JP3307235B2 - Cathode container material and cathode container for sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention has a high strength,
Excellent corrosion resistance to molten sodium polysulfide and molten sulfur (S) (hereinafter referred to as Na.S corrosion resistance);
Therefore, the present invention relates to a positive electrode container material and a positive electrode container that contribute to increasing the capacity and weight of a sodium (Na) -sulfur (S) battery.

[0002]

2. Description of the Related Art Conventionally, a Na-S battery is generally used for electric vehicles and electric power storage, and as shown in FIG. At the opening end of the electrolyte tube 61, an α-alumina insulating ring 62 is sealed with glass, a positive electrode container 63 and a negative electrode rod 64 are placed on the insulating ring 62, and sodium (Na) 65 is contained in the solid electrolyte tube. It is known that the space between this and the positive electrode container has a structure in which sulfur (S) 66 is filled and sealed.

Further, in the Na-S battery having the above structure, the operating temperature is generally 350 ° C., and at the time of discharge, molten Na becomes Na ions and moves inside the solid electrolyte tube 1 to the positive electrode container 3 side. Reacts with the molten S to produce sodium polysulfide, while charging is the reverse of this reaction.

Accordingly, the positive electrode container of the Na-S battery is
Since it is placed in a severe corrosive environment exposed to highly corrosive sodium polysulfide and molten S, it has good Na.S corrosion resistance, for example, Fe as disclosed in JP-A-7-85886. One Cr-based alloy, that is, in% by weight (hereinafter,% indicates weight%), Cr: 25 to 40
%, Mo: 1 to 3.5%, and Al: 0.5 to 3.5%, and a Fe-Cr based alloy or the like having a composition of Fe and unavoidable impurities is used for the remainder.

[0005] On the other hand, Na-S batteries have attracted attention due to the increasing need for pollution-free energy in recent years, and their capacity and weight have been strongly demanded. One of the means for achieving this is to reduce the thickness of the positive electrode container. However, Fe which constitutes the above-mentioned conventional positive electrode container has
One Cr-based alloy and other materials have sufficient strength and N resistance
At present, it is practically difficult to reduce the thickness because it does not have a · S corrosiveness.

[0006] In view of the above, the present inventors have conducted research to develop a positive electrode container of a Na-S battery having higher strength and excellent Na-S corrosion resistance. As a result, the positive electrode container of the Na-S battery was replaced with Cr: 1.
5-30%, Ni: 5-30%, W: 10-20%, F
e 0.1 to 5%, Mn: 0.2 to 2%, C: 0.01 to
0.3:%, and optionally La:
0.01 to 0.2%, with the balance being Co (but 35%).
% Or more) and an unavoidable impurity.
When composed of a base alloy, the resulting positive electrode container material has high strength and excellent Na · S corrosion resistance. The research result that it exerts over the whole was obtained.

[0007]

The Co-based alloy has high strength and excellent Na.S corrosion resistance, but has a high raw material cost.
The production cost of the Na-S battery itself increases if it is attempted to produce it using only the base alloy.

[0008] Further, since the Co-based alloy has a low deformability, it cannot be subjected to composition processing with a large degree of processing, and when a cylindrical positive electrode container is to be manufactured, a rolled plate material is required. It was necessary to adopt a method of forming a cylindrical shape and joining the ends by welding. Therefore,
In the positive electrode container manufactured by welding in this manner, the performance of the welded portion against corrosion is inevitably lower than that of other portions.

The present invention has been made in view of the above circumstances, and provides a positive electrode container material and a positive electrode container of a sodium-sulfur battery capable of reducing manufacturing costs and improving performance against corrosion. The purpose is to do.

[0010]

SUMMARY OF THE INVENTION A positive electrode container material for a sodium-sulfur battery according to the present invention comprises an outer layer portion having corrosion resistance to sodium polysulfide and molten sulfur, and an inner layer portion disposed inside the outer layer portion. A positive electrode container material for a sodium-sulfur battery, wherein the inner layer portion is made of a Co-based alloy. Thereby, Na-S resistance
By placing a corrosive Co-based alloy in the inner layer in contact with sodium polysulfide and molten sulfur, the corrosion resistance of the positive electrode container can be increased, and a material having corrosion resistance to sodium polysulfide and molten sulfur is placed in the outer layer. Therefore, even if sodium polysulfide and molten sulfur pass through the inner layer and reach the outer layer, corrosion does not proceed. Further, since the Co-based alloy is used only for the inner layer portion, the cost of raw materials can be reduced.

In the positive electrode container material of the sodium-sulfur battery, the outer layer portion and the inner layer portion may be integrally formed by cladding. According to this, the bonding strength between the outer layer portion and the inner layer portion can be increased in the cladding process, and the mechanical and electrical adhesion between the two can be enhanced, and the function as a positive electrode container of the battery is sufficiently exhibited. be able to.

The inner layer portion is made of Co on the surface of the outer layer member.
It can also be formed by spraying a base alloy. In this case, expensive Co may be formed to the minimum necessary thickness, which is very economical.

The outer layer may be made of aluminum or aluminum alloy. Accordingly, even if sodium polysulfide and molten sulfur pass through the inner layer and reach the outer layer, corrosion does not proceed. In addition, in the case of aluminum or an aluminum alloy, when it comes into contact with sodium polysulfide and molten sulfur, a film of a passive body which is an electric conductor is formed, but since the outer portion is covered by the inner member, sodium polysulfide and Since the molten sulfur does not come into contact with the battery, the function of the battery is not hindered.

[0014] The positive electrode container material of the present invention is used in a positive electrode container of a sodium-sulfur battery including a cylindrical side wall member and a bottom plate member disposed and fixed to the opening of the side wall member so as to cover the opening. The bottom plate member can be formed of the same material as the inner member, and can be integrated by welding at the boundary between the side wall member and the bottom plate member. In this case, the welding is performed at the same material portion of the inner portion and the bottom plate member, and the welding strength can be increased.

The Co-based alloy includes : Cr: 15 to 30%, Ni: 5 to 30%, W: 10 to 20%, Fe: 0.1 to 5%, Mn: 0.2 to 2% , C: : 0.01 to 0.3%, and if necessary, La: 0.01 to 0.2%, and the balance consists of Co (including 35% or more) and inevitable impurities. It is Co based alloy having a composition.

Next, the reason why the composition of the Co-based alloy constituting the cathode container material of the present invention is limited as described above will be described.

(A) Cr The Cr component has a function of improving the strength by forming a finely dispersed carbide in the base material while improving the Na / S corrosion resistance by forming a solid solution in the base material. 15% content
If it is less than 30%, the desired effect cannot be obtained, while if its content exceeds 30%, the rolling processability and the weldability deteriorate (in each case, cracks occur). Therefore, the content was determined to be 15 to 30%, preferably 20 to 24%.

(B) Ni The Ni component has a function of improving the strength by forming a solid solution in the base material. However, if the content is less than 5%, the desired effect of improving the strength cannot be obtained, while the content is low. If it exceeds 30%, the Na · s corrosion resistance will decrease, so its content is set to 5 to 30%, preferably 20 to 25%.

(C) WW The W component has a function of improving the strength by forming a carbide which forms a solid solution in the base material and is finely dispersed in the base material. When the content exceeds 20%, the rolling workability is reduced.
-20%, preferably 13-16%.

(D) Fe The Fe component has a function of improving the rolling workability by forming a solid solution in the base material. However, if the content is less than 0.1%, a desired improvement effect cannot be obtained. On the other hand, if the content exceeds 5%, the Na.S corrosion resistance decreases, so the content is set to 1 to 5%, preferably 0.1 to 3%.

(E) Mn The Mn component has the effect of forming a solid solution in the base material to improve the Na.S corrosion resistance, but if its content is less than 0.2%, the desired effect is not obtained. Not obtained, while its content is 2
%, The ferrite phase appears on the base material, and the Na · s corrosion resistance tends to decrease. Therefore, the content is 0.2 to 2%, preferably 0.2%.
％ 1.3%.

(F) CC The C component has the effect of forming a solid solution in a base material and solid-solution strengthening it, and forming a carbide by combining with Cr and W, thereby improving the strength. Content 0.01
If the content is less than 0.3%, the desired effect cannot be obtained. If the content is more than 0.3%, the rolling processability is reduced. 3
%, Desirably 0.05 to 0.15%.

(G) La La component has an effect of further improving the Na.S corrosion resistance, and is therefore contained as necessary. If the content is less than 0.01%, the desired improvement effect is obtained. On the other hand, if the content exceeds 0.2%, oxides are formed and the strength is reduced, so that the content is preferably 0.01 to 0.2%. Is 0.03-0.1
It was determined to be 2%.

(H) Co The Co component is an indispensable component for ensuring excellent Na.S corrosion resistance. Therefore, if its content is less than 35%, desired Na.S corrosion resistance can be obtained. Because there is no
The content was determined to be 35% or more.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a positive electrode container according to an embodiment of the present invention and a method for producing the same will be described. First, a method for manufacturing the positive electrode container of the present embodiment will be described with reference to FIGS. Metal Co, thermite chromium, metal W, Fe-Ni alloy, carbon powder, electrolytic Ni, Ni-La alloy, and metal Mn are used as raw materials; And dissolved using Si and Al as deoxidizing agents,
A molten metal having each of the component compositions shown in Table 1 was prepared, and the molten metal was further deoxidized using a Ni-Mg alloy as a deoxidizing agent, and the molten metal was discharged.
(The result is that the ingot is usually 0.1 mm).
1-0.6% Si, 0.1-0.4% A1, and 0.01-0.06% Mg).
After homogenizing the ingot at 1180 ° C. for 10 hours, the ingot is hot rolled at a temperature of 1100 ° C. to 1200 ° C. to form a 3 mm-thick rolled sheet. By applying a cold-rolled sheet having a storage space of 0.5 mm, plate materials 1 to 14 used for the positive electrode container material of the present invention and a conventional positive electrode container material were manufactured.

From the various plate materials and positive electrode container materials obtained as a result, the parallel portion length was 120 m for the purpose of evaluating the strength.
A tensile test piece having a size of mx width: 20 mm x thickness: 0.5 mm was cut out, and in order to evaluate their Na / S corrosion resistance, an outer tube was formed using a tube forming machine and a TIG welding machine. A tube having a diameter of 65 mm × length: 400 mm was formed, and the tube was held at 1180 ° C. for 30 minutes and then subjected to a solution heat treatment under water-cooling conditions to form a positive electrode container of a Na-S battery.

The tensile test was conducted at 350 ° C. to measure the tensile strength. The positive electrode container was incorporated in a Na1S battery, and the operating temperature was 350 ° C. and the charging current density was 23.
A real machine test was performed under acceleration conditions of 0 mA / cm ² , discharge current density: 300 mA / cm ² , and continuous charge / discharge frequency: 150 cycles, and the maximum erosion depth on the inner surface of the positive electrode container was measured.
Table 1 shows the results of these measurements.

[0028]

[Table 1]

As shown in FIG. 1, the above-mentioned plates 1 to 14 are subjected to plastic working and formed into a tubular shape by a tube forming machine. Then, the ends a of the plate material formed into a cylindrical shape are welded and joined by, for example, a TIG welding machine (see b in the drawing), and formed into a tubular shape.

Next, as shown in FIGS. 2 and 3, the plate-like plates 1 to 14 are connected to an aluminum cylindrical body 5.
Press into 0. Here, the aluminum cylinder 50
Is manufactured by extruding an aluminum ingot and has a seamless, so-called seamless pipe.

Next, as shown in FIG. 4, by passing a cylindrical body 50 into which the plates 1 to 14 are press-fitted through a die, a drawing process is performed so that the inner diameter and the outer diameter become a raw material 52 having predetermined dimensions. Apply. Thereby, the adhesion between the plate members 1 to 14 and the cylindrical body 50 is enhanced, and a positive electrode material integrally formed with each other is manufactured. If cobalt plating is applied to the inner surface of the cylindrical body 50, the adhesion between the plate members 1 to 14 and the cylindrical body 50 is improved, and the cylindrical body 50 is further firmly integrated.

Further, by performing the drawing process, the cylindrical body 5 is formed.
0 is elongated, and fine cracks are formed in the passive body which is an electric conductor formed on the surface of the cylindrical body 50. The plate materials 1 to 14 penetrate into the cracks, and the plate materials 1 to 14 Electrical connection with the conductive layer inside the body 50 is achieved, which is suitable when used as a positive electrode container of a battery.

The material 52 obtained as described above is a composite material having an outer layer portion 53 and an inner layer portion 54. In addition, aluminum has sufficient corrosion resistance to sodium polysulfide and molten sulfur. That is, when aluminum comes into contact with sodium polysulfide or molten sulfur, a non-conductive film is formed, and this film prevents corrosion from further progressing.

Next, the raw material 52 is subjected to predetermined processing to manufacture a positive electrode. That is, as shown in FIG. 5, the raw material 52 is cut into a predetermined length, a bottom plate 55 made of a Co-based alloy is inserted into one opening, and the bottom plate 55 and the raw material 52 are cut.
Are welded by an electro-beam method to integrate them. Here, the boundary portion 56 to be welded is a portion where the bottom plate 55 and the inner layer portion 54 are in contact with each other. Since welding is performed in the region between the bottom plate 55 and the inner layer portion 54 formed of the same material, Welding strength can be increased.

Next, the operation of the positive electrode container manufactured by the above manufacturing method will be described.

The inner surface of the positive electrode container is exposed to sodium polysulfide and molten sulfur. In the positive electrode container according to one embodiment of the present invention, an inner layer portion 54 made of a Co-based alloy is disposed on the inner surface. As a result, large corrosion holes do not occur. Also, an outer layer portion 53 made of aluminum
Is hardly corroded by sodium polysulfide or molten sulfur. Even if sodium polysulfide or molten sulfur reaches the outer layer portion, the outer layer portion 53 is not corroded. Particularly, since the outer layer portion 53 is a so-called seamless tube, the safety against corrosion is very high.

Further, when the aluminum comes into contact with sodium polysulfide or molten sulfur, a nonconductive film is formed and the aluminum cannot function as a battery. Since the inner layer portion 54 made of the base alloy is provided, the non-conductive film is not formed, and the function of the battery can always be normally maintained.

Although the inner layer portion 54 is joined to the outer layer portion 53 by drawing, the inner layer portion 54 is formed by spraying a molten Co-based alloy on the inner surface of the outer layer portion 53. Can be
According to this thermal spraying, the necessary minimum thickness (several tens of μm)
Can be formed, the amount of expensive Co-based alloy used can be saved, and the manufacturing cost can be further reduced.

[0039]

As described above, according to the positive electrode container material and the positive electrode container of the sodium-sulfur battery of the present invention,
The following effects are obtained.

The corrosion resistance of the positive electrode container can be enhanced by arranging a Co-based alloy having Na.S corrosion resistance in the inner layer in contact with sodium polysulfide and molten sulfur.
Further, since a material having corrosion resistance to sodium polysulfide and molten sulfur is disposed in the outer layer portion, even if sodium polysulfide and molten sulfur pass through the inner layer portion to reach the outer layer portion, corrosion does not proceed. Further, since the Co-based alloy is used only for the inner layer portion, the cost of raw materials can be reduced.

In the cladding step, the bonding strength between the outer layer portion and the inner layer portion can be increased, the mechanical and electrical adhesion between the outer layer portion and the inner layer portion can be increased, and the function as a positive electrode container of the battery can be sufficiently exhibited. Can be.

According to the thermal spraying, expensive Co may be formed to a necessary minimum film thickness, which is very economical.

In the case of aluminum or aluminum alloy, when in contact with sodium polysulfide and molten sulfur,
Although a film of a passive body, which is an electric conductor, is formed, the outer portion is covered with the inner member, so that sodium polysulfide and molten sulfur do not come in contact with each other, so that the function of the battery is not hindered.

According to the positive electrode container of the present invention, the positive electrode welding is performed on the same material of the inner portion and the bottom plate member, and the welding strength can be increased.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of a positive electrode container of the present invention.

FIG. 2 is a view showing a manufacturing process of the positive electrode container of the present invention.

FIG. 3 is a view showing a manufacturing process of the positive electrode container of the present invention.

FIG. 4 is a view showing a manufacturing process of the positive electrode container of the present invention.

FIG. 5 is a view showing a manufacturing process of the positive electrode container of the present invention.

FIG. 6 is a schematic longitudinal sectional view illustrating the structure of a Na.S battery.

[Explanation of symbols]

 1-14 plate material 50 cylindrical body 51 die 52 material 53 outer layer part 54 inner layer part 61 solid electrolyte tube 62 insulating ring 63 positive electrode container 64 negative electrode rod 65 sodium (Na) 66 sulfur (S)

Claims (6)

(57) [Claims] 1. A cathode container material for a sodium-sulfur battery comprising: an outer layer portion having corrosion resistance to sodium polysulfide and molten sulfur; and an inner layer portion disposed inside the outer layer portion, wherein the inner layer portion comprises: It consists of a Co-based alloy , and the Co-based alloy is, by weight%, Cr: 15 to 30%, Ni: 5 to 30%, W: 10 to 20%, Fe: 0.1 to 5%, Mn: 0. 2 to 2%, C: 0.01 to 0.3%, the balance being inevitable with Co (but containing 35% or more)
A positive electrode container material for a sodium-sulfur battery, characterized by having a composition comprising impurities . 2. For sodium polysulfide and molten sulfur
An outer layer portion having corrosion resistance and
Of a sodium-sulfur battery having a
An electrode container material, wherein the inner layer portion is made of a Co-based alloy, and the Co-based alloy is, by weight%, Cr: 15 to 30%, Ni: 5 to 30%, W: 10 to 20%, Fe : 0.1 to 5%, Mn: 0.2 to 2%, C: 0.01 to 0.3%, and La: 0.01 to 0.2%, and the rest Is inevitable with Co (but contains 35% or more)
A positive electrode container material for a sodium-sulfur battery, characterized by having a composition comprising impurities . 3. The method according to claim 1, wherein the outer layer and the inner layer are clad.
2. The method according to claim 1, wherein the first member is integrated with the second member.
3. The cathode container material for a sodium-sulfur battery described in 2 . 4. The method according to claim 1, wherein the inner layer portion has C on the surface of the outer layer portion.
It is characterized by being formed by spraying an o-base alloy.
A positive electrode container material for a sodium-sulfur battery according to claim 1 or 2 . 5. The method according to claim 1, wherein the outer layer portion is made of aluminum or aluminum.
5. The method according to claim 1, wherein the alloy is made of a minium alloy.
A positive electrode container material for the sodium-sulfur battery according to any one of the above . 6. A cylindrical side wall member and an opening of the side wall member.
And a bottom plate member arranged and fixed so as to cover the opening.
A positive electrode container for a sodium-sulfur battery, wherein the side wall member is in any one of claims 1 to 5.
The bottom plate member is formed of
The side wall member and the bottom plate are formed of the same material as the member.
At the boundary with the member, these parts were welded together.
A positive electrode container for a sodium-sulfur battery.