JPH04237960A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To improve the electric characteristic such as the electromotive force by improving the gas-tightness of a solid electrolyte film. CONSTITUTION:A solid electrolyte film is further formed by the thermal deposition method on a solid electrolyte film formed by the plasma display method. The gas-tightness is improved while the resistance and surface area of the solid electrolyte film formed by the plasma display method are rarely changed, thus a solid electrolyte fuel cell with an excellent electric characteristic such as the electromotive force is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solid electrolyte fuel cells, and more particularly to solid electrolyte membranes thereof.

0002

[Prior Art] Conventionally, in solid oxide fuel cells, electrodes such as oxygen electrodes (or hydrogen electrodes) are formed on a porous substrate such as a porous SUS substrate by a plasma spray method, etc. It is manufactured by forming a solid electrolyte membrane with a thickness of approximately 100 μm using the same method, and then forming an electrode such as a hydrogen electrode (or oxygen electrode) on the solid electrolyte membrane using the same method. LaS was applied using plasma spray method to
A material having an rCoNi film formed thereon is used.

[0003] The electrical properties of the solid electrolyte membrane, such as electromotive force, improve as the surface area increases. Therefore, in order to increase the surface area, the solid electrolyte membrane may have some degree of undulation (roughness) in its surface shape. desirable. When the plasma spray method described above is used, the surface shape of the solid electrolyte membrane formed is rich in undulations, so the surface area of the solid electrolyte membrane is large.

0004

[Problem to be solved by the invention] The solid electrolyte membrane described above needs to be gas-tight with low gas permeability.
Although the solid electrolyte membrane formed by the plasma spray method has a rugged surface and a large surface area, it cannot be said to have sufficient gas tightness. For example, using LaF3 powder with a particle size of 10 to 80 μm as a solid electrolyte, the above plasma spray method is used to form a layer of LaF3 with a thickness of about 100 μm.
After forming the film, a gas tightness test (leak test) was performed using the above-mentioned apparatus, and the result was approximately 1 torr.

FIG. 5 shows a test apparatus used for testing gas tightness. This device includes a vacuum layer 21 and a
It consists of a rotary pump 22, a diffusion pump 23, and a diaphragm vacuum gauge 29, each of which has a valve 26a.
, 26c to a vacuum chamber, and the sample is attached to the sample attachment part 27 via a valve 26d.

[0006] The above leak test was carried out by installing the sample of the solid electrolyte membrane in this device and then using the rotary pump 22.
Then, the inside of the vacuum layer 21 is set to 10-6 (torr) or less by the diffusion pump 23, and the valve 26d is opened while only the rotary pump is operated.
The pressure at the time when the internal pressure became constant was measured with a diaphragm vacuum gauge 29, and this value was taken as the leakage amount.

Although it is possible to reduce the amount of leakage by increasing the thickness of the solid electrolyte membrane, in this case a problem arises in that the resistance of the membrane increases.

It is also possible to reduce the thickness of the formed solid electrolyte membrane by reducing the particle size of the powder used for plasma spraying, but the plasma spray equipment currently in use is not able to achieve this. It is extremely difficult to use powders with small particle sizes.

Furthermore, on the first solid electrolyte membrane formed by the plasma spray method, a second solid electrolyte membrane is formed using another formation method.
Although it is possible to suppress the amount of leakage by forming a solid electrolyte of There was a problem in that the surface area became small and the electrical characteristics deteriorated.

The present invention has been made based on the above background, and it is an object of the present invention to provide a method for manufacturing a solid electrolyte membrane having excellent gas tightness.

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention forms a solid electrolyte layer on a first electrode formed on a porous substrate by a plasma spray method. A solid electrolyte fuel cell in which a second electrode is laminated is characterized in that a solid electrolyte is further formed by a heated vapor deposition method on the solid electrolyte membrane formed by the plasma spray method.

0012

[Effect] As mentioned above, the solid electrolyte membrane formed by the plasma spray method has a relatively rough surface, so the amount of gas leakage is relatively large. However, if a film is further formed on this solid electrolyte membrane using the heating evaporation method, , the rough portions of the solid electrolyte membrane formed by the plasma spray method are covered, thereby improving gas tightness and reducing the amount of gas leakage.

[0013]

[Example] FIG. 2 is an explanatory diagram of a heating vapor deposition experimental apparatus according to this example. In this device, reference numeral 1 denotes a vacuum chamber, and a sample holder 2 is provided inside the vacuum chamber, and a sample 3 is supported by this, and a LaF3 plasma spray film 4 is formed on the lower surface of the sample 3. has been done.

Further, below the sample 3, an electrode column 5 is provided.
A tungsten board 6 is supported by a tungsten board 6 and has a LaF3 source 7 on its upper surface.

To manufacture the solid electrolyte membrane according to this embodiment, first, as shown in FIG. 1(a), a porous SUS substrate 13 is welded to a tube 12, and then as shown in FIG. A sample was manufactured by forming a LaF3 film 14 on a porous SUS substrate 13 by a plasma spray method, and then a heated evaporation method was performed on this using the apparatus shown in FIG. 1 to form a sample as shown in FIG. 2(c).
A LaF3 film 15 as shown in FIG.

In this example, in order to measure the amount of leakage from the LaF3 film itself, a sample was prepared by forming the LaF3 film directly on a porous SUS substrate, and heating vapor deposition was performed on this sample. However, since the LaF3 film formed directly on this SUS substrate has almost the same surface morphology and other properties as the LaF3 film formed on the porous SUS substrate via an electrode such as an oxygen electrode or a hydrogen electrode, this The results obtained in the examples can be directly applied to solid oxide fuel cells. In addition, as the above sample, the thickness of the LaF3 film is 10
Sample a with a leakage amount of 0.835 torr at 0 μm,
and sample b, each having a film thickness of 87 μm and a leakage amount of 1.024 torr, and a LaF3 grain (manufactured by Optron) placed on a tungsten board was used as a target. In addition, the heating vapor deposition conditions were 0.3
×10-4 to 0.8×10-5 torr, the substrate temperature was the same as the inside of the vacuum chamber, and the deposition rate of the LaF3 film was set to 1.
Heated vapor deposition was performed for 8 hours at a rate of 2 μm/hour.

Under the above conditions, a leak test was conducted after heating vapor deposition of sample a for 2 hours, 4 hours, 6 hours, and 8 hours, and results were 0.830 and 0.830, respectively.
, 0.805, and 0.760 (torr) were obtained, and a leak test was also performed on sample b in the same way, and the values were 1.023, 0.990, 0.950, and 0, respectively.
．． A result of 840 (torr) was obtained.

FIG. 3 shows the results of the above leak test, with the horizontal axis representing the heating vapor deposition time (hour) and the vertical axis representing the degree of vacuum attainment (tor).
r). This graph shows that the degree of vacuum attainment is improved by performing thermal evaporation for both samples a and sample b, and particularly in sample a, the degree of vacuum attainment is improved by about 20%.

Note that FIG. 4 shows the X
It is a graph showing a line diffraction result. In this graph, the horizontal axis is the diffraction angle and the vertical axis is the intensity, and the points p, q, and r are LaF3 (110) and LaF3 (11
1) and the peak values of LaF3 (113) are shown. This figure shows that the formed LaF3 film exhibits crystallinity.

Although LaF3 is used as the solid electrolyte in this example, LaOF, La1-xMxF3-x, LaOF, La1-xMxF3-x, La
Similar effects can be obtained by using 1-xMxOF1-x (M is a metal such as Sr, Ba, Ca, etc.).

[0021]

Effects of the Invention In the present invention, by covering a solid electrolyte film formed using a plasma spray method with a rough surface with a solid electrolyte film formed using a heated vapor deposition method, the roughness of the plasma spray film can be reduced. The gas tightness of the solid electrolyte is improved while the film thickness remains almost the same and the film thickness remains almost the same.

Furthermore, since the solid electrolyte membrane formed by the above-mentioned thermal evaporation method is very thin, the resistance value of the membrane itself can be kept low.

Furthermore, in the present invention, since a very thin solid electrolyte membrane is formed by a heated evaporation method on a solid electrolyte membrane formed by a plasma spray method, its surface shape is rich in undulations. Like the solid electrolyte membrane formed by plasma spraying, it has excellent electrical properties such as electromotive force.

[0024] Therefore, by using this solid electrolyte membrane, a solid electrolyte fuel cell having excellent electrical characteristics such as electromotive force can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a solid electrolyte membrane according to this example.

FIG. 2 is an explanatory diagram of a heating vapor deposition apparatus according to the present invention.

FIG. 3 is a graph showing the amount of gas leakage of the solid electrolyte membrane according to the present example.

FIG. 4 is an X-ray diffraction graph of the solid electrolyte membrane according to this example.

FIG. 5 is an explanatory diagram of a gas leak amount measuring device.

[Explanation of symbols]

13 Porous SUS disk 14 LaF3 plasma spray film 15　LaF3 heated evaporation film

Claims (1)

[Claims] Claims: 1. A solid electrolyte fuel cell in which a solid electrolyte layer is formed on a first electrode formed on a porous substrate, and a second electrode is laminated on the solid electrolyte layer, the solid electrolyte layer comprising: A first solid electrolyte film formed by a plasma spray method, and a second solid electrolyte film formed on this film by a heated evaporation method.
A solid electrolyte fuel cell comprising: a solid electrolyte membrane; and a solid electrolyte membrane.