JPH11273694A - Molten carbonate fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deposition of nickel in an electrolyte plate due to coarsening of pores of an electrolyte holding layer accompanying grain growth of electrolyte holding particles, and to suppress occurrence of a nickel short circuit, thereby improving the length of the electrolyte holding layer. Disclosed is a long-life molten carbonate fuel cell. SOLUTION: The present invention relates to a fuel electrode 1 made of a porous material formed of a first powder having conductivity, and an oxidant electrode made of a porous material formed of a second powder having conductivity. 2, a fuel gas supply device for supplying a fuel gas to the fuel electrode 1, an oxidant gas supply device for supplying an oxidant gas to the oxidant electrode 2, the fuel electrode 1 and the oxidant An electrolyte plate 3 disposed between the poles 2 and having an electrolyte holding layer 3a mainly composed of α-lithium aluminate and having an average pore diameter smaller than the average particle diameter of the second powder. It is a carbonate fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten carbonate fuel cell having an electrolyte plate disposed between a pair of conductive electrodes and having a plurality of electrolyte holding layers laminated thereon.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view showing the basic structure of a molten carbonate fuel cell. In FIG. 3, a fuel electrode (hereinafter, referred to as an anode) 1 is a pair of electrodes having conductivity.
An electrolyte plate 3 holding an electrolyte made of a mixed alkali carbonate is incorporated between the oxidizer electrode (hereinafter referred to as a cathode) 2 and the oxidizer electrode 2. The electrolyte plate 3 is melted at a high temperature, the fuel gas (H ₂ , CO ₂ ) is supplied to the anode 1 through the supply port 6 of the housing 4a, and the oxidant gas (air, CO ₂ ) is supplied to the cathode 2 through the supply port 8 of the housing 4b.
₂ ), a reaction of the following formula (1) occurs at the anode 1 and a reaction of the following formula (2) occurs at the cathode 2, and exhaust gas (CO ₂ , H ₂ O) is discharged from the exhaust port 7.
Exhaust gas (N ₂ ) is exhausted from the exhaust port 9.

[0003] ^{_{H 2 + CO 3 2- → H}} 2 O + CO 2 + 2e - (1) 1 / 2O 2 + CO 2 + 2e - → CO 3 2- (2) On the other hand, the molten carbonate fuel cell The electrolyte plate 3 is basically made by impregnating an electrolyte made of mixed alkali carbonate into a porous body composed of electrolyte holding particles for preventing the outflow of an electrolyte that becomes a liquid during high-temperature operation. It is a thing. Here, usually, the alkali carbonate is Li
It is used in the form of a mixed salt of two or three of the three types of ₂ CO ₃ , K ₂ CO ₃ and Na ₂ CO ₃ . Further, as the electrolyte holding particles, the average particle diameter of the primary particles is usually submicron (for example, 0.05 μm or more and 0.2 μm or less).
fine powder is used consisting of gamma-LiAlO ₂ is m or less).

[0004] Usually, reinforcing particles or reinforcing fibers are added to the electrolyte plate 3 in order to prevent the occurrence and cracking of the electrolyte plate 3 when the temperature rises and falls. Coarse particles having an average particle size of several tens of microns (for example, 15 μm) or more are used as the reinforcing particles, and the reinforcing fibers have an aspect ratio (L).
/ D, L: fiber length, D: fiber diameter) of about 100 to 500 are used.

On the other hand, the anode 1 and the cathode 2 are porous sintered bodies using a nickel base alloy or nickel powder having a particle size of 1 to 30 μm. As for the electromotive reaction of the battery, a fuel gas containing hydrogen is supplied to the anode 1 and an oxidant gas is supplied to the cathode 2 as a reaction gas, whereby the reaction between the electrolyte and the reaction gas in the porous body of the gas diffusion electrode is performed. It occurs at a site (three-phase interface) and can be extracted as electric energy from between a pair of electrodes.

In this type of molten carbonate fuel cell, the electrolyte plate 3 mediates the movement of carbonate ions (CO ₃ ²⁻ ), but must be an insulator for electron conduction. Further, it also has a function as a gas barrier layer for preventing the fuel gas and the oxidizing gas from reacting directly. However, the conventional molten carbonate fuel cell has the following two problems. The first problem is that the pore structure of a porous sheet (hereinafter, referred to as an electrolyte retaining layer) made of ceramic powder, which is an electrolyte retaining particle, becomes pores that cannot retain an electrolyte (hereinafter, referred to as coarse pores), and a sufficient amount of electrolyte can be obtained. Cannot function as a gas barrier layer, and hydrogen on the anode 1 side and oxygen on the cathode 2 side react directly in the electrolyte to generate water. This is a gas crossover. The second problem is that nickel in the cathode 2 elutes into the electrolyte during the operation of the battery and precipitates in the electrolyte plate 3, thereby causing a nickel short circuit between the anode 1 and the cathode 2. The above two problems have been the greatest life limiting factor of the molten carbonate fuel cell.

This nickel short circuit is closely related to the coarsening of the pores of the electrolyte holding layer. That is, when the pores of the electrolyte holding layer become coarse, first, nickel oxide particles of the cathode begin to diffuse and invade into the electrolyte plate 3 in a particle state. Furthermore, as the pores become coarser, coarse pores are generated, fuel gas enters the inside of the electrolyte plate 3 through the coarse holes, and nickel ions of the cathode 2 dissolved in the electrolyte are deposited in the electrolyte plate. To be precipitated. When the amount of nickel in the electrolyte plate increases in this way, the precipitated nickel is connected from the anode 1 to the cathode 2 and a nickel short circuit occurs.

[0008]

As described above, in the conventional molten carbonate fuel cell, nickel is contained in the electrolyte plate due to coarsening of the pores of the electrolyte retention layer accompanying the grain growth of the electrolyte retention particles. There was a problem of precipitation and nickel short circuit. The present invention has been made to solve such problems, and provides a long-life molten carbonate fuel cell by preventing the deposition of nickel in an electrolyte plate and suppressing the occurrence of a nickel short circuit. The purpose is to do.

[0009]

According to a first aspect of the present invention, there is provided a fuel electrode comprising a porous body formed of a first powder having conductivity, and a porous electrode formed of a second powder having conductivity. An oxidant electrode comprising a body, a fuel gas supply device for supplying a fuel gas to the fuel electrode, an oxidant gas supply device for supplying an oxidant gas to the oxidant electrode, the fuel electrode and the fuel electrode; A molten carbonic acid, comprising an electrolyte plate disposed between the oxidizer electrodes and having an electrolyte holding layer mainly composed of α-lithium aluminate and having an average pore diameter smaller than the average particle diameter of the second powder. It is a salt type fuel cell.

A second aspect of the present invention is directed to the first aspect, comprising an electrolyte plate on which a plurality of electrolyte holding layers are laminated, wherein at least one layer has an electrolyte holding layer mainly composed of α-lithium aluminate. It is a molten carbonate type fuel cell of the description.

[0011] In a third aspect of the present invention, the average pore diameter of the electrolyte retaining layer in contact with the fuel electrode is larger than the average pore diameter of the other electrolyte retaining layers. It is a carbonate fuel cell.

That is, as an example of the present invention, an electrolyte plate is formed by laminating three electrolyte holding layers, and α-
FIG. 1 is a schematic cross-sectional view of a unit cell electromotive section when an electrolyte holding layer composed of electrolyte holding particles mainly composed of lithium aluminate is used.

The present inventors have found that α-lithium aluminate is much more stable in the operating atmosphere of a molten carbonic acid fuel cell than conventional γ-lithium aluminate, and that the particle morphology hardly changes during battery operation. Was found. Further, when the electrolyte holding layer is formed using the electrolyte holding particles mainly composed of α-lithium aluminate, the pore distribution hardly changes. Therefore, when the α-lithium aluminate electrolyte holding layer is formed so that the average pore diameter is smaller than the average particle diameter of the nickel oxide powder of the oxidizing agent electrode, and used for the laminate of the electrolyte plate 3 (for example, FIG. 3
a), the α-lithium aluminate electrolyte holding layer maintains a fine pore diameter smaller than the particle diameter of the nickel oxide particles of the oxidant electrode 2 even during a long-time power generation, so that the nickel oxide (NiO) particles No. 51 cannot diffuse from the α-lithium aluminate electrolyte holding layer to the fuel electrode 1 side. Further, since the .alpha.-lithium aluminate electrolyte holding layer does not form coarse pores, it is possible to suppress the penetration of the fuel gas into the electrolyte plate 3, thereby reducing the nickel ions on the oxidant electrode 2 side. There is no Ni50 either. Therefore, nickel is not connected from the fuel electrode 1 to the oxidant electrode 2, and nickel short circuit can be suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail. FIG. 2 is a sectional view showing a part of a molten carbonate fuel cell having a structure in which a plurality of unit cells are stacked. The electrolyte plate 3 is disposed between the anode 1 and the cathode 2. The electrolyte plate 3 is formed by impregnating a porous body with an electrolyte containing at least a carbonate such as a lithium carbonate. The electrolyte plate 3, the anode 1, and the cathode 2 constitute a unit cell. The corrugated anode-side and cathode-side current collectors 15 and 16 are arranged on the surfaces of the anode 1 and the cathode 2 opposite to the electrolyte plate 3, respectively. The fuel gas passes through a flow path 17 formed by the anode 1 and the current collector 15. The oxidizing gas is
The flow path 1 formed by the cathode 2 and the current collecting plate 16
8 is distributed. The separator 19 is arranged between the stacked unit cells, and functions as a partition for the unit cells. The separator 19 is an interconnector 1 for separating the flow paths 17 and 18.
0 and two edge seal plates 11 and 12 arranged so as to sandwich the peripheral edge of the electrolyte plate 3. The edge seal plates 11 and 12 form a wet seal in contact with the periphery of the electrolyte plate, and serve to shield the power generation unit of the unit cell from an external atmosphere. In addition, the edge seal plates 11 and 12 are generally applied with a surface pressure of 5 kg / cm ² or less from both sides by spring members 13 and 14 at a sandwiching portion of a peripheral portion of the electrolyte plate 3, so that the wetness is reduced. The performance of the seal is ensured.

The electrolyte plate 3 has, for example, a structure in which an electrolyte is impregnated in a molten state in an electrolyte holding layer mainly composed of lithium aluminate. Examples of the electrolyte include a mixed alkali carbonate such as a mixture of lithium carbonate and potassium carbonate, a mixture of lithium carbonate and sodium carbonate, and a mixture of lithium carbonate, potassium carbonate and sodium carbonate. The electrolytic solution is allowed to have a composition obtained by further adding an alkaline earth carbonate to the mixed alkali carbonate.

Since the electrolyte holding layer is usually manufactured by a doctor blade method in order to obtain a dense and uniform porous sheet, the thickness of one electrolyte holding layer is limited in manufacturing. Therefore, the electrolyte plate 3 requiring a certain thickness from the viewpoint of gas barrier properties and nickel short-circuit is usually formed by laminating a plurality of the electrolyte holding layers.

The anode 1 is formed of a porous material such as a sintered body of a conductive powder such as nickel or a nickel-based alloy. The cathode 2 is made of, for example, an oxide of nickel or a nickel-based alloy and a lithium compound thereof,
Alternatively, it is formed from a porous body such as a sintered body of a conductive powder such as lithium cobaltate or lithium ferrite. Note that an oxide of nickel or a nickel-based alloy is usually lithiated by an electrolyte in a battery and exhibits high conductivity.

In the present invention, at least one of the plurality of electrolyte holding layers constituting the electrolyte plate 3 mainly uses α-lithium aluminate as electrolyte holding particles and has an average pore diameter of: The conductive powder constituting the cathode 2 is smaller than the average particle diameter. Preferably, at least 90 wt% or more of the electrolyte holding layer is α-lithium aluminate, and 95 wt% or more is α-lithium aluminate.
-More preferably, it is lithium aluminate. The remainder is almost γ-lithium aluminate, but when the number of heterocrystalline forms such as γ-type increases, it becomes the center of agglomeration and grain growth of the particles accompanying the phase change, and the change of the microstructure of the porous body is accelerated. This is because that. As an example of the present invention, an electrolyte plate is formed by laminating three electrolyte holding layers, and α-
FIG. 1 is a schematic cross-sectional view of a unit cell electromotive section when an electrolyte holding layer using lithium aluminate as a holding material is used.

The present inventors have found that α-lithium aluminate is extremely stable in the operating atmosphere of a molten carbonic acid fuel cell compared to conventional γ-lithium aluminate, and that the particle morphology hardly changes during battery operation. Was found. Further, when an electrolyte holding layer mainly composed of α-lithium aluminate is used for the electrolyte holding particles, the pore distribution hardly changes. Therefore, when an electrolyte holding layer in which the average pore diameter of the α-lithium aluminate electrolyte holding layer is smaller than the average particle diameter of the nickel oxide powder of the cathode 2 is prepared and used for a laminate of electrolyte plates (for example, 3 in FIG. 1)
a position), the α-lithium aluminate electrolyte holding layer 3 a maintains a fine pore diameter smaller than the particle diameter of the nickel oxide particles of the cathode 2 even during long-time power generation. It cannot diffuse to the anode 1 side from the lithium aluminate electrolyte holding layer 3a. Further, the α-lithium aluminate electrolyte holding layer 3a
Since no coarse pores are formed, penetration of the fuel gas into the electrolyte plate can be suppressed, and there is no reduction precipitation of nickel ions on the cathode 2 side from the α-lithium aluminate electrolyte holding layer 3a. Therefore, nickel is not connected from the anode 1 to the cathode 2, and a nickel short circuit can be suppressed.

The average pore diameter of the electrolyte holding layer is controlled by controlling the particle diameter of the electrolyte holding particles and the amount of binder in the doctor blade method. less than,
A method for producing the α-lithium aluminate electrolyte holding layer will be described. First, the slurry is prepared by mixing the α-lithium aluminate electrolyte holding particles, the organic binder, and the plasticizer in the presence of an organic solvent.

Here, the average particle size of the α-lithium aluminate particles is desirably 0.2 to 0.6 μm. When the particle size is smaller than 0.2 μm, aggregation and particle growth of the particles tend to occur. If it is larger than 0.6 μm, the pore size of the electrolyte holding layer becomes large, and the holding ability of the electrolyte is deteriorated.
In order to increase the strength of the electrolyte holding layer, it is preferable to add coarse particles and fibers such as alumina, lithium aluminate, zirconia, and lithiated zirconia as reinforcing materials to the electrolyte holding layer powder. The average particle size of the reinforcing material coarse particles is preferably 5 to 50 μm. Fiber diameter 1-20 μm, fiber length 5-3000 μm as reinforcement fiber
It is preferred that

Examples of the organic binder include polyvinyl butyral and acrylic resin. Examples of the plasticizer include di-n-butyl phthalate. Desirably, the binder amount is about 40% of the weight of the holding material and the reinforcing material.

Further, examples of the organic solvent include ethyl alcohol, n-butanol, methyl ethyl ketone and the like. Next, the slurry is formed into a sheet by a doctor blade method using a carrier film, and dried. In this case, a predetermined sheet is created by controlling starting materials, molding conditions, and the like. Subsequently, the sheet is peeled from the carrier film, and cut in accordance with the cell dimensions of the fuel cell.

The thickness of the α-lithium aluminate electrolyte holding layer is desirably 50 μm or more. If the thickness is less than 50 μm, the effect as a nickel barrier layer is reduced.

Hereinafter, embodiments of the present invention will be described in detail. Example 1 First, α-lithium aluminate electrolyte holding particles having an average particle diameter of 0.4 μm and α-lithium aluminate having an average particle diameter of 30 μm were used.
The lithium aluminate reinforcing material coarse particles were put in an alumina pot at a volume ratio of 70:30, and wet-mixed with ethanol, polyvinyl butyral, and dibutyl phthalate for 20 hours to prepare a slurry. Subsequently, the slurry was spread on a carrier sheet to form a green sheet having a thickness of 0.4 mm. Thereafter, the green sheet was degreased in the air to form an α-lithium aluminate electrolyte holding layer. When the average pore diameter of the electrolyte retaining layer was measured by a mercury intrusion method, it was about 0.4 μm.

Next, three layers of the α-lithium aluminate electrolyte holding layer obtained as described above are laminated, and a mixed alkali carbonate (Li ₂ CO ₃ : 62 mol) is used as an electrolyte.
%, K ₂ CO ₃ : 38 mol%) was heated to 550 ° C. and melt-impregnated into the electrolyte holding layer to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate thus obtained is placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle size of 0.8 μm. And a separator 19 made of stainless steel, edge seal plates 11 and 12,
The above-described molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Example 2 First, as in Example 1, an α-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm was prepared. Next, similarly to the α-lithium aluminate electrolyte holding layer of Example 1, γ-lithium aluminate electrolyte holding particles having an average particle diameter of 0.4 μm and an average particle diameter of 3 μm were used.
Using γ-lithium aluminate reinforcing material coarse particles of 0 μm, γ-lithium particles having an average pore diameter of about 0.4 μm and a thickness of 0.4 mm are used.
A lithium aluminate electrolyte holding layer was formed.

The α-lithium aluminate electrolyte holding layer thus obtained was laminated on the cathode side, and the γ-lithium aluminate electrolyte holding layer was laminated on the anode side, for a total of three layers. Mixed alkali carbonate (Li
₂ CO ₃ : 62 mol%, K ₂ CO ₃ : 38 mol%)
Was heated to 550 ° C., and the electrolyte holding layer was melt-impregnated to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle diameter of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Example 3 An α-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm and a γ-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm were prepared in the same manner as in Example 2. It was created.

One layer of the α-lithium aluminate electrolyte holding layer obtained as described above is disposed between two layers of the γ-lithium aluminate electrolyte holding layer, and a total of three layers are laminated. (Li ₂ CO ₃ : 62mo
(1%, K ₂ CO ₃ : 38 mol%) was heated to 550 ° C. and melt-impregnated into the electrolyte holding layer to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle size of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Example 4 An α-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm and a γ-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm were prepared in the same manner as in Example 2. It was created.

One layer of the α-lithium aluminate electrolyte holding layer obtained as described above was laminated on the anode side, and two layers of the γ-lithium aluminate electrolyte holding layer were stacked on the cathode side, for a total of three layers. Mixed alkali carbonate (Li
₂ CO ₃ : 62 mol%, K ₂ CO ₃ : 38 mol%)
Was heated to 550 ° C., and the electrolyte holding layer was melt-impregnated to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate obtained as described above is placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle size of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Example 5 An α-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm and a γ-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm were prepared in the same manner as in Example 2. It was created.

One layer of the γ-lithium aluminate electrolyte holding layer obtained as described above is arranged between two α-lithium aluminate electrolyte holding layers, and a total of three layers are laminated. Carbonate (Li ₂ CO ₃ : 62
mol%, K ₂ CO ₃ : 38 mol%) by raising the temperature to 550 ° C. and impregnating the electrolyte holding layer by melting.
An electrolyte plate having a thickness of 1.2 mm was prepared.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle size of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Comparative Example 1 A γ-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm was prepared in the same manner as in Example 2. Three layers of the γ-lithium aluminate electrolyte holding layer obtained as described above are laminated, and a mixed alkali carbonate (Li ₂ CO ₃ : 62 mol) as an electrolyte
%, K ₂ CO ₃ : 38 mol%) was heated to 550 ° C. and melt-impregnated into the electrolyte holding layer to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle diameter of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Comparative Example 2 First, α-lithium aluminate electrolyte holding particles having an average particle diameter of 0.6 μm and an average particle diameter of 3 μm
0 μm α-lithium aluminate reinforcing material coarse particles
Put in an alumina pot at a volume ratio of 0:30, and add ethanol, polyvinyl butyral, and dibutyl phthalate to a pot.
The slurry was prepared by wet mixing for 0 hour. Subsequently, the slurry was spread on a carrier sheet and had a thickness of 0.4 mm.
Green sheets were formed. Thereafter, the green sheet was degreased in the air to form an α-lithium aluminate electrolyte holding layer. When the average pore diameter of the electrolyte retaining layer was measured by a mercury intrusion method, it was about 1 μm.

Further, a γ-lithium aluminate electrolyte holding layer having an average pore diameter of 0.4 μm was prepared in the same manner as in Example 2. One layer of the α-lithium aluminate electrolyte holding layer obtained as described above is on the cathode side, and two layers of γ-lithium aluminate electrolyte holding layer are on the anode side.
A total of three layers are laminated, and a mixed alkali carbonate (L
i ₂ CO ₃ : 62 mol%, K ₂ CO ₃ : 38 mol
%) To 550 ° C. and melt impregnated in the electrolyte holding layer to prepare an electrolyte plate having a thickness of 1.2 mm.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle diameter of 0.8 μm. A separator 19 made of stainless steel and an edge seal plate 11, 1
2. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled using the corrugated collector plates 15 and 16.

Next, a second embodiment of the present invention will be described. Among the plurality of electrolyte holding layers constituting the electrolyte plate 3, the portion of the electrolyte holding layer in contact with the anode 1 has a larger average pore diameter than the other portions. Such an electrolyte plate 3
When the battery is used, the structure of the electrolyte holding layer in contact with the anode 1 becomes coarse and buckling is likely to occur, so that when the battery is assembled and tightened, the electrolyte holding layer at the contact interface with the anode 1 collapses and the holding material becomes Bites into one pore. As a result, the electrolyte is naturally drawn into the anode 1 from the electrolyte plate 3, so that a good contact interface between the anode and the electrolyte plate is formed, and the electrolyte retention amount of the anode 1 is reduced due to electrolyte loss over a long operation. Can also maintain stable performance.

Example 6 In the same manner as in Example 1, the amount of the binder was adjusted to form two types of α-lithium aluminate electrolyte holding layers having an average pore diameter of about 0.4 μm and about 0.6 μm. Produced. Among the α-lithium aluminate electrolyte holding layers obtained as described above, two sheets each having an average pore diameter of about 0.4 μm and one sheet having an average pore diameter of about 0.6 μm were laminated, and a total of three sheets were formed. Mixed alkali carbonate (L
i ₂ CO ₃ : 62 mol%, K ₂ CO ₃ : 38 mol
%) Was raised to 550 ° C., and the electrolyte retaining layer was melt-impregnated to produce an electrolyte plate 3 having a thickness of 1.2 mm.

The electrolyte plate obtained as described above was placed between an anode previously impregnated with an electrolyte composed of a mixed alkali carbonate and a non-impregnated cathode composed of nickel oxide powder having an average particle diameter of 0.8 μm. An electrolyte holding layer having an average pore diameter of about 0.6 μm is arranged on the anode side, and a separator 19 made of stainless steel, edge seal plates 11 and 12, and corrugated current collector plates 15 and 16 are used. The molten carbonate fuel cell shown in FIGS. 1 and 2 was assembled.

Examples 1 to 5 assembled as described above
6. In the molten carbonate fuel cells of Comparative Examples 1 and _2, 80 vol% of H ₂ and ₂₀ vol of CO ₂ were used as fuel gas at the anode.
1% of a mixed gas, a mixed gas of 70 vol% of air and 30 vol% of CO ₂ as an oxidizing agent gas is supplied to the cathode, and a pressure of 5 mA at 650 ° C. and 150 mA / cm 2.
A 000 hour power generation test was performed. After the test, the amount of nickel deposited in the electrolyte plate per unit area and the working potential drop were determined by chemical analysis. Table 1 shows the results.

[0049]

[Table 1]

As is apparent from Table 1, in Examples 1 to 6 in which at least one α-lithium aluminate electrolyte holding layer having an average pore diameter smaller than the average particle diameter of the cathode particles was used for the electrolyte plate, the average particle diameter was 5,000. Even after the time power generation test, the amount of nickel deposited on the electrolyte plate is as small as 10 mg / cm ² or less. In Comparative Example 1 in which the α-lithium aluminate electrolyte holding layer was not used, and in Comparative Example 2 in which the average pore diameter of the α-lithium aluminate electrolyte holding layer was larger than the average particle size of the cathode particles, after the power generation test for 5000 hours The amount of nickel deposited in the electrolyte plate was as large as 20 mg / cm ² or more, and it is considered that nickel short-circuit occurred quickly.

Further, Example 6 in which the average pore diameter of the .alpha.-lithium aluminate electrolyte holding layer in the part in contact with the anode was larger than the other parts, showed the smallest drop in the operating potential.

[0052]

As described in detail above, according to the present invention,
Α- having an average pore diameter smaller than the average particle diameter of the cathode particles
By using the lithium aluminate electrolyte holding layer for at least one layer electrolyte plate, it is possible to suppress nickel deposition in the electrolyte plate during power generation, thereby increasing the nickel short-circuit occurrence time and providing a long-life molten carbonate. Type fuel cell can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a unit cell electromotive section of a molten carbonate fuel cell according to the present invention.

FIG. 2 is a sectional view showing an example of a molten carbonate fuel cell according to the present invention.

FIG. 3 is a schematic diagram showing a basic structure of a molten carbonate fuel cell according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 anode (fuel electrode) 2 cathode (oxidant electrode) 3 electrolyte plate 3a α-lithium aluminate electrolyte holding layer 4a, 4b housing 5a, 5b current collector plate 6, 8 supply port 7, 9 exhaust port 10 interconnector 11, 12 Edge seal plate 13,14 Spring member 15,16 Current collector plate 17,18 Flow path 19 Separator 50 Reduction precipitated nickel (Ni) 51 Nickel oxide (NiO) particles

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuaki Nakagawa 1 Tokoba Toshiba-cho, Komukai-ku, Kawasaki-shi, Kanagawa Inside the Toshiba R & D Center

Claims (3)

[Claims] 1. A fuel electrode comprising a porous body formed of a first powder having conductivity, an oxidizer electrode comprising a porous body formed of a second powder having conductivity, and the fuel A fuel gas supply device for supplying a fuel gas to an electrode, an oxidant gas supply device for supplying an oxidant gas to the oxidant electrode, and a fuel gas supply device disposed between the fuel electrode and the oxidant electrode; A molten carbonate fuel cell comprising: an electrolyte plate mainly composed of lithium aluminate and having an electrolyte holding layer having an average pore diameter smaller than the average particle diameter of the second powder. 2. The molten carbonate type according to claim 1, further comprising an electrolyte plate on which a plurality of electrolyte holding layers are laminated, wherein at least one layer has an electrolyte holding layer mainly composed of the α-lithium aluminate. Fuel cell. 3. The molten carbonate fuel cell according to claim 2, wherein the average pore diameter of the electrolyte retaining layer in contact with the fuel electrode is larger than the average pore diameter of the other electrolyte retaining layers.