KR100659846B1 - Secondary Battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery, and more particularly, a radius of curvature of a vertex portion of the current blocking means used in the cap assembly of the lithium secondary battery, the via hole, which is an electric conducting portion and a breaking portion, is broken in a substantially rectangular shape and is broken below a certain level. The present invention relates to a lithium secondary battery having a constant operating pressure of the current interrupting means, thereby reducing the current interruption distribution of the current interrupting means and improving the stability of the lithium secondary battery.

Lithium secondary battery, current blocking means, via hole, radius of curvature

Description

Lithium Secondary Battery

1 is a cross-sectional view of a cylindrical lithium secondary battery according to an embodiment of the present invention.

Figure 2 is an exploded perspective view of a cap assembly of a cylindrical lithium secondary battery according to an embodiment of the present invention.

Figure 3a is a plan view of a current blocking means according to an embodiment of the present invention.

3B is a cross-sectional view taken along the line A-A of FIG. 3A.

4 is a plan view of a current blocking means according to another embodiment of the present invention.

5 is a plan view of a current blocking means according to another embodiment of the present invention.

6 is a cross-sectional view of the current blocking means according to another embodiment of the present invention.

Figure 7 is a cross-sectional view of the cylindrical lithium secondary battery showing the action of breaking the current blocking means according to an embodiment of the present invention to block the current.

<Description of Symbols for Major Parts of Drawings>

100-cylindrical lithium secondary battery 200-electrode assembly

300-cylindrical can 400-cap assembly

410-Safety Vent 420-Current Breaking Means

422-Insulated Printing Board 424-Outer Ring

426-Crossbar 430-Via Hole

434-Center breaking groove 436-Side breaking groove

440-Upper conductive thin film 450-Lower conductive thin film

460-Conductive Layer 480-Secondary Protection Devices

490-Cap Up

The present invention relates to a lithium secondary battery, and more particularly, a radius of curvature of a vertex portion of the current blocking means used in the cap assembly of the lithium secondary battery, the via hole, which is an electric conducting portion and a breaking portion, is broken in a substantially rectangular shape and is broken below a certain level. The present invention relates to a lithium secondary battery having a constant operating pressure of the current interrupting means, thereby reducing the current interruption distribution of the current interrupting means and improving the stability of the lithium secondary battery.

Lithium secondary batteries are classified into cylindrical lithium secondary batteries and rectangular lithium secondary batteries according to their appearance. Cylindrical lithium secondary battery is a safety of lithium secondary battery by blocking the current inside the secondary battery in the cap assembly when the internal pressure of the battery rises above the specified level due to overcharge or abnormal operation and there is a risk of explosion. Is improving.

The cap assembly structure of the cylindrical lithium secondary battery is disclosed in Korean Patent No. 10-0357950. According to the disclosure, the cylindrical lithium secondary battery includes a cylindrical assembly forming an outer appearance and a cap assembly coupled and sealed through an insulating gasket in an upper opening of the can. The cylindrical can accommodates an electrode assembly electrolyte in which a positive electrode plate, a negative electrode plate, and a separator inserted between the positive electrode plate and the negative electrode plate are wound in a jelly roll form.

The cap assembly includes a safety vent, a current blocking means, a secondary protective element, and a terminal cap (or cap up). The safety vent has a plate-shaped protrusion projecting downward in the center thereof and is positioned below the cap assembly, and the protrusion deforms upward by the pressure generated inside the secondary battery. At a lower surface of the safety van, one electrode plate, for example, a positive electrode tab drawn from the positive electrode plate, of the positive electrode plate and the negative electrode plate of the electrode assembly is welded to electrically connect the safety vane and the positive electrode plate of the electrode assembly. Here, the remaining electrode plate, for example, the negative electrode, of the positive electrode plate and the negative electrode plate is electrically connected to the can by a tab or direct contact method (not shown).

The current interrupting device (hereinafter referred to as "CID") is installed above the safety vent, and conducts current flowing through the safety vent to flow to the secondary protection element. However, when the secondary battery is abnormally operated and the internal pressure of the secondary battery rises above the prescribed level, the protrusion of the safety van is deformed upward, and the current blocking means is destroyed by the protrusion to destroy the flow of current.

Conventional current blocking means is formed in a shape including a circular outer ring and a crossbar crossing the center of the outer ring, the insulating printed circuit board and the insulating printed circuit board having a substantially circular via hole at the center of the crossbar. It is formed to include a conductive thin film in the upper and lower portions, respectively. One side of the upper conductive thin film of the conductive thin film is connected to the outer ring of the insulated printed board, but the other side is formed not to be connected to the outer ring. On the contrary, one side of the lower conductive thin film is not connected to the outer ring, and the other side thereof is connected to the outer ring. In the via hole, a conductive layer is formed of a conductive metal such as copper to electrically connect the upper and lower conductive thin films. The crossbars have breakage portions formed on both sides of the via hole-formed portion so that the crossbars can be easily broken.

However, in the conventional current interrupting means, the via hole at the center of the crossbar and the break portion at the side surface are formed in a circular or curved surface so that the breaking pressure of the crossbar is not constant. Therefore, the current interruption distribution of the current interruption means is not constant. When the current interruption means is not operated, current flow continues even when there is a problem with the lithium secondary battery, thereby causing a problem in the safety of the lithium secondary battery. .

The present invention has been made in order to solve the problems described above so that the curvature radius of the vertex portion of the current blocking means used in the cap assembly of the lithium secondary battery is a rectangular portion of the via hole, which is a breakdown portion and the fracture portion is formed to be less than a certain degree. Accordingly, an object of the present invention is to provide a lithium secondary battery in which the operating pressure of the current blocking means is constant to reduce the current blocking distribution of the current blocking means and improve the stability of the lithium secondary battery.

The lithium secondary battery of the present invention devised to achieve the above object includes a cap assembly having a safety vane and a current blocking means seated on an upper portion of the safety vane, wherein the current blocking means includes an outer ring and an inner surface. An insulated printed substrate including a crossbar having a via hole having a conductive layer formed thereon, an upper conductive thin film formed in a predetermined region of an upper surface of the insulated printed substrate, and a lower conductive thin film formed in a predetermined region of a lower surface of the insulated printed substrate. In the lithium secondary battery is formed, the via hole is characterized in that the one of the diagonal in a substantially rectangular shape is formed to be perpendicular to the longitudinal direction of the crossbar. In this case, the via hole is preferably formed in a square or rhombus. In addition, the via hole may be formed with a corner vertex forming a diagonal perpendicular to the longitudinal direction of the crossbar. In addition, it is preferable that the via hole has a radius of curvature of a fracture vertex forming a diagonal line perpendicular to the longitudinal direction of the crossbar smaller than 0.3 mm. In the present invention, the via hole is preferably formed such that a diagonal line perpendicular to the crossbar has a length of at least 25% of the crossbar width.

In addition, in the present invention, the crossbar may be formed by further comprising a side break groove formed to a predetermined depth on at least one side of the both ends coupled to the outer ring. In this case, the side break groove is preferably formed to a depth such that the cross-sectional area of the crossbar portion where the side break groove is formed is larger than the cross-sectional area of the crossbar portion where the via hole is formed.

In addition, in the present invention, the crossbar may further include a center fracture groove formed in a notch shape at a predetermined angle on at least one side of the position where the via hole is formed. In this case, the center fracture groove may be formed at a right angle. In addition, the center fracture groove may have a radius of curvature of the notch smaller than 0.3 mm. In addition, the center fracture groove is preferably formed to have a depth within 50% of the distance between the side of the crossbar and the via hole.

The crossbar may further include side break grooves formed on at least one side of both side ends coupled with the outer ring together with the center break groove. In this case, the side break groove is preferably formed to a depth such that the cross-sectional area of the crossbar portion where the side break groove is formed is larger than the cross-sectional area of the crossbar portion where the via hole is formed.

Further, in the present invention, the upper conductive thin film and the lower conductive thin film may further include an insulating layer on the surfaces formed on the upper and lower surfaces of the crossbar. In this case, the insulating layer may be formed of a polyimide layer.

In addition, in the present invention, the conductive layer formed on the inner surface of the via hole may be formed of copper metal or copper alloy, and the conductive layer is formed to a thickness of at least 5 μm.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

1 is a cross-sectional view of a cylindrical lithium secondary battery according to an embodiment of the present invention. 2 is an exploded perspective view of a cap assembly of a cylindrical lithium secondary battery according to an embodiment of the present invention. Figure 3a shows a plan view of the current blocking means according to an embodiment of the present invention. 3B is a cross-sectional view taken along the line A-A of FIG. 3A. 4 is a plan view of a current blocking means according to another embodiment of the present invention. 5 is a plan view of a current blocking means according to another embodiment of the present invention. 6 is a sectional view showing a current blocking means according to another embodiment of the present invention. 7 is a cross-sectional view of a cylindrical lithium secondary battery showing an action of breaking current by breaking current blocking means according to an embodiment of the present invention.

Cylindrical lithium secondary battery 100 according to an embodiment of the present invention, referring to Figure 1, the electrode assembly 200, the cylindrical can 300 for receiving the electrode assembly 200 and the electrolyte, and It is formed on the cylindrical can 300 is formed to include a cap assembly 400 for sealing the cylindrical can 300 and flowing the current generated in the electrode assembly 200 to an external device.

The electrode assembly 200 includes a positive electrode plate 210 coated with a positive electrode active material layer on a surface of a positive electrode current collector, and a negative electrode plate 220 coated with a negative electrode active material layer on a surface of a negative electrode current collector, and the positive electrode plate 210 and a negative electrode plate 220. The separator 230, which is positioned between the electrodes and electrically insulates the positive electrode plate 210 and the negative electrode plate 220, is wound and formed in a jelly-roll shape. Although not shown in detail in the drawing, the positive electrode plate 210 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on both surfaces thereof. have. Both ends of the positive electrode plate 210 are provided with a positive electrode current collector region, that is, a positive electrode non-coating portion, in which a positive electrode active material layer is not formed. One end of the positive electrode non-coating portion is generally formed of aluminum (Al), and the positive electrode tab 215 protruding a predetermined length to the upper portion of the electrode assembly 200 is bonded. In addition, the negative electrode plate 220 includes a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces thereof. Both ends of the negative electrode plate 220 are provided with a negative electrode current collector region, that is, a negative electrode non-coating portion, in which a negative electrode active material layer is not formed. One end of the negative electrode non-coating portion is generally formed of nickel (Ni), and the negative electrode tab 225 protruding a predetermined length to the lower portion of the electrode assembly 200 is bonded. In addition, the upper and lower portions of the electrode assembly 200 may further include insulating plates 241 and 245 for preventing contact with the cap assembly 400 or the cylindrical can 300, respectively.

The cylindrical can 300 has a cylindrical side plate 310 having a predetermined diameter and a bottom plate sealing the lower portion of the cylindrical side plate 310 so that a predetermined space in which the cylindrical electrode assembly 200 can be accommodated is formed. 320 is formed, and an upper portion of the cylindrical side plate 310 is opened to insert the electrode assembly 200. By bonding the negative electrode tab 225 of the electrode assembly 200 to the center of the lower plate 320 of the cylindrical can 300, the cylindrical can 300 itself serves as a negative electrode. In addition, the cylindrical can 300 is generally formed of aluminum (Al), iron (Fe) or an alloy thereof. In addition, the cylindrical can 300 is formed with a clipping portion 330 bent from the top to the top to press the upper portion of the cap assembly 400 coupled to the upper opening. In addition, the cylindrical can 300 is beaded inwardly so as to press the lower portion of the cap assembly 400 at a position spaced apart from the creeping portion 330 by a distance corresponding to the thickness of the cap assembly (beading) A portion 340 is further formed.

2, the cap assembly 400 includes a safety vent 410, a current interruption stage 420, a secondary protection element 480, and a cap up 490.

The safety vent 410 is formed in a disk shape by a conductive metal material, and includes a protrusion 412 protruding downward in the center thereof, and is positioned below the cap assembly 400. The safety vent 410 is preferably formed of aluminum metal or nickel metal. The positive electrode tab 215 is electrically coupled to the lower portion of the safety vent 410, and preferably welded to the protrusion 412. The protrusion of the safety vent 410 is formed to protrude downward in a normal state. When the pressure inside the secondary battery increases due to overcharge, discharge, or overheating of the secondary battery, the protrusion protrudes upward. Is formed.

The secondary protection element 480 is formed in a ring shape having an outer diameter and a predetermined width corresponding to the outer diameter of the safety vent 410, is seated and coupled to the upper portion of the current blocking means 420, Increasing the temperature will block the flow of current. The secondary protection device 480 preferably uses a positive temperature coefficient (PTC) device. The PTC element is formed of an element layer formed of a resin and carbon powder and a conductive plate bonded to the upper and lower surfaces of the element layer. When the temperature of the PTC element is increased, the resin of the resin layer expands to connect the carbon powder. To cut off the current. Of course, a ceramic device may be used as the PTC device.

Of course, the secondary protection device 480 may be omitted when configuring the cap assembly 400 as necessary.

The cap up 490 is coupled to the upper seat of the cap assembly 400, and energizes current generated from the lithium secondary battery to the outside.

3A and 3B, the current blocking means 420 is formed to include an insulating printed board 422, an upper conductive thin film 440, a lower conductive thin film 450, and a conductive layer 460. When the protrusion 412 of the safety vent 410 is mounted on the safety vent 410 and the inverted portion of the safety vent 410 is inverted, the insulation printed circuit board is broken to block the current flowing from the safety vent 410.

The insulating printed board 422 is generally formed of an insulating material used for a printed circuit board (PCB), and includes an outer ring 424 and a crossbar 426. The outer ring 424 is formed in a size corresponding to the safety vent 410, and is formed in a ring shape having a predetermined width. The outer ring 424 is preferably seated on the upper portion of the outer ring 424 and is formed to have a width corresponding to the width of the secondary protection element 480 formed in a ring shape.

The crossbar 426 is formed integrally with the outer ring 424 in a bar shape, and is formed to cross the center of the outer ring 424. That is, the crossbar 426 crosses the center of the outer ring 424, and both side ends thereof are integrally connected to the inner side of the outer ring 424. The crossbar 426 is formed with a via hole 430 formed at the center corresponding to the protrusion 412 of the safety vent 410.

The via hole 430 is formed at a position corresponding to the protrusion 412 of the safety vent 410 at the central portion of the crossbar 426, so that the crossbar 426 may be broken at the center portion. That is, when the protrusion of the safety vent 410 is deformed upward by the internal pressure of the lithium secondary battery and the pressure is applied to the center of the crossbar 426, the crossbar 426 is broken at the center of the crossbar 426. ) Are formed to be separated from each other.

The via hole 430 is formed in a substantially rectangular shape such that one of the diagonals is perpendicular to the longitudinal direction of the crossbar 426, and preferably, is formed in a square or rhombus shape. The via hole 430 has a vertex 432 which is a vertex constituting a diagonal line formed perpendicularly to the longitudinal direction of the crossbar 426 among the diagonal lines in a rectangular shape, and is formed in a notch shape having a predetermined angle according to the quadrangle shape. Preferably it is formed at a right angle. Here, the right angle means an angle at which two straight lines forming the break vertexes 432 meet in a straight state so that an arc is not formed. When the fracture vertexes 432 of the via holes 430 cannot be formed at right angles, the radius of curvature is preferably smaller than 0.3 mm. When the radius of curvature of the break vertexes 432 is greater than 0.3 mm, the break position of the crossbar 426 is changed to cause a break pressure. When the fracture vertexes 432 of the via hole 430 are formed at almost right angles, the location at which the fracture ruptures are broken at the via holes becomes constant, and distances from the fracture vertexes 432 to both ends of the crossbar 426 are constant. . Accordingly, the crossbar 426 is broken at a break point 432 of the via hole 430 formed at a uniform position of the via hole 430, that is, a position close to the cross bar 426, and determines the crossbar 426. The pressure becomes uniform.

When the via hole 430 is formed in a quadrangular shape, the diagonal length perpendicular to the longitudinal direction of the crossbar 426, that is, the diagonal connecting the break vertexes 432 on both sides thereof is at least 25 times the width of the crossbar 426. It is formed to have a diameter corresponding to%. When the length of the diagonal of the via hole 426 is smaller than 25% of the width of the crossbar 426, the decrease in the breaking strength of the via hole 430 is weaker than that of other portions, so that the center portion of the crossbar 426 is constantly broken. Will not be.

In addition, a conductive layer 460 is formed on the inner surface of the via hole 430 by a conductive metal, preferably, a copper metal or a copper alloy. The conductive layer 460 of the via hole 430 is preferably formed by a plating process that is easy to control the thickness and the process is simple. The conductive layer 460 is formed to a thickness of at least 5㎛. When the thickness of the conductive layer 460 is smaller than 5 μm, the formation of the conductive layer 460 is incomplete, resulting in the inability of current to flow and an increase in electrical resistance.

 On the other hand, the cross bar 426 should be formed so that the breaking pressure can be broken at a pressure less than the deformation pressure of the safety vent 410. Therefore, in determining the width of the crossbar 426 and the size of the via hole 430, the deformation pressure of the safety vent 410 and the breaking pressure of the crossbar 426 should be considered.

The upper conductive thin film 440 is formed of a conductive metal having a predetermined thickness, and is preferably formed of a copper metal or a copper alloy. However, the material of the upper conductive thin film 440 is not limited thereto. The upper conductive thin film 440 is formed in a region including the via hole 430 from one end of the upper surface of the crossbar 426 and a predetermined region on the upper surface of the outer ring 424 from one end of the upper surface of the crossbar 426. do. The upper conductive thin film 440 is electrically coupled to an upper portion of the conductive layer 460 formed inside the via hole 430. Therefore, the current flowing through the conductive layer 460 flows through the upper conductive thin film 440.

The upper conductive thin film 440 may be preferably formed entirely on the upper surface of the outer ring 424, and the secondary protection device 480 or the cap-up 490 seated on the upper surface of the current blocking means 420. The electrical contact of the can be made smoothly. That is, the upper conductive thin film 440 may be formed only in a region including the via hole 430 on the upper surface of the crossbar 426 and a partial region of the upper surface of the outer ring 424 connected thereto. In this case, the outer ring Since only the conductive thin film formed on a portion of the upper surface is in electrical contact with the secondary protection element 480 or the cap up 490, the current may not flow smoothly or the electrical resistance may increase. Therefore, in order to increase the electrical contact between the current blocking means 420 and the secondary protective element 480 or the cap up 490, it is preferable to form the upper conductive thin film 440 in a larger area.

The lower conductive thin film 450 is formed of a conductive metal having a predetermined thickness, similar to the upper conductive thin film 440, and includes an area including the via hole 430 from the other end of the lower surface of the crossbar 426 and the crossbar 426. ) Is formed in a predetermined area of the lower surface of the outer ring 424 from the other end. In addition, the lower conductive thin film 450 is electrically coupled to a lower portion of the conductive layer 460 formed on the inner surface of the via hole 430. Accordingly, the current flowing through the lower conductive thin film 450 flows through the conductive layer 460 to the upper conductive thin film 440.

The lower conductive thin film 450 may be preferably formed entirely on the lower surface of the outer ring 424, and smoothly makes electrical contact with the safety vent 410 coupled to the lower surface of the current blocking means 420. You can do it. That is, the lower conductive thin film 450 may be formed only in a region including the via hole 430 of the crossbar 426 and a portion of the lower portion of the outer ring 424 connected thereto, but in this case, the outer ring ( 424) Since only the conductive thin film formed on a portion of the lower portion is in electrical contact with the safety vent 410, a problem may occur in that current flow is not smooth or electrical resistance is increased. Therefore, in order to increase the electrical contact between the current blocking means 420 and the safety vent 410, it is preferable to form the lower conductive thin film 450 in a larger area.

4 is a plan view of a current blocking means according to another embodiment of the present invention.

Referring to FIG. 4, the current blocking means 420a according to another embodiment of the present invention is formed by further including side breaking grooves 436 on at least one side of both side ends of the crossbar 426a. The side break groove 436 is preferably formed at both side surfaces of both side ends of the crossbar 426a. The side break groove 436 is formed by cutting inward from the side of the crossbar 426a and is formed in a shape penetrating from the upper surface of the crossbar 426a to the lower surface. The side break groove 436 may be formed in an arc or an angular shape, but the shape is not limited thereto. In addition, the depth of the side break groove 436 (when formed on both sides plus the depth of two side break grooves) is smaller than the length of the diagonal connecting the break vertexes 432 of the via hole 430. Is formed. That is, the crossbar 426a is formed such that the cross-sectional area of the portion where the side break groove 436 is formed is larger than the cross-sectional area of the portion where the via hole 430 is formed. When the deformation pressure of the safety vent 410 is applied to the lower surface of the portion where the via hole 430 is formed, the crossbar 426a is broken while the center portion thereof is raised. In this case, the crossbar 426a may be more easily lifted and broken by forming a weak portion at both ends of the crossbar 426a which is integrally coupled with the outer ring 424a.

5 is a plan view of a current blocking means according to still another embodiment of the present invention.

In the current blocking means 420b according to another embodiment of the present invention, referring to FIG. 5, the crossbar 426b includes a central fracture groove (at least one side of a side surface corresponding to a position where the via hole 430 is formed). 434 may be formed. That is, the center fracture groove 434 may be formed on at least one side of the crossbar 426b in addition to the via hole 430 formed at the center of the crossbar 426. Since the crossbar 426b is effective in breaking the crack from both sides and the inside, it is preferable that the crossbar 426b is formed with the center via hole 430 and the center fracture groove 434 on both sides. . The center fracture groove 434 is preferably formed at both side surfaces of both side ends of the crossbar 426b. The center fracture groove 434 may be formed in an arc or a notch of each shape similarly to the side fracture groove 436, and preferably formed in the same angular shape as the shape of the via hole 430. The center fracture groove 434 is preferably formed in a notch shape having a right angle at a predetermined angle similarly to the via hole 430. In the case where the center fracture groove 434 cannot be formed at a right angle, the radius of curvature of the notch is preferably smaller than 0.3 mm. When the radius of curvature of the central fracture groove 434 is greater than 0.3 mm, as in the via hole 430, the fracture position of the crossbar 426b is changed to cause a problem that the fracture pressure is changed. The center fracture groove 434 is formed to have a depth within 50% of the distance between the side surface of the crossbar 426 and the fracture vertex of the via hole 430. If the depth of the center breaking groove 434 is too deep, the strength of the crossbar 426b is weakened, making it difficult to handle the process, and a problem occurs that is broken by an external impact in a normal state.

In addition, referring to FIG. 5, the current blocking means 420b may further include a side break groove 436 on at least one side of both side ends of the crossbar 426b. The side break grooves 436 are preferably formed at both side surfaces of both side ends of the crossbar 426b. When the deformation pressure of the safety vent 410 is applied to the bottom of the portion where the via hole 430 is formed, the crossbar 426b is broken while the center portion thereof is raised. In this case, the crossbar 426b may be more easily lifted and broken by forming a weak portion at both ends of the crossbar 426b which is integrally coupled with the outer ring 424b. However, when the crossbar 426b is broken in the side break groove 436 instead of the via hole 430, it is difficult to block the current flow, so the side break groove 436 is less than the via hole 430. Break strength should be formed high. Therefore, the crossbar 426b is formed such that the cross-sectional area of the portion where the side break groove 436 is formed is larger than the cross-sectional area of the portion where the via hole 430 is formed. For example, the depth of the side break groove 436 should be formed to have a depth smaller than the sum of the length of the diagonal connecting the break vertex of the via hole 430 and the depth of the center break groove 434. In addition, the side break groove 436, when the side break grooves 436 are formed on both sides, the sum of the depths of the side break grooves 436 is a diagonal connecting the break point of the via hole 430 It should be formed to have a depth smaller than the sum of the length and the depth of the central fracture groove 434.

6 is a sectional view showing a current blocking means according to another embodiment of the present invention.

Referring to FIG. 6, the current blocking means 420c according to another embodiment of the present invention may be formed on the upper and lower surfaces of the crossbar 426 among the upper conductive thin film 440 and the lower conductive thin film 450. It is formed including a separate insulating layer 455. The insulating layer 455 is preferably formed of a polyimide layer used for forming an insulating layer of a circuit board. Accordingly, the insulating layer 455 may prevent the current from flowing when the crossbar 426 is broken and the upper conductive thin film 440 contacts the secondary protective element 480 or the cap up 490. .

7 is a partial cross-sectional view of a cylindrical lithium secondary battery showing the action of the current blocking means according to an embodiment of the present invention.

In the cylindrical lithium secondary battery 100, referring to FIG. 7, an electrode assembly 200 is accommodated in a cylindrical can 300, and a cap assembly 400 is coupled to an opening at an upper end thereof so that the cylindrical can 300 is connected to the cylindrical can 300. To seal. The cap assembly 400 is formed by stacking the safety vent 410, the current blocking means 420, the secondary protection element 480, and the cap up 490, and the cylindrical can with a gasket coupled to an outer surface thereof. 300 is fixed while being pressed up and down at the top.

When the cylindrical lithium secondary battery 100 is in a normal state, current generated in the electrode assembly 200 through the electrode tab 215 coupled to the bottom surface of the safety vent 410 is transferred to the safety vent 410. Will flow. The current blocking means 420 is seated while being in electrical contact with the upper surface of the safety vent 410, the current flowing into the safety vent 410 is the lower conductive thin film 450 and the via hole of the current blocking means (420) 430 and the upper conductive thin film 440. In addition, since the secondary protection element 480 is seated on the current blocking means 420, the secondary protection element 480 is electrically connected to the upper conductive thin film 440 to allow a current to flow. In addition, the cap-up 490 is electrically coupled to the upper portion of the secondary protection element 480 to allow a current flowing from the secondary protection element 480 to flow outside of the secondary battery.

However, when the cylindrical lithium secondary battery 100 operates abnormally, such as overcharge / discharge, gas is generated inside the cylindrical lithium secondary battery 100 and the pressure increases. The protrusion 412 of the safety vent 410 is deformed upward by the pressure generated inside the cylindrical lithium secondary battery 100 to apply pressure to the crossbar 426 of the current blocking means 420. When the crossbar 426 is subjected to pressure, breakage occurs in a portion of the via hole 430 formed at the center, and is completely separated from the left and right around the via hole 430, and no current flows through the via hole 430. At this time, the via hole 430 is formed in a quadrangular shape, so that the break apex is formed in a uniform position, and thus the cross bar 426 has a uniform breaking position, and the breaking pressure is uniform. In the current blocking means 420, the cross bar 426 is broken at the via hole 430, so that no current flows to the cap assembly 400, and the cylindrical lithium secondary battery 100 proceeds further. Since it is not possible to ensure the safety of the lithium secondary battery.

In addition, the current blocking means 420, as shown in Figure 4, when the side break groove 436 is formed on both sides of both ends of the crossbar 426 than when the crossbar 426 is under pressure It can be easily lifted so that the break can proceed more effectively.

In addition, the current blocking means 420, as shown in Figure 5, when the center fracture grooves 434 are formed on both sides of the position where the via hole 430 is formed, the crossbar 426 in the center and both sides As the fracture proceeds, it can be broken more quickly.

Although the embodiment has been described with respect to the cylindrical lithium secondary battery, it can be used for a non-cylindrical lithium secondary battery, of course. In addition, it can be used in other types of secondary batteries other than the lithium secondary battery.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

According to the lithium secondary battery according to the present invention, the current blocking means used in the cap assembly of the lithium secondary battery separately configures the energized portion of the current and the blocking portion of the current and forms a weak part including a central hole in the blocking portion of the current. When an abnormality occurs in the secondary battery, the blocking portion of the current is broken to cut off the flow of current, thereby reducing the current blocking distribution of the component and improving the stability of the lithium secondary battery.

Claims (17)

And a cap assembly having a safety vane and a current blocking means seated on an upper portion of the safety vane. The current blocking means includes an insulated printed circuit board including a outer ring and a cross bar having a via hole having a conductive layer formed on an inner surface thereof. And a lower conductive thin film formed on an upper surface of the insulated printed board and electrically connected to the conductive layer, and a lower conductive thin film formed on a lower surface of the insulated printed substrate and electrically connected to the conductive layer. , The via hole is a lithium secondary battery, characterized in that formed in the square so that one of the diagonal is perpendicular to the longitudinal direction of the crossbar. The method of claim 1, The via hole is a lithium secondary battery, characterized in that formed in a square or rhombus. The method of claim 2, The via hole is a lithium secondary battery, characterized in that the vertex is formed at a right angle forming a diagonal perpendicular to the longitudinal direction of the crossbar. The method of claim 2, The via hole is a lithium secondary battery, characterized in that the radius of curvature of the fracture vertex forming a diagonal perpendicular to the longitudinal direction of the crossbar is smaller than 0.3mm. The method of claim 1, The via hole is a lithium secondary battery, characterized in that the diagonal perpendicular to the crossbar is formed to have a length of at least 25% of the crossbar width. The method of claim 1, The crossbar is a lithium secondary battery further comprises a side break groove formed in a groove shape on at least one side of the both ends coupled to the outer ring. The method of claim 6, The side break groove is a lithium secondary battery, characterized in that the cross-sectional area of the crossbar portion in which the side break groove is formed to a depth larger than the cross-sectional area of the crossbar portion in which the via hole is formed. The method of claim 1, The crossbar may further include a center fracture groove formed in a notch shape on at least one side of the position where the via hole is formed. The method of claim 8, The center break groove is a lithium secondary battery, characterized in that formed at a right angle. The method of claim 8, The center break groove is a lithium secondary battery, characterized in that the radius of curvature of the notch is formed smaller than 0.3mm. The method of claim 8, And the center fracture groove is formed to have a depth within 50% of a distance between the side of the crossbar and the via hole. The method of claim 8, The crossbar is a lithium secondary battery further comprises a side end groove formed in at least one side of the both ends coupled to the outer ring. The method of claim 12, The side break groove is a lithium secondary battery, characterized in that the cross-sectional area of the crossbar portion in which the side break groove is formed to a depth larger than the cross-sectional area of the crossbar portion in which the via hole is formed. The method of claim 1, And the upper conductive thin film and the lower conductive thin film further include an insulating layer formed on the upper and lower surfaces of the crossbar. The method of claim 14, The insulating layer is a lithium secondary battery, characterized in that formed of a polyimide layer The method of claim 1, The conductive layer formed on the inner surface of the via hole is a lithium secondary battery, characterized in that formed of copper metal or copper alloy. The method of claim 16, The conductive layer is a lithium secondary battery, characterized in that formed to a thickness of at least 5㎛.

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