JP4900747B2 - Single-chamber solid electrolyte fuel cell and method for manufacturing the same - Google Patents

Description

【００２９】
表１に示すように、Ｐｄ添加量が１〜１０質量％の範囲で、１０５０Ｗ／ｍ²以上の高い発電性能を得ることができた。また、１〜７質量％の範囲では１０８０Ｗ／ｍ²以上、１〜５質量％の範囲では１１００Ｗ／ｍ²以上の特に高い発電性能を得ることができた。更に、パラジウムをロジウム、白金、ルテニウム及びイリジウムに置き換えても、１〜１０質量％の範囲で高い発電性能を得ることができる。
【００３０】
【発明の効果】
本発明の単室型固体電解質型燃料電池によれば、６００℃以下の温度域でも十分な機械的強度を備えた厚みの酸素イオン伝導性固体電解質を使用して安定した発電を行うことができる。また、十分な機械的強度を備えるため、より信頼性の高い電池が構成できる。このことから、電池本体及び周辺部材の長寿命化と低コスト化などが可能になり、高信頼性の燃料電池を容易に実用化することができる。
【００３１】
更に、電極の間隙を所定の範囲とすることで、高い出力を備えつつ、短絡等を抑制することができる。また、負極にパラジウム等の金属をドープすることで、６００℃以下の温度域でも安定した発電を行うことができる。
【図面の簡単な説明】
【図１】 本単室型固体電解質型燃料電池の説明をするための模式図である。
【図２】 本単室型固体電解質型燃料電池の説明をするための模式図である。
【図３】 酸素イオン伝導性固体電解質の表面粗度による本単室型固体電解質型燃料電池の出力変化を説明するためのグラフである。
【図４】 正極と負極の間隙による本単室型固体電解質型燃料電池の出力変化を説明するためのグラフである。
【符号の説明】
１；酸素イオン伝導性固体電解質、２；正極、３；負極、４；アルミナ管。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single-chamber solid electrolyte fuel cell that does not require the use of a gas seal material, a separator material, and the like that have been required so far because the single-chamber type and the device structure are simple. More specifically, the present invention relates to a single-chamber solid electrolyte fuel cell that does not require a thin electrolyte and can output a stable large current even at a lower temperature than in the past.
[0002]
[Prior art]
A conventional solid oxide fuel cell could not generate electric power unless it was a two-chamber type system in which a fuel gas such as hydrogen or methane was separately supplied to a nickel-zirconia cermet negative electrode and air was separately supplied to a manganese lanthanum positive electrode. For this reason, not only the apparatus becomes complicated by requiring a gas seal material and a separator material, but also a deterioration occurs due to a solid phase reaction between these, a zirconia electrolyte, a positive electrode, and a negative electrode, resulting in a short battery life.
[0003]
In order to solve this drawback, a single-chamber type solid oxide fuel cell that can mix fuel gas and air in advance and generate power in this gas has been developed. An impractical electrode member such as palladium, platinum, or gold had to be used (see Japanese Patent No. 2810977).
[0004]
Furthermore, the power generation start temperature of the single-chamber solid electrolyte fuel cell can shorten the time until start-up, and has the merit that thermal stress and repeated deterioration can be reduced when start-up and stop are repeated. Therefore, the lower one is preferable. In addition, since methane is a main component of general city gas, it is easily available and suitable as a gas raw material for a single-chamber solid electrolyte fuel cell.
[0005]
For this reason, in recent years, research into operating a single-chamber solid electrolyte fuel cell at a relatively low temperature of 700 ° C. or less has become active. For example, the single-chamber solid electrolyte fuel cell proposed by the present inventors in the Journal of The Electrochemical Society, 147 (8) 2888-2892 (2000) is La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _2.85 (hereinafter, LSGM) or Ce _0.8 Sm _0.2 O _1.9 (hereinafter referred to as SDC) as an electrolyte, and Ni-SDC and Sm _0.8 Sr _0.5 CoO _{3 ± δ} as electrodes. It was shown that a stable current output can be obtained in a gas in which hydrocarbon and oxygen are mixed.
[0006]
[Problems to be solved by the invention]
However, since the single-chamber solid electrolyte fuel cell shown above forms electrodes on both sides of the electrolyte, high output cannot be obtained unless the electrolyte is made as thin as possible. There was a concern leading to breakage.
The present invention solves such problems, and a single-chamber solid electrolyte fuel cell capable of stably obtaining a relatively high current at 600 ° C. or lower without forming a thin electrolyte and its An object is to provide a manufacturing method.
[0007]
[Means for Solving the Problems]
The single-chamber solid electrolyte fuel cell of 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 in a single chamber, and introduces a mixed gas of hydrocarbon and air. The positive electrode has a strontium-doped 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, etc., and 0 ≦ δ <1), the negative electrode is nickel, a double oxide mainly composed of cerium oxide , palladium, platinum, rhodium, iridium and wherein the at least one selected from ruthenium, the palladium, platinum, rhodium, at least one content ratio selected from iridium and ruthenium, from 1 to 10 wt%, the oxygen ion Den Sex solid electrolyte, at least a surface roughness Ra of the surface of positive electrode and negative electrode are in contact with 2.0 × ^{10 -6} m or less (more preferably 1.6 × ^{10 -6} m or less, particularly preferably 0.2 × 10 ⁻⁶ m or less).
Moreover, the surface roughness Ra here is a centerline average roughness as defined in JIS B0601.
[0008]
The single-chamber solid oxide fuel cell manufacturing method 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 in a single chamber, and a mixed gas of hydrocarbon and air is introduced. A single-chamber solid oxide fuel cell capable of generating electric power by mixing and pulverizing nickel oxide powder and double oxide powder mainly composed of cerium oxide in an organic solvent, followed by palladium, platinum At least one powder selected from rhodium, iridium and ruthenium is added so that the content in the negative electrode is 1 to 10% by weight, mixed and pulverized to prepare a paste-like negative electrode material, baked on one surface sex solid electrolyte to form a cathode, _{then, Ln 1-x Sr x CoO} 3 ± δ ( although, Ln is a rare earth element, 0.2 ≦ x ≦ 0.8, δ is oxygen defect or the like A paste-like positive electrode material is prepared by mixing and pulverizing 0 ≦ δ <1) in an organic solvent and baking this on the same surface of the oxygen ion conductive solid electrolyte to form a positive electrode It is characterized by.
[0009]
The oxygen ion conductive solid electrolyte can be an oxygen ion conductive solid electrolyte that generally shows high oxygen ion conductivity, such as stabilized zirconia, but in order to obtain high power generation performance even at low temperatures, higher ions can be used at low temperatures. An oxygen ion conductive solid electrolyte exhibiting conductivity is preferred.
As this _{example, Ce 1-y Ln y O} 2- δ [rare earth element (Ln is Sm, Gd or Y), 0.1 ≦ y ≦ 0.3 , δ is oxygen defect amount, 0 ≦ δ < 1] or La _1-z Sr _z Ga _1-w Mg _w O _{3− δ} (0.1 ≦ w ≦ 0.3, 0.1 ≦ z ≦ 0.3, δ is the amount of oxygen deficiency, and 0 ≦ δ <1). Further, specific examples of these include cerium oxide doped with samarium (eg, SDC: Ce _0.8 Sm _0.2 O _1.9 ), and lanthanum gallium oxide doped with Sr at the La site and Mg doped at the Ga site (eg, LSGM: La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _2.85 ).
[0010]
Further, 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 electrode serves as a conduction path for oxygen ions. At this time, the conductivity varies greatly depending on the surface roughness. By setting the surface roughness Ra of at least the surface of the oxygen ion conductive solid electrolyte in contact with each electrode to 2.0 × 10 ⁻⁶ m or less, the oxygen ion conduction path becomes sufficiently short. Further, since the contact resistance with the electrode is reduced, a high output can be obtained.
[0011]
Furthermore, the gap between the positive electrode and the negative electrode can be 100 μm to 3 mm. The electrical resistance value depends on the size of the gap between the electrodes, and the smaller the electrical resistance value, the lower the electrical resistance value and the higher the power generation performance. However, if the gap between the electrodes is too small, inconveniences such as a short circuit are likely to occur. Therefore, by setting the gap within the above range, a short circuit or the like is difficult to occur and a low electrical resistance value is obtained.
[0012]
The negative electrode of the present single-chamber solid electrolyte fuel cell only needs to contain nickel and a double oxide mainly composed of cerium oxide. As the double oxide mainly composed of cerium oxide, Ce _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 ).
The negative electrode contains 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 preferable.
Further, the palladium, platinum, rhodium, at least one content ratio selected from iridium and ruthenium, from 1 to 10% by weight (preferably 1 to 7 mass%, particularly preferably 1 to 5 mass%) is.
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). Examples of these include La _0.6 Sr _0.4 CoO _{3 ± δ} and Sm _0.5 Sr _0.5 CoO _{3 ± δ} .
[0013]
[Action]
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 capable of generating power in the mixed gas.
In such a single-chamber fuel cell, the lower the temperature at which power can be generated, the shorter the time it can start, and the advantage that it can reduce the thermal stress when it is repeatedly started and stopped. In the structure in which the electrode is arranged on the electrode, it is necessary to form a thin oxygen ion conductive solid electrolyte in order to obtain a high output at a low temperature.
[0014]
For this reason, in the present invention, by arranging both electrodes close to each other on the same surface of the oxygen ion conductive solid electrolyte, the oxygen ion conductive solid electrolyte is not made thin, and a high output can be obtained even at a low temperature. . Therefore, the thickness of the oxygen ion conductive solid electrolyte can be arbitrarily selected, and sufficient mechanical strength can be easily ensured.
[0015]
In addition, both electrode materials are selected, and a strontium-doped Ln _1-x Sr _x CoO _{3 ± δ} positive electrode, a negative electrode containing nickel and a double oxide mainly composed of cerium oxide, is used at a low temperature. High output was obtained.
[0016]
In a single-chamber solid electrolyte fuel cell, in order to generate power stably at a lower temperature (600 ° C. or lower), a partial oxidation reaction (for example, 2CH ₄ + O ₂ → 2H ₂ + 2CO) is performed on a nickel-based electrode even at a lower temperature. It is necessary to generate efficiently. At this time, if a small amount of at least one selected from palladium, platinum, rhodium and iridium is added to an electrode in which a double oxide mainly composed of cerium oxide is added to nickel, the partial oxidation reaction proceeds efficiently and stable power generation is achieved. Is possible. The addition of palladium or the like is considered as a kind of catalytic action.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the single-chamber solid electrolyte fuel cell of the present invention will be described in more detail with reference to FIGS.
1. Configuration of Single Chamber Solid Electrolyte Fuel Cell As shown in FIGS. 1 and 2, the single chamber solid electrolyte fuel cell of the present invention has a positive electrode on the same surface of a disk-shaped oxygen ion conductive solid electrolyte 1 respectively. 2 and the negative electrode 3. The single-chamber solid electrolyte fuel cell is housed in an alumina tube 4 and used in a state where a mixed gas of methane and air is circulated through the alumina tube 4.
[0018]
Oxygen ion conductive solid electrolyte 1 is _{La 1-z Sr z Ga 1} -w Mg w O 3- δ and _{Ce 1-y Ln y O 2-} δ is available, use the LSGM or SDC in this embodiment It was. The positive electrode 2 is Ln _1-x Sr _x CoO _{3 ± δ} (Ln: rare earth element, particularly La or Sm) doped with strontium, and Sm _0.5 Sr _0.5 CoO _{3 ± δ} is 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. SDC (Ce _0.8 Sm _0.2 O _1.9 ) was used as the mixture of samarium-doped cerium oxide. The mixing ratio of Ni and SDC was 7: 3 by weight.
Moreover, as shown in FIG. 2, the positive electrode 2 and the negative electrode 3 are provided at intervals so as to form a predetermined gap.
[0019]
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.
[0020]
Next, the positive electrode 2 is formed with a predetermined gap between the negative electrode 3 and the negative electrode 3 on the same side of the surface on which the negative electrode 3 of the oxygen ion conductive solid electrolyte 1 is formed. 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 was screen-printed on the surface opposite to the negative electrode 3 of the oxygen ion conductive solid electrolyte 1, and baked at 900 ° C.
[0021]
Further, the reduction treatment may be performed as necessary, or the reduction treatment can be used. 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. to reduce the nickel oxide and palladium oxide of the negative electrode 3. . Even when no reduction treatment is performed, the flowing mixed gas causes a reaction of CH ₄ + 1 / 2O ₂ → 2H ₂ + CO, and a reduction atmosphere is generated, and reduction of nickel oxide and palladium oxide occurs to obtain output. Will be able to.
The single-chamber solid electrolyte fuel cell produced in this way can obtain power output from the positive and negative electrodes by introducing a mixed gas of methane and oxygen.
[0022]
3. Evaluation of single-chamber solid electrolyte fuel cell (1) Examination of surface roughness of electrolyte In single-chamber solid electrolyte fuel cell using SDC as oxygen ion conductive solid electrolyte 1, the surface roughness of the electrode formation surface The change in output characteristics was investigated.
The oxygen ion conductive solid electrolyte 1 of the single-chamber solid electrolyte fuel cell used for the measurement is □ 7 × 10 ⁻³ m and a thickness of 0.8 × 10 ⁻³ m, and the surface roughness is obtained by polishing the surface. Four types of Ra, 0.06 × 10 ⁻⁶ , 0.2 × 10 ⁻⁶ , 0.8 × 10 ⁻⁶ , and 1.6 × 10 ⁻⁶ m were prepared.
[0023]
The negative electrode 3 is Ni-SDC (7: 3) having a width of 1 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m. The positive electrode 2 is Sm _0.5 Sr _0.5 CoO _{3 ± δ} having a width of 1 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m. Furthermore, the gap between these electrodes is 1 mm. The composition of the mixed gas used was ethane: oxygen = 1: 1, and a power generation test was performed at 600 ° C.
[0024]
As shown in FIG. 3, it was found that a large output of 700 W / m ² or more was obtained at any surface roughness. Further, the output as the surface roughness Ra becomes smaller increases, Ra is 0.2 × 10 ^-6 m in about 750W / m ^2, was a 0.06 × 10 ^-6 m In about 900 W / m ^2. From this, it can be seen that if the surface roughness Ra is 2.0 × 10 ⁻⁶ m or less, a maximum output of 600 W / m ² or more can be expected, and a sufficient output can be obtained.
[0025]
(2) Examination of electrode gap The output by the gap between the positive electrode 2 and the negative electrode 3 was examined. The oxygen ion conductive solid electrolyte 1 was □ 7 × 10 ⁻³ m, thickness 0.8 × 10 ⁻³ m, and surface roughness Ra 0.06 × 10 ⁻⁶ m.
The negative electrode 3 is Ni-SDC (7: 3) having a width of 0.5 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m. The positive electrode 2 is Sm _0.5 Sr _0.5 CoO _{3 ± δ} having a width of 0.5 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m. Furthermore, the gaps between these electrodes were 0.5 × 10 ⁻³ , 1.0 × 10 ⁻³ , 1.5 × 10 ⁻³ m, and 3.0 × 10 ⁻³ m.
The composition of the mixed gas used was ethane: oxygen = 1: 1, and a power generation test was performed at 600 ° C.
[0026]
The results of testing under the above conditions are shown in FIG. As shown in FIG. 4, the electrode spacing in 3.0 × 10 ^-3 m to about 500 W / m ^2, and about 1950W / m ² at 0.5 × 10 ^-3 m, became narrower as high output. It was also found that a sufficient output of about 500 W / m ² or more can be obtained when the distance is 3.0 × 10 ⁻³ m or less.
[0027]
(3) Examination of addition amount of palladium Table 1 shows the results obtained for the open circuit voltage and the maximum output density in the single-chamber solid electrolyte fuel cell in which the addition amount of palladium in the negative electrode was variously changed. The single-chamber solid electrolyte fuel cell used uses SDC as the oxygen ion conductive solid electrolyte 1 and is □ 7 × 10 ⁻³ m, thickness 0.8 × 10 ⁻³ m, surface roughness Ra 0.06 × 10 ⁻⁶ m.
The negative electrode 3 has a width of 0.5 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m, and is Ni—SDC (7: 3) to which Pd is added at a ratio shown in Table 1. The positive electrode 2 is Sm _0.5 Sr _0.5 CoO _{3 ± δ} having a width of 0.5 × 10 ⁻³ m and a length of 5 × 10 ⁻³ m. Furthermore, the gap between these electrodes is 1 mm. Further, the composition of the mixed gas used was ethane: oxygen = 2: 1, and a power generation test was conducted at 550 ° C.
[0028]
[Table 1]

[0029]
As shown in Table 1, high power generation performance of 1050 W / m ² or more could be obtained when the amount of Pd added was in the range of 1 to 10% by mass. Further, in the range of 1 to 7 mass% 1080W / m ² or more, in the range of 1 to 5 wt% could be obtained 1100W / m ² or more, especially high power generation performance. 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]
【Effect of the invention】
According to the single-chamber solid electrolyte fuel cell of the present invention, stable power generation can be performed using an oxygen ion conductive solid electrolyte having a sufficient mechanical strength even in a temperature range of 600 ° C. or lower. . Moreover, since it has sufficient mechanical strength, a more reliable battery can be configured. From this, it becomes possible to extend the life and cost of the battery body and peripheral members, and to easily put a highly reliable fuel cell into practical use.
[0031]
Furthermore, by setting the gap between the electrodes within a predetermined range, it is possible to suppress a short circuit or the like while providing a high output. In addition, 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 view for explaining the single-chamber solid electrolyte fuel cell.
FIG. 2 is a schematic view for explaining the single-chamber solid electrolyte fuel cell.
FIG. 3 is a graph for explaining an output change 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 a change in output of the single-chamber solid electrolyte fuel cell according 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.

Claims (3)

A single-chamber solid oxide type that has a single-chamber battery structure with a positive electrode and a negative electrode on the same surface of an oxygen ion conductive solid electrolyte in a single chamber and can generate power by introducing a mixed gas of hydrocarbon and air A fuel cell,
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 includes nickel, a double oxide mainly composed of cerium oxide, and at least one selected from palladium, platinum, rhodium, iridium and ruthenium ,
The content ratio of at least one selected from the palladium, platinum, rhodium, iridium and ruthenium is 1 to 10% by mass,
The oxygen ion conductive solid electrolyte has a surface roughness Ra of 2.0 × 10 ⁻⁶ m or less at least on a surface where the positive electrode and the negative electrode are in contact with each other, and a single-chamber solid electrolyte fuel cell. 2. The single-chamber solid electrolyte fuel cell according to claim 1, wherein a gap between the positive electrode and the negative electrode is 100 × 10 ^{−6 to} 3 × 10 ⁻³ m. A single-chamber solid oxide type that has a single-chamber battery structure with a positive electrode and a negative electrode on the same surface of an oxygen ion conductive solid electrolyte in a single chamber and can generate power by introducing a mixed gas of hydrocarbon and air A fuel cell manufacturing method comprising:
Nickel oxide powder and double oxide powder mainly composed of cerium oxide are mixed and pulverized in an organic solvent, and at least one powder selected from palladium, platinum, rhodium, iridium and ruthenium has a content of 1 in the negative electrode. added in an amount of 10 wt% were mixed and pulverized by a paste-like negative electrode material was prepared, which was formed a negative electrode printed on one side of the oxygen ion conductive solid electrolyte, then, Ln _{1- x} Sr _x CoO _{3 ± δ} (where Ln is a rare earth element, 0.2 ≦ x ≦ 0.8, 0 ≦ δ <1) is mixed and ground in an organic solvent to prepare a paste-like positive electrode material, A method for producing a single-chamber solid oxide fuel cell, wherein the positive electrode is formed by baking this on the same surface of the oxygen ion conductive solid electrolyte.

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