KR20000042900A - Secondary lithium cell - Google Patents

Abstract

PURPOSE: A secondary lithium cell is provided to enhance the stability and reliability through the current cutoff in a particular pressure range by rupturing a current cutoff member with a safety value risen. CONSTITUTION: A protrusion(42a) is formed toward a cap plate(32) at the center portion. A rupturing unit(42b) is formed to be ruptured in a certain pressure range by deteriorating the strength of a particular portion. A current cutoff member(38) is arranged between a cap plate(32) and a safety value(42). The current cutoff member(38) is formed in a rectangular belt shape. The current cutoff member(38) has at least one rupturing groove(38a) of a wedge shape in one side of the center portion opposite to the protrusion(42a) of a safety valve.

Description

Lithium secondary battery

The present invention relates to a lithium secondary battery, and more particularly, a lithium secondary battery which breaks when the internal pressure rises, thereby breaking the current so that the current blocking member is easily broken in a certain pressure range, thereby improving safety and reliability of the battery. It relates to a battery.

In general, a lithium secondary battery uses a carbon material capable of intercalating or deintercalating lithium ions as a negative electrode active material during a charge / discharge process, and has a high electric capacity per unit mass and generates a high voltage. It has the advantage of high charging and discharging efficiency.

Like other batteries, the lithium secondary battery has a positive electrode group coated with a positive electrode active material and a negative electrode plate coated with a negative electrode active material having a separator plate wound or laminated therebetween, and accommodates the electrode plate group to serve as a negative electrode terminal. And a cap assembly fixed to an upper portion of the can and serving as an anode terminal.

At this time, when the lithium secondary battery becomes overcharged or a large current flows inside the battery due to a short circuit due to misuse, the electrolyte may be decomposed and gas may be generated. Can cause.

Therefore, in order to prevent battery explosion, the cap assembly functions as a safety device to prevent explosion by cutting off current and discharging gas when the internal pressure of the battery is increased. The structure was devised.

Patents relating to the previously claimed cap assembly structure include Japanese Patent Application Laid-open No. Hei 9-199105, U.S. Patent Nos. 4,943,497 and 5,464,705. The above patents are mostly related to a cap plate having holes for gas discharge and electrolyte leakage, a PTC element which becomes an insulator at a constant current or above a certain temperature, a current blocking member that breaks at a certain pressure or higher to block current, and also a certain pressure or more. And a safety valve for releasing the gas to discharge the gas.

The safety valve has a disadvantage in that the portion to be broken when the internal pressure rises is manufactured by a method such as pressing or etching, so that the range of the breaking pressure is widened by the manufacturing characteristics and is not easily broken at a specific pressure.

Here, US Pat. No. 4,943,497 describes a cap assembly of approximately the following configuration. That is, the explosion-proof valve disposed at the lower end of the cap plate has a protrusion formed convexly toward the pole plate group at the center thereof, and the protrusion is welded to the lead plate extending from the positive electrode tab through a hole formed in the insulation stripper.

When the internal pressure of the battery rises, the explosion-proof valve rises in the opposite direction to the electrode plate group due to the internal pressure, and the lead plate welded to the projection ruptures to cut off the current first, and then the thin wall portion of the explosion-proof valve ruptures The gas is discharged secondarily.

However, the patent has the following disadvantages. That is, since the lead plate is simply arranged at the bottom of the insulation stripper without a coupling structure, when the explosion-proof valve is raised due to the internal pressure, the lead plate may be drawn through the hole of the insulation stripper. In this case, since the current is not blocked by cutting the lead plate, it may cause a problem in the safety of the battery.

In addition, the protrusion of the lead plate and the explosion-proof valve is fixed by welding to cut off the current by breaking the welding part or cutting the lead plate when the internal pressure rises. As time passes, the welding part is oxidized to weaken the strength of the welding part. If it is, the welding part or the lead plate is cut even in the case of a weak external impact, so that the battery may not be used.

In addition, the welding of the protrusion valve and the lead plate of the explosion-proof valve is performed after the electrode group is placed in the can and the electrolyte is injected, which has the disadvantage of stimulating the electrolyte by stimulating the electrolyte during welding.

Therefore, the present invention is designed to solve the above problems, an object of the present invention is to break the current breakdown when the internal pressure rises to easily break the current blocking member in a more constant pressure range to improve the safety and reliability of the battery The present invention provides a lithium secondary battery.

Another object of the present invention is to provide a lithium secondary battery capable of preventing disadvantages such as oxidation of an electrolyte by welding by arranging components of a cap assembly without welding.

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

2 is a bottom view of the safety valve.

3 is a partial cross-sectional view of a lithium secondary battery showing an elevated voltage resistance state.

4 is a perspective view of a current interrupting member and an insulator;

5 to 7 are perspective views of the current interruption member showing various embodiments of the current interruption member.

8 is a plan view of a current blocking member and an insulator according to another embodiment.

9 is a cross-sectional view taken along the line A-A of FIG. 8.

10 to 11 are perspective views of the current blocking member and the insulating film showing various embodiments of the current blocking member and the insulating film.

12 is a partial cross-sectional view of a lithium secondary battery according to another embodiment.

13 is a partial cross-sectional view of a lithium secondary battery according to a second embodiment of the present invention.

14 is a partial cross-sectional view of a lithium secondary battery showing an elevated voltage resistance state.

In order to achieve the above object, the present invention,

A lithium secondary battery having a cap plate having a hole for discharging gas, a safety valve causing deformation by an increase in internal pressure, and a current interrupting member that breaks due to deformation of the safety valve to block current.

The safety valve has a protrusion formed convexly toward the cap plate toward the center, and a break that lowers the strength of a specific portion so that the safety valve can be broken under a predetermined pressure, and the current blocking member is disposed between the cap plate and the safety valve. It provides a lithium secondary battery characterized in that the breakage by the pressure applied to the projection when the deformation of the safety valve to cut off the current.

The current blocking member has a rectangular band shape so as to be easily broken in a specific pressure range, and forms at least one break groove as a central portion facing the protrusion of the safety valve, or the width of the central portion is greater than that of other portions. It can be formed narrower to more easily control the breaking pressure.

As a result, the current blocking member is easily broken in a specific pressure range to improve the safety and reliability of the lithium secondary battery, and each part in the cap assembly is configured without welding to prevent ignition of electrolyte by welding and simplify the assembly process. It has the advantage of being able to.

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

1 is a cross-sectional view of a cylindrical lithium secondary battery according to a first embodiment of the present invention. As shown in the drawing, a lithium secondary battery includes a cathode plate group 10 in which a cathode plate 12 and an anode plate 14 are wound with an separator plate 16 interposed therebetween, and accommodates the anode plate group 10. A cap assembly electrically connected to the can 20 to serve as a negative electrode terminal, and having a gasket 22 interposed in an opening of the can 20, and electrically connected to the positive electrode plate 12 to serve as a positive electrode terminal ( 30).

Here, the cap assembly 30 serves to prevent the explosion of the battery by cutting off the current and discharge gas when the internal pressure of the battery rises, for this purpose, the cap assembly according to the present embodiment has the following configuration.

First, a cap plate 32 having a gas discharge hole 32a is disposed at the outermost side, and the PTC element 34, the insulator 36, the current interrupting member 38, and the disk are disposed on the bottom surface of the cap plate 32. 40 is sequentially arranged, and a safety valve 42 and an aluminum plate 44 are disposed on the bottom of the disk 40. The PTC element 34, the insulator 36, the disk 40, and the aluminum plate 44 have a disk shape having a hollow center.

Thus, the current generated in the electrode plate group 10 is cap plate through the aluminum plate 44, the safety valve 42 and the disk 40, the current blocking member 38 and the PTC element 34 in the positive electrode tab 46. Final delivery is to 32.

At this time, the safety valve 42 forms a convex protrusion 42a toward the cap plate 32 toward the center, and breaks the break 42b to lower the strength of a specific portion so that it can be broken in a predetermined pressure range. Form.

FIG. 2 is a bottom view of the safety valve 42. The safety valve 42 forms a circular fracture 42b on the bottom of the periphery 42a. The fracture 42b is etched or laser irradiated. It is the part whose thickness became thin by such a method. As a result, the breaking portion 42b is greatly reduced in strength and breaks at a predetermined pressure range.

In the safety valve 42 having such a configuration, when the internal pressure increases due to gas generation, as shown in FIG. 3, the central portion forming the protrusion 42a is convexly deformed toward the cap plate 32, and accordingly, the current The blocking member 38 is broken by the pressure applied by the protrusion 42a of the safety valve 42 to cut off the current.

Here, the current blocking member 38 is formed in a rectangular band shape so that it can be more easily broken in a specific pressure range applied by the protrusion 42a of the safety valve 42, Figure 4 is the current blocking The perspective view of the member 38 and the insulator 36 is shown.

As shown in the drawing, the current interrupting member 38 has a rectangular band shape having a predetermined horizontal width and a vertical width, and is disposed to penetrate the hollow 36a of the insulator 36 so that both ends of the insulator 36 are formed. It forms a structure that is disposed on the upper and lower surfaces respectively.

At this time, the current blocking member 38 may be manufactured in various shapes to be more easily broken in a specific pressure range, which is shown in Figures 5 to 7, respectively.

The current interruption member 38 shown in FIG. 5 has two wedge-shaped first rupture grooves 38a formed on one surface of the central portion facing the protrusion 42a of the safety valve 42, so that The breakage of the current interruption member 38 during pressurization is made easier.

In addition, as shown in FIG. 6, another embodiment of the current interrupting member 38 forms a square second break groove 38b on both sides of the central portion facing the protrusion 42a of the safety valve 42 to form a central portion. By abruptly reducing the vertical width, it is easier to break the current interruption member 38.

In addition, another embodiment of the current blocking member 38 shown in FIG. 7 forms a semicircular third breaking groove 38c on both sides of the central portion to gently reduce the longitudinal width of the central portion. Makes it easier to break.

As described above, the current blocking member 38 may control the breaking pressure range by modifying the breaking characteristics by modifying the area and the shape of the center portion.

At this time, the current blocking member 38 may perform a fuse function in which the central portion whose width is reduced when the overcurrent flows is melted by the heat to block the current.

In the lithium secondary battery having such a configuration, when the internal pressure rises due to overcharging or misuse, the safety valve 42 is primarily deformed toward the cap plate 32 by the protrusion 42a of the safety valve 42. When the current blocking member 38 is broken to cut off the current, and further pressure is applied, the breaking part 42b of the safety valve 42 is secondarily broken to discharge the gas to prevent the battery from being exploded.

At this time, the lithium secondary battery according to the present embodiment changes the configuration of the current blocking member 38 and the insulator 36 as follows, when the cap assembly 30 is assembled, the push phenomenon or position change of the current blocking member 38. To prevent this.

FIG. 8 is a plan view of the current interrupting member 38 and the insulator 36, and FIG. 9 is a cross-sectional view taken along the line A-A of FIG. As shown, the insulator 36 is formed in a disk shape having a hollow 36a in the middle thereof, and the current interruption member 38 has a structure in which both ends thereof are inserted and fixed into the insulator 36.

More specifically, the current blocking member 38 has a left end portion 38d exposed and protruding from the upper surface of the insulator 36 to contact the PTC element 34 based on the drawing, and the right end portion 38e has contacted with the PTC element 34. Is exposed and protrudes into the lower surface of the insulator 36 to contact the disk 40. As a result, the current transmitted from the positive electrode tab 46 is transmitted to the PTC element 34 via the disk 40 and the current blocking member 38, and both ends of the current blocking member 38 are connected to the insulator 36. It is firmly fixed to prevent the cap assembly 30 from being pushed or changed by another member when the cap assembly 30 is assembled.

Next, in the lithium secondary battery according to the present exemplary embodiment, the structure of the current blocking member 38 may be changed as shown in FIG. 10 to omit the addition of the disk-shaped insulator 36.

As shown in the drawing, the current interruption member 38 has a configuration in which the insulating film 48 is integrally formed with the lower surface of the left end 38d and the upper surface of the right end 38e. The insulating film 48 may be formed by coating an insulating material on both ends of the current blocking member 38 or by attaching an insulating film 48 having adhesiveness to one surface of the current blocking member 38.

As such, when the insulating film 48 is integrally formed at both ends 38d and 38e of the current interrupting member 38, the disk-shaped insulator 36 can be omitted, as shown in FIG. It has the advantage that can be simplified more.

At this time, as shown in FIG. 11, the current interruption member 38 forms a recess 38f in the lower surface of the left end 38d and the upper surface of the right end 38e. The insulating film 48 may be integrally formed in the recess 38f. By forming the insulating film 48 in the concave portion 38f as described above, the overall shape of the current blocking member 38 can be formed in a smooth band shape, and both ends 38d and 38e of the current blocking member 38 protrude. And it is prevented to be arranged concave, it has the advantage that the arrangement state with other members in the cap assembly 30 more smoothly.

In addition, in the lithium secondary battery according to the present exemplary embodiment, as shown in FIG. 12, the cap assembly 30 may be configured by omitting the disk 40 and the aluminum plate 44 in FIG. 1. Therefore, the positive electrode tab 46 having one end joined to the positive electrode plate 12 is directly welded to the bottom of the safety valve 42 to transmit current, and the lithium secondary battery according to the present embodiment has an advantage of simplifying the configuration thereof. Has

Next, a second embodiment of the present invention will be described. FIG. 13 is a partial cross-sectional view of a lithium secondary battery according to a second embodiment of the present invention. The lithium secondary battery according to the present embodiment has a configuration similar to that of the first embodiment, but has a different configuration in the following points.

That is, the safety valve 50 according to the present embodiment forms a fracture portion 50a by a heterogeneous metal film or a polymer film that is thinner than the safety valve 50 body, and the fracture portion 50a is a battery risk. It may be made of a thin aluminum film or polyethylene film or polypropylene film of 20 to 25 ㎛ thicker than the main body of the safety valve 50 so as to break at a pressure of 20 ± 5 kg / ㎠.

A conductive spacer 52 having a predetermined height and width is disposed at the center of the safety valve 50, and a current blocking member 38 is disposed above the spacer 52.

The configuration of the current blocking member 38 and the insulator 40 is the same as described above in the previous embodiment.

In the lithium secondary battery having such a configuration, when the internal pressure is increased, the safety valve 50 is deformed toward the cap plate 32 as shown in FIG. 14, and accordingly the current blocking member 38 is raised due to the rise of the spacer 52. ) Breaks and the current is cut off primarily. When further pressure is applied, the breakage portion 50a of the safety valve 50 is broken to discharge the gas and leak the electrolyte to prevent explosion of the battery.

In this case, the current blocking member 38 may perform a fuse function in which the center portion melts by heat when the overcurrent flows to cut off the current, and the lithium secondary battery according to the present embodiment omits the disk 40 and thus the cap assembly. 30 can be configured.

As described above, the lithium secondary battery according to the present invention, when the internal pressure rises, the current blocking member is easily broken due to the rise of the safety valve, so that the current is reliably cut in a specific pressure range, thereby improving the safety and reliability of the battery. Since welding work is not required between the parts within, it is possible to simplify the assembly process and prevent ignition of the electrolyte due to welding.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the lithium secondary battery according to the present invention easily breaks the current blocking member due to the rise of the safety valve, thereby reliably blocking the current in a specific pressure range, thereby improving safety and reliability of the battery. In addition, since welding is not required between the parts in the cap assembly, the assembly process is simplified, and the ignition of the electrolyte is prevented by welding, thereby improving the production efficiency and quality of the battery.

Claims (16)

A lithium secondary battery having a cap plate having a hole for discharging gas, a safety valve causing deformation by an increase in internal pressure, and a current interrupting member that breaks due to deformation of the safety valve to block current. The safety valve has a protrusion formed convexly toward the cap plate toward the center portion, and a break portion for lowering the strength of a specific portion to break in a predetermined pressure range, wherein the current blocking member is disposed between the cap plate and the safety valve. Lithium secondary battery characterized in that the current is broken by the pressure applied to the projection when the deformation of the safety valve to cut off the current. The lithium secondary battery of claim 1, wherein the current blocking member has a rectangular band shape. The lithium secondary battery of claim 2, wherein the current blocking member forms at least one wedge-shaped fracture groove on one surface of a central portion facing the protrusion of the safety valve. The lithium secondary battery of claim 2, wherein the current interruption member forms a square fracture groove on both sides of the central portion facing the protrusion of the safety valve to drastically reduce the width of the central portion. The lithium secondary battery of claim 2, wherein the current blocking member forms semicircular fracture grooves on both sides of the central portion facing the protrusion of the safety valve to gradually reduce the width of the central portion. The method of claim 1, wherein the lithium secondary battery has a disk-shaped insulator having a hollow; Lithium secondary battery comprising a band-shaped current blocking member disposed so as to penetrate the hollow of the insulator, both ends are disposed on the upper and lower surfaces of the insulator. The method of claim 1, wherein the lithium secondary battery has a disk-shaped insulator having a hollow; Lithium secondary battery comprising a band-shaped current blocking member, both ends of which are inserted into and fixed to the inside of the insulator, and the center portion of which is exposed through the hollow. The lithium secondary battery of claim 7, wherein both ends of the current blocking member are exposed to upper and lower surfaces of the insulator. The method of claim 1, wherein the lithium secondary battery includes a current blocking member having a rectangular band shape; And a pair of insulating films each formed on an upper surface of one end of the current blocking member and a lower surface of an opposite end of the current blocking member. The lithium secondary battery of claim 1, wherein the lithium secondary battery has a rectangular band shape, and includes a current blocking member including respective recesses on a lower surface of an opposite side of an upper surface of the one end; Lithium secondary battery comprising a pair of insulating films respectively formed in the recessed portion of the current blocking member. A lithium secondary battery having a cap plate having a hole for discharging gas, a safety valve causing deformation by an increase in internal pressure, and a current interrupting member that breaks due to deformation of the safety valve to block current. The lithium secondary battery may include: a safety valve having a breakage portion to lower the strength of a specific portion so that the breakage may occur in a predetermined pressure range; A conductive spacer disposed at the center of the safety valve and having a predetermined height; And a current blocking member disposed between the cap plate and the spacer to break the current by breaking the pressure applied by the spacer when the safety valve is deformed. The lithium secondary battery of claim 11, wherein the break portion of the safety valve is formed of a polymer film layer having a thickness thinner than that of the safety valve body. The lithium secondary battery of claim 11, wherein the current blocking member has a rectangular band shape. The lithium secondary battery of claim 13, wherein the current blocking member forms at least one wedge-shaped fracture groove on one surface of a central portion facing the protrusion of the safety valve. The lithium secondary battery of claim 13, wherein the current interruption member forms a angular fracture groove on both sides of the central portion facing the protrusion of the safety valve to drastically reduce the width of the central portion. The lithium secondary battery of claim 13, wherein the current blocking member forms semicircular fracture grooves on both sides of the central portion facing the protrusion of the safety valve to gradually decrease the width of the central portion.