JPH06203847A - Fuel cell solid electrolyte - Google Patents

Abstract

PURPOSE:To restrain polarization resistance from increasing so as to prevent aged deterioration from proceeding by bringing particles of a metal or conductive metal compound of specific particle size into close contact with the surface of fuel-cell side solid electrolyte at specific surface coverage. CONSTITUTION:A solid electrolyte fuel cell comprises an air electrode formed on one side of a solid electrolyte plate and a fuel electrode formed on the other side. Particles of a metal or conductive metal compound, 90% or more of which are of particle size in the range 0.3 to 10mum, are brought into close contact with the surface of solid electrolyte on the fuel cell side at a surface coverage of 30 to 80%. Thus even if the current of the fuel cell increases, the solid electrolyte does not have any increase in polarization voltage and therefore has almost no polarization resistance, resulting in stabilization of its time-related characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte for a fuel cell, which suppresses polarization resistance and stabilizes the output and efficiency of the cell over time, and a solid electrolyte fuel cell using the same.

[0002]

2. Description of the Related Art In a solid oxide fuel cell, a method for preparing a solid electrolyte having electrodes formed on both sides thereof is usually to apply an electrode composition to an electrolyte such as a zirconia electrolyte in the form of a green sheet by coating or the like. After that, a method of integrally sintering or a method of applying an electrode on a sintered electrolyte such as a sintered zirconia electrolyte by coating or printing is used.

In the latter deposition method, the polarization resistance increases as the current increases when the battery formed therefrom is generated, and when the battery is operated for a long time, the anode is sintered and peeled from the electrolyte. However, there is a drawback that polarization resistance increases and deterioration progresses with time.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional solid oxide fuel cell, and increases the polarization resistance even when the current becomes large during power generation or when the battery is operated for a long time. The present invention has been made for the purpose of providing a solid electrolyte for a fuel cell, which provides a solid oxide fuel cell in which the above-mentioned phenomenon is suppressed and does not deteriorate with time.

[0005]

The inventors of the present invention have conducted various studies to develop a solid electrolyte for a fuel cell having the above-mentioned preferable characteristics, and as a result, the polarization resistance, which is a drawback of the conventional deposition method, has been found. The increase in the fuel cell concentration is due to the fact that a strong interface between the fuel electrode and the electrolyte is not formed, and its purpose is to be improved by applying a unique device to form a strong fuel electrode / electrolyte interface. They have found that they can be achieved, and have completed the present invention based on this finding.

That is, the present invention is a solid electrolyte fuel cell in which an air electrode is formed on one surface and a fuel electrode is formed on the other surface with a solid electrolyte plate sandwiched between them. 90% or more has a particle size of 0.3 to 10 μm
The present invention provides a solid electrolyte for a fuel cell, characterized in that particles of a metal or a conductive metal compound in the above range are adhered at a surface coverage of 30 to 80%.

90% or more of the particles of the metal or the conductive metal compound, which form an important component of the solid electrolyte for fuel cell of the present invention, have a particle diameter of 0.3 to 10 μm and serve as a substrate or a matrix. It is firmly and tightly bonded to the electrolyte so that the surface coverage is 30 to 80%.

The fuel electrode can be formed integrally when such a solid electrolyte is formed as described later, or can be formed on such a solid electrolyte by a conventional method such as the above-mentioned deposition method. The particles intervene at the interface between the fuel electrode and the solid electrolyte to firmly hold the fuel electrode. The thickness of the layer formed by the particles intervening at this interface is preferably 10 μm or less, more preferably about 1 to 5 μm.

The solid electrolyte for a fuel cell of the present invention is preferably such that a metal thin film or a metal compound thin film is formed on the fuel electrode side surface of the solid electrolyte, the thin film is used as a metal oxide film, and then this metal oxide film is formed. It is obtained by applying the composition for fuel electrode on the top and then performing a reduction treatment. At that time, the fuel electrode is also integrally formed.

The solid electrolyte used in the present invention includes:
Zirconia-based materials such as stabilized zirconia to which yttria and the like are added and partially stabilized zirconia are preferable.
Further, in order to form a metal thin film or a metal compound thin film on such a solid electrolyte, it is preferable to subject the electrolyte to a surface treatment such as plating, electron beam vapor deposition, and sputtering, which has particularly good adhesion and is uniform. It is preferable to use an electroless plating method that can obtain a film having a film thickness.

The thin film thus obtained is a dense thin film made of a metal or a metal compound, and Ni or Co is preferable as the metal constituting the thin film, and the metal compound is a metal oxide or a metal carbide. Are preferred, and nickel oxide and cobalt oxide are particularly preferred.

When an electrode is formed through a thin film according to a conventional deposition method, the adhesive force between the electrode and the electrolyte becomes stronger as compared with the conventional deposition method in which the electrode is directly formed on the electrolyte. However, since the thin film is too dense, the diffusion of the raw material gas, the product gas generated in the battery reaction and water is delayed, and the diffusion resistance increases.

This increase in diffusion resistance is suppressed by using the thin film obtained as described above as a metal oxide film, then applying the composition for fuel electrode on the metal oxide film, and then applying a reduction treatment. To be done. By such treatment, predetermined particles of the metal or conductive metal compound as described above are formed. Along with that, electrodes are also formed.

As a concrete method, preferably, a metal thin film is oxidized and baked at about 800 to 1200 ° C. for about 1 to 10 hours to form a metal oxide film, and this thin film is used as a fuel electrode / electrolyte interface layer. After coating the composition for fuel electrode on this thin film, the temperature is raised by heating, and the binders are burned off in the process of raising the temperature to 300 to 400 ° C., and 800 ° C. to 1200 ° C.
A method of forming a fuel electrode while reducing the metal oxide thin film into particles by performing a reduction treatment with the method of 1. It is preferable to use nitrogen added with 5 to 20% of hydrogen for the reduction treatment, and it is desirable to start the reduction treatment from the time when the temperature reaches 800 ° C. when the battery is manufactured and the temperature is raised.

The present invention also includes a solid oxide fuel cell using a solid electrolyte in which the above-mentioned predetermined particles are closely formed.

[0016]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 5 (Y ₂ O ₃ ) _0.08 (ZrO ₂ ) of 5 cm square
_{A 0.92} plate was used as the solid electrolyte plate. On this oxygen passage side, a coating composition in which La _0.8 S _r0.2 MnO ₃ powder (average particle size of about 5 μm) was dispersed in an organic binder was applied to an area of 16 cm ² with a thickness of 0.1 to 0.2 mm. Then, a cathode forming film was obtained. In addition, the following interface N on the hydrogen passage side
Ni / ZrO ₂ (weight ratio 10
/ 1) Thickness of the coating composition dispersed in an organic binder cermet powder mixture in an area of 16cm ² of 0.1 to 0.
2 mm was applied to form an anode forming film. For the Ni-based film at the interface, the solid electrolyte plate was immersed in an electroless Ni plating bath for 20 minutes to form a Ni-dense film with a thickness of 2 μm, and then this film was
It was prepared by firing at 000 ° C. in an air atmosphere for 1 hour.

The electrode forming film thus obtained is provided.
The electrolyte plate is integrated with two kinds of terminal plates of the same size as the solid electrolyte plate.
A degradable fuel cell was produced. These terminal boards are for each source gas
Current collector having a groove for conducting electricity on one side, that is, La
_0.8S_r0.2Cr_0.9Co _0.1O_ThreeConsisting of
Consists of sword side current collector and Ni anode current collector
I made it.

The fuel cell thus manufactured was heated. Heated air flows from room temperature to 350 ℃, 350 ℃
From 800 to 800 ° C, nitrogen gas is flowed to prevent oxidation of the anode on the hydrogen passage side.
H ₂ / N ₂ = 5/50 (cc / min) up to 0 ° C
Flowing mixed gas to reduce, 10 ℃ / m
The temperature was raised in. By this treatment, a Ni particle layer was formed at the interface between the solid electrolyte and the anode, and the electrode was formed by firing. After that, the temperature is kept at 1000 ° C. and hydrogen is added to the anode side.
Oxygen at the cathode side of 200 cc / min and 1 respectively
Flowing at a supply rate of 00 cc / min to start power generation.
Table 1 shows the polarization characteristics of the battery depending on the change in current.

[0020]

[Table 1]

From the above, it can be seen that the polarization resistance of the battery of the example does not increase even if the current increases, so that there is almost no resistance due to the electrode reaction.

FIG. 1 shows the time-dependent characteristics of the output density and efficiency when the battery utilization rate (Uf) is 80%. From this, it can be seen that the temporal characteristics of the battery performance are extremely stable.

Comparative Example A coating composition prepared by dispersing the same predetermined cermet powder as in the example into an organic binder without interposing a Ni particle layer on the hydrogen passage side of the solid electrolyte plate was prepared in the same manner as in the example. A fuel cell was prepared in the same manner as in Example except that the anode forming film was formed by coating. This fuel cell was subjected to heat treatment and power generation in the same manner as in the example. Table 2 shows the polarization characteristics of the battery depending on the change in current.

[0024]

[Table 2]

From the above, the battery of the comparative example is the Ni of the example.
The polarization resistance is larger than that of the battery with the particle layer interposed, and the polarization voltage increases as the current increases.
It can be seen that there is a considerable resistance due to the electrode reaction, and the deterioration of polarization over time is large. FIG. 2 shows the time-dependent characteristics of output density and efficiency when the utilization rate of this battery is 80%. From this, Ni
Since the deterioration over time of polarization is obviously larger than that of the battery in which the particle layer is inserted, it can be seen that the insertion of the Ni particle layer prevents an increase in diffusion resistance due to sintering of the anode.

[0026]

INDUSTRIAL APPLICABILITY The solid electrolyte of the present invention has almost no polarization resistance in the fuel cell using the solid electrolyte because the polarization voltage itself does not increase even when the current increases, and the solid electrolyte has a predetermined cell utilization ratio ( The characteristics of Uf) such as output density and efficiency over time are extremely stable, and the polarization resistance under a predetermined constant current is extremely small over time.

[Brief description of drawings]

FIG. 1 is a graph showing the time-dependent characteristics of output density and efficiency when the fuel cell of the present invention is used for a predetermined time.

FIG. 2 is a graph showing a time-dependent characteristic of output density and efficiency when a conventional fuel cell is used for a predetermined time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoo Ando Nishitsurugaoka 1-3-1 Oi-cho, Iruma-gun, Saitama Tonen Co., Ltd. Research Institute (72) Toshihiko Yoshida Nishitsurugaoka, Oi-cho, Saitama 1-3-1 Tonen Co., Ltd. Research Institute

Claims (2)

[Claims] 1. A solid electrolyte type fuel cell in which an air electrode is formed on one surface and a fuel electrode is formed on the other surface with a solid electrolyte plate sandwiched therebetween.
A solid electrolyte for a fuel cell, characterized in that 0% or more of particles of a metal or a conductive metal compound having a particle diameter in the range of 0.3 to 10 μm are adhered at a surface coverage of 30 to 80%. 2. A solid oxide fuel cell using the solid electrolyte according to claim 1.