JPH0665074B2 - Method and apparatus for manufacturing positive electrode for sodium-sulfur battery - Google Patents

Description

The present invention relates to a method and apparatus for manufacturing a sodium-sulfur battery positive electrode capable of efficiently producing a sodium-sulfur battery positive electrode in which a graphite mat is impregnated with sulfur. It is about.

(Prior Art) A sodium-sulfur battery separates sodium, which is a negative electrode active material, and sulfur, which is a positive electrode active material, by a solid electrolyte composed of β-alumina having high sodium ion conductivity, and is separated into 300 to 3
A sealed high-temperature secondary battery operated at a high temperature of 50 ° C., in which a positive electrode is a porous graphite mat serving as a core material impregnated with sulfur. As a method for producing a positive electrode for a sulfur battery, there is known a method in which a flat graphite mat is dipped in molten sulfur to impregnate with sulfur and then press-molded in a mold having a cavity of a predetermined shape.

However, in the conventional manufacturing method, in the step of impregnating the graphite mat with sulfur, air bubbles or sulfur vapor may be entrained in the mat, resulting in a defective product, and it also takes a long time to impregnate sulfur. There was a problem of poor production efficiency. Further, in the conventional method, there is a problem that the process is complicated because the press molding is performed after the impregnation with sulfur.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems and prevents the positive electrode impregnated with sulfur in a graphite mat from being entangled with air bubbles and the like, and in a short time. The present invention has been completed for the purpose of providing a method and an apparatus for manufacturing a positive electrode for a sodium-sulfur battery that can be efficiently manufactured.

(Means for Solving the Problems) The present invention, which is intended to solve the above problems, includes an anode chamber accommodating a positive electrode made of a cylindrical conductor impregnated with sulfur of an anode active material, and a bottomed cylindrical shape. In a method for producing a positive electrode for a sodium-sulfur battery comprising a solid electrolyte tube and a cylindrical conductor impregnated with the sulfur of a sodium-sulfur battery comprising a cathode chamber containing sodium as a cathode active material inside the solid electrolyte tube, , A core material for impregnating sulfur is placed in a mold cavity having a predetermined shape kept at 40 to 60 ° C., and a molten sulfur is forcibly forced from a plurality of injection ports arranged at equal intervals while maintaining a reduced pressure state. A method for producing a positive electrode for a sodium-sulfur battery characterized by impregnation is defined as the first invention, and a molten sulfur supply hole is provided in the lower mold of a vacuum-evacuated mold composed of an upper mold and a lower mold. Via conduit to this A molten sulfur tank is connected to the conduit, and a fixed quantity supply cylinder for forcibly injecting the molten sulfur into the cavity of the mold is attached to the conduit, and a straight tip portion at the front of the fixed quantity supply cylinder is more than the length of the supply hole. A second invention is an apparatus for producing a positive electrode for a sodium-sulfur battery, which is characterized in that a needle valve for opening and closing a long supply hole is provided in the.

(Example) Next, this invention is demonstrated in detail about the Example shown in figure.

(1) is a metal mold in which a cavity having a predetermined shape is formed by an upper mold (1a) for press molding which is vertically movable by a cylinder (2) and a lower mold (1b) fixed on a base (3). The lower mold (1b) is provided with a molten sulfur supply hole (4) which is opened and closed by a needle valve (7) moved up and down by a cylinder (6). A vacuum hole (not shown) is provided in (1a) or the lower mold (1b) so that vacuum suction can be performed. (5) is a molten sulfur tank connected to the supply hole (4) via a conduit (5a), the conduit (5a) at the needle valve (7) at a position close to the supply hole (4). A fixed amount supply cylinder (8) for forcibly injecting a predetermined amount of molten sulfur into the cavity of the mold (1) through the supply hole (4) is connected to the opening and closing of (1). In the molten sulfur tank (5), molten sulfur was produced in the presence of N ₂ purge gas, and the molten sulfur tank (5) was used to produce a lower mold (1
The conduit (5a) up to b) is provided with an overheater 10 for maintaining a molten state of the supplied sulfur and a thermocouple (11) for temperature monitoring. Further molten sulfur tanks (5)
A stirrer (9) is installed in the unit to prevent uneven sulfur temperature.

(Operation) In order to manufacture a positive electrode for a sodium-sulfur battery by using such an apparatus, a porous core material base material (20) such as a graphite mat is supplied to the lower mold (1b) and then shown in FIG. In this way, the upper mold (1a) is lowered to place the core material (21) in the cavity having a predetermined shape to be impregnated with the molten sulfur. The shape of the mold cavity is usually a shape obtained by vertically dividing the cylinder, which is the shape of the positive electrode for sodium-sulfur batteries, into two or three parts.
When the core material (21) is placed in such a mold cavity, the core material (21) is evacuated from a vacuum hole (not shown) provided in the upper mold (1a) or the lower mold (1b). ) Is maintained in a depressurized state in which the air is completely removed, and simultaneously with or after this depressurizing step, the needle valve (7) is operated to lower it, and the molten sulfur is attached to the conduit (5a) to remove it. The fixed amount supply cylinder (8) forcibly injecting into the cavity of the mold (1) is operated to extrude a predetermined amount of molten sulfur from the open supply hole (4) to force the core material (21). Impregnate. In this case, it is preferable to keep the mold temperature at 40 to 60 ° C. to smoothly impregnate the molten sulfur, so a temperature controllable heater may be incorporated in the lower mold (1b), or an appropriate temperature may be set. It is appropriate to provide a flow path that allows a different heat medium to pass through. This is because if the mold temperature is lower than 40 ° C, the flow of sulfur may be poor and impregnation may occur, while if it exceeds 60 ° C, sulfur crystals on the surface of the core material during subsequent cooling This is because there is a case where the oxidization phenomenon occurs and the surface quality is deteriorated. Also, the fourth
As shown in the figure, the tip straight portion (7a) of the needle valve (7) that opens and closes the supply hole (4) of the lower mold (1b) should be sufficiently longer than the length t of the supply hole (4). Even if sulfur is solidified and deposited in the lower part of the lower mold (1b), the needle valve (7) can be always raised to a certain position without being obstructed. Further, as shown in FIG. 3, the lower mold (1b) is provided with a plurality of supply holes (4) at equal intervals along the longitudinal direction, and each is connected to the molten sulfur tank (5). Needle valve (7) and sulfur metering cylinder similar to the above
(8) is provided, and the distance that the injected molten sulfur runs in the mold cavity is shortened as much as possible so that the molten sulfur does not solidify during the molding and can be uniformly impregnated into the entire core material. ing.

(Effects of the Invention) As is clear from the above description, in the first invention, the core material base material is placed in the mold cavity of a predetermined shape and a predetermined temperature before impregnation with molten sulfur, and thereafter, While the core material was maintained in a depressurized state, molten sulfur was forcibly impregnated from a plurality of injection ports arranged at equal intervals, so there were no bubbles inside the core material and the moisture content was extremely high. A low-quality, high-quality positive electrode for sodium-sulfur batteries can be obtained, and the impregnation treatment with sulfur can be performed in a short time, enabling mass production, and thus economical production, and further, the inner surface of the sulfur mold. It is possible to produce a sodium-sulfur battery having a constant electric capacity by preventing the adherence to the battery and always ensuring an accurate filling amount of sulfur. Further, in the second invention, the above method is efficiently performed. What can be Is.

Therefore, the present invention eliminates the conventional problems of sodium-
As a manufacturing method and a manufacturing apparatus for a positive electrode for a sulfur battery, the contribution to industrial development is extremely large.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of an apparatus for producing a positive electrode for a sodium-sulfur battery according to the present invention, FIG. 2 is an enlarged cross-sectional view of the same main part, and FIG. 3 is a part of the same main part. FIG. 4 is a cutaway side view, and FIG. 4 is an enlarged sectional view of the tip portion of the needle valve. (1): Mold, (1b): Lower mold, (4): Supply hole, (5): Molten sulfur tank, (5a): Conduit, (7): Needle valve, (7a): Straight tip part, (8): Constant supply cylinder.

Claims (2)

[Claims] 1. An anode chamber containing a positive electrode made of a cylindrical conductor impregnated with sulfur as an anode active material, a solid electrolyte tube having a bottomed cylindrical shape, and sodium as a cathode active material inside the solid electrolyte tube. In a method for producing a positive electrode for a sodium-sulfur battery, which comprises a cylindrical conductor for impregnating sulfur of the sodium-sulfur battery comprising a stored cathode chamber, a core material impregnated with sulfur has a predetermined shape held at 40 to 60 ° C. The method for producing a positive electrode for a sodium-sulfur battery, wherein the positive electrode for a sodium-sulfur battery is forcibly impregnated with molten sulfur from a plurality of injection ports arranged at equal intervals while being placed in the mold cavity and maintained in a reduced pressure state. 2. A plurality of molten sulfur supply holes (4) are provided at equal intervals in the lower mold (1b) of a mold (1) which is vacuum-sucked and comprises a upper mold (1a) and a lower mold (1b). A fixed quantity supply cylinder (8) is provided which is connected to a molten sulfur tank (5) via a conduit (5a) and forcibly injects molten sulfur into the cavity of the mold (1) in the conduit (5a). ) Is attached, and a needle valve (7) for opening and closing the supply hole is provided at the front of the fixed quantity supply cylinder (8) with the tip straight portion (7a) sufficiently longer than the length of the supply hole (4). Characteristic sodium-sulfur battery positive electrode manufacturing apparatus.