Sodium-sulfur battery production method and sodium-sulfur battery

Abstract

The present invention provides a sodium-sulfur battery production method that can suppress needle breakage and that can improve the efficiency of producing a sodium-sulfur battery. A sodium-sulfur battery production method according to the present invention is for producing a sodium-sulfur battery provided with a sodium container that is disposed in a negative electrode space. The sodium container has a container body which is filled with sodium and a lid 21 which is attached to the container body. The sodium is melted when the sodium-sulfur battery is sued. A flow hole 22 for allowing melted sodium to flow to the inside and outside of the sodium container is formed in the lid 21. The production method comprises a flow hole formation step for forming the flow hole 22 by piercing the lid 21 with a needle 40. The needle 40 has a shaft part 40a and a tapered part 40b which is provided at the tip end of the shaft part 40a. In the flow hole formation step, the tapered part 40b pierces the lid 21 from an outer surface 21a of the lid 21 that faces the outside of the sodium container, and the needle 40 is retracted before the shaft part 40a reaches the outer surface 21a of the lid 21.

Description

Method for manufacturing a sodium-sulfur battery and sodium-sulfur battery

[0001] The present invention relates to a method for manufacturing a sodium-sulfur battery provided with a sodium container disposed in a negative electrode space, and a sodium-sulfur battery.

[0002] In Patent Document 1 below, “a negative electrode chamber is formed inside a bottomed cylindrical solid electrolyte tube disposed in a positive electrode container, and a positive electrode chamber is formed outside. A cylindrical positive electrode mold impregnated with sulfur as a positive electrode active material is accommodated in the positive electrode chamber. Inside the solid electrolyte tube serving as the negative electrode chamber, a bottomed cylindrical partition wall is disposed with a predetermined gap from the solid electrolyte tube. Further, a sodium container accommodating sodium as a negative electrode active material is disposed with a predetermined gap from the partition wall, and a sodium-sulfur battery is disclosed.” Inside the sodium-sulfur battery, a circulation hole (small hole) is provided in the bottom of the sodium container, and sodium can circulate inside and outside the sodium container through the circulation hole.

[0003] Japanese Patent Application Laid-Open No. 2013-114824

[0004] Although not described in detail in Patent Document 1, the sodium container has a container body filled with sodium and a lid attached to the container body. Inside the sodium-sulfur battery, the sodium container is disposed such that the lid forms the bottom, and a circulation hole is formed in the lid. As shown in FIG. 12, by piercing a needle into the lid, a circulation hole is formed in the lid.

[0005] If the formation of the circulation hole by piercing the needle into the lid is repeated in this way, the needle may break and the needle may need to be replaced, and there is room for improvement in the manufacturing efficiency of the sodium-sulfur battery.

[0006] The present invention has been made to solve the above problems, and one of its objects is to provide a method for manufacturing a sodium-sulfur battery and a sodium-sulfur battery that can suppress the breakage of the needle and improve the manufacturing efficiency of the sodium-sulfur battery.

[0007] The inventors of this invention diligently investigated the cause of needle breakage. As a result, they discovered a new finding: when the needle is pulled out of the lid, burrs or sharp edges generated when the needle was inserted into the lid are dragged out of the sodium container by the needle, forming a wall on the lid that protrudes outwards from the sodium container around the flow hole. The friction with this wall causes wear on the sides of the needle, which is the cause of needle breakage. This invention was made based on this new finding.

[0008] <1> The present invention relates to a method for manufacturing a sodium-sulfur battery, in one embodiment, comprising a sodium container disposed in the negative electrode space, wherein the sodium container has a container body filled with sodium and a lid attached to the container body, the sodium is melted when the sodium-sulfur battery is used, the lid has a flow hole formed therein for the molten sodium to flow in and out of the sodium container, and the method includes a flow hole forming step of piercing the lid with a needle to form the flow hole, the needle has a shaft portion and a tapered portion provided at the tip of the shaft portion, and in the flow hole forming step, the tapered portion is pierced into the lid from the outer surface of the lid facing the outside of the sodium container, and the needle is withdrawn before the shaft portion reaches the outer surface of the lid, the present invention relates to a method for manufacturing a sodium-sulfur battery.

[0009] <2> The present invention may relate to a method for manufacturing a sodium-sulfur battery as described in paragraph 1, wherein the process of forming the flow holes is performed with the lid attached to the container body filled with sodium, and the elapsed time from the time the flow holes are formed in the lid is measured.

[0010] <3> The present invention may relate to a method for manufacturing a sodium-sulfur battery as described in paragraph 2, wherein notification is given when the elapsed time exceeds a predetermined threshold.

[0011] <4> The present invention relates to a method for manufacturing a sodium-sulfur battery as described in paragraph 3, wherein the member that partitions and forms the negative electrode space includes a main body and a negative electrode fitting attached to the end of the main body, the negative electrode space is formed when the sodium container is placed inside the main body and the negative electrode fitting is attached to the end of the main body after degassing is performed inside the main body, and the elapsed time is measured until degassing is performed inside the main body.

[0012] <5> The present invention may relate to a method for manufacturing a sodium-sulfur battery as described in paragraph 4, wherein degassing is performed inside the main body so that the elapsed time is within 120 minutes.

[0013] <6> The present invention may relate to a method for manufacturing a sodium-sulfur battery according to paragraph 4 or 5, wherein the main body includes a β-alumina solid electrolyte tube, and the humidity inside the facility in which the sodium container is placed inside the main body is measured.

[0014] <7> The present invention may relate to a method for manufacturing a sodium-sulfur battery according to any one of the first to sixth paragraphs, wherein the lid is press-fitted to the end of the container body and welding is not performed between the lid and the end of the container body.

[0015] <8> The present invention may relate to a method for manufacturing a sodium-sulfur battery as described in paragraph 7, wherein the overlap width between the lid and the end of the container body in the longitudinal direction of the sodium container is greater than or equal to the width of the gap between the bottom of the container body in the longitudinal direction of the sodium container and the member that partitions the negative electrode space when the sodium container is placed in the negative electrode space.

[0016] <9> The present invention may further include an inspection step of imaging the outer surface of the lid and inspecting the flow holes by image analysis after the flow hole formation step, according to any one of the first to eighth paragraphs.

[0017] <10> The present invention may relate to a method for manufacturing a sodium-sulfur battery as described in paragraph 9, wherein the inspection step involves determining the contour and area of ​​the flow hole.

[0018] <11> In one embodiment, the present invention relates to a sodium-sulfur battery comprising a sodium container disposed in the negative electrode space, wherein the sodium container has a container body filled with sodium and a lid attached to the container body, the sodium is melted when the sodium-sulfur battery is used, the lid has a flow hole formed therein for the molten sodium to flow in and out of the sodium container, and the lid has a wall portion that protrudes toward the inside of the sodium container around the flow hole.

[0019] <12> The present invention may relate to the sodium-sulfur battery described in paragraph 11, wherein the lid is press-fitted to the end of the container body and there is no welding between the lid and the end of the container body.

[0020] <13> The present invention may relate to the sodium-sulfur battery described in paragraph 12, wherein the overlap width between the lid and the end of the container body in the longitudinal direction of the sodium container is greater than or equal to the width of the gap between the bottom of the container body in the longitudinal direction of the sodium container and the member that partitions the negative electrode space when the sodium container is placed in the negative electrode space.

[0021] According to one embodiment of the method for manufacturing the sodium container of the sodium-sulfur battery of the present invention, the tapered portion is inserted into the lid from the outer surface of the lid facing the outside of the sodium container, and the needle is pulled back before the shaft reaches the outer surface of the lid, thereby suppressing needle breakage and improving the manufacturing efficiency of the sodium-sulfur battery. Furthermore, according to one embodiment of the sodium-sulfur battery of the present invention, the lid has a wall portion that protrudes toward the inside of the sodium container around the flow hole, thereby suppressing needle breakage and improving the manufacturing efficiency of the sodium-sulfur battery.

[0022] This is a cross-sectional view of a sodium-sulfur battery manufactured by the sodium-sulfur battery manufacturing method according to an embodiment of the present invention. This is an exploded perspective view showing a part of the sodium-sulfur battery in Figure 1. This is a cross-sectional view showing the lid of the sodium container in Figure 1 in more detail. This is a flowchart showing the sodium-sulfur battery manufacturing method according to an embodiment of the present invention. This is an explanatory diagram showing the sodium filling process in Figure 4. This is an explanatory diagram showing the lid attachment process in Figure 4. This is a cross-sectional view of the container body and lid in Figure 6. This is an explanatory diagram showing the flow hole formation process in Figure 4. This is an explanatory diagram showing an enlarged view of the main part of the flow hole formation process in Figure 8. This is an explanatory diagram showing the inspection process in Figure 4. This is an explanatory diagram showing an example of the outer surface of the lid imaged in the inspection process in Figure 10. This is an explanatory diagram showing a conventional sodium-sulfur battery manufacturing method.

[0023] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and can be materialized by modifying the components without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in each embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined.

[0024] <About Sodium-Sulfur Batteries> Figure 1 is a cross-sectional view of a sodium-sulfur battery 1000 manufactured by the manufacturing method of a sodium-sulfur battery 1000 according to an embodiment of the present invention, and Figure 2 is an exploded perspective view showing a part of the sodium-sulfur battery 1000 of Figure 1 disassembled. Note that in Figure 2, some of the components are shown in cross-section.

[0025] The method for manufacturing a sodium-sulfur battery 1000 according to an embodiment of the present invention is for manufacturing a sodium-sulfur battery 1000 as shown in Figures 1 and 2. As shown in Figures 1 and 2, the sodium-sulfur battery 1000 may include a positive electrode container 1001, a plurality of sulfur molds 1002, a β-alumina solid electrolyte tube 1003, a safety tube 1004, a sodium container 1005, sodium 1006, a positive electrode fitting 1007, an insulating ring 1008, and a negative electrode fitting 1009.

[0026] The positive electrode container 1001 is a bottomed cylindrical container. Multiple sulfur molds 1002 are housed inside this positive electrode container 1001. The sulfur molds 1002 are members of a predetermined shape, in which sulfur, which is the positive electrode active material, is impregnated into a conductive material. As the conductive material, for example, a mat can be used. The mat may be a felt in which glass fibers and graphite fibers are intertwined. The mat can be obtained by layering a graphite fiber felt on top of a glass fiber felt and repeatedly inserting multiple needles, each with a barb at the tip, into the felt. As is well known, the melting point of sulfur is 112.8°C, and the sulfur impregnated into the conductive material remains solidified until the sodium-sulfur battery 1000 is started after its manufacture.

[0027] The sulfur mold 1002 may have a plurality of side molds 1002a and one bottom mold 1002b. As is particularly evident in Figure 2, the side molds 1002a may be longitudinal members with arc-shaped end faces. Figure 2 shows an example of a side mold 1002a that forms a cylindrical shape overall when three side molds 1002a are combined. The bottom mold 1002b may be a disc-shaped member. A β-alumina solid electrolyte tube 1003 may be placed inside the cylindrically arranged side molds 1002a, and the bottom mold 1002b may be placed at the bottom of the β-alumina solid electrolyte tube 1003.

[0028] The β-alumina solid electrolyte tube 1003 is a bottomed cylindrical container that has selective permeability to sodium ions and is positioned inside the positive electrode container 1001. A positive electrode space 1010 is formed between the positive electrode container 1001 and the β-alumina solid electrolyte tube 1003, in which molten sulfur is placed after the sodium-sulfur battery 1000 is started.

[0029] The safety tube 1004 is a bottomed cylindrical container. The sodium container 1005 is a bottomed and lidded cylindrical container. More specifically, the sodium container 1005 has a bottomed cylindrical container body 20 filled with sodium 1006 and a lid 21 attached to the container body 20. The safety tube 1004 is placed inside the β-alumina solid electrolyte tube 1003, and the sodium container 1005 is placed inside the safety tube 1004. The sodium container 1005 is positioned such that the bottom 20a of the container body 20 is facing upwards and the lid 21 is facing downwards. Due to this arrangement, the lid 21 may also be called a bottom lid.

[0030] A predetermined gap is provided between the inner surface of the β-alumina solid electrolyte tube 1003 and the outer surface of the safety tube 1004, and between the inner surface of the safety tube 1004 and the outer surface of the sodium container 1005. The sodium 1006 is contained inside the sodium container 1005. As is well known, the melting point of sodium 1006 is 97.79°C, and the sodium 1006 in the sodium container 1005 remains solidified until the sodium-sulfur battery 1000 is started after its manufacture.

[0031] The positive electrode fitting 1007 is attached to the top of the positive electrode container 1001. The insulating ring 1008 is an annular member made of an insulator and is attached to the top of the β-alumina solid electrolyte tube 1003 together with the negative electrode fitting 1009. Inside the β-alumina solid electrolyte tube 1003, the insulating ring 1008, and the negative electrode fitting 1009, a negative electrode space 1011 is formed where molten sodium 1006 is placed after the sodium-sulfur battery 1000 is started. The sodium container 1005 is placed in the negative electrode space 1011. The insulating ring 1008 may electrically insulate the molten sodium 1006 in the β-alumina solid electrolyte tube 1003, the negative electrode fitting 1009, and the negative electrode space 1011 from the positive electrode fitting 1007.

[0032] The sodium-sulfur battery 1000 is a high-temperature operating secondary battery, and is heated to approximately 300°C when in use. When the sodium-sulfur battery 1000 is heated to approximately 300°C, the sulfur in the sulfur mold 1002 and the sodium 1006 in the sodium container 1005 melt. As shown in Figure 1, the sulfur mold 1002 and the sodium container 1005 are provided with an inert gas generating substance 1012, such as a tablet of sodium azide. When the sodium-sulfur battery 1000 is heated to approximately 300°C, an inert gas (such as nitrogen gas) is generated from the inert gas generating substance 1012.

[0033] Here, the lid 21 of the sodium container 1005 has a flow hole 22 formed therein for the molten sodium 1006 to flow in and out of the sodium container 1005. When the sodium-sulfur battery 1000 is heated to about 300°C, inert gas is generated from the inert gas generating material 1012 in the sodium container 1005. This increases the internal pressure of the sodium container 1005, and the molten sodium 1006 is placed in the negative electrode space 1011 through the flow hole 22.

[0034] The amount of gas generated from the inert gas generating material 1012 in the sulfur mold 1002 and the amount of gas generated from the inert gas generating material 1012 in the sodium container 1005 are set so that the internal pressure of the positive electrode space 1010 is greater than the internal pressure of the negative electrode space 1011. By creating this difference in internal pressure, even if damage occurs to the β-alumina solid electrolyte tube 1003, the molten sodium 1006 in the negative electrode space 1011 will not enter the positive electrode space 1010, and the molten sulfur in the positive electrode space 1010 will enter the sodium container 1005. When the molten sulfur in the positive electrode space 1010 enters the sodium container 1005 and reacts with the molten sodium 1006, reaction heat is generated. The safety tube 1004 has a greater coefficient of thermal expansion than the β-alumina solid electrolyte tube 1003. It expands more than the β-alumina solid electrolyte tube 1003 due to the heat of reaction between the molten sulfur and the molten sodium 1006, and can seal the damaged area of ​​the β-alumina solid electrolyte tube 1003. This limits the amount of reaction between the molten sulfur and the molten sodium 1006 when damage occurs to the β-alumina solid electrolyte tube 1003.

[0035] Next, Figure 3 is a cross-sectional view showing the lid 21 of the sodium container 1005 in Figure 1 in more detail. As shown in Figure 3, in the sodium-sulfur battery 1000 of this embodiment, the lid 21 has a wall portion 210 that protrudes toward the inside of the sodium container 1005 around the flow hole 22.

[0036] As described later, the flow holes 22 are formed by piercing the lid 21 with a needle 40 (see Figures 8 and 9). The wall portion 210 protrudes toward the inside of the sodium container 1005, which suppresses the breakage of the needle 40 and improves the manufacturing efficiency of the sodium-sulfur battery 1000.

[0037] More specifically, the tapered portion 40b of the needle 40 is inserted into the lid 21 from the outer surface 21a of the lid 21 facing the outside of the sodium container 1005, and the needle 40 is pulled back before the shaft portion 40a of the needle 40 reaches the outer surface 21a of the lid 21. The wall portion 210 is a burr or sharp edge formed when the tapered portion 40b is inserted. By pulling back the needle 40 before the shaft portion 40a reaches the outer surface 21a of the lid 21, it is possible to prevent the wall portion 210 from being dragged out of the sodium container 1005 by the needle 40. This reduces friction between the wall portion 210 and the needle 40, and reduces wear of the needle 40.

[0038] Furthermore, as described above, a predetermined gap is provided between the inner surface of the safety pipe 1004 and the outer surface of the sodium container 1005. If the wall portion 210 were to protrude outward from the sodium container 1005, the flow of sodium 1006 might be obstructed by the wall portion 210. In the sodium-sulfur battery 1000 of this embodiment, the wall portion 210 protrudes inward from the sodium container 1005, thereby preventing obstruction of the flow of sodium 1006.

[0039] The lid 21 has a disc portion 211 and a peripheral wall portion 212 extending from the outer edge of the disc portion 211 in the direction of the thickness of the disc portion 211. The disc portion 211 is positioned to close the opening at the end 20b of the container body 20. The peripheral wall portion 212 is fitted around the outer circumference of the end 20b of the container body 20.

[0040] The flow holes 22 and the wall portion 210 may be formed in the disc portion 211. The wall portion 210 may be formed in an annular shape so as to surround the flow holes 22. The wall portion 210 may extend inclined with respect to the length direction L of the sodium container 1005 such that the diameter of the flow holes 22 decreases as it approaches the inside of the sodium container 1005.

[0041] Preferably, the lid 21 is press-fitted to the end 20b of the container body 20, and no welding is performed between the lid 21 and the end of the container body 20. This configuration eliminates the need for a welding machine and a dust collector to collect dust generated during welding, thereby reducing the manufacturing cost of the sodium-sulfur battery 1000. For example, if the minimum outer diameter of the sodium container 1005 is φ48.67 mm, the maximum inner diameter of the lid 21 is φ48.63 mm, the fit tolerance is an interference fit of 0.04 mm, and no welding marks are visible on the outer surface of the lid 21, then it can be understood that the lid 21 is press-fitted to the end 20b of the container body 20, and no welding is performed between the lid 21 and the end of the container body 20. In this case, the dimensions in the drawing may be φ48.7 + 0.20 / -0.03 mm for the outer diameter of the sodium container 1005, and φ48.6 + 0.03 / -0.05 mm for the inner diameter of the lid 21.

[0042] The overlap width W1 (see Figure 3) between the lid 21 and the end 20b of the container body 20 along the length L of the sodium container 1005 is preferably greater than or equal to the width W2 (see Figure 1) of the gap between the bottom 20a of the container body 20 along the length L of the sodium container 1005 and the member that partitions the negative electrode space 1011 when the sodium container 1005 is placed in the negative electrode space 1011. Having a width W1 greater than or equal to a width W2 reduces the risk of the lid 21 coming off the end 20b of the container body 20 during use of the sodium-sulfur battery 1000. It is more preferable that the width W1 is greater than the width W2, and even more preferable that the width W1 is 1.5 times or more the width W2. Widths W1 and W2 are dimensions that take tolerances into consideration. For example, width W1 may be 5.5 mm and width W2 may be 3.5 mm.

[0043] The overlapping width W1 between the lid 21 and the end 20b of the container body 20 in the length direction L of the sodium container 1005 can be measured as follows. First, with the lid 21 attached to the end 20b of the container body 20, a scribed line is drawn on the end 20b of the container body 20 at the end position of the lid 21. After that, the lid 21 is removed from the end 20b of the container body 20, and the distance between the tip of the end 20b of the container body 20 in the length direction L of the sodium container 1005 and the scribed line is measured. For the measurement of the distance, an instrument such as a height gauge or calipers may be used.

[0044] The member that partitions and forms the negative electrode space 1011 includes a main body and a negative electrode fitting 1009 attached to the end of the main body. In the present embodiment, the main body includes a positive electrode container 1001, a plurality of sulfur molds 1002, a β-alumina solid electrolyte tube 1003, and an insulating ring 1008. The negative electrode fitting 1009 is attached to the insulating ring 1008. The width W2 of the gap between the bottom 20a of the container body 20 and the member that partitions and forms the negative electrode space 1011 may be the distance between the bottom 20a of the container body 20 and the back surface of the negative electrode fitting 1009.

[0045] The width W2 of the gap between the bottom 20a of the container body 20 and the member that partitions and forms the negative electrode space 1011 can be measured by cutting the sodium-sulfur battery 1000 or by projection such as X-rays.

[0046] <Regarding the manufacturing method of the sodium-sulfur battery> Next, the manufacturing method of the sodium-sulfur battery 1000 according to the embodiment of the present invention will be described with reference to FIGS. 4 to 11.

[0047] Figure 4 is a flowchart showing a method for manufacturing a sodium-sulfur battery 1000 according to an embodiment of the present invention. Figure 5 is an explanatory diagram showing the sodium filling step (step S1) of Figure 4. Figure 6 is an explanatory diagram showing the lid attachment step (step S2) of Figure 4, and Figure 7 is a cross-sectional view of the container body 20 and the lid 21 of Figure 6. Figure 8 is an explanatory diagram showing the through-hole forming step (step S3) of Figure 4, and Figure 9 is an enlarged explanatory diagram showing the main part of the through-hole forming step (step S3) of Figure 8. Figure 10 is an explanatory diagram showing the inspection step (step S4) of Figure 4, and Figure 11 is an explanatory diagram showing an example of the outer surface 21a of the lid 21 imaged in the inspection step (step S4) of Figure 10.

[0048] As shown in Figure 4, the method for manufacturing a sodium-sulfur battery 1000 according to an embodiment of the present invention includes a sodium filling step (step S1), a lid attachment step (step S2), a through-hole forming step (step S3), an inspection step (step S4), a sodium container placement step (step S5), and a negative electrode space forming step (step S6).

[0049] The sodium filling step (step S1) is a step of filling sodium 1006 into the container body 20 of the sodium container 1005. As shown in Figure 5, with the container body 20 arranged such that the bottom 20a is positioned downward, a nozzle 30 is inserted into the interior of the container body 20 from above the container body 20, and molten sodium 1006 is poured into the interior of the container body 20 from the tip of the nozzle 30. When starting the filling of sodium 1006, it is preferable to bring the distance between the tip of the nozzle 30 and the bottom 20a of the container body 20 sufficiently close (for example, 10 mm or less) to weaken the collision between the sodium 1006 from the tip of the nozzle 30 and the bottom 20a and reduce the bubbles contained in the sodium 1006. When the liquid level reaches the nozzle 30, the nozzle 30 is pulled up for quantitative filling.

[0050] The lid attachment step (step S2) is a step in which the lid 21 is attached to the end 20b of the container body 20, which is filled with sodium 1006, after the sodium filling step (step S1). In the manufacturing method of this embodiment, as shown in Figure 6, the lid 21 is press-fitted to the end 20b of the container body 20, and welding of the lid 21 and the end 20b of the container body 20 is not performed. This eliminates the need for a welding machine and a dust collector to collect dust generated during welding, thereby reducing the manufacturing cost of the sodium-sulfur battery 1000.

[0051] As described above, the overlap width W1 (see Figure 7) between the lid 21 and the end 20b of the container body 20 along the length L of the sodium container 1005 is preferably greater than or equal to the width W2 (see Figure 1) of the gap between the bottom 20a of the container body 20 along the length L of the sodium container 1005 and the member that partitions the negative electrode space 1011 when the sodium container 1005 is placed in the negative electrode space 1011. By having a width W1 greater than or equal to a width W2, the risk of the lid 21 coming off the end 20b of the container body 20 during use of the sodium-sulfur battery 1000 can be reduced. The method for measuring widths W1 and W2 is as described above.

[0052] These sodium filling process (step S1) and lid attachment process (step S2) are carried out in an atmosphere of an inert gas, such as nitrogen gas. As shown in Figure 7, at the stage of the lid attachment process (step S2), the flow holes 22 are not formed in the lid 21. The lid 21 without the flow holes 22 may be called the lid base. After the sodium filling process (step S1) and the lid attachment process (step S2), the temperature of the sodium container 1005 is lowered and the sodium 1006 solidifies before the next flow hole formation process (step S3) is carried out. The temperature of the sodium container 1005 is lowered to room temperature (for example, 30°C).

[0053] The flow-through hole formation step (step S3) is a step in which a flow-through hole 22 is formed in the lid 21. The flow-through hole formation step (step S3) may be performed after the lid attachment step (step S2). In the manufacturing method of this embodiment, as shown in Figures 8 and 9, a needle 40 is inserted into the lid 21 to form the flow-through hole 22. The sodium container 1005 may be positioned so that the lid 21 is at the bottom, and the needle 40 may be inserted into the lid 21 from below.

[0054] As shown in particular in Figure 9, the needle 40 has a shaft portion 40a and a tapered portion 40b provided at the tip of the shaft portion 40a. In the flow hole formation process (step S3), the tapered portion 40b of the needle 40 is thrust into the lid 21 from the outer surface 21a of the lid 21 facing the outside of the sodium container 1005, and the needle 40 is pulled back before the shaft portion 40a of the needle 40 reaches the outer surface 21a of the lid 21. This prevents the wall portion 210 (burr or sharp edge) formed when the tapered portion 40b is thrust in from being dragged out of the sodium container 1005 by the needle 40. This reduces friction between the wall portion 210 and the needle 40, and reduces wear of the needle 40. Furthermore, if the wall portion 210 were to protrude outward from the sodium container 1005, the flow of sodium 1006 might be obstructed by the wall portion 210. However, by having the wall portion 210 protrude inward from the sodium container 1005, obstruction of the flow of sodium 1006 can be suppressed.

[0055] The opening diameter of the flow hole 22 can be controlled by adjusting the angle θ of the tapered portion 40b and the amount that the tapered portion 40b penetrates the lid 21.

[0056] The inspection step (step S4) is a step performed after the flow hole formation step (step S3) in which the outer surface 21a of the lid 21 is imaged and the flow holes 22 are inspected by image analysis. As shown in Figure 10, imaging may be performed by a camera 50. In the inspection step (step S4), the contour and area of ​​the flow holes 22 can be determined. In the image of the outer surface 21a of the lid 21, the outer surface 21a of the lid 21 appears relatively bright, while the flow holes 22 appear relatively dark. For example, by setting a predetermined analysis area A (Figure 11) in the image of the outer surface 21a of the lid 21 and binarizing analysis area A, the contour of the flow holes 22 can be detected. A preferred shape of the contour of the flow holes 22 is prepared as a predetermined inspection pattern, and the quality of the contour of the flow holes 22 can be determined by comparing the detected contour of the flow holes 22 with the inspection pattern. In addition, the quality of the area of ​​the flow holes 22 can be determined by determining whether the internal area of ​​the detected contour of the flow holes 22 falls within a predetermined range.

[0057] The sodium container placement step (step S5) is a step in which the sodium container 1005, which was determined to be a good product in the inspection step (step S4), is placed inside the member that partitions the negative electrode space 1011. As described above, the member that partitions the negative electrode space 1011 includes a main body and a negative electrode fitting 1009 attached to the end of the main body. In this embodiment, the main body includes a positive electrode container 1001, a plurality of sulfur molds 1002, a β-alumina solid electrolyte tube 1003, and an insulating ring 1008. The main body (positive electrode container 1001, plurality of sulfur molds 1002, β-alumina solid electrolyte tube 1003, and insulating ring 1008) may be pre-assembled on a separate line, and the safety tube 1004 and sodium container 1005 may be placed inside the main body.

[0058] The negative electrode space formation step (step S6) is a step that forms the negative electrode space 1011 after the sodium container placement step (step S5). A sealed negative electrode space 1011 is formed by attaching the negative electrode fitting 1009 to the end of the main body (insulating ring 1008). Degassing of the inside of the main body is performed after the sodium container 1005 is placed inside the main body and before the negative electrode fitting 1009 is attached to the end of the main body.

[0059] The above-described steps—the flow hole formation step (step S3), inspection step (step S4), sodium container placement step (step S5), and negative electrode space formation step (step S6)—are carried out sequentially in a predetermined facility under an atmospheric environment. Multiple sodium containers 1005 are flowed sequentially within the facility, and the above-described steps are performed for each of the sodium containers 1005.

[0060] As described above, the flow-through hole formation process (step S3) is performed with the lid 21 attached to the container body 20 filled with sodium 1006, and the sodium 1006 begins to oxidize from the moment the flow-through holes 22 are formed in the lid 21. In the manufacturing method of this embodiment, the elapsed time from the moment the flow-through holes 22 are formed in the lid 21 is measured. This makes it possible to control the oxidation of sodium 1006. The elapsed time may be measured for each sodium container 1005.

[0061] An alert may be issued when the elapsed time exceeds a predetermined threshold. This can prevent the manufacture of sodium-sulfur batteries 1000 in which sodium 1006 is excessively oxidized.

[0062] As described above, the component that partitions and forms the negative electrode space 1011 includes a main body and a negative electrode fitting 1009 attached to the end of the main body. In this embodiment, the main body includes a positive electrode container 1001, a plurality of sulfur molds 1002, a β-alumina solid electrolyte tube 1003, and an insulating ring 1008. The negative electrode space 1011 is formed by placing a sodium container 1005 inside the main body, and after degassing is performed inside the main body, the negative electrode fitting 1009 is attached to the end of the main body. The elapsed time is measured until degassing is performed inside the main body. This makes it possible to more reliably avoid the manufacture of a sodium-sulfur battery 1000 in which sodium 1006 is excessively oxidized.

[0063] It is preferable that degassing of the main unit is performed so that the elapsed time is within 120 minutes. This makes it possible to more reliably avoid the manufacture of sodium-sulfur batteries 1000 in which sodium 1006 is excessively oxidized. In this case, the threshold for whether or not to issue an alert may be set to 90 minutes. By setting the threshold in this way, it is possible to respond to the alert and rescue the main unit, etc., so that the elapsed time is within 120 minutes.

[0064] As described above, the main body of the component that partitions the negative electrode space 1011 includes a β-alumina solid electrolyte tube 1003. It is preferable that the humidity inside the equipment in which the sodium container 1005 is placed inside the main body is measured. This allows for the control of moisture absorption by the β-alumina solid electrolyte tube 1003. For example, if the humidity remains below 54% for more than 120 minutes, or if the humidity exceeds 54%, the equipment will automatically shut down and issue a notification to take appropriate action.

[0065] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention.

[0066] 20: Container body 21: Lid 21a: Outer surface 22: Flow hole 40: Needle 40a: Shaft 40b: Tapered part 1000: Sodium-sulfur battery 1005: Sodium container 1006: Sodium 1011: Negative electrode space

Claims

1. A method for manufacturing a sodium-sulfur battery comprising a sodium container placed in the negative electrode space, wherein the sodium container has a container body filled with sodium and a lid attached to the container body, the sodium is melted when the sodium-sulfur battery is used, and the lid has a flow hole formed therein for the molten sodium to flow in and out of the sodium container, the method includes a flow hole forming step of piercing the lid with a needle to form the flow hole, the needle has a shaft portion and a tapered portion provided at the tip of the shaft portion, and in the flow hole forming step, the tapered portion is pierced into the lid from the outer surface of the lid facing the outside of the sodium container, and the needle is withdrawn before the shaft portion reaches the outer surface of the lid, the method for manufacturing a sodium-sulfur battery.

2. The method for manufacturing a sodium-sulfur battery according to claim 1, wherein the process of forming the flow holes is performed with the lid attached to the container body filled with sodium, and the elapsed time from the time the flow holes are formed in the lid is measured.

3. The method for manufacturing a sodium-sulfur battery according to claim 2, wherein notification is given when the elapsed time exceeds a predetermined threshold.

4. The member that partitions and forms the negative electrode space includes a main body and a negative electrode fitting attached to the end of the main body, the negative electrode space is formed when the sodium container is placed inside the main body and after degassing is performed inside the main body, the negative electrode fitting is attached to the end of the main body, and the elapsed time is measured until degassing is performed inside the main body, the method for manufacturing a sodium-sulfur battery according to claim 3.

5. The method for manufacturing a sodium-sulfur battery according to claim 4, wherein degassing is performed inside the main body so that the elapsed time is within 120 minutes.

6. The method for manufacturing a sodium-sulfur battery according to claim 4, wherein the main body includes a β-alumina solid electrolyte tube, and the humidity inside the facility in which the sodium container is placed is measured.

7. A method for manufacturing a sodium-sulfur battery according to any one of claims 1 to 6, wherein the lid is press-fitted to the end of the container body and welding is not performed between the lid and the end of the container body.

8. The method for manufacturing a sodium-sulfur battery according to claim 7, wherein the overlap width between the lid and the end of the container body in the longitudinal direction of the sodium container is greater than or equal to the width of the gap between the bottom of the container body in the longitudinal direction of the sodium container and the member that partitions the negative electrode space when the sodium container is placed in the negative electrode space.

9. A method for manufacturing a sodium-sulfur battery according to any one of claims 1 to 6, further comprising an inspection step of imaging the outer surface of the lid and inspecting the flow holes by image analysis after the flow hole formation step.

10. The method for manufacturing a sodium-sulfur battery according to claim 9, wherein the inspection step involves determining the contour and area of ​​the flow hole.

11. A sodium-sulfur battery comprising a sodium container placed in the negative electrode space, wherein the sodium container has a container body filled with sodium and a lid attached to the container body, the sodium is melted when the sodium-sulfur battery is in use, the lid has a flow hole formed therein for the molten sodium to flow in and out of the sodium container, and the lid has a wall portion that protrudes inward toward the inside of the sodium container around the flow hole.

12. The sodium-sulfur battery according to claim 11, wherein the lid is press-fitted to the end of the container body, and there is no welding between the lid and the end of the container body.

13. The sodium-sulfur battery according to claim 12, wherein the overlap width between the lid and the end of the container body in the longitudinal direction of the sodium container is greater than or equal to the width of the gap between the bottom of the container body in the longitudinal direction of the sodium container and the member that partitions the negative electrode space when the sodium container is placed in the negative electrode space.

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