KR20080077424A - Secondary battery and method therefor - Google Patents

Abstract

A secondary battery is provided to prevent the occurrence of bubbles of an electrolyte and reinforce a welding portion when a circumference of an electrolyte injection hole stopper welds. A secondary battery includes: an electrode assembly obtained by laminating and winding a positive electrode plate with a positive electrode tap, a negative electrode plate with a negative electrode tap, and a separator; a can(200) of which one end is opened and which accommodates the electrode assembly; and a cap assembly of which the upside has an electrolyte injection hole, and which comprises a cap plate(310) that closes the opening of the can, and an electrolyte injection hole stopper(312) that seals the electrolyte injection hole. The whole upside of the electrolyte injection hole stopper is molten, the upper circumference of the electrolyte injection hole is molten, and the molten upside of the electrolyte injection hole stopper and the molten circumference of the electrolyte injection hole are coupled to form a closed passage high-speed revolving type laser welding part(314).

Description

Secondary Battery and Manufacturing Method Thereof {SECONDARY BATTERY AND METHOD THEREFOR}

FIG. 1 is a photograph of a conventional electrolyte injection hole stopper welded down. FIG.

2 is a block diagram of a closed path high-speed rotary laser welding device for explaining an embodiment according to the present invention and a secondary battery according to the present invention.

3 is an exploded perspective view of a rechargeable battery according to an exemplary embodiment of the present invention.

Figure 4 is a photograph of the electrolyte injection hole stopper according to an embodiment of the present invention looking down the state of the high-speed rotary laser welded menopause.

5 is a photograph of a cross section of an electrolyte injection hole stopper coupled to an electrolyte injection hole according to an exemplary embodiment of the present invention.

6 is a photograph of a cross section of a conventional electrolyte injection hole stopper coupled to an electrolyte injection hole.

7 is a flow chart of a secondary battery manufacturing method according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100; Electrode assembly 110; Positive plate

120; Negative plate 130; Separator

140; Positive electrode tab 150; Negative electrode tab

200; Can 300; Cap assembly

310; Cap plate 311; Electrolyte injection hole

312; Electrolyte injection hole stopper 313; Safety vent

314; Menopausal high speed rotary laser weld 315; Smooth cotton

316; Radial pattern 317; Beading part

318; Circular border 320; Electrode terminal

330; Insulating gasket 340; Terminal plate

350; Insulation plate 360; Insulated case

410; Cylindrical prism 420; motor

421; Motor shaft 430; Laser Research Department

440; Condenser lens 450; Unidirectional transmission mirror

460; Second mirror 470; Video camera

480; Laser welding head 500; Conventional laser welding area

510; Blow hole 520; Beading part

SB; Secondary battery

The present invention relates to a secondary battery and a method for manufacturing the same, and more particularly, to welding an electrolyte injection hole plug for sealing an electrolyte injection hole formed in the secondary battery.

Compact and lightweight portable electric / electronic devices such as cell phones, notebook computers and camcorders are actively developed and produced. Therefore, portable electric / electronic devices have a battery pack built therein so that they can be operated even in a place where no separate power source is provided. In consideration of economic aspects, the battery pack has recently adopted a rechargeable battery capable of charging / discharging. In addition, secondary batteries are in the spotlight for hybrid car batteries that require high-density energy and high power, and are under development and production.

Typical secondary batteries include nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) secondary batteries.

In particular, lithium ion secondary batteries have about three times higher operating voltage than nickel-cadmium batteries or nickel-hydrogen batteries, which are widely used as power sources for portable electronic equipment. In addition, it is widely used in view of high energy density per unit weight. The lithium secondary battery uses a lithium oxide as a positive electrode active material and a carbon material as a negative electrode active material. In general, a battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte. A battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. Moreover, although a lithium secondary battery is manufactured in various shapes, typical shapes include cylindrical shape, square shape, and pouch type.

Referring to a general manufacturing process of a secondary battery, first, a positive electrode plate having a positive electrode tab connected to a positive electrode current collector on which a positive electrode active material is formed, a negative electrode plate having negative electrode tabs connected to a negative electrode current collector on which a negative electrode active material is formed, and a separator interposed between the positive electrode plate and the negative electrode plate After laminating, it is wound up to manufacture an electrode assembly. After the electrode assembly is pressed to form a square or elliptical pillar shape, a finishing tape is attached to the outer surface of the electrode assembly and placed in a can, and then the opening of the can is sealed with a cap assembly. Then, the electrolyte is injected into the electrolyte injection hole of the cap assembly and sealed with an electrolyte injection hole stopper. Then, the electrolyte injection hole is sealed with an electrolyte injection hole stopper, and then laser welded around the electrolyte injection hole stopper to seal it.

At this time, the gap formed between the electrolyte injection hole stopper and the electrolyte injection hole in the process of welding the periphery of the electrolyte injection hole stopper flows out of the electrolyte by a capillary phenomenon. Electrolyte flowed out as described above evaporates due to the heat of laser welding and bubbles are generated at the laser welding site to form pores 510 as shown in FIG. 1, so that the electrolyte leaks or the welding site becomes vulnerable to shock. Occurs.

The technical problem of the present invention for solving the above problems is to prevent the generation of bubbles in the electrolyte when welding the periphery of the electrolyte injection hole stopper for sealing the electrolyte injection hole, and at the same time to strengthen the welding site. .

A secondary battery of the present invention for achieving the above object is an electrode assembly wound by stacking a positive electrode plate connected to the positive electrode tab, the negative electrode plate connected to the negative electrode tab and the separator; A can open at one end to receive the electrode assembly; And a cap assembly having an electrolyte injection hole formed on an upper surface thereof and a cap plate closing the opening of the can and an electrolyte injection hole stopper sealing the electrolyte injection hole, wherein an entire upper surface of the electrolyte injection hole stopper is formed. Melt, the upper circumferential portion of the electrolyte injection hole is melted, the molten upper surface of the electrolyte injection hole stopper and the molten circumference of the electrolyte injection hole is combined, characterized in that the high-speed rotary laser welding portion of the closed path.

In addition, the closed path high-speed rotary laser welding unit may form a radial pattern by rotating a circular border around the center of the electrolyte injection hole stopper.

In addition, the diameter of the closed path high-speed rotary laser welding portion may be formed to 80% to 100% larger than the diameter of the electrolyte injection hole.

On the other hand, the secondary battery manufacturing method according to the present invention comprises a laser welding head proximity step of approaching the laser welding head in the center of the electrolyte injection hole stopper; And a laser irradiation step of irradiating the laser while moving the circular path at a high speed based on the center of the electrolyte injection hole plug by rotating the cylindrical prism by condensing the laser refracted through the cylindrical prism having the inclined surface with the condenser lens. Characterized in that it comprises a.

In addition, in the laser welding head proximity step, the position of the electrolyte injection hole stopper may be checked using an image camera.

In addition, the laser irradiation step may proceed by forming a nitrogen atmosphere around the electrolyte injection hole stopper.

In addition, the laser irradiation step may rotate the motor connected to the circumferential surface of the circular prism 600rpm to 7000rpm while irradiating the laser for 0.5 seconds to 2 seconds.

In addition, the laser irradiation step may irradiate the laser discontinuously during the irradiation time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, with reference to Figure 2 will be described a closed path high-speed rotary laser welding apparatus used in a secondary battery according to an embodiment of the present invention.

The closed path high speed rotary laser welding device includes a cylindrical prism 410, a motor 420, a laser irradiation unit 430, a condenser lens 440, a unidirectional transmission mirror 450, a second mirror 460, and an image camera ( 470 is formed.

First, the cylindrical prism 410 is formed with an inclined surface at one end, the laser irradiation unit 430 to pass through the laser to pass through the cylindrical prism 410, the transmitted laser is the inclined surface of the cylindrical prism 410 Passed through one end formed is refracted. At this time, rotating the cylindrical prism 410 forming the refracted laser forms a closed irradiation path, such as circular or elliptical. In addition, when the rotational speed of the cylindrical prism 410 is adjusted, the laser may be irradiated while periodically rotating the irradiation path to which the laser is irradiated. In addition, when the angle of the inclined surface is adjusted, and the bent portion is formed on the inclined surface, the irradiation path of the laser is not limited to a circular or elliptical shape, and various irradiation paths may be formed. That is, it is possible to form a variety of paths. As the material of the cylindrical prism 410 that plays such a role, glass, rock salt, quartz, or plastic, which are generally used at the same time, may have good transmittance with respect to the wavelength of the laser, and the material of the cylindrical prism 410 in the present invention. It is not limiting.

The motor 420 is coupled to the circumferential surface of the cylindrical prism 410 to rotate the cylindrical prism 410. The motor 420 may be a DC motor or an AC motor together with a motor controller, and the control method may be used by adjusting a duty ratio in a PWM (pulse width modulation) method. In addition, the motor may be used with a stepping motor motor controller, the control method is to drive the stepping motor by sending a pulse while varying the frequency in a unipolar or bipolar driving method. However, the present invention does not limit the type or driving method of the motor 420.

The laser irradiation unit 430 irradiates the circular prism 410 with the laser. The laser irradiation unit 430 may irradiate the laser with a medium of the carbon dioxide laser (CO ₂ Laser) or Andy Yag laser (Nd YAG Laser) method and the oscillator according to the present invention, the present invention is to limit the irradiation method no.

The condenser lens 440 condenses the laser beam passing through the cylindrical prism 410. The condenser lens 440 may be formed of a material such as glass or plastic to collect light incident on the condenser lens 440.

The unidirectional transmission mirror 450 reflects the laser beam passing through the cylindrical prism 410 and irradiates the condensing lens 440. In addition, the unidirectional transmission mirror 450 reflects only the wavelength of the laser, and passes through other wavelengths to ensure the field of view of the welded portion by the image camera 470. An optical filter may be further attached to the surface of the unidirectional transmission mirror 450 to prevent the laser from passing through and to pass a different wavelength to secure a view of the welded portion.

The second mirror 460 transmits the photographed image to the unidirectional transmission mirror 450 and reflects the transmitted photographed image.

The image camera 470 processes the photographed image reflected by the second mirror 460.

The driving method of the menopausal high-speed rotary laser welding device having the above-described configuration is a method of irradiating and rotating the cylindrical prism 410 at high speed after passing the laser as a light source through the cylindrical prism 410 and refracting it. First, the cylindrical prism 410 having an inclined surface formed on one side is diverged and refracted by passing a laser having a low energy density. At this time, the laser refracted angle shown in the drawing is shown exaggerated to help understanding. As shown in FIG. 2, the laser, which is refracted and simultaneously emitted, adjusts the density of the light energy by accumulating the light energy emitted by the condenser lens 440. At this time, after the fine welding region is enlarged by using the transmission mirror 450, the second mirror 460 and the image camera 470, the laser beam is irradiated by confirming an accurate measurement region. This method forms a laser refracted by a cylindrical prism 410 having an inclined surface, unlike a conventional method of intensively irradiating a laser beam to a portion to which a laser is irradiated and simultaneously moving a laser welding device (not shown). And, by rotating the cylindrical prism 410 at high speed to repeatedly rotate along the circular menopause path of the irradiation site and to irradiate the laser with uniform energy throughout the irradiation site, thereby the laser path is irradiated laser The entire site forms a welded melt throughout.

Referring to FIG. 3, the secondary battery (SB) of the present invention manufactured using such a closed path high speed rotary laser welding device may be formed including an electrode assembly 100, a can 200, and a cap assembly 300. have.

First, the electrode assembly 100 may be formed by stacking the positive electrode plate 1110 to which the positive electrode tab 140 is connected, the negative electrode plate 120 to which the negative electrode tab 150 is connected, and the separator 130.

The positive electrode plate 110 includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer may be formed of a layered compound containing lithium, a binder to improve bonding strength, and a conductive material to improve conductivity. As the positive electrode current collector, aluminum is generally used, and the positive electrode current collector becomes a passage for the charge generated in the positive electrode active material layer and serves to support the positive electrode active material layer. The positive electrode active material layer is attached to the wide surfaces of the positive electrode current collector, and a positive electrode non-coating portion (not shown) is formed at one end of the positive electrode plate 110, and the positive electrode active material layer is not formed. Is bonded.

The negative electrode plate 120 includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer may be formed of a binder which contains carbon and improves bonding strength between hard carbon, which is commonly used, or graphite and active material particles. As the negative electrode current collector, copper is generally used, and the negative electrode current collector serves as a movement path of charge generated in the negative electrode active material layer, and serves to support the negative electrode active material layer. The negative electrode active material layer is formed on a wide surface of the negative electrode plate 113, in which a negative electrode non-coating portion (not shown) is formed at one end of the negative electrode plate 120. The negative electrode tab 150 is bonded to the negative electrode non-coating portion.

The separator 130 is interposed between the positive electrode plate 110 and the negative electrode plate 120 to insulate the positive electrode plate 110 and the negative electrode plate 120 and allow charges of the positive electrode plate 110 and the negative electrode plate 120 to pass therethrough. Generally, the material of the separator 130 is polyethylene (PE) or polypropylene (PP), but the material is not limited thereto. The separator 130 may include an electrolyte and may be formed in a liquid or gel form.

One end of the can 200 may be opened to accommodate the electrode assembly 100. At this time, the can 200 accommodates the electrolyte. The shape of the can 200 is formed in the shape of a square or track shape in consideration of the shape of the electrode assembly 100. The can 200 having such a shape accommodates the insulating case 360 in the upper portion of the electrode assembly 100, covers the cap plate 131 in the opening of the can 200, and is coupled by a welding method. The material of the can 200 is mainly aluminum, but the material is not limited thereto.

The cap assembly 300 has an electrolyte injection hole stopper 312 that seals a safety vent 313 and an electrolyte injection hole 311 on an upper surface thereof, and is electrically connected to the positive electrode tab 140, and the can 200. The cap plate 310 closing the opening of the electrode plate is seated in the central hole of the cap plate 310 and the electrode terminal 320 is electrically connected to the negative electrode tab 150, the body of the electrode terminal 320 wraps the electrode terminal ( An insulating gasket 330 that insulates the cap plate 310 and the cap plate 310 may include a hole protruding from the positive electrode tab 140 and the negative electrode tab 150, and the electrode assembly 100 may be seated on the electrode assembly 100. Insulation case 360 to insulate the upper surface of the terminal, the terminal plate 340, the terminal plate 340 and the cap plate 310 to provide a hole for pressing and fixing the end of the electrode terminal 320 is insulated and insulated It is formed including the plate 350. At this time, the insulating gasket 330, the insulating case 360 and the insulating plate 350 may be formed of an insulating material such as polypropylene resin or polyethylene resin, the electrode terminal 320 and the cap plate 310 and The terminal plate 340 may be formed of a conductive metal material, such as aluminum, an alloy containing aluminum, or an alloy containing nickel or nickel. However, the material of the cap assembly 300 is not limited in the present invention.

Meanwhile, referring to FIGS. 4 and 5, in the closed path high-speed rotary laser welding part 314 of the present invention formed in the secondary battery, the entire upper surface of the electrolyte injection hole stopper 312 is melted, and the electrolyte injection hole ( The upper circumference of 311 is melted, and the molten upper surface of the electrolyte injection hole stopper 312 and the molten circumference of the electrolyte injection hole 311 are formed to be combined. First, referring to the welding part 500 in which the conventional electrolyte injection hole stopper shown in FIG. 1 is welded, the welding part 500 irradiates the laser using a laser welding device and simultaneously lasers along the path of the welding part. The welding device 500 is moved to form a welding part 500. At this time, the electrolyte is evaporated to a part of the conventional welding part 500 to form pores 510. The high speed rotary laser welding unit 314 of FIG. 2 which solves such a problem is formed by a closed path high speed rotary laser welding device, and rotates the circular prism 410 of the closed path high speed rotary laser welding device to close the electrolyte injection hole plug 312. When forming a circular path with respect to the center of the), when irradiating the laser by rotating very fast, the closed path high-speed rotary laser welding portion 314 shown in the photograph of Figure 4 is formed. At this time, the closed path high-speed rotary laser welding part 314 is melted as the laser irradiated while rotating very quickly, as shown in Figure 5, the entire upper surface of the electrolyte injection hole stopper 312 and at the same time, the electrolyte injection hole stopper 312 And the electrolyte leaking out of the portion where the cap plate 310 abuts continuously to prevent the formation of pores.

Referring to FIG. 4, a smooth surface 315 may be formed at a circumference of the closed path high speed laser welding part 314. The smooth surface 315 is different from the rugged beading portion 520 of FIG. 1, which is formed using a conventional laser welding method of intensively irradiating the interface between the electrolyte injection hole cap 312 and the cap plate 310. The curvature changes very smoothly and smoothly. This is because after polishing the protruding portion of the beading portion 520 generated when the conventional laser welding is smoothly formed, there is no need to check whether the laser welding is well formed, the manufacturing time can be shortened There is this.

In addition, soot may be formed in the circumference of the closed path high speed laser welding part 314. After injecting the electrolyte solution, the electrolyte solution is slowly removed using a closed path high-speed rotary laser welding in order to evaporate the electrolyte residue formed around the electrolyte injection hole or the electrolyte injection hole stopper 312 by the capillary phenomenon. When evaporated, the smooth surface 315 formed around the electrolyte injection hole stopper 312 is blackened.

In addition, the center of the menopausal high-speed rotary laser welding portion 314 may rotate the circular rim 318 around the center to form a radial pattern 316, the high-speed circular path around the center of the electrolyte injection hole plug When irradiating the laser while moving to, the radial pattern 316 is formed on the upper surface of the electrolyte injection hole stopper 312 by the closed path high speed rotary laser welding. This radial pattern 316 may be formed by a constant rotational speed of the circular prism.

Referring to FIG. 5, the diameter of the closed path high-speed rotary laser welding part 314 may be 80% to 100% larger than the diameter of the electrolyte injection hole 311. Referring to FIG. 6, the welded portion of the conventional electrolyte injection hole stopper 312 is welded to be welded by focusing the laser on the circumferential portion where the electrolyte injection hole stopper 312 and the electrolyte injection hole 311 come into contact with each other. do. At this time, the diameter of the irradiated laser is formed without exceeding the center of the electrolyte injection hole stopper 312. If the laser is irradiated beyond the center of the electrolyte injection hole stopper 312, when the laser device is rotated, an overlapping portion is formed at the center portion of the irradiated laser portion, and the irradiated laser portion is overlapped and welded. Defect occurs. Therefore, the diameter of the welded portion formed by the conventional welding method is only about 30% larger than the diameter of the electrolyte injection hole 311. However, the closed path high-speed rotary laser welding part 314 of FIG. 5 melts the entire upper surface of the stopper so that a part of the upper surface of the molten stopper flows down, and thus 80% to 100% of the diameter of the electrolyte injection hole 311. It can be formed large.

On the other hand, with reference to Figure 7, the secondary battery manufacturing method according to the present invention for forming the above-described closed path high-speed laser welding portion is a laser welding head proximity step of approaching the laser welding head in the center of the electrolyte injection hole (S1); And condensing the laser beam refracted through the cylindrical prism with the inclined surface with the condenser lens, and rotating the cylindrical prism to move the circular path at a high speed based on the center of the electrolyte injection hole stopper. It characterized in that it comprises a step (S2).

Referring to FIG. 2, in the laser welding head proximate step S1, the laser welding head 480 is close to the center of the electrolyte injection hole stopper 312. At this time, the electrolyte injection hole stopper 312 is pressed into the electrolyte injection hole 312. 2 is a schematic diagram for detailed description, and it may be different from the ratio of actual components.

Then, the laser irradiation step (S2) condenses the laser having a low energy density refracted by passing through the cylindrical prism 410 having the inclined surface with the condenser lens 440 and at the same time rotate the cylindrical prism 410 to inject the electrolyte The laser beam may be irradiated while moving a circular path at a high speed based on the center of the hole stopper 312. When the laser having a low energy density emitted to the cylindrical prism 410 is irradiated, the laser having short wavelength is refracted at the same time as having a low energy density, and the refracted laser is on the circular path by the rotating cylindrical prism 410. Is investigated at high speed. At this time, the circumferential surface of the cylindrical prism 410 is in contact with the circumferential surface of the cylindrical prism 410 gears, belts or frictional elements connected to the end of the drive shaft 421 of the motor 420 driven by direct current or alternating current, The cylindrical prism 410 may be rotated at high speed by the rotation of the motor 420. If the laser is refracted in this manner to pass through the condenser lens 440 to adjust the laser energy density high, and irradiating the laser while moving the circular path at a high speed based on the center of the electrolyte injection hole cap 312, the cap, The periphery of the electrolyte injection hole stopper 312 coupled with the plate 310 is melted and joined.

After these steps (S1) (S2), the electrolyte injection hole stopper 312 and the electrolyte formed in the periphery of the electrolyte injection hole stopper 312 is gradually evaporated to form a pore that can leak the electrolyte, Can form a very smooth closed path high speed rotary laser weld 314.

In addition, in the laser welding head proximate step S1, the position of the electrolyte injection hole stopper 312 may be checked using the image camera 470. The reason why the image camera 470 is used is that the diameter of the pressurized electrolyte injection hole stopper 312 is formed to be about 1 mm, which is very small, so that the circumferential portion of such a small electrolyte injection hole stopper 312 is finely melted. In order to confirm and enlarge the position of the electrolyte injection hole stopper 312 by installing the image camera 470, the closed path high-speed rotary laser welding must be performed. At this time, while measuring the position of the electrolyte injection hole stopper 312, the irradiation path of the laser and the field of view of the image camera 470 overlap using the unidirectional transmission mirror 450 to position the position of the electrolyte injection hole stopper 312 You can check it. In this case, the image camera 470 may check the position of the electrolyte injection hole stopper transmitted through the unidirectional transmission mirror 450 through the reflection mirror 460.

In addition, in the laser irradiation step (S2) it can proceed by forming a nitrogen atmosphere around the electrolyte injection hole stopper 312. When a nitrogen atmosphere is formed around the electrolyte injection hole stopper 312, the electrolyte solution buried around the electrolyte injection hole stopper 312 may be more quickly evaporated.

In addition, in the laser irradiation step (S2) it is possible to irradiate the laser by rotating the cylindrical prism 410, at this time, the laser irradiation time may be irradiated for 0.5 seconds to 2 seconds. When the rotational speed of the motor 420 connected to the side of the cylindrical prism 410 is adjusted to 600 rpm to 7000 rpm, the laser generates a circular path about 10 to 100 based on the center of the electrolyte injection hole cap 312 for 1 second. It's moving around the streets. At this time, by adjusting the rotational speed and irradiation time of the motor 410 in consideration of the thickness of the electrolyte injection hole cap 312 and the thickness of the cap plate 310, the closed path high-speed rotary laser welding portion 314 having good formability Can be formed.

At this time, by increasing the rotational speed of the cylindrical prism 410 and irradiating the laser point discontinuously, laser welding can be performed several times in a short time. This is to slowly evaporate the electrolyte by irradiating the laser spot continuously so as not to form bubbles generated when the electrolyte evaporates rapidly.

The present invention is not limited to the technical spirit of the specific embodiments or drawings described above, and those skilled in the art without departing from the gist of the invention claimed in the claims Various modifications are possible, of course, and such changes are within the scope of the claims of the present invention.

The secondary battery of the present invention has the effect of preventing the leakage of the electrolyte by forming a closed path high-speed rotary laser welding around the electrolyte injection hole stopper.

In addition, there is an effect that the welded portion is strengthened by forming a closed path high-speed rotary laser welded portion.

The secondary battery manufacturing method of the present invention has the effect of forming a closed path high-speed rotary laser welding portion having a good formability of the welded portion.

Claims (8)

An electrode assembly in which a positive electrode plate connected with a positive electrode tab, a negative electrode plate connected with a negative electrode tab, and a separator are laminated; A can open at one end to receive the electrode assembly; And An upper surface of the cap assembly including a cap plate forming an electrolyte injection hole and closing an opening of the can and an electrolyte injection hole stopper sealing the electrolyte injection hole, The entire upper surface of the electrolyte injection hole stopper is melted, and the upper circumference of the electrolyte injection hole is melted, and the molten upper surface of the electrolyte injection hole stopper and the molten circumference of the electrolyte injection hole are combined to close the high speed rotary laser welding part. Secondary battery, characterized in that formed. The method of claim 1, The secondary path of the secondary path, characterized in that the high-speed rotation laser welding portion of the closed path is formed by rotating a circular border around the center of the electrolyte injection hole stopper. The method of claim 1, The secondary path, characterized in that the diameter of the closed path high speed laser welding portion is formed 80% to 100% larger than the diameter of the electrolyte injection hole. A laser welding head proximity step of bringing the laser welding head closer to the center of the electrolyte injection hole stopper; And A laser irradiation step of irradiating the laser while moving the circular path at a high speed based on the center of the electrolyte injection hole stopper by rotating the cylindrical prism by condensing the laser refracted through the cylindrical prism having the inclined surface with the condenser lens. Secondary battery manufacturing method comprising a. The method of claim 4, wherein The laser welding head proximity step A secondary battery manufacturing method characterized by checking the position of the electrolyte injection hole stopper using an image camera. The method of claim 4, wherein The laser irradiation step The secondary battery manufacturing method, characterized in that to proceed by forming a nitrogen atmosphere around the electrolyte injection hole stopper. The method of claim 4, wherein The laser irradiation step And rotating the motor connected to the circumferential surface of the circular prism at 600 rpm to 7000 rpm and irradiating the laser for 0.5 seconds to 2 seconds. The method of claim 7, wherein The laser irradiation step The secondary battery manufacturing method, characterized in that for irradiating the laser discontinuously during the irradiation time.

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