JPH09102327A - Sodium-sulfur secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sodium-sulfur secondary battery that is excellent in durability and is small in the rate at which its battery capacity decreases by using a corrosion-resisting material for its positive electrode container. SOLUTION: This sodium-sulfur secondary battery has a positive electrode container 2 and a negative electrode container 3 molded in such a way that they are isolated from each other via an insulating rib 4 by an alumina solid electrolyte tube 1 having sodium ion conductivity, with molten sodium polysulfide 5 enclosed in the positive electrode container 2 and with molten metal sodium 6 enclosed in the negative electrode container 3. Further, the inside surface of the positive electrode container 2 is formed by a cobalt-based alloy layer with the addition of a rare earth element or by an alloy-particle- containing layer to improve corrosion resistance to make it possible to reduce peeling, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sodium-sulfur secondary battery, and more particularly to a sodium-sulfur secondary battery having excellent durability and a small battery capacity reduction rate.

[0002]

2. Description of the Related Art A conventional sodium-sulfur secondary battery has a cylindrical positive electrode container for accommodating a positive electrode conductive material of a carbon fiber mat impregnated with molten sulfur as a positive electrode active material and a top end portion of the positive electrode container. Thus, the negative electrode container connected via an α-alumina insulating ring is fixed to the inner peripheral portion of the α-alumina insulating ring, and stores molten metal sodium as a negative electrode active material to improve sodium ion conductivity. And a beta-alumina-based solid electrolyte tube. At the time of discharge, sodium ions are conducted from the negative electrode container through the solid electrolyte tube and react with sulfur S in the positive electrode container to generate sodium polysulfide.

2Na + xS = Na2Sx Further, during charging, a reaction reverse to that during discharging occurs, and sodium and sulfur are produced.

In a sodium-sulfur secondary battery, when the surface of a metal container constituting a positive electrode container is corroded by molten sodium polysulfide, a positive electrode active material is consumed for the formation of a corrosion reaction product, and the battery reacts. The required positive electrode active material is reduced and the battery capacity is reduced, and the internal resistance of the battery is increased due to an increase in the electrical resistance of the metal sulfide on the positive electrode surface, so that the charging efficiency is easily lowered. Conventionally, in a sodium-sulfur secondary battery, a method of forming a cobalt-based chromium alloy layer having excellent corrosion resistance on the surface of a positive electrode container has been proposed in order to prevent corrosion of the surface of the positive electrode container due to sodium polysulfide. For example, Japanese Patent Application Laid-Open No. 2-142065 proposes to form a cobalt-chromium-based, tungsten, nickel, iron, molybdenum alloy layer on the surface of an aluminum alloy by plasma spraying. Further, it has been proposed to form a chromium film on the surface of an iron-based container by CVD (chemical vapor deposition) by a chromizing treatment.

[0005]

The corrosion-resistant material for a positive electrode of a sodium-sulfur secondary battery disclosed in the prior art is corroded by molten sodium polysulfide, but withstands a life of several years. However, in a power storage system using a large number of assembled batteries and a power source for electric vehicles, the battery operating temperature becomes high and the corrosion rate increases. Therefore, it has been difficult to suppress the capacity reduction rate of the battery to 10% or less, preferably 5% or less, after operating for 10 years.

[0006] The problem to be solved by the present invention is to propose an alloy composition having excellent corrosion resistance, a layer having excellent corrosion resistance on the inner surface of a corrosion-resistant positive electrode container such as aluminum, capable of suppressing peeling and making electrical contact. A battery having the following is provided.

[0007]

[Means for Solving the Problems] A first means for solving the above-mentioned problem is that sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is A sodium-sulfur secondary battery housed in a positive electrode container, characterized in that at least a part of the inner surface of the positive electrode container is covered with a cobalt-based alloy containing a rare earth element other than niobium. It is a secondary battery.

The rare earth element is at least one of yttrium and lanthanum.

The composition of the cobalt-based alloy is chromium 27-
31%, Aluminum 4-7%, Yttrium 0.5-
It is characterized by 1.5% residual cobalt.

In the second means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is stored in a positive electrode container.
A sodium-sulfur secondary battery operated at a temperature of 00 ° C. or lower, wherein at least a part of the inside of the positive electrode container is covered with a cobalt-based alloy or an iron-based alloy to which a rare earth is added. The sodium-sulfur secondary battery is characterized in that the capacity decrease rate is 5% / year or less.

In a third means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is stored in a positive electrode container.
In a sodium-sulfur secondary battery operated at a temperature of 00 ° C. or less, at least a part of the inside of the positive electrode container is covered with a cobalt-based alloy to which a rare earth is added, and the battery capacity reduction rate is 3% / year or less. Sodium characterized by
It is a sulfur battery.

In a fourth means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is stored in a positive electrode container.
In a sodium-sulfur secondary battery operated at a temperature of 00 ° C. or lower, at least a part of the inner surface of the positive electrode container has at least one of cobalt-based alloy particles or iron-based alloy particles.
It is a sodium-sulfur secondary battery having a layer formed by burying seeds.

In a fifth means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is stored in a positive electrode container.
In a sodium-sulfur battery operated at a temperature of 00 ° C. or lower, at least a part of the inner surface of the positive electrode container is formed of layered cobalt-based alloy particles or iron-based alloy particles, sodium-sulfur. It is a secondary battery.

In a sixth means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, and the sulfur component is stored in a positive electrode container.
In a sodium-sulfur secondary battery operated at a temperature of 00 ° C. or lower, the positive electrode container is made of aluminum or an aluminum alloy or a highly corrosion-resistant alloy thin plate, and at least a part of the inside of the positive electrode container is a cobalt-based alloy to which a rare earth element is added. It is a sodium-sulfur secondary battery characterized by being covered with and having a battery capacity reduction rate of 5% / year or less. In a seventh means, sodium and a sulfur component are arranged via a solid electrolyte, the sodium is stored in a negative electrode container, the sulfur component is stored in a positive electrode container, and sodium is operated at a temperature of 400 ° C. or lower. -In a sulfur secondary battery, at least a part of the inner surface of the positive electrode container is covered with a cobalt-based alloy to which a rare earth is added, and the positive electrode container and the cobalt-based alloy to which the rare earth is added are reacted with each other. A sodium-sulfur secondary battery characterized by the presence of a layer.

Sodium and sulfur components are arranged via a solid electrolyte, and the sodium is stored in a negative electrode container,
In the method for manufacturing a sodium-sulfur secondary battery in which the sulfur component is housed in a positive electrode container, at least a part of the inside of the positive electrode container is coated with a cobalt-based alloy by thermal spraying treatment to cover the sodium-sulfur secondary battery. The present invention relates to a method for manufacturing a battery.

Corrosion resistant conductive alloy material is cobalt based
7-31% chromium, 5-7% aluminum, 0.5
Contains ~ 1.5% yttrium. Rare earth elements such as lanthanum may be added instead of yttrium. However, the alloy composition changes somewhat. Since the alloy contains a large amount of chromium and a rare earth metal is added, it is difficult to perform not only drawing and extruding but also rolling. As one of the inner surface treatment methods for the positive electrode container material, thermal spraying treatment can be considered. In the case of a thin spray coating, there are few problems,
When the film thickness is large, the amount of creep deformation is small, and therefore film peeling easily occurs. When performing surface treatment by thermal spraying, the film thickness should be 20 μm or less at maximum. If the corrosion rate is low, the film thickness can be reduced. When forming a film by thermal spraying, aluminum is preferable for the positive electrode container base material because of its adhesion to the surface treatment film and the corrosion resistance of the base material, but when the battery operating temperature is low and the corrosion rate is not high, other thin plate processing is required. It is possible to use a corrosion-resistant alloy material that can be used as a base material.

Further, in order to further exert the performance of the alloy of the present invention, it is preferable to form a layer containing alloy particles on the inner surface of the positive electrode container in contact with molten sodium polysulfide. Unlike plating, coatings, and flakes, this is a layer in which a large number of discontinuous particles are aggregated, so that the amount of distortion of the surface coating is smaller than that of plating or the like, so that peeling and falling off can be suppressed.

The buried layer may be formed by mechanically pressing the particles.
With this structure, it is possible to prevent the surface treatment layer (corrosion-resistant layer) in the positive electrode container from being separated and peeled off when stress is applied to the positive electrode container.

The layer is composed of large-diameter and small-diameter corrosion-resistant conductive particles, and small-diameter corrosion-resistant conductive particles are arranged in the gaps between the large-diameter corrosion-resistant conductive particles. The particle size is preferably such that the ratio of the size of the large particles and the size of the small particles is larger than 6/4. This can improve the area ratio of the corrosion-resistant conductive particles on the surface of the layer.

The area ratio of the surface of the corrosion-resistant conductive particles forming the layer is 25 to 100%. The area ratio is determined by a ratio between a predetermined area of the layer and a projected area of the particles existing in the area. An area ratio of 20% or more is required to obtain the effect as the current collector, and the upper limit can be set to about 80% in view of the stability of the layer.

The layer is characterized in that it has a thickness of 10 to 500 μm. In this range, plastic working is possible, the formation of the containing layer on the aluminum base material can be performed more reliably, the corrosion resistance and current collecting properties become sufficient, and the product can withstand long-term use. Since there is a possibility that a corrosion layer of about 10 μm may be formed on the inner surface, it is desirable that the thickness be more than this. When the thickness is 500 μm or more, the deformation of the container material is large, and the residual stress tends to be too large. Further, since it is a waste material and becomes large, it is preferably 20 to 200 μm.

The positive electrode container is made of aluminum or an aluminum alloy. When the coating is formed by the thermal spraying method, as described above, a tube made of an alloy having high corrosion resistance can be used as the positive electrode container.

It is characterized in that a reaction product of the positive electrode container component is present at the interface between the corrosion resistant conductive particles and the positive electrode container. The reactant is formed by heating after forming a buried particle layer. The temperature at which the buried layer is formed is preferably low enough not to form a reactant layer. For example, it is about 200 ° C. This depends on the composition of the alloy. Then, the particles can be prevented from falling off by heating at 450 to 600 ° C. to form the reaction product. As a result, it is possible to form a preferable reaction product as compared with a film formed by heating, such as a film formation by thermal spraying, and effectively prevent peeling.

The diameter of the particles is preferably about 5 to 50 μm. It is adjusted appropriately according to the situation of the layer. If the particle size is reduced, the inner surface of the positive electrode container can be made smoother, which is desirable for uniform current collection. It is preferable that the particle size is about 10 μm or more for particle loss due to thermal strain due to temperature change due to particle corrosion, charge / discharge, and temperature rise / fall.

The battery of the present invention preferably further has a thin layer of stainless steel or the like on the outer periphery of the positive electrode container. Thereby, container strength can be improved.

The sodium-sulfur secondary battery of the present invention is shown in FIG.
As shown in FIG. 3, the positive electrode container 2 and the negative electrode container 3 are separately formed by the solid electrolyte 1 having sodium ion conductivity via the insulating ring 4 made of α-alumina, and the molten sodium polysulfide 5 is housed in the positive electrode container. The molten sodium 6 is contained in the negative electrode container.

As shown in FIG. 2, the layer formed by burying at least a part of the particles on the inner surface of the aluminum or aluminum alloy container 7 forming the positive electrode container is formed by thermal spraying of the particles or the particles. The layer 8 of corrosion-resistant conductive material can be formed by mechanical pressing (mechanical method).

In this case, in the mechanical pushing method, the aluminum and aluminum alloy plates or pipes or vessels are annealed in advance in a vacuum or in an inert gas atmosphere, and then a cobalt alloy is mechanically pushed in and heat treated to carry out the above-mentioned positive electrode vessel. Is preferably produced.

The heat treatment is performed in a vacuum or an inert gas atmosphere for 4 hours.
It is preferable to carry out at 50 to 600 ° C. 500-550
It is more desirable to carry out at a temperature of ° C. The processing time is preferably 20 minutes or more.

The above-mentioned mechanical embedding operation is carried out in a vacuum or an inert gas atmosphere at a container temperature of 250 ° C. to 350 ° C.
It is preferable to perform the following.

It is preferable that the particles are transferred to an adhesive roll, mechanically pushed into the inside of an aluminum or aluminum alloy container, and heat-treated for production.

Manufactured by inserting a core metal into an aluminum or aluminum alloy container, filling the gaps with the particles, and then squeezing to form a corrosion-resistant particle layer inside the aluminum or aluminum alloy container and heat-treating. Is also preferable.

As a result of various studies conducted by the present inventors, the cobalt-based alloy having a proper composition to which a rare earth element is added has remarkably improved corrosion resistance to sodium polysulfide. The added rare earth element forms a stable oxide passivation film on the surface. Therefore, the corrosion rate is reduced with respect to molten sodium polysulfide. Since the film thickness of the passive film is extremely thin, it does not hinder the current collection of the battery. The composition of chromium, aluminum and rare earth elements relative to cobalt is 27-31%,
It is 5 to 7% and 0.05 to 1.5%. Yttrium and lanthanum are preferable as the rare earth element.

Therefore, with the alloy according to the present invention, the inner surface of the positive electrode container can be subjected to corrosion resistance treatment against sodium polysulfide.

[0035]

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

Example 1 Chromium 29 weight percent,
Aluminum alloy 6 weight percent, yttrium 1 weight percent, residual cobalt alloy is melted and solidified to a thickness of 5
mm, width 10 mm, length 20 mm sample is cut out and 400 ℃
It was immersed in sodium tetrasulfide (Na ₂ S ₄ ) for 1000 hours. The corrosion weight loss was 0.07 mg / cm ² . It was 1/20 to 1/10 of the corrosion amount of the chromizing film and Stellite # 6, which are conventional materials, under the same conditions.

(Example 2) 29% by weight of chromium,
Aluminum 4% by weight, yttrium 1% by weight, residual cobalt alloy is melted and solidified to a thickness of 5
mm, width 10 mm, length 20 mm sample is cut out and 400 ℃
It was immersed in sodium tetrasulfide (Na ₂ S ₄ ) for 1000 hours. The corrosion weight loss was 0.07 mg / cm ² . It was 1/10 of the corrosion amount of the chromizing film and Stellite # 6 which are conventional materials under the same conditions.

(Example 3) 22% by weight of chromium,
Nickel 22 weight percent, lanthanum 0.08 weight percent, residual cobalt alloy is melted and solidified to a thickness of 5
mm, width 10 mm, length 20 mm sample is cut out and 400 ℃
It was immersed in sodium tetrasulfide (Na ₂ S ₄ ) for 1000 hours. The corrosion weight loss was 0.09 mg / cm ² .

(Example 4) The alloy of Example 1 was atomized into powder. The average particle size was 20 μm. The alloy particles of the present invention are used in a plasma spraying apparatus as a positive electrode container material of a sodium-sulfur secondary battery in a cylindrical shape (outer diameter 64 m).
Thermal spraying was performed on the inside of an aluminum substrate of m, inner diameter 61 mm, wall thickness 1.6 mm) to form an alloy coating layer of about 20 μm.

(Example 5) The alloy of Example 1 was atomized into powder. The average particle size was 20 μm. The alloy particles of the present invention are used as a positive electrode container material of a sodium-sulfur secondary battery in a low pressure plasma spraying device (cylindrical shape 6).
4 mm, inner diameter 61 mm, wall thickness 1.6 mm) was sprayed on the inside of a corrosion resistant cobalt-based alloy container to form an alloy coating layer of about 20 μm. (Example 6) The alloy of Example 1 was atomized into powder. The average particle size was 20 μm. Cylindrical shape used as positive electrode container material of sodium-sulfur secondary battery (outer shape 64 m
An alloy-containing layer was formed by a mechanical method on the inside of an aluminum substrate having an m, an inner diameter of 61 mm, and a wall thickness of 1.6 mm. Chromium 29 with a polyvinyl alcohol solution added to the surface of the cored bar
Alloy powders of weight percent, aluminum 6 weight percent, yttrium 1 weight percent and residual cobalt were spray applied. Then, after dehumidification and heat treatment for debinding agent,
The inner surface of the cylindrical aluminum substrate was placed in contact with the alloy powder, and die forging was performed at a temperature of 200 ° C. to form the alloy-containing layer on the inner surface of the cylindrical aluminum substrate.
The alloy-containing layer has a thickness of 15 μm. For comparison, a cylindrical aluminum substrate was also prepared.

Example 7 With respect to the samples of Examples 4, 5 and 6, molten sodium polysulfide (Na ₂ S ₄ ) was put in a container and the corrosion resistance and the conductivity were investigated. The test condition is 350
It was immersed for 2000 hours at a temperature of ° C. Table 1 shows the results.

[0042]

[Table 1]

It can be seen from Table 1 that the positive electrode container of the present invention has a smaller decrease in conductivity when immersed in sodium polysulfide than an aluminum substrate alone. Further, as shown in Examples 1 to 3, the corrosion of the alloy material after the immersion test is small and it is excellent as a positive electrode container for a sodium-sulfur secondary battery.

Example 8 An alloy-containing layer was formed on one surface of an aluminum base material in the same manner as in Example 4. First, chromium 2 with an aqueous polyvinyl alcohol solution added as a binder
Alloy powders of 9 weight percent, 6 weight percent aluminum, 1 weight percent yttrium, and residual cobalt were uniformly applied. Then, after the dehumidification, the heat treatment of the debinding agent and the baking, the alloy containing layer was formed on the surface of the aluminum base material by pressing with a hydraulic hammer and warm rolling. The thickness of the alloy-containing layer is 10 μm, 20 μm, 100
μm, 300 μm, and 500 μm.

Example 9 In Example 8, the pressure bonding state of the alloy powder containing layer on the surface of the aluminum substrate was observed.
When the alloy powder containing layer was 300 μm or less, the pressure-bonding property to the aluminum substrate was good, and there was no poor adhesion between the particles and the substrate material, which was sound. On the other hand, when the alloy powder containing layer is 500 μm or more, poor adhesion locally occurs.

(Example 10) In Example 8, a peeling test was performed on the alloy powder-containing layer on the surface of the aluminum substrate.
The peeling test was performed by applying tensile stress to the interface between the aluminum substrate and the alloy powder layer.

When the alloy powder layer was 300 μm or less, the adhesiveness to the aluminum substrate was good and the alloy powder was fractured. On the other hand, when the alloy powder layer was 500 μm or more, the forming layer was partly peeled and broken.

(Embodiment 11) One of the embodiments of the sodium-sulfur secondary battery of the present invention is shown in FIG. A rare earth element-added cobalt-based alloy particle-containing layer 8 which is a corrosion-resistant conductive material was formed on the inner surface of the aluminum alloy pipe 7 forming the positive electrode container by a mechanical method. Carbon is not mixed as an additional element. As a specific method for forming the alloy particle-containing layer 8, at least a part of the particles is embedded in the aluminum alloy by using mechanical force (hammer hammering, pressing, rolling, etc.). Further, in order to strengthen the bonding force at the bonding interface between the alloy particles and the aluminum alloy substrate, the temperature is raised in a vacuum or a reducing atmosphere and kept for a certain period of time. The temperature is 500 to 550 ° C., and the holding time is about 20 minutes. When the temperature is low and the holding time is short, the processing strain at the joint interface between the alloy particles and the aluminum alloy substrate is not released, the compound phase is not formed at the interface, and the joint strength is too weak. During battery operation, sodium polysulfide generated by the battery reaction is highly corrosive, and forms aluminum sulfide which is insulative with aluminum. If the strength and adhesion of the joint interface between the alloy particles and the aluminum alloy substrate are insufficient, insulative aluminum sulfide is generated at the interface and the current collecting resistance increases. When the heat treatment temperature is high and the holding time is long,
The compound phase (Al-Co, Al-Cr) is formed thick,
The strength decreases.

(Embodiment 12) Part of a specific manufacturing method will be described with reference to FIG. The aluminum alloy plate 11 is rolled with a cold rolling roll to a thickness of 2 mm. The alloy particles described in Example 3 having a normal distribution particle size having a peak at 20 μm are uniformly adhered to a roll 9 coated with an adhesive, which is transferred onto a rolled aluminum alloy plate, and pressed by a roll. At the same time, the alloy particles were embedded in an aluminum alloy plate while being rolled to 1.6 mm. The temperature of the aluminum alloy plate at this time is 200 ° C. At this time, the thickness of the particle layer was 15 μm. This plate in a vacuum heat treatment furnace,
Heat treatment was performed at 500 to 550 ° C. for 20 minutes in a vacuum of 10 ⁵ torr or less. The coverage by projection of the alloy particles from the upper surface was 71%. This plate was welded with the alloy particle layer inside to form a cylindrical shape. Further, the bottom was welded to obtain a battery. Even when charge and discharge were repeated, the internal resistance of the battery did not change and stable performance was exhibited.

(Embodiment 13) A space is provided in an aluminum or aluminum alloy base plate, and the embodiment 3 is placed in this space.
The alloy particles shown in 1 were vibration-filled. Next, a corrosion-resistant alloy particle layer was formed by a hammer press at a pressure of 0.5 t / cm ² while heating at a temperature of 250 ° C. The aluminum or aluminum alloy base plate has a thickness of 2 mm and a width of 2
50mm, length; 450mm. The gap between the aluminum or aluminum alloy base plates is 1.0 mm. The peak particle size of the alloy particles is 30 μm, and the particle size distribution is almost normal distribution.

Example 14 The coverage of the particles existing on the surface of the corrosion-resistant alloy particle layer obtained in Example 13 with respect to the substrate area was measured by image analysis of a scanning electron micrograph of characteristic X-rays. The coverage was 75%. Further, the thickness of the alloy-containing layer was investigated by observing the cross-sectional structure. The thickness was 200 μm. A layer was formed in which the particles were embedded in the aluminum or aluminum alloy substrate in multiple stages.

(Example 15) The alloy particle composite material obtained in Example 13 was subjected to a peeling test of the alloy particle layer. The peeling test was performed by applying tensile stress to the interface between the aluminum substrate and the alloy particle-containing layer. The bond strength to the aluminum substrate was good, and the aluminum substrate was broken.

(Example 16) The alloy particle composite material obtained in Example 13 was subjected to a peeling test of the alloy particle layer. The peeling test was carried out by using the sample with the alloy particle layer on the outside so that maximum tensile stress was applied to the surface of the alloy particle layer.
Bent to 0 °. It was confirmed that there was no protrusion of particles and that the alloy particle layer was formed soundly.

(Embodiment 17) FIG. 5 is a sectional view of a positive electrode container according to an embodiment of the present invention. Adjust the gap between the core metal 13 and the aluminum or aluminum alloy pipe 7,
The gap is filled with alloy particles by vibration. After heating to 200 ° C., a swaging treatment is performed to push the alloy particles into an aluminum or aluminum alloy pipe. After the core was pulled out from the pipe, it was corrected to a predetermined inner diameter. After forming a tubular structure by bottom welding, vacuum heat treatment was performed at 500 to 550 ° C. for 30 minutes. The thickness of the layer in which the alloy particles were embedded was 40 μm. Using this bag tube, a sodium-sulfur secondary battery was prepared. The current collection resistance on the positive electrode side of the battery is sufficiently small, and does not lead to a decrease in battery performance. No increase in internal resistance of the battery or decrease in battery capacity was confirmed even after repeated charging and discharging several hundred times.

(Embodiment 18) Based on the amount of corrosion in Embodiments 1 and 2, the positive electrode container material which has been conventionally used is used.
Figure 6 shows the rate of decrease in battery capacity per year. Temperature is 30
It is 0,350,400 degreeC. The surface area inside the positive electrode container of the battery is 600 cm ² , and the corrosion is shown as a width to the power of 1/2 or in proportion to time. Conventional materials have high temperatures (4
At 00 ° C), the battery capacity reduction rate exceeds 1%, and as described for the purpose of the present invention, the present sodium-sulfur secondary battery cannot be used for high load applications. However, with the material of the present invention,
Even at an operating temperature of 400 ° C, the rate of decrease in battery capacity per year is expected to be 0.1% or less.

[0056]

According to the present invention, a sodium-sulfur secondary battery having excellent corrosion resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the overall structure of a sodium-sulfur secondary battery according to one embodiment of the present invention.

FIG. 2 is a sectional view of a positive electrode container according to one embodiment of the present invention.

FIG. 3 is a sectional view of a positive electrode container that is an embodiment of the present invention.

FIG. 4 is a manufacturing process of a corrosion resistant material according to an embodiment of the present invention.

FIG. 5 is a manufacturing process of a corrosion resistant container which is an embodiment of the present invention.

FIG. 6 is an estimation of capacity reduction rate of a battery using the material of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte, 2 ... Positive electrode container, 3 ... Negative electrode container, 4 ... Insulating ring, 5 ... Molten sodium polysulfide, 6 ... Molten sodium metal, 7 ... Aluminum alloy pipe, 8 ... Rare earth element added cobalt-based alloy, 9 ... Roll, 10 ... Corrosion resistant alloy particles, 11 ... Aluminum or aluminum alloy plate, 12 ... Vacuum heat treatment furnace, 13 ... Core metal.

Claims (14)

[Claims] 1. A sodium and a sulfur component are arranged via a solid electrolyte, and the sodium is stored in a negative electrode container,
The sulfur component is a sodium-sulfur secondary battery housed in a positive electrode container, characterized in that at least a part of an inner surface of the positive electrode container is covered with a cobalt-based alloy to which a rare earth element other than niobium is added. A sodium-sulfur secondary battery. 2. The rare earth element is at least one of yttrium and lanthanum.
The sodium-sulfur secondary battery described in 1. 3. The composition of the cobalt-based alloy is chromium 27-31.
%, Aluminum 4-7%, yttrium 0.5-1.5
%, Residual cobalt, sodium-sulfur secondary battery according to claim 1, characterized in that. 4. A sodium and a sulfur component are arranged via a solid electrolyte, and the sodium is stored in a negative electrode container,
In the sodium-sulfur secondary battery in which the sulfur component is housed in a positive electrode container and operated at a temperature of 400 ° C. or lower, at least a part of the inside of the positive electrode container is covered with a cobalt-based alloy or an iron-based alloy to which a rare earth is added. A sodium-sulfur secondary battery, characterized in that the battery capacity reduction rate of the battery is 5% / year or less. 5. A sodium and a sulfur component are arranged via a solid electrolyte, and the sodium is stored in a negative electrode container,
In the sodium-sulfur secondary battery in which the sulfur component is housed in a positive electrode container and operated at a temperature of 400 ° C. or lower, at least a part of the inside of the positive electrode container is covered with a cobalt-based alloy to which a rare earth is added, A sodium-sulfur battery characterized by a reduction rate of 3% / year or less. 6. The sodium-sulfur secondary battery according to claim 5, wherein the added rare earth element is yttrium or lanthanum. 7. The alloy composition according to claim 5, wherein the alloy composition covering at least a part of the inside of the positive electrode container is chromium 27 to 31%, aluminum 4 to 7%, yttrium 0.5 to 1.5%, and residual cobalt. A sodium-sulfur secondary battery characterized by: 8. The sodium composition according to claim 5, wherein the alloy composition inside the positive electrode container is chromium 20 to 25%, nickel 18 to 23%, lanthanum 0.05 to 0.15%, and residual cobalt. Sulfur secondary battery. 9. A sodium and a sulfur component are arranged via a solid electrolyte, and the sodium is stored in a negative electrode container,
In the sodium-sulfur secondary battery in which the sulfur component is housed in a positive electrode container and operated at a temperature of 400 ° C. or lower, at least a part of the inner surface of the positive electrode container has at least one of cobalt-based alloy particles or iron-based alloy particles. A sodium-sulfur secondary battery having a layer formed by burying seeds. 10. A sodium-sulfur component is disposed via a solid electrolyte, the sodium is stored in a negative electrode container, the sulfur component is stored in a positive electrode container, and the sodium is operated at a temperature of 400 ° C. or lower. In the sulfur battery, at least a part of the inner surface of the positive electrode container is formed of layered cobalt-based alloy particles or iron-based alloy particles, a sodium-sulfur secondary battery. 11. The sodium-sulfur battery according to claim 7, wherein the layered cobalt-based alloy particles or iron-based alloy particles have a thickness of 30 to 1500 μm. 12. A sodium-sulfur component is disposed via a solid electrolyte, the sodium is stored in a negative electrode container, the sulfur component is stored in a positive electrode container, and the sodium component is operated at a temperature of 400 ° C. or lower. In the sulfur secondary battery,
The positive electrode container is made of aluminum or an aluminum alloy or a highly corrosion-resistant alloy thin plate, and at least a part of the inside of the positive electrode container is covered with a cobalt-based alloy to which a rare earth is added,
A sodium-sulfur secondary battery having a battery capacity reduction rate of 5% / year or less. 13. A sodium-sulfur component is disposed via a solid electrolyte, the sodium is stored in a negative electrode container, the sulfur component is stored in a positive electrode container, and the sodium is operated at a temperature of 400 ° C. or lower. In the sulfur secondary battery,
At least a part of an inner surface of the positive electrode container is covered with a cobalt-based alloy to which a rare earth is added, and a layer formed by a reaction between the positive electrode container and the cobalt-based alloy to which the rare earth is added is present. And a sodium-sulfur secondary battery. 14. A method for producing a sodium-sulfur secondary battery in which sodium and a sulfur component are arranged via a solid electrolyte, the sodium is contained in a negative electrode container, and the sulfur component is contained in a positive electrode container. A method for manufacturing a sodium-sulfur secondary battery, characterized in that at least a part of the inside of the positive electrode container is spray-coated with a cobalt-based alloy to cover it.