JPH0381972A - Manufacture of solid electrolyte for fuel cell - Google Patents

Abstract

PURPOSE:To accomplish mass production of dense solid electrolyte in the form of thin film within a short time by placing calmly a slip consisting of specified components in a moisture-absorptive mold for a certain time, allowing to grow to a fillet having a specified thickness, and drying it and baking. CONSTITUTION:A slip is composed of fine powder of stabilized ZrO2, solvent, and deflocculating agent. For ex., ZrO2 consisting of particulate having particles size of 0.03mum obtained by turning 8mol% Y2O3 in solid solution and stabilizing is dissolved in distilled water, and thereto a deflocculating agent such as HCl is added. After this slip is poured in recesses 13, 13 provided in a plaster plate 10, it is put in a standstill for two sec. This standstill time is related to the fillet thickness formed, which can be determined through calculation. After elapse of a certain period of time required to generate fillet thickness, the plaster plate 10 is rotated to remove the slip in fluidifying. Then the fillet layer is dried and separated from the plaster plate 10, followed by baking at a temp. between 1000-1500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a solid electrolyte for a fuel cell using a solid electrolyte.

(Prior Art and Problems to be Solved by the Invention) Recently, research and development of fuel cells using solid electrolytes as shown in FIG. 14 have been carried out. In this fuel cell 1, a solid electrolyte 4 is disposed between heat-resistant mullite tubes 2a and 2b via O-rings 3a and 3b.

On one side of this solid electrolyte 4 is a supply pipe 5 for supplying hydrogen H2.
A is facing the other side of the solid electrolyte 4, and a supply pipe 5b for supplying oxygen 02 is facing the other side of the solid electrolyte 4. An anode 6a made of a porous nickel plate is provided on one side of the solid electrolyte 4, and a cathode 6b made of a porous nickel plate is provided on the other side of the solid electrolyte 4.

Solid electrolyte 4 is porous ZrO stabilized with Y2O3
2, and a supply pipe 5 is connected to the anode 6a side of the solid electrolyte 4.
Hydrogen H2 is supplied from a, and the cathode 6 of the solid electrolyte 4
When oxygen 02 is supplied to the b side from the supply pipe 5b, an ionic reaction occurs in the solid electrolyte 4, and the anode 6a,
Voltage is generated across the cathode 6b, but if fuel gas H2,02 leaks, it will not only reduce efficiency but also pose a risk of explosion, so the film thickness of the solid electrolyte 2 is set to 200 μm to 300 μm. There is a need to. However, as the film thickness increases, the resistance to ion conduction increases, so it is desired to reduce the film thickness of the solid electrolyte and to make the porous film denser. An electrochemical vapor deposition method has been proposed as a method for manufacturing this solid electrolyte, but although it is possible to form a thin film, it is incomplete in sealing pinholes, etc., and is not suitable for use as a solid electrolyte in fuel cells. It takes an extremely long time to create a sufficient number of fuel cells, and the problem remains that fuel cells cannot be mass-produced in a short period of time.

(Object of the Invention) The present invention has been made in view of the above circumstances, and aims to enable mass production of a solid electrolyte for fuel cell slow cells in a short time that is denser and thinner than conventional ones. purpose.

(Means for Solving the Problems) In order to achieve the above object, a method for manufacturing a solid electrolyte for a fuel cell slow cell according to the present invention is characterized in that it is configured as claimed in the claims.

(Function) According to the method for manufacturing a solid electrolyte for a fuel cell delay cell according to claim 1 of the present invention, a slip serving as a raw material for the solid electrolyte is placed in a hygroscopic mold, and a time period during which the slip can be inked is placed. When the mold is held still, the slip is deposited on the bottom of the mold.

Since the resting time of this type is proportional to the square of the thickness of the inked layer, the resting time for forming the inked layer of a predetermined thickness can be calculated based on the desired thickness. When the mold is then rotated, the fluidized slip is blown away from the mold by centrifugal force, leaving a very thin, flat slip at the bottom of the mold. Since the slip contains ZrO2, by drying and firing this inked slip, it is possible to obtain a solid electrolyte for a fuel cell delay cell that is thin, flat, and has dense porosity. .

According to the solid electrolyte for a fuel cell delay cell according to claim 2 of the present invention, three slip layers are formed in the mold, and the resting time of the second slip is longer than the resting time of the first slip. Because of its length, the inking layers of the second slip are thicker than the inking layers of the first slip, which are laminated above and below the layers of the second slip. When this three-layer dried slip is fired, a solid electrolyte with a thin outer surface and a thick middle layer is formed.

(Example) Hereinafter, a method for manufacturing a solid electrolyte for a fuel cell slow cell according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a method for manufacturing a solid electrolyte according to a first embodiment, and numeral 10 indicates a gypsum board as a hygroscopic mold. The gypsum board 10 is rotatable about a rotation center axis 11. The gypsum board 10 has a flat part 12 orthogonal to the rotation center axis 11, and the flat part 12 has a solid electrolyte-shaped recess 1 with the rotation center axis 11 as the center of symmetry.
3.13 is drilled. The recesses 13, 13 have bottoms 13a, 13a of uniform depth.

A slip 14 for forming the solid electrolyte of the fuel cell is injected into the recesses 13a, 13a while the gypsum board 10 is kept stationary. For the raw material of slip 14, 8 m
Particle size 0 stabilized by solid solution of o1% Y20a
．． ZrO2 powder consisting of fine particles of 0.3 μm is used. Distilled water (pH 5, 8) as a solvent for ZrO2
is used, but the solid content ratio range of the slip is 5% by volume ~
In this example, the ratio of the solid content of the slip to the distilled water is set to 25 volume %.
(Product name: Dai-Kogyo Seiyaku Co., Ltd.) is used. As the peptizer, inorganic electrolytes such as Hc 1 , CH3C0OH, and NH4OH, or polymer electrolytes such as polyacrylic acid, polymethacrylic acid, and their ammonium salts and sodium salts may be used. The range of addition to the solid content is set at 0.1% by weight to 0.5% by weight, but in this example it is set at 0.4% by weight.

After injecting the slip into the recess 13.13, when the plaster board 10 is kept still for 2 seconds (predetermined time), the distilled water in the slip 14 is absorbed into the bottoms 13a, 13a of the recess 13.13, and the slip 14 is The solid content is at the bottom 13a of the recess 13.13.
, 13a is inked.

Here, the value of 2 seconds is calculated backward from the film thickness of the molded body to be obtained by firing. That is, the thickness of the ink layer 14a is determined by considering the shrinkage rate when the ink layer 14a of the slip 14 shrinks after firing, and then the square of the film thickness of the ink layer 14a is the thickness of the gypsum board 10. The rest time is calculated based on the fact that it is proportional to the rest time. In this embodiment, the rest time is 1.
In order to obtain a molded body of 20 μm, the mold was left at rest for 2 seconds.

Two seconds after injecting the slip 14, the gypsum board 10 is rotated at high speed around the rotation center axis 11, and the recesses 13,
The fluidized slip 14b in 13 is drained from the recess 13.13. Once the slip 14b has been drained from the recess 13.13, the gypsum board 10 is stopped and the ink layer 14a is dried. When the inking layer 14a of the slip 14 inked on the bottom of the recess 13.13 dries, the dried inking layer 14
The molded body a was taken out from the recess 13.13 and
Heat up to 1000 degrees C with a temperature gradient of degrees C. When the temperature reaches 1000 degrees Celsius, the temperature is increased to 1500 degrees Celsius with a temperature gradient of 100 degrees Celsius per hour. After that, the molded body was baked at a temperature of 1500 degrees Celsius for 2 hours, resulting in a thin film of 120
A ZrCh cell (solid electrolyte for fuel cells) of μm (+-2%) is completed.

The stabilized ZrO2 film thickness is between 50 μm and 200 μm.
It may be set in μm.

Figure 13 is a graph showing the voltage and current characteristics of such a ZrO2 cell, and the voltage between the terminals of the fuel cell is at most 1
Bolt became strong. Also, the current density is 250 volts between the terminals.
At millivolts, it was approximately 1500mA/cm2. Note that the gypsum board 10 used in this example has a pair of recesses 13.
13, but it is of course possible to form one recess 13 centered on the rotation center axis 11, as shown in FIG.

A method for producing a solid electrolyte for a fuel cell according to a second embodiment of the present invention is to form a solid electrolyte in three layers, and in this embodiment, two types of slips are used.

The first slip was made by dissolving zrO2 powder with a particle size of 0.02 μm stabilized with 8 mo1% Y2O3 in distilled water as a solvent at a solid content ratio of 15 volume%, and further with a solid content ratio of 0.02 μm. A dissolving agent containing 3% by weight of polyacrylic acid ammonium salt is used. Second
The slip used is the same as the slip used in the first embodiment.

A recess 13 in the plaster board 10 used in the first embodiment,
After pouring the first slip into the plasterboard 13, the gypsum board 10 is allowed to stand still for 2 seconds, which is the resting time calculated based on the thickness of the inked layer to be attached, 20 μm. Once the first slip is deposited on the bottom of the recesses 13.13, the plasterboard 10 is rotated to drain the fluidized first slip from the recesses 13,13. After draining the first slip, the gypsum board 10 is stopped and the ink layer of the first slip is dried.

After the adhesive layer of the first slip has dried, the second slip is again poured into the recesses 13.13 of the plaster board 10, and the plaster board 1
0 for 8 seconds and apply the second slip onto the inking layer of the first slip.
form the inking layer of the slip. This forms an inked layer that is thicker than the inked layer of the first slip. Next, the gypsum board 10 is rotated to drain the flowing portion of the second slip and dry it.

Thereafter, the first slip is further poured into the recess 13.13, the plaster board 10 is held still for 2 seconds, and the first slip is poured to form a third filler layer on the filler layer of the second slip. After the formation of the flesh layer, the plasterboard 10 is rotated again to drain the fluidized first slip from the recesses 13.13 again.

After the fluidized first slip is drained, the molded body in which the first and second slips are formed in three layers is dried.

After drying the molded body, it is removed from the recess 13.13 and fired.

In firing the compact, the temperature is raised to 1000 degrees Celsius with a temperature gradient of 300 degrees Celsius per hour. The temperature is raised at 120 degrees C per hour between 1000 degrees C and 1500 degrees C, and then baked at 1500 degrees C for 2 hours, the outer layer is 20 μm and the inner layer is 140 μm.
A three-layer molded product of μm size is completed.

Next, experimental results of the present invention will be explained.

In the experimental method of the present invention, Y
Zr○2 powder stabilized by dissolving 8 mo1% of 2O3 in solid solution was used. Distilled water (pl(5,8)) was used as a solvent. As a peptizer, polyacrylammonium salt-based Ceramo D-134 (trade name: Dai-Kogyo Seiyaku Co., Ltd.) was used.
It was adjusted to a predetermined concentration (5, 15, 25 volume % Zr○2). The slip characteristics were evaluated based on the change in viscosity depending on the amount of peptizer added and the deposition rate.

The sinterability of the molded body for solid electrolyte is determined at each firing temperature (10
It was investigated by bulk density at 00 to 1500 degrees Celsius.

In addition, a prototype fuel cell was manufactured and evaluated based on voltage-current characteristics.

In the experiment, a slip casting method was used in which slip was poured into a mold, ink was applied to the mold, and then the slip was drained.

When a compact sintered body is obtained by firing the compact after forming the compact by this slip casting method, the dispersibility of particles in the slip can be determined by the viscosity of the slip.

FIG. 10 shows the relationship between slip viscosity and the amount of peptizer added. As shown in this figure, the viscosity of the slip is as low as 100 mPa-5 or less even when no peptizer is added. This is considered to be because impurity chlorine contained in ZrO2 contributes to dispersion. As the peptizer is added, the viscosity increases once due to the agglomeration of particles in any slip, and when a certain amount or more of the peptizer is added, the viscosity decreases again due to the dispersion of the ZrO2 particles.

Polyacrylic acid ammonium salt (-CH-CH2-C00NL), which is the main component of defusing agents. is (-CH-C
H2-COONI(a). -(-C)l-CH2-C
It dissociates during slipping and adsorbs to the particles according to the formula ``OO-) 10nNH4''.As a result, the particles are stabilized by electrostatic steric repulsion.However, if the amount of this peptizer added is When there is a shortage of the polymer ion (-CH-CH2-COO-) 7, bridge aggregation occurs.

Incidentally, as the stirring time increases, the ZrO2 particles in the slip gradually loosen. Therefore, the viscosity of the slip decreased with the minimum amount of peptizer added to reduce the viscosity. Therefore, in the measurement of the deposited layer thickness described below, a slip to which an excess amount of peptizer was added than when the viscosity was at the minimum value shown in FIG. 10 was used.

Figure 11a shows the deposition time (1) and the thickness of the deposited layer (L) when the slip is deposited in one direction (direction of gravity) on the plaster mold.
and the square of the deposited layer thickness (L2). From this figure, it can be seen that the higher the slip concentration, the greater the ratio of the increase in the thickness of the deposited layer to the depositing time. Further, as shown in FIG. 11b, when the slip stability is good, a proportional relationship is established between L2 and t, so film thickness control during film formation is performed based on this diagram.

FIG. 12 shows the relationship between the sintering temperature and the sintering of the sample. The sample prepared by slip with peptizer added has the best sinterability, with a bulk density of 5.5 g/m2 (relative density 85%) at a sintering temperature of 1100 degrees C, and a bulk density of 5.5 g/m2 at 1500 degrees C. It reached 85g/m2 (98%).

When no peptizer was added, the particle size distribution of the Zr02 particles in the slip was wide, and coarse particles were present in the compact.
It is thought that the sinterability was poor.

Based on the above results, Zr○ for fuel cells was prepared using 25% by volume slip added with peptizer, which had the best sinterability.
We made a prototype of 2 cells.

3 to 9 show the molding process.

The molded body was produced according to the following process.

■25M x 25m coated with Vaseline to prevent slippage from flowing sideways! A mold 20 made of urethane No. 1 is placed on a plaster board 21, and a slip 21 is poured into the mold 20 (FIG. 3).

■Based on the inking data shown in Figures 11a and 11b, the plaster mold is kept stationary for a predetermined period of time and the slip 21 is applied to the plaster mold 21 to form the inked layer 21a (see Figure 4). The slip 21b is drained (see Fig. 5).

(2) Next, the area that will become the membrane part is remasked with silicone rubber 22, and the reinforcing part of the membrane is cast (see FIGS. 6 to 8).

(2) After drying, remove the molded body 23 from the frame (see Figure 9).

(2) The molded body 23 thus produced was fired at 1500 degrees C to produce a ZrO2 cell.

FIG. 13 shows the voltage-current characteristics of the manufactured ZrO2 cell.

When measuring voltage-current characteristics, use Laser as a cathode.
, 5Sre, JnO3, and N1p (
A paste of +8 mo1% Zr02 (10 wt%) cermet was applied to both sides of the membrane, baked at 800 degrees Celsius, and measured at 1000 degrees Celsius. still,
In the figure, for comparison, Ar
As can be seen from these figures, which also show the results from the Argonne Institute, the film thickness is approximately 140 μm and is sufficiently dense, so that the voltage-current characteristics are similar to those of the Argonne Institute.
The results are as good as those from national laboratories.

As described above, when a membrane is produced by the slip casting method, it is difficult to take out the membrane itself independently, but it has become clear that a dense membrane can be produced by attaching reinforcing parts. Further, by lapping the film after firing, the film thickness can be further reduced.

(Effects of the Invention) As explained above, according to the method for manufacturing a solid electrolyte element for a fuel cell according to the present invention, the film thickness of the solid electrolyte used in a fuel cell can be made thinner than before, and moreover, it is porous. Since the solid electrolyte can be made denser and the solid electrolyte for fuel cell slow cells can be produced more easily than before, mass production becomes possible.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a gypsum board used in the method for manufacturing a solid electrolyte for a fuel cell delay cell according to an embodiment of the present invention, and FIG. 2 is a schematic explanatory diagram showing a modification of the gypsum board in FIG. 3 to 9 are explanatory diagrams of experiments of the present invention, in which FIG. 3 is an explanatory diagram of a state in which slip is poured into a mold, FIG. 4 is an explanatory diagram of a state in which slip is inked in a mold, Fig. 5 is an explanatory diagram of the state in which the slip inside the mold is removed, Fig. 6 is an explanatory diagram of the state in which silicone rubber is placed on the ink layer applied to the bottom of the mold and masked, Fig. 7, Figure 8 is an explanatory diagram of the reinforcing part of the membrane being cast into the mold shown in Figure 6, Figure 9 is an explanatory diagram of the molded body obtained in the experiment, and Figure 10 is the viscosity of the slip and the addition of peptizer. Graphs showing the relationship between amounts; Figures 11a and 11b are graphs showing the relationship between the resting time for inking in the mold and the thickness of the inking layer; Figure 12 is a molded body obtained by firing the slip. FIG. 13 is a graph showing the voltage-current characteristics of the ZrO2 cell used in the experiment. FIG. 14 is an explanatory diagram showing a conventional solid electrolyte for a fuel cell slow cell. IO... Gypsum board 11... Rotation center axis 13... Recess 14... Slip 14a... Filling layer Figure 1 Figure 7 Figure Figure Figure Zr02B Das inferior solution Kou Qi 19 more L Bi L2 (Pm
2) Figure 12: Private bed (0C) Figure 13: Electric power supply/mA cm' Figure 4

Claims (2)

[Claims] (1) A solid electrolyte forming slip consisting of stabilized ZrO_2 fine powder, a solvent, and a peptizer is poured into a hygroscopic mold, and the mold is molded based on the desired thickness of the inking layer. After allowing a part of the slip to adhere to the bottom of the mold by allowing it to stand still for the calculated resting time, the fluidized slip is drained from the mold to dry the slip in the inked area, and the dried A method for producing a solid electrolyte for a fuel cell, comprising taking out a slip from the mold and firing the taken out dried slip. (2) In the method for producing a solid electrolyte for a fuel cell delay cell according to claim 1, after pouring the first slip into the mold, the resting time is calculated based on the desired thickness of the deposited layer. keeping the mold stationary and depositing a portion of the first slip on the bottom of the mold;
Thereafter, the fluidized first slip is drained from the mold, the inking layer of the first slip is dried, and the second slip is again poured into the mold, and the mold is replaced with the first slip. A second slip is inked on the inked layer of the first slip by letting it stand still for a time longer than the resting time of the slip, and then the second slip in a fluid state is drained, and
The inking layer of the second slip is dried, and the first slip is poured into the mold and is allowed to stand still for a period of time during which the first slip is held still, and the first slip is replaced with the second slip. After inking on the inked layer, the first slip in a fluid state is drained from the mold again, and the molded body in which three inked layers of the first and second slips are formed is dried. A method for producing a solid electrolyte for a fuel cell, which comprises the step of taking out the molded body from the mold and firing the molded body.