Laser welding device and laser welding method using the same

Abstract

A laser welding device according to an exemplary embodiment of the present invention comprises: a laser irradiation unit that emits a welding laser; an upper mask provided between the laser irradiation section and an electrode tab section and an electrode lead that are to be welded; and a lower mask that is provided at a lower portion of the object to be welded. The upper mask includes a through hole through which a laser beam is irradiated to the welding object, and at least one of the upper mask and the lower mask moves in the direction of the welding object and pressurizes the welding object.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser welding apparatus and a laser welding method using the same. BACKGROUND

[0002] Secondary batteries are batteries that can be repeatedly charged and discharged, and with the development of information communication and display industries, secondary batteries are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, notebook computers, etc. In addition, in recent years, a battery pack including a secondary battery is being developed and used as a power source for environmentally friendly vehicles such as electric cars.

[0003] As examples of secondary batteries, lithium secondary batteries, nickel-cadmium batteries, nickel-hydrogen batteries, etc. can be cited, and research and development are being conducted to improve the energy density per unit weight of the lithium secondary batteries among them.

[0004] In order to improve the energy density of the secondary battery, the number of stacks of the electrode core needs to be increased, and in this case, if the existing ultrasonic welding method is applied, the welding quality can be reduced. SUMMARY

[0005] (1) Technical problem to be solved

[0006] One technical problem of the present application is to provide a laser welding apparatus that can reduce the welding defect rate when welding the electrode tab portion and the lead wire.

[0007] One technical problem of the present application is to provide a laser welding method using the laser welding apparatus.

[0008] (2) Technical solution

[0009] The laser welding apparatus according to an exemplary embodiment of the present application includes a laser irradiation portion that emits welding laser light, an upper mask that is disposed between the laser irradiation portion and an electrode tab portion and an electrode lead wire as welding objects, and a lower mask that is disposed at a lower portion of the welding objects. The upper mask includes a through-hole through which the laser light is irradiated to the welding objects, and at least one of the upper mask and the lower mask moves toward the welding objects and presses the welding objects.

[0010] In an exemplary embodiment, the through-hole of the upper mask can be formed in a predetermined pattern, and the lower mask can include a through-hole pattern identical to the through-hole pattern of the upper mask.

[0011] In an exemplary embodiment, the through-hole of the upper mask can be formed in a predetermined pattern, and the lower mask can include a through-hole pattern different from the through-hole pattern of the upper mask.

[0012] In an exemplary embodiment, the lower mask can include a recess in a laser irradiation region of a surface opposite the upper mask.

[0013] In an exemplary embodiment, the lower mask can include a recess in a laser irradiation region of a surface opposite the upper mask.

[0014] In an exemplary embodiment, the lower mask can not include a through-hole.

[0015] In an exemplary embodiment, the lower mask can include a recess in a laser irradiation region of a surface opposite the upper mask.

[0016] In an exemplary embodiment, the lower mask can further include a pressurizing device in a laser irradiation region of a surface opposite the upper mask.

[0017] In an exemplary embodiment, the pressurizing device can include at least one selected from a spring, a cylinder, and a servo cylinder.

[0018] In a laser welding method according to an exemplary embodiment of the present application, one end of an electrode tab portion is aligned with one end of an electrode lead wire so that the one end of the electrode tab portion overlaps the one end of the electrode lead wire. An upper mask and a lower mask disposed in upper and lower portions, respectively, of a region where the electrode tab portion and the electrode lead wire overlap each other apply pressure to the overlapping region. The upper mask includes a through-hole through which a laser is irradiated to the overlapping region.

[0019] In an exemplary embodiment, the through-hole of the upper mask can be formed in a predetermined pattern, and the lower mask can include a through-hole pattern identical to the through-hole pattern of the upper mask.

[0020] In an exemplary embodiment, the through-hole of the upper mask can be formed in a predetermined pattern, and the lower mask can include a through-hole pattern identical to the through-hole pattern of the upper mask.

[0021] In an exemplary embodiment, the through-hole of the lower mask can have a different horizontal cross-sectional shape than the through-hole of the upper mask.

[0022] In an exemplary embodiment, the through-hole of the lower mask can have a different horizontal cross-sectional area than the through-hole of the upper mask.

[0023] In an exemplary embodiment, the lower mask can not include a through-hole.

[0024] In an exemplary embodiment, the lower mask can include a recess in a laser irradiation area of a surface opposite to the upper mask.

[0025] In an exemplary embodiment, the lower mask can further include a pressurizing device in a laser irradiation area of a surface opposite to the upper mask.

[0026] In an exemplary embodiment, the pressurizing device can include at least one selected from a spring, an air cylinder, and a servo air cylinder.

[0027] The laser welding method according to an exemplary embodiment can not include a pre-welding step.

[0028] The lithium secondary battery according to an exemplary embodiment includes an electrode tab and an electrode lead welded according to the above-described laser welding method.

[0029] (III) ADVANTAGEOUS EFFECTS

[0030] The laser welding method using the laser welding apparatus according to an exemplary embodiment of the present application can reduce a welding defect rate and a process time and reduce production costs.

[0031] The secondary battery manufactured by the laser welding method of the present application can be widely applied to the fields of green technology such as electric vehicles using batteries, battery charging stations, solar power generation using batteries, wind power generation, etc. In addition, the lithium secondary battery manufactured by the laser welding method of the present application can be used for eco-friendly electric vehicles (Electric Vehicle) and hybrid vehicles (hybrid vehicle) for preventing climate change by suppressing the emission of atmospheric pollution and greenhouse gases. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 FIG. 1 is a schematic view showing a laser welding apparatus, an electrode tab portion, and an electrode lead according to an exemplary embodiment.

[0033] Figure 2 FIG. 2 is a schematic process flow diagram for explaining a laser welding method according to an exemplary embodiment.

[0034] Figure 3 FIG. 3 is a schematic horizontal cross-sectional view of an upper mask according to an exemplary embodiment.

[0035] Figure 4 FIG. 4 is a schematic horizontal cross-sectional view of a lower mask according to an exemplary embodiment. Figure 5 FIG. 5 is a schematic horizontal cross-sectional view of a lower mask according to an exemplary embodiment.

[0036] Figure 6 is a schematic vertical sectional view of an upper mask and a lower mask including a pressurizing device according to an exemplary embodiment.

[0037] Figure 7 is a schematic view showing the arrangement of an electrode tab, an electrode lead, and a mask in a laser irradiation step according to an exemplary embodiment.

[0038] Figure 8 and Figure 9 are plan and sectional views, respectively, showing a secondary battery according to an exemplary embodiment.

[0039] BRIEF DESCRIPTION OF DRAWINGS

[0040] 100: positive electrode; 105: positive electrode current collector

[0041] 107: positive electrode lead; 110: positive electrode active material layer

[0042] 120: negative electrode active material layer; 125: negative electrode current collector

[0043] 127: negative electrode lead; 130: negative electrode

[0044] 140: separator; 150: electrode assembly

[0045] 160: case; 170: electrode tab

[0046] 180: electrode tab portion; 190: electrode lead

[0047] 200: upper mask; 210, 310: through hole

[0048] 300: lower mask; 320: groove

[0049] 330: pressurizing device; 400: laser irradiation portion DETAILED DESCRIPTION

[0050] According to an exemplary embodiment of the present application, a laser welding device and a laser welding method for laser welding of an electrode tab portion and an electrode lead are provided.

[0051] The exemplary embodiments are described in greater detail with reference to the accompanying drawings. However, the drawings and embodiments of the present specification serve to further understand the technical idea of the present application, and thus the present application should not be interpreted as being limited to the contents recited in the drawings and embodiments.

[0052] The terms "upper", "lower", "top", "bottom", and the like used in the present application are not designations of absolute positions, but are used in a relative sense. For example, the above terms are used relatively to designate different regions with respect to a certain reference surface.

[0053] Figure 1 is a schematic view showing a laser welding apparatus, an electrode tab portion, and an electrode lead according to an exemplary embodiment.

[0054] Referring to Figure 1 , the laser welding apparatus includes a laser irradiation portion 400, an upper mask 200, and a lower mask 300.

[0055] The laser irradiation portion 400 emits a welding laser. The kind of the welding laser is not particularly limited as long as it can be used for welding of the electrode tab portion and the electrode lead, for example, the welding laser can be an IR laser, a Green laser, or the like.

[0056] The upper mask 200 is disposed between the laser irradiation portion 400 and the electrode tab portion 180 and the electrode lead 190 which are welding targets.

[0057] The upper mask 200 includes a through-hole through which the laser is irradiated to the welding targets.

[0058] The lower mask 300 is disposed at a lower portion of the welding targets.

[0059] In the laser welding apparatus according to the exemplary embodiment of the present application, at least one of the upper mask 200 and the lower mask 300 is moved toward the welding targets and presses the welding targets.

[0060] Figure 2 is a schematic process flow diagram for explaining a laser welding method according to an exemplary embodiment. Hereinafter, referring to Figure 2 , the laser welding method will be explained.

[0061] Referring to Figure 2 , in the laser welding method, one end of the electrode tab portion is aligned with one end of the electrode lead so that the one end of the electrode tab portion overlaps the one end of the electrode lead (S10).

[0062] The electrode tab portion can include a plurality of electrode tabs, and the electrode tabs can be positive electrode tabs or negative electrode tabs. The electrode lead aligned in a manner of overlapping the positive electrode tab portion including the positive electrode tabs can be a positive electrode lead, and the electrode lead aligned in a manner of overlapping the negative electrode tab portion including the negative electrode tabs can be a negative electrode lead.

[0063] The electrode tab can be a member formed by extending one end of the current collector, and the electrode tab is a portion connected (electrically connected) to the electrode lead, through which the flow of electric charges generated in the current collector is transmitted to the electrode lead.

[0064] The electrode lead can be a member connected (electrically connected) to the tab of the same polarity and transmitting the flow of electric charges generated in the current collector to the outside of the battery. For example, the electrode lead can be aluminum, nickel, copper, or the like.

[0065] In an exemplary embodiment, an upper mask and a lower mask disposed at upper and lower portions of a region in which the electrode tab portion and the electrode lead overlap, respectively, apply pressure to the overlapping region (S20).

[0066] Since the upper mask and the lower mask apply pressure to the overlapping region, a gap between the plurality of electrode tabs located in the overlapping region can be reduced. Accordingly, when laser is irradiated in S30 described below, welding heat input required for welding can be reduced. Accordingly, a welding defect rate such as disconnection of the electrode tab due to excessive heat input applied to the overlapping region during welding can be reduced. Accordingly, an increase in resistance heating of the tab portion of the secondary battery can be prevented, and the risk of short circuit and fire due to short circuit of the electrode tab can be reduced.

[0067] In some embodiments, the upper mask and the lower mask can be disposed at upper and lower portions of one end of the overlapping electrode tab portion and one end of the electrode lead, respectively. Thereafter, by moving the upper mask and the lower mask toward one end of the overlapping electrode tab portion and one end of the electrode lead disposed between the upper mask and the lower mask, respectively, pressure can be applied to a region in which one end of the electrode tab portion and one end of the electrode lead overlap.

[0068] In some embodiments, in order to effectively apply pressure to the overlapping region, the upper mask and the lower mask can have a larger area than the overlapping region.

[0069] According to an exemplary embodiment, in the overlapping region, the electrode lead can be positioned at a lower portion of the electrode tab, and the laser can be irradiated to the electrode tab side. When the electrode lead is positioned at an upper portion of the electrode tab, welding of the electrode lead and the electrode tab in the overlapping region can require penetration of a relatively thick electrode lead. Accordingly, compared to a case where the electrode lead is positioned at a lower portion of the electrode tab, heat input required for welding can increase, and thus a welding defect rate such as breakage of the electrode tab during welding can increase. Accordingly, when the electrode tab is positioned at an upper portion of the electrode lead, safety of the secondary battery can be improved, for example, a fire risk can be reduced, etc.

[0070] In an exemplary embodiment, the upper mask includes a through-hole through which the laser is irradiated to the overlapping region (S30).

[0071] When the laser is irradiated to the overlapping region through the through-hole of the upper mask, a laser irradiation region can be formed on the overlapping region. Welding heat input of the laser can be transferred to the laser irradiation region, and thus the electrode tab and the electrode lead can be welded.

[0072] The laser welding method according to an exemplary embodiment can be a partial penetration weld method. Accordingly, welding heat input transferred to the laser irradiation region can be reduced, and thus a welding defect rate can be reduced.

[0073] In some embodiments, the lower mask can be a solid type that does not include a through-hole. When the lower mask is a solid type, pressure applied to the laser irradiation region of the electrode tab and the electrode lead can increase when partial penetration welding is performed. Accordingly, a risk of breakage of the electrode tab can be reduced, and thus a risk of short circuit and fire of the secondary battery can be reduced.

[0074] The kind of the laser is not particularly limited as long as it can be used for welding of the electrode tab and the electrode lead, for example, the laser can be an IR laser, a green laser, etc.

[0075] Figure 3 is a schematic horizontal cross-sectional view of an upper mask according to an exemplary embodiment.

[0076] In the present specification, a "horizontal cross-section" refers to a cross-section when cut in a vertical direction with respect to an irradiation direction of a laser.

[0077] In the present specification, a "vertical cross-section" refers to a cross-section when cut in a direction parallel to an irradiation direction of a laser.

[0078] Referring to Figure 3The through holes 210 of the upper mask 200 can be formed in a predetermined pattern. For example, a plurality of the through holes 210 can be arranged on the upper mask 200 along a predetermined line, and a plurality of such lines can be arranged at a predetermined interval.

[0079] For ease of illustration, Figure 3 The horizontal cross section of the through hole 210 illustrated in FIG. 2 is a square, but the shape of the through hole 210 can be a circle, a polygon, etc., and is not limited thereto.

[0080] In an exemplary embodiment, the size of the through hole 210 of the upper mask 200 can be the same throughout.

[0081] For example, when the through hole 210 is a circle, the diameter of the through hole 210 can be 0.1 mm to 10 mm, 0.3 mm to 7 mm, or 0.5 mm to 5 mm.

[0082] For example, when the through hole 210 is a quadrangle, the side length of the through hole 210 can be 0.1 mm to 10 mm, 0.3 mm to 7 mm, or 0.5 mm to 5 mm.

[0083] In an exemplary embodiment, the pitch between the through holes 210 adjacent to each other in the upper mask 200 can be more than 0 and 20 mm or less, more than 0 and 15 mm or less, or more than 0 and 10 mm or less.

[0084] By adjusting the shape, size, pitch, etc. of the through hole 210, the position of the laser irradiation region, the welding heat input, etc. can be adjusted. Thus, the welding defect rate such as disconnection that can occur when the laser is irradiated can be reduced.

[0085] In an exemplary embodiment, the through hole pattern of the lower mask 300 can be the same as the through hole pattern of the upper mask 200.

[0086] In an exemplary embodiment, the through hole pattern of the lower mask 300 can be different from the through hole pattern of the upper mask 200.

[0087] Figure 4 and Figure 5 are schematic horizontal cross-sectional views of a lower mask according to exemplary embodiments, respectively.

[0088] Referring to Figure 4 and Figure 5 , the through holes 310 of the lower mask 300 can be formed in a predetermined pattern.

[0089] Referring to Figure 4 , the horizontal cross-sectional shape of the through hole of the lower mask 300 can be the same as the horizontal cross-sectional shape of the through hole of the upper mask 200.

[0090] Referring to Figure 5 The horizontal cross-sectional shape of the through-hole of the lower mask 300 can be different from that of the through-hole of the upper mask 200.

[0091] In an exemplary embodiment, the horizontal cross-sectional area of the through-hole 310 of the lower mask 300 can be different from that of the through-hole 210 of the upper mask 200. Referring to Figure 4 and Figure 5 The horizontal cross-sectional area of the through-hole 310 of the lower mask 300 can be smaller than that of the through-hole 210 of the upper mask 200. Alternatively, the horizontal cross-sectional shape of the through-hole of the lower mask 300 can be different from that of the through-hole of the upper mask 200. Accordingly, the pressurization area of the laser irradiation region can be increased by the mask, and thus the weld defect rate can be reduced.

[0092] In some embodiments, a center line passing through the center of the through-hole 210 of the upper mask 200 can pass through the center of the through-hole 310 of the lower mask 300. Accordingly, laser welding can also be performed by a full penetration weld method, and welding between the lower mask 300 and the electrode lead can be prevented.

[0093] In an exemplary embodiment, the lower mask 300 can not include a through-hole. When the lower mask 300 is of a solid type not including a through-hole, the pressurization area of the overlapped region by the lower mask can be increased, and thus the weld defect rate can be reduced.

[0094] In an exemplary embodiment, the lower mask 300 can include a groove in the laser irradiation region of the surface opposite to the upper mask 200.

[0095] In an exemplary embodiment, the horizontal cross-sectional area of the groove of the lower mask 300 can be different from that of the through-hole 210 of the upper mask 200. For example, the horizontal cross-sectional area of the groove of the lower mask 300 can be smaller than that of the through-hole 210 of the upper mask 200. Alternatively, the horizontal cross-sectional shape of the groove of the lower mask 300 can be different from that of the through-hole of the upper mask 200. Accordingly, the pressurization area of the laser irradiation region can be increased by the mask, and thus the weld defect rate can be reduced.

[0096] In an exemplary embodiment, the lower mask 300 can further include a pressurization device 330 in the laser irradiation region of the surface opposite to the upper mask 200.

[0097] Figure 6is a schematic vertical sectional view of an upper mask and a lower mask including a pressurizing device according to an exemplary embodiment.

[0098] Referring to Figure 6 Thus, when laser light is irradiated, the laser light irradiation region can be pressurized by the pressurizing device 330, and thus the gap between the electrode tabs can be reduced. Accordingly, the welding defect rate can be reduced.

[0099] In an exemplary embodiment, the pressurizing device can include at least one selected from a spring, an air cylinder, a servo air cylinder, and the like.

[0100] For example, the pressurizing device can be disposed inside the groove 320 of the lower mask 300.

[0101] The laser welding method according to an exemplary embodiment can not include a pre-welding step. In the welding method of the present application according to an exemplary embodiment, the gap between the electrode tabs can be reduced by pressurization of the mask in S20, and thus even if the pre-welding step is omitted and laser welding is performed, the welding defect rate can not increase.

[0102] For example, the pre-welding can include ultrasonic welding. In order to increase the energy density of the secondary battery, it is necessary to increase the number of stacks of the positive electrode and the negative electrode of the electrode assembly, and thus the energy required for welding increases. In this case, if ultrasonic welding is performed before laser welding, the incidence of defects such as adhesion, tearing, and the like of the electrode tabs can increase. In addition, when adhesion of the electrode tabs occurs, it is necessary to interrupt the welding process to regrind or replace the anvil, and thus the production yield of the secondary battery can decrease.

[0103] The welding method of the present application according to an exemplary embodiment does not include a pre-welding step, and thus welding defects that can occur at the time of ultrasonic welding can be reduced, and the production cost of performing ultrasonic welding can be reduced.

[0104] Figure 7 is a schematic view showing the arrangement of the electrode tab portion, the electrode lead, and the mask in the laser irradiation step according to an exemplary embodiment.

[0105] Referring to Figure 7 The electrode tab portion 180 can include a plurality of electrode tabs 170 extending from one end of the electrode assembly 150.

[0106] The electrode assembly 150 can include repeatedly stacked electrodes and a separator 140 disposed between the electrodes. The electrodes can each include an active material layer formed on an electrode current collector.

[0107] The electrode can include a positive electrode 100 and a negative electrode 130. The electrode current collector can include a positive electrode current collector 105 included in the positive electrode 100 and a negative electrode current collector 125 included in the negative electrode 130. The active material layer can include a positive electrode active material layer 110 included in the positive electrode 100 and a negative electrode active material layer 120 included in the negative electrode 130.

[0108] The positive electrode 100 can include a positive electrode current collector 105 and a positive electrode active material layer 110 formed by coating a positive electrode active material on the positive electrode current collector 105. The positive electrode active material can include a compound in which lithium ions are reversibly intercalated and deintercalated. In this case, the secondary battery can be provided as a lithium secondary battery.

[0109] In an exemplary embodiment, the positive electrode active material can include lithium-transition metal composite oxide particles. For example, the lithium-transition metal composite oxide particles can include nickel (Ni), and can further include at least one of cobalt (Co) or manganese (Mn).

[0110] For example, the positive electrode current collector 105 can include stainless steel, nickel, aluminum, titanium, copper, zinc, or an alloy thereof, and preferably, the positive electrode current collector 105 can include aluminum or an aluminum alloy.

[0111] For example, the positive electrode active material can be mixed and stirred with a binder, a conductive material, and / or a dispersing material, etc. in a solvent to prepare a slurry. The slurry can be coated on the positive electrode current collector 105 and then dried and calendered to manufacture the positive electrode 100 including the positive electrode active material layer 110.

[0112] The binder can include, for example, an organic binder such as a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a water-based binder such as styrene butadiene rubber (SBR), and can be used together with a thickening agent such as carboxymethyl cellulose (CMC).

[0113] For example, a PVDF-based binder can be used as a positive electrode binder. In this case, the amount of the binder used to form the positive electrode active material layer can be reduced, and the amount of the positive electrode active material can be relatively increased, so that the power and capacity of the secondary battery can be improved.

[0114] The conductive material can be included to facilitate electron migration between active material particles. For example, the conductive material can include carbon-based conductive materials such as graphite, carbon black, graphene, carbon nanotubes, etc., and / or metal-based conductive materials such as perovskite substances including tin, tin oxide, titanium oxide, LaSrCo03, LaSrMn03, etc.

[0115] The negative electrode 130 can include a negative electrode current collector 125 and a negative electrode active material layer 120 formed by coating a negative electrode active material on the negative electrode current collector 125.

[0116] The negative electrode active material can use an active material that enables lithium ions to be intercalated and deintercalated, as is well known in the art. For example, the negative electrode active material can use carbon-based materials such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, etc.; lithium alloys; silicon (Si)-based active materials, etc. As examples of the amorphous carbon, hard carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc. can be listed.

[0117] As examples of the crystalline carbon, graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc. can be listed. As elements included in the lithium alloy, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc. can be listed.

[0118] The negative electrode current collector 125 can include stainless steel, copper, nickel, aluminum, titanium, or alloys thereof. Preferably, the negative electrode current collector 125 can include copper or a copper alloy.

[0119] For example, the negative electrode active material can be mixed and stirred together with the above-described binder, conductive material, thickening agent, etc. in a solvent to be in a slurry form. The slurry can be coated on at least one side of the negative electrode current collector 125 and then dried and calendered to manufacture the negative electrode 130 including the negative electrode active material layer 120.

[0120] The binder and the conductive material can use substantially the same or similar substances as those used in the positive electrode active material layer 110. In some embodiments, for example, for compatibility with carbon-based active materials, the binder used to form the negative electrode can include a water-based binder such as styrene butadiene rubber (SBR), and can be used together with a thickening agent such as carboxymethyl cellulose (CMC).

[0121] A separator 140 can be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 can include a porous polymer film manufactured by an ethylene homopolymer, a propylene homopolymer, an ethylene / butylene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or the like polyolefin-based polymer. The separator 140 can also include a non-woven fabric formed of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like.

[0122] According to an exemplary embodiment, the electrode assembly 150 can be defined by alternately and repeatedly stacking the positive electrode 100, the negative electrode 130, and the separator 140 disposed between the positive electrode 100 and the negative electrode 130.

[0123] In an exemplary embodiment, the upper mask 200 and the lower mask 300 can be disposed at upper and lower portions of a region in which one end of the electrode tab portion 180 overlaps one end of the electrode lead 190, respectively.

[0124] For convenience of illustration, Figure 7 The electrode assembly 150 illustrated in FIG. 1 is of a stacking type, but the electrode assembly 150 can also have a winding type structure formed, for example, by winding or folding of the separator 140.

[0125] Figure 8 and Figure 9 are a plan view and a cross-sectional view, respectively, illustrating a secondary battery according to an exemplary embodiment. For example, Figure 9 is a cross-sectional view taken along the I-I' line of FIG. 1 in a thickness direction. Figure 8

[0126] Figure 8 and Figure 9 The secondary battery illustrated in FIG. 1 is schematically illustrated for convenience of explanation, and the structure of the secondary battery of the present application is not limited to the structure as illustrated in Figure 8 and Figure 9 .

[0127] According to an exemplary embodiment, a unit cell can be defined by the positive electrode 100, the negative electrode 130, and the separator 140, and a plurality of unit cells can be stacked to form, for example, the electrode assembly 150. The electrode assembly 150 can be of a winding type, a stacking type, a z-folding type, a stack-folding type.

[0128] The electrode assembly 150 can be accommodated in the case 160 together with an electrolyte, and thus a secondary battery can be defined. According to an exemplary embodiment, the electrolyte can use a non-aqueous electrolyte.

[0129] ​Non-aqueous electrolytes may contain a lithium salt as the electrolyte and an organic solvent, wherein the lithium salt may be, for example, Li... + X - This indicates that the anion (X) of the lithium salt is... - ), can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - wait.

[0130] The organic solvents may include, for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used alone or in combination of two or more.

[0131] like Figure 8As shown, the tab (positive electrode tab and negative electrode tab) can protrude and extend from the positive electrode current collector 105 and the negative electrode current collector 125 belonging to each battery cell to one side of the case 160, respectively. The electrode tab can be fused together with the one side of the case 160 to form an electrode lead (positive electrode lead 107 and negative electrode lead 127) extending to the outside of the case 160 or exposed to the outside of the case 160.

[0132] Figure 8 The positive electrode lead 107 and the negative electrode lead 127 are shown to protrude from both side edges of the case 160 in the planar direction, but the position of the electrode lead is not limited thereto. For example, the electrode lead can protrude from the upper edge and the lower edge of the case 160. Alternatively, the positive electrode lead 107 and the negative electrode lead 127 can protrude from the same edge of the case 160. For example, the positive electrode lead 107 and the negative electrode lead 127 can be formed to protrude from the upper edge of the case 160, or can be formed to protrude from the lower edge of the case 160, or can be formed to protrude from the left edge of the case 160, or can be formed to protrude from the right edge of the case 160.

[0133] The secondary battery can be manufactured, for example, in a cylindrical, prismatic, pouch type, or coin type using a can.

[0134] The lithium secondary battery according to the exemplary embodiment of the present application includes an electrode tab and an electrode lead welded according to the above-described laser welding method.

Claims

1. A laser welding apparatus, comprising: A laser irradiation section, wherein the laser irradiation section emits a welding laser; Upper mask, the upper mask being disposed between the laser irradiation section and the electrode tab and electrode lead, which are the objects to be welded; and A lower mask, wherein the lower mask is disposed at the lower part of the object to be welded. The upper mask includes through holes through which laser light irradiates the object to be welded. At least one of the upper mask and the lower mask moves toward the object to be welded and applies pressure to the object to be welded.

2. The laser welding apparatus according to claim 1, wherein, The through-holes of the upper mask are formed with a predetermined pattern, and the lower mask includes the same through-hole pattern as the upper mask.

3. The laser welding apparatus according to claim 1, wherein, The upper mask has through-holes formed with a predetermined pattern, and the lower mask includes a through-hole pattern different from that of the upper mask.

4. The laser welding apparatus according to claim 3, wherein, The horizontal cross-sectional shape of the through hole in the lower mask is different from that of the through hole in the upper mask.

5. The laser welding apparatus according to claim 3, wherein, The horizontal cross-sectional area of ​​the through hole in the lower mask is different from that of the through hole in the upper mask.

6. The laser welding apparatus according to claim 1, wherein, The lower mask does not include through holes.

7. The laser welding apparatus according to claim 6, wherein, The lower mask includes a groove in the laser irradiation region of the surface opposite the upper mask.

8. The laser welding apparatus according to claim 1, wherein, The lower mask further includes a pressurizing device in the laser irradiation area of ​​the surface opposite the upper mask.

9. The laser welding apparatus according to claim 8, wherein, The pressurization device includes at least one selected from springs, cylinders, and servo cylinders.

10. A laser welding method, comprising the following steps: Align one end of the electrode tab with one end of the electrode lead so that one end of the electrode tab overlaps with one end of the electrode lead. Upper and lower masks, respectively located at the upper and lower portions of the area where the electrode tab overlaps with the electrode lead, apply pressure to the overlapping area; and The upper mask includes through-holes through which laser light is irradiated onto the overlapping area.

11. The laser welding method according to claim 10, wherein, The through-holes of the upper mask are formed with a predetermined pattern, and the lower mask includes the same through-hole pattern as the upper mask.

12. The laser welding method according to claim 10, wherein, The upper mask has through-holes formed with a predetermined pattern, and the lower mask includes a through-hole pattern different from that of the upper mask.

13. The laser welding method according to claim 12, wherein, The horizontal cross-sectional shape of the through hole in the lower mask is different from that of the through hole in the upper mask.

14. The laser welding method according to claim 12, wherein, The horizontal cross-sectional area of ​​the through hole in the lower mask is different from that of the through hole in the upper mask.

15. The laser welding method according to claim 10, wherein, The lower mask does not include through holes.

16. The laser welding method according to claim 15, wherein, The lower mask includes a groove in the laser irradiation region of the surface opposite the upper mask.

17. The laser welding method according to claim 10, wherein, The lower mask further includes a pressurizing device in the laser irradiation area of ​​the surface opposite the upper mask.

18. The laser welding method according to claim 17, wherein, The pressurization device includes at least one selected from springs, cylinders, and servo cylinders.

19. The laser welding method according to claim 10, wherein, The laser welding method does not include a pre-welding step.

20. A lithium secondary battery comprising electrode tabs and electrode leads welded by the laser welding method according to claim 10.

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