JP2015162270A - Method of manufacturing cylindrical secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a cylindrical secondary battery that can suppress heat evolution and breaking of a fusion zone in a method of coupling a connection lead and a battery can by laser welding.SOLUTION: A press jig 80 having a tip portion formed of at least a non-conductive material is inserted in a hollow portion 15c of a shaft core 15, the tip face 80a of the tip portion is brought into contact with the surface 50a of a connection lead 50 to press the connection lead 50 against the inner surface of a can bottom 2c of a battery can 2, a laser beam L is applied from the outside of the can bottom 2c while the connection lead 50 and the inner surface of the bottom can 2c are brought into contact with each other, and the connection lead 50 and the can bottom 2c of the battery can 2 are joined to each other so that the fused portion M between the connection lead 50 and the can bottom 2c of the battery can 2 is exposed to the surface 50a of the connection lead 50.

Description

  The present invention relates to a method for manufacturing a cylindrical secondary battery used for in-vehicle applications, and more particularly, to a method for manufacturing a cylindrical secondary battery in which a connection lead connected to a power generation element and a battery can are welded. .

As a method for manufacturing a cylindrical secondary battery, there is one having a step of welding a connection lead shown below to a battery can. A power generation element is manufactured by winding the positive electrode and the negative electrode around a shaft core via a separator. A connection lead is electrically connected to the power generation element via an electrode current collecting member, and this connection lead is joined to the bottom of the battery can by laser welding. In laser welding, the connection lead is pressed against the inner surface of the bottom of the battery can, and in this state, the connection lead and the battery can are joined by irradiating laser from the outside of the bottom of the battery can.
In the conventional method, the melted portion that joins the connection lead and the bottom of the battery can is not exposed on the surface of the connection lead. In other words, the thickness of the connection lead is increased from the outer surface of the bottom of the battery can. It was melted to the middle and welded (see, for example, Patent Document 1).

JP 2004-158318 A

  In the method described in the above-mentioned prior art document 1, since the melting part is from the outer surface of the bottom of the battery can to the middle of the thickness of the connection lead, the sectional area of the melting part is small. In a cylindrical secondary battery, if the cross-sectional area of the melted portion is small, there is a concern that it may generate heat or break at the melted portion due to vibration.

  In the method for producing a cylindrical secondary battery of the present invention, one of the positive electrode and the negative electrode of the power generation element in which the positive electrode and the negative electrode are wound around the shaft core via the separator is connected to the electrode current collector. A wound group assembly in which a connection lead is electrically connected to the electrode current collector, and the wound group assembly is accommodated in the battery can through the opening of the battery can and is formed of at least a non-conductive material. Insert a holding jig with a tip into the shaft core, bring the tip of the holding jig into contact with the surface of the connection lead, and press the connection lead against the inner surface of the bottom of the battery can. With the inner surface of the can bottom in contact, a laser beam is irradiated from the outside of the can bottom, and the melted part that joins the connection lead and the battery can bottom is connected to the surface of the connection lead. The lead and the bottom of the battery can are joined.

  According to the method for manufacturing a cylindrical secondary battery of the present invention, the melting part that joins the connection lead and the bottom of the battery can is melted so as to be exposed on the surface of the connection lead. The area can be increased. Therefore, heat generation in the melted part can be suppressed, and the ability to prevent breakage due to vibration or the like can be improved.

Sectional drawing of the cylindrical secondary battery as one Embodiment by this invention. FIG. 2 is an exploded perspective view of the cylindrical secondary battery illustrated in FIG. 1. The perspective view of the state which cut | disconnected some power generation elements illustrated in FIG. The flowchart which shows the outline | summary of the assembly method of a cylindrical secondary battery. The flowchart which shows the welding method of a connection lead and a battery can. Sectional drawing which shows the method of fixing the battery can in which the connection lead was accommodated. It is a schematic diagram for demonstrating the method of welding a connection lead and a battery can, (a) is an enlarged view of the area | region VIIa of (b). It is a schematic diagram for demonstrating the method of welding the connection lead and battery can of Embodiment 2 of this invention, (a) is an enlarged view of the area | region VIIIa of (b).

Embodiment 1
(Overall configuration of cylindrical secondary battery 1)
Hereinafter, an embodiment of a method for producing a cylindrical secondary battery according to the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view of a cylindrical secondary battery 1. In the following description, the cylindrical secondary battery 1 will be described as a lithium ion cylindrical secondary battery.
A cylindrical secondary battery 1 includes a battery case 4 having a can bottom 2c, a cylindrical battery can 2 having an open top, and a hat-type battery lid 3 that seals the top of the battery can 2. . Inside the battery container 4, each component for power generation described below is accommodated, and a non-aqueous electrolyte 6 is injected.

The cylindrical battery can 2 is made of an iron-based material, and an opening 2b is provided on the upper end side, and a groove 2a protruding to the inside of the battery can 2 is formed on the opening 2b side. The outer surface 2k of the battery can 2 is plated with nickel or the like to prevent corrosion. However, the inner surface 2 m of the battery can 2 is not plated, and the iron-based material is exposed inside the battery can 2.
A power generation element 10 is accommodated in the battery can 2. The power generating element 10 includes an elongated cylindrical shaft core 15 having a hollow portion 15c along the axial direction, and a positive electrode 11 (see FIG. 3) and a negative electrode 12 (see FIG. 3) wound around the shaft core 15. With. The positive electrode current collecting ring 27 includes a disc-shaped base portion 27a, a lower cylindrical portion 27b that protrudes toward the shaft core 15 at the inner peripheral portion of the base portion 27a, and press-fitted into the inner surface of the shaft core 15, and a battery at the outer peripheral edge. And an upper cylindrical portion 27c protruding toward the lid 3 side. The positive electrode current collecting ring 27 is fixed and supported on the upper end portion of the shaft core 15 by the lower cylindrical portion 27b.

  The positive electrode tab 16 of the positive electrode 11 is welded to the upper cylindrical portion 27 c of the positive electrode current collecting ring 27. The positive electrode current collecting ring 27 is formed of, for example, an aluminum-based metal, and the positive electrode tab 16 and the pressing member 28 of the positive electrode 11 are welded to the outer periphery of the upper cylindrical portion 27c. A number of the positive electrode tabs 16 are brought into close contact with the outer periphery of the upper cylindrical portion 27c of the positive electrode current collecting ring 27, and a pressing member 28 is wound around the outer periphery of the positive electrode tab 16 in a ring shape and temporarily fixed. In this state, ultrasonic welding is performed. Are joined together.

  A step portion 15b having a small outer diameter is formed on the outer periphery of the lower end portion of the shaft core 15, and a negative electrode current collecting ring (electrode current collecting member) 21 is press-fitted and fixed to the step portion 15b. . The negative electrode current collector ring 21 is formed of, for example, a copper-based metal, and an opening 21b that is press-fitted into the step portion 15b of the shaft core 15 is formed in a disk-shaped base portion 21a. An outer peripheral cylindrical portion 21c that protrudes toward is formed. An opening 21 d (see FIG. 2) for allowing the nonaqueous electrolyte 6 injected into the hollow shaft of the shaft core 15 to penetrate into the power generation element 10 is formed in the base 21 a of the negative electrode current collecting ring 21.

The negative electrode tab 17 of the negative electrode is joined to the outer peripheral cylindrical portion 21 c of the negative electrode current collecting ring 21.
The negative electrode tab 17 and the pressing member 22 of the negative electrode 12 are welded to the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting ring 21. A number of negative electrode tabs 17 are brought into close contact with the outer periphery of the outer peripheral cylindrical portion 21c of the negative electrode current collecting ring 21, and the presser member 22 is wound around the outer periphery of the negative electrode tab 17 in a ring shape and temporarily fixed, and is welded in this state. . A connection lead 50 is joined to the base 21a of the negative electrode current collecting ring 21 by resistance welding or laser welding. The material of the connection lead 50 is nickel or a nickel alloy.

  The multiple positive electrode tabs 16 are welded to the positive electrode current collecting ring 27, and the multiple negative electrode tabs 17 are welded to the negative electrode current collecting ring 21, whereby the positive electrode current collecting ring 27, the negative electrode current collecting ring 21, and the power generation element 10 are formed. A wound group assembly 20 is formed as a unit. A predetermined amount of non-aqueous electrolyte 6 is injected into the battery can 2. As an example of the non-aqueous electrolyte 6, a solution in which a lithium salt is dissolved in a carbonate solvent is raised. This solution does not react with the iron-based material and does not corrode the battery can 2.

FIG. 2 is an exploded perspective view of the cylindrical secondary battery.
A cylindrical positive current collecting ring 27 is press-fitted above the hollow portion 15 c of the cylindrical shaft core 15. The positive electrode current collector ring 27 is made of, for example, an aluminum-based metal. An opening 27d for releasing gas generated inside the battery is formed in the base 27a of the positive electrode current collecting ring 27. The opening 27 e formed in the positive electrode current collection ring 27 is for inserting a holding jig 80 (see FIG. 5) for welding the connection lead 50 to the battery can 2. Although details will be described later, the holding jig 80 is inserted into the hollow portion 15 c of the shaft core 15 from the opening 27 e formed in the positive electrode current collecting ring 27, and the connection lead 50 is connected to the battery can 2 at the tip of the holding jig 80. The laser is irradiated by pressing against the inner surface of the can bottom 2c. Accordingly, the wound group assembly 20 is fixed to the can bottom 2c of the battery can 2.

  The can bottom 2c of the battery can 2 connected to the negative electrode current collecting ring 21 acts as one output terminal, and the electric power stored in the power generation element 10 can be taken out from the battery can 2. A flexible connecting member 33 formed by laminating a plurality of aluminum foils is joined to the upper surface of the base portion 27a of the positive electrode current collecting ring 27 by welding one end thereof.

A battery lid unit 30 is disposed on the upper cylindrical portion 27 c of the positive electrode current collecting ring 27. The battery lid unit 30 includes a ring-shaped insulating plate 34, a connecting plate 35 fitted in an opening 34a provided in the insulating plate 34, a diaphragm 37 welded to the connecting plate 35, and a diaphragm 37 by caulking and welding. The battery cover 3 is fixed.
The insulating plate 34 has a ring shape made of an insulating resin material having a circular opening 34 a, and is placed on the upper cylindrical portion 27 c of the positive electrode current collecting ring 27.

  The insulating plate 34 has an opening 34a and a side 34b protruding downward. A connecting plate 35 is fitted in the opening 34 a of the insulating plate 34. The other end of the connection member 33 is welded and joined to the lower surface of the connection plate 35.

  The connection plate 35 is made of an aluminum-based metal and has a substantially dish shape that is substantially uniform except for the central portion and is bent to a slightly lower position on the central side. A projection 35a that is thin and formed in a dome shape is formed at the center of the connection plate 35, and a plurality of openings 35b are formed around the projection 35a. The opening 35b has a function of releasing gas generated inside the battery. The protrusion 35 a of the connection plate 35 is joined to the bottom surface of the center portion of the diaphragm 37 by resistance welding or friction stir welding. The diaphragm 37 is formed of an aluminum-based metal, and has a circular cut 37 a centering on the center portion of the diaphragm 37. The cut 37a is formed by crushing the upper surface side into a V shape by pressing and thinning the remainder. The diaphragm 37 is provided for ensuring the safety of the battery, and has a function of cleaving at the cut 37a and releasing the internal gas when the internal pressure of the battery increases.

  The diaphragm 37 fixes the peripheral edge of the battery lid 3 at the peripheral edge. As shown in FIG. 2, the diaphragm 37 initially has a side wall 37 b erected vertically at the peripheral portion toward the battery lid 3 side. The battery lid 3 is accommodated in the side wall 37b, and the side wall 37b is bent and fixed to the upper surface side of the battery lid 3 by caulking.

  The battery lid 3 is made of iron such as carbon steel, nickel plated on both front and back surfaces, a disc-shaped peripheral edge 3a that contacts the diaphragm 37, and a cylindrical portion 3b that protrudes upward from the peripheral edge 3a. Having a hat shape. An opening 3c is formed in the cylindrical portion 3b. The opening 3c is for releasing gas to the outside of the battery when the diaphragm 37 is cleaved by the gas pressure generated inside the battery. The battery lid 3 acts as one power output end, and the stored electric power can be taken out from the battery lid 3.

A gasket 43 is interposed between the opening 2 b of the battery can 2 and the battery lid 3. The gasket 43 is formed of an insulating member and covers the caulked portion between the diaphragm 37 and the battery lid 3. The gasket 43 is made of rubber, and is not intended to be limited, but one example of a preferable material is a fluorine-based resin.
The gasket 43 has a shape having an outer peripheral wall portion 43b that is formed to rise substantially vertically toward the upper direction at the peripheral edge of the ring-shaped base portion 43a.

  The outer peripheral wall 43b of the gasket 43 is bent together with the battery can 2 by pressing or the like, and the diaphragm 37 and the battery lid 3 are crimped by the base 43a and the outer peripheral wall 43b so as to be pressed in the axial direction. Thereby, the battery lid unit 30 in which the battery lid 3, the diaphragm 37, the insulating plate 34 and the connection plate 35 are integrally formed is fixed to the battery can 2 via the gasket 43. At the same time, the insulating plate 34 comes into contact with the positive electrode current collecting ring 27 of the wound group assembly 20 and presses the wound group assembly 20 against the can bottom 2 c side of the battery can 2.

FIG. 3 is a perspective view of a state in which a part of the power generation element 10 is cut to show details of the structure of the power generation element 10.
The power generating element 10 has a structure in which a positive electrode 11, a negative electrode 12, and first and second separators 13 and 14 are wound around an axis 15. The shaft core 15 is formed of an insulating material such as PP (polypropylene) and has a cylindrical shape having a hollow portion 15c. A first separator 13, a negative electrode 12, a second separator 14, and a positive electrode 11 are sequentially stacked and wound on the shaft core 15. Inside the innermost negative electrode 12, the first separator 13 and the second separator 14 are wound several times (one turn in FIG. 3). The first separator 13 and the second separator 14 are formed of an insulating porous body.

  In the innermost circumference (axial core 15 side), the start of the negative electrode 12 extends in the circumferential direction from the start of the positive electrode 11. Further, at the outermost periphery (battery can 2 side), the negative electrode 12 is wound more outward than the positive electrode 11, and the end of the negative electrode 12 is extended in the circumferential direction from the end of the positive electrode 11. ing. A second separator 14 is wound around the outer periphery of the outermost negative electrode 12. The end of the second separator 14 on the outermost periphery is stopped with an adhesive tape 19. In some cases, the first separator 13 and the second separator 14 are wound several times on the outermost periphery and then stopped by the adhesive tape 19.

  The positive electrode 11 is formed of an aluminum foil, has a long shape, and includes a positive electrode metal foil 11a and a positive electrode mixture layer 11b in which a positive electrode mixture is applied to both surfaces of the positive electrode metal foil 11a. The upper side edge extending in the longitudinal direction of the positive electrode metal foil 11a is a positive electrode foil exposed portion 11c where the positive electrode mixture is not applied and the positive electrode metal foil 11a is exposed. A large number of positive electrode tabs 16 protruding upward along the axis of the shaft core 15 are integrally formed at equal intervals on the positive electrode foil exposed portion 11c.

The positive electrode mixture includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. Examples of the positive electrode active material include lithium oxides such as cobalt, manganese, and nickel.
Examples of the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber.

  Examples of the method for applying the positive electrode mixture to the positive electrode metal foil 11a include a roll coating method and a slit die coating method. A slurry obtained by kneading a dispersion solution in a positive electrode mixture is uniformly applied to both surfaces of an aluminum foil having a thickness of 20 μm, dried, pressed, and cut. An example of the coating thickness of the positive electrode mixture is about 40 μm on one side. When the positive electrode metal foil 11a is cut, the positive electrode tab 16 is integrally formed. All the positive electrode tabs 16 have substantially the same length.

  The negative electrode 12 includes a negative electrode metal foil 12a formed of copper foil and having a long shape, and a negative electrode mixture layer 12b in which a negative electrode mixture is applied to both surfaces of the negative electrode metal foil 12a. The side edge on the lower side extending in the longitudinal direction of the negative electrode metal foil 12a is a negative electrode foil exposed portion 12c where the negative electrode mixture is not applied and the copper foil is exposed. A large number of negative electrode tabs 17 extending in the direction opposite to the positive electrode tab 16 along the axis of the shaft core 15 are integrally formed at equal intervals on the negative electrode foil exposed portion 12c.

  The negative electrode mixture includes a negative electrode active material, a negative electrode binder, and a thickener. An example of the negative electrode active material is graphite carbon.

Examples of the method for applying the negative electrode mixture to the negative electrode metal foil 12a include a roll coating method and a slit die coating method.
A slurry obtained by kneading a dispersion solvent in a negative electrode mixture is uniformly applied to both sides of a rolled copper foil having a thickness of 10 μm, dried, and then cut. An example of the coating thickness of the negative electrode mixture is about 40 μm on one side. When the negative electrode metal foil 12a is cut by pressing, the negative electrode tab 17 is integrally formed. All the negative electrode tabs 17 have substantially the same length.

  The width (length in the axial direction) of the first and second separators 13 and 14 is larger than the width (length in the axial direction) of the negative electrode mixture layer 12 b of the negative electrode 12. The width of the negative electrode mixture layer 12 b of the negative electrode 12 is larger than the width (length in the axial direction) of the positive electrode mixture layer 11 b of the positive electrode 11. The width and length of the negative electrode mixture layer 12b are made larger than the width and length of the positive electrode mixture layer 11b, and the entire region of the positive electrode mixture layer 11b is covered with the negative electrode mixture layer 12b. In the case of a lithium ion secondary battery, lithium, which is a positive electrode active material, is ionized, penetrates the separator, and is occluded by the negative electrode active material. In this case, if the negative electrode active material is not formed on the negative electrode side and the negative electrode metal foil 12a is exposed, lithium is deposited on the negative electrode metal foil 12a, causing an internal short circuit. As described above, by covering the entire region of the positive electrode mixture layer 11b with the negative electrode mixture layer 12b, it is possible to prevent such an internal short circuit due to lithium deposition.

  The first separator 13 and the second separator 14 are each formed of, for example, a polyethylene porous film having a thickness of 40 μm.

(Assembly method of cylindrical secondary battery)
With reference to FIG. 4, the outline | summary of the assembly method of the cylindrical secondary battery 1 is demonstrated.
In step S1, the power generation element 10 shown in FIG. 3 is assembled.
In step S2, the wound group assembly 20 is assembled. In this step, a positive current collecting ring 27 is attached to the upper end side of the shaft core 15 of the power generation element 10, the positive electrode tab 16 of the positive electrode 11 is welded to the positive current collecting ring 27, and a negative electrode is attached to the lower end side of the shaft core 15. The current collecting ring 21 is attached, and the negative electrode tab 17 of the negative electrode 12 is welded to the negative electrode current collecting ring 21.

In step S <b> 3, the wound group assembly 20 is accommodated in the battery can 2.
In step S4, the connection lead 50 of the wound group assembly 20 is joined to the inner surface of the can bottom 2c of the battery can 2 by laser welding. Details of this method will be described later.

  In step S <b> 5, the non-aqueous electrolyte 6 is injected into the battery can 2, and the positive and negative electrodes 11 and 12 of the power generation element 10 are infiltrated with the non-aqueous electrolyte 6.

Prior to step S6, the battery lid unit 30 is prepared in advance (see step S11).
In order to manufacture the battery lid unit 30, first, the diaphragm 37 is caulked on the periphery of the battery lid 3, and the battery lid 3 and the diaphragm 37 are integrated by welding. Next, the connecting plate 35 is fitted and attached to the opening 34 a of the insulating plate 34. And the protrusion part 35a of the connection board 35 is joined to the bottom face of the diaphragm 37 with which the battery cover 3 was fixed by resistance welding or friction stir welding. Thereby, the battery lid unit 30 in which the battery lid 3, the diaphragm 37, the insulating plate 34, and the connection plate 35 are integrated is formed.

  In step S6, one end of the connection member 33 is joined to the positive electrode current collecting ring 27 by welding, and then the other end of the connection member 33 is joined to the diaphragm 37 in which the connection plate 35 is integrated by welding.

  In step S7, the diaphragm 37, the battery lid 3 and the gasket 43 to which the insulating plate 34 and the connecting plate 35 are joined are disposed in the opening 2b of the battery can 2, and the battery lid unit 30 is constituted by caulking, whereby the battery can 2 opening 2b is sealed. Thereby, the cylindrical secondary battery 1 sealed from the outside is produced.

(Welding method for connecting lead and battery can)
Details of steps S3 to S4 in FIG. 4 will be described with reference to a flow chart showing a welding method between the connection lead 50 and the battery can 2 shown in FIG.
In step S2, the wound group assembly 20 is assembled. In step S3, the wound group assembly 20 is accommodated in the battery can 2.
In step S <b> 3, the connection lead 50 of the wound group assembly 20 is inserted from the opening 2 b of the battery can 2 toward the can bottom 2 c side of the battery can 2. Therefore, in a state where the wound group assembly 20 is housed in the battery can 2, the lower surface of the connection lead 50 is in contact with the inner surface of the can bottom 2 c of the battery can 2.

  In step S31, the battery can 2 in which the wound group assembly 20 is accommodated is attached to the fixing jig 70 as shown in FIG. The fixing jig 70 includes a cylindrical tube wall 71 that houses the battery can 2 and an installation portion 72 that is provided perpendicular to the tube wall 71. The can bottom 2 c of the battery can 2 is placed on the upper surface of the installation portion 72.

In step S <b> 32, a rod-shaped holding jig 80 having a circular cross section is inserted into the hollow portion 15 c of the shaft core 15, and the surface 50 a of the connection lead 50 is pressed by the tip surface 80 a of the holding jig 80. Is pressed against the inner surface of the bottom 2c of the battery can 2.
This state is illustrated in FIG.
The holding jig 80 has a straight portion 81 and a tip portion 82 that gradually decreases in diameter toward the tip surface 80 a (see FIG. 7). The tip surface 80 a has a cross-sectional area from the straight portion 81. Is a small flat surface. The holding jig 80 is made of, for example, a ceramic material such as alumina, zirconia, silicon carbide, or silicon nitride.

  In step S33, the laser beam L is irradiated from the outside of the can bottom 2c of the battery can 2 as shown in FIG. The welding device 60 includes a laser oscillator 61, a control device 62, and a condensing system lens 63. Based on a control signal obtained from the control device 62, a pulsed laser beam L is generated in the laser oscillator 61, and is emitted toward the condensing system lens 63 with a predetermined intensity at a predetermined timing. The laser beam L is condensed in a region to be a welded portion by the condensing system lens 63, and the can bottom 2c and the connection lead 50 of the battery can 2 in the region irradiated with the laser beam L are melted.

As the laser beam L, a general laser beam L such as a YAG laser or a CO ₂ laser can be used. The welding apparatus 60 includes a plurality of condensing system lenses 63, and adjusts the position of the lens to shape the outer periphery of the laser beam L into a predetermined shape. The control device 62 controls the intensity of irradiation of the laser beam L generated in the laser oscillator 61 and the timing of irradiation.

  By irradiation with the laser beam L, as described above, the bottom 2c of the battery can 2 and the irradiation region of the connection lead 50 are melted and joined. As shown in FIG. 7A, the laser beam L is irradiated until the melted portion M appears on the surface 50a of the connection lead 50 facing the inside of the battery can 2. The cross-sectional shape of the melting part M is the largest on the outer surface side of the can bottom 2c of the battery can 2 on the side irradiated with the laser beam L, and gradually decreases toward the surface 50a side of the connection lead 50. When the melted part M exposed on the surface 50a of the connection lead 50 reaches a predetermined area, the irradiation of the laser beam L is stopped, the melted part M is solidified, and the connection lead 50 and the can bottom 2c of the battery can 2 Wait until and stick. That is, the state where the connection lead 50 is pressed against the can bottom 2 c of the battery can 2 by the holding jig 80 is maintained. This standby time is, for example, about 2 to 3 ms.

Since the holding jig 80 is formed of ceramics, it does not adhere to the melting part M. Further, as shown in FIG. 7A, when the area of the melted portion M exposed on the surface 50a of the connection lead 50 is smaller than the area of the front end surface 80a of the holding jig 80, the holding jig 80 is The front end surface 80 a is supported by a non-melting region around the melting portion M in the connection lead 50. For this reason, the front-end | tip part of the holding jig 80 is not pushed into the fusion | melting part M. FIG.
As described above, when step S4 for joining the connection lead 50 and the can bottom 2c of the battery can 2 is completed, the holding jig 80 is inserted and removed, and steps S5 to S7 are performed. The secondary battery 1 is obtained.

According to the one embodiment, the following effects are obtained.
(1) In the state where the connection lead 50 is pressed against the can bottom 2c of the battery can 2, the laser beam L is irradiated from the outside of the can bottom 2c, and the melting part M that melts by the irradiation of the laser beam L is It is melted so as to be exposed on the inner surface 50a. For this reason, the cross-sectional area of the fusion | melting part M can be enlarged compared with the conventional method with which the fusion | melting part M is fuse | melted to the intermediate position of the thickness of the connection lead 50. FIG. Thereby, the heat_generation | fever in the fusion | melting part M can be suppressed and the prevention ability with respect to a fracture | rupture by vibration etc. can be improved.

(2) The holding jig 80 for pressing the connection lead 50 against the can bottom 2c of the battery can 2 was made of a ceramic material. For this reason, even if the fusion part M appears on the inner surface 50a of the battery can 2 of the connection lead 50, the holding jig 80 does not adhere to the fusion part M, and the joining by welding is performed efficiently. be able to.

(3) The battery can 2 was formed of an iron-based material, and the non-aqueous decomposition solution was a solution in which a lithium salt was dissolved in a carbonate-based solvent without corroding the iron-based material. For this reason, even if the fusion | melting part M appears on the surface 50a inside the battery can 2 of the connection lead 50, the battery can 2 does not corrode after welding, and it can improve reliability.

Embodiment 2
FIG. 8 is a second embodiment of the present invention, and FIG. 8A is an enlarged view of a region VIIIa in FIG. 8B, for explaining a method of welding the connection lead 50 and the battery can 2. FIG.
The difference between the second embodiment and the first embodiment is that the area of the front end surface 80a of the holding jig 80 is smaller than the area of the melted portion M exposed on the inner surface 50a of the battery can 2 of the connection lead 50. This is the point.
As shown in FIG. 8A, the melting portion M that appears on the inner surface 50 a of the battery can 2 of the connection lead 50 extends to the outside of the outer periphery of the front end surface 80 a of the holding jig 80. ing.
If the area of the melted part M exposed on the surface 50a of the connection lead 50 in the second embodiment is the same as that in the first embodiment, the area of the tip surface 80a of the holding jig 80 in the second embodiment is the same as that in the first embodiment. The area of the front end surface 80a of the holding jig 80 is smaller.
In this way, the cross-sectional area of the surface perpendicular to the axial direction of the hollow portion 15c of the shaft core 15 through which the pressing jig 80 is inserted, that is, the cross-sectional area of the surface perpendicular to the axial direction of the shaft core 15 is reduced. It becomes possible. If the cross-sectional area of the shaft core 15 is reduced, the number of turns of the positive and negative electrodes 11 and 12 wound around the shaft core 15 can be increased, and the length of the positive and negative electrodes 11 and 12 is increased. Can do. That is, the capacity of the cylindrical secondary battery 1 can be increased.

  In the second embodiment, since the area of the front end surface 80a of the holding jig 80 is smaller than the area of the melted portion M exposed inside the battery can 2 of the connection lead 50, the battery can is irradiated with the laser beam L. In the state in which the can bottom 2c and the connecting lead 50 are melted, the tip end portion of the holding jig 80 is pushed into the melting portion M. In order to avoid this, a restricting means such as a stopper for restricting the holding jig 80 from moving downward is provided, and the tip of the holding jig 80 has a predetermined depth or more in the melted part M. It is only necessary to prevent it from being pushed into.

Other configurations in the second embodiment are the same as those in the first embodiment. Corresponding components are denoted by the same reference numerals and description thereof is omitted.
Also in the second embodiment, the effects (1) to (3) of the first embodiment can be obtained.

  In the above-described embodiment, the pressing jig 80 is formed of ceramics, but may be formed of a non-conductive material other than ceramics such as Teflon (registered trademark).

  The holding jig 80 does not need to be entirely formed of a non-conductive material, only the tip side including the tip surface 80a is formed of a non-conductive material, and the rest is formed of a conductive material. Good.

  Although the battery can 2 is formed of an iron-based material, the present invention is applicable even when the battery can 2 is formed of another material such as an aluminum-based alloy.

  Although the connection lead 50 is exemplified as being connected to the negative electrode 12, there is also a cylindrical secondary battery 1 having the battery can 2 as the positive electrode side. In the present invention, the connection lead 50 connected to the positive electrode 11 is used as the battery can. 2 can also be applied to laser welding.

  Further, the present invention is not limited to the lithium ion secondary battery, and can also be applied to the cylindrical secondary battery 1 using a water-soluble electrolytic solution such as a nickel metal hydride battery, a nickel cadmium battery, or a lead storage battery. is there.

  Further, although the opening 2b of the battery can 2 is exemplified as being sealed by the battery lid unit 30, it may be sealed by a single battery lid. In addition, the cylindrical secondary battery manufacturing method of the present invention can be applied in various modifications within the scope of the gist of the invention. In short, the connection lead and the inner surface of the can bottom are in contact with each other. In the state, the connection lead and the bottom of the battery can are exposed so that a melted part that joins the connection lead and the bottom of the battery can is exposed to the laser beam from the outside of the can bottom. What is necessary is just to join.

DESCRIPTION OF SYMBOLS 1 Cylindrical secondary battery 2 Battery can 2c Can bottom 2k Outer surface 2m Inner surface 3 Battery cover 4 Battery container 6 Nonaqueous electrolyte 10 Power generation element 11 Positive electrode 12 Negative electrode 15 Shaft core 15c Hollow part 20 Winding group assembly 21 Negative electrode collection Electric ring (electrode current collector)
30 Battery lid unit 50 Connection lead 50a Surface 60 Welding device 70 Fixing jig 80 Holding jig 80a Tip surface 82 Tip L Laser beam M Melting part

Claims (4)

One of the positive electrode and the negative electrode of a power generation element in which a positive electrode and a negative electrode are wound around a shaft core via a separator is connected to an electrode current collector, and a connection lead is connected to the electrode current collector Prepare electrically connected winding group assembly;
Accommodating the wound group assembly into the battery can from an opening of the battery can;
A holding jig having a tip formed of at least a non-conductive material is inserted into the shaft core, and the tip of the tip of the holding jig is brought into contact with the surface of the connection lead to connect the connection lead. Press against the inner surface of the bottom of the battery can,
In the state where the connection lead and the inner surface of the can bottom are in contact with each other, a melting part that irradiates a laser beam from the outside of the can bottom and joins the connection lead and the can bottom of the battery can is the connection lead. A method of manufacturing a cylindrical secondary battery, wherein the connection lead and the bottom of the battery can are joined so as to be exposed on the surface of the battery. In the manufacturing method of the cylindrical secondary battery according to claim 1,
A method for manufacturing a cylindrical secondary battery, wherein at least the tip of the pressing jig is made of ceramics. In the manufacturing method of the cylindrical secondary battery according to claim 1,
After joining the connection lead and the bottom of the battery can, the battery can includes a step of injecting a non-aqueous electrolyte into the battery can. The battery can is formed of an iron-based material, and the inner surface of the battery can An iron-based material forming the battery can without being plated is exposed inside the battery can, and the non-aqueous electrolyte is a solution in which a lithium salt is dissolved in a carbonate-based solvent. A method for manufacturing a secondary battery. In the manufacturing method of the cylindrical secondary battery of any one of Claims 1 thru | or 3,
The method of manufacturing a cylindrical secondary battery, wherein an area of the tip surface of the tip part of the holding jig is smaller than an area of the melted part exposed on the surface of the connection lead.

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