JP5746747B1 - Solid oxide fuel cell - Google Patents

Abstract

A solid oxide fuel cell capable of suppressing the occurrence of peeling between a solid electrolyte layer and a seal portion is provided. A solid oxide fuel cell includes a power generation unit, an interconnector, and a seal unit. The power generation unit 30 includes a fuel electrode current collecting layer 31, a solid electrolyte layer 33, and an air electrode active layer 35. The interconnector 40 is connected to the anode current collecting layer 31. Seal unit 50 is connected to solid electrolyte layer 33 and interconnector 40. The solid electrolyte layer 33 includes a contact part 100 that contacts the surface 50S of the seal part 50. At least a part of the outer edge portion 110 of the contact portion 100 protrudes in a direction away from the surface 50 </ b> S of the seal portion 50. [Selection] Figure 2

Description

  The present invention relates to a solid oxide fuel cell including a seal portion disposed between an interconnector and a solid electrolyte layer.

  Conventionally, a solid oxide fuel cell includes a power generation unit and a dense interconnector. The power generation unit includes a fuel electrode, a dense solid electrolyte layer, and an air electrode. The interconnector is electrically connected to the fuel electrode of the power generation unit and the air electrode of another adjacent power generation unit. Gas leakage in the power generation unit is suppressed by the interconnector and the solid electrolyte layer.

Here, in order to suppress the formation of a non-dense layer between the interconnector and the solid electrolyte layer, a method of inserting a seal portion made of NiO—Y ₂ O ₃ or Ni—Y ₂ O ₃ Has been proposed.

JP 2009-134930 A

  However, there is a problem that peeling is likely to occur between the solid electrolyte layer and the seal portion. Therefore, as a result of intensive studies by the present inventors, the inventors have obtained a novel finding that the cause is that the outer edge of the solid electrolyte layer falls from the surface of the seal portion.

  The present invention has been made on the basis of the above-described novel findings, and an object thereof is to provide a solid oxide fuel cell capable of suppressing the occurrence of peeling between the solid electrolyte layer and the seal portion.

  The solid oxide fuel cell according to the present invention includes a power generation part, a dense interconnector, and a dense seal part. The power generation unit includes a fuel electrode, an air electrode, and a dense solid electrolyte layer disposed between the fuel electrode and the air electrode. The interconnector is electrically connected to the fuel electrode. The seal portion is connected to the solid electrolyte layer and the interconnector. The solid electrolyte layer has a contact portion in contact with the surface of the seal portion. At least a part of the outer edge portion of the contact portion protrudes away from the surface of the seal portion.

  ADVANTAGE OF THE INVENTION According to this invention, the solid oxide fuel cell which can suppress that peeling arises between a solid electrolyte layer and a seal | sticker part can be provided.

Cross section of solid oxide fuel cell Partial enlarged view of FIG.

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

  In the following embodiments, a so-called horizontal-striped solid oxide fuel cell will be described as an example. However, the present invention relates to a vertical-striped, fuel electrode support, electrolyte flat plate, or cylindrical solid oxide fuel cell. Applicable to batteries.

(Configuration of Solid Oxide Fuel Cell 10)
A configuration of a solid oxide fuel cell (SOFC) 10 will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a solid oxide fuel cell 10.

  The solid oxide fuel cell 10 includes a support substrate 20, a plurality of power generation units 30, a plurality of interconnectors 40, and a seal unit 50.

The support substrate 20 is formed in a flat plate shape. The support substrate 20 is made of a porous material. A flow path 21 for flowing fuel gas is formed inside the support substrate 20. The support substrate 20 may contain nickel (Ni) and / or nickel oxide (NiO). When the support substrate 20 contains NiO, NiO may be reduced to Ni by hydrogen gas during power generation. The support substrate 20 may contain Ni and yttria (Y ₂ O ₃ ) as main components.

  In the present embodiment, “the composition A contains the substance B as a main component” preferably means that the content of the substance B in the composition A is 60% by weight or more, and more preferably, the composition It means that the content of substance B in A is 70% by weight or more. Further, “the composition A contains the substance B as a main component” is a concept including the case where the composition A is composed of only the substance B.

  The plurality of power generation units 30 are electrically connected in series via the plurality of interconnectors 40. Each power generation unit 30 includes a fuel electrode current collecting layer 31 (an example of a fuel electrode), a fuel electrode active layer 32, a solid electrolyte layer 33, a reaction preventing layer 34, and an air electrode active layer 35 (an example of an air electrode). And an air electrode current collecting layer 36.

The anode current collecting layer 31 is embedded in the support substrate 20. The anode current collecting layer 31 may contain Ni or / and NiO. When the anode current collecting layer 31 contains NiO, NiO may be reduced to Ni by hydrogen gas during power generation. The anode current collecting layer 31 may contain yttrium (Y) and / or cerium (Ce) in addition to Ni. The anode current collecting layer 31 may contain Y ₂ O ₃ and / or ceria (CeO ₂ ). The anode current collecting layer 31 may contain Ni and Y ₂ O ₃ as main components, and may contain Ni and gadolinia doped ceria (GDC) as main components.

The anode active layer 32 is embedded in the anode current collecting layer 31. The anode active layer 32 may contain Ni or / and NiO. When the anode active layer 32 contains NiO, NiO may be reduced to Ni by hydrogen gas during power generation. The anode active layer 32 may contain zirconia (ZrO ₂ ). A rare earth element may be dissolved in ZrO ₂ . The anode active layer 32 may contain the zirconia-based material contained in the solid electrolyte layer 33.

  The solid electrolyte layer 33 is formed on the support substrate 20 so as to cover the anode current collecting layer 31 and the anode active layer 32. The solid electrolyte layer 33 is denser than the support substrate 20, the fuel electrode current collecting layer 31, and the fuel electrode active layer 32. The porosity of the solid electrolyte layer 33 is preferably 10% or less. The solid electrolyte layer 33, together with the interconnector 40 and the seal part 50, constitutes a gas seal layer for separating air and fuel gas.

The solid electrolyte layer 33 may contain ZrO ₂ . The solid electrolyte layer 33 can contain a zirconia-based material such as yttria-stabilized zirconia (3YSZ, 8YSZ, 10YSZ, etc.) or scandia-stabilized zirconia (ScSZ) as a main component, and particularly contains 8YSZ as a main component. It is preferable. The thickness of the solid electrolyte layer 30 can be 3 μm to 30 μm.

  In the present embodiment, the first end portion 33 a of the solid electrolyte layer 33 is disposed on the seal portion 50 of the self-power generation unit and is exposed from the reaction preventing layer 34. The second end portion 33 b of the solid electrolyte layer 33 is disposed on the seal portion 50 of the adjacent other power generation unit and is covered with the reaction preventing layer 34. The configuration of the first end portion 33a of the solid electrolyte layer 33 will be described later.

The reaction preventing layer 34 is formed on the solid electrolyte layer 33. The reaction preventing layer 34 may contain CeO ₂ . The reaction preventing layer 34 may contain a ceria-based material containing CeO ₂ and a rare earth metal oxide dissolved in CeO ₂ as a main component. Examples of ceria-based materials include gadolinium-doped ceria (GDC) and samarium-doped ceria (SDC).

  The air electrode active layer 35 is provided on the reaction preventing layer 34. The air electrode active layer 35 may contain, for example, a lanthanum-containing perovskite complex oxide as a main component. Specific examples of the lanthanum-containing perovskite complex oxide include LSCF (lanthanum strontium cobalt ferrite), lanthanum manganite, lanthanum cobaltite, and lanthanum ferrite. The lanthanum-containing perovskite complex oxide may be doped with Sr, Ca, Cr, Co, Fe, Ni, Al or the like.

  The air electrode current collecting layer 36 is formed on the reaction preventing layer 34 and the air electrode active layer 35. One end of the air electrode current collecting layer 36 is coupled to an interconnector 40 connected to the adjacent power generation unit 30. The air electrode current collecting layer 36 only needs to have conductivity, and can be made of, for example, the same material as that of the air electrode active layer 35.

  The interconnector 40 is embedded in the anode current collecting layer 31. The side of the interconnector 40 is surrounded by the seal portion 50. The interconnector 40 includes an interconnector layer 41 and an intermediate layer 42.

  The interconnector layer 41 is denser than the support substrate 20, the fuel electrode current collecting layer 31, and the fuel electrode active layer 32. The interconnector layer 41, together with the solid electrolyte layer 33 and the seal portion 50, constitutes a gas seal layer for separating air and fuel gas. The interconnector layer 41 may contain a chromite-based material represented by the general formula (1) as a main component.

Ln _1-x A _x Cr _1-yz B _y O ₃ (1)
However, in the formula (1), Ln is at least one element selected from the group consisting of Y and a lanthanoid. The A site contains at least one element selected from the group consisting of Ca, Sr and Ba. The B site contains at least one element selected from the group consisting of Ti, V, Mn, Fe, Co, Cu, Ni, Zn, Mg, and Al. Further, 0.025 ≦ x ≦ 0.3, 0 ≦ y ≦ 0.22, and 0 ≦ z ≦ 0.15.

  The intermediate layer 42 is interposed between the interconnector layer 41 and the anode current collecting layer 31. The intermediate layer 42 may contain an element (for example, Ni) contained in the anode current collecting layer 31 and a chromite-based material. The chromite material contained in the intermediate layer 42 may be the same as or different from the chromite material contained in the interconnector 40.

  The seal part 50 is connected to the first end part 33 a of the solid electrolyte layer 33 of the self-power generation part and the interconnector 40. In the present embodiment, the seal part 50 is formed so as to surround the side of the interconnector 40 and is also connected to the solid electrolyte layer 33 and the reaction preventing layer 34 of the adjacent other power generation part. However, the sealing part 50 should just be arrange | positioned between the solid electrolyte layer 33 and the interconnector 40 of a self-power generation part, and may have a shape different from FIG.

  The seal part 50 is denser than the support substrate 20, the fuel electrode current collecting layer 31, and the fuel electrode active layer 32. The seal part 50 constitutes a gas seal layer for separating air and fuel gas together with the solid electrolyte layer 33 and the interconnector layer 41.

The seal part 50 preferably contains a metal oxide (two or more kinds of metal oxides may be mixed). Examples of the metal oxide include at least one oxide selected from the group consisting of (AE) ZrO ₃ , MgO, MgAl ₂ O ₄ , and Ce _x Ln _1-x O ₂ . AE is an alkaline earth metal such as Mg, Ca, Sr, and Ba, and Ca is particularly preferable. Accordingly, for example, CaZrO ₃ is suitable as the metal oxide represented by (AE) ZrO ₃ . Ln is at least one element selected from the group consisting of Y and lanthanoids. X satisfies 0 <x ≦ 0.3.

The seal part 50 particularly preferably contains a metal oxide and MgO as main components. Moreover, the seal part 50 may contain Fe ₂ O ₃ , Al ₂ O _3, Y ₂ O _{3 and the} like in addition to the metal oxide and MgO.

The content rate of (AE) ZrO ₃ in the seal part 50 may be 5 to 99 wt%, preferably 5 to 95 wt%, and more preferably 10 to 90 wt%. The content of MgO in the seal part 50 may be 1 to 95 wt%, preferably 5 to 95 wt%, and more preferably 10 to 90 wt%. By setting it as such a range, the intensity | strength of the sealing film in the seal | sticker part 50 can be improved more, and durability can be improved more. The ratio (weight ratio) of (AE) ZrO ₃ and MgO in the seal part 50 may be 5:95 to 99: 1, preferably 5:95 to 95: 5, and more preferably 10:90 to 90:10. preferable. By setting it as such a ratio, the intensity | strength of the sealing film in the seal | sticker part 50 can be improved more, and durability can be improved more.

(Configuration of the first end portion 33a of the solid electrolyte layer 33)
Next, the configuration of the first end portion 33a of the solid electrolyte layer 33 will be described with reference to the drawings. FIG. 2 is a partially enlarged view of FIG.

  The first end portion 33 a of the solid electrolyte layer 33 is disposed on the surface 50 </ b> S of the seal portion 50. The first end portion 33 a of the solid electrolyte layer 33 includes a contact portion 100 and a separation portion 200.

The contact part 100 is in direct contact with the surface 50S of the seal part 50. The contact part 100 contains Ca and Zr. The contact part 100 may contain CaZr ₄ O ₉ and / or CaZrO ₃ . The contact part 100 may contain CaZr ₄ O ₉ and / or CaZrO ₃ as a main component. Moreover, the contact part 100 may contain the same material (8YSZ, ScSZ, etc.) as the separation part 200. The contact part 100 has an outer edge part 110 and a flat part 120.

  The outer edge portion 110 is provided at the tip of the first end portion 33a. The outer edge portion 110 protrudes away from the surface 50 </ b> S as compared to the flat portion 120. That is, the thickness of the contact portion 100 is greater at the outer edge portion 110 than at the flat portion 120. In the present embodiment, the outer edge portion 110 has a substantially semi-elliptical cross section, but may have a rectangular shape, a triangular shape, a sawtooth shape, or the like.

  The protrusion height from the surface 50S of the outer edge portion 110 (that is, the thickness of the outer edge portion 110) can be 10% to 80% of the thickness of the solid electrolyte layer 33, and is preferably 20% or more. The protruding height of the outer edge portion 110 can be 3 μm to 25 μm, and is preferably 5 μm or more.

  The flat portion 120 continues to the inside of the outer edge portion 110. The thickness of the flat portion 120 may be uniform. The thickness of the flat portion 120 can be 0.3 μm to 5 μm, and is preferably 1 μm or more.

  The separation portion 200 is a region that is separated from the seal portion 50 in the first end portion 33a. The separation part 200 is separated from the surface 50 </ b> S via the contact part 100. The thickness of the separation part 200 can be 3 μm to 100 μm, and preferably 10 μm to 50 μm. However, since the distal end of the separation portion 200 is disposed on the outer edge portion 110 of the contact portion 100, it is formed in a tapered shape. Therefore, the thickness of the separation portion 200 may be thinner toward the tip.

  Such a solid electrolyte layer 33 can be formed by applying a slurry in which water and a binder are mixed with powder for a solid electrolyte layer in an overlapping manner by a screen printing method or the like. Hereinafter, a method for producing the solid electrolyte layer 33 will be described.

First, a material powder containing Ca and Zr (for example, CaZr ₄ O ₉ powder or CaZrO ₃ powder) is mixed with water and a binder (for example, polyvinyl alcohol) to prepare a slurry.

  Next, slurry is applied on the flat molded bodies of the seal portion 50, the anode current collecting layer 31, and the anode active layer 32. As a result, a molded body of the base portion of the outer edge portion 110 and the flat portion 120 is formed. Subsequently, the slurry is applied a plurality of times on the base portion of the outer edge portion 110. As a result, a molded body of the outer edge portion 110 is formed.

  Next, water and a binder (for example, polyvinyl alcohol) are mixed with zirconia-based material powder (for example, 8YSZ powder) to prepare a slurry. Next, the slurry produced on each molded body of the outer edge portion 110 and the flat portion 120 is applied a plurality of times. Thereby, a molded body of the separation portion 200 is formed.

  The solid electrolyte layer 33 formed as described above is co-fired with the respective molded bodies of the anode current collecting layer 31, the anode active layer 32, the interconnector 40, and the seal portion 50, thereby forming the solid electrolyte layer 33. Is formed.

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

  For example, although not particularly mentioned in the above embodiment, the entire outer edge portion 110 of the solid electrolyte layer 33 may not protrude in a direction away from the surface 50S. That is, it is sufficient that at least a part of the outer edge portion 110 protrudes in a direction away from the surface 50S, and the protruding portion and the portion that does not protrude may be formed continuously.

  In the above embodiment, as shown in FIG. 1, the interconnector 40, the seal portion 50, the anode current collecting layer 31, and the anode active layer 32 are embedded in the support substrate 20. It may be laminated on the substrate 20. In this case, the first end portion 33 a of the solid electrolyte layer 33 only needs to be in contact with the surface 50 </ b> S of the seal portion 50.

  Moreover, in the said embodiment, although the fuel electrode current collection layer 31 (an example of a fuel electrode) was directly connected with the interconnector 40, it should just be electrically connected with the interconnector 40. FIG. Therefore, an intermediate layer may be interposed between the anode current collecting layer 31 and the interconnector 40.

(Preparation of sample according to level 1)
A sample according to Level 1 was produced as follows.

  First, a support substrate molded body having a plurality of recesses formed on the surface was prepared.

  Next, a molded body of the anode current collecting layer was formed in each recess of the molded body of the support substrate by using a printing method. At this time, the surface of the molded body of the anode current collecting layer was flush with the surface of the molded body of the support substrate, and the first and second recesses were formed on the surface of the molded body of the anode current collecting layer.

  Next, a molded body of the anode active layer was formed in the first recess of the molded body of the anode current collecting layer using a printing method. At this time, the surface of the molded body of the anode active layer was flush with the surface of the molded body of the anode current collecting layer.

  Next, using the printing method, after forming the molded part of the seal portion into the second concave portion of the molded body of the anode current collecting layer, the inner side of the molded body of the seal part using the printing method. An interconnector molded body was formed. At this time, the surfaces of the molded parts of the seal portion and the interconnector were flush with the surface of the molded body of the fuel electrode current collecting layer.

  Next, 8YSZ powder was mixed with water and polyvinyl alcohol to prepare a solid electrolyte layer slurry. Subsequently, the prepared solid electrolyte layer slurry was applied by a printing method to form a solid electrolyte layer formed body so as to be in contact with two adjacent seal portions. At this time, a molded body of the solid electrolyte layer was formed with a uniform thickness.

  Next, the molded body of the reaction preventing layer was formed on the solid electrolyte layer using a printing method.

  Next, the molded body of each of the support substrate, the fuel electrode, the solid electrolyte layer, the reaction preventing layer, the interconnector, and the seal portion was co-fired (1350 to 1450 ° C., 1 to 20 hours).

  Next, using a printing method, an air electrode molded body was formed on the reaction preventing layer and fired (1000 to 1100 ° C., 1 to 10 hours).

(Production of samples according to levels 2 to 8)
As described below, samples according to levels 2 to 8 were produced in the same manner as level 1 except that the formation process of the solid electrolyte layer compact was different.

Specifically, first, water and polyvinyl alcohol were mixed with CaZr ₄ O ₉ powder to prepare a contact portion slurry. Subsequently, the contact portion molded body was formed so as to be in contact with two adjacent seal portions by applying the prepared slurry for the contact portion by a printing method. At this time, by forming the slurry only on the outer edge and printing, a molded body of the contact portion having the outer edge portion protruding from the flat portion was formed. Next, by forming a separation portion slurry prepared by mixing water and polyvinyl alcohol into 8YSZ powder onto the contact portion molding by a printing method, a separation portion molding is formed on the contact portion molding. did. In addition, the thickness of the solid electrolyte layer and the protrusion height of the outer edge portion in the samples according to levels 3 to 8 were as shown in Table 2.

(Reduction treatment)
First, a reduction treatment was performed on the fuel electrode of each sample. Specifically, after raising the temperature of the fuel electrode side of each sample from room temperature to 750 ° C. while maintaining a 4% hydrogen atmosphere, the sample was switched from 4% hydrogen atmosphere to 100% hydrogen atmosphere and maintained at 750 ° C. for 100 hours. . Thereafter, the temperature was lowered to room temperature over 12 hours while maintaining a reducing atmosphere by supplying Ar gas and hydrogen gas (4% with respect to Ar).

(Confirmation of peeling)
By observing the cross section of each sample subjected to the reduction treatment with a microscope, the presence or absence of peeling between the seal portion and the solid electrolyte layer was confirmed. The confirmation results are shown in Tables 1 and 2.

  As can be seen from Tables 1 and 2, in the samples of levels 2 to 8 in which the outer edge portion of the solid electrolyte layer was protruded, it was possible to suppress the separation of the solid electrolyte layer. This is because by projecting the outer edge portion of the solid electrolyte layer, it was possible to improve the strength of the outer edge portion that is likely to be a starting point of peeling, and therefore, it was possible to suppress peeling so that the outer edge portion was swollen.

  Further, as can be seen from Table 2, it was confirmed that in the samples of level 4 to 8 where the protruding height of the outer edge portion of the solid electrolyte layer is 20% or more of the total thickness, slight peeling of the solid electrolyte layer can be suppressed. .

  Further, as can be seen from Table 2, it was confirmed that in the samples of levels 4 to 8 where the protruding height of the outer edge portion of the solid electrolyte layer was 5 μm or more, slight peeling of the solid electrolyte layer could be suppressed.

DESCRIPTION OF SYMBOLS 10 Solid oxide fuel cell 20 Support substrate 30 Electric power generation part 31 Fuel electrode current collecting layer 32 Fuel electrode active layer 33 Solid electrolyte layer 33a 1st end part 33b 2nd end part 34 Reaction prevention layer 35 Air electrode active layer 36 Air electrode Current collecting layer 40 Interconnector 41 Interconnector layer 42 Intermediate layer 50 Sealing part 100 Contacting part 110 Outer edge part 120 Flat part 200 Spacing part

Claims (5)

A power generation unit having a fuel electrode, an air electrode, and a dense solid electrolyte layer disposed between the fuel electrode and the air electrode;
A dense interconnector electrically connected to the fuel electrode;
A dense seal portion connected to the solid electrolyte layer and the interconnector;
With
The solid electrolyte layer includes a contact portion that comes into contact with the surface of the seal portion, and a separation portion that is separated from the surface of the seal portion via the contact portion,
The tip of the spacing portion is disposed on the outer edge portion of the contact portion,
At least a part of the outer edge portion of the contact portion protrudes away from the surface of the seal portion.
Solid oxide fuel cell. The solid electrolyte layer contains Ca and Zr in the contact portion.
The solid oxide fuel cell according to claim 1. The solid electrolyte layer includes a spacing part spaced from the seal part via the contact part,
The spacing portion contains yttria-stabilized zirconia as a main component,
The seal portion contains CaZrO ₃ as a main component.
The solid oxide fuel cell according to claim 1 or 2. The protruding height of the outer edge portion from the surface of the seal portion is 20% or more of the thickness of the solid electrolyte layer.
The solid oxide fuel cell according to any one of claims 1 to 3. The protruding height of the outer edge portion from the surface of the seal portion is 5 μm or more.
The solid oxide fuel cell according to any one of claims 1 to 4.

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