JP2003223928A - Sodium-sulfur battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sodium-sulfur battery with improved safety, especially suitable for high output in which, even if over voltage begins to occur in single cells, voltage monitoring is made easy by delaying start of voltage drop or making voltage drop speed small, and even if a solid electrolyte pipe is broken by a sudden temperature rise of the single cells, extensive reaction between active materials is prevented, so as not result in an immediate opening circuit break of the single cells. <P>SOLUTION: The sodium-sulfur battery is constituted by accommodating a cylinder-shape positive-electrode mold 7 in a positive-electrode room R2, by arranging a cylinder-shape partition 8 with a bottom inside a solid electrolyte pipe 4 to be used as a negative-electrode room R1, and by further arranging a sodium container 5 inside the partition 8. A positive-electrode active material that is accumulated in the upper part of the positive-electrode room R2 during electric discharging stays in a space 11 by arranging a small-diameter positive- electrode mold 7' with an outside diameter smaller than the outside diameter of the positive-electrode mold 7 in the upper part of the positive-electrode mold 7, and by forming the space 11 outside the small-diameter positive-electrode mold 7'. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sodium-sulfur battery that is preferably used as a secondary battery for power storage and the like, and particularly to a high output type.

[0002]

2. Description of the Related Art A sodium-sulfur battery has molten metal sodium, which is a cathode active material, on one side and molten sulfur, which is an anode active material, on the other side, and both have a selective permeability to sodium ions. It is a high temperature secondary battery which is isolated by a β-alumina solid electrolyte and is operated at 290 to 360 ° C.

As an example of such a sodium-sulfur battery, a structure shown in FIG. 3 is known.
In the figure, 4 is a cylindrical solid electrolyte tube with a bottom, and by disposing this in the anode container 1, an anode chamber R2 is formed outside the solid electrolyte tube 4. In the anode chamber R2, a cylindrical anode mold 7 impregnated with sulfur S which is an anode active material.
Is housed. Further, a constriction 9 for absorbing and relaxing expansion and contraction due to heat change of the container is formed near the upper end of the anode container 1.

On the other hand, inside the solid electrolyte tube 4, a cathode chamber R1 is formed, and a sodium container 5 containing molten metal sodium Na as a cathode active material is arranged.
The anode container 1 and the solid electrolyte tube 4 are connected via an insulating ring 2, and the upper end surface of the insulating ring 2 has a cathode lid 3
Are joined. In the upper space of the sodium container 5,
The inert gas G is sealed at a predetermined pressure, and the inert gas G pressurizes the sodium Na in the sodium container 5 in a direction to flow out from a small hole 6 provided at the bottom of the sodium container 5.

Further, a bottomed cylindrical partition wall (safety tube) 8 is arranged between the solid electrolyte tube 4 and the sodium container 5. The partition wall 8 is arranged with a predetermined gap from the solid electrolyte tube 4 and the sodium container 5, and when the battery is discharged, sodium Na flowing out from the small hole 6 at the bottom of the sodium container 5 is first separated from the sodium container 5 and the partition wall 8. The upper part of the partition wall 8, and
It moves downward in the gap between the solid electrolyte tube 4 and the partition wall 8 and stays in this gap.

Here, sodium Na emits electrons to become sodium ions, passes through the solid electrolyte tube 4, moves to the anode chamber R2, and reacts with sulfur S in the anode chamber R2 and electrons that have passed through an external circuit. It generates sodium polysulfide and generates a voltage. In addition, the reaction of generating sodium Na and sulfur S occurs at the time of charging, contrary to the time of discharging.

When the solid electrolyte tube 4 is damaged during use of the battery and the sulfur S in the anode chamber R2 directly contacts the sodium Na of the cathode to initiate the reaction, the partition wall 8 is heated by the direct reaction. It thermally expands and reduces the distance between the partition wall 8 and the solid electrolyte tube 4, thereby directly reducing the amount of reaction. As a result, the heat generated by the direct reaction accelerates the temperature of the battery and protects the defective battery from danger such as melting the anode container 1.

In the sodium-sulfur battery, for example, as shown in FIG. 4, single cells 14 are arranged in a heat insulating container 12, and a heater 13 arranged below the battery is heated to heat the cells 290 to 360.
Used as a module battery operated at ℃.

[0009]

By the way, in recent years, as a sodium-sulfur battery having the above-described structure, there is a growing need for a high output type battery in addition to the conventional load leveling type battery. In the load-leveling type, the current per cell is small, the temperature difference between the cells or inside the module below the cell and the temperature difference inside the cell are small, and the cells self-heat during charging and discharging. Even if the temperature rises, the operation can be stopped by the detection at the temperature measurement point, so there is no problem of abnormal heat generation.

On the other hand, in the high output type, a large current flows, so that the internal temperature of the unit cell rises sharply, and there is a possibility that sufficient monitoring cannot be performed due to a response delay in the measurement of the temperature inside the module. Further, in a high-power type module battery, it is necessary to serialize all the single cells as shown in the connection circuit diagram of FIG. 5 without parallelizing the single cells inside the module battery.

In the case of this one-serialized module battery, due to the manufacturing variation in the gap between the solid electrolyte tube and the partition wall and the presence of the temperature distribution in the module battery, the surface area of the solid electrolyte tube, which contributes to energization in high-power discharge, decreases There are variations in the way, and the internal resistance of the unit cell, whose current-carrying area began to decrease quickly, increases.

However, the current I flowing through this unit cell hardly decreases. When the open-circuit voltage is V _O and the internal resistance is R, the voltage V of the unit cell is V = V _O -IR, but when the internal resistance of only one unit cell in the module rises, V is a large negative voltage. (V <−20 (V)), which is applied as an overvoltage to the solid electrolyte tube.

At this time, if the temperature monitoring and the voltage monitoring function sufficiently, such an overvoltage can be prevented. However, if the temperature monitoring and the voltage monitoring are insufficient, the partition wall 8 expands due to a further temperature increase, and the gap with the solid electrolyte tube 4 is increased. Becomes extremely small, and finally a large current concentrates on a portion P (see FIG. 3) corresponding to the height of the upper end of the anode mold 7 of the solid electrolyte tube 4, and the solid electrolyte tube 4 is destroyed from that portion.

When the discharge is continued even after the solid electrolyte tube 4 is damaged, the partition wall 8 inside the solid electrolyte tube 4 is melted by the discharge energy, and further the sodium container 5 inside the partition wall 8 is melted and damaged. As a result, there is a problem that a large amount of sulfur S, which is the anode active material, reacts with sodium Na, which is the cathode active material, and leaks out of the battery (open breakdown).

The present invention has been made in view of such circumstances, and an object of the present invention is to flow a large current even after the resistance of one unit cell starts to increase, and as a result, the unit cell has a high current. Even when an overvoltage starts to occur in the battery, voltage monitoring can be facilitated by delaying the start of the voltage drop or decreasing the voltage drop rate, and even if the solid electrolyte tube is destroyed due to a sudden temperature rise in the cell, It is an object of the present invention to provide a sodium-sulfur battery, which is suitable for high output, in which safety is improved so that a large amount of reaction between substances is prevented and immediate open cell destruction is not caused.

[0016]

According to the present invention, a cathode chamber is formed inside a solid electrolyte tube having a bottomed cylindrical shape, and an anode chamber is formed outside thereof, and the anode chamber is impregnated with sulfur as an anode active material. In the inside of the solid electrolyte tube that serves as a cathode chamber, the cylindrical partition wall having a bottom is disposed with a predetermined gap between the solid electrolyte tube and the solid electrolyte tube. A sodium-sulfur battery in which a sodium container containing sodium that is a cathode active material is disposed inside with a predetermined gap between the partition and the partition wall,
A small-diameter anode mold having an outer diameter smaller than that of the anode mold is arranged on the upper part of the anode mold, a space is formed outside the small-diameter anode mold, and an anode active material that accumulates in the upper part of the anode chamber during discharge is formed. There is provided a sodium-sulfur battery (first invention), characterized in that a substance is retained in the space.

Further, according to the present invention, a cathode chamber is formed inside a bottomed cylindrical solid electrolyte tube, and an anode chamber is formed outside the solid electrolyte tube, and the inside of the anode chamber has a cylindrical shape impregnated with sulfur as an anode active material. Inside the solid electrolyte tube that houses the anode mold and serves as the cathode chamber, it is formed in a cylindrical shape with a bottom so that the gap between the solid electrolyte tube and the solid electrolyte tube becomes large above the portion lower than the upper end of the anode mold. A partition wall with a predetermined gap between the solid electrolyte tube and a sodium container containing sodium as a cathode active material inside the partition wall with a predetermined gap between the partition wall and the solid electrolyte tube. In the sodium-sulfur battery, the small-diameter anode mold having an outer diameter smaller than the outer diameter of the anode mold is arranged on the anode mold, and the outside of the small-diameter anode mold. There is provided a sodium-sulfur battery (second invention), characterized in that a space is formed in the space, and the anode active material accumulated in the upper part of the anode chamber during discharge stays in the space.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 is a sectional view showing an example of an embodiment of a sodium-sulfur battery according to the first invention.
In the figure, 4 is a bottomed cylindrical solid electrolyte tube having a function of selectively permeating sodium ions. This solid electrolyte tube 4 is arranged in the anode container 1, and thereby an anode chamber R2 is formed outside the solid electrolyte tube 4. Anode chamber R2
Accommodates a cylindrical anode mold 7 impregnated with sulfur S that is an anode active material. The solid electrolyte tube 4 is made of β-alumina, β ″ -alumina or the like, and the anode container 1 is made of aluminum, stainless steel or the like.
A constriction 9 for absorbing and relaxing expansion and contraction due to heat change of the container is formed near the upper end of the container.

On the other hand, inside the solid electrolyte tube 4, a cathode chamber R1 is formed, and aluminum, aluminum alloy,
The bottomed cylindrical partition wall 8 made of a metal material having excellent corrosion resistance to sodium such as stainless steel is used as the solid electrolyte tube 4.
And a closed bottomed cylindrical sodium container 5 containing molten metal sodium Na, which is a cathode active material, is disposed inside the partition wall 8 with a predetermined gap.
And a predetermined gap therebetween.

The anode container 1 and the solid electrolyte tube 4 are connected via an insulating ring 2, and a cathode lid 3 is bonded to the upper end surface of the insulating ring 2. The insulating ring 2 is preferably made of ceramics having an insulating property because it is necessary to maintain electrical insulation between the anode chamber R2 and the cathode chamber R1, and α-alumina or the like is preferably used in view of strength, cost and the like. To be done.

A small hole 6 is provided through the bottom of the sodium container 5, and an inert gas G such as nitrogen gas or argon gas is sealed in the upper space of the sodium container 5 at a predetermined pressure. The inert gas G pressurizes the sodium Na in the sodium container 5 in the direction of flowing out from the small holes 6.

In the sodium-sulfur battery of the first invention, as a characteristic structure thereof, a small-diameter anode mold 7 ′ having an outer diameter smaller than the outer diameter of the anode mold 7 is arranged above the anode mold 7. Then, a space 11 is formed outside the small-diameter anode mold 7 ′ so that the anode active material accumulated in the upper part of the anode chamber R 2 during the discharge stays in the space 11.

In this way, on the upper part of the anode mold 7,
Further, by arranging the small-diameter anode mold 7 ', the area of the anode mold in contact with the solid electrolyte tube 4 is increased and the energization area is expanded, so that the internal resistance of the cell is reduced and the high output performance of the cell is improved. improves.

Further, when the battery exceeds the operating upper limit temperature and is further discharged, the partition wall 8 thermally expands and N
Even when the gap between the partition wall 8 serving as the flow path of a and the solid electrolyte tube 4 is reduced, the current-carrying area is expanded as described above, so that the degree of concentration of the current is relieved, which reduces the voltage drop start time. It has the effect of delaying or slowing down the voltage drop rate.

Further, a small-diameter anode mold 7 ′ is arranged,
By pressing the solid electrolyte tube 4 to the upper part by the repulsive force, even when the solid electrolyte tube 4 is finally broken, the fragments are less likely to fall off and the safety is improved.

Furthermore, by forming the space 11 outside the small-diameter anode mold 7 ′, the R of the anode chamber during discharge can be reduced.
Since the anode active material accumulated in the upper part of 2 stays in the space 11 and the state where it does not exist on the solid electrolyte tube 4 side is achieved, even when the solid electrolyte tube 4 is damaged, the anode active material and the cathode The direct reaction with the active material can be limited, and the active material does not easily leak to the outside of the battery.

The outer peripheral portion of the small-diameter anode mold 7 ′ is preferably held by a ring-shaped member (backup ring) 10, so that when the solid electrolyte tube 4 is damaged, the damaged portion is less likely to fall off. Therefore, the safety is further improved. As a material of the ring-shaped member 10,
A material in which corrosion resistance to an active material is enhanced by plating chromium on aluminum or an aluminum alloy can be preferably used.

FIG. 2 is a sectional view showing an example of an embodiment of a sodium-sulfur battery according to the second invention. The basic structure of this sodium-sulfur battery is the same as that of the first invention, and the same effect as that of the first invention is exerted. Further, as its characteristic structure, the partition wall 8 is the upper end of the anode mold 7. The solid electrolyte tube 4 is located above the lower part 8a.
Is formed so that the gap between and is large.

With such a structure, the temperature rise due to a large current narrows the gap between the solid electrolyte tube 4 and the partition wall 8 in one unit cell, so that even if the unit cell has higher resistance, Since the gap between the solid electrolyte tube 4 and the partition wall 8 in the vicinity of the upper end of the anode mold 7 is larger than in the conventional case, the voltage drop start time is further delayed or the voltage drop speed becomes slower. As a result, the resolution of voltage measurement on the time axis can be reduced, voltage monitoring can be facilitated, and the cost of the measuring device can be reduced.

[0030]

As described above, the sodium-sulfur battery of the present invention, even when the overvoltage starts to be applied to the unit cell,
By delaying the start of the voltage drop or slowing the voltage drop rate, it is possible to reduce the resolution of the voltage measurement, which facilitates voltage monitoring. In addition, even if the solid electrolyte tube is damaged due to an abnormal temperature rise due to overvoltage, there is no possibility of immediate discharge failure or active material leaking out of the battery for a while. Can safely continue to output. The present invention is particularly effective for high-power type sodium-sulfur batteries.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment of a sodium-sulfur battery according to the first invention.

FIG. 2 is a sectional view showing an example of an embodiment of a sodium-sulfur battery according to the second invention.

FIG. 3 is a cross-sectional view showing an example of a conventional sodium-sulfur battery.

FIG. 4 is a cross-sectional view showing an example of the structure of a sodium-sulfur module battery.

FIG. 5 is a connection circuit diagram of a high-power type module battery in which a sodium-sulfur cell is connected in series.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode container, 2 ... Insulation ring, 3 ... Cathode lid, 4 ... Solid electrolyte tube, 5 ... Sodium container, 6 ... Small hole, 7 ... Anode mold, 7 '... Small diameter anode mold, 8 ... Partition wall, 9 ... Constriction. 10 ... Ring-shaped member (backup ring), 11
... Space, 12 ... Insulation container, 13 ... Heater, 14 ... Single cell, R1 ... Cathode chamber, R2 ... Anode chamber, Na ... Sodium,
S ... Sulfur, G ... Inert gas.

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Claims (4)

[Claims] 1. A cathode chamber is formed inside a bottomed cylindrical solid electrolyte tube, and an anode chamber is formed outside, and a cylindrical anode mold impregnated with sulfur as an anode active material is accommodated in the anode chamber, Inside the solid electrolyte tube serving as the cathode chamber, a cylindrical partition wall with a bottom is arranged with a predetermined gap between the partition wall and the solid electrolyte tube, and inside the partition wall, sodium as a cathode active material is placed. A sodium container containing the sodium container arranged with a predetermined gap between the sodium container and the
A sulfur battery, wherein a small-diameter anode mold having an outer diameter smaller than the outer diameter of the anode mold is arranged on the upper part of the anode mold, and a space is formed outside the small-diameter anode mold to form an anode during discharge. A sodium-sulfur battery, characterized in that the anode active material accumulated in the upper part of the chamber is retained in the space. 2. The sodium-sulfur battery according to claim 1, wherein an outer peripheral portion of the small-diameter anode mold is held by a ring-shaped member. 3. A bottomed cylindrical solid electrolyte tube is provided with a cathode chamber inside and an anode chamber outside, and a cylindrical anode mold impregnated with sulfur as an anode active material is housed in the anode chamber, Inside the solid electrolyte tube to be the cathode chamber, a bottomed cylindrical shape, a partition wall formed so that the gap between the solid electrolyte tube and the upper part of the anode mold is higher than the upper part of the anode mold, Sodium-sulfur, which is arranged with a predetermined gap between the electrolyte tube and a sodium container containing sodium as a cathode active material inside the partition with a predetermined gap between the partition and the partition. In the battery, a small-diameter anode mold having an outer diameter smaller than the outer diameter of the anode mold is arranged on the upper part of the anode mold, and a space is formed outside the small-diameter anode mold to form a space. Sulfur battery - sodium anode active material accumulated in the anode chamber top in it, characterized in that so as to stay in the space. 4. The sodium-sulfur battery according to claim 3, wherein the outer peripheral portion of the small diameter anode mold is held by a ring-shaped member.