JP2002050370A - Current collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air pole current collector of a solid electrolyte fuel cell. SOLUTION: The current collector is made of a porous Ni group alloy which contains in mass % Cr: 13-45% and as necessary Fe: 1-38%, and as necessary one or two or more kinds out of W: 0.1-20%, Mo: 0.1-10%, Nb: 0.1-4%, Ta: 0.1-4%, Co: 0.1-10%, and as necessary one or two or more kinds out of Al: 0.1-10%, Si: 0.01-3%, and Ti: 0.01-3%, and further as necessary one or two or more kinds out of La: 0.001-0.05%, Y: 0.001-0.05%, Zr: 0.001-0.2%, and the content of C and Mn is defined respectively as C: 0.15% or less and Mn: 2% or less and the rest is composed of Ni and unavoidable impurity, and which has a total porosity of 70-97%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current collector for a solid oxide fuel cell, and more particularly to a cathode current collector for a solid oxide fuel cell.

[0002]

2. Description of the Related Art Generally, a solid oxide fuel cell has a capacity of 10%.
Since it operates at a high temperature of 00 ° C, it can efficiently convert the chemical energy of the fuel into electric energy, and can use waste heat, and also from the viewpoint of resource saving and environmental issues. Attention has been paid. This solid oxide fuel cell has a laminated structure shown in the schematic sectional view of FIG. In FIG. 2, 1 is an air electrode current collector, 2 is an air electrode, 3 is a solid electrolyte, 4 is a separator,
5 is an anode, 6 is an anode current collector, 7 is a groove through which hydrogen passes, 8
Is a groove through which air passes. Air electrode 2 on one side of solid electrolyte 3
Are stacked, and the fuel electrode 5 is formed on the other surface to form the cell 9.

The solid electrolyte 3 is generally composed of zirconia stabilized with yttria (hereinafter referred to as YSZ). In recent years, however, Ln _1-x A _x Ga _1-yz B ₁ B ₂ O ₃ (where Ln = One or more of La, Ce, Pr, Nd, Sm, A = one or more of Sr, Ca, Ba, B ₁ = _one or more of Mg, Al, In, B _Two
= One or more of Co, Fe, Ni, Cu, x =
0.05-0.3, y = 0-0.29, z = 0.01-
0.3, y + z = 0.025 to 0.3) or the like is used. Further, the separator 4 is made of a dense ceramic made of lanthanum chromite (LaCrO ₃ ), and the air electrode 2 is made of (Sm, Sr) Co.
O ₃ , (La, Sr) MnO _3, etc., and the fuel electrode 5 is made of Ni / YSZ cermet, Ni
/ (Ce, Sm) O ₂ cermet or the like. The cathode current collector 1 is made of a platinum mesh, and the anode current collector 6 is made of a Ni mesh.

[0004]

In a solid electrolyte fuel cell, a platinum mesh is used as a cathode current collector in a small laboratory fuel cell. However, in a fuel cell of a practical size, platinum mesh is used. Although it is excellent in current collecting properties, it cannot be used because it is expensive, and was used as an air electrode current collector by engraving a groove in a lanthanum chromite separator. From such a background, there has been a demand for a material that is inexpensive and has excellent high-temperature strength, heat resistance, and oxidation resistance, which can be used instead of a platinum mesh that can be used for a fuel cell having a practical size.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
From the viewpoints described above, based on the recognition that Ni-based alloys have excellent high-temperature strength, heat resistance, and oxidation resistance, various N
A current collector was prepared from an i-based alloy, and this current collector was incorporated into a solid oxide fuel cell as an air electrode current collector to conduct a test study. As a result, the current collector of the solid oxide fuel cell was measured by mass% (hereinafter,% indicates mass%), and (1) C
r: a Ni-based alloy containing 13 to 45% and a balance of Ni and unavoidable impurities, (2) Cr: 1
A Ni-based alloy having a composition of 3 to 45% and Fe: 1 to 38%, with the balance being Ni and unavoidable impurities;
(3) Cr: 13-45%, and W: 0.
1 to 20%, Mo: 0.1 to 10%, Nb: 0.1 to 4
%, Ta: 0.1 to 4%, and Co: 0.1 to 10%, and a Ni-based alloy having a composition consisting of Ni and inevitable impurities, with the balance being (4) ) C
r: 13 to 45%, Fe: 1 to 38%, W: 0.1 to 20%, Mo: 0.1 to 10%, Nb:
0.1-4%, Ta: 0.1-4%, Co: 0.1-1
A Ni-based alloy containing one or more of 0% and a balance of Ni and unavoidable impurities,
(5) Cr: 13 to 45% is contained, and further, Al:
0.1 to 10%, Si: 0.01 to 3%, Ti: 0.0
One or more of 1 to 3%, and the remainder is N
(6) Cr: 13 to 45%, Fe: 1 to 38%, Al: 0.1 to 10%, Si: 0.01
(3) Cr: 13 to 45%, a Ni-based alloy containing one or two or more of Ti: 0.01 to 3% and a balance of Ni and unavoidable impurities. W: 0.1 to 20%, Mo: 0.1 to 1
0%, Nb: 0.1 to 4%, Ta: 0.1 to 4%, C
o: 0.1 to 10%, one or more of the following: Al: 0.1 to 10%, Si: 0.01 to
Ni-based alloy containing 3%, one or more of Ti: 0.01 to 3%, and the balance having Ni and unavoidable impurities, (8) Cr: 13 to 45%, F
e: 1 to 38%, W: 0.1 to 20%,
Mo: 0.1 to 10%, Nb: 0.1 to 4%, Ta:
0.1 to 4%, Co: 0.1 to 10%, one or more of which are contained. Further, Al: 0.1 to 10%, S:
i: 0.01 to 3%, Ti: 0.01 to 3%, a Ni-based alloy containing one or two or more of the following components, the balance being composed of Ni and unavoidable impurities, (9) La: 0.001 to 0.05%, Y: 0.001 to Ni-base alloy according to any one of the above (1) to (8)
A Ni-based alloy having a composition containing one or more of 0.05% and Zr: 0.001 to 0.2% is used at a temperature around 1000 ° C. which is an operating temperature range of a solid oxide fuel cell. Total porosity obtained by sintering a Ni-based alloy powder having the most excellent corrosion resistance in an air atmosphere and having this component composition:
The air electrode current collector made of a porous Ni-based alloy having 70 to 97% exhibits almost the same or better effect as the air electrode current collector made of platinum mesh. (10) The above (1) And M contained in the Ni-base alloy according to any one of (1) to (9).
n content of C: 0.15% or less, Mn: 2%
Research results have shown that it is more preferable to define the following.

The present invention has been made based on the above research results, and the porous Ni-based alloy constituting the current collector of the present invention has a skeleton (hereinafter referred to as a skeleton).
And a sponge structure comprising pores. In the porous Ni-based alloy constituting the current collector of the present invention, fine pores exist in the skeleton, but fine pores in the skeleton may not be present. If the skeleton has pores, it is preferably less than 10% of the whole, and if the porosity is 10% or more, the strength as a current collector is undesirably reduced.

Next, the reason why the component composition and the porosity of the porous Ni-based alloy constituting the current collector of the present invention are limited as described above will be described. (A) Component composition (a) Cr Cr is added because it has an effect of improving corrosion resistance and strength at high temperatures, but if its content is less than 13%, sufficient corrosion resistance and strength at high temperatures cannot be secured. Therefore, the effect as an air electrode current collector cannot be obtained. On the other hand, if the Cr content exceeds 45%, the sinterability of the powder decreases and the porosity of the skeleton increases, which is not preferable. Therefore, the Cr content is set to 13 to 45%. A more preferable range of the Cr content is 15 to 25%.
And an even more preferred range is 15 to 20%.

(B) Fe Fe has the effect of improving the high-temperature strength, but if its content is less than 1%, it is not possible to secure a desired high-temperature strength, so that the porous material as the air electrode current collector cannot be obtained. It is not preferable because the quality cannot be ensured.
If the content exceeds 38%, the high-temperature oxidation resistance is extremely deteriorated, so that it is not preferable as a material for the air electrode current collector. Therefore, the content of Fe was determined to be 1 to 38%. A more preferred range for the Fe content is 1.5-20%, and an even more preferred range is 1.5-10%.

(C) W, Mo, Nb, Ta, Co All of these components are dissolved in the base material and added to improve the high-temperature strength, but W: less than 0.1%, Mo:
If the content is less than 0.1%, Nb: less than 0.1%, Ta: less than 0.1%, and Co: less than 0.1%, the desired effects cannot be obtained, while W exceeds 20% and Mo is 10%. %, Nb is 4
%, More than 4%, and more than 10% of Co, a brittle intermetallic compound is precipitated and the ductility, elasticity and workability are reduced.
-20%, Mo: 0.1-10%, Nb: 0.1-4
%, Ta: 0.1 to 4%, and Co: 0.1 to 10%. A more preferred range for these components is W: 12-18.
%, Mo: 1 to 4%, Nb: 1 to 4%, Ta: 1 to 4
%, Co: 1 to 4%.

(D) Al, Si, Ti These components are added because they form a dense oxide film and have an effect of improving corrosion resistance at high temperatures.
If it is less than 1%, Si: less than 0.01%, and Ti: less than 0.01%, the desired effects cannot be obtained, while Al exceeds 10%, Si exceeds 3%, and Ti exceeds 3%. And the ductility, elasticity and workability are reduced, so that the content is set to Al: 0.1 to 10%, Si: 0.01 to 3%,
Ti: 0.01 to 3% was determined. A more preferred range of the Al content is 0.3 to 5%, a more preferred range of the Si content is 0.01 to 1%, and a more preferred range of the Ti content is 0.01 to 1%. .

(E) La, Y, Zr These components are added because they have the effect of improving the adhesion of the oxide film and improving the corrosion resistance at high temperatures.
La: less than 0.001%, Y: less than 0.001%, Z
r: If less than 0.001%, the desired effect cannot be obtained, while La exceeds 0.05%, Y exceeds 0.05%,
If Zr exceeds 0.2%, ductility decreases and cracks occur during rolling, which is not preferable. Therefore, the content is La: 0.001 to 0.05%, Y: 0.001 to
0.05%, Zr: 0.001 to 0.2%. A more preferred range of these components is La: 0.01 to 0.0.
3%, Y: 0.01 to 0.03%, Zr: 0.05 to
0.1%.

(D) Mn, C These components are preferably not contained at all as a material for the cathode current collector of the solid oxide fuel cell, but it is difficult to completely remove these components in terms of cost. is there. However, there is no actual harm even if Mn is contained up to 2% and C is contained up to 0.2%. If Mn exceeds 2% and C exceeds 0.2%, the rolling workability and the formability are reduced. Therefore, it was determined that Mn: 2% or less and C: 0.2% or less.

(B) Porosity The porous Ni-based alloy constituting the current collector of the present invention has a sponge structure composed of a skeleton (skeleton portion) and pores, and the overall porosity should be as large as possible. Preferably, it is in the range of 70 to 97%. The skeleton may have fine pores, but the skeleton preferably has less than 10% of the total pores. If the porosity of the skeleton is 10% or more, the strength of the current collector decreases. Is not preferred. The overall specific surface area of such a porous Ni-based alloy is 80 to 3
It is preferably less than 00 cm ² / cm ³ .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the current collector of the present invention will be specifically described with reference to examples. In a normal melting furnace, Ni-based alloy atomized powders having the average particle diameter of 2 μm, each having the component compositions shown in Tables 1 to 5, were prepared. Further, n-hexane is used as an organic solvent, and sodium dodecylbenzenesulfonate (hereinafter referred to as D) is used as a surfactant.
BS), hydroxypropyl methylcellulose (hereinafter referred to as HPMC) as a water-soluble resin binder, and glycerin as a plasticizer. Further, distilled water was prepared as water.

The Ni-based alloy atomized powder and HPMC
(Water-soluble resin binder) is charged into a strong shearing type kneader and 3
After kneading for 0 minutes, 50% of the total amount of distilled water to be added is distilled water, and the mixture is kneaded. The remaining 50% of distilled water and other additives such as n-hexane (organic solvent) and DBS ( (Surfactant) and glycerin (plasticizer) are added and kneaded for 3 hours. By mass%, Ni-based alloy atomized powder: 50.0%, n-hexane: 1.5%, HPMC: 5.0% , DBS: 2.0%, glycerin: 3.0%, distilled water: remaining, and a mixed slurry having the following composition was prepared.

The mixed slurry is formed into a molded body having a thickness of 1 mm by a doctor blade method, and the molded body is subjected to foaming, degreasing and sintering under the following conditions to obtain a thickness:
A porous Ni-based alloy plate having a size of 0.7 mm and having an overall porosity shown in Tables 6 and 7 was produced.
The air electrode current collectors 1 to 59 of the present invention were cut out from the base alloy plate. (I) Foaming conditions Humidity: 90%, Temperature: 35 ° C, Holding time: 10 minutes, (ii) Degreasing conditions Atmosphere: N ₂ -5% H ₂ Temperature: 450 ° C, Holding time: 60 minutes, (iii) Sintering Conditions Atmosphere: vacuum (0.5 torr H ₂ ) Temperature: 1150 ° C., Holding time: 10 minutes,

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Table 5]

Further, La ₂ O ₃ , Sr
Prepare each powder of CO ₃ , Ga ₂ O ₃ , MgO, CoO,
These raw material powders were used as La _0.8 Sr _0.2 Ga _0.8 Mg _0.15 Co
After weighing and mixing well to obtain _0.05 O ₃ ,
The calcined body was preliminarily calcined at 0 ° C., and the obtained calcined body was pulverized. A general binder, a solvent and the like were added, and the mixture was pulverized with a ball mill to prepare a slurry. The slurry was formed into a green sheet by a doctor blade method. The formed green sheet was sufficiently dried in the air, cut into a predetermined size, and sintered at 1450 ° C. The thickness of the obtained sintered body was 110 μm.

The sintered body thus obtained was used as an electrolyte, and Ni and (Ce _0.8 Sm _0.2 ) O ₂ were provided on one side of the electrolyte.
NiO and (Ce) mixed so that the volume ratio of
_A fuel electrode is formed by baking the mixed powder of _0.8 Sm _0.2 ) O ₂ at 1100 ° C., and an air electrode is formed by baking (Sm _0.5 Sr _0.5 ) CoO ₃ at 1000 ° C. on the other side of the electrolyte. Was formed to form a cell.

Further, the slurry is poured into a mold,
A green body having a groove is prepared, and this green body is
By sintering at 50 ° C., a separator having a groove on one side was produced. In addition, Ni felt was prepared as a fuel electrode current collector, and a platinum mesh was prepared to be used as an air electrode current collector of a conventional solid electrolyte fuel cell.

Ni-Felt, which is an anode current collector, is laminated on the fuel electrode side of the cell fabricated in this manner, and the components having the component compositions and the total porosity shown in Tables 1 to 7 are provided on the air electrode side of the cell. The cathode current collectors 1 to 59 of the present invention made of a porous Ni-based alloy are laminated, and the separator is laminated on the anode current collector and the cathode current collector, as shown in FIG. Was manufactured, and a solid electrolyte fuel cell was manufactured using a conventional air electrode current collector made of a platinum mesh.

While maintaining these solid electrolyte fuel cells at 700 ° C., a dry hydrogen gas is supplied as a fuel gas, air is supplied as an oxidant gas, and a conventional solid electrolyte fuel cell incorporating a platinum mesh as an air electrode current collector. And Table 1
The current density at 0.7 V was measured for each of the solid electrolyte fuel cells incorporating the air electrode current collectors 1 to 59 of the present invention made of a porous Ni-based alloy having the component compositions shown in FIGS. The power generation characteristics were evaluated by showing the results in Tables 6 and 7.

[0027]

[Table 6]

[0028]

[Table 7]

[0029]

From the results shown in Tables 1 to 7, the solid oxide fuel cell incorporating the air electrode current collector made of the porous Ni-based alloy having the component composition of the present invention has the air electrode made of platinum mesh. Since the present invention shows almost the same power generation characteristics as a solid electrolyte fuel cell incorporating a current collector, the present invention can reduce the manufacturing cost without lowering the power generation characteristics of the solid electrolyte fuel cell. It greatly contributes to the development of industry.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a structure of a solid oxide fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air electrode current collector 2 Air electrode 3 Electrolyte 4 Separator 5 Fuel electrode 6 Fuel electrode current collector 7 Groove 8 Groove 9 Cell

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiro Wada 1-297 Kitabukuro-cho, Omiya-shi, Saitama F-term in Mitsubishi Materials Corporation Research Laboratory (reference) 5H026 AA06 CC03 CX01 EE08 HH04 HH05

Claims (9)

[Claims] 1. The method according to claim 1, wherein in mass% (% indicates mass%),
r: a solid electrolyte fuel cell comprising a porous Ni-based alloy having a composition of 13 to 45%, the balance being Ni and unavoidable impurities, and having a total porosity of 70 to 97%. Current collector. 2. Cr: 13 to 45%, Fe: 1 to 38%
, A balance of Ni and unavoidable impurities, and having a total porosity of 70 to 97%.
A current collector for a solid oxide fuel cell, comprising a base alloy. 3. Cr: 13 to 45%, W: 0.1 to 20%, Mo: 0.1 to 10%, Nb: 0.1 to 4%, Ta: 0.1 to 4% 4%, Co: 0.1 to 10%, and one or more of the following, with the balance being composed of Ni and unavoidable impurities, and having a total porosity of 70 to
A current collector for a solid oxide fuel cell, comprising a porous Ni-based alloy having 97%. 4. Cr: 13 to 45%, Fe: 1 to 38%
W: 0.1 to 20%, Mo: 0.1 to 10%, Nb: 0.1 to 4%, Ta: 0.1 to 4%, Co: 0.1 to 10% A porous Ni-base containing one or more of one or more of the following, the balance comprising Ni and unavoidable impurities, and having a total porosity of 70 to 97%. A current collector for a solid oxide fuel cell, comprising an alloy. 5. The porous Ni-based alloy according to claim 1, further comprising: 0.1 to 10% of Al, 0.01 to 3% of Si, and 0.01 to 3 of Ti. %, Porous Ni having a composition containing one or more of the following:
A current collector for a solid oxide fuel cell, comprising a base alloy. 6. The porous Ni-based alloy according to claim 1, further comprising: La: 0.001 to 0.05%, Y: 0.001 to 0.05%, Zr : Porous Ni having a composition containing one or more of 0.001 to 0.2%
A current collector for a solid oxide fuel cell, comprising a base alloy. 7. The method of claim 1, 2, 3, 4, 5, or 6.
A collector for a solid oxide fuel cell, wherein the contents of C and Mn contained in the porous Ni-based alloy described above are specified as: C: 0.15% or less, Mn: 2% or less, respectively. . 8. The solid electrolyte fuel cell according to claim 1, wherein said current collector is an air electrode current collector of a solid oxide fuel cell. Current collector. 9. A solid oxide fuel cell incorporating the current collector according to claim 1 as an air electrode current collector.