WO2019012666A1

WO2019012666A1 - Material for air electrodes of solid oxide fuel cells and use of same

Info

Publication number: WO2019012666A1
Application number: PCT/JP2017/025604
Authority: WO
Inventors: 聖一須田; ヴェルドゥゴファンパウロウィフ; 宏松橋
Original assignee: ＦＣＯＰｏｗｅｒ株式会社
Priority date: 2017-07-13
Filing date: 2017-07-13
Publication date: 2019-01-17

Abstract

The present invention provides, as a material for air electrodes of solid oxide fuel cells, a material which contains a perovskite oxide expressed as (La1-xSrx)(Mn1-yNiy)O3 (wherein 0 < y < 0.3).

Description

Material for cathode of solid oxide fuel cell and use thereof

This specification relates to a cathode material for solid oxide fuel cells and its use.

As a stack structure used for a solid oxide fuel cell (hereinafter simply referred to as SOFC), two or more of a cell including a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are stacked via a separator layer Patent Document 1 discloses a stacked structure. If such a stack structure is made using co-sintering, it can itself have excellent self-supporting and integrity.

Co-sintering at least a portion of the stack structure often requires heat treatment at relatively high temperatures to achieve sufficient sintering with various materials. On the other hand, it is well known that heat treatment at high temperature may cause an undesirable reaction between the cathode material and the solid electrolyte material, and such a reaction product reduces the power generation characteristics.

For example, even if lanthanum strontium manganate (LSM), which is an air electrode material relatively excellent in heat resistance, is used as a reaction phase with yttria stabilized zirconia (YSZ) which is a solid electrolyte material, La ₂ Zr ₂ O ₇ ( LZO) and SrZrO ₃ (SZO) are known. The high resistance of these substances significantly degrades the power generation characteristics of the SOFC.

The following methods have been proposed as methods for suppressing the formation of LZO and SZO. For example, a buffer layer such as ceria is introduced between YSZ and LSM (Non-Patent Documents 1 and 2), LSM with A site defect is used (Non-patent document 3), Ce is added to LSM (Non-Patent Document 4).

International Publication 2009/119772 Pamphlet

However, cathode materials that can sufficiently withstand relatively high heat treatment conditions such as co-sintering have not been obtained so far. That is, the method (1) has a problem that the buffer layer is easily peeled off. In the methods (2) and (3), although the reduction of the reaction phase is possible, the generation thereof has not been suppressed to the extent that the power generation characteristics of the solid oxide fuel cell are sufficiently reduced.

In view of such conventional problems, the present inventors provide an air electrode material and an air electrode for a solid oxide fuel cell which is excellent in heat resistance. Further, the present specification provides a solid oxide fuel cell having excellent power generation characteristics.

The present inventors have found that the air electrode material, was studied, obtained by addition of Ni solid solution _{_{LSM (La 1-x Sr x}} ) (Mn 1-y Ni y) O 3 is in the SOFC It has been found that even at temperatures at which the elements can be co-sintered, they exhibit excellent electrode characteristics without forming a harmful reaction phase with a solid electrolyte or the like. That is, it has been unexpectedly found that, even in heat treatment at high temperatures, such a composite oxide can sufficiently exhibit the power generation characteristics as a solid oxide fuel cell by suppressing or avoiding the formation of a reaction phase with YSZ. I got This specification provides the following means based on such knowledge.

(1) A material for an air electrode of a solid oxide fuel cell
Material containing a perovskite oxide _{_{(La 1-x Sr x)}} (Mn 1-y Ni y) O 3 ( however, 0 <y <0.3).
(2) the _{_{(La 1-x Sr x)}} (Mn 1-y Ni y) O 3 _{_{_{is, (La 1-x Sr x}}} ) (Mn 1-y Ni y) O 3 ( however, 0 <x ≦ 0 .3), the material according to (1).
(3) The material according to (1) or (2), further comprising a rare earth element stabilized zirconia.
(4) The material according to (2) or (3), wherein the rare earth element is yttrium.
(5) The material according to any one of (1) to (3), containing 10% by mass or more and 60% by mass or less of the rare earth element-stabilized zirconia.
(6) An air electrode of a solid oxide fuel cell, which is a sintered body of the air electrode material according to any one of (1) to (5).
(7) A solid oxide fuel cell comprising the sintered body of the air electrode material according to any one of (1) to (5) as an air electrode.
(8) A solid oxide fuel cell having a laminated structure of one or more solid oxide fuel cells comprising the sintered body of the air electrode material according to any one of (1) to (5) as an air electrode Stack structure.
(9) The stack structure according to (8), wherein the first cell including the cathode layer and the second cell including the cathode layer are co-sintered in the stack structure.
(10) A method for producing a solid oxide fuel cell, comprising
A laminate of two or more cells including one or more cells comprising a fuel electrode layer, a solid electrolyte layer, and an air electrode layer containing the air electrode material according to any one of (1) to (5). Obtaining a precursor of a solid oxide fuel cell stack structure in which at least some of the elements are not integrated with one another;
Firing the precursor to integrate the at least some of the elements;
A manufacturing method.

It is a figure which shows the XRD profile of the sintered compact which baked LSMNi synthesize | combined in the Example in air at 1300 degreeC for 5 hours. It is a figure which shows the electrical conductivity of the sintered compact which baked the synthesized LSMNi in air at 1300 degreeC for 5 hours. It is a figure which shows the XRD profile of the sintered compact which baked the mixture of mass ratio 1: 1 of the synthesize | combined LSMNi and YSZ in air at 1300 degreeC for 5 hours. It is a figure which shows the XRD profile shown in FIG. 3 as a relationship between Sr content and a SZO production | generation ratio. In the figure which shows the XRD profile of the sintered compact which calcinated the mixture of LSMNi and YSZ which were synthesize | combined by various y value (0.1-0.3) in mass ratio 1: 1 with 1,300 degreeC in air for 5 hours. is there. The XRD profile of a sintered body obtained by firing a mixture of LSM, LSMNi (x = 0.2, y = 0.2) and YSZ in a mass ratio of 1: 1 in air at 1300 ° C. for 5 hours or 24 hours FIG. It is a figure which shows the electroconductive evaluation result when Bring LSM and LSMNi (x = 0.2, y = 0.2) into YSZ.

The present specification relates to an SOFC air electrode material, and further relates to an SOFC air electrode, an SOFC including the air electrode, a stack structure including the air electrode, and a method of manufacturing the same. The air electrode material (hereinafter, also simply referred to as the present material) disclosed in the present specification is manganese (Mn) of the B site element in the lanthanum strontium manganite (LSM) based acid compound which is a perovskite type oxide. By partially replacing with nickel (Ni), it is possible to suppress the formation of the air electrode, the solid electrolyte, and the undesirable reaction phase, even when heat treatment at high temperature is required at the time of cell or stack structure preparation. It can be avoided to provide a SOFC cell or stack structure with good electrode properties and thus power generation properties.

Moreover, according to the present material, the generation of the reaction phase with the solid electrolyte can be significantly suppressed, and the generation of the reaction phase can be avoided even at the operating temperature of the SOFC. Therefore, the produced SOFC and the stack structure can exhibit good power generation characteristics over a long period of time.

The material is suitable for use in any SOFC. Among them, although not particularly limited, it can be suitably used for the production of an SOFC cell or stack structure produced by co-sintering at least a part of the SOFC cell or stack structure.

Hereinafter, representative and non-limiting specific examples of the present disclosure will be described in detail with reference to the drawings as appropriate. This detailed description is merely intended to show the person skilled in the art the details for practicing the preferred embodiments of the present invention, and is not intended to limit the scope of the present disclosure. In addition, additional features and disclosure disclosed below may be used to provide a further improved cathode material for SOFC, cathode, SOFC cell, SOFC stack structure, and a method of manufacturing the same. It can be used separately or together with the disclosure.

Also, the combination of features and steps disclosed in the following detailed description is not essential to the practice of the present disclosure in the broadest sense, and in particular, to illustrate representative examples of the present disclosure. It is described. Furthermore, various features of the above and below described representative embodiments, as well as various features of what is set forth in the independent and dependent claims, are set forth herein to provide additional and useful embodiments of the present disclosure. It does not have to be combined as per the example given or in the order listed.

All features described in the specification and / or claims are separately from the configuration of the features described in the examples and / or claims, individually as limitations on the initial disclosure of the application and the specific matters claimed. And intended to be disclosed independently of each other. In addition, the descriptions of all numerical ranges and groups or groups are intended to disclose intermediate constructions as limitations on the initial disclosure and the specific matters claimed.

(Air electrode material for SOFC)
This material is an oxide obtained by substituting a part of the Mn element of the B site of the (LaSr) Mn-based oxide (hereinafter, also simply referred to as LSM), which is a perovskite type oxide, with Ni (hereinafter simply referred to as LSMNi) Can be included. In the present specification, LSM refers to a solid solution oxide obtained by substituting a part of La of the A site metal of LaMnO ₃ which is a perovskite type oxide with Sr. The total molar amount of La and Sr is consistent with the perovskite structure and is approximately one.

LSMNi can set the mole fraction y of Ni to 0 <y <0.3, when M in LSM is 1 mole. That is, such LSMNi, for example, represented by the general formula _{_{(La 1-x Sr x)}} (Mn 1-y Ni y) O 3. In this general formula, the constituent molar amount of the oxygen atom O is “3” in the same manner as described above, but the molar fraction of Sr and Ni constitutes a numerical value which forms the perovskite structure stoichiometrically And can be “3 + δ”. That can be represented by _{_{(La 1-x Sr x)}} (Mn 1-y Ni y) O 3 + δ. Note that, for example, −0.4 ≦ δ ≦ + 0.2.

When y is in this range, it is possible to obtain the reaction phase suppression effect with the solid electrolyte by the addition of Ni. If y is 0.3 or more, the amount of SZO (SrZrO ₃ ) and LZO (La ₂ Zr ₂ O ₇ ), which are high resistance reaction phases generated from YSZ contained in the solid electrolyte, tends to increase. . The lower limit and the upper limit of x can be set in consideration of, for example, the mole fraction of Sr with respect to La, conductivity, etc., in addition to the amount of reaction phase produced. Although not particularly limited, for example, y is 0.05 or more, for example, 0.1 or more, and for example, 0.15 or more, for example, 0.2 or more. Also, y is, for example, 0.25 or less, and for example, 0.2 or less. The range of y can also be set, for example, by combining the above lower limit and upper limit as appropriate, and for example, it is 0.05 or more and less than 0.3, 0.05 or more and 0.25 or less, 0. More than 05 and less than 0.2, for example more than 0.1 and less than 0.3, more than 0.1 and less than 0.25, and more than 0.1 and less than 0.2, for example more than 0.15 It is less than 0.3, 0.15 or more and 0.25 or less, and 0.15 or more and 0.2 or less.

In LSMNi, a molar fraction x of Sr when a part of La, that is, La in LSM is 1 mole, is not particularly limited, but can be 0 <x ≦ 0.3. Within this range, the effect of suppressing the reaction phase with the solid electrolyte can be obtained by the addition of Sr. When x exceeds 0.3, the amount of SZO (SrZrO ₃ ), which is a high resistance reaction phase generated from YSZ contained in the solid electrolyte, tends to increase. The lower limit and the upper limit of x can be set in consideration of, for example, the conductivity and the like in addition to the amount of reaction phase produced. Although not particularly limited, for example, x is 0.05 or more, for example, 0.1 or more, and for example, 0.15 or more, for example, 0.2 or more. Also, x is, for example, 0.25 or less, and for example, 0.2 or less. The range of x can also be set, for example, by appropriately combining the lower limit and the upper limit described above, but for example, it is 0.05 or more and 0.3 or less, 0.05 or more and less than 0.3, 0. It is 05 or more and 0.25 or less, 0.05 or more and 0.2 or less, and for example, 0.1 or more and 0.3 or less, 0.1 or more and less than 0.3, 0.1 or more and 0 .25 or less, 0.1 or more and 0.2 or less, and for example, 0.15 or more and 0.3 or less, 0.15 or more and less than 0.3, and 0.15 or more and 0.25 or less It is 0.15 or more and 0.2 or less, for example, 0.2 or more and 0.3 or less, 0.2 or more and less than 0.3, and 0.2 or more and 0.25 or less.

LSMNi can be produced by a known ceramic synthesis method. That is, a solid phase method, a sol-gel method, a spray pyrolysis method, a hydrothermal method, an alkoxide method, a coprecipitation method, an emulsion method, a complex polymerization method, a glycine method and the like can be mentioned. Although not particularly limited, for example, it is preferable to use a glycine method using glycine. This is because the LSMNi precursor powder or LSMNi powder with higher uniformity can be obtained by this synthesis method.

For example, _LSMNi represented by (La 1 _-0.8 Sr _0.2 ) (Mn _0.8 Ni _y _0.2 ) O ₃ can be synthesized by the following method. That is, glycine, lanthanum nitrate hexahydrate _{_{(La (NO 3) 3 ·}} 6H 2 O), strontium nitrate hexahydrate _{_{(Sr (NO 3) 2 ·}} 6H 2 O), manganese nitrate hexahydrate ( Compound Mn (NO ₃ ) ₃ · 6 H ₂ O) and nickel nitrate hexahydrate (Ni (NO ₃ ) ₂ · 6 H ₂ O) as raw materials in the intended molar fraction LSMNi, room temperature Dissolve in water and heat to 180 ° C, then heat at 450 ° C for several hours to remove water and organic matter, then heat bake at 850 ° C in air for 5 hours to obtain LSMNi precursor powder or LSMNi powder Can.

The present material can also include other materials that can be used as the cathode material of SOFC in addition to such LSMNi. For example, an ABO ₃ -type perovskite-type oxide containing La or La and Sr may be mentioned oxides other than LSMNi. As such perovskite type oxides, transition metal perovskite type oxides, for example, LaCoO ₃ based oxides, LaMnO ₃ based oxides, LaFeO ₃ based oxides, etc. in which La or La and Sr or Ca coexist at A site, etc. It can be mentioned. In addition, La or a LaTiO ₃ based oxide in which La and La together with Sr or Ca coexist at A site can be mentioned. In addition to Co, Mn, and Ti, other elements such as Cr, Fe, Mg, and the like may exist in the B site of various oxides. More specifically, (LaSr) MnO ₃ , (LaCa) MnO ₃ , LaCoO ₃ , (LaSr) CoO ₃ , (LaSr) (CoFe) O ₃ , (LaSr) (TiFe) O _{3 and the} like can be mentioned.

This material can contain the oxide of the element contained in a solid electrolyte similarly to the cathode material of well-known SOFC. The oxide contained in the solid electrolyte is useful for controlling the thermal expansion coefficient and the like. Such an oxide is not particularly limited, and examples thereof include ZrO ₂ (zirconia) which is at least partially stabilized by a rare earth element such as Y, Sc, and Yb. Typically, the rare earth element is YSZ which is yttrium. In addition, CeO ₂ (ceria) doped with a rare earth element such as Gd and Sm, LaGaO ₃ (lanthanum gallate) in which La and Ga are partially substituted with an alkaline earth metal such as Sr and Mg, and the like can be mentioned. LSMNi is advantageous in the case of containing zirconia as a solid electrolyte or in the case of containing zirconia in the present material because LSMNi can suppress or avoid the formation of a reaction phase containing Zr.

In the present material, although not particularly limited, as a substantial electrode constituent material, it is preferable to contain 50 mass% or more of LSMNi, more preferably 60 mass% or more, and still more preferably 70 mass% or more It is more preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 99% by mass or more.

In addition, although the present material can appropriately contain a solid electrolyte material, the ratio thereof is not particularly limited, and for example, 10% by mass to 60% by mass with respect to the total mass of the present material be able to. Within this range, even when coexisting with the solid electrolyte material, the generation of the reaction phase can be suppressed, and an air electrode with sufficiently good characteristics can be configured. Although not particularly limited, for example, the solid electrolyte material is 20% by mass or more and 60% by mass or less, for example, 30% by mass or more and 60% by mass or less, for example 40% by mass or more and 60% by mass % Or less.

(Air electrode)
The air electrode disclosed in the present specification (hereinafter, also simply referred to as the present air electrode) is a sintered body of the present material. The cathode can be obtained as an independent SOFC element or component, or as an SOFC cell and a SOFC stack structural component, as described below, in their inherent form.

The air electrode is generally porous, and its porosity is appropriately set. Although not particularly limited, the porosity is preferably 15% or more, and more preferably about 20% or more and 40% or less. In the present specification, the porosity can be measured from the area ratio of the pore portion to the dense portion of a cross-sectional image of a cross-sectional image taken by a scanning electron beam microscope, for a plurality of cross-sections created by mechanical cutting and polishing. . For example, the area ratio is determined by binarizing the pore portion and the dense portion of the layer by image processing in a field of view of 500 μm × 500 μm including the layer for each of five cut planes, and taking an average of all the cut planes. The porosity can be determined by

When the pores in the air electrode are spherical, the average pore diameter is preferably 1 μm to 10 μm. More preferably, it is 2 micrometers or more and 5 micrometers or less. In the present specification, it is assumed that the average pore diameter is obtained by connecting a plurality of spherical cross-sections obtained by mechanically cutting and polishing a plurality of cross-sections taken by a scanning electron microscope with a plurality of spherical pores. It can measure from the average diameter in the case of For example, when the pores and dense parts of the layer are binarized by image processing in a field of view of 500 μm × 500 μm including the layer for each of the five cut surfaces, and circular approximation is performed for all pores included in the field of view. The average pore diameter can be determined by calculating the average diameter of all the cut surfaces.

The thickness of the air electrode is not particularly limited, and varies depending on the presence or absence of an oxidizing gas flow passage in the electrode and the flow passage form, but can be, for example, 15 μm to 500 μm, and for example, 20 μm or more It can be 500 μm or less. More preferably, it can be 50 μm or more and 400 μm or less.

The form and manufacturing method of the present air electrode are variously different depending on the SOFC to be obtained, for example, the form of the stack structure, the manufacturing method thereof and the like, and the present air electrode can take various forms. The form and manufacturing method of the present air electrode will be described in detail later in the SOFC and SOFC stack structures.

(Solid oxide fuel cell)
The solid oxide fuel cell (hereinafter, also referred to as the present SOFC) disclosed herein can include an air electrode layer including the present air electrode. With regard to the other elements that the present SOFC includes the present air electrode, the other elements known in the art, ie, the fuel electrode, solid electrolyte, separator or interconnector, gas flow path for supplying reducing gas to the fuel electrode, and air A gas channel or the like for supplying the oxidizing gas to the electrode can be provided. Further, the present SOFC can be produced by a known method, and can also be produced in cell units according to the method for producing a stacked structure of the present SOFC described in detail later.

(Fuel electrode and fuel electrode layer)
The fuel electrode is not particularly limited, and can be a porous body made of one or more conductive ceramic materials applied to the SOFC fuel electrode. For example, the fuel electrode material can include zirconia or ceria in which a rare earth element is solid-solved, and Ni / NiO. As the rare earth element, for example, yttrium (Y), scandium (Sc), samarium (Sm), gadolinium (Gd), etc. can be used. Specifically, mention may be made of Ni cermet containing yttria partially stabilized or stabilized zirconia (YSZ), scandia partially stabilized or stabilized zirconia (ScSZ), gadolinia solid solution ceria (GDC) and Ni / NiO.

The fuel electrode is generally porous, and its porosity is appropriately set. Although not particularly limited, the porosity is preferably 15% or more, and more preferably about 20% or more and 40% or less.

The shape of pores in the fuel electrode can be any shape such as irregular shape, fibrous shape, and spherical shape. In the case of a spherical shape, the average pore diameter is preferably 1 μm to 10 μm. More preferably, it is 2 micrometers or more and 5 micrometers or less.

The thickness of the fuel electrode is not particularly limited, and varies depending on the presence or absence of the gas flow channel 22 and the flow channel configuration, but can be, for example, 15 μm to 500 μm. More preferably, it can be 20 μm to 500 μm. More preferably, it can be 50 μm or more and 400 μm or less, and still more preferably 50 μm or more and 300 μm or less. As described later, the thicknesses of the fuel electrode and the air electrode are not necessarily constant in one layer. Thus, references to anode and cathode thicknesses mean that one layer is in this thickness range, unless stated otherwise.

(Solid electrolyte and solid electrolyte layer)
The solid electrolyte can be a compact body made of one or more kinds of oxide ion conductive materials applied to a solid electrolyte of SOFC without limitation. For example, examples of the solid electrolyte material include the oxide ion conductive materials exemplified above.

The solid electrolyte is generally dense and preferably has the same relative density as the interconnector from the viewpoint of blocking gas permeability. The thickness of the solid electrolyte is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less. More preferably, it can be 3 μm or more and 40 μm or less, and still more preferably 5 μm or more and 30 μm or less.

(Separator or interconnector)
Separators or interconnectors are used in SOFCs comprising a fuel electrode, a solid electrolyte, and an air electrode, and are separation elements provided with gas blocking properties to shut off gas as intended, and conductivity to draw current from each cell It is. Such a separation element is referred to as a separator from the viewpoint of gas barrier property and an interconnector from the viewpoint of conductivity. Hereinafter, in the present specification, it is referred to as an interconnector.

As the interconnector, materials of conventionally known interconnectors can be easily applied. Typically, conductive materials such as various known perovskite oxides of ABO ₃ can be mentioned. For example, such an oxide is a perovskite-type oxide doped with a rare earth element, and is (Ln _a M ¹ _b ) M ² O ₃ (however, it is a numerical value consistent with the perovskite structure such as a + b = 1). Is represented. Ln is a rare earth element and includes elements of atomic numbers 57 to 71. As the rare earth element, for example, an element having a relatively large ion radius such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm) can be used, and La is preferably used be able to. M ¹ represents an alkaline earth metal, and examples thereof include calcium (Ca), strontium (Sr) and barium (Ba), and one or more kinds can be used. M ² is one or more selected from transition elements such as titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and the like. Can be mentioned. Preferably, it is one or more selected from Ti, Cr, Mn, Fe and Co.

As such a conductive ceramic material, for example, LaCoO ₃ based oxide, LaMnO ₃ based oxide, La (CoFe) O ₃ based oxide, LaCrO ₃ based oxide, in which La and Sr or Ca coexist at A site, LaTiO ₃ based acid compounds and the like can be mentioned. In the B site of various oxides, Cr, Fe, Mg, etc. may be present as another element together with Co, Mn, Ti. More specifically, (LaSr) MnO ₃ , (LaSr) CoO ₃ , (LaSr) (CoFe) O ₃ , (LaSr) TiO ₃ , LaCrMgO _{3 and the} like can be mentioned.

The interconnector can further include an oxide material of elements contained in the solid electrolyte. Such materials are as already described as materials that may be included for this material.

The conductive ceramic material included in the interconnector and the oxide material of the element included in the solid electrolyte are, for example, the material of the fuel electrode of SOFC to which the present interconnector is applied, the material of the cathode, the operating temperature, and the burning of the stack. It is appropriately selected in consideration of the congee temperature and the like.

The interconnector generally has the compactness of the interconnector. For example, the interconnector preferably has a relative density (according to the Archimedes method) of 93% or more, more preferably 95% or more.

The thickness or the like of the interconnector is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less in consideration of, for example, the size and conductivity of the entire stack. Preferably, it can be 2 μm or more and 60 μm or less, and more preferably 2 μm or more and 40 μm or less.

(Gas flow path)
The cells of the SOFC are each provided with a gas flow path for a reducing gas containing hydrogen supplied to the fuel electrode and an oxidizing gas containing oxygen supplied to the air electrode. The gas flow path can be formed across one or two layers constituting a single cell. That is, the gas flow path may be provided in each of the fuel electrode and the air electrode, may be provided in the interconnector, or may be provided over the fuel electrode and the interconnector. It may be provided across the poles and the interconnectors. The form of gas flow path in SOFC is well known to those skilled in the art.

The thickness of the unit cell (fuel electrode, air electrode, solid electrolyte) configured in this manner is not particularly limited, but can be, for example, 100 μm or more and 1000 μm or less. Moreover, Preferably it can be 150 micrometers or more and 1000 micrometers or less. Furthermore, preferably it can be 200 micrometers or more and 1000 micrometers or less. Moreover, Preferably it can be 300 micrometers or more and 600 micrometers or less.

In addition to this, the present SOFC can be provided with various elements that can be included in the conventionally known SOFC, as needed.

(SOFC stack structure and manufacturing method thereof)
The SOFC stack structure disclosed herein (hereinafter, also simply referred to as the present stack structure) is a stack structure of a plurality of cells including one or more solid oxide fuel cells including the present air electrode. It can have. That is, it is only necessary to further include an air electrode layer including the present air electrode.

The stack structure may be co-sintered with a first cell comprising the air electrode and a second cell comprising the air electrode. By co-sintering a plurality of cells including the air electrode, even during co-sintering requiring a high temperature, generation of an undesirable reaction phase can be suppressed or avoided, and suitable electrode characteristics can be exhibited, and good power generation can be achieved. It can exhibit the characteristics.

In the present stack structure, an interconnector or a part thereof can be provided for a single cell. In a stack structure, generally, a unit cell in which a fuel electrode, an air electrode and a solid electrolyte are stacked has a structure in which the unit cell and another unit cell are stacked and connected via an interconnector.

The manufacturing method of the present stack structure is a laminate of two or more cells including one or more cells including a fuel electrode layer, a solid electrolyte layer, and an air electrode layer including the present air electrode, Obtaining a precursor of a solid oxide fuel cell stack structure in which the elements of the part are not integrated with each other; and calcining the precursor to integrate the at least part of the elements; Can be provided. According to the present manufacturing method, even if the precursor including such non-integrated elements is integrated by co-sintering, the generation of the harmful reaction phase in the air electrode layer is suppressed or avoided. It is possible to obtain a stack structure with excellent power generation efficiency.

The integration step of the present manufacturing method can take a step of sintering the precursors all together. By taking such a process, it is possible to obtain a stack structure having excellent power generation efficiency while being compactly integrated and having sufficient strength. The stack structure and the method for producing the same by such integral sintering have already been described, for example, by JP-A-2014-56824, WO 2016-9542, WO 2015/05613, WO. The stack structure can be manufactured by appropriately referring to methods disclosed in the 20154/122807 and the like and disclosed therein.

The firing temperature in the integration step is not particularly limited, but can be, for example, 1200 ° C. or more. It is because it is difficult to densify the electrolyte and the interconnector if the temperature is less than 1200 ° C. Also, for example, the temperature can be higher than 1200 ° C., can be, for example, 1250 ° C. or higher, can be, for example, 1300 ° C. or higher, and can be, for example, 1350 ° C. or higher. And can be 1400 ° C. or higher. Although not particularly limited, for example, the temperature can be 1600 ° C. or less, for example 1550 ° C. or less, for example 1500 ° C. or less, for example 1450 ° C. or less, for example 1400 ° C. or less. The range of the firing temperature can be set by appropriately combining the upper limit temperature and the lower limit temperature described above, for example, 1200 ° C. to 1400 ° C., for example, 1250 ° C. to 1350 ° C., for example, 1250 ° C. to 1300 It can be set to, for example, less than

Further, in the integration step, the heating time by the above-mentioned baking temperature is not particularly limited either, and is appropriately determined in a range where good integrity can be obtained, for example, 30 minutes or more, for example 45 minutes or more, For example, it can be 1 hour or more, for example 2 hours or more, for example 3 hours or more, for example 4 hours or more, for example 5 hours or more. In addition, an integration process can be implemented in air.

In addition, although the integration step is not particularly limited, it can be carried out in a state where the precursor is pressurized as necessary. The pressurizing method is not particularly limited, but, for example, CIP can be adopted.

Moreover, the heating time by the said baking temperature in an integration process is not specifically limited, either, Although it determines suitably in the range from which favorable integrity is obtained, For example, 30 minutes or more, 45 minutes or more, For example, 1 hour or more, for example, 2 hours or more, for example, 3 hours or more, for example, 4 hours or more, for example 5 hours or more. In addition, an integration process can be implemented in air.

According to the present manufacturing method, since the integration process can be performed at such a high temperature, layers having suitable interconnector properties (conductivity and gas barrier properties) can be applied to each of the fuel electrode and the air electrode. Conductivity and integrity can be exhibited. It is possible to integrally sinter the stack structure without complicating the manufacturing process.

The manufacturing method of the SOFC stack is not particularly limited, but generally, a green sheet including materials of single cells and one or more elements constituting the stack is prepared in advance and then laminated, or, as appropriate, such materials While laminating the layers directly as a slurry, they are laminated in the required order and integrally fired. Those skilled in the art can appropriately determine and carry out what kind of elements to prepare a green sheet containing the element, or supply it as a slurry, and further, the stacking order and the like as long as the SOFC stack can be obtained.

The integration step is performed such that at least a part of the elements constituting the precursor sinter and integrate. Preferably, all the elements are co-sintered. The precursor may be crimped by cold isostatic pressing (CIP) at a temperature of about 60 ° C. to 120 ° C., if necessary, prior to the integration step. The degreasing treatment can be performed within the range of 300 ° C. to 500 ° C.

The methods for producing the slurry and the green sheet itself are well known to those skilled in the art. For example, the slurry for each layer can be prepared by further adding an appropriate amount of a binder resin, an organic solvent, etc., with the material of each element as the main component. In addition, the green sheet can be prepared by using a sheet forming method by casting such as tape casting using a coating apparatus such as knife coating or doctor blade, or using a screen printing method, a spray method, or the like. You can get A green sheet (an unfired ceramic green sheet) can be obtained by drying the obtained sheet precursor according to a conventional method, and then heat treatment as necessary.

Also, methods of making the fuel electrode and the air electrode are well known to those skilled in the art. For example, a person skilled in the art may add a particulate disappearance material to the slurry formulation according to a known method, or include a pore forming agent or the like to obtain a desired average pore size, porosity, pore size distribution, etc. It is possible to produce a green sheet which can express its quality by firing. In addition, while the lost material itself is also known, various materials are commercially available.

The method of manufacturing the SOFC stack described above is only an example of the method of manufacturing the SOFC stack disclosed in the present specification. Therefore, according to the conventionally known SOFC manufacturing method, lamination of green sheets including at least one layer of SOFC single cells or layers constituting an SOFC stack or lamination by directly applying a slurry etc. is appropriately combined, SOFC single cells and SOFC stacks can be manufactured.

Methods of forming gas passages in the fuel electrode, air electrode and interconnector are also well known to those skilled in the art. A person skilled in the art appropriately arranges an expendable material capable of forming a desired gas flow path pattern on a green sheet of a fuel electrode material, etc. according to a known method, and further laminates a green sheet of a fuel electrode material etc. can do.

In addition, it is possible to manufacture an electrode green sheet provided with a seal material layer which becomes a seal portion adjacent to the fuel electrode material layer or the air electrode material layer, as appropriate.

Further, according to need, the stack structure described above further connects current collectors, etc., appropriately connects sources of reducing gas and oxidizing gas, etc., and further includes a heating device. , SOFC system can be built.

Hereinafter, examples embodying the disclosure of the present specification will be described, but the disclosure of the present specification is not limited to the following examples.

_{_{(La 1-x Sr x)}} (Mn 1-y Ni y) O 3 as a (LSMNi), fixed with y = 0.2, x = 0.1,0.2,0.3,0.4, The synthesis was performed using the glycine method with a composition of 0.5. That is, for 20 g of glycine, lanthanum nitrate hexahydrate (La (NO ₃ ) ₃ .6H ₂ O), strontium nitrate hexahydrate (Sr (NO ₃ ) so as to obtain a composition as intended stoichiometrically. _2. ) Mix 20 g of a mixture of ₂ · 6 H ₂ O), manganese nitrate hexahydrate (Mn (NO ₃ ) ₃ · 6 H ₂ O), nickel nitrate hexahydrate (Ni (NO ₃ ) ₂ · 6 H ₂ O) The raw material is dissolved in water at room temperature, heated to 180 ° C., heated at 450 ° C. for several hours to remove water and organic substances, and then heat-fired at 850 ° C. in air for 5 hours to obtain LSM Ni or its The precursor was obtained.

The various LSMNis obtained were calcined in air at 1300 ° C. for 5 hours. The XRD profile of the obtained calcined powder is shown in FIG. As shown in FIG. 1, it was found that no impurity phase was observed even in the heat treatment at 1300 ° C. in the above-described raw material range of molar fraction, and all single phase was obtained. From the above, it was found that it is possible to replace a part of the B site (Mn site) of LSM with Ni.

In the present example, the conductivity of each of the various LSM Ni synthesized in Example 1 was measured. Samples for measuring conductivity were formed into pellets of 20 mm diameter and 4 mm thickness by CIP using various LSMNi powders, and then fired in air at 1300 ° C. for 5 hours for 5 hours, then both sides of the pellet were # 400 It manufactured by grind | polishing in order with # 1500 SiC grinding paper. The conductivity was measured from room temperature to 800 ° C. with the DC four probe method at the Van der Pauw setting. Silver mesh and wire were used as conductors. The results are shown in FIG.

As shown in FIG. 2, x exhibits a high conductivity at 0.1 to 0.4, and exhibits a high conductivity at 0.2 to 0.3, and exhibits the highest conductivity at 0.3. I understood it.

Generally, the air electrode is in contact with a solid electrolyte such as YSZ, etc., and the solid electrolyte is mixed with the air electrode to control the thermal expansion coefficient. In order to use the material as an air electrode material, it is important that the reactivity with YSZ etc. be as small as negligible. In this example, the reactivity between LSMNi and YSZ (8 mol% Y ₂ O ₃ stabilized ZrO ₂ ) which is a material of a solid electrolyte and also an air electrode material was evaluated. Various kinds of LSMNi and YSZ synthesized in Example 1 are thoroughly mixed at 50:50 (mass ratio) and formed into pellets of 20 mm in diameter and 4 mm thickness by CIP, and heat treated in air at 1300 ° C. for 5 hours A sintered body was obtained to obtain a sintered body, and then both sides of the pellet were polished in order with # 400 to # 1500 SiC abrasive paper to prepare a sample. XRD diffraction was performed on these samples to obtain an XRD profile. The results are shown in FIG.

As shown in FIG. 3, when x = 0.1 and 0.2, no formation of reaction phases other than LSM and YSZ is observed, but when x = 0.3, a small but high resistance reaction is obtained. A phase SZO reaction phase was formed. Furthermore, when x was 0.4 or more, on the other hand, when x was more than 0.3, it was observed that the high resistance reaction phase, the SZO phase, tended to be generated remarkably. From the above, by setting x to 0.3 or less, or less than 0.3, it is possible to obtain an air electrode material in which the generation of the SZO reaction phase is effectively suppressed or avoided even at a high-temperature firing temperature. all right. From the viewpoint of reaction phase suppression, it was found that x is preferably 0.2 or less, and preferably 0.1 or less.

Furthermore, with respect to the amount of SZO produced, the (110) peak intensity ratio of SZO was estimated based on the (111) peak intensity of 8YSZ. The results are shown in FIG. As shown in FIG. 4, it was found that when x is 0.24 or less, it can be said that the SZO phase, which is a high resistance reaction phase, is hardly generated.

In this example, the optimum mole fractions of Mn and Ni in LSMNi were examined. According to Example 1, LSMNi in which y is changed to 0.1, 0.2, and 0.3 was synthesized as La _0.8 Sr _0.2 Mn _1-y Ni _y O _3-d , and 50: 50 with YSZ. A mixed powder of (mass ratio) was prepared, and a sintered body sample obtained from this mixed powder according to Example 2 was subjected to powder XRD analysis to obtain an XRD profile. As a control, a mixed powder-derived sintered body sample of mere 50: 50 (mass ratio) of LSM and YSZ was used. The results are shown in FIG.

As shown in FIG. 5, when y = 0.1 and 0.2, formation of reaction phases other than LSMNi and YSZ is not observed, but when y exceeds 0.3, SZO which is a high resistance reaction phase It was found that the tendency to generate LZO and LZO increases. Therefore, by synthesizing LSMNi with y being 0.3 or less, or less than 0.3, etc., it is possible to obtain an air electrode material capable of effectively suppressing or avoiding the formation of a high resistance reaction phase even in heat treatment at high temperatures. I understand.

In this example, LSM Ni ((La _0.8 Sr _0.2 ) (Mn _0.8 Ni _0.2 ) O ₃ ) and LSM were compared. Each sintered body sample was mixed with YSZ at 50:50 (mass ratio) and molded according to Example 2 and fired in air at 1300 ° C. for 5 hours or 24 hours according to Example 2 , XRD diffraction was performed to obtain an XRD profile. The results are shown in FIG.

As shown in FIG. 6, in LSM, the formation of LZO was already observed after 5 hours of heat treatment, but in LSMNi, it was found that high resistance reaction phases such as LZO and SZO were not formed even after 24 hours of calcination. . Therefore, it was suggested that the fall of the electrode resistance by high temperature baking can be suppressed significantly by using this air electrode.

In this example, the conductivity of the air electrode manufactured from LSMNi and LSM evaluated in Example 5 was examined. LSM or LSMNi was screen printed on both sides of a 300 μm thick YSZ electrolyte and baked at 1300 ° C. The temperature dependence of the conductivity of this sample was measured in air. The conductivity was evaluated using the reciprocal value of ASR (resistance normalized by area). The conductivity was measured in the same manner as in Example 3. The results are shown in FIG.

As shown in FIG. 7, it has been clarified that the conductivity can be significantly improved by using LSMNi.

Claims

A material for an air electrode of a solid oxide fuel cell,
Material containing a perovskite oxide (La 1-x Sr x) (Mn 1-y Ni y) O 3 ( however, 0 <y <0.3).
The (La 1-x Sr x) (Mn 1-y Ni y) O 3 is, (La 1-x Sr x ) (Mn 1-y Ni y) O 3 ( however, 0 <x ≦ 0.3) The material according to claim 1, which is
The material according to claim 1, further comprising a rare earth element stabilized zirconia.
The material according to claim 3, wherein the rare earth element is yttrium.
The material according to any one of claims 2 to 4, containing 10% by mass or more and 60% by mass or less of the rare earth element-stabilized zirconia.
An air electrode of a solid oxide fuel cell, which is a sintered body of the air electrode material according to any one of claims 1 to 5.
A solid oxide fuel cell comprising the sintered body of the air electrode material according to any one of claims 1 to 5 as an air electrode.
A solid oxide having one or more solid oxide fuel cell comprising a plurality of solid oxide fuel cell cells each having a stacked structure, the solid oxide fuel cell comprising an air electrode layer including an air electrode comprising a sintered body of the air electrode material according to any one of claims 1 to 5 Fuel cell stack structure.
The stack structure according to claim 8, wherein in the stack structure, the first cell including the air electrode layer and the second cell including the air electrode layer are co-sintered.
A method of manufacturing a solid oxide fuel cell, comprising:
A laminate of two or more cells comprising one or more cells comprising a fuel electrode layer, a solid electrolyte layer, and an air electrode layer comprising the air electrode material according to any one of claims 1 to 5, Obtaining a precursor of a solid oxide fuel cell stack structure in which at least some of the elements are not mutually integrated;
Firing the precursor to integrate the at least some of the elements;
A manufacturing method.