Method of manufacturing secondary battery and secondary battery manufactured using the same

Abstract

The method of manufacturing a secondary battery according to the present application includes a welding preparation step of preparing a bottom can including a housing portion that houses an electrode assembly and a top cover that covers an upper opening of the bottom can, a clamping step of clamping an end portion of a bottom can peripheral portion and an end portion of a top cover peripheral portion from upper and lower portions by using an upper clamp and a lower clamp such that the bottom can peripheral portion and the top cover peripheral portion are welded so as to be joined to each other, the bottom can peripheral portion being a portion that extends outward from an edge of the housing portion, the top cover peripheral portion being a peripheral area of the top cover, and a welding step of irradiating a laser beam onto a joining portion, at which the bottom can peripheral portion and the top cover peripheral portion are joined, after the clamping step so as to join the bottom can peripheral portion and the top cover peripheral portion to each other by means of laser welding, wherein, in the welding step, the laser welding is performed when a height of the housing portion is formed to be higher than a height of the end portion of the bottom can peripheral portion. Further, in the secondary battery according to the present application, a height of the joining portion at which the bottom can peripheral portion and the top cover peripheral portion are joined can be lower than a height (b) of the housing portion.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2020-0119504, filed on September 16, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0004] This invention relates to a method for manufacturing a secondary battery and a secondary battery manufactured using the method. More specifically, it relates to a method for manufacturing a secondary battery and a secondary battery manufactured using the method in which, when welding a thin-film canister, the adhesion force of the joint is increased to prevent unwelded portions, thereby significantly improving the sealing performance. Background Technology

[0005] In recent years, the depletion of fossil fuels has led to rising energy prices, amplifying concerns about environmental pollution and making eco-friendly alternative energy sources an indispensable part of future life. Consequently, research into various power generation technologies such as solar, wind, and tidal power is ongoing, and energy storage devices such as batteries, designed to utilize the generated electricity more efficiently, are also receiving considerable attention.

[0006] Furthermore, with technological advancements and the increasing demand for battery-powered electronic mobile devices and electric vehicles, the demand for batteries as an energy source is also rapidly increasing. Therefore, much research has been conducted on batteries capable of meeting diverse needs.

[0007] In particular, there is a high demand for lithium secondary batteries (such as lithium-ion batteries and lithium-ion polymer batteries) with advantages such as high energy density, discharge voltage and output stability in terms of materials.

[0008] Secondary batteries are classified according to the shape of their casing into cylindrical batteries, prismatic batteries, and pouch batteries. In cylindrical and prismatic batteries, the electrode assembly is embedded in a cylindrical or prismatic metal canister. In pouch batteries, the electrode assembly is embedded in a pouch-shaped casing made of aluminum laminate. Furthermore, recently, due to increased customer preference for high output and long lifespan, thin-film canister batteries using metal films have been developed and are being used.

[0009] These thin-film can-type batteries are typically manufactured by housing the electrode assembly in a can, covering the electrode assembly, and then laser-welding (a thin-film can refers to a thin metal). Furthermore, during laser welding, it is necessary to create a product with excellent sealing by preventing any unwelded sections.

[0010] However, in existing technologies, strong clamping is used during laser welding to prevent unwelded portions. But this can cause deformation of the metal film, leading to problems. Conversely, if the clamping is not secure, problems arise due to inadequate bonding, resulting in unwelded portions and poor sealing. Summary of the Invention

[0011] Technical issues

[0012] The present invention has been designed to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a secondary battery and a secondary battery manufactured by using the manufacturing method, wherein when the thin film can is welded, the adhesion force of the joint is increased to prevent the appearance of unwelded parts, thereby significantly improving the sealing performance.

[0013] Technical solution

[0014] The method for manufacturing a secondary battery according to the present invention includes: a welding preparation process for preparing a lower can, the lower can including a receiving portion for accommodating an electrode assembly and an upper cover covering an upper opening of the lower can; a clamping process, the clamping process using an upper clamp and a lower clamp to clamp the ends of the peripheral portion of the lower can and the peripheral portion of the upper cover at an upper and lower portion, respectively, so as to weld the peripheral portion of the lower can, which is a portion extending outward from the edge of the receiving portion, to the peripheral portion of the upper cover, which is a peripheral region of the upper cover; and a welding process, the welding process irradiating a joint with a laser to join the peripheral portion of the lower can to the peripheral portion of the upper cover by laser welding, the joint being the point where the peripheral portion of the lower can and the peripheral portion of the upper cover join together.

[0015] During the welding process, laser welding can also be performed with the height (b) of the receiving portion being higher than the height (a) of the end of the peripheral portion of the lower tank.

[0016] During the welding process, the height of the center point of the upper cover can be higher than the height b of the receiving part.

[0017] The lower clamp may include a bottom and a sidewall, on which the lower can is placed, the sidewall being formed on the periphery of the bottom, the height (b) being the distance from the bottom to the upper end of the receiving portion, and the height (a) of the end of the periphery of the lower can being the distance from the bottom to the end of the periphery of the lower can.

[0018] During the welding process, the upper pressing surface of the upper clamp, which is used to press the end of the periphery of the upper cover, and the lower pressing surface of the lower clamp, which is used to press the end of the periphery of the lower can, can be parallel to the bottom.

[0019] The value (ba) obtained by subtracting the height (a) of the end of the peripheral portion of the lower tank from the height (b) of the receiving portion can be greater than or equal to the thickness of the thinner substrate of the lower tank and the upper cover as welding substrate, and less than three times the thickness of the thinner substrate.

[0020] During the welding process, the upper pressing surface in the upper fixture, which is the surface that presses the end of the periphery of the upper cover, can extend further in the direction toward the laser than the lower pressing surface in the lower fixture, which is the surface that presses the end of the periphery of the lower can.

[0021] The width (c) of the upper pressing surface can be greater than the width (d) of the lower pressing surface.

[0022] The outer ends of the upper pressing surface and the lower pressing surface can be set along the same vertical line.

[0023] The upper clamp can be set in the shape of a right triangle, and during the welding process, the upper clamp can be set such that the hypotenuse of the right triangle faces the laser.

[0024] The secondary battery according to the present invention includes: an electrode assembly; a lower can including a receiving portion in which the electrode assembly is received; and a top cover configured to cover an upper opening of the lower can, wherein the lower can may include a lower can periphery extending outward from the edge of the receiving portion, the top cover including a top cover periphery that serves as a peripheral region of the top cover and engages with the lower can periphery, and a joining portion being a point where the lower can periphery and the top cover periphery engage with each other, the height of the joining portion being lower than the height of the receiving portion (b).

[0025] The height of the center point of the upper cover can be higher than the height of the receiving part (b).

[0026] Beneficial effects

[0027] The method for manufacturing a secondary battery according to the present invention may include: a welding preparation process for preparing a lower can, the lower can including a receiving portion for accommodating electrode assemblies and an upper cover covering an upper opening of the lower can; a clamping process, the clamping process using an upper clamp and a lower clamp to clamp the ends of the peripheral portion of the lower can and the peripheral portion of the upper cover at the upper and lower parts, respectively, so as to weld the peripheral portion of the lower can, which is a portion extending outward from the edge of the receiving portion, to the peripheral portion of the upper cover, which is a peripheral area of ​​the upper cover; and a welding process, the welding process irradiating a joint with a laser to join the peripheral portion of the lower can to the peripheral portion of the upper cover by laser welding, the joint being the point where the peripheral portion of the lower can and the peripheral portion of the upper cover join together. Therefore, when the thin-film can is welded, the adhesion force of the joint is improved and unwelded portions are prevented, thereby significantly improving the sealing performance of the thin-film can battery.

[0028] The secondary battery according to the present invention includes: an electrode assembly; a lower can including a receiving portion in which the electrode assembly is received; and a top cover configured to cover an upper opening of the lower can, wherein the lower can may include a peripheral portion extending outwardly from the edge of the receiving portion, the top cover may include a peripheral portion of the top cover that engages with the peripheral portion of the lower can, and a joining portion, the joining portion being a point where the peripheral portion of the lower can and the peripheral portion of the top cover can engage with each other, the height of the joining portion being lower than the height of the receiving portion (b). Therefore, sealing performance can be significantly improved in thin-film can-type batteries. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view illustrating, as a comparative example, a method for manufacturing secondary batteries by laser welding according to the prior art.

[0030] Figure 2 This is a cross-sectional view illustrating a method for manufacturing a secondary battery by laser welding according to Embodiment 1 of the present invention.

[0031] Figure 3 This is a cross-sectional view illustrating a method for manufacturing a secondary battery by laser welding according to Embodiment 2 of the present invention.

[0032] Figure 4 The figure illustrates the experimental results of testing weldability for each of the comparative and manufactured examples. Detailed Implementation

[0033] Preferred embodiments of the invention will be described below with reference to the accompanying drawings, enabling those skilled in the art to readily practice the invention. However, the invention may be embodied in many different forms and is not limited to or construed as described below.

[0034] To clearly explain the invention, detailed descriptions of relevant known technologies that are irrelevant to the description or may unnecessarily obscure the spirit of the invention have been omitted, and in this specification, reference numerals have been added to the components in each figure. In this case, throughout the specification, the same or similar reference numerals are assigned to the same or similar elements.

[0035] Furthermore, the terms or wording used in this specification and claims should not be construed as having a general meaning or dictionary-based meaning, but should be interpreted as meanings and concepts that are within the scope of this invention, based on the principle that the inventor can properly define a term’s concept in order to best describe and explain his or her invention.

[0036] Method for manufacturing secondary batteries according to comparative examples

[0037] Figure 1 This is a cross-sectional view illustrating, as a comparative example, a method for manufacturing secondary batteries by laser welding according to the prior art.

[0038] Reference Figure 1 In a method for manufacturing a secondary battery according to a comparative example of the present invention, firstly, a lower can 10 can be prepared, the lower can 10 including a receiving portion 11 and an upper cover 30, wherein an electrode assembly 20 is received in the receiving portion 11, and the upper cover 30 covers the upper opening of the lower can, and the peripheral portion 12 of the lower can and the peripheral portion 32 of the upper cover can be welded to manufacture a secondary battery. Here, each of the lower can 10 and the upper cover 30 can be a thin film can made of thin metal.

[0039] The lower can periphery 12 and the upper cover periphery 32 can be configured to overlap each other to weld the lower can periphery 12 to the upper cover periphery 32. The lower can periphery 12 is the portion extending outward from the edge of the receiving portion 11, and the upper cover periphery 32 is the peripheral area of ​​the upper cover 30. Alternatively, the end 13 of the lower can periphery and the end 33 of the upper cover periphery can be clamped at their upper and lower portions using an upper clamp 50 and a lower clamp 40, respectively. When there is no gap between the lower can periphery 12 and the upper cover periphery 32 during laser welding, no unwelded portions will appear, and welding can be performed well. For example, when welding a thin plate with a thickness of 75 μm, unwelded portions may appear, and even gaps between the substrate metals may exceed 10 μm.

[0040] After clamping the lower and upper parts using the upper clamp 50 and the lower clamp 40, the laser L is irradiated onto the joint to join the lower can periphery 12 to the upper cover periphery 32 by laser welding. The joint is the point where the lower can periphery 12 and the upper cover periphery 32 join each other.

[0041] However, in the comparative example, laser welding is performed when the height b of the receiving portion 11 and the height a of the end portion 13 of the lower tank periphery are equal during the laser welding process.

[0042] Specifically, the lower clamp 40 includes a bottom 42 and a side wall 43, on which the lower can 10 is placed, and the side wall 43 is formed on the periphery of the bottom 42. Height b refers to the distance from the bottom 42 to the upper end of the receiving portion 11, and the height a of the end 13 of the peripheral portion of the lower can refers to the distance from the bottom 42 to the end 13 of the peripheral portion of the lower can.

[0043] Furthermore, when the surface pressing the end 33 of the upper cover periphery is referred to as the upper pressing surface 51 in the upper clamp 50 and the surface pressing the end 13 of the lower can periphery is referred to as the lower pressing surface 41, in the comparative example, the width c of the upper pressing surface 51 and the width d of the lower pressing surface 41 are formed to be the same. That is, the upper pressing surface 51 and the lower pressing surface 41 have corresponding widths and face each other vertically, and the orthographic projection of the upper pressing surface 51 is the lower pressing surface 41. In this case, the inner endpoints of the upper pressing surface 51 and the lower pressing surface 41 can be arranged along the same vertical line.

[0044] According to existing technology, secondary batteries are manufactured by laser welding in the same manner as in the comparative example. In this case, even if the two substrates (i.e., the lower tank periphery 12 and the upper cover periphery 32) are in close contact with each other at both ends, there is a high possibility that gaps will occur at the parts where the actual welding is performed. Therefore, there is a problem of improper jointing, resulting in unwelded parts and poor sealing.

[0045] Method for manufacturing a secondary battery according to Embodiment 1

[0046] Figure 2 This is a cross-sectional view illustrating a method for manufacturing a secondary battery by laser welding according to Embodiment 1 of the present invention.

[0047] Reference Figure 2 The method for manufacturing a secondary battery according to Example 1 of the present invention includes a welding preparation process, a clamping process, and a welding process.

[0048] The welding preparation process involves fabricating a lower can 110, which includes a receiving portion 111 for accommodating an electrode assembly 120 and an upper cover 130 covering the upper opening of the lower can 110. The receiving portion 111 of the lower can 110 may have a downwardly recessed space, and the upper cover 130 may have a flat plate shape. Each of the lower can 110 and the upper cover 130 may be a thin-film can made of thin metal.

[0049] In order to weld the lower can peripheral portion 112, which is a portion extending outward from the edge of the receiving portion 111, to the upper cover peripheral portion 132, which is the peripheral area of ​​the upper cover 130, during the clamping process, the lower can peripheral portion 112 and the upper cover peripheral portion 132 are arranged to overlap each other, and the ends 113 of the lower can peripheral portion and the ends 133 of the upper cover peripheral portion are clamped at their upper and lower parts by using the upper clamp 150 and the lower clamp 140.

[0050] After clamping the lower and upper parts using the upper clamp 150 and the lower clamp 140, during the welding process, the laser L is irradiated onto the joint to join the lower tank periphery 112 to the upper cover periphery 132 by laser welding. The joint is the point where the lower tank periphery 112 and the upper cover periphery 132 join each other.

[0051] In the method for manufacturing a secondary battery according to Embodiment 1 of the present invention, during the welding process, laser welding is performed with the height b of the receiving portion 111 being higher than the height a of the end portion 113 of the lower tank periphery.

[0052] Specifically, the lower clamp 140 includes a bottom 142 and a side wall 143. The lower can 110 is placed on the bottom 142, and the side wall 143 is formed on the periphery of the bottom 142. The height b refers to the distance from the bottom 142 to the upper end of the receiving portion 111, and the height a of the end 113 of the peripheral portion of the lower can refers to the distance from the bottom 142 to the end 113 of the peripheral portion of the lower can.

[0053] According to Embodiment 1 of the present invention, the method for manufacturing a secondary battery can prevent the appearance of unwelded portions by improving the adhesion of the joint through welding in this way, thereby achieving a significant improvement in sealing performance.

[0054] One way to explain this is that as the bottom 142 of the lower clamp 140 pushes the receiving portion 111 of the lower can 110 upward, the edge of the receiving portion 111 applies a force that pushes the peripheral portion 112 of the lower can upward, so that a tight contact is reliably achieved at the joint.

[0055] Another way to explain this is that the upper clamp 150 applies a relatively downward thrust to the end 133 of the periphery of the upper cover, so that a tight contact is reliably achieved at the joint.

[0056] Furthermore, in the method for manufacturing a secondary battery according to Embodiment 1 of the present invention, during the welding process, the upper pressing surface 151 of the upper clamp 150, which serves as the surface for pressing the end 133 of the peripheral portion of the upper cover, and the lower pressing surface 141 of the lower clamp 140, which serves as the surface for pressing the end 113 of the peripheral portion of the lower can, can be parallel to the bottom 142 of the lower clamp 140. When formed in this manner, the force by which the edge of the receiving portion 111 pushes the peripheral portion 112 of the lower can upward can be applied more strongly. Alternatively, the force by which the upper clamp 150 pushes the end 133 of the peripheral portion of the upper cover downward can be applied more strongly.

[0057] Additionally, the height of the center point 131 of the top cover may be higher than the height b of the receiving portion 111. This could be due to the shape of the top cover 130 being provided as a thin-film container.

[0058] In the method for manufacturing a secondary battery according to Embodiment 1 of the present invention, the value ba obtained by subtracting the height a of the end 113 of the lower can periphery from the height b of the receiving portion 111 can be greater than or equal to the thickness of the thinner substrate of the lower can 110 and the upper cover 130 as a welding substrate, and less than three times the thickness of the thinner substrate.

[0059] If the value ba is less than the thickness of the thinner substrate, the effects of the present invention described above may be diminished. Furthermore, when the value ba is greater than three times the thickness of the thinner substrate, the deformation of the film can becomes severe, and the inclination of each of the lower can periphery 112 and the upper cover periphery 132 increases, leading to a relative deterioration in welding performance and efficiency.

[0060] In the method for manufacturing a secondary battery according to Embodiment 1 of the present invention, the width c of the upper pressing surface 151 and the width d of the lower pressing surface 141 are formed to be the same. That is, the upper pressing surface 151 and the lower pressing surface 141 have corresponding widths and face each other vertically, and the orthographic projection of the upper pressing surface 151 is the lower pressing surface 141.

[0061] In this case, the height b of the receiving portion 111 may be higher than the height f of the lower can periphery portion 112, and the height f of the lower can periphery portion 112 may be higher than the height a of the end 113 of the lower can periphery portion. This may be because a sequential inclination is formed from the upper end of the receiving portion 111 through the lower can periphery portion to the end 113 of the lower periphery portion.

[0062] In the method for manufacturing a secondary battery according to Embodiment 1 of the present invention, since the width c of the upper pressing surface 151 and the width d of the lower pressing surface 141 are the same, the effect of the force exerted by the upper clamp 150 on the end 133 of the peripheral portion of the upper cover that pushes it downward is less than the effect of the force in Embodiment 2, which will be described below.

[0063] Method for manufacturing a secondary battery according to Embodiment 2

[0064] Figure 3 This is a cross-sectional view illustrating a method for manufacturing a secondary battery by laser welding according to Embodiment 2 of the present invention.

[0065] According to Embodiment 2 of the present invention, the difference from Embodiment 1 is that the upper pressing surface and the lower pressing surface have different shapes than those in Embodiment 1.

[0066] Content that overlaps with Implementation 1 should be omitted as much as possible, and the main differences should be described. In other words, it is obvious that content not described in Implementation 2 can be regarded as part of Implementation 1 as needed.

[0067] Reference Figure 3 In the method for manufacturing a secondary battery according to Embodiment 2 of the present invention, during the welding process, the upper pressing surface 251, which is the surface of the upper clamp 250 that presses the end 233 of the peripheral portion of the upper cover, may extend further along the direction toward the laser L than the lower pressing surface 241, which is the surface of the lower clamp 240 that presses the end 213 of the peripheral portion of the lower can.

[0068] In this case, the force exerted by the upper clamp 250 to push the end 233 of the peripheral portion 232 of the upper cover downward can be applied more strongly. Therefore, a more reliable and tighter contact can be achieved at the joint where welding is performed.

[0069] In Embodiment 2 of the present invention, the height b of the receiving portion 211 may be higher than the height a of the end portion 213 of the lower can periphery. This is the same as in Embodiment 1.

[0070] Furthermore, in Embodiment 2 of the present invention, the width c of the upper pressing surface 251 can be greater than the width d of the lower pressing surface 241. Additionally, the outer endpoints 251-1 of the upper pressing surface and the outer endpoints 241-1 of the lower pressing surface can be arranged along the same vertical line. When each of the upper clamp 250 and the lower clamp 240 has the above-described shape, the lower can periphery 212 and the upper cover periphery 232 can be very stably clamped and supported at their upper and lower portions without wobbling.

[0071] In the method for manufacturing a secondary battery according to Embodiment 2 of the present invention, the upper clamp 250 is configured with a right-angled triangle cross-section, and during the welding process, the upper clamp 250 can be configured such that the hypotenuse 252 of the right-angled triangle faces the laser L. When formed as described above, the possibility of the laser nozzle moving and colliding with the upper cover 230 when the laser irradiates the joint portion on the periphery of the cover is reduced. Therefore, a more stable weld is possible.

[0072] Secondary batteries

[0073] The secondary battery according to the present invention includes a lower tank, an upper cover, and an electrode assembly, and may have the following characteristics.

[0074] The electrode assembly can be formed by alternately stacking electrodes and diaphragms. The lower can may include a housing in which the electrode assembly is housed. The upper cover may have a shape that covers the upper opening of the lower can.

[0075] The lower can includes a lower can periphery that extends outward from the edge of the receiving portion, and the upper cover includes an upper cover periphery that serves as the periphery region of the upper cover and engages with the lower can periphery. The joint where the lower can periphery and the upper cover periphery engage with each other may have a height lower than the height b of the receiving portion. Furthermore, the height of the center point of the upper cover may be higher than the height b of the receiving portion.

[0076] The secondary battery according to the present invention can have significantly improved sealing at the joint.

[0077] <Experimental Results>

[0078] Comparative Example 1-①

[0079] The lower can and the upper cover were welded together. Welding was performed using a 500W laser from IPG. Welding was performed under the following conditions: laser beam size of 30μm to 200μm (micrometers), power of 50W to 500W, lower can material of SUS316L with a thickness of 75μm, upper cover material of SUS316L with a thickness of 75μm.

[0080] In Comparative Example 1, welding was performed under the condition that the value ba obtained by subtracting the height a of the end of the lower tank periphery from the height b of the receiving part was 0 μm.

[0081] Manufacturing Example 1-②

[0082] According to the present invention, the lower can and the upper cover are welded together. Welding is performed using a 500W laser from IPG. Welding is performed under the following conditions: laser beam size of 30μm to 200μm (micrometers), power of 50W to 500W, lower can material of SUS316L with a thickness of 75μm, upper cover material of SUS316L with a thickness of 75μm.

[0083] In manufacturing example 1, welding was performed under the condition that the value ba obtained by subtracting the height a of the end of the lower tank periphery from the height b of the receiving part was 75 μm.

[0084] Manufacturing Example 2-③

[0085] Except for the condition that welding is performed under the same conditions as in Manufacturing Example 1, where the value ba obtained by subtracting the height a of the end of the lower tank periphery from the height b of the receiving part is 150 μm.

[0086] Experimental Example - Solderability Comparison

[0087] Figure 4 The figure illustrates the experimental results of testing weldability for each of the comparative example and manufacturing examples 1 and 2.

[0088] In Comparative Example 1, where welding was performed under the condition that the value of ba was 0 μm (i.e., the values ​​of a and b were the same), Figure 4 The left side ① shows a cross-sectional view of the welded portion. In Comparative Example 1, it can be seen that an unwelded portion appears due to the gap between the lower can and the upper cover.

[0089] In Manufacturing Example 1, where welding was performed under the condition that the value ba was 75 μm (i.e., the value b was 75 μm greater than the value a), Figure 4 The middle section ② shows a cross-sectional view of the welded portion. In the case of manufacturing example 1, it can be seen that no gap is generated between the lower can and the upper cover, thus achieving a good weld.

[0090] In Manufacturing Example 2, where welding was performed under the condition that the value ba was 150 μm (i.e., the value b was 150 μm larger than the value a), Figure 4 The right side ③ shows a cross-sectional view of the welded portion. In the case of manufacturing example 2, it can be seen that welding is performed under conditions that provide strong adhesion between the lower can and the upper cover, and a stronger joint is provided than in manufacturing example 1.

[0091] Although embodiments of the invention have been described with reference to specific examples, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

[0092] [Description of reference numerals in the attached figures]

[0093] 10, 110, 210: Lower tank

[0094] 11, 111, 211: Reception Department

[0095] 12, 112, 212: Peripheral area of ​​the lower can

[0096] 13, 113, 213: Ends of the peripheral rim of the lower can

[0097] 20, 120, 220: Electrode assemblies;

[0098] 30, 130, 230: Top cover

[0099] 31, 131, 231: Center point of the top cover

[0100] 32, 132, 232: Peripheral part of the top cover

[0101] 33, 133, 233: Ends of the perimeter of the top cover

[0102] 40, 140, 240: Lower clamp

[0103] 41, 141, 241: Press down on the surface

[0104] 42, 142, 242: Bottom

[0105] 43, 143, 243: Sidewall

[0106] 50, 150, 250: Upper clamp

[0107] 51, 151, 251: Upper pressing surface

[0108] 52, 152, 252: The hypotenuse of a right triangle

[0109] L: Laser

Claims

1. A method for manufacturing a secondary battery, the method comprising the following steps: A welding preparation process for preparing a lower tank and an upper cover, wherein the lower tank includes a receiving portion for accommodating an electrode assembly, and the upper cover covers the upper opening of the lower tank; The clamping process involves using an upper clamp and a lower clamp to clamp the ends of the upper cover periphery and the lower can periphery at the upper and lower parts, respectively, so as to weld the lower can periphery to the upper cover periphery. The lower can periphery is the portion extending outward from the edge of the receiving part, and the upper cover periphery is the periphery area of ​​the upper cover. as well as The welding process involves irradiating the joint with a laser to join the periphery of the lower tank to the periphery of the upper cover via laser welding. The joint is the point where the periphery of the lower tank and the periphery of the upper cover meet each other. Specifically, during the welding process, the laser welding is performed with the height (b) of the receiving portion being higher than the height (a) of the end of the peripheral portion of the lower tank. Each of the lower can and the upper cover is a thin-film can made of metal.

2. The method according to claim 1, wherein, During the welding process, the laser welding is performed when the height (b) of the receiving portion is higher than the height (f) of the peripheral portion of the lower tank and the height (f) of the peripheral portion of the lower tank is higher than the height (a) of the end of the peripheral portion of the lower tank.

3. The method according to claim 1, wherein, During the welding process, the height of the center point of the upper cover is higher than the height of the receiving part (b).

4. The method according to claim 1, wherein, The lower clamp includes a bottom and sidewalls, on which the lower can is placed, and the sidewalls are formed on the periphery of the bottom. The height (b) refers to the distance from the bottom to the upper end of the receiving portion, and The height (a) of the end of the peripheral portion of the lower tank refers to the distance from the bottom to the end of the peripheral portion of the lower tank.

5. The method according to claim 4, wherein, During the welding process, the upper pressing surface of the upper clamp, which is the surface that presses the end of the periphery of the upper cover, and the lower pressing surface of the lower clamp, which is the surface that presses the end of the periphery of the lower can, are parallel to the bottom.

6. The method according to claim 1, wherein, The value (ba) obtained by subtracting the height (a) of the end of the peripheral portion of the lower tank from the height (b) of the receiving portion is greater than or equal to the thickness of the thinner substrate of the lower tank and the upper cover as welding substrate, and less than three times the thickness of the thinner substrate.

7. The method according to claim 1, wherein, During the welding process, the upper pressing surface of the upper clamp, which is the surface that presses the end of the periphery of the upper cover, extends further in the direction toward the laser than the lower pressing surface of the lower clamp, which is the surface that presses the end of the periphery of the lower can.

8. The method according to claim 7, wherein, The width (c) of the upper pressing surface is greater than the width (d) of the lower pressing surface.

9. The method according to claim 8, wherein, The outer endpoints of the upper pressing surface and the lower pressing surface are arranged along the same vertical line.

10. The method according to claim 1, wherein, The cross-section of the upper clamp is set as a right triangle, and During the welding process, the upper clamp is configured such that the hypotenuse of the right triangle faces the laser.

11. A secondary battery, the secondary battery comprising: Electrode assembly; The lower tank includes a receiving portion in which the electrode assembly is housed. as well as A top cover, configured to cover the upper opening of the lower can. The lower can includes a peripheral portion, which extends outward from the edge of the receiving portion. The upper cover includes a peripheral portion, which is joined to the peripheral portion of the lower can as a peripheral area of ​​the upper cover. The junction where the periphery of the lower can and the periphery of the upper cover meet each other has a height lower than the height (b) of the receiving part. Wherein, the height of the center point of the upper cover is higher than the height of the receiving part (b), and Each of the lower can and the upper cover is a thin-film can made of metal.

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