JPH08306373A - Operation method for high-temperature type fuel cell, and high-temperature type fuel cell - Google Patents

Abstract

PURPOSE: To restrict the deterioration at the time of operation under heat cycle load, or the deterioration such as distortion by contact resistance or thermal stress by repeated application of the heat cycle load especially. CONSTITUTION: In operation of a high-temperature type fuel cell having an electrode terminal separator 12, and an output terminal which faces it to electrically get in contact with it under heat cycle load, a buffer layer 13a which restricts deterioration by the heat cycle load is provided between the separator 2 and the output terminal. Otherwise, a high-temperature type fuel cell is provided having a terminal collector member comprising an electrode terminal separator, buffer material which restricts deterioration by heat cycle load, and an output terminal integrated with each other in order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method of operating a high temperature fuel cell such as a solid oxide fuel cell, that is, deterioration during operation under heat cycle load, particularly contact resistance due to repeated application of heat cycle load. The present invention relates to an operating method capable of suppressing deterioration such as strain due to heat stress, and a solid oxide fuel cell in which deterioration during operation such as contact resistance and distortion is suppressed.

[0002]

2. Description of the Related Art In a high temperature fuel cell such as a solid oxide fuel cell, the contact resistance and stress strain between the respective constituent members are increased under a thermal cycle load, especially by repeatedly applying the load, resulting in a low resistance. Also, there is a problem that low stress strain cannot be stably maintained for a long period of time and battery performance is deteriorated. Therefore, conventionally, it has been proposed to prevent oxidation of a metal material used at high temperature by a LaMnO ₃ coat or the like, or to suppress oxidation by doping with yttrium or cerium, but these are not always sufficiently satisfactory.

[0003]

Under the circumstances described above, the present invention is directed to a high temperature fuel in which deterioration such as strain due to contact resistance or thermal stress is suppressed even under a thermal cycle load, especially under repeated application thereof. The present invention has been made for the purpose of providing a battery and a method for operating a high temperature fuel cell capable of suppressing such deterioration.

[0004]

DISCLOSURE OF THE INVENTION The present inventors previously proposed a structure in which a lanthanum chromite-based composite oxide sintered body and a cermet are laminated via at least one selected from metals and conductive ceramics. (Japanese Patent Application No. 6-320850), this separator can significantly reduce the contact resistance due to the predetermined intervening layer.

The inventors of the present invention have further noted that the problem of contact resistance is common not only to the inner central member such as the separator but also to the outer end member, and the electrode terminal separator and the output terminal corresponding thereto are also noted. When a high temperature type fuel cell having the above is operated under a thermal cycle load, particularly when the load is repeatedly applied, by interposing a predetermined buffer layer between the separator and the output terminal, contact resistance and thermal stress can be improved. It was found that the deterioration of strain and the like due to the above was suppressed, and the present invention was completed based on this finding.

That is, the present invention is: (1) When a high temperature fuel cell having an electrode terminal separator and an output terminal facing and electrically contacting the separator is operated under a thermal cycle load, the separator and the separator are used. A method of operating a high-temperature fuel cell, characterized in that a buffer layer capable of suppressing deterioration due to a thermal cycle load is interposed between the output terminal and (2) an electrode terminal separator, a buffer material, and an output terminal in order. A high temperature fuel cell having integrated terminal current collecting members, wherein a buffer material can suppress deterioration due to a thermal cycle load during operation. is there.

In a preferred embodiment of the present invention, (3) the electrode terminal separator is a lanthanum chromite-based composite.
Made of compound oxide, the output terminal is made of metal,
And the buffer layer has the general formula La_1-zSr_zCrO₃ Or La_1-zSr_zCr_1-wCo_wO₃ (In the formula, 0.05 ≦ z ≦ 0.5 and 0 <w ≦ 0.5
From the lanthanum chromite complex oxide represented by
(4) The electrode terminal separator is a lanthanum chromite-based compound.
Made of compound oxide, the output terminal is made of metal,
And the buffer material is the general formula La_1-zSr_zCrO₃ Or La_1-zSr_zCr_1-wCo_wO₃ (In the formula, 0.05 ≦ z ≦ 0.5 and 0 <w ≦ 0.5
From the lanthanum chromite complex oxide represented by
A high temperature fuel cell according to item (2) above, (5) a lanthanum roma composing an electrode terminal separator
Ito-based complex oxide has the general formula (La_1-uA_u)_c(Cr_1-vB '_v)_dO₃ (A in the formula is Sr or Ca, B'is Co, Ni, Fe,
At least one selected from Zn, Cu and Mn
Metal, 0 <u ≦ 0.2, 0 <v ≦ 0.05,
0.95 ≦ c / d ≦ 1.05)
(3) The method described in the item (6), or a lanthanum chroma that constitutes the electrode terminal separator.
Ito-based complex oxide has the general formula (La_1-uA_u)_c(Cr_1-vB '_v)_dO₃ (A in the formula is Sr or Ca, B'is Co, Ni, Fe,
At least one selected from Zn, Cu and Mn
Metal, 0 <u ≦ 0.2, 0 <v ≦ 0.05,
0.95 ≦ c / d ≦ 1.05)
(4) The high temperature fuel cell according to the item (7), wherein the metal-based output terminal is a nickel-based alloy
The method according to item (3) or (5), (8) wherein the metal-based output terminal is a nickel-based alloy
The high-temperature fuel cell according to item (4) or (6), and more preferably (9) the buffer layer and the electrode.
LaMnO between the polar end separators_Three, La_1-pSr_p
MnO₃, LaCrO₃, La_1-qSr_qCrO₃, LaC
oO₃Or La_1-rSr _rCoO₃(However, 0 <p ≦ 0.
5, 0 <q ≦ 0.5, 0 <r ≦ 0.5)
Item (3), (5) or (7) with the interposition of the laser layer
(10) L between the buffer material and the electrode terminal separator
aMnO_Three, La_1-pSr_pMnO₃, LaCrO₃, La
_1-qSr_qCrO₃, LaCoO₃Or La_1-rSr_rCoO
₃(However, 0 <p ≦ 0.5, 0 <q ≦ 0.5, 0 <r
≤0.5) with a buffer layer interposed
High temperature fuel cell according to item (4), (6) or (8)
Ike, (11) LaCrO between the buffer layer and the output terminal₃,
La_1-qSr_qCrO₃Or La_1-sSr_sCr_1-tNi_tO₃
(However, 0 <s ≦ 0.5, 0 <t ≦ 0.5)
The above item (3), item (5) or with a buffer layer interposed
(7) Method, (12) LaCrO between the buffer material and the output terminal₃,
La_1-qSr_qCrO₃Or La_1-sSr_sCr_1-tNi_tO₃
(However, 0 <s ≦ 0.5, 0 <t ≦ 0.5)
(4), (6) or with a buffer layer interposed
The high temperature fuel cell according to the item (8) can be mentioned.

Preferred as the high temperature fuel cell used in the present invention is a solid oxide fuel cell, especially a flat plate type stack cell. Further, the electrode terminal separator has an anode terminal and a cathode terminal.For example, in a plate-shaped solid electrolyte fuel cell stack, it is interposed between solid electrolyte plates having electrodes on both surfaces, and each raw material is on both surfaces. It is an outermost separator that is superposed on each electrode of each outermost solid electrolyte plate, which is different from the separator having a gas flow path. An output terminal is disposed on the outer side of the electrode terminal separator so as to be in electrical contact therewith. In the method of the present invention, the operation of the high temperature fuel cell is usually carried out by heating and starting up, operating at a high temperature for a required time, and then leaving it to cool and resting. However, during operation under such a thermal cycle load, a predetermined buffer layer is interposed between the electrode terminal separator and the output terminal to deteriorate the high temperature fuel cell, particularly increase in contact resistance and thermal stress strain. It is important to suppress Further, in the high temperature fuel cell of the present invention, such deterioration can be suppressed, and a separator for an electrode terminal and a buffer material capable of suppressing deterioration due to thermal cycle load during cell operation, particularly repetition thereof. It is important to have an end current collecting member in which the output terminal and the output terminal are integrated in this order.

In the present invention, the preferred material for the electrode terminal separator is a rare earth complex oxide, such as a lanthanum chromite complex oxide or a yttrium chromite complex oxide. The lanthanum chromite-based composite oxide and the yttrium chromite-based composite oxide are not particularly limited, but preferably have the general formula (I) (Ln _1-x A _x ) _a (Cr _{1- y By} ) _b O ₃ (I). (Ln in the formula is La or Y, A is Sr or Ca, B is F
e, Ni, Co, Mg, Mn, Zn, Cu, Al, P
at least one metal selected from d, V, Ir, Mo, Li and W, and 0.9 ≦ a / b ≦ 1.1,
Those represented by 0 <x ≦ 0.2 and 0 <y ≦ 0.2) are preferable. Among them, lanthanum chromite-based composite oxides are preferable, and in particular, general formula (II) (La _{1-u Au} ) _c (Cr _{1-v B'v} ) _d O ₃ (II) (A in the formula is Sr or Ca. , B ′ are Co, Ni, Fe,
At least one metal selected from Zn, Cu and Mn, 0 <u ≦ 0.2, 0 <v ≦ 0.05,
0.95 ≦ c / d ≦ 1.05) is preferable.

A preferable material for the output terminal is a metal-based material, especially a nickel-based alloy-based material. As the nickel-based alloy, Inconel 600 and Hastelloy 80 are used.
0 and the like.

Further, a preferable material for the buffer layer is represented by the general formula (III) or (IV) La _1-z Sr _z CrO ₃ (III) La _1-z Sr _z Cr _1-w Co _w O ₃ (IV) (formula) Lanthanum chromite complex oxide represented by 0 <z ≦ 0.5 and 0 <w ≦ 0.5, among which La
_{It is 0.8} Sr _0.2 CrO ₃ .

The buffer layer is further expected as a multilayer.
The effect can be obtained. For example, above
Lanthanum chromite-based complex oxide, especially the general formula (II
Buffer consisting of I) or (IV) and general formula (II)
Layer and the separator at the end of the electrode
Lanthanum-based complex acid that further suppresses deterioration due to cargo
Compounds, especially buffers of perovskite type
Layers can be disposed and intervened. This lanthanum complex oxide
For example, LaMnO₃, La_1-pSr_pMnO₃,
LaCrO₃, La_1-qSr_qCrO₃, LaCoO₃, L
a_1-rSr_rCoO ₃And the like. Note that these
In the chemical formula, 0 <p ≦ 0.5, 0 <q ≦ 0.5, 0 <r ≦
It is 0.5. In addition, the lanthanum chromite complex acid
Compound, especially a buffer comprising the general formula (III) or (IV)
There is a thermal cycle load between the fur layer and the output terminals.
The metal component that makes it possible to suppress the deterioration due to
Lanthanum-based composite oxide that does not react with, for example, L
aCrO₃, La_1-qSr_qCrO₃, La_1-sSr_sCr_1-
tNi_tO₃, Especially a perovskite type bag
A fur layer may be provided and intervened. Note that these chemistries
In the formula, 0 <s ≦ 0.5 and 0 <t ≦ 0.5. Especially yes
The effective multi-layered buffer layer is the above-mentioned lanthanum chromite system.
A buffer layer composed of a complex oxide, and the buffer layer and the electrode.
Between the terminal separator and between the buffer layer and the output terminal
And the heat cycle
Curb load deterioration suppression, for example, contact resistance increase suppression
Lanthanum-based complex oxide that enables
-Type buffer layer, and thermal
Curb load deterioration suppression, for example, contact resistance increase suppression
Etc., and reacts with the metal components that make up the output terminals.
Lanthanum-based complex oxide, especially perovskite
It consists of a buffer layer consisting of molds. Multi-layered bus
The stuffer layer is preferably a thin layer formed on the base layer by a conventional method, particularly
It is applied by a coating method or a printing method such as a screen printing method.
It was made.

These buffer layers are not particularly dense or rigid, and porous or flexible ones can be used, and are suitable for practical use. The thickness of the buffer layer, whether it is a single layer or a multilayer, is usually 10 to 150 μm,
It is preferably selected in the range of 30 to 100 μm.

In the method of the present invention, the following method can be used for interposing the buffer layer. That is, a buffer plate is prepared together with an electrode terminal separator and an output terminal, and after being molded into a shape suitable for lamination, a method of laminating, an electrode terminal separator and an output terminal are prepared, and after molding into a shape suitable for lamination. ,, at least one of these, a buffer layer is deposited, then a method of laminating them, a separator for an electrode terminal and an output terminal are prepared, and after molding into a shape suitable for laminating,
For example, a method of inserting a buffer layer paste between them and then firing it.

The buffer plate may have a single-layer structure, but preferably has a multi-layer structure, and among them, suitable buffer layers of different kinds are provided on the electrode terminal separator side and the output terminal side of the base buffer plate, respectively. It is better to use the one to which is attached.

The shape suitable for the above-mentioned lamination is preferably a plate shape having the same size, and the flat shape is particularly suitable for a flat-plate high temperature fuel cell, which is promising in the future. Is useful. The buffer layer deposition method includes a plating method such as electrolytic plating and electroless plating, a method of firing after coating treatment, a spraying method such as a plasma spraying method, a sputtering method, a CVD method,
A vapor deposition method, a coating method or the like is used.

Next, in the high temperature fuel cell of the present invention, an electrode terminal separator, a buffer material capable of suppressing thermal cycle load during cell operation, particularly deterioration due to repeated cycles, and an output terminal are integrated in this order. It is important to have an end current collecting member made of More preferably, lanthanum-based composite oxides, especially those of the perovskite type, particularly LaMnO ₃ , La _1-p Sr _p MnO ₃ , LaCrO ₃ , L.
a _1-q Sr _q CrO ₃ , LaCoO ₃ or La _1-r Sr _r Co
LaMnO ₃ , La _1-p S, which is interposed between a buffer material made of O ₃ and an electrode terminal separator made of a rare earth compound oxide of the general formula (I), especially the general formula (II).
r _p MnO ₃ , LaCrO ₃ , La _1-q Sr _q CrO ₃ , La
A buffer layer made of CoO ₃ or La _1-r Sr _r CoO ₃ , and LaCrO interposed between such a buffer material and an output terminal, especially an output terminal made of a nickel-based alloy.
_{3, La 1-q Sr q} CrO 3 or _{La 1-s Sr s Cr 1} -t Ni t
It is preferable to have a buffer layer made of O ₃ . The buffer material is the same as the buffer layer used in the method of the present invention, and may be a single layer or a multilayer structure. The single-layer buffer material is preferably a lanthanum-based composite oxide, more preferably a perovskite type, particularly LaMnO ₃ , La _1-p Sr _p MnO ₃ ,
LaCrO ₃ , La _1-q Sr _q CrO ₃ , LaCoO ₃ , L
An example is a _1-r Sr _r CoO ₃ . Also,
The multilayer buffer material is preferably a lanthanum-based composite oxide, more preferably a perovskite type, particularly LaMnO ₃ , La _1-p Sr _p MnO ₃ , LaCrO ₃ , L.
a _1-q Sr _q CrO ₃ , LaCoO ₃ or La _1-r Sr _r Co
LaMnO ₃ , La _1-p Sr _p MnO ₃ and L are provided between the buffer material composed of O ₃ and the electrode terminal separator composed of the general formula (I), particularly the rare earth compound oxide of the general formula (II).
aCrO ₃ , La _1-q Sr _q CrO ₃ , LaCoO ₃ or L
a _1-r Sr _r CoO _{3 with} a buffer layer disposed and interposed, such a buffer material and an output terminal,
In particular, LaCrO is placed between the output terminals made of nickel-based alloy.
_{3, La 1-q Sr q} CrO 3 or _{La 1-s Sr s Cr 1} -t Ni t
It is advantageous to arrange and interpose a buffer layer made of O ₃ (however, 0 <s ≦ 0.5, 0 <t ≦ 0.5). Above all, both buffer layers are arranged and intervened. Those that are allowed are preferable. In order to form such a buffer layer, it is preferable to use a method in which a plate-shaped buffer material is adhered by a conventional method such as the above-mentioned coating method or printing method. Further, the buffer material does not have to be a particularly dense or rigid one, and a porous or flexible one can be used, and is suitable for practical use. The thickness of the buffer material is
Whether it is a single layer or a multilayer, it is usually selected in the range of 10 to 150 μm, preferably 30 to 100 μm.

[0018]

According to the method of the present invention, when a high temperature fuel cell such as a solid oxide fuel cell is operated, a buffer layer is interposed so as to deteriorate during operation under a heat cycle load, particularly a heat cycle load. It is possible to suppress deterioration of contact resistance and distortion due to thermal stress due to repeated addition, and it is possible to maintain the high performance of the entire cell for a long time. In the high temperature fuel cell of the present invention, the same effect as described above can be obtained by incorporating the buffer material in the terminal current collecting member.

The buffer layer and the buffer material have a function of buffering and adjusting the contact resistance between the members sandwiching the buffer layer under a thermal cycle load, the difference in the physical properties between the members, particularly the difference in the thermal expansion characteristics such as the coefficient of thermal expansion. Have. As such a buffer material, for example, when the material for the electrode terminal separator is a lanthanum chromite complex oxide and the material for the output terminal is a nickel-based metal, a lanthanum complex oxide having a coefficient of thermal expansion between them is used. The thing which uses ceramics, such as a thing, as a composition component is used. In addition, the buffer layer and buffer material,
It does not have to be a particularly dense or rigid one, and a porous or flexible one can be used, so that it is suitable for practical use. By buffer-matching the thermal expansion characteristics in this way, the occurrence of distortion, warpage, and peeling due to the difference in thermal expansion during thermal history is suppressed, and good adhesion between the members of the fuel cell is maintained. It enables strong bonding and improves battery characteristics.

[0020]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

EXAMPLE 1 Consisting of stabilized zirconia containing 8% yttria,
L on both sides of a 20 cm square solid electrolyte plate with a thickness of 200 μm
A cathode made of a _0.8 Sr _0.2 MnO ₃ and an anode made of cermet of nickel and zirconia with an equimolar ratio were attached to form a solid electrolyte plate with electrodes. The separator was made of La _0.9 Sr _0.1 Cr _0.98 Co _0.02 O ₃ . The separator is interposed between the solid electrolyte plates with electrodes,
The electrode terminal separator is in contact with the solid electrolyte plate with the terminal electrode. The output terminal portion was made of Inconel 600. As shown in FIG. 1, La _0.9 Sr _0.1 Cr _0.98 Co is provided between the output terminal plate 11 and the electrode terminal separator plate 12.
_0.02 the output terminal side of the O ₃ buffer plate 13 made of 'L
A multilayer buffer plate 13 having a buffer layer 13a made of a _0.8 Sr _0.2 CrO ₃ adhered was interposed. In this way, each member was integrated to prepare a three-stage stack type solid oxide fuel cell. The battery was heated from room temperature to 1000 ° C., operated at 1000 ° C. for 300 hours, and then allowed to cool to lower the temperature, and after 2 days, the same operation was repeated. As a result, the contact resistance after repeated operation was as low as 0.25 mΩ, and the battery performance was good.

Example 2 As shown in FIG. 2, a separator for the output terminal side and the electrode terminal of a buffer plate 23 'made of La _0.9 Sr _0.1 Cr _0.98 Co _0.02 O ₃ instead of the multilayer buffer plate of Example 1 was used. A multilayer buffer plate 23 having a buffer layer 23a made of La _0.8 Sr _0.2 CrO ₃ and a buffer layer 23 b made of La _0.8 Sr _0.2 MnO ₃ on each side was used, and this was used as an output terminal plate 21 and an electrode terminal separator. A solid oxide fuel cell was prepared in the same manner as in Example 1 by interposing it between the plate 22 and the plate 22. An operation test was performed on this battery in the same manner as in Example 1. As a result, the contact resistance after repeated operation was as low as 0.15 mΩ, and the battery performance was good.

Comparative Example 1 Inconel 6 having dimensions of 50 × 50 × 5 mm.
00 output terminal board and La _0.9 Sr _0.1 Cr _0.98 Co
_A sample was prepared by stacking an electrode terminal separator made of _0.02 O ₃ and the contact resistance of the sample was measured by the 4-terminal method. Moreover, the contact resistance when a thermal cycle of 1000 ° C. → normal temperature → 1000 ° C. was applied was measured. The contact resistance was 1 mΩ before the thermal cycle and 350 mΩ after the thermal cycle.

Reference Example 1 La _0.8 Sr _{0.2 is} placed between the output terminal plate and the electrode terminal separator.
A sample was prepared in the same manner as in Comparative Example 1 except that a buffer plate made of CoO ₃ was interposed, and the contact resistance was measured. The contact resistance was 11 mΩ before the thermal cycle and 17 mΩ after the thermal cycle.

Reference Example 2 La _0.8 Sr _0.2 between the output terminal plate and the electrode terminal separator.
A sample was prepared in the same manner as in Comparative Example 1 except that a buffer plate made of MnO ₃ was interposed, and the contact resistance of the sample was measured. The contact resistance was 12 mΩ before the thermal cycle and 17 mΩ after the thermal cycle.

Reference Example 3 La _0.8 Sr _0.2 between the output terminal plate and the electrode terminal separator.
A sample was prepared in the same manner as in Comparative Example 1 except that a buffer plate made of CrO ₃ was interposed, and the contact resistance was measured. The contact resistance was 8 mΩ before the thermal cycle and 5 mΩ after the thermal cycle.

From the above results, it is found that it is preferable to interpose the multi-layered buffer plate between the output terminal and the electrode terminal separator in the solid oxide fuel cell.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a terminal current collecting member structure in an example of a fuel cell of the present invention.

FIG. 2 is a schematic cross-sectional view of a terminal current collecting member structure in another example of the fuel cell of the present invention.

[Explanation of symbols]

 11, 21 Output terminal board 12, 22 Separator board for electrode terminal 13, 23 Multi-layer type buffer board 13 ', 23' Buffer board 13a, 23a, 23b Buffer layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Someya 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (2)

[Claims] 1. When a high temperature fuel cell having an electrode terminal separator and an output terminal opposed to and in electrical contact with the separator is operated under a thermal cycle load, heat is generated between the separator and the output terminal. A method for operating a high-temperature fuel cell, characterized in that a buffer layer capable of suppressing deterioration due to cycle load is interposed. 2. A high temperature fuel cell having a terminal current collecting member formed by sequentially integrating an electrode terminal separator, a buffer material and an output terminal, wherein the buffer material suppresses deterioration due to a thermal cycle load during operation. A high-temperature fuel cell, which is characterized by being volatile.