JPH01124964A - Flat plate type solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To increase the strength in a joint and to prevent breakage in a baking process by alternately stacking corrugated solid electrolyte films and interconnector films, and forming fuel electrodes and oxygen electrodes in regions surrounded by these films. CONSTITUTION:A corrugated solid electrolyte film 21 and a flat plate-like interconnector film 23 are joined together through an adhesive 22. An oxygen electrode 25 having an oxidizing agent passage 25a and a fuel electrode 26 having a fuel passage 26a are installed in a passage 24 formed with the solid electrolyte film 21 and the interconnector film 23. By directly joining the solid electrolyte film and the interconnector film, both are a dense film, the strength in the joint is increased. Since the solid electrolyte film is corrugated, both films are joined in a straight line, and baked in an almost tree state. Deformation during baking is therefore free and breakage is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat plate type solid electrolyte fuel cell, which can also be used in electrolytic cells such as water electrolysis and CO2 electrolysis by passing a current through the cell.

[Prior Art and Problems] As is well known, a solid electrolyte fuel cell (hereinafter referred to as 5OFC) uses an electrolyte such as yttria-stabilized zirconia (hereinafter referred to as YSZ), electrodes are provided on both sides of the electrolyte, and approximately 10
Fuel and oxidizer (usually air) heated to 00°C
When supplied, power is generated directly through an electrochemical reaction, and it has features such as high efficiency and no pollution, and is expected to be a next-generation power generation method.

Conventionally, battery structures include a cylindrical 5OFC and a flat plate 5
OFC is being considered. Representative examples of the former are JP-A-54-73240 (hereinafter referred to as conventional example 1) shown in FIG. 4 and JP-A-57-130381 (hereinafter referred to as conventional example 1) shown in FIG.
There is a conventional example 2 (hereinafter referred to as conventional example 2), and research is currently underway, including conducting power generation tests of several kilowatts for each. On the other hand, as the latter, there is a flat plate type 5OFC (hereinafter referred to as conventional example 3) in which a corrugated thin film and a flat thin film are laminated as shown in FIG.

In FIGS. 6 and 6, 1 is a unit cell. This unit cell 1 has an oxygen electrode 2. Solid electrolyte membrane 3. A corrugated laminated membrane 5 composed of a fuel electrode 4 and a fuel electrode 6. Interconnector membrane7. A module (battery assembly) 10 is made up of a flat laminated film 9 composed of an oxygen electrode 8 and has a plurality of single cells 1 connected in series. Further, among the spaces partitioned by the corrugated laminated film, the one in contact with the fuel electrode 4 is a fuel passage 11, and the one in contact with the oxygen electrode 2 is an oxidizer passage 12. In addition, the film thickness of each constituent layer is 50 to 100 μs.
That's about it. In terms of material, the oxygen electrode 2.8 is made of an oxygen electrode material such as LaSrMnO3, which has high conductivity in a high-temperature oxidizing atmosphere and has a coefficient of thermal expansion that is approximately the same as that of the other constituent materials. Similarly, fuel electrode 4.6 has high conductivity in a high-temperature reducing atmosphere, taking into account the coefficient of thermal expansion (Ni O + YS
Use fuel electrode materials such as Z). Further, the solid electrolyte membrane 3 is made of YSz or the like having ionic conductivity, and the interconnector membrane 7 is made of a material such as La Mg Cr 03 which can withstand both high temperature oxidation and reduction atmospheres and also has conductivity.

As for the manufacturing method, all of the battery components mentioned above are molded in a green state before firing using a thin film manufacturing method called tape casting. Using them, the laminated film 5 is formed into an oxygen electrode 2. After stacking the solid electrolyte membrane 3° and the tape casting membrane of the fuel electrode 4, they are bent into a corrugated plate shape. Moreover, the laminated film 9 is a fuel electrode 6. Interconnector membrane7. oxygen electrode 8
The tape casting films are laminated to form a flat plate. The corrugated laminated film 5 and the flat laminated film 9 thus produced are alternately stacked and fired in this state at once. After the battery is completed, if air or the like is supplied to the fuel passage 11 and the oxidizing agent passage 12 while maintaining the temperature at about 1000°C, electricity can be directly obtained through an electrochemical reaction.

By the way, when comparing cylindrical 5OFC and flat plate 5OFC, cylindrical 5OFC is relatively easy to prototype, and research is already progressing considerably, but its power generation performance (current density, output density, etc.) is not so good. It is expected that the manufacturing cost per unit output will also increase.

On the other hand, the fuel cell of Conventional Example 3 is composed only of thin films, and the interval between each cell is as small as 1 to 2 mm, so the current density and output density per unit area of the power generation part are high, and it is composed only of thin films. Since the weight is light, the output per weight of cell capacity is dramatically improved compared to the conventional example 1.2. However, flat plate type 5OFC is difficult to manufacture and the most important issue is the establishment of manufacturing technology. Below, the flat plate type 5OF in Figure 6
The problems with C will be explained.

(1) The fuel electrode and oxygen electrode are made of materials selected mainly taking into consideration the electrical conductivity and coefficient of thermal expansion at 1000°C, and due to the requirements for the electrode, they are made porous, so the strength of the fuel electrode and oxygen electrode is low. Therefore, the joints between the fuel electrodes and the oxygen electrodes are weak and easily break from these parts.

(2) Solid electrolyte membrane, interconnector membrane, oxygen electrode.

A 3-layer film and a wavy 3-layer film obtained by deforming it are formed from the 4M class materials of the fuel electrode in an unsintered green state before firing, and they are fired at one time after being laminated. Materials originally have different optimal firing temperatures.

■Requirements differ depending on the constituent membranes, such as solid electrolyte membranes and interconnector membranes requiring dense membranes, while oxygen electrodes and fuel electrodes require porous membranes. Therefore, it is difficult to perform optimal firing for all four types of materials in one firing.

Also, if you fire at a high temperature to match a material that has a high firing temperature, the material will deteriorate on the side of the material that has a low firing temperature.

Problems such as densification of the electrode and harmful interfacial reactions as a battery occur. On the other hand, if the material is fired at a low temperature to match a material that requires a low firing temperature, the material that requires a high firing temperature will not be sufficiently sintered, resulting in problems such as insufficient density and insufficient electrical properties.

(3) 4 tI class materials are selected taking into account the coefficient of thermal expansion, but even if the temperature is raised under the same conditions when firing from an unsintered green state, sintering or That is, the temperature at which shrinkage starts due to sintering and the amount of shrinkage are different.

For example, the difference in thermal expansion coefficient between materials is I x 10-6/'
The difference in deformation when changing the temperature from 0℃ to 1000℃ when C is different is 1 x 1O-6x (1000℃-0
℃)X100 glue is only 0.1%, but the difference in shrinkage before sintering is on the order of 10%. Moreover, the binder evaporates or burns, and the ceramic is insufficiently sintered and has almost no strength, and this unbalanced shrinkage causes it to crack.

Deformation is very likely to occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flat solid electrolyte fuel cell that can improve the strength of the joint and prevent cracking during firing.

[Means for Solving the Problems] The present invention provides a plurality of solid electrolyte membranes and interconnector membranes that are alternately stacked and at least one of which is corrugated, and a region surrounded by these solid electrolyte membranes and interconnector membranes. The main feature is that the fuel electrode is provided with a fuel electrode and an oxygen electrode, each of which is formed in a fuel cell and has a passage therein.

[Function] According to the present invention, (1) Since the solid electrolyte membrane and the interconnector membrane, which are dense membranes, are directly bonded (or via an adhesive layer), the strength of the bonded portion is improved.

(2) Since either or both of the solid electrolyte membrane and the interconnector membrane are corrugated, their contact is linear or dotted. In this way, since both films can be fired in a substantially free state, they can be deformed during firing and are less prone to cracking.

(3) An example of material composition is a solid electrolyte membrane; YSZ.

Interconnector membrane; LaMgCr03, fuel electrode;
(NiO+YSZ), oxygen electrode; In the case of LaSrMnO3, the solid electrolyte membrane and interconnector membrane, which are dense and have a high firing temperature, are first fired, and then the porous fuel electrode and oxygen electrode, which are porous and have a slightly lower firing temperature, are fired. In this way, since materials are fired in order from materials with higher firing temperatures to materials with lower firing temperatures, each material can be fired under optimal conditions.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Example 1 In FIG. 1, 21 is a corrugated solid electrolyte membrane made of YSz or the like. This solid electrolyte membrane 21 is coated with adhesive 2.
A planar interconnector film 23 made of La Mg Cr 03 or the like is bonded via 2 . Here, the material of the adhesive 22 is zro2. Ano 2031
Use a material whose main component is ceramic, such as S t 02, and which can withstand high temperatures. However, if graphite powder or the like is filled as a filler and the solid electrolyte membrane 21 and interconnector membrane 23 are directly joined by a method such as hot pressing, the adhesive 22 is not necessary. The solid electrolyte membrane 2
2 and the interconnector membrane 23, the passage 24 is formed by
An oxygen electrode 25 made of (NiO+YSZ) or the like having a fuel passage 25a inside, and a fuel electrode 26 having an oxidizer passage 26a inside are provided, respectively. Here, the fuel passage 25a and the oxidizer passage 26a are formed by the unevenness of the solid electrolyte 821, and both roads 25a and 25b form parallel flows. In this way, the solid electrolyte membrane 21, the interconnector membrane 23. An oxygen electrode 25, a fuel electrode 26, and a single cell 27 are formed, and by stacking these single cells 27, a module (collected battery) 28 is formed.

Next, a method for manufacturing a flat plate type 5OFC having the above structure will be explained with reference to FIGS. 2(a) to 2(e).

■First, the green tape of the solid electrolyte membrane 21 is formed by tape casting and bent into a wave shape (see Fig. 2 (a)
). In addition, 31 in the figure is a container containing YSZ,
32 is a dryer, and 33 is a cutter.

■Next, Interconnector II! A green tape of No. 23 is molded by a tape casting method (as shown in FIG. 2(b)).

■Subsequently, an adhesive 22 is applied to the tip of the convex part of the corrugated solid electrolyte membrane 21, and it is laminated with the flat interconnector membrane 23. In this state, it is fired at 1400 to 1600°C (Fig. 2 (C) ).

(2) Furthermore, the slurry of the fuel electrode 26 is applied to a predetermined surface by a method such as pouring, and fired at 1300 to 1500°C (as shown in FIG. 2(d)).

■Finally, add oxygen electrode 2 to the surface that was not installed in ■ above.
The slurry of Step 5 is applied and fired at 1100 to 1400°C to produce a flat solid electrolyte membrane fuel cell (see Figure 2 (e).
).

However, after the battery is completed, if fuel and oxidizer are supplied while maintaining the temperature at approximately 1000°C, electricity is obtained through an electrochemical reaction, and from a macroscopic perspective, the electricity is
Flows in the vertical direction.

According to the first embodiment, the structure is such that the corrugated solid electrolyte membrane 21 and the flat interconnector membrane 23 are laminated via the adhesive 22 and bonded by firing. The strength of the joint portion of the 21° interconnector film 23 is improved.

Further, since the solid electrolyte membrane 21 has a wave shape, the portion in contact with the interconnector membrane 23 has a linear shape. Therefore, since both films 21 and 23 can be fired in a substantially free state, they can be deformed during firing and cracks are less likely to occur. Furthermore, the solid electrolyte membrane 21 is dense and has a high firing temperature. First, the interconnector film 23 is fired, and then the fuel electrode 26, which is porous and has a slightly lower firing temperature. If a battery is constructed by firing the oxygen electrode 25, the materials will be fired in order from materials with higher firing temperatures to materials with lower firing temperatures, making it possible to perform firing under optimal conditions for each material.

Embodiment 2 This embodiment is based on the fuel cell shown in FIG.
This is a flat plate type 5OFC that has been improved so that the oxidizing agent passage 25a and the oxidizing agent passage 25a are orthogonal to each other (as shown in FIG. 3).

Note that the fuel electrode, oxygen electrode, and adhesive are omitted from this figure for clarity.

41 in the figure is a corrugated plate-shaped interconnector film, which is laminated so that the directions of the corrugated plates are perpendicular to each other. Further, 42 is a sealing material at the end of the battery, which has a structure in which the fuel 43 and the oxidizer 44 do not mix. However, the fuel passage 26. Due to the presence of the sealing material 42 from the end face of the cell, the oxidizer passage 25a has a space where gas can flow only through the fuel passage 26a or only the oxidizer passage 25a, but inside the current, there is a space between the electrolyte membrane 21 and the interconnector membrane 41. are flowing alternately. In this way, the fuel passage 26a and the oxidizer passage 25
Since a is orthogonal, the header construction method for gas supply and exhaust becomes easy. Next, a method for manufacturing the flat plate type 5OFC shown in FIG. 3 will be explained.

(1) First, the green tape of the solid electrolyte membrane 21 is formed by tape casting and bent into a wave shape. Next, a corrugated interconnector film 41 is formed in the same manner.

(2) Next, the corrugated solid electrolyte membrane 21 and the corrugated interconnector membrane 4 are stacked perpendicularly to each other, and an adhesive is applied to the contacting portions. 1400-1600 in that state
Bake at ℃.

■After this, a sealing material 42 is packed into the end of the battery to prevent gas leakage. The width of the sealing material 42 is at least the width of the solid electrolyte membrane 21. The interconnector film 41 should be equal to or more than one pitch of the corrugated plate. By sealing as shown in FIG. 3, only the lower side of the corrugated plate of the interconnector membrane 41 penetrates the end face in the A direction, and the fuel 43 can flow there. Similarly, a solid electrolyte membrane 21 is provided on the end face in the B direction.
The oxidizing agent 44 will be flowed under the corrugated plate. In this way, in the second embodiment, it is possible to flow the fuel and the oxidizer in orthogonal directions.

■Next, from the third stage, stand the battery upright, pour in the fuel electrode slurry, and form the required film thickness.
Sinter at 400 ℃ to produce a flat plate type 5OFC.

[Effects of the Invention] As detailed above, the present invention provides a flat plate with high power generation efficiency that can improve the strength of joints, prevent cracking during firing, and can be fired under optimal conditions for each material. type solid electrolyte fuel cell can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a flat plate type 5OFC according to Example 1 of the present invention, FIGS. FIG. 4(a) is a cross-sectional view of a flat plate type 5OFC according to Example 2 of the invention, and FIG. 4(b) is a perspective view of a cylindrical type 5OFC according to conventional example 1. The figure shows a cylindrical 5OF according to conventional example 2.
FIG. 6 is a perspective view of C and a cross-sectional view of a flat plate type 5OFC according to Conventional Example 3. 21...Solid electrolyte membrane, 22...Adhesive, 23゜4
1... Interconnector film, 25... Oxygen electrode, 25
a...Fuel passage, 26...Fuel cell, 26a...
Oxidizer passage, 27... Single cell, 28... Module, 42... Seal material, 43... Fuel, 44... Oxidizer. Applicant's agent Patent attorney Takehiko Suzue ra D Φ ″ To ward ^
^1) ,
Oh! ! ? X Figure 6

Claims (1)

[Claims] A plurality of solid electrolyte membranes and interconnector membranes that are alternately laminated and at least one of which is corrugated; and a fuel electrode that is formed within a region surrounded by these solid electrolyte membranes and interconnector membranes and each has a passage therein. and an oxygen electrode.