JP3256919B2 - Solid electrolyte fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates are those related to the solid electrolyte fuel cell using a solid electrolyte fuel cell, in particular praseodymium based solid fuel cell air electrode material.

[0002]

2. Description of the Related Art In recent years, interest has been growing in solid electrolyte fuel cells using oxygen ion conductors. In particular, from the viewpoint of effective use of energy, solid fuel cells are not limited by the Carnot efficiency, and have inherently high energy conversion efficiencies, and are expected to have better environmental conservation.

FIG. 1 schematically shows a cross section of a single cell (flat plate type) of a solid fuel cell. As a solid electrolyte, YSZ (yttrium-stabilized zirconia) is most promising for operation at 1000 ° C., but for operation at a low temperature of 800 ° C.
Studies have been made on zirconia-scandium-based, ceria-based, and YSZ thinner layers.

[0004] Table 2 shows the coefficients of thermal expansion of substances currently most frequently studied as constituent materials of solid fuel cells. The solid electrolyte, which requires complete denseness, and the interconnector material have almost the same thermal expansion coefficient. On the other hand, the fuel electrode Ni-YSZ and the air electrode La _0.8 Sr _0.2
MnO ₃ has a large thermal expansion coefficient of about 24 to 40%,
Stress is applied to the electrolyte due to thermal expansion and contraction.

As electrode materials, La _1-x Sr _x MnO ₃ , which is a perovskite-type manganese-based oxide, (x = 0.1
5-0.4) is most often studied. YSZ and La
_{Since 1-x} Sr _x MnO ₃ has a thermal expansion difference, YSZ may be cracked through a temperature cycle between room temperature and an operating temperature of 1000 to 800 ° C. In particular, when a cell is assembled using the air electrode as a support, the cross-sectional area of the air electrode increases, and the thermal expansion of the air electrode determines the thermal expansion of the cell. There must be. Further, even when a solid electrolyte is used as a support, one side of the cell is proportional to the mismatch between the electrolyte and the electrode due to the difference in thermal expansion.

Therefore, there is a demand for an air electrode having the same electrical conductivity as that of a manganese-based material and having a thermal expansion coefficient substantially equal to that of YSZ, which is a solid electrolyte.

Table 2 Thermal expansion coefficient of solid fuel cell material ───────────────────────────────── Material Thermal expansion coefficient Partial ───────────────────────────────── (ZrO ₂ ) _0.9 (Sc ₂ O ₃ ) _0.09 (Al ₂ O ₃ ) _0.01 10.2 × 10 ^-6 Solid electrolyte ───────────────────────────────── YSZ 10.0 Solid electrolyte ─── ────────────────────────────── La _0.8 Sr _0.2 MnO ₃ 12.4 Air electrode ─────────── ────────────────────── YSZ-Ni cermet (Ni: 60mol%) 13.0 Fuel electrode ─────────────── ────────────────── La _0.8 Sr _0.2 CrO ₃ 10.0 interconnector ───────────────────────示 す Indicates the average value of the coefficient of thermal expansion at 25 to 1000 ° C.

[0008]

An object of the present invention is to provide a solid electrolyte fuel cell which simultaneously satisfies the two requirements of the electrical characteristics and the thermal expansion coefficient matching with the electrolyte required for the cathode for a solid fuel cell.
The purpose is to provide a pond .

[0009]

Means for Solving the Problems] To achieve the above object, the solid electrolyte fuel cell according to the present invention is a solid electrolyte fuel cell comprising the air electrode and the solid electrolyte and the fuel electrode,
The air electrode contains an air electrode material of Pr _1-x A _x MnO ₃ , wherein A is an alkaline earth metal element or C
e and x is 0.05 ≦ x ≦ 0.
4, wherein the solid electrolyte is yttrium- zirconia.
A or zirconium compounds-scandium compounds-
It is characterized by being made of alumina .

[0010]

[0011] That is, the electrical conductivity of the conventional material La _1-x
Pr _1-x A _x M, which is equivalent to Sr _x MnO ₃ , (x = 0.15-0.4) and has a coefficient of thermal expansion almost equal to that of the solid electrolyte
It is characterized by using nO ₃ (A: alkaline earth metal element or Ce element).

More specifically, the cathode material used in the solid oxide fuel cell according to the present invention is Pr
_1-x A _x MnO ₃ . Here, in the formula, A is an alkaline earth metal element or Ce, and x is 0.05 ≦ x ≦
0.4.

In the above formula, A is an alkaline earth metal or C
e. In particular, Sr and Ca can be suitably used as alkaline earth metal elements, and Ce can also be suitably used in order to satisfy lattice matching depending on the magnitude of the ion radius.

Further, x is determined from the viewpoint of the consistency of the coefficient of thermal expansion.
As is clear from the examples described below, 0.05 ≦ x ≦ 0.4
It is.

The solid electrolyte fuel cell according to the present invention
The air electrode material is used .

As described above, a solid electrolyte having a coefficient of thermal expansion of about 10.0 × 10 ⁻⁶ can be used. As such a solid electrolyte, for example, a zirconium compound-scandium compound-alumina solid electrolyte (for example, (ZrO ₂ ) _0.9 (Sc ₂ O ₃ ) _0.09 (A
l like ₂ O _{3) 0.01),} yttrium - can be cited zirconia (e.g. YSZ).

As a fuel electrode, conventionally used as a fuel cell
You can use what you did effectively.

[0018]

The operation of the present invention will be described below.

Examination of Pr _1-x A _x MnO ₃ (A: alkaline earth metal element or Ce element) in which lanthanum of the air electrode was replaced by praseodymium showed that the electric conductivity was almost the same as that of the conventional material, Expansion coefficient is La of conventional material
_{It was found that 1-x} Sr _x MnO ₃ was closer to YSZ, which is a solid electrolyte, than _1-x Sr _x MnO ₃ . With the above configuration, air for a solid electrolyte fuel cell that simultaneously satisfies the two requirements of the electrical characteristics and the matching of the coefficient of thermal expansion with the electrolyte.
Extreme materials can be realized.

[0020]

Embodiments of the present invention will be described below. The present invention is not particularly limited to the following examples.

[0021]

EXAMPLE 1 In order to show the effect of the present invention, a test was conducted with a single cell having the structure shown in FIG. In FIG. 1, 1 is a fuel electrode, 2 is a solid electrolyte, and 3 is an air electrode. Also the cathode,
The thickness of the fuel electrode is 0.1 mm, the thickness of the solid electrolyte is 0.3 mm, and the diameter is 20 mm. The solid electrolyte is
YSZ (yttrium 8 mol%; Zr _0.84 Y
_0.16 O ₂ ) and Ni powder dispersed in YSZ (yttrium 8 mol%) for the fuel electrode (Ni: 60 mol%;
Ni _0.6- (Zr _0.84 Y _0.16 O ₂ ) _0.4 ) and Pr _1-x Sr _x MnO ₃ for the air electrode.

Here, x = 0.05, 0.1, 0.2,
Single cells were prepared at 0.3 and 0.4, respectively. A method for manufacturing a single cell used in this example is described below. First,
A green sheet of a solid electrolyte ceramic thin plate is formed by a doctor blade method and baked at 1600 ° C.
Ni-YSZ was applied to the fuel electrode by screen printing and baked at 1400 ° C., and then the above air electrode was applied and baked at 1100 ° C.

Table 1-1 shows the test results of these single cells at 800 ° C. Here, the terminal voltage has a current density of 0.
The value at 2 A / cm ² . For the measurement of the coefficient of thermal expansion, a material obtained by sintering the air electrode material into a pellet at 1300 ° C. was cut into a rod, and the temperature was measured from room temperature to 800 ° C. using a thermal expansion measuring device.
The measurement was performed in air in the temperature range up to. Table 1-1 shows the dependency of the coefficient of thermal expansion on the air electrode composition in the air electrode.
Here, the coefficient of thermal expansion is an average value from 25 to 800 ° C.

When these air electrodes of the present invention were used, all exhibited better characteristics than the conventional cell using La _0.8 Sr _0.2 MnO ₃ as the air electrode. It can be seen that when the substitution amount of praseodymium (ratio of x) is 5 to 40%, the material has a thermal expansion coefficient lower than that of the conventional material, and the compatibility with the electrolyte material is improved.

Table 1-1 Dependence of Terminal Voltage and Thermal Expansion Coefficient on Air Electrode Composition in Example 1 ─── Pr _1-x Sr _x MnO _3- terminal voltage Thermal expansion coefficient ────────────────────────────── Pr _0.95 Sr _0.05 MnO ₃ 0.22 (V) 9.3 × 10 ^-6 ────────────────────────────── Pr _0.90 Sr _0.10 MnO ₃ 0.24 9.4 ─ ───────────────────────────── Pr _0.80 Sr _0.20 MnO ₃ 0.28 9.5 ───────────── ───────────────── Pr _0.70 Sr _0.30 MnO ₃ 0.30 11.0 ───────────────────────── ───── Pr _0.60 Sr _0.40 MnO ₃ 0.32 12.0 ────────────────────────────── La _0.8 Sr _0.2 MnO ₃ ( Comparative example) 0.22 12.0 ──────────────────────────────

Terminal voltage: value at current 0.2 A / cm ² Thermal expansion coefficient: average value from room temperature to 800 ° C.

[0027]

[Embodiment 2] A single cell similar to that of Embodiment 1 was used as a solid electrolyte instead of YSZ instead of (ZrO ₂ ) _0.9 (Sc ₂ O ₃ ).
An oxide having a composition of _0.09 (Al ₂ O ₃ ) _0.01 and an air electrode material as Pr _1-x Ca _x MnO ₃ (0.05 ≦ x ≦
0.3), the same experiment as in Example 1 was performed. Table 1-2 shows the results. Here, the terminal voltage is a value when the current density is 1.0 A / cm ² . In almost the same manner as in Example 1, good results were obtained in comparison with the conventional material La _0.8 Sr _0.2 MnO ₃ .

Table 1-2 Dependence of Terminal Voltage and Thermal Expansion Coefficient on Air Electrode Composition in Example 2 ─── Pr _1-x Ca _x MnO ₃ terminal voltage Thermal expansion coefficient ────────────────────────────── Pr _0.95 Ca _0.05 MnO ₃ 0.20 (V) 9.3 × 10 ^-6 ────────────────────────────── Pr _0.90 Ca _0.10 MnO ₃ 0.22 9.3 ─ ───────────────────────────── Pr _0.80 Ca _0.20 MnO ₃ 0.24 9.4 ───────────── ───────────────── Pr _0.70 Ca _0.30 MnO ₃ 0.26 10.0 ───────────────────────── ───── Pr _0.60 Ca _0.40 MnO ₃ 0.26 11.0 ────────────────────────────── La _0.8 Sr _0.2 MnO ₃ ( Comparative example) 0.20 12.0 ──────────────────────────────

Terminal voltage: value at current of 1.0 A / cm ² Thermal expansion coefficient: average value from room temperature to 800 ° C.

[0030]

EXAMPLE 3 Only the material of the air electrode of the single cell as in Example _{2 Pr 1-x Ce x MnO} 3 (0.05 ≦ x ≦ 0.
As 4), the same experiment as in Example 1 was performed. As shown in Table 1-3, the results were almost the same as those of Example 1 and all were better than the conventional material, La _0.8 Sr _0.2 MnO ₃ .

Table 1-3 Dependence of Terminal Voltage and Thermal Expansion Coefficient on Air Electrode Composition in Example 3 ─── Pr _1-x Ce _x MnO _3- terminal voltage Thermal expansion coefficient ────────────────────────────── Pr _0.95 Ce _0.05 MnO ₃ 0.21 (V) 9.3 × 10 ^-6 ────────────────────────────── Pr _0.90 Ce _0.10 MnO ₃ 0.22 9.8 ─ ───────────────────────────── Pr _0.80 Ce _0.20 MnO ₃ 0.26 10.6 ───────────── ───────────────── Pr _0.70 Ce _0.30 MnO ₃ 0.28 11.4 ───────────────────────── ───── Pr _0.60 Ce _0.40 MnO ₃ 0.30 11.8 ──────────────────────────────

Terminal voltage: value at current of 1.0 A / cm ² Thermal expansion coefficient: average value from room temperature to 800 ° C.

[0033]

As described above, when the air electrode material of the solid oxide fuel cell is Pr _1-x A _x MnO ₃ (A: alkaline earth metal element or Ce element), the thermal expansion coefficient The mismatch is lower than that of the conventional material La _0.8 Sr _0.2 MnO ₃ , and the electrical characteristics are almost the same as those of the conventional material. That is, an air electrode having characteristics that simultaneously satisfy both the electrical characteristics and the coefficient of thermal expansion is obtained. Succeeded. others
Therefore, the solid electrolyte fuel cell according to the present invention can operate with high efficiency.
It has the great advantage of being capable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a single cell used in an example.

[Explanation of symbols]

 1 fuel electrode 2 solid electrolyte 3 air electrode

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-225821 (JP, A) JP-A-7-14584 (JP, A) JP-A-2-504445 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) H01M 8/02 H01M 8/12 H01M 4/86

Claims (2)

(57) [Claims] 1. A solid comprising a cathode and a solid electrolyte and a fuel electrode
An electrolyte fuel cell , wherein the air electrode comprises Pr _1-x A _x Mn.
Wherein the air electrode material is O ₃ , wherein A is an alkaline earth metal element or Ce, and x is 0.05 ≦ x ≦ 0.4, and the solid electrolyte is yttrium. -Zirconia-based or zirconium-based
Compound-scandium compound-alumina
Features solid electrolyte fuel cells. 2. The method according to claim 1, wherein said alkaline earth metal element is Sr or C.
2. The solid electrolyte fuel according to claim 1, wherein
Battery .