JP2000058109A - Bonding structure between an insulating ring and an anode cylindrical metal fitting in a sodium-sulfur battery - Google Patents

Abstract

(57) [Problem] To improve the strength reliability of a joint portion between an insulating ring and an anode cylindrical metal fitting against a load generated due to a difference in thermal shrinkage between a solid electrolyte tube and an anode container when a battery temperature falls. SOLUTION: An insulating ring 4 is provided at an open end of a solid electrolyte tube 5.
An anode cylindrical metal fitting 13 having a cylindrical portion 13a and a flange portion 13b projecting from the lower end of the cylindrical portion 13a toward the inside of the cylindrical portion 13a is attached to the insulating ring 4, and the upper surface of the flange portion 13b is Is a joining structure of the insulating ring 4 of the sodium-sulfur battery and the anode cylindrical fitting 13 which are joined by heat and pressure so as to be joined to the lower end surface of the anode. The cylindrical portion 13a of the anode tubular fitting 13, the cylindrical portion wall thickness upper and lower portions of 13a has a different stepped shape, the thickness of the lower portion relative to the thickness t ₁ of the upper portion t ₂ Is formed to be thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining structure of an insulating ring and an anode cylindrical metal fitting in a sodium-sulfur battery, and more particularly, to a load caused by a difference in thermal contraction between a solid electrolyte tube and an anode container when the temperature of the battery drops. Also, the present invention relates to a joining structure capable of improving the strength reliability of a joining portion between an insulating ring and an anode cylindrical metal fitting.

[0002]

2. Description of the Related Art A sodium-sulfur battery is provided with molten metal sodium as a cathode active material on one side and molten sulfur as an anode active material on the other side, and both have selective permeability to sodium ions. This is a high-temperature secondary battery operated at 300 to 350 ° C. isolated by a β-alumina solid electrolyte.

[0003] The structure of such a sodium-sulfur battery includes, for example, as shown in FIG. 4, a cylindrical anode container 1 containing molten sulfur S impregnated in carbon felt or the like,
A cartridge (sodium protective tube) 6 for containing molten sodium metal sodium, a bottomed cylindrical solid electrolyte tube 5 containing the cartridge 6 therein and having a function of selectively transmitting sodium ions Na ⁺ , In the gap between the solid electrolyte tube 5 and the solid electrolyte tube 5, the cartridge 6 and the solid electrolyte tube 5 are each provided with a bottomed cylindrical partition tube 11 arranged at a predetermined interval from the solid electrolyte tube 5.

The solid electrolyte tube 5 is connected to the anode container 1 via an α-alumina insulating ring 4 and an anode cylindrical metal fitting 3 glass-joined to the open end thereof. A cathode metal fitting 8 is joined to the upper end surface of the insulating ring 4 by heat and pressure, and a cathode lid 9 is fixed to the cathode metal fitting 8 by welding. An anode-side terminal 2 and a cathode-side terminal 10 are provided on the outer peripheral upper portion of the anode container 1 and the upper surface of the cathode lid 9, respectively. In the upper space of the cartridge 6, an inert gas G such as nitrogen gas or argon gas is sealed at a predetermined pressure, and the inert gas G causes sodium Na in the cartridge 6 to pass through a small hole 7 provided at the bottom of the cartridge. Pressurized in the outflow direction.

In the sodium-sulfur battery having such a structure, at the time of discharge, sodium Na supplied from the small hole 7 of the cartridge 6 moves upward in the gap between the partition tube 11 and the cartridge 6, After passing over the upper end, the solid electrolyte tube 5 moves downward in the gap between the partition tube 11 and the solid electrolyte tube 5, and further passes through the solid electrolyte tube 5 as sodium ions, thereby passing through the sulfur S in the anode container 1 and the external circuit. Reacts with passing electrons to produce sodium polysulfide. At the time of charging, a reaction of forming sodium and sulfur occurs in reverse to discharging.

FIG. 5 shows such a conventional sodium-
It is principal part sectional drawing which shows the joining structure of the insulating ring and anode cylindrical fitting in a sulfur battery. The anode tubular metal fitting 3 has a cylindrical portion 3a and a flange portion 3b projecting from the lower end of the cylindrical portion 3a toward the inside of the cylindrical portion 3a. The insulating ring 4 is inserted into the cylindrical portion 3a of the anode tubular metal fitting 3, and the upper surface of the flange portion 3b and the lower end surface of the insulating ring 4 are heat-pressure bonded via a bonding material 12 such as a metal brazing material. ing. The thickness of the cylindrical portion 3a of the anode cylindrical metal fitting 3 is substantially constant.

Meanwhile, in a sodium-sulfur battery, there is a temperature difference between when the battery is operating and when it is stopped. In a low temperature state when the battery is stopped, sodium polysulfide or sulfur solidifies, and the solid electrolyte tube 5 and the anode container 1 Will be mutually bound. When the temperature of the battery is lowered, both the solid electrolyte tube 5 and the anode container 1 undergo thermal contraction, but the thermal contraction of the metal anode container 1 is large, and the contraction of the anode container 1 is suppressed by the solid electrolyte tube 5 having small thermal contraction. Therefore, a downward load acts on the joint between the insulating ring 4 connecting the solid electrolyte tube 5 and the anode container 1 to the anode cylindrical metal fitting 3 (in the direction of the arrow in FIG. 5).

Therefore, conventionally, in order to prevent the joint portion between the insulating ring 4 and the anode cylindrical metal fitting 3 from being damaged due to this load, a part of the peripheral surface of the anode container 1 is shrunk in the axial direction. Measures such as forming a constriction in the plane direction to give a spring effect and reduce the load have been taken.

[0009]

However, even when the above-described countermeasures are taken, if the strength of the joint between the insulating ring 4 and the anode cylindrical metal fitting 3 is weak, the insulating ring 4 may be damaged. Breakage or shear breakage of the anode cylindrical fitting 3 may occur, and this problem has become more prominent as the size of the sodium-sulfur battery has increased.

The present invention has been made in view of such a situation, and an object thereof is to provide an insulating ring and an insulating ring for a load caused by a difference in thermal shrinkage between a solid electrolyte tube and an anode container when a battery temperature drops. It is an object of the present invention to provide a joint structure capable of improving the strength reliability of a joint with an anode cylindrical metal fitting and preventing damage to the joint.

[0011]

According to the present invention, an insulating ring is joined to an open end of a solid electrolyte tube, and the insulating ring projects from a cylindrical portion and a lower end of the cylindrical portion toward the inside of the cylindrical portion. An anode cylindrical fitting having a flange portion,
In the joint structure of the insulating ring of the sodium-sulfur battery and the anode tubular metal fitting which are hot-pressed so that the upper surface of the flange portion is joined to the lower end surface of the insulating ring, the cylindrical part of the anode tubular metal fitting is A sodium having a stepped shape in which the upper portion and the lower portion of the cylindrical portion have different wall thicknesses, and wherein the lower portion has a smaller thickness than the upper portion. -A joining structure of an insulating ring and an anode cylindrical metal fitting in a sulfur battery is provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the joint structure of the insulating ring and the anode cylindrical metal fitting in the sodium-sulfur battery of the present invention, as shown in the sectional view of the main part of FIG.
The cylindrical portion 13a of the anode tubular fitting 13, and has a thickness different stepped shape and its upper and lower portions, the wall thickness t ₂ of the lower portion relative to the thickness t ₁ of the upper portion is thin It is formed so that it becomes.

[0013] By thus forming the cylindrical portion 13a of the anode cylindrical metal fitting 13 into a stepped shape, the joining structure of the present invention has an anode cylindrical shape as shown in FIG. Higher bonding strength than conventional bonding structures using metal fittings. Although the reason for this is not clear, it is considered that the provision of the thin portion improves the holding force from the side of the joining jig during joining and reduces the shearing force to the flange portion.

In the joint structure of the present invention, the cylindrical portion 1
3a thickness t ₂ and a lower portion formed in a thin, by changing the height h, measured from the flange portion 13b lower surface of the lower portion, it is possible to control the bonding strength. Specifically, the wall thickness t ₂ of the lower part, preferably in terms of bonding strength to a 1-3 fold thickness t ₃ of the flange portion 13b, more preferably to 1 to 2 times, It is even more preferable that the ratio be 1 to 1.5 times. In addition, the height h measured from the lower surface of the lower portion of the flange portion 13b is preferably 20 to 80% of the height H of the anode cylindrical fitting from the viewpoint of bonding strength, and more preferably 20 to 40%. More preferably, it is still more preferably 20 to 30%.

Further, it is preferable to form a taper 14 or R at a corner of the insulating ring 4 as shown in FIG.
Thereby, the insulating ring 4 can be made harder to break. However, if the taper 14 or R is excessively large, the gap 15 becomes large, the joint area between the insulating ring 4 and the anode cylindrical metal 13 decreases, and the strength reliability of the joint decreases.

The joining structure of the present invention is the same as the above-described conventional joining structure, except that the cylindrical portion 13a of the anode tubular metal fitting 13 has a stepped shape as described above. That is, as in the conventional case, the insulating ring 4 is attached to the anode cylindrical metal fitting 1.
3 and the upper surface of the flange portion 13b of the anode cylindrical metal fitting 13 and the lower end surface of the insulating ring 4 are joined by a heat and pressure through a joining material 12 such as a metal brazing material.

Meanwhile, in the joining structure of the present invention, the joining strength between the anode tubular fitting 13 and the insulating ring 4 is improved by forming the cylindrical portion 13 a of the anode tubular fitting 13 into a stepped shape as described above. However, when a heat cycle caused by a temperature difference between when the sodium-sulfur battery operates and when the sodium-sulfur battery is stopped is applied, stress is applied to the corner 16 of the step-shaped portion that transitions from the thin portion to the thick portion of the cylindrical portion 13a. Concentrated
Cracks tend to occur in the corners 16. Then, when a heat cycle is applied for a long time, cracks grow,
The anode cylindrical fitting 13 may be broken. In addition, it is assumed that the stress due to this heat cycle is further increased as the size of the battery increases.

Therefore, in order to solve such a problem, it is preferable to implement the following measures in the present invention. First, as a first countermeasure, the height h measured from the lower surface of the flange portion 13b of the thinly formed lower portion of the cylindrical portion 13a is equal to 10 mm of the outer diameter of the sodium-sulfur battery.
% Or more. That is,
With the increase in size of the sodium-sulfur battery, the height h of the thinner lower portion of the cylindrical portion 13a with respect to the outer diameter thereof
Is relatively large, the amount of distortion generated in the anode cylindrical fitting 13 during the heat cycle load is reduced,
The generation and propagation of cracks from the corners 16 are suppressed.

The second measure is, as shown in FIG.
The angle .theta. Of the corner 16 of the step-shaped portion 3a which transitions from the thinner lower portion 3a to the thicker upper portion 3a is an obtuse angle. By making the corners 16 obtuse in this manner, the concentration of stress on the corners 16 is alleviated, and the generation and propagation of cracks due to the heat cycle load are suppressed. In this measure, the angle θ of the corner 16
Is preferably 150 ° or more.

As a third measure, as shown in FIG.
An R is formed at the corner 16 of the step-shaped portion 3a that transitions from the thinner lower portion to the thicker upper portion 3a. By forming the R in the corner 16 in this manner, the concentration of the stress on the corner 16 is reduced, and the generation and propagation of cracks due to the heat cycle load are suppressed. In this measure, the value of the radius of curvature R of the corner 16 is preferably 1 mm or more. In addition, these first
Each of the measures (3) to (3) may be performed independently, but a higher effect can be obtained by performing two or more measures in combination.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0022] (Example 1) anode tubular fitting 13 that the thickness t ₂ of the thin which is formed in the lower portion of the cylindrical portion 13a is set to 0.8~4mm as shown in Table 1 shown in FIG. 1 produced And
These were used for thermo-compression bonding with the insulating ring 4 to produce test pieces. The thickness t ₃ of the flange portion 13b of the test piece after the bonding was 1 mm. In addition, the height h measured from the lower surface of the flange portion 13b of the thinly formed lower portion of the cylindrical portion 13a is all 20% of the height H of the anode cylindrical metal fitting 13.
And

As shown in FIG. 6, a load is applied to each of the test pieces manufactured as described above from above the anode cylindrical metal fitting 13 via the pressing jig 20, and the receiving jig 21 is provided below the insulating ring 4. While receiving the load, the breaking strength of the joint between the anode cylindrical fitting 13 and the insulating ring 4 was measured. The results are shown in Table 1 and FIG.

[0024]

[Table 1]

As shown in Table 1 and FIG. 7, the breaking strength decreases as the thickness t ₂ of the lower part of the cylindrical part of the anode cylindrical metal fitting increases, and the lower part of the cylindrical part is thinned to a certain extent. It was found that high bonding strength can be obtained by forming the first and second layers.

(Embodiment 2) Anode cylindrical fitting 13 shown in FIG.
Has a height H of 25 mm, and a height h measured from the lower surface of the flange portion 13b of the thin lower portion of the cylindrical portion 13a.
Were prepared as shown in Table 2 to form an anode tubular metal fitting 13 having a thickness of 0 to 25 mm, and using them, heat-pressure bonded to the insulating ring 4 to produce a test piece. Incidentally, the thickness t ₂ of the thin which is formed in the lower portion of the cylindrical portion 13a is set to 1.5 times the thickness t ₃ of all flange portion 13b.

As shown in FIG. 6, a load is applied to each of the test pieces manufactured as described above from above the anode cylindrical metal fitting 13 via the pressing jig 20, and the receiving jig 21 is provided below the insulating ring 4. While receiving the load, the breaking strength of the joint between the anode cylindrical fitting 13 and the insulating ring 4 was measured. The results are shown in Table 2 and FIG.

[0028]

[Table 2]

As shown in Table 2 and FIG. 8, the breaking strength decreases as the height h measured from the lower surface of the flange portion 13b of the thinly formed lower portion of the cylindrical portion 13a increases, and the height h It was found that the joint strength could be controlled by changing the value of.

(Embodiment 3) Side view of FIG. 9A and FIG.
As shown in the cross-sectional view of (b), the same material as the anode cylindrical fitting, the width d is 10 mm, the length L is 25 mm, and the cross-section in the thickness direction has the same cross-sectional shape as the anode cylindrical fitting. The thickness t _{2 of the} thinner lower portion is 1.5 mm, the height h of the lower portion, the angle θ of the corner 16 of the stepped portion, and the same angle 1
A test piece 22 was prepared in which the curvature radius R of No. 6 was variously changed as shown in Table 3.

A fatigue cycle test was performed on each of the test pieces prepared as described above. In this fatigue cycle test, as shown in FIG. 10, the lower end of the thinner lower part of the test piece 22 is fixed at the normal temperature and the upper end of the thicker upper part of the test piece 22 is repeatedly displaced at normal temperature to measure the fracture life of the test piece. In this test, the cycle conditions were repeated 2500 cycles with a displacement width of 1 mm and a cycle speed of 15 cycles / min. Table 3 shows the results.

[0032]

[Table 3]

(Example 4) Sodium having an outer diameter of 90 mm
Assuming a sulfur battery, the height H of the anode cylindrical fitting 13 shown in FIG. 11 is 25 mm, the height h of the thinly formed lower portion of the cylindrical portion 13a, and the angle θ of the corner 16 of the stepped portion. ,
The anode fittings 13 in which the radius of curvature R of the corner portions 16 were variously changed as shown in Table 4 were produced, and the anode fittings 13 were hot-press bonded to the insulating ring 4 using them to produce test pieces. The thickness t ₃ of the flange portion 13b of the test piece after the bonding was 1 mm.

A heat cycle test was performed on each of the test pieces prepared as described above. This heat cycle test is performed at 280 ° C. to 360 ° C. to 280 ° C.
The heat cycle load of 1 ° C. was taken as one cycle, and this was 25
Repeated for 00 cycles. Table 4 shows the test results.

[0035]

[Table 4]

[0036]

As described above, according to the present invention, it is possible to improve the strength reliability of the joint between the insulating ring and the anode tubular metal fitting. The reliability of the sulfur battery can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part showing one embodiment of a joint structure of the present invention.

FIG. 2 is a cross-sectional view showing an example of a measure for suppressing generation and propagation of a crack in a corner of a stepped portion.

FIG. 3 is a cross-sectional view showing another example of a measure for suppressing generation and propagation of a crack in a corner of a stepped portion.

FIG. 4 is a sectional view showing a general structure of a sodium-sulfur battery.

FIG. 5 is a sectional view of a main part showing a conventional joining structure.

FIG. 6 is an explanatory view showing a method for measuring the breaking strength of a joint in an example.

FIG. 7 is a graph showing the results of Example 1.

FIG. 8 is a graph showing the results of Example 2.

FIGS. 9A and 9B are explanatory views showing the shape of a test piece used in Example 3; FIG. 9A is a side view, and FIG.

FIG. 10 is an explanatory diagram showing a test method performed in Example 3.

FIG. 11 is a sectional view showing the shape of a test piece used in Example 4.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode container, 2 ... Anode side terminal, 3 ... Anode cylindrical fitting, 4
... insulating ring, 5 ... solid electrolyte tube, 6 ... cartridge,
7 ... Small hole, 8 ... Cathode fitting, 9 ... Cathode cover, 10 ... Cathode side terminal, 11 ... Partition tube, 12 ... Bonding material, 13 ... Anode cylindrical fitting, 16 ... Corner.

Claims (6)

[Claims] 1. An anode cylindrical metal fitting having an insulating ring joined to an open end of a solid electrolyte tube, and having a cylindrical portion and a flange projecting from a lower end of the cylindrical portion toward an inside of the cylindrical portion. In a joint structure of an insulating ring of a sodium-sulfur battery and an anode tubular metal fitting that are hot-pressed so that the upper surface of the flange portion is joined to the lower end face of the insulating ring, the cylindrical portion of the anode tubular metal fitting is The upper portion and the lower portion of the cylindrical portion have a stepped shape having different thicknesses, and the lower portion has a smaller thickness than the upper portion. The joining structure of the insulating ring and the anode cylindrical fitting in the sodium-sulfur battery. 2. The joining structure according to claim 1, wherein the thickness of the thinner lower portion is 1 to 3 times the thickness of the flange portion. 3. The height measured from the lower surface of the flange portion of the lower part formed as a thin part is 20 to 20 of the height of the anode cylindrical metal fitting.
The joint structure according to claim 1, which is 80%. 4. The joint structure according to claim 1, wherein a height of the thinner lower portion measured from a lower surface of the flange portion is 10% or more of an outer diameter of the sodium-sulfur battery. 5. The joining structure according to claim 1, wherein the angle of the corner of the step-shaped portion that transitions from the thinner lower portion of the cylindrical portion to the thicker upper portion is obtuse. . 6. The joint structure according to claim 1, wherein the corner portion of the stepped portion that transitions from the thinner lower portion of the cylindrical portion to the thicker upper portion is formed with R.