JPH06111833A - Solid electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To provide a fuel cell, having no thermal expansion difference between the composition member of an SOFC and YSZ, electrolyte material, also no distortion and no deformation and excellent in high temperature strength. CONSTITUTION:MgO, MgAl2O4, and YSZ pulverized respectively, then magnesia and spinel are mixed at 1/9-1/1 at a weight ratio, CaO is added by a given % as an assistant, and a resultant is formed by a doctor blade method. Then many single cells 11, in which collecting porous plates 28 abut on both upper and lower electrode surfaces are laminated via gas separators l baked at a constant temperature, to be adopted as fuel cell battery stacks, and the stacks are housed in a given box body to form a solid electrolyte type fuel cell. This provides a fuel cell, inexpensive, light, and moreover excellent in high temperature strength, and having no torsion and a high sealing property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell, and more particularly, it relates to a solid oxide fuel cell which is free from distortion, is light in weight and has improved high temperature strength.

[0002]

2. Description of the Related Art Solid oxide fuel cells are roughly classified into a flat plate type and a cylindrical type. For example, a flat plate type fuel cell stack has an oxygen side electrode film and a fuel side electrode on both sides of a flat plate type solid electrolyte membrane. The porous plates for current collection were brought into contact with the both electrode surfaces of the single cells in which the membranes were respectively laminated, and a large number of these were laminated via an interconnector, a separator or a gas flow path member to electrically connect the single cells. It is a thing. on the other hand,
The cylindrical fuel cell stack has, for example, a cylindrical single cell in which a fuel-side electrode film, a solid electrolyte film, and an oxygen-side electrode film are sequentially laminated on the surface of a cylindrical substrate tube, and a cylindrical single cell having a different diameter is used as a gas flow path. It is secured and laminated concentrically, and these are electrically connected.

Such a solid oxide fuel cell (hereinafter,
(Sometimes referred to as SOFC), the constituent materials for the separator, the gas flow path member, the base pipe, etc. are, for example, calcia-stabilized zirconia (CSZ), alumina,
The aCrO ₃ type perovskite and the like were used. That is, for example, CSZ or alumina is used for a base tube of a cylindrical stack, a NiO-YSZ or LaCrO ₃ system perovskite that is a fuel electrode material is used for a gas flow path member of a flat plate type cell stack, and a gas manifold that stores a fuel cell stack Alumina was used for each.

[0004]

Since the SOFC has a high operating temperature, the high temperature strength and the coefficient of thermal expansion of the constituent members become problems. In particular, the coefficient of thermal expansion of each constituent member is yttrium-stabilized zirconia (electrolytic material). Hereinafter, it is required to be as close as possible to YSZ) or its approximation. Therefore, the present inventor has made a solid oxide fuel cell using a composite ceramic, which is a lightweight material having a thermal expansion coefficient close to that of YSZ and is a lightweight material, in which magnesia (MgO) and spinel (MgAl ₂ O ₄ ) are mixed at a predetermined ratio. (Japanese Patent Application No. 4-71625).

However, it has been found as a result of subsequent research that the above-mentioned unknown composite material proposed by the present inventor has poor sinterability and the behavior during sintering is significantly different from that of YSZ which is an electrolyte material. It was also found that there is a problem that high reliability cannot be obtained in terms of water resistance and carbon dioxide gas resistance. The object of the present invention is to solve the above-mentioned problems of the prior art, eliminate the difference in thermal expansion between the constituent members of the SOFC such as the separator, the gas flow path member, the base pipe, and the solid electrolyte membrane YSZ, and prevent distortion and deformation. Another object of the present invention is to provide a solid oxide fuel cell excellent in high temperature strength.

[0006]

The present inventor has earnestly studied the sintering behavior of a composite ceramic of MgO and MgAl ₂ O ₄ , the coefficient of thermal expansion of which is substantially the same as that of YSZ which is an electrolyte material. As a result, MgO and MgAl ₂
By mixing YSZ with a composite material in which O ₄ is mixed in a weight ratio of 1/9 to 1/1, the sinterability can be improved without impairing the high temperature strength of the ceramic made of the composite material. , YSZ, MgO and Mg
The mixing ratio is 20 to 8 with respect to the composite material composed of Al ₂ O _4.
The required sintering behavior is obtained by mixing so as to be 0 wt%, and the whole or a part of the member composed of the MgO particles in the composite material or the composite ceramic composed of MgO, MgAl ₂ O ₄ , and YSZ. To MgAl ₂
The inventors have found that coating with O ₄ or Al ₂ O ₃ significantly improves the water resistance and reliability of the member, and has reached the present invention.

That is, the first invention of the present application is that magnesia (MgO), spinel (MgAl) is used as a constituent material of a solid oxide fuel cell using yttrium-stabilized zirconia (YSZ) or a similar substance as a solid electrolyte membrane.
₂ O ₄ ) and yttrium-stabilized zirconia (YS
Z) as a main component, the mixing ratio of the magnesia and spinel is 1/9 to 1/1 by weight, and the yttrium-stabilized zirconia is mixed with the composite material of the magnesia and spinel. And a solid oxide fuel cell.

A second invention is the same as the first invention,
A component made of magnesia (MgO) in the composite material or a composite ceramic of magnesia (MgO), spinel (MgAl ₂ O ₄ ) and yttrium-stabilized zirconia (YSZ) is used as the spinel (MgAl).
_{The present} invention relates to a solid oxide fuel cell characterized by being coated with ₂ O ₄ ) or alumina (Al ₂ O ₃ ).

FIG. 1 is a diagram showing the relationship between the mixing ratio of MgO in a composite ceramic containing MgO and MgAl ₂ O ₄ as main components and the thermal expansion coefficient at 1000 ° C. In the figure, the mixing ratio of MgO is 10 to 50 wt.
%, The coefficient of thermal expansion is 9 × 10 ^{−6 to} 11 × 10 ⁻⁶ , which is about the same as the coefficient of thermal expansion of YSZ which is an electrolyte material at 1000 ° C. of 10.6 × 10 ⁻⁶ . That is, this composite ceramic is made of MgO and MgA.
By changing the mixing ratio with l ₂ O _{4 in} the range of 1/9 to 1/1 in terms of weight ratio, the coefficient of thermal expansion can be adjusted to the same level as YSZ or its approximation. Thus, even if the mixing ratio of MgO is changed, the chemical stability of the ceramic does not change.

Further, YS is added to the composite material of the above ceramics.
By adjusting the mixing ratio of the YSZ in the composite ceramics mixed with Z, the sinterability can be adjusted without impairing the high temperature strength. In the present invention, it is preferable to coat MgO particles in the composite material before firing, or all or part of the SOFC constituent member formed of the composite ceramics with MgAl ₂ O ₄ or Al ₂ O ₃ . Among the composite materials, MgO is added to adjust the coefficient of thermal expansion of the composite ceramics and to reduce the cost and the weight, but it is easily dissolved in water, which is one of the causes of impairing the reliability of the constituent members. . Therefore, the reliability and chemical stability of the constituent member can be improved by coating the constituent member of the SOFC in which the MgO particles are formed in advance or a composite ceramic thereof with MgAl ₂ O ₄ or alumina Al ₂ O _3. it can.

In the present invention, the SOFC constituent member composed of the MgO particles or the composite ceramic is Mg
Examples of the method for coating with Al ₂ O ₄ or alumina Al ₂ O ₃ include dipping method, spin coating method, C
VD method, PVD method and the like can be mentioned, and the thickness of the coating is preferably 0.005 to 1 μm. Table 1 shows M
The mixing ratio of gO, MgAl ₂ O ₄ and YSZ is 19:31.
The surface of the composite ceramic with a pair of 50 is MgAl ₂ O ₄
2 shows the results of an immersion test of a test piece coated with 1. in distilled water.

[0012]

[Table 1] In Table 1, it can be seen that the one coated with MgAl ₂ O ₄ has a much smaller amount of MgO eluted than the untreated one and is stable.

[0013]

EXAMPLES Next, the present invention will be described in more detail by way of examples. FIG. 2 is a perspective view of a gas separator of a flat plate stacked solid oxide fuel cell according to an embodiment of the present invention. This gas separator is a member that is arranged between the unit cells when the unit cells are stacked to form a fuel cell stack, and includes a gas separator body having a stacking unit 3 and a gas inlet / outlet frame 4, Gas separator body separator 2
Mainly composed of an electron flow path 6 arranged so as to penetrate through and a current collector support portion 5 arranged between the electron flow paths 6, magnesia (MgO), spinel (MgAl)
₂ O ₄ ) and yttrium-stabilized zirconia (YS
Z) is mixed in a weight ratio of 19:31:50 to form a composite ceramic.

The gas separator body is made of MgO, MgAl
₂O_FourAnd YSZ to 0.1 μm to 10 μm respectively
After crushing, mix so that the weight ratio is 19:31:50.
In addition, 0.2 wt% of CaO, for example, is added as an auxiliary agent
Then, this is molded by the doctor blade method, and then 100
It was baked at 0 to 1600 ° C. for 5 hours. This gas
The thermal expansion coefficient of the separator body at 1000 ° C is 1
0.6 x 10 ^-6 And a solid electrolyte material, YSZ
Expansion coefficient at 1000 ℃ of 10.6 × 10^-6Toho
It was the same. The bending strength at 1000 ° C is 2
2 kg / mm²And has sufficient high temperature strength and
The behavior at the time was also good.

FIG. 3 is an explanatory view showing the structure of a fuel cell stack in which a large number of single cells 11 are stacked by using the gas separator 1 in which the electronic flow path 6 is fitted in the gas separator body. In the figure, the current collecting perforated plates 28 are provided on the upper and lower surfaces respectively.
A large number of single cells 11 contacted with each other are stacked via the gas separator 1. This single cell laminated body is housed in a predetermined box to form a solid oxide fuel cell.

According to this embodiment, MgO and MgAl ₂ O
A composite material consisting of ₄ which, by further configured gas separator with a ceramic made of a composite material obtained by mixing a YSZ, since the difference in thermal expansion coefficient between the gas separator and the single cell can be reduced as much as possible Prevents distortion during sintering and deformation during high temperature operation,
It is possible to obtain a fuel cell having excellent high temperature strength as well as high adhesion to cells and gas sealability.

In this embodiment, MgO, MgAl ₂ O
MgAl ₂ O ₄ or Al ₂ O on the surface of a gas separator composed of a composite ceramic of ₄ and YSZ.
_By applying ₃ and ₃ in the form of an organic compound of Al and baking and coating, elution of MgO can be prevented and a more reliable fuel cell can be obtained. Further, the same effect can be obtained by immersing MgO particles of the composite material before firing in an organic compound solution of Al and firing it to coat MgAl ₂ O ₄ or Al ₂ O ₃ .

In the present embodiment, the gas separator has been described as a constituent member of the SOFC, but other constituent members such as the interconnector and the gas flow path member are similarly composed of MgO, MgAl ₂ O ₄ and YSZ. Can be composed of

[0019]

According to the first invention of the present application, MgO and M
By forming the SOFC constituent member by using a composite ceramic in which YSZ is mixed with a composite material composed of gAl ₂ O ₄ , a fuel cell that is inexpensive, lightweight, excellent in high temperature strength, and has a high gas sealing property can be obtained. can get.

According to the second invention of the present application, the composite material
The MgO particles should be replaced with MgAl ₂O_FourOr Al₂
O₃Coated with or formed of composite ceramics
The surface of the SOFC component is MgAl₂O_FourOr Al
₂O₃By being coated with, the effect of the first invention can be obtained.
In addition, it prevents the elution of MgO from the constituent members and stabilizes it.
A highly reliable fuel cell can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 is a perspective view showing a gas separator according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a fuel cell stack that is an embodiment of the present invention.

[Explanation of symbols]

1 ... Gas separator, 2 ... Separator part, 3 ... Laminated part,
4 ... Gas inflow frame, 5 ... Current collector support part, 6 ... Electron flow path, 1
1 ... Single cell, 28 ... Perforated plate for current collection.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutoshi Murata 3-1-1 Tam, Tamano-shi, Okayama Mitsui Engineering & Shipbuilding Co., Ltd. Tamano Works (72) Inventor Masateru Shimozu 3-1-1 Tamama, Tamano-shi, Okayama Mitsui Engineering & Shipbuilding Co., Ltd., Tamano Works

Claims (2)

[Claims] 1. Magnesia (Mg) is used as a constituent material of a solid oxide fuel cell using yttrium-stabilized zirconia (YSZ) or its approximation as a solid electrolyte membrane.
O), spinel (MgAl ₂ O ₄ ) and yttrium-stabilized zirconia (YSZ) as main components, and the mixing ratio of magnesia and spinel is 1/9 to 1/1 by weight. 7. A solid oxide fuel cell, characterized in that a composite ceramic, in which the yttrium-stabilized zirconia is mixed, is used as the composite material. 2. Magnesia (Mg) in the composite material
O), or the above magnesia (MgO), spinel (M
gAl₂O_Four) And yttrium-stabilized zirconia
A component member made of a composite ceramic of (YSZ) is spun.
Flannel (MgAl₂O _Four) Or alumina (Al
₂O₃) Coating.
The solid oxide fuel cell described.