Multi-roller system, battery can forming device, and forming method

Abstract

The present specification relates to a multi-roller system including two or more pairs of rollers, the two or more pairs of rollers rotate based on rotation axes independent of each other, the change in height of each of the two or more pairs of rollers is controlled, and the cross sections of the two or more pairs of rollers have different shapes, and the two or more pairs of rollers are spaced apart at equal intervals to approach and pressurize a battery can.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0030312, filed with the Korean Intellectual Property Office on March 8, 2021, and all of the contents disclosed in the documents of the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a multi-roller system, a battery can forming apparatus, and a forming method.

Background Art

[0003] When compared with conventional models (1865 / 2170), the battery cans of cylindrical secondary battery models developed in recent years have a larger inner diameter and are made of a material having a thicker thickness. Therefore, in forming such battery cans of cylindrical secondary batteries, a larger load is applied and a longer process time is required.

[0004] The battery cans of cylindrical secondary batteries are usually sequentially formed through various processes such as CBD (Cylindrical beading), CCR 1-2-3 (Cylindrical crimping 1-2-3), and CSZ (Cylindrical sizing), and thus a considerable amount of process time is required. Therefore, in order to achieve the target production volume for battery cans, a large number of forming facilities have to be installed in parallel.

[0005] Currently, by installing a large number of forming facilities in parallel to form battery cans, it is possible to mass-produce the maximum number of battery cans within a specified time, but it takes time to transfer the facilities for the parallel-installed facilities. In addition, there is a problem that re-fixing of the battery cans is required according to the movement of the facilities, and there may be variations in the setting values during re-fixing. This also leads to a problem of variations in the forming quality.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In order to solve the above problems, one object of the present invention is to provide a multi-roller system, a battery can forming apparatus, and a forming method according to an embodiment of the present invention, thereby shortening the time required for transferring equipment and preventing variations in setting values that occur during re-fixing due to equipment transfer.

[0007] However, the problems to be solved by the present invention are not limited to the above problems, and other problems not mentioned in this specification can be clearly understood by those of ordinary skill in the art from the description of the invention described below.

Means for Solving the Problems

[0008] In order to achieve the above object, the present invention provides a multi-roller system, a battery can forming apparatus, and a forming method according to the following aspects.

[0009] According to one aspect of the present invention, there is provided a multi-roller system including two or more pairs of rollers, wherein the two or more pairs of rollers rotate with respect to independent rotation axes, and the height change of each is controlled, wherein at least one cross-section of the two or more pairs of rollers has a different shape respectively, and a multi-roller system in which the distance between each pair of rollers and the battery can is different respectively.

[0010] According to one aspect of the present invention, there is provided a battery can forming apparatus, a fixing unit configured to fix a battery can; and a battery can forming apparatus including the above multi-roller system is provided.

[0011] According to one aspect of the present invention, there is provided a battery can forming method, After arranging an electrode assembly having a structure in which a first electrode, a separator, and a second electrode are sequentially stacked and wound around a battery can and injecting an electrolytic solution, it is formed so as to have a beading portion formed at a side end portion adjacent to the open portion of the battery can and press-fitted inward, and a gasket and a cap assembly are laminated on the beading portion; the first step; The second step of fixing the battery can; A third step of pressing an end portion of the open portion above the beading portion to form an inclined section in which the end portion of the open portion of the battery can is inclined toward the central axis of the battery can; A fourth step of pressing an end portion of the open portion of the battery can in which the inclined section is formed to form a sealed section in which the end portion of the open portion of the battery can is parallel to the side portion of the battery can; and A fifth step of pressing an end portion of the open portion of the battery can in which the inclined section and the sealed section are formed to form a flat section parallel to the lower surface of the battery can; including Provided is a method for forming a battery can, wherein at least two steps out of the third to fifth steps utilize the above-described multi-roller system.

Advantages of the Invention

[0012] According to one aspect of the present invention, the forming processes of conventional battery cans arranged in parallel can be unified.

[0013] Or, according to one aspect of the present invention, since pressure is applied to various pressurizing points of the battery can, it is advantageous in terms of force transmission, and thereby the load applied to each roller can be minimized.

[0014] Or, according to one aspect of the present invention, a complex forming process can be efficiently achieved while the process is unified.

[0015] Or, according to one aspect of the present invention, since forming can be quickly performed with relatively little force through continuous operation, the process time can be significantly shortened.

[0016] Or, according to one aspect of the present invention, since the equipment is not transferred, the time required for transfer can be shortened. Furthermore, variations in setting values during re-fixing caused by the transfer of the equipment can also be minimized. Therefore, a synergistic effect of minimizing speed and variations between processes can be expected.

[0017] Or, according to one aspect of the present invention, the quality of forming the battery can is improved.

[0018] However, the effects obtained by the present invention are not limited to the above-mentioned effects, and other technical effects not mentioned in this specification can be clearly understood by those skilled in the art from the description of the invention to be described later.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0020] The present invention can be subjected to various modifications and can include several embodiments, but specific embodiments are illustrated in the drawings and will be described in detail based thereon. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, or alternatives included in the technical idea and technical scope of the present invention.

[0021] In this specification, terms such as first and second can be used to describe various components, but the components should not be limited by these terms. These terms are only used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

[0022] In this specification, the term "and / or" includes combinations of a plurality of related items or a part of a plurality of related items.

[0023] In this specification, when a component is represented in the singular, it includes a plurality unless otherwise specified in this specification.

[0024] In this specification, terms such as "including" and "having", unless otherwise defined in this specification, mean that features, numbers, steps, operations, processes, components, members, etc. described in this specification, or combinations thereof, exist as such, and do not mean to exclude other features, numbers, etc.

[0025] Unless otherwise defined, all terms used in this specification, including technical terms or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains.

[0026] Hereinafter, the prior art and preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

[0027] FIG. 1 is a perspective view of a roller system according to the prior art, showing a pair of first rollers A for pressing (or forming) the end of the open portion of the battery can 1. Here, the first roller is applied only to one process, for example, one process can be the first crimping process. In order for subsequent processes to proceed, the battery can pressed by the first roller must be transferred to another roller system. For example, another roller system can be one to which a second roller is attached. Here, variations in the processes associated with the transfer occur.

[0028] According to one embodiment of the present invention, there is provided a multi-roller system including two or more pairs of rollers, wherein the two or more pairs of rollers rotate with respect to independent rotation axes, and the change in height of each is controlled, at least one cross-section of the two or more pairs of rollers has a different shape respectively, and the distance between each pair of rollers and the battery can is different respectively. A multi-roller system is provided.

[0029] Specifically, referring to FIG. 2, there are two or more pairs of rollers applied to the battery can 1, for example, a first roller A, a second roller B, and a third roller C, and there is a fixing unit 2 for fixing the battery can 1. Such first to third rollers A to C rotate with respect to independent or different rotation axes, and the change in height of each is controlled. Also, at least one cross-section of the two or more pairs of rollers has a different shape respectively. Here, the fact that at least one cross-section of the roller has a different shape means that the region approaching the battery can is different, or the shape of the cross-section is different when the roller is cut in the width direction.

[0030] Also, such first to third rollers may approach and press the battery can 1 with a time difference.

[0031] Also, the pressure applied to the battery can 1 by such first to third rollers may be the same or different from each other.

[0032] According to the above embodiment, after fixing the battery can once and utilizing the fact that the distances between each pair of the first to third rollers and the battery can are different, one process is advanced by the roller that first approaches the battery can, and then subsequent processes proceed sequentially. Therefore, different from the prior art, it is not necessary to transfer the battery can pressurized by the first roller to another roller system. As a result, variations in the processes associated with transfer do not occur.

[0033] According to an embodiment of the present invention, the two or more pairs of rollers are a pair of first rollers that pressurize the end of the open portion of the battery can so as to form an inclined section in which the end of the open portion of the battery can inclines toward the central axis of the battery can; a pair of second rollers that pressurize the end of the open portion of the battery can in which the inclined section is formed so as to form a sealed section perpendicular to the side of the battery can; and a pair of third rollers that pressurize the side of the open portion of the battery can in which the inclined section and the sealed section are formed so as to form a flat section parallel to the lower surface of the battery can to provide a multi-roller system including at least two pairs among them.

[0034] Specifically, referring to FIGS. 2 and 3, in the cylindrical secondary battery 3, the end 10 of the open portion of the battery can 1 is pressurized by the first roller A (in FIG. 3, the cross-section A' of the first roller is shown), and an inclined section 14 inclined toward the central axis of the battery can is shown. In some cases, the gasket 11 also inclines toward the central axis of the battery can by the first roller A.

[0035] Also, referring to FIGS. 2 and 4, the end 10 of the open portion of the battery can in which the inclined section 14 is formed is pressurized by the second roller B (in FIG. 4, the cross-section B' of the second roller is shown), and a sealed section 15 perpendicular to the side 12 of the battery can is shown. This sealed section 15 can serve to seal the battery can 1 by a subsequent third roller.

[0036] Referring to FIGS. 2 and 5, a battery can having an inclined section 14 and a sealed section 15 formed therein is pressed by a third roller C (in FIG. 5, a cross-section C' of the third roller is shown) between a beading section 100 and an end 10 of an open section, and a flat section 16 is formed. Thereby, a crimping section 200 is formed.

[0037] The process of forming the inclined section 14, the sealed section 15, and the flat section 16 described above is called a crimping process, and is a process of injecting an electrolytic solution into the battery can and then coupling and sealing an upper end cap. Also, the cross-sectional shapes of the first roller to the third roller are different from each other. Further, if necessary, those skilled in the art may change the pressure applied by the first roller to the third roller, the pressure application position, the pressure application area, etc. Further, if necessary, those skilled in the art may control the height change, the rotation direction, the rpm, the moving speed, etc. of the first roller to the third roller respectively, so as to change to enable a desired pressure forming (for example, a crimping process).

[0038] The cylindrical secondary battery 3 includes a battery can 1, a jelly roll type electrode assembly (a structure in which a first electrode, a separator, and a second electrode are laminated and wound) (not shown) accommodated inside the battery can 1, a beading section 100 for attaching a cap assembly 13 coupled to the upper part of the battery can 1, and a crimping section 200 for sealing the battery.

[0039] Here, the cap assembly 13 may have a structure in which an upper cap forming a cathode terminal, a PTC element (Positive temperature coefficient element) that significantly increases the resistance of the battery and cuts off the current when the temperature inside the battery rises, a safety vent that cuts off the current and / or exhausts gas when the pressure inside the battery rises, an insulating member that electrically separates the safety vent from the cap plate at a certain portion, and a cap plate to which a tab connected to the cathode is connected are sequentially laminated. Further, with the gasket 11 mounted, the cap assembly 13 is mounted on the beading portion 100 press-fitted inside by beading the upper end portion of the battery can 1.

[0040] As described above, the multiple roller system may include at least two pairs among the first roller A to the third roller C.

[0041] The crimping process by the first roller A to the third roller C described above is specifically performed in 1 to 3 steps, and the crimping process may be sequentially performed by the first to third rollers.

[0042] Also, referring to FIGS. 3 to 5, the cross-sections of the first to third rollers are different in shape from each other depending on the intended molding, the height of each is controlled, and the rotation axes are also independent.

[0043] According to an embodiment of the present invention, there is provided a multiple roller system in which the inclined section at the end of the open portion of the battery can forms an angle greater than 0 degrees and less than 90 degrees with respect to the central axis of the battery can.

[0044] According to another embodiment, the inclined section at the end of the open portion of the battery can may form an angle greater than 0 degrees, greater than 10 degrees, greater than 20 degrees, greater than 30 degrees, or greater than 40 degrees with respect to the central axis of the battery can.

[0045] According to another embodiment, the inclined section at the end of the opening of the battery can may form an angle of less than 90 degrees, less than 80 degrees, less than 70 degrees, less than 60 degrees, or less than 50 degrees with respect to the central axis of the battery can.

[0046] Specifically, referring to FIG. 3, the inclined section 14 at the end 10 of the opening of the battery can 1 forms an angle of about 30 degrees with respect to the central axis of the battery can.

[0047] According to an embodiment of the present invention, there is provided a multi-roller system in which the length of the flat section is 5% or more and 30% or less based on the diameter of the battery can.

[0048] According to another embodiment, the length of the flat section may be 5% or more, 10% or more, or 15% or more based on the diameter of the battery can.

[0049] According to still another embodiment, the length of the flat section may be 30% or less, 25% or less, or 20% or less based on the diameter of the battery can.

[0050] Specifically, referring to FIG. 5, when the length of the flat section 16 satisfies the above range, the length of the flat section 16 can sufficiently provide a space for performing the subsequent welding process, reduce the defective rate, and ensure structural stability. However, when the length of the flat section 16 is less than 5%, the length of the flat section may be too small to sufficiently provide a space for the subsequent welding process. As a result, the defective rate that may occur during the welding process may increase, or at the welded part, a stable bonding force cannot be exerted, and the structural stability may be reduced. Also, when the length of the flat section 16 exceeds 30%, the end 10 of the opening of the battery can may contact the electrode terminal formed at the center of the upper end of the cap assembly 13, which may cause a short circuit and reduce the performance of the secondary battery.

[0051] According to one embodiment of the present invention, there is provided a multi-roller system in which the pressure applied by the second roller is 101% or more and 300% or less with respect to the pressure applied by the first roller.

[0052] According to other embodiments, the pressure applied by the second roller may be 101% or more, 110% or more, 120% or more, 130% or more, 140% or more, 150% or more, 160% or more, 170% or more, 180% or more, or 190% or more with respect to the pressure applied by the first roller.

[0053] According to other embodiments, the pressure applied by the second roller may be 300% or less, 290% or less, 280% or less, 270% or less, 260% or less, 250% or less, 240% or less, 230% or less, 220% or less, or 210% or less with respect to the pressure applied by the first roller.

[0054] Specifically, referring to FIG. 5, when the pressure applied by the second roller is less than 101% with respect to the pressure applied by the first roller, it may not be easy to further bend the end portion 10 of the open portion of the battery can so as to form a flat section 16 in the crimping portion 200. Also, when the pressure applied by the second roller exceeds 300% with respect to the pressure applied by the first roller, the magnitude of the pressure becomes too large and it may be difficult to adjust the deformation of the end portion 10 of the open portion of the battery can, whereby the defective rate of the product generated by excessive deformation in the process of forming a flat section in the crimping portion may increase.

[0055] According to one embodiment of the present invention, there is provided a forming device for a battery can, a fixing unit provided to fix the battery can; and a forming device for a battery can including the multi-roller system according to any one of the above embodiments.

[0056] Specifically, referring to FIG. 2, the fixing unit 2 wraps the middle or lower part of the battery can 1 so that the battery can 1 is fixed. As an example of the fixing unit 2, a chuck, a jaw, etc. may be used. Also, depending on the formed state of the battery can and the size of the application model, etc., the number of fixing units may vary.

[0057] According to an embodiment of the present invention, there is provided a method for forming a battery can, After arranging an electrode assembly having a structure in which a first electrode, a separator, and a second electrode are sequentially laminated and wound around the battery can and injecting an electrolytic solution, it is formed to have a beading portion that is formed at a side end portion adjacent to the open portion of the battery can and is press-fitted inward, and a first step of laminating a gasket and a cap assembly on the beading portion; A second step of fixing the battery can; A third step of pressing an end portion of the open portion above the beading portion to form an inclined section in which the end portion of the open portion of the battery can is inclined toward the central axis of the battery can; A fourth step of pressing an end portion of the open portion of the battery can in which the inclined section is formed to form a sealed section in which the end portion of the open portion of the battery can is parallel to the side portion of the battery can; A fifth step of pressing an end portion of the open portion of the battery can in which the inclined section and the sealed section are formed to form a flat section parallel to the lower surface of the battery can including, A method for forming a battery can is provided, wherein at least two of the third to fifth steps utilize any one of the above-described multiple roller systems.

[0058] In the above embodiment, the term "first electrode" refers to the anode, and the term "second electrode" refers to the cathode, but the reverse may also be true.

[0059] The cathode includes a cathode current collector and a cathode active material applied to at least one surface of the cathode current collector. Examples of the cathode current collector include, but are not limited to, aluminum or an alloy. Examples of the cathode active material include, but are not limited to, lithium-containing transition metal oxides.

[0060] The anode includes an anode current collector and an anode active material applied to at least one surface of the anode current collector. Examples of the anode current collector may include, but are not limited to, copper or an alloy. Examples of the anode active material include, but are not limited to, carbon materials.

[0061] The separator is a film interposed between the cathode and the anode, and serves to facilitate the movement of ions required to block the circuit while separating the cathode and the anode. Examples of the separator include, but are not limited to, microporous films made of polyolefin-based membranes.

[0062] Also, the battery can is a substantially cylindrical receptacle having an opening formed on one side, and is composed of a conductive metal material. Generally, the side surface of the battery can and the surface opposite to the opening are integrally formed. That is, the battery can generally has a form in which the upper end is open and the lower end has a closed form except for the central portion with respect to its height direction. The lower surface of the battery can may have a substantially flat form. The battery can houses the electrode assembly through an opening formed on one side in its height direction. The battery can can also house the electrolyte together through the opening.

[0063] First, an electrode assembly having a structure in which a first electrode, a separator, and a second electrode are sequentially laminated and wound around the battery can is disposed, and an electrolytic solution is injected. Next, the battery can is formed to have a beading portion that is formed at a side end portion adjacent to the open portion of the battery can and is press-fitted inward. After preparing the battery can with the beading portion formed, a gasket and a cap assembly are laminated on the beading portion. Up to this point corresponds to the pre-process of the crimping process.

[0064] Next, referring to FIGS. 2 to 5, the crimping process performed by the first roller to the third roller is shown.

[0065] Referring to FIGS. 2 and 3, a first roller A (a cross-section A' of the first roller is shown in FIG. 3) presses an end portion 10 of the open portion of the battery can 1 to form an inclined section 14 inclined toward the central axis of the battery can.

[0066] Also, referring to FIGS. 2 and 4, a second roller B (a cross-section B' of the second roller is shown in FIG. 4) presses an end portion 10 of the open portion of the battery can in which the inclined section 14 is formed to form a sealing section 15 perpendicular to the side portion 12 of the battery can. This sealing section 15 may serve to seal the battery can 1 by a subsequent third roller.

[0067] Also, referring to FIGS. 2 and 5, a third roller C (a cross-section C' of the third roller is shown in FIG. 5) presses the battery can in which the inclined section 14 and the sealing section 15 are formed between the beading portion 100 and the end portion 10 of the open portion to form a flat section 16. The process of forming the inclined section 14, the sealing section 15, and the flat section 16 described above is called the crimping process, and it is a process of coupling and sealing the upper cap after injecting the electrolytic solution into the battery can.

[0068] The above-described method is a subdivided crimping process, and it may be sequentially performed from the first stage to the third stage that are subdivided.

[0069] Also, referring to FIGS. 3 to 5, the cross-sections of the first to third rollers are different in shape from each other depending on the intended molding, each can control the height, and the rotation axes are also independent.

[0070] According to one embodiment of the present invention, there is provided a method for forming a battery can in which the inclined section at the end of the open portion of the battery can forms an angle greater than 0 degrees and less than 90 degrees with respect to the central axis of the battery can.

[0071] According to other embodiments, the inclined section at the end of the open portion of the battery can may form an angle greater than 0 degrees, greater than 10 degrees, greater than 20 degrees, greater than 30 degrees, or greater than 40 degrees with respect to the central axis of the battery can.

[0072] According to other embodiments, the inclined section at the end of the open portion of the battery can may form an angle less than 90 degrees, less than 80 degrees, less than 70 degrees, less than 60 degrees, or less than 50 degrees with respect to the central axis of the battery can.

[0073] Specifically, referring to FIG. 3, the inclined section 14 at the end 10 of the open portion of the battery can 1 forms an angle of about 30 degrees with respect to the central axis of the battery can.

[0074] According to one embodiment of the present invention, there is provided a method for forming a battery can in which the length of the flat section is 5% or more and 30% or less based on the diameter of the battery can.

[0075] According to other embodiments, the length of the flat section may be 5% or more, 10% or more, or 15% or more based on the diameter of the battery can.

[0076] According to other embodiments, the length of the flat section may be 30% or less, 25% or less, or 20% or less based on the diameter of the battery can.

[0077] Specifically, referring to FIG. 5, when the length of the flat section 16 satisfies the above range, the length of the flat section 16 can sufficiently provide the space for the subsequent welding process, reduce the defect rate, and ensure the structural stability. However, when the length of the flat section 16 is less than 5%, the length of the flat section may be too small to sufficiently provide the space for the subsequent welding process. As a result, the defect rate that may occur during the welding process may increase, or at the site where the welding is performed, a stable bonding force cannot be exerted, and the structural stability may be reduced. Further, when the length of the flat section 16 exceeds 30%, the end 10 of the open portion of the battery can may contact the electrode terminal formed at the center of the upper end of the cap assembly 13. Thus, there is a problem that the performance of the secondary battery may be reduced due to a short circuit.

[0078] According to an embodiment of the present invention, there is provided a method for forming a battery can, wherein the pressure applied to form the sealed section is 101% or more and 300% or less with respect to the pressure applied to form the inclined section.

[0079] According to another embodiment, the pressure applied by the second roller may be 101% or more, 110% or more, 120% or more, 130% or more, 140% or more, 150% or more, 160% or more, 170% or more, 180% or more, or 190% or more with respect to the pressure applied by the first roller.

[0080] According to another embodiment, the pressure applied by the second roller may be 300% or less, 290% or less, 280% or less, 270% or less, 260% or less, 250% or less, 240% or less, 230% or less, 220% or less, or 210% or less with respect to the pressure applied by the first roller.

[0081] Specifically, referring to FIG. 5, when the pressure applied by the second roller is less than 101% of the pressure applied by the first roller, it may not be easy to further bend the end portion 10 of the open portion of the battery can so as to form the flat section 16 in the crimping portion 200.

[0082] Further, when the pressure applied by the second roller exceeds 300% of the pressure applied by the first roller, the magnitude of the pressure becomes too large, making it difficult to adjust the deformation of the end portion 10 of the open portion of the battery can. As a result, the defective rate of the product caused by excessive deformation may increase during the process of forming the flat section 16 in the crimping portion 200.

[0083] As described above, the preferred embodiments of the present invention have been explained. However, the present invention is not limited thereto, and various modifications can be made and implemented within the scope of the claims and the detailed description of the invention, which also belong to the scope of the present invention.

Explanation of Reference Numerals

[0084] 1 ··· Battery can 2 ··· Fixing unit 3 ··· Cylindrical secondary battery 10 ··· End portion of the open portion (of the battery can) 11 ··· Gasket 12 ··· Side portion of the battery can 13 ··· Cap assembly 14 ··· Inclined section 15 ··· Sealed section 16 ··· Flat section 100 ··· Beading portion 200 ··· Crimping portion A ··· First roller B ··· Second roller C ··· Third roller A' ··· Cross-section of the first roller B' ··· Cross-section of the second roller C' ··· Cross-section of the third roller

Claims

1. A multi-roller system including two or more pairs of rollers, wherein the two or more pairs of rollers rotate with respect to rotation axes independent of each other, and the height change of each is controlled, at least one cross-section of the two or more pairs of rollers has a different shape respectively, the distance between each pair of rollers and the battery can is different respectively, the two or more pairs of rollers include: a pair of first rollers that press the end of the open portion of the battery can so as to form an inclined section in which the end of the open portion of the battery can inclines toward the central axis of the battery can; a pair of second rollers that press the end of the open portion of the battery can in which the inclined section is formed so as to form a sealing section perpendicular to the side of the battery can; and a pair of third rollers that press the side of the open portion of the battery can in which the inclined section and the sealing section are formed so as to form a flat section parallel to the lower surface of the battery can including at least two pairs of a multi-roller system.

2. The multi-roller system according to claim 1, wherein the inclined section forms an angle greater than 0 degrees and less than 90 degrees with respect to the central axis of the battery can.

3. The multi-roller system according to claim 1 or claim 2, wherein the length of the flat section is 5% or more and 30% or less based on the diameter of the battery can.

4. The multi-roller system according to any one of claims 1 to 3, wherein the pressure applied by the second roller is 101% or more and 300% or less with respect to the pressure applied by the first roller.

5. A forming device for a battery can for a secondary battery, comprising: a fixing unit provided to fix the battery can for the secondary battery; and a forming device for a battery can for a secondary battery including the multi-roller system according to any one of claims 1 to 4.

6. A method for forming a battery can, comprising: a first step of disposing an electrode assembly having a structure in which a first electrode, a separator, and a second electrode are sequentially laminated and wound around the battery can, injecting an electrolytic solution, and then forming a beading portion that is formed at a side end adjacent to the open portion of the battery can and is press-fitted inward; laminating a gasket and a cap assembly on the beading portion; a second step of fixing the battery can; a third step of pressing the end of the open portion above the beading portion so as to form an inclined section in which the end of the open portion of the battery can inclines toward the central axis of the battery can; Pressing an end portion of the open portion of the battery can in which the inclined section is formed to form a sealed section in which the end portion of the open portion of the battery can is perpendicular to the side portion of the battery can; and Pressing an end portion of the open portion of the battery can in which the inclined section and the sealed section are formed to form a flat section parallel to the bottom surface of the battery can as a fifth step including At least two steps out of the third step to the fifth step are a method for forming a battery can using the multi-roller system according to any one of claims 1 to 4.

7. The method for forming a battery can according to claim 6, wherein the inclined section of the end portion of the open portion of the battery can forms an angle greater than 0 degrees and less than 90 degrees with reference to the central axis of the battery can.

8. The method for forming a battery can according to claim 6 or claim 7, wherein the length of the flat section is 5% or more and 30% or less based on the diameter of the battery can.

9. The method for forming a battery can according to any one of claims 6 to 8, wherein the pressure applied to form the sealed section is 101% or more and 300% or less with respect to the pressure applied to form the inclined section.

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