JP2000058108A - Sodium-sulfur battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly safe battery by applying an interfering provision reducing the flow of sodium to the upper section of a positive electrode chamber, arranging an object having affinity to liquid sodium at the upper section of a negative electrode chamber, and providing a sodium limiting tube having a structure preventing the rapid inflow of sodium. SOLUTION: A sodium flow limiting ring 14, having a function for preventing the liquid sodium flowing into a positive electrode chamber from being instantaneously brought into contact with sulfur and sodium polysulfide constituting a positive electrode active material, is used. The inner diameter of the sodium flow limiting ring 14 is preferably set equal to the outer diameter of a solid electrolyte tube 1. As the sodium limiting ring 14, for example, a densely packed carbon ring or a ring weakly sintered with alumina powder is preferably used. The sodium flow limiting ring 14 limits the contacting quantity (speed) between the positive electrode active material and the negative electrode active material when the solid electrode electrolyte tube 1 is broken.

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.

[0002]

2. Description of the Related Art In a conventional sodium-sulfur battery, a cathode chamber and an anode chamber are formed inside and outside a bottomed cylindrical solid electrolyte tube, and the cathode chamber contains sodium as a cathode active material. And a sulfur as an anode active material is accommodated in the anode chamber. Then, while being heated to 300 to 350 ° C., sodium in a molten state is supplied from the inside of the cartridge to the gap between the cartridge and the solid electrolyte tube, and sodium is ionized on the cathode-side solid electrolytic chamber tube surface. Discharge is performed by sodium ions permeating the inside of the solid electrolyte tube and reacting with sulfur or sodium polysulfide in the positive electrode chamber.

In this type of sodium-sulfur battery, when the solid electrolyte tube is broken during operation, liquid sodium in the cathode chamber and sulfur in the liquid state in the anode chamber directly react to generate very large heat. In some cases, there is a risk that the cartridge may dissolve and a large amount of liquid sodium and sulfur present inside the cartridge may explosively react to explode the battery.

In order to prevent such an explosive direct reaction between sodium and sulfur, for example, in Japanese Unexamined Patent Publication No. 2-112168, a metal material such as aluminum or stainless steel is provided in a gap between a cartridge and a solid electrolyte tube. A sodium-sulfur battery provided with a bottomed cylindrical safety tube is disclosed. Japanese Patent Application Laid-Open No. 5-54908 discloses a sodium-sulfur battery in which a protective tube is further provided between the safety tube and the solid electrolyte tube.

[0005]

However, the conventional sodium-sulfur battery described above has a problem that the direct reaction between sodium and sulfur in a state close to full charge cannot be sufficiently suppressed.

An object of the present invention is to provide a sodium-sulfur battery with high safety.

[0007]

The objects of the present invention are as follows: (1) To prevent the liquid sodium flowing into the positive electrode chamber from immediately meeting the positive electrode active material, an obstruction measure such as reducing the flow rate of sodium at the upper part of the positive electrode chamber is provided. (2) Arrange a liquid sodium having a high affinity to the upper part of the negative electrode chamber to reduce or prevent the speed of the liquid sodium flowing into the positive electrode chamber side.
(3) This is achieved by providing a sodium restriction tube having a structure that prevents sodium from flowing rapidly.

FIG. 3 shows a structure of a battery using a sodium flow restricting ring 14 having a function of preventing liquid sodium flowing into the positive electrode chamber from immediately contacting sulfur or sodium polysulfide as a positive electrode active material. . The material of the sodium flow restriction ring must be a material that does not react with sulfur or sodium polysulfide. Also, the sodium flow restricting ring needs to be sufficiently weak in comparison with the strength of the solid electrolyte tube so as not to damage the solid electrolyte tube due to the difference in thermal expansion due to the temperature rise and fall of the battery. The sodium flow restriction ring may be located above the top of the carbon in the anode chamber. The inner diameter of the sodium flow restricting ring is preferably the same as the outer diameter of the solid electrolyte tube, and the outer diameter of the sodium flow restricting ring is preferably the same as the inner diameter of the positive electrode container. As the sodium flow restricting ring, for example, a densely packed carbonaceous ring or a ring obtained by weakly sintering alumina powder is preferable. This ring limits the amount (speed) of contact between the positive electrode active material and the negative electrode active material that occurs when the solid electrolyte tube breaks.

[0009] The sodium flow restricting ring and the sodium flow restricting fiber assembly can be used without being adhered or fixed to any place, so that the cost is low. It is suitable for a battery having a structure in which a metal container is provided inside a solid electrolyte tube.

FIG. 4 shows a structure of a battery using a sodium flow restricting mat 15 having a function of preventing liquid sodium flowing into the positive electrode chamber from immediately contacting sulfur or sodium polysulfide as a positive electrode active material. . The material of the sodium flow restriction mat must be a material that does not react with sulfur or sodium polysulfide. Also, the sodium flow restricting mat must be sufficiently weak in comparison with the strength of the solid electrolyte tube so that the solid electrolyte tube is not damaged by the thermal expansion difference due to the temperature rise and fall of the battery. The inner diameter of the sodium flow restriction mat is preferably the same as the outer diameter of the solid electrolyte tube, and the outer diameter of the sodium flow restriction mat is preferably the same as the inner diameter of the positive electrode container. The lower end surface of the sodium flow rate limiting mat may be in contact with the uppermost surface of the positive electrode conductive material carbon 10 or may be apart therefrom, but the gap is preferably as small as possible. As the sodium flow rate limiting mat, for example, a ring woven from stainless steel fiber or aluminum fiber is preferable. This means that a fiber assembly for restricting the flow rate of sodium is disposed in the space inside the anode chamber.

FIG. 5 shows the structure of a battery using a sodium retaining material 16 for preventing liquid sodium accumulated in the upper part of the negative electrode chamber from flowing into the positive electrode chamber quickly. The material of the sodium retaining material must be a material that does not react with sodium. Also, the sodium holding material needs to be sufficiently weaker than the strength of the solid electrolyte tube so as not to damage the solid electrolyte tube due to the difference in thermal expansion due to the temperature rise and fall of the battery. Preferably, the inner diameter of the sodium retaining material is the same as the outer diameter of the safety tube. As the sodium retaining material, for example, a ring woven from stainless steel fiber or aluminum fiber is preferable.

FIG. 6 shows the structure of a battery using a sodium flow rate limiting mat 17 for preventing liquid sodium accumulated in the upper part of the negative electrode chamber from flowing into the positive electrode chamber quickly. The material of the sodium flow restriction mat must be a material that does not react with sodium. Also, the sodium flow restricting mat must be sufficiently weak in comparison with the strength of the solid electrolyte tube so that the solid electrolyte tube is not damaged by the thermal expansion difference due to the temperature rise and fall of the battery. Preferably, the inner diameter of the sodium flow restriction mat is the same as the outer diameter of the safety tube. As the sodium flow rate limiting mat, for example, a ring woven from stainless steel fiber or aluminum fiber is preferable.

FIGS. 7 and 8 show the structure of a battery using a sodium flow restricting plate 18 for preventing liquid sodium accumulated in the upper part of the negative electrode chamber from flowing into the positive electrode chamber quickly. The metal sheet is rolled and inserted between the cartridge and the solid electrolyte tube. If the sodium flow restriction plate is rolled and inserted within the elastic range, the sodium flow restriction plate will come into contact with the inner wall of the solid electrolyte tube due to the restoring force, so it will be between the sodium flow restriction plate and the solid electrolyte tube. It is more preferable from the viewpoint of safety, since the amount of liquid sodium to be reduced is reduced. When the solid electrolyte tube breaks,
Most of the liquid sodium that existed in the upper part of the negative electrode chamber
From the inside of the sodium flow restriction plate, through the overlapping portion of the plate, through the broken portion of the solid electrolyte tube, and into the cathode chamber, the inflow speed is much slower than when the sodium flow restriction plate is not provided. The battery will not be damaged. The material of the sodium flow restriction plate must be a material that does not react with sodium. Further, the sodium flow restricting plate needs to be sufficiently weak in comparison with the strength of the solid electrolyte tube so that the solid electrolyte tube is not damaged by the difference in thermal expansion due to the temperature rise and fall of the battery. As the sodium flow restriction plate, a thin plate of aluminum or a thin plate of nickel can be considered.
A stainless steel plate or the like is more preferable.

In FIGS. 7 and 8, the sodium flow restricting plate has an overlapping portion, but a gap may be provided as shown in FIG. However, if the gap is too large, the flow rate of liquid sodium cannot be limited, so the gap needs to be sufficiently small. The upper part of FIG. 9 is a top view of the sodium flow rate limiting plate, and the lower part is a front view. 10-1 to 10-6
Some variations of the sodium flow rate limiting plate are shown in FIG. When the charge speed and the discharge speed when the battery is operated normally are high to some extent, it is necessary to supply liquid sodium to the inner wall surface of the solid electrolyte tube at a certain speed. In such a case, it is necessary to provide a gap corresponding to the required sodium flow rate between the sodium flow rate limiting plate and the inner wall surface of the solid electrolyte tube. In such a case, it is necessary to make the surface of the sodium flow rate limiting plate uneven. A plurality of projections, particularly linear projections, may be formed on the surface of the sodium flow restriction plate that is in contact with the solid electrolyte tube. Instead of making the surface of the sodium flow rate limiting plate uneven, one or more holes may be provided.

FIGS. 11 and 12 show the structure of a battery using a sodium flow restricting tube 19 for preventing liquid sodium accumulated in the upper part of the negative electrode chamber from flowing into the positive electrode chamber quickly. The upper end of the sodium flow restricting tube needs to be positioned higher than the maximum liquid level of liquid sodium in the negative electrode chamber. In addition, the flow rate of the sodium in the sodium flow restriction tube should be less than a certain amount so that liquid sodium can move in the part between the safety pipe and the sodium flow restriction pipe and the part between the sodium flow restriction pipe and the solid electrolyte pipe. One or more holes need to be drilled. The diameter of this hole defines the rate at which liquid sodium on the negative electrode chamber side continuously flows into the positive electrode chamber when the solid electrolyte tube is broken. Need to be designed first. The position of this hole must be provided below the lowest level of the sodium liquid level in the negative electrode chamber at the end of battery discharge. The sodium flow restricting tube may be fixed to the safety tube 6 or the negative electrode cap 7, but may not be fixed anywhere. When fixed, the joining strength of the fixed portion needs to be reduced in order to reduce the risk of the sodium flow restricting tube breaking the solid electrolyte tube. It is preferable that the sodium flow restricting tube is not fixed anywhere, since the risk of damaging the solid electrolyte tube is low. When not fixed, it is preferable to provide a guide or the like so as to be present at the center. When the solid electrolyte tube is broken and liquid sodium directly reacts with the positive electrode active material, a large amount of heat is generated. If the sodium flow restricting tube is melted by this heat, a very serious accident will occur. Therefore, the material of the sodium restricting tube is preferably a metal having a melting point as high as possible. In addition, it is preferable that the thickness is somewhat large. It is essential that the material is not corroded by liquid sodium. For example, a stainless steel bottomed cylindrical tube is a preferable candidate. FIG. 14 shows the structure of a battery using a cartridge 21. The method of installing the sodium flow rate restriction tube 19 is the same.

FIG. 13 shows a sodium flow restricting tube 19 for preventing liquid sodium accumulated in the upper part of the negative electrode chamber from flowing into the positive electrode chamber promptly. The structure of is shown. In this case, the sodium flow restricting tube must have at least two or more holes. At least one hole needs to be positioned higher than the maximum liquid level of liquid sodium in the negative electrode chamber in order to maintain the same pressure inside and outside the sodium flow restriction tube. Also, at least one hole is provided in the negative electrode chamber at the end of battery discharge to allow liquid sodium to move between the cartridge and the sodium flow restriction tube and between the sodium flow restriction tube and the solid electrolyte tube. Must be below the lowest level of sodium level. The diameter of this hole defines the rate at which liquid sodium on the negative electrode chamber side continuously flows into the positive electrode chamber when the solid electrolyte tube is broken. Need to be designed first. It is essential that the material of the sodium restriction tube is not corroded by liquid sodium. For example, stainless steel and aluminum are preferred candidates. Preferably, the sodium restriction tube is not fixed and is movable. The sodium restriction tube may be joined to a part of the wall forming the cathode chamber or a sodium storage container with a strength lower than that of the solid electrolyte.

In the battery of the present invention whose structure is shown in FIG.
The sodium flow rate limiting ring 14 is provided for limiting the flow rate of sodium so that a large amount of liquid sodium does not immediately come into contact with the positive electrode active material in the event that the solid electrolyte is broken and liquid sodium flows into the positive electrode chamber. Liquid sodium has a function of restricting a flow rate of the liquid sodium flowing through the sodium flow rate restriction ring into a portion of the positive electrode active material existing below the ring.

In the battery of the present invention whose structure is shown in FIG.
The sodium flow rate limiting mat 15 is provided for limiting the sodium flow rate so that a large amount of liquid sodium does not immediately come into contact with the positive electrode active material in the event that the solid electrolyte is broken and liquid sodium flows into the positive electrode chamber. It functions to limit the flow rate of liquid sodium flowing into the portion of the positive electrode active material below the mat through the sodium flow rate limiting mat.

In the battery of the present invention whose structure is shown in FIG.
When the solid electrolyte is broken,
By holding the liquid sodium present in the negative electrode chamber, the flow rate of liquid sodium flowing from the negative electrode chamber to the positive electrode chamber is restricted, thereby suppressing the reaction within a unit time to thereby prevent the battery from being destroyed.

In the battery of the present invention whose structure is shown in FIG.
When the solid electrolyte is damaged, the sodium flow rate limiting mat 17 holds the liquid sodium present in the negative electrode chamber to limit the flow rate of liquid sodium flowing from the negative electrode chamber to the positive electrode chamber, thereby suppressing a reaction within a unit time. By doing so, it plays a role in preventing the battery from being destroyed.

In the battery of the present invention whose structure is shown in FIGS. 7 and 8, the sodium flow restricting plate reduces the amount of liquid sodium existing between the sodium flow restricting plate and the solid electrolyte tube, so that the solid electrolyte tube is The absolute amount of liquid sodium flowing into the positive electrode chamber immediately after the damage is reduced to prevent the battery from being broken. Also, when the solid electrolyte tube is broken,
Most of the liquid sodium that existed in the upper part of the negative electrode chamber
From the inside of the sodium flow restriction plate, through the overlapping portion of the plate, through the broken portion of the solid electrolyte tube, and into the cathode chamber, the inflow speed is much slower than when the sodium flow restriction plate is not provided. The battery will not be destroyed.

In the battery of the present invention whose structure is shown in FIG.
The gap is for ensuring the necessary flow rate of liquid sodium during rated operation of the battery.

In the battery of the present invention whose structure is shown in FIG. 10, the variation of the sodium flow rate limiting plate is a means for controlling the flow rate of liquid sodium according to the battery design.

In the battery of the present invention whose structure is shown in FIGS. 11 and 12, the sodium flow restricting tube 19 is provided by reducing the amount of liquid sodium existing between the sodium flow restricting tube and the solid electrolyte tube. The absolute amount of liquid sodium flowing into the positive electrode chamber immediately after the battery is damaged is reduced to prevent the battery from being broken. In addition, when the solid electrolyte tube was broken, most of the liquid sodium that was present in the upper part of the negative electrode chamber passed from the inside of the sodium flow restriction tube through the hole provided in the sodium flow restriction tube, and the solid electrolyte tube was damaged. Since it flows into the positive electrode chamber through the part, its inflow speed is much slower than when the sodium flow restriction tube is not provided,
The battery will not be destroyed. If the position of the upper end of the sodium flow restricting tube is lower than the maximum liquid level of the liquid sodium in the negative electrode chamber, the liquid sodium accumulated above the upper end of the sodium flow restricting tube will be blown at once when the solid electrolyte tube is damaged. Into the cell, a large amount of the positive electrode active material and liquid sodium react instantaneously, causing battery breakdown.
The position of the upper end of the sodium flow restriction tube must be higher than the maximum liquid level of liquid sodium in the negative electrode chamber. Since the diameter of the hole provided in the sodium flow rate restriction tube defines the speed at which the liquid sodium on the negative electrode chamber side continuously flows into the positive electrode chamber when the solid electrolyte tube is broken, the hole diameter is normally used during normal operation. The diameter must be such that the required flow rate of liquid sodium can be ensured and the flow rate of liquid sodium can be limited so that the battery does not break down when the solid electrolyte is broken. The position of this hole must be provided below the lowest level of the sodium liquid level in the negative electrode chamber at the end of battery discharge. When the sodium liquid level is lower than the position of the hole, liquid sodium is not supplied to the inner wall surface of the solid electrolyte tube, so that the effective area of the battery reaction is reduced, the battery resistance is increased, and the efficiency is deteriorated. The same applies to the battery of the present invention whose structure is shown in FIG.

Also in the battery of the present invention whose structure is shown in FIG. 13, the sodium flow restricting tube 19 is damaged by reducing the amount of liquid sodium existing between the sodium flow restricting tube and the solid electrolyte tube. Immediately after this, the absolute amount of liquid sodium flowing into the positive electrode chamber is reduced to prevent the battery from being broken. Also, when the solid electrolyte tube is broken,
Most of the liquid sodium that existed in the upper part of the negative electrode chamber
From the inside of the sodium flow restriction tube, through the hole provided in the sodium flow restriction tube, through the broken portion of the solid electrolyte tube, and into the positive electrode chamber, the inflow speed is higher than when the sodium flow restriction tube is not provided. It is much slower and does not destroy the battery. The upper hole of the sodium flow restricting tube serves to keep the pressure between the sodium flow restricting tube and the solid electrolyte tube equal to the pressure between the sodium flow restricting tube and the safety tube. The lower hole defines the rate at which the liquid sodium on the negative electrode chamber side continuously flows into the positive electrode chamber when the solid electrolyte tube is broken. The diameter must be such that the flow rate of liquid sodium can be ensured and the flow rate of liquid sodium can be restricted so that the flow rate of the battery does not break down when the solid electrolyte is broken. The position of this hole must be provided below the lowest level of the sodium liquid level in the negative electrode chamber at the end of battery discharge.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, comparative examples and examples for illustrating the present invention in detail will be shown.

Comparative Example 1 FIG. 1 shows the structure of the sodium-sulfur battery of Comparative Example 1. During operation of the battery, the gas pressure P1 in the upper space in the cartridge and the gas pressure P2 in the upper space in the negative electrode
Are kept at the same pressure. As shown in FIG. 2, when sodium does not sufficiently remain in the cartridge 21 (sufficiently discharged), P1 has a low pressure, and the liquid level L2 of sodium outside the cartridge is lower than that at the start of discharging. It is going down. However, if L2 is lower than the liquid level L3 of the positive electrode active material inside the positive electrode chamber, the area where the battery reaction occurs decreases and the battery efficiency deteriorates, so that even at the end of discharge, L2 falls significantly below L3. P1 and P2 at the time of manufacture are selected so as not to cause a problem. Therefore, when the sodium is sufficiently present in the cartridge (in a sufficiently charged state), P1 is at a high pressure, and the liquid level L2 of sodium outside the cartridge is at a considerably high position, and in some cases, the upper end of the cartridge 21 May reach higher. In such a state, if the solid electrolyte tube is broken at a position substantially equal to L3, the liquid sodium above the upper end surfaces of the protection tube 20 and the safety tube 6 all flows into the positive electrode chamber. There is a problem that the active material reacts rapidly and the battery is destroyed.

One hundred sodium-sulfur batteries having the structure shown in FIG. 1 were manufactured. The material of the solid electrolyte tube 1 is β ″ -alumina, the materials of the positive electrode container 3, the negative electrode container 4, the negative electrode cap 7, the positive electrode cap 11, and the protective tube 20 are SUS310S, the safety tube 6, the positive electrode terminal 12, the negative electrode terminal 13, the cartridge 21. Was made of aluminum metal.

The upper space of the cartridge 21 is filled with argon gas for pushing out sodium inside the cartridge. The outer diameter of the protection tube 20 is 1 mm smaller than the inner diameter of the solid electrolyte tube 1, the outer diameter of the safety tube 6 is 0.4 mm smaller than the inner diameter of the protection tube 20, and the outer diameter of the cartridge 21 is 0.2 mm smaller than the inner diameter of the safety tube 6. I made it smaller. The bottom of the cartridge 21 was provided with a hole having a diameter of 0.14 mm for supplying liquid sodium.

The sodium liquid level L2 outside the cartridge when the battery is charged to 100 is approximately higher than the uppermost surface L3 of the carbon current collector, which is a cathode conductive material impregnated with sulfur as a cathode active material in the cathode chamber. It came to be 40mm higher.

In the process of manufacturing the battery, on the outer wall surface of the solid electrolyte tube 1 5 mm above the uppermost surface L3 of the carbon current collector, which is a cathode conductive material impregnated with sulfur as the cathode active material in the cathode chamber,
A battery having a length of about 5 mm was made to prepare a battery.

This battery was placed in an electric furnace, and 3 hours in 10 hours.
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time. If the opening of the broken part of the solid electrolyte tube is sufficiently large, about 20
cm ³ of liquid sodium was allowed to flow into the cathode compartment.

Of the 100 batteries manufactured, 30 were damaged during the temperature rise, and a large amount of sodium and sulfur inside leaked out of the battery. When a mechanical shock was applied to the remaining 70 batteries at 330 ° C., 52 batteries exploded explosively, and the metal portion was melted in about the upper third of the battery. In addition, 12 batteries were broken, and α-
Large separation occurred between the alumina ring 2 and the positive electrode container 3, and a large amount of active material inside the battery leaked. Remaining 6
The battery did not break, but immediately after the mechanical shock, the battery temperature began to rise sharply, and the maximum temperature rose to about 400 to 550 ° C.

From these facts, in the structure of the conventional sodium-sulfur battery, if the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%, the battery is explosively destroyed. It turned out that there was.

Comparative Example 2 100 sodium-sulfur batteries having the structure shown in FIG. 15 were manufactured. The material of the solid electrolyte tube 1 is β ″ -alumina, the positive electrode container 3, the negative electrode container 4, the safety tube 6, the negative electrode cap 7, the sodium injection tube 8, the material of the positive electrode cap 11 are SUS310S, the positive electrode terminal 12, and the negative electrode terminal 13.
Was made of aluminum metal.

The upper space inside the safety pipe 6 is filled with argon gas for pushing out sodium in the safety pipe. The outer diameter of the safety tube 6 is 1 mm from the inner diameter of the solid electrolyte tube 1.
I made it smaller. At the bottom of the safety tube 6, two holes having a diameter of 0.10 mm were provided for supplying liquid sodium.

The sodium liquid level L2 outside the safety tube when the battery is charged 100 times is higher than the uppermost surface L3 of the carbon current collector, which is a cathode conductive material impregnated with sulfur as a cathode active material in the cathode chamber. It was about 40mm higher.

In the process of manufacturing the battery, a position 5 mm above the top surface L3 of the carbon collector, which is a cathode conductive material impregnated with sulfur, which is a cathode active material, in the cathode chamber on the outer wall surface of the solid electrolyte tube 1,
A battery having a length of about 5 mm was made to prepare a battery.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time. If the opening of the broken part of the solid electrolyte tube is sufficiently large, about 10
cm ³ of liquid sodium flows into the cathode compartment.

Of the 100 batteries manufactured, 27 were damaged during the temperature rise, and a large amount of sodium and sulfur inside leaked out of the battery. When a mechanical shock was applied to the remaining 73 batteries at 330 ° C., 43 batteries explosively destroyed the battery, and the metal portion was melted in about the upper third of the battery. In addition, 21 batteries were destroyed, and α-
Large separation occurred between the alumina ring 2 and the positive electrode container 3, and a large amount of active material inside the battery leaked. 9 remaining
The battery did not break, but immediately after the mechanical shock, the battery temperature began to rise sharply, and the maximum temperature rose to about 400 to 550 ° C.

From these facts, it can be seen that the conventional sodium-free filter without the sodium flow restriction ring 14, the sodium flow restriction mat 15, the sodium retaining material 16, the sodium flow restriction mat 17, the sodium flow restriction plate 18, the sodium flow restriction tube 19, etc. In the structure of a sulfur battery, almost 10
It can be seen that there is a serious safety problem that the battery is explosively destroyed if the upper portion of the solid electrolyte tube is damaged in a charged state of nearly 0%.

Example 1 One hundred sodium-sulfur batteries having the same structure as the battery fabricated in Comparative Example 2 and having a sodium flow restricting ring 14 added as shown in FIG. 3 were fabricated. The sodium flow restricting ring 14 is formed by compacting carbon, the outer diameter is the same as the inner diameter of the positive electrode container, the diameter of the ring hole is the same as the outer diameter of the solid electrolyte tube 1, and the thickness is 3
mm. Other conditions of the battery were the same as those of the battery manufactured in Comparative Example 2. Therefore, the sodium liquid level outside the safety tube when the battery is charged 100 is also about 40 mm higher than the top surface of the carbon collector, which is a cathode conductive material impregnated with sulfur as the cathode active material in the cathode chamber. come.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 28 batteries showed a temperature rise greater than the trend of the temperature rise rate during the temperature rise, but no change was observed in the appearance of the batteries. For the other 72 batteries, the battery temperature began to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, by using the sodium flow restricting ring 14, it is possible to obtain a nearly 100% charged state,
It can be seen that even if the upper portion of the solid electrolyte tube is damaged, the battery can be prevented from being explosively destroyed.

Example 2 100 sodium-sulfur batteries having the same structure as the battery fabricated in Comparative Example 2 and having a sodium flow rate limiting mat 15 added thereto were fabricated as shown in FIG. The sodium flow rate limiting mat 15 is a mat-like material in which carbon fibers are densely knitted. The outer diameter is 4 mm larger than the inner diameter of the positive electrode container, and the ring hole diameter is 4 mm smaller than the outer diameter of the solid electrolyte tube 1. The diameter and thickness were 10 mm. Other conditions of the battery were the same as those of the battery manufactured in Comparative Example 2.

The battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 31 batteries showed a temperature rise during the temperature rise that was greater than the trend of the rate of temperature rise, but the appearance of the batteries did not change. As for the other 69 batteries, the battery temperature started to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, by using the sodium flow rate limiting mat 15, the charged state is almost 100%.
It can be seen that even if the upper portion of the solid electrolyte tube is damaged, the battery can be prevented from being explosively destroyed.

Example 3 As shown in FIG. 5, 100 sodium-sulfur batteries having the same structure as that of the battery fabricated in Comparative Example 2 and having a sodium retaining material 16 added thereto were fabricated. SUS made of SUS304 fiber densely knitted for sodium retaining material 16
Wool was used. SUS304 is a substance having a high affinity for Na. Other conditions of the battery were the same as those of the battery manufactured in Comparative Example 2.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 29 batteries showed a temperature rise during the temperature rise that was greater than the trend of the temperature rise rate, but no change was observed in the appearance of the batteries. As for the other 71 batteries, the battery temperature began to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, the sodium holding material 16
It can be seen that the use of a battery can prevent explosive destruction of the battery even when the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%.

Example 4 100 sodium-sulfur batteries having the same structure as the battery fabricated in Comparative Example 2 and having a sodium flow rate limiting mat 17 added thereto were fabricated as shown in FIG. The flow limiting mat 17 used was a densely woven aluminum fiber. Other conditions of the battery were the same as those of the battery manufactured in Comparative Example 2.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries produced, 30 batteries showed a temperature rise during the temperature rise that was greater than the trend of the rate of temperature rise, but no change was seen in the appearance of the batteries. As for the other 70 batteries, the battery temperature began to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, by using the sodium flow rate limiting mat 17, the charged state is almost 100%.
It can be seen that even if the upper portion of the solid electrolyte tube is damaged, the battery can be prevented from being explosively destroyed.

Example 5 One hundred sodium-sulfur batteries having the same structure as the battery fabricated in Comparative Example 2 and having a sodium flow restricting plate 18 added thereto as shown in FIGS. 7 and 8 were fabricated. As the flow rate limiting plate 18, a thin plate of SUS304 having a thickness of 0.1 mm was used. The uppermost height of the flow rate limiting plate 18 was set to be 10 mm higher than the liquid level of the liquid sodium in the negative electrode chamber when the battery was charged 100%. Other conditions of the battery were the same as those of the battery manufactured in Comparative Example 2. The battery was placed in an electric furnace, heated to 330 ° C. in 10 hours, maintained for 1 hour, discharged for 8 hours with a current of 30 A, stopped for 4 hours, and charged for 10 hours with a current of 24 A Then, a series of operations of stopping the current and holding the current for 3 hours was repeated five times, and then charged at a voltage of 2.5 V for 5 hours to charge the battery for approximately 100 hours.
After the battery was charged, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether or not the battery was broken at that time.

Of the 100 batteries manufactured, 31 batteries showed a temperature rise greater than the trend of the temperature rise rate during the temperature rise, but the appearance of the batteries did not change. As for the other 69 batteries, the battery temperature started to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, it can be seen that the use of the sodium flow rate limiting plate 18 prevents the battery from being explosively destroyed even when the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%. I understand.

Example 6 A sodium-sulfur battery having the same structure as that of the battery fabricated in Comparative Example 2 and adding a sodium flow restricting tube 19 as shown in FIGS.
0 were produced. However, since it is necessary to additionally insert a sodium flow restriction pipe 19 between the safety pipe 6 and the solid electrolyte pipe 1, the outer diameter of the safety pipe 6 is 2.8 m from the inner diameter of the solid electrolyte pipe 1.
m was made smaller.

The bottomed cylindrical sodium flow restricting tube 19 is
It was made of SUS304 and had a thickness of 1 mm. Sodium flow restriction tube 19
Was set to be 10 mm higher than the liquid level of liquid sodium in the negative electrode chamber at the time of 100% charging of the battery. The sodium flow restriction tube 19 was provided with two holes having a diameter of 0.1 mm at a position 20 mm lower than the level of the liquid sodium in the negative electrode chamber at the end of the battery discharge. Other battery conditions were the same as those of the battery manufactured in Comparative Example 2.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 28 batteries showed a temperature rise during the temperature rise that was greater than the trend of the temperature rise rate, but no change was observed in the appearance of the batteries. For the other 72 batteries, the battery temperature began to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, it can be seen that the use of the sodium flow restricting tube 19 can prevent the battery from being explosively destroyed even when the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%. I understand.

Example 7 One hundred sodium-sulfur batteries having the same structure as that of the battery fabricated in Comparative Example 2 and adding a sodium flow restricting tube 19 as shown in FIG. 13 were fabricated. However, since it is necessary to additionally insert a sodium flow restricting pipe 19 between the safety pipe 6 and the solid electrolyte pipe 1, the outer diameter of the safety pipe 6 is made 2.8 mm smaller than the inner diameter of the solid electrolyte pipe 1.

The bottomed cylindrical sodium flow restricting tube 19 is
It is made of SUS304 and has a thickness of 0.8 mm.
Welded. The sodium flow restriction tube 19 has a 10
10mm from the liquid level of liquid sodium in the negative electrode chamber at 0% charge
Two holes having a diameter of 1 mm were provided at a higher position, and two holes having a diameter of 0.1 mm were provided at a position lower by 20 mm than the level of liquid sodium in the negative electrode chamber at the end of discharge of the battery. Other battery conditions were the same as those of the battery manufactured in Comparative Example 2.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 33 batteries showed a temperature rise during the temperature rise that was greater than the trend of the temperature rise rate, but no change was observed in the appearance of the batteries. With respect to the other 67 batteries, the battery temperature started to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, it can be seen that the use of the sodium flow restriction tube 19 can prevent the battery from being explosively destroyed even when the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%. I understand.

Example 8 One hundred sodium-sulfur batteries having the same structure as the battery manufactured in Comparative Example 1 and having a sodium flow restricting tube 19 added as shown in FIG. 14 were manufactured. However, since it is necessary to additionally insert a sodium flow restricting pipe 19 between the safety pipe 6 and the solid electrolyte pipe 1, the outer diameter of the safety pipe 6 is made 2.8 mm smaller than the inner diameter of the solid electrolyte pipe 1.

The bottomed cylindrical sodium flow restricting tube 19 is
It was made of SUS304 and had a thickness of 1 mm. Sodium flow restriction tube 19
Was set to be 10 mm higher than the liquid level of liquid sodium in the negative electrode chamber at the time of 100% charging of the battery. The sodium flow restricting tube 19 was provided with two holes having a diameter of 0.1 mm at a position 40 mm lower than the level of the liquid sodium in the negative electrode chamber at the end of the battery discharge. Other battery conditions were the same as those of the battery manufactured in Comparative Example 2.

This battery was placed in an electric furnace,
After heating to 30 ° C. and holding for 1 hour, discharging at 30 A current for 8 hours, stopping current for 4 hours, charging at 24 A current for 10 hours, stopping current and holding for 3 hours After repeating the above operation 5 times, 2.5 V
After charging for about 100 hours to charge the battery, a mechanical shock was applied to the battery to promote breakage of the solid electrolyte tube, and it was examined whether the battery was broken at that time.

Of the 100 batteries manufactured, 30 batteries showed a temperature rise during the temperature rise that was greater than the trend of the rate of temperature rise, but no change was seen in the appearance of the batteries. As for the other 70 batteries, the battery temperature began to rise slowly immediately after the application of the mechanical shock at 330 ° C., and the maximum temperature rose to about 380 ° C. to 450 ° C.

From these facts, even if the basic structure of the battery is different, by using the sodium flow restricting tube 19,
It can be seen that the battery can be prevented from being explosively destroyed even when the upper portion of the solid electrolyte tube is damaged in a charged state of almost 100%. As can be seen from the results of Comparative Examples 1 and 2, in the conventional sodium-sulfur battery, after the first temperature rise of the battery or when the battery was charged to a state close to 100%, the upper part of the solid electrolyte tube was damaged. When this occurs, the battery is severely destroyed with a very high probability, indicating that the practical safety is insufficient.

As shown in Examples 1 to 8, in the sodium-sulfur battery according to the present invention, even if the solid electrolyte tube is broken, the battery does not break down.
It can be seen that the safety is much higher than that of the sulfur battery.

[0077]

According to the present invention, a highly safe sodium-sulfur battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a sodium-sulfur battery of a comparative example of the present invention.

FIG. 2 is a diagram schematically showing a change in liquid level of liquid sodium caused by charging and discharging of a sodium-sulfur battery.

FIG. 3 is a diagram showing a structure of a battery using a sodium flow rate limiting ring according to an embodiment of the present invention.

FIG. 4 is a diagram showing the structure of a battery using a sodium flow rate limiting mat according to an embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a battery using the sodium retaining material of the example of the present invention.

FIG. 6 is a diagram showing a structure of a battery using a sodium flow rate limiting mat of an example of the present invention.

FIG. 7 is a diagram showing a structure of a battery using a sodium flow rate limiting plate according to an example of the present invention.

8 is a view showing a cross-sectional structure of a battery using the sodium flow rate limiting ring of the embodiment of the present invention shown in FIG. 7;

FIG. 9 is a view showing one of variations of a sodium flow rate limiting plate used for a battery using the sodium flow rate limiting plate of the embodiment of the present invention.

FIG. 10 is a view showing six variations of a sodium flow rate limiting plate used in a battery using the sodium flow rate limiting plate of the embodiment of the present invention.

FIG. 11 is a diagram showing a structure of a battery using a sodium flow rate restriction tube according to an example of the present invention.

FIG. 12 is a view showing a cross-sectional structure of a battery using the sodium flow restricting tube of the embodiment of the present invention shown in FIG. 11;

FIG. 13 is a view showing a structure of a battery using a sodium flow rate restriction tube according to an example of the present invention.

FIG. 14 is a diagram showing a structure of a battery using a sodium flow rate restriction tube according to an example of the present invention.

FIG. 15 is a diagram showing a structure of a battery according to a comparative example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte tube, 2 ... Alpha-alumina ring for positive / negative electrode insulation, 3 ... Positive electrode container, 4 ... Negative electrode container, 5 ... Negative electrode active material sodium, 6 ... Safety tube, 7 ... Negative electrode cap, 8 ... Sodium injection tube, 9: Positive electrode active material sulfur, 10: Positive electrode conductive carbon, 11: Positive electrode cap, 12: Positive electrode terminal, 13: Negative electrode terminal, 14: Sodium flow restricting ring, 15, 17 ...
Sodium flow restriction mat, 16 ... Sodium retention material,
18 ... Sodium flow restricting plate, 19 ... Sodium flow restricting tube, 20 ... Protective tube, 21 ... Cartridge.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiko Nishimura 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Seiji Koike 7, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Yuichi Kamo 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi, Ltd. Hitachi Research Laboratory F-term (reference) 5H029 AJ02 AJ12 AL13 AM15 BJ02 BJ21 CJ04 DJ02 DJ07 DJ11 EJ04 HJ04 HJ06

Claims (6)

[Claims] A cathode chamber inside a bottomed solid electrolyte tube;
In a sodium-sulfur battery, an anode chamber is formed outside, sodium is stored in the cathode chamber, and carbon for collecting current and sulfur as an active material are stored in the anode chamber. A cylindrical sodium flow-restricting tube with an open bottom having an outer diameter smaller than the inner diameter of the solid electrolyte tube was formed inside the tube and a sodium flow-in / out hole was formed in the lower part inside the sodium flow-restriction tube. It has a sodium storage container, and the uppermost position of the sodium flow restriction tube is located higher than the highest liquid level of sodium inside the cathode chamber, and a hole is provided at a position lower than the lowest liquid level of sodium. Sodium-sulfur battery. 2. A cathode chamber inside a cylindrical solid electrolyte tube having a bottom,
In a sodium-sulfur battery, an anode chamber is formed outside, sodium is stored in the cathode chamber, and carbon for collecting current and sulfur as an active material are stored in the anode chamber. A sodium-sulfur battery, wherein a sodium holding material is arranged in an upper space portion of the battery. 3. A cathode chamber inside a bottomed cylindrical solid electrolyte tube,
In a sodium-sulfur battery, an anode chamber is formed outside, sodium is stored in the cathode chamber, and carbon for collecting current and sulfur as an active material are stored in the anode chamber. A sodium-sulfur battery, characterized in that a sodium flow restriction mat is arranged in an upper space portion of the battery. 4. A cathode chamber inside a cylindrical solid electrolyte tube having a bottom,
In a sodium-sulfur battery in which an anode chamber is formed outside, sodium is accommodated in the cathode chamber, and carbon for collecting current and sulfur as an active material are accommodated in the anode chamber, a solid electrolyte tube is provided. A sodium-sulfur battery, characterized in that a rectangular metal plate is rounded on a side inner wall and a sodium flow limiting plate in contact with the metal plate is arranged. 5. A cathode chamber inside a bottomed solid electrolyte tube.
In a sodium-sulfur battery in which an anode chamber is formed outside, sodium is accommodated in the cathode chamber, and carbon for collecting current and sulfur as an active material are accommodated in the anode chamber, a solid electrolyte tube is provided. A sodium flow rate limiting plate is arranged in a form in which a rectangular metal plate is rolled and contacted with the side inner wall of the surface, and the position of the uppermost portion of the sodium flow rate limiting plate is higher than the highest liquid level of sodium in the cathode chamber. A sodium-sulfur battery. 6. A cathode chamber inside a bottomed cylindrical solid electrolyte tube,
In a sodium-sulfur battery, an anode chamber is formed outside, sodium is stored in the cathode chamber, and carbon for collecting current and sulfur as an active material are stored in the anode chamber. Inside the tube, a bottomed cylindrical metallic sodium flow restricting tube with a closed upper part slightly smaller in outer diameter than the inner diameter of the solid electrolyte tube, and a hole for sodium ingress and egress at the lowermost part inside the sodium flow restricting tube. The formed sodium storage container is arranged, and at least one or more holes are formed in the sodium flow restricting tube at a position higher than the highest liquid level of sodium in the cathode chamber, and the sodium storage container is formed with a lower than the lowest liquid level of sodium in the cathode chamber. A sodium-sulfur battery, wherein at least one or more holes for reducing the flow rate of sodium to a certain flow rate or less are formed at a low position.