal of
The Electrochemical Society, 147 (8) 2888-2892 (2000)
Proposed single-chamber solid electrolyte fuel cell at the, La _0.9
Ni-SDC and Sm _0.8 Sr _0.5 CoO ₃ are used as electrolytes of Sr _0.1 Ga _0.8 Mg _0.2 O _2.85 (hereinafter, referred to as LSGM) and Ce _0.8 Sm _0.2 O _1.9 (hereinafter, referred to as SDC).
_By using _{± δ} as an electrode, it was shown that a stable current output can be obtained in a gas mixture of methane or a lower hydrocarbon and oxygen at 600 ° C. or higher.

[0006]

However, in the single-chamber solid electrolyte fuel cell described above, electrodes are formed on both sides of the electrolyte. Therefore, high output cannot be obtained unless the electrolyte is formed as thin as possible. When the strength of the material is low, there is a concern that the cell may be damaged. The present invention is intended to solve such a problem, and it is possible to achieve a temperature of 600 ° C. without forming a thin electrolyte.
An object of the present invention is to provide a single-chamber solid oxide fuel cell capable of stably obtaining a relatively high current and a method for manufacturing the same.

[0007]

A single-chamber solid electrolyte fuel cell according to the present invention has a single-chamber battery structure in which a positive electrode and a negative electrode are provided on the same surface of an oxygen ion conductive solid electrolyte, and comprises a hydrocarbon and air. Is a single-chamber solid oxide fuel cell capable of generating power by introducing a mixed gas of Ln _1-x Sr _x CoO _{3 ± δ} doped with strontium (where Ln is a rare earth element). , 0.2 ≦ x ≦ 0.8, δ is the amount of oxygen deficiency or the like, and is comprised of 0 ≦ δ <1), and the negative electrode contains nickel and a complex oxide mainly composed of cerium oxide. The oxygen ion conductive solid electrolyte has a surface roughness Ra of 2.0 × 10 ⁻⁶ m or less (more preferably 1.6 × 10 ⁻⁶ m or less) at least on the surface where the positive electrode and the negative electrode are in contact.
m, particularly preferably 0.2 × 10 ⁻⁶ m or less). The surface roughness Ra here is
It is the center line average roughness described in JIS B0601.

The method for manufacturing a single-chamber solid oxide fuel cell has a single-chamber cell structure in which a positive electrode and a negative electrode are provided on the same surface of an oxygen ion-conductive solid electrolyte, and a mixed gas of hydrocarbon and air is introduced. Is a single-chamber solid oxide fuel cell capable of generating power by mixing and pulverizing a nickel oxide powder and a double oxide powder mainly composed of cerium oxide in an organic solvent to form a paste-like negative electrode. A material is prepared and baked on one surface of the oxygen ion conductive solid electrolyte to form a negative electrode, and then Ln _1-x Sr _x CoO _{3 ± δ} (where Ln is a rare earth element, 0.2 ≦ x ≦ 0.8, δ is the amount of oxygen deficiency or the like, and 0 ≦ δ <1) is mixed and pulverized in an organic solvent to prepare a paste-like positive electrode material. Characterized by baking on the same surface of the electrolyte to form a positive electrode To.

The oxygen ion conductive solid electrolyte has a stabilization
Oxygen such as zirconia, which generally has high oxygen ion conductivity
Ion conductive solid electrolyte can be used, but high
In order to obtain high power generation performance, higher ion
Oxygen ion conductive solid electrolytes exhibiting conductivity are preferred.
As an example of this, Ce_1-yLn_yO_{2- δ}[Rare earth elements (Ln
Is Sm, Gd or Y), 0.1 ≦ y ≦ 0.3, δ is oxygen
The amount of deficiency, 0 ≦ δ <1] or La_1-zSr_zGa
_1-wMg_wO_{3- δ}(0.1 ≦ w ≦ 0.3, 0.1 ≦ z ≦
0.3 and δ are oxygen deficiency amounts, and 0 ≦ δ <1)
Can be Further, as specific examples of these, the summary
-Doped cerium oxide (eg, SDC: Ce
_0.8Sm_0.2O _1.9) And La site doped with Sr
Lanthanum oxide gallium doped with Mg at the Ga site
(For example, LSGM: La_0.9Sr_0.1Ga_0.8Mg_0.2
O_2.85).

When both electrodes are arranged on the same surface of the oxygen ion conductive solid electrolyte, the vicinity of the surface of the solid in contact with the electrodes becomes an oxygen ion conduction path. At this time, the conductivity greatly changes depending on the surface roughness. By setting the surface roughness Ra of at least the surface of the oxygen ion conductive solid electrolyte to be in contact with each electrode to 2.0 × 10 ⁻⁶ m or less, the conduction path of oxygen ions becomes sufficiently short. Further, since the contact resistance with the electrode is reduced, a high output can be obtained.

Further, the gap between the positive electrode and the negative electrode is 10
It can be 0 μm to 3 mm. The electrical resistance depends on the size of the gap between the electrodes. The smaller the gap, the lower the electrical resistance and the higher the power generation performance. However, if the gap between the electrodes is too small, inconveniences such as short-circuiting are likely to occur significantly. Therefore, by setting the gap in the above range, short-circuiting and the like are less likely to occur, and a low electric resistance value is obtained.

The negative electrode of the single-chamber solid oxide fuel cell may be any one containing nickel and a composite oxide mainly composed of cerium oxide. _{1-y Ln y O 2- δ} (Ln is Sm, Gd
Or Y, 0.1 ≦ y ≦ 0.3, δ is the amount of oxygen deficiency, and 0 ≦ δ <1, more specifically Ce _0.8 Sm
_0.2 O _1.9 ). Further, the negative electrode may include at least one selected from palladium, platinum, rhodium, iridium, and ruthenium. By adding a small amount of these metals, the catalytic action of the negative electrode, which is a nickel-based electrode, is affected, and high power generation performance can be obtained. Further, among the above metals, palladium is most preferred. Further, the content ratio of at least one selected from the above-mentioned palladium, platinum, rhodium, iridium and ruthenium is 1 to 10% by mass (more preferably 1 to 7% by mass).
% By mass, particularly preferably 1 to 5% by mass).
The rare earth element represented by Ln in Ln _1-x Sr _x CoO _{3 ± δ} used for the positive electrode is preferably lanthanum (La) or samarium (Sm). As an example of these, La
_0.6 Sr _0.4 CoO _{3 ± δ} and Sm _0.5 Sr _0.5 CoO _{3 ± δ} .

[Operation] The single-chamber solid electrolyte fuel cell of the present invention has a structure in which a positive electrode 2 and a negative electrode 3 are provided on the same surface of an oxygen ion conductive solid electrolyte 1 as shown in FIGS. This is a single-chamber fuel cell that can generate power in a mixed gas of hydrocarbon and air. Such a single-chamber fuel cell has the merit that the lower the temperature at which power can be generated, the shorter the start-up time and the lower the thermal stress when the start and stop are repeated. In order to obtain high output at low temperature,
It is necessary to form the oxygen ion conductive solid electrolyte thin.

For this reason, in the present invention, by disposing both electrodes close to the same surface of the oxygen ion conductive solid electrolyte,
The oxygen ion conductive solid electrolyte was not thinned, and high output could be obtained even at low temperatures. Therefore, the thickness of the oxygen ion conductive solid electrolyte can be arbitrarily selected, and sufficient mechanical strength can be easily secured.

Further, both electrode materials are selected, and a strontium-doped Ln _1-x Sr _x CoO _{3 ± δ} positive electrode and a negative electrode containing nickel and a complex oxide mainly composed of cerium oxide are used. As a result, a high output could be obtained at a low temperature.

In a single-chamber solid electrolyte fuel cell, in order to stably generate power in a lower temperature range (600 ° C. or lower), a partial oxidation reaction (for example, 2CH ₄ + O ₂ → 2H ₂₎ on a nickel-based electrode even in a low temperature range. + 2CO) must be generated efficiently. At this time, palladium, platinum, and nickel were added to an electrode obtained by adding a composite oxide mainly composed of cerium oxide to nickel.
When a small amount of at least one selected from rhodium and iridium is added, the above-described partial oxidation reaction proceeds efficiently and stable power generation becomes possible. This addition of palladium or the like is considered to be a kind of catalytic action.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a single-chamber solid electrolyte fuel cell according to the present invention will be described in more detail with reference to FIGS. 1. Configuration of Single Chamber Solid Electrolyte Fuel Cell The single chamber solid electrolyte fuel cell of the present invention is shown in FIGS.
As shown in the figure, a disk-shaped oxygen ion conductive solid electrolyte 1
Are provided with a positive electrode 2 and a negative electrode 3 respectively on the same surface. The single-chamber solid electrolyte fuel cell is housed in an alumina tube 4 and used with a mixed gas of methane and air flowing through the alumina tube 4.

The oxygen ion conductive solid electrolyte 1 is La
Although _{1-z Sr z Ga 1-} w Mg w O 3- δ and _{Ce 1- y} Ln _y O _2- δ can be used, in the present embodiment using LSGM or SDC. The positive electrode 2 is made of Ln doped with strontium.
_1-x Sr _x CoO _{3 ± δ} (Ln: rare earth element, especially La or Sm), and Sm _0.5 Sr _0.5 CoO _{3 ± δ} was used. Furthermore, the negative electrode 3 are nickel and mixtures _{(Ce 1-y Sm y O} 2- δ) and the electrode with the addition of palladium 1% by weight in the cerium oxide doped with samarium. The mixture of samarium-doped cerium oxide is SDC (Ce
_0.8 Sm _0.2 O _1.9 ). The mixing ratio of Ni and SDC was 7: 3 by weight. The positive electrode 2 and the negative electrode 3
As shown in FIG. 2, are provided at intervals so as to form a predetermined gap.

2. Production of Single-chamber Solid Electrolyte Fuel Cell This single-chamber solid electrolyte fuel cell was produced as follows. First, the negative electrode 3 is formed on the surface of the oxygen ion conductive solid electrolyte 1. A predetermined amount of nickel oxide powder and SDC powder are weighed, mixed and pulverized using an appropriate organic solvent, and then a predetermined amount of palladium oxide powder is added and mixed and pulverized to prepare a paste-like electrode material. This was screen-printed on the oxygen ion conductive solid electrolyte 1 and baked at 1400 ° C.

Next, a positive electrode 2 is formed on the same side of the surface of the oxygen ion conductive solid electrolyte 1 on which the negative electrode 3 is formed with a predetermined gap between the negative electrode and the negative electrode. Ln _1-x Sr _x CoO _{3
± δ} (here, Sm _0.5 Sr _0.5 CoO _{3 ± δ} was used) was dissolved in an organic solvent and pulverized to prepare a paste-like electrode material. This is converted to oxygen ion conductive solid electrolyte 1
Was screen-printed on the side opposite to the negative electrode 3 and baked at 900 ° C.

Further, if necessary, a reduction treatment may be performed, or the reduction treatment may be performed without the reduction treatment. When performing the reduction treatment, H ₂ gas is introduced into the oxygen ion conductive solid electrolyte 1 on which the electrodes 2 and 3 are formed at a temperature of 450 to 550 ° C., and the nickel oxide and the palladium oxide of the negative electrode 3 are reduced. . Also, even if the reduction process is not performed,
The flowing mixed gas causes a reaction of CH ₄ + ／ O ₂ → 2H ₂ + CO, and the atmosphere becomes a reducing atmosphere, whereby nickel oxide and palladium oxide are reduced, and an output can be obtained. In the single-chamber solid electrolyte fuel cell manufactured as described above, a power output can be obtained from the positive and negative electrodes by introducing a mixed gas of methane and oxygen.

3. Evaluation of single-chamber solid electrolyte fuel cell (1) Examination of surface roughness of electrolyte In a single-chamber solid electrolyte fuel cell using SDC as the oxygen ion-conductive solid electrolyte 1, the surface roughness of the electrode formation surface was reduced. The corresponding change in output characteristics was examined. The oxygen ion conductive solid electrolyte 1 of the single-chamber solid electrolyte fuel cell used for the measurement was □ 7 × 10 ⁻³ m, thickness 0.8 × 10 ⁻³ m,
The surface roughness Ra is reduced to 0.06 × 1 by polishing the surface.
0 ^-6 , 0.2 × 10 ^-6 , 0.8 × 10 ^-6 , and 1.6 ×
Four types of 10 ^-6 m were prepared.

The negative electrode 3 has a width of 1 × 10^-3m, length 5 ×
10^-3m-Ni-SDC (7: 3). Positive electrode 2
Width 1 × 10^-3m, length 5 × 10^-3Sm of m_0.5Sr_0.5C
oO _{Three ± δ}It is. Further, the gap between these electrodes is 1 mm.
is there. Also, the composition of the mixed gas used was ethane: oxygen =
A power generation test was performed at 600 ° C. at a ratio of 1: 1.

As shown in FIG. 3, it was found that a maximum output of 700 W / m ² or more was obtained at any surface roughness. Further, the output increases as the surface roughness Ra decreases, and when the surface roughness Ra is 0.2 × 10 ⁻⁶ m, about 7
50W / m ^2, 0.06 × in 10 ^-6 m to about 900 W / m ²
It became. From this, the surface roughness Ra is 2.0 × 10
If ^-6 m or less up to 600W / m ² or more output can be expected, it can be seen that a sufficient output can be obtained.

(2) Examination of the gap between the electrodes The output by the gap between the positive electrode 2 and the negative electrode 3 was examined. oxygen
The ion conductive solid electrolyte 1 is □ 7 × 10^-3m, thickness
0.8 × 10^-3m, surface roughness Ra 0.06 × 10 ^-6m and
did. The negative electrode 3 has a width of 0.5 × 10^-3m, length 5 × 1
0^-3m-Ni-SDC (7: 3). Positive electrode 2 has a width
0.5 × 10^-3m, length 5 × 10^-3Sm of m_0.5Sr_{0 .Five}
CoO_{Three ± δ}It is. Further, the gap between these electrodes is 0.1 mm.
5 × 10^-3, 1.0 × 10^-3, 1.5 × 10^-3m, and
3.0 × 10^-3m. Also, the set of mixed gas used
Power generation test at 600 ° C with ethane: oxygen = 1: 1
Was done.

FIG. 4 shows the results of the test performed under the above conditions. As shown in FIG. 4, the distance between the electrodes is 3.0 × 10 ⁻³ m.
About 500 W / m ² and about 195 at 0.5 × 10 ⁻³ m.
The output was higher as the width was as narrow as 0 W / m ² . In addition, it was found that a sufficient output of about 500 W / m ² or more could be obtained if the distance was 3.0 × 10 ⁻³ m or less.

(3) Investigation of the amount of palladium added The single-chamber type solid with various amounts of palladium added to the negative electrode was varied.
Open-circuit voltage and maximum output density of solid electrolyte fuel cells
Table 1 shows the results obtained for the degrees. Single chamber type solid electrolysis used
Quality fuel cell is used as an oxygen ion conductive solid electrolyte 1.
□ 7 × 10 using SDC^-3m, thickness 0.8 × 10
^-3m, surface roughness Ra 0.06 × 10^-6m. Also,
The negative electrode 3 has a width of 0.5 × 10^-3m, length 5 × 10^-3m
In addition, Ni-SDC to which Pd was added at a ratio shown in Table 1
(7: 3). The positive electrode 2 has a width of 0.5 × 10 ^-3m, long
5 × 10^-3Sm of m_0.5Sr_0.5CoO_{Three ± δ}It is.
Further, the gap between these electrodes is 1 mm. Also use
The composition of the mixed gas was ethane: oxygen = 2: 1, and 550
A power generation test was performed at ℃.

[0028]

[Table 1]

As shown in Table 1, the amount of Pd added was 1 to 10
High power generation performance of 1050 W / m ² or more could be obtained in the range of mass%. In the range of 1 to 7% by mass, 1
080 W / m ² or more, 1100 in the range of 1 to 5% by mass.
Particularly high power generation performance of W / m ² or more could be obtained.
Furthermore, even if palladium is replaced with rhodium, platinum, ruthenium and iridium, high power generation performance can be obtained in the range of 1 to 10% by mass.

[0030]

According to the single-chamber solid electrolyte fuel cell of the present invention, stable power generation can be achieved using an oxygen ion conductive solid electrolyte having sufficient mechanical strength even at a temperature range of 600 ° C. or less. It can be performed. In addition, since the battery has sufficient mechanical strength, a highly reliable battery can be formed.
This makes it possible to extend the life of the cell body and the peripheral members, reduce the cost, and the like, and easily commercialize a highly reliable fuel cell.

Furthermore, by setting the gap between the electrodes to a predetermined range, short-circuiting and the like can be suppressed while providing a high output. Also, by doping the negative electrode with a metal such as palladium, stable power generation can be performed even in a temperature range of 600 ° C. or lower.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the present single-chamber solid oxide fuel cell.

FIG. 2 is a schematic diagram for describing the present single-chamber solid oxide fuel cell.

FIG. 3 is a graph for explaining a change in output of the single-chamber solid electrolyte fuel cell according to the surface roughness of the oxygen ion conductive solid electrolyte.

FIG. 4 is a graph for explaining an output change of the present single-chamber solid oxide fuel cell due to a gap between a positive electrode and a negative electrode.

[Explanation of symbols]

1; oxygen ion conductive solid electrolyte; 2; positive electrode; 3; negative electrode; 4; alumina tube.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H018 AA06 AS01 BB01 BB11 BB12 EE03 EE13 HH03 5H026 AA06 BB01 BB06 BB08 EE02 EE13 HH00 HH03

Claims (5)

[Claims] 1. A single-chamber solid oxide structure having a single-chamber battery structure in which a positive electrode and a negative electrode are provided on the same surface of an oxygen ion-conductive solid electrolyte, and capable of generating power by introducing a mixed gas of hydrocarbon and air. Wherein the positive electrode is made of Ln _1-x Sr _x CoO _{3 ± δ} (where Ln is a rare earth element, 0.2 ≦ x ≦ 0.8, 0 ≦ δ <1), The negative electrode contains nickel and a composite oxide mainly composed of cerium oxide, and the oxygen ion conductive solid electrolyte has a surface roughness Ra of at least 2.0 × on a surface where the positive electrode and the negative electrode are in contact.
A single-chamber solid oxide fuel cell having a size of 10 ^-6 m or less. 2. The gap between the positive electrode and the negative electrode is 100 ×
The single-chamber solid oxide fuel cell according to claim 1, wherein the thickness is 10 ^{−6 to} 3 × 10 ⁻³ m. 3. The single-chamber solid electrolyte fuel cell according to claim 1, wherein the negative electrode includes at least one selected from palladium, platinum, rhodium, iridium, and ruthenium. 4. The single-chamber solid electrolyte fuel cell according to claim 3, wherein the content ratio of at least one selected from the group consisting of palladium, platinum, rhodium, iridium and ruthenium in the negative electrode is 1 to 10% by mass. 5. The same surface of an oxygen ion conductive solid electrolyte
It has a single-chamber battery structure with a positive electrode and a negative electrode,
Unit that can generate power by introducing a mixed gas of
A method for producing a chamber-type solid oxide fuel cell, comprising: a composite oxide mainly composed of nickel oxide powder and cerium oxide.
Powder and mixed in an organic solvent
An electrode material is prepared, and this is
Baking on one side of the material to form a negative electrode,
_1-xSr_xCoO _{Three ± δ}(Where Ln is a rare earth element,
0.2 ≦ x ≦ 0.8, 0 ≦ δ <1) mixed in an organic solvent
This is crushed to prepare a paste-like positive electrode material, which is then acidified.
Baking on the same side of the solid ion conductive solid electrolyte
Forming a single-chamber solid oxide fuel cell
Manufacturing method.