JP2014216252A - Square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a secondary battery including an electrode group in which two sheets of separators are simply wound around an axis center with a sufficient strength.SOLUTION: A square secondary battery 1 of the present invention includes an electrode group 40 in which a positive electrode 41 and a negative electrode 42 are wound around an axis center 40a with separators 43, 44 interposed therebetween. The separators 43, 44 comprise a first separator 43 and a second separator 44. In the first separator 43, a winding start end of the first separator 43 is thermally welded to the axis center 40a to be wound. In the second separator 44, a winding start end of the second separator 44 is rolled in by the first separator 43 to be wound together with the first separator 43.

Description

  The present invention relates to a prismatic secondary battery having an electrode group that winds an electrode around an axis.

  In recent years, secondary batteries with high energy density have been developed as power sources for electric vehicles and the like, and one of them is a prismatic secondary battery. A prismatic secondary battery has a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween. The wound electrode group has a structure in which the winding start end portion of the separator is heat-welded to the shaft core, and the electrode is superimposed on the separator and wound. Specifically, the winding start ends of two separators are overlapped on the shaft core and heat-welded, and wound so that each separator is interposed between the positive electrode and the negative electrode. .

JP 2011-175749 A

  Conventionally, since the winding start ends of the two separators were overlapped and thermally welded to the shaft core, heating temperature and time corresponding to the overlapped thicknesses were required. Of the two stacked separators, the heater block is directly pressed against the outer separator and melted, and the inner separator is melted by the heat and thermally welded to the shaft. In order to prevent problems such as excessive melting of the outer separator due to insufficient adjustment of the heating temperature and insufficient welding strength to the inner core of the inner separator due to insufficient adjustment of the heating temperature, the heating temperature is subtle. Adjustment was necessary.

  The present invention has been made in view of the above problems, and an object thereof is to provide a prismatic secondary battery having an electrode group in which two separators are easily wound around a shaft core with sufficient strength. It is to be.

  The prismatic secondary battery of the present invention that solves the above problems is a prismatic secondary battery having an electrode group in which a positive electrode and a negative electrode are wound around an axis with a separator interposed therebetween, and the separator is a first separator. And a second separator, wherein the first separator is wound with the winding start end portion of the first separator being thermally welded to the shaft core, and the second separator is wound around the second separator. A starting end portion is wound around the first separator and wound together with the first separator.

  According to the present invention, it is possible to provide a secondary battery having an electrode group in which two separators are easily wound around a shaft core with sufficient strength and the separator is not displaced. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The external appearance perspective view of the secondary battery concerning the form of this form. FIG. 2 is an exploded perspective view of the secondary battery shown in FIG. 1. FIG. 3 is an external perspective view showing a state where a part of the electrode group shown in FIG. 2 is developed. The figure which shows the structure of an electrode group manufacturing apparatus. FIG. 3 is an exploded view schematically showing a configuration of a winding start end portion of the separator in the first embodiment. FIG. 3 is an assembly diagram schematically illustrating a configuration of a winding start end portion of the separator according to the first embodiment. FIG. 5 is a diagram illustrating a separator winding method according to the first embodiment. FIG. 6 is a diagram for explaining a separator winding method according to the second embodiment.

  The electrode group of the prismatic secondary battery in the present embodiment uses the first separator and the second separator in which the heat-resistant layer is formed on at least one surface of the resin layer, and the heat-resistant layer of the first separator and the second separator The second separator is disposed on the axial center side so as to face the heat-resistant layer, the first separator is disposed outside so as to cover the winding start end of the second separator, and the winding start end of the first separator is arranged. The second separator is welded to the shaft core, and the second separator is sandwiched between the shaft core and the first separator, and is wound like the first separator welded by contact resistance.

Hereinafter, the present embodiment will be described with reference to the drawings.
First, the overall configuration of the prismatic secondary battery will be described, and then the characteristic configuration of each example will be described.

FIG. 1 is an external perspective view of a secondary battery according to this embodiment, and FIG. 2 is an exploded perspective view of the secondary battery shown in FIG.
The prismatic secondary battery 1 is configured in such a manner that an electrode group 40 is accommodated in a thin and substantially rectangular parallelepiped battery case 2 and a non-aqueous electrolyte is injected (not shown). As shown in FIG. 1, the battery container 2 has a battery lid 3 and a battery can 4. The battery lid 3 and the battery can 4 are made of a metal material such as aluminum or an aluminum alloy, for example. As shown in FIG. 2, a positive electrode current collector plate 21, a negative electrode current collector plate 31, and the like are integrally assembled with the battery lid 3, and the battery lid unit 10 is configured.

  The positive electrode current collector plate 21 and the negative electrode current collector plate 31 of the battery lid unit 10 are respectively joined to the positive electrode mixture untreated portion 41c or the negative electrode mixture untreated portion 42c of the electrode group 40 by, for example, ultrasonic welding. As a result, the battery lid / power generation unit 50 is formed and accommodated from the opening at the upper end of the battery can 4.

  In FIG. 2, the battery lid / power generation unit 50 is directly accommodated in the battery can 4, but the battery lid / power generation unit 50 is temporarily electrically insulated from a sheet or the like. The structure may be accommodated after being wrapped in.

  The battery lid 3 is provided with a liquid injection port (not shown) for injecting a non-aqueous electrolyte and is sealed with a liquid injection stopper 11. In addition, the battery cover 3 is a gas discharge valve for releasing the pressure by releasing the battery container 2 when the internal pressure of the lithium ion secondary battery 1 exceeds a preset upper limit value due to overcharge or the like. 12 is provided. The gas discharge valve 12 has a breaking groove 12a for cleavage.

The non-aqueous electrolyte is a solution in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved at a concentration of 1 mol / liter in a mixed solution in which ethylene carbonate and dimethyl carbonate are mixed at a volume ratio of 1: 2. Can be used.

  The battery lid 3 is joined to the battery can 4 by laser welding to close the upper end opening of the battery can 4. Then, after injecting the electrolytic solution from the liquid injection port 3a, the liquid injection port 3a is closed with the liquid injection plug 11, and the liquid injection plug 11 is laser welded to the battery lid 3 and sealed from the outside. The battery lid unit 10 includes a battery lid 3, a positive electrode side terminal component 20, and a negative electrode terminal component 30.

  The positive electrode side terminal component 20 includes an external positive electrode terminal 24, a positive electrode connection terminal 25, a positive electrode terminal plate 26, an insulating plate 27, a gasket (not shown), and a positive electrode current collector plate 21. The external positive electrode terminal 24, the positive electrode terminal plate 26, the positive electrode connection terminal 25, and the positive electrode current collector plate 21 are integrally fixed and attached to the battery lid 3.

  The positive electrode side terminal component 20 is produced as follows. In advance, the positive electrode current collecting plate 21 is caulked and fixed to the positive electrode connection terminal 25. Then, a gasket is inserted into the through hole of the battery lid 3. Then, the insulating plate 27 is disposed on the battery lid 3 so that the through holes of the battery lid 3 and the through holes of the insulating plate 27 are aligned.

  Next, the external positive terminal 24 is fitted into a through hole provided in the positive terminal plate 26 and fixed to the positive terminal plate 26 on the insulating plate 27. The external positive terminal 24 may be caulked to the positive terminal plate 26. Further, the positive electrode connection terminal 25 with the positive electrode current collector plate 21 crimped is inserted into the through hole of the gasket from the back side of the battery lid 3, and the tip end side of the positive electrode connection terminal 25 is the through hole of the insulating plate 27 and the positive electrode terminal plate 26. Insert through. The tip end side of the positive electrode connection terminal 25 has a cylindrical shape slightly smaller than the through hole of the positive electrode terminal plate 26, and is fixed to the positive electrode connection terminal 25 by caulking the tip portion of the positive electrode connection terminal 25. The positive electrode side terminal component 20 is integrally assembled to the battery lid 3.

  In this state, the positive electrode current collector plate 21, the positive electrode connection terminal 25, the positive electrode terminal plate 26, and the external positive electrode terminal 24 are electrically connected. Further, the positive electrode current collector plate 21, the positive electrode connection terminal 25, the positive electrode terminal plate 26 and the external positive electrode terminal 24 are insulated from the battery cover 3 by an insulating plate 27 and a gasket (not shown).

  The negative electrode side terminal component 30 includes an external negative electrode terminal 34, a negative electrode connection terminal 35, a negative electrode terminal plate 36, an insulating plate 37, a gasket (not shown), and a negative electrode current collector plate 31. The external negative electrode terminal 34, the negative electrode terminal plate 36, the negative electrode connection terminal 35, and the negative electrode current collector plate 31 are assembled integrally with the battery lid 3.

  The negative electrode side terminal component 30 is produced as follows. The negative electrode current collecting plate 31 is caulked and fixed to the negative electrode connection terminal 35 in advance. Then, a gasket is inserted into the through hole of the battery lid 3. Then, the insulating plate 37 is disposed on the battery lid 3 so that the through holes of the battery lid 3 and the through holes of the insulating plate 37 are aligned.

  Next, the external negative electrode terminal 34 is fitted into a through hole provided in the negative electrode terminal plate 36 and fixed to the negative electrode terminal plate 36 on the insulating plate 37. Further, the negative electrode connection terminal 35 with the negative electrode current collecting plate 31 crimped is inserted into the through hole of the gasket from the back side of the battery lid 3, and the tip end side of the negative electrode connection terminal 35 is the through hole of the insulating plate 37 and the negative electrode terminal plate 36. Insert through.

  The tip end side of the negative electrode connection terminal 35 has a cylindrical shape slightly smaller than the through hole of the negative electrode terminal plate 36, and is fixed to the negative electrode terminal plate 36 by caulking the tip portion of the negative electrode connection terminal 35. The negative electrode side terminal component 30 is integrally assembled to the battery lid 3.

  In this state, the negative electrode current collector plate 31, the negative electrode connection terminal 35, the negative electrode terminal plate 36, and the external negative electrode terminal 34 are electrically connected. In addition, the negative electrode current collector plate 31, the negative electrode connection terminal 35, the negative electrode terminal plate 36, and the external negative electrode terminal 34 are insulated from the battery lid 3 by an insulating plate 37 and a gasket (not shown).

  The positive electrode current collector plate 21 and the negative electrode current collector plate 31 of the battery lid unit 10 are joined to and electrically connected to the positive electrode electrode foil 41a or the negative electrode electrode foil 42a of the electrode group 40 by ultrasonic welding, respectively. -It becomes the electric power generation unit 50.

  As described above, the prismatic secondary battery 1 has a structure capable of charging / discharging the external electronic device connected to the external positive terminal 24 and the external negative terminal 34.

FIG. 3 is an external perspective view showing the details of the electrode group shown in FIG.
The electrode group 40 is formed by winding a flat shape around the shaft core 40a in a state where the positive electrode 41, the negative electrode 42, the first separator 43, and the second separator 44 are overlapped. .

  The shaft core 40a is made of a synthetic resin insulating material capable of heat-welding the second separator 44, and is constituted by a rectangular flat plate member having a pair of flat surfaces. The winding start end portion of the first separator 43 is thermally welded to the shaft core 40a and the first separator 43 is wound. The first separator 43 wound on the shaft core 40a causes the second separator 44 to The winding start end is wound and the second separator 44 is wound together with the first separator 43. That is, the first separator 43 has its winding start end fixed by being thermally welded to the shaft core 40a, and is wound around the shaft core 40a. The second separator 44 has a winding start end portion wound around and sandwiched by the first separator 43 wound around the shaft core 40a, and is fixed by friction. Has been wound around.

  The positive electrode 41 and the negative electrode 42 are wound so that the first separator 43 and the second separator 44 are interposed therebetween.

  The positive electrode 41 has a positive electrode mixture layer 41b formed on both front and back surfaces of a conductive positive electrode foil 41a made of, for example, an aluminum foil. The positive electrode mixture layer 41b is formed by applying the positive electrode mixture to the positive electrode foil 41a so that the positive electrode mixture untreated portion 41c in which the positive electrode foil 41a is exposed is formed on one side edge.

  The negative electrode 42 is obtained by forming a negative electrode mixture layer 42b on both front and back surfaces of a conductive negative electrode foil 42a made of, for example, copper foil. In the negative electrode mixture layer 42b, a negative electrode mixture untreated portion 42c in which the negative electrode electrode foil 42a is exposed is formed on the other side edge which is a side edge opposite to the side edge where the positive electrode mixture untreated portion 41c is disposed. Thus, the negative electrode mixture 42 is formed by applying the negative electrode mixture to the negative electrode foil 42a.

The positive electrode mixture layer 41b is obtained by adding scaly graphite as a conductive material and polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder to lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. N-methylpyrrolidone (hereinafter referred to as NMP) as a dispersion solvent is added and kneaded. This positive electrode mixture is applied to both surfaces of a 20 μm thick aluminum foil that is the positive electrode foil 41a, leaving the positive electrode mixture untreated portions 41c. Thereafter, drying, pressing, and cutting are performed to obtain a positive electrode 41 having a thickness of 90 μm (total of both front and back surfaces) of the positive electrode active material application portion that does not include the aluminum foil.

  The negative electrode mixture layer 42b is prepared by adding PVDF as a binder to amorphous carbon powder as a negative electrode active material, and adding and kneading NMP as a dispersion solvent thereto. This negative electrode mixture is applied to both surfaces of a 10 μm thick copper foil, which is the negative electrode foil 42a, leaving the untreated portion 42c of the negative electrode mixture. Thereafter, drying, pressing, and cutting are performed to obtain a negative electrode 42 having a thickness of 70 μm (total of both front and back surfaces) of the negative electrode active material coating portion not including the copper foil.

  The 1st separator 43 and the 2nd separator 44 consist of an insulating sheet member which can permeate | transmit electrolyte solution. The first separator 43 has a resin layer 43a and a heat-resistant layer 43b, and the second separator 44 has a resin layer 44a and a heat-resistant layer 44b (see, for example, FIG. 5). The heat-resistant layers 43b and 44b are respectively formed on at least one surface (one surface) of the resin layers 43a and 44a. The resin layers 43a and 44a are formed of, for example, a polypropylene porous film, and the heat-resistant layers 43b and 44b are mainly composed of, for example, a ceramic filler and have pores communicating in the thickness direction. The resin layers 43a and 44a have a thickness of 20 μm, for example, and the heat-resistant layers 43b and 44b have a thickness of 5 μm, for example (resin layer: heat-resistant layer = 4: 1).

  The width of the negative electrode mixture layer 42b (the length in the winding axis direction) is formed wider than the width of the positive electrode mixture layer 41b. Moreover, the width | variety of the 1st separator 43 is set as the dimension which exposes the positive electrode mixture unprocessed part 41c of the positive electrode 41 to the exterior in one side edge. Similarly, the width of the second separator 44 is set such that the negative electrode mixture untreated portion 42c of the negative electrode 42 is exposed to the outside at the other side edge.

  FIG. 4 is a diagram illustrating the configuration of the electrode group manufacturing apparatus. The electrode group manufacturing apparatus 73 is wound around the flat shaft core 40a in a state where the positive electrode 41, the negative electrode 42, the first separator 43, and the second separator 44 are overlapped, and the electrode of the rectangular secondary battery 1 The group 40 is manufactured.

  The electrode group manufacturing apparatus 73 includes a heater block 70 that presses only the winding start end portion of the first separator 43 against the shaft core 40a and thermally welds it, and a holding unit that holds the shaft core 40a so as to be rotatable around the winding axis. The pressing means presses the heater block 70 in a direction orthogonal to the flat surface of the shaft core 40a held by the holding means.

  As shown in FIG. 4, the holding means includes a gripping rotation mechanism 66 that positions and grips a flat shaft core 40 a at the center of the apparatus from both sides in the winding axis direction and rotates it. In the present embodiment, the gripping rotation mechanism 66 grips the shaft core 40a so that the rotation center of the shaft core 40a is arranged along the horizontal direction.

  The pressing means raises the heater block 70 to a predetermined position and presses it against the shaft core 40a, and a back-holding mechanism 72 that presses the shaft core 40a from the back side so that the shaft core 40a is not bent and bent by the pressing. With.

  The positive electrode 41, the first separator 43, the negative electrode 42, and the second separator 44 are arranged in a roll state on the side of the grip rotation mechanism 66 so that they can be supplied to the grip rotation mechanism 66. It has become. Further, feed mechanisms (rollers) 60a to 60d for supplying each electrode and separator by a predetermined length and cutters 61a to 61d for cutting at a predetermined length are provided. The first separator 43 and the second separator 44 are supplied to the gripping rotation mechanism 66 so that the heat-resistant layers 43b and 44b face each other and sandwich the positive electrode 41 between them when wound around the shaft core 40a. .

  A separator that temporarily positions the first separator 43 and the second separator 44 by pressing the first separator 43 and the second separator 44 against the shaft core 40a after the first separator 43 and the second separator 44 are fed between the shaft core 40a and the heater block 70 by the feeding mechanisms 60d and 60b. A temporary presser 68 is provided. Then, after winding the electrode group 40, an attaching means 67 for attaching the tape 63 is provided so as not to be unwound. The tape 63 is cut into a predetermined length by the cutter 65 via the feeding mechanism 64. The feeding mechanisms 60a to 60d described above also have a role of applying back tension to the positive electrode 41, the first separator 43, the negative electrode 42, and the second separator 44 during winding.

  In order to form the electrode group 40, first, the winding start end portion of the first separator 43 is thermally welded and fixed to the shaft core 40a, and the first separator 43 is wound around the shaft core 40a by rotating the shaft core 40a. Then, the first separator 43 wound around the shaft core 40 a winds and fixes the winding start end portion of the second separator 44, and the second separator 44 is wound together with the first separator 43. Then, the winding start end of the negative electrode 42 and the winding start end of the positive electrode 41 are wound together with the first separator 43 and the second separator 44, respectively, so that the first separator 43 and the second separator 44 are interposed therebetween. The negative electrode 42 and the positive electrode 41 are integrally wound.

  In the electrode group manufacturing apparatus 73, the shaft core 40a is gripped by the gripping rotation mechanism 66, the winding start end portion of the second separator 44 is disposed on the shaft core 40a side, and the winding start end portion of the second separator 44 is covered. A first separator 43 is disposed outside. Then, the heater block 70 heated to a high temperature is pressed against the winding start end of the first separator 43, and only the winding start end of the first separator 43 is thermally welded to the shaft core 40a. Then, the shaft core 40 a is rotated to wind the first separator 43 around the shaft core 40 a, the first separator 43 winds the winding start end of the second separator 44, and the second separator 44 together with the first separator 43 Turn.

  Then, while winding the first separator 43 and the second separator 44 around the shaft core 40 a, the winding start end portion of the negative electrode 42 is inserted between the first separator 43 and the second separator 44 and the negative electrode 42 is wound up. Further, the winding start end of the positive electrode 41 is inserted between the first separator 43 and the second separator 44 and the negative electrode 42 is not sandwiched so that the positive electrode 41 is wound. The negative electrode 42 is wound so as to be sandwiched between the resin layers 43 a and 44 a facing each other of the first separator 43 and the second separator 44, and the positive electrode 41 is connected to the first separator 43 and the second separator 44. It winds so that it may be pinched | interposed between the heat-resistant layers 43b and 44b which oppose.

  Then, after winding the positive electrode 41 and the negative electrode 42 by a predetermined length, the positive electrode 41 and the negative electrode 42 are cut by the cutters 61 a to 61 d, the negative electrode 42 covers the outer periphery of the positive electrode 41, and the outer periphery is further covered by the first separator 43. In a state where at least one of the second separators 44 is wound, the tape 63 is attached to the end portion of the separator by the attaching means 67 so as not to be unwound.

  According to the rectangular secondary battery 1 described above, the first separator 43 is wound after the winding start end portion of the first separator 43 is thermally welded and fixed to the shaft core 40a. A winding start end portion of the second separator 44 is wound around the first separator 43 wound around the core 40 a and wound together with the first separator 43. Therefore, at the time of assembling and manufacturing the electrode group 40, only one first separator 43 needs to be thermally welded to the shaft core 40a. Compared to the case where two conventional sheets are thermally welded, the heater The heating temperature of the block 70 can be lowered and the welding time can be shortened. Therefore, the cost can be reduced and the tact time can be shortened compared to the conventional case, and the heat welding operation can be facilitated.

  In addition, since only one separator needs to be thermally welded, it is not necessary to finely adjust the heating temperature of the heater block 70, and problems such as excessive melting of the separator and insufficient welding strength to the shaft core 40a can be prevented. And can be surely welded with a constant strength. And since the winding start end part of the 2nd separator 44 is wound up by the 1st separator 43 wound by the shaft core 40a, and the 2nd separator 44 is wound with the 1st separator 43, two separators 43 44 can be easily and sufficiently wound around the shaft core 40a.

  In particular, the shaft core 40a of the electrode group 40 is formed of a rectangular flat plate member, and the second separator 44 is bent at the end of the shaft core 40a according to the rotation of the shaft core 40a. Accordingly, the contact resistance with the shaft core 40a or with the first separator 43 is increased, so that a so-called edge is effective, and the winding start end portion of the second separator 44 is securely fixed to the shaft core 40a. And can be wound stably. Therefore, the second separator 44 can be reliably wound around the shaft core 40a while preventing the second separator 44 from being displaced.

  For example, in a secondary battery with high energy density, since a large current flows, the positive electrode of the electrode group may generate heat. On the other hand, a technique for providing a heat-resistant layer on the surface of the separator has been devised. When applying a separator having a heat-resistant layer on the surface, problems arise in the production of welding the separator. Among these, a technique is disclosed that does not fix with a tape when welding the separator on the outer peripheral side (Patent Document 1). In Patent Document 1, a winding end end portion of a separator is folded inward and overlapped with an outer surface of a portion before one round of the separator so that resin layers are opposed to each other and welded. In Patent Document 1, no consideration is given to the welding between the shaft core and the separator. When two separators are welded to the shaft core, particularly when the heat-resistant layers of the separators are arranged to face each other, there is a problem that the welding temperature must be increased.

  With respect to such problems, the prismatic secondary battery 1 according to the present embodiment has the first separator 43 and the second separator 44 in which the heat-resistant layers 43b and 44b are formed on at least one surface of the resin layers 43a and 44a. And the start of winding of the second separator 44 disposed on the side of the shaft core 40a. The shaft core 40a is wound around the heat-resistant layer 43b of the first separator 43 and the heat-resistant layer 44b of the second separator 44 facing each other. The winding start end of the first separator 43 is disposed outside the winding start end of the second separator 44 so as to cover the end, and only the winding start end of the first separator 43 is welded to the shaft core 40a. An electrode group 40 is provided. The heat-resistant layer 43b of the first separator 43 is disposed to face the shaft core 40a, and the heat-resistant layer 44b of the second separator 44 is disposed to face the heat-resistant layer 43b of the first separator 43. In the present embodiment, only one separator (first separator 43) is welded to the shaft core 40a, and only one heat-resistant layer 43b is disposed between the shaft core 40a. Therefore, it is not necessary to increase the welding temperature, and welding can be performed easily.

Example 1
5 and 6 are an exploded view and an assembly view schematically showing the configuration of the winding start end portion of the separator in the first embodiment, and FIG. 7 is a diagram for explaining a winding method of the separator in the first embodiment. is there.

  In Example 1, as shown in FIG. 5, the first separator 43 and the second separator 44 have a two-layer structure having heat-resistant layers 43b and 44b on one side of the resin layers 43a and 44a, respectively. And it superimposes so that mutual heat-resistant layer 43b, 44b may oppose. Note that the heat-resistant layers 43b and 44b may be overlapped so that they are separated from each other.

  In the second separator 44, the winding start end of the second separator 44 is disposed on the side of the shaft core 40a (hereinafter referred to as the inside), and the first separator 43 is disposed on the side away from the shaft core 40a (hereinafter referred to as the outside). However, as shown in FIG. 7A, the winding start end portion of the first separator 43 is put out before the winding start end portion of the second separator 44, and the first separator 43 causes the second separator The winding start end portion of 44 is covered, and the heat resistant layer 43b of the winding start end portion of the first separator 43 is disposed so as to be in contact with the shaft core 40a.

  Then, as shown in FIGS. 6 and 7B, the winding start end portion of the first separator 43 is welded to the shaft core 40a in this state. The x mark in the figure indicates the weld location. In the welding of the first separator 43 to the shaft core 40a, the resin layer 43a of the first separator 43 is heated by the pressure of the heated heater block 70, and the molten resin passes through the holes of the heat-resistant layer 43b. This is achieved by reaching the shaft core 40a and melting the molten resin into the shaft core 40a, and the desired welding strength is such that it does not peel off due to the back tension during winding. The second separator 44 is in a state in which the winding start end portion is sandwiched between the shaft core 40 a and the first separator 43.

  Then, as shown in FIG. 7C, the shaft core 40a is rotated to wind the first separator 43 around the shaft core 40a. The first separator 43 wound around the shaft core 40a causes the second separator 44 to rotate. The winding start end is wound, and the second separator 44 is wound together with the first separator 43.

  The second separator 44 is sandwiched between the first separator 43 and the shaft core 40a when the shaft core 40a makes a half turn with the winding start end portion sandwiched between the first separator 43 and the shaft core 40a. Is done. And it bends in the edge part of the shaft core 40a with the 1st separator 43, and it will be in the state in which what is called an edge worked, and is fixed to the shaft core 40a reliably by contact resistance, and is pulled according to rotation of the shaft core 40a. Therefore, the second separator 44 is not displaced from the initial position, and the same winding driving force as that of the first separator 43 is transmitted, and is wound around the shaft core 40a.

  As shown in FIG. 7D, when the first separator 43 is wound once, the negative electrode 42 is interposed between the surfaces where the resin layers 43a and 44a face each other, and the heat-resistant layers 43b and 44b. Are interposed between the surfaces facing each other. At that time, the winding start end of the negative electrode 42 is ahead of the winding start end of the positive electrode 41 so that the negative electrode 42 is disposed on the inner peripheral side (axial core 40a side) of the positive electrode 41. Sandwiched between. In this way, the negative electrode 42 can always be arranged inside the innermost positive electrode 41 by causing the winding start end of the positive electrode 41 to be wound slightly later than the winding start end of the negative electrode 42.

  According to the present embodiment, the first separator 43 is disposed so as to cover the outside of the winding start end portion of the second separator 44, and only the winding start end portion of the first separator 43 is welded to the shaft core 40a. The handling of the separator becomes easy. Therefore, it can be realized simply by adding a handling device having a simple structure to the existing electrode group manufacturing apparatus 73, and costs such as equipment costs and maintenance costs can be kept low.

  In each of the above-described embodiments, the resin layers 43a and 44a have the same thickness, and the heat-resistant layers 43b and 44b have the same thickness. Are not limited to the same, and may be different. Moreover, you may have a heat-resistant layer on both surfaces of a resin layer.

(Example 2)
Next, Example 2 will be described below with reference to FIG. FIG. 8 is a diagram illustrating a separator winding method according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  What is characteristic in the present embodiment is that only the first separator 43 is wound around the shaft core 40a for one or more turns, and then the winding start end portion of the second separator 44, the positive electrode 41, and the negative electrode 42 are wound together. It is a configuration.

  First, as shown to Fig.8 (a), it arrange | positions so that the heat-resistant layer 43b of the winding start end part of the 1st separator 43 may contact the axial center 40a. Then, as shown in FIG. 8B, the winding start end portion of the first separator 43 is welded to the shaft core 40a. Then, the shaft core 40a is rotated as shown in FIG. 8C, and only the first separator 43 is wound around the shaft core 40a one or more times. As shown in FIG. The first separator 43 wound around the second separator 44 and the winding start end portions of the positive electrode 41 and the negative electrode 42 are wound together with the first separator 43.

  The second separator 44 has a winding start end portion sandwiched between the inner surface and the outer surface of the first separator 43 facing each other according to the rotation of the shaft core 40a, and at the end portion of the shaft core 40a together with the first separator 43. It bends and has a so-called edge effect, is securely fixed to the shaft core 40a by contact resistance, and is pulled according to the rotation of the shaft core 40a. Therefore, the second separator 44 is not displaced from the initial position, and the same winding driving force as that of the first separator 43 is transmitted, and is wound around the shaft core 40a.

  The negative electrode 42 is interposed between the surfaces of the resin layers 43a and 44a facing each other, and the positive electrode 41 is interposed between the surfaces of the heat resistant layers 43b and 44b facing each other. At that time, the winding start end of the negative electrode 42 is ahead of the winding start end of the positive electrode 41 so that the negative electrode 42 is disposed on the inner peripheral side (axial core 40a side) of the positive electrode 41. Sandwiched between. In this way, the negative electrode 42 can always be arranged inside the innermost positive electrode 41 by causing the winding start end of the positive electrode 41 to be wound slightly later than the winding start end of the negative electrode 42.

  According to the present embodiment, as in the first embodiment, only the winding start end portion of the first separator 43 is welded to the shaft core 40a, so that the handling of the separator is facilitated, and the existing electrode group manufacturing apparatus 73 can be used. Thus, it can be realized simply by adding a handling device having a simple structure, and costs such as equipment costs and maintenance costs can be kept low.

  And compared with Example 1, the length of the 2nd separator 44 wound by the axial center 40a can be shortened by 1 round. Therefore, the winding length of the positive electrode 41 and the negative electrode 42 can be increased by that much, and the capacity can be increased.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Square secondary battery 40 Electrode group 40a Shaft core 43 1st separator 43a Resin layer 43b Heat-resistant layer 44 2nd separator 44a Resin layer 44b Heat-resistant layer

Claims (6)

A prismatic secondary battery having an electrode group in which a positive electrode and a negative electrode are wound around an axis through a separator,
The separator has a first separator and a second separator,
The first separator is wound with the winding start end of the first separator being thermally welded to the shaft core,
The square secondary battery, wherein the second separator has a winding start end portion of the second separator wound around the first separator and wound together with the first separator. The first separator and the second separator have a resin layer and a heat-resistant layer formed on at least one surface of the resin layer,
In the first separator, the heat-resistant layer is disposed to face the shaft core,
2. The prismatic secondary battery according to claim 1, wherein the second separator has a heat resistant layer of the second separator disposed opposite to the heat resistant layer of the first separator.   The prismatic secondary battery according to claim 2, wherein a winding start end portion of the second separator is sandwiched between the first separator and the shaft core.   The prismatic secondary battery according to claim 2, wherein the first separator and the second separator have the heat-resistant layer formed on both surfaces of the resin layer.   The winding start end portion of the second separator is sandwiched between an inner surface and an outer surface facing each other of the first separator by winding only the first separator around the shaft one or more times. The prismatic secondary battery according to claim 2. A method for producing a prismatic secondary battery having an electrode group in which a positive electrode and a negative electrode are wound around an axis with a separator interposed therebetween,
Heat welding the winding start end of the first separator to the shaft core;
Winding the first separator around the shaft core to wind the winding start end of the second separator, and winding the second separator together with the first separator;
The manufacturing method of the square secondary battery characterized by including.

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