JPS60180067A - Molten carbonate type fuel cell and its manufacturing method - Google Patents

Abstract

PURPOSE:To reduce internal resistance caused by the thinness of an electrolytic layer by inserting a fine powder layer obtained from fine powder material and organic binder between a pair of porous electrode plates and the electrolytic layer that comprise a unit battery. CONSTITUTION:A unit battery 1 for a molten carbonate type fuel cell is formed as the five-layer structure by coating a fuel electrode 3 made of a porous sintering body such as an Ni-Cr alloy and an oxidizing electrode 4 made of the porous sintering body such as Ni with fine powder layers 5 and 6 in which ceramic fine powder such as LiAlO2, organic binder, and nonaqueous solvent are kneaded and applying an electrolytic layer 7 in which mixed carbonate, carbonate holding material such as LiAlO2, organic binder, and nonaqueous solvent are kneaded to the fine powder layers 5 and 6. Then a battery main body X is formed by laminating the unit battery together with connectors 2. As a result, the intersected mixture of gas can be prevented by improving mechanical strength even if the electrolytic layer 7 is made thin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a molten carbonate fuel cell that has excellent characteristics and can achieve high output, and a method for manufacturing the same.

[Technical background of the invention and its problems]

Conventionally, fuel cells have been widely known as a highly efficient energy conversion device. Fuel cells are classified into phosphoric acid type, molten carbonate type, and solid electrolyte type depending on the electrolyte used. Among these, molten carbonate fuel cells have major characteristics such as high operating temperature, which facilitates electrode reactions, no need for expensive precious metal catalysts, and high heat generation efficiency. ◎ A molten carbonate fuel cell is a unit consisting of a pair of porous electrode plates placed opposite each other, that is, an oxidizer electrode and a fuel electrode, and an electrolyte layer interposed between these electrodes that uses an alkali carbonate as the electrolyte. Usually, a plurality of batteries are stacked together via ink connectors. During operation, the alkali carbonate is molten at a high temperature of 500 to 750°C, and this carbonate is reacted with the oxidant gas and fuel gas diffused in each electrode plate, resulting in an electrochemical reaction. DC output is obtained through a process of

The electrolyte layer of such a molten carbonate fuel cell needs to satisfy the following conditions. That is, ■ It not only has sufficient holding capacity for molten carbonate, but also has sufficient mechanical strength, especially compressive strength, at operating temperatures to prevent cross-mixing of gases from occurring due to cracks in the electrolyte layer within the fuel cell. Things not to do 1 ■ In order to reduce the internal resistance of the unit battery, it must be as thin as possible and have sufficient contact with each electrode; ■ It must be large enough to increase the output of the unit battery, and The goal is to have high productivity so that fuel cell power plants can scale up.

By the way, in conventional molten carbonate fuel cells, the electrolyte layer consists of a mixture of an electrolyte holding material and a carbonate.
A plate-shaped body called an electrolyte tile, which is hot-pressed and torn under conditions of 0 to 500°C and 200 to 500 kglα2, is used.

However, the electrolyte J@ formed as above
Although it has a sufficient maintenance function for molten carbonate, it has poor mechanical strength, and if the electrolyte tile is larger than 50 crn square, it will easily break due to normal handling, making it difficult to incorporate it into the battery. In addition, even after assembly, gas cross-mixing is likely to occur due to cracks in the electrolyte layer caused by thermal cycling of the battery.

For this reason, there are limits to making the electrolyte layer thinner and larger.
The thickness was limited to about 100 yen.

Further, even if the electrolyte layer could be made thinner by some method, fuel cells with conventional structures still have the following problems. That is, during fuel cell operation, oxidant gas and fuel gas are usually separated by a layer of molten carbonate.

Therefore, the thinner this layer is, the lower its ability to withstand gas pressure is, causing the problem that molten carbonate is forced downstream of the gas, resulting in gas cross-mixing.

Furthermore, when forming the entire electrolyte layer by hot pressing as described above, it is necessary to apply a high pressure per unit area, which requires the use of large press equipment, which incurs large equipment costs. There was a problem. Moreover, with this manufacturing method, is it a mixture of retaining material and carbonate? Since it is necessary to pressurize at high temperature, it may take some time to heat the above mixture, but since sudden mechanical shock cannot be applied during press processing, the production speed per sheet can be reduced to within 10 minutes. There were problems in that it was difficult to do so, and productivity was extremely low. Therefore, there is a problem in that a large amount of cost is required to manufacture a large-sized fuel cell using such a manufacturing method.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and its purpose is to provide a molten carbonate fuel cell that can improve energy efficiency and increase output, and a highly productive fuel cell thereof. Our objective is to provide a J-building method.

[Summary of the invention]

In the molten carbonate fuel cell according to the present invention, an electrolyte layer is formed between a pair of porous electrode plates with a mixture of a mixed carbonate, a carbonate retaining material, and an organic binder, and this electrolyte layer and each of the above-mentioned porous It is characterized in that a thin fine powder layer made of a mixture of a fine powder material and an organic binder is interposed between the electrode plate and the electrode plate.

Further, the method for manufacturing a molten carbonate fuel cell according to the present invention includes forming a thin fine powder layer on one surface of the first porous electrode plate using a mixture of a fine powder material and an organic binder; After forming an electrolyte layer by applying a mixture of a mixed carbonate, a carbonate retaining material, and an organic binder to the upper surface of the fine powder layer, a thin fine powder made of a fine powder material and an organic binder is deposited on the electrolyte layer. It is characterized in that the second porous electrode plate is laminated with layers interposed therebetween.

〔Effect of the invention〕

According to the present invention, since a thin fine powder layer containing a fine powder material is formed between each porous electrode plate and the electrolyte layer,
The hydrodynamic resistance between the electrode and the electrolyte layer increases and the gas pressure can stop the movement of molten carbonate. Therefore, by reducing the thickness of the electrolyte N, the conventional drawback that cross-mixing of gases tends to occur can be overcome. As a result, it is possible to reduce the internal resistance by making the electrolyte thinner and to prevent gas cross-mixing at the same time, and it is possible to provide a molten carbonate fuel cell with high energy efficiency.

Further, according to the manufacturing method of the present invention, a method is adopted in which a fine powder layer and an electrolyte layer are formed on a porous electrode plate having high mechanical strength. Therefore, even if the electrolyte layer is formed extremely thin, the mechanical strength of the electrode plate serving as the base is high.
The electrolyte layer will not crack during handling during manufacturing.

Furthermore, since the electrolyte layer contains an organic binder and is extremely flexible, this layer also becomes difficult to break. Therefore, according to the manufacturing method of the present invention, it is possible to make the electrolyte layer thinner and larger, and as a result, a fuel cell with high output can be manufactured.

In addition, this method is different from the conventional hot press method in that it is possible to form an electrolyte layer at room temperature, and
Since a method is adopted in which a slurry-like material is simply applied onto the upper surface of the fine powder layer formed on the electrode plate, productivity is extremely high. Therefore, mass production of large-sized fuel cells becomes possible.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A molten carbonate fuel cell according to an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, X is a fuel cell main body installed in a manifold (not shown). The fuel cell main body X is constructed by alternately stacking unit cells and interconnectors 2.

The unit cell J includes a pair of porous electrode plates, that is, a fuel electrode 3
It has a five-layer structure in which an electrolyte layer 7 is formed between the electrode 4 and the oxidizer electrode 4 with a fine powder layer 56 interposed therebetween. The fuel electrode 3 is
For example, it is formed of a porous sintered body made by sintering powder of Ni-Cr alloy, Co-Cr alloy, etc. to have a desired porosity. The oxidizer electrode 4 is formed of, for example, a porous sintered body of a NirNs alloy. The fine powder layers 5 and 6 are made of LiA
It is formed by kneading ceramic fine powder such as t0□, an organic binder, and a non-aqueous solvent and applying the mixture onto the fuel electrode 3 and oxidizer electrode 4. In addition, the electrolyte layer contains mixed carbonate and Li
It is formed by kneading a carbonate retaining material such as A102, an organic binder, and a non-aqueous solvent and applying the mixture onto the fine powder layer 5 or 6.

The interconnector 2 is made of, for example, a stainless steel plate with a plurality of grooves extending perpendicularly to each other on both sides, and the grooves formed on one side are used as gas passages 8 for oxidizing gas. , the groove formed on the other surface serves as a gas passage 9 for fuel gas.

Therefore, when operating the fuel cell configured in this way, the temperature of the fuel cell main body Xi is raised to 500 to 750°C. In the process of this temperature increase, the electrolyte layer 7 and the fine powder layers 5 and 6
At the same time as the organic binder inside is volatilized, a portion of the fine powder begins to fuse. Thereafter, the oxidizing gas is made to flow through the gas passage 8 of the interconnector 2 in the direction shown by the arrow P in the figure, and the fuel gas is made to flow through the gas passage 9 in the direction shown by the arrow Q. This causes an electrode reaction and generates a DC voltage between each electrode.

Next, a specific example of a method for manufacturing such a fuel cell and its experimental results will be described.

A Ni sintered body with a porosity of 75% was used as the oxidizer electrode 4, a Ni-Cr sintered body with a porosity of 65% was used as the fuel electrode 3, 20 m2/7 of fine powder of LiA102 (lithium aluminate), and polyvinyl butyral. A slurry containing 3 wt. . After drying this fine powder layer, 60.9 g of mixed carbonate, 240 γ-LiAtO, P, and 2 g of polyvinyl butyral were thoroughly kneaded in isopropyl alcohol, and then a fine powder formed on the oxidizing agent electrode 4 was added. The electrolyte layer 7 was coated on the upper surface of N6 to form an electrolyte layer 7 having a uniform thickness as shown in FIG. 2(b). After drying this electrolyte layer 7, it was pressurized at 9/cr++2 to integrate it. Furthermore, the fuel electrode 3 on which the fine powder layer 5 previously produced was formed was laminated on the upper surface of the electrolyte layer 7 to form a unit cell If with a five-layer structure as shown in FIG. 2(e).

This unit cell 1'i was heated to a temperature between 3.50 and 550°C to melt the carbonate and volatilize the organic binder, and then raised to 650°C to cause an electromotive reaction. .

When the current-voltage characteristics of this unit battery 1 were measured, the third
The results shown in Figure A were obtained. For comparison, Figure B shows the current-voltage characteristics of a unit battery using an electrolyte layer with a thickness of 2 μm obtained by the conventional hot pressing method. As is clear from this figure, the unit battery manufactured by the method of this example was able to obtain a higher output voltage than the conventional one. This is because the thickness of the electrolyte layer 7 could be made thinner.

However, the unit battery 1 obtained by the method of this example is as follows:
It was confirmed that the bubbling pressure at the battery operating temperature increased by 50 inches compared to the conventional model, and that there was less cross-mixing of gases. This is because the fine powder layers 5.6 formed on both sides of the electrolyte layer 7 prevent the molten carbonate from moving due to gas pressure.

In this case, it was confirmed that the electrolyte layer could be formed within 91 minutes per sheet, and the productivity was extremely good, so that the productivity of the fuel cell was also high.

As described above, according to the fuel cell manufacturing method of this embodiment, it is possible to sufficiently achieve the above-mentioned effects.

In addition, as another example, an electrolyte layer of 1 m square and 0.6 mm thick was made of fine powder N? : was formed on the electrode through the layer to form a three-layer structure. When both ends of this three-layer structure were held, it did not break under its own weight.

Further, a fine powder layer and an electrode were further added to this three-layer structure to form a unit battery, and a plurality of unit batteries were stacked and tightened with a total pressure of k1 kg/α2. As a result, it was confirmed that approximately 10% of the thickness of the electrolyte layer bit into one of the electrodes, and the compatibility between the electrolyte layer and the electrode was improved compared to the conventional method.

In addition, two methods using conventional hot-pressed electrolyte layers
When a 0-layer stacked battery was tightened with a pressure of e2 kg/α2, cracks occurred in the three electrolyte layers, whereas no cracks occurred in the case of this example.

Thus, according to this example, it was confirmed that all of the above-mentioned effects were fully achieved.

Note that the present invention is not limited to the above embodiments.

For example, carbonate retaining material (lithium alumina) (LiA
Not limited to t0□), strontium titanium) (5r
TiOs) or cerium oxide (CeO2) may be used. Moreover, as the fine powder used for the fine powder layers 5 and 6, nickel powder or nickel alloy powder may be used. Both of these fine powder layers do not need to be formed on the electrode plate in advance; for example, the electrode plate, the fine powder layer, the electrolyte layer, the fine powder layer, and the electrode plate may be laminated in this order. .

Further, the organic binder may be polytetrafluoroethylene, polyethylene glycol, polymethyl methacrylate, etc., and the non-aqueous solvent may be alcohol of 02 to C6, toluene, acetone, etc.

Further, although the mixed carbonate was not specifically described in the above embodiments, the following combinations may be employed.

Li2C03A2CO3, Li2CO3/2CO3Aa2C03, Na2CO3
/ to 2CO3, Li2CO3/ to 2CO3/5rC03, L1□C03
A2CO3//CaCO3゜

[Brief explanation of drawings]

Figure 1 is a perspective view showing the configuration of the main parts of a molten carbonate fuel cell according to an embodiment of the present invention, Figures 2) to (c) are diagrams for explaining the manufacturing process of the fuel cell, FIG. 3 is a diagram for explaining the cell characteristics of the same fuel cell in comparison with a conventional example. L...unit battery, 2...interconnector, 3...
Fuel electrode, 4... Oxidizer electrode, 5, 6... Fine powder layer, 7
... Electrolyte layer, 8, 9... Gas passage, A... Characteristics of the example, B... Characteristics of the comparative example. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (3)

[Claims] (1) A pair of porous electrode plates, an electrolyte layer formed between these porous electrode plates and made of a mixture of a mixed carbonate, a carbonate holding material, and an organic binder; A molten carbonate fuel cell comprising: a fine powder layer formed between an electrode plate and made of a mixture of a fine powder material and an organic binder. (2) The molten carbonate fuel cell according to claim 1, wherein the fine powder material C is made of lithium aluminate, nickel powder, nickel alloy powder, or a mixture thereof. (3) a step of forming a thin fine powder layer made by mixing a fine powder material and an organic binder on one side of the first porous electrode plate; and the above fine powder obtained by this step. A step of forming an electrolyte layer by applying a mixture of a mixed carbonate, a carbonate retaining material, and an organic binder on the layer, and forming a thin wall made of a fine powder material and an organic binder on the electrolyte layer obtained in this step. and laminating a second porous electrode plate through a fine powder layer.