JPH0658809B2 - Sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sodium-sulfur battery having excellent battery efficiency, good corrosion resistance of an anode container, and long battery life.

(Prior Art) Recently, research and development of a high-temperature type sodium-sulfur battery, which is excellent in both performance and economy as a secondary battery for electric vehicles and nighttime electricity storage, has been advanced.

That is, in terms of performance, the sodium-sulfur battery has a higher theoretical energy density than a lead storage battery, there is no side reaction such as generation of hydrogen or oxygen during charge / discharge, the utilization rate of the active material is high, and sodium and sulfur are economically used. Sulfur has the advantage of being inexpensive.

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

2Na + XS → Na ₂ Sx During charging, the opposite reaction 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 insulating plate made of α-alumina fixed to the upper end of the anode container 2, and 4 is the insulating plate 3. It is a solid electrolyte tube made of β-alumina that is fixed to the inner peripheral portion and forms a cylindrical bag tube extending downward, and has a function of allowing sodium ions, which is a cathode acting substance, to permeate.

Reference numeral 5 is a cylindrical reservoir (cathode container) fixed to the upper end surface of the insulating plate 3, and 6 is a long and narrow cathode fixed to the center of the upper lid of the reservoir 5 and extending to the bottom of the solid electrolyte tube 4 through the reservoir 5. The tube, 7 is a cathode terminal fixed to the upper end of the cathode tube 6.

Reference numeral 8 is a conductive material for an anode such as carbon mat containing sulfur as an anode acting substance.

The space formed by the anode container 2 and the solid electrolyte tube 4 of the sodium-sulfur battery as described above, that is, the space for accommodating the conductive material 8 for the anode is a simple cavity as shown in FIG.
Anode conductive material 8 is housed in the entire cavity.

(Problems to be Solved by the Invention) As described above, since the space formed by the anode container 2 and the solid electrolyte tube 4 of the conventional sodium-sulfur battery is a mere cavity, it is an anode acting substance during discharge. Sodium sulfide, which is a reaction product of sulfur and sodium that is a cathode active substance, is produced, and sodium trisulfide, which has particularly high specific gravity, large electric resistance, and corrosiveness, is precipitated in the cavity at the end of the period. The current does not flow in that portion, and the current density flows unevenly because it flows upward.

Therefore, the charging / discharging power efficiency represented by the ratio of the discharging power to the charging power decreases.

Further, since sodium trisulfide finally generated during discharge has a high corrosive property, there is a problem that when the precipitated sodium trisulfide comes into contact with the anode container, the anode container is corroded, and sulfur is generated based on the corrosion. Reacting with iron to produce iron sulfide (Fe ₂ S ₃ ) and reducing the sulfur involved in the reaction with sodium, the problem that the battery capacity may decrease by 40% by corrosion of 0.5 mm, for example There is a point.

Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention divides a conductive material accommodating space for an anode formed between a solid electrolyte tube and an anode container into upper and lower layers. The partition member is formed of a corrosion-resistant material, and a storage portion that stores the corrosion product for most of the time during discharge in a non-contact state with the anode container is formed on the upper surface side of the partition member.

(Operation) By adopting the above-mentioned configuration, a precipitate mainly composed of sodium trisulfide having a large electric resistance and a high corrosiveness does not concentrate at the bottom of the space formed by the anode container and the solid electrolyte tube, It is distributed vertically and the electric resistance is made uniform,
Further, the sediment is substantially less likely to contact the anode container.

(Embodiment) Next, an embodiment embodying the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the sodium-sulfur battery of the present invention has a partition member for dividing the space into a plurality of upper and lower layers in a storage space for the anode conductive material 8 formed between the anode container 2 and the solid electrolyte tube 4. 10 is provided, and the structure of the other parts is the same as the structure of the conventional sodium-sulfur battery as shown in FIG.

The structure of the characteristic portion of the sodium-sulfur battery of the present invention is
As shown in FIG. 1, 2 is an anode container made of stainless steel or nickel, 4 is a solid electrolyte tube, and 10 is a space formed between the anode container 2 and the solid electrolyte tube 4 for accommodating an anode conductive material 8. The partition member has a shape of an inverted conical cylinder having a high anode container 2 side. P is a storage portion formed on the upper surface side of the partition member 10, and since the solid electrolyte tube 4 side is low, sodium trisulfide having a large specific gravity is stored.

Reference numeral 8 denotes a conductive material for an anode housed in each space defined by the partition member 10 and is, for example, a carbon mat impregnated with sulfur which is an anode acting substance.

It is desirable that the partition member interval and the angle of the partition member 10 be as follows.

Partition member spacing: 1 to 30 times the thickness of the conductive material for the anode If the partition member spacing is less than 1 time the thickness of the conductive material for the anode, the effective volume in the anode chamber is reduced and the effective area of the surface of the solid electrolyte tube 4 is reduced. Is decreased, the capacity of the battery is decreased and the polarization is increased, which is likely to cause a problem in practical use. When it exceeds 30 times, the storage volume of sodium trisulfide becomes extremely small compared to the partitioned volume of the anode chamber, and it becomes difficult to exert the effect of the present invention. Therefore, it is desirable that the partition member interval be 1 to 30 times the thickness of the conductive material for the anode.

Angle: 5 degrees to 60 degrees If the partition member angle is less than 5 degrees, it becomes difficult to store sodium trisulfide without contacting the anode container, and the effect becomes low. On the other hand, when the angle exceeds 60 degrees, the storage amount of sodium trisulfide increases, and the problem of corrosion of the anode container disappears, but the internal resistance of the anode increases to more than double,
The charging / discharging efficiency is lowered and it becomes practically difficult to use. Therefore, the partition member angle is preferably in the range of 5 degrees to 60 degrees.

The partition member 10 is made of a corrosion resistant material such as molybdenum.

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

In the above embodiment, when the battery is discharged, sodium becomes sodium ions and permeates the solid electrolyte tube 4, and enters the anode conductive material 8 accommodating space defined by the anode container 2, the solid electrolyte tube 4 and the partition member 10. There, it reacts with sulfur based on the above reaction formula to produce sodium polysulfide, and finally sodium trisulfide. Since the generated sodium trisulfide is heavy, it settles and is stored in the storage portion P formed on the upper surface side of the partition member 10 in order from the bottom. The storage portion P is a space having an inverted triangular cross section surrounded by the partition member 10 and the solid electrolyte tube 4.

Therefore, sodium trisulfide contacts the partition member 10 and the solid electrolyte tube 4, but does not substantially contact the anode container 2. In other words, the corrosive product sodium trisulfide remains in non-contact with the anode vessel 2 for most of the time the battery is discharged.

Therefore, as to the corrosion resistance, there is no problem even if the charging and discharging of the battery is repeated 1000 times.

Since the partition member 10 is made of a corrosion-resistant material such as molybdenum, it does not corrode even when contacted with sodium trisulfide.

Further, since the precipitated sodium trisulfide is dispersed in the space partitioned by the partition member 10, the current density becomes more uniform, and the decrease in charge / discharge power efficiency is very small.
It can sufficiently withstand repeated charging and discharging of 0 cycles or more.

The sodium-sulfur battery of the present invention is not limited to the above embodiment, but may be configured as follows.

(1) Although the partition member 10 has an inverted conical shape in the above embodiment, a gas vent hole 11 can be provided at the upper end of the partition member 10 as shown in FIG. In this case, it is possible to prevent the partition member 10 from being stressed and damaged due to pressure fluctuations due to the non-uniform progress of the reaction between sodium and sulfur in the anode conductive material 8 housing space.

(2) The partition member 10 can be formed in an L shape as shown in FIG. 4 so as to stand up along the inner surface of the anode container 2. Also in this case, since the precipitated sodium trisulfide does not come into contact with the anode container 2, there is no problem of corrosion.

(3) The partition member 10 may be dish-shaped as shown in FIG. Such a dish-shaped partition member 10
It is suitable when the amount of sodium trisulfide produced is small, that is, when the discharge time is short.

(4) The partition member 10 can be formed in a V shape as shown in FIG. 6 or a U shape as shown in FIG. Such a V-shaped or U-shaped partition member 10 can be preferably used when the discharge time is relatively long and the amount of sodium trisulfide produced is large.

EFFECTS OF THE INVENTION In addition to exhibiting excellent charge / discharge power efficiency of 1000 charge / discharge cycles, even if highly corrosive sodium trisulfide is generated, it can be stored in the storage part of the partition member. Sodium sulfide is not concentratedly deposited downward, and corrosion of the anode container at the partition member position is prevented, so damage to the anode container is reduced and the life of the battery is extended. Furthermore, since sodium trisulfide is stored by being dispersed in each compartment, most of sodium trisulfide is decomposed into sodium and sulfur again during charging, and a high charge capacity can be maintained. Further, since the solid electrolyte tubes are dispersed in each section and charged and discharged in each section, local deterioration is prevented from occurring, which also contributes to prolonging the life of the battery.

[Brief description of drawings]

FIG. 1 is a partially enlarged vertical sectional view of a sodium-sulfur battery showing an embodiment of the present invention, FIG. 2 is a vertical sectional view of a sodium-sulfur battery, and FIGS. 3 to 7 are sodium showing another example of the present invention. -A partially enlarged vertical sectional view of a sulfur battery, and Fig. 8 is a partially enlarged vertical sectional view of a conventional sodium-sulfur battery. 2 ... Anode container, 4 ... Solid electrolyte tube, 8 ... Anode conductive material, 10 ... Partitioning member, P ... Storage part.

Continuation of the front page (56) References JP 62-17964 (JP, A) JP 59-10539 (JP, B2)

Claims (4)

[Claims] 1. A partition member (10) for dividing a space for accommodating a conductive material for an anode (8) formed between a solid electrolyte tube (4) and an anode container (2) into a plurality of upper and lower layers is made of a corrosion resistant material. A storage part (P) for forming and storing the corrosive products for most of the time during discharge in a non-contact state with the anode container (2).
Formed on the upper surface side of the partition member (10)
Sulfur battery. 2. The partition member (10) is in the shape of an inverted conical cylinder having a high anode container (2) side, and corrosive products are stored in the storage section (P) by contacting only with the solid electrolyte tube (4) side. Sodium according to claim 1
Sulfur battery. 3. The section of the partition member (10) is L-shaped, dish-shaped,
The sodium-sulfur battery according to claim 1, wherein the sodium-sulfur battery is V-shaped or U-shaped and has a storage portion (P) formed on the upper surface side. 4. The partition member (10) has a gas vent hole (1) at the top.
Claims 1 to 3 provided with 1).
The sodium-sulfur battery according to the item.