JP5285115B2 - Composite materials and their use - Google Patents

Description

  The present invention relates to a composite material suitably used for the construction of a solid oxide fuel cell (SOFC), a solid oxide fuel cell using the composite material, and the solid oxide fuel. The present invention relates to a method for manufacturing a solid oxide fuel cell system including a battery.

A solid oxide fuel cell generally called “SOFC” has a high power generation efficiency, a low environmental load, and a variety of fuels can be used among various types of fuel cells. Has advantages. As a typical structural example of this solid oxide fuel cell, an anode (fuel electrode) having a porous structure, a dense solid electrolyte (eg, a dense membrane layer) made of an oxide ion conductor, and a porous structure Examples include a cell in which cathodes (air electrodes) are stacked in this order (hereinafter, a cell structure including a solid electrolyte, an anode, and a cathode constituting an SOFC is simply referred to as an “SOFC cell”).
In a solid oxide fuel cell having such a structure (that is, a SOFC cell), a fuel gas (typically hydrogen (H ₂ ) gas or methane (CH ₄ ) gas) is supplied to the anode, and oxygen (O ₂ ) is supplied to the cathode. ) Containing gas (typically air) is supplied.

  In a general solid oxide fuel cell, a zirconium oxide-based material is used for a solid electrolyte, and an oxide having an oxide ion conductive perovskite structure (hereinafter referred to as “perovskite oxide”) is used for a cathode. It is done. In order to laminate the cathode on the solid electrolyte, a method of applying a precursor of the cathode to the surface of the solid electrolyte and baking it is employed. At this time, a solid phase reaction may occur at a portion (interface) where the solid electrolyte and the cathode are in contact. If the solid-phase reaction occurs, the conductivity of oxide ions between the solid electrolyte and the cathode may decrease, which is not preferable. Examples of the method for preventing the solid phase reaction include a method in which an intermediate layer made of cerium oxide is interposed between the solid electrolyte and the cathode. An example of such a method is disclosed in Non-Patent Document 1.

  However, when the intermediate layer is provided, a process of providing the intermediate layer occurs in the manufacturing process of the solid oxide fuel cell, and thus manufacturing cost and manufacturing time increase. Further, the intermediate layer can be a resistance layer for conducting oxide ions between the solid electrolyte and the cathode. Therefore, in recent years, a technique for suppressing the occurrence of the solid-phase reaction by using a material having low reactivity with respect to the solid electrolyte for the cathode has been proposed. An example of such a cathode material is Fe-based perovskite oxide. The Fe-based perovskite oxide is a perovskite oxide that contains iron (Fe) as an essential constituent element and does not contain cobalt (Co) or manganese (Mn), and a solid electrolyte material (for example, yttria-stabilized zirconia) and The reactivity of is low. Examples of this Fe-based perovskite oxide are disclosed in Non-Patent Documents 2 to 4 and Patent Documents 1 to 3. Moreover, as a prior art regarding the other cathode material, patent document 4, 5 is mentioned, for example.

JP 2002-313406 A JP 2007-51035 A JP 2007-51036 A JP 2002-333428 A JP 2008-243744 A

Electrochemical Solid-State Letters, Vol. 2, no. 9, (1999) 428-430 Solid State Ionics, Vol. 181, (2010) 300-305 Journal of Power Sources, Vol. 168, (2007) 236-239 Journal of Power Sources, Vol. 161, (2006) 115-122

  As described above, when the cathode is composed of an Fe-based perovskite oxide, generation of a solid phase reaction can be suppressed. However, since Fe-based perovskite oxides are inferior in performance as electrode catalysts compared to Co-containing Co-based and Mn-containing Mn-based perovskite-type oxides, from the viewpoint of battery performance, as a cathode material, It is hard to say that it is preferable. Thus, in the current solid oxide fuel cell, suppression of solid-phase reaction and cell performance are in a trade-off relationship, and a technology that can break this relationship is demanded.

  The present invention has been made in view of the above-mentioned problems, and one of the purposes thereof is suitably used to form a SOFC cathode capable of suppressing the occurrence of a solid-phase reaction and exhibiting high battery performance. Is to provide a material that can be used. The present invention also provides a solid oxide fuel cell having a cathode formed using such a cathode material, and a method for producing a solid oxide fuel cell system having a solid oxide fuel cell. To do.

In order to achieve the above object, the present invention provides a composite material having the following constitution.
That is, the composite material disclosed here has the following general formula (1):
(Ln _1-x Ae _x ) (M _1-y Fe _y ) O _3-δ (1)
And a ceramic coating particle in which the surface of a core made of a metal that catalyzes ionization of oxygen is coated with a ceramic in a porous state.
Here, Ln in the general formula (1) is at least one element selected from lanthanoids, and Ae is one or more elements selected from the group consisting of Sr, Ba and Ca. , M is one or more elements selected from the group consisting of Ti, Ni, Al, Zr, Ga, Mg, Cu, In, Sn, V, Cr, Zn, Ge, Sc and Y, x is a real number satisfying 0 ≦ x <1, y is a real number satisfying 0 <y ≦ 1, and δ is a value determined to satisfy the charge neutrality condition.
The composite material disclosed here is preferably used as a cathode forming material for forming a cathode of a solid oxide fuel cell (SOFC cell). In particular, when used in such applications, it is preferable that the composition contains at least one dispersion medium and is prepared in a paste form (including a slurry form and an ink form).

The composite material disclosed here includes particles made of an Fe-based perovskite oxide containing iron (Fe) as an essential constituent element. Since the Fe-based perovskite oxide has low reactivity with a material (for example, yttria-stabilized zirconia) constituting the solid electrolyte of the SOFC cell, it is possible to form a cathode in which a solid-phase reaction hardly occurs.
On the other hand, as described above, the Fe-based perovskite oxide is inferior in performance as an electrode catalyst compared to a Co-based or Mn-based perovskite oxide. However, in the composite material disclosed here, since a core made of a metal (catalyst metal) that catalyzes the ionization of oxygen includes ceramic coating particles coated in a porous state, an Fe-based perovskite oxide is used. Nevertheless, a cathode having a high electrocatalytic ability can be formed.
Thus, according to the composite material of the present invention, it is possible to form a cathode that exhibits high electrocatalytic ability while suppressing the occurrence of a solid-phase reaction. In other words, according to the composite material of the present invention, the trade-off relationship described above can be overcome.

By the way, the SOFC cell is exposed to a high temperature environment during the manufacturing process and operation. For this reason, when a catalytic metal used for the core is contained in the cathode, the catalytic metal may be sintered by the high temperature environment. In this case, the effective surface area of the catalyst metal becomes narrow, which causes the cathode to deteriorate.
On the other hand, in the composite material disclosed here, the surface of the catalyst metal particles (that is, the core portion) is coated with ceramic, so that the cathode deterioration due to the sintering of the catalyst metal (core) is suitably prevented. can do.
Moreover, the ceramic coat | covers the surface of a catalyst metal (core) in the porous state. Here, “coating in a porous state” means that the catalyst metal (core) itself is not completely coated until the catalytic function of the catalyst metal (core) disappears, and at least a part of the surface of the catalyst metal is in contact with the outside air (that is, oxygen). In a state in which ionization of the catalyst can be catalyzed). That is, the ceramic coating particles prevent sintering without impairing the catalytic function of the core by covering the surface of the core with ceramic in a porous state.
Thus, according to the composite material of the present invention, a problem newly generated by breaking the trade-off relationship is also solved.

In a preferred embodiment of the composite material disclosed herein, the ceramic coating particles are contained in a ratio of 10 parts by mass to 90 parts by mass with respect to 100 parts by mass of the Fe-based perovskite oxide particles.
Since the composite material including the ceramic coating particles in the above ratio includes the ceramic coating particles using the catalytic metal in the core in an appropriate ratio, a cathode having higher electrocatalytic ability can be formed. That is, according to such a composite material, an SOFC cell with higher power generation performance (for example, a power density at an operating temperature of 700 ° C. of 0.3 W / cm ² or more) can be constructed.

In a preferred embodiment of the composite material disclosed herein, the core is made of silver (Ag).
In general, silver has a merit that it has a high catalytic function and can be obtained at a relatively low cost, but it has a lower melting point (962 ° C.) than other catalytic metals, so it has a high temperature environment. Easy to sinter when exposed to. For this reason, when silver is contained in the cathode as a catalyst metal, there is a demerit that the possibility of deterioration of the cathode is increased. On the other hand, in the composite material disclosed here, the surface of the core is coated with ceramic, so that the core can be prevented from being sintered. In other words, the composite material having the above configuration eliminates the demerit of “deterioration of the cathode” that can be caused by adding silver to the cathode, and obtains only the merit of “having a high catalytic function and being inexpensive”. Can do.

The ceramic as the coating material is preferably composed of aluminum oxide (Al ₂ O ₃ ) or zirconium oxide (ZrO ₂ ), and zirconium oxide is particularly suitable.

Moreover, this invention provides the SOFC cell provided with the anode, the solid electrolyte, and the cathode as another side surface. Such a SOFC cell has a cathode formed of the above-described composite material. The cathode formed of the above composite material suppresses the generation of a solid phase reaction with a solid electrolyte, and can exhibit a high electrocatalytic ability. For this reason, the SOFC cell has high battery performance.
Moreover, in the SOFC cell disclosed here, the ceramic coating particles are included in the cathode. In such a cathode, the bonding phase with the solid electrolyte is improved as compared with the cathode made of only the perovskite oxide due to the presence of the ceramic of the ceramic coating particles. Therefore, according to the SOFC cell disclosed here, peeling of the cathode from the solid electrolyte can be suitably prevented.

In a preferred embodiment of the SOFC cell disclosed herein, the solid electrolyte contains zirconium oxide, and the ceramic constituting the ceramic coating particles is zirconium oxide.
In the SOFC cell having the above configuration, since the zirconium oxide is contained in both the solid electrolyte and the cathode, the interface resistance between the solid electrolyte and the cathode is reduced, and the joining property between the solid electrolyte and the cathode is further improved. Therefore, according to the SOFC cell configured as described above, it is possible to more suitably prevent the cathode from peeling.

Moreover, this invention provides the manufacturing method of a SOFC system as another aspect. In this specification, the “SOFC system” means a power generation system having one or a plurality of the SOFC cells and a joint portion formed by joining the cells or the cells and a connection member connected to the cells. Point to.
The SOFC system manufacturing method disclosed herein provides an anode-solid electrolyte laminate comprising an anode and a solid electrolyte formed on the anode; the surface of the laminate on the solid electrolyte side is the above-mentioned Giving a composite material; Giving a joining material constituting the joint to the laminates or places where the laminate and the connecting member are joined; giving the composite material and the joining material Forming the cathode and the joint at the same time by firing the laminate.

In general, an SOFC system is manufactured by applying a cathode material on the solid electrolyte of the anode-solid electrolyte laminate and then firing it at a relatively high temperature (eg, 1000 ° C. to 1200 ° C.). Form. Then, a bonding material is applied between the cells or between the cells and the connection member, and the bonding material is fired at a relatively low temperature (for example, 700 ° C. to 900 ° C.). In order to reduce the number of manufacturing steps in such a manufacturing process, a method of simultaneously firing the cathode and the bonding material is conceivable. However, if the co-firing is performed at the calcining temperature of the cathode, the bonding material is denatured, which may reduce the durability at the joint. On the other hand, if the co-firing is performed at the firing temperature of the relatively low temperature bonding material, the cathode is not sufficiently fired, and the cathode is easily peeled off from the solid electrolyte.
On the other hand, in the manufacturing method disclosed here, the composite material is used as a cathode material. As described above, the cathode made of the composite material includes ceramic coating particles and thus has high bonding properties with the solid electrolyte. Therefore, even when the cathode material (composite material) and the bonding material are fired at the same time, it is possible to form a cathode that does not easily peel from the solid electrolyte. That is, according to the manufacturing method disclosed herein, the bonding material and the cathode can be fired at the same time without causing peeling of the cathode and a decrease in durability of the bonded portion, thereby reducing manufacturing costs and manufacturing efficiency. High-quality SOFC system can be manufactured after realizing the improvement of
In a preferred embodiment of the manufacturing method, the firing temperature of the composite material and the bonding material is preferably set to 700 ° C. to 900 ° C.

In a preferred embodiment of the production method disclosed herein, the solid electrolyte contains zirconium oxide, and the ceramic constituting the ceramic coating particles is zirconium oxide.
In the manufacturing method having the above-described configuration, it is possible to manufacture an SOFC system in which the solid electrolyte and the cathode are highly bonded and the cathode is more difficult to peel off. That is, according to the manufacturing method having such a configuration, the simultaneous firing of the composite material and the bonding material can be more suitably performed.

FIG. 1 is a cross-sectional view schematically showing an SOFC system according to an embodiment of the present invention. FIGS. 2A to 2D are diagrams schematically showing a manufacturing process of the SOFC system according to one embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification (for example, composition of composite material, manufacturing method of SOFC system, etc.) and matters necessary for implementing the present invention (for example, configuration of SOFC system, etc.) Can be understood as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Composition of composite material>
The composite material disclosed herein includes particles made of Fe-based perovskite oxide (hereinafter referred to as “Fe-based perovskite particles” as appropriate) and a surface of a core having a catalytic function with respect to an ionization reaction of oxygen. The content and composition of other components can be determined in light of various standards without departing from the object of the present invention.
The “composite material” in this specification may be a powder, a paste containing the powder and a dispersion medium, or a solid obtained by drying (or firing) the paste. When the composite material is a powder, the average particle diameter of the composite material is 0.1 μm to 10 μm, preferably 0.1 μm to 3 μm. In the present specification, the “average particle diameter” refers to D ₅₀ (median diameter) in the particle size distribution to be measured. Such D ₅₀ is, for example, can be easily measured by a conventionally known laser diffraction method, the particle size distribution measurement apparatus based on light scattering method or the like.

1. Fe-based perovskite particles The Fe-based perovskite oxide that constitutes the Fe-based perovskite particles contains iron (Fe) as an essential constituent element, and has the following general formula (1):
(Ln _1-x Ae _x ) (M _1-y Fe _y ) O _3-δ (1)
It can be expressed as
Here, “Ln” in the general formula (1) is at least one element selected from lanthanoids, and elements having atomic numbers of 57 to 71 (for example, lanthanum (La), cerium (Ce), praseodymium). (Pr), neodymium (Nd), samarium (Sm), etc.) can be selected from any one or more. Among these, La can be particularly preferably used. When “Ln” contains two or more elements, it is preferable that the La content is high.
“Ae” in the general formula (1) represents a metal element belonging to an alkaline earth metal, and among these alkaline earth metal elements, strontium (Sr), barium (Ba), and calcium (Ca 1) or 2 or more elements selected from the group consisting of: Further, among these, those containing Sr, Ba (or a combination of Sr and Ba) are preferable. Further, a composition having a high Sr or Ba content in “Ae” is suitable, and it is composed of only Sr (or Ba) or contains a high content of Sr (or Ba) ( For example, Sr (or Ba) is contained in 50% by mole or more in “Ae”).
“M” in the general formula (1), which is a metal element constituting an Fe-based perovskite oxide together with “Fe”, is titanium (Ti), nickel (Ni), aluminum (Al), zirconium (Zr), Gallium (Ga), magnesium (Mg), copper (Cu), indium (In), tin (Sn), vanadium (V), chromium (Cr), zinc (Zn), germanium (Ge), scandium (Sc) and One or more elements selected from the group consisting of yttrium (Y). Among these, any one of Ti, Ni, Al, Zr, and Ga, or a combination of any two of these is preferable. An Fe-based perovskite oxide containing Ti, Ni, Al, Zr or Ga together with Fe has high oxide ion conductivity, and can contribute to the formation of a high-performance cathode.
Further, “x” in the general formula (1) is a value indicating a ratio in which “Ln” (typically La) is replaced by “Ae” in the Fe-based perovskite oxide. The range that “x” can take may be any real number within the range of 0 ≦ x <1, as long as the structure can be maintained without breaking the perovskite structure. Depending on the purpose of this configuration, the composition ratio of Ln (1-x) and Ae (x) is appropriately selected, but preferably 0 ≦ x ≦ 0.6, particularly preferably 0 ≦ x ≦ 0. .4.
As described above, the Fe-based perovskite oxide includes iron (Fe) as an essential constituent element. “Y” in the general formula (1) is a value that determines the composition ratio of “M” and “Fe” in the Fe-based perovskite oxide. The possible value of “y” may be a real number satisfying the range of 0 <y ≦ 1 (typically 0 <y <1). By determining the value of “y”, “Fe” The content ratio of the metal element “M” other than “” is also determined. The composition ratio of Fe (y) and M (1-y) can be appropriately selected according to the purpose of this configuration. An example of the value of “y” is 0.1 ≦ y <1, and preferably 0.4 ≦ y <1.
In the above general formula, the number of oxygen atoms may be 3 or less (typically less than 3). However, the number of oxygen atoms in the general formula (1) depends on the type of the atom that substitutes a part of the perovskite structure (for example, a part of “Ae” or “M” in the formula), the substitution ratio, and other conditions. It is determined to satisfy the charge neutrality condition. Here, “δ”, which is a variable for determining the number of oxygen atoms in the above general formula, is typically a positive number not exceeding 1 (0 ≦ δ <1). In addition, since the number of oxygen atoms in the general formula (1) varies depending on other elements constituting the perovskite oxide as described above, it is difficult to display accurately. That is, (3-δ) in the general formula (1) is not intended to limit the technical scope of the present invention.
The Fe-based perovskite oxide represented by the general formula (1) contains iron as an essential metal element, and a Co-based perovskite oxide containing cobalt (Co) or Mn containing manganese (Mn). Compared with the system perovskite type oxide, the reactivity with the material (for example, zirconium oxide etc.) used as a solid electrolyte of SOFC is low. For this reason, when it uses as a material for cathodes, it has the characteristics that the solid-phase reaction between a cathode and a solid electrolyte hardly arises.
Specific examples of such Fe-based perovskite oxides include LNF oxides that do not include “Ae” (x = 0) and select Ni as “M” (ie, Ln (typically La), Ni, Fe Oxide as a constituent element: LnNi _1-y Fe _y O _3-δ (0 <y <1)). As another example, an LSTF oxide (Ln _1−x Sr _x Ti _1−y Fe _y O _3−δ ) which is an oxide containing Ln (typically La), Sr, Ti, and Fe as constituent elements is used. 0 <x <1, 0 <y <1)) and LSZF oxide (Ln _1-x Sr _x Zr ₁ ) which is an oxide containing Ln (typically La), Sr, Zr, Fe as constituent elements _-Y Fe _y O _{3 -δ} (0 <x <1, 0 <y <1)) or LBAF oxide which is an oxide containing Ln (typically La), Ba, Al, Fe as constituent elements _{(Ln 1-X Ba x Al} 1-y Fe y O 3-δ (0 <x <1,0 <y <1)) and the like.

2. Ceramic Coated Particles The composite material disclosed herein includes ceramic coated particles formed by coating the surface of the core with ceramic. The ceramic coating particles are contained in a mass ratio of 10 parts by mass to 90 parts by mass (preferably 50 parts by mass to 80 parts by mass, for example, 70 ± 5 parts by mass) with respect to 100 parts by mass of the Fe-based perovskite particles. Good. Such a composite material can form a cathode having a higher electrocatalytic ability.

2-1. Core The core of the ceramic coating particle is composed of a metal that catalyzes an ionization reaction of oxygen (1 / 2O ₂ + 2e ⁻ → O ²⁻ ) (hereinafter referred to as “catalytic metal” as appropriate). The catalyst metal constituting the core includes metal elements belonging to noble metals (silver (Ag), gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru). , Osmium (Os), etc.) (or an alloy mainly composed of these noble metals). Among the above-mentioned noble metal particles, silver particles (or silver alloys) have a high catalytic ability and have an advantage that they can be obtained at a lower cost than other noble metal particles.

By the way, members constituting the SOFC cell (SOFC system) are exposed to a high temperature environment (for example, a general operation temperature is about 700 ° C. to 1000 ° C.) during manufacturing and operation, and thus have high heat resistance. Is required. Silver (Ag) mentioned above as a suitable material for the core, which is a catalyst metal, has a relatively low melting point (962 ° C.) compared to other noble metals, so that it is conventionally preferred as a catalyst metal to be added to the cathode. It was hard to say that the material.
On the other hand, in the composite material disclosed here, the surface of the core is coated with ceramic, so that the core can be prevented from being sintered by heating. Therefore, the composite material disclosed here can eliminate the demerit of “deterioration due to sintering” and enjoy only the “low cost and high catalyst function” which is a merit. For this reason, in the composite material disclosed here, it is possible to use silver as a material (core) having a catalytic function.

2-2. Coating Material In the ceramic coating particles, the surface of the core made of the catalyst metal is coated with a predetermined ceramic. As the ceramic covering the surface of the core, a ceramic having excellent heat resistance is preferable. For example, those having a melting point of 1000 ° C. or higher (for example, 1000 ° C. to 3000 ° C., more preferably 2000 ° C. to 3000 ° C.) can be preferably used. Moreover, as a ceramic, the thing of a composition with favorable joining compatibility with the solid electrolyte of SOFC is preferable. For this reason, the kind of the ceramic used for the coating material can be appropriately changed in consideration of heat resistance and bonding compatibility with the solid electrolyte. For example, aluminum oxide (alumina: Al ₂ O ₃ ), zirconium oxide (zirconia: ZrO ₂ ), magnesium oxide (magnesia: MgO), silicon oxide (silica: SiO ₂ ), titanium oxide (titania: TiO ₂ ), cerium oxide (Ceria: CeO ₂ ). Among these, aluminum oxide and zirconium oxide are preferable because they are porous ceramics having excellent heat resistance and can be obtained at low cost. Further, as zirconium oxide, stabilized zirconia in which the crystal structure is stabilized by dissolving a rare earth oxide can be preferably used. Examples of such stabilized zirconia include yttria stabilized zirconia (YSZ) in which an oxide of yttrium (Y) (for example, yttria (Y ₂ O ₃ )) is dissolved, and scandium (Sc) oxide (for example, scandia (Sc)). Scandia-stabilized zirconia (ScSZ) in which ₂ O ₃ )) is dissolved can be used particularly preferably.
The coating layer made of ceramic covers the surface of the core in a porous state. Thus, a plurality of micropores are formed in the coating layer formed in a porous state. The porosity of the coating layer made of ceramic (according to gas adsorption measurement) is preferably about 10% to 60%. Here, if the porosity of the ceramic coating layer is 60% or less, the sintering of the catalytic metal as the core can be suitably prevented. Moreover, if the porosity is 10% or more, the effective surface area of the core covered with the ceramic is increased, so that a cathode having a high electrocatalytic ability can be formed. The thickness of the coating layer made of ceramic is preferably about 1 nm to 500 nm (preferably 1 nm to 100 nm, more preferably 1 nm to 10 nm). If the thickness of the coating layer is significantly less than 1 nm, it is difficult to prevent the core from being sintered. On the other hand, if it greatly exceeds 500 nm, the coating layer tends to peel off. The coating layer having a thickness within the above numerical range is preferable because it suitably prevents the core from being sintered and hardly peels from the surface of the core.

3. Other Additives The composite material disclosed herein may contain additives other than the above-described Fe-based perovskite particles and ceramic coating particles.
For example, as described above, the composite material disclosed herein may be prepared in a paste form. The paste-like composite material contains at least one dispersion medium. The dispersion medium may be any organic dispersion medium or inorganic dispersion medium as long as the constituent material of the composite material can be suitably dispersed. As the organic dispersion medium, for example, terpineol, butyl diglycol acetate, isobutyl alcohol and the like are preferably used. Moreover, as an inorganic dispersion medium, water etc. are used suitably, for example. The composite material prepared in a paste form is preferable because it can be easily applied onto the solid electrolyte when forming the cathode of the SOFC cell.
Moreover, a thickener, a binder, etc. may be added to the composite material as other additives. Examples that can be used here include ethyl cellulose and butyral. By adding the additives as described above, application of the composite material onto the solid electrolyte is further facilitated.

The composite material having the above structure includes particles made of an Fe-based perovskite oxide having low reactivity with the solid electrolyte. For this reason, it is possible to form a cathode that hardly causes a solid-phase reaction with the solid electrolyte. Such composite materials also include ceramic coating particles. Since the core of the ceramic coating particle has a catalytic function for the ionization reaction of oxygen, a cathode having a high electrocatalytic ability can be formed even though the Fe-based perovskite particle is used. Can do. Furthermore, since this ceramic coating particle is comprised by coat | covering the said core with a ceramic, the sintering of the core which consists of a catalyst metal can be prevented suitably.
As described above, the composite material disclosed herein can form a high-performance cathode in various respects, and in particular, “prevention of solid-phase reaction” and “ It has a favorable effect in that both “improvement of electrode catalyst ability” can be achieved.

<Production method of composite material>
Next, a method for producing the composite material will be described. The composite material manufacturing method disclosed herein includes, for example, (I) mixing the Fe-based perovskite particles and the ceramic coating particles to prepare a mixed powder; (II) performing an annealing treatment on the mixed powder. And then pulverizing to obtain a composite material.

I. Preparation of mixed powder First, a mixed powder in which the above-described Fe-based perovskite particles and ceramic coating particles are mixed is prepared. The detailed configuration of the Fe-based perovskite particles and ceramic coating particles used here has been described in the sections of “1. Fe-based perovskite particles” and “2. Ceramic coating particles”, and thus description thereof is omitted here.
Fe-based perovskite particles used for preparing the mixed powder may have an average particle size of 0.1 μm to 10 μm (preferably 0.5 μm to 5 μm, more preferably 1 ± 0.5 μm). Ceramic coating particles having an average particle size of 0.1 μm to 10 μm (preferably 0.5 μm to 5 μm, more preferably 1 μm to 3 μm) may be used.
Note that the Fe-based perovskite particles and ceramic coating particles may be prepared from raw materials or purchased, for example.

I-1. Production of Ceramic Coating Particles Here, an example of a method for producing ceramic coating particles from raw materials will be described. In addition, the ceramic coating particle used here should just be produced by coat | covering the surface of a core with a ceramic in a porous state, and there is no restriction | limiting in particular in the production method. Therefore, a conventionally known method for producing ceramic coating particles can be applied as it is. Hereinafter, an example of a method for producing ceramic coating particles will be described.
Here, first, an organic metal compound containing a metal element constituting the ceramic is dissolved or dispersed in an organic solvent. As the organic metal compound, an organic acid metal salt, metal alkoxide, chelate compound, or the like containing a metal element constituting a ceramic can be used. For example, when zirconia is selected as the coating material, zirconium ethoxide, zirconium butoxide, or the like is preferably used as the metal alkoxide (zirconium alkoxide) containing zirconium (Zr). As the organic solvent for dispersing (dissolving) the organic metal compound, toluene, xylene, various alcohols, and the like are preferably used.
Next, a catalyst metal (for example, noble metal particles) serving as a core is added to the obtained solution or dispersion (sol) and dispersed (suspended). By standing or stirring this suspension for a predetermined time, the surface of the core in the suspension can be coated with the organometallic compound.
Next, the core coated with the organic metal compound is heat-treated (typically 350 ° C. to 700 ° C.) in an air atmosphere. As a result, the organic compound is removed from the organic metal compound, and the metal element contained in the organic metal compound is oxidized to form a ceramic (metal oxide). At this time, the portion where the organic compound or the dispersion medium that has escaped from the organic metal compound is disposed becomes a micropore, and a porous structure is formed in the ceramic covering the core. In this way, ceramic coated particles are obtained in which the surface of the core is coated with a ceramic in a porous state.

II. Production of Composite Material To obtain a composite material from a mixed powder composed of the ceramic coating particles and Fe-based perovskite particles, first, the mixed powder is annealed. The annealing temperature may be set to 700 ° C. to 900 ° C. (preferably 800 ± 50 ° C.), and the time may be set to 30 minutes to 4 hours (preferably 30 minutes to 2 hours).
Next, the result of the annealing treatment is pulverized. As a result, a powdery composite material containing Fe-based perovskite particles and ceramic coating particles is obtained. For this pulverization treatment, for example, a ball mill, a jet mill or the like can be used. In the pulverization treatment, the pulverization speed and the pulverization time may be adjusted so that a powdery composite material having an average particle diameter of 0.5 μm to 2 μm (preferably 0.5 μm to 1.5 μm) is obtained.

III. Preparation of Paste Composite Material As described in the section “3. Other Additives”, the composite material may be prepared in a paste form here. When preparing such a paste-like composite material, additives such as a dispersion medium (for example, terpineol) and a thickener (for example, ethyl cellulose) are added to the powdered composite material obtained by the above pulverization treatment and kneaded. Good. For this kneading treatment, for example, a roll mill, a mixer or the like can be used. In such a kneading process, the powdery composite material and other additives are kneaded at a stirring speed of 50 rpm to 300 rpm for 0.5 hour to 1 hour, so that the powdery composite material is suitably dispersed. A pasty composite material is obtained.

<SOFC cell>
The composite material disclosed here has been described above. Such a composite material can be suitably used, for example, as a cathode material for a solid oxide fuel cell (ie, SOFC cell). Hereinafter, an SOFC cell in which a cathode is formed of the composite material will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating a cross-sectional configuration of an SOFC system 100 including the SOFC cell 50. The SOFC cell 50 having the configuration shown in FIG. 1 is an anode-supported SOFC cell. The SOFC cell 50 has a laminated structure including an anode (fuel electrode) 10, a solid electrolyte 20, and a cathode (air electrode) 30.

A. Anode The anode constituting the SOFC cell has a porous structure. Examples of the material constituting the anode include a group 8 to group 10 metal element (or platinum group element) such as nickel (Ni) and ruthenium (Ru), and a ceramic (for example, yttria stabilized zirconia (YSZ)). A porous material composed of cermet with calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), etc. is preferably employed.
The anode should just be comprised so that it can contact the fuel gas supplied to a SOFC cell, and the shape can be suitably selected according to the shape of a SOFC cell. For example, a sheet shape (or flat plate shape), a hollow box shape or a cylindrical shape provided with a hollow portion (gas flow path) for allowing fuel gas to flow into the anode, or a hollow flat shape (flat tubular shape) Etc. In the SOFC cell 50 having the configuration shown in FIG. 1, a thick sheet-like anode 10 is formed as a support for the SOFC cell 50. The thickness of the anode 10 as such a support is typically about 0.1 mm to 10 mm, and preferably about 0.5 mm to 5 mm, but is not limited to this thickness.

B. Solid electrolyte The solid electrolyte has a dense structure. As a material constituting the solid electrolyte, for example, an oxide containing a metal element of zirconium (Zr), cerium (Ce), lanthanum (La), gallium (Ga) can be used, and among these, an oxide of zirconium. Zirconium oxide (zirconia: ZrO ₂ ) can be preferably used. Furthermore, as the material for the solid electrolyte, stabilized zirconia in which the crystal structure is stabilized by dissolving a rare earth oxide in the zirconium oxide can be more preferably used. Among these stabilized zirconia, yttria stabilized zirconia (YSZ) in which an oxide of yttrium (Y) (for example, yttria (Y ₂ O ₃ )) is dissolved, and scandium (Sc) oxide (for example, scandia ( Scandia-stabilized zirconia (ScSZ) in which Sc ₂ O ₃ )) is dissolved can be particularly preferably used.
The solid electrolyte is laminated on the anode, and the shape can be appropriately changed according to the shape of the anode. In the SOFC cell 50 having the configuration shown in FIG. 1, a membrane-like solid electrolyte 20 is laminated on a sheet-like anode 10. The thickness of the solid electrolyte 20 is typically about 5 μm to 100 μm, and preferably about 10 μm to 30 μm, but is not limited to this thickness.

C. Cathode The cathode has a porous structure like the anode. In the SOFC cell disclosed here, the cathode is formed of the composite material. Note that the configuration of the “composite material” has been described in the above section <Composition of the composite material>, and thus the description in this section is omitted.
The ceramic of the ceramic coating particles contained in the composite material is composed of a material (for example, zirconium oxide, aluminum oxide, titanium oxide, etc.) having a good bonding phase with the solid electrolyte layer. For this reason, even when the cathode is fired at a relatively low temperature (for example, 900 ° C. or lower, typically 700 ° C. to 900 ° C., preferably 800 ± 50 ° C.), it is possible to form a cathode that does not easily peel off from the solid electrolyte. .
Further, in order to form a cathode that is more difficult to peel, it is preferable to use ceramic coated particles in which the core is coated with the same kind of ceramic as the metal oxide constituting the solid electrolyte. For example, when zirconium oxide (such as YSZ) is contained in the solid electrolyte, it is preferable to use zirconium oxide for the ceramic of the ceramic coating particles. In this case, since zirconium oxide exists in both the solid electrolyte and the cathode, the interface resistance between the solid electrolyte and the cathode is lowered, and the joining property between the solid electrolyte and the cathode can be further improved.
The cathode is laminated on the solid electrolyte layer and is formed so as to be in contact with an oxygen-containing gas (for example, air). The shape of the cathode can be appropriately changed according to the shape of the anode or the solid electrolyte. For example, in the SOFC cell 50 configured as shown in FIG. 1, a sheet-like cathode 30 is laminated on the solid electrolyte 20. At this time, the surface of the cathode 30 opposite to the surface in contact with the solid electrolyte 20 is exposed to outside air (air) that is an oxygen-containing gas. The thickness of the cathode 30 is preferably about 5 μm to 100 μm (preferably 10 μm to 50 μm).

<SOFC system>
By using the SOFC cell having the above-described configuration, an SOFC system having one or a plurality of the cells can be constructed. Specifically, the SOFC system can be constructed by joining the SOFC cells to each other or a connection member connected to the cells.

D. Connection member The connection member in this specification refers to all members to be connected to the SOFC cell in constructing the SOFC system. Examples of such connection members include a gas pipe for supplying gas to the cells, and an interconnector interposed between the cells in a stack in which the cells are connected to each other. Such a connection member is connected to the SOFC cell by a joint 40 described later. In the SOFC system 100 having the configuration shown in FIG. 1, a gas pipe 60 is used as a connection member, and the gas pipe 60 and the SOFC cell 50 are joined by a joint portion 40.

D-1. Gas pipe The gas pipe will be described. The gas pipe is used to supply gas (fuel gas or oxygen-containing gas) to a cell (or a stack in which a plurality of the cells are connected). The structure of such a gas pipe may be the same as that of a conventional gas pipe, and is not particularly limited. For example, a pipe formed by molding a dense body of zirconia-based oxide such as YSZ, which is the same material as the solid electrolyte, or a metal pipe made of SUS430 metal that is commercially available for SOFC systems is preferably used. Among them, a gas pipe made of a dense body of zirconia-based oxide can be suitably used because of its good bonding compatibility with the anode / solid electrolyte. About the shape and size of a gas pipe, it can change suitably according to the shape of the cell (stack) connected.
In the SOFC system 100 having the configuration shown in FIG. 1, the connecting surface 12 of the anode 10 of the SOFC cell 50 and the end surface 62 of the cylindrical gas pipe 60 are connected.

D-2. Interconnector Moreover, an interconnector (separator) is mentioned as another connection member with which a SOFC system is provided. The interconnector is a member disposed between the cells when the cells are electrically connected to each other. As the interconnector, a flat plate member (not shown) that physically blocks oxygen supply gas (for example, air) and fuel gas and has electronic conductivity can be preferably used. As a material constituting such an interconnector, a lanthanum chromite oxide, a refractory metal such as SUS430, or the like can be used.
The lanthanum chromite oxide constituting the interconnector is
General formula: La _(1-x) Ma _(x) Cr _(1-y) Mb _(y) O ₃ (2)
It can be expressed as In the general formula (2), “Ma” and “Mb” are the same or different alkaline earth metals, and “x” and “y” are 0 ≦ x <1 respectively. 0 ≦ y <1. Preferable examples include LCC oxide (lanthanum calcia chromite: La _(1-x) Ca _(x) CrO ₃ (0 <x <1)) in which LaCrO ₃ or Ma or Mb is calcium. In the above general formula, the number of oxygen atoms is shown to be 3, but in actuality, the number of oxygen atoms in the composition ratio may be 3 or less (typically less than 3).

E. Junction part A junction part joins the above-mentioned connection member and SOFC cell (or these cells). The joining portion seals between the SOFC cell and the connection member (or between the cells) so that gas (fuel gas or air) does not flow out (inflow) from the joining portion described above. In the SOFC system 100 having the configuration shown in FIG. 1, the joint 40 is formed so as to cover a connection portion (a boundary between the coupling surface 12 and the end surface 62) between the anode 10 and the gas pipe 60.
The joining portion can be formed, for example, by firing a joining material composed mainly of glass. The firing temperature of the bonding material is preferably close to the firing temperature of the cathode material (composite material), for example, 900 ° C. or lower (typically 700 ° C. to 900 ° C., preferably 800 ± 50 ° C.). There should be.

E-1. Glass for bonding material The glass that can be used as the bonding portion (bonding material) will be described. Such glass for bonding materials may contain, for example, SiO ₂ , Al ₂ O ₃ , K ₂ O, Na ₂ O and optional additives (MgO, CaO, B ₂ O _3, etc.) as constituent components. . Further, it is preferable that cristobalite crystals and / or leucite crystals are precipitated in the matrix of the bonding material glass. In the description of the bonding agent glass, the “content ratio” of the constituent component is a value indicating a mass ratio in terms of oxide with respect to the entire bonding agent glass.
Of the above-described constituent components, SiO ₂ is a main component of glass and is a component constituting the crystal lattice of the cristobalite crystal (leucite crystal). The content of SiO ₂ may When it is within the scope of 55mass% ~75mass% (preferably 60mass% ~70mass%). A glass containing SiO ₂ within the above numerical range is preferable because the softening point (firing temperature) does not become too high (for example, 900 ° C. or less) and has sufficient water resistance and chemical resistance.
Al ₂ O ₃ is a component involved in adhesion stability by controlling the fluidity of glass. When leucite crystals are precipitated in the glass matrix, Al ₂ O ₃ becomes a component constituting the crystal lattice of the leucite crystals. The content of Al ₂ O _3, may in the range of from 10mass% ~20mass% (preferably 10mass% ~15mass%). A glass containing Al ₂ O ₃ within the above numerical range is preferable because it has high adhesion stability and can be easily applied and has sufficient chemical resistance.
K ₂ O and Na ₂ O are components that increase the thermal expansion coefficient (thermal expansion coefficient) of the glass. When a leucite crystal is precipitated in the glass, K ₂ O is a component constituting the crystal lattice of the leucite crystal. The content of _{K 2} O is, may is 1mass% ~15mass% (preferably 5mass% ~15mass%). On the other hand, the content of Na ₂ O may When it is within the scope of 1mass% ~15mass% (preferably 5mass% ~15mass%). Furthermore, the total content of K ₂ O and Na ₂ O is particularly preferably 5 mass% to 25 mass% (preferably 10 mass% to 20 mass%).
MgO and CaO, which can be included as optional additives, can be adjusted in the thermal expansion coefficient by adding them to the glass. For example, MgO is a component capable of adjusting the viscosity at the time of glass melting, and CaO is a component capable of improving the wear resistance by increasing the hardness of the glass matrix. The content of MgO (or CaO) is preferably in the range of 0 mass% (no addition) to 5 mass% (preferably 1 mass% to 5 mass%).
Another optional additive component is B ₂ O ₃ . B ₂ O ₃ is considered to exhibit the same action as Al ₂ O ₃ in glass, and can contribute to the multi-componentization of the glass matrix. Moreover, it is a component which contributes to the improvement of the meltability at the time of bonding material preparation. The content of B ₂ O ₃ is preferably in the range of 0 mass% (no addition) to 5 mass% (preferably 1 mass% to 5 mass%).
In addition to the components described above, the glass for bonding material includes ZnO, Li ₂ O, Bi ₂ O ₃ , SrO, SnO, SnO ₂ , CuO, Cu ₂ O, TiO ₂ , ZrO ₂ , La ₂ O _3. Etc. may be included.

<Manufacturing method of SOFC system>
Next, a method for manufacturing an SOFC system according to another aspect of the present invention will be described. Such a manufacturing method includes:
(A) preparing an anode-solid electrolyte laminate comprising an anode and a solid electrolyte formed on the anode;
(B) applying the above-mentioned composite material to the surface of the laminate on the solid electrolyte side;
(C) Applying a bonding material that constitutes a bonding portion to a position where the laminated bodies or the laminated body and the connection member are joined;
(D) forming the cathode and the joint at the same time by firing the laminate to which the composite material and the joint material have been applied. Hereinafter, this manufacturing method will be described in detail with reference to FIGS. 2 (a) to 2 (d).

a. Preparation of Anode-Solid Electrolyte Laminate In the present specification, the “anode-solid electrolyte laminate” refers to a state in which an anode and a solid electrolyte are laminated, and is formed in the manufacturing process of the SOFC cell. In addition, there is no restriction | limiting in particular about the method of preparing an anode-solid electrolyte laminated body. Therefore, the “anode manufacturing method” and the “solid electrolyte manufacturing method” in the conventionally known SOFC system (SOFC cell) manufacturing method can be applied as they are.
Hereinafter, as an example of “a method for preparing an anode-solid electrolyte laminate”, a method for forming the anode 10 of the anode-supported SOFC cell 50 having the configuration shown in FIG. 1 and a method for forming the solid electrolyte 20 will be described. .

a-1. Formation of Anode Here, as shown in FIG. 2A, the anode 10 having a porous structure is formed as a support substrate (support). Here, particles of group 8 to group 10 metal elements (for example, nickel particles) and ceramic (for example, YSZ) are mixed to prepare a cermet material. At this time, the average particle diameter of the metal particles is preferably about 1 μm to 10 μm, and the average particle diameter of the ceramic is preferably about 0.1 μm to 10 μm. And the said cermet material is disperse | distributed to a solvent (for example, xylene) with a binder (for example, methacrylate polymer) and a dispersing agent (for example, sorbitan trioleate), and the paste-form (slurry) anode material is prepared. Next, the anode material is molded, and the molded body is fired to form a sheet-like anode 10 (see FIG. 2A). At this time, for example, sheet molding or the like can be used for molding the anode material. Moreover, it is good to perform the baking process of the said molded object by heating at the temperature of 1200 to 1400 degreeC for 1 hour-5 hours. In addition, you may perform the baking process of the material for anodes simultaneously with the baking process of the material for solid electrolytes in "a-2. Formation of a solid electrolyte" mentioned later.

a-2. Formation of Solid Electrolyte Next, the solid electrolyte 20 is formed on the anode 10. Here, a raw material (for example, YSZ) of the solid electrolyte 20 is dispersed in a solvent (for example, xylene) together with a binder (for example, a methacrylic ester-based polymer) and a dispersant (for example, sorbitan trioleate) to obtain a paste-like (slurry) solid. An electrolyte material is prepared. At this time, the average particle diameter of the raw material of the solid electrolyte is preferably about 0.1 μm to 10 μm. Next, the prepared solid electrolyte material is applied onto the anode 10 (or a molded body of the anode material) to form a molded body of the solid electrolyte material. For molding of the solid electrolyte material, printing molding or the like can be used.
And after drying the molded object of the material for solid electrolytes, this molded object is baked in air | atmosphere atmosphere. The firing temperature at this time is preferably in the range of 1200 ° C. to 1400 ° C., for example, and the firing time is preferably in the range of 1 hour to 5 hours, for example. When this firing process is performed, a film-like solid electrolyte 20 is formed on the anode 10. As a result, an anode-solid electrolyte laminate 110 (see FIG. 2B) including the anode 10 and the solid electrolyte 20 formed on the anode 10 is obtained.

b. Application of Composite Material Next, in the manufacturing method disclosed herein, the above-described composite material is applied to the surface of the anode-solid electrolyte laminate 110 on the solid electrolyte 20 side. At this time, it is preferable to use a paste-like composite material as described in the section “3. Other additives” because it is easy to uniformly apply the composite material. When a paste-like composite material is used, as a method for providing the composite material on the solid electrolyte 20, printing molding or the like can be used. As a result, a cathode material molded body 31 (see FIG. 2C) made of a composite material is formed on the surface of the anode-solid electrolyte laminate 110 on the solid electrolyte 20 side.

c. Application of bonding material Next, the bonding material constituting the bonding portion is applied to a position where the laminated body and the connection member are bonded (or a position where the formed bodies are bonded to each other). Specifically, as shown in FIG. 3 (d), the connecting surface 12 of the anode 10 of the anode-solid electrolyte laminate 110 and the end surface 62 of the gas pipe (connecting member) 60 are in contact with each other. Then, the bonding material 41 is applied so as to cover the contact surface. Further, here, the bonding material 41 may be applied so as to extend beyond the contact surface to the end of the solid electrolyte membrane 20. At this time, the bonding material 41 is applied so as to block the contact surface between the gas pipe 60 and the anode 10 and to cover the anode 10 having a porous structure. Then, the bonding material 41 is applied to the other side of the anode 10 so as to cover the connection surface 12 and the end surface 62 of the gas pipe 60. By applying the bonding material 41 in this manner, a gap that may be generated at the contact surface between the anode 10 and the gas pipe 60 is closed, and the anode 10 having a porous structure is covered with the bonding material 41.

d. Next, the laminate to which the composite material and the bonding material are applied is simultaneously fired. Specifically, the laminated body 110 provided with the composite material 31 and the bonding material 41 is heated to a temperature at which the bonding material 41 does not flow out of the bonded portion (for example, 700 ° C. to 900 ° C., preferably 800 ± 50 ° C.). Bake.
When the firing process is performed, the cathode material molded body (composite material) 31 is fired to become the cathode 30, and the SOFC cell 50 in which the anode 10, the solid electrolyte 20, and the cathode 30 are laminated is formed. . On the other hand, the bonding material 41 is also fired by the firing process to become the joint 40. Thereby, the contact surface of the anode 10 and the gas pipe 60 and the anode 10 having a porous structure are sealed, and the SOFC system 100 in which the gas pipe 60 as a connecting member is connected to the SOFC cell 50 (FIG. 1). Reference) is constructed. Thus, in the manufacturing method disclosed here, the cathode material molded body 31 and the bonding agent 41 are fired simultaneously.

In the above, the manufacturing method of the SOFC system disclosed here was demonstrated.
According to the above manufacturing method, since the cathode and the joint are fired simultaneously, the number of manufacturing steps can be reduced as compared with the conventional manufacturing method. At this time, the composite material used as the cathode material contains ceramic coating particles. Due to the presence of the ceramic of the ceramic coating particles, the cathode of the SOFC system disclosed herein has better bonding compatibility with the solid electrolyte than the conventional cathode, and the bonding material and the cathode material (composite material) are fired simultaneously. Even in this case, it is difficult to peel off from the solid electrolyte. Therefore, in the manufacturing method disclosed here, the number of manufacturing steps can be reduced without reducing the quality of the SOFC system, and the manufacturing cost can be reduced and the manufacturing efficiency can be improved.

<Use of SOFC system>
In the SOFC system 100 as shown in FIG. 1, oxide ions are obtained from oxygen in an oxygen-containing gas (air) at the cathode 30 of the SOFC cell 50 (oxygen is ionized). At this time, the cathode 30 contains ceramic coating particles, and the ionization of the oxygen is promoted by the core (catalyst metal) present in the particles.
The oxide ions ionized at the cathode are transported from the cathode 30 to the solid electrolyte 20, reach the anode 10 through the solid electrolyte 20, and hydrogen (H ₂ ) in the fuel gas supplied to the anode 10. Reacts with and emits electrons. In this way, the power generation system configured as described above generates power. In the SOFC system disclosed herein, since the cathode is formed of the above-described composite material, a solid-state reaction between the cathode and the solid electrolyte is preferably prevented, and the cathode having a high electrocatalytic ability is included. ing. For this reason, the SOFC system 100 can exhibit high battery performance.

<Example>
Next, examples relating to the present invention will be described. In this example, 15 types of solid oxide fuel cells having cathodes with different constituent materials were produced and their performance was evaluated. Note that the examples described below are not intended to limit the present invention.

(Sample 1)
First, mixed particles of yttria-stabilized zirconia (YSZ) powder having an average particle diameter of 1 μm and nickel oxide (NiO) powder having an average particle diameter of 3 μm are mixed with a binder (methacrylic ester polymer) and a dispersant (sorbitan). Trioleate) and a solvent (xylene) were added and kneaded to prepare a slurry anode material. And the said anode material was shape | molded by sheet molding, and the molded object for anodes of (phi) 20mm and thickness about 1mm was obtained.

  Next, a binder (methacrylic ester polymer), a dispersant (sorbitan trioleate) and a solvent (xylene) are added to yttria-stabilized zirconia (YSZ) having an average particle diameter of 1 μm and kneaded to form a slurry solid electrolyte. Preparation materials were prepared. Then, the solid electrolyte material was printed on the anode molded body to form a solid electrolyte molded body having a diameter of 20 mm. In addition, the thickness of the solid electrolyte molded body at this time was 10 μm to 30 μm. Then, after drying the two formed compacts, firing (temperature: 1200 ° C. to 1400 ° C., time: 3 hours) was performed to produce an anode-solid electrolyte laminate including an anode and a solid electrolyte.

Next, as the catalyst powder to be added to the cathode, ceramic coated particles (hereinafter referred to as “Zr-coated Ag powder”) in which the surface of silver (Ag) particles was coated with zirconium oxide (zirconia: ZrO ₂ ) were prepared. A composite material of this Zr-coated Ag powder and LNF oxide (LaNi _0.6 Fe _0.4 O ₃ ) particles that are Fe-based perovskite oxides was produced.
Specifically, mixed powder was obtained by mixing Zr-coated Ag powder (particle size: 1 μm to 3 μm) and LNF oxide particles (average particle size: 1 μm). At this time, the mixing ratio of the LNF oxide particles and the Zr-coated Ag powder was adjusted so that the Zr-coated Ag powder was included at a ratio of 5 parts by mass with respect to 100 parts by mass of the LNF oxide particles. Next, the mixed powder was annealed at 800 ° C. for 1 hour in an air atmosphere. The grinding process was performed for 1 hour. Thus, a powdery composite material (average particle diameter of 1. .mu.m) containing LNF oxide particles and Zr-coated Ag powder and containing Zr-coated Ag powder at a ratio of 5 parts by mass with respect to 100 parts by mass of LNF oxide particles. 5 μm) was obtained.

Next, the powdery composite material was added to a dispersion medium (terpineol) together with a thickener (ethyl cellulose), and kneaded in a roll mill for 0.5 hours to obtain a slurry-like composite material. Then, this slurry-like composite material was used as a cathode material and screen-molded on the solid electrolyte layer to form a 16 mm cathode molded body on the solid electrolyte layer. In addition, the thickness of the molded object for cathodes at this time was about 10 micrometers-50 micrometers. And the cathode was formed by baking the said molded object for cathodes (800 degreeC, 1 hour).
As a result, an anode-supported SOFC cell in which the anode, the solid electrolyte, and the cathode were laminated in this order was obtained. Hereinafter, this SOFC cell is referred to as Sample 1.

  Next, SOFC cells according to Samples 2 to 15 manufactured by changing the manufacturing conditions (the cathode configuration) from Sample 1 will be described. In addition, in the description of the production of Samples 2 to 15, processes that are not particularly mentioned are assumed to be performed in the same manner as Sample 1 described above.

(Sample 2)
In sample 2, the mixing ratio of the LNF oxide and the Zr-coated Ag powder was adjusted so that 10 parts by mass of the Zr-coated Ag powder was contained with respect to 100 parts by mass of the LNF oxide particles.

(Sample 3)
In Sample 3, the mixing ratio of the LNF oxide and the Zr-coated Ag powder was adjusted so that 70 parts by mass of the Zr-coated Ag powder was contained with respect to 100 parts by mass of the LNF oxide particles.

(Sample 4)
In Sample 4, the mixing ratio of the LNF oxide and the Zr-coated Ag powder was adjusted so that 90 parts by mass of the Zr-coated Ag powder was contained with respect to 100 parts by mass of the LNF oxide particles.

(Sample 5)
In Sample 5, the mixing ratio of the LNF oxide and the Zr-coated Ag powder was adjusted so that 95 parts by mass of the Zr-coated Ag powder was contained with respect to 100 parts by mass of the LNF oxide particles.

(Sample 6)
In sample 6, “Al-coated Ag powder” (particle size: 1 μm to 3 μm) in which the surface of silver particles was coated with alumina (Al ₃ O ₂ ) was produced as ceramic coating particles (catalyst powder) contained in the composite material. And the mixing ratio of LNF oxide and Al coating Ag powder was adjusted so that 80 mass parts of Al coating Ag powder might be contained with respect to 100 mass parts of LNF oxide particles.

(Sample 7)
In Sample 7, LSTF oxide (La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O ₃ ) particles having an average particle diameter of 1 μm were used as Fe-based perovskite particles. Further, Zr-coated Ag powder having a particle diameter of 1 μm to 3 μm is used as the ceramic coating particle, and the LSTF oxide particle and Zr are contained so that the Zr-coated Ag powder is contained in a ratio of 70 parts by mass with respect to 100 parts by mass of the LSTF oxide. The mixing ratio with the coated Ag powder was adjusted.

(Sample 8)
In sample 8, LSTF oxide particles having an average particle diameter of 1 μm were used as Fe-based perovskite particles, and Al-coated Ag powder having a particle diameter of 1 μm to 3 μm was used as ceramic coating particles. Moreover, the mixing ratio of the LSTF oxide particles and the Al-coated Ag powder was adjusted so that the Al-coated Ag powder was contained in a proportion of 70 parts by mass with respect to 100 parts by mass of the LSTF oxide particles.

(Sample 9)
In Sample 9, LSZF oxide (La _0.6 Sr _0.4 Zr _0.2 Fe _0.8 O ₃ ) particles having an average particle diameter of 1 μm were used as Fe-based perovskite particles. Further, Zr-coated Ag powder having a particle diameter of 1 μm to 3 μm was used as ceramic coating particles. Then, the mixing ratio of the LSZF oxide and the Zr-coated Ag powder was adjusted so that the Zr-coated Ag powder was contained at a ratio of 70 parts by mass with respect to 100 parts by mass of the LSZF oxide particles.

(Sample 10)
In sample 10, LBAF oxide (La _0.6 Ba _0.4 Al _0.1 Fe _0.9 O ₃ ) particles having an average particle diameter of 1 μm were used as Fe-based perovskite particles. Further, Zr-coated Ag powder having a particle diameter of 1 μm to 3 μm was used as ceramic coating particles. Then, the mixing ratio of the LBAF oxide and the Zr-coated Ag powder was adjusted so that the Zr-coated Ag powder was contained at a ratio of 70 parts by mass with respect to 100 parts by mass of the LBAF oxide particles.

(Sample 11)
In sample 11, LNF oxide particles having an average particle diameter of 1 μm were used as Fe-based perovskite particles. In this sample, Ag powder (uncoated Ag powder) having a particle size of 1 to 3 μm was used as a catalyst powder to be added to the cathode. Then, the mixing ratio of the LNF oxide and the uncoated Ag powder was adjusted so that the uncoated Ag powder was included at a ratio of 80 parts by mass with respect to 100 parts by mass of the LNF oxide particles.

(Sample 12)
In sample 12, the catalyst powder was not added to the cathode, and the cathode was formed only from LNF oxide particles having an average particle diameter of 1 μm.

(Sample 13)
In Sample 13, the catalyst powder was not added to the cathode, and the cathode was formed only from LSTF oxide particles having an average particle diameter of 1 μm.

(Sample 14)
In Sample 14, particles of LSCF oxide (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ), which is a cobalt (Co) -based perovskite oxide, without adding catalyst powder to the cathode A cathode was formed only with (average particle diameter of 1 μm).

(Sample 15)
In sample 15, the catalyst powder was not added to the cathode, and only the particles (average particle diameter 1 μm) of LSM oxide (La _0.6 Sr _0.4 MnO ₃ ) which is a manganese (Mn) -based perovskite oxide. A cathode was formed.

  In the above, the samples 1-15 produced by the present Example were demonstrated. Table 1 summarizes the cathode configurations of the SOFC cells according to Samples 1-15.

<Performance evaluation of each sample 1-15>
Next, the performance of the above samples 1 to 15 was evaluated. Here, “power generation performance”, “joining state”, “sintered state”, and “solid phase reaction” were examined as evaluation items of each sample. Table 2 shows the results of the above evaluation items.

(Power generation performance)
Here, each sample 1-15 was operated at an operating temperature of 700 ° C. and a voltage of 0.6 V to 0.8 V, and the power density (W / cm ² ) of each sample under the above conditions was measured. In this item, the obtained power density (W / cm ² ) was evaluated as “power generation performance” of each sample.

As shown in Table 2, the SOFCs of Samples 1 to 10 showed a high power density exceeding 0.15 W / cm ² . From this, it was found that a SOFC cell having high power generation performance can be obtained by forming the cathode with a composite material containing ceramic coating particles (Zr-coated Ag powder or Al-coated Ag powder).
Further, when samples 1 to 5 having different content ratios of the ceramic coating particles (Zr-coated Ag powder) were compared, the samples 2 to 4 showed very high battery performance (0.3 W / cm ² or more). From this, it was found that when the ratio of the ceramic coating particles to 100 parts by mass of the Fe-based perovskite particles is adjusted within the range of 10 parts by mass to 90 parts by mass, an SOFC cell having particularly high power generation performance can be obtained.

(Joint state with solid electrolyte)
The surface of the cathode of each sample 1 to 15 was observed with a scanning electron microscope (SEM), and the “bonding state” of the cathode was evaluated based on whether or not a peeled portion was peeled off from the solid electrolyte at the cathode. . The “joined state” in Table 2 is “◯”, which indicates a state where the peeled portion is not confirmed (that is, the joined state is good). On the other hand, “x” indicates a state in which the peeled portion is confirmed (that is, the bonding state is poor).

As shown in Table 2, since the peeled portion was not confirmed in Samples 1 to 11, it is considered that the bonding state between the cathode and the solid electrolyte is good (◯). On the other hand, in Samples 12 to 15, since the peeled portion was confirmed, it is considered that the bonding state between the cathode and the solid electrolyte is poor (x). Samples 1 to 11 in which the bonding state was good (◯) contained materials (ceramic coating particles or silver) other than the perovskite oxide in common.
As described above, in this embodiment, the cathode is fired at a temperature (800 ° C.) lower than a general cathode firing temperature (1000 ° C. to 1200 ° C.). In Samples 1 to 11, even when the cathode is fired at such a low temperature, a good bonded state can be obtained. Therefore, by adding an additive (for example, ceramic coating particles) to the cathode material, the solid electrolyte and the cathode It is thought that the bondability of the can be improved.

(Sintered cathode)
Next, after operating each sample 1-11 at 700 degreeC, the cathode of each sample was observed with the scanning electron microscope, and the "sintered state" of the cathode was evaluated. Specifically, the evaluation criterion was whether or not aggregated portions were observed in materials other than the perovskite oxide (here, Zr-coated Ag powder, Al-coated Ag powder, uncoated Ag powder). The “sintered state” in Table 2 is “◯”, which indicates a state in which the agglomerated part is not confirmed (that is, a material other than the perovskite oxide is sintered). A state in which the agglomerated part is confirmed (that is, a material other than the perovskite oxide is sintered) is shown. In addition, about samples 12-15, since materials other than a perovskite type oxide were not added to the cathode, this item was not evaluated.

  As shown in Table 2, only in sample 11, agglomerated parts due to the sintering of silver particles were observed. From this, it was found that when the uncoated Ag powder was added, the sintering of the uncoated Ag powder proceeded due to the operation of the SOFC. On the other hand, no agglomerated part was observed in the cathodes of Samples 1 to 10. For this reason, ceramic coated particles formed by coating the surface of the core (here, silver) with ceramic (typically zirconia or alumina) do not sinter the core even when heated, which is suitable for deterioration of the cathode. It was found that it can be prevented.

(Solid phase reaction)
Next, the cathode was peeled from the SOFC cells according to Samples 1 to 15, and the surface where the solid electrolyte and the cathode were in contact was observed with SEM and EDX to evaluate the item of “solid phase reaction”. In Table 2, the item “Solid State” in “Solid State” indicates that no solid phase reaction has occurred on the contact surface, and “X” indicates that the above solid phase reaction has occurred. Is shown.

  As shown in Table 2, the occurrence of solid phase reaction was confirmed in samples 14 and 15, whereas the occurrence of solid phase reaction was not confirmed in samples 1 to 13. This is understood that in Samples 1 to 13, the constituent material of the cathode contained an Fe-based perovskite oxide. From this, it was found that the solid-state reaction between the solid electrolyte and the cathode can be suitably prevented by using the Fe-based perovskite oxide as the constituent material of the cathode.

  Summarizing the above evaluation results, the SOFCs according to Samples 1 to 10 have high power generation performance, good bondability with the solid electrolyte, a suitable porous structure, and a solid phase between the cathode and the solid electrolyte. Since reaction is suitably prevented, it can be said that it is high performance compared with the other samples 11-15. Samples 1 to 10 use a composite material containing ceramic coating particles and Fe-based perovskite particles as a cathode material. From this, it is understood that the composite material having such a configuration can realize high performance of SOFC.

  The composite material of the present invention includes particles made of an Fe-based perovskite oxide and ceramic coated particles in which the surface of a core having a catalytic function for oxygen ionization reaction is coated with ceramic. The cathode made of such a composite material is suitably prevented from a solid phase reaction with a solid electrolyte, and has a high electrocatalytic ability. Therefore, the composite material of the present invention can contribute to the construction of a high performance SOFC cell (or SOFC system). In addition, when such a composite material is used, an SOFC cell with high power generation performance can be constructed, which can contribute to lowering the operating temperature of the SOFC system. Furthermore, the cathode made of the composite material can be suitably fired at a temperature lower than that of the conventional material, and hardly peels from the solid electrolyte after firing. Therefore, since the cathode and the bonding material can be fired simultaneously in the manufacturing process of the SOFC system, it is possible to contribute to the reduction of the manufacturing process in the manufacturing of the SOFC system.

10 Anode 20 Solid electrolyte 30 Cathode (Cathode)
31 Composite material (Cathode material molding)
40 Joining part 41 Joining material 60 Gas pipe 100 Solid oxide fuel cell (SOFC)
110 Anode-solid electrolyte molded body

Claims (11)

The following general formula (1):
(Ln _1-x Ae _x ) (M _1-y Fe _y ) O _3-δ (1)
(Here, Ln is at least one element selected from lanthanoids, Ae is one or more elements selected from the group consisting of Sr, Ba and Ca, and M is Ti, Ni, Al) , Zr, Ga, Mg, Cu, In, Sn, V, Cr, Zn, Ge, Sc, and Y are one or more elements, and x is 0 ≦ x <1 (Y is a real number satisfying 0 <y ≦ 1, and δ is a value determined to satisfy the charge neutrality condition.)
Particles composed of an Fe-based perovskite oxide represented by:
A composite material comprising ceramic coated particles in which a surface of a core made of a metal that catalyzes ionization of oxygen is coated with a ceramic in a porous state.   2. The composite material according to claim 1, wherein the ceramic coating particles are contained at a ratio of 10 parts by mass to 90 parts by mass with respect to 100 parts by mass of the Fe-based perovskite oxide particles.   The composite material according to claim 1, wherein the core is made of silver (Ag).   The composite material according to claim 1, wherein the ceramic is made of aluminum oxide or zirconium oxide.   The composite material according to any one of claims 1 to 4, comprising at least one dispersion medium and prepared in a paste form. The composite material according to any one of claims 1 to 5, which is used to form a cathode of a solid oxide fuel cell. A solid oxide fuel cell comprising an anode, a solid electrolyte and a cathode,
A solid oxide fuel cell, wherein the cathode is made of the composite material according to claim 1.   The solid oxide fuel cell according to claim 7, wherein zirconium oxide is contained in the solid electrolyte, and the ceramic constituting the ceramic coating particle is zirconium oxide. A solid having one or a plurality of solid oxide fuel cells each including an anode, a cathode, and a solid electrolyte, and having a joint formed by joining the cells or the cells and a connection member connected to the cells. A method for manufacturing an oxide fuel cell system, comprising:
Providing an anode-solid electrolyte laminate comprising an anode and a solid electrolyte formed on the anode;
Applying the composite material according to any one of claims 1 to 6 to the surface of the laminate on the solid electrolyte side;
Imparting a bonding material constituting the bonding portion to a position where the stacked bodies or the stacked body and the connecting member are bonded;
Forming the cathode and the joint at the same time by firing the laminate to which the composite material and the joining material have been applied;
Manufacturing method.   The manufacturing method according to claim 9, wherein the solid electrolyte contains zirconium oxide, and the ceramic constituting the ceramic coating particles is zirconium oxide. The manufacturing method according to claim 9 or 10, wherein a firing temperature of the composite material and the bonding material is set to 700C to 900C.

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