JP2020071987A - Solid oxide fuel cell and current collector forming material used therein - Google Patents

Abstract

To provide a solid oxide fuel cell (SOFC) including a current collecting unit which has high current collecting efficiency and can suppress an increase in resistance due to use.SOLUTION: A solid oxide fuel cell (SOFC) according to the present invention includes a power generator 40 in which a fuel electrode 10 and an air electrode 30 face each other via a solid electrolyte layer 20, and a current collector 30e disposed on the surface of at least one of the fuel electrode 10 and the air electrode 30. The current collector 30e is a sintered body including a silver-containing material of at least one of silver and a silver alloy, and a perovskite type oxide, and the electrical conductivity exceeds 8000 S/cm, and the average equivalent-circle diameter of the sintered silver-containing material based on electron microscope observation is 2.9 μm or less.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a solid oxide fuel cell and a material for forming a current collector used therein.

  Solid oxide fuel cells (SOFCs) are next-generation fuel cells of the next generation because of their high power generation efficiency and low environmental impact among various types of fuel cells. It is being developed as an energy source. The SOFC has a power generator having a structure in which a fuel electrode (anode) and an air electrode (cathode) face each other via a solid electrolyte layer. The electric power generated by the power generator is taken out to the outside via the collector terminals of the air electrode and the fuel electrode. In this regard, Patent Documents 1 to 6 disclose that a current collector is provided on the surface of the air electrode and / or the fuel electrode, and electric power is taken out from the power generator via the current collector. For example, Patent Document 1 discloses an air electrode current collector forming material containing a silver-containing material and perovskite type oxide powder, and an air electrode current collector using the same.

JP, 2005-050636, A JP, 2010-140895, A JP, 2004-355814, A JP 2004-165074 A JP, 2006-139966, A JP, 2010-118338, A

  For the SOFC current collector, it is required to further reduce the resistance and improve the current collection efficiency. In addition, SOFC is expected to be used for a long period of time, for example, exceeding 100,000 hours. Therefore, it is also required to stably maintain high power generation performance by suppressing deterioration over time due to use, for example, an increase in the resistance of at least one of the air electrode, the fuel electrode, and the current collector.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an SOFC having a current collector that has high current collection efficiency and can suppress an increase in resistance due to use. Further, another object of the present invention is to provide a material for forming a current collecting portion for forming such a current collecting portion of an SOFC.

  According to the present invention, a fuel electrode and an air electrode, a power generator facing each other via a solid electrolyte layer, a current collector arranged on the surface of at least one of the fuel electrode and the air electrode, There is provided a solid oxide fuel cell comprising: The current collector is a sintered body containing at least one silver-containing material of silver and a silver alloy and a perovskite type oxide, and has a conductivity of more than 8000 S / cm and is sintered. The average equivalent-circle diameter of the above silver-containing material observed by an electron microscope is 2.9 μm or less.

  In the current collector, the network between Ag particles is well developed and the electrical conductivity of a predetermined value or more is realized. Further, in the current collector, the average equivalent circle diameter of the silver-containing material in the sintered state is kept small. As a result, in the SOFC including the current collector, the ohmic resistance can be suppressed small, and the resistance increase due to the use of the SOFC can be suppressed to suppress the power loss. Therefore, the SOFC disclosed herein can exhibit good power generation characteristics for a long period of time.

  In a preferred aspect disclosed herein, the proportion of the silver-containing material in the current collector is more than 50% by mass. As a result, the conductivity of the current collector can be further improved, and power loss can be further suppressed.

  In a preferred aspect disclosed herein, the average thickness T of the current collector is 100 μm or less, and the product of the conductivity (S / cm) and the average thickness T (cm) is 30. (S / cm) · cm or more. Thereby, even when the current collector is formed thicker, as in a cylindrical SOFC, the conductivity of the current collector can be improved and the current collection efficiency can be improved.

  In a preferred embodiment disclosed herein, the average circle equivalent diameter of the silver-containing material is Ds1 (μm), and the number-based average particle diameter of the perovskite oxide based on electron microscope observation is Ds2 (μm). Then, the Ds1 and the Ds2 satisfy the following relationship: 10 ≦ (Ds1 / Ds2) ≦ 20. Thereby, the initial characteristics and the durability characteristics of the SOFC can be balanced at a higher level.

In a preferred embodiment disclosed herein, the perovskite-type oxide is an oxide represented by the general formula: ABO ₃ ; containing A and Sr at the A site and containing Co at the B site. Thereby, the effect of the technique disclosed here can be exhibited more effectively.

  In a preferred aspect disclosed herein, the air electrode contains a perovskite oxide, and the current collector is arranged on the surface of the air electrode. As a result, it is possible to enhance the consistency and integrity of the coefficient of thermal expansion between the air electrode and the current collector, and to improve the durability of the SOFC, for example, the heat cycle resistance.

  In a preferred aspect disclosed herein, the power generator is configured such that the solid electrolyte layer and the air electrode are laminated in this order on the surface of the cylindrical fuel electrode, The current collector is arranged on the surface.

  Further, according to the present invention, there is provided a material for forming a current collector of a solid oxide fuel cell, which contains at least one silver-containing material of silver and a silver alloy and a perovskite oxide. When the number-based average particle diameter of the silver-containing material based on electron microscope observation is D1 (μm), and the number-based average particle diameter of the perovskite oxide based on electron microscope observation is D2 (μm), The above D1 and D2 both satisfy the following relationships: D2 ≦ 0.5 μm; 4 ≦ (D1 / D2).

  In the material for forming the current collecting portion, the average particle diameter D2 of the perovskite type oxide is suppressed small, and the ratio (D1 / D2) of the average particle diameter D1 of the silver-containing material to the average particle diameter D2 is equal to or more than a predetermined value. Has been adjusted to. By forming the SOFC current collecting portion using this current collecting portion forming material, the ohmic resistance of the current collecting portion can be reduced and higher power generation performance can be realized for a long period of time.

  In a preferred aspect disclosed herein, the ratio of the silver-containing material exceeds 50 mass% when the total of the silver-containing material and the perovskite oxide is 100 mass%. As a result, it is possible to realize a current collecting unit with improved current collecting efficiency.

  In a preferred aspect disclosed herein, the compounding ratio of the silver-containing material and the perovskite type oxide is 70:30 to 80:20. As a result, the reduction of ohmic resistance and the maintenance of the SOFC power generation performance can be balanced at a higher level.

  In a preferred aspect disclosed herein, the above D1 / D2 satisfies the following relationship: 4 ≦ (D1 / D2) ≦ 6; As a result, it is possible to realize a current collecting unit in which the conductivity and the gas permeability are balanced at a high level.

In a preferred embodiment disclosed herein, the perovskite-type oxide is an oxide represented by the general formula: ABO ₃ ; containing A and Sr at the A site and containing Co at the B site. Thereby, the effect of the technique disclosed here can be exhibited more effectively.

  In a preferred embodiment disclosed herein, a dispersion medium and a binder are included and prepared in a paste form. Thereby, the current collector can be easily formed at a desired position and in a desired size.

  In a preferred embodiment disclosed herein, it is used to form an air electrode current collector on the surface of the air electrode of a solid oxide fuel cell.

It is a side view which shows typically SOFC which concerns on one Embodiment. FIG. 2 is a partial sectional view schematically showing a portion (II) of FIG. 1. It is sectional drawing which shows typically SOFC which concerns on another embodiment. It is an SEM observation image of a current collection part, (A) is an example 1, (B) is a comparative example 2, (C) is a comparative example 4. It is explanatory drawing for demonstrating how to calculate | require an average circle equivalent diameter, (A) is an example of an SEM observation image, (B)-(D) is an example of an analysis result. It is a schematic diagram for explaining an example of a calculation formula of the average equivalent circle diameter. It is a Bode Plot obtained by impedance measurement, (A) is of Example 1 and (B) is of Comparative Example 6.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. It should be noted that matters other than matters particularly referred to in the present specification and matters necessary for carrying out the present invention (for example, a manufacturing process of SOFC, etc.) are design matters for those skilled in the art based on conventional techniques in the field. Can be grasped. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field. Further, in the following drawings, members / sites having the same action will be described with the same reference numerals, and redundant description may be omitted or simplified. In this specification, the notation “X to Y (where X and Y are arbitrary values)” indicating a numerical range means “X or more and Y or less”.

<Solid oxide fuel cell>
First, the solid oxide fuel cell (SOFC) of this embodiment will be described.
FIG. 1 is a side view schematically showing an SOFC 50 according to one embodiment. FIG. 2 is a partial cross-sectional view schematically showing the portion (II) of FIG. 1 and 2, the symbol L represents the major axis direction of the SOFC 50, and the symbol D represents the direction orthogonal to the major axis direction L and represents the radial direction of the SOFC 50. However, this is a direction for convenience of description and does not limit the installation form or the like.

  The SOFC 50 has a cylindrical shape as a whole. The SOFC 50 includes a fuel electrode (anode) 10, a solid electrolyte layer 20, an air electrode (cathode) 30, a power generator 40, a fuel electrode current collector 10e disposed on the surface of the fuel electrode 10, The air electrode current collector 30e disposed on the surface of the air electrode 30. The power generator 40 has a structure in which the fuel electrode 10 and the air electrode 30 are opposed to each other with the solid electrolyte layer 20 in between. The power generator 40 may further include layers other than the above. The power generation body 40 is physically integrated. In the SOFC 50, the fuel electrode 10 is formed thicker than the solid electrolyte layer 20 and the air electrode 30. The SOFC 50 is a so-called fuel electrode supported type (ASC: Anode-Supported Cell).

  The fuel electrode 10 has both a role as a support for supporting the SOFC 50 and a role as an electrode. The fuel electrode 10 has a hollow cylindrical shape here. The hollow portion serves as a flow path for fuel gas when the SOFC 50 generates electric power. The shape of the fuel electrode 10 can be appropriately selected according to the shape of the SOFC 50. The fuel electrode 10 has a porous structure so that the fuel gas supplied to the power generator 40 can flow. Here, the fuel electrode 10 has a single-layer structure having a uniform porosity in the radial direction D. However, the fuel electrode 10 may have a two-layer structure or a structure having three or more layers. The average thickness (length in the radial direction D) of the fuel electrode 10 may be, for example, 0.1 mm or more, 0.5 mm or more, and 1 mm or more from the viewpoint of improving handleability and durability (strength retention). Good. Further, from the viewpoint of improving the gas diffusibility and reducing the resistance, it may be, for example, 10 mm or less and 5 mm or less.

  The constituent material of the fuel electrode 10 is not particularly limited, and may be one kind or two or more kinds of materials conventionally used for the fuel electrode of this type of SOFC. As an example, nickel (Ni), copper (Cu), gold (Au), platinum (Pt), palladium (Pd), ruthenium (Ru), cobalt (Co), lanthanum (La), strontium (Sr), titanium ( Examples thereof include metals such as Ti) and metal oxides containing one or more of these metals. Among them, Ni is preferable because it is cheaper than other metals and exhibits high catalytic activity (reactivity with fuel gas is sufficiently large).

  Furthermore, for example, a composite material in which the above-mentioned metal or metal oxide is mixed with a constituent material (typically an oxide ion conductor) of the solid electrolyte layer 20 described later can be used. An example is a cermet of a nickel-based metal material (for example, NiO) and stabilized zirconia (for example, yttria-stabilized zirconia (YSZ)). The mixing ratio of the metal or metal oxide and the oxide-ion conductor composite material is not particularly limited, but may be approximately 90:10 to 40:60, for example, 80:20 to 45:55 by mass ratio. Thereby, electrical conductivity and durability can be compatible at a higher level.

  The fuel electrode current collectors 10e are arranged at both ends of the fuel electrode 10 in the major axis direction L, respectively. The electric power is taken out from the power generator 40 via the fuel electrode current collector 10e. The fuel electrode current collector 10e is also used when a plurality of SOFCs 50 are electrically connected to each other to form a high output stack or the like. The fuel electrode current collector 10e is formed, for example, by covering the exposed portion of the fuel electrode 10 with a metal cap. However, the fuel electrode current collector 10e may be made of the same material as the air electrode current collector 30e described later, for example.

  The solid electrolyte layer 20 is arranged on the surface of at least a part of the fuel electrode 10. The shape of the solid electrolyte layer 20 can be appropriately changed depending on, for example, the shape of the fuel electrode 10. The solid electrolyte layer 20 has both the role of conducting oxygen ions and the role of separating the fuel gas and the oxygen-containing gas. The solid electrolyte layer 20 is densely configured so as to form a partition wall between the fuel gas flowing through the fuel electrode 10 and the oxygen-containing gas flowing through the air electrode 30. The solid electrolyte layer 20 is formed in a relatively thin film shape as compared with the fuel electrode 10 and the air electrode 30. The average thickness (length in the radial direction D) of the solid electrolyte layer 20 may be, for example, 0.1 μm or more, 1 μm or more, 5 μm or more from the viewpoint of suppressing the occurrence of defects such as gas leaks and cracks. .. From the viewpoint of reducing the resistance, the thickness may be, for example, 50 μm or less, 40 μm or less, or 20 μm or less.

  The constituent material of the solid electrolyte layer 20 is not particularly limited, and may be one kind or two or more kinds of materials conventionally used for the solid electrolyte layer of this kind of SOFC. An example is an oxide ion conductor. Examples of the oxide ion conductor include zirconium (Zr), cerium (Ce), magnesium (Mg), scandium (Sc), titanium (Ti), aluminum (Al), yttrium (Y), calcium (Ca), Oxidation containing elements such as gadolinium (Gd), samarium (Sm), barium (Ba), lanthanum (La), strontium (Sr), gallium (Ga), bismuth (Bi), niobium (Nb) and tungsten (W). Things can be mentioned.

More specifically, for example, yttria _{(Y 2 O} 3), calcia (CaO), scandia _{(Sc 2 O} 3), magnesia (MgO), ytterbia _{(Yb 2 O} 3), erbia _(Er 2 _{O 3),} etc. Zirconia (ZrO ₂ ) whose crystal structure has been stabilized by a stabilizer, gadolinia (Gd ₂ O ₃ ), lanthanum (La ₂ O ₃ ), Samaria (Sm ₂ O ₃ ), yttria (Y ₂ O ₃ ). Cerium oxide (CeO ₂ ) doped with a doping agent such as Of these, YSZ (Yttria stabilized zirconia) and GDC (Gadolinium doped Ceria) are preferable. The content of the stabilizer or the dopant is not particularly limited, but it is preferably about 5 to 20 mol% when the entire oxide ion conductor is 100 mol%.

  The air electrode 30 is arranged on the surface of at least a part of the solid electrolyte layer 20. The shape of the air electrode 30 can be appropriately changed depending on, for example, the shape of the solid electrolyte layer 20. Here, the air electrode 30 is configured to have a structure exposed to the outside air. The air electrode 30 has a porous structure so that an oxygen-containing gas (typically air) supplied to the power generation body 40 can flow. The porosity of the air electrode 30 may be, for example, 5% by volume or more, 10% by volume or more, and 15% by volume or more from the viewpoint of improving gas diffusibility. Further, from the viewpoint of enhancing the strength, it may be, for example, 50% by volume or less, 40% by volume or less, and 30% by volume or less. The average thickness (the length in the radial direction D) of the air electrode 30 may be, for example, 1 μm or more, 5 μm or more, and 10 μm or more from the viewpoint of obtaining high catalytic activity. Further, from the viewpoint of improving the gas diffusibility and reducing the resistance, it may be, for example, 200 μm or less and 100 μm or less.

The constituent material of the air electrode 30 is not particularly limited, and may be one kind or two or more kinds of materials conventionally used for the air electrode of this kind of SOFC. An example is a perovskite type oxide represented by the general formula: ABO ₃ . The A site contains one or more kinds of lanthanoid elements (Ln), for example, lanthanum (La), cerium (Ce), samarium (Sm), neodymium (Nd), gadolinium (Gd) and the like. The A site is an element other than Ln, for example, a monovalent alkali metal element or a divalent alkaline earth metal element (Ae) such as magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). ) And the like may be further included. The B site is one or more kinds of transition metal elements, for example, titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu). ) Etc. are included. The B site may further contain an element other than a transition metal element, for example, a metal element having a valence of 3 or more and a metal element classified into a typical metal or a rare earth.

Specific examples of the perovskite type oxide include, for example, lanthanum cobaltite-based materials such as LaCoO ₃ , (LaSr) CoO ₃ , and (LaSr) (CoFe) O ₃ ; (LaSr) (CoFe); (LaSr) MnO ₃ ; Lanthanum manganate-based materials such as (LaCa) MnO ₃ ; lanthanum titanate-based materials such as (LaSr) (TiFe) O ₃ ; and the like. Of these, a lanthanum strontium cobaltite-based material containing lanthanum (La) and strontium (Sr) at the A site and at least cobalt (Co) at the B site is preferable, and particularly, lanthanum (La) and strontium (A) at the A site are preferable. A lanthanum strontium cobalt ferrite based material containing Sr) and containing cobalt (Co) and ferrite (Fe) at the B site is preferable.

  The air electrode current collector 30e is arranged on the surface of at least part of the air electrode 30. The air electrode current collector 30e constitutes a part of the outer surface of the SOFC 50. The air electrode current collector 30e is formed long along the air electrode 30 in the major axis direction L. The air electrode current collector 30e is shorter than the air electrode 30 in the major axis direction L here, and is arranged on a part of the surface of the air electrode 30. The electric power is extracted from the power generator 40 via the air electrode current collector 30e. The air electrode current collector 30e is also used when a plurality of SOFCs 50 are electrically connected to each other to form a high output stack or the like.

  The air electrode current collector 30e has a porous structure so that the oxygen-containing gas (typically air) supplied to the power generator 40 can flow. The porosity of the air electrode current collector 30e may be higher than that of the air electrode 30, may be the same as that of the air electrode 30, or may be lower than that of the air electrode 30. The average thickness (the length in the radial direction D) of the air electrode current collector 30e may be, for example, 10 μm or more, 20 μm or more, and 25 μm or more from the viewpoint of reducing resistance. The average thickness of the air electrode current collector 30e may be thicker than the average thickness of the air electrode 30. The average thickness of the air electrode current collector 30e may be, for example, 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, and further 90 μm or less from the viewpoint of improving gas permeability. The air electrode current collector 30e of the present embodiment contains a silver-containing material and a perovskite type oxide. The silver-containing material and the perovskite type oxide are integrally sintered to form a sintered body.

  The silver-containing material is at least one of silver and silver alloy. The silver-containing material may be a mixture of silver and silver alloy. Examples of silver alloys include silver-palladium (Ag-Pd) alloys, silver-platinum (Ag-Pt) alloys, and silver-copper (Ag-Cu) alloys. The silver alloy may be a composite. The silver-containing material may be, for example, core-shell particles including a core made of a metal other than silver, such as copper or a silver alloy, and a shell made of silver, which covers the core. The silver-containing material preferably contains silver in an amount of more than 50% by mass based on 100% by mass as a whole, and particularly, 80% by mass or more, 90% by mass or more, 95% by mass or more of silver, for example, It is preferably 98% by mass or more. Thereby, the resistance of the air electrode current collector 30e can be further reduced, and the power loss of the SOFC 50 can be further suppressed.

  The shape of the silver-containing material contained in the air electrode current collector 30e changes so that the gaps between the particles are smaller than in the state before sintering (for example, the state contained in the material for forming the current collector). ing. The silver-containing material may be in a state in which a plurality of particles are fused and integrated with each other due to, for example, sintering. In other words, a plurality of particles may be sintered or necked to form one particle. Therefore, the silver-containing material contained in the air electrode current collector 30e typically has a relatively large size compared to the state before sintering. In the technology disclosed herein, the silver-containing material has an average equivalent circle diameter (hereinafter, referred to as “sintered particle size”, Ds1) based on an electron microscope observation of 2. It is 9 μm or less. As a result, it is possible to suppress an increase in the resistance of the SOFC 50 and realize good power generation characteristics for a long period of time.

  The sintered grain size Ds1 of the silver-containing material may be 2.7 μm or less, for example. As a result, the silver-containing material is better dispersed in the air electrode current collector 30e, and as a result, the network between particles of the silver-containing material is further developed and the conductivity of the air electrode current collector 30e is improved. can do. The sintered grain size Ds1 of the silver-containing material may be on the order of micron, for example, more than 1 μm and 2 μm or more, 2.1 μm or more and 2.2 μm or more. As a result, the effect of suppressing the increase in resistance described above can be better exhibited.

  The sintered grain size Ds1 of the silver-containing material can be obtained by analyzing the image obtained by electron microscope observation. The detailed calculation method will be described later in the example section. Further, the sintered particle diameter Ds1 of the silver-containing material is adjusted by the material for forming the current collecting portion described later, for example, (a) the mixing ratio of the silver-containing material and the perovskite type oxide in the material for forming the current collecting portion, ( b) average particle diameter D1 of the silver-containing material used as the current collecting portion forming material, (c) average particle diameter D2 of the perovskite type oxide used as the current collecting portion forming material, (d) current collecting portion forming material Achieved by adjusting the ratio of the average particle diameter D1 of the silver-containing material used and the average particle diameter D2 of the perovskite oxide, (e) the crystallite diameter of the perovskite oxide used as the material for forming the current collector, and the like. can do.

  The perovskite oxide is at least one of the following: (1) a function of matching the coefficient of thermal expansion with the air electrode 30 to enhance the integrity; (2) suppressing aggregation and sintering of the silver-containing material. , (3) a function of keeping the particle size of the silver-containing material uniform, and (3) a function of trapping impurities contained in the supply gas and suppressing the composition deviation of the constituent material of the air electrode 30. Regarding the above (3), in the operating temperature range of the SOFC 50, impurities contained in the supply gas may diffuse into the three-phase interface between the oxygen-containing gas, the solid electrolyte layer 20, and the air electrode 30. As a result, the perovskite-type oxide of the air electrode 30 may react with impurities and the composition may shift (change). As a result, the catalytic activity of the air electrode 30 may decrease, and the power generation efficiency of the SOFC 50 may decrease. By including the perovskite type oxide in the air electrode current collector 30e, the impurities of the silver-containing material can be captured before they diffuse to the three-phase interface, and such a problem can be prevented.

  The perovskite type oxide is not particularly limited, and one kind or two or more kinds can be appropriately used from the materials exemplified as those that can be used for the air electrode 30. From the viewpoint of enhancing the matching and the integration of the coefficient of thermal expansion with the air electrode 30, the air electrode current collector 30e preferably contains the same type of perovskite oxide as the air electrode 30. As an example, when the air electrode 30 contains a lanthanum cobaltite material, for example, when the content ratio of the lanthanum cobaltite material in the air electrode 30 is approximately 50 mass% or more, for example 80 mass% or more, the air electrode current collector It is preferable that the portion 30e also contains a lanthanum cobaltite material. As a result, the durability of the SOFC 50 (for example, heat cycle resistance) can be further improved.

As a preferable example of the lanthanum cobaltite material, the following general formula (1):
(La _α Ae _1-α ) (Co _β B ^I _1-β ) O _3-δ (1);
A complex oxide represented by In addition, δ in the general formula (1) is a value determined to satisfy the neutral condition of charge, typically −1.2 ≦ δ ≦ 1.2, for example, −1 ≦ δ ≦ 1.
Further, α is a real number that satisfies 0 <α ≦ 1. α is typically 0.3 ≦ α ≦ 0.9, preferably 0.4 ≦ α ≦ 0.8, for example 0.5 ≦ α ≦ 0.7. When 0 <α, Ae is one or more alkaline earth metal elements. Among them, it is preferable to contain Sr. In other words, an oxide of the general formula ABO ₃ containing La and Sr at the A site and Co at the B site, that is, a lanthanum strontium cobaltite-based material is preferable.

Further, β is a real number that satisfies 0 <β ≦ 1. β is typically 0.01 ≦ β ≦ 0.9, preferably 0.05 ≦ β ≦ 0.8, for example 0.1 ≦ β ≦ 0.3. When β <1, B ^I is one or more of the elements other than Co among the elements exemplified as the elements that can be contained in the B site. Among them, it is preferable to contain at least one of Ni, Ti and Fe, and it is particularly preferable to contain Fe. For example, an oxide of the general formula ABO ₃ containing La and Sr at the A site and containing Co and Fe at the B site, that is, a lanthanum strontium cobalt ferrite material is preferable.

  The average particle diameter of the perovskite type oxide contained in the air electrode current collector 30e (hereinafter, referred to as "sintered particle size" in order to distinguish from the particle size before sintering) is determined by the air electrode current collector 30e. From the viewpoint of favorably developing a network between particles of the silver-containing material, it is typically smaller than the sintered particle size Ds1 of the silver-containing material. The sintered particle size Ds2 of the perovskite type oxide may be smaller than the average particle size of the perovskite type oxide contained in the air electrode 30 from the viewpoint of increasing the current collection efficiency of the air electrode current collector 30e. The sintered particle size Ds2 of the perovskite type oxide is almost the same as that before the sintering. The sintered particle diameter Ds2 of the perovskite oxide is, for example, 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, and even if 0.3 μm or less, 0.25 μm or less, 0.21 μm or less. Good. By setting the sintered particle size Ds2 of the perovskite type oxide to a predetermined value or more, the gas permeability of the air electrode current collector 30e can be increased. By setting the sintered particle size Ds2 of the perovskite type oxide to be a predetermined value or less, it is possible to better exhibit at least one of the function of uniformly maintaining the particle size of the silver-containing material and the function of trapping impurities. You can

  The ratio (Ds1 / Ds2) between the sintered grain size Ds1 (μm) of the silver-containing material and the sintered grain size Ds2 (μm) of the perovskite-type oxide allows the network between grains of the silver-containing material to be well developed. Then, from the viewpoint of improving current collection efficiency, for example, it may be 9.5 or more, 10 or more, 11 or more, for example, 12 or more. Further, Ds1 / Ds2 may be, for example, 50 or less, 30 or less, or 20 or less, from the viewpoint of enhancing gas permeability of the air electrode current collector 30e. By setting such a ratio range, the initial characteristics and the durability characteristics of the SOFC 50 can be balanced at a high level.

  The air electrode current collector 30e is preferably composed mainly of a silver-containing material (in other words, as a component having the largest mass ratio). As a result, the conductivity of the air electrode current collector 30e can be improved and the current collection efficiency can be improved. Although not particularly limited, the ratio of the silver-containing material is, for example, more than 50% by mass, 60% by mass or more, and 70% by mass or more when the total amount of the air electrode current collector 30e is 100% by mass. , 80% by mass or more and 95% by mass or less, 90% by mass or less, and 85% by mass or less. Further, when the entire air electrode current collector 30e is set to 100% by mass, the ratio of the perovskite oxide is 5% by mass or more, 10% by mass or more, 15% by mass or more, and 40% by mass or less, The content is preferably 30% by mass or less and 20% by mass or less. In addition to the silver-containing material and the perovskite-type oxide described above, the air electrode current collector 30e may further include another material.

  Further, when the total amount of the silver-containing material and the perovskite type oxide is 100% by mass, the ratio of the silver-containing material is preferably more than 50% by mass. The content ratio of the silver-containing material and the perovskite-type oxide is, for example, silver-containing material: perovskite-type oxide = 60: 40 to 95: 5, 65:35 to 90:10, 70:30 to 80:20. May be. Thereby, in the air electrode current collector 30e, high current collection efficiency can be better maintained over a long period of time. Therefore, the initial characteristics and the durability characteristics of the SOFC 50 can be balanced at a high level.

  The air electrode current collector 30e has a conductivity of more than 8000 S / cm based on the DC four-terminal method at 700 ° C., and is preferably 9000 S / cm or more, 9500 S / cm or more, and 10,000 S / cm or more, for example. The conductivity is preferably higher, and the upper limit thereof is not particularly limited, but in one example, it may be 100,000 S / cm or less, 50,000 S / cm or less, for example, 20,000 S / cm or less. The product ((S / cm) · cm) of the electric conductivity (S / cm) and the average thickness T (cm) of the air electrode current collector 30e is, for example, 30 or more, 35 or more, 40 or more, 50. It is good that it is above. Thereby, the current collection efficiency of the air electrode current collector 30e can be further improved. The upper limit is not particularly limited, but in one example, it may be 1000 or less, 500 or less, for example 200 or less.

  In addition, the above-mentioned conductivity and / or the product of the conductivity (S / cm) and the average thickness T (cm) is adjusted by a material for forming a current collector described later, for example, (a) formation of the current collector. Of the silver-containing material and the perovskite-type oxide in the material for use in manufacturing, (b) average particle diameter D1 of the silver-containing material used as the material for forming the current collecting portion, and (c) perovskite-type oxidation used as the material for forming the current collecting portion The average particle diameter D2 of the product, (d) the ratio of the average particle diameter D1 of the silver-containing material used as the material for forming the current collecting portion to the average particle diameter D2 of the perovskite oxide, and (e) as the material for forming the current collecting portion. It can be realized by adjusting the crystallite size of the perovskite type oxide used.

The SOFC 50 is heated to a high temperature range of 600 ° C. or higher, for example, about 600 to 900 ° C. during power generation. In this temperature range, the fuel gas, for example, hydrogen (H ₂ ) is supplied to the hollow portion of the fuel electrode 10 of the SOFC 50. Further, the air electrode 30 is exposed to a gas containing oxygen (O ₂ ), for example, air. In this way, by supplying gases having different oxygen partial pressures to one surface and the other surface of the solid electrolyte layer 20, the difference in oxygen concentration between the fuel electrode 10 side and the air electrode 30 side of the power generator 40 is reduced. Occurs. Then, in the air electrode 30, oxygen is decomposed and oxygen ions are formed. The oxygen ions move inside the solid electrolyte layer 20 from the air electrode 30 toward the fuel electrode 10. In the fuel electrode 10, oxygen ions react with the fuel gas to generate water (H ₂ O) and electrons are emitted. This produces electrical energy.

  As described above, in the air electrode current collector 30e of the SOFC 50, the network between Ag particles is well developed, and the electric conductivity of a predetermined value or more is realized. Further, in the air electrode current collector 30e, the average equivalent circle diameter of the silver-containing material is kept small. As a result, in the SOFC 50, the ohmic resistance is suppressed to be small due to the formation of the air electrode current collector 30e, and the resistance hardly increases even after the endurance, so that the power loss can be suppressed. Therefore, the SOFC 50 can exhibit good power generation characteristics for a long time.

  In this embodiment, the current collector disclosed here is provided on the surface of only the air electrode 30. However, it is not limited to this. The current collectors disclosed herein may be provided on the surfaces of the fuel electrode 10 and the air electrode 30, respectively, or may be provided on the surface of only the fuel electrode 10.

  In addition, in the present embodiment, the overall shape of the SOFC 50 is cylindrical. Further, the SOFC 50 is a fuel electrode supporting type. However, the overall shape of the SOFC and the support are not limited to this. The SOFC is, for example, a conventionally known flat plate type (Planar), MOLB type, vertical striped cylinder type (Tubular), flat cylindrical type (Flat tuber) in which the peripheral side surface of the cylindrical type is vertically crushed, or integral laminated type. May be. Further, the SOFC may be, for example, a so-called cathode-supported cell (CSC) in which the air electrode is formed thick, and a so-called electrolyte-supported type (CSC: Cathode-Supported Cell) in which the solid electrolyte layer is formed thick. ESC: Electrolyte-Supported Cell) or the like. Further, the SOFC may be a metal-supported cell (MSC) having a porous metal sheet on the surface of the fuel electrode opposite to the solid electrolyte layer.

  FIG. 3 is a sectional view schematically showing an SOFC 50A according to another embodiment. The SOFC 50A has a flat plate shape as a whole. The SOFC 50A includes a power generator 40A. The power generation body 40A includes a fuel electrode 10A, a solid electrolyte layer 20A, and an air electrode 30A. The fuel electrode 10A includes a fuel electrode support 12A arranged relatively far from the solid electrolyte layer 20A, and a fuel electrode active layer 14A arranged relatively close to the solid electrolyte layer 20. It has a two-layer structure. A fuel electrode current collector (not shown) is arranged in the fuel electrode active layer 14A. Further, a reaction suppressing layer 22A for stabilizing the interface between the solid electrolyte layer 20A and the air electrode 30A is arranged. An air electrode current collector 30eA is arranged on the air electrode 30A. Such SOFC50A can also be used suitably.

<Material for forming current collector>
For forming the air electrode current collector 30e described above, the following current collector forming materials can be preferably used. The current collector forming material disclosed herein includes a powdery silver-containing material and a powdery perovskite type oxide.

  The silver-containing material may be at least one of silver and silver alloy. The type of the silver-containing material has already been described in the air electrode current collector 30e, and thus the description thereof is omitted here. The average particle diameter D1 of the silver-containing material is preferably 2.9 μm or less, for example, 1.5 μm or less and 1 μm or less, from the viewpoint of satisfying the above-described range of the sintered particle diameter Ds1. The average particle diameter D1 of the silver-containing material may be larger than the average particle diameter D2 of the perovskite-type oxide from the viewpoint of favorably developing a network between particles of the silver-containing material in the air electrode current collector 30e. The average particle diameter D1 of the silver-containing material may be, for example, 0.1 μm or more, 0.3 μm or more, and 0.5 μm or more.

  The type of perovskite-type oxide has already been described in the air electrode current collector 30e, and thus the description thereof is omitted here. The average particle diameter D2 of the perovskite type oxide may be smaller than the average particle diameter D1 of the silver-containing material from the viewpoint of favorably developing a network between particles of the silver-containing material in the air electrode current collector 30e. The average particle diameter D2 of the perovskite-type oxide may be smaller than the average particle diameter of the perovskite-type oxide used as the material for forming the air electrode 30 from the viewpoint of improving current collection efficiency. The average particle diameter D2 of the perovskite oxide is such that, in the air electrode current collector 30e, at least one of the function of uniformly maintaining the particle size of the silver-containing material and the function of trapping impurities is better exhibited. Therefore, it may be 0.5 μm or less, for example, 0.4 μm or less, 0.3 μm or less, 0.25 μm or less, 0.21 μm or less. The average particle diameter D2 of the perovskite type oxide may be, for example, 0.01 μm or more, 0.05 μm or more, and 0.1 μm or more from the viewpoint of enhancing the gas permeability of the air electrode current collector 30e.

  The ratio (D1 / D2) of the average particle diameter D1 (μm) of the silver-containing material and the average particle diameter D2 (μm) of the perovskite oxide is a network between particles of the silver-containing material in the air electrode current collector 30e. From the viewpoint of satisfactorily developing, it may be 4 or more, for example, 5 or more. D1 / D2 may be, for example, 10 or less or 6 or less from the viewpoint of enhancing the homogeneity of the air electrode current collector 30e and suppressing the air electrode current collector 30e from becoming too dense. By setting the ratio within such a range, it is possible to form the air electrode current collector 30e in which the conductivity and the gas permeability are balanced at a high level.

  The crystallite diameter of the perovskite type oxide may be, for example, 5 or more, 10 or more, 14 or more, and 50 or less, 30 or less, 24 or less. This makes it possible to form the air electrode current collector 30e in which the conductivity and the durability are balanced at a high level. The crystallite diameter of the perovskite type oxide can be obtained from the half-width of the X-ray diffraction pattern obtained by X-ray diffraction based on Scherrer's formula. The detailed calculation method will be described later in the example section.

  When the total amount of the silver-containing material and the perovskite type oxide is 100% by mass, the proportion of the silver-containing material is preferably more than 50% by mass. The content ratio of the silver-containing material and the perovskite-type oxide is, for example, silver-containing material: perovskite-type oxide = 60: 40 to 95: 5, 65:35 to 90:10, 70:30 to 80:20. May be. This makes it possible to form the air electrode current collector 30e in which the conductivity and the durability are balanced at a high level.

  The material for forming the current collector may further contain other material in addition to the above-mentioned silver-containing material and perovskite type oxide. For example, it may be prepared in a paste form (including an ink form, a slurry form, and a suspension form) containing a dispersion medium and a binder. As the dispersion medium, a solvent conventionally used for this type of application can be used without particular limitation. Examples thereof include organic solvents such as alcoholic solvents such as terpineol, menthanol and dihydroterpineol; glycol ether solvents such as ethylene glycol and diethylene glycol derivatives; hydrocarbon solvents such as toluene and xylene. As the binder, compounds conventionally used for this type of application can be used without particular limitation. Examples thereof include cellulosic polymer compounds such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; acrylic resins; epoxy resins; phenolic resins. The material for forming the current collector may further contain various additives such as a pore former (pore forming material), a plasticizer, an antioxidant, a thickener, and a dispersant.

  The air electrode current collector 30e can be formed, for example, as follows using the above-described current collector forming material. That is, first, the above-described silver-containing material, the perovskite oxide, the dispersion medium, and the binder are mixed to prepare a paste. When the paste is prepared, for example, a conventionally known ball mill or roll mill can be used. Next, the current collector forming material prepared in paste form is applied to a desired position on the surface of the air electrode 30 by a method such as coating or printing. Next, this is fired at a temperature at which the silver-containing material can be sintered, for example, 800 to 1000 ° C. As a result, the dispersion medium and the binder are burned out. As described above, the air electrode current collector 30e made of a sintered body of the silver-containing material and the perovskite type oxide can be formed on the surface of the air electrode 30.

  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.

[Preparation of material for forming current collector]
First, Ag powder (average particle diameter D1: 0.9 μm) and a general formula: La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (hereinafter, simply referred to as “LSCF”). The powder of the perovskite type oxide shown (average particle diameter D2: 0.15 to 0.48 μm) was prepared. The average particle diameter of LSCF was adjusted by first pulverizing with a ball mill using φ5 mm zirconia balls and then secondary pulverizing with a bead mill using φ1 mm beads. Then, the Ag powder and the perovskite type oxide were mixed at the compounding ratio (mass ratio) shown in Table 1 to obtain powdery current collector forming materials (Examples 1 to 5 and Comparative Examples 1 to 4). .. In Comparative Example 5, only the Ag powder was used as the material for forming the current collector.

  Table 1 also shows the ratio (D1 / D2) of the average particle diameter D1 of the Ag powder and the average particle diameter D2 of the LSCF, and the crystallite diameter S of the LSCF. The average particle diameters D1 and D2 and the crystallite diameter S were measured and calculated by the methods described below.

(1) Average particle size D1, D2
First, each of the Ag powder and the LSCF powder was observed with a field emission scanning electron microscope (FE-SEM). In addition, SEM observation was performed at a magnification of 10,000 times using an SU8200 manufactured by Hitachi High-Technologies Co., Ltd. with an accelerating voltage of 10 kV. Then, from the obtained SEM observation images, the equivalent circle diameters of a plurality of particles (here, 100 or more) were obtained by image analysis, and the number-based average particle diameter was calculated.

(2) Crystallite size The LSCF of each example was subjected to X-ray diffraction analysis. As the powder X-ray diffractometer, RINT-TTRIII manufactured by Rigaku Corporation was used, and the analysis conditions were as follows.
Excited X-ray: CuKα (wavelength λ = 1.54056Å), 50 kV, 50 mA
Measuring range: 2θ = 10 to 60 °, step width: 0.01 °
Scan speed: 5 ° / min

Then, from the full width at half maximum (FWHM) of the main peak of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ seen near 2θ = 43 ° in the obtained XRD diffraction pattern, the following Scherrer ( The average crystallite diameter of the LSCF phase was calculated based on the Scherrer's formula: S = Kλ / (β × cos θ); In the formula, S is the average crystallite diameter, K is the Scherrer constant (0.92), λ is the wavelength of the X-ray used, β is the full width at half maximum of the diffraction line (diffraction peak), and θ is the diffraction angle. Is represented.

[Production of SOFC]
An SOFC for evaluation as shown in FIG. 3 was produced using the material for forming the current collecting portion prepared above. Specifically, first, nickel oxide (NiO, average particle size: 0.5 μm) powder and 8% yttria-stabilized zirconia (8YSZ, average particle size: 0.5 μm) powder were mixed at a mass ratio of 60:40. To prepare a mixed powder for forming the fuel electrode. Then, the mixed powder, the pore-forming material (carbon component), the binder (polyvinyl butyral; PVB), the plasticizer, and the dispersion medium (xylene) are mixed in a proportion of 48 to 58: 5 to 15: 8.5: 4. By kneading the mixture at a mass ratio of 5:24, a paste-like composition for forming a fuel electrode support was prepared. Next, this composition was applied onto a carrier sheet by a doctor blade method and dried repeatedly to form a fuel electrode support green sheet having a thickness of 0.5 to 1.0 mm. Next, the NiO powder, the 8YSZ powder, the binder (ethyl cellulose; EC), and the dispersion medium (terpineol; TE) are mixed in a mass ratio of 48: 32: 2: 18 to form a fuel electrode. A composition for use was prepared. Next, this composition was screen-printed on the fuel electrode support green sheet and dried to form a fuel electrode green sheet having a thickness of 10 μm.

  Next, 8YSZ (average particle diameter: 0.5 μm) powder as a solid electrolyte material, a binder (EC), and a dispersion medium (TE) are kneaded at a mass ratio of 65: 4: 31 to give a solid. A composition for forming an electrolyte layer was prepared. Next, this composition was screen-printed on the fuel electrode green sheet and dried to form a solid electrolyte layer green sheet having a thickness of 10 μm. Then, a 10% gadolinium-doped ceria powder (10 GDC, average particle size: 0.5 μm) as a reaction suppressing layer material, a binder (EC), and a dispersion medium (TE) were mixed at a mass ratio of 65: 4: 31. The composition for the reaction suppressing layer was prepared by kneading with. Next, this composition was screen-printed on the solid electrolyte layer green sheet and dried to form a reaction-inhibiting layer green sheet having a thickness of 5 μm.

  Next, the green sheet (fuel electrode support / fuel electrode / solid electrolyte layer / reaction suppression layer green sheet) laminated and formed as described above is cut into a circle and co-fired at 1350 ° C. An SOFC half cell (calcined body) in which the solid electrolyte layer and the reaction suppressing layer were laminated in this order and integrated was obtained. The shape of the half cell after firing was a circle with a diameter of 20 mm.

Next, a LSCF powder as an air electrode material _{(La 0.6 Sr 0.4 Co 0.2 Fe} 0.8 O 3), a binder (EC), and a dispersion medium (TE), 80: 3: A composition for forming an air electrode was prepared by mixing in a mass ratio of 17. Next, this composition was supplied onto the half-cell reaction-inhibiting layer in a circular sheet shape by a screen printing method, and dried to form an air electrode green sheet. Next, the air electrode green sheet was fired at 1100 ° C. together with the half cell to form an air electrode.

  Next, the current collector forming materials (Examples 1 to 5 and Comparative Examples 1 to 5) prepared above, the binder (EC), and the dispersion medium (TE) were mixed at a mass ratio of 80: 3: 17. By mixing, a composition for forming a current collector was prepared. Next, this composition was screen-printed on the air electrode, dried, and then fired at 850 ° C. to form an air electrode current collector. As a result, SOFCs of each example (Examples 1 to 5 and Comparative Examples 1 to 5) were created. Table 1 shows the average thickness (μm) of the air electrode current collector after firing. For comparison, an SOFC (Comparative Example 6) having no air electrode current collector was also prepared.

[Measurement of physical properties of air electrode current collector]
(1) FE-SEM Observation Using the FE-SEM described above, the acceleration voltage was set to 10 kV, and the surface of the air electrode current collector was observed at a magnification of 10,000 times to confirm the microstructure. As an example, FIG. 4 shows an SEM observation image. 4A shows the result of Example 1, FIG. 4B shows the result of Comparative Example 2, and FIG. 4C shows the result of Comparative Example 4. In this SEM observation image, brightly appearing particles are Ag and darkly appearing particles are LSCF.

(2) Calculation of Average Circle Equivalent Diameter of Ag Particles FIG. 5 is an explanatory diagram for explaining how to determine the average circle equivalent diameter Ds1.
Here, first, a cross-section polisher (trademark) was used, and a cross-section was performed on the air electrode current collector of the SOFC of each example. Next, using the FE-SEM described above, the acceleration voltage was set to 10 kV, and the cross section of the air electrode current collector was observed at a magnification of 10,000 times. An example of the SEM observation image is shown in FIG. In this SEM observation image, the entire observation visual field is occupied by the air electrode current collector.

  Next, the obtained SEM observation image was subjected to image analysis with image processing software (here, open source ImageJ). Specifically, first, the SEM observation image was automatically ternarized to classify Ag, LSCF, and voids. Next, this image was automatically binarized and converted into a black-and-white image in which Ag was black, as shown in FIG. Next, watershed subdivision processing was performed to automatically divide each particle as shown in FIG. 5 (C). Next, as shown in FIG. 5D, Analyze Particles processing was performed to automatically perform particle analysis, and the area per particle was calculated.

Next, the diameter when the above area was assumed to be the area of a circle was automatically calculated. Then, this diameter was weighted by the area, and the average equivalent circle diameter (average equivalent circle diameter) Ds1 of Ag particles was calculated. As a specific example, the average equivalent circle diameter Ds1 of four particles A to D as shown in the schematic diagram of FIG. 6 is calculated by the following formula: Ds1 = (S _A d _A + S _B d _B + S _C d _C + S _D d _D ) / (S _A + S _B + S _C + S _D ); In the formula, S _A , S _B , S _C and S _D represent the area of each particle, and d _A , d _B , d _C and d _D represent the diameter of each particle.

(3) Conductivity Measurement The conductivity (S / cm) of the air electrode current collector was measured at a temperature of 700 ° C. using the direct current 4-terminal method. The results are shown in Table 1. In addition, Table 1 also shows the product of the conductivity and the average thickness.

  As a result of the physical property measurements (that is, FE-SEM observation, calculation of the average equivalent circular diameter of Ag particles, and conductivity measurement) in the above (1) to (3), the Ag particles were collected in the air electrode current collector of Example 1. It was found that the particles were sintered in a well-dispersed state, and the average equivalent circular diameter of the Ag particles was relatively small. It was also found that the network between Ag particles was well developed and the conductivity was high. On the other hand, in the air electrode current collector of Comparative Example 2, even though the compounding ratio of Ag and LSCF was the same as in Example 1, Ag particles solidified and the average equivalent circle diameter was relatively large. Was there. In addition, the network between Ag particles was partially cut off, and the conductivity was low. Further, in the air electrode current collector of Comparative Example 4, the average equivalent circle diameter of Ag particles was larger than that of Comparative Example 2.

[SOFC ohmic resistance]
First, a Pt mesh for current collection is provided on each of the SOFC fuel electrode support and the air electrode current collector prepared in the above (however, in Comparative Example 6 having no air electrode current collector, the air electrode itself). They were brought into contact with each other to carry the current distribution. Next, the SOFC was operated under the following conditions, and the ohmic resistance when the current density was 0.5 A / cm ² was measured by impedance measurement. The results are shown in the column of "Initial ohmic resistance" in Table 1.
Fuel electrode supply gas: 25 ° C humidified hydrogen gas (200 ml / min)
Air electrode supply gas: Air (200 ml / min)
Operating temperature: 700 ℃

  As shown in Table 1, in Examples 1 to 5 and Comparative Examples 4 and 5, the ohmic resistance was relatively reduced as compared with Comparative Example 6 having no air electrode current collector. As a cause of this, it can be considered that, for example, the network between Ag particles was well developed in the air electrode current collector, and the conductivity of the air electrode current collector was increased. On the other hand, in Comparative Examples 1 to 3, the ohmic resistance was relatively high. The causes include, for example, (1) that the network between Ag particles is not fully developed in the air electrode current collector, and the conductivity of the air electrode current collector is low, and (2) the air electrode. It is conceivable that the contact resistance between the air electrode and the air electrode current collector has increased.

[Increase in SOFC resistance]
In addition, the SOFC of each example was continuously operated for 200 hours under the same conditions as above so that the current density was 0.5 A / cm ^2, and a resistance component near 100 Hz (a resistance component corresponding to the activity of the air electrode). The increase in resistance was calculated from the change of. The results are shown in the column "Increase in resistance after endurance" in Table 1. Further, as an example, FIG. 7 shows a Bode Plot obtained by impedance measurement. FIG. 7A shows the result of Example 1, and FIG. 7B shows the result of Comparative Example 6. In FIG. 7, the vertical axis represents the magnitude of −Z ″ (Ω · cm ² ), and the horizontal axis represents the frequency (Hz).

  As shown in Table 1 and FIG. 7, in Examples 1 to 5 and Comparative Examples 1 to 3, an increase in −Z ″ at 100 Hz after endurance was suppressed as compared with Comparative Example 6 having no air electrode current collector. It was being done. Since the difference between the examples is only the air electrode current collector, it is considered that the air electrode current collector suppressed the increase in the resistance component at 100 Hz. On the other hand, in Comparative Examples 4 and 5, the increase in −Z ″ at 100 Hz after endurance was relatively high.

Although it is not necessary to clarify the reason for this, the present inventors set the conductivity of the air electrode current collector to the above range and set the sintered particle diameter Ds1 of Ag in the air electrode current collector to 2.9 μm or less. As a result, (1) the dispersibility of Ag in the air electrode current collector is improved, and the microscopic current concentration is suppressed, so that the current distribution is uniform (the variation in the current distribution is suppressed). (2) Ag aggregation and sintering were suppressed in the SOFC operating temperature range, and the particle size of Ag could be maintained homogeneous. (3) By trapping impurities contained in the supply gas This is probably because the deviation of the composition of the air electrode material could be suppressed.
Further, the air electrode current collector (which can suppress the increase in the resistance component of SOFC) as described above is an air electrode current collector including Ag powder and LSCF having a D1 / D2 ratio of 4 or more. It could be realized by using a forming material.

  Specific examples of the present invention have been described above in detail, 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.

10, 10A fuel electrode (anode)
20, 20A Solid electrolyte layer 30, 30A Air electrode (cathode)
30e, 30eA Air electrode current collector 40, 40A Power generator 50, 50A Solid oxide fuel cell (SOFC)

Claims (14)

A fuel electrode and an air electrode, a power generator facing each other via a solid electrolyte layer,
A current collector arranged on the surface of at least one of the fuel electrode and the air electrode;
Equipped with
The current collector is
A sintered body containing at least one silver-containing material of silver and a silver alloy, and a perovskite type oxide,
Conductivity exceeds 8000 S / cm,
An average equivalent circle diameter of the sintered silver-containing material based on an electron microscope observation is 2.9 μm or less,
Solid oxide fuel cell. In the current collector, the proportion of the silver-containing material exceeds 50% by mass.
The solid oxide fuel cell according to claim 1. The average thickness T of the current collector is 100 μm or less, and
The product of the electric conductivity (S / cm) and the average thickness T (cm) is 30 (S / cm) · cm or more,
The solid oxide fuel cell according to claim 1. When the average circle equivalent diameter of the silver-containing material is Ds1 (μm) and the number-based average particle diameter of the perovskite oxide based on electron microscope observation is Ds2 (μm), the Ds1 and Ds2 are Satisfies the following relationship: 10 ≦ (Ds1 / Ds2) ≦ 20;
The solid oxide fuel cell according to claim 1. The perovskite oxide is an oxide represented by the general formula: ABO ₃ ; containing La and Sr at the A site and containing Co at the B site.
The solid oxide fuel cell according to any one of claims 1 to 4. The air electrode contains a perovskite type oxide,
The current collector is arranged on the surface of the air electrode,
The solid oxide fuel cell according to any one of claims 1 to 5. The power generator is formed by laminating the solid electrolyte layer and the air electrode in this order on the surface of the cylindrical fuel electrode,
On the surface of the air electrode, the current collector is arranged,
The solid oxide fuel cell according to claim 1. A silver-containing material of at least one of silver and a silver alloy,
A perovskite oxide,
Including,
The number-based average particle diameter of the silver-containing material based on electron microscopic observation is D1 (μm),
When the number-based average particle diameter of the perovskite oxide based on electron microscopic observation is D2 (μm), the D1 and D2 are
The following relationships are both satisfied: D2 ≦ 0.5 μm; 4 ≦ (D1 / D2);
A material for forming a current collector of a solid oxide fuel cell. When the total amount of the silver-containing material and the perovskite-type oxide is 100% by mass, the ratio of the silver-containing material exceeds 50% by mass.
The material for forming a current collector according to claim 8. The compounding ratio of the silver-containing material and the perovskite type oxide is 70:30 to 80:20,
The material for forming a current collecting portion according to claim 8 or 9. The above D1 / D2 satisfies the following relationship: 4 ≦ (D1 / D2) ≦ 6;
The material for forming a current collector according to any one of claims 8 to 10. The perovskite oxide is an oxide represented by the general formula: ABO ₃ ; containing La and Sr at the A site and containing Co at the B site.
The material for forming a current collector according to any one of claims 8 to 11. Contains a dispersion medium and a binder, and is prepared into a paste,
The material for forming a current collector according to any one of claims 8 to 12. Used to form an air electrode current collector on the surface of the air electrode of the solid oxide fuel cell,
The material for forming a current collector according to any one of claims 8 to 13.