JPS59194366A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To limit flow out of sodium to increase safety when an inner container is broken by sealing inactive gas in a gap between an inner container which is an anode constructor and the outer container, and forming a sodium connecting path in an opposite U-shape in the inner container. CONSTITUTION:In a battery using molten sodium as anode active material, molten sulfur-sodium polysulfide as cathode active material, and a solid electrolyte tube 21 which is sodium ion conductive as electrolyte, a closed gap A is installed between a container 26 which is an anode constructor and an outer container 27, and a substance which generates inactive gas by heat decomposition under larger pressure than gas pressure of the inner container 26 is filled in this gap, and an opposite U-shaped sodium connecting path 28 is formed in a bottom cover 29 of the inner container 26. Flow out of sodium, when a battery is broken, is limited by gas pressure inside the gap A and the opposite U-shaped sodium connecting path 28. Therefore, safety of the battery is increased.

Description

Detailed Description of the Invention The present invention uses molten sodium as a cathode active material, molten sulfur-sodium polysulfide as an anode active material, and a sodium ion conductive solid electrolyte tube as an electrolyte.
It concerns sulfur batteries and aims to improve safety.

j) Lithium-sulfur batteries are made of sodium ion conductive bottomed solid electrolyte tubes, such as β-alumina, β′-alumina,
Separate the above-mentioned active materials using Nasicon etc. and
This is a secondary battery that operates at a high temperature of 400'C.

The conventional sodium-sulfur battery has the structure shown in Fig. 1, and even if the solid electrolyte tube 1 is damaged, the amount of direct sodium-sulfur reaction can be suppressed to some extent. When the battery is subjected to various battery destruction tests, in addition to the destruction being completed within the battery and a bulge occurring in the battery container 5, a hole is formed in the battery container 5 and the active material leaks, causing a thermal effect on adjacent batteries. The safety and reliability have decreased. That is, even if the solid electrolyte tube 1 is damaged, the heat generated when sodium and sulfur react directly due to the damage will destroy the outer container 9 and the inside of the inner container 8 and the solid electrolyte tube 1. The reason for this is that the scale of destruction varies depending on the stop time and stop state when stopping the supply of sodium from the inner container 8 through the sodium communication path 10 by making the gap between Met.

In addition to the above-mentioned destruction, in the structure shown in Fig. 1, the inner container 8 and the outer container 9 are in communication, so when filling the container sodium into the inner container 8, it is necessary to fill the gap between the containers.) If the IJum is filled inadvertently, or if it is difficult to fill a certain amount of sodium, the battery performance may deteriorate, such as when the specified amount of sodium cannot be filled, resulting in less sodium contributing to the battery reaction. had.

The present invention eliminates the above-mentioned drawbacks and will be explained in detail by way of examples. FIG. 2 shows a battery sectional view of the cathode structure of the embodiment. 21 is a solid electrolyte tube made of β'-alumina whose upper end is polished to obtain a constant diameter and whose bottom is rounded, and 22 is a lower part. Solid electrolyte tube 2 in the groove of
A fixing member made of an electrically insulating material such as α-alumina into which the open end of 1 is inserted and sealed airtight and liquid-tight with glass solder, 23 a cathode cover made of a sodium-resistant metal such as stainless steel, and 24 a fixing member. A cathode auxiliary cover 2 made of aluminum-coated steel bonded to the upper surface of the member 22 by heat and pressure;
5 is a melt-resistant sodium metal fiber, such as stainless steel fiber, which is arranged in a compressed state between the cathode structure and the cathode lid 23 and impregnated with sodium to provide good electrical contact;
6 is an inner container filled with sodium and made of stainless steel with a wall thickness of 600 to 900μ, and 27 is a wall thickness of 60 to 500μ.
The inner container 26 and the outer container 27 are completely isolated from each other, and the mA is sealed between them.

Reference numeral 28 denotes a sodium communication path made of a sodium-resistant metal, such as a stainless steel tube, which has an inverted U-shape inside the inner container 26, and has one end connected to the cathode structure from the bottom 29, and the other end connected to the bottom cover 29. Located approximately 0.5-1.5+* away from the inner surface. Further, the mA is filled with an inert gas or a gasified substance that is thermally decomposed under reduced pressure to generate an inert gas before welding.

Regarding the battery of the present invention having the above structure, when the battery operating temperature is raised to approximately 350°C, discharged, and then charged, the solid electrolyte tube 21 cracks due to application of an overvoltage that exceeds the charging end voltage of approximately 6V. was generated and destroyed. The gas pressure P1 in the gap between the outer container 27 and the inner container 26 is determined by adjusting the gas pressure or space volume, etc. at the time of creating the rigid structure so that PI>P2 with respect to the maximum gas pressure P2 in the inner container 26. Adjust. In the @polar operation leading to the above-mentioned destruction, cracks occur in the solid electrolyte tube 21, causing a direct reaction between sodium and sulfur, and generating an enormous amount of heat. This amount of heat generated damages the outer container 27 by making a hole in the vicinity of the crack. When the outer container 27 is destroyed, the inert gas in the gap between the outer container 27 and the inner container 26 is released into the solid electrolyte tube 2.
1 and the cathode structure (the outer surface of the outer container 27). Since this gas pressure is higher than the gas pressure in the inner container 26, the sodium supply from the inner container 26 through the sodium communication passage 28 is stopped, and conversely, the sodium communication is carried out so as to push out the molten sodium in the interval @A. The molten sodium was caused to flow into the inner container 26 through the passage 28, and the molten sodium between A and A was discharged to drastically reduce the amount of sodium that directly reacts with the molten sulfur, thereby reducing the scale of destruction.

That is, when this battery was destroyed by applying overvoltage in a charging test, there was a voltage fluctuation at the battery voltage of about 7V, and the battery voltage became OV at about 15.4V. Power was cut off approximately 60 minutes after the voltage reached Ov, but the battery temperature rose by only 50°C on the side of the battery container (maximum temperature 4
01°C). After further cooling at 350° C. for 24 hours, the battery was disassembled and inspected, and the surface of the battery container was found to have hardly any discoloration. In addition, sodium remained in the solid electrolyte tube 21 in an area approximately 10 meters below the crack occurrence point, but at the crank point and the outer container 9.
There was almost no sodium in the castle above the damaged area, and the inner container 8' was filled with it.

Furthermore, since the sodium communication passage 28 in the present invention has an inverted U-shape, molten sodium enters from the internal opening of the sodium communication passage 28 near the top surface of the bottom cover 29, moves in the sodium communication passage 28, and is transferred to the outside. Once the molten sodium flows out from the opening, the gas pressure within the inner container 26 continues, even if slightly, due to the siphon principle, causing the molten sodium to move. Therefore, since the gas pressure inside the inner container 26 can also be reduced, the pressure inside the cathode chamber at the time of battery damage can be reduced to, for example, 1 atmosphere or less, and battery damage due to internal pressure can be prevented.

As described above, the present invention provides a gap between the inner container and the outer container, which are cathode components, and fills the gap with an inert gas or a substance that is gasified by thermal decomposition. By providing an inverted U-shaped sodium communication path in the bottom cover that communicates with the chamber, the outflow of sodium when the inner container is destroyed is restricted by the gas pressure and the inverted U-shaped sodium communication path, and the battery It has improved potability,
Its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional sodium-sulfur battery, and FIG. 2 is a longitudinal sectional view of a sodium-sulfur battery according to an embodiment of the present invention. 1.21...Solid electrolyte tube, 8,26...Inner container, 9.27...Outer container, 10,28...IJum communication path. Applicant Yuasa Battery Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1) An inner container filled with sodium is covered with an outer container and integrally welded with a bottom cover provided with an end of an inverted U-shaped sodium communication path that connects the inner container and the cathode chamber. The +A electrode is used to seal the gap between the inner container and the outer container, and fill the gap with an inert gas, or to fill it with a gasified substance that thermally decomposes at a temperature below or above the battery operating temperature to release an inert gas. A sodium-sulfur battery in which a component is inserted into a solid electrolyte tube. 2) An IJ Umu sulfur battery according to claim 1, in which the gas pressure in the gap is higher than the gas pressure in the inner container.