JPS6217964A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To uniformize current density, by molding circular felts made of metal fibers having a perforated hole at their central part, and laminating them so that their directions of fibers become vertical to the longitudinal direction of a solid-electrolyte tube, and then making a negative-electrode-collector- terminal pipe pass through the perforated holes. CONSTITUTION:Circular felts 9-1 and 9-2 made of metal fibers are molded 40-41mm in outer diameter, 5mm in perforated-hole diameter, and 2-30mm in thickness, by using stainless steel of 8-25mu in fiber diameter, or the like. The circular felts 9-1 and 9-2, with their thickness made about 7mm, are laminated so that their directions of fibers, facing differently to each other, become vertical to the longitudinal direction of a solid-electrolyte tube, and a negative- electrode-collector-terminal-pipe 8 is inserted into the solid-electrolyte tube, with it made to pass through the perforated holes. Besides, a circular-plate felt 9', having the same material and dimention as the circular felts 9-1 and 9-2, is layered on the bottom part of the solid-electrolyte tube 1. Hence, because sodium added as negative polar active material moves moves uniformly along the surface, on which the circular felts are laminated, the current density on the surface of the solid-electrolyte tube 1 can be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to sodium-sulfur batteries, and more particularly to the construction of the cathode chamber thereof.

Conventional technology and its problems Sodium-sulfur batteries have a cathode chamber filled with molten sodium as the cathode active material and a cathode chamber filled with molten sodium as the cathode active material, in a completely sealed battery case to prevent it from being affected by air, moisture, etc. This is a high-temperature secondary battery that is provided with a cathode chamber filled with molten sulfur and separated from each other by a solid electrolyte tube such as R-alumina.

A conventional example of the above-mentioned sodium-sulfur battery will be explained with reference to FIG. In FIG. 3, reference numeral 1 denotes a sodium ion conductive solid electrolyte tube such as r-alumina, and an a-alumina ring 2 is bonded to the upper end of the tube. Furthermore, a cathode auxiliary lid 3' is bonded to the upper surface of the α-alumina ring 2 via an aluminum layer through heat pressure bonding, while metal fibers 7 are filled in the solid electrolyte tube 1, and the cathode lid 3' is The cathode current collector terminal tube 8 welded thereto is inserted, and the cathode auxiliary lid 3' and cathode ti3 are welded to form an electrode chamber. Molten sodium as the cathode active material is about 15
The cathode chamber is impregnated with vacuum from the tip of the cathode current collector terminal tube 8 while being kept at 0.degree. C., and then the tip is vacuum-sealed. In addition, a cathode lid 4 is heat-pressure bonded to the bottom surface of the α-aluminum ζ ring 2 via an aluminum layer, and a bottom lid is fitted and welded to a battery case made of molten sulfur-resistant and sodium polysulfide metal. A cathode conductive material 6 impregnated with molten sulfur as a cathode active material made of graphite felt or the like is housed in a cylindrical shape inside the container 5, and a solid three-piece electrolyte tube 1 is inserted into the central space. The upper end of the cathode lid 4 is welded in vacuum to form an electrode chamber.

In such a sodium-sulfur battery, the metal fibers 7 filled in the solid electrolyte tube 1 are lumpy stainless steel webs, so when discharged at about 350°C, the IJium in the cathode chamber becomes a lumpy stainless steel web. Since the ions are ionized through the gaps and moved to the cathode chamber, the current density on the surface of the solid electrolyte tube 1 becomes non-uniform, causing cracks and damaging the battery. Furthermore, filling the solid electrolyte tube 1 with the stainless steel web in the form of a block requires skill, and there is also the drawback that the number of manufacturing steps increases.

Purpose of the Invention The present invention solves the above-mentioned drawbacks, and aims to prevent the current density on the surface of a solid electrolyte tube from becoming non-uniform during discharge, and to reduce the number of manufacturing steps (an object of the present invention is to provide a lithium-sulfur battery). That is.

Structure of the Invention The sodium-sulfur battery of the present invention has a solid electrolyte tube filled with gold I! 74 fibers are formed into an annular felt with a through hole in the center, and multiple sheets are laminated so that the main fiber direction is perpendicular to the length direction of the solid electrolyte tube, and a cathode current collector terminal is attached to the through hole of the annular felt. The tube is passed through and inserted into a solid electrolyte tube to form a cathode chamber.

EXAMPLES The present invention will be explained below using examples. FIG. 1 is a partially cutaway perspective view of the cathode chamber of the sodium-sulfur battery of the present invention, and FIG. 2 is a perspective view of another embodiment of the present invention, in which annular felts and metal members are alternately laminated. It is.

The annular felt made by molding metal fibers used in the lithium-sulfur battery of the present invention is 9-1.9-2, and is made of stainless steel 8US316L with a fiber diameter of 8μ to 25μ and an outer diameter of 40μ.
It is molded so that the diameter of the through hole is 5M-1 and the thickness is 2 to 30 mm. Circular felt 9-1 and 9
-2 has a thickness of about 7 fins, and the main fiber directions are different from each other, but 45 sheets are stacked so that they are perpendicular to the length direction of the solid electrolyte tube, and the cathode current collector terminal tube 8 is inserted into the through hole. is inserted into the solid electrolyte tube 1 by penetrating it. In addition, at the bottom of the solid electrolyte tube 1, the annular 7L) 9-1.9-2
Disc felts 9' made of the same material and having the same dimensions are stacked up to a height of about 10 cm. Therefore, sodium as a cathode active material moves uniformly along the surface where the 1-W4-shaped felts are laminated, and the current density on the surface of the solid electrolyte tube 1 becomes uniform.

Next, FIG. 2 shows heat-resistant and sodium-resistant metal members 10-1, 10-2, such as stainless steel, in a part of the gap between the laminated annular felts 9-1 and 9-2, and/or in the upper part.
10-5 and 10', which makes the filling density of the annular felt in the solid electrolyte tube uniform and suppresses the downward movement of sodium due to gravity. Note that these metal members include a perforated disk 10'.
, 10-1, a metal net 10-2, a non-porous disk 10-3, etc., and the shape thereof is not particularly limited.

In addition, in FIGS. 1 and 2, the outer diameter of the cathode current collector terminal tube 8 is made larger than the through-hole diameter of the annular felt, and the outer diameter of the annular felt is made larger than the inner diameter of the solid electrolyte tube 1 to improve adhesion. We are trying to improve.

Now, the sodium chloride of the present invention having a cathode chamber as shown in FIG.
For a sulfur battery and a conventional sodium-sulfur battery as shown in FIG. 3, the distribution of IJum remaining in the annular felt and metal fibers at the end of discharge and the time required for filling the metal fibers were compared. As a result, the time required for filling the metal fibers 7 was 5 minutes to 15 people per cell in the conventional battery, but it was 1 to 2 minutes per cell in the battery of the present invention. In addition, the sodium remaining at the end of discharge was uniformly distributed in the battery of the present invention, whereas in the conventional battery, a large amount of sodium was distributed in the lower part of the metal fiber 7, and a sodium-deficient area was observed in the upper part.

Furthermore, the thickness of the annular fer) 9-1.9-2 is 2 to 30
The reason why the fin was used was to improve the retention effect of sodium as a cathode active material, and within this range, 95% of the sodium would contribute to the battery reaction. On the other hand, when the thickness was reduced to 2 mm or less, it was about 85%, and the number of layers to be laminated also increased.

Moreover, when the thickness is set to 30 fII11 or more, it is about 87%, and although the number of laminated sheets may be reduced, the contribution rate to one cell reaction is reduced.

In the above embodiments, there are no particular limitations on the material, fiber diameter, and density of the metal fibers formed into the annular felt, and the packing density of the annular felt into the solid electrolyte tube.

Effects of the Invention As detailed in the examples, the sodium-sulfur battery of the present invention can reduce the number of manufacturing steps, increase the contribution rate of sodium as a cathode active material to the battery reaction, and ensure a uniform reaction. This allows the current density to be made uniform.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view of the cathode chamber of the sodium-sulfur battery of the present invention, Fig. 2 is a perspective view of essential parts of another embodiment of the invention, and Fig. 83 is a conventional IJ Umu sulfur battery. FIG.

Claims (4)

[Claims] (1) In a sodium-sulfur battery equipped with a cathode chamber made by impregnating sodium ion-conducting solid electrolyte tubes with metal fibers, the metal fibers are formed into an annular felt with a through hole in the center. A sodium-sulfur battery characterized in that the solid electrolyte tubes are stacked so that the main fiber direction thereof is perpendicular to the length direction of the solid electrolyte tubes, and a cathode current collector terminal tube is passed through the through hole. (2) The sodium-sulfur battery according to claim 1, wherein a heat-resistant and sodium-resistant metal member is disposed in a part of the gap between and/or above the laminated annular felt. (3) The thickness of one layer of laminated annular felt is 2 mm.
Claim 1, characterized in that the length is 30 mm.
, the sodium-sulfur battery according to item 2. (4) The annular felt has a through-hole diameter smaller than the outer diameter of the cathode current collector terminal tube and an outer diameter larger than the inner diameter of the solid electrolyte tube. sodium-sulfur battery.