JPH0675408B2 - Sodium-sulfur battery - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to sodium-sulfur batteries, and more particularly to a reduction in the extent of battery damage associated with the expanding structure of the anode lid.

2. Description of the Related Art Sodium-sulfur batteries have a completely sealed structure in which sodium as a cathode active material and sulfur as an anode active material are separated by a sodium ion conductive solid electrolyte tube such as β ″ -alumina. In the conventional structure of this sodium-sulfur battery, the α-alumina ring 2 is glass-soldered to the upper end of the solid electrolyte tube 1 as shown in FIG. The cathode lid 3 and the anode lid 4 are thermocompression bonded to the upper surface and the lower surface, respectively.
A cathode terminal 5 is welded to the cathode lid 3, a cathode pipe 6 is welded through the central portion thereof, and the lower portion is inserted into the solid electrolyte tube 1. Inside this solid electrolyte tube 1, metal fibers 7 are arranged, and while keeping the temperature at about 150 ° C., vacuum filled with sodium 8 melted at the same temperature after evacuation from the cathode pipe 6, and the upper end of the filled cathode tube 6 is filled. Are sealed. Such a structure is inserted into a battery case 9 which also functions as an anode current collector in which a cylindrical sulfur molded body 10 is inserted, and is welded to the anode lid 4 in a vacuum to form a completely sealed structure. To be done. In the conventional sodium-sulfur battery as described above, since the solid electrolyte tube 1 is firmly bonded to the α-alumina ring 2, the heat of the sulfur molded body 10 is increased during the process of raising the temperature of the battery to 350 ° C. Due to the expansion, the solid electrolyte tube 1 may be subjected to bending stress, and the solid electrolyte tube 1 may be broken at the glass joint.

When such damage to the solid electrolyte tube 1 occurs, sulfur and sodium directly react with each other, increasing the internal pressure in the battery (about 10
Atmospheric pressure), when the joint portion of the cathode lid 3 cannot withstand the internal pressure, the cathode lid 3 peels off from the α-alumina ring surface and pops out. When the cathode lid 3 came off, substances inside the battery, such as sulfur, sodium, graphite felt, metal fibers, and solid electrolyte tube pieces, jumped out and adhered to the upper part of the adjacent battery, causing an electrical short circuit and secondary damage.

An object of the present invention is to solve the above problems by making the connection between the anode lid and the battery case flexible and increasing the internal pressure when the solid electrolyte tube is broken by welding between the upper end of the battery tank and the anode cover. It is an object of the present invention to absorb by expansion and deformation of the battery case auxiliary lid and the anode auxiliary lid and prevent the cathode lid from falling off.

Structure of the Invention In the sodium-sulfur battery of the present invention, the anode auxiliary lid A is welded to the anode lid 4'which is thermocompression-bonded to the lower surface of the α-alumina ring 2 as shown in the enlarged view of the main part of FIG. The battery case auxiliary lid B is welded to the upper end of 9, and the anode auxiliary cover A and the battery case auxiliary lid B are welded.

Examples Hereinafter, examples will be described. FIG. 2 is an enlarged cross-sectional view of the essential parts of the sodium-sulfur battery of the present invention.

After filling the inside of the solid electrolyte tube 1 made of β ″ -alumina tube having an outer diameter of 46 mm and a length of 400 mm with iron fiber 7 (fiber diameter of about 10 to 20 μm) with a porosity of 94.5%, the cathode current collector 6 (outer (Diameter 8 mm, inner diameter 4 mm) is arranged.The cathode terminal 5 is provided on the upper end of the cathode current collector 6.
After screwing, the cathode lid 3 and the cathode terminal 5 were welded. Subsequently, the electric insulating materials 11 and 12 (made of α-alumina or asbestos) are arranged on the cathode lid 3, and the anode lid 4 ′ having a rising portion on the outside has a concave section inside the outside rising portion. The auxiliary lid A (0.5 mm thick Al-coated Fe) is welded as shown in the figure, and the outside of the battery case auxiliary lid B (0.5 mm-thick Al coated Fe) having a concave cross section inside the upper end of the battery case 9 The rising portion was welded as shown, and the inside rising portion of the anode auxiliary lid A and the inside rising portion of the battery case auxiliary lid B were welded. Further, the outside of the auxiliary lid B was welded to the upper end of the battery case. Then, while keeping the temperature at about 150 ° C., the solid electrolyte tube 1 and the upper space are evacuated through the cathode terminal 5 and the cathode current collector 6 to impregnate sodium 8 in a vacuum and the upper end of the cathode terminal 5 is welded to hermetically seal the cathode chamber. did. Furthermore, sulfur molded body 10
After being inserted into this battery container from the bottom, a bottom lid 13 was fitted and welded in a vacuum state to manufacture a sodium-sulfur battery.

We manufactured 10 cells of each of the conventional structure and the invention structure, and confirmed the effects by a battery breakdown test (overcharging at 350 ° C until the battery voltage drops sharply) and a heat cycle test (room temperature ⇔ 350 ° C). After 10 cycles in the heat cycle test, a battery destruction test was carried out when the battery was not damaged. The results are shown in Table 1.

The number on the left side of the number of damaged batteries in () is the number of protrusions of the cathode lid, the number on the right side is the number of protrusions, and the number on the right side is the number of batteries without protrusion.

As shown in Table 1, the battery according to the present invention can sufficiently withstand the heat cycle test. This is because the anode auxiliary lid A and the battery case auxiliary lid B alleviate the bending stress of the solid electrolyte tube 1 due to the thermal expansion of the sulfur molding 10 and prevent the breakage at the glass solder joint.

As for the state of damage to the battery according to the present invention, the auxiliary anode cover A and the auxiliary battery case lid B swelled and pressed the electric insulating material 11 to prevent the cathode cover 3 from peeling off and preventing an electrical short circuit between the cathode and the anode. . Therefore, the substance inside the battery was not scattered to the outside. On the other hand, in many conventional batteries, the cathode lid was peeled off and the contents were scattered.

Effect of the Invention As described in detail in the examples, in the sodium-sulfur battery of the present invention, even if the solid electrolyte tube is damaged due to mechanical stress or the like applied to the solid electrolyte tube, the content of the battery scatters to the outside of the battery and is adjacent to the battery. It does not deposit on the upper part of the battery to cause an electrical short circuit and destroy other batteries. Furthermore, the structure is highly reliable against heat cycles. The anode auxiliary lid A and the battery case auxiliary lid B according to the present invention have a thickness of about 0.3 mm to about 0.7 mm so that they can be easily deformed, and materials such as chrome-diffused iron, chrome-diffused stainless steel, stainless steel, and aluminum-coated iron are suitable. Is.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a conventional sodium-sulfur battery, and FIG.
The figure is an enlarged cross-sectional view of a main part of the sodium-sulfur battery of the present invention. 1 ... Solid electrolyte tube, 2 ... Alumina ring 3 ... Cathode cover 4, 4 '... Anode cover 5 ... Cathode terminal, 6 ... Cathode current collector 7 ... Metal fiber, 8 ... Sodium 9 …… Battery case, 10 …… Sulfur molded body 11 …… Electrical insulation material, 12 …… Electrical insulation material A …… Anode auxiliary lid, B …… Battery case auxiliary lid

Claims (2)

[Claims] 1. A sodium ion conductive solid electrolyte tube is used as a cathode chamber, the outside of the tube is used as an anode chamber, and an α-alumina ring is glass-soldered to the upper end of the tube and the α-alumina ring is used. A cathode cover and an anode cover are bonded to the upper and lower surfaces of the alumina ring by thermocompression bonding, and the cathode chamber is sealed by welding the cathode terminal to the cathode cover, and auxiliary is provided between the anode cover and the upper end of the battery case. In a sodium-sulfur battery in which the anode chamber is sealed by welding the lid, the auxiliary lid comprises an anode auxiliary lid having a concave cross section and a battery case auxiliary lid, and the anode lid has a rising portion on the outside. Then, the outer rising part of the anode auxiliary lid is welded to the inside of the rising part, and the outer rising part of the battery case auxiliary lid is welded to the inside of the upper end of the battery case. And the above A sodium-sulfur battery characterized in that the anode chamber is sealed by welding the inner rising portion of the auxiliary tank lid. 2. The sodium-sulfur battery according to claim 1, wherein an electric insulating material is arranged between the anode auxiliary lid and the cathode lid.