JP4851692B2 - Solid electrolyte fuel cell stack, bundle and fuel cell - Google Patents

Description

  The present invention relates to a solid electrolyte fuel cell stack, a bundle, and a fuel cell in which a power generation element portion (cell) is provided on the surface of a support body having a fuel circulation portion therein.

  In recent years, various fuel cells have been proposed as next-generation energy. Various types of fuel cells such as solid polymer type, phosphoric acid type, molten carbonate type, and solid electrolyte type are known. Among them, a solid oxide fuel cell (SOFC) is known. ) Has a high operating temperature of 800 to 1000 ° C., but has advantages such as high power generation efficiency and the ability to use exhaust heat, and its research and development is being promoted.

The solid oxide fuel cell has a plurality of fuel cell stacks, and these fuel cell stacks are electrically connected to each other to form a bundle, and the bundle is accommodated in a storage container. In the fuel cell stack, a so-called “horizontal stripe” type is known depending on how the power generation element portion is arranged in the fuel cell stack.
In this horizontal stripe fuel cell stack, a plurality of power generating element portions are arranged along the longitudinal direction of the cell stack and connected in series. For example, only one electromotive force of 0.7 V can be obtained for each power generating element portion, but by connecting a plurality of power generating elements in series, a considerable electromotive force can be obtained per cell stack.

In the horizontally striped fuel cell stack, a plurality of power generating element portions are arranged at predetermined intervals in the longitudinal direction on the surface of a support that is a porous insulator. Each power generating element portion has a layer structure in which a fuel electrode, a solid electrolyte, and an air electrode are sequentially stacked. The power generating element portions adjacent to each other are connected in series by an interconnector. That is, the fuel electrode of one power generation element part and the air electrode of the other power generation element part are connected by the interconnector. A fuel gas flow path is formed inside the support.

The power generation principle of the horizontal stripe fuel cell stack having the above structure is as follows.
Since the oxygen ion conductivity of the solid electrolyte increases from about 600 ° C., by supplying a gas containing oxygen to the air electrode and a gas containing hydrogen to the fuel electrode in a temperature range of 600 ° C. or higher, A difference in oxygen concentration occurs between the fuel electrodes.
Oxygen ions that have moved from the air electrode to the fuel electrode through the solid electrolyte are combined with hydrogen ions at the fuel electrode to become water. At this time, an electrode reaction of the following formula (1) occurs at the air electrode, and an electrode reaction of the following formula (2) occurs at the fuel electrode. As a result, electrons move and generate electricity.

Air electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte) (1)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)
In the horizontal stripe fuel cell stack, a plurality of power generating element parts that cause the above reaction are formed in the longitudinal direction on the support surface and connected in series with each other, so that a high voltage can be obtained with a small number of cell stacks. There is an advantage that
JP 10-003932 A

As the material for the fuel electrode, it is necessary to use a material having hydrogen ion adsorption ability and high electrical conductivity. Therefore, for example, a material Ni-YSZ in which Ni is mixed with YSZ that is originally a solid electrolyte material is used.
However, the thermal expansion coefficient of the fuel electrode is far from the thermal expansion coefficient of the support, so if it is attached directly to the support, the fuel cell stack is heated for power generation or the power generation is completed when the fuel cell is manufactured. When cooling, there was a problem such as cracking or peeling.

The thinner the fuel electrode, the less the problem of delamination due to the difference in thermal expansion coefficient.However, in the horizontal stripe fuel cell stack, the current flows in the longitudinal direction on the support surface, so the fuel electrode is thinned. Then, although current flows, sheet resistance increases and the problem that electric power generation efficiency falls arises. Therefore, the fuel electrode cannot be made too thin .

The present invention reduces the difference in thermal expansion coefficient between a fuel electrode and a support body that supports a plurality of power generating element portions arranged along the longitudinal direction of the cell stack, and has a solid electrolyte type that is excellent in durability and reliability. An object is to provide a fuel cell stack, a bundle, and a fuel cell.

According to the present invention, the electrically insulating support includes Ni or Ni oxide and ZrO ₂ in which the rare earth element oxide is dissolved , and the fuel electrode is an active fuel electrode on the solid electrolyte side. and then are formed by and a current collecting fuel electrode on the support side, the active fuel electrode of the solid electrolyte side is made of a mixture of a Ni or Ni oxide, and ZrO ₂ with a rare earth element in solid solution , current collecting fuel electrode of support side, and Ni or Ni oxide, fuel cell stack, characterized by comprising a mixture of rare earth oxide is provided.

With this structure, the thermal expansion coefficient of the current collecting fuel electrode and the thermal expansion coefficient of the support can be made closer to those of the conventional technique, so that the fuel cell stack can be manufactured , heated, and cooled. In some cases, the thermal stress generated due to the difference in thermal expansion between the two can be reduced, and cracking or peeling of the fuel electrode can be suppressed. For this reason, even in the case of generating power by flowing fuel gas, the consistency of the thermal expansion coefficient with the support is stably maintained, and the durability and reliability of the fuel cell stack can be increased.

In order to make the thermal expansion coefficient of the current collecting fuel electrode substantially coincide with the thermal expansion coefficient of the support, the composition ratio of the Ni or Ni oxide may be adjusted.
Specifically, Ni or Ni oxide in the support is contained in an amount of 5% to 25% by volume in terms of Ni, and the Ni amount or NiO amount in terms of Ni of the collector fuel electrode on the support side is set to 35%. By preparing within the range of ˜60% by volume, the difference in thermal expansion between the support and the collector fuel electrode on the support side can be made to be 1 × 10 ⁻⁶ / ° C. or less.

The ZrO ₂ in which the rare earth element is dissolved is preferably Y—ZrO ₂ or Sc—ZrO ₂ . This is because the electric conductivity is increased by solid solution, and since this material is used as a solid electrolyte material, the active fuel electrode can be well fixed to the solid electrolyte layer.
The rare earth element oxide is preferably Y ₂ O ₃ or Yb ₂ O ₃ . The reason for this is a reduction in raw material costs.

Before Symbol support is preferably a flat. In such a fuel cell stack, since the area of the power generation element can be increased and the amount of power generation can be increased, the number of cell stacks for obtaining the required amount of power generation can be reduced. Therefore, the connection location between cell stacks can be reduced. Therefore, the structure and the assembly are simplified and the reliability is improved.

Further, when a bundle formed by electrically connecting such fuel cell stacks is stored in a storage container to form a fuel cell, the fuel cell stack is denser than a cylindrical fuel cell stack. Since it can arrange | position, the volume which the bundle per power generation amount occupies can be made small, and a small and highly efficient fuel cell can be provided.
Further, according to the present invention, the inter-cell stack connecting member for electrically connecting to the power generating element of another fuel cell stack is used at one or both ends of the fuel cell stack. A bundle formed by electrically connecting a plurality of battery cell stacks to each other is provided. With this structure, it is possible to increase the power generation voltage per fuel cell stack, and to obtain a highly reliable bundle with a small internal resistance and capable of extracting a large amount of power.

  By configuring a fuel cell in which a plurality of bundles described above are stored in a storage container, a small and highly efficient fuel cell can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a structure of a fuel cell stack according to the present invention, and FIG. 2 is a plan view thereof.
The fuel cell stack 1 shows a state before the power generation element connecting member 7 (see FIG. 3) is applied.

This fuel cell stack 1 has a “horizontal stripe” in which a plurality of power generating element portions are arranged along a longitudinal direction of a cell stack on a hollow and flat support 2 and connected in series by an interconnector 6. It is called “shape”. The power generation element portions are formed on the front surface and the back surface of the support 2, respectively.
In FIG. 1A, a power generation element portion (not shown) at the front end of the cell stack and a power generation element portion (not shown) at the front end of the cell stack are connected by a metal band that goes around the cell stack. 1 shows a type in which the direction of current on the cell stack surface is opposite to the direction of current on the back surface of the cell stack.

FIG. 1B shows that each power generation element portion on the cell stack surface and each power generation element portion on the back surface of the cell stack are connected by an interconnector 6 that circulates around the cell stack. The power generation element unit and the power generation element unit on the back surface of the cell stack are connected in parallel.
FIG. 3 is a cross-sectional view of the cell stack showing a portion where the power generation element portion is formed, taken along line AA in FIG.

The fuel cell stack 1 is configured by arranging a plurality of power generation element portions on the surface of a support 2 at a predetermined interval in the longitudinal direction.
Each power generation element section is formed by sequentially laminating a current collecting fuel electrode 3a, an active fuel electrode 3b (the current collecting fuel electrode 3a and the active fuel electrode 3b are collectively referred to as “fuel electrode 3”), a solid electrolyte 4 and an air electrode 5. It has a layered structure.

Adjacent power generation element portions are connected in series by an interconnector 6 and a power generation element connection member 7. That is, an interconnector 6 is formed on the fuel electrode 3 of one power generation element portion, and the interconnector 6 and the air electrode 5 of the other power generation element portion are electrically connected by a power generation element connection member 7. It has become.
A plurality of fuel gas passages 8 having a small inner diameter are formed in the support 2 so as to penetrate in the longitudinal direction (see FIG. 1). Thus, by forming a plurality of fuel gas flow paths 8 inside the support body 2, the support body 2 has a flat plate shape as compared with the case where one large fuel gas flow path is formed inside the support body 2. The strength of the support 2 is also increased.

By flowing a fuel gas (hydrogen gas) through the fuel gas flow path 8 and exposing the air electrode 5 to an oxygen-containing gas such as air, the above-described equations (1), ( The electrode reaction shown in 2) occurs, a potential difference is generated between the two electrodes, and power is generated.
A bundle is assembled by assembling a plurality of the fuel cell stacks 1 and connecting the fuel cell stacks 1 with each other through an inter-cell stack connecting member. A fuel cell can be manufactured by attaching conductive members (not shown) for taking out the electric power generated in the bundle to the outside of the fuel cell at both ends of the bundle and storing the conductive member in the storage container. An oxygen-containing gas such as air is introduced into the storage container, and a fuel gas such as hydrogen is introduced into the fuel gas manifold M through an introduction pipe. When the fuel gas is introduced into the fuel cell stack 1 through the fuel gas manifold M and the fuel cell stack 1 is heated to a predetermined temperature, the fuel cell stack 1 can generate electric power. The used fuel gas and oxygen-containing gas are discharged out of the storage container.

Hereinafter, the material of each member constituting the cell stack will be described in detail.
The support 2 is made of Ni or Ni oxide (NiO) and ZrO _{2 in} which, for example, a rare earth element oxide is dissolved. Examples of rare earth elements constituting rare earth element oxides include Y, La, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr. Preferred are oxides of Y It is. Y ₂ O ₃ and Yb ₂ O ₃ , particularly Y ₂ O ₃ are preferred. Further, as the support 2, it can be in place of ZrO ₂ to the oxide of the rare earth element in solid solution, such as a spinel, off O Rusuteraito, also possible to use calcium zirconate and the like.

Ni or NiO (NiO is usually reduced by hydrogen gas and exists as Ni during power generation) is contained in the support 2 in a range of 5 to 25% by volume, particularly 5 to 10% by volume in terms of Ni. It is good to be.
The thermal expansion coefficient of the support 2 is usually about 10.5 to 11.5 × 10 ⁻⁶ (1 / K).

The support 2 needs to be electrically insulative in order to prevent an electrical short circuit between the power generating element portions, and preferably has a resistivity of 10 Ω · cm or more with the content of Ni or the like being in the above range.
Further, the remaining amount other than Ni or the like is usually ZrO _{2 in} which a rare earth element oxide is dissolved. However, other oxides such as MgO and SiO ₂ or composite oxides such as calcium zirconate may be contained in a small amount, for example, in the range of 5% by weight or less.

The support 2 must be able to introduce the fuel gas in the fuel gas flow path 8 to the surface of the fuel electrode 3 and therefore needs to be porous. In general, the open porosity should be 25% or more, especially in the range of 30-40%.
The fuel electrode 3 causes an electrode reaction of the above formula (2). In the present embodiment, the fuel electrode 3 has two layers of an active fuel electrode 3b on the solid electrolyte side and a collecting fuel electrode 3a on the support 2 side. Formed in the structure.

The active fuel electrode 3b on the solid electrolyte side is formed of porous conductive ceramics. For example, it is composed of ZrO ₂ (stabilized zirconia) in which a rare earth element is dissolved, and Ni and / or Ni oxide NiO (hereinafter referred to as Ni or the like). As the stabilized zirconia in which the rare earth element is dissolved, the same one used for the solid electrolyte 4 described later can be used .

The stabilized zirconia content in the active fuel electrode 3b is preferably in the range of 35 to 65% by volume, and the content of Ni or the like is 65 to 35% by volume in terms of Ni in order to exhibit good current collecting performance. It is good to be in the range.
Further, the open porosity of the active fuel electrode 3b is preferably 20% or more, particularly 25 to 40%.

The thermal expansion coefficient of the active fuel electrode 3b is usually about 12.3 × 10 ⁻⁶ (1 / K).
The thickness of the active fuel electrode 3b is desirably in the range of 3 μm or more and less than 10 μm. If the thickness is 10 μm or more, the thermal stress generated due to the difference in thermal expansion from the solid electrolyte 4 cannot be absorbed, and the active fuel electrode may be cracked or peeled off.
The active fuel electrode 3b is preferably conductive, and the content of Ni or the like is within the above range, and can have a conductivity of 400 S / cm or more.

On the other hand, the current collecting fuel electrode 3a on the support 2 side of the fuel electrode 3 is a mixture of Ni or Ni oxide and rare earth element oxide. Examples of the rare earth element constituting the rare earth element oxide include Y, La, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr. Preferred is an oxide of Y. . Y ₂ O ₃ and Yb ₂ O ₃ , particularly Y ₂ O ₃ are preferred .

The Ni or Ni oxide (NiO is usually reduced by hydrogen gas and present as Ni during power generation) is contained in the rare earth element oxide in a range of 35 vol% to 60 vol% in terms of Ni. It is good to be. By preparing in this range, the thermal expansion coefficient of the current collecting fuel electrode 3a is usually about 11.5 × 10 ⁻⁶ (1 / K).
Therefore, the thermal expansion difference between the support 2 and the current collecting fuel electrode 3a can be set to 1.0 × 10 ⁻⁶ / ° C. or less.

The current collecting fuel electrode 3a is also preferably conductive so as not to impair the flow of current, like the active fuel electrode 3b, and the content of Ni or the like is within the above range and has a conductivity of 400 S / cm or more. Can do.
The thickness of the current collecting fuel electrode 3a is preferably 100 μm or more. If it is less than 100 μm, resistance when a current flows in the longitudinal direction increases, and a voltage drop that cannot be ignored occurs in the fuel cell stack 1.

As described above, if the fuel electrode 3 is formed in two layers of the active electrolyte electrode 3b on the solid electrolyte side and the current collecting fuel electrode 3a on the support side, the Ni conversion of the current collecting fuel electrode 3a on the support side is performed. the Ni amount or NiO amount of by preparing in the range of 35 to 60 vol%, without compromising the bonding of the active fuel electrode 3 b, the coefficient of thermal expansion, the thermal expansion coefficient of the support 2 It can be brought close, for example, the thermal expansion difference therebetween, Ru can be less than 1.0 × 10 ^-6 / ℃.
Therefore, since the thermal stress generated due to the difference in thermal expansion between the fuel electrode 3 and the support 2 can be reduced during the production , heating, cooling, etc. of the fuel cell stack 1, Cracks and peeling can be suppressed. Even when power generation is performed by flowing fuel gas (hydrogen gas), the consistency of the thermal expansion coefficient with the support 2 is stably maintained.

The solid electrolyte 4 has a function as an electrolyte for bridging electrons between the electrodes, and at the same time has gas barrier properties to prevent leakage of fuel gas and oxygen-containing gas such as air. is necessary. Therefore, as the solid electrolyte 4, it is preferable to use dense ceramics having such characteristics, for example, stabilized ZrO _{2 in} which ₃ to 15 mol% of a rare earth element is dissolved. Examples of rare earth elements in the stabilized ZrO ₂ include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. However, Y and Yb are preferable because they are inexpensive. A lanthanum gallate solid electrolyte having a thermal expansion coefficient substantially equal to that of 8YSZ (stabilized ZrO ₂ in which 8 mol% of Y is dissolved) can also be suitably used.

It is desirable that the solid electrolyte 4 has a thickness of 10 to 100 μm from the viewpoint of preventing gas permeation, and has a relative density (according to Archimedes method) of 93% or more, particularly 95% or more.
The air electrode 5 formed on the solid electrolyte 4 causes the above-described electrode reaction of the formula (1), and is formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. As such a perovskite type oxide, at least one of transition metal type perovskite oxides, particularly LaMnO ₃ oxides, LaFeO ₃ oxides, and LaCoO ₃ oxides having La at the A site is preferable. 600 LaFeO ₃ -based oxides are particularly suitable because they have high electrical conductivity at a relatively low temperature of about ˜1000 ° C.

In the perovskite oxide, Sr may exist together with La at the A site, and Fe, Co, and Mn may coexist at the B site.
The air electrode 5 must have gas permeability, and its open porosity is preferably 20% or more, particularly 30 to 50%. Furthermore, the thickness is preferably 30 to 100 μm from the viewpoint of current collection.

The interconnector 6 used for connecting adjacent power generation element portions in series connects the fuel electrode 3 of one power generation element portion and the air electrode 5 of the other power generation element portion, and is electrically conductive. Although it is formed from ceramics, it needs to have reduction resistance and oxidation resistance because it comes into contact with a fuel gas (hydrogen gas) and an oxygen-containing gas such as air.
The interconnector 6 is a conductor having a thickness of about 10 μm to 100 μm. The interconnector 6 connects the active fuel electrode 3b of one power generation element part and the air electrode 5 of the other power generation element part via a power generation element connection member 7, and is formed of conductive ceramics. In order to come into contact with fuel gas (hydrogen gas) and oxygen-containing gas such as air, it is necessary to have reduction resistance and oxidation resistance. For this reason, lanthanum chromite perovskite oxides (LaCrO ₃ oxides) are generally used as the conductive ceramics. Further, in order to prevent leakage between the fuel gas passing through the fuel gas flow path 8 and the oxygen-containing gas such as air passing outside the air electrode 5, the conductive ceramics must be dense, for example, 93% or more In particular, it is preferable to have a relative density (Archimedes method) of 95% or more. In addition, a sealing property can also be improved by interposing an appropriate bonding layer (for example, Y ₂ O ₃ ) between the end face of the interconnector 6 and the end face of the solid electrolyte 4.

The power generation element connecting member 7 connects the interconnector 6 of one power generation element part and the air electrode 5 of the other power generation element part. Like the interconnector 6, the power generation element connection member 7 is made of a material having conductivity and oxidation resistance. It is formed. However, since the gas barrier property is not required, it may not be as dense as the interconnector 6.
The inter-cell stack connecting member is a member that connects the interconnector 6 of one fuel cell stack and the air electrode 5 of another fuel cell stack. The inter-cell stack connecting member is preferably made of at least one of Pt, Ag, Ni-base alloy, and Fe—Cr steel alloy from the viewpoint of heat resistance, oxidation resistance, and electrical conductivity. Using the paste containing a noble metal such as Ag or Pt or a metal such as Ni as a conductive adhesive at the connection part between the cell stack connection member and the interconnector 6 and between the cell stack connection member and the air electrode 5 Reliability can also be improved.

The fuel cell stack 1 described above can be manufactured, for example, as follows.
First, as a material for the support 2, a ZrO ₂ powder in which a rare earth element oxide such as Y ₂ O ₃ having an average particle diameter of 0.1 to 10 μm is dissolved, and Ni powder (NiO powder may be used) are prepared. These powders are mixed at a predetermined ratio. The mixed powder is mixed with a solvent composed of a pore agent, a cellulose organic binder, and water, extruded, and formed into a hollow and flat support molded body having a fuel gas channel 8 inside. Make it.

Next, a material for the current collecting fuel electrode is prepared . For example, NiO powder, Ni powder, and rare earth element oxide powder such as Y ₂ O ₃ are mixed, a pore agent is added thereto, an acrylic binder and toluene are added to form a slurry, and a doctor blade method is used. A current collecting fuel electrode tape having a thickness of 100 to 150 μm is prepared .
Hereinafter, the fuel cell stack manufacturing process will be described with reference to FIG.

In the cut current collecting fuel electrode tape 3a, a portion for forming an insulator is punched out (FIG. 4A).
Next, the active fuel electrode 3b is printed on the interconnector forming portion on the current collecting fuel electrode tape 3a (FIG. 4B).
Further, the interconnector 6 is printed on the active fuel electrode 3b (FIG. 4C).

Then, once again, the active fuel electrode 3b is printed on the entire surface except for the central portion of the interconnector 6 (FIG. 4D).
Next, in this state, the fuel electrode tape 3a is affixed to the support body 2 in a horizontal stripe pattern. In this case, the fuel electrode tape 3a and the other fuel electrode tape 3a are arranged with an interval of about 3 mm. And this laminated body is dried and calcined in the temperature range of 900-1100 degreeC. (FIG. 4 (e)).

An organic material sheet (masking tape) 10 is attached to the central portion of the interconnector 6 where the active fuel electrode 3b is not printed (FIG. 4 (f)).
Next, this laminate is immersed in a solid electrolyte solution obtained by adding an acrylic binder and toluene to 8YSZ (ZrO ₂ powder in which 8 mol% of Y is solid-dissolved), and is taken out from the solid electrolyte solution. By this dipping, a layer of the solid electrolyte 4 is applied to one surface of the multilayer body, and the space punched in (a) is filled with the solid electrolyte 4 that is an insulator.

In this state, calcining is performed at 800 ° C for 1 hour. During the calcination, the organic material sheet 10 and the layer of the solid electrolyte 4 applied thereon can be removed (FIG. 4G).
Next, the reaction preventing layer 11 is applied to the portion where the air electrode is formed and baked at 1480 ° C. for 2 hours (FIG. 4H). From above the reaction preventing layer 11, the air electrode 5 is printed and baked at 1050 ° C. for 2 hours (FIG. 4 (i)).

Finally, a power generation element connecting member 7 for connecting the interconnector 6 of one power generation element section and the air electrode 5 of the power generation element section adjacent thereto is pasted (FIG. 4 (j)), and the fuel cell The cell stack is completed.
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, in the above example, the support 2 is described as a hollow plate having a plurality of fuel gas passages 8 inside. However, the support 2 may be cylindrical and the number of fuel gas passages 8 is the same. Needless to say, there may be only one. In addition, various modifications can be made within the scope of the present invention.

It is a perspective view which shows the shape of the fuel cell stack of this invention. (A) shows a type in which the current direction on the cell stack surface is opposite to the current direction on the cell stack back surface, and (b) shows the current direction on the cell stack surface and the current direction on the cell stack back surface are the same. Indicates the type to be. It is a top view of a fuel cell stack. It is a longitudinal cross-sectional view which expands and shows the connection structure of a fuel cell stack. It is a manufacturing-process figure of a fuel cell stack .

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Support body 3 Fuel electrode 3a Current collecting fuel electrode 3b Active fuel electrode 4 Solid electrolyte 5 Air electrode 6 Interconnector 7 Power generation element connection member
8 Fuel gas passage 10 Organic sheet 11 Reaction prevention layer

Claims (6)

A single or multiple fuel gas passages are provided on the surface of a columnar electrically insulating support formed in the longitudinal direction, and a power generation element portion in which a fuel electrode, a solid electrolyte, and an air electrode are laminated in this order in the longitudinal direction. A plurality of power generating element portions connected in series via an interconnector at a predetermined interval,
The support comprises Ni or Ni oxide, and ZrO ₂ in which a rare earth element oxide is dissolved,
The fuel electrode is formed to include an active fuel electrode on the solid electrolyte side and a current collecting fuel electrode on the support side,
The active fuel electrode is made of a mixture of Ni or Ni oxide and ZrO ₂ in which a rare earth element is dissolved,
The fuel cell stack, wherein the current collecting fuel electrode is made of Ni or a mixture of Ni oxide and rare earth element oxide.   Ni or Ni oxide in the support contains 5 vol% to 25 vol% in terms of Ni, and Ni or Ni oxide in the collector fuel electrode contains 35 vol% to 60 vol% in terms of Ni The fuel cell stack according to claim 1. 3. The fuel cell stack according to claim 1, wherein ZrO ₂ in which the rare earth element is dissolved is Y—ZrO ₂ or Sc—ZrO ₂ . The fuel cell stack according to any one of claims 1 to 3 , wherein the support has a flat shape. A bundle formed by electrically connecting a plurality of the fuel cell stacks according to any one of claims 1 to 4 using a connection member between cell stacks. A fuel cell in which a plurality of bundles according to claim 5 are stored in a storage container.

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