JPH0794198A - Current collector for high temperature fuel cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To decrease the capability of stress generation, prevent the peeling off of a plating film, reduce contact resistance with an anode, and stabilize the output of a fuel cell over a long period of time without any change with time by almost equalizing the thermal expansion coefficient of a current collecting base with that of a composite plating film. CONSTITUTION:An electroless plating thin film and an electrolytic plating (metal/ceramic) composite film are stacked in that order on one side of a current collector base made of a perovskite structure composite oxide. A current collector is obtained by forming a metallic thin film by electroless plating on one side of a current collector base made of a perovskite structure composite oxide, then forming a metal/ceramic composite film by electrolytic plating from a plating solution in which a ceramic is dispersed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel current collector for a high temperature fuel cell, which has a low contact resistance, is stable over time, and does not peel off a coating, and a method for easily and efficiently producing the same. Regarding

[0002]

2. Description of the Related Art As current collectors for high temperature fuel cells, heat resistant alloys, oxide ceramics, metal / ceramic composites and the like are used. As the oxide ceramics, the general _{formula: (La 1-x M x} ) a (Cr 1-y M 'y) b O 3 ( alkaline earth metals excluding M magnesium in the formula,
M ′ is a transition metal, 0 <x ≦ 0.5, 0 <y ≦ 0.5,
0.95 ≦ a / b ≦ 1.05), and a perovskite structure type composite oxide represented by a lanthanum chromite type oxide mainly composed of a perovskite structure is often used. If it is used on the side, desorption of oxygen occurs and the surface has a high resistance.

For this reason, conventionally, a coating film of a metal such as Ni, Co or Cr is formed on the anode side by plasma spraying, electroless plating, vacuum deposition, sputtering, ion plating or the like to lower the contact resistance. Prevents high resistance. However, plasma spraying can cause 30
A high temperature of 0 ° C. or higher is applied, and since the temperature distribution varies, minute cracks are likely to occur, and those requiring a vacuum process such as vacuum deposition, sputtering, and ion plating have complicated steps, and It is extremely difficult to cover the entire surface of a complex shape / structure such as a current collector for a high temperature fuel cell, and electroless plating has a simple manufacturing process, but P and B existing in the film Therefore, there is a drawback that the stress is strong and the film is easily peeled off.

[0004]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional metal / ceramic composite coated current collector for a high temperature type fuel cell, has a small contact resistance, is stable over time, and has a coating film. The present invention has been made for the purpose of providing a metal / ceramic composite-coated current collector for high-temperature fuel cells, which does not peel off.

[0005]

The inventors of the present invention have conducted various studies to develop a metal / ceramic composite coated current collector for a high temperature fuel cell having the above-mentioned preferable characteristics, and as a result, the film peeling has been confirmed. Main coating is metal /
The ceramic composite film has the same thermal expansion characteristics as the base, and the film formation method uses a plating method that is extremely small in damage to the perovskite structure type oxide, has a simple process, and can cover the entire surface. In order to prevent this, a special measure is taken in which electroless plating is applied only to the interface with the ceramics, and then electrolytic plating is further applied to form a metal / ceramics composite film that occupies most of the composite coating film. As a result, the inventors have found that the object can be achieved, and have completed the present invention based on this finding.

That is, according to the present invention, an electroless plated metal thin film and electrolytic plating (metal / ceramics) are formed on one surface of a current collector base made of a perovskite structure type composite oxide.
It is intended to provide a current collector for a high temperature fuel cell, which is characterized in that a composite membrane is laminated in that order. In a preferred embodiment, (2) the perovskite structure type composite oxide is represented by the general formula (I): (A _1-x M _x ) _a (Cr _1-y M ' _y ) _b O ₃ (I) (A in the formula is La or Y, M is an alkaline earth metal except magnesium, M'is a transition metal, 0 <x ≦ 0.5, 0 <
y ≦ 0.5, 0.8 ≦ a ≦ 1.2, 0.8 ≦ b ≦ 1.2
And (3) the metal represented by A in the general formula (I) above is La, which is mainly composed of a perovskite structure. And (4) a perovskite structure type composite oxide having the general formula (II): (A _1-x A ′ _x ) _a (Cr _1-y B _y ) _b O ₃ (II) (A in the formula is La or Y, A ′ is Sr or Ca, and B is F.
e, Ni, Co, Mg, Mn, Zn, Cu, Al, P
at least one metal selected from d, V, Ir, Mo, Li and W, 0 <x ≦ 0.3, 0 <y ≦ 0.3,
0.95 ≦ a / b ≦ 1.05), which is mainly composed of a perovskite structure (1)
(5) The metal of A in the general formula (II) is La, (4)
And a current collector for a high temperature fuel cell described in the item. The current collector of the present invention comprises a metal thin film formed by electroless plating on one surface of a current collector base made of a perovskite structure type composite oxide, and then electrolytic plating using a plating solution mixed with ceramics. It can be manufactured by forming a metal / ceramics composite film. Thus, according to the present invention, (6) a metal thin film is formed by electroless plating on one surface of a current collector base made of a perovskite structure type composite oxide, and then a plating solution mixed with ceramics is used. It is intended to provide a method for producing a current collector for a high temperature fuel cell, which is characterized in that a metal / ceramic composite film is formed by the electroplating used.

In the present invention, a perovskite structure type composite oxide is used as a base material of the current collector, which is preferably represented by the general formula (I): (A _1-x M _x ) _a (Cr _{1- y} M ′ _y ) _b O ₃ (I) (A in the formula is La or Y, M is an alkaline earth metal except magnesium, M ′ is a transition metal, 0 <x ≦ 0.5, 0 <
y ≦ 0.5, 0.8 ≦ a ≦ 1.2, 0.8 ≦ b ≦ 1.2
In particular, in the general formula (II): (A _1-x A ′ _x ) _a (Cr _{1- y By} ) _b O ₃ (II) (A in the formula is La or Y, A ′ is Sr or Ca and B are F
e, Ni, Co, Mg, Mn, Zn, Cu, Al, P
at least one metal selected from d, V, Ir, Mo, Li and W, 0 <x ≦ 0.3, 0 <y ≦ 0.3,
0.95 ≦ a / b ≦ 1.05) and is mainly composed of a perovskite structure, and in particular, the metal represented by A in these formulas is La.

In the present invention, first, a metal thin film is applied to one surface of the base by electroless plating. In the electroless plating, it is preferable to perform a pretreatment such as an alkali degreasing treatment on the base and an etching treatment with hydrofluoric acid according to a conventional method for the plating. Further, it is preferable that Pd be added to the base which has been subjected to such pretreatment.
It is desirable to carry out an activation treatment by plating with a catalytic metal such as. In electroless plating, practically, the base is placed in a plating bath of a desired metal and electroless plating is performed to form a metal thin film. As the plating bath, for example, NiSO ₄ · 6
_{H 2 O, NaH 2 PO 2} · H 2 O, lactate, etc. bath having a composition of sodium acetate and disodium succinate are preferred. Further, as the metal material for electroless plating, Ni, C
O, Cu and the like are preferable. The thickness of the plating film formed by electroless plating is usually 20 μm or less, preferably 5 μm
m or less. Adhesion is good by electroless plating, and a film having a uniform film thickness can be obtained.

Next, a metal / ceramic composite film is formed on the metal thin film formed by electroless plating by electrolytic plating using a plating solution containing ceramics.
Practically, electrolytic plating is carried out by placing a base provided with a metal thin film by electroless plating in a plating bath of a desired metal mixed with ceramic powder. As the plating bath, a sulfamic acid bath, for example, a bath having a composition of Ni (NH ₂ SO ₃ ) ₂ , H ₃ BO ₃ and ceramic powder, etc., is preferable because the stress is the smallest. Further, as the metal material for electrolytic plating, Ni, Co, Cr, Z
Transition metals such as n and Ti and noble metals such as Ru, Rh, Pd and Pt are preferable. As the ceramic material, zirconia, ceria, magnesia, yttria, alumina and the like are preferable, and the content thereof is 20 with respect to the capacity of the plating film.
The range of ˜70% by volume is preferred. The thickness of the plating film formed by electrolytic plating is not particularly limited as long as it does not peel off, but is preferably about 20 to 100 μm.

In the method of the present invention, the other surface not plated is masked. As the masking process, for example, tape masking, masking technology using a rubber material, or the like is used.

[0011]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. Example 1 5 cm square and 6 mm thick made of a lanthanum chromite complex oxide having a composition of La _0.8 Sr _0.2 Cr _0.9 Co _0.1 O _3.
After tape-masking one side of the current collector base plate (having a groove only on one side), it was placed in a 10 g / l concentration sodium hydroxide aqueous solution and alkali degreased at 50 ° C. for 5 minutes, then 47% Etching treatment was performed for 3 minutes at room temperature with a hydrofluoric acid solution having a concentration, and then ultrasonic cleaning was performed for 1 minute at room temperature. Then, after holding this at 50 ° C. for 5 minutes,
Washed with hot water for 1 minute, SnCl ₂ 6 g / l, sodium hydroxide 23 g / l, tartaric acid 39 g / l, NaCN 18
After sensitizing by immersing in an aqueous solution having a composition of 5 g / l and thiourea 55 g / l, Sn was dispersed on the surface, PdCl _{2 2} g / l, 38% hydrochloric acid 4 ml /
1, 28% ammonium hydroxide 160 ml / l, ammonium chloride 27 g / l and NaH ₂ PO ₂ · H ₂ O
Pd was supported on the surface by immersing it in an aqueous solution having a composition of 10 g / l. This process was repeated twice to perform Pd activation treatment.

The lanthanum chromite base plate thus activated was treated with nickel sulfate 20 g / l, sodium hypophosphite 10 g / l and sodium acetate 5 g.
Dip it in a plating bath of pH 6.0 having a composition of 1 / l,
An electroless Ni plating treatment was performed at 90 ° C. for 4 minutes. Then, the obtained Ni thin film plated base plate was immersed in a plating bath having a composition of nickel sulfamate (450 g / l), H ₃ BO _{3 (} 30 g / l) and ZrO _{2 (} 250 g / l) and having a pH of 4.0, and 2.0 A. Under the current density of / dm ² ,
Electrolytic Ni / ZrO ₂ plating treatment was applied at 50 ° C. for 120 minutes to form a plating film having a film thickness of 50 μm. Then
The tape masking was released by removing the tape for that purpose. Further, it was rust-proofed at room temperature for 1 minute and then dried. The thermal expansion coefficient of each part of the thus obtained current collector was 11.0 × 10 ⁻⁶ / K for the lanthanum chromite base and 11.2 × for the composite plating film.
It was equivalent to 10 ^-6 / K.

Then, in a measurement system as shown in FIG. 1, the current collector 11 thus obtained was treated with the plating surface side and the anode electrode 12 (Ni / ZrO ₂ = 10/1 weight ratio composition). And an electrode area of 16 cm ² )
Contact at 1.2 cm, and hydrogen gas at 200
The flow rate was set to cc / min, and the contact resistance was obtained by using a Ni plate as the collector terminal of the anode electrode. The results are shown in Table 1.

[0014]

[Table 1] After the measurement was completed, the composite plating film was attached to the entire surface of the base.

Comparative Example 1 An electroless Ni-plated current collector having a plating film thickness of 50 μm was prepared in the same manner as in Example 1 except that the electroless Ni plating treatment time was changed to 300 minutes and electrolytic plating was not performed. The contact resistance was calculated. The results are shown in Table 2.

[0016]

[Table 2] After the measurement, the plating film was peeled off from the base.

Comparative Example 2 A lanthanum chromite base having the same composition as that of Example 1 which was surface-treated with a Ni plasma sprayed film (film thickness 200 μm) was used as a current collector, and the contact resistance was the same as in Example. I asked. The results are shown in Table 3.

[0018]

[Table 3] After the measurement was completed, the sprayed film had cracks.

Example 2 A solid oxide fuel cell was prepared according to the assembly mode shown in FIG.
It was 8 mol% of yttria was added to the solid electrolyte plate 21.
50 consisting of partially stabilized zirconia which is zirconia
A plate-like material having a size of x50x0.2 mm was used. Of solid electrolyte plate
La on the oxygen passage side _0.8Sr_0.2MnO₃Powder (average particle size approx.
5 μm) dispersed in organic binder, area 16 cm²
Area of 0.1-0.2mm thickness and apply as a cathode
No. 22 and Ni / ZrO on the hydrogen passage side₂(Weight ratio 1 /
1) Disperse the cermet mixed powder in an organic binder,
16 cm area similar to cathode²Area of 0.1-0.2m
The anode 23 was coated with a thickness of m. Each current collector 24
Is a corresponding collector base plate (with a groove only on one side)
Or grooves provided on both sides) in the same manner as in Example 1
The obtained one was used. In addition, the contact between the anode and the collector
The measuring terminal 25 was inserted so that the contact resistance could be measured.

The fuel cell thus manufactured was heated. From room temperature to 350 ° C, heat up at 10 ° C / min,
At 350 ° C or higher, nitrogen gas is flown on the hydrogen passage side to prevent oxidation of the anode, and 1000 ° C is supplied at 10 ° C / min.
The temperature was raised to ° C. Then, the temperature was maintained at 1000 ° C., hydrogen was flown to the anode side and oxygen was flown to the cathode side to start power generation. The result per unit cell is output 7.8W, cell resistance 2
The contact resistance between the anode and the current collector was 5 mΩ and 1 mΩ. Table 4 shows changes over time in the output and the contact resistance between the anode and the current collector.

[0021]

[Table 4]

Comparative Example 3 La _0.8 Sr _0.2 Cr _0.9 Co was used as the anode side current collector.
Ni plasma sprayed film (film thickness 200 μm) on _0.1 O ₃ substrate
A battery was prepared and a power generation test was conducted in the same manner as in Example 2 except that the battery having the above-mentioned structure was used. The results per unit cell were an output of 7.6 W, a cell resistance of 28 mΩ, and a contact resistance between the anode and the current collector of 7 mΩ. Table 5 shows the changes over time in the output and the contact resistance between the anode and the current collector.

[0023]

[Table 5]

Example 3 La_0.8Sr_0.2Cr_0.98Co_0.02O₃Composition of lanterns
20cm square composed of chromite complex oxide, thickness 6
mm current collector base plate (with a groove only on one side or
(Provided with grooves on both sides) requires the following treatment on one side.
The surface not covered with tape masking, 10g / l concentration
In a sodium hydroxide aqueous solution at 50 ° C for 5 minutes.
After degreasing Lucari, with 47% hydrofluoric acid solution
Etch at room temperature for 3 minutes, then at room temperature for more than 1 minute
Sonicated. It was then held at 50 ° C for 5 minutes
After that, rinse with hot water for 1 minute, SnCl₂ 6g / l, sodium hydroxide
Thorium 23g / l, Tartaric acid 39g / l, NaCN
 Water solution having a composition of 185 g / l and thiourea 55 g / l
Immerse in liquid and perform sensitizing to separate Sn on the surface.
After dispersing, PdCl₂ 2 g / l, 38% hydrochloric acid 4
ml / l, 28% ammonium hydroxide 160 ml /
1, ammonium chloride 27 g / l and NaH ₂PO₂・
H₂The Pd was exposed by immersing it in an aqueous solution having a composition of O 10 g / l.
It was carried on the surface. Repeat this process twice to activate Pd
Treated.

The lanthanum chromite base plate thus activated was treated with nickel nitrate 20 g / l, sodium hypophosphite 10 g / l and sodium acetate 5 g.
Dip it in a plating bath of pH 6.0 having a composition of 1 / l,
An electroless Ni plating treatment was performed at 90 ° C. for 4 minutes. Then, the obtained Ni thin film plated base plate was immersed in a plating bath having a composition of nickel sulfamate (450 g / l), H ₃ BO _{3 (} 30 g / l) and ZrO _{2 (} 250 g / l) and having a pH of 4.0, and 2.0 A. Under the current density of / dm ² ,
Electrolytic Ni / ZrO ₂ plating treatment was applied at 50 ° C. for 120 minutes to form a plating film having a film thickness of 50 μm. Then
The tape masking was released by removing the tape for that purpose. Further, it was rust-proofed at room temperature for 1 minute and then dried. In this way, each current collector having a thickness of 6 mm was produced. The coefficient of thermal expansion of each part of this current collector is 11.0 × 10 ^-6 / lanthan chromite base
K, the composite plating film was equivalent to 11.2 × 10 ⁻⁶ / K.

According to the assembly mode of FIG. 2, each of the current collectors 24 is
Was used to prepare a solid oxide fuel cell. The solid electrolyte plate 21 is made of partially stabilized zirconia, which is zirconia containing 8 mol% of yttria, and is 200 × 200 ×.
A 0.2 mm plate was used. The oxygen passage side of the solid electrolyte plate is La _0.8 Sr _0.2 MnO ₃ powder (average particle size of about 5 μm).
Is dispersed in an organic binder and applied in a region of 324 cm ² to a thickness of 0.1 to 0.2 mm to form the cathode 22, and the hydrogen passage side is Ni / ZrO ₂ (weight ratio 7/3) cermet mixed powder. Was dispersed in an organic binder and applied to a region having an area of 324 cm ² in a thickness of 0.1 to 0.2 mm like the cathode to form an anode 23. Further, a measuring terminal 25 was inserted so that the contact resistance between the anode and the current collector could be measured.

The fuel cell thus produced was heated. Raise the temperature from room temperature to 350 ° C at 1 ° C / min, and
At 50 ° C. or higher, in order to prevent oxidation of the anode on the hydrogen passage side, nitrogen gas was flown and the temperature was raised to 1000 ° C. at 1 ° C./min. Then, the temperature was maintained at 1000 ° C., propane and H ₂ O were flown on the anode side, and air was flown on the cathode side to start power generation. Output per unit cell is 67 W, cell resistance 1.3 mΩ, contact resistance between anode and collector 0.4 m
It was Ω. Table 6 shows the changes over time in the output and the contact resistance between the anode and the current collector.

[0028]

[Table 6] After the measurement was completed, the composite plating film was attached to the entire surface of the base.

From these results, the current collector of the example has a small contact resistance between it and the anode, is stable without change over time, and the output of the fuel cell incorporating it is also over time. While stable, the current collector of the comparative example has a large contact resistance, changes with time, and gradually increases, and the output of the fuel cell incorporating the current collector decreases significantly with time. I understand.

[0030]

In the current collector for a high temperature fuel cell of the present invention, since the thermal expansion characteristics of the base and the composite plating film are substantially the same, stress is unlikely to occur and the plating film is not likely to peel off. , The contact resistance with the anode is small,
Moreover, there is a remarkable effect that the output does not change with time and is stable, and the output of a fuel cell incorporating the same can be stabilized with time. Further, according to the method of the present invention, it is possible to easily and efficiently obtain a current collector excellent in such characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a measurement system for determining a contact resistance between a current collector and an anode electrode.

FIG. 2 is a schematic view of an example of an assembly mode of a solid oxide fuel cell.

[Explanation of symbols]

 11 Anode Electrode 12 Current Collector 21 Solid Electrolyte Plate 22 Cathode 23 Anode 24 Current Collector 25 Measuring Terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoo Ando Nishitsurugaoka 1-3-1 Oi-cho, Iruma-gun, Saitama Tonen Co., Ltd. Research Institute (72) Toshihiko Yoshida Nishitsurugaoka, Oi-cho, Saitama 1-3-1 Tonen Co., Ltd. Research Institute

Claims (2)

[Claims] 1. A high temperature characterized by laminating an electroless plated metal thin film and an electrolytic plated (metal / ceramics) composite film in that order on one surface of a current collector base made of a perovskite structure type composite oxide. Type fuel cell current collector. 2. A metal / ceramics is formed by forming a metal thin film on one surface of a current collector base made of a perovskite structure type complex oxide by electroless plating, and then performing electrolytic plating using a plating solution mixed with ceramics. A method for producing a high temperature fuel cell current collector, which comprises forming a composite film.