JPH02189865A - Electrode of fuel battery and manufacture thereof, and fuel battery - Google Patents

Abstract

PURPOSE:To prevent plastic deformation of an electrode and creeping, decreasing the contact resistance of the electrode with a current collecting plate, and provide stable operation for a long period of time by making the electrode porous, and forming metal composite oxide and solid solution layer on the particle surfaces of this porous electrode. CONSTITUTION:At first a metal powder 11 is used as a starting material and mixed with an organic binder 12, and the mixture is agitated 13, decompressed, deaerated 14, and viscosity adjusted 15 to produce specified slurry 16 as crude material. This slurry 16 is attached to wire meshing 20 of Ni, etc., in the forming/baking process 30, and the product is shaped 32 into specified thickness, dried 33, and reductive baked 34 in hydrogen atmosphere. Thus a porous electrode 35 is obtained. Then the electrode 35 is immersed in a material solution 41 for metal composite oxide solid solution in the metal composite oxide solid solution layer forming process 40 for impregnation 42 of its fine voids, followed by drying. After oxidation and baking 44 under oxidative atmosphere, reductive baking is made to yield an electrode 46 for fuel battery.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a molten carbonate type fuel cell, etc., and particularly relates to a fuel cell that has been improved to prevent plastic deformation and creep deformation of electrodes and elution of electrode materials. This invention relates to an electrode, its manufacturing method, and a fuel cell.

[Conventional technology]

For example, in a molten carbonate type fuel cell, electrodes are arranged on both sides of an electrolyte plate, and a separator is arranged outside the electrodes to form a unit cell. As electrodes used in such fuel cells, electrodes in which nickel powder is attached to nickel wire mesh or stainless steel wire mesh have been proposed (Japanese Patent Laid-Open No. 57-3466, Japanese Patent Laid-Open No. 52-1).
36336, Japanese Patent Application Laid-open No. 57-4.0866)
.

[Problem to be solved by the invention]

In the conventional electrodes mentioned above, plastic deformation and creep deformation occurs over time during battery operation, especially at the anode, and sintering progresses after short-term use, resulting in a decrease in specific surface area and a decrease in electrode pore volume. There is a problem in that this leads to a decrease in the performance of the fuel cell. On the other hand, in KAN-1-, there was a problem in that the electrode material was eluted over time, and the battery performance deteriorated accordingly.

In order to solve these problems, a method of mixing ceramic materials with nickel electrodes (Japanese Unexamined Patent Publication No. 6
1----271749, JP 62-2455, JP 61-267267, JP 62-1988
JP-A-59-107543) and a method of coating ceramic powder with an electrode material (JP-A-59-107543).

However, electrodes containing a mixture of ceramic materials have problems in that contact resistance increases and electrode activity decreases due to the coexistence of inert substances, making it impossible to exhibit sufficient battery performance. Further, electrodes made of ceramic powder coated with an electrode material have poor sintering properties, and there is a problem in that cracks and warpage occur during the electrode manufacturing process.

One object of the present invention is to stabilize the electrodes of a fuel cell, prevent plastic deformation and creep deformation of the electrodes during battery operation, and reduce contact resistance between the electrodes and the current collector plate, thereby achieving stable battery performance over a long period of time. An object of the present invention is to provide an electrode and a method for manufacturing the same, and a fuel cell using the electrode, for improving the performance of the electrode and preventing elution of the electrode material.

[Means to solve the problem]

In order to achieve the above object, a fuel cell electrode according to the present invention is a fuel cell electrode formed by sintering metal particles or metal oxide particles, wherein the electrode is formed porous. In addition, a solid solution layer of a metal composite oxide is formed on the surface of the particles.

The present invention also provides an electrode for a fuel cell formed by sintering metal particles or metal oxide particles, in which the electrode is formed porous and a metal composite oxide is formed between the particles. Solid solution particles are dispersed therein. Here, the particle size of the metal or metal oxide is preferably larger than the particle size of the solid solution particles.

The present invention also provides a fuel cell electrode that is porous and made of a solid solution of a metal composite oxide.

In the electrode, the solid solution of metal composite oxide is AX
B1. Examples include metal composite oxides consisting of x Oy (where A and B are metal atoms).

Here, metal atoms Al: iMg, Al, Li, La.

At least one of Ca, Ta, T], Mo, and Nb, and metal atom B is one or more components selected from Ni, Co, and Cu. Here, in the metal composite oxide solid solutions A, xB, and xOy, the value of X is preferably in the range of 0.01 to 0.8 in terms of atomic ratio, and the value of y is preferably in the range of 1 to 3. The ionic radius of metal atoms Δ and B is 0
．． It is desirable to have 6 to 0.7 people. Further, the metal composite oxide solid solution is preferably a substitutional metal oxide solid solution. The ionic radii of various metal atoms are shown below.

The metal atom Δ is Mg2(6)0.66, Ca'
(6) 0.62. Ta' (6) 0.68. Tj4
(6) 0.68°Mo' (6) 0,62. Nb"
“0.69.Lj (6)0.68゜All (6)
0.51. La (8) is 1.18 people, and as metal atom B, N12 (4) is 0.65. Co2(4)0
．． 68, Cu"' (4) is 0.68 people. Here, () indicates the expected coordination. In the combination in which the difference in ionic radius between metal atom A and metal atom B is within 0.1 people, the metal composite is Easy to form oxide solid solution.

The method for producing electrodes for fuel cells according to the present invention includes a step of forming and firing metal particles or metal oxide particles as a raw material slurry to form a porous electrode, and forming the electrode with a metal composite oxide solid solution raw material solution. and a step of drying the electrode and then oxidizing it in an oxidizing atmosphere to form a metal composite oxide solid solution layer on the particle surface of the porous electrode. It is something that

That is, Mg, Ca, TarTi, Mo
A substitution type composite oxide solid solution is formed by impregnating a solution containing , Nb, and Li, drying, and then oxidizing and firing. Alternatively, magnesium (Mg) or aluminum (All), nickel (Ni), cohal 1-(C
o) Prepare a mixed solution using one or more components selected from copper (Cu), impregnate a porous electrode with this, dry it, and oxidize and bake it to form a metal composite oxide solid solution on the electrode surface. It can also form layers.

Further, the electrode manufacturing method according to the present invention includes a step of previously forming a metal composite oxide solid solution layer on the surface of metal particles or metal oxide particles, and a step of forming and firing after this step to form a porous electrode. It includes.

Further, the electrode manufacturing method according to the present invention includes a step of coating particles of a metal composite oxide solid solution with metal particles or metal oxide particles, and a step of forming and firing after this step to form a porous electrode. , including. This makes it possible to easily manufacture electrodes with low contact resistance.

The fuel cell according to the present invention includes an electrolyte body, a cathode and an anode disposed on both sides of the electrolyte body, and a cathode and an anode disposed on both sides of the electrolyte body.
a separator disposed on the outside of the anno-1 and the anno-1;
In a fuel cell formed of a unit cell equipped with a fuel cell, the cathode and/or anode are formed of any of the electrodes described above.

[Effect]

The metal composite oxide solid solution layer formed on the particle surface of a porous electrode composed of partially sintered metal or metal oxide particles is extremely stable even in a reducing atmosphere, and can be used as an anode in a hydrogen atmosphere. Even when used, it prevents sintering, plastic deformation, and creep deformation of the porous electrode, and maintains high electrode activity with little increase in electrical resistance. On the other hand, when used as a cathode, the metal oxide solid solution layer suppresses elution of the electrode material. This is thought to be due to the fact that the coexistence of magnesium (Mg) and lithium (Li) increases the basicity of the electrode, or that the alkali resistance improves due to the formation of metal composite oxides. .

〔Example〕

The electrode according to the present invention will be explained below with reference to FIG.

The porous electrode was created by the following steps.

First, in the metal slurry manufacturing process 10, the metal powder 11
as a starting material, mixed and stirred 13 with an organic binder 12,
Next, the slurry is degassed under reduced pressure 14 and the viscosity is adjusted 15 to obtain a predetermined raw material slurry 16.

Next, this raw material slurry 16 is attached to a wire mesh 20 made of nickel or the like in a molding/firing step 30, molded to a thickness of approximately 1.0 mm (32), dried at room temperature (33), and heated to a temperature of 75% in a hydrogen atmosphere.
Reduction firing 34 was performed at 0° C. for 1 hour. As a result, a porous electrode 35 was obtained.

Next, in a metal composite oxide solid solution layer forming step 40, this porous electrode 35 is immersed in a metal composite oxide solid solution raw material solution 41 to impregnate the inside of the pores of the porous electrode,
Dry 43 for 5-20 hours at °C.

Then at a temperature of 400-1000°C in an oxidizing atmosphere
After oxidizing and calcining for 1.0 hour (44), the mixture is oxidized for 1 to 10 hours at a temperature of 600 to 900°C to obtain a fuel cell electrode. If the oxidation firing temperature is below 400°C, the metal oxide solid solution layer will not be sufficiently formed.

On the other hand, if the temperature exceeds 1000°C, the electrode pore volume will decrease significantly, which is not preferable. Furthermore, if the reduction firing temperature is below 600°C, sufficient activity cannot be obtained. Moreover, if it is more than 90,000, sintering of the electrode occurs and the specific surface area of the electrode decreases, which is not preferable.

A metal composite oxide solid solution layer is formed on the particle surface of the porous electrode, and the thickness of the solid solution layer is preferably 0.01 to 1 μm. If the thickness is less than 0.01 μm, plastic deformation or creep deformation of the electrode during battery operation cannot be suppressed. On the other hand, if the thickness is less than -μm, the contact resistance between the electrode and the dyeing plate increases, resulting in a problem that the battery performance deteriorates. Furthermore, when an electrode with a metal composite oxide solid solution layer is applied to the cathode,
If the thickness of the layer is 0.01 μm or more, elution of the electrode material can be suppressed.

Mg and Ca are used as the metal composite oxide solid solution.

A component selected from Ta, Ti, Mo, Nb, Afl, Li or La, and 1 selected from Nj, Co, Cu.
The B component or more has a composition ratio of A x B1-, Oy, and the atomic ratio of X is in the range of 0.01 to 0.8, and y is in the range of 1 to 3, forming a substitution type complex oxide solid solution. is preferable. Figure 2 shows the Mg/Ni composition ratio and (200
) is a diagram showing the relationship of peak changes in the plane. In addition, here ``
"Substitution type" refers to one in which lattice points Nj of the crystal lattice are partially replaced with Mg. If the value of cause On the other hand, the value of X is 0
．． In the case of 8 or more, the electrical resistance increases and the electrode activity decreases, which is not preferable.

When the starting material of the porous electrode is any of Nj, Co, Cu, Mg, Ta, Ti, Mo, NtzLi, Al,
A desired fuel electrode can be obtained by impregnating with a La-containing solution, drying, oxidizing and firing, and then reducing and firing.

On the other hand, the starting materials for the porous electrode are N i and G o.

In the case of manufacturing with components other than Cu, Mg, Ta, Ti, Mo, Nb, and Li are used in advance.

One or more selected from Al, La and Nj, Co and C
A mixed solution of one or more selected from u is prepared, and a porous electrode is impregnated with the mixed solution.

(Example 1) Nickel powder (average particle size 2.5 μm) was used as the starting material for the electrode.
) and carboxymethyl cellulose (CM
C) After adding the 0.2% solution and stirring and mixing, the mixture was degassed under reduced pressure and the slurry viscosity was adjusted to about 120 poise. This was applied as a raw material slurry to nickel metal (20, mesh) to a thickness of 1 mm, dried at room temperature for about 20 hours, and then heated to 750°C in a mixed gas of 70% hydrogen and 30% nitrogen.
, and baked for 1 hour to create a porous electrode. The thickness of the obtained porous electrode was 0.8 mm, the porosity was 72 VoQ%, and the specific surface area was 0.9 m''/g. Magnesium was impregnated into the pores of the porous electrode by immersing it in a magnesium solution dissolved in IQ.
After drying at 600° C. for about 10 hours, it was oxidized and fired in an air atmosphere at 600° C. for 7 hours. Next, reduction firing was performed at 800'C for 1 hour in a 70% hydrogen-30% nitrogen atmosphere to obtain a fuel cell electrode according to the present invention.

The X-ray diffraction pattern of the obtained electrode is shown in FIG. It was confirmed from the X-ray diffraction peak that a magnesium-nickel composite oxide solid solution was formed. The lattice constant (200 planes) determined from the diffraction peak value is 4,204,
This results in MgxNilx.

When the X value was calculated, it was found that X = 0, 7. From this result, the crystal structure formula of the composite oxide solid solution formed on the electrode surface is Mgo,7N]. , was found to be 30.

(Example 2) Magnesium nitrate (M
Magnesium and nickel were immersed in a mixture of 584 g (N 03)2 6H20) and 663 g nickel nitrate (N](NO3)2 6H7○) dissolved in 1Ω distilled water to inject magnesium and nickel into the pores of the porous electrode. Impregnated at the same time.

This was dried, oxidized and fired under the same conditions as in Example 1 to obtain a fuel cell electrode. The X-ray diffraction results of this electrode are shown in FIG. Lattice constant from diffraction peak (200 planes)
Find 4. ．． 193 people, M gx N ]1
-v O(7) The X value was 0.5, and the crystal structure formula of the sonocomposite oxide solid solution was found to be M g N j○2.

(Example 3) The nickel porous electrode obtained in the intermediate step of Example 1 (porous electrode 35 in FIG. 1), the fuel cell electrode obtained in Example 1, and the fuel obtained in Example 2 Plastic deformation of each battery electrode was measured from thickness changes. Experimental conditions include atmospheric gas of 80% hydrogen-20% carbon dioxide and temperature of 65%.
100 hours at 0℃, load applied to the electrode 4kg/cm2
I did it. The results are shown in Table 1. By forming a composite oxide solid solution layer on the electrode surface, thickness deformation was significantly reduced.

(Example 4) The specific surface area of the test electrode tested in Example 3 was measured and compared with the specific surface area of the electrode before the test. The results are shown in Table 2. By forming a composite oxide solid solution layer on the surface of the electrode particles, a decrease in specific surface area is suppressed.

was set in a small battery performance evaluation device, and 8
Using a mixed gas of 0% hydrogen-20% carbon dioxide gas and a mixed gas of 70% air-30% carbon dioxide gas for cup-1, the temperature was 650°C and the load current density was 150 mA/cn? A continuous power generation test was conducted using The results are shown in Table 3. Although the initial performance of the batteries to which the electrode of Example 1 and the electrode of Example 2 in which a composite oxide solid solution layer was formed on the electrode surface was applied was slightly low, the deterioration in performance was very small.

(Example 5) Next, a power generation system will be explained. The test electrode used in Example 3 was applied to Anno-1 (a nickel oxide-silver electrode was used as the cathode, and the electrolyte plate was impregnated with 45vOΩ% carbonate electrolyte. A battery with an effective electrode area of 64 cm (8 cm square) was assembled using a nickel porous electrode obtained in an intermediate step in the electrode manufacturing method shown in FIG. 1 (Example 6). The fuel cell electrode obtained in Example 1 and the fuel cell electrode obtained in Example 2 were each oxidized and calcined at 700°C for 5 hours in an air atmosphere.This electrode was applied to the cathode, and the anode was applied to the anode in Example 3. A unit cell was assembled using the obtained fuel cell electrode, and a continuous test was conducted for 1,000 hours in the same manner as in Example 5. After that, the cell was disassembled and the amount of nickel oxide eluted was examined. After completely separating from the electrode, it was dissolved in 6N hydrochloric acid solution and analyzed by atomic absorption spectrometry.

The results are shown in Table 4. The amount of nickel eluted from the electrode of Example 1 and Example 2, both of which had a composite oxide solid solution layer on the particle surface of the electrode, was very small.

(Example 7) A porous sintered plate with a thickness of 0.7 mm was produced using nickel powder (particle size 3 to 4 μm) for the anode and 1-powder (particle size 6 to 8 μm) for the edge as starting materials, After impregnating this with 5 atom% of aluminum nitrate solution, 120
℃ for 5 hours, then 600℃ in an air atmosphere for 1 hour.
It was fermented and baked for an hour. This was reduced and fired at 750'C for 1 hour in a 70% H2-30% N2 atmosphere.

For Can-1, a porous sintered plate with a thickness of 0.6 mm was prepared using nickel powder (particle size 23 to 4 μm) as a starting material.
This was impregnated with 10 atom % of magnesium nitrate solution, dried at 120° C. for 5 hours, and then oxidized and calcined at 700° C. for 5 hours in an air atmosphere.

For the electrolyte plate, a porous plate with a thickness of 1.2 mm and a porosity of 60 v/v% was prepared using lithium alumina h as a starting material, and lithium carbonate + potassium carbonate (62:38
(mol%) electrolyte was impregnated at 600'C.

Using these anodes, can-1, and electrolyte plate, a laminated cell (10 cells laminated) as shown in FIG. 5 was assembled. In the figure, 1 is an electrolyte plate, 2 is an anode, 3 is a cathode, 4 is a separator, 5 is a flow of reaction waste for the anode, and 6 is a flow of reaction gas for the cathode. The effective electrode area of this cell is 3.600c+&. 7 for the anode
A power generation test was conducted by supplying 0% hydrogen, 20% carbon dioxide gas and 10% moisture, and supplying 70% air and 30% carbon dioxide gas to the anode.

As a result, the initial load current density was 150mA/
An average voltage of 0.79 V per cell was obtained in af. In addition, the battery performance after continuous testing for 00 hours is that the average voltage at the same load battery density is 0.76V.
, and very stable battery performance was obtained.

〔Effect of the invention〕

According to the electrode according to the present invention, since a solid solution of a metal composite oxide is provided that coats the particle surface of the porous electrode made of metal particles or metal oxide particles or is mixed between the particles, battery operation is possible. Plastic deformation and creep deformation of the electrodes inside are suppressed, preventing reduction in battery specific surface area and providing stable battery performance over a long period of time.

On the other hand, when used as a cathode, elution of the electrode material can be suppressed and the life of the battery can be improved.

Moreover, according to the electrode manufacturing method according to the present invention, the above-mentioned electrode can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing the electrode of the present invention and its manufacturing process;
Figure 2 is a diagram showing the relationship between the Mg/N3 composition ratio and the peak change of the (200) plane, Figure 3 is an X-ray diffraction pattern diagram of the electrode surface created by adding magnesium to a nickel porous electrode, and Figure 4 The figure shows an X-ray diffraction pattern of an electrode created by simultaneously impregnating magnesium and nickel on a nickel porous electrode. Figure 5 shows a fuel cell power generation system using an electrode with a metal oxide solid solution layer formed on the anode and cathode. FIG. 2 is a perspective view showing the basic structure of. 1. Electrolyte plate, 2. Anode 1, 3. Cathode,
4. Separator, 5. Reaction gas flow to anno-1, 6
...Reaction gas flow for cathode.

Claims (1)

[Claims] 1. In a fuel cell electrode formed by sintering metal particles or metal oxide particles, the electrode is formed porous and a metal composite oxide is formed on the surface of the particle. A fuel cell electrode characterized in that a solid solution layer of a substance is formed. 2. In a fuel cell electrode formed by sintering metal particles or metal oxide particles, the electrode is formed porous, and solid solution particles of metal composite oxide are dispersed between the particles. A fuel cell electrode characterized by: 3. The fuel cell electrode according to claim 2, wherein the particle size of the metal or metal oxide is larger than the particle size of the solid solution particles. 4. A fuel cell electrode made of a porous solid solution of a metal composite oxide. 5. The fuel cell electrode according to claim 1 or 2, wherein the metal composite oxide solid solution is a metal composite oxide solid solution consisting of AxB_1_-__xOy (where A and B are metal atoms). 6. In claim 5, the metal atom A is Mg, Ca, Ta.
, Ti, Mo, Nb, Al, Li, and La.
and the metal atom B is one or more components selected from Ni, Co, and Cu. 7. In claim 5, the value of x is 0.01 to 0 in atomic ratio.
．． 8, and the value of y is in the range of 1 to 3. 8. Forming and firing metal particles or metal oxide particles as a raw material slurry to form a porous electrode, and immersing this electrode in a metal composite oxide solid solution raw material solution to impregnate the inside of the pores. A method for producing an electrode for a fuel cell, comprising the steps of: drying the electrode and then oxidizing and baking it in an oxidizing atmosphere to form a metal composite oxide solid solution layer on the particle surface of the porous electrode. 9. Manufacture of electrodes for fuel cells, including the steps of forming a metal composite oxide solid solution layer on the surface of metal particles or metal oxide particles in advance, and forming and firing a porous electrode after this step. Method. 10. A fuel cell electrode manufacturing method comprising the steps of coating metal composite oxide solid solution particles with metal particles or metal oxide particles, and forming and firing after this step to form a porous electrode. . 11. In a fuel cell configured by stacking unit cells each including an electrolyte body, a cathode and an anode disposed on both sides of the electrolyte body, and a separator disposed outside the cathode and anode. , the cathode and/or
Or a fuel cell, wherein the anode is constituted by the electrode according to claim 1, 2 or 4. 12. The fuel cell electrode according to claim 5, wherein the metal atoms A and B have an ionic radius of 0.6 to 0.7 Å. 13. The fuel cell electrode according to claim 5, wherein the metal composite oxide solid solution is a substitutional metal oxide solid solution.