Secondary battery case manufacturing method

Abstract

The present invention relates to a method for manufacturing a secondary battery case, and a method for welding a secondary battery prismatic cell case and a cap assembly, which may include a manufacturing step for manufacturing the prismatic cell case, an alignment step for aligning the open surface of the prismatic cell case with the cap assembly, a welding step for heating and melting the joint area by irradiating a laser beam from the outside of the prismatic cell case toward the cap assembly, a cooling step in which the joint is formed as the molten material solidifies, and a cleaning step for cleaning the inside of the prismatic cell case and the cap assembly after cooling.

Description

Technology Field

[65535] The present invention relates to a method for manufacturing a case, and more specifically, to a laser welding method for a cap and cap assembly that eliminates the risk factor in which a laser introduced into the can during welding of the can and cap assembly—which is one of the causes of fire in prismatic cells among secondary battery form factors—damages the positive and negative electrode plates or melts the separator to deform its shape, and a method for manufacturing a secondary battery case to maximize the effect. Background Technology

[0002] A secondary battery is an energy storage device that utilizes the phenomenon of electron transfer resulting from a reversible oxidation-reduction reaction through an electrolyte of two electrodes with a large difference in ionization tendency.

[0003] In particular, lithium-ion rechargeable batteries, which have the highest energy density among rechargeable batteries, are generally composed of a carbon-based anode, an organic electrolyte, and a lithium oxide cathode.

[0004] Because these lithium-ion secondary batteries require a robust sealed structure, it is common to weld the components together.

[0005] Regarding the technology for welding components of a lithium-ion secondary battery, Korean Registered Patent No. 10-1583408 discloses a welding apparatus and a laser welding method for manufacturing a lithium-ion secondary battery, wherein a metal pre-assembly, in which a first metal component and a second metal component are pre-joined, is transported into a shield separately installed at a location away from a transport rail for transporting the metal pre-assembly, and laser welding is performed by irradiating a laser beam onto the welding portion of the metal pre-assembly in a welding chamber inside a partially open shield, thereby causing most of the slag generated during laser welding to fall into the shield, and laser welding can be performed while the metal pre-assembly is placed on a jig.

[0006] The welding device and laser welding method for manufacturing such lithium-ion secondary batteries had limitations in accurately irradiating only the area of ​​the object to be welded with the laser.

[0007] In other words, since the object to be welded is transported only by the transport rail within the welding room, there was a problem where laser welding was unstable and ripple beads or humping beads occurred when laser welding was performed simultaneously with the process of transporting the object to be welded.

[0008] In addition, conventional secondary battery cases are formed with rounded corners, causing the internal negative electrode plate to be pressed.

[0009] Furthermore, this causes secondary battery ignition and thermal runaway, and even if a certain gap is secured, there is a problem in that it is difficult to maintain safety because secondary batteries that expand during use experience additional stress and damage to the corners due to the characteristics of bare cells or jelly rolls. Prior art literature

[0010] Korean Intellectual Property Office Application No. 10-2010-0112453 The problem to be solved

[0011] The objective of the present invention is to provide a method for forming the corner R value of a secondary battery case in a right angle range of 0.5 or less, and welding using overlap welding so that a laser beam does not enter the interior of the secondary battery case. means of solving the problem

[0012] A method for manufacturing a secondary battery case according to the present invention may include a manufacturing step for manufacturing a prismatic cell case and a cap assembly, an alignment step for aligning an open surface of the prismatic cell case with a cap assembly, a welding step for heating and melting a joint area by irradiating a laser beam from the outside of the prismatic cell case toward the cap assembly, a cooling step in which the joint is formed as the molten material solidifies, and a cleaning step for cleaning the inside of the prismatic cell case and the cap assembly after cooling.

[0013] In addition, the welding step may be performed by selecting at least one welding method among lap welding or butt welding.

[0014] In addition, the welding step may include a gas supply step that supplies shielding gas during welding to prevent oxidation of the molten pool.

[0015] In addition, the manufacturing step may include a corner forming step in which the corner of the case is formed to have a rounded shape with an R value of 0.5 mm or less.

[0016] And the above manufacturing step may further include a body having open top and bottom ends and a perimeter formed as a rectangular prism, and a joining step of inserting a panel into an open part of the body and welding it. Effects of the invention

[0017] The present invention has the effect of preventing secondary battery fire accidents because the laser beam does not enter the inside of the can.

[0018] In addition, it has the effect of being safe from stress and damage to the bare cell or jelly roll caused by compression and bending of the negative plate during use. Brief explanation of the drawing

[0019] FIGS. 1 to 3 are drawings showing a conventional secondary battery case; FIG. 4 is a flowchart of a method for manufacturing a secondary battery case according to an embodiment of the present invention; FIG. 5 is a drawing for explaining that a cap assembly is coupled to a prismatic cell case in a method for manufacturing a secondary battery case according to an embodiment of the present invention; FIGS. 6 to 10 are drawings for explaining overlap welding in a method for manufacturing a secondary battery case according to an embodiment of the present invention. Specific details for implementing the invention

[0020] A preferred embodiment according to the present invention will be described in detail below with reference to the attached drawings.

[0021] The advantages and features of the present invention and the method for achieving them will become clear by referring to the embodiments described in detail below together with the accompanying drawings.

[0022] However, the present invention is not limited by the embodiments disclosed below but may be implemented in various different forms, and these embodiments are provided merely to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0023] In addition, in describing the present invention, if it is determined that related known technologies, etc., may obscure the essence of the present invention, a detailed explanation thereof will be omitted.

[0024] The present invention relates to a method for welding a can and a cap assembly, which is one of the causes of fire in prismatic cells among secondary battery form factors.

[0025] The present invention for this purpose is a method for welding a secondary battery prismatic cell case (10) and a cap assembly (20), and may include a manufacturing step (100) for manufacturing the prismatic cell case (10), an alignment step (200) for aligning the open surface of the prismatic cell case (10) with the cap assembly (20), a welding step (300) for heating and melting the joint by irradiating a laser beam from the outside of the prismatic cell case (10) toward the cap assembly (20), a cooling step (400) in which the bond is formed as the molten material solidifies, and a cleaning step (500) for performing an internal cleaning process after welding.

[0026] First, the secondary battery prismatic cell case (10) according to the present invention may have one side open and a cap assembly (20) welded to the open side.

[0027] Further details will be explained by referring to the drawings.

[0028] FIGS. 1 to 3 are drawings showing a conventional secondary battery case.

[0029] As described above, a conventional secondary battery case may be in the form where a portion of a cap assembly is inserted into an open side of a can. Additionally, it can be observed that the corners of such a can are formed to be rounded.

[0030] Such a rounded shape can cause the negative plate inside the secondary battery to be compressed, which may lead to ignition and thermal runaway of the secondary battery.

[0031] Specifically, secondary batteries that expand during use face a problem where maintaining stability becomes difficult due to additional stress and damage to the edges caused by the characteristics of bare cells or jelly rolls.

[0032] The present invention for solving this problem will be explained through the following drawings.

[0033] FIG. 4 is a flowchart of a welding method for a secondary battery prismatic cell case (700) and a cap assembly (800) according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating the coupling of a cap assembly (800) to a prismatic cell case (700) in a welding method for a secondary battery prismatic cell case (700) and a cap assembly (800) according to an embodiment of the present invention.

[0034] The step of manufacturing a secondary battery case according to the present invention can be broadly composed of five steps.

[0035] First, the method may include a step of manufacturing a rectangular cell case (700) (100), a step of aligning a cap assembly (800) on an open surface of the rectangular cell case (700), and a welding step (300) of heating and melting a joint by irradiating a laser beam from the outside of the rectangular cell case (700) toward the cap assembly (800).

[0036] It may also include a cooling step (400) in which bonding is achieved as the molten material solidifies, and a cleaning step (500) in which an internal cleaning process is performed after cooling.

[0037] And after welding, the case can be completed by cooling and cleaning.

[0038] The manufacturing step (100) of the rectangular cell case (700) for this purpose may be as follows.

[0039] The present invention may be in the form of a rectangular cell case (700) formed by assembling two or more parts by welding, and a can closing one side of the rectangular cell case (700).

[0040] Specifically, the method may further include the steps of extruding a rectangular pipe (in the present invention, the case shape may include a polygonal pipe), cutting and trimming the elongated pipe to a predetermined length, and cutting and trimming a metal plate.

[0041] The method may further include the step of welding a metal plate cut to a size corresponding to one side to one of the open sides of the continuously cut square pipe.

[0042] And the step of washing this may be a step of manufacturing the rectangular cell case (700).

[0043] A cap assembly may be welded to the other side of the rectangular cell case (700) manufactured by the above method.

[0044] Alternatively, the present invention may be in the form where the sides of a plurality of panels are welded together.

[0045] The above multiple panels are welded together to form a cuboid shape, and one side may be open.

[0046] And a cathode tab, a positive tab, a cathode plate, a positive plate, and an electrolyte can be accommodated inside.

[0047] In addition, the rectangular cell case (700) according to the present invention can have the angle of the welded corner of the panel formed by combining the plurality of panels into a right angle, and at least the corner curvature value (R) can be formed to be 0.5 or less.

[0048] The corner mentioned here may refer to the inner corner of the square cell case (700) and the cap assembly, and the outer corner may have the same curvature value as the inner corner.

[0049] Alternatively, the shape may have an inner edge that maintains a curvature value (R) of 0.5 or less, while the outer edge has a relatively larger curvature value.

[0050] Therefore, if a curvature value is required according to user settings, the corners of the square cell case (700) and cap assembly (800) can be formed to be bent with curvature.

[0051] The curvature value of the inner corner of the rectangular cell case (700) and cap assembly (800) of the present invention is formed to be 0.5 or less, which may differ from the result value of the conventional technology.

[0052] The conventional method of manufacturing a rectangular cell case (10) involves blanking a metal plate (aluminum) and then drawing it to form a three-dimensional shape, and then cutting off the irregular edges of the formed product through a trimming process.

[0053] If the conventional process described above is followed, the R value of the inner corner is inevitably formed to a level large enough to cause the negative plate to be compressed.

[0054] Therefore, to solve the conventional problem, a cut square pipe can be cut and a metal plate welded to the opening to form a structure with a curvature value of 0.5 or less.

[0055] The welding method for the secondary battery prismatic cell case (700) and cap assembly (800) according to the present invention described above can weld the prismatic cell case (700) by selecting either lap welding or butt welding.

[0056] This can be confirmed in Figures 6 to 10.

[0057] FIGS. 6 to 10 are drawings for explaining overlap welding in a welding method for a secondary battery prismatic cell case (700) and a cap assembly (800) according to an embodiment of the present invention.

[0058] In this embodiment, the rectangular cell case (700) can be welded using an overlap welding method.

[0059] Overlap welding is a method of welding two metals by overlapping them. It has the advantage of being strong due to the large welded surface area and relatively easy to align.

[0060] Welding can also be performed using the butt welding method. Butt welding is a method of welding two metals by bringing them into contact on the same plane.

[0061] First, referring to FIG. 6, the vertically standing rod represents the side of the main body of the cap assembly (800), and the horizontally elongated part may be a rectangular cell case (700).

[0062] As described, welding can be performed along the longitudinal direction of the square cell case (700) while in contact with the inner surface of the cap assembly (800) on both end surfaces of the square cell case (700).

[0063] Alternatively, welding may be performed along the longitudinal direction of the cap assembly (800).

[0064] This differs from conventional welding with two gaps by irradiating a laser beam in a direction facing the square cell case (700) or cap assembly (800) that are facing each other in the welding direction.

[0065] This prevents the laser beam from leaking into the interior where the space is formed through the rectangular cell case (700) and the cap assembly (800) when welding is performed, and also prevents damage to the secondary battery provided in the space.

[0066] Looking at Fig. 7, overlap welding can be performed with a part of the cap assembly (800) overlapping along the longitudinal direction of the rectangular cell case (700).

[0067] The direction in which welding is performed may be either the longitudinal direction of the cap assembly (800) described above or the longitudinal direction of the square cell case (700), in which a laser beam can be irradiated.

[0068] Meanwhile, according to the welding method of the secondary battery prismatic cell case (700) and the cap assembly (800) according to the present invention, the angle at which the prismatic cell case (700) and the cap assembly (800) are in contact with each other can be adjusted in various ways.

[0069] This is illustrated in FIGS. 9 and FIGS. 10.

[0070] FIGS. 9 and FIGS. 10 are arranged in a direction perpendicular to each other, and the ends of the rectangular cell case (700) and the cap assembly (800) are formed to be inclined so that the respective inclined ends are in contact.

[0071] And the rectangular cell case (700) and the cap assembly (800) can form a 90-degree angle.

[0072] Looking at FIG. 9, it can be seen that the angle between the rectangular cell case (700) and the cap assembly (800) is formed at a 45-degree angle and is in contact with each other.

[0073] In FIG. 10, it can be seen that the thickness of the rectangular cell case (700) is formed to be relatively narrower than the thickness of the cap assembly (800).

[0074] This means that the rectangular cell case (700) and the cap assembly (800) are in contact, and although the two are formed at a right angle to each other, the contact angle can be varied from 5 degrees to 85 degrees as the thickness of the rectangular cell and the case varies.

[0075] The above-described angle change can be varied by the thickness of the rectangular cell case (700) and the cap assembly (800).

[0076] Meanwhile, the cap assembly (800) of the present invention may have a slit (not shown) formed on one side facing the rectangular cell case (700) into which the end of the negative plate can be inserted.

[0077] This is due to the cause of the problem with stability, which occurs when the negative plate is formed to protrude relatively outward compared to the positive plate, and at this time, the negative plate is pressed at the corner portion of the rectangular cell case (700) as the corner of the conventional rectangular cell case (700) is formed rounded.

[0078] As a result, it may be preferable for the slit to be formed in the cap assembly (800) so that a negative plate can be inserted.

[0079] Although specific embodiments regarding the welding method of a secondary battery prismatic cell case (700) and a cap assembly (800) according to the present invention have been described so far, it is obvious that various modifications are possible within the scope of the present invention.

[0080] Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

[0081] That is, the aforementioned embodiments should be understood as exemplary in all respects and not limiting, and the scope of the invention is defined by the claims set forth below rather than by the detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the invention. Explanation of the symbols

[0083] 10: Conventional rectangular cell case 20: Conventional cap assembly 100: Manufacturing stage 200: Alignment step 300: Welding stage 400: Cooling stage 500: Cleaning step 700: Rectangular cell case 800: Cap Assembly

Claims

Claim 1 A method for manufacturing a secondary battery case comprises: a manufacturing step for manufacturing a rectangular cell case, comprising the steps of extruding a long rectangular pipe, cutting and trimming the pipe to a predetermined length, cutting and trimming a metal plate, welding the cut metal plate to one of the open sides of the cut rectangular pipe, and cleaning; an alignment step for aligning the open side of the rectangular cell case with a cap assembly; a welding step for heating and melting the joint area by irradiating a laser beam from the outside of the rectangular cell case toward the cap assembly; a cooling step in which the joint is formed as the molten material solidifies; and a cleaning step for cleaning the inside of the rectangular cell case and the cap assembly after cooling, wherein the manufacturing step includes a corner forming step in which the corner of the rectangular cell case is formed to have a rounded shape with an R value of 0.5 mm or less, and the welding step is performed by butt welding, wherein the contact surface between the rectangular cell case and the cap assembly is formed diagonally, and the respective ends of the rectangular cell case and the cap assembly are formed to be inclined, and the respective inclined A method for manufacturing a secondary battery case, wherein the ends are in contact, and the welding step prevents the laser beam from leaking into the interior where a space is formed through the rectangular cell case and the cap assembly by irradiating the laser beam in a direction facing the rectangular cell case or the cap assembly where the welding direction is facing, and the welding step includes a gas supply step that prevents oxidation of the molten pool by supplying a shielding gas during welding. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A method for manufacturing a secondary battery case according to claim 1, wherein the manufacturing step further comprises a body having an open top and bottom and a perimeter formed of a rectangular prism, and a joining step of inserting a panel into an open part of the body and welding it.

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