Secondary battery and manufacturing method for secondary battery

Abstract

To provide a secondary battery and a manufacturing method for the same, in which the expansion of distance between a positive electrode and a negative electrode in a part of an electrode body that is curved and stacked can be suppressed.SOLUTION: An electrode body 40 is accommodated in a case 22, and is formed in a flat shape wound around a winding axis in such a way that positive and negative electrode sheets 50, 60 are stacked with a separator 70 therebetween. The separator 70 includes an attached part 70A attached to electrode sheets 50, 60 only in a curved parts 70R on both end sides in an axial direction of the winding axis and a direction orthogonal to a thickness direction of the electrode body 40 (up-down direction in FIG. 1). In a part 40R of the electrode body 40 that is curved and stacked, the separator 70 and the electrode sheets 50, 60 are attached together.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a secondary battery and a method for manufacturing a secondary battery. [Background technology]

[0002] The following Patent Document 1 discloses a technology related to a secondary battery including a flat wound electrode group (electrode body) and an electrolyte. Briefly, in this prior art, the flat wound electrode group includes a strip-shaped negative electrode, a strip-shaped positive electrode, and a strip-shaped separator, and is wound along the long side direction of the negative electrode and the positive electrode such that the separator is interposed between the negative electrode and the positive electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-84454 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a secondary battery having a flat wound electrode assembly is arranged as a part of a battery stack, the flatly stacked portion of the electrode assembly may be configured to receive a restraint load. In such a case, the restraint load can suppress the increase in the inter-electrode distance between the positive and negative electrodes in the flatly stacked portion, but cannot suppress the increase in the inter-electrode distance between the positive and negative electrodes in the curvedly stacked portion of the electrode assembly.

[0005] In consideration of the above facts, the present invention aims to provide a secondary battery and a method for manufacturing a secondary battery that can suppress the increase in the inter-electrode distance between positive and negative electrodes in the curved and stacked portions of the electrode body. [Means for solving the problem]

[0006] A secondary battery according to a first aspect of the present invention is a secondary battery having a case, a flat electrode body contained in the case, in which positive and negative electrode sheets are stacked with a separator in between and wound around a winding axis, and an electrolyte contained in the case, wherein the separator has an adherend portion adhered to the electrode sheet only at curved portions on both end sides in a direction perpendicular to the axial direction of the winding axis and the thickness direction of the electrode body.

[0007] A secondary battery of a second aspect of the present invention is a secondary battery of the first aspect of the present invention, wherein in a curved portion to be bonded, among the multiple curved portions provided in the winding circumferential direction of the separator, the curved portion has the bonded portion to which adhesive is attached and a non-bonded portion to which no adhesive is attached, on at least one surface of the curved portion.

[0008] A manufacturing method for a secondary battery according to a third aspect of the present invention is a method for manufacturing a secondary battery comprising: a case; a flat electrode body in which positive and negative electrode sheets are stacked with a separator sandwiched between them and wound around a winding axis; and an electrolyte solution contained in the case, wherein the separator has an adherend portion adhered to the electrode sheet only at curved portions on both end sides in a direction perpendicular to the axial direction of the winding axis and the thickness direction of the electrode body, the method comprising: a winding step of winding the alternately stacked electrode sheets and the separators in a flat shape around a flat winding core; and a removal step of removing the winding core after the winding step.

[0009] A fourth aspect of the present invention is a method for manufacturing a secondary battery according to the third aspect of the present invention, further comprising an adhesive application step of applying a thermoplastic adhesive to the bonded portion of the separator prior to the winding step, and heating the curved portion after the winding step.

[0010] A fifth aspect of the present invention relates to a method for producing a secondary battery according to the fourth aspect of the present invention, wherein the core is provided with heating sources at both ends in directions perpendicular to the winding axis and thickness direction of the core, and the curved portion is heated from the inner side by the heating sources after the winding step and before the removal step.

[0011] A sixth aspect of the present invention relates to a method for producing a secondary battery according to the fourth or fifth aspect of the present invention, and further relates to a method for producing a secondary battery according to the fourth or fifth aspect of the present invention, in which the curved portion is heated from an outer periphery side after the winding step. Effect of the Invention

[0012] In the secondary battery of the first aspect of the present invention, the separator has an adherend portion adhered to the electrode sheet only at the curved portions on both ends in the direction perpendicular to the axial direction of the winding shaft and the thickness direction of the electrode body, and the separator and the electrode sheet are adhered to the curved and stacked portion of the electrode body. Therefore, it is possible to suppress the increase in the inter-electrode distance between the positive and negative electrodes in the curved and stacked portion of the electrode body. In addition, since the adhesion between the separator and the electrode sheet is only in the curved and stacked portion of the electrode body, it is possible to suppress an increase in battery resistance due to the adhesive.

[0013] In the secondary battery of the second aspect of the present invention, in the curved portion to be bonded, which is one of the multiple curved portions provided in the winding direction of the separator and has an adherend portion, at least one surface of the curved portion has an adherend portion and a non-adhesive portion, so that an increase in battery resistance due to the adhesive can be suppressed compared to when no non-adhesive portion is provided.

[0014] In the method for producing a secondary battery according to the third aspect of the present invention, in the winding step, the alternately stacked electrode sheets and separators are wound flat around a flat core, and in the removal step following the winding step, the core is removed. Therefore, compared to, for example, a case in which the alternately stacked electrode sheets and separators are spirally wound and then pressed flat, it is possible to suppress the inter-electrode distance between the positive and negative electrodes in the curved laminated portion of the electrode body from increasing.

[0015] In the method for producing a secondary battery according to the fourth aspect of the present invention, a thermoplastic adhesive is applied to the bonded portion of the separator in an adhesive application step prior to the winding step, and the curved portion is heated after the adhesive application step and after the winding step, whereby the adhesive can be plasticized, and the temperature of the plasticized adhesive can be lowered to harden it, thereby bonding the bonded portion in the curved portion of the separator to the electrode sheet via the thermoplastic adhesive.

[0016] In the method for producing a secondary battery according to the fifth aspect of the present invention, the core is provided with heating sources at both ends in the direction perpendicular to the winding axis and thickness direction of the core, and the curved portion is heated from the inner periphery side by the heating sources after the winding step and before the removal step. This makes it possible to bond the bonded portion in the curved portion of the separator to the electrode sheet via a thermoplastic adhesive without providing a separate heating source.

[0017] In the manufacturing method for a secondary battery according to the sixth aspect of the present invention, after the winding step, the curved portion is heated from the outer periphery, so that the curved and stacked portions of the electrode body can be well bonded, particularly the outer periphery portions where the inter-electrode distance between the positive and negative electrodes is likely to increase. [Brief description of the drawings]

[0018] [Figure 1] 1 is a vertical cross-sectional view showing, in a simplified form, a portion of a battery stack including a secondary battery according to an embodiment as a cell. [Diagram 2] 2 is a simplified cross-sectional view of the secondary battery of FIG. 1 as seen from the front. [Diagram 3] 2 is a schematic diagram for explaining the configuration of an electrode body in the secondary battery of FIG. 1. [Figure 4] FIG. 4 is an image diagram showing the separator in an expanded state before being wound. [Diagram 5] 4A to 4C are schematic diagrams for explaining a winding step in the manufacturing method of the secondary battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The secondary battery according to the embodiment will be described with reference to Fig. 1 to Fig. 5. Fig. 1 shows a simplified vertical cross-sectional view of a part of a battery stack 10 including a secondary battery 20 according to the embodiment as a cell. The battery stack 10 is used, for example, as an on-board power source for an electric vehicle or the like.

[0020] (Schematic configuration of battery stack 10) The battery stack 10 shown in FIG. 1 includes a secondary battery 20, a spacer 12, and an end plate 14. Although detailed illustration is omitted, the battery stack 10 includes a plurality of secondary batteries 20 and spacers 12 (one of each is shown in FIG. 1) arranged alternately, and a pair of end plates 14 (only one on one side is shown in FIG. 1) arranged on both sides in the direction in which the secondary batteries 20 and spacers 12 are arranged sandwich the secondary batteries 20 and spacers 12 arranged alternately. A known configuration can be applied to the configuration for sandwiching the batteries using the end plates 14, so detailed explanation is omitted. The battery stack 10 is configured to restrain the secondary batteries 20 by the spacers 12 and the end plates 14.

[0021] (Configuration of secondary battery 20) 2 shows a simplified cross-sectional view of the front view of the secondary battery 20. The secondary battery 20 is a lithium-ion secondary battery. The secondary battery 20 has a case 22, an electrode body 40 housed in the case 22, an electrolyte (not shown) housed in the case 22, an insulating film 26 disposed in the case 22 to cover the electrode body 40, and a lid assembly 28 provided on the upper side of the case 22.

[0022] The case 22 is made of metal (aluminum alloy, for example), and is formed into a rectangular box shape that is open at the top and long in the width direction of the battery (direction of arrow W). The electrode body 40 has an electrode main body portion 42 that forms the middle portion in the width direction, and positive and negative uncoated portions 44, 46 provided on both sides in the width direction. Details of the electrode body 40 will be described later. The insulating film 26 is formed into a bag shape. The electrode body 40 is stored in the insulating film 26.

[0023] The lid assembly 28 has a lid member 30, positive and negative current collecting terminals 32, 34 for inputting and outputting electric power from the electrode body 40, and external terminals 36, 38 for external connection. The lid member 30 is formed in a rectangular plate shape that is long in the battery width direction. The lid member 30 is attached so as to close the opening of the case 22. The external terminals 36, 38 are electrically connected to the corresponding positive and negative current collecting terminals 32, 34.

[0024] FIG. 3 shows a schematic diagram for explaining the configuration of the electrode body 40. In FIG. 3, the dimensional ratio of each component may be changed in order to easily show the configuration. The electrode body 40 shown in FIG. 3 is formed by stacking positive and negative electrode sheets 50, 60, in which composite layers 54, 64 are applied to a part of the surface of sheet-shaped positive and negative electrode collectors 52, 62, sandwiching a separator 70 (see the partially enlarged view of FIG. 1), and winding the electrode sheets 50, 60 around a winding axis 40L to form a flat shape. The electrode body 40 is arranged so that the axial direction of the winding axis 40L is the same as the battery width direction (direction of the arrow W). The electrode body 42 in the electrode body 40 includes a stacked portion of the current collectors 52, 62, the composite layers 54, 64, and the separator 70.

[0025] Two separators 70 are provided. In the drawing, the separator 70 that is to be disposed at the outermost periphery of the electrode assembly 40 is indicated by "70X" in parentheses after the reference numeral 70. The separator 70 that is to be disposed at the innermost periphery of the electrode assembly 40 is indicated by "70Y" in parentheses after the reference numeral 70. The separator 70 is made of an insulating resin material such as polypropylene. The separator 70 has many minute holes formed therein. Other aspects of the separator 70 will be described later.

[0026] The positive electrode current collector 52 constituting a part of the positive electrode sheet 50 is made of, for example, a foil of an aluminum alloy or the like. A composite layer 54 is applied to both sides of the current collector 52 except for a part along one edge in the width direction. The composite layer 54 is configured to contain at least an active material that constitutes the positive electrode. The negative electrode current collector 62 constituting a part of the negative electrode sheet 60 is made of, for example, a foil of a copper alloy. A composite layer 64 is applied to both sides of the current collector 62 except for a part along the other edge in the width direction. The composite layer 64 is configured to contain at least an active material that constitutes the negative electrode.

[0027] The uncoated portion 44 of the positive electrode, which is a part of the positive current collector 52 and is not coated with a composite layer, protrudes from the electrode main body 42 along the axial direction of the winding shaft 40L. The uncoated portion 44 of the positive electrode is disposed on one side of the electrode main body 42 in the axial direction of the winding shaft 40L, and is provided in plurality in the same direction as the thickness direction of the electrode main body 42. The protruding tip portions of these uncoated portions are bundled and stacked to form a foil collecting portion 44X (see FIG. 2). As shown in FIG. 2, the positive current collecting terminal 32 is welded to the surface of the foil collecting portion 44X.

[0028] As shown in Fig. 3, the negative electrode uncoated portion 46, which is a part of the negative electrode current collector 62 and is not coated with a composite layer, protrudes from the electrode main body 42 along the axial direction of the winding shaft 40L. The negative electrode uncoated portion 46 is disposed on the other side of the electrode main body 42 in the axial direction of the winding shaft 40L, and a plurality of negative electrode uncoated portions 46 are provided in the same direction as the thickness direction of the electrode main body 42, and the protruding tip sides of these portions are bundled and stacked to form a foil collecting portion 46X (see Fig. 2). As shown in Fig. 2, the negative electrode current collecting terminal 34 is welded to the surface of the foil collecting portion 46X.

[0029] The separator 70 shown in Fig. 3 has adherend portions 70A (see the partial enlargement of Fig. 4; in Fig. 3, the portions where dot-like adhesive 74 are arranged) adhered to the electrode sheets 50, 60 only at curved portions 70R on both ends in a direction perpendicular to the axial direction of the winding shaft 40L and the thickness direction of the electrode body 40. As shown in the partial enlargement of Fig. 1, the adherend portions 70A are set on both sides of the separator 70. Note that, except for the partial enlargement, Fig. 1 does not show the alternately laminated electrode sheets 50, 60 and the separator 70 in a stacked state, and the curved portions 70R are shown by curved lines.

[0030] FIG. 4 shows an image of the separator 70 in an unfolded state before being wound. As shown in FIG. 4, the separator 70 in an unfolded state has a plurality of bonded regions 72, which are regions to which dot-shaped adhesive 74 is attached. Each bonded region 72 is provided in a strip shape extending in the width direction. The adhesive 74 is, for example, polyvinylidene fluoride (PVDF) or the like having lithium ion conductivity, and is attached to the separator 70 by dot coating. In this embodiment, the strip-shaped bonded regions 72 are set, as an example, to correspond to the portions that will become the curved portion 70R (see FIG. 1) after winding. The short-side length of each bonded region 72 (the length in the vertical direction in FIG. 4) is set slightly longer for those located closer to the outer periphery when the separator 70 is wound (details not shown).

[0031] In this embodiment, in all of the multiple curved portions 70R (see Figure 1) provided in the winding direction of the separator 70, at least one side of the curved portion 70R (basically both sides with some exceptions) is provided with an adherend portion 70A to which adhesive 74 is attached and a non-adhesive portion 70B to which no adhesive is attached, as shown in the partially enlarged view of Figure 4.

[0032] (Configuration of the winding core 80, etc. for manufacturing the electrode body 40) Next, the winding core 80 (see FIG. 5) and the like used in the manufacture of the electrode body 40 (see FIG. 2) will be described. As shown in FIG. 5, the winding core 80 is formed in a flat shape and extends in a direction perpendicular to the paper surface of FIG. 5. The winding core 80 is provided with heaters 82 (illustrated in a simplified manner for convenience in the figure) as a heat source at both end portions 80A and 80B in a direction perpendicular to the winding axis direction (direction perpendicular to the paper surface of FIG. 5) and thickness direction (up and down direction in FIG. 5) of the winding core 80. As an example, the heater 82 is configured to include an electric heating wire and is configured to generate heat by passing electricity through the electric heating wire. The heater 82 is electrically connected to a control device (not shown), and the passage of electricity through the electric heating wire of the heater 82 is controlled by the control device.

[0033] (Manufacturing method of secondary battery 20) Next, a method for manufacturing the secondary battery 20 shown in FIG. 2 will be described.

[0034] First, as shown in Fig. 4, a thermoplastic adhesive 74 is applied by dot coating to the adherend portion 70A (see partial enlarged view) in each adherend region 72 of the separator 70 in the unfolded state (adhesive application process). In this embodiment, as an example, the adhesive 74 is basically applied to both the front and back surfaces of each of the two separators 70 as shown in Fig. 4. However, the adhesive 74 is not applied to a portion that will be the outermost outer surface of the separator 70 (70X) (see Fig. 3) that will be disposed at the outermost periphery, and the adhesive 74 is not applied to a portion that will be the innermost inner surface of the separator 70 (70Y) (see Fig. 3) that will be disposed at the innermost periphery.

[0035] Next, as shown in Fig. 3, the electrode sheets 50, 60 and the separator 70 are alternately stacked and wound flat around a flat-shaped winding core 80 shown in Fig. 5 (winding step). Note that in Fig. 5, detailed illustration of the alternately stacked electrode sheets 50, 60 and the separator 70 (see Fig. 3) is omitted, and the winding direction is indicated by an arrow R. Also, in Fig. 5, the start of winding of the alternately stacked electrode sheets 50, 60 and the separator 70 (see Fig. 3) is denoted by the symbol S. The position of the start of winding S can be appropriately selected.

[0036] In this embodiment, after the adhesive application step, the curved portion 70R of the separator 70 (shown by a curved line in the drawing for convenience) is locally heated from the inner periphery side by the heater 82 after the winding step. Here, in this embodiment, since the heater 82 is provided on the winding core 80, the curved portion 70R of the separator 70 can be heated without providing a separate heating source. In this embodiment, as an example, the curved portion 70R of the separator 70 is heated from the inner periphery side by the heater 82 while the winding step is being performed. The adhesive 74 (see FIG. 4) is plasticized by heating by the heater 82. The temperature of the plasticized adhesive 74 (see FIG. 4) is further reduced to harden the adhesive, thereby bonding the curved portion 70R of the separator 70 to the electrode sheets 50 and 60 (see FIG. 3). Next, the winding core 80 is removed (removal step), and then the electrode body 40 is pressed in the thickness direction.

[0037] Thereafter, the protruding tip end portions of the uncoated portions 44, 46 of the positive and negative electrodes of the electrode body 40 shown in FIG. 2 are bundled together to form foil collecting portions 44X, 46X, and parts of the current collecting terminals 32, 34 are welded to the foil collecting portions 44X, 46X. Next, the electrode body 40 is housed in the insulating film 26, and the insulating film 26 housing the electrode body 40 is inserted into the case 22. Then, the lid member 30 is attached to the opening of the case 22. Thereafter, an electrolyte is injected from an injection port (not shown) of the lid member 30, and a cap (not shown) is attached to the injection port. In this manner, a rechargeable secondary battery 20 is manufactured.

[0038] (Actions and Effects of Secondary Battery 20) Next, the function and effect of the secondary battery 20 will be described.

[0039] In the secondary battery 20 shown in FIG. 1, the separator 70 has an adherend portion 70A adhered to the electrode sheets 50, 60 only at the curved portion 70R at both ends in a direction perpendicular to the axial direction of the winding shaft 40L (see FIG. 3) and the thickness direction of the electrode body 40 (the vertical direction in FIG. 1), and the separator 70 and the electrode sheets 50, 60 are adhered to each other in the curved and stacked portion 40R of the electrode body 40. Therefore, it is possible to suppress the inter-electrode distance between the positive and negative electrodes (the distance between the positive electrode sheet 50 and the negative electrode sheet 60) in the curved and stacked portion 40R of the electrode body 40 from increasing. In this way, it is possible to suppress the inter-electrode distance between the positive and negative electrodes in the curved and stacked portion 40R of the electrode body 40 from increasing, thereby suppressing the deposition of lithium in the curved and stacked portion 40R of the electrode body 40.

[0040] As described above, the separator 70 and the electrode sheets 50, 60 are bonded only to the curved laminated portion 40R of the electrode body 40. Therefore, an increase in battery resistance due to the adhesive 74 can be suppressed.

[0041] Furthermore, in the secondary battery 20, among the multiple curved portions 70R provided in the winding direction of the separator 70, in the curved portions 70R to be bonded that have the bonded portion 70A (in this embodiment, all the curved portions 70R), at least one surface of the curved portion 70R has the bonded portion 70A and a non-bonded portion 70B, as shown in the enlarged partial view of Figure 4. Therefore, the increase in battery resistance due to the adhesive 74 can be suppressed compared to, for example, a case in which no non-bonded portion is provided.

[0042] (Modification of the embodiment) In the manufacturing method of the secondary battery 20 (see FIG. 1) in the above embodiment, the curved portion 70R of the separator 70 is heated from the inner periphery side by the heater 82 shown in FIG. 5 after the winding step. However, as a modified example, after the winding step, the curved portion (70R) may be heated from the outer periphery side by a known heater (not shown) arranged on the outer periphery side of the curved and stacked portion (40R (see FIG. 1)) of the electrode body (40). In such a modified example, the curved and stacked portion (40R) of the electrode body (40) on the outer periphery side where the interelectrode distance between the positive and negative electrodes is likely to increase can be bonded well. In another modified example, in addition to heating the curved portion (70R) of the separator (70) from the inner periphery side by the heater (82), the curved portion (70R) of the separator (70) may be heated from the outer periphery side by a known heater (not shown).

[0043] Furthermore, in the above embodiment, the adhesive 74 shown in FIG. 4 is applied to the portion that will become the curved portion 70R (see FIG. 1) of the separator 70 by dot coating. However, as a variation of the above embodiment, the adhesive (74) may be applied to the portion that will become the curved portion (70R) of the separator (70) by a method other than dot coating, such as spiral coating in which the adhesive is applied in a spiral shape or spray coating in which the adhesive is applied in a wave shape.

[0044] In addition, in the above embodiment, as an example, all of the multiple curved portions 70R provided in the winding direction of the separator 70 shown in FIG. 1 are curved portions to be bonded having the adherend portion 70A, but as a modified example of the above embodiment, a configuration in which not all but some of the multiple curved portions (70R) provided in the winding direction of the separator (70) are curved portions to be bonded having the adherend portion (70A) can also be adopted.

[0045] In addition, in the above embodiment, an area of ​​non-adhesive portion 70B is provided on all of the surfaces having adhered portions 70A in the curved portions 70R of the multiple objects to be bonded. However, as a variation of the above embodiment, a configuration in which an area of ​​non-adhesive portion is provided on one or more of the surfaces having adhered portions in the curved portions of the multiple objects to be bonded, but not on all of the surfaces, can also be adopted.

[0046] As another modified example, a configuration may be adopted in which no non-adhesive region is provided on any of the surfaces having adherends in the curved portions of the multiple adhesion targets.

[0047] In addition, in the above embodiment, the adherend portion 70A provided on the curved portion 70R is set on both sides of the separator 70, and such a configuration is preferred, but as a modified example of the above embodiment, a configuration in which the adherend portion (70A) provided on the curved portion (70R) is set on only one side of the separator 70 may also be adopted.

[0048] In the above embodiment, a thermoplastic adhesive is applied to the bonded portion 70A, but as a modification of the above embodiment, an adhesive other than a thermoplastic adhesive may be applied to the bonded portion (70A) and the curved portion (70R) of the separator (70) and the electrode sheet (50, 60) may be bonded by such an adhesive. Even when an adhesive other than a thermoplastic adhesive is used, pressure is applied to the bonded portion (70A) and its opposing portion during winding, so that the bonded portion (70A) can be firmly bonded to its opposing portion, thereby ensuring adhesive strength.

[0049] The above-described embodiment and the multiple modified examples can be implemented in appropriate combinations.

[0050] While one example of the present invention has been described above, the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modified forms without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0051] 20 Secondary battery 22 cases 40 Electrode body 40L winding shaft 50 Electrode Sheet 60 Electrode Sheet 70 Separator 70A Glued part 70B Non-adhesive part 70R curved section 74 Adhesive 80 Roll core 82 Heater (heat source)

Claims

1. Case and a flat electrode assembly housed in the case, in which positive and negative electrode sheets are laminated with separators sandwiched therebetween and wound around a winding axis; An electrolyte contained in the case; A secondary battery having the separator has adhered portions adhered to the electrode sheet only at curved portions on both ends in a direction perpendicular to the axial direction of the winding shaft and the thickness direction of the electrode body.

2. 2. The secondary battery according to claim 1, wherein in a curved portion to be bonded, among the curved portions provided in the winding circumferential direction of the separator, the curved portion has the bonded portion to which adhesive is attached and a non-bonded portion to which no adhesive is attached, on at least one surface of the curved portion.

3. A method for manufacturing a secondary battery comprising: a case; a flat electrode assembly housed in the case, in which positive and negative electrode sheets are stacked with a separator sandwiched therebetween and wound around a winding axis; and an electrolyte housed in the case, wherein the separator has bonded portions bonded to the electrode sheets only at curved portions on both end sides in a direction perpendicular to the axial direction of the winding axis and the thickness direction of the electrode assembly, a winding step of winding the alternately stacked electrode sheets and the separators in a flat shape around a flat winding core; a removal step of removing the winding core after the winding step; A method for manufacturing a secondary battery having the above structure.

4. an adhesive applying step of applying a thermoplastic adhesive to the bonded portion of the separator before the winding step; The method for manufacturing a secondary battery according to claim 3 , wherein the curved portion is heated after the adhesive applying step and after the winding step.

5. The core is provided with a heating source at both ends in a direction perpendicular to the winding axis direction and the thickness direction of the core, The method for manufacturing a secondary battery according to claim 4 , wherein the curved portion is heated from an inner periphery side by the heating source after the winding step and before the removing step.

6. The method for producing a secondary battery according to claim 4 , further comprising the step of heating the curved portion from an outer periphery side after the winding step.

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