JP3110265B2 - Bonding material and bonding method for solid oxide fuel cell stack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining material and a joining method for a solid oxide fuel cell stack, and more particularly to a fuel cell electrode of a single cell constituting a solid oxide fuel cell operating at a high temperature or the fuel. The present invention relates to a joining material interposed between a fuel-side current collector abutting on a side electrode and an interconnector and a joining method of a fuel cell stack using the same.

[0002]

2. Description of the Related Art When a fuel cell electrode of a single cell in a solid oxide fuel cell or a fuel collector contacting the fuel electrode is connected to an interconnector, an electrical contact resistance is suppressed to be low. It is necessary to provide a method of electrically connecting by strongly pressing each other during power generation,
2. Description of the Related Art A method is known in which a joining material is used in advance of joining before power generation.

However, in the method of pressing strongly against each other during power generation, since solids are brought into contact with each other, electrical contact resistance cannot be sufficiently reduced, and constituent members such as a single cell which is fragile due to a high pressing force. There was a problem of damage. On the other hand, the method of joining before power generation
Since the affinity between the interconnector and the fuel-side electrode of the single cell or the fuel-side current collector contacting the fuel-side electrode is poor, and the thermal expansion difference between them is large, the electrical contact resistance can be reduced. There was a problem that a good joining material could not be found.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a fuel cell electrode of a single cell constituting a solid oxide fuel cell, or an abutment with the fuel electrode. Provided is a joining material for joining a fuel-side current collector and an interconnector, which is capable of significantly reducing electrical contact resistance without damaging constituent members, and a joining method using the joining material. Is to do.

[0005]

The invention claimed in this application to achieve the above object is as follows. (1) The fuel of the single cell when electrically connecting a single cell composed of a solid electrolyte membrane and a fuel-side electrode and an oxygen-side electrode respectively laminated on both surfaces of the solid electrolyte membrane via an interconnector A bonding material interposed between the side electrode or the fuel-side current collector abutting the fuel-side electrode and the interconnector, wherein NiO, Sr, Ca, Mg,
Ba, Ni, Fe, Mn, Al, Co, Cu, Zn, M
A composite material in which an interconnector material made of LaCrO ₃ to which at least one element of o and Pd is added at a molar ratio of 0.5 to 5.0 is mixed to a thickness of 0.1 to 3 m.
m. A bonding material for a solid oxide fuel cell stack, wherein the bonding material is shaped into m. (2) Joining of a solid electrolyte fuel cell stack in which a single cell composed of a solid electrolyte membrane and a fuel-side electrode and an oxygen-side electrode respectively laminated on both surfaces of the solid electrolyte membrane is electrically connected via an interconnector. A method comprising the steps of: providing NiO between a fuel-side electrode of the single cell or a fuel-side current collector abutting the fuel-side electrode and the interconnector ;
r, Ca, Mg, Ba, Ni, Fe, Mn, Al, C
at least one of o, Cu, Zn, Mo and Pd
A bonding method for a solid oxide fuel cell stack, comprising sintering while bonding a bonding surface by interposing a bonding material made of an interconnector material made of LaCrO ₃ to which various kinds of elements are added .

(3) A slurry made of an interconnector material is applied in advance to a joining surface between the joining material and the interconnector, and the joining material and a fuel-side electrode or a fuel-side current collector abutting the fuel-side electrode are applied. The method for bonding a solid oxide fuel cell stack according to the above (2), wherein a slurry made of a fuel-side electrode material is applied to the bonding surface in advance, and then sintering is performed while pressing the bonding surface. (4) the bonding material, and the NiO, mixing said Lee centers connector material in a molar ratio of 0.5 to 5.0, a thickness of 0.1
The method for joining a solid oxide fuel cell stack according to the above (2) or (3), comprising a composite material molded to a thickness of 3 mm.

[0007]

According to the present invention, N, which is a main component of the constituent material of the fuel electrode and the fuel current collector, is provided between the interconnector and the fuel electrode of the single cell or between the fuel collector and the fuel collector in contact with the fuel electrode.
By sintering a bonding material made of a composite material of iO and an interconnector material, the affinity between the fuel electrode and the fuel collector contacting the fuel electrode and the interconnector is improved. Improved and high bonding strength can be obtained.

In addition, NiO in the bonding material made of the composite material used on the fuel electrode side, which is a hydrogen-rich atmosphere in a fuel cell, is reduced to Ni in the hydrogen-rich atmosphere. The synergistic effect with the conductivity of the interconnector material, which is another main component and is originally a conductive material, improves the conductivity of the joint and significantly reduces the electrical contact resistance.

In the present invention, the constituent materials of the fuel-side electrode and the fuel-side current collector include, for example, NiO—ZrO ₂ —
And Y ₂ O ₃ . Further, as interconnector materials, Sr, Ca, Mg, Ba, Ni, Fe, Mn,
LaCrO ₃ to which at least one element selected from the group consisting of Al, Co, Cu, Zn, Mo and Pd is added. The interconnector is a joining member that is arranged between single cells constituting a solid oxide fuel cell stack and electrically connects the single cells in series.

[0010] In the bonding material of the present invention, the mixing ratio of NiO and the interconnector material is 0.5 to 5.
It is preferably 0, and particularly preferably 2.0 to 3.0. When the molar ratio is smaller than 0.5 or larger than 5.0, the thermal expansion coefficient of the composite material as the bonding material is increased by the thermal expansion of the fuel-side electrode and the fuel-side current collector contacting the fuel-side electrode. The thermal expansion coefficient is not a value between the coefficient and the thermal expansion coefficient of the interconnector, so that thermal stress due to a difference in thermal expansion cannot be reduced, and distortion or the like may occur.

In the present invention, the bonding material made of a composite material in which NiO and an interconnector material are mixed is 0.1 to 0.1%.
It is preferably formed to have a thickness of 3 mm, more preferably 0.5 to 1.0 mm. When the thickness is less than 0.1 mm, the difference in thermal expansion cannot be absorbed. On the other hand, when the thickness is more than 3 mm, the electric resistance increases. In the preparation of the bonding material of the present invention, an additive is added as necessary when mixing NiO and the interconnector material. Additives and methods of mixing, kneading and post-treatment after mixing and kneading differ depending on the molding method. The molding method is roughly classified into a dry method and a wet method. In the present invention, the wet method is preferable in order to obtain a relatively thin molded body. Examples of the wet molding method include a doctor blade method, an extrusion molding method, and a tape casting method.

In the joining method of the present invention, a slurry made of an interconnector material is applied in advance to the joining surface between the joining material and the interconnector, and the joining material and the fuel-side electrode or the fuel-side current collector contacting the fuel-side electrode. It is preferable to apply a slurry made of a fuel-side electrode material to the surface to be bonded to the fuel cell. As a result, the unevenness of the bonding surface can be corrected to form a strong bonding surface, and the electrical contact resistance can be reduced.

[0013]

Next, the present invention will be described in more detail by way of examples. FIG. 1 is an explanatory diagram showing a manufacturing process of a bonding material for a solid oxide fuel cell stack according to one embodiment of the present invention. Hereinafter, a method for preparing the bonding material will be described with reference to the manufacturing process diagram.

First, for example, N ground to a size of 0.1 to 2 μm
The iO powder and the interconnector material powder pulverized to 0.1 to 5 μm are collected so that the mixing ratio thereof is 0.5 to 5.0 in terms of molar ratio, and a solvent is added thereto and weighed (1). ,
For example, the mixture is sufficiently mixed by a pot mill (2) and, if necessary, dried (3). A binder, a plasticizer, a solvent and / or a dispersant are added to the obtained mixed powder and weighed. (4), mixing and kneading (5). After mixing and kneading, the viscosity of the slurry is adjusted (6), and then the bubbles contained in the slurry are removed (7), and then molded, for example, by a doctor blade device (8). The obtained molded body is sufficiently dried to obtain a green body (9), and the green body is cut into a predetermined size (10).
It is baked at 0 ° for 5 hours to obtain a bonding material (11).

In this embodiment, an organic solvent or an aqueous solvent is used as the solvent. When using an organic solvent as a solvent, as a binder, for example, polyvinyl butyral, polyethylene, polyvinyl chloride, polymethyl methacrylate, nitrocellulose, etc., as a plasticizer,
For example, dibutyl phthalate, dimethyl phthalate, butyl benzyl phthalate, butyl stearate, methyl abietate, polyethylene glycol, tricresyl phosphate, etc., and as the dispersant, for example, fatty acids, fish oil, benzene sulfonic acid, etc. are used. . On the other hand, when an aqueous solvent is used as the solvent, as the binder, for example, acrylic acid polymer, ethylene oxide polymer, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol,
Isocyanate, wax, etc., as a plasticizer, for example, glycerin, dibutyl phthalate, ethyl toluenesulfonate, polyalkylene glycol, triethylene glycol, tributyl phosphate, etc., and as a dispersant,
For example, phosphate glass, allyl sulfonate and the like are used.

FIG. 2 is an explanatory view showing a method for joining a solid oxide fuel cell stack according to one embodiment of the present invention.
In the figure, a bonding material made of the composite material obtained as described above is arranged between the fuel-side current collector and the interconnector, and the bonding surface between the bonding material and the interconnector is A slurry in which fine powder of 1 μm or less of the connector material is kneaded with a mixture of toluene and ethanol is applied, and 1 μm of the fuel-side current collector material is previously applied to the joining surface between the joining material and the fuel-side current collector. A slurry obtained by kneading the following fine powder with the above-mentioned mixed solution of toluene and ethanol is applied. The laminated body thus laminated is bonded by being baked at, for example, 1200 to 1600 ° for 1 hour while being pressed under a pressure of 300 to 500 kPa.

In the present invention, the slurry applied to the joint surface at the time of joining is prepared by adding a binder, a solvent, and other dispersants as necessary to a ceramic powder as a fuel-side electrode material or an interconnector material and sufficiently kneading the slurry. It is prepared by The smaller the particle size of the ceramic powder, the better,
It is preferably at most 1 μm or less. The additive is appropriately selected and used from those used for preparing the above-described bonding material. The coating thickness of the slurry is, for example, 20 to
The thickness is preferably 200 μm, but is appropriately changed depending on the state of the unevenness of the joining surface of the material to be joined. That is, when the unevenness of the bonding surface is large, the slurry is applied thicker.

Next, a specific embodiment of the present invention will be described. Example 1 NiO powder pulverized to 2 μm or less and La _0.7 Ca _0.3 CrO which is an interconnector material pulverized to 5 μm
₃ powder and NiO / La _0.7 Ca _0.3 CrO _{3 in} molar ratio
Was added to the mixture, and toluene was added thereto as a solvent, and the mixture was sufficiently kneaded with a pot mill. The mixture was evaporated to form a mixed powder. To 100 g of the obtained mixed powder, a binder was added. 7 g of polyvinyl butyral, 7 g of dibutyl phthalate as a plasticizer, and 100 cc of a mixed solution of toluene and ethanol as a solvent, and thoroughly mixed and kneaded with a pot mill to form a slurry. Then, the viscosity of the slurry was adjusted. It is defoamed and formed into a green body having a predetermined thickness by a doctor blade device. After sufficiently drying the green body, it is cut into a required size, and then fired at 1500 ° C. for 5 hours to have a thickness of 1 mm. A joining material was obtained.

The obtained joining material is applied to the joining surface in advance.
NiO / Y as fuel-side current collector material _TwoO_ThreeStabilized ZrO
_TwoCermet powder of 1 μm or less, toluene and ethanol
100 µm of a slurry obtained by mixing the mixed solution with
NiO / Y applied thick_TwoO_ThreeStabilized ZrO_TwoSirmi
The fuel-side current collector consisting of
La, which is a material for interconnectors_0.7Ca_0.3CrO_Threeof
A slurry obtained by mixing a powder having a particle size of 1 μm or less with a mixture of the above solvents.
La coated at a thickness of 100 μm, La_0.7Ca_{0. Three}CrO
_ThreeBetween the interconnectors consisting of
g / cm^TwoBaking at 1500 ° C for 1 hour
A conjugate was obtained. At this time, it is joined with the current collector on the fuel side of the joining material.
The surface of the fuel-side current collector material slurry
Apply with a thickness of 00μm and apply to the surface to be joined with the interconnector
Is a 100 μm thick interconnect material slurry.
Applied.

The joining strength of the obtained joined body was measured by a four-point bending strength test at room temperature, and the conductivity was measured by a DC four-terminal method in humidified hydrogen at 1000 ° C. The bending strength was 73 MPa and the conductivity was 73 MPa. It was 10 S / cm. Example 2 Molar ratio of bonding material NiO / La _0.7 Ca _0.3 CrO ₃
When the same joining material and joined body were obtained in the same manner as in Example 1 except that
The bending strength was 95 MPa, and the conductivity was 15 S / cm.

Example 3 Molar ratio of bonding material NiO / La _0.7 Ca _0.3 CrO ₃
Was set to 2.0, a similar joining material and joined body were obtained in the same manner as in Example 1, and a similar test was performed.
The bending strength was 52 MPa, and the conductivity was 18 S / cm. Comparative Example 1 A joined body was obtained in the same manner as in Example 1 except that the above-described joining material was not used, and a similar test was performed. The flexural strength was 21 MPa and the conductivity was 5 S / cm.

[0022] Examples 1-3 and Comparative Example 1, the molar ratio _{NiO / La 0.7 Ca 0. 3 CrO} 3 bonding material, shown in Table 1 and Table 2 the results flexural strength of and conductivity measurements. From Table 2, it is found that Examples 1 to 3 in which a bonding material made of a composite material is interposed between the interconnector and the fuel-side current collector have higher bonding strength and higher bonding strength than Comparative Example 1 in which no bonding material is interposed. It can be seen that high conductivity was obtained. Also NiO
When the mixing molar ratio of the metal and the interconnector material was 1 (Example 2), the highest bonding strength was obtained. On the other hand, the conductivity is N
It was found that the value became higher as the ratio of iO increased.

[0023]

According to the invention as set forth in claim 1 of the present application, the connection surface between the interconnector of the solid oxide fuel cell and the fuel-side electrode of the single cell or the fuel-side current collector in contact with the fuel-side electrode is formed. The joining material to be arranged is composed of a composite material of NiO, which is a main component of the fuel-side electrode and the fuel-side current collector material, and an interconnector material, so that the electric resistance of the joining portion is reduced and the joining strength is improved. Can be significantly increased.

According to the invention described in claim 2 of the present application, when the interconnector in the solid oxide fuel cell and the fuel-side electrode of the single cell or the fuel-side current collector in contact with the fuel-side electrode are joined, By interposing a bonding material made of a composite material of NiO, which is a main component of the fuel-side electrode and fuel-side current collector material, and an interconnector material, the electrical resistance of the bonding part is significantly reduced, and the bonding strength is improved. . Therefore, the function between the fuel-side electrode of the single cell and the interconnector is improved, and the performance of the fuel cell stack is greatly improved.

According to the third aspect of the present invention, a composite material obtained by mixing NiO, which is a fuel-side electrode material, and an interconnector material at a molar ratio of 0.5 to 5.0 is 0.1 to 3 mm.
By using a thick joining material, the thermal expansion coefficient of the joining material becomes an intermediate value between that of the fuel-side electrode and the fuel-side current collector and that of the interconnector. A joined body having high joining strength and low electric contact resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of a bonding material made of a composite material.

FIG. 2 is an explanatory diagram showing a method of joining a fuel-side current collector and an interconnector.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-41172 (JP, A) JP-A-2-288162 (JP, A) JP-A-5-325994 (JP, A) 215778 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/02 H01M 8/12 C04B 37/00

Claims (4)

(57) [Claims] 1. A single cell for electrically connecting a single cell comprising a solid electrolyte membrane and a fuel-side electrode and an oxygen-side electrode respectively laminated on both surfaces of the solid electrolyte membrane via an interconnector A bonding material interposed between the fuel-side electrode or the fuel-side current collector contacting the fuel-side electrode and the interconnector, wherein NiO, Sr, Ca,
Mg, Ba, Ni, Fe, Mn, Al, Co, Cu, Z
A composite material obtained by mixing an interconnector material composed of LaCrO ₃ to which at least one element of n, Mo and Pd is added at a molar ratio of 0.5 to 5.0 to a thickness of 0.1 to 5.0
A joining material for a solid oxide fuel cell stack, characterized in that the joining material is formed to 3 mm. 2. A solid electrolyte fuel cell stack for electrically connecting a single cell composed of a solid electrolyte membrane and a fuel-side electrode and an oxygen-side electrode respectively laminated on both surfaces of the solid electrolyte membrane via an interconnector. Wherein the fuel cell electrode of the single cell or a fuel collector contacting the fuel electrode and the interconnector are connected between the fuel cell electrode and the interconnector.
iO , Sr, Ca, Mg, Ba, Ni, Fe, Mn,
Less of Al, Co, Cu, Zn, Mo and Pd
With one element is interposed the LaCrO ₃ consists in-<br/> terpolymers connector material consisting of bonding material added, bonding of the solid oxide fuel cell stack and firing while bonding the bonding surface Method. 3. A slurry made of an interconnector material is previously applied to a joining surface between the joining material and the interconnector, and the joining material is joined to a fuel-side electrode or a fuel-side current collector contacting the fuel-side electrode. 3. The method for bonding a solid oxide fuel cell stack according to claim 2, wherein a slurry made of a fuel-side electrode material is applied to the surface in advance, and firing is performed while pressing the bonding surface. Wherein said bonding material, mixing said said NiO Lee printer <br/> over connector material in a molar ratio from 0.5 to 5.0, a composite material was formed into a thickness 0.1~3mm 4. The method for joining a solid electrolysis chamber type fuel cell stack according to claim 2, wherein: