JP6795359B2 - Electrolyte layer for electrochemical cell, and electrochemical cell containing it - Google Patents

Description

The present invention relates to an electrolyte layer for an electrochemical cell and an electrochemical cell containing the same.

In recent years, electrochemical cells have been attracting attention as a clean energy source. Among the electrochemical cells, solid oxide fuel cells and solid oxide fuel cells that use solid ceramics as the electrolyte can utilize waste heat due to their high operating temperature, and are more efficient in power and hydrogen fuel. It has the advantage of being able to obtain fuel cells, and is expected to be used in a wide range of fields. As a basic structure, the electrochemical cell has a structure in which an electrolyte layer is arranged between a fuel electrode and an air electrode.

Patent Document 1 describes Scandia having a bulk density of 0.9 g / mL or more and 1.05 g / mL or less for the purpose of producing a scandia-stabilized zirconia film in which a decrease in oxygen ion conductivity with time is suppressed. A scandia-stabilized zirconia film comprising a step of obtaining a scandia-stabilized zirconia film using a mixed powder obtained by mixing a stabilized zirconia powder and a scandia-stabilized zirconia powder having a bulk density of more than 1.05 g / mL and 1.4 g / mL or less. The method for manufacturing is described.

Patent Document 2 has an average particle size of 0.1 μm or more and 1 μm or less for the purpose of producing a dense electrolyte for a solid oxide fuel cell which can be obtained at a low firing temperature without using a sintering aid. An electrolyte for a solid oxide fuel cell produced by using the first particle and the second particle having an average particle diameter of 1 nm or more and 20 nm or less is described.
However, there is room for improvement in the efficiency (output) of electrochemical cells such as solid oxide fuel cells and solid electrolyte electrochemical cells.

Japanese Unexamined Patent Publication No. 2016-69237 Japanese Unexamined Patent Publication No. 2016-100080

Therefore, an object of the present invention is to provide an electrolyte layer that provides an electrochemical cell having excellent current-voltage characteristics, and an electrochemical cell that includes the electrolyte layer.

The present inventor includes an electrolyte layer for an electrochemical cell, and an electrolyte layer that provides an electrochemical cell having excellent current-voltage characteristics by controlling the particle size distribution based on the number of particles in the electrolyte layer. We have found that an electrochemical cell can be manufactured, and have completed the present invention.

That is, the electrolyte layer for an electrochemical cell of the present invention is an electrolyte layer for an electrochemical cell containing a zirconia oxide as a main component, and the particles observed by a scanning electron microscope in the cross section of the electrolyte layer. It is characterized by having two or more peaks in a number-based particle size distribution.

Further, in the electrochemical cell of the present invention, the fuel electrode, the electrolyte layer for the electrochemical cell, and the air electrode are arranged in this order.

According to the present invention, it is possible to provide an electrolyte layer that provides an electrochemical cell having excellent current-voltage characteristics, and an electrochemical cell that includes the electrolyte layer.

It is a graph which shows the particle diameter distribution based on the number of particles observed by the scanning electron microscope of the cross section of the electrolyte layer in the electrochemical cell of an Example.

1. 1. Electrochemical cell The electrochemical cell of the present invention is an electrochemical cell in which a fuel electrode, an electrolyte layer, and an air electrode are arranged in this order. A barrier layer may be arranged between the electrolyte layer and the air electrode. Examples of the electrochemical cell of the present invention include a solid oxide fuel cell and a solid electrolyte electrolytic cell, and a solid oxide fuel cell is a preferable form. The electrochemical cell may be a fuel electrode support cell having a fuel electrode as a support, a solid electrolyte support cell having an electrolyte layer as a support, or an air electrode support cell having an air electrode as a support. Further, the single cell for an electrochemical cell is a metal support cell in which a fuel electrode, an electrolyte layer, and an air electrode are arranged in this order on a support substrate composed of a metal partition wall and having a plurality of through holes. Alternatively, the fuel electrode, the electrolyte layer, the barrier layer, and the air electrode may be metal supports arranged in this order.

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

1-1 Electrolyte layer As the electrolyte constituting the electrolyte layer for an electrochemical cell of the present invention, a zirconia-based oxide may be contained as a main component, and known ones can be used without particular limitation. In the present specification, the term "containing zirconia-based oxide as a main component" means that, for example, 50% by mass or more, preferably 60% by mass or more, of zirconia-based oxide is contained in 100% by mass of the electrolyte.

Examples of the zirconia-based oxide constituting the electrolyte layer for an electrochemical cell of the present invention include alkaline earth metal elements such as Mg, Ca, Sr, and Ba, Sc, Y, La, Ce, Pr, Nd, and Sm. Zirconia containing one or more rare earth elements such as Eu, Gd, Tb, Dy, Ho, Er, Yb, and other metal elements such as In, preferably one or more of these elements. Stabilized zirconia that is solid-dissolved as a stabilizer; Furthermore, Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₃ , Nb ₂ O _{5 and the} like are added to the above zirconia (preferably stabilized zirconia) as dispersion strengthening agents. Examples include added zirconia; and the like.

The electrolyte layer may contain other oxide ion conductive materials, for example, ceria containing yttrium, samarium, gadolinium, ytterbium, etc., preferably one or more of these elements. Dopeed ceria; lanthanum gallate, and lanthanum gallate-type perovskite structural oxide in which a part of lanthanum or gallium of lanthanum gallate is replaced with strontium, calcium, barium, magnesium, aluminum, indium, cobalt, iron, nickel, copper, etc. ; Etc. can be exemplified.

As the zirconia-based oxide, at least one selected from scandium, yttrium, cerium, and ytterbium as stabilized zirconia having higher thermal properties, mechanical properties, chemical properties, and oxide ion conduction properties. Elementally stabilized ones are more preferred. Further, (partially) stabilized zirconia containing a tetragonal crystal or a cubic crystal as a crystal structure is preferable.

Among zirconia oxides, stabilized zirconia whose crystal structure is stabilized by solid dissolution of at least one element (also called stabilizing element) selected from the group consisting of rare earth elements such as yttrium, scandium, and ytterbium. Is preferable.
Of these, stabilized zirconia in which at least one element selected from the group consisting of yttrium, scandium and ytterbium is dissolved is preferable.
As a more preferable form, zirconia (scandia-stabilized zirconia) containing scandium at a ratio of 7.0 to 27.5 mol% in terms of the number of atoms with respect to 100 mol% of the zirconium constituting the stabilized zirconia. 6. Zirconia (scandia, yttria-stabilized zirconia) containing 17.0 to 25.0 mol% of scandium and 0.5 to 2.5 mol% of cerium in terms of atomic number, and yttria in terms of atomic number. Zirconia containing 0 to 22.5 mol% (yttria-stabilized zirconia) or zirconia containing itterbium at a ratio of 6.0 to 35.5 mol% (yttria-stabilized zirconia) can be mentioned. Be done.

As a more preferable form, zirconia containing scandium at a ratio of 13.0 to 25.0 mol% in terms of atomic number with respect to 100 mol% of zirconium constituting stabilized zirconia, and scandium in terms of atomic number are used. Zirconia (scandium, ceria-stabilized zirconia) containing 16.0 to 22.0 mol% and cerium in a proportion of 0.5 to 2.0 mol%, yttrium 12.0 to 28.0 mol in terms of atomic number Zirconia and yttrium containing% are preferable, and zirconia containing 12.0 to 28.0 mol% in terms of atomic number is preferable.
In particular, zirconia containing ytterbium at a ratio of 12.0 to 28 mol% in terms of atomic number is preferable with respect to 100 mol% of zirconium constituting stabilized zirconia.
The electrolyte layer preferably contains zirconia (preferably stabilized zirconia) in an amount of 50% by mass or more, more preferably 80% by mass or more, and further preferably 85% by mass or more, 90% by mass. It is particularly preferable that the content is mass% or more.

The film thickness of the electrolyte layer 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, 1 to 50 μm is preferable, 1 μm or more and less than 30 μm is more preferable, and 1 to 20 μm is further preferable. Oxide ion conductivity can be improved by reducing the film thickness.

The electrolyte layer for an electrochemical cell of the present invention has two or more peaks in the particle size distribution based on the number of particles observed by a scanning electron microscope in the cross section of the electrolyte layer. It is preferable to have three or more peaks in the particle size distribution.

The positions of the two or more peaks are preferably in the range of 1.0 μm or more in particle size, and more preferably in the range of 1.1 μm or more in particle size. In other words, when peak 1, peak 2, ... Peak n (n: 2 or more) is set in ascending order of particle size at the peak position, the position of peak 1 may be in the range of particle diameter of 1.0 μm or more. It is preferably in the range of 1.1 μm or more, more preferably.
The position of the peak means the particle diameter of the maximum value of the peak.

Further, the difference (also referred to as peak interval) between the position (particle size) of the peak 1 and the position (particle size) of the peak 2 is preferably 0.50 μm or more, and more preferably 0.70 μm or more. On the other hand, the peak interval is preferably 1.80 μm or less, and more preferably 1.50 μm or less. For the positions of all existing peaks, the peak spacing of adjacent peaks is preferably in the above range. In particular, it is preferable that the peak intervals of adjacent peaks are observed in the range of 0.25 to 1.5 μm for all peak positions.
Within the above range, the particles are arranged so as to fill the gaps between the core particles, so that the grain boundary resistance is reduced, the conduction of oxide ions is improved, and the performance is improved.

Observation of particles in the cross section of the electrolyte layer with a scanning electron microscope is preferably carried out with a secondary electron image. If it is a secondary electron image, the image that can be acquired becomes clearer than that of the backscattered electron image, so that it becomes easier to distinguish each particle. However, as long as the particles can be discriminated, a backscattered electron image may be used instead of the secondary electron image.
In measuring the particle size, it is preferable to evaluate the electrochemical cell in the reduced state (the state in which the conductive component in the fuel electrode is reduced) to measure the particle size. This is because if it is in the reduced state, it is possible to measure an electrochemical cell in a state close to the operating state. However, unlike the conductive component used for the fuel electrode, zirconia-based oxides are difficult to change in particle size due to oxidation and reduction, and can be observed at high temperatures without reduction treatment. It doesn't matter.
As for the particles in the electrolyte layer, as a representative of the entire region of the electrolyte layer, it is preferable to measure 100 or more particles of the acquired image, and more preferably 200 or more particles. It can be said that the larger the number, the more preferable, but since it takes time, it is sufficient to measure 500 pieces.
In finding the number of peaks in the particle size distribution of the particle size, for the class and class interval, find the difference between the maximum value: Pmax and the minimum value: Pmin: ΔP = Pmax-Pmin, and set ΔP to a number close to 20. You can decide by referring to the value (see Applied Statistics Handbook, Applied Statistics Handbook Committee: Yokendo, p12-).

In the particle size distribution, among the observed peaks, the peak with the highest frequency was designated as the first peak, the peak with the second highest frequency was designated as the second peak, and the peak with the third highest frequency was designated as the third peak. In this case, the value represented by (frequency of second peak / frequency of first peak) is preferably 20% or more and 50% or less, and more preferably 25% or more and 40% or less. When the particle size distribution has three or more peaks, the value represented by (frequency of third peak / frequency of first peak) is preferably 8% or more and 25% or less, and 10% or more. More preferably, it is 20% or less.
Further, it is preferable that the peak 1 is the first peak, and it is more preferable that the peak 2 is the second peak. When three or more peaks are observed, it is preferable that peak 1 is the first peak, peak 2 is the second peak, and peak 3 is the third peak.

The particles observed by the scanning electron microscope in the cross section of the electrolyte layer are preferably particles made of zirconia-based oxide, and the particles made of zirconia-based oxide preferably satisfy the above-mentioned regulations. The preferred embodiment described above can also be applied to particles made of zirconia-based oxides.

By controlling the peak of the particle size distribution of the particles constituting the electrolyte layer as described above, the particles are arranged so as to fill the gaps between the core particles, so that the grain boundary resistance is reduced and the conduction of oxide ions is reduced. It is thought that the performance will improve and the performance will improve. The particles in the electrolyte layer are preferably particles made of a zirconia-based oxide. In this case, the peak of the particle size distribution of the zirconia-based oxide in the electrolyte layer is controlled as described above to obtain a nucleus. Since the particles are arranged so as to fill the gaps between the particles, it is considered that the intergranular resistance is reduced, the conduction of oxide ions is improved, and the performance is improved.

In order to have two or more peaks of particle size distribution in the electrolyte layer, a method of controlling the particle size distribution of the electrolyte powder as a raw material and firing conditions performed to form the electrolyte layer (for example, when firing). A method of controlling the rate of ascending / descending temperature, firing temperature and firing time, and a combination thereof) can be mentioned. For example, the size of the raw material powder may be adjusted so as to fall within the above range, or the rate of elevating temperature during firing may be controlled, and the firing temperature and firing time may be controlled, or a combination thereof may be used. Is also good. As another method, a powder obtained by calcining the raw material powder at a temperature similar to the firing temperature for forming the electrolyte layer is prepared, and the electrolyte layer is formed by using only this powder, or the raw material powder. And calcined powder may be mixed to form an electrolyte layer, and in this method, the firing conditions for forming the electrolyte layer (for example, the rate of ascending / descending temperature at the time of firing, the firing temperature and the firing time, and these) The method of controlling the combination) may be combined.

Further, in the cross section of the electrolyte layer, the average particle diameter D50 based on the number of particles observed by the scanning electron microscope is the following formula (1) with respect to the thickness T of the electrolyte layer.
D50 × 1.30 ≦ T ≦ D50 × 25 (1)
Is preferably satisfied, and the following equation (2)
D50 × 1.50 ≦ T ≦ D50 × 15 (2)
Is more preferable, and the following equation (3)
D50 × 1.80 ≦ T ≦ D50 × 10 (3)
It is more preferable to satisfy the following equation (4).
D50 × 2.30 ≦ T ≦ D50 × 3 (4)
Is particularly preferable.
In the cross section of the electrolyte layer, the particles observed by the scanning electron microscope are preferably particles made of a zirconia-based oxide.

Further, in the cross section of the electrolyte layer, the coefficient of variation obtained by dividing the standard deviation of the particle size of the particles observed by the scanning electron microscope by the average value (average particle size D50) is preferably 20% or more, preferably 30%. More preferably, it is more preferably 40% or more. The upper limit of the coefficient of variation is not particularly limited, but is preferably 80% or less, more preferably 60% or less, and particularly preferably 50% or less.

The observation of the particles in the cross section of the electrolyte layer with a scanning electron microscope is preferably performed in the cross section near the center of the plane of the electrolyte layer, and in the thickness direction, it is preferable to observe the particle diameters of all the particles. .. In the observation in the cross section near the central portion, when observing the particle diameters of all the particles in the thickness direction, the number of observed particles is preferably 80 or more, more preferably 100 or more at a plurality of places. It is preferable to carry out with.

1-2 Fuel electrode The fuel electrode is a layer containing at least one of nickel, cobalt, copper, iron, ruthenium, and other metals having fuel electrode catalytic activity in electrochemical cells and metal oxides that are precursors thereof. If so, there are no particular restrictions. The metal oxide, which is a precursor of the metal having fuel electrode catalytic activity, is reduced under the operating atmosphere of the electrochemical cell, and the layer becomes a layer containing the metal having fuel electrode catalytic activity. The fuel electrode further comprises the above-mentioned zirconia-based oxide (preferably stabilized zirconia), ceria (preferably doped ceria), oxide ion conductive metal oxides such as stabilized bismuth and lanthanum gallate, and oxide ions and electrons. It is preferable that the layer is a mixture of one or more of the mixed conductive metal oxides.

As the fuel electrode, a layer in which Ni or NiO and zirconia are mixed; or a layer in which Ni or NiO and ceria are mixed is more preferable. The volume ratio of Ni or NiO to the oxide (zirconia or ceria) 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 the bulk of NiO and each oxide. The fuel electrode preferably contains a compound common to the electrolyte layer in direct contact.
The fuel electrode is preferably a layer having pores under operating conditions from the viewpoint of high fuel gas permeability. The film thickness is preferably 3 to 30 μm, more preferably 4 to 25 μm.

1-3 Air electrode The air electrode 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. As the metal oxide having air electrode catalytic activity, various composite oxides (for example, strontium) containing at least one of La, Pr, Sm, Sr, Ba, Co, Fe, Mn, Ni and the like are solidified. Melted lanthanum manganate, lanthanum ferrite, lantern cobalt ferrite, lantern cobaltite, lantern strontium cobaltite, etc.) can be mentioned. 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. It is preferable that the layer is formed.

The film thickness of the air electrode is preferably 5 to 100 μm, more preferably 10 to 40 μm. Further, the air electrode is a layer prepared from raw material particles having an average particle diameter of 0.01 μm or more and 1 μm or less provided on the side of the electrolyte layer or the barrier layer which may be preferably provided, and on the layer. It may consist of a layer prepared from raw material particles having an average particle diameter of more than 1 μm and 10 μm or less provided on the side opposite to the surface on which the electrolyte layer or a barrier layer which may be preferably provided is provided. ..

1-4 Barrier layer The electrochemical cell of the present invention facilitates the formation of an insulating substance due to the direct contact between the air electrode and the electrolyte layer during the fabrication or reaction of the electrochemical cell, and suppresses the formation of this insulating substance. A barrier layer may be provided for the purpose of this. The barrier layer is preferably arranged between the electrolyte layer and at least one of the fuel electrode and the air electrode, and more preferably arranged between the electrolyte layer and the air electrode. It may not be necessary if the formation of the insulating layer is sufficiently suppressed.

The components constituting the barrier layer are not particularly limited, but are oxide ion conductive materials, and have oxygen ion conductivity between the barrier layer and the air electrode or the electrolyte layer during the production of an electrochemical cell or during a reaction. It is preferable that the component does not easily generate a component that inhibits.
The components constituting the barrier layer are not particularly limited, but mainly ceria containing rare earth elements such as Sc, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb. It is preferably contained as a component, and more preferably the ceria constitutes a solid solution with these elements. The rare earth element may be contained alone or in combination of two or more. The term "containing the ceria as a main component" means that the barrier layer contains 50% by mass or more of the ceria in 100% by mass, preferably 60% by mass or more, and more preferably 70% by mass or more. Further, in the barrier layer, the molar ratio of rare earth element / Ce 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 further preferable. Further, it is particularly preferable that Yb is contained as the second rare earth element in addition to Gd and Sm.

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

The thickness of the barrier layer is not particularly limited, but is preferably 0.2 to 20 μm, for example.

1-5 Support The electrochemical cell having a support of the present invention preferably has a fuel electrode as a support (fuel electrode support cell) and an electrolyte layer as a support (solid electrolyte support cell). ), A form in which an air electrode is used as a support (air electrode support type cell), a form in which a support substrate composed of a metal partition wall and having a plurality of through holes is used as a support (metal support cell), and a ceramic material as a base material. Examples thereof include a form in which a conductive substance is mixed or modified to serve as a support.
Among them, a preferred form of the support includes a fuel electrode support substrate, and in general, one 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 or more and 80% by mass or less. Can be.

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

The stabilized zirconia used in the electrolyte layer, the fuel electrode, and the fuel electrode support substrate may contain other metallic elements in addition to particularly preferred stabilizing elements such as yttrium, scandium, and ytterbium. The addition of additional metal elements may further improve properties 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; and rare earth elements such as Ce, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; Al. , In and other Group 13 elements; 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, it is selected from the group consisting of lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), aluminum (Al) and titanium (Ti). One or more metal elements are particularly preferred. These other metal elements may be only one kind or a combination of two or more kinds. As for the ratio of these other metal elements, the total content of these elements is 0.05 mol% or more and 5.0 mol% or less with respect to 100 mol% of zirconium contained in stabilized zirconia in terms of atomic number. preferable.

The fuel electrode support substrate has a role of supplying a fuel gas such as hydrogen to the fuel electrode so as not to be non-uniform, passing 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 contains, in addition to stabilized zirconia, a conductive component that is reduced under reducing conditions during power generation and exhibits conductivity. Nickel oxide, iron oxide, copper oxide and the like can be used as such a conductive component, and nickel oxide is the most common.

The thickness of the fuel electrode support substrate is not particularly limited, but is preferably 100 μm or more, more preferably 120 μm or more, still more preferably 150 μm or more, for example. The thickness of the fuel electrode support substrate is preferably 3 mm or less, more preferably 2 mm or less, further preferably 1 mm or less, and particularly preferably 500 μm or less. When the thickness of the fuel electrode support substrate is within the above range, it becomes easy to achieve a good balance between the mechanical strength of the fuel electrode support substrate and the gas permeability.

2. 2. Method for Manufacturing Electrochemical Cell In the electrochemical cell of the present invention, the method for producing the electrochemical cell by arranging a barrier layer in which a fuel electrode, an electrolyte layer, and an air electrode may be more preferably contained in this order is particularly limited. However, a known method can be used.

Preferably, the method (S) for producing an electrochemical cell of the present invention is
(I) A step of forming an electrode precursor film on a support or a support precursor film, and
(Ii) A step of forming an electrolyte layer precursor membrane on the electrode precursor membrane and
(Iii) A step of forming a barrier layer precursor membrane on the electrolyte layer precursor membrane formed in the above step, and a step of forming the barrier layer precursor membrane.
(Iv) A firing step of co-firing the support or support precursor film, the electrode precursor film, the electrolyte layer precursor film, and the barrier layer precursor film.
(V) A step of forming another electrode precursor film on the barrier layer formed in the above step (vi) The support, the electrode, the electrolyte layer, the barrier layer, and the other electrode. It may include a firing step of co-firing with the precursor film.

In order to have two or more peaks of particle size distribution in the electrolyte layer, a method of controlling the particle size distribution of the electrolyte powder as a raw material and firing conditions performed to form the electrolyte layer (for example, when firing). A method of controlling the rate of ascending / descending temperature, firing temperature and firing time, and a combination thereof) can be mentioned. For example, the size of the raw material powder may be adjusted so as to fall within the above range, or the rate of elevating temperature during firing may be controlled, and the firing temperature and firing time may be controlled, or a combination thereof may be used. Is also good. As another method, a powder obtained by calcining the raw material powder at a temperature similar to the firing temperature for forming the electrolyte layer is prepared, and the electrolyte layer is formed by using only this powder, or the raw material powder. And calcined powder may be mixed to form an electrolyte layer, and in this method, the firing conditions (rate of ascending / descending temperature at the time of firing, firing temperature and firing time) when forming the electrolyte layer are controlled. You may combine the methods.

Further, the electrolyte layer precursor membrane may be formed by overcoating two or more kinds of pastes for the electrolyte layer precursor membrane using raw material particles having the same composition but different firing temperatures, or the particles having the same composition. Two or more kinds of electrolyte layer precursor membrane pastes using raw material particles having different diameters may be overcoated to form.
The electrode and the other electrode may be either a fuel electrode or an air electrode, respectively, but it is preferable that the electrode is the fuel electrode and the other electrode is the air electrode.
In the above-mentioned production 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, a barrier layer precursor film and a barrier layer are formed between the electrolyte layer and the air electrode. Is omitted.

The above-mentioned method for producing an electrochemical cell (S) can be preferably adopted as a method for producing an electrochemical cell having a support.

Further, preferably, the method (T) for producing an electrochemical cell of the present invention is
(1) A step of forming an electrolyte layer precursor film on an electrode or an electrode precursor film, and
(2) A firing step of co-firing the electrode or the electrode precursor membrane and the electrolyte layer precursor membrane.
(3) A step of forming a barrier layer precursor film on the electrolyte layer formed in the above step, and
(4) A step of forming another electrode precursor film on the barrier layer precursor film formed in the above step and a step of forming another electrode precursor film.
(5) A firing step of co-firing the electrode, the electrolyte layer, the barrier layer precursor film, and the other electrode precursor film is included, or
(11) A step of forming an electrolyte layer precursor film on an electrode or an electrode precursor film, and
(12) A step of forming a barrier layer precursor membrane on the electrolyte layer precursor membrane formed in the above step, and a step of forming the barrier layer precursor membrane.
(13) A step of forming another electrode precursor film on the barrier layer precursor film formed in the above step and a step of forming another electrode precursor film.
(14) A firing step of co-firing the electrode or the electrode precursor film, the electrolyte layer precursor film, the barrier layer precursor film, and the other electrode precursor film may be included.

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

The electrode and the other electrode may be 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 air electrode may have two layers of an air electrode precursor film 1 and an air electrode precursor film 2.
The above-mentioned method for manufacturing an electrochemical cell (T) is a method for manufacturing an electrode-supported cell (fuel pole-supported cell, air-pole-supported cell) having a fuel electrode or an air electrode as a support, and a method for manufacturing a metal support cell. It can be preferably adopted.

Further, preferably, the method (A) for producing an electrochemical cell of the present invention is
(20) A step of preparing an electrolyte precursor membrane from an electrolyte slurry by a doctor blade method or the like, and
(21) A step of calcining the electrolyte precursor membrane to produce an electrolyte layer, and
(22) A step of forming an electrode precursor film on the electrolyte layer and
(23) A step of forming a barrier layer precursor film on the surface of the electrolyte layer opposite to the surface on which the electrode precursor film is formed.
(24) A step of forming another electrode precursor film on the surface of the barrier layer precursor film, and
(25) The step of firing the electrolyte layer, the electrode precursor film, the barrier layer precursor film, and the other electrode precursor film may be included.

The firing of the electrode precursor film and the barrier layer precursor film is performed between steps (23) and (24), and the electrode precursor film and the barrier layer precursor film are formed in step (24). It may be placed as an electrode and a barrier layer before the above.
The firing of the electrode precursor film and the barrier layer precursor film is preferably performed between the steps (23) and the steps (24).
The electrode and the other electrode may be a fuel electrode or an air electrode, but the electrode is preferably a fuel electrode and the other electrode is preferably an air electrode. The air electrode may have two layers of an air electrode precursor film 1 and an air electrode precursor film 2.

Further, preferably, the method (B) for producing an electrochemical cell of the present invention is
(31) Step of manufacturing the electrolyte layer precursor membrane and
(32) A step of forming an electrode precursor film on the electrolyte layer precursor film, and
(33) A step of forming a barrier layer precursor film on the surface of the electrolyte layer precursor film opposite to the surface on which the electrode precursor film is formed.
(34) A step of forming another electrode precursor film on the barrier layer precursor film, and
(35) The step of firing the electrolyte layer precursor film, the electrode precursor film, the barrier layer precursor film, and the other electrode precursor film may be included.

The firing of the electrolyte layer precursor film, the electrode precursor film, and the barrier layer precursor film is performed between the steps (33) and (34), and the electrolyte layer precursor film and the electrode precursor are formed. The membrane and the barrier layer precursor membrane may be used as an electrolyte layer, an electrode, and a barrier layer before the step (34).
The firing of the electrolyte layer precursor membrane, the electrode precursor membrane, and the barrier layer precursor membrane is preferably performed between steps (33) and (34).
The electrode and the other electrode may be 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 air electrode may have two layers of an air electrode precursor film 1 and an air electrode precursor film 2.

The above-mentioned methods (A) and (B) for producing an electrochemical cell can be particularly preferably adopted as a method for producing a solid electrolyte-supported cell.

As a method for forming each of the precursor films (green layers) described above, each raw material powder is mixed with a known binder and / or solvent (dispersion medium), and if necessary, a dispersant, a plasticizer, or the like, and the coating ink ( These coating inks are also referred to as pastes and slurries), and these coating inks are applied onto a smooth substrate such as a polyester sheet by the doctor blade method, calendar roll method, extrusion method, etc., and dried to volatilize and remove the dispersion medium. A sheet (green sheet) may be formed. Further, the coating film 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.
Further, 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.

A conventionally known method can be adopted for forming the support that the electrochemical cell of the present invention may have. For example, in the production of the fuel electrode support substrate, the stabilized zirconia powder and the conductive component are used. Those containing powder can be preferably used. The slurry is prepared by coating it on a substrate and then drying it. The slurry contains 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, a defoaming agent and the like may be added.

Examples of the solvent used for preparing the slurry include alcohols such as methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol and α-terpineol; ketones such as acetone and 2-butanone; pentane, hexane and heptane. Aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; acetic acid esters such as methyl acetate, ethyl acetate and butyl acetate can be exemplified, and they are appropriately selected and used. To do. These solvents can be used alone, or two or more kinds can be mixed and used.

The amount of the solvent used is preferably adjusted in consideration of the viscosity of the slurry at the time of green sheet molding, preferably the slurry viscosity is 1 Pa · s or more and 80 Pa · s or less, and more preferably 1 Pa · s or more and 50 Pa · s or less. It is better to adjust it so that it is within the range.

The type of binder used in 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 ethylene-based copolymers, styrene-based copolymers, (meth) acrylate-based copolymers, vinyl acetate-based copolymers, maleic acid-based copolymers, polyvinyl butyral resins, vinyl acetal resins, and the like. Examples thereof include vinyl formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose.

Among these, a (meth) acrylate-based copolymer having a number average molecular weight of 5,000 or more and 200,000 or less, 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, if necessary. Particularly preferred is a polymer of monomers containing 60% by weight or more of n-butyl methacrylate, isobutyl methacrylate and / or 2-ethylhexyl acrylate.

The amount of the binder used may be appropriately adjusted, but is preferably about 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total of the stabilized zirconia powder and the conductive component powder.

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

In preparing the slurry, a dispersant may be added in order to promote the ungluing and dispersion of the solid electrolyte material, increase the fluidity of the slurry, and suppress the 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 and the electrode and to promote the diffusion of gas inside the support and the electrode, and is removed by decomposition or combustion by firing. There is no particular limitation as long as it does. Examples of the conventionally known pore-forming material include a carbon material such as carbon black. The blending amount of the pore-forming material is preferably about 0.01 part 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, but inside the support or the electrode. If the diffusion of the gas is sufficient, it may not be added.

Each of the above components may be mixed by a conventional method. For example, the mixture may be mixed using a disper or the like, or the aggregated particles of the raw material powder may be mixed while being crushed using a ball mill or the like.

The method of applying the slurry on the substrate is not particularly limited, and a conventional method such as a doctor blade method, a calender roll method, or a printing method can be used. Specifically, for example, the slurry is transported to a coating dam, cast on a substrate such as a PET film so as to have a uniform thickness by a doctor blade or a screen printing machine, and dried to support a fuel electrode support substrate. Use a green sheet.

The drying conditions of the green sheet may be appropriately adjusted according to the type of solvent used and the like, but are usually set to about 40 ° C. or higher and 150 ° C. or lower. The drying may be carried out at a constant temperature, or the temperature may be continuously raised at 50 ° C., 80 ° C., 120 ° C. and the like, and the drying may be performed by heating.

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

The fuel electrode support substrate green sheet may be used as a single fuel electrode support substrate by firing. However, in the present invention, the fuel electrode support substrate green sheet may not be fired at this stage, but a fuel electrode green layer or the like may be formed on the fuel electrode support substrate green sheet, cut into a desired shape, and then co-fired together. Further, in the description of the following steps, even if it is described only that another green layer is formed on the green layer, another green layer may be formed after appropriately firing the green layer. To do. Subsequent firing conditions can be applied to firing and co-firing of any layer.

The firing conditions may be adjusted as appropriate. For example, firing is performed at 1200 ° C. or higher and 1500 ° C. or lower in the presence of a sufficient amount of oxygen. Sintering at 1200 ° C. or higher provides a sufficient firing effect and sufficient strength. On the other hand, if the firing temperature is too high, the crystal grain size of each layer may become excessive and the toughness may rather decrease. Therefore, the upper limit is set to 1500 ° C. More preferably, it is 1250 ° C. or higher and 1450 ° C. or lower.
The heating rate up to the firing temperature may be appropriately adjusted, but is usually about 0.05 ° C./min or more and 4 ° C./min or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Further, in the examples described below, "parts" represents "parts by mass" and "%" represents "% by mass".

<Evaluation of powder particle size>
Sodium pyrophosphate [manufactured by Wako Pure Chemical Industries, Ltd., trade name "sodium pyrophosphate + hydrate"] was dissolved in pure water to a concentration of 0.2% by weight to prepare 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 measuring device [manufactured by HORIBA, Ltd., model number LA-920].

<Evaluation of maximum particle size of aggregates in paste>
The maximum particle size of the agglomerates in the paste is JIS K5600-2-5. It was measured using a grind meter according to the degree of dispersion. Specifically, a paste is dropped in a groove of a grind meter (manufactured by BYK), and a paste layer having a continuously changed thickness is formed in the ironing groove using a scraper. At this time, the thickness of the layer at the place where remarkable spots due to the agglomerates in the paste began to appear is read and used as the maximum particle size of the agglomerates. This measurement was performed three times, and the average value of the three times was calculated to obtain the maximum particle size of the agglomerates in the paste.

<Example 1>
(Preparation of support substrate green sheet)
Nickel oxide as a conductive component [manufactured by Shodo Chemical Industry Co., Ltd.] 60 parts by mass, 3 mol% itria stabilized zirconia powder as a skeletal component [manufactured by Toso Co., Ltd., trade name "TZ3Y"] 40 parts by mass, empty Carbon black as a pore-forming agent [manufactured by SEC Carbon Co., Ltd., SGP-3] 10 parts by mass, a binder composed of a methacrylate-based 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 dibutylphthalate as a plasticizer, and 80 parts by mass of a mixed solvent of toluene / isopropyl alcohol (mass ratio = 3/2) as a dispersion medium were mixed by a ball mill to prepare a slurry. .. Using the obtained slurry, a sheet was formed by a doctor blade method and dried at 70 ° C. for 5 hours to prepare a fuel electrode support substrate green sheet. Regarding the thickness of the green sheet, a preliminary experiment was conducted using a slurry having the same composition, and the thickness after firing was controlled to be 400 μm in consideration of the thickness of the green sheet and after firing. It was.

(Preparation of 8YbSZ raw material powder)
8 mol% yttria-stabilized zirconia [8YbSZ: (Yb) after firing ytterbium (III) chloride hydrate [manufactured by Wako Pure Chemical Industries, Ltd.] and zirconium chloride (IV) [manufactured by Wako Pure Chemical Industries, Ltd.] ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 ] was weighed. Pure water was prepared, and the water temperature was controlled to be 20 ° C. using a magnetic stirrer with a heating function to dissolve the above chloride. If it did not dissolve even after 30 minutes, pure water was further added, and the mixture was visually dissolved until the chloride was dissolved. After visually confirming that the chloride has dissolved, add an amount equivalent to 10% of the pure water required for dissolution, and further stir for 1 hour while heating and keeping the aqueous solution at 25 ° C. And the chloride was completely dissolved. The obtained aqueous solution was added dropwise to aqueous ammonia, and the obtained precipitate was washed, dried, and then calcined at 800 ° C. for 1 hour. Ethanol was added to the calcined powder, pulverized and mixed for 10 hours in a ball mill, dried, and further crushed in a mortar, and the crushed powder was calcined at 1200 ° C. to obtain an 8YbSZ raw material powder. The obtained raw material powder, ethanol, and YSZ balls were placed in a plastic container, pulverized with a ball mill while adjusting the rotation speed and time, and dried to obtain an 8YbSZ raw material powder having an average particle size of 0.23 μm.

(Preparation of paste for fuel electrode layer)
In a plastic container, 60 parts by mass of nickel oxide as a conductive component [manufactured by Nikko Rika Co., Ltd., trade name "high-purity nickel oxide F"], 40 parts by mass of 8YbSZ raw material powder prepared as an ionic conductive component, and as a dispersion medium. Ethanol and YSZ balls were added, and the powder was pulverized and mixed in a ball mill and then dried to obtain a ball milled NiO / 8YbSZ mixed powder.
60 parts by mass of NiO / 8YbSZ mixed powder, 36 parts by mass of α-terpineol as a solvent [manufactured by Wako Pure Chemical Industries, Ltd.], 4 parts by mass of ethyl cellulose as a binder [manufactured by Wako Pure Chemical Industries, Ltd.], as a plasticizer Dibutylphthalate [manufactured by Wako Pure Chemical Industries, Ltd.] 6 parts by mass and 4 parts by mass of a sorbitan fatty acid ester-based surfactant as a dispersant were mixed using a dairy pot, and then three roll mills (manufactured by EXAKT technologies). A paste for the fuel electrode layer was prepared by crushing using a model "M-80S", roll material: alumina). In this pasting treatment, the gap between the three roll mills and the rotation speed were adjusted to crush / knead the aggregates until the maximum particle size of the agglomerates measured by the grind meter became 10 μm or less.

(Preparation of paste for electrolyte layer)
60 parts by mass of the 8YbSZ raw material powder prepared 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 mass of dibutylphthalate [manufactured by Wako Pure Chemical Industries, Ltd.] as an agent and 5 parts by mass of a sorbitan acid ester-based surfactant [manufactured by Sanyo Kasei Kogyo Co., Ltd., trade name "Ionet S-80"] as a dispersant Was mixed using a dairy pot and then crushed using a 3-roll mill (manufactured by EXAKT technologies, model "M-80S" roll material: alumina) to prepare a paste for an 8YbSZ electrolyte layer. In this pasting treatment, the gap between the three roll mills and the rotation speed were adjusted to crush / knead the aggregates until the maximum particle size of the agglomerates measured by the grind meter became 10 μm or less.

(Preparation of paste for barrier layer)
60 parts by mass of ceria powder [manufactured by Anan Kasei Co., Ltd.] doped with 10 mol% gadlinear as a ceramic, 5 parts by mass of ethyl cellulose [manufactured by Wako Pure Chemical Industries, Ltd.] as a binder, α-terpineol as a solvent [Manufactured by Wako Pure Chemical Industries, Ltd.] 40 parts by mass, dibutylphthalate as a plasticizer [Manufactured by Wako Pure Chemical Industries, Ltd.] 6 parts by mass and a sorbitan acid ester-based surfactant as a dispersant [Sanyo Kasei Kogyo (Sanyo Kasei Kogyo) Made by Co., Ltd., trade name "Ionet S-80"] 5 parts by mass are mixed using a dairy pot, and then using a 3-roll mill (manufactured by EXAKT technologies, model "M-80S", roll material; alumina). Crushed. As a result, a paste for the barrier layer was obtained. In this pasting treatment, the gap between the three roll mills and the rotation speed were adjusted to crush / knead the aggregates until the maximum particle size of the agglomerates measured by the grind meter became 10 μm or less.

(Formation of green layer for fuel electrode layer)
The paste for the fuel electrode layer obtained above is printed on the support substrate green sheet obtained above by screen printing so that the thickness after firing is 20 μm, dried at 100 ° C. for 30 minutes, and used for the fuel electrode layer. A green layer was formed.

(Formation of green layer for electrolyte layer)
The paste for the electrolyte layer obtained above was printed on the green layer for the fuel electrode layer obtained above by screen printing so as to have a thickness of 4 μm after firing.

(Formation of green layer for barrier layer)
The above-mentioned paste for the barrier layer 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 green layer for the barrier layer.

(Baking)
After the paste for the barrier layer is dried, 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 layer obtained above are formed, and the one side after firing is 60 mm. It was punched out to form a square. After punching, it was calcined at 1300 ° C. for 2 hours to obtain a half cell having a barrier layer.

(Preparation of LSC powder material)
As a powder material that is a raw material for the LSC air electrode, lanthanum nitrate (III) hydrate, strontium nitrate, and cobalt (II) nitrate hydrate [all manufactured by Wako Pure Chemical Industries, Ltd.] are fired and then La _{0. It} was dissolved in purified water so as to have ₆ Sr _0.4 CoOx. After dissolution, this solution was adjusted to 0.1 mol / L by adding purified water (solution: A). Prepared solution (solution: B) in which ammonium oxalate hydrate [manufactured by Kanto Chemical Co., Ltd.] having a quantitative ratio of 1.2 times to A was dissolved in purified water, and stirred with a stirrer. Solution: A was added dropwise to the solution: B in the state of being fresh.
After distilling off a certain amount of water with a rotary evaporator, the mixed solution after dropping was transferred to an evaporating dish and dried at 100 ° C. The obtained solid was pulverized in a mortar, thermally decomposed at 400 ° C. for 4 hours, calcined at 800 ° C. for 6 hours, and calcined at 1100 ° C. for 7 hours to obtain a powder.
Ethanol was added to the obtained powder, which was further pulverized and mixed with a ball mill and then dried to obtain an LSC (6-4-10) powder. The obtained powder was confirmed by X-ray diffraction to be a single phase composed of perovskite. Further, after that, by pulverizing while adjusting the rotation speed and the rotation time, LSC powder: A having an average particle diameter (D50) of 0.52 μm and LSC powder: B having an average particle diameter (D50) of 2.3 μm were obtained.

(Preparation of slurry for air electrode layer)
LSC powder prepared by the above method: Ethyl cellulose as a binder was added in a proportion of 3% by mass and α-terpineol as a solvent was added in a proportion of 30% by mass with respect to 100 parts by mass of A, and this was added using a mortar. Mixed. Then, it was kneaded using a three-roll mill (manufactured by EXAKT technologies, model "M-80S", roll material: alumina) to obtain a slurry for an air electrode layer: A.
Similarly, a slurry for an air electrode layer: B was obtained in the same manner except that the LSC powder: A was changed to the LSC powder: B.

(Formation of LSC air electrode)
On the barrier layer surface of the fuel electrode support type half cell having the barrier layer, the slurry for the air electrode layer: A is applied in a square shape at 1 cm × 1 cm and the thickness after firing is about 10 μm by screen printing. It was dried at 90 ° C. for 1 hour. After drying, the above slurry for air electrode layer: B is applied in a square shape at 1 cm × 1 cm so that the thickness after firing is about 10 μm, dried at 90 ° C. for 1 hour, and is composed of two layers of green for air electrode layer. A layer was formed. This green layer for the air electrode layer was calcined at 1000 ° C. for 2 hours to obtain an electrochemical cell according to Example 1.

<Comparative example 1>
In the formation of the green layer for the electrolyte layer in Example 1, the electrochemical cell according to Comparative Example 1 was obtained by the same method as described in Example 1 except that printing was performed so that the thickness after firing was 2 μm. ..

<Comparative example 2>
In the firing step of Example 1, the electrochemical cell according to Comparative Example 2 was obtained by the same method as described in Example 1 except that it was fired at 1400 ° C. for 2 hours.

<Electrical performance evaluation of electrochemical cell (battery performance evaluation test)>
The battery performance of the electrochemical cells of Example 1 and Comparative Examples 1 and 2 was evaluated 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 measured temperature (750 ° C.) at a rate of 100 ° C./hour. After the temperature was raised, the flow rates of the gas on the outlet side of the fuel electrode and the air electrode were measured with a flow meter, and it was confirmed that there was no leakage.
Next, hydrogen was supplied at 6 mL / min and nitrogen was supplied at a water temperature of 194 mL / min at a water temperature of 25 ° C., and a mixed gas humidified by a bubbler was supplied to the fuel electrode, and 400 mL / min of air was supplied to the air electrode. After 10 minutes or more, electromotive force was generated and it was confirmed again that there was no leakage, and then the gas on the fuel electrode side was supplied to the fuel electrode at a flow rate of 194 mL / min with hydrogen humidified by a bubbler at a water temperature of 25 ° C. After 10 minutes or more passed after the electromotive force became stable, the current density (load) was changed to 1.0 A / cm ² , and the obtained voltage was recorded. The results are shown in Table 1.

<Measurement of particle size>
For the samples after electrical performance evaluation prepared in Example 1 and Comparative Examples 1 and 2 (for Examples, the sample before evaluation was also carried out), the central portion of the surface coated with the air electrode was set to a length of 10 mm. A sample was cut out so as to have a width of 5 mm and used as a sample for cross-sectional observation. A field emission scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.) was used for observation, and a secondary electron image with a magnification of 10,000 times for cross-sectional observation was prepared so as not to include the same observation point. Obtained for any 10 points of the cross-sectional observation sample.
With respect to the acquired image, the area circle equivalent diameter: d of each particle in the electrolyte layer was determined using image analysis software (“Image Pro Plus version 4.0” manufactured by Media Cybernetics). For the zirconia particles in the electrolyte layer, the cross-sectional observation images obtained were performed so that the number of particles was 100 or more, and the number of peaks in the particle size distribution of the particle size was calculated. [For class and class interval, applied statistics handbook ( Applied Statistics Handbook Committee ed .: Yokendo, p12-)]. The results are shown in Table 1. In addition, values were also obtained for the electrolyte thickness: t, the average of the number of particles: D50, and the standard deviation: Dσ. The results are shown in Table 2. When the number of particles obtained from each of the acquired cross-sectional observation images was less than 100, the number of acquired cross-sectional observation images was increased to 100 or more.
Regarding the boundary between the fuel electrode and the electrolyte, and the boundary between the electrolyte and the barrier layer, the interface was obtained as follows, and the inside was determined to be the electrolyte layer. Regarding the acquired image, there are two places, one where Ni (NiO) penetrates most into the electrolyte layer (toward the barrier layer) and the other where Ni (NiO) penetrates most into the electrolyte layer at a distance of 2 μm or more from that location. The straight line connecting the places was defined as the electrolyte layer / fuel electrode interface. In the case of the barrier layer, the place where Ce (CeO ₂ ) penetrates most into the electrolyte layer (in the direction of the fuel electrode) and the place where Ce (CeO ₂ ) penetrates most into the electrolyte layer at a distance of 2 μm or more from that place. The straight line connecting the two points was used as the electrolyte layer / barrier layer interface, and the space between them was used as the electrolyte layer.

FIG. 1 shows a particle size distribution based on the number of particles observed by a scanning electron microscope in a cross section of an electrolyte layer in the electrochemical cell of Example 1. White arrows in FIG. 1 indicate peak positions. As shown in FIG. 1, in the particle size distribution based on the number of particles, the particle size is more than 1.5 μm and 1.75 μm or less, the particle size is more than 2.5 μm and 2.75 μm or less, and the particle size is more than 3.5 μm and 3.75 μm. A total of three peaks were observed in the following ranges, one for each.

As shown in Tables 1 and 2, in the particle size distribution of the particle size, the electrochemical cell having two or more peaks had a higher voltage than the electrochemical cell having only one peak, and was excellent in power generation performance. Therefore, when it was used for power generation, the overvoltage was suppressed to a low level, and it was possible to demonstrate that the output was excellent. On the other hand, since the overvoltage was suppressed to a low level, it is expected that the overvoltage will be suppressed to a low level even when used for electrolysis, suggesting that the power consumption is low and efficient electrolysis is possible. ..

The electrochemical cell of the present invention has excellent current-voltage characteristics. Therefore, the electrolyte layer for an electrochemical cell of the present invention and the electrochemical cell including the electrolyte layer can contribute to higher performance and higher reliability of the electrochemical cell.

Claims (2)

An electrolyte layer for an electrochemical cell containing a zirconia oxide as a main component.
Wherein in the cross section of the electrolyte layer, the particle size distribution based on the number of particles observed by scanning electron microscopy, have a plurality of peaks is two or more,
Each class in the particle size distribution is defined at intervals of 0.25 μm.
Each of the plurality of peaks has a particle size in the range of 1.0 μm or more, and has a particle size of 1.0 μm or more.
The distance between two adjacent peaks among the plurality of peaks is 0.25 μm or more and 1.5 μm or less.
When the peak with the highest frequency is set as the first peak and the peak with the second highest frequency is set as the second peak among the plurality of peaks, the frequency of the second peak is set to the frequency of the first peak. The ratio divided by is 20% or more and 50% or less.
Electrolyte layer for electrochemical cells. An electrochemical cell in which a fuel electrode, an electrolyte layer for an electrochemical cell according to claim 1, and an air electrode are arranged in this order.