JPS60148071A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To reduce internal resistance of a battery and increase voltage performance and capacity by making a cathode matrix thin and moving cathode active material into a unit cell container. CONSTITUTION:A cathode current collector 20 is installed in a cathode container 8, and a battery reaction zone 21 comprising a 2mm. thick cathode matrix is arranged in a gap between beta''-alumina 3 and the cathode current collector 20. The cathode container 8 is separated into a sulfur chamber 22 and a sodium polysulfide chamber 23 by the cathode current collector 20. In this battery, sodium polysulfide is produced in the battery reaction zone 21 and new sulfur is supplied from the sulfur chamber 22. Sulfur is supplied by gas pressure difference in each gas line installed in the sulfur chamber 22 and sodium polysulfide chamber 23. Thereby, internal resistance of the battery is reduced and voltage performance and capacity are increased.

Description

[Detailed Description of the Invention] [Fields of Application of 抛明] The present invention relates to a power storage system using a sodium-sulfur battery (IJ) which has good voltage characteristics and a large charge/discharge capacity and is particularly suitable for a large capacity storage system. Regarding Umu sulfur batteries.

[Background of the invention]

) There are two types of IJ Umu sulfur batteries: single cell type and loop type. First, we will explain the principle and characteristics of single-cell batteries. A specific structural example of a sodium-sulfur battery with a capacity of 100 Ah is shown in Figure 1 (@This battery uses molten sulfur as the cathode active material 1), molten sulfur and sodium polysulfide as the anode active material 2, and the electrolyte In this example, a solid electrolyte 3 having sodium ion conductivity is used. This solid electrolyte is composed of glass or ceramics, but especially β“-alumina (
Since Na20.6At20g) has high conductivity for sodium ions, most of the batteries currently under development use this as the electrolyte, and Figure 1 also shows an example using β''-alumina. - Since alumina does not have electron conductivity, it also serves as a separator that separates the anode 4 and cathode 5. Sodium polysulfide has
Although it has ionic conductivity, it has no electronic conductivity, and sulfur also has no electronic conductivity, so the anode active material is impregnated into a conductive material, mainly graphite felt 9, in order to help transfer electrons during electrochemical reactions. has been done. Considering the melting point of the anode active material, an operating temperature of 300"C or higher is considered effective.
50°C is commonly used.

In the figure, 6 is an α-alumina ring, which maintains electrical insulation. 7 is a corrosion-resistant metal plate made of molybdenum or the like, and 8 is an anode container made of stainless steel.

The charge/discharge reaction is As for the battery as a whole However, ・X is usually in the range of 2 to 5.

FIG. 2 shows the voltage characteristics of the 100Ah cell shown in FIG. 1.

The voltage characteristic 10 in the figure is the surface current density 1 of β〃-alumina.
This is a characteristic of 00mA/Crr12. The terminal voltage is almost constant at the beginning of the discharge, but tends to drop rapidly at the end of the discharge. Terminal voltage drop! This is because as the pond reaction progresses, the reaction product changes from a mixture of Na285 and S at the initial stage of discharge to 25 g of Na2S41Na. By the way, l'Jazsg at the beginning of the discharge.
In the +8 state, the open circuit voltage is 2,07 V.

This battery has the following characteristics because the electrolyte is solid and the anode 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.

(2) High theoretical energy density, which is several times higher than that of conventional lead-acid batteries (theoretical value 180Wh/Kg), which is 30 to 50Wh/KV (theoretical value 780Wh/Kg)
is considered possible.

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

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

However, in a single cell system in which a battery active material is sealed in an airtight container as shown in FIG. 1, the energy (battery capacity) that can be stored in a 1 ff5 battery is limited. What they came up with was a loop-type sodium-sulfur battery.

A specific structural example of a loop type sodium-sulfur battery is shown in Part 3.
As shown in the figure. The basic principle and characteristics of the loop type sodium-sulfur battery are the same as those of the sodium-sulfur battery described above, so the structure and characteristics will be described here. Sodium 1 was put into the solid electrolyte tube 3 to serve as a cathode, and sulfur 2 was injected between the solid electrolyte tube and the outer anode container 8 to serve as an anode. Sodium 1 is supplied from sodium storage tank 11 to cathode container 16 through sodium impurity removal tank 14 . If necessary, it can be circulated to the sodium storage tank 11 via the drain line 13.

Sulfur 2 can also be supplied from the sulfur storage tank through the sulfur impurity removal tank 15 to the anode container 8, and can be circulated to the sulfur storage tank 12 as required.

The circulation of each active material is carried out by controlling the pressure of the gas system piped to the container or tank. 17 is an argon gas cylinder, 18.19 is a flow! In the IJ Umu sulfur battery, the battery capacity can be increased because the battery active material can be supplied to the battery reaction region according to the progress of the battery reaction. However, even in a loop type battery, if the thickness of the anode layer in the battery reaction area is the same as that of a single battery, the voltage characteristics cannot be improved as will be detailed in the examples. In the IJ Umu sulfur battery (loop type), the depth of discharge is as shallow as 60%, that is, Na2S4 and Na2Sg in the sodium polysulfide produced in the battery reaction.
By preventing the formation of low-sulfide substances such as those shown in FIG. 2, it is possible to prevent the terminal voltage from decreasing as shown in FIG. However, in this case, the amount of anode active material is 1
．． Since about 4 times as much is required, the following explanation will be given assuming that even low sulfides are used for battery reactions.

As mentioned above, the conventional single battery system is easy to handle because it is hermetically sealed, but the battery capacity is small and it is not suitable for power storage.
◎ On the other hand, loop type batteries can be expected to increase capacity compared to single battery systems, but they cannot improve voltage characteristics, and operation and control are complicated, and the equipment is also complicated. This makes maintenance and management difficult.

In order to solve these problems, it is desired to develop a sodium-sulfur battery that has good voltage characteristics, a large capacity per battery, and is easy to operate and operate.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, reduce the internal resistance of the battery, and provide a large capacity IJ Umu sulfur battery with good voltage characteristics.

[Summary of the invention]

The present invention has experimentally confirmed that most of the internal resistance of IJ Umu sulfur batteries is accounted for by the anode matrix portion, and that the internal resistance decreases when the anode matrix is made thinner, and when the anode matrix is made thinner. However, as a means to overcome this decrease in capacity, the sodium-sulfur battery is characterized by moving the positive electrode active material within the cell container.

[Embodiments of the invention]

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

The example of the present invention has a battery capacity of 200 Ah without changing the dimensions of the β"-alumina compared to the 100 Ah battery shown in FIG. The anode collector plate 20 is attached to the anode container 8 of the battery, and the anode collector plate 21 with a thickness of 2111111 is placed in the gap between the β"-alumina 3 and the anode electrode plate 20. The battery reaction area 21f made of IJ socks is placed at the provided point. be. The second feature is that the anode container 8 is separated into a sulfur chamber 22 and a sodium polysulfide chamber 23 by an anode current collector tube 20. In the battery of the present invention, sulfur reacts with sodium ions passing through β"-alumina in the battery reaction region 21 to generate sodium polysulfide. When the reaction region is filled with sodium polysulfide, new sulfur is introduced from the sulfur chamber 22. To supply sulfur, gas systems are installed in the sulfur chamber and the sodium polysulfide chamber, and the difference in gas pressure is utilized.In addition, in order to return the sodium polysulfide 34 to the sulfur chamber 22 during charging, the partition wall 27 is installed. Regarding the 0 cathode side, there is no particular difference in structure from the 100Ah conventional cell shown in Figure 1.In Figure 4, the battery capacity is 200Ah, which is twice that of the conventional cell, so the amount of sodium has changed. This has doubled the size of the cathode container 16.

The voltage characteristics of the battery of the present invention are shown in FIG. In the figure, reference numeral 28 indicates the voltage characteristics of the battery of the present invention.For comparison, the voltage characteristics 10 of the conventional cell shown in FIG. 2 are also shown. Note that β“−
The current fi degree per unit surface area of alumina is 1OOcrrI
A/crn2. From Figure 5.

In the present invention, the terminal voltage is high at 9V! The pressure characteristics have been improved compared to conventional single cells. This is attributable to the decreased internal resistance of the battery of the present invention. Also, the battery capacity is 200Ah.
This is twice as much as a conventional single battery.Here, we will explain in detail the circumstances in which the method of the present invention increased the battery capacity and reduced the internal resistance.

The following two methods can be considered to increase the battery capacity in a single cell system. First, the capacity of the solid electrolyte is increased, and the amount of active material is also increased in proportion to the increase in area. Second, the amount of active material is increased without changing the solid electrolyte. However, with the current solid electrolyte manufacturing technology, the former has a diameter of 50 and a length of 6.
It is difficult to produce a solid electrolyte with a size of 00M or more, and further enlargement cannot be expected in the future due to problems with the material strength of the solid electrolyte.

In the latter method, since the surface area of the solid electrolyte does not change, suppose that the conventional cell shown in Figure 1 has a capacity of 20 times the capacity t.
If we consider the case of setting it to 0Ah, the shape will be as shown in FIG. 6. That is, on the anode side, the diameter of the anode container 8 becomes larger, and the thickness of the anode matrix formed of the anode active material and graphite felt increases from 7 m of a 100Ah battery to 12 mm. Since the size is doubled, the cathode container becomes larger and the cathode current collector tube 5 becomes longer.

In the structure shown in FIG. 6, the battery capacity increases, but the internal resistance increases as described below.

ff1r! Looking at the breakdown of the internal resistance of the 100Ah battery shown in Figure 1, the resistance per unit area of the β''-alumina portion is 1.2Ω, and the anode matrix portion is 2.8Ω.

Other battery containers and electrode extensions can be ignored compared to the above two cases. Therefore, the resistance of a sodium-sulfur battery is β
- It can be said that the resistance of the alumina part is 30%, and the remaining 70% is the resistance of the anode matrix part. The reason why the anode matrix portion accounts for most of the resistance is the difference in thickness between β"-alumina and the anode matrix. The resistivity of β"-alumina is 60 at the battery operating temperature of 350"C. α, and the resistivity of the positive coffin matrix made of sulfur, sodium polysulfide, and graphite felt is 3 to 4ΩQn
It is. The thickness of the anode matrix is 71HJn-β“-
The thickness of the alumina is approximately 2 mm. Therefore, although the anode matrix has a low resistivity, it accounts for 70%'ii of the battery's internal resistance.

Therefore, in the structure shown in FIG. 6, when the battery capacity is doubled, the anode matrix thickness increases from 7 to 12 layers to 1.
The resistance of the anode matrix increases by 7 times, and the internal resistance of the entire pond increases by approximately 1.5 times. Therefore, the sixth
If the voltage characteristics of the pond shown in the figure are added to Figure 5, it becomes 29.
An extreme drop in terminal voltage can be seen.

In contrast, in Figure 4 of the present invention, the thickness of the anode matrix is 2 Term, so the resistance of the anode matrix per unit area is 0.8Ω, and the internal resistance of the entire battery is 200Ah. 2Ω per unit area and 1/of the internal resistance of the 100Ah cell in Figure 1.
It becomes 2. Therefore, the voltage characteristics are improved as previously shown at 28 in FIG.

The reason for choosing the thickness of the anode matrix in this example is based on the current resistivity of β''-alumina. It becomes the resistance value.

Even if the thickness of the anode matrix is made thinner than this, the effect is small. However, in the future, if the resistivity of β"-alumina can be further reduced, it will be desirable to make the anode matrix even thinner. Furthermore, the thickness of the anode matrix in conventional single cells depends on the discharge time and the current density per solid electrolyte surface. It is determined by the selection of

For example, in the example shown in Figure 1, the discharge time is 8 hours and the current density is 10
0 nl A/tyn'', the thickness of the anode matrix is 7 mm.

As described above, the capacity of the battery is increased by the method of the present invention,
It was also revealed that internal resistance could be reduced and voltage characteristics could be improved.

Furthermore, the electric power that can be extracted by the battery of the present invention is shown in FIG.

From the figure, the internal resistance of the battery of the present invention is 1/1 compared to the conventional single battery.
2, the power loss is 172 for the same battery current, and the energy efficiency of the battery is improved. For example β
“-Alumina surface current density 100 mA/crn”
(Discharging specifications using a conventional single cell) The output power can be changed to 1.2 times that of the conventional single cell shown in Fig. 1. Furthermore, when comparing the maximum power of the batteries, it can be seen from the peak value of the power curve in FIG. 7 that one battery of the present invention can obtain twice the output power of a conventional single battery. The ability to obtain a large instantaneous output is effective not only for IJ sulfur batteries (for power storage) but also for automobiles, etc., which require instantaneous output.

In the battery of the present invention shown in FIG. 4, there were concerns about the fluidity of the anode (IJ) because the thickness of the anode was as thin as 2tcn, and the IJ (highly viscous sulfur and polysulfide).

As shown in Figure 8, there was no need to worry. The 200Ah battery of the present invention requires a flow rate of 0.25 (77+"/mjn, but even with highly viscous sulfur, the flow rate is 0.03K
It is possible to flow with a pressure drop of less than SI/cm" and can be operated at very low pressure.The viscosity of sulfur is 500CP at 350'c, and the viscosity of sodium polysulfide is 2
It is 0CP.

The sodium-sulfur battery of the present invention has been described in detail above. By inserting an anode current collector tube into the anode container, the thickness of the anode matrix portion can be reduced, internal resistance can be reduced, and voltage characteristics can be improved.

and - It has become clear that even if the battery capacity is increased, the internal resistance does not increase. ◇ FIG. 9 shows another embodiment of the present invention. In FIG. 6, the vertical relationship of the embodiment shown in FIG. 4 is reversed to simplify the structure of the anode current collector tube provided in the anode container 8 and to make it polysulfurized.)
The partition wall 27 of the aluminum chamber 23 is removed and the number of joints between α-alumina and metal is reduced to reduce manufacturing costs. Regarding the cathode side, n) When the liquid level of the IJium 1 drops, an attempt is made to suck up and supply sodium with the mesh 32. The operation of the battery is the same as in the embodiment shown in FIG.

FIG. 10 shows another embodiment of the invention. In the figure, the anode active material is placed in β''-alumina, and the arrangement of the active material is reversed from the examples of the present invention shown in Figures 4 and 9. In the single cell system, the method of placing the positive electrode active material in β''-alumina is rarely adopted for the following two reasons. Firstly, the battery capacity cannot be increased, and secondly, β"-alumina is often damaged when the battery temperature rises. However, according to the method of the present invention, the anode material is inside the β"-alumina. Even if the sulfur in the β"-alumina is added, it will not cause a decrease in capacity. To prevent damage to the β"-alumina, when lowering the battery temperature, the sulfur in the β"-alumina can be flushed out into the sulfur chamber 22 using gas pressure and stored. For example, troubles caused when the battery temperature rises are eliminated.

In Figure 10, considering that the battery of the present invention is used to form an assembled battery for power storage, it is undesirable to have unnecessary protrusions, piping, electrodes, etc. around the battery container, so the active material on the anode side is All the gas piping for flowing the battery was constructed from the upper end of the battery, and the electrode terminals were taken out from the upper and lower ends of the battery.

FIG. 11 is a diagram showing an assembled battery constructed using IJ Umu sulfur batteries according to the present invention. The feature of this assembled battery is that the outer shape of the battery container of the present invention is a hexagonal column, and the cells are arranged in a hexagonal close-packed structure to improve space utilization. Electrode terminal 3
3 was concentrated at the top and bottom ends of the battery.

In Figure 11, each battery is connected with a lead wire, but if the batteries are in close contact, each cathode container 16 and anode container 8 themselves will serve as a lead wire, so the connection is not necessarily necessary. Not necessary. At this time, α-alumina 6, which electrically insulates the anode side and the cathode side, also functions effectively to insulate both electrodes of the assembled battery.

〔Effect of the invention〕

According to the present invention, even if the battery capacity is increased, the internal resistance of the battery can be reduced, resulting in a large capacity with good voltage characteristics.
You can get a Jumu sulfur battery.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional 100Ah single cell type IJ Umu sulfur battery. Figure 2 is a battery voltage characteristic diagram of Figure 1. Figure 3 is a cross-sectional view of a conventional Loopya sodium-sulfur battery.
FIG. 4 is a cross-sectional view of the sodium-sulfur battery of the present invention, and FIG.
The figure is a comparison diagram of the voltage characteristics of the battery of the present invention and a conventional battery. Figure 6 is a cross-sectional view showing an example of a conventional unit cell with double the battery capacity using β"-alumina of the conventional unit cell. , FIG. 7 is a comparison diagram of the power characteristics of the battery of the present invention and a conventional battery, FIG. 8 is a graph of the flow characteristics of the anode active material, FIGS. 9 and 10 are cross-sectional views of modified examples of the battery of the present invention, Fig. 11 is a perspective view showing an example in which the battery of the present invention is applied to an assembled battery. 1... Cathode active material, 2... Anode active material, 3... Solid electrolyte, 4... Anode. 5... Cathode, 7... Corrosion-resistant metal plate, 8 Anode container, 9... Conductive material, 11...) IJum storage tank 212... Sulfur storage tank,
13... Drain line, 16... Cathode container, 20
...Anode current collector tube, 22...Sulfur chamber, 23...Polysulfide) IJ chamber, 27...Partition wall, 33...Electrode terminal. Destination 1 Flash 2 Capacity C7=) =F] 30 Fig. 4 50 Capacity (Phantom No. 60 Foil q mouthpiece 5t!!, Current hair 80 Pressure k Mu P (Tsu/C G2) Yu 9 10th []

Claims (1)

[Claims] 1. With a solid electrolyte through which sodium ions can pass as a boundary, a cathode active material containing IJium as an essential component,
In an IJ Umu sulfur battery (in which an anode active material containing sulfur or sodium polysulfide as an essential component is in contact), an anode current collector tube facing the surface of the solid electrolyte is provided in the container of the anode active material. Sodium-sulfur battery @