JPH01246772A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To prevent breakage and prolong the lifetime by fixing the end of a solid electrolyte tube, which is inserted in the hollow of a positive electrode conductor, to an insulative ring through a soft metal layer, and thereby relieving the stress applied in the solid electrolyte tube with difference in the coefficient of thermal expansion. CONSTITUTION:By hot press, etc., an Al soft metal layer 9 of approx. 1mm thick is jointed to the joint part of an insulative ring 3 with a solid electrolyte tube 5. Because the internal and external surfaces of this layer 9 receive stresses from the tube 5 and the ring 3, the layer is not in perfect sealed condition, but the vapor of molten sulfur within a positive electrode vessel 2 causes reaction with Al to form an aluminum sulfide layer so as to share sealing function. This suppresses application of stress due to difference in the coefficient of thermal expansion between the conductor M for positive electrode and the tube 5 onto the joint part of the tube 5 with the ring 3, which prevents the tube 5 from breakage and enhances the life of battery.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sodium-sulfur battery, and more particularly to a sodium-sulfur battery that can improve battery life (heat cycle resistance).

(Prior art) Recently, as a secondary battery for electric vehicles and nighttime power storage, it has been developed to be excellent in both performance and economical aspects.
Research and development is progressing on high-temperature sodium-sulfur batteries that operate at ℃.

In other words, in terms of performance, sodium-sulfur batteries have a higher theoretical energy density than lead-acid batteries, have no side reactions such as generation of hydrogen or oxygen during charging and discharging, have a high utilization rate of active materials, and are economically superior to sodium and sulfur batteries. Sulfur has the advantage of being cheap.

A conventional sodium-sulfur battery will be explained based on FIG. 6. In the figure, 2 is an anode container equipped with an anode terminal 1, and 4 is connected to the anode container 2 via an insulating ring 3, and is connected to the anode container 2 through an insulating ring 3. This is a cathode container for storage. Further, 5 is a bottomed cylindrical solid electrolyte tube fixed to the insulating ring 3, and is inserted into the center of the anode conductive material M housed in the anode container 2. A cathode tube 6 penetrates the cathode container 4 and enters the solid electrolyte tube 5, and is provided with a cathode terminal 7 at its outer end.

The insulating ring 3 and the solid electrolyte tube 5 were fused and bonded using glass solder 11.

(Problem to be Solved by the Invention) However, in the conventional sodium-sulfur battery, since the insulating ring 3 and the solid electrolyte tube 5 are firmly connected by the glass solder 11, the insulating ring 3 , due to the difference in the coefficient of thermal expansion of the solid electrolyte tube 5 and the glass solder 11, or the difference in the coefficient of thermal expansion between the solid electrolyte tube 5 and the anode conductive material M, or due to an assembly error between the two. Since stress is concentrated at the upper end, there is a problem that the thin solid electrolyte tube 5 is damaged and the battery life is shortened.

An object of the present invention is to provide a sodium-sulfur solution that can solve the above problems, alleviate stress concentration at the joint between the solid electrolyte tube and the insulating ring, prevent damage to the solid electrolyte tube, and improve battery life. The goal is to provide batteries.

(Means for Solving the Problems) In order to achieve the above object, the sodium-sulfur battery of the present invention has an insulating ring bonded and fixed to an anode container housing a hollow anode conductive material impregnated with sulfur as an anode active material. The insulating ring is provided with a cathode container for storing sodium, and the end of a solid electrolyte tube inserted into the hollow part of the anode conductive material is bonded and fixed to the insulating ring via a soft metal layer. I am taking measures.

(Function) The sodium-sulfur battery of the present invention has stress caused by the difference in thermal expansion coefficient between the insulating ring and the solid electrolyte tube during temperature rise and fall of the battery.
Alternatively, even if stress is generated at the upper end of the solid electrolyte tube due to the difference in thermal expansion coefficient between the conductive material for the anode and the solid electrolyte tube, or due to assembly errors between the two, it is absorbed by the soft metal layer and acts on the solid electrolyte tube. Stress is relieved, its damage is prevented, and battery life is improved.

(Example) Next, an example embodying the sodium-sulfur battery of the present invention will be described with reference to FIGS. 1 to 3.

The sodium-sulfur battery of this embodiment includes an anode container 2 having an anode terminal 1 at the bottom thereof, and an anode container 2 which is housed inside the anode container 2 and is made of carbon fibers or ceramic fibers formed into a mat-like and cylindrical shape. An anode conductive material M impregnated with molten sulfur, which is an anode active material, is connected to the upper end of the anode container 2 via an α-alumina insulating ring 3, and stores molten metallic sodium Na. A tube made of β-alumina is fixed to the inner periphery of the cathode container 4 and the insulating ring 3, and forms a downwardly extending cylindrical bag tube that has the function of selectively transmitting sodium ions, which are the cathode active material. It consists of a solid electrolyte tube 5. In addition, an elongated cathode tube 6 extending through the cathode container 4 to the bottom of the solid electrolyte tube 5 is supported through the center of the upper lid of the cathode container 4, and a cathode terminal 7 is provided at the upper end of the cathode tube 6. It is fixed.

During discharge, sodium ions pass through the solid electrolyte tube 5 through the following reaction and enter the housing space of the anode conductive material M defined by the anode container 2 and the solid electrolyte tube 5, and the inside of the conductive material M. reacts with molten sulfur to form sodium polysulfides, especially finally sodium trisulfide.

2Na +X5-Naz Sx Also, during charging, a reaction opposite to that during discharging occurs, and sodium and sulfur are generated.

A stainless steel wick 8 is filled in the cathode container 4 and the solid electrolyte tube 5 as a safety measure in case the solid electrolyte tube 5 is damaged.

Next, the characteristic structure of the sodium-sulfur battery of the present invention will be explained.

For example, an aluminum soft metal layer 9 is joined to the joint between the insulating ring 3 and the solid electrolyte tube 5 by intervening joining, such as thermo-pressure welding. The thickness of this soft metal layer 9 is usually l11
A certain degree is fine. Since the inner and outer peripheral surfaces of the soft metal layer 9 receive stress from the solid electrolyte tube 5 and the insulating ring 3,
Although the anode container 2 is not completely sealed, the molten sulfur vapor in the anode container 2 reacts with the aluminum to form an aluminum sulfide layer, which functions as a seal.

Now, in this embodiment, the insulating ring 3 and the solid electrolyte tube 5 are
Since the soft metal layer 9 is interposed between them, the difference in thermal expansion coefficient between the insulating ring 3 and the solid electrolyte tube 5 when the temperature of the battery increases or decreases, or the difference between the conductive material M for the anode and the conductive material M inserted into the conductive material M for the anode. Even if stress occurs at the upper end of the solid electrolyte tube 5 due to a difference in thermal expansion coefficient with the solid electrolyte tube 5 or an assembly error between the two, it is absorbed by the soft metal layer 9 and no excessive stress is applied to the solid electrolyte tube 5. Stress concentration can be alleviated, damage to the solid electrolyte tube 5 can be suppressed, and battery life can be improved.

Note that the present invention can also be embodied as follows.

(1) As shown in FIG. 4, the soft metal layer 9 should have an inverted U-shaped cross section. In this embodiment, the stress absorption effect of the soft metal layer 9 is promoted by the connecting portion 9a, so that the stress acting on the solid electrolyte tube can be further alleviated.

(2) As shown in FIG. 5, a stepped portion 3a is provided on the inner peripheral portion of the insulating ring 3, and a soft metal layer 9 is provided on the upper surface of the stepped portion 3a.
The lower surface of the flange portion 5a of the solid electrolyte tube 5 is bonded and fixed via the solid electrolyte tube 5. In this embodiment, since it is easy to apply a pressing force to the insulating ring 3 and the flange portion 5a of the solid electrolyte tube 5,
This has the advantage that the joining work becomes easier.

(Effects of the Invention) As detailed above, the sodium-sulfur battery of the present invention is characterized by stress caused by the difference in thermal expansion coefficient between the insulating ring and the solid electrolyte tube during temperature rise and fall, and stress caused by the difference in thermal expansion coefficient between the anode conductive material and the solid electrolyte tube. This has the effect of suppressing stress due to differences in thermal expansion coefficients from acting on the joint portion of the solid electrolyte tube with the insulating ring, preventing breakage of the solid electrolyte tube, and improving battery life.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged sectional view showing the vicinity of the joint between the insulating ring and the solid electrolyte tube of the sodium-sulfur battery of the present invention;
The figure is a longitudinal sectional view of the central part of a sodium-sulfur battery, FIG. 3 is a sectional view taken along line A-A in FIG. 2, and FIGS. 4 and 5 are partial sectional views showing another embodiment of the present invention, respectively. FIG. 6 is a longitudinal cross-sectional view of the center of a conventional sodium-sulfur battery. 2... Anode container, 3... Insulating ring, 4... Cathode container 5... Solid electrolyte tube, 6... Cathode tube, 9...
Soft metal layer, 9a...Connecting portion, M...Anode conductive material.

Claims (1)

[Claims] 1. An insulating ring (3) is bonded and fixed to an anode container (2) that houses a hollow anode conductive material (M) impregnated with sulfur as an anode active material, and sodium is stored in the insulating ring (3). A cathode container (4) is provided, and the end of the solid electrolyte tube (5) to be inserted into the hollow part of the anode conductive material (M) is inserted into the insulating ring (3) via a soft metal layer (9). A sodium-sulfur battery characterized by being bonded and fixed using