JP3293482B2 - 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,
And 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, Na.S batteries are generally used for electric vehicles and electric power storage, and as shown in FIG. An α-alumina insulating ring 62 is sealed to the open end of the electrolyte tube 61 with glass, a positive electrode container 63 and a negative electrode rod 64 are mounted on the insulating ring 62, sodium (Na) 65 is contained in the solid electrolyte tube, and 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 where it is exposed to strongly corrosive sodium polysulfide and molten sulfur, 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, all indicate% by weight), Cr: 25 to 4
0%, Mo: 1 to 3.5%, A1: 0.5 to 3.5%,
, And a Fe-Cr alloy having a composition of Fe and inevitable 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 them 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.

Accordingly, the present inventors have studied from the above-mentioned viewpoint 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 Na1S battery was replaced with Cr: 2
0 to 35%, Fe: 10 to 30%, Mo and / or W: 1 to 10%, Mn: 0.2 to 2%, and if necessary, (a) Cu: 0.5 ~ 5%, (b) C
o: 1 to 5%, (c) Nb and / or Ta: 0.5
-3%, one or more of the above-mentioned (a)-(c), and the remainder is composed of a Ni-based alloy having a composition of Ni (but 35% or more) and unavoidable impurities. The Ni-based alloy cathode material has high strength and excellent N-resistance.
a · S corrosive, so even if it is thinned, Na
Research results have shown that a sufficiently satisfactory performance can be exhibited over a long period of time in practical application to a -S battery.

[0007]

The Ni-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 Ni-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 used. 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 Ni-based alloy. Thereby, Na-S resistance
The corrosion resistance of the positive electrode container can be improved by disposing a corrosive Ni-based alloy in the inner layer portion in contact with sodium polysulfide and molten sulfur, and a material having corrosion resistance to sodium polysulfide and molten sulfur is disposed in the outer layer portion. 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 Ni-based alloy is used only for the inner layer, 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 Ni on the surface of the outer layer member.
It can also be formed by spraying a base alloy. In this case, expensive Ni 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 Ni-based alloy contains 20 to 35% of Cr, 10 to 30% of Fe, 1 to 10% of Mo and / or W, and 0.2 to 2 of Mn.
(A) Cu: 0.5 to 5%, (b) Co: 1 to 5%, (c) Nb and / or Ta :: 0.5 to 3% A Ni-based alloy containing at least one of the above (a) to (c), and the remainder having a composition of Ni (including 35% or more) and unavoidable impurities .

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

(A) Cr The Cr component has a function of improving the Na / S corrosion resistance by forming a solid solution in the base material. If the content is less than 20%, a desired effect of improving the above function can be obtained. But the content is 3
If it exceeds 5%, the rolling workability and the weldability will deteriorate (in each case, cracks will occur), so that the content is 20 to 35%, preferably 2%.
5-30% was determined.

(B) Fe The Fe component has a function of improving the rolling workability by forming a solid solution in the base material, but if its content is less than 10%, a desired improvement effect cannot be obtained in the above function. If the content exceeds 30%, the Na · S corrosion resistance and strength decrease, so the content is set to 10 to 30%, preferably 15 to 20%.

(C) Mo and W Each of these components has a function of improving the strength and Na.S corrosion resistance by forming a solid solution in the base material. If the desired improvement effect cannot be obtained, and if the content exceeds 10%, rolling workability and weldability are reduced, so that the content is 1 to 10%, preferably 4 to 9%. It was decided.

(D) 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 1 to 2%.
%.

(E) Cu The Cu component has a function of dissolving solidly in the base material to further improve the Na · S corrosion resistance. Therefore, the Cu component is contained as necessary. If the content is less than 5%, a desired improvement effect cannot be obtained, while if the content exceeds 5%, a low-melting point compound is formed, so that the rolling processability and the weldability are reduced. Therefore, the content was determined to be 0.5 to 5%, preferably 1 to 3%.

(F) Co Since the Co component has a function of further improving the strength by forming a solid solution in the base material, it is contained as necessary. If the content is less than 1%, the desired strength improving effect is obtained. On the other hand, if the content exceeds 5%, no further improvement effect is obtained, so the content is set to 1 to 5%, preferably 2 to 5%.

(G) Nb and Ta These components have an action of bonding with Ni to form an intermetallic compound and thus further improving the strength. Therefore, these components are contained as necessary. Is less than 0.5%, the desired strength-improving effect cannot be obtained, while the content is 3%.
%, The rolling workability and the weldability deteriorate, so the content is set to 0.5 to 3%, preferably 0.5 to 2.5%.

(H) Ni The Ni component is an indispensable component for ensuring high strength and excellent Na.S corrosion resistance. Therefore, if its content is less than 35%, the desired high strength and Na.S. Since S corrosion was not obtained, the content was determined to be 35% or more.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a positive electrode container material according to an embodiment of the present invention and a method for manufacturing 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. As raw material, Fe-Cr alloy (containing 66% Cr), metal Cr, pure iron, metal Mo, metal W, metal Mn, oxygen-free copper, metal C
Using o, metal Nb, metal Ta, and electrolytic Ni, these raw materials were blended in a predetermined ratio, and this was melted in a high-frequency induction melting furnace using Si and A1 as deoxidizers, and each of Tables 1 to 3 was used. A molten metal having the component composition shown in No. 4 was prepared, and the molten metal was further deoxidized by 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% Al, and 0.01-0.06% Mg).
The ingot was homogenized at 1200 ° C. for 10 hours, and then hot-rolled at a temperature of 1100 to 1200 ° C. to obtain a hot-rolled sheet having a thickness of 3 mm. By applying a cold rolled sheet having a thickness of 0.5 mm, plate materials 1 to 43 used for the positive electrode container material of the present invention, comparative positive electrode container materials 1 to 4, and a conventional positive electrode container material were manufactured.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

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 the Na / S corrosion resistance of the test piece, a tube tester and a TlG welding machine were used. A positive electrode container of a Na1S battery having a size of diameter: 65 mm × length: 400 mm was formed.

The tensile test was carried out at 350 ° C. to measure the tensile strength. The above-mentioned positive electrode container was incorporated into a Na1S battery, and the operating temperature was 350 ° C. and the charging current density was 20.
0 mA / cm 2, discharge current density: 270 mA / cm ² ,
The number of continuous charge / discharge cycles: An actual machine test was performed under acceleration conditions of 150 cycles, and the maximum erosion depth on the inner surface of the positive electrode container was measured. Tables 5 and 6 show the results of these measurements.

[0033]

[Table 5]

[0034]

[Table 6]

As shown in FIG. 1, the above-mentioned plate members 1 to 43 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 FIG. 2 and FIG.
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 plate materials 1 to 43 are pressed into a die, a drawing process is performed so that the inner diameter and the outer diameter become a material 52 having predetermined dimensions. Apply. Thereby, the adhesion between the plate members 1 to 43 and the cylindrical body 50 is enhanced, and a positive electrode material integrally formed with each other is manufactured. If nickel plating is applied to the inner surface of the cylinder 50, the adhesion between the plate members 1 to 43 and the cylinder 50 is improved, and the cylinder 50 is more 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, and the plate materials 1 to 43 penetrate into these cracks, and the plate materials 1 to 43 and the cylindrical 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 in contact with sodium polysulfide or molten sulfur, a film of an immobile body is formed, and the 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 material 52 is cut into a predetermined length, a bottom plate 55 made of a Ni-based alloy is inserted into one opening, and the bottom plate 55 and the 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 Ni-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 film of an immobile body is formed and the aluminum cannot function as a battery. Since the inner layer portion 54 made of the base alloy is provided, the film of the immovable body 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 Ni-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 Ni-based alloy used can be saved, and the manufacturing cost can be further reduced.

[0045]

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 improved by disposing a Ni-base alloy having Na.S corrosion resistance in the inner layer portion 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 Ni-based alloy is used only for the inner layer, 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 Ni 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 at the same material portion of the inner portion and the bottom plate member, so that 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 to 43 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)

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) C22C 19/05 C23C 4/08 H01M 2/02 H01M 10/39

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: Ri Do from Ni-based alloy, the Ni-based alloy, in weight%, Cr: 20~35%, Fe : 10~30%, Mo and / or W: 1~10%, Mn: 0.2-2
%, And the remainder is inevitable with Ni (containing 35% or more)
A positive electrode container material for a sodium-sulfur battery , comprising a Ni-based alloy having a composition of 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 Ni-based alloy, and the Ni-based alloy is 20 to 35% by weight of Cr, 10 to 30% of Fe, Mo and / or W: 1 to 1% by weight. 10%, Mn: 0 to 2-2
%, And Cu: 0.5 to 5%, or Co: 1 to 5%, or N
b and / or Ta: 0.5 to 3%, and the remainder is composed of a Ni-based alloy having a composition of Ni (including 35% or more) and unavoidable impurities. sodium you wherein - sulfur battery of the positive electrode container material. And wherein the outer layer portion and inner layer portion, characterized in that it is integrated with the cladding according to claim 1 or 2
A positive electrode container material for a sodium-sulfur battery described in 1. 4. The method according to claim 1, wherein the inner layer portion has N
sodium according to claim 1 or 2, characterized in that it is formed by spraying a i based alloy - sulfur battery of the positive electrode container material. 5. A sodium according to any one of claims 1 to 4, characterized in that the outer layer portion is made of aluminum or an aluminum alloy - sulfur battery of the positive electrode container material. 6. A positive electrode container for a sodium-sulfur battery, comprising: a cylindrical side wall member; and a bottom plate member disposed and fixed at an opening of the side wall member so as to cover the opening, wherein the side wall member is It is formed by the positive electrode container material according to any one of claims 1 to 3 and 5, the bottom plate member is formed by the same material as the inner member, these welding at the boundary between the sidewall member and the bottom plate member A positive electrode container for a sodium-sulfur battery, which is integrated.