JPS58137974A - Sodium-sulphur cell system - Google Patents

Abstract

PURPOSE:To facilitate taking out and cleaning of active masses in both electrodes by making a cell an a loop construction and transferring active masses by using an inactive gas, and installing cleaning systems in between. CONSTITUTION:When power is decreased during charge-discharge cycling, a valve 33 is opend, and argon gas is fed to a unit cell 35 from a bomb 31 to recover molten sodium 34 and a sulphur mixture 37 in a sodium tank 26 and a sulphur tank 30 respectively. Then the sodium tank 26 and the sulphur tank 30 are pressurized with argon gas 31 through a valve 32, and thereby impurities in molten sodium which is an anode active mass are removed with a cold trap 38 and the molten sodium is fed to the unit cell 35 again, and impurities in sulphur mixture which is a cathode active mass are removed with a zirconium filter 38 and the molten sulphur is returned to the unit cell 35. By this process, since active masses in both electrodes are purified, almost same electric power as an initial stage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power storage system using a sodium sulfur battery, and relates to a loop type sodium-sulfur battery with a long life and high safety, which is suitable for a large capacity storage system of 1%.

A specific structural example of a sodium-sulfur battery is shown in Figure 1. This battery uses molten sodium as the cathode active material 10, molten sulfur and sodium polysulfide as the anode active material 12, and sodium sulfur as the electrolyte. This was used for the solid electrolyte 14 containing the following properties. This solid electrolyte is composed of glass or ceramics, but β-alumina (N~40.) is made of sodium-
Because of its high ionic conductivity, most of the batteries currently under development use it as an electrolyte. Since β-Al has no electronic conductivity, the anode 16 and cathode 18
It also serves as a separator to separate the two. Sodium polysulfide.

Although it has ionic conductivity, it has no electronic conductivity.
Since it has no electron conductivity, the anode active material is immersed in a conductive material to help transfer electrons during electrochemical reactions. The operating temperature is 300 to 50, considering the melting point of the anode active material.
0C is valid.

In the figure, 20t;tα-alumina ring, 22 is a corrosion-resistant metal plate made of molybdenum or the like, and 24 is a stainless steel casing.

What is the photodischarge reaction?

The battery as a whole is 2Na+ 8- Na18 In this battery, the electrolyte is solid, and the anode active material is molten MIIl.
Since it is in liquid form, it has the following characteristics.

Since there are no side reactions during charging and discharging, there is no self-discharge and the entire photoelectric capacity can be photoelectrically charged.

b) The decrease in yit during high rate discharge is extremely small.

C) The theoretical energy density is 3 for conventional lead-acid batteries.
0 to 50Wb/Kf (theoretical value 10Wh/hour), but several times that amount (theoretical value 1178G1W・h/Kf)
is considered possible.

d) Sodium and sulfur, which are used as active materials, have extremely small electrochemical equivalents and are abundant and inexpensive resources, so they are useful for saving resources and energy.

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

However, single batteries have the following problems.

That is, (1) since highly active substances such as molten sodium and sulfur are used at high temperatures, the purity of the active material decreases due to corrosion of the container, etc., resulting in a decrease in performance during long-term use.

(2) If the solid electrolyte such as β-alumina is damaged, etc.
There is a risk of a rapid reaction between sodium and sulfur, but there is no repair method.

(3) Since any active material is oxidized and loses its activity when exposed to air, it is not easy to seal it together with an inert gas such as argon in a small battery.

In order to solve these issues, we have developed a long-life, highly safe battery that allows impurities to be removed from the active material, is easy to take out and contain the active material if necessary, and can be repaired inside the battery. Development of a system is desired.

The object of the invention is the drawbacks of conventional batteries. In order to solve problems such as shortened battery life due to deterioration of the purity of the active material, removal of the active material, and impossibility of repair due to the incorrosiveness of the containment, a loop type structure is used to make the active material inert. The object of the present invention is to provide a 7'C sodium-sulfur battery system using gas for transport and installing a purification thread in the middle.

The difference from conventional batteries is that the battery has a loop structure that allows the active materials in the battery to be transferred into tanks as needed using the pressure of inert gas. As a result, in an emergency such as damage to a solid electrolyte such as β-alumina, the active material can be removed in an emergency, which has not been possible in conventional batteries.

Furthermore, this system is notable in that it is possible to purify the active material by providing a trap (impurity purification system) within the loop. Therefore, as will be described later, there is an advantage that the battery life can be extended. Another feature is that the loop-type battery simplifies the sealing method, which was a problem with conventional batteries that sealed inert gas.

An embodiment of the present invention will be explained below with reference to FIG. 350 x 1 molten metal sodium 34t as cathode - 200 crll'' sodium polysulfide, (Na, 8
m) and a mixture of sulfur and carbon felt.
A single cell 35' using β-alumina as a diaphragm 36 separating the two is heated to 300 to 350C and kept at this temperature. The cell was placed in a stainless steel container lined with molybdenum steel to prevent leakage of negative and anode active materials. This battery initially provided approximately aoowh of power. After repeated charging and discharging times, the power decreased to about 290 Wh, so the molten metal sodium 34 and the sulfur and yellow mixture were sent from the argon gas pump 31 with 33 tons of pulp to the cell 35. '37 are collected into tank 26 for the sodium receiver and tank 30 for the sulfur receiver, and then 32 tons of pulp are passed through the argon gas 31 into the tank 26 for the disodium receiver and the tank 3 for the sulfur receiver.
By pressurizing 0.

The molten metal sodium of the anode active material is placed in cold trap 3.
8, impurities are removed and returned to the cell 35, and the sulfur mixture of the anode active material is removed by the zirconium metal filter 28 and returned to the cell 35. In this way, the active materials of both electrodes are purified and purified. KotoK, I was able to get the same amount of power as I did in the early days.

As described above, according to this embodiment, it is possible to extract and purify the active material of the n-by-one polarity, which has the effect of completely preventing a decrease in the battery's performance and also reducing the risk of long-term hemorrhoids.

In the above embodiment, argon gas is used to extract the active material, but it is of course possible to use an inert gas. Helium, nitrogen gas, etc. can also be used, but nitrogen is suitable in terms of cost.

Of course both are possible.

According to the present invention, since the active material of both electrodes can be extracted and purified, the life of the battery can be extended, and emergency extraction of the active material in the event of an abnormality and replacement of parts such as β-alumina of the diaphragm are facilitated. This has the effect of significantly improving safety.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a conventional sodium-sulfur battery, and FIG. 2 is a system flow diagram of the sodium-sulfur battery of the present invention. 35! :L6I...
Sodium-sulfur cell, 4...molten metal 30
38 thorium receiver, H...
・Sulfur mixture receiver, Giko-0

Claims (1)

[Claims] 1. In a sodium-sulfur battery in which a cathode active material such as molten sodium and an anode active material such as molten sulfur are in contact with each other with a solid electrolyte such as alumina as the boundary. A sodium-sulfur battery system in which each active material storage tank is provided externally and the active material can be transferred between the battery and the tank by pressurizing an inert gas. 2. The sodium-sulfur battery system according to claim 1, characterized in that it is provided with a purification device for removing impurities from the trapped active material during transport. 3.% Claims [As an active material purification device for a sodium-sulfur battery system according to item 2, a combination of one or both of a high temperature) 1 ruta and a cold trap]
Patented use of nine purifying devices for sodium
Sulfur battery system.