Method for manufacturing sodium-sulfur battery
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NGK CORP
- Filing Date
- 2025-01-30
- Publication Date
- 2026-08-06
Smart Images
Figure JP2025003107_06082026_PF_FP_ABST
Abstract
Description
Method for manufacturing a sodium-sulfur battery
[0001] The present invention relates to a method for manufacturing a sodium-sulfur battery, and more particularly to a method for manufacturing a sodium-sulfur battery applicable to the inspection of a sodium-sulfur battery.
[0002] A sodium-sulfur battery has, for example, a configuration in which a bottomed cylindrical component made of a solid electrolyte such as β-alumina is disposed in a metal container on the anode side, sodium as a cathode active material is accommodated inside the bottomed cylindrical component, and sulfur as an anode active material is accommodated outside. In this sodium-sulfur battery, when discharging, ionized sodium permeates through the solid electrolyte and reacts with sulfur to generate sodium polysulfide while generating electricity. On the contrary, sodium and sulfur are generated by the reverse reaction to perform charging.
[0003] After such a sodium-sulfur battery is manufactured, the initial conditioning and initial performance characteristic inspection of the battery are performed by heating the manufactured sodium-sulfur battery to a raised temperature and performing charge and discharge. Patent Document 1 describes a method of initializing a battery by heating a sodium-sulfur battery after assembly in a heating furnace to a raised temperature and discharging it by a resistive discharge method until the initial peak resistance of the battery is obtained.
[0004] Patent Document 2 describes that in the temperature raising step, the sodium-sulfur battery is heated from room temperature to a temperature equal to or higher than the melting point of sodium polysulfide. In Patent Document 2, it is described that the temperature raising step of the sodium-sulfur battery has three or more temperature gradients until it is heated from room temperature to a temperature equal to or higher than the melting point of sodium polysulfide. Specifically, from 30°C to 90°C, the sodium-sulfur battery is heated at about 8.6°C / h, from 90°C to 150°C, it is heated at about 2.6°C / h, and from 150°C to 300°C, it is heated at about 5.0°C / h.
[0005] Japanese Patent Application Laid-Open No. 2003-163028 International Publication No. 2010 / 082528
[0006] The process of heating and charging / discharging sodium-sulfur batteries after manufacturing to test their initial characteristics is one of the important steps in ensuring the safety and reliability of sodium-sulfur batteries. From a production efficiency standpoint, it is preferable to complete the inspection of sodium-sulfur batteries as early as possible, but the rapid temperature increase of sodium-sulfur batteries due to heating during charge / discharge testing may degrade the thermal or mechanical properties of the sodium-sulfur batteries.
[0007] In view of the above issues, the present invention provides a method for manufacturing a sodium-sulfur battery that can suppress the deterioration of the thermal or mechanical properties of the sodium-sulfur battery during charge-discharge testing.
[0008] The inventors of the present invention have diligently studied to solve the above problems and have created the present invention as illustrated below. [Aspect 1] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery, in which an inspection step for inspecting a sodium-sulfur battery includes a heating step for heating the sodium-sulfur battery before performing a charge-discharge test on the sodium-sulfur battery, the heating step comprising: a first heating step of heating the sodium-sulfur battery from room temperature to 100±10°C at a rate of 0.5 to 5.0°C / h; a second heating step after the first heating step of heating the sodium-sulfur battery to 180±10°C at a rate of 1.0 to 4.0°C / h; and a third heating step after the second heating step of heating the sodium-sulfur battery to 320±10°C at a rate of 1.0 to 10.0°C / h. [Aspect 2] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to Aspect 1, wherein in the first heating step, the sodium-sulfur battery is heated at a rate of 2.0 to 3.5°C / h. [Aspect 3] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 1 or 2, wherein in the second heating step, the sodium-sulfur battery is heated at 1.0 to 2.0°C / h. [Aspect 4] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to any one of aspects 1 to 3, wherein the total heating time in the heating step is 120 hours or less. [Aspect 5] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to any one of aspects 1 to 4, wherein the sodium-sulfur battery is a module battery in which a plurality of cells are connected in series and parallel in a container. [Aspect 6] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 5, wherein after the charge-discharge test, a cooling step is included to lower the temperature of the module battery, and the cooling step includes flowing air into the container of the module battery. [Aspect 7] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 6, wherein the cooling step includes flowing air through a heat dissipation duct located inside the module battery to indirectly cool the cells without directly contacting the cells inside the module battery with air.[Aspect 8] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 6 or 7, wherein the cooling step includes circulating air at a temperature of 305 ± 10°C or lower for the module battery. [Aspect 9] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 8, wherein the cooling step includes circulating air at a temperature of 8.0 to 12.0°C / h for the module battery. [Aspect 10] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 6, wherein the cooling step includes circulating air at a temperature of 90 ± 10°C or lower for the module battery. [Aspect 11] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to aspect 10, wherein the cooling step includes naturally cooling the module battery after charge / discharge testing until the temperature of the module battery is 90 ± 10°C or lower. [Aspect 13] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to any one of aspects 6 to 12, wherein the cooling step includes a temperature measurement step for measuring the temperature of a module battery to be cooled, a prediction step for predicting the start time of air supply to the module battery to be cooled based on the measurement result of the temperature measurement step and the temperature measurement results of other module batteries in past cooling steps, and a control step for controlling the supply of air into the container of the module battery to be cooled based on the prediction result of the prediction step. [Aspect 14] In one embodiment, the present invention is a method for manufacturing a sodium-sulfur battery according to any one of aspects 6 to 13, wherein the module battery is equipped with a temperature measuring instrument capable of measuring the temperature of the side and bottom surfaces of a cell housing container that houses a plurality of cells, and the supply of air into the container of the module battery is controlled so that the difference in the measured temperatures of the side and bottom surfaces is within 20°C.
[0009] According to one embodiment of the present invention, a method for manufacturing a sodium-sulfur battery is provided that can suppress the deterioration of the thermal or mechanical properties of the sodium-sulfur battery during charge-discharge testing.
[0010] This is an explanatory diagram showing an example of the structure of a sodium-sulfur battery according to an embodiment of the present invention. This is an explanatory diagram showing a modified example of a sodium-sulfur battery according to an embodiment of the present invention.
[0011] Embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below are illustrative examples of devices and methods for realizing the technical concept of this invention, and the technical concept of this invention is not limited to the structure, arrangement, etc., of the components described below.
[0012] A method for manufacturing a sodium-sulfur battery according to an embodiment of the present invention includes a heating step in which the sodium-sulfur battery is heated before performing a charge-discharge test on the sodium-sulfur battery, in an inspection step for inspecting the sodium-sulfur battery.
[0013] A sodium-sulfur cell comprises multiple sodium-sulfur cells within a container. The cells of the sodium-sulfur cell are cylindrical in shape. Each cell has a bottomed cylindrical solid electrolyte tube made of β-alumina, with a cathode chamber formed inside and an anode chamber formed outside. The anode chamber contains a mold impregnated with sulfur, the anode active material. Inside the solid electrolyte tube forming the cathode chamber, a cathode container is positioned to house sodium, the cathode active material. Outside the cathode container, a bottomed cylindrical safety tube is positioned between the solid electrolyte tube and the cathode container, with a predetermined gap.
[0014] In the inspection process, it is preferable to inspect a module battery, which is a sodium-sulfur battery, in which multiple cells are connected in series and parallel within a container. The module battery has a configuration in which multiple cells are arranged in a row within a cell housing container for housing the cells, and the multiple cells are electrically connected to each other. Insulating sheets, heaters, wiring, etc. are arranged on the inner surface and bottom surface of the cell housing container. A sand layer formed by laying sand is placed on the top surface of the multiple cells, and a top cover is placed on the top surface of the sand layer via insulating material, heat-resistant material, fire-resistant material, etc.
[0015] During charge-discharge testing, the temperature inside the module battery is controlled by measuring the temperature using a thermometer, typically a thermocouple, inserted at a predetermined location within the module battery. The thermometer is typically located on the side and bottom of the container, but its placement is not particularly limited. During the testing process, the module battery is placed in a testing furnace to raise its temperature. However, depending on the heating conditions, the temperature of the cells inside the module battery container may become uneven. Specifically, if the heating conditions are not appropriate, the temperature at the corners of the cell container may be higher than the temperature at the center, which can lead to a large difference in thermal expansion between the anode container and the solid electrolyte tube of cells located at the corners. As a result, thermal stress may occur between the anode container and the solid electrolyte tube, causing deformation or damage to the solid electrolyte tube, which may prevent proper pre-shipment testing.
[0016] According to the method for manufacturing a sodium-sulfur battery in an embodiment of the present invention, the inspection step for inspecting the sodium-sulfur battery includes a heating step for heating the sodium-sulfur battery before performing a charge-discharge test on the sodium-sulfur battery. The heating step includes a first heating step of heating the sodium-sulfur battery from room temperature to 100 ± 10°C at a rate of 0.5 to 5.0°C / h, a second heating step after the first heating step of heating the sodium-sulfur battery to 180 ± 10°C at a rate of 1.0 to 4.0°C / h, and a third heating step after the second heating step of heating the sodium-sulfur battery to 320 ± 10°C at a rate of 1.0 to 10.0°C / h.
[0017] Thus, the heating process is divided into a first heating process, a second heating process, and a third heating process. By appropriately controlling the heating rate in each process, the temperature distribution of multiple cells within the sodium-sulfur battery module becomes more uniform compared to conventional methods. As a result, it becomes possible to suppress the deterioration of the thermal or mechanical properties of the sodium-sulfur battery due to heating during charge-discharge testing, particularly the deformation or damage of the solid electrolyte tubes of the cells in the corners of the module battery container.
[0018] In sodium-sulfur batteries, the deterioration of the thermal or mechanical properties due to the melting of sodium and sulfur is minimal until the temperature reaches around 100°C. Therefore, even if the heating rate of a sodium-sulfur battery is increased to a certain extent, deterioration of the thermal or mechanical properties of the sodium-sulfur battery is unlikely to occur. On the other hand, if the heating rate of a sodium-sulfur battery is increased too much before reaching around 100°C, the temperature distribution inside the battery becomes uneven, and the temperature difference between multiple cells in the module battery that makes up the sodium-sulfur battery may become large.
[0019] The first heating step preferably involves raising the sodium-sulfur cell temperature from room temperature to 100 ± 10°C at a rate of 1.0 to 4.5°C / h, more preferably 1.5 to 4.0°C / h, even more preferably 2.0 to 3.5°C / h, and even more preferably 3.5 to 3.0°C / h. Room temperature refers to a temperature approximately equal to the temperature of the atmosphere in which the sodium-sulfur cell is placed.
[0020] The second heating step includes the temperature range in which the sodium and sulfur in the sodium-sulfur cell are dissolved. If the heating rate is too high, it may accelerate the deterioration of the thermal or mechanical properties of the sodium-sulfur cell. The second heating step is preferably performed by heating from 100±10°C to 180±10°C at a rate of 1.0 to 3.0°C / h, more preferably 1.0 to 2.0°C / h, even more preferably 1.2 to 1.8°C / h, and still more preferably 1.4 to 1.6°C / h.
[0021] The third heating step involves raising the temperature above the melting point of sodium polysulfide (Na2S5), and includes the temperature range in which sodium polysulfide begins to form in the sodium-sulfur cell. Therefore, the heating rate should not be too high, but if the heating rate is too low, the time required for charge-discharge testing will be longer.
[0022] The third heating step is preferably performed by raising the temperature from 180±10°C to 320±10°C at a rate of 1.0 to 7.0°C / h, more preferably at a rate of 3.0 to 6.0°C / h, and even more preferably at a rate of 4.0 to 5.5°C / h.
[0023] In the above description, the heating rate of the sodium-sulfur battery is expressed as the average heating rate in "°C / hr". The heating temperature of the sodium-sulfur battery is the temperature obtained by considering a tolerance of ±10°C as a temperature control range from the set value of the heating temperature of the sodium-sulfur battery. In this embodiment, the tolerance may be ±7°C, ±5°C, ±3°C, or ±0°C. For example, a heating temperature up to 100±10°C means any temperature within the range of 90 to 110°C, but it may be 93 to 107°C considering a tolerance of ±7°C, 95 to 105°C considering a tolerance of ±5°C, 97 to 103°C considering a tolerance of ±3°C, or 100°C. Furthermore, the heating rate of the sodium-sulfur battery can be measured by the measurement value of the temperature measuring instrument provided in the sodium-sulfur battery. Multiple temperature measuring instruments may be placed at arbitrary locations within the module battery. Temperature control of a sodium-module battery can be achieved, for example, by utilizing the measurements of temperature measuring instruments placed on the central bottom surface and the central side of the module battery. In particular, in this embodiment, the measurement result from the central bottom surface can be used as a representative point for the temperature of the sodium-sulfur battery.
[0024] If the total heating time for the first to third heating processes in the heating process is too long, the time required for the inspection process will become too long, which may not be desirable in terms of production efficiency. The total heating time is preferably within 120 hours, more preferably within 115 hours, and even more preferably within 110 hours.
[0025] After the sodium-sulfur battery reaches the test temperature of 320 ± 10°C, a charge-discharge test is performed. The specific method of the charge-discharge test is not particularly limited. For example, the charge-discharge test may be performed by dividing the discharge current value into multiple stages using a resistive discharge method until the initial peak resistance of the sodium-sulfur battery is obtained. The charge-discharge test of the sodium-sulfur battery can be performed at around 300°C (290°C to 310°C).
[0026] After the charge-discharge test, a cooling process is performed to lower the temperature of the sodium-sulfur battery. When testing a module battery in which multiple cells are connected in series and parallel within a container as a sodium-sulfur battery, it is preferable to circulate air inside the module battery container during the cooling process.
[0027] For example, as shown in Figure 1, the module battery 100 includes a fan 103 positioned on the outer surface of a cell housing container 102a that constitutes the lower part of the container 102 and has a battery area 101 for housing a plurality of cells (not shown) inside, and a heat dissipation duct 104 positioned above the battery area 101 and below the upper lid 102b that constitutes the upper part of the container 102, and connected to the fan 103. In the cooling process, it is preferable to drive the fan 103 to flow air through the heat dissipation duct 104 located inside the module battery 100, thereby indirectly cooling the cells without directly exposing them to air.
[0028] As shown in Figure 2, the module battery 100 may be equipped with a heat dissipation duct 114 at the bottom of the battery region 101. In the cooling process, the cells may be indirectly cooled without direct contact of air with the cells inside the module battery 100 by flowing air through at least one of the heat dissipation ducts 104 and 114 located inside the module battery 100.
[0029] In the cooling process, it is preferable to circulate air inside the module battery 100 when the temperature of the module battery 100 is 305±10℃ or lower. After the charge / discharge test of the module battery 100, cooling by supplying air is started immediately when the temperature of the module battery 100 falls below 305±10℃, thereby shortening the time required to cool the module battery 100. The cooling rate of the module battery 100 is preferably 8.0 to 12.0℃ / h, more preferably 9.0 to 11.0℃ / h, and even more preferably 9.5 to 10.5℃ / h.
[0030] Because the module battery 100 contains insulating materials and the like, it can take a long time to cool down. For example, when the module battery 100 is allowed to cool naturally, the cooling time is usually around 0.3°C / h. According to the cooling process of this embodiment, the module battery 100 can be cooled to 8.0 to 12.0°C / h, which significantly reduces the cooling time compared to natural cooling. As a result, the production volume of the module battery 100 can be increased.
[0031] In the cooling process, it is preferable to circulate air inside the module battery 100 when the temperature of the module battery 100 is 90±10℃ or lower. When the temperature of the module battery 100 is 90±10℃, the sodium and sulfur inside the module battery 100 solidify. By starting the cooling of the module battery 100 when the temperature of the module battery 100 reaches 100±10℃, cooling by air supply occurs after the sodium inside the cell has solidified. As a result, cell failure caused by forcibly cooling during the state change of the active material inside the cell from liquid phase to solid phase can be suppressed.
[0032] Specifically, it is preferable that the module battery temperature is 90 ± 10°C or lower, and that the module battery 100 be cooled down at a rate of 8.0 to 12.0°C / h by circulating air inside the module battery 100, more preferably at a rate of 9.0 to 11.0°C / h, and even more preferably at a rate of 9.5 to 10.5°C / h.
[0033] In the cooling process, if the cooling process is started when the temperature of the module battery 100 is too high, the temperature difference depending on the location of the cells within the module battery 100 may become too large, potentially causing some cells to fail. On the other hand, if the cooling process is started when the temperature of the module battery 100 is too low, the cooling effect will be small, and the time required for the cooling process may be prolonged.
[0034] The cooling process preferably involves allowing the module battery 100 to cool naturally after the charge / discharge test until its temperature drops to 90°C ± 10°C or below, and then starting to circulate air inside the module battery 100 when its temperature is 90°C ± 10°C or below. This suppresses the deterioration of the thermal or mechanical properties of the module battery 100 during the charge / discharge test.
[0035] In the cooling process, it is preferable to minimize the temperature difference within the module battery 100 in order to prevent deterioration of the thermal or mechanical properties of some of the cells within the module battery 100. In one embodiment, the module battery 100 is equipped with a temperature measuring device capable of measuring the temperature of the side and bottom surfaces of the cell housing container 102a in which a plurality of cells are housed, and it is preferable that the cooling process controls the supply of air into the container of the module battery 100 so that the difference in the measured temperatures of the side and bottom surfaces of the cell housing container 102a is within 20°C. The difference in measured temperatures of the side and bottom surfaces is preferably within 18°C, more preferably within 15°C, and even more preferably within 10°C. The cooling rate by supplying air is preferably controlled, for example, by controlling the time for which the fan 103 is turned on or off.
[0036] In addition, automatic control using a general-purpose computer or other processing unit may be performed during the cooling process of the module battery 100. This embodiment may include a temperature measurement step for measuring the temperature of the module battery to be cooled, a prediction step for predicting the start time of air supply to the module battery to be cooled based on the measurement results of the temperature measurement step and the temperature measurement results of other module batteries in past cooling processes, and a control step for controlling the supply of air into the container of the module battery to be cooled based on the prediction results of the prediction step.
[0037] For example, the temperature measurement result of the module battery 100 is configured to be output to the processing unit. The processing unit measures the temperature of the module battery 100 to be cooled (temperature measurement step). The processing unit is equipped with a memory device that stores the temperature measurement results of other module batteries in past cooling steps, and can perform a process to predict the start time of air supply to the module battery to be cooled based on the measurement result of the module battery 100 in the temperature measurement step and the temperature measurement results of other module batteries in past cooling steps (prediction step).
[0038] The specific form of the prediction process is not particularly limited. For example, the processing device may predict the air supply start time or the cooling start temperature by performing regression analysis with the temperature changes of other module batteries in past cooling processes and the measurement results of module battery 100 as explanatory variables, and the air supply start time of module battery as the dependent variable. The processing device may also predict the air supply start time or the cooling start temperature of module battery by performing machine learning using the temperature measurement results of other module batteries in past cooling processes and the measurement results of module battery 100 in the temperature measurement process. Based on the prediction results of the prediction process, the processing device controls the supply of air into the container of the module battery to be cooled (control process). Based on the failure results of other module batteries in past cooling processes, the processing device can control the air supply time to module battery 100 so that the cooling rate of module battery 100 is appropriate. According to this embodiment, since the processing device can automatically control the cooling process of module battery 100 based on the measurement results of module battery 100, the cooling process can be automated and optimized while suppressing the deterioration of the quality of module battery 100.
[0039] Although the present invention has been described by the embodiments described above, the descriptions and drawings that constitute part of this disclosure should not be understood as limiting the invention. This disclosure is not limited to the embodiments described above, and its components can be combined and modified to embody it without departing from its spirit.
[0040] For example, in the above example, the inspection process for sodium-sulfur batteries was described as the inspection process for module batteries. However, this method can also be applied to a cell inspection process in which, after assembling the cells of a sodium-sulfur battery, the assembled cells are heated to perform initial conditioning and cell inspection to check whether they meet predetermined electrical characteristics. This can suppress cell failures caused by heating during initial conditioning and cell inspection.
[0041] The following are embodiments of the present invention, provided to better understand the present invention and its advantages, and are not intended to limit the present invention.
[0042] A module battery A was prepared, consisting of multiple cells connected in series and parallel within a container. Module battery A was placed in a test furnace and heated from room temperature to 100°C at a rate of 3.0°C / hr. After the temperature at the bottom center of the cell housing container of module battery A reached 100°C, module battery A was heated to 180°C at a rate of 1.4°C / hr. After module battery A reached 180°C, it was heated to 310°C at a rate of 5.1°C / hr and the heating was stopped. The total heating time for module battery A was 108 hours. After heating, electrical characteristics such as resistance, withstand voltage, and insulation resistance of module battery A were tested, followed by a charge-discharge test. The charge-discharge test was performed correctly until the end of the discharge. After the charge-discharge test, module battery A was removed from the test furnace and allowed to cool naturally. After it reached 90°C, air was flowed through a heat dissipation duct located inside the module battery to cool it to room temperature at a rate of 8.0°C / hr. By supplying air into module battery A to lower its temperature, the cooling time could be reduced by more than 14 days compared to natural cooling, thereby increasing the production volume of module batteries.
[0043] Module battery B, in which multiple cells were connected in series and parallel within a container, was placed in a test furnace. The temperature was raised from room temperature to 90°C at 8.6°C / h, then from 90°C to 150°C at approximately 2.6°C / h, and from 150°C to 300°C at approximately 5.0°C / h before the heating was stopped. The temperature of module battery B during heating was controlled by measurements taken at the bottom center of the cell housing, similar to module battery A. For both module battery A and module battery B, the temperature change at each position during heating was evaluated using a temperature measuring device installed at the bottom center of the cell housing and a temperature measuring device grounded at the corners of the cell housing. In the temperature range of 100 to 180°C, which is most likely to accelerate the deterioration of the thermal or mechanical properties of sodium-sulfur batteries, the temperature difference between the corners and the center of module battery A was smaller than that of module battery B, and the heating rates were also almost identical. On the other hand, in the case of module battery B, the temperature at the corners was unstable in the temperature range below 150°C, and it was confirmed that the temperature difference between the corners and the center was larger than that of module battery A. In addition, the difference in the rate of heating between the corners and the center of module battery B in the temperature range below 150°C was also larger than that of module battery A.
[0044] 100: Module battery 101: Battery area 102: Container 102a: Cell housing container 102b: Top cover 103: Fan 104, 114: Heat dissipation duct
Claims
1. A method for manufacturing a sodium-sulfur battery, comprising: an inspection step for inspecting a sodium-sulfur battery, in which, before performing a charge-discharge test on the sodium-sulfur battery, a heating step for heating the sodium-sulfur battery, wherein the heating step includes: a first heating step of heating the sodium-sulfur battery from room temperature to 100 ± 10°C at a rate of 0.5 to 5.0°C / h; a second heating step, after the first heating step, of heating the sodium-sulfur battery to 180 ± 10°C at a rate of 1.0 to 4.0°C / h; and a third heating step, after the second heating step, of heating the sodium-sulfur battery to 320 ± 10°C at a rate of 1.0 to 10.0°C / h.
2. The method for producing a sodium-sulfur battery according to claim 1, comprising raising the temperature of the sodium-sulfur battery at 2.0 to 3.5°C / h in the first heating step.
3. The method for producing a sodium-sulfur battery according to claim 1, comprising raising the temperature of the sodium-sulfur battery by 1.0 to 2.0°C / h in the second heating step.
4. The method for manufacturing a sodium-sulfur battery according to claim 1, wherein the total heating time in the heating step is within 120 hours.
5. A method for manufacturing a sodium-sulfur battery according to any one of claims 1 to 4, comprising inspecting a module battery in which a plurality of cells are connected in series and parallel within a container, as the sodium-sulfur battery.
6. The method for manufacturing a sodium-sulfur battery according to claim 5, comprising a cooling step for lowering the temperature of the module battery after the charge-discharge test, wherein the cooling step includes circulating air into the container of the module battery.
7. The method for manufacturing a sodium-sulfur battery according to claim 6, wherein the cooling step includes indirectly cooling the cells in the module battery without directly exposing them to air by flowing air through a heat dissipation duct located inside the module battery.
8. The method for manufacturing a sodium-sulfur battery according to claim 6, wherein the cooling step includes flowing the air when the temperature of the module battery is 305 ± 10°C or lower.
9. A method for manufacturing a sodium-sulfur battery according to claim 8, comprising lowering the temperature of the module battery at 8.0 to 12.0°C / h.
10. The method for manufacturing a sodium-sulfur battery according to claim 6, wherein the cooling step includes flowing the air when the temperature of the module battery is 90 ± 10°C or lower.
11. A method for manufacturing a sodium-sulfur battery according to claim 10, comprising lowering the temperature of the module battery at 8.0 to 12.0°C / h.
12. The method for manufacturing a sodium-sulfur battery according to claim 10, wherein the cooling step includes allowing the module battery to cool naturally after the charge / discharge test until the temperature of the module battery is 90°C ± 10°C or less.
13. The method for manufacturing a sodium-sulfur battery according to claim 6, wherein the cooling step includes: a temperature measurement step of measuring the temperature of a module battery to be cooled; a prediction step of predicting the start time of air supply to the module battery to be cooled based on the measurement result of the temperature measurement step and the temperature measurement results of other module batteries in past cooling steps; and a control step of controlling the supply of air into the container of the module battery to be cooled based on the prediction result of the prediction step.
14. The method for manufacturing a sodium-sulfur battery according to claim 6, comprising: a temperature measuring device capable of measuring the temperature of the side and bottom surfaces of a cell housing container in which the plurality of cells are housed; and controlling the supply of air into the container of the module battery so that the difference in the measured temperatures of the side and bottom surfaces is within 20°C.