Secondary battery manufacturing method and secondary battery manufacturing apparatus used therein

Abstract

The present invention relates to a manufacturing method for a secondary battery and a manufacturing apparatus for a secondary battery used therein, and more particularly to a manufacturing method for a secondary battery that manufactures a secondary battery including a plurality of electrode tabs and electrode leads, and a manufacturing apparatus for a secondary battery used therein. The present invention provides a method for manufacturing a secondary battery, including: a tab-lead laminate welding step of welding a tab-lead laminate in which a plurality of electrode tabs and electrode leads are stacked, to connect the electrode tabs and the electrode leads; and a tab-lead laminate processing step of continuously applying pressure to a welded portion of the tab-lead laminate along a length direction to process the welded portion.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0015837 filed on February 7, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a manufacturing method for a secondary battery and a manufacturing apparatus for a secondary battery used therein, and more particularly to a manufacturing method for a secondary battery that manufactures a secondary battery including a plurality of electrode tabs and electrode leads, and a manufacturing apparatus for a secondary battery used therein. [Background technology]

[0003] As portable wireless devices such as video cameras, mobile phones, and portable PCs become lighter and more functional, the demand for secondary batteries as an energy source is rapidly increasing. Of these secondary batteries, lithium secondary batteries, which have high energy density and discharge voltage, have been actively researched and are now commercially available and in wide use.

[0004] Secondary batteries are also attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which have been presented as a solution to air pollution caused by existing gasoline and diesel vehicles that use fossil fuels.

[0005] Recently, pouch-type batteries, which have a structure in which a stack-type or stack / folding-type electrode assembly is built into a pouch-type battery case made of an aluminum laminate sheet, have been attracting much attention due to their low manufacturing cost, small weight, easy shape modification, etc., and their usage is gradually increasing.

[0006] Such a pouch-type secondary battery typically includes an electrode assembly in which electrode plates are stacked in order with a separator interposed therebetween, and a battery case which is an exterior material for housing the electrode assembly. Here, the electrode assembly has a plurality of electrode tabs extending from the electrode plates. In addition, the electrode tabs may be connected to electrode leads protruding from the battery case, so that the electrode assembly inside the battery case may be electrically connected to an external electric device or an external secondary battery.

[0007] Meanwhile, the electrode tabs are fixed to each other by welding or connected to an electrode lead. However, after welding the electrode tabs or the electrode tabs and the electrode lead, the surface of the welded portion becomes relatively rough as shown in FIG. 1, and surface tensile residual stress is added due to welding. In this case, the roughened surface in a fatigue fracture environment provides a place for microcracks to occur, and in this case, the surface tensile residual stress acts as a kind of driving force that promotes the growth and propagation of the microcracks. As a result, the fracture time of the welded portion becomes earlier, which causes a problem of reduced product reliability.

[0008] Therefore, in the past, after welding a plurality of electrode tabs or a plurality of electrode tabs and an electrode lead, the welded portion was pressed to eliminate the surface roughness of the welded portion, but even in this case, there was a limit to the improvement of surface characteristics such as the degree of surface roughness and the length and magnitude of surface compressive residual stress. Therefore, a technology that can solve the above problems is required. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above problems, and an object of the present invention is to provide a method and an apparatus for manufacturing a secondary battery that can effectively process the welded portions of the electrode tab and the electrode lead. [Means for solving the problem]

[0010] The present invention provides a method for manufacturing a secondary battery, including: a tab-lead laminate welding step of welding a tab-lead laminate in which a plurality of electrode tabs and electrode leads are stacked, to connect the plurality of electrode tabs and the electrode leads; and a tab-lead laminate processing step of continuously applying pressure to welded portions of the tab-lead laminate along a length direction to process the welded portions.

[0011] A plurality of shape deformation portions, in which deformation occurs due to welding, are formed along at least one direction at the welding portion of the tab-lead laminate, and the tab-lead laminate processing step may process the welding portion by sequentially applying pressure to the plurality of shape deformation portions along a direction in which the plurality of shape deformation portions are formed.

[0012] The tab-lead laminate processing step can be performed by a roll-burnishing or ball-burnishing process.

[0013] The tab-lead laminate processing step may apply a pressure of 100 kgf or more to the welded portion.

[0014] The tab-lead laminate welding step can be performed by ultrasonic welding or laser welding.

[0015] In addition, the method for manufacturing a secondary battery according to the present invention may further include, before the tab-lead stack welding step, an electrode tab stack having a plurality of electrode tabs stacked thereon is welded to connect the plurality of electrode tabs.

[0016] In addition, the method for manufacturing a secondary battery according to the present invention may further include, between the electrode tab laminate welding step and the tab-lead laminate welding step, an electrode tab laminate processing step of continuously pressurizing a welding point of the electrode tab laminate along a length direction to process the welding point.

[0017] At the welding points of the electrode tab laminate, a plurality of shape-deformed portions, in which deformation of the shape occurs due to welding, are formed along at least one direction, and the electrode tab laminate processing step can process the welding points by sequentially applying pressure to the plurality of shape-deformed portions along the formation direction of the shape-deformed portions.

[0018] In addition, the method for manufacturing a secondary battery according to the present invention may further include, after the tab-lead laminate processing step, a tape attaching step of attaching an insulating tape to a welding portion of the tab-lead laminate.

[0019] Meanwhile, the present invention provides an apparatus for manufacturing a secondary battery for processing a welding point of at least one of a tab-lead laminate in which a plurality of electrode tabs and electrode leads are stacked, and an electrode tab laminate in which a plurality of electrode tabs are stacked, the apparatus including: a main body; and a processing unit installed in the main body for continuously applying pressure to the welding point to process it.

[0020] The processing unit may include a pressure unit that rotates and moves while applying pressure to the welding point, and a support unit that rotatably supports the pressure unit.

[0021] The pressure unit may include a roller or a ball.

[0022] The material of the pressure member may be iron or ceramic. Effect of the Invention

[0023] The present invention can effectively reduce the surface roughness of the welded portion by continuously applying pressure to the welded portion of the tab-lead laminate or electrode tab laminate along the length direction, thereby suppressing the expansion of microcracks at the welded portion.

[0024] In addition, the present invention effectively imparts surface residual stress to the welded portion of the tab-lead laminate or electrode tab laminate by continuously pressurizing the welded portion along the length direction, thereby mitigating the expansion and growth of microcracks and increasing the fatigue strength, fatigue limit and weld tensile strength of the welded object. [Brief description of the drawings]

[0025] [Figure 1] 1 is an image showing the state of the welded portion after welding of the electrode tab laminate has been performed. [Diagram 2] 3 is a flowchart showing a flow of a method for manufacturing a secondary battery according to the first embodiment of the present invention. [Diagram 3] FIG. 11 is a perspective view showing an apparatus for manufacturing a secondary battery according to a second embodiment of the present invention. [Figure 4] 4 is a conceptual diagram showing how the secondary battery manufacturing apparatus of FIG. 3 sequentially applies pressure to welded portions of a tab-lead laminate. FIG. [Figure 5a] 4 is a graph showing a comparison of residual stress values ​​of a tab-lead laminate after a method for manufacturing a secondary battery according to the present invention and a method for manufacturing a secondary battery according to the related art; [Figure 5b] 4 is a graph showing a comparison of heights of deformed portions of a tab-lead laminate after a conventional method for manufacturing a secondary battery and a method for manufacturing a secondary battery according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in order to enable those skilled in the art to easily carry out the present invention. However, the present invention may be embodied in various different forms and should not be construed as being limited to the following embodiments.

[0027] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the description or related known technologies that may obscure the gist of the present invention have been omitted, and in this specification, when referring to components in each drawing, the same or similar reference symbols will be used throughout the specification for the same or similar components.

[0028] Furthermore, the terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a manner that is consistent with the technical ideas of the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0029] Secondary battery manufacturing method The present invention provides a method for manufacturing a secondary battery, including a tab-lead laminate welding step (S30) of welding a tab-lead laminate 100 in which a plurality of electrode tabs and electrode leads are stacked, to connect the electrode tabs and the electrode leads, and a tab-lead laminate processing step (S40) of processing a welding point W of the tab-lead laminate 100 by continuously applying pressure along a length direction to the welding point W.

[0030] First, the tab-lead stack welding step (S30) is a step of welding the tab-lead stack 100 in which a plurality of electrode tabs and electrode leads are stacked, to connect the electrode tabs and the electrode leads, and can be performed by various methods.

[0031] Specifically, the tab-lead laminate welding step (S30) may be performed by welding at least one region of the overlapping portions of the electrode tab and the electrode lead to weld and join the electrode tab and the electrode lead. Here, the tab-lead laminate welding step (S30) may be performed by various welding methods, for example, ultrasonic welding or laser welding.

[0032] The tab-lead laminate welding step (S30) can form a welded area W of a predetermined size on the tab-lead laminate 100. Here, the welded area W can be understood as a concept including not only the area where the electrode tab and the electrode lead are directly connected by welding on the tab-lead laminate 100, but also the area indirectly affected by welding, such as deformation of the external shape and deformation of the connection structure between internal metals, etc. Also, the area on the tab-lead laminate 100 other than the welded area W can be defined as an unwelded area N below.

[0033] Here, the welded portion W may be a portion whose surface shape is deformed by pressure and / or heat during welding. For example, a plurality of shape-deformed portions a, which are deformed by welding, may be formed along at least one direction on the surface of the welded portion W. Here, the shape-deformed portions a are portions on the tab-lead laminate 100 whose shape is deformed by welding heat, pressure, vibration, etc., and may be understood as portions formed as protrusions and / or depressions from at least one surface of the tab-lead laminate 100.

[0034] Such shape deformation portion a increases the surface roughness of the tab-lead laminate 100, generates tensile residual stress, causes stress concentration, and leads to the occurrence of microcracks, which has a fatal impact on the reliability of the semi-finished product.

[0035] Therefore, the present invention effectively prevents the above-mentioned problems by performing the tab-lead stack processing step (S40) after the tab-lead stack welding step (S30) as shown in FIG. 2.

[0036] The tab-lead laminate processing step (S40) is a step of continuously pressing the welding points W of the tab-lead laminate 100 along the length direction to process the welding points W, and may be performed by various methods. Here, the welding points W may be pressed with various pressures, for example, with a pressure of 100 kgf or more.

[0037] Specifically, in the tab-lead laminate processing step (S40), a processing unit 20, which will be described later, can process the welding points W of the tab-lead laminate 100 while pressing the welding points W of the tab-lead laminate 100 in a vertical direction (a direction parallel to the Z axis in FIG. 3) and moving horizontally along the length direction of the welding points W (X direction in FIG. 3). However, it goes without saying that the tab-lead laminate processing step (S40) is not limited to the processing unit 20 moving horizontally along the length direction of the welding points W (X direction in FIG. 3), and can move horizontally along the width direction of the welding points W (Y direction in FIG. 3).

[0038] Here, when a plurality of shape deformation portions a are formed at the welding point W, the tab-lead laminate processing step (S40) can process the welding point W by continuously pressing the plurality of shape deformation portions a along the formation direction of the shape deformation portions a. For example, as shown in Fig. 4, the tab-lead laminate processing step (S40) can process the welding point W of the tab-lead laminate 100 while a processing unit 20 described below moves and presses along the formation direction of the shape deformation portions a (X direction in Fig. 4).

[0039] As a result, the tab-lead laminate processing step (S40) can apply pressure to the welding points W for a relatively long period of time compared to a press process in which the entire area of ​​the welding points W is instantaneously compressed, and can provide shear deformation simultaneously with compressive deformation, thereby effectively imparting compressive residual stress in the thickness direction (Z direction in FIG. 3) of the tab-lead laminate 100 and significantly reducing surface roughness. Here, the press process can apply pressure to the welding points W for about 0.2 seconds, but the tab-lead laminate processing step (S40) according to the present invention can apply pressure to the welding points W for 0.2 seconds or more.

[0040] The tab-lead laminate processing step (S40) may be performed by a roll burnishing or ball burnishing process, etc. Here, the moving path, moving speed, size and shape of the roll and ball may be variously set according to the process time, number of times of processing, etc.

[0041] For example, the tab-lead laminate processing step (S40) may perform roll burnishing or ball burnishing at least once on the welded portion W. Specifically, the tab-lead laminate processing step (S40) may perform a roll burnishing or ball burnishing process by reciprocating a roll and a ball on the welded portion W. Here, the tab-lead laminate processing step (S40) may perform roll burnishing or ball burnishing not only on the welded portion W but also on the unwelded portion N.

[0042] Also, in the tab-lead laminate processing step (S40), the size of the roll can be adjusted to adjust the pressing area of ​​the welding points W. That is, in the tab-lead laminate processing step (S40), the size of the roll can be set relatively small to pressurize the welding points W more finely, and in the tab-lead laminate processing step (S40), the size of the roll can be set relatively large to quickly pressurize the welding points W, thereby shortening the processing time. In this case, it goes without saying that the size of the roll can be adjusted according to the number and intervals of the shape deformation portions a described above.

[0043] Meanwhile, after the tab-lead laminate processing step (S40), a tape attaching step (S50) of attaching an insulating tape to the welding portion W of the tab-lead laminate 100 may be performed.

[0044] Here, the tape attaching step (S50) may be performed by attaching insulating tape to the welding points W of the tab-lead laminate 100 to prevent the welding points W from being exposed to the outside and being damaged.

[0045] Meanwhile, before the tab-lead stack welding step (S30), an electrode tab stack welding step (S10) may be performed in which a plurality of electrode tabs are also welded together.

[0046] Specifically, the electrode tab stack welding step (S10) is a step of connecting a plurality of electrode tabs by welding an electrode tab stack (not shown) in which a plurality of electrode tabs are stacked, and may be performed by various methods.

[0047] Specifically, the electrode tab stack welding step (S10) may be performed by welding at least one region among the portions where the electrode tabs are stacked to weld the electrode tabs together. Here, the electrode tab stack welding step (S10) may be performed by various welding methods, for example, ultrasonic welding or laser welding.

[0048] The electrode tab laminate welding step (S10) can form a welded area W of a predetermined size in the electrode tab laminate, like the tab-lead laminate welding step (S30) described above. Here, the welded area W can be understood as a concept including not only areas on the electrode tab laminate where the electrode tabs are directly joined to each other by welding, but also areas indirectly affected by welding, such as deformation of the external shape and deformation of the joint structure between internal metals, etc. Also, areas on the electrode tab laminate other than the welded area W can be defined as unwelded areas N below.

[0049] Here, the welded portion W may be a portion whose surface shape is deformed by pressure and / or heat during welding. For example, a plurality of shape-deformed portions a, which are deformed by welding, may be formed along at least one direction on the surface of the welded portion W. Here, the shape-deformed portions a are portions on the electrode tab laminate whose shape is deformed by welding heat, pressure, vibration, etc., and may be understood as portions formed as protrusions and / or depressions from at least one surface of the electrode tab laminate.

[0050] Such a shape deformation portion a increases the surface roughness of the electrode tab laminate, generates tensile residual stress, and causes stress concentration, which leads to the occurrence of microcracks, resulting in a fatal effect on the reliability of the semi-finished product.

[0051] Therefore, as shown in FIG. 2, the present invention effectively prevents the above-mentioned problems by performing the electrode tab laminate processing step (S20) after performing the electrode tab laminate welding step (S10).

[0052] The above-mentioned electrode tab laminate processing step (S20) is a step of continuously pressurizing the welding point W of the electrode tab laminate along the length direction between the electrode tab laminate welding step (S10) and the tab-lead laminate welding step (S30) to process the welding point W, and may be performed by various methods. Here, the welding point W may be pressurized with various pressures, for example, with a pressure of 100 kgf or more.

[0053] Specifically, the electrode tab laminate processing step (S20) may process the welding point W of the electrode tab laminate by vertically pressing the welding point W of the electrode tab laminate and moving horizontally along the longitudinal direction of the welding point W.

[0054] However, it goes without saying that the electrode tab laminate processing step (S20) is not limited to the processing unit 20 moving horizontally along the length direction of the welding area W, but may also move horizontally along the width direction of the welding area W.

[0055] Here, when a plurality of shape deformed portions a are formed at the welding point W, the electrode tab laminate processing step (S20) can process the welding point W by continuously pressurizing the plurality of shape deformed portions a along the formation direction of the shape deformed portions a. For example, in the electrode tab laminate processing step (S20), a processing unit 20 described later can process the welding point W of the electrode tab laminate while pressing and moving along the formation direction of the shape deformed portions a.

[0056] As a result, the electrode tab laminate processing step (S20) can apply pressure to the welding points W for a relatively long period of time compared to a press process in which the welding points W are instantaneously compressed, and can provide shear deformation simultaneously with compressive deformation. This makes it possible to effectively impart compressive residual stress in the thickness direction of the electrode tab laminate, and greatly reduce surface roughness.

[0057] The electrode tab laminate processing step (S20) may be performed by a roll burnishing or ball burnishing process, etc. Here, the moving path, moving speed, size, shape, etc. of the roll and ball may be variously set according to the process time, number of treatments, etc.

[0058] For example, the electrode tab laminate processing step (S20) may perform roll burnishing or ball burnishing at least once on the welded portion W. Specifically, the electrode tab laminate processing step (S20) may perform a roll burnishing or ball burnishing process by reciprocating a roll and a ball on the welded portion W. Here, the electrode tab laminate processing step (S20) may perform roll burnishing or ball burnishing not only on the welded portion W but also on the unwelded portion N.

[0059] Also, in the electrode tab laminate processing step (S20), the size of the roll can be adjusted to adjust the pressing area of ​​the welding points W. That is, in the electrode tab laminate processing step (S20), the size of the roll can be set relatively small to pressurize the welding points W more finely, and in the electrode tab laminate processing step (S20), the size of the roll can be set relatively large to quickly pressurize the welding points W, thereby shortening the processing time. In this case, it goes without saying that the size of the roll can be adjusted according to the number and intervals of the shape deformation portions a described above.

[0060] Secondary battery manufacturing equipment Meanwhile, the present invention provides a secondary battery manufacturing apparatus 1 for processing at least one welding point W of a tab-lead laminate 100 in which a plurality of electrode tabs and electrode leads are stacked, and an electrode tab laminate in which a plurality of electrode tabs are stacked, the secondary battery manufacturing apparatus 1 including a main body 10 and a processing unit 20 installed on the main body 10 for continuously applying pressure to the welding point W to process it.

[0061] The above-mentioned secondary battery manufacturing apparatus 1 can be provided at various positions from the tab-lead laminate 100 and the electrode tab laminate. For example, the secondary battery manufacturing apparatus 1 may be provided above, below, or both above and below the tab-lead laminate 100 and the electrode tab laminate.

[0062] Here, the main body 10 is configured to have the above-mentioned processing unit 20 installed therein, and may have various configurations. For example, the main body 10 may include a moving device (not shown) that allows the processing unit 20 to move. Here, the moving device may be configured with a hydraulic cylinder or the like, and may be connected to an industrial computer or the like via wire / wireless to be controlled.

[0063] The processing unit 20 is installed on the main body 10 and is configured to continuously apply pressure to the welding spot W to process it, and various configurations are possible.

[0064] Here, the processing section 20 can perform pressure processing not only on the welded portion W but also on the boundary between the welded portion W and the unwelded portion N, thereby making it possible to expand the processing area.

[0065] Such a processing unit 20 can have various structures. For example, the processing unit 20 can include a pressure unit 21 that applies pressure to the welding spot W while rotating, and a support unit 22 that rotatably supports the pressure unit 21.

[0066] Here, the pressure unit 21 is configured to apply pressure to the welding spot W while rotating, and various configurations are possible.

[0067] For example, the pressure unit 21 may include a roller or a ball so as to rotate and pressurize the welding point W. However, the structure of the pressure unit 21 is not limited to the roller and ball, and any structure may be used as long as the structure can rotate and pressurize the welding point W.

[0068] The material of the pressure member 21 may be various materials. For example, the material of the pressure member 21 may include iron or ceramic material in order to minimize wear due to contact with the welding point W. More specifically, the material of the pressure member 21 may be provided as cemented carbide tool steel and tool ceramic.

[0069] On the other hand, the support portion 22 is configured to rotatably support the pressure portion 21, and various configurations are possible.

[0070] For example, one end of the support portion 22 rotatably supports the pressure portion 21, and the other end is connected to the main body 10 described above so that the pressure portion 21 can be moved along the welding point W while being pressed.

[0071] Meanwhile, the quantitative effects of the present invention can be more specifically confirmed with reference to Figures 5a to 5b, where Figure 5a is a graph showing a comparison of the residual stress values ​​of the tab-lead laminate 100 after the conventional manufacturing method of a secondary battery and the manufacturing method of a secondary battery of the present invention, and Figure 5b is a graph showing a comparison of the surface roughness of the tab-lead laminate 100 after the conventional manufacturing method of a secondary battery and the manufacturing method of a secondary battery of the present invention.

[0072] Here, the conventional method for manufacturing a secondary battery involves welding the tab-lead laminate 100 and then performing a press process to instantly press the entire area of ​​the welding point W of the tab-lead laminate 100, whereas the method for manufacturing a secondary battery according to the present invention can be understood as performing the above-mentioned roll burnishing process on the welding point W of the tab-lead laminate 100 after performing the welding step of the tab-lead laminate 100.

[0073] First, referring to Fig. 5a, the change in residual stress of the tab-lead laminate 100 according to the conventional manufacturing method of a secondary battery and the change in residual stress of the tab-lead laminate 100 according to the manufacturing method of a secondary battery of the present invention can be compared. It should also be noted that the values ​​of the tab-lead laminate 100 subjected to the conventional manufacturing method of a secondary battery are represented on the graph as Press_0.2s or Press_1.0s, and the values ​​of the tab-lead laminate 100 subjected to the manufacturing method of a secondary battery of the present invention are represented as Burnishing_0.2s or Burnishing_1.0s. It should also be noted that the tensile residual stress is represented as a positive value and the compressive residual stress is represented as a negative value.

[0074] Specifically, in the graph of Fig. 5a, the maximum absolute value of the compressive residual stress of the tab-lead laminate 100 after the conventional manufacturing method of a secondary battery (Press_0.2s, Press_1.0s) was confirmed to be about 35 MPa. In addition, the maximum absolute value of the compressive residual stress of the tab-lead laminate 100 after the manufacturing method of a secondary battery according to the present invention (Burnishing_0.2s) was confirmed to be about 80 MPa. In addition, the maximum absolute value of the compressive residual stress of the tab-lead laminate 100 after the manufacturing method of a secondary battery according to the present invention (Burnishing_1.0s) was confirmed to be about 70 MPa.

[0075] That is, when comparing the maximum absolute values ​​of compressive residual stress according to the conventional manufacturing method of a secondary battery and the manufacturing method of a secondary battery of the present invention with reference to the graph of Fig. 5a, it is confirmed that the manufacturing method of a secondary battery according to the present invention can impart approximately twice as much compressive residual stress to the tab-lead laminate 100 as the conventional manufacturing method of a secondary battery. Furthermore, it was confirmed that the manufacturing method of a secondary battery according to the present invention can impart compressive residual stress not only to the electrode leads but also to the electrode tabs provided below the electrode leads, thereby providing an advantage of being able to more effectively impart compressive residual stress to the tab-lead laminate 100.

[0076] Meanwhile, referring to Fig. 5b, the change in height of the shape-deformed portion a when the conventional manufacturing method of a secondary battery is performed and the change in height of the shape-deformed portion a when the manufacturing method of a secondary battery of the present invention is performed can be compared. Here, the height of the shape-deformed portion a can be understood as the maximum protruding height of the shape-deformed portion a before and after the manufacturing method of a secondary battery is performed. It should also be noted that the values ​​of the tab-lead laminate 100 subjected to the conventional manufacturing method of a secondary battery are represented as Press_0.2s or Press_1.0s on the graph, and the values ​​of the tab-lead laminate 100 subjected to the manufacturing method of a secondary battery of the present invention are represented as Burnishing_0.2s or Burnishing_1.0s.

[0077] Specifically, referring to the graph of FIG. 5b, after the conventional manufacturing method of the secondary battery (Press_0.2s, Press_1.0s), the height of the shape-deformed portion a was 0.054 mm, which was reduced by about 19.4% compared to the conventional height of the shape-deformed portion a (0.067 mm). Meanwhile, after the manufacturing method of the secondary battery of the present invention (Burnishing_0.2s) was performed for 0.2 sec, the height of the shape-deformed portion a was 0.035 mm, which was reduced by about 52.2% compared to the conventional height of the shape-deformed portion a (0.067 mm). In addition, after the manufacturing method of the secondary battery of the present invention (Burnishing_1.0s) was performed for 1 sec, the height of the shape-deformed portion a was 0.020 mm, which was reduced by about 70.1% compared to the conventional height of the shape-deformed portion a (0.067 mm).

[0078] That is, referring to the graph of FIG. 5b, a comparison was made between the change in height of the shape-deformed portion a according to the conventional manufacturing method of a secondary battery and the manufacturing method of a secondary battery of the present invention. As a result, it was confirmed that the manufacturing method of a secondary battery according to the present invention can effectively improve the surface roughness by at least 2.7 times more than the conventional manufacturing method of a secondary battery.

[0079] Furthermore, in the case of conventional secondary battery manufacturing methods, the degree of improvement in surface roughness is unrelated to the process processing time, but in the case of the secondary battery manufacturing method according to the present invention, it has been confirmed that the surface roughness improves in proportion to the process execution time (e.g., 0.2 sec, 1 sec). Therefore, there is an advantage in that the degree of improvement in surface roughness can be easily adjusted by adjusting the process execution time.

[0080] The present invention has been described above using limited embodiments and drawings, but the present invention is not limited thereto, and various implementations are possible within the technical spirit of the present invention and the equivalent scope of the claims described below by a person having ordinary knowledge in the technical field to which the present invention belongs. [Explanation of symbols]

[0081] 1. Secondary battery manufacturing equipment 10 Main unit 20 Processing Department 21 Pressurizing section 22 Support part W Welding point N Unwelded area 100 Tab-lead laminate A Shape transformation section S10 Electrode tab stack welding step S20 Electrode tab laminate processing step S30 Tab-Lead Laminate Welding Step S40 Tab-lead laminate processing step S50 Tape attachment step

Claims

1. a tab-lead laminate forming step of laminating a plurality of electrode tabs and electrode leads to form a tab-lead laminate; a tab-lead laminate welding step of welding the tab-lead laminate to connect the plurality of electrode tabs and the electrode leads; and a tab-lead laminate processing step of sequentially applying pressure to the welded portions of the tab-lead laminate to process the welded portions.

2. A plurality of shape deformed portions, the shape of which is deformed by the welding, are formed along at least one direction at the welded portion, 2. The method for manufacturing a secondary battery according to claim 1, wherein the tab-lead laminate processing step processes the welded portion by continuously pressing the plurality of shape deformation portions along a direction in which the plurality of shape deformation portions are formed.

3. 2. The method of claim 1, wherein the tab-lead laminate processing step is performed by a roll-burnishing or ball-burnishing process.

4. The method for manufacturing a secondary battery according to claim 1 , wherein the tab-lead laminate processing step applies pressure to the welded portion with a pressure of 100 kgf or more.

5. The method for manufacturing a secondary battery according to claim 1 , wherein the tab-lead laminate welding step is performed by ultrasonic welding or laser welding.

6. Prior to the tab-lead laminate forming step, an electrode tab stack forming step of stacking the plurality of electrode tabs to form an electrode tab stack; The method of claim 1 , further comprising: an electrode tab stack welding step of welding the electrode tab stack to connect the plurality of electrode tabs.

7. between the electrode tab stack welding step and the tab-lead stack forming step, The method for manufacturing a secondary battery according to claim 6 , further comprising: a step of processing the electrode tab laminate by sequentially applying pressure to the welded portions of the electrode tab laminate to process the welded portions.

8. After the tab-lead laminate processing step, The method of claim 1, further comprising the step of attaching an insulating tape to the welded portion of the tab-lead laminate.

9. An apparatus for manufacturing a secondary battery, which processes a welding portion of at least one of a tab-lead laminate in which a plurality of electrode tabs and electrode leads are laminated, and an electrode tab laminate in which a plurality of electrode tabs are laminated, The main body, a processing unit that is installed on the main body and sequentially applies pressure to and processes the welding points.

10. The secondary battery manufacturing apparatus according to claim 9 , wherein the processing unit includes a roller or a ball that rotates and applies pressure to the welding portion.

11. The secondary battery manufacturing apparatus according to claim 9 , wherein the material of the processed portion is iron or a ceramic material.

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