WO2020261935A1 - Fuel electrode-solid electrolyte layer composite body, fuel electrode-solid electrolyte layer composite member, fuel cell and method for producing fuel cell - Google Patents

Abstract

A fuel electrode-solid electrolyte layer composite body which comprises a porous fuel electrode, a first solid electrolyte layer that is formed on the fuel electrode, and a second solid electrolyte layer that is superposed on the first solid electrolyte layer on the reverse side from the fuel electrode and has a lower void fraction than the fuel electrode, wherein: the first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing elemental nickel and a metal element that constitutes the first solid electrolyte material; the second solid electrolyte layer contains a second solid electrolyte material but does not substantially contain elemental nickel; and the fuel electrode contains a third solid electrolyte material and nickel metal.

Description

Fuel pole-solid electrolyte layer composite, fuel pole-solid electrolyte layer composite member, fuel cell, and method for manufacturing the fuel cell.

The present disclosure relates to a fuel electrode-solid electrolyte layer composite, a fuel electrode-solid electrolyte layer composite member, a fuel cell, and a method for manufacturing a fuel cell.
This application claims priority based on Japanese Application No. 2019-122150 filed on June 28, 2019, and incorporates all the contents described in the Japanese application.

As solid electrolyte materials applicable to PCFC (Protonic Ceramic Fuel Cell), Patent Document 1 and Patent Document 2 are metal oxides having a perovskite type structure of ABO ₃ and A site. Discloses a metal oxide containing Ba and a B site containing Zr and a trivalent substituent.

Japanese Unexamined Patent Publication No. 2001-307546 JP-A-2007-197315

One aspect of the present disclosure is from the porous fuel electrode, the first solid electrolyte layer formed on the fuel electrode, and the fuel electrode laminated on the opposite side of the first solid electrolyte layer to the fuel electrode. Also includes a second solid electrolyte layer having a small void ratio, and the first solid electrolyte layer is a composite oxidation containing a first solid electrolyte material, a nickel element, and a metal element constituting the first solid electrolyte material. The second solid electrolyte layer contains a second solid electrolyte material and substantially contains no nickel element, and the fuel electrode contains a third solid electrolyte material and metallic nickel. Regarding the fuel electrode-solid electrolyte layer complex.

Another aspect of the present disclosure is a cell structure comprising the fuel electrode-solid electrolyte layer composite and an air electrode, wherein the second solid electrolyte layer is interposed between the fuel electrode and the air electrode. The present invention relates to a fuel cell including an oxidant flow path for supplying an oxidant to an air electrode and a fuel flow path for supplying fuel to the fuel electrode.

Yet another aspect of the present disclosure is the second solid electrolyte laminated on the first solid electrolyte layer side of the laminate of the fuel electrode, the first solid electrolyte layer, and the fuel electrode and the first solid electrolyte layer. The first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing a nickel element and a metal element constituting the first solid electrolyte material, and the second solid electrolyte layer is contained. The solid electrolyte layer comprises a second solid electrolyte material and is substantially free of nickel elements, and the fuel electrode relates to a fuel electrode-solid electrolyte layer composite member containing a third solid electrolyte material and nickel oxide. ..

Yet another aspect of the present disclosure is a first solid electrolyte layer containing a fuel electrode containing nickel oxide, a first solid electrolyte material, and a composite oxide of nickel and a metal element constituting the first solid electrolyte material. At 850 ° C. or lower, a second solid electrolyte layer containing a second solid electrolyte material and substantially no nickel element was provided on the first solid electrolyte layer side of the laminate. It has a step of forming and obtaining a fuel electrode-solid electrolyte layer composite member and a step of forming an air electrode on the second solid electrolyte layer side of the fuel pole-solid electrolyte layer composite member to obtain a cell structure. , Regarding the manufacturing method of fuel cells.

It is sectional drawing which shows typically the structure of the fuel cell which concerns on one Embodiment of this disclosure. It is sectional drawing which shows typically the cell structure which has the fuel electrode-solid electrolyte layer complex contained in the fuel cell of FIG. FIG. 5 is a cross-sectional view schematically showing a cell structure having a fuel electrode-solid electrolyte layer composite member used in the manufacture of the fuel cell of FIG. 1.

[Issues to be solved by this disclosure]
In a fuel cell (Solid Oxide Fuel Cell, SOFC) having a solid electrolyte having ionic conductivity, the fuel electrode (anode) contains a nickel (Ni) component as a hydrogen dissociation catalyst and a solid electrolyte (metal oxide). Such a fuel electrode is generally made by sintering a material containing a solid electrolyte and nickel oxide (NiO). The anode-supported solid electrolyte layer is generally prepared by forming a coating film containing the solid electrolyte on the surface of a molded product of a mixture of a nickel component (for example, NiO) and the solid electrolyte, and firing (co-sintering) the film. Will be done.

The fuel electrode produced in this way is initially dense. However, by undergoing the process of reducing NiO to Ni, the function of Ni as a catalyst is enhanced, and at the same time, the fuel electrode is made porous so that the fuel gas can permeate. In many cases, the reduction treatment is performed in the state of a fuel cell. When used as an SOFC, NiO in the fuel electrode is reduced to Ni by hydrogen supplied to the fuel electrode as fuel, and changes to porous by volumetric shrinkage that occurs at the same time as this reduction.

Specifically, for example, when yttrium-doped barium ceriumate (BCY) or yttrium-doped barium zirconate (BZY) is used as the solid electrolyte and NiO is used as the nickel component, BCY powder, BZY powder and NiO are used. A fuel electrode containing a mixed powder of powder is formed, and BCY powder or BZY powder, which is a material of the solid electrolyte layer, is thinly applied to the fuel electrode, and then co-sintered at a temperature at which both are densified. As a result, a fuel electrode-solid electrolyte layer composite member including a layer containing BCY and BZY and a layer containing BCY, BZY and NiO is obtained. Next, the fuel electrode-solid electrolyte layer composite member is incorporated into a fuel cell and is reduced in a reducing gas atmosphere such as hydrogen to obtain an anode-supported solid electrolyte layer.

However, during co-sintering, Ni in the fuel electrode can diffuse to the solid electrolyte layer side. Ni diffused to the solid electrolyte side forms a conductive path in the solid electrolyte, and the leakage current may increase. Further, when the metal oxide is used for the solid electrolyte layer, Ni in the fuel electrode may diffuse into the metal oxide and the ionic conductivity may decrease. Therefore, the power generation performance of the fuel cell (or the electrolysis performance of the steam electrolysis cell) tends to deteriorate. In particular, when a proton conductive metal oxide having a perovskite-type structure doped with yttrium, such as BCY and BZY described above, is used for the solid electrolyte layer, it is usually at a high temperature of 1400 ° C. or higher in consideration of low sinterability. Co-sintering is performed. Therefore, Ni tends to diffuse into the solid electrolyte layer, and the proton conductivity tends to decrease. Further, when Ni is dissolved in these materials as a solid solution, hole conduction is likely to occur in an oxygen atmosphere, and the leakage current increases.

In order to suppress the diffusion of Ni, it is conceivable to form a solid electrolyte layer on the fuel electrode after sintering by a low temperature process such as application of paste. However, in this case, the bonding strength between the fuel electrode and the solid electrolyte layer tends to be weak. In the reduction treatment step, the solid electrolyte layer cannot follow the volume change (shrinkage) of the fuel electrode, and the solid electrolyte layer may be cracked or cracked, or a part of the solid electrolyte layer may be peeled off from the anode. ..

The larger the contact area (opposite area) between the solid electrolyte layer and the fuel electrode, the larger the amount of shrinkage of the fuel electrode, and the more likely the solid electrolyte layer is cracked or peeled off. Therefore, it is difficult to increase the facing area between the solid electrolyte layer and the fuel electrode, and it is difficult to obtain a large fuel cell and a steam electrolytic cell. That is, there is a problem in realizing a fuel cell or a steam electrolysis cell having a high output (high output current).

[Effect of the present disclosure]
A large fuel cell or steam electrolytic cell can be easily obtained by using the fuel electrode-solid electrolyte layer composite or the fuel electrode-solid electrolyte layer composite member according to the present disclosure.

[Explanation of Embodiments of the present disclosure]
First, the contents of the embodiments of the present disclosure will be listed and described.
(1) One embodiment of the present disclosure is from a porous fuel electrode, a first solid electrolyte layer formed on the fuel electrode, and a fuel electrode laminated on the opposite side of the first solid electrolyte layer from the fuel electrode. Also relates to a fuel electrode-solid electrolyte layer complex comprising a second solid electrolyte layer having a small void ratio. Here, the first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing a nickel element and a metal element constituting the first solid electrolyte material. The second solid electrolyte layer contains the second solid electrolyte material and is substantially free of nickel elements. The fuel electrode contains a third solid electrolyte material and metallic nickel. By using this fuel electrode-solid electrolyte layer composite, it is easy to increase the size, and a high-power fuel cell and a steam electrolytic cell can be realized.

The fuel electrode is also called the hydrogen electrode and corresponds to the anode in the fuel cell. On the other hand, the cathode in a fuel cell is also called an air electrode or an oxygen electrode. The fuel electrode-solid electrolyte layer composite is also called a fuel electrode-solid electrolyte layer conjugate, an anode-solid electrolyte layer conjugate, or an anode-supported solid electrolyte layer.

The first solid electrolyte layer is interposed between the fuel electrode and the second solid electrolyte layer. The second solid electrolyte layer corresponds to the solid electrolyte layer in the anode-supported solid electrolyte layer having the conventional configuration. While the fuel electrode is porous, the second solid electrolyte layer is usually a dense layer having almost no voids. The void ratio of the first to second solid electrolyte layers is determined based on a cross-sectional image of the fuel electrode-solid electrolyte layer composite by an electron micrograph. In the cross-sectional image, the ratio of the area of the region of the void portion of the solid electrolyte layer to the total area of the formation region of the solid electrolyte layer is defined as the porosity. Usually, the porosity of the fuel electrode and the porosity of the second solid electrolyte layer are significantly different, and the difference can be clearly confirmed by visually recognizing the cross-sectional image.

The first solid electrolyte layer has a role of relaxing the stress (shrinkage force) applied to the solid electrolyte layer due to the shrinkage of the fuel electrode in the reduction treatment step, and suppressing cracking and peeling of the second solid electrolyte layer.

The first solid electrolyte layer contains a nickel element like the fuel electrode, but in the first solid electrolyte layer, at least a part of nickel contains the nickel and a metal element constituting the first solid electrolyte material. It exists in the form of a composite oxide. 60% or more or 85% or more of the nickel atoms contained in the first solid electrolyte layer may be present in the state of a composite oxide. More preferably, 95% or more of the nickel atoms contained in the first solid electrolyte layer are present in the state of a composite oxide.

The composite oxide is a stable oxide that is harder to reduce than nickel oxide (NiO), and even when the nickel component contained in the fuel electrode is reduced and converted to metallic nickel, nickel in the first solid electrolyte layer Is easily maintained in the state of a composite oxide. Therefore, by containing the composite oxide, the volume shrinkage associated with the reduction treatment of the first solid electrolyte layer is suppressed. Therefore, the stress generated by the shrinkage of the fuel electrode in the reduction treatment step is applied to the first solid electrolyte layer containing the composite oxide, while the stress transmitted to the second solid electrolyte layer is reduced. Therefore, cracking and peeling of the second solid electrolyte layer are suppressed. As a result, the facing area between the fuel electrode and the second solid electrolyte layer can be made large, and a large fuel cell having a high output current can be easily realized.

Further, since the second solid electrolyte layer does not substantially contain the nickel element, the increase in the leakage current in the second solid electrolyte layer is suppressed. Further, when a metal oxide is used for the second solid electrolyte layer, a decrease in ionic conductivity can be suppressed. In particular, when a proton conductive oxide having a perovskite structure, which will be described later, is used, a decrease in proton conductivity is remarkably suppressed, and high power generation performance can be obtained. The fact that the second solid electrolyte layer does not substantially contain nickel element means that the ratio C _{2 of} Ni atoms contained in the second solid electrolyte layer is below the detection limit (for example, 0.01% or less in atomic fraction). ). The ratio C _{2 of} Ni atoms is determined by an electron probe microanalyzer (EPMA). C ₂ may be obtained at a plurality of points (for example, 10 points or more) in the second solid electrolyte layer, and the average value of the plurality of points may be obtained.

In the fuel electrode-solid electrolyte layer composite of the conventional configuration, the first solid electrolyte layer is not provided between the fuel electrode and the second solid electrolyte layer, and the second solid electrolyte layer is directly laminated on the fuel electrode. .. The fuel electrode and the second solid electrolyte layer are usually formed by co-sintering. In this case, nickel contained in the fuel electrode diffuses into the second solid electrolyte layer, the leakage current tends to increase, and the performance of the fuel cell (for example, OCV (open circuit voltage)) tends to decrease. For example, when a fuel electrode containing a nickel component and a second solid electrolyte layer molded without intentionally containing a nickel element are co-sintered, the nickel in the fuel electrode diffuses at a high temperature during sintering, and the nickel is diffused. 2 Nickel can be uniformly distributed in the solid electrolyte layer. In this case, the second solid electrolyte layer may contain, for example, about 2% nickel at a depth of 5 μm from the boundary with the fuel electrode.

On the other hand, in the conventional configuration, when the second solid electrolyte layer is formed on the fuel electrode by a low temperature process such as paste coating or sputtering, the diffusion of nickel is suppressed, but the fuel electrode and the second solid electrolyte layer are formed. Poor adhesion. Therefore, when the stress associated with the contraction of the fuel electrode is directly transmitted to the second solid electrolyte layer in the reduction treatment step, the second solid electrolyte layer is cracked or cracked, or the second solid electrolyte layer is peeled off from the fuel electrode. In some cases.

On the other hand, in the fuel electrode-solid electrolyte layer composite of the present disclosure, the stress associated with the reduction shrinkage of the fuel electrode is caused by the presence of the first solid electrolyte layer between the fuel electrode and the second solid electrolyte layer. 1 The solid electrolyte layer absorbs and the contraction force is suppressed from being transmitted to the second solid electrolyte layer. Therefore, cracking and peeling of the second solid electrolyte layer are suppressed. Further, the second solid electrolyte layer can be formed on the first solid electrolyte layer by a low temperature process such as a sputtering method. As a result, the diffusion of nickel existing in the fuel electrode or the first solid electrolyte layer into the second solid electrolyte layer is suppressed, so that high power generation performance or electrolytic performance can be obtained.

The fuel electrode-solid electrolyte layer composite having the first and second solid electrolyte layers includes, for example, a precursor of the fuel electrode (first precursor) and a precursor of the first solid electrolyte layer (second precursor). After laminating and co-sintering the laminate at a high temperature of 1400 ° C. or higher, a second solid electrolyte layer substantially free of nickel is formed on the first solid electrolyte layer by, for example, a low temperature process of 850 ° C. or lower. Can be manufactured by The specific manufacturing method will be described later.

(2) The nickel content in the first solid electrolyte layer may be smaller than the nickel content in the fuel electrode. The nickel content in the fuel electrode, the ratio of Ni atoms included in the fuel electrode (atomic fraction) means a C _A. The nickel content ratio in the first solid electrolyte layer means the ratio (atomic fraction) C ₁ of Ni atoms contained in the first solid electrolyte layer. C _A and _{C 1} are similar to _{C 2,} obtained by EPMA. A plurality of locations of the solid electrolyte layer (e.g., more than 10 points) seeking C _A and / or C ₁ at may obtain an average value. In this case, the shrinkage rate of the first solid electrolyte layer in the reduction treatment step tends to be smaller than the shrinkage rate of the fuel electrode. Therefore, the stress generated by the contraction of the fuel electrode is easily relaxed in the first solid electrolyte layer and is not easily transmitted to the second solid electrolyte layer.

(3) The first solid electrolyte layer may be substantially free of metallic nickel. By the reduction treatment, at least a part of nickel oxide in the solid electrolyte layer can be changed to metallic nickel. Therefore, the fact that the first solid electrolyte layer does not substantially contain metallic nickel means that the nickel oxide content in the first solid electrolyte layer before reduction is extremely low and the volume change is small.
Most of the nickel in the first solid electrolyte layer may be contained in the state of a nickel compound (for example, the above-mentioned composite oxide) which is difficult to reduce so as not to be changed to metallic nickel by the reduction treatment. In this case, since the first solid electrolyte layer is hardly changed in volume even in the reduction treatment step, the stress due to the contraction of the fuel electrode is absorbed by the first solid electrolyte layer, and the stress is almost transmitted to the second solid electrolyte layer. There is no. Therefore, cracking and peeling of the second solid electrolyte layer are effectively suppressed.

Here, the fact that the first solid electrolyte layer does not substantially contain metallic nickel means that the proportion C _{1M of} Ni atoms present in the metallic nickel state in the first solid electrolyte layer is equal to or less than the detection limit (for example, atomic fraction). It means that it is 0.01% or less). Ratio C _1M is the proportion (atomic fraction) C ₁ of Ni atoms included in first solid electrolyte layer, the ratio of Ni atoms present in metallic nickel condition for the total number of Ni atoms included in first solid electrolyte layer Calculated by multiplying r _M. The ratio r _M is determined, for example, by X-ray photoelectron spectroscopy (XPS). r _M may be the average value of the measured values at a plurality of points (for example, 10 points or more) in the first solid electrolyte layer.
Further, the ratio C _1M can be calculated by comparing the analysis result by EPMA with the photographic image of SEM (Scanning Electron Microscope). The X-ray diffraction (XRD) spectrum may be analyzed by the RIR (Reference Intensity Ratio) method to obtain the ratio C _1M .

(4) The first solid electrolyte layer does not have to contain substantially nickel oxide. In this case, the volume change of the first solid electrolyte layer in the reduction treatment step is suppressed. Therefore, the stress associated with the contraction of the fuel electrode is absorbed by the first solid electrolyte layer, and the stress transmitted to the second solid electrolyte layer is remarkably reduced. As a result, cracking and peeling of the second solid electrolyte layer are effectively suppressed.

Here, the fact that the first solid electrolyte layer does not substantially contain nickel oxide means that the proportion C _{1O of} Ni atoms present in the state of nickel oxide (NiO) in the first solid electrolyte layer is equal to or less than the detection limit (for example). , 0.01% or less in atomic fraction). Ratio C _1O is the proportion (atomic fraction) C ₁ of Ni atoms included in first solid electrolyte layer, the ratio of Ni atoms present in the nickel oxide state for the total number of Ni atoms included in first solid electrolyte layer It is a value multiplied by r _O. The ratio C _1O is obtained by the same method as the ratio C _1M .

(5) The thickness of the second solid electrolyte layer may be 0.2 μm or more and 20 μm or less. As a result, the resistance of ionic conduction of the solid electrolyte layer can be kept low.

When a conventional fuel electrode-solid electrolyte layer composite in which a second solid electrolyte layer is formed on the fuel electrode without passing through the first solid electrolyte layer is used, the second solid electrolyte is caused by the volume shrinkage of the fuel electrode during the reduction treatment. The thickness of the second solid electrolyte layer must be increased to a certain level or more so that the layer does not crack or peel off. However, as a result, the resistance of ion conduction increases, and the power generation efficiency tends to decrease.

On the other hand, in the fuel electrode-solid electrolyte layer composite according to the embodiment of the present disclosure, cracking and peeling of the second solid electrolyte layer are suppressed by the intervention of the first solid electrolyte layer, so that the second solid electrolyte layer There is no need to increase the thickness. The thickness of the second solid electrolyte layer can be reduced to 10 μm or less, or 5 μm or less. Therefore, a fuel cell with high power generation efficiency can be easily realized.

(6) At least one of the first solid electrolyte material, the second solid electrolyte material, and the third solid electrolyte material has a perovskite-type structure and has the following formula (1):
A _x B _{1- y My} O _3-δ
It may contain a metal oxide represented by.
Here, the element A is at least one selected from the group consisting of Ba, Ca and Sr. Element B is at least one selected from the group consisting of Ce and Zr. The element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In and Sc. δ is the amount of oxygen deficiency, which satisfies 0.95 ≦ x ≦ 1, 0 <y ≦ 0.5.

A metal oxide that satisfies the above conditions has high proton conductivity even in a temperature range of 400 ° C. or higher and 600 ° C. or lower. Therefore, by forming a fuel cell by using this metal oxide in the solid electrolyte layer, high power generation performance can be exhibited. Further, by forming a steam electrolysis cell by using this metal oxide in the second solid electrolyte layer, high steam electrolysis performance can be exhibited. Of the first to third solid electrolyte materials, it is preferable that at least the second solid electrolyte material contains a metal oxide represented by the above formula (1).

Element A may contain Ba, element B may contain Zr, and element M may contain Y. This makes it possible to improve the durability of the fuel electrode-solid electrolyte layer composite.

(7) Another embodiment of the present disclosure is a cell structure including the fuel electrode-solid electrolyte layer composite and an air electrode, in which a second solid electrolyte layer is interposed between the fuel electrode and the air electrode. The present invention relates to a fuel cell including an oxidant flow path for supplying an oxidant to an air electrode and a fuel flow path for supplying fuel to a fuel electrode. This fuel cell has excellent power generation performance and can be easily increased in size.

(8) Yet another embodiment of the present disclosure is a second solid laminated on the first solid electrolyte layer side of a laminate of the fuel electrode, the first solid electrolyte layer, and the fuel electrode and the first solid electrolyte layer. The present invention relates to a fuel electrode-solid electrolyte layer composite member having an electrolyte layer. Here, the first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing a nickel element and a metal element constituting the first solid electrolyte material. The second solid electrolyte layer contains the second solid electrolyte material and is substantially free of nickel elements. The fuel electrode contains a third solid electrolyte material and nickel oxide. By subjecting such a fuel electrode-solid electrolyte layer composite member to a reduction treatment, the above fuel electrode-solid electrolyte layer composite can be obtained.

(9) In the fuel electrode-solid electrolyte layer composite member of (8) above, the first solid electrolyte layer does not substantially contain nickel oxide, or the content ratio of nickel oxide in the first solid electrolyte layer is the fuel electrode. It may be smaller than the content ratio of nickel oxide in. When the first solid electrolyte layer contains nickel oxide, the nickel oxide contained in the fuel electrode and the first solid electrolyte layer is reduced to metallic nickel in the reduction treatment step, and accordingly, the fuel electrode and the first solid electrolyte layer are converted into metallic nickel. Shrinks. However, when the content ratio of nickel oxide in the first solid electrolyte layer is smaller than that of the fuel electrode, the shrinkage rate of the first solid electrolyte layer tends to be smaller than the shrinkage rate of the fuel electrode. Therefore, it is easy to suppress the contraction force generated in the fuel electrode from being transmitted to the second solid electrolyte layer due to the intervention of the first solid electrolyte layer.

(10) In the fuel electrode-solid electrolyte layer composite member of (8) above, the first solid electrolyte layer does not have to substantially contain nickel oxide. In this case, since the first solid electrolyte layer hardly shrinks even in the reduction treatment step, the stress associated with the shrinkage of the fuel electrode is absorbed by the first solid electrolyte layer, and the stress is hardly transmitted to the second solid electrolyte layer. Therefore, cracking and peeling of the second solid electrolyte layer are effectively suppressed.

(11) In the fuel electrode-solid electrolyte layer composite member of (8) above, at least one of the first solid electrolyte material, the second solid electrolyte material, and the third solid electrolyte material has a perovskite type structure. And the following formula (2):
A _x B _{1- y My} O _3-δ
It may contain a metal oxide represented by.
Here, the element A is at least one selected from the group consisting of Ba, Ca and Sr. Element B is at least one selected from the group consisting of Ce and Zr. The element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In and Sc. δ is the amount of oxygen deficiency, which satisfies 0.95 ≦ x ≦ 1, 0 <y ≦ 0.5. As a result, a fuel cell with high power generation performance or a steam electrolysis cell with high electrolysis performance can be realized in a temperature range of 400 ° C. or higher and 600 ° C. or lower. Of the first to third solid electrolyte materials, it is preferable that at least the second solid electrolyte material contains a metal oxide represented by the above formula (2).

(12) Yet another embodiment of the present disclosure comprises a first embodiment comprising a fuel electrode containing nickel oxide, a first solid electrolyte material, and a composite oxide of nickel and a metal element constituting the first solid electrolyte material. A step of obtaining a laminate of the solid electrolyte layer and a second solid electrolyte layer containing the second solid electrolyte material and substantially free of the nickel element on the first solid electrolyte layer side of the laminate at 850 ° C. It has a step of forming the fuel electrode-solid electrolyte layer composite member as follows and a step of forming an air electrode on the second solid electrolyte layer side of the fuel electrode-solid electrolyte layer composite member to obtain a cell structure. , Regarding the manufacturing method of fuel cells. By this manufacturing method, a large fuel cell can be easily obtained.

The second solid electrolyte layer can be formed by using a second solid electrolyte material that does not intentionally contain the nickel element. Since the formation of the second solid electrolyte layer is performed at a low temperature of 850 ° C. or lower, the nickel contained in the fuel electrode or the first solid electrolyte layer is suppressed from diffusing into the second solid electrolyte layer. Therefore, the second solid electrolyte layer is maintained in a state in which it is substantially free of nickel. As a result, in the fuel cell after production, the leakage current caused by nickel existing in the second solid electrolyte layer is suppressed. In addition, the ionic conductivity of the second solid electrolyte layer can be maintained high.

(13) The method for manufacturing a fuel cell may further include a reduction treatment step of reducing nickel oxide contained in the fuel electrode to metallic nickel. As a result, the fuel electrode becomes porous, and the solid electrolyte composite member changes into a fuel electrode-solid electrolyte layer composite. The reduction treatment step may be performed after the cell structure is obtained (after the formation of the air electrode), or by heat-treating the fuel electrode-solid electrolyte layer composite member in, for example, a hydrogen atmosphere before the formation of the air electrode. You may go.

At this time, if nickel oxide is contained in the first solid electrolyte layer, the nickel oxide contained in the first solid electrolyte layer can be reduced and changed to metallic nickel. On the other hand, the composite oxide contained in the first solid electrolyte layer is difficult to reduce and exists in the state of the composite oxide even in the reduction treatment step. In this case, the shrinkage rate of the first solid electrolyte layer in the reduction treatment can be smaller than the shrinkage rate of the fuel electrode.

Therefore, since the first solid electrolyte layer contains the composite oxide, the stress generated by the contraction of the fuel electrode due to the reduction of nickel oxide is relaxed by the first solid electrolyte layer, and the crack of the second solid electrolyte layer and Peeling is suppressed.

(14) In the step of obtaining the laminate, the first solid electrolyte layer may be substantially free of nickel oxide, or the content ratio of nickel oxide may be smaller than that of the fuel electrode. The fuel electrode and the first solid electrolyte layer can shrink in volume due to the reduction of nickel oxide. However, when the content ratio of nickel oxide in the first solid electrolyte layer is smaller than that of the fuel electrode, the shrinkage rate of the first solid electrolyte layer tends to be smaller than the shrinkage rate of the fuel electrode. On the other hand, since the second solid electrolyte layer does not substantially contain nickel oxide, it hardly shrinks. Therefore, since the shrinkage rate of the first solid electrolyte layer is smaller than the shrinkage rate of the fuel electrode, the stress generated by the shrinkage of the fuel electrode is relaxed by the first solid electrolyte layer, and the shrinkage force transmitted to the second solid electrolyte layer. Is reduced.

In particular, when the first solid electrolyte layer does not substantially contain nickel oxide, the stress associated with the contraction of the fuel electrode is absorbed by the first solid electrolyte layer and hardly transmitted to the second solid electrolyte layer. Therefore, cracking and peeling of the second solid electrolyte layer can be effectively suppressed.

(15) The steps for obtaining the laminate include a step of forming a second precursor layer containing the first solid electrolyte material on the first precursor layer containing the third solid electrolyte material and nickel oxide, and a step of forming the first precursor. The layer and the second precursor layer may be heat-treated at 1400 ° C. or higher to obtain a fuel electrode corresponding to the first precursor layer and a first solid electrolyte layer corresponding to the second precursor layer.

By heat-treating the first precursor layer and the second precursor layer at 900 ° C. or higher, a laminate of the fuel electrode and the first solid electrolyte layer can be obtained. When the heat treatment temperature is 900 ° C. or higher, nickel in the first precursor layer can diffuse into the second precursor layer to form a composite oxide. More preferably, by heat-treating the first precursor layer and the second precursor layer at 1400 ° C. or higher, the first precursor layer and the second precursor layer can be integrated in a strongly bonded state. On the other hand, by heat treatment at 900 ° C. or higher, nickel in nickel oxide contained in the first precursor layer is likely to diffuse. The diffused nickel can combine with the elements constituting the first solid electrolyte material in the second precursor layer to form various composite compounds. In the first solid electrolyte layer after the heat treatment, at least a part of the diffused nickel may exist in the state of a composite oxide containing the metal element and nickel constituting the first solid electrolyte material.

(16) In (15) above, the second precursor layer does not have to substantially contain the nickel element. That is, when the second precursor layer is formed by the coating method, it is sufficient that the raw material of the second precursor layer contains the first solid electrolyte material, and it does not have to contain nickel. Alternatively, when the second precursor layer is formed by the vapor phase method (for example, the sputtering method), only the target containing the elements constituting the first solid electrolyte material may be used, and the target containing nickel may not be used. By the heat treatment, a part of nickel contained in the first precursor layer is diffused, and a composite oxide can be formed in the second precursor layer. As a result, a first solid electrolyte layer containing the first solid electrolyte material and the composite oxide is formed.

The upper limit of the heat treatment temperature of the laminated body is not particularly limited, but may be 1800 ° C. or lower.

For example, when the first solid electrolyte material is BZY, nickel may be present in the first solid electrolyte layer after the heat treatment in a state where Ba or Zr in BZY is substituted. Further, it may exist in the form of a composite oxide such as BaY ₂ NiO ₅ and Ban NiO ₂ .

In the above (12), the step of obtaining the laminate may be performed, for example, by applying the raw material of the second precursor layer on the first precursor layer, heating and co-sintering, or by performing the first precursor. The second precursor layer may be grown on the body by the vapor phase method. The first precursor layer contains a third solid electrolyte material and nickel oxide as essential components. The raw material of the second precursor layer contains the first solid electrolyte material as an essential component. The raw material of the second precursor layer may be a mixture of the first solid electrolyte material and the powder of the composite oxide in advance. The first precursor layer and / or the second precursor layer may contain at least one additive selected from a binder, a surfactant, a glue, and the like, if necessary.

When the second precursor layer is formed by coating, screen printing, spray coating, spin coating, dip coating and the like can be used. A paste in which the raw material of the second precursor layer is dispersed in a dispersion medium such as water or an organic solvent may be applied. The dispersion medium and additives are removed by drying the coating film and performing heat treatment, the first precursor layer is transformed into a fuel electrode, the second precursor layer is transformed into a first solid electrolyte layer, and the fuel electrode is transformed. A laminate of the first solid electrolyte layer and the first solid electrolyte layer is obtained.

When the second precursor layer is formed by the vapor phase method, a sputtering method, a PVD (physical vapor deposition) method, a CVD (chemical vapor deposition) method, or the like can be used as the vapor phase method. For example, when the sputtering method is used, a target containing elements constituting the first solid electrolyte material and a target containing nickel can be used. The substrate temperature at the time of film formation may be, for example, 400 ° C. or higher and 700 ° C. or lower. A composite oxide can be formed in the first solid electrolyte layer by performing a heat treatment after the film formation.

At least one of the first precursor layer and the second precursor layer may be formed by pressure molding. For example, a pellet-shaped first precursor layer may be obtained by filling a mold with a powder of a mixture of a third solid electrolyte material and nickel oxide and pressurizing the mold, and the powder of the first solid electrolyte material is packed in a mold. By pressing, a pellet-shaped second precursor layer may be obtained. More preferably, the mixed powder of the third solid electrolyte material and nickel oxide is packed in a mold, and then the powder of the first solid electrolyte material is packed in the same mold, and the second precursor layer is placed on the first precursor layer. The laminated body may be obtained by forming the first precursor layer and the second precursor layer at the same time.
Since the first precursor layer constitutes a fuel electrode, it is usually formed thicker than the second precursor layer. Therefore, the first precursor layer may be formed into pellets by pressure molding, and the second precursor layer may be formed by applying a paste on the first precursor layer.

Further, in the above (12), the formation of the second solid electrolyte layer after obtaining the laminate may be carried out by coating and forming the raw material of the second solid electrolyte layer containing no nickel element, or the vapor phase. It may be grown by law. When the second solid electrolyte layer is formed by coating, screen printing, spray coating, spin coating, dip coating and the like can be used. The raw material of the second solid electrolyte layer contains the powder of the second solid electrolyte material. If desired, additives such as binders, surfactants, and / or glutinous agents may be included. A paste in which the second solid electrolyte material is dispersed in a dispersion medium such as water or an organic solvent may be applied. By drying the coating film and subjecting it to heat treatment, the dispersion medium and additives can be removed and a second solid electrolyte layer can be formed.
When the second solid electrolyte layer is formed by the vapor phase method, a sputtering method, a PVD method, a CVD method or the like can be used as the vapor phase method.

[Details of Embodiments of the present disclosure]
Hereinafter, specific examples of the embodiments of the present disclosure will be described below with reference to the drawings as appropriate. It should be noted that the present invention is not limited to these examples, and is indicated by the appended claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

(Fuel cell)
FIG. 1 shows a specific example of a fuel cell using the fuel electrode-solid electrolyte layer composite of the present embodiment. FIG. 1 is a schematic view showing a cross-sectional structure of a fuel cell (solid oxide fuel cell).

The fuel cell 10 includes the cell structure 1. An example of the cross-sectional structure of the cell structure is schematically shown in FIG. As shown in FIG. 2, the cell structure 1 includes an air electrode (cathode) 2, a fuel electrode (anode) 3, and a solid electrolyte layer 4 interposed between them. The fuel electrode 3 and the solid electrolyte layer 4 are integrated to form a complex.

The fuel cell 10 includes, in addition to the cell structure 1, an oxidant flow path 23 for supplying an oxidant to the air electrode 2 and a fuel flow path 53 for supplying fuel to the fuel electrode 3. In the example shown in FIG. 1, the oxidant flow path 23 is formed by the air pole side separator 22, the fuel flow path 53 is formed by the fuel pole side separator 52, and the cell structure 1 is formed by the air pole side separator 22. , It is sandwiched between the fuel electrode side separator 52 and the fuel electrode side separator 52. The oxidant flow path 23 of the air pole side separator 22 is arranged so as to face the air pole 2 of the cell structure 1, and the fuel flow path 53 of the fuel pole side separator 52 is arranged so as to face the fuel pole 3. Will be done.

(Fuel electrode-solid electrolyte complex)
The fuel electrode 3 is porous. The solid electrolyte layer 4 includes a first solid electrolyte layer 4a formed on the fuel electrode 3 and a second solid electrolyte layer 4b which has a smaller porosity than the fuel electrode 3 and is densely formed. The second solid electrolyte layer 4b is laminated on the side opposite to the fuel electrode 3 of the first solid electrolyte layer 4a. The fuel electrode 3, the first solid electrolyte layer 4a, and the second solid electrolyte layer 4b are integrated to form the fuel electrode-solid electrolyte layer composite 5.

(1st solid electrolyte layer)
The first solid electrolyte layer 4a, together with the second solid electrolyte layer 4b, constitutes at least a part of the solid electrolyte layer 4. The first solid electrolyte layer 4a is interposed between the fuel electrode 3 and the second solid electrolyte layer 4b.

For the first solid electrolyte layer, as the first solid electrolyte material, a metal oxide having a perovskite-type structure (ABO _three- phase) and having a composition represented by the above formula (1) can be used. Element A is contained in the A site of the perovskite type structure, and element B (which does not indicate boron) is contained in the B site. A part of the B site is replaced with the element M from the viewpoint of ensuring high proton conductivity.

The ratio x of element A to the total of element B and element M is preferably 0.95 ≦ x ≦ 1 from the viewpoint of ensuring high proton conductivity and ion transport number, and 0.98 ≦ x ≦ 1. More preferably. Further, when x does not exceed 1, the precipitation of the element A is suppressed, and the corrosion of the proton conductor due to the action of water can be suppressed. From the viewpoint of ensuring proton conductivity, y is preferably 0 <y ≦ 0.5, more preferably 0.1 <y ≦ 0.3.

Element A is at least one selected from the group consisting of Ba (barium), Ca (calcium) and Sr (strontium). Among them, the element A preferably contains Ba in that excellent proton conductivity can be obtained. The ratio of Ba to the element A is preferably 50 atomic% or more, and more preferably 80 atomic% or more. It is more preferable that the element A is composed only of Ba.

Element B is at least one selected from the group consisting of Ce (cerium) and Zr (zirconium). Among them, the element B preferably contains Zr from the viewpoint of durability. The ratio of Zr to the element B is preferably 50 atomic% or more, and more preferably 80 atomic% or more. It is more preferable that the element B is composed only of Zr.

The element M is selected from the group consisting of Y (yttrium), Yb (ytterbium), Er (erbium), Ho (holmium), Tm (thulium), Gd (gadrinium), In (indium) and Sc (scandium). At least one kind. The element M is a dopant, which causes oxygen defects, and the metal oxide having a perovskite-type structure exhibits proton conductivity.

In the formula (1), the oxygen deficiency amount δ can be determined according to the amount of the element M, for example, 0 ≦ δ ≦ 0.15. The ratio of each element in the metal oxide can be determined using, for example, wavelength dispersive X-ray analysis (Wavelength Dispersive X-ray spectrum, hereinafter referred to as WDX) using an electron probe microanalyzer.

Specific examples of the metal oxide include yttrium-doped barium zirconate [Ba _x Zr _1-y Y _y O _3-δ (hereinafter referred to as BZY)] and yttrium-doped barium cerium acid [Ba _x. Ce _1-y YyO _3-δ (BCY)], yttrium-doped barium zirconate / barium cerium acid mixed oxide [Ba _x Zr _1-y-z Ce _z Y _y O _3-δ (BZCY)] And so on. As a specific example of BZY, BaZr _0.8 Y _0.2 O _2.9 (x = 1, y = 0.2, δ = 0.1) may be used. As a specific example of BCY, BaCe _0.8 Y _0.2 O _2.9 (x = 1, y = 0.2, δ = 0.1) may be used. BCY and BZY show high proton conductivity in the medium temperature range of 400 ° C. or higher and 600 ° C. or lower.

The first solid electrolyte layer contains a nickel component in addition to the above metal oxide. However, in the first solid electrolyte layer, at least a part of nickel exists in the state of a composite oxide containing nickel and a metal element constituting the metal oxide of the first solid electrolyte layer. For example, when the first solid electrolyte layer contains BZY, the first solid electrolyte layer may contain composite oxides such as BaY ₂ NiO ₅ and BaNiO ₂ . These composite oxides are stable compounds that are hard to be reduced, and even when they come into contact with a fuel gas (for example, hydrogen gas), Ni in the composite oxide is hard to be reduced and changed to metallic nickel. Therefore, the volume change of the first solid electrolyte layer due to the reduction treatment is smaller than that of the fuel electrode described later.

The thickness of the first solid electrolyte layer is, for example, 1 μm or more and 20 μm or less, preferably 2 μm or more and 10 μm or less.

(Second solid electrolyte layer)
The second solid electrolyte layer 4b, together with the first solid electrolyte layer 4a, constitutes at least a part of the solid electrolyte layer 4.
In the second solid electrolyte layer, as the second solid electrolyte material, the proton conductive metal oxide having the perovskite type structure described above in the first solid electrolyte layer can be used. The metal oxide of the second solid electrolyte layer may have the same composition as the metal oxide of the first solid electrolyte layer, or may be different from the metal oxide.

The second solid electrolyte layer is manufactured so as to substantially contain no nickel component. As a result, a fuel cell having high power generation performance can be obtained.

The thickness of the second solid electrolyte layer is, for example, 0.2 μm or more and 20 μm or less, preferably 0.2 μm or more and 10 μm or less. When the thickness of the second solid electrolyte layer is in such a range, the resistance of the solid electrolyte layer can be suppressed low.

(Fuel pole)
At the fuel electrode 3, a reaction (fuel oxidation reaction) of oxidizing a fuel gas (for example, hydrogen gas) introduced from a fuel flow path and releasing protons and electrons proceeds.

As the fuel electrode, as the third solid electrolyte material, the proton conductive metal oxide having the above-mentioned perovskite type structure in the first solid electrolyte layer can be used. The metal oxide of the fuel electrode may have the same composition as the metal oxide of the first solid electrolyte layer or the metal oxide of the second solid electrolyte layer, or may be different in composition. Metal oxide of the first solid electrolyte layer (first solid electrolyte material), metal oxide of the second solid electrolyte layer (second solid electrolyte material), and metal oxide of the fuel electrode (third solid electrolyte material), The metal elements entering the A-site and the B-site of the perovskite-type structure may be the same. However, the composition ratio of the metal element in each solid electrolyte material does not necessarily have to be the same, and may be different.

The fuel electrode contains a nickel component in addition to the above metal oxide. The nickel component is, for example, metallic nickel, which acts as a catalyst for promoting a hydrogen dissociation reaction.

The thickness of the fuel electrode can be appropriately determined from, for example, 10 μm or more and 2 mm or less, and may be 10 μm or more and 100 μm or less.

(Air pole)
The air electrode 2 has a porous structure. When the second solid electrolyte layer 4b (solid electrolyte layer 4) has proton conductivity, in the air electrode 2, the reaction between the protons conducted via the second solid electrolyte layer 4b and the oxide ions (reduction of oxygen). Reaction) proceeds. Oxide ions are generated by the dissociation of the oxidant (oxygen) introduced from the oxidant flow path.

As the material of the air electrode, a known material can be used. As the material of the air electrode, for example, a compound containing lanthanum and having a perovskite structure (ferrite, manganite, and / or cobaltite, etc.) is preferable, and among these compounds, those containing strontium are more preferable. Specifically, lanthanum strontium cobalt ferrite _{(LSCF, La 1-x1 Sr} x1 Fe 1-y1 Co y1 O 3-δ1, 0 <x1 <1,0 <y1 <1, δ1 is the oxygen deficiency amount), Lantern Strontium Manganite (LSM, _La1-x2 Sr _x2 MnO _3-δ1 , 0 <x2 <1, δ1 are oxygen deficient amounts), Lantern Strontium Cobaltite (LSC, La _1-x3 Sr _x3 CoO _3-δ1) , 0 <x3 ≦ 1, δ1 is the amount of oxygen deficiency) and the like. From the viewpoint of promoting the reaction between the proton and the oxide ion, the air electrode may contain a catalyst such as Pt. The formation of the air electrode is preferably performed at 850 ° C. or lower from the viewpoint of suppressing the diffusion of nickel into the second solid electrolyte layer.

The air electrode can be formed, for example, by applying a raw material of the above material. If necessary, at least one selected from binders, additives, dispersion media, and the like may be used together with the raw materials.
The thickness of the air electrode is not particularly limited, but can be appropriately determined from, for example, 5 μm or more and 2 mm or less, and may be about 5 μm or more and 40 μm or less.

In FIGS. 1 and 2, the thickness of the fuel electrode 3 is made thicker than the thickness of the air electrode 2, and the fuel electrode 3 is a solid electrolyte layer 4 (first solid electrolyte layer 4a and second solid electrolyte layer 4b) and thus a cell. It functions as a support that supports the structure 1. The thickness of the fuel electrode 3 does not necessarily have to be thicker than that of the air electrode 2. For example, the thickness of the fuel electrode 3 may be about the same as the thickness of the air electrode 2.

(Oxidizing agent flow path and fuel flow path)
The oxidant flow path 23 has an oxidant inlet into which the oxidant flows and an oxidant discharge port for discharging water generated by the reaction, an unused oxidant, and the like (neither is shown). Examples of the oxidizing agent include a gas containing oxygen. The fuel flow path 53 has a fuel gas inlet into which a fuel gas containing water vapor and a hydrocarbon gas flows in, and a fuel gas discharge port for discharging unused fuel, H ₂ O, N ₂ , CO _2, etc. generated by the reaction. Has (neither is shown).

(Separator)
When a plurality of cell structures are laminated to form a fuel cell, for example, the cell structure 1, the air electrode side separator 22, and the fuel electrode side separator 52 can be laminated as one unit. The plurality of cell structures 1 may be connected in series by, for example, a separator having gas flow paths (oxidizer flow path and fuel flow path) on both sides.

Examples of the material of the separator include heat-resistant alloys such as stainless steel, nickel-based alloys, and chromium-based alloys in terms of electrical conductivity and heat resistance. Of these, stainless steel is preferable because it is inexpensive. In a proton conductive solid oxide fuel cell (PCFC: Protomic Ceramic Fuel Cell), since the operating temperature is about 400 ° C. or higher and 600 ° C. or lower, stainless steel can be used as a material for the separator.

(Current collector)
The fuel cell 10 may include a fuel pole side current collector 51 that is arranged between the fuel pole 3 and the fuel pole side separator 52 and is in contact with the fuel pole 3. In addition to the current collecting function, the fuel electrode side current collector 51 fulfills a function of diffusing and supplying the fuel gas introduced from the fuel flow path 53 to the fuel electrode 3. The fuel cell 10 may also include an air electrode side current collector 21 which is arranged between the air electrode 2 and the air electrode side separator 22 and comes into contact with the air electrode 2. In addition to the current collecting function, the air electrode side current collector 21 has a function of diffusing and supplying the oxidizing agent gas introduced from the oxidizing agent flow path 23 to the air electrode 2.
That is, the air pole side current collector 21 forms at least a part of the oxidant flow path 23, and the fuel pole side current collector 51 forms at least a part of the fuel flow path 53. Therefore, it is preferable that each current collector has a structure having sufficient air permeability.

Examples of the structure used for the air electrode side current collector and the fuel pole side current collector include metal porous bodies containing silver, silver alloys, nickels, nickel alloys and the like, metal meshes, punching metals, expanded metals and the like. Be done. Of these, a metal porous body is preferable in terms of lightness and breathability. In particular, a metal porous body having a three-dimensional network-like structure is preferable. The three-dimensional network-like structure refers to a structure in which rod-shaped or fibrous metals constituting a metal porous body are three-dimensionally connected to each other to form a network. For example, a sponge-like structure or a non-woven fabric-like structure can be mentioned.

The metal porous body can be formed, for example, by coating a resin porous body having continuous voids with the metal as described above. When the resin inside is removed after the metal coating treatment, a cavity is formed inside the skeleton of the metal porous body to become hollow. As a commercially available metal porous body having such a structure, nickel "Celmet" manufactured by Sumitomo Electric Industries, Ltd. or the like can be used.

The fuel cell can be manufactured by a known method except that the above cell structure is used.

(Fuel electrode-solid electrolyte layer composite member)
FIG. 3 is a schematic view showing a cross-sectional structure of a cell structure 1Z having a fuel electrode-solid electrolyte layer composite member used in the manufacturing process of the fuel cell shown in FIG. As shown in FIG. 3, the cell structure 1Z includes an air electrode (cathode) 2 and a fuel electrode-solid electrolyte layer composite member 5Z. The fuel electrode-solid electrolyte layer composite member 5Z is a laminate in which the fuel electrode 6a, the first solid electrolyte layer 6b, and the second solid electrolyte layer 6c are laminated in this order. The second solid electrolyte layer 6c is in contact with the air electrode 2. The fuel electrode 6a, the first solid electrolyte layer 6b, and the second solid electrolyte layer 6c are each before the fuel electrode 3, the first solid electrolyte layer 4a, and the second solid electrolyte layer 4b shown in FIG. 2 are reduced. It is in the state of.

The first solid electrolyte layer 6b contains nickel and a first solid electrolyte material. In the first solid electrolyte layer 6b, at least a part of nickel exists in the form of a composite oxide with a metal element constituting the first solid electrolyte material. The metal element constituting the first solid electrolyte material has a perovskite-type structure (ABO _3- phase) and has a composition represented by the above formula (2). The details of the perovskite-type structure of the above formula (2) are the same as those of the perovskite-type structure of the above formula (1) described in the details of the embodiments of the present disclosure. The first solid electrolyte layer 6b can be formed, for example, by applying a paste containing a powder of the first solid electrolyte material on the fuel electrode 6a and then drying it.

The second solid electrolyte layer 6c contains the second solid electrolyte material and substantially does not contain the nickel component. The second solid electrolyte layer 6c can be formed, for example, by a vapor phase method (for example, a sputtering method). The film formation of the second solid electrolyte layer 6c is performed at 850 ° C. or lower in order to suppress the diffusion of nickel from the first solid electrolyte layer 6b.

The fuel electrode 6a contains nickel oxide and a third solid electrolyte material. The fuel electrode 6a can be formed, for example, by placing a powder of a mixture of nickel oxide and a third solid electrolyte material in a mold and press-molding the fuel electrode 6a.

It is preferable that the fuel electrode 6a and the first solid electrolyte layer 6b are co-sintered. Co-sintering is performed, for example, at a high temperature of 1400 ° C. or higher. As a result, the first solid electrolyte layer 6b is firmly adhered to the fuel electrode 6a. Further, the nickel element contained in the fuel electrode 6a diffuses into the first solid electrolyte layer 6b, and a composite oxide is formed in the first solid electrolyte layer 6b.

In FIGS. 1 and 2, a fuel cell in which the cell structure 1 is replaced with the cell structure 1Z shown in FIG. 3 is assembled. After assembling the fuel cell, by supplying fuel gas from the fuel electrode 6a side via the fuel flow path 53, nickel oxide in the fuel electrode 6a is reduced and changed to metallic nickel. At this time, the fuel electrode 6a contracts with the change to metallic nickel and changes to a porous fuel electrode 3a. On the other hand, the composite oxide contained in the first solid electrolyte layer 6b is hardly reduced and hardly shrinks. Therefore, the fuel cell 10 shown in FIG. 1 can be manufactured.

A shrinking force is applied to the first solid electrolyte layer 6b (4a) as the fuel electrode 6a (3) shrinks. However, due to co-sintering at a high temperature, the bonding between the fuel electrode 6a and the first solid electrolyte layer 6b is strong. Therefore, cracks and peeling are unlikely to occur in the first solid electrolyte layer 4a in the reduction treatment. The stress associated with the contraction is relaxed in the first solid electrolyte layer 4a, and the stress transmitted to the second solid electrolyte layer 4b is reduced. Therefore, the second solid electrolyte layer 4b is unlikely to crack or peel off.

Therefore, by using the fuel electrode-solid electrolyte layer composite member 5Z, cracking and peeling of the fuel electrode-solid electrolyte layer composite 5 are suppressed, so that the solid electrolyte layer (second solid electrolyte layer 4b) and the fuel electrode 3 are suppressed. It is easy to increase the facing area with the fuel cell, and a fuel cell having a large output current can be easily realized. Further, since this fuel cell does not substantially contain a nickel component in the second solid electrolyte layer 4b, the power generation efficiency is high.

[Example]
Hereinafter, the present disclosure will be specifically described based on Examples and Comparative Examples, but the present disclosure is not limited to the following Examples.

[Example 1]
(1) Preparation of fuel electrode-solid electrolyte layer composite member NiO and BZY (BaZr _0.8 Y _0.2 O _2.9 ) powder are mixed with a binder (polyvinyl alcohol) and a surfactant (polycarboxylic acid type interface). The activator) and an appropriate amount of ethanol were mixed with a ball mill and granulated. At this time, NiO and BZY were mixed at a volume ratio of 70:30. The amounts of the binder and the surfactant were 10 parts by mass and 0.5 parts by mass, respectively, with respect to 100 parts by mass of the total amount of NiO and BZY. The obtained granulated product was uniaxially molded to obtain a molded product having a first precursor layer (diameter 200 mm, thickness 0.6 mm).

By mixing BZY (BaZr _0.8 Y _0.2 O _2.9 ), a binder (ethyl cellulose), a surfactant (polycarboxylic acid type surfactant), and an appropriate amount of butyl carbitol acetate. A paste of two precursor layers was prepared. The amounts of the binder and the surfactant were 6 parts by mass and 0.5 parts by mass, respectively, with respect to 100 parts by mass of BZY. The paste of the second precursor layer was applied to one surface of the molded product by screen printing.

The molded product after forming the coating film was heated at 750 ° C. for 10 hours to perform a binder removal treatment. Next, the molded product was fired at 1600 ° C. for 10 hours in an air atmosphere to obtain a laminate of a fuel electrode and a first solid electrolyte layer. The thickness of the second precursor layer (first solid electrolyte layer) after sintering was 5 μm.

Then, 5 μm of BZY as the second solid electrolyte layer was formed on the first solid electrolyte layer by a sputtering method. The film formation temperature was 650 ° C. As a result, a fuel electrode-solid electrolyte layer composite member X1 was obtained.

(2) Reduction Treatment Subsequently, the fuel electrode-solid electrolyte layer composite member X1 was heated at 600 ° C. for 10 hours in a hydrogen atmosphere to reduce NiO contained in the fuel electrode to Ni. As a result, a fuel electrode-solid electrolyte layer composite was obtained.

(3) Preparation of fuel cell Next, on the surface of the second solid electrolyte layer, a powder of LSCF (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ ), which is a material for the air electrode. The LSCF paste, which is a mixture of and an organic solvent (butyl carbitol acetate), was screen-printed and dried at 120 ° C. to form an air electrode. As a result, the cell structure shown in FIG. 2 was obtained.
The thickness of the air electrode was 10 μm.

A stainless steel fuel pole side separator having a gas flow path is laminated on the surface of the fuel electrode of the cell structure obtained above, and a stainless steel cathode side separator having a gas flow path is laminated on the surface of the air electrode. Was laminated to assemble the fuel cell Y1.
One end of the lead wire was joined to each of the anode side separator and the cathode side separator. The other end of each lead was pulled out of the fuel cell and connected to a measuring instrument so that the current and voltage values between each lead could be measured.
(4) Evaluation The fuel cell was operated under operating conditions of 600 ° C. Hydrogen humidified to a dew point of 25 ° C is supplied to the fuel electrode side at a flow rate of 1 L / min, and synthetic air (a mixture of oxygen and nitrogen only) having a dew point of -40 ° C or less is supplied to the air electrode side at a flow rate of 1 L / min. OCV (open circuit voltage) was measured.

[Comparative Example 1]
NiO and BZY (BaZr _0.8 Y _0.2 O _2.9 ) powder are mixed with a binder (polyvinyl alcohol), a surfactant (polycarboxylic acid type surfactant), and an appropriate amount of ethanol in a ball mill. And granulated. At this time, NiO and BZY were mixed at a volume ratio of 70:30. The amounts of the binder and the surfactant were 10 parts by mass and 0.5 parts by mass, respectively, with respect to 100 parts by mass of the total amount of NiO and BZY. The obtained granulated product was uniaxially molded to obtain a molded product having a first precursor layer (diameter 200 mm, thickness 0.6 mm). The molded product was heated at 750 ° C. for 10 hours to perform a binder removal treatment. Next, the molded product was fired at 1600 ° C. for 10 hours in an air atmosphere to obtain a sintered body of fuel electrodes.

After that, 10 μm of BZY as the second solid electrolyte layer was formed on the fuel electrode by a sputtering method. The film formation temperature was 650 ° C. As a result, a fuel electrode-solid electrolyte layer composite member X2 was obtained.

Using the fuel electrode-solid electrolyte layer composite member X2 described above, a fuel cell Y2 was prepared in the same manner as in Example 1 and evaluated in the same manner.

[Comparative Example 2]
NiO and BZY (BaZr _0.8 Y _0.2 O _2.9 ) powder are mixed with a binder (polyvinyl alcohol), a surfactant (polycarboxylic acid type surfactant), and an appropriate amount of ethanol in a ball mill. And granulated. At this time, NiO and BZY were mixed at a volume ratio of 70:30. The amounts of the binder and the surfactant were 10 parts by mass and 0.5 parts by mass, respectively, with respect to 100 parts by mass of the total amount of NiO and BZY. The obtained granulated product was uniaxially molded to obtain a molded product having a first precursor layer (diameter 200 mm, thickness 0.6 mm).

By mixing BZY (BaZr _0.8 Y _0.2 O _2.9 ), binder (ethyl cellulose), surfactant (polycarboxylic acid type surfactant), and an appropriate amount of butyl carbitol acetate. A paste of two solid electrolyte layers was prepared. The amounts of the binder and the surfactant were 6 parts by mass and 0.5 parts by mass, respectively, with respect to 100 parts by mass of BZY. The paste was applied to one surface of the molded product by screen printing.

The molded product after forming the coating film was heated at 750 ° C. for 10 hours to perform a binder removal treatment. Next, the molded product was fired at 1600 ° C. for 10 hours in an air atmosphere to obtain a sintered body of a fuel electrode and a second solid electrolyte layer. The thickness of the second solid electrolyte layer after sintering was 5 μm. As a result, a fuel electrode-solid electrolyte layer composite member X3 was obtained.

Using the above fuel electrode-solid electrolyte layer composite member X3, a fuel cell Y3 was prepared in the same manner as in Example 1, and evaluated in the same manner.

The fuel cell Y1 of Example 1 using the fuel electrode-solid electrolyte layer composite member X1 showed a high OCV of 1.05V. Further, when the fuel cell after the evaluation was disassembled and the fuel electrode-solid electrolyte layer composite was taken out, no cracks or peeling were observed in the second solid electrolyte layer.

On the other hand, in the fuel cell Y2 of Comparative Example 1 using the fuel electrode-solid electrolyte layer composite member X2, the OCV was 0.3 V or less, and it was difficult to generate electricity. When the fuel cell after the evaluation was disassembled and the fuel electrode-solid electrolyte layer composite was taken out, a part of the second solid electrolyte layer was peeled off from the fuel electrode. In addition, many cracks were visually confirmed in the second solid electrolyte layer.

Further, in the fuel cell Y3 of Comparative Example 2 using the fuel electrode-solid electrolyte layer composite member X3, the OCV was 0.96V, which was lower than that of the fuel cell Y1 of Example 1. When the fuel cell after the evaluation was disassembled and the fuel electrode-solid electrolyte layer composite was taken out, no cracks or peeling were observed in the second solid electrolyte layer. The reason why the OCV of the fuel cell Y3 is lower than that of the fuel cell Y1 is that the second solid electrolyte layer is co-sintered together with the fuel electrode (first precursor layer) at a high temperature (1600 ° C.). It is considered that a part of the nickel contained in the fuel cell diffused into the second solid electrolyte layer, and the proton conductivity of the second solid electrolyte layer decreased.

1, 1Z: Cell structure 2: Air pole 3: Fuel pole 4: Solid electrolyte layer 4a: First solid electrolyte layer 4b: Second solid electrolyte layer 5: Fuel pole-solid electrolyte layer composite 5Z: Fuel pole-solid Electrolyte layer composite member 6a: Fuel electrode 6b: First solid electrolyte layer 6c: Second solid electrolyte layer 10: Fuel cell 21, 51: Current collector 22, 52: Separator 23: Oxidating agent flow path 53: Fuel flow path

Claims (16)

1. Porous fuel electrode and
   The first solid electrolyte layer formed on the fuel electrode and
   A second solid electrolyte layer having a porosity smaller than that of the fuel electrode, which is laminated on the opposite side of the first solid electrolyte layer to the fuel electrode, is included.
   The first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing a nickel element and a metal element constituting the first solid electrolyte material.
   The second solid electrolyte layer contains a second solid electrolyte material and is substantially free of nickel elements.
   The fuel electrode is a fuel electrode-solid electrolyte layer composite containing a third solid electrolyte material and metallic nickel.
2. The fuel electrode-solid electrolyte layer composite according to claim 1, wherein the nickel content ratio in the first solid electrolyte layer is smaller than the nickel content ratio in the fuel electrode.
3. The fuel electrode-solid electrolyte layer composite according to claim 1 or 2, wherein the first solid electrolyte layer is substantially free of metallic nickel.
4. The fuel electrode-solid electrolyte layer composite according to any one of claims 1 to 3, wherein the first solid electrolyte layer does not substantially contain nickel oxide.
5. The fuel electrode-solid electrolyte layer composite according to any one of claims 1 to 4, wherein the thickness of the second solid electrolyte layer is 0.2 μm or more and 20 μm or less.
6. At least one of the first solid electrolyte material, the second solid electrolyte material, and the third solid electrolyte material has a perovskite-type structure, and the following formula (1):
   A _x B _{1- y My} O _3-δ
   Contains metal oxides represented by
   Element A is at least one selected from the group consisting of Ba, Ca and Sr.
   Element B is at least one selected from the group consisting of Ce and Zr.
   The element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In and Sc.
   The fuel electrode-solid electrolyte layer composite according to any one of claims 1 to 5, wherein δ is an oxygen deficiency amount and satisfies 0.95 ≦ x ≦ 1 and 0 <y ≦ 0.5.
7. The fuel electrode-solid electrolyte layer composite according to any one of claims 1 to 6 and an air electrode are included, and the second solid electrolyte layer is interposed between the fuel electrode and the air electrode. Cell structure,
   An oxidant flow path for supplying the oxidant to the air electrode, and
   A fuel cell comprising a fuel flow path for supplying fuel to the fuel electrode.
8. It has a fuel electrode, a first solid electrolyte layer, and a second solid electrolyte layer laminated on the first solid electrolyte layer side of a laminate of the fuel electrode and the first solid electrolyte layer.
   The first solid electrolyte layer contains a first solid electrolyte material and a composite oxide containing a nickel element and a metal element constituting the first solid electrolyte material.
   The second solid electrolyte layer contains a second solid electrolyte material and is substantially free of nickel elements.
   The fuel electrode is a fuel electrode-solid electrolyte layer composite member containing a third solid electrolyte material and nickel oxide.
9. The eighth aspect of the present invention, wherein the first solid electrolyte layer is substantially free of nickel oxide, or the content of nickel oxide in the first solid electrolyte layer is smaller than the content of nickel oxide in the fuel electrode. Fuel electrode-solid electrolyte layer composite member.
10. The fuel electrode-solid electrolyte layer composite member according to claim 9, wherein the first solid electrolyte layer does not substantially contain nickel oxide.
11. At least one of the first solid electrolyte material, the second solid electrolyte material, and the third solid electrolyte material has a perovskite-type structure, and the following formula (2):
    A _x B _{1- y My} O _3-δ
    Contains metal oxides represented by
    Element A is at least one selected from the group consisting of Ba, Ca and Sr.
    Element B is at least one selected from the group consisting of Ce and Zr.
    The element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In and Sc.
    The fuel electrode-solid electrolyte layer composite member according to any one of claims 8 to 10, wherein δ is an oxygen deficiency amount and satisfies 0.95 ≦ x ≦ 1 and 0 <y ≦ 0.5.
12. A step of obtaining a laminate of a fuel electrode containing nickel oxide, a first solid electrolyte material, and a first solid electrolyte layer containing a composite oxide of nickel and a metal element constituting the first solid electrolyte material. ,
    On the first solid electrolyte layer side of the laminate, a second solid electrolyte layer containing a second solid electrolyte material and substantially free of nickel elements is formed at 850 ° C. or lower, and a fuel electrode-solid electrolyte layer composite is formed. The process of obtaining parts and
    A method for manufacturing a fuel cell, comprising a step of forming an air electrode on the second solid electrolyte layer side of the fuel electrode-solid electrolyte layer composite member to obtain a cell structure.
13. The method for manufacturing a fuel cell according to claim 12, further comprising a reduction treatment step of reducing nickel oxide contained in the fuel electrode to metallic nickel.
14. The fuel according to claim 12 or 13, wherein in the step of obtaining the laminate, the first solid electrolyte layer contains substantially no nickel oxide, or the content ratio of nickel oxide is smaller than that of the fuel electrode. How to make a battery.
15. The step of obtaining the laminate is
    A step of forming a second precursor layer containing the first solid electrolyte material on the first precursor layer containing the third solid electrolyte material and nickel oxide, and
    The first precursor layer and the second precursor layer are heat-treated at 1400 ° C. or higher to form the fuel electrode corresponding to the first precursor layer and the first solid electrolyte layer corresponding to the second precursor layer. The method for manufacturing a fuel cell according to any one of claims 12 to 14, which comprises a step of obtaining the fuel cell.
16. The method for manufacturing a fuel cell according to claim 15, wherein the second precursor layer does not substantially contain a nickel element.

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