JP2913009B2 - Cylindrical high temperature steam electrolysis cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical high-temperature steam electrolysis cell having a four-layer structure in which a porous inner electrode, a dense electrolyte, and a porous outer electrode are sequentially laminated on the outer periphery of an insulating substrate tube. .

[0002]

2. Description of the Related Art A high-temperature steam electrolysis cell is an apparatus for producing hydrogen and oxygen by electrolyzing steam, and is usually operated at a high temperature of about 1000 ° C. Among them, a cylindrical high-temperature steam electrolysis cell has a conventional cylindrical shape. There are a four-layer structure in which a porous inner electrode, a dense electrolyte, and a porous outer electrode are sequentially laminated on the outer periphery of an insulating base tube, and a three-layer structure in which a base tube is not provided. Is characterized in that it is easier to form an interconnector portion for connecting an inner electrode and an outer electrode in an electrolyte than a three-layer structure.

A cylindrical high-temperature steam electrolysis cell having a four-layer structure is manufactured by sequentially forming an inner electrode, an electrolyte, and an outer electrode on the outer periphery of an insulating base tube by sintering, spraying, EVD, or the like.

In this case, the electrode material has a coefficient of thermal expansion of 1.2.
× 10 ^-5 Ni-YSZ (yttria stabilized zirconia), L
aSrMnO ₃ material is used, YSZ with a thermal expansion coefficient of about 1.03 × 10 ^-5 is used as the electrolyte material, and CSZ, which has a thermal expansion coefficient similar to that of the electrolyte, is conventionally used as the base tube material.
(CaO stabilized zirconia: coefficient of thermal expansion 9.1 to 10 × 10 ⁻⁶ ) is used.

[0005]

However, the thickness of each layer of this cell is about 2 mm for the basic tube and about 0.1 mm for the electrolyte and the electrodes, but the film formation temperature is generally as high as 1000 ° C. or higher, and the operation is also difficult. Since the heat treatment is performed at about 1000 ° C., there is a possibility that a stress may be applied at room temperature to lead to deterioration and breakage of each layer of the electrolytic cell.

[0006] The inventors of the present application have studied the residual stress in the circumferential direction of a cylindrical high-temperature steam electrolysis cell having a four-layer structure, and have obtained an analysis result as shown in FIG.

According to this, the inner electrode layer and the outer electrode layer are
A tensile stress of 200MPa or more works, and the electrolyte layer has 150MPa.
It was found that a certain degree of compressive stress works.

In this case, the electrolyte layer composed of YSZ etc.
Even if a compressive stress of 150 MPa or more acts, the electrolyte layer does not deteriorate or break, but a tensile stress of 200 MPa or more
The tensile strength of -YSZ, La _1-x Sr _x MnO ₃ based electrode material is greatly exceeded, and reduction of this stress is a serious issue.

In view of the above situation, the present invention is configured by sequentially laminating respective layers of a porous inner electrode, a dense electrolyte, and a porous outer electrode on the outer periphery of an insulating base tube, and further comprising the inner electrode material or the outer electrode material In a cylindrical high-temperature steam electrolysis cell having a higher coefficient of thermal expansion than that of the electrolyte, the insulating base tube is formed using a sintered body of a mixture of MgO and MgAl ₂ O ₄ and has a coefficient of thermal expansion of 1.3. × ^10-5 ~
1.1 × ^10−5, and the coefficient of thermal expansion of the insulating base tube is defined as the coefficient of thermal expansion of the inner electrode material or the outer electrode material.
Proposes a cylindrical high-temperature steam electrolysis cell, characterized in that the larger and to the same extent as only.

[0010]

In the electrolytic cell having the above structure, by setting the coefficient of thermal expansion of the base tube to be substantially the same as the coefficient of thermal expansion of the electrode material, the residual tensile stress acting on the electrode can be reduced to 20 MPa or less. Deterioration and damage can be avoided.

On the other hand, no tensile residual stress is generated in the electrolyte, and a compressive residual stress of 600 MPa or more acts. However, in the case of an electrolyte material such as YSZ, the electrolyte is not damaged by the compressive residual stress.

In the present invention, as the electrode material, a Ni-YSZ mixture having a mixing ratio of Ni 40 to 50% and YSZ 60 to 50%, La _1-x Sr _x Mn
O ₃ (x = 0.1 to 0.3) material, YSZ as electrolyte, La _1-x Sr _x CrO ₃ (x = 0.15) for the interconnector, and slurry coating on the outer periphery of the base tube The inner electrode is formed by a sputtering method, a thermal spraying method, etc., and the electrolyte is EVD outside the inner electrode.
The outer electrode is formed by slurry coating, thermal spraying, or the like on the outside of the interconnector portion by the PVD method.

When there is a difference in the coefficient of thermal expansion between the inner electrode and the outer electrode, the coefficient of thermal expansion of the base tube is adjusted to the larger coefficient of thermal expansion.

When it is difficult to make the coefficient of thermal expansion of the electrode and the coefficient of thermal expansion of the base tube equal, it is adjusted so that the coefficient of thermal expansion of the base tube is slightly larger than that of the electrode.

[0015] Incidentally, as means for the thermal expansion coefficient comparable to electrode material the thermal expansion coefficient of the substrate tube in the present invention, the substrate tube configured using MgO, the MgAl ₂ O ₄ mixture, MgO and MgAl ₂ O
By adjusting the mixing ratio of _4, the coefficient of thermal expansion of the base tube can be made approximately equal to the coefficient of thermal expansion of the electrode material.

The mixing ratio of the mixture of MgO and MgAl ₂ O _{4 is} represented by the weight ratio MgO:
In the range of Al ₂ O ₃ = 100: 0 to 0: 100, the coefficient of thermal expansion of
The coefficient of thermal expansion of the base tube can be adjusted in the range of 1.3 × 10 ^{-5 to} 0.8 × 10 ^-5 , preferably by adjusting the weight ratio MgO: Al ₂ O ₃ = 65:35 to 83:17. The 1.1 × 10 ^{-5 to} 1.2 ×
Can be adjusted within the range of 10 ^-5 .

From the viewpoint of protection of the underlayer, it is desirable to lower the film forming temperature outward, but in this case also, in the present invention, by setting the film forming temperature higher than the operating temperature of the cell, the room temperature can be maintained even during operation. Even at this time, the tensile residual stress acting on the electrode and the base tube can be reduced to 10 MPa or less, while only the compressive residual stress can be generated in the electrolyte and the interconnector.

In addition, by adopting such a film forming temperature, the magnitude of the stress during the operation becomes much smaller than that at the room temperature, so that the deterioration and breakage of the battery can be prevented.

[0019]

【Example】

EXAMPLES Hereinafter, Ni-YSZ, La _1-x Sr _x MnO ₃ (x = about 0.1),
An example in which a cylindrical high-temperature steam electrolysis cell is manufactured using YSZ as an electrolyte and a MgO, MgAl ₂ O ₄ spinel mixture as a base tube will be described below.

A mixture of MgO and MgAl ₂ O ₄ spinel is treated with a porosity of 30.
The base tube is manufactured by sintering into a cylinder having a thickness of about 2 mm and an inner diameter of about 10 to 20 mm.

In this case, the coefficient of thermal expansion of the electrode material between the higher temperature of the temperature at the time of manufacturing the cell or the temperature at the time of operation and the room temperature was measured, and the thermal expansion coefficient of the mixture sintered body of MgO and MgAl ₂ O ₄ was measured. MgO and MgO are used so that the coefficient of expansion matches or is slightly larger than the larger coefficient of thermal expansion of the measured electrode materials.
The mixing ratio with MgAl ₂ O ₄ spinel is adjusted.

In this embodiment, the temperature during cell operation is about 1000
The maximum temperature during cell fabrication is 1300-1400
° C., as a result of measuring the coefficient of thermal expansion of the electrode material between 1400 ° C. and room temperature, the coefficient of thermal expansion of the Ni-YSZ fuel electrode and La _1-x Sr _x MnO ₃ air electrode was 1.2 × 10 ^-5 . Therefore, the base tube is made of MgO and MgAl ₂ O ₄ spinel in a weight ratio of MgO: Al ₂ O
₃ After adjusting so that it becomes 83:17, inner diameter 12mm, thickness 2mm
A pipe having a coefficient of thermal expansion of about 1.2 × 10 ⁻⁵ was manufactured.

A Ni-YSZ fuel electrode or La _1-x S
r _x MnO ₃ (x = about 0.1) Air electrode is made by slurry coating of about 100 μm to 500 μm, then YSZ by EVD method
A dense electrolyte membrane was formed, and finally, the remaining electrodes were formed to make a single cell. Table 1 below shows the conditions for forming each layer and the thickness of each layer.

[0024]

[Table 1]

FIG. 1 shows the result of measuring the residual stress in the circumferential direction of the single cell thus produced.

According to this, the Ni-YSZ fuel electrode or La _1-x Sr _x
MnO ₃ (x = 0.1) Residual tensile stress acting on the air electrode and the outer electrode is less than 20MPa.
It will not be damaged.

Further, no tensile residual stress is generated in the electrolyte layer, and a compressive residual stress of 600 MPa or more acts, but the electrolytic layer is not damaged by the compressive residual stress.

[0028]

In summary, according to the present invention, in a cylindrical high-temperature steam electrolysis cell having a four-layer structure, the residual tensile stress acting on the electrode layer can be reduced to 1/10 or less of that of the prior art, and therefore, the temperature frequently rises and falls during the temperature rise and fall process Deterioration and breakage that occur can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing circumferential residual stress in a cylindrical high-temperature steam electrolysis cell according to the present invention.

FIG. 2 is a view showing a residual stress in a circumferential direction in a conventional cylindrical high-temperature steam electrolysis cell having a four-layer structure.

Claims (1)

(57) [Claims] 1. A structure in which a porous inner electrode, a dense electrolyte, and a porous outer electrode are sequentially laminated on an outer periphery of an insulating base tube, and a coefficient of thermal expansion of the inner electrode material or the outer electrode material is the same as that of the electrolyte. In the cylindrical high-temperature steam electrolysis cell having a size larger than that of
l ₂ O ₄ mixture sintered body formed by using a, and the thermal expansion coefficient and 1.3 × 10 ^-5 to 1.1 × 10 ^-5, the absolute
Cylindrical high-temperature steam electrolysis cell, characterized in that the thermal expansion coefficient of the edge substrate tube was the larger only the same level of thermal expansion coefficient of the inner electrode material or the outer electrode material.