JP6433168B2 - SOLID ELECTROLYTE FUEL CELL AND MATERIAL FOR RESULTING INHIBITION LAYER FORM - Google Patents

Description

  The present invention relates to a solid oxide fuel cell including a reaction suppression layer. In detail, it is related with the material used in order to form the reaction suppression layer of this solid oxide fuel cell.

Solid oxide fuel cells (SOFCs) (SOFCs) are the next generation of energy because of their high power generation efficiency and low environmental impact among various types of fuel cells. It is expected to be a supply source and is being developed.
The smallest unit cell (single cell) constituting the SOFC includes a dense layered solid electrolyte made of an oxygen ion conductor, and a porous air electrode (cathode) formed on one surface of the solid electrolyte layer. And a fuel electrode (anode) having a porous structure formed on the other surface of the solid electrolyte layer. Then, an O ₂ -containing gas typified by air or the like is supplied to the surface of the solid electrolyte on the cathode formation side of the single cell, and a fuel gas such as H ₂ is supplied to the surface of the solid electrolyte on the anode formation side. As a battery reaction, oxygen ions generated by reducing O ₂ gas in the air at the cathode pass through the solid electrolyte, and oxidize fuel gas such as H ₂ gas at the anode to release electrons to an external load. . Along with this, electric energy is generated.

As a material constituting the SOFC solid electrolyte, stabilized zirconia doped with yttria, scandia, etc. (YSZ, ScSZ, etc.) is widely used from the viewpoint of ion conductivity and stability. As the solid electrolyte layer becomes thinner, the SOFC (single cell) performance improves. Therefore, in recent years, development of a so-called anode-supported SOFC in which the solid electrolyte is formed as a thin film on the porous substrate constituting the anode has been advanced. .
Typically, a slurry-like (paste-like) material obtained by adding a pore-forming agent, a solvent, a vehicle (resin), etc. to a mixture of nickel oxide (NiO) and YSZ is mixed by a doctor blade method or the like. Then, a desired number of the sheets are laminated to form an anode support layer. Then, a solid electrolyte layer, a reaction inhibition layer, and a cathode layer are sequentially laminated (formed) on the formed anode support layer, and the obtained laminate is fired (that is, co-fired), thereby obtaining an anode supported SOFC (single cell). ). For example, Patent Document 1 below describes an example of a conventional anode-supported SOFC.

Conventionally, SOFC has been operated in a high temperature range of 700 ° C. or higher, typically about 800 ° C. to 1000 ° C. However, in recent years, from the viewpoint of improving durability and reducing costs, the operating temperature has been lowered. It is hoped to do. For example, it has been studied to reduce the operating temperature of SOFC to about 600 ° C.
Cathode materials are being studied as an aid to effectively achieve low temperature operation. For example, by constructing a cathode using a so-called electron-oxygen ion mixed conductor material exhibiting electronic conductivity and oxygen ion conductivity, not only at the three-phase interface where the electrode / electrolyte / gas phase contacts but also at the cathode surface Is also expected to promote electrode reaction and increase electrode activity. Examples of such a cathode material include lanthanum cobaltite materials (for example, LaSrCoO _{3 -δ} materials) and lanthanum strontium cobalt ferrite (LSCF) materials that are perovskite oxide materials. For example, Patent Document 2 below describes an example of a cathode material that can be used in a low-temperature operation type SOFC.

JP 2008-258064 A JP 2008-010325 A

A cathode made of the perovskite type oxide material as described above has high reactivity with a solid electrolyte made of stabilized zirconia such as YSZ, and it is relatively easy to obtain a high reaction rate between the solid electrolyte layer and the cathode by a solid-phase reaction. A resistive phase may be formed. For this reason, a reaction suppression layer typically made of a ceria-based material (for example, GDC doped with gadolinium) is disposed between the solid electrolyte layer and the cathode.
However, such a ceria-based material has low sinterability and, for example, may not be sufficiently densified in a temperature range of 1300 to 1400 ° C. that is a sintering temperature of SOFC having a general configuration. In addition, since the shrinkage rate during sintering is lower than that of the solid electrolyte, in the case of co-firing the solid electrolyte and the reaction inhibiting layer, or when firing the reaction inhibiting layer after firing the solid electrolyte in advance, There was a possibility that peeling occurred at the interface with the reaction inhibiting layer.

  The present invention has been created to solve such conventional problems, and prevents separation between the reaction-suppressing layer and the solid electrolyte layer in the solid oxide fuel cell, and the adhesion at the interface between the two layers ( An object of the present invention is to provide an SOFC having improved interface bondability (for example, the above-described anode-supported SOFC operated at a low temperature). Another object of the present invention is to provide a reaction inhibiting layer forming material for realizing such SOFC.

  In order to achieve the above object, the material provided by the present invention is a material for forming a reaction suppression layer of a solid oxide fuel cell, and is used as a cerium oxide particle component doped with rare earth elements. It is a material containing a large particle size cerium oxide particle component and a small particle size cerium oxide particle component having different particle size distribution and average particle size. Preferably, the average particle size of the large particle size cerium oxide particle component is 2 μm or less, and the average particle size of the small particle size cerium oxide particle component is 0.5 μm or less. Preferably, the average particle size of the large particle size cerium oxide particle component is 3 to 30 times the average particle size of the small particle size cerium oxide particle component. The difference in average particle diameter is more preferably 4 times or more and 10 times or less.

  In the material for forming a reaction suppression layer having such a structure, the particle component of the cerium oxide forming the main component of the reaction suppression layer is two different types of powder, that is, a large particle size cerium oxide particle component having the above-described conditions. And a small particle size cerium oxide component. As a result, the sinterability of the reaction suppression layer formed on the solid electrolyte can be improved. As a result, the adhesion (interface adhesion rate) at the interface between the formed (baked) reaction-suppressing layer and the solid electrolyte layer can be increased, and peeling between the two can be prevented.

Moreover, one aspect suitable as a material for forming a reaction suppression layer disclosed herein further contains a titanium compound. Preferably, the titanium compound is an organometallic compound having titanium as a constituent element.
By including an inorganic titanium compound such as titanium oxide, preferably an organic titanium compound such as titanium alkoxides or titanium chelates, the adhesiveness (interface adhesion rate) at the interface between the reaction inhibition layer and the solid electrolyte layer is further increased. Can be improved. For this reason, according to the material for forming a reaction suppression layer of this embodiment, even when a perovskite oxide material that is highly reactive with a solid electrolyte layer such as YSZ is used as a cathode (air electrode) material, for example, the solid electrolyte layer A good reaction inhibiting layer can be formed between the cathode and the cathode. Moreover, since the adhesion (interfacial adhesion rate) between the reaction suppression layer and the solid electrolyte layer is high, a solid oxide fuel cell (particularly, a low-temperature operation type SOFC) having excellent power generation performance can be manufactured.
Particularly preferably, the content of the titanium compound is 0.001% by mass to 10% by mass of the whole. By including the titanium compound with such a content, high adhesion (interfacial adhesion rate) between the reaction inhibition layer and the solid electrolyte layer can be realized.

Preferably, the reaction inhibiting layer forming material disclosed herein further comprises an organic solvent and a binder, and is prepared in a paste form (including a slurry form and an ink form; the same applies hereinafter). To do.
According to such a paste-like reaction inhibiting layer forming material (hereinafter also referred to as “reaction inhibiting layer forming paste”), a solid electrolyte layer (or the solid electrolyte layer) targeted for the reaction inhibiting layer forming paste is used. A reaction inhibiting layer having a predetermined thickness can be easily formed by applying it onto a green sheet for forming by firing).
A preferred embodiment of such a reaction inhibiting layer forming paste is a paste material in which the titanium compound is dispersed or dissolved. In particular, according to the paste material in which organic titanium compounds such as titanium alkoxides and titanium chelates are dissolved in an organic solvent (that is, including Ti resinate), it has high adhesiveness (interfacial adhesion rate) and peels off. A solid oxide fuel cell having a laminated structure of a difficult solid electrolyte layer and a reaction inhibiting layer can be manufactured.

The present invention also provides a solid oxide fuel cell to achieve the above object. That is, the solid oxide fuel cell provided by the present invention is a solid oxide fuel in which a reaction inhibiting layer is disposed between a solid electrolyte layer mainly composed of zirconia (zirconium oxide) and an air electrode (cathode). In the battery, the reaction suppression layer is formed by firing cerium oxide particles doped with a rare earth element. Typically, the reaction inhibition layer is formed from any of the reaction inhibition layer forming materials disclosed herein.
The length of the entire interface between the reaction inhibition layer and the solid electrolyte layer adjacent to the reaction inhibition layer, which is derived by observing the cross section of the solid oxide fuel cell with an electron microscope (typically, SEM observation). The interfacial adhesion rate (%), which represents the percentage of the length of the bonded portion of the interface in the percentage, is 60% or more. Here, the “adhesion portion” refers to a portion where peeling at the interface is not observed by electron microscope observation (in other words, a portion where the solid phase of the reaction suppression layer and the solid electrolyte layer are in close contact with each other under electron microscope observation). .
In the SOFC disclosed here, the interfacial adhesion ratio between the solid electrolyte layer mainly composed of zirconia (typically stabilized zirconia such as YSZ) and the reaction inhibition layer made of cerium oxide is 60% or more. High price. Therefore, it is possible to provide a low temperature operation type SOFC having an air electrode (cathode) made of, for example, a perovskite-type oxide material and having high durability and good power generation performance.

Of the SOFCs disclosed herein, a more preferable one is characterized in that the interfacial adhesion rate is 70% or more. Further, among the SOFCs disclosed herein, a particularly preferable one is characterized in that the reaction suppression layer includes an oxide having titanium as a constituent metal element.
For example, the reaction inhibition layer formed from the reaction inhibiting layer forming material containing the above titanium compound contains an appropriate amount of titanium oxide, and as a result, peeling between the reaction inhibition layer and the solid electrolyte layer is prevented, and heat durability SOFC with high performance and power generation performance is provided.

It is sectional drawing which shows typically the laminated structure of SOFC (single cell) disclosed here. It is an electron micrograph (SEM image) which shows the adhesion state of the interface between the reaction suppression layer and solid electrolyte layer in SOFC (single cell) which concerns on one Example.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, general items of SOFC not characterizing the present invention, manufacturing process, operation method of SOFC, 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 implemented based on the contents disclosed in the present specification and technical knowledge in the field.

<Cerium oxide particle component>
The material for forming a reaction inhibition layer disclosed herein contains two kinds of cerium oxide particle components having different particle size distributions and average particle sizes as main components. That is, it includes a large particle size cerium oxide particle component and a small particle size cerium oxide particle component having the above-described configuration. Here, the “average particle size” is a particle size at an integrated value of 50% (50% cumulative volume average particle size (median diameter); D50) in a particle size distribution measured by a particle size distribution measuring apparatus based on a laser diffraction / scattering method. Means.
Examples of the cerium oxide doped with rare earth elements include ceria doped with samaria (SDC), ceria doped with yttria (YDC), and ceria doped with gadolinia (GDC). Of these, GDC is preferred. Moreover, the suitable doping amount of rare earth elements is about 5 to 20 mol% (preferably 5 to 15 mol%). By forming such a reaction inhibiting layer composed of a cerium oxide component, it is possible to inhibit the reaction between a solid electrolyte layer mainly composed of zirconia such as YSZ and an air electrode (cathode) composed of a perovskite oxide material. it can.

<Average particle size>
As the large-diameter cerium oxide particle component, those having an average particle diameter (D50) of 2 μm or less are preferable, and those having a particle diameter of 1 μm or less are particularly preferable. From the viewpoint of improving handling properties and interfacial adhesion between the reaction inhibiting layer and the solid electrolyte layer, cerium oxide particles having an average particle size of 0.8 μm or less are preferably adopted as the large particle size cerium oxide particle component. Can do. For example, a large-diameter cerium oxide particle component having an average particle size of 0.1 μm or more and 2 μm or less is preferable, 0.3 μm or more and 1 μm or less is more preferable, and 0.5 μm or more and 0.8 μm or less is particularly preferable.

  On the other hand, the small particle size cerium oxide particle component is not particularly limited as long as the average particle size is at least 1/3 times smaller than the large particle size cerium oxide particle component. Usually, the average particle size of the small particle size cerium oxide particle component is preferably 0.5 μm or less. From the viewpoint of improving handling properties and interfacial adhesion between the reaction inhibiting layer and the solid electrolyte layer, the average particle size of the small particle size cerium oxide particle component is preferably 0.4 μm or less, more preferably 0.3 μm or less. Particularly preferably, it is 0.2 μm or less. For example, a small particle size cerium oxide particle component having an average particle size of 0.005 μm or more and 0.5 μm or less is preferable, 0.01 μm or more and 0.4 μm or less is more preferable, and 0.05 μm or more and 0.2 μm or less. Is particularly preferred.

  The average particle size of the large particle size cerium oxide particle component is the small particle size cerium from the viewpoint of better exhibiting the effect of combining the large particle size cerium oxide particle component and the small particle size cerium oxide particle component. The average particle size of the oxide particle component is preferably 3 times or more, more preferably 3.3 times or more, and particularly preferably 4 times or more. From the viewpoint of enhancing the interfacial adhesion between the anti-resistive layer and the solid electrolyte layer, the reaction-suppressing layer-forming material disclosed herein includes, for example, a large particle size cerium oxide particle component having an average particle size of a small particle size The average particle size of the cerium oxide particle component is 3 to 30 times, more preferably 3.3 to 20 times, still more preferably 4 to 10 times, and particularly preferably 4 to 5 times. The embodiment can be preferably implemented.

  The average particle size of the large particle size cerium oxide particle component is preferably 0.3 μm or more, and more preferably 0.5 μm or more larger than the average particle size of the small particle size cerium oxide particle component. The reaction-suppressing layer forming material disclosed herein is implemented, for example, in such a manner that the average particle size of the large particle size cerium oxide particle component is 0.6 μm or more larger than the average particle size of the small particle size cerium oxide particle component Can be done. Thereby, better interfacial adhesion between the solid electrolyte layer and the reaction inhibition layer can be realized.

<Content>
The ratio (mass ratio) between the content of the large particle size cerium oxide particle component and the content of the small particle size cerium oxide particle component is not particularly limited. From the viewpoint of better exerting the effect of combining the large particle size cerium oxide particle component and the small particle size cerium oxide particle component, the content of the large particle size cerium oxide particle component is small particle size cerium oxide. It is preferable that it is more than content of a particle component. For example, from the viewpoint of interfacial adhesion to the solid electrolyte layer, it is appropriate that the mass ratio of the large particle size cerium oxide particle component to the small particle size cerium oxide particle component is 10: 1 to 1: 1. 5: 1 to 1: 1 is preferable, 4: 1 to 2: 1 is more preferable, and 4: 1 to 3: 1 is particularly preferable.

  The material for forming a reaction suppression layer disclosed here is a cerium oxide particle component doped with a rare earth element, a large particle size cerium oxide particle component and a small particle size cerium oxide having mutually different particle size distribution and average particle size. Physical particle component. The average particle size of the large particle size cerium oxide particle component is 2 μm or less, the average particle size of the small particle size cerium oxide particle component is 0.5 μm or less, and the average particle size of the large particle size cerium oxide particle component The particle size is 3 to 30 times the average particle size of the small-diameter cerium oxide particle component. Thus, by using two types of cerium oxide particles having different average particle sizes in combination so as to have a specific average particle size ratio, the sinterability of the reaction suppression layer formed on the solid electrolyte can be improved. Can do. As a result, the adhesion (interface adhesion rate) at the interface between the formed (baked) reaction-suppressing layer and the solid electrolyte layer can be increased, and peeling between the two can be prevented.

  The material for forming a reaction suppression layer containing a large particle size cerium oxide particle component and a small particle size cerium oxide particle component includes, for example, a large particle size cerium oxide particle component, a small particle size cerium oxide particle component, and a dispersion medium. It can be prepared in the form of a paste by mixing an optional component (a titanium compound or a binder described later) used as necessary in a desired quantitative ratio.

<Dispersion medium (solvent)>
The reaction inhibiting layer forming material disclosed here may contain additives other than the above-described large particle size cerium oxide particle component and small particle size cerium oxide particle component. For example, as described above, the reaction inhibition layer forming material disclosed herein may be prepared in a paste form. The paste-like reaction inhibition layer forming material (hereinafter also referred to as reaction inhibition layer forming paste) contains at least one dispersion medium (solvent). As the dispersion medium, one or two or more of the above-mentioned cerium oxide particles that can be suitably dispersed can be used without any particular limitation. As the dispersion medium, either an organic solvent or an inorganic solvent may be used. When the later-described titanium compound is an organometallic compound containing titanium as a constituent element, it is preferable to use an organic solvent in which the organometallic compound is soluble. Examples of such organic solvents include alcohol solvents, ether solvents, ester solvents, ketone solvents, and other organic solvents. For example, terpineol, butyl diglycol acetate, isobutyl alcohol, tilcellosolve acetate, butyl carbitol acetate, butyl carbitol, ethylene glycol, toluene, xylene, mineral spirit, etc. are preferably used. In addition, the inorganic solvent is preferably water or a mixed solvent mainly composed of water. As the solvent other than water constituting the mixed solvent, for example, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. The content of the dispersion medium (solvent) in the paste is not particularly limited, but is preferably about 10% by mass to 50% by mass (typically 20% by mass to 35% by mass) of the entire paste. Such a paste for forming a reaction suppression layer is preferable because it can be easily applied onto a solid electrolyte layer (or a green sheet for forming the solid electrolyte layer by firing) intended for the paste for forming a reaction suppression layer. . Moreover, it is preferable to apply by coating or the like because a reaction inhibiting layer having a predetermined thickness can be easily formed.

<Titanium compound>
The material for forming a reaction suppression layer disclosed herein may further contain a titanium compound. Examples of the titanium compound include inorganic titanium compounds such as titanium oxide, and organic titanium compounds such as titanium alkoxides and titanium chelates. By including such a titanium compound, the adhesiveness (interface adhesion rate) at the interface between the reaction inhibition layer and the solid electrolyte layer can be further improved.

  The material for forming a reaction inhibition layer disclosed herein can be particularly preferably implemented in an embodiment containing at least an organic titanium compound (a compound in which a titanium atom and an organic component are bonded) as a titanium compound. If it can handle under normal temperature normal pressure, the kind in particular of an organic component will not be restrict | limited, The organic titanium compound comprised from this organic component and a titanium element can be used preferably as a titanium compound which concerns on this invention. Specific examples of the organic titanium compound include carboxylic acids having a relatively high carbon number (for example, 8 or more carbon atoms) such as octylic acid, 2-ethylhexanoic acid, abietic acid, oleic acid, naphthenic acid, linolenic acid, and neodecanoic acid. Ti salt of sulfonic acid, Ti salt of sulfonic acid, or alkyl mercaptide (alkyl thiolate), aryl mercaptide (aryl thiolate), mercaptocarboxylic acid ester and the like containing Ti. Of these, Ti salt of octylic acid is preferable. One or more of these can be used without any particular limitation.

From the viewpoint of enhancing the interfacial adhesion between the reaction inhibiting layer and the solid electrolyte layer, the content of the titanium compound in terms of oxide (TiO ₂ ) is typically 0.001% by mass or more of the whole, It is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 1% by mass or more, and particularly preferably 5% by mass or more. By increasing the content of the titanium compound, better interfacial adhesion between the reaction inhibiting layer and the solid electrolyte layer can be realized. On the other hand, from the viewpoint of power generation performance, the content is usually 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less.

<Binder>
The reaction inhibiting layer forming material disclosed herein can further contain various resin components as a binder. By adding such a resin component, the application of the reaction inhibiting layer forming material onto the solid electrolyte layer is further facilitated. Such a resin component is not particularly limited as long as it can impart a good viscosity and coating film-forming ability (for example, including printability and adhesion) to prepare a paste, and is used for this type of conventional paste. Can be used without particular limitation. Examples thereof include those mainly composed of acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulosic polymer, polyvinyl alcohol, rosin resin and the like. Among these, it is particularly preferable that a cellulosic polymer such as ethyl cellulose is contained.

  Although not particularly limited, the ratio of the cerium oxide particles (the total amount of the large-diameter cerium oxide particle component and the small-diameter cerium oxide particle component) to the entire reaction-suppressing layer forming material is approximately 40 mass. % Or more (typically 40 to 80% by mass), preferably about 55 to 70% by mass. Moreover, in the composition containing a binder, the ratio of the binder to the whole reaction suppression layer forming material can be 1-15 mass%, for example, and it is preferable that it is about 3-10 mass%.

  The reaction-suppressing layer forming material disclosed herein is a known additive that can be used for this kind of reaction-suppressing layer forming material, such as a dispersant and a plasticizer, as long as the effects of the present invention are not significantly hindered. If necessary, it may be further contained.

<SOFC>
The reaction inhibiting layer forming material disclosed here has been described above. Such a reaction suppression layer forming material can be suitably used as a reaction suppression layer forming material that suppresses the reaction between the solid electrolyte layer of a solid oxide fuel cell (that is, SOFC) and the air electrode (cathode), for example. . Hereinafter, the SOFC provided by the present invention will be described with reference to specific embodiments of the SOFC configured using the reaction-suppressing layer forming material disclosed herein.

As shown in FIG. 1, the solid oxide fuel cell (SOFC) in this embodiment includes a fuel electrode support type SOFC 100. In this SOFC 100, oxide ion conduction mainly composed of zirconia is sequentially formed on the surface (upper surface) of the fuel electrode (anode) support 12 having a porous structure and the fuel electrode (anode) 14 formed on the support 12. A dense layered solid electrolyte layer 20 made of a body, a porous structure reaction inhibiting layer 30, and a porous structure air electrode (cathode) 40 are formed. During the operation of the SOFC, the fuel gas (typically hydrogen (H ₂ )) passes through the fuel electrode 14 to the surface of the solid electrolyte layer 20 on the fuel electrode 14 side, and passes through the air electrode 40 to the surface of the solid electrolyte layer 20 on the air electrode 40 side. An oxygen (O ₂ ) containing gas (typically air) is supplied. In a general operation, the O ₂ gas in the oxygen (O ₂ ) -containing gas is reduced at the air electrode 40 to become an O ²⁻ anion, moves to the fuel electrode 14 through the solid electrolyte layer 20, and H ₂ gas. Oxidizes the fuel. And with this oxidation reaction, electric energy is generated.

  In the present embodiment, the fuel electrode support type SOFC 100 can be constructed as follows. That is, as a fuel electrode support material, particles of group 8 to group 10 metal elements having an average particle size of 0.1 to 10 μm (for example, nickel oxide powder) and ceramics having an average particle size of 0.1 to 10 μm (for example, 8 mol% yttria). Stabilized zirconia) powder and mixed powder. This mixed powder, a binder (for example, polyvinyl butyral), a pore former (for example, carbon particles), a plasticizer (for example, octyl phthalate), and a solvent (for example, toluene: ethanol) are blended at a predetermined mass ratio, By mixing, a paste-like composition for forming a fuel electrode support is prepared. Subsequently, this composition for forming a fuel electrode support is applied in a sheet form by a doctor blade method and dried to form a fuel electrode support green sheet having a thickness of 0.3 mm to 1 mm.

  Next, as fuel electrode materials, particles of group 8 to group 10 metal elements having an average particle size of 0.1 to 10 μm (for example, nickel oxide powder) and ceramics having an average particle size of 0.1 to 10 μm (for example, 8 mol% yttria). A paste-like fuel electrode forming composition is prepared by kneading a stabilized zirconia) powder, a binder (for example, ethyl cellulose), and a solvent (for example, α-terpineol) at a predetermined mass ratio. The fuel electrode green sheet is formed by supplying this on the fuel electrode support green sheet in a sheet form by a screen printing method.

  Next, as a solid electrolyte material, a ceramic (for example, 8 mol% yttria stabilized zirconia) powder mainly composed of zirconia having an average particle size of 0.1 to 10 μm, a binder (for example, ethyl cellulose), and a solvent (for example, terpine) are used. Then, a paste-like composition for forming a solid electrolyte layer is prepared by kneading at a predetermined mass ratio. A solid electrolyte layer green sheet having a thickness of about 1 to 20 μm is formed by supplying this to the fuel electrode green sheet in a sheet form by a screen printing method.

  Further, as the reaction inhibiting layer forming material, the aforementioned large particle size cerium oxide particle component and small particle size cerium oxide particle component are mixed at a predetermined mass ratio to obtain a mixed powder. The mixed powder, a binder (for example, ethyl cellulose), and a solvent (for example, terpineol) are kneaded at a predetermined mass ratio to prepare a paste-like composition for forming a reaction inhibition layer. Further, a titanium compound is added. This is supplied on the solid electrolyte layer green sheet in a sheet form by a screen printing method, thereby forming a reaction suppression layer green sheet having a thickness of about 1 to 10 μm.

  The laminated green sheet thus prepared is co-fired at 1200 ° C. to 1400 ° C. (preferably 1300 ° C. to 1400 ° C.) to obtain a SOFC half cell.

  Next, as an air electrode material, a perovskite type oxide (for example, lanthanum cobaltite-based material, typically lanthanum strontium iron cobaltite (LSCF)) powder having an average particle size of 0.1 to 10 μm, a binder (for example, ethyl cellulose), A paste-like composition for forming an air electrode is prepared by kneading a solvent (for example, alcohol) at a predetermined mass ratio. An air electrode green sheet is formed by supplying this in a sheet form by a screen printing method on the half-cell reaction inhibition layer. Next, this is fired at 1000 ° C. to 1200 ° C. (for example, 1100 ° C.), and the air electrode 40 is fired to obtain SOFC.

  The solid oxide fuel cell (SOFC) 100 thus obtained has a solid oxide in which a reaction inhibiting layer 30 is disposed between a solid electrolyte layer 20 mainly composed of zirconia and an air electrode (cathode) 40. In the fuel cell, the reaction suppression layer 30 is formed by firing cerium oxide particles doped with a rare earth element. Typically, the reaction suppression layer 30 is formed from the reaction suppression layer forming material disclosed herein. Therefore, the obtained SOFC 100 can have good adhesion (interface adhesion rate) at the interface between the reaction inhibition layer 30 and the solid electrolyte layer 20. For example, the total length of the interface between the reaction inhibition layer 30 and the solid electrolyte layer 20 adjacent to the reaction inhibition layer 30 derived by observing the cross section of the SOFC 100 with an electron microscope (typically SEM observation) is occupied. The interfacial adhesion rate (%), which indicates the percentage of the length of the bonded portion of the interface, is generally 60% or more, preferably 65% or more, more preferably 70% or more, and even more preferably 75. % Or more, and particularly preferably 80% or more. For example, the SOFC having an interfacial adhesion rate of 85% or more is preferable, 90% or more is more preferable, and 95% or more is particularly preferable. Within such a range of the interfacial adhesion rate, since the adhesion (interfacial adhesion rate) between the reaction inhibition layer 30 and the solid electrolyte layer 20 is high, a solid oxide fuel cell excellent in power generation performance (particularly, Can construct a low-temperature operation type SOFC).

  In addition, among the SOFCs disclosed herein, the reaction suppression layer 30 includes an oxide having titanium as a constituent metal element. For example, the reaction inhibition layer 30 formed from the reaction inhibition layer forming material containing the titanium compound contains an appropriate amount of titanium oxide. As a result, separation between the reaction suppression layer 30 and the solid electrolyte layer 20 is prevented, and the SOFC 100 with high thermal durability and high power generation performance is realized.

In addition, as a material which comprises the fuel electrode 14, various aspects can be considered other than the mixture which consists of a combination of the transition metal component (NiO) illustrated above and 8YSZ. For example, specifically, as the transition metal component, cobalt (Co), cobalt oxide (CoO, Co ₂ O ₃ , Co ₃ O ₄ ), copper (Cu), copper oxide (CuO, Cu ₂ O), silver (Ag), silver oxide (AgO, Ag ₂ O), tungsten (W), tungsten oxide (WO, W ₂ O ₃ , WO ₃ , WO ₆ ), platinum (Pt), platinum-palladium alloy, platinum-rhodium alloy Etc. are considered.

Further, as a material constituting the air electrode 40, for example, the following conductive perovskite oxide can be used instead of the LSCF exemplified above. Specifically, lanthanum manganate (LaMnO ₃ ) -based perovskite oxides represented by (LaSr) MnO ₃ and (LaCa) MnO ₃ , LaCoO ₃ , (LaSr) CoO ₃ , (LaSr) (CoFe ) _{O 3} or the like typified by, lanthanum cobaltite (LaCoO ₃₎ perovskite type oxide, _{furthermore, (LaSr) (TiFe) O} 3 or the like typified by, lanthanum titanate (LaTiO ₃₎ perovskite of What consists of an oxide is illustrated. It should be noted that the general formulas listed here simply indicate combinations of main elements constituting such oxides, as are commonly used by those skilled in the art, and represent the actual composition of the electrode material. It is not shown. Moreover, you may make it dope elements other than the main element shown above.

  Hereinafter, some test examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the test examples. Here, a circular fuel electrode-supported SOFC having a fuel electrode diameter of 20 mm and an air electrode diameter of about 10 mm was manufactured by the following procedure.

<Example 1>
As a fuel electrode support material, nickel oxide (NiO) powder having an average particle diameter of 0.5 μm and 8 mol% yttria-stabilized zirconia (8 mol% Y 2 O 3 —ZrO 2; hereinafter referred to as 8YSZ) powder having an average particle diameter of 0.5 μm are used. : 8YSZ = 60: 40 was mixed at a mass ratio to obtain a mixed powder. This mixed powder, a binder (polyvinyl butyral; PVB), a pore former (carbon particles, average particle diameter: about 5 μm), a plasticizer (octyl phthalate), and a solvent (toluene: ethanol = 1: 3) Were mixed at a mass ratio of 58: 8.5: 5: 4.5: 24 and mixed to prepare a paste-like composition for forming a fuel electrode support. Subsequently, this composition for forming a fuel electrode support was applied to a sheet by a doctor blade method and dried to form a fuel electrode support green sheet having a thickness of 0.5 mm to 1 mm.

  Next, as an anode material, nickel oxide (NiO) powder having an average particle size of 0.4 μm, 8YSZ powder having an average particle size of 0.3 μm, binder (ethyl cellulose; EC), and solvent (α-terpineol; TE) Were mixed at a mass ratio of 48: 32: 2: 18 to prepare a paste-like composition for forming a fuel electrode. This was supplied in the form of a sheet by screen printing on the fuel electrode support green sheet to form a fuel electrode green sheet.

  Next, as a solid electrolyte material, an 8YSZ powder having an average particle diameter of 0.5 μm, a binder (ethyl cellulose; EC), and a solvent (terpine) are kneaded at a mass ratio of 65: 4: 31 to obtain a paste. A solid electrolyte layer forming composition was prepared. A solid electrolyte layer green sheet having a thickness of about 10 μm was formed by supplying the sheet on the fuel electrode green sheet by a screen printing method.

Further, as a material for forming a reaction suppression layer, 10 mol% gadolinia doped ceria (10GDC) having an average particle size of 2.0 μm as a large particle size cerium oxide particle component (hereinafter also referred to as “large particle size Ce particles A”). ) And 10 GDC having an average particle size of 0.4 μm as a small particle size cerium oxide particle component (hereinafter also referred to as “small particle size Ce particle B”), a large particle size Ce particle A: a small particle size Ce particles B were mixed at a mass ratio of 3: 1 to obtain a mixed powder. This mixed powder, binder (ethylcellulose), and solvent (terpineol) were kneaded at a mass ratio of 65: 4: 31 to prepare a paste-like reaction-inhibiting layer forming composition. Further, Ti salt of octylic acid as an organic titanium compound was added and dissolved in the solvent (that is, Ti resinate was included). The content of the titanium compound in terms of oxide (TiO ₂ ) was 0.001% by mass of the whole (ie, when the entire composition was 100% by mass). This was supplied on the solid electrolyte layer green sheet in a sheet form by a screen printing method to form a reaction suppression layer green sheet having a thickness of about 5 μm. The laminated green sheet thus prepared was cofired at 1350 ° C. to obtain a SOFC half cell.

Next, as an air electrode material, an lanthanum strontium iron cobaltite (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ; LSCF) powder having an average particle diameter of 1.0 μm, a binder (ethyl cellulose), and a solvent (Alcohol-based) was kneaded at a mass ratio of 80: 3: 17 to prepare a paste-like composition for forming an air electrode. An air electrode green sheet was formed by supplying this in a sheet form by a screen printing method on the half-cell reaction inhibition layer. Subsequently, this was baked at 1100 degreeC and the air electrode was baked, and SOFC was obtained.

<Examples 2-9 and Comparative Examples 1-6>
In Examples 2 to 9 and Comparative Examples 1 to 6, the average particle size of the large particle size Ce particles A, the average particle size of the small particle size Ce particles B, and the content of the titanium compound in the material for forming a reaction suppression layer were implemented. Different from Example 1. Other than that, SOFC was produced in the same procedure as Example 1. The configuration of each example is summarized in Table 1.

<Interfacial adhesion rate>
Taking 10 views of the cross sections of the SOFCs of Examples 1 to 9 and Comparative Examples 1 to 6 described above, and observing the SEM as shown in FIG. 2, the entire interface between the reaction inhibition layer and the solid electrolyte layer is observed. The ratio of the length of the bonded portion of the interface in the length was calculated as a percentage as the interface adhesion rate. Here, the “adhesion portion” was defined as a portion where peeling at the interface was not observed by SEM observation (in other words, a portion where the solid phase of the reaction inhibition layer and the solid electrolyte layer were in close contact under SEM observation). The results are shown in the corresponding column of Table 1.

<Power generation performance>
The power density when the SOFCs of Examples 1 to 9 and Comparative Examples 1 to 6 produced above were operated under the following conditions was measured, and the output (W / cm ² ) at a voltage of 0.8 V was used as the power generation performance. It was shown in 1.
Operating temperature: 700 ° C
Fuel electrode supply gas: H ₂ gas (50 ml / min)
Air electrode supply gas: Air (100 ml / min)

As shown in Table 1, in Examples 1 to 9, the average particle size of the large particle size Ce particles is 2 μm or less, the average particle size of the small particle size Ce particles is 0.5 μm or less, and the large particles The average particle size of the Ce particles is 3 to 30 times the average particle size of the small Ce particles. In all of Examples 1 to 9, the interfacial adhesion rate was 60% or more, and the interfacial adhesion between the reaction inhibition layer and the solid electrolyte layer was better than those of Comparative Examples 1 to 6. Further, the power generation performance exceeded 0.6 W / cm ² , which was suitable as SOFC. From this result, by using two kinds of cerium oxide particles having different average particle diameters in combination so as to have a specific average particle diameter ratio, the interfacial adhesion between the reaction inhibiting layer and the solid electrolyte layer is improved, It was confirmed that peeling can be prevented.

  In Examples 3 to 7 and Comparative Example 4, the average particle size of the large particle size Ce particles is 0.8 μm, and the average particle size of the small particle size Ce particles is 0.2 μm. When Examples 3 to 7 and Comparative Example 4 were compared, Comparative Example 4 in which the titanium compound was not used was not as effective as Examples 3 to 7 in which the titanium compound was used. From this result, it was confirmed that when two types of cerium oxide particles having different average particle diameters are used in combination, a higher performance improvement effect is exhibited when the titanium compound is contained.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

12 Fuel Electrode Support 14 Fuel Electrode 20 Solid Electrolyte Layer 30 Reaction Suppression Layer 40 Air Electrode 100 Solid Oxide Fuel Cell (SOFC)

Claims (4)

A paste-like material for forming a reaction suppression layer of a solid oxide fuel cell,
An organic solvent,
A binder,
A titanium compound which is an organometallic compound containing titanium as a constituent element, and is a titanium compound dissolved in the organic solvent;
As a cerium oxide particle component doped with a rare earth element, a large particle size cerium oxide particle component and a small particle size cerium oxide particle component having different particle size distribution and average particle size,
Including
Here, the average particle size of the large particle size cerium oxide particle component is 2 μm or less, the average particle size of the small particle size cerium oxide particle component is 0.5 μm or less, and
The average particle diameter of the large particle size of cerium oxide particle component, characterized in that said small particle size of cerium oxide having an average particle diameter of the particle component is 3 times or more 30 times or less, pasty reaction preventing layer formed Materials. The material for forming a reaction suppression layer according to claim 1 , wherein the content of the titanium compound is 0.001% by mass to 10% by mass of the whole. A solid oxide fuel cell in which a reaction suppression layer is disposed between a solid electrolyte layer and an air electrode,
The said reaction inhibition layer is formed from the sintered body of the reaction inhibition layer forming material of Claim 1 or 2 , and has cerium oxide particles doped with rare earth elements and titanium as constituent metal elements. Containing titanium oxide,
Here, the interface occupies the total length of the interface between the reaction suppression layer and the solid electrolyte layer adjacent to the reaction suppression layer, which are derived by observing a cross section of the solid oxide fuel cell with an electron microscope. A solid oxide fuel cell, characterized in that the interfacial adhesion rate (%), which indicates the percentage of the length of the bonded portion, is 60% or more. The solid oxide fuel cell according to claim 3 , wherein the interfacial adhesion rate is 70% or more.