JP3095593B2 - Anode container for sodium-sulfur battery and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an anode container for a sodium-sulfur battery and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in an anode container of a sodium-sulfur battery, a corrosion-resistant film is formed on the inner wall surface of the anode container by plating such as chromizing treatment in order to enhance corrosion resistance to sodium polysulfide. In addition, JP-A-61
Japanese Patent No. 264659 discloses a method of forming a corrosion resistant film by plasma spraying in a low-pressure atmosphere.

[0003]

SUMMARY OF THE INVENTION The present inventor has conducted an experimental study using such a method of forming a film of an anode container for a sodium-sulfur battery by plasma spraying.
I found the following: The formation of the coating by thermal spraying
It consists of a stack of dissolved particles, and the shape, size, distribution, etc. of the spraying powder are greatly affected by the quality (density) of the coating. Generally, the porosity in the thermal spray coating of a metal material is 3% or more, and that of a ceramic material is 8% or more. The particle size range of the thermal spraying powder used for these is 5 to 5.
125 μm. In the thermal spray coating composed of the above-mentioned laminate, many pores, which are defects peculiar to the thermal spray coating, remain between the laminates. Further, the temperature becomes higher due to a change in the plasma conditions, and the particle surface is significantly oxidized, leaving a large amount of oxide film. The presence of pores, oxide film, and undissolved particles in this film is largely caused by rapid capacity deterioration and increase in internal resistance due to penetration of sodium polysulfide during long-term operation of the sodium-sulfur battery. Further, there is a case where the metal material which is the base material is reached and the metal material is also corroded and cannot be operated.

On the other hand, in the long-term operation of a sodium-sulfur battery, defects such as cracking and peeling of a film due to temperature rise and fall (thermal cycle) become a serious problem as described above. The same is true for the chromizing steel, that is, defects such as cracks caused by processing of the chromium carbide layer on the outermost surface of the chromizing steel are greatly opened due to thermal cycles, so that long-term operation becomes impossible. .

[0005] Regarding thermal spraying, there are various parameters due to the quality of the coating (densification), but it is generally reported that the plasma conditions, the primary gas amount, and the spraying distance largely depend. On the other hand, the adhesion of the thermal spray coating is reported to be mainly due to the surface roughness by blasting, but is not clear. In addition, although there are a cooling method and a preheating method for the workpiece as a distinction of the thermal spraying method, it is not clear which one is more effective in use and thermal spraying. In particular, at present, the correlation between these conditions and the particle size of the powder is not known.

However, the anode container having a corrosion-resistant film formed by plating of a chromizing treatment or the like has hair cracks on the surface of the film due to the processing of the chromium carbide layer on the outermost surface of the film, and the sodium-sulfur battery has Hair cracks in the outermost layer of the corrosion-resistant coating grow due to thermal stress caused by repeated temperature rise and fall during operation and shutdown, and sodium polysulfide penetrates into the coating through the grown hair cracks, turning the coating into a sulfide or an anode container. Various problems such as deterioration of the battery capacity due to corrosion of itself, reduction of the energy efficiency of the battery due to increase of the internal resistance, etc. occur.
Long-term stable operation was impossible. On the other hand, plasma spraying in a low-pressure atmosphere is not suitable for industrial mass production due to extremely low productivity and high cost.

An object of the present invention is to solve the above-mentioned various problems and to provide a method of forming a film which is industrially excellent in productivity and economy by plasma spraying in an air atmosphere. Excellent corrosion resistance to sodium polysulfide, with less deterioration of battery capacity even during long-term operation,
An object of the present invention is to provide a film having low internal resistance and which does not peel off from the anode container.

In general, the porosity of a metal film formed by plasma spraying is 3% or more, and pores remain in a stacked state between molten metal liquid particles during spraying. Further, when the thermal spraying is performed in an air atmosphere, the surface of the sprayed high-temperature metal particles is oxidized, and an oxide film remains. Furthermore, a part of the sprayed metal powder remains as undissolved particles in the coating and on the coating surface during thermal spraying. Such a coating is not suitable as an anticorrosion coating for an anode container of a sodium-sulfur battery, even if the coating itself is a material having corrosion resistance to sodium polysulfide.

An object of the present invention is to form a corrosion-resistant coating on the inner wall surface of an anode container for a sodium-sulfur battery, and to improve the adhesion of the coating by making the coating ultra-dense and having a very small oxide content. An object of the present invention is to provide an anode container for a sulfur battery and a method for manufacturing the same. Another object of the present invention is to provide a method for manufacturing an anode container for a sodium-sulfur battery, which has significantly improved plasma spraying efficiency when forming a corrosion-resistant film on the inner wall of the anode container.

[0010]

In order to achieve the above object, an anode container for a sodium-sulfur battery according to the present invention comprises:
In a sodium-sulfur battery anode container having a sprayed coating made of a stellite alloy formed on the inner wall of a cylindrical metal anode container of a sodium-sulfur battery, the coating has a porosity of 1.0% or less and an oxide content. Is very small and the average surface roughness of the film is 4.2 μm or less.

In the method for producing the anode container for a sodium-sulfur battery, the sprayed powder for forming a film has a particle size range of 5 to 25 μm.
m, using a stellite alloy having an average particle size of 10 to 20 μm, and a blast surface average surface roughness of the inner wall surface of the base material of 1 to 10 μm
m, a film is formed on the inner wall of the anode container by plasma spraying.

[0012]

In the battery using the anode container for a sodium-sulfur battery of the present invention, the penetration of sodium polysulfide into the film can be suppressed, and the decrease in battery capacity can be suppressed. Further, in the film of the sodium-sulfur battery anode container of the present invention, the internal resistance of the battery is significantly reduced due to the decrease in porosity due to ultra-densification, and the energy efficiency is improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a method for manufacturing an anode container for a sodium-sulfur battery according to the present invention. In the production method of this example, stellite 6 having an average particle size of 15 μm was used as a film forming powder as a raw material for a corrosion resistant film formed on the inner wall of the anode container. As shown in FIG. 1, powder material 3 is applied to the inner wall surface of a cylindrical container body 2 made of a non-ferrous metal material such as aluminum or an aluminum alloy using a thermal spray gun 1.
Is subjected to plasma spraying in the atmosphere to form a corrosion resistant film 4.

In plasma spraying, argon gas is used as a primary gas, and hydrogen gas is added as a secondary gas.
The supply amount of the gas is argon gas: 40 liter / mi.
n, hydrogen gas: set in the range of 0.2 to 3.0 liter / min, current is 250 A, and voltage V is 28 to 32 V
And The surface temperature (surface temperature of the pipe) of the container main body 2 before thermal spraying is set to 210 ° C. or higher, and the rotation speed is 400 rpm.
And The blast surface roughness of the inner wall surface of the container substrate is 2 to 10μ
m. The film thickness was 85 μm.

(Experiment 1) The relationship between the spraying distance and the surface roughness and porosity of the coating was examined. The sprayed powder used in the experiment was a cobalt-based alloy, and its powder particle size: 14.5 μm, coating thickness: 65 μm, surface roughness: 1 to 5 μm, base material of the anode container body: aluminum alloy, and plasma conditions were as follows: Ar gas: 42 l / min, H ₂ gas: 0.4 l / min
The current A was 255 A and the voltage V was 29.3 V.
The result is shown in FIG.

As shown in FIG. 2, the porosity of the coating decreases and the surface roughness of the coating decreases when the spraying distance is in the range of 10 to 25 mm. Therefore, it was found that the content of the oxide which was densified in this range was extremely small. (Experiment 2) In Experiment 2, the surface temperature of the anode container before the start of thermal spraying (the surface temperature before the start of thermal spraying of the pipe) and the adhesion between the formed coating and the surface temperature were tested.

The experimental conditions were as follows: coating material: cobalt-based alloy,
Film thickness: 78 μm, base material of anode container body: blast,
An aluminum alloy having a surface roughness of 6 to 10 μm was used. The results were as shown in Table 1.

[0018]

[Table 1]

In Table 1, in the evaluation of adhesion, it was judged that the symbol ○: no peeled portion, Δ: small amount peeled, ×: large amount peeled. As shown in Table 1, it was found that the surface temperature of the anode container before the start of thermal spraying was effective when the temperature was 150 ° C. or more as shown in Examples 1, 2, and 3. On the other hand, in Comparative Examples 1 to 5, it was found that the lower the temperature, the worse the adhesion was, and even at a temperature of 80 to 150 ° C., the adhesion was not sufficient.

The adhesion test was determined based on the state of peeling of the film generated from the bending test. The device after the bending test used for the judgment was as shown in FIGS. That is, a corrosion-resistant coating 32 is formed on the surface of a cylindrical aluminum alloy base material 30 and is stretched by applying a load with a jig 36. As a result, the flat plate-shaped aluminum alloy base material 30 The coating 32 was formed. Then, the quality of the adhesion was determined based on the occurrence of cracks 34, peeled portions 35, and the like in the coating 32 on the substrate 30 after the bending test in FIG.

(Experiment 3) In Experiment 3, the porosity of the film obtained by changing the average particle size of the raw material powder, the number of undissolved particles in the film, the yield of the powder, and the evaluation of the fluidity of the powder were performed. The experimental conditions were as follows: substrate: aluminum alloy, substrate thickness: 2.5 mm, raw material powder: cobalt-based alloy powder, substrate preheating temperature: 200 to 250 ° C., and film thickness: 85 μm. Table 2 shows the results.

[0022]

[Table 2]

As shown in Table 2, Examples 11, 12, and 13 and Comparative Examples 11, 12, 13, 14, 15, and 16 were performed in the range of an average particle diameter of the thermal spraying powder of 5 to 70 mm. As shown in Table 2, the porosity was measured for n = 5 in the film, and the average porosity of the five was determined.

Regarding the number of undissolved particles, the number of undissolved particles visually observed on the film surface was counted. The yield of the powder was calculated from the degree of effective film formation of the powder. Regarding the fluidity evaluation of the powder, ◎: good, ：: normal,
Δ: acceptable, ×: unacceptable.

As shown in Table 2, Examples 11 and 1
In Nos. 2 and 13, it was found that when a thermal spraying powder having an average particle diameter of 10 to 20 μm was used, the porosity was less than 1.0%, and a super-densified film was obtained. The number of undissolved particles was 0. From this, it was found that the condition of the film surface was also good. The yield of the powder was 80% or more, which was very good. The powder flow proved to be good.

(Experiment 4) Experiment 4 shows the relationship between the charge / discharge cycle of a sodium-sulfur battery using the anode container and the battery capacity. FIG. 5 shows the results. In Example 11, it was found that the decrease in battery capacity was small even when the number of charge / discharge cycles was increased, as compared with Comparative Examples 11, 12, 13, 14, 15, and 16.

(Experiment 5) In Experiment 5, the relationship between the charge / discharge cycle of a sodium-sulfur battery using the anode container and the internal resistance was measured. The operating temperature of the battery was 310 ° C. FIG. 6 shows the results. As shown in FIG. 6, when the charge / discharge cycle was repeated, Comparative Examples 11, 12, 13, 1
In Example 11, the increase in the internal resistance was lower than in Examples 4, 15, and 16. Also, the initial internal resistance is low. As a result, it was found that the internal resistance of Example 11 was smaller than that of Comparative Examples 11, 12, 13, 14, and 15, and the battery efficiency was good.

[0028]

As described above, according to the anode container for a sodium-sulfur battery according to the present invention, the porosity of the stellite film formed on the inner wall of the anode container can be reduced to 1.0% or less, and the oxide content is reduced. The ratio was extremely small, and the average surface roughness was 4.2 μm or less. As a result, the adhesion of the film was good, and the decrease in battery capacity during thermal cycling during battery use was reduced. In addition, since an increase in internal resistance is suppressed, a reduction in battery efficiency during long-term use is significantly suppressed.

[Brief description of the drawings]

FIG. 1 is a view illustrating a method for forming a film of an anode container for a sodium-sulfur battery according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the plasma spray distance and the porosity and surface roughness of a coating.

FIG. 3 is a schematic diagram showing an apparatus used for evaluating the adhesion of a film used in an experiment.

FIG. 4 is a schematic perspective view showing the state of a film on a substrate stretched by the apparatus of FIG. 3;

FIG. 5 is a data diagram showing a relationship between a charge / discharge cycle and a battery capacity performed in an experiment.

FIG. 6 is a data diagram showing a relationship between a charge / discharge cycle and an internal resistance performed in an experiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal spray gun 2 Container main body 3 Thermal spray powder 4 Corrosion resistant coating

────────────────────────────────────────────────── (5) References JP-A-4-284371 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/39 C23C 4/08 H01M 4 / 64

Claims (3)

(57) [Claims] 1. An anode container for a sodium-sulfur battery in which a corrosion-resistant film made of a stellite alloy is formed on the inner wall of a cylindrical metal anode container of a sodium-sulfur battery by thermal spraying, wherein the porosity of the corrosion-resistant film is 1.0. % Or less, the oxide content is extremely small, and the average surface roughness is 4.2 μm or less. 2. The method for producing an anode container for a sodium-sulfur battery according to claim 1, wherein the sprayed powder for forming a film uses a stellite alloy having a particle size range of 5 to 25 μm and an average particle size of 10 to 20 μm. , Substrate inner wall
Having an average surface blast surface roughness of 1 to 10 μm
A method for producing an anode container for a sodium-sulfur battery, wherein a film is formed on the inner wall of the container by plasma spraying. 3. The method for producing an anode container for a sodium-sulfur battery according to claim 2, wherein the temperature of the container before the start of the plasma spraying is 150 ° C. or higher.