JPH0665073B2 - Sodium-sulfur battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sodium-sulfur battery capable of improving safety when a solid electrolyte tube is broken.

[Prior Art] As shown in FIG.
Cylindrical anode container 1 containing a conductive material M for anode such as carbon mat impregnated with molten sulfur S which is an anode active material 1
And a cathode metal fitting 3 connected to the upper end of the anode container 1 via an insulating ring 2 made of α-alumina, and fixed to the inner peripheral portion of the insulating ring 2 and is a cathode active material. Stores molten metal sodium Na, sodium ion N
There is also provided a bottomed cylindrical solid electrolyte tube 4 made of polycrystalline β ″ -alumina having a function of selectively transmitting a ^+, and the inside of the battery by the solid electrolyte tube 4. Is divided into an anode chamber R1 and a cathode chamber R2, a sodium container 5 for storing sodium is housed inside the cathode chamber R2, and sodium is allowed to flow in and out through a small hole 5b provided in the bottom portion 5a. further,
Between the sodium container 5 and the solid electrolyte tube 4, a bottomed cylindrical sodium holder 11 made of a stainless steel wick is housed.

Then, at the time of discharge, sodium discharged from the small holes 5b of the sodium container 5 is once impregnated into the sodium holder 11, and then sodium ions Na ⁺ from the cathode chamber R2 permeate the solid electrolyte tube 4 and sulfur in the anode chamber R1. It reacts with S as follows to form sodium polysulfide.

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

When the solid electrolyte tube 4 is damaged due to deterioration or thermal stress and cracks, for example, metallic sodium in the cathode chamber R2 reacts with sulfur in the anode chamber R1 in a large amount and rapidly to generate abnormally high heat. However, there was a problem that the entire battery was destroyed and, as a result, sodium leaked out and was dangerous. In order to solve this, in the above conventional example, the sodium container 5 and the sodium holder 11 are provided in the cathode chamber R2.

[Problems to be Solved by the Invention] However, in the conventional safety measures for batteries, the small hole 5b of the sodium container 5 and the solid electrolyte tube 4 are close to each other, and the solid electrolyte tube 4 is damaged near the small hole 5b. At that time, the sodium outflow pressure from the sodium container 5 was high, so that the reaction amount of the active material was large and the safety was insufficient.

Further, since the gap between the solid electrolyte tube 4 and the sodium container 5 accommodates the sodium holder 11, the amount of sodium existing in the entire gap is large, and the reaction amount of the active material when the solid electrolyte tube 4 is damaged. However, safety was insufficient from this point as well.

Furthermore, when the solid electrolyte tube 4 is damaged, the sodium holder 11 has no mechanical strength, and the sodium container 5 is easily damaged together. If damaged, a large amount of sodium in the container 5 reacts with sulfur and the battery is destroyed. There was a problem that

Further, since the sodium holder 11 made of stainless wick is used, the small hole 5b of the sodium container 5 is used.
It was not possible to move the sodium from the
There is also a problem that the discharge characteristics of the battery deteriorate.

An object of the present invention is to reduce the sodium pressure on the surface of the solid electrolyte tube by increasing the distance between the sodium small holes of the sodium container and the solid electrolyte tube, and to reduce the amount of sodium in contact with the solid electrolyte tube by the bottomed safety tube. In addition, it is possible to prevent damage to the sodium container and ensure safety,
Another object of the present invention is to provide a sodium-sulfur battery that can smoothly move sodium and obtain stable charge / discharge characteristics.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides, inside the cathode chamber side of a bottomed bag-shaped solid electrolyte tube for partitioning the anode chamber and the cathode chamber,
A sodium container containing metal sodium is housed, a small hole is formed through the bottom of the sodium container, and an upper pressure chamber inside the sodium container is filled with an inert gas for pressurizing the metal sodium. A bottomed bag-shaped safety tube is housed between the solid electrolyte tube and the sodium container, and the space between the inner peripheral surface of the safety tube and the outer peripheral surface of the sodium container and the outer peripheral surface of the safety tube and the inner peripheral surface of the solid electrolyte tube. Means are provided between the surface and the surface so as to provide an inner gap and an outer gap for vertically guiding the metallic sodium flowing in and out of the small holes when the battery is charged and discharged.

In the present invention, the inner gap may be set to 0.1 to 1 mm and the outer gap may be set to 0.1 to 0.5 mm.

Further, in the present invention, a biasing member for pressing the sodium container toward the bottom side of the safety pipe may be arranged in the cathode chamber.

[Operation] In the present invention, since the safety pipe exists between the sodium container and the solid electrolyte pipe, and the inner gap and the outer gap are provided on both inner and outer sides thereof, the distance from the small hole of the sodium container to the solid electrolyte pipe is Since the pressure of sodium decreases as the length increases, the reaction between sodium and sulfur is suppressed even if the solid electrolyte tube is damaged, and safety is improved.

Also, if the solid electrolyte tube is broken, a reaction between a small amount of sodium and sulfur inside the outer gap occurs, but thereafter, sodium must climb over the upper edge of the safety tube, thus suppressing the reaction between the active materials, Moreover, since the sodium container is protected by the safety pipe, damage to the sodium container is prevented, and the safety is improved from this point as well.

Furthermore, the sodium flowing out of the small holes of the sodium container moves upward in the inner gap and then moves from the upper edge of the safety pipe to the outer gap, so that the sodium flow is less than that in the case of using the stainless steel wick. And become smooth,
Therefore, the sodium is uniformly supplied to the inner peripheral surface of the solid electrolyte tube, and the discharge characteristics are stabilized.

The inner gap is 0.1 to 1 mm, and the outer gap is 0.1 to 0.
When it is set to 5 mm, the amount of sodium in both gaps is small, so that the reaction between sodium and sulfur is easily suppressed.

When a biasing member that presses the sodium container toward the bottom side of the safety tube is arranged in the cathode chamber, even if most of the sodium flows out of the container and the whole becomes lightweight, it prevents the floating of the container. The gap between the bottom and the bottom of the safety pipe is kept constant, and a stable supply of sodium is performed.

Embodiment An embodiment embodying the present invention will be described below with reference to FIGS. 1 and 2.
It will be described with reference to the drawings.

In the sodium-sulfur battery of this example, the lower surface of an insulating ring 2 made of α-alumina is thermocompressively bonded to the upper end surface of an anode container 1 having a bottomed cylindrical shape, and the upper surface of the insulating ring 2 has a cathode. The metal fitting 3 is thermocompression bonded. Further, the upper outer peripheral surface of the solid electrolyte tube 4 made of β ″ -alumina is joined and fixed to the inner peripheral surface of the insulating ring 2.

In the anode chamber R1 formed between the anode container 1 and the solid electrolyte tube 4, a conductive material M for anode such as carbon mat impregnated with molten sulfur S as an anode active material is housed. In addition, the cathode chamber R formed inside the solid electrolyte tube 4
Inside 2, a sodium container 5 having a cylindrical shape with a lid and a bottom for storing metallic sodium Na as a cathode active material is housed. The bottom surface 5a of the sodium container 5 is provided with a small hole 5b through which sodium flows in and out. Further, an inert gas such as nitrogen gas or argon gas is sealed at a predetermined pressure in the pressurizing chamber R3 in the upper closed space of the sodium container 5 so that sodium always flows out from the small hole 5b to the outside. Pressurized. Further, the liquid level of sodium in the sodium container 5 is completely discharged from the inside of the sodium container 5 at the position shown by the solid line in FIG. 1 when the charging is completed, and when the discharge is completed, as shown by the chain line in FIG. I try to stop at a position where it does not end up. During the charging process, sodium smoothly flows into the container 5.

If the safety pipe 6 described below is damaged due to some cause, it is dangerous for the sodium container 5 to melt and rupture the container 5 in which a large amount of sodium is stored. Steel (SUS30
It is formed by 4).

Further, the diameter of the small holes 5b is set to 2 mm or less, because this is because the flow rate of sodium is appropriately suppressed experimentally.

Further, a safety tube 6 having a bottomed tubular shape is arranged between the inner peripheral surface of the solid electrolyte tube 4 and the outer peripheral surface of the sodium container 5, and the outer peripheral surface of the sodium container 5 is An inner gap G1 is formed between the inner peripheral surface of the safety pipe 6 and an outer gap communicating with the inner gap G1 at the upper end between the outer peripheral surface of the safety pipe 6 and the inner peripheral surface of the solid electrolyte pipe 4. A gap G2 is formed, and the safety pipe 6 is made of a metal having excellent sodium resistance, for example, aluminum, aluminum alloy, or stainless steel.

Since it is as described above, the small hole 5b of the container 5 at the time of discharge
The sodium flowing out from the inside moves upward in the inner gap G1, then moves over the upper end edge of the safety pipe 6 and moves downward in the outer gap G2, permeates the solid electrolyte pipe 4 as sodium ions and permeates into the anode chamber R1. Moving. Further, during charging, sodium moves in the opposite direction to the above and is stored in the sodium container 5.

The inner gap G1 is 0.1 to 1 mm, preferably 0.15
mm, the outer gap G2 is 0.1 to 0.5 mm, preferably 0.
It is set to 3 mm. From the viewpoint of safety, it is better to make both the gaps G1 and G2 as small as possible so as to reduce the amount of sodium, but it is difficult to be less than 0.1 mm due to technical restrictions, and if it is too narrow, the pressure loss becomes too high. The supply of sodium to the surface of the solid electrolyte tube 4 becomes unstable. The inner gap G1 and the outer gap G2 must be set within the above range in consideration of safety, although it is necessary to consider the shape of the battery or the operating conditions (sodium moving speed: discharge current).

A flow rate control plate 7 is interposed between the bottom surface 5a of the sodium container 5 and the bottom surface of the safety pipe 6 to control the flow rate (pressure) of sodium flowing out from the small hole 5b. As the flow rate control plate 7, for example, a disc-shaped wire net made of aluminum or stainless steel may be used, or a stainless wick or felt may be used.

As the battery discharges, the sodium in the sodium cartridge 5 flows out, the container 5 becomes lighter, and when it floats up, the gap between the bottom surface 5a of the container 5 and the upper surface of the bottom portion 6a of the safety pipe 6 becomes large, which causes a safety problem. Occurs. Therefore, an urging member 8 such as a spring washer is interposed between the sodium container 5 and the cathode fitting 3, and the container 5 is urged toward the flow rate control plate 7 to keep the gap constant. keeping.

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

Now, when the sodium-sulfur battery is fully charged,
Most of the sodium is stored in the sodium container 5 as shown by the solid line in FIG. 1, and molten sulfur is present in the anode conductive material M.

When the discharge is started in this state, the pressure in the pressurizing chamber R3 causes the sodium in the container to move into the inner gap G1 through the small holes 5b. After that, from the upper edge of the safety pipe 6 to the outer gap G
2 is introduced into the solid electrolyte tube 4, and sodium is converted into sodium ions and permeates the solid electrolyte tube 4, and reacts with sulfur in the anode conductive material M to generate sodium polysulfide.

In the embodiment of the present invention, the safety pipe 6 is present between the sodium container 5 and the solid electrolyte pipe 4, and the inner gap G1 and the outer gap G2 are provided on both inner and outer sides thereof. Since the distance from 5b to the solid electrolyte tube 4 becomes long and the pressure of sodium becomes low, even if the solid electrolyte tube 4 is damaged, the rapid and large amount of reaction between sodium and sulfur is suppressed, and the safety is improved.

Further, even if the solid electrolyte tube 4 is damaged, a reaction between sodium and sulfur inside the outer gap G2 occurs, but thereafter, sodium has to climb over the upper edge of the safety tube 6, and thus the reaction between the active materials is suppressed. Moreover, since the sodium container 5 is protected by the safety pipe 6, the sodium container 5 is prevented from being damaged, and the safety is improved also from this point.

Further, since sodium that has come out of the small holes 5b of the sodium container 5 moves upward in the inner gap G1 and then moves from the upper end edge of the safety pipe 6 to the outer gap G2, compared with the case where a stainless steel wick is used, The flow of sodium becomes uniform and smooth, so that the supply of sodium to the inner peripheral surface of the solid electrolyte tube 4 becomes uniform and the discharge characteristics become stable.

The present invention can be embodied as follows.

As shown in FIG. 3, with respect to the upper surface of the bottom portion 6a of the safety pipe 6,
A locking projection 6b for locking the bottom 5a of the sodium container 5 is provided so that a predetermined gap is formed between the lower surface of the bottom 5a and the upper surface of the bottom 6a, or as shown in FIG. The bottom portion 6a of the safety pipe 6 is provided with a groove 6c that allows movement of metallic sodium, and although not shown, a groove is formed on the lower surface of the bottom portion 5a of the sodium container 5.

[Effects of the Invention] As described in detail above, the invention according to claim 1 reduces the sodium pressure on the surface of the solid electrolyte tube by increasing the distance between the sodium small holes of the sodium container and the solid electrolyte tube, Moreover, the amount of sodium in contact with the solid electrolyte tube can be reduced by the bottomed safety tube, and the sodium container can be prevented from being damaged to ensure safety, and the sodium can be smoothly moved to obtain stable charge / discharge characteristics. There is an effect that can be.

Further, the invention according to claim 2 can further improve the safety by reducing the amount of sodium in both gaps.

Further, according to the invention of claim 3, even if most of the sodium flows out of the container and becomes lighter in weight, the sodium is prevented from rising and the gap between the bottom of the container and the bottom of the safety pipe is kept constant, thereby ensuring stability. There is an effect that the discharge characteristics can be further improved by supplying the generated sodium.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a central portion showing an embodiment of a sodium-sulfur battery embodying the present invention, and FIG. 2 is A- of FIG.
A sectional view taken along the line A, FIGS. 3 and 4 are partial perspective views showing another example of the present invention, and FIG. 5 is a central longitudinal sectional view showing a conventional example. 1 ... Anode container, 2 ... Insulation ring, 3 ... Cathode metal fittings,
4 ... Solid electrolyte tube, 5 ... Sodium container, 6 ... Safety tube, 7 ... Flow control plate, 8 ... Energizing member, M ... Anode conductive material, R1 ... Anode chamber, R2 ... Cathode chamber, R3 ...
Pressurization chamber

Claims (3)

[Claims] 1. A sodium container (5) for containing metallic sodium inside a cathode chamber (R2) side of a bottomed bag-shaped solid electrolyte tube (4) for partitioning an anode chamber (R1) and a cathode chamber (R2). The bottom (5) of the sodium container (5)
a) is provided with a small hole (5b), and an upper pressurizing chamber (R3) inside the sodium container is filled with an inert gas for pressurizing the metallic sodium, and the solid electrolyte tube (4) and sodium are further added. A bottomed bag-shaped safety pipe (6) is housed between the safety pipe (6) and the container (5), and between the inner peripheral surface of the safety pipe (6) and the outer peripheral surface of the sodium container (5) and the safety pipe (6). Between the outer peripheral surface of the solid electrolyte tube and the inner peripheral surface of the solid electrolyte tube (4), an inner gap (G1) and an outer gap that vertically guide the metallic sodium flowing in and out of the small hole (5b) during charging and discharging of the battery. A sodium-sulfur battery provided with (G2). 2. The sodium-sulfur battery according to claim 1, wherein the inner gap (G1) is set to 0.1 to 1 mm and the outer gap (G2) is set to 0.1 to 0.5 mm. 3. The sodium-sulfur battery according to claim 1, wherein a biasing member (8) for pressing the sodium container (5) toward the bottom side of the safety pipe (6) is arranged in the cathode chamber (R2).