JP5023250B1 - Fuel cell - Google Patents

Abstract

A fuel cell capable of improving cell characteristics is provided.
In a fuel cell, a joint occupancy ratio of a joint portion 15b at a joint interface 15a between an air electrode 15 and a barrier layer 14 is defined as 30% to 80%.
[Selection] Figure 1

Description

  The present invention relates to a solid oxide fuel cell.

  In recent years, attention has been focused on fuel cells from the viewpoint of environmental problems and effective use of energy resources. The fuel cell includes a fuel cell and an interconnector. A fuel cell generally includes a solid electrolyte layer, and a fuel electrode and an air electrode facing each other with the solid electrolyte layer interposed therebetween.

  Here, in order to suppress the formation of a high-resistance layer at the interface between the solid electrolyte layer and the air electrode, a method of interposing a barrier layer between the solid electrolyte layer and the air electrode has been proposed ( Patent Document 1).

JP 2010-3478 A

  However, Patent Document 1 does not define any interface structure between the air electrode and the barrier layer. Therefore, further improvement of the cell characteristics (power generation performance, durability, etc.) of the fuel cell is expected by defining the interface structure between the air electrode and the barrier layer.

  The present invention has been made in view of the above-described situation, and an object thereof is to provide a fuel battery cell capable of improving cell characteristics.

  The fuel cell according to the first aspect of the present invention includes a fuel electrode, a solid electrolyte layer, a barrier layer co-fired with the solid electrolyte layer, and a barrier interface disposed on the barrier layer. And a porous layer having a plurality of bonding portions bonded to the barrier layer and a plurality of pores provided between the plurality of bonding portions. The occupation ratio of the joint per unit length at the joint interface is 20% to 70%.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell which can improve a cell characteristic can be provided.

Sectional view showing the configuration of the fuel cell Graph showing cerium concentration distribution and zirconium concentration distribution in solid electrolyte layer, intermediate layer and barrier layer SEM image showing a cross section near the interface between the barrier layer and the air electrode Sectional view showing the configuration of the fuel cell

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  In the following embodiments, a solid oxide fuel cell (SOFC) will be described as an example of a fuel cell. In the following, a vertical stripe fuel cell having a plurality of stacked fuel cells will be described, but the present invention can also be applied to a horizontal stripe fuel cell having a plurality of fuel cells arranged on a substrate. It is.

≪Configuration of fuel cell 1≫
The configuration of the fuel cell 1 will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of the fuel cell 1.

  As shown in FIG. 1, the fuel cell 1 includes a fuel cell (hereinafter abbreviated as “cell”) 10 and a current collecting member 20. In the fuel cell 1, although not shown, a plurality of cells 10 are stacked in the y-axis direction via the current collecting member 20.

  Hereinafter, the configuration of the cell 10, the configuration of the current collecting member 20, the detailed configuration of the intermediate layer 13, and the detailed configuration of the air electrode 15 will be described in this order.

<Configuration of cell 10>
The cell 10 includes a fuel electrode 11, a solid electrolyte layer 12, an intermediate layer 13, a barrier layer 14, and an air electrode 15. The cell 10 is a thin plate extending in the x-axis direction orthogonal to the y-axis direction. The cell 10 is made of a ceramic material. The thickness of the cell 10 is, for example, 30 μm to 3 mm, and the diameter of the cell 10 is, for example, 5 mm to 50 mm.

(Fuel electrode 11)
The fuel electrode 11 is an anode of the cell 10. The fuel electrode 11 may have a function as a substrate (in other words, “support”) that supports other layers included in the cell 10.

  As a material of the fuel electrode 11, for example, a material used for a fuel electrode of a known fuel cell can be used. Specifically, the fuel electrode 11 may contain nickel oxide-yttria stabilized zirconia (NiO-YSZ) as a main component. In the present embodiment, “the composition A contains the substance B as a main component” preferably means that the content of the substance B in the composition A is 60% by weight or more, and more preferably, the composition It means that the content of substance B in A is 70% by weight or more.

  The thickness of the fuel electrode 11 may be, for example, about 10 μm to 3 mm. The thickness of the fuel electrode 11 may be larger than the thickness of other layers included in the cell 10 when the fuel electrode 11 functions as a substrate.

(Solid electrolyte layer 12)
The solid electrolyte layer 12 is disposed between the fuel electrode 11 and the intermediate layer 13. The solid electrolyte layer 12 is co-fired with the intermediate layer 13 and the barrier layer 14 and has a dense structure. The porosity of the solid electrolyte layer 12 can be set to 7% or less, for example. The solid electrolyte layer 12 has a function of transmitting oxygen ions generated at the air electrode 15.

The solid electrolyte layer 12 contains zirconium. The solid electrolyte layer 12 may contain zirconium as zirconia (ZrO ₂ ). The solid electrolyte layer 12 may contain zirconia as a main component. The solid electrolyte layer 12 may contain additives such as yttria (Y ₂ O ₃ ) and / or scandium oxide (Sc ₂ O ₃ ) in addition to zirconia. These additives function as stabilizers. In the solid electrolyte layer 12, the molar composition ratio of the stabilizer to zirconia (stabilizer: zirconia) may be about 3:97 to 20:80. That is, examples of the material of the solid electrolyte layer 12 include zirconia-based materials such as yttria-stabilized zirconia such as 3YSZ, 8YSZ, and 10YSZ and scandia-stabilized zirconia (ScSZ).

  The thickness of the solid electrolyte layer 12 should just be 30 micrometers or less, for example.

(Intermediate layer 13)
The intermediate layer 13 is disposed between the solid electrolyte layer 12 and the barrier layer 14. The intermediate layer 13 is co-fired with the solid electrolyte layer 12 and the barrier layer 14.

The intermediate layer 13 contains zirconium and cerium. The intermediate layer 13 may contain zirconium as zirconia and cerium as cerium oxide (CeO ₂ : ceria). In the intermediate layer 13, cerium (or ceria) and zirconium (or zirconia) may be mixed, but both preferably constitute a solid solution. Further, the intermediate layer 13 may contain an additive contained in the solid electrolyte layer 12 and the barrier layer 14 in addition to cerium and zirconium. Examples of such additives include yttrium (Y) and scandium (Sc) contained in the solid electrolyte layer 12, and gadolinium (Gd) and samarium (Sm) contained in the barrier layer 14.

  Here, the cerium concentration in the intermediate layer 13 and the zirconium concentration in the intermediate layer 13 may satisfy one or more of the following conditions (1) to (8). In the following description, the cerium concentration in the intermediate layer 13 is “D1”, the zirconium concentration in the intermediate layer 13 is “D2”, the cerium concentration in the barrier layer 14 is “D3”, and the zirconium concentration in the solid electrolyte layer 12 is Is “D4”.

Condition (1): The ratio of D2 to D1 (D2 / D1) preferably satisfies 0.1 ≦ D2 / D1. Condition (2): D2 / D1 preferably satisfies D2 / D1 ≦ 1. ): D1 preferably satisfies D1 ≦ 80 mol% Condition (4): D1 preferably satisfies 40 mol% ≦ D1 Condition (5): D2 preferably satisfies D2 ≦ 50 mol% Condition (6): D2 preferably satisfies 10 mol% ≦ D2 Condition (7): Ratio of D1 to D3 (D1 / D3) satisfies D1 / D3 ≦ 0.9 Condition (8): Ratio of D2 to D4 (D2 / D4) satisfies D2 / D4 ≦ 0.5 Here, in this embodiment, the “concentration” of the component in each layer is the average content of the component in each layer. Such “concentration” can be obtained, for example, by line analysis using an atomic concentration profile, that is, comparison of characteristic X-ray intensities using EPMA (Electron Probe Micro Analyzer). Specifically, concentration distribution data of each element is obtained by performing line analysis with EPMA along the y-axis direction in the cross section of the cell 10 parallel to the thickness direction (y-axis direction in FIG. 1). That is, the above-described D1 to D4 can be determined by elemental mapping using EPMA. In the present embodiment, EPMA is a concept including EDS (Energy Dispersive x-ray Spectroscopy).

  The intermediate layer 13 may have a thickness of 0.5 μm or more, preferably 10 μm or less, and more preferably 5 μm or less.

The thermal expansion coefficient (that is, the linear expansion coefficient) of the intermediate layer 13 is a value between the thermal expansion coefficient of the solid electrolyte layer 12 and the thermal expansion coefficient of the barrier layer 14. For example, the thermal expansion coefficient of the intermediate layer 13 is larger than that of YSZ, which is an example of the material of the solid electrolyte layer 12, and gadolinium-doped ceria ((Ce, Gd) O ₂ ), which is an example of the material of the barrier layer 14, Smaller than the coefficient of thermal expansion of GDC).

  In addition, as shown in FIG. 1, the intermediate | middle layer 13 has the 1st surface 13a, the 2nd surface 13b, and the pore 13c. The detailed configuration of the intermediate layer 13 will be described later.

(Barrier layer 14)
The barrier layer 14 is disposed between the intermediate layer 13 and the air electrode 15. The barrier layer 14 is co-fired with the solid electrolyte layer 12 and the intermediate layer 13 and has a dense structure. Specifically, the porosity of the barrier layer 14 is preferably 10% or less. The barrier layer 14 suppresses formation of the high resistance layer by suppressing diffusion of cations from the air electrode 15 to the solid electrolyte layer 12. This suppresses a decrease in the output density of the cell 10 and extends the life of the cell 10.

The barrier layer 14 contains cerium. The barrier layer 14 may contain cerium as ceria. As a material for the barrier layer 14, a ceria-based material containing ceria and a rare earth metal oxide solid-dissolved in ceria can be used. Examples of the ceria-based material include GDC and samarium-doped ceria ((Ce, Sm) O ₂ : SDC). The molar composition ratio of the rare earth metal oxide to ceria (rare earth metal oxide: ceria) may be about 5:95 to 20:80. The barrier layer 14 may contain a ceria-based material as a main component, and may contain an additive.

  The thickness of the barrier layer 14 may be, for example, 40 μm or less, 30 μm or less, or 20 μm or less.

(Air electrode 15)
The air electrode 15 is disposed on the barrier layer 14. The air electrode 15 is a cathode of the cell 10. The air electrode 15 includes more fine holes than the barrier layer 14 having a dense structure. In the present embodiment, the air electrode 15 is an example of a “porous layer”.

As a material of the air electrode 15, for example, a material used for an air electrode of a known fuel cell can be used. Specifically, the air electrode 15 may contain lanthanum strontium cobalt ferrite ((LaSr) (CoFe) O ₃ : LSCF) as a main component. The composition of LSCF can be, for example, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ , but is not limited thereto. Moreover, when using LSCF as a material of the air electrode 15, the air electrode 15 which concerns on this embodiment is formed by baking LSCF which has an average particle diameter of 0.1 micrometer-3 micrometers at 900 to 1200 degreeC.

  The thickness of the air electrode 15 should just be about 5 micrometers-50 micrometers.

  As shown in FIG. 1, the air electrode 15 has a bonding interface 15a, a bonding portion 15b, and pores 15c. The detailed configuration of the air electrode 15 will be described later.

<Configuration of current collecting member 20>
As illustrated in FIG. 1, the current collecting member 20 includes a plurality of conductive connection portions 21 and a conductive adhesive 22.

  The conductive connection portion 21 is a recess provided in the current collecting member 20. A bottom portion of the conductive connection portion 21 is connected to the air electrode 15 via a conductive adhesive 22. During power generation, air is supplied from the periphery of the conductive connection portion 21 to the air electrode 15.

<Detailed configuration of the intermediate layer 13>
Next, the detailed configuration of the intermediate layer 13 will be described with reference to the drawings.

  As shown in FIG. 1, the intermediate layer 13 has a first surface 13a, a second surface 13b, and a plurality of pores 13c. The intermediate layer 13 is bonded to the solid electrolyte layer 12 on the first surface 13a, and is bonded to the barrier layer 14 on the second surface 13b.

(First surface 13a and second surface 13b)
FIG. 2 is a graph schematically showing an example of the cerium concentration distribution and the zirconium concentration distribution in the solid electrolyte layer 12, the intermediate layer 13, and the barrier layer 14. The density distribution data shown in FIG. 2 is acquired by performing line analysis with EPMA along the y-axis direction in a cross section parallel to the y-axis direction as described above.

  As shown in FIG. 2, the cerium concentration gradually decreases from the barrier layer 14 to the solid electrolyte layer 12. On the other hand, the zirconium concentration gradually increases from the barrier layer 14 to the solid electrolyte layer 12.

  Here, in the present embodiment, the first surface 13a of the intermediate layer 13 is defined by a line in which the cerium concentration and the zirconium concentration match. The second surface 13b of the intermediate layer 13 is defined by a 85% concentration line of the maximum cerium concentration in the cross section.

(Pore 13c)
The plurality of pores 13 c are located in the intermediate layer 13. At least some of the plurality of pores 13c may be closed pores. The closed pores are pores that are entirely present in the intermediate layer 13 and are blocked from the outside air of the cell 10.

  The shape of the pore 13c is not particularly limited, but the cross section of the pore 13c may be circular or substantially elliptical. The diameter or major axis of the pores 13c is preferably 0.05 μm or more, and more preferably 1 μm or less. The number of pores 13c in the cross section parallel to the y-axis direction is preferably 5 or less per 10 μm length in the direction parallel to the first surface 13a and the second surface 13b.

  Here, the porosity (in other words, “space factor”) of the intermediate layer 13 is preferably 1% or more and 15% or less. The porosity of the intermediate layer 13 is higher than the porosity of the barrier layer 14. Further, the porosity of the intermediate layer 13 is higher than the porosity of the solid electrolyte layer 12.

  The porosity is represented by the ratio (V2 / V1) of the void volume V2 to the total volume V1 of the desired layer, and may be approximate to the occupied area of the pores per unit area in the cross section of the desired layer. it can. Specifically, the porosity can be regarded as [total pore area / total layer area] in an electron microscope (SEM or FE-SEM) image of a cross section parallel to the y-axis direction. As described above, a method for estimating a three-dimensional structure from a two-dimensional structure is described in “Mizutani Rin, Ozaki Yoshiharu, Kimura Toshio, Yamaguchi Satoshi,“ Ceramic Processing ”, Gihodo Publishing Co., Ltd., March 25, 1985. Issuance, pages 190 to 201 ".

  Note that the porosity calculated in one field of view may be regarded as the porosity of the entire layer, and the average value of the porosity calculated in a plurality of fields of view may be regarded as the porosity of the entire layer.

<Detailed configuration of air electrode 15>
Next, the detailed configuration of the air electrode 15 will be described with reference to the drawings. FIG. 3 is an SEM image showing an example of a cross section near the interface between the barrier layer 14 and the air electrode 15. In FIG. 3, the 13 μm region in the x-axis direction perpendicular to the y-axis direction is magnified 10,000 times. FIG. 3 shows a barrier layer 14 formed using GDC and an air electrode 15 formed using LSCF having an average particle diameter of 0.3 μm.

  As shown in FIG. 3, the air electrode 15 has a bonding interface 15a, a plurality of bonding portions 15b, and a plurality of pores 15c. The air electrode 15 is bonded to the barrier layer 14 at the bonding interface 15a.

  As shown in FIG. 3, the bonding interface 15a is formed in a substantially linear shape. That is, the bonding interface 15a extends along the xz plane perpendicular to the y-axis direction. Since the bonding interface 15a is a boundary between the barrier layer 14 having a dense structure and the air electrode 15 having a porous structure, the bonding interface 15a is clearly visible as shown in FIG.

  The plurality of bonding portions 15b are bonded to the barrier layer 14 at the bonding interface 15a. The plurality of joint portions 15b are alternately formed with the plurality of pores 15c.

  The plurality of pores 15c are provided between the plurality of joints 15b at the joint interface 15a. That is, each pore 15c is a space sandwiched between two joints 15b. The plurality of pores 15 c may be closed pores that do not open to the outside of the cell 10, or may be open pores that open to the outside of the cell 10. The plurality of pores 15c may include both closed pores and open pores.

  The shape of the pores 15c is not particularly limited, but the cross section of the pores 15c may be a semicircle or a semi-ellipse. The porosity of the air electrode 15 is preferably 20% or more and 50% or less. It is preferable that the porosity of the air electrode 15 is higher than the porosity of each of the solid electrolyte layer 12, the intermediate layer 13, and the barrier layer 14.

  Here, the occupation ratio (hereinafter referred to as “junction occupation ratio”) of the bonded portion 15b per unit length in the bonded interface 15a is preferably 20% to 70%, and preferably 25% to 65%. Is more preferable. In other words, the occupation ratio of the pores 15c per unit length (hereinafter referred to as “pore occupation ratio”) in the bonding interface 15a is preferably 30% to 80%, and preferably 35% to 75%. Is more preferable. The joint occupancy is the proportion of the joint 15b in the unit length, and the pore occupancy is the proportion of the pore 15c in the unit length. The joint occupancy and the pore occupancy can be calculated by actually measuring the total width of all joints 15b and / or all pores 15c on an SEM image as shown in FIG. 3, for example. Such a fine structure can be digitized by, for example, analyzing an SEM image using image analysis software HALCON manufactured by MVTec (Germany).

  In the present embodiment, the bonding occupation ratio at the bonding interface 15a is an index indicating the characteristics of the microstructure at the interface between the barrier layer 14 and the porous layer (“air electrode 15” in the present embodiment). This is a concept different from the density (that is, the filling rate) in the entire pole 15. Therefore, as described above, the density of the entire air electrode 15 and the joint occupation ratio at the joint interface 15a may be different from each other.

  Similarly, in this embodiment, the porosity occupancy at the bonding interface 15a is an index indicating the characteristics of the microstructure at the interface between the barrier layer 14 and the porous layer, and is a concept different from the porosity in the entire air electrode 15. is there. Therefore, as described above, the porosity of the entire air electrode 15 and the porosity occupancy at the bonding interface 15a may be different from each other.

  Note that the joint occupancy ratio and the pore occupancy ratio may be an arithmetic average of actually measured values in SEM images of a plurality of arbitrarily obtained visual fields (for example, 10 visual fields).

  The average width (hereinafter referred to as “average bonding width”) at which the bonding portion 15b is bonded to the barrier layer 14 at the bonding interface 15a may be 0.1 μm or more and 2.0 μm or less, but may be 0.12 μm. More preferably, it is 1.8 μm or less. Furthermore, the standard deviation of the average joint width is preferably 0.04 or more and 1.20 or less. Further, the average width of the pores 15c (hereinafter referred to as “average pore width”) at the bonding interface 15a may be 0.12 μm or more and 1.5 μm or less, but may be 0.15 μm or more and 1.2 μm or less. More preferred. Further, the standard deviation of the average pore width is preferably 0.05 or more and 0.80 or less. The average joint width can be obtained by dividing the total width of all the joint portions 15b per unit length by the number of joints. Similarly, the average pore width can be obtained by dividing the total width of all the pores 15c per unit length by the number of pores.

  The average bonding width and the average pore width are average values of actually measured values in SEM images of a plurality of visual fields set at different positions. Specifically, it is preferable to calculate the average bonding width or the average pore width based on the result of observing 20 or more different positions at a magnification of 5000 to 20000 times. Thus, the cell characteristics are improved by appropriately defining the average bonding width and the average pore width over a wide range of the bonding interface 15a.

  The joint occupation ratio, pore occupation ratio, average joint width, and average pore width can be controlled by adjusting not only the type of material constituting the air electrode 15 and the average particle diameter, but also the firing conditions of the air electrode 15.

<< Manufacturing Method of Cell 10 >>
Next, an example of a method for manufacturing the cell 10 will be described. However, various conditions such as the material, particle size, temperature, and coating method described below can be changed as appropriate.

  First, the 1st material layer used as the fuel electrode 11 is formed by laminating | stacking several ceramic green sheets and carrying out thermocompression bonding. The ceramic green sheet is made of, for example, nickel oxide (NiO), a zirconia-based material (for example, 8YSZ), a pore forming agent (for example, PMMA (polymethyl methacrylate resin)), or the like.

  Next, a second material layer that becomes the solid electrolyte layer 12 is formed by laminating a ceramic green sheet composed of a zirconia-based material on the first material layer.

  Next, a third material layer to be the barrier layer 14 is formed by laminating a ceramic green sheet made of a ceria-based material on the second material layer.

  Next, the first to third material layers are degreased and then cofired at 1300 to 1500 ° C. for 1 hour to 20 hours to form a cofired body. As a result, the first material layer becomes the fuel electrode 11, the second material layer becomes the solid electrolyte layer 12, the third material layer becomes the barrier layer 14, and ceria at the boundary between the second material layer and the third material layer. The intermediate layer 13 is formed by solid solution of zirconia and zirconia.

  Next, on the barrier layer 14 of the co-fired body, for example, an LSCF material having an average particle diameter of 0.1 μm to 3.0 μm is applied by a printing method to form a fourth material layer that becomes the air electrode 15. To do.

  Next, the fourth material layer is fired at 900 ° C. to 1200 ° C. for 1 hour to 10 hours, for example. Thereby, the fourth material layer becomes the air electrode 15 and the cell 10 is completed.

≪Action and effect≫
(1) In the fuel battery cell 10 according to the present embodiment, the joint occupation ratio of the joint portion 15b in the joint interface 15a between the air electrode 15 and the barrier layer 14 is defined as 20% to 70%.

  Here, as a result of intensive studies on the microstructure of the air electrode 15 at the bonding interface 15a, the present inventors have found that the initial output of the fuel cell varies depending on the bonding occupation ratio of the bonding portion 15b. This indicates that the junction occupancy affects the optimization and stabilization of the electrode reaction field.

  In this embodiment, since the formation of an appropriate and stable electrode reaction field at the bonding interface 15a is realized by defining the bonding occupation ratio to 20% to 70%, the initial output of the fuel cell is improved. Can do. It has also been confirmed from experimental examples described later that the initial output can be improved by defining the junction occupation ratio to 20% to 70%.

  (2) The average bonding width of the bonding portion 15b at the bonding interface 15a is regulated to 0.1 μm to 2.0 μm.

  Here, as a result of intensive studies on the interface strength of the bonding interface 15a, the present inventors have found that the thermal cycle characteristics of the fuel cells vary depending on the average bonding width of the bonding portion 15b. This indicates that the average bonding width affects the interface strength.

  In this embodiment, since the interface strength is improved at the bonding interface 15a by defining the average bonding width to be 0.1 μm to 2.0 μm, the thermal cycle characteristics (that is, durability) of the fuel cell unit are achieved. Can be improved. It has also been confirmed from experimental examples described later that the thermal cycle characteristics can be improved by defining the average bonding width to 0.1 μm to 2.0 μm.

  (3) In the fuel cell 10 according to this embodiment, the porosity of the intermediate layer 13 is higher than the porosity of the barrier layer 14.

  Therefore, the distortion generated in the solid electrolyte layer 12 and the barrier layer 14 due to the co-firing of the solid electrolyte layer 12 and the barrier layer 14 can be alleviated by the plurality of pores 13 c included in the intermediate layer 13. . Therefore, it can suppress that the solid electrolyte layer 12 and the barrier layer 14 peel.

  (4) At least some of the plurality of pores 13c are closed pores.

  Therefore, the strain relaxation effect (that is, the thermal stress relaxation effect) by the intermediate layer 13 can be improved, and even if a crack is generated, the growth of the crack can be stopped by the closed pore 13c. it can.

<< Other Embodiments >>
The present invention is not limited to the embodiment described above, and various modifications or changes can be made without departing from the scope of the present invention.

  (A) In the above embodiment, the cell 10 includes the fuel electrode 11, the solid electrolyte layer 12, the intermediate layer 13, the barrier layer 14, and the air electrode 15. However, the present invention is not limited to this. The cell 10 only needs to include the fuel electrode 11, the solid electrolyte layer 12, the barrier layer 14, and the air electrode 15, and between the fuel electrode 11 and the solid electrolyte layer 12 and between the barrier layer 14 and the air electrode 15. Other layers may be inserted.

  For example, as shown in FIG. 4, the cell 10 may include a porous barrier layer 16 as an example of a “porous layer” between the barrier layer 14 and the air electrode 15. The porous barrier layer 16 has a porosity that is higher than the porosity of the barrier layer 14. The porous barrier layer 16 may be made of the same material as the barrier layer 14, but may be made of a known material different from the barrier layer 14. The porous barrier layer 16 has a bonding interface 16a, a bonding portion 16b, and pores 16c. Such a porous barrier layer is obtained by cofiring the fuel electrode 11, the solid electrolyte layer 12, the intermediate layer 13, and the barrier layer 14, and then applying the material of the porous barrier layer 16 onto the barrier layer 14 and firing it. Can be formed.

  Here, in the case of the configuration shown in FIG. 4, as can be seen from an experimental example to be described later, the joint occupation ratio of the joint portion 16 b in the joint interface 16 a is regulated to 22% to 68%, more preferably 25%. By defining it to ˜65%, the initial output of the cell 10 can be improved. In other words, the initial output of the cell 10 can be improved by defining the pore occupancy ratio of the pores 16c at the bonding interface 16a to 32% to 78%, more preferably 35% to 75%. it can.

  Further, by defining the average joint width of the joint portion 16b at the joint interface 16a to 0.15 μm to 1.8 μm, more preferably 0.18 μm to 1.5 μm, the interface strength of the joint interface 15a can be increased. Can be improved. Further, by defining the average pore width of the pores 16c in the bonding interface 16a to 0.15 μm to 1.5 μm, more preferably 0.18 μm to 1.3 μm, the interface strength of the bonding interface 15a is improved. Can be made.

  (B) Although not specifically mentioned in the above embodiment, the shape of the cell 10 may be a fuel electrode support type, a flat plate shape, a cylindrical shape, a vertical stripe type, a horizontal stripe type, a single-end holding type, a double-end holding type, or the like. The cross section of the cell 10 may be elliptical.

(C) Although not particularly mentioned in the above embodiment, the fuel electrode 11 may be composed of two or more layers. For example, the fuel electrode 11 may be constituted by a substrate and a fuel electrode active layer (fuel side electrode) formed on the substrate. The substrate and the anode active layer may be made of the above-described material as the material of the anode 11, but for example, the substrate is made of NiO—Y ₂ O ₃ and the anode active layer is made of NiO—YSZ. can do.

  (D) Although the air electrode 15 mainly composed of LSCF is described as an example of the “porous layer” in the above embodiment, the present invention is not limited to this. The air electrode 15 only needs to have a function as an air electrode. For example, a composite material (for example, LSCF) of a well-known air electrode material (for example, LSCF) and a material of the barrier layer 14 (for example, GDC). -GDC).

  (E) Although not particularly mentioned in the above embodiment, pores may be formed in the inside or the outer surface of the air electrode 15.

  (F) In the above embodiment, the air electrode 15 has a single-layer structure made of a single material, but is not limited thereto. The air electrode 15 may have a multilayer structure composed of different materials. In this case, by adjusting the kind of material constituting the bonding layer in contact with the barrier layer 14 in the multilayered air electrode 15, the average particle diameter, or the firing conditions, the bonding occupancy, pore occupancy, and average bonding width are adjusted. And the average pore width can be controlled.

Experimental example

  Hereinafter, experimental examples of the cell according to the present invention will be described, but the present invention is not limited to the experimental examples described below.

[Production of Experimental Examples No. 1 to No. 13]
Cells according to Experimental Examples No. 1 to No. 13 including an air electrode as a porous layer were produced as follows. In addition, the difference in the manufacturing conditions of the cells according to Experimental Examples No. 1 to No. 13 is that the average particle diameter and firing temperature of the LSCF material constituting the air electrode are arbitrarily set within the ranges described below. It is.

  First, ceramic green sheets (thickness 100 μm) made of nickel oxide (NiO), zirconia-based material (8YSZ), and pore former (PMMA) were laminated to 300 μm and thermocompression bonded (60 ° C., 3 MPa). In this way, an integrated molded body was produced.

  Next, a separately produced ceramic green sheet made of 8YSZ and a ceramic green sheet made of GDC were sequentially laminated and thermocompression bonded. Thus, a laminate in which the fuel electrode material, the zirconia-based material layer, and the ceria-based material layer were sequentially stacked was manufactured.

  Next, the laminate was co-fired at 1300 ° C to 1500 ° C for 1 to 20 hours. As a result, a fuel electrode is formed from the fuel electrode material, a solid electrolyte layer is formed from the zirconia-based material layer, a barrier layer is formed from the ceria-based material layer, and the boundary between the zirconia-based material layer and the ceria-based material layer is further formed. An intermediate layer was formed.

  Next, an LSCF material (thickness of 30 μm) having an average particle diameter in the range of 0.1 μm to 3.0 μm was applied on the barrier layer.

  Next, the LSCF layer was baked in the range of 1000 ° C. to 1200 ° C. for about 2 hours. As a result, an air electrode having a porous structure was formed from the LSCF layer.

≪Observation of interface between air electrode and barrier layer≫
Experimental Example No. 1 to No. 13 cells were prepared two by two and the SEM-EDS (Scanning Electron Microscopy-Energy Dispersive x-ray Spectroscopy) was applied to the bonding interface between the air electrode and the barrier layer in a cross section parallel to the thickness direction. ). Moreover, a 10 μm-wide cross-sectional image magnified 10,000 times was obtained using image software (see FIG. 3).

  Next, with reference to the acquired cross-sectional image, the occupation ratio (that is, the junction occupation ratio) and the average width (that is, the average junction width) of the junction at the junction interface between the air electrode and the barrier layer were measured. .

  Next, with reference to the acquired cross-sectional image, the occupancy ratio (that is, the occupancy ratio) of pores and the average pore width (that is, average pore width) at the bonding interface between the air electrode and the barrier layer were measured.

  The measurement results are summarized in Table 1 below.

≪Measurement of initial output≫
The initial output (power density) of each of the cells of Experimental Examples No. 1 to No. 13 was measured by raising the temperature to the power generation temperature while supplying gas to each of the cells of Experimental Examples No. 1 to No. 13.

  The power generation conditions were as follows.

・ Power generation temperature: 750 ℃
・ Gas type: Hydrogen on the fuel electrode side, air on the air electrode side ・ Gas utilization rate: 5% or less for both hydrogen and air ・ Output: Output density at rated 0.8V The measurement results are summarized in Table 1 below.

≪Thermal cycle test≫
Experimental Example No.1 to No.13 cells were prepared, and in an infrared lamp type electric furnace in an air atmosphere, the temperature was raised to 700 ° C. for 5 minutes, and the heat cycle test (cooling in 20 minutes by furnace cooling) ( 100 times continuously).

  After completion of the thermal cycle test, the presence or absence of delamination at the interface between the air electrode and the barrier layer in each cell was evaluated by visual observation and microscopic observation. The presence or absence of interfacial peeling is summarized in Table 1 below.

≪Conclusion≫
From the results of the initial output measurement according to Experimental Examples No. 1 to No. 13, in the cell including the air electrode as the porous layer, the joint occupation ratio is 20% to 70% (that is, the pore occupation ratio is 30% to 80%). %) Was confirmed to be preferable. Moreover, when the joint occupancy was 25% to 65% (that is, the pore occupancy was 35% to 70%), a good initial output of about 600 mW / cm ² or more could be obtained.

  From this result, the junction occupancy affects the optimization and stabilization of the electrode reaction field. By defining the junction occupancy to 20% to 70%, more preferably 25% to 65%. It was found that an appropriate and stable electrode reaction field can be formed.

  Moreover, from the result of the thermal cycle test about Experimental Examples No. 1 to No. 13, it is preferable that the average bonding width is 0.1 μm to 2.0 μm in the cell including the air electrode as the porous layer. confirmed. In addition, when the average bonding width is 0.12 μm to 1.8 μm, occurrence of slight interface peeling can be suppressed.

  From this result, the average bonding width has an influence on the interface strength of the bonding interface, and by defining the average bonding width to 0.1 μm to 2.0 μm, it is more preferably defined to 0.12 μm to 1.8 μm. It was found that the interface strength can be improved.

[Production of Experimental Examples No.14 to No.26]
Cells according to Experimental Examples No. 14 to No. 26 including a porous barrier layer as a porous layer were produced as follows. The difference in the production conditions of the cells according to Experimental Examples No. 14 to No. 26 is that the average particle diameter and firing temperature of the GDC material constituting the porous porous barrier layer are arbitrarily set within the ranges described below. It is a point that has been.

  First, ceramic green sheets (thickness 100 μm) made of nickel oxide (NiO), zirconia-based material (8YSZ), and pore former (PMMA) were laminated to 300 μm and thermocompression bonded (60 ° C., 3 MPa). In this way, an integrated molded body was produced.

  Next, a separately produced ceramic green sheet made of 8YSZ and a ceramic green sheet made of GDC were sequentially laminated and thermocompression bonded. Thus, a laminate in which the fuel electrode material, the zirconia-based material layer, and the ceria-based material layer were sequentially stacked was manufactured.

  Next, the laminate was co-fired at 1300 ° C to 1500 ° C for 1 to 20 hours. As a result, a fuel electrode is formed from the fuel electrode material, a solid electrolyte layer is formed from the zirconia-based material layer, a ceria-based material layer dense barrier layer is formed, and the boundary between the zirconia-based material layer and the ceria-based material layer is further formed. An intermediate layer was formed.

  Next, the ceramic green sheet which consists of GDC which has an average particle diameter in the range of 0.1 micrometer-3.0 micrometers on the barrier layer was arrange | positioned, and it baked at 1100 to 1400 degreeC over 1 to 20 hours. As a result, a porous barrier layer was formed on the dense barrier layer.

  Next, an LSCF material (thickness 30 μm) was applied on the porous barrier layer, and baked at about 1100 ° C. for about 2 hours. Thereby, an air electrode was formed on the porous barrier layer.

≪Observation of interface between dense barrier layer and porous barrier layer≫
Two cells of Experimental Examples No. 14 to No. 26 were prepared, and the junction interface between the dense barrier layer and the porous barrier layer was observed with a SEM-EDS in a cross section parallel to the thickness direction. Moreover, a 10 μm-wide cross-sectional image magnified 10,000 times was acquired using image software.

  Next, with reference to the acquired cross-sectional image, the bonding occupation ratio and the average bonding width at the bonding interface between the dense barrier layer and the porous barrier layer were measured.

  Next, referring to the acquired cross-sectional image, the pore occupancy average pore width at the bonding interface between the dense barrier layer and the porous barrier layer was measured.

  The measurement results are summarized in Table 2 below.

≪Measurement of initial output and thermal cycle test≫
For each of the cells of Experimental Examples No. 14 to No. 26, the same initial output measurement and thermal cycle test as those of Experimental Examples No. 1 to No. 13 were performed. The results are summarized in Table 2 below.

≪Conclusion≫
From the results of the initial output measurement according to Experimental Examples No. 14 to No. 26, in the cell including the porous barrier layer as the porous layer, the bonding occupation ratio is 22% to 68% (that is, the pore occupation ratio is 32%). (-78%) was confirmed to be preferable. Further, when the joint occupancy was 25% to 65% (that is, the pore occupancy was 35% to 75%), a good initial output of about 600 mW / cm ² or more could be obtained.

  From this result, the junction occupancy affects the optimization and stabilization of the electrode reaction field. By defining the junction occupancy to 22% to 68%, more preferably 25% to 65%. It was found that an appropriate and stable electrode reaction field can be formed.

  Further, from the results of the thermal cycle test for Experimental Examples No. 14 to No. 26, it is preferable that the average bonding width is 0.15 μm to 1.8 μm in the cell including the porous barrier layer as the porous layer. Was confirmed. In addition, when the average bonding width is 0.18 μm to 1.5 μm, occurrence of slight interface peeling can be suppressed.

  From this result, the average bonding width has an influence on the interface strength of the bonding interface 15a, and by specifying the average bonding width to 0.15 μm to 1.8 μm, more preferably 0.18 μm to 1.5 μm. It was found that the interfacial strength can be improved.

DESCRIPTION OF SYMBOLS 1 Fuel cell 10 Fuel cell 11 Fuel electrode 12 Solid electrolyte layer 13 Intermediate | middle layer 13a 1st surface 13b 2nd surface 13c Pore 14 Barrier layer 15 Air electrode 15a Joining interface 15b Joining part 15c Pore 20 Current collecting member 21 Conductive connection part 22 Conductive adhesive

Claims (14)

An anode,
A solid electrolyte layer;
A barrier layer co-fired with the solid electrolyte layer;
A porous material disposed on the barrier layer and having a plurality of joints joined to the barrier layer at a joint interface with the barrier layer, and a plurality of pores provided between the plurality of joints Layers,
With
The occupation ratio of the plurality of joints per unit length at the joint interface is 20% to 70%.
Fuel cell. The porous layer is an air electrode;
The fuel battery cell according to claim 1. The average width at which each of the plurality of bonding portions is bonded to the barrier layer at the bonding interface is 0.1 μm to 2.0 μm.
The fuel battery cell according to claim 2. The porosity of the pores per unit length at the bonding interface is 30% to 80%.
The fuel battery cell according to claim 2 or 3. The average width that each of the plurality of pores opens toward the barrier layer at the bonding interface is 0.12 μm to 1.5 μm.
The fuel battery cell according to claim 4. Further comprising an air electrode formed on the porous layer,
The porous layer is a porous barrier layer formed between the barrier layer and the air electrode and having a porosity higher than the porosity of the barrier layer.
The fuel battery cell according to claim 1. The average width at which each of the plurality of bonding portions is bonded to the barrier layer at the bonding interface is 0.15 μm to 1.8 μm.
The fuel battery cell according to claim 6. The porosity of the pores per unit length at the bonding interface is 32% to 78%.
The fuel battery cell according to claim 6 or 7. The average width at which the plurality of pores open toward the barrier layer at the bonding interface is 0.15 μm to 1.5 μm.
The fuel cell according to claim 8. Comprising zirconium and cerium, interposed between the solid electrolyte layer and the barrier layer, comprising an intermediate layer having a higher porosity than the barrier layer;
The solid electrolyte layer comprises zirconium;
The barrier layer includes cerium,
The fuel cell according to any one of claims 1 to 9. The porosity in the intermediate layer is 1% or more and 15% or less.
The fuel cell according to claim 10. The porosity in the barrier layer is 10% or less,
The fuel cell according to claim 10 or 11. The major axis of the pores contained in the intermediate layer is 1 μm or less,
The fuel cell according to any one of claims 10 to 12. The intermediate layer includes closed pores,
The fuel cell according to any one of claims 10 to 13.