JPH0982336A - Hollow flat board-shaped electrode substrate and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the peeling off or breakage of a sheet and increase the strength of a substrate by complicating the bonding interfaces of different kind materials to increase the bonding area, and enhancing the adhesion of the different kind material sheets during sintering, or in raising or lowering temperature of a cell stack. SOLUTION: In a hollow flat board-shaped substrate having a plurality of gas flow paths on the inside, used in a solid electrolyte fuel cell, an air electrode and a fuel electrode are constituted with two kinds of electrode materials 3', 3" having different composition in the thickness direction of the substrate on each side of the gas flow paths. Both materials are bonded in pillar-shaped parts P for forming the gas flow paths, and the bonded surfaces are made complicate. As a result, stress caused by the difference in shrinkage factors on the sheet interfaces in sintering is relaxed, the peeling off or breakage of the sheet is suppressed, the flat board-shaped substrate with no distortion can be manufactured and the strength of the electrode substrate is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode substrate for a solid oxide fuel cell, and more specifically, a hollow flat plate electrode substrate having a gas flow passage therein, which is made of an electrode material for a solid oxide fuel cell, and its manufacture. It is about the method.

[0002]

[Prior Art and Problems] The principle of the solid oxide fuel cell is to directly convert the chemical energy of the fuel into electric energy, and research has been advanced as a next-generation power generation technology with high efficiency and little impact on the environment. There is. A single cell of this solid oxide fuel cell is composed of an air electrode, a fuel electrode, an electrolyte, and an interconnector, and the operating temperature of the cell is 100.
Since the temperature is as high as 0 ° C., a ceramic material as shown in Table 1 is generally used for each component.

Table 1

The basic structure of a solid oxide fuel cell is to arrange a fuel electrode and an air electrode with an electrolyte in between, and to supply fuel (hydrogen) and air (oxygen) gas to both electrodes, respectively. In a simple cell design, it is important to have a structure that facilitates gas sealing in order to prevent a decrease in power generation efficiency due to direct contact of these gases. In addition, although actual power generation is performed in the form of a stack in which a plurality of single cells are stacked in order to obtain a sufficient output, the single cell is also required to have a strength capable of withstanding the load applied at the time of stacking.

As a cell structure satisfying these requirements, there has been considered a method of forming cells on a flat electrode substrate having a plurality of gas flow passages therein as shown in FIG. 5-36417). In FIG.
Is an electrolyte, 2 is a fuel electrode, 3 is an air electrode, 4 is an interconnector, 5 is an internal gas flow path, and 6 is a dense membrane.

In this system, one of the reaction gases flows through the gas flow path in the hollow substrate, so that airtightness can be maintained only by sealing the gas at both ends of the substrate. In addition, the strength of the single cell is ensured by the thick hollow electrode substrate,
It is possible to reduce the thickness of the electrolyte with low conductivity, and it is expected that the power generation characteristics will be improved.

As a method for producing such a cell, a hollow electrode substrate is produced in advance by an extrusion molding method, and then an electrolyte, an electrode and an interconnector are sprayed on the surface of the hollow electrode substrate, E
A method of forming by the VD method or the like, and a co-sintering method of forming and sintering the ceramic sheets of the respective cell parts produced by the doctor blade method or the like are conceivable.

[0008] The extrusion molding method is suitable for molding a large number of materials having a constant cross-sectional shape, but
The physical properties of the sintered body such as density and conductivity cannot be partially changed in the thickness direction, and the degree of freedom of shape is small. In addition, since multiple steps are required to form a single cell, the equipment to be used becomes large and the high temperature treatment process becomes multiple, so the electrode substrate that should be porous becomes dense and lost during that time. It has the drawback of being activated.

On the other hand, in the co-sintering method, layers of different materials are laminated,
It is a method that can be said to be economical because it is a method in which the cells are bonded by pressure bonding and then sintered, and the deterioration of the electrodes can be minimized because the high temperature treatment process is done only once and the equipment used is simple. . Further, when manufacturing a substrate by stacking sheets, controlling the thickness of the molded body by the number of stacked sheets,
By changing the composition of the sheets to be laminated, it is possible to manufacture substrates having partially different physical properties.

Taking advantage of such advantages of the sheet laminating method,
Up to now, an electrode substrate having a combination of air electrode materials having different compositions as shown in FIG.
-72319). In FIG. 5, 3'is LSM (x = 0.3)
, A second electrode made of LSM (x = 0.5) and a second electrode made of LSM (x = 0.5). 5 is a gas flow path. Small LSM
By using the composite substrate of (x = 0.5), it is possible to manufacture an electrode substrate having high strength and high electrical conductivity, which takes advantage of the respective advantages of both air electrode materials.

Similarly, for a hollow flat plate electrode substrate using a fuel electrode material, the production of a composite substrate can be considered.
As shown in Table 1, NiO and YSZ cermet which is an electrolyte material are used as the fuel electrode material. By mixing NiO and YSZ in this way, the difference in the coefficient of thermal expansion from the electrolyte is reduced and the adhesion between the two is improved, but if the proportion of YSZ in the cermet is increased, the conductivity as an electrode is reduced. Therefore, in the production of the hollow flat plate electrode substrate using the fuel electrode material, the side on which the electrolyte is formed is NiO /
_{ZrO 2 -Y 2 O 3 (NiO} : 40wt%) cermet,
On the other side, NiO / ZrO ₂ —Y ₂ O ₃ (Ni
O: 60 wt%) By using a cermet, it is possible to obtain an electrode substrate having good adhesion to the electrolyte and high conductivity.

As shown in FIG. 6, the molding of such a hollow substrate is performed by forming two strip-shaped sheet laminates (flat plate portions) L ', which are strip-shaped sheet laminates (columnar portions) P arranged at equal intervals. L "
It is carried out by sandwiching and thermocompression bonding. However, when thermocompression-bonding these laminated bodies, the sheet containing the binder is softened and the hollow portion is easily crushed. Therefore, it is necessary to take care not to apply excessive pressure. Adhesion of different material sheets is poorer in adhesion than the same material, so that sufficient pressure is particularly required. However, as shown in FIG. 6, both materials are formed at the boundary between the columnar portion P and the flat plate portions L ′ and L ″. However, it is not possible to adhere them sufficiently by the above-mentioned reason.

Therefore, in order to improve the adhesion at the time of molding the substrate, as shown in FIG. 7, two plate-shaped sheet laminates L'and L "are formed.
As a strip-shaped sheet laminated body P sandwiched between two sheets, a plate-shaped sheet laminated body L ′ in which both sheets are sufficiently pressed and bonded in advance,
It is conceivable that a cell in which different materials are bonded together is formed at the center of the columnar portion P forming the gas flow path as shown in FIG. 5 by using a strip of L ″ cut into pieces. Although the adhesion between both materials during thermocompression bonding improves,
Since the contraction rate of both sheets in sintering and the coefficient of thermal expansion after sintering are different, stress may occur at the adhesive interface, causing peeling of the sheet or distortion of the substrate plane. Such substrate distortion must be minimized because a large stress is locally applied when single cells are stacked and stacked to cause cracking.

Therefore, in the present invention, in order to solve the problem of such a hollow flat substrate made of different kinds of materials, the bonding interfaces of different kinds of materials are made to be intricate with each other to increase the adhesion area, and at the time of sintering or cell stacking. The purpose is to improve the substrate strength by improving the adhesion of different material sheets at the time of temperature rise and fall, thereby preventing the sheets from peeling and cracking.

[0015]

In order to solve the above problems, a hollow flat plate electrode substrate having a plurality of gas flow passages inside, which is used in a solid oxide fuel cell according to the present invention, has a thickness direction of the substrate. The electrode is composed of two kinds of electrode materials having different compositions at the air electrode or the fuel electrode with the gas flow path as a boundary. The two materials are adhered to each other at the columnar portion forming the gas flow path, and the adhering surfaces are intricate with each other. It has a shape.

The hollow flat plate electrode substrate is La
_(1-x) Sr _x MnO ₃ (x = 0.3 ± 0.1) and La _(1-x)
It is characterized by being composed of Sr _x MnO ₃ (x = 0.5 ± 0.05).

The hollow flat electrode substrate is made of NiO.
_{/ ZrO 2 -Y 2 O 3 (} NiO: 40 ± 10wt%) and N
iO / ZrO ₂ —Y ₂ O ₃ (NiO: 60 ± 10 wt%)
It is characterized by being composed of.

Further, the hollow flat plate electrode substrate of the solid oxide fuel cell described above is La _(1-x) Sr _x MnO ₃ (x =
0.3 ± 0.1) and La _(1-x) Sr _x MnO ₃ (x = 0.
5 ± 0.05) or NiO / ZrO ₂ —Y ₂ O
₃ (NiO: 40 ± 10 wt%) and NiO / ZrO ₂ -Y
_A plurality of ceramic sheets of ₂ O ₃ (NiO: 60 ± 10 wt%) are prepared, and a plurality of strip-shaped sheet laminates prepared by laminating and cutting both sheets are arranged at equal intervals in the vertical direction. It is characterized in that it is sandwiched between two plate-shaped sheet laminates composed of sheets of the composition, pressure-bonded, and sintered.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 1 shows an embodiment of the present invention, and the numbers in FIG. 1 are the same as those in FIG. Although a substrate made of an air electrode material is shown here, the present invention can be similarly applied to an electrode substrate using a fuel electrode material.

Specific examples of the present invention will be described in detail below, but the present invention is not limited to the following examples. From Table 1, there are two possible electrode materials for SOFC, LSM as an air electrode material and Ni-YSZ as a fuel electrode material. An example using LSM will be described below. Further, in this embodiment, LSM (x = 0.3) and LSM (x =
0.5), but the present invention is not limited to the combination of these compositions.

Polyvinyl butyral as a binder and a mixed solvent of isopropyl alcohol and toluene as a dispersion medium were added to each material powder and mixed by a ball mill, and then defoamed to prepare clay. Next, this slurry was formed into a sheet having a thickness of about 100 μm by the doctor blade method. Hereafter, for simplicity of description, the one formed from the LSM (x = 0.3) sheet S ′ is used as the first electrode 3 ′, LSM.
The one formed from the (x = 0.5) sheet S ″ is the second electrode 3 ″. Then, the respective sheets thus produced were laminated and thermocompression-bonded to each other so as to have a thickness of 2 mm, and the sheet-like sheet laminates L ′ and L ″ were cut out into 10 × 5 cm to produce one sheet each. .

Further, the sheet S ′: S ″ = 1: 1 and the thickness 3
The plate-shaped sheet laminated body having a size of 10 mm was cut into a length of 10 cm and a width of 0.2 cm to prepare 10 strip-shaped sheet laminated bodies P. Next, as shown in FIG. 2, after these strip-shaped sheet laminated bodies P are arranged on one plate-shaped sheet laminated body (L ′ or L ″) at equal intervals so that the cut surfaces are in the vertical direction. Then, the other plate-shaped sheet laminate (L 'or L ") was superposed thereon, and these were adhered by hot pressing to obtain a hollow flat plate-shaped body. The hollow flat plate-shaped molded product thus formed was degreased at 360 ° C. and then sintered at 1300 ° C. for 2 hours to give LSM (x = 0.3) and LSM (x = 0.5).
A two-layer hollow flat plate electrode substrate as shown in FIG. 1 was prepared. In the thus manufactured hollow flat substrate, the adhesiveness at the interface between the two kinds of electrode sheets was good, and neither peeling or cracking between the sheets nor distortion in the plane portion of the substrate was observed.

The above hollow flat plate electrode substrate can be manufactured in exactly the same manner even if NiO-YSZ cermet containing 40 wt% NiO and NiO-YSZ cermet containing 60 wt% NiO are used as the fuel electrode material. it can.

NiO and YSZ are 4: 6 (NiO 40 wt.
%), 6: 4 (NiO 60 wt%), to each material powder, polyvinyl butyral as a binder and a mixed solvent of isopropyl alcohol and toluene as a dispersion medium were added and mixed in a ball mill, and then degreased to prepare clay. . Next, the slurry was formed into a sheet with a thickness difference of about 100 μm by the doctor blade method. Then, the respective sheets produced in this manner were laminated and thermocompression-bonded to each other so as to have a thickness of 2 mm, and plate-like sheet laminated bodies L ′ and L ″ were cut out into 10 × 5 cm to form one sheet each. The sheet-like sheet laminate having a thickness of 3 mm and a ratio of 1: 1 was cut out into a length of 10 and a width of 0.2 to prepare 10 strip-like sheet laminates. Then, the hollow flat plate-shaped product was bonded by hot pressing to form a hollow flat plate-shaped product. A hollow flat plate type electrode substrate made of -YSZ cermet and NiO-YSZ cermet containing 60 wt% NiO was produced.

Further, in order to further improve the adhesiveness at the interface between both sheets, it is possible to manufacture a hollow substrate as shown in FIG. Sheets 3 ′ and 3 ″ are laminated and hot pressed to obtain 3 ′: 3 ″: 3 ′ = 1: 1: 1 (I), 3 ″:
3 ′: 3 ″ = 1: 1: 1 (II) was used to form a laminate having a thickness of 3 mm, and I and II were each cut into a length of 10 × a width of 0.2 cm to prepare five strip-shaped sheet laminates. Next, these strip-shaped sheet laminated bodies were placed on one plate-shaped sheet laminated body so that the cut surface was in the vertical direction as in FIG.
After arranging I and II in every other row at equal intervals, the other plate-shaped sheet laminate was superposed thereon, and these were bonded by hot pressing to obtain a hollow flat plate-shaped body as shown in FIG. By increasing the adhesion area of the different material sheets in this way, peeling of both sheets is less likely to occur, and cracking and warpage of the substrate can be suppressed, so that the strength of the hollow substrate is increased.

[0026]

As described above, according to the present invention, in the production of a hollow flat plate-like electrode substrate made of two kinds of electrode materials having different compositions, either the air electrode or the fuel electrode material of the solid oxide fuel cell. By making the adhesive surfaces of the two electrode materials in the columnar portion forming the hollow portion intricate with each other, the adhesiveness at the adhesive interface is improved. As a result, the stress due to the difference in shrinkage ratio at the interface between the two sheets is relieved during the sintering of the molded body, so that peeling or cracking of the sheet is suppressed, and a flat plate-like substrate without distortion can be produced. Strength is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of manufacturing a hollow flat substrate according to the present invention.

FIG. 2 is a perspective view of the embodiment.

FIG. 3 is a perspective view showing an application example of a hollow flat substrate according to the present invention.

FIG. 4 is a perspective view of a fuel cell using an electrode substrate having a gas channel inside.

FIG. 5 is a perspective view of a hollow flat plate-shaped substrate composed of two kinds of electrode materials.

FIG. 6 is a perspective view showing fabrication of the hollow flat substrate by a sheet laminating method.

FIG. 7 is a perspective view showing the production of a hollow flat substrate in which the adhesion positions of two types of electrode material sheets are changed by the sheet laminating method.

FIG. 8 is a perspective view of the hollow flat substrate.

[Explanation of symbols]

 1 Electrolyte 2 Fuel Electrode 3 Air Electrode 3'First Electrode Substrate 3 "Second Electrode Substrate 4 Interconnector 5 Gas Channel 6 Dense Membrane P Strip Sheet Laminate L'Plate Sheet Forming First Electrode Laminated body L ″ Plate-shaped sheet forming second electrode Laminated body S ′ Sheet forming first electrode S ″ Sheet forming second electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01M 8/12 C04B 35/00 J

Claims (4)

[Claims] 1. A hollow flat substrate used for a solid oxide fuel cell, having a plurality of gas passages inside, and having different compositions at the air electrode or the fuel electrode with the gas passages as boundaries in the thickness direction of the substrate. A hollow flat plate electrode substrate comprising two kinds of electrode materials, both materials being adhered to each other in a columnar portion forming a gas flow path, and the adhering surfaces being intricate with each other. 2. The hollow plate electrode substrate is La _(1-x) Sr _x
MnO ₃ (x = 0.3 ± 0.1) and La _(1-x) Sr _x Mn
The hollow flat plate-like electrode substrate according to claim 1, which is composed of O ₃ (x = 0.5 ± 0.05). 3. The hollow flat electrode substrate is made of NiO / Zr.
O ₂ -Y ₂ O ₃ (NiO: 40 ± 10 wt%) and NiO /
The hollow flat electrode substrate according to claim 1, which is composed of ZrO ₂ —Y ₂ O ₃ (NiO: 60 ± 10 wt%). 4. An electrode material for a solid oxide fuel cell, which is La
_(1-x) Sr _x MnO ₃ (x = 0.3 ± 0.1) and La _(1-x)
Sr _x MnO ₃ (x = 0.5 ± 0.05) or NiO
_{/ ZrO 2 -Y 2 O 3 (} NiO: 40 ± 10wt%) and N
iO / ZrO ₂ —Y ₂ O ₃ (NiO: 60 ± 10 wt%)
2 pieces of ceramic sheets are prepared, and a plurality of strip-shaped sheet laminates produced by stacking and cutting both sheets are arranged at equal intervals with the cut surface being the vertical direction. 2. A method for manufacturing a hollow flat plate-shaped electrode substrate, which comprises sandwiching the plate-shaped sheet laminates of [1], press-bonding, and sintering.