JP7009271B2 - Manufacturing method of closed battery and closed battery - Google Patents

Description

The present disclosure relates to a method for manufacturing a closed battery and a closed battery.

In recent years, secondary batteries are expected not only to be used by being incorporated in electronic devices such as personal computers, but also as a power source for supplying electric power to a motor for traveling a vehicle. In a non-aqueous electrolyte secondary battery, although high energy can be obtained, if an internal short circuit occurs due to the inclusion of metallic foreign matter or the like in the battery, problems such as heat generation of the battery itself may occur.

Conventionally, the outer can and the lead connected to one of the positive electrode and the negative electrode of the electrode body are mainly connected by resistance welding. However, this resistance welding has a problem that spatter occurs inside the battery during the welding process and metal foreign matter is mixed in the battery, which deteriorates the manufacturing quality, safety, and reliability of the battery due to a voltage failure. Therefore, in recent years, there are some that irradiate an energy beam, for example, a laser beam from the outside of the outer can to weld the outer can and the lead to prevent the generation of spatter (see, for example, Patent Documents 1 to 3). ..

Further, Patent Document 4 describes a method of manufacturing a battery in which an energy beam is irradiated from the outside of an outer can in two stages to weld the outer can and the cap body. In the method for manufacturing this battery, a laser beam irradiated with a first laser output and a second laser output is used as the pulsed laser beam. The first laser output heats the laser irradiation side member of the superposition member and removes organic substances between the superposition members. The second laser output melts the laser irradiation side member of the superposition member and welds a plurality of superposition members.

Japanese Unexamined Patent Publication No. 2010-3686 Japanese Patent Application Laid-Open No. 2015-162326 Japanese Unexamined Patent Publication No. 2016-207412 Japanese Unexamined Patent Publication No. 11-24066

In the conventional method of manufacturing a battery in which a lead is welded to an outer can by irradiating an energy beam from the outside of the outer can, a hole may be formed in the outer can from the inside when the outer can is irradiated with the energy beam. There is. Specifically, a solid or liquid resin may be present between the outer can and the lead immediately before the lead is welded to the outer can. This resin is derived from a lubricating oil-based resin, a dust-generating resin in the process, a resin adhering to a battery component, and the like. When a resin is present between the outer can and the lead, if the energy beam is applied to the outer can, the heat generated by the irradiation may sublimate the solid resin or vaporize the liquid resin. There is. Due to the sublimation or vaporization of this resin, the volume of gas expands at once between the outer can and the reed, and the gas may escape toward the outside of the outer can melted by the energy beam. As a result, a hole leading from the inside to the outside is formed in the outer can, and the airtightness inside the battery may not be maintained. Even if the hole does not reach the outside of the outer can, a concave hole may be formed on the weld surface with the lead on the inner surface of the outer can, and this hole increases the welding area between the outer can and the lead. By reducing it, the welding strength may decrease.

In the battery described in Patent Document 4, two stages of continuous energy beams are irradiated from the outside of the outer can, and the electrolytic solution, which is an organic substance between the overlapping members, is eliminated by the first laser output. On the other hand, Patent Document 4 only discloses that after the electrolytic solution is injected into the outer can, the inconvenience when the electrolytic solution enters between the superposition members is eliminated.

It is an object of the present disclosure to prevent the generation of holes penetrating the outer can when welding leads to the outer can in the method for manufacturing a closed battery and the closed battery, and to obtain stable welding strength.

In the method for manufacturing a closed battery according to the present disclosure, an electrode body in which at least one positive electrode and at least one negative electrode are wound or laminated via a separator, and a bottomed tubular outer can accommodating the electrode body are provided. A method for manufacturing a sealed battery including a welding process, which comprises a welding process of irradiating an energy beam from the outside of the outer can to weld a lead connected to one of a positive electrode and a negative electrode to the outer can, and the welding process is performed on the outer can. The first irradiation that irradiates the portion of the outer surface where the leads face each other through the inner surface of the outer can with a first energy beam controlled so that the first molten portion, which is a melt mark, stays inside the outer can. After the step and the first irradiation step, a second molten portion, which is a melting mark, is formed from the outer surface of the outer can to the inside of the lead inside the portion of the outer surface of the outer can where the first molten portion is exposed. It is a method of manufacturing a sealed battery, comprising a second irradiation step of irradiating a second energy beam controlled so as to be.

The sealed battery according to the present disclosure is a sealed battery including an electrode body in which at least one positive electrode and at least one negative electrode are wound or laminated via a separator, and a bottomed tubular outer can for accommodating the electrode body. The outer can is formed of nickel-plated iron, and the lead connected to one of the positive electrode and the negative electrode and the outer can are welded at a welded portion formed from the outer surface of the outer can toward the lead. The welded portion includes a first melting portion and a second melting portion which are melting marks, and the first melting portion is formed in a range of 50 to 99% of the thickness of the outer can from the outer surface of the outer can. The second melting portion is formed from the outer surface of the outer can to the inside of the lead, and is a sealed battery inside the first melting portion when the welded portion is viewed from the outside of the outer can.

According to the method for manufacturing a closed battery and the closed battery according to the present disclosure, it is possible to prevent the generation of holes penetrating the outer can when welding leads to the outer can, and to obtain stable welding strength.

It is sectional drawing of the bottom side half part of the closed battery manufactured by the manufacturing method of an example of Embodiment. This is the bottom surface of the sealed battery shown in FIG. It is an enlarged view of the part A of FIG. It is the B part enlarged view of FIG. FIG. 3 is a sectional view taken along the line CC of FIG. It is a figure which irradiates a 1st energy beam in the manufacturing method of an Embodiment. It is a figure which irradiates a second energy beam in the manufacturing method of an embodiment. It is a figure which irradiates a 1st energy beam in the manufacturing method of another example of embodiment. It is sectional drawing of the bottom side half part of the sealed battery of another example of embodiment. It is a bottom view of the sealed battery shown in FIG.

Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the specific shape, material, numerical value, direction, etc. are examples for facilitating the understanding of the present disclosure, and can be appropriately changed according to the specifications of the sealed battery. Further, in the following, the term "abbreviation" is used to mean, for example, not only when they are completely the same but also when they can be regarded as substantially the same. Further, when a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that those characteristic portions are appropriately combined and used.

Further, although the case where the sealed battery is a cylindrical non-aqueous electrolyte secondary battery will be described below, the sealed battery is not limited to the cylindrical battery, and may be a square battery or the like. Further, the sealed battery is not limited to the non-aqueous electrolyte secondary battery as described below, but may be another secondary battery such as a nickel hydrogen battery or a Nikkado battery, or a primary battery such as a dry battery or a lithium battery. You may. The electrode body of the battery is not limited to the winding type as described below, and may be a laminated type in which a plurality of positive electrodes and negative electrodes are alternately laminated via a separator.

FIG. 1 is a cross-sectional view of a bottom half of a sealed battery 20 manufactured by the manufacturing method of an example of the embodiment. FIG. 2 is a bottom view of the sealed battery 20. FIG. 3 is an enlarged view of part A of FIG. FIG. 4 is an enlarged view of part B of FIG. FIG. 5 is a sectional view taken along the line CC of FIG. Hereinafter, the sealed battery 20 will be referred to as a battery 20.

As illustrated in FIGS. 1 and 2, the battery 20 includes a wound electrode body 22, a non-aqueous electrolyte (not shown), and an outer can 50. The winding type electrode body 22 has a positive electrode 23, a negative electrode 24, and a separator 25, and the positive electrode 23 and the negative electrode 24 are laminated via the separator 25 and wound in a spiral shape. In the following, one side in the axial direction of the electrode body 22 may be referred to as “up”, and the other side in the axial direction may be referred to as “down”. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt such as a lithium salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to the liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like.

The positive electrode 23 has a band-shaped positive electrode current collector 23a, and a positive electrode lead (not shown) is connected to the positive electrode current collector 23a. The positive electrode lead is a conductive member for electrically connecting the positive electrode current collector 23a to the positive electrode terminal (not shown), and is one side of the axial direction α of the electrode body 22 from the upper end of the electrode group (FIG. 1). It extends upward). Here, the electrode group means a portion of the electrode body 22 excluding each lead. The positive electrode lead is provided, for example, in the substantially central portion of the electrode body 22 in the radial direction β.

The negative electrode 24 has a band-shaped negative electrode current collector 24a, and the negative electrode lead 26 is connected to the negative electrode current collector 24a. The negative electrode lead 26 is a conductive member for electrically connecting the negative electrode current collector 24a to the outer can 50 which is the negative electrode terminal, and is the other side in the axial direction α from the lower end of the winding end side end portion of the electrode group. It extends to the bottom of FIG. 1).

The constituent material of each lead is not particularly limited. The positive electrode lead can be composed of a metal containing aluminum as a main component, the negative electrode lead 26 can be composed of a metal containing nickel or copper as a main component, or a metal containing both nickel and copper. The negative electrode lead 26 may be formed of nickel-plated iron.

The negative electrode lead 26 is bent at a substantially right angle so as to face the winding core portion of the electrode body 22 via the insulating plate 30 and comes into contact with the inner surface of the bottom plate portion 51. Then, in this state, the outer can 50 and the negative electrode lead 26 are welded by the welded portion 54 by sequentially irradiating the first laser beam 40 and the second laser beam 41 from the outside of the outer can 50 toward the bottom plate portion 51. do. The welded portion 54 refers to a portion formed by melting marks that are melted and solidified by being irradiated with the laser beams 40 and 41, respectively. The welded portion 54 is formed from the outer surface of the outer can 50 toward the negative electrode lead 26. The first laser beam 40 corresponds to the first energy beam, and the second laser beam 41 corresponds to the second energy beam. The welded portion 54 and the welding process will be described in detail later.

The outer can 50 is a container formed by processing a nickel-plated iron material into a bottomed cylindrical shape. The iron used for the outer can 50 can contain dissimilar metals and the like as long as it does not adversely affect the battery characteristics.

The opening of the outer can 50 is sealed by a sealing body (not shown). The outer can 50 houses the electrode body 22 and the non-aqueous electrolyte. An insulating plate 30 is arranged below the electrode body 22. The negative electrode lead 26 extends to the bottom side of the outer can 50 through the outside of the insulating plate 30 and is welded to the inner surface of the bottom plate 51 of the outer can 50. The thickness of the bottom plate portion 51, which is the bottom portion of the outer can 50, is, for example, 0.2 to 0.5 mm.

The electrode body 22 has a winding structure in which the positive electrode 23 and the negative electrode 24 are spirally wound via the separator 25. The positive electrode 23, the negative electrode 24, and the separator 25 are all formed in a band shape, and are wound in a spiral shape so as to be alternately laminated in the radial direction β of the electrode body 22. In the present embodiment, the winding core portion 29 including the winding center axis O of the electrode body 22 is a columnar space.

The positive electrode 23 has a positive electrode active material layer formed on the positive electrode current collector 23a. For example, positive electrode active material layers are formed on both sides of the positive electrode current collector 23a. For the positive electrode current collector 23a, for example, a metal foil such as aluminum, a film on which the metal is arranged on the surface layer, or the like is used. A suitable positive electrode current collector 23a is a metal foil that is stable in the potential range of the positive electrode, such as a metal containing aluminum or an aluminum alloy as a main component.

The positive electrode active material layer preferably contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 23 is dried after applying a positive electrode mixture slurry containing, for example, a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) on both surfaces of the positive electrode current collector 23a. And produced by rolling.

Examples of the positive electrode active material include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. The lithium-containing transition metal oxide is not particularly limited, but is limited to the general formula Li _{1 + x} MO ₂ (in the formula, −0.2 <x ≦ 0.2, M contains at least one of Ni, Co, Mn, and Al). It is preferably a composite oxide represented by.

Examples of the conductive agent include carbon materials such as carbon black (CB), acetylene black (AB), Ketjen black, and graphite. Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. Be done. Further, these resins may be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO) and the like. One of these may be used alone, or two or more of them may be used in combination.

The negative electrode 24 has a negative electrode active material layer formed on the negative electrode current collector 24a. For example, negative electrode active material layers are formed on both sides of the negative electrode current collector 24a. For the negative electrode current collector 24a, for example, a foil of a metal stable in the potential range of the negative electrode such as aluminum or copper, a film on which the metal is arranged on the surface layer, or the like is used.

It is preferable that the negative electrode active material layer is formed on both sides of the negative electrode current collector 24a in the entire area excluding the plain portion described later. The negative electrode active material layer preferably contains a negative electrode active material and a binder. The negative electrode active material layer may contain a conductive agent, if necessary. The negative electrode 24 is manufactured by applying a negative electrode mixture slurry containing, for example, a negative electrode active material, a binder, water, and the like to both surfaces of the negative electrode current collector 24a, and then drying and rolling the negative electrode 24.

The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions, for example, carbon materials such as natural graphite and artificial graphite, metals alloying with lithium such as Si and Sn, or these. Alloys containing, composite oxides and the like can be used. As the binder contained in the negative electrode active material layer, for example, the same resin as in the case of the positive electrode 23 is used. When preparing a negative mixture slurry with an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid or a salt thereof, polyvinyl alcohol and the like can be used. One of these may be used alone, or two or more of them may be used in combination.

The negative electrode 24 is provided with a plain portion where the surface of the negative electrode current collector 24a is exposed. The plain portion is a portion to which the negative electrode lead 26 is connected, and the surface of the negative electrode current collector 24a is not covered with the negative electrode active material layer. The plain portion has a substantially rectangular shape in front view extending long along the axial direction α which is the width direction of the negative electrode 24, and is formed wider than the negative electrode lead 26.

The negative electrode lead 26 is joined to the surface of the negative electrode current collector 24a by, for example, ultrasonic welding. In addition to the winding end side end of the negative electrode 24, a negative electrode lead different from the negative electrode lead 26 is provided at the winding direction intermediate part, the winding start side end, and the like, and extends from the electrode group to the bottom plate portion 51 side. It is also possible to extend the negative electrode lead, superimpose the extended negative electrode lead on the negative electrode lead 26 at the winding core portion, and weld it to the outer can 50 by irradiation with a laser beam. By providing the negative electrode leads at a plurality of positions of the negative electrode 24, the current collecting property is improved. The plain portion is provided, for example, by intermittent coating in which the negative electrode mixture slurry is not applied to a part of the negative electrode current collector 24a.

The positive electrode lead is bonded to a plain portion formed on the positive electrode current collector 23a, and a portion protruding upward from the positive electrode current collector 23a is bonded to a positive electrode terminal or a portion connected to the positive electrode terminal.

A porous sheet having ion permeability and insulating property is used for the separator 25. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a non-woven fabric. As the material of the separator 25, an olefin resin such as polyethylene or polypropylene is preferable.

The welded portion 54 is formed by melting marks as described above. When the welded portion 54 is viewed from the outside (lower side of FIG. 1) of the bottom plate portion 51 of the outer can 50, as shown in FIG. 4, the second melting portion 58 is first melted so as to surround the entire circumference. It is inside the portion 56 and is exposed on the outer surface of the outer can 50. In this state, the second melting portion 58 welds the outer can 50 and the negative electrode lead 26 (FIG. 3). The second melting portion 58 is formed deeper than the first melting portion 56.

The first melting portion 56 is formed so as to stay inside the outer can 50. The first melting portion 56 is formed by irradiating the first laser beam 40 from the outside of the outer can 50 toward the bottom plate portion 51 in the first irradiation step described later. The second melting portion 58 is formed by irradiating the second laser beam 41 from the outside of the outer can 50 toward the bottom plate portion 51 in the second irradiation step after the first irradiation step as described later.

As shown in FIG. 4, the first melting portion 56 has a linear planar shape when viewed from the outside of the bottom plate portion 51 of the outer can 50. The plane shape of the second melting portion 58 when viewed from the outside of the bottom plate portion 51 is also linear, and the width w2 of the second melting portion 58 is smaller than the width w1 of the first melting portion 56. Further, the second molten portion 58 has a higher nickel content (mass%) than the first molten portion 56. The presence of the first melting portion 56 and the second melting portion 58 can be confirmed, for example, by observing from the outside of the outer can 50. In addition to this, the presence of the first melting portion 56 and the second melting portion 58 can be confirmed, for example, by observing the cross section of the outer can 50 in the thickness direction of the melting mark with an optical microscope or the like.

As each laser beam, it is preferable to use the laser beam of a fiber laser. Since the spot diameter of the fiber laser can be made very small, for example, about 0.02 mm to 0.05 mm, the width of the melting marks formed by the fiber laser can also be made very small, about 0.1 mm. Therefore, the power density of the focusing point of the laser beam can be made very high. The second laser beam 41 irradiates the outer can 50 so that the melting marks formed by the irradiation of the second laser beam 41 do not penetrate the negative electrode lead 26.

The spot diameter of the first laser beam 40 when forming the first melting portion 56 is preferably larger than the spot diameter of the second laser beam 41. The first laser beam 40 is irradiated so that the melting marks formed by the irradiation of the first laser beam 40 do not penetrate the outer can 50 and reach the negative electrode lead 26. At this time, for example, the irradiation portion of the first laser beam 40 is moved on the outer surface of the bottom plate portion 51 of the outer can 50 toward one side (for example, the right side in FIG. 1) along the linear direction, and the first melting is performed. The portion 56 is formed. The second melting portion 58 formed by the second laser beam 41 is formed inside the first melting portion 56 formed by irradiation with the first laser beam 40.

Further, by moving the battery 20 relatively in a direction orthogonal to the irradiation direction of the laser beam, the welded portion 54 by the laser beam tends to be linear when viewed from the outside of the bottom plate portion 51. At this time, the battery 20 can be arranged with the bottom plate portion 51 facing up, and the laser beam can be irradiated toward the bottom portion thereof. It is also possible to arrange the battery 20 in a state of being tilted sideways and irradiate the bottom plate portion 51 with a laser beam.

Next, a method of manufacturing a battery according to an embodiment including a welding step of irradiating a laser beam, which is an example of an energy beam, from the outside of the outer can 50 to weld the outer can 50 and the negative electrode lead 26 will be described. In this manufacturing method, the welding step includes a first irradiation step and a second irradiation step. The first irradiation step and the second irradiation step are performed before injecting the electrolyte into the outer can 50. FIG. 6 is a diagram of irradiating the first laser beam 40 in the first irradiation step in the manufacturing method of the embodiment. FIG. 7 is a diagram for irradiating the second laser beam 41 in the second irradiation step in the manufacturing method of the embodiment.

Before performing the first irradiation step, the electrode body 22 is housed in the outer can 50 with the negative electrode lead 26 facing the inner surface of the bottom plate portion 51 of the outer can 50. Then, in this state, the laser beam is irradiated from the outside of the outer can 50 toward the bottom plate portion 51 in two steps by the first irradiation step and the second irradiation step. Specifically, as shown in FIG. 6, before irradiating the first laser beam 40 forming the first melting portion 56, the pressing rod 70 is inserted from above inside the outer can 50, and the pressing rod 70 is used. The negative electrode lead 26 is pressed from above via the insulating plate 30. As a result, the outer can 50 and the negative electrode lead 26 are brought into close contact with each other, and in that state, the first portion of the outer surface of the bottom plate portion 51 where the negative electrode lead 26 faces via the inner surface of the bottom plate portion 51. The first molten portion 56 is formed by irradiating the first laser beam 40 having an energy amount. At this time, the first melting portion 56, which is a melting mark, does not penetrate the outer can 50 at the irradiation position of the first laser beam 40, stays inside the outer can 50, and does not reach the negative electrode lead 26. The laser beam 40 is controlled. At this time, it is preferable that the spot diameter of the first laser beam 40 is larger than the spot diameter of the second laser beam 41 described later. Further, the irradiation portion of the first laser beam 40 is moved on the outer surface of the bottom plate portion 51 of the outer can 50 toward one side (for example, the right side in FIG. 6) along the linear direction. At this time, the light source of the laser beam is moved so as to move the battery 20 relatively in the direction orthogonal to the irradiation direction of the laser beam. In the present embodiment, the negative electrode lead 26 is pressed by the holding rod 70 via the insulating plate 30, but a hole is provided in the center of the insulating plate 30, and the holding rod penetrating the hole directly presses the negative electrode lead 26. You may.

Next, in the second irradiation step, as shown in FIG. 7, before irradiating the second laser beam 41 forming the second melting portion 58, the outer can is formed by the holding rod 70 as in the case of the first irradiation step. The 50 and the negative electrode lead 26 are in close contact with each other. Then, in that state, the second laser beam 41 having a second energy amount is irradiated from the outside toward the bottom plate portion 51 to the inside of the portion where the first melting portion 56 is exposed, and the second melting portion 58 is irradiated. Form. At this time, the second laser beam 42 is controlled so that the second melting portion, which is a melting mark, is formed from the outer surface of the bottom plate portion 51 to the inside of the negative electrode lead 26. At this time, for example, the irradiation portion of the second laser beam 41 is moved on the outer surface of the bottom plate portion 51 of the outer can 50 toward one side (for example, the right side in FIG. 7) along the above linear direction. 2 The molten portion 58 is formed. The second melting portion 58 is formed so as to melt a part of the outer can 50 and the negative electrode lead 26 within the range inside the melting mark formed by the irradiation of the first laser beam 40. A part of the first melting section 56 is melted and solidified to change to the second melting section 58, and the second melting section 58 remains unchanged in the second melting section 58 of the first melting section 56. It is formed so as to be adjacent to the portion. In the second irradiation step as well, as in the first irradiation step, the light source of the laser beam is moved so as to move the battery 20 in the direction orthogonal to the irradiation direction of the laser beam.

With the outer can 50 and the negative electrode lead 26 in close contact with each other by the holding rod 70 as described above, the first laser beam 40 is irradiated from the outside of the outer can 50 to weld the outer can 50 and the negative electrode lead 26. It is easy to prevent spattering from occurring inside the battery 20.

The second melting portion 58 is formed inside the first melting portion 56 on the outer surface of the bottom plate portion 51, and extends toward the inside of the bottom plate portion 51 (upper side in FIG. 1), the first melting portion 56 and the second melting portion 58. The boundary with and is located inside the bottom plate portion 51. As described above, the first laser beam 40 and the second laser beam 41 irradiate the irradiated portion so as to move along the same linear direction on the outer surface of the bottom plate portion 51. As a result, the planar shape when viewed from the outside of the bottom plate portion 51 of the first melting portion 56 and the second melting portion 58 is formed linearly. Further, when viewed from the outside of the bottom plate portion 51, it is preferable that the entire second melting portion 58 is surrounded by the first melting portion 56. The laser beam irradiation portion may be moved relative to the outer surface of the outer can 50, and of the laser beam and the outer can 50, the outer can 50 may actually be moved.

According to the battery manufacturing method and the battery 20 of the above embodiment, the hole penetrating the outer can 50 when the negative electrode lead 26 is welded to the outer can 50 before the electrolyte is injected into the outer can 50. It is possible to prevent the occurrence and obtain stable welding strength. Specifically, when the resin is present between the outer can 50 and the negative electrode lead 26 by irradiating the bottom plate portion 51 with the first laser beam 40 forming the first melting portion 56, the resin is sublimated or the like. Vaporize. As a result, the second laser beam 41 forming the second molten portion 58 is irradiated to the inside of the first molten portion 56 in a state where no resin is present between the outer can 50 and the negative electrode lead 26, and the outer can 50 and the negative electrode are irradiated. The lead 26 can be welded. Therefore, it is possible to prevent the generation of holes penetrating the outer can 50 and suppress the generation of recesses that do not penetrate in the outer can 50. Therefore, the recesses on the inner surface of the outer can 50 facing the negative electrode lead 26 are formed. Occurrence can be suppressed and stable welding strength can be obtained.
be able to.

Further, in the above battery 20, since the welded portion 54 includes the first molten portion 56 and the second molten portion 58 shown in FIGS. 1 and 2, stress corrosion cracking occurs in the bottom plate portion 51 caused by the welded portion 54. It becomes difficult.

FIG. 8 is a diagram for irradiating the first laser beam 40 in another manufacturing method of the embodiment. In the manufacturing method of this example, when the outer surface of the bottom plate portion 51 is irradiated with the first laser beam 40 forming the first melting portion 56 in the first irradiation step, a gap is provided between the outer can 50 and the negative electrode lead 26. S1 is open. At this time, unlike the case of the manufacturing method shown in FIG. 6, when irradiating the first laser beam 40, the negative electrode lead 26 is pressed from above without inserting the holding rod from above inside the outer can 50. Do not do.

The gap S1 formed between the outer can 50 and the negative electrode lead 26 may be about 0.005 mm to 0.2 mm. Due to the presence of the gap S1, the heat generated by the irradiation of the first laser beam 40 stays in the outer can 50 and stays in the negative electrode lead 26 or the holding rod that brings the outer can 50 and the negative electrode lead 26 into close contact with each other. No heat is absorbed. Therefore, the resin existing between the outer can 50 and the negative electrode lead 26 is efficiently vaporized. After that, as in the manufacturing method shown in FIG. 7, when the second laser beam 41 forming the second molten portion 58 is irradiated to the bottom plate portion 51, the outer can 50 and the negative electrode lead 26 are brought into close contact with each other by the holding rod 70. Then, the outer can 50 and the negative electrode lead 26 are welded in that state.

Further, the laser spot diameter of the first laser beam 40 forming the first melting portion 56 should be larger than the laser spot diameter of the second laser beam 41 forming the second melting portion 58. Since the first laser beam 40 is irradiated to vaporize the resin existing between the outer can 50 and the negative electrode lead 26 by heat, the resin is vaporized and removed in a region wider than the region forming the second molten portion 58. It is preferable to do so. In other words, the second laser beam 41 forms the second molten portion 58 by irradiating the region from which the resin existing between the outer can 50 and the negative electrode lead 26 has been removed by the first laser beam 40. The outer can 50 and the negative electrode lead 26 are welded. As a result, it is possible to prevent the generation of holes penetrating the outer can 50 and to obtain stable welding strength.

Further, when a fiber laser is used as each laser beam, the irradiation depth of the first laser beam 40 and the second laser beam 41 and the irradiation area of the first laser beam 40 can be accurately controlled. As a result, the dimensions (thickness, width, length) of the first melting portion 56 and the second melting portion 58 can be accurately controlled, and the resin existing between the outer can 50 and the negative electrode lead 26 is efficiently vaporized. Can be removed. The planar shapes of the first melting portion 56 and the second melting portion 58 when the welded portion 54 is viewed from the outside of the outer can 50 may be linear, and is not limited to a linear shape. For example, the planar shape of the first melting portion 56 and the second melting portion 58 may be curved.

Next, the results of an experiment conducted to confirm the effect of the above embodiment will be described. In the experiment, the batteries manufactured by the methods for manufacturing the batteries of Examples 1 and 2 and Comparative Examples below were used.

[Example 1]
Although the dimensions of the configuration of Example 1 are exemplified, the present disclosure is not limited to the following dimensions. With reference to FIG. 4, the width w1 in the short direction when the first melting portion 56 is viewed from the outside of the outer can 50 and the width in the short direction when the second melting portion 58 is viewed from the outside of the outer can 50. It is larger than w2 and less than 3 times the width w2. Further, the length L1 in the long direction when the first melting portion 56 is viewed from the outside of the outer can 50 is the length L2 in the long direction when the second melting portion 58 is viewed from the outside of the outer can 50. It is larger and less than twice the length L2. Further, referring to FIG. 3, the thickness D1 of the first melting portion 56 is 0.5 to 0.99 times the thickness Dc of the outer can 50.

As more specific dimensions, the outer can 50 is made of nickel-plated iron, and the nickel-plated layer on the outer surface has a thickness of 3.5 μm. The total thickness of the outer can 50 including the nickel-plated layer is 300 μm. Further, the dimensions of the first melting portion 56 and the second melting portion 58 of the welded portion 54 are as follows.
(1st melting part 56)
(1) Width w1: 170 μm in the short direction when viewed from the outside of the outer can 50
(2) Length in the long direction when viewed from the outside of the outer can 50 L1: 1600 μm
(3) Thickness (length formed by the first molten portion 56 from the outer surface of the outer can 50) D1: 270 μm
(Second melting part 58)
(1) Width w2 in the short direction when viewed from the outside of the outer can 50: 80 μm
(2) Length in the long direction when viewed from the outside of the outer can 50 L2: 1000 μm
(3) Thickness (length from the outer surface of the outer can 50 to the end inside the negative electrode lead 26) D2: 350 μm

In the manufacturing method of Example 1, general equipment lubricating oil was applied between the outer can 50 and the negative electrode lead 26 in order to confirm the effect of the embodiment. After that, in the first irradiation step, the first laser beam 40 forming the first melting portion 56 is emitted from the outside of the outer can 50 with the outer can 50 and the negative electrode lead 26 in close contact with each other by the holding rod 70 (FIG. 6). The bottom plate portion 51 was irradiated. After that, in the second irradiation step, the outer can 50 and the negative electrode lead 26 are brought into close contact with each other by the holding rod 70 (FIG. 7), and the second laser beam 41 forming the second molten portion 58 is irradiated. The outer can 50 and the negative electrode lead 26 were welded.

The irradiation conditions of the first laser beam 40 and the second laser beam 41 are as follows.
(1st laser beam 40)
(1) Energy: 1.44J
(2) Laser spot diameter: 170 μm
(3) Movement speed: 470 mm / sec
(Second laser beam 41)
(1) Energy: 0.6J
(2) Laser spot diameter: 20 μm
(3) Movement speed: 470 mm / sec

When the welded portion 54 was formed in Example 1 under the above conditions, a melting mark was formed inside the outer can 50 by irradiation with the first laser beam 40. The melting marks have a width of 170 μm in the short direction on the outer surface of the outer can 50, a length of 1600 μm in the long direction, and a thickness (the length formed by the first melting portion 56 from the outer surface of the outer can 50). ) Was 270 μm. Subsequently, by irradiation with the second laser beam 41, the outer can 50 is irradiated with the first laser beam 40, inside the melting mark, the width in the short direction is 80 μm, the length in the long direction is 1000 μm, and the thickness (exterior). From the outer surface of the can 50, a melting mark of 350 μm (the length in which the second melting portion 58 was formed) was formed.

[Example 2]
Example 2 corresponds to another manufacturing method of the embodiment shown in FIG. The configuration and dimensions of the battery of the second embodiment are the same as those of the first embodiment. In the manufacturing method of Example 2, a general equipment lubricating oil was applied between the outer can 50 and the negative electrode lead 26 in the same manner as in Example 1. After that, in the second embodiment, as shown in FIG. 8, in the first irradiation step, a gap is provided between the outer can and the negative electrode lead without bringing the outer can and the negative electrode lead into close contact with each other by the holding rod. Then, the first laser beam 40 forming the first melting portion 56 was irradiated onto the bottom plate portion 51 from the outside of the outer can 50.

After that, in the second irradiation step, as in the first embodiment, the second laser beam forming the second molten portion 58 in a state where the outer can 50 and the negative electrode lead 26 are in close contact with each other by the holding rod 70 (FIG. 7). By irradiating 41, the outer can 50 and the negative electrode lead 26 were welded. The irradiation conditions of the first laser beam 40 and the second laser beam 41 are the same as those in the first embodiment.

[Comparison example]
Further, as a comparative example, the second molten portion 58 is formed by irradiating the second laser beam 41 without irradiating the first laser beam 40 forming the first molten portion 56 (FIGS. 6 and 8). A battery in which the outer can and the negative electrode lead were welded was manufactured. As a result, in the battery manufacturing method of the comparative example, the first melting portion was not formed at the bottom of the outer can, and only the second melting portion 58 for welding the negative electrode lead and the outer can was formed. The other battery configurations and dimensions, and the irradiation conditions of the second laser beam are the same as those in the first embodiment.

[Experimental result]
Table 1 shows the results of confirming the probability of occurrence of a hole penetrating the outer can 50 using the batteries of Examples 1, 2 and Comparative Examples produced by each of the above manufacturing methods. In the experiment, a plurality of batteries were prepared in each of Examples 1, 2 and Comparative Example, and the probability of hole generation was confirmed.

As shown in Table 1, when the second laser beam 41 is irradiated to form the second molten portion 58 without irradiating the first laser beam forming the first molten portion as in the comparative example. The probability of occurrence of a hole penetrating the outer can 50 was 10%.

On the other hand, as in the first embodiment, when the first laser beam 40 forming the first melting portion 56 is irradiated and then the second laser beam 41 is irradiated to form the second melting portion 58, the outer can 50 is formed. It was confirmed that the probability of occurrence of a hole penetrating the laser was reduced to 5%.

Further, as in the second embodiment, when a gap is provided between the outer can 50 and the negative electrode lead 26 and the outer can is irradiated with the first laser beam 40 forming the first melting portion 56 in a state where the outer can 50 and the negative electrode lead 26 are not in close contact with each other. It was confirmed that the probability of occurrence of a hole penetrating 50 was reduced to 0%. As a result, in the case of the second embodiment, as in the first embodiment, when the outer can 50 and the negative electrode lead 26 are in close contact with each other without forming a gap at the time of irradiation with the first laser beam. In comparison, the probability of occurrence of a hole penetrating the outer can 50 could be reduced. The reason is that, in the second embodiment, the heat generated by the irradiation of the first laser beam 40 stays in the outer can 50, and the negative electrode lead 26 or the holding rod that brings the outer can 50 and the negative electrode lead 26 into close contact with each other. This is because heat is not absorbed. Therefore, in Example 2, the resin existing between the outer can 50 and the negative electrode lead 26 could be efficiently vaporized.

FIG. 9 is a cross-sectional view of the bottom surface side half of the battery 20a of another embodiment. FIG. 10 is a bottom view of the battery 20a shown in FIG.

In another example shown in FIGS. 9 and 10, a welding group 60 composed of three linear parallel welded portions 54a, 54b, 54c for welding the outer can 50 and the negative electrode lead 26 is formed. By forming the welding group 60 including the three welded portions 54a, 54b, 54c, it is easy to secure the welding strength between the outer can 50 and the negative electrode lead 26. 9 and 10 show a welding group 60 consisting of three parallel welds, but of course, the number of welds is not limited to three, and two or a plurality of welds of four or more. A welded portion of the book may be formed. When forming such a welded portion locally, it is preferable to use a laser beam of a fiber laser. In this example, other configurations and operations are the same as those of FIGS. 1 to 7.

In each of the above examples, the case where the negative electrode lead connected to the negative electrode is welded to the outer can is described, but the configuration of the present disclosure is also applied to the case where the positive electrode lead connected to the positive electrode is welded to the outer can. Can be done.

In each of the above examples, the case where the negative electrode lead connected to the winding end side end of the negative electrode is welded to the outer can, but the negative electrode lead connected to the winding start side end of the negative electrode is welded to the outer can. The configuration of the present disclosure may also be applied in some cases.

In each of the above examples, the case where one negative electrode lead connected to the negative electrode is welded to the outer can is described, but the present disclosure also includes the case where a plurality of negative electrode leads connected to the negative electrode are welded to the outer can. Configuration can be applied.

20, 20a Sealed battery (battery), 22 Electrode body, 23 Positive electrode, 23a Positive electrode current collector, 24 Negative electrode, 24a Negative electrode current collector, 25 Separator, 26 Negative electrode lead, 29 Winding core, 30 Insulation plate, 40 1st Laser light, 41 2nd laser light, 50 exterior can, 51 bottom plate, 54, 54a, 54b, 54c weld, 56 1st melt, 58 2nd melt, 60 weld group, 70 holding rod.

Claims (5)

A method for manufacturing a sealed battery including an electrode body in which at least one positive electrode and at least one negative electrode are wound or laminated via a separator, and a bottomed cylindrical outer can for accommodating the electrode body.
A welding step of irradiating an energy beam from the outside of the outer can to weld a lead connected to one of the positive electrode and the negative electrode to the outer can is provided.
The welding process is
The first energy controlled so that the first melting portion, which is a melting mark, stays inside the outer can on the portion of the outer surface of the outer can where the leads face each other through the inner surface of the outer can. The first irradiation step of irradiating the beam and
After the first irradiation step, the second melting portion, which is a melting mark from the outer surface of the outer can to the inside of the lead, is inside the portion of the outer surface of the outer can where the first melting portion is exposed. Has a second irradiation step of irradiating a second energy beam controlled to form.
How to manufacture a sealed battery. The method for manufacturing a closed battery according to claim 1, wherein in the first irradiation step, the first energy beam is irradiated with a gap provided between the lead and the outer can. The method for manufacturing a closed battery according to claim 1 or 2, wherein the beam spot diameter of the first energy beam is larger than the beam spot diameter of the second energy beam. A sealed battery comprising an electrode body in which at least one positive electrode and at least one negative electrode are wound or laminated via a separator, and a bottomed cylindrical outer can for accommodating the electrode body.
The outer can is made of nickel-plated iron.
The lead connected to one of the positive electrode and the negative electrode and the outer can are welded at a welded portion formed from the outer surface of the outer can toward the lead.
The welded portion includes a first molten portion and a second molten portion which are melting marks, and includes a first melting portion and a second melting portion.
The first melting portion is formed in the range of 50 to 99% of the thickness of the outer can from the outer surface of the outer can.
A sealed battery in which the second melting portion is formed from the outer surface of the outer can to the inside of the lead, and is inside the first melting portion when the welded portion is viewed from the outside of the outer can. The sealed battery according to claim 4, wherein the nickel concentration (mass%) of the second molten portion is higher than that of the first molten portion.

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