JPS59154776A - Forming method of sodium sulfur battery and battery using this method - Google Patents

Abstract

PURPOSE:To reduce a heat loss as well as to form a sodium sulfur which checks corrosion or the like in a battery jar vessel, by making the volume of a reaction range smaller so as to feed a battery reaction range part with a necessary amount of active materials by slow degrees. CONSTITUTION:Bounding to a solid electrolyte 14 where sodium slufur passes through, a battery reaction range part 20 is formed by means of a negative pole active material 9 composed of sodium and a positive pole active material 19 comprising sulfur and sodium polysulfide as an indispensable component. At this time, a battery jar part 13 leading both these active materials 9 and 10 is installed, thereby making the volume of the reaction range part 20 smaller, and a necessary amount of both active materials 9 and 10 is fed by degrees. These active materials 9 and 10 being led into the battery jar part 13 make contact chemically with each other adjoining to the solid electrolyte 14, thus a battery is formed up. Owing to this battery, dangerousness by a sudden reaction between sodium and sulfur can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] Related to batteries. This type of battery can of course be used as a power source as a normal battery, and can also be suitably used for power storage by storing power by charging when power is not needed and discharging it when power is needed.

[Prior art]

A specific structural example of a conventional sodium-sulfur battery is shown below.
As shown in the figure. This battery uses molten sodium as the cathode active material 1, molten sulfur and sodium polysulfide as the anode active material 2, and uses a solid electrolyte 3 having sodium ion conductivity as the electrolyte. The solid electrolyte 3 can be made of glass or ceramics, but so-called β-alumina (Na20.ktzos) containing aluminum oxide and sodium oxide in its molecules is effective.

This is because β-alumina has high sodium ion conductivity, and it can be said that most sodium-sulfur batteries currently under development use this as the electrolyte. Furthermore, since β-alumina does not have electron conductivity, it also serves as a separator that separates the anode 4 and the cathode 5.

Sodium polysulfide, which makes up the anode active material, has ionic conductivity but not electron conductivity, and sulfur, which also makes up the anode active material, also has no electron conductivity, so it is used to help transfer electrons during electrochemical reactions. , the anode active material 2 is impregnated with a conductive material (eg, fibrous graphite). Considering the melting point of the anode active material, an effective operating temperature is 3000 or higher.

Furthermore, in Fig. 1, 6 is α-alumina (
A4203) plate, 7 is a corrosion-resistant metal plate such as molybdenum,
8 is a stainless steel casing.

The charge/discharge reaction is So, the entire battery is as follows.

Such sodium-sulfur batteries have the following characteristics because the electrolyte is solid and the positive electrode active material is molten liquid.

(1) Since there are no side reactions during charging and discharging, there is no self-discharge, and the entire charged capacity can be discharged.

(11) High theoretical energy density, 30 to 50 wh/kg (theoretical value 180 Wh 7k) for conventional lead-acid batteries
g), whereas the value several times that (theoretical value 780wh)
/kg) is considered possible.

(il+) Sodium and sulfur used as active materials have extremely small electrochemical reactions, are abundant in resources, and are inexpensive, so they are useful for resource and energy conservation.

As described above, sodium-sulfur batteries have many advantages and are therefore considered promising as future power storage systems.

However, this battery also has the following problems.

(a) Since the battery active materials such as sodium and sulfur are used in a high-temperature molten state, heat loss is large in order to maintain the operating temperature. At present, it amounts to approximately 30% of the amount of discharged power. As shown schematically in Figure 2, increasing the operating temperature improves the voltage characteristics, but currently the entire battery is heated with heater gas using an external power source, etc. Heat loss increases significantly.

(The resistance of β-alumina also adds a little to the loss, but most of the loss is due to heat radiation.) Corrosion of the container may occur if used. For corrosion reactions of brackets, etc.
The active material such as sulfur is consumed, the active material decreases, and the battery capacity decreases.

This tendency is seen when used for a long time.

(c) If the solid electrolyte made of β-alumina or the like is damaged, or if sodium and sulfur come into contact with each other, there is a risk that a rapid reaction between sodium and sulfur will occur.

Due to the above-mentioned circumstances, it is necessary to solve these problems and develop a highly safe sodium-sulfur battery that has low heat loss during battery operation, less corrosion of the container, and less tendency to decrease battery capacity. desired.

[Purpose of the invention]

The purpose of the present invention is to solve the problem of heat loss required for battery operation, which is a drawback of conventional sodium-sulfur batteries.

To provide an advantageous sodium-sulfur battery that solves problems such as corrosion of the battery container due to active materials, reduction in battery capacity, and danger of rapid reaction between sodium and sulfur due to damage to the solid electrolyte. There is a particular thing.

[Summary of the invention]

The present inventors have developed the present invention by focusing on the possibility of achieving the above object by reducing as much as possible the amount of bipolar active material present in the battery reaction region.

That is, in the present invention, the volume of the battery reaction area can be reduced by gradually supplying the required amount of image material to the battery reaction area formed of both cathode and anode active materials. take a method.

In addition, by implementing this method, the amount of image material is secured as required for the power generation capacity of the battery, and the area where the image material is in contact with the solid electrolyte in the battery reaction area is secured as necessary for the power generation capacity. At the same time, it is possible to construct a sodium-sulfur battery in which the volume of the battery reaction area is reduced.

[Embodiments of the invention]

An embodiment of the present invention will be explained below with reference to FIG.

The illustrated sodium-sulfur battery has the following configuration. Solid electrolyte 14 through which sodium ions can pass
A cathode active material 9 consisting of sodium and an anode active material 10 containing sulfur and sodium polysulfide as essential components.
This constitutes the battery reaction area section 20. The battery reaction area 20 is configured to have a small volume by gradually supplying a necessary amount of image material to the battery reaction area 20.

As described above, this sodium-sulfur battery is different from conventional batteries in that the battery reaction area 20 is made small and the active material present in the battery reaction area is gradually supplied.

As a result, the heat capacity of the battery reaction region can be significantly reduced. In this example, it was possible to make it 1/10 or less of the conventional battery. It seems possible to make it even smaller in the future. This makes it possible to reduce the amount of heat required to maintain the operating temperature, which was not possible with batteries of conventional structure. Furthermore, since the battery reaction region 20 can be maintained at a high temperature, a battery with good voltage characteristics and a large charge/discharge capacity can be obtained. Furthermore, since the battery containers 11, 12, and 15 that store active materials for replenishment may be maintained at low temperatures, highly corrosive sodium polysulfide and the like can be maintained at low temperatures. As a result, corrosion of the battery case material is prevented,
It is possible to prevent battery capacity from decreasing during long-term use. Furthermore, by reducing the volume of the battery reaction region 20 where active sodium and sulfur come into contact, even if the solid electrolyte 14 is damaged, abnormal reactions between sodium and sulfur can be minimized.

The specific structure of this embodiment is as follows. In this example, a battery case 11 is filled with 300 crr I3 of molten metal sodium as the cathode active material 9, and a battery case 12 is filled with 340 cm3 of molten sulfur 10 as the anode active material 10.

The image materials 9 and 10 are introduced into the squeezed battery case 13, where they come into electrochemical contact with the solid electrolyte 14 as a boundary to form a battery.

The battery reaction area 20 is defined by the battery case part 3 thus narrowed, and its volume is reduced. There is a narrow gap between the solid electrolyte 14 and the battery case 13, and in this example, this gap is 2
It was arranged. In this example, the central portion of the battery reaction area 20, that is, the central portion of the solid electrolyte 14, is a vacuum structure portion 21. This is to reduce the heat capacity of the battery reaction area 20. In this example, this vacuum structure part 21 is also defined by an inner cylinder 21' made of a solid electrolyte, and the inner cylinder 21' is surrounded by a solid electrolyte 14 forming an outer cylinder, and this is further connected to the battery case part 13.
Although the reaction region section 20 is constructed by surrounding the inner tube 21' with a metal, the vacuum structure section 21 may be formed by forming the inner cylinder 21' from another material such as metal.

In this example, the active material 9.degree. 10 is gradually supplied to the battery reaction region 2o as follows. Upper and lower battery containers 11, 12
．． 15 is connected in advance to a gas pressure regulator 16 via a regulating valve 19. Therefore, this gas pressure regulator 1
6 and the regulating valve 19 to apply a differential pressure to the sodium polysulfide produced as the discharge reaction progresses
5 side, and at the same time, molten gold-rich sodium is replenished from the upper battery container 12.

The temperature distribution during operation of this battery is 3.
75C, each other battery case 11, 12゜15 is 275C
maintained so that As a result, an output of about 200 A, h was obtained between the electrodes 17 and 18.

In addition, during charging, the lower tank 15 in which sodium polysulfide is stored is pressurized, and in the battery reaction area 20, it is decomposed into sodium and sulfur, contrary to the discharging process, and the sodium polysulfide is decomposed into sodium and sulfur, respectively. I returned it to .

Figure 4 shows the charging and discharging characteristics of this battery. This figure shows the capacity @
) is a graph showing the voltage characteristics during discharge at a current density (output current divided by the area of the solid electrolyte) of 100 Ill A /cms. From this figure, when the operating temperature is 375C (graph ■), 275C
It can be seen that the terminal voltage is higher than in the case of (graph ■), and the terminal voltage is stable even if the depth of discharge becomes deeper (even if the capacitance increases and becomes close to 100%).

This is because as the operating temperature rises, the discharge reaction at the anode and the convection and diffusion of the reaction products become more effective, and the specific resistance of β-alumina that forms the solid electrolyte 14 decreases as the temperature rises, resulting in voltage characteristics. This is thought to be because the discharge capacity is improved and the discharge capacity is also increased.

In this embodiment, temperature maintenance of the battery reaction area 20 can be achieved without external heating. That is, the temperature of the reaction region 20 of this battery is maintained at 375C, but external heating is not necessary when raising the temperature due to Joule heat during battery discharge and heat generated due to battery reaction. The time required to raise the temperature from 275C to 375C was within 20 minutes.

The reason why the temperature rise rate is so fast is that this battery has a heat capacity of the reaction region less than 1/10 of that of conventional batteries.

This heating time of 20 minutes means that the reaction area 2 of the active material
Although the replenishment rate to 0.0 is slow at about 0.2 cm 2 /miA, and the residence time of the active material in the reaction region is approximately 2.5 hours, this is sufficiently fast.

Since this battery does not require special heating for the reaction area 20, the external heating of the battery only requires heating the entire area including the reaction area 3 to 275C. Therefore, heat loss could be reduced to less than 1/2 compared to the case where the entire sodium-sulfur battery is heated to 375C as in conventional batteries.

As explained above, according to this embodiment, the volume of the battery reaction area 2o is reduced to reduce the amount of active material present in the reaction area, thereby reducing the heat capacity of this part. This has the effect of reducing heat loss caused to maintain the operating temperature of the section 20. Particularly in the case of this example, there is an advantage that no special external heating is required to raise the temperature of the reaction region 20 or to maintain the temperature. In addition, unlike conventional batteries, it is not necessary to keep the entire battery at a high temperature, but only the reaction area is kept at a higher temperature than the active material storage area. The battery containers 11 and 12 that store the active material for replenishment can be kept at a low temperature, and as a result, the heating energy can be reduced and the temperature of the reaction region can be easily raised, resulting in a battery with good voltage characteristics and a large charge/discharge capacity. It will be done.

Furthermore, by reducing the volume of the battery reaction region 20 where active sodium and sulfur come into contact, there is an effect of minimizing the risk of abnormal reaction between sodium and sulfur when the solid electrolyte is damaged.

In the above example, argon gas was used to transfer the active material. However, as a matter of course, any inert gas can be used, such as p1 helium, nitrogen gas, etc. Nitrogen is suitable in terms of cost.

FIG. 5 shows another embodiment of the invention. In this example, the solid electrolyte 14 in the reaction area section 20 is formed into a small diameter tube and is configured by arranging several tubes in parallel. Sodium 9, which is the cathode active material 9, is introduced into the tubular solid electrolyte 14 from the upper battery case 11. Further, the gap between the capillaries is made as narrow as possible, and sulfur is introduced from the upper battery case 12 through the anode active material 10. The purpose of making the gap as small as possible is to make the heat capacity as small as possible.

As described above, the solid electrolyte 14 is formed into a small diameter tube and arranged in parallel,
A cathode active material is placed inside the tube, and an anode active material 1 is placed in the gap between the tubes.
By introducing 0, the area in which the image-sensitive substances 9 and 10 come into contact with each other via the electrolyte 14 increases. As a result,
Compared to the volume of the image material present in the reaction area section 20, the contact area between the two can be large. Therefore, even though the reaction area portion 20 is formed narrowly by the collapsed battery case 13, sufficient battery performance can be exhibited.

The configuration of other parts of this example is similar to the example described in FIG. 3.

In this example, as in the previous example, the heat capacity of the battery reaction area section 20 is reduced, so that heat loss can be reduced. Further, raising the temperature of the reaction region 20 and maintaining the temperature do not require external heating. The overall heating energy is also small, and the battery reaction area 20 can be maintained at a high temperature even though it is SB.Therefore, the voltage characteristics are good, and the charging and discharging capacity can be maintained as well. The risk of damage to the solid electrolyte 14 is also small.

In each of the above embodiments, the battery containers 11, 12, 13° 15 and the solid electrolyte 14 are cylindrical, but even if they are rectangular or other shapes, the effects of the present invention will not be impaired. It goes without saying that a specific configuration can be adopted as appropriate in terms of its thin shape and structure, the active material used, the physical conditions during its use, and the like.

〔Effect of the invention〕

As mentioned above, the sodium-sulfur battery of the present invention has low heat loss required for battery operation, and therefore has extremely high efficiency, and can solve the problems of corrosion of the battery container and decrease in battery capacity due to the active material. This also eliminates the risk of rapid reaction between sodium and sulfur due to breakage. Therefore, the present invention can be said to be extremely advantageous in that it eliminates the drawbacks of conventional sodium-sulfur batteries. Not only can it be effectively used as a normal battery, but it can also be advantageously used to store surplus power at night.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional sodium-sulfur battery. FIG. 2 is a graph useful for explaining its characteristics. FIG. 3 is a cross-sectional view of one embodiment of the sodium-sulfur battery of the present invention. FIG. 4 is a characteristic diagram of the battery under test. Fifth
The figure is a sectional view showing an example of another embodiment of the present invention. 9... Cathode active material, 10... Anode active material, 20...
・Battery reaction area section, 13... Battery container section, 14... Solid electrolyte, 16... Gas pressure regulator (transfer means), 17.
...Cathode, 18...Anode, 19...Adjusting valve (moving means), 21...Vacuum structure section, 21'...Inner cylinder. Agent Patent Attorney Masami Akimoto's 2-diagram capacity (γ・2 40 capacity (:/-)

Claims (1)

[Claims] 1. A cathode active material consisting of sodium and an anode active material containing sulfur or l-'Jium polysulfide as an essential component, with a solid electrolyte through which sodium ions can pass as a boundary. A sodium hydroxide solution comprising a stain pond reaction area, and a necessary amount of an image substance is gradually supplied to the battery reaction area, thereby reducing the volume of the battery reaction area. - A method of forming a sulfur battery. 2. The active material is gradually supplied using a transportation means for supplying the active material according to claim 1).
- A method for forming a 1J sulfur battery. 3. A sodium ion F7 battery in which a cathode active material made of sodium and a cathode active material whose essential component is sulfur or sodium polysulfide are in contact with each other, with a solid electrolyte through which sodium ions can pass, forming a battery reaction region. In the battery, the amount of the image material is secured as required for the power generation capacity of the battery, and the area in which the image material is in contact with the solid electrolyte in the battery reaction area is secured as necessary for the power generation capacity. A sodium-sulfur battery characterized by being formed by reducing the volume of a reaction region. 4. The sodium-sulfur battery according to claim 3, wherein the battery reaction region is provided with a moving means for gradually supplying the active material to the region. 5. The battery reaction area includes an inner cylinder made of metal or solid electrolyte whose interior is kept in vacuum, an outer cylinder made of solid electrolyte surrounding the inner cylinder, and a battery container further surrounding the outer cylinder. The gap between the inner cylinder and the outer cylinder is configured as narrow as possible, and the gap between the outer cylinder and the battery case is also configured as narrow as possible, and a flow path for the active material is formed in each gap. A sodium-sulfur battery according to claim 3 or 4, characterized in that: 6. The battery reaction area includes a solid electrolyte arranged in a thin tubular shape in parallel, and a battery container surrounding the solid electrolyte,
Claim 3 or 4, characterized in that the gap between the solid electrolyte thin tubes is configured to be as narrow as possible, and the gap and the solid electrolyte thin tube are used as a flow path for the active material.
The sodium-sulfur battery described in .