JPH05174850A - Solid electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To provide a solid electrolyte type fuel cell which is low in reaction resistance and high in output density. CONSTITUTION:In a solid electrolyte type fuel cell where a plural number of cells 4 each of which has a fuel electrode 2 and an oxidant electrode 3 while being faced to each other via a solid electrolytic plate 1, and separators 5 are interchangeably laminated so as to be formed into a stack, a great number of fuel gas passages 31 and oxidant gas passages 21 are provided in the laminated direction of the aforesaid stack. And fuel gas seal sections 1a and 5a preventing fuel gas from coming in the oxidant electrodes 3 are provided for the circumferential surfaces of the fuel gas passages 31 of the aforesaid solid electrolytic plates 1 and of the separators 5, and oxidant gas sealing sections 1b and 5b preventing oxidant gas from coming in the fuel electrodes 2, are meanwhile, provided for the circumferential surfaces of the oxidant gas passages 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell using an ion conductive ceramic as an electrolyte.

[0002]

2. Description of the Related Art Solid oxide fuel cells (hereinafter referred to as "SOF
(Hereinafter referred to as "C") has attracted attention as a completely solidified third generation fuel cell following a phosphoric acid fuel cell and a molten carbonate fuel cell, and has been studied in various fields. In particular, the SOFC using ion conductive ceramics as an electrolyte has the advantages that it can completely solve the problem of electrolyte loss, and that it has a high operating temperature (about 1000 ° C) and higher power generation efficiency than conventional batteries. is there.

The SOFC is, for example, as shown in FIG. 6, a cell 14 in which a fuel electrode 13 and an oxidant electrode 12 face each other with an electrolyte plate 11 in between, and a fuel gas passage 1 on both sides.
3a and separator 15 having oxidant gas passage 12a
A flat plate type SOFC in which and are laminated is used.

[0004]

However, in the conventional battery shown in FIG. 6, a large number of passages 1 extending only in one direction are provided.
Since 2a and 13a are provided in parallel with the electrode surface, there is a problem such as a difference in gas density between the gas supply side and the gas discharge side of the passages 12a and 13a. Therefore, it is difficult to uniformly supply the gas within the cell surface. In this case, when the gas utilization rate is increased, the area where the gas is not supplied (where the gas does not reach) increases in the cell surface, so the effective area of the electrode reaction decreases. As a result, there is a problem that the reaction resistance of the battery increases.

In addition, the passages 12 are formed on both sides of the separator 15.
Since the a 13a is formed, the thickness of the separator 15 is increased. As a result, the distance between the cells 14 becomes large, which causes a problem that the power density of the battery becomes small. In view of the above problems, it is an object of the present invention to provide a solid oxide fuel cell having a low reaction resistance and a high output density.

[0006]

In order to solve the above problems, the present invention is a stack in which a plurality of separators and cells in which a fuel electrode and an oxidizer electrode face each other through a solid electrolyte plate are alternately laminated. In the solid oxide fuel cell constituting the above, a large number of fuel gas passages and oxidant gas passages are provided in the stacking direction of the stack, and an oxidant electrode is provided on the peripheral surfaces of the fuel gas passages of the solid electrolyte plate and the separator. While a fuel gas seal portion is provided to prevent the entry of fuel gas into the fuel cell, an oxidant gas seal portion is provided on the peripheral surface of the oxidant gas passage to prevent entry of the oxidant gas into the fuel electrode. And

[0007]

As described above, if a large number of fuel gas passages and oxidant gas passages are provided in the stacking direction of the stack, gas can be supplied to each electrode substantially uniformly through these passages. As a result, the gas is supplied substantially uniformly within the cell surface, so that the effective area of the electrode reaction increases and the reaction resistance of the cell decreases.

Further, since it is not necessary to form the fuel gas passage and the oxidant gas passage in the separator, the thickness of the separator can be reduced. As a result, the distance between cells can be shortened, and the power density of the battery is improved. In addition, since each passage is provided with a seal portion, it is possible to prevent gas from entering the counter electrode.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a solid oxide fuel cell according to an embodiment of the present invention, in which a porous oxidizer electrode 2 and a porous fuel electrode 3 are arranged via a solid electrolyte plate 1. An oxidant gas passage 21 is formed in the stacking direction of a stack formed by alternately stacking a plurality of cells 4 and separators 5.
Also, a large number of fuel gas passages 31 are provided. 1 in the figure
Numerals b and 5b are oxidant gas seal portions that prevent the oxidant gas from entering the fuel electrode 3, and numerals 1a and 5a are fuel gas seal portions that prevent the fuel gas from entering the oxidant electrode 2.

As the solid electrolyte plate 1, a dense 3 mol% Y ₂ O ₃ -added partially stabilized ZrO ₂ plate (size 100 mm × 100 mm, thickness 200 μm) made of superplastic ion conductive ceramics was used. Here, the solid electrolyte plate 1 having the above structure was produced as follows. First, La _0.9 Sr _0.1 MnO ₃ powder (average particle size 2 μm) was prepared as a raw material for the oxidizer electrode 2, and was slurried using a terpineol solvent. On the other hand, as raw materials for the fuel electrode 3, NiO powder (average particle size 2 μm) and 8 mol% Y ₂ O ₃ added partially stabilized ZrO ₂ powder (average particle size 1 μm) were prepared, and a mixture of these was used with a terpineol solvent. It was made into a slurry.

Next, after a plurality of circular masks 1c (φA = 2 mm) as shown in FIG. 2 are arranged on one surface of the solid electrolyte plate 1 (distance between circles d: d = 8
mm), and a slurry for an oxidizer electrode was applied to a thickness of 220 μm. Then, a mask was placed on the other surface of the solid electrolyte plate 1 in the same manner as the oxidizer electrode, and the slurry for the fuel electrode was applied to a thickness of 220 μm.

Subsequently, the solid electrolyte plate 1 having both surfaces coated with the oxidizer electrode 2 and the fuel electrode 3 has a temperature (1150) at which it exhibits superplasticity.
C.) and then using a compression mold made of silicon carbide, compression was performed for 100 seconds at a pressurization rate of 10 g / cm ² · s until the load changed from 10 g / cm ² to 100 g / cm ² . .. By this compression, the through hole (φ
Convex portion 1a and concave portion 1b having C = 1 mm (height of convex portion =
A large number of concave portions having a depth φB: φB = 400 μm) were formed over the entire surface to prepare a solid electrolyte plate 1.

On the other hand, the separator 5 having the above structure was produced as follows. First, a separator 5 (size 100) made of a heat-resistant alloy or superplastic electronically conductive ceramics is used.
mm × 100 mm, thickness 200 μm), and the separator 5 was compressed under the same conditions by using a compression mold that was substantially the same as that used when the solid electrolyte plate 1 was compressed. By this compression, the through hole (φE = 1mm,
A separator 5 was produced in which a large number of convex portions 5a having φF <φA and concave portions 5b (height of convex portions = depth of concave portions φD: φD = 200 μm) were formed over the entire surface.

The cell 4 shown in FIG. 3 manufactured as described above,
1 is formed by alternately stacking the separator 5 shown in FIG. 4 to form a stack, and then tightening the entire stack from above and below.
A battery as shown in was prepared. By this tightening, the convex portion 1a and the concave portion 1b of the solid electrolyte plate 1 and the convex portion 5a and the concave portion 5b of the separator 5 come into contact with each other, so that the contact surface seals the gas between the oxidizer electrode 2 and the fuel electrode 3. It can be performed. In addition, electrodes 2 and 3 and separator 5
Contact with will be improved.

The gas flow in the solid oxide fuel cell configured as described above will be described with reference to FIG.
First, the air supplied from the oxidant gas supply port is supplied to the cell 4
Air is supplied to each oxidant electrode 2 while flowing from the bottom to the top in FIG. 1 through the oxidant gas passage 21 formed in the stacking direction of. On the other hand, the hydrogen gas supplied from the fuel gas supply port is supplied to the fuel gas passage 31 extending in the stacking direction of the cells 4.
1, hydrogen gas is supplied to each fuel electrode 3 while flowing from top to bottom in FIG. When hydrogen gas and air are supplied to the electrodes 2 and 3, power is generated in each cell 4. The water vapor generated during this power generation is discharged to the outside along the laminated surface of the solid electrolyte plate 1.

The stack thus manufactured is hereinafter referred to as (A) stack. [Comparative Example] As shown in FIG. 6, a stack having a structure in which a large number of passages 12a and 13a extending only in one direction were provided in parallel with the electrode surface was used. The stack having such a structure is hereinafter referred to as (X) stack. [Experiment] The relationship between the current density and the average cell voltage was investigated using the (A) stack of the present invention and the (X) stack of the comparative example. The results are shown in FIG.

As is apparent from FIG. 5, (A) of the present invention.
It can be seen that the stack has an improved average cell voltage as compared to the (X) stack of the comparative example. Therefore, it is understood that the stack (A) of the present invention can supply the gas substantially uniformly into the cell surface. Further, the (A) stack of the present invention is
Battery height is about 1/5 compared to the (X) stack of the comparative example
Therefore, it has been confirmed by experiments that the power density is improved about 6 times. It is considered that this is because the separator 5 in the stack (A) of the present invention has a small thickness, and thus the output density is improved by reducing the distance between the cells 4.

According to the above-mentioned embodiment, since superplastic ceramics is used as the solid electrolyte plate 1, it is possible to perform molding at a relatively low stress and temperature, and it is possible to freely deform a dense sintered body. can do. Therefore, the dimensional accuracy is higher and the processing is easier than the ceramics molded and sintered in the state of the green tape. [Other Matters] The method for producing the electrodes 2 and 3 is not limited, but, for example, after preparing the electrodes 2 and 3 having a large porosity in advance and applying the electrodes 2 and 3 to the solid electrolyte plate 1 with a slightly thicker thickness, It is preferable to produce the electrodes 2.3 having the desired porosity and thickness by clamping the stack during battery operation. If the electrodes 2 and 3 are produced in this way, the contact between the electrodes 2 and 3 and the separator 5 can be improved, and the gas permeability can be improved. The thickness of the solid electrolyte plate 1 is preferably 100 μm to 500 μm, and the thickness of the separator 5 is preferably 10 μm to 5 mm. The height φB of the convex portion 1a (or the depth of the concave portion 1b) φB of the solid electrolyte plate 1 is preferably φB = 200 μm to 500 μm. However, it must be slightly higher (or deeper) than the height φD (or the depth of the recess 5b) φD of the separator 5. In addition, the diameter φA of the lower end opening of the through hole of the convex portion 1a of the solid electrolyte plate 1 (or the upper end opening of the through hole of the concave portion 1b) is the lower end opening (or concave portion) of the through hole of the convex portion 5a of the separator 5. It must be slightly larger than the diameter φF of the upper end opening of the through hole 5b). The diameter φC of the upper end opening of the through hole of the convex portion 1a of the solid electrolyte plate 1 (or the lower end opening of the through hole of the concave portion 1b) is
φC = 0.5 mm to 5 mm is preferable. However, it must be slightly smaller than the diameter φE of the upper end opening of the through hole of the convex portion 5a of the separator 5 (or the lower end opening of the through hole of the concave portion 5b).

[0019]

As described above, according to the present invention, the gas can be supplied substantially uniformly within the surface of the battery, so that the effective area of the electrode reaction is increased. Therefore, the reaction resistance of the battery is reduced. Furthermore, since the distance between the cells can be shortened, the power density of the battery is improved. From these, there is an effect that the power generation efficiency of the battery can be improved.

In addition, since each passage is provided with a seal portion, it is possible to prevent gas from entering the counter electrode.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a (A) stack of the present invention.

FIG. 2 is a schematic cross-sectional view of a cell according to the (A) stack of the present invention.

FIG. 3 is a schematic cross-sectional view of a cell according to the (A) stack of the present invention.

FIG. 4 is a schematic cross-sectional view of a separator according to the (A) stack of the present invention.

FIG. 5 is a graph showing the relationship between the current density and the average cell voltage in the (A) stack of the present invention and the (X) stack of the comparative example.

FIG. 6 is an exploded perspective view of a conventional flat plate SOFC.

[Explanation of symbols]

 1 Solid Electrolyte Plate 2 Oxidant Electrode 3 Fuel Electrode 4 Cell 5 Separator 21 Oxidant Gas Passage 31 Fuel Gas Passage 1b ・ 5b Oxidant Gas Seal Part 1a ・ 5a Fuel Gas Seal Part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shuzo Murakami 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd. Within

Claims (1)

[Claims] 1. A solid electrolyte fuel cell in which a stack is formed by alternately stacking a plurality of cells and separators in which a fuel electrode and an oxidizer electrode face each other via a solid electrolyte plate, and stacking the stacks. A large number of fuel gas passages and oxidant gas passages are provided in the direction, and a fuel gas seal portion for preventing the fuel gas from entering the oxidant electrode is provided on the peripheral surfaces of the fuel gas passages of the solid electrolyte plate and the separator. On the other hand, the solid oxide fuel cell is characterized in that an oxidant gas seal portion for preventing the oxidant gas from entering the fuel electrode is provided on the peripheral surface of the oxidant gas passage.