JP3341320B2 - Battery case for sodium-sulfur battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery case of a sodium-sulfur battery, and more particularly to improvement of corrosion resistance to an anode active material.

[0002]

2. Description of the Related Art A sodium-sulfur battery having an anode chamber formed outside a solid electrolyte tube having sodium ion conductivity and a cathode chamber formed therein has a cathode cover for sealing the cathode chamber and an electrode for sealing the anode chamber. A tank is used.

[0003] As the battery case, a battery case having corrosion resistance to sulfur as an anode active material and sodium polysulfide generated by electric discharge and having electric conductivity capable of acting as an anode current collector is used. .

[0004] As a material satisfying the above conditions, there is known a material in which chromium-iron alloy phase is formed by thermally diffusing chromium on the surface of carbon steel or stainless steel as a base material, that is, a chromized material.

[0005]

In the above-mentioned materials, the carbon and chromium contained in the base material react with each other on the outside of the chromium-iron alloy layer to form Cr ₂₃ C ₆ or Cr ₇ C _3.
Chromium carbides such as those described above, and the diffusion of chromium into the base material is hindered by the chromium carbide layer, and the chromium-iron alloy layer having corrosion resistance to the anode active material cannot be thickened. there were.

[0006]

According to the present invention, a cathode chamber is formed inside a sodium ion-conductive solid electrolyte tube, and an anode chamber is formed outside the tube. In a battery case of a sodium-sulfur battery in which the anode chamber is sealed with a battery case, the battery case contains 0.05% or less of carbon and 0.05% to 0.5% of titanium. And iron containing at least 0.05 to 2% of a metal selected from the group consisting of tungsten and tantalum, and a single layer of a chromium-iron alloy phase is formed on the surface of the iron by chromizing. It is characterized by being done.

[0007]

[For work] Accordingly, the present invention, since the titanium atom, tungsten atom relative to the radius r _c of the carbon atoms, the radius r _Ti tantalum atoms, r _w, r _Ta is less than 0.59, titanium carbon atoms TiC, W which penetrates between the crystal lattices of atoms, tungsten atoms, and tantalum atoms and has preferentially high stability
₂ C, WC, formed many interstitial carbides, such as TaC formation of chromium carbides is suppressed.

[0008]

EXAMPLE As the battery case material of the present invention, iron A having a carbon content of 0.05% or less, iron B having a carbon content of 0.08%, and iron B having a carbon content of 0.18% or less were used.
% Iron C, iron A 0.8% tungsten,
0.8% tantalum and 0% titanium
%, 0.05%, 0.1%, 0.3% and 0.5%, and then 10 to 60% by weight of chromium powder, 0.5%
~ 2.0% ammonium chloride powder and 50-80%
After enclosing it in an iron box with alumina powder of above and performing chromizing by heating in a hydrogen atmosphere at about 950 ° C. for several hours, the structure was examined with an X-ray and an optical microscope. The result was obtained.

[0009]

[Table 1]

From Table 1, the materials for the battery case of the present invention include:
The content of carbon is 0.05% or less, and the content of titanium is 0.1% or less.
0.5-0.5% and at least tungsten;
It can be seen that iron containing one kind of metal selected from tantalum may be used.

In the above embodiment, the content of titanium is 0.05
It is assumed that the content should be 0.5% to 0.5%. However, the content of tungsten and tantalum is set to 0.05 to 2%, and the total addition amount is set to about 2% to suppress the formation of intermetallic compounds, Needless to say, it is necessary to secure the strength.

Next, of the battery case material that has been chromized as described above, the most corrosive sodium polysulfide Na ₂ S ₃ containing iron A, iron B and iron C containing 1% of titanium is encapsulated. Placed in a Pyrex glass container and heated to 350 ° C, and the weight loss rate was investigated at regular intervals,
The results are shown in FIG.

From FIG. 1, it can be seen that iron A containing 1% of titanium has the smallest weight reduction rate, and sodium polysulfide Na ₂ S
It turns out that corrosion resistance is high with respect to ₃ . This indicates that the iron A is suitable for use in a battery case of a sodium-sulfur battery.

[0014]

As described above, since the battery case of the sodium-sulfur battery of the present invention has high corrosion resistance to sodium polysulfide, the life of the sodium-sulfur battery can be extended.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of an investigation on the corrosion resistance of sodium used in a battery case of a sodium-sulfur battery of the present invention and iron used in a battery case of a conventional sodium-sulfur battery against sodium polysulfide.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 10/39 C22C 38/00 301 C23C 10/40

Claims (1)

(57) [Claims] 1. A cathode chamber is formed inside a solid electrolyte tube of sodium ion conductivity, and an anode chamber is formed outside. The cathode chamber is sealed with a cathode lid, and the anode chamber is sealed with a battery case. In a battery case of a sodium-sulfur battery, the battery case contains 0.05% or less of carbon and 0.05 to 0.5% of titanium, and at least 0.05 to 2% of tongue. A battery case for a sodium-sulfur battery, comprising iron containing a kind of metal selected from stainless steel and tantalum, and a single layer of a chromium-iron alloy phase formed on the surface of the iron by chromizing. .