KR20140022531A - Electrode assembly and fabricating method of electrochemical cell containing the electrode assembly, electrochemical cell - Google Patents

Abstract

The present invention relates to a method for improving the reliability of an electrode tap and a lead welding, and an electrochemical cell fabricated by the same. Provided is an electrode assembly that includes an electrode including a current collector coated with an active material, an electrode tap connected to the current collector, and a lead part connected to the electrode tap. The density of the insulating material of the welding surface of the lead part and the electrode tap is lower than that of a region excluding the welding surface.

Description

ELECTRODE ASSEMBLY AND FABRICATING METHOD OF ELECTROCHEMICAL CELL CONTAINING THE ELECTRODE ASSEMBLY, ELECTROCHEMICAL CELL}

The present invention relates to a method for enhancing the reliability of electrode tab and lead welding, and to an electrochemical device manufactured through the same.

With the rapid development of the electronics, telecommunications, and computer industries, the rapid development of camcorders, mobile phones, laptops, and the like, the demand for lithium secondary batteries as a power source capable of driving these portable electronic communication devices is increasing day by day.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Representatively, there is a high demand for rectangular secondary batteries and pouch secondary batteries, which can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium ion batteries with high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion polymer batteries.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

Referring to FIG. 1, the pouch type secondary battery 100 may include an electrode assembly 300, electrode tabs 310 and 320 extending from the electrode assembly 300, and electrodes welded to the electrode tabs 310 and 320. And a battery case 200 accommodating the leads 410 and 420 and the electrode assembly 300.

The electrode assembly 300 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and has a stack type or a stack / fold type structure. The electrode tabs 310, 320 extend from each pole plate of the electrode assembly 300, and the electrode leads 410, 420 are welded with a plurality of electrode tabs 310, 320 extending from each pole plate, eg, welded. Each is electrically connected to each other, and part of the battery case 200 is exposed to the outside. In addition, an insulating film 430 is attached to upper and lower portions of the electrode leads 410 and 420 to increase the sealing degree with the battery case 200 and to secure an electrical insulating state. The case 200 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 300, and has a pouch shape as a whole. In the stacked electrode assembly 300 as shown in FIG. 1, a plurality of positive electrode tabs 310 and a plurality of negative electrode tabs 320 may be coupled together to the electrode leads 410 and 420. The upper end is spaced apart from the electrode assembly 300 at predetermined intervals.

FIG. 2 is a partially enlarged view of an inner top of a battery case in which the positive electrode tabs are densely coupled in the secondary battery of FIG. 1 and connected to the positive electrode lead.

2, a plurality of positive electrode tabs 310 protruding from a positive electrode current collector 301 of an electrode assembly 300 are formed in the form of a bonded portion integrally joined by welding, for example, (Not shown). Such a cathode lead 410 is sealed by the battery case 200 in a state in which the opposite end portion 412 to which the positive electrode tab weld portion is connected is exposed.

As such, there are many metal parts in the secondary battery, including leads, current collectors, and electrode tabs. These metal parts are welded or connected to each other as necessary.

However, when joining by welding, welding reliability is lowered due to the presence of an oxide film formed on the surface of the anode lead, for example, Al ₂ O ₃ , and an increase in internal resistance occurs.

Patent Registration No. 10-1068618

The present invention has been made to solve the above-described problem, an object of the present invention is to remove the aluminum oxide film (Al ₂ O ₃ ) formed on the anode lead at the time of welding the electrode tab and the lead by a laser to remove the ultrasonic wave By welding, to improve the welding strength and at the same time provide a welding method for improving the heat generated by the battery internal resistance and the electrode assembly produced through the same.

As a means for solving the above problems, the present invention is a process for removing the oxide film by applying a laser to the surface of the electrode tab connected to the electrode current collector and the step of performing ultrasonic welding by bringing the lead portion in close contact with the region where the oxide film is removed To provide.

In particular, the electrode assembly manufactured through the above-described process includes an electrode including a current collector coated with the active material; An electrode tab connected to the current collector; And a lead portion connected to the electrode tab, wherein the density of the insulating material on the welding surface of the electrode tab and the lead portion is lower than the density of a region outside the welding surface.

According to the present invention, when welding the electrode tab and lead, by welding the aluminum oxide film (Al2O3) formed on the anode lead with a laser to remove the welding portion and the periphery, to improve the welding strength and to reduce the battery internal resistance Improved heat generation has the effect of improving battery performance.

FIG. 1 is a schematic exploded perspective view of a general structure of a conventional representative pouch type secondary battery.
FIG. 2 is a partially enlarged view of an inner top of a battery case in which the positive electrode tabs are densely coupled in the secondary battery of FIG. 1 and connected to the positive electrode lead.
3 is a sectional view showing main parts of a welding region according to an exemplary embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description with reference to the accompanying drawings, the same reference numerals denote the same elements regardless of the reference numerals, and redundant description thereof will be omitted. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

3 and 4 are conceptual views illustrating enlarged weld regions X of an electrode tab and a lead part in the structure of FIG. 2.

2 and 3, the electrode assembly according to the present invention has a structure of an electrode including a current collector coated with an active material, an electrode tab 310 connected to the current collector 301, and the electrode tab 310. The lead portion 410 is connected to the electrode, characterized in that the density of the insulating material of the electrode tab and the welding surface (C) of the lead portion is lower than the density of the area outside the welding surface. In the following embodiments, the current collector is a concept including a positive electrode or a negative electrode current collector, and the electrode tab is also a concept including a positive electrode tab and a negative electrode tab.

That is, according to the present invention, the welding region (X) is formed through a process of removing an oxide film by applying a laser to a surface of an electrode tab connected to the electrode current collector, and performing an ultrasonic welding by bringing the lead part into close contact with the region where the oxide film is removed. By removing the oxide film in the) and performing the welding it is possible to implement the electrode assembly of the above-described structure.

In particular, referring to the structure of FIGS. 2 and 3, an electrode tab 310 is provided at an end of an electrode current collector 301 that basically forms a positive electrode or a negative electrode, and the electrode tab 310 has a lead portion 410. Will be connected with

The electrode tab 310 is coated on the entire surface of a material that does not affect the electrochemical reaction of the battery, that is, an insulating material containing a piezoelectric material. The plurality of electrode tabs 310 coated with the piezoelectric material-containing insulating material are bonded by performing ultrasonic welding while applying a predetermined pressure to each lead portion 410. The coating layer is energized by a piezoelectric material. At this time, if a current is applied to the lead unit 410, local melting of the coating layer is facilitated when ultrasonic application is generated by heat generation due to high resistance at the time of energization.

Specifically, the ultrasonic welding between the electrode tab 310 and the lead portion 410 will be described as follows. The high frequency vibration generated by the ultrasonic wave of about 20 KHz causes the vibration energy to be converted into thermal energy by friction at the interface between the electrode tabs 310 and between the electrode tab 310 and the electrode lead portion 410. The surface of the newly exposed electrode tab 410 is brought into close contact with each other by breakage of the surface coating layer and local plastic deformation, and diffusion of atoms and recrystallization are promoted by temperature rise due to frictional heat, so that a strong pressure point is formed and welding is rapidly performed. Is done.

In this case, however, the existence of a film forming an insulating material formed on the surface of the lead portion or the surface of the electrode tab inevitably causes a decrease in the reliability (strength) of the welding. The insulating material on the surface of the electrode tab or the lead portion may be a naturally occurring natural oxide film or the above-mentioned insulating material film intentionally coated. For example, when the above-described electrode tab 310 is assumed to be a positive electrode tab, the positive electrode tab generally uses aluminum, and the lead part may also use aluminum. In this case, in consideration of the fact that the insulating tape 430 is used for sealing the pouch in the structure of FIG. 1, an aluminum oxide film having a porous layer structure may be formed on the surface of the lid to improve adhesion. Although the aluminum oxide film formed has the advantage of improving the adhesiveness with the insulating tape to improve the sealing characteristics, when welding with the electrode tab serves as a factor that reduces the welding characteristics.

Accordingly, as shown in FIG. 3, the oxide film 410 present on the surface of the lead portion 410 or the surface of the electrode tab 310 is removed through a laser and then bonded by ultrasonic welding. It will be possible to improve. That is, the structure shown in (a) of FIG. 3 illustrates the welding area A and the non-contact area B of the lead portion 410 and the electrode tab 310, and the oxide film ( 440 is illustrated. As described above, the oxide film 440 degrades the welding characteristic.

Accordingly, in the present invention, as shown in FIG. 3 (b), after the oxide film 410 existing in the welding region A of the electrode tab 310 and the lead portion 410 is removed through a laser, ultrasonic welding is performed. In this way, the welding characteristics can be improved. That is, FIG. 3B illustrates a structure in which the oxide film 410 is removed from the welding surface C. As shown in FIG. Although the oxide film 440 in the present embodiment may be formed on the surface of the lead portion, the oxide film 311 formed on the surface of the electrode tab 310 may also be removed in the present invention.

In this case, it is most preferable that the insulating material such as an oxide film existing on the welding surface C is completely removed by a laser, so that the surface of the lead portion or the electrode tab is exposed. However, when an insulating material having a fine density exists, the concentration of the insulating material in the welding area A in which the welding surface C is present is 0.01 to 0.9 in the concentration of the insulating material in the non-contacting area B. It is desirable to perform the laser treatment to be present in proportions.

In this case, it is preferable that the thickness of the insulating material 440 such as an aluminum oxide film of the electrode tab and lead portion other than the welding surface C, that is, the non-contacting region B, satisfies the range of 7 nm to 400 nm.

Meanwhile, in the above-described embodiment of the present invention, the welding region of the electrode tab and the lead portion has been limited, but the present invention is not limited thereto. The welding method according to the present invention may be applied to a portion where welding is performed in an external region of the pouch. Of course it can.

The electrode assembly according to the present invention may be configured as a secondary battery having a structure consisting of any one of a winding type, a stack type, and a stack / fold type structure. Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood that the following embodiments are for the purpose of illustration only and are not intended to limit the scope of the present invention.

{Example}

The electrode assembly is embedded in the battery case accommodating part, and a plurality of electrode tabs and leads are formed by welding the lead part and protruding from the current collector of the electrode assembly to form a V-forming part. Then, electrolyte is injected and the upper laminate of the battery case The outer peripheral surface where the sheet and the lower laminate contact each other was heat-sealed to form a sealing portion in the battery case.

In particular, in the process of welding a plurality of electrode tabs and leads, the insulating material film existing on the surface of the lead portion is removed by a laser, and the portion of the electrode tab welded with the lead portion is also removed by an oxide film through a laser and then ultrasonic welding is performed. Was performed.

{Comparative Example}

A pouch type secondary battery was manufactured in the same manner as in the above example, except that the oxide layer was removed through the laser.

{Experimental Example 1}

Table 1 shows the drop test results of the batteries prepared in Examples and Comparative Examples.

In this experiment, 100 cells were repeatedly performed, and the forward drop test was performed by 100 times of free-falling on the iron plate at a height of 180 cm so that the electrode terminal portion face downward.

Number of short-circuit generating batteries at the welding surface when falling Example 0 Comparative Example 37

There was no short circuit in all 100 cells in this experiment. On the other hand, the batteries of Comparative Examples were short-circuited and ignited in a large number of batteries, and in particular, it was confirmed by disassembling the battery that the short-circuit of the welded part was dropped. Therefore, according to the present invention, during welding of the electrode tab and the lead, the aluminum oxide film (Al ₂ O ₃ ) formed on the anode lead is ultrasonically welded by removing the welding portion and the periphery with a laser, thereby improving the welding strength and at the same time, It can be seen that the battery performance can be improved by improving heat generation due to a decrease in internal resistance.

{Experiment 2}

An experiment was performed in which seven samples from which the aluminum oxide film of the anode lead of the electrode tab region manufactured by the above-described embodiment were removed, and the internal resistance of the seven electrode leads which were not removed were measured. An energizing current was applied at 12 A, and a gripper pressure for measuring internal resistance was applied at 12 kg.

1) Measurement of Internal Resistance of Laser Etched Group of Aluminum Oxide Films of Seven Samples Prepared by Examples According to the Present Invention)

2) Measurement of the internal resistance of the electrode leads to 7 individuals in the comparison group)

As can be seen from the results of Experimental Example 2, it can be seen that the internal resistance of the sample subjected to laser etching of the oxide film according to the present invention is significantly lowered. This is a testament to the remarkable improvement in the heat generation characteristics of the individual to which the embodiment according to the present invention is applied due to the reduction of internal resistance.

Hereinafter, specific materials and structural features of the components constituting the electrode assembly according to the present invention will be described.

Anode structure

In the present invention, the electrode formed on the base unit is divided into a positive electrode or a negative electrode, and the positive electrode and the negative electrode are prepared by mutually bonding with a separator therebetween. The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture. This structure is implemented in a sheet form can be applied to the process in the form of mounting on the loading roll.

[Positive collector]

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like on the surface of may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as film, sheet, foil, net, porous body, foam, and nonwoven fabric. In the embodiment according to the present invention described above, the electrode tab may be formed to have the same material as the material of the positive electrode current collector.

[Positive electrode active material]

The cathode active material may be a lithium secondary battery, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; Formula _{LiMn 2 - x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; and the like, but Fe ₂ (MoO _{4) 3,} but is not limited to these.

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

Cathode structure

The negative electrode is manufactured by coating, drying, and pressing a negative electrode active material on a negative electrode current collector, and optionally, the conductive material, binder, filler, and the like as described above may be further included. This structure is implemented in a sheet form can be applied to the process in the form of mounting on the loading roll.

[Cathode collector]

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics. In the exemplary embodiment according to the present invention, the electrode tab may be formed to have the same material as that of the negative electrode current collector.

[Cathode active material]

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

[Separation membrane]

The separator according to the present invention implements simple lamination by forming a basic unit by a simple lamination process regardless of a folding process or a roll process. In particular, the adhesion of the separator, the positive electrode, and the negative electrode in the laminator is such that the separator sheet itself is melted by heat and adhered to the inside of the laminator. This allows the pressure to be maintained continuously, thereby enabling stable interfacial contact between the electrode and the separator sheet.

As long as the separator interposed between the anode and the cathode of the separator sheet or cell has an insulating property and a porous structure capable of moving ions, the material thereof is not particularly limited, and the separator and the separator sheet may or may not be the same material. It may be.

The separator or separator sheet may be a thin insulating film having high ion permeability and mechanical strength. The separator or separator sheet generally has a pore diameter of 0.01 to 10 mu m, 300 mu m. Examples of the separator or separator sheet include olefin polymers such as polypropylene, which is resistant to chemicals and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used.

When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane. Preferably, a multilayer film produced by a polyethylene film, a polypropylene film, or a combination of these films, or a film made of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or poly A polyvinylidene fluoride hexafluoropropylene copolymer or the like, or a polymer film for a gel-type polymer electrolyte.

It is preferable that the separator has an adhesive function by heat fusion in order to form a basic unit cell, and the separator sheet does not necessarily have such a function, but it is preferable to use an adhesive function.

The electrode assembly according to the present invention can be applied to an electrochemical cell that produces electricity by an electrochemical reaction between a positive electrode and a negative electrode. Representative examples of the electrochemical cell include a super capacitor and an ultra capacitor. ), Secondary batteries, fuel cells, various sensors, electrolysis devices, electrochemical reactors, and the like, and secondary batteries are particularly preferred.

The secondary battery has a structure in which the electrode assembly capable of charging and discharging is embedded in a battery case in a state impregnated with an ion-containing electrolyte solution. In one preferred embodiment, the secondary battery may be a lithium secondary battery.

Recently, a lithium secondary battery has attracted much attention as a power source for large devices as well as small mobile devices, and it is desirable to have a small weight when applied to such a field. As one way to reduce the weight of the secondary battery, a structure in which the electrode assembly is incorporated in a pouch type case of an aluminum laminate sheet may be preferable. Since such a lithium secondary battery is known in the art, the description thereof will be omitted.

In addition, as described above, when used as a power source for a medium-to-large device, a secondary battery having a structure capable of minimizing the deterioration of operation performance even during long-term use, having excellent life characteristics, and capable of mass production at low cost is preferable. In this regard, the secondary battery including the electrode assembly of the present invention may be preferably used in a medium-large battery module having the unit cell.

In the case of a battery pack including a battery module including a plurality of secondary batteries, a power tool (power tool); Electric vehicles selected from the group consisting of electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); E-bikes; E-scooters; Electric golf cart; Electric truck; And it can be used as one or more power source selected from the medium-large device group consisting of electric commercial vehicles.

The medium-large battery module is configured to provide a high output capacity by connecting a plurality of unit cells in series or in series / parallel manner, which is well known in the art, and thus, description thereof is omitted herein.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical idea of the present invention should not be limited to the embodiments of the present invention but should be determined by the equivalents of the claims and the claims.

100: secondary battery
200: battery case
300: electrode assembly
310, 320: electrode tab
410, 420: lead portion (electrode lead)
430: insulating film
440: insulating material layer (oxide film)

Claims (13)

An electrode including a current collector coated with an active material;
An electrode tab connected to the current collector;
Including a lead connected to the electrode tab;
And the density of the insulating material on the welding surface of the electrode tab and the lead portion is lower than the density of a region outside the welding surface.
The method according to claim 1,
Wherein the insulating material
An electrode assembly, which is an oxide film formed on a surface of the electrode tab or the lead portion.
The method according to claim 2,
The electrode is an anode,
The insulating material layer is an aluminum oxide (Al ₂ O ₃ ) electrode assembly.
The method according to claim 2,
The insulating material layer present on the welding surface,
Electrode assembly in a ratio of 0.01 ~ 0.9 to the concentration of the insulating material layer other than the weld surface.
The method according to claim 2,
The electrode assembly of the electrode assembly is a structure in which the aluminum oxide film is removed by a laser to weld the electrode tab surface and the lead portion surface directly.
The method according to claim 5,
The thickness of the aluminum oxide film on the surface of the electrode tab and the lead portion except for the welding surface is
Electrode assembly of 7 nm to 400 nm.
Pouch for receiving the electrode assembly of any one of claims 1 to 6;
A secondary battery having at least one welding region in which electrode tabs and lead portions are welded inside or outside the pouch.
The method of claim 7,
The electrode assembly includes:
A secondary battery comprising any one of a wound type, a stacked type or a stack / foldable structure.
The method of claim 9,
Wherein the positive electrode slurry coated on the positive electrode current collector is Li ₂ MnO ₃ and LiMO ₂ as a positive electrode active material, wherein M is a transition metal element.
An electrochemical device which is any one selected from the group consisting of a battery module including a secondary battery of claim 7 and a module of a plurality of batteries.
Removing an oxide film by applying a laser to a surface of an electrode tab connected to an electrode current collector or to a surface of a lead connected to the electrode tab;
Performing ultrasonic welding by bringing the electrode tab and the lead into close contact with the region from which the oxide film is removed;
Manufacturing process of a secondary battery comprising a.
The method of claim 11,
The step of removing the oxide film,
A process of manufacturing a secondary battery, the process of removing the oxide film with a laser so that the surface of the electrode tab or the lead portion of the welding region.
The method of claim 12,
The electrode tab is an electrode tab of the positive electrode, the oxide film is a manufacturing process of a secondary battery is silver Al ₂ O ₃ .

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