JP2504467B2 - Molten carbonate fuel cell electrolyte plate and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrolyte plate for a molten carbonate fuel cell and a method for producing the same, and particularly to an electrolyte plate for a molten carbonate fuel cell which is smooth without warping and The present invention relates to a method for manufacturing the electrolyte plate.

[Conventional technology]

Generally, a molten carbonate fuel cell is a fuel cell of a type that operates at a high temperature of 600 to 700 ° C. with a mixed carbonate mixed with an alkali metal carbonate such as lithium carbonate and potassium carbonate as an electrolyte, and has a mixed carbonate at an operating temperature. The salt becomes molten, and the carbonate ion (CO ₃ ²⁻ ) plays a role as an ion conductor.

The basic configuration of this battery is that an anode (fuel electrode) and a cathode (oxidant electrode), which are electrodes, are provided on both sides of an electrolyte plate formed by holding the above-mentioned electrolyte in an electrolyte matrix material.
Are arranged respectively. A fuel gas chamber and an oxidant gas chamber are provided on the outside of these chambers. A predetermined battery voltage can be obtained by using a stacked battery in which a plurality of the batteries are stacked as a unit battery.

In a molten carbonate fuel cell having such a basic structure, a conventional general electrolyte plate is disclosed in JP-A-60-10187.
As proposed in Japanese Patent Publication No. 7, an electrolyte plate (tile) is prepared by applying a pressure of 0.1 to 0.6 ton / cm ² to a mixed powder of lithium carbonate and potassium carbonate at a temperature above their eutectic point (491 ° C.). And a mixture of an alkali carbonate (electrolyte) and an oxide (lithium aluminate) is heat treated at a temperature not lower than the melting point of the carbonate, as proposed in JP-A-60-105174. After that, it is cold-pressed and further heat-treated to form an electrolyte plate (tile). As proposed in JP-A-58-8775, a binder, a carbonate (electrolyte) and a matrix bone in an organic solvent are proposed. A method for forming a thin electrolyte plate by pressure-bonding a mixture of a material (lithium aluminate) and kneading
As proposed in Japanese Patent Laid-Open No. 58-119169, a mixture of an electrolyte-holding aggregate (lithium aluminate) powder and an organic binder is pressure-bonded to a pair of electrodes, and these surfaces are faced to each other. There is a method of forming an electrolyte plate by sandwiching, heating this to a temperature not lower than the melting point of the electrolyte, and further applying pressure.

[Problems to be solved by the invention]

The above conventional technique has various problems as described below.

That is, in the method proposed in Japanese Patent Laid-Open No. 60-101877, it is necessary to press at a temperature higher than the eutectic point of the electrolyte, so an electric furnace is required and the manufacturing process becomes long,
In addition, since pressure must be applied at a high pressure of 0.1 to 0.6 ton / cm ² , a large-capacity pressure molding machine (press) is required, resulting in a large equipment cost.

In the method proposed in JP-A-60-105174, a mixture of a carbonate (electrolyte) and an oxide (lithium aluminate) is heat-treated at a temperature not lower than the melting point of the carbonate (electrolyte), and then cold-pressed. Since the heat treatment is performed, the manufacturing process becomes very long, and an electric furnace is required as in the method proposed in JP-A-60-101877. Therefore, there is a problem that the equipment cost is increased.

In the method proposed in Japanese Patent Laid-Open No. 58-8777, there is a problem that the manufacturing cost is increased because the organic solvent is used.

In the method proposed in JP-A-58-119167, the electrolyte is finally heated to a temperature equal to or higher than the melting point of the electrolyte to melt it, and the aggregate (lithium aluminate) for retaining the electrolyte is impregnated with the electrolyte to form the electrolyte. Since a plate is formed, the above-mentioned JP-A-60
As in the methods proposed in Japanese Patent Laid-Open No. 101877 and Japanese Patent Laid-Open No. 60-105174, there is a problem that the manufacturing process becomes long and an electric furnace is required, resulting in high equipment cost.

An object of the present invention is to provide an electrolyte plate for a molten carbonate fuel cell that can be formed at a low temperature and a low pressure without using a liquid such as an organic solvent or water, and a method for producing the same.

[Means for solving problems]

The present invention has been made based on the findings described below. That is, there is a problem of the method proposed in the above-mentioned prior arts JP-A-60-101777, JP-A-58-105174, and JP-A-58-119169, that is, at a temperature above the melting point of the electrolyte. The reason why the electrolyte plate has to be formed is that the electrolyte plate is first prepared outside the battery, and then it is incorporated into the battery to raise the temperature again to construct the battery. is there.

The electrolyte is melted at a temperature equal to or higher than its melting point, and is naturally impregnated into a porous matrix-shaped matrix for holding an electrolyte, which holds the electrolyte. Therefore, if the electrolyte powder is filled between the electrolyte holding matrix molded body and the electrolyte holding matrix molded body at room temperature, it is incorporated into the battery as it is and the temperature of the battery is raised to 650 ° C which is the operating temperature. During the process, the electrolyte is naturally impregnated into the electrolyte retaining matrix molding. As a result, the temperature can be raised or lowered only once, and the manufacturing process can be shortened.

Further, as a result, the electrolyte plate has a structure in which the electrolyte is filled between the matrix-holding matrix molded body for electrolyte holding and the matrix-holding matrix molding for electrolyte holding at room temperature, as long as it can withstand handling such as assembling a battery. It will be good.

However, in reality, in the case where only the electrolyte is filled between the electrolyte holding matrix molded body and the electrolyte holding matrix molded body, the electrolyte powder particles are integrated with each other and the electrolyte powder and the electrolyte holding matrix molded body ( Since it is not adhered), the electrolyte powder spills during handling, resulting in a shortage of the electrolytic mass of the specified amount, and when the battery is assembled, the matrix-holding matrix for electrolyte retention and the electrolyte filling layer are misaligned. The problem of uneven impregnation remains.

These problems can be solved if the particles of the electrolyte powder and the electrolyte powder and the electrolyte-holding matrix molded body are integrated (bonded) together. Further, these constitutions can be realized by adhering the particles of the electrolyte powder and the electrolyte powder and the matrix-holding material for holding the electrolyte with a binder and integrating them.

The electrolyte plate having the above structure is manufactured by the following method.

Between at least two sheet-shaped electrolyte-holding matrix moldings, a mixture of an electrolyte and a binder (thermoplastic resin) is filled, and the temperature range (70 to 200 ° C.) above the softening point of the binder and before decomposition starts. ), And 50 kg / cm ²
Thermocompression bonding is performed under the following pressure conditions.

As a result, the particles of the electrolyte and the particles of the electrolyte and the sheet-shaped electrolyte-holding matrix molded article are bonded to each other through the binder, so that the sheet-shaped electrolyte holding matrix molded article and the electrolyte powder layer are integrated at a low temperature, The electrolyte plate having the above structure can be manufactured at low pressure and without using a solvent.

That is, the electrolyte plate is filled with a mixture of an electrolyte powder and a binder between an electrolyte-holding matrix matrix and an electrolyte-holding matrix matrix, and put them in a metallic mold to form a metallic top and bottom. It can be obtained by sandwiching with a plate and thermocompression bonding at a temperature above the softening point of the binder and before the decomposition starts (70 to 200 ° C) and at a pressure of 50 kg / cm ² or less.

[Action]

When the integrated electrolyte plate is directly installed in the battery and the temperature of the battery is raised, the decomposition of the binder in the matrix holding body for electrolyte retention and the binder in the mixture of the electrolyte and the binder are first decomposed between 250 ° C and 450 ° C. Done. As a result, fine pores are formed in the electrolyte matrix molded body where the binder decomposes and disappears. Further, the binder in the mixture of the electrolyte and the binder is decomposed to become only the electrolyte. In this state, when the temperature reaches 491 ° C., which is the melting point of the electrolyte, the electrolyte becomes in a molten state, and the fine pores formed in the electrolyte-holding matrix molded body are naturally impregnated. The molten and impregnated electrolyte is retained in the micropores by the capillary force of the micropores. At this point, an electrolyte plate of an ion conductor equivalent to that of the conventional example is formed. The temperature of the battery is further raised to 650 ° C., which is the battery operating temperature, and power generation is started.

Therefore, since the electrolyte plate need only withstand handling at room temperature until it is incorporated into the battery, it can be molded at low temperature (70 to 200 ° C) and low pressure (50 kg / cm ² or less). Therefore, the manufacturing process of the electrolyte plate is shortened, and the manufacturing time of the entire battery is shortened.

〔Example〕

Hereinafter, the electrolyte plate according to the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view for explaining the outline of the electrolyte plate showing the first embodiment.

The electrolyte plate of this example is a sheet-shaped electrolyte holding matrix molded body 2a, 2a, 2b, 2b in which two identical sheets are stacked.
And the mixed powder 1 of the electrolyte and the binder, and the mixed powder 1 of the electrolyte and the binder is filled between the sheet-shaped electrolyte molded matrix moldings 2a and 2b.

In this example, the sheet-shaped electrolyte holding matrix materials 2a and 2b each had an average thickness of about 0.4 mmt. A mixed carbonate such as lithium carbonate and potassium carbonate was used as the electrolyte.

The mixture of the electrolyte and the binder used in this example had a mixing ratio of 95: 5 wt%, and the electrolyte 95 wt% was debindered by firing the sheet-shaped electrolyte retaining matrix molded body 2a, 2b. After that, the matrix molded body 2a, 2
The amount was 115 vol% of the pore volume of b. The binder 5 wt% was polyethylene oxide (PEO). It should be noted that the addition of an electrolyte having a pore volume of 100% or more is a result of including the electrolytic mass for electrode helicitation, and the wettability by the electrolyte of the electrode is controlled by this extra added electrolyte, This is because the purpose is to improve the battery performance. Therefore, this amount is not limited to 115 vol% and may be 100 vol% or more, for example, 120 vol%.
%, 130vol% is also acceptable.

FIG. 2 is a vertical sectional view for explaining the outline of the electrolyte plate showing the second embodiment. In this example, the same members, materials and the like as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this example, the mixed powder 1 of the electrolyte and the binder is filled between the four sheet-shaped electrolyte-holding matrix molded bodies 2a, 2b, 2c and 2d.

Next, a method for manufacturing the electrolyte plate for a molten carbonate fuel cell described above will be described.

First, mix powder 1 of electrolyte and binder at a mixing ratio of 95: 5 wt.
Adjust in%. The electrolytic mass of 95 wt% is 115 vol of the pore volume of the matrix molded body 2 after the sheet-shaped electrolyte molded matrix molded bodies 2a to 2e are fired to remove the binder.
%, And the binder added at 5 wt% was polyethylene oxide (PEO). A sheet-shaped electrolyte holding matrix molded body is formed above and below the mixed powder 1.
A laminated body in which 2a and 2b are arranged and the mixed powder 1 is sandwiched is formed.

At this time, if the sheet-shaped electrolyte-holding matrix molded body and the mixed powder are filled so as to be alternately laminated, it can be formed as in the second embodiment shown in FIG.

Next, the sheet-shaped electrolyte holding matrix moldings 2a, 2b
On the outside of the, as shown in Fig. 3, polyester film 3
Arrange a and 3b.

Silicon is coated on one side of the polyester film 3a, 3b, and the silicon coating surface is
The sheet-shaped electrolyte holding matrix molded bodies 2a, 2b are brought into contact with each other to improve the peeling property between the sheet-shaped electrolyte holding matrix molded bodies 2a, 2b and the templates 5a, 5b.

Next, these laminated bodies are housed in a mold 4, and mold plates 5a and 5b are arranged above and below the mold. And 150 by rod heater 6
Place on the push-up plate 7 kept at ℃,
The hydraulic cylinder 9 pushes up to the vicinity of the constant plate 8 (gap with the constant plate 8: about 1 mm) kept at.

In the unpressurized state, the system thus arranged was left for about 30 minutes until the temperature of the system reached 150 ° C. The above system is 150
After the temperature reaches ℃, thermocompression bonding with a pressure of 50 kg / cm ²
Hold for 15 minutes.

At this point in time, since the sheet-shaped electrolyte holding matrix molded bodies 2a, 2b also contain a binder, the molded bodies 2a, 2a, 2b, 2b are bonded together and integrated into two sheets, and filled between them. The electrolyte powder particles and the electrolyte powder and the sheet-shaped electrolyte-holding matrix moldings 2a and 2b are also bonded by the binder (polyethylene oxide), so that the entire electrolyte plate is integrated.

After that, the electrolyte plate integrated by thermocompression bonding is removed from the mold and cooled while applying a load of 8 g / cm ² , whereby the electrolyte plate having the above-mentioned configuration can be manufactured. The electrolyte plate produced by the manufacturing method of this example has a very small warpage of 0.2 mm at maximum, and is flat and good.

In this embodiment, the thermocompression bonding is performed by the hot press molding machine, but the hot roll molding machine has the same effect and a good electrolyte plate can be molded. Further, according to this example, since a total of four sheet-shaped electrolyte-holding matrix molded bodies 2a and 2b are already used at this point, the amount of electrolyte retained can be increased, and as a result, the life of battery performance can be increased. Can be lengthened. Further, since the mixed powder 1 and the sheet-shaped electrolyte holding matrix molded bodies 2a, 2b, etc. are housed in the mold 4, the mixed powder 1 does not spill to the outside and the end portions of the sheet-shaped electrolyte matrix molded bodies 2a, 2b are prevented. A layer of mixed powder can be formed neatly. In addition, there is a unique effect that the sheet-shaped electrolyte holding matrix molded bodies 2a and 2b are not displaced from each other.

Furthermore, this electrolyte plate was directly incorporated into the battery, and the electrolyte was formed into a sheet-shaped electrolyte matrix molded body during the process of heating the battery.
By impregnating a and 2b, the manufacturing process of the electrolyte plate can be shortened for the above-mentioned reason, so that the time required to form a battery can be shortened.

〔The invention's effect〕

As described above, the electrolyte plate for a molten carbonate fuel cell of the present invention uses a structure in which the mixture of the electrolyte and the binder is filled between the matrix-holding matrix for holding the electrolyte, so that the electrolyte is smooth and electrolyte spillage A good electrolyte plate without displacement of the matrix material for holding can be obtained. That is, by thermocompression bonding the laminated system having the above-mentioned configuration at a low temperature of about 70 to 200 ° C. and a low pressure of 50 kg / cm ² or less,
It is possible to manufacture an excellent electrolyte plate having a simple structure without using a solvent at low temperature and low pressure.

Further, by directly incorporating this electrolyte plate into a battery and raising the temperature of the battery, the electrolyte matrix is naturally impregnated into the electrolyte-holding matrix molded body in the process of raising the temperature, and the electrolyte plate of the ion conductor is formed. Therefore, there is no need to heat-treat the outside of the battery to impregnate it with the electrolyte, and the manufacturing process of the electrolyte plate can be shortened by that amount, and the time required to form the battery can be shortened overall.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the structure of an embodiment of the present invention, FIG. 2 is a vertical sectional view showing another embodiment of the structure of FIG. 1, and FIG. FIG. 3 is a schematic diagram showing a device and a material structure for obtaining the structure shown in FIG. 2. 1 ... Mixed powder of electrolyte and binder, 2a, 2b, 2c, 2d ...
… Sheet-like electrolyte matrix holding material, 3a, 3b…
… Polyester film, 4 …… Mold, 5a, 5b …… Mold plate, 6 …… Rod heater, 7 …… Push plate, 8 …… Regular plate, 9 …… Cylinder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Iwamoto 4026 Kujimachi, Hitachi City Hitachi Ltd.Hitachi Research Laboratory (72) Inventor Yoshio Iwase 4026 Kujimachi Hitachi City Hitachi Ltd. Hitachi Research Co., Ltd. (72) Inventor Masato Takeuchi 4026 Kujimachi, Hitachi City Hitachi Ltd., Hitachi Research Laboratory (72) Inventor Yuichi Kamo 4026 Kujicho, Hitachi City Hitachi Ltd. Hitachi Research Laboratory

Claims (5)

(57) [Claims] 1. A molten carbonate fuel cell electrolyte plate in which an electrolyte composed of a mixed carbonate is held between electrolyte-holding matrix molded bodies, wherein the electrolyte-holding matrix molded body contains lithium aluminate as a main raw material. , A two-layer sheet containing a binder, and a mixture of an electrolyte and a binder is filled between the two-layer sheet-shaped electrolyte-holding matrix molded body, and the mixture and the electrolyte-holding matrix molded body An electrolyte plate for a molten carbonate fuel cell, characterized in that and are integrated by thermocompression bonding. 2. The electrolyte is filled in an amount of 100 to 130% with respect to the volume of pores formed when the matrix holding body for electrolyte holding is used, that is, in the debindered state. An electrolyte plate for a molten carbonate fuel cell according to the item. 3. An electrolyte-retaining matrix molded body is formed into a two-layer sheet shape containing lithium aluminate as a main raw material and containing a binder, and between the two-layer sheet-shaped electrolyte retaining matrix molded body. Filling a mixture containing a mixture of an electrolyte and a binder into a mold, and integrating the mold by thermocompression bonding from above and below within a temperature range not lower than the softening point of the binder and before the decomposition starts. The method for producing an electrolyte plate for a molten carbonate fuel cell, comprising: 4. The method for producing an electrolyte plate for a molten carbonate fuel cell according to claim 3, wherein the temperature range is 70 ° C. to 200 ° C. 5. The method for producing an electrolyte plate for a molten carbonate fuel cell according to claim 3, wherein the thermocompression bonding is performed by a hot press molding machine or a hot roll molding machine.