JP2003123788A - Single cell for fuel cell and solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single cell for a fuel cell capable of easily reducing thickness of a solid electrolyte layer and exhibiting good operation performance at a high temperature and to provide a cell plate and the solid electrolyte fuel cell. SOLUTION: In this single cell for the fuel cell, the solid electrolyte layer is clamped by means of an oxidation electrode and a reduction electrode, and the oxidation electrode has oxidation resistance and oxygen permeability at a high temperature and includes a metal sheet as a good electric conductor. The metal sheet is formed of silver, gold, platinum, palladium, copper and the like and provided with a thickness below 200 μm. The cell plate for the fuel cell is formed when a plurality of single cells are connected together two- dimensionally to be integrated together. The solid electrolyte fuel cell uses the single cell or the cell plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell (SOFC) that uses a solid electrolyte to obtain electric energy by an electrochemical reaction, and more specifically, a solid electrolyte fuel cell (SOFC) sandwiched between electrodes. The present invention relates to a cell, a cell plate and a solid oxide fuel cell.

[0002]

2. Description of the Related Art In recent years, fuel cells have attracted attention as a clean energy source capable of high energy conversion and friendly to the global environment. Solid oxide fuel cell (hereinafter referred to as "SOF
(Abbreviated as “C”) is configured such that a solid electrolyte having ionic conductivity such as oxygen ions or protons is sandwiched between a porous air electrode and a fuel electrode, and an oxidizing gas containing oxygen gas is supplied to the air electrode side. Then, a reducing gas containing hydrogen or carbonized gas is supplied to the fuel electrode side, and these gases electrochemically react through the solid electrolyte to generate electromotive force.

Generally, solid electrolytes include stabilized zirconia obtained by adding yttria (Y ₂ O ₃ ) or scandia (Sc ₂ O ₃ ) to zirconia (ZrO ₂ ), ceria (CeO ₂ ), Bi ₂ O ₃ A lanthanum gallate (LaGdO ₃ ) material having a perovskite structure is used.
It is important that the solid electrolyte layer does not allow electrons to pass therethrough, but allows ions to pass therethrough, and when oxygen ions are a conductor for power generation, it is desirable that the oxygen ions have high conductivity characteristics. An important function of the solid electrolyte layer is that it is gas impermeable.

The air electrode has silver (Ag) and platinum (P).
Metal oxides such as t) and oxide materials having a perovskite structure represented by LaSrMnO and LaSrCoO are generally used. The function of the air electrode is required to be strong against oxidation, permeate an oxidizing gas, have high electric conductivity, and have an excellent catalytic action for converting oxygen molecules into oxygen ions.

Further, nickel (Ni) or cermet of nickel and solid electrolyte is generally used for the fuel electrode. The function of the fuel electrode is required to be strong in a reducing atmosphere, permeate a reducing gas, have high electric conductivity, and have an excellent catalytic action for converting hydrogen molecules into protons.

[0006]

SOFC is composed of a film (layer) having the above characteristics. Also,
A general SOFC unit power generation cell (hereinafter abbreviated as “single cell”) has a structure in which a solid electrolyte layer is sandwiched between a fuel electrode layer and an air electrode layer, as shown in FIG. Such SOFCs are roughly classified into two types: a cylindrical type in which an electrode and a solid electrolyte are coated around a cylinder, and a flat plate type in which a solid electrolyte and an electrode are formed in a flat plate shape. Cylindrical SOFC
Does not require a gas seal and is relatively easy to stack, but it is difficult to increase the area of the power generation part of the single cell (area of the solid electrolyte), and when connecting the single cells, Since the power generation density per unit volume of is low, how to improve it is a basic issue. on the other hand,
The flat-plate SOFC has a structure that is advantageous for increasing the power density per unit volume of the battery, and it is relatively easy to increase the area of the power generation part of a single cell. It is expected to be a suitable SOFC.

Further, the conventional SOFC is 800-100
An operating temperature of 0 ° C was assumed, but this temperature was high, and there were problems such as the stability and reliability of SOFC operation and the high cost of high temperature resistant materials. Therefore, SOFC
Low-temperature operation is taken up as an important issue, and the development of materials for realizing low-temperature operation, especially the solid electrolyte material that is the key to low-temperature operation, is being energetically carried out. As a result, solid electrolyte materials such as a lanthanum gallate (LaGdO ₃ ) system, which exhibits higher ionic conductivity at a lower temperature than conventionally used yttria-stabilized zirconia, have been developed. Further, a thin film-supported SOFC structure that improves the power generation efficiency at low temperature by thinning the solid electrolyte layer has also been reported.

In order to make the solid electrolyte layer thin, it is necessary to form the solid electrolyte layer on the air electrode or the fuel electrode.
However, since the air electrode (fuel electrode) has a function of transmitting gas, the surface is not dense and it is difficult to form a solid electrolyte membrane that does not transmit gas on the surface.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a single cell for a fuel cell, a cell plate, and a fuel cell in which the solid electrolyte layer can be easily thinned. The object is to provide a solid oxide fuel cell.

[0010]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, P
It has been found that the above problems can be solved by using a metal sheet, which is suitable as a substrate for thin film deposition such as VD, which is strong against oxidation and has oxygen permeability at high temperature, as an air electrode or an air electrode supporting substrate. The invention was completed.

That is, the single cell for a fuel cell of the present invention is a single cell for a solid oxide fuel cell in which a solid electrolyte layer is sandwiched between an air electrode and a fuel electrode, and the air electrode is resistant to oxidation. And is permeable to oxygen at 300 to 800 ° C., and includes a metal sheet that is a good electric conductor.

In a preferred embodiment of the unit cell for fuel cells of the present invention, the metal sheet is at least one metal selected from the group consisting of silver, gold, platinum, palladium and copper, or mainly these metals. It is characterized by being composed of an alloy as a component.

Further, another preferred embodiment of the unit cell for fuel cell of the present invention is characterized in that the metal sheet is made of a composite material in which a metal oxide is added to the metal.

Furthermore, the fuel cell plate of the present invention comprises:
It is characterized in that a plurality of the unit cells for fuel cells are two-dimensionally connected and integrated in a direction substantially perpendicular to the stacking direction.

The solid oxide fuel cell of the present invention comprises:
It is characterized by comprising the above-mentioned fuel cell single cell or the above-mentioned fuel cell cell plate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The unit cell and cell plate for a solid oxide fuel cell of the present invention will be described in detail below. In the present specification, “%” indicates a mass percentage unless otherwise specified. Further, for convenience of description, one surface of each layer such as a substrate or an electrode layer is referred to as “upper surface, front surface”, and the other surface is referred to as “lower surface, rear surface”, but these are equivalent elements and are mutually replaced. It goes without saying that the configuration is also included in the scope of the present invention. Furthermore, the cell plate is a practical product form for promoting the integration of single cells and increasing the output of the obtained fuel cell.

As described above, the unit cell and cell plate of the present invention have the solid electrolyte layer sandwiched between the air electrode (cathode) and the fuel electrode (anode). Here, the air electrode comprises a metal sheet that has oxidation resistance, transmits oxygen at 300 to 800 ° C., and is a good electric conductor. Thus, when manufacturing a single cell or a cell plate, a dense solid electrolyte membrane, specifically a solid electrolyte layer of several μm, can be easily formed on the air electrode surface, and the fuel electrode can be formed thereon. Further, by using a metal sheet as a base material, it is possible to attach a single cell or a cell plate manufactured in a flat plate shape to a cylindrical base material to manufacture a cylindrical SOFC, and to easily increase the area of the SOFC. (Fig. 10).

Examples of the metal sheet include silver (Ag), gold (Au), platinum (Pt), palladium (Pd) or copper (Cu), and metals related to any combination thereof, and these metals as main components. Can be used as a material. In particular, it is more preferable to use an alloy containing Ag and / or Au as a main component. These metals are good electric conductors desirable as air electrode materials, and have the above temperature range (3
It is effective because it has a function of permeating oxygen at 0 to 800 ° C. In addition, since the solid electrolyte layer can be thinned, S
The internal resistance of the OFC can be reduced. Further, the above metal has a catalytic function of converting oxygen into oxygen ions, and is therefore suitable as a material for the air electrode. Also, by using a ductile metal, an SOFC that is resistant to thermal stress can be formed.
Further, a metal sheet can be formed from a composite material in which a metal oxide is added together with the above metal. In this case, the strength of the sheet is improved and the coefficient of thermal expansion can be adjusted, which is effective.

Further, the metal sheet has a thickness of 200 μm.
It is preferably less than m. When the sheet is thick, oxygen is not sufficiently transmitted to the solid electrolyte, and particularly when the sheet thickness is 200 μm or more, the power generation characteristics of SOFC may be affected.

Furthermore, such a metal sheet is provided with LaSr.
It is also possible to obtain a single cell and a cell plate by laminating a layer made of an oxide having a perovskite structure represented by MnO or LaSrCoO, and laminating a solid electrolyte layer and a fuel electrode on the layer. In this case, since an air electrode having a lower polarization resistance is used as the air electrode of the fuel cell than the metal electrode, the output characteristic is also improved, which is advantageous.

The unit cell and cell plate of the present invention have a small electric resistance between unit cells and unit cells, and can be suitably used for SOFC.

The fuel cell cell plate of the present invention is formed by integrally connecting the above-mentioned single cells two-dimensionally in a direction substantially perpendicular to the stacking direction of the air electrode, the solid electrolyte layer and the fuel electrode. .

Next, the solid oxide fuel cell of the present invention will be described. Such a solid oxide fuel cell (SOF
C) is formed by using the above-mentioned single cell or cell plate for a fuel cell. At this time, in each unit cell or each cell plate, the reaction gas passage (air passage or fuel passage) and the electrode layer (air electrode or fuel electrode) corresponding thereto may be in contact with each other. It is possible to change the coating position of the air electrode) or change the upper and lower sides of the single cell or the cell plate for connection.

Next, a method for manufacturing the above fuel cell single cell will be described. In such a manufacturing method, first, on one surface of a metal sheet (eg, Ag sheet), a physical vapor deposition method such as sputtering or ion plating, a chemical vapor deposition method such as plasma CVD, a doctor blade method, or the like is used. A solid electrolyte layer (for example, yttria-stabilized zirconia) is formed by the printing method of 1. Then, a fuel electrode is formed into a film by a method similar to that for the solid electrolyte layer to form a single cell as shown in FIG.

The metal sheet can be manufactured by employing, for example, a rolling method or an electrolytic method. The solid electrolyte layer must be a gas impermeable layer, and the fuel electrode must be a gas permeable layer. Further, since the single cell manufactured by the above method is formed by using the metal sheet, it cannot stand on its own (use it as a battery element). So, for example, as shown in FIG.
It can be overlaid with a base material (for example, Ni) that is resistant to a reducing atmosphere and has a gas flow path formed by chemical processing such as etching using Ni brazing, electric discharge processing, or mechanical processing.
In addition, as shown in FIG. 4, Ag is applied to a base material (for example, SUS430) that is resistant to an oxidizing atmosphere and has a gas flow path formed by chemical processing such as etching, electric discharge processing, or mechanical processing.
It is possible to form a self-supporting single cell by means such as applying a wax and then adhering the single cell thereon.

Next, a method for manufacturing the solid oxide fuel cell will be described. In the above-mentioned fuel cell, typically, the single cell or cell plate is arranged by using a substrate or the like so as to secure a reaction gas flow port, and an inorganic adhesive is applied to at least a part of the substrate or the like. Then, a plurality of the above-mentioned single cells or cell plates are connected in the stacking direction, and then joined by pressurizing and heating.

[0027]

The present invention will be described in more detail with reference to the following examples with reference to the drawings, but the present invention is not limited to these examples. In addition, the conduction confirmation is shown in Example 1,
Example 2 shows the measurement of power generation efficiency, and Examples 3 to 5 show preferred embodiments.

Example 1 Thickness 50 μm, 30 mm × 3
A 0 mm Ag sheet was fixed to a substrate holder of a sputtering film forming apparatus, and a yttria-stabilized zirconia electrolyte (hereinafter abbreviated as “8YSZ”) containing 8 mol of yttria was used as Ag.
A 500 nm film was formed on the sheet. Furthermore, N on 8YSZ
A film of i was formed to a thickness of 800 nm to prepare a SOFC single cell. When the conduction of the Ni surface of this single cell and the Ag sheet was confirmed using a tester, no conduction was observed, and it was confirmed that a thin electrolyte layer of 500 nm was formed so that the Ag sheet and Ni were not conducted. It was Similarly, a lanthanum gallate-based electrolyte (La0.9, Sr0.1) (Ga
0.8, Mg0.2) O3-d (hereinafter, LSGM) and N
When i was formed into a film and conduction was checked, conduction between the Ag sheet and Ni was not recognized. This outline is shown in FIG.
Shown in.

Example 2 Thickness of 50 μm, 100 μm,
200μm 3 level Ag sheet (30mm × 3
LSGM of 800 mm using a sputter film forming device
nm film formation, and further 1 μm Ni film formation on LSGM,
An SOFC single cell was produced. After forming a single cell, N on the Ni surface
i paste is applied in a ring shape, and the outer diameter is 20 mmφ,
A Ni ring having an inner diameter of 16 mmφ was attached to produce a self-supporting SOFC single cell as shown in FIG. As shown in FIG. 7, air is supplied to the Ag sheet side of these unit cells by N
Hydrogen was supplied to the i film side, and the OCV (open end voltage) of the single cell was measured at 600 ° C. As a result, Ag sheet thickness 50μ
An OCV of about 1.0 V could be confirmed in the single cell of m and 100 μm, but an OCV of 1.0 V could not be confirmed in the single cell of Ag sheet thickness of 200 μm.

(Embodiment 3) An Ag sheet (30 mm × 30 mm) having a thickness of 50 μm was set to L by using a sputtering film forming apparatus.
SGM 800nm film is formed, and Ni is further deposited on LSGM.
Was deposited to a thickness of 500 nm to prepare an SOFC single cell. After forming the single cell, a 200 nm thick SiN film was formed as a mask on the Ni surface so that the Ag sheet and LSGM did not appear in the surface layer. Next, a Ni paste was applied to the Ni film and the SiN film, and a foamed metal plate of a Ni-based alloy was attached on the Ni paste to fabricate a self-supporting foamed metal plate-supported SOFC single cell. This configuration is shown in FIG.

Example 4 Ag ₂ % by weight Al ₂ O ₃
Composite material sheet (30mm × 30mm, 5
LSGM to 80 μm) using a sputter film forming apparatus.
0nm film is formed, and Ni is further 500nm on LSGM.
A film was formed and a SOFC single cell was produced. The single cell was processed into a SUS430 plate (30
(mm × 30 mm, 2 mmt) was brazed with Ag to a separator to prepare a SOFC single cell supporting a SUS430 separator. This configuration is shown in FIG.

(Embodiment 5) 800 nm of LSGM was formed on a 100 μm thick Ag sheet (15 mm × 100 mm) using a sputtering film forming apparatus, and N was formed on the LSGM.
A film of i was formed to a thickness of 1 μm to prepare a SOFC single cell. Also,
On the other hand, an Ag sheath was prepared by forming a large number of 1 mmφ through holes in an Ag sheath material having an outer diameter of 5 mmφ and an inner diameter of 3 mmφ and a length of 100 mm. The Ag paste was applied to the portion outside the pores of the Ag sheath, and a single cell was wound to produce a cylindrical SOFC. This structure is shown in FIG. With the conventional technique, a cylindrical cell having such large pores could not be produced, but with the present invention, such a cylindrical cell can be produced.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited to these, and various modifications can be made within the scope of the gist of the present invention. For example, in the present invention, the shapes of the unit cell and the cell plate can be arbitrarily selected, and the fuel cell can be manufactured according to the target output.

[0034]

As described above, according to the present invention, a metal sheet that is suitable as a substrate for thin film deposition such as PVD such as sputtering, is resistant to oxidation, and has oxygen permeability at high temperature. Since it is used for the air electrode or the air electrode supporting substrate, it is possible to provide a single cell for fuel cells, a cell plate and a solid oxide fuel cell in which the solid electrolyte layer can be easily thinned.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an SOFC unit power generation cell.

FIG. 2 is a schematic view showing an example of a unit power generation cell according to the present invention.

FIG. 3 is a cross-sectional view showing an application example of a unit power generation cell according to the present invention.

FIG. 4 is a cross-sectional view showing another application example of the unit power generation cell according to the present invention.

FIG. 5 is a schematic view showing Example 1.

6 is a schematic diagram of a single cell used in Example 2. FIG.

FIG. 7 is a schematic diagram showing an evaluation method of Example 2.

FIG. 8 is a schematic diagram showing the configuration of a single cell of Example 3.

FIG. 9 is a schematic view showing a single cell of Example 4.

FIG. 10 is a schematic view showing a unit cell of Example 5.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Bunki Sato             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Shoji Hadano             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Keiko Kushibiki             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Tatsuhiro Fukuzawa             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Satoshi Shibata             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Makoto Uchiyama             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F-term (reference) 5H018 AA06 AS03 EE02 EE13 HH03                       HH04 HH08                 5H026 AA06 CX04 EE02 EE08 EE12                       HH03 HH08

Claims (8)

[Claims] 1. A single cell for a solid oxide fuel cell, comprising a solid electrolyte layer sandwiched between an air electrode and a fuel electrode, wherein the air electrode has oxidation resistance and oxygen at 300 to 800 ° C. A single cell for a fuel cell, characterized in that it comprises a metal sheet that is transparent to electricity and is a good electric conductor. 2. The unit cell for a fuel cell according to claim 1, wherein the air electrode is a laminate of the metal sheet and a layer made of an oxide having a perovskite structure. 3. The metal sheet is made of at least one metal selected from the group consisting of silver, gold, platinum, palladium and copper, or an alloy containing these metals as a main component. The single cell for a fuel cell according to 1 or 2. 4. The metal sheet is made of an alloy containing silver and / or gold as a main component.
The single cell for a fuel cell according to any one of items. 5. The unit cell for a fuel cell according to claim 3 or 4, wherein the metal sheet is made of a composite material in which a metal oxide is added to the metal. 6. The unit cell for a fuel cell according to claim 1, wherein the metal sheet has a thickness of less than 200 μm. 7. The fuel cell unit cell according to claim 1 is provided in a direction substantially perpendicular to the stacking direction.
A cell plate for a fuel cell, characterized in that a plurality of cells are dimensionally connected and integrated. 8. A solid oxide fuel cell comprising the single cell for fuel cell according to any one of claims 1 to 6 or the cell plate for fuel cell according to claim 7. .