JPH05121060A - Separator material for high temperature type fuel cell - Google Patents

Abstract

PURPOSE:To provide a separator material for a high-temperature type fuel cell, which provides sufficient stability and corrosion resistance to each of high-temperature corrosive gases both on the side of oxidizer gas and on the side of reducer gas and also is free of such deformation as a warp, a curve and the like, and also free of peeling or the like, while the strength and conductivity of the separator material are kept respectively at given levels. CONSTITUTION:In a separator material composed of a metal radical component forming metal, an alloy or an intermetallic compound, and also a ceramics component, a portion of the separator material on the side of oxidizer gas is rich in the ceramics component while a portion thereof on the side of reducer gas is rich in the metal radical component, and the composition of each of the components for the separator material is inclinedly changed in succession or in stages from the side of oxidizer gas to the side of reducer gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is sufficiently stable and corrosion resistant to high temperature corrosive gases on both the oxidizing gas side and the reducing gas side while maintaining strength and conductivity. Moreover, the present invention relates to a novel high temperature type fuel cell separator material that does not cause deformation such as warping or bending and peeling.

[0002]

2. Description of the Related Art As a high temperature type fuel cell separator material, a composite material comprising a metal base component such as a metal or an alloy and a ceramic component, particularly a conductive ceramic component is known. However, this is homogeneous throughout and has a certain ratio of metal base component and ceramics component on both the oxidizing gas side and the reducing agent gas side, and the ceramic component stable to the oxidizing gas is the reducing agent gas. The metal base component, which is weak against heat and is stable to reducing agent gas, is easily oxidized by the oxidizing agent gas and is likely to cause deterioration of corrosion resistance and deterioration of conductivity, so that both sides are not always sufficiently stable against high temperature corrosive gas. There is a problem that it cannot be called a thing.

On the other hand, in order to solve this problem, a material having different front and back surfaces, such as a bonding material having a front surface made of metal and a back surface made of ceramics, can be considered. Due to the different physical properties of the product, problems such as warping and bending and peeling are likely to occur due to changes in the operating environment such as temperature and pressure.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional separator material for a high temperature fuel cell, and has high temperature corrosiveness on both the oxidant gas side and the reducing agent gas side. The purpose of the present invention is to provide a high temperature fuel cell separator material which is sufficiently stable to gas and has corrosion resistance, and which does not cause problems such as warping, bending and other deformations and peeling.

[0005]

The inventors of the present invention have conducted various studies to develop a separator material for a high temperature fuel cell having the above-described preferable properties, and as a result, a metal base component and a conductive ceramic component, particularly It was found that the object can be achieved by combining the rare earth / chromium complex oxide-based conductive ceramics component to form a composite and changing the composition of these components from one side to the other side. The present invention has been completed based on the above.

That is, the present invention comprises at least one metal base component selected from metals, alloys and intermetallic compounds and a conductive ceramic component, and the oxidant gas side is rich in the conductive ceramic component and reduced. Provided is a separator material for a high temperature fuel cell, characterized in that the agent gas side is rich in a metal group component, and the composition of the component is continuously or stepwise changed from the oxidizing agent gas side to the reducing agent gas side. is there.

As the metal base component used in the present invention, a metal, an alloy or an intermetallic compound is used. Examples of the metal include Ni and Co. As the alloy, for example, Ni-Cr system, Ni-Cr-Fe system, N
i-Cr-Mo system, Ni-Cr-Mo-Co system, Ni-
Ni-based alloys such as Cr-Mo-Fe system, Co-Cr
System, Co-Cr-Fe system, Co-Cr-W system, Co-C
Examples thereof include Co-based alloys such as r-Ni-W system.
Further, as the intermetallic compound, for example, Ni ₃ Al, Ni ₂
Ni such as Al ₃ , NiAl, IC218 and IC264
-Al system, Ni-Ti-Al such as Ni ₂ TiAl
System, Co-Ti system such as Co ₃ Ti, TiAl, Ti
Ti-Al system such as Al ₃ , VA such as VAl ₃
l system, NbAl systems such as NbAl _3, ZrAl systems such as ZrAl _3, FeAl systems such as FeAl,
Examples include Mo-Si-based materials such as MoSi ₂ and Ti-Si-based materials such as Ti ₅ Si ₃ , especially Ni-Al.
Intermetallic compounds are preferred.

The conductive ceramic component is not particularly limited, but rare earth oxides, especially rare earth / chromite composite oxides such as lanthanum chromite composite oxide and yttrium chromite composite oxide, especially the general formula (I)

[Chemical 2] (L is La or Y, M is at least one element selected from Mg, Sr, Ca and Ba, M ′ is Co, N
i, Fe, Ti, V, Mn, Al, Si, Zn, Cu,
At least one element selected from Mo, Pd, W, Rh, Ir, and Pt, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.
5, 0.95 ≦ b / a ≦ 1.05) and has a perovskite structure. These may be used alone or in combination of two or more.

The high temperature fuel cell separator material of the present invention comprises these metal base component and conductive ceramic component, and the oxidizing gas side is rich in conductive ceramic component and the reducing agent gas side is rich in metal base component. The composition is gradually or gradually changed from the oxidant gas side to the reducing agent gas side.

In the present invention, by gradually changing the component composition in this manner, it is possible to make the physical properties change in the same tendency.

That is, by varying the type of the metal-based component, the type of the conductive ceramics component, and the composition thereof, the physical properties of any part or each layer, in particular the coefficient of thermal expansion, are aligned in a substantially similar manner, or one of them is matched. By gradually or gradually changing the inclination from one side to the other side as much as possible, it is possible to prevent at least part of the inconveniences such as warpage and bending of the separator material, and delamination.

As described above, in order to have a matching or gradient change in thermal expansion in accordance with the change in the ratio of the metal base component and the conductive ceramics component between the respective parts or layers, fixing the composition of the metal base component causes the thermal expansion. It is preferable to combine a conductive ceramic component having a composition having a lower coefficient of thermal expansion in a region or layer having a higher ratio of the metal base component having a higher coefficient. In other words, the coefficient of thermal expansion increases as the proportion of the metal-based component increases, but the coefficient of thermal expansion of the composition of the conductive ceramics component, which is the other composite component, is decreased to reduce the coefficient of thermal expansion of each part or layer as a whole. It is preferable that the control adjustment is made to be substantially constant. For this purpose, it is practical to change the composition of the conductive ceramics component or change the component.

Further, the ratio of the metal group component is higher toward the reducing side, and the coefficient of thermal expansion of the metal group component is higher than that of the conductive ceramics component. For example, the coefficient of thermal expansion of the metal group component is relatively high. The thermal expansion coefficient of Ni ₂ Al ₃ as an example of an intermetallic compound having a low thermal conductivity is also about 13 × 10 ⁻⁶ ° C. ⁻¹ , so that a conductive ceramic component having a lower thermal expansion coefficient is used on the reducing side. Is advantageous.

As the conductive ceramic component having a lower coefficient of thermal expansion, perovskite type rare earth chromite type oxide, especially lanthanum chromite type (coefficient of thermal expansion 10
^{X10 -6} ° C ^-1 ) or yttrium chromite system having a smaller coefficient of thermal expansion than that (coefficient of thermal expansion 8x10 ^-6 ° C ^-1 )
Are preferred. Further, the rare earth chromite oxide is mixed and used, or the perovskite structure (AB
It is preferable to change the composition component of the A site or B site in O ₃ ) or the ratio or ratio between the components. This B
By controlling the amount of metal that replaces part of the Cr in the site, for example, Co, the thermal expansion coefficient can be increased or decreased by increasing or decreasing it, and by controlling the amount of alkaline earth metal that replaces part of the rare earth in the A site. The coefficient of thermal expansion can be lowered or raised by the increase or decrease. In this way, the coefficient of thermal expansion of the entire high temperature fuel cell separator material of the present invention can be appropriately adjusted.

The ratio of each of the above components in the whole high temperature fuel cell separator material of the present invention is 1: 9 to 5: 5, particularly 2: 8 to 5 by volume ratio of the metal base component and the conductive ceramics component. It is preferably in the range of 4: 6. If this ratio is too large, the corrosion resistance such as oxidation resistance will be poor, and if it is too small, the conductivity and densification will be insufficient.

The high temperature fuel cell separator material of the present invention can be produced by a conventional film / sheet forming technique, for example, a coating method such as a doctor blade method, a CVD method, a vapor deposition method,
It is prepared by a plasma spray method, a particle sintering method, a self-heating method such as an electric heating method, or a combination thereof. In particular, a large number of films composed of a metal-based component and a conductive ceramics component prepared by changing the component ratio to each predetermined ratio are laminated in multiple layers so that the component composition gradually changes between the films, and they are pressed together. After molding, it is obtained by firing in an appropriate atmosphere, for example, a reducing atmosphere or a non-oxidizing atmosphere such as an inert gas atmosphere, or in vacuum. This lamination method is practical because the separator for a high temperature fuel cell usually has a thickness of up to 1 cm and is suitable for forming a laminated sheet.

The problems in preparing the high temperature fuel cell separator of the present invention are that the degree of shrinkage during firing or heat treatment varies depending on an arbitrary site or each layer to be laminated, and the adhesion between the layers. Although peeling occurs from an insufficient point, a suitable method for improving this is liquid phase sintering. For example, there is a method in which an electric current is applied while pressurizing the laminated multi-layered structures to heat an object to be energized to cause the metal component to self-heat and melt and fire. According to this method, the molten metal wets the ceramic particles, so that the difference in shrinkage during firing can be controlled by such liquid phase sintering. Such a melt-molded product has a form in which a molten metal is mixed in a conductive ceramic component having a different porosity.

Further, in the high temperature fuel cell separator material of the present invention, since the coefficient of thermal expansion differs for each part or layer, there is a concern that bending or distortion may occur especially at the time of temperature increase or decrease, but the conductivity is high. The lanthanum chromite composite oxide, which is a ceramic component, has the excellent property that the coefficient of thermal expansion is smaller than that of zirconia and the yttria chromite composite oxide is smaller than that of the lanthanum chromite composite oxide. Even if the volume ratio between the metal-based component and these conductive ceramics components changes, the coefficient of thermal expansion represented by the linear expansion coefficient or the like can be appropriately adjusted by changing the composition of the ceramics component. For example, the separator material for a high temperature fuel cell can easily have a coefficient of thermal expansion almost equal to that of a zirconia-based material commonly used for solid electrolyte materials such as fuel cells, for example, yttria-stabilized zirconia.

Therefore, the separator material for a high temperature fuel cell of the present invention is used for a solid electrolyte fuel cell, etc.
As a separator for high-temperature fuel cells, the characteristics of the metal-based component, which is originally excellent in conductivity, can be achieved, as well as the strong bonding of each member that can sufficiently withstand the change in environmental conditions up to high temperature up to around 1000 ° C. It is possible to sufficiently maintain the conductive region within a sufficiently practical range. Particularly preferably, the metal base component has a Ni-Al intermetallic compound, the conductive ceramic component has a perovskite structure represented by the general formula (I), and the volume ratio of the two is the whole high temperature fuel cell separator. Regarding the former: the latter, which is in the range of 1: 9 to 5: 5, preferably 2: 8 to 4: 6 is used.

Next, a solid oxide fuel cell using the separator of the present invention will be described. First, each member will be described. The solid electrolyte is not particularly limited as long as it has oxygen ion conductivity, and for example, yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CS) is used.
Known solid electrolytes such as Z) are mentioned, and they are usually formed in a plate shape. When used as a plate, its thickness is usually 0.05.
˜0.3 mm, preferably 0.1 to 0.25 mm. If the thickness is less than 0.05 mm, the strength will decrease, and if it exceeds 0.3 mm, the resistance will be too large, which is not preferable.

[0021] Since the cathode oxidant gas passage side such as oxygen or air, the conductive material with a corrosion resistance against oxidizing gas at a high temperature, for example, conductive complex oxide such as La _{x Sr} 1-x MnO ₃ It is formed by applying a material. As the coating method, a brush coating method, a screen printing method or the like is used. In addition, as a method of forming the cathode, CV
D method, plasma CVD method, sputtering method, thermal spraying method and the like are used.

Since the anode is on the side of the fuel gas passage such as hydrogen, it is formed of a conductive material having corrosion resistance to the fuel gas at high temperature, such as Ni / ZrO ₂ cermet.

As described above, the solid electrolyte plates having the respective electrodes formed on both sides are joined and integrated through the high-temperature fuel cell separator, and external terminals are provided at both ends of the solid electrolyte plate to form a multi-stage series composed of a large number of cells. Molded battery is formed.

[0024]

EFFECTS OF THE INVENTION The high temperature fuel cell separator material of the present invention is sufficiently resistant to high temperature corrosive gases on both the oxidant gas side and the reducing agent gas side while maintaining strength and conductivity. It is stable and resistant to corrosion, and does not cause warping, bending, or other deformation or peeling.

Therefore, the high temperature fuel cell separator made of the material of the present invention can maintain the performance of the high temperature fuel cell incorporating the separator for a long period of time.

Among them, a solid oxide fuel cell separator, particularly one using a rare earth / chromite complex oxide such as yttrium chromite or lanthanum chromite as a conductive ceramic component, has a coefficient of thermal expansion smaller than that of zirconia. Therefore, it is possible to control the thermal expansion coefficient represented by the linear expansion coefficient by appropriately changing the ratio of the metal-based component and those conductive ceramics components, without impairing the conductivity, and with the solid electrolyte material and the like. Since the consistency of the coefficient of thermal expansion can be enhanced, by optimizing the ratio and making the coefficient of thermal expansion substantially coincide with that of the solid electrolyte of the fuel cell, in the fuel cell incorporating the separator for a high temperature fuel cell, A remarkable effect that enables strong bonding, excellent gas sealing stability, and improved battery characteristics. Unlikely to.

[0027]

【Example】

Example 1 Ni ₂ Al ₃ (manufactured by Kyoritsu Kiln Raw Materials Co., Ltd., trade name N2A3) powder and La _x Y _0.8-x Sr _0.2 C having a particle size of 1 μm or less.
r _1-y Co _y O ₃ powder was blended at a predetermined ratio and mixed by a ball mill, and then these were formed into a sheet by a doctor blade method. After drying each of the obtained sheets, they were punched into a size of 100 mmφ and laminated so that the component composition gradually changed between the sheets, integrated by thermocompression bonding, and subjected to degreasing treatment in air at 400 ° C for one day. went. Then, in a nitrogen atmosphere, 1150 ° C, 250 kg
Press firing was performed under a pressure of / cm ² to prepare a separator material.

This separator material is 800 to 1000 ° C.
Shows a sufficient conductivity within the Ni ₂ Al ₃ content range of the volume ratio under a predetermined atmosphere, and the coefficient of linear expansion at 1000 ° C. is 10.3 × 10 ⁻⁶ ° C. ⁻¹ , which is close to that of zirconia. showed that.

Table 1 shows the results of measuring the composition and the coefficient of thermal expansion at 1000 ° C. of the conductive ceramics of each layer of this material and the entire layers.

[Table 1] * Ni ₂ Al ₃ : conductive ceramics

Example 2 A solid oxide fuel cell of a three-stage series cell was prepared as follows. First, a high temperature fuel cell separator and external terminals were produced using the high temperature fuel cell separator material obtained in Example 1. The separator for the high temperature fuel cell and the external terminals are both 50 × 50 × 5 mm square plates with groove width 2
mm, the groove depth is 1.5 mm, and eight grooves each are formed. In the high-temperature fuel cell separator, the grooves formed on both sides were orthogonal to each other.

Further, yttria is used as the solid electrolyte plate.
50 × 5 consisting of partially stabilized zirconia added with mol%
A plate having a size of 0 × 0.2 mm was used. Then, La ₀ . ₉ Sr ₀ . ₁ MnO ₃ powder (average particle size 5μ
m) was applied to a thickness of 0.3 mm to serve as a cathode, and a cermet mixed powder of Ni / ZrO ₂ (10/1 weight ratio) was applied to the hydrogen passage side to a thickness of 0.3 mm to serve as an anode.

The solid electrolyte plate provided with this electrode and the laminate shown in Table 1 obtained in Example 1 were used as a separator for a high temperature fuel cell and a single cell was used as a separator for a high temperature fuel cell with a layer consisting only of conductive ceramics as the cathode side. Are integrated so that there are 3 layers,
A zirconia-based inorganic adhesive was used to bond the electrode-attached solid electrolyte plate and the high-temperature fuel cell separator to each other, and a glass paste having a softening point of about 800 ° C. was applied to seal the gas. This glass paste softens at the operating temperature of the battery and seals the gas.

The battery body thus integrated was placed in a cylindrical alumina manifold. The contact portion between the manifold and the battery body was coated with glass paste and gas-sealed.
A platinum lead wire was inserted into the external terminal for electrical connection.

The fuel cell thus produced was heated. That is, the solvent of the glass paste was evaporated by heating from room temperature to 150 ° C at 1 ° C / min. 150-35
The temperature was raised to 0 ° C at 5 ° C / min. At 350 ° C. or higher, nitrogen gas was flown on the hydrogen passage side to prevent oxidation of the anode, and the temperature was raised to 1000 ° C. at 5 ° C./min. afterwards,
The temperature was maintained at 1000 ° C., hydrogen was flown on the anode side and oxygen was flown on the cathode side to start power generation. The open circuit voltage was 3.8V.

Next, the discharge characteristics are shown in Table 2.

[Table 2]

Continued Front Page (72) Inventor Satoshi Sakurada 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Co., Ltd.

Claims (5)

[Claims] 1. At least one metal base component selected from the group consisting of metals, alloys and intermetallic compounds and a conductive ceramic component, wherein the oxidant gas side is rich in the conductive ceramic component and the reducing agent gas side is a metal. A separator material for a high temperature fuel cell, which is rich in a base component and whose composition is gradually or gradually changed from the oxidizing gas side to the reducing gas side. 2. A multi-layered structure, wherein the composition of components is gradually changed from the oxidant gas side toward the reducing agent gas side in each layer.
The high temperature fuel cell separator material described. 3. The high temperature fuel cell separator material according to claim 1, wherein the conductive ceramic component is a rare earth / chromite complex oxide represented by the following general formula. [Chemical 1] (L is La or Y, M is at least one element selected from Mg, Sr, Ca and Ba, M ′ is Co, N
i, Fe, Ti, V, Mn, Al, Si, Zn, Cu,
At least one element selected from Mo, Pd, W, Rh, Ir, and Pt, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.
5, 0.95 ≦ b / a ≦ 1.05) 4. The high temperature fuel cell separator material according to claim 1, wherein the volume ratio of the metal base component to the conductive ceramics component is 1: 9 to 5: 5. 5. A multiplicity of films comprising a metal-based component and a conductive ceramics component prepared by changing the component ratio to each predetermined ratio are laminated in multiple layers so that the component composition gradually changes between the films, A method for producing a separator material for a high temperature fuel cell, which comprises press-molding integrally and firing.