JPH1064580A - Sodium-sulfur battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sodium-sulfur battery which can stop the feeding of sodium to a solid electrolyte pipe rapidly when the battery is made at an abnormal high temperature, and can manufacture a member necessary for the above purpose, having little unevenness of the form and at a low cost. SOLUTION: This battery is composed by housing a sulphur S in a positive electrode chamber R2; providing a cylindrical partition 8 with bottom inside a solid electrolyte pipe 4 to be a negative electrode chamber R1, at a prescribed interval between the solid electrolyte pipe 4; and a sodium container 5 housing a sodium Na at the inside of the partition 8, at a prescribed interval between the partition 8. To the outer periphery of the upper end (the opening) of the partition 8, a ring form member 9 comprising a material with the thermal expansion coefficient smaller than that of the sodium container 5 is fitted, so as to block a gap g between the upper part of the partition 8 and the sodium container 5, when the battery is made at an abnormal high temperature, and the feeding of the sodium Na to the solid electrolyte pipe 4 is to be stopped.

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 suitably used as a secondary battery for storing electric power.

[0002]

2. Description of the Related Art A sodium-sulfur battery has molten metal sodium as a cathode active material on one side and molten sulfur as an anode active material on the other side, and both have selective permeability to sodium ions. This is a high-temperature secondary battery that is operated at 290 to 350 ° C. isolated by a β-alumina solid electrolyte.

As an example of such a sodium-sulfur battery, Japanese Patent Application Laid-Open No. 2-112168 describes a battery having a structure as shown in FIG. In the drawing, reference numeral 4 denotes a bottomed cylindrical solid electrolyte tube, which is disposed in the anode container 1 to form an anode chamber R2 outside the solid electrolyte tube 4. The anode chamber R2 contains molten sulfur S impregnated in the anode conductive material 7 made of carbon mat or the like as an anode active material.

On the other hand, a cathode chamber R1 is formed inside the solid electrolyte tube 4, and a sodium container 5 containing molten metal sodium Na as a cathode active material is arranged. The anode container 1 and the solid electrolyte tube 4 are connected via an insulating ring 2, and a cathode lid 3 is joined to an upper end surface of the insulating ring 2. An inert gas G such as nitrogen gas or argon gas is sealed at a predetermined pressure in the upper space of the sodium container 5.
The internal sodium Na is pressurized in a direction of flowing out of a small hole 6 provided at the bottom of the sodium container 5.

A solid electrolyte tube 4 and a sodium container 5
A bottomed cylindrical partition (safety tube) 8 is disposed between the two. The partition 8 is composed of the solid electrolyte tube 4 and the sodium container 5
When the battery is discharged, the sodium Na flowing out of the small hole 6 at the bottom of the sodium container 5 first moves upward in the gap between the sodium container 5 and the partition 8, and After moving over the upper edge, it moves downward in the gap between the solid electrolyte tube 4 and the partition 8 and stays in this gap.

Here, sodium Na releases electrons to become sodium ions, passes through the solid electrolyte tube 4, moves to the anode chamber R2, and reacts with sulfur S in the anode chamber R2 and electrons that have passed through the external circuit. Generates sodium polysulfide and generates voltage. At the time of charging, a reaction of forming sodium Na and sulfur S occurs in reverse to the discharging.

As described above, by disposing the partition wall 8 between the solid electrolyte tube 4 and the sodium container 5, the distance from the small hole 6 at the bottom of the sodium container 5 to the solid electrolyte tube 4 is increased, and Since the sodium pressure on the surface of the tube 4 can be reduced and the amount of sodium staying inside the solid electrolyte tube 4 can be reduced, when the solid electrolyte tube 4 is cracked due to deterioration or thermal stress, for example, The sodium Na in the cathode chamber R1 and the sulfur S in the anode chamber R2 react in large quantities and suddenly to generate abnormally high heat,
The situation where the whole battery is destroyed can be prevented.

However, in the sodium-sulfur battery having such a structure, the space between the solid electrolyte tube 4 and the partition 8 is
Since the predetermined gap is always formed, even when the solid electrolyte tube 4 is broken, the supply of sodium Na is continued, and the direct reaction between sodium Na and sulfur S can be suppressed. Therefore, sufficient security cannot be secured.

Accordingly, the applicant of the present application has first set the gap between the solid electrolyte tube and the partition wall to a predetermined value at the battery operating temperature and closed at an abnormally high temperature of the battery. A sodium-sulfur battery provided with a partition having a large coefficient of thermal expansion has been proposed (JP-A-6-208854).
issue). In this battery, when the battery becomes abnormally high temperature due to breakage of the solid electrolyte tube, the gap between the solid electrolyte tube and the partition wall becomes
Since the blockage is caused by the difference in thermal expansion between the two and the subsequent supply of sodium to the gap is stopped, the direct reaction between sodium and sulfur can be promptly converged and suppressed.

[0010]

In the sodium-sulfur battery described in Japanese Patent Application Laid-Open No. 6-208854, the supply of sodium at an abnormally high temperature of the battery can be reliably stopped. It is necessary to precisely control the gap between them. However, since the solid electrolyte tube is formed of β-alumina, which is a kind of ceramics, and the shape tends to vary, it is difficult to control the gap between the solid electrolyte tube and the partition wall to a predetermined value. There was a problem that the cost of the battery also became expensive.

The present invention has been made in view of such circumstances, and when the battery temperature becomes abnormally high, the supply of sodium to the solid electrolyte tube can be stopped promptly, and necessary for that purpose. There is little variation in the shape of the
It is an object to provide a sodium-sulfur battery that can be manufactured at lower cost.

[0012]

According to the present invention, a cathode chamber and an anode chamber are formed inside and outside a bottomed solid electrolyte tube, and sulfur is contained in the anode chamber to form a cathode chamber. On the inside of the solid electrolyte tube, a bottomed cylindrical partition is arranged with a predetermined gap between the bottom and the solid electrolyte tube, and further inside the partition,
In a sodium-sulfur battery in which a sodium container accommodating sodium is disposed with a predetermined gap between the sodium container and the partition wall, a material having a smaller thermal expansion coefficient than the sodium container is provided on the outer peripheral portion of the upper end (opening end) of the partition wall. Sodium-sulfur, characterized by closing the gap between the upper part of the partition and the sodium container at abnormally high temperature of the battery to stop the supply of sodium to the solid electrolyte tube. A battery is provided. In the present invention, the abnormally high temperature of the battery refers to a high temperature exceeding the operating temperature (290 to 350 ° C.) of the battery, for example, a temperature of 370 ° C. or higher.

[0013]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged view of a main part thereof, (a) shows a state at the time of operating temperature of a battery, and (b) shows an abnormal state. The state at the time of high temperature is shown. In the figure, reference numeral 4 denotes a bottomed solid electrolyte tube having a function of selectively transmitting sodium ions. This solid electrolyte tube 4 is disposed in the anode container 1, whereby an anode chamber R 2 is formed outside the solid electrolyte tube 4. The anode chamber R2 contains molten sulfur S impregnated in the anode conductive material 7 made of carbon mat or the like as an anode active material. The solid electrolyte tube 4 is made of β-alumina or β ″-
The anode container 1 is made of aluminum, stainless steel or the like.

On the other hand, inside the solid electrolyte tube 4, a cathode chamber R1 is formed, and a bottomed cylindrical partition wall 8 made of a metal material having excellent corrosion resistance to sodium, such as aluminum, aluminum alloy, and stainless steel, is formed as a solid. A closed / bottomed cylindrical sodium container 5 containing a molten metal sodium Na serving as a cathode active material is disposed inside the partition 8 with a predetermined gap between the partition 8 and the electrolyte tube 4. They are arranged with a predetermined gap between them.

The anode container 1 and the solid electrolyte tube 4 are connected via an insulating ring 2, and a cathode lid 3 is joined to an upper end surface of the insulating ring 2. The insulating ring 2 is preferably made of an insulating ceramic because it is necessary to maintain electrical insulation between the anode chamber R2 and the cathode chamber R1, and α-alumina is preferably used in view of strength, cost, and the like. Is done. A small hole 6 is provided at the bottom of the sodium container 5, and an inert gas G such as nitrogen gas or argon gas is sealed at a predetermined pressure in the upper space of the sodium container 5. The sodium Na in the sodium container 5 is pressurized by the active gas G in a direction of flowing out of the small holes 6.

The basic structure of the battery described above is the same as that described in the above-mentioned JP-A-2-112168. However, in the sodium-sulfur battery of the present invention, the characteristic structure of the partition wall 8 is as follows. A ring-shaped member 9 made of a material having a smaller thermal expansion coefficient than that of the sodium container 5 is fitted in the outer peripheral portion of the upper end (open end).

In the battery of the present invention, at the operating temperature of the battery, a gap g having a predetermined value is formed between the partition 8 and the sodium container 5 as shown in FIG. Then, due to the breakage of the solid electrolyte tube 4, sodium Na and sulfur S start a direct reaction, and when the heat of the reaction causes the battery to reach an abnormally high temperature exceeding the operating temperature, as shown in FIG. The gap between the upper part of the partition 8 in which the 9 is fitted and the sodium container 5 is closed.

That is, when a high-temperature sodium polysulfide is produced by a direct reaction between sodium Na and sulfur S,
The sodium container 5 thermally expands according to the heat expansion coefficient of the sodium container material due to the heat generation.
The ring-shaped member 9 made of a material having a smaller thermal expansion coefficient than that of the sodium container 5 suppresses free thermal expansion, and allows only a smaller thermal expansion than the sodium container 5 according to the thermal expansion coefficient of the ring-shaped member 9. Therefore, the gap g between the upper portion of the partition 8 and the sodium container 5 is closed by the difference in thermal expansion between the sodium container 5 and the ring-shaped member 9. Due to the closing of the gap g, the supply of sodium Na to the solid electrolyte tube 4 is cut off, and the subsequent sodium Na and sulfur S
Direct convergence is quickly suppressed.

The ring-shaped member 9 used for suppressing the thermal expansion of the upper part of the partition 8 and closing the gap g with the sodium container 5 is a small member having a simple shape, and the material is not necessarily limited to ceramics. Because it is not
Compared with a member made of β-alumina having a thin and elongated shape such as a solid electrolyte tube, variations in shape are less likely to occur. The manufacturing cost of the whole battery can be lower than that of the structure in which the supply of sodium is stopped by closing the battery.

The ring-shaped member 9 used in the sodium-sulfur battery of the present invention is made of a material having a smaller coefficient of thermal expansion than the sodium container 5. Also, the ring-shaped member 9
It is desirable that both the sodium container 5 and the sodium container 5 be made of a material having excellent corrosion resistance to sodium. From such a viewpoint, examples of preferable combinations of the constituent materials of the ring-shaped member 9 and the sodium container 5 include the following (1) to (3).

(1) The sodium container is made of aluminum or A
Aluminum alloy such as 3003, and the ring-shaped member is α
-Ceramics such as alumina. (2) The sodium container is made of aluminum or aluminum alloy such as A3003, and the ring-shaped member is made of ferritic stainless steel such as SUS430 or martensitic stainless steel such as SUS410. (3) The sodium container is made of austenitic stainless steel such as SUS304, and the ring-shaped member is made of ferritic stainless steel such as SUS430, martensitic stainless steel such as SUS410, or ceramics such as α-alumina.

The following equation shows a calculation example of the gap between the sodium container and the partition in the present invention. In order to close the gap between the sodium container and the upper part of the partition at an abnormally high temperature, the gap at room temperature (at the time of assembling the battery) may be set so that the following equation is satisfied.

[0023]

D ₁ × (1 + α ₁ × (T ₂ −T ₀ )) = D ₂ × (1
+ Α ₂ × (T ₂ −T ₀ )) D ₁ : inner diameter of partition wall D ₂ : outer diameter of sodium container α ₁ : thermal expansion coefficient of ring-shaped member α ₂ : thermal expansion coefficient of sodium container T ₂ : abnormally high temperature T ₀ : room temperature (temperature at the time of assembly)

For example, the sodium container is made of aluminum (coefficient of thermal expansion α ₂ : 24 × 10 ⁻⁶ ), and the ring-shaped member is made of α.
-In the case of using alumina (coefficient of thermal expansion α ₁ : 7.2 × 10 ⁻⁶ ), the inner diameter D ₁ of the partition wall is 35.60 mm, the room temperature T ₀ is 20 ° C., and the abnormal high temperature T ₂ is 420 ° C. When the outer diameter D ₂ of the sodium container is obtained from the above equation,
D ₂ will be 35.36mm. The difference between D ₁ and D ₂ is 0.2
Since it is 4 mm, the gap between the sodium container and the partition at room temperature in this case is 0.12 mm.

[0025]

As described above, in the sodium-sulfur battery of the present invention, a ring-shaped member made of a material having a smaller thermal expansion coefficient than that of the sodium container is provided on the outer peripheral portion of the upper end (opening end) of the partition wall. When the battery is heated to an abnormally high temperature due to the breakage of the solid electrolyte tube, the gap between the upper part of the partition and the sodium container is closed due to the difference in thermal expansion between the sodium container and the ring-shaped member. The supply of sodium to the electrolyte tube is stopped, and the direct reaction between sodium and sulfur can be quickly suppressed. Further, in the present invention, the ring-shaped member used for closing the gap is easier to produce with high shape accuracy than the solid electrolyte tube, and is less likely to vary in shape. It can be manufactured at lower cost than a conventional battery in which the gap is closed. Furthermore, using the ring-shaped member for closing the gap, the gap between the solid electrolyte tube and the partition wall, which is the prior art, was precisely controlled, and the battery became abnormally high due to the breakage of the solid electrolyte tube. At times, the safety can be further improved by combining the closing of the gap between the solid electrolyte tube and the partition wall.

[Brief description of the drawings]

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

FIGS. 2A and 2B are enlarged cross-sectional views of essential parts showing one embodiment of a sodium-sulfur battery according to the present invention, wherein FIG. 2A shows a state at an operating temperature of the battery, and FIG. Show.

FIG. 3 is a sectional view showing an example of a conventional sodium-sulfur battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode container, 2 ... Insulation ring, 3 ... Cathode lid, 4 ... Solid electrolyte tube, 5 ... Sodium container, 6 ... Small hole, 7 ... Conductive material for anode, 8 ... Partition wall, 9 ... Ring-shaped member, R1 ... Cathode room,
R2: anode chamber, Na: sodium, S: sulfur, G: inert gas

Claims (4)

[Claims] A cathode chamber and an anode chamber are formed inside and outside a bottomed solid electrolyte tube, sulfur is contained in the anode chamber, and a bottomed solid electrolyte tube is provided inside the solid electrolyte tube serving as a cathode chamber. A sodium-sulfur having a cylindrical partition wall arranged with a predetermined gap between the solid electrolyte tube and a sodium container containing sodium inside the partition wall with a predetermined gap between the partition wall and the solid electrolyte tube. In the battery, a ring-shaped member made of a material having a smaller thermal expansion coefficient than that of the sodium container is fitted into the outer peripheral portion of the upper end (opening end) of the partition, and the gap between the upper portion of the partition and the sodium container at abnormally high temperature of the battery. A sodium-sulfur battery, wherein the sodium-sulfur battery is closed to stop supplying sodium to the solid electrolyte tube. 2. The sodium-sulfur battery according to claim 1, wherein the sodium container is made of aluminum or an aluminum alloy, and the ring-shaped member is made of ceramic. 3. The sodium-sulfur battery according to claim 1, wherein the sodium container is made of aluminum or an aluminum alloy, and the ring-shaped member is made of ferritic stainless steel or martensitic stainless steel. 4. The sodium-sulfur battery according to claim 1, wherein the sodium container is made of austenitic stainless steel, and the ring-shaped member is made of ferritic stainless steel, martensitic stainless steel or ceramics.