JPH1116585A - Plate type solid electrolyte fuel cell and stacking method thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the initial performance due to deformation of lanthanum chromite due to reduction expansion in an operating environment and to prevent deterioration of battery performance over time, and to use a heat cycle caused by reduction expansion of lanthanum chromite. To provide a flat solid electrolyte fuel cell that does not cause performance deterioration. SOLUTION: In a flat plate type solid electrolyte fuel cell having a lanthanum chromite separator, a lanthanum chromite separator is formed by reinforcing material 10 and / or support material 11.
And mechanically prevent deformation of the lanthanum chromite separator due to reduction expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat solid electrolyte fuel cell and a method for stacking the same.

[0002]

2. Description of the Related Art Recently, fuel cells which directly convert chemical energy inherent in fuel into electric energy by using, for example, air and hydrogen as oxidizing gas and fuel gas, respectively, have attracted attention from the viewpoint of resource saving and environmental protection. Research and development are progressing because solid electrolyte fuel cells have many advantages such as high power generation efficiency and effective use of waste heat.

In order to supply a fuel gas and an oxidizing gas to a solid electrolyte fuel cell, gas supply / exhaust holes are provided in a separator and a solid electrolyte layer of the solid electrolyte fuel cell, and each electrode of each unit cell is formed through this hole. The one that supplies and exhausts each gas to and from the surface is called an internal manifold type.

[0004] A flat solid electrolyte fuel cell of the internal manifold type has a flat solid electrolyte layer made of a zirconia sintered body (YSZ) doped with yttria or the like.
The air electrode of (La, Sr) MnO ₃ and Ni / Y
A flat plate cell in which the SZ cermet fuel electrode is arranged, and a separator that electrically connects adjacent cells in series and distributes fuel gas and oxidant gas to each cell alternately The stack is formed by interposing a nickel felt or a nickel mesh between the fuel electrode and the fuel gas flow path side of the separator, and interposing a sealant or a spacer between the solid electrolyte layer of the unit cell and the separator, respectively. And a fuel cell and an oxidant gas are brought into contact with each electrode surface of each unit cell to generate an electromotive force. For this reason,
The method of laminating battery members such as electrodes and separators has an important effect on the cell performance of a flat solid electrolyte fuel cell.

The separator separates the fuel gas and the oxidizing gas supplied to the fuel electrode and the air electrode, respectively, to prevent cross leakage therebetween, and to electrically connect the cells in series. It has. When fuel gas and oxidant gas leak and mix inside the stack,
Of course, the efficiency of the fuel cell is reduced due to the decrease in fuel utilization, and the mixture of both gases burns to cause a local temperature rise, resulting in uneven thermal stress distribution, cracks and distortions, and a Shorten life. At a high temperature of about 1000 ° C., which is the operating temperature of the fuel cell,
Chemically stable, dense, impermeable to gas, low in electric resistance, high in electronic conductivity, negligible in ionic conductivity, hardly chemically reacts with other battery materials, and has low expansion coefficient. Battery material, especially YSZ used as a solid electrolyte layer, and must have characteristics such as high mechanical strength.

Lanthanum chromite oxide LaCrO ₃ is widely used as a material for a separator of a solid oxide fuel cell, and it is one of the materials most satisfying the above characteristics.
Because it is one.

[0007]

As described above, lanthanum chromite LaCrO ₃ is a conductor that is chemically stable in both oxidation and reduction atmospheres, and is one of the most excellent materials for a separator. The lanthanum chromite separator is convexly warped toward the reducing atmosphere under the fuel cell operating atmosphere due to the reductive expansion at a high temperature. As a result, the contact area between the electrode and the lanthanum chromite separator decreases,
The internal resistance of the battery increases. In addition, when a thermal cycle is applied, lanthanum chromite may undergo reductive expansion, causing poor contact due to irreversible dimensional changes of the current-collecting elastic body such as a nickel mesh between the separator and the electrode, and deterioration of the lanthanum chromite itself due to creep. is there.

[0008] The present invention has been made in view of the above points, the good contact between each electrode and the separator in the operating environment, the reduction of the initial performance due to IR loss due to deformation caused by the reductive expansion of lanthanum chromite Further, it is an object of the present invention to provide a flat solid electrolyte fuel cell in which the cell performance does not deteriorate with time and the performance does not deteriorate due to a thermal cycle caused by the reduction expansion of lanthanum chromite, and a method for stacking the same.

[0009]

In order to achieve the above object, the present invention relates to a flat solid electrolyte fuel cell having a lanthanum chromite separator, wherein deformation of the lanthanum chromite separator due to reduction expansion is mechanically suppressed. It is characterized by.

Further, the present invention is characterized in that a reinforcing material is stacked on the lanthanum chromite separator.

Further, the present invention is characterized in that a support material is interposed between the lanthanum chromite separator and the reinforcing material.

Further, the present invention is characterized in that the reinforcing material or the support material is made of ceramics.

In the present invention, the ceramic is Al ₂ O.
_3, MgO, characterized in that it is made in one or more combinations in the ZrO _2.

Further, the present invention is characterized in that the reinforcing material or the supporting material is made of metal.

In the present invention, the metal of the support material is F
It is a heat-resistant alloy containing one of e, Cr, and Ni.

Further, the present invention is characterized in that the reinforcing material is made of metal and the support material is made of ceramic.

Further, the present invention is characterized in that the reinforcing material is made of ceramics and the support material is made of metal.

Further, the present invention is characterized in that the reinforcing material and the support material are integrated.

Further, the present invention is characterized in that a contact portion of the reinforcing material or the support material with the lanthanum chromite separator is ring-shaped.

Further, the present invention is characterized in that a contact portion of the reinforcing material or the support material with the lanthanum chromite separator is a solid columnar body.

Further, the present invention is characterized in that the contact portions of the reinforcing material or the support material with the lanthanum chromite separator are dispersed at two or more places.

Further, the present invention is characterized in that at least one contact portion of the reinforcing material or the support material with the lanthanum chromite separator is near the center of the lanthanum chromite separator.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a flat solid electrolyte fuel cell according to the present invention.

The flat plate type solid electrolyte fuel cell of the internal manifold type shown in FIG. 1 has (La, Sr) MnO _{3 on} both surfaces of a plate type solid electrolyte layer 4 made of a zirconia sintered body (YSZ) doped with yttria or the like. Air pole 6
And a flat unit cell in which a fuel electrode 5 of Ni / YSZ cermet is disposed, and a composite separator 3 comprising a lanthanum chromite separator 1 and a reinforcing material 10 superposed thereon are alternately laminated, and the fuel electrode 5 and the separator 1 and a fuel gas flow path side, a nickel felt or a nickel mesh 2 is interposed therebetween, and a stack is formed by interposing a sealant or a spacer (not shown) between the solid electrolyte layer 4 and the separator 1 of the unit cell. (Stack) and a load was applied vertically downward from the top of the stack.
An electromotive force is generated by bringing a fuel gas and an oxidizing gas into contact with the surfaces of the electrodes 5 and 6, respectively. The composite separator 3 separates the fuel gas and the oxidizing gas supplied to the fuel electrode 5 and the air electrode 6, respectively, to prevent cross leakage therebetween, and to connect the cells in series electrically. And

The lower surface of the lanthanum chromite separator 1 and the upper surface of the reinforcing material 10 are almost in contact with each other, and the reinforcing expansion of the lanthanum chromite separator 1 is supported by the reinforcing material 10.

As shown in FIG. 1, the lanthanum chromite separator 1 and the reinforcing member 10 have a rectangular shape in plan view.
Gas supply / exhaust holes are formed in the four corners, gas is supplied / exhausted from the gas supply / exhaust holes to the surfaces of the fuel electrode 5 and the air electrode 6 of the unit cell, and the gas is evenly distributed to the corners of these electrode surfaces. For distribution, a plurality of oxidizing gas circulation grooves 6A are formed on the surface of the separator 1 in the composite separator 3 facing the surface of the air electrode 6, and the inside of the composite separator 3 facing the surface of the fuel electrode 5 is formed. A plurality of fuel gas flow grooves 5A are formed on the surface of the reinforcing member 10. Gas supply / exhaust holes are also formed in the peripheral portion of the solid electrolyte layer 4 of the unit cell that does not come into contact with the electrodes 5 and 6. The peripheral surfaces of the lanthanum chromite separator 1 and the reinforcing material 10 are sealing surfaces that are in surface contact with the solid electrolyte layer 4 and the spacer.

FIG. 2 is a sectional view of a flat solid electrolyte fuel cell according to a conventional method. The structure of the flat solid electrolyte fuel cell of FIG. 2 is almost the same as the structure of the flat solid electrolyte fuel cell of FIG. 1 described above, but in the case of FIG. 2, the lanthanum chromite separator 1 and the reinforcing member 10 are located at the peripheral portion. And the middle part is filled with nickel felt 2.

FIG. 3 is a sectional view of an embodiment of the flat solid electrolyte fuel cell according to the present invention.

The structure of the flat solid electrolyte fuel cell shown in FIG. 3 is almost the same as the structure of the flat solid electrolyte fuel cell shown in FIG. 2, but different points are as follows. In the flat solid electrolyte fuel cell shown in FIG. 3, a support material 11 is sandwiched between a lanthanum chromite separator 1 and a reinforcing material 10. The illustrated support member 11 has a ring shape, and is filled with nickel felt or nickel mesh 2 between the lanthanum chromite separator 1 and the fuel electrode 5 through a central hole.

The reinforcing material 10 and the support material 11 are for preventing the lanthanum chromite separator 1 from being protruded toward the reducing gas side (downward in FIGS. 1, 2 and 3) due to reduction expansion. The following countermeasures are taken to increase the effect of preventing the deformation due to the reduction expansion. First, as a material for the production, one or a combination of two or more of Al ₂ O ₃ , MgO, and ZrO ₂ of ceramics is used, or a heat-resistant alloy containing one of Fe, Cr, and Ni is used. Made. In addition, the reinforcing material 10
Is made of metal and the support material 11 is made of ceramic, or the reinforcing material 10 is made of ceramic and the support material 11 is made of ceramic.
May be made of metal. Reinforcement material 10 and support material 11
When formed integrally, the effect of preventing deformation is increased. As shown in the illustrated embodiment, the contact portion of the reinforcing member 10 or the support member 11 with the lanthanum chromite separator 1 may be ring-shaped, and may be a solid columnar member (a columnar member having no hollow portion therein). Sometimes. When the contact portion of the reinforcing material 10 or the support material 11 with the lanthanum chromite separator 1 is dispersed at two or more places, or when at least one of the contact portions is located near the center of the lanthanum chromite separator 1, The effect of preventing deformation due to the reductive expansion is increased. This is because the deformation of the lanthanum chromite separator 1 is greatest at its center.

[0032]

EXAMPLE On a 3Y-YSZ electrolyte layer having a thickness of 100 μm, Ni / YSZ cermet was used as a fuel electrode at a thickness of 30 μm.
LaMnO ₃ doped with 15% Sr was used as an air electrode.
Those coated with 50 μm and fired at 1450 ° C. and 1150 ° C. were used as single cells. S for separator
LaCrO ₃ doped with 10% of r and 2% of Co was used. The thermal expansion coefficient of this LaCrO ₃ (25 to 1000
C) is 10.5 × 10 ⁻⁶ cm / cmK in an air atmosphere, and 11.0 × 10 ⁻⁶ cm / cm in hydrogen and + 20% steam.
K. Also, alumina was used as a reinforcing material of the separator, and an air flow path was formed on one surface of the lanthanum chromite, and a fuel flow path was formed on the alumina reinforcing material, respectively, to obtain a composite separator.

The following power generation test was conducted on the flat solid electrolyte fuel cell assembled using the composite separator having the above-described structure. a) As shown in FIG. 2, a load of 0.2 kg / cm ² was applied vertically downward from the top of the stack in which the unit cells and the lanthanum chromite separator were stacked, and a power generation test was performed under the following conditions.

Number of layers 3 Fuel gas Hydrogen + 20% steam Oxidant gas Air Fuel utilization 50% Test temperature 1000 ° C. b) As shown in FIG. 3, a support material made of alumina which fills a gap between the lanthanum chromite separator and the reinforcing material is used. The lanthanum chromite is inserted into the reducing gas side so that the lanthanum chromite does not mechanically warp, and a load of 0.2 kg / cm ² is applied vertically downward from the top of the stack under the same conditions as in the above a). A power generation test was performed.

FIG. 5 is a diagram showing the results of a power generation test performed under the above conditions a) and b). FIG. 4 is a sectional view of the flat solid electrolyte fuel cell according to the conventional method shown in FIG. 2 after a power generation test.

FIG. 5 shows the power density (Wcm ^-2 ) on the ordinate and the operation time (h) on the abscissa. The following is clear from FIG.

When a power generation test is performed under the condition a), the initial performance is poor and the durability is poor, as shown by the curve A in FIG. 5, and the deterioration of the performance due to an increase in IR loss is remarkable from about 10 hours. is happening. When the lanthanum chromite separator was examined at room temperature after the power generation test, it was warped to the reducing gas side by about 100 μm as shown in FIG. 4, and it was confirmed that the contact area with the air electrode was reduced.

When a power generation test is performed under the condition b), it can be seen that the initial performance is good and the durability is not deteriorated at all even after 60 hours as shown by a curve B in FIG. further,
When the lanthanum chromite was examined at room temperature after the power generation test, the deformation due to the reduction and expansion of the lanthanum chromite was mechanically suppressed by the reinforcing material and the support material, no warping occurred, and the initial state of FIG. 3 was maintained.

The above power generation test results show that the mechanical suppression of the reduction expansion of lanthanum chromite according to the present invention greatly affects the performance improvement of the flat solid electrolyte fuel cell.

[0040]

As described above, according to the present invention, in a flat solid electrolyte fuel cell having a lanthanum chromite separator, the lanthanum chromite separator is provided with a reinforcing material in order to prevent the lanthanum chromite separator from being deformed due to reduction expansion. And, if necessary, a support material is interposed between the lanthanum chromite separator and the reinforcing material, so that the following excellent effects can be obtained. (1) In the operating environment, good contact between each electrode and the separator is obtained, and deterioration of the initial performance and deterioration of battery performance with time due to deformation of the lanthanum chromite separator due to reduction expansion do not occur. (2) Performance degradation due to thermal cycling due to reduction expansion of the lanthanum chromite separator does not occur.

[Brief description of the drawings]

FIG. 1 is a sectional view of a flat solid electrolyte fuel cell according to the present invention.

FIG. 2 is a cross-sectional view of a flat solid electrolyte fuel cell according to a conventional method.

FIG. 3 is a cross-sectional view of a flat solid electrolyte fuel cell according to an embodiment of the present invention.

4 is a cross-sectional view of the flat solid electrolyte fuel cell according to the conventional method shown in FIG. 2 after a power generation test.

FIG. 5 is a diagram showing the results of a power generation test of the flat solid electrolyte fuel cell according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separator 2 Nickel felt 3 Composite separator 4 Solid electrolyte layer 5 Fuel electrode 5A Fuel gas flow groove 6 Air electrode 6A Oxidant gas flow groove 10 Reinforcement material 11 Support material

Claims (14)

[Claims] 1. A method for laminating a flat solid electrolyte fuel cell comprising a lanthanum chromite separator, wherein deformation of the lanthanum chromite separator due to reduction expansion is mechanically suppressed. 2. The flat solid electrolyte fuel cell according to claim 1, wherein a reinforcing material is stacked on the lanthanum chromite separator. 3. The flat solid electrolyte fuel cell according to claim 2, wherein a support material is interposed between the lanthanum chromite separator and the reinforcing material. 4. The flat solid electrolyte fuel cell according to claim 2, wherein the reinforcing material or the support material is made of ceramics. 5. The method according to claim 1, wherein the ceramic is Al ₂ O ₃ , Mg.
O, plate type solid electrolyte fuel cell according to claim 4, characterized in that is made of one or more combinations in the ZrO _2. 6. The flat solid electrolyte fuel cell according to claim 2, wherein the reinforcing material or the support material is made of metal. 7. The metal of the support material is Fe, Cr,
The flat solid electrolyte fuel cell according to claim 6, wherein the flat solid electrolyte fuel cell is a heat-resistant alloy containing one of Ni. 8. The method according to claim 3, wherein the reinforcing member is made of metal, and the support member is made of ceramics.
4. The flat solid electrolyte fuel cell according to 1. 9. The method according to claim 3, wherein the reinforcing material is made of ceramics, and the support material is made of metal.
4. The flat solid electrolyte fuel cell according to 1. 10. The flat solid electrolyte fuel cell according to claim 3, wherein the reinforcing material and the support material are integrated. 11. The flat solid electrolyte fuel cell according to claim 3, wherein a contact portion of the reinforcing material or the support material with the lanthanum chromite separator has a ring shape. 12. The flat solid electrolyte fuel cell according to claim 3, wherein a contact portion of the reinforcing material or the support material with the lanthanum chromite separator is a solid columnar body. 13. The lanthanum chromite separator according to claim 3, wherein a contact portion of the reinforcing material or the support material with the lanthanum chromite separator is dispersed at two or more places.
4. The flat solid electrolyte fuel cell according to 1. 14. The lanthanum chromite separator according to claim 3, wherein at least one contact portion of the reinforcing material or the support material with the lanthanum chromite separator is near a center of the lanthanum chromite separator. Flat plate type solid electrolyte fuel cell.