JP3104295B2 - Method for producing molten salt fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a molten salt fuel cell using a molten salt as an electrolyte, and more particularly to a method for manufacturing a molten salt fuel cell in which an electrode and an electrolyte holder are integrally formed.

[0002]

2. Description of the Related Art FIG. 3 is a side sectional view of a unit cell constituting a conventional molten salt fuel cell. In the figure, 1 is an electrolyte holder, 2 is an anode electrode impregnated with a molten salt as an electrolyte, and 3 is a cathode electrode impregnated with the same electrolyte as the anode electrode 2.

In manufacturing such a conventional molten salt fuel cell, the electrolyte holder 1, the anode electrode 2, and the cathode electrode 3 are individually manufactured as follows. For example, the electrolyte holder 1 is obtained by suspending a ceramic powder as an aggregate thereof in a mixed solution of an organic solvent, an organic binder and a plasticizer, and forming a slurry into a sheet having a certain thickness by a doctor blade method. dry. Then, several sheets of this sheet after drying are stacked and pressed to have a predetermined thickness, and then cut out to produce a predetermined size. The anode electrode 2 and the cathode electrode 3 are
The slurry obtained by suspending the metal powder is formed into a sheet in the same manner as the electrolyte holder 1, and the sheet is sintered at a high temperature in a furnace, and the electrolyte is sprayed on the electrodes 2 and 3. This electrolyte is melted by raising the temperature again in a furnace, and the electrodes 2 and 3 are impregnated with the electrolyte. As shown in FIG. 3, each of the members thus manufactured was stacked on the electrolyte holder 1 on the cathode electrode 3 and further stacked on the anode electrode 2 to form a unit cell of the fuel cell. . In order to stack the unit cells constructed as described above in series to produce a fuel cell stack, hydrogen gas must flow through the anode electrode 2 and air and carbon dioxide must flow through the cathode electrode 3. For this purpose, a separator plate (not shown) was sandwiched between the unit cells.

[0004]

As described above, each member is first manufactured individually to form a unit cell, and then the unit cells are stacked to manufacture a fuel cell. In the method, the separator plates, the electrolyte holder, the anode electrode, and the cathode electrode, which are individually manufactured, need to be stacked while being positioned one by one, which is very inefficient. Further, the flatness of individual electrolyte holders, electrodes, separator plates and the like is limited to several tens of μm, and therefore, a gap due to the unevenness of the flatness often occurs between members after forming the laminate. Was. This gap became insulated when the fuel cell thus manufactured was operated to generate power, and as a result, only a part of the electrode was operated and power generation efficiency was greatly reduced. In addition, when a stacked body having a large number of stacked layers is operated as a battery, the gap shrinks during the operation of the battery, and the dimensions of the stacked body are greatly changed. Therefore, a method of integrally manufacturing the electrolyte support and the electrode has been proposed. For example, Japanese Patent Application Laid-Open No. 58-87774 discloses a method in which an electrolyte holder and an electrode are heated and pressed together. In this method, the electrolyte is melted and pressed, so that high-pressure pressing at a high temperature of 500 ° C. is required. There is a device
Both processes require considerably complicated ones. Further, when pressing is performed at such a high temperature and a high pressure, there is a problem that the electrode shrinks and it becomes impossible to obtain a fuel cell having an optimal pore structure. Further, in the method of forming an electrode by the doctor blade method on the electrolyte holder formed by the doctor blade method disclosed in Japanese Patent Application Laid-Open No. 62-15768, the shape of the electrode formed on the electrolyte holder is solely determined. It is difficult to control with high accuracy, and sintering of the electrodes is performed in a state where the electrodes and the electrolyte holder are laminated.Therefore, when hundreds of laminated bodies are formed, the surface pressure is several kg / cm2 at the upper and lower parts.
Therefore, it is practically impossible to control the optimum hole structure of the electrode. Further, the thickness of the electrode is greatly reduced with the operation time of the fuel cell, and a gap is easily formed between the electrode and the electrolyte holder, so that the characteristics of the fuel cell are greatly reduced. In such a case, the dimensions of the laminate are greatly changed, and there is a problem that there is a great problem in connection with the gas supply manifold and in maintaining the surface pressure of the laminate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can easily provide an integrated unit cell of a molten salt fuel cell having no gap between an electrode and an electrolyte holder. It is intended to provide a manufacturing method.

[0006]

A method of manufacturing a molten salt fuel cell according to the present invention comprises the steps of: forming an anode electrode in which a metal sintered body is impregnated with an electrolyte made of molten carbonate; Forming a cathode electrode impregnated with a metal sintered body, forming an electrolyte holder containing an organic binder and having a lower softening temperature than the anode electrode and the cathode electrode by a doctor blade method, The method includes a step of sandwiching the electrolyte holder between an electrode and a cathode electrode to form a unit cell, and a step of performing hot press bonding that satisfies predetermined conditions on the unit cell.

A method for manufacturing a molten salt fuel cell according to a second invention comprises a step of forming an electrolyte holder made of ceramics, and an anode electrode in which a metal carbonate is impregnated with an electrolyte made of molten carbonate. Forming a cathode electrode in which the electrolyte is impregnated in a metal sintered body, and forming an adhesive sheet containing an organic binder and having a lower softening temperature than the anode electrode, the cathode electrode and the electrolyte holder. And a step of sandwiching the adhesive sheet between the anode electrode and the cathode electrode and the electrolyte holder to form a unit cell, and a step of performing hot pressing that satisfies predetermined conditions on the unit cell. It is provided.

[0008]

In the method of manufacturing a molten salt fuel cell according to the present invention, after the unit cell of the fuel cell is constructed as described above,
By performing the hot pressing, the organic binder contained in the electrolyte holder is softened, and enters into the gap between the electrode and the electrolyte holder to fill the gap.

In the method for manufacturing a molten salt fuel cell according to the second invention, the organic binder contained in the pressure-sensitive adhesive sheet is softened by forming the unit cell of the fuel cell as described above and then performing hot pressing. -The gap is filled by filling the gap between the electrolyte holders.

[0010]

[Embodiment 1] FIG. 1 is a side sectional view of a unit cell of a molten salt fuel cell showing one embodiment of the present invention. In the figure, 1 is 64% by weight of LiAlO2 as an aggregate, 21% by weight of polyvinyl butyral as an organic binder,
An electrolyte holder prepared by a doctor blade method using polyethylene glycol as a plasticizer in a composition ratio of 15% by weight, 2 is a carbonate which is an electrolyte in 90% of the pore volume of a porous body made of a sintered Ni-Al alloy. (Li2CO3 +
K2CO3, molar ratio of 62:38) was impregnated at 650 DEG C. The anode electrode 3 contained carbonate (Li2) as an electrolyte in 60% of the pore volume of the sintered Ni porous body.
CO3 + K2 CO3, molar ratio 62:38) at 650 ° C.

First, the electrolyte holder 1, the anode electrode 2 and the cathode electrode 3 are individually formed in a predetermined shape in the same manner as in the conventional example, and then the cathode electrode 3 and the electrolyte holder are placed on a press. The body 1 and the anode electrode 2 are positioned and superposed to form a unit cell of the fuel cell. Next, this unit cell is heated to 100 ° C. to 13 ° C., which exceeds the softening point of the organic binder contained in the electrolyte holder 1.
Raise the temperature to 0 ° C. In addition, the electrodes 2 and 3 are integrated with the electrolyte holder 1 by applying pressure at the same time as the temperature is raised. To determine the applied pressure, a hot compression test was performed in advance using unit cells having the same specifications. , Surface pressure 50
kg / cm2, the thickness deformation of the electrolyte holder 1 is 30 to
When a pressure higher than 60 μm is applied, the electrolyte holder 1 is excessively crushed and deformed. At a pressure lower than 60 μm, the deformation amount of the electrolyte holder 1 is too small and the electrodes 2 and 3 are deformed.
And the electrolyte holder 1 did not adhere to each other.
It was pressed for several minutes at a surface pressure of 0 kg / cm2. At this pressurized pressure, the deformation amount of the electrodes 2 and 3 is 10 μm or less for the anode electrode 2 and 30 μm or less for the cathode electrode 3. The unit cell including the electrolyte holder 1, the anode electrode 2 and the cathode electrode 3 has a thickness of The thickness was reduced by 70 μm from the sum of the thicknesses of the respective members before hot pressing. When the cross section of this integrated product was observed, it was confirmed that the electrolyte holder 1 entered the gap between the electrodes 2 and 3 and the electrolyte holder 1 and was uniformly joined without any gap. When the battery was operated using this unit cell, the resistance was reduced by 50 mΩcm 2 as compared with the case of using the unit cell manufactured by the method of the conventional example.

Embodiment 2 FIG. FIG. 2 is a side sectional view of a unit cell of the molten salt fuel cell according to the second invention. In the figure, 1 is 65% by weight of LiAlO2 as an aggregate, 20% by weight of polyvinyl butyral as an organic binder, and 15% by weight of polyethylene glycol as a plasticizer.
The electrolyte holder 2 was prepared as the composition ratio of 2 and the carbonate (Li2CO3 + K2CO3, molar ratio of 6) was used as an electrolyte in 90% of the pore volume of the porous body composed of the sintered Ni.Al alloy.
2:38) is impregnated at 650 ° C., and 3 has a pore volume of 6 of a sintered Ni porous body.
A cathode electrode prepared by impregnating 0% with a carbonate (Li2CO3 + K2CO3, molar ratio 62:38) as an electrolyte;
Reference numeral 4 denotes a pressure-sensitive adhesive sheet prepared by using 63% by weight of LiAlO2 as an aggregate, 22% by weight of polyvinyl butyral as an organic binder, and 15% by weight of polyethylene glycol as a plasticizer.

First, an electrolyte holder 1, an anode electrode 2,
After the cathode electrode 3 and the adhesive sheet 4 are individually formed into predetermined shapes as in the conventional example, the cathode electrode 3, the adhesive sheet 4, the electrolyte holder 1,
The pressure-sensitive adhesive sheet 4 and the anode electrode 2 are positioned and superimposed in this order to form a unit cell of the fuel cell. Next, the temperature of the unit cell is raised to 100 ° C. to 130 ° C. which exceeds the softening point of the organic binder contained in the pressure-sensitive adhesive sheet 4.
Further, the same hot pressing test as in Example 1 was performed, the pressing pressure was determined to be 50 kg / cm 2, and the unit cell was pressed for several minutes. Electrodes 2 and 3 at this pressure
The amount of deformation of the anode electrode 2 is 10 μm or less, the cathode electrode 3 is 30 μm or less, the electrolyte holder 1 is 10 μm or less, and a unit cell comprising the electrolyte holder 1, the anode electrode 2, the cathode electrode 3 and the adhesive sheet 4 Was 9 μm thinner than the sum of the thicknesses of the members before hot pressing. When the cross section of this integrated product was observed, it was confirmed that the pressure-sensitive adhesive sheet 4 penetrated without gap between the electrodes 2 and 3 and the electrolyte holder 1 and was integrated. Furthermore, when the battery was operated using this unit cell, the resistance was 50% higher than when the unit cell manufactured by the method of the conventional example was used.
mΩcm ² could be reduced.

In the above-described embodiment, polyvinyl butyral is used as an organic binder and polyethylene glycol is used as a plasticizer in preparing the slurry for the electrolyte holder 1 and the adhesive sheet 4. Other materials that soften below the melting point may be used. Further, the electrolyte holder 1,
Although LiAlO2 is used as an aggregate of the adhesive sheet 4, these may be other ceramic powders. Further, in the pressure-sensitive adhesive sheet 4, a metal powder as a reinforcing body may be mixed into the aggregate. Further, a reinforcing member for preventing cracks, such as a metal mesh or a ceramic fiber, may be embedded in the electrolyte holder 1 or the adhesive sheet 4. The cathode electrode may be an oxide of a metal sintered body. In short, according to the present invention, the organic substance contained in the electrolyte holder 1 or the pressure-sensitive adhesive sheet 4 is heated to be softened so as to enter the gap between the electrodes 2 and 3 and the electrolyte holder 1 so as to fill the gap. This is for producing an integrated product of the electrodes 2, 3 and the electrolyte holder, which are unit cells of a fuel cell, and any combination of materials, compositions, and devices can be used as long as the conditions described above are satisfied. May be.

[0015]

As described above, according to the present invention, there is provided a unit cell of a fuel cell, which is an integrated electrode-electrolyte holder having a predetermined shape with no gap between the electrode and the electrolyte holder and having high adhesion. There is an effect that it can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a unit cell of a molten salt fuel cell according to one embodiment of the present invention.

FIG. 2 is a side sectional view showing a unit cell of a molten salt fuel cell according to an embodiment of the second invention.

FIG. 3 is a side sectional view showing a unit cell of a conventional molten salt fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyte holder 2 Anode electrode 3 Cathode electrode 4 Adhesive sheet

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Yoshioka 8-1-1 Tsukaguchi Honcho, Amagasaki City Mitsubishi Electric Corporation Central Research Laboratory (56) References JP-A-58-119169 (JP, A) 1979-3967 (JP, A) JP 39-27392 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (2)

(57) [Claims] A step of impregnating an electrolyte made of molten carbonate into a metal sintered body to form an anode electrode; a step of forming a cathode electrode impregnated with the electrolyte in a metal sintered body; A step of forming an electrolyte holder having a softening temperature lower than the anode electrode and the cathode electrode by a doctor blade method containing a binder, and forming a unit cell by sandwiching the electrolyte holder between the anode electrode and the cathode electrode And a step of hot pressing the unit cells to satisfy the following condition. (A) The temperature at which the organic binder softens. (B) Pressure bonding is performed at a pressure lower than a pressure at which the anode electrode and the cathode electrode are deformed. 2. A step of forming an electrolyte holder made of ceramics, a step of forming an anode electrode in which a metal sintered body is impregnated with an electrolyte made of molten carbonate, and a step of applying the electrolyte to the metal sintered body. A step of forming an impregnated cathode electrode, a step of forming an adhesive sheet containing an organic binder and having a softening temperature lower than that of the anode electrode, the cathode electrode and the electrolyte holder, and the step of forming the anode electrode, the cathode electrode and the electrolyte holder A method for producing a molten carbonate fuel cell, comprising: a step of sandwiching the pressure-sensitive adhesive sheet between the body and a unit cell; and a step of hot pressing the unit cell to satisfy the following conditions. . (A) a temperature at which the organic binder softens.
When. (B) the anode electrode, the cathode electrode, and the electrode;
Crimping should be performed below the pressure at which the degraded holding body deforms.