阅读说明：本技术 圆柱形二次电池 (Cylindrical secondary battery ) 是由 金大奎 高诚贵 金神中 田炳玟 于 2017-12-14 设计创作，主要内容包括：本发明提供了一种圆柱形二次电池,该圆柱形二次电池可以具有增大的安全性和容量以及在外部接触表面的增强的耐刮擦性和耐压性。为此,公开了一种圆柱形二次电池,该电池包括：圆柱形壳体；电极组件,被容置在壳体中；以及盖组件,用于密封壳体,其中,盖组件包括顶板、中间板和底板并且包括通过对顶板的表面进行表面处理以具有凹凸结构而形成的表面处理区域,顶板具有形成在其至少一个表面上的凹口,中间板结合到顶板并且包括穿过其中心形成的第一通孔,底板与电极组件电连接并且通过中间板的第一通孔结合到顶板。(The present invention provides a cylindrical secondary battery that may have increased safety and capacity and enhanced scratch resistance and pressure resistance at an external contact surface. To this end, a cylindrical secondary battery is disclosed, the battery including: a cylindrical housing; an electrode assembly accommodated in the case; and a cap assembly for sealing the case, wherein the cap assembly includes a top plate having a recess formed on at least one surface thereof, an intermediate plate bonded to the top plate and including a first through-hole formed through a center thereof, and a bottom plate electrically connected to the electrode assembly and bonded to the top plate through the first through-hole of the intermediate plate, and including a surface treatment region formed by surface-treating a surface of the top plate to have a concavo-convex structure.)

1. A cylindrical secondary battery comprising:

a cylindrical housing;

an electrode assembly accommodated in the case; and

a cap assembly for sealing the case,

wherein the cap assembly includes a top plate having a recess formed on at least one surface thereof, an intermediate plate bonded to the top plate and including a first through-hole formed through a center of the intermediate plate, and a bottom plate electrically connected to the electrode assembly and bonded to the top plate through the first through-hole of the intermediate plate, and includes a surface treatment region formed by surface-treating a surface of the top plate to have a concavo-convex structure.

2. The cylindrical secondary battery according to claim 1, wherein the surface treatment region is formed on the surface of the top plate as a region offset from where the notch is located.

3. The cylindrical secondary battery according to claim 1, wherein the surface treatment region is formed on the surface of the top plate so as to be positioned inward with respect to a region where the notch is positioned.

4. The cylindrical secondary battery according to claim 3, wherein the surface treatment region is additionally formed on the surface of the top plate so as to be positioned outwardly with respect to the region where the notch is positioned.

5. The cylindrical secondary battery according to claim 1, wherein the surface-treated region is formed to have at least one shape selected from a knurled shape, an embossed shape, and grooves arranged in a mesh shape or a parallel line shape.

6. The cylindrical secondary battery according to claim 1, wherein the top plate including a centrally positioned upper region and an edge region bonded to the upper region by a stepped region seals the case, the surface treatment region being formed with respect to the upper region.

7. The cylindrical secondary battery according to claim 6, wherein the edge region is crimped using a crimp part formed on the case to then be bonded to the case.

8. The cylindrical secondary battery according to claim 1, further comprising an insulating plate between the bottom plate and the middle plate, the insulating plate including a hole corresponding to the first through-hole of the middle plate.

9. The cylindrical secondary battery according to claim 1, wherein the intermediate plate further comprises one or more second through holes arranged outside the first through holes.

10. The cylindrical secondary battery according to claim 1, wherein the bottom plate further comprises a groove positioned at a region joined to the top plate through the first through hole of the middle plate.

11. The cylindrical secondary battery according to claim 10, wherein the groove is positioned horizontally inward with respect to the notch of the top plate.

Technical Field

The present invention relates to a cylindrical secondary battery that may have increased safety and capacity and enhanced scratch resistance and pressure resistance of an external contact surface.

Background

Lithium ion secondary batteries are being widely used in portable electronic devices as well as power sources for hybrid cars or electric vehicles due to various advantages including high operating voltage, high energy density per unit weight, and the like.

The lithium ion secondary battery may be generally classified into a cylindrical secondary battery, a prismatic secondary battery, and a pouch-shaped secondary battery. In particular, 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 allow movement of lithium ions, and a cap assembly coupled to one side of the can to prevent leakage of the electrolyte and separation of the electrode assembly.

Disclosure of Invention

Technical problem

The present invention provides a cylindrical secondary battery that may have improved safety and capacity and enhanced scratch resistance and pressure resistance at an external contact surface.

Technical scheme

According to an embodiment of the present invention, there is provided a cylindrical secondary battery including: a cylindrical housing; an electrode assembly accommodated in the case; and a cap assembly for sealing the case, wherein the cap assembly includes a top plate having a recess formed on at least one surface thereof, an intermediate plate bonded to the top plate and including a first through-hole formed through a center thereof, and a bottom plate electrically connected to the electrode assembly and bonded to the top plate through the first through-hole of the intermediate plate, and including a surface treatment region formed by surface-treating a surface of the top plate to have a concavo-convex structure.

Here, the surface treatment region may be formed on the surface of the top plate to deviate from a region where the notch is located.

In addition, the surface treatment region may be formed on the surface of the top plate so as to be positioned inward with respect to a region where the notch is positioned.

In addition, the surface treatment region may be additionally formed on the surface of the top plate to be positioned outwardly with respect to a region where the notch is positioned.

In addition, the surface treatment region may be formed to have at least one shape selected from a knurled shape, an embossed shape, grooves arranged in a mesh shape or a parallel line shape.

In addition, a top plate comprising a centrally located upper region and an edge region joined to the upper region by a stepped region may seal the housing, and a surface treatment region may be formed relative to the upper region.

In addition, the edge area may be crimped using a crimp formed on the housing to then be bonded to the housing.

In addition, the cylindrical secondary battery may further include an insulation plate between the bottom plate and the middle plate, the insulation plate including a hole corresponding to the first through hole of the middle plate.

In addition, the middle plate may further include one or more second through holes disposed outside the first through holes.

In addition, the bottom plate may further include a groove positioned at a region joined to the top plate through the first through hole of the middle plate.

Further, the slot may be positioned horizontally inward relative to the notch of the top plate.

Advantageous effects

As described above, the present invention provides a cylindrical secondary battery that may have improved safety by blocking a current path through a cap assembly when the pressure of internal gas is greater than a preset first reference pressure (operating pressure), and by enabling the cap assembly to be broken to release the internal gas to the outside when the pressure of the internal gas is greater than a second reference pressure (rupture pressure).

In addition, the present invention provides a cylindrical secondary battery that can increase the battery capacity while reducing the battery size by reducing the total height of the battery by the reduced height of the cap assembly.

In addition, the present invention provides a cylindrical secondary battery that can reduce surface scratches and can withstand pressure (such as load) by performing surface treatment (such as knurling or embossing) on the surface of the top plate of the cap assembly.

Drawings

Fig. 1a and 1b are a perspective view and a sectional view of a cylindrical secondary battery according to an embodiment of the present invention, and fig. 1c is an enlarged sectional view showing only a cap assembly.

Fig. 2 shows the top surface and the side surfaces of the top plate together in the cylindrical secondary battery according to the embodiment of the present invention.

Fig. 3a is a sectional view illustrating a state in which a cap assembly in a cylindrical secondary battery according to an embodiment of the present invention is operated, and fig. 3b is a sectional view illustrating a state in which the cap assembly in the cylindrical secondary battery according to an embodiment of the present invention is ruptured.

Fig. 4 shows together the top surface and the side surfaces of the top plate in the cylindrical secondary battery according to another embodiment of the present invention.

Fig. 5 shows together the top surface and the side surfaces of the top plate in a cylindrical secondary battery according to still another embodiment of the present invention.

[ brief description of reference numerals ]

140: the lid assembly 141: top board

141 a: top surface 141 b: bottom surface

141 c: notch 141 d: top area

141 e: edge region 141 f: step area

141 g: side region 141 h: bottom zone

142: intermediate plate 142 a: first through hole

142 b: second through hole 142 c: bending zone

143: insulating plate 143 a: through hole

144: bottom plate 144 a: first region

144 b: second region 144 c: a third region

144 d: grooves 146A, 146B: welding zone

10. 20, 30: surface treated area

Detailed Description

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

Embodiments of the present invention may, however, be modified in many different forms and should not be construed as limited to the example (or exemplary) embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will convey embodiments and features of the invention to those skilled in the art.

In addition, in the drawings, the size or thickness of various components may be exaggerated for clarity and conciseness. Like reference numerals refer to like elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. In addition, it will be understood that when element a is referred to as being "connected to" element B, element a can be directly connected to element B, or an intermediate element C can exist between element a and element B, such that element a and element B are indirectly connected to each other.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or variations thereof, when used in this specification, specify the presence of stated features, amounts, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, amounts, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, for example, a first member, a first element, a first region, a first layer and/or a first portion discussed below could be termed a second member, a second element, a second region, a second layer and/or a second portion without departing from the teachings of the present invention.

Spatially relative terms such as "below … …," "below … …," "below," "above … …," "above," and the like may be used herein for ease of description to describe one element or feature's relationship to another (other) element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if an element or feature in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the exemplary term "below … …" can encompass both an orientation of above and below.

The configuration of the cylindrical secondary battery according to the embodiment will now be described below.

Fig. 1a and 1b are a perspective view and a sectional view of a cylindrical secondary battery according to an embodiment of the present invention, and fig. 1c is an enlarged sectional view showing only a cap assembly.

First, as shown in fig. 1a, 1b, and 1c, a cylindrical secondary battery 200 according to various embodiments may include a case 110, an electrode assembly 120, and a cap assembly 140. In some cases, the cylindrical secondary battery 100 may further include a center pin 130.

The cylindrical housing 110 includes a circular bottom 111 and a sidewall 112 extending upward from the bottom 111 by a predetermined length. The top of the case 110 is open during the manufacture of the secondary battery. Accordingly, the electrode assembly 120 and the center pin 130 may be inserted into the case 110 together with the electrolyte during the manufacture of the secondary battery. The housing 110 may be made of steel, stainless steel, aluminum alloy, or equivalents thereof, but embodiments of the present invention are not limited to the above materials. In addition, the case 110 includes an inwardly depressed beading portion 113 formed at a lower portion of the cap assembly 140 to prevent the cap assembly 140 from being deviated to the outside, and an inwardly bent crimping portion 114 formed at an upper portion of the cap assembly 140. Here, the electrolyte may be in a liquid phase, a solid phase, or a gel phase, but embodiments of the present invention are not limited to the above-described phases.

The electrode assembly 120 is accommodated in the case 110. The electrode assembly 120 includes a negative electrode plate 121 coated with a negative active material (e.g., graphite, carbon, etc.), a positive active material (e.g., such as LiCoO), and a negative electrode₂、LiNiO₂、LiMn₂O₄Etc.) and a separator 123 positioned between the negative and positive electrode plates 121 and 122 to prevent an electrical short and allow only movement of lithium ions. The negative electrode plate 121, the positive electrode plate 122, and the separator 123 are wound into a substantially cylindrical shape. Here, the negative electrode plate 121 may be made of copper (Cu) foil, the positive electrode plate 122 may be made 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 to the above materials. In addition, a negative electrode tab 124 protruding downward and extending by a predetermined length may be welded to the negative electrode plate 121, and a positive electrode tab 125 protruding upward by a predetermined length may be welded to the positive electrode plate 122, 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 embodiments of the present invention are not limited to the above materials.

In addition, the negative electrode tab 124 of the electrode assembly 120 may be welded to the bottom 111 of the case 110. Thus, the case 110 may function as a negative electrode. Instead, the positive electrode tab 125 may be welded to the bottom 111 of the case 110, in which case the case 110 may serve as a positive electrode.

In addition, a first insulating plate 126 coupled to the case 110 and having a first hole 126a formed at a central portion thereof and a second hole 126b formed at an outer side thereof may be interposed between the electrode assembly 120 and the bottom 111. The first insulating plate 126 prevents the electrode assembly 120 from electrically contacting the bottom 111 of the case 110. Specifically, the first insulating plate 126 prevents the positive plate 122 of the electrode assembly 120 from electrically contacting the bottom 111. Here, when a large amount of gas is generated due to an abnormality of the secondary battery, the first hole 126a allows the gas to rapidly move upward through the center pin 130, and the second hole 126b allows the negative electrode tab 124 to pass through the center pin 130 to be welded to the bottom 111.

In addition, a second insulating plate 127 coupled to the case 110 and having a first hole 127a formed at the center portion thereof and a plurality of second holes 127b formed at the outer side thereof may be interposed between the electrode assembly 120 and the cap assembly 140. The second insulating plate 127 prevents 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 large amount of gas is generated due to an abnormality of the secondary battery, the first hole 127a allows the gas to rapidly 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, the second hole 127b allows the electrolyte to rapidly flow into the electrode assembly 120 during the electrolyte injection process.

In addition, since the first hole 126a of the first insulating plate 126 and the first hole 127a of the second insulating plate 127 have a smaller diameter than the center pin 130, it is possible to prevent the center pin 130 from electrically contacting the bottom 111 of the case 110 or the cap assembly 140 due to external impact.

The center pin 130 is shaped as a hollow cylindrical tube, and is coupled to a substantially central portion of the electrode assembly 120. The center pin 130 may be made of steel, stainless steel, aluminum alloy, or polybutylene terephthalate, but embodiments of the present invention are not limited to the above materials. The center pin 130 prevents the electrode assembly 120 from being deformed during the charge or discharge of the secondary battery, and may serve as a gas movement path.

The cap assembly 140 may include a top plate 141, an intermediate plate 142, an insulating plate 143, and a bottom plate 144.

The top plate 141 includes a substantially flat top surface 141a and a substantially flat bottom surface 141b opposite the top surface 141 a. Specifically, the top plate 141 may further include at least one notch 141c formed on the bottom surface 141 b. Here, the notch 141C may have, for example, a substantially circular, oval, or "C" shape when viewed from below, but embodiments of the present invention are not limited to the above-described shape. The notch 141c is ruptured or ruptured when the internal gas pressure of the secondary battery is greater than a predetermined reference pressure (rupture pressure), thereby rapidly releasing the internal gas of the battery to the outside.

In addition, the top plate 141 may include an upper region 141d, an edge region 141e, a side region 141g, and a lower region 141 h. The upper region 141d may be positioned on the middle plate 142 and may be substantially planar. The upper region 141d may serve as a terminal of the secondary battery and thus may be electrically connected to an external device (e.g., a load or a charger).

In addition, as will be described later, the surface treatment region 10 may be further formed in the upper region 141 d. The surface treatment region 10 may be formed by performing surface treatment on the top surface of the upper region 141d by knurling or embossing, and thus the surface treatment region 10 may become highly scratch-resistant and may be able to withstand external loads.

The edge region 141e may be coupled to the upper region 141d by a step region 141f having a predetermined height, and thus may be formed at a lower position than the upper region 141 d. The edge region 141e may be substantially shaped as a ring positioned along the edge of the upper region 141 d. In addition, the outside of the edge area 141e may be bonded to the case 110 by crimping the edge area 141e with the side area 141g and the lower area 141h by the crimping part 114 of the case 110.

When viewed from below, the stepped region 141f may be shaped as a substantially circular ring. As an example, the upper region 141d positioned inside the stepped region 141f may be positioned higher than the edge region 141e positioned outside the stepped region 141 f. In addition, a notch 141c may be formed on the bottom surface of the upper region 141d positioned inside the step region 141 f.

The side regions 141g may be bent downward from the edge region 141e to substantially surround the sides of the middle plate 142.

The lower region 141h is horizontally bent inward from the side region 141g and then bonded to the bottom of the middle plate 142. In this manner, the top plate 141 may be bonded to the middle plate 142 through the upper region 141d, the edge region 141e, the side region 141g, and the lower region 141 h.

The top plate 141 may be made of, for example, aluminum, an aluminum alloy, or equivalents thereof, but embodiments of the present invention are not limited to the above-described materials. Accordingly, an aluminum bus bar, an external lead, or an external device may be easily connected (or welded) to the top plate 141.

Here, the top plate 141 may be made of one selected from the group consisting of 1XXX series alloys (i.e., pure aluminum of 99.0% or higher purity), 2XXX series alloys (i.e., Al — Cu alloys), 3XXX series alloys (i.e., Al — Mn alloys), 4XXX series alloys (i.e., Al — Si alloys), 5XXX series alloys (i.e., Al — Mg alloys), 6XXX series alloys (i.e., Al — Mg — Si alloys), and 7XXX series alloys (i.e., Al — Zn- (Mg, Cu) alloys).

In particular, the top plate 141 is preferably made of soft aluminum among the above-mentioned series of alloys. For example, the top plate 141 may be made of 5XXX series (e.g., 5052, 5056, 5083, or 5454) Al — Mg alloy having high strength, excellent corrosion resistance, and good weldability, but is not limited thereto. In addition, 1XXX, 3XXX, or 4XXX series alloys, which are non-heat treatable alloys, may be used as the material of the top plate 141.

Therefore, as will be described later, when the internal pressure of the case 110 is greater than or equal to a predetermined reference pressure (operating pressure), the upper region 141d may be expanded upward, thereby enabling the top plate 141 to be physically separated from the middle plate 142 to then be electrically disconnected from the middle plate 142. In addition, when the internal pressure of the case 110 is greater than or equal to a predetermined reference pressure (operation pressure), the notch 141c may be broken and opened, and thus the internal gas may be released to the outside, thereby increasing safety.

In addition, since the top plate 141 has a smaller height than the upwardly protruded upper cover structure, the overall height of the cylindrical secondary battery 100 according to the embodiment of the present invention is reduced, thereby reducing the size of the secondary battery 100 and increasing the capacity of the secondary battery 100 at the same height as that of the conventional secondary battery.

The middle plate 142 may be positioned below the top plate 141 and may be substantially planar. In addition, the middle plate 142 may include a first through hole 142a formed at a substantially central portion. In addition, the middle plate 142 may include a plurality of second through holes 142b formed around the first through holes 142 a.

Here, a bottom plate 144, which will be described later, may pass through the first through hole 142a to then be electrically connected to the top plate 141, and may allow internal gas pressure to be directly applied to the top plate 141. In addition, the second through hole 142b may also allow the internal gas pressure to be directly applied to the top plate 141.

Here, the at least one notch 141c formed on the bottom surface 141b of the top plate 141 may be positioned to correspond to, for example, an area between the first through hole 142a of the middle plate 142 and each of the second through holes 142b of the middle plate 142.

In addition, the middle plate 142 may also include a bent region 142c formed on a region corresponding to the stepped region 141f of the top plate 141. Accordingly, the middle plate 142 may be generally configured such that it is in close contact with the bottom surface 141b of the top plate 141.

In order to maintain the shape of the top plate 141 when pressure is applied during crimping for forming the crimp portion 114 of the housing 110, the intermediate plate 142 may be made of, for example, aluminum, an aluminum alloy, or an equivalent thereof. However, when the pressure applied during crimping is not relatively large, the intermediate plate 142 may be made of an insulating material such as Polyethylene (PE), polypropylene (PP), or ethylene propylene diene monomer (M-type) rubber (EPDM rubber). In this case, since the bottom plate 144 is coupled to the top plate 141 through the first through hole 142a of the middle plate 142, it is possible to still perform electrical connection at a normal time or electrical disconnection at an operating pressure and a fracture pressure, which will be described later.

The insulating plate 143 may be positioned under the middle plate 142 (attached to the bottom of the middle plate 142), and may include a through hole 143a positioned to correspond to the first through hole 142 a. The insulating plate 143 may be shaped into a substantially circular ring having a predetermined width when viewed from below. In addition, the insulating plate 143 serves to insulate the middle plate 142 and the bottom plate 144 from each other. For example, the insulating plate 143 may be positioned between the middle plate 142 and the bottom plate 144 and may be subjected to ultrasonic welding, but embodiments of the present invention are not limited thereto.

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

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 142a of the middle plate 142 to then be 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 142a of the middle 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. In fig. 1c, undefined reference numeral 144e denotes a welding region in which the first region 144a of the bottom plate 144 is welded to the bottom surface 141b of the upper region 141d of the top plate 141.

Here, the positive electrode tab 125 may be electrically connected to the third region 144c of the base plate 144. Additionally, the first region 144a of the bottom plate 144 may also include one or more recessed grooves 144 d. The groove 144d may serve to separate the first region 144a from the second region 144b of the bottom plate 144 if the top plate 141 is convexly deformed upward when the internal gas pressure of the battery is greater than a predetermined pressure (operating pressure). Accordingly, a current path between the top plate 141 and the bottom plate 144 may be blocked.

The bottom plate 144 may be made of, for example, aluminum, an aluminum alloy, or their equivalents, so that a positive electrode tab made of aluminum may be easily welded to the bottom plate 144.

The cap assembly 140 may further include an insulation plate 145 insulating the top plate 141 and the sidewall 112 of the case 110 from each other. Here, the insulating plate 145 is substantially compressed between the crimping portion 113 and the crimping portion 114 formed on the side wall 112 of the case 110. In addition, the insulating plate 145 may substantially cover the edge region 141e of the top plate 141 and the side regions 141g and the lower region 141h positioned around the edge region 141 e.

In addition, an electrolyte (not shown) is injected into the case 110, and allows lithium ions generated by electrochemical reactions in the negative and positive electrode plates 121 and 122 in the secondary battery to move during charge and discharge. 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 electrolyte using a polymer or a solid electrolyte. However, embodiments of the present invention are not limited to the above-described electrolyte.

Hereinafter, the construction of the cylindrical secondary battery according to the embodiment of the present invention will be described in more detail.

Fig. 2 shows the top surface and the side surfaces of the top plate together in the cylindrical secondary battery according to the embodiment of the present invention.

Referring to fig. 2, the top plate 141 may include a surface treatment region 10 formed on at least a portion of a top surface of the upper region 141 d. The surface treatment region 10 may include a plurality of concave-convex structures prepared on the top surface of the upper region 141d by knurling or embossing treatment. The concave-convex structures may be formed at regular distances from each other on the upper region 141 d. The surface treatment region 10 may have enhanced scratch resistance when the surface treatment region 10 is in contact with an external device (such as a charge/discharge pin or a load) compared to a plane that is not surface-treated. In addition, the formation of the surface treatment region 10 can improve pressure resistance, and the upper region 141d can withstand pressure such as a load applied from an external device by the formation of the surface treatment region 10.

Meanwhile, the surface treatment region 10 may be formed on the upper region 141d to be offset from the notch 141c formed on the bottom surface of the top plate 141, particularly, to be positioned horizontally inward with respect to the notch 141 c. With this arrangement, when the notch 141c and the surface treatment region 10 intersect each other, particularly when knurling treatment is performed, the thickness of the top plate 141 is reduced at the corresponding position, thereby preventing the top plate 141 from opening at a pressure lower than a suitable reference pressure (fracture pressure). In addition, in the case when an external device is coupled to the top plate 141, the external device is generally in contact with the central portion of the upper region 141d, and thus scratch resistance or pressure resistance may be maintained with such an arrangement of the surface treatment region 10.

Hereinafter, the operation of the cylindrical secondary battery according to the embodiment of the present invention will be described in more detail.

Fig. 3a is a sectional view illustrating a state in which a cap assembly in a cylindrical secondary battery according to an embodiment of the present invention is operated, and fig. 3b is a sectional view illustrating a state in which the cap assembly in the cylindrical secondary battery according to an embodiment of the present invention is ruptured.

As shown in fig. 3a, in the cylindrical secondary battery according to the embodiment, when the internal gas pressure of the case is greater than a predetermined first pressure (operating pressure) and less than a predetermined second pressure (rupture pressure), the top plate 141 may be convexly deformed or inverted upward by the internal gas pressure, so that the top plate 141 is electrically disconnected from the bottom plate 144. That is, as the first region 144a of the bottom plate 144 is broken, the first region 144a is separated from the second region 144 b. In other words, as the groove 144d of the first region 144a is broken, some regions of the first region 144a may be separated upward in a state where the first region 144a is connected to the top plate 141, thereby finally blocking the current path established between the top plate 141 and the bottom plate 144.

However, when the internal gas pressure of the cylindrical secondary battery is less than the second pressure (rupture pressure), the sealed state of the cylindrical secondary battery is still maintained by the top plate 141, thereby preventing the internal gas from being released to the outside.

When the cylindrical secondary battery is overcharged, when the cylindrical secondary battery is internally short-circuited due to permeation and/or collapse, or when the cylindrical secondary battery is externally short-circuited, internal gas may be generated due to decomposition of the electrolyte or decomposition of the active material layer, resulting in an increase in the internal gas pressure of the cylindrical secondary battery.

Such an increase in the internal gas pressure of the cylindrical secondary battery may indicate that the cylindrical secondary battery is in an abnormal state, and thus the current path is blocked by the above-described mechanical mechanism, thereby improving the safety of the secondary battery.

As shown in fig. 3b, in the cylindrical secondary battery according to the embodiment of the present invention, when the internal gas pressure of the case is greater than the predetermined second pressure (rupture pressure), the top plate 141 is ruptured, and thus the internal gas is rapidly released without any hindrance. That is, as the notch 141c formed on the bottom surface 141b of the top plate 141 is broken, gas existing within the cylindrical secondary battery is rapidly released to the outside, thereby preventing the cylindrical secondary battery from exploding and eventually increasing the safety of the cylindrical secondary battery. From the viewpoint of safety, it is better to release the internal gas to the outside in advance than to explode the cylindrical secondary battery at high pressure in such a manner as described above.

In addition, the fracture pressure (or the second pressure) of the top plate 141 may be adjusted by the position and depth of the notch 141 c. For example, the fracture pressure may be increased by arranging the notch 141c to be positioned outward with respect to the upper region 141d and decreasing the depth of the notch 141c, and the fracture pressure may be decreased by arranging the notch 141c to be positioned inward with respect to the upper region 141d and increasing the depth of the notch 141c, but the embodiment of the present invention is not limited thereto.

Hereinafter, the construction of a cylindrical secondary battery according to another embodiment of the present invention will be described.

Fig. 4 shows together the top surface and the side surfaces of the top plate in the cylindrical secondary battery according to another embodiment of the present invention.

Referring to fig. 4, a cylindrical secondary battery according to another embodiment may be different from the cylindrical secondary battery according to the previous embodiment in consideration of the configuration of the top plate 241.

The top plate 241 may include not only the surface treatment region 10 positioned horizontally inwardly with respect to the notch 141c with respect to the upper region 241d, but also the surface treatment region 20 positioned outwardly with respect to the notch 141 c. That is, the surface treatment regions 10 and 20 may be formed on portions of the upper region 241d other than the region where the notch 141c is located.

This enables battery safety to be achieved by maintaining a predetermined first pressure (operating pressure) caused by the formation of the recess 141c while maximizing scratch resistance and pressure resistance when the surface treatment region is in contact with an external device. Of course, the distance between the concave-convex structures formed on the surface treatment regions 10 and 20 and the depth (or height) thereof may be selected according to options made by those skilled in the art.

Hereinafter, the construction of a cylindrical secondary battery according to still another embodiment of the present invention will be described.

Fig. 5 shows together the top surface and the side surfaces of the top plate in the cylindrical secondary battery according to still another embodiment of the present invention.

Referring to fig. 5, the cylindrical secondary battery according to still another embodiment may be different from the cylindrical secondary battery according to the previous embodiment in consideration of the configuration of the top plate 341.

The top plate 341 may be configured such that the surface treatment region 30 is formed by forming a plurality of grooves on the top surface of the upper region 341d in advance. Although a lattice groove is shown in fig. 5, the groove may be formed in a plurality of parallel line shapes instead of a lattice shape according to options made by those skilled in the art. In addition, although the illustrated embodiment shows that the grooves of the surface-treated region 30 are formed only to be positioned inward with respect to the notch 141c in the horizontal direction on the upper region 341d, the grooves may be formed to be positioned outward with respect to the notch 141c in addition. The groove shape may help to simplify the surface treatment process and reduce the surface treatment process time when forming the surface treatment region 30, compared to knurling or embossing treatment. Alternatively, the groove shape of the present embodiment may be combined with the above-described knurled or embossed shape.

Although the foregoing embodiments have been described to practice the cylindrical secondary battery of the present invention, the embodiments are set forth for the purpose of illustration, and are not intended to limit the invention. Those skilled in the art will readily appreciate that many modifications and variations are possible without departing from the spirit and scope of the invention as defined in the appended claims, and that such modifications and variations are encompassed within the scope and spirit of the invention.