JPH07230823A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To secure supply of sodium, and maintain a discharge capacity of a battery by preventing reduction of gas pressure of gas in a cartridge containing sodium. CONSTITUTION:An insulation ring 2 is jointed and fixed to an upper end of a positive electrode container 1 of a cylindrical form. With an inner circumference of the insulation ring 2, a solid electrolyte tube 3 which sodium ions permeate selectively is jointed. In a negative electrode chamber 6 inside the solid electrolyte tube 3, a cartridge 8 containing sodium as negative electrode active material is disposed. Sulfur as positive electrode active material is contained in a positive electrode chamber 4 between the positive electrode container 1 and the solid electrolyte tube 3. The cartridge 8 is formed to be closed, and nitrogen gas is enclosed in space inside it in the pressurized condition. The cartridge 8 is formed of metal or alloy such as zinc (Zn), nickel (Ni), etc., which are less reactive to nitrogen. Otherwise, a coating layer of the metal or allay is formed on inner surfaces of the cartridge 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sodium-sulfur battery used as a secondary battery for power storage and the like.

[0002]

2. Description of the Related Art Generally, in a sodium-sulfur battery, a ring-shaped insulator made of alpha alumina is attached and fixed to the upper end of a bottomed cylindrical anode container, and the inner peripheral surface of this insulator is made of beta alumina. The bottomed cylindrical solid electrolyte tube is joined and fixed. This solid electrolyte tube selectively permeates sodium ions, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. Further, sulfur as an anode active material is accommodated in the anode chamber between the anode container and the solid electrolyte tube.

The container is made of stainless steel. Nitrogen gas or argon gas is filled in the upper part of the container at a pressure higher than that of the outside of the container, and sodium is introduced from the sodium flow hole provided at the bottom of the container into the cathode chamber. (For example, JP-A-57-147880).
Issue). Then, at the time of discharge, sodium in the storage container is supplied into the cathode chamber through the sodium flow hole under the pressure of nitrogen gas, becomes sodium ions, passes through the solid electrolyte tube, reacts with sulfur in the anode chamber, and reacts with sodium polysulfide. To generate. On the contrary, at the time of charging, sodium polysulfide is decomposed in the anode chamber, and the generated sodium ions permeate the solid electrolyte tube and return to the cathode chamber. Further, sodium passes through the sodium flow hole and reaches the inside of the container.

[0004]

However, when the battery is repeatedly charged and discharged, the operating temperature of the battery is 300 to 350 ° C.
Therefore, the nitrogen gas sealed in the container at a higher pressure than the outside of the container reacts with the stainless steel forming the container and is absorbed. For this reason, the pressure of the nitrogen gas in the container gradually decreases, and it becomes difficult for sodium in the container to be supplied into the cathode chamber from the sodium flow holes. As a result, there has been a problem that the pressure of nitrogen gas is lowered particularly at the end of discharge when the amount of sodium in the container is reduced, supply of sodium becomes difficult, and the discharge capacity of the battery is gradually reduced.

When argon gas is used, if the set pressure of argon gas in the container is low, sodium in the container cannot flow out of the container at the end of discharge. On the other hand, when the set pressure of argon gas is high, there is a problem that if the cathode seal is damaged at the end of charging, sodium in the container flows out of the battery and adversely affects the surroundings.

The present invention has been made by paying attention to the problems existing in the prior art. It is an object of the present invention to provide a sodium-sulfur battery capable of preventing a decrease in gas pressure of a gas in a container for containing sodium, ensuring the supply of sodium, and maintaining the discharge capacity of the battery. .

Another object is to ensure that the sodium in the container can be discharged out of the container even at the end of discharge, and the sodium in the cathode can be damaged even if the cathode seal is damaged at the end of charge. It is intended to provide a sodium-sulfur battery capable of preventing hydrogen from flowing out of the battery.

[0008]

In order to achieve the above object, in the sodium-sulfur battery of the invention according to claim 1, a solid electrolyte that selectively permeates sodium ions in an anode container via an insulator. A tube is arranged, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube, and sulfur as an anode active material is provided in an anode chamber between the anode container and the solid electrolyte tube. In a sodium-sulfur battery which is housed and in which the nitrogen gas is housed in the inner space of the housing container at a higher pressure than outside the housing container, the housing container is filled with zinc (Zn), nickel Ni), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag), gold (A
u) and at least one metal or alloy selected from the group consisting of platinum (Pt).

According to the second aspect of the invention, a solid electrolyte tube that selectively permeates sodium ions through an insulator is arranged in the anode container, and a cathode active material is used as a cathode active material in the cathode chamber of the solid electrolyte tube. A storage container for storing sodium is placed, sulfur as a positive electrode active material is stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas is contained in the internal space of the storage container outside the storage container. In a sodium-sulfur battery housed at a higher pressure, the container is made of at least one ceramic material selected from the group consisting of alumina, carbide and nitride, which have low reactivity with nitrogen. is there.

Further, according to the invention described in claim 3, a solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in the anode container, and a cathode active material is provided in a cathode chamber in the solid electrolyte tube. A storage container for storing sodium is placed, sulfur as a positive electrode active material is stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas is contained in the internal space of the storage container outside the storage container. In a sodium-sulfur battery housed at a higher pressure than that, zinc (Zn), nickel (Ni), cobalt (C) having low reactivity with nitrogen is formed on at least the inner surface of the container.
o), copper (Cu), molybdenum (Mo), silver (Ag),
It is formed by coating with a coating layer of at least one metal or alloy selected from the group consisting of gold (Au) and platinum (Pt).

Further, in the invention according to claim 4, a solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in an anode container, and a cathode active material is provided in a cathode chamber in the solid electrolyte tube. A storage container for storing sodium is placed, sulfur as a positive electrode active material is stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas is contained in the internal space of the storage container outside the storage container. A sodium-sulfur battery housed at a higher pressure than that in which at least one ceramic material selected from the group consisting of alumina, carbides and nitrides is coated on at least the inner surface of the container. Is.

[0012] In addition, in the invention according to claim 5, a solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in the anode container, and a cathode active material is provided in a cathode chamber in the solid electrolyte tube. As a storage container for storing sodium as the storage container, the anode chamber between the anode container and the solid electrolyte tube contains sulfur as an anode active material, and nitrogen gas is stored in the internal space of the storage container. In a sodium-sulfur battery housed under a higher pressure than outside, a nitriding layer is provided on at least the inner surface of the container.

Further, in the invention according to claim 6, a solid electrolyte tube that selectively permeates sodium ions through an insulator is arranged in the anode container, and a cathode active material is provided in the cathode chamber in the solid electrolyte tube. A storage container for storing sodium is placed, and sulfur as a positive electrode active material is stored in the anode chamber between the anode container and the solid electrolyte tube, and gas is introduced into the internal space of the storage container from outside the storage container. In a sodium-sulfur battery housed at a high pressure, neon (Ne), argon (Ar), and krypton, which are inert to the container and have a low solubility in sodium, are contained in the space inside the container. It is filled with at least one kind of rare gas selected from the group consisting of (Kr).

Further, in the invention of claim 7, in the invention of claim 6, the gas contained in the container contains the rare gas and the impurity gas, and the content of the impurity gas is the discharge. It is calculated by setting the pressure of the rare gas at the end of the battery to be equal to or higher than the pressure of sodium outside the container and setting the total pressure of the rare gas and the impurity gas at the end of charging to be lower than the atmospheric pressure.

[0015]

According to the first aspect of the invention, the container for containing sodium is zinc (Zn), nickel (Ni),
Cobalt (Co), copper (Cu), molybdenum (Mo),
It is formed of at least one metal or alloy selected from the group consisting of silver (Ag), gold (Au) and platinum (Pt). Since these metals or alloys are materials having a low reactivity with nitrogen, the nitrogen enclosed in the container does not react with the container itself even if charging and discharging are repeated. Therefore, the pressure of nitrogen in the accommodating container is not lowered so much that the amount of sodium pushed out by the nitrogen pressure can be prevented from changing with time. Therefore, the discharge capacity of the battery can be maintained for a long period of time.

Further, in the invention described in claim 2,
The container is made of at least one ceramic material selected from the group consisting of alumina, carbides and nitrides. Since these materials also have low reactivity with nitrogen, it is possible to prevent the nitrogen enclosed in the container from reacting with the container itself. Therefore, the pressure of nitrogen in the container is maintained.

Further, in the invention according to claim 3, at least the inner surface of the container is zinc (Z) having a low reactivity with nitrogen.
n), nickel (Ni), cobalt (Co), copper (C
u), molybdenum (Mo), silver (Ag), gold (Au), and platinum (Pt), and a coating layer of at least one metal or alloy selected from the group consisting of them. Since this coating layer has low reactivity with nitrogen, the nitrogen enclosed in the container is prevented from reacting with the container itself.

In addition, in the invention described in claim 4, at least the inner surface of the container is coated with at least one ceramic material selected from the group consisting of alumina, carbide and nitride. Since this coating layer has low reactivity with nitrogen, the nitrogen enclosed in the container is prevented from reacting with the container itself.

According to the invention of claim 5, a nitride layer is provided on at least the inner surface of the container. This nitrided layer is obtained by reacting metal with nitrogen in advance, and has low reactivity with nitrogen in the container. Therefore, the nitrogen enclosed in the container is prevented from reacting with the container itself.

Further, in the invention according to claim 6, in the space in the container, at least one rare gas selected from the group consisting of neon (Ne), argon (Ar) and krypton (Kr). Is filled. In this case, since these rare gases have low reactivity with the container and have low solubility in sodium, the gas pressure in the container is prevented from decreasing with time even during repeated charging and discharging.

In addition, in the invention of claim 7, the gas contained in the container contains the rare gas and the impurity gas. The content of the impurity gas in the gas is such that the pressure of the rare gas at the end of discharge is equal to or higher than the pressure of sodium outside the container, and the total pressure of the rare gas and the impurity gas at the end of charge is lower than atmospheric pressure. Calculated according to the conditions. A low-purity gas containing the amount of impurity gas calculated in this way can be used. Therefore, sodium can be smoothly supplied from the container, and sodium can be prevented from flowing out from the battery when the cathode seal is damaged.

[0022]

Embodiments (Embodiment 1) Embodiments embodying the present invention will be described below with reference to the drawings. As shown in FIG. 1, the anode container 1 is made of aluminum and has a bottomed cylindrical shape. The insulating ring 2 as an insulator is formed of alpha alumina and is joined and fixed to the upper end edge of the anode container 1. The solid electrolyte tube 3 made of beta-alumina has a bottomed cylindrical shape, and its upper end is joined to the inner peripheral surface of the insulating ring 2 to allow sodium ions to pass therethrough. The anode chamber 4 is formed between the anode container 1 and the solid electrolyte tube 3 and accommodates an anode mat 5 impregnated with sulfur S as an anode active material. The cathode chamber 6 is formed inside the solid electrolyte tube 3. The bottomed cylindrical partition wall 7 is provided inside the solid electrolyte tube 3 to prevent a rapid reaction of the active material when the solid electrolyte tube 3 is damaged.

The cartridge 8 as a container for containing sodium is formed in a sealed state and contains sodium Na therein. The sodium flow hole 9 is transparently provided at the bottom of the cartridge 8, and nitrogen gas G is sealed in the upper space of the cartridge 8 under pressure. Then, at the time of discharging, the pressure of the nitrogen gas G causes sodium Na to flow out from the sodium flow hole 9 into the cathode chamber 6. The cathode lid 10 is joined and fixed to the upper end of the insulating ring 2 via the cathode fitting 12. Further, a protrusion is provided on the outer peripheral surface of the bottom portion of the cartridge 8, and the cartridge 8 and the partition wall 7
Hold the gap with.

The cartridge 8 includes zinc (Zn), nickel (Ni), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag), gold (Au) and platinum (P).
It is formed of at least one metal or alloy selected from the group consisting of t). Since these metals or alloys have low reactivity to nitrogen, the nitrogen gas G in the cartridge 8 is prevented from decreasing due to the reaction with the cartridge 8.

The cartridge 8 is made of alumina (Al ₂ O ₃ ), carbide such as silicon carbide (SiC),
Titanium carbide (Ti) and nitrides such as silicon nitride (Si
N), titanium nitride (TiN), aluminum nitride (Al
It is formed of at least one ceramic material selected from the group consisting of N). This ceramic material also has low reactivity with nitrogen, and the decrease of the nitrogen gas G in the cartridge 8 is prevented.

At the time of discharging, the sodium Na in the cartridge 8 is supplied into the cathode chamber 6 through the sodium flow hole 9 under the pressure of the nitrogen gas G, and permeates the solid electrolyte tube 3 as sodium ions. This sodium ion reacts with sulfur S in the anode chamber 4 to produce sodium polysulfide. On the contrary, at the time of charging, sodium polysulfide is decomposed in the anode chamber 4, and the generated sodium ions permeate the solid electrolyte tube 3 and return to the cathode chamber 6. Further, sodium Na passes through the sodium flow hole 9 and reaches the inside of the cartridge 8. In the sodium-sulfur battery, which is a secondary battery,
Such charge / discharge reaction is repeated.

At this time, in this embodiment, since the material of the cartridge 8 is made of a metal, an alloy or a ceramic material having a low reactivity with the nitrogen gas G in the cartridge 8, the nitrogen gas G is not contained in the cartridge 8. Is prevented from decreasing with the passage of time. Therefore, the supply of sodium Na from the inside of the cartridge 8 to the cathode chamber 6 is secured, and the discharge capacity of the battery can be maintained for a long period of time.

By the way, in order to confirm the reaction with the nitrogen gas G, the metal, alloy or ceramic material was subjected to the following tests. That is, the sample of each material is 10c vertically.
It was processed into a test piece of m, width 2 cm, and thickness 0.1 cm, pyrolyzed at high temperature, and enclosed in a quartz ampoule together with an azide that produces nitrogen gas. The azide was weighed and sealed so that the amount of nitrogen at room temperature was 10 atm cc.

Then, the quartz ampoule is heated at 400 ° C. for 12 hours.
After holding for 00 hours and cooling to room temperature, the decrease amount of nitrogen gas in the quartz ampoule was measured. The amount of gas reduction was calculated from the difference between the amount of nitrogen gas collected by breaking the quartz ampoule in water and the amount of initial filling gas. The results are shown in Table 1. In addition, in the copper (Cu) -zinc (Zn) alloy in the table, zinc is 35% by weight and the balance is copper.

[0030]

[Table 1]

As shown in Table 1, it can be seen that the metal or ceramic material used in the present invention shows almost no decrease in nitrogen as compared with stainless steel (SUS304) and is suitable as a material for the cartridge 8. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. It should be noted that, in this embodiment, parts different from the first embodiment will be mainly described.

As shown in FIG. 2, in this embodiment, the cartridge 8 is made of stainless steel (SUS304),
A coating layer 11 is formed on the inner surface by a vacuum vapor deposition method, a chemical vapor deposition method (CVD), an electrolytic plating method, an electroless plating method, a plasma spraying method, or the like. That is, the coating layer 11 includes zinc (Zn), nickel (Ni), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag), gold (Au), and platinum, which have low reactivity with nitrogen. It is formed of at least one metal or alloy selected from the group consisting of (Pt).

The coating layer 11 is made of at least one ceramic material selected from the group consisting of alumina, carbide and nitride, which have low reactivity with nitrogen.
The thickness of these coating layers 11 may be 0.01 μm or more, but is usually about 0.1 to 5 μm.

In this embodiment, since the coating layer 11 has low reactivity with nitrogen, the nitrogen gas G in the cartridge 8 is prevented from decreasing. Therefore, sodium Na
Is secured and the discharge capacity of the battery is maintained.

By the way, the amount of nitrogen reduction when the coating layer 11 was provided was measured. That is, a stainless steel tube provided with a coating layer formed of the above metal, alloy or ceramic material was produced by the method shown in Table 2 below. The tube has an inner diameter of 3 cm and a length of 12 cm. Then, the azide that is thermally decomposed in the tube at high temperature to generate nitrogen gas is weighed so that the amount of nitrogen at room temperature is 10 atm cc, and after putting this into the tube, both ends of the tube are the same as the tube. A stainless steel lid covered with a material was used to hermetically seal the mouth. 1200 these tubes at 400 ℃
After holding for a period of time, the reduced nitrogen content was measured. The results are shown in Table 3.

[0036]

[Table 2]

[0037]

[Table 3]

Although the amount of nitrogen reduction is somewhat recognized in Cu, if it is this amount, there is no problem for about 5 years. As shown in Table 3, compared to stainless steel (SUS304),
Each metal and ceramic material of this embodiment has no problem with the nitrogen reduction amount. (Third Embodiment) Next, a third embodiment of the present invention will be described. It should be noted that, in this embodiment, parts different from the second embodiment will be mainly described.

In this embodiment, the cartridge 8 is made of stainless steel (SUS304), and the inner surface thereof is provided with a nitride layer of nitride. The thickness of this nitride layer is
Generally, it may be 1 μm or more. This nitriding layer is formed by causing glow discharge in the stainless steel cartridge 8 under a reduced pressure of 1 to 10 Torr in a nitrogen atmosphere for 2 hours. The thickness of the nitride layer thus formed is about 50 μm.
m.

In this embodiment, the inner surface of the cartridge 8 is preliminarily formed with a nitriding layer by nitriding, and this nitride layer has a low reactivity with nitrogen, so that the reduction of the nitrogen gas G in the cartridge 8 is prevented. It Therefore, the supply of sodium Na is secured and the discharge capacity of the battery is maintained. (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. It should be noted that, in this embodiment, parts different from the first embodiment will be mainly described.

In this embodiment, at least one selected from the group consisting of neon (Ne), argon (Ar) and krypton (Kr) is provided in the space inside the cartridge 8.
Seed noble gas is filled. These rare gases are inactive to the material of the cartridge 8 and have low solubility in sodium. Therefore, it is possible to prevent a decrease due to the reaction of the rare gas in the cartridge 8 and a decrease due to the dissolution. Therefore, the supply of sodium Na is secured and the discharge capacity of the battery is maintained.

Incidentally, in the following cases, the relationship between the discharge capacity and the charge / discharge cycle was measured. The results are shown in Fig. 3. As the material of the cartridge 8, (1) zinc is used and nitrogen gas is used in the internal space of the cartridge 8, or (2) alumina is used and nitrogen gas is used in the internal space of the cartridge 8.

When (3) nickel is used as the coating layer 11 on the inner surface of the cartridge 8 formed of stainless steel (SUS 304) and nitrogen gas is used in the internal space of the cartridge 8, or (4) alumina is used, When nitrogen gas is used in the internal space of the cartridge 8.

In the case where (5) a nitride layer is provided on the inner surface of the cartridge 8 and nitrogen gas is used in the internal space of the cartridge 8. When the cartridge 8 is made of stainless steel (SUS 304) only and (6) Argon gas is used as the gas in the cartridge 8.

As a comparative example, the cartridge 8 is formed of (7) stainless steel (SUS 304) only, and nitrogen gas is used in the internal space of the cartridge 8. From the result of Figure 3, (1)
In the cases of (6) to (6), the discharge capacity hardly decreased even after 2000 cycles. On the other hand, in the case of (7), the discharge capacity drops sharply after about 1500 cycles. (Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to FIGS. It should be noted that, in this embodiment, parts different from the first embodiment will be mainly described.

As shown in FIG. 4, the argon gas G ₀ is sealed in the upper space in the cartridge 8. In this embodiment, low-purity argon gas having an impurity gas content of 10% by volume or less or high-purity argon gas having an impurity gas content of 0.1% by volume or less is used. FIG. 4 shows the state of the battery after charging, and FIG. 5 shows the state of discharging. The cartridge 8 is made of stainless steel (SUS304). The position of the opening end of the partition wall 7 may be any position as long as it is above the upper end of the anode mat 5 of the anode chamber 4.

The pressure of the argon gas G _{0 in} the cartridge 8 is maximum at the end of charge when the volume of the upper space inside the cartridge 8 is minimum, and is minimum at the end of discharge when the volume is maximum. Therefore, the lower limit of the set pressure of the argon gas G ₀ is set to be equal to or higher than the pressure of sodium existing between the cartridge 8 and the partition 7 at the end of discharge. The reason is that sodium in the cartridge 8 can flow out from the sodium flow hole 9 even after discharge. On the other hand, the upper limit of the set pressure of the argon gas G ₀ is set to be equal to or lower than the atmospheric pressure at the end of charging. The reason is that even if the cathode seal is damaged, sodium in the cartridge 8 does not flow out of the battery.

The pressure of the argon gas G ₀ is specifically set as follows. As a prerequisite, the operating temperature of the battery is 300 ° C., the density of sodium at 300 ° C. ρ = 0.88 g / cm ³ , and the acceleration of gravity g = 980.6.
It is cm / s ² . The volume of the upper space in the cartridge 8 at the end of charging was V ₁ cm ³ , and the volume of the upper space in the cartridge 8 at the end of discharging was V ₂ cm ³ . Further, the height from the liquid surface of sodium in the cartridge 8 to the upper end of the partition 7 at the end of discharge was set as H _max . Further, the partial pressure of the argon gas G ₀ in the cartridge 8 is P _Ar .

For the above-mentioned reason, at the end of discharge, P _Ar
It is necessary to satisfy the relation of ≧ ρgH _max . Therefore, the pressure of argon gas at the end of discharge P _2Ar ≧ 0.88 × 98
0 × H _{ma x,} i.e. it is necessary to satisfy the relationship of P _2Ar ≧ 860 × H _max.

In this case, the argon gas G at the end of charging
The partial pressure of ₀ is represented by P _1Ar = P _2Ar × V ₂ / V ₁ . Then, H _max is 30 cm, V ₁ is 40 cm ³ , and V ₂ is 280
The partial pressure ratio of cm ³ and low-purity argon gas was set to 0.9.

In this case, P _2Ar ≧ 860 × 30, that is, P _2Ar ≧ 26000 (g / cm.s ² ), and when this unit is converted, P _2Ar ≧ 2600 (Pa) and further P _2Ar ≧ 26 (hPa). .

The inside of the cartridge 8 at the end of discharge
The total pressure in the space is P_2Ar/0.9, that is 26 /
It is 0.9 = 29 (hPa). Therefore, the power at the end of charging
The total pressure in the space inside the trench 8 is 29 × V₂/ V ₁,
That is, 29 × 280/40 = 210 (hPa). This
Is less than 1000 (hPa) atmospheric pressure.

The battery in which the pressure of the argon gas G ₀ in the cartridge 8 was set as described above was operated for a long period of time. For comparison, a battery in which the nitrogen gas G was enclosed in the upper space of the cartridge 8 was operated for a long time. The results are shown in FIG. As can be seen from FIG. 6, under these conditions, even if a slight decrease in gas pressure makes it difficult for sodium to flow out from the cartridge 8 at the end of discharge, either high-purity argon gas or low-purity argon gas is used. Even when used ((a) in FIG. 6), the discharge capacity does not decrease over 1000 cycles. On the other hand, when nitrogen gas is enclosed ((b) in FIG. 6), the discharge capacity rapidly decreases after 500 cycles of charging and discharging.

As described above, according to this embodiment, sodium in the cartridge 8 can be surely discharged to the outside of the cartridge 8 even at the end of discharging, and the cathode seal is damaged at the end of charging. However, sodium in the cartridge 8 can be prevented from flowing out of the battery. Moreover, since argon gas having a low purity can be used as the gas and the purification of the gas can be omitted, the manufacturing cost of the battery can be reduced.

Here, the impurity concentration α allowed in the low-purity argon is determined. Assuming that the total pressure of gas in the upper space of the cartridge 8 at the end of charging is P, it is necessary to keep P below atmospheric pressure (1000 hPa) as described above. The relationship between this P and the partial pressure P _1Ar of the argon gas G ₀ is P _1Ar = (1−α) P, that is, P = P _1Ar / (1
-Α).

Further, as described above, P _2Ar = 860 × H
_max (g / cm.s ² ) = 0.86H _max (hPa), P _1Ar = P
_2Ar × V ₂ / V ₁ Therefore, P _1Ar = 0.86H _max × V ₂ / V ₁ Therefore, P = 0.86H _max × V ₂ / V ₁ (1-α) <1
000 From this, α <1- (0.86 × 10 ⁻³ H _max × V ₂ /
V ₁ ) For example, as described above, H _max = 30 cm, V ₁ = 40 c
When m ³ and V ₂ = 280 cm ³ , α <0.76. Therefore, the impurity concentration in argon should be less than 76%. (Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, the parts different from the fifth embodiment will be mainly described.

As shown in FIG. 7, the partition wall 7 is omitted in this embodiment. Therefore, the sodium in the cartridge 8 flows out through the outflow hole 9 and directly functions as a cathodically acting substance. In addition, in this embodiment, H of the fifth embodiment is used.
h corresponding to _{max max} represents the height from the liquid level of the sodium in the cartridge 8 to the lower end of the cathode member 12 at the time of discharge.

Therefore, the pressure of the argon gas G ₀ in the upper space of the cartridge 8 and the impurity concentration in the argon gas G ₀ are calculated in the same manner as in the fifth embodiment. In this embodiment, since the partition wall 7 is omitted, the structure is simplified.

The structure of the present invention may be embodied by being arbitrarily changed as follows. (1) The cartridge 8 is made of the metal or ceramic of the first or second embodiment, and its inner surface is covered with the coating layer 11 of the third embodiment. Further, after forming the nitride layer of the fourth embodiment, the coating layer 11 is further formed on the surface thereof. With this configuration, the reduction of nitrogen gas can be prevented more effectively. (2) Use neon (Ne) or krypton (Kr) instead of argon (Ar) in the fifth or sixth embodiment.

The technical idea of the embodiment will be described below together with its effects. (1) The pressure of the rare gas in the upper space inside the container is
The sodium-sulfur battery according to claim 7, which is set so as to satisfy both (1) and (2). With this configuration, sodium in the storage container can be reliably supplied to smoothly operate the battery, and when the cathode seal is damaged, sodium in the cathode is prevented from flowing out of the battery. can do.

P _Ar ≧ ρg H _max (1) where P _Ar is the partial pressure of argon at the end of discharge, ρ is the density of sodium at the operating temperature of the battery, g is the acceleration of gravity, and H _max is the end of discharge. It represents the height from the liquid level of sodium in the container to the top of the partition. Further, as H _max , the height h _max from the liquid level of sodium in the container at the end of discharge to the lower end of the cathode fitting forming the cathode chamber may be used.

P _Ar × V ₂ / (V ₁ × r) <1000 (hPa) (2) where V ₁ is the volume of the upper space in the cartridge 8 at the end of charging, and V ₂ is a container at the end of discharging. The volume of the inner upper space, r represents the ratio of argon in the upper space of the accommodation container. (2) The sodium-sulfur battery according to claim 7, wherein the content of the impurity gas is calculated by the following formula (3). With this configuration, the limit of the impurity gas contained in the rare gas can be easily calculated.

Α <1− (ρ × g × 10 ⁻³ H _max × V ₂ / V ₁ ) (3) where α is the ratio of impurities contained in argon, and ρ is the operating temperature of the battery , G is the acceleration of gravity, V ₁ is the volume of the upper space in the cartridge 8 at the end of charging, and V ₂ is the volume of the upper space in the container at the end of discharging. H _max represents the height from the liquid level of sodium in the container at the end of discharge to the upper end of the partition.
Further, as H _max , the height h _max from the liquid level of sodium in the container at the end of discharge to the lower end of the cathode fitting forming the cathode chamber may be used.

[0064]

As described above in detail, the sodium-sulfur battery of the present invention has the following excellent effects. That is, according to the invention described in claims 1 to 6,
It is possible to effectively prevent a decrease in the gas pressure of the gas in the storage container that stores sodium, ensure the supply of sodium, and maintain the discharge capacity of the battery.

Further, according to the invention described in claim 7, in addition to the above effects, sodium in the container can be reliably flowed out of the container even at the end of discharge, and the cathode is sealed at the end of charge. Even when damaged, sodium in the cathode can be prevented from flowing out of the battery.

[Brief description of drawings]

FIG. 1 is a sectional view showing a sodium-sulfur battery of a first embodiment.

FIG. 2 is a partial sectional view showing a cartridge according to a second embodiment.

FIG. 3 is a graph showing the relationship between discharge capacity and charge cycle.

FIG. 4 is a sectional view showing a sodium-sulfur battery of a fifth embodiment.

FIG. 5 is a sectional view showing a sodium-sulfur battery of a fifth embodiment as well.

FIG. 6 is a graph showing the relationship between discharge capacity and charge cycle.

FIG. 7 is a sectional view showing a sodium-sulfur battery of a sixth embodiment.

[Explanation of symbols] 1 ... Anode container, 2 ... Insulating ring, 3 ... Solid electrolyte tube, 4
... Anode chamber, 6 ... Cathode chamber, 8 ... Cartridge as a container, 11 ... Coating layer, S ... Sulfur, Na ... Sodium, G
... nitrogen gas, G ₀ ... argon gas.

Claims (7)

[Claims] 1. A solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in an anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sulfur as the anode active material was stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas was stored in the internal space of the storage container at a higher pressure than outside the storage container. In the sodium-sulfur battery, the accommodating container is made of zinc (Zn), nickel (Ni), cobalt (Co), copper (Cu), molybdenum (Mo), silver (Ag), and gold (Au), which have low reactivity with nitrogen. ) And platinum (P
A sodium-sulfur battery formed of at least one metal or alloy selected from the group consisting of t). 2. A solid electrolyte tube for selectively passing sodium ions through an insulator is arranged in the anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sulfur as the anode active material was stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas was stored in the internal space of the storage container at a higher pressure than outside the storage container. In the sodium-sulfur battery, the storage container is formed of at least one ceramic material selected from the group consisting of alumina, carbide and nitride, which have low reactivity with nitrogen. 3. A solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in the anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sulfur as the anode active material was stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas was stored in the internal space of the storage container at a higher pressure than outside the storage container. In the sodium-sulfur battery, zinc (Zn), nickel (Ni), cobalt (Co), which has low reactivity with nitrogen, is formed on at least the inner surface of the container.
Copper (Cu), molybdenum (Mo), silver (Ag), gold (A
u) and a sodium-sulfur battery coated with a coating layer of at least one metal or alloy selected from the group consisting of platinum (Pt). 4. A solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in an anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sulfur as the anode active material was stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas was stored in the internal space of the storage container at a higher pressure than outside the storage container. In the sodium-sulfur battery, the sodium-sulfur battery is formed by coating at least the inner surface of the container with a coating layer of at least one ceramic material selected from the group consisting of alumina, carbides and nitrides. 5. A solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in an anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sulfur as the anode active material was stored in the anode chamber between the anode container and the solid electrolyte tube, and nitrogen gas was stored in the internal space of the storage container at a higher pressure than outside the storage container. A sodium-sulfur battery, wherein a nitriding layer is provided on at least the inner surface of the container. 6. A solid electrolyte tube for selectively permeating sodium ions through an insulator is arranged in an anode container, and a container for containing sodium as a cathode active material is arranged in a cathode chamber in the solid electrolyte tube. In addition, sodium as the anode active material is stored in the anode chamber between the anode container and the solid electrolyte tube, and sodium is stored in the internal space of the storage container at a higher pressure than outside the storage container. −
In a sulfur battery, neon (Ne), argon (Ar), and krypton (Kr), which are inert to the container and have a low solubility in sodium, are provided in the space inside the container.
A sodium-sulfur battery filled with at least one rare gas selected from the group consisting of: 7. The gas contained in the container contains the rare gas and the impurity gas, and the content of the impurity gas is such that the pressure of the rare gas at the end of discharge is equal to or higher than the pressure of sodium outside the container. The sodium-sulfur battery according to claim 6, which is calculated by setting the total pressure of the rare gas and the impurity gas at the end of charging to be lower than the atmospheric pressure.