KR20130122051A - Cylindrical battery - Google Patents

Abstract

The present invention relates to a battery which includes a clamping unit which is formed on the upper side of a can to mount a cap assembly on the open side of the upper side of the cylindrical can in which an electrode assembly is embedded and provides a cylindrical battery with the clamping unit which includes a variable curved part to maintain or improve sealing properties in the battery due to an increase in pressure with regard to a gasket which is located inside when a temperature rises.

Description

Cylindrical Battery

The present invention relates to a cylindrical battery having a novel structure, and more particularly, to a battery in which a crimping portion for mounting a cap assembly to an open upper end of a cylindrical can having an electrode assembly therein is formed at an upper end of the can, And the clamping portion includes a variable bending portion for maintaining or enhancing the sealing force inside the battery due to an increase in the pressing force against the gasket positioned on the inner surface side at the time of temperature rise.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been made on lithium secondary batteries having high energy density and high discharge voltage among such secondary batteries, and commercialization Widely used.

As the application fields and products of the secondary battery are diversified, the type of the battery is also diversified to provide an appropriate output and capacity. For example, small mobile devices such as mobile phones, PDAs, digital cameras, and notebook computers use one or more small and lightweight secondary batteries per device correspondingly to the tendency to miniaturize their products.

The secondary battery is roughly classified into a cylindrical battery, a prismatic battery, and a pouch-shaped battery according to external and internal structural features. The secondary battery is classified into a jelly-roll type Type) and a stacked type (laminated type).

In the jelly-roll type electrode assembly commonly used, an electrode active material or the like is coated on a metal foil used as a collector, dried and pressed, cut into a band shape having a desired width and length, And then spirally wound. The jelly-roll type electrode assembly is mainly used for a cylindrical battery. In some cases, the jelly-roll type electrode assembly is compressed into a plate shape to be applied to a prismatic or pouch type battery.

1 shows a structure of a conventional cylindrical battery as a vertical sectional view.

1, a cylindrical battery 10 generally includes a cylindrical can 20, a jelly-roll type electrode assembly 30 housed in the can 20, a cap assembly 20 coupled to the top of the can 20, A cap assembly 40, and a clamping unit 50 for mounting the cap assembly 40.

The electrode assembly 30 has a structure in which the separator 33 is sandwiched between the anode 31 and the cathode 32 and is wound in a jelly-roll state. A positive electrode tab 34 is attached to the anode 31, And a negative electrode tab (not shown) is attached to the cathode 32 and connected to the lower end of the can 20.

The cap assembly 40 includes a top cap 41 for forming a positive terminal, a positive temperature coefficient element 42 for blocking the current due to a significant increase in battery resistance when the temperature inside the battery rises, An insulating member 44 for electrically isolating the safety vent 43 from the cap plate 45 except for a specific portion thereof, an insulating member 44 connected to the anode 31, And a cap plate 45 to which the positive electrode tab 34 is connected are stacked in order.

The clamping portion 50 is formed at the upper end of the can 20 so that the cap assembly 40 can be mounted on the open upper end of the can 20. More specifically, the crimping portion 50 is formed by bending the upper end portion of the can 20 to form the indentation 21 inward, and the cap plate 45, the insulating member 44, The vent 43 and the outer circumferential surface of the top cap 41 are sequentially inserted, and then the upper end portion is bent. As a result, the gasket 60 is wrapped around the inner surface of the clamping portion 50, and the cap assembly 40 is mounted by performing a crimping and pressing process.

However, it has been found that the cylindrical battery having such a structure has poor sealability against external impact, variable resistance of the electrically connecting portions, low safety, and difficulty in exhibiting a desired level of battery performance.

On the other hand, when the battery is exposed to a high temperature environment, a decomposition reaction of the electrolyte occurs at the positive electrode interface, thereby generating a large amount of gas. Since the gas generated in such a large amount causes an increase in the internal pressure of the battery, when the internal pressure rises to a predetermined pressure or higher, the safety vent or the like operates to discharge the high-pressure gas. However, if the clamping portion deforms before the safety vent is activated by such high-pressure gas, the sealing force of the gasket is lowered, so that the electrolyte inside the battery is discharged to the outside of the battery together with the high-pressure gas.

Specifically, when deformation of the clamping portion occurs due to an increase in internal pressure, a gap is formed on the contact surface between the tap cap and the safety vent and the gasket, or the shearing front end of the clamping portion does not strongly press the gasket, So that the contact surface between the safety vent and the top cap is momentarily spaced apart. Therefore, it has been confirmed that the electrolyte leakage in the battery along the clearance gap can cause the battery to ignite or explode, thus greatly reducing the safety of the battery.

Therefore, there is a high demand for development of a cylindrical battery capable of maintaining the sealing property from high temperature and withstand pressure while fundamentally solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

SUMMARY OF THE INVENTION An object of the present invention is to improve the safety of a battery by including a variable bending portion in a clamping portion to maintain or improve the sealing force inside the battery by increasing the pressing force against the gasket located on the inner surface side at the time of temperature rise.

It is a further object of the present invention to provide a gasket for a gasket which is formed by slanting a sidewall of a clamping part itself and an upper part of the clamping part at an angle so as to face inward and by setting a bending structure under specific conditions, Thereby minimizing deformation of the clamping portion due to strong external impact and internal pressure.

A cylindrical battery according to the present invention is a cell in which a crimping portion for mounting a cap assembly on an open upper end of a cylindrical can containing an electrode assembly is formed on an upper end of a can, And a variable bending portion that maintains or improves the sealing force inside the battery due to an increase in the pressing force for the battery.

Therefore, since the clamping portion of the cylindrical battery according to the present invention includes the variable bending portion, the variable bending portion is bent inward when the temperature is elevated so that the gasket is pressurized and sealed to prevent the electrolyte in the battery from leaking to the outside, Improves the safety by increasing the driving probability of the safety device.

In one preferred embodiment, the variable bent portion of the clamping portion may have a structure in which the radius of curvature of the end portion pressing the gasket decreases with an increase in temperature, so that the pressing force against the gasket increases.

Specifically, the fact that the radius of curvature of the end portion is small means that the end portion of the variable bent portion of the clamping portion is bent inward.

In a specific example, the variable bent portion may include a bimetal structure made of two metals having different coefficients of thermal expansion.

The bimetallic structure is not particularly limited as long as it has a structure for flexibly bending the clamping portion at the time of heating, and various examples are available.

In one example, the bimetallic structure has a structure in which a first metal having a relatively low coefficient of thermal expansion is located on the inner side and a second metal having a relatively large thermal expansion rate is located on the outer side, Since the metal has a thermal expansion coefficient higher than that of the first metal located on the inner side, the second metal located on the outer side at the time of heating elevates the inner metal while pressing the first metal. For example, the thermal expansion coefficient of the first metal may be 80% or less, preferably 20 to 80%, more preferably 30 to 70% of the thermal expansion coefficient of the second metal.

The first metal and the second metal are not particularly limited as far as they have different thermal expansion coefficients, but the first metal may be iron and the second metal may be copper.

The bimetallic structure is a structure in which, for example, a metal bonding body in which an inner first metal having a relatively low coefficient of thermal expansion and a second metal having a relatively large thermal expansion ratio are bonded to each other is welded to the upper end of the can .

In this case, it is preferable that the can is made of stainless steel so as to facilitate welding with the bimetal.

In some cases, in the bimetallic structure, a structure (a) in which a first metal having a relatively smaller coefficient of thermal expansion than that of the can is bonded to the inside of the can, or a structure in which a second metal having a relatively higher coefficient of thermal expansion And a structure (b) bonded to the substrate.

The clamping portion is gently bent at an upper end of the clamping portion so as to cover the gasket with a predetermined radius of curvature R. The bending sheath extends inward to urge the gasket, And a slope may be formed at a predetermined angle such that the upper portion thereof faces the inside.

Therefore, in the cylindrical battery according to the present invention, the sidewall of the clamping portion is inclined at a predetermined angle so that the sidewall itself and the upper portion of the clamping portion face inward, so that it may occur when a physical shock is applied from the outside By minimizing the deformation of the crimping portion, leakage of the electrolytic solution can be prevented.

Particularly, when a strong external force is applied to the side or corner of the battery, the impact is partially absorbed by the tilted portion of the side wall, and the impact is concentrated on the lower portion of the side wall of the clipping portion relatively, Lt; / RTI > Therefore, in spite of a strong external impact, the deformation of the crimping portion hardly occurs, or only the deformation to the extent of securing the safety of the battery is caused, so that a remarkable effect can be exerted in the safety of the battery.

Furthermore, in the secondary battery according to the present invention, when the angle of the bending shear end of the clamping portion is set to a predetermined condition, the deformation of the clamping portion due to the increase of the internal pressure can be minimized, thereby further improving the safety of the battery.

The inclined angle of the side wall of the clamping portion can be appropriately determined in consideration of the mechanical strength of the can, the elasticity and durability of the gasket, and the like, preferably within a range that does not cause deformation of the cap assembly. Preferably, To 8 degrees, more preferably from 1 to 5 degrees.

When the inclination angle is more than 8 degrees, the gasket is excessively pressed, so that it is difficult to maintain the inclination due to the elastic force of the gasket, and it is possible to cause deformation of the safety component inside. If it is less than 1 degree, the effect according to the present invention is difficult to exhibit.

The starting point of the inclined portion formed on the sidewall of the clamping portion is not particularly limited but may be a structure disclosed in the lower end portion of the clamping portion or a structure initiated in the vicinity of the center of the clamping portion.

For example, when an external force is applied horizontally in the lateral direction of the battery, in the structure in which the sidewall slope starts at the lowermost end of the side wall, the impact is concentrated on the narrow portion, so cracks are generated inside, As pressure is applied, a large deformation may be caused. On the contrary, when the sidewall inclination starts at a position deviated much toward the upper end thereof, the upper end portion of the clamping portion is also subjected to an impact of approximately the same degree as the lower end portion, so that the effect of the impact reduction is small, so that it is difficult to minimize deformation of the clamping portion. Therefore, the slope of the sidewall is preferably set to a range that minimizes deformation of the clamping portion, and it is particularly preferable that the sidewall slope is initiated within a range of up to 30% with respect to the total length of the sidewalls with respect to the center of the sidewall .

The slope forming method and process are not particularly limited. For example, the slope forming method and the slope forming step may be formed during manufacturing of the battery can, or may be formed in the process of forming the clamping part after inserting the electrode assembly into the battery can, May be formed after mounting the cap assembly on the open upper end of the can of the battery to facilitate mounting of the cap assembly and to sufficiently press the gasket located on the inner side of the clamping portion.

Further, the crimping portion according to the present invention is gently bent so as to cover the gasket located on the inner side. The gasket electrically separates the safety vent from the top cap and seals the inside of the battery. However, when the internal pressure of the battery rises due to overcharging or the like of the battery, the gasket may be subjected to severe deformation, thereby greatly reducing the sealing force inside the battery and causing leakage. It is important. Therefore, the bending shear end of the clamping portion extends inward so as to sufficiently press the gasket while preventing the gasket from being severely deformed, and is inclined at a predetermined angle with respect to the side surface of the clamping portion.

The extension length of the clamping portion to the inside can be appropriately determined in consideration of the mechanical strength of the can, the elasticity and durability of the gasket, etc. In one preferred example, the bending shear is 2 to 3 mm As shown in FIG.

The bending shear may be inclined at an angle of 60 to 85 degrees with respect to the side wall of the clamping portion so that the gasket can be pressed by applying a predetermined pressure while maintaining the adhesion between the gasket and the clamping portion. have. Therefore, since the gasket is properly pressed by the bending shear, the leakage of the electrolyte due to the internal pressure (leakage of the electrolyte solution) can be prevented and ultimately the safety of the battery can be greatly improved.

When the extension length to the inner side is too short or the angle of the shear bending is too large, the gasket can not be sufficiently pressed due to the deformation of the clamping portion, so that there is a possibility that leakage of the electrolytic solution occurs. Conversely, if the extension length to the inner side is too long or the angle of the bending shear is too small, it is not preferable because the bent end strongly presses the gasket and damages the gasket.

The bending process is not particularly limited, but may be carried out discontinuously, for example. That is, the bending shear is first bent so as to be substantially perpendicular to the central axis direction of the top cap with respect to the side surface of the clamping portion, and the bent portion is secondarily bent at an angle of 60 to 85 degrees so as to be in close contact with the upper end of the gasket And may be discontinued by a post-compression process. In this case, the time difference between the first bending process and the second bending process means a time difference in the amount of time that the stress can be dispersed from the bent portion where the stress is concentrated to the surrounding portion. This discontinuous bending can greatly reduce the possibility of breakage of the bending portion.

The clamping portion may be such that its upper end portion is gently bent to a predetermined radius of curvature (R value), and the radius of curvature is preferably 0.3 to 2 mm, as defined above.

When the radius of curvature (R value) is 2 mm or more, when the external force is applied from the side direction, the bent portion is deformed due to the generation of stress, so that the bending shear is separated from the gasket and leakage of electrolyte may occur. On the other hand, when the bending change (R value) is smaller than 0.3 mm, the deformation of the bent portion and the separation of the bent end portion due to the external force or the internal pressure from the lateral direction can be prevented, Stress is concentrated at the bending portion at the time of application, cracks are generated at the corresponding portion, and a sharp angle is formed in the cross-sectional direction, so that handling during use is not preferable.

The thickness of the cylindrical can is preferably 0.15 to 0.35 mm. If the thickness of the cylindrical can is too thin, the mechanical strength is inevitably lowered, and welding failure may occur in the process of welding the negative electrode lead to the lower surface of the cylindrical can, There is concern. Conversely, if the thickness of the can is too large, the total weight of the battery increases and the area of the electrode assembly relatively decreases, resulting in a reduction in the capacity of the battery, and beading and crimping It is not easy.

Meanwhile, since the cap assembly has a stacked structure of a top cap, a positive temperature coefficient element, and a safety vent, in which at least one gas outlet is formed, and a gasket is mounted on the outer circumferential surface thereof, Can be welded to the safety vent to enable fabrication of the cap assembly by a continuous process.

The safety vent is a kind of safety element that secures 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 deterioration of the battery components. For example, when gas is generated inside the battery and the internal pressure increases beyond the threshold, the safety vent ruptures, and the gas discharged to the ruptured portion is discharged through one or two gas outlets formed in the top cap .

Accordingly, 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 enough to be ruptured by an increase in the internal pressure of the critical value or more.

In a preferred example, the safety vent has a downwardly recessed shape, and a first notch and a second notch are formed in the upper bending portion and the lower bending portion forming the indentation portion, respectively, And the second notch formed at the lower portion has a structure of an open curve with one side opened and the second notch can have a structure that is deeper than the first notch.

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

The battery according to the present invention can be used as a power source for a device requiring a high degree of safety because it is often subjected to an external impact or an internal short circuit of the battery. It can be used as a power tool or a cylindrical battery for a notebook PC, which is often exposed to impact.

Meanwhile, in the cylindrical battery of the present invention, the cap assembly is coupled to the open upper end of the metal can while the jelly-roll type electrode assembly is mounted on the cylindrical metal can, the cathode of the electrode assembly is welded to the lower end of the can , And welding the positive electrode of the electrode assembly to a cap assembly coupled to the top of the electrode assembly to seal the battery with the electrolyte built-in.

The battery according to the present invention may preferably be a lithium secondary battery having 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.

Generally, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte containing a lithium salt, and the like.

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

The separation membrane 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 nonaqueous electrolyte solution is composed of a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte solution, a liquid nonaqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte are used.

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

The lithium secondary battery according to the present invention can be manufactured by a conventional method known in the art. That is, a porous separator may be inserted between the anode and the cathode, and an electrolyte may be injected into the separator.

The anode can be produced, for example, by applying a slurry containing the above-described lithium transition metal oxide active material, a conductive material and a binder on a current collector, followed by drying. Likewise, the negative electrode can be produced, for example, by 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.

As described above, the cylindrical battery according to the present invention includes the variable bending portion of the clamping portion. Therefore, the sealing force inside the battery can be maintained or improved by increasing the pressing force against the gasket positioned on the inner surface side at the time of temperature rise, Can greatly improve.

Since the side wall itself of the clamping portion and the upper portion thereof are inclined at a predetermined angle so as to face inward and the bending structure is set under a specific condition, the external impact is partially absorbed and the gasket is strongly adhered, Thereby minimizing deformation of the clamping portion due to impact and internal pressure.

1 is a schematic cross-sectional view showing a top structure of a conventional cylindrical battery;
2 is a schematic cross-sectional view showing a top structure of a cylindrical battery according to one embodiment of the present invention;
3 is a cross-sectional schematic diagram illustrating a bimetal structure according to various embodiments of the present invention;
FIG. 4 is a schematic cross-sectional view showing that the bimetallic structures of FIG. 3 are deformed at an elevated temperature; FIG.
5 is a perspective view of a safety vent used in the cylindrical battery of FIG. 2;
6 is a schematic cross-sectional view showing a top structure of a cylindrical battery according to another embodiment of the present invention;
Fig. 7 is an enlarged view of a modification of the clamping portion in the cylindrical battery of Fig. 6;

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

FIG. 2 is a schematic cross-sectional view showing an upper structure of a cylindrical battery according to an embodiment of the present invention.

2, the cylindrical battery 100 includes a clamping portion 500 for mounting the cap assembly 300 at the open upper end of the cylindrical can 200 having the electrode assembly 110 therein, And is formed at the upper end.

The clamping part 500 includes a variable bending part 700 for increasing or decreasing the sealing force inside the battery 100 by increasing the pressing force against the gasket 400 located on the inner surface side during the temperature increase.

The variable bending portion 700 has a bimetal structure composed of two metals having different coefficients of thermal expansion. The radius of curvature of the end portion that presses the gasket 400 decreases with an increase in temperature, so that the pressing force against the gasket 400 increases .

Specifically, the cylindrical battery 100 is manufactured by inserting the electrode assembly 110 into the can 200, injecting the electrolyte therein, and mounting the cap assembly 300 at the open upper end of the can 200 .

The cap assembly 300 has a laminated structure of a top cap 310, a PTC element 315 and a safety vent 320 having four gas outlets 312. The gasket 400 is formed on the outer circumferential surface of the cap cap 310, Respectively.

That is, the cap assembly 300 includes a top cap 310 and a safety vent 320 for lowering the inner pressure in close contact with each other in the airtightness maintaining gasket 400 mounted on the upper beading portion 210 of the can 200 And is attached to the open upper end of the can 200 by the crimping portion 500 of the structure. The top cap 310 protrudes upward to serve as a positive terminal by connection with an external circuit and has a gas outlet 312 through which compressed gas in the can 200 can be discharged along the periphery of the protrusion Are formed.

The safety vent 320 is a thin film structure through which the current passes. The central portion of the safety vent 320 is depressed to form a recessed central portion 322. The upper and lower bent portions of the central portion 322 are formed with two notches 324 and 326 are formed. A current blocking member 600 for discharging gas inside the battery and for blocking current is provided below the safety vent 320.

3 is a cross-sectional schematic diagram illustrating a bimetal structure according to various embodiments of the present invention.

Referring to FIG. 3 together with FIG. 2, the bimetallic structure (a) is a metal having a first metal 702 having a relatively small coefficient of thermal expansion and an outer second metal 704 having a relatively large thermal expansion coefficient The joined body is welded to the upper outer surface of the can 200.

The bimetallic structure (b) has a first metal (702) having a relatively smaller thermal expansion coefficient than the can (200) is bonded to the inside of the can (200), and the bimetallic structure (c) The large second metal 704 is bonded to the outside of the can 200.

Depending on the case, the upper end portion of the can 200 itself may be made of a bimetallic structure of an inner first metal 702 having a relatively small coefficient of thermal expansion and an outer second metal 704 having a relatively large thermal expansion coefficient It should be understood that various modifications may be made without departing from the scope of the present invention.

FIG. 4 is a schematic cross-sectional view showing that the bimetallic structures of FIG. 3 are deformed at an elevated temperature.

Referring to FIG. 4 together with FIG. 2 and FIG. 3, the bimetallic structure a 'at the time of heating is higher than the thermal expansion rate of the first metal 702' because the second metal 704 ' The first metal 702 'and the end of the can 200' are pressed and bent inward to increase the sealing force of the gasket 400.

In addition, the bimetal structure (b ') at the time of temperature elevation is such that the can 200' has a thermal expansion rate higher than that of the first metal 702 'so that the end portion of the first metal 702' And the bimetallic structure c 'is formed such that the second metal 704' has a thermal expansion rate higher than that of the can 200 ', so that the end of the can 200' is bent by the thermal expansion at the time of temperature increase.

5 is a perspective view of a safety vent used in the cylindrical battery of FIG. 2; FIG.

Referring to FIG. 5 together with FIG. 2, the safety vent 320 is a thin film structure through which current flows. The central portion of the safety vent 320 is depressed to form a recessed central portion 322, Two notches 324 and 326 having different depths are formed in the regions.

Meanwhile, the first notch 324 formed in the upper portion of the notches 324 and 326 forms a closed curve, and the second notch 326 formed in the lower portion has an open curve structure with one side opened. Since the engaging force of the second notch 326 is made smaller than the engaging force of the first notch 324, the second notch 326 is deeper than the first notch 324.

Accordingly, when the inner 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 in the can 200 flows into the top cap 310 Through the through-hole 312 of the base plate 311. As shown in FIG.

6 is a schematic cross-sectional view showing an upper structure of a cylindrical battery according to another embodiment of the present invention, and FIG. 7 is a schematic view showing an enlarged view of a modification of the crimping portion in the cylindrical battery of FIG. 6 have.

Referring to these figures, in the cylindrical battery 100a, the end portion 328 of the safety vent 320a surrounds the outer peripheral surface of the top cap 310 and the PTC element 315, and the clamping portion 501 2, and the top surface of the sidewall has a somewhat gentle shape in the case of the same angle.

7, the side wall portion 521 is structured such that the inclination starts at a portion deflected downward with respect to the center of the side wall portion 521 within a range of 30% with respect to the total length of the clamping portion 501 . This inclination forms an angle (?) Of 1 to 8 degrees with respect to the vertical plane of the side wall, whereby the side wall portion 521 has a large pressing force against the gasket 400 and exhibits high sealing performance.

Therefore, when a strong external force is applied in the lateral direction, the impact is partially absorbed by the sidewall slope formed at the predetermined angle?, And the impact is concentrated on the lower end side of the side wall portion 521 of the clamping portion 501, Since the relatively low impact is applied to the bending front end 511 positioned at the upper end of the pinging portion 501, the adhesion with the gasket 400 located on the inner side surface of the clamping portion 501 can be maintained.

In addition, when a strong external force is applied in the corner direction, the sidewall portion 521 is generally deformed outward, so that the front end of the bending tendency tends to be moved upward. However, Adhesion to the surface is maintained. Therefore, the clamping portion 501 having a slope at a predetermined angle? Has a high resistance to an external force and plays a role of suppressing deformation.

Further, the bending shear 511 bent at an angle? Of 60 to 85 degrees is excellent in shape retention even when the internal pressure of the battery is increased. Therefore, the adhesion with the gasket 400 is not significantly reduced, can do.

The bending shear end 511 extends inward while being bent at a predetermined angle alpha from the side of the clamping portion 501 and the radius of curvature R, the bending angle alpha, the inner extension length, etc. are as described above .

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (19)

A battery in which a crimping portion for mounting a cap assembly on an open upper end of a cylindrical can in which an electrode assembly is embedded is formed at an upper end of the can, wherein the crimping portion is formed by an increase in pressing force against a gasket located on an inner surface side at an elevated temperature. A cylindrical battery comprising a variable bending portion for maintaining or improving the sealing force therein. The cylindrical battery according to claim 1, wherein the variable bending portion of the clamping portion has a radius of curvature at an end portion where the gasket is pressed against the gasket, the pressing force of the gasket being increased. The cylindrical battery according to claim 1, wherein the variable bending part includes a bimetal structure made of two metals having different thermal expansion coefficients. 4. The cylindrical battery according to claim 3, wherein the bimetal structure has a structure in which a first metal having a relatively low thermal expansion rate is located inside and a second metal having a relatively high thermal expansion rate is located outside. The cylindrical battery according to claim 4, wherein the first metal is iron and the second metal is copper. 4. The bimetallic structure of claim 3, wherein the bimetallic structure is formed by joining a metal joined body, in which a first inner metal having a relatively low coefficient of thermal expansion and a second outer metal having a relatively large thermal expansion, is joined to the top of the can by welding. Cylindrical battery, characterized in that consisting of a structure. The cylindrical battery according to claim 6, wherein the can is made of stainless steel. 4. The bimetallic structure of claim 3, wherein the bimetal structure includes a structure in which a first metal having a relatively smaller thermal expansion coefficient is bonded to the inside of the can, or a second metal having a larger thermal expansion coefficient than the can. A cylindrical battery comprising a structure (b) bonded to the outside. 2. The gasket according to claim 1, wherein the clamping portion has an upper end portion thereof gently bent at a predetermined radius of curvature (R) so as to cover the gasket, a bending shear extends inward to urge the gasket, Wherein a slope is formed at a predetermined angle so that the upper portion of the side wall faces the inside. The cylindrical battery according to claim 9, wherein the predetermined angle is 1 to 8 degrees with respect to the side surface of the can. 10. The cylindrical battery according to claim 9, wherein the inclination is started within 30% up and down with respect to the total length of the side wall with respect to the center of the side wall. The cylindrical battery according to claim 9, wherein the bending shear extends from the side of the crimping portion to a length of 2 to 3 mm. The cylindrical battery according to claim 9, wherein the bent front end is inclined at an angle of 60 to 85 degrees with respect to a side wall of the clamping portion. The cylindrical battery according to claim 9, wherein the R value is 0.3 to 2 mm. The cylindrical battery according to claim 9, wherein the thickness of the cylindrical can is 0.15 to 0.35 mm. The cap assembly according to claim 1, wherein the cap assembly has a stacked structure of a top cap having at least one gas outlet, a positive temperature coefficient element, and a safety vent, and a gasket is mounted on an outer circumferential surface thereof Features a cylindrical battery. 17. The cylindrical battery according to claim 16, wherein the safety vent is an aluminum plate having a thickness of 0.15 to 0.4 mm. The method of claim 16, wherein the safety vent has a center indented downwardly, the upper bent portion and the lower bent portion forming the indentation is formed with a first notch and a second notch, respectively, the first notch Has 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 deeper than the first notch. The cylindrical battery according to claim 1, wherein the battery is used as a power source for a device exposed to frequent vibration and shock.

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