KR20150021732A - Cap Assembly Having Safety Vent with Notch - Google Patents

Abstract

The present invention relates to a cap assembly which is installed to the open upper part of a can which has a structure of forming a cylindrical can in an electrode assembly. It includes a safety vent which has a notch which is broken when the withstand voltage of a battery increases, an upper cap of an upward protrusion type which is connected to it along the outer surface of the safety vent, and a current blocking member which is attached to the lower end of the safety vent and blocks a current when the withstand voltage of a battery increases. The safety vent includes a first bending part which is bent from the outer surface to a lower part, a slope part which is extended from the first bending part to the lower part, and a second bending part which is horizontally bent from the slope part to a center part. The notch is formed in the first bending part of the first bending part and the second bending part.

Description

[0001] The present invention relates to a cap assembly having a notched vent,

The present invention relates to a cap assembly comprising a notched safety vent.

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 conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet . Among them, the cylindrical battery has a relatively large capacity and is structurally stable.

The electrode assembly is embedded in a battery case. The electrode assembly includes a positive electrode / separator / negative electrode laminate structure. The positive electrode / separator / negative electrode has a jelly-roll type structure in which a separator is interposed between a positive electrode and a negative electrode coated with an active material. A stacked type in which a plurality of positive and negative electrodes of a predetermined size are stacked in a state in which a separator is interposed, and a stacked / folded type in which unit cells such as a pull cell or a bi-cell are wound by a separation film. Among them, the jelly-roll type electrode assembly has an advantage of being easy to manufacture and having a high energy density per weight.

In this regard, Fig. 1 schematically shows a vertical cross-sectional perspective view of a general cylindrical battery.

1, a cylindrical secondary battery 10 includes a jelly-roll type (wound type) electrode assembly 12 accommodated in a cylindrical case 13, an electrolyte is injected into the cylindrical case 13, And a cap assembly 14 having an electrode terminal (for example, a positive electrode terminal; not shown) formed at the open upper end of the cap assembly 14.

The electrode assembly 12 has a structure in which a positive electrode 12a and a negative electrode 12b are sandwiched between a separator 12c and a separator 12c therebetween. The electrode assembly 12 has a cylindrical center pin (15) is inserted. The center pin 15 is generally made of a metal material in order to impart a predetermined strength and has a hollow cylindrical structure in which the plate material is bent in a round shape. The center pin 15 serves as a channel for fixing and supporting the electrode assembly and a gas for discharging gas generated by an internal reaction during charging, discharging and operation.

On the other hand, the lithium secondary battery has a disadvantage of low safety. For example, when the battery is overcharged to about 4.5 V or more, decomposition reaction of the cathode active material occurs, and dendrite growth of lithium metal at the cathode and decomposition reaction of the electrolyte occur. In this process, the decomposition reaction and the many side reactions are rapidly proceeded with heat accompanied by heat, and the ignition and explosion of the battery may be caused.

Gas is generated due to the decomposition reaction of the electrolyte by heat at high temperature, and if the amount of heat generated by the battery rapidly increases within a short time, thermal runaway phenomenon may occur. Thermal runaway occurs when the battery is kept in a continuously energized state or is further accelerated, so that there is a serious problem in safety because the risk of explosion of the battery due to ignition or gas pressure becomes very large.

Accordingly, there is a high demand for development of a cylindrical battery capable of securing safety by shutting off the current and quickly discharging the generated gas to the outside when the internal pressure increases due to high temperature or the like.

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 provide a cap assembly with improved safety that can quickly discharge an internal gas to the outside when the internal pressure of the cell rises due to the generation of gas inside the cell due to malfunction or the like.

It is another object of the present invention to provide a lithium secondary battery improved in safety by using a cap assembly with improved safety.

According to an aspect of the present invention,

A cap assembly mounted on an open upper end of a can in a battery having a structure in which an electrode assembly is built in a cylindrical can,

A safety vent in which a notch ruptured when the internal pressure of the battery rises;

An upward protruding upper cap connected to the safety vent along an outer circumferential surface thereof; And

A current blocking member attached to a lower end of the safety vent and interrupting a current when the internal pressure of the battery rises;

And,

Wherein the safety vent includes a first bent portion bent downward from the outer circumferential surface, an inclined portion extending downward from the first bent portion, and a second bent portion bent horizontally from the inclined portion toward the center, And the notch may be formed in the first bent portion of the first and second bent portions.

That is, the safety vent may be formed in a downwardly bent structure by the first bent portion and the second bent portion. When the notch is formed in the first bent portion and the notch is broken when the internal pressure of the cell rises, And is discharged to the outside.

Such a safety vent has a structure in which when the internal pressure of the battery is increased, the shape is reversed and the depressed portion is deformed so as to be convex upward and the notch formed in the first bent portion is broken when the internal pressure of the cell is further increased .

The current blocking member is a member that ruptures when the internal pressure of the battery rises and blocks the current. Specifically, the current blocking member is formed at the center with a protruding protruding portion protruding upward by welding or the like at the lower end of the safety vent. Or more than two through holes may be formed.

The current blocking member breaks the current while rupturing the connection portion between the current blocking member and the anode due to the shape reversal of the safety vent due to the increase in the internal pressure. In a specific example, a notch may be formed on the outer circumferential surface of the protruding portion, and the notch portion may be ruptured according to the shape reversal of the safety vent, so that the protruding portion may be connected to the connection portion between the current blocking member and the positive electrode of the electrode assembly, It can be easily separated.

The through-holes may be formed in an arc shape at a radially symmetrical position with respect to the center of the current blocking member. In the case of the radially symmetric position, the gas discharge can be prevented from being excessively concentrated in one direction, and the strength of the current blocking member itself can be secured.

The first bent portion formed with the notch as described above may be formed at a position where gas upwardly moved from the current blocking member can directly apply pressure to the notch. Specifically, the first bent portion has a radius R of the safety vent, May be in the range of 0.2R to 0.5R from the outer circumferential surface with respect to the outer circumferential surface.

The angle of the inclined portion may be in the range of 5 to 30 degrees. If the angle of the inclined portion is too small, the blocking of the current blocking member does not work even if the safety vent is reversed due to the high pressure. On the contrary, if the angle is too large, Lt; / RTI >

The second bent portion bent from the inclined portion may be formed in a range of 0.6R to 0.9R from the outer circumferential surface with reference to the radius R of the safety vent.

Meanwhile, the notch formed in the safety vent may be formed in a vertical V-shaped structure or an inverted structure thereof so as to be broken by the internal pressure of the battery.

Such a notch may be formed at a position corresponding to the through-hole of the current blocking member so that when the notch is broken by the internal pressure of the battery, the gas inside can easily be discharged to the fractured portion of the notch via the through- Structure.

The shape of the notch is not particularly limited. For example, it may be formed as a closed curve structure such as a circle or an ellipse on a plane.

In addition, the notch may be formed in an open-curved structure having one side opened in a plan view. At this time, the portion where the one side is opened, that is, the minutely notch portion, can be prevented from being separated even if the notch is broken by the high pressure gas.

Specifically, the notch may have a circular arc shape in which one side is opened in a plan view, and a portion where the one side is opened may be formed in a region of 5 to 120 degrees with respect to the center of the arc. If the open portion of the one side is too small, the effect of the open portion is small. On the other hand, if the open portion is too large, the induction of breakage due to the breakdown voltage of the battery does not occur. In a preferred example, the portion where the one side is opened may be formed in a size ranging from 10 to 45 degrees with respect to the center of the arc.

In some cases, the cap assembly may further include a member such as a positive temperature coefficient (PTC) element that greatly increases the resistance of the battery when the temperature rises inside the battery, thereby blocking the current. Such a PTC element may, for example, be interposed between the upper cap and the safety vent.

The cap assembly may have a laminated structure of a current blocking member, a gasket for a current blocking member, a safety vent, a PTC device, and an upper cap having at least one gas outlet formed therein. Lt; / RTI >

The electrode assembly may be, but is not limited to, a positive electrode, a negative electrode, and a jelly-roll type electrode assembly wound with a separator structure interposed between the positive electrode and the negative electrode.

The material of the cylindrical can is not particularly limited, and preferably, it can be formed of any one of stainless steel, steel, aluminum, and alloys thereof.

The present invention also provides a cylindrical battery comprising the cap assembly. The cylindrical battery can be, but is not limited to, a lithium secondary battery that provides high energy density, discharge voltage, and output stability.

As described above, the cap assembly according to the present invention can effectively discharge the high-pressure gas inside the battery by breaking the notch of the safety vent, and also prevents the ignition and explosion of the battery by blocking the current to the current blocking member The safety can be greatly improved.

1 is a cross-sectional view of a conventional cylindrical battery;
2 is a cross-sectional view of a cap assembly in accordance with one embodiment of the present invention;
Figure 3 is a cross-sectional view of the structure in which the safety vent is reversed in Figure 2;
4 is a perspective view of the current blocking member of Fig. 2;
Figure 5 is a top view of the safety vent of Figure 2;
Figure 6 is a vertical cross-sectional view of the safety vent of Figure 2;
7 is a plan view of a safety vent according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 2 is a cross-sectional view of a cap assembly according to one embodiment of the present invention, and FIG. 3 is a cross-sectional view of the structure in which the safety vent of FIG. 2 is reversed.

Referring to FIGS. 2 and 3, the cap assembly 100 includes a top cap 110, a safety vent 120, and a current blocking member 130.

Specifically, the cap assembly 100 includes a current blocking member 130, a gasket 138 for the current blocking member 130, a safety vent 120, a PTC device 140, and an upper end Cap 110, and a gasket 150 is further attached to the outer circumferential surface of the laminated structure.

When the internal pressure of the battery increases, the shape of the safety vent 120 is reversed and the recessed portion is reversed so that the recessed portion is convex upward. When the internal pressure of the battery further increases, the notch 125 ruptures As shown in FIG.

The current blocking member 130 is a member that ruptures when the internal pressure of the battery rises and blocks the current. The upward protruding protrusion 132 attached to the lower end of the safety vent 120 by welding is formed at the center, Through holes 136 for discharging the exhaust gas are formed.

In this current blocking member 130, the connecting portion between the current blocking member 130 and the anode ruptures due to the shape reversal of the safety vent 120 due to an increase in the internal pressure, thereby blocking the current. The notch 135 is formed on the outer circumferential surface of the protrusion 132 and the notch 135 is ruptured as the shape of the safety vent 120 is reversed. The protrusion 132 is connected to the safety vent 120, And is separated from the connection portion between the blocking member 130 and the anode of the electrode assembly.

Fig. 4 is a perspective view of the current blocking member of Fig.

Referring to FIG. 4 together with FIG. 2, the current blocking member 130 is formed at the center thereof with a protruding protrusion 132 protruding upwardly welded to a lower end of the recess of the safety vent 120, The cathode lead 20 connected to the anode of the electrode assembly is electrically connected to a portion of the lower end surface of the electrode assembly other than the protrusion 132.

The protrusion 130 is formed with a bridge in which a notch 135 connecting three through holes 137 and a through hole 137 concentrically around the protrusion 130 is formed.

Further, on the outer circumferential surface of the current blocking member 130, three through-holes 136 for discharging gas are formed in an arc shape at a radial symmetrical position about the central axis.

Figs. 5 and 6 are respectively a plan view and a vertical sectional view of the safety vent of Fig.

Referring to FIGS. 5 and 6 together with FIG. 2, the safety vent 120 includes a first bent portion 122 that is bent downward from the outer circumferential surface, an inclined portion 128 that extends downward from the first bent portion 122, And a second bent portion 126 that is horizontally bent toward the center from the inclined portion 128. The first bending portion 122 and the second bending portion 126 are provided with a notch (Not shown).

The safety vent 120 is formed to be downwardly bent by the first bent portion 122 and the second bent portion 126. The notch 125 is formed in the first bent portion 122, The notch 125 is broken and the gas is discharged to the outside.

The first bent portion 122 having the notch 125 is formed at a position where the gas upwardly moved from the current blocking member 130 can apply pressure directly to the notch 125. The angle of the inclined portion 128 may be varied within a range of 5 to 30 degrees and the second bent portion 126 bent from the inclined portion 128 may have a radius R of the safety vent 120, And is located in the range of 0.6R to 0.9R from the outer peripheral surface.

7 is a plan view of a safety vent according to another embodiment of the present invention.

Referring to FIG. 7, the notch 225 of the safety vent 220 is formed in a circular arc shape with one side opened in a plan view. The angle of the open side of one side is formed to be 30 degrees with respect to the center of the arc. The portion where the one side is opened, that is, the minus portion, is prevented from being separated even if the notch is broken by the high pressure gas.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (17)

A cap assembly mounted on an open upper end of a can in a battery having a structure in which an electrode assembly is built in a cylindrical can,
A safety vent in which a notch ruptured when the internal pressure of the battery rises;
An upward protruding upper cap connected to the safety vent along an outer circumferential surface thereof; And
A current blocking member attached to a lower end of the safety vent and interrupting a current when the internal pressure of the battery rises;
And,
Wherein the safety vent includes a first bent portion bent downward from the outer circumferential surface, an inclined portion extending downward from the first bent portion, and a second bent portion bent horizontally from the inclined portion toward the center, And the notch is formed in the first bent portion of the first bent portion and the second bent portion. 2. The apparatus according to claim 1, wherein the current blocking member is formed with a protruding protruding portion protruding upward from a lower end of the safety vent, and two or more through-holes for discharging the gas are formed Cap assembly. The cap assembly according to claim 2, wherein the through-holes are formed in an arc shape at a radial symmetrical position with respect to a center of the current blocking member. The cap assembly according to claim 1, wherein the first bent portion is positioned in a range of 0.2R to 0.5R from the outer circumferential surface with respect to a radius R of the safety vent. The cap assembly according to claim 1, wherein the inclined portion is formed in a size of 5 to 30 degrees. The cap assembly according to claim 1, wherein the second bent portion is positioned in a range of 0.6R to 0.9R from the outer circumferential surface with respect to a radius R of the safety vent. The cap assembly of claim 1, wherein the notch is a V-shaped structure or an inverted structure thereof in a vertical section. The cap assembly according to claim 1, wherein the notch is formed at a position corresponding to a through-hole of the current blocking member. The cap assembly of claim 1, wherein the notch is formed in a planar closed curve structure. The cap assembly of claim 1, wherein the notch is formed in an open-curved structure with one side open in a plan view. 11. The cap assembly of claim 10, wherein the notch is formed in a planar shape with an open circular arc, and the open side of the notch is in a range of 5 to 120 degrees with respect to the center of the circular arc. 12. The cap assembly according to claim 11, wherein the one side of the cap assembly is opened at an angle of 10 to 45 degrees with respect to the center of the arc. The cap assembly of claim 1, wherein a PTC device is interposed between the upper cap and the safety vent. The cap assembly according to claim 1, wherein the cap assembly comprises a laminate structure of a current blocking member, a gasket for a current blocking member, a safety vent, a PTC device, and an upper cap having at least one gas outlet formed therein, And a gasket is additionally mounted on the cap assembly. The cap assembly of claim 1, wherein the electrode assembly is a jelly-roll type electrode assembly. A cylindrical battery comprising a cap assembly according to any one of claims 1 to 15. 17. The cylindrical battery according to claim 16, wherein the battery is a lithium secondary battery.

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