JPH0696779A - Solid electrolytic fuel cell - Google Patents

Abstract

PURPOSE:To increase the effective area of the whole cell, and provide a solid electrolytic fuel cell increased in cell output. CONSTITUTION:A solid electrolytic fuel cell is constituted by plurally laminating a cell 4 having a fuel electrode 3 and an oxidizing agent electrode 2 mutually opposed through a solid electrolytic plate 1, and a separator 5 having irregular parts for forming reaction gas passages 6, 7 formed thereon. The average porosity or average pore diameter of the part making contact with the protruding part 5a of the separator in at least one electrode of both the electrodes 2, 3 is set larger than the average porosity or average pore diameter of the part making no contact with the protruding part 5a of the separator.

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 improvement of its electrode.

[0002]

2. Description of the Related Art A fuel cell directly converts chemical energy of a supplied gas into electric energy, so that high power generation efficiency can be expected. In particular, solid oxide fuel cells (SO
FC) has attracted attention as a third-generation fuel cell next to phosphoric acid fuel cells (PAFCs) and molten carbonate fuel cells (MCFCs), and since it operates at a high temperature of approximately 1000 ° C, it is necessary to use waste heat. If the power generation efficiency is included, the PAFC, M
It has been studied in various fields because it has the advantage that it can be improved compared to CFC.

FIG. 6 is an exploded perspective view showing the basic structure of a flat plate type SOFC. A cell 14 having an oxidizer electrode 12 and a fuel electrode 13 on both sides of a solid electrolyte plate 11 and a separator 15 are shown. Are alternately stacked, and the entire battery is tightened to reduce the internal resistance of the battery.

[0004]

However, the contact resistance between the respective components can be reduced by tightening the entire battery as described above. However, as shown in FIG. 7, as shown in FIG. It is difficult to diffuse the reaction gas (oxidant gas in the illustrated example) into the electrode portion (oxidant electrode in the illustrated example) 12a that is in contact with the electrode 15a, so that it is not possible to effectively generate power in the electrode surface. . Therefore, since the effective area of the entire electrode is reduced, there is a problem that the battery output is reduced.

Therefore, a method of narrowing the rib width of the separator can be considered in order to effectively generate power in the electrode surface. However, when tightening the whole battery, a slight deviation of the positions of the ribs of the upper and lower separators causes Unnecessary stress acts on the electrolyte plate interposed between the separators, which causes a problem that the electrolyte plate is damaged. Further, considering the manufacturing cost of cutting the alloy that is the separator material and the like, it is currently difficult to reduce the rib width to 2 mm or less.

In view of the above problems, it is an object of the present invention to provide a solid oxide fuel cell in which the effective area of the whole cell is increased and the cell output is increased.

[0007]

In order to solve the above problems, the present invention forms a cell in which a fuel electrode and an oxidizer electrode face each other through a solid electrolyte plate, and an uneven portion which forms a reaction gas flow path. In a solid oxide fuel cell comprising a plurality of laminated separators, the average porosity of the portion in contact with the convex portion of the separator in at least one of the two electrodes, or the average pore diameter is the convex portion of the separator. It is characterized in that it is configured to be larger than the average porosity or the average pore diameter of the non-contact portion.

[0008]

As described above, if the average porosity of the electrode portion in contact with the convex portion (rib) of the separator is large, that is, if the gas passage portion which is a cavity in that portion is large, it has been difficult for the reaction gas to diffuse conventionally. Since the reaction gas is easily diffused and supplied to the electrode portion in contact with the convex portion (rib) of the separator, it is possible to effectively generate power within the electrode surface. Therefore, the effective area of the entire electrode increases, so that the reaction resistance,
Loss due to contact resistance and the like can be reduced, and the battery output increases.

[0009]

【Example】

(First Embodiment) [First Embodiment] FIG. 1 is a cross-sectional view of a main part of a solid oxide fuel cell according to a first embodiment of the present invention, in which an oxidizer electrode 2 and a fuel electrode are interposed via a solid electrolyte plate 1. Cell 4 consisting of 3 and
This is a structure in which a plurality of separators 5 are laminated. The separator 5 has ribs (width 2 mm) 5a for forming the oxidant gas flow channel 6 and the fuel gas flow channel 7 on one of the upper and lower surfaces.
Is composed of a plurality of metal plates (for example, Inconel 600) provided at intervals of 2 mm. The solid electrolyte plate 1 is a dense 3 mol% yttria-added partially stabilized zirconia plate (electrode area 100 cm ² , thickness 0.2 m) made of superplastic ion conductive ceramics.
m) was used. Reference numeral 8 in the drawing denotes a seal portion at the interface with the solid electrolyte plate 1, and for example, a seal material made of a non-conductive high viscosity melt such as Pyrex glass is used.

The battery was manufactured as follows. First, as a raw material for the fuel electrode 3, a NiO powder having an average particle size of 1 μm prepared by mixing 50 wt% of 8 mol% yttria-added stabilized zirconia (YSZ) powder having an average particle size of 0.3 μm was prepared, and slurried using a terpineol solvent. The slurry was used for the fuel electrode.

On the other hand, as the raw material for the oxidizer electrode 2, the average particle size is 1
Stabilized zirconia with 8 μm yttria of μm (YS
Z) Powder mixed with 20 wt% and having an average particle diameter of 2 μm, and 2
0 μm La _0.9 Sr _0.1 MnO ₃ was prepared and slurried using a terpineol solvent to prepare a 2 μm slurry for the oxidant electrode and a 20 μm slurry for the oxidant electrode, respectively.

Next, the fuel electrode slurry was applied to one surface of the solid electrolyte plate 1 so as to have a thickness of 70 μm, and this was baked in air at 1250 ° C. for 2 hours. Then, the two types of oxidizer electrode slurries are respectively applied to the other surface of the solid electrolyte plate 1 by a method described later to a thickness of 70 μm.
It was applied so that it would be m. That is, as shown in FIG. 2, the electrode portion 2a in contact with the rib 5a of the separator is coated with the 20 μm slurry for the oxidant electrode, and the electrode portion 2b not in contact with the rib 5a of the separator (that is, the oxidant gas flow channel 6 is 2 μm slurry for oxidizer electrode is applied to the facing electrode part),
This was calcined in air at 1100 ° C. for 4 hours. In the oxidant electrode 2 thus produced, the average porosity (or the average pore diameter) of the electrode portion 2a in contact with the rib 5a of the separator is larger than that of the electrode portion 2b not in contact with the rib 5a of the separator.

The battery thus manufactured is hereinafter referred to as (A) battery. [Comparative Example 1] Only the 2 μm slurry for the oxidant electrode was applied to the entire surface of the solid electrolyte plate on the side opposite to the fuel electrode side, and the oxidant electrode was composed of only a material having a small average porosity (or average pore diameter). A battery was produced in the same manner as in Example 1 except that the above was performed. The whole battery was tightened with a pressure of 3 kgf / cm ² .

The battery thus prepared is
₁ ) Called battery. [Comparative Example 2] Only the 20 μm slurry for the oxidant electrode was applied to the entire surface of the solid electrolyte plate on the side opposite to the fuel electrode side, and the oxidant electrode was composed of only a material having a large average porosity (or average pore diameter). A battery was produced in the same manner as in Example 1 except that the above was performed.

The battery thus prepared is
₂ ) Called battery. [Experiment 1] The (A) battery of the present invention and the (X) of the comparative example
_The current-voltage characteristics of the ₁ ). (X ₂ ) battery were investigated, and the results are shown in FIG. As is clear from FIG. 3, the battery (A) of the present invention is (X ₁ ) · (X ₂ ) of the comparative example.
It can be seen that the battery characteristics are improved compared to the battery.

The battery characteristics of the battery (A) of the present invention are improved as compared with the battery (X ₁ ) of the comparative example, because the battery (A) of the present invention has an average gas distribution of the electrode portion 2a in contact with the rib 5a of the separator. This is because the pore diameter (average porosity) is larger than that of the (X ₁ ) battery of the comparative example, so that the oxidant gas is diffused and supplied to the electrode portion 2a where it was difficult for the oxidant gas to diffuse conventionally. In addition, as a result of battery characteristic analysis, in the (X ₁ ) battery of the comparative example, the oxidant gas was supplied to the electrode portion (width about 2 mm) in contact with the rib of the separator even at the electrode portion 0.5 mm from both ends. There wasn't.

In addition, the battery characteristics of the battery (A) of the present invention are improved as compared with the battery (X ₂ ) of the comparative example, because the battery portion (A) of the present invention has an electrode portion which is not in contact with the rib 5a of the separator. This is because the average pore diameter (average porosity) of 2b (that is, the electrode portion facing the oxidant gas flow channel 6) is smaller than that of the (X ₂ ) battery of the comparative example, so that the electrode activity increases.
From the above results, the average porosity (or average pore diameter) of the electrode portion 2a in contact with the rib 5a of the separator is determined by the battery portion 2a not in contact with the rib 5a of the separator (that is, the electrode portion facing the oxidant gas flow channel 6). It is understood that it is preferable to use a material larger than that of Example 2. [Example 2] The electrode portion 2 in contact with the rib 5a of the separator
Example 1 except that a hardly sinterable substance is used for a and a highly conductive substance is used for the electrode portion 2b that does not contact the rib 5a of the separator.
A battery was prepared in the same manner as in.

Here, the battery was manufactured as follows. First, as a raw material for the fuel electrode 3, a NiO powder having an average particle size of 1 μm prepared by mixing 50 wt% of 8 mol% yttria-added stabilized zirconia (YSZ) powder having an average particle size of 0.3 μm was prepared, and slurried using a terpineol solvent. The slurry was used for the fuel electrode.

On the other hand, as the raw material of the oxidizer electrode 2, the average particle size is 1
Stabilized zirconia with 8 μm yttria of μm (YS
Z) La having an average particle size of 2 μm mixed with 20 wt% of powder
_0.9 Sr_0.1MnO₃ Prepare the terpineol solvent
It was made into a slurry to obtain an oxidizer electrode slurry A. Well
In addition, 8 mol% yttria with a mean particle size of 1 μm
Average particle size of 20 wt% of luconia (YSZ) powder
20 μm La_0.9 Ca _0.1CrO₃ Prepare and Terpi
Slurry using Neol solvent, slurry for oxidizer electrode
-B.

Next, the fuel electrode slurry was applied to one surface of the solid electrolyte plate 1 so as to have a thickness of 70 μm, and this was baked in air at 1250 ° C. for 2 hours. Then, the two types of oxidizer electrode slurries are respectively applied to the other surface of the solid electrolyte plate 1 by a method described later to a thickness of 70 μm.
It was applied so that it would be m. That is, the rib 5a of the separator
The oxidizer electrode slurry B is applied to the electrode portion 2a in contact with the oxidizer electrode slurry B for the electrode portion 2b not in contact with the rib 5a of the separator (that is, the electrode portion facing the oxidant gas flow channel 6). Was applied, and this was baked in air at 1100 ° C. for 4 hours.

The above-mentioned hardly sinterable substance has the general formula (I)
A perovskite type oxide represented by La _1-x M _x CrO ₃ (I) [In the above formula, M is Mg, Ca, Sr, Ba, and x is 0 ≦
x ≦ 0.5 is shown. Examples of the highly conductive substance include the perovskite oxide represented by the general formula (II).

(La_1-xM_x)_yMnO₃ (II) [In the above formula, M is Mg, Ca, Sr, or Ba, and x is 0 ≦
x ≦ 0.5, and y represents 0.7 ≦ y ≦ 1. ] Generally (La_1-xM_x)_yMnO₃System perovskite type
The oxide is La_1-xM _xCrO₃System perovskite type acid
It is a substance that is easier to sinter and has higher conductivity than other compounds.
The conductivity at 1000 ° C. is (La_1-xM_x)_yMn
O₃10 perovskite oxides²S · cm^-1To a degree
Yes, La_1-xM_xCrO₃-Based perovskite oxide
Is 10 cm^-1It is a degree. [Other Matters] In the above embodiment, the oxidizer electrode is used as an example.
As described above, only the fuel electrode or the oxidizer electrode, and
Of course, it is also possible to apply to both electrodes of the fuel electrode.

(Second Embodiment) [Embodiment] FIG. 4 is a plan view (partially broken section) of a cell of a solid oxide fuel cell according to a second embodiment of the present invention. The cell 24 is made of La _0.9 Sr via the solid electrolyte plate 21.
_This structure has an oxidizer electrode 22 made of _0.1 MnO ₃ and a fuel electrode 23, which will be described later. The solid electrolyte plate 21 is
Dense 3mo made of superplastic ion conductive ceramics
l% yttria-added partially stabilized zirconia plate (size 1
50 mm × 150 mm) was used.

As shown in FIG. 4, in the fuel electrode 23, the electrode high temperature portion 23a is a nickel-zirconia cermet (hereinafter referred to as "cermet A") using nickel having an average particle diameter of 10 μm, and the electrode low temperature. The portion 23b is a nickel-zirconia cermet (hereinafter referred to as "cermet B") using nickel having an average particle size of 1 μm. Here, the fuel electrode 23 was manufactured as follows.

First, as a raw material for the fuel electrode 23, a mixed amount of 50
A paste in which cermet A powder and turpentine oil were mixed at a weight ratio of 10: 3 was applied to a wt% zirconia fired body and dried at 80 ° C. After this was gradually cooled to room temperature, a paste in which cermet B powder and turpentine oil were mixed at a weight ratio of 10: 3 was applied and dried at 80 ° C. Next, after the fuel electrode 23 was assembled in the form of a single cell, the temperature was raised to a predetermined temperature so that the maximum temperature in the cell plane did not exceed 1100 ° C. during operation.

The battery thus manufactured is hereinafter referred to as (B) battery. [Comparative Example 1] A battery was produced in the same manner as in the above-described example except that the entire surface of one surface of the solid electrolyte plate was cermet A. The battery thus produced is hereinafter referred to as a (Y ₁ ) battery. [Comparative Example 2] A battery was prepared in the same manner as in the above Example except that the whole surface of one surface of the solid electrolyte plate was cermet A and the temperature was controlled so that the minimum temperature in the cell surface did not fall below 1000 ° C. It was made.

The battery thus produced is
₂ ) Called battery. [Experiment 1] The above-mentioned (B) battery of the present invention and (Y) of the comparative example
_{Using the 1} ) and (Y ₂ ) batteries, changes in cell voltage with time were examined. The results are shown in FIG. The experiment is 3
It was carried out at a load of 00 mA / cm ² .

As is apparent from FIG. 5, (B) of the present invention.
It was recognized that the battery had improved battery characteristics as compared with the (Y ₁ ) and (Y ₂ ) batteries of Comparative Example, and no significant change in voltage was observed until after about 700 hours. Further, after 900 hours of operation, the cell was disassembled and subjected to SEM analysis, and no rapid sintering was observed in any part of the fuel electrode. This is because the high temperature electrode portion 23a is composed of nickel powder having a large particle diameter.

On the other hand, the (Y ₁ ) battery of the comparative example did not show a large drop in voltage until after about 700 hours, but the cell voltage was low from the beginning of the operation. This is because the low temperature part of the electrode is composed of nickel powder with a large particle size.
This is probably because the reaction effective area of the electrolyte interface was small and the electrode activity was not sufficient. In addition, (Y ₂ ) of the comparative example
The voltage of the battery at the initial stage of operation was almost the same as that of the battery (B) of the present invention, but then gradually decreased and reached the end of its life at about 500 hours. Then, as a result of SEM analysis, abrupt sintering of the fuel electrode was partially observed. It is considered that this is because the exothermic reaction during SOFC power generation caused a portion where the in-plane temperature of the cell exceeded 1100 ° C.

According to the above-mentioned embodiment, in a large area cell in which a non-uniform temperature distribution occurs, sintering of the fuel electrode is suppressed,
The battery life can be extended and the battery characteristics can be improved. [Other Matters] In the above embodiment, the fuel electrode was described as an example, but it is of course possible to apply it to only the oxidant electrode or both the oxidant electrode and the fuel electrode. The particle size of the raw material powder used for the low temperature part of the electrode is 0.001-1
The particle size of the raw material powder used for the high temperature part of the electrode is 0 μm.
It is preferable to use a raw material powder having a particle diameter of 1 to 100 μm and a particle diameter of the electrode low temperature portion <a particle diameter of the electrode high temperature portion.
If raw material powder with a small particle size is used in the low temperature part of the electrode,
Since the effective reaction area of the electrolyte interface is increased, the electrode activity is improved. Further, if a raw material powder having a large particle size is used in the high temperature part of the electrode, it becomes difficult to sinter.

[0031]

According to the present invention described above, the average porosity and the like of the electrode portion in contact with the convex portion (rib) of the separator is large,
That is, since the gas flow passage part that is a cavity in that part is large,
Conventionally, the reaction gas is easily diffused and supplied also to the electrode portion that is in contact with the convex portion (rib) of the separator, which is difficult to diffuse the reaction gas in the past. Therefore, it is possible to effectively generate power within the electrode surface. As a result, the effective area of the entire electrode is increased, so that the loss due to reaction resistance, contact resistance, etc. can be reduced, and the excellent effect of increasing the battery output is achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a solid oxide fuel cell according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of a solid oxide fuel cell according to a first embodiment of the present invention.

FIG. 3 shows the battery (A) of the present invention and the battery (X ₁ ) of the comparative example.
In (X ₂₎ when a battery is used, a graph showing current ─ voltage characteristics.

FIG. 4 is a plan view (partially broken surface) of a cell of a solid oxide fuel cell according to a second embodiment of the present invention.

FIG. 5 is a battery of the present invention (B) and a comparative example of (Y ₁ ).
(Y ₂₎ in the case of using a battery, is a graph showing a change with time of the cell voltage.

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

FIG. 7 is an enlarged cross-sectional view of a main part of a conventional flat plate SOFC.

[Explanation of symbols]

 1 Solid Electrolyte Plate 2 Oxidizer Electrode 3 Fuel Electrode 4 Cell 5 Separator 5a Separator Projection (Rib) 6.7 Reaction Gas Flow Path

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yukinori Akiyama 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 comprising a stack of a plurality of cells in which a fuel electrode and an oxidizer electrode are opposed to each other via a solid electrolyte plate, and a separator having concavo-convex portions forming reaction gas flow paths. In the battery, the average porosity of the portion in contact with the convex portion of the separator in at least one of the electrodes, or the average pore diameter, the average porosity of the portion not in contact with the convex portion of the separator, or than the average pore diameter A solid oxide fuel cell, which is configured to be large.