JP2018129237A - Air electrode for electrochemical cell, and electrochemical cell including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air electrode for an electrochemical cell, which is superior in current-voltage characteristics and an electrochemical cell.SOLUTION: An air electrode 12 for an electrochemical cell is 6 μm or more in film thickness. When parameters LS1 and LS2, which are defined as the ratio of Circumference circle equivalent diameter/Area circle equivalent diameter of air electrode particles in a region of the air electrode, bordering an electrolyte 16 within a range of a thickness W1, and a region on a side where the air electrode does not border the electrolyte 16 within a range of a thickness W2, are determined by measurement with a scanning electron microscope, the ratio LS1/LS2 is less than 1.0. In the air electrode 12, the thicknesses W1 and W2 may be the same or not, and they are each 3 μm or more; the ranges for which the parameters LS1 and LS2 are determined shall be set so that they do not overlap with each other. The air electrode 12, 22 is one for an electrochemical cell in which a fuel electrode, an electrolyte layer 16 and an air electrode 12 are disposed in this order, or a fuel electrode, an electrolyte layer, a barrier layer 24 and an air electrode 22 are disposed in this order.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an air electrode for an electrochemical cell and an electrochemical cell including the same.

  In recent years, electrochemical cells have attracted attention as clean energy sources. Among the electrochemical cells, solid oxide fuel cells and solid oxide electrolytic cells that use solid ceramics as the electrolyte can use exhaust heat because of their high operating temperature, and are more efficient for power and hydrogen fuel. It is expected to be used in a wide range of fields. The electrochemical cell has a structure in which an electrolyte layer is disposed between a fuel electrode and an air electrode as a basic structure.

  Patent Document 1 discloses a first powder that is arranged on the electrolyte layer side and has ion conductivity for the purpose of suppressing peeling that occurs between the cathode and a layer (electrolyte layer or the like) adjacent to the cathode. An active layer formed of a porous body made of a body material, and a porous body made of a second powder material disposed on the active layer in contact with the active layer and having electron conductivity. A solid oxide fuel cell having a cathode with a two-layer structure in which the average particle size of the second powder material is larger than the average particle size of the first powder material. ing.

In Patent Document 2, the air electrode is formed on the other surface side of the electrolyte layer for the purpose of improving the electrical bondability at the interface between the active layer and the current collecting layer constituting the air electrode. An active layer, at least a first current collecting layer formed on and in contact with the active layer, and a second current collecting layer formed on and in contact with the first current collecting layer, the active layer comprising: The first current collecting layer is made of a material having electron conductivity and has an average particle size smaller than 0.8 μm. Solid oxide fuel cell comprising a sintered body, wherein the second current collecting layer is made of a sintered body of a powder made of a material having electron conductivity and having an average particle size larger than 0.8 μm Is described.
However, there has been room for improvement in the efficiency (output) of electrochemical cells such as solid oxide fuel cells and solid electrolyte electrochemical cells.

JP 2013-77397 A JP 2011-19178 A

  Therefore, the subject of this invention is providing the air electrode for electrochemical cells excellent in the current-voltage characteristic, and an electrochemical cell including the same.

  The inventor has found that, by controlling the structure of the air electrode for the electrochemical cell air electrode, an electrochemical cell air electrode excellent in current-voltage characteristics, and an electrochemical cell including the same can be produced. The present invention has been completed.

That is, the electrochemical cell air electrode of the present invention is an electrochemical cell air electrode in which a fuel electrode, an electrolyte layer, and an air electrode are arranged in this order, and the air electrode has a film thickness of 6 μm or more. In the cross section, the ratio LS1 / LS2 of LS1 and LS2 shown below measured with a scanning electron microscope is less than 1.0.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the electrolyte layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode components in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the electrolyte layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of particle 2) / (Average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

  Moreover, the electrochemical cell of this invention arrange | positions a fuel electrode, an electrolyte layer, and the said air electrode in this order.

Further, the electrochemical cell air electrode of the present invention is an electrochemical cell air electrode in which a fuel electrode, an electrolyte layer, a barrier layer, and an air electrode are arranged in this order, and the air electrode has a film thickness of 6 μm. An air electrode for an electrochemical cell as described above, wherein a ratio LS1 / LS2 of LS1 and LS2 shown below is less than 1.0 as measured with a scanning electron microscope in a cross section.
LS1: (a plurality of air electrode component particles) in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the barrier layer in a direction in which the barrier layer of the air electrode is not formed. 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: (a plurality of air electrode component particles in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the barrier layer is not formed to the interface between the air electrode and the barrier layer) (Average value of circumference equivalent circle diameter of 2) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

  Furthermore, the electrochemical cell of the present invention comprises a fuel electrode, an electrolyte layer, a barrier layer, and the air electrode arranged in this order.

  ADVANTAGE OF THE INVENTION According to this invention, the air electrode for electrochemical cells excellent in the current-voltage characteristic, and an electrochemical cell including the same can be provided.

It is one form of the electrochemical cell of this invention. It is another one form of the electrochemical cell of this invention. In the cross section in one embodiment of the air electrode for an electrochemical cell of the present invention, from the interface between the air electrode and the electrolyte layer or the barrier layer to the surface direction S where the electrolyte layer and / or the barrier layer of the air electrode is not formed, Range 1 up to a position away from W1 in the direction perpendicular to the interface, and from the surface of the air electrode where the electrolyte layer and / or barrier layer is not formed, to the interface direction T between the air electrode and the electrolyte layer or barrier layer, It is a figure which represents typically the range 2 to the position away from W2 to the said perpendicular | vertical direction. In the cross section in one embodiment of the air electrode for an electrochemical cell of the present invention, from the interface between the air electrode and the electrolyte layer or the barrier layer to the surface direction S where the electrolyte layer and / or the barrier layer of the air electrode is not formed, It is a figure which represents typically the rectangular area | region 3 of 2 micrometers x 5 micrometers of 5 micrometers width between the position 1 micrometer away from the interface, and the position 3 micrometers away. In the cross section in one embodiment of the air electrode for an electrochemical cell of the present invention, from the interface between the air electrode and the electrolyte layer or the barrier layer to the surface direction S where the electrolyte layer and / or the barrier layer of the air electrode is not formed, From the surface of the air electrode where the electrolyte layer and / or the barrier layer are not formed, and a 2 μm × 5 μm rectangular region 3 having a width of 5 μm between a position 1 μm apart and a position 3 μm away from the interface in the vertical direction, A diagram schematically showing a 2 μm × 5 μm rectangular region 4 having a width of 5 μm between a position 1 μm apart and a position 3 μm apart in the direction perpendicular to the plane in the interface direction T between the air electrode and the electrolyte layer or barrier layer It is. It is a figure which shows an example of the scanning electron micrograph of the cross section of the air electrode for electrochemical cells of an Example (The figure which fractured | ruptured the sample at the observation location and observed the fracture surface). It is the figure which showed the method of calculating | requiring the area equivalent circle diameter and circumference equivalent circle diameter of the air electrode component particle | grains in the range 1 observed with the scanning electron microscope in the cross section of the air electrode for electrochemical cells of an Example (sample). The figure which fractured | ruptured at the observation part and observed the fracture surface). It is the figure which showed the method of calculating | requiring the area equivalent circle diameter of a pore in the range 1, and the circumference equivalent circle diameter observed with the scanning electron microscope in the cross section of the air electrode for electrochemical cells of an Example. Figure of fracture to size, polishing to the observation site after embedding resin, and observing the polished surface). It is the figure which showed the rectangular area | region 3 observed with the scanning electron microscope in the cross section of the air electrode for electrochemical cells of an Example. (A sample is fractured | ruptured to a suitable magnitude | size, and it grind | polished to an observation part after resin embedding. The figure which performed and observed the polished surface). It is the figure which showed the method of calculating | requiring the interface length of the pore and air electrode component particle | grains in the rectangular area | region 3 measured with the scanning electron microscope in the cross section of the air electrode for electrochemical cells of an Example. Figure of fracture to size, polishing to the observation site after embedding resin, and observing the polished surface). It is a histogram which shows distribution of the interface length of the pore and air electrode component particle | grains in the rectangular area | region 3 measured with the scanning electron microscope in the cross section of the air electrode for electrochemical cells of an Example.

1. Electrochemical cell The electrochemical cell of the present invention comprises a fuel electrode, an electrolyte layer, and an air electrode arranged in this order. The air electrode has a film thickness of 6 μm or more, and has a cross section with a ratio LS1 / LS2 of LS1 and LS2 shown below of less than 1.0 as measured with a scanning electron microscope. .
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the electrolyte layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode components in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the electrolyte layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of particle 2) / (Average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

Moreover, the electrochemical cell of this invention arrange | positions a fuel electrode, an electrolyte layer, a barrier layer, and the said air electrode in this order. The air electrode has a film thickness of 6 μm or more, and has a cross section with a ratio LS1 / LS2 of LS1 and LS2 shown below of less than 1.0 as measured with a scanning electron microscope. .
LS1: (a plurality of air electrode component particles) in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the barrier layer in a direction in which the barrier layer of the air electrode is not formed. 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: (a plurality of air electrode component particles in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the barrier layer is not formed to the interface between the air electrode and the barrier layer) (Average value of circumference equivalent circle diameter of 2) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

  Examples of the electrochemical cell of the present invention include a solid oxide fuel cell and a solid oxide electrolytic cell, and a solid oxide fuel cell is a preferred form. The electrochemical cell may be a fuel electrode support cell using a fuel electrode as a support, a solid electrolyte support cell using an electrolyte layer as a support, or an air electrode support cell using an air electrode as a support. The single cell for an electrochemical cell is a metal support cell in which a fuel electrode, the electrolyte layer, and an air electrode are arranged in this order on a support substrate that is composed of metal partition walls and has a plurality of through holes. Alternatively, a metal support cell in which the fuel electrode, the electrolyte layer, the barrier layer, and the air electrode are arranged in this order may be used.

  When the electrochemical cell of the present invention is used as a solid oxide fuel cell, the overvoltage at the air electrode is preferably low, and the output of the solid oxide fuel cell can be increased. In addition, when the electrochemical cell of the present invention is used as a solid oxide electrolytic cell, it can preferably proceed a highly efficient electrolysis reaction with low power consumption.

In FIG. 1, the electrochemical cell 10 as one form of the electrochemical cell of this invention is shown. The electrochemical cell 10 is an electrochemical cell in which a fuel electrode 18, an electrolyte layer 16, and an air electrode 12 are arranged in this order.
FIG. 2 shows an electrochemical cell 20 as another embodiment of the electrochemical cell of the present invention. The electrochemical cell 20 is an electrochemical cell in which a fuel electrode 28, an electrolyte layer 26, a barrier layer 24, and an air electrode 22 are arranged in this order.

1-1 Electrolyte Layer The electrolyte component constituting the electrolyte layers 16 and 26 is not particularly limited, and a known oxide ion conductive material can be used, but preferably contains a zirconia-based oxide as a main component. . In the present specification, “including as a main component” means that, for example, 50% by mass or more, preferably 60% by mass or more is contained in 100% by mass of the electrolyte.

Examples of the oxide ion conductive material constituting the electrolyte layers 16 and 26 include alkaline earth metal elements such as Mg, Ca, Sr, and Ba, Sc, Y, La, Ce, Pr, Nd, Sm, and Eu. Zirconia containing one or more rare earth elements such as Gd, Tb, Dy, Ho, Er, Yb, and other metal elements such as In, preferably one or more of these elements is stable. Stabilized zirconia as a solidifying agent; Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₃ , Nb ₂ O _5, etc. are added to the zirconia (preferably stabilized zirconia) as a dispersion strengthening agent Zirconia-based oxides such as zirconia; ceria-based oxides such as ceria containing yttrium, samarium, gadolinium, ytterbium, etc. Doped ceria in which one or more of these elements are in solid solution; lanthanum gallate, and lanthanum or gallium in lanthanum gallate are part of strontium, calcium, barium, magnesium, aluminum, indium, cobalt, iron, nickel, Examples thereof include lanthanum gallate type perovskite structure oxides substituted with copper or the like.

  Among the above, zirconia-based oxides are preferred, and selected from scandium, yttrium, cerium, and ytterbium as stabilized zirconia having higher thermal characteristics, mechanical characteristics, chemical characteristics, and oxide ion conduction characteristics Those stabilized with at least one element are more preferred. Further, (partial) stabilized zirconia containing tetragonal crystals or cubic crystals as the crystal structure is preferable.

Among the zirconia-based oxides, stabilized zirconia in which the crystal structure is stabilized by dissolving at least one element (also referred to as a stabilizing element) of rare earth elements such as yttrium, scandium, and ytterbium is preferable.
As a more preferable embodiment, zirconia (scandia stabilized zirconia) containing scandium in a ratio of 7.0 to 27.5 mol% in terms of the number of atoms with respect to 100 mol% of zirconium constituting the stabilized zirconia, Zirconia (scandia, ceria-stabilized zirconia) containing scandium in a proportion of 17.0 to 25.0 mol% and cerium in a proportion of 0.5 to 2.5 mol% in terms of number of atoms, and yttrium in terms of number of atoms. Zirconia (yttria-stabilized zirconia) containing 0 to 28.0 mol%, or zirconia (ytterbia-stabilized zirconia) containing ytterbium in an amount of 6.0 to 35.5 mol% in terms of the number of atoms is mentioned. It is done.

As a more preferable embodiment, zirconia containing scandium in a ratio of 13.0 to 25.0 mol% in terms of the number of atoms with respect to 100 mol% of the zirconium constituting the stabilized zirconia, scandium in terms of the number of atoms is included. Zirconia (scandia, ceria-stabilized zirconia) containing 17.0 to 24.0 mol% and cerium in a proportion of 0.5 to 2.0 mol%, 12.0 to 28.0 mol% in terms of raw materials Zirconia containing zirconia and ytterbium in a proportion of 12.0 to 28.0 mol% in terms of the number of atoms is preferable.
In particular, zirconia containing ytterbium in an amount of 12.0 to 28.0 mol% in terms of the number of atoms is preferable with respect to 100 mol% of zirconium constituting the stabilized zirconia.

  The electrolyte layers 16 and 26 preferably contain 50% by mass or more of zirconia-based oxides (preferably stabilized zirconia), more preferably contain 80% by mass or more, and contain 85% by mass or more. It is more preferable that it is 90% by mass or more.

  The film thickness of the electrolyte layers 16 and 26 is, for example, 1 to 1000 μm, preferably 1 to 500 μm, and more preferably 1 to 300 μm. When used for an electrode-supported cell or a metal-supported cell, the thickness is preferably 1 to 50 μm, more preferably 1 μm or more and less than 30 μm, further preferably 1 to 20 μm. By reducing the film thickness, the oxide ion conductivity can be further improved.

1-2 Fuel Electrode The fuel electrodes 18 and 28 are one or more kinds of metals, such as nickel, cobalt, copper, iron, and ruthenium, that have fuel electrode catalytic activity in electrochemical cells and metal oxides that are precursors thereof. If it is a layer containing, there will be no restriction | limiting in particular. The metal oxide which is a precursor of the metal having the fuel electrode catalytic activity is reduced in the operating atmosphere of the electrochemical cell, and the layer becomes a layer containing the metal having the fuel electrode catalytic activity. The fuel electrode further includes the above-mentioned zirconia-based oxide (preferably stabilized zirconia), ceria-based oxide (preferably doped ceria), oxide ion conductive metal oxides such as stabilized bismuth and lanthanum gallate, and oxide ions. A layer in which one or more kinds of mixed conductive metal oxides with electrons are mixed is preferable.

As the fuel electrodes 18 and 28, a layer in which Ni or NiO and a zirconia-based oxide are mixed; or a layer in which Ni or NiO and a ceria-based oxide are mixed is more preferable. The volume ratio of Ni or NiO to oxide (zirconia-based oxide or ceria-based oxide) is preferably NiO / oxide = 40/60 to 70/30 in terms of NiO for Ni or NiO. These volume ratios can be converted into weight ratios from the specific gravity of NiO and the bulk of each oxide. The fuel electrode preferably contains a compound common to the electrolyte layer that is in direct contact therewith.
The fuel electrodes 18 and 28 are preferably layers having pores under operating conditions from the viewpoint of high fuel gas permeability. The film thickness is preferably 3 to 30 μm, and more preferably 4 to 25 μm.

1-3 Air Electrode The composition of the air electrodes 12 and 22 is not particularly limited as long as it is a layer containing a metal oxide having an air electrode catalytic activity during the reaction of the electrochemical cell. The material constituting the air electrode is preferably a conductive material, more preferably an electronic conductive material, and particularly preferably a material having mixed conductivity (ionic conductivity, electronic conductivity). Specifically, various composite oxides containing at least one of La, Pr, Sm, Sr, Ba, Co, Fe, Mn, Ni, etc. (for example, lanthanum manganite, lanthanum in which strontium is dissolved) Ferrite, lanthanum cobalt ferrite, lanthanum cobaltite, lanthanum strontium cobaltite, etc.). The air electrode is further mixed with one or more of the above-mentioned stabilized zirconia, doped ceria, oxide ion conductive metal oxides such as stabilized bismuth and lanthanum gallate, and mixed conductive metal oxides of oxide ions and electrons. However, it may be omitted when a material having mixed conductivity is used for the air electrode and the oxide ion conductivity is sufficient.

  Among the mixed conductive materials, perovskite type oxides are preferable, and composite oxides containing Sr and Co are more preferable. Fe content is preferably small, for example, Fe / (Co + Fe) (atomic ratio) is preferably less than 0.7, more preferably less than 0.5, even more preferably less than 0.3, and particularly preferably less than 0.1. Preferably, it is substantially 0. By reducing the Fe content, the air electrode catalytic activity and sinterability can be improved.

The film thickness of the air electrodes 12 and 22 is 6 μm or more, more preferably 8 μm or more, and further preferably 10 μm or more. Moreover, although an upper limit is not specifically limited, 100 micrometers or less are preferable and 40 micrometers or less are more preferable. The air electrode may preferably be composed of two or more layers. The first layer and the second layer preferably include conductive materials having the same composition, and more preferably the first layer and the second layer have the same composition.
In addition, it is preferable that the shape and size of the particles and pores constituted by the first layer and the second layer are different. The first layer refers to a layer adjacent to the electrolyte layer or the barrier layer, and the second layer is a layer adjacent to the surface of the first layer where the electrolyte layer and / or the barrier layer is not formed.

1-3-1 Ratio between the predetermined areas of the average value of the area circle equivalent diameter and the average value of the circumference equivalent circle diameter in each predetermined area of the air electrode component particles (LS1 / LS2)
The air electrode for an electrochemical cell according to the present invention is an air electrode for an electrochemical cell in which a fuel electrode, an electrolyte layer, and an air electrode are arranged in this order, and has a film thickness of 6 μm or more. The ratio LS1 / LS2 of LS1 and LS2 shown below measured with a microscope is less than 1.0.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the electrolyte layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode components in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the electrolyte layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of particle 2) / (Average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

Moreover, the electrochemical cell of this invention arrange | positions a fuel electrode, an electrolyte layer, and an air electrode in this order. The air electrode has a film thickness of 6 μm or more, and has a ratio LS1 / LS2 of LS1 and LS2 shown below of less than 1.0 as measured with a scanning electron microscope in the cross section.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the electrolyte layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode component particles in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the electrolyte layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of 2) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

The air electrode for an electrochemical cell of the present invention is also an air electrode for an electrochemical cell in which a fuel electrode, an electrolyte layer, a barrier layer, and an air electrode are arranged in this order, and has a film thickness of 6 μm or more and a cross section. The ratio LS1 / LS2 of LS1 and LS2 shown below measured with a scanning electron microscope is less than 1.0.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the barrier layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode components in a range within W2 in a direction perpendicular to the surface from the surface of the air electrode where the barrier layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of particle 2) / (Average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

Moreover, the electrochemical cell of this invention arrange | positions a fuel electrode, an electrolyte layer, a barrier layer, and an air electrode in this order. The air electrode has a film thickness of 6 μm or more, and has a ratio LS1 / LS2 of LS1 and LS2 shown below of less than 1.0 as measured with a scanning electron microscope in the cross section.
LS1: (a plurality of air electrode component particles) in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the barrier layer in a direction in which the barrier layer of the air electrode is not formed. 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: (a plurality of air electrode component particles in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the barrier layer is not formed to the interface between the air electrode and the barrier layer) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
However, the W1 and the W2 may be the same or different and each is 3 μm or more, and the range for obtaining the LS1 and the LS2 is set so as not to overlap.

  The air electrode component particles 1 and 2 are preferably particles containing Co, more preferably contain Sr, and more preferably contain the same element in addition to Co and Sr. Particularly preferred are perovskite complex oxide particles. Mole% of Co in metal element other than oxygen contained in air electrode component particle 1: M1 and Mole% of Co in metal element other than oxygen contained in air electrode component particle 2: M2 Ratio: M1 / M2 is preferably 1 or more, more preferably 1 or more and 5 or less, and even more preferably 1.

  In the present invention, the area equivalent circle diameter of the air electrode component particles indicates the diameter of a circle having a circular area equal to the area, obtained from the area of the air electrode component particles, and the circumference equivalent circle diameter of the air electrode component particles. Indicates the diameter of a circle having a circumference equal to the interface length, obtained from the interface length of the air electrode component particles.

Observation of the air electrode component particles in the cross section of the air electrode by a scanning electron microscope is preferably measured so that the number of air electrode component particles observed is preferably 80 or more, more preferably 100 or more, If the number of measured air electrode component particles is less than the above number, increase the number of cross-sectional observation images to be acquired or increase the magnification to 8000 times so that the number of measured air electrode component particles is equal to or greater than the above number. Is preferred.
Observation of the cross section of the air electrode with a scanning electron microscope is preferably performed with a secondary electron image. If it is a secondary electron image, the image which can be acquired becomes clear rather than a reflected electron image, Therefore It becomes easy to distinguish each particle | grain. However, as long as particles can be identified, a reflected electron image may be used instead of a secondary electron image. The number of measured air electrode component particles is the same for the following.

Referring to FIG. 3, the air electrodes 12, 22 are cross-sectionally observed by a scanning electron microscope in a range 1 (from the interface 8 between the air electrodes 12, 22 and the electrolyte layer 16 or the barrier layer 24. In the direction of the air electrode 12, 22 where the electrolyte layer 16 or the barrier layer 24 is not formed, in the direction indicated by the black arrow S, the range perpendicular to the interface 8 and within W1) LS1 and range 2 (from the surface 9 of the air electrodes 12, 22 where the electrolyte layer 16 or barrier layer 24 is not formed to the interface 8 between the air electrodes 12, 22 and the electrolyte layer 16 or barrier layer 24) The ratio LS1 / LS2 with respect to LS2 in the direction indicated by the black arrow T in the direction perpendicular to the surface 9 and within W2) is less than 1.0. The ratio LS1 / LS2 is preferably 0.3 or more and less than 1.0, more preferably 0.4 or more and 0.95 or less, and further preferably 0.5 or more and 0.90 or less. .
When the ratio LS1 / LS2 at the air electrode is in the above range, the air electrode component particles 1 in the range 1 on the interface side with the electrode have a more complicated shape than the air electrode component particles 2 in the range 2. Therefore, since the interface between the electrode particles and the pores increases, the electrode activity is excellent and the conduction between the electrode particles is less likely to be impaired. When used as an air electrode in an electrochemical cell, current-voltage characteristics An electrochemical cell excellent in the above can be obtained.

W1 and W2 are each independently 3 μm or more, preferably 4 μm or more, and more preferably 5 μm or more. More preferably, both W1 and W2 are 5 μm.
That is, the range 1 is a surface where the electrolyte layer 16 or the barrier layer 24 of the air electrodes 12 and 22 is not formed from the interface 8 between the air electrodes 12 and 22 and the electrolyte layer 16 or the barrier layer 24. 9 toward the position indicated by the black arrow S in the direction indicated by a black arrow S, and is a range up to 3 μm or more in the direction perpendicular to the interface 8, preferably within 3 μm, and within 4 μm. More preferably, the range is within 5 μm.
Similarly, the range 2 includes the air electrodes 12 and 22 and the electrolyte layer 16 or the barrier layer 24 from the surface 9 of the air electrodes 12 and 22 where the electrolyte layer 16 or the barrier layer 24 is not formed. It is a range up to a position 3 μm or more away from the surface 9 in the direction indicated by the black arrow T toward the interface 8, preferably within 3 μm, more preferably within 4 μm. Preferably, the range is within 5 μm.
In particular, in the range 1, the electrolyte layer 16 or the barrier layer 24 of the air electrodes 12, 22 is not formed from the interface 8 between the air electrodes 12, 22 and the electrolyte layer 16 or the barrier layer 24. The surface 9 is preferably in a range up to a position 3 μm away from the interface 8 in the direction indicated by the black arrow S, and the range 2 is the electrolyte layer of the air electrodes 12 and 22. 16 or the surface 9 on which the barrier layer 24 is not formed, to the interface 8 between the air electrodes 12 and 22 and the electrolyte layer 16 or the barrier layer 24, perpendicular to the surface 9 in the direction indicated by the black arrow T. A range up to a position 3 μm away in the direction is preferable.

The interface 8 between the air electrodes 12 and 22 and the electrolyte layer 16 or the barrier layer 24 is, for example, a place where the air electrode component is most penetrating into the electrolyte layer 16 or the barrier layer 24 and 2 μm or more from the place. It can be determined from a straight line connecting two places where the air electrode component enters the electrolyte layer 16 or the barrier layer 24 apart.
The ranges 1 and 2 include the vicinity 7 of the central portion of the air electrodes 12 and 22 in the direction parallel to the interface 8 for the purpose of measuring a representative portion of the entire air electrode, and the electrolyte layer 16 or the barrier layer. 24 is preferably a region that is separated by a distance L or more from the end in the interface direction with respect to 24 toward the center. L is preferably 0.3 mm or more, more preferably 0.8 mm or more, and further preferably 1.0 mm or more. The two Ls at both ends may be the same value or different values. It is preferable to select rectangular areas 3 and 4 to be described later within the above area (see FIGS. 4 and 5).

  In order to set the ratio LS1 / LS2 in the above range, a layer formed on the electrolyte layer side (on the surface of the electrolyte layer or the surface of the barrier layer) among the plurality of precursor layers constituting the air electrode is formed. As a slurry used in the above, “a raw material powder such as a solid obtained from a mixed solution containing a predetermined metal is further molded and fired to prepare a fired molded body (pellet), which is obtained by crushing It is preferable to use a slurry containing fine particles and coarse particles. Preferably, as a slurry used for forming a precursor layer formed on the precursor layer formed from the slurry, “a raw material powder such as a solid obtained from a mixed solution containing a predetermined metal is further formed. Then, it is preferably formed using a slurry containing coarse particles obtained by firing and preparing a fired molded body (pellet) and pulverizing it.

1-3-2 Ratio of Fluctuation Coefficient of Area Circle Equivalent Diameter of Air Electrode Component Particles in Predetermined Area Preferably, in the air electrode for electrochemical cells of the present invention, the area circle of air electrode component particles measured in the above range 1 The ratio CVLS1 / CVLS2 of the variation coefficient CVLS1 of the equivalent diameter and the variation coefficient CVLS2 of the area circle equivalent diameter of the air electrode component particles measured in the range 2 is 0.3 or more and 0.9 or less, 0.5 More preferably, it is 0.8 or less. Thereby, while exhibiting the air electrode catalytic activity to the maximum, the effect of good electronic conductivity is obtained, and when used in an electrochemical cell, the electrochemical cell is more excellent in current-voltage characteristics.

1-3-3 The average value D _L ratio D _L / D _S of the circumference equivalent circle diameter of the pores to the average value D _S of the area equivalent circle diameter of the pores
Preferably, an electrochemical cell for air electrode of the present invention is observed with a scanning electron microscope in the range 1, to the average value D _S of the area circle equivalent diameters of the plurality of pores, the peripheral oval of the plurality of pores The ratio D _L / D _S of the average value D _L of equivalent diameters is 1.75 or more, more preferably 1.8 or more.
In the present invention, the area equivalent circle diameter indicates the diameter of a circle having a circular area equal to the area obtained from the pore area, and the circumference equivalent circle diameter indicates the interface length between the pore and each air electrode component in contact with the pore. The diameter of a circle having a circumference equal to the interface length obtained from the above is shown. When the D _{L /} D _S at the air electrode within the above range, since the shape of the pores have a complex shape, without compromising the continuity between the electrode grains, to the reaction region, good gas diffusibility Therefore, when used as an air electrode in an electrochemical cell, the electrochemical cell is more excellent in current-voltage characteristics.

  Observation of the pores in the cross section of the air electrode with a scanning electron microscope is preferably performed so that the number of observed pores is preferably 80 or more, more preferably 100 or more. In the case where it is less than the above, it is preferable to increase the number of cross-sectional observation images to be acquired or to increase the number of pores to be equal to or greater than the above number by increasing the magnification to 8000 times. The number of pores is the same in the following.

1-3-4 Distribution of Pore Area Circle Equivalent Diameter Preferably, in the air electrode for an electrochemical cell of the present invention, the area circle equivalent diameter of the plurality of pores observed in a scanning electron microscope in the above range 1 is set. In the case of a histogram, it has two or more peaks. As a result, the effect of being able to supply oxygen without being deficient even in a region close to the electrolyte layer (or barrier layer) in the air electrode while obtaining the maximum air electrode catalytic activity is obtained. It is done.
In obtaining the number of peaks in the area circle equivalent diameter distribution of the pores, for the class and class interval, the maximum value of the area circle equivalent diameter: Pmax, the minimum value: the difference between Pmin: ΔP = Pmax−Pmin, and ΔP is set to 20. Divide by a close number and determine the value by reference [Applied Statistics Handbook: Applied Statistics Handbook Editorial Committee (Representative: Chuichi Okuno), Yokendo Co., Ltd., 1978, 1st Edition, p12-15 (Chapter 1) Distribution and testing / estimation, 1.1 data summary, 1.1.1 frequency distribution)].

1-3-5 Pore Area Ratio of Peak Numbers in Distribution of Equivalent Circle Diameter Preferably, in the air electrode for an electrochemical cell of the present invention, the area of the plurality of pores observed with a scanning electron microscope in the above range 1 The number of peaks Pb1 obtained when the equivalent circle diameter is made into a histogram and the number of peaks Pb2 obtained when the area equivalent circle diameters of a plurality of pores are made into a histogram in the above range 2 are observed. The ratio Pb1 / Pb2 is greater than 1. More preferably, it is 2 or more, More preferably, it is 3 or more.
As a result, oxygen can be supplied without being deficient even in a region near the electrolyte layer (or barrier layer) in the air electrode while maximizing the air electrode catalytic activity. When used in an electrochemical cell, the effect of excellent current-voltage characteristics can be obtained.

1-3-6 Total value of interface length between pores and air electrode component particles in a predetermined region Preferably, the air electrode has a cross section from the interface between the air electrode and the electrolyte layer or the barrier layer. In a 2 μm × 5 μm rectangular region having a width of 5 μm between a position 1 μm away from a position perpendicular to the interface and a position 3 μm away in a direction in which the electrolyte layer and / or barrier layer of the air electrode is not formed, The total value of the interface length between the pores and the air electrode component particles measured with a scanning electron microscope is 18 μm or more and 80 μm or less.
When the total value of the above interface lengths in the cross section of the air electrode is in such a range, when used in an electrochemical cell, the electrochemical cell is more excellent in current-voltage characteristics.

If it demonstrates using FIG. 4, in the cross section of the air electrodes 12 and 22, about 10 visual fields will be observed with an electron microscope so that it may not mutually overlap, and in these visual fields, several rectangular area | region 3 (above-mentioned) A black arrow S extends from the interface 8 between the air electrodes 12 and 22 and the electrolyte layer 16 or the barrier layer 24 to the surface 9 of the air electrodes 12 and 22 where the electrolyte layer 16 or the barrier layer 24 is not formed. In the direction shown, a plurality of 2 μm × 5 μm rectangular regions with a width of 5 μm between a position 1 μm apart and a position 3 μm apart in the direction perpendicular to the interface 8, for example, at a plurality of locations ( Preferably, 10 or more locations are selected, and a plurality of total value data of interface lengths between pores and air electrode component particles in each rectangular region 3 are acquired. The average value of a plurality of (preferably 10 or more) total value data obtained in this way is defined as the total value (t1) of the interface length between the pores and the air electrode component particles. When measuring at 10 or more locations, the width of the air electrode is preferably 500 μm or more.
In the air electrode for electrochemical cells of the present invention, the total value t1 of the interface length between the pores and the air electrode component particles is preferably 18 μm or more and 80 μm or less. The total interface length t1 in the rectangular region 3 is more preferably 20 μm or more and 70 μm or less, and further preferably 25 μm or more and 60 μm or less.

1-3-7 Ratio of the total value of the interface lengths of pores and air electrode component particles in a predetermined region Preferably, in the air electrode for an electrochemical cell of the present invention, the thickness is 6 μm or more and the width is 500 μm or more, The total length t1 of the interface length between the pores and the air electrode component particles, and the rectangular region 4 of the air electrodes 12 and 22 (from the surface 9 where the electrolyte layer 16 or the barrier layer 24 is not formed) , 22 in the direction indicated by the black arrow T in the direction of the interface 8 between the electrolyte layer 16 or the barrier layer 24 and a width of 5 μm between a position 1 μm away from the surface 9 and a position 3 μm away from the surface 9. The ratio t1 / t2 of the total value t2 of the interface length between the pores and the air electrode component particles in a region of 2 μm × 5 μm (see FIG. 5) is 1.2 or more. When t1 / t2 is set in this way, an effect is obtained that oxygen (in the air) is supplied without deficiency to a region near the electrolyte layer (or barrier layer) in the air electrode.
Here, similarly to t1, t2 is selected so as not to overlap each other in a plurality of, for example, about 10 visual fields that are selected so as not to overlap each other. The plurality of rectangular regions 4 are observed, for example, at a plurality of locations (preferably 10 or more), and the interface length total value data is obtained for each of the rectangular regions 4, and the interface length total value data is obtained. The average value obtained from

1-3-8 Standard Deviation of Total Value Data of Interface Length between Pore and Air Electrode Component Particles in Predetermined Area Preferably, in the electrochemical cell air electrode of the present invention, a plurality of rectangular regions 3 from which t1 is obtained The standard deviation d1 of the total value data of the interface lengths between the pores and the individual air electrode component particles is 8.0 μm or less. Furthermore, the standard deviation d1 is preferably 1.7 μm or more. More preferably, they are 1.8 micrometers or more and 7.0 micrometers or less, and it is still more preferable that they are 2.0 micrometers or more and 5.0 micrometers or less. If the standard deviation is within the above range, oxygen is more easily supplied to the region near the electrolyte layer (or barrier layer) in the air electrode while maximizing the air electrode catalytic activity. It becomes a highly active air electrode.

1-3-9 Ratio of standard deviation of total value data of interface length between pores and air electrode component particles in a predetermined region Preferably, in the air electrode for an electrochemical cell of the present invention, a plurality of rectangles obtained from the above t2 The interface between the pores and the individual air electrode component particles in the plurality of rectangular regions 3 for which the above-mentioned t1 is obtained with respect to the standard deviation d2 of the total value data of the interface length between the pores and the individual air electrode component particles in the region 4 The ratio d1 / d2 of the standard deviation d1 of the total length data is 1.1 or more. More preferably, it is 1.2 or more, and it is further more preferable that it is 1.3 or more. When d1 / d2 is set in this way, the supply and reaction of oxygen is more uniform and more uniform in the entire area of the air electrode, so that it is deactivated under the influence of local heat. Can be more effectively prevented.

1-3-10 Coefficient of variation of total value data of interface length between pores and air electrode component particles in a predetermined region Preferably, in the air electrode for an electrochemical cell of the present invention, a plurality of rectangular regions 3 for which the above t1 is obtained The variation coefficient cv1 of the total value data of the interface lengths of the pores and the individual air electrode component particles is 11% to 30%, more preferably 11.5% to 25%, More preferably, it is 12% or more and 20% or less. Here, the coefficient of variation is a value obtained by dividing the standard deviation by the average value. If the standard deviation is within the above range when the coefficient of variation is set in this way, oxygen is insufficient to the region close to the electrolyte layer (or barrier layer) in the air electrode while maximizing the air electrode catalytic activity. Therefore, the air electrode is highly active.

1-3-11 Ratio of coefficient of variation of total value data of interface length between pores and air electrode component particles in a predetermined region Preferably, in the air electrode for an electrochemical cell of the present invention, a plurality of rectangles obtained from the above t2 The interface between the pores and the individual air electrode component particles in the plurality of rectangular regions 3 where the above t1 is obtained with respect to the coefficient of variation cv2 of the total value data of the interface length between the pores and the individual air electrode component particles in the region 4 The ratio cv1 / cv2 of the coefficient of variation cv1 of the total length data is 1.1 or more and 5.0 or less, more preferably 1.2 or more and 4.0 or less, and 1.3 or more and 3.0 or less. More preferably. When cv1 / cv2 is set in this way, the reaction proceeds more uniformly and more uniformly in the entire area of the air electrode, so it is more effective to deactivate due to the influence of local heat. Can be prevented.

1-3-12 Distribution of Interface Length between Pore and Air Electrode Component Particles in Predetermined Area Preferably, in the air electrode for an electrochemical cell of the present invention, the pores and the individual in the plurality of rectangular areas 3 for which t1 is obtained When the interface length with the air electrode component particles is a histogram, it has two or more peaks. More preferably, it is 3 or more. Moreover, although an upper limit is not specifically limited, 6 or less is preferable and 5 or less is more preferable.
In such a case, oxygen can be supplied without being deficient even in a region near the electrolyte layer (or barrier layer) in the air electrode while maximizing the air electrode catalytic activity. It becomes a more highly active air electrode.

  In determining the number of peaks in the above-mentioned interface length distribution, for the class and class interval, the maximum value of interface length: Pmax, the minimum value: difference of Pmin: ΔP = Pmax−Pmin is determined, and ΔP is a number close to 20. [Applied Statistics Handbook: Editorial Committee for Applied Statistics Handbook (Representative: Chuichi Okuno) edited by Yokendo Co., Ltd., 1978, 1st Edition, p12-15 (Chapter 1 Distribution and See Test / Estimation, 1.1 Data Summary, 1.1.1 Frequency Distribution)].

1-3-13 Ratio of number of peaks in distribution of interface length between pores and air electrode components in a predetermined region Preferably, in the air electrode for an electrochemical cell of the present invention, in the plurality of rectangular regions 3 for which the above t1 is obtained The peak number Pa1 when the interface length between the pores and the individual air electrode component particles is made into a histogram, and the peak when the total value data of each interface length in the plurality of rectangular regions 4 obtained from the above t2 is made into a histogram The ratio Pa1 / Pa2 with a few Pa2 is larger than 1. More preferably, it is 2 or more, More preferably, it is 3 or more. When Pa1 / Pa2 is set in this way, oxygen can be supplied without being deficient even in a region near the electrolyte layer (or barrier layer) in the air electrode while maximizing the air electrode catalytic activity. Therefore, the air electrode is more highly active.

1-4 Barrier Layer The electrochemical cell of the present invention is easy to produce an insulating material because the air electrode and the electrolyte layer are in direct contact with each other during the production or reaction of the electrochemical cell, and suppresses the generation of this insulating material. For this purpose, a barrier layer may be provided. The barrier layer is preferably disposed between the electrolyte layer and at least one of the fuel electrode and the air electrode. In the electrochemical cell 20 as one embodiment of the electrochemical cell of the present invention, it is disposed between the electrolyte layer 26 and the air electrode 22. When the generation of the insulating layer is sufficiently suppressed, the barrier layer may be omitted as in the electrochemical cell 10 as one embodiment of the electrochemical cell of the present invention.

The component constituting the barrier layer is not particularly limited, but is an oxide ion conductive material, and oxygen ion conductivity between the barrier layer and the air electrode or the electrolyte layer at the time of production or reaction of the electrochemical cell. It is preferable that it is a component which is hard to produce | generate the component which inhibits.
Although it does not restrict | limit especially as a component which comprises the said barrier layer, It is preferable to contain a ceria-type oxide as a main component, Sc, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, It is preferable to contain ceria containing rare earth elements such as Er and Yb as a main component, and it is more preferable that the ceria constitutes a solid solution with these elements. One or more of the rare earth elements may be contained. The inclusion of the ceria-based oxide as a main component means that the ceria-based oxide is contained in an amount of 50% by mass or more, preferably 60% by mass or more, and 70% by mass or more in 100% by mass of the barrier layer. More preferably. In the barrier layer, the rare earth element / Ce molar ratio is preferably 0.01 to 0.40, and more preferably 0.05 to 0.30.

  As the rare earth element, Y, Gd, Sm, and Yb are more preferable, and Gd and Sm are more preferable. In addition to Gd and Sm, it is particularly preferable that Yb is contained as the second rare earth element.

  The barrier layer preferably contains the rare earth element in a total amount of 5 to 50 mol%, more preferably 7 to 40 mol%, more preferably 8 to 35, based on 100 mol% of the cerium element. It is more preferable that it contains mol%.

  Although the thickness of a barrier layer is not specifically limited, For example, it is preferable that it is 0.2-20 micrometers.

1-5 Support The electrochemical cell preferably having a support in the present invention includes a form using a fuel electrode as a support (fuel electrode support type cell) and a form using an electrolyte layer as a support (solid electrolyte support type cell). ), A form using an air electrode as a support (air electrode support type cell), or a form using a support substrate composed of a metal partition wall and having a plurality of through holes (metal support cell), and a ceramic material as a base material And the like in which a conductive material is mixed or modified as a support.
Among these, a preferable form of the support is a fuel electrode support substrate. In general, a support containing stabilized zirconia and a conductive component can be preferably used. The ratio of the stabilized zirconia and the conductive component in the fuel electrode support substrate may be appropriately adjusted. For example, the mass ratio of the conductive component to the total of the stabilized zirconia and the conductive component is about 40% by mass to 80% by mass. It can be.

The stabilized zirconia constituting the fuel electrode support substrate has a crystal structure formed by dissolving at least one element selected from the group consisting of yttrium, scandium, ytterbium, calcium, magnesium and lanthanum (also referred to as a stabilizing element). Is preferably stabilized zirconia (stabilized zirconia).
The content ratio of elements such as yttrium in the stabilized zirconia, preferably the solid solution amount is 4.0 mol% or more and 35.5 mol% in terms of the number of atoms with respect to 100 mol% of zirconium contained in the stabilized zirconia. The following is preferable. When the ratio is 4.0 mol% or more, effects such as a crystal phase stabilization effect can be obtained more reliably. On the other hand, if the proportion is excessive, the strength may be lowered. Therefore, the proportion is preferably 35.5 mol% or less. As the said ratio, 5.0 mol% or more and 27.0 mol% or less are more preferable.

  The stabilized zirconia used for the electrolyte layer, the fuel electrode, and the fuel electrode support substrate may further contain other metal elements in addition to particularly preferable stabilizing elements such as yttrium, scandium, and ytterbium. Additional metal elements may further improve the characteristics such as oxygen ion conductivity, strength and durability. Examples of such metal elements include alkaline earth metal elements such as Mg, Ca, Sr, and Ba; rare earth elements such as Ce, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; Al Group 13 elements such as In, In; Group 14 elements such as Si, Ge and Sn; Group 15 elements such as Bi and Sb; Group 4 elements such as Ti and Hf; Group 5 elements such as Nb and Ta And so on. Among these, lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), aluminum (Al), and titanium (Ti) are selected. One or more metal elements are particularly preferred. Any one of these other metal elements may be used, or a combination of two or more thereof may be used. Further, as a ratio of these other metal elements, the total content thereof is 0.05 mol% or more and 5.0 mol% or less with respect to 100 mol% of zirconium contained in the stabilized zirconia in terms of the number of atoms. preferable.

  The fuel electrode support substrate has a role of supplying fuel gas such as hydrogen to the fuel electrode so as not to be non-uniform, transferring electrons generated by the reaction to the interconnector, and supporting the electrolyte layer and the cathode layer. Therefore, it is preferable that the fuel electrode support substrate includes a conductive component that exhibits conductivity by being reduced under reducing conditions during power generation, in addition to stabilized zirconia. As such a conductive component, nickel oxide, iron oxide, copper oxide or the like can be used, and nickel oxide is the most common.

  Although the thickness of the said fuel electrode support substrate is not specifically limited, For example, 100 micrometers or more are preferable, 120 micrometers or more are more preferable, and 150 micrometers or more are further more preferable. The thickness of the fuel electrode support substrate is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. If the thickness of the fuel electrode support substrate is within the above range, the mechanical strength and gas permeability of the fuel electrode support substrate can be easily balanced.

2. Method for producing electrochemical cell In the electrochemical cell of the present invention, a method for producing a fuel electrode, an electrolyte layer, an air electrode in this order, or a fuel electrode, an electrolyte layer, a barrier layer, and an air electrode in this order. There is no particular limitation, and a known method can be used.

Preferably, the method (A) for producing an electrochemical cell of the present invention comprises:
(I) forming an electrode precursor layer on the support or the support precursor layer;
(Ii) forming an electrolyte layer precursor layer on the electrode precursor layer;
(Iii) forming a barrier layer precursor layer on the electrolyte layer precursor layer formed in the above step;
(Iv) a firing step of co-firing the support or support precursor layer, the electrode precursor layer, the electrolyte layer precursor layer and the barrier layer precursor layer;
(V) forming another electrode precursor layer on the barrier layer formed in the above step;
(Vi) A firing step of co-firing the support, the electrode, the electrolyte layer, the barrier layer, and the other electrode precursor layer may be included.

  The electrode and the other electrode may be either a fuel electrode or an air electrode, respectively, but the electrode is preferably a fuel electrode and the other electrode is preferably an air electrode. The other electrode precursor layer as the air electrode precursor layer may be formed by recoating two or more types of air electrode precursor layer pastes using raw material particles having the same composition but different firing temperatures. Alternatively, two or more types of air electrode precursor layer pastes using raw material particles having the same composition but different particle diameters may be formed by recoating. This also applies to the following manufacturing method.

  In the above manufacturing method, in the electrochemical cell in which the fuel electrode, the electrolyte layer, and the air electrode of the present invention are arranged in this order, the formation of the barrier layer precursor layer and the barrier layer between the electrolyte layer and the air electrode Is omitted. This also applies to the following manufacturing method.

  The electrochemical cell production method (A) can be preferably employed as a method for producing an electrochemical cell having a support.

Also preferably, the electrochemical cell production method (B) of the present invention comprises:
(1) forming an electrolyte layer precursor layer on the electrode or electrode precursor layer;
(2) a firing step of co-firing the electrode or electrode precursor layer and the electrolyte layer precursor layer;
(3) forming a barrier layer precursor layer on the electrolyte layer formed in the above step;
(4) A step of forming another electrode precursor layer on the barrier layer precursor layer formed in the above step;
(5) includes a firing step of co-firing the electrode, the electrolyte layer, the barrier layer precursor layer, and the other electrode precursor layer, or
(11) forming an electrolyte layer precursor layer on the electrode or electrode precursor layer;
(12) forming a barrier layer precursor layer on the electrolyte layer precursor layer formed in the above step;
(13) A step of forming another electrode precursor layer on the barrier layer precursor layer formed in the above step;
(14) A firing step of co-firing the electrode or electrode precursor layer, the electrolyte layer precursor layer, the barrier layer precursor layer, and the other electrode precursor layer may be included.

The electrode precursor layer, the electrolyte layer precursor layer, and the barrier layer precursor layer are fired between the step (12) and the step (13), and the electrode precursor layer and the electrolyte layer precursor are fired. The layer and the barrier layer precursor layer may be formed as an electrode, an electrolyte layer and a barrier layer before the step (13).
The firing of the electrode precursor layer, the electrolyte layer precursor layer, and the barrier layer precursor layer is preferably performed between step (12) and step (13).

  The above electrochemical cell production method (B) is a method for producing an electrode-supported cell (fuel electrode-supported cell, air electrode-supported cell) using a fuel electrode or an air electrode as a support, and a method for producing a metal support cell. Can be preferably employed.

Also preferably, the electrochemical cell production method (C) of the present invention comprises:
(20) A step of preparing an electrolyte layer precursor layer by using a doctor blade method or the like for an electrolyte slurry;
(21) a step of firing an electrolyte layer precursor layer to produce an electrolyte layer;
(22) forming an electrode precursor layer on the electrolyte layer;
(23) forming a barrier layer precursor layer on the surface of the electrolyte layer opposite to the surface on which the electrode precursor layer is formed;
(24) forming another electrode precursor layer on the surface of the barrier layer precursor layer;
(25) A step of firing the electrolyte layer, the electrode precursor layer, the barrier layer precursor layer, and the other electrode precursor layer may be included.

The electrode precursor layer and the barrier layer precursor layer are baked between the step (23) and the step (24), and the electrode precursor layer and the barrier layer precursor layer are converted into the step (24). Before the step, an electrode and a barrier layer may be provided.
The firing of the electrode precursor layer and the barrier layer precursor layer is preferably performed between step (23) and step (24).

Also preferably, the electrochemical cell production method (D) of the present invention comprises:
(31) a step of producing an electrolyte layer precursor layer;
(32) forming an electrode precursor layer on the electrolyte layer precursor layer;
(33) forming a barrier layer precursor layer on the surface of the electrolyte layer precursor layer opposite to the surface on which the electrode precursor layer is formed;
(34) forming another electrode precursor layer on the barrier layer precursor layer;
(35) A step of firing the electrolyte layer precursor layer, the electrode precursor layer, the barrier layer precursor layer, and the other electrode precursor layer may be included.

The electrolyte layer precursor layer, the electrode precursor layer, and the barrier layer precursor layer are fired between the step (33) and the step (34), and the electrolyte layer precursor layer and the electrode precursor are fired. The layer and the barrier layer precursor layer may be formed as an electrolyte layer, an electrode, and a barrier layer before the step (34).
The firing of the electrolyte layer precursor layer, the electrode precursor layer, and the barrier layer precursor layer is preferably performed between step (33) and step (34).

  The above electrochemical cell production methods (C) and (D) can be particularly preferably employed as a method for producing a solid electrolyte-supported cell.

As a method for forming each precursor layer (green layer) described above, each raw material powder is mixed with a known binder and / or solvent (dispersion medium) and, if necessary, a dispersing agent, a plasticizer, etc. By applying these coating inks on a smooth substrate such as a polyester sheet by a doctor blade method, a calender roll method, an extrusion method, etc., and drying to volatilize and remove the dispersion medium. A sheet (green sheet) may be formed. Alternatively, the coating ink may be formed by applying the coating ink by a coating method such as blade coating or slit die coating, screen printing, or the like, and drying to volatilize and remove the dispersion medium.
Each of the above layers may be formed by using a powder film forming method such as a thermal spraying method or a powder jet deposition method. In this case, the precursor layer forming step, the degreasing step and the firing step can be omitted.

  In the production of the air electrode for an electrochemical cell of the present invention, the metal oxide powder material described in the above 1-3 air electrodes 12 and 22 can be used as a raw material. The above metal oxide powder material may be used by mixing a commercially available metal oxide powder so as to have a predetermined composition, or manufactured by drying and firing a solution containing a predetermined metal. May be. Especially, in the air electrode for electrochemical cells of the present invention, in order to ensure that the ratio LS1 / LS2 of LS1 and LS2 is less than 1.0, it is obtained from a mixed solution containing a predetermined metal. It is preferable to produce the obtained solid by drying and baking by the following predetermined method.

  Specifically, when forming the air electrode of the present invention, it is preferable that a plurality of precursor layers are applied and fired even if the air electrode is a single layer. As a slurry used for forming a layer formed on the electrolyte layer side (on the surface of the electrolyte layer or the surface of the barrier layer) among the plurality of precursor layers constituting the air electrode, “from a mixed solution containing a predetermined metal” The obtained raw material powder such as a solid material is further shaped and fired to prepare a fired molded body (pellet), which is obtained by crushing this, and a slurry containing fine particles and coarse particles is used. preferable. Preferably, as a slurry used for forming a precursor layer formed on the precursor layer formed from the slurry, “a raw material powder such as a solid obtained from a mixed solution containing a predetermined metal is further formed. Then, it is preferably formed using a slurry containing coarse particles obtained by firing and preparing a fired molded body (pellet) and pulverizing it.

As a manufacturing method of the raw material powder for air electrodes of this invention, the following process can be illustrated more specifically, for example.
(1) After a certain amount of water is distilled off from the solid obtained from the mixed solution containing a predetermined metal, it is transferred to an evaporating dish and dried at a temperature of 150 ° C. or lower.
(2) About the obtained solid substance, after crushing with a mortar, it thermally decomposes at 350-450 degreeC for 4 to 6 hours.
(3) Further, the solid obtained in (2) is calcined at 750 to 850 ° C. for 4 to 6 hours.
(4) Furthermore, the solid material obtained in (3) is baked at 900 to 1100 ° C. for 8 to 12 hours.
The temperature and time of pyrolysis, calcination, and firing are the same as the measurement results of the differential thermal-thermogravimetric measurement device (TG-DTA) or the like for the solid matter obtained in (1). Accordingly, it may be determined, and it is preferable to appropriately adjust according to the kind of solid matter to be used and the processing amount.
(5) An ethanol solvent is added to the solid obtained in (4), and the mixture is crushed with a ball mill and dried. In addition to ethanol, any organic solvent used in normal wet crushing such as methanol, isopropanol, toluene, hexane, etc. can be efficiently crushed.
(6) The powder obtained in (5) is compressed for about 5 minutes at about 1.5 t / cm ² so that the size after molding is about 1.5 to 5 μm in Φ20 mm thickness using a tablet molding machine. Mold.
(7) The molded product obtained in (6) is fired at 1000 to 1200 ° C. for 5 to 7 hours to obtain pellets having a uniform composition.
(8) The obtained pellet is pulverized until it becomes a sieve having an opening of 100 μm.
(9) After that, the powder obtained, ethanol and YSZ balls are put into a container and adjusted with a ball mill while adjusting the YSZ ball diameter, rotation speed and time so as to obtain a predetermined average particle diameter (D50) and specific surface area. Crush and dry.

  As a paste for an air electrode precursor layer (slurry for air electrode) using the raw material powder obtained above, the slurry for the first layer provided on the electrolyte layer or preferably the barrier layer side which may be provided, and the layer It is preferable to use a slurry for the second layer provided on the opposite side of the electrolyte layer or preferably the barrier layer which may be provided.

As the slurry for the first layer, it is preferable to mix and use a fine raw material powder (fine powder) and a coarse raw material powder (coarse powder).
The fine powder preferably has an average particle size (D50, the same applies hereinafter) of less than 1.0 μm, and more preferably less than 0.6 μm. Moreover, it is preferable that an average particle diameter is 0.2 micrometer or more. The specific surface area is preferably ⁵ to 10 m ² / g.
The coarse powder preferably has an average particle size of more than 1.2 μm, and more preferably 1.5 μm or more. The specific surface area is preferably ¹ to 5 m ² / g.
The average particle size ratio between the fine powder and the coarse powder is preferably such that the average particle size of the coarse powder / the average particle size of the fine powder is 3 times or more, more preferably 3.5 times or more. More preferably, it is at least twice.
The mixing ratio of the fine powder and the coarse powder is preferably 5% by mass to 30% by mass of the coarse powder with respect to 100% by mass of the mixture of the fine powder and the coarse powder.
The slurry for the first layer is prepared by mixing a known pore forming agent such as carbon black and organic fine particles with a mixture of fine and coarse particles 100 for the purpose of adjusting the interface length between the pores and the air electrode component and the structure thereof. You may add 1-10 mass parts with respect to a mass part. Since the purpose of the pore former is to adjust the interface length between the pores and the air electrode component and its structure, it is sufficient that the air electrode has the desired structure after firing, and no pore former is added. Even in such a case, it may be omitted if the target structure can be adjusted.

  As the slurry for the second layer, it is preferable to use the coarse raw material powder.

  The first layer slurry and the second layer slurry preferably contain conductive materials having the same composition, and the raw material powders of the conductive materials contained in the first layer slurry and the second layer slurry have the same composition. It is more preferable that

  As the binder and / or solvent used in the preparation of the slurry for the air electrode, known materials can be used in known amounts.

  The method for coating the air electrode slurry is not particularly limited, and conventional methods such as a doctor blade method, a calender roll method, and a printing method can be used. The application of the slurry for the air electrode is performed by applying two types of slurry, a slurry for the air electrode precursor layer 1 (slurry for the first layer) and a slurry for the air electrode precursor layer 2 (slurry for the second layer). It is preferable that the air electrode precursor layer 1 and the air electrode precursor layer 2 are closely attached without any gap. For example, a first layer slurry is applied to the surface of an electrolyte layer or a barrier layer by a screen printing method and dried, and then a second layer slurry is applied by a screen printing method and dried to form an air electrode precursor having two layers. A layer is obtained. When the air electrode precursor layer 1 is formed after the air electrode precursor layer 1 is formed and is peeled off between the two air electrode precursor layers, the air electrode with higher electronic conductivity is obtained. Thus, the internal resistance is further reduced.

  The drying conditions for the air electrode slurry may be adjusted as appropriate according to the type of solvent used, but are usually about 40 ° C. or higher and 150 ° C. or lower. Drying may be performed at a constant temperature, or may be performed by heating by successively raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C.

  Firing conditions may be adjusted as appropriate. For example, firing is performed at a temperature of about 800 ° C. to 1200 ° C. in the presence of a sufficient amount of oxygen. Sintering at 950 ° C. or higher is more preferable because a sufficient firing effect can be obtained and a sufficient strength can be obtained. On the other hand, if the firing temperature is too high, the sintering proceeds and the particle size becomes excessive or the pores tend to decrease, and the ratio LS1 / LS2 between the LS1 and LS2 in the air electrode is less than 1.0. Can be difficult.

  In the present invention, the raw material powder used for the air electrode is produced under predetermined drying and firing conditions, and is a powder having a predetermined average particle diameter (D50) and specific surface area, whereby the above LS1 and LS2 in the air electrode The ratio LS1 / LS2 can be reliably reduced to less than 1.0, and an air electrode for an electrochemical cell excellent in current-voltage characteristics and an electrochemical cell including the same can be obtained.

  For forming the support that the electrochemical cell of the present invention may have, a conventionally known method can be adopted. For example, in the production of the fuel electrode support substrate, the stabilized zirconia powder and the conductive component What contains a powder can be used preferably. The slurry is coated on a substrate and then dried. The slurry includes at least a stabilized zirconia powder, a conductive component powder, a solvent, and a binder, and in addition, for example, a plasticizer, a dispersant, a pore forming material, an antifoaming agent, and the like may be added.

  As a solvent used for slurry preparation, for example, alcohols such as methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol and α-terpineol; ketones such as acetone and 2-butanone; pentane, hexane, heptane and the like Aliphatic hydrocarbons; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and acetic acid esters such as methyl acetate, ethyl acetate, and butyl acetate. To do. These solvents can be used alone or in combination of two or more.

  The amount of solvent used should be adjusted in consideration of the viscosity of the slurry during green sheet molding, preferably the slurry viscosity is 1 Pa · s to 80 Pa · s, more preferably 1 Pa · s to 50 Pa · s. It is better to adjust the range.

  The type of binder used when producing the slurry is not particularly limited as long as it is decomposed by firing or removed by burning, and a conventionally known organic binder is appropriately selected and used. be able to. Examples of the organic binder include an ethylene copolymer, a styrene copolymer, a (meth) acrylate copolymer, a vinyl acetate copolymer, a maleic acid copolymer, a polyvinyl butyral resin, a vinyl acetal resin, Examples thereof include vinyl formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose.

  Among these, a (meth) acrylate copolymer having a number average molecular weight of 5,000 or more and 200,000 or less, and more preferably 10,000 or more and 100,000 or less is particularly preferable. These organic binders can be used alone or in combination of two or more as necessary. Particularly preferable is a polymer of a monomer containing 60% by mass or more of n-butyl methacrylate, isobutyl methacrylate and / or 2-ethylhexyl acrylate.

  Although the usage-amount of a binder should just be adjusted suitably, about 10 to 50 mass parts is preferable with respect to a total of 100 mass parts of stabilized zirconia powder and electroconductive component powder.

  A plasticizer may be added to impart flexibility to the green sheet. Examples of the plasticizer include a low molecular plasticizer, a co-oligomer plasticizer, and a high molecular plasticizer. Examples of the low molecular plasticizer include phthalic acid esters such as dibutyl phthalate and dioctyl phthalate. Examples of the co-oligomer plasticizer and the polymer plasticizer include polyesters. The blending amount of the plasticizer depends on the glass transition temperature of the binder to be used, but it should be about 0.5 to 10 parts by mass with respect to 100 parts by mass in total of the stabilized zirconia powder and the conductive component powder. Is preferred.

  In preparing the slurry, a dispersant may be added to promote peptization and dispersion of the solid electrolyte material, increase the fluidity of the slurry, and suppress sedimentation of the solid electrolyte material in the slurry. The blending amount of the dispersant is preferably about 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass in total of the stabilized zirconia powder and the conductive component powder.

  The pore forming material is added to promote the formation of pores in the support or electrode, and to promote the diffusion of gas inside the support or electrode, and is removed by decomposition or burning by firing. There is no particular limitation as long as it is. Conventionally known pore forming materials include known carbon materials such as carbon black and organic fine particles. The blending amount of the pore forming material is preferably about 0.01 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass in total of the stabilized zirconia powder and the conductive component powder. If the gas diffusion is sufficient, it may not be added.

  What is necessary is just to mix said each component by a conventional method. For example, mixing may be performed using a disper or the like, or the aggregated particles of the raw material powder may be mixed while being pulverized using a ball mill or the like.

  The method for applying the slurry onto the substrate is not particularly limited, and conventional methods such as a doctor blade method, a calender roll method, and a printing method can be used. Specifically, for example, the slurry is transported to a coating dam, cast on a base material such as a PET film so as to have a uniform thickness by a doctor blade, a screen printing machine, etc. Use green sheets.

  The drying conditions of the green sheet may be adjusted as appropriate according to the type of solvent used, but are usually about 40 ° C. or higher and 150 ° C. or lower. Drying may be performed at a constant temperature, or may be performed by heating by successively raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C.

  The fuel electrode support substrate green sheet may be cut into a desired shape. The shape of the fuel electrode supporting substrate green sheet is not particularly limited, and may be matched with the shape of a target half cell or single cell, for example. For example, it may be a circle, an ellipse, a square with R (R), or the like, and may have a hole such as a circle, an ellipse, or a square with R in these sheets. .

  The fuel electrode support substrate green sheet may be a single fuel electrode support substrate by firing. However, in the present invention, the fuel electrode supporting substrate green sheet may not be fired at this stage, and a fuel electrode green layer or the like may be formed thereon, and may be cofired together after being cut into a desired shape. . Also, in the description of the subsequent steps, it is described that only another green layer is formed on the green layer, but another green layer may be formed after firing the green layer as appropriate. To do. The subsequent firing conditions can be applied to firing and co-firing of any layer.

Firing conditions may be adjusted as appropriate. For example, firing is performed at about 1200 ° C. to 1500 ° C. in the presence of a sufficient amount of oxygen. If it sinters at 1200 degreeC or more, sufficient baking effect will be acquired and sufficient intensity | strength will be acquired. On the other hand, if the firing temperature is too high, the particle size of the particles in each layer may be excessive and the toughness may be reduced, so the upper limit is set to 1500 ° C. More preferably, it is 1250 degreeC or more and 1450 degrees C or less.
The heating rate up to the calcination temperature may be adjusted as appropriate, but it can usually be about 0.05 ° C./min to 4 ° C./min.

  Hereinafter, the present invention will be described in detail using examples.

<Evaluation of particle size of powder>
Sodium pyrophosphate [manufactured by Wako Pure Chemical Industries, Ltd., trade name “Sodium Pyrophosphate + Hydrate”] was dissolved in 0.2% by weight in pure water to obtain a dispersion medium. The powder was dispersed in this dispersion medium, and the particle size of the powder was measured using a laser diffraction / scattering type particle size distribution analyzer [manufactured by Horiba, Ltd., model number LA-920].
<Evaluation of specific surface area>
The specific surface area of the powder was measured using a BET specific surface area measuring device [manufactured by Macsorb, model number Model-HM1210].

<Example 1>
(Production of support substrate green sheet)
60 parts by mass of nickel oxide as a conductive component [manufactured by Shodo Chemical Industry Co., Ltd.], 3 mol% yttria-stabilized zirconia powder as a skeleton component [trade name “TZ3Y”] by 40 parts by mass, Carbon black as a pore-forming material [manufactured by SEC Carbon Co., SGP-3], 10 parts by mass, a binder comprising a methacrylate copolymer (molecular weight: 30,000, glass transition temperature: −8 ° C., solid content concentration : 50 parts by mass) 30 parts by mass, 2 parts by mass of dibutyl phthalate as a plasticizer and 80 parts by mass of a mixed solvent of toluene / isopropyl alcohol (mass ratio = 3/2) as a dispersion medium are mixed by a ball mill to prepare a slurry. did. Using the obtained slurry, a sheet was formed by a doctor blade method and dried at 70 ° C. for 5 hours to produce a fuel electrode supporting substrate green sheet. Regarding the thickness of the green sheet, a preliminary experiment was performed using a slurry having the same composition, and the green sheet and the thickness after firing were taken into consideration and the thickness after firing was controlled to be 400 μm. It was.

(Preparation of 8YbSZ raw material powder)
After firing ytterbium (III) chloride hydrate [manufactured by Wako Pure Chemical Industries, Ltd.] and zirconium chloride (IV) [manufactured by Wako Pure Chemical Industries, Ltd.], 8 mol% ytterbia stabilized zirconia [8YbSZ: ( Yb ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 ]. Pure water was prepared, and the water temperature was controlled to 20 ° C. using a magnetic stirrer with a heating function to dissolve the chloride. In addition, when it did not melt | dissolve even if 30 minutes passed, more pure water was added and it was made to melt | dissolve until a chloride melt | dissolves visually. After visually confirming that the chloride was dissolved, add an amount equivalent to 10% of pure water required for dissolution, and stir for 1 hour while heating and keeping the aqueous solution at 25 ° C. The chloride was completely dissolved. A precipitate obtained by dropping the obtained aqueous solution into aqueous ammonia was washed, dried, and calcined at 800 ° C. for 1 hour. Ethanol was added to the calcined powder, crushed with a ball mill for 10 hours, dried, further crushed in a mortar, and the crushed powder was baked at 1200 ° C. to obtain 8YbSZ raw material powder. The raw material powder, ethanol, and YSZ balls obtained in a plastic container were placed, crushed with a ball mill while adjusting the rotation speed and time, and dried to obtain 8YbSZ raw material powder having an average particle diameter of 0.49 μm.

(Preparation of YbGdDC raw material powder)
Ytterbium chloride (III) hydrate [Wako Pure Chemical Industries, Ltd.] and gadolinium chloride (III) hydrate [Wako Pure Chemical Industries, Ltd.], cerium (III) chloride hydrate [Wako Pure] Ceria [YbGdDC: (YbO _1.5 ) _0.10 (GdO _1.5 ) _0.10 (CeO ₂ ) in which 10 mol% ytterbia 10 mol% gadolinia was dissolved after firing. _0.80 , separate notation: Yb _0.10 Gd _0.10 Ce _0.80 Ox].
Pure water was prepared, and the water temperature was controlled to 20 ° C. using a magnetic stirrer with a heating function to dissolve the chloride. In addition, when it did not melt | dissolve even if 30 minutes passed, more pure water was added and it was made to melt | dissolve until a chloride melt | dissolves visually. After visually confirming that the chloride was dissolved, add an amount equivalent to 10% of pure water required for dissolution, and stir for 1 hour while heating and keeping the aqueous solution at 25 ° C. The chloride was completely dissolved. A precipitate obtained by dropping the obtained aqueous solution into aqueous ammonia was washed, dried, and calcined at 800 ° C. for 1 hour. Ethanol was added to the calcined powder, crushed with a ball mill for 10 hours, and then dried, and further crushed in a mortar. The crushed powder was baked at 1200 ° C. to obtain a baked powder. Ethanol was added to the obtained fired powder, and the rotational speed and time were adjusted so as to be 0.5 μm or less with a ball mill, pulverized, and dried to obtain a YbGdDC raw material powder.

(Preparation of fuel electrode paste)
In a plastic container, 60 parts by mass of nickel oxide as a conductive component [manufactured by Nikko Rica Co., Ltd., trade name “high purity nickel oxide F”], 40 parts by mass of adjusted 8YbSZ raw material powder as an ion conductive component, and further a dispersion medium Ethanol and YSZ balls as were added, and this was crushed and mixed by a ball mill and then dried to obtain a ball milled NiO / 8YbSZ mixed powder.
NiO / 8YbSZ mixed powder 60 parts by mass, α-terpineol as a solvent [manufactured by Wako Pure Chemical Industries, Ltd.] 36 parts by mass, ethyl cellulose as a binder [manufactured by Wako Pure Chemical Industries, Ltd.] 4 parts by mass, as a plasticizer 6 parts by mass of dibutyl phthalate [manufactured by Wako Pure Chemical Industries, Ltd.] and 4 parts by mass of a sorbitan fatty acid ester surfactant as a dispersing agent were mixed using a mortar, and then a three-roll mill (manufactured by EXAK technologies, Crushing was performed using a model “M-80S” (roll material: alumina) to produce a fuel electrode paste.

(Preparation of electrolyte layer paste)
60 parts by mass of 8YbSZ raw material powder, 5 parts by mass of ethyl cellulose [manufactured by Wako Pure Chemical Industries, Ltd.] as a binder, 40 parts by mass of α-terpineol [manufactured by Wako Pure Chemical Industries, Ltd.] as a solvent, and dibutyl phthalate as a plasticizer 6 parts by weight [manufactured by Wako Pure Chemical Industries, Ltd.] and 5 parts by weight of a sorbitan acid ester surfactant [manufactured by Sanyo Chemical Industries, Ltd., trade name “IONET S-80”] as a dispersant After using and mixing, the mixture was crushed using a three-roll mill (manufactured by EXAK technologies, model “M-80S” roll material: alumina) to prepare an 8YbSZ electrolyte layer paste.

(Preparation of paste for barrier layer)
60 parts by mass of YbGdDC raw material powder synthesized above, 5 parts by mass of ethyl cellulose [manufactured by Wako Pure Chemical Industries, Ltd.] as a binder, 40 parts by mass of α-terpineol [manufactured by Wako Pure Chemical Industries, Ltd.] as a solvent, plastic 6 parts by weight of dibutyl phthalate [manufactured by Wako Pure Chemical Industries, Ltd.] as an agent and 5 parts by mass of a sorbitan acid ester surfactant as a dispersant [trade name “IONET S-80”, manufactured by Sanyo Chemical Industries, Ltd.] The parts were mixed using a mortar, and then pulverized using a three-roll mill (manufactured by EXKT technologies, model “M-80S”, roll material: alumina). As a result, a barrier layer paste was obtained.

(Formation of green layer for fuel electrode)
The fuel electrode paste obtained above is printed on the support substrate green sheet obtained above by screen printing so that the thickness after firing is 16 μm, dried at 100 ° C. for 30 minutes, and the fuel electrode green layer Formed.

(Formation of green layer for electrolyte layer)
On the green layer for the fuel electrode obtained above, the paste for the electrolyte layer obtained above is printed by screen printing so that the thickness after firing becomes 8 μm, dried at 100 ° C. for 30 minutes, and used for the electrolyte layer A green layer was formed.

(Formation of green layer for barrier layer)
The barrier layer paste was printed on the green layer of the electrolyte layer obtained above so as to have a thickness of 2 μm by screen printing. This was dried at 100 ° C. for 30 minutes to form a barrier layer green layer.

(Baking)
After drying the barrier layer paste, the green sheet for the support substrate on which the green layer for the barrier layer, the green layer for the electrolyte layer, and the green layer for the fuel electrode obtained above are formed is a square having a side of 60 mm after firing. I punched it to become. After punching, a half cell having a barrier layer was obtained by firing at 1300 ° C. for 2 hours.

(Preparation of LSC powder material)
As a powder material to be used as a raw material for the LSC air electrode, lanthanum nitrate (III) hydrate, strontium nitrate, cobalt nitrate (II) hydrate [all manufactured by Wako Pure Chemical Industries, Ltd.] are calcined, and then La _{0. It} was dissolved in pure water so as to be ₆ Sr _0.4 CoOx. After dissolution, this solution was adjusted by adding pure water to a concentration of 0.1 mol / L (solution: A). Prepared solution: A solution (solution: B) prepared by dissolving ammonium oxalate hydrate [manufactured by Kanto Chemical Co., Ltd.] having a stoichiometric ratio of 1.2 times with A in pure water is prepared and stirred with a stirrer. Solution: A was added dropwise to the solution: B in a fresh state.
After a certain amount of water was distilled off from the mixed solution after the dropping by a rotary evaporator, the mixed solution was transferred to an evaporating dish and dried at 100 ° C. The obtained solid was crushed in a mortar, then pyrolyzed at 400 ° C. for 5 hours, calcined at 800 ° C. for 5 hours, and baked at 1000 ° C. for 10 hours.
Ethanol was added to the obtained powder, and it was further crushed with a ball mill and then dried. The obtained powder was weighed in an amount of 2.00 g each, and each was used at 1.5 t / cm ² using a tablet molding machine with a diameter of 20 mm. Compression molded for 5 minutes. The resulting molded product was fired at 1100 ° C. for 6 hours to obtain pellets made of LSC (6-4-10). The obtained pellet was confirmed to be a single phase composed of perovskite by X-ray diffraction [confirmed that there was no unreacted substance (lanthanum oxide, strontium oxide, cobalt oxide)]. About the obtained pellet, after roughly crushing using a mortar, it was crushed using a stamp mill until it became a sieve having an opening of 100 μm. After that, the powder obtained in a plastic container, ethanol and YSZ balls are placed, pulverized with a ball mill while adjusting the ball diameter, rotation speed and time, and dried, so that the average particle diameter (D50) is 0.31 μm. LSC powder: A having a specific surface area of 7.8 m ² / g and LSC powder: B having an average particle diameter (D50) of 1.92 μm and a specific surface area of 2.5 m ² / g were obtained.

(Preparation of slurry for air electrode)
LSC powder prepared by the above method: 90 parts by mass of A, LSC powder: 10 parts by mass of B, 2 parts by mass of carbon black having an average particle diameter of 3 μm as a pore forming material, and ethyl cellulose as a binder 3 parts by mass, α-terpineol as a solvent was added so as to have a ratio of 30 parts by mass, and this was mixed using a mortar. Then, it knead | mixed using the 3 roll mill (EXAKT technologies company make, model "M-80S", roll material: Alumina), and obtained slurry for air electrodes: A.
Similarly, as an LSC powder to be used, an air electrode slurry: B was obtained in the same manner except that 100 parts by mass of LSC powder: B was used and no pore forming material was used.

(Formation of LSC air electrode)
On the barrier layer surface of the half cell having the above barrier layer, the above-mentioned slurry for air electrode: A is applied in a square so that the thickness after firing is about 1 μm and the thickness after firing is about 10 μm by screen printing, and at 90 ° C. for 1 hour. Dried. After drying, the air electrode slurry: B is applied in a square shape with a size of 1 cm × 1 cm so that the fired thickness is about 10 μm, and dried at 90 ° C. for 1 hour to form a two-layer green layer for the air electrode. Formed. The air electrode green layer was baked at 1050 ° C. for 2 hours to obtain an electrochemical cell according to Example 1.

<Example 2>
In the preparation of the air electrode slurry in Example 1, the air electrode slurry: A was the same as in Example 1 except that 2 parts by mass of resin particles having an average particle diameter of 2 μm were used as the pore forming material. The electrochemical cell according to Example 2 was obtained.

<Comparative Example 1>
In the formation of the LSC air electrode in Example 1, the slurry for air electrode: B was 1 cm × 1 cm, and was applied in the same manner as in Example 1 except that it was applied in a square shape so that the thickness after firing was about 20 μm. The electrochemical cell according to Comparative Example 1 was obtained.

<Comparative example 2>
In the formation of the LSC air electrode in Example 1, the same method as in Example 1 except that the air electrode slurry: A was applied to a square so that the thickness after firing was 1 cm × 1 cm and the thickness after firing was about 20 μm. The electrochemical cell according to Comparative Example 2 was obtained. The air electrode produced by this method was cracked and peeled when viewed from the surface.

<Electrical performance evaluation of electrochemical cells (battery performance evaluation test)>
Battery performance was evaluated for the electrochemical cells of each Example and Comparative Example by the following method. While supplying 100 mL / min of nitrogen to the fuel electrode of the electrochemical cell and 100 mL / min of air to the air electrode, the temperature was raised to the measurement temperature (750 ° C.) at a rate of 100 ° C./hour. After the temperature rise, the flow rate of the gas on the outlet side of the fuel electrode and air electrode was measured with a flow meter, and it was confirmed that there was no leakage.
Next, a mixed gas humidified by a bubbler was supplied to the fuel electrode at a water temperature of 25 ° C. at 6 mL / min for hydrogen and 194 mL / min for nitrogen, and air at 400 mL / min was supplied to the air electrode. After confirming again that an electromotive force is generated after 10 minutes or more and that there is no leakage, the gas on the fuel electrode side is supplied with hydrogen humidified by a bubbler at a water temperature of 25 ° C. at a flow rate of 194 mL / min. After the electromotive force was stabilized, the current density (load) was changed to 1.0 A / cm ² after 10 minutes or more to obtain a voltage as electrical characteristics. The results are listed in Tables 1 and 2.

<Observation of air electrode A>
About the samples after electrical performance evaluation produced in each Example and Comparative Example, the sample was broken to have a length of 10 mm and a width of 6 mm so as to include a portion near the center of the surface on which the air electrode was applied. A sample for cross-sectional observation was used. For observation, a field emission scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.) was used to obtain an image with a magnification of 15,000 times for cross-sectional observation. In addition, the acquired image has one point near the center of the air electrode of the produced cross-sectional observation sample, two points near 1 mm from each end, and seven points so as not to include the same observation point in other parts, A total of 10 points were obtained.

Using the image analysis software (“Media Pro Plus version 4.0” manufactured by Media Cybernetics) for the 10 acquired images,
-(Average value of the circumference equivalent circle diameter) of a plurality of air electrode component particles in a range 1 (see FIG. 3) within 5 μm in the direction perpendicular to the air electrode surface direction from the interface between the air electrode and the barrier layer / ( Ratio LS1 which is an average value of equivalent circle diameters)
・ In the range 2 (see FIG. 3) within 5 μm from the surface of the air electrode to the interface with the barrier layer (see FIG. 3), (average value of circumference equivalent circle diameter) / (area equivalent circle diameter) Ratio LS2 which is an average value)
-Variation coefficient CVLS1 (%) of the area equivalent circle diameter of a plurality of air electrode component particles in range 1
-Variation coefficient CVLS2 (%) of the area equivalent circle diameter of a plurality of air electrode component particles in range 2
A value was obtained for the ratio between the coefficient of variation CVLS1 and the coefficient of variation CVLS2. In ranges 1 and 2, when the number of measured particles obtained from the acquired cross-sectional observation image is less than 100, measurement is performed by increasing the cross-sectional observation image to be acquired or increasing the magnification to 8000 times. The number was set to 100 or more.
6 and 7 show examples of acquired images. PG1, PG2, PG3,. . . Is the peripheral edge of each air electrode component particle, and the area circle equivalent diameter and the circumferential ellipse equivalent diameter of each air electrode component particle were obtained from these. The results are shown in Table 1.

<Observation of air electrode B>
The samples after electrical performance evaluation produced in each example and comparative example were broken so that the length was 10 mm and the width was 6 mm so as to include a portion near the center of the surface on which the air electrode was applied. After embedding resin with resin, it was polished so that the central part of the air electrode could be observed, and used as a sample for cross-sectional observation. For observation, a field emission scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.) was used to obtain an image with a magnification of 15,000 times for cross-sectional observation. In addition, the acquired image has one point near the center of the air electrode of the produced cross-sectional observation sample, two points near 1 mm from each end, and seven points so as not to include the same observation point in other parts, A total of 10 points were obtained.

Using the image analysis software (“Media Pro Plus version 4.0” manufactured by Media Cybernetics) for the 10 acquired images,
The average value D _L (μm) of the circumference equivalent circle diameter of a plurality of pores in the range 1, the average value D _S (μm) of the area equivalent circle diameter, and the number of histogram peaks for the plurality of area equivalent circle diameters Pb1
-The peak number Pb2 of the histogram about the area equivalent circle diameter of the plurality of pores in the range 2
- the _{D L} and _{D S,} for each ratio of the Pb1 and Pb2, was determined value. In the range 1 and 2, when the number of pores obtained from the acquired cross-sectional observation image is less than 100, the number of measurement is increased by increasing the cross-sectional observation image to be acquired or increasing the magnification to 8000 times. It was made to become 100 or more. The class and class interval in the histogram were determined by referring to the maximum value of the interface length: Pmax, the minimum value: difference of Pmin: ΔP = Pmax−Pmin, and ΔP divided by a number close to 20.
FIG. 8 shows an example of the acquired image. PG1, PG2, PG3,. . . Is the peripheral part of each pore, and from these, the area circle equivalent diameter and the circumferential ellipse equivalent diameter of each pore were obtained. The results are shown in Table 1.

  As for the boundary between the air electrode and the barrier layer, the air electrode component enters the barrier layer at a position where the air electrode component enters the barrier layer most (in the direction of the electrolyte layer) and 2 μm or more away from the location. A straight line connecting two places was defined as an air electrode / barrier layer interface. As for the boundary between the air electrode and the surface, a straight line connecting the two portions of the portion where the air electrode component protrudes most to the surface and the portion where the air electrode component protrudes most apart from the portion by 2 μm or more. The cathode / surface boundary was used. The same applies to the following.

Similarly, using the image analysis software (“Image Pro Plus version 4.0” manufactured by Media Cybernetics) for the 10 acquired images,
A rectangular region 3 of 2 μm × 5 μm with a width of 5 μm between the position 1 μm away from the interface perpendicular to the interface from the interface between the air electrode and the barrier layer in the direction perpendicular to the interface 3 (see FIG. 5) ), The total value data of the interface length between the pores and the air electrode component particles is obtained for each of the 10 acquired images, and the average value t1, the standard deviation d1 and the coefficient of variation cv1 of these images are obtained.
In the rectangular region 4 (see FIG. 5) of 2 μm × 5 μm in width of 5 μm between the position 1 μm away from the surface in the direction perpendicular to the surface from the surface of the air electrode and the position 3 μm away from the surface. The total value data of the interface length between the pores and the air electrode component particles is obtained for each of the 10 acquired images, and the average value t2, the standard deviation d2 and the coefficient of variation cv2 of these images are obtained.
A value was obtained for each ratio of t1 and t2, d1 and d2, and cv1 and cv2. The results are shown in Table 2. In Table 2, t1 and t2 are abbreviated as “interface length”.
In addition, each of the rectangular regions 3 and 4 was selected at 10 or more locations to obtain each value. 9 and 10 show examples of acquired images. T1, T2, T3,. . . Is the interface length between the pores and the individual air electrode component particles, and the total of these was used as the total value data of the interface.

The interfacial lengths of 100 or more pores and air electrode component particles obtained in the rectangular regions 3 and 4 of the air electrode in Examples 1 and 2 and Comparative Examples 1 and 2, respectively, in the rectangular regions 3 and 4 respectively. A histogram was used. Regarding the class and class interval, the maximum value of the interface length: Pmax, the minimum value: difference of Pmin: ΔP = Pmax−Pmin was obtained, and ΔP was divided by a number close to 20 to determine the value.
FIG. 11 shows a histogram of the interface length between the pores and the air electrode component particles in the rectangular region 3 in Example 1. As shown by the arrows in FIG. 11, there were two peaks when the interface length in the rectangular region 3 was made into a histogram (Pa1 = 2). In the range of the interface length on the horizontal axis in FIG. 11, for example, 0.0 to 0.1 is 0.0 μm or more and less than 0.1 μm, and the others are the same.
Table 2 shows values of the peak number Pa1 in the histogram in the rectangular region 3, the peak number Pa2 in the histogram in the rectangular region 4, and Pa1 / Pa2.

  As shown in Table 1, in the cross section of the air electrode, in the above range 1, (the average value of the circumference equivalent circle diameter of the plurality of air electrode component particles 1) / (corresponding to the area circle of the plurality of air electrode component particles 1) LS1 and (average value of circumference equivalent circle diameters of the plurality of air electrode component particles 2) / (average value of area equivalent circle diameters of the plurality of air electrode component particles 2) in the above range 2 The electrochemical cells of Examples 1 and 2 in which the ratio LS1 / LS2 to LS2 is less than 1.0 showed excellent current-voltage characteristics.

  The electrochemical cell of the present invention is excellent in current-voltage characteristics. Therefore, the air electrode for an electrochemical cell of the present invention and the electrochemical cell including the same can contribute to high performance and high reliability of the electrochemical cell.

10, 20 Electrochemical cell 12, 22 Air electrode 24 Barrier layer 16, 26 Electrolyte layer 18, 28 Fuel electrode 1, 2, Range 3, 4, Rectangular region 7 Center of air electrode in interface direction with electrolyte layer or barrier layer Near the part 8 Interface between the air electrode and the electrolyte layer or barrier layer 9 Surface of the air electrode where the electrolyte layer and / or barrier layer is not formed L End of the air electrode in the interface direction with the electrolyte layer or barrier layer Distance S from the interface between the air electrode and the electrolyte layer or the barrier layer in the direction of the surface where the electrolyte layer and / or the barrier layer of the air electrode is not formed T The direction of the electrolyte layer of the air electrode and / or Or, from the surface where the barrier layer is not formed, toward the interface between the air electrode and the electrolyte layer or barrier layer, the direction perpendicular to the above surface W1 From the interface between the air electrode and the electrolyte layer or barrier layer, Distance away from the interface in the direction perpendicular to the interface in the surface direction where the electrolyte layer and / or barrier layer of the electrode is not formed. W2 From the surface where the electrolyte layer and / or barrier layer of the air electrode is not formed, the air electrode and the electrolyte layer Or distance away from the surface perpendicular to the surface in the direction of the interface with the barrier layer

Claims (4)

An air electrode for an electrochemical cell in which a fuel electrode, an electrolyte layer, and an air electrode are arranged in this order,
The air electrode has a film thickness of 6 μm or more, and a cross-sectional ratio LS1 / LS2 of LS1 and LS2 shown below measured by a scanning electron microscope is less than 1.0. Air electrode for electrochemical cells.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the electrolyte layer in a direction in which the electrolyte layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: a plurality of air electrode components in a range within W2 in a direction perpendicular to the surface from the surface of the air electrode where the electrolyte layer is not formed to the interface between the air electrode and the electrolyte layer. (Average value of circumference equivalent circle diameter of particle 2) / (Average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, W1 and W2 may be the same or different and each is 3 μm or more, and the range for obtaining LS1 and LS2 is set so as not to overlap. An air electrode for an electrochemical cell in which a fuel electrode, an electrolyte layer, a barrier layer, and an air electrode are arranged in this order,
The air electrode has a film thickness of 6 μm or more, and a cross-sectional ratio LS1 / LS2 of LS1 and LS2 shown below measured by a scanning electron microscope is less than 1.0. Air electrode for electrochemical cells.
LS1: (a plurality of air electrode component particles in a range within W1 in a direction perpendicular to the interface from the interface between the air electrode and the barrier layer in a direction in which the barrier layer of the air electrode is not formed) 1 (average value of circumference equivalent circle diameter of 1) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 1)
LS2: (a plurality of air electrode component particles in a range within W2 in the direction perpendicular to the surface from the surface of the air electrode where the barrier layer is not formed to the interface between the air electrode and the barrier layer) (Average value of circumference equivalent circle diameter of 2) / (average value of area equivalent circle diameter of the plurality of air electrode component particles 2)
However, W1 and W2 may be the same or different and each is 3 μm or more, and the range for obtaining LS1 and LS2 is set so as not to overlap.   An electrochemical cell comprising a fuel electrode, an electrolyte layer, and the air electrode according to claim 1 arranged in this order. An electrochemical cell comprising a fuel electrode, an electrolyte layer, a barrier layer, and the air electrode according to claim 2 arranged in this order.