Cylindrical lithium ion secondary battery

Abstract

The present invention relates to a cylindrical lithium ion secondary battery capable of preventing deformation of a cap assembly to improve safety when an upper end of a cylindrical can is clamped. For example, disclosed is a cylindrical lithium ion secondary battery, the battery comprising: a cylindrical can; an electrode assembly accommodated in the cylindrical can; and a cap assembly for sealing the cylindrical can, wherein: the cover assembly includes a top plate having a notch formed thereon, a support plate disposed in close contact with a lower surface of the top plate and including a first through hole formed through a center thereof; a bottom plate electrically connected with the electrode assembly and protruding upward at a central portion to be connected to a lower surface of the top plate through the first through hole; and an insulating plate located between the support plate and the bottom plate and having a through hole located at a center to correspond to the first through hole of the support plate, and the support plate has a strength greater than a strength of the top plate.

Description

[0001] This application is a divisional application of a patent application with an application date of December 13, 2017, application number 201780098162.5, and invention name “Cylindrical lithium-ion secondary battery”. Technical Field

[0002] The invention relates to a cylindrical lithium ion secondary battery. Background Art

[0003] Lithium ion secondary batteries are widely used as power sources for portable electronic devices and hybrid cars or electric vehicles due to various advantages including high operating voltage, high energy density per unit weight, etc.

[0004] Lithium-ion secondary batteries can be generally classified into cylindrical secondary batteries, prismatic secondary batteries, and pouch-type secondary batteries. Specifically, a cylindrical lithium-ion secondary battery generally includes a cylindrical electrode assembly, a cylindrical can coupled to the electrode assembly, an electrolyte injected into the can to move lithium ions, and a cap assembly coupled to one side of the can to prevent electrolyte leakage and separation of the electrode assembly. Summary of the invention

[0005] Technical issues Various embodiments of the present invention provide a cylindrical lithium ion secondary battery that can prevent deformation of a cap assembly when an upper end of a cylindrical can is clamped to improve safety.

[0006] Technical Solution According to various embodiments of the present invention, there is provided a cylindrical lithium-ion secondary battery, comprising: a cylindrical can; an electrode assembly housed in the cylindrical can; and a cover assembly for sealing the cylindrical can, wherein the cover assembly comprises a top plate having a recess formed thereon, a support plate closely disposed with respect to a lower surface of the top plate and comprising a first through hole formed through a center thereof, and a bottom plate electrically connected to the electrode assembly and connected to the lower surface of the top plate through the first through hole; wherein the support plate has a strength greater than that of the top plate.

[0007] The support plate may include a first region having the first through holes formed thereon, a second region at an outer side of the first region and positioned lower than the first region, and a third region connecting the first and second regions to each other and including a plurality of second through holes formed thereon.

[0008] The third region may be formed to be inclined so as to disperse stress generated when the upper end of the cylindrical can is clamped to fix the cap assembly to the cylindrical can.

[0009] An annular groove may be formed on the second region to disperse stress generated when the upper end of the cylindrical can is clamped to fix the cap assembly to the cylindrical can.

[0010] The groove may be formed to have a depth of 5% to 20% of the thickness of the support plate.

[0011] The cylindrical lithium ion secondary battery may further include an insulating plate located between the support plate and the bottom plate and having a through hole at a center position corresponding to the first through hole of the support plate.

[0012] If the internal gas pressure of the cylindrical tank is greater than a predetermined working pressure and less than a predetermined rupture pressure, the top plate may be deformed to convexly upward, and the top plate may then be electrically disconnected from the bottom plate.

[0013] If the internal gas pressure of the cylindrical tank is greater than a predetermined rupture pressure, the notch of the top plate may rupture.

[0014] The cylindrical lithium ion secondary battery may further include an insulating gasket located between the cap assembly and the cylindrical can and insulating the cap assembly and the cylindrical can from each other.

[0015] Advantageous Effects of the Invention As described above, the cylindrical lithium ion secondary battery according to various embodiments of the present invention includes a support plate having strength greater than that of a top plate to relieve stress generated toward the center of a cap assembly when the upper end of a cylindrical can is clamped, thereby preventing deformation of the top plate and improving safety.

[0016] A cylindrical lithium ion secondary battery according to various embodiments of the present invention includes a support plate having a stepped portion to disperse stress generated toward the center of a cap assembly when an upper end of a cylindrical can is clamped, thereby preventing deformation of a top plate and improving safety.

[0017] A cylindrical lithium ion secondary battery according to various embodiments of the present invention includes a support plate having a groove to disperse stress generated toward the center of a cap assembly when an upper end of a cylindrical can is clamped, thereby preventing deformation of a top plate and improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a perspective view of a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0019] Figure 2 is a cross-sectional view of a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0020] Figure 3 is an enlarged cross-sectional view showing only a cap assembly of a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0021] Figure 4 is a plan view showing a support plate of a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0022] Figure 5 is a cross-sectional view illustrating stress generated when a crimping portion is formed in a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0023] Figure 6 FIG. 4 is a cross-sectional view of a cylindrical lithium-ion secondary battery according to another embodiment of the present invention.

[0024] Figure 7 is a plan view showing a support plate of a cylindrical lithium ion secondary battery according to another embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present invention will be described in detail.

[0026] However, the embodiments of the present invention may be modified in many different forms and should not be interpreted as limited to the example (or exemplary) embodiments set forth herein. Rather, these example embodiments are provided so that the present invention will be thorough and complete and will convey aspects and features of the present invention to those skilled in the art.

[0027] In addition, in the accompanying drawings, for simplicity and clarity, the size or thickness of various components is exaggerated. The same reference numerals always refer to the same elements. As used herein, the term "and / or" includes any combination and all combinations of one or more of the related listed items. In addition, it will be understood that when element A is referred to as "connected to" element B, element A can be directly connected to element B, or an intermediate element C can be present between element A and element B, so that element A and element B are indirectly connected to each other.

[0028] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. It will also be understood that when the terms "comprise" and / or "comprising" are used in this specification, it means that there are stated features, quantities, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, quantities, steps, operations, elements, components and / or their groups.

[0029] It will be understood that, although the terms first, second, etc. can be used here to describe various members, elements, regions, layers and / or parts, these members, elements, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish a member, element, region, layer and / or part from another member, element, region, layer and / or part. Therefore, for example, without departing from the teachings of the present invention, the first member, first element, first region, first layer and / or first part discussed below can be named as the second member, second element, second region, second layer and / or second part.

[0030] For ease of description, spatially relative terms such as "under", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature to another (other) element or feature as shown in the figure. It will be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the elements or features in the figure are turned over, the elements described as "under" or "beneath" other elements or features will then be positioned as "on" or "above" the other elements or features. Therefore, the exemplary term "under" can include both above and below orientations.

[0031] Figure 1 is a perspective view of a cylindrical lithium ion secondary battery according to an embodiment of the present invention. Figure 2 is a cross-sectional view of a cylindrical lithium ion secondary battery according to an embodiment of the present invention. Figure 3 is an enlarged cross-sectional view showing only a cap assembly of a cylindrical lithium ion secondary battery according to an embodiment of the present invention. Figure 4 is a plan view showing a support plate of a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0032] Reference Figures 1 to 4 , the cylindrical lithium ion secondary battery 100 according to the embodiment includes a cylindrical can 110, an electrode assembly 120, and a cap assembly 140. In some cases, the cylindrical lithium ion secondary battery 100 may further include a center pin 130.

[0033] The cylindrical can 110 includes a circular bottom 111 and a side wall 112 extending upward from the bottom 111 by a predetermined length. In the process of manufacturing the secondary battery, the top or top end of the cylindrical can 110 remains open. Therefore, in the process of assembling the secondary battery, the electrode assembly 120 and the center pin 130 can be placed in the cylindrical can 110 together with the electrolyte. The cylindrical can 110 can be made of steel, steel alloy, aluminum, aluminum alloy or their equivalents, but the embodiments of the present invention are not limited thereto. In addition, an inwardly recessed curling portion 113 can be formed below the cap assembly 140 to prevent the cap assembly 140 from deviating to the outside, and an inwardly bent crimping portion 114 can be formed on or above the curling portion 113.

[0034] The electrode assembly 120 is housed in the cylindrical can 110. The electrode assembly 120 includes a negative electrode plate 121 coated with a negative electrode active material (e.g., graphite or carbon), a positive electrode plate 122 coated with a positive electrode active material (e.g., a transition metal oxide such as LiCoO2, LiNiO2, or LiMn2O4), and a separator 123 disposed between the negative electrode plate 121 and the positive electrode plate 122 to prevent a short circuit between the negative electrode plate 121 and the positive electrode plate 122 while allowing only lithium ions to move. The negative electrode plate 121, the positive electrode plate 122, and the separator 123 are wound into a substantially cylindrical shape or a cylindrical configuration. Here, the negative electrode plate 121 may be formed of copper (Cu) foil, the positive electrode plate 122 may be formed of aluminum (Al) foil, and the separator 123 may be made of polyethylene (PE) or polypropylene (PP), but embodiments of the present invention are not limited thereto. In addition, the negative electrode tab 124 may be welded to the negative electrode plate 121 to protrude downward from the negative electrode plate 121 and extend a predetermined length, and the positive electrode tab 125 may be welded to the positive electrode plate 122 to protrude upward from the positive electrode plate 122 and extend a predetermined length, or vice versa. In addition, the negative electrode tab 124 may be made of nickel (Ni), and the positive electrode tab 125 may be made of aluminum (Al), but the embodiment of the present invention is not limited thereto.

[0035] In addition, the negative electrode tab 124 of the electrode assembly 120 may be welded to the bottom 111 of the cylindrical can 110. Thus, the cylindrical can 110 may be used as a negative electrode. In other embodiments, the positive electrode tab 125 may be welded to the bottom 111 of the cylindrical can 110. In these embodiments, the cylindrical can 110 may be used as a positive electrode.

[0036] In addition, a first insulating plate 126 may be interposed between the electrode assembly 120 and the bottom 111 of the cylindrical can 110, wherein the first insulating plate 126 is coupled to the cylindrical can 110 and has a first hole 126a formed at the center thereof and a second hole 126b formed near the first hole 126a. The first insulating plate 126 may prevent the electrode assembly 120 from electrically contacting the bottom 111 of the cylindrical can 110. Specifically, the first insulating plate 126 prevents the positive electrode plate 122 of the electrode assembly 120 from electrically contacting the bottom 111. Here, when a relatively large amount of gas is generated due to an abnormality in the secondary battery, the first hole 126a allows the gas to quickly move upward via the center pin 130, and the second hole 126b allows the negative electrode tab 124 to pass therethrough to be welded to the bottom 111.

[0037] In addition, a second insulating plate 127 may be placed between the electrode assembly 120 and the cap assembly 140, wherein the second insulating plate 127 is coupled to the cylindrical can 110 and has a first hole 127a formed at the center thereof and a plurality of second holes 127b formed around the first hole 127a. The second insulating plate 127 may prevent the electrode assembly 120 from electrically contacting the cap assembly 140. Specifically, the second insulating plate 127 prevents the negative electrode plate 121 of the electrode assembly 120 from electrically contacting the cap assembly 140. Here, when a relatively large amount of gas is generated due to an abnormality in the secondary battery, the first hole 127a allows the gas to quickly move to the cap assembly 140, and the second hole 127b allows the positive electrode tab 125 to pass therethrough to be welded to the cap assembly 140. In addition, during the injection of the electrolyte, the other second holes 127b allow the electrolyte to quickly flow into the electrode assembly 120.

[0038] In addition, since the diameter of the first hole 126a of the first insulating plate 126 and the diameter of the first hole 127a of the second insulating plate 127 are smaller than the diameter of the center pin 130, the center pin 130 can be prevented from electrically contacting the bottom 111 of the cylindrical can 110 or the cover assembly 140 due to external impact.

[0039] The center pin 130 is a hollow cylindrical tube and may be coupled to a substantially central region of the electrode assembly 120. The center pin 130 may be made of steel, steel alloy, aluminum, aluminum alloy, or polybutylene terephthalate, but the embodiments of the present invention are not limited thereto. The center pin 130 may suppress deformation of the electrode assembly 120 during charging and discharging of the secondary battery and may serve as a moving passage for gas generated in the secondary battery.

[0040] The cap assembly 140 may include a top plate 141 , a support plate 142 , an insulation plate 143 , and a bottom plate 144 .

[0041] The top plate 141 may include a substantially flat first surface 141a and a substantially flat second surface (or lower surface) 141b opposite to the first surface, and may further include at least one notch 141c formed on the lower surface 141b. The notch 141c may be broken when the internal gas pressure of the secondary battery is greater than a predetermined fracture pressure, thereby quickly releasing the internal gas of the secondary battery to the outside.

[0042] In addition, the top plate 141 may include an upper region 141d, a side region 141e, and a lower region 141f. The upper region 141d may be positioned on the support plate 142 and may be substantially flat. The upper region 141d may be used as a terminal of the secondary battery and may be electrically connected to an external device (e.g., a load or a charger). The side region 141e may be bent downward from the upper region 141d to substantially surround the side of the support plate 142. The lower region 141f is bent horizontally inward from the side region 141e and then positioned at the bottom of the support plate 142. In this way, the top plate 141 may be formed integrally with the support plate 142 by the upper region 141d, the side region 141e, and the lower region 141f.

[0043] The top plate 141 may be made of, for example, aluminum, aluminum alloy, or their equivalents, but the embodiments of the present invention are not limited to the above materials. Therefore, a bus bar or an external lead made of aluminum may be easily welded to the top plate 141. Specifically, the top plate 141 may be made of soft aluminum having a first strength, and thus may be broken when the internal gas pressure of the secondary battery is greater than or equal to a predetermined reference pressure.

[0044] In some cases, the top plate 141 may also include a curved region 141g formed at the upper region 141d. When viewed from below, the curved region 141g may be shaped as a substantially circular ring. As an example, the upper region 141d located inside the curved region 141g may be positioned higher than the upper region 141d located outside the curved region 141g. In addition, the notch 141c may be formed on the upper region 141d located inside the curved region 141g.

[0045] The support plate 142 may be positioned under the top plate 141, and may include a first region 142a, a second region 142b, and a third region 142c. The first region 142a may be formed at a region corresponding to the upper region of the top plate 141. Specifically, the first region 142a is formed close to the upper region 141d of the top plate 141 located inside the curved region 141g. In addition, the first through hole 142d is formed approximately at the center of the first region 142a. Here, the bottom plate 144, which will be described later, may pass through the first through hole 142d and then be electrically connected to the top plate 141, and the first through hole 142d may allow the internal gas pressure to be directly applied to the top plate 141. The second region 142b is positioned at the outer side of the first region 142a and is positioned lower than the first region 142a. That is, a step difference is generated between the first region 142a and the second region 142b. Specifically, the second area 142b is arranged close to the upper area 141d located outside the curved area 141g of the top plate 141. Therefore, the second area 142b is surrounded by the upper area 141d, the side area 141e and the lower area 141f located outside the curved area 141g. The third area 142c is located between the first area 142a and the second area 142b and connects the first area 142a and the second area 142b to each other. In addition, the third area 142c can be tilted (bent) so that the first area 142a and the second area 142b with different heights are connected to each other. That is, the third area 142c is formed to correspond to the curved area 141g of the top plate 141. In this way, the support plate 142 is generally configured to contact the lower surface 141b of the top plate 141.

[0046] In addition, the third region 142c can prevent deformation of the cap assembly 140 by dispersing the force applied to the cap assembly 140 (particularly the stress generated toward the center of the cap assembly 140 when the upper end of the cylindrical can 110 is clamped). In addition, a plurality of second through holes 142e are formed in the third region 142c. Here, the second through holes 142e can allow the internal gas pressure to be directly applied to the top plate 141. For example, the recess 141c formed on the lower surface 141b of the top plate 141 can be positioned at an area corresponding to the first region 142a located between the first through hole 142d and each second through hole 142e of the support plate 142, but embodiments of the present invention are not limited thereto.

[0047] The support plate 142 may be made of aluminum, aluminum alloy, or their equivalents. Specifically, the support plate 142 may be made of rigid aluminum having a second strength higher than the first strength of the top plate 141. Therefore, when an external force is applied to the cap assembly 140, particularly when the upper end of the cylindrical can 110 is clamped, the support plate 142 may prevent deformation of the top plate 141 by supporting the top plate 141.

[0048] The insulating plate 143 may be positioned below the support plate 142 (attached to the bottom of the support plate 142), and may include a through hole 143a positioned to correspond to the first through hole 142d. When viewed from below, the insulating plate 143 may be shaped as a substantially circular ring having a predetermined width. In addition, the insulating plate 143 is used to insulate the support plate 142 and the bottom plate 144 from each other. For example, the insulating plate 143 may be located between the support plate 142 and the bottom plate 144, and may be subjected to ultrasonic welding, but embodiments of the present invention are not limited thereto.

[0049] The insulating plate 143 may be made of, for example, polyethylene (PE), polypropylene (PP), ethylene propylene diene monomer (M-type) rubber (EPDM rubber), or equivalents thereof, but embodiments of the present invention are not limited to the above materials.

[0050] The bottom plate 144 is electrically connected to the top plate 141 through the through hole 143a of the insulating plate 143 and the first through hole 142d of the support plate 142, and then attached to the insulating plate 143. That is, the bottom plate 144 may include a first region 144a connected (welded) to the upper region 141d of the top plate 141, a second region 144b bent from the first region 144a and passing through the first through hole 142d of the support plate 142 and the through hole 143a of the insulating plate 143, and a third region 144c bent from the second region 144b and attached to the insulating plate 143. Figure 3 , an undefined reference numeral 144 e refers to a welding region where the first region 144 a of the bottom plate 144 is welded to the lower surface 141 b of the upper region 141 d of the top plate 141 .

[0051] Here, the positive electrode tab 125 may be electrically connected to the third region 144c of the bottom plate 144. In addition, one or more notches 144d may also be formed on the first region 144a of the bottom plate 144. When the internal gas pressure of the secondary battery is greater than a predetermined reference pressure, the top plate 141 may be deformed to convexly bulge upward, and the notch 144d may be used to electrically separate the first region 144a from the second region 144b of the bottom plate 144. Therefore, the current path between the top plate 141 and the bottom plate 144 may be blocked.

[0052] The bottom plate 144 may be made of, for example, aluminum, an aluminum alloy, or their equivalents, and thus the positive electrode tab 125 made of aluminum may be easily welded to the bottom plate 144 .

[0053] For example, in the cylindrical lithium ion secondary battery 100 according to the embodiment, when the internal gas pressure of the cylindrical can 110 is greater than the predetermined first pressure (working pressure) and less than the predetermined second pressure (fracture pressure), the top plate 141 can be deformed to convexly upward by the internal gas pressure, so that the top plate 141 is electrically disconnected from the bottom plate 144. In addition, in the cylindrical lithium ion secondary battery 100 according to the embodiment, when the internal gas pressure of the cylindrical can 110 is greater than the predetermined second pressure (fracture pressure), the notch 141c formed on the top plate 141 is broken, and the internal gas existing in the secondary battery can be quickly released to the outside, thereby preventing the explosion of the secondary battery and ultimately improving the safety.

[0054] The cap assembly 140 may further include an insulating gasket 145 that insulates the top plate 141 and the side wall 112 of the cylindrical can 110 from each other. Here, the insulating gasket 145 is configured to be substantially compressed between the curling portion 113 and the crimping portion 114, each of which is formed at the side wall 112 of the cylindrical can 110. In addition, the insulating gasket 145 may substantially surround the side region 141e of the top plate 141 and the upper region 141d and the lower region 141f located around the side region 141e.

[0055] In addition, an electrolyte (not shown) is injected into the cylindrical can 110, and lithium ions generated by electrochemical reactions in the negative electrode plate 121 and the positive electrode plate 122 in the secondary battery during charge and discharge are allowed to move. The electrolyte may be a non-aqueous organic electrolyte including a mixture of a lithium salt and a high-purity organic solvent. In addition, the electrolyte may be a polymer using a polymer electrolyte or a solid electrolyte, but the embodiments of the present invention are not limited to the above electrolytes.

[0056] Figure 5 is a cross-sectional view illustrating stress generated when a crimping portion is formed in a cylindrical lithium ion secondary battery according to an embodiment of the present invention.

[0057] like Figure 5 As shown in , when the upper end of the cylindrical can 110 is clamped to fix the cap assembly 140 to the cylindrical can 110, a force F1 is applied in a downward direction relative to the cap assembly 140 and in an inward direction relative to the cap assembly 140. When the force F1 is applied, a stress F2 is generated toward the center of the cap assembly 140, causing the cap assembly 140 to deform, so that the center of the cap assembly 140 is recessed. Therefore, the cylindrical lithium-ion secondary battery 100 may suffer from changes in component characteristics. Specifically, the first pressure (working pressure) and the second pressure (fracture pressure) of the top plate 141 may change, and the top plate 141 may not work properly at a given pressure.

[0058] However, in the present invention, a support plate 142 having a strength higher than that of the top plate 141 (that is, having a second strength higher than the first strength of the top plate 141) is provided to relieve stress generated toward the center of the cap assembly 140 when the upper end of the cylindrical can 110 is clamped. Therefore, the support plate 142 can improve the safety of the cylindrical lithium ion secondary battery 100 by preventing deformation of the top plate 141.

[0059] In addition, since the third region 142c (in which a step difference is generated in the third region 142c due to the height difference between the first region 142a and the second region 142b) is formed in the support plate 142, the stress generated toward the center of the cap assembly 140 when the upper end of the cylindrical can 110 is clamped can be dispersed. Therefore, the support plate 142 can improve the safety of the cylindrical lithium ion secondary battery 100 by preventing deformation of the top plate 141.

[0060] Figure 6 is a cross-sectional view of a cylindrical lithium ion secondary battery according to another embodiment of the present invention, Figure 7 is a plan view showing a support plate of a cylindrical lithium ion secondary battery according to another embodiment of the present invention.

[0061] Reference Figure 6 and Figure 7 , a cylindrical lithium ion secondary battery 200 according to another embodiment includes a cylindrical can 110, an electrode assembly 120, and a cap assembly 240. Figure 5 Compared to the cover assembly 140 shown in FIG. 1 , the cover assembly 240 is substantially the same as the cover assembly 140 except for the configuration of the support plate 242. Therefore, the following description will focus only on the support plate 242.

[0062] The support plate 242 may be positioned under the top plate 141, and may include a first region 242a, a second region 242b, and a third region 242c. The first region 242a is formed in close proximity to an upper region 141d located inside the curved region 141g of the top plate 141. In addition, a first through hole 242d is formed approximately at the center of the first region 242a, and a plurality of second through holes 242e may be formed in the third region 242c. The second region 242b is positioned at the outside of the first region 242a and is positioned lower than the first region 242a. Specifically, the second region 242b is disposed in close proximity to an upper region 141d located outside the curved region 141g of the top plate 141. Therefore, the second region 242b is surrounded by the upper region 141d, the side region 141e, and the lower region 141f located outside the curved region 141g. In addition, a groove 242f is formed on the top surface of the second region 242b. As Figure 7As shown in FIG. 1 , the groove 242f is formed in an annular shape on the top surface of the second region 242b and contacts the upper region 141d formed at the outer side of the curved region 141g of the top plate 141. The groove 242f may be used to disperse stress generated toward the center of the cap assembly 240 when the upper end of the cylindrical can 110 is clamped.

[0063] The groove 242f may be formed to have a depth of about 5% to about 20% of the thickness of the support plate 242. If the depth of the groove 242f is less than 5% of the thickness of the support plate 242, stress generated toward the center of the cap assembly 240 when the upper end of the cylindrical can 110 is clamped may not be sufficiently dispersed. In addition, if the depth of the groove 242f is greater than 20% of the thickness of the support plate 242, the support plate 242 may be easily deformed due to stress generated toward the center of the cap assembly 240 when the upper end of the cylindrical can 110 is clamped.

[0064] Although the foregoing embodiments have been described to practice the cylindrical lithium ion secondary battery of the present invention, these embodiments are set forth for the purpose of illustration and are not intended to limit the invention. It will be readily understood by those skilled in the art that many modifications and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims, and such modifications and variations are included within the scope and spirit of the present invention.

Claims

1. A cylindrical lithium-ion secondary battery, comprising: Cylindrical tank; an electrode assembly housed in a cylindrical can; as well as Cover assembly for sealing cylindrical cans, The cap assembly includes: a top plate having a notch formed thereon; a support plate closely disposed with a lower surface of the top plate and including a first through hole formed through a center thereof; a bottom plate electrically connected to the electrode assembly and protruding upward at a center portion to be connected to the lower surface of the top plate through the first through hole; and an insulating plate located between the support plate and the bottom plate and having a through hole located at the center to correspond to the first through hole of the support plate, and The support plate has a strength greater than that of the top plate.

2. The cylindrical lithium ion secondary battery according to claim 1, wherein: Top plate includes: an upper region, positioned on a support plate; a side region bent downward from the upper region to surround a side portion of the support plate; and The lower region is bent horizontally inward from the side region to be positioned at the bottom of the support plate.

3. The cylindrical lithium ion secondary battery according to claim 2, wherein: The top plate further includes a curved region formed at the upper region, wherein the upper region located inside the bending region is positioned higher than the upper region located outside the bending region, and The notch is formed on an upper region located inside the bending region.

4. The cylindrical lithium ion secondary battery according to claim 3, wherein: The support plate includes: A first region corresponding to an upper region of the top plate located inside the curved region and having a first through hole formed in the first region; a second region located at an outer side of the first region and corresponding to an upper region of the top plate located outside the curved region, the second region being positioned lower than the first region; as well as The third region, corresponding to the bent region of the top plate, connects the first region and the second region to each other, and includes a plurality of second through holes.

5. The cylindrical lithium ion secondary battery according to claim 4, wherein: The third area is formed to be inclined so as to disperse stress generated when the upper end of the cylindrical can is clamped to fix the cap assembly to the cylindrical can.

6. The cylindrical lithium ion secondary battery according to claim 4, wherein: An annular groove is formed on the second region to disperse stress generated when the upper end of the cylindrical can is clamped to fix the cap assembly to the cylindrical can.

7. The cylindrical lithium ion secondary battery according to claim 6, wherein: The groove is formed to have a depth of 5% to 20% of the thickness of the support plate.

8. The cylindrical lithium ion secondary battery according to claim 1, wherein: If the internal gas pressure of the cylindrical tank is greater than the predetermined working pressure and less than the predetermined rupture pressure, the top plate convexly deforms upward, and the top plate is then electrically disconnected from the bottom plate, and Wherein, if the internal gas pressure of the cylindrical tank is greater than a predetermined rupture pressure, the notch of the top plate ruptures. 9 . The cylindrical lithium ion secondary battery according to claim 1 , further comprising an insulating gasket located between the cap assembly and the cylindrical can and insulating the cap assembly and the cylindrical can from each other.

10. The cylindrical lithium ion secondary battery according to claim 1, wherein: One or more recesses are formed in the bottom plate.

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