KR20080036248A - Cap assembly of improved safety by preventing leakage and cylindrical secondary battery employed with the same - Google Patents

Abstract

A cap assembly, and a cylindrical battery containing the cap assembly are provided to prevent the penetration of moisture and the leakage of an electrolyte solution due to a pin hole, thereby improving the safety of a battery. A cap assembly is mounted at the open upper part of a can of a battery, wherein a current interception member(600) is combined to the lower end of a safety vent(320) having a certain notch(324,326) by welding to be broken to intercept current in case on the increase of internal pressure, and a polymer resin is coated on the corresponding part of the safety vent to seal the welding combination part. Preferably the safety vent is an aluminum plate having a thickness of 0.15-0.4 mm.

Description

Cap Assembly of Improved Safety by Preventing Leakage and Cylindrical Secondary Battery Employed with the Same}

1 is a vertical cross-sectional perspective view of a general cylindrical secondary battery;

2A to 2C are vertical cross-sectional views of a series of processes in which a current is cut off and a high pressure gas is discharged by the operation of a CID in a cylindrical secondary battery;

3 is a schematic cross-sectional view of a cylindrical secondary battery according to one embodiment of the present invention;

4 is a perspective view of a safety vent used in the battery of FIG. 3;

5 is a perspective view of a current blocking member used in the battery of FIG. 3;

6 is a pinhole photograph of a welded portion of a battery in which leakage occurs in the battery according to Comparative Example 1 in Experimental Example 1. FIG.

The present invention relates to a cap assembly having improved safety by leakage leakage and a cylindrical secondary battery including the same. More specifically, an electrode assembly (jelly-roll) having a cathode / separation membrane / cathode structure is embedded in a cylindrical can. A cap assembly mounted on an open upper end of a can in a battery having a structure, and at the lower end of a safety vent having a predetermined notch for releasing a high pressure gas while rupturing when a high pressure occurs inside the battery, a rupture occurs when a pressure rises inside the battery. The current blocking member which cuts off is coupled by welding, and in order to ensure the sealing of this welding joint part, the polymer resin is coated on the corresponding part of the safety vent, so that water penetration by the pinhole formed in the welding joint part, Essentially avoid delays in CID shorts due to electrolyte leakage and improper discharge of gases. Which relates to a cap assembly and a cylindrical secondary battery which contains it.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized and widely used for lithium secondary batteries with high energy density and discharge voltage. It is used.

According to the shape of the battery case, secondary batteries are classified into cylindrical batteries and rectangular batteries in which the electrode assembly is embedded in a cylindrical or rectangular metal can, and pouch-type batteries in which the electrode assembly is embedded in a pouch type case of an aluminum laminate sheet. . Among them, the cylindrical battery has the advantage of relatively large capacity and structurally stable.

In addition, the electrode assembly embedded in the battery case is a power generator capable of charging and discharging composed of a laminated structure of the anode / separator / cathode, a jelly-roll type wound through a separator between the long sheet-type anode and cathode coated with the active material And a plurality of positive and negative electrodes of a predetermined size are classified into a stack type in which a plurality of positive and negative electrodes are sequentially stacked in a state where a separator is interposed therebetween. Among them, the jelly-roll type electrode assembly has advantages of easy manufacturing and high energy density per weight.

1 is a vertical cross-sectional perspective view of a typical cylindrical battery.

Referring to FIG. 1, the cylindrical secondary battery 100 receives a jelly-roll type (wound) electrode assembly 120 in a cylindrical case 130 and injects an electrolyte solution into the cylindrical case 130, and then the case 130. ) Is manufactured by combining the top cap 140 having an electrode terminal (for example, a positive electrode terminal; not shown) formed at an open upper end thereof.

The electrode assembly 120 has a structure in which the anode 121, the cathode 122, and the separator 123 are sequentially stacked and wound in a round shape. A cylindrical center pin 150 is formed at its core (center of the jelly-roll). Is inserted. The center pin 150 is generally made of a metal material to impart a predetermined strength, and has a hollow cylindrical structure in which a plate is rounded. The center pin 150 acts as a passage for fixing and supporting the electrode assembly and for discharging gas generated by internal reaction during charging and discharging and operation.

On the other hand, lithium secondary batteries have the disadvantage of low safety. For example, when the battery is overcharged to approximately 4.5 V or more, decomposition reaction of the positive electrode active material occurs, dendrite growth of lithium metal at the negative electrode, decomposition reaction of electrolyte solution, and the like occur. In this process, heat is accompanied, so that the decomposition reaction and a number of side reactions are rapidly progressed, and the air supply may cause the battery to ignite and explode.

Therefore, in order to solve this problem, the general cylindrical secondary battery has a current interrupting member (CID) is mounted in the space between the electrode assembly and the top cap to cut off the current during abnormal operation of the battery and to break down the internal pressure. have.

2A-2C illustrate a step by step sequence of operation of such a CID.

Referring to these drawings, the top cap 10 has a positive electrode terminal formed in a protruding shape, and an exhaust port is perforated, and a PTC element for blocking current due to a large increase in battery resistance when the temperature inside the battery increases. Positive temperature coefficient element: 20), in the normal state has a downwardly protruding shape, the safety vent 30 to explode and exhaust gas when the pressure inside the battery rises, and the upper one side is coupled to the safety vent 30 The connection plate 50, which is connected to the anode of the electrode assembly 40, is positioned sequentially.

Therefore, under normal operating conditions, the anode of the electrode assembly 40 is connected to the top cap 10 through the lead 42, the connection plate 50, the safety vent 30, and the PTC element 20 to conduct electricity. .

However, when gas is generated from the electrode assembly 40 due to a cause such as overcharge, and the internal pressure increases, as shown in FIG. 2B, the safety vent 30 protrudes upward while its shape is reversed. The vent 30 is separated from the connection plate 50 so that the current is cut off. Therefore, overcharging does not proceed any more to ensure safety. Nevertheless, if the internal pressure continues to increase, as shown in FIG. 2C, the safety vent 30 is ruptured and the pressurized gas is exhausted through the exhaust port of the top cap 10 via such a rupture portion, thereby preventing the explosion of the battery. Will be prevented. Therefore, when the series of processes are sequentially performed, the safety of the battery can be ensured.

However, since one side of the upper end of the connection plate 50 and the safety vent 30 are joined by welding, there is a possibility that a pin hole having a minute size or the like is formed in the weld joint by overwelding. Moisture infiltration or electrolyte leakage may occur through the pinholes. When such leakage occurs, the electrolyte, which is a flammable substance, may leak out and come into contact with oxygen in the air, causing ignition, and moisture penetrating into the battery may cause decomposition reaction of the electrolyte, causing fire or explosion. have.

In addition, the internal gas of the battery is partially leaked to the outside, thereby preventing the internal pressure necessary for CID operation. Specifically, the operation of the CID is absolutely dependent on the amount of gas generated at the electrode assembly, so if the amount of gas generated is not sufficient or does not increase to a predetermined level within a short time, the CID short circuit is delayed and the electrode assembly continues. Thermal runaway can occur due to constant energization. The thermal runaway phenomenon occurs when the battery is in a continuous energized state or is further accelerated, thereby increasing the risk of the battery igniting or exploding, which is a serious problem in safety. Moreover, the importance of the safety of the battery has been further emphasized as recent ignition events of the notebook PC occur.

However, in the prior art, there are no recognitions or solutions for the problems caused by leakage of electrolyte and improper discharge of gas due to the pinholes of the minute size formed in the weld joint. Therefore, there is a high demand for the development of a battery capable of maintaining the sealing property from the pinholes that may be formed during over welding of the safety vent.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application, after extensive research and various experiments, the current blocking member is welded to the lower end of the safety vent of the cap assembly by welding, and when the welding joint is coated with a polymer resin, the current blocking during the welding process In the case where a pinhole having a small size is formed in a welding portion of a member or a safety vent, it has been found that by maintaining the excellent sealing property by the coated polymer resin, the safety of the battery can be greatly improved. Reached.

Accordingly, the cap assembly according to the present invention is a cap assembly mounted on an open upper end of a can in a battery having a structure in which an electrode assembly (jelly-roll) having a cathode / separation membrane / cathode structure is embedded in a cylindrical can. At the lower end of the safety vent, which has a predetermined notch for releasing high pressure gas while bursting when high pressure is generated, a current blocking member that ruptures when the pressure inside the battery rises to cut off the current is joined by welding. To ensure that it consists of a polymer resin applied on the relevant part of the safety vent.

In general, the safety vent and the current blocking member are made of a very thin aluminum plate, and the welding process is performed by the slight process variation during the welding process with the current blocking member. Can be.

In this case, water infiltration and leakage of the electrolyte may occur through the pinholes, and when the pinholes gradually increase due to repeated charge / discharge cycles or external shocks, the bonding force of the welded portion is weakened. In addition, since the internal pressure required to operate the CID may not be maintained, a fire or explosion of the battery may occur due to thermal runaway, thereby causing serious safety problems.

On the other hand, even when a total inspection through machine vision or the like is performed in the process of manufacturing the cap assembly, it is impossible to detect pinholes having a fine size in reality. In addition, due to the nature of the safety component, it is difficult to devise a separate inspection method in addition to the non-destructive inspection. Therefore, it is extremely difficult to detect in advance whether a pinhole is formed at the coupling portion between the safety vent and the CID element.

In order to prevent the formation of such pinholes, when the welding is weak, damage occurs at the joining site, so that the current is blocked before the CID short-circuit, thereby making it impossible to perform a function as a battery.

On the other hand, on the safety vent according to the present invention, as defined above, a polymer resin is applied to a corresponding portion of the weld joint to ensure the seal of the weld joint.

Therefore, even when undesired pinholes are formed during welding of the safety vent and the current blocking member, the penetration of water or leakage of the electrolyte may be fundamentally prevented by the polymer resin, thereby greatly improving battery safety. Can be. In addition, it is possible to prevent the weakening of the coupling force between the safety vent and the current blocking member due to the weak welding or the penetration of moisture or electrolyte to gradually increase the size of the pinhole. .

Here, the "corresponding part of the welding joint part" is a part corresponding to the point where the safety vent and the current blocking member are joined by welding, and are not particularly limited as long as there is a possibility that a pinhole may occur during welding of the members. The upper surface of the safety vent may be a portion of the top surface of the PTC element or the top cap mounted on the safety vent.

The safety vent is a kind of safety device that ensures the safety of the battery by discharging the gas to the outside when the internal pressure of the battery rises due to abnormal operation of the battery or degradation of battery components. For example, when gas is generated inside the cell and the internal pressure increases above the threshold, the safety vent ruptures, and the gas discharged to the rupture site is externally discharged through one or more gas outlets formed in the top cap. Can be discharged.

Therefore, the safety vent is not particularly limited, but may be made of an aluminum plate having a thickness of preferably 0.15 to 0.4 mm in order to have a rigidity that can be ruptured by an increase in the internal pressure or more.

In one preferred embodiment, the safety vent has a shape in which the center is downwardly indented to cut off the current before the gas is discharged under abnormal conditions, and each of the upper bent portion and the lower bent portion, which form the indentation portion, has a first A notch and a second notch are formed, the first notch forms a closed curve, and the second notch formed at the lower portion has a structure of an open curve having one side open, and the second notch is dug deeper than the first notch. It may consist of what is present.

Therefore, the second notch is formed deeper than the first notch, so that the second notch is cut when the pressurized gas above the second critical pressure presses the safety vent. On the other hand, the first notch acts with the second notch when pressurized gas below the second threshold pressure acts on the safety vent so that the indentation can be lifted up.

The current blocking member is a member that ruptures when the pressure rises inside the battery to block the current, and is not particularly limited as long as it performs such a role, and preferably includes one or more through holes for discharging gas. An upwardly protruding protrusion that is welded to the bottom of the indentation portion of the safety vent is formed at the center, and an anode lead connected to the anode of the jelly-roll is electrically connected through the lower surface of the portion except for the protrusion. It may be made of a structure in which a bridge in which notches are formed by connecting the through holes of 3 to 5 and the through holes concentrically around the protrusions is formed, but is not limited thereto.

Therefore, if the pressure inside the battery rises abnormally, the pressurized gas passes through the through-hole and through-hole of the current blocking member to apply an upward pressure to the safety vent, and the downward indentation of the safety vent is lifted by such pressure. The protrusions welded to the indents are easily separated from the current blocking member above a certain pressure (hereinafter, abbreviated as " first critical pressure ") to cut off electricity from the current blocking member to the safety vent. In spite of the interruption of such current, when the pressure continues to rise and reaches a certain level (hereinafter, abbreviated as "second critical pressure"), the second notch of the safety vent is cut off and the pressurized gas inside the top gap is cut off. It is discharged to the outside through the hole of.

In some cases, a PTC element (positive temperature coefficient element) that blocks a current due to a large increase in battery resistance when the temperature rises inside the battery may be interposed between the upper cap and the safety vent.

The welding method for coupling the current blocking device and the safety vent is not particularly limited. For example, the welding method may be performed by ultrasonic welding, or may be achieved by laser welding such as irradiating a carbon dioxide laser beam. In the case of ultrasonic welding, it may be necessary to hold the plate around by a welding jig for precise welding. On the other hand, in the case of laser welding by irradiating carbon dioxide laser beam or the like, the welding width can be easily adjusted. Therefore, a separate device is not required, the energy capacity is large, and the welding speed is increased because it is absorbed as thermal energy on the metal foil surface. Since it can set quickly, productivity can be improved and it is more preferable.

The polymer resin is not particularly limited as long as the polymer resin has a predetermined sealing property to prevent penetration of moisture or leakage of electrolyte. However, since the polymer resin is applied on the safety vents, when the material is very high in electrical conductivity, it covers the notch formed in the safety vents during application of the safety vents, thereby preventing the safety vents from operating properly. There is a risk of harm.

Therefore, the polymer resin may have a viscosity that is not too large by having a predetermined viscosity, and particularly preferably may be an ultraviolet curable resin. In the case of coating by the photocuring method using an ultraviolet curable resin, since the polymer resin coating layer can be formed in a desired portion in a relatively short time, the curing time can be shortened. The phenomenon of covering the notch can be prevented in advance.

The ultraviolet curable resin may be, for example, a urethane resin, an acrylic resin, a thermoplastic elastomer, a polyester resin, an epoxy resin, or a mixture thereof, but is not limited thereto. It may be preferably an epoxy resin.

In one preferred embodiment, the cap assembly consists of a stack structure of a top cap, a positive temperature coefficient element, a safety vent and a current blocking member having one or more gas outlets formed therein, and a gasket on the outer circumferential surface thereof. It may be configured to be mounted.

Therefore, after mounting the current blocking member, by coupling the safety vent by welding, by applying a polymer material on the upper surface of the safety vent it is possible to manufacture the cap assembly by a continuous process.

The present invention also provides a cylindrical cell consisting of including the cap assembly.

In the cylindrical secondary battery according to the present invention, in the state in which the jelly-roll type electrode assembly is mounted on a cylindrical metal can, the cap assembly is coupled to the open top of the metal can, and the negative electrode of the electrode assembly is welded to the bottom of the can, It is manufactured by welding the positive electrode of the electrode assembly to the protruding terminal of the top cap coupled to the top of the electrode assembly and the electrolyte in order to seal the battery in the built-in state.

The battery according to the present invention may preferably be a lithium secondary battery of high energy density, discharge voltage, and output stability. Other components of the lithium secondary battery according to the present invention will be described in detail below.

In general, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, a lithium salt-containing nonaqueous electrolyte, and the like.

The positive electrode is produced by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector, followed by drying, and further, a filler may be further added as necessary. The negative electrode is also manufactured by coating and drying the negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The separator is interposed between the cathode and the anode, and an insulating thin film having high ion permeability and mechanical strength is used.

The lithium salt-containing non-aqueous electrolyte solution consists of a nonaqueous electrolyte solution and a lithium salt, and a liquid nonaqueous electrolyte solution, a solid electrolyte, an inorganic solid electrolyte, and the like are used as the nonaqueous electrolyte solution.

Since the current collector, the electrode active material, the conductive material, the binder, the filler, the separator, the electrolyte, the lithium salt, and the like are known in the art, a detailed description thereof will be omitted herein.

The lithium secondary battery according to the present invention can be produced by conventional methods known in the art. That is, it may be prepared by inserting a porous separator between the anode and the cathode and injecting the electrolyte therein.

The positive electrode may be manufactured by, for example, applying a slurry containing the lithium transition metal oxide active material, the conductive material, and the binder described above onto a current collector and then drying. Similarly, the negative electrode can be prepared by, for example, applying a slurry containing the above-described carbon active material, a conductive material and a binder onto a thin current collector and then drying it.

Hereinafter, the present invention will be further described with reference to the drawings, but the scope of the present invention is not limited thereto.

3 illustrates a cap assembly structure of a secondary battery according to an exemplary embodiment of the present invention, and FIGS. 4 and 5 illustrate perspective views of the safety vent and the current blocking member used in the battery of FIG. 3, respectively.

First, referring to FIG. 3, the battery 100 according to the present invention inserts an electrode assembly (not shown) into the can 200, injects electrolyte therein, and caps on the open top of the can 200. Manufactured by mounting the assembly 300.

The cap assembly 300 has a structure in which the upper cap 310 and the internal pressure drop safety vent 320 are in close contact with the inside of the airtight gasket 400 mounted on the upper beading part 210 of the can 200. consist of. The upper cap 310 protrudes upward in the center to serve as a positive electrode terminal by connection with an external circuit, and a through hole 312 through which the compressed gas inside the can 200 can be discharged along the periphery of the protrusion. Many are formed.

Safety vent 320 is a current-carrying thin film structure, its center portion is recessed to form an indented center portion 322, and two notches having different depths at the upper and lower bending portions of the central portion 322, respectively. Fields 324 and 326 are formed.

As shown in FIGS. 3 and 4, the first notch 324 formed at the upper portion of the notches 324 and 326 forms a closed curve, and the second notch 326 formed at the lower portion has an open curve at one side thereof. It is structured. In addition, since the engagement force of the second notch 326 is made smaller than the engagement force of the first notch 324, the second notch 326 is dug deeper than the first notch 324.

When the internal pressure of the can 200 rises above the critical pressure, the second notch 326 of the safety vent 320 fails to withstand the pressure and the pressurized gas inside the can 200 causes the hole of the upper cap 310 to break. Exit at 312.

In this process, the current blocking member 600 for discharging the gas inside the battery and at the same time cut off the current is installed below the safety vent 320. The current blocking member 600 is provided with an auxiliary gasket as a member of the conductive plate.

As shown in FIG. 5, the current blocking member 600 includes a plurality of through holes 610 through which gas is discharged along a side surface thereof, and an upwardly protruding protrusion 620 is formed in the center thereof, and the protrusion 620 is formed in the current blocking member 600. Three through holes 630 and three bridges 640 connecting the through holes 630 are formed symmetrically on a concentric circle. The notch 650 is formed in the bridge 640 so that when the pressurized gas is applied to the safety vent (FIG. 2: 320) due to the pressure increase inside the battery, the indented center portion 322 is lifted up and the indented center portion is lifted. The protrusion 620 coupled with the 322 is separated from the main body of the current blocking member 600 while the notch 650 is cut out.

4 and 5, the upper surface of the protruding portion 620 and the lower surface of the indented central portion 322 of the safety vent 320 are joined by a method such as welding to form a welding coupling portion 660. However, since the safety vent 320 is made of a very thin metal plate, a pinhole or the like may occur during the welding process, which may cause moisture to penetrate or leak the electrolyte. Therefore, in order to prevent this, the upper surface of the indented central portion 322 of the safety vent 320 in a position corresponding to the welding coupling portion 660, which is a portion where the current blocking member 600 and the safety vent 320 is coupled, Polymer resin 700 is applied.

Therefore, it is possible to fundamentally improve the safety of the battery by blocking leakage and fundamentally preventing the occurrence of thermal runaway by delaying CID short circuit due to insufficient gas generation due to the pinhole. The polymer resin 700 may be made of an ultraviolet curable resin so that the notch 326 is not covered in the process of applying the polymer resin 700.

Hereinafter, the present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

Example 1

Using Ni-plated SPCE (cold rolled steel sheet), a top cap and a cylindrical can are fabricated, the electrode assembly is mounted on the cylindrical can, and then a crimping process is performed on a cylindrical can of a portion corresponding to the upper end of the electrode assembly. After forming the site, the gasket was inserted into the inner surface of the crimping site, the current blocking member was mounted, and the safety vent was combined by laser welding. At this time, welding was performed at a power about 5% higher than the general rated welding power. Then, the polyurethane oligomer mixture was applied to the site corresponding to the weld joint at the top of the safety vent, and cured by irradiation with UV. Then, a PTC element and a top cap were mounted, the top of the can was bent inward, and then a crimping and pressing process was performed to produce a cylindrical transfer battery of 18650 (diameter 18 mm, length 65 mm).

Comparative Example 1

A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that the polyurethane oligomer mixture resin was not coated on the safety vent.

Experimental Example 1

In the state where 30 batteries manufactured in Examples 1 and 2 and 30 batteries manufactured in Comparative Example 1 were inverted, the electrolyte was applied before the current blocking member (safety vent) was operated while applying pressure to the inside of the cell up to 15 kgf. Check for leaks. The results are shown in Table 1 below.

TABLE 1

As shown in Table 1, in the battery of Example 1 according to the present invention, no leakage of the electrolyte occurred in any case, whereas the cells of Comparative Example 1 were prepared before and after the operation of the current blocking member. It was confirmed that the leakage of the electrolyte occurred at. Therefore, it can be seen that the batteries according to the present invention exhibit excellent sealing properties by applying a polymer resin to the weld joint. In addition, a photograph of a welded site is shown in FIG. 6 by disassembling a battery in which electrolyte is leaked among the batteries of Comparative Example 1. As shown in FIG. 6, several pinholes were formed in the welded portion of the battery in which the electrolyte leaked, and it was confirmed that the leakage of the electrolyte occurred in the current blocking member and the safety vent welding member.

Experimental Example 2

30 batteries prepared in Example 1 and Comparative Example 1 were respectively subjected to an overcharge test of 1 C and 10 V to determine whether the batteries were ignited. The results are shown in Table 2 below.

TABLE 2

As shown in Table 2, the battery according to the embodiments of the present invention did not ignite, the battery of Comparative Example 1 can be confirmed that the two batteries ignited.

This is because the battery decomposes the electrolyte under overcharging conditions, and the internal gas is generated with an increase in temperature. In the battery according to Example 1, when the internal pressure is higher than a predetermined level, a short circuit occurs in the CID element, thereby preventing the internal high-pressure gas. This is because the ignition of the battery is prevented while being ejected.

However, in the battery of Comparative Example 1, the internal gas partially flows out through the pinhole formed in the weld joint on the safety vent, so that the CID short circuit is not caused, and the battery is ignited by the thermal runaway phenomenon.

As described above, the cap assembly according to the present invention is formed by welding a current blocking member to the bottom of the safety vent and applying a polymer resin on the corresponding portion of the safety vent to ensure the sealing of the weld joint. It is possible to fundamentally prevent moisture penetration through the pinholes, leakage of electrolyte, and delay of CID short circuit, thereby greatly improving battery safety.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (9)

A cap assembly mounted on an open upper end of a can in a battery in which an electrode assembly (jelly-roll) having a cathode / membrane / cathode structure is embedded in a cylindrical can, and which discharges a high pressure gas while rupturing when a high pressure occurs inside the battery. At the bottom of the safety vent where the notch is formed, a current blocking member that ruptures when the pressure inside the battery rises to block the current is joined by welding, and on the corresponding part of the safety vent to ensure the sealing of the welding joint. Cap assembly characterized in that the polymer resin is applied. The cap assembly of claim 1, wherein the safety vent is an aluminum sheet having a thickness of 0.15 to 0.4 mm. The safety vent of claim 1, wherein the safety vent has a shape in which the center is indented downward, and a first notch and a second notch are formed at an upper bent portion and a lower bent portion, respectively, which form the indented portion. Has a closed curve, and the second notch formed at the lower portion has a structure of an open curve on one side, and the second notch is deeper than the first notch. According to claim 1, wherein the current blocking member includes one or more through-holes for the discharge of the gas, an upwardly projecting protrusion is welded to the lower end of the indentation of the safety vent is formed in the center, jelly The anode lead connected to the anode of the roll is electrically connected through the bottom surface of the portion excluding the protrusion, and connects the through holes of 3 to 5 and the through holes concentrically around the protrusion. Cap assembly, characterized in that made of a structure in which the bridge is formed. The cap assembly of claim 1, wherein the polymer resin is an ultraviolet curable resin. 6. The cap assembly of claim 5, wherein the ultraviolet curable resin is an epoxy resin. 2. The cap assembly of claim 1, wherein the cap assembly is formed of a laminated structure of a top cap, a positive temperature coefficient element, a safety vent, and a current blocking member having one or more gas outlets, and a gasket is mounted on an outer circumferential surface thereof. Cap assembly characterized in that. A cylindrical battery comprising a cap assembly according to any one of claims 1 to 7. 9. The cylindrical battery according to claim 8, wherein the battery is a lithium secondary battery.

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