JPH02126570A - Sodium-sulphur cell - Google Patents

Abstract

PURPOSE:To improve the charge and discharge property and to make the manufacture easier by coating ceramics particles with a sulphur-withstanding and sodiumpolysulfide-withstanding properties such as alpha-alumina, beta-alumina, or zirconia, and with a specific particle diameter, on the peripheral surface of a solid electrolyte tube, so as to provide a ceramics particle high resistance layer of a specific thickness. CONSTITUTION:On the peripheral surface of a solid electrolyte tube 4, ceramics particles 7 with a sulphur-withstanding and a sodiumpolysulfide-withstanding properties, such as alpha-alumina, beta-alumina, or zirconia, with the particle diameter 10 to 500mum is coated to form a ceramics particle high resistance layer 8 with the thickness about 20 to 1000mum. By coating the ceramics particles 7 in an even thickness on the surface of the solid electrolyte tube or on the inner surface of conductive material M for cathode impregnated with sulphur in such a way, a ceramics particle high resistance layer 8 is formed. As a result, the property control can be carried out easily, and the thickness of the ceramics particle high resistance layer 8 can be reduced within an adequate scope. Consequently, the charge and discharge property can be improved and the manufacture can be made easier.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to sodium-sulfur batteries.

[Prior Art] As shown in FIG. 4 as a conventional sodium-sulfur battery, the upper part of a bottomed cylindrical anode container 1 houses a porous conductive material M impregnated with molten sulfur S, which is an anode active material. For,
An insulating ring 2 made of α-alumina is fixed, a genital container 3 is fixed to the upper part of the insulating ring 2, and the inner peripheral surface of the insulating ring 2 has a function of selectively transmitting sodium ions Na+. There was one in which the upper outer circumferential surface of a bottomed cylindrical solid electrolyte tube 4 made of polycrystalline Bader alumina and extending downward was bonded and fixed. Furthermore, the interior of the battery is divided by the solid electrolyte tube 4 into an anode chamber R1 that accommodates a conductive material M impregnated with molten sulfur S, and a cathode chamber R2 that stores sodium Na.

During discharge, sodium becomes sodium ions Na+ from the cathode chamber R2, passes through the solid electrolyte tube 4, reacts with sulfur S in the anode chamber R1 as follows, and produces sodium polysulfide.

2Na+XS-"Naz Sx Also, during charging, a reaction opposite to that during discharging occurs, and sodium Na and sulfur S are generated.

Therefore, the generation of sulfur during charging occurs at the interface between the anode conductive material M, which is an electron conductor, and the sodium polysulfide Nat Sx. If they are in contact, sulfur will adhere to the surface of the solid electrolyte tube 4. If the surface of the solid electrolyte tube 4 is completely covered with sulfur, the resistance will increase rapidly and it will be impossible to continue charging. Furthermore, if the solid electrolyte tube 4 is locally covered with sulfur, the current will be concentrated in the uncovered portion, leading to destruction of the solid electrolyte tube 4.

In order to solve the above problem, a porous insulator 11 made of ceramic felt or glass fiber is conventionally interposed between the solid electrolyte tube 4 and the anode conductive material M. (Japanese Patent Publication No. 59-10539) Then, during charging, the porous insulator 11 is formed during discharging with sodium polysulfide (Na2).
S3, NazS5> are maintained in a moist state, and Na + ions are always uniformly present near the solid electrolyte tube 4 to prevent local sulfur adhesion to the solid electrolyte tube surface and eliminate damage thereto.

[Problem to be Solved by the Invention] However, in the conventional sodium-sulfur battery, the porous insulator is formed into a thin envelope, and therefore, the porous insulator on the surface of the solid electrolyte tube contains Since the thickness of sodium polysulfide could not be reduced, resistance could not be reduced and charging/discharging efficiency could not be improved. Also, insulator 1
When the thickness of 1 was reduced to about 200 μm, it was very difficult to set it evenly inside the battery, which caused manufacturing problems such as the glass fibers breaking, and furthermore, it was difficult to control the characteristics.

An object of the present invention is to provide a sodium-sulfur battery that can improve charge and discharge characteristics and is easy to manufacture.

[Means for Solving the Problems] In order to achieve the above object, the present invention partitions an anode chamber and a cathode chamber with a solid electrolyte tube, stores molten sulfur or molten sodium polysulfide in the anode chamber, and stores metal in the cathode chamber. In a sodium-sulfur battery containing sodium, the particle size is approximately 10 to 50% relative to the outer peripheral surface of the solid electrolyte tube.
A method is adopted in which ceramic particles having sulfur and sodium polysulfide resistance such as α-alumina, 2β-alumina or zirconia of 0Jim are coated to provide a ceramic particle high resistance layer having a thickness of about 20 to 1000 μm.

[Function] This invention can form a ceramic particle high resistance layer by applying ceramic particles to a uniform thickness on the surface of a solid electrolyte tube or the inner surface of an anode active material impregnated with sulfur.
Easy to manufacture and easy to control performance.

Furthermore, since the thickness of the ceramic particle high resistance layer can be reduced to an appropriate range, battery capacity can be improved.

[Example] Hereinafter, an example embodying a sodium-sulfur battery will be described based on FIGS. 1 to 3.

As shown in FIG. 1.3, the lower surface of an insulating ring 2 made of α-alumina is fixed by thermo-pressure bonding to the upper end of an anode container 1 having the shape of a contracted cylinder with a bottom. Further, a lower end portion of a cathode container 3 having a cylindrical shape with a lid is fixed to the upper surface of the insulating ring 2 by thermopressure bonding. On the inner peripheral surface of the insulating ring 2, the upper end outer peripheral surface of a solid electrolyte tube 4 made of β''-alumina and having the shape of a bottomed bag tube is adhesively fixed with glass or the like.

In an anode chamber R1 formed between the anode container 1 and the solid electrolyte tube 4, a conductive material M for an anode such as a carbon mat impregnated with molten sulfur S as an anode active material is housed. Further, in the cathode chamber R2 formed between the cathode container 3 and the solid electrolyte tube 4, metallic sodium Na is stored as a cathode active material. Note that 5 is an anode terminal, and 6 is a negative terminal.

Next, the gist of the present invention will be explained with reference to FIG.

The outer surface of the solid electrolyte tube 4 has a particle size of 10 to 500.
Ceramic particles 7 to 7 having sulfur resistance and sodium polysulfide resistance such as α-alumina, zirconia, or β-alumina with a thickness of approximately 20 μm without deforming the particle size.
A ceramic particle high resistance layer 8 is formed by applying the ceramic particles to a thickness of 1000 μm.

If the ceramic particle high-resistance layer 8 is too thick, resistance loss during charging and discharging will increase and battery efficiency will decrease; if it is too thin, sulfur will saturate at the boundary during charging and discharging, and charging will end prematurely. At the same time, the above-mentioned range is desirable because thickness unevenness tends to occur in the part of the particle high-resistance layer 8, resulting in non-uniform characteristics. Particularly desirable particle size range is 30-30
It is 0 μm. The reason for this is that if the particle size is too small, the porosity of the high-resistance layer will become small, which will hinder the movement of active materials such as sodium ions, Na+, and if the particle size is too large, it will be difficult to form a layer with a uniform thickness. It is from.

The method for forming the ceramic particle high resistance layer 8 is to apply molten sulfur S or sodium polysulfide Na1Sx to the surface 4a of the solid electrolyte tube 4, and apply ceramic particles 7 to 7 on the surface of the sulfur S or sodium polysulfide NatSx. There is a method of spreading and fixing it. Furthermore, ceramic particles 7 to 7 may be scattered on the inner circumferential surface of the anode conductive material M impregnated with molten sulfur S.

Now, in this invention, a ceramic particle high resistance layer 8 is formed by scattering ceramic particles 7 to 7 to a uniform thickness on the surface 4a of the solid electrolyte tube 4 or the inner surface of the anode conductive material M impregnated with sulfur S. Therefore, manufacturing becomes easy.

In addition, since the thickness of the ceramic particle high-resistance layer 8 can be reduced to an appropriate range, charging and discharging efficiency is improved by reducing battery resistance, and the capacity is also improved by reducing the amount of particles remaining in the porous insulator upon completion of charging. Since the amount of sodium polysulfide can be reduced, the amount of charge increases.

Figure 3 shows the results of experimental measurements of the differences in battery characteristics between the sodium-sulfur battery of the present invention and the conventional example.As is clear from this graph, the internal resistance of the present invention is approximately 10% lower than that of the conventional example. It can also be seen that the charge and discharge capacity is excellent.

[Effects of the Invention] As detailed above, the present invention has the advantage of being able to improve charge and discharge characteristics and to facilitate manufacturing.

[Brief explanation of drawings]

Fig. 1 is a sectional view of only the main parts showing an embodiment of a sodium-sulfur battery embodying the present invention, Fig. 2 is a vertical sectional view of the central part showing the entire sodium-sulfur battery, and Fig. 3 is a cross-sectional view of the battery. A graph showing the relationship between operating time and battery capacity, and FIG. 4 is a longitudinal cross-sectional view of the central part showing a conventional example. DESCRIPTION OF SYMBOLS 1...Anode container, 2...Insulating ring, 3...Cathode container, 4...Solid electrolyte etc., 7...Ceramic particles, 8...Ceramic particle high resistance layer, M... Conductive material for anode, R1... anode chamber, R2... cathode chamber. Patent applicant Nippon Insulator Co., Ltd. Agent Patent attorney On 1) Hironobu No. 3 Kanden light capacity (Ah) Figure 4

Claims (1)

[Claims] 1. Connect the anode chamber (R1) and cathode chamber (R2) to the solid electrolyte tube (
In a sodium-sulfur battery which is partitioned according to 4) and stores molten sulfur or molten sodium polysulfide in the anode chamber (R1) and stores metallic sodium in the cathode chamber (R2),
The particle size is approximately 10 mm with respect to the outer peripheral surface of the solid electrolyte tube (4).
Approximately 20 to 1000 μm in thickness by coating ceramic particles with sulfur and sodium polysulfide resistance such as α-alumina, β-alumina, or zirconia of ~500 μm.
A sodium-sulfur battery characterized by being provided with a ceramic particle high resistance layer (8).