Secondary battery sealing process and secondary battery manufacturing method including the process

Abstract

The present invention provides a sealing process for a secondary battery. The sealing process thermally melts and seals a sealing portion extending along an edge surface of a battery case. The sealing process includes: an arranging operation of disposing the sealing portion of the battery case between an anvil and a sonotrode; a first region fixing operation of pressing and fixing a first region of the sealing portion by the anvil and the sonotrode; and a first region primary sealing operation of applying ultrasonic waves to the first region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby thermally melting and sealing the first region of the sealing portion.

Description

Technical Field

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of Korean Patent Application No. 10-2020-0100764, filed on Aug. 11, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0004] The present invention relates to a secondary battery sealing process for improving the sealing force of a sealing portion of a pouch-type battery case in a secondary battery and a secondary battery manufacturing method including the secondary battery sealing process. Background Art

[0005] Generally, unlike a primary battery that cannot be charged, a secondary battery refers to a battery that can be charged and discharged, and such secondary batteries are widely used in high-tech electronic fields such as mobile phones, laptop computers, and portable video cameras.

[0006] Secondary batteries are classified into can-type secondary batteries in which an electrode assembly is stored in a metal can and pouch-type secondary batteries in which an electrode assembly is stored in a pouch. Moreover, the pouch-type secondary battery includes: an electrode assembly having an electrode tab, an electrode lead wire coupled to the electrode tab, and a battery case that houses the electrode assembly in a state where the front end of the electrode lead wire is pulled to the outside. Moreover, the battery case includes a housing portion for housing the electrode assembly and a sealing portion formed along an edge surface of the housing portion.

[0007] Meanwhile, the sealing portion of the battery case in the secondary battery is sealed by using a sealing device for the secondary battery, and the sealing device for the secondary battery seals the sealing portion of the battery case by using ultrasonic waves.

[0008] However, the conventional sealing device for a secondary battery has limitations in uniformly sealing the sealing portion of the battery case. That is, in the conventional sealing device for a secondary battery, heat is unevenly applied to the sealing portion of the battery case, resulting in welding failure. Summary of the Invention

[0009] Technical Problem

[0010] The present invention has been made to solve the above problems. An object of the present invention is to provide a secondary battery sealing process that can make the heat applied to the sealing portion of the battery case uniform by setting optimal welding conditions when sealing the sealing portion of the battery case, and as a result, welding failure can be prevented. Moreover, a secondary battery manufacturing method including using the above process is provided.

[0011] Technical Solution

[0012] To achieve the above object, the sealing process for a secondary battery of the present invention hot-melts and seals a sealing portion extending along the edge surface of the battery case, and includes: an arranging operation of disposing the sealing portion of the battery case between an anvil and a sonotrode; a first region fixing operation of pressing and fixing a first region of the sealing portion by the anvil and the sonotrode; and a first region primary sealing operation of applying ultrasonic waves to the first region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the first region of the sealing portion.

[0013] The set frequency may be from 10 kHz to 40 kHz, the set amplitude may be from 5 μm to 50 μm, and the set time may be from 0.1 second to 2.0 seconds.

[0014] The sealing portion may have a stacked structure including a coating layer, a metal layer, and an insulating layer in a direction from the inside to the outside of the battery case, and the thickness of the coating layer may be from 30 μm to 85 μm.

[0015] After the first region primary sealing operation, a first region secondary sealing operation may be further performed to secondarily hot-melt the first region of the sealing portion by secondarily applying ultrasonic waves to the first region of the sealing portion through the sonotrode, wherein the first region secondary sealing operation is performed at the same ultrasonic frequency and set time as the first region primary sealing operation, but the amplitude is reduced by 40% to 60%.

[0016] The sonotrode may be capable of rotating left or right toward the sealing portion, and is mounted to a converter including a booster, and may press the entire first region of the sealing portion with uniform pressure.

[0017] After the first region primary sealing operation, the sealing process may further include: a second region fixing operation of pressing and fixing a second region of the sealing portion, which is spaced apart from the first region, by the anvil and the sonotrode; and a second region sealing operation of applying ultrasonic waves to the second region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the second region of the sealing portion.

[0018] The second region sealing operation may be set to the same ultrasonic frequency, amplitude, and time as the first region primary sealing operation.

[0019] After the second region sealing operation, the sealing process may further include: a third region fixing operation of pressing and fixing a third region of the sealing portion located between the first region and the second region by the anvil and the sonotrode; and a third region sealing operation of applying ultrasonic waves to the third region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the third region of the sealing portion.

[0020] The ultrasonic frequency, amplitude, and time of the sealing operation in the third region can be set to be different from those of the first region's initial sealing operation.

[0021] The ultrasonic frequency, amplitude, and time of the third region can be set to be higher than those of the first region's initial sealing operation.

[0022] Meanwhile, the method for manufacturing a secondary battery of the present invention includes: a manufacturing process of manufacturing an electrode assembly by stacking electrodes and a separator; a housing process of housing the electrode assembly in a pouch-type battery case; and a sealing process of heat-sealing and sealing a sealing portion extending from an edge surface of the pouch-type battery case, wherein the sealing process includes: an arranging operation of disposing the sealing portion extending along the edge surface of the pouch-type battery case between an anvil and a sonotrode; a first region fixing operation of pressing and fixing a first region of the sealing portion by the anvil and the sonotrode; and a first region initial sealing operation of applying ultrasonic waves to the first region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby heat-sealing the first region of the sealing portion.

[0023] The set frequency can be from 10 kHz to 40 kHz, the set amplitude can be from 5 μm to 50 μm, and the set time can be from 0.1 second to 2.0 seconds.

[0024] The sealing process may further include a first region secondary sealing operation of secondarily applying ultrasonic waves to the first region of the sealing portion by the sonotrode after the first region initial sealing operation, wherein the first region secondary sealing operation is performed at the same ultrasonic frequency and set time as the first region initial sealing operation, but the amplitude is reduced by 40% to 60%.

[0025] After the first region initial sealing operation, the sealing process may further include: a second region fixing operation of pressing and fixing a second region of the sealing portion spaced apart from the first region by the anvil and the sonotrode; and a second region sealing operation of applying ultrasonic waves to the second region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby heat-sealing the second region of the sealing portion.

[0026] After the second region sealing operation, the sealing process may further include: a third region fixing operation of pressing and fixing a third region of the sealing portion located between the first region and the second region by the anvil and the sonotrode; and a third region sealing operation of applying ultrasonic waves to the third region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby heat-sealing the third region of the sealing portion.

[0027] Advantageous Effects

[0028] The sealing process for a secondary battery according to the present invention includes an arrangement operation, a first area fixing operation, and a first area primary sealing operation. The first area primary sealing operation applies ultrasonic waves to a first area of a sealing part provided in a battery case at a set frequency and a set amplitude for a set time, thereby heat-sealing the first area of the sealing part. Here, the set frequency may be from 10 kHz to 40 kHz, the set amplitude may be from 5 μm to 50 μm, and the set time may be from 0.1 second to 2.0 seconds. Accordingly, when sealing the first area of the sealing part included in the battery case, optimal sealing conditions can be set. As a result, the uniformity of heat transfer to the first area of the sealing part can be enhanced, and as a result, the first area of the sealing part can be sealed without failure.

[0029] Moreover, in the sealing process for a secondary battery according to the present invention, a first area secondary sealing operation is further performed. The first area secondary sealing operation has the same sealing conditions as the first area primary sealing operation, but is performed in a state where only the amplitude is reduced by 50%. Accordingly, bubbles generated in the sealing part of the battery case during the first area primary sealing operation can be effectively discharged and eliminated, and accordingly, the occurrence of failures can be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a cross-sectional view illustrating a secondary battery according to a first embodiment of the present invention.

[0031] Figure 2 is a perspective view illustrating a sealing device for a secondary battery according to a first embodiment of the present invention.

[0032] Figure 3 is a cross-sectional view illustrating a sealing device for a secondary battery according to a first embodiment of the present invention.

[0033] Figure 4 is a flowchart showing a sealing process for a secondary battery according to a first embodiment of the present invention.

[0034] Figure 5 is a perspective view showing an arrangement operation of a sealing process for a secondary battery according to a first embodiment of the present invention.

[0035] Figure 6 is a side view showing a first area fixing operation of a sealing process for a secondary battery according to a first embodiment of the present invention.

[0036] Figure 7 is a side view showing a first area sealing operation of a sealing process for a secondary battery according to a first embodiment of the present invention.

[0037] Figure 8It is a cross-sectional view showing a state in which air bubbles are generated in a sealing portion in a sealing process for a secondary battery according to a first embodiment of the present invention.

[0038] Figure 9 It is a cross-sectional view showing a state in which air bubbles are eliminated in a sealing portion in a sealing process for a secondary battery according to a first embodiment of the present invention.

[0039] Figure 10 It is a flowchart showing a method for manufacturing a secondary battery according to a second embodiment of the present invention.

[0040] Figure 11 It is a plan view illustrating a secondary battery sealing process according to a third embodiment of the present invention.

[0041] Figure 12 It is a table showing experimental examples of a sealing device for a secondary battery of the present invention.

[0042] Figure 13 It is a picture in which Figure 12 an image of the experimental result of Comparative Example 1 is taken.

[0043] Figure 14 It is a picture in which Figure 12 an image of the experimental result of Preparation Example 1 is taken.

[0044] Figure 15 It is a picture in which Figure 12 an image of the experimental result of Preparation Example 2 is taken.

[0045] Figure 16 It is a picture in which Figure 12 an image of the experimental result of Comparative Example 2 is taken. Detailed Embodiments

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily implement these embodiments. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. Also, in the drawings, parts irrelevant to the description will be omitted to clearly describe the present invention, and throughout the specification, similar elements will be denoted by similar reference numerals.

[0047] [Secondary Battery According to a First Embodiment of the Present Invention]

[0048] As Figure 1 shown, a secondary battery according to a first embodiment of the present invention includes an electrode assembly 10 having electrode tabs, an electrode lead 20 coupled to the electrode tabs, and a battery case 30 that houses the electrode assembly 10 in a state where the front end of the electrode lead 20 is pulled to the outside.

[0049] Moreover, the battery case 30 includes an upper case and a lower case. Since the accommodation groove of the upper case is connected to the accommodation groove of the lower case, an accommodation part 31 for accommodating the electrode assembly 10 is formed. Since the sealing surface of the upper case is connected to the sealing surface of the lower case, a sealing part 32 for sealing the accommodation part 31 is formed.

[0050] That is to say, the battery case 30 includes an accommodation part 31 and a sealing part 32. The accommodation part 31 accommodates the electrode assembly 10, and the sealing part 32 extends along the edge surface of the accommodation part 31 and seals the accommodation part 31.

[0051] Moreover, with reference to Figure 8 , each of the upper case and the lower case has a stacked structure, in which a coating layer 30a, a metal layer 30b, and an insulating layer 30c are sequentially stacked from the inside to the outside of the battery case 30.

[0052] Herein, the sealing part of the battery case is sealed by a sealing device for a secondary battery according to the first embodiment of the present invention. In particular, the sealing device for a secondary battery according to the first embodiment of the present invention hot-melts and seals the sealing part of the battery case by using ultrasonic waves. Herein, the sealing device for a secondary battery according to the first embodiment of the present invention sets optimal conditions when generating ultrasonic waves, so that the sealing part of the battery case can be sealed without failure.

[0053] Hereinafter, a sealing device for a secondary battery according to the first embodiment of the present invention will be described in detail with reference to the drawings.

[0054] [Sealing Device for Secondary Battery According to the First Embodiment of the Present Invention]

[0055] As Figure 2 and Figure 3 shown, the secondary battery sealing device 100 according to the first embodiment of the present invention includes: an anvil 110, on which the sealing part 32 of the battery case 30 is disposed; and a sonotrode 120, which heats and seals the sealing part 32 disposed on the anvil 110 while the sealing part is under pressure.

[0056] That is to say, in the secondary battery sealing device 100 according to the first embodiment of the present invention, the sealing part 32 of the battery case 30 is disposed between the anvil 110 and the sonotrode 120. Then, through the anvil 110 and the sonotrode 120, the sealing part 32 is under pressure and fixed. Next, when ultrasonic waves are applied to the sealing part 32 through the sonotrode 120, a part of the coating layer included in the sealing part 32 is hot-melted. Accordingly, the sealing part can be sealed.

[0057] As an example, the secondary battery sealing device 100 according to the first embodiment of the present invention applies ultrasonic waves to the first region A of the sealing portion 32 via the welding head 120 at a set frequency and a set amplitude for a set time. Accordingly, the uniformity of the heat generated in the first region A of the sealing portion 32 can be improved, and as a result, the first region A of the sealing portion 32 can be sealed without failure.

[0058] Here, when the thickness of the coating layer 30a provided in the sealing portion 32 is 30 μm to 85 μm, the set frequency may be 10 kHz to 40 kHz, the set amplitude may be 5 μm to 50 μm, and the set time may be 0.1 second to 2.0 seconds.

[0059] As described above, when the secondary battery sealing device 100 according to the first embodiment of the present invention seals the coating layer included in the sealing portion 32, the coating layer can be sealed without failure by setting the ultrasonic welding conditions.

[0060] Meanwhile, the secondary battery sealing device 100 according to the first embodiment of the present invention includes a converter 130, and the converter 130 has a booster 131 that transfers thermal energy to the welding head 120. Here, the center of the welding head 120 is rotatably coupled to the booster 131 through a hinge portion 121. Accordingly, both ends of the welding head 120 rotate around the hinge portion 121. That is, since the welding head 120 rotates when the sealing portion 32 is subjected to the pressure of the anvil 110 and the welding head 120, the entire sealing portion 32 can be uniformly subjected to the pressure via the anvil 110 and the welding head 120. As a result, uniform ultrasonic waves can be applied to the entire sealing portion. Therefore, the sealing force can be increased.

[0061] Hereinafter, a sealing process using the secondary battery sealing device 100 according to the first embodiment of the present invention will be described.

[0062] [Sealing Process for Secondary Battery According to the First Embodiment of the Present Invention]

[0063] As Figures 4 to 9 shown, the secondary battery sealing process (S30) according to the first embodiment of the present invention is to thermally melt and seal the sealing portion 32 extending along the edge surface of the battery case 30, and the secondary battery sealing process includes an arrangement operation (S31), a first region fixing operation (S32), a first region primary sealing operation (S33), and a first region secondary sealing operation (S34).

[0064] Arrangement operation

[0065] In the arrangement operation (S31), the first region A defined in the sealing portion 32 of the battery case 30 is disposed between the anvil 110 and the welding head 120 of the sealing device 100 for the secondary battery.

[0066] First - area fixing operation

[0067] In the first region fixing operation (S32), the first region A of the sealing portion 32 is pressed and fixed by the anvil 110 and the sonotrode 120. Here, the sonotrode 120 is coupled to the converter 130 so as to be rotatable left and right about the hinge portion 121. Accordingly, the sonotrode 120 rotates according to the arrangement angle of the anvil 110, and as a result, the pressure on the entire pressing surface of the anvil 110 and the sonotrode 120 can be made uniform. Thereby, the entire surface of the sealing portion 32 fixed between the anvil 110 and the sonotrode 120 can be pressed with a uniform force.

[0068] First - area primary sealing operation

[0069] In the first region primary sealing operation (S33), ultrasonic waves are generated in the first region A of the sealing portion 32 by the sonotrode 120, and the first region A of the sealing portion 32 is heat-melted. In particular, in the first region primary sealing operation (S33), since ultrasonic waves are applied by the sonotrode 120 at a set frequency and a set amplitude for a set time, the first region A of the sealing portion 32 is heat-melted. That is, the sonotrode 120 applies ultrasonic waves to the coating layer included in the sealing portion 32. Since a part of the coating layer is melted and then solidified, the sealing portion 32 is sealed.

[0070] Meanwhile, the battery case 30 includes an upper case and a lower case. Since the accommodation groove of the upper case is connected to the accommodation groove of the lower case, an accommodation portion 31 for accommodating the electrode assembly 10 is formed. Since the sealing surface of the upper case is connected to the sealing surface of the lower case, a sealing portion 32 for sealing the accommodation portion 31 is formed. Moreover, each of the upper case and the lower case has a structure in which a coating layer 30a, a metal layer 30b, and an insulating layer 30c are sequentially stacked from the inside of the battery case toward the outside.

[0071] Here, when the thickness of the coating layer 30a included in the sealing portion 32 is 30 μm to 85 μm, the set frequency as the first condition may be 10 kHz to 40 kHz, the set amplitude as the second condition may be 5 μm to 50 μm, and the set time as the third condition may be 0.1 second to 2.0 seconds. Here, an amplitude of 5 μm to 50 μm is regarded as 100%.

[0072] Meanwhile, when the frequency as the first condition is less than or equal to 10 kHz, a long time is required to melt the coating layer 30a included in the sealing portion 32. Moreover, when the frequency is greater than or equal to 40 kHz, the coating layer 30a included in the sealing portion 32 can be rapidly melted, but damage to the coating layer may also occur.

[0073] Moreover, when the set amplitude as the second condition is equal to or less than 5 μm, the coating layer 30a included in the sealing portion 32 does not melt, or it takes a long time. Moreover, when the set amplitude is greater than or equal to 50 μm, the coating layer 30a included in the sealing portion 32 can melt rapidly, but damage to the coating layer may also occur.

[0074] Moreover, when the set time as the third condition is less than or equal to 0.1 second, the coating layer 30a included in the sealing portion 32 does not melt because the time for applying ultrasonic waves to the coating layer 30a is short. Moreover, when the set time is greater than or equal to 2.00 seconds, the coating layer 30a included in the sealing portion 32 can melt rapidly, but damage to the coating layer may also occur.

[0075] As an example, when the thickness of the coating layer 30a included in the sealing portion 32 is 35 μm to 80 μm, when the ultrasonic frequency is set to 10 kHz or 40 kHz, the amplitude is set to 100%, and the time is set to 0.1 second or 2.0 seconds, the sealing effect of the sealing portion becomes extremely good (see Figure 14 and Figure 15 for the experimental pictures). At the same time, when the ultrasonic frequency is 15 kHz, the amplitude is 100%, and the time is less than or equal to 0.1 second, heat is not evenly transferred to the coating layer of the sealing portion 32, so the coating layer does not melt sufficiently. Accordingly, a sealing failure may occur (see Figure 13 for the experimental pictures). At the same time, when the ultrasonic frequency is 35 kHz, the amplitude is 50%, and the time is 0.1 second, heat is not evenly transferred to the coating layer of the sealing portion 32, so the coating layer does not melt sufficiently (see Figure 16 for the experimental pictures).

[0076] Therefore, in the first region primary sealing operation (S33), the set frequency as the first condition is set to 10 kHz to 40 kHz, the set amplitude as the second condition is set to 5 μm to approximately 50 μm, and the set time as the third condition is set to 0.1 second to 2.0 seconds. Accordingly, the uniformity of heat transfer can be enhanced, and as a result, the first region A of the sealing portion 32 can be uniformly sealed without failure.

[0077] Here, as shown in Figure 8 , in the first region primary sealing operation (S33), as the coating layer 30a of the sealing portion 32 melts, bubbles C are generated in the sealing portion 32. The first region secondary sealing operation (S34) can be further performed to eliminate the bubbles C generated in the coating layer 30a of the sealing portion 32.

[0078] That is, after the first region primary sealing operation (S33), a first region secondary sealing operation (S34) is further performed to secondarily apply ultrasonic waves to the first region A of the sealing portion 32 through the horn 120.

[0079] First - area secondary sealing operation

[0080] As Figure 9 shown, the first region secondary sealing operation (S34) is to secondarily seal the sealing portion and simultaneously eliminate the bubbles generated in the sealing portion during the first region primary sealing operation. That is, in the first region secondary sealing operation (S34) after the first region primary sealing operation (S33), ultrasonic waves are secondarily applied to the first region A of the sealing portion 32 through the horn 120, and the first region A of the sealing portion 32 is secondarily heat-sealed.

[0081] Here, the first region secondary sealing operation (S34) is performed at the same ultrasonic frequency and set time as the first region primary sealing operation (S33), but the amplitude is reduced by 40% to 60%, preferably 50%.

[0082] That is, in the first region secondary sealing operation (S34), the ultrasonic frequency as the first condition is set to 10 kHz to 40 kHz, the set amplitude as the second condition is set to 40% to 60% of the amplitude set in the first region primary sealing operation (S33), and the set time as the third condition is set to 0.1 second to 2.0 seconds.

[0083] As described above, in the first region secondary sealing operation (S34), the optimal sealing conditions including the first to third conditions are set. Next, frictional heat is generated in the sealing portion 32 using ultrasonic waves. Therefore, the bubbles C generated in the sealing portion 32 are guided and gradually discharged to the outside. As a result, the bubbles C generated in the sealing portion 32 can be effectively eliminated.

[0084] Therefore, the secondary battery sealing process (S30) according to the first embodiment of the present invention includes an arrangement operation (S31), a first region fixing operation (S32), a first region primary sealing operation (S33), and a first region secondary sealing operation (S34), so that the optimal sealing conditions can be set. Accordingly, the uniformity of the heat transferred to the sealing portion can be enhanced. As a result, the sealing portion can be sealed without failure. In particular, the bubbles generated in the sealing portion can be effectively eliminated, so that the productivity can be improved.

[0085] Hereinafter, when describing another embodiment of the present invention, components having the same functions as those in the foregoing embodiments are given the same reference numerals, and their repeated descriptions will be omitted.

[0086] Method for manufacturing secondary battery according to second embodiment of the present invention

[0087] As Figure 10 shown, the method for manufacturing a secondary battery according to the second embodiment of the present invention includes: a manufacturing process (S10) of stacking electrodes and a separator and manufacturing an electrode assembly 10; a housing process (S20) of coupling electrode leads 20 to electrode tabs of the electrode assembly 10 and housing the electrode assembly 10 in a pouch-type battery case 30 with the front ends of the electrode leads 20 pulled to the outside; and a sealing process (S30) of heat-sealing and sealing a sealing portion 32 extending from an edge surface of the pouch-type battery case 30.

[0088] Here, the sealing process (S30) includes: an arranging operation (S31) of disposing the sealing portion 32 extending along the edge surface of the pouch-type battery case 30 between an anvil 110 and a welding head 120; a first region fixing operation (S32) of pressing and fixing a first region A of the sealing portion 32 by the anvil 110 and the welding head 120; and a first region primary sealing operation (S33) of applying ultrasonic waves to the first region A of the sealing portion 32 by the welding head 120 at a set frequency and a set amplitude for a set time, thereby heat-sealing the first region A of the sealing portion 32.

[0089] Meanwhile, the set frequency may be 10 kHz to 40 kHz, the set amplitude may be 5 μm to 50 μm, and the set time may be 0.1 second to 2.0 seconds.

[0090] Meanwhile, after the first region primary sealing operation (S33), a first region secondary sealing operation (S34) is further provided to secondarily apply ultrasonic waves to the first region of the sealing portion by the welding head. The first region secondary sealing operation is performed at the same ultrasonic frequency and set time as the first region primary sealing operation, but the amplitude is reduced by 40% to 60%.

[0091] Meanwhile, the sealing process (S30) has the same process as the above-described secondary battery sealing process (S30) according to the first embodiment of the present invention, and accordingly, repeated descriptions will be omitted.

[0092] Therefore, the method for manufacturing a secondary battery according to the second embodiment of the present invention can manufacture a secondary battery having improved sealing force.

[0093] Sealing process for secondary battery according to third embodiment of the present invention

[0094] In the secondary battery sealing process (S30) according to the third embodiment of the present invention, after completing the first region primary sealing operation or the first region secondary sealing operation of the above-mentioned secondary battery sealing process (S30) according to the first embodiment of the present invention, an operation of further sealing the second region B of the sealing portion 32 included in the pouch-type battery case 30 is further performed. Accordingly, the sealing force of the sealing portion 32 included in the pouch-type battery case 30 can be significantly increased.

[0095] As an example, the secondary battery sealing process (S30) according to the third embodiment of the present invention includes an arrangement operation (S31), a first region fixing operation (S32), a first region primary sealing operation (S33), a first region secondary sealing operation (S34), a second region fixing operation (S35), and a second region sealing operation (S36).

[0096] Herein, the arrangement operation (S31), the first region fixing operation (S32), the first region primary sealing operation (S33), and the first region secondary sealing operation (S34) have been described in detail in the secondary battery sealing process (S30) according to the first embodiment, and thus the detailed description of these operations will be omitted here.

[0097] Meanwhile, in the secondary battery sealing process (S30) according to the third embodiment of the present invention, the sealing portion 32 included in the pouch-type battery case 30 is divided into three regions along the width direction of the sealing portion, as Figure 11 shown, and sealing is performed. That is, first, the first region A inside the sealing portion 32 is sealed, secondly, the second region B outside the sealing portion 32 is sealed, and finally, the third region C between the first region A and the second region B is sealed.

[0098] Herein, the first region A and the second region B are sealed under the same settings, and the third region C is sealed at a higher temperature and for a longer time than the first region A and the second region B.

[0099] Second - area fixing operation

[0100] In the second region fixing operation (S35), the second region B of the sealing portion 32 spaced apart from the first region A is disposed on the anvil 110 and the welding head 120, and then, the second region B of the sealing portion 32 is pressed and fixed by the anvil 110 and the welding head 120.

[0101] Second - area sealing operation

[0102] In the second region sealing operation (S36), as ultrasonic waves are applied to the second region B of the sealing portion 32 by the sonotrode 120 at a set frequency and a set amplitude for a set time, the second region B of the sealing portion 32 is melted by heat. Accordingly, the second region B of the sealing portion 32 can be sealed.

[0103] Herein, the second region sealing operation (S36) includes a second region primary sealing operation and a second region secondary sealing operation.

[0104] The second region primary sealing operation primarily seals the second region of the sealing portion under the same conditions as the above-described first region primary sealing operation (S33). That is, regarding the sealing conditions of the second region primary sealing operation, the set frequency is 10 kHz to 40 kHz, the set amplitude is 5 μm to 50 μm, and the set time is 0.1 second to 2.0 seconds.

[0105] The second region secondary sealing operation secondarily seals the second region B of the sealing portion under the same conditions as the above-described first region secondary sealing operation (S34). Herein, the second region secondary sealing operation has the same sealing conditions as the second region primary sealing operation in terms of ultrasonic frequency and set time, but is performed at an amplitude reduced by 40% to 60%, preferably at an amplitude reduced by 50%. Herein, the bubbles generated in the second region B of the sealing portion can also be eliminated together. As a result, the second region of the sealing portion can be sealed without failure.

[0106] Therefore, in the secondary battery sealing process (S30) according to the third embodiment of the present invention, the first region and the second region of the sealing portion can be sealed without failure. As a result, the sealing force of the secondary battery can be increased.

[0107] Meanwhile, the secondary battery sealing process (S30) according to the third embodiment of the present invention further includes a third region fixing operation (S37) and a third region sealing operation (S38).

[0108] Third - area fixing operation

[0109] In the third region fixing operation (S37), after the second region sealing operation, the third region C of the sealing portion located between the first region A and the second region B is pressed and fixed by the anvil 110 and the sonotrode 120.

[0110] Third - area sealing operation

[0111] In the third region sealing operation (S38), as ultrasonic waves are applied to the third region C of the sealing portion 32 by the sonotrode 120 at a set frequency and a set amplitude for a set time, the third region C of the sealing portion 32 is melted by heat.

[0112] Here, the ultrasonic frequency, amplitude, and time of the third region sealing operation (S38) are set to be different from those of the first region initial sealing operation.

[0113] That is, the ultrasonic frequency, amplitude, and time of the third region sealing operation (S38) are set to be higher than those of the first region initial sealing operation. Accordingly, the third region of the sealing portion located between the first region and the second region can be effectively melted, and thus the sealing force can be increased.

[0114] In particular, in the third region sealing operation (S38), the ultrasonic time of the third region is set to 1 second to 2 seconds. Accordingly, the entire third region can be stably melted, and as a result, the sealing force can be increased.

[0115] Therefore, in the secondary battery sealing process (S30) according to the third embodiment of the present invention, the third region of the sealing portion is further sealed, and thus the sealing force of the secondary battery can be significantly increased.

[0116] [Experimental Example]

[0117] As Figure 12 shown in the table, four secondary batteries including an electrode assembly, electrode leads, and a battery case are prepared. These four secondary batteries are the same product. Moreover, in these four secondary batteries, the sealing portion of the secondary battery is sealed under different sealing conditions. Here, the coating layer provided in the sealing portion has a thickness of 30 μm to 85 μm. Moreover, an amplitude of 5 μm to 50 μm is set to 100%.

[0118] Comparative Example 1

[0119] In Comparative Example 1, the first region A of the sealing portion included in the secondary battery was sealed by generating ultrasonic waves at a frequency of 10 kHz to 40 kHz and an amplitude of 100% for 0.1 second or less, and then, an image of the surface of the sealing portion was taken. As a result, a picture as shown in Figure 13 was obtained.

[0120] Preparation Example 1

[0121] In Preparation Example 1, the first region A of the sealing portion included in the secondary battery was sealed by generating ultrasonic waves at a frequency of 10 kHz to 40 kHz and an amplitude of 100% for 0.35 seconds, and then, an image of the surface of the sealing portion was taken. As a result, a picture as shown in Figure 14 was obtained.

[0122] Preparation Example 2

[0123] In Preparation Example 2, the first region A of the sealing portion included in the secondary battery was sealed by generating ultrasonic waves at a frequency of 10 kHz to 40 kHz and an amplitude of 100% for 2.0 seconds, and then, an image of the surface of the sealing portion was taken. As a result, an image as shown in Figure 15 was obtained.

[0124] Comparative Example 2

[0125] In Comparative Example 2, the first region A of the sealing portion included in the secondary battery was sealed by generating ultrasonic waves at a frequency of 10 kHz to 40 kHz and an amplitude of 50% of the amplitude in Preparation Example 1 for 0.35 seconds, and then, an image of the surface of the sealing portion was taken. As a result, an image as shown in Figure 16 was obtained.

[0126] Experimental results

[0127] Referring to Figure 13 of Comparative Example 1, it was confirmed that there was no protruding trace of the welding head or anvil on the sealing portion. Thus, since the frequency and time of the ultrasonic waves applied to the first region A of the sealing portion were small, the first region A of the sealing portion was not stably melted. As a result, it was confirmed that a sealing failure occurred. Here, the measurement result of the adhesion strength in the coating layer of the sealing portion was 0.0 N / mm.

[0128] Referring to Figure 14 of Preparation Example 1, it was clearly confirmed that the sealing surface had a protruding trace of the welding head or anvil. Thus, the first region A of the sealing portion was stably melted and sealed. As a result, it was found that the sealing portion was sealed without failure. Here, the measurement result of the adhesion strength in the coating layer of the sealing portion was 5.0 N / mm.

[0129] Referring to Figure 15 of Preparation Example 2, it was confirmed that a part of the sealing surface had a protruding trace of the welding head or anvil. However, due to excessive melting, the adhesion strength was lower than that in Preparation Example 1, but the adhesion strength could be higher than that in the comparative example. Therefore, the sealing portion was sealed without failure. At the same time, the measurement result of the adhesion strength in the coating layer of the sealing portion was 3.0 N / mm.

[0130] Referring to Figure 16 of Comparative Example 2, it was confirmed that there was no protruding trace of the welding head or anvil on the sealing surface. Thus, since the time of the ultrasonic waves was sufficient but the amplitude was insufficient, the first region A of the sealing portion was not melted. As a result, it was confirmed that a sealing failure occurred. At the same time, the measurement result of the adhesion strength in the coating layer of the sealing portion was 0.0 N / mm.

[0131] Therefore, as shown in the experimental results, when the sealing part is sealed by using ultrasonic sealing in the secondary battery sealing process according to the first embodiment of the present invention, the frequency is set to 10 kHz to 40 kHz, the amplitude is set to 50% to 100%, and the time is set to 0.1 second to 2.0 seconds. Therefore, the sealing part can be stably sealed.

[0132] The scope of the present invention is defined by the appended claims rather than the specific description, and various embodiments derived from the meaning and scope of the claims and their equivalent concepts are also possible.

[0133] [Reference Signs]

[0134] 10: Electrode Assembly

[0135] 20: Electrode Lead

[0136] 30: Battery Case

[0137] 31: Accommodating Portion

[0138] 32: Sealing Part

[0139] 100: Secondary Battery Sealing Device

[0140] 110: Anvil

[0141] 120: Sonotrode

[0142] 121: Hinge Portion

[0143] 130: Converter

[0144] 131: Step-Up Transformer

Claims

1. A sealing process for a secondary battery, the sealing process hot-melting and sealing a sealing portion extending along an edge surface of a battery case, wherein the sealing portion has a stacked structure that includes a coating layer, a metal layer, and an insulating layer in a direction from the inside to the outside of the battery case, and the sealing process includes: An arranging operation of disposing the sealing portion of the battery case between an anvil and a sonotrode; A first area fixing operation of pressing and fixing a first area of the sealing portion by the anvil and the sonotrode; And A first area primary sealing operation of applying ultrasonic waves to the first area of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the first area of the sealing portion, wherein after the first area primary sealing operation, a first area secondary sealing operation is further performed to secondarily hot-melt the first area of the sealing portion by secondarily applying ultrasonic waves to the first area of the sealing portion via the sonotrode. wherein the first area secondary sealing operation is performed at the same ultrasonic frequency and set time as the first area primary sealing operation, but the amplitude is reduced by 40% to 60%.

2. The sealing process according to claim 1, wherein the set frequency is 10 kHz to 40 kHz, the set amplitude is 5 μm to 50 μm, and the set time is 0.1 second to 2.0 seconds.

3. The sealing process according to claim 2, wherein the thickness of the coating layer is 30 μm to 85 μm.

4. The sealing process according to claim 1, wherein the sonotrode is capable of rotating left or right toward the sealing portion and is mounted to a converter including a booster, and the sonotrode presses the entire first area of the sealing portion with uniform pressure.

5. The sealing process according to claim 1, further including, after the first area primary sealing operation: a second area fixing operation of pressing and fixing a second area of the sealing portion, the second area being spaced apart from the first area, by the anvil and the sonotrode; and a second area sealing operation of applying ultrasonic waves to the second area of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the second area of the sealing portion.

6. The sealing process according to claim 5, wherein the second area sealing operation is set to the same ultrasonic frequency, amplitude, and time as the first area primary sealing operation.

7. The sealing process according to claim 5, further including, after the second area sealing operation: a third area fixing operation of pressing and fixing a third area of the sealing portion located between the first area and the second area by the anvil and the sonotrode; and a third area sealing operation of applying ultrasonic waves to the third area of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time, thereby hot-melting the third area of the sealing portion.

8. The sealing process according to claim 7, wherein the ultrasonic frequency, amplitude, and time of the third region sealing operation are set to be different from those of the first region initial sealing operation.

9. The sealing process according to claim 8, wherein the ultrasonic frequency, amplitude, and time of the third region are set to be higher than those of the first region initial sealing operation.

10. A method for manufacturing a secondary battery, the method comprising: a manufacturing process of manufacturing an electrode assembly by stacking electrodes and a separator; a housing process of housing the electrode assembly in a pouch-type battery case; and a sealing process of heat-fusing and sealing a sealing portion extending from an edge surface of the pouch-type battery case, wherein the sealing portion has a stacked structure including a coating layer, a metal layer, and an insulating layer in a direction from the inside to the outside of the battery case, wherein the sealing process includes: an arranging operation of disposing the sealing portion extending along the edge surface of the pouch-type battery case between an anvil and a sonotrode; a first region fixing operation of pressing and fixing a first region of the sealing portion by the anvil and the sonotrode; and a first region initial sealing operation of applying ultrasonic waves to the first region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time to heat-fuse the first region of the sealing portion, wherein the sealing process further includes a first region secondary sealing operation of secondarily applying ultrasonic waves to the first region of the sealing portion by the sonotrode after the first region initial sealing operation, wherein the first region secondary sealing operation is performed at the same ultrasonic frequency and set time as the first region initial sealing operation, but the amplitude is reduced by 40% to 60%.

11. The method according to claim 10, wherein the set frequency is 10 kHz to 40 kHz, the set amplitude is 5 μm to 50 μm, and the set time is 0.1 second to 2.0 seconds.

12. The method according to claim 10, wherein after the first region initial sealing operation, the sealing process further includes: a second region fixing operation of pressing and fixing a second region of the sealing portion spaced apart from the first region by the anvil and the sonotrode; and a second region sealing operation of applying ultrasonic waves to the second region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time to heat-fuse the second region of the sealing portion.

13. The method according to claim 12, wherein after the second region sealing operation, the sealing process further includes: a third region fixing operation of pressing and fixing a third region of the sealing portion located between the first region and the second region by the anvil and the sonotrode; and a third region sealing operation of applying ultrasonic waves to the third region of the sealing portion by the sonotrode at a set frequency and a set amplitude for a set time to heat-fuse the third region of the sealing portion.

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