JPH08171931A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE: To minimize direct reaction between sodium and sulfur in the case of damage of a solid electrolyte tube so as to improve its safety. CONSTITUTION: A safe tube 6A which has an exit 6B of negative electrode activated substance in bottom surface, contains sodium 8 as the negative electrode activated substance in its inside, and positions a spherical body 6D surrounded by metal of low melting point or metal alloy of low melting point in star-shaped, pyramid-shaped or radially in the vicinity of the exit 6B of the negative activated substance is inserted into a negative electrode chamber in a solid electrolyte tube 1. Further, textile fabric or non-textile fabric of metal fiber 7 is inserted between outer periphery surface of the safe tube 6A and inner periphery of the solid electrolyte tube 1, and also upper end of this safe tube 6A is connected to a negative electrode terminal 5. Therefore, in the case of damage of the solid electrolyte tube, the exit of negative electrode activated substance can be closed by the spherical body so that direct reaction between sodium and sulfur can be minimized thereby to improve safety of the battery.

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, and more particularly to a structure capable of minimizing the direct reaction between sodium and sulfur when the solid electrolyte tube is broken and improving its safety. Is.

[0002]

2. Description of the Related Art A sodium-sulfur battery in which a cathode chamber is formed inside a sodium ion conductive solid electrolyte tube and an anode chamber is formed outside is formed by a cathode lid and a cathode terminal welded to the cathode lid. Is sealed, and the anode chamber is sealed by an anode lid and a battery case welded to the anode lid. Sodium as the cathode active material is filled in the cathode chamber, and the anode active material is placed in the anode chamber. Sulfur is stored as.

In such a sodium-sulfur battery, metal fibers are filled in the cathode chamber, the molten sodium as a cathode active material is retained by the metal fibers, and the molten sodium is evenly distributed on the inner peripheral surface of the solid electrolyte tube. I try to make contact.

Further, in the above-mentioned sodium-sulfur battery, when the molten sodium as the cathode active material and the molten sulfur as the anode active material directly react due to the breakage of the solid electrolyte tube, the heat of the reaction breaks the solid electrolyte tube. Various safety measures have been taken to prevent the expansion of the direct reaction area and the area of the direct reaction.

For example, in Japanese Unexamined Patent Publication No. 5-198314, a cathode active material container is arranged in a cathode chamber to limit the amount of molten sodium as a cathode active material supplied to the inner surface of a solid electrolyte tube. It is described that the amount of instantaneous reaction between sodium and sulfur when a pipe is broken is minimized.

Further, in JP-A-6-208854, a safety tube having a large coefficient of thermal expansion is provided inside the solid electrolyte tube, and the clearance between the safety tube and the solid electrolyte tube is 0.01 mm to 0.1 mm. As described above, the safety tube thermally expands due to the heat of the direct reaction between sodium and sulfur when the solid electrolyte tube breaks, thereby closing the gap between the safety tube and the solid electrolyte tube. Has been done.

Further, in JP-A-59-23475, an insert body containing an alkali metal having an outlet is arranged in a solid electrolyte tube, and a meltable alloy is arranged inside the insert body, and It is described that a material for increasing the melting point of the alloy is arranged at the outlet.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the method described in Japanese Patent Publication No. 198314, the direct reaction between sodium and sulfur can be suppressed to a minimum,
There was a problem that it could not be cut off completely.

The above-mentioned Japanese Patent Laid-Open No. 6-208854.
In the one described in the publication, the direct reaction between sodium and sulfur can be temporarily blocked by the difference in the coefficient of thermal expansion between the safety tube and the solid electrolyte tube, but once the direct reaction between sodium and sulfur is blocked. When the sodium-sulfur battery is cooled to the operating temperature, the direct reaction between sodium and sulfur may be initiated again, and it is difficult to form a gap between the safety tube and the solid electrolyte tube. there were.

Further, the above-mentioned Japanese Patent Laid-Open No. 59-2347.
In the one described in Japanese Patent Publication No. 5, the material that raises the melting point of the alloy provided at the outlet is melted by the molten alloy, and the melting point raises the melting point of the alloy and solidifies it to block the outlet. Since it takes a long time to recover, there is a problem that the direct reaction between sodium and sulfur cannot be blocked early.

[0011]

In order to solve the above problems, the present invention relates to a sodium ion conductive solid electrolyte tube having an opening to which an α-alumina ring is bonded, the cathode chamber being inside and the anode chamber being outside. And sealing the cathode chamber with a cathode lid joined to one surface of the α-alumina ring and a cathode terminal welded to the cathode lid, and on one surface or the other surface of the α-alumina ring. In a sodium-sulfur battery in which the positive electrode chamber is sealed with a joined positive electrode lid and a battery case welded to the positive electrode lid, a safety tube having a negative electrode active material outlet on the bottom surface and containing the negative electrode active material therein is provided. While inserting into the cathode chamber and connecting the upper end to the cathode terminal,
Disposing a woven or non-woven metal fiber between the outer peripheral surface of the safety tube and the inner peripheral surface of the solid electrolyte tube, and star-shaped by a low melting point metal or low melting point metal alloy in the vicinity of the cathode active material outlet, It is characterized by locating spherical bodies that are pyramidal, conical, or radially encapsulated.

[0012]

According to the present invention, a star-shaped member made of a low melting point metal or a low melting point metal alloy is provided in the vicinity of the cathode active material outlet of the safety tube.
By positioning the pyramidal, conical, and radially encapsulated spheres, they were star-shaped, pyramidal, conical, and radially encapsulated by a low-melting point metal or a low-melting point metal alloy at the operating temperature of a sodium-sulfur battery. A sphere forms a gap at the cathode active material outlet, so that sodium can be supplied to the cathode chamber from the cathode active material outlet.

Further, according to the present invention, when the solid electrolyte tube is damaged for some reason, the sulfur as the anode active material directly reacts with sodium in the gap between the safety tube and the solid electrolyte tube, and the reaction heat When the temperature inside the battery rises above 400 ° C, the low melting point metal or low melting point metal alloy that is star-shaped, pyramid-shaped, conical-shaped, or radially melts to expose the sphere, and the cathode on the bottom of the safety tube is exposed. Since the active material outlet is closed, the supply of sodium can be stopped.

[0014]

EXAMPLE FIG. 1 is a sectional view of a sodium-sulfur battery according to an example of the present invention.

The characteristics of the sodium-sulfur battery of the present invention are as follows:
The α-alumina ring 2 is glass-soldered to the opening of the solid electrolyte tube 1, and the upper surface of the α-alumina ring 2 is heated with a cathode lid 3 via aluminum, and the lower surface is heated with an anode lid 4 via aluminum. Along with being pressure-bonded, a cathode terminal 5 is welded to the cathode cover 3, and a low melting point metal or low melting point metal alloy 6C is formed inside the cathode terminal 5 in a star shape, a pyramid shape, a conical shape, or a radial shape. A safety tube 6A having an encapsulated sphere 6D is welded by passing through a cathode pipe 6 welded downward, and the safety tube 6A has a cathode active material outlet 6B on its bottom surface and its outer peripheral surface and a solid electrolyte tube. 1 is a metal fiber 7 arranged in a gap between the inner peripheral surface of the No. 1 and the inside of the safety pipe 6A is exhausted from the cathode pipe 6 under a temperature of about 150 ° C., and sodium 8 melted at the same temperature is then discharged. Vacuum fill, then The upper end of the cathode pipe 6 is sealed to form a cathode chamber constituting body, and this cathode chamber constituting body is inserted into a battery case 9 in which a cylindrical sulfur molded body 10 is inserted, and its upper end is connected to the anode lid 4. It is made by vacuum welding.

The safety pipe 6A is selected from stainless steel, nickel, tungsten, molybdenum or a metal thereof which has a low electric resistance, does not melt due to the reaction heat during the direct reaction of sodium and sulfur, and is resistant to sodium polysulfide. Preferably, it is an alloy of the specified metals.

Further, the cathode active material outlet 6B provided on the bottom surface of the safety tube 6A has a star shape as shown in FIG. 2 (a) by a low melting point metal or a low melting point metal alloy 6C in the vicinity thereof. The pyramidal shape as shown in (b), the conical shape as shown in FIG. 2 (c), and the radially encapsulated sphere 6D as shown in FIG. It is formed in a funnel shape toward the cathode active material outlet 6B, and it is possible to supply sodium 8 which is capable of uniformly discharging the sodium-sulfur battery. The diameter is preferably 0.5 to 2.0 mm so that the direct reaction with sulfur can be suppressed as much as possible.

The low melting point metal or low melting point metal alloy 6C has a melting sodium resistance and a melting point of 4C.
The temperature is preferably from 0 to 450 ° C., and a metal such as aluminum or zinc or an alloy such as an aluminum-magnesium alloy, an aluminum-silicon alloy, or an aluminum-zinc alloy is preferable.

The sphere 6D which is star-shaped, pyramidal-shaped, conical-shaped, or radially encapsulated by the low-melting-point metal or the low-melting-point metal alloy 6C is not melted by the reaction heat during the direct reaction between sodium and sulfur. , Stainless steel or ceramics having resistance to molten sodium and sodium polysulfide, and those having a diameter of about 3 to 12 mm are preferable.

The metal fibers 7 are made of stainless woven cloth or non-woven cloth, and are formed on the outer peripheral surface of the safety tube 6A by pasting or the like. The outer peripheral surface of the safety tube 6A and the inner peripheral surface of the solid electrolyte tube 1 are 0.2-1.5m formed between
It is designed such that it is filled in a gap of about m.

When the sodium-sulfur battery having such a structure is heated to about 350 ° C., which is the operating temperature of the battery, the woven or non-woven fabric of the metal fibers 7 in the gap between the safety tube 6A and the solid electrolyte tube 1 is produced. Is a safety tube 6 due to the capillary phenomenon.
Sodium 8 filled in A is sucked up from the cathode active material outlet 6B on the bottom surface of the safety tube, and sodium is uniformly supplied to the inner peripheral surface of the solid electrolyte tube to uniformly charge and discharge the entire inner peripheral surface of the solid electrolyte. Therefore, the internal resistance of the battery can be reduced, and the charge / discharge efficiency can be improved.

In the sodium-sulfur battery described above, even if sodium 8 and sulfur directly react with each other when the solid electrolyte tube 1 is damaged, the cathode active material outlet 6 on the bottom surface of the safety tube 6A can be used.
When the amount of sodium supplied from B is limited, and the heat generated by the direct reaction between sodium and sulfur is quickly transferred to the sphere 6D along the safety pipe 6A, and the surface temperature becomes 400 ° C or more, the sphere The low melting point metal or low melting point metal alloy 6C enclosing 6D in a star shape, a pyramid shape, a conical shape, or a radial shape is melted, and the sphere 6D descends by its own weight to the cathode active material outlet 6B on the bottom surface of the safety tube 6A. Then exit 6B
The direct reaction between sodium and sulfur can be minimized since it is blocked.

Next, as the above-mentioned battery of the present invention, a cathode active material outlet 6B having a diameter of 1.0 mm is provided on the bottom surface, and zinc-3% aluminum as a low melting point metal alloy 6C is provided inside the battery as shown in FIG. 2 (d). Radially encapsulated like 10.0m in diameter
A safety tube 6A having m spherical spheres 6D made of stainless steel is inserted into the solid electrolyte tube 1 so that there is a 1 mm gap between the outer circumferential surface of the safety tube 6A and the inner circumferential surface of the solid electrolyte tube 1. A woven fabric of metal fibers having a thickness of 0.8 mm is inserted into this gap, and as a conventional battery, only metal fibers are arranged in the cathode chamber of the solid electrolyte tube 1 and the safety tube 6A is not inserted. Were manufactured and their discharge characteristics were examined at 350 ° C., and the results shown in Table 1 were obtained.

[0024]

[Table 1]

It can be seen from Table 1 that the battery of the present invention can obtain a capacity of 40 Ah or more at any discharge rate.

Next, regarding the above-described battery of the present invention and the conventional battery, a charging current was applied until the solid electrolyte tube 1 was damaged, and the temperature change of each battery after the damage was investigated. As shown in FIG. Results were obtained.

From FIG. 3, in the battery of the present invention, even if the solid electrolyte tube is damaged, the cathode active material outlet 6 provided on the bottom surface of the safety tube 6A.
It was found that no extreme temperature rise was observed because B was blocked.

[0028]

As described above, according to the sodium-sulfur battery of the present invention, when the solid electrolyte tube 1 is broken, the cathode active material outlet 6B provided on the bottom surface of the safety tube 6A is closed so that sodium and sulfur can be removed. Since the direct reaction with the can be minimized, its safety can be improved, and by providing a woven or non-woven fabric of metal fibers on the inner peripheral surface of the solid electrolyte tube and the outer peripheral surface of the safety tube, The discharge performance of the sodium-sulfur battery can be improved.

Further, the sodium-sulfur battery of the present invention is
A low melting point metal or low melting point metal alloy 6C can be easily formed inside the safety tube 6A when the battery is assembled into a star shape, a pyramid shape, a conical shape,
It is possible to arrange the spheres 6D that are radially encapsulated, and since the spheres 6D are encapsulated in a star shape, a pyramidal shape, a conical shape, and a radial shape, it is possible to smoothly supply sodium during the operation of the battery. it can.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a sodium-sulfur battery of the present invention.

FIG. 2 is a perspective view of a sphere encapsulated with a low melting point metal or a low melting point metal alloy used in the sodium-sulfur battery of the present invention.

FIG. 3 is a diagram comparing the temperature changes of the battery of the present invention and the conventional battery when the solid electrolyte tube is broken.

[Explanation of symbols]

 1 Solid Electrolyte Tube 2 α-Alumina Ring 3 Cathode Lid 4 Anode Lid 5 Cathode Terminal 6 Cathode Pipe 6A Safety Tube 6B Cathode Active Material Outlet 6C Low Melting Point Metal or Low Melting Point Metal Alloy 6D Sphere 7 Metal Fiber 8 Sodium 9 Battery Case 10 Sulfur Molded body

Claims (3)

[Claims] 1. A cathode chamber is formed inside a sodium ion conductive solid electrolyte tube having an α-alumina ring joined to its opening, and an anode chamber is formed outside the same, and is joined to one surface of the α-alumina ring. While sealing the cathode chamber with the cathode lid and the cathode terminal welded to the cathode lid, the anode lid joined to one surface or the other surface of the α-alumina ring and the battery case welded to the anode lid In a sodium-sulfur battery in which the anode chamber is sealed, a bottom surface has a cathode active material outlet, and a safety tube containing the cathode active material inside is inserted into the cathode chamber and the upper end is connected to the cathode terminal. ,
Disposing a woven or non-woven metal fiber between the outer peripheral surface of the safety tube and the inner peripheral surface of the solid electrolyte tube, and star-shaped by a low melting point metal or low melting point metal alloy in the vicinity of the cathode active material outlet, A sodium-sulfur battery characterized in that spheres that are pyramidal, conical, and radially encapsulated are positioned. 2. The sodium-sulfur battery according to claim 1, wherein the sphere is made of stainless steel, ceramics or the like having resistance to molten sodium or sodium polysulfide. 3. The sodium-sulfur battery according to claim 1, wherein the low melting point metal or the low melting point metal alloy has a melting point of 40.
A sodium-sulfur battery comprising a metal at 0 ° C. to 450 ° C. or an alloy mainly containing these metals.