JPS63250065A - Oxygen ion conductive membrane and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to oxygen ion conductors such as high-temperature solid electrolyte fuel cells (hereinafter abbreviated as solid fuel cells) using solid electrolytes, oxygen sensors, and acid bongs. be.

Conventional technology As an oxygen ion conductor, zirconium chloride (ZrO,
) K yttrium oxide A (Y, 0.) or calcium oxide (CaO) in a molar ratio of 90:10 to 8
A solid solution of 0:20 is used.

In addition, sintering methods, glazma spraying methods, flame spraying methods, and CVD methods are used to manufacture ion conductors.

Sputtering method and coating film pyrolysis method are used.

Problems to be solved by the invention Zirconium oxide (ZrO□) IC yttrium oxide (
In stabilized zirconia containing Y, Os) as a solid solution, 1
The ionic conductivity at 000℃ is 9X10"(Ω-1・
am-'),2XIO-''(Ω-1 at 6QQ℃
・―″″′) and small. Therefore, 1. For example, solid stimulant -
2~ When used as a solid electrolyte in a battery, it can only operate at a high temperature of about 1000°C. The present invention aims to improve oxygen ion conductivity. It is something.

Means for Solving the Problems The present invention is a solid solution consisting of ceria-yttria, which has an oxygen ion conductive His structure.

Cerium oxide, or ceria, was selected as a material with high ionic conductivity for oxygen ions, and cerium oxide (CeO,) and yttrium oxide (Yt03) were selected.

That is, we selected a material with a molar ratio of 70:30 to 96.5:3.5, which contains ittria as a solid solution and has a high ionic conductivity. The oxygen ion conductive film was formed into a thin film in the range of 5 to 750 (μrn).

Function The function when the oxygen ion conductive membrane of the present invention is applied to a solid fuel cell will be explained. Figure 1 shows the operating principle of a solid fuel cell. The oxygen ion conductive membrane 2 is a solid electrolyte and allows oxygen ions 02- to pass therethrough. For example, zirconitum oxide (ZrO, ) and yttrium oxide (L
When Zr ions are dissolved in solid solution, Zr ions have a valence of 4.

The solid-dissolved yttrium has 34 planes, and vacancies of oxygen ions are generated, and the vacancies cause the movement of oxygen ions.

1 is a hydrogen side electrode, and 3 is an oxygen side 'tPL electrode. The acid gas entered from 07 to 4 times is 1/2.0 at the interface 12 between the oxygen side electrode 3 and the electrolyte 2. It is partially ionized by the reaction +2e→02-, moves in the electrolyte 2, and reaches the water electrode IK. Excess oxygen is discharged from the oxygen gas outlet 8. On the other hand, a part of the fuel gas salt introduced from the fuel gas population 9 is connected to the hydrogen side electrode 1 and 'IJtP! H at the I-quality interface 11,
-f-0'' -→H,0+ The reaction of 26 turns into water vapor. This water vapor is discharged from the fuel gas outlet 10 along with the remaining water vapor into the υP river. On the other hand.

The electrons generated at the hydrogen side electrode 1 pass through the external circuit and become negative #
Shun, who worked at 4, reached pole 3 on the oxygen side. At this time, the current value of the starting force at both ends of the load 40 is measured using the ammeter 6 using a voltage of 1 ft5. Furthermore, the electromotive force associated with water vapor generation when hydrogen is used as fuel is given by a linear equation.

[=33θ 10T/2F 1%CP (Hz)”〆゛・
P(HO)/P(H2O))Eθ: Standard electromotive force (V)
P(0,): Oxygen partial pressure on the oxygen electrode side R: Number of gas chambers P
CHt) "Hydrogen partial pressure in fuel P (Hz Ox)"
Partial pressure of hydrogen in fuel T: Absolute temperature F Near Alladay number This formula gives the electromotive force at no load, that is, at an open circuit.

Also, the current-voltage characteristics when a load is applied to the battery, that is, 1
A schematic diagram of the −V characteristics is shown in FIG. As the current per unit area of the electrode, or current density, increases, the terminal voltage decreases due to the solid electrolyte and internal resistance within the electrode. This voltage drop is mainly due to resistance to the movement of ions and electrons, but it can be reduced by the following means. That is, 1) A material with high oxygen ion conductivity and low electron conductivity is selected as the RL solute.

■ Lower the total resistance by using a thin electrolyte film.

■ To maintain a high ratio of Kazuhiro partial pressures on both sides of the electrolyte (-ζ -), a dense film is formed to prevent gas from passing through the electrolyte.

In the present invention, the solid electrolyte indicated by ■ in FIG.
e) yttrium oxide (YmOs) to CeO,:
A solid solution of 70:30 to 96,5:3.5 is used. Similar to zirconia-yttria, this material has a fluorite-type crystal structure in which 34 yttrium ions are substituted for 4 cerium ion positions, creating oxygen ion vacancies, and these vacancies provide oxygen ion conductivity. occurs. For example, when yttrium oxide is dissolved in cerium oxide at lOmol/l/%,
Acid-based materials exhibit high conductivity.

In addition, zirconia-based 1000℃ operation and ceria-based 5
00°C operation shows similar conductivity.

Example Figure 3 shows a fuel cell element that has been put to practical use.

In addition to the inner cylindrical porous semi-mix tube, a plurality of sets of electrodes, electrolytes, and current lead-out portions, which will be described later, were formed. 7
Fuel gas 31 is discharged into the fuel cell element which is kept at a high temperature of 00 to 1000 degrees Celsius. 46 and 47 are current deriving parts.

In Figure 4, which is an enlarged cross-sectional view of the fuel cell element shown in Figure 3, 42 is an electrode on the hydrogen side, and 43 is a solid electrolyte.

■ is the oxygen side electrode, 45 is the connection part, 46°4
7 is a current lead-out part, and the power can be increased by removing and removing multiple Mizochika batteries shown in Figure 4 in series.

Examples of materials other than the electrolyte include nickel oxide (MJ, 0) for the hydrogen side electrode 42, lanthanum cobalt oxide (Labors) for the nitrogen side electrode material, and connection part 45'P.
1tfN, the lead-out parts 45 and 47 are made of nickel aluminum (
NtAx) etc. were used.

In addition, the plasma spraying apparatus used as a thin film forming method has, for example, a groove breaker according to the invention of Japanese Patent Application No. Showa ω-101082. , is melted to form a dense conductive film 54. By forming a solid electrolyte using the ceria-yttria solid solution with high ionic conductivity as described above,
The initial objective was to reduce the internal resistance of the fuel cell, prevent oxygen and fuel gas leaks, and achieve high power generation characteristics.

In Figure 5, 55 is a substrate, 56 is a cathode, 57 is an anode, and 58 is a molten coating material. Note that the above-mentioned plasma spraying apparatus is not limited thereto, and for example, an apparatus such as that disclosed in Japanese Patent Application No. 101081/1981 can be used.

Effects of the Invention Since the present invention uses the above-mentioned groove bottom, #R elementary ion conductivity can be significantly improved. Furthermore.

This article describes the effect on power generation characteristics when the red ion conductive membrane prepared according to the present invention is applied as a solid electrolyte to a solid electrolyte fuel cell.

A fuel cell using a 2-layer zirconia-yttria solid solution electrolyte made using a conventional sintering method.

Thickness 200/200 mm produced by plasma spraying according to the present invention
The power generation characteristics of a fuel cell using a ceria-yttria solid solution electrolyte of JS are compared at 800°C. As shown in Figure 6, in the i-v characteristics, the slope of the straight line is approximately 177 for the zirconia-yttria sintered electrolyte with a slope of 62, and the sprayed electrolyte membrane of ceria-yttria of 62.
and decreased.

This indicates that the internal resistance of the electrolyte was reduced to about 1/7. In addition, as shown in Figure 7, the current-power characteristics (
I-P characteristics) In comparison, the ceria-yttria sprayed electrolyte membrane of 72 compared to the zirconia-yttria sintered electrolyte of 71.

Approximately 2.5 times the power density can be obtained at the peak value.

In addition, 1 the thickness 2 created by plasma spraying according to the present invention.
The power generation characteristics of a fuel cell using a ceria-yttria solid solution electrolyte with a thickness of 00 μm are compared at 900°C. Figure 8 shows the current-power characteristics at 900°C, and 81 shows the ceria-power characteristics.
The yttria-based thermal sprayed electrolyte 82 is a zirconia-yttria-based thermal sprayed electrolyte, and a power density of about 1.7 times the peak value was obtained.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a fuel cell using the oxygen ion conductive membrane of the present invention, Figures 2 and 2 are current ■ - voltage V diagrams when a load is applied to the fuel cell shown in Figure 1, and Figure 3 is a diagram of the current Figure 114 is a partial enlarged sectional view of Figure 3, Figure 5 is a sectional view showing the method for manufacturing the oxygen ion conductive membrane of the present invention, Figure Ar6 is a partially cutaway front view of the embodiment of the fuel cell of the present invention. 1 is a diagram showing the current I-voltage characteristic of the present invention and the conventional example, and Figures 7 and 8 are diagrams showing the current I-power P characteristic of the present invention and the conventional example. 1...Hydrogen side electrode 2...Solid electrolyte 3...Oxygen side electrode 7...Oxygen gas inlet 9...Fuel gas inlet...Conductive membrane agent Yu Shishifuji, ]- “-(2 others)-

Claims (1)

[Claims] 1. An oxygen ion conductive membrane characterized by being formed of a solid solution of ceria-yttria. 2 Seria-Yttria comparison 70:30 to 96
．． An oxygen ion conductive membrane characterized in that the ratio is in the range of 5:3.5. 3. An oxygen ion conductive membrane characterized in that a solid solution consisting of ceria-yttria is formed in the form of a membrane on an air-permeable base material by thermal spraying. 4. An oxygen ion conductive membrane characterized in that the thickness of the membrane-like solid solution is 5 μm to 750 μm. 5 Particle size 10-8 consisting of ceria-yttria solid solution
A method for producing an oxygen ion conductive membrane, comprising spraying a 0 μm sprayed material onto a breathable base material to form a thin film.