JP2899526B2 - Sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sodium-sulfur battery used as a secondary battery for adjusting a power load, for powering an electric vehicle, and the like.

[0002]

2. Description of the Related Art As shown in Japanese Patent Application Laid-Open No. Hei 5-275109, a sodium-sulfur battery generally has a bottomed cylindrical anode container and a sodium ion disposed inside the anode container. A possible bottomed cylindrical solid electrolyte, a cathode active material composed of metallic sodium contained in the solid electrolyte, and an anode active material composed of sulfur contained between the solid electrolyte and the anode container were provided. It has a configuration.
This type of sodium-sulfur battery performs charging and discharging operations in a state where the battery is heated to 300 to 350 ° C. At the time of discharge, sodium in the cathode chamber and sulfur in the anode chamber are ionized, and the ionized sodium is discharged. It permeates the solid electrolyte and reacts with sulfur to produce sodium polysulfide and discharge, and at the time of charging, the opposite reaction occurs to charge.

[0003] As one type of the sodium-sulfur battery, there is a type in which the anode container is formed of a metal material and the solid electrolyte is formed of a ceramic material. When the heating and cooling of maintaining the heating state of 300 ° C. to 350 ° C. during operation and cooling to the outside air temperature during operation stop are repeatedly performed, the difference between the thermal expansion and thermal contraction of the anode container and the solid electrolyte, Due to the change between the solid phase and the liquid phase of sodium polysulfide formed at the time of discharge, the anode container is gradually elongated in the longitudinal direction, adversely affecting the connection relationship between the anode container and the terminal between the solid electrolyte and A large stress may act on the electrolyte to damage the solid electrolyte.

When the anode container is made of a light metal such as aluminum or aluminum alloy in order to make the anode container lightweight and inexpensive, the thermal expansion and thermal contraction of the anode container is large and the thermal expansion and the solid electrolyte and the solid electrolyte are caused. The difference in heat shrinkage becomes even more pronounced. For this reason, in order to restrict the longitudinal elongation due to the thermal expansion of the anode container to a predetermined amount, means for externally fitting a rigid container made of stainless steel or the like having a smaller thermal expansion coefficient than the anode container to the anode container is used. JP-A-5-10
No. 9433.

Although the sodium-sulfur batteries are used independently of each other, they are usually used in fields requiring a large energy capacity.
As shown in Japanese Patent No. 4355, a single sodium-sulfur battery (hereinafter sometimes referred to as a single battery).
A large unit is accommodated in a large accommodation box to form one unit. In this case, in consideration of the fact that the contained substance leaks from each cell and adversely affects the adjacent cell, means for supporting each cell in a protective container made of ceramic, metal or the like, respectively. Is adopted.

[0006]

When a large number of sodium-sulfur batteries are used as a single unit, the number of cells per unit area is increased to increase the energy density. Is important in practical use. However, when the above-mentioned storage means is adopted, the dedicated area occupied by the protective container occupies a considerable ratio with respect to the dedicated area occupied by the unit cell. Therefore, the energy density corresponds to the exclusive area occupied by the protective container. Becomes smaller.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the use of a protective container which has been conventionally employed when a large number of sodium-sulfur batteries are housed in a housing box as single cells, and the same housing box for single cells is used. The purpose is to increase the number of containers to be accommodated.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a bottomed cylindrical anode vessel made of a light metal material and a bottomed cylindrical ceramic material provided inside the anode vessel and capable of transmitting sodium ions. A solid electrolyte, a cathode active material made of metallic sodium housed in the solid electrolyte, an anode active material made of sulfur housed between the solid electrolyte and the anode container, A sodium-sulfur battery comprising a rigid container having a small coefficient of thermal expansion compared to the same anode container that regulates the longitudinal elongation due to thermal expansion of the anode container to a predetermined amount and performing a charge / discharge operation in a heated state, A coating layer made of a metal material having higher corrosion resistance than the rigid container is provided on at least the inner peripheral surface of the inner and outer peripheral surfaces of the rigid container.

In the sodium-sulfur battery, the anode container is formed of aluminum or an aluminum alloy, the rigid container is formed of stainless steel, and the coating layer is formed of chromium, a chromium alloy, or a cobalt alloy. It is preferable that it is formed.

[0010]

In the sodium-sulfur battery having the above-mentioned structure, at least the inner peripheral surface of the rigid container has extremely high corrosion resistance to the contained substances such as sodium polysulfide contained in the anode container. The rigid container prevents the contained material from leaking from the rigid container to the outside even if the contained material leaks from the outside. For this reason, when storing a large number of such sodium-sulfur batteries in a storage box as unit cells, it is not necessary to use a number of protective containers corresponding to each unit cell as in the prior art, and use of these protective containers is not required. It can be abolished and the cells can be accommodated in the dedicated area occupied by these protective containers. Therefore, the number of cells that can be accommodated in the accommodation box can be increased, and the number of cells that can be accommodated in the accommodation box per unit area can be increased.
The energy density per unit can be significantly improved.

[0011]

【Example】

(Sodium-sulfur battery) Hereinafter, the sodium-sulfur battery according to the present invention will be described with reference to the drawings. FIG. 1 shows a partial longitudinal side view of a sodium-sulfur battery according to one embodiment of the present invention. The sodium-sulfur battery has an anode container 10a, a solid electrolyte 10b, and a rigid container 10c as main components, and a cathode active material 10d and an anode active material 10e as main components. The anode container 10a includes a cylindrical base body 11 and a bottom cover 12 that seals a lower end opening of the base body 11, and the base body 11 and the bottom cover 12 are formed of aluminum or an aluminum alloy. A constricted portion 11a that is bent in the radial direction is formed on an upper portion of the base 11. The constricted portion 11a is easy to thermally deform in the longitudinal direction of the base 11, and functions to absorb and reduce thermal expansion and contraction of the base 11 by being thermally deformed when the anode container 10a is heated and cooled.

The solid electrolyte 10b is a bottomed cylinder having sodium ion permeability, and is made of beta-alumina. The solid electrolyte 10b is disposed concentrically in the anode container 10a in a state of being fitted to an insulating ring 13 made of alpha alumina, and is covered with a lid 14b having a cathode terminal 14a. . Thus, the insulating ring 13 and the lid 14b seal the anode container 10a and the solid electrolyte 10b, configure the inside of the solid electrolyte 10b as a cathode chamber, and configure the space between the anode container 10a and the solid electrolyte 10b as an anode chamber. ing. The base 11 constituting the anode container 10a has an anode terminal (not shown) on its outer periphery.

In the sodium-sulfur battery, a cathode compartment contains a cathode active material 10d, and an anode compartment contains an anode active material 10e. The cathode active material 10d is made of metallic sodium, and is housed in the cathode chamber with metal fibers interposed. The anode active material 10e is made of sulfur, and is accommodated in the anode chamber with graphite felt interposed. In the sodium-sulfur battery, when the battery is heated to 300 to 350 ° C., about 2.08
V indicates an open circuit voltage, and when an external load is connected to the battery, sodium as a cathode active material is ionized in the battery, and sodium ions pass through the solid electrolyte 10b to reach the anode active material 10e, which is the active material 10e. It reacts with sulfur to produce sodium polysulfide and is discharged. In addition, in the sodium-sulfur battery, a reaction opposite to the above occurs at the time of charging, and the battery is charged.

The rigid container 10c comprises a bottomed cylindrical base 15 and
An inward flange 16 is fixed to the upper end of the base 15, and these are formed of stainless steel. Further, on the inner peripheral surface and the outer peripheral surface of the base 15, corrosion-resistant coating layers 15a and 15b are formed. Each of the coating layers 15a and 15b is composed of a sprayed or plated layer of chromium, a chromium-based alloy, a cobalt-based alloy, or the like, and has a thickness of 10 μm or more.
It has a thickness of about 100 μm. Rigid container 10c
Is externally fitted to the anode container 10a with a tubular mica 17 as an insulating member interposed therebetween, and the anode container 10a is housed inside the external container in this externally fitted state. Rigid container 1
0c functions to regulate the longitudinal thermal expansion of the anode container 10a during heating and cooling of the sodium-sulfur battery to a predetermined amount, and has high corrosion resistance due to the formation of the coating layers 15a and 15b. It has. In this embodiment, the coating layer 1 is provided on both inner and outer peripheral surfaces of the rigid container 10c.
Although an example is shown in which 5a and 15b are formed to impart corrosion resistance to both peripheral surfaces, in the sodium-sulfur battery, corrosion resistance is imparted to the inner peripheral surface of the rigid container 10c from the viewpoint of use. It is important that the coating layer 15a is formed only on the inner peripheral surface.
May be formed.

In the sodium-sulfur battery having such a configuration, the thermal expansion in the longitudinal direction of the anode container 10a is regulated to a predetermined amount by the function of the rigid container 10c. Therefore,
In the sodium-sulfur battery, when the operation and the shutdown are repeatedly performed and the anode container 10a thermally expands and contracts, the expansion and contraction of the anode container 10a is absorbed and reduced by the constricted portion 11a of the base 11, and the base is reduced. 11 is regulated to a predetermined amount by the action of the rigid container 10c.

Further, in the sodium-sulfur battery, if the inner peripheral surface of the substrate 11 which is in direct contact with sodium polysulfide generated during discharge is corroded and damaged by sodium polysulfide, it is accommodated in the anode container 10a. There is a danger that the contained substances such as sulfur and sodium polysulfide may leak to the outside,
c prevents further leakage to the outside. Since the rigid container 10c is provided with the corrosion-resistant coating layer 15a particularly on the inner peripheral surface thereof, the rigid container 10c is not corroded and damaged by the leaked containing material, and the rigid container 10c is corroded and damaged. As a result, the contained substance does not leak from the container 10c to the outside.

Therefore, when the sodium-sulfur battery is a unit cell and a large number of the cells are housed in a housing box to form one unit, each unit cell is housed and supported in a ceramic or metal protective container, respectively. It is not at all necessary to prevent adverse effects such as corrosion on adjacent cells due to leakage of the contained material of each cell. For this reason, when accommodating each cell, these protective containers can be omitted and the number of cells accommodated can be increased. That is, in the sodium-sulfur battery, when a large number of the batteries are housed in a housing box to constitute one unit, the number of cells housed per unit area can be increased to increase the energy density.

FIGS. 2 to 4 show the outline of the housing state when the sodium-sulfur battery is housed in the housing box as a single cell. In each of these figures, FIG. 2 shows an accommodation example of the sodium-sulfur battery 10 according to the present embodiment, and FIG.
Shows an example of housing a sodium-sulfur battery 20 housed using a metal protection container, and FIG. 4 shows an example of housing a sodium-sulfur battery 30 housed using a ceramic protection container. . 2 shows the rigid container 10c and the mica 18 from the inside, and FIG. 3 shows the rigid container 20a, the mica 21, and the metal protective container 2
FIG. 4 shows a rigid container 30a, a mica 31 and a ceramic protective container 32.
Is shown. As is apparent from these examples, in the sodium-sulfur battery 10 according to the present embodiment, it is not necessary to use the protective containers corresponding to the protective containers 22 and 32 when the single cells are stored in the storage box. The dedicated area occupied by the protective containers 22 and 32 can be used as a space for accommodating the cells, and the number of cells per unit area can be increased.

(Experiment) Outer diameter 60 mm, height 100 mm,
A rigid container made of stellen lith steel with a thickness of 0.2 mm,
Chrome plating is applied to both inner and outer peripheral surfaces of the rigid container.
A chromium plating layer (a) having a thickness of 0 to 15 μm, and a chromium (70% by weight or more) -iron alloy
A corrosion test using sodium polysulfide was carried out on the chromium-iron alloy sprayed layer (b) having a thickness of の 40 μm. In the corrosion test, about half of the sodium polysulfide taken out of the sodium-sulfur battery was placed in a rigid container and heated to 400 ° C., and this heating state was maintained for 3 months (21 days).
For 60 hours), the leakage of sodium polysulfide in each protective container and the corrosion state of the rigid container were observed. Table 1 shows the obtained results. However, in the column of the results in the same table, the mark ○ indicates that no corrosion holes were found in the protective container and there was no leakage of sodium polysulfide, and the mark × indicates that corrosion holes were found in the protective container and sodium polysulfide was not found. This indicates a state in which leakage of air is recognized.

[0020]

[Table 1]

Referring to the table, a rigid container provided with a corrosion-resistant coating layer on both the inner and outer peripheral surfaces (Experiments NO. 1 to NO. 4)
Does not show corrosion by sodium polysulfide and its leakage, whereas in a rigid container not provided with the coating layer (Experiment Nos. 5 and 6), corrosion by sodium polysulfide was observed, and Leakage of sodium polysulfide due to this corrosion is observed. Therefore, when a large number of sodium-sulfur batteries having the former rigid container are accommodated in the accommodation box as single cells, it is not necessary to consider leakage of sodium polysulfide from the rigid container, and FIGS. Whereas the use of the protective container can be omitted, in the case where a large number of the sodium-sulfur battery provided with the latter rigid container are housed in the housing box as single cells,
Considering the leakage of sodium polysulfide from the rigid container
And the use of a protective container as shown in FIG.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal front view of a sodium-sulfur battery according to one embodiment of the present invention.

FIG. 2 is a partial vertical sectional view showing a state where the sodium-sulfur battery is housed in a housing box as a unit cell.

FIG. 3 is a partial vertical sectional view showing an example of a conventional case in which a sodium-sulfur battery is housed in a housing box as a unit cell.

FIG. 4 is a partial longitudinal sectional view showing another example of a conventional case in which a sodium-sulfur battery is housed in a housing box as a unit cell.

[Explanation of symbols]

10, 20, 30: sodium-sulfur battery, 10a: anode container, 10b: solid electrolyte, 10c: rigid container, 10
d: cathode active material, 10e: anode active material, 11: base, 1
5 ... base, 15a, 15b ... coating layer, 20a, 30a ...
Rigid containers, 22, 32 ... protective containers, 18, 21, 23,
31 ... Mica.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 10/39 H01M 2/02

Claims (2)

(57) [Claims] 1. A bottomed cylindrical anode container made of a light metal material, a solid electrolyte made of a bottomed cylindrical ceramic material disposed inside the anode container and permeable to sodium ions, and the solid electrolyte A cathode active material composed of metallic sodium contained in the anode, an anode active material composed of sulfur contained between the solid electrolyte and the anode container, and a thermal expansion of the anode container caused by externally fitting the anode container. A sodium-sulfur battery comprising a rigid container having a small coefficient of thermal expansion compared to the same anode container that regulates longitudinal elongation to a predetermined amount, and performing a charge / discharge operation in a heated state, the inner and outer peripheral surfaces of the rigid container. A sodium-sulfur battery, wherein a coating layer made of a metal material having higher corrosion resistance than the rigid container is provided on at least the inner peripheral surface of the battery. 2. The sodium-sulfur battery according to claim 1, wherein the anode container is formed of aluminum or an aluminum alloy, the rigid container is formed of stainless steel, and the coating layer is made of chromium or chromium. A sodium-sulfur battery formed of an alloy or a cobalt-based alloy.