KR100399343B1 - Lithium ion battery with current interrupt device - Google Patents

Abstract

PURPOSE: A lithium ion battery provided with a current cutoff device is provided, to isolate the flow of current firstly in case of the increase of internal pressure of a battery and to discharge the gas outward in case of the additional increase of internal pressure, thereby preventing the explosion of a battery. CONSTITUTION: The lithium ion battery comprises a can acting as a negative electrode terminal, a first insulating gasket(20) for sealing formed on top of the can and upper cap(10) acting as a positive electrode terminal formed inside the first insulating gasket, wherein the cap assembly comprising an upper cap, a first metal plate and a second metal plate connected electrically with a positive electrode current collector; the upper cap and the first metal plate are closely adhered to the inside of the first gasket and the second metal plate is closely adhered to the second gasket(60); the upper cap has at least one gas discharge hole; the first metal plate has a central depressed part(46), first and second notches(42, 44) are formed on the upper and lower bent parts of the depressed part, the first notch forms a closed curve while the second notch forms an open curve, and the average radius of the closed curve is greater than that of the open curve; the lower bent part is lift up by the first and second notch when the depressed part of the first metal plate is pressed by a first gas pressure, and the notch part of the second notch of the first metal plate is broken when the pressure greater than the first gas pressure is applied; the second metal plate can be separated from the second metal plate by the gas discharge hole and pressure and has a projected part(54) towards the first metal plate; and the projected part is fixed to the bottom of the depressed part of the first metal plate, and is lift up together with the depressed part when the depressed part is lift up, thereby being separated from the second metal plate and insulating electrically the first metal plate and the second metal plate.

Description

Lithium-ion battery with current interrupt device {LITHIUM ION BATTERY WITH CURRENT INTERRUPT DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery, and more particularly, to a lithium ion battery equipped with a current blocking device that blocks current flow and discharges gas to the outside when the pressure inside the battery increases.

Recently, the demand for high-performance secondary batteries with high energy density has exploded with the expansion of high-performance notebook computers and cordless phones. Such secondary batteries include carbonaceous anodes, lithium metal oxide anodes, and polyolefin separators. Configured lithium ion battery is a situation that is widely produced and used around the world.

However, since the lithium ion battery has a high operating potential of the battery, high energy may flow instantaneously, and a dendrite phase of lithium metal is formed on the negative electrode surface, thereby degrading the safety of the battery.

In addition, since the positive electrode materials used in the battery greatly increase the chemical activity during overcharging, it is suggested that the battery may explode in severe cases by rapidly increasing the internal pressure of the battery by rapidly reacting with the electrolyte and generating a large amount of gas.

Therefore, a lot of research on the safety of the battery is in progress, each battery manufacturer has installed a unique safety valve in the battery to be able to properly discharge the gas when the internal pressure rise of the battery.

Since the safety valve forms a negative electrode terminal with a can into which the pole plate group is inserted, the safety valve is usually installed in a cap assembly, which is a positive terminal coupled to an upper opening of the can.

Therefore, the cap assembly only serves to seal the inside of the battery when the internal pressure of the battery is lower than the specified value. However, when the internal pressure of the battery rises above the specified value, the gas is discharged to the outside of the can by the safety valve. By doing so, the internal pressure of the battery is adjusted to fall below a prescribed value.

However, the conventional cap assembly provided with a safety valve as described above has a problem in that the structure is complicated and its volume occupies a large amount in the battery, which burdens the optimum design of the battery.

Accordingly, the present invention has been made to solve the above problems, it is possible to prevent the explosion of the battery by first blocking the flow of current when the internal pressure of the battery rises and the secondary discharge of gas to the outside when the additional pressure rises. It is an object of the present invention to provide a lithium ion battery equipped with a current interrupt device.

It is another object of the present invention to provide a cap assembly that can simplify the structure and shorten the assembly process.

1 is a cross-sectional view showing a lithium ion battery equipped with a current blocking device according to the present invention;

Figure 2 is a perspective view showing only the safety valve mounted to the cap assembly of the present invention,

3 is a perspective view showing a metal blocking plate mounted to the cap assembly of the present invention,

4 is an operational state diagram of the present invention.

Explanation of symbols on the main parts of the drawings

10: upper cap 12: hole

20: upper gasket 30: positive temperature coefficient plate

40: metal plate 42, 44: notch

46: groove 50: metal block

52: hole 54: protrusion

60: lower gasket

In order to achieve the above object, the present invention includes a gas discharge safety valve and a current blocking means inside the cap assembly, so that the current blocking and the gas discharge are sequentially performed to increase safety and eliminate the possibility of re-energization after the current blocking. It is characterized by the ability to do so.

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

1 is a cross-sectional view illustrating a secondary battery in which a cap assembly according to the present invention is installed.

As shown, the battery inserts a group of electrode plates (not shown) into the can 70 and injects an electrolyte therein, and the cap assembly includes an opening of the can 70 to seal the inside of the can 70. It is configured by mounting.

Wherein the cap assembly of the present invention, the safety valve for lowering the internal pressure of the upper cap 10 and the can 70 is in close contact with the airtight gasket 20 seated on the upper beading portion of the can 70 The lower part of the gasket 20 has a structure in which a current blocking means interlocked with the safety valve is installed.

The upper cap 10 has a structure in which a central portion protrudes upward and a plurality of holes 12 through which gas in the can 70 is discharged along the periphery of the protruding portion.

As shown in FIG. 2, the safety valve is a thin metal plate 40 through which a current flows, and recesses a central portion of the metal plate 40 to form a groove 46, and the groove 46 is bent up and down. The notches 42 and 44 having different depths are formed in the portions, but the notches 42 formed at the upper side of the notches 42 and 44 form a closed curve, and the notches 44 formed at the lower side thereof are formed at one side thereof. It has a structure of open open curve.

The upper cap 10 and the metal plate 40 which is a pressure control means are installed in close contact with each other inside the upper gasket 20 which is sealed at the top of the can 70. Here, the reference numeral 30 is a positive temperature coefficient plate installed between the upper cap 10 and the metal plate 40 to prevent the occurrence of overcurrent due to the abnormal electrode reaction.

When the internal pressure of the can 70 rises by a predetermined pressure or more, the notch 44 of the metal plate 40 does not withstand the pressure and breaks, so that the gas inside the can 70 is capped. It exits through the hole of.

Preferably, the metal plate 40 is formed to have a thickness of about 0.3 mm with respect to an outer diameter of 16 mm, and the grooves 46 formed in the metal plate 40 have upper and lower diameters of about 10 mm and 4 mm, respectively. The notches 42 and 44 formed on the upper and lower portions of the groove 46 are about 0.10 mm and about 0.05 mm, respectively.

In addition, the material of the metal plate 40 is to be made of an aluminum-based material.

Accordingly, as the internal pressure of the can 70 increases, the groove 46 of the metal plate 40 first rises, and the notch 44 formed on the lower bent portion breaks. At this time, the corresponding pressure is 6-8kgf / ㎠ and 13-15kgf / ㎠.

On the other hand, the current blocking means is installed in the lower gasket 60 which is located below the metal plate 40 installed in the upper gasket 20 as the metal blocking plate 50 of the thin film passing current.

Preferably, the material of the metal blocking plate 50 is also made of the same material as the metal plate 40, and the lower gasket 60 prevents the metal blocking plate 50 and the metal plate 40 from being energized. It should be made of polypropylene material.

3 illustrates an example of the metal blocking plate serving as the current blocking means.

According to the drawings, the metal blocking plate 50 has a plurality of holes 52 through which the gas is discharged, and the central portion protrudes upward to form the protrusion 54 so that the protrusion 54 is the metal blocking plate. The protrusion 54 is welded to the bottom of the groove 46 of the safety valve.

According to an embodiment of the present invention, the metal blocking plate 50 is made of aluminum material having a thickness of 0.4-0.5 mm with respect to an outer diameter of 11 mm, and the holes are formed with six holes centered on the center with a diameter of 2 mm. The protrusion 54 formed at the center portion is press-processed so that the diameter is 2.4 mm and the height of the protrusion is about 0.38 mm so that the thickness of the interface between the protrusion 54 and the metal blocking plate 50 is about 0.02 mm.

Therefore, a crack is generated in the interface between the protrusion 54 and the metal blocking plate 50 in the rolling process, so that the protrusion 54 can be easily separated by external pressure.

Here, the bottom surface of the groove 46 of the safety valve and the protrusion 54 of the metal blocking plate 50 use laser welding, ultrasonic welding, resistance welding, or the like.

In the manufacturing process of each of these components, the metal blocking plate 50 of the current interruption device is first inserted into the lower gasket 60, and the protrusion 54 and the safety valve protruding in the center of the metal blocking plate 50 are formed. The groove 46 is welded and attached, and the safety valve is inserted into the upper gasket 20, and the positive temperature coefficient plate 30 and the upper cap 10 are stacked and assembled in the following process, and then the upper end of the can 70 is assembled. The upper gasket 20 is installed by pressing.

Hereinafter, the operation of the present invention will be described with reference to FIG. 4.

When the internal pressure of the battery rises due to the gas generated due to overcharging of the battery, the gas escapes through the hole 52 formed in the metal blocking plate 50, which is a current blocking device, to press the metal plate 40, which is a safety valve. Will be added.

When the pressure of the gas is greater than or equal to the reference value, the groove 46 formed in the metal plate 40 is lifted upward by the pressure of the gas that presses the metal plate 40.

At this time, the protrusion 54 of the metal blocking plate 50 welded to the bottom of the groove 46 is lifted off along the groove 46 while being separated from the metal blocking plate 50 and the metal blocking plate 50. You will be disconnected.

The groove 46 of the metal plate 40 can be lifted up because of the notches 42 and 44 formed in the metal plate 40 and formed at the upper and lower bent portions of the groove 46 by gas pressure. The notches 42 and 44 are flexed and bent upward to lift the grooves 46 that are bent downward.

Therefore, the current, which is connected to the first metal blocking plate 50, the metal plate 40, and the upper cap 10 and is energized, is separated from the metal blocking plate 50 by the protrusion 54 attached to the metal plate 40. Will be blocked.

In the case where additional gas is generated even after the current is first cut off, the metal plate 40, which is the safety valve, is continuously applied by the increased gas pressure. When the gas pressure is higher than a predetermined pressure, the metal plate 40 As the notch 44 breaks, gas inside the battery is discharged to the outside.

That is, as shown in FIG. 4, the notch 44 formed at the lower bent portion of the notches 42 and 44 formed in the metal plate 40 does not endure the gas pressure in the battery and breaks. The groove 46 is cut off from the metal plate 40 and lifted up, and the gas leaked out through the break gap is discharged to the outside through a hole formed in the upper cap 10 to lower the internal pressure of the battery.

Here, the notch 44 is an open curve, and a part of which the notch 44 is not formed is not broken, so that only the part where the notch 44 is formed is broken without breaking. The groove 46 is in a state of being stuck without being completely separated from the metal plate 40.

Therefore, it is possible to exclude the possibility of re-energization due to the fragments separated from the metal plate 40.

According to the lithium ion battery provided with the current interruption device according to the present invention, the current interruption and the gas discharge can be sequentially performed to reliably prevent the risk of battery explosion and the like, thereby greatly increasing the safety of the battery.

It also simplifies the parts used and minimizes the assembly process, resulting in lower part costs and higher productivity.

Claims (15)

In a battery provided with a can serving as a negative electrode terminal, a first insulating gasket for hermetic sealing installed on the upper portion of the can, and an upper cap serving as a positive electrode terminal in the first insulating gasket, And a cap assembly comprising a top cap, a first metal plate, and a second metal plate, wherein the top cap, the first metal plate, and the second metal plate are made of a current carrying material, and the second metal plate supports the second metal plate. Electrically connected to the positive electrode current collector by a positive electrode (+) conductive piece, The upper cap and the first metal plate are stacked in close contact with the inside of the first insulating gasket for maintaining airtightness, and the second metal plate is installed in close contact with the inside of the second insulating gasket disposed under the first insulating gasket. The upper cap has one or more gas outlets, The first metal plate forms a groove portion in which a central portion is recessed, and a first notch and a second notch are formed in the upper bent portion and the lower bent portion of the groove portion, respectively, wherein the first notch formed on the upper part of the two notches is formed. The second notch formed in the closed curve and formed in the lower portion has a structure of an open curve having one side open, and the average radius of the closed curve of the first notch is larger than the average radius of the open curve of the second notch, The first notch is spaced apart from the second metal plate by the second insulating gasket, When the groove portion of the first metal plate is pressurized by the first gas pressure inside the can, the groove portion bent downward by the first notch and the second notch is lifted upward, The notch portion of the second notch of the first metal plate is broken when a second gas pressure inside the can is greater than the first gas pressure, The second metal plate includes one or more gas outlets and protrusions detachable from the second metal plate by pressure and protruding in the direction of the first metal plate, The protrusion is fixed to the bottom of the groove portion of the first metal plate to be integrally operated. When the groove portion is lifted upward, the protrusion is lifted upward with the groove portion and the protrusion is separated from the second metal plate. 1 A cell characterized in that the metal plate and the second metal plate are disconnected, wherein the hinge portion of the first notch of the first metal plate is not electrically connected to the second metal plate by the second insulating gasket. delete The battery of claim 1, wherein the first gas pressure is 6-8 kgf / cm 2 and the second gas pressure is 13-15 kgf / cm 2. delete delete The battery of claim 1 wherein the second notch is deeper than the first notch. The battery according to claim 1, 3 or 6, wherein the first metal plate is made of an aluminum-based material in a thin film. The battery of claim 1, wherein the first metal plate has a thickness of 0.3 mm with respect to an outer diameter of 16 mm, and groove portions formed in the first metal plate have upper and lower diameters of 10 mm and 4 mm, respectively. The battery according to claim 1 or 6, wherein the first notch and the second notch have a depth of 0.10 mm and 0.05 mm, respectively. delete The battery of claim 1, wherein the second metal plate is made of an aluminum-based material as a thin film. The battery of claim 1, wherein the second insulating gasket is made of a polypropylene-based material. 12. The method of claim 11, wherein the second metal plate is made of an aluminum material of 0.4-0.5mm thickness with respect to the outer diameter 11mm, the discharge port is 2mm in diameter to form six centered around the center, while the protrusions formed in the center diameter The battery is characterized by having a height of 2.4 mm and a height of 0.38 mm. The battery according to claim 1, wherein the protrusion is press-processed to produce a thickness of 0.02 mm between the protrusion and the second metal plate. The battery according to claim 1, wherein the bottom of the groove portion of the first metal plate and the protrusion of the second metal plate are welded to each other.