JPH0381963A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To obtain a unit cell whose voltage drop is small by stacking a first electrode thin film, a pinhole-free solid electrolyte thin film, and a second electrode thin film on the surface of a porous base plate in order to form a unit cell structure. CONSTITUTION:A metal plating layer is formed on the surface of a porous base plate 1, and the plating layer is polished to make the surface uniform, and immersed into an acidic solution to remove the plating layer, then metal plating is conducted again to form a porous electrode thin film 2 having fine, uniform pores. A pinhole-free solid electrolyte thin film 3 is stacked thereon, and furthermore an electrode thin film 4 is stacked on the solid electrolyte thin film 3 to form a unit cell. The periphery of each pore on the surface of the porous base plate is extruded toward the inside of the pore, and the inner diameter of the pore is made fine and uniform by the plating layer formed on the surface, and the solid electrolyte thin film is formed so as to block the pores. Pinholes caused by the breakage of the solid electrolyte thin film on the large pores are not produced and adverse effect on electromotive force caused by pinholes is avoided.

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.

B0 Summary of the Invention The present invention provides a solid oxide fuel cell having a stack of single cells, in which a metal plating layer is formed on the surface of a porous substrate, the top is polished and leveled, and then an acidic liquid is applied. The plating layer is removed by immersion in water, and a porous electrode thin film with fine and uniform pores is formed by further plating with metal.A solid electrolyte thin film without pinholes is laminated on the surface of the porous electrode thin film. A good fuel cell is constructed by laminating thin electrode films to construct a single battery cell.

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 type battery 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 (h) 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. It is composed of a manifold 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 6 uses a solid electrolyte.

Although it is constructed by combining an oxygen electrode and a hydrogen electrode, it has a drawback in strength. However, although strength can be ensured by a current collector plate provided outside the picture electrode after the unit cell structure is assembled, 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 From the relationship expressed by (the thickness of the electrolyte), it can be seen that the thinner the solid electrolyte is, the greater the voltage drop.However, in the conventional configuration, the thickness of the solid electrolyte is related to strength. It has to be formed to be somewhat thick, 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.

81 Means for Solving the Problems The solid oxide fuel cell of the present invention includes plating a metal on the surface of a porous substrate to form a plating layer, and blocking the pores by polishing the surface of the plating layer. In this state, the porous substrate is immersed in an acid solution to dissolve and remove the plating layer, and the surface of the porous substrate is plated with metal to form an electrode layer that makes the pores on the surface fine and uniform. The present invention is characterized in that a solid electrolyte thin film without pinholes is laminated on the surface, and an electrode thin film is laminated on the surface of the solid electrolyte thin film to constitute a single cell of the battery.

F1 effect By configuring as described above, the peripheral part of the pore on the surface of the porous substrate protrudes into the pore, and the inner diameter of the pore is reduced by the plating layer formed on the surface. By uniformizing the fineness and forming a thin film of solid electrolyte to fill these pores, we eliminate the occurrence of pinholes caused by the thin film of solid electrolyte breaking on the thick pores. It has the effect of eliminating negative effects on power.

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

Figure 1 is a vertical cross-sectional view of a solid oxide fuel cell main body stacked. In Figure 1, hydrogen electrode thin films (first electrode thin films) are sequentially formed on the surface of a stainless steel porous substrate l.
2. A single cell structure is constructed by laminating a pinhole-free solid electrolyte thin film 3 and an oxygen electrode thin film (second electrode thin film) 4.

Next, using the porous substrate l as a support structure, the hydrogen electrode thin film 2 is
The first manufacturing example will be described.

The porous substrate 1 was made of 5US316L, had a porosity of 40%, a nominal pore diameter of 0.5 μm, and a thickness of about 1 mm.

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

First, in the first step, as shown in FIG.
form 4. As a result, the pores having a diameter of about 4 μm or less are substantially closed by the metal plating layer 14. On the other hand, the large-diameter holes become small-diameter holes by the thickness of the metal plating 14. In addition, the plating conditions at this time were the same plating bath as Cu5O.
,,220g/Q, HtS0450g/Q temperature-room temperature, current 10-30mA, time 60-120 minutes.

Next, as a second step, the surface of the metal plating layer 14 of the porous substrate 1 is polished using a sandpaper 7.

In this polishing operation, the top of the metal plating layer 14 is first polished using #220 sandpaper until the surface of the underlying stainless steel porous substrate l is visible. Thereafter, it is sequentially polished using fine sandpaper, and finally it is polished using #600 sandpaper.

As a result of this polishing work, the holes that are closed by the metal plating layer 14 remain unchanged, but the holes that are not closed are plastically deformed and the stainless steel material on the side of the hole extends laterally, so-called stainless steel material. 3), the metal plating layer 14 on the peripheral side of the hole sticks together, and the hole is closed as shown in FIG.

Next, as a third step, the porous substrate 1 described above is heated with nitric acid (1-
I N O 3) Immersion in aqueous waves and the metal plating layer 14
Dissolve and remove. As a result, large-diameter pores on the surface of the porous substrate 1 disappear, and uniform pores 15a and 15b of 4 to 6 μm in size are formed on the surface of the porous substrate 1 as shown in FIG. .

In the fourth step, the above-mentioned holes 15a of 4 to 6 μm are formed.

A nickel electrode layer 16 having a thickness of 1 to 2 μm is plated on the surface of the porous substrate 1 having a structure 15b, which becomes a hydrogen electrode thin film.
As shown in FIG. 5, a porous substrate 1 is constructed having a processed surface portion in which large-diameter holes are eliminated and small-diameter holes 17a and 17b are left.

Although stainless steel has been used as the porous substrate in the above embodiments, a nickel material may also be used. Since nickel porous substrates are manufactured by sintering using Ni powder,
Since the particle shape of the Ni powder is angular, the pore diameters are irregular, ranging from 3 μm to 50 μm. However, since it has better adhesion to the Ni powder electrode, its hydrogen resistance is superior to that of stainless steel.

Next, another manufacturing example of the electrode thin film 2 for hydrogen will be described.

In this production example, after forming the electrode layer 16 in the above production example, platinum (Pt) is laminated to a thickness of 200 μm on the surface of the electrode layer 16 by sputtering.

Sputtering was carried out using a high-frequency sputtering apparatus in an atmosphere of argon gas under a pressure of 5 x 10-'' mmHg for 1 hour using Pt as a target.

When Pt is coated on the electrode layer I'6 in this way,
Because platinum acts as a catalyst, the reaction can be accelerated as shown in the following chemical formula, making it easier to extract large currents.

02-　10Hz→HtO+　2　e The above is an example of manufacturing the electrode thin film 2 for hydrogen.

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 coated 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 1.
to form. For this purpose, an electron beam evaporation method is used, and a turbo pump is used for the evaporation to achieve a vacuum level of 10-11.
mm Hg, vary the substrate temperature from room temperature to 580 °C,
The deposition rate was controlled by a controller.

Note that single crystal LaFs is used as the solid electrolyte, and the conditions for forming the thin film of the solid electrolyte are a substrate temperature of 500° C., a vapor rate of 20 in/sec, and an accelerating voltage of −3.0 kV.

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 employs the resistance heating method, the vacuum level is set to IO-'mm Hg using the same pump as above, and the substrate temperature is 40°C.
The temperature was 0°C. And the deposition rate is 3 to 5 people/S, about 5
A 10 μm thick film was obtained in ~6 hours. The thin film obtained by this method also has no pinholes, as in the above example.

In addition to L a F 3, as a solid electrolyte, L
using a + -x S r F s-3, especially L
a0. As a result of X-ray diffraction of thin films made from ssS r o, esF x, and es as raw materials, only the L a F 3 peak was observed. From this, it can be confirmed that this solid electrolyte thin film is not a mixture of L a P s 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 LaF3 powder as a target under a pressure of 10-3 mmHg to form a 10μ
A thin film of m thickness 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 LaF is used as a raw material for the solid electrolyte thin film.

The following may also be used without being limited to:

(b) L a o, ss S r o, ns F 2
．． 15 (b) L a o, ss S r o, +o
Pt,g.

(c) L a o, ss B a o, oa F *
, ta (d) L a o, so B a o, +o
F t, t.

Even if the thin film obtained by the above magnetron sputtering has a complex composition, the obtained thin film has a composition that is roughly the same as the raw material, so Lao, esS r o, osF 2
．． Suitable for thin films such as SS.

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

In this fourth manufacturing example, an organometallic compound containing La and F in its molecules is thermally decomposed on the surface of the third nickel layer I3 configured as shown in FIG. 5 to form La.

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.

[CFa-CFt-CFt-C-CI(t-C-CHt
-(C11+)t)LaThe film forming conditions are substrate temperature 60
The temperature was 0°C, the organometallic compound was kept at 230°C, and argon gas (Ar) was flowed as a carrier gas M 100 m
A thin film of L a F s is obtained by moving the organometallic compound vapor to the surface of the porous substrate l in the reactor and causing a reaction.

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, as r 0.4COOX). This includes cobalt acetate (CHs COO) t C0・4H20
, lanthanum acetate (CH3COO) * La, strontium acetate (CH3COO), and S r were used as raw materials, and the powders were weighed and mixed Ea according to the composition ratio of La o, es r 11.4c 00 x, and placed in an oxygen atmosphere. 100
It was heated at 0° C. and IL'Jm was formed at 5 o'clock. The electrical resistivity of the perovskite compound created in this way is 4.4.
It was Ωcm.

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

(1) Dissolve the 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 at a ratio of 3:■ 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 performed under a pressure of txto-mmHg of argon gas at a deposition rate of 0.5 μm/hour for about 2 hours 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 (H, P t C12B) in propylene glycol, applying this in the same manner as above, and baking under the same conditions as above. .

As mentioned above, generally available porous substrates 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 the substrate had large holes, pinholes were likely to form in the solid electrolyte above the holes.

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)xc n (P, /P,) 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 Pl and Pt 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 film 4 and the end separator 7,
The fuel cell main body 20a is constructed by interposing an insulator 6 between the cell case 5 and the end separator 7. The porous substrate of the 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 this separator 8 in the same manner as described above, and the hydrogen electrode thin film 2 and cell case 5 are also electrically connected. An insulator 6 is interposed between them 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 from the air inlet 9 of the separator 7.8, and hydrogen is supplied from the air inlet IO of the cell case 5, thereby generating electricity.

H0 Effects of the Invention As described above, according to the present invention, a first electrode thin film, a pinhole-free solid electrolyte thin film, and a second electrode thin film are sequentially formed on the surface of a porous substrate. Since the single cell structure is 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.
5 to 5 are enlarged sectional views showing different methods of manufacturing electrode thin films for hydrogen, and FIG. 6 is a diagram showing the principle of a stacked fuel cell. l...Porous substrate, 2...Hydrogen electrode thin film serving as the first electrode thin film, 3...Solid electrolyte thin film, 4...Second electrode thin film
of? 1 [Oxygen electrode thin film to become a thin film, 5... Cell case, 6... Insulator, 7.8... Separator, 20a
, 20b, 20c... Fuel cell main body. Figure 1 Longitudinal cross-sectional view of main parts 0a l... Porous substrate 2... Electrode NI film for hydrogen (first electrode thin film) 3... Solid electrolyte thin film 4 - Electrode thin film for oxygen (second electrode thin film) 5, cell case 6, insulator 78, separator 20b, fuel cell main body

Claims (1)

[Claims] (1) Plating metal on the surface of the porous substrate to form a plating layer, polishing the surface of the plating layer to close the pores, and in this state immersing the porous substrate in an acidic solution for plating. The layer is dissolved and removed, a metal is plated on the surface of the porous substrate to form an electrode layer that makes the pores on the surface fine and uniform, and a pinhole-free solid electrolyte thin film is laminated on the surface of the electrode layer. , A solid electrolyte fuel cell characterized in that a single cell of the battery is constructed by laminating an electrode thin film on the surface of the solid electrolyte thin film.