JPH0955222A - Sodium-sulfur battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sodium-sulfur battery and its manufacturing method, capable of holding the battery at high operating temperature at 310 deg.C or higher for a long time, maintaining corrosion resistance to sodium in a joint part even in the using condition repeating thermo cycles of heating and cooling between the operating temperature and room temperature, and keeping reliability for a long time. SOLUTION: A flange part 3A of an anode cover 3, an α-alumina insulating ring 7, and a flange part 5A of a cathode container 5 are joined through an inserting material 10. As the inserting material 10, a high purity Al-Si alloy 10b having a total content of elements other than Al and Si of 0.001-2.4wt.% is used, and for joining, pressure of 20-50MPa is applied at a temperature of solidus line or less of the alloy, or pressure of 10-20MPa is applied at a temperature of solid-liquid coexistence of the alloy.

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, for example, electric power storage and electric vehicles, and more particularly, an insulating ceramic for insulating a cathode lid and an anode container, a cathode lid and The present invention relates to a sodium-sulfur battery in consideration of corrosion resistance at a joint with each anode container and a method for manufacturing the same.

[0002]

2. Description of the Related Art A sodium-sulfur battery uses molten sodium as a cathode active material, sulfur and sodium polysulfide as an anode active material, separates the cathode active material and the anode active material with a solid electrolyte, and keeps them at 310 ° C. or higher. It is a battery that operates at the temperature of. As the solid electrolyte, β ″ alumina is generally used. In order to insulate the cathode and the anode of such a sodium-sulfur battery, an α-alumina insulating ring is arranged between them.

[0003] In the sodium-sulfur battery having the above-mentioned structure, the cathode lid that conducts to the sodium (hereinafter, appropriately referred to as Na), the anode container that contains sulfur, and the insulating ring made of α-alumina are provided. Regarding joining, JP-A-3-241674 (first prior art)
And Japanese Patent Laid-Open No. 6-36796 (second prior art).
As disclosed in US Pat. No. 5,242,071, each of the flange portions of the cathode lid and the anode container and the insulating ring made of α-alumina are joined via an insert material made of an aluminum (hereinafter, appropriately referred to as Al) alloy. The method of doing is known.

Regarding the joining of ceramics and metal, Japanese Patent Laid-Open No. 5-194050 (third prior art), Japanese Patent Laid-Open No. 5-228686 (fourth prior art), and Japanese Patent Laid-Open No. 60-71579. The technique described in Japanese Patent Publication (fifth prior art) is known. Among them, in the third conventional technique, an Al—Si—Mg alloy is arranged as an insert material (brazing material) between ceramics and a metal, and the pressure is 20 to 60 MPa at a temperature below the solidus line in a non-oxidizing atmosphere. The pressure is applied with pressure to join, and Na corrosion resistance is taken into consideration.
i, magnesium is referred to as Mg). The fourth conventional technique relates to a brazing material made of an Al alloy containing Mg and Cu, which also takes Na corrosion resistance into consideration (hereinafter, copper is referred to as Cu as described above). . Further, in the fifth conventional technique, an Al-Si alloy is arranged between alumina and a metal, and pressure is applied at a temperature above the solidus to join them.

[0005]

Since the operating temperature of the sodium-sulfur battery is 310 ° C. or higher, the junction between the cathode lid and the anode container and the α-alumina insulating ring is 31.
It is exposed to the vapor of Na even if it comes into contact with molten Na having a high temperature of 0 ° C. to 450 ° C. or does not come into direct contact with molten Na. In addition, when the battery is not in operation due to maintenance or long holidays, the battery is cooled to room temperature, and when used, it is heated again to an operating temperature of 310 ° C. or higher. However, the number of pauses differs depending on the use of the battery, for example, when used as a battery for power storage, it is more than once a year,
When used as a battery for automobiles, the number of times is higher. Thus, the sodium-sulfur battery has a temperature of 310 ° C.
While being kept at the above high temperature for a long time, the heat cycle between heating and cooling between the operating temperature of the battery and room temperature is repeated every time the battery is stopped, and the heat cycle repeats the cathode lid and the anode container and the α-alumina container. Thermal stress will be applied to the joint between the insulating ring and the insulating ring. In this way, when a thermal cycle is applied while molten Na and Na vapor are in contact with each other, Na
Corrosion of the above-mentioned joint due to is remarkable.

In the above-mentioned first and second prior arts, the cathode lid and the anode container are joined to the insulating ring made of α-alumina through an insert material made of an Al alloy, so that Trying to prevent Na corrosion,
The Na corrosion of the joint is evaluated by, for example, the first prior art when immersed and held in molten Na at 450 ° C. for 1,000 hours, and the second prior art is evaluated as 450.
It is an evaluation when operating under a temperature of ℃ for 3 months,
It was not evaluated by applying a thermal cycle in molten Na or Na vapor. Further, in the third prior art, the evaluation was made when a ceramic and a metal were joined through an Al-Si-Mg alloy insert material and immersed and held in molten Na at 430 ° C for 120 hours. It was not evaluated by applying a heat cycle in Na or Na vapor.

In the above-mentioned three conventional techniques, the result of a small amount of corrosion (corrosion length) was obtained, but in an actual sodium-sulfur battery, the operating temperature of 310 ° C. or higher was cooled to room temperature, and the temperature was changed to 310 ° C. again. Since the heat cycle of heating to the above temperature is also added, the amount of corrosion by Na is considered to be larger than the evaluation result of the above-mentioned conventional technique. That is, in the above-mentioned three conventional techniques, Na corrosion of the joint portion under the condition that the thermal stress due to the thermal cycle is applied is not taken into consideration, and therefore, it is exposed to the molten Na or Na vapor and the operating temperature and The long-term reliability of the joint cannot be guaranteed under the operating conditions in which thermal cycling with room temperature is applied.

In the above-mentioned fourth prior art, it has been shown that the brazing material of Al alloy containing at least one of Mg and Cu is excellent in Na corrosion resistance.
Here, the above brazing material is simply immersed in molten Na for evaluation, and it is considered that no remarkable corrosion is certainly observed according to such an evaluation method. However, if this brazing material is used as an insert material in the above-mentioned joint, the joint interface will be significantly corroded. This is because the chemical state when Mg, Cu and other impurities are present inside the brazing filler metal is different from the chemical state when they are present at the joint interface when used as the insert material in the joint. It is believed that there is. In other words, when it is used as an insert material in the joint, it becomes a state in which impurities are concentrated at the joint interface due to the reaction and diffusion during the joining of alumina and the brazing filler metal and are easily eluted in Na, and a compound state in which Na is easily corroded. Because of the change, the joint interface is easily corroded. On the other hand, when the Al alloy brazing filler metal alone is used,
It is considered that g, Cu, and impurities are in the state of solid solution or precipitation in Al of the base material and are present in a stable state with respect to Na, so that significant corrosion does not occur.

In the above-mentioned fifth conventional joining method, there is practically no problem with respect to the strength and airtightness of the joint between alumina and metal, but the corrosion resistance of the joint in molten Na or Na vapor is high. Is not disclosed and, of course, no measures are taken against the corrosion.

As described above, in any of the above-mentioned conventional techniques,
No consideration is given to corrosion due to Na when a thermal cycle is applied in a state where molten Na or Na vapor is in contact, and therefore there is a problem in long-term reliability from the viewpoint of Na corrosion resistance.

The object of the present invention is to maintain a high operating temperature of 310 ° C. or higher for a long period of time, and to bond even under use conditions in which a thermal cycle between heating and cooling between the operating temperature and room temperature is repeated. It is an object of the present invention to provide a sodium-sulfur battery having long-term reliability without impairing the sodium corrosion resistance of a part and a method for manufacturing the same.

[0012]

In order to achieve the above object, according to the present invention, a sodium-sulfur battery in which sodium conducting to a cathode lid and sulfur contained in an anode container are separated by a solid electrolyte is manufactured. At this time, the cathode lid is attached to one surface of the insulating ring made of α-alumina,
While disposing the anode container on the other surface of the insulating ring made of alumina, each of the cathode lid and the anode container and the insulating ring made of α-alumina were joined via an insert material made of an aluminum alloy. In the method for manufacturing a sodium-sulfur battery, the content of elements other than aluminum and silicon is in the range of 0.001 to 2.4 wt% as an insert material between at least the insulating ring made of α-alumina and the cathode lid. Using high-purity aluminum-silicon alloy, the high-purity aluminum-
Heating to a temperature below the solidus of silicon alloy and 20MP
a to 50 MPa, or heating to a temperature in the range above the solidus and below the liquidus of the high-purity aluminum-silicon alloy and from 10 MPa to 20 MPa.
A method for manufacturing a sodium-sulfur battery is provided, in which the α-alumina insulating ring and the cathode lid are pressure-bonded by applying a pressure in the range of MPa.

In the above, it is preferable that, as an insert material between at least the insulating ring made of α-alumina and the cathode lid, both surfaces of a core material made of an aluminum alloy have a total content of elements other than aluminum and silicon. A three-layer structure sandwiched between skin materials of the high-purity aluminum-silicon alloy in the range of 0.001 to 2.4 wt%, or an element other than aluminum and silicon on the insulating ring side made of α-alumina. Total content 0.0
A two-layer structure is used in which the high-purity aluminum-silicon alloy in the range of 01 to 2.4 wt% is located and the aluminum alloy is located on the cathode lid side.

Further, in the above, preferably, as the insulating ring made of α-alumina, α-alumina having a purity of 99.5 wt% or more is used.

In order to achieve the above-mentioned object, according to the present invention, when a sodium-sulfur battery in which sodium conducted to a cathode lid and sulfur contained in an anode container are separated by a solid electrolyte is manufactured, -The cathode lid and the anode container are arranged apart from each other on one surface of an insulating ring made of alumina, and an aluminum alloy is used between each of the cathode lid and the anode container and the insulating ring made of α-alumina. In the method for producing a sodium-sulfur battery joined via an insert material,
-A high-purity aluminum-silicon alloy having a content of elements other than aluminum and silicon in the range of 0.001 to 2.4 wt% is used as an insert material between the insulating ring made of alumina and the cathode lid. Heating to a temperature below the solidus of the pure aluminum-silicon alloy and
By applying a pressure in the range of MPa to 50 MPa, or by heating to a temperature in the range above the solidus and below the liquidus of the high-purity aluminum-silicon alloy and applying a pressure in the range from 10 MPa to 20 MPa. α-
A method for manufacturing a sodium-sulfur battery is provided, in which an alumina insulating ring and the cathode lid are pressure-bonded to each other.

In order to achieve the above object, according to the present invention, there is provided a sodium-sulfur battery in which sodium conducted to the cathode lid and sulfur contained in the anode container are separated by a solid electrolyte. The cathode lid on one surface of the insulating ring made of alumina, the anode container is arranged on the other surface of the insulating ring made of α-alumina, and each of the cathode lid and the anode container and the α-alumina In the sodium-sulfur battery joined between the insulating ring of and through an insert material made of an aluminum alloy,
Under the battery operating conditions, the battery is kept under the operating temperature range of 310 ° C. or higher for t hours to repeat charging / discharging, and in the middle of the charging / discharging, a cycle of cooling to room temperature and then heating to the operating temperature range is repeated C times. The average amount of corrosion due to sodium at the joint interface between the α-alumina insulating ring and the insert material on the cathode lid side is 0.00126 × t ^1/2 +
Provided is a sodium-sulfur battery characterized by having a value of 0.005 × C (mm) or less.

Further, in order to achieve the above object, according to the present invention, in the sodium-sulfur battery as described above, at least the insert material between the insulating ring made of α-alumina and the cathode lid is Sodium-containing a high-purity aluminum-silicon alloy having a content of elements other than aluminum and silicon in the range of 0.001 to 2.4 wt% at the joint interface with the α-alumina insulating ring. A sulfur battery is provided.

In the above, the insulating ring made of α-alumina is preferably α-alumina having a purity of 99.5 wt% or more.

[0019]

In the case where the cathode lid and the anode container and the insulating ring made of α-alumina are heated and pressure-bonded through the insert material made of Al alloy, the joint portion is corroded by Na. By repeating the heat cycle of heating and cooling, elements other than Al and Si, namely Mg,
Impurities such as Cu, Fe, Ni, Mn, Zn, and Ca are concentrated during bonding due to diffusion, and these impurity elements are eluted into Na or form a reaction phase with Na, and bonding in such a state. It has been clarified by experiments that peeling occurs due to thermal stress generated at the interface due to repeated thermal cycles (hereinafter, iron is Fe, nickel is Ni, manganese is Mn, and zinc is as described above. Zn,
Calcium is referred to as Ca).

By the way, the reason why Si is added to the Al alloy insert material is that the Si-added Al alloy is easy to bond to both metal and alumina. This is because the purpose is to improve the bonding strength and airtightness, but in the third conventional technique, the cause of Na corrosion is solidification after completely melting and brazing a brazing material made of an Al-Si alloy. Considering that it is resin-like Si that is sometimes crystallized, the content of Si is limited, the joining temperature is set to the solidus line of the Al-Si alloy or less, and the insert material is joined without melting. On the other hand, when the insert material is heated to a temperature above its solidus and melted, most of the Al-Si molten phase is discharged out of the joint surface due to the pressurization, and inside the joint surface, Resinous Si
Will almost never exist. Certainly, the solubility of Si in molten Na is large, and Si is eluted into Na, so that the corrosion of the Si present in the insert material in contact with molten Na becomes significant. However, it is considered that the Al-Si molten phase is almost eliminated by the pressurization as described above, and thus Si of resinous crystal which causes Na corrosion is hardly present.

According to this concept, when joining below the solidus line as in the third conventional technique, Si in the Al--Si alloy insert material remains as it is and S in the entire joining interface.
The abundance of i should be larger than that at the solidus or above, so that Na corrosion is less likely to occur at the solidus or above where resinous Si hardly remains in the joining interface. Nevertheless, as described in the third conventional technique, the fact that the corrosion is less in the bonding below the solidus is that Si is not the main cause of Na corrosion. Suggests.

As described above, in the third conventional technique,
The improvement of Na corrosion resistance at the joining temperature below the solidus is
The lower the bonding temperature, the more Mg, Cu, Fe, Ni, Mn, Z
It is considered that this is because the diffusion of impurity elements such as n and Ca in Al is slow, and as a result, the concentration at the bonding interface is suppressed. However, even if the joining temperature is low, a large amount of Mg, Cu, Fe, Ni, Mn, Zn,
If elements such as Ca are present, they are used at a high temperature (310 ° C to 450 ° C) like a secondary battery for power storage, and are subjected to a thermal cycle between a temperature of 310 ° C or higher and room temperature. Below, long-term reliability is due to the concentration of the above-mentioned impurity elements at the bonding interface due to diffusion and the thermal stress due to thermal cycles (stress caused by the difference in Young's modulus and thermal expansion coefficient of ceramics, insert materials, and electrode containers). Sex cannot be guaranteed.

As described above, the corrosion caused by Na is not due to the presence of Si, but as described above, Mg, Cu, F
This is because impurities such as e, Ni, Mn, Zn, and Ca contained in Al are concentrated in the joint interface due to repeated thermal cycles, and thermal stress due to the thermal cycle is generated in the joint interfaces. Therefore, M in the insert material
The content of elements (impurity elements) other than Al and Si, such as g, Cu, Fe, Ni, Mn, Zn, and Ca, is intentionally reduced as much as practically possible so that the impurity elements are not concentrated at the bonding interface. That is an effective means for improving the Na corrosion resistance of the joint.

As described above, in the present invention, the total content of the impurity elements such as Mg, Cu, Fe, Ni, Mn, Zn, and Ca in the insert material should be as small as possible, but the total content of the impurity elements should be small. The lower limit of the amount is 0.001 wt%
This is because the content does not pose a practical problem in producing a high-purity Al-Si alloy, and the analysis accuracy limit of the content of the impurity element is at that level. In particular, it is impossible for modern technology to set impurities to 0 wt% in practical use, and 0.001 wt% is used based on the practically possible quantitative analysis accuracy.
% Was the lower limit. On the other hand, the upper limit of the total content of impurities is set to 2.
4 wt% was determined because the content of 2.4 wt% is a transition point where the amount of Na corrosion rapidly increases, as will be described later, and Na corrosion does not pose a problem below that in practical use. did. Incidentally, the impurity content in the insert material is usually analyzed by the cantback method from the viewpoint of simplicity and speed, but since the measurement can be performed only up to 0.01 wt%, the analysis accuracy is low. Poor and insufficient as an analytical method. Therefore, in the present invention,
The impurity content should be measured and controlled to the ppm order by wet chemical analysis or the like so that the above lower limit is satisfied.

Further, in the present invention, when the joining temperature is set to the solidus line of the high-purity Al--Si alloy or less, a liquid phase does not occur at the joining interface at that temperature, so that the joining surfaces are sufficiently adhered to each other. The pressure for joining is 20 to 50
It is necessary to set it in the range of MPa. When joining at a pressure lower than 20 MPa, adhesion is insufficient and voids remain at the joining interface, and the strong oxide film on the surface of the insert material cannot be sufficiently destroyed, and the oxide film hinders joining. . Further, when the pressure is higher than 50 MPa, the amount of deformation of the insert material becomes large, which causes a problem of protrusion to the outside of the joint surface.

Further, in the present invention, when the joining temperature is set to a temperature in the range above the solidus line and below the liquidus line of the above high-purity Al--Si alloy, solids and liquids coexist, so that it is excessively high. No joining pressure is required and 10 to 20 MPa is an appropriate range. For example, at a high joining pressure such as 50 MPa, a large amount of the insert material is extruded to the outer peripheral portion of the joining portion, which causes a problem that the negative electrode container and the anode container are short-circuited. When the pressure is lower than 10 MPa or no pressure is applied, voids are formed due to gas generation from the insert material, and the molten Al-Si alloy has poor wettability with the insulating member made of α-alumina. Will cause poor bonding, resulting in deterioration of airtightness and bonding strength.

Further, when the joining temperature exceeds the liquidus of the high-purity Al--Si alloy, the diffusion of the impurity element in the insert material becomes remarkable and the impurity element is concentrated at the joint interface. Bonding at temperatures above the phase line promotes Na corrosion and is undesirable.

Further, as the insert material, a two-layer structure having the above-mentioned high-purity Al-Si alloy on the insulating ring made of α-alumina and the Al alloy on the cathode lid side may be used. , An insulating ring made of α-alumina, which is particularly apt to be corroded by Na, by using a three-layer structure in which both surfaces of the core material made of Al alloy are sandwiched by the skin materials of the high-purity Al-Si alloy as described above. It is possible to improve the Na corrosion resistance of the joint portion with the insert material.

In general, impurities such as Fe and Ca may enter the alumina powder which is the raw material of the α-alumina insulating ring, and MgO (sintering aid) is used as a sintering aid when sintering the alumina powder. Manganese oxide) or the like is added. Thereby, in the α-alumina grain boundary, Mg, Fe,
Impurity elements such as Ca are present, and during joining,
The impurity element in the alumina grain boundary is concentrated at the bonding interface due to diffusion. Therefore, it is considered that the Na corrosion resistance is adversely affected when the above-mentioned many impurity elements are contained. In the present invention, the α-alumina insulating ring α-
Since the purity of alumina is increased to 99.5 wt% or more to increase the purity, the above-mentioned adverse effects on Na corrosion resistance are suppressed.

Further, in the present invention, the cycle of maintaining the operating temperature range of 310 ° C. or higher for t hours to repeat charging / discharging, and cooling to room temperature during the charging / discharging and heating again to the operating temperature range is repeated C times. Under battery operating conditions,
The average amount of corrosion of Na at the bonding interface between the α-alumina insulating ring and the insert member on the cathode lid side is 0.00126 × t ^1/2 + 0.005 × C (mm).
The following is expressed for the following reasons. That is, Al
And high purity Al with reduced total content of impurities other than Si
-The joint part using the insert material of Si alloy is 450 ° C.
When held in molten Na or Na vapor for 2 hours, the average corrosion length X ₁ estimated from the experimental result is given by X ₁ = 0.00126 × t ^1/2 (mm). The method of deriving this formula will be described in detail later.

On the other hand, the average corrosion length X ₂ estimated from the experimental results when the thermal cycle of heating and cooling between 450 ° C. and room temperature was given C times was X ₂ = 0.005 × C ( mm). The method of deriving this formula will also be described later in detail.

Therefore, the average corrosion length X estimated at the junction of the sodium-sulfur battery of the present invention is the sum of the above X ₁ and X ₂ , that is, X = 0.00126 × t ^1/2 + 0.005 × It will be represented by C (mm). The temperature of the molten Na is 450
The estimated corrosion length will be shorter than the above at ℃ or below, but depending on the operating method of the battery, the temperature may rise to about 450 ℃.
The estimation formula in ° C was calculated. Therefore, the estimated average corrosion length when used in an operating temperature range of 310 ° C. or higher is the value of X or less.

Further, the above-mentioned configuration is applied to
It may be a sodium-sulfur battery having a junction part in which a cathode lid is arranged on one surface of an α-alumina insulating ring and an anode container is arranged on the other surface of the α-alumina insulating ring. It may be a sodium-sulfur battery having a joint part in which a cathode lid and an anode container are arranged separately from each other on one surface of an insulating ring made of alumina.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
1 will be described. FIG. 1 is a cross-sectional view of the sodium-sulfur battery of this example. As shown in FIG. 1, sodium 1 is contained in a safety tube 2, and the cathode lid 3 is electrically connected to the sodium 1 via the safety tube 2. Further, the cathode lid 3 is provided with a cathode terminal 3a and a sodium injection tube 3b. On the other hand, sulfur 4 is contained in the anode container 5 while being impregnated in the ring-shaped impregnation member made of mesh carbon. Further, the anode container 5 is provided with an anode terminal 5a. Further, sodium 1 and sulfur 4 are separated by a β ″ alumina tube 6 which is a solid electrolyte.

In the above, the safety pipe 2 is provided with a bottom hole 2a, and the sodium 1 gradually melted from the bottom hole 2a.
Is supplied to the inner surface of the β ″ alumina tube 6, which prevents an accident in which the reaction between sodium 1 and sulfur 4 explosively occurs.

FIG. 2 shows a portion II of FIG. 1, that is, the flange portion 3A of the cathode lid 3, the flange portion 5A of the anode container 5, and α.
-An enlarged view of a joint (hereinafter, appropriately referred to as a joint) of the insulating ring 7 made of alumina is shown. Flange portion 3 of cathode lid 3
An insulating ring 7 made of α-alumina for electrical insulation between the two is disposed between A and the flange portion 5A of the anode container 5, and one surface of the insulating ring 7 made of α-alumina (upper side in the figure). The flange portion 3A of the cathode lid 3 on the surface), and the flange portion 5A of the anode container 5 on the other surface (the lower surface in the drawing) of the insulating ring 7 made of α-alumina through the insert material 10. Are joined together (pressure contact). Note that α-
Between the insulating ring 7 made of alumina and the β ″ alumina tube 6 is α
-It is joined by glass solder inside the insulating ring 7 made of alumina.

In the insert material 10, both surfaces of the Al alloy 10a (core material) are sandwiched by high-purity Al-Si alloys 10b.
It has a layered structure. The joint interface between the α-alumina insulating ring 7 and the flange portion 3A and the joint interface between the α-alumina insulating ring 7 and the flange portion 5A are required to have strength and airtightness with respect to Na and sulfur. 3 side α-
The joint interface between the alumina insulating ring 7 and the flange portion 3A is exposed to molten Na or Na vapor, and since a thermal cycle is applied as described above, corrosion by Na becomes a problem. In particular, since the joint surface between the α-alumina insulating ring 7 and the high-purity Al—Si alloy 10b of the insert material 10 (indicated by the arrow 10c in the figure) is the joint surface between ceramics and metal, corrosion by Na is particularly noted. It becomes a problem.
The present example is for solving the problem of corrosion due to Na, and as the high-purity Al-Si alloy 10b,
High-purity Al with a total content of elements other than Al and Si in the range of 0.001 to 2.4 wt%
20 MPa-5 at a temperature below the solidus of Si alloy 10b
A pressure in the range of 0 MPa is applied, or the above high purity A
10 MPa to 2 at the temperature of solid-liquid coexistence of the 1-Si alloy 10b
Bonding is performed under the condition that a pressure in the range of 0 MPa is applied.

In FIG. 2, the insert material 10 similar to that on the cathode lid 3 side is also arranged at the joint interface between the insulating ring 7 made of α-alumina on the anode container 5 side and the flange portion 5A. Since it is the portion that contacts the sulfur 4 and does not contact Na, it is not necessary to consider corrosion by Na, and therefore it is not always necessary to arrange the insert material 10 using the high-purity Al-Si alloy 10b as described above. There is no.

Further, as shown in FIG. 3, the high-purity Al--Si alloy 10b is located on the side of the α-alumina insulating ring 7, and the Al alloy 10a (the one used as the core material in FIG. 2) on the side of the flange portion 3A. ) May be used for the two-layer structure insert material 11. The reason for this is the flange portion 3
Since the joining surface between A and the high-purity Al—Si alloy 10b of the insert material 10 is a joining surface between metals, it is not necessary to consider the corrosion due to Na so much.
This is because it is not necessary to dispose the —Si alloy 10b.

By the way, as the cathode lid 3 and the anode container 5, Al alloy, steel coated with corrosion resistance, stainless steel and the like are used. The reason is that the Al alloy has good workability and is inexpensive, the steel with a corrosion-resistant coating has excellent corrosion resistance, and the stainless steel has the above-mentioned α-alumina insulating ring 7 in pressure contact and during operation. This is because the thermal deformation and the thermal influence hardly occur even by the heating at the time.

The sodium-sulfur battery as described above is rarely used as a single cell as shown in FIG. 4 (a) (it is possible to supply electric power of about several tens W).
Usually, it is used as a battery system in which a plurality of batteries are combined as shown in FIGS. For example, as a battery for an automobile, as shown in FIG. 4B, several to several tens of sub-modules (power of about several kW can be supplied)
Is installed somewhere on the vehicle body in the form of, and in the power storage system, a module in which a plurality of sub-modules are combined as shown in FIG. 4 (c) (power of about several tens of kW can be supplied),
Alternatively, as shown in FIG. 4D, the unit is installed in the city area or its vicinity in the form of a unit (several MW can be supplied) in which thousands are combined. Therefore, FIG.
When adopting the usage patterns such as (b) to (d),
In terms of space, the smaller the sodium-sulfur battery, the better. However, if a conventional sodium-sulfur battery is attempted to be made compact, the dimensions of the flange portion of the cathode lid, the flange portion of the anode container, and the joint portion of the α-alumina insulating ring must be reduced, and Na must be reduced.
Corrosion life is shortened due to high corrosion rate. On the contrary, in order to extend the life, it is necessary to increase the size of the above-mentioned joint portion, and there is a limit to downsizing the battery system.

On the other hand, in this embodiment, since the Na corrosion resistance is improved as described below, the size of the joint portion can be reduced and therefore the battery system can be downsized. .

Next, an explanation will be given of an experimental example which serves as a basis for selecting the composition of the high-purity Al--Si alloy of the insert material and the joining condition of the joint as described above.

(Experimental Example 1) This experimental example is an experimental example relating to the influence of the amount of impurity elements other than Al and Si in the insert material. FIG. 5 is a view showing the test piece used here, which is a model of the battery having the structure shown in FIG. Here, in order to examine the characteristics of the high-purity Al-Si alloy, the high-purity Al-Si alloy was used alone as the insert material 110 without using the clad material as shown in FIGS. This test piece is an α-alumina insulating ring (purity 9
9.9 wt% or more) 107 and a steel anode member 105 having a Cr layer coated on the surface, and between an α-alumina insulating ring 107 and a steel cathode member 103 having a Cr layer formed on the surface. High purity Al-Si alloy (thickness of 0.
6 mm) is arranged as the insert material 110 and joined (pressed).

As the high-purity Al--Si alloy, Al
And impurity elements other than Si, that is, Mg, Cu, Fe, N
The total content of i, Mn, Zn, Ca, etc. is 0.15 wt%
From 10 to 2.8 wt% Al-10 wt% Si
An alloy is used, and the joining conditions are such that the joining temperature is 545 ° C. (Al-
The temperature is below the solidus of the 10 wt% Si alloy) and the joining pressure is 30 MPa. Also, the bonding pressure is 10 MPa,
A test piece having a joining temperature of 580 ° C. (solid-liquid coexisting temperature of Al-10 wt% Si alloy) and 610 ° C. (temperature above liquidus line of Al-10 wt% Si alloy) was also prepared. Note that A
The 1-10 wt% Si alloy has a solidus temperature of about 577 ° C and a liquidus temperature of about 590 ° C.

As shown in the pattern of FIG. 6, heating and pressurization at this time is performed by heating to the joining temperature T (° C.) and pressurizing to the joining pressure P (MPa) while maintaining the temperature.
The cooling is performed after a certain period of time. However, as shown in FIG. 6, pressurization may be continued until cooling and the pressure may be lowered after the temperature has dropped to some extent.

Each test piece as described above was melted at 350.degree.
The sample was kept in a for 1000 hours, and during that 1000 hours, a heat cycle of cooling to room temperature and heating to 350 ° C. again was added 40 times to obtain Na at the bonding interface between the insert material 110 and the α-alumina insulating ring 107. The corrosion length was measured by.

The results are shown in FIG. FIG. 7 is a diagram showing the influence of impurity elements on the corrosion length (mm) by Na, with the horizontal axis representing the total amount of impurity elements (wt%). As can be seen from FIG. 7, in the test piece having a bonding temperature of 545 ° C. (below the solidus line), when the amount of impurity elements in the insert material 110 is small, the corrosion length is 0.1 mm or less, but the amount of impurity elements is 2 or less. If it exceeds 0.5 wt%, the corrosion length increases rapidly. On the other hand, the bonding temperature was set to 580 ° C where the solid-liquid coexistence temperature was set.
Corrosion is not significant in the test piece of No. 1 in the range where the amount of impurity elements is small. Further, when the bonding temperature is 610 ° C., which is higher than the liquidus temperature, corrosion becomes very remarkable even if the amount of impurity elements is small. This is because, as will be described later, the diffusion of the impurity element becomes remarkable due to the increase of the bonding temperature, and the impurity element is likely to be concentrated near the bonding interface. From the above, the bonding temperature must be below the liquidus temperature.

When the fracture surface of the joint corroded by Na is observed in the above experiment, a striped pattern indicating that corrosion has progressed due to repeated thermal stress generated in the thermal cycle indicates the number of times of the thermal cycle. Observed accordingly.

Further, in FIG. 7, there is a transition point in the content of the impurity element with respect to the corrosion length. That is, FIG.
Corrosion curves (bonding temperature 545 ° C and bonding temperature 580
A tangent line is drawn to the rising part of (° C.), and the content of the intersection point is seen as a transition point, which is approximately 2.4 wt% in each case. From this, it can be seen that the corrosion can be considerably suppressed if the total amount of the impurity elements is 2.4 wt% or less. If the bonding temperature is 545 ° C. or lower, the diffusion of the impurity element is further suppressed, and if the amount of the impurity element is the same, the corrosion length is considerably shortened.
Since the bondability between 10 and the α-alumina insulating ring 107 is deteriorated, it is necessary to raise the bonding pressure to about 50 MPa.

Further, Mg and C in the insert material 110
It is better that the total content of impurity elements such as u, Fe, Ni, Mn, Zn, and Ca is as small as possible.
It is impossible in modern technology to set t%, and 0.001 wt% is set as the lower limit based on the accuracy of quantitative analysis of possible impurity content. Further, if the content is about 0.001 wt%, it is considered that there is no practical problem in producing a high-purity Al—Si alloy.

(Experimental Example 2) This experimental example is an experimental example relating to the corrosion length of the joint interface due to Na. Insert material 11
0, Al-10 wt with a total amount of impurity elements of 0.85 wt% on both surfaces of the core material of Al alloy (A3003)
Using a three-layer clad material (thickness: 0.6 mm, clad ratio: 5%) sandwiched between two skin materials of% Si alloy, a joining temperature of 565
The test piece as shown in FIG. 2 was prepared by joining under the joining conditions of ℃, joining pressure of 30 MPa and joining time of 15 min. In addition, for comparison, as the insert material 110, an Al alloy (A3
The total amount of impurity elements is 2.8w on both sides of the core material of (003)
Using a three-layer clad material (thickness 0.6 mm, clad ratio 5%) sandwiched between both skin materials of Al-10 wt% Si-1.5 wt% Mg alloy (A4004), which is t%, the same joining as above A test piece joined under the conditions was also prepared. These 4
After soaking in molten Na at 50 ° C. for various times (Hr),
FIG. 8 shows the result of measuring the corrosion length (mm) of Na at the bonding interface. However, A3003 and A4004 are J
Indicates the IS standard number (the same applies below).

As can be seen from FIG. 8, the corrosion length increases with time, but the test using a material having a large impurity element amount of 2.8 wt% (the conventional insert material is considered to be almost equivalent to this) The corrosion length of the piece is considerably longer than that of a test piece (corresponding to this example) using a small impurity element amount of 0.85 wt%.

Here, the α-alumina insulating ring 107 is used.
The average amount of corrosion due to Na at the joint interface between the and insert material 110 is calculated. First, assuming that the corrosion at the bonding interface proceeds in a diffusion-controlled manner, the estimated corrosion length X ₁ becomes longer in proportion to the 1/2 power of time. That is, X ₁ = (2Dt) ^1/2 = K · t ^1/2 . Where D is the diffusion coefficient, t is the time, and K = (2D) ^1/2 . Therefore, high-purity Al-10 wt% S in which the total amount of impurity elements is 2.4 wt% or less
The test piece using the i alloy as the insert material 110 is 450 ° C.
The average estimated corrosion length X when immersed in the molten Na for t hours is represented by X ₁ = 0.00126 × t ^1/2 (mm) from the experimental results shown in FIG.

On the other hand, in order to investigate the effect of the heat cycle, the corrosion length of a test piece which was subjected to 40 heat cycles of heating from room temperature to 450 ° C. in a state of being immersed in molten Na and then cooling to room temperature was measured. , The amount of impurities is 0.85w
The t% insert material and the 2.8 wt% insert material were 0.2 mm and 2.1 mm, respectively. Thus, when the amount of impurities is reduced, the corrosion length is significantly reduced.
Here, it was found that when a high-purity Al—Si alloy is used as the insert material 110, the repeated heat cycle from 450 ° C. to room temperature results in a corrosion length of 50 μm per cycle. That is, assuming that the corrosion progresses in proportion, the average estimated corrosion length X ₂ after C thermal cycles is given by X ₂ = 0.005 × C (mm).

Therefore, the average corrosion length X estimated at the joint of the sodium-sulfur battery of this example is the above X ₁
And X ₂ , that is, X = 0.00126 × t ^1/2 + 0.005 × C (m
m). The temperature of the molten Na is 450
The estimated corrosion length will be shorter than the above at ℃ or below, but depending on the operating method of the battery, the temperature may rise to about 450 ℃.
The estimation formula in ° C was calculated. Therefore, the estimated average corrosion length when used in an operating temperature range of 310 ° C. or higher is the value of X or less.

(Experimental Example 3) This experimental example is an experimental example relating to bonding conditions. As the insert material 110, both surfaces of the core material of Al alloy (A3003) are Al-10 wt% Si.
A three-layer clad material (thickness: 0.6 mm, clad ratio: 5) sandwiched between both skin materials of a 1.5 wt% Mg alloy (A4004)
%), The corrosion length (mm) by Na after the test in which each test piece bonded at various bonding temperatures is heated and lowered 20 times from room temperature to 340 ° C. is shown in FIG. In FIG. 9, the horizontal axis represents the joining temperature. In addition, this insert material 1
The impurities in the Al-Si-Mg alloy of No. 10 are Fe 0.
35wt%, Cu 0.25wt%, Mn 0.08w
t%, Zn 0.15 wt%, Ca 0.005 wt%
Below, the total content of the impurity elements other than Al and Si is 2.335 wt%. The joining pressure was changed depending on the joining temperature, and was set to be relatively high at 30 MPa below 560 ° C. (below the solidus temperature of the Al—Si—Mg alloy), and relatively low at 10 MPa above 560 ° C. The liquidus temperature of the Al-Si-Mg alloy is about 590.
° C.

As can be seen from FIG. 9, there is a temperature at which the corrosion length increases in the solid-liquid coexistence temperature range, and when the joining temperature exceeds the liquidus line, the corrosion length rapidly increases. That is, when the amount of the impurity element in the insert material 110 is large, and when the bonding temperature of the insert material 110 is above the liquidus line and the diffusion of the impurity element becomes remarkable, Na corrosion tends to become remarkable.

In order to investigate the diffusion phenomenon of the impurity element, the vicinity of the bonding interface of the test pieces bonded at various bonding temperatures was observed by a transmission electron microscope to examine the EDX (Energy Dispe
element analysis by point analysis on the order of nanometers by rsiveAnalysis). Among them, the analysis result of Cu in the vicinity of the bonding interface is shown in FIG. 10 (a), and the analysis result of Fe in the vicinity of the bonding interface is shown in FIG. 10 (b).

As can be seen from FIG. 10 (a), when the bonding temperature is high, the diffusion is remarkable, so that Cu is likely to be concentrated, and the temperature is 590 ° C.
In the vicinity of the bonding interface (on the insert material 110 side and at α
-On both the alumina insulation ring 107 side) the Cu concentration is considerably higher than the initial content. In particular, it is abnormally high at the bonding interface. However, when the joining temperature is as low as 545 ° C., the Cu concentration on the insert material 110 side is higher than the initial content, but the degree of concentration is lower than at 590 ° C. FIG.
The result of Fe analysis shown in (b) shows that the result is almost the same as that of Cu. When the joining temperature is high, the concentration of Fe in the vicinity of the joining interface is remarkable, and when the joining temperature is low, the degree of enrichment is low. Has become. Furthermore, Ni, Mn other than Cu and Fe,
Similarly for Mg and the like, the higher the bonding temperature, the more remarkable the concentration of elements at the bonding interface. From these results, it can be said that when the bonding temperature is low, the impurity element is less likely to be concentrated, and the Na corrosion can be suppressed accordingly.
It is desirable to perform the joining at the solid phase temperature of the insert material 110 or the temperature range of solid-liquid coexistence.

Further, when the joining temperature is below the solidus line of the insert material 110, a liquid phase does not occur at the joining interface, and therefore the joining pressure is set to 2 in order to sufficiently bring the joined surfaces into close contact with each other.
It is necessary to set it in the range of 0 to 50 MPa. 20
When joining at a pressure lower than MPa, the adhesion is insufficient and a void remains at the joining interface, and the insert material 110
The strong oxide film on the surface cannot be sufficiently destroyed, and the oxide film hinders bonding. Further, when the pressure is higher than 50 MPa, the amount of deformation of the insert material 110 becomes large, which causes a problem of protrusion to the outside of the joint surface.

On the other hand, when the joining temperature is the temperature at which the insert material 110 coexists with solid and liquid, since solid and liquid coexist, an excessively high joining pressure is not required, and the joining pressure is 10 to 2
0 MPa is a suitable range. For example, at a high joining pressure such as 50 MPa, the insert material 11 is formed on the outer periphery of the joining portion.
There is a problem that a large amount of 0 is extruded and the cathode member 103 and the anode member 105 are short-circuited. Also,
When the pressure is lower than 10 MPa or no pressure is applied, voids are formed due to gas generation from the insert material 110,
In addition, since the molten Al-Si alloy has poor wettability with respect to the insulating member made of α-alumina, a joint failure also occurs in the joint portion, resulting in deterioration of airtightness and joint strength.

(Experimental Example 4) This is an experimental example relating to the influence of Mg. As the insert material 110, Fe, Cu, Mn, and Z are formed on both surfaces of the Al alloy (A3003) core material.
3 sandwiched between both skin materials of Si-1.5 wt% Mg alloy in which the total content of impurity elements such as n and Ca is 0.25 wt%.
A layer clad material (thickness 0.6 mm, clad rate 5%) is used, and the joining temperature is 545 ° C., 555 ° C., 565 ° C. and 59.
A Na corrosion test was performed on a test piece manufactured by changing the temperature to 0 ° C. As a result, the bonding interface corroded only slightly at 565 ° C or lower, but the Na corrosion amount increased when the bonding temperature increased to 590 ° C.

This cause is considered to be related to the evaporation of Mg during joining. FIG. 11 shows the results of investigation on the evaporation of Mg, in which the insert material clad with the Al—Si—Mg alloy was heated in a vacuum furnace, and water (H ₂ O), M
g, is a diagram showing the results of sequential measured by the quadrupole mass spectrometer of the relative sensitivity of each gas partial pressure of hydrogen (H _2). From FIG. 11, it can be seen that Mg gradually evaporates in the temperature rising process, but the evaporation amount starts to increase from around 470 ° C. and particularly increases above 550 ° C. Also, H ₂ O is Mg at around 470 ° C.
The amount of evaporation of H ₂ begins to decrease as the amount of evaporation of H ₂ increases, and the amount of evaporation of H ₂ begins to increase from that point. Such H ₂ O and H ₂
Changes in, as is commonly known in the vacuum brazing of Al, evaporated Mg and H ₂ O react chemically is considered to be caused for generating the H _2.

From the above, when the Mg concentration is low, Na corrosion is not remarkable even if the insert material 110 is joined at a temperature at which it is partially melted, but when the temperature exceeds 570 ° C.
Vaporization of Mg increases and Mg concentrates at the bonding interface,
It is considered that corrosion is likely to occur. Therefore,
If the insert material 110 inevitably contains Mg, it is desirable to set the joining temperature to a relatively low temperature of about 565 ° C. or lower.

(Experimental Example 5) In this example, the insert material 11 was used.
It is an experiment example regarding the composition of the 0 skin material. Table 1 shows the results of measuring the corrosion length due to Na when the skin material of the insert material 110 was variously changed. The conditions of the Na corrosion test are the same as in Experimental Example 1, and each test piece is
Hold in molten Na at 0 ° C for 1000 hours, and
It is a condition that a thermal cycle of cooling to room temperature and heating to 350 ° C. again during 40 hours is added 40 times.

[0067]

[Table 1]

As can be seen from Table 1, Na corrosion also occurs in the case of pure Al (A1080) having a very low impurity element concentration. The impurity element content of the pure Al used here is 0.18 wt%. The cause of this corrosion is due to defective bonding due to voids and oxide film, and the corrosion mechanism is different from the above-described corrosion when the insert material 110 is an Al—Si alloy containing a large amount of impurity elements. That is, when the insert material 110 and the α-alumina insulating ring 107 are joined, it is necessary that the insert material contains Si, or otherwise, a joint failure due to a void or an oxide film may occur. I will end up.

Also, Al-1.5 wt containing no Si
Similar corrosion also occurred with the% Mg alloy. The total content of the impurity elements other than Mg in the Al-Mg alloy used here is 0.25 wt% or less. The cause of this corrosion is Si
This is because the same poor bonding as described above occurs due to the absence of Al, and the impurity elements and Mg in the insert material 110 evaporate to concentrate these elements at the bonding interface. Although not shown in the table, Mg is 3
With an Al-Mg alloy of less than wt%, the solidus temperature is 6
When the temperature is as high as 00 ° C. or higher and the bonding is performed at 580 ° C., Na corrosion occurs despite the bonding in the solid state. This is because heating to 570 ° C. or higher causes remarkable evaporation of Mg as described with reference to FIG. 11, and Mg is concentrated on the joint surface. According to an experiment conducted by the present inventor, Mg
If the bonding temperature is set to 0.5 wt% or less and the bonding temperature is set to 565 ° C. and the bonding pressure is increased, the bondability is improved and Na corrosion can be suppressed to some extent, but this is not a fundamental measure.
Increasing the joining pressure causes protrusion of the insert material and reduction in dimensional accuracy, which is a practical problem. In any case, it can be said that it is desirable that the Mg content be reduced as much as possible.

In the case of an Al-10 wt% Si alloy which does not contain Mg and whose total content of other impurity elements is 0.85 wt%, when the joining temperature becomes high and the liquid phase state is reached (610 ° C. in Table 1). ), Since the diffusion is quite remarkable, the impurity element is concentrated at the bonding interface, and Na corrosion becomes remarkable. But,
The Na corrosion length decreases as the bonding temperature decreases, and the Na corrosion length can be suppressed by bonding at a temperature below the solidus temperature or at a temperature where solid and liquid coexist.

From the above results, even when pure Al or Al-Mg alloy containing no Si is used as the insert material, Na corrosion occurs, and the Al-Si alloy containing Si is used as the insert material and the solidus temperature is lower than the solidus temperature. Although Na corrosion is suppressed when joining at the temperature of or the temperature of solid-liquid coexistence,
This suggests that Si is not the main cause of Na corrosion.

(Experimental Example 6) This is an experimental example relating to the influence of the purity of alumina on Na corrosion. In general,
Impurities such as Fe and Ca may enter the alumina powder that is the raw material of the α-alumina insulating ring 107.
When sintering the alumina powder, MgO or the like is added as a sintering aid. As a result, impurity elements such as Mg, Fe, and Ca are present in the α-alumina grain boundaries, and the impurity elements in the alumina grain boundaries are concentrated at the bonding interface due to diffusion during bonding. Therefore, it is considered that the Na corrosion resistance is adversely affected when the above-mentioned many impurity elements are contained.

Table 2 shows the results of the investigation on the influence of the purity of alumina on Na corrosion as described above. The α-alumina insulating ring 107 has a purity of 99.9 wt%, 99.5 wt% and 99.0 wt%.
The test pieces as shown in FIG. Again, the conditions of the Na corrosion test are the same as those in Experimental Example 1, and each test piece is held in molten Na at 350 ° C. for 1000 hours, and the heat for cooling to room temperature and heating it again to 350 ° C. is maintained for 1000 hours. The condition is that the cycle is added 40 times. As the insert material 110, high-purity Al-10 having a total amount of impurity elements of 0.14 wt% on both surfaces of a core material of Al alloy (A3003).
A three-layer clad material (thickness 0.6 mm, clad ratio 5%) sandwiched between both skin materials of wt% Si alloy was used. Also, the bonding temperature is 565 ° C., and the bonding pressure is 30M.
Pa.

[0074]

[Table 2]

As can be seen from Table 2, the lower the purity of alumina, the more likely Na corrosion will occur. Although the effect of the purity of alumina on Na corrosion is much smaller than the effect of the impurity elements in the insert material 110 on Na corrosion described above, the purity of alumina is 99.0 wt. %, The corrosion length is 0.3 mm
Therefore, Na corrosion occurs to the extent that it poses a practical problem. On the other hand, when the purity of alumina is 99.5 wt% or more, the corrosion length is suppressed to 0.1 mm. Therefore, by increasing the purity of alumina to 99.5 wt% or more, Na corrosion is reduced. It can be said that it is possible to do.

According to this embodiment as described above, the total content of elements other than Al and Si in the insert material 10 is 0.0.
The high-purity Al-Si alloy 10b in the range of 01 to 2.4 wt% is used, and a pressure in the range of 20 MPa to 50 MPa is applied at a temperature below the solidus line of the high-purity Al-Si alloy 10b, or the above-mentioned high Since the joining is performed under the condition that a pressure in the range of 10 MPa to 20 MPa is applied at the solid-liquid coexisting temperature of the pure Al—Si alloy 10b, Mg, Cu, Fe, Ni, Mn, and Z contained in the insert material 10 are included.
Impurity elements such as n and Ca are prevented from concentrating at the bonding interface during bonding, and Na corrosion at that location is prevented.

Therefore, according to the sodium-sulfur battery of this embodiment, the operating temperature of 310 ° C. or higher is maintained for a long time, and the thermal cycle between heating and cooling between the operating temperature and room temperature is repeated. Even under use conditions, long-term reliability can be expected without impairing the Na corrosion resistance of the joint, and thus without lowering the joint strength and airtightness of the joint.

Further, since the sodium corrosion resistance is improved, the size of the joint portion can be reduced, so that the battery system can be downsized.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 12 is an enlarged view of the flange portion of the cathode lid, the flange portion of the anode container, and the joint portion of the α-alumina insulating ring in the sodium-sulfur battery of this example, and is a view corresponding to FIG. 2. . The cathode lid 203 is provided on one surface (the upper surface in the figure) of the α-alumina insulating ring 207.
The flange portion 203A of the anode container 205 and the flange portion 205A of the anode container 205 are spaced apart from each other, and the flange portion 203A of the cathode lid 203 and the flange portion 205A of the anode container 205 are both joined (pressed together) via the insert material 210. ) Has been. This joining condition is exactly the same as that of the above-mentioned embodiment. The distance between the flange portion 203A and the flange portion 205A is such that the softened insert materials 210 do not come into contact with each other (for example, about 3 mm).
Or more). The β ″ alumina tube 206, which is a solid electrolyte, is the same as the β ″ alumina tube 6 in FIG.

The insert material 210 is made of Al alloy 2
High purity Al-Si alloy 210 on both sides of 10a (core material)
It has a three-layer structure sandwiched by b, and the composition of the high-purity Al—Si alloy 210b is exactly the same as that of the above-mentioned embodiment.

Further, also in this embodiment, the anode container 2
The joint interface between the .alpha.-alumina insulating ring 207 on the 05 side and the flange portion 205A does not come into contact with Na and it is not necessary to consider corrosion due to Na.
It is not necessary to dispose the same insert material 210 as the 3 side. Further, for the same reason as described with reference to FIG. 3, the high-purity Al—Si alloy 210b is located on the α-alumina insulating ring 207 side, and the Al alloy 210a (for the core material in FIG. 12 is used on the flange portion 203A side. It is also possible to use an insert material having a two-layer structure in which the insert material is located.

Also according to this embodiment, the above-described FIGS.
The same effect as the embodiment described in 1 is obtained.

[0083]

According to the present invention, the total content of elements other than Al and Si is 0.00 in the insert material in the joint.
The high-purity Al-Si alloy 10b in the range of 1 to 2.4 wt% is used, and a pressure in the range of 20 MPa to 50 MPa is applied at a temperature below the solidus line of the high-purity Al-Si alloy, or the above high-purity Al-Si alloy 10b is used. Since the joining is performed under the condition that a pressure in the range of 10 MPa to 20 MPa is applied at the solid-liquid coexisting temperature of the Al-Si alloy 10b, the working temperature of 310 ° C or higher is maintained for a long time, and the working temperature and the room temperature are maintained. Even under operating conditions in which heat cycles between heating and cooling are repeated, impurity elements are prevented from concentrating at the joint interface, and the sodium corrosion resistance of the joint is not impaired. In addition, long-term reliability can be expected without lowering the airtightness.

Further, since the sodium corrosion resistance is improved, the size of the joint portion can be reduced, and hence the battery system can be downsized.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a portion II of FIG. 1, that is, a flange portion of a cathode lid, a flange portion of an anode container, and a joint portion of an α-alumina insulating ring.

FIG. 3 is a diagram showing a modified example of FIG. 2 using an insert material having a two-layer structure.

FIG. 4 is a diagram showing a situation where a sodium-sulfur battery is used as a battery system, where (a) is used as a single battery and (b) is several to several tens of sub-cells. When used in a module, (c) is used in a module in which a plurality of submodules are combined, (d)
Indicates the case where thousands are used in the form of a combined unit.

5 is a cross-sectional view of an experimental test piece that models the battery having the structure shown in FIG.

FIG. 6 is a diagram showing a pattern of heating and pressing at the time of joining.

FIG. 7 is a diagram showing the influence of the impurity element in the insert material on the corrosion length due to Na.

FIG. 8 is a diagram showing changes in corrosion length due to Na depending on the time of immersion in molten Na.

FIG. 9 is a diagram showing the influence of the joining temperature on the corrosion length due to Na.

FIG. 10 shows the results of point analysis by EDX near the bonding interface of the test piece, where (a) is the analysis result of Cu and (b) is F.
It is an analysis result of e.

FIG. 11 is a diagram showing a result of measuring relative sensitivities of respective gas partial pressures of water (H ₂ O), Mg, and hydrogen (H ₂ ) released from the insert material with heating in a vacuum furnace. .

FIG. 12 is a view illustrating a sodium-sulfur battery according to another embodiment of the present invention, which is an enlarged view of a flange portion of a cathode lid, a flange portion of an anode container, and a joint portion of an α-alumina insulating ring. is there.

[Explanation of symbols]

 1 Sodium 2 Safety Tube 3 Cathode Lid 3A (Cathode Lid 3) Flange Part 4 Sulfur 5 Anode Container 5A (Anode Container 5) Flange Part 6 β ″ Alumina Tube (Solid Electrolyte) 7 α-Alumina Insulation Ring 10 Insert Material 10a Al alloy (core material) 10b (high purity) Al-Si alloy 103 Cathode member 105 Anode member 107 α-alumina insulating ring 110 Insert material 203 Cathode cover 203A (cathode cover 203) flange portion 205 Anode container 205A (Anode container) 205) Flange portion 206 β ″ alumina tube (solid electrolyte) 207 α-alumina insulating ring 210 insert material 210a Al alloy (core material) 210b (high purity) Al—Si alloy

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshimi Sato, 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture, Institute of Mechanical Research, Hiritsu Manufacturing Co., Ltd. Hitachi, Ltd., Hitachi Plant (72) Inventor, Hiroshi Sugiyama 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd., Hitachi, Ltd. (72) Inventor, Shigeru Sakaguchi, 3-chome, Sachimachi, Hitachi, Ibaraki No. 1 Hitachi Ltd. Hitachi factory

Claims (10)

[Claims] 1. When manufacturing a sodium-sulfur battery in which sodium conducted to a cathode cover and sulfur contained in an anode container are separated by a solid electrolyte, the cathode cover is provided on one surface of an α-alumina insulating ring. While disposing the anode container on the other surface of the α-alumina insulating ring, an insert made of an aluminum alloy is provided between each of the cathode lid and the anode container and the α-alumina insulating ring. Sodium bonded through the wood-
In the method for manufacturing a sulfur battery, the content of elements other than aluminum and silicon is 0.001 to 2.4 wt% as an insert material between at least the insulating ring made of α-alumina and the cathode lid.
And a high-purity aluminum-silicon alloy having a temperature range below the solidus line of the high-purity aluminum-silicon alloy and applying a pressure in the range of 20 MPa to 50 MPa to the α-alumina insulating ring. A method for manufacturing a sodium-sulfur battery, which comprises press-bonding the cathode lid. 2. When manufacturing a sodium-sulfur battery in which sodium conducted to a cathode lid and sulfur contained in an anode container are separated by a solid electrolyte, the cathode lid is formed on one surface of an α-alumina insulating ring. While disposing the anode container on the other surface of the α-alumina insulating ring, an insert made of an aluminum alloy is provided between each of the cathode lid and the anode container and the α-alumina insulating ring. Sodium bonded through the wood-
In the method for manufacturing a sulfur battery, the content of elements other than aluminum and silicon is 0.001 to 2.4 wt% as an insert material between at least the insulating ring made of α-alumina and the cathode lid.
By using a high-purity aluminum-silicon alloy having a temperature range of 10 MPa to 20 MPa and applying a pressure in the range of 10 MPa to 20 MPa to the solidus line and the liquidus line of the high-purity aluminum-silicon alloy. α-
A method of manufacturing a sodium-sulfur battery, comprising press-bonding an alumina insulating ring and the cathode lid. 3. A core material made of an aluminum alloy is used as the insert material between at least the insulating ring made of α-alumina and the cathode lid so that the total content of elements other than aluminum and silicon is 0.001. To 2.
3. The method of manufacturing a sodium-sulfur battery according to claim 1, wherein a three-layer structure sandwiched between skin materials of the high-purity aluminum-silicon alloy in the range of 4 wt% is used. 4. As the insert material between at least the insulating ring made of α-alumina and the cathode lid, the total content of elements other than aluminum and silicon is 0. 001 to 2.4 wt
%. The sodium-sulfur battery according to claim 1 or 2, wherein the high-purity aluminum-silicon alloy in the range of 1% is used and a two-layer structure in which the aluminum alloy is positioned on the cathode lid side is used. How to make. 5. The sodium ring according to claim 1, wherein the insulating ring made of α-alumina is α-alumina having a purity of 99.5 wt% or more.
Sulfur battery manufacturing method. 6. When manufacturing a sodium-sulfur battery in which sodium conducted to a cathode lid and sulfur contained in an anode container are separated by a solid electrolyte, the cathode lid is formed on one surface of an α-alumina insulating ring. And a sodium-sulfur battery in which the anode container is arranged apart from each other, and each of the cathode lid and the anode container and the insulating ring made of α-alumina are joined via an insert material made of an aluminum alloy. In the manufacturing method, the content of elements other than aluminum and silicon is 0.001 to 2.4 wt% as an insert material between at least the insulating ring made of α-alumina and the cathode lid.
And a high-purity aluminum-silicon alloy having a temperature range below the solidus line of the high-purity aluminum-silicon alloy and applying a pressure in the range of 20 MPa to 50 MPa to the α-alumina insulating ring. A method for manufacturing a sodium-sulfur battery, which comprises press-bonding the cathode lid. 7. When manufacturing a sodium-sulfur battery in which sodium conducted to the cathode lid and sulfur contained in the anode container are separated by a solid electrolyte, the cathode lid is formed on one surface of an α-alumina insulating ring. And a sodium-sulfur battery in which the anode container is arranged apart from each other, and each of the cathode lid and the anode container and the insulating ring made of α-alumina are joined via an insert material made of an aluminum alloy. In the manufacturing method, the content of elements other than aluminum and silicon is 0.001 to 2.4 wt% as an insert material between at least the insulating ring made of α-alumina and the cathode lid.
By using a high-purity aluminum-silicon alloy having a temperature range of 10 MPa to 20 MPa and applying a pressure in the range of 10 MPa to 20 MPa to the solidus line and the liquidus line of the high-purity aluminum-silicon alloy. α-
A method of manufacturing a sodium-sulfur battery, comprising press-bonding an alumina insulating ring and the cathode lid. 8. A sodium-sulfur battery in which sodium conducted to a cathode cover and sulfur contained in an anode container are separated by a solid electrolyte, wherein the cathode cover is provided on one surface of an insulating ring made of α-alumina. An insert material formed of an aluminum alloy between the cathode lid and the anode container and the insulating ring made of α-alumina while the anode container is arranged on the other surface of the α-alumina insulating ring. In a sodium-sulfur battery joined via a battery, a cycle of maintaining the operating temperature range of 310 ° C. or higher for t hours to repeat charging / discharging, cooling to room temperature during the charging / discharging, and heating again to the operating temperature range is performed. Under repeated battery operation conditions, the sodium at the joint interface between the α-alumina insulating ring and the insert material on the cathode lid side was used. Average corrosion amount is 0.00126 × t ^1/2
A sodium-sulfur battery represented by a value of + 0.005 × C (mm) or less. 9. A sodium-sulfur battery in which sodium conducted to a cathode cover and sulfur contained in an anode container are separated by a solid electrolyte, wherein the cathode cover is provided on one surface of an α-alumina insulating ring. An insert material formed of an aluminum alloy between the cathode lid and the anode container and the insulating ring made of α-alumina while the anode container is arranged on the other surface of the α-alumina insulating ring. In the sodium-sulfur battery bonded via, the insert material between at least the insulating ring made of α-alumina and the cathode lid is made of materials other than aluminum and silicon at the bonding interface with the insulating ring made of α-alumina. Natri having a high-purity aluminum-silicon alloy having an element content in the range of 0.001 to 2.4 wt%. Beam - sulfur battery. 10. The α-alumina insulating ring comprises:
The sodium-sulfur battery according to claim 8 or 9, which is α-alumina having a purity of 99.5 wt% or more.