JPH08138690A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE: To exhibit a function comparable to that of a solid electrolyte fuel cell requiring high-temperature operation even in low-temperature operation or a greater function in pressurized operation, so as to reduce costs. CONSTITUTION: A slid electrolyte fuel cell is provided with a structure as a cell structure wherein an anode constituted of an anode electrode supporting body containing porous materials made of heat resisting metal containing iron- base alloy, nickel-base alloy and cobalt-base alloy and an anode electrode, a cerium oxide electrolyte and a cathode are laminated in this order. It can be provided by forming the anode by fixing the anode electrode to the anode electrode supporting body, and then sequentially laminating the cerium oxide electrolyte and the cathode on it, or laminating a cell through a separator.

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 which has high performance and high reliability even at low temperature and can be produced at low cost, and a method for producing the same.

[0002]

2. Description of the Related Art A fuel cell uses a combustible chemical substance such as hydrogen, carbon monoxide, or hydrocarbon or a fuel containing the same as an active material and causes an oxidation reaction of the chemical substance or the fuel to be performed electrochemically. A battery that directly converts the energy change in the oxidation process into electric energy, and is expected to have high energy exchange efficiency. Among them, particularly high efficiency can be expected in recent years as a third generation solid oxide fuel cell following the first generation phosphoric acid type and the second generation molten carbonate type, and among them, the highly integrated flat plate type Is attracting attention.

[0003]

A conventional solid oxide fuel cell uses a zirconia-based oxide as an electrolyte, but since this has a sufficient ionic conductivity at around 1000 ° C., the operating temperature is There is no choice but to raise the temperature to around 1000 ° C. On the other hand, the theoretical efficiency of the fuel cell becomes smaller as the operating temperature becomes higher, and in terms of materials, the higher the temperature, the more expensive the material becomes. In other words, solid electrolyte fuel cells are strongly demanded to achieve an effective reduction in operating temperature in terms of both performance and cost. Under such circumstances, an object of the present invention is to provide a solid oxide fuel cell that can be operated at a lower temperature than before.

[0004]

The inventors of the present invention have conducted extensive studies to develop a solid oxide fuel cell that can be operated at low temperatures, and as a result, have found that cerium oxide-based oxide as an electrolyte material and further anode electrode It has been found that the object can be achieved by adopting a porous body of a predetermined heat resistant metal as a support, and the present invention has been completed based on this finding.

That is, the present invention provides (1) a porous material made of a heat-resistant metal containing at least one heat-resistant alloy selected from an iron-based alloy, a nickel-based alloy and a cobalt-based alloy as a unit cell structure. And a solid electrolyte fuel cell having a structure in which an anode composed of an anode electrode support and an anode electrode, a cerium oxide-based electrolyte, and a cathode are sequentially laminated, and (2) an iron-based alloy, nickel An anode electrode is fixed to an anode electrode support containing a porous material made of a refractory metal containing at least one refractory alloy selected from a base alloy and a cobalt base alloy to form an anode, and then this anode A cerium oxide-based electrolyte and a cathode are laminated in this order, or the cells thus obtained are laminated with a separator interposed. It is intended to provide a method of manufacturing a solid oxide fuel cell according to claim.

In a preferred aspect of the present invention, (3) the solid electrolyte fuel cell according to the above item (1), wherein the refractory metal is ferritic stainless steel, and (4) the anode electrode support is porous of the refractory metal. Base made of quality material,
And a solid oxide fuel cell according to the above (1) or (3), which is composed of a surface layer portion formed of a mixture of the porous material and an anode electrode material, and (5) cerium oxide-based The oxide is ceria doped with 5 to 30 mol% of a rare earth oxide, and the solid oxide fuel cell according to item (1), (3) or (4), (6) above (1). ), (3) or (4), the unit cell structure, wherein a solid electrolyte fuel cell is formed by stacking the unit cells using the separator made of the refractory metal according to (1) above.
(7) The solid oxide fuel cell according to the item (6), wherein the refractory metal is ferritic stainless steel.

The anode used in the present invention comprises an anode electrode support containing a porous material made of the above refractory metal and an anode electrode. Examples of the anode electrode support include those made of the porous material alone, Examples thereof include a composite composed of a base made of a porous material alone and a surface layer made of the porous material and an anode electrode material. In such an anode, the strength is maintained by the anode electrode support, and the electrochemical reaction is performed by the anode electrode.

The anode electrode support is usually 10-90.
%, Preferably 30-70% relative density, usually 1
The gas vent has a pore size of 0 to 500 μm, preferably 50 to 200 μm, and its thickness varies depending on the material, the relative density, the pore size of the gas vent, etc., but is usually 0.1 to 5 mm.
It is preferably selected in the range of 0.5 to 2 mm. The porous metal as the material can be easily produced by using the powder metallurgy method, and the porosity and the pore size can be easily controlled.

In the present invention, the refractory metal which is the material of the porous material used for the anode electrode support contains at least one refractory alloy selected from iron-based alloys, nickel-based alloys and cobalt-based alloys. Examples of such a material include the heat-resistant alloy only and the alloy further containing at least one metal selected from Ni, Co and Fe. As the iron-based alloy, Fe-Cr alloy, Fe-Ni-Cr alloy, F
e-Cr-Ni-based alloys, Fe-Cr-Ni-Co-based alloys, and the like. Among them, ferritic stainless steel, particularly Fe as a main component, containing 5 to 30% of Cr,
10% or less of Si, Mn, Al, Ti, Mo in some cases
Alloys with a composition including, for example, SUS430, SUH409
L, etc. have sufficient corrosion resistance near the operating temperature of 600 ° C. when a cerium oxide-based electrolyte is used, and are much cheaper than Ni- and Co-based heat-resistant alloys for higher temperatures, and have a thermal expansion coefficient of 12 ×. It is preferable because it is approximately 10 ⁻⁶ / K ^−1, which is almost the same as that of the cerium oxide-based electrolyte. These heat-resistant alloys may be used alone or in combination of two or more. Other typical products on the market are:
INCOLOY Alloy 800, 800H
(T), 802, and INCO Alloy 330.

The nickel-base alloy is Ni-C.
r-based alloy, Ni-Cr-Fe-based alloy, Ni-Cr-Mo
Alloys, Ni-Cr-Mo-Co alloys, other Ni-
Examples thereof include Cr-Mo-Fe based alloys, and among them, Ni-Cr based alloys are particularly preferable. These may be used alone or in combination of two or more. A typical commercially available product is INCONEL
Alloy 600, 601, 617, 625, 69
0, X-750, 751, NIMONIC Alloy
75, 80A, 90, INCO Alloy HX,
UHM etc.

The cobalt-based alloy is Co-C.
Examples include r-based alloys, Co-Cr-Fe-based alloys, Co-Cr-W-based alloys, Co-Cr-Ni-W-based alloys, and among these, Co-Cr-based alloys are particularly preferable. These may be used alone or in combination of two or more. A typical commercially available product is Haines Alloy No. 25, Haines Alloy No. 188, Mitsubishi Stellite No. 6B, UMC050, etc.

The anode electrode used in the present invention is not particularly limited as long as it has sufficient gas permeability and electrochemical activity, and examples thereof include Ni / ZrO _{2 which} is usually used in a solid oxide fuel cell. , Its thickness is usually 5 to 200 μm, preferably 20 to 100 μm
It is selected in the range of m.

As the cerium oxide-based electrolyte used in the present invention, cerium oxide or a metal oxide,
Among them, rare earth oxides and alkaline earth metal oxides such as CaO and MgO, particularly one or more oxides selected from Sm ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ . Cerium oxide doped with a dopant consisting of 5 to 30 mol% is mentioned. In the cerium oxide alone or the cerium oxide containing the dopant, ceria (CeO ₂ ) is preferable as the cerium oxide. As the dopant-containing cerium oxide, ceria doped with 10 to 20 mol% of Sm ₂ O ₃ or Gd ₂ O ₃ as a dopant is preferable. These cerium oxide-based electrolytes, has good electrical conductivity, the range of differences also acceptable thermal expansion characteristics to said refractory metal, among others Sm ₂ O ₃ or Gd ₂ O ₃ dopant content ceria in 600 ° C. 5 × 10 ^{-3 to} 5 × 10 ^-2 Ω ^-1 cm
^{It has} a good electrical conductivity of ^-1 and a coefficient of thermal expansion of about 12 × 10 ^-6 / K ^-1, which is almost the same as that of ferritic stainless steel.
As for the electrolyte, it is recommended to reduce the thickness to about 10 μm.
It is preferable because even at a low temperature of around 0 ° C, the performance of the fuel cell using the zirconia-based electrolyte can be equal to or higher than that at around 1000 ° C.

The cathode used in the present invention is not particularly limited as long as it has sufficient gas permeability and electrochemical activity, and it is usually used in a solid oxide fuel cell.
_1-x Sr _x MnO ₃ , La _1-x Sr _x CoO ₃ , La _1-x Sr _x
FeO _{3 and the} like can be mentioned.

When the fuel cell of the present invention adopts a stack type in which a separator is interposed between the unit cells, the above-mentioned heat-resistant metal, preferably a heat-resistant metal containing an iron-based alloy, as a separator material, in particular ferritic stainless steel. steel,
In particular, it is preferable to use the bulk body because it is excellent in compatibility with the unit cell.

In the solid oxide fuel cell of the present invention, an anode electrode is fixed to the anode electrode support to form an anode, and then a cerium oxide-based electrolyte and a cathode are sequentially laminated on the anode, or It is possible to manufacture by stacking the single cells obtained in the above with a separator interposed.

The structure of the anode is, for example, a structure in which an anode electrode is laminated on an anode electrode supporting substrate as shown in FIG. 1, a structure in which an anode electrode is formed between anode electrode supporting substrates as shown in FIG. 2, and a structure shown in FIG. To form an anode electrode support by laminating a composite comprising a mixture of the base material and the anode electrode material on the anode electrode support base,
There may be mentioned a structure in which an anode electrode is laminated thereon, and a predetermined composite is interposed between the anode electrode and the anode electrode supporting base to give a compositionally graded structure. In the case of the structure shown in FIG. 1, the anode electrode may be formed on the anode electrode supporting substrate by a method such as doctor blade, screen printing or thermal spraying. When the structure shown in FIG. 2 is used, the anode electrode may be manufactured by a dip coating method or the like. When the structure shown in FIG. 3 is used,
It may be manufactured by a method such as integral sintering.

Next, a cerium oxide-based electrolyte is laminated on the anode thus manufactured. As the laminating method, a film forming method is preferably used, and above all, it is sufficiently dense so as not to pass gas and has a small resistance.
Since the film thickness is required to be 20 μm or less, preferably 10 μm or less, the CVD method, the EB method, the ion plating method, the slurry method, the method of coating / baking an organometallic compound, etc. are advantageous. Of these, a particularly preferred method is to prepare a solution of an organometallic compound in an organic solvent,
It is a method of applying by spin coating, dipping, etc. and baking.

Further, a cathode is laminated on the cerium oxide type electrolyte. As the laminating method, a film forming method is preferably used, among which a screen printing method, a doctor blade method, a thermal spraying method and the like are used.

After stacking as described above, it is preferable to apply a sealing treatment to the side surface as shown in FIG. Of the four side surfaces, two facing surfaces are made into a set, two surfaces of one set seal the cathode and the electrolyte, and two surfaces of the other set seal the anode and the electrolyte. The sealing material is not particularly limited, but for example, glass, ceramics, etc. are used. The unit cell is manufactured as described above.

Further, a stack type battery main body is manufactured by preparing a required plurality of unit cells thus manufactured and stacking a required number of layers with a separator interposed between the unit cells. Further, the stacking method / manifold type, etc. may be any one commonly used in a flat plate type fuel cell, and is not particularly limited. For example, as shown in FIG. Examples include a cylindrical manifold arranged in a battery body.

[0022]

EXAMPLES Next, the present invention will be described in more detail by way of examples. A solid oxide fuel cell comprising a single cell was produced as follows. First, SUS with a thickness of 1-5 mm
Ni / ZrO ₂ cermet was formed into a 100 μm thick film by a screen printing method on an anode electrode supporting substrate made of ferritic stainless steel such as 430 or SUH409L to form an anode electrode, thereby producing an anode. Then, on this anode, ceria doped with 20 mol% of Sm ₂ O ₃ was used as a solid electrolyte to form a film having a thickness of 5 μm. The method was such that a solution containing an organic Sm compound, an organic Ce compound and methanol prepared so as to have the above composition was applied by a spin coating method and baked at 1000 ° C. for 2 hours. Furthermore, La is deposited on this solid electrolyte.
_0.8 Sr _0.2 MnO ₃ 100μ by screen printing
A m-thick film was formed to form a cathode.

[0023]

EFFECTS OF THE INVENTION Since the solid oxide fuel cell of the present invention uses the anode electrode support made of the cerium oxide type electrolyte and the predetermined heat-resistant metal porous material, the conventional 1000 ° C. even at a low temperature operation of about 600 ° C. Performance equivalent to that of solid electrolyte fuel cells that require high-temperature operation in the vicinity, and even higher performance when pressurized operation is possible, and further cost reduction is possible. Further, they can be laminated, and when the anode electrode support and the separator are made of ferritic stainless steel, it is possible to match the thermal expansion characteristics with the electrolyte, and further excellent battery performance can be exhibited.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of an anode.

FIG. 2 is a schematic diagram of another example of an anode.

FIG. 3 is a schematic diagram of yet another example of an anode.

FIG. 4 is an explanatory view of a sealed state of a unit cell.

FIG. 5 is a development schematic diagram showing a stacking mode of a battery body.

FIG. 6 is a schematic view of a cylindrical manifold arranged in the battery body.

Claims (2)

[Claims] 1. An anode electrode support containing, as a unit cell structure, a porous material made of a heat-resistant metal containing at least one heat-resistant alloy selected from an iron-based alloy, a nickel-based alloy and a cobalt-based alloy. And a solid oxide fuel cell having a structure in which an anode composed of an anode electrode, a cerium oxide-based electrolyte, and a cathode are sequentially stacked. 2. An anode electrode is fixed to an anode electrode support containing a porous material made of a heat-resistant metal containing at least one heat-resistant alloy selected from iron-based alloys, nickel-based alloys and cobalt-based alloys. To form the anode,
Next, a method for producing a solid oxide fuel cell, characterized in that a cerium oxide-based electrolyte and a cathode are successively laminated on this anode, or the single cells thus obtained are laminated with a separator interposed.