JPH08148182A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE: To provide an inexpensive and highly reliable sodium-sulfur battery by simplifying a structure and preventing the occurrence of a shortcircuit between electrodes through the absorption of displacement resulting from a thermal expansion and shrinkage difference between a solid electrolyte and an electrode vessel via plastic deformation. CONSTITUTION: This battery is equipped with a negative electrode vessel 8 having a negative electrode flange 3 and sealing sodium 7, a solid electrolyte 4 having an insulation ring 2 jointed with glass or the like and sealing the sodium 7 as well as the vessel 8, and a positive electrode vessel 6 having a positive electrode flange 1 and sealing sulfur 5 as well as the electrolyte 4. The vessel 8 is laid at an inner position and the vessel 6 at an outer position via the electrolyte 4, and the flange 3 and the ring 2 are jointed to each other via a negative electrode joint 10. In addition, the flange 1 and the ring 2 are jointed to each other via a positive electrode joint 9, and the vessels 8 and 6 are insulated from each other. Also, a plastic deformation absorbing section has a stepped structure formed out of a low rigidity flange section 1a, a vertical flange section 1c and a high rigidity flange section 1b, and is provided on the flange 1.

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 having a displacement absorbing portion for absorbing a displacement due to a difference in thermal expansion and contraction between a solid electrolyte and an electrode container, and particularly to a sodium-sulfur battery having a displacement absorbing portion on a flange. Regarding sulfur batteries.

[0002]

2. Description of the Related Art FIG. 8 shows an example in which displacement absorption sites are provided as independent absorption sites, and a conventional technique for absorbing displacement due to a difference in thermal expansion and contraction between a solid electrolyte and an electrode container will be described.

An insulating ring 2 is bonded to a solid electrolyte 4 made of ceramics having sodium ion conductivity via glass or the like, and a positive electrode flange 1 and a negative electrode flange 3 are bonded to the insulating ring 2 by thermocompression bonding. A negative electrode container 8 and sodium 7 which is a negative electrode active material are enclosed inside the solid electrolyte 4, and a solid electrolyte 4 and sulfur 5 which is a positive electrode active material are enclosed inside a positive electrode container 6 made of metal. And a sodium-sulfur battery is constructed.

By the way, in the temperature-decreasing operation process of a sodium-sulfur battery, when the temperature drops from about 350 ° C. to about 120 ° C. and further to room temperature, sulfur 5 solidifies. The solid electrolyte 4 and the positive electrode container 6 are constrained by the solidified sulfur 5, and the thermal contraction displacement δ (hereinafter referred to as thermal displacement) due to the difference in the linear expansion coefficient between the solid electrolyte 4 and the positive electrode container 6 is a positive electrode joint portion. 9 occurs.

Since the coefficient of thermal expansion of the positive electrode container 6 made of metal is generally larger than that of the solid electrolyte 4 made of ceramics, the thermal displacement due to contraction is as shown in FIG. It occurs in the downward direction. This thermal displacement causes the positive electrode flange 1 to be deformed, and the rigidity of the positive electrode flange 1 causes a tensile load P that pulls the joining portion 9 of the positive electrode downward. When the tensile load P exceeds the peel strength Pc of the positive electrode joint portion 9, peeling occurs. The relationship between this temperature change and the tensile load P is shown in FIG. The figure shows the change in the tensile load P when the temperature is lowered from about 350 ° C. to room temperature, and shows the case where there is no displacement absorption site and the tensile load P exceeds the peel strength Pc.

Therefore, in the conventional sodium-sulfur battery,
A displacement absorbing portion 11 is provided which absorbs thermal displacement by elastic deformation so as not to exceed Pc and reduces the tensile load P.

[0007]

In the above-mentioned prior art, the displacement absorbing portion 11 is a separate and independent absorbing portion so as to secure low rigidity and absorb thermal displacement by elastic deformation. It has a complicated bellows structure welded to a flange as shown in FIG. In addition, the structure is such that the difference between the inner and outer diameters is widened to secure low rigidity, and the upper space of the insulating ring 2 is overhanged for a long time. As a result, the gap between the positive electrode flange 1 or the displacement absorbing portion 11 and the negative electrode flange 3 becomes narrow, and there is a possibility that both electrodes may come into contact with each other when they are deformed, resulting in a short circuit.

Therefore, an object of the present invention is to provide a low-cost and highly reliable sodium-sulfur battery by simplifying the structure of the displacement absorbing portion and widening the gap between the positive electrode and the negative electrode to prevent a short circuit.

[0009]

The above object is to provide a negative electrode container, a solid electrolyte containing the negative electrode container and sodium and having sodium ion conductivity, and a positive electrode container containing the solid electrolyte and sulfur. In the sodium-sulfur battery including a solid electrolyte, an insulating ring for insulatingly joining the negative electrode container and the positive electrode container, between the insulating ring and either one of the positive electrode container and the negative electrode container, either one of This is achieved by providing a plastic deformation absorbing portion that absorbs the displacement due to the difference in thermal expansion and contraction between the electrode container and the solid electrolyte by plastic deformation.

Specifically, for example, the positive electrode container has a positive electrode flange and is insulated and joined to the insulating ring via the positive electrode flange, and the plastic deformation absorbing portion is provided on the positive electrode flange.

[0011]

With the above structure, since the plastic deformation absorbing portion absorbs the thermal displacement by the plastic deformation of the positive electrode flange itself, the structure of the displacement absorbing portion is simplified as compared with the conventional structure in which the elastic deformation absorbs the positive displacement. Since the gap with the negative electrode flange can be wide, short circuit can be prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a half sectional view showing the structure of a sodium-sulfur battery according to an embodiment of the present invention. Figure 2
FIG. 3 is a partially enlarged cross-sectional view of FIG. 1, showing a plastic deformation absorbing portion of one embodiment. FIG. 2 is also a cross-sectional view showing a plastic deformation absorbing portion of one embodiment when it is provided on the positive electrode flange. The configuration will be described with reference to FIGS. 1 and 2 at the same time.

The sodium-sulfur battery of the present embodiment has a negative electrode container 8 having a negative electrode flange 3 and containing sodium 7.
And a solid electrolyte 4 having an insulating ring 2 joined by glass or the like for enclosing sodium 7 and a negative electrode container 8, and a positive electrode container 6 having a positive electrode flange 1 for enclosing sulfur 5 and solid electrolyte 4. And the solid electrolyte 4 is sandwiched therebetween, the negative electrode container 8 is arranged inside, and the positive electrode container 6 is arranged outside.
And the insulating ring 2 are joined at the negative electrode joint portion 10 and the positive electrode flange 1 and the insulating ring 2 are joined at the positive electrode joint portion 9 to insulate the negative electrode container 8 and the positive electrode container 6 from each other.

The plastic deformation absorbing portion provided on the positive electrode flange 1 of this embodiment has a step structure having a step made up of a low-rigidity flange portion 1a, a vertical flange portion 1c and a high-rigidity flange portion 1b. . Then, this stepped structure is plastically deformed in the arrow direction R shown in FIG. 1 to absorb the thermal displacement.

By the way, the conventional deformation absorbing portion has been elastically deformed so that the stress of the deformation absorbing portion becomes a stress within the elastic deformation region to absorb the thermal displacement. Therefore, in order to suppress the stress at the deformation absorbing portion within the elastic deformation region, the conventional deformation absorbing portion has a structure in which the upper space of the insulating ring 2 is overhanged largely and largely as shown in FIG. On the other hand, the stepped structure of the plastic deformation absorbing portion according to the present invention uses the stress in the plastic deformation region, and therefore does not need to have a structure that overhangs long and large as in the conventional case. As a result, the structure of the plastic deformation absorption site is simplified, and
As shown in FIG. 2, a wide gap D is provided between the negative electrode flange 3 and the positive electrode flange 1 (the low rigidity flange portion 1a in the figure), which may cause a short circuit between the negative electrode flange 3 and the positive electrode flange 1. Disappear.

In FIG. 2, a gap G is provided between the outer peripheral surface of the insulating ring 2 and the inner peripheral surface of the vertical flange portion 1c. The gap G is provided so that when the positive electrode flange 1 heated at the hot press contact temperature of 500 to 600 ° C. during the manufacturing process is cooled to room temperature and is collapsed inward due to the difference in thermal contraction with the insulating ring 2, the positive electrode flange 1 is bent. This is to generate the moment M. This bending moment M
Is the compressive load Q in the direction opposite to the peeling direction on the joining portion 9 of the positive electrode.
Is added, there is an effect of helping to prevent the peeling of the bonding portion 9 of the positive electrode. If there is no gap G, the positive electrode flange 1 is prevented from collapsing and the compressive load Q is not generated, so that the above effect cannot be obtained.

FIG. 3 is a diagram showing a stress analysis result "No. 1" of the positive electrode flange 1 of the embodiment shown in FIG. 1 by the finite element method. 4 shows the relationship between the tensile load P applied to the positive electrode container 6, the low-rigidity flange stress σ1 of the low-rigidity flange portion 1a, and the high-rigidity flange stress σ2 of the high-rigidity flange portion 1b. From the analysis result of FIG. 3, when the tensile load P of 6 (kN) is applied, the low rigidity flange stress σ1
Was 1.5 times the yield stress σy of the material of the positive electrode flange 1, and it was found that the low-rigidity flange portion 1a was plastically deformed in all sections.

FIG. 4 is a diagram showing a stress analysis result "2" of the positive electrode flange 1 by the finite element method. 3 shows the relationship between the thermal displacement δ of the positive electrode flange 1, the low-rigidity flange stress σ1 and the tensile load P.

As shown in FIG. 4, the thermal displacement δ becomes large,
When the low-rigidity flange stress σ1 also gradually increases and reaches the full-section plastic deformation state of 1.5 times the yield stress σy,
A load of tensile load Pmax = 6 (kN) is generated.
This tensile load Pmax also acts on the positive electrode joint portion 9. Further, even if the thermal displacement is further increased, since the low-rigidity flange portion 1a is plastically deformed in the entire cross section, P
No load of more than max is generated, and no more load acts on the positive electrode joint portion 9. Therefore, this tensile load Pm
ax (kN) is the peeling strength Pc (kN) of the positive electrode joint portion 9.
It can be seen that peeling does not occur if the design is made smaller.

In the present invention, as described above, the structure of the displacement absorbing portion is simplified by the method of absorbing the displacement by the plastic deformation of the positive electrode flange 1. Thereby, the positive flange 1
A wide space is provided between the negative electrode flange 3 and the negative electrode flange 3 to prevent a short circuit.

In general, the designed battery life of the sodium-sulfur battery of this system is about 10 years, and the heating / cooling operation endurance cycle during this period is about 60 times.
If steel is used as the material of the positive electrode flange 1, the allowable number of repeated fatigue strengths in the case of plastic deformation is about 10,000, whereas the cyclic fatigue strength is sufficient. I can say no.

FIG. 5 is a sectional view showing a plastic deformation absorbing portion of another embodiment when it is provided on the positive electrode flange.

The plastic deformation absorbing portion provided on the positive electrode flange 1 of this embodiment has a stepped structure composed of a high-rigidity flange portion 1b, a vertical flange portion 1c, and a low-rigidity flange portion 1a. On the contrary, is a stepped structure that is provided downward so as to be separated from the insulating ring 2. Then, the thermal displacement is absorbed by the plastic deformation of the stepped structure. Further, in the case of the present embodiment, the gap between the positive electrode flange 1 and the negative electrode flange 3 can be made wider than that of the stepped structure of FIG. 1, and there is an effect that it is more excellent in prevention of short circuit.

FIG. 6 is a sectional view showing a plastic deformation absorbing portion of another embodiment provided on the positive electrode flange.

The plastic deformation absorbing portion provided on the positive electrode flange 1 of the present embodiment has a stepped structure having a thin low rigidity flange portion 1d in which the outer peripheral portion of the positive electrode flange 1 is partially thinned. The thermal displacement is absorbed by the plastic deformation of the thin low rigidity flange portion 1d. Similar to the embodiment of FIG. 5, in the case of this embodiment, the distance between the positive electrode flange 1 and the negative electrode flange 3 is wide, and it is suitable for preventing a short circuit.

FIG. 7 is a partial sectional view showing a plastic deformation absorbing portion of another embodiment. It is also sectional drawing which shows the plastic deformation absorption site | part of one Example at the time of being provided in a negative electrode flange.
In the plastic deformation absorbing portion provided on the negative electrode flange 3 of this embodiment, a step made up of a low-rigidity flange portion 3a, a vertical flange portion 3c, and a high-rigidity flange portion 3b is directed upward with respect to the insulating ring 2. It is structured. The step structure in this case absorbs thermal displacement due to expansion.

By the way, the sodium-sulfur battery having a structure having a flange is used in the above embodiment, but there is a battery having a structure in which the positive electrode flange 1 and the positive electrode container 6 are integrated. In this case, not the flange but the positive electrode container. 6 itself is provided with a plastic deformation absorbing portion.

[0028]

According to the present invention, the structure of the deformation absorbing portion is simplified and the short circuit between the positive electrode flange and the negative electrode flange (short circuit between the electrodes) is prevented, so that the sodium is inexpensive and highly reliable. There is an effect that a sulfur battery can be obtained.

[Brief description of drawings]

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

FIG. 2 is a partially enlarged cross-sectional view of FIG. 1, showing a plastic deformation absorbing portion of an embodiment.

FIG. 3 is a diagram showing a stress analysis result “No. 1” of the positive electrode flange 1 of the embodiment shown in FIG. 1 by the finite element method.

FIG. 4 is a diagram showing a stress analysis result “No. 2” of the positive electrode flange 1 by the finite element method.

FIG. 5 is a sectional view showing a plastic deformation absorbing portion of another embodiment when it is provided on the positive electrode flange.

FIG. 6 is a sectional view showing a plastic deformation absorbing portion of another embodiment when it is provided on the positive electrode flange.

FIG. 7 is a sectional view showing a plastic deformation absorbing portion of another embodiment.

FIG. 8 is a diagram showing a conventional example in which displacement absorption parts are separately provided as independent absorption parts.

FIG. 9 is a diagram showing a relationship between temperature change and tensile load P.

[Explanation of symbols]

1 ... Positive electrode flange, 1a, 3a ... Low rigidity flange portion, 1
b, 3b ... High-rigidity flange portion, 1c, 3c ... Vertical flange portion, 1d ... Thin-walled low-rigidity flange portion, 2 ... Insulation ring,
3 ... Negative electrode flange, 4 ... Solid electrolyte, 5 ... Sulfur, 6 ... Positive electrode container, 7 ... Sodium, 8 ... Negative electrode container, 9 ... Positive electrode joint part, 10 ... Negative electrode joint part, 11 ... Displacement absorption site | part.

Claims (5)

[Claims] 1. A negative electrode container, and a solid electrolyte having a sodium ion conductivity by enclosing the negative electrode container and sodium therein.
In a sodium-sulfur battery including a positive electrode container for enclosing the solid electrolyte and sulfur, and an insulating ring for insulatingly joining the solid electrolyte, the negative electrode container and the positive electrode container, the insulating ring and the positive electrode container or Between any one of the electrode containers of the negative electrode container, a plastic deformation absorption portion for absorbing the displacement due to the difference in thermal expansion and contraction between the one of the electrode containers and the solid electrolyte by plastic deformation is provided. Sodium-sulfur battery. 2. The positive electrode container according to claim 1, wherein the positive electrode container has a positive electrode flange and is insulated and joined to the insulating ring through the positive electrode flange, and the plastic deformation absorbing portion is provided on the positive electrode flange. Sodium-sulfur battery. 3. The load Pmax according to claim 1 or 2, wherein the plastic deformation absorbing portion is plastically deformed in full section,
A sodium-sulfur battery characterized by having a peel strength Pc of a joint portion with the insulating ring or less. 4. The sodium-sulfur battery according to claim 2, wherein the plastic deformation absorbing portion is a step having a partially thinned outer peripheral portion of the positive electrode flange. 5. Displacement absorption of a sodium-sulfur battery for absorbing a displacement due to a difference in thermal expansion and contraction generated between both the solid electrolyte and the electrode container, which are jointly restrained via an insulating ring, by providing a displacement absorbing portion. The method for absorbing displacement of a sodium-sulfur battery, wherein the displacement absorbing portion absorbs the displacement by plastic deformation.