JPH0766831B2 - Sodium-sulfur battery - Google Patents

Description

The present invention relates to a sodium-sulfur battery, and more particularly to a high safety battery structure in which the direct reaction amount of sodium and sulfur is suppressed. The sodium-sulfur battery can be used as a power source as a normal battery, and is also suitable for storing surplus power at night.

[Prior Art] In a conventional sodium-sulfur battery, sodium which is a cathode active material is arranged on the inner diameter side of a bag-shaped solid electrolyte, and sulfur or a polysulfide substance which is an anode active material is arranged on the outer diameter side. Become. Should the solid electrolyte be damaged during operation, sodium and sulfur mix and react directly. As a result, there is a possibility that the temperature and pressure rise suddenly and the battery container is damaged. Therefore, various measures have been taken to alleviate the rapid reaction between sodium and sulfur even if the solid electrolyte is damaged.

The structure of a conventional sodium-sulfur battery (for example, Japanese Patent Application No. 58-28540) will be described in detail with reference to FIG.

In FIG. 4, 1 is an upper container and 2 is a lower container.
3 is a solid electrolyte, which is usually composed of β-alumina (Na ₂ O.Al ₂ O ₃ ) having conductivity of sodium ions.
The solid electrolyte 3 is connected to an α-alumina plate 4 having an insulating property by glass solder or the like, and the α-alumina plate 4 is connected to the upper container 1 and the lower container 2 by thermocompression bonding or the like. The α-alumina 4 functions to insulate the upper container 1 and the lower container 2 from each other. Further, since β-alumina does not have electronic conductivity, it also serves as a separator for separating the anode 5 and the cathode 6.

In this battery, molten sodium is used as the cathode active material 7, and molten sulfur and sodium polysulfide are used as the anode active material 8. Sodium polysulfide, which is the anode active material, has ionic conductivity but no electronic conductivity, and similarly, sulfur, which is the anode active material, also has no electronic conductivity, so that it aims to help transfer electrons accompanying the electrochemical reaction. The anode active material 8 is impregnated with a conductive material (for example, fibrous graphite). Considering the melting point of the anode active material, the operating temperature is considered to be 300 ° C or higher.

The charge / discharge reaction is Therefore, the battery as a whole is as follows.

A cathode active material injection pipe 9 and an anode active material injection pipe 10 are provided with blind plugs 11 after the active material injection. 12 indicates the liquid level of the cathode active material, and 13 indicates the liquid level of the anode active material.

When the solid electrolyte 3 is damaged due to some influence such as life, sodium which constitutes the cathode active material 7 and sulfur which constitutes the anode active material 8 directly react with each other to cause a sudden high temperature and high pressure in the battery. The reaction formula in that case is as follows.

2Na + 3S → Na ₂ S ₃ −107.3 kcal / mol As a means for relaxing such a reaction, conventionally, as shown in FIG. 4, a safety pipe 15 having a small hole 14 is provided on the inner diameter side of the solid electrolyte 3, A filler (usually a metal mesh or the like) 16 is filled in the gap between the safety tubes 15 of the solid electrolyte 3. That is, when the solid electrolyte 3 is damaged, the filler suppresses the flow of sodium that participates in the reaction with sulfur,
On the other hand, the safety pipe has an effect of reducing the volume of sodium retained in the gap with the inner diameter side of the solid electrolyte and restricting the flow of sodium from the inside of the safety pipe through the small holes. However, such means cannot reduce the total amount of sodium contained in the solid electrolyte, that is, the amount of sodium involved in the reaction with sulfur. In order to obtain a safer sodium-sulfur battery, it is desired to reduce the absolute amount of sodium in the solid electrolyte that directly participates in the reaction with sulfur.

[Problems to be Solved by the Invention]

The above-mentioned conventional technology has a total amount of sodium involved in the battery reaction in the solid electrolyte, and when the solid electrolyte is damaged, a direct reaction between the total sodium and sulfur occurs, the reaction progresses and expands, and the inside of the battery This may cause a rapid temperature rise and pressure rise, which may cause damage to the battery container.

In order to solve the above problems, the present invention suppresses a direct reaction between sodium and sulfur when the solid electrolyte is broken, which is a drawback of the conventional sodium-sulfur battery, and prevents a rapid temperature rise and pressure rise inside the battery. It is an object of the present invention to provide a sodium-sulfur battery capable of preventing the battery from being destroyed due to being brought.

[Means for Solving the Problems]

In order to achieve the above object, the present invention is a battery composed of a solid electrolyte through which sodium ions can pass, and a cathode active material made of sodium and an anode active material made of sulfur or sodium polysulfide with the solid electrolyte as a boundary. A reaction area, a storage tank for storing sodium provided in the upper portion of the battery reaction area, a partition wall for separating the storage tank and the battery reaction area portion, and a solid electrolyte and a narrow space provided on the inner diameter side of the solid electrolyte tube. In a sodium-sulfur battery having a bottomed tube and a hole provided in a partition wall so that the narrow gap and the storage tank communicate with each other,
An absorption tube in which the tube provided on the inner diameter side of the solid electrolyte tube is made of a material that softens or dissolves at a temperature of 400 ° C. or higher, and an inert gas inside is filled with the gas under reduced pressure or atmospheric pressure,
A feature is that a shape memory alloy piece that is closed by the temperature generated when the positive electrode active material and the negative electrode active material are directly reacted is fitted in the hole.

[Action]

According to the above configuration, the absorption pipe is easily plastically deformed due to the temperature generated when sodium and sulfur directly react, and the absorption pipe itself breaks the pressure generated when sodium and sulfur directly react. Alternatively, it is deformed and absorbed to reduce the influence on the battery container.

In addition, by using shape memory alloy pieces in the partition walls or in the holes provided in the partition walls, the holes are blocked by the temperature generated when sodium and sulfur directly react, blocking sodium outflow from the storage tank and expanding the destruction of the battery. Prevent.

〔Example〕

Next, examples of the present invention will be described. An example thereof is shown in FIG. FIG. 1 is a vertical cross-sectional configuration diagram of a battery of one embodiment.

In FIG. 1, 1 is an upper container, 2 is a lower container, 3 is a solid electrolyte, 4 is an α-alumina plate, and the structure up to this point is the same as the conventional sodium-sulfur battery shown in FIG. . The α-alumina of 4 and the solid electrolyte 3 are generally connected by glass solder or the like, and the α-alumina plate 4 serves to electrically insulate the upper container 1 and the lower container 2 from each other, and the upper and lower containers are subjected to thermal pressure welding or the like. Connected by. Generally, β-alumina (Na ₂ O.Al ₂ O ₃ ) is used for the solid electrolyte 3. Upper container 1
A partition 17 is provided on the upper part of the solid electrolyte 3, that is, on the α-alumina plate 4, and a sodium storage tank 21 is formed with the upper container of 1.

An upper end of an absorption tube 19 which is inserted into the solid electrolyte 3 and whose lower end is blind is attached to the partition wall 17. This absorption tube 19
Is for buffering the pressure when a direct reaction between sodium and sulfur occurs due to breakage of the solid electrolyte 3. That is, it absorbs the internal pressure of the battery and prevents the battery container from bursting. The absorption tube 19 is plastically deformed beyond a certain value of elastic deformation upper limit.

A narrow gap 22 is formed between the inner diameter surface of the solid electrolyte 3 and the outer diameter surface of the absorption tube 19, and a small hole 18 connecting the gap 22 and the sodium storage tank 21 is provided in the partition wall 17. An inert gas, such as argon gas, is usually contained in the absorption tube 19 under reduced pressure or at atmospheric pressure.

The absorption tube 19 is made of a material that softens or dissolves at a temperature increased by the reaction of sodium and sulfur, or a material or structure that is easily broken or deformed (crushed to reduce the apparent volume) by pressure. The material has a battery operating temperature of 300-350
Since it is ℃, the temperature of softening or melting may be about 500 ℃. The absorption tube 19 has a pipe shape, and the material is SUS304 or the like. The absorption tube 19 must be resistant to sodium corrosion. The reason why the inert gas is filled is that air may accelerate the reaction between sodium and sulfur. The other absorption tube 19 may be a solid pipe-shaped one made of a soft material. In addition, as a structure that is destroyed by pressure, as shown in FIG. 2, a notch groove 30 that causes stress concentration on the surface of the absorption tube 19 and promotes destruction can be provided.
In FIG. 2, (1) shows a vertical sectional view of the absorption tube 19,
(2) is a sectional view taken along the line II 'of FIG. 2 (1). In the gap 23 formed by the lower container 2 and the outer diameter surface of the solid electrolyte 3,
Sulfur 8, which is the anode active material, has a liquid level 13 and is enclosed. Sulfur 8 is injected by means of an injection tube 10, after which the injection tube is sealed with a blind plug 11. On the other hand, the cathode active material 7 flows from the injection pipe 9 through the sodium storage tank 21 and the small holes 18 of the partition wall 17 and fills the gap 22 formed by the solid electrolyte 3 and the absorption pipe 19. The volume formed by the gap 23 filled with the sulfur 8 must be large enough to fill the total amount of sulfur required for the battery reaction.
On the other hand, the gap 22 between the solid electrolyte 3 filling the sodium and the absorption tube 19 does not fill the total amount of sodium necessary for the battery reaction, but has a size that can fill the inner surface of the solid electrolyte 3 with sodium. I wish I had it. The size of this gap can be arbitrarily determined by the inner diameter of the solid electrolyte 3 and the outer diameter of the absorption tube 19. When sodium in the gap 22 is consumed by the discharge reaction, sodium is supplied from the sodium storage tank 21 through the small holes 18 of the partition wall 17. On the contrary, when sodium is generated in the charging reaction, it is smaller than the gap 22.
Flush 18 to return sodium to the sodium reservoir. Taking a 1Kwh class sodium-sulfur battery with an 8-hour charge / discharge cycle as an example, the sodium supply required for the battery reaction is 0.23g / sec.
Is. As for the small hole 18 for flowing the sodium, only one having a diameter of 0.5 mm or less is required. However, considering the clogging of sodium, generally, one or two holes having a diameter of about 1 to 2 mm are provided. There may be a plurality of small holes.

If the size of the small holes 18 provided in the partition wall 17 is reduced, the small holes 18 are closed by the reaction product generated in the gap 22 by the direct reaction between sodium and sulfur. Therefore, it is possible to prevent sodium from flowing out from the sodium storage tank 21 and prevent the battery from expanding and breaking. The small hole 18 may be provided with a wick such as a metal mesh so that sodium easily flows during operation. The presence of this wick makes it easier to plug the reaction product during the sodium-sulfur direct reaction.

As described above, according to the present embodiment, even if the solid electrolyte 3 is damaged due to deterioration or the like, the amount of sodium that directly participates in the sulfur 8 can be minimized, the direct reaction between sodium and sulfur can be suppressed, and the temperature rise, The pressure rise can be minimized. Further, even if the temperature and pressure inside the battery rise, the absorption tube 19 is melted or broken and absorbs the pressure, so that the outermost battery container is not damaged.

In addition, the filling 16 described in FIG.
Can be placed in 22. On the sulfur side, the conductive auxiliary material described in the conventional example is used.

Next, another embodiment of the sodium-sulfur battery according to the present invention will be described.

By making the holes 18 provided in the partition wall 17 smaller, the direct reaction product of sulfur with sodium clogs and prevents the outflow of sodium from the sodium storage tank. Rise or sodium,
Means exist to plug the pores 18 by changing their shape or properties by reaction with sulfur and its compounds. As shown in FIG. 3, a material having the above function may be fitted around the small holes 18. FIG. 3 is a sectional view near the hole 18. A shape memory alloy is specifically considered as a material that deforms depending on temperature. The partition wall 17 itself is made of a shape memory alloy whose pores are closed due to a temperature rise, or a small holed piece 31 made of a shape memory alloy is fitted into the partition wall 17.

〔The invention's effect〕

According to the present invention, the absorption tube has a material and a structure which are likely to be plastically deformed by a temperature generated when sodium and sulfur directly react with each other, and have an effect of absorbing the pressure by the plastic deformation to reduce the influence on the battery container.

Further, by using the shape memory alloy pieces in the partition walls or in the holes provided in the partition walls, there is an effect of preventing sodium from flowing out from the storage tank when sodium and sulfur directly react with each other, and preventing the destruction and expansion of the battery.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional structural view showing an embodiment of the sodium-sulfur battery of the present invention, FIG. 2 is a cross-sectional structural view of one embodiment of the structure of the absorption tube of the present invention, and FIG. 3 is a partition wall of the present invention. FIG. 4 is a cross-sectional view showing the structure around a hole, and FIG. 4 is a vertical cross-sectional configuration diagram showing the structure of a conventional sodium-sulfur battery. 17 ... Partition wall, 18 ... Small hole, 19 ... Absorption tube, 21 ... Sodium storage tank, 22 ... Gap.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Gen Yamamoto, 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture, Hiritsu Manufacturing Co., Ltd. Energy Research Institute (72) Kazuo Takahashi 1168, Moriyama-cho, Hitachi City, Ibaraki Hitachi, Ltd. Energy Research Laboratory (72) Inventor Naoshi Soma 1168 Moriyama-cho, Hitachi City, Ibaraki Hitachi, Ltd. Energy Research Laboratory (72) Inventor Gen Wada 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Hitoshi Sugawara 3-1-1 Hitachi-machi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Masaaki Nakamura 1-3-1 Uchisai-cho, Chiyoda-ku, Tokyo Tokyo Within the Electric Power Company (72) Inventor Masaaki Oshima 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (56) References Patent Sho 63-170868 (JP, A) JP Akira 50-41025 (JP, A)

Claims (3)

[Claims] 1. A battery reaction region composed of a solid electrolyte through which sodium ions can pass, and a cathode active material made of sodium and an anode active material made of sulfur or sodium polysulfide with the solid electrolyte as a boundary, A storage tank for storing the sodium, which is provided in an upper portion of the battery reaction region, a partition wall for separating the storage tank and the battery reaction region portion, and an inner diameter side of the solid electrolyte tube with a narrow gap between the solid electrolyte and the solid electrolyte. In a sodium-sulfur battery having a bottomed tube and a hole provided in the partition wall so that the narrow gap and the storage tank communicate with each other, the tube provided on the inner diameter side of the solid electrolyte tube is 400 ° C. An absorption tube made of a material that softens or dissolves at the above temperature and is filled with an inert gas at a reduced pressure or at atmospheric pressure, wherein the positive electrode active material and the negative electrode active material directly react in the holes. Sodium and wherein the fitted shape memory alloy piece that closes the temperature generated when - sulfur battery. 2. The sodium-sulfur battery according to claim 1, wherein a cutout groove is provided on the surface of the absorption tube. 3. The sodium-sulfur battery according to claim 1, wherein a shape memory alloy is used for the partition wall.