JPH0381962A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To form a porous electrode thin film having fine, uniform pores and to stack a pinhole-free solid electrolyte thereon to make the film thin and to obtain a unit cell structure whose voltage drop is small by applying nickel powder on the surface of a porous base plate, and pressing, then sintering. CONSTITUTION:A porous electrolyte thin film 2 having fine, uniform pores is formed by applying nickel powder onto the surface of a porous base plate 1, and pressing, then sintering. A pinhole-free solid electrolyte 3 is stacked thereon to make the film thin. An electrode thin film 4 is stacked on the solid electrolyte 3 to form a unit cell. The solid electrolyte thin film 3 is formed in such a way that, for example, a 10mum thick solid electrolyte thin film is formed by electron beam vapor deposition on the electrode thin film for hydrogen on the porous base plate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a fuel cell in which a single cell is constructed by laminating electrodes and a solid electrolyte thin film on a porous substrate.

B9 Summary of the Invention The present invention provides a solid oxide fuel cell having a stack of single cells stacked on top of each other, by applying nickel powder to the surface of a porous substrate and sintering it after pressing to make it fine and uniform. By forming a porous electrode thin film with holes, laminating a pinhole-free solid electrolyte thin film on its surface, and laminating an electrode thin film on that surface to form a single battery cell, a good fuel cell can be produced. This is how it is configured.

C0 conventional technology Fuel cells are conventionally applied products using porous substrates.

One type of fuel cell is a flat plate fuel cell.

In general, a fuel cell main body consists of a unit cell structure (hereinafter referred to as a unit cell structure) by arranging an anode and a cathode electrode plate on both sides of a solid electrolyte. A plurality of them are arranged in series so that they face each other. Hydrogen gas (hydrogen) is supplied as a fuel to the cathode side of the fuel cell body configured in this way, and air (oxygen) is supplied as an oxidizing agent to the anode side, causing the hydrogen and oxygen to react to generate an electromotive force. is occurring. Note that water is produced during this reaction. Next, a conventional fuel cell will be described with reference to FIG.

That is, the fuel cell main body 30, as shown in FIG.
A plurality of single cell structures S and a holding plate 31a for stacking and fixing these single cell structures S in series.

31b, a hydrogen gas supply manifold 32 that supplies hydrogen gas H7 to the cathode plate side of each single cell structure S of the stacked and fixed battery body 30, and an air supply manifold 32 that supplies air (oxygen) to the anode plate side. 33, and current collecting leads 34 and 35 that take out electricity from the anode plate and cathode plate of each single cell structure S, respectively.

In the stacked fuel cell configured in this manner, the gas supply manifolds 32 and 33 are attached to the outside of the cell main body 30. In addition, water and electrical energy are generated by the reaction between the supplied hydrogen gas and air via the electrolyte, and the current collector leads (busbars) 34 and 35 that extract this generated electrical energy to the outside have a single cell structure. attached to the outside of the body.

Problems that the D1 invention attempts to solve The conventional fuel cell shown in Figure 7 uses a solid electrolyte.

Although it is constructed by combining an oxygen electrode and a hydrogen electrode, it has a drawback in strength. However, after the unit cell structure is assembled, the current collector provided outside the picture electrode can ensure strength, but there is a risk of damage during assembly. Furthermore, in order to ensure a certain degree of strength, it was necessary to form the solid electrolyte layer thickly.

When the solid electrolyte layer is formed thickly, the voltage drop V due to the resistance of the solid electrolyte itself is V-1-r-t×1O-4 (i is the current flowing through the solid electrolyte, R is the resistance of the solid electrolyte, and t is the solid From the relationship expressed by (the thickness of the electrolyte), it can be seen that the thinner the solid electrolyte is, the better the voltage drop will be. However, in the conventional structure, the thickness of the solid electrolyte must be made thick to a certain extent due to strength, which causes a problem in that the voltage drop becomes large.

In view of the above points, the present invention forms a solid electrolyte into a thin film,
An object of the present invention is to provide a solid oxide fuel cell in which a single cell structure of a fuel cell with a small voltage drop can be obtained.

E. Means for Solving the Problems The solid oxide fuel cell of the present invention is produced by mixing equal amounts of submicron-sized nickel powder and nickel powder with a diameter of 3 μm on the surface of a porous substrate. , apply a solution dissolved in water to a uniform thickness, press it and sinter it to form a coated area, polish the surface of this coated area to make it flat, and then apply submicron nickel powder on top of it. After grinding and pressing, a hydrogen electrode layer with fine and uniform pores is formed on the surface by sintering, and a pinhole-free solid electrolyte thin film is laminated on top of the electrode layer. ,
A feature of this battery is that a single cell of this battery is constructed by laminating an electrode thin film for oxygen on the solid electrolyte thin film.

16 Effect By configuring as described above, the nickel powder is layered to fill the large diameter pores on the surface of the porous substrate, forming a thin film having fine and uniform pores. The solid electrolyte is laminated so that no holes are formed, and the film thickness is reduced.

G. Example Embodiments of the present invention will be described below based on the drawings.

Fig. 1 is a vertical cross-sectional view of the solid oxide fuel cell main body in a stack configuration. In Fig. 1, a hydrogen electrode layer B (first electrode thin film) is sequentially formed on the surface of a stainless steel porous substrate l
2. A single cell structure is constructed by laminating the solid electrolyte layer H3 that does not generate pinholes and the oxygen electrode thin film (second electrode layer WX) 4.

Next, using the porous substrate l as a support structure, the hydrogen electrode thin film 2 is
This article describes the production of .

As the porous substrate 1, a material of 5US316L, a porosity of about 40%, a nominal pore diameter of 0.5 μm, and a thickness of about 1 mm was used.

Although the nominal pore diameter is 0.5 μm, the actual pore diameter varies, and there are many pores with a diameter of about 10 μm.
There are large pores with a diameter of about 40 μm in some places.

The diameter of the porous substrate l configured as above is 1/2.
The porous substrate 1 is punched out into a disk shape, subjected to ultrasonic cleaning in a trichloride solution, and then dried. This porous substrate 1 is shown in FIG.

Next, nickel powder with a diameter of 1 μm or less (hereinafter referred to as submicron diameter) and nickel powder with a diameter of 3 μm are mixed in a volume ratio of 1:1.
The aqueous solution dissolved in water was applied approximately evenly to the disk surface of the porous substrate l shown in Fig. 2, dried at room temperature, and then sintered in a hydrogen atmosphere to form a third A first nickel layer II shown in the figure is formed. The sintering conditions at this time are too
About 1 hour at 0°C.

Next, the surface of the first nickel layer 11 is polished to a flat surface as shown in FIG. 4, and the protrusions present on the first nickel layer 11 are removed. Grid paper #600 was used as this polishing agent. This is followed by ultrasonic cleaning for 10 minutes in deionized water and trichlorethylene, followed by drying at room temperature.

Next, approximately 50 mg of nickel powder with a diameter of 3 μm was placed on the surface of the first nickel layer 11 of the porous substrate I so as to have a uniform thickness, and then pressed with a pressure of approximately 700 kg/cm″G. Then, this is sintered in a hydrogen atmosphere to form the second nickel layer 12 as shown in Fig. 5. Sintering at this time is performed at 750° C. for 1 hour.

Next, nickel powder with a submicron diameter is rubbed into the surface of the second nickel layer 12 of the porous substrate l, and approximately 700 kg/
Press with a contact force of cm"G.

Thereafter, nickel powder having a submicron diameter is rubbed in and sintered in a hydrogen atmosphere to form a third nickel layer 13 as shown in FIG. Sintering at this time is performed at 750° C. for 1 hour.

By going through the above steps, the surface of the porous substrate 1 is coated with the first nickel layer 11. The hydrogen electrode thin film 2 consisting of the second nickel layer 12 and the third nickel layer 13 has a thickness of approximately 100 μm.
The surface is formed with uniform pores with a diameter of 1 to 3 μm.

In the above embodiments, stainless steel is used as the porous substrate, but the porous substrate is not limited to this, and materials such as nickel and copper may also be used. Since a porous substrate made of nickel is manufactured by sintering using Ni powder, the particle shape of the Ni powder is angular, so that the pore diameters are irregular, ranging from 3 μm to 50 μm.

However, since it has better adhesion to the Ni Paug electrode, its hydrogen resistance is superior to that of stainless steel.

Further, since the particle shape of the copper powder in a copper porous substrate is round, the shape of the pores can be made neat, but the pore diameter is approximately 3 μm to 40 μm, similar to that of Ni. In addition,
When this copper porous substrate comes into contact with oxygen, it oxidizes and Cu
Since it is an insulator of 1O, it is ideal for hydrogen electrodes.

Next, an example of manufacturing the solid electrolyte thin film 3 will be described.

First, in the first production example, a thin film of solid electrolyte is applied to a thickness of 10 μm on the upper surface of a hydrogen electrode thin film 2 formed on the surface of a porous substrate l.
to form. For this purpose, an electron beam evaporation method is used, and a turbo pump is used for the evaporation at a vacuum level of 10-”m.
The substrate temperature was varied from room temperature to 580° C. at m Hg, and the deposition rate was controlled by a controller.

Note that a single crystal L a P s was used as the solid electrolyte, and the conditions for forming the thin film of the solid electrolyte were a substrate temperature of 500° C., a vapor rate of 20 people/sec, an acceleration voltage of 3, and OkV.

When a thin film of solid electrolyte is formed as described above, a film free from pinholes can be obtained.

Next, a second manufacturing example of the solid electrolyte thin film 3 will be described.

The second fabrication example adopted the resistance heating method, the vacuum level was set to 10 mmHg using the same pump as above, and the substrate temperature was set to 400°C.The deposition rate was 3 to 5 persons/S, and the vacuum was set to 10 mmHg. A thin film with a thickness of 10 μm was obtained in 6 hours.The thin film obtained by this method also had no pinholes as in the above example.

In addition to Lad, the solid electrolytes include La +
-as r F 3-x, especially Lao, ss
As a result of X-ray diffraction of a thin film using S r o, esF *, *s as raw materials, only the L a F 3 peak was observed. From this, the RWX of this solid electrolyte is LaF,
It can be confirmed that it is not a mixture of SrF and SrF.

Next, a third manufacturing example of the solid electrolyte thin film 3 will be described. The third production example uses magnetron sputtering at a substrate temperature of 400°C and 5.3X in an argon gas atmosphere.
Sputtering was performed for 40 hours using L a F s powder as a target under a pressure of 10 mmHg.
A thin film with a thickness of 10 μm was obtained.

As a result of X-ray diffraction of this thin film, it was found to be polycrystalline LaF3 with poor crystallinity.

Note that the raw material for the solid electrolyte thin film is not limited to L a F s, and the following materials may also be used.

(b) L a o, ss S r o, os F y
, ss (b) L a o, ss S r o, +o
F t,s.

(c) L a o, ss B a o, os F t
, ts (d) L a o, so B ao, +o F
t, ts Even if the thin film obtained by the above magnetron sputtering has a complicated composition, the obtained thin film has a composition that is roughly the same as the raw material, so Lao, siS r o,
Suitable for thin films such as osFz and es.

Next, a fourth manufacturing example of the solid electrolyte thin film 3 will be described.

In this fourth manufacturing example, La is formed by thermally decomposing an organometallic compound containing La and F in its molecules on the surface of the third nickel layer 13 configured as shown in FIG.

A thin film of F3 was formed. The above organometallic compound is Lant
It is a compound called hanun fod.

The structural formula of this compound is as follows.

[CPs-CFt CFz-C-Cut-C-CH--
(CH-)t:]LaThe film forming conditions are substrate temperature 600
℃, the organometallic compound was kept at 230℃, and argon gas (Ar) was used as a carrier gas at a flow rate of f00m&/m.
A thin film of L a F 3 is obtained by moving the organometallic compound vapor to the surface of the porous substrate l in the reactor and reacting with it.

Next, a fifth manufacturing example of the solid electrolyte thin film 3 will be described.

This fifth manufacturing example is a third manufacturing example constructed as shown in FIG.
Using a high frequency sputtering device, the surface of the nickel layer 13 is
The sputtering conditions were a substrate temperature of 800°C, an argon pressure of 5.3xl O'ml Hg, and sputtering for 40 hours using itria-stabilized zirconia as a target. Laminate.

In addition, cerium oxide or the like may also be used.

Finally, an example of manufacturing the oxygen electrode thin film 4 will be described.

In the first manufacturing example, a thin electrode film for oxygen is created from a perovskite compound.
o, es r 0.4COOX). This includes cobalt acetate (CH3COO) z C0.4 Ht
Using O, lanthanum acetate (CHsCOO) tL a, and strontium acetate (CH2OOO) vs r as raw materials, the powders were weighed and mixed according to the composition ratio of L a o, sS r O, 4COOx, and heated at 1000°C in an oxygen atmosphere. and baked for 5 hours. The electrical resistivity of the perovskite compound thus produced was 4.4 Ωcm.

There are three methods for forming an oxygen electrode thin film using the perovskite compound prepared as described above.

(1) Dissolve a perovskite compound in propylene glycol, apply it to the surface of the solid electrolyte thin film 3, apply a slight pressure, and heat it in an oxygen atmosphere at a temperature of 300°C.
The electrode thin film 4 is obtained by baking for a period of time.

(2) A perovskite compound and platinum black are mixed in a ratio of 3=1 and dissolved in propylene glycol. Thereafter, this liquid is applied to the surface of the solid electrolyte thin film 3 and fired under the same conditions as above to obtain the electrode thin film 4.

(3) A perovskite compound is formed on the surface of the solid electrolyte thin film 3 using a high frequency sputtering device. This is carried out for about 2 hours under a pressure of I x 10 mmHg of argon gas and at a deposition rate of 0.5 μm/hour to obtain an electrode thin film 4 with a thickness of about 1 μm.

The perovskite compound has performance equivalent to that of platinum, but is much cheaper than platinum.

Next, a second manufacturing example of an electrode thin film for oxygen will be described.

In this second production example, Ag powder is dissolved in propylene glycol, and this solution is applied to the surface of the solid electrolyte thin film 3.
An electrode thin film is obtained by baking in an oxygen atmosphere at a temperature of 300° C. for 8 hours while applying a slight pressure force.

Next, a third manufacturing example of the oxygen electrode thin film 4 will be described.

In the third production example, an electrode thin film is obtained by dissolving chloroplatinic acid (HzP t C12e) in propylene glycol, applying this in the same manner as above, and baking under the same conditions as above.

As mentioned above, porous substrates that can be made by hand generally have pore diameters that vary, for example, from 0.5 to 40 μm, and when hydrogen and oxygen electrodes and solid electrolyte thin films are laminated on the surface of this porous substrate, If there were large holes in the curtain plate, pinholes were likely to form in the solid electrolyte above the hole.

However, when hydrogen and oxygen electrodes and solid electrolytes were created as described above, pinholes no longer occurred. Due to the difference in oxygen partial pressure between the solid electrolyte and the fuel cell,
It constitutes a type of oxygen agrochemical battery, in which an electromotive force is generated at both ends of a solid electrolyte. The electromotive force Eo at this time is expressed by the following formula.

Eo-(RT/4F)XI2 n (P, /Pt) From the above equation, the electromotive force Eo increases in proportion to the ratio of oxygen partial pressures.

In the formula, R is a gas constant, T is an absolute temperature, F is a Faraday constant, and P l + P t are oxygen partial pressures across the solid electrolyte.

From the above equation, if a pinhole is formed in the solid electrolyte, the ratio of oxygen partial pressure will be small, and the electromotive force Eo will be small. However, by manufacturing a solid electrolyte that does not have pinholes as in the present invention, The electromotive force no longer decreases.

The single cell structure configured as described above is housed in a conductive cell case so that the hydrogen electrode thin film 2 of the single cell structure and the cell case 5 are electrically connected, and
A conductive end separator 7 is attached to the oxygen electrode thin film 4 side to electrically connect the thin WA 4 and the end separator 7, and an insulator 6 is placed between the cell case 5 and the end separator 7. The fuel cell main body 20a is constructed by interposing the fuel cell main body 20a.

Porous substrate 1 of cell case 5 of this fuel cell main body 20a
As shown in FIG. 1, conductive separators 7.8 are electrically connected to the sides. The oxygen electrode thin film 4 of the single cell structure is electrically connected to the separator 8 in the same manner as described above, and the hydrogen electrode thin film 2 and the cell case 5 are electrically connected to the separator 8.
are also electrically connected, and an insulator 6 is interposed between the separator 8 and the cell case 5 to form a fuel cell main body 20b.

Similarly, the fuel cell bodies 20c, 20d, . . . are stacked, and the fuel cells can be connected in series by simply stacking the fuel cell bodies 20a, 20b, . . . with a single cell structure. Then, oxygen is supplied through the air inlet 9 of the separator 7.8, and hydrogen is supplied through the air inlet 10 of the cell case 5, thereby generating electricity.

H1 Effects of the Invention As described above, according to the present invention, a first electrode thin film, a thin solid electrolyte film that does not generate pinholes, and a second electrode thin film are sequentially formed on the surface of a porous substrate. Since the single-cell structure was formed using the same method, a single-cell structure with a small voltage drop can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a cell stack part of a fuel cell for explaining an embodiment of a solid oxide fuel cell of the present invention, and FIG.
6 are enlarged cross-sectional views showing the manufacturing process of a hydrogen electrode thin film, and FIG. 7 is a diagram showing the principle of a stacked fuel cell. DESCRIPTION OF SYMBOLS 1...Porous substrate, 2...Hydrogen electrode thin film serving as a first electrode thin film, 3...Solid electrolyte thin film, 4...Second electrode thin film
5...Cell case, 6...Insulator, 7°8...Separator, 20a. 0 b, 20c...Fuel cell main body. Figure 1 Longitudinal cross-sectional view of main parts 0a 1 Porous substrate 2, hydrogen electrode thin (first electrode thin film) 3, solid electrolyte Wl@4 oxygen electrode thin (second electrode thin film) 5・Cell case 6・Insulator 7 B・Separator 20b・Fuel cell main body Figure 2: Enlarged sectional view of essential parts Figure 4: Enlarged sectional view of essential parts Figure 5: Enlarged sectional view of essential parts

Claims (1)

[Claims] (1) On the surface of a porous substrate, mix equal amounts of nickel powder with a submicron diameter and nickel powder with a diameter of ~3 μm, dissolve it in water, and apply it to a uniform thickness. After pressing and sintering, the coated part is formed, and the surface of the coated part is polished and flattened, and then nickel powder with a submicron diameter is rubbed on it, pressed, and then sintered to form the surface. An electrode layer for hydrogen having fine and uniform pores is formed on the electrode layer, a solid electrolyte thin film without pinholes is laminated on the electrode layer, and an electrode thin film for oxygen is laminated on the solid electrolyte thin film. A solid oxide fuel cell is characterized in that it consists of a stack of single cells.