JPS6215996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to alkali metal-sulfur batteries, and more specifically, the electrochemical reactants include liquid sodium as the negative active material (anode) and liquid sulfur as the positive active material (cathode). This invention relates to an alkali metal-sulfur battery in which a cathode chamber and an anode chamber are separated by a solid electrolyte, which is a sodium ion conductor such as β-alumina.

One factor in battery failure is damage to the solid electrolyte, which causes the liquid alkali metal and sulfur to come into direct contact with each other. In some cases, this results in an exothermic reaction that increases the temperature of the battery above its normal operating temperature.

The object of the invention is to provide an alkali metal-sulfur battery in which the risk of battery failure is extremely small.

According to the present invention, a tubular battery case is provided, and an inner tube made of a solid electrolyte is provided at intervals inside the battery case to form an annular space between the inner tube and the annular space. A cathode chamber is formed in either one of the inner tube and the annular space, and an anode chamber is formed in the other of the inner tube and the annular space, and at least a part is formed by the battery case, and the anode chamber is configured such that an alkali metal can be supplied. An alkali metal-sulfur battery is provided, in which the anode chamber is filled with a loose fine filler in order to reduce the storage volume of the alkali metal in the anode chamber in a configuration with a connected alkali metal reservoir. Ru.

In the above configuration, by filling the anode chamber with the fine filler to reduce the capacity for alkali metal, the anode chamber immediately contacts and reacts with the cathode material when the inner tube, which is a solid electrolyte, is damaged. The amount of alkali metal can be limited to a small amount.

The fine filler may be spherical, granular or powdery, but the filler must not be reactive with the battery reactants. Suitable fillers include spheres, granules, and powders of glass, steel, ceramics, silicon carbide, graphite, and the like.

The annular space contains liquid battery reactants (e.g.
A flow restrictor, for example made of a porous material, may be provided between the annular space and the reservoir. Carbon, ceramic, glass, etc. can be used as the material for the flow restrictor.

In a preferred embodiment of the invention, the inner tube may be strengthened by depositing a porous coating on at least the surface of the inner tube facing the anode chamber.

The porous coating tends to hold the inner tube in case it breaks, which is the solid electrolyte and the cell reactants (e.g. sodium and sulfur).
Holes are not readily formed that would allow direct contact between the two.

The porous coating is formed by plasma spraying a material forming the porous coating.
It can be formed by adhering to the surface of the inner tube by spraying, and the porous coating can have fibers or mesh embedded therein to reinforce it. Suitable porous coating forming materials include nickel and aluminum.

Recent studies have also revealed that such porous coatings have a wicking effect and function to uniformly distribute alkali metals on the surface of the solid electrolyte inner tube. At present, it is unclear whether this wicking effect arises primarily from the capillary action of the pores present within the porous coating, or whether it is due to the difference in thermal expansion between the inner tube and the porous coating when the cell reaches its operating temperature. It is not clear whether this results primarily from the small capillary action that occurs at the interface with the porous coating.

If the primary purpose of such a porous coating is to provide a wicking effect, such as when formed from aluminum, a non-porous layer of strong material is applied to the porous coating. Non-porous layers can be formed in a variety of ways. For example, (a) after the porous coating has been formed, the same material is sprayed onto the porous coating under different spray conditions, (b) the inner tube coated with the porous coating is immersed in molten metal, or (c) the porous coating is (d) electrolytically depositing a metal onto a porous coating; (e) applying a separately prepared non-porous thin film onto a porous coating. A non-porous layer can be formed.

The method currently found to be suitable is to immerse the inner tube with the porous coating in molten metal, and by repeating the immersion several times in progressively increasing thicknesses, the inner tube is coated with a porous coating. Forms a strong non-porous layer. At this time, it is of course necessary to ensure that the immersion metal does not block the pores of the porous coating. This is because this blockage inhibits the flow of alkali metal within the porous coating. It is also necessary to select the type of metal material, soaking temperature and time to avoid melting of the porous coating. Various combinations of materials can be used to form the porous coating and the non-porous layer. One example is to form the porous coating with aluminum or copper and form the non-porous layer with aluminum or an aluminum alloy. Preferably, the melting point of the metal of the non-porous layer is lower than the melting point of the material of the porous coating.

In another preferred embodiment of the invention, sodium polysulfide (sodium polysulfide) is added to the inner surface of the battery case.
It has a protective layer of material that is not easily attacked by polysulfides. Materials for forming the protective layer include (a) carbon or graphite, (b) ceramic or glass, (c) corrosion-resistant metals, (d) mica or synthetic materials containing mica, and (e) carburized steel. steel), etc. The protective layer may be formed by preparing a thin film from the above-mentioned material in advance and adhering it to the inner surface of the battery case, or by attaching the above-mentioned material to the inner surface of the battery case by thermal spraying, vapor deposition, etc. Alternatively, a coating may be formed. Further, when the battery case is made of steel, by carburizing the inner surface thereof, only the inner surface skin of the battery case may be made of carburized steel as a protective layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate understanding of the present invention, embodiments of sodium-sulfur batteries embodying the above features will be described below with reference to the accompanying drawings.

In FIG. 1, the cell comprises an inner tube 1 of beta-alumina which is closed at the top and constitutes the solid electrolyte of the cell, and an outer tube 2 of stainless steel which is closed at the top and constitutes the battery case. The interior of the inner tube 1 forms the cathode compartment of the battery and therefore contains sulfur in the charged state of the battery.

The annular space 3 between the inner tube 1 and the outer tube 2 forms the anode compartment of the cell and therefore contains sodium in the charged state of the cell. The outer tube 2 extends above the inner tube 1 to form a sodium reservoir 4, and the sodium reservoir 4 has a circular flow restriction plate 6 made of a porous sintered ceramic body.
It is separated from the annular space 3 by. In order to limit the amount of sodium available for the reaction in the anode chamber, the annular space 3 is made as narrow as possible;
Its volume is further reduced by filling it with glass beads 7 as a loose, fine filler. The glass beads 7 restrict the flow of sodium from the sodium reservoir 4 and the annular space 3
It also helps distribute the sodium evenly within the body.

The outer surface of the beta-alumina inner tube 1 is coated with a porous coating, which is not shown in FIG. Furthermore, a protective layer 8 is provided on the inner surface of the outer tube 2 over its entire length.

The battery anode collector electrode is a stainless steel outer tube 2
However, its outer surface can be coated with, for example, aluminum to improve its electrical conductivity. The outer tube 2 is electrically connected to an anode terminal 9 via a seal/clamp device 10, which will be described later. The cathode collector electrode of the battery is a carbon tube 11 extending inside the inner tube 1 and carrying a cathode terminal 92 at the end located outside the inner tube 1.
Consists of. In order to improve the electrical conductivity of the carbon tube 11, its inner surface can be coated with a highly conductive metal, for example by spraying.

The sealing and clamping device 10 has an inner tube 1 and an outer tube 2.
Seal the open bottom end of. For this purpose, the inner tube 1,
An annular flange 1 is provided on the outer tube 2 and the carbon tube 11, respectively.
2, 13, and 14 are provided. A flange 13, which may consist of alpha-alumina, is attached to the inner tube 1 by means of a glass seal and abuts the flange 12 via an aluminum gasket 15 to close off the annular space 3. The flange 14 has an annular projection 16 which abuts against the flange 13 via a Grafoil gasket 17. Each flange 12, 13, 14 is compressively fastened together by a sleeve structure. This sleeve structure is connected to the flange 1 through an insulating gasket 20.
a metal outer sleeve 18 having an inner flange 19 at its upper end that abuts on the elastic ring 2;
4 and an inner sleeve 21 with an inner flange 23 pressing the flange 14 onto the flange 14.

According to such a configuration, when the inner tube 1 is damaged, the sodium in the anode chamber immediately contacts and reacts with sulfur as the cathode material. However, there are 7 glass beads in the anode chamber.
Since the reactor is filled with sodium, the amount of sodium that can be accommodated is extremely small, and the amount of sodium in which the above reaction is carried out can be made very small.

In the above embodiment, it goes without saying that the interior of the inner tube, which is a solid electrolyte, may be modified so that it constitutes an anode chamber, and the annular space between the inner tube and the battery case constitutes a cathode chamber. Nor.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional elevational view of one embodiment of the invention. 1... Inner tube (solid electrolyte), 2... Outer tube (battery case), 3... Annular space, 4... Sodium reservoir (alkali metal reservoir), 7... Glass beads (discrete fine filler).

Claims (1)

[Claims] 1. A tubular battery case 2 is provided, and an inner tube 1 made of a solid electrolyte is provided at an interval inside the battery case 2 to form an annular space 3 between the inner tube 1 and the annular space 3. A cathode chamber is configured in either one of the spaces 3, an anode chamber is configured in the inside of the inner tube 1 and the other of the annular space 3, and at least a part is formed by the battery case 2, and the alkali metal can be supplied. In a configuration in which an alkali metal reservoir 4 connected to the anode chamber is provided,
An alkali metal-sulfur battery characterized in that the anode chamber is filled with a loose fine filler 7 in order to reduce the storage capacity of the alkali metal in the anode chamber.