Method for manufacturing sealed storage battery

Abstract

To provide a method for manufacturing a sealed storage battery, capable of removing or reducing, before an injection port is welded, an electrolyte adhering to the back side of a battery case, where the injection port is formed, to reduce defects in a welded portion, thereby improving the sealability of a battery case.SOLUTION: There is provided a method for manufacturing a sealed storage battery 10 that includes a battery case 1 and an electrode body 2, and that has an injection port 121 through which an electrolyte 5 is injected into the battery case and a plug body 122 sealing the inlet port by welding, on one case wall part 12 constituting the battery case. The method includes: an electrolyte injection step S1 of injecting the electrolyte through the injection port into the battery case; an electrolyte vaporization step S2 of, after the electrolyte injection step, heating the top face 12a side of the one case wall part and vaporizing the electrolyte adhering to the back face 12b side of the one case wall part; and a plug body welding step S3 of, after the electrolyte vaporization step, welding the injection port and the plug body together. In the electrolyte vaporization step, the top face side of the one case wall part is heated while the pressure in the battery case is reduced to less than one atmosphere.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The disclosed technology relates to a method for manufacturing a sealed battery.

Background Art

[0002] For example, Patent Document 1 discloses a method for manufacturing a battery in which, after an electrode body is housed in a battery case, an electrolyte injection nozzle is inserted into the battery case through an injection port, and the electrolyte is discharged from a discharge port formed on the side surface of the tip of the injection nozzle to inject a required amount of the electrolyte into the battery case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above method for manufacturing a battery, droplets of the electrolyte discharged from the discharge port of the injection nozzle may adhere to the back surface side of the battery case. Also, usually, after the injection of the electrolyte, the injection port is sealed with a plug and welded. Therefore, when droplets of the electrolyte adhere to the back surface side of the battery case, the droplets are vaporized by the welding heat, and the pressure inside the battery case increases. As a result, gas inside the battery case intrudes as bubbles into the molten metal formed during the welding of the injection port and the plug, causing defects such as pinholes in the welded portion and reducing the sealing performance of the battery case.

[0005] The disclosed technology has been made in view of such problems, and an object thereof is to provide a method for manufacturing a sealed battery that can reduce defects in the welded portion by removing or reducing the electrolyte adhering to the back surface side of the battery case having an injection port before welding the injection port, and improve the sealing performance of the battery case.

Means for Solving the Problems

[0006] (1) One aspect of the disclosed technology for solving the above problems includes a battery case and an electrode body housed in the battery case. In a method for manufacturing a sealed rechargeable battery having an injection port for injecting an electrolytic solution into the battery case and a plug body for sealing the injection port by welding on one case wall portion constituting the battery case, after housing the electrode body in the battery case, an electrolytic solution injection step of injecting the electrolytic solution into the battery case through the injection port, an electrolytic solution vaporization step of heating the surface side of the one case wall portion after the electrolytic solution injection step to vaporize the electrolytic solution adhering to the back side of the one case wall portion, and a plug body welding step of welding the injection port and the plug body after the electrolytic solution vaporization step are provided. In the electrolytic solution vaporization step, it is a method for manufacturing a sealed rechargeable battery in which the surface side of the one case wall portion is heated in a state where the pressure inside the battery case is reduced to less than one atmosphere.

[0007] (2) In the method for manufacturing a sealed rechargeable battery according to (1), in the plug body welding step, it is preferable to seal the injection port with the plug body in a state where the pressure inside the battery case is reduced to less than one atmosphere and then weld the injection port and the plug body.

[0008] (3) In the method for manufacturing a sealed rechargeable battery according to (1) or (2), in the electrolytic solution vaporization step, it is preferable to heat the vicinity of the injection port closer to the injection port more strongly than the injection port separation portion separated from the injection port.

[0009] (4) In the method for manufacturing a sealed rechargeable battery according to any one of (1) to (3), the electrolytic solution includes a plurality of solvents having different boiling points. In the electrolytic solution vaporization step, it is preferable to heat the surface side of the one case wall portion to a temperature at which more of the solvents having a lower boiling point than the solvent having the highest boiling point among the solvents are vaporized.

[0010] (5) In the method for manufacturing a sealed rechargeable battery according to any one of (1) to (4), in the electrolytic solution vaporization step, it is preferable to heat the surface side of the one case wall portion using a far-infrared heater having a current control function.

Brief Description of the Drawings

[0011]

Figure 1

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Embodiments for Carrying Out the Invention

[0012] <Description of the Present Sealed Rechargeable Battery> Next, the configuration of the sealed rechargeable battery manufactured by the method for manufacturing a sealed rechargeable battery according to one aspect of the above-disclosed technology will be described in detail with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of the sealed rechargeable battery manufactured by the method for manufacturing a sealed rechargeable battery according to one aspect of the present embodiment. FIG. 2 shows a schematic perspective view of a state during winding in which the positive electrode body and the negative electrode body of the electrode body shown in FIG. 1 are laminated with a separator interposed therebetween and wound. FIG. 3 shows a cross-sectional view taken along line A-A shown in FIG. 1. FIG. 4 shows a cross-sectional view taken along line B-B shown in FIG. 1. Here, the X direction indicates the longitudinal direction of the sealing body, the Y direction indicates the short-side direction of the sealing body, and the Z direction indicates the vertical direction of the sealing body.

[0013] As shown in FIGS. 1 to 4, the sealed rechargeable battery 10 includes a battery case 1, an electrode body 2, a current collecting terminal 4, and an electrolytic solution 5. One case wall portion 12 constituting the battery case 1 has an injection port 121 for injecting the electrolytic solution 5 into the battery case 1 and a plug body 122 for sealing the injection port 121 by welding. A welded portion 123 is formed over the entire circumference at the boundary between the injection port 121 and the plug body 122. The electrolytic solution 5 injected from the injection port 121 is impregnated into the electrode body 2, and a part of it is stored near the bottom of the battery case 1. The stored electrolytic solution 5 can be replenished into the electrode body 2. Further, one case wall portion 12 is provided with a safety valve 124 formed to be able to open as the pressure in the battery case 1 rises.

[0014] Here, the battery case 1 includes a bottomed rectangular tube-shaped case body 11 having a rectangular opening 111 and a long and flat sealing body 12 for sealing the opening 111. The sealing body 12 corresponds to one case wall portion 12. The case body 11 corresponds to the other case wall portions 11 (including the long side wall portions 11A and 11B, the short side wall portions 11C and 11D, and the bottom wall portion 11E). The battery case 1 is made of, for example, aluminum or an aluminum alloy. Note that the battery case 1 only needs to be airtight inside, and is not limited to the above form.

[0015] Further, the electrode body 2 is formed by laminating a positive electrode body 21 and a negative electrode body 22 with a separator 23 interposed therebetween, and is housed in the battery case 1. The positive electrode body 21 and the negative electrode body 22 each have an active material coating portion 212, 222 in which active materials KT1, KT2 are coated on electrode foils 21K, 22K, and an active material non - coating portion 211, 221 in which the active materials KT1, KT2 are not coated on one - end portions 21K1, 22K1 of the electrode foils 21K, 22K.

[0016] The active material non - coating portion 211 of the positive electrode body 21 and the active material non - coating portion 221 of the negative electrode body 22 are arranged to face each other in the longitudinal direction (X direction) of the sealing body (one case wall portion) 12. The active material coating portions 212, 222 are formed on the other - end portions 21K2, 22K2 and the intermediate portions 21K3, 22K3 of the electrode foils 21K, 22K. Here, the electrode body 2 is formed by laminating a positive electrode body 21 and a negative electrode body 22 with a separator 23 interposed therebetween and is wound in a flat shape, but the sheet - like positive electrode body 21 and negative electrode body 22 may be laminated in a planar shape with a separator 23 interposed therebetween.

[0017] For example, in a lithium - ion secondary battery which is an example of the sealed storage battery 10, the electrode foil 21K of the positive electrode body 21 uses, for example, an aluminum foil, and the active material KT1 coated thereon uses, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNiO 2 etc.). Also, the electrode foil 22K of the negative electrode body 22 uses, for example, a copper foil, and the active material KT2 coated thereon uses, for example, graphite, hard carbon, soft carbon, etc. Also, the separator 23 can use a porous sheet such as a polypropylene resin or a polyethylene resin. Note that as the electrolytic solution 5, a known non - aqueous electrolytic solution can be used.

[0018] Further, the current collector terminal 4 has a positive current collector terminal 4A and a negative current collector terminal 4B. The positive current collector terminal 4A is made of, for example, aluminum, and the negative current collector terminal 4B is made of, for example, copper. The positive and negative current collector terminals 4 (4A, 4B) each have a base portion 41, a base adjacent portion 42, and a lead portion 43 that are integrally formed. Here, the base portion 41 is coupled to the back surfaces of both end portions 12R in the longitudinal direction (X direction) of the sealing body (one case wall portion) 12 with an insulating member 3 interposed therebetween, but it is not necessarily limited to this. For example, the base portion 41 may be coupled to the back surfaces of both end portions in the longitudinal direction (X direction) of the case body (another case wall portion) 11 with an insulating member 3 interposed therebetween.

[0019] Also, the base adjacent portion 42 is adjacent to the base portion 41 and is in contact with the insulating member 3. Here, the lead portion 43 is bent downward in the case direction (Z direction) from the base adjacent portion 42 at the position of the lead upper end portion 43a above the case. The electrode foils 21K, 22K of the non-active material coated portions 211, 221 of the electrode body 2 are welded and joined to the lead lower end portion 43b below the case of the lead portion 43 in a superposed state (current collecting foil state) and are electrically connected.

[0020] Note that the base portion 41 is coupled to an external connection portion 45 located at both longitudinal ends 12R on the surface 12a side of the sealing body (one case wall portion) 12 by, for example, caulking pins 46 or the like. An insulating member 3 also serving as a sealing material is interposed between the caulking pins 46 and the external connection portion 45 and the sealing body (one case wall portion) 12. The insulating member 3 can use, for example, polyphenylene sulfide (PPS) resin. When a plurality of the hermetically sealed secondary batteries 10 are connected, a connecting bus bar (not shown) is connected to the external connection portion 45. Further, the external connection portion 45 may be integrally formed with the base portion 41. In this case, the sealing body (one case wall portion) 12, the external connection portion 45, and the base portion 41 may be insert molded with the insulating member 3.

[0021] <Method for manufacturing the hermetically sealed secondary battery> Next, a method for manufacturing a sealed storage battery according to another embodiment of the disclosed technology will be described in detail with reference to the drawings. FIG. 5 shows a flowchart representing the method for manufacturing the sealed storage battery shown in FIG. 1. FIG. 6 shows a schematic cross-sectional view in the C-C cross-section shown in FIG. 4, depicting a state in which an electrolytic solution is being injected into the battery case in the electrolytic solution injection step shown in FIG. 5. FIGS. 7 and 8 are schematic cross-sectional views in the C-C cross-section shown in FIG. 4, showing a state in which the electrolytic solution is being vaporized with the pressure inside the battery case reduced to below atmospheric pressure in the electrolytic solution vaporization step shown in FIG. 5, and a state in which the boundary between the injection port and the plug body is being welded in the plug body welding step shown in FIG. 6, respectively.

[0022] As shown in FIG. 5, the method for manufacturing the sealed storage battery 10 includes an electrolytic solution injection step S1, an electrolytic solution vaporization step S2, and a plug body welding step S3. As shown in FIG. 6, the electrolytic solution injection step S1 is a step of injecting the electrolytic solution 5 into the battery case 1 through the injection port 121 after housing the electrode body 2 in the battery case 1. Here, the electrolytic solution 5 is injected into the battery case 1 from an injection nozzle 6 inserted into the gap between the sealing body (one case wall portion) 12 and the electrode body 2, but it may also be injected by other methods.

[0023] As shown in FIG. 6, on the side wall of the injection nozzle 6, a circular discharge port 61 for discharging the electrolytic solution 5 is opened in the longitudinal direction (X direction) of the sealing body (one case wall portion) 12 in the gap between the back surface 12b of the sealing body (one case wall portion) 12 and the upper end portion 24 of the electrode body 2. The electrolytic solution 5 is scattered radially in the longitudinal direction (X direction) of the sealing body (one case wall portion) 12 from the discharge port 61. Therefore, the electrolytic solution 5 may adhere as droplets 51 to the back surface 12b side of the sealing body (one case wall portion) 12. The droplets 51 of the electrolytic solution 5 are more likely to adhere to the injection port vicinity portion 121K closer to the injection port 121 than to the injection port separation portion 121L separated from the injection port 121 of the sealing body (one case wall portion) 12. The injection nozzle 6 is connected to a supply device (not shown) for the electrolytic solution 5. In the electrolytic solution injection step S1, a required amount of the electrolytic solution 5 supplied from the supply device is injected into the battery case 1 from the discharge port 61 of the injection nozzle 6.

[0024] Further, as shown in FIG. 7, the electrolytic solution vaporization step S2 is a step of heating the surface 12a side of the sealing body (one case wall portion) 12 by the heating device 7 after the electrolytic solution injection step S1 and vaporizing the electrolytic solution 5 (51) adhering to the back surface 12b side of the sealing body (one case wall portion) 12. In the electrolytic solution vaporization step S2, the surface 12a side of the sealing body (one case wall portion) 12 is heated in a state where the pressure P1 in the battery case 1 is reduced to less than atmospheric pressure. The heating device 7 may be in contact with or separated from the surface 12a of the sealing body (one case wall portion) 12. By heating in a state where the pressure P1 in the battery case 1 is reduced to less than atmospheric pressure in this way, the boiling point of the electrolytic solution 5 (51) adhering to the back surface 12b side of the sealing body (one case wall portion) 12 can be lowered, and it can be rapidly vaporized at a lower temperature.

[0025] Note that, for example, as shown in FIG. 7, a method of reducing the pressure P1 in the battery case 1 to less than atmospheric pressure is to connect a suction tube 8 connected to a vacuum pump (not shown) to the injection port 121 and discharge the gas in the battery case 1 to the outside through the suction tube 8 to reduce the pressure, or to store the battery case 1 with the injection port 121 opened in a chamber (not shown) where the pressure P1 is reduced to less than atmospheric pressure to reduce the pressure, etc. Here, the injection port 121 is formed in a stepped shape with a large-diameter plug body joining hole 121a that joins with the plug body 122 and a small-diameter nozzle insertion hole 121c through which the injection nozzle 6 is inserted. An annular flange portion 121b that abuts against the back surface of the plug body 122 is formed between the plug body joining hole 121a and the nozzle insertion hole 121c. The suction tube 8 can be fitted into the plug body joining hole 121a.

[0026] Also, in the method of reducing the pressure by discharging the gas in the battery case 1 to the outside through the suction tube 8, the vaporized electrolytic solution 5 (51) is discharged to the outside and is less likely to remain in the battery case 1. Therefore, when the sealing body (one case wall portion) 12 is heated by welding heat in the plug body welding step S3, re-vaporization of the electrolytic solution 5 (51) remaining in the battery case 1 is also less likely to occur. Therefore, the pressure in the battery case 1 is less likely to rise further, and the risk of welding defects such as pinholes occurring in the welded portion 123 between the injection port 121 and the plug body 122 can be reduced.

[0027] Further, as shown in FIG. 8, the plug body welding step S3 is a step of welding the injection port 121 and the plug body 122 after the electrolytic solution vaporization step S2. As described above, the injection port 121 is formed with a large-diameter plug body joining hole 121a that joins with the plug body 122 and a small-diameter nozzle insertion hole 121c through which the injection nozzle 6 is inserted in a stepped manner. An annular flange portion 121b that abuts against the back surface of the plug body 122 is formed between the plug body joining hole 121a and the nozzle insertion hole 121c. In the plug body welding step S3, after the electrolytic solution vaporization step S2, the plug body 122 is inserted into the plug body joining hole 121a of the injection port 121, and with the back surface of the plug body 122 and the annular flange portion 121b in contact, the inner periphery of the plug body joining hole 121a and the outer periphery of the plug body 122 are butt-welded to form a welded portion 123 over the entire boundary portion between the injection port 121 and the plug body 122. Note that, for example, a laser welding method in which the laser beam 91 of the fiber laser welder 9 is irradiated from the surface 12a side of the sealing body (one case wall portion) 12 is preferable as the welding method for the above butt welding. This is because the heat input to the sealing body (one case wall portion) 12 is small and welding can be performed in a short time.

[0028] As described above, since the manufacturing method of the sealed rechargeable battery 10 includes the electrolytic solution injection step S1, the electrolytic solution vaporization step S2, and the plug body welding step S3, in the plug body welding step S3, the pressure inside the battery case 1 is less likely to rise, and the risk of welding defects such as pinholes occurring in the welded portion 123 between the injection port 121 and the plug body 122 can be reduced. As a result, it is possible to provide a manufacturing method for manufacturing a high-quality sealed rechargeable battery 10 with improved sealing performance of the welded portion 123. Further, in the electrolytic solution injection step S1, by lowering the boiling point of the electrolytic solution 5, the heating time can be shortened to improve productivity, while manufacturing a high-performance and high-quality sealed rechargeable battery 10 with less deterioration of the electrolytic solution 5, the electrode body 2, etc. due to the temperature rise.

[0029] Further, in the method for manufacturing the sealed battery 10, in the plug welding step S3, as shown in FIG. 8, after the inlet 121 is sealed with the plug body 122 in a state where the pressure P2 inside the battery case 1 is reduced to less than atmospheric pressure, it is preferable to weld the inlet 121 and the plug body 122. Note that, as a method for reducing the pressure P2 inside the battery case 1 to less than atmospheric pressure, for example, as shown in FIG. 7, after reducing the pressure P2 inside the battery case 1 to less than atmospheric pressure by discharging the gas inside the battery case 1 to the outside through the suction tube 8, immediately sealing the inlet 121 with the plug body 122, a method of reducing the pressure, or a method of reducing the pressure by sealing the inlet 121 with the plug body 122 in a state where the battery case 1 is housed in a chamber (not shown) in which the pressure P2 is reduced to less than atmospheric pressure, etc. are available.

[0030] In this case, in the plug welding step S3, since welding is performed in a state where the pressure P2 inside the battery case 1 is reduced to less than atmospheric pressure, even if the electrolyte 5 attached to the back surface 12b side of the sealing body (one case wall portion) 12 cannot be sufficiently vaporized in the electrolyte vaporization step S2, the pressure P2 inside the battery case 1 is unlikely to rise to atmospheric pressure or higher in the plug welding step S3, and the risk of welding defects such as pinholes occurring in the welded portion 123 between the inlet 121 and the plug body 122 can be reduced.

[0031] Further, in the method for manufacturing the sealed battery 10, in the electrolyte vaporization step S2, it is preferable to heat the vicinity portion 121K of the inlet near the inlet 121 more strongly than the separated portion 121L of the inlet separated from the inlet 121. For example, the heating device 7 shown in FIG. 7 is a far-infrared heater having a current control function, and is formed so as to heat the vicinity portion 121K of the inlet more strongly than the separated portion 121L of the inlet. In this case, in the electrolyte vaporization step S2, by heating the vicinity portion 121K of the inlet more strongly than the separated portion 121L of the inlet, a convection of air flow is formed near the inlet 121 inside the battery case 1, and the gas containing the vaporized electrolyte 5 (51) can be effectively discharged from the inlet 121 to the outside of the battery case 1. Further, even when a large amount of the electrolyte 5 adheres near the inlet 121, the electrolyte 5 can be quickly removed.

[0032] Incidentally, the heating range of the heating device 7 preferably extends from the vicinity of the injection port 121 to the vicinity of the insulating member 3 of the external connection portion 45 coupled to both longitudinal ends 12R of the sealing body (one case wall portion) 12. This is because more of the electrolytic solution 5 adhering to the back surface 12b side of the sealing body (one case wall portion) 12 can be vaporized. Even in this case, the injection port separation portion 121L separated from the injection port 121 is heated less strongly than the injection port vicinity portion 121K, so that deterioration of the insulating member 3 of the external connection portion 45 can be reduced and the sealing property of the insulating member 3 can be ensured.

[0033] Further, in the method for manufacturing the sealed storage battery 10, the electrolytic solution 5 includes a plurality of solvents 5A, 5B, 5C having different boiling points. In the electrolytic solution vaporization step S2, it is preferable to heat the surface 12a side of the sealing body (one case wall portion) 12 to a temperature at which more of the solvents 5B, 5C having boiling points lower than that of the solvent 5A having the highest boiling point among the solvents 5A, 5B, 5C are vaporized. The electrolytic solution 5 can include, for example, ethylene carbonate (EC) 5A having a boiling point of about 244°C, ethyl methyl carbonate (EMC) 5B having a boiling point of about 107°C, and dimethyl carbonate (DMC) 5C having a boiling point of about 90°C as the plurality of solvents 5A, 5B, 5C having different boiling points.

[0034] In this case, in the electrolytic solution vaporization step S2, by heating the surface 12a side of the sealing body (one case wall portion) 12 to, for example, about 110°C, more of the solvents 5B, 5C having boiling points lower than that of the solvent 5A having the highest boiling point are vaporized. Therefore, it is possible to preferentially and rapidly vaporize the highly volatile solvents 5B, 5C while reducing the heating temperature. As a result, it is possible to manufacture a high-performance and high-quality sealed storage battery 10 with less deterioration of the electrolytic solution 5, the electrode body 2, etc. due to temperature rise while shortening the heating time and increasing productivity.

[0035] Also, in the method for manufacturing the sealed storage battery 10, in the electrolytic solution vaporization step S2, it is preferable to heat the surface 12a side of one case wall portion 12 using the far-infrared heater 7 having a current control function. In this case, in the electrolytic solution vaporization step S2, since heating is performed using the far-infrared heater 7 having a current control function, there is less thermal energy that reflects like, for example, laser light, and the thermal energy of the far-infrared heater 7 can be quickly transmitted to the back surface 12b side of the sealing body (one case wall portion) 12, reducing energy loss. Also, by flowing a large current in a short time by the current control function, heating can be performed quickly at an optimal temperature. Therefore, a high-quality sealed storage battery 10 with little deterioration of the electrolytic solution 5, the electrode body 2, etc. can be manufactured at low cost while increasing productivity at low cost.

[0036] <Modification example> As described in detail above, the present embodiment is merely an example and does not limit the disclosed technology in any way. Therefore, the disclosed technology can be variously improved and modified without departing from the gist thereof.

Explanation of reference numerals

[0037] 1 Battery case 2 Electrode body 5 Electrolytic solution 5A, 5B, 5C Solvent 7 Far-infrared heater 10 Sealed storage battery 12 One case wall portion, sealing body 12a Surface 12b Back surface 121 Injection port 121K Portion near the injection port 121L Portion separated from the injection port 122 Plug body P1, P2 Pressure S1 Electrolytic solution injection step S2 Electrolytic solution vaporization step S3 Plug body welding step

Claims

1. A battery case; An electrode assembly housed in the battery case, a manufacturing method of a sealed storage battery, the method comprising the steps of: providing a case wall portion constituting the battery case with an injection port for injecting an electrolyte into the battery case; and sealing the injection port by welding, the method comprising the steps of: an electrolyte injection step of injecting the electrolyte into the battery case through the injection port after the electrode body is housed in the battery case; an electrolyte vaporization step of heating a front surface side of the first case wall portion after the electrolyte injection step to vaporize the electrolyte attached to the rear surface side of the first case wall portion; a plug welding step of welding the injection port and the plug after the electrolyte vaporization step, In the electrolyte vaporization step, the surface side of the first case wall is heated while the pressure inside the battery case is reduced to less than one atmosphere. A method for manufacturing a sealed storage battery.

2. The method for producing a sealed storage battery according to claim 1, In the plug welding step, the injection port is sealed with the plug in a state where the pressure inside the battery case is reduced to less than one atmosphere, and then the injection port and the plug are welded together. A method for manufacturing a sealed storage battery.

3. The method for producing a sealed storage battery according to claim 1, In the electrolyte vaporization step, a portion close to the injection port is heated more strongly than a portion far from the injection port. A method for manufacturing a sealed storage battery.

4. The method for producing a sealed storage battery according to claim 1, The electrolyte solution includes a plurality of solvents having different boiling points, In the electrolyte vaporization step, the surface side of the first case wall is heated to a temperature at which a solvent having a lower boiling point than a solvent having a highest boiling point is vaporized in a larger amount. A method for manufacturing a sealed storage battery.

5. The method for producing a sealed storage battery according to any one of claims 1 to 4, In the electrolyte vaporization step, a surface side of the one case wall is heated using a far-infrared heater having a current control function. A method for manufacturing a sealed storage battery.

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