JP3351186B2 - Sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the durability of a joint portion and a weld portion of a sodium-sulfur battery used for power storage, power peak cut, and battery for electric vehicle.

[0002]

2. Description of the Related Art The following materials are disclosed as materials for a positive electrode flange and a positive electrode container of a conventional sodium-sulfur battery as corrosion-resistant materials against sulfur or sodium polysulfide as a battery active material.

[0003] 1. JP-A-57-57861: Cr, Mo, Al, Fe (Bal) alloy JP-A-56-130071: Cr, Fe (Bal) alloy JP-A-58-152377: Cr, Fe (Bal) alloy JP-A-59-165378: Cr, Al, Y, Fe (Bal) alloy

[0004]

The material shown in the prior art has a thermal expansion (7 × 10 ⁻⁶ / ° C.) of about 18 × 10 ^{−6 for} the insulating ring.
Since it is as large as × 10 ⁻⁶ / ° C., a large residual thermal stress is generated at the joint between the insulating ring and the flange, and there is a problem that the durability of the joint with respect to temperature rise and fall is low.

In order to avoid this problem, there has been a problem that when a material having a small thermal expansion such as carbon steel or a material obtained by subjecting carbon steel to corrosion treatment is used for the flange, the corrosion resistance of the welded portion is reduced.

[0006]

SUMMARY OF THE INVENTION Corrosion resistance to sulfur and sodium polysulfide and a thermal expansion of about 13.times.10
The ^-6 / ° C. and less two-phase stainless steel, the use as a positive electrode flange and positive container material, the corrosion resistance of the welded portion of the two can also be maintained to the same extent as the welded portion. In addition, it has good weldability with the duplex stainless steel of the positive electrode flange material, and has corrosion resistance to sulfur and sodium polysulfide. Fe-based component of 18 to 28% Cr, 8 to 24% of Ni, and C ≦ 0.2% The same effect can be obtained even if the constituted austenitic steel is used as a positive electrode container.

[0007] As a duplex stainless steel, Fe-based Cr
18% to 28%, Ni 1% to 8%, and C ≦ 0.2% can be used. In addition, duplex stainless steel reduces Mo to 1
It is desirable to contain 〜5%.

[0008]

The insulating ring and the positive electrode flange are joined under pressure at a temperature of 500 to 600 ° C. through aluminum as an insert material. In the cooling process after this pressure bonding,
Residual thermal stress occurs due to the difference in thermal expansion between the insulating ring and the flange. This residual thermal stress damages the insulation ring,
Alternatively, fatigue fracture of the joint interface occurs due to the fluctuation of the residual thermal stress during the temperature raising / lowering operation in the battery operation process.

According to the present invention, the flange has a thermal expansion of about 1
By using a ^duplex stainless steel as small as 3 × 10 ⁻⁶ / ° C., the residual thermal stress can be reduced, and the breakage of the insulating ring and the bond interface can be prevented.

Further, since the positive electrode flange and the positive electrode container are joined by welding, by using the same material as the positive electrode flange and the positive electrode container material, the corrosion resistance of the welded portion can be maintained at the same level as the welded portion. Also, it has good weldability with the duplex stainless steel of the positive electrode flange material, and has corrosion resistance to sulfur and sodium polysulfide. Fe-based Cr 18 to 28%,
Similar effects can be obtained by using an austenitic steel composed of 8 to 24% Ni and C ≦ 0.2% as the positive electrode container.

[0011] The Cr content in the duplex stainless steel is 18
A range of ~ 28% is preferred. Below this range, the corrosion resistance becomes insufficient, and above this range, processing is difficult. Similarly, if the C content exceeds 0.2%, the workability deteriorates, which is not preferable. Further, Ni is appropriate in a range of 1 to 8% in order to maintain a two-phase structure. Although the addition of Mo brings about a further improvement in the corrosion resistance, if it is too much, the workability is inferior.
% Is particularly preferred.

As described above, according to the present invention, the durability of the joint between the insulating ring and the flange and the weld between the positive electrode flange and the positive electrode container can be improved, and a highly practical sodium-sulfur battery can be realized.

[0013]

【Example】

Example 1 A test piece having the structure shown in FIG. 1 was heated in the air from room temperature to an operating temperature of the present battery of 400 ° C.
Cooling from ℃ to room temperature was repeated 1,000 times, but no destruction of the insulating ring and the joint occurred. The required value of the temperature rise and fall is about 100 times.

Here, 1: insulating ring, 2: aluminum insert, 3: positive electrode flange, 4: negative electrode flange,
The aluminum insert 2 and the negative electrode flange 4 are arranged on the upper end surface of the insulating ring 1, and the aluminum insert 2 and the positive electrode flange 3 are arranged on the lower end surface.
Bonded with N.

The positive and negative electrode flange materials used in this embodiment are JIS symbols SUS329J1, SUS329J2L, SUS329J3L,
SUS329J4L.

The chemical components are shown below.

[0017]

[Table 1]

Example 2 A test piece having the structure shown in FIG.
In sodium polysulfide, the temperature was raised from room temperature to 400 ° C. and the cooling from 400 ° C. to room temperature was repeated 200 times, but the insulation ring and the joint were not broken, and the weld was not selectively deteriorated. .

Here, 1: an insulating ring, 2: an aluminum insert, 3: a positive electrode flange, 4: a negative electrode flange, 5: a positive electrode container, wherein an aluminum insert 2 and a negative electrode flange 4 The aluminum insert 2 and the positive electrode flange 3 are arranged on the end face, and the
Joining was performed at 30 ° C. and a pressure of 30 kN. Thereafter, the positive electrode flange 3 and the positive electrode container 5 were TIG-welded.

The positive and negative electrode flange materials used in this embodiment are JIS SUS329J1 and the positive electrode container is JIS SUS329J1, SUS309, SUS309S, SUS310, SUS310S, SU
S304 and SUS304L were used.

The chemical components are shown below.

[0022]

[Table 2]

Example 3 A test piece having the structure shown in FIG.
An immersion test at 400 ° C. for 1,000 hours was performed in sodium polysulfide, but no selective corrosion of the weld occurred.

Here, 6: positive electrode flange TP, 7: positive electrode container TP, 8: TIG welded portion, positive electrode flange TP
6 and the positive electrode container TP7 were TIG-welded.

The material of the positive electrode flange TP used in this embodiment is JIS SUS 329J1 and the material of the positive electrode container TP is J
IS symbol SUS329J1, SUS309, SUS309S, SUS310, SUS31
0S, SUS304, SUS304L.

(Example 4) A sodium-sulfur battery having the structure shown in FIG. 4 was charged and discharged 500 times. However, the battery characteristics (charge / discharge capacity, charge / discharge efficiency) were reduced, and the insulating ring and the joint were not changed. No destruction and selective corrosion of the welds were observed.

Further, the temperature of the sodium-sulfur battery having the structure shown in FIG. 4 was raised and lowered 200 times, but no destruction of the insulating ring and the joint and no selective corrosion of the welded portion occurred.

Here, the sodium-sulfur battery of FIG.
The following procedure was used.

(1) The solid electrolyte tube 9 and the insulating ring 1 are joined by glass solder.

(2) The insulating ring is joined to the aluminum insert 2, the positive electrode flange 3, and the negative electrode flange 4.

(3) Sodium 10 in the solid electrolyte tube
And the negative electrode cap 11 and the negative electrode flange 4 are welded.

(4) The space formed between the outside of the solid electrolyte tube and the positive electrode container 5 is filled with a sulfur mold 12 (carbon mat impregnated with sulfur), and the positive electrode flange 3 and the positive electrode container 5 are welded.

The material of the positive electrode flange and the negative electrode flange used in this example is SUS329J1 of JIS symbol, and the positive electrode container is J
SUS329J1 and SUS310S of IS symbol were used.

In addition to the alloy combinations shown in the fourth embodiment, the alloys shown in the first to third embodiments can be used.
It is apparent from the result of Example 3 that the same result as in Example 4 can be obtained.

[0035]

According to the present invention, the durability of the joint between the insulating ring and the flange and the weld between the positive electrode flange and the positive electrode container can be improved, and a highly practical sodium-sulfur battery can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an air temperature rising / falling test piece according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a temperature raising / lowering test piece in sodium polysulfide as an example of the present invention.

FIG. 3 is an external view of a test piece immersed in sodium polysulfide as an example of the present invention.

FIG. 4 is a longitudinal sectional view of a sodium-sulfur battery according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulation ring, 2 ... Aluminum insert, 3 ... Positive electrode flange, 4 ... Negative electrode flange, 5 ... Positive electrode container, 6 ... Positive electrode flange TP, 7 ... Positive electrode container TP, 8 ... TIG welded part, 9 ...
Solid electrolyte tube, 10: sodium, 11: negative electrode cap, 12: sulfur mold.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-57861 (JP, A) Stainless Steel Association, “Stainless Steel Handbook-Third Edition-”, Nihon Kogyo Shimbun, pp. 632-639 ( 58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 10/39 C22C 38/00 H01M 2/02

Claims (3)

(57) [Claims] 1. A solid electrolyte tube having sodium ion conductivity, an insulating ring joined to the solid electrolyte tube, a negative electrode flange and a positive electrode flange joined to the insulating ring, a negative electrode active material: sodium, and a positive electrode active material: sulfur or a sodium polysulfide, sodium composed of a positive electrode container for storing a sulfur or sodium polysulfide - in sulfur battery, the positive electrode flange of about 13 × thermal expansion coefficient
Formed by 10 ^-6 / ° C. and less two-phase stainless steel, the <br/> positive electrode container, Cr in the two-phase stainless steel or Fe-base
A sodium-sulfur battery characterized by being formed of an austenitic steel composed of 18 to 28%, Ni 1 to 8% and C ≦ 0.2%. 2. The method according to claim 1, wherein the positive electrode flange comprises:
Duplex stainless steel as small as about 13 × 10 ^-6 / ° C. Or 18 to 28% Cr, 1 to 8% Ni,
A sodium-sulfur battery, characterized in that it is an austenitic steel having a composition of ≤0.2%. 3. The sodium-sulfur battery according to claim 2, wherein said two-phase stainless steel contains 1 to 5% of Mo.