JP3253827B2 - Cathode structure of sodium-sulfur battery and sodium-sulfur battery using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode structure of a sodium-sulfur battery using molten sodium as a cathode active material and molten sulfur as an anode active material, and a sodium-sulfur battery using the same.

[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. A high-temperature secondary battery operated at 300 to 350 ° C., isolated by a beta-alumina solid electrolyte.

As shown in FIG. 2, for example, a configuration of such a sodium-sulfur battery is a cylindrical anode container 3 containing an anode conductive material 6 such as carbon felt impregnated with sulfur as an anode active material, Placed inside the anode container 3,
It comprises a bottomed cylindrical solid electrolyte tube (beta-alumina tube) 5 having a function of selectively transmitting sodium ions, and a cartridge 10 which is disposed inside the solid electrolyte tube 5 and stores sodium 7. The cartridge 10 is made of stainless steel, steel, or an aluminum alloy. The solid electrolyte tube 5 is joined to the upper end of the anode container 3 via an insulator ring 1 made of, for example, alpha alumina. A cathode fitting 11 is joined to the upper surface of the insulator ring 1 by heat and pressure. A sodium protection tube may be interposed between the cartridge 10 and the solid electrolyte tube 5.

In the sodium-sulfur battery 4 having the above-described configuration, at the time of discharge, the molten sodium 7 emits electrons to become sodium ions, which are converted into solid electrolyte tubes 5.
It passes through the inside and moves to the anode side, reacts with the sulfur in the anode conductive material 6 and the electrons passed through the external circuit to generate sodium polysulfide, and generates a voltage of about 2V. On the other hand, at the time of charging, a reaction of producing sodium and sulfur occurs in reverse to the discharging.

In the initial state where the sodium-sulfur battery 4 is not operating, the sodium 7 in the cartridge 10 is solid. Therefore, in order for the above-mentioned discharge reaction to occur, the sodium 7 melted by heating flows out of the small hole 12 provided at the bottom of the cartridge 10 into the space 13 between the solid electrolyte tube 5 and the cartridge 10,
It is necessary to make contact with the solid electrolyte tube 5 and the cathode fitting 11.

[0006] Previously, sodium azide (NaN) stored in the upper space of the cartridge 10 at the time of assembling the battery was used.
₃ ) uses the pressure of nitrogen gas generated by decomposition by heating during operation of the battery to remove molten sodium 7 into small holes 12
It was more extruded.

However, when sodium azide is stored in the cartridge 10, it takes a long time to determine the sodium azide, and the workability is poor because it must be performed in a low moisture atmosphere as much as possible. Furthermore, since sodium azide is harmful to the human body, sufficient care must be taken when handling it.

Therefore, without using sodium azide,
An inert gas 15 such as argon is sealed in the upper space 14 of the cartridge 10, and the molten sodium 7 is
Is pushed out into the space 13.

[0009]

However, when heating the sodium-sulfur battery 4, the cartridge 1
Since the melting of sodium 7 starts near the inner wall of the inert gas 0, the inert gas 15
Also leaks into the space 13 through the space between the inner wall of the cartridge 10 and the solidified sodium. On the other hand, space 13
The molten sodium extruded to form sodium ions and move to the anode side through the solid electrolyte tube 5,
The volume of the leaked inert gas increases as the volume of sodium decreases, and the inner wall of the solid electrolyte tube 5 and the cathode fitting 1 increase.
Start covering 1.

When the inert gas comes into contact with the inner wall of the solid electrolyte tube 5, the permeation of sodium ions in that portion is hindered, and the electric resistance increases. Also, when the inert gas covers the entire cathode fitting 11, the cathode fitting 11 is changed from sodium.
Discharge of electrons is stopped because transfer of electrons to the cells is hindered.

In order to prevent the leakage of the inert gas 15 into the space 13, as shown in FIG. 3, an upper space 14 separated by a partition 2 having a communication hole 17 in the cartridge 10.
And a lower space 16 is provided, and a communication hole 17 is closed by a solder 18. Solder 18
Is 100 ° C. or more, which is the melting temperature of sodium, and
It has a melting point below 300-350 ° C., which is the operating temperature of the battery. That is, after the sodium 7 occupying the lower space 16 is completely melted, the solder 18 is melted, and the inert gas 15 occupying the upper space 14 pushes the molten sodium 7 into the space 13. In this structure, since the upper space 14 and the lower space 16 communicate with each other after sodium is completely melted, the inert gas 15 does not leak out of the cartridge 10.

As shown in FIG. 4, when the temperature reaches a certain temperature equal to or higher than the melting point of sodium, a needle 20 installed in the shape memory alloy 19 provided in the upper space 14 makes a hole in the partition wall 2 and A structure in which the space 14 communicates with the lower space 16 has also been proposed.

However, the structure using solder has a problem that solder has poor bonding property with stainless steel and that there is no substance having an appropriate melting point except for solder. Regarding the structure using a shape memory alloy, there are few shape memory alloys that operate at 100 ° C. or higher, which is the melting point of sodium, and such alloys are not produced in Japan and are expensive. .

[0014]

Means for Solving the Problems The present invention has been made in view of such circumstances, and an object of the present invention is to prevent sodium gas from leaking from a cartridge at a low cost. -To provide a cathode structure of a sulfur battery.

That is, according to the present invention, there is provided a sodium-sulfur battery in which sulfur is disposed as an anode active material outside a bottomed solid electrolyte tube and sodium contained in a cartridge is disposed as a cathode active material inside. An inert gas is provided in the upper space of the cartridge, and sodium is provided in the lower space, and sodium is supplied between the cartridge and the solid electrolyte tube by the pressure of the inert gas through a small hole provided at the bottom of the cartridge. A cathode structure of a sodium-sulfur battery to be supplied to the space, wherein an upper space and a lower space in the cartridge are partitioned by a partition, and all or a part of the partition is an inert gas after sodium melting is completed. A cathode structure of a sodium-sulfur battery, which is broken by the pressure of the above and communicates the upper space and the lower space.

In the above-described cathode structure of the sodium-sulfur battery, the partition has a communication hole and a rupture disk for closing the communication hole, and the rupture disk is destroyed by the pressure of the inert gas after the melting of sodium is completed. It may be something that is done. It is preferable to use stainless steel, steel, nickel, a nickel alloy, or an aluminum alloy as a material of the rupture disk and a cartridge for mounting the rupture disk. When the cartridge is made of an aluminum alloy, the rupture disk must be made of an aluminum alloy. In other cases, different materials may be used for the rupture disk and the cartridge.

According to the present invention, there is provided a sodium-sulfur battery in which sulfur is disposed as an anode active material outside a bottomed cylindrical solid electrolyte tube, and sodium contained in a cartridge is disposed as a cathode active material inside. An inert gas is disposed in the upper space of the cartridge, and sodium is disposed in the lower space.Sodium is supplied between the cartridge and the solid electrolyte tube by the pressure of the inert gas through a small hole provided at the center of the bottom of the cartridge. A cathode structure of a sodium-sulfur battery to be supplied to a space between the cartridges, wherein the cartridge has a flow path blocking wall extending from the bottom surface near the small hole provided at the bottom to the inside of the cartridge; Provides a cathode structure of a sodium-sulfur battery made of a material having a lower thermal conductivity than sodium.

It is preferable to use stainless steel, steel, nickel, a nickel alloy or an aluminum alloy as a material of the flow path blocking wall and the cartridge. When the material of the cartridge is made of an aluminum alloy, it is necessary to use an aluminum alloy for the flow path blocking wall. However, in other cases, different materials may be used for the flow path blocking wall and the cartridge.

Further, according to the present invention, there is provided a sodium-sulfur battery in which sulfur is disposed as an anode active material outside a bottomed solid electrolyte tube and sodium contained in a cartridge is disposed as a cathode active material inside. An inert gas is provided in the upper space of the cartridge, and sodium is provided in the lower space, and sodium is supplied between the cartridge and the solid electrolyte tube by the pressure of the inert gas through a small hole provided at the bottom of the cartridge. A cathode structure of a sodium-sulfur battery for supplying space, wherein the cartridge partitions a lower space up and down and includes a partition having a communication hole in the center, and the partition has a lower thermal conductivity than sodium. A cathode structure for a sodium-sulfur battery comprising a material is provided.

It is preferable to use stainless steel, steel, nickel, a nickel alloy, or an aluminum alloy as a material of the partition wall and the cartridge. When the material of the cartridge is an aluminum alloy, it is necessary to use a partition made of an aluminum alloy, but in other cases, different materials may be used for the partition and the cartridge.

Further, according to the present invention, there is provided a sodium-sulfur battery in which sulfur is disposed as an anode active material outside a bottomed solid electrolyte tube and sodium contained in a cartridge is disposed as a cathode active material inside. , An inert gas in the upper space of the cartridge, sodium in the lower space, and through a small hole provided in the bottom of the cartridge,
A cathode structure of a sodium-sulfur battery for supplying sodium to a space between a cartridge and a solid electrolyte tube by the pressure of an inert gas, wherein the space between the cartridge and the solid electrolyte tube is filled with a gas. The getter is arranged in the space, the pressure of the gas outside the cartridge and the pressure of the inert gas inside the cartridge are equal before the discharge of the sodium-sulfur battery, and the getter is activated after the melting of the sodium in the cartridge is completed. There is provided a cathode structure of a sodium-sulfur battery to be converted.

The above gas is preferably a nitrogen gas or a carbon dioxide gas, and more preferably a nitrogen gas. As a getter, a Zr-V-Fe alloy or Zr-
Although it is preferable to use an Al alloy, it is preferable to use a Zr-V-Fe alloy because it is activated at a lower temperature.

Further, according to the present invention, there is provided a sodium-sulfur battery having the above-described cathode structure.

[0024]

According to the present invention, in the solid electrolyte tube, the pressure of the inert gas disposed on the upper portion of the cartridge is prevented from being applied to the sodium until all of the sodium or the sodium in the outer portion of the cartridge is melted by the volume or more. Inert gas is prevented from leaking out of the cartridge.

Specifically, in the cartridge,
While separating sodium and inert gas with a partition,
After the melting of sodium is completed, adjust the strength of the partition wall and the pressure of the inert gas when filling the cartridge so that the pressure of the inert gas increases due to the temperature rise and exceeds the strength of the partition wall to break the partition wall. It is effective.

A configuration may be adopted in which a part of the partition is destroyed. For example, a communication hole is provided in the partition, and the communication hole is closed with a rupture disk having appropriate strength. Alternatively, only the rupture disc may be destroyed by an increase in the inert gas pressure due to the temperature rise.

It is also effective to form a flow path blocking wall extending from the bottom near the small hole provided in the center of the bottom of the cartridge to the inside of the cartridge. When operating the battery, the melting of sodium starts near the inner wall of the cartridge, so by providing such a flow path blocking wall,
The sodium melting time of the flow path blocking wall portion can be delayed, and as a result, when sodium flows out of the small hole at the bottom, a sufficient amount of sodium to fill the space between the cartridge and the solid electrolyte tube is melted. This is because gas does not flow out. Therefore, in this case, it is preferable that the flow path blocking wall is formed of a material having a thermal conductivity equal to or lower than that of sodium.

The object of the present invention can also be achieved by dividing the lower space of the cartridge up and down by a partition wall having a communication hole in the center, for the same reason as the case where the flow path blocking wall is provided. . The partition walls are preferably formed of a material having a thermal conductivity equal to or lower than that of sodium.

Further, in order to achieve the object of the present invention,
It is also effective to fill the space between the cartridge and the solid electrolyte tube with gas and to arrange a getter in the space, which is activated after the melting of sodium in the cartridge is completed. In this case, the pressure of the gas filling the space between the cartridge and the solid electrolyte tube needs to be equal to the pressure of the inert gas in the cartridge before discharging and charging the sodium-sulfur battery.

By adopting such a cathode structure, the getter starts to adsorb the gas outside the cartridge after the sodium is melted by heating, and the gas pressure inside the cartridge becomes higher than that outside the cartridge. Thus, sodium is discharged out of the cartridge. Thus, the outflow of sodium will begin after melting is complete.

[0031]

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments, but the present invention is not limited to these embodiments.

Embodiment 1 FIG. 1 shows an example of a cathode structure in which a partition which is broken under a certain condition is provided in a cartridge. In FIG. 1, a cartridge 10 having a small hole 12 is shown.
The upper space 14 is provided with an inert gas 15, the lower space 16 is provided with sodium 7, and the upper space 14 and the lower space 16 are partitioned by a partition 21. The partition 21 has a communication hole 22, and the rupture disk 23 closes the communication hole 22.

The inert gas 15 is generated by heating during the operation of the battery.
When the gas pressure reaches a certain value, the rupture disk 23 is broken, the upper space 14 communicates with the lower space 16, and the pressure of the inert gas 15 causes sodium 7 to flow out of the small holes 12. Destruction of rupture disk 23 is sodium 7
And the inert gas 15 filled in the upper space 14 so as to occur after the melting of the
The pressure has been adjusted.

The structure may be such that the rupture disk provided in a part of the partition is not destroyed but the entire partition is destroyed.

The partition wall or the rupture disk needs to be broken at 100 ° C. or more, which is the melting temperature of sodium, and is preferably broken at 100 to 350 ° C.

The cartridge is made of stainless steel,
It is preferable to use steel, nickel, a nickel alloy, an aluminum alloy, or the like. It is preferable to use stainless steel, steel, nickel, a nickel alloy, an aluminum alloy, or the like as a material of the partition wall or the rupture disk. It is preferable that the material of the cartridge and the partition wall or the rupture disk be the same, but different materials may be used except when an aluminum alloy is used. For example, in order to break a partition wall or a rupture disk made of a stainless steel and destroyed at 3.2 atm at 230 ° C., the pressure of the inert gas at the time of sealing the cartridge is about 1.9 atm.
For breaking at 50 ° C., about 1.5 atm is preferable.

Embodiment 2 FIG. 5 shows an example of a cathode structure in which a flow path blocking wall is provided near a small hole of a cartridge. FIG.
The cartridge 1 having a small hole 12 in the center of the bottom surface
The inert gas 15 and the sodium 7 are disposed in the upper space and the lower space, respectively. The cartridge 10 has a flow path blocking wall 24 extending from the bottom surface near the small hole 12 into the cartridge 10.

Although the shape of the flow path blocking wall 24 is preferably cylindrical, the cross-sectional shape may be polygonal or elliptical. Further, it is preferable that the cross-sectional area of the flow path blocking wall 24 is constant.
Conversely, the size may be reduced.

The major diameter of the flow path blocking wall 24 is preferably 30 to 70% of the diameter of the bottom surface of the cartridge 10.
The length of the flow path blocking wall 24 is preferably 3 to 20% of the axial length of the cartridge 10. If it is less than 3%, sodium near the inner surface of the cartridge that melts at an early stage flows into the flow path blocking wall 24 and does not function as a blocking wall. On the other hand, if it exceeds 20%, the amount of sodium that cannot be used is large, which is not economically preferable.

The thermal conductivity of sodium is 132 W / m ·
However, it is desirable to use a material having a thermal conductivity of 132 W / m · K or less, more preferably 100 W / m · K or less, as the material of the flow path blocking wall 24.
Specifically, it is preferable to use a ceramic such as alumina, but SUS304 (thermal conductivity: about 16 W / m ·
It is particularly preferable to use a stainless steel alloy such as K) or nickel or a nickel alloy (thermal conductivity: about 85 W / m · K) in terms of assemblability.

(Embodiment 3) FIG. 6 shows an example of a cathode structure provided with a partition which vertically partitions a lower space of a cartridge. In FIG. 6, an inert gas 15 is disposed in an upper space of a cartridge 10 having a small hole 12 at the bottom center, and sodium 7 is disposed in a lower space. The lower space of the cartridge 10 has a communication hole 25 in a central portion. It is vertically divided by a partition 26.

The partition 26 is preferably provided in the vicinity of the central portion of the length of sodium in the cartridge 10 in the axial direction. The shape of the communication hole 25 is preferably circular, but may be another shape such as a polygon or an ellipse.
The long diameter of the communication hole 25 is 10 mm of the diameter of the bottom of the cartridge 10.
It is preferably about 50%. As a material for forming the partition wall 26, a material similar to the material used for forming the flow path blocking wall in the first embodiment can be used.

Embodiment 4 FIG. 7 shows an example of a cathode structure in which a space between a cartridge and a solid electrolyte tube is filled with a gas and a getter is provided. In FIG. 7, the space 13 between the cartridge 10 and the solid electrolyte tube 5 is filled with a gas 27, and the gas 27 and the inert gas 15 in the cartridge 10 are separated from each other before the charge / discharge operation of the sodium-sulfur battery. Is equal pressure. Furthermore, space 13
Is provided with a getter 28 which is activated after the melting of the sodium 7 in the cartridge 10 is completed.

As the gas 27 filled in the space 13, nitrogen gas, carbon dioxide gas or the like is preferably used, but it is particularly preferable to use nitrogen gas which has little reaction with sodium 7 and has a property of being absorbed by the getter. The getter 28 must be selected from those that do not react with sodium 7 and must be activated at 100 ° C., which is the melting temperature of sodium 7. More preferably, 100 to
Those activated at 350 ° C. are desirable. Therefore, it is preferable to use a Zr-V-Fe alloy or a Zr-Al alloy for the getter 28, but Zr-
It is more preferable to use a V-Fe alloy.

[0045]

EFFECT OF THE INVENTION By employing the cathode structure for a sodium-sulfur battery of the present invention, it is possible to effectively stop the discharge and increase the electric resistance caused by the leakage of the inert gas from the cartridge at a low cost. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a cathode structure of a sodium-sulfur battery of the present invention.

FIG. 2 is a sectional view showing a structure of a sodium-sulfur battery.

FIG. 3 is a schematic diagram illustrating an example of a cathode structure of a conventional sodium-sulfur battery.

FIG. 4 is a schematic diagram showing another example of a cathode structure of a conventional sodium-sulfur battery.

FIG. 5 is a schematic view showing another example of the cathode structure of the sodium-sulfur battery of the present invention.

FIG. 6 is a schematic view showing still another example of the cathode structure of the sodium-sulfur battery of the present invention.

FIG. 7 is a schematic diagram showing still another example of the cathode structure of the sodium-sulfur battery of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulator ring, 2 ... Partition, 3 ... Anode container, 4 ...
Sodium-sulfur battery, 5: solid electrolyte tube, 6: conductive material for anode, 7: sodium, 10: cartridge, 1
DESCRIPTION OF SYMBOLS 1 ... Cathode fitting, 12 ... Small hole, 13 ... Space between cartridge and solid electrolyte tube, 14 ... Upper space, 15 ...
Inert gas, 16 ... lower space, 17 ... communication hole, 18 ...
Solder, 19 shape memory alloy, 20 needle, 21 partition wall, 22 communication hole, 23 rupture disk, 24
-Flow path blocking wall, 25 ... communication hole, 26 ... partition wall, 27 ... gas, 28 ... getter.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-111127 (JP, A) JP-A-2-112168 (JP, A) JP-A-3-254072 (JP, A) JP-A-7-107 230823 (JP, A) JP-A-8-329981 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/39

Claims (13)

(57) [Claims] 1. A sodium-sulfur battery in which sulfur is disposed as an anode active material outside a cylindrical solid electrolyte tube having a bottom and sodium contained in a cartridge is disposed as a cathode active material inside the solid electrolyte tube. An inert gas and sodium in a lower space, and the sodium is transferred between the cartridge and the solid electrolyte tube by the pressure of the inert gas through a small hole provided at the bottom of the cartridge. A cathode structure of a sodium-sulfur battery to be supplied to the space, wherein the upper space and the lower space are partitioned by a partition, and all or a part of the partition is inactive after the melting of the sodium is completed. A cathode structure for a sodium-sulfur battery, wherein the cathode structure is broken by gas pressure and the upper space communicates with the lower space. 2. The partition has a communication hole and a rupture disk for closing the communication hole, and the rupture disk is destroyed by the pressure of the inert gas after the melting of the sodium is completed with a rise in temperature. The cathode structure of the sodium-sulfur battery according to claim 1. 3. The cartridge according to claim 2, wherein said cartridge is made of stainless steel, steel,
The cathode structure of a sodium-sulfur battery according to claim 2, wherein the cathode disk is made of nickel, a nickel alloy, or an aluminum alloy, and the rupture disk is made of stainless steel, steel, nickel, a nickel alloy, or an aluminum alloy. 4. The cathode structure of a sodium-sulfur battery according to claim 3, wherein the rupture disk and the cartridge are made of the same material. 5. A sodium-sulfur battery in which sulfur as an anode active material is disposed outside a bottomed cylindrical solid electrolyte tube and sodium contained in a cartridge is disposed as a cathode active material inside the solid electrolyte tube, wherein the upper space of the cartridge is provided. And a sodium in the lower space, and through the small hole provided at the center of the bottom of the cartridge, the sodium is transferred between the cartridge and the solid electrolyte tube by the pressure of the inert gas. A cathode structure of a sodium-sulfur battery for supplying to a space between the sodium-sulfur battery, wherein the cartridge has a flow path blocking wall extending from the bottom surface near the small hole to the inside of the cartridge. Construction. 6. The cartridge according to claim 1, wherein the cartridge is made of stainless steel, steel,
The cathode structure for a sodium-sulfur battery according to claim 5, wherein the cathode structure is made of nickel, a nickel alloy, or an aluminum alloy, and the flow path blocking wall is made of stainless steel, steel, nickel, a nickel alloy, or an aluminum alloy. 7. The cathode structure for a sodium-sulfur battery according to claim 6, wherein the flow path blocking wall and the cartridge are made of the same material. 8. A sodium-sulfur battery in which sulfur is disposed outside a cylindrical solid electrolyte tube having a bottom as an anode active material, and sodium contained in a cartridge is disposed inside as a cathode active material inside the solid electrolyte tube. An inert gas and sodium in a lower space, and the sodium is transferred between the cartridge and the solid electrolyte tube by the pressure of the inert gas through a small hole provided at the bottom of the cartridge. A cathode structure of a sodium-sulfur battery for supplying space, wherein the cartridge partitions the lower space up and down and includes a partition having a communication hole in the center, and the partition has a lower thermal conductivity than sodium. A cathode structure of a sodium-sulfur battery, comprising a material. 9. The cartridge according to claim 8, wherein the cartridge is made of stainless steel, steel,
The cathode structure of a sodium-sulfur battery according to claim 8, wherein the cathode structure is made of nickel, a nickel alloy, or an aluminum alloy, and the partition is made of stainless steel, steel, nickel, a nickel alloy, or an aluminum alloy. 10. The cathode structure of the sodium-sulfur battery according to claim 9, wherein the partition and the cartridge are made of the same material. 11. A sodium-containing material in which sulfur is disposed as an anode active material outside a bottomed cylindrical solid electrolyte tube, and sodium contained in a cartridge is disposed as a cathode active material inside.
In the sulfur battery, an inert gas is disposed in an upper space of the cartridge and sodium is disposed in a lower space, and the sodium is supplied to the cartridge by a pressure of the inert gas through a small hole provided in a bottom of the cartridge. And a cathode structure of a sodium-sulfur battery to be supplied to a space between the solid electrolyte tube and the solid electrolyte tube. The space between the cartridge and the solid electrolyte tube is filled with gas, and a getter is arranged in the space. Wherein the gas and the inert gas are isobaric before operation of the sodium-sulfur battery, and the getter is activated after the melting of sodium in the cartridge is completed. Battery cathode structure. 12. The gas is a nitrogen gas or a carbon dioxide gas, and the getter is a Zr-V-Fe alloy or a Zr-A
The cathode structure of a sodium-sulfur battery according to claim 11, which is an alloy. 13. A sodium-containing solid electrolyte tube in which sulfur is disposed as an anode active material outside a bottomed cylindrical solid electrolyte tube, and sodium contained in a cartridge is disposed as a cathode active material inside.
A sodium-sulfur battery, comprising the cathode structure according to claim 1.