WO2007091642A1

WO2007091642A1 - Air electrode material for solid oxide fuel cell

Info

Publication number: WO2007091642A1
Application number: PCT/JP2007/052247
Authority: WO
Inventors: Kazuo Hata
Original assignee: Nippon Shokubai Co., Ltd.
Priority date: 2006-02-10
Filing date: 2007-02-08
Publication date: 2007-08-16
Also published as: JPWO2007091642A1; JP5525564B2; JP2012164672A; JP5044392B2

Abstract

This invention provides an air electrode material for a fuel cell, which is superior in electrode activity persistence to conventional materials and has durability high enough to withstand even repeating heat history between room temperature during stop of the operation and a high temperature above 700ºC during operation. The air electrode material for a solid oxide fuel cell is characterized by comprising a perovskite oxide represented by general formula (I): (PrxA1-x)(FeyB1-y)O3 ······ (I) wherein A represents an alkaline earth metal element or the like; B represents a group 7a element or the like; x is 0.5 ≤ x ≤ 1; and y is 0.5 ≤ y ≤ 1.

Description

Specification

Air electrode materials for solid oxide fuel cells

Technical field

[0001] The present invention relates to an air electrode material for a solid oxide fuel cell. The present invention also relates to an air electrode formed from the air electrode material and a fuel cell having the air electrode.

Background art

In recent years, fuel cells have attracted attention as clean energy sources. Fuel cells are rapidly being studied for improvement and practical use mainly for household power generation, commercial power generation, and automobile power generation.

[0003] By the way, as a cathode material for a solid oxide fuel cell, a generalized bumskite oxide (ABO: A and B represent metal elements) is generally used. Among them, A site

Three

Lanthanum with lanthanum and B-site manganese manganese are widely used. However, the electrode activity of this lanthanum-manganate material is low. Therefore, in order to increase the power generation efficiency, the operating temperature of the fuel cell power generation system must be raised to 900 ° C or higher.

[0004] On the other hand, if the fuel cell material is exposed to such a high temperature for a long time, the material is more likely to be sintered, and the influence of poisoning by chromium contained in the separator increases, resulting in a decrease in power generation efficiency. Resulting in. Therefore, it is desirable to keep the operating temperature of the fuel cell below 850 ° C, preferably below 800 ° C.

[0005] Therefore, there is a demand for an air electrode material that has excellent conductivity so that it can withstand use at high temperatures and that has a thermal expansion coefficient close to that of the electrolyte material. In line with these demands, perovskite-type oxides containing lanthanum and cobalt are being studied because they exhibit excellent electrode activity even at high conductivity of 750 ° C. However, since the oxide is highly reactive with the zirconium oxide electrolyte, it is easy to produce an insulating compound. In addition, there is a problem in stability that the thermal expansion coefficient is about twice as large as that of zirconium oxide electrolyte.

[0006] Japanese Patent Application Laid-Open No. 7-226208 adds manganese having high activity to manganese. Perovskite type oxides are disclosed. Furthermore, Solid State Ionics, Vol. 118 (1999) p.241 shows that the crystal structure and thermal expansion of an air electrode material with praseodymium, strontium at the A site, and cobalt / manganese velobskite-type oxides. The rate has been reported.

[0007] In addition, the electrode activity at 750 ° C is inferior to that of an oxide containing cobalt. As an example of an electrode activity superior to that of an oxide containing manganese, a velovskite-type oxide containing iron is also used. It leaves and speaks. The ί row shows Proceedings of the 3rd.International Symposium on bolid Oxide Fuel Cells p.241, 1993, Honolulu Hawaii.Perovskite-type oxides with lanthanum 'strontium at A site and cobalt' iron at B site Is described. Japanese Patent Publication No. 11 242960 and Japanese Patent Application Laid-Open No. 2002-1510918 disclose perovskite-type oxides containing iron and Nikkenore. US Pat. No. 6,946,213 describes an air electrode material using a perovskite oxide containing a transition element and magnesium, or a transition element and zinc.

However, for practical use as a fuel cell system, durability of 40,000 hours is required. In response to these demands, the air electrode material is not satisfactory in terms of long-term stability of electrode activity. In addition, it cannot be said that the system operating conditions, especially the high temperature of about 750-900 ° C exposed during operation and the thermal history of repeated cooling down to room temperature when operation is stopped, are not sufficient.

Disclosure of the invention

[0009] The present invention has been made paying attention to the above situation. Its purpose is to maintain long-term electrode activity sustainability as a cathode material compared to conventional materials, and to withstand the heat history of repeated high temperatures exceeding 700 ° C at room temperature during operation and operation. The object is to provide an air electrode material for a fuel cell having high durability. Another object of the present invention is to provide a high-performance air electrode and fuel cell using the air electrode material.

[0010] As described above, among the perovskite oxides, perovskite oxides containing lanthanum and iron'cobalt have excellent electrode activity at 750 ° C or higher, and thus air. Used as an extreme material. However, there is a problem in long-term heat resistance that it is easy to produce an insulating compound because of its high reactivity with the zirconium oxide electrolyte.

[0011] Accordingly, the present inventors based on iron-containing mouthbushite oxides, and their drawbacks. In addition, the performance as an air electrode material was investigated by variously changing the constituent metal of the A site and B site in the iron-containing perovskite oxide, which should improve the performance further.

As a result, the following knowledge was found and the present invention was completed.

(1) In addition to the iron that constitutes the B site of iron-containing perovskite-type oxides, if an appropriate amount of a 7a group element or a 8 group element is mixed, the conductivity and electrode activity are further improved, which is preferable as an air electrode material. Become a composition.

(2) If praseodymium is used as the main element constituting the A site of the perovskite type oxide, the reactivity with the electrolyte is suppressed and the high-temperature stability is improved as compared with lanthanum.

(3) When a suitable amount of alkaline earth metal or rare earth element is mixed with praseodymium, the difference in thermal expansion from the electrolyte is reduced, and a very excellent air electrode material can be obtained.

[0013] An air electrode material for a solid oxide fuel cell according to the present invention that has solved the above-mentioned problems is characterized by containing a velovskite oxide represented by the following general formula (I):

(Pr A) (Fe B) O

x l-χ y 1-y 3 …… (I)

[Wherein A represents at least one element selected from alkaline earth metal elements and rare earth elements; B represents at least one element selected from group 7a elements and group 8 element forces] Χί or 0.5 ≤ x ≤ l; y «0. Indicates 5 ≤ y ≤ l]

The air electrode for a solid oxide fuel cell of the present invention is an air electrode formed on one side of a solid electrolyte in a solid oxide fuel cell, and is formed of the air electrode material according to the present invention. It is characterized by that.

[0014] The solid oxide fuel cell of the present invention is a solid oxide fuel cell in which an air electrode is formed on one side of a solid electrolyte and a fuel electrode is formed on the other side. The electrode is formed of the air electrode material according to the present invention.

Brief Description of Drawings

FIG. 1 is a conceptual diagram showing a single cell power generation evaluation apparatus used in an experiment. In the figure, 1 indicates a heater, 2 indicates an alumina outer tube, 3 indicates an alumina inner tube, 4 indicates a platinum lead wire, 5 indicates a solid electrolyte sheet, 6 indicates a force sword, 7 indicates an anode 8 indicates a sealing material. BEST MODE FOR CARRYING OUT THE INVENTION

[0016] An air electrode material for a solid oxide fuel cell according to the present invention is characterized in that it includes a peculiar bskite oxide represented by the following general formula (I).

(Pr A) (Fe B) O …… (I)

x l-χ y 1-y 3

In the above formula, preferred alkaline earth metals used as the element A are Ca, Sr, Ba and the like. Preferred rare earth elements include La, Ce, Sm, Gd and the like. These can be used alone, or two or more of them may be used in any combination as required. Of these, Sr and Ce are particularly preferable.

[0017] In addition, the 7a group element and the 8 group element used as the B element are described in “Science and Chemistry Dictionary” (issued by Iwanami Shoten, December 20, 2004, 5th edition, 20th edition, page 1525). Group 7a and group 8 elements classified as “periodic rules of elements” (short-period type). Preferred group 7a elements include Mn, and preferred group 8 elements include Co, Ni, Cu and the like. These can be used alone, or two or more of them can be used in any combination as required. Of these, Ni and Cu are particularly preferred.

[0018] The values of X and y in the above formula are also important, and it is necessary to set the value of X in the range of 0.5≤x≤l in order to exert the combined effect of the above elements effectively It is. More preferably, 0.5 5≤x≤0.95, even more preferably 0.660≤x≤0.90. Incidentally, if the force is less than 5, the difference in thermal expansion from the electrolyte is too large, so when the fuel cell is operated, it undergoes repeated thermal cycles between room temperature and operating temperature, so that the interface between the electrolyte membrane and the air electrode When stress is generated, the electrolyte membrane and the air electrode are easily separated or cracks are easily generated in the electrolyte membrane.

[0019] On the other hand, the value of y needs to be set in the range of 0.5≤y≤1. More preferably 0.

55≤y≤0.95, more preferably 0.660≤y≤0.90. Incidentally, if the y force is less than 0.05, it is difficult to exhibit the excellent electrode activity inherent in the iron-containing mouthbskite-type air electrode, and in particular, the stability of the electrode activity with time decreases.

[0020] In the above description, the atomic ratio of oxygen in the perovskite-type acid complex is expressed as 3. ing. As is apparent to those skilled in the art, for example, when the atomic ratio X or y is not 1, oxygen vacancies are generated, so in practice, the oxygen atomic ratio often takes a value smaller than 3. . However, since the number of oxygen vacancies varies depending on the type of element added and the manufacturing conditions, in formula (I), the atomic ratio of oxygen is represented as 3 for convenience.

[0021] Further, in the present invention, doped preria doped with at least one kind selected from yttrium, samarium, and gadolinium force together with the above praseodymium 'iron-containing perovskite-type acid oxide; or from yttrium, scandium, ytterbium A mixture of at least one of stable zirconium oxides stabilized by at least one of the selected elemental oxides is also an excellent air electrode material. A preferable mixing ratio in this case is 5 to 30% by mass in total power of at least one of the doped silica and the stable zirconium oxide to 70 to 95% by mass of the above-mentioned brazeodymium iron-containing perovskite oxide. This is the range.

[0022] The doped ceria has electronic conductivity and ionic conductivity, and also has a characteristic of absorbing oxygen when the oxygen concentration is high and releasing the absorbed oxygen when the oxygen concentration is low. As a result, when doped ceria is mixed, the characteristics of the perovskite type oxide as an air electrode are further improved. In addition, the above stable zirconium oxide has an effect of further increasing the consistency of the thermal expansion coefficient with the electrolyte, and contributes to the improvement of the binding property with the electrolyte.

[0023] The effect of the doped ceria and Z or stable zirconium oxide is effectively exerted by blending 5% by mass or more with respect to praseodymium / iron-containing perovskite oxide: 70 to 95% by mass. On the other hand, if the total amount exceeds 30% by mass, the absolute amount of the electrode active ingredient, the velobskite-type acid oxide, becomes dull and the activity decreases, and the volume mixing ratio becomes 60% or less. Therefore, the conductivity is also lowered, and the original object of the present invention cannot be achieved. The more preferable blending ratio of doped ceria and Z or stable zirconia is 10% by mass or more and 25% by mass or less, and more preferably 20% by mass or less. The preferred mixing ratio of doped ceria and stable zirconia is the ratio by weight ratio of doped ceria Z stable zirconia = 1Z4 ~ 2Z1, more preferably 1Z3 ~: LZl, more preferred Or 1Z2 ~ 7Z8.

[0024] An embodiment in which coarse particles and fine particles of doped ceria are collected is also suitable. Doped ceria The blending amount of the coarse particles and fine particles is preferably 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 25% by mass or less, and further preferably 20% by mass or less. The preferable blending ratio of the doped doseria coarse particles and fine particles is, as a mass ratio, coarse particles Z fine particles = 1Z 4 to 2Zl, more preferably 1Z3 to: LZl, still more preferably 1Z2 to 7Z8.

[0025] In addition, when praseodymium 'iron-containing perovskite type oxides, doped ceria coarse particles and stabilized zircoure are mixed as described above, the average particle size of each component is "doped ceria coarse particles> praseodymium iron-based perovskite" The particle size should be adjusted to satisfy the relationship of “type oxide particles> stable Zircoyu particles”. In addition, when mixing doped ceria coarse particles and fine particles, it is preferable to adjust the particle size so that the average particle size of each component satisfies the relationship of “doped ceria coarse particles> velobskite oxide particles> doped ceria fine particles”. . By satisfying such a relationship of the average particle diameter, even when the air electrode is exposed to a high temperature for a long time, changes in the pore diameter and the pore volume in the air electrode over time can be suppressed. Further, not only the pores important as the air electrode are stably maintained and excellent gas permeability is maintained, but also the strength of the air electrode layer itself is increased, so that the air electrode layer can be prevented from being damaged during handling. In addition, the sintering of the velovskite-type oxide particles is suppressed, and the long-term sustainability of the electrode activity is further enhanced.

[0026] In particular, when satisfying the above average particle size relationship, when the temperature is lowered from a high temperature of 750 to 950 ° C during operation to room temperature when the operation is stopped! /, The durability against severe heat cycle is remarkably excellent. It will be a thing.

[0027] In order to more effectively exhibit these characteristics, after satisfying the relationship of the average particle size of each particle described above, the average particle size of the doped ceria coarse particles is 1 to 30 111, the perovskite type The average particle diameter of the oxide particles is preferably in the range of 0.3 to 3 μm, and the average particle diameter of the stabilized zirconia particles is preferably in the range of 0.1 to m. In addition, when the doped ceria coarse particles and the fine particles are mixed, the average particle diameter of the doped ceria coarse particles is 1 to 30 μm and the perovskite oxide particles are satisfied after satisfying the above-mentioned relationship of the average particle sizes of the respective particles. It is preferable that the average particle size is 0.3 to 3 μm, and the average particle size of the doped ceria fine particles is 0.1 to 1 μm.

Here, the average particle diameter refers to the particle diameter at 50 volume% in the cumulative graph after measuring the particle size distribution of the particles. For example, the average particle size of the bottom buxite oxide particles is 0.3-3. m means an aggregate of the same particles whose 50 volume% diameter is in the range of 0.3-3 / ζ πι.

[0029] The functions of the doped ceria particles having an average particle size of 1 to 30 m are the formation and maintenance of pores in the air layer and the prevention of aggregation of the mouth bumskite type oxide particles as the electrode catalyst. In addition, the stabilized zirconia particles or doped ceria fine particles having an average particle diameter of 0.1 to 1 / ζ πι increase the adhesion between the doped ceria particles and the velovskite-type oxide particles and reliably form a conductive path. It exhibits the function of enhancing the bondability with the electrolyte.

[0030] Incidentally, when the doped ceria coarse particles are mixed, if the average particle size is less than 1 μm, there is a possibility that an appropriate gap is not formed between the particles and the air permeability is insufficient. In addition, sintering is likely to proceed when exposed to high temperatures, and the porosity may tend to decrease over time. On the other hand, if the average particle size of the doped ceria particles becomes too large exceeding 30 m, the gaps between the particles are sufficiently secured and the decrease in porosity due to the progress of sintering is suppressed, but the strength as the air electrode layer May feel down. Therefore, in order to increase the strength, it is necessary to mix a large amount of easily sinterable zirconia and doped ceria fine particles, and the amount of perovskite-type oxide particles for forming a conductive path in the air electrode is relatively high. It seems to be deficient. As a result, there is a risk of impeding conductivity. Considering this, the more preferable average particle diameter of the doped ceria coarse particles is 1.5 μm or more and 25 μm or less, more preferably 2 μm or more and 20 μm or less.

[0031] In the present invention, in addition to the above-mentioned average particle size (50% by volume) of the doped ceria coarse particles, the 90% by volume diameter is 3 μm or more and 60 μm. In the following, it is more preferably 5 μm or more and 50 / zm or less, and further preferably 7 m or more and 40 m or less. This is because the amount of mixing of extremely coarse particles is suppressed as much as possible to achieve a homogeneous air electrode layer.

[0032] As the doped ceria coarse particles, particles of cerium oxide alone, cerium oxide / aluminum oxide mixed particles, and acid / cerium / acid / zirconium mixed particles can be used. Particularly preferably used in the present invention is a ceria particle doped with at least one element selected from yttrium, samarium, and gadolinium forces to give mixed conductivity. Doping amount is not particularly limited, 5 to 40 atoms relative to preferred cerium ^_0/0, more preferably from 10 to 30 atomic%. Doped ceria fine particles have the same composition. Can be used. In particular, in order to suppress the sintering that proceeds when exposed to high temperatures for a long period of time, a product heat-treated at 1300 ° C or higher for 5 hours or longer is pulverized with a bead mill or ball mill within the above average particle size range and 90 volumes. Doped silica coarse particles and fine particles adjusted within the% diameter range are preferably used. A more preferable heat treatment temperature condition is 1350 ° C. or more, more preferably 1400 ° C. or more, and a more preferred heat treatment time condition is 10 hours or more, more preferably 20 hours or more. By heat-treating under strong conditions, it becomes a material that has a history of exposure to high temperatures, and it has higher heat resistance and is difficult to sinter.

[0033] The perovskite type oxide used in the present invention is preferably adjusted so that the average particle diameter is within a range of 0.3 to 3 μm in order to form a conductive path. .

[0034] Incidentally, when the average particle size of the perovskite-type oxide is less than 0.3 μm, sintering is likely to proceed when exposed to a high temperature for a long time, and the conductive path is blocked. There is a risk of impeding conductivity. On the other hand, if the average particle size of the perovskite type oxide exceeds 3 μm, the sintering does not easily proceed even when exposed to high temperatures, but the electrode activity tends to decrease. In view of the above, the average particle size of the perovskite type oxide is more preferably not less than 0.4 m and not more than 2. More preferably not less than 0.5 m and not more than 2 m.

[0035] Also, in the case of perovskite-type oxides, as in the case of the doped ceria particles described above, it is more preferable that the mixture of extremely coarse particles be suppressed as much as possible to achieve a homogeneous air electrode. The volume% diameter may be 1 μm or more and 15 m or less, more preferably 2 μm or more and 10 μm or less, and even more preferably 2 / zm or more and 8 / zm or less. In particular, in order to suppress the sintering that proceeds when exposed to a high temperature for a long time, a product heat-treated at 1300 ° C or higher for 5 hours or longer is pulverized with a bead mill or ball mill within the above average particle size range. Perovskite-type oxides adjusted within the volume% diameter range are preferably used. A more preferable heat treatment temperature condition is 1350 ° C. or more, more preferably 1400 ° C. or more, and a more preferred heat treatment time condition is 10 hours or more, more preferably 20 hours or more. By heat-treating under such conditions, a material having a history of exposure to high temperatures is obtained, and further heat resistance is obtained, making the material difficult to sinter.

[0036] Stable Zirconia particles and doped ceria fine particles increase the consistency of thermal expansion with the electrolyte and increase the strength of the air electrode due to its easy sinterability to prevent segregation from the electrolyte. Demonstrate the effect. These average particle diameters should be adjusted to be in the range of 0.1 to 1 m.

[0037] Incidentally, when the average particle size of the stabilized zircoure particles and the doped ceria fine particles is less than 0.1 m, the cohesive force of the zircoure particles and the like becomes large, and the above effect is not sufficiently exhibited. On the other hand, if the average particle size exceeds 1 m, the sinterability decreases, and it becomes difficult to sufficiently exert the action of increasing the strength of the air electrode and the ability to suppress the powder separation from the electrolyte. Considering this, the average particle size of the stabilized zirconia particles and doped ceria fine particles is preferably 0.2 μm or more and 0.8 m or less, more preferably 0.2 μm or more, and 0.2 μm or more. It is less than 6 m.

[0038] In addition, with respect to the stable zirconium oxide particles and the doped ceria fine particles, as in the case of the doped ceria coarse particles described above, the mixing amount of relatively coarse particles is suppressed as much as possible, and the air polar layer homogeneity is reduced. It is preferable to plan. Therefore, the 90 volume% diameter is 0.5 m or more and 5 m or less, more preferably 0.8 m or more and 3 m or less, and still more preferably 0.8 m or more and 2 m or less.

In the present invention, the average particle diameter (50 volume% diameter) of each particle is measured as follows. That is, using a laser diffraction particle size distribution analyzer “LA-920” manufactured by HORIBA, Ltd., an aqueous solution in which 0.2% by mass of sodium metaphosphate as a dispersant is added to distilled water is used as a dispersion medium. Each particle is added in an amount of 0.01 to 0.5% by mass in about 100 cm ^{3 of the} dispersion medium, and dispersed by sonication for 3 minutes, and then the particle size distribution is measured. The average particle size is the particle size at 50% by volume in the cumulative graph in the measurement result of particle size distribution. The 90 volume% diameter means the particle diameter at a position of 90 volume% in the particle size distribution of each sample particle measured by the same method.

[0040] As described above, the stable zirconium oxide particles are stabilized with at least one kind of oxide selected from yttrium, scandium, and ittenorium force, and the total amount of these oxides is 3 to 15 mol%. It is a certain Zircoyu. In order to effectively exhibit the composite action with the doped ceria particles, tetragonal zircoure having better toughness and strength than cubic zirconia is preferred. Then, in the case of yttria-stabilized Jirukoyua, stabilized with 3-6 mole ^_0/0 yttria, also in the case of Sukanjia stabilization Jirukoyua, 3-7 mol% of Sukanjia In the case of ytterbia-stabilized zircoure, tetragonal-based partially stable zircoure powders stabilized with 4-8 mol% of ytterbia are particularly preferred.

[0041] When the air electrode is manufactured using the above three kinds of particles as the air electrode material, each raw material powder is weighed so as to have the above-mentioned preferred blending ratio and uniformly mixed by a mill or the like. Yes. The type of the mixing apparatus used in this case is not particularly limited, but a preferable mixing apparatus used by the present inventors is, for example, a multipurpose mixer manufactured by Mitsui Mining Co., Ltd. For example, after rotating a rotating blade at a high speed in the combined treatment tank of the mixer to attach perovskite-type oxide particles to the surface of the doped ceria particles, the stable zirconium oxide particles are added thereto, Rotate the rotating blades at low speed to mix. If a powerful method is adopted, it is confirmed that the three kinds of particles can be mixed evenly and uniformly.

[0042] The mixed powder material thus obtained is mixed with a paste component. Components for pastes include binders such as ethyl cellulose, polyethylene glycol, polybutyral resin; solvents such as ethanol, toluene, a terpineol, carbitol; plasticizers such as glycerin, glycol, dibutyl phthalate; Can include dispersants, antifoaming agents, surfactants, and the like, which are blended as necessary. Examples of the mixing means include a three roll mill and a planetary mill. If the viscosity is appropriately adjusted using such a mixing means, a paste for an air electrode can be obtained.

[0043] As a noinder, there is no particular limitation on the type as long as it is easily decomposed by heat and dissolves in a solvent and exhibits fluidity suitable for printing and coating. It can be appropriately selected and used. Examples of the organic binder include an ethylene copolymer, a styrene copolymer, an acrylate copolymer and a metatarylate copolymer, a vinyl acetate copolymer, a maleic acid copolymer, and a bull petital resin. Examples thereof include celluloses such as buracetal resin, burformal resin, butyl alcohol resin, waxes, and cellulose.

Of these, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, and cyclohexyl acrylate are preferable from the viewpoints of film formation of the air electrode layer and thermal decomposability during baking. Alkyl acrylates having an alkyl group having 10 or less carbon atoms, such as 2-ethylhexyl acrylate, and the like; Tylmetatalylate, butylmetatalylate, isobutylmethacrylate, octylmethacrylate, 2-ethylhexylmethacrylate, decylmethacrylate, dodecylmethacrylate, laurylmethacrylate, cyclohexylmeta Alkyl metatalylates having an alkyl group of 20 or less carbon atoms such as tallylate; hydroxy having hydroxyalkyl groups such as hydroxyethyl talylate, hydroxypropyl phthalate, hydroxyethyl methallylate, hydroxypropyl metatalylate Alkyl acrylates or hydroxyalkyl methacrylates; aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; acrylic acid Number average molecular weight force obtained by polymerizing or copolymerizing at least one monomer selected from carboxylic group-containing monomers such as methacrylic acid, maleic acid, maleic acid half ester such as monoisopropyl malate, etc. ~ 200,000, more preferred <(50,000) -100,000 (meth) acrylate copolymers are preferred and recommended.

[0045] As the solvent, those having low volatility at room temperature are preferred in order to reduce the viscosity change during printing. For example, terbinol, dibutyl carbitol, butyl carbitol acetate, 2, 2, 4 trimethyl 1 , 3 Pentanediol monoisobutyrate, 2, 2, 4-trimethyl-1,3-pentanediol diisobutylate, oleyl alcohol and other high boiling point solvents alone or in admixture of two or more Low boiling organic solvents such as acetone, methyl ethyl ketone, methanol, ethanol, isopropanol, butanols, denatured alcohol, ethyl acetate, toluene, xylene and the like are mixed with the high boiling solvent.

[0046] As the dispersant, in order to improve dispersion of each raw material powder, polyhydric alcohol ester type such as glycerin and sorbitan; polyether (polyol) type namine type; polyacrylic acid, polyacrylic acid ammonium Polyelectrolytes such as: organic acids such as citrate and tartaric acid; copolymers of isobutylene or styrene and maleic anhydride and their ammonium salts; amine salts; copolymers of butadiene and maleic anhydride and The power with which the ammonium salt is used Particularly preferred is sorbitan triol. As the plasticizer, polyethylene glycol derivatives and phthalic acid esters are preferred, with dibutyl phthalate and dioctyl phthalate being particularly preferred. [0047] The air electrode paste is prepared by adding a solvent or a binder to the raw material powder and kneading with a ball mill or the like by a known method. At this time, a bonding aid, an antifoaming agent, a leveling improver, a rheology modifier, etc. may be added as necessary.

[0048] The leveling improver mainly has an action of suppressing the generation of pinholes in the air electrode layer, and exhibits the same effect as a so-called lubricant. Examples include hydrocarbon-based polyethylene wax, urethane-modified polyether, alcohol-based polyglycerol, polyhydric alcohol, fatty acid-based higher fatty acid, and oxyacid. Particularly preferred are fatty acid systems such as stearic acid and hydroxystearic acid.

[0049] Then, a binder or a solvent is added to the raw material powder described above, and then kneaded with a machine, a ball mill, a three-roll mill or the like and mixed uniformly to obtain a paste. When the air electrode is formed by coating or dipping, the viscosity should be adjusted to 1 to 50 mPa's, more preferably 2 to 20 mPa · s with a B-type viscometer. The preferable slurry viscosity when forming the air electrode by screen printing is 50, 000 to 2,000, OOOmPa-s, more preferably 80,000 to 1,000, OOOmPa-s, more preferably, with a Brookfields viscometer. The range is from 1 00, 000 to 500, OOOmPa, s.

[0050] After the viscosity is adjusted, for example, it is coated on the solid electrolyte by a bar coater, spin coater, dating apparatus or the like, or formed into a thin film by a screen printing method, and then a temperature of 40 to 150 ° C, for example, The air electrode layer is formed by heating at a constant temperature such as 50 ° C, 80 ° C, 120 ° C, or successively by heating.

[0051] The thickness of the air electrode layer is suitably about 10 to 300 µm, preferably 15 to: LOO µm, particularly preferably 20 to 50 µm.

[0052] Examples of oxides used for forming the solid electrolyte membrane include zirconia, alkaline earth metal oxides such as MgO, CaO, SrO, and BaO, YO, LaO, CeO, PrO, NdO, SmO,

2 3 2 3 2 2 3 2 3 2 3

Rare earth metal oxides such as EuO, GdO, TbO, DyO, HoO, ErO, YbO

2 3 2 3 2 3 2 3 2 3 2 3 2 3

In addition, Zircoure ceramics containing one or more of ScO, BiO, InO, etc.

2 3 2 3 2 3

C: CeO or BiO, alkaline earth metal oxides such as MgO, CaO, ScO, BaO,

2 2 3

Y O, La O, CeO, Pr O, Nd O, Sm O, Eu O, Gd O, Tb O, Dy O, Ho

2 3 2 3 2 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2

Rare earth metal oxides such as O, ErO, YbO, ScO, InO, PbO, WO, MoO, V

3 2 3 2 3 2 3 2 3 3 3 2 Ceria-based or bismuth-based ceramics containing one or more of O, Nb O, etc.

5 2 5

; In addition, AZrO with a perovskite structure (A: alkaline earth elements such as Sr) and In

Three

, Ga doped, etc .; LaGaO, MgO, CaO, SrO, BaO and other alkaline earths

Three

Metal oxide, Y 2 O, CeO, Pr 2 O, Nd 2 O

3, Sm O

2 3 2 2 3 2 2 3, Eu O

2 3, Gd O

2 3, Tb O

2 3, Dy O 2 3

, Ho O, Er O, Yb O and other rare earth metal oxides, as well as Sc O, TiO, V O, C

2 3 2 3 2 3 2 3 2 2 5 Transition metal oxidation of rO, MnO, FeO, CoO, NiO, CuO, ZnO, NbO, WO, etc.

2 3 2 3 2 3 3 4 2 5 3

Doping or separation of metal oxides, typical metal oxides such as AlO, SiO, InO, SbO, and BiO

2 3 2 2 3 2 3 2 3

Dust-reinforced gallate ceramics; Indium such as Ba In O with brown millelite structure

2 2 5

Examples of such are ceramics. These ceramics may further contain other oxides such as Si 2 O 3, Al 2 O 3, GeO 2, SnO 2, Sb 2, PbO, Ta 2, Nb 2, and the like.

2 2 3 2 2 2 3 2 5 2 5

[0053] Among these, particularly preferable is a solid electrolyte having a zirconate-acid power stabilized by one or more acids selected from yttrium, scandium, and itumbumka as described above. . In addition, it is recommended that these solid electrolytes contain 0.1 to 2% by mass of at least one selected from the group consisting of alumina, titer and silica.

[0054] The shape of the electrolyte may be any of a flat plate shape, a corrugated plate shape, a corrugated shape, a Hercam shape, a cylindrical shape, a cylindrical flat plate shape, and the like. The thickness of the electrolyte is 5 to 500 / ζ πι, preferably 30 to 300 μm, more preferably 50 to 200 μm.

[0055] For example, when an electrolyte-supported solid electrolyte fuel cell is produced using the air electrode paste, the fuel electrode paste is applied to one side of the electrolyte membrane by screen printing or the like. Examples of the fuel electrode paste include NiO, ceria doped with at least one element selected from yttrium, samarium, and gadolinium power, and at least one oxide selected from Z or yttrium, scandium, and ytterbium power. There may be mentioned those with the addition of zirconia stabilized with seeds. For example, more specific fuel electrode materials? ^ 0: 50-70% by mass, 10 mol% scandia, 1 mol% ceria, stable zirconia: 30-50% by mass, etc. After the fuel electrode paste is dried, for example, it is baked at 1100 to 1400 ° C. to form a fuel electrode to form a half cell. On the other side of the half cell, the powder for the air electrode material is mixed with binder, solvent, plastic It is applied by screen printing or coating using a paste or slurry obtained by kneading uniformly with an agent, dispersant and the like. Next, for example, baking is performed at a temperature of 900 to 1300 ° C, preferably 950 to 1250 ° C, more preferably 1000 to 1200 ° C to form an air electrode, and a solid electrolyte fuel cell having a three-layer membrane structure And

[0056] Since the solid electrolyte material and the air electrode material are exposed to a high temperature for a long time to cause a solid-phase reaction and an insulating material may be generated at the interface between them, the solid electrolyte layer and the air electrode layer An intermediate layer may be provided between them. As an intermediate layer material for this purpose, the yttria-doped ceria, samariado pud ceria, and gadria-doped ceria are materials having oxygen ion conductivity and electron conductivity and functioning as a barrier layer of the air electrode material. It can be used preferably. Then, an intermediate layer paste using these materials may be prepared in the same manner and formed as an intermediate layer film on the opposite electrolyte surface where the fuel electrode film is formed.

In this case, since the air electrode is formed on the intermediate layer film, a four-layer film cell is obtained.

[0058] In the present invention, there is no limitation on the material constituting the solid electrolyte membrane, the intermediate layer, the fuel electrode, and the film forming method. The above is only an example.

[0059] In the above description, the case of producing a flat solid electrolyte fuel cell has been briefly described. However, the air electrode material of the present invention may be an electrode-supported fuel cell or a cylindrical solid electrolyte fuel cell. The same applies to the manufacture of fuel cells. Further, the air electrode material of the present invention is applied to a solid electrolyte fuel cell having a structure in which a fuel electrode, a solid electrolyte, and an air electrode are formed on the surface of a porous support tube or a support plate. Of course, it is possible to fabricate a cell.

[0060] The air electrode material of the present invention has excellent long-term sustainability of electrode activity and good sintering resistance, and also has a severe heat history due to repetition of room temperature and high operating temperature when the fuel cell is stopped. High performance that can withstand Further, by using the air electrode material of the present invention, it is possible to provide a high-performance and durable air electrode, and further a fuel cell.

Example

[0061] Hereinafter, the configuration and operational effects of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as well as the present invention. Of course, it is possible to carry out the present invention with appropriate modifications within the range to be obtained, and they are all included in the technical scope of the present invention.

[0062] Examples

(1) Preparation of air electrode paste

Perovskite type oxide powder, which is a raw material, is commercially available with a purity of 99.9% Pr 2 O 3 La

twenty three

O, CeO, GdO, SmO, CaCO, SrCO, BaCO, FeO, NiO, MnO, Co

2 3 2 2 3 2 3 3 3 3 2 3 2 3 3

O and CuO powders were used. These were mixed so as to have the compositions shown in Tables 1 and 2.

Four

Ethanol was added to the mixture and pulverized and mixed with a bead mill for 1 hour. Next, it was dried and calcined at 800 ° C for 1 hour. Further, ethanol was added and pulverized and mixed in a bead mill for 1 hour, followed by drying. Thereafter, a solid phase reaction was carried out at 1100-1300 ° C. for 5 hours.

[0063] Ethanol was added to the obtained powder, which was further pulverized and mixed with a ball mill for 16 hours and then dried to obtain powders having an average particle diameter shown in Tables 1 to 3. The obtained powder was confirmed to be a single phase composed of perovskite by X-ray diffraction. In Examples 4 to 6, 8 and 9, the perovskite powder was further heat-treated at 1400 ° C for 10 hours and then pulverized with a planetary ball mill while adjusting the rotation speed and rotation time. The average particle size and 90% by volume were set.

[0064] The doped ceria particles that are raw materials include commercially available CeO, GdO having a purity of 99.9% or more.

2 2 3

, Sm 2 O 3, and S 粉末 powder were used. These were prepared to have the composition shown in Table 2.

2 3 2 3

. Thereafter, pulverization and mixing in a bead mill in ethanol was performed in the same manner as described above. Next, after drying, it was calcined at 800 ° C. for 1 hour, and ethanol was further added, and the mixture was pulverized and mixed in a bead mill for 1 hour to dry the force. Finally, the doped ceria coarse particles and fine particles having the average particle sizes shown in Tables 2 and 3 were obtained by grinding with a planetary ball mill while adjusting the rotation speed and rotation time.

[0065] As the stable zircoure powder, a commercial product manufactured by Daiichi Rare Element Co., Ltd. was used except for ytterbia stable zircoure.

[0066] As 1 lYb stable zirconia powder, a powder prepared as follows was used. Zircoyu powder (trade name “OZC-OY”) manufactured by Sumitomo Osaka Cement Co., Ltd. was impregnated with an aqueous solution of ytterbium nitrate. The impregnated product was dried and then calcined at 1000 ° C. Then obtained The powder was ground in a bead mill in ethanol. After drying, when a mortar and pestle were further attached, or by pulverizing with a machine, 11 mol% ytterbia stable zircoure powder having an average particle size shown in Table 2 was obtained.

[0067] The obtained powders were prepared so as to have the composition ratios shown in Tables 1 to 3. To 50 g of the obtained air electrode material, 2 g of ethylcellulose as a binder, 38 g of tervineol as a solvent, and sorbitan acid ester as a dispersant (trade name “IONET S-80” manufactured by Sanyo Chemical Co., Ltd.) 0 Added 5 g. The mixture was stirred and mixed with a mortar and pestle, and then milled using a three-roll mill to prepare an air electrode paste.

[0068] (2) Fabrication of fuel cell

On one side of 4 mol ^_0/0 consists stabilized Jirukoyua in Sukanjia 4ScSZ electrolyte membrane (thickness 15 0 mX diameter 30mm), NiOZlO mol% Sukanjia 1 mol% ceria stabilized di Rukoyua force also the fuel electrode was formed . The air electrode paste obtained above was screen-printed on the other surface of the half-cell using a 100-mesh stainless steel mesh printing plate. After drying, it was baked at 950-1200 ° C to form an air electrode film with a film thickness of about 45 / zm, and a fuel cell was produced. Four similar fuel cells were produced for each example.

[0069] Test example 1 Power generation test

Using the small single-cell power generator schematically shown in Fig. 1, a power generation test was conducted on the cell produced above, and the cell output density was measured. The fuel gas used was 3% steam-humidified hydrogen at 800 ° C, and air was used as the oxidant. The product name “R8240” manufactured by Advantest was used as the current measuring device, and the product name “R6240” manufactured by Advantest was used as the current-voltage generator. The results are shown in Tables 1-3.

[0070] Test Example 2 Cell terminal voltage drop rate

In order to confirm the deterioration tendency of the output density due to continuous power generation, the cell terminal voltage was measured by supplying a current of 300 mAZcm ² , and the deterioration rate after 200 hours, 500 hours, and 1000 hours from the initial stage was measured. The results are shown in Tables 1-3. The cell terminal voltage drop rate was obtained as follows. In Comparative Examples 1 to 4, 6 and 7, the initial output density measured in Test Example 1 was low, so the measurement was strong. Also, Examples 5, 6, and 20 according to the present invention In order to shorten the experimental time, measurements after 500 hours or 1000 hours were omitted in and.

[Cell terminal voltage drop rate] = [(initial output voltage minus output voltage after elapse of a predetermined time) Z initial output voltage] X 100 (%)

[0071] Test Example 3 Thermal cycle deterioration rate

Using a new cell, after 100 hours of continuous operation, stop the heater, lower the temperature to room temperature, hold it at room temperature for 20 hours and repeat the heat cycle to raise the power to 800 ° C 3 to 5 times. The reduction rate of the cell terminal voltage was also measured. The results are shown in Tables 1 to 3 as thermal cycle deterioration rates. In Control Examples 3 and 4, the initial power density measured in Test Example 1 was very low, so the measurement was strong.

[0072] Test Example 4 Deterioration Acceleration Test

Two of the fuel cells of each Example produced above were inserted into an electric furnace and heated at 950 ° C. for 500 hours. Thereafter, the power density was measured, and the deterioration rate was calculated to perform a deterioration promotion test. The results are shown in Tables 1-3.

[0073] [Table 1]

[] [^] 00742 [] 0 Mi 613-

When using a gas electrode material, the initial power density is 0.2 WZcm ² or less and the electrode activity is poor. In contrast, when the air electrode material of the present invention is used, an initial output density of approximately 0.3 WZcm ² or more is obtained. Therefore, it can be seen that the fuel battery cell according to the present invention has excellent electrode activity.

[0077] When the praseodymium / cobaltite oxide in Control Example 2 is used, the initial output density is superior to the air electrode material of the present invention. However, the rate of decrease in power density after heating in an electric furnace has become very large. On the other hand, in the examples of the present invention, it can be seen that the rate of decrease is small and the stability of the electrode activity is also excellent.

[0078] Further, both when the doped ceria is added to the perovskite type oxide and when the stable zirconia is added to the perovskite type oxide, the perovskite type oxide is used. The initial output density and the cell terminal voltage drop rate after 500 hours are the same as in the case of a single object, and the superiority of the present invention can be confirmed. Furthermore, when the blending ratio of the perovskite type oxide and the doped silica or stable zirconium oxide is outside the specified range of the present invention, the initial output density is greatly reduced, and the electrode activity is remarkably deteriorated.

[0079] Also, when doped ceria and stable zirconium oxide are mixed with perovskite type oxides, the same initial output density and cell terminal voltage after 500 hours as with perovskite type oxides alone. The rate of decline is shown. In addition, the cell voltage drop rate after the thermal cycle test is small. This result shows that the fuel cell according to the present invention has excellent simultaneous durability. In particular, among those satisfying the composition and blending ratio specified in the present invention, the average particle size of the velovskite-type oxide particles and the average particle size of the doped ceria particles and the stable zirconia particles satisfy the above-mentioned preferred relationship. The thing shows the outstanding thermal cycle endurance.

Claims

The scope of the claims

[1] An air electrode material for a solid oxide fuel cell, characterized by containing a berbskite oxide represented by the following general formula (I).

(Pr A) (Fe B) O

x l-χ y 1-y 3 …… (I)

[2] In addition, doped ceria doped with at least one element selected from the group force consisting of yttrium, samarium and gadolinium; or the group force consisting of yttrium, scandium and ytterbium selected from acids of at least one element selected 2. The cathode material for a solid oxide fuel cell according to claim 1, comprising at least one of stable zirconium oxides stabilized with an electrolyte.

[3] containing 70 to 95% by weight of perovskite oxide;

The air electrode material for a solid oxide fuel cell according to claim 2, comprising 5 to 30% by mass of a total of at least one of doped ceria and stable zirconium oxide.

[4] Perovskite type oxide particles, doped ceria coarse particles, and stabilized zirconia particles. The average particle size of each particle is "Dope ceria coarse particles> perovskite type oxide particles> stable. The air electrode material for a solid oxide fuel cell according to claim 2 or 3, wherein the air electrode material satisfies the relationship of "Zirconia particles".

[5] The average particle size of the doped ceria coarse particles is 1 to 30 μm, the average particle size of the perovskite oxide particles is 0.3 to 3 μm, and the average particle size of the stabilized zirconia particles is 0.1 to 5. The cathode material for a solid oxide fuel cell according to claim 4, which is 1 μm.

[6] Perovskite type oxide particles, doped ceria coarse particles, and a mixture of doped ceria fine particles, each particle having an average particle size of “Dope Ceria Coarse Particles” perovskite type oxide particles 4. The air electrode material for a solid oxide fuel cell according to claim 2, which satisfies the relationship of “> doped ceria fine particles”.

[7] The average particle size of the doped ceria coarse particles is 1 to 30 μm, the average particle size of the perovskite oxide particles is 0.3 to 3 μm, and the average particle size of the doped ceria fine particles is 0.1 to 1 μm. claim which is m Item 7. The cathode material for a solid oxide fuel cell according to Item 6.

[8] The air electrode formed on one side of the solid electrolyte in the solid oxide fuel cell, wherein the air electrode is formed of the air electrode material according to any one of claims 1 to 7. Characteristic air electrode for solid oxide fuel cell.

[9] A solid oxide fuel cell having an air electrode formed on one side of a solid electrolyte and a fuel electrode formed on the other side, wherein the air electrode is any one of claims 1 to 7. A solid oxide fuel cell formed of the air electrode material described in 1.

[10] The fuel cell according to claim 9, wherein the solid electrolyte has a zirco-ure force stabilized by an oxide of at least one element selected from the group force consisting of scandium, yttrium and ytterbium.