Cylindrical battery with reinforced sealing

Abstract

The present invention relates to a cylindrical battery including a cylindrical can containing an electrode assembly, a cap assembly mounted on an opening of the cylindrical can, and a gasket interposed between the cylindrical can and the cap assembly, wherein the upper portion of the cylindrical can has a crimping portion surrounding the outer periphery of the gasket, and an end of the crimping portion has a bent portion that is further bent into the gasket, the bent portion having a length of less than 0.175 mm, a sealing method for the cylindrical battery, and a crimping device for the cylindrical battery. The present invention solves the problem of poor sealing that occurs during primary crimping, which applies a primary pressure, and secondary crimping, which applies a secondary pressure, when sealing a cylindrical battery using a crimping portion. Therefore, the cylindrical battery according to the present invention has the characteristic of having stronger sealing due to the secondary sealing.

Description

[Technical Field]

[0001] The present invention relates to a cylindrical battery with enhanced sealing, and more particularly to a cylindrical battery with enhanced sealing of a crimping portion, a sealing method for the cylindrical battery, and a crimping device for the cylindrical battery. [Background technology]

[0002] Lithium secondary batteries are classified into cylindrical and prismatic batteries, in which an electrode assembly is housed in a cylindrical or prismatic metal case, and pouch-type batteries, in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet, depending on the shape of the battery case. Cylindrical batteries have the advantages of being relatively large in capacity and structurally stable.

[0003] 1 and 2 are two examples of cross-sectional views showing a conventional cylindrical battery. Figures 1 and 2 show a cylindrical battery including an electrode assembly including a positive electrode, a negative electrode, and a separator. The battery also includes a cylindrical can with an upper opening, a cap assembly formed on the outer periphery of the upper part of the cylindrical can and connected to the cylindrical can by a crimping portion formed by bending a portion of the upper opening inward, and a gasket interposed between the cylindrical can and the cap assembly.

[0004] The crimping portion is formed at the top end of the cylindrical can so that the cap assembly can be attached to the open end of the cylindrical can. More specifically, the crimping portion is formed by forming an indentation on the inside of the top end of the cylindrical can by beading, mounting a gasket on the open end, inserting the top cap, PTC element, and outer periphery of the safety vent in that order, and then bending the top end of the cylindrical can inward. As a result, the crimping portion surrounds the gasket located on the inner surface of the crimping portion, and the cap assembly is attached by performing crimping and pressing processes.

[0005] The crimping portion has a structure in which the end is bent inward so that the cap assembly can be stably attached to the open top of the cylindrical can with the gasket interposed therebetween, and the side walls of the crimping portion are formed vertically, similar to the side walls of the battery.

[0006] The material of the cylindrical can is not particularly limited, and it may be made of any one of stainless steel, steel, aluminum, or the equivalent. Since the cylindrical can must be electrically conductive, it uses a metal component, and such a metal component may be susceptible to corrosion when in contact with external moisture.

[0007] Referring to FIG. 1, a cylindrical battery 100 includes a cylindrical can 20 that houses an electrode assembly 10 together with an electrolyte, a cap assembly 30 that is hermetically joined to the open end of the cylindrical can 20, and a gasket 40 that is interposed between the cylindrical can 20 and the cap assembly 30.

[0008] The cap assembly 30 may include a top cap that seals the open end of the cylindrical can 20, and a safety vent 36 that is bent so that one surface contacts the side, top, and bottom surfaces of the top cap and the other surface contacts the inner surface of a gasket 40, and is electrically connected to the electrode assembly 10.

[0009] A battery equipped with such a cap assembly 30 can provide instantaneous high output when used as a power source for a power tool such as an electric drill, and can be stable against external physical shocks such as vibrations and drops.

[0010] In the cap assembly 30, in which the safety vent 36 is bent to surround the top cap, the contact surfaces between the safety vent 36 and the top cap may form one or more connection portions, and the connection portions may be formed by welding or the like. The term "welding" used in the present invention is used to include not only literal welding such as laser welding, ultrasonic welding, and resistance welding, but also fastening methods such as soldering. Welding may be performed during the assembly process of the cap assembly 30 itself, or may be performed after the cap assembly 30 is installed on the cylindrical can 20.

[0011] The safety vent 36 serves to cut off current or release gas when pressure inside the battery increases, and is preferably made of a metal material. The thickness of the safety vent 36 may vary depending on the material and structure, and is not particularly limited as long as it can burst and release gas when a predetermined high pressure is generated inside the battery, and may be, for example, 0.2 to 0.6 mm.

[0012] The thickness of the top cap portion in contact with the safety vent 36 is not particularly limited as long as it is within a range that can protect many components of the cap assembly 30 from external pressure, and may be, for example, 0.3 to 0.5 mm. If the thickness of the top cap portion is too thin, it is difficult to provide mechanical rigidity, and conversely, if it is too thick, it is undesirable because it may increase the size and weight, reducing the capacity of the battery compared to the same specification.

[0013] The gasket 40 has an overall cylindrical shape with both ends open, and one end facing the inner surface of the cylindrical can 20 is preferably bent at a right angle toward the center so as to be placed in the open portion, i.e., the crimping portion, of the cylindrical can 20. The other end of the gasket 40 is initially spread out linearly toward the axial direction of the cylindrical gasket 40, and is bent at a right angle toward the center during the pressing process with the cylindrical can 20, so that the inner and outer circumferential surfaces are folded in close contact with the top cap of the cap assembly 30 and the inner surface of the cylindrical can 20, respectively.

[0014] The gasket 40 is made of an electrically insulating, flexible polymer resin, which must have electrical insulation, impact resistance, elasticity, and durability. Generally, a gasket must have insulating properties, excellent chemical resistance to the electrolyte to prevent electrolyte leakage, and heat resistance to maintain airtightness under the harsh conditions of high temperature and humidity inside the battery. Such gaskets are typically made of polypropylene, but are not limited to this. The gasket 40 may also contain a volatile corrosion inhibitor.

[0015] The electrode assembly 10 preferably has a structure wound up in a so-called "jelly roll" shape, including two electrode plates 11 having opposite polarities and wide roll-shaped plates, and a separator 12 disposed between the electrode plates 11 or on the left or right side of one of the electrode plates 11 to insulate the electrode plates 11 from each other. Of course, the electrode assembly 10 may also have a structure in which positive and negative electrode plates of a predetermined specification are stacked with the separator 12 sandwiched between them.

[0016] Each of the two electrode plates 11 has a structure in which an active material slurry is applied to a current collector in the form of a metal foil or metal mesh containing aluminum and copper. The slurry is typically formed by adding granular active material, auxiliary conductor, binder, plasticizer, etc. to a solvent and stirring the mixture. The solvent is removed in a subsequent process. Uncoated areas where no slurry is applied may exist at the beginning and end of the current collector in the direction in which the electrode plate 11 is wound. A pair of leads corresponding to each electrode plate 11 is attached to the uncoated areas. A first lead 13 attached to the upper end of the electrode assembly 10 is electrically connected to the cap assembly 30, and a second lead (not shown) attached to the lower end of the electrode assembly 10 is connected to the bottom of the cylindrical can 20. Both the first lead 13 and the second lead may extend toward the cap assembly 30. The electrode assembly 10 is preferably disposed on a first insulating plate (not shown) installed at the bottom of the cylindrical can 20, and a second insulating plate (not shown) is preferably disposed at the upper end of the electrode assembly 10. The first insulating plate provides insulation between the electrode assembly 10 and the bottom of the cylindrical can 20 , and the second insulating plate provides insulation between the electrode assembly 10 and the cap assembly 30 .

[0017] The cylindrical can 20 is made of a lightweight, conductive metal material such as aluminum or an aluminum alloy and has a cylindrical structure with an open top and a closed bottom. The electrode assembly 10 and an electrolyte (not shown) are accommodated in the interior space of the cylindrical can 20. The electrolyte transports lithium ions generated by an electrochemical reaction of the electrode plates 11 during charging and discharging of the cylindrical battery 100. The electrolyte may be a non-aqueous organic electrolyte, which is a mixture of lithium salt and a high-purity organic solvent, or a polymer using a polymer electrolyte, but the type of electrolyte is not limited to this invention.

[0018] Meanwhile, a center pin (not shown) may be inserted into the center of the cylindrical can 20 to prevent the electrode assembly 10, which is wound in a jelly roll shape, from unraveling and to serve as a passageway for gas movement inside the cylindrical battery 100. A beading portion 24 is provided at the top of the cylindrical can 20, i.e., the upper end of the electrode assembly 10, by being pressed inward from the outside and bent, thereby preventing the electrode assembly 10 from moving up and down.

[0019] The cap assembly 30 is assembled to the opening of the cylindrical can 20 in a sealed state with a gasket 40 interposed therebetween, and includes a top cap and a safety vent 36. The top cap includes an electrode terminal (not shown) formed to be electrically connected to the outside. The safety vent 36 is bent to surround the outer periphery of the top cap.

[0020] The cylindrical battery 100 may further include a current interrupting device welded to the lower end of the safety vent 36, the lower portion of which may be connected to the electrode assembly 10. Specifically, the safety vent 36 protrudes in a bulging manner at the center and is welded to a current interrupting device (CID) 38, which may be deformed together with the safety vent 36 due to the internal pressure of the cylindrical battery 100 and may be divided into a CID gasket and a CID filter.

[0021] The cylindrical battery 100 may further include an auxiliary gasket. The auxiliary gasket 42 is a gasket for the current interrupting element 38 and is configured to surround the outer circumferential surface of the current interrupting element 38. In particular, the auxiliary gasket 42 contacts the top and side portions of the outer circumferential surface of the current interrupting element 38 to support the top and side portions of the current interrupting element 38. The auxiliary gasket 42 serves to electrically insulate the current interrupting element 38 and the safety vent 36 from each other, except for the portion where the protruding portion of the safety vent 36 contacts the current interrupting element 38.

[0022] The positive electrode lead welded to the positive electrode foil of the jelly-roll-type electrode assembly 10 is electrically connected to the cap assembly 30 and connected to a protruding terminal at the top end of the top cap, and the negative electrode lead welded to the negative electrode foil is welded to the closed end of the cylindrical can 20, so that the cylindrical can 20 itself constitutes the negative electrode terminal. The material of the cylindrical can 20 is not particularly limited and may be made of any one of stainless steel, steel, aluminum, or equivalents. With the electrode assembly 10 housed in the cylindrical can 20, an electrolyte is poured into the cylindrical can 20, and the cap assembly 30 is attached to the open end of the cylindrical can 20 and sealed, completing the assembly of a secondary battery.

[0023] The secondary battery may be a lithium (ion) secondary battery having a high energy density, a high discharge voltage, and high output safety. Such a lithium secondary battery comprises a positive electrode, a negative electrode, a separator 12, and a non-aqueous electrolyte solution containing a lithium salt. The positive electrode is fabricated by, for example, coating a mixture of a positive electrode active material, a conductive material, and a binder on a positive electrode current collector and drying the coating. A filler may be added, if necessary. The negative electrode is fabricated by coating a negative electrode active material on a negative electrode current collector and drying the coating. If necessary, the above-mentioned components may also be added. The separator 12 is interposed between the negative electrode and the positive electrode and is an insulating thin film having high ion permeability and mechanical strength. The lithium salt-containing non-aqueous electrolyte solution comprises a non-aqueous electrolyte solution and a lithium salt. The non-aqueous electrolyte solution may be a liquid non-aqueous electrolyte solution, a solid electrolyte, an inorganic solid electrolyte, or the like. Here, the current collector, electrode active material, conductive material, binder, filler, separator 12, electrolyte, lithium salt, etc. are widely known in the art, and therefore detailed description thereof will be omitted.

[0024] FIG. 2 is another example of a cross-sectional view showing a conventional cylindrical battery. Among the reference numerals shown in FIG. 2, the same components as those shown in FIG. 1 have the same functions. Referring to FIG. 2, the cap assembly 30 may include a top cap that seals the open end of the cylindrical can 20 and is positioned to contact the protruding portion of the gasket 40, a PTC (positive temperature coefficient) element 34 that is positioned to contact the top cap, and a safety vent 36 that is positioned such that one side contacts the PTC element 34 and a portion of the other side contacts the gasket 40. The gasket 40 is the same as the gasket used in FIG. 1.

[0025] The PTC element 34 functions to interrupt current by significantly increasing the battery resistance when the internal temperature of the battery rises. The thickness of the PTC element 34 varies depending on the material and structure, and may be, for example, 0.2 mm to 0.4 mm. If the thickness of the PTC element 34 is thicker than 0.4 mm, the internal resistance increases, increasing the battery size and potentially reducing the battery capacity compared to a battery of the same specification. Conversely, if the thickness of the PTC element 34 is thinner than 0.2 mm, it may not be able to achieve the desired current interruption effect at high temperatures and may be destroyed even by a weak external impact. Therefore, the thickness of the PTC element 34 can be appropriately determined within the above thickness range, taking these factors into consideration.

[0026] The thickness of the top cap portion in contact with the PTC element 34 is not particularly limited as long as it is within a range that can protect the various components of the cap assembly 30 from externally applied pressure, and may be, for example, 0.3 to 0.5 mm. If the thickness of the top cap portion is too thin, it is difficult to exhibit mechanical rigidity, and conversely, if it is too thick, it is undesirable because it may increase the size and weight, reducing the capacity of the battery compared to the same specification.

[0027] In this way, a secondary battery including the cap assembly 30 with a top cap, PTC element 34, and safety vent can be used as a power source for mobile phones, notebook PCs, etc., providing a stable, constant output.

[0028] The present invention relates to a cylindrical battery with enhanced sealing, specifically a cylindrical battery with enhanced sealing of the crimping portion. The following description will be given with schematic illustrations of the components related to the sealing of the crimping portion, including the crimping portion, beading portion, gasket, cylindrical can, and cap assembly.

[0029] A cylindrical battery has an open end and is sealed by a crimping portion formed at the open end. Cylindrical batteries are sealed using a mechanical compression method, and if minute gaps occur between the two interfaces when sealing using this mechanical compression method, the gaps may act as a path for leakage. As a result, cylindrical batteries have a disadvantage of poorer sealing characteristics than pouch-type batteries. When cylindrical batteries are used as power sources for electric vehicles, hybrid vehicles, and the like, they require a long lifespan and many battery cells are densely packed, so the sealing characteristics of such batteries are very important.

[0030] Much research has been done on the sealing of can-type batteries, including cylindrical batteries.

[0031] Patent Document 1 discloses a configuration in which an O-shaped positive electrode ring is inserted into the space formed between the gasket and the sealed can to fill the space, while Patent Document 2 discloses a configuration in which a sealing film is used to improve the airtightness of the internal space between the gasket and the can. Patent Document 3 discloses a configuration in which a sealant and a binder are used to fill the space between the gasket and the can and between the can and the positive electrode plate to improve sealing performance and provide electrical insulation.

[0032] The positive electrode ring and sealing film in Patent Documents 1 and 2 only serve to seal the space between the gasket and the sealed can, and do not explicitly mention the basic characteristics of a washer, such as electrical insulation and corrosion prevention, making it unlikely that the positive electrode ring is used as a washer. The sealant and binder in Patent Document 3 are not components, but rather substances that fill the space between the gasket and the can and between the can and the positive electrode plate. Even if they have insulating and sealing functions, they would not be considered washers. Furthermore, the structure of injecting the sealant and binder in Patent Document 3 is simply for sealing and insulation purposes, and is unlikely to be considered a washer between the gasket and the can that fills the minute gaps in the internal space by absorbing the electrolyte.

[0033] Patent Document 4 discloses a cylindrical can in which the upper end of the crimping portion is bent twice in succession under predetermined conditions to prevent the sealed portion from expanding when subjected to external physical impacts such as vibration or dropping, or when the internal pressure increases, thereby preventing leakage of electrolyte and minimizing deformation such as wrinkles that form on the can when it is bent with a small radius of curvature.

[0034] Patent Document 5 relates to a cylindrical battery that includes a primary crimping die that applies a primary pressure to the end of the upper open portion so that the end of the upper open portion forms a slope that is inclined toward the central axis of the metal can on a vertical cross section, and a secondary crimping die that applies a secondary pressure to the end of the upper open portion where the slope is formed so that a flat section that is parallel to the bottom surface of the metal can is formed in the crimped portion, and a flat section corresponding to the flat section is formed on the bottom surface of the secondary crimping die that faces the end of the upper open portion so that a flat section is formed in the crimped portion.

[0035] Patent Document 4 aims to strengthen sealing, but does not recognize that a unique phenomenon may occur when bending the crimping portion. Patent Document 5 simply aims to form a flat section at the crimping portion to facilitate welding, but does not propose a solution to strengthen sealing.

[0036] In particular, the inventors of the present invention have observed an abnormal phenomenon in which the sealing (pressure) decreases when performing a second or more additional crimping in addition to the first crimping, but the prior art has not even recognized this, nor has it provided a solution to this problem.

[0037] In relation to the above configuration, a simulation was conducted to observe that the pressing force of the crimping part changes between +, 0, and - depending on the length or angle of the bend. Normally, it is recognized that the pressing force increases when a bend part is provided, but the simulation results showed a negative effect in which the pressing force decreases beyond a certain length. This is not something that an ordinary engineer would easily predict. [Prior art documents] [Patent documents]

[0038] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-213126

[0039] [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-079355

[0040] [Patent Document 3] Patent No. 5238153

[0041] [Patent Document 4] Korean Patent Publication No. 10-2008-0053538

[0042] [Patent Document 5] Korean Patent Publication No. 10-2018-0072990 Summary of the Invention [Problem to be solved by the invention]

[0043] The present invention has been made to solve the above problems, and aims to provide a cylindrical battery with enhanced sealing at the crimping part and a method for enhancing sealing at the crimping part of a cylindrical battery by solving the problem of reduced sealing that occurs during primary crimping, which applies a primary pressure, and secondary crimping, which applies a secondary pressure, when sealing a cylindrical battery using the crimping part.

[0044] The secondary crimping mentioned here refers to crimping that is additionally performed after the primary crimping, more specifically, the process of processing the final bend of the crimped portion. [Means for solving the problem]

[0045] To achieve the above object, the present invention provides a cylindrical battery including a cylindrical can containing an electrode assembly, a cap assembly mounted on an opening of the cylindrical can, and a gasket interposed between the cylindrical can and the cap assembly,

[0046] The cylindrical can has a crimped portion at the top that surrounds the outer periphery of the gasket, and a bent portion at an end of the crimped portion that is further bent into the gasket, the bent portion having a length of less than 0.175 mm, which corresponds to less than 31.8% of the thickness of the gasket.

[0047] The length of the bent portion may be 0.15 mm or less, and the length of the bent portion may be 27.2% or less of the thickness of the gasket.

[0048] The bending angle of the bending portion may be from 15 degrees downward to 90 degrees, which is a right angle, relative to the horizontal.

[0049] The gasket may include polybutylene terephthalate (PBT).

[0050] The crimping portion may include a horizontal portion forming a horizontal surface at an uppermost end, and the bent portion may be provided at an end of the horizontal portion.

[0051] The horizontal portion may have a length of 0.9 mm or more.

[0052] The cylindrical can may have a thickness of 0.3 mm or more.

[0053] The present invention also provides a method for sealing a cylindrical battery, the method including: a cylindrical can accommodating an electrode assembly; a cap assembly mounted on an opening of the cylindrical can; and a gasket interposed between the cylindrical can and the cap assembly,

[0054] The method includes bending the top of the cylindrical can to form a crimped portion surrounding the outer periphery of the gasket, and further bending an end of the crimped portion toward the inside of the gasket to form a folded portion, wherein the length of the folded portion is less than 0.175 mm, and the length of the folded portion corresponds to less than 31.8% of the thickness of the gasket.

[0055] The length of the bent portion may be 0.15 mm or less, and the length of the bent portion may be 27.2% or less of the thickness of the gasket.

[0056] The bending angle of the bending portion may be from 15 degrees downward to 90 degrees, which is a right angle, relative to the horizontal.

[0057] The gasket may include polybutylene terephthalate (PBT).

[0058] The crimping portion may include a horizontal portion forming a horizontal surface at an uppermost end, and the bent portion may be provided at an end of the horizontal portion.

[0059] The horizontal portion may have a length of 0.9 mm or more.

[0060] The cylindrical can may have a thickness of 0.3 mm or more.

[0061] The present invention also provides a battery pack including the cylindrical battery.

[0062] The present invention also provides a cylindrical battery crimping device that processes the top of a cylindrical battery can to form a crimped portion that surrounds the outer periphery of a gasket, the device including three jaws that secure the sides of the cylindrical can, one or more crimping sections that crimp the cylindrical battery in stages, and a final crimping section that finally crimps the cylindrical battery, wherein the final crimping section further folds the end of the crimped portion into the inside of the gasket with a length of less than 0.175 mm, which corresponds to less than 31.8% of the gasket thickness.

[0063] The length of the bent portion may be 0.15 mm or less, and the length of the bent portion may be 27.2% or less of the thickness of the gasket.

[0064] The bending angle of the bending portion may be from 15 degrees downward to 90 degrees, which is a right angle, relative to the horizontal.

[0065] The crimping portion may include a horizontal portion forming a horizontal surface at an uppermost end, and the bent portion may be provided at an end of the horizontal portion.

[0066] The horizontal portion may have a length of 0.9 mm or more.

[0067] The cylindrical can may have a thickness of 0.3 mm or more.

[0068] The present invention can also be provided as a configuration in which the above-mentioned problems to be solved are combined in any desired manner. [Effects of the Invention]

[0069] As described above, the present invention provides a cylindrical battery including a cylindrical can containing an electrode assembly, a cap assembly mounted on an opening of the cylindrical can, and a gasket interposed between the cylindrical can and the cap assembly, wherein the upper part of the cylindrical can is provided with a crimping portion surrounding the outer periphery of the gasket, and an end of the crimping portion is provided with a bent portion that is further bent into the inside of the gasket, and the length of the bent portion is less than 0.175 mm.

[0070] The present invention also provides a method for sealing a cylindrical battery including a cylindrical can containing an electrode assembly, a cap assembly mounted on an opening of the cylindrical can, and a gasket interposed between the cylindrical can and the cap assembly, the method including: bending an upper portion of the cylindrical can to form a crimped portion surrounding an outer periphery of the gasket; and further bending an end of the crimped portion toward the inside of the gasket to form a folded portion, wherein the length of the folded portion is less than 0.175 mm.

[0071] The present invention also provides a cylindrical battery crimping device that processes the top of a cylindrical battery can to form a crimped portion that surrounds the outer periphery of a gasket, the device including three jaws that secure the sides of the cylinder of the cylindrical can, one or more crimping portions that crimp the cylindrical battery in stages, and a final crimping portion that finally crimps the cylindrical battery, wherein the final crimping portion further folds the end of the crimped portion into the inside of the gasket with a bending portion length of less than 0.175 mm.

[0072] As a result, the problem of poor sealing that occurs during the primary crimping process where a primary pressure is applied and the secondary crimping process where a secondary pressure is applied in sealing the crimping part of a cylindrical battery has been solved.The cylindrical battery according to the present invention has the feature that the sealing is further strengthened by the secondary sealing. [Brief explanation of the drawings]

[0073] [Figure 1] FIG. 1 is a diagram showing an example of a cross-sectional view of a cylindrical battery.

[0074] [Figure 2] FIG. 10 is a diagram showing another example of a cross-sectional view showing a cylindrical battery.

[0075] [Figure 3] 1 is a schematic diagram of a crimping section according to the present invention;

[0076] [Figure 4] 10A and 10B are diagrams illustrating exemplary calculation methods performed in simulations according to the present invention.

[0077] [Figure 5] 10 is a diagram showing another example of a calculation method performed by a simulation according to the present invention. FIG.

[0078] [Figure 6] FIG. 10 is a diagram showing a simulation result according to the present invention.

[0079] [Figure 7] 1 is an exploded perspective view of a clipping device according to the present invention;

[0080] [Figure 8] 1 is a cross-sectional view of a clipping device according to the present invention;

[0081] [Figure 9] FIG. 2 is a partial enlarged view of the final clipping processing portion according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0082] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that will enable a person of ordinary skill in the art to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0083] Furthermore, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0084] FIG. 3 is a schematic diagram of a crimping section according to the present invention. FIG. 3 is a simplified schematic diagram of the crimping section for simulation purposes. A cylindrical battery is provided with a beading section 24, and a gasket 40 is primarily sealed by the crimping section 21, which also seals the cap assembly 30. The crimping section 21 includes a horizontal section 26 that forms a horizontal surface at its uppermost end, and a bent section 25 is provided at the end of the horizontal section 26. The length of the bent section 25 and the bent angle 25D of the bent section are variables used in the simulation.

[0085] Table 1 is a list of the sets used to perform simulations in an embodiment of the present invention.

[0086] [Table 1]

[0087] The simulation was carried out in the following interpretation manner.

[0088] Secondary crimping was simulated using interference fit analysis. Tertiary crimping was simulated by applying a hinge (edge) and boundary conditions to the bending part of the cylindrical can. The contact pressure of the gasket (PBT) was calculated according to the angle of the bend. The gasket used in the simulation was 0.55 mm thick and made of PBT. The physical properties of the PBT were calculated by dividing it into an elastic region and a plastic region. Plastic stress of 42 MPa or less was considered to be in the elastic region, and stress was calculated by multiplying the elastic modulus (1567) by the elongation rate. For the plastic region, a plastic stress-plastic strain curve was used.

[0089] The length of the horizontal part was calculated based on a minimum of 0.9 mm. The cylindrical can was made of nickel-plated steel, and the thickness of the crimping area was considered to be 0.3 mm.

[0090] FIG. 4 is an example of a calculation method performed by a simulation according to the present invention, and FIG. 5 is another example of a calculation method performed by a simulation according to the present invention.

[0091] 4 and 5, the dark gray areas on the left side of FIGS. 4 and 5 are areas where contact pressure was calculated. FIGS. 4 and 5 show the pressure inside and outside the gasket for one case. The upper left part of the dark gray area, i.e., the beginning of the U-shape, was designated as 0, and the contact pressure corresponding to each part was calculated by moving along this. The calculation results for one example are shown on the right side of FIGS. 4 and 5. The contact pressure in the graph on the right was integrated by length to calculate the contact pressure for each part, and all cases in FIGS. 4 and 5 were combined to derive the overall contact pressure for one case. The dark gray areas in FIGS. 4 and 5 are areas where sealing is actually achieved by the gasket, and the contact pressure was calculated in all of these areas to determine the pressure generated by overall sealing.

[0092] FIG. 6 shows the results of a simulation according to the present invention.

[0093] Referring to Figure 6, when the bending length is 0.15mm or less, the contact pressure increases as the bending angle of the bending increases. In other words, sealing by additional bending is only effective when the bending length is 0.15mm or less, and it was found to have an adverse effect when the bending length exceeds 0.15mm. When compared to a gasket thickness of 0.55mm, this corresponds to a case where the contact pressure is less than 27.3% of the gasket thickness.

[0094] When the bending length is 0.175mm or more, the contact pressure actually decreases as the bending angle increases. Compared to a gasket thickness of 0.55mm, this corresponds to a value of 31.8% or more of the gasket thickness. In other words, sealing with additional bending parts is understood to have an adverse effect. This is interpreted as a decrease in contact pressure due to the creation of dead space between the gasket and the cylindrical can caused by the bending part. It is also interpreted as a decrease in contact pressure due to the significant plastic deformation of the gasket caused by the bending part.

[0095] When performing secondary sealing at the bends, it can be seen that, contrary to normal expectations, the contact pressure (sealing strength) may actually decrease. In order to strengthen the sealing at the bends, the bends must not create a dead space between the gasket and the cylindrical can, and the size and angle of the bends must be limited to a range that does not cause significant plastic deformation of the gasket.

[0096] The crimping section usually consists of two or more stages, and the top of the cylindrical can is crimped by bending it in stages. Three jaws hold the cylindrical can in place based on the beading of the can, and the end of the cylindrical can is bent and deformed by the crimping section that descends from the top.

[0097] In the crimping device of the present invention, the crimping process normally performed is the same as that of the conventional crimping device. The crimping process, which is performed in stages, is performed sequentially along a circular track by a cam-type device. However, since the crimping device of the present invention is characterized by the final crimping section, only this section is shown in Figures 7 to 9.

[0098] FIG. 7 is an exploded perspective view of a crimping device according to the present invention, FIG. 8 is a cross-sectional view of a crimping device according to the present invention, and FIG. 9 is a partially enlarged view of a final crimping processing portion according to the present invention.

[0099] 7 to 9, a cylindrical battery crimping device is provided that processes the top of a cylindrical can of a cylindrical battery 100 to form a crimped portion surrounding the outer periphery of a gasket, the device including three jaws 50 that secure the sides of the cylindrical can, one or more crimping sections that crimp the cylindrical battery in stages, and a final crimping section 60 that finally crimps the cylindrical battery, where the final crimping section 60 further folds the end of the crimped portion into the inside of the gasket with a length of less than 0.175 mm. The length of the folded portion corresponds to less than 31.8% of the thickness of the gasket.

[0100] In order to show the state in which the jaws and the final crimping section 60 are joined together, the cylindrical battery is omitted from Figure 8. The four diagrams at the bottom of Figure 9 are enlarged views of the portion that is actually crimped in the final crimping section 60. Referring to Figures 9 and 3, the portion enclosed by a dotted square in the four diagrams at the bottom of Figure 9 is the portion that contacts the horizontal section 26, which forms a horizontal plane at the top of the crimping section 21 of the cylindrical battery. In actual processing, the horizontal section 26 has already been bent by the previous crimping section, but it also comes into contact during the final crimping process.

[0101] The dotted circle in Figure 9 is the area where the folding portion 25 at the end of the horizontal portion 26 is processed. The length of the folding portion 25 is 0.175 mm, which corresponds to less than 31.8% of the gasket thickness. Because the final crimping portion 60 shown in Figure 9 only folds the cylindrical can 20 without performing any additional cutting, the length of the inclined surface of the circle in Figure 9 must not be much longer than the 0.175 mm length of the folding portion 25. Because the folding portion 25 contacts the gasket 40 and is inserted into the gasket 40, the length of the inclined surface of the circle in Figure 9 must be shorter than or approximately the same as the length of the folding portion 25. If the length of the inclined surface of the final crimping portion 60 is too long, it may damage the gasket.

[0102] The angle at which the bending portion 25 is bent downward from the horizontal is between 15 degrees and 90 degrees, which is a right angle, so the angle of the inclined surface of the circular portion in Figure 9 must also be between 15 degrees and 90 degrees, which is a right angle. The bottom part of Figure 9 shows this separately for each case.

[0103] That is, the final crimping processing portion according to the present invention includes a horizontal processing portion that contacts the horizontal portion 26 and a folding processing portion for processing the folding portion 25, and the length of the folding processing portion must be shorter than or approximately the same as the length of the folding portion 25, preferably less than the length of the folding portion 25, and the angle formed between the horizontal processing portion and the folding processing portion is greater than 15 degrees and less than 90 degrees, which is a right angle.

[0104] Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content. [Explanation of symbols]

[0105] 10 Electrode assembly

[0106] 11 Electrode plate

[0107] 12 Separation membrane

[0108] 13 First Lead

[0109] 20 cylindrical cans

[0110] 21 Crimping section

[0111] 24 Beading section

[0112] 25 Bend section

[0113] 25D Bending angle of the bending part

[0114] 26 Horizontal section

[0115] 30 Cap assembly

[0116] 34 PTC element

[0117] 36 Safety Vent

[0118] 38 Current interruption device

[0119] 40 gasket

[0120] 42 Auxiliary gasket

[0121] 50 Jaw

[0122] 60 Final crimping processing section

[0123] 100 Cylindrical Battery

Claims

1. a cylindrical can containing the electrode assembly; a cap assembly mounted on the opening of the cylindrical can; a gasket interposed between the cylindrical can and the cap assembly; A cylindrical battery comprising: The upper portion of the cylindrical can is provided with a crimping portion surrounding the outer periphery of the gasket; The end of the crimping portion is provided with a folding portion that can be further folded into the inside of the gasket, A cylindrical battery, wherein the length of the bent portion is less than 0.175 mm.

2. 2. The cylindrical battery according to claim 1, wherein the length of the bent portion is 0.15 mm or less.

3. 2. The cylindrical battery according to claim 1, wherein the bending angle of the bending portion is from 15 degrees downward to 90 degrees, i.e., a right angle, relative to the horizontal.

4. The crimping portion includes a horizontal portion at its uppermost end that forms a horizontal surface, The cylindrical battery according to claim 1 , wherein the bent portion is provided at an end of the horizontal portion.

5. 5. The cylindrical battery according to claim 4, wherein the horizontal portion has a length of 0.9 mm or more.

6. 2. The cylindrical battery according to claim 1, wherein the cylindrical can has a thickness of 0.3 mm or more.

7. a cylindrical can containing the electrode assembly; a cap assembly mounted on the opening of the cylindrical can; a gasket interposed between the cylindrical can and the cap assembly; A method for sealing a cylindrical battery, comprising: bending an upper portion of the cylindrical can to form a crimp that surrounds an outer periphery of the gasket; and further bending the end of the crimping portion toward the inside of the gasket to form a bent portion, The length of the bent portion is less than 0.175 mm.

8. The method for sealing a cylindrical battery according to claim 7, wherein the length of the bent portion is 0.15 mm or less.

9. The method for sealing a cylindrical battery according to claim 7, wherein the bending angle of the bending portion is from 15 degrees downward to 90 degrees perpendicular to the horizontal.

10. The crimping portion includes a horizontal portion at its uppermost end that forms a horizontal surface, The method of claim 7 , wherein the bent portion is provided at an end of the horizontal portion.

11. The method for sealing a cylindrical battery according to claim 10, wherein the horizontal portion has a length of 0.9 mm or more.

12. A crimping device for cylindrical batteries that processes the top of a cylindrical can to form a crimped portion that surrounds the outer periphery of a gasket, Three jaws for fixing the cylindrical side of the cylindrical can; One or more crimping units that crimp the cylindrical battery in stages; a final crimping section that performs final crimping on the cylindrical battery; Including, A crimping device for cylindrical batteries, wherein the length of the bent portion where the final crimping processing portion further bends the end of the crimping portion into the inside of the gasket is less than 0.175 mm.

13. The cylindrical battery crimping device according to claim 12, wherein the length of the bent portion is 0.15 mm or less.

14. The cylindrical battery crimping device according to claim 12, wherein the bending angle of the bending portion is from 15 degrees downward to 90 degrees perpendicular to the horizontal.

15. The crimping portion includes a horizontal portion at its uppermost end that forms a horizontal surface, The cylindrical battery crimping device according to claim 12 , wherein the bent portion is provided at an end of the horizontal portion.

16. The cylindrical battery crimping device according to claim 15, wherein the horizontal portion has a length of 0.9 mm or more.

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