JPH09147884A - Flat solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator by which the cross leak of fuel gas and oxide gas can be prevented in a flat solid electrolyte fuel cell of an inside manifold type. SOLUTION: A separator is a composite separator 1 composed of a (LA1-x Ax ) (Cr1-y By )O3 layer and a reinforcing layer, and a heat resistant metal gasket 17 is inserted in the joining face of the (la1-x Ax ) (Cr1-y By )O3 layer 1B and the reinforcing layer 1A. Where A is a combination of one or two or more of any of Sr, Ca, Ba, and B is a combination of one or two or more of any of Mn, Ni, Mg, Co, Zr, Ce, Fe, Al. Since (x) and (y) are set to meet the following formulas, 0<=x<=0.50, and 0<=y<=0.50, the cross leak of fuel gas and oxidizing agent gas can be prevented, and a voltage drop resulting from concentration polarization even in high current density can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal manifold type flat plate type 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 are progressing because solid electrolyte fuel cells have many advantages such as high power generation efficiency and effective use of waste heat.

FIG. 4 is a sectional view of a conventional internal manifold type flat plate type solid electrolyte fuel cell.

In order to supply the fuel gas and the oxidant gas to the solid electrolyte fuel cell, supply and exhaust holes for the respective gas are provided in the separator and the solid electrolyte layer of the solid electrolyte fuel cell, and from these holes, the electrodes of each unit cell are provided. An internal manifold type is one in which each gas is supplied and exhausted.

[0005] plate type solid electrolyte fuel cell of the internal manifold type, on both sides of the flat plate type solid electrolyte layer 4 made of yttria and doped zirconia sintered body (YSZ), respectively (La, Sr) air electrode MnO ₃ 6 and N
The flat cell 3 in which the fuel electrode 5 of the i / YSZ cermet is arranged and the adjacent cells are electrically connected in series, and the fuel gas and the oxidant gas are distributed to each cell. The separators 1 are alternately laminated, and the nickel mesh 15 is provided between the fuel electrode 5 and the fuel gas flow passage side of the separator 1.
And a sealant or a spacer 2 is interposed between the solid electrolyte layer 4 and the separator 1 of the unit cell to form a stack, and the electrodes 5 and 6 of each unit cell 3 are provided with a fuel gas. An electromotive force is generated by bringing the oxidizer gas and the oxidant gas into contact with each other.

The separator 1 separates the fuel gas and the oxidant gas supplied to the fuel electrode 5 and the air electrode 6, respectively, to prevent their cross-leakage, and the cells 3 are electrically connected in series. And the action of connecting. When the fuel gas and the oxidant gas leak and mix inside the stack, the fuel utilization rate decreases and the efficiency of the fuel cell decreases, as well as the combustion of both gases causes a local temperature rise. , The thermal stress distribution becomes non-uniform, cracks and strains occur, and the stack life is shortened. Separator 1
Is chemically stable, dense, gas impermeable, low in electrical resistance, high in electronic conductivity, ionic conductivity is negligibly small, etc. It is difficult to chemically react with the battery material (1), has the same expansion coefficient as other battery materials, particularly YSZ used as the solid electrolyte layer 4, and has characteristics such as high mechanical strength. In particular, it is necessary to satisfy the two conditions of (1) being stable in an oxidizing atmosphere and reducing atmosphere, and (2) having good electrical conductivity, in other words, having low electric resistance.

The lanthanum chromite oxide LaCrO ₃ doped with strontium is widely used as the material of the separator 1 of the solid oxide fuel cell, because it is the material that most satisfies the above two conditions. Also,
A typical separator 1 currently used is the above-mentioned La.
A conductive oxide layer such as CrO ₃ is used alone, or a reinforcing material 1 composed of this conductive oxide layer 1B and a heat-resistant metal plate such as Ni having high strength or Al ₂ O ₃
It is a composite separator system in which A and A are superposed.

[0008]

As described above, the LaCr
O ₃ is a conductor that is chemically stable in both oxidizing and reducing atmospheres, and is one of the most excellent materials for the separator 1. However, the reinforcing material 1A such as Ni or Al ₂ O ₃ and the composite separator are used. LaCrO ₃ layer 1B and reinforcing material 1 when forming
At the joint surface with A, a cross leak occurs between the fuel gas and the oxidant gas, causing combustion. As a result, when the current density is increased, the battery characteristics are significantly deteriorated due to the influence of concentration polarization.

The present invention has been made in view of the above points. It is possible to prevent a cross leak between a fuel gas and an oxidant gas, and suppress a voltage drop due to concentration polarization even under a high current density. An object of the present invention is to provide a flat plate type solid electrolyte fuel cell of an internal manifold type capable of preventing deterioration of cell characteristics.

[0010]

In order to achieve the above object, the present invention provides a flat plate type cell in which an air electrode and a fuel electrode are arranged on both sides of a flat plate type solid electrolyte layer and adjacent cell units. In the flat plate type solid electrolyte fuel cell of the internal manifold system, in which the separators are electrically connected in series and the separators for distributing the fuel and the oxidant gas are alternately laminated to each unit cell, the separator is (La _{1- x} A _x ) (Cr
_1-y B _y) is a composite separator O ₃ layer and comprising a reinforcing layer, heat at the interface between the said _{(La 1-x A x)} (Cr 1-y B y) O 3 layer and the reinforcing layer A metallic gasket is inserted, where A is any one or a combination of two or more of Sr, Ca and Ba, and B is Mn, Ni, Mg and C.
Any one of O, Zr, Ce, Fe, and Al or a combination of two or more, and 0 ≦ x ≦ 0.50, 0 ≦
It is characterized in that y ≦ 0.50.

In the present invention, the heat-resistant metal gasket is F
It is characterized in that it is an e-Cr based alloy and that the surface of the heat resistant metal gasket is subjected to aluminum alloying treatment.

Further, according to the present invention, the reinforcing layer is made of ceramics, alumina, magnesia, zirconia,
It is characterized by being made of a combination of one or more of yttria and ceria, being made of Ni or a Ni-based alloy, or being made of a Fe-Cr-based alloy.

Further, according to the present invention, the surface of the heat resistant metal reinforcing layer is aluminum alloyed or coated with ceramics, and the material of the ceramic coating layer is alumina, magnesia, zirconia,
It is characterized in that it is a combination of one or more of yttria and ceria.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings.

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

FIG. 2 is a perspective view of a separator used in the internal manifold type flat plate type solid electrolyte fuel cell of the present invention.

The flat type solid oxide fuel cell of FIGS.
An air electrode 6 of (La, Sr) MnO ₃ and Ni are formed on both sides of the flat solid electrolyte layer 4 made of SZ so as to sandwich it.
/ YSZ cermet fuel electrode 5 is arranged in a flat plate-shaped unit cell 3 and adjacent unit cells 3 are electrically connected in series and each unit cell 3 is supplied with fuel gas and air (oxidant gas). And the separators 1 for distributing the are alternately laminated, and a sealant or a spacer 2 is respectively interposed between the solid electrolyte layer 4 of the unit cell 3 and the separator 1 to form a stack.

The flat plate type solid electrolyte fuel cell of the internal manifold type is a unit cell 3, a separator 1 and a spacer 2.
Is a one-piece structure in which the cell materials such as have the functions of air supply and exhaust, distribution of gas and fuel, and electrical connection.

As shown in the figure, the separator 1 has a rectangular shape in plan view and has a high strength reinforcing layer 1A made of Al ₂ O ₃ or a metal such as Ni or Ni-based alloy, and (La _1-x
Is _{A x) (Cr 1-y} B y) composite separator that is composed of two layers of O ₃ layer 1B (in the illustrated embodiment is shown as a LaCrO ₃ layers 1B). Here, (La _1-x A _x ) (C
A in r _1-y B _y ) O ₃ is any one of Sr, Ca and Ba or a combination of two or more thereof, and B is Mn,
One or a combination of two or more of Ni, Mg, Co, Zr, Ce, Fe and Al, and 0 ≦ x ≦
0.50 and 0 ≦ y ≦ 0.50.

As shown in FIGS. 1 and 2, the reinforcing layer 1A needs to be provided with conductive holes 13 and 14 for packing a conductive member, but when the reinforcing layer 1A is made of conductive Ni or a Ni-based alloy, Not necessarily required. The layer 1B and the gasket 17 are placed in the recess 7 of the reinforcing layer 1A in a state of being overlapped with each other. The gasket 17 is made of heat resistant metal. Thus, according to the present invention, (La _1-x A _x ) (Cr _{1- y By} )
The gasket 17 is characterized in that the gasket 17 is inserted into the joint surface between the O ₃ layer 1B and the reinforcing layer 1A. The nickel mesh 16 is interposed between the layer 1B and the reinforcing layer 1A, and the reinforcing layer 1A
A nickel mesh 15 is interposed between the fuel electrode 5 and the fuel electrode 5.

The heat resistant metal gasket and the reinforcing layer are made of the following materials and are surface-treated.

(1) The heat resistant metal gasket is Fe-Cr
Made of base alloy.

(2) The Fe--Cr based alloy contains Al in an amount of 0.5 to
Contains 10%.

(3) The surface of the heat resistant metal gasket is aluminum alloyed.

(4) The reinforcing layer is made of ceramics.

(5) The reinforcing layer is made of one or a combination of two or more of alumina, magnesia, zirconia, yttria and ceria.

(6) The reinforcing layer is made of a heat resistant metal.

(7) The reinforcing layer is made of Ni or a Ni-based alloy.

(8) The reinforcing layer is made of Fe-Cr based alloy.

(9) The surface of the heat resistant metal reinforcing layer is aluminum alloyed.

(10) The surface of the heat resistant metal reinforcing layer is coated with ceramics.

(11) The material of the ceramic coating layer is one or a combination of two or more of alumina, magnesia, zirconia, yttria, and ceria.

Gas supply / exhaust holes 9 are opened at the four corners of the separator 1, and gas is supplied / exhausted from the gas supply / exhaust holes 9 to the surfaces of the fuel electrode 5 and the air electrode 6 of the unit cell 3, and further, these electrode surfaces In order to evenly distribute the gas in every corner, a plurality of flow grooves 10 and 11 are formed on the surface of the separator 1 facing the electrode surfaces. Gas distribution groove 10
Is the reinforcing layer 1A itself (the lower surface of the reinforcing layer 1A shown in FIG. 2)
And the gas flow groove 11 (see FIG. 1) is formed in the layer 1B. For example, on the upper surface of the reinforcing layer 1A in FIG. 2, air enters the gas flow passage 12 from the gas supply / exhaust hole 9,
It flows through the gas circulation groove 11 and is discharged from the gas flow passage 12 to the gas supply / exhaust hole 9. Although not shown, a gas flow passage 12 is also formed on the lower surface of the reinforcing layer 1A shown in FIG. 2, and gas flows in the same manner.

Further, gas supply / exhaust holes 9 are also formed in the periphery of the solid electrolyte layer 4 of the unit cell 3 where the electrodes 5 and 6 do not exist, and these gas supply / exhaust holes 9 are stacked when stacked in a stack. Is continuously connected from the top to the bottom of the stack,
Further, the peripheral surface 8 of the separator 1 serves as a sealing surface that comes into surface contact with the solid electrolyte layer 4 and the spacer 2 in an airtight manner.

[0035]

EXAMPLE The unit cell used in the example has a thickness of 0.15 μm.
Ni / YSZ of 30 μm on one side of 3Y-YSZ of m, and (La, Sr) MnO ₃ of 80 μm on the other side of the 3m-YSZ were applied by screen printing as a fuel electrode and an air electrode, respectively, and fired at 1450 ° C. and 1150 ° C. Was used.

In the internal manifold type flat plate type solid electrolyte fuel cell (stack) assembled by using the above-mentioned unit cell and using alumina as the separator, hydrogen was supplied to the fuel electrode side and air was supplied to the air electrode side. .

The temperature at which the experiment was conducted was 1000.degree.

A load was applied from the top of the stack, and an electric current was applied to the platinum plates arranged on the top and bottom.

With and without a heat-resistant metal gasket inserted on the joint surface between the LaCrO ₃ layer and the alumina reinforcing layer of the separator, the voltage for one layer of the stack (in FIG. The voltage between the lower conductive holes 14) was measured. The result is shown in FIG.

FIG. 3 is a diagram showing the results of performance tests of the solid electrolyte fuel cell of the present invention in which a heat resistant gasket is used on the joint surface of the composite separator and the conventional solid electrolyte fuel cell in which the heat resistant gasket is not used.

In FIG. 3, the horizontal axis represents the current density (unit: A / cm).
² ), the vertical axis represents voltage (V), the curve A in the figure shows the performance of the solid electrolyte fuel cell of the present invention using the heat resistant gasket, and the curve B shows the conventional solid electrolyte without the heat resistant gasket. The performance of the fuel cell is shown.

From FIG. 3, it is apparent that the voltage drop is small in the solid electrolyte fuel cell of the present invention at the same current density, and the higher the current density is, the smaller the voltage drop is as compared with the conventional one. This is because the cross leak between the fuel gas and the oxidant gas at the joint surface between the LaCrO ₃ layer of the separator and the alumina reinforcing layer is suppressed.

[0043]

As described above, according to the present invention, a flat plate type single cell in which an air electrode and a fuel electrode are arranged on both sides of a flat plate type solid electrolyte layer and an adjacent single cell are electrically connected to each other. In a flat plate type solid electrolyte fuel cell of an internal manifold type, which is connected in series to each of the cells and in which the separators for distributing the fuel and the oxidant gas are alternately stacked, the separator is (La _1-x A _x ) (Cr _{1- y By} ) O ₃
A composite separator comprising a layer and a reinforcing layer, the (La
_1-x A _x) (Insert the refractory metal gasket at the interface between the _{Cr 1-y B y) O} 3 layer and the reinforcing layer, wherein, A is S
Any one of r, Ca and Ba or a combination of two or more thereof, B is Mn, Ni, Mg, Co, Zr and C
e, Fe, Al, or a combination of two or more, 0 ≦ x ≦ 0.50, 0 ≦ y ≦ 0.50
In the flat plate type solid electrolyte fuel cell of the internal manifold system, (La _1-x A _x )
_{(Cr 1-y B y)} O 3 layer and the fuel gas in the junction surface between the reinforcing layer can be prevented cross leak of the oxygen-containing gas, the drop in voltage in the fuel cell even at high current density under It is possible to obtain an extremely excellent effect of suppressing the deterioration of the battery characteristics due to concentration polarization.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a separator used in the internal manifold type flat plate solid electrolyte fuel cell of the present invention.

FIG. 3 is a diagram showing the results of performance tests of the solid electrolyte fuel cell of the present invention using a heat resistant gasket on the joint surface of the composite separator and the conventional solid electrolyte fuel cell not using the heat resistant gasket.

FIG. 4 is a cross-sectional view of a conventional internal manifold type flat-plate solid electrolyte fuel cell.

[Explanation of Codes] 1 Separator 1 A Reinforcing Layer 1 BLaCrO ₃ Layer 2 Spacer 3 Flat Single Cell 4 Solid Electrolyte Layer 5 Fuel Electrode 6 Air Electrode 7 Dimple 8 Surface 9 Gas Supply / Exhaust Hole 10 Gas Flow Groove 11 Gas Flow Groove 12 Gas flow path 13 Conductive hole 14 Conductive hole 15 Nickel mesh 16 Nickel mesh 17 Gasket

Claims (11)

[Claims] 1. A flat plate type cell having an air electrode and a fuel electrode arranged on both sides of a flat plate type solid electrolyte layer, and adjacent cell units are electrically connected in series, and fuel is supplied to each cell unit. In a flat plate type solid electrolyte fuel cell of an internal manifold system, in which a separator for distributing an oxidant gas and a separator for distributing an oxidant gas are alternately laminated, the separator is (La _1-x A _x ) (C
r _1-y B _y) is O ₃ layer composite separator comprising a reinforcing layer, the bonding surface between the _{(La 1-x A x)} (Cr 1-y B y) O 3 layer and the reinforcing layer Insert a heat resistant metal gasket, where A is any one of Sr, Ca and Ba or a combination of two or more, and B is Mn, Ni, Mg and C.
Any one of O, Zr, Ce, Fe, and Al or a combination of two or more, and 0 ≦ x ≦ 0.50, 0 ≦
The flat type solid electrolyte fuel cell is characterized in that y ≦ 0.50. 2. The heat resistant metal gasket is Fe—Cr.
It is a base alloy, The flat plate type solid electrolyte fuel cell of Claim 1 characterized by the above-mentioned. 3. The Fe-Cr based alloy contains Al in an amount of 0.5 to 0.5.
The flat plate type solid electrolyte fuel cell according to claim 2, wherein the flat type solid electrolyte fuel cell contains 10%. 4. The flat plate type solid electrolyte fuel cell according to claim 1, wherein the surface of the heat resistant metal gasket is treated with an aluminum alloy. 5. The flat plate type solid electrolyte fuel cell according to claim 1, wherein the reinforcing layer is made of ceramics. 6. The plate type solid electrolyte fuel according to claim 5, wherein the reinforcing layer is made of one or a combination of two or more of alumina, magnesia, zirconia, yttria, and ceria. battery. 7. The flat plate type solid electrolyte fuel cell according to claim 1, wherein the reinforcing layer is made of Ni or a Ni-based alloy. 8. The flat-plate solid electrolyte fuel cell according to claim 1, wherein the reinforcing layer is made of a Fe—Cr based alloy. 9. The flat-plate solid electrolyte fuel cell according to claim 7, wherein the surface of the heat-resistant metal reinforcing layer is aluminum alloyed. 10. The flat-plate solid electrolyte fuel cell according to claim 7, wherein the surface of the heat-resistant metal reinforcing layer is coated with ceramics. 11. The plate-type solid electrolyte fuel according to claim 10, wherein the material of the ceramic coating layer is one or a combination of two or more of alumina, magnesia, zirconia, yttria, and ceria. battery.