JPH10134828A - Current collecting method between fuel electrode and separator of flat solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current collecting method between a fuel electrode and a separator which can prevent the transmission of the thermal stress resulting from the thermal expansion difference between the separator of a flat solid electrolyte fuel cell, and the solid electrolyte layer of the cell, to the solid electrolyte layer of the cell, so as to prevent the generation of a crack of this solid electrolyte layer. SOLUTION: In a current collecting method between the fuel electrode 2 and the separator 3 in an inner manifold system of a flat solid electrolyte fuel cell made by laminating a plate form cell which is composed by providing an air electrode and a fuel electrode 2 on both surfaces of a flat solid electrolyte layer 1 respectively; and a separator 3 having a thermal expansion coefficient different from the thermal expansion coefficient of the electrolyte layer 1; alternately, the separator 3 is made in a compound separator consisting of a separator main body 3A at the air electrode side, and a separator reinforcing member 3B at the fuel electrode side. And a collector layer 4 is superposed on the upper side of the fuel electrode 2, and a conjugation preventive layer 5 with the same content as the solid electrolyte layer of the cell is formed on the surface of the separator reinforcing member 3B, opposing to the collector layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for collecting current between a fuel electrode and a separator in a flat solid electrolyte fuel cell.

[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 of solid electrolyte fuel cells have been progressing because they have many advantages such as high power generation efficiency and effective use of waste heat.

FIG. 2 is a cross-sectional view for explaining a schematic structure of a conventional flat plate type solid electrolyte fuel cell of an internal manifold type.

In order to supply the fuel gas and the oxidizing gas to the solid electrolyte fuel cell, gas supply / exhaust holes for the respective gas are provided in the separator 3 and the solid electrolyte layer 1 of the solid electrolyte fuel cell. A structure in which each gas is supplied to and exhausted from each electrode surface is referred to as an internal manifold type. A flat solid electrolyte fuel cell of the internal manifold type is made of a zirconia sintered body (Y
An air electrode (not shown) of (La, Sr) MnO ₃ and an N electrode are provided on both surfaces of the flat solid electrolyte layer 1 made of SZ).
i / YSZ cermet, in order to electrically connect a flat cell having the fuel electrode 2 disposed thereto and adjacent cells in series and to distribute fuel gas and oxidizing gas to each cell. , Separator body 3A and separator reinforcing material 3
B are alternately stacked, and a current collecting layer 4 made of a mesh or felt made of nickel is interposed between the fuel electrode 2 and the fuel gas flow path side of the separator reinforcing material 3B. A stack is formed by stacking a sealant or a spacer between the layer 1 and the separator 3, and an electromotive force is generated by bringing a fuel gas and an oxidizing gas into contact with each electrode surface of each unit cell. It is supposed to.

[0005]

Conventionally, the current collection between the fuel electrode 2 and the separator main body 3A is performed by using nickel felt or nickel as a current collecting layer 4 between the fuel electrode 2 and the separator reinforcing material 3B facing the fuel electrode 2. The mesh is packed and the operation is performed through conductive holes formed in the separator reinforcing material 3B. The separator reinforcing material 3B is usually made of alumina.

However, during operation of the solid oxide fuel cell, the current collecting layer 4 made of nickel felt or nickel mesh is used.
Becomes high temperature and adheres to the separator reinforcing material 3B. Therefore, the thermal stress of the separator 3 generated due to the difference in the thermal expansion coefficient between the separator 3 and the solid electrolyte layer 1 is transmitted to the solid electrolyte layer 1 via the current collecting layer 4 and the solid electrolyte layer 1 is cracked.

The present invention has been made in view of the above points, and has been made to prevent the thermal stress of a separator of a flat solid electrolyte fuel cell from being transmitted to a solid electrolyte layer of a unit cell, and thereby to provide a space between the separator and the solid electrolyte layer. It is an object of the present invention to provide a method for collecting electricity between a fuel electrode and a separator, which can prevent the solid electrolyte layer from cracking due to a difference in thermal expansion coefficient of the solid electrolyte layer.

[0008]

In order to achieve the above object, the present invention provides a flat cell having an air electrode and a fuel electrode disposed on both sides of a flat solid electrolyte layer, respectively, and a heat treatment for the electrolyte layer. A fuel electrode in a flat solid electrolyte fuel cell of an internal manifold system in which separators having different coefficients of thermal expansion and thermal expansion coefficients are alternately laminated, a method of collecting power between the separators, wherein the separator has an air electrode side separator body and fuel A composite separator comprising a separator reinforcing material on the electrode side, a current collecting layer is stacked on the upper surface of the fuel electrode,
A bonding prevention layer having the same component as the solid electrolyte layer of the unit cell is formed on the surface of the separator reinforcing member so as to face the current collecting layer.

In the present invention, the bonding prevention layer on the separator reinforcing material is applied with a slurry of the bonding prevention layer component and then fired so that the relative density ρ is 30% ≦ ρ ≦ 90%. It is characterized by being formed.

[0010] The present invention is also characterized in that the slurry of the bonding preventing layer component contains a metal organic compound of zirconium or yttrium.

Further, the present invention is characterized in that the slurry of the bonding preventing layer component is applied by a screen printing method.

Further, the present invention is characterized in that the slurry of the bonding preventing layer component is applied by a spray coating method.

Further, the present invention is characterized in that the slurry of the bonding preventing layer component is applied by brush coating.

Further, in the present invention, the material of the separator is a (La ₁ -xA _x ) (Cr _{1 -y By} ) O ₃ layer, wherein A is any one of Sr, Ca and Ba. One or a combination of two or more, B is Mn, Ni, Mg, Co, Z
any one or a combination of two or more of r, Ce, Fe, and Al, 0 ≦ x ≦ 0.50, 0 ≦ y
≦ 0.50.

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

Further, the present invention is characterized in that the separator is made of a heat-resistant metal.

Further, the present invention is characterized in that the electrolyte layer is doped ZrO ₂ , CeO ₂ , LaGaO ₃ .

[0018]

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

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a flat solid electrolyte fuel cell of the internal manifold type according to the present invention.

The flat solid electrolyte fuel cell shown in FIG. 1 is formed on both sides of a flat solid electrolyte layer 1 made of a zirconia sintered body (YSZ) doped with yttria or the like, similarly to the above-mentioned conventional flat solid electrolyte fuel cell. , Respectively (La, S
r) a flat cell in which an air electrode (not shown) of MnO ₃ and a fuel electrode 2 of Ni / YSZ cermet are arranged;
Adjacent cells are electrically connected in series, and separators 3 for distributing fuel gas and oxidizing gas are alternately laminated on each cell (the separator 3 is reinforced with the separator body 3A and the separator reinforcement). A fuel electrode 2 and a separator reinforcing material 3
A current collecting layer 4 made of nickel mesh or felt is interposed between B and the fuel gas flow path side.

However, in the present invention, as shown in FIG. 1, the joining prevention layer 5 is sandwiched between the fuel gas flow path side of the separator reinforcing member 3B (the lower surface of the separator reinforcing member 3B in FIG. 1) and the current collecting layer 4. ing. The bonding prevention layer 5 is made of the same components as the solid electrolyte layer of the unit cell. as a result,
Due to the high temperature generated during operation of the solid oxide fuel cell, even if the joining prevention layer and the current collecting layer are joined, the powder on the surface of the current collecting layer is separated from the base (current collecting layer main body) and slips. Is not transmitted to the solid electrolyte layer of the unit cell, so that the solid electrolyte layer does not crack due to a difference in thermal expansion coefficient between the solid electrolyte layer and the separator.

After the application of the slurry of the anti-bonding layer component, the anti-bonding layer has a relative density ρ of 30% ≦ ρ ≦ 90%
And formed by firing. Further, the slurry of the component of the bonding preventing layer contains a metal organic compound of zirconium or yttrium. The slurry of the bonding preventing layer component is applied by a screen printing method, a spray coating method, or a brush coating.

The material of the separator (reinforcing member 3B) is a (La _1-x A _x ) (Cr _{1- y By} ) O ₃ layer,
Here, A is any one or a combination of two or more of Sr, Ca, and Ba, and B is Mn, Ni, Mg, C
o, Zr, Ce, Fe, or any one or a combination of two or more of 0, 0 ≦ x ≦ 0.50, 0
.Ltoreq.y.ltoreq.0.50.

Further, the separator reinforcing material is made of ceramics, heat-resistant metal, doped ZrO ₂ , CeO ₂ , La.
Made of GaO ₃ .

[0025]

EXAMPLE A LaCrO ₃ separator and a thermal expansion coefficient of 7.
In a composite manifold comprising an alumina separator reinforcing material of 8 × 10 ⁻⁶ cm / cmK, a nickel mesh current collecting layer of the manifold reinforcing material (thermal expansion coefficient is 14 × 1
0 ^-6 cm / cmK) and fuel channel protrusions facing, zirconia powder having an average particle diameter of 1.5μm was 3 mol% doping yttria was applied by screen printing, 1000 ° C.
For 2 hours to form a bonding prevention layer. The surface of the anti-joining layer is granular, and the particles have such a weak adhesion that they can be easily removed by hand.

A zirconia sheet doped with 3 mol% of yttria having a thickness of 100 μm (having a thermal expansion coefficient of 10.8 × 1
On one side of the 0 ^-6 cm / cmK), 30μm nickel and zirconia cermet fuel electrode, as the cathode on the opposite face, with a cell formed of lanthanum manganate 150μm respectively, a) the formation of the anti-bonding layer Manifold b) A power generation test was performed at 1000 ° C. by using each of the manifolds on which a bonding prevention layer was not formed, by flowing hydrogen as fuel and air as oxidant.

In the case of b), after the power generation test, when disassembled at room temperature and examined, the alumina separator reinforcing material, the nickel mesh current collector, and the battery were respectively joined, and the battery was cracked by tensile stress due to alumina. Had occurred.

In the case of a), the nickel mesh current collector and the battery were joined, but the alumina separator reinforcing material and the nickel mesh current collector were not joined because of the joining prevention layer, and the stress of alumina Did not reach the battery, so that the battery did not crack.

[0029]

As described above, according to the present invention, in a method for collecting fuel between a fuel electrode and a separator in a flat solid electrolyte fuel cell of an internal manifold system, the separator is composed of a separator body portion on the air electrode side and a fuel electrode. A composite separator comprising a separator reinforcing material on the side, a current collecting layer is superimposed on the upper surface of the fuel electrode, and the same components as the solid electrolyte layer of the unit cell are joined on the surface of the separator reinforcing material facing the current collecting layer. Since the prevention layer is formed, the following excellent effects can be obtained. (1) When the joining prevention layer and the current collecting layer are joined, the powder on the surface of the current collecting layer is separated from the base (the current collecting layer main body) and slips, so that the thermal stress of the separator decreases the solid electrolyte layer of the unit cell. Will not be transmitted to. (2) The solid electrolyte layer can be prevented from cracking due to a difference in thermal expansion coefficient between the solid electrolyte layer and the separator of the unit cell. (3) The range of material selection between the solid electrolyte layer and the separator of the unit cell is expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a schematic configuration of a flat solid electrolyte fuel cell of an internal manifold type according to the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a conventional internal manifold type flat solid electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid electrolyte layer 2 Fuel electrode 3 Separator 3A Separator main body 3B Separator reinforcing material 4 Current collection layer 5 Join prevention layer

Claims (10)

[Claims] 1. A flat cell having an air electrode and a fuel electrode disposed on both sides of a flat solid electrolyte layer, and separators having a thermal expansion coefficient different from that of the electrolyte layer, alternately. The fuel electrode in the laminated internal manifold type flat solid electrolyte fuel cell, a method of collecting power between the separators, wherein the separator is a composite separator comprising a separator body on the air electrode side and a separator reinforcing material on the fuel electrode side, A flat solid electrolyte, wherein a current collecting layer is stacked on the upper surface of the fuel electrode, and a bonding prevention layer of the same component as the solid electrolyte layer is formed on the surface of the separator reinforcing material so as to face the current collecting layer. A method for collecting current between a fuel electrode and a separator of a fuel cell. 2. An anti-joining layer on the separator reinforcing material is formed by applying a slurry of the anti-joining layer component and then baking so that the relative density ρ is 30% ≦ ρ ≦ 90%. The method of claim 1, wherein the current is collected between the fuel electrode and the separator of the flat solid electrolyte fuel cell. 3. The method for collecting electricity between a fuel electrode and a separator of a flat solid electrolyte fuel cell according to claim 1, wherein the slurry of the anti-joining layer component contains a metal organic compound of zirconium or yttrium. . 4. The method according to claim 2, wherein the slurry of the bonding preventing layer component is applied by a screen printing method.
4. The method for collecting current between a fuel electrode and a separator of a flat solid electrolyte fuel cell according to item 1. 5. The method according to claim 2, wherein the slurry of the anti-joining layer component is applied by a spray coating method. 6. The method according to claim 2, wherein the slurry of the anti-joining layer component is applied by brush coating. 7. The material of the separator is (La _1-x A
_{x) (Cr 1-y B} y) is O ₃ layer, wherein, A is S
any one or a combination of two or more of r, Ca, and Ba; B is Mn, Ni, Mg, Co, Zr, Ce,
0 ≦ x ≦ 0.50, 0 ≦ y ≦ 0.50, any one or a combination of two or more of Fe and Al
2. The method for collecting current between a fuel electrode and a separator of a flat solid electrolyte fuel cell according to claim 1, wherein: 8. The method according to claim 1, wherein the separator reinforcing member is made of ceramics. 9. The method according to claim 1, wherein the separator is made of a heat-resistant metal. 10. The method according to claim 1, wherein the electrolyte layer is doped with ZrO ₂ ,
_{2. The} method for collecting electricity between a fuel electrode and a separator of a flat solid electrolyte fuel cell according to claim 1, wherein CeO ₂ and LaGaO ₃ are used.