JPH0626135B2 - Sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a sodium-sulfur battery which prevents damage due to joint deformation of a solid electrolyte tube and an insulating plate and improves efficiency in a manufacturing process. Is.

(Prior Art) In recent years, secondary batteries for electric vehicles and night-time power storage have been actively developed. Above all, sodium-sulfur batteries have been regarded as important because they are superior in terms of performance and economy. There is. That is, in terms of performance, the theoretical energy density is higher than that of a lead storage battery, there are no side reactions such as the generation of hydrogen and oxygen during charging and discharging, the utilization rate of the active material is high, and economically, sodium and sulfur are inexpensive. It has the feature.

Such a sodium-sulfur battery is composed of molten sulfur in the anode, molten metal sodium in the cathode, and a solid electrolyte tube made of β-alumina which separates both of them and has a selective permeability for sodium ions. By such a reaction, sodium ions permeate the solid electrolyte and react with sulfur in the anode to produce sodium polysulfide.

2Na + XS → Na ₂ Sx During charging, a reaction opposite to that during discharging occurs, and sodium and sulfur are produced.

The structure of the sodium-sulfur battery is as shown in FIG.
Is an anode terminal, 2 is a cylindrical anode container standing on the upper end of the anode terminal 1, 3 is an α-alumina insulating plate fixed to the upper end of the cylindrical anode container 2, 4 is the insulating plate A cylindrical solid electrolyte tube made of β-alumina that is fixed to the inner end portion of 3 and forms a cylindrical bag tube extending downward, and has a function of allowing sodium ions, which is a cathode acting substance, to permeate.

5 is a cylindrical reservoir (cathode container) fixed to the upper end of the insulating plate 3, 6 is fixed to the center of the upper lid of the reservoir 5, and extends through the reservoir 5 to the bottom of the cylindrical solid electrolyte tube 4. An elongated cathode tube that also serves as the cathode terminal.

Further, 7 is a conductive material for anode such as carbon mat containing sulfur which is an anode acting substance, and 8 is a stainless steel wick impregnated with molten sodium which is a cathode acting substance.

In the structure near the joint between the insulating plate 3 and the solid electrolyte tube 4 of the conventional sodium-sulfur battery, the solid electrolyte 4 is glass-bonded to the insulating plate 3 as shown in FIG. It was joined to the cathode container 2 via.

(Problems to be Solved by the Invention) In the above-mentioned conventional sodium-sulfur battery, the solid electrolyte 4 and the insulating plate 3 are glass-bonded to each other. As a result, there is a problem that the solid electrolyte tube 4 and the insulating plate 3 are damaged from the joint.

Moreover, not only the number of parts of the solid electrolyte tube 4 and the insulating plate 3 of the sodium-sulfur battery becomes two, but also the solid electrolyte tube 4
Since there is a step of glass bonding to the insulating plate 3, there is a problem that the number of steps is increased by one in the manufacturing process and the manufacturing cost is increased.

Constitution of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention is directed to a sodium-containing mounting flange on the upper part of the solid electrolyte tube between the lower end of the cathode container and the upper end of the anode container. In a sulfur battery, the mounting flange on the upper part of the fixed electrolyte tube is integrally formed with β-alumina on the solid electrolyte tube, and the mounting flange is formed on the upper part and / or
Alternatively, the cathode container and / or the anode container is thermocompression-bonded to each other via an insulating plate at the bottom.

(Operation) By adopting the above configuration, it is possible to eliminate the internal stress of the flange mounting portion that has been generated by the glass bonding heat treatment, and to omit the glass bonding process between the solid electrolyte tube and the insulating plate. The cathode container and the anode container can be further joined by thermocompression bonding in the vertical direction with the mounting flange interposed therebetween, so that the cathode container, the anode container and the solid electrolyte tube are firmly joined together, and the expansion during temperature rise and fall, It can sufficiently withstand strain stress due to shrinkage.

(Embodiment) An embodiment embodying the present invention will be described below with reference to FIG.

The structure of the solid electrolyte tube 4 and the joint portion between the solid electrolyte tube 4 and the anode container 2 and the cathode container 5 is the same as that of the conventional sodium-sulfur battery in which the solid electrolyte tube 4 is glass-bonded to the inner peripheral portion of the insulating plate 3. On the other hand, as shown in FIG. 1, a solid electrolyte tube 4 also made of β-alumina, which has an attachment flange 4a made of β-alumina in the upper part, is used integrally.

From the viewpoint of yield and airtightness in the thermocompression bonding process between the solid electrolyte tube 4 and the anode container 2 and the cathode container 5, or between the anode container 2 and the cathode container 5, the maximum thickness of the mounting flange 4a is The length is preferably 1 mm or more and 0.2 times or more the width of the flange portion of the solid electrolyte tube 4.

FIG. 5 shows the ratio of the flange thickness to the flange width and the flange breakage probability. As shown in the figure, it can be seen that a thickness of 0.2 times or more is desirable. This is considered to be the result because the residual stress at the time of joining is affected by the flange width, because the fracture at the time of hot-pressing occurs especially at the time of cooling after the hot-press joining.

Fig. 6 shows the flange thickness and the flange breakage probability. As shown in the figure, it can be seen that a thickness of 1 mm or more is desirable. The heat-pressure bonding usually applies a pressure of 50 to 500 Kg / cm ² , and at this time, if the flange thickness is 1 mm or less, the probability of breakage is high. Since the flange thickness is large, there is no particular problem. However, in practice, if the ratio of the flange thickness to the length of the solid electrolyte bag tube is 20% or more, the surface area where the solid electrolyte and the anode are in contact with each other is reduced, and the volume efficiency and weight efficiency of the battery are reduced. Occurs.

The joint structure between the mounting flange 4a and the anode container 2 is
An α-alumina insulating plate 3a is interposed between both members, and an aluminum plate 9 is interposed between the insulating plate 3a and the flange 4a and between the anode container 2 and the upper and lower parts are joined by aluminum thermocompression bonding. The joint structure of the mounting flange 4a and the cathode container 5 is also formed by an α-alumina insulating plate 3a between the two members, and between the insulating plate 3a and the mounting flange 4a and the cathode container 5. It is formed by joining the upper and lower parts by an aluminum thermocompression bonding method with an aluminum plate 9 interposed therebetween. The aluminum thermocompression bonding can be performed simultaneously above and below the mounting flange 4a.

Other structures are the same as those of the conventional sodium-sulfur battery, 7 is an anode conductive agent filled between the anode container 2 and the solid electrolyte tube 4, and 8 is filled in the solid electrolyte tube 4. A stainless steel wick, 6 is a cathode tube located at the center of the sodium-sulfur battery.

Next, the operation of the sodium-sulfur battery configured as described above will be described.

Since the solid electrolyte tube 4 made of β-alumina having the mounting flange 4a on the upper part is integrated, even if the battery is heated, the difference in the coefficient of thermal expansion between α-alumina and β-alumina and the solid electrolyte are the same as in the conventional case. No thermal strain due to glass bonding between the tube 4 and the insulating plate 3 occurs.

In addition, it is possible to reliably reduce the number of parts and the number of steps in manufacturing a sodium-sulfur battery, and to improve efficiency.

In this embodiment, the α-alumina plate 3a as an insulating material is interposed between the mounting flange 4a and the anode container 2 and between the cathode container 5 to connect the solid electrolyte tube 4 to the anode container 2 and the cathode container 5. Since there was insulation between them, there was no migration of sodium ions at the flange.

The present invention is not limited to the above embodiment, but may be configured as follows.

(1) The joint structure between the mounting flange 4a and the cathode container 5 is
In the above embodiment, an insulating plate 3a made of α-alumina is provided between both members.
The aluminum plate 9 is interposed between the insulating plate 3a and the mounting flange 4a, and between the cathode container 5 and the upper and lower sides by thermocompression bonding.
As shown in the figure, it is also possible to join the mounting flange 4a and the cathode container 5 without interposing the insulating plate 3a and the aluminum plate 9. Even in this case, the object of the present invention can be achieved.

(2) The mounting flange 4a has a flat annular shape in the above embodiment, but as shown in FIG. 3, the mounting flange 4a can be formed thicker on the inner peripheral side and thinner on the outer peripheral side. . In this case, the anode container 2 and the cathode container 5 are configured to engage with the thinly formed portion on the outer peripheral side of the mounting flange 4a. In this way, the attachment of the anode container 2 and the cathode container 5 to the mounting flange 4a is accurate and reliable. The thickness of the thin portion on the outer peripheral side of the mounting flange 4a is preferably 1 mm or more.

(3) By making the thickness of the mounting flange 4a thicker than that of the embodiment as shown in FIG. 4, the mounting flange 4a and the anode container 2 and the cathode container 5 can be directly engaged with each other. it can.

In this case, since the battery voltage is applied to the upper and lower surfaces of the flange portion, polarization of Na ⁺ ions occurs and the airtightness of the thermocompression bonded portion is deteriorated. FIG. 8 shows the airtightness when a heat cycle is performed when a voltage is applied.

In the test method, the He leak rate was measured after one thermal cycle between room temperature and 350 ° C. was performed while applying 2 V to the cathode and anode containers of the thermocompression bonded one as shown in FIG.

In all the tests, a He leak rate of 10 ^-9 or less was used.

As can be seen from FIG. 8, the flange thickness is preferably 5 mm or more.

(4) Further, as shown in FIGS. 1 to 4, the lower end of the cathode container 5 and the upper end of the anode container 2 are in the shape of flanges bent inward. It is free to change it in accordance with 4a at any time. Also,
It is not necessary to form the upper end of the anode container 2 and the lower end of the cathode container 5 in a flange shape particularly if the side walls of the anode container 2 and the cathode container 5 are formed thick and a margin for pressure bonding to the mounting flange 4a can be taken.

EFFECTS OF THE INVENTION The sodium-sulfur battery of the present invention has a solid electrolyte tube integrally formed with a β-alumina mounting flange so that the solid electrolyte tube and the mounting flange are not glass-bonded to each other. And, it is possible to eliminate the internal stress in the vicinity thereof, and the reliability is improved while preventing the damage at the joint between the mounting flange and the solid electrolyte tube and the vicinity thereof caused by the thermal strain due to the heating and cooling of the battery, and The number of parts and the number of steps in the manufacturing process of the sodium-sulfur electric field can be reduced, and the cost required for manufacturing can be reduced.

Further, since the cathode container and the anode container are thermocompression bonded via the mounting flange, the cathode container, the anode container and the solid electrolytic tube are firmly joined together, and distortion due to expansion and contraction during temperature rise and fall. Even if a stress is generated, damage to these members and the vicinity of these members is prevented, and reliability is improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of the sodium-sulfur battery of the present invention, and FIGS. 2 to 4 are longitudinal sectional views of an essential part showing another example of the sodium-sulfur battery of the present invention. Fig. 5 is a graph showing the ratio of flange thickness to flange width and flange breakage probability, Fig. 6 is a graph showing the relationship between flange thickness and flange probability, and Fig. 7 shows the voltage between the anode container and the cathode container. FIG. 8 is a vertical cross-sectional view showing the applied state, FIG. 8 is a graph showing the relationship between the flange thickness and He leak rate, FIG. 9 is a vertical cross-sectional view showing a conventional sodium-sulfur battery, and FIG. It is a principal part longitudinal cross-sectional view of a sodium-sulfur battery. 2 ... Anode container, 4 ... Solid electrolyte tube, 4a ... Mounting flange, 5 ... Anode container.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Kato 1-1-1, Nakamaru-cho, Kita-ku, Nagoya-shi, Aichi (56) Reference JP-A-62-26767 (JP, A) JP-A-57-187875 (JP) , A) Japanese Patent Publication Sho 61-41102 (JP, B2)

Claims (2)

[Claims] 1. A sodium-sulfur battery in which a mounting flange (4a) above a solid electrolyte tube (4) is arranged between the lower end of a cathode container (5) and the upper end of an anode container (2). 4) The upper mounting flange (4a) is integrally molded with the solid electrolyte tube (4) by β-alumina, and the mounting flange (4a) is attached to the upper and / or lower part of the solid electrolyte tube (4) via an insulating plate (9) to form a cathode container. (5) and / or the anode container (2) is thermocompression bonded, a sodium-sulfur battery. 2. The sodium-sulfur battery according to claim 1, wherein the mounting flange (4a) has an annular shape or an annular shape in which the outer peripheral side is thin and the inner peripheral side is thick.